Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/08—Felts
  • D21F7/083—Multi-layer felts
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/08—Felts
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2401/00—Physical properties
  • D10B2401/02—Moisture-responsive characteristics
  • D10B2401/022—Moisture-responsive characteristics hydrophylic
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2401/00—Physical properties
  • D10B2401/06—Load-responsive characteristics
  • D10B2401/063—Load-responsive characteristics high strength

Definitions

• the present invention relates to a papermaking felt and a method for producing a papermaking felt.
• a papermaking machine that removes water from a raw paper material is generally provided with a wire part, a press part and a dryer part. These wire part, press part and dryer part are arranged in this order along the wet paper web transfer direction.
• a wet paper web is transferred and moisture thereof is removed while the wet paper web is being successively passed through papermaking devices provided in the wire part, the press part, and the dryer part, and the wet paper web is finally dried in the dryer part.
• the papermaking devices corresponding to a function of dehydrating the wet paper web (wire part), a function of squeezing water (press part), and a function of drying the wet paper web (dryer part) are used.
• the felt carrying a wet paper web moves along the wet paper web transfer direction, passing through either the roll press mechanism or the shoe press mechanism, where the water is squeezed out of the wet paper web by pressing the felt carrying the wet paper web such that the papermaking felt continuously absorbs water or the water passes through the felt to be drained to the outside.
• JP 2007-100277 A proposes a papermaking transfer felt for shoe-press , characterized in that it comprises a base layer, a first batt layer formed on the surface of the wet paper web side of the base layer, a second batt layer formed on the surface of the roll side or shoe side of the base layer, and a wet paper web contact fiber layer comprising a hydrophilic fiber and formed on the surface of the wet paper web side of the first batt layer so as to be in direct contact with the wet paper web, wherein the hydrophilic fiber is fibrillated by being pressed by the roll and the shoe.
• the water amount (water content) of the wet paper web at the outlet of the press part is directly related to the energy consumption for drying in the dryer part at the later stage. Therefore, it is preferable that the water amount of the wet paper web at the outlet of the press part can be further reduced by further preventing the rewetting phenomenon.
• the present inventors have made a diligent investigation in order to achieve the above-described object and have focused on a configuration in which a batt layer and a nonwoven fabric are arranged on a base fabric. Then, the present inventors have found that there is a correlation between the rewetting phenomenon and the needle penetration resistance during needle punch treatment of the nonwoven fabric, and as a result of further diligent investigation, reached the present invention.
• a gist of the present invention is as follows:
• FIG. 1 is a cross-sectional view in a cross machine direction showing an example of a papermaking felt according to a preferred embodiment of the present invention.
• each member has been emphasized in size as appropriate for ease of illustration and thus does not indicate the actual proportion and size of each member.
• CMD cross machine direction
• MD machine direction
• the papermaking felt 1 shown in FIG. 1 is used for carrying and transferring a wet paper web and squeezing water from wet paper web in the press part of a papermaking machine.
• the papermaking felt 1 forms an endless band-shaped body. That is, the papermaking felt 1 is an annular belt.
• the papermaking felt 1 is normally placed such that its circumferential direction runs along a machine direction (MD) of the papermaking machine.
• MD machine direction
• the side of one surface is usually a wet paper web carrying surface 41 side which will be in contact with the wet paper web, and the side of the other surface is a roll contact surface 51 side which will support the papermaking felt 1.
• the papermaking felt 1 comprises a substrate 10; a first batt layer 20 and a nonwoven fabric 30 and a second batt layer 40 which are placed on the wet paper web carrying surface 41 side the substrate 10; and a third batt layer 50 placed on the roll contact surface side.
• the first batt layer 20 and the nonwoven fabric 30 and the second batt layer 40 are arranged in this order from the substrate 10 toward the wet paper web carrying surface 41.
• these layers of the papermaking felt 1 are all joined to each other by needle punch treatment.
• the substrate 10 is a reinforcing fibrous substrate that ensures physical strength (such as tensile strength) of the papermaking felt 1.
• the substrate 10 is not particularly limited, and, for example, a woven fabric consisting of warp yarns and weft yarns woven by a weaving machine, etc., may generally be used.
• An unwoven grid-like web material in which warp rows and weft rows are superimposed on each other can also used.
• the woven fabric, grid-like material, etc. may be used in combination of two or more.
• polyester polyethylene terephthalate, polybutylene terephthalate, etc.
• aliphatic polyamide polyamide 6, polyamide 11, polyamide 12, polyamide 612, etc.
• aromatic polyamide aromatic polyamide
• polyvinylidene fluoride polypropylene
• polyether ether ketone polytetrafluoroethylene
• polyethylene sheep wool, cotton, metal, etc.
• the fineness of the fiber constituting the substrate 10 is not particularly limited, and can be, for example, equal to or more than 300 and equal to or less than 10,000 dtex, preferably, equal to or more than 500 and equal to or less than 6,000 dtex.
• the fineness of the fiber that constitutes the substrate 10 may vary depending on the part in which the fiber is used. For instance, the warp yarns and weft yarns of the substrate 10 may have different fineness.
• the thickness of the above-mentioned substrate 10 is not particularly limited, and can be, for example, equal to or more than 0.2 mm and equal to or less than 3.5 mm, preferably equal to or more than 0.5 mm and equal to or less than 3.0 mm.
• the weight of 1 m 2 of the substrate 10 is not particularly limited, and can be, for example, equal to or more than 150 g/m 2 and equal to or less than 1,200 g/m 2 , and preferably equal to or more than 300 g/m 2 and equal to or less than 1,000 g/m 2 .
• the first batt layer 20 is a short fiber layer provided adjacent to the substrate 10 on the wet paper web carrying surface 41 side of the substrate 10.
• a nonwoven fabric 30 is disposed adjacently.
• the material of the short fiber which constitutes the first batt layer 20 is not particularly limited, and a polyester (polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), an aliphatic polyamide (polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, etc.), an aromatic polyamide (aramid), polyvinylidene fluoride, polypropylene, polyether ether ketone, polytetrafluoroethylene, polyethylene, sheep wool, cotton, metals, etc., can be used either alone or in combination of two or more types.
• polyamide is preferred as the material for the short fiber from the viewpoints of abrasion resistance, compression recoverability, impact resistance, hydrophilicity, hydrolysis resistance, chemical resistance, etc.
• the fineness of the short fiber constituting the first batt layer 20 is not particularly limited, but is, for example, equal to or more than 0.1 dtex and equal to or less than 200 dtex.
• the fineness of the first short fiber constituting the first batt layer 20 is not particularly limited, though it is, for example, equal to or more than 0.1 dtex and equal to or lower than 200 dtex, preferably equal to or more than 2.0 dtex and equal to or lower than 70 dtex, more preferably equal to or more than 6.0 dtex and equal to or lower than 70 dtex.
• the first batt layer 20 can have a sufficient strength while sufficiently absorbing moisture from the wet paper web through the capillary phenomenon caused by fine short fibers.
• the weight of 1 m 2 of the first batt layer 20 is not particularly limited, and can be, for example, equal to or more than 50 g/m 2 and equal to or less than 800 g/m 2 , preferably equal to or more than 50 g/m 2 and equal to or less than 700 g/m 2 , and more preferably equal to or more than 50 g/m 2 and equal to or less than 600 g/ m 2 .
• a moderate space for absorbing water under pressure can be maintained.
• the nonwoven fabric 30 is a layer provided adjacent the first batt layer 20 on the wet paper carrying surface 41 side of the first batt layer 20.
• a second batt layer 40 is disposed adjacently.
• the nonwoven fabric 30 functions as a barrier layer to suppress the migration of moisture from the first batt layer 20 side to the wet paper carrying surface side when a negative pressure is generated on the papermaking felt 1 and the wet paper web immediately after pressing, and thereby suppresses the rewetting phenomenon in the wet paper web after pressing.
• the present inventors focused on this function of the nonwoven fabric 30 as the barrier layer to suppress the rewetting phenomenon and investigated the conditions for improving the function.
• the present inventors have found that there is a significant correlation between the needle penetration resistance of the unwoven fabric 30 and the rewetting phenomenon, and reached the present invention.
• the present inventors have found that the rewetting phenomenon can suitably be suppressed and the moisture content of wet paper web after pressing can sufficiently be reduced when the unwoven fabric 30 have a penetration resistance of 2.0 N / (100 g/m 2 x number of needles) or less per one needle when the basis weight of the fabric is 100 g/m 2 .
• a large penetration resistance of the nonwoven fabric 30 against the needle means that many fibers in the nonwoven fabric 30 collide with the needle and become entangled with fibers in adjacent layers, e.g., the first batt layer 20 and the second batt layer 40.
• the fibers in the nonwoven fabric 30 When many fibers in the nonwoven fabric 30 become entangled with fibers of adjacent layers, the fibers in the nonwoven fabric 30 are dispersed in the thickness direction, thereby reducing the substantial density of the nonwoven fabric 30 after the needle punch treatment. It is therefore considered that if the substantial density of the nonwoven fabric 30 is reduced, its function as the barrier layer as described above will be reduced. Accordingly, it is considered that the substantial decrease in the density of the nonwoven fabric 30 will be suppressed by using the nonwoven fabric 30 having a relatively small penetration resistance against the needle, and as a result, the nonwoven fabric 30 will sufficiently function as the barrier layer.
• the penetration resistance of the nonwoven fabric 30 for the basis weight of 100 g/m 2 per one needle may be within the range mentioned above, and it is preferably equal to or less than 1.8 N / (100 g/m 2 x number of needles), further preferably equal to or less than 1.5 N / (100 g/m 2 x number of needles), and particularly preferably equal to or less than 1.2 N / (100 g/m 2 x number of needles).
• the nonwoven fabric 30 can fully exert its function, and can further suppress the rewetting phenomenon in the wet paper web after pressing.
• the lower limit of the penetration resistance of the nonwoven fabric 30 for the basis weight of 100 g/m 2 per one needle is not particularly limited, though the penetration resistance is, for example, equal to or more than 0.10 N / (100 g/m 2 x number of needles), preferably equal to or more than 0.30 N / (100 g/m 2 x number of needles), and further preferably equal to or more than 0.50 N / (100 g/m 2 x number of needles).
• This configuration enables the contact between the first batt layer 20 and the nonwoven fabric 30 created by needle punching during manufacturing to be maintained, makes the layering of the second batt layer 40 easy, can sufficiently increase the density of the nonwoven fabric 30 itself before the needle punch treatment, and can further suppress the rewetting phenomenon in the wet paper web after pressing.
• FIG. 2 is a schematic diagram to illustrate a method for measuring the needle penetration resistance of a nonwoven fabric.
• the penetration resistance of a nonwoven fabric against a needle can be measured using a tensile testing machine.
• the jigs 101A and 101B of the tensile testing machine shown in FIG. 2 are arranged in a vertical direction facing each other.
• a holder 105 having a plurality of needles 103 is attached to the upper jig 101A.
• the number of needles 103 is not particularly limited, though it can be, for example, equal to or more than 10 and equal to or less than 100 needles.
• the needle implanting density is not particularly limited, though it can be, for example, equal to or more than 0.030 needles/cm 2 and equal to or less than 0.20 needles/cm 2 .
• the lower jig 101B is a pedestal with a space in the center, on which a nonwoven fabric 30 sandwiched between two fixing plates 109 is arranged.
• a plurality of nonwoven fabrics 30 are arranged in layers as necessary such that their total basis weight becomes approximately 100 g/m 2 .
• the total basis weight of the layered nonwoven fabrics 30 need not strictly be 100 g/m 2 , and may be adjusted appropriately for example, between 70 g/m 2 and 150 g/m 2 .
• the fixing plate 109 is provided with a through hole 1091 corresponding to the position of the needle 103, and the fixing plate 109 is arranged in a relative position such that the through hole 1091 and the needle 103 do not interfere with each other during measurement.
• the needle 103 is moved to the nonwoven fabric 30 side using the tensile testing machine to penetrate the first barb of the needle 103 into the nonwoven fabric 30.
• the maximum value of the resistance force loaded on the needle 103 at this time can be set as the penetration resistance.
• the moving speed of the needle 103 can be, for example, equal to or more than 50 mm/min and equal to or less than 400 mm/min.
• the penetration resistance obtained as above is converted so as to be per 100 g/m 2 of the basis weight of the nonwoven fabric 30 and per one needle 103 to obtain the penetration resistance per 100 g/m 2 of the basis weight of the unwoven fabric 30 per one needle as described above. Specifically, it is expressed as in the following Equation (1).
• R R T ⁇ W NWF ⁇ 100 ⁇ N NDL
• R is the penetration resistance of the nonwoven fabric 30 for the basis weight of 100 g/m 2 per one needle [N / (100 g/m 2 x number of needles)]
• R T is the maximum resistance force [N] of the nonwoven fabric 30 at the time of penetration of the needle 103
• W NWF is the total basis weight (g/m 2 ) of the nonwoven fabric 30
• N NDL is the number of the needles 103.
• the penetration resistance of the nonwoven fabric 30 as mentioned above can be changed as appropriate by changing the material and fineness of the fibers constituting the nonwoven fabric, the density of the nonwoven fabric, the form of the nonwoven fabric, the manufacturing method, etc.
• the material of the fiber constituting the nonwoven fabric 30 is not particularly limited, and in addition to the materials listed as the material of the short fiber of the first batt layer 20, includes hydrophilic fibers such as cellulose-based fibers such as rayon, polynosic, lyocell, cupra, cellulose nanofibers, cotton and linen, and silk and wool, which can be used alone or in combination of two or more.
• hydrophilic fibers such as cellulose-based fibers such as rayon, polynosic, lyocell, cupra, cellulose nanofibers, cotton and linen, and silk and wool, which can be used alone or in combination of two or more.
• the fiber constituting the nonwoven fabric 30 preferably includes a hydrophilic fiber.
• the nonwoven fabric 30 comprises a hydrophilic fiber, the nonwoven fabric 30 can easily retain moisture, and as a result can more suitably suppress the rewetting phenomenon after pressing.
• the hydrophilic fiber can be a fiber that has an official moisture regain of, for example, equal to or more than 4.0%, preferably equal to or more than 5.0%.
• an official moisture regain is 4.5% for nylon, 11.0% for rayon, 11.0% for polynodic, 13.0% for lyocell, 11.0% for cupra, 8.5% for cotton, 12.0% for hemp, 12.0% for silk, and 13.0% for wool.
• the official moisture regain of the hydrophilic fiber is more preferably equal to or more than 8.0 %, and particularly preferably equal to or more than 10.0%.
• the difference between the official moisture regain of the fiber constituting the nonwoven fabric 30 and that of the short fiber constituting the first batt layer 20 is not particularly limited, though it is, for example, equal to or more than 2.0% and equal to or less than 12%, and preferably equal to or more than 4.0% and equal to or less than 10%.
• the moisture transferred to the first batt layer 20 side via the nonwoven fabric 30 during pressing is suitably discharged to the substrate 10 and out of the papermaking felt 1.
• the difference between the official moisture regain of the fiber constituting the nonwoven fabric 30 and that of the short fiber constituting the second batt layer 40 is not particularly limited, though it is, for example, equal to or more than 2.0% and equal to or less than 12%, and preferably equal to or more than 4.0% and equal to or less than 10%.
• the nonwoven fabric 30 can easily retain moisture when a negative pressure is generated on the papermaking felt 1 and the wet paper web immediately after pressing, thereby more certainly suppress the rewetting phenomenon.
• the fiber constituting the nonwoven fabric 30 preferably comprises one or more fibers selected from nylon, cupra, rayon, lyocell, silk, hemp and wool, and more preferably one or more fibers selected from cupra, rayon, lyocell, silk, hemp and wool.
• Nylon has a moderate hydrophilicity as well as an excellent strength.
• Other preferred fibers also have a moderate strength and furthermore have an excellent hydrophilicity.
• the fiber constituting the nonwoven fabric 30 can be a short fiber yarn (200 mm or less), a long fiber yarn (more than 200 mm and 15,000 mm or less), or a continuous yarn.
• the fiber constituting the nonwoven fabric 30 preferably comprises a long fiber yarn and/or a continuous yarn, and more preferably a continuous yarn.
• the "continuous yarn” as used herein refers to a yarn which is continuously manufactured in the manufacturing process and ideally does not have an end portion, and is a so-called filament whose end portion is formed for a reason relating processes such as, for example, cutting of the nonwoven fabric 30.
• the fiber diameter of the fiber constituting the nonwoven fabric 30, especially the fiber diameter of the continuous yarn is not particularly limited, though it is, for example, equal to or more than 5.0 ⁇ m and equal to or less than 30 ⁇ m, preferably equal to or more than 10 ⁇ m and equal to or less than 25 ⁇ m.
• the nonwoven fabric 30 can have a sufficient strength while ensuring a moderate water permeability during pressing.
• the nonwoven fabric 30 can have a sufficient water retention capacity through the capillary phenomenon, thus the moisture can smoothly migrate from the second batt layer 40 to the nonwoven fabric 30 during pressing and at the same time the migration of moisture from the nonwoven fabric 30 to the second batt layer 40 immediately after pressing can be suppressed.
• the nonwoven fabric 30 can be manufactured by, for example, a dry method, a wet method, a spun-bond method, a melt-blowing method, or the like. Among those mentioned above, it is preferable that the nonwoven fabric 30 is a spun-bond nonwoven fabric manufactured by the spun-bond method. In the spun-bond method, it is possible to manufacture the nonwoven fabric 30 with continuous yarns.
• the nonwoven fabric 30 may be processed by a processing method such as a thermal bonding method, a chemical bonding method, a needle punching method, or a hydroentanglement method (spunlace). By being processed in these ways, the penetration resistance of the nonwoven fabric 30 can be adjusted.
• a processing method such as a thermal bonding method, a chemical bonding method, a needle punching method, or a hydroentanglement method (spunlace).
• the weight of 1 m 2 (basis weight) of the nonwoven fabric 30 is not particularly limited, and can be, for example, equal to or more than 10 g/m 2 and equal to or less than 100 g/m 2 , preferably equal to or more than 15 g/m 2 and equal to or less than 60 g/m 2 , and more preferably equal to or more than 20 g/m 2 and equal to or less than 50 g/ m 2 .
• the nonwoven fabric 30 can ensure an appropriate air permeability while sufficiently functioning as a barrier layer to suppress the rewetting phenomenon.
• a plurality of nonwoven fabrics may be prepared so as to be a target basis weight, for example, which are layered to make a single-layer nonwoven fabric 30.
• the second batt layer 40 is a layer constituted with short fibers, provided adjacent to the nonwoven fabric 30 on the wet paper web carrying surface 41 side of the nonwoven fabric 30.
• the second batt layer 40 is arranged with the first batt layer 20 across the nonwoven fabric 30.
• the second batt layer 40 is located on the outermost layer of the papermaking felt 1, forming the wet paper web carrying surface 41 for carrying the wet paper web.
• the material for the short fiber constituting the second batt layer 40 is not particularly limited, and includes the materials that constitute the first batt layer 20, which can be used alone or in combination of two or more types.
• Polyamide is preferred as the material for the short fiber from the viewpoints of abrasion resistance, compression recoverability, impact resistance, hydrophilicity, hydrolysis resistance, chemical resistance, etc.
• the fineness of the second short fiber constituting the second batt layer 40 is not particularly limited, and it is, for example, equal to or more than 0.1 dtex and equal to or less than 200 dtex, preferably equal to or more than 2.0 dtex and equal to or less than 70 dtex, and more preferably equal to or more than 2.0 dtex and equal to or less than 30 dtex.
• the second batt layer 40 can have a sufficient strength while providing the wet paper web carrying surface 41 with a sufficient smoothness and at the same time sufficiently absorbing the moisture from the wet paper web through the capillary phenomenon caused by the fine second short fibers.
• the weight of 1 m 2 of the second batt layer 40 is not particularly limited, and can be, for example, equal to or more than 50 g/m 2 and equal to or less than 800 g/m 2 , preferably equal to or more than 50 g/m 2 and equal to or less than 700 g/m 2 , and more preferably equal to or more than 50 g/m 2 and equal to or less than 600 g/ m 2 .
• a moderate space for absorbing water under pressure can be maintained.
• the total basis weight of the first batt layer 20 and the second batt layer 40 can be equal to or more than 100 g/m 2 and equal to or less than 1,600 g/m 2 , preferably equal to or more than 100 g/m 2 and equal to or less than 1,400 g/m 2 , and more preferably 100 g/m 2 and equal to or less than 1,200 g/ m 2 .
• the total basis weight of the first batt layer 20 and the second batt layer 40 is appropriately set according to the intended characteristics such as the strength, porosity and air permeability of the papermaking felt 1.
• a third batt layer 50 is a layer constituted with short fibers, provided adjacent to the substrate 10 on the roll contact surface 51 side of the substrate 10. Moreover, the third batt layer 50 is located on the outermost layer of the papermaking felt 1, forming the roll contract surface 51 that comes in contact with the roll. Note that, without being limited to the illustrated embodiments, the papermaking felt 1 can also be constructed without a third batt layer 50.
• the material for the short fiber constituting the third batt layer 50 is not particularly limited, and includes the materials that constitute the first batt layer 20, which can be used alone or in combination of two or more types.
• Polyamide is preferred as the material for the short fiber from the viewpoints of abrasion resistance, compression recoverability, impact resistance, hydrophilicity, hydrolysis resistance, chemical resistance, etc.
• the fineness of the third short fiber constituting the third batt layer 50 is not particularly limited, and it is, for example, equal to or more than 3.0 dtex and equal to or less than 150 dtex, preferably equal to or more than 6.0 dtex and equal to or less than 100 dtex, and more preferably equal to or more than 10 dtex and equal to or less than 70 dtex.
• the third batt layer 50 can have a sufficient strength and abrasion resistance.
• the weight of 1 m 2 of the third batt layer 50 is not particularly limited, and can be, for example, equal to or more than 50 g/m 2 and equal to or less than 200 g/m 2 . By this configuration, a moderate space for absorbing water under pressure can be maintained.
• the weight of 1 m 2 of the papermaking felt 1 is not particularly limited, and is, for example, in entirety, equal to or more than 250 g/m 2 and equal to or less than 3,000 g/m 2 , and preferably equal to or more than 400 g/m 2 and equal to or less than 2,000 g/m 2 .
• the thickness of the papermaking felt 1 is not particularly limited, and is, for example, equal to or more than 1.0 mm and equal to or less than 6.0 mm, and preferably equal to or more than 2.0 mm and equal to or less than 4.0 mm.
• FIG. 3 is a schematic diagram to illustrate the behavior of the papermaking felt and the wet paper web before and after pressing according to the present embodiment. Note that, although a single-felt press roll mechanism has been exemplified as a press device in the figure, a similar explanation can be made for a single-felt or double-felt shoe press mechanism, or for a double-felt press roll mechanism.
• the papermaking felt 1 carries the wet paper web W on its wet paper web carrying surface 41 and runs along the machine direction MD and passes through the press mechanism comprising press rolls 200A and 200B. At this time, in a region 201, the wet paper web W and the papermaking felt 1 are yet to enter the press mechanism and are not under pressure in the thickness direction.
• the papermaking felt 1 can suppress the rewetting phenomenon in the wet paper web and sufficiently reduce the water content of wet paper web after being pressed.
• FIG. 4 is a cross-sectional view in a machine direction showing a papermaking felt according to one modified example of the present invention.
• the papermaking felt 1A shown in FIG. 4 has a substrate 10, a first batt layer 20A, a nonwoven fabric 30A, and a third batt layer 50, and the second batt layer 40 is omitted. Furthermore, the nonwoven fabric 30A is arranged between the first batt layer 20A and the substrate 10. Such papermaking felt 1A can also suitably suppress the rewetting phenomenon.
• the papermaking felt 1 has been described as having an endless form, though the present invention is not limited thereto.
• the papermaking felt according to the present invention may be an ended band-shaped felt.
• seam loops are provided at the both machine direction ends of the papermaking felt. Then, the seam loops at both ends are engaged with each other, and a pintle wire is inserted into the seam loops to form an annular (endless) papermaking felt, which is then installed inn the papermaking machine.
• the method for manufacturing a papermaking felt according to the present invention comprises a step of laminating a nonwoven fabric and a short fiber on one side of the substrate and performing a needle punch treatment to form the nonwoven fabric and a batt layer consisting of the short fiber on the one side of the substrate, wherein the penetration resistance of the nonwoven fabric for the basis weight of 100 g/m 2 per one needle is 2.0 N / (100 g/m 2 x number of needles) or less.
• the method of manufacturing the papermaking felt 1 described in FIG.1 is explained as one example.
• the substrate 10 is prepared.
• a card of short fiber that will become the first batt layer 20, the nonwoven fabric 30, a card of second short fibers which will become the second batt layer 40, and a card of short fibers which will become the third batt layer 50 are prepared.
• these cards and the nonwoven fabric 30 are laminated together with the substrate 10.
• the cards, the substrate 10 and the nonwoven fabric 30 are laminated such that each layer of the papermaking felt 1 is formed in the order of the third batt layer 50, the substrate 10, the first batt layer 20, the nonwoven fabric 30, and the second batt layer 40.
• the number of cards and nonwoven fabrics 30 may be adjusted so as to provide the necessary basis weight.
• the needle punch treatment is carried out such that the cards, the nonwoven fabric 30 and the substrate 10 are entangled and integrated to give a precursor of paper felt 1. It should be noted that, in the present embodiment, it was explained that all of the cards, nonwoven fabric 30 and substrate 10 are laminated at once and collectively processed by needle punch treatment, but it is also possible that the cards are laminated one by one per layer onto the substrate 10 and subjected to needle punch treatment, and this process is repeated so that all layers are laminated and integrated.
• the nonwoven fabric 30 has a relatively small penetration resistance as mentioned above. Therefore, the dispersion of fibers of the nonwoven fabric 30 in the thickness direction in the needle punch treatment is suppressed, and the density of the nonwoven fabric 30 is maintained in a relatively high state. As a result, in the papermaking felt 1, too, the nonwoven fabric 30 can suitably suppress the rewetting phenomenon in the wet paper web.
• the precursor of the papermaking felt 1 is subjected to chemical treatment, heat set, press working, etc. as necessary, to give the papermaking felt 1.
• a woven fabric having the following configuration was prepared:
• Examples 1 to 4 a nonwoven fabric of cupra (official moisture regain: 11%; weight of 1 m 2 : 20 g/m 2 ; fiber diameter: 20 ⁇ m; a spun-bond nonwoven fabric processed by a water jet (hydroentanglement method)) was used, and the number of sheets was adjusted according to the required weight of 1 m 2 .
• Examples 4 to 8 a nonwoven fabric of rayon (official moisture regain: 11%; weight of 1 m 2 : 20 g/m 2 ; fiber diameter: 20 ⁇ m; a spun-bond nonwoven fabric) was used, and the number of sheets was adjusted according to the required weight of 1 m 2 .
• Example 9 a nonwoven fabric of lyocell (official moisture regain: 13%; weight of 1 m 2 : 20 g/m 2 ; fiber diameter: 16 ⁇ m; a spunlace nonwoven fabric) was used, and the number of sheets was adjusted according to the required weight of 1 m 2 .
• Example 13 to 15 a nonwoven fabric of nylon (official moisture regain: 4.5%; weight of 1 m 2 : 20 g/m 2 ; fiber diameter: 18 ⁇ m; a spun-bond nonwoven fabric) was used, and the number of sheets was adjusted according to the required weight of 1 m 2 .
• nylon official moisture regain: 4.5%; weight of 1 m 2 : 20 g/m 2 ; fiber diameter: 18 ⁇ m; a spun-bond nonwoven fabric
• the cards of the third batt layer, the substrate, the first batt layer, and the second batt layer were laminated in this order, and needle punch treatment was performed on them to produce papermaking felts of Examples 1 to 15 and comparative examples.
• the needle punching density was 4000 times/inch 2 (3000 times/inch 2 on the front surface and 1000 times/inch 2 on the back surface).
• the needle penetration resistance was measured for each of the nonwoven fabrics used in Examples 1 to 15.
• the penetration resistance was measured by performing a compression test using the tensile testing machine shown in FIG. 2 . Specifically, several nonwoven fabrics 30 sandwiched by fixing plates 109 were fixed to a jig 101B. Here, the number of the nonwoven fabrics 30 to be laminated was adjusted such that their weight of 1 m 2 becomes about 100 g/m 2 .
• needles 103 were moved to the nonwoven fabric 30 side using the tensile testing machine to penetrate the first barb of the needles into the nonwoven fabric 30.
• the maximum value of the resistance force loaded on the needles 103 at this time was set as the penetration resistance.
• the number of needles was 54, the area in which needles are implanted was 602 cm 2 , the density of needles implanted was 0.090 cm/cm 2 , and the moving speed of the needles 103 was 200 mm/min.
• needles used had a needle count of 32nd, a point diameter of 0.08 mm, a point-to-first barb distance of 6.35 mm, a barb depth of 0.09 mm, a kick-up of 0.01 mm, and a barb length of 0.5 mm.
• R is the penetration resistance of the nonwoven fabric 30 for the basis weight of 100 g/m 2 per one needle [N / (100 g/m 2 x number of needles)]
• R T is the maximum resistance force [N] of the nonwoven fabric 30 at the time of penetration of the needle 103
• W NWF is the total basis weight (g/m 2 ) of the nonwoven fabric 30
• N NDL is the number of the needles 103.
• FIG. 5 is a schematic diagram to illustrate the method for testing water-squeezing property.
• a papermaking felt F according to any one of Examples 1 to 15 and Comparative Example that was cut out to have a diameter of 7 cm was placed, and the moisture content of the papermaking felt F was adjusted to 30%.
• the moisture content is the mass of water divided by the sum of the mass of papermaking felt and the water.
• a metal top plate 302 (6 kg) was allowed to fall freely from 20 cm above the wet paper web W to press it.
• the pressing pressure at this time had been adjusted to be 50 kg/cm 2 .
• the top plate 302 which has been made to fall freely rebounds and moves upwards upon hitting the wet paper web W. Therefore, the test was conducted by fixing the top plate 302 at the time when the top plate 302 moves upward after the first pressing so that the second press is not performed.
• the water content of the wet paper web W after pressing was calculated from the mass of wet paper web W after pressing, the water amount in wet paper web W (the dry weight of the wet paper web W being subtracting from the weight of the wet paper web W) and the dry weight of the wet paper web W, and the dryness ⁇ K (%) was calculated as a value obtained by subtracting the water content of the wet paper web W after pressing from 100.
• the dryness ⁇ K (%) represents the degree of the moisture content reduced by pressing.
• a 1% reduction in the moisture content of wet paper web in the press part can reduce the energy required for drying in the dryer part in the later stage by about 4%.
• the obtained dryness ⁇ K (%), and the estimated reducible energy for drying from the Comparative Example calculated based thereon are shown in Table 1.

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