Golf ball having a thermosetting intermediate and outer cover and thermoplastic inner cover

1. A golf ball comprising:

a core; and

a cover disposed adjacent the core, the cover comprising:

a thermoplastic inner cover layer disposed about the core and having a hardness between 55 and 60 Shore D;

an outer cover layer having a hardness between 55 and 60 Shore D; and

a thermosetting polyurethane or polyurea intermediate cover layer disposed between the inner and outer cover layers, the intermediate cover layer having a hardness of 80 Shore D to 90 Shore D and being greater than the inner cover layer hardness and the outer cover layer hardness;

wherein the inner cover comprises a fully-neutralized ionomer and the outer cover layer comprises a polyurethane, a polyurea, or a urethane-urea blend.

2. The golf ball of claim 1 , wherein the intermediate layer hardness is greater than the inner cover layer hardness and greater than the outer cover layer hardness by at least 5 Shore D.

3. The golf ball of claim 2 , wherein the intermediate layer hardness is greater than the inner cover layer hardness and greater than the outer cover layer hardness by at least 10 Shore D.

4. The golf ball of claim 1 , wherein the polyurethane, polyurea, or urethane-urea blend is a castable thermoset or reaction injection moldable thermoset.

5. The golf ball of claim 1 , wherein the outer cover comprises a castable thermoset polyurea, the inner cover layer comprises an ionomer blend of two or more ionomers having differing metal cations, and the intermediate cover layer comprises a thermosetting polyurea.

6. The golf ball of claim 1 , wherein the core comprises a center and at least one outer core layer.

7. The golf ball of claim 1 , wherein the center is a single solid layer formed from a homogeneous composition.

8. The golf ball of claim 1 , wherein the thermosetting polyurethane or polyurea intermediate layer further comprises a polyolefin, a polyamide, or an acrylonitrile-butadiene-styrene polymer.

9. The golf ball of claim 1 , wherein the outer cover comprises a thermoplastic polyurethane, the inner cover layer comprises an ionomer blend of two or more ionomers having differing metal cations, and the intermediate cover layer comprises a polyurea formed from the reaction product of a prepolymer comprising an isocyanate and an amine-terminated PTMEG and an amine-terminated curing agent.

10. The golf ball of claim 1 , wherein the thermoplastic inner cover layer further comprises polyolefins, metallocenes, polyesters, polyamides, thermoplastic elastomers, copolyether-amides, copolyether-esters, or mixtures thereof.

11. The golf ball of claim 1 , wherein a combination of the inner cover, the intermediate cover, and the outer cover have a total thickness of 0.125 inches or less.

12. The golf ball of claim 10 , wherein the total thickness is 0.115 inches or less.

13. The golf ball of claim 1 , wherein the outer cover layer hardness is less than the inner cover layer hardness.

14. A golf ball comprising:

a core; and

a cover disposed adjacent the core, the cover comprising:

a fully-neutralized ionomeric thermoplastic inner cover layer disposed about the core and having a hardness of 55 Shore D to 60 Shore D;

a castable thermoset outer cover layer having a hardness between 55 Shore D and 60 Shore D; and

a non-ionomeric thermosetting intermediate cover layer disposed between the inner and outer cover layers and having a hardness of 80 Shore D to 90 Shore D and being greater than the inner cover layer and the outer cover layer;

wherein the inner cover layer has a first thickness, the outer cover layer has a second thickness, and the intermediate cover layer has a third thickness less than the first or second thickness by at least 20%.

15. A golf ball comprising:

a core; and

a cover disposed adjacent the core, the cover comprising:

a fully-neutralized ionomeric thermoplastic inner cover layer disposed about the core and having a hardness of 55 Shore D to 60 Shore D;

a castable thermoset polyurethane outer cover layer having a hardness between 55 Shore D and 60 Shore D; and

a non-ionomeric thermosetting polyurethane polyurea intermediate cover layer disposed between the inner and outer cover layers and having a hardness greater than the inner cover layer and the outer cover layer;

wherein the inner cover layer has a first thickness, the outer cover layer has a second thickness, and the intermediate cover layer has a hardness greater than 75 Shore D, and a third thickness less than the first or second thickness by at least 20%.