Polymerization of siloxanes

Abstract

A polymerization process comprising mixing siloxanes having silicon-bonded groups R′ with ionic phosphazene base catalysts and allowing condensation via reaction of Si—R′ groups with the formation of a Si—O—Si linkage, R′ denoting a hydroxyl group or a hydrocarbonoxy group having up to 8 carbon atoms is claimed. The catalysts may be of the general formulae: {((R12N)3P═N—)x(R12N)3−xP—N(H)R2}+{A−} or {((R12N)3P═N—)y(R12N)4−yP}+{A}− in which R1 is hydrogen or an optionally substituted hydrocarbon group or in which two R1 groups bonded to the same N atom may be linked to complete a heterocyclic ring, R2 is hydrogen or an optionally substituted hydrocarbon group, x is 1, 2 or 3, y is 1, 2, 3 or 4 and A is an anion. Also claimed is a process which comprises mixing siloxanes having silicon-bonded groups R′ and cyclic or linear siloxanes having no silicon-bonded groups R′ with ionic phosphazene base catalysts and allowing the siloxane having silicon-bonded groups R′ to condense and the cyclic and linear siloxanes having no silicon-bonded R′ groups to polymerize by equilibration.

Dependencies are inferred from the claim text.