| 摘要 |
A rubber-modified impact-resistant polystyrene resin composition is disclosed, which contains dispersed particles comprising a rubber-like polymer in amount of from 1 to 25% by weight, the rubber-like polymer being a high-cis high-vinyl polybutadiene which comprises from 65 to 95% cis-1,4-structures and from 30 to 4% 1,2-structures, and in which when the relationship between the 1,4-structures and 1,2-structures of the rubber-like polymer is represented by the expression .beta.=P1,2-1,4/(2xP1,2xP1,4) (wherein P1,2 represents the content of 1,2-structures, P1,4 represents the content of 1,4-structures, and P1,2-1,4 represents the content of 1,2-structures/1,4-structures diads in all diads), then 1.0<.beta.~1.43. The relationship between the viscosity of a 5% styrene solution of the rubber-like polymer as measurement at 25.degree.C (5% SV) and the Mooney viscosity (ML1+4) of the polymer preferably satisfies the expression 2.0~(5% SV)/ML1+4~7.0. Another rubber-modified impact-resistant polystyrene resin composition is disclosed, which contains dispersed particles comprising a rubber-like polymer in an amount of from 3 to 15% by weight, the rubber-like polymer being a high-cis high-vinyl polybutadiene which comprises from 65 to 95% cis-1,4-structures and from 30 to 4% 1,2-structures, and in which when the relationship between the tensile elongation (E) of the rubber-modified impact-resistant polystyrene resin composition and the dispersed-particle diameter (X1) and amount (X2) of the rubber-like polymer is represented by the expression E=-17.8X1+5.6X2+38.5, then 20%<E<90%. The compositions have a well balanced combination of improved properties such as reactivity with styrene monomer, impact resistance, low-temperature properties, gloss, tensile strength, and tensile elongation.
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