GOLF BALL DIMPLES EXHIBITING TWO DISTINCT HARDNESS REGIONS DERIVED FROM A SINGLE COVER LAYER AND METHODS OF MAKING SAME
The present invention is directed to a golf ball having a cover in which the dimples have two distinct hardness regions. The cover of the present invention is formed from a castable formulation including at least one prepolymer that incorporates some degree of unsaturation in the backbone of the polymer, at least one curative, and at least one free radical initiator. The present invention also explores the methods of making such golf balls. The methods of the present invention allow for the production of a golf ball dimple with two distinct hardnesses to be formed using a single castable formulation.
1 . A golf ball comprising:
a core; and
a cover disposed about the core, wherein the cover has an outermost surface and comprises the reaction product of at least one prepolymer, at least one curative, and at least one free radical initiator, wherein the outermost surface comprises at least a first portion and a second portion, wherein at least a portion of the first portion or second portion comprises a plurality of dimples, wherein the first portion has a first hardness and the second portion has a second hardness, and wherein the first and second hardnesses are different.
2 . The golf ball of claim 1 , wherein the first hardness is about 55 Shore D to about 75 Shore D and the second hardness is about 30 Shore D to about 50 Shore D.
3 . The golf ball of claim 1 , wherein the first hardness is at least 20 percent greater than second hardness.
4 . The golf ball of claim 1 , wherein the first portion has a first crosslinking density and the second portion has a second crosslinking density, and wherein the first crosslinking density is greater than the second crosslinking density by at least about 15 percent.
5 . The golf ball of claim 1 , wherein the prepolymer is a reaction product of an isocyanate-containing component and an isocyanate-reactive component.
6 . The golf ball of claim 5 , wherein the isocyanate-reactive component comprises a conjugated diene hydrocarbon.
7 . The golf ball of claim 1 , wherein the free radical initiator is present in an amount of about 5 pph or less.
8 . A golf ball comprising:
a core; and
a cover disposed about the core, wherein the cover has an outermost surface comprising a first portion comprising a plurality of dimples and a second portion comprising a plurality of land areas, wherein the first portion has a first hardness and the second portion has a second hardness, and wherein the first and second hardnesses are different.
9 . The golf ball of claim 8 , wherein the first hardness is about 55 Shore D to about 75 Shore D and the second hardness is about 30 Shore D to about 50 Shore D.
10 . The golf ball of claim 8 , wherein the second hardness is about 55 Shore D to about 75 Shore D and the first hardness is about 30 Shore D to about 50 Shore D.
11 . The golf ball of claim 8 , wherein the first hardness is at least 10 percent greater than second hardness.
12 . The golf ball of claim 8 , wherein the second hardness is at least 10 percent greater than first hardness.
13 . The golf ball of claim 8 , wherein the first portion has a first crosslinking density and the second portion has a second crosslinking density, and wherein the first crosslinking density is greater than the second crosslinking density by at least about 10 percent.
14 . The golf ball of claim 8 , wherein the first portion has a first crosslinking density and the second portion has a second crosslinking density, and wherein the second crosslinking density is greater than the first crosslinking density by at least about 10 percent.
15 . A golf ball comprising:
a core; and
a cover disposed about the core, wherein the cover has an outermost surface comprising a first portion comprising a plurality of dimples and a second portion comprising a plurality of land areas, wherein each dimple in the plurality of dimples comprises a first area and a second area, wherein the first area has a first hardness and the second area has a second hardness, wherein the second portion has a third hardness, and wherein the first and second hardnesses are different.
16 . The golf ball of claim 15 , wherein the second and third hardnesses are the same.
17 . The golf ball of claim 16 , wherein the first hardness is at least about 10 percent greater than the second and third hardnesses.
18 . The golf ball of claim 17 , wherein the first hardness is about 35 Shore D to about 70 Shore D and the second hardness is about 30 Shore D to about 65 Shore D.
19 . The golf ball of claim 16 , wherein the first area has a first crosslinking density and the second area has a second crosslinking density, and wherein the first crosslinking density is greater than the second crosslinking density by at least about 10 percent.
20 . The golf ball of claim 20 , wherein the second portion has a third crosslinking density, and wherein the third crosslinking density is less than the first crosslinking density.