Propylene block copolymer and propylene resin composition

The present invention relates to a block copolymer comprising polypropylene and an ethylene-propylene copolymer, and more particularly to a block copolymer having good impact resistance. Disclosed are a propylene polymer composition possessing excellent balance among rigidity and low warpage, resistance to deterioration caused by thermal oxidation during processing, weathering resistance, antistatic properties, and low bleeding properties, and a propylene resin composition which can easily produce molded products having excellent balance between rigidity and impact resistance (particularly low-temperature impact resistance) or heat resistance. The propylene polymer composition and the propylene resin composition comprise a propylene block copolymer consisting essentially of the following blocks (a) and (b) and having a melt flow rate of 0.1 to 200 g/10 min:block (a): a polymer block of a homopolymer of propylene or a random copolymer of propylene with a comonomer selected from the group consisting of ethylene and C-C -olefins, the content of the comonomer being not more than 10% by mole; andblock (b): a polymer block of a random copolymer of propylene with at least one comonomer selected from the group consisting of ethylene and C-C -olefins, the content of the comonomer being 10 to 80% by mole, the average chain length of the comonomer block and the gross average chain length of the comonomer having a relationship represented by formula (I)wherein nrepresents the average chain length of the comonomer block; and n represents the gross average chain length of the comonomer.