Modulus control in silicone sealant

Claim 1

A silicone sealant, containing polydiorganosiloxane having alkoxy endblocking, alkoxy functional crosslinker and/or chain extender, and titanium catalyst, produced by a method comprising (A) mixing in the absence of moisture (1) 100 parts by weight of a polymer mixture of the average formula ##STR13## where each R is free of aliphatic unsaturation and is at least one selected from the group consisting of monovalent hydrocarbon, monovalent halohydrocarbon, and monovalent cyanoalkyl radicals of 1 to 18 inclusive carbon atoms, each D is selected from the group consisting of the vinyl radical and radicals of the formula ##STR14## where each R" is at least one selected from the group consisting of methyl, ethyl, propyl, and butyl, Z is a divalent hydrocarbon radical or combination of divalent hydrocarbon radicals and siloxane radicals, m is 0 or 1, and x is of a value such that the polymer has a viscosity of from 0.5 to 3000 Pa.s at 25° C., from 3 to 40 percent of the total of endblocking radicals D in the polymer mixture being vinyl radicals, (2) from 0.1 to 14 parts by weight of an alkoxysilane of the formula R'.sub.a Si(OR").sub.4-a where R' is at least one selected from the group consisting of methyl, ethyl, propyl, phenyl, and vinyl, R" is as defined above and a is 0, 1, or 2 and (3) from 0.2 to 6 parts by weight of titanium catalyst, and (4) optional filler, (B) storing the mixture in the absence of moisture, to give a sealant which is stable in the absence of moisture and has a modulus which is at a desired level after cure of the sealant.