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 90 Shore C, and a surface hardness of from 50 Shore C to 95 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;
an inner cover layer having a surface hardness of from 50 Shore D to 65 Shore D; and
an outer cover layer having a surface hardness of from 40 Shore D to 60 Shore D;
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 1 , wherein the surface hardness of the intermediate core layer is from 65 Shore D to 80 Shore D.
12. 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.
13. The golf ball of claim 1 , wherein the first and second thermoset rubber compositions are the same or different diene rubber-based compositions.
14. The golf ball of claim 1 , wherein the second thermoset rubber composition comprises from 1 phr to 100 phr of a stiffening agent.
15. 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.