Patent ID: 7304111

Claim:
A polypropylene copolymer which has a polymer principal chain (A) that is derived from a propylene-based polymer having the following characteristics (1) and (2) and which has a functional group and which further has a side chain containing a polymer chain (B) which is different from the principal chain (A), wherein the weight ratio of (A)/(B) is in the range of 20/1 to 1/20: (1) in a 13 C-CMR spectrum of the propylene-based polymer whose sequential propylene units are formed by head-to-tail bonding, when the peak (S 1 ) in the spectrum that is attributable to the carbon atom of the methyl group of each propylene unit in a pentad sequence of propylene monomer units in the mmmm configuration appears at 21.8 ppm, the ratio (S 1 /S) of the area of peak S 1 to the total area (S) of all peaks that appear in the spectrum from 19.8 ppm to 22.2 ppm ranges from 20 to 60%; and when an area S 2 of a peak derived from a pentad sequence of mmmr having a peak top located at about 21.5 to 21.7 ppm, the relationship of {(4+2S 1 /S 2 )>5}, and (2) the melting point [Tm] of the propylene-based polymer, as measured by a differential scanning calorimeter, is not higher than 100° C., or the heat required for melting of the crystal of the polymer is not at a value of 5 J/g or more.