| 摘要 |
1,272,705. Silicone rubber stock containing two types of organo-hydrogen siloxane. DOW CORNING CORP. 21 July, 1970 [21 Aug., 1969], No. 35183/70. Heading C3T. A silicone rubber stock comprises (A) a polydiorganosiloxane having two vinyl radicals per molecule, on different Si atoms, the remaining organic radicals being methyl (at least 50%), ethyl, phenyl or trifluoropropyl radicals, and having triorganosiloxane end units and a viscosity of 100-10,000 cp/25‹ C., and (B) a mixture of compounds providing 0À75-1À25 Sibonded H atoms per vinyl radical of (A) and comprising (1) an organosiloxane of no more than 500 Si atoms having 2 Si-bonded H atoms per molecule, on different Si atoms, the organic radicals being methyl, ethyl, phenyl or trifluoropropyl radicals, and (2) an organosiloxane of no more than 75 Si atoms having 3-10 SiH groups per molecule, on different Si atoms, the organic radicals being methyl, ethyl, phenyl or trifluoropropyl radicals, the ratio of SiH groups provided by (1) to those provided by (2) being between 1 : 9 and 9 : 1. The composition may also contain a Pt catalyst for the Si-H/vinyl radical reaction and an inhibitor for the Pt catalyst and other conventional additives, e.g. fillers and pigments. In examples compositions are prepared containing (A) a vinyl-terminated dimethylpolysiloxane of 1280 or 424 cps/25‹ C., (1) HMe 2 SiO(Me 2 SiO) 10 SiMe 2 H or Me 3 SiO(HMeSiO) 2 SiMe 3 and (2) Me 3 SiO(Me 2 SiO) 5 (HMeSiO) 3 SiMe 3 or Me 3 SiO(Me 2 SiO) 3 (HMeSiO ) 5 SiMe 3 or Me 3 SiO(HMeSiO) 4 SiMe 3 or Si(OSiMe 2 H) 4 or Me 3 SiO(MeHSiO) 3 SiMe 3 or C 6 H 5 Si(OSiMe 2 H) 3 with a treated fume silica of 250 or 400 m.<SP>2</SP>/g. and optionally 5 Á ground quartz; they are cured with a catalyst of H 2 PtCl 6 in a polydimethylsiloxane liquid. |
