Multi-layer core golf ball
View Patent ↗Golf balls consisting of a multi-layer core and a cover are disclosed. The multi-layer core comprises a thermoset rubber center, a thermoplastic intermediate core layer, and a thermoset rubber outer core layer.
1. A golf ball comprising:
a center formed from a first thermoset rubber composition and having a diameter of from 1.250 inches to 1.580 inches, a center hardness of from 40 Shore C to 65 Shore C, and a surface hardness of from 50 Shore C to 90 Shore C;
an intermediate core layer formed from a thermoplastic composition and having a thickness of 0.005 inches to 0.100 inches and a surface hardness of greater than 60 Shore D;
an outer core layer formed from a second thermoset rubber composition and having a thickness of 0.010 inches to 0.100 inches and a surface hardness of 50 Shore C or greater; and
a cover layer having a thickness of from 0.010 inches to 0.050 inches and a surface hardness of 60 Shore D or less;
wherein each of the core layers has a specific gravity of 1.25 g/cc or less.
2. The golf ball of claim 1 , wherein the center has a positive hardness gradient wherein the difference between the center hardness and the surface hardness of the center is from 10 to 45.
3. The golf ball of claim 1 , wherein the center has a compression of 80 or less.
4. The golf ball of claim 1 , wherein the outer core layer has a surface hardness of 80 Shore C or greater.
5. The golf ball of claim 4 , wherein the surface hardness of the outer core layer is greater than the surface hardness of the center.
6. The golf ball of claim 1 , wherein the outer core layer has a surface hardness of from 50 Shore C to 80 Shore C.
7. The golf ball of claim 6 , wherein the surface hardness of the outer core layer is less than the surface hardness of the center.
8. The golf ball of claim 1 , wherein the center has a diameter of from 1.400 inches to 1.500 inches.
9. The golf ball of claim 8 , wherein the intermediate core layer has a thickness of from 0.040 inches to 0.060 inches.
10. The golf ball of claim 9 , wherein the outer core layer has a thickness of from 0.030 inches to 0.040 inches.
11. The golf ball of claim 10 , wherein the cover layer has a thickness of from 0.025 inches to 0.035 inches.
12. The golf ball of claim 1 , wherein the surface hardness of the intermediate core layer is from 65 Shore D to 80 Shore D.
13. The golf ball of claim 1 , wherein the surface hardness of the intermediate core layer is greater than the surface hardness of both the center and the outer core layer.
14. The golf ball of claim 1 , wherein the first and second thermoset rubber compositions are the same or different diene rubber-based compositions.
15. The golf ball of claim 1 , wherein the second thermoset rubber composition comprises from 1 phr to 100 phr of a stiffening agent.
16. The golf ball of claim 1 , wherein the thermoplastic composition of the intermediate core layer is selected from the group consisting of partially- and fully-neutralized ionomers optionally blended with a maleic anhydride-grafted non-ionomeric polymer, polyester elastomers, polyamide elastomers, and blends thereof.
17. A golf ball comprising:
a center formed from a first diene rubber composition and having a diameter of from 1.250 inches to 1.580 inches, a center hardness of from 40 Shore C to 65 Shore C, and a surface hardness of from 70 Shore C to 90 Shore C;
an intermediate core layer formed from a thermoplastic composition and having a thickness of 0.005 inches to 0.100 inches and a surface hardness of greater than 60 Shore D;
an outer core layer formed from a second diene rubber composition and having a thickness of 0.010 inches to 0.100 inches and a surface hardness of 75 Shore C or greater; and
a cover layer having a thickness of from 0.010 inches to 0.050 inches and a surface hardness of 60 Shore D or less;
wherein each of the core layers has a specific gravity of 1.25 g/cc or less.
18. The golf ball of claim 17 , wherein the surface hardness of the outer core layer is greater than the surface hardness of the center.
19. A golf ball consisting essentially of:
a center formed from a first diene rubber composition and having a diameter of from 1.350 inches to 1.490 inches, a center hardness of from 40 Shore C to 65 Shore C, and a surface hardness of from 70 Shore C to 90 Shore C;
an intermediate core layer formed from a thermoplastic composition and having a thickness of 0.005 inches to 0.100 inches and a surface hardness of greater than 60 Shore D;
an outer core layer formed from a second diene rubber composition and having a thickness of 0.010 inches to 0.100 inches and a surface hardness of 75 Shore C or greater; and
a cover layer having a thickness of from 0.010 inches to 0.050 inches and a surface hardness of 60 Shore D or less;
wherein each of the core layers has a specific gravity of 1.25 g/cc or less.
20. The golf ball of claim 19 , wherein the cover layer is formed from a composition selected from polyurethanes, polyureas, and copolymers and blends thereof.