Golf balls including crosslinked thermoplastic polyurethane

1. A golf ball comprising:

a crosslinked thermoplastic polyurethane elastomer;

the crosslinked thermoplastic polyurethane elastomer including hard segments and soft segments;

wherein the crosslinked thermoplastic polyurethane elastomer includes crosslinks formed from allyl ether side groups, and the crosslinked thermoplastic polyurethane elastomer is the reaction product formed from reacting an organic isocyanate with a mixture of the following reactants:

(a) an unsaturated diol chain extender, wherein the unsaturated diol chain extender has two primary hydroxyl groups and at least one allyl ether side group, of the formula

in which R is alkyl group with or without modified functional groups, and x and y are integers of 1 to 4;

(b) a secondary chain extender, having at least two reaction sites with isocyanates and having a molecular weight of less than about 450;

(c) a long chain polyol having a molecular weight of between about 500 and about 4,000; and

(d) a sufficient amount of free radical initiator, so as to be capable of generating free radicals that induce crosslinking structures in the hard segments by free radical initiation.

2. The golf ball of claim 1 , wherein

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the secondary chain extender is about 100:6;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the long chain polyol is about 100:44;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the organic isocyanate is about 100:39;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the free radical initiator is about 100:0.5.

3. The golf ball of claim 1 , wherein the free radical initiator is present in the crosslinked thermoplastic polyurethane elastomer in a weight ratio of free radical initiator to unsaturated diols of from about 0.1:100 to about 100:100.

4. The golf ball of claim 3 , wherein a weight ratio of the free radical initiator to the unsaturated diols is about 5:100.

5. The golf ball of claim 1 , wherein a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the unsaturated diols is from about 100:0.1 to about 100:25.

6. The golf ball of claim 1 , wherein a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the unsaturated diols is about 100:10.

7. The golf ball of claim 1 , wherein the unsaturated diol is trimethylolpropane monoallylether.

8. The golf ball of claim 1 , wherein the free radical initiator generates free radicals through at least one of thermal cleavage and UV radiation.

9. The golf ball of claim 1 , wherein the free radical initiator is selected from the group consisting of peroxides, sulfurs, and sulfides.

10. The golf ball of claim 1 , wherein the NCO index of the reactants which form the crosslinked thermoplastic polyurethane elastomer is from about 0.9 to about 1.3.

11. The golf ball of claim 1 , wherein:

the golf ball comprises a core and a cover layer substantially surrounding the core; and

the cover layer comprises the crosslinked thermoplastic polyurethane elastomer having crosslinks located in the hard segments.

12. The golf ball of claim 1 , wherein:

the golf ball comprises a core and a cover layer substantially surrounding the core;

the cover layer comprises an inner cover layer substantially surrounding the core and an outer cover layer substantially surrounding the inner cover layer;

wherein the inner cover layer comprises the crosslinked thermoplastic polyurethane elastomer having crosslinks located in the hard segments.

13. The golf ball of claim 1 , wherein:

the golf ball comprises a core and a cover layer substantially surrounding the core;

the cover layer comprises an inner cover layer substantially surrounding the core and an outer cover layer substantially surrounding the inner cover layer;

wherein the outer cover layer comprises the crosslinked thermoplastic polyurethane elastomer having crosslinks located in the hard segments.

14. The golf ball of claim 13 , wherein the outer cover layer has a Shore D hardness of between about 20 and about 75.

15. A golf ball comprising: an inner core layer, an outer core layer substantially surrounding the inner core layer, an inner cover layer substantially surrounding the outer core layer, and an outer cover layer substantially surrounding the inner cover layer;

wherein the outer cover layer comprises a crosslinked thermoplastic polyurethane elastomer having crosslinks located in hard segments, the crosslinks being the reaction product of unsaturated of unsaturated bonds located in the hard segments as catalyzed by a free radical initiator; and

the golf ball satisfies the following requirements:

(1) the golf ball has a compression deformation of from about 2 to about 4 millimeters under a load of 10 to 130 kilograms;

(2) the inner core layer has a coefficient of restitution at 40 meters per second from about 0.79 to about 0.92, the coefficient of restitution of the inner core being higher than that of the golf ball;

(3) the outer cover layer has a Shore D hardness from about 20 to about 75; and

(4) the outer cover layer has a flexural modulus of from about 1 kpsi to about 150 kpsi.

16. The golf ball of claim 15 , wherein the crosslinked thermoplastic polyurethane elastomer comprises unsaturated diols as chain extenders.

17. The golf ball of claim 16 , wherein the weight ratio of the crosslinked thermoplastic polyurethane elastomer to the unsaturated diols is from 100:0.1 to 100:15.

18. The golf ball of claim 15 , wherein the free radical initiator is present in the crosslinked thermoplastic polyurethane elastomer in a weight ratio of free radical initiator to unsaturated diols of from about 0.1:100 to about 100:100.

19. The golf ball of claim 15 , wherein the crosslinked thermoplastic polyurethane elastomer includes crosslinks formed from allyl ether side groups, and the crosslinked thermoplastic polyurethane elastomer is the reaction product formed from reacting an organic isocyanate with a mixture of the following reactants:

(a) an unsaturated diol chain extender, wherein the unsaturated diol chain extender has two primary hydroxyl groups and at least one allyl ether side group, of the formula

in which R is alkyl group with or without modified functional groups, and x and y are integers of 1 to 4;

(b) a secondary chain extender, having at least two reaction sites with isocyanates and having a molecular weight of less than about 450;

(c) a long chain polyol having a molecular weight of between about 500 and about 4,000; and

(d) a sufficient amount of free radical initiator, so as to be capable of generating free radicals that induce crosslinking structures in the hard segments by free radical initiation.

20. The golf ball of claim 15 , wherein the wherein the unsaturated diol chain extender is trimethylolpropane monoallylether.

21. The golf ball of claim 19 , wherein a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the unsaturated diol chain extender is about 100:10.

22. The golf ball of claim 19 , wherein

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the secondary chain extender is about 100:6;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the long chain polyol is about 100:44;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the organic isocyanate is about 100:39;

a weight ratio of the crosslinked thermoplastic polyurethane elastomer to the free radical initiator is about 100:0.5.