Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-03-16
2002-07-16
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C524S588000, C524S444000, C524S442000, C524S494000, C524S492000, C528S032000, C528S031000, C528S015000, C549S215000, C280S728100, C526S243000
Reexamination Certificate
active
06420037
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a silicone rubber based coating composition for air bags used in automobile air bags and such. More specifically, it relates to a silicone rubber based coating composition for air bags which is superior in terms of thin film coating properties in the absence of solvents, and, upon curing, possesses an adhesive strength such that it is capable of withstanding the impact of distension at high temperatures, and, moreover, exhibits an extremely low tackiness of the coating film surface.
Base fabrics made by coating fabrics of synthetic fibers, such as Nylon 66, with silicone rubbers possess the advantage of superior temperature characteristics, flame resistance, and low degradation over time, and have been used in automobile air bags and such. Usually, when a silicone rubber is coated on a fabric of synthetic fiber, it is applied in a thin, uniform layer, with toluene, xylene, and other diluent solvents used so as to obtain a sufficient strength of adhesion to the foundation fabric. However, in order to meet the recent demand for solvent-free processes for the purposes of environmental protection, there have been offered liquid silicone rubber compositions which permit coating without using solvents (see Japanese Kokai (Unexamined) Patent Publication No. Hei 05(1993)-214295). However, the problem with coated base fabrics made with the help of such liquid silicone rubber compositions is that because the coating film surface retains a certain amount of tackiness after the curing of the silicone rubber, its processability during sewing is inferior and the coating film adheres together when folded and stored, which makes it necessary to dust the coating film surface with talc, calcium carbonate, or clay.
As a result of in-depth investigations aimed at eliminating the above described problems, the authors of the present invention discovered that a liquid silicone rubber composition obtained by admixing a specific organotitanium compound exhibits excellent thin film coating properties and penetrability with respect to synthetic fiber fabrics, as well as provides for a reduction in the tackiness of the coating film surface, and these characteristic make the composition especially useful as a liquid silicone rubber coating composition for air bags (see Japanese Kokai (Unexamined) Patent Publication No. Hei 09(1997)-87585). Later, as a result of further investigations, they discovered that if a certain amount of a specific spherical powder was compounded with the liquid silicone rubber composition, the tackiness of the coating film surface upon curing was noticeably reduced, thus arriving at the present invention. Namely, it is an object of the present invention to provide a silicone rubber based coating composition for air bags which is superior in its characteristics as a coating for air bags and, in particular, exhibits no coating film surface tackiness.
SUMMARY OF INVENTION
A silicone rubber based coating composition for air bags comprising about 0.1 to 50 wt % of a spherical powder with an average particle size of about 10 &mgr;m to 300 &mgr;m.
DESCRIPTION OF INVENTION
The above described object is accomplished by using a silicone rubber based coating composition for air bags which is characterized by containing about 0.1 to 50 wt % of a spherical powder with an average particle size of about 10 &mgr;m to 300 &mgr;m. To explain the preceding in greater detail, the spherical powder used in the present invention is a component believed to be essential in the reduction of the surface tackiness of the air bag's coating film. It is necessary that such spherical powder should have an average particle size within the range of from 10 &mgr;m to 300 &mgr;m. Hollow aluminosilicate powders, glass spheres, silica spheres, shirasu spheres, carbon spheres, alumina spheres, plastic spheres, hollow silicone resin powders, and other hollow powders; alumina powders, glass powders, plastic powders, and the like are suggested as such spherical powders. Among them, the hollow powders are preferable because they can be uniformly dispersed over the surface of the coating film of the air bag. In addition, it is preferable that the viscosity at 25° C. of the silicone rubber based coating composition of the present invention containing such spherical powders should be within a range of from 5 Pa·s to 300 Pa·s.
The silicone rubber based coating composition of the present invention contained about 0.1 to 50 wt % of the above described spherical powder. Well-known prior-art silicone rubber compositions used as air bag coating agents can be used here as the silicone rubber based composition containing the spherical powder. Organic peroxide curing type silicone rubber compositions, addition reaction curing type silicone rubber compositions, condensation reaction curing type silicone rubber compositions, silicone latexes which turn into rubber via crosslinking as a result of water evaporation can all be used. Among them, addition reaction curing type silicone rubber compositions are preferable, such as an addition reaction curing type liquid silicone rubber compositions comprising:
(A) 100 parts by weight of a diorganopolysiloxane having a viscosity at 25° C. of about 100 to 100,000 mPa·s and having at least two alkenyl groups in one molecule
(B) an organohydrogenpolysiloxane having at least three silicon-bonded hydrogen atoms in one molecule in an amount such that the mole ratio of the silicon-bonded hydrogen atoms in this component to the alkenyl groups in component (A) is about 0.6:1 to 20:1,
(C) a platinum catalyst in an amount providing about 0.1 to 500 parts by weight of platinum metal per 1,000,000 parts by weight of component (A), and
(D) about 0.1 to 100 parts by weight of a spherical powder whose average particle size is about 10 &mgr;m to
300 &mgr;m.
To provide further explanations regarding the addition reaction curing type silicone rubber composition, the diorganopolysiloxane of component (A) is the main ingredient, and it is necessary for it to have at least two alkenyl groups in one molecule. Such diorganopolysiloxane is a substantially linear organopolysiloxane represented by the average unit formula:
RnSiO
4
-
n
2
where R is a substituted or non-substituted monovalent hydrocarbon group exemplified by alkyl groups such as methyl, ethyl, and propyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; and halogenated alkyl groups such as 3,3,3-trifluoropropyl. The subscript n is about 1.9 to 2.1. It is preferred that the diorganopolysiloxane have a viscosity at 25° C. of about 100 to 100,000 mPa·s, with a viscosity at 25° C. of 1000 mPa·s to 50,000 mPa·s being even more preferable when the strength of the silicone rubber coating film, compounding properties, and the like are taken into consideration. Specific examples of the diorganopolysiloxane include dimethylpolysiloxane endblocked with dimethylvinylsiloxy groups at both terminals, copolymers of methylvinylsiloxane and dimethylsiloxane endblocked with dimethylvinylsiloxy groups at both terminals, copolymers of methylphenylsiloxane and dimethylsiloxane endblocked with dimethylvinylsiloxy groups at both terminals, and copolymers of methylvinylsiloxane and methyl (3,3,3-trifluoropropyl)siloxane endblocked with dimethylvinylsiloxy groups at both terminals.
The organohydrogenpolysiloxane of component (B), which has at least three silicon-bonded hydrogen atoms in one molecule, is a crosslinking agent. Such organohydrogenpolysiloxane is exemplified by methylhydrogenpolysiloxane endblocked with trimethylsiloxy groups at both terminals, copolymers of methylhydrogensiloxane and dimethylsiloxane endblocked with trimethylsiloxy groups at both terminals, copolymers of methylhydrogensiloxane and methylphenylsiloxane endblocked with dimethylphenylsiloxy groups at both terminals, cyclic methylhydrogenpolysiloxane, copolymers made up of dimethylhydrogensiloxy units and SiO
4/2
units. The viscosity of the organopolysiloxane is usually in the range of from 1 m
Nakamura Akito
Tsuji Yuichi
Boley William F.
Dawson Robert
De Cesare Jim L.
Dow Corning Toray Silicone Co. Ltd.
Peng Kim-Liang
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