WO2001051693A1 - Method for producing a complex nonwoven fabric and resulting novel fabric - Google Patents

Abstract

The invention concerns a method for producing a complex nonwoven fabric which consists in continuously producing a complex wherein a first web of cellulosic fibres (4) is continuously sandwiched between two webs of spunbonded filaments (2, 7), and which consists in: producing a first web of spunbonded filaments (2), the bundle of extruded and drawn filaments being received on a mobile conveyor belt (3) in the form of a non-bonded lap; depositing on said web (2) by airlaid process a second web of cellulosic fibres (4); depositing on the textile web (4) a second web (7) of non-bonded continuous filaments; transferring the resulting complex onto an installation (9) for water-jet bonding and hydro-entanglement consolidation; and in drying the nonwoven mixed product and then recuperating it, for example in the form of a cloth wind-up (18).

Description

PROCESS FOR THE PRODUCTION OF A NON-TTSSE MATERIAL

COMPLEX AND NEW TYPE OF MATERIAL SO OBTAINED.

Technical Field For decades, it has been proposed to replace traditional textile tablecloths (fabric, knitting) with so-called "non-woven" structures.

In general, such nonwoven structures can be classified into three main categories, resulting from their very manufacturing process, namely the so-called “dry” nonwovens formed by carding and / or aeraulic route, this last technique being commonly designated by the expression "airlaid technique", the nonwovens obtained by "melted", technique commonly designated by the expression "spunbond", and the technique known as "wet", derived from paper techniques .

Furthermore, it has been known for a very long time that it is possible to adapt the final properties of the product obtained by making mixtures of materials, for example by combining together several webs made up of fibers of different nature, for example fibers natural, artificial or synthetic.

The invention relates to a new process making it possible to produce such a type of nonwoven article made up of a mixture of fibers of different nature and which, in the following description, will be designated by the expression “mixed nonwoven "Or" composite nonwoven ".

Previous techniques

Very many proposals have been made to date for making mixed or composite nonwovens by associating between them veils of artificial or synthetic fibers and a veil of cellulosic fibers. The association of the various constituents with one another can be carried out in different ways, for example by means of binders, mechanical needling or hydraulic entanglement, the latter technique, known for a very long time, being described in particular in US Pat. No. 3,508,308. This document describes in particular the production of mixed plies produced by the "airlaid" technique by intimate mixing of fibers, for example a mixture of synthetic fibers (polyester or acrylic) and rayon fibers (see examples 10 and 11). It also describes (see examples 12 and 13), the production of complexes comprising a central layer consisting of continuous filaments and two outer layers based on fibers, in particular polyester, distributed by air, the different layers being linked together by the action of fluid jets.

It has also been proposed, as is apparent from EP 423 619, to produce absorbent fabrics by association, still by means of water jets, of a sheet made up of continuous filaments and of a sheet made up of a mixture of cellulose fibers, wood fibers in particular.

Finally, it is known to produce nonwovens by sandwiching a sheet of fibers between two webs of continuous filaments already consolidated by hot calendering, the final connection of the different layers also being ensured by the action of water jets. .

This latter relatively simple implementation technique has many major drawbacks, namely: the fact that the webs of continuous filaments (spunbond) are already consolidated by a calendering heat treatment prohibits intimate mixing of these filaments with the wood fibers veil deposited by air, which reduces the absorption capacity of the complex and also leads to the production of a rough product lacking flexibility; moreover, it is necessary, to ensure satisfactory cohesion between the layers and to avoid delamination of the complex, to use, during the phase of consolidation by water jets, very high fluid velocities, because the calendering points of the sails spunbond prevent any mobility of the synthetic filaments; these high speeds of the water jets generate an additional cost of energy consumption as well as an increased loss of cellulosic fibers; the connection points between the filaments obtained by calendering can represent up to 20 to 25% of the surface of the sails based on continuous filaments and therefore constitute as many obstacles to the passage of water jets;

^ finally, the fact that the continuous filaments of the sails are not mobile gives significant rigidity to the material which loses its textile properties and looks more like paper than real textile. Statement of the invention

However, we have found, and this is the subject of the present invention, an improved process which makes it possible to continuously produce perfectly bonded mixed nonwovens, having high mechanical characteristics while retaining the appearance, feel and flexibility of a conventional textile, such as a fabric.

The resolution of such a problem is obtained by the combination, in a very precise manner, of prior techniques implemented continuously and under very precise conditions, namely:

_ the techniques for producing nonwoven sheets made from short fibers, the distribution of which is obtained by air flow (airlaid technique);

_ the techniques for producing plies obtained by direct spinning (spunbond) and,

_ the consolidation of the complex formed by the action of water jets.

In general, the method according to the invention consists in continuously producing a complex in which a sandwich is interposed between two veils of continuous filaments, a fibrous veil based on cellulosic fibers, method which consists in: producing a first web of continuous filaments, the bundle of extruded and drawn continuous filaments being received on a movable conveyor belt in the form of an unbound web; to deposit on this veil, by air, a second veil of cellulosic fibers; depositing on the fibrous web a second web of unbound continuous filaments; transferring the complex formed to a binding system by water jets and consolidating the assembly by hydraulic entanglement and;

* drying the mixed nonwoven product and then receiving it, for example in the form of a roll.

According to a preferred embodiment of implementation of the method according to the invention, the cellulosic fibers used in the production of the complex are wood fibers and their deposition is carried out by pneumatic coating. Furthermore, if it can be envisaged to carry out only one binding treatment by water jet, the complex formed is preferably subjected to two successive treatments acting against the two opposite faces of the complex.

The invention also relates to a new type of nonwoven product obtained by the implementation of this method.

Such a mixed nonwoven, which therefore consists of a mixture of fibers of different nature, is characterized in that it consists of a layer of natural fibers, wood in particular, trapped between two nonwoven sheets made of filaments , extruded and drawn, based on synthetic material, the cohesion of the different layers being obtained by entanglement thanks to the action of water jets.

Brief description of the drawings

The invention and the advantages which emerge therefrom will however be better understood thanks to the examples of embodiment which follow, given below by way of indication, but not limitation, and which are illustrated by the appended diagrams in which: FIG. 1 is a schematic view of an assembly of a production line for a complex material produced in accordance with the method according to the invention;

_ Figures la, lb, lc and ld are enlarged views of the circled areas of this figure 1.

Way of realizing the invention

On a production line, as illustrated in FIG. 1, a composite nonwoven is produced continuously.

To do this, a first web (2) of continuous filaments is produced by means of a production unit, designated by the general reference (1), by fusion, spinning and drawing. These filaments are deposited and distributed over a mobile conveyor belt (3). Optionally, immediately after formation, this first web (2) can be subjected to compaction by means of a pressing cylinder or by the action of jets coming from a ramp of hydraulic injectors.

The continuous filaments of this first veil (2) can be based on a polymer consisting of polypropylene, polyester or other synthetic materials such as polyethylene, polyamide, this list not being limiting. The continuous filaments can optionally consist of so-called “bicomponent” filaments, such as those obtained by coextrusion of polypropylene and polyethylene.

The web of unbound continuous filaments (2) is then transferred under a unit, designated by the general reference (4), which, by air flow, makes it possible to deposit on the surface of the first ply (2) of staple fibers ( 4), of another nature, and more particularly of cellulose fibers, wood in particular.

The cellulosic fibers are deposited on the surface of the first web (2) by means of a stream of air. Preferably, the veil of filaments (2) is held on the conveyor belt (3) by means of a suction (5). As a result, under the effect of the suction, said fibers (4) are preferably deposited between the unbound filaments of the web (2), thus allowing excellent integration of the two constituents.

The complex (2,4) which is still maintained supported by the conveyor belt (3), is then brought below a second formation zone (6) of a second web of continuous filaments (7), also synthetic, of the same or different nature as those of the first veil (2).

A pressure roller (8) is preferably disposed after this zone for depositing the web (7), and makes it possible to ensure compaction of the assembly with a view to its transfer to the hydroliage installation, designated by the general reference. (9), which follows the production line.

Optionally, this compacting operation could be carried out by means of a ramp of hydraulic injectors. The complex is then introduced into the hydroliage zone (9) on a conveyor (10) on which the operations of compacting and pre-wetting of the assembly are successively carried out by means of an upper conveyor (11) tangent to the conveyor lower (10), and inside which is disposed a hydraulic injector (12).

After compacting and pre-wetting, the complex is subjected to the action of a succession of water jets (13) delivered by several hydraulic injectors arranged in series.

These water jets (13) consolidate the assembly formed by the various layers of the complex and confer good resistance to abrasion of the upper layer.

The structure thus treated is then transferred, by inversion, to a cylinder (14), or to another conveyor, associated with several injectors (15) which also deliver water jets on the other face of the complex, thus strengthening the consolidation of all of the layers, while providing good abrasion resistance of the layer facing the jets.

The complex thus obtained is then transferred to an expressing conveyor (16) on which it is expressed using a suction box connected to a vacuum generator.

It is then dried by means of a through-air cylinder (17) and then received in a conventional manner, for example in the form of a winding (18).

Example A product according to the invention is produced in the following manner.

A continuous veil of filaments (2), weighing 15 g / m ² is produced on an installation marketed by the Applicant under the name "spunjet", which allows a nonwoven web to be produced by extrusion, drawing and distribution of continuous filaments. In this exemplary embodiment, polypropylene such as that sold by the company AMOCO under the reference 100 ZA 35 is extracted as a polymer.

The veil formed consists of 7000 filaments per meter of width and is produced at a speed of 250 meters per minute. The diameter of the filaments after drawing is approximately 15 microns.

A suction located opposite the stretching slot (20) makes it possible to precisely control the deposition of the filament and its regularity on the conveyor belt (3).

Above the same conveyor (3), is arranged an assembly (4) allowing aeraulic distribution of staple fibers on the sheet (2) previously formed.

Such a fiber distribution assembly can be constituted by a conventional installation such as that sold by the Company M & J.

In the concrete example, 35 g / m ² of cellulose fibers, and more particularly of wood fibers, sold by the company Korsnaes, are deposited on the veil of continuous filaments (2), these wood fibers, with a length of of the order of 3 mm, being commonly designated by the expression "fluff paste".

A suction box (5) is placed under the conveyor under the entire surface of the distribution air head (4). This suction head (5) is connected to a vacuum generator which allows the wood fibers to be distributed uniformly while preserving the homogeneity of the web of continuous filaments (2).

A pressure roller (not shown), the speed of which is synchronized with said belt (3), compacts the assembly thus formed.

After compaction, a second veil of continuous filaments weighing 15 g / m ² 'of the same type as the first veil (2) is deposited on the surface of the complex.

This veil can be formed either on the same conveyor (3), or on an independent conveyor. This veil (7) is therefore distributed over the layer of cellulosic fibers (4). Preferably, the transfer is carried out in a positive manner using a suction box (5a) arranged under the main conveyor opposite the transfer point.

The structure obtained, which weighs 65 g / m2, is optionally compacted by means of a cylinder (8). This compaction can possibly be achieved by means of an additional ramp of hydraulic injectors.

The complex is then transferred to the conveyor (10) of the hydraulic binding unit (9).

Such a binding unit comprises a main conveyor (10) above which is disposed an upper conveyor (11), tangent thereto, and inside which is disposed a hydraulic injector (12), delivering 4000 jets of water per meter, these jets having a diameter of 130 microns and a speed of 34 meters per second.

The “sandwich” thus compacted and wetted is treated on its upper face by six hydraulic injectors (13), arranged in series which project water jets of 120 microns in diameter spaced from one another by 0.6 mm at speeds respectively 110, 125, 140, 140, 140,140 m / second.

The treated complex is then transferred by inversion onto a cylinder (14) around which are arranged four hydraulic injectors (15) which project water jets of 120 microns in diameter spaced from one another by 0.6 mm at respective speeds. 125, 140, 140, 140 m / second.

The complex thus consolidated is transferred to an expressing conveyor (16) on which it is expressed by a suction box in which there is a vacuum of 400 mbar.

Then the assembly is dried at a temperature of 120 ° C by a cylinder (17) with through air, then received at (18). At the outlet of the production line, it can be seen that the product obtained weighs approximately 60 g / m ² , has excellent homogeneity, good feel, great flexibility and excellent abrasion resistance both in the dry state and in the dry state. 'in the wet state.

Its water absorption capacity is significant, around 850%.

Such a water absorption capacity is comparable to mixed nonwovens made up of staple fibers and which have been produced by carding.

On the other hand, the abrasion resistance both in the dry state and in the wet state, as well as the mechanical characteristics, are very superior.

Such a product is perfectly suited to various applications, such as industrial or domestic wiping products, impregnated wipes, gowns and operating theater drapes, such applications being given as an indication but not limiting.

Claims

1 / Process for the production of a complex nonwoven material which consists in producing continuously, a complex in which one sandwiches between two webs of continuous filaments (2,7), a fibrous web based on cellulosic fibers ( 4) and which consists in: producing a first web of continuous filaments (2), the bundle of extruded and drawn continuous filaments being received on a conveyor belt (3) movable in the form of an unbound sheet; to deposit on this veil (2), by air, a second veil of cellulosic fibers (4); depositing on the fibrous web (4) a second web (7) of unbound continuous filaments; transferring the complex thus formed onto an installation (9) for binding by water jets and consolidating the assembly by hydraulic entanglement and; * drying the mixed nonwoven product and then receiving it, for example in the form of a winding (18). 2 / A method according to claim 1, characterized in that the cellulosic fibers (4) involved in the production of the complex are wood fibers. 3 / Method according to one of claims 1 and 2, characterized in that the complex is subjected to two successive binding treatments by water jets acting against the two opposite faces of said complex. 4 / mixed nonwoven obtained by the implementation of the method according to one of claims 1 to 3, characterized in that it consists of a layer of natural fibers (4), wood in particular, trapped between two layers nonwovens (2,7) made of continuous filaments, extruded and drawn, based on synthetic material, the cohesion of the different layers being obtained by entanglement thanks to the action of water jets.