Abstract: A polystyrene resin composition comprising a rubber-reinforced polystyrene, a fibrous potassium titanate and a higher fatty acid and/or its metal salt in specific proportions. The composition exhibits greatly improved stiffness without sacrificing its excellent impact strength, melt flowability and good appearance. The composition is useful as a material for manufacturing large-sized molded articles, such as parts and housings for large-sized TV sets and frames for air conditioners. The composition may further comprise a fire retardant and a carbon fiber in specific proportions. The resultant fire-retardant composition is not only excellent in the above-mentioned properties of mechanical strength but also exhibits excellent fire retardance and, therefore, is advantageously used as a material for manufacturing the above-mentioned articles especially when the articles are required to have high fire retardance.

Abstract: This invention relates to a rubber-reinforced polystyrene composition having a rubbery polymer dispersed in the form of particles therein, characterized in that:(A) the particles have an area-averaged particle diameter in the range of 0.20 to 1.00 micron,(B) the dispersed particles of rubbery substance have polystyrene included in the form of minute particles therein and not less than 80% of the total number of the polystyrene particles have diameters of not more than 0.3 micron, and(C) the composition contains polydimethyl siloxane in an amount falling in the range of 0.005 to 0.8% by weight.The resin composition of this invention is superior in appearance such as coloring and gloss and has balanced properties of impact resistance and rigidity. Excellent coloring represents a profound commercial significance in that the cost of dye and pigment to be used for the coloring can be appreciably saved.