EP0140798B1 - Process for the manufacture of a coated fabric - Google Patents

Abstract

A method for producing a coated woven fabric, in which the support material comprises disintegrable chemical weft threads which are subsequently removed without the other threads being affected, method wherein: a first support fabric is produced of which only part of the weft threads are disintegrable, and in a weave in which said disintegrable weft thread is so arranged that, were it to be removed, the result would be, not a woven fabric any longer, but a superposition of three criss-crossed layers of parallel warp threads, one layer of weft threads being squeezed between two layers of warp threads, respectively; then, said support fabric is coated with a coating composition; and finally, the deposited coating is gelled in the right temperature conditions to remove the disintegrable weft thread.

Description

The invention relates to a method for manufacturing a coated fabric; it also relates to the coated fabric produced in this way.

In coated fabrics, in particular those which are intended for the manufacture of tarpaulins for trucks and more particularly for the manufacture of side sliding curtains for trucks, there is essentially a search for tear resistance, in particular for primed tear, since the resistance to traction is very largely sufficient.

In fact, if the basic support fabric, generally made of synthetic fibers, exhibits excellent properties of tear resistance, in particular to primed tear, it is known that after coating, this resistance is notably degraded because, inter alia, the threads elementary are blocked in the new structure. Thus it is common to see this resistance to tearing started going from fifty kilos and more for the unbleached support fabric, to only eight kilos for the same fabric after coating.

To overcome this drawback, the most widely used solution on the industrial level consists in increasing the number of wires or the size of these wires, or both at the same time, or even in making them work with special "plaited" type armor called also "Panama". It is thus possible, under the most favorable conditions, to double the resistance to primed tear, but by unnecessarily increasing the weight of the raw materials, therefore the price of the support, as well as the thickness, therefore the total weight of the fabric. The increase in the tear obtained remains nevertheless insufficient.

It has also been proposed to use fabrics no longer woven but knitted-sewn such as those called "Rachel" or "Malimo". If the resistance to tearing is effectively improved, this technique is poorly developed industrially, because the support fabrics are too expensive and too thick.

At the same time, the use of woven or non-woven grids, that is to say heavily perforated fabrics cannot be envisaged as a support, because, by the very fact of the network structure in which the wires are not precisely positioned, uniform and homogeneous coating of such grids is practically impossible at the industrial stage, at least for this application.

In French Patent No. FR-A-1 457 488, it has been suggested to use as support fabrics whose warp alternates between permanent threads and fleeting threads which are partially eliminated during the coating process. This technique made it possible to save textile material at the time when synthetic threads were expensive. Unfortunately, this technique does not make it possible to improve, if not in a small proportion, the resistance to initiated tearing of fabrics coated in this way.

In the patent US-A-2 898 665, a method has been described for manufacturing a ply of tire threads, in which a very ply of warp ply of parallel tire threads is made with a fleeting thread of binding and then eliminated later this binding wire under the conditions not affecting the warp son. This elimination of the binding wire is carried out either by heat or by dissolution, with subsequent elimination of the solvent by heating. This process is not suitable for coating fabrics for tarpaulins, because by the very fact of the loose structure of the textile assembly, this textile assembly cannot be coated correctly, and even it would be, after disappearance of fleeting threads weft, we obtain a single uni-directional web of warp threads, so that the resulting product would have good resistance to tear in the weft, but no resistance to tear in the warp. In addition, the elimination of the fleeting thread, calling on the temperature, would sometimes cause a retraction of these fleeting threads, shrinking which would disturb the flatness of the web of warp threads, which in practice would make impossible a regular coating with the doctor blade. .

The invention overcomes these drawbacks. It relates to a process for the production of coated fabrics which is economical, easy to carry out and which leads to fabrics exhibiting quite unexpectedly tear resistance properties, primed in particular, very markedly improved, without however that the other properties, in particular of tensile strength, be degraded, some of these other properties, such as adhesion, being even also improved.

This process for the manufacture of a woven warp and weft woven fabric, in which the support fabric comprises fugitive chemical weft threads, and in which this fleeting weft yarn is subsequently removed without affecting the other threads, is characterized:

• - puis, en ce que l'on recouvre ensuite ce tissu au moyen d'une composition d'enduction;
• - et enfin, en ce que l'on gélifie la composition d'enduction déposée dans des conditions de température suffisantes pour éliminer le fil fugace de trame.

- in that first of all, a support fabric is produced of which only part of the weft threads is fleeting threads, and in a weave in which the fleeting weft thread is in an arrangement such that if this fleeting thread is removed , one would no longer obtain a woven fabric, but a superposition of three plies of parallel warp threads, crossed between them, respectively two plies of warp threads enclosing a ply of weft threads;

• - Then, in that this fabric is then covered by means of a coating composition;
• - And finally, in that one gels the coating composition deposited under conditions of temperature sufficient to eliminate the fleeting weft yarn.

As we know, the "weave" of a designated fabric is the mode of interweaving of warp and weft threads. The rhythm of an "armor" is the enunciation of the threads that are taken and the threads that are left successively in each pick. A technician will easily be able to see where it should be placed in weft the fleeting thread, so that after disappearance in the fabric of this fleeting weft thread, we no longer obtain a woven fabric, that is to say in which the warp and weft threads are intertwined, but on the contrary, a superposition of plies of threads parallel to each other, crossed between them, in particular orthogonally, respectively in order a first ply of threads parallel to the warp, in the middle a second ply of threads parallel to weft orthogonal to the first ply, a third ply of weft threads parallel to the first, but whose threads are offset from those of the first ply.

• l'armure est un taffetas (armure dénommée également unie ou toile) et le fil fugace est tramé un coup sur deux;
• - l'armure est un natté (dénommé égalément toile nationale) ou Panama et le fil fugace est tramé à raison d'un groupe de deux sous le pas, ce groupe étant reproduit une fois sur deux;
• -le fil fugace est éliminé par fusion ou décomposition lors de l'enduction et plus précisément lors de la gélification;
• - le fil fugace est en chlorofibres et la composition d'enduction est un plastisol de chlorure de polyvinyle (PVC), déposé par exemple à la râcle;
• - le tissu support revêtu de la couche d'enduction, tout en étant fermement maintenu sous tension transversale afin d'empêcher le retrait des chlorofibres, est tout d'abord prégélifié pour empêcher ce retrait, puis toujours sous tension transversale, après une nouvelle enduction notamment des deux côtés, est gélifié dans des conditions de température suffisantes pour faire fondre les chlorofibres et ainsi les faire disparaitre dans la couche d'enduction en PVC;
• - on prégélifie pendant six à quarante secondes à 130°C environ et on gélifié pendant quarante à quatre vingt-dix secondes à 180°C environ;
• - le tissu support est un tissu serré.

Advantageously in practice:

• the weave is a taffeta (also known as plain weave or canvas) and the fleeting thread is woven every other time;
• - the armor is a basket weave (also called national fabric) or Panama and the fleeting thread is woven in a group of two under the step, this group being reproduced once in two;
• the fleeting thread is eliminated by fusion or decomposition during the coating and more precisely during gelling;
• the fleeting thread is made of chlorofibers and the coating composition is a plastisol of polyvinyl chloride (PVC), deposited for example with a doctor blade;
• - the support fabric coated with the coating layer, while being firmly maintained under transverse tension in order to prevent the withdrawal of the chlorofibres, is first of all pregelified to prevent this withdrawal, then always under transverse tension, after a new coating in particular on both sides, is gelled under conditions of temperature sufficient to melt the chlorofibers and thus make them disappear in the PVC coating layer;
• - Pre-gel for six to forty seconds at approximately 130 ° C and gel for forty to ninety seconds at approximately 180 ° C;
• - the support fabric is a tight fabric.

• - tout d'abord, à enduire de manière connue un tissu de contexture particulière, comportant en trame en partie des fils fugaces, dans une disposition appropriée;
• - puis, à gélifier la couche d'enduction déposée dans des conditions aptes à faire fondre le fil de trame fugace, de sorte qu'après enduction, le support textile ne soit plus un tissu, mais une superposition de nappes de fils parallèles superposés en se croisant.

In other words, schematically, the disadvantage consists:

• - firstly, to coat in a known manner a fabric of particular texture, partly comprising weft fleeting threads, in an appropriate arrangement;
• - Then, to gel the coating layer deposited under conditions suitable for melting the fleeting weft yarn, so that after coating, the textile support is no longer a fabric, but a superposition of layers of parallel son superimposed in crossing each other.

Thus, one operates with all the advantages in coating a tight fabric, and one obtains in addition, all the advantages inherent in the structure in layers of parallel threads, like an openwork grid whose threads remain perfectly positioned .

As we deposit the coating layer on a tight fabric, we can obtain a regular and homogeneous coating then, after coating, we obtain an assembly in which the threads are free to move between them without being blocked by the texture of the initial armor, which has completely disappeared. This new structure of plies of parallel threads crossed between them makes it possible to obtain properties of tear resistance, notably initiated, very markedly improved and this, in completely unpredictable proportions, therefore unexpected.

As already said, the fleeting thread is advantageously of the same chemical nature as the coating. With chlorofibres, a PVC coating will be used. Likewise with copolyamide yarns with a low melting point, it is possible to use polyamide coatings. Polypropylene yarns or better still polyethylene yarns with a low melting point can be used advantageously with coatings based on polyolefin.

The fleeting weft thread can be mono- or multifilamentary, or even made of fibers. In order to reduce the cost price, so-called second choice yarns are advantageously used. The title of the fleeting thread is as fine as possible, while remaining compatible with the smooth running of the looms.

The manner in which the invention can be carried out and the advantages which result therefrom will emerge more clearly from the following exemplary embodiments given by way of indication but not limiting in support of the appended figures.

• Figure 1 shows the weave of a woven base support fabric according to the invention.
• Figure 2 shows the texture of this fabric after coating and disappearance of the fleeting threads.
• Figure 3 is an exploded summary perspective view of a coated fabric for tarpaulin produced according to the method of the invention.

• les références (1, 2, 3 et 4) désignent des fils successifs de chaîne;
• - les références (5, 7 et 9) désignent les fils de trame fugaces;
• - les références (6 et 8) désignent les fils de trame permanents, c'est-à-dire non fugaces;
• - la référence (10) désigne la couche d'enduction.

In these figures:

• the references (1, 2, 3 and 4) designate successive warp threads;
• - The references (5, 7 and 9) designate the fleeting weft threads;
• - The references (6 and 8) designate the permanent weft threads, that is to say non-fleeting;
• - The reference (10) designates the coating layer.

Example 1:

• - armure: natte de 2 (Panama);
• - chaîne: 12 fils par centimètre de polyester 1100 dtex/192 brins, tordus à 130 tours par mètre;
• - trame: 12 coups par centimètre, par groupe de deux coups d'un fil de polyester de 1100 dtex/192 brins sans torsion;
• - tissage en 185 cm de large, de sorte que, après enduction et affranchissement de lisières, on obtienne une largeur utile de 180 cm, ce qui se traduit par un retrait en trame nul;
• - poids du tissu de base: environ 300 g/m2,
• - enduit: plastisol de PVC déposé en plusieurs passes dans les conditions décrites dans le brevet français d'un des co-demandeurs FR-A-2 245 165 (correspondant connu: US-A-4 052 521); poids déposé: 550 g/m², avec en continu maintien sous tension transversale et prégélification pendant trente secondes à 130° C et gélification pendant une minute à 18090C.

A coated fabric is produced, in accordance with the current traditional method described in the preamble, having the following characteristics:

• - armor: mat of 2 (Panama);
• - warp: 12 threads per centimeter of polyester 1100 dtex / 192 strands, twisted at 130 turns per meter;
• - weft: 12 strokes per centimeter, per group of two strokes of a polyester thread of 1100 dtex / 192 strands without twist;
• - weaving in 185 cm wide, so that, after coating and franking of selvedges, we obtain a useful width of 180 cm, which translated by a zero frame withdrawal;
• - weight of the base fabric: approximately 300 g / m2,
• - coating: PVC plastisol deposited in several passes under the conditions described in the French patent of one of the co-applicants FR-A-2 245 165 (known correspondent: US-A-4 052 521); deposited weight: 550 g / m ² , with continuous maintenance under transverse tension and pre-gelation for thirty seconds at 130 ° C and gelation for one minute at 18090C.

• - poids: 850 g/m2;
• - résistance à la traction (rupture mesurée sur des bandes de cinq centimètres de large): en chaîne comme en trame: 450 kg.
• - résistance à la déchirure amorcée (norme AFNOR G 07.055, selon la méthode C dite au mouton pendulaire): 15 kg;
• - adhérence (force d'arrachement de deux bandes de cinq centimètres de large soudées entre elles): 10 kg.

This fabric has the following properties:

• - weight: 850 g / m2;
• - tensile strength (breakage measured on strips five centimeters wide): in warp as in weft: 450 kg.
• - resistance to initiated tearing (standard AFNOR G 07.055, according to method C known as pendular sheep): 15 kg;
• - adhesion (pulling force of two strips of five centimeters wide welded together): 10 kg.

Example 2:

Example 1 is repeated with only one variant, namely that, in the weft, the texture is modified, namely twelve strokes per centimeter distributed in groups of two under the step, at the rate of two polyester threads 2200 dtex / 420 strands without twist and two yarns of chlorofibers Nm 2/40. Thus, in the weft, there is successively a group of two chlorofiber yarns, then a group of two polyester yarns.

Under the effect of heat, chlorofibres which tend to shrink cannot do so because of the transverse tension applied during pregelling, as during gelling. As is known, these wires decompose at 175-180 ⁰ _C.

• - poids: 830 g/m2,
• - résistance en chaîne: 450 kg
• - résistance en trame: 450 kg,
• - amorce de déchirure à la rupture anorcée supérieure à 50 kg, qui est la limite supérieure du déchirometre utilisé,
• - adhérence: 20 kg.

After coating, a fabric is obtained having the following characteristics:

• - weight: 830 g / m2,
• - chain resistance: 450 kg
• - weft resistance: 450 kg,
• - an initiated tear at break greater than 50 kg, which is the upper limit of the tear meter used,
• - grip: 20 kg.

In practice, during primed tear or adhesion tests, in the long run, delamination is observed, but no tear. This proves that the coating has passed on both sides of the textile support.

Example 3:

• - en trame: neuf coups par centimètre, à savoir respectivement dans l'ordre:
  • un coup en fil polyester (6,9) de 2200 dtex/ 420 brins sans torsion,
  • un coup en chlorofibres (5 7 9) Rhovyl (marque déposée de Rhône-Poulenc Fibres) formé par un retors de deux bouts initiaux Nm 40.

We make a plain taffeta weave fabric comprising: - a warp: nine threads per centimeter (1, 2, 3, 4), in polyester: 1100 dtex / 192 strands twisted at 130 turns / dtex meter;

• - in the weft: nine strokes per centimeter, namely respectively in the order:
  • a stroke in polyester thread (6,9) of 2200 dtex / 420 strands without twist,
  • a blow in chlorofibers (5 7 9) Rhovyl (registered trademark of Rhône-Poulenc Fibers) formed by a twist of two initial ends Nm 40.

The ecru fabric, 185 cm wide, weighs 210 g / m ² . A plastisol of PVC is coated under the same conditions as in Example 1, taking care to first deposit an undercoat on each side of the fabric about IOOg / m ² , then ending with a coating of the same plastisol composition on the abrasion layer. As said in Example 1, throughout the coating treatment, the fabric was held tightly in the weft direction.

The finished fabric weighs 680 g / m ² and after franking of selvedges has a width of 180 cm, which shows that there has been practically no shrinkage in the direction of the weft.

The tensile strength of this fabric is in the warp direction of 300 kg and in the weft direction 300 kg.

The resistance to initiated tear is measured under the same conditions and greater than 50 kg, the upper limit of the tear meter used.

The adhesion also measured on five-centimeter strips is 20 kg.

• - une premiè nappe de fils de chaîne (2,4),
• - une deuxième nappe de fils de trame (6, 8) perpendiculaire à la première nappe (2, 4),
• - une troisième nappe de fils de chaîne (1, 3) parallèles à la première nappe (2,4), mais dont les fils (1, 3) sont décalés par rapport aux fils (2, 4) de 1a première nappe;
• - le tout enrobé dans une couche d'enduction (10) régulière et homogène.

It is also observed (see FIG. 2) that the initially woven textile support is transformed after coating, therefore disappearance of the chlorofibres (5, 7, 9), into a superposition of three layers of parallel polyester threads, namely respectively:

• - a first layer of warp threads (2,4),
• - a second ply of weft threads (6, 8) perpendicular to the first ply (2, 4),
• - A third ply of warp threads (1, 3) parallel to the first ply (2,4), but whose threads (1, 3) are offset relative to the threads (2, 4) of the first ply;
• - all coated in a regular and homogeneous coating layer (10).

The results obtained clearly show the totally unexpected progress obtained, since, all the other properties being maintained, the resistance to initiated tearing is more than multiplied by three.

Example 4:

The previous example is repeated, but replacing the fleeting weft yarns made of chlorofibres with polyester yarns of the same title and the same characteristics as the other weft yarns, namely polyester 1100 Dtex / 192 strands without twist.

The fabric obtained weighs approximately 700 g / m ² , has a width of 180 cm, a tensile strength also of 300 kg in each warp and weft direction, but has only an initiated tear of eight kilos (against fifty) and an adhesion of ten kilos (against twenty).

This perfectly illustrates the completely unexpected progress obtained by the method according to the invention.

Example 5:

Example 4 is repeated by alternately placing one out of two chlorofibers in the chain, as taught in French patent FR-A-1 457 488 cited in the preamble.

During the coating heat treatment, the chlorofibers placed in a chain shrink violently when they enter the oven, which leads to the defect known as the "pulling wire". This results in large chain locks; which makes coating practically impossible at the industrial stage.

The fabrics produced in accordance with the invention are essentially characterized by a very markedly improved resistance to tearing, notably initiated. In this way, they can be advantageously used for making the sliding curtains of tarpaulins for trucks, fabrics for containers, for silos, conveyor belts, ventubes, cut fabrics for straps, fabrics for inflatable structures.

Claims (8)

1/ Method for producing a coated woven fabric, in which the support material comprises disintegratable chemical weft threads which are subsequently removed without the other threads being affected, method wherein:

- first, a support fabric is produced of which only part of the weft threads are disintegratable, and in a weave in which said disintegratable weft thread (5, 7, 9) is so arranged that, were it to be removed, the result would be not a woven fabric any longer, but a superposition of three criss- crossed layers of parallel threads (2, 4/6, 8/1, 3), one layer of weft threads (6, 8) being squeezed between two layers of warp threads (2, 4/1, 3), respectively;

- then, said support fabric is coated with a coating composition;

- and finally, the deposited coating is gelled in the right temperature conditions to remove the disintegratable weft thread (5, 7, 9).

2/ Method as claimed in claim 1, wherein the weave of the fabric is a taffeta weave and the disintegratable weft thread in the weave is alternate.

3/ Method as claimed in claim 1, wherein the weave of the fabric is a basket weave, and the disintegratable weft threads (5, 7, 9) are woven two at a time in the shed in alternate manner.

4/ Method as claimed in claim 1, wherein the disintegratable weft threads (5,7,9) are removed by melting or decomposition, during gelation of the deposited coating.

5/ Method as claimed in claim 1, wherein the disintegratable weft thread (5, 7, 9) is in chlorofibers, and the coating composition is a polyvinyl chloride plastisol (PVC).

6/ Method as claimed in claim 5, wherein the fabric coated with the coating layer, being firmly kept under weft tension, is first pre-gelled to prevent the withdrawal of the chlorofibers, and then gelled in temperature conditions that are adequate to cause the chlorofibers to melt, and thus causing them to disappear in the PVC coating layer.

7/ Method as claimed in claim 6, wherein pre- gelling is conducted for ten to forty seconds at 130 °C, and in continuous manner and still under weft tension,gelling is conducted for forty to ninety seconds at 180 °C.

8/ Method as claimed in claim 1, wherein the support fabric is a closely-woven fabric.

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