WO2005095689A1

WO2005095689A1 - Technical fabric production method and carbon fabric thus produced

Info

Publication number: WO2005095689A1
Application number: PCT/FR2005/000781
Authority: WO
Inventors: Alain Lengrand; Stéphanie Lambour
Original assignee: Porcher Tissages
Priority date: 2004-03-31
Filing date: 2005-03-31
Publication date: 2005-10-13
Also published as: FR2868440A1; FR2868440B1

Abstract

The invention relates to a method of producing technical fabric (1) from a primary fabric (1A), comprising a step consisting in increasing the optical blocking rate F of the primary fabric. The inventive method is characterised in that, during the aforementioned step, the primary fabric (1A) is conveyed past a device (6) that emits a curtain of fluid (7) with pressure P, such that at least one of the faces (4, 5) of the primary fabric (1A) is subjected to the impact of the fluid curtain (7), pressure P being essentially within a range of between 0.05 and 5 bar. According to the invention, the primary fabric (1A) is supported by a transport tension force and does not rest on any solid support. The invention also relates to methods of producing technical fabrics as well as to the design and use of said fabrics.

Description

PROCESS FOR OBTAINING A TECHNICAL FABRIC AND CARBON FABRIC LIKELY TO BE OBTAINED BY THIS PROCESS

TECHNICAL AREA

The present invention relates to the general technical field of technical fabrics, that is to say fabrics having structural properties giving them an aptitude for an industrial use, in particular as reinforcements or as supports in various applications, as well as their production processes.

The present invention relates more particularly to a process for obtaining a technical fabric having structural properties giving it an aptitude for industrial use, from a primary fabric having a lower face and an opposite upper face, said method comprising a step of increasing the rate of optical closure F of the primary tissue to obtain a closed tissue.

The present invention also relates to a technical carbon fabric capable of being obtained by the process according to the invention, said fabric having structural properties giving it an aptitude for industrial use, and using warp and weft threads carbon of size 1K, 3K or 6K.

PRIOR ART

Technical fabrics, and in particular glass or carbon fabrics, are at present widely known and widespread because of their multiple and particularly advantageous applications in various industrial fields such as for example the sector of composite materials, the electronic and electrical field, aeronautics, automobile, building or even shipbuilding.

The technical fabrics known to date are produced using weaving looms using the crossover of warp threads with weft threads. The fabric “fomibé of trade” thus obtained can thereafter be subjected to treatments aiming at improving its structural characteristics, with a view for example to confer better mechanical properties on the composite material which will be manufactured from the fabric thus treated.

A known treatment consists in subjecting the fabric to the action of water jets, so as to spread the filaments composing the threads of the fabric, and thus "close" the fabric, that is to say reduce the surface of the voids present between the wires.

The known fluid jet treatment methods are however generally complex and expensive to implement, and sometimes cause the degradation of the tissue, so that the latter is no longer suitable for certain demanding applications in terms of quality and thus loses all or part of it. of its initial technical nature.

For the reasons mentioned above, it is impossible to date to obtain, in certain ranges of fabrics, technical fabrics having an excellent rate of closure and suitable for the most demanding applications in the industrial field.

This problem is particularly acute in the field of technical carbon fabrics, which by their very nature are very difficult to modify once woven without it prohibitively altering their structural properties.

STATEMENT OF THE INVENTION

The invention therefore aims to remedy the various drawbacks listed above, and to propose a new process for obtaining a technical fabric which is simple and inexpensive to implement, while making it possible to obtain a technical fabric having improved technical characteristics.

Another object of the invention is to propose a new process for obtaining a technical fabric which is particularly quick to implement.

Another object of the invention is to propose a new process for obtaining a technical fabric having an excellent compromise between simplicity of implementation and quality of the fabric obtained.

Another object of the invention is to propose a new process for obtaining a technical fabric which makes it possible to obtain a fabric with particularly regular and homogeneous characteristics.

Another object of the invention is to propose a new process for obtaining a technical fabric which implements a reduced number of steps.

Another object of the invention is to propose a new process for obtaining a technical fabric which is effective whatever the size coating the primary fabric.

Another object of the invention is to propose a new technical carbon fabric which has improved general characteristics. Another object of the invention aims to propose a new technical fabric of particularly economical carbon.

The objects assigned to the invention are achieved using a process for obtaining a technical fabric having structural properties giving it an aptitude for industrial use, from a primary fabric having a lower face and an opposite upper face, said method comprising a step of increasing the rate of optical closure F of the primary tissue to obtain a closed tissue, characterized in that during said step of increasing the rate of optical closure F, we do scrolling said primary fabric opposite a device for emitting a curtain of pressure fluid P, so as to subject at least one of the faces of said primary fabric to the local and momentary impact of the curtain of fluid, the pressure P being appreciably included in a range extending between 0.05 and 5 bars, the primary fabric being maintained, at least at the level of the impact of the curtain of fluid, by the exercise of a transport tension and does not pressing s ur no solid support.

The objects assigned to the invention are also achieved using a technical carbon fabric capable of being obtained by the process according to the invention, said fabric having structural properties giving it an aptitude for industrial use, and using warp and weft of carbon threads of size 1K, said fabric being of surface mass M expressed in g / m ² , having an optical closure rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F ', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8 .

The objects assigned to the invention are also achieved using a technical carbon fabric capable of being obtained by the process in accordance with the invention, said fabric having structural properties giving it an aptitude for industrial use, and using warp and weft of carbon threads of size 3K, said fabric having a surface mass M expressed in g / m ² , having an optical closing rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8.

The objects assigned to the invention are also achieved using a technical carbon fabric capable of being obtained by the process according to the invention, said fabric having structural properties giving it an aptitude for industrial use, and using warp and weft of carbon threads of size 6K, said fabric being of areal mass M expressed in g / m ² , having an optical closing rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F ', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{' 3} M ² - 0.157 M + 76.8 .

SUMMARY OF DRAWINGS

Other particular objects and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the appended drawings below, purely by way of non-limiting illustration, in which:

- Figure 1 illustrates, generally in a side view in section, an installation allowing the implementation of the method according to the invention. - Figure 2 illustrates, schematically in top view, the structure of a primary tissue prior to the implementation of the method according to the invention.

- Figure 3 shows a graph representing, in a comparative manner, the evolution, as a function of the surface mass M, of the ratio R of a fabric according to the invention (curve A), compared to a conventional fabric (curve B).

BEST WAY TO IMPLEMENT THE INVENTION

FIG. 1 represents the implementation of a process for obtaining a technical fabric 1 from a primary fabric 1A having a lower face 5 and an opposite upper face 4.

The method according to the invention makes it possible to obtain a technical fabric 1 having structural properties which give it an aptitude for industrial use, that is to say for technical use other than clothing or decoration for example.

The expression “technical fabric having structural properties giving it an aptitude for industrial use” therefore designates fabrics whose structural properties (thickness, flatness, surface condition, texture, etc.) are extremely precisely predetermined and are homogeneous. , stable and durable.

Such technical fabrics can thus be used in various applications, in particular in the manufacture of composite materials or the manufacture of supports for electronics, applications which require, as is well known to those skilled in the art, fabrics with very high properties. specific. The primary fabric 1A, from which the process according to the invention allows the technical fabric 1 to be obtained, is itself a technical fabric having structural properties giving it an aptitude for industrial use.

The process according to the invention is therefore a process which makes it possible to improve existing technical fabrics, and in particular to give them a thinner and more regular thickness than that of fabrics of the prior art.

The primary fabric 1A is conventionally obtained by a weaving operation, that is to say an operation of interlacing warp threads 2 and weft threads 3 (cf. FIG. 2).

In the context of the invention, the primary fabric 1A may have any type of weave, and may for example consist of a canvas, twill, satin or even a basket weave.

As for the texture of the primary fabric, it can be balanced or else accentuated in the number of warp threads per centimeter, or in the number of weft threads per centimeter.

Advantageously, the twist in the threads making up the primary tissue 1A is low, and even more preferably substantially zero, in order to facilitate and optimize the step of increasing the optical closure rate F of the primary tissue 1A described below. . The implementation of the inventive method is however not dependent on a particular level of torsion.

According to the invention, the method comprises a step of increasing the rate of optical closure F of the primary tissue 1A in order to obtain a closed technical fabric 1, that is to say a tissue whose rate of optical closure F 'is higher than the rate F of primary tissue 1 A. The optical closure rate is a parameter well known to those skilled in the art.

This parameter can be obtained by an optical measurement in which: - a black and white photograph is taken of one of the faces of the fabric, for example the upper face 4; - this photograph is then processed using software (for example the “BIOCOM VISIOL @ B 2000” brand software) which, thanks to the definition of a black level and a white level suitable for lighting in photography, to delimit the surfaces occupied by holes 5 and the surfaces occupied by wires 2, 3.

The total white surface S _b and / or the total black surface S _{n is} then calculated using the software.

The closing rate is then given by the following formula: F = (S _t -S _b ) / S _t,

where S _t is the total area of the photograph.

The closing rate F can obviously also be calculated as follows: F = S _n / S _t

The optical closure rate F is therefore between 0 and 1, the value 1 corresponding to a completely closed tissue, that is to say free of holes 5.

The optical closure rate F thus makes it possible, from a very simple optical measurement, which does not necessarily require software for its implementation, to have indirect information on the rate of coverage of the fabric, that is to say the "covering capacity" of the fabric, a capacity which is itself correlated with the porosity of the fabric.

However, in very many industrial applications, it is necessary to have available fabrics which have the highest possible coverage rate, while allowing their other characteristics to unchanged, or possibly improved, quality levels.

To this end, the method according to the invention therefore comprises a step of increasing the rate of optical closure F of the primary tissue 1A, during which said primary tissue 1A is scrolled opposite a transmission device 6 of a fluid curtain 7 of preferably continuous pressure P, so as to subject at least one of the faces 4, 5 of said primary fabric 1A to the local and momentary impact of the fluid curtain 7.

Advantageously, the fluid used is a liquid, and for example consists of water (at room temperature or heated), or else of a specific treatment solution, of the finishing solution type (“finish” solution). In what follows, reference will be made to a fluid of a liquid nature, of the aqueous fluid type.

In the example shown in FIG. 1, and to which reference will be made in the following, the movement of the primary fabric 1A opposite the emission device 6 is obtained by keeping the emission device 6 fixed while the fabric primary 1A is driven by a continuous longitudinal translational movement.

It is however entirely conceivable, without departing from the scope of the invention, for the scrolling of the primary fabric 1A to be obtained while retaining the fixed fabric 1A, while the emitting device 6 moves along the fabric 1A.

The emission device 6 advantageously comprises a single ramp mounted in line perpendicular to the direction of travel of the fabric and on which are mounted, preferably in transverse alignment relative to the primary fabric 1A, a series of projection nozzles, regularly spaced opposite all the width of fabric to be treated, so that the projection surfaces of each nozzle overlap to form a single fluid blade constituting the fluid curtain 7.

It is however entirely conceivable that instead of a series of nozzles spaced from each other, the emission device 6 comprises a single nozzle, the orifice of which has a form of slot, possibly of thickness adjustment (for example from 1 to 15 mm), said slot extending, preferably continuously, over the entire width of the primary fabric 1A.

Advantageously, the emission device 6 is positioned relative to the primary tissue 1A so that the fluid curtain 7 is directed on the primary tissue 1A with an angle of incidence substantially equal to 90 °, it being understood that other angles of incidence may be adopted without departing from the scope of the invention.

Advantageously, the impact of the fluid curtain on the primary fabric 1A takes place according to a substantially continuous impact line (in space and time) and rectilinear, which extends over the entire width of the primary fabric. 1A.

According to an important characteristic of the process according to the invention, the pressure P of the fluid curtain 7 is substantially within a range extending between 0.05 and 5 bars, and is preferably included in a range extending between 0.4 and 4.5 bars.

The applicant has in fact established that, unexpectedly and surprisingly, this pressure range makes it possible to obtain, even in a single passage of the fabric 1A under the curtain of fluid 7, a technical fabric 1 having an optical closing rate F ' (and therefore an associated coverage rate) higher than that of the 1A fabric of the prior art, while having remarkable and improved characteristics for all of the other criteria taken into account for the industrial use of the fabric (flatness, stability and dimensional regularity, thickness, etc.).

The aforementioned technical effect is also obtained regardless of the nature of the size of the primary fabric 1A. In particular, the method according to the invention does not require that the primary fabric 1A be covered with a size specially formulated to facilitate the closing of the fabric. On the contrary, the process according to the invention produces a technical effect even with conventional sizes.

The pressure P may of course, within the range 0.05 - 5 bars, be adapted by those skilled in the art to the particular type of primary tissue 1A which it proposes to submit to the inventive process. A person skilled in the art will in particular have to take into account the surface mass Mp of the primary fabric 1 A and the nature of the latter (glass or carbon for example).

In particular, the technical effect provided by the invention can be modulated in particular by adjusting the following different parameters: - the distance H between the emission device 6 of the fluid curtain 7 and the primary fabric 1A, this distance preferably being adjustable and being for example between 0.01 and 20 cm, and preferably being substantially equal to 3 cm; - the dimensional characteristics of the fluid curtain 7; thus, when the fluid curtain 7 is produced using a series of aligned nozzles, the person skilled in the art can determine the diameter of the most suitable nozzle orifices (for example between 2 and 5 mm), as well than the shape of the section of the nozzle orifices (fixed flat jet, fixed square jet or rotary round jet for example); it will also be possible to adjust the spacing of the nozzles, which are advantageously regularly spaced 4 cm (from center to center); - The running speed V of the primary fabric 1A, called the transport speed V, which is preferably between 0.1 and 100 m / min, said speed being controlled by winding devices 9 and unwinding 8 which will be described in more detail in the following; - The physical characteristics of the fluid curtain 7 which include, in addition to the pressure P, the volume flow rate of said curtain, and in particular, in the case where the impact of the fluid curtain 7 on the primary fabric 1A takes place along a line of substantially rectilinear impact which extends over the entire width of the primary fabric 1A, the volume flow rate per unit length of width D, for example substantially between 0.1 and 10 L / min / cm.

In other words, a person skilled in the art, as a function of the characteristics of the primary fabric 1A that he wishes to "close", and in particular of the surface mass of this fabric, and according to the pressure level P, between 0, 5 and 5 bars, which he will have determined, will adapt the other parameters, and in particular the parameters mentioned above, to obtain the technical effect. The method according to the invention thus makes it possible to obtain, from a primary technical fabric 1A, a “closed” technical fabric 1 whose set of structural characteristics is equivalent to or greater than the structural characteristics of the “open” primary fabric 1 A.

Advantageously, in the context of the step of increasing the optical closing rate F, the primary fabric 1A is passed through only once opposite the emission device 6 of the fluid curtain 7.

Thus, a single passage of the primary tissue 1A opposite a single fluid emission device 6 makes it possible to obtain an excellent result, without it being necessary to subject the tissue again to complementary jets of fluid or any other operation.

The step of increasing the optical closing rate F in particular makes it possible, in a single pass of the primary fabric 1A facing the fluid curtain 7, to close the fabric in a regular and homogeneous manner both in the warp direction and in the direction of the weft, and this over the entire width of said fabric 1A.

According to the invention, the primary fabric 1A is maintained, at least at the level of the impact of the fluid curtain 7, by the exercise of a transport tension and is not supported on any solid support.

In other words, the primary fabric 1A is not conveyed by a material element of the conveyor belt or conveyor belt type, but is simply moved by being put in traction longitudinally.

This technical arrangement makes it possible, by a synergistic effect with the pressure level P retained by the invention, to increase the effects of the curtain of fluid 7, and thus to contribute to a better homogeneity of the properties of the technical fabric obtained by the process. subject of the invention. Preferably, the transport voltage is chosen to correspond to the minimum tension, called standard tension, necessary to compensate for the flaccidity of the primary fabric 1A and to give it substantially a flat character in the absence of other stresses.

This tension is therefore just sufficient to give a substantially flat character to the fabric 1 A in the impact zone of the fluid curtain 7, and therefore allows possible deformations of the primary fabric 1A under the effect of the fluid curtain 7, this which allows said fabric to "work" under the effect of the curtain of fluid, without being blocked by a solid support, thereby helping to optimize the final properties of the technical fabric 1 obtained.

For example, for a primary carbon fabric, the tension exerted should not be greater than substantially 30 kg for a width of 1270 mm, and will generally be, for such a width, preferably of the order of 10 kg.

Advantageously, the movement of the primary fabric 1A, as well as the exercise of the transport tension, are both ensured by a unwinding means 8, formed for example by a first reel around which the primary fabric 1A is wound, cooperating with a winding means 9, formed for example by a second reel around which is wound the technical fabric 1 obtained.

Preferably, the unwinding means 8 and the winding means 9 are arranged opposite, at a distance from each other, so that their respective centers of rotation 8A, 9A belong to a substantially horizontal right.

The fabric 1A is thus routed substantially horizontally, its guidance between the winding means 9 and unwinding means 8 being preferably provided by guide rollers 14, 15, for example two in number, distributed on either side of the emission device 6, and on which the fabric rests.

Advantageously, as shown in FIG. 1, only one of the faces 4, 5 of the primary fabric 1A, and for example the lower face 5, is subjected to the direct impact of the curtain of fluid 7.

Advantageously, a cover 10 is arranged opposite one of the faces 4, 5 of the primary fabric 1A, and preferably opposite the face 4 of the primary fabric opposite to the face 5 subjected to the direct impact of the curtain of fluid. 7, in this case the upper face 4 in the example of FIG. 1. Said cover 10 is arranged in such a way that the primary fabric 1A, when it travels, is interposed between the emission device 6 of the curtain fluid 7 on the one hand and the cover 10 on the other hand.

The cover 10 is thus preferably fixedly mounted in position relative to the fluid curtain 7.

Advantageously, the distance separating the primary fabric 1A from the cover 10 is adapted (that is to say is sufficiently small) to create a layer of fluid 11 between the cover 10 and the primary fabric 1A, said layer of fluid 11 being supplied by a fraction of the fluid from the fluid curtain 7, a fraction which passes through the primary tissue A.

The fluid layer 11 thus forms a fluid and flexible counter-support for the fabric 1A, which further increases the technical effect provided by the fluid curtain 7. However, it is quite conceivable that the cover 10 alone forms a counter-support, without a fluid mattress 11 forming between the fabric 1A and the cover 10, or even that there is no counter-support.

Advantageously, the emission device 6 of the fluid curtain 7 is situated at an altitude lower than that of the cover 10, as illustrated in FIG. 1. This technical arrangement, in cooperation with the other characteristics presented above (presence of 'a cover 10, maintaining the fabric 1A substantially exclusively by tensioning), allows to obtain a fabric 1 having excellent characteristics.

It is however quite possible to adopt a reverse arrangement, in which the cover 10 is located under the fabric 1A, while the emission device 6 is located above the fabric 1A, so as to project the curtain of fluid 7 directly on the upper face 4 of the fabric 1 A.

Furthermore, a fluid recovery tank 12 is advantageously provided, so as to recover the fluid coming from the curtain of fluid 7 possibly with a view, via a recycling circuit (not shown), of replenishing the device d 'emission 6 with this recovered fluid, which will have been previously treated and / or filtered if necessary.

Advantageously, the step of increasing the closure rate is carried out directly on the primary fabric 1A fallen from the loom, in particular without prior sizing operation.

Thus, surprisingly, the simple application of the fluid curtain 7 under the conditions explained above makes it possible to spread the constituent fibers of the wires 2, 3 and thus fill the voids 5, without it being necessary to remove the sizing products beforehand allowing the mechanical strength of the wires 2, 3.

In reality, the step of increasing the closing rate simultaneously makes it possible to wash the primary tissue 1A, washing which causes total or partial desizing, ridding the primary tissue 1A of all or part of the particles or additional products which it could contain.

In the case where the fluid used is a finishing solution (of “finish” type), the fluid curtain 7 even simultaneously performs at least the following three functions: spreading of the fibers constituting the threads 2, 3 to increase the rate of closure optic F, fabric washing, and fabric finishing treatment.

Advantageously, the method according to the invention comprises, after the step of increasing the optical closing rate F, a step of wringing the closed tissue 1, during which said closed tissue 1 is subjected to the action an expression scarf 13.

This scarf 13 is conventionally composed of two rollers 13A, 13B located vertically opposite and between which the fabric is interposed, which thus undergoes a wringing pressure.

The pressure exerted by the scarf 13 will of course be adapted to the fabric so as not to impart irreversible deformation or deterioration to the latter. In particular, with regard to the finest or lightest fabrics, the use of a scarf 13 will be avoided.

Advantageously, the method according to the invention comprises, after the step of increasing the optical closing rate F, a step for drying the closed fabric 1, this step also being able to take place after the spinning step.

We will now focus more particularly on the process according to the invention in the case where the primary fabric 1A is a glass fabric, that is to say a fabric produced by weaving glass threads, or at least mainly glass-based.

In the case where the impact of the fluid curtain 7 on the primary glass fabric 1A takes place along a substantially rectilinear impact line which extends substantially continuously over the entire width of the primary fabric, the volume flow rate by unit of length of width D is preferably substantially between 1 and 3 L / min / cm, the pressure P being preferably preferably within a range extending between 0.1 and 2 bars.

Table 1 below gives some examples of parameters applicable for certain specific glass fabrics.

Table 1

Advantageously, the primary glass fabric 1A is scrolled during the step of increasing the optical closing rate, at a transport speed V substantially less than or equal to 100 m / min, and even more preferably less than or equal to 80 m / min. Anyone skilled in the art will in any case be able to determine the transport speed V that is best suited to the physicochemical characteristics of the glass fabric 1 A that it proposes to treat.

We will now describe in more detail a process according to the invention in which the primary fabric 1 A is a carbon fabric, that is to say a fabric produced by weaving carbon threads (or at least mainly made from carbon) both in warp and weft.

Advantageously, when the primary fabric 1A is a carbon fabric, the impact of the fluid curtain 7 on the primary carbon fabric 1A takes place along a substantially rectilinear impact line which extends substantially continuously over the whole of the width of the primary fabric 1A, with a volume flow rate per unit length of width D substantially between 0.5 and 2 L / min / cm, the pressure P being substantially within a range extending between 1 and 5 bars.

Advantageously, during the step of increasing the optical closing rate F, the primary carbon fabric 1A is passed through at a transport speed V comprised substantially in a range extending between 0.1 m / min and 30 m / min.

Even more preferably, in the case where the method according to the invention is implemented in line with the weaving operation of the primary fabric 1 A, the transport speed V will be adapted to the speed of the operation of weaving, and will preferably be between substantially 0.1 m / min and 5 m / min.

In the case where the method according to the invention is implemented independently of the weaving operation of the primary fabric 1 A, the speed of transport V will be substantially within a range extending between 1 m / min and 15 m / min.

In general, a transport speed V will preferably be adopted, in the case of a primary fabric 1 A of carbon, of the order of 5 m / min.

Table 2 below gives some examples of transport speeds V adapted to certain carbon fabrics whose width is 400 mm, the curtain of fluid being obtained using a line of nozzles regularly spaced 40 mm ( center to center), the average flow rate per nozzle being substantially between 2 and 15 L / min.

Table 2

Table 3 below gives some examples of specific pressure and flow values adapted to certain references of primary carbon fabrics.

Table 3

The process according to the invention has been more particularly described, in the foregoing, for primary glass fabrics or primary carbon fabrics, but it is obviously adaptable to other types of fabrics. Ultimately, the method according to the invention thus implements a preferred pressure range which makes it possible to obtain excellent results in terms of closure, without altering the other physicochemical characteristics of the primary tissue 1A.

Depending on this pressure, and considering in particular the surface mass M _P of the primary tissue 1A, as well as the width L of said primary tissue 1A, the person skilled in the art will be able to adapt the other parameters, and in particular the transport speed V and the volume flow per unit length of width D.

Complementarily and independently, the invention also relates to a process in which the primary tissue 1A, which has a mass surface M _P , travels at a transport speed V, while the impact of the fluid curtain 7 on the primary fabric 1A takes place along a substantially straight impact line extending over the entire width L, with a volume flow per unit length of width D, the speed V, the pressure P, and the flow D being all chosen so that the impact energy E of the fluid curtain 7 on the primary tissue 1A, conventionally calculated according to the following formula:

8 V.M P '

is substantially between 5.918 J / kg (10 ^'6 hp.hr/lb) and 5.918.10 ⁶ J / kg (1 hp.hr/lb), and more preferably between 59.18 J / kg (10 ^"5 hp.hr / lb) and 5,918.10 ⁵ J / kg (0.1 hp.hr/lb).

In other words, the invention therefore also relates to a method in which the step of increasing the optical closing rate F is carried out so that the energy E is included in the aforementioned range.

Advantageously, when the primary fabric 1A is a glass fabric, the impact energy E is between approximately 5.918 J / kg (10 ^"6 hp.hr/lb) and 5.918.10 ⁵ J / kg (10 ^{" 1} hp. hr / lb), and more preferably between 59.18 J / kg (10 ^"5 hp.hr/lb) and 5.918.10 ⁴ J / kg (0.01 hp.hr/lb).

In the case where the primary fabric 1A is a carbon fabric, the impact energy E will advantageously be comprised substantially between 5,918.10 ² J / kg (10 ^"4 hp.hr/lb) and 5,918.10 ⁶ J / kg ( 1hp.hr/lb) and more preferably between 5918 J / kg (10 ^"3 hp.hr/lb) and 5,918.10 ⁵ J / kg (0.1 hp.hr/lb).

Table 4 below gives two examples of energy E applicable for carbon fabrics.

Table 4

The invention also relates to a technical carbon fabric having structural properties giving it a suitability for industrial use.

According to the invention, the technical carbon fabric implements, in warp and weft, carbon threads of size 1 K, or 3 K or 6 K, said fabric being of surface mass M (expressed in g / m ² ) and having an optical closing rate F '(determinable as indicated above, and between 0 and 1).

Preferably, the fabric according to the invention uses carbon threads of identical sizes in warp and in weft. In other words, the carbon fabric according to the invention may be composed only of 1 K yarns, or else only of 3 K yarns, or even only of 6 K yarns.

According to an important characteristic of the invention, the fabric is characterized by a ratio R, equal to M / F ', located substantially on the experimental interpolation curve A defined by the following equation (i): (i) R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8. Equation (i) above corresponds to curve A illustrated in Figure 3, while curve B, whose equation (ii) is: (ii) R = -9.39.10 ^"6 M ³ + 6.06.10 ^"3 M ² - 0.136 M + 76.17,

corresponds to the fabrics of the prior art.

It can therefore be seen that the curve A is systematically below the curve B, which means that the fabrics of the invention have an optical closure rate F 'greater than that of the fabrics of the prior art.

The invention makes it possible in particular to obtain fabrics which, for the great majority of them, have an optical closing rate F ′ which is at least 5% higher than the closing rate F of the fabrics known to date.

Curve A is derived from experimental data, and must therefore be considered by those skilled in the art as a means of characterizing the invention, to which obviously a certain margin of error applies.

This margin of error is dependent on the surface mass M of the fabric considered, as it clearly emerges from the relative positioning of the curves A and B shown in FIG. 3.

Advantageously, the surface mass M of the fabric according to the invention is between approximately 50 and 400 g / m ² .

Even more advantageously, the surface mass M of the fabric will be between 100 and 350 g / m ² and even more preferably between 150 and 300 g / m ² . In a particularly advantageous variant of the invention, the surface mass M of the fabric is less than 119 g / m ² and is preferably between 100 and 119 g / m ² .

It is indeed in these ranges of surface mass that the fabrics of the invention are most clearly distinguished from those of the prior art.

The carbon fabrics in accordance with the invention thus have particularly high closing rates F ′, which make it possible to obtain excellent results during the use of these fabrics, for example as reinforcements in composite materials.

The invention makes it possible in particular to obtain fabrics produced from 3K thickness yarns which have surface weights M much lower than the surface weights Mp of the technical fabrics known to date made from such 3K yarns. For example, the invention relates to technical fabrics produced from 3K thickness yarns whose mass M is substantially less than 150 g / m ² , preferably between approximately 100 and 150 g / m ² , and even more preferably between 100 and 119 g / m ² .

Likewise, the invention makes it possible to obtain fabrics made from yarns of size 6K, the surface mass M of which is significantly lower than the area Mp of technical fabrics known to date made from yarns 6K. For example, the invention relates in particular to technical fabrics produced from yarns of size 6K whose mass M is substantially less than 280 g / m ² , and is preferably between approximately 200 and 280 g / m ² .

The invention also relates in particular, separately and independently, to each of the following fabrics: - technical fabric made from 1K High Resistance yarns woven to form a fabric with an area density M substantially equal to 50 g / m ² , and having an optical closure rate F 'substantially equal to 0.6; - technical fabric made from 1K High Strength yarns woven to form a fabric with an area density M substantially equal to 95 g / m ² , and having an optical closure rate F 'substantially between 0.94 and 1;

- technical fabric produced from 3K High Resistance yarns woven to form a fabric with a surface mass M substantially equal to 120 g / m ² , and having an optical closure rate F 'substantially between 0.9 and 1;

- technical fabric made from 1K High Strength yarns woven to form a 2/2 twill with a surface mass M substantially equal to 150 g / m ² , and having an optical closing rate F 'substantially between 0.97 and 1;

- technical fabric made from 3K High Strength yarns woven to form a fabric with an area density M substantially equal to 150 g / m ² , and having an optical closure rate F 'substantially between 0.96 and 1;

- technical fabric made from 3K High Strength yarns woven to form a 2/2 twill with an area weight M substantially equal to 150 g / m ² , and having an optical closure rate F 'substantially between 0.9 and 1; - technical fabric made from 3K High Strength yarns woven to form a fabric with a surface mass M substantially equal to 160 g / m ² , and having an optical closure rate F 'substantially between 0.97 and 1; - technical fabric made from 3K High Strength yarns woven to form a fabric with an area density M substantially equal to 196 g / m ² , and having an optical closure rate F 'substantially between 0.96 and 1; - technical fabric produced from 3K High Strength yarns woven to form a 2/2 twill with a surface mass M substantially equal to 196 g / m ² , and having an optical closure rate F 'substantially between 0.98 and 1; - technical fabric made from 3K High Resistance yarns woven to form a fabric with a surface mass M substantially equal to 200 g / m ² , and having an optical closing rate F 'substantially between 0.9 and 1; - technical fabric produced from 1 K High Resistance yarns woven to form a fabric with an area density M substantially equal to 150 g / m ² , and having an optical closure rate F ′ substantially between 0.97 and 1.

Table 5 below finally contains a series of examples of fabrics according to the invention, which were obtained using the process according to the invention.

It should however be noted that the fabrics according to the invention could also be obtained by methods which differ from that described above, without going beyond the ambit of the invention.

Table 5

POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its industrial application in the design, manufacture and use of technical fabrics.

Claims

- Method for obtaining a technical fabric (1) having structural properties giving it a suitability for industrial use, from a primary fabric (1A) having a lower face (5) and an upper face (4) opposite, said method comprising a step of increasing the rate of optical closure F of the primary tissue to obtain a closed tissue, characterized in that during said step of increasing the rate of optical closure F, said tissue is passed through primary (1A) opposite a device (6) for emitting a curtain of fluid (7) of pressure P, so as to subject at least one of the faces (4, 5) of said primary fabric (1A) to the local and momentary impact of the curtain of fluid (7), the pressure P being substantially comprised in a range extending between 0.05 and 5 bars, the primary fabric (1A) being maintained, at least at the level of the impact of the fluid curtain (7), by the exercise of a transport tension and not relying on any solid support.

- Method according to claim 1 characterized in that a cover (10) is disposed opposite one of the faces (4, 5) of the primary fabric (1A), so that the primary fabric is interposed between the device emission (6) of the fluid curtain (7) and the cover (10), the distance H separating the primary fabric (1A) from the cover (10) being adapted to create a layer of fluid (11) between the cover ( 10) and the primary fabric (1A), said layer (11) being supplied with a fraction of the fluid from the fluid curtain (7), a fraction which passes through the primary fabric (1A). - Method according to claim 2 characterized in that the emission device (6) of the fluid curtain (7) is located at an altitude lower than that of the cover (10).

- Method according to one of claims 1 to 3 characterized in that the transport voltage is chosen to correspond to the minimum tension, called standard tension, necessary to compensate for the flaccidity of the primary tissue (1A) and give it substantially a flat character in the absence of other requests.

- Method according to one of claims 1 to 4 characterized in that the primary fabric (1A) is passed through only once opposite the emission device (6) of the curtain of fluid (7).

- Method according to one of claims 1 to 5 characterized in that the movement of the primary fabric (1A) and the exercise of the transport tension are provided by a unwinding means (8) cooperating with a winding means ( 9).

- Method according to one of claims 1 to 6 characterized in that only the underside (5) of the primary fabric (1A) is subjected to the direct impact of the fluid curtain (7).

- Method according to one of claims 1 to 7 characterized in that the step of increasing the closing rate F is carried out directly on the primary tissue (1A) fallen from the loom, without prior desensing operation.

- Method according to one of claims 1 to 8 characterized in that it comprises, after the step of increasing the optical closing rate F, a step of wringing the closed fabric (1), during which subject said closed fabric (1) to the action of an expression scarf (13).

-A method according to one of claims 1 to 9 characterized in that it comprises, after the step of increasing the rate of optical closure F, a step of drying the closed fabric (11).

-A method according to one of claims 1 to 10 characterized in that the primary fabric (1A) is a carbon fabric.

-A method according to claim 11 characterized in that the impact of the fluid curtain (7) on the primary fabric (1A) takes place along a substantially straight impact line which extends over the entire width of the fabric primary, with a volume flow rate per unit length of width D substantially between 0.5 and 2 L / min / cm, the pressure P being substantially within a range extending between 1 and 5 bars.

-A method according to claim 11 or 12 characterized in that during the step of increasing the optical closing rate F, the primary tissue (1A) is made to pass according to a transport speed V comprised substantially within a range extending between 0.1 m / min and 30 m / min, and more preferably between 0.1 m / min and 5 m / min if the process is carried out in line with the weaving operation of the primary fabric (1 A ), or between 1 m / min and 15 m / min if the process is carried out independently of the weaving operation of the primary fabric (1 A).

- Method according to one of claims 1 to 10 characterized in that the primary fabric (1 A) is a glass fabric.

- Method according to claim 14 characterized in that the impact of the fluid curtain (7) on the primary fabric (1A) takes place along a line of substantially rectilinear impact which extends over the entire width of the primary tissue, with a volume flow per unit length of width D substantially between 1 and 3 L / min / cm, the pressure P being substantially within a range between 0.1 and 2 bars.

-A method according to claim 14 or 15 characterized in that during the step of increasing the optical closing rate F, the primary tissue (1A) is passed through at a transport speed V substantially less than or equal to 100 m / min.

- Method according to one of claims 1 to 16 characterized in that the primary fabric (1A) has a surface mass p and passes according to a transport speed V, while the impact of the curtain of fluid (7) on the fabric primary (1A) is carried out along a substantially rectilinear impact line which extends over the entire width L of the primary fabric (1A), with a volume flow rate per unit length of width D, the speed V, the pressure P and the flow rate D being chosen so that the impact energy E of the curtain of fluid on the primary tissue (1A), calculated according to the following formula: E is substantially between

5.918 J / Kg (10 ^"6 hp.hr/lb) and 5.918.10 ^e J / Kg (1hp.hr/lb).

- Method according to claims 14 and 17 characterized in that the impact energy E is substantially between 5.918 J / Kg (10 ^"6 hp.hr/lb) and 5.918.10 ⁵ J / Kg (10 ^_1 hp.hr/ lb).

- Method according to claims 11 and 17 characterized in that the impact energy E is comprised substantially between 5,918.10 ² J / Kg (10 ^"4 hp.hr/lb) and 5,918.10 ^e J / Kg (1 hp.hr/ lb). -A method according to one of claims 1 to 19 characterized in that the fluid is a liquid.

-Technical carbon fabric (1) capable of being obtained by the process according to one of claims 1 to 20, said fabric having structural properties giving it an aptitude for industrial use, and implementing in chain and in weft of carbon threads of size 1K, said fabric having an areal mass M expressed in g / m ² , having an optical closure rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F ', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8.

-Technical carbon fabric (1) capable of being obtained by the process according to one of claims 1 to 20, said fabric having structural properties giving it an aptitude for industrial use, and implementing in chain and in weft of carbon threads of size 3K, said fabric having an areal mass M expressed in g / m ² , having an optical closure rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F ', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8.

-Technical carbon fabric (1) capable of being obtained by the process according to one of claims 1 to 20, said fabric having structural properties giving it an aptitude for industrial use, and implementing in chain and in weft of carbon threads of size 6K, said fabric having an areal mass M expressed in g / m ² , having an optical closure rate F 'of between 0 and 1, and being characterized by a ratio R, equal to M / F ', located substantially on the interpolation curve defined by the following equation: R = -7.54.10 ^"6 M ³ + 5.38.10 ^{" 3} M ² - 0.157 M + 76.8.

-Fabric according to one of claims 21 to 23 characterized in that it uses carbon son of identical sizes in warp and weft.

-Fabric according to one of claims 21 to 24 characterized in that its mass M is substantially between 50 and 400 g / m ² .

-Fabric according to one of claims 21 to 25 characterized in that it is made from 3K thickness son and in that its mass M is substantially less than 150 g / m ² , and is preferably included substantially between 100 and 150 g / m ² .

-Fabric according to one of claims 21 to 26 characterized in that it is made from son of size 6K and in that its mass M is substantially less than 280 g / m ² , and is preferably included substantially between 200 and 280 g / m ² .