Abstract: A method for the preparation of a modified crystalline propylene polymer usable as a bonding material is disclosed, in which method a crystalline propylene polymer, for example, isotactic polypropylene and a propylene-ethylene block or random copolymer, is uniformly admixed with a modifying composition consisting of at least one organic peroxide, and a modifying agent consisting of .gamma.-methacryloyloxypropyl trimethoxysilane (Component (1)) and at least one ethylenically unsaturated organic compound (Component (2)) selected from the groups consisting of the formulae (I) through (V): ##STR1## wherein R.sub.1 through R.sub.

Abstract: A modified crystalline propylene polymer usable as a bonding material is prepared by uniformly admixing a crystalline propylene polymer, for example, isotactic polypropylene and propylene-ethylene block or random copolymer, with at least (a) one modifying agent of the formula (I) or (II): ##EQU1## or ##SPC1##Wherein R represents a hydrogen atom or methyl radical, Me represents a Metal atom selected from Groups I, II, III and VIII in the Periodic Table, l represents an integer corresponding to the valence of the Metal atom Me, and m and n each represent 0 or 1, and (b) an organic peroxide, and heating the above admixture at a temperature not lower than the melting point and not higher than the thermal decomposing point of said crystalline propylene polymer.