Dual cured castable polyurethane system for use in golf balls

1. A golf ball comprising a core and a cover, wherein the cover is formed from a composition comprising:

a prepolymer consisting essentially of the reaction product of an isocyanate-containing component and a first isocyanate-reactive component, wherein the first isocyanate-reactive component comprises a conjugated diene hydrocarbon comprising at least two secondary amino groups; and

a curative blend comprising a second isocyanate-reactive component comprising a trifunctional hydroxy-terminated compound, an amine-terminated compound selected from the group consisting of dipropylene triamine, diethylene triamine, propylene oxide based triamine, and combinations thereof, and at least one free radical source;

wherein the composition comprises crosslinks between the hydrocarbons.

2. The golf ball of claim 1 , wherein the isocyanate-containing component comprises at least two isocyanate groups.

3. The golf ball of claim 1 , wherein the free radical source is selected from the group consisting of peroxides, persulfates, azo compounds, benzophenones, hydrazides, and combinations thereof.

4. The golf ball of claim 3 , wherein the free radical source is present in the curative blend in an amount of about 5 pph or less.

5. The golf ball of claim 4 , wherein the free radical source is present in the curative blend in an amount of about 2.5 pph or less.

6. The golf ball of claim 1 , wherein the core comprises a thermoset material.

7. The golf ball of claim 6 , wherein the thermoset material comprises butadiene rubber.

8. The golf ball of claim 1 , wherein the at least one free radical source comprises peroxide.

9. The golf ball of claim 8 , wherein the peroxide comprises dicumyl peroxide, α, α-bis(t-butyl peroxy) diisopropylbenzene, or a mixture thereof.

10. A golf ball comprising:

a core; and

a cover formed from a composition comprising:

a prepolymer consisting essentially of:

a polymer backbone comprising a conjugated diene groups and urea linkages; and

a plurality of terminal ends comprising isocyanate groups;

a curative blend comprising an isocyanate-reactive component, an amine-terminated compound selected from the group consisting of dipropylene triamine, diethylene triamine, propylene oxide based triamine, and combinations thereof, and a free radical source, wherein the isocyanate-reactive component comprises a trifunctional hydroxy-terminated compound capable of reacting with the isocyanate groups, and wherein the free radical source is capable of crosslinking the polymer backbone.

11. The golf ball of claim 10 , wherein the polymer backbone comprises polybutadiene.

12. The golf ball of claim 10 , wherein the free radical initiator comprises peroxide.

13. The golf ball of claim 10 , wherein the composition further comprises an ionomer.

14. The golf ball of claim 10 , wherein the free radical source is selected from the group consisting of peroxides, persulfates, azo compounds, benzophenones, hydrazides, and combinations thereof.

15. The golf ball of claim 12 , wherein the peroxide is selected from the group consisting of dicumyl peroxide, α, α-bis(t-butyl peroxy) diisopropylbenzene, di-t-amyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, di-t-butyl peroxide, 2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, n-butyl-4,4-bis(t-butylperoxy) valerate, lauryl peroxide, benzoyl peroxide, t-butyl hydroperoxide, t-butyl cumylperoxide, t-butyl peroxybenzoate, 2,4-dichloro-benzoyl peroxide, and mixtures thereof.

16. The golf ball of claim 15 , wherein the peroxide is selected from the group consisting of dicumyl peroxide, α, α-bis(t-butyl peroxy) diisopropylbenzene, and mixtures thereof.

17. A method of forming a golf ball comprising a core and a cover comprising the steps of:

providing a core;

providing a conjugated diene comprising a plurality of terminal ends comprising secondary amine groups;

reacting the conjugated diene with an isocyanate-containing component to form a prepolymer comprising urea linkages;

forming a curative blend comprising:

a trifunctional hydroxy-terminated curing agent;

an amine-terminated compound selected from the group consisting of dipropylene triamine, diethylene triamine, propylene oxide based triamine, and combinations thereof; and

an organic peroxide;

reacting the prepolymer and curative blend to form a composition comprising urethane linkages and crosslinks between the hydrocarbons; and

casting a golf ball cover about the core from the composition.

18. The golf ball of claim 17 , wherein the isocyanate-containing component comprises at least two isocyanate groups.

19. The method of claim 17 , wherein the step of providing a core comprises selecting a thermoset material and forming the core from the thermoset material.

20. The method of claim 17 , wherein the step of forming a curative blend comprises:

selecting an organic peroxide from the group consisting of dicumyl peroxide, α, α-bis(t-butyl peroxy) diisopropylbenzene, and mixtures thereof; and

adding the organic peroxide to the curative blend.