Organosiloxane compositions for liquid injection

Claim 1

A curable composition suitable for use in a method of liquid injection molding of elastomeric articles, consisting essentially of (a) 100 parts by weight of an essentially linear polydiorganosiloxane fluid copolymer having two siloxane-bonded vinyl groups per molecule and having the average formula ##STR24## wherein from 25 to 75 percent of all R' groups are 3,3,3-trifluoropropyl and the remaining R' groups are methyl and n has an average value such that the viscosity of (a) has a value of from 500 to 10,000 centistokes at 25° C., (b) an organosiloxane, soluble in (a) and consisting essentially of (i) a polyorganosiloxane consisting essentially of H(CH 3 ) 2 SiO 1/2 units and units selected from the group consisting of QSiO 3/2 units and SiO 4/2 units, there being from 3 to 10 inclusive silicon-bonded hydrogen atoms per molecule of (i), Q is 3,3,3-trifluoropropyl, phenyl or an alkyl group having 1 to 6 inclusive carbon atoms and the ratio of the total number of SiO 4/2 units and QSiO 3/2 units to H(CH 3 ) 2 SiO 1/2 units in (i) has an average value of from 0.25 to 0.75 and, (ii) a polydiorganosiloxane consisting essentially of H(CH 3 ) 2 SiO 1/2 units and R" 2 SiO units, wherein each R" methyl, ethyl, phenyl, or 3,3,3-trifluoropropyl, there being two silicon-bonded hydrogen atoms per molecule of (ii) and an average of from 3 to 10 silicon atoms per molecule of (ii), the amounts of (i) and (ii) being sufficient to provide a total of from 0.75 to 3.0 silicon bonded hydrogen atoms in (b) for every silicon-bonded vinyl group in the composition and from 0 to 1 inclusive silicon-bonded hydrogen atom in (ii) for every silicon-bonded hydrogen atom in (i), (c) a platinum-containing catalyst, soluble in (a) and providing at least 1 part by weight of platinum for every 1 million parts by weight of the composition, (d) an effective amount of a platinum catalyst inhibitor selected from the group consisting of acetylenic silanes of the formulae ##STR25## and olefinic siloxanes of the formulae ##STR26## wherein R" is, independently, methyl, ethyl, phenyl or 3,3,3-trifluoropropyl, u is an integer from 1 to 2 inclusive, v is an integer from 0 to 2 inclusive and w is an integer from 3 to 6 inclusive, and (e) at least 5 parts by weight of a reinforcing silica filler having a surface area of at least 50 square meters per gram and having the surface thereof treated with an organosilicon compound to prevent appreciable crepe-aging of the curable composition; said curable composition having a Standard Injection Rate of greater than 100 grams per minute at 25° C. a Standard Cure Time of less than 100 seconds at 121° C., a Standard Pot Life of greater than 10 hours at 25° C., and when heated at 150° C. for 15 minutes and at 200° C. for 8 hours, will cure to an elastomeric material characterized by a tensile strength greater than 42 kg./sq.cm., and elongation at break greater than 300 percent and a tear strength greater than 7 kg./cm.