GOLF BALL COMPOSITIONS
Disclosed herein are soft and stiff compositions, i.e., compositions which have a flexural modulus that is greater than the value that is expected based on the composition's hardness. The compositions preferably have a hardness/modulus relationship represented by the formula H ≦11.889 Ln( M )+42, where H is the hardness of the composition, in JIS-C, and M is the flexural modulus of the composition, in ksi; or a softness/stiffness relationship represented by the formula if M <56, then H ≦8.5218 Ln( M )+26.5 if M ≧56, then H <8.5218 Ln( M )+28.5, where H is the hardness of the composition, in Shore D, and M is the flexural modulus of the composition, in ksi.
1 . A golf ball comprising:
a core;
an inner cover layer having a surface hardness of 60 Shore D or greater; and
an outer cover layer having a surface hardness of 65 Shore D or less;
wherein the surface hardness of the outer cover layer is less than the surface hardness of the inner cover layer; and
wherein the inner cover layer is formed from a composition having a JIS-C hardness (H) and a flexural modulus in ksi (M) wherein H≦11.889 Ln(M)+42, and wherein M>6 ksi.
2 . The golf ball of claim 1 , wherein H≦11.889 Ln(M)+41.
3 . The golf ball of claim 1 , wherein H≦11.889 Ln(M)+40.
4 . The golf ball of claim 1 , wherein M>40 ksi.
5 . The golf ball of claim 4 , wherein H≦9.45 Ln(−0.0105M 2 +3.95M−14)+40.
6 . A golf ball comprising:
a core;
an inner cover layer having a surface hardness of 60 Shore D or greater; and
an outer cover layer having a surface hardness of 65 Shore D or less;
wherein the surface hardness of the outer cover layer is less than the surface hardness of the inner cover layer; and
wherein the outer cover layer is formed from a composition having a JIS-C hardness (H) and a flexural modulus in ksi (M) wherein H≦11.889 Ln(M)+42, and wherein M>6 ksi.
7 . The golf ball of claim 6 , wherein H≦11.889 Ln(M)+41.
8 . The golf ball of claim 6 , wherein H≦11.889 Ln(M)+40.
9 . The golf ball of claim 6 , wherein M>40 ksi.
10 . The golf ball of claim 9 , wherein H≦9.45 Ln(−0.0105M 2 +3.95M−14)+40.