Golf ball multilayer core having a gradient quotient
A golf ball including a core having an inner core having an outer surface and a geometric center; and an outer core layer. The outer core layer has an outer surface and includes a soft transition region. An outer cover layer is formed over the core. The soft transition region has a thickness of up to 4 mm, has about 5 to 15 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to about 10 Shore C. The core has an overall positive hardness gradient of about 5 Shore C to 15 Shore C and has a gradient quotient, GQ, defined by the equation: 1 ≤ G + T 10 × COR ≤ 4 where G is the overall positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution measured at an incoming velocity of 125 ft/s.
1. A golf ball comprising:
a core comprising an inner core having an outer surface and a geometric center; and an outer core layer disposed about the inner core; the outer core layer having an outer surface and comprising a soft transition region adjacent to the outer surface; and
an outer cover layer;
wherein the soft transition region has a thickness of up to 4 mm, comprises about 5 to 15 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to about 10 Shore C; and wherein the core has an overall positive hardness gradient of about 5 Shore C to 15 Shore C and has a gradient quotient, GQ, defined by the equation:
1
≤
G
+
T
10
×
COR
≤
4
where G is the overall positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution measured at an incoming velocity of 125 ft/s.
2. The golf ball of claim 1 , wherein the soft transition region comprises about 8 to 12 percent trans-polybutadiene isomer.
3. The golf ball of claim 2 , wherein the soft transition region comprises about 9.5 to 10.5 percent trans-polybutadiene isomer.
4. The golf ball of claim 1 , wherein the overall positive hardness gradient of the core is about 5 Shore C to about 10 Shore C.
5. The golf ball of claim 1 , wherein the core has a COR of about 0.800 or greater.
6. The golf ball of claim 5 , wherein the COR is about 0.820 or greater.
7. The golf ball of claim 1 , wherein the gradient quotient, GQ, is about 1.2 to 3.7.
8. The golf ball of claim 7 , wherein the gradient quotient, GQ, is about 1.5 to 2.5.
9. The golf ball of claim 1 , wherein the golf ball comprises an inner cover layer comprising an ionomer.
10. The golf ball of claim 9 , wherein the ionomer comprises a lithium ionomer and a sodium ionomer.
11. The golf ball of claim 1 , wherein the outer core layer has an overall negative hardness gradient.
12. The golf ball of claim 11 , wherein the negative hardness gradient is about 1 to about 5 Shore C.
13. The golf ball of claim 11 , wherein the negative hardness gradient is about 6 to about 20 Shore C.
14. The golf ball of claim 1 , wherein the outer core layer has an overall positive hardness gradient.
15. The golf ball of claim 14 , wherein the positive hardness gradient is about 1 to about 5 Shore C.
16. The golf ball of claim 14 , wherein the positive hardness gradient is about 6 to about 20 Shore C.