| 摘要 |
1,217,349. Carbonic acid polyesters. INSTYTUT TWORZYW SZTUCZNYCH. 3 May, 1968 [5 May, 1967], No. 21052/68. Heading C3R. Polycarbonates are produced by transesterifying an aromatic carbonic acid diester and a dihydroxy diphenyl alkane in the presence of a salt of fluoroboric acid or of hydroxyfluoroboric acid or of a mixture of two or more such salts as catalyst. The salt is preferably an alkali metal salt, particularly of Li, Na, K or Rb, and may be used in an amount of up to 1% by weight of the dihydroxy diphenyl alkane. The salt may be produced in situ, e.g. from alkali metal fluoride and boric acid. Up to 1% by weight of the dihydroxy diphenylalkane of alkali metal chloride may also be present. Up to 1% of an alkylarylsilane, arylsilane, alkyl arylalkoxy-silane, alkylalkoxysilane and/or arylalkoxysilane may be present. In examples the reactants are diphenyl carbonate and bisphenol A or the phenol adduct thereof. Reference has been directed by the Comptroller to Specification 1,141,869. |
