Organopolysiloxanelastomere

摘要

1284115 Elastomer-forming vinyl-containing organopolysiloxane compositions GENERAL ELECTRIC CO 4 Sept 1969 [9 Sept 1968] 43824/69 Heading C3T An elastomer-forming composition comprises (A) 100 p.b.w. of a blend of (i) an organopolysiloxane gum of viscosity 100,000-2,000,000,000 cp./25‹ C. containing 0À01-0À6 mole per cent of units (1) CR 2 =CHSiR a O 3-a/2 , the remainder being units (2) R1 b SiO 4-b/2 , (ii) an organopoly- siloxane of viscosity 1-1,000,000,000 cp./25‹C. containing 2-100 mole per cent of units (3) CH 2 = CH Si(CH 3 ) c O 3-c , the remainder being units (CH 3 ) d SiO 4-d/2 , and optionally (iii) an organopolysiloxane of viscosity 100,000- 2,000,000,000 cp./25‹ C. containing no vinyl groups, composed of units (2) above, wherein R is methyl, phenyl or vinyl, R1 is methyl or phenyl, a and c are each 0, 1 or 2 and b and dare each 1, 2, or 3, the ratio of phenyl+methyl+ vinyl groups to silicon in each of (i), (ii) and (iii) being 1À95-2À01 : 1 and each containing no more than 10 mole per cent of phenylsiloxane units, the polysiloxanes (i) and (ii) together providing at least 1-3À5 wt. per cent of methyl vinylsiloxane units in the total blend, and (B) 10-60 p.b.w. of a reinforcing silica filler, and (C) 2-15 p.b.w. of an organosilicon process aid which is a hydroxy- or alkoxy-terminated polydiorganosiloxane or a silazane or silylamine. In examples compositions are prepared containing a vinyl-containing dimethylpolysiloxane gum (i) and tetravinyl tetramethyl cyclotetrasiloxane or a poly-dimethylsiloxane-methylvinylsiloxane (ii) and optionally a polydimethylsiloxane gum (iii), with a fumed silica (B) and a process aid (C) which is dihydroxy polydimethylsiloxane or dimethoxy polydimethylsiloxane or a mixture of the latter or both with hexamethyldisilazane, and an iron oxide or rare earth metal octoate heat additive and benzoyl peroxide, dichlorobenzoyl peroxide or 2 : 5-dimethyl-2 : 5-ditert.-butylperoxy-hexane. In Example 6 the gums (i) and (iii) contain diphenylsiloxane units; in Example 8 a powdered quartz filler is also added.