TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The ester bond is formed by the esterification of a carboxylic acid group of the ethylene-unsaturated carboxylic acid copolymer with the polyalkylene oxide having a hydroxyl group at one terminal or with a derivative, preferably the ester bond is formed by the ester interchange reaction of an alkyl ester of the ethylene-unsaturated carboxylic acid copolymer or an alkyl ester derivative with the polyalkylene oxide having a hydroxyl group at one terminal. The polymer is formed by (A) with (B) at a molar ratio expressed by the following formulaBHYD/ACARBHYD = a number of moles of hydroxyl groups of the polyalkylene oxide having a hydroxyl group at one terminal or of the derivativeACAR = a number of moles of carboxylic acid groups of the ethylene-unsaturated carboxylic acid copolymer or of the derivative of 0.3 - 2.5.The remaining amount of the unreacted carboxylic acid groups in the polymer is not larger than 30 mol% on the basis of the carboxylic acid group of the ethylene-unsaturated carboxylic acid copolymer or the derivative (A). (A) has a composition containing ethylene in an amount 50- 98 wt.%, an unsaturated carboxylic acid or an anhydride amount of 2 - 50 wt.%, and other monomers in an amount 0 - 30 wt.%, preferably an alkyl ester of an unsaturated carboxylic acid or an alkyl ester derivative in an amount of 2 - 50 wt.% by weight. the alkyl ester of the ethylene-unsaturated carboxylic acid copolymer is a methyl ester or an ethyl ester. (A) is an ionomer of which the carboxylic acid is partly neutralized with a monovalent metal or a multi-valent metal, the neutralization degree is 0.5 - 60 mol%. (A) has a melt flow rate of 0.1 - 500 g/10 min. at 190 degreesC - under a load of 2160 g. (B) has a number average molecular weight of 200 - 100,000 and contains the ethylene oxide in an amount of 30 - 100 mol%. (B) is blocked by the etherification, esterification or by the reaction with a monoisocyanate. The esterification of (A) with (B) is conducted in the presence of an acid catalyst. The formation of the ester bond by the ester interchange reaction is conducted in the presence of an organometal catalyst. The polymer is partly crosslinked in the presence of at least one kind of crosslinking agent selected from polyhydric alcohol, mono(meth)acrylic acid or an ester, polyethylene glycol di(meth)acrylate, unsaturated higher fatty acid or an ester and polyethylene glycol diglycidyl ether. The crosslinking agent is present in the- reaction system in an amount 0.1 - 30 wt.%.