| 摘要 |
1,216,916. After-chlorinated vinyl chloride copolymer. IMPERIAL CHEMICAL INDUSTRIES Ltd. 29 July, 1969 [22 Aug., 1968], No. 40235/68. Heading C3P. An after-chlorinated vinyl chloride copolymer is obtained by (1) polymerizing vinyl chloride at a first polymerization temperature, (2) when at least 40% has been polymerized, adding a comonomer in an amount less than the remaining vinyl chloride monomer, (3) polymerizing the mixture at a temperature at least 5‹ C. higher than the first and (4) chlorinating the product. In examples, the comonomers used are vinyl acetate and propylene added in an amount of 2À6% of the total vinyl chloride after 66% conversion using suspension technique and chlorination is effected in carbon tetrachloride in the presence of azodiisobutyronitrile. Reference has been directed by the Comptroller to Specification 1,178,054. |
