| 摘要 |
1,197,380. Silicone rubber compositions. DOW CORNING CORP. 11 Sept., 1968 [10 Oct., 1967], No. 43193/68. Heading C3T. A composition curable to a silicone rubber which is non-adhesive to metal surfaces comprises (A) 100 parts by weight (pbw) of a mixture of a polysiloxane gum of average unit formula R n SiO 4-n/2 wherein each R is a methyl, vinyl or phenyl radical and n is 1À98-2À01, at least 75% of the radicals R being methyl radicals, a reinforcing silica, and an organic peroxide, and (B) from 0À05 to 2 pbw of diethylene glycol distearate or a salt of a C 16-26 carboxylic acid and Ni, Al, Cd, Zn, Mg or Li. Suitable peroxides include benzoyl, 2 : 4- dichlorobenzoyl, dicumyl and di-t-butyl peroxides, 2 : 5 - bis - (t - butylperoxy) - 2 : 5 - dimethylhexane and t-butylperbenzoate, in amount 0À1-10 pbw per 100 of the gum. Mixture (A) may also contain organic and inorganic fillers and heat stability, compression set, handling, and crepe ageing additives. The silica may be fume or aerogel silica in amount 10-200 pbw per 100 of the gum. Many suitable salts (B) are listed. In Example 1 100 pbw dimethylvinylsiloxy - terminated polydimethyl siloxane are milled with 35 pbw silica, 8 pbw hydroxylated methylpolysiloxane liquid, 4 pbw diphenylsilanediol and 3À5 pbw methylvinylpolysiloxane; 100 parts of this are mixed with 1 pbw of 2 : 5 - bis - (t - butylperoxy) - 2 : 5 - dimethylhexane and 0-2 pbw nickel stearate In Examples 2-6 the nickel stearate is replaced by the stearates of diethylene glycol or Cu, Zn, Cd, Mg, Al or Li or by Ni palmitate, nonadecanoate or tricosanoate, Zn cerotate, heneicosanoate, or tetracosanoate, Zn or Li behenate, or Al arachidate or pentacosanoate. In Example 7 the siloxane gum is replaced by trimethylsiloxy - endblocked polydimethylsiloxane, with no or 0À142 mol. per cent methylvinylsiloxane units, or a hydroxy-terminated gum having 30 mol. per cent Me 2 SiO, 60 mol. per cent MePhSiO and 10 mol. per cent Ph 2 SiO units, or a methylvinyl-phenylsiloxy-terminated gum containing 2 mol. per cent MeSiO 3 / 2 and 7À5 mol. per cent MePhO units and the rest Me 2 SiO, or a 70/30 by weight mixture of a trimethylsiloxy-endblocked polydimethyl-siloxane and a gum having 70 mol per cent Me 2 SiO and 30 mol. per cent MeViO units. |
