Highly-neutralized acid polymers and their use in golf balls

1. A golf ball having a cover layer, wherein the cover layer is formed from a polymer composition comprising:

at least 25 wt %, based on the total polymeric weight of the polymer composition, of an acid polymer having acid groups, wherein 100% of the acid groups are neutralized; and

at least 10 wt %, based on the total polymeric weight of the polymer composition, of a non-fatty acid melt flow modifier selected from the group consisting of polyesters, polyacrylates, polyurethanes, polyethers, thermoplastic polyureas, and combinations thereof;

wherein the polymer composition is substantially free of fatty acids and their salts and has a melt flow index of from 0.5 g/10 min to 10.0 g/10 min.

2. The golf ball of claim 1 , wherein the non-fatty acid melt flow modifier has a melt flow index of from 10 g/10 min to 1,000 g/10 min and a weight average molecular weight of from 1,000 to 100,000.

3. The golf ball of claim 1 , wherein the cover layer is an inner cover layer having a thickness of from 0.010 in to 0.060 in.

4. The golf ball of claim 1 , wherein the cover layer has a material hardness of from 30 Shore D to 80 Shore D.

5. The golf ball of claim 1 , wherein the polymer composition consists essentially of:

from 25 wt % to 90 wt %, based on the total polymeric weight of the polymer composition, of the acid polymer;

from 10 wt % to 75 wt %, based on the total polymeric weight of the polymer composition, of the non-fatty acid melt flow modifier; and

from 0 wt % to 60 wt %, based on the total weight of the polymer composition, of an inorganic additive.

6. The golf ball of claim 1 , wherein the polymer composition has a flexural modulus of from 10,000 psi to 125,000 psi.

7. The golf ball of claim 1 , wherein the polymer composition has a notched izod impact strength of at least 2 ft·lb/in.