Three-layer-core golf ball having highly-neutralized polymer outer core layer
View Patent ↗A golf ball including an inner core layer formed from a thermoset rubber composition and having a first surface hardness; a thermoplastic outer core layer having a second surface hardness, an inner surface hardness, and being formed from a copolymer of ethylene and an α,β-unsaturated carboxylic acid, an organic acid or salt thereof, and sufficient cation source to fully-neutralize the acid groups of the copolymer; an inner cover layer; and an outer cover layer; wherein the first surface hardness is substantially the same as the second surface hardness and the inner surface hardness.
1. A golf ball comprising:
an inner core layer comprising a thermoset rubber composition and having a first outer Shore D hardness and an outer diameter of about 1.3 inches to about 1.56 inches;
a thermoplastic outer core layer having a second outer Shore D hardness, and comprising a copolymer of ethylene and an α,β-unsaturated carboxylic acid, a magnesium salt of oleic acid, and sufficient cation source to fully-neutralize the acid groups of the copolymer;
an inner cover layer; and
an outer cover layer;
wherein the first outer hardness is greater than the second outer hardness and the outer core layer has a thickness of about 0.01 inches to about 0.05 inches.
2. The golf ball of claim 1 , wherein the inner core has a diameter of about 1.4 inches to about 1.55 inches.
3. The golf ball of claim 1 , wherein the outer core layer has a thickness of about 0.02 inches to about 0.04 inches.
4. The golf ball of claim 1 , wherein the cation source is selected from a group consisting of metal cations of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, and aluminum.
5. The golf ball of claim 1 , wherein the first outer surface hardness is about 46 Shore D to about 60 Shore D.
6. The golf ball of claim 5 , wherein the first outer surface hardness is about 49 Shore D to about 55 Shore D.
7. The golf ball of claim 1 , wherein the second outer surface hardness is about 40 Shore D to about 54 Shore D.
8. The golf ball of claim 7 , wherein the second outer surface hardness is about 45 Shore D to about 51 Shore D.
9. The golf ball of claim 1 , wherein the inner cover layer comprises an ionomer and the outer cover layer comprises a cast polyurethane.