WO2000077286A1 - Method for producing a nonwoven material, installation therefor and resulting nonwoven - Google Patents

Abstract

The invention concerns a method and an installation for producing a spunbonded fabric, characterised in that it consists in: producing a spunbonded lap (5) against the surface of which is delivered at least a web (V1 and/or V2) of discontinuous fibres, obtained by carding. The formed complex is compacted by pressing and is continuously transferred onto a line (10) for water jet binding treatment, driving the fibres in the direction of thickness, the fibres which are bound together like a splice between and around the continuous filaments while remaining visible at the surface. After drying, the final product is obtained.

Description

PROCESS POTTR THE REALTSATTON OF TTN MATERTATT NON TTSSF,

TNSTAEUATTON FOR ITS MTSE IN WORK AND NOT TTSSF ATNST

GOT.

T) nmaine Technique

For decades, it has been proposed to replace traditional textile tablecloths (fabrics, knits) by so-called "non-woven" structures which, in general, can be classified into three main categories, resulting from their very process. manufacturing, namely: _ non-woven fabrics known as "wet" produced using a technology close to the manufacture of paper; _ nonwovens known as "dry" made of staple fibers, natural or chemical, obtained by carding, coating or any other material for textile preparation; _ nonwovens known as “melted” made up of continuous chemical filaments and commonly designated under the generic name of “spunbond”.

The present invention relates to an improvement made to the technology allowing such spunbond type nonwoven plies to be produced and more specifically relates to a process, an installation and a new type of product obtained by the use of these means, product having the appearance and the properties such as touch, mechanical characteristics, flexibility, close to a conventional textile, fabric in particular.

Previous techniques

The production of non-woven “spunbond” type tablecloths dates back to decades, as is evident in patents GB-A-932 482, US-A-3 286 896 which are among the oldest documents describing it.

Generally, such a technique consists of:

_ extruding a molten or even dissolved organic polymer through a die pierced with holes, so as to form a bundle or curtain of filaments;

_ then, to orient the extruded filaments by drawing by means of one or more fluid jets devices, in particular with compressed air, _ and finally, to receive the bundle of filaments in the form of a sheet on a movable conveyor belt, generally subjected to a source of suction, and the speed of which is adjusted according to the characteristics which it is desired to obtain, grammage in particular.

After production, and in general continuously, the sheet is consolidated, for example by performing a calibration or calendering, preferably hot, so that the elementary filaments are linked to each other.

As a result, such “spunbond” nonwovens, which have very good mechanical characteristics equivalent to conventional fabrics, have found wide development in many technical sectors, for example with a view to using them as coating substrates, elements reinforcement of complexes used in particular for producing laminates, technical products such as waterproofing coatings, as anti-contamination layers in the field of public works, for many applications as geotextiles ...

On the other hand, their use in the field of conventional textile applications, such as clothing, disposable clothing, wiping materials, furniture, interior textiles, etc., has not developed, because a bond by calendering, which results in a partial thermofusion of the fibers, without deteriorating the mechanical characteristics of the product, on the other hand destroys the flexibility, the feel and the textile appearance.

In the context of the consolidation of “spunbond” plies, in addition to a calibration or calendering treatment as mentioned above, it has also been envisaged to subject such plies to a needling treatment, either conventional by means of barbed needles. , or by jets of fluid.

Such treatments are frequently used when it is desired to produce complexes consisting of a superposition of discontinuous fibrous plies possibly comprising an internal reinforcement, such as a fabric, knitted fabric, unidirectional or bidirectional ply consisting of one or more series of threads. parallel or not. On the other hand, at least to the knowledge of the Applicant, these needling techniques have never been proposed with a view to solving the problem of consolidating a “spunbond” sheet as such, while communicating with such a sheet. the characteristics of flexibility, feel ... of conventional textiles

Indeed, if a needling treatment with barbed needles was applied to a “spunbond” ply alone, this can cause the continuous filaments which constitute such a ply to break and, consequently, it can deteriorate the mechanical characteristics which are 'one of the main advantages of such materials.

Regarding the use of a conventional binding treatment by fluid jets, in particular water, such a technology is not suitable. Indeed, it is well known that in such spunbond plies consisting of continuous filaments, these are difficult to move relative to each other. Consequently, it is practically impossible to envisage obtaining with such a technology a “spunbond” sheet having a cohesion comparable to that which is obtained by calendering, without affecting the mechanical properties of the material.

Show the invention

However, we have found, and this is the subject of the present invention, an improved process which makes it possible to produce such nonwoven plies of the “spunbond” type, perfectly bonded, having high mechanical characteristics (resistance to traction, tear ...) equivalent to "spunbond" sheets consolidated by hot calendering, and which, moreover, have the appearance, feel and flexibility of a conventional textile, such as a fabric.

In general, the process according to the invention making it possible to obtain a nonwoven of the “spunbond” type having the appearance and the properties of a conventional textile, consists, continuously:

_ producing a “spunbond” type sheet, the bundle of extruded and drawn continuous filaments being received on a movable conveyor belt in the form of an unbound sheet; _ to deliver, against at least one face of the “spunbond” sheet thus formed, a veil of staple fibers - natural and / or artificial and / or synthetic - obtained by carding or other conventional technique; _ compacting the complex thus formed by pressing; _ to transfer, always continuously, said complex onto a binding treatment line by means of water jets, acting against the surface or surfaces of the complex consisting of staple fibers, entraining said fibers in the thickness direction, fibers which bind like a splice between and around the continuous filaments while remaining visible on the surface; _ to carry out a drying treatment;

_ then receive the finished product.

It should be noted that, in accordance with the invention, before carrying out the hydraulic tying operation, compaction is carried out by pressing of the assembly constituted by the supeφosition of the layer or layers of staple fibers which cover or trap between them the "spunbond" tablecloth produced.

Such compaction, which can be carried out by any suitable means, such as in particular by means of a pressing roller, can in no case be assimilated to a calendering operation since it is carried out cold.

According to the invention, a single veil of staple fibers can be associated with the veil with the “spunbond” type web, said veil of staple fibers being able to be delivered either upstream of the zone of formation of the “spunbond” veil and being brought on the conveyor belt on which are deposited the filaments coming from the “spunbond” installation, filaments which are therefore distributed on the surface of this veil, that is to say, delivered downstream of the zone of formation of the veil of continuous filaments.

According to an embodiment proper, the “spunbond” type sheet is covered on its two faces by a veil of discontinuous fibers, produced one upstream of the zone of formation of the “spunbond” veil, the other downstream , the web of continuous filaments thus being trapped sandwiched between the two layers of staple fibers. In such a case, the complex thus made up of three layers is, after compacting by pressing, transferred, always continuously, onto a binding treatment line by means of water jets, jets which act successively against the surfaces of said complexes entraining the staple fibers in the thickness direction, fibers which bond in the manner of a splice between and around the continuous filaments while remaining visible on the two outer faces.

Furthermore, after the binding operation by water jets and before drying, it is possible to carry out an additional “texturing” treatment (carried out for example in accordance with the teachings of patent EP-059 608), consisting in transferring the complex linked on a conveyor constituted by a coarse cloth and to subject the tablecloth to the action of water jets obtained by the intermediary of an assembly essentially comprising a rotary perforated drum, inside which is disposed a fuel injector in pressurized water, this assembly producing jets reorienting the fibers, a suction assembly for removing water being provided below the conveyor.

The invention also relates to an installation allowing the continuous implementation of the above method.

Generally, such an installation comprises, arranged in line:

_ a formation assembly, on a conveyor belt, of a web of continuous spunbond type filaments; _ at least one card or other equivalent system making it possible to deliver against at least one face of the “spunbond” sheet produced a web of staple fibers;

_ means for pressing the complex formed, followed by a treatment zone by means of jets of fluid, acting at least against the surface covered with staple fibers and driving said fibers in the thickness direction, fibers which bind to the way of a splice between and around the continuous filaments, while remaining visible on the surface;

_ means for drying and receiving the bound complex. Optionally, such an installation comprises, between the means of binding by water jets and the drying means, a set of texturing producing jets redirecting the fibers.

Compared to the “spunbond” sheets produced previously, the article obtained is characterized in that the continuous filaments which compose it are associated with discontinuous fibers, fibers which cover the sheet based on continuous filaments and penetrate inside this. the latter by binding around said filaments.

Such a product retains all the mechanical characteristics of resistance of conventional spunbond plies, the cohesion of which is given by a calendering treatment, the product obtained also having the appearance and the properties such as feel and flexibility comparable to a conventional textile.

It should be noted that the staple fibers which are associated with the spunbond layer, can be of any type, natural or chemical, hydrophobic or hydrophilic, depending on the applications for which the product is intended, the length of said fibers being between 5 mm and 60 mm and their titer between 0.8 dtex and 6.6 dtex.

Concerning the grammage of the veil (s) of staple fibers which are associated with the spunbond batt, it may vary depending on the applications, but will advantageously be between 10 g / m2 and 50 g / m2, a batt having a lower grammage at 10 g / m2 which does not allow correct binding of the spunbond ply, while a ply greater than 50 g / m2 reduces the economic advantage of the process.

Brief description of the drawings The invention and the advantages which it provides will however be better understood thanks to the description which follows and which is illustrated by the appended figures in which:

_ Figure 1 illustrates, seen from the side, an entire production line for implementing the method according to the invention; _ Figure 2 is also a side view, showing in more detail how the binding operation is carried out by means of water jets and any additional texturing treatment.

Way of realizing the invention

Referring to the appended figures, the invention therefore relates to a method and an installation which makes it possible to produce, continuously, a new type of “spunbond” plies made of continuous synthetic filaments, plies which not only retain the properties of mechanical resistance ( elongation, tensile strength, tear resistance ...), equivalent to conventional "spunbond" plies consolidated by hot calendering and which, moreover, have the appearance, feel and flexibility of a conventional textile such than a fabric.

In accordance with the invention, on an installation intended by the general reference (1), a “spunbond” type nonwoven sheet is produced according to the conventional technique which consists in extruding a molten organic polymer, through a die (2) pierced with holes so as to form a bundle or curtain of filaments (3).

After cooling, making it possible to obtain at least superficial solidification of the extruded filaments (3), these are oriented and drawn by means of one or more devices (4) with jets of fluid at the outlet of which they are distributed. on a receiving surface in the form of a sheet (S).

In accordance with the invention, in order to consolidate the “spunbond” sheet (S) thus formed and to give cohesion to this sheet and high mechanical characteristics of tensile and tear resistance while giving it an appearance, a feel and the flexibility of a conventional textile, the “spunbond” sheet (S) is received not directly on the surface of a conveyor belt (5) subjected to a suction source, but, on a veil (NI) of fibers discontinuous - natural and / or artificial and / or synthetic - produced immediately upstream of the “spunbond” installation (1).

This veil (NI) is for example produced by means of a conventional assembly (6) consisting of a card possibly associated with a lapper spreader assembly, the veil (NI) produced being delivered to the conveyor belt (5) of the “spunbond” installation (1) by a supply assembly also consisting of a conveyor belt (7).

The two textile layers (NI) and (S) supeφosées then pass, still being held on the conveyor belt (5), on a first assembly (8), constituted for example by two cylinders to ensure compaction.

By means of a second assembly (9), such as a card or other equivalent installation, the three textile layers are delivered to the surface of the spunbond ply (S), a second web (N2) of staple fibers. elementary supeφoses (NI, S and N2) being compacted again by pressing between two cylinders (8).

Still continuously, the compacted assembly is then brought to a treatment line, illustrated in more detail in FIG. 2, designated by the general reference (10) enabling said complex to be subjected to a binding treatment by means of jets of water, acting successively against the two surfaces of said complex.

In the embodiment described, such a treatment assembly (10) is constituted by a hydraulic binding unit of the “Jetlace 2000” type marketed by the Applicant and implementing the teachings of FR-A-

2,730,246 (US-A-5,718,022), and FR-A-2,734,285 (US-A-5,768,756) on behalf of

Applicant.

Such a binding unit essentially consists of a conveyor (11) onto which the fibrous structure constituted by the three supeφosed layers (NI, S and N2) is transferred.

As can be seen more particularly from FIG. 2, the structure is compacted between the conveyor (11) and a first suction cylinder (12), preferably coated with a microperforated envelope, the holes of which are arranged randomly as described in French patent 2,734,285.

In another embodiment, this cylinder can be covered with a wire mesh. Optionally at the level of the compaction zone between the surface of the conveyor (11) and that of the cylinder (12), the complex sheet (N1 / S / N2), designated in the following description by the reference (Ν), can receiving a first wetting treatment, by means of a ramp (13), illustrated in dotted lines in FIG. 2, and which delivers a curtain of water which passes through the conveyor belt (11) as well as the supeφosed layers.

However, such a wetting operation is not essential.

The compacted complex, supported by the suction drum (12), is then subjected to the action of water jets coming from an injector (14), the jets therefore acting against the surface formed by the fibrous web (NI) and entraining the fibers which constitute this veil inside the complex.

The ramp or injector (14) arranged parallel to a generator of the cylinder (12), is a conventional ramp which makes it possible to create jets or needles of water having a diameter of 100 to 170 microns, the jets being spaced from each other with a value between 0.5 and 2.2 mm, the supply pressure itself between 50 and 150 bars depending on the grammage of the complex.

Optionally, it can be envisaged to perform a second treatment by jets on this first cylinder (12) by means of a second injector.

At the outlet of this cylinder (12), the treated complex is brought to the surface of a second cylinder (15), identical to the previous suction cylinder, associated with one or two series of injectors (16,17) delivering jets of water which therefore act on the face of the sheet (Ν) formed by the web (N2).

During this second consolidation treatment, the ramps (16,17) create jets or needles of water having a diameter of 100 to 170 microns, said jets being spaced as before from each other between 0.5 and 2.4 mm, and the supply pressure being between 50 bars and 400 bars. The action of the injectors (16,17) therefore makes it possible to entrain the fibers of the NI veil in the thickness of the sheet (Ν), said fibers surrounding the continuous filaments and binding to the latter.

At the exit of this assembly, the linked spun web, designated by the reference (18) can be brought directly to the drying assembly (19) by passing over a conventional heating drum (26) before being received.

Optionally, and as can be seen from the appended figures, a third hydraulic binding treatment can be carried out by means of a third suction drum (20) associated with a ramp of injectors (21), the jets of which act against the face which was constituted by the veil (NI).

After this last treatment, an additional texturing treatment can possibly be carried out. Such treatment consists, as more particularly of FIG. 2, of transferring the linked “spun” ply (18) onto an assembly produced for example in accordance with the teachings of patent EP 059

608.

In general, such an assembly is constituted by a conveyor belt (22), of the "Fourdrinier" type, used in the paper industry. The linked spun (18) maintained on this canvas, is subjected to the action of a series of water jets obtained by means of a ramp (23) projecting a curtain of water against the internal surface of a perforated rotary cylinder (24), these jets redirect the fibers.

A suction assembly (25) for removing water is of course provided below the conveyor (22).

Thanks to such an installation, it is possible either to produce complexes in which the “spunbond” type nonwoven veil is associated with two veils made of staple fibers, all of the means described above being implemented, or to produce articles in which the “spunbond” type veil is associated with a single veil of staple fibers which can be distributed either upstream or downstream of the zone of formation of the “spunbond” veil. Example 1

This example uses the realization of a complex in which the veil the "spunbond" sheet is trapped between two veils of staple fibers.

Such a product is produced in accordance with the invention in the following manner:

By means of a conventional card (6), a veil of fibers (NI) weighing 30 g / m ² and composed of 100% viscose fibers of 1.7 dtex and 38 mm in length is produced.

This veil is produced at a speed of 100 m / minute.

At the outlet of the card (6), the web (NI) is transferred to the receiving mat (5) of the installation (1) for producing a ply (S) of the "spunbond" type.

The “spunbond” sheet produced is obtained from polypropylene and is distributed over the web (NI) so as to form a sheet made up of filaments having a titer of 1.7 dtex, weighing 40 g / m ² .

The two superposed layers (NI) and (S) are compressed by means of a pressing cylinder (8) and a second veil of fibers (N2) reproduced in a similar manner to the veil (NI), weighing 30 g / m ² , is delivered to the surface of the tablecloth

"Spunbond" (S), the supeφosed layers then being subjected to a new compaction also by means of a pressing cylinder.

Continuously, the complex formed is brought to a treatment line comprising a hydraulic binding unit (10) of the “Jetlace 2000” type, sold by the Applicant.

Such an installation essentially comprises a conveyor belt (11), and three sets of treatment by jets comprising suction cylinders

(12,15,20) having a diameter of 516 mm and coated with a microperforated envelope whose holes are distributed randomly as described in French patent 2,634,285. To these suction drums (12,15,20) are associated with ramps injectors (14,16,17,21) which act against the surfaces of the complex (N) constituted by the supeφosition of the veil (NI) of the spunbond (S) and the veil (N2).

The arrangement of these injectors is such that one acts successively against the opposite faces of the complex (Ν).

The ramps (14,16,17,21) all produce 1666 jets per meter and are adjusted as follows.

Downstream of the last hydraulic tying system (20), there is disposed a texturing assembly constituted by a conveyor belt (22) made of a polyester fabric, associated with a texturing assembly proper comprising a rotary perforated drum (24) with inside which is arranged an injector (23) supplied with water at 150 bars.

This injector (23) produces water jets of 130 μm in diameter which redirect the fibers. The water coming from the injector (23) is recovered by means of the suction assembly (25) arranged below the conveyor (22).

By proceeding under the aforementioned conditions, a sheet according to the invention is obtained at the outlet of the installation which, after drying on a heating drum, weighs 95 g / m ² .

This sheet is perfectly bonded and has great flexibility, feel, appearance and mechanical characteristics comparable to a traditional textile of equivalent grammage obtained with fibers of the same kind. Example 2

This example illustrates the implementation of the method according to the invention for the production of a structure composed of a “spunbond” type sheet associated with a single fibrous sheet which, in this embodiment, is formed upstream of the spunbond formation area.

In accordance with the invention, the procedure is as follows.

By means of a conventional card (6), a veil of fibers (NI) weighing 20 g / m2 is produced, composed of 100% viscose fibers of 1.7 dtex and 38 mm in length.

This veil is produced at a speed of 150 m / min.

On leaving the card (6), the web (NI) is transferred to the receiving mat (5) of the spunbond unit.

A spunbond sheet (S) made of polypropylene filaments is deposited on the web (NI).

This 25 g / m2 spunbond tablecloth is made of 2 dtex filaments.

The two superposed layers (NI) and (S) are compressed by means of a pressure roller (8) thus forming a complex of 45 g / m2 which is transferred continuously onto a hydraulic binding unit (10) of the “Jetlace” type. 2000 ”marketed by the Applicant.

This installation comprises a conveyor belt (11) and two sets of treatment by water jets consisting of suction cylinders (12) and (15) followed by a final conveyor (22) on which is placed a patterning / texturing device.

The two cylinders (12) and (15) are covered with a microperforated envelope, the holes of which are arranged randomly as described in French patent 2,634,285. These cylinders are associated with injector ramps (14) (16) (17).

The arrangement of these injectors is such that one acts successively on both sides of the complex.

The injectors produce all 1,666 water jets of 120 microns per meter and the water pressure in these injectors is 60, 80 and 110 bars respectively.

The bonded complex is textured on the preceding cylinders by a perforated drum (23) as described in the previous example, the injector of which is supplied at a water pressure of 80 bars.

After drying, the final product of 45 g / m2 has excellent mechanical characteristics, superior to those of a spunlace veil made of fibers of the same kind.

The aspect and the flexibility of the veil are also remarkable, very superior to those of a spunbond in polypropylene or polyester of equivalent grammage bound by calendering.

Claims

1/ Process for producing a “spunbond” type nonwoven having the appearance and properties of a conventional textile which consists, continuously: _ in producing a sheet (5) of the “spunbond” type, the bundle of continuous filaments extradited and stretched being received on a mobile conveyor belt in the form of an unbound sheet; _ to deliver, against at least one face of the “spunbond” sheet thus formed, a veil (NI and/or N2) of discontinuous fibers, natural and/or artificial and/or synthetic, obtained by carding or other conventional technique; _ to compact by pressing the complex thus formed; _ to transfer, always continuously, said complex to a binding treatment line (10) by means of water jets, acting against the surface(s) of the complex made up of discontinuous fibers, driving said fibers in the direction thickness, fibers which bind like a splice between and around the continuous filaments while remaining visible on the surface; _ to carry out a drying treatment; _ then receive the finished product. 2/ Method according to claim 1, characterized in that the sheet (5) of the "spunbond" type is covered on both sides by a veil (N1/N2) of staple fibers, one (NI) being produced directly in upstream of the “spunbond” web formation zone and being brought onto the conveyor belt (11) on which the filaments coming from the “spunbond” installation are deposited, said filaments therefore being distributed over the surface of this web (NI) , the second (N2) being delivered downstream of the zone of formation of the sheet of continuous filaments which is thus trapped in a “sandwich” between the two fibrous layers (N1,N2), the complex thus formed being, after compaction by pressing, transferred, always continuously, to a line (10) for binding treatment by means of water jets, acting successively against the surfaces of said complex and driving the staple fibers in the direction of the thickness, fibers which bind like a splice between and around the continuous filaments while remaining visible on the two exterior faces. 3/ Method according to one of claims 1 and 2, characterized in that, after the water jet binding operation and before drying, an additional “textilization” treatment is carried out. 4/ Method according to claim 3, characterized in that the textilization treatment consists of transferring the bonded complex onto a coarse canvas (22) and subjecting the web to the action of water jets obtained by means of an assembly essentially comprising a rotating perforated drum (24) inside which is arranged an injector (23) supplied with water under pressure, this assembly producing jets reorienting the fibers, a suction assembly (25) for elimination water being provided below the conveyor. 5/ Installation for producing a “spunbond” type nonwoven comprising, arranged in a line: _ an assembly (1) for forming, on a conveyor belt (5), a sheet (S) continuous filaments of the “spunbond” type; _ at least one card (6 and/or 9) or other equivalent system making it possible to deliver a veil against at least one face of the “spunbond” sheet produced (NI and/or N2) of staple fibers; _ means for pressing the complex formed followed by a treatment zone (10) by means of jets of fluid, acting at least against the surface covered with discontinuous fibers and driving said fibers in the direction of the thickness, fibers which are bind like a splice between and around the continuous filaments, while remaining visible on the surface; _ means of drying and receiving the bound web. 6/ Installation according to claim 5, characterized in that it comprises between the means (10) for binding by water jets and the drying means, a textileization assembly comprising a coarse canvas (22) intended to support the complex linked, associated with a rotating perforated drum inside which is arranged an injector (23) supplied with water under pressure, this assembly producing jets reorienting the fibers, a suction assembly (25) for the elimination of water being placed below the conveyor. 11 Installation according to one of claims 5 and 6, characterized in that it comprises, upstream and downstream of the zone of formation of the sheet “spunbond”, means (6.9) making it possible to produce a veil of fibers, the veil (NI) upstream product being distributed on the conveyor belt (5) of the line "spunbond", the extradited and stretched bundle of filaments being received directly on said web, the second (N2) being placed downstream of the zone of formation of the "spunbond" web and being distributed on the surface of the latter. 8/ non-woven fabric obtained by implementing the method according to one of claims 1 to 5, characterized in that it consists of a sheet made from continuous filaments associated with discontinuous fibers, fibers which cover at least one face of the sheet based on continuous filaments and penetrate inside the latter by binding around said filaments.