POLYOLEFIN-BASED RESIN COMPOSITION AND AUTOMOTIVE MOLDED PLASTIC MADE FROM SAME

摘要

The invention relates to a polyolefin-based resin composition that is in an amount of 100 wt % in total. This composition includes (a) 60-66 wt % of a crystalline propylene-ethylene block copolymer, (b) 12-20 wt % of an ethylene-propylene copolymer rubber, and (c) 18-25 wt % of an inorganic filler. The block copolymer contains a first segment of a homopolymer of propylene and a second segment of a copolymer of propylene and ethylene, and has an isotactic pentad tacticity of at least 0.96. The ratio of the weight average molecular weight of the block copolymer to the number average molecular weight thereof is not greater than 6. The copolymer rubber contains therein 50-60 wt % of ethylene, and has a Mooney viscosity of from 45 to 55 at 125° C. The inorganic filler is one selected from the group consisting of a talc, a first combination of the talc and a glass fiber, and a second combination of the talc and a whisker. The talc has an average particle diameter of not greater than 2 mum. The glass fiber has an average fiber length of from 5 to 10 mm and an average diameter of from 15 to 20 mum. The whisker has an average fiber length of from 15 to 25 mum and an average diameter of from 0.5 to 1 mum. A molded plastic article made from the resin composition is substantially improved in scratch resistance.