DUAL CORE GOLF BALL HAVING POSITIVE-HARDNESS-GRADIENT THERMOPLASTIC INNER CORE AND SHALLOW NEGATIVE-HARDNESS-GRADIENT OUTER CORE LAYER

• US 20110275456A1
• Filed: 05/09/2011
• Published: 11/10/2011
• Est. Priority Date: 11/14/2007
• Status: Active Grant

• Current Assignee: Acushnet Company (FILA Holdings Corp.)
• Original Assignee: Acushnet Company (FILA Holdings Corp.)
• Inventors: Sullivan, Michael J., Comeau, Brian
• Granted Patent: US 8,740,725 B2
• Time in Patent Office: Days
• US Class Current: 473/373
• CPC Class Codes: A63B 37/0003 Golf balls
• CPC Class Codes: A63B 37/0044 Hardness gradient
• CPC Class Codes: A63B 37/0051 Materials other than polybutadienes; Constructional details
• CPC Class Codes: A63B 37/00621 Centre hardness
• CPC Class Codes: A63B 37/00622 Surface hardness
• CPC Class Codes: A63B 37/0063 Hardness gradient
• CPC Class Codes: A63B 37/02 Special cores balls with finger holes A63B37/0001, golf ball cores A63B37/005

Abstract

A golf ball includes a thermoplastic inner core layer having a geometric center hardness less than a surface hardness to define a “positive hardness gradient.” An outer core layer is disposed about the inner core, the outer core being formed from a thermoset rubber composition and having a surface hardness less than a hardness at a point about 0.5 to 2 mm from an interface between the inner core and the outer core layer to define a shallow “negative hardness gradient.” An inner cover layer is formed over the outer core layer and an outer cover layer is formed over the inner cover layer. The “positive hardness gradient” of the inner core is up to about 10 Shore C and the shallow “negative hardness gradient” of the outer core layer is less than about 10 Shore C.

Claims

1. A golf ball comprising:

an inner core layer consisting essentially of a thermoplastic material and having a geometric center hardness less than a surface hardness to define a positive hardness gradient;

an outer core layer disposed about the inner core, the outer core being formed from a thermoset rubber composition and having a surface hardness less than a hardness at a point about 0.5 to 2 mm from an interface between the inner core and the outer core layer to define a shallow negative hardness gradient;

an inner cover layer disposed outer core layer; and

an outer cover layer disposed about the inner cover layer,

wherein the positive hardness gradient is up to about 10 Shore C and the shallow negative hardness gradient is less than about 10 Shore C.

2. The golf ball of claim 1, wherein the thermoplastic material comprises an ionomer, a highly-neutralized ionomer, a thermoplastic polyurethane, a thermoplastic polyurea, a styrene block copolymer, a polyester amide, polyester ether, a polyethylene acrylic acid copolymer or terpolymer, or a polyethylene methacrylic acid copolymer or terpolymer.

3. The golf ball of claim 2, wherein the thermoplastic material is a highly-neutralized ionomer.

4. The golf ball of claim 1, wherein the geometric center of the thermoplastic inner core has a hardness of about 60 Shore C to 70 Shore C.

5. The golf ball of claim 1, wherein the surface of the thermoplastic inner core has a hardness of about 68 Shore C to 78 Shore C.

6. The golf ball of claim 1, wherein the surface of the outer core layer has a hardness of about 60 Shore C to 70 Shore C.

7. The golf ball of claim 1, wherein the hardness at a point about 0.5 to 2 mm from the interface is about 66 Shore C to 76 Shore C.

8. The golf ball of claim 1, wherein the surface of the thermoplastic inner core has a hardness of about 72 Shore C to 77 Shore C.

9. The golf ball of claim 1, wherein the surface of the outer core layer has a hardness of about 70 Shore C to 80 Shore C.

10. The golf ball of claim 1, wherein the hardness at a point about 0.5 to 2 mm from the interface is about 70 Shore C to 80 Shore C.

11. The golf ball of claim 1, wherein the positive hardness gradient is about 2 to 7 Shore C.

12. The golf ball of claim 11, wherein the positive hardness gradient is about 3 to 5 Shore C.

13. The golf ball of claim 1, wherein the shallow negative hardness gradient is about 2 to 8 Shore C.

14. The golf ball of claim 13, wherein the shallow negative hardness gradient is about 3 to 6 Shore C.

15. The golf ball of claim 1, wherein the outer core layer comprises diene rubber and a metal salt of a carboxylic acid in an amount of about 25 phr to about 40 phr and has a ratio of antioxidant to initiator of about 0.40 or greater when normalized to 100% activity.

16. The golf ball of claim 15, wherein the ratio of antioxidant to initiator is about 0.50 or greater.

17. The golf ball of claim 15, wherein the initiator is present in the amount from about 0.25 phr to about 5.0 phr at 100% activity and the antioxidant is present in amount of about 0.2 phr to about 1 phr.

18. The golf ball of claim 1, wherein the outer core layer comprises a soft and fast agent.