Multi-layer core golf ball
View Patent ↗Golf balls having a very high positive gradient multilayer core are provided. The multilayer core includes an outer core layer and a very soft, low compression inner core layer. The inner core layer is formed from an unfoamed composition and has a center hardness that is at least 40 Shore C points less than the outer surface hardness of the outer core layer.
1. A golf ball comprising a core and a cover, wherein the core consists of:
a solid inner core layer formed from an unfoamed first polybutadiene composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H center ) of 40 or less,
one or more optional intermediate core layers, and
an outer core layer formed from a second polybutadiene composition and having a thickness of 0.150 inches or greater and an outer surface Shore C hardness (H outer surface ) of 80 or greater,
wherein H outer surface >H center , and H outer surface −H center ≧40, and
wherein the core has a gradient quotient, Q, of from 7 to 12, as defined by the equation:
G
+
T
10
×
COR
=
Q
where G is the hardness gradient of the core in Shore C as defined by H outer surface minus H center , T is the percent of trans-polybutadiene isomer at the surface of the outer core layer, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.
2. The golf ball of claim 1 , wherein the hardness gradient, G, is from 60 to 90.
3. The golf ball of claim 1 , wherein the percent of trans-polybutadiene isomer at the surface of the outer core layer, T, is from 1 to 5.
4. The golf ball of claim 1 , wherein the COR of the core is from 0.790 to 0.840.
5. The golf ball of claim 1 , wherein H outer surface −H center ≧45.
6. The golf ball of claim 1 , wherein H outer surface −H center ≧55.
7. The golf ball of claim 1 , wherein H outer surface −H center ≧60.
8. The golf ball of claim 1 , wherein the inner core layer has a compression of <0.
9. The golf ball of claim 8 , wherein the core has an overall compression of ≧70.
10. A golf ball comprising a core and a cover, wherein the core consists of:
a solid inner core layer formed from an unfoamed first polybutadiene composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H center ) of 30 or less,
one or more optional intermediate core layers, and
an outer core layer formed from a second polybutadiene composition and having a thickness of 0.150 inches or greater and an outer surface Shore C hardness (H outer surface ) of 80 or greater,
wherein H outer surface ≧H center , and H outer surfac −H center ≧50, and
wherein the core has a gradient quotient, Q, of from 7 to 12, as defined by the equation:
G
+
T
10
×
COR
=
Q
where G is the hardness gradient of the core in Shore C as defined by H outer surface minus H center , T is the percent of trans-polybutadiene isomer at the surface of the outer core layer, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.
11. The golf ball of claim 10 , wherein the hardness gradient, G, is from 60 to 90.
12. The golf ball of claim 10 , wherein the percent of trans-polybutadiene isomer at the surface of the outer core layer, T, is from 1 to 5.
13. The golf ball of claim 10 , wherein the COR of the core is from 0.790 to 0.840.
14. The golf ball of claim 10 , wherein H outer surfac −H center ≧55.
15. The golf ball of claim 10 , wherein H outer surfac −H center ≧60.
16. The golf ball of claim 10 , wherein H outer surfac −H center ≧65.
17. The golf ball of claim 10 , wherein H outer surfac −H center ≧70.
18. The golf ball of claim 10 , wherein the inner core layer has a compression of <0.
19. The golf ball of claim 18 , wherein the core has an overall compression of ≧70.
20. The golf ball of claim 10 , wherein the inner core layer composition is a thermoset composition consisting essentially of:
polybutadiene;
from 0.1 phr to 2.0 phr of a peroxide;
optionally 5 phr or less of a metal oxide;
optionally 5 phr or less of a metal coagent;
optionally 5 phr or less of a metal carbonate; and
optionally one or more additional components selected from the group consisting of fillers, colorants, and antioxidants.