Land vehicles – Wheeled – Attachment
Reexamination Certificate
2000-08-09
2002-03-12
Dawson, Robert (Department: 1712)
Land vehicles
Wheeled
Attachment
C442S099000, C442S136000, C427S387000, C428S447000, C524S493000, C106S287130, C106S287140, C106S287160, C528S015000, C528S031000, C528S032000, C525S478000
Reexamination Certificate
active
06354620
ABSTRACT:
This invention is concerned with textile fabrics coated with silicone-based coating compositions. More particularly the invention is concerned with textile fabrics that are coated directly or indirectly with silicone-based coating compositions capable of maintaining a pressure barrier between two areas with a pressure differential. The invention also relates to a process of preparing such textile fabrics and to textile articles, e.g. airbags made with coated textile fabrics.
EP 553840 describes a liquid silicone rubber coating composition for application to airbags in automobiles, which comprises a certain polydiorganosiloxane having alkenyl groups, an polyorganosiloxane resin, an inorganic filler, a certain polyorganohydrosiloxane, a platinum group metal catalyst and an epoxy group-containing organosilicon compound. EP 646672 describes a fabric impregnated with a silicone composition comprising a certain linear polyorganosiloxane having aliphatic unsaturation, a certain polyorganohydrosiloxane, a catalyst promoting addition reaction, a hydrophobic silica, a flame retardant and optionally an adhesion-promoting agent, and suggests the use of the fabrics in the construction of airbags.
The benefit of using silicone-coated compositions over other, e.g. organic coating compositions, lies e.g. in the improved weatherability, ability to maintain flexibility and heat resistance of the silicone-based composition.
It is often desirable to provide coated textile fabrics with a finish that is relatively smooth. It is particularly desirable that textile fabrics that are intended for use in applications where they are subject to undesired friction have a low friction surface, i.e. a surface with a relatively low coefficient of friction. A particular example relates to the use of coated textile fabrics in the manufacture of airbags. When airbags are deployed, due to the use of an explosive charge friction is inevitable. Such friction takes place where textile rubs over textile, and also where textile comes into contact with the interior of the automobile or a driver or passenger in an automobile during or after deployment. The amount of friction created can in some circumstances slow down the deployment of the airbag or cause burns to the skin of the driver or passenger.
EP 712956 describes a coating composition for a rubber-coated fabric, comprising a rubber coating composition which comprises a rubber component and a specific solvent and added thereto a powder of an inorganic compound or an organic compound having an average particle size of from 0.5 to 20 &mgr;m, preferably at 20 to 50 parts by weight per 100 parts of the rubber component. The coating composition is said to improve the feeling of a rubber-coated film by eliminating the sticky feeling of the rubber-coated film itself. Examples of the inorganic or organic powders are aluminium hydroxide, mica, polymethyl-silsesquioxane, carbon, polyamide and polyfluoroethylene. Preferred powders are spherical, as a flaky powder is said to be liable to weaken the rubber properties. Particles with an average size over 20 &mgr;m are stated as giving a poor coating property. The presence of a solvent is indicated to be very important, as it has a function of uniformly spreading the powder. Solvents are however, preferably avoided in the coating industry in general.
EP 150385 describes a method of imparting improved tear strength and flame retardancy to a base fabric material comprising applying to at least one side of said base fabric a base silicone coating composition containing an amount of non-abrasive filler effective for imparting said properties. The main application in mind is one of architectural fabric where translucency or transparency of the coating is important. Exemplified coating compositions use about 40 parts of the non-abrasive filler (preferably being calcium carbonate or hydrated alumina), per 100 parts of a siloxane polymer. Excessive viscosities, e.g. obtained if fumed silica or another reinforcing non-abrasive filler is incorporated, are handled by dilution with solvents.
EP 953675 describes a textile fabric coated with an elastomer-forming silicone-based composition, comprising (A) an organopolysiloxane polymer having a siloxane backbone being end-blocked with at least two silicon-bonded groups R, wherein R denotes an olefinically unsaturated hydrocarbon substituent, an alkoxy group or a hydroxyl group, (B) a cross-linking organosilicon material having at least 3 silicon-bonded reactive groups, (C) a catalyst capable of promoting the reaction between the silicon-bonded groups R of compound (A) and the silicon-bonded reactive group of compound B, (D) a first filler which is a reinforcing filler for the silicone-based composition and (E) at least 2 parts by weight for every part of the first filler, of a second filler, which has a substantially laminar form. The use of a laminar second filler tends to reduce the physical properties of the cured elastomeric coating.
We have now surprisingly found that if a certain silicone-based composition is coated on top of another coating, the good physical properties of the underlying coating are not impaired and the coefficient of friction can be reduced.
A curable silicone-based coating composition according to the invention, curable to a flexible coating at a coat weight of up to 15 g/m
2
when cured, comprises
A. an organopolysiloxane polymer having a siloxane backbone of degree of polymerisation no more than 150 end-blocked with at least two silicon-bonded groups R, wherein R denotes an olefinically unsaturated hydrocarbon substituent, an alkoxy group or a hydroxyl group,
B. a cross-linking organosilicon material having at least 3 silicon-bonded reactive groups,
C. a catalyst capable of promoting the reaction between the silicon-bonded groups R of compound A and the silicon-bonded reactive group of compound B,
D. optionally a non-reinforcing filler and
E. optionally up to a maximum of 3% by weight of reinforcing filler.
The curable silicone-based coating composition can be coated onto a substrate and cured in situ. Because the coating composition is curable to a flexible coating at a thickness up to 15 g/m
2
, it is suitable for textile fabrics. Flexibility means that the coated fabric can be folded easily, as is for example required by an airbag which needs to be stored in a small compartment in a vehicle, e.g. inside the steering wheel or the roof void of a car. This is very surprising in view of the short chain length of polymers (A), which in most circumstances tend to form very brittle coatings upon curing, and are therefore unsuitable for applications where flexibility is crucial.
Useful organopolysiloxane polymers (A) for use in the curable silicone-based compositions according to the invention have units of the general formula R
1
a
R
2
b
SiO
4−a−b/2
(I), wherein R
1
is a monovalent hydrocarbon group having up to 18 carbon atoms, R
2
is a monovalent hydrocarbon or hydrocarbonoxy group or a hydroxyl group, a and b have a value of from 0 to 3, the sum of a+b being no more than 3. Preferably the organopolysiloxane polymers have a generally linear nature having the general structure II
wherein R
1
and R
2
have the same meaning as above, and wherein x is an integer of no more than 148, preferably having a value of from 5 to 100, more preferably 8 to 50. It is particularly preferred that R
1
denotes an alkyl or aryl group having from 1 to 8 carbon atoms, e.g. methyl, ethyl, propyl, isobutyl, hexyl, phenyl or octyl. More preferably at least 50% of all R
1
groups are methyl groups, most preferably substantially all R
1
groups are methyl groups. R
2
is preferably selected from a hydroxyl group, an alkoxy group or an aliphatically unsaturated hydrocarbon group. More preferably R
2
denotes either a hydroxyl group or alkoxy group having up to 3 carbon atoms suitable for condensation reactions, or an alkenyl or alkynyl group having up to 6 carbon atoms, more preferably vinyl, allyl or hexenyl, suitable for addition reactions.
Preferably the organopolysilox
Budden Graham D.
Kosal Diane Marie
Rolley Patricia Ann
Cesare James L. De
Dawson Robert
Dow Corning Corporation
Warren Jennifer S.
Zimmer Marc S.
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