Verschaeumbare Zweikomponenten-Komposition

摘要

1,137,420. Foamed polysiloxane compositions. GENERAL ELECTRIC CO. 9 Dec., 1966 [17 Dec., 1965], No. 55334/66. Headings C3C and C3T. [Also in Division B2] A foamable composition comprises, by weight, (a) 100 parts of a polysiloxane CH 2 = CHSi(R 2 )O-[R1 2 SiO] n SiR 2 -CH = CH 2 wherein R and R1 are monovalent hydrocarbon radicals substantially free of aliphatic unsaturation with at least 50 mol per cent of R1 being methyl, and n is 50 to 2000; (b) 10 to 100 parts of a copolymer containing (R11) 3 SiO 0À5 units and SiO 2 units wherein R11 is the same as R or a vinyl radical, and 2À5 to 10 mole per cent of the Si atoms are directly bonded to vinyl groups; (c) 10 to 100 parts of asbestos or fibrous potassium titanate or mixtures thereof; (d) 0 to 100 parts of a finely divided inorganic filler; (e) a platinum catalyst; (f) a liquid organohydrogenopolysiloxane having units of the formula (R) a (H) b SiO 4-a-b/2 wherein a is 1À00 to 2À10, b is 0À1 to 1À0, a + b is 2À00 to 2À67 and there are 0À5 to 1 silicon-bonded hydrogen atoms per silicon-bonded vinyl group in the composition; and (g) 1 to 5 parts of a blowing agent. The cured elastic foam is generally prepared by mixing a package made of (a), (b), (c), (d) and (e) with a second package of (f) and (g) which may optionally also contain some (a), and heating the mixture to 80-180‹ C. The composition can also be maintained under refrigeration for several weeks without premature curing or reaction, in the form of viscous liquids or pastes. Component (b) may, in addition to the (R11) 3 SiO 0 . 5 and SiO 2 units, also comprise (R11) 2 SiO units in amounts up to 10% molar; this component may be dissolved in a solvent e.g. benzene or toluene, then this solution is dissolved in component (a) and the solvent then may be stripped off. The inorganic filler (d) is preferably silica. The platinum catalyst (e) may be elemental, chloroplatinic acid, or a hydrocarbon or alcoholate complex in amounts sufficient to provide 10-3 to 10-6 gm. atoms Pt per mole of vinyl group in the composition. The organohydrogenpolysiloxane (f) should have at least 2 Si-bonded hydrogen groups per molecule, e.g. 1,3,5,7-tetramethylcyclotetrasiloxane. The blowing agent (g) is exemplified by N,N1- dinitroso -N,N1-dimethylterephthalamide.