| 摘要 |
862,978. Preparing vinyl chloride/vinyl ester/ vinyl alcohol co-polymers. PECHINEY COMPAGNIE DE PRODUCTS CHIMIQUES ET ELECTROMETALLURGIQUES. May 13, 1957 [May 15, 1956], No. 15159/57. Class 2(6). Vinyl chloride/vinyl ester/vinyl alcohol copolymers are prepared by heating an alcoholic suspension of a vinyl chloride/vinyl ester copolymer. The vinyl chloride/vinyl ester copolymer may be an acetate, propionate or butyrate and may be in the form of pearls, grains, powder or spongy particles; the more porous the structure of the co-polymer and the higher the content of ester groups, the greater is the rate of reaction. Alcohols specified are methyl, ethyl and propyl, and the lower their water content, the greater is the rate of reaction. The reaction is preferably carried out at 50-80 ‹C., at or below atmospheric pressure, in the presence of esterification catalysts such as H 2 SO 4 , HCI, H 3 PO 4 , sulphonic acids, KOH, NaOH and C 2 H 5 ONa; the ester formed between the alcohol and the acid radical of the co-polymer is continuously distilled off, and when the desired stage is reached (as measured by the amount of ester distilled off) the catalyst is neutralized (e.g. by Na acetate) and the polymer is filtered, washed and dried. |
