Patent GB-1528204-A (GB)
Title: Crosslinker platinum catalyst inhibitor and method of preparation thereof
IPC: C08L83/00
Filed: 1975-10-15
Abstract: 1528204 Crosslinker-platinum catalyst-inhibitor composition DOW CORNING CORP 15 Oct 1975 [2 Dec 1974] 42203/75 Headings C3T and C3S A crosslinker-platinum catalyst-inhibitor composition is prepared by a method comprising mixing a siloxane, an acetylenic alcohol and a Pt catalyst and heating the resultant mixture in a closed system for 10 to 30 hours at a temperature of from 50 C. to 90 C., said siloxane having an average of at least 3 Si-bonded hydrogen atoms per molecule, there being in addition an average of up to 2 monovalent organic radicals per Si atom selected from monovalent hydrocarbon and fluorinated hydrocarbon radicals free of aliphatic unsaturation,-the remaining valencies of the Si atoms being satisfied by divalent radicals selected from oxygen atoms, hydrocarbon and hydrocarbon ether radicals free of aliphatic unsaturation and fluorinated arylene radicals, wherein at least one divalent radical is -O-, the divalent radicals linking Si atoms, said siloxane being liquid at 50 to 90 C. in said mixture; the acetylenic alcohol preferably having a vapour pressure sufficient for the unreacted acetylenic alcohol to be removed from the mixture after the heating step by applyingareduced pressure of 700 to 750 mm.Hg.for at least 10 hours at a temperature of from 20 to 30C. Suitable acetylenic alcohols include 3- methyl-1-butyn-3-ol, 3-phenyl- 1 -butyn-3-ol, 1 - ethynylcyclohexan - 1 - ol, 3,5 - dimethyl - 1- hexyn - 3 - ol and 3 - methyl - 1 - pentyn - 3 - ol. Suitable Pt catalysts are chloroplatinic acid, Pt deposited on silica, alumina or charcoal, platinous halides, and complexes of platinous halides with olefinic compounds. The crosslinker-Pt catalyst-inhibitor composition can be used in a curable composition comprising an organosilicon polymer having an average of from 1-3 groups per Si atom selected from monovalent hydrocarbon radicals, aliphatic-unsaturationfree monovalent halohydrocarbon radicals and cyanoalkyl radicals, there being an average per molecule of said polymer of at least 2 monovalent hydrocarbon radicals containing aliphatic unsaturation, the remaining valencies of the Si atoms being satisfied by divalent radicals selected from oxygen atoms, hydrocarbon, hydrocarbon ether and haloarylene radicals, the divalent radicals linking Si atoms. The curable compositions may additionally contain fillers such as carbon black, silica aerogels, silica soots, treated silicas, alumina, clays, metal oxides, metal carbonates and metal silicates. In Examples 1 and 2 crosslinker-Pt catalystinhibitor compositions prepared by heating a mixture of 3-methyl-1-butyn-3-ol, a siloxane copolymer of average formula and a Pt complex catalyst of chloroplatinic acid, tetramethyldisiloxane and divinyltetramethyldisiloxane at 70 C. for 16 hours in tightly capped bottles and stripping the resultant product at room temperature under reduced pressure, are added to a base formulation comprising 76% wt. of methylphenylvinylsiloxy endblocked polydimethylsiloxane (400 c.p.); 19À3% wt. of 5 micron quartz, 2À8% wt. fume SiO 2  1À1 wt.% of an OH-terminated polyphenylmethylsiloxane fluid and 0À8 wt.% of Carbon black to form compositions which are cured at temperatures ranging from 25 to 150 C.