Patent GB-794629-A (GB)
Title: Improvements in or relating to organo-siloxanes
IPC: C08G77/08
Filed: 1956-04-16
Abstract: A process for polymerizing and curing organopolysiloxanes comprises (1) mixing one or more liquid organosiloxanes containing at least one alkenyl radical per molecule and having the average general formula <FORM:0794629/IV (a)/1> wherein R is a monovalent hydrocarbon radical and n has an average value of from 1.0 to 2.1, with (a) from 0.002 to 0.03 mols. per gram atom of silicon present in the siloxane(s) of a diorganoperoxide containing at least one tertiary alkyl group, and (b) an alkaline catalyst which is a quaternary ammonium hydroxide or siloxane salt thereof or a quaternary ammonium alkoxide, in amount such that the ratio of nitrogen atoms to silicon atoms present in the siloxane(s) is at least 1 : 200,000, but in molecular amount less than the peroxide (a); (2) heating the mixture in the range from room temperature to below that at which the peroxide (a) initiates free radicals, until the viscosity is constant; and (3) heating the mixture to a temperature above that at which the peroxide (a) initiates free radicals, until the desired cure is obtained. Siliconbonded hydrocarbon radicals specified are alkyl, aryl, alkaryl, alkenyl and cycloaliphatic radicals.  Organic peroxides specified are ditertiary butyl-, tertiary amyl butyl-, tertiary butyl cyclohexyl- and di-cumyl-peroxides, tertiary hexyl peracetate and tertiary butyl perbenzoate.  Alkaline catalysts specified are quaternary ammonium compounds of the formul  R4NOH, R4NOR1, RmSi(ONR4)nO4-m-n and R4NO(R2SiO)xNR4, wherein each R is a monovalent hydrocarbon or hydroxyhydrocarbon radical, e.g. methyl, ethyl, octadecyl, vinyl, allyl, hexenyl, cyclohexyl, cyclopentyl, cyclohexenyl, phenyl, tolyl, benzyl, hydroxyethyl, hydroxycyclohexyl, hydroxyphenyl or hydroxylhexenyl, and R1 is an alkyl radical, e.g. methyl, ethyl, hexyl or octadecyl.  The quaternary ammonium hydroxides and alkoxides are preferably used as solutions in an alkanol, e.g. methanol, and the siloxane salts are preferably used as solutions in liquid siloxanes.  Fillers, pigments, &c., may also be added.  The specified compounds can be mixed in any order and heated initially in the range e.g. of 10 DEG  to 90 DEG  C. and finally in the range e.g. of 100 DEG  to 250 DEG  C.  In examples siloxane resins are made in the above manner from (1) a mixture of phenyl vinyl siloxane cyclic tetramer and pentamer and phenylmethylcyclotetrasiloxane, a methanol solution of benzyltrimethylammonium hydroxide and di-tertiary butylperoxide; (2) a phenylvinylsiloxane-phenylmethylsiloxane copolymer, benzyldimethyl - beta - hydroxyethylammonium butoxide in butanol and di-tertiary butylperoxide; (3) a phenylvinylsiloxane-phenylmethyl siloxane copolymer, a phenylmethylsiloxane salt of benzyltrimethylammonium hydroxide and di-tertiary butyl peroxide; (4) the siloxane and peroxide of Example 3 and the phenylmethyl siloxane salt of ethyltris(beta-hydroxyethyl) ammonium hydroxide; (5) the siloxane and alkaline catalyst of Example 2 and dicumylperoxide; (6) the siloxane and alkaline catalyst of Example 2 and tertiary butylperbenzoate; (7) a mixture of dimethylsiloxane and methylvinylsiloxane cyclic tetramers and the catalysts of Example 3; (8) methylvinylcyclotetrasiloxane and the catalysts of Example 3; (8) methylvinylcyclotetrasiloxane and the catalysts of Example 7; (9) monovinylsiloxane and the catalysts of Example 8; (10) allylphenylsiloxane or hexenylphenylsiloxane and the catalysts of Example 1.  The siloxane salts of quaternary ammonium bases may be made by heating the base with an organosiloxane, e.g. <FORM:0794629/IV (a)/2> Specification 755,198 is referred to.