| 摘要 |
1,187,406. Polypropylene. JOHNSON & JOHNSON. 18 April, 1967 [8 Aug., 1966; 31 March, 1967], No. 17773/67. Heading C3P. Isotactic randiotactic stereoblock polypropylene having a diethyl ether solubility of at least 1% and containing randiotactic blocks linked end to end to intervening isotactic elements, the randiotactic blocks comprising by weight 40 to 60% heterotactic polypropylene, 20 to 30% isotactic polypropylene and 20 to 30% syndiotactic polypropylene, is prepared by reacting isotactic polypropylene at 325‹ to 600‹ F. with a free radical initiator in amount sufficient to provide at least 0À001 weight per cent active oxygen or equivalent and a bromine compound in amount sufficient to provide at least 0À005 weight per cent active bromine, said active bromine and active oxygen being present in a ratio of at least 0À2 to 1 part by weight. Specified free radical initiators are dicumyl peroxide, 2,5-dimethyl-2,5.bis-(t.-butylperoxy) hexane or hexyne-3, and di-t.-butyl peroxide. Specified bromine compounds are tris - (2,3 - dibromopropyl) phosphate, 1,2 - dibromocyclohexane,α,α<SP>1</SP> - dibromo - p - xylene, 1,1,2,2 - tetrabromoethane, 1 - bromododecane, 2,3 - dibromopropanol, carbon tetrabromide and mixtures thereof. A non-reactive dispersant, e.g. stearic acid, may also be present, and the products may be compounded with conventional pigments and stabilizers and made into filaments, films, sheets, electrical insulation, gaskets, tubes and adhesives. Many examples of the racemization of isotactic polypropylene to the stereoblock polymer of the invention are given.
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