Highly-neutralized acid polymer compositions having a low moisture vapor transmission rate and their use in golf balls

1. A golf ball comprising a core and a cover, wherein the ball has a moment of inertia of 85 g·cm 2 or greater, and wherein the core has a specific gravity of 1.05 or less and is formed from a moisture resistant composition, the moisture resistant composition having a moisture vapor transmission rate (MVTR) of 12.5 g·mil/100 in 2 /day or less and comprising a highly neutralized acid polymer.

2. The golf ball of claim 1 , wherein the core has a specific gravity of 0.95 or less.

3. The golf ball of claim 1 , wherein the moisture resistant composition is foamed.

4. The golf ball of claim 1 , wherein the moisture resistant composition further comprises a specific gravity reducing filler.

5. The golf ball of claim 1 , wherein at least 80% of the acid groups present in the moisture resistant composition are neutralized to salts.

6. The golf ball of claim 5 , wherein at least 50% of the acid groups present in the moisture resistant composition are neutralized to salts having counterions selected from the group consisting of Zn, Ca, and combinations thereof.

7. The golf ball of claim 1 , wherein the cover consists of an inner cover layer and an outer cover layer, and wherein the inner cover layer is formed from a composition comprising a high density filler.

8. The golf ball of claim 1 , wherein the core is an inner core layer, and wherein the golf ball further comprises an outer core layer having a specific gravity of 1.05 or less.

9. The golf ball of claim 8 , wherein the outer core layer is formed from a foamed composition.

10. The golf ball of claim 8 , wherein the outer core layer is formed from a composition comprising a specific gravity reducing filler.

11. The golf ball of claim 8 , wherein the inner core layer is non-spherical.

12. The golf ball of claim 11 , wherein the specific gravity of the inner core layer is less than the specific gravity of the outer core layer.

13. The golf ball of claim 8 , wherein the inner core layer has a diameter of 1.50 inches or less and the outer core layer has a thickness of from 0.03 inches to 0.15 inches.

14. The golf ball of claim 8 , wherein the ball further comprises an intermediate layer disposed between the cover and the outer core layer, and wherein the intermediate layer is a thin dense layer having a specific gravity of 1.2 or greater and a thickness of from 0.001 inches to 0.05 inches.

15. The golf ball of claim 1 , wherein the ball has a moment of inertia of 90 g·cm 2 or greater.

16. The golf ball of claim 1 , wherein the ball has a moment of inertia of 95 g·cm 2 or greater.