Multi-layer cover golf ball having thermoset rubber intermediate cover layer
View Patent ↗A golf ball including a core and a cover including a thermoplastic inner cover layer having a material hardness of 60 to 80 Shore D; a thermoset outer cover layer comprising a castable polyurea and having a material hardness of 20 to 60 Shore D; and a thermoset intermediate cover layer disposed between the inner and outer cover layers and having a hardness substantially the same as the inner cover layer hardness and greater than the outer cover layer hardness. The inner cover includes one or more high- or low-acid ionomers and, optionally, a maleic anhydride modified polyolefin. The intermediate layer is formed from a castable liquid polybutadiene rubber.
1. A golf ball comprising a core and a three-layer cover, the cover comprising:
a thermoplastic inner cover layer disposed about the core and having a material hardness of about 60 Shore D to about 80 Shore D;
a thermoset outer cover layer comprising a polyurethane, polyurea, or hybrid thereof and having a material hardness of about 20 Shore D to about 60 Shore D; and
a thermoset intermediate cover layer disposed between the inner and outer cover layers and having a hardness substantially the same as the inner cover layer hardness and greater than the outer cover layer hardness;
wherein the inner cover comprises a stiff resilient polymer, and the intermediate layer is formed from a thermoset liquid rubber composition comprising a liquid styrenebutadiene rubber, or a liquid ethylene propylene diene monomer (EPDM) polymer.
2. The golf ball of claim 1 , wherein the liquid rubber composition comprises about 30% to about 70% solids at a submersion time of about 10 sec to about 60 sec.
3. The golf ball of claim 1 , wherein the liquid rubber composition, when in a solid state, can be extended under ambient conditions at least twice its resting length, and upon stress release can return to within 15% of its original length.
4. The golf ball of claim 1 , wherein the liquid rubber composition further comprises a crosslinking agent comprising one or more metallic salts of a carboxylic acid.
5. The golf ball of claim 1 , wherein the liquid rubber composition is a polybutadiene vulcanized with a reactive co-agent, a peroxide, a sulfur, or a mixture thereof.
6. The golf ball of claim 1 , wherein the liquid rubber composition is a polybutadiene functionalized with epoxy, (meth)acrylate, hydroxyl, vinyl, isocyanate, ester, carboxyl, or carbonyl groups.
7. The golf ball of claim 1 , wherein the liquid rubber composition is a polybutadiene comprising (meth)acrylated liquid polybutadiene, epoxidized liquid polybutadiene, liquid polybutadiene dimethacrylate, and liquid polybutadiene urethane diacrylate.
8. The golf ball of claim 1 , wherein the liquid rubber composition has a viscosity of about 10,000 cp or less.
9. The golf ball of claim 8 , wherein the viscosity is about 1,000 cp or less.
10. The golf ball of claim 1 , wherein the liquid rubber composition is vulcanized with peroxide or sulfur cure accelerators.
11. The golf ball of claim 1 , wherein the EPDM polymer comprises ethylidene norborene diene monomer or dicyclopentadiene.
12. The golf ball of claim 1 , wherein the stiff resilient polymer comprises partially- and fully-neutralized ionomers, polyolefins, metallocenes, polyesters, polyamides, thermoplastic elastomers, copolyether-amides, copolyether-esters, or mixtures thereof.
13. The golf ball of claim 1 , wherein a combination of the inner cover, the intermediate cover, and the outer cover have a total thickness of 0.125 inches or less.
14. The golf ball of claim 1 , wherein the total thickness is 0.115 inches or less.
15. The golf ball of claim 1 , wherein the outer cover layer is cast or reaction injection molded.
16. A golf ball comprising a core and a three-layer cover, the cover comprising:
a thermoplastic inner cover layer disposed about the core and having a material hardness of about 60 Shore D to about 80 Shore D;
a thermoset outer cover layer comprising a castable polyurea and having a material hardness of about 20 Shore D to about 60 Shore D; and
a thermoset intermediate cover layer disposed between the inner and outer cover layers and having a hardness substantially the same as the inner cover layer hardness and greater than the outer cover layer hardness;
wherein the inner cover layer comprises a high-acid ionomer and the intermediate cover layer is formed from a liquid ethylene propylene diene monomer (EPDM) polymer.
17. The golf ball of claim 16 , wherein the inner cover layer further comprises a maleic anhydride modified polyolefin.
18. A golf ball comprising a core and a three-layer cover, the cover comprising:
a thermoplastic inner cover layer disposed about the core and having a material hardness of about 60 Shore D to about 80 Shore D;
a thermoplastic polyurethane outer cover layer having a material hardness of about 20 Shore D to about 60 Shore D; and
a thermoset intermediate cover layer disposed between the inner and outer cover layers and having a hardness substantially the same as the inner cover layer hardness and greater than the outer cover layer hardness;
wherein the inner cover layer comprises one or more low-acid ionomers and the intermediate cover layer is formed from a ethylene propylene diene monomer-based liquid rubber polymer.
19. The golf ball of claim 18 , wherein the inner cover layer comprise a blend of Li and Na low-acid ionomers.
20. The golf ball of claim 18 , wherein the outer cover layer is cast or reaction injection molded.