28-07-1965 дата публикации
Номер: GB999984A
A siloxane elastomer-forming composition comprises a peroxide curing agent, a filler if desired and a high molecular weight siloxane polymer containing units of the formulae [NC(CaH2a)Si(R)O]x, [R12SiO]y and/or [R112SiO]z, wherein x, y and z represent the weight percentages of the respective units, with x being at least 0.2, y + z being greater than zero, and the sum x+y+z being equal to 100; a is 2, 3, 4 or 5, and the -CN radical is separated from Si by at least 2 C atoms; R and R1 are each a monovalent hydrocarbon radical free of aliphatic unsaturation and contain 1 to 10 C atoms; R11 is a monovalent saturated or unsaturated hydrocarbon radical of 1 to 10 C atoms, the siloxane having been made by mixing at 100 DEG to 170 DEG C., in the presence of a basic polymerization catalyst, polysiloxane reactants consisting of at least 0.25 (wt. per cent) of [NC(CaH2a)Si(R)O] units and up to 99.75 (wt. per cent) of [R12SiO] units and/or [R11SiO] units. The polymers are made by co-equilibration of suitable linear (preferably hydroxyl-terminated) or cyclic siloxanes, the catalysts specified being Na, K and Cs hydroxides and K, Cs and (CH3)4N-silanolates. Fillers specified are C black, SiO2, esterified SiO2, ZnO, Fe2O3, TiO2, Al2O3, CaCO3 and ZnSiO4. Curing catalysts specified are di-t-butyl-, di-cumyl-, di-benzoyl- and tris-dichlorobenzoyl-peroxides, and t-butyl-peracetate and -perbenzoate. The gum stock, without the catalyst, may be pre-cured by heating at 120 DEG to 300 DEG F. for 1 to 2 hours to cause wetting of the fillers by the gum and to eliminate volatiles, the catalyst is then added and the stock replasticized as by milling, and the composition is then mould-cured and, if desired, post-cured. Examples are given describing the above preparation of the polymers and elastomers therefrom.
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