| 摘要 |
PURPOSE:The organic lithium compound is added in two portions to effect polymerization whereby the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene is adjusted to give the title composition which is used suitably to make food-packaging vessels, because it is clear and high in surface hardness and impact strength. CONSTITUTION:After a living polymer of a vinyl aromatic hydrocarbon and a conjugated diene at a weight ration of more than 60/40 is formed by polymerization of M1pts.wt. of monomers using C1 moles of the organic lithium compound, M2pts.wt. of monomers at less than 80/20 ratio of the vinyl aromatic hydrocarbon to the conjugated diene are polymerized with C2 moles of the organic lithium compound and further, M3pts.wt. of monomers at more than 60/40 ratio are polymerized where the amounts of the organic lithium compound and monomers satisfy equations I and II where M1+M2+M3=100pts.wt. These operations give a block copolymer composition at 60/40-95/5 ratio of the vinyl aromatic hydrocarbon to the conjugated diene.
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