Game Balls with Cover Containing Post Crosslinkable Thermoplastic Polyurethane and Method of Making Same
A game ball having a cover formed from a crosslinkable thermoplastic polyurethane is disclosed. By selective exposure to radiation, the thermoplastic polyurethane cover is crosslinked and its hardness is increased. Typically, increases in hardness values of at least 2 units on the Shore D scale are realized upon exposure to 3.5 Mrads of gamma radiation.
1 . A golf ball, comprising:
a core, and
a cover layer formed over said core, said cover layer comprising a crosslinkable thermoplastic polyurethane and a saturated co-agent capable of crosslinling said crosslinkable thermoplastic polyurethane via free radical initiation.
2 . The golf ball according to claim 1 , wherein said crosslinkable thermoplastic polyurethane is a post crosslinkable thermoplastic polyurethane.
3 . The golf ball according to claim 1 , wherein said saturated co-agent is a short chain diene.
4 . The golf ball according to claim 1 , wherein said crosslinkable thermoplastic polyurethane has a Shore D hardness of from about 35 to about 72 before crosslinking and undergoes an increase in Shore D hardness of at least 2 units upon exposure to gamma radiation at a dosage of 3.5 Mrads.
5 . The golf ball according to claim 1 , wherein said crosslinkable thermoplastic polyurethane has a Shore D hardness of from about 35 to about 72 before crosslinking and experiences an increase in Shore D hardness of at least 5 units upon exposure to gamma radiation at a dosage of 3.5 Mrads.
6 . The golf ball according to claim 1 , wherein said crosslinkable thermoplastic polyurethane comprises at least one of a polyether based polyurethane and a polyester based polyurethane.
7 . The golf ball according to claim 1 , wherein said core is at least one member selected from the group consisting of solid cores, wound cores and liquid filled cores.
8 . A golf ball comprising:
a core; and
a cover layer disposed about said core, said cover comprising a thermoplastic polyurethane capable of undergoing crosslinking upon exposure to about 3.5 Mrads of radiation, and thereby increasing in hardness by at least 2 units on the Shore D hardness scale, wherein said cover layer further comprises a saturated co-agent capable of crosslinking said thermoplastic polyurethane.
9 . The golf ball according to claim 8 , wherein said saturated co-agent is a short chain diene.
10 . The golf ball according to claim 10 , wherein said cover layer comprises at least an inner cover layer and an outer cover layer.
11 . A golf ball, comprising:
a core;
an inner cover layer disposed over the core; and
a cover layer formed over said core, said cover layer comprising a crosslinkable thermoplastic polyurethane and a saturated co-agent capable of crosslinking said crosslinkable thermoplastic polyurethane via free radical initiation.
12 . The golf ball according to claim 11 wherein the core is a dual core.