Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coated or impregnated natural fiber fabric
Reexamination Certificate
1999-04-22
2001-03-13
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coated or impregnated natural fiber fabric
C442S071000, C442S081000, C442S097000, C442S099000, C442S134000, C442S136000, C280S728100, C425S027000, C425S035000, C425S043000, C428S035700, C428S036100, C428S036600, C428S036700
Reexamination Certificate
active
06200915
ABSTRACT:
This invention is concerned with textile fabrics coated with silicone-based coating compositions. More particularly the invention is concerned with textile fabrics which are coated 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.
Coating textile fabrics with silicone-based coating compositions has been know for a while. These compositions may impart a variety of benefits to the coated fabric. For example in EP 553,840, there is described 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. In EP 646,672, there is described 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. The latter patent specification suggests the use of the composition for fabrics used 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. Although the prior art provides several systems which are satisfactory in many ways, there is a desire to improve the coating compositions used for making coated textile fabrics.
It is often desirable to provide coated textile fabrics with a finish which is relatively smooth. It is particularly desirable that textile fabrics which are intended for use in applications where they are subject to a certain amount of undesired friction have a smooth 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 for use in automobiles. When such 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. There is a desire to provide coated textile fabrics which have a relatively low coefficient of friction.
In other instances there is a desire to reduce the coating thickness, e.g. to minimise the weight of the coated fabric, whilst maintaining good physical properties, for example adequate coverage of the fabric surface by the coating, good adhesion to the textile fabric, ease of application of the coating to the textile fabric. At other times it is important to achieve an improved level of gas impermeability, especially where the textile fabric is to be used as an envelope for pressurised gas, e.g. as an automotive airbag, whilst maintaining good flexibility and a relatively low weight. There is often also a desire to improve the flame retardancy of coated textile fabrics. At other times it may be important that the textile fabric is particularly resistant against impact of very hot particles or the effect of hot gases. This latter property is again one which may be desired in the manufacture of airbags for automobiles, as an explosive charge is often used to inflate the airbag upon impact. Said explosive charges produce at times extremely hot particles, which may be thrown against the textile fabric. It is extremely important for safety and efficiency purposes that such particles do not cause a hole to be burnt through the envelope of the airbag.
EP 0712956 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-sylsesquioxane, 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.
We have now found that if a mixture of certain filler particles are used in elastomer-forming silicone compositions used for coating textile fabrics, one or more of the above mentioned needs for improvement can be met, even in the absence of a solvent.
According to the invention there is provided a textile fabric which has been 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
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 elastomer-forming silicone based composition is able to form elastomers upon curing. Many organosiloxane systems are known and commercially available and many have been described in the literature which can be used to prepare such compositions.
Useful organopolysiloxane polymers (A) for use in elastomer-forming silicone based compositions 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, preferably having a value of from 10 to 1500. 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
Adams Graham
Budden Graham
Lawson David
Dow Corning Ltd
Morris Terrel
Singh Arti
Warren Jennifer S.
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