Golf ball single layer core having a gradient quotient
A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The core is formed from a substantially homogenous composition. An outer cover layer is formed over the core. The soft transition region has a thickness of up to 4 mm, includes about 15 to 30 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to about 10 Shore C. The unitary core has an overall positive hardness gradient of about 15 to 22 Shore C and has a gradient quotient, GQ, defined by the equation: 5 ≤ G + T 10 x COR ≤ 6 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 unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, the core comprising a substantially homogenous composition; and
an outer cover layer;
wherein the soft transition region has a thickness of up to 4 mm, comprises about 15 to 30 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to about 10 Shore C; and wherein the unitary core has an overall positive hardness gradient of about 15 Shore C to 22 Shore C and has a gradient quotient, GQ, defined by the equation:
5
≤
G
+
T
10
x
C
O
R
≤
6
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 20 to 30 percent trans-polybutadiene isomer.
3. The golf ball of claim 2 , wherein the soft transition region comprises about 23 to 27 percent trans-polybutadiene isomer.
4. The golf ball of claim 1 , wherein the overall positive hardness gradient of the core is about 15 Shore C to about 20 Shore C.
5. The golf ball of claim 1 , wherein the core has a COR of about 0.795 or greater.
6. The golf ball of claim 5 , wherein the COR is about 0.810 or greater.
7. The golf ball of claim 1 , wherein the gradient quotient, GQ, is about 5.1 to 5.9.
8. The golf ball of claim 1 , wherein the gradient quotient, GQ, is about 5.3 to 5.7.
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 golf ball comprises an outer core layer disposed about the unitary core.
12. The golf ball of claim 11 , wherein the outer core layer has an overall negative hardness gradient.
13. The golf ball of claim 12 , wherein the negative hardness gradient is about 1 to about 5 Shore C.
14. The golf ball of claim 12 , wherein the negative hardness gradient is about 6 to about 20 Shore C.
15. The golf ball of claim 11 , wherein the outer core layer has an overall positive hardness gradient.
16. The golf ball of claim 15 , wherein the positive hardness gradient is about 1 to about 5 Shore C.
17. The golf ball of claim 15 , wherein the positive hardness gradient is about 6 to about 20 Shore C.