Transparent, rubber-modified styrene resin and production process thereof

摘要

A transparent, rubber-modified styrene resin comprises 70 to 96 parts by weight of a copolymer formed of 20 to 70 wt.% of styrene monomer units and 30 to 80 wt.% of alkyl (meth)acrylate monomer units and 4 to 30 parts by weight of a rubbery polymer. The rubbery polymer is dispersed in the copolymer as particles having an average particle size of 0.1 to 2.0 mu m. At least 70 wt.% of the rubbery polymer is a styrenebutadiene block copolymer which is formed of 5 to 50 wt.% of styrene units and 50 to 95 wt.% of butadiene units, has a viscosity in a range of 3 to 60 mPa.s when measured as a 5 wt.% styrene solution at 25 DEG C and possesses a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) in a range of 1.0 to 1.8. The copolymer and the rubbery polymer have substantially the same refractive index. Also disclosed is a production process of the transparent, rubber-modified styrene resin, which comprises polymerizing a styrene monomer and an alkyl (meth)acrylate to a high degree of polymerized conversion in the presence of the rubbery polymer so that the rubbery polymer is formed into particles while allowing the copolymer to occur with substantially the same refractive index as the rubbery polymer.