Patent ID: 6040369
Filing Date: 2000-03-21
Classification: C08K,H01B,Y10T

Abstract:
An uncured elastomer blend composition suitable for curing by cross linking, the composition comprising two aliquots in combination:the first aliquot comprising an intimately admixed mixture of the following components:(1) approximately 23 to 45 percent by weight of silica that had been silyliated by treatment and contains trialkylsilyl groups;(2) approximately 55 to 77 per cent by weight of a polysiloxane copolymer composed of divalent --R.sub.1 R.sub.2 SiO--, divalent --R.sub.3 R.sub.4 SiO-- and end-blocking R.sub.5 R.sub.6 R.sub.7 SiO-- units,where R.sub.1 and R.sub.2 independantly are lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, R.sub.3 is vinyl, allyl, or other olefinic group having up to 4 carbons, R.sub.4 is lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, and R.sub.5, R.sub.6, and R.sub.7 independantly are lower alkyl of 1 to 6 carbons, phenyl, vinyl, allyl, or other olefinic group having up to 4 carbons and one double bond, the polysiloxane copolymer has a degree of polymerization (D. P.) approximately in the range of 3500 to 6500, and the olefin containing --R.sub.3 R.sub.4 SiO-- groups are present randomly distributed in the polysiloxane copolymer and approximately in the 0.05 to 0.3 mol percent range, with the provisos that when R.sub.1, or R.sub.2, or both represent phenyl groups then proportion of the phenyl-containing divalent siloxane units does not exceed 15 mol per cent. and when R.sub.1 or R.sub.2 or both represent trifluoropropyl groups, then the proportion of the trifluoropropyl-containing divalent siloxane units does not exceed approximately 40 mol per cent in the polysiloxane copolymer; and a(3) a catalyst,the second aliquot comprising an intimately admixed mixture of the following components:(1) approximately 23 to 45 percent by weight of silica that had been silyliated by treatment and contains trialkylsilyl groups;(2) approximately 55 to 77 per cent by weight of a polysiloxane copolymer composed of divalent --R.sub.1 R.sub.2 SiO--, divalent --R.sub.3 R.sub.4 SiO-- and end-blocking R.sub.5 R.sub.6 R.sub.7 SiO-- units,where R.sub.1 and R.sub.2 independantly are lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, R.sub.3 is vinyl, allyl, or other olefinic group having up to 4 carbons, R.sub.4 is lower alkyl of 1 to 6 carbons, phenyl or trifluoropropyl, and R.sub.5, R.sub.6, and R.sub.7 independantly are lower alkyl of 1 to 6 carbons, phenyl, vinyl, allyl, or other olefimic group having up to 4 carbons and one double bond, the polysiloxane copolymer has a degree of polymerization (D. P.) approximately in the range of 3500 to 6500, and the olefin containing --R.sub.3 R.sub.4 SiO-- groups are present randomly distributed in the polysiloxane copolymer and approximately in the 0.05 to 0.3 mol percent range, with the provisos that when R.sub.1, or R.sub.2, or both represent phenyl groups then proportion of the phenyl-containing divalent siloxane units does not exceed 15 mol per cent. and when R.sub.1 or R.sub.2 or both represent trifluoropropyl groups, then the proportion of the trifluoropropyl-containing divalent siloxane units does not exceed approximately 40 mol per cent in the polysiloxane copolymer, and(3) an organohydrogen polysiloxane cross-linker,the catalyst and the cross-linker being present in the first and second aliquots respectively in sufficient amounts to cause the cross-linking reaction to occur after the first and second aliquots are intimately mixed.