| 摘要 |
PROBLEM TO BE SOLVED: To provide a rubber-modified styrene polymer having excellent transparency and excellent impact strength and moldability, and a method for preparing same. SOLUTION: The rubber-modified styrene polymer is obtained by polymerizing different types of monomers indicated below in the presence of a rubbery elastomer meeting requirements (a) to (c) indicated below. The modified styrene polymer comprises 1 to 15 pts. of the rubbery elastomer and 99 to 85 pts., in total, of 35 to 75% of styrene monomer units, 65 to 25% of (meth)acrylate monomer units and 0 to 20% of copolymerizable monomer units wherein the rubbery elastomer has an average particle size of 0.2 to 0.8μm. The requirements for the elastomer include: (a) the elastomer is made of a styrene- butadiene block copolymer composed of 30 to 50% of styrene and 70 to 50% of butadiene; (b) the styrene block moiety has a weight average molecular weight of 60,000 to 75,000; and the styrene block moiety has a molecular weight of 68,000 to 74,000 at a peak portion of a GPC chromatogram.
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