GB1492616A - Process for making dental impressions - Google Patents

Abstract

1492616 Organopolysiloxane dental impression compositions DOW CORNING Ltd 6 March 1975 [7 March 1974 6 Nov 1974] 10258/74 and 47908/74 Heading C3T [Also in Division B5] A composition which may be used for making dental impressions comprises: (A) a polydiorganosiloxane having from 1À95 to 2À01 organic radicals per silicon atom, at least 90% of the organic radicals being methyl radicals, at least two organic radicals per molecule being vinyl radicals and any remaining radicals being either alkyl radicals having less than 19 carbon atoms or phenyl radicals; (B) an organosiloxane having at least two silicon-bonded hydrogen atoms per molecule, and in which he silicon-bonded organic radicals are alkyl radicals having less than 19 carbon atoms, the sum of the number of vinyl radicals per molecule of (A) and the number of silicon-bonded hydrogen atoms per molecule of (B) being at least five; and (C) a catalyst which promotes the reaction of #Si-H groups with silicon-bonded vinyl radicals. In component (A) the vinyl radicals preferably constitute 0À1 to 1% of the total number of organic radicals; component (B) is preferably a linear methylhydrogen polysiloxane e.g. a copolymer containing trimethylsiloxane units, dimethylsiloxane units and methylhydrogensiloxane units. Components (A) and (B) are preferably employed in such proportions that the ratio of the number of silicon-bonded hydrogen atoms provided by (B) to the number of silicon-bonded vinyl radicals provided by (A) is from 2:1 to 5:1. Component (C) is preferably a platinum compound or complex, e.g. the reaction product of chloroplatinic acid and a siloxane containing silicon-bonded vinyl radicals, in which case the composition preferably contains additionally a cobalt salt of a carboxylic acid, e.g. cobalt naphthenate, as an accelerator.