EP0772705B1 - Apparatus for producing fluid jet-bonded non-woven webs - Google Patents

Abstract

PCT No. PCT/FR96/00227 Sec. 371 Date Mar. 5, 1997 Sec. 102(e) Date Mar. 5, 1997 PCT Filed Feb. 13, 1996 PCT Pub. No. WO96/27040 PCT Pub. Date Sep. 6, 1996Apparatus for the production of a nonwoven material wherein a web of material is drawn over a series of parallelly aligned porous rolls. The web is treated with a jet of pressurized water as it moves in contact over each roll. The web is compressed between the first roll in the series and is wetted by a curtain of water as it is being compressed to increase the density of the web material prior to its being treated with the pressurized jets of water.

Description

The present invention relates to an improvement made to installations allowing the production of non-woven fibrous webs, the cohesion of which is obtained by intermingling of fibers in the thickness of said web thanks to the action of jets of fluid, and more particularly of jets of pressurized water.

It has been proposed for a long time _, as is apparent from US-A-3 214 819 and US-A-3 508 308, (which serves as the basis for the preamble of claim 1), to realize nonwoven textile webs in which cohesion is given by the interlacing of the elementary fibers between them, interlacing obtained by the action of pressurized water jets which act on the fibrous structure in the manner of needles and allow to redirect a part of the fibers constituting the sheet in the thickness direction.

Such technology has been widely developed these days and is used not only for making nonwoven fabrics for textile use, such as in particular for applications in the medical or hospital fields, wiping, filtration, envelopes for tea bags ..., but also for making tiny perforations in continuous supports, such as paper, cardboard, films, or even sheet of plastic or other material, the articles obtained possibly having hollow patterns or in relief as shown in particular from FR-A-2 068 676, FR-A-2 536 432, EP-A -0 400 249.

As is apparent from US-A-3,214,819 which, to the knowledge of the Applicant, is the basic patent on such technology, the action of water jets can be exerted in different ways against article which is treated, either for example against only one of its faces, or successively against the two faces. The lessons brought by this document are however essentially theoretical and the indications given concerning the practical conditions of treatment do not allow a satisfactory industrial production. Thus, when it is envisaged to carry out a binding by acting alternately against the two faces, one of the phases of the treatment is done through the fabric supporting the fibrous web. Such a procedure results in very high energy absorption of the water jets by the support fabric when the latter opposes the passage of said jets as well as a separation of the fibrous structure from the surface of said support fabric, the jets repelling the fibrous structure, resulting in an elongation of the latter and the formation of folds.

In view of these drawbacks, the installations proposed to date for carrying out a treatment on both sides of the basic product are of the type described in US Pat. No. 3,508,308 (see in particular FIGS. 7 and 8 and corresponding description ), and are designed so that the basic fibrous structure passes through a succession of actual interlacing zones each consisting of a rotary perforated cylinder associated with a plurality of injectors (three successive ramps for each rotary cylinder in the example illustrated) which make it possible to act first against one of the faces of the product, then, by means of detour provided between two successive cylinders, to act then on the reverse side and, possibly , to carry out a third treatment on the right side before drying and receiving the product produced.

In general, the successive ramps are adjusted to different pressures depending on the articles to be produced, pressure generally between 30 and 100 bars or more.

• un encombrement en longueur important,
• et surtout, la nécessité d'effectuer la première série de traitements d'entrelaçage sur une face avec une pression réduite pour éviter que les fibres ne ressortent sur l'autre face et créent des défauts ; en effet, si la pression est élevée, les fibres de la face non liée ont tendance à pénétrer dans la toile support du premier cylindre ; il est donc nécessaire, pour compenser la moindre efficacité de liage résultant de cette pression réduite, d'augmenter le nombre de rampes de traitement (désignées couramment par l'expression "injecteurs"), ce qui augmente notablement le coût de l'installation, complique la mise en oeuvre industrielle et entraîne une dépense d'énergie et de consommation en eau élevée.

Such installations which give satisfaction from a practical point of view, however have a certain number of drawbacks among which we can cite:

• a significant overall length,
• and above all, the need to carry out the first series of interlacing treatments on one side with reduced pressure to prevent the fibers from coming out on the other side and creating defects; in fact, if the pressure is high, the fibers of the unbound face tend to penetrate into the support fabric of the first cylinder; it is therefore necessary, to compensate for the lower binding efficiency resulting from this reduced pressure, to increase the number of treatment ramps (commonly referred to as "injectors"), which significantly increases the cost of the installation, complicates industrial implementation and results in high energy and water consumption.

However, we have found, and this is the subject of the present invention, an improved installation which makes it possible to carry out such treatment by jets of fluid making it possible to give cohesion to nonwoven fibrous sheets, which can be base of natural, synthetic fibers, alone or in mixture, or constituted by the association of nonwoven plies and internal reinforcement, such as textile grids, fabrics, knits, woven plies, longitudinal reinforcements ...

The installation in accordance with the invention not only makes it possible to adapt the treatment conditions much more easily to each type of textile structure, leads to surface appearances after the action of the fluid much more regular and above all allows, for equivalent articles, lead to reduced water consumption and a lower number of passages under the interlacing ramps.

Furthermore, the installation according to the invention also makes it possible to treat fibrous webs of a higher grammage than conventional installations where a series of successive interlacing treatments is carried out on each of the faces of the article. In fact, in conventional machines, when the fibrous webs have a weight greater than 100 g / m2, and in particular when they are made of low denier fibers, it has been observed that surface appearance defects are produced (raised and recessed areas) which makes them unsuitable for most applications.

In general, the installation according to the invention comprises, in a known manner, means making it possible to compress, and introduce a fibrous sheet inside a treatment zone in which the moving sheet is subjected to the action of a succession of ramps of pressurized water jets which act alternately against the two faces of said sheet, said installation being characterized in that the interleaving means consist of at least one series of perforated cylinders , each cylinder being associated with a ramp (or injector) projecting jets of water under pressure against the surface of said sheet, said ramps being staggered from one treatment cylinder to the next, the jets acting perpendicularly against the surface of the processed product and the peripheral speed of the cylinders increasing slightly from one treatment cylinder to the next.

The increase in speed from one treatment cylinder to the next keeps the sheet under tension during the succession of treatment phases, and leads to the elimination of surface defects which appear on conventional machines. As an indication, an increase in speed of between 0.5 and 3% is suitable for most grammages of treated webs.

According to an embodiment according to the invention, the installation comprises four superposed treatment rollers each associated with a ramp projecting jets of water under pressure against the surface of the material, the first cylinder if we consider the cycle of production being associated with means making it possible to ensure densification of the untreated basic fibrous web.

Such means for ensuring densification consist essentially of a porous endless conveyor belt which supports the material and which is in tangential abutment against the surface of the first rotary perforated cylinder inside which a partial vacuum is applied and which allows therefore compressing the base ply before it is subjected to the action of the first ramp of pressurized jets; in this embodiment, when the base ply is compressed between the conveyor belt and the rotary perforated cylinder, the said ply is wetted by means of a curtain of water, produced by means of an additional ramp disposed inside the volume defined by the conveyor belt, which is directed against the surface of the latter and which passes successively through said porous belt, the compressed sheet before being sucked through the perforated cylinder.

If, for most applications, two successive treatments on each of the right and wrong sides allows good results to be obtained, it may be envisaged, in a variant of an installation according to the invention, to carry out a second series of alternating treatments by means of a second set of perforated cylinders and superimposed injectors arranged opposite the first series of treatment elements.

Thanks to such a design, it is not only possible to obtain a very compact installation making it possible to carry out interlacing treatments of the sheet in which one acts alternately against each face of the basic product, but, moreover, it has been found that when such an installation included compaction means with pre-wetting, it was possible to reduce the number of treatment ramps compared to a similar product produced on conventional installations in which several successive interlacing treatments are carried out on one of the faces of the support, then on the other face.

It is obvious that it is not going beyond the ambit of the invention to produce an installation in which the cylinders are not arranged in a superimposed manner, but side by side, the ramps or injectors acting, in accordance with the invention, alternately against each side of the fibrous web.

• la figure 1 est une vue schématique en perspective montrant la structure générale d'une installation réalisée conformément à l'invention ;
• la figure 2 est une vue de détail en perspective montrant la structure d'une zone élémentaire de traitement d'entrelaçage que comporte une telle machine.

The invention and the advantages which it brings will however be better understood thanks to the embodiment given below by way of indication but not limitation, and which is illustrated by the appended figures in which:

• FIG. 1 is a schematic perspective view showing the general structure of an installation produced in accordance with the invention;
• FIG. 2 is a detailed perspective view showing the structure of an elementary interlacing treatment zone that such a machine comprises.

Referring to the attached diagrams and more particularly to Figure 1, the installation according to the invention comprises, if one follows the direction of production of the article, means designated by the general reference (1) which allow to produce, compress and introduce a fibrous web (2) inside a treatment zone proper designated by the general reference (3), zone in which the moving web (2) is subjected to the action of '' a succession of ramps of pressurized water jets, ramps designated by the same reference (R) assigned an index and which act alternately against the two faces (N) and (S) of said ply (2), ply which, after treatment, is taken up by an evacuation assembly, designated by the general reference (4) where additional treatment may possibly be applied to it.

As can be seen from the appended FIG. 1, according to a characteristic of the invention, all the perforated cylinders (C1, C2, C3, C4) of the treatment zone, are mounted superimposed with respect to each other, each cylinder being associated with a ramp of injectors (R1, R2, R3, R4) projecting jets of water under pressure against the surface of the sheet (2), said ramps being staggered from one treatment roller to the next and the jets acting perpendicularly against the surface of the product to be treated. Furthermore, the peripheral speed of the cylinders (C1, C2, C3, C4) is adjusted so that it gradually increases from one cylinder to the next in order to ensure the tensioning of the sheet during the various phases of the treatment. Such a machine design therefore makes it possible to easily carry out an alternating treatment against the faces (S) and (N) of the product.

In the exemplary embodiment illustrated, a second series of perforated cylinders (C5, C6, C7) associated with ramps (R5, R6, R7) is arranged in parallel and facing the first series. This second series. ramps is not essential and possibly, it could be envisaged to receive the treated product immediately at the exit of the last interlacing treatment zone constituted by the cylinder (C4) and the ramp (R4).

Each treatment assembly (C) and ramp (R) has a structure as illustrated in FIG. 2.

The perforated cylinder (C) consists of a cylinder, preferably of stainless steel, having a diameter between 200 mm and 1000 mm, and is rotated by any suitable means so as to have a peripheral speed equal to the speed d entry of the material (2) into the installation. In general, this speed is between 10 m / min and 200m / min and the increase in speed from one cylinder to the next is of the order of 0.5 to 3%.

The perforations (10) that the cylinder has are cylindrical or honeycomb, said cylinder advantageously being covered with a fabric made of steel or plastic monofilament or of a perforated sheet having a porosity of between 3 and 20% (element not shown in Figure 2). The ramp or injector (R) which is arranged parallel to a generator of the cylinder (C) is a conventional ramp making it possible to create jets or needles of water (11) with a usual pressure of at least 30 bars, sometimes more, so as to cause the elementary fibers of the web (2) to become entangled.

Such an injector can be designed in a similar manner to the teachings of EP-A-0 400 249.

Inside the cylinder (C), there is a suction box (12), fixed, coaxial with the rotary cylinder (C), connected to a suction source making it possible to create a partial vacuum inside the latter. This fixed suction box (12) has in the alignment of the water jets (11) a slot (13) of about 10 mm in width allowing the suction of the water which passes through the fibrous web and the perforated cylinder (10). .

In the embodiment illustrated in FIG. 1, the cylinder (C1) of the first processing assembly is designed not only to allow the interlacing operation as explained above, but also to cooperate in the compression of the ply ( 2) untreated before it is subjected to interlacing treatment.

To do this, the cylinder (C1) has a diameter which preferably is greater than the diameter of the other cylinders of the installation, and which is advantageously between 500 mm and 1000 mm. This cylinder is in abutment against an endless porous conveyor belt (14), which allows the introduction of the sheet inside the treatment zone. This porous support has a speed synchronized with that of the cylinder. It therefore allows compression of the ply (1) between the surface of the cylinder (C1) and its own surface before it is subjected to the action of the first ramp of high pressure jets (R1). It was found that it was advantageous during this operation of compressing the sheet, to make a wetting of the latter. To do this, inside the volume defined by the conveyor belt (14), is arranged a ramp (15) creating a curtain of water under slight pressure acting through the porous support assembly (14) / compressed sheet (2) and perforated cylinder (1). To allow the elimination of water passing through the aforementioned elements, a second slot (16) is provided on the fixed suction box (12), and this opposite the water ramp. This discharge slot has a width of between 10 and 20 mm.

This mooring ramp (15) forms a continuous curtain of water under slight pressure and is arranged opposite the porous support fabric (14) at a distance between 10 and 100 mm from said porous support. The water pressure from these jets is between 3 and 15 bars, and preferably close to 3 to 8 bars. Below 3 bars, the curtain disperses too quickly and beyond 15 bars, the additional cost is not justified. It is important that the curtain of water from this first ramp acts perpendicularly to the moving base sheet which advances and compresses so as to wet it under optimal conditions.

On leaving the treatment zone (3), the dried sheet (2) is received in a conventional manner at (4), for example by means of an endless conveyor belt (17). In the reception area, the sheet (2) can undergo an additional treatment, for example a treatment making it possible to produce perforated patterns in the sheet by means of an assembly (16) of the type described in European patent 0 400 249.

The advantages of the installation according to the invention will however emerge more clearly from the concrete example of implementation given below.

Example

On an installation as defined above, a nonwoven web (2) based on polyester fibers is introduced having a titer of 3.3 dtex and a length of 38 mm, weighing 200 g / m2 and the thickness of which is 8 cm. The speed of introduction of the sheet is 20 m / min.

This sheet is brought to the zone proper (3) by passing over a conveyor belt (14) having a porosity of 46%. The sheet is compressed between the first rotary cylinder (13) and said conveyor belt and subjected to the action of a curtain of water produced by the ramp (15), the outlet of which is at a distance of 100 mm from the internal surface. of the conveyor belt (14). The pressure of the water coming from the ramp (15) is adjusted to 10 bars.

The compressed sheet is then subjected to the action of the water jets from the ramps (R1, R2, R3, R4) which act alternately on the faces (N) and (S) of said sheet.

The four ramps (R1-R4) all produce 1250 jets per meter and are adjusted as follows. Ramp order Jet diameter Pressure Cylinder speed in m / min R1: side N 140 µm 150 bars C1: 20m / min R2: face S 140 µm 180 bars C2: 20.2m / min R3: side N 140 µm 180 bars C3: 20.4m / min R4: S side 140 µm 180 bars C4: 20.6m / min

The ply then passes directly over the receiving conveyor belt (4) without being treated in the second series of sets of perforated jets cylinders illustrated in FIG. 1.

• résistance sens long : 418 Newton
• résistance sens travers : 1066 Newton.

Such a sheet has a very regular surface condition, identical on both sides, and has the following mechanical characteristics measured on a sample 50 mm wide:

• resistance long sense: 418 Newton
• cross direction resistance: 1066 Newton.

As an indication, the production of a similar article on a conventional installation in which several successive treatments are carried out on one side before treating the other side in a similar manner, the speed of the material being constant and adjusted to 20 m / min , requires working under the following conditions: Ramp order Jet diameter Pressure 1st side N no. 1 140 µm 150 bars no. 2 140 µm 180 bars no. 3 140 µm 180 bars 2nd side S no. 1 140 µm 180 bars no. 2 140 µm 180 bars no. 3 140 µm 180 bars

The article treated under these conditions has similar mechanical characteristics, but it is found that a portion of the fibers redirected during treatment on the N side appear on the second side S which has a fluffy and not regular appearance. In addition, the flatness of the article is less good than that of the article produced on a machine according to the invention.

Furthermore, the energy consumption necessary for binding is, in a machine produced in accordance with the invention, of the order of 0.65 Kwh per kilogram of nonwoven, while it amounts to 0.94 Kwh in the case of a conventional installation.

In addition, if the previous installations only have two perforated cylinders each associated with a plurality of treatment ramps, the installation according to the invention involves as many cylinders as treatment ramps, the latter however proving to be of a lower cost since for the production of similar articles, it requires a lower number of treatment ramps, lower water consumption with an energy saving of almost 50%, and this to obtain a better final result .

Of course, the invention is not limited to the embodiment described and illustrated, but covers all the variants produced in the same spirit, in particular those which would include perforated cylinders arranged parallel to each other provided that the ramps projecting the water jets act alternately against the two faces of the treated fibrous web and that the peripheral speed of the cylinders gradually increases from one treatment zone to the next.

Claims (6)

1. Installation for the production of nonwoven webs, the cohesion of which is obtained by the action of fluid jets, comprising means (1) allowing a fibrous web (2) to be produced, compressed and introduced into a processing zone (3) in which the moving web (2) is subjected to the action of a succession of bars of pressurised water jets which act alternately against the two sides of the said web (2), characterized in that the interlacing means are formed by at least one series of perforated cylinders (C1, C2, C3, C4), each cylinder being associated with a bar (R1, R2, R3, R4) spraying jets of pressurised water onto the surface of the said web (2), the said bars (R1, R2, R3, R4) being arranged in a staggered manner from one processing cylinder to the next, the jets acting perpendicularly on the surface of the processed product, and the peripheral speed of the cylinders increasing progressively from one processing zone to the next.
2. Installation according to claim 1, characterized in that the perforated cylinders (C1, C2, C3, C4) are superposed one on top of another.
3. Installation according to one of claims and 2, characterized in that the increase in speed from one cylinder to the next is comprised between 0.5 and 3%.
4. Installation according to one of claims 1 to 3, characterized in that the first cylinder (C1), if the production direction is taken into account, is associated with means allowing the web (2) to be densified.
5. Installation according to claim 4, characterized in that the densifying means are formed by a porous endless conveyor belt (14) which supports the material and which bears tangentially on the surface of the first perforated rotating cylinder (C1), inside which a partial vacuum is applied, and which allows the base web to be compressed before it is subjected to the action of the first bar of pressurised jets, the wetting of the said web being obtained by means of a curtain of water produced by means of an additional bar (15) disposed inside the volume defined by the conveyor belt (14), this curtain of water being directed against the surface of the said belt and passing in succession through the latter and the compressed web before being drawn out through the perforated cylinder (C1).
6. Installation according to one of claims 2 to 5, characterized in that it comprises a second set of superposed perforated cylinders (C5, C6, C7) and of injectors (R5, R6, R7) which are superposed and placed opposite the first series of processing elements.

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