IL150139A

IL150139A - Method for producing a complex nonwoven fabric and resulting novel fabric

Info

Publication number: IL150139A
Application number: IL150139A
Authority: IL
Original assignee: Rieter Perfojet
Priority date: 2000-01-11
Filing date: 2002-06-11
Publication date: 2007-05-15
Also published as: DK1246958T3; DE60003086T2; IL150139A0; FR2803604B1; WO2001051693A1; TR200201707T2; ES2199189T3; EP1246958B1; CN100379919C; CN1423714A; EP1246958A1; DE60003086D1; ATE241718T1; US20020168910A1; AU2001220142A1; FR2803604A1

Abstract

The invention concerns a method for producing a complex nonwoven fabric which consists in continuously producing a complex wherein a first web of a 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 92) 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

METHOD FOR PRODUCING A COMPLEX NONWOVEN FABRIC AND RESULTING NOVEL FABRIC i Ίχνηη νπηπ j ixm i I N ΡΊΝ -n^ πυν^ Technical field For decades, - it has been proposed to replace conventional textile webs, (wovens and knits) with structures called "nonwovens". . : In general, such nonwove structures can be; classified in three broad . categories , resulting ' from their actual manufacturing process, namely nonwovens produced by a so-called "dry process", these being formed ] by carding and/or, the airlaid technique, nonwovens obtained by the "melt route", which technique is usually referred to by the expression "spunbond", and the technique' called "wet process" derived from papermaking techniques.

Moreover, it has been known for a very long time that it ' is ' possible to adapt the final properties of the product obtained by producing mixtures of .materials, for example, by combining together webs consisting of fibers ■ of . different type, for example natural, artificial or synthetic fibers. , ■ ' The invention .provides a novel method making it possible to produce such a type of nonwoven article consisting of a mixture of fibers- of different type, which nonwoven will, in the rest of the description, be. referred to by . the- expression "hybrid nonwoven" or "composite nonwoven".

Prior art Very many proposals have been made hitherto for producing hybrid or composite nonwovens by combining together webs of artificial or synthetic fibers with a web of cellulosic fibers. The various constituents may be combined in various ways, for example by means of bonding techniques - mechanical needle bonding or hydro-entanglement - the latter technique, known for a very long time, being described for example in patent US 3 508 308. In particular, this document describes the production of hybrid webs produced by the airlaid technique by intimately mixing fibers, for example mixing synthetic (polyester . or acrylic) fibers with rayon fibers (see examples 10 and 11). It also describes (see . examples 12 and 13) the production of complexes having a central ply consisting of, continuous filaments and two outer plies based on fibers, especially polyester fibers, which are distributed by the airlaid technique, the various plies being bonded together by the action of fluid jets.

It has also been proposed, as indicated in EP 423 619, to produce absorbent fabrics- by combining, again by means of water jets, a web consisting of .continuous filaments, with a web consisting of a mixture of cellulosic fibers, especially wood fibers.

Finally, it is known to produce nonwovens ' by sandwiching a lap of fibers between two webs of continuous filaments already consolidated by hot calendering, the final bonding of the various plies also being provided by the action of water jets. .

The latter relatively simple processing technique has many major drawbacks, namely: • the' fact that the.' webs of continuous (spunbond) filaments have already been consolidated by a calendering heat treatment prevents intimate mixing . of these filaments with the wood fibers of the airlaid web, which reduces the absorptivity of the !complex and also results in the formation of. a product which is rough and lacking in flexibility; • moreover, it is necessary, in order to ensure ■ satisfactory cohesion between the plies and prevent delamination of the complex, to use, !during the water-jet consolidation phase, very high fluid velocities, since' the calendering points of the spunbond webs prevent any mobility of the synthetic filaments; these high water-jet velocities incur an extra energy consumption cost and a greater loss of cellulosic fiber; ; · the points of bonding , between the; filaments obtained by calendering may represent up to 20 to 25% of the area of the spunbond-based webs and therefore constitute an equivalent amount of obstacles to the passage of the water jets; · finally, the fact that the continuous filaments of the webs cannot move makes the material very stiff, it losing its textile properties and being more like a paper than a true textile. ,: .

Summary of the invention An improved method has now been found,, and it is this which forms the subject of the present invention, which allows the continuous production of perfectly bonded hybrid nonwovens exhibiting high mechanical properties while retaining the appearance, handle and flexibility of a conventional textile, such as a woven.

Such a problem is solved by combining, ; in a very precise way, techniques of' the prior, art used continuously and under very .precise conditions, namely: the techniques for producing nonwoven webs made from short fibers, which are distributed by the airlaid technique; the techniques for producing spunbond webs; and 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 fibrous web based on cellulosic fibers is sandwiched between two webs of continuous filaments, which method consists: • in producing a first web of continuous', filaments, the bundle of extruded and drawn continuous filaments being taken up on a moving conveyor belt in the form of a nonbonded lap; . • in: depositing on : this web, by the airlaid technique, a second web of cellulosic fibers;: • in depositing on the fibrous web a second web of. nonbonded continuous filaments; • in transferring the complex formed onto a water-jet bonding unit and . in consolidating the assembly by hydro-entanglement; and • m drying the hybrid nonwoven produced and then taking it up, for example in the form of a wound package According to . a preferred way of implementing 1 the method according to the invention, the cellulosic fibers used in the' production of the complex are wood fibers and they are deposited by pneumatic layering.

Moreover, if it is conceivable to carry out only a single water-jet bonding treatment, the complex formed is preferably subjected to two successive treatments acting against the two opposed sides of the .complex.

The invention also relates to a novel type jof nonwoven product obtained by implementing this method-.

Such a hybrid nonwoven, which therefore consists of a mixture of fibers of different type, is characterized in that it is. composed of a ply of natural- fibers, especially wood fibers, trapped between two nonwoven webs consisting of extruded and drawn filaments, based on a 'synthetic material, the cohesion of the various plies being obtained by entanglement thanks to the action of water jets.

Brief description of the drawings The invention and the advantages which stem therefrom will, however, be more clearly understood from the illustrative examples which follow, given below by way of indication but implying no limitation, and which are illustrated by the appended drawings in which: figure 1 is a schematic view of an entire line for producing a complex fabric produced in accordance with the method according to the invention; and figures la, lb, lc and Id are enlarged views of the regions circled in this figure 1.

Manner, of realizing the invention A composite nonwoven is produced continuously on a production line, like that illustrated' in figure 1.

To do this, a first web (2) of continuous filaments is produced by means of a production unit, denoted by the general reference (1), by melting, spinning and drawing, which filaments are deposited and distributed over a moving conveyor belt. (3) .

Optionally, immediately after formation, thi's first web (2) may be subjected to a compacting operation by means of a press roll or by the action- of jets coming from a rail of water injectors. ' : The continuous filaments .of this first web : (2) may be based on a polymer consisting of polypropylene, polyester or other synthetic materials,, such as a polyethylene or polyamide, this list ;not being exhaustive. Optionally, the continuous filaments ma consist of what are called "bicomponent" filaments,, such as those obtained by the coextrusion of polypropylene and polyethylene. .

The web (2) of nonbonded continuous filaments is then transferred under a unit, denoted ■ by the general reference (4), which, by the airlaid technique, allows discontinuous fibers (4), of another type,1 and more particularly cellulosic, especially wood, fibers, to be deposited on the surface of the first .web (2) .

The cellulosic fibers are deposited on the surface of the first web (2) by means of a stream of air. Preferably, the filamentary web (2) is held in place on the conveyor belt (3) by means of a suction; unit (5) . Thereafter, said fibers (4). are preferably deposited between the nonbonded filaments of the web (2) by the effect : of the suction, thus allowing excellent integration of the two constituent s .

The complex (2, 4) which is still helcl in place supported by the conveyor' belt (3) is then taken under a second zone (6) for forming a second ;web (7) of continuous filaments, these also being synthetic filaments, of the same type as or of a different type from those of the first web (2) .

A press roll (8) is preferably placed after this zone for depositing the web (7) and makes it possible to compact . the assembly for the purpose of transferring it to the water-jet bonding unit, denoted by the general reference ('9) , which follows the production line.

Optionally, this compacting operation could be carried out by means of a rail of water injectors. ; The complex is then introduced into the water-bonding zone (9) on a conveyor (10) on which are carried out, in succession, the '■ operations of compacting and prewetting the assembly by means of an upper conveyor (11) tangential to the lower conveyor (10)',' and within which a water injector (12) is placed.

After the complex has been compacted and prewetted, it is subjected to the action of a succession of water jets (13) delivered by several water injectors placed in series.

These water jets (13) consolidate the assembly consisting of the various plies of the complex and give the upper ply good abrasion resistance.

The structure thus treated is then transferred, by being turned upside down, onto a cylinder (14), or onto another conveyor, associated with several; injectors (15) which also deliver water jets onto the . other . side , of the complex, thus reinforcing . the consolidation of the assembly of plies, while giving the ply : facing the jets good abrasion resistance.

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

It is then dried by means of a traversing air cylinder (17) and then taken up in a conventional manner, for example in the form of a wound package (18) . ■ Example ' ' A product in accordance- with the invention is produced in the following way.

A web (2) of continuous filaments, weighing 15 g/m2, is produced on a unit sold 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 embodiment, as polymer, polypropylene such as that sold by Amoco under the reference 100 ZA 35 is extruded. 1 The web formed consists, of 7000 filaments per meter of width and- is produced at a rate of 250 meters per minute.; The . diameter of the filaments after drawing is about 15 microns. : ' A suction unit placed opposite the drawing slit (20) allows precise control of the way in which the filament is deposited on the conveyor belt (3) and of its uniformity thereover.

Placed above the same conveyor (3) is a unit (4) for distributing, by the airlaid technique, discontinuous fibers over the web (2) formed beforehand.

Such a fiber-distributing unit, may consist conventional unit such as that sold by M & J.

In the- specific example, 35 g/m2 of cellulosic fibers, and more particularly wood fibers, sold by Korsnaes, were deposited, on the spunbond web (2), ;these wood fibers, with a length of around 3 mm, being usually referred to by the expression "fluff; pulp" . ; , ■ i ' A suction box (5) is placed beneath the conveyor under the entire surface of the airlaid distributing head (4). This suction head (5) is connected to a vacuum generator which allows the wood fibers to be uniformly distributed while maintaining the homogeneity : of the spunbond web (2) . · A press ,roll (not shown) , · the speed of1 which is synchronized with said belt (3), compacts the assembly thus formed. · ; After compacting, a ' second spunbond web/ weighing 15 g/m2, of' the same type as the first web (2) is deposited on the surface of the complex. ; This second web may be formed either on1 the same conveyor (3) or on a separate conveyor.

This web (7) is therefore distributed over the ply (4) of cellulosic fibers.. Preferably, transfer takes place in a positive manner using a suction box . (.5a) placed beneath the main conveyor opposite the ' point of transfer.

The structure obtained, which weighs 65' g/m2, is optionally compacted by means of a roller (8). This compacting may optionally be carried out by means of an additional rail of water injectors. ; The complex is then transferred onto the conveyor (10) of the water-jet bonding unit (9). .

Such a bonding unit comprises a main conveyor · (10) above which is placed an upper conveyor (11) tangential to the latter, and inside which is placed a water injector (12) delivering 4000 jets of water per meter, these .jets having a diameter of 130 microns and a velocity of 34 meters per second. • . . i The sandwich thus compacted and .wetted is j treated on its topside by six water injectors (13),· placed in series, which blast water jets 120 microns ;in diameter spaced apart by .0.6 irra with velocities of 110, 125, i 140, 140, 140 and 140 m/s respectively.

The treated complex is then transferred, by turning it over, onto a cylinder (14) around which are placed four water injectors (15) which blast, water jets 120 microns in diameter spaced apart by 0.6 mm with velocities of 125, 140, 140 and 140 m/s, respectively. : ■ The complex thus consolidated is transferred onto an expressing conveyor (16) , on which it is expressed by a suction box in which there is a vacuum of 400 mbar. ■ i The assembly is then dried at a temperature of 120°C by a traversing air cylinder (17), and then taken up at (18). ' ; It is observed that the product obtained at; the end of the production line weighs about 60 g/m2, exhibits excellent homogeneity, has a good, handle and great pliancy, and excellent abrasion resistance both in the dry state and in the wet state.

It has a high water absorptivity, of around 8;50%.

[ Such a water absorptivity is comparable to that of hybrid nonwovens consisting of discontinuous ; fibers and produced by carding.

On the other hand, the abrasion resistance both in the dry state and in the wet state, together with' the mechanical properties, are greatly superior. : Such a product is perfectly adapted to various applications, such as industrial or- domestic wiping products, impregnated wipes and operating' gowns and drapes, such . applications being given by way of indication, but implying no limitation.

Claims

inon rtrnn, 12 150,139/2 WHAT IS CLAIMED IS:

1. A method for producing a complex nonwoven fabric which consists in continuously producing a complex in which a fibrous web based on cellulosic fibers is sandwiched between two webs of continuous filaments, which method consists: in producing a first web of continuous filaments, the bundle of extruded and drawn continuous filaments being received on a moving conveyor belt in the form of a nonbonded lap; in depositing on this web, by the airlaid technique, a second web of cellulosic fibers; in depositing on the fibrous web a second web of nonbonded continuous filaments; in transferring the complex thus formed onto a water-jet bonding unit and in consolidating the assembly by hydro-entanglement, and in drying the hybrid nonwoven produced and then taking it up, for example in the form of a wound package.

2. The method as claimed in claim 1, characterized in that; the cellulosic fibers used in the production of the complex are wood fibers.

3. The method as claimed in either of claims 1 and 2, characterized in that the complex is subjected to two successive bonding treatments by water jets acting against the two opposed sides of said complex.

4. A hybrid nonwoven obtained by implementing the method as claimed in one of claims 1 to 3, characterized in that it is composed of a ply of natural fibers, especially wood fibers, trapped between two nonwoven webs consisting of continuous, extruded and drawn filaments, based on a synthetic material, the cohesion of the various plies being obtained by entanglement thanks to the action of water jets. 13 150,139/2

5. A method for producing a complex nonwoven fabric according to claim 1, substantially as hereinbefore described and with reference tot he accompanying drawings. ;

6. A hybrid nonwoven according to claim 4, substantially as hereinbefore described and with reference to the accompanying drawings. for the Applicant: WOLFF, BREGMAN AND GOLLER