Provided are an adhesive composition which has high holding strength and leaves no residual glue by using a polyolefinic polymer, and an adhesive tape using the same. A polyolefin which satisfies the following conditions (a-1), (b1), and (b2):(a-1) the relationship between the limiting viscosity and the stereoregularity is represented by the formula (i): 20+56mmmm20+64 (wherein represents the limiting viscosity measured in tetralin at 135 C., and mmmm represents the meso pentad fraction (mol %)); (b1) the meso pentad fraction (mmmm) is from 20 to 60 mol %; and (b2) the limiting viscosity [] measured in tetralin at 135 C. is from 0.01 to 2.0 dL/g.

Provided are an adhesive composition which has high holding strength and leaves no residual glue by using a polyolefinic polymer, and an adhesive tape using the same. A polyolefin which satisfies the following conditions (a-1), (b1), and (b2):(a-1) the relationship between the limiting viscosity and the stereoregularity is represented by the formula (i): 20+56mmmm20+64 (wherein represents the limiting viscosity measured in tetralin at 135 C., and mmmm represents the meso pentad fraction (mol %)); (b1) the meso pentad fraction (mmmm) is from 20 to 60 mol %; and (b2) the limiting viscosity [] measured in tetralin at 135 C. is from 0.01 to 2.0 dL/g.

Provided are a propylene-based polymer which enhances heat creep resistance and a hot-melt adhesive having excellent heat creep resistance. A propylene-based polymer which satisfies the following (1) and (2): (1) 125a modulus of elasticity in tension (MPa) at 23 C.400; and (2) 100an elongation at break (%) at 23 C.1,000, and a hot-melt adhesive containing the propylene-based polymer in an amount of 1 to 50% by mass.

Provided are a propylene-based polymer which enhances heat creep resistance and a hot-melt adhesive having excellent heat creep resistance. A propylene-based polymer which satisfies the following (1) and (2): (1) 125a modulus of elasticity in tension (MPa) at 23 C.400; and (2) 100an elongation at break (%) at 23 C.1,000, and a hot-melt adhesive containing the propylene-based polymer in an amount of 1 to 50% by mass.

A composition comprising the following components: A) propylene/ethylene copolymer that has a density 0.880 g/cc, and a MWD(conv) from 2.00 to 3.00 and a melt viscosity (177 C)80,000 mPa*s; B) olefin multi-block copolymer that has a density 0.890 g/cc and a melt index (I2)0.5 g/10 min.

Provided is a pressure-sensitive adhesive sheet for semiconductor processing having excellent solvent resistance. The pressure-sensitive adhesive sheet for semiconductor processing includes a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a base polymer, and a base material. The pressure-sensitive adhesive composition has a swelling degree S.sub.A of 2.1 times or less when immersed in an N,N-dimethylpropionamide solution at 23 C. for 1 hour.