Polypropylene composition giving injection moldings of outstanding stiffness/impact strength balance is obtained by reacting peroxide with filled mixture containing propylene/ethylene block copolymer and polyolefin rubber

摘要

A polypropylene resin composition with melt index (230[deg]C; 2.16kgf) of 70-120 g/10 minutes, bending modulus 1300-4000 MPa and Izod impact strength 30-100 kJ/m2 is claimed which is obtained by addition of an organic peroxide (0.01-0.04 parts wt.) to specified polyolefin mixture, followed by kneading at 170-280[deg]C. A polypropylene resin composition with melt index (230[deg]C; 2.16kgf) of 70-120 g/10 minutes, bending modulus 1300-4000 MPa and Izod impact strength 30-100 kJ/m2 is claimed which is obtained by addition of an organic peroxide (0.01-0.04 parts wt.) to a specified mixture (100 parts wt.), followed by kneading at 170-280[deg]C. The specified mixture comprises by weight (a) a propylene/ethylene block copolymer (60-80%) consisting of a polypropylene homopolymer part and a statistical propylene/ethylene copolymer part and fulfilling conditions (A1) and (A2) below; (b) a rubber (10-30%) which is a copolymer of ethylene with 1-butene, 1-hexene and/or 1- octene with a melt index (190[deg]C; 2.16 kgf) of 2-10 g/10 minutes; and (c) an inorganic filler (5-20 wt.%). The conditions are (A1) the propylene/ethylene block copolymer has a melt index (230[deg]C; 2.16kgf) of 100-140 g/10 minutes and an ethylene content of 3-6.5 wt.%; and (A2) the statistical propylene/ethylene copolymer part is present at 5-15 wt.% and has a limiting viscosity of 3-5 dl/g and an ethylene content of 20-60 wt.%.