PURPOSE: To obtain a product excellent in adhesion to metal, by treating an ethylene/butadiene block copolymer with 5-norbornene-2,3-dicarboxylic anhydride.

CONSTITUTION: 0.01W10pts.wt. 5-norbornene-2,3-dicarboxylic anhydride is added to 100pts.wt. styrene/butadiene copolymer of an MFR of 0.01W50g/10min and a styrene content of 1W50wt%, and the mixture is melt-kneaded at the m.p. of the block copolymer W280°C and a shear rate of 50'200/sec to obtain product of an MFR of 0.01W60g/min, a density of 0.90W1.20g/cm3, a tensile strength of 200W350kg/cm2, an elongation of 10W500%, Young's modulus in flexture of 8,000W20,000kg/cm2, a notched impact strength (a specimen with a notch) of 1.0W50kg.cm/cm and a Rockwell hardness (scale D) of 70W85.