WO2005066412A1 - Silicon composition and useful method for increasing the friction coefficient of an airbag for the protection of the occupant of a vehicle - Google Patents

Abstract

The invention relates to the general field of airbags. The invention more specifically relates to a method and composition enabling the friction of coated fabrics which are used in airbags to be increased by using a silicon composition comprising an additive made up of particles of a resin (III) comprising at least one (co)polyamide. After the composition has been coated on the fabric media and cross-linking has occurred, the coated media have optimum friction coefficient properties.

Description

The general field of the invention is that of silicone coating compositions, in particular those of the bicomponent or multicomponent type, the composition of the invention being useful for the protection of an inflatable bag frictional bag. crosslinkable by polyaddition, hydrosilylation or radical reactions to produce a thin layer elastomer. These crosslinked compositions are suitable, inter alia, as a coating, for example of protection or mechanical reinforcement of different substrates of textile material such as for example fibrous, woven, knitted or nonwoven supports. Such silicone coatings are generally obtained by coating the substrate then hardening resulting from the polyaddition of the unsaturated groups (alkenyls, eg Si-Vi) of a polyorganosiloxane on hydrogens of the same or of another polyorganosiloxane. Currently, many motor vehicles are equipped with an acceleration sensor which measures the decelerations of the vehicle. When the reference value of the deceleration is exceeded, an explosive tablet initiates the combustion of an additional charge, then that of the solid fuel; it turns into gas (for example nitrogen) and inflates the cushion. For more details on these individual protective bags or "airbags", reference may be made in particular to French patent FR-A- 2 668 106. Historically, these are formed by a canvas of synthetic fiber, for example polyamide, covered on at least one of these faces with a layer of an elastomer of the chloroprene type. The airbag (or airbag) is an airbag made of polyamide fabric, folded and tight. The silicone compositions easily supplanted the chloroprenes in this application, as it has been found that the latter do not satisfactorily meet all of the abovementioned specifications. These silicone compositions have therefore found an important outlet in the coating of flexible materials - woven, knitted or non-woven - used for the manufacture of individual occupant protection bags for vehicles, also called "airbags". This is how the present invention relates to the application of silicones in the manufacture of such protective bags. The front airbags can be adaptive and deploy in proportion to the severity of the impact. They can be supplemented with side airbags and curtains. The presence of such a layer or such a protective coating is dictated by the fact that the gases released by the gas generator in the event of an impact, are extremely hot and contain incandescent particles capable of damaging the nylon bag. ^® . The internal protective elastomer layer must therefore be particularly resistant to high temperatures and mechanical stresses. It is also important that this elastomeric coating is in the form of a film, uniform and perfectly adherent to the support of synthetic fabric, forming the walls of the "airbag". However, when the deposition of silicone increases, an increase in the coefficient of friction is observed, that is to say a degradation of the sliding properties of the airbag. In addition, when the silicone layer is on the outside of the airbag, it makes it possible to seal the bag after deployment and inflation. However, these airbags must be designed with fabrics having good sliding properties or a good coefficient of friction so as not to delay the deployment of the bag all this without calling into question the other expected properties, or even improving them, in particular the resistance to fire and temperature, resistance to wrinkling and abrasion (“scrub test”), resistance to tearing and resistance to combing. These good sliding properties are also necessary to improve the manual positioning of an airbag under the sights during its manufacture, especially during sewing operations and reinforcement of the area surrounding the generator. Better sliding properties also reduce the risk of passenger injuries to the face. The prior art EP-A-0 533 840 and US-5 296 298 describes silicone compositions for airbag applications. According to EP-A-0 553 840, these known silicone compositions comprise: - (A) a polydiorganosiloxane having at least two alkenyl groups per molecule, - (B) a polyorganohydrogensosiloxane having at least two hydrogen atoms bonded to silicon in each molecule , - (C) a platinum group metal catalyst, - (D) an adhesion promoter consisting of an epoxy-functional organosilicon compound, - (E) an inorganic filler, the amount of which by weight is defined relative to the amount polyorganosiloxane (A), - (F) a polyorganosiloxane resin, and optionally - (G) a compound useful as a crosslinking inhibitor. However, this reference only presents solutions for obtaining homogeneous and adhesive films for airbag coatings and is silent when the problem cited above is resolved.

According to US Pat. No. 5,296,298, these silicone compositions comprise: - (A) a polydiorganosiloxane having at least two alkenyl groups per molecule,

- (B) a polyorganohydrogensiloxane having at least two hydrogen atoms bonded to silicon in each molecule,

- (C) a siiane with a methacrylic function, - (D) an epoxyalkoxysilane,

- (E) an aluminum chelate, and

- (F) a metallic catalyst from the platinum group. This reference only presents solutions for obtaining silicone films having good adhesion to the airbag support. These compositions are not adapted to the new expectations of airbag manufacturers regarding the control of the sliding properties of the airbag.

The document EP-A-0 681 014 describes a silicone composition, applicable in particular as an internal "airbag" coating and having for this purpose good properties, in particular in terms of fire and temperature resistance, mechanical properties, resistance with aging, adhesion and uniformity of surface, adhesion to textile substrates being more particularly sought after. The solution proposed by this invention consists in using: - a silicone coating composition consisting in the mixture formed of: (1) at least one polyorganosiloxane having, per molecule, at least two C2-C6 alkenyl groups linked to silicon, (2) at least one polyorganosiloxane having, per molecule, at least two hydrogen atoms bonded to silicon, (3) a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the group of platinum, (4) an adhesion promoter, (5) optionally a mineral filler, (6) optionally at least one crosslinking inhibitor, and (7) optionally at least one polyorganosiloxane resin, Composition in which the adhesion promoter is constituted exclusively by the association at least ternary of the following ingredients: - (4-1) at least one alkoxylated organosilane containing, per molecule, at least one C2-C6 alkenyl group, - (4-2) at least one organosilicon compound comprising at least one epoxy radical, and - (4-3) at least one metal chelate M and / or a metal alkoxide of general formula: M (OJ) n, with n = valence of M and J = linear alkyl or branched in C1 - C8, M being chosen from the group formed by: Ti, Zr, Ge, Li, Mn, Fe, Al and Mg. These formulations have the drawback that the elastomer obtained can have a more or less tacky feel, which, in addition to the unpleasantness to the touch, can be detrimental to the properties and the mechanical behavior of the coated support. In the field of air bags for the protection of the occupants of a vehicle, since the value of the coefficient of friction depends in particular on the ability to deploy the bag, an improvement would be particularly welcome.

These compositions are therefore not adapted to the new expectations of airbag manufacturers concerning the control of the sliding properties of the airbag. French Patent No. 2,765,884 describes a silicone composition comprising as a mixture: (1) at least one polyorganosiloxane having, per molecule, at least two alkenyl groups, of C2-C6 bonded to silicon, (2) at least one polyorganosiloxane having , per molecule, at least two hydrogen atoms bonded to silicon, (3) a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the platinum group, (4) an adhesion promoter , (5) optionally a reinforcing system which can be at least one polyorganosiloxane resin and / or at least one reinforcing filler, (6) optionally at least one crosslinking inhibitor, and (7) hollow organic or mineral microspheres. These expandable organic microspheres comprising a polymeric wall containing a liquid or a gas. The expansion of these microspheres is caused by heating beyond the softening point of the polymer and at a temperature sufficient to vaporize the liquid or suitably expand the gas which may be, for example, an alkane such as isobutane or isopentane. The polymers used in its walls are prepared from vinyl chloride, vinylydene chloride, acrylonitrile, methyl methacrylate or styrene monomers or from acrylonitrile / methacrylonitrile or acrylonitrile / vinylidene chloride copolymers. However, the product obtained by this type of composition after crosslinking is a foam whose mechanical properties (for example resistance to combing) are insufficient. It is therefore desirable to find an alternative to this type of composition. The present invention aims to remedy the drawbacks of the prior art. In this perspective, one of the essential objectives of the invention is to provide a method for improving the coefficient of friction of a woven, knitted or coated nonwoven fibrous support. These supports treated by the method according to the invention are useful in particular for applications in the field of safety air bags for vehicles, or airbags. A second objective of the invention is to provide a silicone composition for crosslinking by polyaddition or free radical reactions useful in particular for applications in the field of safety air bags for vehicles, or airbags, having after crosslinking and coating on a fabric, optimal sliding properties, that is to say having a good coefficient of friction. A third objective of the invention is to provide a crosslinkable silicone coating composition for "airbag", which is easy to implement and apply and which, moreover, is economical. A final objective is to provide a woven, knitted or nonwoven fibrous support coated on one or two faces with a silicone elastomer according to the invention which is particularly useful in the field of airbags. More specifically, the present invention, taken in a first object, relates to a method for improving the coefficient of friction of a woven, knitted or coated nonwoven fibrous support, comprising the following steps: a) the preparation of a silicone composition coating (A) crosslinkable comprising: (1) components (a-1) or (a-2): - (a-1) corresponding to at least one polyorganosiloxane capable of crosslinking by the action of a catalyst to base of at least one organic peroxide, and - (a-2) corresponding to a mixture of polyorganosiloxane capable of crosslinking by polyaddition reactions comprising: - at least one polyorganosiloxane (I) having, per molecule, at least two alkenyl groups , in C2-C6 bonded to silicon, and - at least one polyorganosiloxane (II) having, per molecule, at least two hydrogen atoms bonded to silicon, (2) an effective amount of crosslinking catalyst consisting: when (a- 1) is implemented in at least one organic peroxide and when (a-2) is used in at least one metal (or compound) of the platinum group, (3) particles of at least one resin (III) comprising at least one ( co) polyamide; (4) optionally at least one reinforcing filler, (5) at least one adhesion promoter (IV), (6) optionally, an additive system (B) whose constituents are added sequentially or simultaneously, consisting of the mixture of: at least one polyorganosiloxane resin (V) present up to 60% by weight relative to the total weight of the mixture and optionally mixed with at least one polyorganosiloxane serving as diluent, and - calcium carbonate (CaC0 ₃ ) present up to 30% by weight relative to the total weight of the mixture. and (7) optionally at least one crosslinking inhibitor (VI), b) the application of at least 10 g / m ² on one or two sides of a woven, knitted or nonwoven fibrous support of the silicone coating composition (A) prepared in step a), and c) crosslinking of the deposit formed at step b) to form an elastomer by heating to a temperature which can reach 210 ° C. or by electromagnetic radiation, in particular by infrared radiation. The presence of the particles of the resin (III) comprising at least one (co) polyamide have the effect of increasing the roughness of the coating, which results in a reduction in the coefficient of friction without deteriorating the mechanical properties of the fabric. Preferably, the particles of the resin (III) comprise at least one (co) polyamides selected from the group consisting of: polyamide-6, polyamide-6.6, polyamide-4, polyamide-11, polyamide- 12, polyamides 4-6, 6-10, 6-12, 6- 36, 12-12, their copolymers and mixtures. According to a preferred embodiment, the particles of the resin (III) comprise polyamide-12. In another preferred embodiment, the particles of the resin (III) are spherical in shape. The (co) polyamide particles will preferably have an average diameter of between 5 and 100 μm and in particular between 10 and 50 μm. Preferably, these particles are present up to 40% by weight, preferably at a rate of 1 to 30% by weight, and even more preferably at a rate of 5 to 20% by weight relative to the total weight of the mixture.

The polyorganosiloxane (ai) capable of crosslinking by the action of a catalyst based on at least one organic peroxide is advantageously a product having siloxy units of formulas:

R _a SiO _ - - ¹ 0-1) in which: - the symbols R ¹ , identical or different, represent a hydrocarbon group having from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, optionally substituted, and - a is 1, 2 or 3. Preferably, the symbols R ¹ are chosen from: - methyl, ethyl, propyl, butyl, hexyl and dodecyl groups, - cycloalkyl groups such as, for example, cyclohexyl, - alkenyl groups such as, for example, vinyl, allyl, butenyl and hexenyl groups, - aryl groups such as, for example, phenyl, tolyl, aralkyl groups such as β-phenylprolyl, and - the groups mentioned above in which one or more hydrogen atoms are replaced by one or more halogen atoms, a cyano group or equivalent of a cyano group such as, for example, chloromethyl, trifluoropropyl or cyanoethyl. Even more preferably, the polyorganosiloxanes (a-1) are terminated at the chain end with trimethylsilyl, dimethylvinyl, dimethylhydroxysilyl, trivinylsilyl units. In a particularly advantageous embodiment, the polyorganosiloxanes (a-1) contain at least two alkenyl groups per molecule. Among the organic peroxides useful according to the invention, there may be mentioned benzoyl peroxide, bis (p-chlorobenzoyl) peroxide, bis (2,4-dichlorobenzoyie) peroxide, dicumyl peroxide, di-t peroxide -butyl, 2,5-dimethyl- 2,5-di (t-butylperoxy) hexane, t-butyl-perbenzoate, t-butylcumyl peroxide, halogen derivatives of the peroxides mentioned above such as peroxide of bis (2,4-dichlorobenzoyl), 1,6-bis (p-toluoylperoxycarbonyloxy) hexane, 1,6- bis (benzoylperoxy-carbonyloxy) hexane, 1,6-bis (p-toluoylperoxycarbonyloxy) butane and 1,6-bis (2,4-dimethylbenzoylperoxycarbonyloxy) hexane.

(1-1) dans laquelle : - les symboles R¹, un groupe alcényle, de préférence vinyle ou allyle, - les symboles Z, identiques ou différents, représentent chacun un groupe hydrocarboné monovalent, exempt d'action défavorable sur l'activité du catalyseur et choisi parmi les groupes alkyles ayant de 1 à 8 atomes de carbone inclus, éventuellement substitués par au moins un atome d'halogène, et ainsi que parmi les groupes aryles, - a est 1 ou 2, b est 0, 1 ou 2 et la somme a + b est égale à 1 , 2 ou 3, et éventuellement (ii) des autres motifs siloxyles de formule : Zc SiO ^ ⁹- (I-2) dans laquelle : - Z a la même signification que ci-dessus et c est 0, 1 , 2 ou 3. Ce polydiorganosiloxane (I) pourra avoir une viscosité au moins égale à 200 mPa.s et de préférence inférieure à 200.000 mPa.s.The polyorganosiloxane (I) of the silicone coating composition (A) used for the mode of crosslinking by polyaddition reactions comprises: (i) siloxy units of formula:

(1-1) in which: - the symbols R ¹ , an alkenyl group, preferably vinyl or allyl, - the symbols Z, identical or different, each represent a monovalent hydrocarbon group, free from any adverse action on the activity of catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms inclusive, optionally substituted with at least one halogen atom, and also from aryl groups, - a is 1 or 2, b is 0, 1 or 2 and the sum a + b is equal to 1, 2 or 3, and optionally (ii) other siloxy units of formula: Zc SiO ^ ⁹ - (I-2) in which: - Z has the same meaning as above and c is 0, 1, 2 or 3. This polydiorganosiloxane (I) may have a viscosity at least equal to 200 mPa.s and preferably less than 200,000 mPa.s .

All the viscosities referred to in the present specification correspond to a quantity of dynamic viscosity which is measured, in a manner known per se, at 25 ° C. The polyorganosiloxane (I) can be formed only of units of formula (1-1) or can additionally contain units of formula (I-2). Likewise, it may have a linear, branched cyclic or network structure. Z is generally chosen from methyl, ethyl and phenyl radicals, at least 60 mol% (or by number) of the radicals Z being methyl radicals. Examples of siloxyl units of formula (1-1) are the vinyidimethylsiloxyl, vinylphenylmethylsiloxyl, vinylmethylsiloxyl and vinylsiloxyl units. Examples of siloxyl units of formula (I-2) are the Si0 _4/2 , dimethylsiloxyl, methylphenylsiloxyl, diphenylsiloxyl, methylsiloxyl and phenylsiloxyl units.

Examples of polyorganosiloxanes (I) are linear and cyclic compounds such as: dimethylpolysiloxanes with dimethylvinylsilyl ends, copolymers (methylvinyl) (dimethyl) polysiloxanes with trimethylsilyl ends, copolymers (methylvinyl) (dimethyl) polysiloxanes with dimethylvinylsyl vinyl ends .

dans laquelle :Advantageously, the polyorganosiloxane (II) comprises siloxyl units of formula:

in which :

the groups L, which are identical or different, each represent a monovalent hydrocarbon group, free from any unfavorable action on the activity of the catalyst and chosen, preferably, an alkyl group having from 1 to 8 carbon atoms included, optionally substituted with at least one halogen atom, advantageously from the methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups, an aryl group and, advantageously, an xylyl, tolyl or phenyl radical,

(11-2) dans laquelle les groupements L ont la même signification que ci-dessus et g est égal à 0, 1 , 2 ou 3.- d is 1 or 2, e is 0, 1 or 2, the sum d + e is equal to 1, 2 or 3, and - optionally, at least part of the other motifs being motifs of average formula:

(11-2) in which the groups L have the same meaning as above and g is equal to 0, 1, 2 or 3.

Les exemples de motifs de formule (II-2) sont les mêmes que ceux donnés plus haut pour les motifs de formule (I-2). Des exemples de polyorganosiloxane (II) sont des composés linéaires et cycliques comme :The dynamic viscosity of this polyorganosiloxane (II) is at least equal to 10 mPa.s and, preferably, it is between 20 and 1000 mPa.s. The polyorganosiloxane (II) can only be formed of units of formula (11-1) or additionally comprise units of formula (II-2). The polyorganosiloxane (II) can have a linear, branched, cyclic or network structure. Group L has the same meaning as group Z above. Examples of units of formula (11-1) are H (CH _{3) 2} SiOι / _2, HCH ₃ Si0 _2/2 and

The examples of units of formula (II-2) are the same as those given above for the units of formula (I-2). Examples of polyorganosiloxane (II) are linear and cyclic compounds such as:

- dimethylpolysiloxanes with hydrogenodimethylsilyl ends,

- copolymers with (dimethyl) (hydrogenomethyl) polysiloxane units with trimethylsilyl ends, - copolymers with (dimethyl) (hydrogenomethyl) polysiloxane units with hydrogenodimethylsilyl ends,

- hydrogenomethylpolysiloxanes with trimethylsilyl ends,

- cyclic hydrogenethylpolysiloxanes. Compound (II) can optionally be a mixture of a dimethylpolysiloxane with hydrogenodimethylsilyl ends and a polyorganosiloxane comprising at least 3 hydrogenosiloxyl groups. The ratio of the number of hydrogen atoms bonded to silicon in the polyorganosiloxane (II) to the total number of alkenyl unsaturated groups in the polyorganosiloxane (I) is between 0.4 and 10, preferably between 0.6 and 5 .

The bases of silicone polyaddition compositions may contain only linear polyorganosiloxane (I) and (II) such as, for example, those described in the patents: US-A-3,220,972, US-A-3,697,473 and US- A-4 340 709 or contain both branched or networked polyorganosiloxane (I) and (II), such as those described in the patents: US-A-3,284,406 and US-A-3,434,366. a particular embodiment, we implement:

- at least one linear polyorganosiloxane (I) comprising chains formed of units of formula (1-2) where c = 2, blocked at each of their ends by patterns of formula (1-1) where a = 1 and b = 2, and

- at least one linear polyorganosiloxane (II) comprising in its structure at least three hydrogen atoms bonded to silicon, located in the chains and / or at the chain ends; and more particularly:

- at least one linear polyorganosiloxane (I) comprising chains formed of units of formula (I-2) where c = 2, blocked at each of their ends by units of formula (1-1) where a = 1 and b = 2, and

- at least one linear polyorganosiloxane (I) comprising chains formed of units of formula (11-1) where d = 1 and e = 1 and optionally of units of formula (II-2) where g = 2, blocked at each of their ends by patterns of formula (11-1) where d = 1 and e = 2.

The crosslinking catalysts when (a-2) is used consists of at least one metal (or compound) from the platinum group which are also well known. The metals of the platinum group are those known under the name of platinoids, a designation which includes, in addition to platinum, ruthenium, rhodium, palladium, osmium and iridium. The compounds of platinum and rhodium are preferably used. It is possible, in particular, to use the complexes of platinum and of an organic product described in patents US-A-3,159,601, US-A-3,159,602, US-A-3,220,972 and European patents EP- A-0 057 459, EP-A-0 188 978 and EP-A-0 190 530, the complexes of platinum and vinylated organosiloxanes described in the patents US-A-3,419,593,

US-A-3,715,334, US-A-3,374,432 and US-A-3,814,730. The generally preferred catalyst is platinum. In this case, the quantity by weight of catalyst (III), calculated by weight of platinum-metal, is generally between 2 and 400 ppm, preferably between 5 and 200 ppm based on the total weight of the polyorganosiloxanes (I) and (II ).

The presence of the additive system (B) in the silicone coating composition (A) according to the invention makes it possible to control the combing resistance and the tear resistance of the coated woven, knitted or nonwoven fibrous support. The calcium carbonate does not need to undergo a compatibilization treatment (by heating or surface treatment) for its implementation in the system (B) and cannot therefore be assimilated to a simple semi-reinforcing filler. The resin (V) preferably comprises at least one alkenyl residue in its structure. According to a preferred embodiment, the polyorganosiloxane resin (V) comprises siloxy units Q of formula Si0 _{/ 2} . According to another particular mode, the polyorganosiloxane resin (V) comprises in its structure from 0.1 to 20% by weight of alkenyl group (s), preferably greater than 4% by weight, said structure having siloxyl units type M, identical or different, siloxy units of type (s) T, identical or different, and or Q and optionally siloxy units of type D. In a particularly preferred manner, the polyorganosiloxane resin (V) comprises at least 2% by weight, and preferably at least 5% by weight of type Q siloxyl units. These resins (V) are well-known branched organopolysiloxane oligomers or polymers which are commercially available. They are in the form of solutions, preferably siloxane. They have, in their structure, at least two different units chosen from those of formula R ₃ SiOo, ₅ (unit M), R ₂ SiO (unit D), RSiOι _ι5 (unit T) and Si0 ₂ (unit Q), l at least one of these units being a T or Q unit. The radicals R are identical or different and are chosen from linear or branched C1-C6 alkyl radicals, C2-C4 phenyl alkenyl radicals, trifluoro-3,3 , 3 propyl, and hydroxyl groups. Mention may be made, for example: as alkyl radicals R, methyl, ethyl, isopropyl, tert-butyl and n-hexyl radicals, and as alkenyl radicals R, vinyl radicals. It should be understood that in the resins (V) of the aforementioned type, part of the radicals R are alkenyl radicals. Examples of oligomers or branched organopolysiloxane polymers that may be mentioned are MQ resins, MDQ resins, TD resins and MDT resins, the alkenyl functions being able to be carried by the M, D and / or T units. As an example of resins which are particularly suitable, mention may be made of vinylated MDQ resins having a weight content of vinyl group of between 0.2 and 10% by weight.

In the case where the crosslinkable silicone coating composition (A) according to the invention comprises a reinforcing filler, this may be a silica with a BET specific surface of at least 50 m ² / g. The fillers are advantageously treated by treatment with the various organosilicon compounds usually used for this use. Thus, these organosilicon compounds can be organochlorosilanes, diorganocyclopolysiloxanes, hexaorganodisiloxanes, hexaorgano-disilazanes or diorganocyclopolysilazanes (French patents FR-A-1 126 884, FR-A-1 136 885, FR-A-1 236 505, English patent GB-A-1,024,234). The crosslinking silicone composition (A) according to the invention may also comprise a semi-reinforcing filler or conventional stuffing, for example diatomaceous earth or ground quartz. Other non-siliceous mineral materials can intervene as semi-reinforcing or tamping mineral fillers: carbon black, titanium dioxide, aluminum oxide, hydrated alumina, expanded vermiculite, non-vermiculite expanded, calcium carbonate having undergone a compatibilization treatment, zinc oxide, mica, talc, iron oxide, barium sulphate and slaked lime, etc. These fillers may be present at a rate of 5 to 30%, preferably 15 to 25% for reinforcing fillers and 5 to 40%, preferably 10 to 30% for semi-reinforcing or tamping fillers, compared to the total composition.

Without being limiting, it can be considered that the adhesion promoter (IV) exclusively comprises: - (IV.1) at least one alkoxylated organosilane containing, per molecule, at least one C2 - C6 alkenyl group, - (IV.2) at least one organosilicon compound comprising at least one epoxy radical, and - (IV.3) at least one metal chelate M and / or a metal alkoxide of general formula: M (OJ) n, with n = valence of M and J = linear or branched C1 - C8 alkyl, M being chosen from the group formed by: Ti, Zr, Ge, Li, Mn, Fe, Al and Mg.

In accordance with a preferred arrangement of the invention, the alkoxylated organosilane (IV.1) of the promoter (IV) has the following general formula:

(IV.1 ) formule dans laquelle :

(IV.1) formula in which:

- R1, R2, R3 are hydrogenated or hydrocarbon radicals identical or different from each other and represent hydrogen, a linear or branched C1-C4 alkyl or a phenyl optionally substituted by at least one C1-C3 alkyl, U is a linear or branched C1 - C4 alkylene, W is a valence bond, R4 and R5 are the same or different radicals and represent a linear or branched C1 - C4 alkyl, - x '= 0 or 1, and x = 0 to 2 Without being limiting, it can be considered that vinyltrimethoxysilane is a particularly suitable compound (IV.1). As regards the organosilicon compound (IV.2), it is provided in accordance with the invention to choose it: a) either from the products (IV.2a) corresponding to the following general formula:

(IV.2a) formule dans laquelle :

(IV.2a) formula in which:

R6 is a linear or branched C1-C4 alkyl radical, R7 is a linear or branched alkyl radical, y is equal to 0, 1, 2 or 3, and X being defined by the following formula:

avec : - E et D qui sont des radicaux identiques ou différents choisis parmi les alkyles en C1-C4 linéaires ou ramifiés, - z qui est égal à 0 ou 1 , - R8, R9, R10 qui sont des radicaux identiques ou différents représentant l'hydrogène ou un alkyle linéaire ou ramifié en C1-C4, et - R8 et R9 ou R10 pouvant alternativement constituer ensemble et avec les deux carbones porteurs de l'époxy, un cycle alkyle ayant de 5 à 7 chaînons, ou b) soit parmi les produits (IV.2b) constitués par des polydiorganosiloxanes époxyfonctionnels comportant : (i) au moins un motif siloxyle de formule : _{Gα S}iθ il^±f

with: - E and D which are identical or different radicals chosen from linear or branched C1-C4 alkyls, - z which is equal to 0 or 1, - R8, R9, R10 which are identical or different radicals representing l hydrogen or a linear or branched C1-C4 alkyl, and - R8 and R9 or R10 which may alternately constitute together and with the two carbons carrying the epoxy, an alkyl ring having from 5 to 7 members, or b) either from the products (IV.2b) constituted by epoxyfunctional polydiorganosiloxanes comprising: (i) at least one siloxyl unit of formula: _{Gα S} iθ il ^ ± f

(IV.2 b1) formula in which: - X is the radical as defined above for formula (IV.2 a) - G is a monovalent hydrocarbon group, free from any adverse action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms inclusive, optionally substituted with at least one halogen atom, and also from aryl groups, - p = 1 or 2, - q = 0, 1 or 2, - p + q = 1, 2 or 3. and and (2i) optionally at least one siloxyl unit of formula: ^r 2 (IV.2 b2) formula where G has the same meaning as above and r is 0, 1, 2 or 3.

As regards the last compound (IV.3) of the adhesion promoter (IV) of the silicone composition (EVF) according to the invention, the preferred products are those whose metal

M of the chelate and or of the alkoxide (IV.3) is chosen from the following list: Ti, Zr, Ge, Li or

Min. It should be emphasized that titanium is more particularly preferred. It can be associated, for example, with an alkoxy radical of the butoxy type.

The adhesion promoter (IV) may be made up of: (IV.1) alone (IV.2) alone - (IV.1) + (IV.2) according to two preferred methods: (IV.1) x (IV .3) (IV.2) x (IV.3) and finally according to the most preferred method: (IV.1) + (IV.2) + (IV.3).

According to the invention, an advantageous combination for forming the adhesion promoter is as follows:

- vinyltrimethoxysilane (VTMO) representative of the formula (IV.1),

- 3-glycidoxypropyltimethoxysilane (GLYMO) representative of the formula (IV.2), and - butyl titanate representative of the formula (IV.3).

On the quantitative level, it can be specified that the weight proportions between (IV.1), (IV.2) and (IV.3), expressed in percentages by weight compared to the total of the three, are as follows: - ( IV.1)> 10, preferably between 15 and 70 and more preferably still between 25 and 65, - (IV.2) <90, preferably between 70 and 15 and more preferably still between 65 and 25, and - (IV.3)> 1, preferably between 5 and 25 and more preferably still between 8 and 18 , it being understood that the sum of these proportions in (IV.1), (IV.2) and (IV.3) is equal to

100%. For better adhesion properties, the weight ratio (IV.2): (IV.1) is preferably between 2: 1 and 0.5: 1, the 1: 1 ratio being more particularly preferred. Advantageously, the adhesion promoter (IV) is present in an amount of 0.1 to 10, preferably 0.5 to 5 and more preferably still 1 to 3% by weight relative to all of the constituents of the silicone composition. coating (A) crosslinkable.

According to a preferred embodiment, a crosslinkable silicone coating composition (A) is used in the process according to the invention which comprises a mixture formed of: (1) at least one polyorganosiloxane (I) having, per molecule , at least two alkenyl groups, in C2-C6 bonded to silicon, (2) at least one polyorganosiloxane (II) having, per molecule, at least two hydrogen atoms bonded to silicon, (3) a catalytically effective amount of at least one catalyst composed of at least one metal belonging to the platinum group, (4) at least one adhesion promoter (IV), (5) particles of at least one resin (III) comprising at least one ( co) polyamide (6) an additive system (B), the constituents of which are added sequentially or simultaneously, consisting of the mixture formed from: - at least one polyorganosiloxane resin (V) present up to 60% by weight relative to the total weight of the mixture and possibly mixed at least one polyorganosiloxane diluent, and - calcium carbonate (CaC0 ₃₎ present at up to 30% by weight relative to the total weight of the mixture; (7) optionally at least one reinforcing filler, (8) optionally at least one crosslinking inhibitor (VI), (9) optionally at least one coloring additive (VII), and (10) optionally at least one additive (VIII) to improve fire resistance.

The crosslinking inhibitor (VI), possibly chosen from the following compounds: - polyorganosiloxanes substituted with at least one alkenyl which may optionally be in cyclic form, tetramethylvinyl-tetrasiloxane being particularly preferred, - pyridine, - organic phosphines and phosphites, - unsaturated amides, - alkyl maleates, and - acetylenic alcohols.

These acetylenic alcohols (Cf. FR-B-1 528 464 and FR-A-2 372 874), which are part of the preferred hydrosilylation reaction thermal blockers, have the formula: (R ') (R ") C (OH) - C ≡ CH formula in which, R 'is a linear or branched alkyl radical, or a phenyl radical; R "is H or a linear or branched alkyl radical, or a phenyl radical; the radicals R ', R "and the carbon atom located at α of the triple bond possibly being able to form a ring; the total number of carbon atoms contained in R' and R" being at least 5, preferably from 9 to 20. For said alcohols, there may be mentioned as examples: - 1-ethynyl-1-cyclohexanol; - 3-methyl-dodecy-1 ol-3; - trimethyl-3,7,11 dodécyne-1 ol-3; - diphenyl-1, 1 propyne-2 ol-1; - 3-ethyl-6-ethyl nonyne-1 ol-3; - 2-methyl-butyne-3 ol-2; - 3-methyl-pentadecyne-1 ol-3. - diallylmaleate or derivatives of diallylmaleate. These α-acetylenic alcohols are commercial products. Such a retarder (VI) is present at a rate of 3000 ppm at most, preferably at the rate of 100 to 1000 ppm relative to the total weight of the organopolysiloxanes (I) and (II).

As an additive (VIII) to improve the fire resistance, there may be mentioned, for example, compounds with a phenyl group substituted by an amino group (secondary or tertiary). Examples of such additives can be found in the reference US 5,516,938. The useful amounts of such additives are generally between 0.01 and 1 part by weight relative to the total amount of the composition. In a manner known per se, the crosslinkable silicone coating composition (A) according to the invention can be added with various conventional additives such as, for example, the dyes. The invention also relates to the crosslinkable silicone coating composition (A) as used in the method according to the invention and described above.

According to another of its aspects, the present invention relates to a two-component or multi-component precursor system (C) of the crosslinkable silicone coating composition (A) described above. Such a precursor system comprises at least two separate parts A and B, intended to be mixed to form the composition, one of these parts

A or B comprising the catalyst and a single species (I) or (II) of polyorganosiloxane. When a promoter system (IV-1) (IV-2) and (IV-3) is used, another characteristic of this precursor system is that its part A or B containing the polyorganosiloxane (II) is free of compounds ( IV-3) of the promoter (IV) and that its part A or B including the compound (IV-1) of the promoter (IV) does not include the catalyst (III). The viscosity of parts A and B and of their mixture together can be adjusted by varying the amounts of the constituents and by choosing polyorganosiloxanes of different viscosities. Once mixed together, parts A and B form a ready-to-use silicone composition, which can be applied to the support by any suitable coating means (for example doctor blade or cylinder). In general, a final deposited thickness after crosslinking will be aimed at between 25 and 300 μm, in particular between 50 and 200 μm. It is not necessary to have a uniform layer, because if the surface of the support is not regular, it can result in an irregular deposit. The compositions according to the invention are crosslinked thermally and / or by electromagnetic radiation (radiation of accelerated electrons or "electron beam"). The compositions according to the invention can be used for coating or coating flexible supports, in particular woven, knitted or nonwoven fibrous textiles, and preferably woven, knitted or nonwoven supports made of synthetic fibers, advantageously of polyester or polyamide.

The invention also relates to a woven, knitted or nonwoven fibrous support coated on one or two faces with an elastomer capable of being obtained: a) - by applying at least 10 g / m ² to one or more two sides of a woven, knitted or nonwoven fibrous support of the crosslinkable silicone coating composition (A) described above or of the composition resulting from the mixture of parts A and B of the bicomponent or multicomponent system (B) described above, and - The crosslinking of the deposit formed in the previous step to form an elastomer by heating to a temperature up to 210 ° C, by electromagnetic radiation, or by infrared radiation, or b) by the process according to the invention described above.

Another aspect of the invention relates to an airbag for the protection of a vehicle occupant, formed from a coated support according to the procedure of the invention described above. The invention also relates to the use of the bicomponent or multicomponent system.

(B) according to the invention, of a silicone coating composition (A) crosslinkable according to the invention for coating woven, knitted or nonwoven fibrous support. Preferably, these supports are intended to form air bags for the protection of vehicle occupants. In a preferred embodiment, the support is an open-textured fabric having a porosity> 10 l / dm ² / min according to ISO 9237 standard.

The coating or coating of at least one of the faces of the flexible support material, in particular textile (polyamide fabric for example) is useful for the manufacture of technical fabrics such as in particular the air bags for the individual protection of occupants of vehicles, in the event of an impact, tent fabrics, parachute fabrics and the like. In this context, the compositions or the method according to the invention prove to be remarkable not only for the coating of supports conventionally used in particular in the manufacture of airbags, but also for the coating of supports with open texture. By support with open texture, we mean supports with porosity> 10 l / dm ² / min according to ISO 9237. In the case of a fabric, we can especially define the open texture as corresponding to a number of warp threads and weft per centimeter the sum of which is less than or equal to 36. As fabrics particularly recommended in the context of the present invention, mention will generally be made of fabrics whose weight in the uncoated state is less than 200 g / m ² and in particular less than or equal to 160 g / m ² . Mention may therefore be made of such fabrics, in particular of polyamide, having from 16 x 16 to 18 x 18 threads / cm, for example fabrics of 470 dtex (decitex) having these characteristics. It will be noted that it will also be possible to use substrates, in particular fabrics, formed from technical textile fibers, that is to say textile fibers having improved properties compared to conventional fibers, for example increased toughness, in order to impart specific or reinforced properties depending on the applications of the support or coated fabric. The invention therefore also relates to such a flexible support, in particular textile, coated in accordance with the invention and can therefore have the characteristics and properties indicated above.

Thanks to the properties and characteristics indicated above, it is possible to produce airbags for the personal protection of the occupants of a vehicle from open-textured fabrics as described above, in particular polyamide or polyester fabrics, which once coated, have a good coefficient of friction and good resistance to combing and tearing, which also have optimal properties, in particular of impermeability, thermal protection, porosity, pliability, fire resistance. This makes it possible to produce inflatable bags which are more efficient and less expensive than the bags produced from coated fabrics of the prior art. It is also possible, for equal weight, to increase the coating thickness without deteriorating the coefficient of friction. In general, the coating in question here may correspond to the deposition of a single layer on at least one of the faces of the flexible support material (primary coating). However, it may also be the deposition of a second layer or possibly a third layer on at least one of the faces of the support material already coated (secondary coating) to have the desired total thickness guaranteeing the best possible performance. waterproof material and favorable touch characteristics.

The examples which follow of the preparation of compositions and their application as a polyamide fabric covering according to the method of the invention will make it possible to better understand the invention and to highlight its advantages and its variant embodiments. The performance of the products resulting from the process according to the invention will be highlighted by comparative tests.

EXAMPLES

In these examples, the viscosity is measured using a BROOKFIELD viscometer according to the indications of standard AFNOR NFT-76-106 of May 82. Example 1:

1) Definition of the constituents:

- Polyorganosiloxane (I): polydimethylsiloxane oil blocked at each of the ends of the chains by a motif (CHs ^ ViSiOo.s, having a viscosity of 100,000 mPa.s and containing 0.003 Si-Vi function per 100 g of oil [constituent named here -after oil (I);

- Polyorganosiloxane, called diluent below (A), a polydimethylsiloxane oil blocked at each end of the chains by a pattern (CHs ^ ViSiOo.s, having a viscosity of 60,000 mPa.s.

- Polyorganosiloxane (II): poly (dimethyl) (hydrogenethyl) siloxane oil blocked at each end of the chains by a (CH ₃ ) ₂ HSiOo, ₅ motif, having a viscosity of 25 mPa.s and containing a total of 0.7 functions Si-H per 100 g of oil (including 0.6 Si-H function located in the chain) [constituent hereinafter referred to as oil (II)]; - Catalyst: platinum metal, introduced in the form of an organometallic complex containing 10% by weight of platinum metal, known under the name of Karstedt catalyst [constituent hereinafter called catalyst];

- ethynylcyclohexanol 1 (ECH inhibitor),

- adhesion promoters (IV), mixture composed of: - (IV-1) vinyltrimethoxysilane (VTMO), - (IV-2) glycidoxypropyltrimethoxysilane (GLYMO), and - (IV-3) butyl titanate Ti (OBu) 4 (TBT),

- resin (V): polyorganosiloxane of formula MM 'DD O containing 0.8% by weight of vinyl groups (Vi) and consisting of 27% by weight of units (CHs ^ SiOo.s, 0.15% by weight of units (CH3 ) ₂ ViSiOo, 5.60% by weight of units (CHs ^ SiO, 2.4% by weight of units (CH ₃ ) ViSiO and 9.6% by weight of units Siθ ₂ and a residue of OH groups.

- calcium carbonate, CaC0 _3, (albacar ^® 5970), which has not been the subject of a compatibilization treatment (heating or surface functionalization),

- Orgasol ^® 2002 ES3 NAT3 (ATOFINA company), polyamide-12 beads, average particle diameter: 30μm.

2) Procedure and results: a) A composition is prepared from a two-component precursor: - A control composition (C-1) is obtained by mixing, at room temperature, 100 parts by weight of part A and 10 parts by weight of part B of a two-component system (see composition in Table 1). - A composition (1-1) according to the invention is obtained by mixing, at room temperature, of: - 125 parts by weight of part A-1 obtained by mixing 100 parts by weight of Part A of the C-1 composition and 25 parts by weight of beads Orgasol ^® 2002 NAT3 ES3, and

- 10 parts by weight of a composition B-1 the composition of which is identical to part B of the composition C-1 b) each mixture (C-1 and 1-1) is coated (variable coating rate, expressed in g / m ² ) to form a deposit using doctor blades or cylinders on a polyhexamethyleneadipamide type 6.6 desized with a title of 235 decitex (dtex), and c) the resulting layer is crosslinked for 80 seconds at 180 ° C. in a MATHIS oven to obtain an elastomer. The results of the compared tests are shown in Tables II to IV. The friction coefficient (Ks) measurements are made according to standard NFQ 03-082. Table II represents the measurements of the coefficients of friction obtained by friction on a glass plate. Table III represents the measurements of the coefficients of friction obtained by friction of the sample of coated fabric on itself, coated side on coated side. Table I

Tableaux II

Tables II

It can be seen that composition 1-1 according to the invention leads to a lower coefficient of friction (COF) than that obtained with the control composition C-1 when the deposits are comparable in terms of quantity / unit area of the coated fabric.

Then, the coated fabric samples are tested according to conventional methods of the airbag manufacturing profession. The results are collated in the following Table IV. The crumple and abrasion resistance test (scrub test) (standard ISO 5981 A) reflects the adhesion and the aging resistance of the composition. This test consists in subjecting the fabric, on the one hand, to a shearing movement using two jaws pinching the two opposite edges of a test tube and moving in an alternating movement with respect to each other and, on the other hand, to abrasion by contact with a mobile support. Table IV.

It is therefore found, with equivalent coating deposition, that formula 1-1 makes it possible to preserve the properties of use of the fabric as obtained with formula C-1 while improving the coefficient of friction.

Claims

CLAIMS - Method for improving the friction coefficient of a coated woven, knitted or nonwoven fibrous support, comprising the following steps: a) the preparation of a crosslinkable silicone coating composition (A) comprising: (1) components (a-1) or (a-2): - (a-1) corresponding to at least one polyorganosiloxane capable of crosslinking by the action of a catalyst based on at least one organic peroxide, and - (a -2) corresponding to a mixture of polyorganosiloxane capable of crosslinking by polyaddition reactions comprising: - at least one polyorganosiloxane (I) having, per molecule, at least two alkenyl groups, in C2-C6 bonded to silicon, and - at least a polyorganosiloxane (II) having, per molecule, at least two hydrogen atoms bonded to silicon, (2) an effective amount of crosslinking catalyst consisting: when (a-1) is used in at least one organic peroxide and when (a-2) is implemented re in at least one metal (or compound) of the platinum group, (3) particles of at least one resin (III) comprising at least one (co) polyamide; (4) optionally at least one reinforcing filler, (5) at least one adhesion promoter (IV), and (6) optionally, an additive system (B) whose constituents are added sequentially or simultaneously, consisting of the mixture of : - at least one polyorganosiloxane resin (V) present up to 60% by weight relative to the total weight of the mixture and optionally mixed with at least one polyorganosiloxane serving as diluent, - calcium carbonate (CaC0 ₃ ) present up to 30% by weight relative to the total weight of the mixture, and (7) optionally at least one crosslinking inhibitor (VI), b) the application of at least 10 g / m ² on one or both sides of a support woven, knitted or nonwoven fibrous of the silicone coating composition (A) prepared in step a), and c) crosslinking the deposit formed in step b) to form an elastomer by heating to a temperature capable of reach 210 ° C, by electromagnetic radiation or p ar infrared radiation. Method for improving the coefficient of friction of a coated woven, knitted or nonwoven fibrous support according to claim 1, in which the crosslinkable silicone coating composition (A) comprises a mixture formed of: (1) at least one polyorganosiloxane (I) having, per molecule, at least two alkenyl groups, in C2-C6 bonded to silicon, (2) at least one polyorganosiloxane (II) having, per molecule, at least two atoms of hydrogen bonded to silicon, (3) a catalytically effective amount of at least one catalyst composed of at least one metal belonging to the platinum group, (4) at least one adhesion promoter (IV), (5) of the particles at least one resin (III) comprising at least one (co) polyamide (6) an additive system (B) whose constituents are added sequentially or simultaneously, consisting of the mixture formed from: - at least one polyorganosiloxane resin (V) has up to 60% by weight relative to the total weight of the mixture and optionally mixed with at least one polyorganosiloxane serving as diluent, and - calcium carbonate (CaC0 ₃ ) present up to 30% by weight the total weight of the mixture; (7) optionally at least one reinforcing filler, (8) optionally at least one crosslinking inhibitor (VI), (9) optionally at least one coloring additive (VII), and (10) optionally at least one additive (VIII) to improve fire resistance. 3- A method for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to one of the preceding claims in which the particles of the resin (III) are spherical in shape. 4- A method for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to claim 3 in which the average diameter of the particles of the resin (III) is between 5 and 100 μm. 5- Method for improving the coefficient of friction of a woven, knitted or coated nonwoven fibrous support according to one of the preceding claims in which the particles of the resin (III) comprise at least one (co) polyamide selected from the group consisting of: polyamide-6, polyamide-6.6, polyamide-4, polyamide-11, polyamide-12, polyamides 4-6, 6-10, 6-12, 6-36, 12-12 , their copolymers and mixtures. 6- A method for improving the friction coefficient of a coated woven, knitted or nonwoven fibrous support according to claim 5 in which the particles of the resin (III) comprise polyamide-12. 7- A method for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to one of the preceding claims in which the particles of the resin (III) are present up to 40% by weight, preferably at a rate of 1 to 30% by weight and even more preferably between 5 and 20% by weight relative to the total weight of the mixture. 8 - Process for improving the coefficient of friction of a coated woven, knitted or nonwoven fibrous support according to one of the preceding claims in which the adhesion promoter (IV) of the crosslinkable silicone composition (A) contains exclusively: (IV.1) at least one alkoxylated organosilane containing, per molecule, at least one C2 - C6 alkenyl group, (IV.2) at least one organosilicon compound comprising at least one epoxy radical, (IV.3) at least one metal chelate M and / or a metal alkoxide of general formula: M (OJ) n, with n = valence of M and J = linear or branched C1-C8 alkyl, M being chosen from the group formed by: Ti, Zr, Ge, Li, Mn, Fe, Al and Mg, 9 - Process for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to claim 8 in which the alkoxylated organosiloxane (IV.1) of the promoter (IV) corresponds to the following general formula:

(IV.1) formula in which: - R1, R2, R3 are hydrogenated or hydrocarbon radicals identical or different between them and represent hydrogen, a linear or branched C1-C4 alkyl or a phenyl optionally substituted by at least one C1-C3 alkyl, - U is a linear or branched C1-C4 alkylene, W is a valence bond, R4 and R5 are the same or different radicals and represent a linear or branched C1 - C4 alkyl, x '= 0 or 1, and - x = 0 to 2. 10 - Process for improving the coefficient of friction of a coated woven, knitted or nonwoven fibrous support according to claim 8 in which the organosilicon compound (IV.2) of the promoter (IV) is chosen: a) either from the products (IV.2a) corresponding to the following general formula:

(IV.2a) formula in which: R6 is a linear or branched C1-C4 alkyl radical, - R7 is a linear or branched alkyl radical, y is equal to 0, 1, 2 or 3, and - X being defined by the following formula:

with: - E and D which are identical or different radicals chosen from linear or branched C1-C4 alkyls, - z which is equal to 0 or 1, - R8, R9, R10 which are identical or different radicals representing l hydrogen or a linear or branched C1-C4 alkyl, and - R8 and R9 or R10 may alternately constitute together and with the two carbons carrying the epoxy, an alkyl ring having from 5 to 7 members, b) either among the products (IV.2b) consisting of epoxyfunctional polydiorganosiloxanes comprising: (i) at least one siloxyl unit of formula: χ _Λ Siθ il ^ ± (IV.2 b1) formula in which: - X is the radical as defined above for the formula (IV.2 a) - G is a monovalent hydrocarbon group, free from any unfavorable action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 carbon atoms included, optionally substituted by at least one halogen atom, and also from aryl groups, - p = 1 or 2, - q = 0, 1 or 2, - p + q = 1, 2 or 3. and (2i) optionally at least one siloxyl unit of formula: A - τ G SiO - - ^x 2 (IV.2 b2) formula in which G has the same meaning as above and r is equal to 0, 1, 2 or 3. 11 - Process for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to claim 8 in which the metal M of the chelate and / or the alkoxide (IV.3) is chosen from the list following: Ti, Zr, Ge, Li or Mn. 12 - Process for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to claims 9, 10 and 11 in which the adhesion promoter (IV) comprises a mixture of: - vinyltrimethoxysilane (VTMO) representative of the formula (IV.1), - 3-glycidoxypropyltimethoxysilane (GLYMO) representative of the formula (IV.2), and - butyl titanate representative of the formula (IV.3). 13 - Process for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to one of the preceding claims in which the polyorganosiloxane (I) has: (i) siloxy units of formula: 1 4- fa + tf) RaZb SiO - (1-1) formula in which: - the symbols R ¹ , an alkenyl group, preferably vinyl or allyl, - the symbols Z, identical or different, each represent a monovalent hydrocarbon group, free of unfavorable action on the activity of the catalyst and chosen from alkyl groups having from 1 to 8 atoms of carbon included, optionally substituted by at least one halogen atom, and also among the aryl groups, - a is 1 or 2, b is 0, 1 or 2 and the sum a + b is 1, 2 or 3 , and optionally (ii) other siloxy units of formula: Zc SiO ^ ^~ (I-2) formula in which: - Z has the same meaning as above and c is 0, 1, 2 or 3. 14 - Method for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to one of the preceding claims in which the polyorganosiloxane (II) comprises: - siloxyl units of formula: H _d L _e SiO ^{4 d + é} > ² (11-1) in which: - the groups L, identical or different, each represent a monovalent hydrocarbon group, free of unfavorable action on the activity of the catalyst and chosen, preferably an alkyl group having from 1 to 8 carbon atoms inclusive, optionally substituted by at least one halogen atom, advantageously, from methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups, an aryl group and, advantageously, a xylyl, tolyl or phenyl radical, and - d is 1 or 2, e is 0, 1 or 2, the sum d + e is equal to 1, 2 or 3, and - optionally, at least some of the others patterns being patterns of medium formula: L „Siθ i ^ ² (II-2) in which the groups L have the same meaning as above and g is equal to 0, 1, 2 or 3. 15 - Process for improving the coefficient of friction of a woven, knitted or nonwoven coated fibrous support according to one of the preceding claims in which the proportions of the polyorganosiloxanes (I) and (II) are such that the molar ratio of the atoms of hydrogen bonded to silicon in (II) on the alkenyl radicals bonded to silicon in (I) is between 0.4 and 10, preferably between 0.6 and 5. 16 - Crosslinkable silicone coating composition (A) comprising: (1) components (a-1) or (a-2): - (a-1) corresponding to at least one polyorganosiloxane capable of crosslinking by the action d '' a catalyst based on at least one organic peroxide, and - (a-2) corresponding to a mixture of polyorganosiloxane capable of crosslinking by polyaddition reactions comprising: - at least one polyorganosiloxane (I) having, per molecule, at at least two alkenyl groups, at C2-C6 bonded to silicon, and - at least one polyorganosiloxane (II) having, per molecule, at least two hydrogen atoms bonded to silicon, (2) an effective amount of crosslinking catalyst consisting of: when (a-1) is used in at least one organic peroxide and when (a-2) is used in at least one platinum group metal (or compound), (3) particles of at least a resin (III) comprising at least one (co) polyamide; (4) optionally at least one reinforcing filler, (5) optionally at least one crosslinking inhibitor (VI), (6) optionally at least one coloring additive (VII), and (7) optionally at least one additive (VIII) to improve fire resistance. (8) at least one adhesion promoter (IV), and (9) optionally, an additive system (B) improving the combing resistance and the tear resistance, the constituents of which are added sequentially or simultaneously, constituted by the mixture of: - at least one polyorganosiloxane resin (V) present up to 60% by weight relative to the total weight of the mixture and optionally mixed with at least one polyorganosiloxane serving as diluent, and - calcium carbonate (CaC0 ₃ ) present up to 30% by weight relative to the total weight of the mixture. 17 - silicone coating composition (A) crosslinkable according to claim 16 comprising: (1) at least one polyorganosiloxane (I) having, per molecule, at least two alkenyl groups, C2-C6 bonded to silicon, (2) to at least one polyorganosiloxane (II) having, per molecule, at least two hydrogen atoms bonded to silicon, (3) a catalytically effective amount of at least one catalyst (III), composed of at least one metal belonging to the group of platinum, (4) particles of at least one resin (III) comprising at least one (co) polyamide, (5) at least one adhesion promoter (IV), (6) an additive system (B) whose constituents are added sequentially or simultaneously to the mixture, consisting of the mixture of: - at least one polyorganosiloxane resin (V) present up to 60% by weight relative to the total weight of the mixture and optionally mixed with at least one polyorganosiloxane serving as diluent, and - calcium carbonate (CaC0 ₃ ) present up to 30% by weight relative to the total weight of the mixed ; (7) optionally at least one crosslinking inhibitor (VI), (8) optionally at least one reinforcing filler (9) optionally at least one coloring additive (VII), and (10) optionally at least one additive (VIII) for improve fire resistance. 18 - silicone coating composition (A) crosslinkable according to any one of claims 16 and 17 wherein the resin particles (III) are spherical in shape. 19 - silicone coating composition (A) crosslinkable according to claim 18 wherein the average diameter of the resin particles (III) is between 5 and 100 microns. 20 - silicone coating composition (A) crosslinkable according to any one of claims 16 to 19 in which the particles of the resin (III) are based on (co) polyamides selected from the group consisting of: polyamide-6 , polyamide-6.6, polyamide-4, polyamide-11, polyamide-12, polyamides 4-6, 6-10, 6-12, 6- 36, 12-12, their copolymers and mixtures. 21 - silicone coating composition (A) crosslinkable according to claim 20 wherein the resin particles (III) are based on polyamide-12. 22 - Composition according to any one of claims 16 to 21 in which the adhesion promoter (IV) comprises a mixture of: - vinyltrimethoxysilane (VTMO) representative of the formula (IV.1), - 3-glycidoxypropyltimethoxysilane (GLYMO) representative of formula (IV.2), and - butyl titanate representative of formula (IV.3). 23 - - Composition according to any one of claims 16 to 22 in which the particles of the resin (III) are present up to 40% by weight, preferably at a rate of 1 to 30% by weight and even more preferably between 5 and 20% by weight relative to the total weight of the mixture. 24 - Two-component or multi-component system (C) precursor of the silicone coating composition (A) according to any one of claims 16 to 23 comprising: - two separate parts A and B intended to be mixed to form the composition, and - one of these parts A and B comprises the catalyst and a single species (I) or (II) of polyorganosiloxane. 25 - Woven, knitted or nonwoven fibrous support coated on one or two faces with an elastomer capable of being obtained: a) - by applying at least 10 g / m ² to one or two faces of a woven, knitted or nonwoven fibrous support of the silicone coating composition (A) according to any one of claims 16 to 23 or of the composition resulting from the mixture of parts A and B of the two-component system (B) according to the claim 24, and - the crosslinking of the deposit formed in the preceding step to form an elastomer by heating to a temperature up to 210 ° C, by electromagnetic radiation or by infrared radiation, or b) by the method according to any one of claims 1 to 15. 26 - Use of the crosslinkable silicone composition (A) according to any one of Claims 16 to 23, of the bicomponent or multicomponent system (C) according to Claim 24 or of the woven, knitted or nonwoven fibrous support coated on one or two faces according to claim 25 in the field of vehicle air bags. 27 - Airbag comprising a woven, knitted or nonwoven fibrous support coated on one or two faces according to claim 25.