Abstract: A feed containing 100 parts by weight of reactants consisting of 88 to 98% by weight of a styrene-based monomer or its mixture with other comonomers and 2 to 12% by weight of high-viscosity rubber with a viscosity of 400 to 2,000 centipoises in a 5% by weight styrene solution at 25.degree. C., 0.01 to 0.2 part by weight of an organic peroxide, and 0 to 30 parts by weight of an inert organic solvent is supplied continuously to the first complete mixing type reactor where it is polymerized under the condition prevailing before the rubber phase inversion, the initial reaction mixture is withdrawn continuously and supplied to the second complete mixing type reactor where the rubber is transformed into particles with the conversion of the monomers in the reactants held at 40% by weight or less, and the conversion is raised in the following reactor to yield impact-resistant rubber-modified styrene resins containing rubber particles with a weight average particle diameter of 1.5 to 4 .mu.m.

Abstract: Mould assembly for foam moulding of plastic materials, which comprises stationary and movable dies and an auxiliary die plate device between the stationary and movable dies. A gas passage is formed for introducing pressurized inert gas into the mould cavity. The auxiliary die device comprises separated inner and outer auxiliary dies both being spring biased toward the stationary die. O-ring seals are disposed between the opposite surfaces of the outer auxiliary die and the stationary and movable dies.

Abstract: This invention relates to an improved injection foam molding method in which a foamable mixture of molten synthetic polymer resin and a chemical blowing agent in unfoamed condition is injected into a gas-pressurized expandable mold having a mold section movable for expanding the mold cavity to a position in which the surface of that section is in registry to the surface of another mold section, in which process the mold is filled under conditions resisting foaming of the material prior to filling of the mold and a novel controlled time sequence effective to form a fine mold crease line is employed in releasing the gas pressure and expanding the mold to allow foaming of the mixture into conformity with the mold surface.