Dual cured castable system for use in golf balls

1. 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 amino groups;

reacting the conjugated diene with an isocyanate-containing component to form a prepolymer comprising about 5 percent to about 9 percent NCO groups;

forming a curative blend comprising:

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

a hydroxy-terminated curing agent comprising at least three functional groups; and

an organic peroxide;

reacting the prepolymer and curative blend to form a composition comprising urea linkages and crosslinks between the hydrocarbons, wherein the composition has a material hardness as measured on a button of about 60 Shore D or greater and an Atti compression of about 140 to about 180; and

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

2. The method of claim 1 , wherein the step of providing a conjugated diene comprises providing a polybutadiene comprising a plurality of terminal ends comprising amino groups.

3. The method of claim 2 , wherein the plurality of terminal ends comprise primary amino groups, secondary amino groups, or a combination thereof.

4. The method of claim 1 , wherein the composition has a material hardness as measured on a button of about 62 Shore D or greater.

5. The method of claim 1 , wherein the step of reacting the prepolymer and curative blend comprises the steps of:

mixing the prepolymer and curative blend to form a mixture;

pouring the mixture into a mold;

heating the mold to a first temperature for a first period of time; and

elevating the mold to a second temperature greater than the first temperature.

6. The method of claim 1 , wherein the composition has a gel time of about 45 seconds to about 120 seconds.

7. A method of forming a golf ball comprising the steps of:

providing a core;

forming a prepolymer comprising 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 functional amino groups, and wherein the prepolymer comprises about 5 weight percent to about 9 weight percent NCO groups;

mixing the prepolymer with a curative blend to form a mixture, wherein the curative blend comprises:

a second isocyanate-reactive component comprising a trifunctional hydroxy-terminated component and an amine-terminated component selected from the group consisting of dipropylene triamine, diethylene triamine, propylene oxide based triamine, and combinations thereof; and

at least one free radical initiator;

placing a first portion of the mixture in a first cavity of a first mold half for a predetermined gel time at a first mold temperature;

positioning the core within the first cavity;

placing a second portion of the mixture in a second cavity of a second mold half for the predetermined gel time at the first mold temperature;

mating the first and second mold halves; and

raising the first mold temperature to a second mold temperature for a predetermined period of time to form a cured cover,

wherein the cured cover has an Atti compression of about 140 to about 180.

8. The method of claim 7 , wherein the predetermined gel time is about 45 seconds to about 120 seconds.

9. The method of claim 7 , wherein the cured cover has a hardness of about 60 Shore D or greater.

10. The method of claim 7 , wherein the cured cover has a hardness of about 62 Shore D or greater.

11. The method of claim 7 , wherein the first isocyanate-reactive component comprises amine-terminated polybutadiene.

12. The method of claim 7 , wherein the at least one free radical initiator comprises peroxide.

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

providing a core;

providing an amine-terminated polybutadiene;

reacting the amine-terminated polybutadiene with an isocyanate-containing component to form a prepolymer comprising-about 5 percent to about 9 percent NCO groups;

forming a curative blend consisting essentially of:

a trifunctional hydroxyl-terminated component;

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

a free radical initiator;

reacting the prepolymer and curative blend to form a composition consisting essentially of urea linkages and crosslinks between the hydrocarbons, wherein the composition has a material hardness as measured on a button of about 60 Shore D or greater and an Atti compression of about 140 to about 180; and

casting a cover about the core from the composition.

14. The method of claim 13 , wherein the free radical initiator comprises an organic peroxide.

15. The method of claim 13 , wherein the step of casting comprises the steps of:

placing a first portion of the composition in a first cavity of a first mold half for a predetermined gel time at a first mold temperature;

positioning the core within the first cavity;

placing a second portion of the composition in a second cavity of a second mold half for the predetermined gel time at the first mold temperature;

mating the first and second mold halves; and

raising the first mold temperature to a second mold temperature for a predetermined period of time to form a cured cover.

16. The method of claim 15 , wherein the predetermined gel time is about 45 seconds to about 120 seconds.

17. The method of claim 15 , wherein the cured cover has a hardness of about 64 Shore D or greater.

18. The method of claim 7 , wherein the at least one free radical initiator is selected from the group consisting of persulfates, azo compounds, benzophenones, hydrazides, and combinations thereof.