A material comprising a heated mixture of (A) an olefin-unsaturated carboxylic acid copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylate copolymer, a metal ion neutralized product thereof, or a mixture thereof, (B) a polyurethane elastomer, and (C) an organic or inorganic basic compound has improved thermal stability, flow and moldability. Using the material, golf balls having good rebound are effectively manufactured.