THERMOPLASTIC RESIN COMPOSITION AND PRODUCTS OF INJECTION MOLDING THEREOF

摘要

According to this invention, there is provided a thermoplastic resin composition using a crystalline polypropylene as the main component, satisfying the impact strength and rigidity required as an automobile interior trim material in respect of physical properties, has high flow and good balance between impact strength and rigidity as compared with conventionally used ethylene-propylene copolymer rubber compositions, and being short in molding cycle and good in surface quality in respect of injection moldability, and further provided an injection molded article using the composition, particularly an injection molded article for automobile interior trim. The above thermoplastic resin composition comprises in the specific proportions (A) a specific crystalline polypropylene; at least one member selected from (B) a specific ethylene-butene-1 copolymer rubber, (C) a specific ethylene-propylene copolymer rubber and (D) a specific vinyl aromatic compound-containing rubber; (E) talc; and if necessary, (F) fibrous magnesium oxysulfate, has a melt flow index (JIS-K-6758, 230 DEG C) of 25 to 35 g/10 minutes and a flexural modulus at 23 DEG C of not less than 20,000 kg/cm<2>. Here, the crystalline polypropylene (A) is the following (i) or (ii): (i) a crystalline ethylene-propylene copolymer in which the propylene homopolymer portion which is the first segment has a Q value of 3 to 5 which is the weight average molecular weight (Mw)/number average molecular weight (Mn) ratio according to a gel permeation chromatography (GPC) method, an isotactic pentad fraction of not less than 0.98 as calculated by <13>C-NMR and an intrinsic viscosity of 0.9 to 1.1 dl/g as measured at 135 DEG C in tetralin; and the ethylene-propylene random copolymer portion which is the second segment has an intrinsic viscosity of 4.5 to 5.5 dl/g as measured at 135 DEG C in tetralin and an ethylene/propylene ratio of 25/75 to 35/65 (weight % ratio), (ii) a mixture of the crystalline ethylene-propylene block copolymer of (i) above with a specific crystalline propylene homopolymer.