| 摘要 |
A benzene-soluble phenylsilsesquioxane, having an intrinsic viscosity in benzene of at least 0.4 decilitre per gram when measured at 25 DEG C., is made (1) by heating a preformed octaphenylsilsesquioxane with an alkaline rearrangement and condensation catalyst until a prepolymer having an intrinsic viscosity of from 0.01 to 0.35 is obtained, (2) isolating the prepolymer, and (3) heating the prepolymer at elevated temperature in a solvent for the prepolymer in the presence of an alkaline rearrangement and condensation catalyst to yield the desired polymer. The starting material can be made from PhSiCl3 by methods described in U.S. Specification 3,000,858, and this can be converted into the prepolymer by heating it in a polar solvent, e.g. chlorobenzene, o-dichlorobenzene and chlorinated diphenyl, in the presence of an alkaline catalyst, e.g. K, Cs or Rb-hydroxide, tetramethyl- or tetrabutyl-ammonium hydroxide, trimethylammonium butoxide, tetraethyl- or tetrabutyl-phosphonium hydroxide, or the K salt of methyl- or phenyl silane triol either alone or in the form of an alcoholate. The solvents used in step (3) are diphenyl and/or diphenyl oxide, methylphenyl ether, ethylphenylether, cyclohexane, benzonitrile, mesitylene, durene, m-dimethoxybenzene, benzene and toluene. Examples 1 and 2 describe the preparation of (PhSiO 3/2 )8 and the prepolymer respectively, and examples describe the polymers of present invention and the prior art respectively. Fillers, e.g. SiO2, C black, TiO2, Fe2O3 and metals, plasticizers, dyes and pigments may also be added. Uses.-For coating metal conductors; in film form as slot liners and as end turn winding insulation in motors; for rendering textiles heat-resistant; for bonding surfaces; and for making laminates (see Division B5). |
