CN1440480A - Method for making tissue paper towels on a modified conventional wet press - Google Patents

Abstract

In an improved wet-pressing process using an integrally sealed air press, tissue paper is made using an improved wet press. After initial formation and conventional vacuum dewatering, the wet web conforms to the surface contour of the relatively coarse fabric belt, thereby giving the web a textured surface. By generating a pressure differential across the web of at least 30 inches of mercury and across the web of at least 500SCFM/in²The air press noncompressively dewaters the wet web to a consistency of from about 30% to about 40% prior to heating the drying cylinder. The web is dried to substantially retain its three-dimensional, dry-through texture. This process provides a paper web with exceptionally high bulk and high absorbency, which is undesirable in wet presses.

Description

Method for making tissue paper towels on a modified conventional wet press

technical field

The present invention generally relates to methods of making paper products. In particular it relates to a method of making a high bulk and high absorbency cellulosic web on a modified conventional wet press.

Background technique

There are generally two different methods used to make the base sheet of paper products such as paper towels, napkins, tissues, wipes and the like. These methods are commonly referred to as wet pressing and through drying. Although the two methods may be the same at the front and back end of the process, there are marked differences in the way water is removed from the wet paper web after initial formation.

More specifically, in the wet pressing process, a newly formed wet paper web is typically transferred onto a papermaking felt and then, while still supported by the felt, pressed against a steam-heated Yankee dryer. On the surface. As the web passes to the Yankee dryer surface, water is forced from the web and absorbed by the felt. The dewatered web, typically having a consistency of about 40%, is then dried on the hot surface of a Yankee dryer. Next, the web is creped to soften and stretch the final paper. A disadvantage of wet pressing is that the pressing step increases the density of the web, thereby reducing the bulk and absorbency of the paper. Subsequent creping steps can only partially restore these desired paper properties.

In the throughdrying process, a newly formed web is first vacuum dewatered, then conveyed to a relatively porous web belt, and hot air is passed through the web for non-squeezing drying. The resulting web is then transferred to a Yankee dryer for creping. Since the web is substantially dry when it is transferred to the Yankee dryer, the density of the web does not increase significantly as a result of the transfer. Also, throughdrying paper is inherently less dense because the web is dried while supported on the throughdrying fabric. Disadvantages of the through-drying method are higher operating energy losses and higher capital costs associated with the through-dryer.

Since the vast majority of existing paper machines use the old wet press method, it is extremely important for producers to find ways to improve existing wet press machines to produce low density product while not requiring costly retrofits for existing machines. Of course, it is possible to repurpose a wet press into a through-dry configuration, but this is usually not done due to the prohibitive cost. To supply the strikethrough dryer and its associated equipment, many complex and costly changes are necessary. In addition, the length of the through-air drying paper machine is relatively large, requiring additional buildings or modifications to the buildings. In some cases, retrofitting a building is impractical or impossible, or prohibitively expensive because it would affect other existing equipment or a useful restricted area on the site. Therefore, there has been great interest in trying to improve existing wet presses without significantly changing the machine design.

In some cases, it is more convenient and economical to modify the press section of a wet press paper machine than to modify the wet end, especially if the wet end and headbox are in good condition. Additionally, older wet presses can have existing equipment associated with bottom felt operation that can easily be repurposed for other purposes, making retrofit simpler and even more cost effective. The present invention discloses a simple method of retrofitting a wet press to produce low density products with improved consumer satisfaction.

As a special case of another embodiment of the present invention, because there are many existing crescent-former paper machines, they can use the improved method to make low-density products that are satisfactory to consumers and benefit, so especially There is a need for a method of retrofitting a crescent former paper machine. Many older crescent former paper machines were provided with a lower felt run which could easily be used as an additional fabric run to meet the needs of certain embodiments of the present invention. The present invention discloses a simple method for retrofitting a crescent former paper machine.

In US Patent 5,230,776, Andersson et al., issued July 27, 1993, a simple method for producing softer, higher bulk paper towels by modifying a wet press is described. This patent discloses replacing the felt with a perforated belt of the mesh type and sandwiching the web between the forming wire and this perforated belt up to the press rolls. This patent also discloses additional dewatering devices, such as steam blowpipes, blow nozzles and/or separate press felts, which can be placed within the confines of the sandwich structure to further increase dry solids prior to the Yankee dryer Content (drysolid content). These additional drying means are said to allow the machine to run at a speed at least substantially equal to that of a through-drying machine.

It is important to reduce the moisture content of the web entering the Yankee dryer to maintain machine speed and prevent web blistering or lack of adhesion. See US Patent 5,230,776 where a separate press felt is used, however, tends to increase the density of the fabric in the same manner as a conventional wet press. Thus, the increased density due to the separate press felt will negatively affect the web bulk and absorbency.

Also, the air jets used to dehydrate the fabric are not by themselves effective in terms of moisture removal or energy efficiency. Blowing air over paper to dry it is well known in the art and may be used in the hood of a Yankee dryer for convection drying. However, in the hood of a Yankee dryer, most of the air from the nozzles does not penetrate the web. Thus, if it is not heated to a high temperature, most of the air will be wasted and not used to effectively remove moisture. In the hood of the Yankee dryer, the air is heated to 900F and allowed to sit for a long time to complete drying.

Thus, what is lacking and needed in the art is a practical method of making thin paper with a higher bulk density and higher absorbency than throughdried paper using a modified conventional wet press.

Contents of the invention

It has now been found that it is possible to manufacture wet pressed wipes having the same bulk and absorbency properties as similar throughdried products while maintaining reasonable machine throughput rates. In particular, wet-pressed cellulosic webs can be made by vacuum dewatering the wet web to a consistency of up to about 30% and then using integrally sealed air pressure devices to non-pressively dewater the paper to a consistency of 30% to 30%. 40% consistency. The wet web is then preferably transferred to a "molded" fabric belt instead of a conventional wet press felt, in order to give the wet web more shape, or to impart a three-dimensional character to the wet web. The wet web is then preferably pressed against the Yankee dryer while being supported by the molding fabric and drying. The resulting product has a higher wet bulk and absorbency than conventional wet-pressed towels and paper towels, and the same wet bulk and absorbency as existing throughdry products.

As used herein, "non-compressive dewatering" and "non-compressive drying" refer to dewatering or drying methods for removing water from a cellulosic web, respectively, which do not involve compressive nip, or Other steps during dewatering that result in a substantial increase in the density of or compress a portion of the web.

In this process the wet paper web is wet molded to improve the three-dimensional properties and absorbency of the paper web. As used herein, "wet molded" tissue means conforming to the surface contours of a strip of molded fabric at about 30% to about 40% consistency, and then, prior to optional additional drying means, formed with, for example, The paper towels thus produced are dried through other drying means such as a through dryer as opposed to heat conduction drying means, such as using a heated dryer.

"Molding fabrics" suitable for the purposes of the present invention include, but are not limited to, papermaker's fabrics that exhibit distinct open areas or three-dimensional surface contours sufficient to impart significant Z-direction deflection to the paper web. This The fabric strips include single-layer, multi-layer or composite permeable structures. Preferred fabric strips have at least some of the following features: (1) on the side of the molded fabric strip in contact with the wet paper web (top surface), The number of strands (mesh) per inch in the machine direction (MD) is from 10 to 200 (3.94 to 78.74 per cm), and the number of strands (counts) per inch in the machine direction (CD) is also from 10 to 200 (per cm 3.94 to 78.74). Strand diameters are generally less than 0.050 inches (1.27 mm); (2) on the top surface, the distance between the highest point of the MD node and the highest point of the CD node is from about 0.001 to about 0.02 or 0.03 inches ( 0.025mm to about 0.508mm or 0.762mm). Between these two highest points, there are knots formed by MD strands or CD strands to give the paper a three-dimensional peak/valley appearance during the wet molding step configuration; (3) on the top surface, the length of the MD section is equal to or greater than the length of the CD section; (4) if the fabric belt is a multi-layer structure, it is best that the bottom layer has a finer mesh than the top layer in order to control the web (5) It can make the fabric belt present some geometric patterns that are visually pleasing, and this pattern is usually repeated every 2 to 50 warp yarns.

Accordingly, in one aspect, the present invention relates to a method for making a cellulosic paper web, the steps of the method comprising: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper web (b) dewatering the wet paper web to a consistency of about 10% to about 30%; (c) transferring the wet paper web to a second fabric belt which circulates; (d) sandwiching the wet paper web between the second fabric belt and between supporting fabric belts, and dewater the wet paper web to a consistency of about 30% or greater using a non-squeezing dewatering pressurized fluid flows substantially through the web at a pressure (gauge) of about 5 psi or greater; (e) pressing the dewatered web against the surface of a heated dryer to at least partially dry a paper web; and (f) drying the dewatered wet paper web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper web, wherein The paper web; (b) the wet paper web is transferred to the second fabric belt of circulation; (c) the wet paper web is sandwiched between the second fabric belt and the support fabric belt, and the wet paper web is dehydrated until about 30 % consistency; (d) additionally dewatering the wet paper web to a consistency of about 30% to about 40% using an air pressure device, due to pressurized fluid flowing substantially through the fabric at a pressure of about 5 psig or greater (e) making the second fabric belt be constructed in such a way that it is capable of providing a dewatered wet paper web around the unsupported paper angle of the press roll; (f) making the dewatered paper web press against the heated dryer surface to at least partially dry the dewatered wet paper web; and (g) drying the dewatered wet paper web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper (b) dewatering the wet paper web to a consistency of up to about 10%; (c) transferring the wet paper web to the circulating second fabric; (d) sandwiching the wet paper web between the second fabric and the support fabric between the belts; (e) using the second fabric belt positioned between the wet paper web and the collection device, the wet paper web sandwiched between the second fabric belt and the support fabric belt passes between the gas plenum and the collection device , the gas plenum is operably associated with the collection device and is adapted to produce a pressure differential of about 30 inches of mercury or greater across the wet web, and a pressure differential of about 30 inches of mercury or greater across the wet web at a rate of A pressurized fluid stream of about 10 standard cubic feet or greater; (f) dewatering the wet paper web to a consistency of about 30% to about 40% using the pressurized fluid stream; (g) dewatering the dewatered web through a second fabric pressing the web against the heated dryer surface; and (h) drying the dewatered wet web to final dryness.

In another aspect, the present invention relates to a method for improving a conventional wet press having at least one felt and a press dewatering device, the method comprising: (a) replacing at least one felt with at least one fabric belt; (b) replacing at least one felt with a non-thermal The non-squeezing dehydration device replaces the squeeze dehydration device. The wet pressing process and apparatus described in US Patent 4,139,410, Tapio et al., issued February 13, 1979, is hereby incorporated by reference.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper (b) dewatering the wet paper web to a consistency of about 10% to about 30%; (c) transferring the wet paper web to a circulating second fabric; (d) clamping the wet paper web between the second fabric The wet web is dewatered to a consistency of greater than about 30% between the support fabric and the non-squeezing dewatering unit, which is adapted to dewater about 5 psi or A pressurized fluid of greater pressure flows substantially through the wet paper web; (e) conveys the wet paper web back to the second fabric belt; (f) presses the dewatered wet paper web against the heated dryer surface, thereby at least partially drying the wet paper web; (g) drying the dewatered wet paper web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper (b) transfer the wet paper web to the circulating second fabric belt; (c) sandwich the wet paper web between the second fabric belt and the support fabric belt, and dehydrate the wet paper web to a consistency of about 30% (d) further dewatering the wet paper web to a consistency greater than about 30% to 40% using an air pressure device adapted to make about 5 lbs/ A pressurized fluid of pressure in square inches or greater flows substantially through the wet web; (e) conveying the wet web back to the second fabric belt so that the wet web has a paper wrap angle of less than 90° on the press rolls (f) pressing the dewatered wet paper web against the surface of a heated dryer cylinder, thereby at least partially drying the high humidity paper web; (g) drying the dewatered wet paper web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper (b) dewatering the wet paper web to a consistency of about 10% to about 30%; (c) transferring the wet paper web to another fabric belt; (d) sandwiching the wet paper web between the second fabric belt and the support Between the fabric belts, one of the two fabric belts utilizes the space and components originally used in the bottom felt run of a tow press wet press machine; (e) further dewaters the wet web to Greater than about 30% to 40% consistency, the pneumatic device is adapted to allow a pressurized fluid at a pressure of about 5 psig or greater to flow substantially through (f) conveying the wet paper web back to the second fabric belt; (f) pressing the dewatered wet paper web against the surface of the heated drying cylinder, thereby at least partially drying the wet paper web; (g) drying the web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper (wet web) to make wet paper web (wet web); (b) transfer the wet paper web to the circulating second fabric belt; (c) sandwich the wet paper web between the second fabric belt and the supporting fabric belt , and dewatering the wet paper web to a consistency of about 10% to about 30%; (d) further dewatering the wet paper web to a consistency of greater than about 30% to 40% using an air pressure device, due to the form an integral seal therebetween, so that the air pressure device is adapted to substantially flow a pressurized fluid of about 5 psi pressure through the wet paper web; (e) convey the wet paper web back to the second fabric belt, thereby making the web have a bulk density of about 8 cc/g or greater; (f) pressing the dewatered wet web against the surface of a heated dryer with a fabric belt to maintain a bulk density of about 8 cc/g or greater bulk; (g) drying the wet web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic fabric comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a circulating first fabric belt to form a wet paper web; (b) ) transferring the wet paper web to the circulating second fabric; (c) sandwiching the wet paper web between the second fabric and the supporting fabric; (d) making the second fabric and the supporting fabric sandwiched between The wet paper web passes together between the air pressure device and the collection device, while the second fabric belt is located between the wet paper web and the collection device, the air pressure device and the collection device are operatively connected and adapted to generate A pressure differential of about 30 inches of mercury or greater and a pressurized fluid flow of about 10 standard cubic feet per minute per square inch or greater across the wet paper web; (e) utilizing the pressurized fluid flow to make the wet Dewatering the web to a consistency of about 30% or greater; (e) pressing the wet web against the heated dryer surface by a second fabric belt; and (f) drying the web to final dryness.

Accordingly, another embodiment of the present invention is directed to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating first fabric belt; Between two fabric belts to form a wet paper web, wherein the wet paper web is sandwiched between the first fabric belt and the second fabric belt; (b) using a non-extrusion dewatering device to dehydrate the wet paper web to about 30% or more A large consistency suitable for substantially flowing a pressurized fluid of about 5 psig or greater through the wet paper web due to the integral seal formed by the non-squeeze dewatering device and the wet paper web; ( c) pressing the wet dewatered paper web against the surface of a heated dryer cylinder, thereby at least partially drying the wet dewatered paper web; (d) drying the wet dewatered paper web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating second fabric belt; between the belts to form a wet paper web, wherein the wet paper web is sandwiched between the first fabric belt and the second fabric belt;

(b) dewatering the wet paper web to a consistency of about 10% to about 30%; (c) additionally dewatering the wet paper web to a consistency of greater than about 30% to 40% using an air pressure device due to the gas plenum and An integral seal is formed between the collecting means so that the air pressure means is adapted to allow a pressurized fluid of about 5 psi or greater to flow substantially through the wet web so that the web has a mass of about 8 cc/ Grams or greater bulk density; (d) the dewatered wet paper web is pressed against the surface of the heated dryer by a fabric belt to maintain a bulk density of about 8 cubic centimeters per gram or greater; (e) The dewatered wet web is dried to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating second fabric belt; between the belts to form a wet paper web, wherein the wet paper web is sandwiched between the first fabric belt and the second fabric belt; (b) passing the wet paper web sandwiched between the first fabric belt and the second fabric belt through air pressure device and the collecting device, and the second fabric belt is located between the wet paper web and the collecting device, the air pressure device and the collecting device are operably connected, and are adapted to generate about 30 inches of mercury or more across the wet paper web a high pressure differential and a flow of pressurized fluid of about 10 standard cubic feet per minute per square inch or greater across the wet paper web; (c) using the pressurized fluid flow to dewater the wet paper web to about 30% or higher consistency; (d) pressing the wet web against the heated dryer surface by a second fabric belt; and (e) drying the dewatered web to final dryness.

In another aspect, the present invention relates to a method for improving a conventional crescent former tissue making machine having at least one felt and press dewatering means, the method comprising: (a) replacing at least one felt with at least one fabric belt; ( b) Replace the press dewatering unit with a non-thermal, non-squeezing dewatering unit. The crescent forming process and apparatus described in US Patent 3,224,928 to Lee et al., issued December 21, 1965, is hereby incorporated by reference.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating second fabric belt; between belts to form a wet web; (b) using a combination of centrifugal force around forming rolls and fabric belt tension to dewater the wet web to a consistency of about 10% or greater; (c) using a non-extrusion dewatering device , since the non-squeezing dewatering device forms an integral seal with the wet web, it is adapted to allow pressurized fluid to flow substantially through the web at a pressure differential of about 5 psig or greater; (d) the wet The web is conveyed back or held on the second fabric belt; (e) pressing the dewatered web against the heated dryer surface to at least partially dry the wet web; and (f) causing the wet web to Web drying to final drying.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating second fabric belt; between the belts to form a wet web; (b) using a combination of centrifugal force around the forming rolls and fabric belt tension to dewater the wet web to a consistency of about 10% or greater; (c) further dewater the wet web to 10% to about 30% consistency; (d) supplementary dewatering of the wet web to a consistency of about 30% to about 40% using an air pressure device, the The pneumatic means is adapted to cause a pressurized fluid to flow substantially through the wet paper web at a pressure of about 5 psig or greater; (e) return or retain the wet paper web on the second fabric; (f) cause pressing the dewatered web against the heated dryer surface to at least partially dry the wet web; (g) drying the wet web to final dryness.

In another aspect, the present invention relates to a method of making a cellulosic paper web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers on a recirculating first fabric belt and a recirculating second fabric belt; between belts to form a wet web; (b) dewatering the wet web to a consistency of about 10% to about 30%; (c) additionally dewatering the web to a consistency of about 30% to about 40% using an air pressure device, The pneumatic device is adapted to flow pressurized fluid substantially through the wet web at a pressure of about 5 psi or greater due to the integral seal formed between the gas plenum and the collection device; (d) The wet paper web is conveyed back or held on the second fabric belt so that the wet paper web has a bulk density of about 8 cubic centimeters per gram or greater; (e) the dewatered wet paper web is pressed against by the fabric belt On the surface of the heated dryer to maintain a bulk density of about 8 cc/g or greater; (f) drying the wet web to final dryness.

In yet another aspect, the present invention is directed to a method of making a cellulosic fabric, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers between a circulating first fabric belt and a circulating second fabric belt to forming a wet paper web, wherein at least one of the endless fabric belts is a three-dimensional molded fabric belt; (b) causing the first fabric belt and the second fabric belt with the wet paper web sandwiched therebetween and the collection device, and the three-dimensional molded fabric belt is located between the wet paper web and the collection device, the air pressure plenum and the collection device are operatively connected, and are adapted to generate about 30 inches of mercury or greater pressure differential and a pressurized fluid flow of about 10 standard cubic feet per minute per square inch or greater across the wet paper web; (d) dewatering the wet paper web using the pressurized fluid flow to a consistency of about 30% or greater; (e) pressing the dewatered wet web against the surface of a heated dryer cylinder through a fabric belt; and (f) drying the wet web to final dryness.

The term "first fabric strip" as used herein refers to any fabric strip known in the art or as described herein in the tissue making process, including, but not limited to, the forming fabric used in tissue making. , molded and other supporting fabric straps. Preferably, however, the first fabric is a forming fabric. The term "second fabric" as used herein refers to any fabric known in the art or as described herein in the tissue making process, including, but not limited to, the forming fabric used in tissue manufacturing , molded and other supporting fabric straps. Preferably, however, the second fabric is a molded fabric as described herein. Here the second fabric is a molding fabric and the resulting paper web is a molded paper web. As used herein, the term "support fabric" means any fabric known in the art or as described herein in the tissue manufacturing process, including, but not limited to, forming, Molded and other supporting fabric straps.

As used herein, the terms "integrally sealed" and "integrally sealed" refer to the relationship between the air plenum and the wet web, the air plenum being operatively associated with and in indirect contact with the fabric so that when the air is increased about 85 percent or more of the air supplied to the air plenum flows through the web when the plenum operates at a pressure differential of about 30 inches of mercury or greater across the web; and the air plenum and The relationship between the collection device, the gas plenum is in operative communication with and in indirect contact with the web and the collection device so that when the gas plenum and the collection device have a pressure differential of about 30 inches of mercury or greater across the web During downtime operation, about 85% or more of the air supplied to the air plenum flows through the web into the collecting device.

Mainly due to the high pressure difference generated on both sides of the paper web, and the resulting air flow through the paper web, the air pressure device can dehydrate the wet paper web to a very high consistency. For example, in particular embodiments, the air pressure device can increase the consistency of the web by about 3% or more, especially about 5% or more, such as about 5% to about 20%, more particularly about 7% or more Large, more particularly also about 7% or greater, such as from about 7% to 20%. Like this, the consistency of the wet paper web exiting air device can be about 25% or greater, about 26% or greater, about 27% or greater, about 28% or greater, about 29% or greater, and most Well about 30% or more, especially about 31% or more, more especially about 32% or more, such as from about 32% to about 42%, especially about 33% or more, even more especially About 34% or greater, such as from about 34% to about 42%, and more particularly about 35% or greater.

By adding a dewatering step to the method with an integrally sealed pneumatic device, a significant improvement over the previously described prior methods can be obtained. First and foremost, a sufficiently high consistency is obtainable so that the process can be operated at industrially useful speeds. As used herein, "high speed operation" or "industrial use speed" of a tissue machine means a machine speed in feet per minute that is at least as high as any of the following values or ranges: 1,000; 1,500; 2,000; 2,500; 3,000; 3,500; 4,000; 4,500; 5,000; 5,500; 6,000; 6,500; 7,000; 8,000; 9,000; 10,000, and a range with upper and lower limits of any of the above values. Furthermore, molding the paper at high consistency significantly improves the ability of the paper to retain its three-dimensionality, and this also significantly improves the final thickness of the paper. As used herein, the term "textured" or "three-dimensional" as applied to the surface of a fabric belt, felt or uncalendered paper web means that the surface is not substantially smooth or coplanar. In addition, the machine configuration is suitable for a rapid transfer step, which again leads to a significant increase in bulk density and absorbency relative to existing wet pressing methods.

An optional steam injector or the like may be used prior to the air press to increase post air press consistency and/or improve the cross-machine direction moisture profile of the web. Also, higher consistency can be obtained when the machine speed is slower and the residence time in the pneumatic device is longer.

The differential pressure across the wet paper web provided by the air pressure device may be 25 inches of mercury or higher, such as from about 25 to about 120 inches of mercury, especially about 35 inches of mercury or higher, such as from about 35 to about 60 inches of mercury, and more particularly from about 40 to about 50 inches of mercury. The fluid pressure on one side of the wet paper web is maintained greater than 0 to about 60 pounds per square inch (psig), particularly greater than 0 to about 30 psig, more particularly about 5 psig or greater, such as about 5 to about 30 psig, and still more particularly from about 5 to about 20 psig, so that the aforementioned differential pressure can be achieved in part. The collection device of the pneumatic device is preferably used as a vacuum box, which vacuum box is at a vacuum of 0 to about 29 inches of mercury, especially a vacuum of 0 to about 25 inches of mercury, especially a vacuum of greater than 0 to about 25 inches of mercury, and more In particular, a vacuum of from about 10 to about 20 inches of mercury, such as about 15 inches of mercury, is operated. In some cases, the collection device of the pneumatic device can operate at a vacuum of 30 inches of mercury or higher. The collection means is preferably, but not necessarily, integrally sealed with the gas plenum and evacuated so that it acts as an air and liquid collection means. The pressure levels in the gas plenum and collection means are preferably monitored and controlled to predetermined levels.

Obviously, the pressurized fluid used within the air press is sealed from the outside air to create an air flow substantially through the web which results in the enormous dewatering capacity of the air press. The flow of pressurized fluid through the pneumatic device is suitably from about 5 to about 500 standard cubic feet per minute (SCFM) per square inch of open area, particularly about 10 SCFM per square inch of open area or greater, such as from the open area From about 10 to about 200 SCFM per square inch of the open area, more particularly about 40 SCFM per square inch of the open area or greater, such as from about 40 to about 120 SCFM per square inch of the open area. Desirably, 70% or greater, especially 80% or greater, more particularly 90% or greater of the pressurized fluid supplied to the gas plenum is drawn through the wet web to Inside the vacuum box. For the purposes of the present invention, the term "standard cubic feet per minute" means: cubic feet per minute measured at an absolute value of 14.7 psi and a temperature of 60 degrees Fahrenheit (°F).

The terms "air" and "pressurized fluid" are used interchangeably herein to refer to any gaseous substance used in an air pressure device to dewater a wet paper web. Gaseous substances suitably include air, steam or the like. Preferably, the pressurized fluid comprises air at ambient temperature, or a heated gas raised to a temperature of about 300°F or less, especially about 150°F or less, only by pressurization gas.

The wet paper web is preferably attached to the surface of a Yankee dryer or other heated drying cylinder (heated drying cylinder) in such a way that it retains a substantial portion of the texture formed by the previous treatment, especially by molding on a three-dimensional fabric belt. Formed texture. The traditional method used to produce wet-pressed creped paper is not suitable for this purpose because in this traditional method press rolls are used to dewater the web and press it uniformly into a dense and flat state. For purposes of the present invention, the conventional substantially smooth press felt is replaced by a textured material such as an apertured fabric belt, and preferably a throughdrying fabric belt. In another aspect of the present invention, the conventional substantially smooth press felt of a conventional crescent former towel machine is replaced by a textured material such as an apertured fabric belt, and preferably a throughdrying fabric belt. The tissue web made according to the method of the present invention preferably has about 8 cubic centimeters per gram (cc/g) or more, especially about 10 cc/g or more, and more preferably after molding on the three-dimensional fabric belt. In particular, a bulk density of about 12 cc/g or greater is maintained after pressing it onto a heated drying cylinder using a textured fabric mesh belt.

For best results, significantly reduced pressing pressures can be used compared to conventional tissue manufacturing methods. Preferably, the area of maximum load applied to the web should be about 400 psi or less, especially about 350 psi or less, more especially about 150 psi or less, such as between about 2 and about 50 psi, and most particularly about 30 psi or less. Preferably the pressing pressure measured in pounds per linear inch (pli) at the point of maximum pressure is about 400 pli or less, and especially about 350 pl or less. Applying the three-dimensional web structure to the heated dryer cylinder with low pressure helps maintain a substantially uniform density in the dried web. By using non-squeezing means to effectively dewater the web prior to connection to the Yankee dryer, and by selecting an apertured fabric belt so that the web contacts the dryer, this will help to achieve a substantially uniform web density, the dryer is relatively free from high, rigid protrusions that exert high local pressure on the web. The fabric is preferably treated with an effective amount of a fabric release agent to promote separation of the web from the fabric once it contacts the dryer surface.

The absorbency of a tissue can be characterized by its absorbent capacity and its absorption rate. As used herein, "Absorptive Capacity" is the maximum amount of distilled water that a paper can absorb, expressed as grams of water per gram of sample paper. More specifically, the absorbency of a sample paper can be measured by cutting a 4 inch by 4 inch (101.6 by 101.6 mm) sample of dry paper weighing to the nearest 0.01 gram. The sample is dropped onto the surface of a room wet distilled water tank and left in the tank for 3 minutes. Then remove the sample using pliers or tweezers and hang it vertically with three-prong clamps to drain excess water. Each sample can be drained for 3 minutes. The sample is then placed on the weighing pan by placing the weighing pan under the sample and loosening the three prong clamps. Wet samples were weighed to the nearest 0.01 gram. The absorbent capacity is the wet weight of the sample minus the dry weight (amount of water absorbed), divided by the dry weight of the sample. At least 5 representative samples of each product may be measured and the results averaged.

"Absorption rate" is: the time it takes for the product to completely wet out in distilled water. The rate of absorption is determined by dropping a paper pad consisting of 20 sheets of paper measuring 2.5 inches by 2.5 inches (63.5 by 63.5 mm) each onto the water in a tank of distilled water having a temperature of 30°C. The time elapsed in seconds from the moment the sample hits the water until it is completely wetted (determined visually) is the rate of absorption.

The method is suitable for use in the manufacture of a variety of absorbent products including face towels, bath tissues, towels, napkins or wipes or similar products. For the purposes of the present invention, the term "tissue" or "tissue product" is used generally to describe the structure of such a product, while the term "cellulose web" is used to refer broadly to any tissue containing or consisting of cellulose regardless of the structure of the finished product. A paper web made of fibers.

Many fiber types can be used with the present invention, including hardwood or softwood, straw, hemp, milkweed lint fiber, abaca, hemp, kenaf, sugar cane Bagasse, cotton, reed or similar material. All known papermaking fibers including bleached or unbleached fibers, naturally occurring fibers (including wood fibers and other cellulosic fibers, cellulose derivatives and chemically hardened or crosslinked fibers), or synthetic fibers (synthetic papermaking fibers) can be used. Fibers include some forms of fibers made from polypropylene, acrylic, aramids, acetates, and the like), virgin and recycled or recycled fibers, hardwoods and softwoods, and Pulping by mechanical methods (such as groundwood), chemical pulping (including but not limited to kraft pulping and sulfite pulping), thermomechanical pulping Pulp, fibers made into pulp by chemithermomechanical or similar methods. Mixtures of any subset of the above or related types of fibers may be used. Fibers can be prepared in a variety of advantageous ways known in the art. Useful methods for preparing fibers include dispersing them to bend them and improving their drying properties, as disclosed in, for example, U.S. Patent No. 5,348,620 issued September 20, 1994 and U.S. Patent No. 5,501,768 issued March 26, 1996, both of which Both by M.A. Hermans et al.

Chemical additives may also be used and may be added to the virgin fibers, to the fiber slurry suspension, or to the paper web during or after production. Such additives include opacifiers, pigments, wet strength agents, dry strength agents, softeners, emollients, humectants ( humectants), viricides, bactericides, buffers, waxes, fluoropolymers, odor control materials and deodorants , zeolites, dyes, fluorescent dyes or whiteners, perfumes, debonders, vegetable and mineral oils, humectants, sizing agents, superabsorbents Superabsorbents, Surfactants, Moisturizers, UV blockers, Antibiotics, Lotions, Fungicides, Preservatives ( preservatives), aloe-vera extract, vitamin E or similar additives. The chemical additives do not have to be added evenly, but can vary in different locations and from one side of the tissue to the other. Hydrophobic materials deposited on portions of the surface of the web can be used to enhance the properties of the web.

The headbox can be layered so that a multilayer structure can be produced from a single headbox jet during the web forming process. In specific embodiments, the web is made with a layered or layered headbox so that short fibers are preferentially deposited on one side of the web to improve softness, and then on the other side of the web or for three For one or more layers of paper web, longer fibers are deposited in the inner layer. The web is preferably formed on an endless loop of a foraminous forming fabric where fluid drainage and partial dewatering of the web are permitted.

The many features and advantages of the invention will be apparent from the following description. In the following description, preferred embodiments of the present invention are explained with reference to the accompanying drawings. These examples do not represent the full scope of the invention. Accordingly, the claims hereof are regarded as expressing the full scope of protection of the present invention.

Description of drawings

Fig. 1 representatively shows a schematic process flow diagram of a method for producing a high bulk and high absorbency cellulose paper web according to the present invention.

Fig. 2 representatively shows the process flow diagram of another method according to the present invention.

Figure 3 representatively shows an enlarged end view of the pneumatic device used in the method of Figures 1-2 with the gas plenum seal of the pneumatic device in a raised position relative to the warm fabric and vacuum box.

FIG. 4 representatively shows a side view of the pneumatic device of FIG. 3 .

Figure 5 representatively shows an enlarged cross-sectional view taken generally along line 6-6 of Figure 3, but with the seal loaded against the fabric strip.

FIG. 6 representatively shows an enlarged cross-sectional view similar to FIG. 5 taken generally along line 7-7 in FIG. 3 .

FIG. 7 representatively shows a perspective view of several components of a gas plenum seal disposed against a fabric strip, partially broken away and shown in cross-section for purposes of illustration.

FIG. 8 representatively shows an enlarged cross-sectional view of another sealing structure used in the pneumatic device of FIG. 3 .

FIG. 9 is an enlarged schematic view representatively showing a sealing portion of the pneumatic device of FIG. 3 .

Figure 10 representatively shows a schematic process flow diagram of a method for making a high bulk and high absorbency cellulosic web according to the present invention.

Fig. 11 representatively shows a schematic process flow diagram of another method according to the present invention.

FIG. 12 representatively shows a schematic process flow diagram of another alternative implementation method according to the present invention.

Detailed ways

The invention will now be described in detail with reference to the appendix, in which the same

Elements are denoted by the same reference numerals. For simplicity, the different tensioning rods used to define the travel paths of several fabric belts are schematically represented but not numbered. Various conventional papermaking equipment and operations are used for stock preparation, headbox, forming fabric, web transfer, creping and drying. Nevertheless, in order to provide a background introduction that may be used with various embodiments of the present invention, specific conventional components are shown in the drawings.

The method of the present invention can be practiced on the apparatus shown in Figure 1, which is a modification of a typical wet press towelmaking machine. A primary embryonic wet web 10 forming a papermaking fiber slurry is deposited from a headbox 12 onto an endless loop of a first fabric belt 14 . Note that as an alternative embodiment it is also possible to use a forming device such as a twin wire forming machine without changing the functionality of this modification. The consistency and flow rate of the slurry determine the dry web basis weight (basic weight), which is preferably between about 5 and about 80 grams per square meter (gsm), more preferably between about 8 and about 40 gsm .

The primary wet paper web 10 is partially dewatered by the natural drainage normally associated with the first fabric 14 and forming rolls 52 while the primary wet paper web 10 is carried on the first fabric 14 . Additional dewatering may be performed by any dewatering means or equipment such as vacuum box 46 . Once the partial dewatering step is complete, the wet paper web 10 is transferred or held on the second fabric belt 24 with or without the use of a vacuum shoe 50 . At least one of the fabric strips 14 and 24 may be a forming fabric strip, preferably the first fabric strip 14 . Alternatively, at least one of the fabric strips 14 and 24 may be a molded fabric strip, preferably the second fabric strip 24 .

In order to realize the high-speed operation of the present invention, the traditional paper towel dehydration method before the heated drying cylinder 30 may not be able to sufficiently remove moisture, thus requiring an additional dehydration device. As an alternative, a vacuum box 47 can be used to further dewater the wet web. In the illustrated embodiment, an air pressure device 16 is used to dewater the web 10 non-pressively. The air pressure device 16 shown comprises: a pressurized air gas plenum 18 device arranged above the wet paper web 10; a water and fluid collection device 20, shown in the form of a vacuum box, arranged below the support fabric belt 14, It is also in operative communication with the gas plenum 18 for pressurized air and the second fabric belt 24 . (In a further alternative embodiment, fluid collection device 20 may be positioned adjacent to second fabric 24 in operative communication with pressurized air gas plenum 18 and support fabric 22). While passing through the air pressure device 16, the wet paper web 10 is sandwiched between the second fabric 24 and the support fabric 22 so as to seal against the wet paper web 10 without damaging the wet paper web 10.

The air pressure device 16 provides a substantial rate of moisture release, enabling the web to be dry to a degree greater than 30% prior to attachment to a dryer cylinder 30 such as a Yankee dryer, preferably without the need for substantial dewatering. Several embodiments of the pneumatic device 16 are described in more detail below. Other suitable embodiments are disclosed in U.S. Patent Application No. 08/647,508, filed May 14, 1996 by M.A. Hermans et al., entitled "Method and Apparatus in Making Soft Paper," which The patent literature is hereby incorporated by reference.

After the air pressure device 16, the wet paper web 10 is further run sandwiched between the second fabric belt 24 and the support fabric belt 22 with or without the help of the vacuum transfer slide 26 at the transfer station until the wet paper web 10 is conveyed back to a second fabric belt 24, preferably a textured fabric belt.

The second fabric 24 may comprise a three-dimensional throughdrying fabric such as that disclosed in U.S. Patent 5,429,686 to K.F. Chiu et al., issued July 4, 1995, which is incorporated herein by reference. , or the second fabric strip 24 may comprise other woven, textured fabric or non-woven fabric strips. The second fabric 24 may be treated with a fabric release agent such as silicon or a mixture of hydrocarbons in order to subsequently separate the wet paper web 10 from the second fabric 24 . A fabric release agent may be sprayed on the second fabric 24 prior to grabbing the web. Once placed on the second fabric belt 24, although the wet paper web 10 can be adequately molded at least due to the vacuum force at the transfer skid 26 during gripping, the wet paper web 10 can also be molded by utilizing vacuum pressure. Or light pressure (not shown) is further molded against the second fabric strip 24 .

The wet paper web 10 on the second fabric belt 24 is then pressed against a heated dryer cylinder 30 by a press roll 32 . The heated drying cylinder 30 is equipped with a steam hood or Yankee dryer hood 34 . The enclosure 34 is typically utilized at a temperature of about 300°F or higher, particularly about 400°F or higher, more particularly about 500°F or higher, and most particularly about 700°F or higher. A jet of heated air directed from a nozzle or other flow-through device directly at the wet paper web 10, such that, in the hood 34, the gas jet has a maximum velocity or a partial average velocity of one of the following levels: about 10 m/s (m/s) or more, about 50 m/s or more, about 100 m/s or more, about 250 m/s or more.

The wet web when attached to the heated dryer cylinder 30 suitably has a fiber consistency of about 30% or greater, especially about 35% or greater, such as between about 35% and about 50%, and more preferably about 38% % or greater fiber consistency. When removed from the heated drying cylinder 30, the dryness of the wet paper web 10 increases to about 60% or greater, particularly about 70% or greater, more particularly about 80% or greater, more particularly 90% % or greater, most particularly between about 90% and about 98%. The wet web may be partially dried on heated dryer cylinder 30 and wet creped at about 40% to about 80% consistency, then dried (post-dry) to about 95% or greater consistency. Non-traditional hood and impingement systems may be used in place of or in addition to the Yankee dryer hood 34 to enhance wet web dryness. Additional heated dryers 30 or other drying equipment, especially non-squeezable dryers, may be used after the first heated dryer 30 . Suitable post-drying equipment includes one or more heated drying cylinders 30, such as Yankee and empty can dryers, through dryers, or any other commercially effective drying equipment. As an alternative embodiment, if the second fabric belt 24 is a molded fabric, then it may be that the molded wet paper web 10 can be completely dried and dry-creped on the heated dryer cylinder 30 . The degree of dryness on the heated dryer cylinder 30 depends on factors such as the speed of the wet paper web 10, the size of the heated dryer cylinder 30, the amount of moisture in the wet paper web 10, and the like.

The resulting dry fabric 36 is drawn or passed out of the heated dryer cylinder, for example by means of a creping doctor 28 , after which it is wound onto rolls 38 . The illustrated interface control mixture 40 is sprayed in the form of a spray from a spray tube 42 onto the surface of the rotating heated dryer cylinder 30 before the wet paper web 10 comes into contact with the heated cylinder surface. As an alternative to spraying directly onto the surface of the rotating heated dryer 30, the interface control mixture 40 may be applied directly to the wet paper web 10 or heated dryer surface 30 by gravure printing, or may be incorporated into the paper machine in the aqueous fiber slurry suspension in the wet end. While on the surface of the heated dryer 30, the wet paper web 10 may also be treated chemically, such as by printing or spraying a solution directly on the dry web 10, including the addition of solvents to facilitate separation from the heated dryer 30 surface.

The interface control mixture 40 may include conventional creping adhesives and/or dryer release agents for wet pressing and creping operations. It is also possible to use an interface controlling compound of the type below to remove the wet paper web 10 from the surface of the heated dryer cylinder 30 without creping it, filed on the same day as this application by F.G. Druecke et al. Disclosed in U.S. Patent Application for "Method of producing low density resilient webs", incorporated herein by reference.

Figure 2 shows an alternative embodiment which is similar to Figure 1 except for the following differences. The running rollers 55 of the support fabric 22 are positioned to change the direction of the second fabric 24, the support fabric 22 and the wet paper web 10 so that the wet paper web 10 is conveyed to the Yankee dryer or other heated dryer cylinder 30 , which is less likely to separate from the suction roller 32. The rollers 55 reduce the unsupported paper wrap angle α, thereby minimizing the chance of the wet paper web 10 separating from the second fabric 24 before it is transferred to the heated dryer cylinder 30 . A primary wet paper web 10 formed into a papermaking fiber slurry is deposited from a headbox 12 onto a circulating loop of a first fabric belt 14 . At least one of the fabric strips 14 and 24 may be a forming fabric strip, preferably the first fabric strip 14 . Alternatively, at least one of the fabric strips 14 and 24 may be a molded fabric strip, preferably the second fabric strip 24 .

The primary wet paper web 10 is partially dewatered by natural drainage normally associated with the first fabric 14 and forming rolls 52 while being carried on the first fabric 14 . While being carried on the first fabric belt 14, further dewatering of the wet paper web 10 may be performed by an optional vacuum box 46 or other suitable dewatering equipment. Once the partial dewatering step is complete, the wet paper web 10 is transferred onto the second fabric belt 24 with or without the use of vacuum slides 50 . The wet paper web 10 is sandwiched between the second fabric 24 and the support fabric 22, and optionally, while it is sandwiched between the second fabric 24 and the support fabric 22, is vacuumed by a vacuum box 47 or other suitable Dehydration papermaking comes to further dehydration.

The air pressure device 16 is used to dewater the wet paper web 10 non-pressively while the wet paper web 10 is sandwiched between the second fabric 24 and the support fabric 22 . The illustrated pneumatic device 16 includes means of a pressurized air gas plenum 18 arranged in operative communication with a vacuum box 20 . As it passes through the air pressure device 16 , the wet paper web 10 is sandwiched between the second fabric 24 and the support fabric 22 which is located between the wet paper web 10 and the vacuum box 20 . (In a further alternative embodiment, the second fabric strip 24 may be disposed between the wet paper web 10 and the vacuum box 20).

The wet paper web 10 is then conveyed further back to the second fabric belt 24 with or without the aid of the vacuum slide 26 . The wet paper web 10 on the second fabric 24 is then pressed against the dryer cylinder 30 by means of the press roll 32, preferably in such a way that the unsupported paper wrap angle α on the press roll 32 is minimized. The unsupported sheet wrap angle α can range in angle from 0 to about 90 degrees, from 0 to about 45 degrees, and from 0 to about 10 degrees. In addition, the smaller unsupported sheet wrap angle a reduces the size of the required vacuum zone, thereby reducing the energy required to create a vacuum within the press rolls. When the wet paper web 10 is conveyed onto the dryer cylinder 30, the unsupported paper wrap angle α is defined as the portion of the circumference of the press roll 32 wrapped around the wet paper web 10 (expressed in degrees) from the wet paper web 10 on the press. The first point of contact on roll 32 to the last point of contact of wet paper web 10 on press roll 32 .

The heated drying cylinder 30 is equipped with a steam hood or Yankee dryer hood 34 . The resulting dry web 36 is drawn or passed from the dryer cylinder 30 and removed without creping before being wound onto a roll 38 . The angle at which the dry web 36 is drawn from the surface of the heated dryer 30 is suitably from 0 degrees to about 100 degrees and is measured along a tangent to the surface of the heated dryer 30 at the point of separation, although it may vary depending on the operating speed rather different.

The interface control mixture 40 is sprayed from the spray tube 42 onto the surface of the rotating heated dryer cylinder 30 in the form of a spray. For example, the interface control mixture 40 may include a mixture of polyvinyl alcohol, sorbitol and Hercules M1336 polyglycol, added with less than 5% solids by weight, between 50 and Doses between 75 mg/m2 in aqueous solution. The amounts of adhesion compound and release agent must be balanced to adhere the wet web 10 so that it does not rise into the hood and allow the dry web 36 to be pulled from the dryer cylinder 30 without creping.

3-6 illustrate an air pressure device 200 for dewatering the wet paper web 10. As shown in FIG. The pneumatic device 200 generally comprises an upper gas plenum 202 combined with a lower collection device 204 in the form of a vacuum box. The wet paper web 10 moves in the macbine direction 205 between the gas plenum 202 and the vacuum box 204 as the wet paper web 10 runs sandwiched between the upper support fabric 206 and the lower support fabric 208 . The gas plenum 202 and the vacuum box 204 are operably coupled to each other such that pressurized fluid supplied to the gas plenum 202 is advanced through the wet paper web 10 and removed or exhausted through the vacuum box 204 .

Each continuous web 206 and 208 is advanced over a series of rollers (not shown) for guiding, driving and tensioning the webs 206 and 208 in a manner known in the art. The stretch of the fabric tape is set to a predetermined value, suitably from about 10 to about 60 pounds per linear inch (pli), especially from about 30 to about 50 pli, and most preferably from about 35 to about 45 pli. Fabrics that can be used to transport the wet paper web 10 through the air pressure device 200 include almost any fluid permeable fabric such as Albany International 94M, Appleton Mills 2164B or the like.

FIG. 3 shows an end view of the air pressure device 200 across the width of the wet paper web 10 , while FIG. 4 shows an inverted view of the air pressure device in the machine direction 205 . In both Figures 3 and 4, several components of the gas plenum 202 are shown in a raised or retracted position relative to the wet paper web 10 and the vacuum box 204. In the retracted position, an effective seal against pressurized fluid is not possible. For the purposes of the present invention, the "retracted position" of air pressure device 200 means that components of air plenum 202 do not impinge on wet paper web 10 and support fabric belts 206 and 208 .

The illustrated gas plenum 202 and vacuum box 204 are mounted within a suitable frame structure 210 . The frame structure 210 shown includes upper and lower support plates 211 separated by a plurality of vertically oriented support bars 212 . The gas plenum 202 defines a plenum chamber 214 (FIG. 6) adapted to receive pressurized fluid through one or more suitable air chambers operably connected to a source of pressurized fluid (not shown). Tube 215 supplies. Accordingly, vacuum box 204 defines a plurality of vacuum chambers (described below in connection with FIG. Figure) is operably connected. The moisture removed from the wet paper web 10 is then separated from the air stream. The various fasteners used to mount the components of the pneumatic device 200 are shown in Figures 4, 5 and 6 but are not numbered.

5 and 6 show enlarged cross-sectional views of the pneumatic device 200 . In these Figures 5 and 6, the air pressure device 200 is shown in the operating position with the components of the air plenum 202 lowered into impinging relationship with the wet paper web 10 and support fabrics 206 and 208. The degree of impingement has been found to result in a proper seal of the pressurized fluid with minimal contact force, and thus reduced wear of the fabric belt as described in more detail below.

The gas plenum 202 includes a stationary part 220 fixedly mounted to the frame structure 210 and a sealing device 260 movably mounted relative to the frame structure 210 and the wet paper web 10 . As an alternative embodiment, the entire gas plenum 202 can be mounted movably relative to the frame structure 210 .

With particular reference to FIG. 6 , the stationary part 220 of the gas plenum 202 includes a pair of upper support means 222 spaced apart from each other and disposed below the upper support plate 211 . Upper support means 222 defines facing surfaces 224 that face each other and partially define plenum chamber 214 therebetween. The upper support device 222 also defines a bottom surface 226 facing the vacuum box 204 . In the illustrated embodiment, each bottom surface 226 defines an elongated recessed portion 228 within which an upper pneumatic loading tube 230 is fixedly mounted. The upper pneumatic loading tube 230 is suitably centrally located in the cross-machine direction and preferably extends across the entire width of the wet paper web 10.

The stationary part 220 of the gas plenum 202 also includes a pair of lower support means 240 spaced apart from each other and vertically from the upper support means 222 . The lower support device 240 defines a top surface 242 and a facing surface 244 . The top surface 242 faces directly toward the bottom surface 226 of the upper support device 222 and, as shown, defines an elongated recessed portion 246 in which a lower pneumatic loading tube 248 is fixedly mounted. The lower pneumatic loading tube 248 is suitably centrally located in the cross-machine direction and suitably extends about 50% to 100% beyond the width of the wet paper web. In the illustrated embodiment, the lateral support plate 250 is fixedly connected to the facing surface 244 of the lower support device 240 and serves to stabilize the vertical movement of the sealing device 260 .

Referring also to FIG. 7 , the seal assembly 260 includes: a pair of transverse seals called CD seals 262 ( FIGS. 5-7 ), which are spaced apart from each other; a plurality of brackets 263 connected to the CD seals 262 (FIG. 7); and a pair of longitudinal seals, referred to as MD seals 264 (5 and 7). The CD seal 262 is vertically movable relative to the stationary component 220 . An optional but desirable bracket 263 is fixedly attached to the CD seal 262 to provide structural support so that it can move vertically with the CD seal 262 . Along the longitudinal direction 205 , MD seals 264 are arranged between the upper bearings 222 and between the CD seals 262 . As described in detail below, portions of the MD seal 264 are vertically movable relative to the stationary component 220 . In the transverse direction, the MD seals 264 are disposed near the edges of the wet paper web 10 . In one particular embodiment, the MD seal 264 is movable in the cross direction in order to accommodate possible variations in wet web width.

The illustrated CD seal 262 includes: an upstanding main wall portion 266; a transverse flange 268 extending outwardly from a top 270 of the wall portion, and a sealing tab 272 mounted on an opposing bottom 274 of the wall portion 266 (FIG. 6) . Thus, the outwardly projecting flanges 268 form opposing upper and lower control surfaces 276 and 278 that are substantially perpendicular to the direction of movement of the sealing device 260 . Wall portion 266 and flange 268 may comprise separate components as shown or one single component.

As noted above, the components of the sealing device 260 are vertically movable between a retracted position shown in FIGS. 3 and 4 and an operative position shown in FIGS. 5 and 6 . In particular, wall portion 266 of CD seal 262 is disposed within position control plate 250 and is slidable relative thereto. The amount of vertical movement is determined by the ability of the lateral flange 268 to move between the bottom surface 226 of the upper support device 222 and the top surface 242 of the lower support device 240 .

The vertical position of the transverse flange 268 and the vertical position of the CD seal 262 are controlled by opening the pneumatic loading tubes 230 and 248 . Loading tubes 230 and 248 are operably connected to a pneumatic source and control system (not shown) of the pneumatic device. Activation of the upper loading tube 230 can generate a downward force on the upper control surface 276 of the CD seal 262, causing the flange 268 to move downward until it contacts the top surface 242 of the lower support device 240, or when the lower loading tube 248 or under the upward force produced by the tension of the fabric belt to stop the movement. Retraction of the CD seal 262 can be accomplished by activating the lower load tube 248 and deactivating the upper load tube 230 . In this case, the lower loading tube 248 presses upwardly onto the lower control surface 278 to move the flange 268 toward the bottom surface of the upper support 222 . Of course, the upper and lower load tubes 230 and 248 could be operated at different pressures to move the CD seal 262 . Additional means for controlling the vertical movement of the CD seal 262 may include other forms and connections such as air cylinders, hydraulic cylinders, bolts, jacks, mechanical linkages, or other suitable means. Suitable loading tubes 230 and 248 are available from Seal Master Corporation of Kent, Ohio.

As shown in FIG. 6 , a pair of bridge plates 279 span the gap between upper bearing 222 and CD seal 262 to prevent pressurized fluid from escaping. As such, the bridge plate 279 defines a portion of the plenum chamber 214 . The bridge plate 279 can be fixedly mounted on the facing surface 224 of the upper support 222 and can slide relative to the inner surface of the CD seal, and vice versa. The bridge plates 279 may be made of a fluid permeable semi-rigid low friction material such as LEXAN, sheet metal or the like.

The function of sealing sheet 272 in combination with other features of air pressure device 200 is to minimize the escape of pressurized fluid between air plenum 202 and wet paper web 10 in the machine direction. Additionally, the sealing tab 272 is preferably shaped in such a way as to reduce the amount of wear on the fabric. In particular embodiments, sealing sheet 272 is made of a resilient plastic compound, ceramic, coated metal substrate, or the like.

Referring particularly to FIGS. 5 and 7 , the MD seals 264 are spaced from one another and adapted to prevent loss of pressurized fluid along the sides of the pneumatic device 200 . 5 and 7 each show an MD seal 264 disposed near the edge of the wet paper web 10 in the transverse direction. As shown, each MD seal 264 includes: a transverse support 280; an end frame band 282, which is operatively connected to the transverse support 280; The deckle belt 282 moves relative to the cross support 280 . The transverse supports 280 are generally disposed near the sides of the wet paper web 10 and are generally located between the CD seals 262 . As shown, each transverse support 280 defines a downwardly directed channel 281 (FIG. 7) into which an end frame strip 282 is mounted. Additionally, each transverse support 280 defines an annular aperture 283 within which a driver 284 is mounted.

The end carton belt 282 is movable relative to the cross support 280 due to the action of the pneumatic cylinder drive 284 . A coupling 285 ( FIG. 5 ) couples the end frame belt 282 to the output shaft of the air cylinder drive 284 . Couplings 285 may include one or more inverted T-bars so that end frame strip 282 may slide within channel 281, for example for replacement.

As shown in FIG. 7, the transverse supports 280 and end frame strips 282 define slots to accommodate a fluid impermeable sealing strip 286, such as an O-ring material or the like. Sealing strip 286 helps to seal plenum chamber 214 of pneumatic device 200 from leaks. The slot in which the sealing strip 286 is located preferably widens at the interface between the cross support member 280 and the end frame strip 282 to accommodate relative movement between these components.

A bridge plate 287 ( FIG. 5 ) is disposed between the MD seal 264 and the upper support plate 211 and is fixedly mounted on the upper support plate 211 . A lateral portion of the plenum chamber 214 ( FIG. 6 ) is defined by a bridge plate 287 . A seal, such as a fluid impermeable gasket material, is preferably disposed between the bridge plate 287 and the MD seal 264 to allow relative movement therebetween and to prevent loss of pressurized fluid.

Regardless of the vertical position of the CD seal 262 , the drive 284 suitably provides controlled loading and unloading of the end carton belt 282 against the upper support fabric belt 206 . The load can be precisely controlled to meet the necessary sealing force. The end carton belt 282 can be retracted when it is not necessary to eliminate all end carton and fabric wear. Suitable drivers are available from Bimba Corporation. Alternatively, springs (not shown) may be used to hold the end carton bands 282 against the upper support fabric band 206, although the ability to control the position of the end carton bands 282 may be sacrificed.

Referring to FIG. 5, each end carton strip 282 has: a top surface or edge 290 disposed adjacent to the coupling member 285; an opposite bottom surface or edge 292, which is arranged to contact the fabric strip 206 in use; and A side surface or edge 294 is immediately adjacent to the CD seal 262 . The bottom surface 292 is suitably shaped to match the curvature of the vacuum box 204 . Where CD seal 262 impinges fabric strips 206 and 208, bottom surface 292 is preferably shaped to conform to the curvature of the impingement fabric strips. As such, the bottom surface 292 has a central portion 296 surrounded laterally in the machine direction by spaced-apart end portions 298. The shape of the center portion 296 generally conforms to the shape of the vacuum box, while the shape of the end portions 298 generally accommodates deflection of the fabric straps 206 and 208 caused by the CD seal 262 . To prevent the protruding ends 298 from fraying, the end carton strips 282 are preferably retracted before the CD seal 262 is retracted. Ending carton strips 282 are preferably made of a gas impermeable material which minimizes abrasion of the fabric strips. Specific materials suitable for end carton tape 282 include polyethylene, nylon or the like.

The MD seal 264 is preferably laterally movable such that it is preferably slidably disposed against the CD seal 262 . In the illustrated embodiment, movement of the MD seal 264 in the transverse direction is controlled by a lead screw or bolt 305 held in place by a bracket 306 (FIG. 7). Lead screw 305 passes through a threaded hole in cross support 280, rotation of the lead screw moves MD seal 264 along the shaft. Additional means for moving the MD seal in the lateral direction, such as pneumatic means or similar, may also be used. In an alternative embodiment, the MD seal 264 is fixedly mounted on the CD seal 262 so that the entire seal assembly 260 is raised and lowered together (not shown). In another alternative embodiment, the cross support 280 is fixedly mounted on the CD seal 262, and the end carton strip 282 is adapted to move independently of the CD seal 262 (not shown).

The vacuum box 204 includes a vacuum box cover 300 having a top surface 302 over which the lower support fabric belt 208 travels. The vacuum box lid 300 and seal 260 are preferably slightly curved to facilitate web control. The illustrated vacuum box cover 300 is formed like this: a first outer sealing slide rail 311, a first sealing vacuum zone 312, a first inner sealing slide rail 313, and three inner sliding rails 315 are arranged along the longitudinal direction 205 from the front edge to the rear edge. , 317 and 319 are a series of four high vacuum areas 314, 316, 318 and 320, a second inner sealing slide 321, a second sealing vacuum area 322, and a second outer sealing slide 323 (FIG. 6). Each of these seal slides 315, 317 and 319 and vacuum zones 314, 316, 318 and 320 preferably extend across the full width of the web in the transverse direction. Each slide rail 315, 317 and 319 includes a top surface preferably made of a ceramic material so as to seat against the lower support fabric 208 without causing significant fabric wear. Suitable vacuum box covers and slides can be made of plastic, nylon, coated steel or the like and are available from JWI Corporation or IBS Corporation.

The four high vacuum regions 314, 316, 318, and 320 are channels within the lid 300 that are operatively connected to one or more vacuum sources (not shown) to draw to relatively high vacuum levels. For example, high vacuum regions 314, 316, 318, and 320 may operate at a vacuum of 0 to about 25 inches of mercury, and more particularly, a vacuum of about 10 to about 25 inches of mercury. As an alternative to the passages shown, the cover 300 may define holes or other shaped openings (not shown) which are connected to a vacuum source to create pressurized fluid flow through the web. In one embodiment, the high vacuum zones 314, 316, 318, and 320 include slots each measuring 0.375 inches in the machine direction and spanning the full width of the wet paper web extend. The residence time of exposure to the pressurized fluid stream at any given point on the web, in the illustrated embodiment the time over the slots 314, 316, 318 and 320, is suitably about 10 milliseconds or less , especially about 7.5 milliseconds or less, more particularly about 5 milliseconds or less, such as about 3 milliseconds or less, even about 1 millisecond or less. The number and width of the high pressure vacuum slots 314, 316, 318 and 320 and the speed of the machine determine the dwell time. The selected residence time depends on the type of fibers contained in the wet web and the amount of dewatering required.

First and second sealed vacuum regions 312 and 322 may be employed to minimize loss of pressurized fluid from pneumatic device 200 . Sealed vacuum zones 312 and 322 are passages within lid 300 that can be operatively connected to one or more vacuum sources (not shown), as compared to the four high vacuum zones 314, 316, 318 and 320, which Ideal for pumping down to a relatively low vacuum. In particular, the ideal vacuum level for the sealed vacuum zone is 0 to about 100 inches of water column vacuum.

Pneumatic device 200 is preferably constructed such that CD seal 262 is disposed within sealed vacuum regions 312 and 322 . Specifically, the seal piece 272 of the CD seal 262 at the front side of the air pressure device 200 is arranged longitudinally between the first outer seal slide rail 311 and the first inner seal slide rail 313 , particularly at the center therebetween. The rear sealing sheet 272 of the CD sealing member 262 is similarly disposed between the second inner sealing rail 321 and the second outer sealing rail 323 along the longitudinal direction, especially in the center between them. As a result, sealing device 260 may be lowered so that CD seal 262 deviates from the normal trajectory of wet paper web 10 and fabric belts 206 and 208 toward vacuum box 204, shown on a somewhat enlarged scale in FIG. 6 for illustration.

The function of the sealed vacuum zones 312 and 322 is to minimize the loss of pressurized fluid from the air pressure device 200 across the width of the wet paper web 10 . The vacuum within sealed vacuum regions 312 and 322 draws pressurized fluid from gas plenum 202 and ambient gas from outside pneumatic device 200 . As a result, gas flow is introduced into sealed vacuum regions 312 and 322 from outside the pneumatic device 200, rather than pressurized fluid leaking in the opposite direction. Due to the relative difference in vacuum between high vacuum zones 314, 316, 318 and 320 and sealed vacuum zones 312 and 322, the vast majority of the pressurized fluid from gas plenum 202 flows into high vacuum zones 314, 316, 318 and 320, Instead of sealing the vacuum regions 312 and 322.

In another alternative embodiment shown in part in FIG. 8, either or both of sealed vacuum regions 312 and 322 are not evacuated. Instead, a deformable sealing deckle band 330 is disposed within sealing areas 312 and 322 (only 322 is shown) to prevent leakage of pressurized fluid in the longitudinal direction. In this case, the air pressure device 200 is formed in the longitudinal direction by the sealing sheet 272 which hits the fabric belts 206 and 208 and the wet paper web 10, and the fabric belts 206 and 208 and the wet paper web 10 which are arranged in close proximity to or in contact with the deformable sealing deckle belt 330. The paper web 10 is sealed. The configuration in which the CD seal 262 hits the fabric belts 206 and 208 and the wet paper web 10 and the CD seal 262 is positioned on the opposite side of the fabric belts 206 and 208 and the wet paper web 10 by the deformable sealing deckle 330 has been It was found that a particularly effective gas plenum seal could be formed.

The deformable sealed deckle band 330 preferably extends across the full width of the wet paper web 10 . To seal the front end or the rear end of the pneumatic device 200 or both. The sealed vacuum zones 312 and 322 can be disconnected from the vacuum source when the deformable sealed deckle belt 330 extends across the full width of the web. Where a full-width deformable sealed deckle belt 330 is employed at the rear end of the air press 200, a vacuum or blow box may be employed downstream of the air press 200 to deflect the web as the fabric belts 206 and 208 separate. 10 is held on one of the fabric straps 206 or 208.

The deformable sealed paper frame belt 330 preferably comprises two materials: one material is a material that wears preferentially with respect to the fabric belt 208, which means that when the fabric belt 208 is used with this material, the material wears while the fabric belt No appreciable wear would occur, the other material being resilient and deflecting as it hits the fabric strap 208 . In either case, the deformable sealed carpenter band 330 is preferably gas impermeable, and preferably comprises a material having a high dead volume, such as closed cell foam or the like. In one particular embodiment, the deformable sealed deckle belt comprises closed cell foam measuring 0.25 inches in thickness. Optimally, the deformable sealing deckle belt 330 wears itself to match the path of the fabric belts 206 and 208 . The deformable sealed deckle belt 330 is preferably accompanied by backing plates 332 for structural support, such as aluminum rods.

In embodiments where a full width sealed deckle belt is not used, some sort of sealing arrangement is required in the cross-web direction. The deformable sealing deckle belt 330 described above or other suitable means known in the art may be used to impede the flow of pressurized fluid laterally through the fabric belts 206 and 208 to the outside of the wet paper web 10 .

To produce an effective seal across the web, it has been found that the extent to which the CD seal 262 impinges on the upper support fabric 206 evenly across the width of the wet web 10 is an important factor. It has also been found that the necessary degree of collision is the maximum tension of the upper and lower support fabrics 206 and 208, the pressure differential across the web and in this case between the plenum chamber 214 and the sealed vacuum zones 312 and 322, A function of the gap between the CD seal 262 and the vacuum box lid 300 .

Referring also to the schematic diagram of the rear seal portion of the pneumatic device 200 shown in FIG. 9, the minimum ideal impact amount for the CD seal 262 to impact into the upper support fabric band 206, i.e. h(min), was found to be represented by the following equation: $h\left(\min \right)=\frac{T}{W}(\cosh \left(\frac{\mathrm{Wd}}{T}\right)-1);$

Where T is the measured tension of the fabric tape in lbs/in;

W is the differential pressure across the web measured in psi; and

D is the clearance in the longitudinal direction measured in inches.

Figure 9 shows the amount of offset of the upper support fabric 206 by the rear CD seal 262, indicated by arrow "h". The maximum tension of the upper and lower support fabric straps 206 and 208 is indicated by arrow "T" as measured by a standard tensiometer supplied by Huyck Corporation or by other suitable means. The gap between the seal plate 272 of the CD seal 262 and the second inner seal slide 321 as measured along the longitudinal direction 205 is indicated by arrow "d". The gap "d" used to determine the degree of collision is the gap on the higher differential pressure side of the seal plate 272, i.e. towards the gap on the plenum chamber 214, because the differential pressure on this side is between the fabric belt 206 and 208 and the position of the web 10 have the greatest impact. Preferably, the gap between the sealing sheet 272 and the second outer slide rail 323 is almost the same as or even smaller than the gap "d".

Adjusting the vertical position of the CD seal 262 to the minimum impact as described above is a determining factor in the effectiveness of the CD seal. The loading force exerted on the sealing device 260 plays a minor role in determining the effectiveness of the seal and must only be adjusted to the amount required to maintain the necessary degree of impact. Of course, the amount of fabric wear will adversely affect the commercial use of the pneumatic device 200 . In order to achieve an effective seal without substantial wear of the fabric, the degree of collision is preferably equal to or slightly greater than the minimum degree of collision mentioned above. In order to minimize variations in the degree of wear of the fabric across its width, the force applied to the fabric is preferably kept constant in the transverse direction. This can be achieved by controlled and uniform loading of the CD seal 262 , or a controlled position of the CD seal 262 and a uniform geometry of the impact of the CD seal 262 .

In use, the control system lowers the seal 260 of the gas plenum 202 to the working position. First, the CD seal 262 is lowered so that the seal sheet 272 hits the upper support fabric 206 to the extent described above. In particular, the pressure in the upper and lower loading tubes 230 and 248 is regulated so that the CD seal 262 moves downward until it is stopped by contact with the lower support 240 by the transverse flange 268, or until it is stopped by the fabric strap. until the tension is balanced. Second, the end carton strip 282 of the MD seal 264 is lowered into contact with or immediately adjacent to the upper support fabric strip 206 . As a result, both the gas plenum 202 and the vacuum box 204 are sealed against the wet web to prevent pressurized fluid from escaping.

Then, the pneumatic device 200 is activated so that the pressurized fluid fills the gas plenum 202 and creates an air flow through the web 10 . In the embodiment shown in FIG. 6, high and low vacuums are applied to high vacuum zones 314, 316, 318 and 320 and sealed vacuum zones 312 and 322 to facilitate gas flow, seal and remove moisture. In the embodiment of FIG. 8 , pressurized fluid flows from gas plenum 202 to high vacuum regions 314 , 316 , 318 , and 320 , and deformable sealing deckle band 330 seals pneumatic device 200 in the transverse direction. The resulting pressure differential across the wet web 10 and airflow through the web 10 effectively dewaters the web 10.

A number of structural and operational features of the pneumatic device 200 help to allow little escape of the pressurized fluid, combined with less wear of the fabric strap. Initially, the air pressure device 200 uses a CD seal 262 that impinges the fabric strips 206 and 208 and the wet paper web 10 . The degree of impact is determined to optimize the effectiveness of the CD seal. In one embodiment, the air pressure device 200 utilizes sealed vacuum zones 312 and 322 to generate ambient air that flows across the width of the wet paper web 10 into the air pressure device 200 . In another embodiment, deformable seal 330 is disposed within sealed vacuum regions 312 and 322 opposite CD seal 262 . In either case, to minimize the need for precise alignment of the mating surfaces between the gas plenum 202 and the vacuum box 204 , the CD seal 262 is preferably positioned at least partially within the passageway of the vacuum box lid 300 . Furthermore, the sealing device 260 can be loaded against a stationary part, such as the lower support device 240 connected to the frame structure 210 .

As a result, the loading force of the pneumatic device 200 is independent of the pressurized fluid pressure within the gas plenum 202 . Webbing wear is minimized due to the use of low webbing wear materials and the lubrication system. Suitable lubricating systems may include chemical lubricants such as emulsified oils, release agents or other similar chemicals, or water. Typical lubricant application methods include spraying diluted lubricant in a uniform pattern in a transverse direction, hydraulically or air atomized solutions, blanket wiping of more concentrated solutions, or other spray system applications known method.

Observations indicate that the ability of the plenum to operate at higher pressures depends on the ability to prevent leaks. Leaks can be detected by excessive airflow relative to previous or anticipated operations, increased operating noise, dispersion of moisture, and in extreme cases regular or irregular defects within the wet web including holes and threads The presence. Repairs can be made to avoid leaks by calibrating or adjusting the sealing components of the pneumatic device.

In the pneumatic device 200, uniform airflow in the cross direction desirably provides uniform dewatering of the web 10. Flow uniformity in the transverse direction can be improved using mechanisms such as tapered ducts on the pressure and vacuum sides, the shape of which can be designed using computational fluid dynamic models. Because the web basis weight and moisture content cannot be uniform in the cross direction, it is better to use additional devices to obtain a uniform air flow in the cross direction, for example: separate control areas with buffers on the pressure or vacuum side, so that according to the paper properties To vary the air flow; a baffle to achieve a significant pressure drop in the air flow ahead of the wet web; or other directing means. Additional alternative methods of controlling CD dehydration uniformity may also include external devices such as: regionally controlled steam injectors, eg Dublin. A Devronizer steam injector or similar device from Honeywell-Measurex Systems of Ohio.

The process of other embodiments of the present invention can be carried out on the apparatus shown in Figure 10 as a retrofit of a typical crescent former tissue machine. A primary wet paper web 410 formed into a papermaking fiber slurry is deposited from the headbox 412 between the circulating loop of the first fabric belt 414 and the circulating loop of the second fabric belt 424 . The second fabric belt 424 typically replaces the felt in a standard crescent former tissue machine. The consistency and flow rate of the pulp determine the basis weight of the dry web, which desirably ranges from about 5 to about 80 grams per square meter (gsm), more preferably from about 8 to about 40 gsm. At least one of the fabric strips 414 and 424 may be a forming fabric strip, preferably the first fabric strip 414 . Additionally, at least one of the fabric strips 414 and 424 may be a molded fabric strip, preferably the second fabric strip 424 .

While the primary wet paper web 410 is conveyed between the first fabric belt 414 and the second fabric belt 424, due to the tension on the first fabric belt 414 and the centrifugal force generated when it passes around the forming roll 452, the primary wet paper web 410 The wet paper web 410 is partially dewatered. Once the partial dewatering step is complete, the wet paper web 410 is transferred to or held on the second fabric belt 424 with or without the use of vacuum slides 450 .

In order to realize the high-speed operation of the present invention, the traditional paper towel dehydration method before the heated drying cylinder 430 may not be able to remove moisture sufficiently, so an additional dehydration device is required. In the illustrated embodiment, air pressure device 416 is used to dewater web 410 non-pressively. The air pressure device 416 is shown comprising: a pressurized air gas plenum 418 device disposed above the wet paper web 410; a fluid collection device 420, shown in the form of a vacuum box, disposed below a support fabric belt 422 and in contact with A gas plenum 418 of pressurized air is in operative communication with the second fabric strip 424 . (In a further alternative embodiment, fluid collection device 20 may be positioned adjacent to second fabric 424 in operative communication with pressurized air gas plenum 418 and support fabric 422). While passing through air pressure device 416 , wet paper web 410 is sandwiched between second fabric 424 and support fabric 422 so as to seal against wet paper web 410 without damaging wet paper web 410 .

The air pressure device 416 provides a substantial rate of moisture release, enabling the web to be dry to a degree greater than 30% prior to attachment to a dryer cylinder 430 such as a Yankee dryer, preferably without the need for substantial dewatering. Several embodiments of pneumatic device 416 are described in more detail below. Other suitable embodiments are disclosed in U.S. Patent Application No. 08/647,4508, filed May 14, 1996 by M.A. Hermans et al., entitled "Method and Apparatus in Making Soft Paper ", this patent document is hereby incorporated by reference.

After the air pressure device 416, the wet paper web 410 is further run with the second fabric 424 and the support fabric 422, with or without the help of the vacuum transfer skid 426 at the transfer station, until the transfer back reaches the preferably A second fabric strip 424 of textured fabric strip.

The second fabric 424 may comprise a three-dimensional throughdrying fabric such as that disclosed in U.S. Patent 5,429,686 to K.F. Chiu et al., issued July 4, 1995, which is incorporated herein by reference. , or the second fabric strip 424 may comprise other woven, textured fabric or non-woven fabric strips. The second fabric 424 may be treated with a fabric release agent such as silicon or a mixture of hydrocarbons to subsequently separate the wet paper web 410 from the second fabric 424 . A fabric release agent may be sprayed on the second fabric 424 prior to grabbing the web. Once sprayed on the second fabric belt 424, although the wet paper web 410 can be fully molded at least due to the vacuum force at the transfer skid 426 during gripping, the wet paper web 410 can also be molded by using vacuum pressure. Or light pressure (not shown) is further molded against the second fabric strip 424 .

The wet paper web 410 on the second fabric belt 424 is then pressed against a heated dryer cylinder 430 by press rolls 432 . The drying cylinder 430 is equipped with a steam hood or Yankee dryer hood 434 . The hood 434 typically utilizes a hood at a temperature of about 300°F or higher, particularly about 400°F or higher, more particularly about 500°F or higher, and most particularly about 700°F or higher. The jet of heated air is directed from the nozzle or other flow-through device directly at the tissue web 410 so that, in the hood 434, the gas jet has a maximum velocity or a partial average velocity of one of the following levels: about 10 m/s (m/s) or more, about 50 m/s or more, about 100 m/s or more, about 250 m/s or more.

The wet web when attached to the heated dryer cylinder 430 suitably has a fiber consistency of about 30% or greater, particularly about 35% or greater, such as between about 35% and about 50%, and more preferably about 38% % or greater fiber consistency. When removed from the heated dryer cylinder 430, the dryness of the wet paper web 410 increases to about 60% or greater, particularly about 70% or greater, more particularly about 80% or greater, more particularly 90% % or greater, most particularly between about 90% and about 98%. The wet paper web 410 may be partially dried on heated dryer cylinder 430 and wet creped at about 40% to about 80% consistency, and then dried (post-dried) to about 95% or greater consistency. Non-traditional hood and impingement systems may be used in place of or in addition to the Yankee dryer hood 434 to enhance the dryness of the wet paper web 410 . Additional heated dryers 430 or other drying equipment, particularly non-squeeze dryers, may be used after the first heated dryers 430 . Suitable post-drying equipment includes one or more heated drying cylinders 430, such as Yankee and empty can dryers, through dryers, or any other commercially effective drying equipment. As an alternative embodiment, if the second fabric 424 is a molded fabric, then the molded wet paper web 410 can be completely dried and dry-creped on the heated dryer 430 . The degree of dryness on the heated dryer 430 depends on factors such as: the speed of the wet paper web 410, the size of the heated dryer 430, the amount of moisture in the wet paper web 410, and the like.

The resulting dry fabric 436 is drawn or passed from the heated dryer cylinder 430 , for example by a creping blade 428 , and it is then wound onto rolls 438 . The illustrated interface control mixture 440 is sprayed in the form of a spray from spray tubes 442 onto the surface of the rotating heated dryer cylinder 430 before the wet paper web 410 comes into contact with the heated dryer cylinder 430 surface. As an alternative to spraying directly on the surface of the rotating heated dryer 430, the interface control mixture 440 can be applied directly to the wet paper web 410 or the heated dryer surface 430 by gravure printing, or can be incorporated into the wet end of the paper machine in an aqueous fiber slurry suspension. While on the surface of the heated dryer 430, the wet web 410 may also be treated chemically, such as by printing or spraying a solution directly on the dry web 410, including the addition of solvents to facilitate separation from the heated dryer 430 surface.

The interface control mixture 440 may include conventional creping adhesives and/or dryer release agents for wet pressing and creping operations. An interface controlling compound 440 of the type described below, filed on the same day as this application by F.G. US Patent Application entitled "Method of Producing Low Density Elastic Paper Web" is incorporated herein by reference.

Fig. 11 shows another alternative embodiment, in which the primary wet paper web 510 formed as papermaking fiber slurry is deposited from the headbox 512 to the circulation loop of the first fabric belt 514 and the circulation of the second fabric belt 524. between loops. The second fabric belt 524 typically replaces the felt in a standard crescent former tissue machine. At least one of the fabric strips 514 and 524 may be a forming fabric strip, preferably the first fabric strip 514 . Additionally, at least one of the fabric strips 514 and 524 may be a molded fabric strip, preferably the second fabric strip 524 .

While the primary wet paper web 510 is conveyed between the first fabric belt 514 and the second fabric belt 524, due to the tension on the first fabric belt 514 and the centrifugal force generated when it passes around the forming roll 552, the primary wet paper web 510 The wet paper web 510 is partially dewatered. Once the partial dewatering step is complete, while it is between the first fabric belt 514 and the second fabric belt 524, it can optionally be further dewatered by a vacuum box 546 or other suitable means, with or without the use of a vacuum slide 550. , and the wet paper web 510 is transferred to or held on the second fabric belt 524 .

The air pressure device 516 is used to dewater the wet paper web 510 non-pressively while the wet paper web 510 is sandwiched between the second fabric 524 and the support fabric 522 . The air pressure device 516 is shown comprising means of a pressurized air gas plenum 518 arranged in operative communication with a vacuum box 520 . As it passes through the air pressure device 516 , the wet paper web 510 is sandwiched between the second fabric 524 and the support fabric 522 which is located between the wet paper web 510 and the vacuum box 520 . (In a further alternative embodiment, the second fabric belt 524 may be disposed between the wet paper web 510 and the vacuum box 520).

The wet paper web 510 is then conveyed further back to the second fabric belt 524 with or without the aid of the vacuum slide 526 . The running rollers 555 of the support fabric 522 are positioned to change the direction of the second fabric 524, the support fabric 522 and the wet paper web 510 so that the wet paper web 410 is conveyed to the Yankee dryer or other heated dryer cylinder 530 Before, it was less likely to separate from the suction roller 532 . The rollers 555 reduce the unsupported paper wrap angle α, thereby minimizing the chance of the wet paper web 510 separating from the second fabric belt 524 before it is transferred to the heated dryer cylinder 530 .

Afterwards, the wet paper web 510 on the second fabric belt 524 is pressed against the drying cylinder 530 by means of a pressure roller 532. The wet paper web 510 on the second fabric 524 is pressed against the dryer cylinder 530 by the press roll 532 preferably in such a way that the unsupported paper wrap angle α on the press roll 532 is minimized. The unsupported sheet wrap angle α can range in angle from 0 to about 90 degrees, from 0 to about 45 degrees, from 0 to about 10 degrees. In addition, the smaller unsupported sheet wrap angle a reduces the size of the required vacuum zone, thereby reducing the energy required to create a vacuum within the press rolls. When the wet paper web 510 is conveyed onto the drying cylinder 530, the unsupported paper wrap angle α is defined as the portion of the circumference of the press roll 532 wrapped by the wet paper web 510 (expressed in degrees) from the wet paper web 510 on the press. The first point of contact on roll 532 to the last point of contact of wet paper web 510 on press roll 532 .

The heated drying cylinder 530 is equipped with a steam hood or Yankee dryer hood 534 . The resulting dry web 536 is drawn or passed from the dryer cylinder 530 and removed without creping before being wound onto rolls 538 . The angle at which the dry web 536 is drawn from the surface of the heated dryer 530 is suitably from about 80 degrees to about 100 degrees, as measured along a tangent to the surface of the heated dryer 530 at the point of separation, although it may vary depending on the operating speed. rather different.

The interface control mixture 540 is sprayed from a spray boom 542 onto the surface of the rotating heated dryer cylinder 530 in the form of a spray. For example, the interface control mixture 540 may include a mixture of polyvinyl alcohol, sorbitol, and Hercules M1336 polyglycol added with less than 5% solids by weight at 50 and 75 mg/sq. The dose between m in aqueous solution. The amount of adhesion compound and release agent must be balanced to adhere the wet web 510 so that it does not rise into the hood, while allowing the dry web 536 to be pulled from the dryer cylinder 530 without creping.

Another alternative embodiment is shown in FIG. 12 . This embodiment is similar to the embodiment of FIG. 11 except that the first fabric strip 614 is extended to serve as the support fabric 522 shown in FIG. 11 . This offers the potential for reductions in capital and operating costs due to the reduced number of fabric strips required to improve the process. In the embodiment shown in FIG. 12, a primary wet paper web 610 formed as a papermaking fiber slurry is deposited from a headbox 612 between the circulating loop of a first fabric belt 614 and the circulating loop of a second fabric belt 624. . The second fabric belt 624 typically replaces the felt in a standard crescent former tissue machine. At least one of the fabric strips 614 and 624 may be a forming fabric strip, preferably the first fabric strip 614 . Additionally, at least one of the fabric strips 614 and 624 may be a molded fabric strip, preferably the second fabric strip 624 .

When the primary wet paper web 610 is between the first fabric belt 614 and the second fabric belt 624, due to the tension on the first fabric belt 614 and the centrifugal force generated when it passes around the forming roller 652, the primary wet paper web The web 610 is partially dewatered and further dewatered by an optional vacuum box 646 or other suitable means. The air pressure device 616 is used to dewater the wet paper web 610 non-pressively while the wet paper web 610 is sandwiched between the first fabric belt 614 and the second fabric belt 624 . The illustrated air pressure device 616 includes a device for pressurizing an air gas plenum 618 arranged in operative communication with a vacuum box 620 . As it passes through the air pressure device 616 , the wet paper web 610 is sandwiched between the second fabric 624 and the support fabric 622 which is located between the wet paper web 610 and the vacuum box 620 . (In a further alternative embodiment, the second fabric belt 624 may be disposed between the wet paper web 610 and the vacuum box 620).

The wet paper web 610 is then conveyed further back to the second fabric belt 624 with or without the aid of the vacuum slide 626 . The wet paper web 610 on the second fabric belt 624 is pressed against the drying cylinder 630 by means of a pressing roller 632 . The heated drying cylinder 630 is equipped with a steam hood or Yankee dryer hood 634 . The resulting dry web 636 is drawn or passed from the dryer cylinder 630 and removed without creping before being wound onto rolls 638 . The angle at which the dry web 636 is drawn from the surface of the heated dryer 630 is suitably from about 80 degrees to about 100 degrees, as measured along a tangent to the surface of the heated dryer 630 at the point of separation, although it may vary depending on the operating speed. rather different.

Interface control mixture 640 is sprayed from spray tube 642 onto the surface of rotating heated dryer cylinder 630 in the form of a spray. For example, the interface control mixture 640 may include a mixture of polyvinyl alcohol, sorbitol, and Hercules M1336 polyglycol added with less than 5% solids by weight at 50 and 75 mg/sq. The dose between m in aqueous solution. The amount of adhesion compound and release agent must be balanced to adhere the wet web 610 so that it does not rise into the hood 634, but allow the dry web 636 to be pulled from the dryer cylinder 630 without creping.

As mentioned above, an air pressure device 200 for dewatering a wet paper web 410, 510 or 610 is illustrated in FIGS. 3-6. The sealing means that may be used on the apparatus shown in Figures 10, 11 and 12 is the same as the sealing means 260 described above in Figures 7, 8 and 9 .

【Example】

The following examples help to understand the present invention in more detail. Specific contents, ratios, components and parameters are exemplary and not intended to specifically limit the scope of the present invention.

Example 1

Twelve inch wide towels made from a fiber slurry comprising bleached kraft northern softwood fibers and bleached kraft eucalyptus were manufactured on an experimental towel machine with a 22 inch wide fabric belt Unrefined 50:50 fiber mixture of kraft eucalyptus fibers. The tissue was formed by depositing the slurry from each layer using a layered, three layer headbox to form a blended paper having a nominal basis weight of 19 gsm. The headbox sprays the slurry between two Lindsay Wire 2164B forming fabric belts in a twin wire forming section with a suction roll former. To control strength, Parez 631NC at 6% solids was added to the stock at a rate of 1000 ml/min prior to the forming process.

While depositing at 1000 feet per minute (fpm) between two forming fabric belts, the primary wet paper web is conveyed on four vacuum boxes located near 11, 14, 13 and 19 Working under a vacuum pressure of inches Hg vacuum. Also, the primary wet paper web contained between the two forming fabric belts passes through air pressure means comprising a gas plenum and a collection box operably interconnected and integrally sealed from each other. The gas plenum pressurizes air to 15 psi at about 150 Fahrenheit, while the collection box operates at a vacuum of about 11 inches of mercury. The wet web was exposed to a final differential pressure of approximately 41.5 inches of Hg, and was exposed to 68 SCFM/ Airflow in square inches. The wet web had a consistency of about 30% just before the air unit and about 39% consistency when leaving the air unit.

The dewatered wet paper web was then conveyed using a vacuum pick-up sled under a vacuum of about 10 inches Hg on a three-dimensional fabric belt of Lindsay Wire T-216-3 TAD fabric Work. A silica latex in water was sprayed onto the paper side of the T-216-3 fabric just prior to transfer from the forming fabric for eventual transfer to the Yankee dryer. The silicone resin was applied at a flow rate of 400 ml/min at 1.0% solids. The TAD fabric belt was then pressed against the face of the Yankee Dryer using conventional press rolls operating at a maximum press pressure of 350 pli. The webbing was wrapped about 39 inches over the face of the Yankee dryer by transfer rolls that could be unloaded or moved slightly away from the Yankee dryer.

The wet paper web is adhered to the Yankee dryer using an adhesive mixture made of polyvinyl alcohol AIRVOL 523 manufactured by Air Products and Chemical and sorbitol added to water at about 0.4 The water was added through four #6501 nozzles manufactured by Spraying Systems, Inc. at a gallon per minute (gpm) flow rate and approximately 40 psig operating conditions. The spray has a solids concentration of about 0.5% by weight. The dry web was creped as it came off the Yankee dryer, had a final dryness of about 92% consistency, and was wound on a core. The product is then converted into a 2-ply bathroom tissue using standard techniques. The results of Example 1 are shown in Table 1 below.

Table 1 test unit Example 1 Invention (creping) Example 2 Invention (no crepe) Example 3 (comparative example) Example 4 (comparative example) roll hardness 0.001″ 104 140 134 178 roll diameter mm 126 128 125 125 Number of sheets 253 180 280 198 Core outer diameter (core0D) mm 40 40 46 46 Paper thickness (2kPa, 8 layers) Micron 1667 2402 1288 1719 MD intensity g/3″ 1739 1911 2285 1719 MD extension % 14 13 twenty two 15 Rate CD intensity g/3″ 972 1408 718 700 GMT g/3″ 1300 1640 1281 1097 dry roll weight G 133 95 158 106 dry basis weight g/m2 19.1 18.8 20.6 20.4 Absorptive capacity G 97.4 117.2 79.0 97.0 Absorptive capacity g water)/g (fiber) 11.8 14.1 10.8 11.0

Example 2

Twelve-inch wide paper towels were made on an experimental towel machine with a 22-inch wide fabric belt from a fiber slurry comprising unrefined bleached kraft northern softwood fibers and bleached kraft eucalyptus fibers. 50:50 fiber mixture. A hybrid paper having a nominal basis weight of 19 gsm was formed by depositing the slurry from each layer using a layered, three-layer headbox. The headbox sprays the slurry between two Lindsay Wire 2164B forming fabric belts in a twin wire forming section with a suction roll former. To control the strength, Parez 631 NC at 6% solids was added to the raw material at a rate of 1000 ml/min prior to the forming process.

When deposited between two forming fabric belts and at a speed of 1000 feet per minute (fpm), the primary wet paper web is conveyed on four vacuum boxes, which are located near 11, 14, 13 and Works under vacuum pressure of 19 inches Hg vacuum. Also, the primary wet paper web, still contained between the two forming fabric belts, passes through air pressure means comprising a gas plenum and a collection box operably interconnected and integrally sealed from each other. The gas plenum pressurizes air to 15 psi at about 150 Fahrenheit, while the collection box operates at a vacuum of about 11 inches of mercury. The wet web was exposed to a final pressure differential of about 41.5 inches of Hg and was exposed to a With an airflow of 68 SCFM per square inch. The consistency of the wet paper web just before the air device was about 30%, and the consistency when leaving the air device was about 39%.

The dewatered wet paper web was then conveyed using a vacuum pick-up sled under a vacuum of about 10 inches Hg on a three-dimensional fabric belt of Lindsay Wire T-216-3 TAD fabric work, its conveying speed is 20% slower than that of forming fabric belt. A silica latex in water was sprayed onto the paper side of the T-216-3 fabric just prior to transfer from the forming fabric for eventual transfer to the Yankee dryer. The TAD fabric belt was then pressed against the face of the Yankee Dryer using conventional press rolls operating at a maximum press pressure of 350 pli. The webbing was wrapped about 39 inches over the face of the Yankee dryer by transfer rolls that could be unloaded or moved slightly away from the Yankee dryer.

The wet web was adhered to the Yankee dryer in a controlled manner using an interface control mixture comprising, in percent active solids, approximately 26% polyvinyl alcohol, 46% sorbitol and 28% Hercules (Hercules) M1336 polyglycol, these ingredients are added at a dose between 50 and 75 mg/m ² . The mixture is prepared as an aqueous solution with less than 5% solids by weight. The wet web is dried on a Yankee dryer to approximately 90% consistency, and the sheet is then "peeled" from the Yankee dryer by applying sufficient wind tension to remove the dried sheet just prior to the creping blade. The paper is then wound on the core without additional pressing. The product is then converted into a 2-ply bathroom tissue using standard techniques. The results of Example 2 are shown in Table 1 above.

Example 3 (comparative example)

The paper was formed from a blend of bleached kraft northern softwood, bleached kraft eucalyptus, and cork BCTMP fibers in a 50:40:10 blend ratio, formed using a Fourdrinier former at approximately 3500 fpm operating conditions. The resulting wet web having a basis weight of approximately 20 gsm is transferred from the forming fabric belt to a standard wet press felt (using couch rolls). The wet web was carried to a 15 foot Yankee dryer and transferred to the Yankee dryer using standard methods. The wet paper web was dried on a Yankee dryer using standard techniques, and the paper was removed from the dryer at about 95% consistency with a creping blade.

To further increase thickness, the web is conveyed via an open draw to a second Yankee dryer (which operates without the usual shields) and adhered using a latex adhesive onto the Yankee dryer. Next, the dry web is recreped and wound on a core. The product is then reconstituted into 2-ply bathroom tissue using standard techniques. The method used in this example is called the separate recreping method, and the method can be found in British figure patent documents GB 2179949B, GB2152961A, and GB 2179953B, which are hereby incorporated by reference. The results of Example 3 are shown in Table 1 above.

Example 4 (comparative example)

The wet paper web was formed from a blend of bleached kraft northern softwood and bleached kraft eucalyptus fibers in a 65:35 mix ratio. A wet paper web of layered structure was formed using a twin wire former with eucalyptus fibers on the outside (air side) of the wet paper web. Using conventional vacuum dewatering techniques, the wet paper web is dewatered to a consistency of approximately 27% and then through dried to a consistency of approximately 90% using standard techniques. The wet web was then transferred to a Yankee dryer, adhered using PVA as an adhesive, and dried to 97% consistency. The wet paper web is then rolled onto a core. The product is then reconstituted into a two-ply bathroom tissue using standard techniques. The results of Example 4 are shown in Table 1 above.

The data in Table 1 clearly demonstrate the improved sheet/roll properties that can be obtained using the present invention. In creped form (Example 1), the bathroom tissue product produced according to the present invention has a greater sheet caliper compared to the caliper that is controlled (Example 3) by specifically employing an additional re-creping step to increase controlled bulk (Example 3) , and its thickness ratio is 1667 microns to 1288 microns. Without this restrepe step, the difference in caliper would be even greater, as the recrepe step typically increases caliper by about 30% or more. From a roll performance standpoint, this additional thickness allows 27 sheets to be removed (counts from 280 to 253) while maintaining the same roll diameter. In fact, despite the reduced number of sheets, roll paper produced using the present invention was stronger for the same roll diameter (104 vs. 134, with lower numbers representing greater stiffness). Considered as a whole, the present invention allows the roll weight to be reduced from 158 grams to 133 grams (16%) while producing excellent web properties.

The improvement in roll performance is even more pronounced when considering the uncreped example (Example 2). Here, while maintaining the diameter and stiffness of the roll, the number of sheets was reduced to 180 (compared to 280 in the control case). In this case, the weight of the roll was reduced by 40%.

Additionally, the product of the present invention was compared to the creped throughdried product described in Example 4. Apparently, this product has approximately equal performance in terms of roll paper bulk, etc. In fact, the through-dried examples showed lower hardness, suggesting that the products of the present invention are even better than the through-dried products.

Example 5

The wet web was formed from a fiber blend of southern bleached kraft pine, bleached kraft northern softwood, and bleached kraft eucalyptus in a 50:30:20 mix ratio on an experimental towel machine operating at about 50 fpm. The resulting wet web having a basis weight of about 41 g/m2 was carried on a forming fabric and then transferred to a T-216-3 molding fabric. At the transfer point, the primary web passes through a pneumatic device comprising a gas plenum and a collection box operably interconnected and (integrally) sealed from each other. At this point, the wet web is dewatered from a postformed approximately 10% consistency to a 32-45% consistency. The wet web is then conveyed to a Yankee dryer where it is transferred to the Yankee dryer which adheres the wet web using polyvinyl alcohol sprayed through a standard nozzle and dries to 55 % of consistency. The wet web is then conveyed to afterdriers for final drying and winding onto a core. The resulting dry paper web is then embossed using a butterfly embossing pattern to obtain the final single ply paper towel product. The results of Example 5 are shown in Table 2 below.

Example 6

A blend of bleached kraft southern softwood and softwood BCTMP fibers in a 65:35 mix ratio was formed into a wet web using a modified long tube former (Fourdrinier styleformer) operating at a machine speed of 250 fpm. The final wet web, with a basis weight of approximately 50 grams per square meter, is transferred to a standard wet press felt and conveyed to a Yankee dryer. At the press nip, the wet web is transferred to the Yankee dryer using standard wet pressing techniques. The wet web was adhered to the dryer using polyvinyl alcohol and creped at approximately 55% consistency. The dry web is then conveyed via an open draw to a series of empty can dryers where the wet web is dried to approximately 95% consistency and wound on a core. The product is then converted into a ply of paper towels using standard techniques. The results of Example 6 are shown in Table 2 below.

Table 2 clearly shows the inherent product advantages of the present invention. Despite a 19% reduction in basis weight, paper towels produced using the present invention have superior caliper and absorbency compared to large scale wet crepe control.

Table 2 test unit Example 5 The present invention Example 4 (comparative example) roll hardness inch 0.191 0.277 roll diameter inch 5.3 5.0 Number of sheets 80 85 Core outer diameter (coreOD) mm 42 37 Paper thickness (10 inch 0.252 0.195 layer) MD intensity g/3″ 2934 2750 MD elongation % 13.2 7.8 CD intensity g/3″ 1420 1086 CD elongation % 8.1 7.3 GMT g/3″ 2041 1728 base weigh g/ ^m2 41.3 50.9 Absorptive capacity G 2.56 1.73 Absorptive capacity g(water)/g(fiber) 5.86 3.84

Additionally, the product of the present invention has a relatively high CD elongation so that it adds "toughness" to the paper towels in use. As a final product, roll paper produced using the present invention had a larger diameter (5.3 inches versus 5.0) and greater stiffness (0.191 versus 0.277). At the same time, the weight of roll paper is reduced by 19% due to the fixed paper size and number of sheets.

Example 7

A 50:50 blend of fibers of bleached kraft northern softwood and bleached kraft eucalyptus was formed into a wet web using the forming equipment and configuration described in Example 1. In this case, the machine speed is 2500fpm. The final wet web, with a basis weight of approximately 20 lbs/2880 ^ft2 , was passed through four vacuum boxes of 19.8, 19.8, 22.6 and 23.6 inches of mercury. The resulting wet paper web was then conveyed through an additional integral seal dewatering system also described in Example 1. The air pressure was set to maintain a pressure of 15 psig in the air plenum, and the consistency was measured using pre and post air pressure samples. The results of Example 7 are shown in Table 3 below.

Example 8

This time, the test of Example 7 was repeated except that the pneumatic device was reconfigured to eliminate the integral seal between the gas plenum of the pneumatic device and the associated collection box. In particular, the seal load and thus the collision of the transverse seal flaps is reduced until a leak between the plenum chamber and the collection box is evident. At this point, the pneumatic device gas plenum/collection box arrangement is set to a nominal 0.1 inch gap, although it is impossible to actually see the space between the plenum and the collection box as it is covered by fabric straps and wet The web occupies. The flow into the gas plenum is increased to the maximum flow available from the compressor and subsequent dehydrated consistency samples are taken. The results of Example 8 are shown in Table 3 below.

table 3 test unit Example 7 Example 8 (comparative example) After dehydration consistency % 34.2 32.1 pre-dehydrated consistency % 26.8 26.8 dehydrated 1b. Water/1b. Fiber 0.81 0.61

As shown in Table 3, any reduction in the overall degree of sealing results in a significant loss in the dehydration capacity of the pneumatic device. In particular, nearly 25% less water was shed (0.61 lb/lb vs. 0.81) when the overall seal was lost, even though the gas plenum and collection box were still in significant contact with the fabric strip. The associated 2% loss in post-drying consistency would translate into an approaching 10% reduction in machine speed, which is limited due to drying constraints. This limitation is desired on wet presses converted to the configuration of the present invention.

The preceding experiments attempted to illustrate the best possible results possible using known techniques such as those described in US Patent 5,230,776 to Valmet Corporation. In practical application, it is not possible for the equipment to work as described above due to the excessive noise that would be generated during the test and the air jets generated by the non-integrally sealed dehydration equipment. Although not specifically stated, in practice, it is contemplated that the apparatus described in US Patent 5,230,776 would operate at a gap of 1 inch or greater, where dehydration would be significantly reduced and greater air consumption would result. In practice, this inefficiency results in more additional energy consumption and reduced speed, so this technique is not suitable for commercial devices.

Example 9

A 20 gsm wet web was formed as described in Example 1 using a 50:50 blend ratio of bleached kraft northern softwood and bleached kraft eucalyptus fibers blended at 2000 fpm. The wet web was then vacuum dewatered using 4 vacuum boxes approaching vacuum levels of 18, 18, 17 and 21 inches, respectively. Take a vacuum box consistency sample. The results are shown in Table 4.

Example 10

The experiment of Example 9 was repeated, but with the addition of a steam "blowing box" (Devronizer), thereby increasing the dewatering capacity. The steam box is not integrally sealed from the vacuum box, and it is expected that it will be similar to the device disclosed in US Patent No. 5,230,776. Steam flow to the Devronizer is approximately per hour (300 lbs). Also a consistency sample was taken to determine the increase due to the additional steam blow box. The results are shown in Table 4.

Example 11

The experiment of Example 8 was repeated, but the integral sealed pneumatic device of Example 1 was added to the process. The pneumatic unit operates at a boost pressure of 15 psig and a vacuum level of 17 inches of mercury. Also, consistency samples were taken in order to determine the increase due to the addition of the integral air seal. The results are shown in Table 4.

Table 4 serial number Consistency% Example 9 24.2 Example 10 24.8 Example 11 33.3

The data in Table 4 clearly show that the use of the integral seal air pressure unit resulted in a greater increase in consistency than the use of the steam blow box. Box blowing resulted in a 0.6% increase in consistency, while the integral seal pneumatic device provided an additional 8.5% increase in consistency on top of the increase in consistency caused by steam blowing. Since the wet web had been dewatered to a consistency of 24.2% through four vacuum boxes (Example 9), it was impractical to add enough vacuum and/or steam blow boxes to increase the consistency to a level at which commercially viable speeds could be achieved. actual. However, the addition of an integrally sealed air press (Example 11) increased the consistency to commercial speed levels achievable with the improved wet press design.

The foregoing detailed description is for purposes of explanation. Thus, many modifications and changes may be made to the present invention without departing from the spirit and scope of the invention. For example, alternative or optional features that are part of one example may be used to form other embodiments. Additionally, two named components may represent parts of the same structure. Also, different alternative process and equipment configurations can be used, such as, inter alia, stock preparation, headbox, forming fabric belt, fabric conveyor, creping and drying. Accordingly, the invention should not be limited by the specific embodiments described, but only by the claims and their equivalents.

Claims (109)

1, a kind of method of making the cellulose paper web, the step of this method comprises:

(a) water slurry with paper fibre is deposited on first webbing of circulation, to form wet web;

(b) wet web is dewatered to about 10% to about 30% denseness;

(c) wet web is sent to second webbing of circulation;

(d) wet web is clipped between second webbing and the supports fabrics band, and adopt non-extruding dewater unit that wet web is dewatered to denseness greater than 30%, because this non-extruding dewater unit and wet web form integral sealing, so it is fit to make pressure fluid mobile through paper web basically with about 5 pounds/square inch or bigger pressure;

(e) wet web that took off water is pressed against on the dryer surface of heating, so that to small part dry wet paper web; With

(f) make the wet web that took off water be dried to final drying.

2, a kind of method of making cellulosic fabric, this method comprises the steps:

(a) water slurry with paper fibre is deposited on first webbing of circulation, to form wet web, wherein this wet web;

(b) wet web is sent to second webbing of circulation;

(c) wet web is clipped between second webbing and the supports fabrics band, and wet web is dewatered to denseness up to about 30%;

(d) use pneumatic shuttle that wet web is replenished and be dewatered to about 30% to about 40% denseness, owing to form whole sealing between gas boosting chamber and gathering-device, so this pneumatic shuttle is fit to make pressure fluid to see through fabric basically with about 5 pounds/square inch or bigger pressure to flow;

(e) second webbing is configured to like this: the wet web that took off water is spent less than 90 around the not supported paper cornerite of pressure roller;

(f) wet web that took off water is pressed against on the dryer surface of heating, so that the dry at least in part wet web that took off water; With

(g) make the wet web that took off water be dried to final drying.

3, a kind of method of making cellulosic fabric, this method comprises the steps:

(a) water slurry with paper fibre is deposited on first webbing of circulation, to form wet web;

(b) wet web is dewatered to denseness up to about 10%;

(c) wet web is sent to second webbing of circulation;

(d) wet web is clipped between second webbing and the supports fabrics band;

(e) by second webbing between wet web and gathering-device, make the wet web that is clipped between second webbing and the supports fabrics band by between gas boosting chamber and the gathering-device, this gas boosting chamber and gathering-device operatively associate, and be applicable to produce pass wet web, about 30 inches of mercury or bigger pressure reduction and pass wet web, about per square inch 10 standard cubic foots of per minute or bigger flow of pressurized fluid;

(f) use flow of pressurized fluid wet web to be dewatered to about 30% to about 40% denseness;

(g) by second fabric paper web that took off water is pressed against on the dryer surface of heating; With

(h) make the wet web that took off water be dried to final drying.

4, the method for claim 1 is characterized in that, non-extruding dewater unit improves about 5% to about 20% with the denseness of wet web.

5, method as claimed in claim 2 is characterized in that, this wet web is replenished be dewatered to about 32% or higher denseness.

6, method as claimed in claim 5 is characterized in that, this wet web is replenished be dewatered to about 34% or higher denseness.

As claim 1,2 or 3 described methods, it is characterized in that 7, the pressure reduction that crosses wet web is about 30 inches of mercury or bigger.

8, method as claimed in claim 7 is characterized in that, the pressure reduction that crosses wet web is that about 35 inches of mercury are to about 60 inches of mercury.

9, as claim 1,2 or 3 described methods, it is characterized in that, pressure fluid is pressurized to about 5 to about 30 pounds of/square inch pressure.

10, as claim 1,2 or 3 described methods, it is characterized in that this gathering-device is made of vacuum tank, this vacuum tank is pumped into greater than 0 vacuum to about 25 inches of mercury.

As claim 2 or 3 described methods, it is characterized in that 11, the holdup time in pneumatic shuttle is about 10 milliseconds or still less.

12, method as claimed in claim 11 is characterized in that, the holdup time in pneumatic shuttle is about 7.5 milliseconds or still less.

As claim 2 or 3 described methods, it is characterized in that 13, wet web advances with about 1000 feet per minute clocks or faster speed, and leave this pneumatic shuttle from entering into, the denseness of wet web increases about 5% or more.

As claim 2 or 3 described methods, it is characterized in that 14, wet web advances with about 2000 feet per minute clocks or faster speed, and leave this pneumatic shuttle from entering into, the denseness of wet web increases about 5% or more.

15, method as claimed in claim 1 or 2 is characterized in that, wet web advances with about 2000 feet per minute clocks or faster speed.

As claim 2 or 3 described methods, it is characterized in that 16, about 85% or the more pressure fluid of supplying with this gas boosting chamber pass this wet web and flow.

17, method as claimed in claim 16 is characterized in that, about 90% or the more pressure fluid of supplying with this gas boosting chamber pass this wet web and flow.

As claim 1,2 or 3 described methods, it is characterized in that 18, the temperature of pressure fluid is 300 ℃ or lower approximately Celsius.

19, method as claimed in claim 18 is characterized in that, the temperature of pressure fluid is 150 ℃ or lower approximately Celsius.

20, as claim 2 or 3 described methods, it is characterized in that heated drying cylinder comprises the drier hood, before wet web entered the drier hood, this second webbing and the drier hood that are pressed against on this drying cylinder separated.

As claim 2 or 3 described methods, it is characterized in that 21, this second webbing that is pressed against on this drying cylinder is wrapped on the drying cylinder, whole distances that it keeps in touch less than this paper web and drying cylinder.

22, as claim 1,2 or 3 described methods, it is characterized in that the wet web that uses a pair of transfer roller will take off water is sent on the heated drying cylinder, this twines the extension that transfer roller forms predetermined span.

23, method as claimed in claim 22 is characterized in that, these two transfer rollers or one of them do not load heated drying cylinder.

24, method as claimed in claim 22 is characterized in that, these two transfer rollers or one of them lean against on the heated drying cylinder and load.

25, method as claimed in claim 1 or 2 is characterized in that, with about 350 pounds/linear inch or littler pressure the wet web that took off water is pressed against on the drying cylinder.

26, as claim 2 or 3 described methods, it is characterized in that, antitack agent is added on second webbing, and this second webbing is pressed against on the heated drying cylinder, so that took off the transmission of the wet web of water.

27, method as claimed in claim 1 or 2 is characterized in that, the wet web that will take off water that flows of pressure fluid is sent to second webbing.

28, method as claimed in claim 1 or 2 is characterized in that, the wet web that will take off water is sent to second webbing fast.

29, as claim 2 or 3 described methods, it is characterized in that, the paper web of drying is not removed from heated drying cylinder with not creasing.

As claim 1,2 or 3 described methods, it is characterized in that 30, the wet web that will take off water is dried to about 95% denseness or bigger denseness, creases then.

As claim 1,2 or 3 described methods, it is characterized in that 31, the wet web that will take off water on the surface of heated drying cylinder partly is dried to from about denseness of 40% to 80%, wet creasing, and finally be dried to about 95% or bigger denseness afterwards.

32, adopt claim 1,2 or 3 described methods to make absorbent tissue-towel.

33, method as claimed in claim 1 or 2 is characterized in that, further comprises: before using non-squeezing dehydration device, this wet web is sent to second webbing, and this wet web is clipped between second webbing and the supports fabrics band.

As claim 1,2 or 3 described methods, it is characterized in that 34, this device is that paper napkin machine is made in improved wet pressing.

As claim 1,2 or 3 described methods, it is characterized in that 35, this second webbing has replaced in traditional wet pressing makes woollen blanket on the paper napkin machine.

As claim 1,2 or 3 described methods, it is characterized in that 36, this gas boosting chamber is positioned at the loop of second webbing of circulation.

37, method as claimed in claim 1 or 2 is characterized in that, this gas boosting chamber is positioned at the loop of supports fabrics band.

As claim 1,2 or 3 described methods, it is characterized in that 38, before the wet web that took off water was sent to heated drying cylinder, the wet web that the vacuum slide rail will take off water was sent on second webbing.

As claim 1,2 or 3 described methods, it is characterized in that 39, first webbing is the forming fabric band.

As claim 1,2 or 3 described methods, it is characterized in that 40, second webbing is molded webbing.

As claim 1,2 or 3 described methods, it is characterized in that 41, this gas boosting chamber is positioned at the press sections that paper napkin machine is made in improved wet pressing.

42, as claim 1 or 3 described methods, it is characterized in that, further comprise: second webbing is configured to like this, that is: make the wet web that took off water around the cornerite that does not support paper of pressure roller for less than 90 °.

43, method as claimed in claim 2 is characterized in that, the wet web that took off water around the cornerite that does not support paper of pressure roller for less than 45 °.

44, method as claimed in claim 42 is characterized in that, the wet web that took off water around the cornerite that does not support paper of pressure roller for less than 45 °.

45, method as claimed in claim 2 is characterized in that, the wet web that took off water around the cornerite that does not support paper of pressure roller for less than 10 °.

46, method as claimed in claim 42 is characterized in that, the wet web that took off water around the cornerite that does not support paper of pressure roller for less than 10 °.

47, the method for claim 1 is characterized in that, non-extruding dewater unit is made up of gas boosting chamber and gathering-device.

48, as claim 2,3 or 47 described methods, it is characterized in that, further comprise: the transverse sealing positioning parts is become to make the course of wet web, first and second webbings towards the gathering-device deflection.

49, method as claimed in claim 48 is characterized in that, the minimum impact momentum h (min) that the collision of transverse sealing parts enters in this supporting fabrics band is determined by following equation: $h\left(\min \right)=\frac{T}{W}(\cosh \left(\frac{\mathrm{Wd}}{T}\right)-1);$

Wherein, T is to be the tension force of first and second webbings of measuring of unit with pound/inch; W is to be the pressure reduction that crosses paper web that unit measures with pound/square inch; D is vertical gap of going up between diaphragm seal and the gathering-device of measuring with inch unit.

50, improving one's methods of a kind of conventional wet press with at least one woollen blanket and squeeze dehydration unit, this method comprises:

(a) replace at least one woollen blanket with at least one webbing;

(b) replace squeeze dehydration unit with extruding dewater unit non-heat, non-.

51, method as claimed in claim 50 is characterized in that, this webbing comes free first webbing, second webbing, supports fabrics band and their group in conjunction with formation.

52, method as claimed in claim 50 is characterized in that, replaces at least two woollen blankets with first webbing and second webbing.

53, method as claimed in claim 50 is characterized in that, replaces at least two woollen blankets with first webbing and supports fabrics band.

54, method as claimed in claim 50 is characterized in that, replaces at least two woollen blankets with second webbing and supports fabrics band.

55, method as claimed in claim 50 is characterized in that, replaces at least two woollen blankets with first webbing and supports fabrics band.

56, method as claimed in claim 50 is characterized in that, the non-extruding dewater unit of non-heat is selected from following group: the non-extruding pressure roller of vacuum tank, pneumatic shuttle, non-heat, perhaps their combination.

57, a kind of method of making the cellulose paper web, this method comprises the steps:

(a) water slurry of paper fibre is deposited between second webbing of first webbing of circulation and circulation to form wet web, wherein wet web is clipped between first webbing and second webbing;

(b) use non-extruding dewater unit that wet web is dewatered to about 30% or bigger denseness, because this non-extruding dewater unit and wet web form integral sealing, so that it is suitable for making the pressure fluid of about 5 pounds/square inch or bigger pressure to pass this wet web basically is mobile;

(c) wet web that will take off water is pressed against on the surface of heated drying cylinder, thus the dry at least in part wet web that took off water;

(d) make the wet web that took off water be dried to final drying.

58, a kind of method of making the cellulose paper web, this method comprises the steps:

(a) water slurry of paper fibre is deposited between second webbing of first webbing of circulation and circulation to form wet web, wherein wet web is clipped between first webbing and second webbing;

(b) wet web is dewatered to about 10% to about 30% denseness;

(c) use pneumatic shuttle that wet web is replenished and be dewatered to about denseness of 30% to 40%, owing between gas boosting chamber and gathering-device, form integral sealing, so this pneumatic shuttle is suitable for making the pressure fluid of about 5 pounds/square inch or bigger pressure to pass this wet web basically and flows, thus make this paper web have about 8 cubic centimetres/gram or bigger bulk density;

(d) wet web that will take off water by webbing is pressed against on the surface of heated drying cylinder, with keep about 8 cubic centimetres/gram or bigger bulk density;

(e) make the wet web that took off water be dried to final drying.

59, a kind of method of making the cellulose paper web, this method comprises the steps:

(a) water slurry of paper fibre is deposited between second webbing of first webbing of circulation and circulation to form wet web, wherein wet web is clipped between first webbing and second webbing;

(b) make the wet web that is clipped between first webbing and second webbing by between pneumatic shuttle and the gathering-device by second webbing, wherein second webbing is between wet web and gathering-device, this pneumatic shuttle and gathering-device operatively associate, and be suitable for producing about 30 inches of mercury of crossing wet web or the more pressure reduction of high pressure and about per square inch 10 scfm or the bigger flow of pressurized fluid of passing wet web;

(c) use flow of pressurized fluid to make this wet web be dewatered to about 30% or higher denseness;

(d) wet web is pressed against on the dryer surface of heating by second webbing; With

(e) make the wet web that took off water be dried to final drying.

60, method as claimed in claim 57 is characterized in that, non-extruding dewater unit can improve the denseness of wet web about 5% to about 20%.

61, method as claimed in claim 58 is characterized in that, wet web is replenished be dewatered to about 32% or higher denseness.

62, method as claimed in claim 61 is characterized in that, wet web is replenished be dewatered to about 34% or higher denseness.

As claim 57,58 or 59 described methods, it is characterized in that 63, the pressure reduction that crosses wet web is about 30 inches of mercury or bigger.

As the described method of claim 63, it is characterized in that 64, the pressure reduction that crosses wet web is about 35 to about 60 inches of mercury or bigger.

65, as claim 57,58 or 59 described methods, it is characterized in that, pressure fluid is pressurized to about 5 to about 30 pounds/square inch pressure.

66, as claim 57 or 58 described methods, it is characterized in that this gathering-device comprises vacuum tank, this vacuum tank is pumped into greater than 0 vacuum to about 25 inches of mercury.

As claim 58 or 59 described methods, it is characterized in that 67, the holdup time in pneumatic shuttle is about 10 milliseconds or still less.

As the described method of claim 67, it is characterized in that 68, the holdup time in pneumatic shuttle is about 7.5 milliseconds or still less.

As claim 58 or 59 described methods, it is characterized in that 69, wet web advances with about 1000 feet per minute clocks or faster speed, and increase about 5% or more from entering into the denseness of leaving this pneumatic shuttle wet web.

As claim 58 or 59 described methods, it is characterized in that 70, wet web advances with about 2000 feet per minute clocks or faster speed, and increase about 5% or more from entering into the denseness of leaving this pneumatic shuttle wet web.

As claim 57 or 58 described methods, it is characterized in that 71, wet web advances with about 2000 feet per minute clocks or faster speed.

As claim 58 or 59 described methods, it is characterized in that 72, about 85% or the more pressure fluid of supplying with this gas boosting chamber pass this wet web and flow.

As the described method of claim 72, it is characterized in that 73, about 90% or the more pressure fluid of supplying with this gas boosting chamber pass this wet web and flow.

As claim 57,58 or 59 described methods, it is characterized in that 74, the temperature of pressure fluid is 300 ℃ or lower approximately Celsius.

As the described method of claim 74, it is characterized in that 75, the temperature of pressure fluid is 150 ℃ or lower approximately Celsius.

76, as claim 58 or 59 described methods, it is characterized in that heated drying cylinder comprises the drier hood, before the wet web that took off water entered the drier hood, this second webbing and the drier hood that are pressed against on this drying cylinder separated.

As claim 58 or 59 described methods, it is characterized in that 77, this second webbing that is pressed against on this drying cylinder is wrapped on the drying cylinder, so that the whole distances that keep in touch less than this paper web and drying cylinder.

78, as claim 57,58 or 59 described methods, it is characterized in that the wet web that uses a pair of transfer roller will take off water is sent on the heated drying cylinder, this twines the extension that transfer roller forms predetermined span.

As the described method of claim 78, it is characterized in that 79, these two transfer rollers or one of them do not load heated drying cylinder.

As the described method of claim 78, it is characterized in that 80, these two transfer rollers or one of them lean against on the heated drying cylinder and load.

As claim 57 or 58 described methods, it is characterized in that 81, the wet web that will take off water with about 350 pounds/linear inch or littler pressure is pressed against on the drying cylinder.

82, as claim 58 or 59 described methods, it is characterized in that, antitack agent is added on second webbing that is pressed against on the heated drying cylinder, so that took off the transmission of the wet web of water.

As claim 57 or 58 described methods, it is characterized in that 83, the wet web that flow of pressurized fluid will be taken off water is sent to second webbing.

84, as claim 58 or 59 described methods, it is characterized in that, will take off the wet web of water and from heated drying cylinder, not remove with not creasing.

As claim 57,58 or 59 described methods, it is characterized in that 85, the wet web that will take off water is dried to about 95% denseness or bigger denseness, creases then.

86, as claim 57,58 or 59 described methods, it is characterized in that, the wet web that will take off water on the surface of heated drying cylinder partly is dried to from about denseness of 40% to 80%, wet creasing, and finally be dried to about 95% or bigger denseness afterwards.

87, adopt claim 57,58 or 59 described methods to make absorbent tissue-towel.

88, as claim 57 or 58 described methods, it is characterized in that, further comprise: before using non-squeezing dehydration device, this wet web is sent to second webbing, and this wet web is clipped between second webbing and the supports fabrics band.

As claim 57,58 or 59 described methods, it is characterized in that 89, this device is that improved crescent former is made paper napkin machine.

As claim 57,58 or 59 described methods, it is characterized in that 90, this second webbing is substituted in crescent former and makes woollen blanket on the paper napkin machine.

As claim 57,58 or 59 described methods, it is characterized in that 91, this gas boosting chamber is positioned at the loop of second webbing of circulation.

92, as claim 57 or 58 described methods, it is characterized in that this gas boosting chamber is positioned at the loop of supports fabrics band.

93, method as claimed in claim 59 is characterized in that, this gas boosting chamber is positioned at the loop of first webbing of circulation.

As claim 57,58 or 59 described methods, it is characterized in that 94, before the wet web that took off water was sent to heated drying cylinder, the wet web that the vacuum slide rail will take off water was sent on second webbing.

As claim 57,58 or 59 described methods, it is characterized in that 95, first webbing is the forming fabric band.

As claim 57,58 or 59 described methods, it is characterized in that 96, second webbing is molded webbing.

97, method as claimed in claim 57 is characterized in that, non-extruding dewater unit is made up of gas boosting chamber and gathering-device.

98, as claim 58,59 or 97 described methods, it is characterized in that, further comprise: the transverse sealing positioning parts is become to make the course of wet web, first and second webbings towards the gathering-device deflection.

As the described method of claim 98, it is characterized in that 99, the minimum impact momentum h (min) that the collision of transverse sealing parts enters in this supporting fabrics band is determined by following equation: $h\left(\min \right)=\frac{T}{W}(\cosh \left(\frac{\mathrm{Wd}}{T}\right)-1);$

Wherein, T is to be the tension force of first and second webbings of measuring of unit with pound/inch; W is to be the pressure reduction that crosses paper web that unit measures with pound/square inch; D is vertical gap of going up between diaphragm seal and the gathering-device of measuring with inch unit.

100, as claim 57,58 or 59 described methods, it is characterized in that, further comprise: second webbing is configured to like this, promptly provide around the cornerite that does not support paper of the wet web that took off water of pressure roller for less than 90 °.

101, as the described method of claim 100, it is characterized in that, around the cornerite that does not support paper of the wet web that took off water of pressure roller for less than 45 °.

102, as the described method of claim 100, around the cornerite that does not support paper of the wet web that took off water of pressure roller for less than 10 °.

103, a kind of traditional crescent former with at least one woollen blanket and squeeze dehydration unit is made improving one's methods of paper napkin machine, and this method comprises:

(a) replace at least one woollen blanket with at least one webbing;

(b) replace squeeze dehydration unit with extruding dewater unit non-heat, non-.

As the described method of claim 103, it is characterized in that 104, this webbing comes free first webbing, second webbing, supports fabrics band and their group in conjunction with formation.

105, as the described method of claim 103, it is characterized in that, replace at least two woollen blankets with first webbing and second webbing.

106, as the described method of claim 103, it is characterized in that, replace at least two woollen blankets with first webbing and supports fabrics band.

107, as the described method of claim 103, it is characterized in that, replace at least two woollen blankets with second webbing and supports fabrics band.

108, as the described method of claim 103, it is characterized in that, replace at least two woollen blankets with first webbing and supports fabrics band.

As the described method of claim 103, it is characterized in that 109, the non-extruding dewater unit of non-heat is selected from following group: the non-extruding pressure roller of vacuum tank, pneumatic shuttle, non-heat, perhaps their combination.

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