EP0564331A1 - Reinforcing yarn with controlled electrical losses and process for manufacturing the same - Google Patents

Abstract

A yarn for textile reinforcement with controlled electrical losses and process for its manufacture, this yarn comprising nonconductive noncontinuous fibres (6) and conductive noncontinuous fibres (4). These fibres are approximately parallel and the proportion by weight of conductive fibres (4) does not exceed 20 %. The conductive fibres (4) are carbon fibres or metal fibres. The nonconductive fibres (6) are inorganic fibres or ceramic fibres or technical fibres with low elongation. <IMAGE>

Description

The invention relates to a thread for textile reinforcement with controlled electrical losses, and its manufacturing process.

For homogeneous materials, electrical losses are conventionally represented by electrical conductivity. In the case of heterogeneous media or elements, such as textiles, this physical quantity is more complex. The term “electrical losses” designates the ability of a material to dissipate energy by displacement of charges. These electrical losses are part of the electrical properties of materials.

It is possible to manufacture textile reinforcements with controlled electrical losses, which include non-conductive threads, based on mineral fibers, which ensure the mechanical and thermal resistance of the textile, and charged threads which allow electrical losses.

Such loaded yarns consist of a mixture of non-conductive staple fibers and conductive staple fibers. They have low conductivity and must have properties, particularly homogeneous electrical properties over their entire length.

The invention relates to such threads and their manufacturing process.

French patent FR-2,608,641 describes a process for manufacturing carbon fiber yarns, according to which carbon multifilament cables are transformed by cracking-stretching, so as to obtain long fibers.

Furthermore, American patent US-4,180,968, for example, describes a process for manufacturing composite yarns comprising a mixture of cellulose acetate and polyester fibers, in which the fibers are twisted together, so as to form the son ; the fibers then undergo a false twist.

French patent FR-2,634,790 describes a process for obtaining a yarn consisting of a mixture of yarns of reinforcing fibers, for example carbon fibers, and a yarn of thermoplastic fibers.

According to the technique described in this document, each of the yarns is produced by cracking-stretching a set of multifilaments. The yarns are mixed, the mixture then being drawn and combined with a similar mixture; the whole being stretched again. This technique makes it possible to obtain an intimate mixture of the fibers, in which the relative proportions of the reinforcing fibers and of the thermoplastic fibers are of the order of 65-35%.

None of these known techniques offers and allows the production of yarn for textile reinforcement, which has both low conductivity and constant electrical properties over its entire length.

An objective of the present invention is to provide such a wire and its manufacturing process.

Another objective is to allow the production of such a yarn based on mineral fibers.

It is also an objective of the invention to allow the production of such a wire usable at high temperature (over 400 ° C.).

To this end, the invention relates to a thread for textile reinforcement with controlled electrical losses, comprising non-conductive staple fibers and conductive staple fibers.

According to the invention, the fibers are approximately parallel, and the proportion by weight of conductive fibers is less than 20%.

In a preferred embodiment, the proportion by weight of conductive fibers is less than 5%.

The conductive fibers are advantageously carbon fibers.

The non-conductive fibers are preferably mineral fibers. They can also be ceramic fibers.

The invention also relates to a method for manufacturing these threads, in which filaments, respectively conductive and non-conductive, are used.

One of the manufacturing methods consists in hybridizing in successive stages a conductive yarn by non-conductive yarns. To do this, the filaments, conductive on the one hand, nonconductive on the other hand, are subjected to cracking-stretching, so as to obtain a conductive yarn and a non-conductive yarn.

A conducting yarn is mixed with at least one non-conducting yarn, so as to obtain a level 1 mixed yarn; this level 1 mixed yarn is drawn, then mixed with at least one non-conductive yarn, so as to obtain a level 2 mixed yarn.

These last steps are repeated as often as necessary to obtain a level n yarn, in which the proportion of conductive fibers and the linear mass of the yarn correspond to the desired values.

• la Figure 1 est une représentation schématique en coupe droite d'un fil selon l'invention ;
• la Figure 2 est une vue en coupe horizontale du fil de la Figure 1 ;
• la Figure 3 est une vue en coupe droite du fil de l'invention, lorsque les fibres sont tordues ;
• la Figure 4 est une vue en coupe horizontale du fil de la Figure 3 ;
• la Figure 5 est une vue en coupe droite du fil de l'invention, lorsqu'il est guipé ;
• la Figure 6 est une vue en coupe horizontale du fil de la Figure 5
• la Figure 7 est une représentation schématique du procédé de l'invention.

An embodiment of the invention is described below, with reference to the accompanying drawings, in which:

• Figure 1 is a schematic representation in cross section of a wire according to the invention;
• Figure 2 is a horizontal sectional view of the wire of Figure 1;
• Figure 3 is a cross-sectional view of the yarn of the invention, when the fibers are twisted;
• Figure 4 is a horizontal sectional view of the wire of Figure 3;
• Figure 5 is a cross-sectional view of the yarn of the invention, when it is wrapped;
• Figure 6 is a horizontal sectional view of the wire of Figure 5
• Figure 7 is a schematic representation of the method of the invention.

The thread 2 is intended for the manufacture of a textile reinforcement with controlled electrical losses.

It comprises a mixture of discontinuous non-conductive fibers 6 and discontinuous conductive fibers 4. Here, the term "discontinuous" means fibers whose average length is between 5 and 200 mm.

The conductive staple fibers 4 are carbon fibers, metallic fibers (aluminum, steel, copper, gold ...).

The non-conductive staple fibers 6 are mineral fibers, glass fibers, silica fibers, ceramic fibers, or technical fibers with low elongation such as: aramid, polyethylene, etc. We can mix fibers of different types (glass / aramid, glass / para-aramid, glass / PEEK (Polyether-Ether -Ketone) ...).

The conductive staple fibers 4 and the non-conductive staple fibers 6 are approximately parallel, and their proportion is determined to give textiles the desired electrical properties.

The mass concentration of conductive elements 4 is low, it must not exceed 20%, and preferably be of the order of 5% at most.

Preferably, the diameter of the discontinuous filaments 4, 6 conductors, or non-conductors, is between 1 and 30 micrometers.

The mixture of fibers, respectively conductive 4 and non-conductive 6, can be twisted, so as to give it a better cohesion and a certain mechanical resistance facilitating its textile transformation, such as doubling, weaving, knitting, needling, ... and / or its integration into other processes, such as: impregnation, injection, etc.

In a particular embodiment, a covering yarn 7 is used to reinforce the cohesion of the yarn. This covering thread is then compatible with subsequent use, or can be eliminated.

A particularly advantageous method of manufacturing the wire is described below.

Filaments, respectively conductive 11 and non-conductive 12, preferably having a diameter between 1 and 30 micrometers, are respectively subjected to cracking-stretching operations.

The number of filaments subjected to these cracking-stretching operations depends on the yarn that one wants to obtain. There may be several non-conductive filaments, either of the same kind, for example of glass, or of different natures (glass / aramid, glass / PEEK, etc.).

A cracking-stretching element 13 is supplied with conductive filaments. It is composed of at least two sets of rollers 131/132, 133/134.

The rotational speeds of these two sets of cylinders are different, so that they produce an elongation of the filaments in the region 135 between the two sets of rollers 131/132 and 133/134.

The respective speeds of these two sets of rollers are adjusted according to the material of the filaments and their diameters, so as to produce long staple fibers, that is to say whose average length is between 5 and 200 mm .

The cracking-stretching unit 15 performs the same treatment on the non-conductive filaments 12.

It has two sets of cylinders 151/152, 153/154.

Thus, two yarns 14, 16, respectively conductive and non-conductive, are obtained.

These yarns 14 and 16 are mixed in the mixer 17 of the "intersecting" type and produce a mixed yarn 18 of level 1.

This level 1 mixed yarn 18 feeds a device 19, which produces a stretched mixed yarn 110 of level 1.

The drawing device 19 comprises two sets of rollers 191/192, 193/194 which have different rotational speeds, so as to produce the elongation of the yarn in the intermediate zone 195.

The drawn mixed yarn 110 is itself mixed with a yarn 16 of non-conductive fibers in the mixer 111. Thus, the mixed yarn 120 of level 2 is produced;

This level 2 yarn 120 is itself stretched, then mixed with a new yarn 16 of non-conductive fibers ...

From one level to another, the nature of the non-conductive fibers can change, so as to allow the production of yarns with more than two components, for example glass / aramid / carbon, glass / PEEK / carbon, ... .

These operations are repeated until the desired proportions of conductive fibers and non-conductive fibers are obtained.

This hybrid lock undergoes a set of drawing operations making it possible to obtain the desired linear mass and ends with an operation making it possible to improve the cohesion of the wire. This process is preferably a twisting operation, and / or possibly a wrapping operation.

This manufacturing method is not limiting. Indeed, other procedures, such as simultaneous cracking of hybrid locks, then drawing / spinning, can also be envisaged.

The following three embodiments, given by way of example, were thus obtained.

Example 1

A cracked glass ribbon is produced on the one hand, and a cracked carbon ribbon on the other hand.

These two ribbons are mixed on an "intersecting" type machine, in order to obtain a hybrid ribbon of 86% of glass and 14% carbon.

This ribbon is then stretched on a continuous spinning machine, so as to obtain a 68 tex yarn twisted at 300 rpm.

This yarn is then treated by assembly / twisting at 220 turns / meter at both ends.

The yarn obtained has a titer of 136 tex and contains:
86% glass
14% carbon

Example 2

A hybrid glass / carbon ribbon is produced with a rate of 96% glass and 4% carbon.

This hybrid ribbon is stretched, so as to obtain a yarn of 68 tex without twisting, but wrapped at 500 revolutions / meter with a PVA (Polyvinyl-Acrylic) yarn of 5 tex.

The yarn obtained has a titer of 73 tex and contains:
89% E glass
4.1% carbon
6.9% PVA (Polyvinyl-Acrylic)

Example 3

A hybrid yarn is obtained obtained from the mixture of a cracked glass ribbon, a cracked PEEK ribbon and a cracked carbon ribbon, in the respective percentage of 60% / 35% / 5%.

We stretch to obtain a titer of 68 tex and twisted at 350 turns / meter.

This yarn is then treated by assembly / twisting at 250 turns / meter at both ends.

The yarn obtained has a titer of 136 tex and contains:
60% E glass
35% PEEK (Polyether-Ether-Ketone)
5% carbon

Claims (11)

Yarn for textile reinforcement with controlled electrical losses comprising discontinuous non-conductive fibers (6) and discontinuous conductive fibers (4), characterized in that said fibers are approximately parallel, and that the proportion by weight of conductive fibers does not exceed 20 %. Wire for textile reinforcement with controlled electrical losses according to claim 1, characterized in that the conductive fibers (4) are carbon fibers. Wire for textile reinforcement with controlled electrical losses according to claim 1, characterized in that the conductive fibers (4) are metallic fibers. Yarn for textile reinforcement with controlled electrical losses according to one of claims 1 to 3, characterized in that the non-conductive fibers (6) are mineral fibers. Yarn for textile reinforcement with controlled electrical losses according to one of claims 1 to 3, characterized in that the non-conductive fibers (6) are fibers with low elongation. Yarn for textile reinforcement with controlled electrical losses according to one of claims 1 to 3, characterized in that the non-conductive fibers (6) are ceramic fibers. Yarn for textile reinforcement with controlled electrical losses according to any one of claims 1 to 6, characterized in that the proportion by weight of conductive fibers (4) is less than 5%. Yarn for textile reinforcement with controlled electrical losses according to any one of claims 1 to 7, characterized in that it comprises non-conductive fibers (6) PEEK. Process for manufacturing yarn according to any one of Claims 1 to 7, characterized in that: a) respectively conductive filaments (11) and non-conductive (12), are used; b) the filaments, conductive (11) on the one hand, nonconductive (12) on the other hand, are subjected to cracking-stretching, so as to obtain a conductive yarn (14) and a non-conductive yarn (16) ; c) a conductive yarn (14) is mixed with a non-conductive yarn (16), so as to obtain a mixed yarn (18) of level 1; d) the level 1 mixed yarn (18) is drawn; e) the level 1 drawn mixed yarn (110) is mixed with a non-conductive yarn (16), so as to obtain a level 2 mixed yarn (120); f) steps d) and e) are repeated as often as necessary to obtain a level n yarn, in which the proportion of conductive fibers corresponds to the desired value, then stretching to obtain the desired linear mass. Method according to claim 6, characterized in that the yarn of level n, having undergone a drawing operation, is subjected to a twist. Method according to claim 6, characterized in that the yarn of level n, having undergone a drawing operation, is wrapped.

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