PURPOSE: To obtain a concentrate by incorporating a specified amt. of a modifier for a thermoplastic polymer into an α-olefin polymer having a specified heat of crystallization.

CONSTITUTION: A particulate copolymer (A) of ethylene with one or more comonomers selected from among carbon monoxide, vinyl acetate, and an alkyl (meth)acrylate having a 1-4C alkyl, wherein the copolymer has a heat of crystallization of not more than 70 J/g and, when the copolymer is an ethylene/vinyl acetate copolymer, has a vinyl acetate content of not less than 18 wt.%, is brought into contact with a modifier (B) selected from an ethylenically unsatd. carboxylic acid (deriv.) and an organosilane in an amt. of not less than 30 wt.% of the carrier polymer.