GOLF BALLS HAVING DUAL-LAYER CORES WITH METAL-CONTAINING CENTERS

1 . A golf ball having a multi-layered core, comprising:

i) an inner core having a diameter of from 0.100 inches to 1.100 inches and formed from a metal material dispersed in a polymer matrix, wherein the polymer matrix is a highly neutralized polymer composition comprising:

an 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;

a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof;

an organic acid or salt thereof; and

a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition;

ii) an outer core layer disposed about the inner core, the outer core layer being formed from a thermoset material and having a thickness of from 0.200 inches to 1.200 inches, an outer surface of from 40 Shore D to 85 Shore D, an inner surface hardness of from 42 Shore D to 87 Shore D, and a zero or negative hardness gradient; and

iii) a cover having at least one layer disposed about the multi-layered core; and

wherein the specific gravity of the inner core is greater than the specific gravity of the outer core layer.

2 . The golf ball of claim 1 , wherein the acid copolymer of ethylene and an α,β-unsaturated carboxylic acid does not include a softening monomer, the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and the organic acid salt is magnesium oleate present in an amount of 20 parts or greater per 100 parts of acid copolymer and non-acid copolymer combined.

3 . The golf ball of claim 1 , wherein the cation source is present in an amount sufficient to neutralize 110% or greater of all acid groups present in the composition.

4 . A golf ball having a multi-layered core, comprising:

i) an inner core having a diameter of from 0.100 inches to 1.100 inches and formed from a metal material dispersed in a polymer matrix, wherein the polymer matrix is a highly neutralized polymer composition comprising:

an 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;

a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof;

an organic acid or salt thereof; and

a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition;

ii) an outer core layer disposed about the inner core, the outer core layer being formed from a thermoset material and having a thickness of from 0.200 inches to 1.200 inches, an outer surface of from 43 Shore D to 88 Shore D, and an inner surface hardness of from 40 Shore D to 85 Shore D, and a positive hardness gradient; and

iii) a cover having at least one layer disposed about the multi-layered core; and

wherein the specific gravity of the inner core is greater than the specific gravity of the outer core layer.

5 . The golf ball of claim 4 , wherein the acid copolymer of ethylene and an α,β-unsaturated carboxylic acid does not include a softening monomer, the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and the organic acid salt is magnesium oleate present in an amount of 20 parts or greater per 100 parts of acid copolymer and non-acid copolymer combined.

6 . The golf ball of claim 4 , wherein the cation source is present in an amount sufficient to neutralize 110% or greater of all acid groups present in the composition.

7 . A golf ball having a multi-layered core, comprising:

i) an inner core having a diameter of from 0.100 inches to 1.100 inches, a positive hardness gradient, and formed from a metal material dispersed in a thermoset polymeric matrix;

ii) an outer core layer disposed about the inner core, the outer core layer having a thickness of from 0.200 inches to 1.200 inches and formed from a highly neutralized polymer composition comprising:

an 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;

a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof;

an organic acid or salt thereof; and

a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition; and

iii) a cover having at least one layer disposed about the multi-layered core;

wherein the specific gravity of the inner core is greater than the specific gravity of the outer core layer.

8 . The golf ball of claim 7 , wherein the acid copolymer of ethylene and an α,β-unsaturated carboxylic acid does not include a softening monomer, the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and the organic acid salt is magnesium oleate present in an amount of 20 parts or greater per 100 parts of acid copolymer and non-acid copolymer combined.

9 . The golf ball of claim 7 , wherein the cation source is present in an amount sufficient to neutralize 110% or greater of all acid groups present in the composition.

10 . A golf ball having a multi-layered core, comprising:

i) an inner core having a diameter of from 0.100 inches to 1.100 inches, a zero or negative hardness gradient, and formed from a metal material dispersed in a thermoset polymeric matrix;

ii) an outer core layer disposed about the inner core, the outer core layer having a thickness of from 0.200 inches to 1.200 inches and formed from a highly neutralized polymer composition comprising:

an 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;

a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof;

an organic acid or salt thereof; and

a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition; and

iii) a cover having at least one layer disposed about the multi-layered core;

wherein the specific gravity of the inner core is greater than the specific gravity of the outer core layer.

11 . The golf ball of claim 10 , wherein the acid copolymer of ethylene and an α,β-unsaturated carboxylic acid does not include a softening monomer, the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and the organic acid salt is magnesium oleate present in an amount of 20 parts or greater per 100 parts of acid copolymer and non-acid copolymer combined.

12 . The golf ball of claim 10 , wherein the cation source is present in an amount sufficient to neutralize 110% or greater of all acid groups present in the composition.

13 . A golf ball having a multi-layered core, comprising:

i) an inner core having a diameter of from 0.100 inches to 1.100 inches and formed from a metal material dispersed in a polymer matrix, wherein the polymer matrix is a first highly neutralized polymer composition;

ii) an outer core layer disposed about the inner core, the outer core layer having a thickness of from 0.200 inches to 1.200 inches and formed from a second highly neutralized polymer composition; and

iii) a cover having at least one layer disposed about the multi-layered core;

wherein at least one of the first highly neutralized polymer composition and the second highly neutralized polymer composition comprises:

an 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;

a non-acid polymer selected from the group consisting of polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, and functionalized derivatives thereof;

an organic acid or salt thereof; and

a cation source present in an amount sufficient to neutralize greater than 80% of all acid groups present in the composition; and

wherein the specific gravity of the inner core is greater than the specific gravity of the outer core layer.

14 . The golf ball of claim 13 , wherein the acid copolymer of ethylene and an α,β-unsaturated carboxylic acid does not include a softening monomer, and wherein the acid is selected from acrylic acid and methacrylic acid and is present in the acid copolymer in an amount of from 15 mol % to 30 mol %.

15 . The golf ball of claim 14 , wherein the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates and is present in an amount of greater than 50 wt %, based on the combined weight of the acid copolymer and the non-acid polymer.

16 . The golf ball of claim 15 , wherein the non-acid polymer is ethylene-n-butyl acrylate, wherein the n-butyl-acrylate is present in an amount of 20 wt % or greater, based on the total weight of the non-acid polymer.

17 . The golf ball of claim 16 , wherein the highly neutralized polymer composition has a solid sphere compression of 40 or less and a coefficient of restitution of 0.820 or greater.

18 . The golf ball of claim 14 , wherein the non-acid polymer is an alkyl acrylate rubber selected from ethylene-alkyl acrylates and ethylene-alkyl methacrylates and is present in an amount of less than 50 wt %, based on the combined weight of the acid copolymer and the non-acid polymer.

19 . The golf ball of claim 18 , wherein the non-acid polymer is ethylene-n-butyl acrylate, wherein the n-butyl-acrylate is present in an amount of 20 wt % or greater, based on the total weight of the non-acid polymer.

20 . The golf ball of claim 19 , wherein the highly neutralized polymer composition has a solid sphere compression of 100 or greater and a coefficient of restitution of 0.860 or greater.

21 . The golf ball of claim 13 , wherein the organic acid salt is magnesium oleate, and wherein the magnesium oleate is present in an amount of 30 parts or greater, per 100 parts of acid copolymer and non-acid copolymer combined.

22 . The golf ball of claim 21 , wherein the cation source is present in an amount sufficient to neutralize 110% or greater of all acid groups present in the composition.