| 摘要 |
A chlorinated copolymer made from vinyl chloride monomers and vinyl containing comonomers such as vinyl acetate has good low (e.g., about 120 DEG C.) and high (e.g., about 170 DEG C.) temperature stability as measured by hydrogen chloride elimination. The copolymer is made by suspension polymerizing vinyl chloride monomers (from about 70 to about 95 percent by weight) and vinyl containing comonomers (from about 5 to about 30 percent by weight) and subsequently chlorinating the copolymer to add chloride sites to the vinyl chloride units as well as to the comonomer units such as vinyl acetate. After chlorination, the copolymer is subjected to a heat treatment chlorination process whereby the stability of the copolymer is dramatically improved. The heat treatment chlorination process comprises heating the copolymer to temperatures generally in excess of 100 DEG C. to degrade the resin whereby hydrogen chloride is liberated and then chlorinating the resin by adding pressurized chlorine thereto. One or more of such heat treatment additions are made. The heat treated chlorinated copolymer achieves better dispersement of magnetic materials and thus can be utilized in magnetic tapes and disks.
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