Golf ball core with soft outer transition volume and negative hardness gradient
View Patent ↗A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, and is formed from a substantially homogenous composition. The ball further includes an outer cover layer. The soft transition region has a thickness of up to 4 mm, has about 8 to 20 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to 15 Shore C. The core has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ, defined by the equation: G + T 10 × COR ≤ 7 where G is the overall negative 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 being formed from a substantially homogenous composition; and
an outer cover layer;
wherein the soft transition region has a thickness of up to 4 mm, comprises about 8 to 20 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to 15 Shore C, and wherein the unitary core has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ, defined by the equation:
G
+
T
10
×
COR
≤
7
where G is the overall negative 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 transition region comprises about 9 to about 15 percent trans-polybutadiene isomer.
3. The golf ball of claim 1 , wherein the core geometric center comprises about 5 to 15 percent trans-polybutadiene isomer.
4. The golf ball of claim 1 , wherein the core outer surface comprises about 10 to 30 percent trans-polybutadiene isomer.
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 0.810 or greater.
7. The golf ball of claim 1 , wherein the gradient quotient, GQ, is about 6 or less.
8. The golf ball of claim 7 , wherein the gradient quotient, GQ, is about 5 or less.
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 a 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 comprises a 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.
18. A one-piece golf ball comprising:
a sphere having a dimpled outer surface, a geometric center, and a soft transition region adjacent to the dimpled outer surface, the sphere being formed from a substantially homogenous composition; wherein the soft transition region has a thickness of up to 4 mm, comprises about 8 to 20 percent trans-polybutadiene isomer, and has a negative hardness gradient of up to 15 Shore C, and wherein the sphere has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ, defined by the equation:
G
+
T
10
×
COR
≤
7
where G is the overall negative 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.