Negative Hardness Gradient Inner Core for Dual Core Golf Ball

• US 20090011859A1
• Filed: 08/06/2008
• Published: 01/08/2009
• Est. Priority Date: 07/03/2007
• Status: Active Grant

• Current Assignee: Acushnet Company (FILA Holdings Corp.)
• Original Assignee: Acushnet Company (FILA Holdings Corp.)
• Inventors: Bulpett, David A., Sullivan, Michael J., Ladd, Derek A., Comeau, Brian
• Granted Patent: US 7,582,027 B2
• Time in Patent Office: Days
• US Class Current: 473/373
• 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 37/0064 Diameter
• CPC Class Codes: A63B 37/0075 Three piece balls, i.e. cover, intermediate layer and core
• CPC Class Codes: A63B 37/0076 Multi-piece balls, i.e. having two or more intermediate layers
• CPC Class Codes: A63B 37/008 Diameter
• CPC Class Codes: A63B 37/0092 Hardness distribution amongst different ball layers

Abstract

A golf ball includes an inner core having a first outer surface and a geometric center and is formed from a first substantially homogenous formulation throughout such that the inner core has a hardness of 30 Shore C to 45 Shore C. An outer core layer is formed around the inner core and has a second outer surface and an inner surface and is formed from a second substantially homogenous formulation throughout such that the outer core layer has a hardness of 60 Shore C to 95 Shore C. A cover layer is formed around the outer core layer. The hardness of the first outer surface is lower than the hardness of the geometric center to define a negative hardness gradient, and the hardness of the second outer surface is greater than the hardness of the inner surface to define a positive hardness gradient.

Claims

1. A golf ball comprising:

an inner core having a first outer surface and a geometric center and being formed from a first substantially homogenous formulation throughout such that the inner core has a hardness of 30 Shore C to 45 Shore C;

an outer core layer disposed about the inner core having a second outer surface and an inner surface and being formed from a second substantially homogenous formulation throughout such that the outer core layer has a hardness of 60 Shore C to 95 Shore C; and

a cover layer disposed about the outer core layer;

wherein the geometric center, the first and second outer surfaces, and the inner surface each have a hardness, the hardness of the first outer surface being lower than the hardness of the geometric center to define a negative hardness gradient, and the hardness of the second outer surface being greater than the hardness of the inner surface to define a positive hardness gradient.

2. The golf ball of claim 1, wherein the inner core comprises a metal salt of a carboxylic acid in an amount of about 10 phr to about 40 phr and has a ratio of antioxidant to initiator of about 0.40 or greater when normalized to 100% activity, and the outer core layer comprises a metal salt of a carboxylic acid in an amount of about 30 phr to about 45 phr.

3. The golf ball of claim 2, wherein the ratio of antioxidant to initiator is about 0.50 or greater.

4. The golf ball of claim 2, 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.

5. The golf ball of claim 1, wherein the hardness of the first outer surface is 42 Shore C to 60 Shore C, the hardness of the geometric center is 52 Shore C to 65 Shore C, and the negative hardness gradient has a magnitude up to −

10.

6. The golf ball of claim 1, wherein the hardness of the second outer surface is 62 Shore C to 89 Shore C, the hardness of the inner surface is 58 Shore C to 82 Shore C, and the positive hardness gradient has a magnitude of 10 to 20.

7. The golf ball of claim 1, wherein the inner core has an outer diameter of 0.75 inches to 1.4 inches and the outer core layer has an outer diameter of 1.5 inches to 1.59 inches.

8. The golf ball of claim 1, wherein the cover layer comprises an inner cover layer and an outer cover layer.

9. The golf ball of claim 8, wherein the inner cover layer comprises a high-acid ionomer and a metallocene-grafted polymer.

10. The golf ball of claim 1, wherein the cover layer comprises a castable polyurea.

11. The golf ball of claim 1, wherein the inner core and the outer core layer comprise a diene rubber and, optionally, a soft and fast agent.

12. A golf ball comprising:

an inner core having a first outer surface and a geometric center and being formed from a first substantially homogenous formulation throughout such that the first outer surface has a Shore C hardness of about 55 and the geometric center has a Shore C hardness of about 65;

an outer core layer having a second outer surface and an inner surface and being formed from a second substantially homogenous formulation throughout such that the second outer surface has a Shore C hardness of about 85 and the inner surface has a Shore C hardness of about 75; and

a cover layer;

wherein the geometric center, the first and second outer surfaces, and the inner surface each have a hardness, the hardness of the first outer surface being lower than the hardness of the geometric center to define a negative hardness gradient of about −

10, and the hardness of the second outer surface being greater than the hardness of the inner surface to define a positive hardness gradient of about 10.