SILICONE COMPOSITION AND PROCESS USEFUL FOR IMPROVING THE CREASE RESISTANCE AND ABRASION RESISTANCE OF AIRBAGS, INTENDED FOR PROTECTING A VEHICLE OCCUPANT

Abstract

The general field of the invention is that of silicone coating compositions, in particular those of two-component or multi-component type, that can be crosslinked by polyaddition or hydrosilylation reactions to produce a support coated by a silicone elastomer as a thin layer. These silicone compositions, when they are crosslinked, are suitable, inter alia, as coatings, for example for the protection or mechanical reinforcement of various textile substrates such as for example fibrous, woven, knitted or nonwoven supports. The targeted objective is to provide a silicone elastomer coating composition that can be crosslinked by polyaddition reactions and that is useful in particular for applications in the field of inflatable safety bags for vehicles, or airbags, having, after crosslinking, optimum properties in terms of adhesion, thinness, lightness and crease and abrasion resistance, but also good mechanical properties. This silicone coating composition should also be easy to use and to apply.

Claims

1- A silicone composition A comprising a silicone base B capable of crosslinking or curing by polyaddition and comprising an adhesion promoter system D comprising at least one organic titanium compound M and at least one additive X which is a linear organopolysiloxane comprising siloxyl units (I.1) to (I.3) having the formulae below: $\begin{array}{cc}{Y}_a.Math.Z_b^1.Math.\mathrm{Si}.Math..Math.O_{\frac{4-\left(a+b\right)}{2}}& \left(I.Math.\mathrm{.1}\right)\\ Z_3^2.Math.\mathrm{Si}.Math..Math.O_{\frac{1}{2}}& \left(I.Math.\mathrm{.2}\right)\\ H_d.Math.Z_e^3.Math.\mathrm{Si}.Math..Math.O_{\frac{4-\left(d+e\right)}{2}}& \left(I.Math.\mathrm{.3}\right)\end{array}$ and not comprising units of formula (I.4):
Z.sub.2.sup.2SiO.sub.2/2 (I.4) in which a=1 and b=1 or 2 d=1 and e=1 or 2 the symbol Y represents a radical comprising a hydrocarbon-based group having from 2 to 20 carbon atoms and an epoxy function, with optionally one or more heteroatoms such as an oxygen atom, optionally the symbol Y is chosen from the radicals consisting of the group: alkyl glycidyl ether, linear, branched or cyclic epoxyalkyl, linear, branched or cyclic epoxyalkenyl and carboxylic acid glycidyl ester, the symbols Z.sup.1, Z.sup.2 and Z.sup.3, which may be identical or different, represent a monovalent hydrocarbon-based group having from 1 to 30 carbon atoms, optionally chosen from the group formed by alkyl groups having from 1 to 8 carbon atoms and aryl groups having from 6 to 12 carbon atoms, and optionally chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl group, with the condition according to which the additive X comprises, per molecule, at least two siloxyl units (I.1) bearing epoxyfunctional hydrocarbon-based groups and at least three siloxyl units (I.3) bearing hydrosiloxyl groups.

2- The silicone composition A as claimed in claim 1, wherein the additive X has a total number of siloxyl units of between 7 and 30.

3- The silicone composition A as claimed in claim 1, wherein the additive X does not contain alkoxy, vinyl, hydroxyl or methacryloxy functional groups.

4- The silicone composition A as claimed in claim 1, wherein the additive X has a molar ratio between the siloxyl units (I.1) and the siloxyl units (I.3) of between 0.5 and 4, optionally between 0.8 and 3 and optionally between 0.8 and 2.5.

5- The silicone composition A as claimed in claim 1, wherein the adhesion promoter system D also comprises an organosilane G comprising at least one epoxy radical.

6- The silicone composition A as claimed in claim 1, wherein the concentration of epoxy units is between 10 and 60 mmol per 100 g of composition A and optionally between 15 and 40 mmol per 100 g of composition A.

7- The silicone composition A as claimed in claim 1, wherein the silicone base B comprises at least one organopolysiloxane E having, per molecule, at least two C.sub.2-C.sub.12 alkenyl groups each bonded to a different silicon atom, at least one organopolysiloxane resin F comprising from 0.1% to 20% by weight of C2-C6 alkenyl groups each bonded to a different silicon atom, optionally at least one organohydropolysiloxane H having, per molecule, at least two hydrogen atoms each bonded to a different silicon atom, and optionally at least three hydrogen atoms each bonded to a different silicon atom, an effective amount of a polyaddition catalyst C which is a metal or metal compound of the platinum group, at least one inhibitor I, and optionally at least one filler J.

8- A two-component precursor system for the composition A as defined in claim 7 which is in two distinct parts A1 and A2 intended to be mixed so as to form the composition A, wherein one of said parts contains the catalyst C while the other part contains the additive X and the organohydropolysiloxane H.

9- A silicone elastomer that can be obtained by crosslinking and/or curing the silicone composition A as defined in claim 1.

10- A process for preparing a fibrous support coated with a silicone elastomer, comprising: a) preparing a silicone composition A as defined in claim 1, b) applying onto one or two faces of a fibrous support at least 10 g/m.sup.2 of the silicone composition A prepared in a), and c) crosslinking the deposit formed in b) so as to form an elastomer by heating at a temperature that can reach 210 C., optionally through action of electromagnetic radiation or hot air.

11- The process as claimed in claim 10, wherein the fibrous support is made of polyamide or of polyester.

12- The process as claimed in claim 10, wherein the fibrous support has not undergone washing after weaving.

13- The process as claimed in claim 10, wherein the fibrous support has not undergone heat-treatment after weaving.

14- A fibrous support coated with a silicone elastomer that can be obtained by means of the process as defined in claim 10.

15- Airbag comprising a silicone elastomer as defined in claim 9 or a fibrous support coated with said silicone elastomer.

16- A product comprising the silicone composition A as defined in claim 1, for coating a woven, knitted or nonwoven fibrous support.

17- A product comprising the silicone composition A as defined in claim 1, for coating an airbag intended for protection of a passenger in a vehicle

Description

EXAMPLES

1) Definition of the Constituents

[0214] Organopolysiloxane E1: polydimethylsiloxane oil blocked at each of the chain ends by a (CH.sub.3).sub.2ViSiO.sub.1/2 unit, having a viscosity of 60 000 mPa.Math.s. [0215] Resin F1: organopolysiloxane of formula MM.sup.ViQ containing 1.1% by weight of vinyl groups. [0216] Catalyst C1: platinum metal, introduced in the form of an organometallic complex containing 10% by weight of platinum metal, known as Karstedt catalyst. [0217] Organohydropolysiloxane H1: poly(dimethyl)(hydromethyl)siloxane oil having a viscosity of 25 mPa.Math.s and containing 0.7 mol of SiH function per 100 g of oil. [0218] Inhibitor I1: 1-ethynyl-1-cyclohexanol or ECH. [0219] Filler J1: Non-treated precipitated calcium carbonate with a mean equivalent diameter of 2 m.
Components tested as adhesion promotors: [0220] glycidoxypropyltrimethoxysilane (GLYMO), [0221] butyl titanate Ti(OBu).sub.4 (TBT) [0222] Various additives K1 to K11, details provided hereinafter (see table 1)

2) Synthesis of the Additives K1 to K11

[0223] Various additives were synthesized, consisting of: [0224] n YCH.sub.3SiO.sub.2/2 units [0225] m HCH.sub.3SiO.sub.2/2 units [0226] p (CH.sub.3).sub.2SiO.sub.2/2 units [0227] 2 R.sup.1(CH.sub.3).sub.2Si.sub.1/2 units with R.sup.1CH.sub.3 or H
wherein Y is the epoxy group of formula below

##STR00010##

Additive K1:

[0228] 181.0 g of toluene are introduced into a 1 l reactor under nitrogen. The medium is stirred and heated to 85 C. When the temperature is reached, 10.2 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore H5432, are introduced. A mixture of allyl glycidyl ether (AGE) (236.8 g, 2.07 mol) and of a polymethylhydrosiloxane H2 with 9 (CH.sub.3)HSiO.sub.2/2 units and two (CH.sub.3).sub.3SiO.sub.1/2 end units (363.2 g, SiH=4.77 mol) is then added dropwise over the course of 4 hours. After returning to ambient temperature, the reaction medium is devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 85 C. (setpoint) under 1 mbar for 3 h, to give a functionalized silicone oil composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=9; [SiH]=586 mmol/100 g; [Epoxy]=291 mmol/100 g; Viscosity=32 mPa.Math.s.

Additive K2:

[0229] 181.92 g of toluene are introduced into a 1 l reactor under nitrogen. The medium is stirred and heated to 85 C. When the temperature is reached, 10.3 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, are introduced. A mixture of allyl glycidyl ether (AGE) (280.3 g, 2.46 mol) and of polymethylhydrosiloxane H2 (320.6 g, SiH=4.25 mol) is then added dropwise over the course of 7 hours. After returning to ambient temperature, the reaction medium is devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 85 C. (setpoint) under 1 mbar for 3 h, to give a functionalized silicone oil composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=9; [SiH]=433 mmol/100 g; [Epoxy]=347 mmol/100 g; Viscosity=67 mPa.Math.s.

Additive K3:

[0230] 1733.9 g of toluene and 2.7 g of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, in solution in toluene, are introduced into a 10 l reactor under nitrogen. This mixture is stirred and heated to 77 C. A mixture of allyl glycidyl ether (AGE) (390.5 g, 3.42 mol) and of polymethylhydrosiloxane H3 comprising 20 (CH.sub.3)HSiO.sub.2/2 units and two (CH.sub.3).sub.3SiO.sub.1/2 end units (5599.5 g, SiH=82.23 mol) is added by means of a pump over the course of 54 min. When the addition has ended, the heating is maintained for 1 hour. The heating is then stopped and, after returning to ambient temperature, the reaction medium is devolatilized at 40 C. under 5 mbar for 1 hour and then the temperature is gradually increased up to 85 C. over the course of 4 h. The temperature is maintained at 85 C. for 1 hour, to give a functionalized silicone oil (7727.8 g) composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=20; [SiH]=1.30 mol/100 g; [Epoxy]=37.7 mmol/100 g; Viscosity=12.3 mPa.Math.s.

Additive K4:

[0231] 142.0 g of toluene are introduced into a 1 l three-necked flask under nitrogen. The medium is magnetically stirred and heated to 85 C. When the temperature is reached, 1.1910 g of Pt/C are introduced. A mixture of allyl glycidyl ether (AGE) (180.6 g, 1.58 mol) and of polymethylhydrosiloxane H3 (420.0 g, SiH=6.27 mol) is then added dropwise over the course of 16 hours. After returning to ambient temperature, the reaction medium is filtered, treated and filtered, then devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 90 C. (setpoint) under 1 mbar for 3 h, to give a functionalized silicone oil composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=20; [SiH]=892 mmol/100 g; [Epoxy]=198 mmol/100 g; Viscosity=103 mPa.Math.s.

Additive K5:

[0232] 100.1 g of toluene and 10 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, are introduced into a 500 ml round-bottomed flask under nitrogen. This mixture is magnetically stirred and heated to 85 C. A mixture of allyl glycidyl ether (AGE) (150.2 g, 1.32 mol) and of polymethylhydrosiloxane H3 (349.0 g, SiH=5.21 mol) is added dropwise over the course of 3 hours. When the addition has ended, the dropping funnel is rinsed with 30 g of toluene and the heating is maintained for 2 hours. After returning to ambient temperature, the reaction medium is devolatilized at 92 C. under 1 mbar for 3 hours, to give a functionalized silicone oil (455.0 g) composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=20; [SiH]=999 mmol/100 g; [Epoxy]=189.7 mmol/100 g; Viscosity=101 mPa.Math.s.

Additive K6:

[0233] 105.1 g of toluene and 11 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, are introduced into a 500 ml round-bottomed flask under nitrogen. This mixture is magnetically stirred and heated to 85 C. A mixture of allyl glycidyl ether (AGE) (249.2 g, 2.18 mol) and of polymethylhydrosiloxane H3 (302.6 g SiH=4.52 mol) is added dropwise over the course of 3 hours. When the addition has ended, the dropping funnel is rinsed with 45.4 g of toluene and the heating is maintained for 2 hours. After returning to ambient temperature, the reaction medium is devolatilized at 92 C. under 1 mbar for 3 hours, to give a functionalized silicone oil (449.0 g) composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=20; [SiH]=568 mmol/100 g; [Epoxy]=324.3 mmol/100 g; Viscosity=186 mPa.Math.s.

Additive K7:

[0234] 107.1 g of toluene and 13.3 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, are introduced into a 500 ml round-bottomed flask under nitrogen. This mixture is magnetically stirred and heated to 85 C. A mixture of allyl glycidyl ether (AGE) (333.8 g, 2.92 mol) and of polymethylhydrosiloxane H3 (291.1 g SiH=4.35 mol) is added dropwise over the course of 3 hours. When the addition has ended, the dropping funnel is rinsed with 30 g of toluene and the heating is maintained for 2 hours. After returning to ambient temperature, the reaction medium is devolatilized at 92 C. (setpoint) under 1 mbar for 3 hours, to give a functionalized silicone oil (534.0 g) composed of n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: n+m=20; [SiH]=376.7 mmol/100 g; [Epoxy]=380.7 mmol/100 g; Viscosity=610 mPa.Math.s.

Additive K8:

[0235] 469.7 g of allyl glycidyl ether (AGE) (4.11 mol) and 14.3 mg of a platinum-carbene complex, sold by Umicore under the trade name Umicore HS432, are introduced into a 500 ml round-bottomed flask under nitrogen. This mixture is magnetically stirred and heated to 85 C. The polymethylhydrosiloxane H3 (205.4 g, SiH=3.01 mol) is added dropwise over the course of 5 hours. An exotherm of 90 C. is observed. When the addition has ended, the heating is maintained for 3 hours. After returning to ambient temperature, the reaction medium is devolatilized at 90 C. under 1 mbar for 3 hours, to give a functionalized silicone oil composed of 20 YCH.sub.3SiO.sub.2/2 units and two (CH.sub.3).sub.3Si.sub.1/2 units with the following characteristics: [SiH]=0 mmol/100 g; [Epoxy]=537 mmol/100 g; Viscosity=929 mPa.Math.s.

Additive K9:

[0236] 178.2 g of toluene are introduced into a 1 l three-necked flask under nitrogen. The medium is magnetically stirred and heated to 85 C. When the temperature is reached, 0.6280 g of Pt/C is introduced. A mixture of allyl glycidyl ether (AGE) (77.6 g, 0.68 mol) and of polymethylhydrosiloxane H4 comprising 16 (CH.sub.3)HSiO.sub.2/2 units, 18 (CH.sub.3).sub.2SiO.sub.2/2 units and two (CH.sub.3).sub.2HSiO.sub.1/2 end units (522.9 g, SiH=6.80 mol) is then added dropwise over the course of 8 hours. After returning to ambient temperature, the reaction medium is filtered, treated and filtered, then devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 90 C. under 1 mbar for 2 h, to give a functionalized silicone oil composed of 18 (CH.sub.3).sub.2SiO.sub.2/2 units, n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two H(CH.sub.3).sub.2Si.sub.1/2 units with the following characteristics: n+m=16; [SiH]=519 mmol/100 g; [Epoxy]=102 mmol/100 g; Viscosity=64 mPa.Math.s.

Additive K10:

[0237] 188.9 g of toluene are introduced into a 1 l three-necked flask under nitrogen. The medium is magnetically stirred and heated to 85 C. When the temperature is reached, 0.6504 g of Pt/C is introduced. A mixture of allyl glycidyl ether (AGE) (136.3 g, 1.19 mol) and of polymethylhydrosiloxane H4 (465.7 g, SiH=2.77 mol) is then added dropwise over the course of 8 hours. After returning to ambient temperature, the reaction medium is filtered, treated and filtered, then devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 90 C. (setpoint) under 1 mbar for 2 h, to give a functionalized silicone oil composed of 18 (CH.sub.3).sub.2SiO.sub.2/2 units, n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two H(CH.sub.3).sub.2Si.sub.1/2 units with the following characteristics: n+m=16; [SiH]=347 mmol/100 g; [Epoxy]=171.2 mmol/100 g; Viscosity=90.4 mPa.Math.s.

Additive K11:

[0238] 104.0 g of toluene are introduced into a 1 l three-necked flask under nitrogen. The medium is magnetically stirred and heated to 80 C. When the temperature is reached, 887 mg of Pt/C are introduced. A mixture of allyl glycidyl ether (AGE) (171.5 g, 1.50 mol) and of polymethylhydrosiloxane H5 comprising 27 (CH.sub.3)HSiO.sub.2/2 units, 7 (CH.sub.3).sub.2SiO.sub.2/2 units and two (CH.sub.3).sub.2HSiO.sub.1/2 end units (250.0 g, SiH=3.16 mol) is then added dropwise over the course of 6 hours. After returning to ambient temperature, the reaction medium is filtered, then devolatilized at 25-30 C. under 0-3 mbar for 30 min, then at 90 C. (setpoint) under 1 mbar for 1 h, to give a functionalized silicone oil composed of 7 (CH.sub.3).sub.2SiO.sub.2/2 units, n YCH.sub.3SiO.sub.2/2 units, m HCH.sub.3SiO.sub.2/2 units and two H(CH.sub.3).sub.2Si.sub.1/2 units with the following characteristics: n+m=27; [SiH]=517 mmol/100 g; [Epoxy]=293 mmol/100 g; Viscosity=140 mPa.Math.s.
Table 1 below gives details of the various synthesized linear organopolysiloxanes K1 to K11.

TABLE-US-00001 TABLE 1 Synthesized linear organopolysiloxanes K1 to K11 Additive K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11 Total number 11 11 22 22 22 22 22 22 36 36 36 of siloxyl units Number of 0 0 0 0 0 0 0 0 18 18 7 (CH.sub.3).sub.2SiO.sub.2/2 units [epoxy] 291 347 38 198 190 324 381 537 102 171 293 mmol/100 g [SiH] 586 433 1300 892 999 568 377 0 519 347 517 mmol/100 g [SiH]/[epoxy] 2.2 1.2 34.2 4.5 5.3 1.8 1 0 5.1 2 1.8

3) Preparation of the Coated Fibrous Supports

[0239] a) Preparation of a Composition from a Two-Component Precursor:

The compositions are obtained by mixing, at ambient temperature, 100 parts by weight of a part A and 10 parts by weight of a part B of a two-component system (see compositions in table 2),

[0240] b) the mixture is coated, with a deposited weight of approximately 30 to 36 g/m.sup.2 of fibrous support, so as to form a layer, by means of scrapers or rolls, onto the chosen fabric, and

[0241] c) the resulting layer is crosslinked for 60 seconds at 190 C. in a Mathis oven so as to obtain an elastomer.

4) Tests Carried Out on the Coated Fabrics

[0242] The various coated fabrics are subjected to the scrub test described in detail below, in order to measure the adhesion performances of the silicone elastomer on the various fabrics.
The crease and abrasion resistance test, called scrub test, characterizes the good adhesion of the silicone elastomer on the fibrous support. It is carried out according to the standard EN ISO 5981-Method A. This test consists in subjecting a test specimen of coated textile support with dimensions of 50 mm100 mm, on the one hand, to a shear movement by means of two jaws clamping the opposite two edges of the test specimen and performing an alternating movement with respect to one another, and, on the other hand, to an abrasion by contact with a mobile support or skate which applies a 5 N force on the test specimen. This test is carried out either 24 hours after the coating or after accelerated aging for 7 days at 80 C. and 95% relative humidity. After 500 creasing operations, the coated fabric is verified. If the coating has not been delaminated, the abrasion resistance is satisfactory and a further 500 creasing operations are carried out before verifying the condition of the fabric. The test is finalized when the condition of the coated fabric is not satisfactory.

[0243] The silicone compositions described in detail in table 2 below were evaluated as compositions for coating airbag fabrics.

TABLE-US-00002 TABLE 2 Search for an improved adhesion promoter system Composition C1 C2 C3 C4 Patent Comparative I1 I2 Comparative Comparative EP0681014 example Invention Invention example example Part A (parts by weight) Vinylated oil E1 52.7 52.7 52.7 50.7 49.7 48.0 Organohydropolysiloxane H1 5.8 0.0 0.0 0.0 5.8 5.8 Resin F1 20.0 21.1 21.1 21.1 20.0 20.0 ECH 0.025 0.025 0.025 0.025 0.025 0.025 Calcium carbonate J1 18.5 18.5 18.5 18.5 18.5 18.5 Adhesion promoters 0.0 VTMO 1.0 GLYMO 2.0 2.0 6.0 7.7 Additive K1 7.7 7.7 7.7 0.0 0.0 TOTAL 100 100 100 100 100 100 Part B (parts by weight) Vinylated oil E1 8.28 9.48 8.68 8.68 8.68 8.68 Coloring base 0.9 0.5 0.5 0.5 0.5 0.5 TBOT 0.8 0 0.8 0.8 0.8 0.8 Catalyst C 0.02 0.02 0.02 0.02 0.02 0.02 TOTAL 10 10 10 10 10 10 H/Vi composition 2.4 4 4 4.3 4 4 [epoxy] composition in 7.13 22.2 20.9 27.5 21.4 27.5 mmol/100 g [SiH] composition in 36.4 39.3 39.3 41 36.4 36.4 mmol/100 g
100 parts by weight of part A and 10 parts by weight of part B are mixed so as to obtain the coating compositions. These compositions were coated onto and then crosslinked on two types of polyester fabric: a washed and heat-set polyester fabric and a non-heat-set loomstate polyester fabric. The scrub test results for evaluating the adhesion and the abrasion resistance of the silicone coating are presented in table 3 below.

TABLE-US-00003 TABLE 3 abrasion resistance tests on polyester fabrics after coating and crosslinking Compositions C1 C2 I1 I2 C3 C4 Scrub test results- washed and heat-set Polyester Fabric After 24 h 500 1500 1000 1500 500 500 After 7 d/80 C., 95% RH 1000 1000 1000 1000 0 500 Scrub test results- Loomstate Polyester Fabric After 24 h 500 0 500 500 0 0 After 7 d/80 C., 95% RH 0 500 1000 1000 0 0

[0244] The PET fabric coated with a composition I1 according to the invention comprising as adhesion promoter the SiH-functionalized and Si-epoxy-functionalized organopolysiloxane K1 and butyl titanate exhibits very good abrasion resistance after 24 h and after aging at 80 C. at 95% relative humidity for 7 days. This is verified on a PET fabric that has been washed and heat-set and also on a loomstate PET fabric that has been neither washed nor heat-set. In the absence of butyl titanate (composition C2), the adhesion obtained after 24 h on loomstate PET is not satisfactory.

[0245] The comparative examples C3 and C4 show that, when the same concentration of epoxy and SiH units in the silicone composition is obtained by using as adhesion promoter glycidoxypropyltrimethoxysilane (GLYMO) and TBOT and a crosslinking SiH oil without epoxy units, the abrasion resistance of the heat-set or loomstate coated PET fabric is not satisfactory.

[0246] By way of comparison, the composition C1 according to the prior art EP0681014, comprising GLYMO, VTMO and TBOT as adhesion promoters, does not make it possible to obtain good abrasion resistance after humid aging when the coated fabric is loomstate PET.

[0247] The additive K1 comprising SiH and Si-epoxy units and acting as adhesion promoter and crosslinking agent makes it possible to obtain better adhesion of the silicone coating on PET.

[0248] The organopolysiloxanes K2 to K11 were tested as adhesion promoters as a replacement for K1 in a silicone composition such as that of I1 described in detail in table 2. The amount of adhesion promoter K2 to K11 is adjusted so as to have a concentration of epoxy functions in the silicone composition of between 20 and 22 mmol/100 g and to maintain the molar ratio of SiH units to SiVi units of the composition (H/Vi ratio) between 2 and 5, which is optimal for this application. Consequently, when the adhesion promoter has few SiH units and many epoxy units, crosslinking organohydropolysiloxane H1 is added so as to keep the SiH concentration in the network constant. This is the case with the compositions C1, C8 and 15. On the other hand, when the adhesion promoter tested has many SiH units, in order to maintain the H/Vi ratio below 5, the epoxy concentration in the silicone composition is less than 20 mmol/100 g of silicone composition. The concentrations of SiH units and of epoxy units and the H/Vi ratio of the silicone coating compositions are described in detail in table 4 below.

TABLE-US-00004 TABLE 4 Silicone coating compositions Test C2 I1 I3 C5 C6 C7 I4 I5 C8 C9 C10 C11 Additive Glymo K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11 [epoxy] 21.4 20.9 24.3 1.5 9 7.1 22.2 22.2 22 7.7 18.8 22 composition in mmol/100 g [SiH] composition 36.4 39.3 30.3 59.8 38.9 37.6 38.9 38 36.4 38.9 38.2 39 in mmol/100 g Addition yes yes yes organohydropoly siloxane H1 H/Vi 4.3 4.4 3.5 4.2 4.1 4.3 4.2 4.0 4.3 4.2 4.3

[0249] These compositions were coated onto and then crosslinked on fabrics made of polyester or polyamide or on(to) both. The results are presented in tables 5 and 6 below.

[0250] Table 5 presents the scrub test results for evaluating the adhesion and the abrasion resistance of the silicone coating on two types of polyester fabric: a polyester fabric that has been washed and heat-set and a loomstate polyester fabric that has not been heat-set.

TABLE-US-00005 TABLE 5 Abrasion resistance tests on polyester fabrics after coating and crosslinking Test C2 I1 I3 C5 C6 C7 I4 C8 C9 C10 C11 Additives K1 K2 K3 K4 K5 K6 K8 K9 K10 K11 Scrub test results- washed and heat-set Polyester Fabric After 24 h 500 500 500 0 1000 500 1500 500 0 500 500 After 7 d/80 C., 0 1500 1000 0 0 0 1500 500 0 0 1000 95% RH Scrub test results- Loomstate Polyester Fabric After 24 h 0 500 500 0 0 0 500 0 0 0 0 After 7 d/80 C., 0 1000 1000 0 0 0 1000 0 0 0 0 95% RH
The silicone compositions C5, C6, C7 and C9 comprising adhesion promoters with a ratio of SiH/epoxy units 4 which result in a silicone composition with less than 10 mmol of epoxy units per 100 g of composition do not have sufficient abrasion resistance.
The silicone compositions C10 and C11 comprising adhesion promoters comprising units D not functionalized with Si(CH.sub.3).sub.2O.sub.2/2 despite a ratio of SiH/epoxy units <4, and a concentration of SiH and epoxy units in the composition that are comparable to those of I1, have poor abrasion resistance on loomstate polyester fabric.

[0251] The composition C8 comprising an adhesion promoter K8 comprising only epoxy units and a concentration of SiH and epoxy units in the composition that are comparable to those of I1 by the addition of crosslinking organohydropolysiloxane H1 also does not give good abrasion resistance. The additive X comprising SiH and Si-epoxy units and acting as adhesion promoter and crosslinking agent is consequently essential for improving the adhesion.

[0252] Table 6 presents the scrub test results for evaluating the adhesion and the abrasion resistance of the silicone coating on two types of polyamide fabric: a polyamide fabric that has been washed and heat-set and a loomstate polyamide fabric that has not been heat-set.

TABLE-US-00006 TABLE 6 Abrasion resistance tests on polyamide fabrics after coating and crosslinking Test I1 C6 C7 I5 C6 C7 C8 C9 Additives K1 K4 K5 K7 K8 K9 K10 K11 Scrub test results- washed and heat-set Polyamide Fabric After 24 h 1000 0 1000 1500 0 0 0 500 After 7 d/80 C., 2500 0 2500 4000 1500 0 500 500 95% RH Scrub test results- Loomstate Polyamide Fabric After 24 h 1000 0 0 500 0 0 0 0 After 7 d/80 C., 1000 0 0 5500 0 0 0 0 95% RH

[0253] It was verified that, after coating and crosslinking of the compositions according to the invention, the coated fabrics attain the combing-resistance and tear-resistance values in accordance with what is required for the airbag application.