Random copolymer, and process for production thereof

A modified random copolymer resulting from grafting 0.1 to 50 parts by weight of a monomer selected from the group consisting of (a) alpha, beta-unsaturated carboxylic acids and/or their derivatives, (b) styrenes, (c) organic silicon compounds having an olefinically unsaturated bond and a hydrolyzable group, and (d) unsaturated epoxy monomers to 100 parts by weight of a random copolymer characterized in that

• (A) the copolymer comprises polymerized units from ethylene and polymerized units from at least one cycloolefin selected from the group consisting of compounds represented by the following formula (I) ##STR30## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 are identical or different and each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 10 carbon atoms, and R.sup.9 and R.sup.10 are identical or different and each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 10 carbon atoms, or R.sup.9 and R.sup.10 are bonded to each other to form a group of the following formula ##STR31## in which R.sup.11 and R.sup.12 are identical or different and each represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 10 carbon atoms, and l is an integer of 3 to 4, and n is 0 or a positive integer of 1 to 3,
• (B) the mole ratio of the polymerized units from the cycloolefin to the polymerized units from ethylene is from 3:97 to 60:40,
• (C) the cycloolefin of formula (I) is incorporated in the polymer chain as polymerized units represented by the following formula (II) ##STR32## wherein all symbols are as defined above, (D) the copolymer has an intrinsic viscosity, measured in decalin at 135.degree. C., of 0.01 to 20 dl/g,
• (E) the copolymer has a molecular weight distribution (Mw/Mn), measured by gel permeation chromatography, of not more than 4,
• (F) the copolymer has a crystallinity, measured by x-ray diffractometry, of 0 to 10%, and
• (G) the copolymer has a glass transition temperature (Tg) of at least 10.degree. C.