Patent ID: 7368498

Claim:
A polypropylene-based resin composition consisting essentially of: from 60 to 94.9% by weight of propylene-ethylene block copolymer (A) which satisfies requirement (A-1) and (A-2) defined below or a mixture of the propylene-ethylene block copolymer (A) and 20% by weight or less of propylene homopolymer, wherein the copolymer (A) does not satisfy one or more of the requirements (B-1), (B-2) and (B-3) defined below; from 0.1 to 15% by weight of resin (B) which satisfies the requirement (B-1), (B-2) or (B-3); and from 5 to 25% by weight of inorganic filler (C), wherein said amounts of the components (A), (B) and (C) are each based on the combined weight of these components and said amount of the propylene homopolymer is based on the weight of the mixture of the propylene-ethylene block copolymer (A) and the propylene homopolymer: requirement (A-1): the copolymer is a propylene-ethylene block copolymer composed of a propylene homopolymer portion (A1) and a propylene-ethylene random copolymer portion (A2); requirement (A-2): the copolymer has a propylene homopolymer portion (A1) in a content of from 60 to 75% by weight and a propylene-ethylene random copolymer portion (A2) in a content of from 25 to 40% by weight, wherein said contents of the portions A1 and A2 are each based on the weight of the propylene-ethylene block copolymer composed of the portions A1 and A2 and the sum of both contents is 100% by weight; requirement (B-1): the resin has a melt tension (MT), measured at 190° C. at a winding rate of 15.7 in/mm, of 0.03 N or more; requirement (B-2): the resin has a swelling ratio (SR), measured at 220° C. at an orifice L/D of40and at a shear rate of 1.2×10 3 sec −1 , of 1.5 or more; and requirement (B-3): when the resin is measured for its relaxation modulus at 210° C., it needs 5 seconds or more, measured from the start of the measurement, until it exhibits a relaxation modulus G(t) satisfying an equation G(t)/G(0.02)=0.01 wherein G(0.02) represents a relaxation modulus exhibited at a time of 0.02 seconds measured from the start of the measurement.