Silicone composition and process that is useful for improving the tear strength and the combing strength of an inflatable bag for protecting an occupant of a vehicle
The general field of the invention is that of airbags. The invention relates to a process for improving the tear strength and the combing strength of coated fabrics intended for uses in the field of inflatable bags using a silicone composition comprising an additive containing a polyorganosiloxane resin (V) and a calcium carbonate. After coating the composition onto the fabric supports and curing, the coated supports not only have optimum adhesion and crease resistance properties, but also have good properties in terms of combing strength and tear strength.
1. A process for improving the combing strength and the tear strength of a woven, knitted or nonwoven fibrous support, comprising the following steps:
a) preparing a curable silicone coating composition comprising:
(i) at least one polyorganosiloxane (I) containing, per molecule, at least two C2-C6 alkenyl groups linked to silicon,
(ii) at least one polyorganosiloxane (II) containing, per molecule, at least two hydrogen atoms linked to silicon,
(iii) a catalytically effective amount of at least one catalyst (III), comprising at least one metal belonging to the platinum group,
(iv) at least one adhesion promoter (IV) consisting of,
(IV.1) at least one alkoxylated organosilane containing, per molecule, at least one C2-C6 alkenyl group,
(IV.2) at last one organosilicon compound comprising at least one epoxy radical, and
(IV.3) at least one metal chelate M and/or a metal alkoxide of general formula: M(OJ)n, where n=valency of M, J=linear or branched C1-C8 alkyl group, and M is selected from the group consisting of Ti, Zr, Ge, Li, Mn, Fe, Al and Mg;
(v) an additive system for improving the combing strength and the tear strength, said additive system comprising a pre-mix formed from:
at least one polyorganosiloxane resin (V), optionally mixed with at least one polyorganosiloxane serving as diluent, in which the polyorganosiloxane resin (V) comprises in its structure from 4% to 20% by weight of alkenyl group(s), the said structure containing identical or different siloxyl units of type M, identical or different siloxyl units of type(s) T and/or Q, and optionally siloxyl units of type D, and
calcium carbonate (CaCO 3 );
(vi) optionally, at least one curing inhibitor (VI),
(vii) optionally, at least one coloration additive (VII), and
(viiii) optionally, at least one additive (VIII) for improving the fire resistance,
wherein said at least one polyorganosiloxane resin (V) is present at up to 60% by weight relative to the total weight of curable silicone coating composition and calcium carbonate is present from 10% to 24% by weight relative to the total weight of curable silicone coating composition,
b) applying to one or two faces of a woven, knitted or nonwoven fibrous support at least 10 g/m 2 of the curable silicone coating composition prepared in step a), and
c) curing the curable silicone coating composition applied in step b) to form an elastomer by heating to a temperature up to 210° C., optionally by electromagnetic radiation.