SILICONE COATINGS FOR AIR BAGS

Abstract

A hydrosilylation curable textile coating composition comprises: (a) a linear organopolysiloxane polymer having at least two alkenyl and/or alkynyl groups per molecule; (b) a reinforcing filler comprising at least one of fumed silica, precipitated silica, or calcium carbonate; (c) a cross-linker containing at least two silicon-bonded hydrogen groups per molecule; (d) a hydrosilylation cure catalyst; (e) an organosilicon resin containing M and Q units; and (f) an adhesion promoter comprising a mixture and/or reaction product of (i) one or more alkoxysilanes having an epoxy group in the molecule; (ii) a linear organopolysiloxane oligomer containing at least one alkenyl group and at least one hydroxy or alkoxy group per molecule; and (iii) an organometallic condensation reaction catalyst comprising organoaluminum or organozirconium compounds. A textile, e.g. air bag or air bag fabric, can be coated with the hydrosilylation curable textile coating composition, and resulting air bags and fabrics generally have improved properties.

Claims

1. A hydrosilylation curable textile coating composition, the composition comprising: (a) a linear organopolysiloxane polymer having at least two alkenyl and/or alkynyl groups per molecule; (b) a reinforcing filler comprising at least one of fumed silica, precipitated silica, or calcium carbonate; (c) a cross-linker containing at least two, optionally at least three, silicon-bonded hydrogen groups per molecule, and selected from the group consisting of: C-1) a trimethyl or dimethyl hydrogen terminated polydimethyl methylhydrogen methylsilsesquioxane siloxane; C-21 a trimethyl or dimethyl hydrogen terminated polymethyl hydrogen siloxane; C-31 a dimethyl hydrogen terminated polydimethyl methylhydrogen siloxane; C-41 an organosilicon resin; and C-5) a cyclic siloxane; optionally wherein the molar ratio of silicon-bonded hydrogen groups to alkenyl groups and alkynyl groups in the composition is from 1:1 to 5:1; (d) a hydrosilylation cure catalyst; (e) an organosilicon resin containing M and Q units, optionally where a proportion of the M units are M.sup.vi units; and (f) an adhesion promoter comprising a mixture and/or reaction product of: (i) one or more alkoxysilanes having an epoxy group in the molecule; (ii) a linear organopolysiloxane oligomer containing at least one alkenyl group and at least one hydroxy or alkoxy group per molecule; and (iii) an organometallic condensation reaction catalyst comprising organoaluminum or organozirconium compounds.

2. The composition in accordance with claim 1, wherein i) the molar ratio of silicon-bonded hydrogen groups to alkenyl groups and alkynyl groups in the composition is from 1:1 to 5:1 in accordance with ASTM E168, and/or ii) the cross-linker (c) is present in an amount of from 1 to 30% by weight of the composition.

3. The composition in accordance with claim 1, wherein the adhesion promoter (f) is present in the composition in a cumulative amount of components (f)(i), (ii) and (iii) of from about 0.3 to 6% by weight of the composition.

4. The composition in accordance with claim 1, wherein component (f) (i) is selected from the group consisting of 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, 4-glycidoxybutyl trimethoxysilane, 5,6-epoxyhexyl triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl) ethyltriethoxysilane, and/or ii) is present in an amount of from 0.1 to 5% by weight of the composition.

5. The composition in accordance with claim 1, wherein component (f) (ii) is i) a methylvinylpolysiloxane in which both molecular terminals are dimethylhydroxysiloxy units, or a copolymer of a methylvinyl siloxane and dimethylsiloxane units in which both molecular terminals are dimethylhydroxysiloxy units, in each case having a viscosity not exceeding 500 mPa.Math.s at 25° C., and/or ii) is present in an amount of from 0.1 to 5% by weight of the composition.

6. The composition in accordance with claim 1, wherein component (f) (iii) is a zirconate based catalyst selected from the group consisting of zirconium tetrapropylate, zirconium tetrabutyrate, tetra-isopropyl zirconate, zirconium (IV) tetraacetyl acetonate, zirconium (IV) hexafluoracetyl acetonate, zirconium (IV) trifluoroacetyl acetonate, tetrakis (ethyltrifluoroacetyl acetonate) zirconium, tetrakis (2,2,6,6-tetramethyl-heptanethionate) zirconium, zirconium (IV) dibutoxy bis(ethylacetonate), zirconium tributoxyacetylacetate, zirconium butoxyacetylacetonate bisethylacetoacetate, zirconium butoxyacetylacetonate bisethylacetoacetate, diisopropoxy bis (2,2,6,6-tetramethyl-heptanethionate) zirconium, and zirconium complexes having β-diketones.

7. The composition in accordance with claim 1, wherein the composition further comprises an inhibitor to inhibit cure of the composition.

8. The composition in accordance with claim 1, wherein the composition is stored in two parts, Part A and Part B, in which Part A comprises components (a), (b), (d), and (f)(iii) and optionally component (e), and Part B comprises components (a), (b), (c), (f) (i), and (f)(ii) and optionally component (e).

9. The composition in accordance with claim 1, which upon cure on a fabric substrate has a total volatile organic compound content of <40 ppm in accordance with VDA277.

10. An airbag fabric coated with an elastomeric coating which is a cured product of the hydrosilylation curable textile coating composition in accordance with claim 1.

11. The airbag fabric in accordance with claim 10, which has a total volatile organic compound content of <40 ppm in accordance with VDA277.

12. A method of coating a textile with the hydrosilylation curable textile coating composition in accordance with claim 1, comprising mixing the composition, coating a textile with the composition, and curing the composition on the textile.

13. A method of coating a textile with the hydrosilylation curable textile coating composition in accordance with claim 1, wherein the textile is coated with the composition by spraying, gravure coating, bar coating, coating by knife-over-roller, coating by knife-over-air, padding, dipping and screen-printing, and/or wherein the composition is applied at a coat-weight of from 10 g/m.sup.2 to 150 g/m.sup.2.

14. (canceled)

15. (canceled)

Description

EXAMPLES

[0114] In the following examples, % ages are given in weight unless otherwise stated and all viscosity measurements occur at 25° C. unless otherwise indicated. Unless otherwise indicated, the viscosity of the polymers was measured in accordance with ASTM D1084 using a Brookfield rotational viscometer with the most appropriate spindle for the viscosity being measured at 1 rpm, unless otherwise indicated. Cross-linker viscosities were measured using a glass capillary viscometer. Vinyl group and Si—H group content was measured by Infrared spectroscopy in accordance with ASTM E168 using standards of the carbon double bond stretch and silicon-hydrogen bond stretch respectively.

Preparation Process

[0115] As a first step an in-situ treated fumed silica masterbatch was prepared in a Kneader mixer by mixing the ingredients depicted in Table 1 and the stripping off residual water and treatment agents.

TABLE-US-00003 TABLE 1 In-situ treated fumed silica masterbatch ingredients Weight % Fumed silica surface area of about 300 m.sup.2/g 28.15 (ISO 9277: 2010) dimethylvinyl-terminated polydimethylsiloxane 65.0 (1) having a viscosity of 65,000 mPa .Math. s Hexamethyldisilazane 5.0 Dimethylhydroxy terminated vinylmethyl dimethyl 0.15 polysiloxane having a viscosity of about 30 mPa .Math. s and a vinyl content of 12.5% wt. Water 1.7

[0116] The resulting fumed silica masterbatch was then utilised to make the two-part liquid silicone rubber compositions depicted below in the following Tables in which

Resin/Polymer 1 Mixture: is a mixture of an organosilicon resin and a dimethylvinyl terminated polydimethylsiloxane polymer. The organosilicon resin has number average molecular weight of about 21,000 g/mol (GPC), a molar ratio of M groups to Q groups of about 0.8:1 and a vinyl content of about 5% wt. The polymer has a vinyl content of 0.23% wt., and the mixture contains 34 wt. % resin and has a viscosity of about 6000 mPa.Math.s.
Polymer 1: Dimethylvinyl terminated polydimethylsiloxane polymer having a vinyl content of 0.14% wt. and a viscosity of 12,000 mPa.Math.s.
Cross-linker type (C-1): is a trimethyl terminated polydimethyl methylhydrogen methylsilsesquioxane siloxane having a viscosity of about 15 mPa.Math.s and a silicone bonded hydrogen (Si—H) content of 0.85% wt.
Cross-linker type (C-2): trimethyl terminated polymethyl hydrogen siloxane; having a viscosity of about 25 mPa.Math.s and an Si—H content of 1.57% wt.
Cross-linker type (C-3): dimethyl hydrogen terminated polydimethyl methylhydrogen siloxane having a viscosity of about 9 mPa.Math.s and a Si—H content of 0.39% wt.
Cross-linker type (C-4): an organosilicon resin having a viscosity of about 35 mPa.Math.s and a Si—H content of 0.96% wt.
Cross-linker type (C-5): cyclic siloxanes having a viscosity of about 1.0 mPa.Math.s and a Si—H content of 1.67% wt.

[0117] Part A containing Pt catalyst and Part B containing SiH crosslinker, were then mixed in a suitable ratio from 1:100 to 1:1. In the following the composition is designed to be mixed in a 1:1 weight ratio in a Turello mixer.

TABLE-US-00004 TABLE 2 LSR Part A Comp. 1 Standard Formulation (wt. %) (wt. %) Fumed Silica Masterbatch 31 30 Resin/Polymer 1 Mixture 67.08 30 Polymer 1 38.08 Pt catalyst masterbatch containing 5,000 ppm Pt 0.32 0.32 1:1 wt. ratio zirconium tetrakisacetylacetonate/ 1.6 1.6 Polymer 1 mixture

[0118] Excepting comp. 1 all other examples and comparatives used the Part A composition indicated as standard in Table 1.

TABLE-US-00005 TABLE 3a LSR Part B Comp. 1 Comp. 2 Ex. 1 Ex. 2 Formulation (wt. %) (wt. %) (wt. %) (wt. %) Fumed Silica Masterbatch 22 30 30 30 Resin/Polymer 1 Mixture 58.92 30 30 30 Polymer 1 27.42 28.82 33.72 Trimethyl terminated poly 16.3 9.8 dimethyl methylhydrogen siloxane, viscosity 5 mPa .Math. s and 0.75% wt. Si—H content Cross-linker type (C-1) 8.4 Cross-linker type (C-2) 3.5 Ethynyl Cyclohexanol 1.0 1.0 1.0 1.0 Glycidoxypropyl- 1.42 1.42 1.42 1.42 trimethoxysilane Dimethylhydroxy terminated 0.36 0.36 0.36 0.36 vinylmethyl dimethyl poly- siloxane having a viscosity of about 30 mPa .Math. s and vinyl content of 12.5% wt

TABLE-US-00006 TABLE 3b LSR Part B Ex. 3 Ex. 4 Ex. 5 Formulation (wt %) (wt %) (wt %) Fumed Silica Masterbatch 30 30 30 Resin/Polymer 1 Mixture 30 30 30 Polymer 1 28.02 28.62 34.02 Cross-linker type (C-3) 9.2 Cross-linker type (C-4) 7.6 Cross-linker type (C-5) 3.2 Ethynyl Cyclohexanol 1.0 2.0 1.0 Glycidoxypropyltrimethoxysilane 1.42 1.42 1.42 Dimethylhydroxy terminated vinylmethyl 0.36 0.36 0.36 dimethyl polysiloxane having a viscosity of about 30 mPa .Math. s and vinyl content of 12.5% wt.
The Si—H to vinyl ratio for all comparatives and examples were in the region of 2.5 to 3:1.

[0119] The physical properties of the different examples and comparatives depicted in Tables 2 and 3 above were determined to ensure they were satisfactory. Samples were press cured to a thickness of 2 mm, at a temperature of 120° C. for 10 minutes. Other physical property testing followed ASTM standard (D2204 for Hardness, D412 for Tensile strength and Elongation at break, D4287 for viscosity, and D624 for tear strength).

TABLE-US-00007 TABLE 4 Physical properties Comp. 1 Comp. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Mixed viscosity 10/s 17 20 22 25 25 26 28 (Pa.s, ASTM D4287) Hardness (Shore A, 41 32 33 37 18 36 40 ASTM D2204) Tensile strength (MPa, 4.9 4.1 4.5 4.9 3.3 4.1 4.3 ASTM D412) Elongation at break (%, 237 293 335 298 358 279 223 ASTM D412) Tear Strength (Die C, 19.3 15.8 16.5 16.5 15.3 17.4 18.7 KN/m, ASTM D624)

[0120] Samples of coated fabrics, coated with the example and comparative examples depicted above were prepared using a Mathis lab coater. The Part A and Part B compositions were mixed in a 1:1 weight ratio in a speed mixer with. Then the resulting mixture was coated on PA66 (Nylon 66 woven fabric) and PET (polyethylene terephthalate woven fabric) respectively in the Mathis lab coater by knife coating. The coated fabrics were then heated at 190° C. for 1 min. to cure the coating on the fabric and then subsequent to cooling the coat weight was determined and was found to be approximately 35±5 g/m.sup.2 for each sample. The resulting coated fabrics were then tested for TVOC in accordance with VDA277.

TABLE-US-00008 TABLE 5 TVOC of coated fabrics (ppm) (μg C/g, ppm, VDA 277) Comp. 1 Comp. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 lab coated PA66 122 85 37 28 39 32 26 lab coated PET 105 70 36 33 37 34 31 coated PA66 120 26 19 coated PET 90 20 12 lab coated PA66 122 85 37 28 39 32

[0121] Comparing with example 1 and 2 with traditional SiH crosslinker, the TVOC of LSR compositions using special SiH crosslinkers was reduced significantly. The application of these special SiH crosslinker is effective to TVOC reduction in examples of the compositions herein and all samples tested gave a TVOC of <40 ppm and in several instances <30 ppm.

[0122] Samples of the coated fabrics were also analysed for scrub (abrasion) resistance before and after heat/humidity aging at 70° C. and 95% relative humidity for 408 hrs according to EASC 99040180 A09 and the results are shown in Tables 6a and 6b below.

TABLE-US-00009 TABLE 6a Scrub Resistance (Strokes) Comp. 1 Comp. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Coated PA66 1600 2000 2000 2000 1000 1000 1000 Coated PET 1600 2000 2000 2000 1000 1000 1000

TABLE-US-00010 TABLE 6b Scrub Resistance (strokes) after heat humidity aging Comp. 1 Comp. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Coated PA66 1200 1600 1600 1600 600 600 600 Coated PET 1200 1600 1600 1600 600 600 600

[0123] Some of the compositions, for example 2, 3 and 4, also shown excellent scrub resistance and high stability after heat/humidity aging (i.e., >600 strokes).