| 摘要 |
<p>1533906 Polyvinyl alcohol/boric acid complexes HOECHST AG 2 July 1976 [4 July 1975] 27671/76 Heading C3P The water sensitivity of polyvinyl alcohol is reduced by heating a mixture containing polyvinyl alcohol and boric acid in aqueous solution, with a compound or buffer system which maintains the mixture, at a temperature of 18‹ to 28‹ C., at a pH not exceeding 7 and which, on heating only, is altered irreversibly in a manner such that the pH of the mixture is increased to the alkaline range. Suitable compounds are alkali metal, alkalene earth metal or ammonium salts of trichloro- or tribromo-acetic acid, or amine salts of these acids, e.g. sodium trichloroacetate. The buffer system may comprise an alkali metal salt of a volatile weak acid and the free acid.</p> |
