| 摘要 |
1534709 Heat stable organopolysiloxane composition TORAY SILICONE CO Ltd 3 Dec 1975 [6 Dec 1974] 49627/75 Heading C3T A mixture for imparting heat stability to organopolysiloxanes comprises (1) a reaction product of (a) an alkali metal siloxanolate having from 1 to 3 organic groups attached to each Si through silicon-carbon bonds and containing an average of at least 3 organosiloxane units per molecule, with (b) a cerium salt of an organic carboxylic acid or cerium chloride, the said cerium salt being soluble in an aromatic hydrocarbon solvent or a chlorinated hydrocarbon solvent, and (2) at least one metal compound selected from organic carboxylic acid salts and alkoxy compounds of zirconium, titanium and iron. The organopolysiloxane which is heat stabilized may be a fluid or a silicone rubber stock and is generally an essentially linear diorganopolysiloxane of unit formula R x SiO (4-x)/2 , where R is an alkyl radical of less than 7 carbon atoms, phenyl, a #-perfluoroalkylethyl radical of 3-9 carbon atoms or a C 2 -C 6 alkenyl radical and x is 1À98 to 2À01. The organopolysiloxane composition may also contain inorganic fillers, metal soaps, pigments, vulcanizing agents and crosslinking agents. The alkali metal siloxanolate is preferably prepared by preparing a siloxanolate having alkali metal atoms on each of the terminal siloxane units and then further reacting with a linear diorganopolysiloxane to form a siloxanolate having alkali metal atoms on only one terminal siloxane unit. Suitable organic carboxylic acid cerium salts include cerium-2- ethyl-hexanoate and cerium naphthenate. Suitable Zr, Ti or Fe salts of organic carboxylic acids include those of 2-ethylhexanoic acid, naphthenic acid, oleic acid, lauric acid and stearic acid. In the Examples heat stability mixtures are prepared (1) by mixing either zirconium 2-ethyl hexanoate or tetrabutylzirconate with a reaction product prepared by reacting either cerium 2-ethyl-hexanoate or cerium chloride with a potassium siloxanolate, which siloxanolate has been prepared from KOH, hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane followed by further reaction with a trimethyl silyl-endblocked dimethylpolysiloxane of viscosity 20 c.s. in the presence of hexamethylphosphoramide; or (2) by mixing either tetrabutyltitanate or iron-2-ethylhexanoate with a reaction product obtained by reacting sodium trimethylsilanolate with a trimethyl silyl - endblocked dimethylpolysiloxane (20 c.s.) and then with either cerium chloride or cerium - 2 - ethyl hexanoate. The above heatstability mixtures were used to stabilize dimethylpolysiloxane fluids or a phenylmethylsiloxane-dimethylsiloxane copolymer fluid. |
