Polypropylene-based resin composition and foam sheet

A polypropylene-based resin composition comprising:

• (X) 5 to 99% by weight of a polypropylene resin having a structure with long chain branches, and
• (Y) 1 to 95% by weight of a propylene-based block copolymer produced by sequential polymerization, which comprises:
• (Y-1) a propylene (co)polymer, and
• (Y-2) a propylene-ethylene copolymer,
• wherein the resin (X) has the following properties (X-i) to (X-iv):
• (X-i):
• MFR of 0.1 to 30.0 g/10 minutes,
• (X-ii):
• a molecular weight distribution Mw/Mn of 3.0 to 10.0 measured by GPC and Mz/Mw of 2.5 to 10.0,
• (X-iii):
• a melt tension (MT) (unit:
• g) satisfying the relationship:
• log(MT)≧−0.9×log(MFR)+0.7, or
• MT≧15,
• (X-iv):
• a content of p-xylene soluble components (CXS) at 25° C. of less than 5% by weight based on a total amount of the resin (X), and
• the block copolymer (Y) has the following properties (Y-i) to (Y-v):
• (Y-i):
• ratios of the amounts of the (Y-1) and (Y-2) of 50 to 99% by weight and 1 to 50% by weight, respectively, with the proviso that each ratio is calculated based on a total of 100% by weight of the block copolymer (Y),
• (Y-ii):
• MFR of the block copolymer (Y) of 0.1 to 200.0 g/10 minutes,
• (Y-iii):
• melting point of the block copolymer (Y) of more than 155° C.,
• (Y-iv):
• an ethylene content of the (Y-2) of 11.0 to 38.0% by weight, with the proviso that the ethylene content is calculated based on a total of 100% by weight of monomers constructing the (Y-2), and
• (Y-v):
• an intrinsic viscosity [η] (unit:
• dl/g) of the (Y-2) measured at 135° C. in decalin of 5.3 or more.