Methods and compositions for cross-linking thermoplastic polyurethane covers for golf balls

A method for treating a cover for a golf ball, comprising the steps of:

• providing a golf ball sub-assembly comprising at least one core layer;
• forming an outer cover layer over the sub-assembly, wherein the outer cover layer is formed from a composition comprising:
• a) a thermoplastic polyurethane,
• b) an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates;
• and
• c) a multi-functional amine-containing compound;
• and
• d) a cation source present in an amount sufficient to neutralize from about 0 to about 100% of all acid groups present in the composition,
• applying a composition comprising:
• i) at least one compound selected from the group consisting of multi-functional isocyanates;
• multi-functional amine-containing compounds;
• and silane-containing compounds to the outer cover to form at least a partially cross-linked cover for the golf ball.