Patent GB-1527144-A (GB)
Title: Olefinic siloxanes as platinum inhibitors
IPC: C08G77/04
Filed: 1975-10-24
Abstract: 1527144 Olefinic siloxanes as Pt-catalyst inhibitors DOW CORNING CORP 24 Oct 1975 [2 Dec 1974] 43781/75 Headings C3S and C3T A polyorganosiloxane useful as an inhibitor for Pt catalysts comprises from 3-10 siloxanes units in which (a) at least one siloxane unit is either RHSiO or R 2 HSiO 0À5 , and (b) at least one siloxane unit is either R(CH = CHR<SP>1</SP>)SiO or R 2 (CH=CHR<SP>1</SP>)SiO 0À05 , the number of siloxane units (a) plus (b) being at least 3; and (c) any remaining siloxane units being selected from R 3 SiO 0À5 , RSiO 1À5  and SiO 2 , where each type of siloxane unit (c) does not exceed 3 in number, in which R is a monovalent hydrocarbon or perfluoroalkylethylene radical, both having no more than 6 carbon atoms, and R<SP>1</SP> is a monovalent hydrocarbon readcal having a secondary or tertiary hydroxy substitution and having no more than 10 carbon atoms. The polyorganosiloxane may be prepared either (1) by continuously passing a liquid mixture of (A) an acetylenic alcohol, (B) a Pt catalyst and (C) a siloxane compound having at least 3 Si-H atoms through a heating means at a temperature at least above 100‹ C. and above the temperature at which the product no longer inhibits the reaction and under sufficient pressure to maintain the reaction mixture in the liquid state; or (2) by heating a mixture of (A), (B) and (C) for 16 hours at 70‹ C. and then removing the unreacted acetylenic alcohol by stripping at room temperature under reduced pressure and then distilling the remainder; or (3) by injecting a mixture of (A) and (C) into the injection port of a GLC column the said port being coated with (B) and heating the column to 350‹ C.; or (4) by injecting a mixture of (A), (B) and (C) into a tube heated to 300‹ to 400‹ C. and cooling the reaction product from the tube either in a single condenser followed by distillation, or in a multiple condenser series. The above polyorganosiloxane can be added to a curable composition in an amount to effectively retard the cure at ambient temperatures, the amount generally being 0À5 to 3% wt, based on the composition, the composition comprising (1) an organosilicon polymer having from 1-3 groups per Si atom selected from monovalent hydrocarbon radicals, aliphatic-unsaturationfree halohydrocarbon radicals and cyanoalkyl radicals, there being an average of at least 2 monovalent aliphatically-unsaturated hydrocarbon radicals per molecule of (1), the remaining valencies of the Si atoms being satisfied by divalent radicals selected from divalent oxygen atoms, hydrocarbon, hydrocarbon ether and haloarylene radicals, the divalent radicals linking Si atoms; (2) an organosilicon compound containing an average of at least 2 Si-H atoms per molecule, there being in addition an average of up to 2 monovalent organic radicals per Si atom selected from hydrocarbon and halohydrocarbon radicals free of aliphatic unsaturation and cyanoalkyl radicals, the remaining valencies of the Si atoms being satisfied by divalent radicals linking Si atoms selected from -O-, hydrocarbon and hydrocarbon ether radicals each free of aliphatic unsaturation and haloarylene radicals; the sum of the average number of aliphatic unsaturated monovalent radicals in (1) and the average number of Si-H atoms in (2) being at least 4; and (3) a Pt catalyst in an amount of at least 0À1 p.b.w. of Pt per million p.b.w. of (1) + (2). Component (1) is preferably a triorganosiloxy-terminated polydiorganosiloxane having a viscosity of at least 100 cs. at 25‹ C., wherein the organo radicals are methyl and vinyl and optionally phenyl. The Pt catalyst may be Pt itself, Pt deposited on silica gel or charcoal, platinic chloride, salts of Pt and chloroplatinic acid and complexes of platinous halide with various organic compounds, numerous examples of which are listed. The compositions can be cured normally at temperatures in excess of 70‹ C. The compositions may comprise other ingredients, e.g. fillers, such as carbon black, silica aerogels, silica soots, treated silicas, alumina, clays, metal oxides, metal carbonates and silicates. In Example 1 olefinic siloxanes are prepared by heating a siloxane of formula with 3 - methyl - 1 - butyn - 3 - ol in the presence of Pt for 16 hours at 70‹ C., stripping the product of unreacted ingredients at reduced pressure and vacuum distilling the product to obtain the mono- and di-adducts. In Example 4 the mono-adduct prepared as above is added in an amount of from 1-8 p.b.w. to a composition comprising (1) 400 p.b.w. of a base formulation comprising 75 p.b.w. of a phenylmethylvinylsiloxy-endblocked polydimethylsiloxane (450 cs.), 19 p.b.w. of 5 micron quartz, 2À8 p.b.w. fume SiO 2 , 0À4 p.b.w. lampblack, 0À8 p.b.w. ZnO and 2À2 p.b.w. of an OH-endblocked polymethylphenylsiloxane; (2) 25 p.b.w. of a siloxane of average formula and (3) 7 p.p.m. of a Pt catalyst prepared from chloroplatinic acid hexahydrate, tetramethyldisiloxane and divinyltetramethyldisiloxane. The compositions are cured at temperatures ranging from room temperature to 150‹ C. Other examples are given.