EP1268905A2

EP1268905A2 - Installation for producing nonwoven webs whereof the cohesion is obtained by fluid jet action

Info

Publication number: EP1268905A2
Application number: EP01907878A
Authority: EP
Inventors: Frédéric NOELLE; Thierry Ouvrier-Neyret
Original assignee: Rieter Perfojet SAS
Current assignee: Rieter Perfojet SAS
Priority date: 2000-03-16
Filing date: 2001-02-22
Publication date: 2003-01-02
Also published as: AU3574601A; WO2001068966A3; FR2806426A1; FR2806426B1; WO2001068966A2

Abstract

The invention concerns an installation for making nonwoven webs whereof the cohesion is obtained by the action of fluid jets. Said installation comprises two perforated rolls (3, 6) associated with injectors (4, 5, 7, 8) producing jets acting against the surface of the web (N). The invention is characterised in that the treated web is delivered: either on a conveyor belt (10) supported by four guide rollers (20, 21, 22, 23), the two upper rollers (20, 21) defining a plane inclined downwards, the entrance zone (20) being arranged substantially at the horizontal plane tangent to the upper perforated roll (6) and the web of material being subjected to the action of a dead roll (18) enabling it to be tensioned about the upper roll (6) to prevent the material from being lifted during the action of the last series of water jets; or on a receiving fabric (17) which follows the path so that it is supported not only on said guide rollers (20, 21, 22, 23), but also around the upper roll (6) for water jet treatment, the intermediate dead roll (18) being in that case retracted to be located at a higher level above the path of said fabric (17).

Description

INSTALLATION FOR THE PRODUCTION OF NON WOVEN TABLECLOTHS WHICH COHESION IS OBTAINED BY THE ACTION OF .TETS OF FLUID-

Technical area

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 water of small diameter and having a high speed.

Previous techniques

It has been proposed for a long time, as is apparent from US-A-3,214,819 and from US-A-3,508,308, to produce nonwoven textile webs in which cohesion is given by interlacing of the elementary fibers therebetween, interlacing obtained by the action of pressurized water jets which act on the fibrous structure in the manner of needles and make it possible to redirect a part of the fibers constituting the sheet in the thickness direction .

Such technology has been widely developed nowadays and makes it possible to obtain a wide range of different products, for example for producing non-woven fabrics for textile use, such as in particular for applications in the medical or hospital fields, of wiping, filtration, envelopes for tea bags ..., but also to make tiny perforations on continuous supports, such as paper, cardboard, film, or even sheet of plastic or other material, the articles obtained possibly having recessed or raised patterns.

In general, these different types of nonwovens can be classified into four main families, namely:

_ solid nonwovens that do not have particular patterns; _ nonwoven openwork or simply marked on the surface, whose perforations or surface marks are obtained by the action of water jets on a synthetic conveyor, conveyor made of son of large diameter, but generally less than 1 , 2 mm in diameter; _ openwork nonwovens having large perforations obtained by the action of water jets on the fibrous material supported by a cylinder covered with a metallic fabric made up of threads of large diameter, generally greater than 1.2 mm in diameter and; _ nonwovens with three-dimensional patterns.

Among the different types of installations proposed to date for producing such products, mention may be made of those subject to US Pat. No. 3,508,308 (see in particular FIGS. 7 and 8 and corresponding description of this patent), in which the line production comprises a zone for forming the basic fibrous structure which, continuously, passes around a succession of interleaving zones proper 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 and then, using detour means provided between two successive cylinders, then act on the reverse and possibly perform a third treatment on the right side before drying and receiving the product produced.

Such installations, which give satisfaction from a practical point of view, however have drawbacks among which there may be mentioned a considerable overall length and above all the need to carry out the first series of interlacing treatment on one side with pressure. reduced to prevent the fibers from coming out on the other side and creating defects.

Consequently, this implies increasing the number of treatment ramps, which notably increases the cost of the installation, complicates industrial implementation and results in high energy and water consumption.

More recently, the Applicant has proposed a multi-purpose machine configuration of the type as illustrated in FIG. 1.

In general, in such an installation, the fibrous sheet (N) is brought to the treatment zone by jets of fluid by means of a horizontal conveyor conveyor (1), which brings it to the level of a first cylinder (3). The fiber web is compacted between the conveyor (1) and the surface of the cylinder (3). In the compressed state, it is wetted by the action of water jets obtained by a first injector (2) disposed below the conveyor belt (1). After pre-wetting, the sheet still supported by the drum (3) is then subjected to the action of two successive injectors (4,5). Such treatment is carried out substantially in accordance with the teachings of FR-A-2 734 285 (corresponding to FUS 5 718 022).

Advantageously, the cylinder (3) is covered with a jacket comprising micro-orifices arranged randomly, and this in accordance with the teachings of FR 2 734 285 (US 5 768 756).

The sheet (N) thus treated on one side, is then brought to a second cylinder (6) around which are arranged two injectors (7,8) which carry out the treatment of the other side of the veil of fibers.

In such a configuration, the cylinders (3,6) are superimposed in a vertical plane, which reduces the overall length of the machine.

At the outlet of the cylinder (6), the treated sheet is brought, by passage around a detour roller (9), to a horizontal conveyor (10) equipped with two injectors

(11,12) and a drying box (13) in which is applied a high vacuum to express a maximum of water before drying in an oven, through air for example, not shown in Figure 1 attached.

Such a configuration therefore comprising a total of six injectors and two conveyors, makes it possible to produce either full nonwovens, or openwork nonwovens or simply marked on the surface or comprising large perforations, or even patterns in three dimensions.

For the production of each nonwoven type on such a type of installation, the procedure is as follows.

_ for solid nonwovens which do not have particular patterns, cylinders (3,6) are used which have a random micro-perforated surface coating and two conveyor belts (1,10) with fine mesh, and submit the tablecloth pre-wetted by the action of the two series of injectors (4,5,7,8) associated with the cylinders (3,6), the injectors (11,12) associated with the conveyor belt (10) not being used ;

_ for non-woven openwork fabrics or simply marked on the surface, cylinders (3,6) are also used comprising a random micro-perforated coating, the conveyor belt (1) being fine mesh and the conveyor belt (10) being, meanwhile, made up of wires with a large diameter, but less than 1.2 mm; in this form of implementation, the pre-wetted sheet is subjected to the action of the injectors (4,5) associated with the first cylinder (3), the injectors (7,8) associated with the second cylinder (6) being, as for them, neutralized, and the injectors (11,12) associated with the mat (10) being, in turn, implemented with a high flow of water;

_ for open-woven nonwovens with large perforations, the cylinder (3) has a random micro-perforated coating while the cylinder (6) is covered with a metallic fabric made of large diameter threads, the conveyor belt (10) being fine mesh; in this form of implementation, the injectors (4,5) are put into action and as well as the injectors (7,8), the latter with a high flow rate, while the injectors (11,12) associated with the mat ( 10) are neutralized;

_ finally, for nonwovens with three-dimensional patterns, the drum (3) is always coated with a random micro-perforated coating while the drum (6) is coated with a structure having reliefs, the carpet conveyor (10) being, in turn, fine mesh; in this form of implementation, the injectors (4) and (5) and the injectors (7) and (8) are used as before, supplied with a high flow rate, the injectors (11,12) being neutralized.

Statement of the invention

However, it has been found, and this is what is the subject of the present invention, that, by means of simple adaptations, it was possible not only to reduce the overall length of the installations of the aforementioned type as illustrated. in FIG. 1, while retaining the possibility of being able to produce the four types of nonwovens, and this by using only four injector ramps associated with the two perforated suction cylinders without additional injectors at the level of the expressing conveyor .

In general, the invention therefore relates to an installation for producing nonwoven webs which comprises: _ a porous transport conveyor, endless, for a fibrous web previously produced, on which rests a first perforated rotary cylinder inside which a partial vacuum is applied and which allows to compress the base web, said web being in this state subjected to a pre-wetting, carried out by means of water jets produced by means of an injector disposed inside the volume defined by the conveyor belt, these water jets being directed against the surface of said belt and successively passing through it and the compressed sheet, before being sucked through said perforated cylinder, the pre-wetted sheet carried by said cylinder being subjected to the action of two successive injectors producing jets acting against its surface;

_ a second cylinder, rotary, perforated and suction, disposed above the first cylinder, and with which are associated two successive injectors whose jets act perpendicularly against the surface of the sheet opposite to that which has been previously treated; _ a conveyor assembly, intended to receive the tablecloth thus treated and subjected to a suction source making it possible to eliminate the water which impregnates the tablecloth, said installation being characterized in that the reception of the treated tablecloth is carried out: • either on a conveyor belt supported by four guide rollers, the two upper rollers defining a downward inclined plane, the entry zone being arranged substantially at the horizontal plane tangent to the upper perforated cylinder and the sheet of material being subjected to the 'action of a support roller allowing it to interlock around the upper cylinder to avoid a lifting of the material during the action of the last series of water jets;

• or on a receiving canvas which follows a path such that it bears not only on the aforementioned guide rollers, but also around the upper cylinder for treatment with water jets, the intermediate support roller being in such a case retracted to be located at a level above the path of said canvas.

When the treated web is received on a conveyor belt supported by four guide rollers, the second treatment cylinder is coated either of a shirt comprising micro-perforations distributed in a random manner, thus making it possible to obtain regular nonwovens, or by a coarse canvas or a covering comprising patterns in relief and in hollow making it possible to obtain nonwovens openwork or with three-dimensional patterns.

When the reception of the treated tablecloth is carried out on a reception canvas which follows a path such that it rests not only on the guide rollers, but also around the upper cylinder for treatment with water jets, said canvas is formed by an openwork fabric of which at least the warp threads are advantageously synthetic threads, the diameter of which is less than 1.2 mm and is advantageously between 0.3 and 1 mm.

Optionally, the receiving fabric can, in such a case, be constituted by an openwork fabric whose warp threads are synthetic filaments (polyester) and whose weft threads are metallic threads (stainless steel).

Thanks to such a machine structure, it is therefore possible to obtain both regular nonwovens and nonwovens having more or less pronounced effects, by using only four injectors after pre-wetting the web, by a simple adaptation of the coating of the second cylinder, coating which, in one form of implementation, is constituted by the conveyor assembly which receives the sheet.

Brief description of the drawings The invention and the advantages which it brings will however be better understood thanks to the appended diagrams in which:

_ Figure 1 is a schematic view of a jet treatment installation produced in accordance with the prior art; _ Figure 2 illustrates an installation produced in accordance with the invention; _ Figure 3 is a variant of such an installation comprising a pre-mixing zone; _ Figures 4, 5 and 6 are schematic views illustrating the different possibilities of implementation of such an installation, Figures 4a, 5a and 6a being enlarged views of the circled areas. Way of realizing the invention

Using the same references as those used to describe the state of the prior art as illustrated in FIG. 1, in an installation according to the invention as illustrated in FIGS. 2 and 3, the fibrous sheet (N) which can come from a production line (carding, lapping ...) of a veil placed continuously with the jet treatment zone, is brought to the latter via a transport conveyor (1) , horizontal, which brings it to the level of a first rotary suction cylinder.

The veil of fibers is compacted between the conveyor (1) and the surface of the cylinder (3) and is pre-wetted by the action of water jets produced by an injector (2) disposed below the conveyor belt (1), l water being sucked through the drum (3).

The pre-wetted sheet, maintained on the surface of the drum (3), is then subjected to the action of two injectors (4,5). The cylinder (3) is covered with a jacket comprising randomly distributed micro-perforations.

The sheet (N) thus treated then passes around a second cylinder (6) associated with two injectors (7,8) which carry out the treatment on the other face of the sheet.

All these treatments are carried out in a conventional manner.

According to the invention, after treatment with the series of jets, the sheet is then transferred by an assembly making it possible to express the excess water which impregnates it before drying it in an oven, with air passing through for example.

According to the invention, downstream of the cylinder (6) and spaced relative to the latter, there is a receiving assembly essentially comprising four idler rollers (20,21,22,23) mounted on a frame, the rollers ( 20,21) being positioned so that they form an inclined plane whose upper level formed by the roller (20) is arranged in a plane substantially at the level of the horizontal plane tangent to the cylinder (6), and preferably in below this plan.

An intermediate retractable roller (18) is placed between the cylinder (6) and the input roller (20), so that this roller can take two positions, one retracted in which it is spaced relative to the plane tangent to the cylinder (6) and the roller (20), the other lowered according to which it is below the level of this tangent plane.

Furthermore, an additional detour roller (19) may possibly be provided between the roller (20) and the drum (6).

Thanks to such a configuration, it is possible to produce the four main families of products mentioned in the preamble, such a possibility being illustrated by FIGS. 4, 5 and 6.

In a first form of implementation as illustrated in FIG. 4, it is possible to obtain plain, solid nonwovens.

In such a case, the roller (6) is covered with a random micro-perforated coating (see FIG. 4a) and the product is received on a conventional drying carpet (10) consisting of a fabric having a high opening. In such a case, the retractable guide (18) bears against the surface of the nonwoven so as to form an interlock around the cylinder (6) subjected to the action of the last injector (8) and preventing the material from is lifted from the drum (6).

It is also possible to use such a configuration with an independent drying mat (10) to produce perforated nonwovens having large openings, or even patterns in relief.

To do this, as can be seen in FIG. 5, a coating consisting of a coarse fabric (see FIG. 5a), for example made of stainless steel, or even an embossed canvas when one wishes to make, is used as coating for the cylinder (6) relief patterns.

In this form of implementation, the treated material is also held in abutment against the cylinder (6) by action of the retractable guide (18).

Finally, as is apparent from FIG. 6, it can also be envisaged to use such an installation for producing perforated nonwovens with perforations or marked on the surface. In such a case, a receiving conveyor (17) is used which not only rests around the guides (20,21,22,23), but also embeds around the return guide (19) to wrap the cylinder. upper (6).

Such a receiving conveyor (17) has a structure as illustrated in FIG. 6a and is constituted by a woven fabric forming an openwork structure and produced from wires having a diameter less than 1.2 mm and preferably between 0.3 and 1 mm. This woven fabric can be produced from warp and weft threads, in particular polyester, or optionally comprise a warp of synthetic threads and a weft based on stainless steel threads.

In such an embodiment, the retractable guide (18) is raised and does not bear on the material which is therefore supported by said fabric (17), both during its passage around the upper cylinder (6) and in the pressing area located between the rollers (20) and (21).

It should be noted that in FIG. 2 as well as in the variant illustrated by FIG. 3, both the conventional drying carpet (10) and the variant implementing a receiving conveyor (17) have been represented. surround the upper cylinder (6), it being understood that one or the other of these elements is used depending on the type of product to be produced.

Such a machine configuration therefore makes it possible to obtain the four families of products mentioned in the preamble to the description by using, in addition to the pre-wetting assembly, only four injectors, which reduces the overall cost of the installation, the structure of the machine also being much more compact than previous installations of the type illustrated in FIG. 1.

The versatility of such a machine will however be better understood thanks to the four concrete examples of embodiment given below, these examples being produced by supplying the installation according to the invention with a nonwoven web (N), produced immediately in upstream of the treatment plant by carding or pneumatic covering, a covering based on a mixture of viscose / polyester fibers weighing 60 g / m ² and comprising 70% viscose fibers of length 40 mm / l, 7dtex and 30% polyester fibers 38 mm / 1.7 dtex in length. The speed of introduction of the sheet onto the conveyor belt (1) is 60 m / min.

The conveyor belt (1) has a mesh void of 24%.

The sheet is compressed between the first rotary cylinder (3) and is subjected to the action of water jets produced by the injector (2), the outlet of which is at a distance of 30 mm from the internal surface of the conveyor belt (1). The water pressure in the injector (2) is adjusted to 10 bars.

The compressed sheet is then subjected to the action of the water jets from the injectors (4) and (5) to then be brought to the second drum (6).

In the following four examples, the first drum (3) has a diameter of 515 mm and is constituted by a perforated stainless steel honeycomb cylinder rotated at a peripheral speed equal to the input speed of the ply (N) on the belt (1), namely 60 m / min. This drum (3) is covered with a lining comprising micro-perforations, distributed randomly of the type illustrated in FIG. 4a.

The ramps (4) and (5) produce 1666 jets / meter, the water jets having a diameter of 120 μm and the pressure inside the injectors being respectively 40 bars for the injector (4) and 60 bars for the injector (5).

At the outlet of the drum (3), a preloaded sheet is obtained which is then brought to the second treatment zone, making it possible to give the product its final characteristics, the treatment conditions therefore varying between the following four examples.

Example 1

The installation is configured as illustrated in Figure 4.

In such a case, the second suction cylinder (6) also includes a lining comprising randomly distributed micro-perforations. The sheet coming from the first cylinder (3) passes around the cylinder (6) coated with such a coating and is subjected to the action of two successive ramps

(7,8) which also produce 1666 jets per meter, having a diameter of 120 μm, the supply pressure of the injector (7) being 80 bars and that of the injector (8) 80 bars.

The structure produced is then brought to the drying conveyor belt constituted in the present case by a canvas with a large opening and which therefore surrounds the rollers (20,21,22,23).

The intermediate roller (18) presses lightly on the treated ply so that it perfectly matches the surface of the cylinder (6). The drying box is arranged below the outlet conveyor, the relative vacuum level being 450 millibars, which allows the excess water contained in the structure to be expressed, the total drying being carried out by passage through an oven. through air (not shown).

At the outlet of the machine, a nonwoven sheet weighing 55 g / m ² is obtained, of regular and uniform appearance which can be used as prepreg wipes, for example for baby hygiene.

Example 2

Example 1 is repeated except that the second suction cylinder (6) is coated with a cover made of a coarse fabric (see FIG. 5a), made of stainless steel, the wires having 3.5 wires / cm , wires with a diameter of 1.6 mm.

The injectors (7,8) produce 4000 jets / meter, having a diameter of 120 μm and are supplied with a pressure between 90 and 100 bars.

The increase in the number of jets compared to Example 1 is obtained by simply changing the perforated plate (strip) that each injector has.

The article produced is also received on a carpet (10) similar to that of Example 1. At the outlet of the machine, a perforated nonwoven having rectangular openings is obtained.

This article weighs 55 g / m ² and can be used for example as an industrial wiping cloth.

Example 3

Example 2 is repeated, except that the coarse cloth which surrounds the cylinder (6) is replaced by a metallic bronze cloth, embossed so that it has raised and hollow parts.

In addition to this modification, the injectors (7,8) are supplied with water under pressure at 80 bars.

After treatment, an article is obtained which weighs 55 g / m ² , having a crimped appearance and which can be used as wipes, hygiene products, etc.

Example 4 The conveyor belt (10) used in the previous examples is removed and replaced by a canvas (17) consisting of an openwork fabric.

In this example, the fabric constituting the canvas (17) comprises a warp made from polyester threads, with a diameter of 0.5 mm at the rate of five threads per centimeter, and the weft is made up of steel threads stainless, having a diameter of 0.38 mm and this, at a rate of nine weft threads per centimeter.

This fabric is mounted on the installation as illustrated in Figure 6, that is to say that it surrounds not only the rollers (20,21,22,23), but also the perforated cylinder (6) thus constituting its surface coating.

This canvas also rests on the detour roller (19).

In this form of implementation, the roller (18) and in the raised position and the fabric thus supporting the treated article follows a direct path between the cylinder (6) and the roller (20). The injector (7) is adjusted to produce 1666 jets / meter of diameter 120 υm, its supply pressure being 70 bars, while the injector (8) is adjusted to produce 4000 jets / meter having a diameter of 120 μm, the supply pressure being 80 bars.

After expressing and drying, an openwork or simply surface-marked article is obtained which can be used in the medical field (gauze, dressing), or as conventional wiping products.

The foregoing examples clearly show the advantages provided by the invention, and in particular the great flexibility of use of such an installation which therefore only comprises four injectors, which reduces the cost of the material and makes it possible to obtain a clearly encumbered space. reduced (of the order of 20% in length) compared to the solutions proposed previously.

Furthermore, as illustrated in FIG. 3, it is possible to mount a pre-tightening assembly (24) at the level of the inlet conveyor, and this without increasing the overall size of the installation.

Such a pre-mixing assembly is particularly useful when it is desired to treat heavy sheets, the weight of which can exceed 150 g / m ² and which can reach 300 g / m ² or more.

Claims

1. Installation for the production of nonwoven webs whose cohesion is obtained by the action of fluid jets of the type comprising: _ a porous transport conveyor (1), endless, for a fibrous web

(N) previously produced, on which rests a first perforated rotary cylinder (3) inside which a partial vacuum is applied and which makes it possible to compress the base ply, said ply (N) being in this state subjected to a pre-wetting carried out by means of water jets produced by means of an injector (2) disposed inside the volume defined by the conveyor belt (1), these water jets being directed against the surface of said belt and successively passing through it and the compressed sheet, before being sucked through said perforated cylinder (3), the pre-wetted sheet carried by said cylinder being subjected to the action of two successive injectors (4,5) producing jets acting against its surface; _ a second cylinder (6), rotary, perforated and suction, placed above the first cylinder (3), and with which are associated two successive injectors (7,8) whose jets act perpendicularly against the surface of the sheet opposite to that that has been previously processed;

_ a conveyor assembly, intended to receive the sheet thus treated and subjected to a suction source (13) making it possible to eliminate the water which impregnates the sheet, said installation being characterized in that the reception of the treated sheet is carried out :

• either on a conveyor belt (10) supported by four guide rollers (20,21,22,23), the two upper rollers (20,21) defining a plane inclined downwards, the entry area (20) being disposed substantially at the horizontal plane tangent to the upper perforated cylinder (6) and the sheet of material being subjected to the action of a support roller (18) allowing it to interlock around the upper cylinder (6) to avoid a lifting of the material during the action of the last series of water jets;

• or on a receiving canvas (17) which follows a path such that it rests not only on the aforementioned guide rollers (20,21,22,23), but also around the upper cylinder (6) for processing by water jets, the intermediate support roller (18) being in such a case retracted to be located at a level above the path of said fabric (17).

2. Installation according to claim 1, in which the reception of the treated sheet is carried out on a conveyor belt (10) supported by four guide rollers (20,21,22,23), characterized in that the second treatment cylinder (6) is covered either with a shirt comprising randomly distributed micro-perforations, making it possible to obtain regular nonwovens, or with a coarse canvas or a covering comprising raised and hollow patterns making it possible to obtain openwork nonwovens or three-dimensional patterns.

3. Installation according to claim 1 in which the reception of the treated sheet is carried out on a reception canvas (17) which follows a path such that it bears not only on the guide rollers (20,21,22,23 ), but also around the upper cylinder (6) for treatment with water jets, the intermediate support roller (18) being in such a case retracted to be located at a level higher than the path of said fabric (17 ), this fabric possibly resting on a bar feeder guide (19) and being constituted by an openwork fabric of which at least the warp threads are synthetic filaments (polyester), the diameter of which is less than 1.2 mm and is advantageously included between 0.3 and 1 mm.

4. Installation according to claim 3, characterized in that the fabric (17) is constituted by an openwork fabric whose warp threads are synthetic filaments (polyester) and whose weft threads are metallic son (stainless steel).