Golf balls having at least one layer formed from a plasticized acid copolymer composition
The present invention is directed to multi-layer golf balls including a layer formed from a relatively soft or low modulus HNP composition and a layer formed from a relatively hard or high modulus HNP composition. Optionally, the soft (or low modulus) HNP composition and/or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.
1. A four-piece golf ball consisting of the following four layers:
(a) a thermoset rubber center having a diameter of from 1.200 inches to 1.500 inches, a center hardness of from 55 Shore C to 75 Shore C, and a surface hardness of from 45 Shore C to 90 Shore C;
(b) a first intermediate layer having a thickness of from 0.032 inches to 0.075 inches and formed from a composition comprising a first acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates;
(c) a second intermediate layer having a thickness of from 0.032 inches to 0.080 inches, a surface hardness greater than or equal to the surface hardness of the center and the center hardness of the center, and formed from a composition comprising a second acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates; and
(d) an outer cover layer having a surface hardness of from 58 Shore D to 75 Shore D;
wherein at least one of the first intermediate layer composition and the second intermediate layer composition is a plasticized composition comprising from 0.5 wt % to 80 wt %, based on the total weight of the composition, of a plasticizer; and
wherein at least one of the first intermediate layer composition and the second intermediate layer composition is at least partially neutralized such that at least 70% of all acid groups present in the composition are neutralized.
2. The golf ball of claim 1 , wherein the first intermediate layer composition is at least partially neutralized such that at least 70% of all acid groups present in the first intermediate layer composition are neutralized.
3. The golf ball of claim 1 , wherein at least 95% of all acid groups present in the first intermediate layer composition are neutralized.
4. The golf ball of claim 1 , wherein the surface hardness of the second intermediate layer is greater than the surface hardness of the first intermediate layer.
5. The golf ball of claim 1 , wherein the plasticizer is selected from the group consisting of fatty acid esters.