# US 7,407,449 B2 · Golf ball

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- Number: US 7,407,449 B2
- Document ID: US7407449B2
- Status: Granted
- Kind: B2
- Application number: 11/878,944
- Filed: 2007-07-27
- Published: 2008-01-31
- Granted: 2008-08-05
- Earliest claimed: 2006-01-04
- Assignees: Bridgestone Sports Co., Ltd.
- Inventors: Jun Shindo; Eiji Takehana; Kae Yamazaki
- Web page: https://patentgrep.com/patent/US7407449B2

## CPC

- A63B 37/0003: {Golf balls}
- A63B 37/0033: {Thickness}
- A63B 37/0039: {characterised by the material}
- A63B 37/0043: {Hardness}
- A63B 37/0045: {Thickness}
- A63B 37/0051: {Materials other than polybutadienes; Constructional details}
- A63B: APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT (apparatus for passive exercising, massage A61H)

## Abstract

The present invention provides a golf ball having a core, an outermost cover layer and an intermediate layer therebetween. The core is made of a material obtained by molding under heat a rubber composition containing polybutadiene having a stress relaxation time (T80) of 3.5 or less. The intermediate layer, which is of a specific thickness, is made primarily of a resin material of a specific hardness obtained by blending together (I) a sodium ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer with (II) a magnesium ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer. The outermost cover layer, which is of a specific thickness, is made primarily of a non-ionomeric resin material of a specific hardness. The golf ball has an excellent rebound, a good feel on impact, and an excellent scuff resistance.

## Claims

### Claim 1

A golf ball comprising a core, an outermost cover layer and an intermediate layer therebetween, wherein the core is made of a material obtained by molding under heat a rubber composition comprising (a) a base rubber containing polybutadiene having a stress relaxation time (T80), defined as the time in seconds from the moment when rotation is stopped immediately after measurement of the ML1+4 (100° C.) value (the Mooney viscosity measured at 100° C. in accordance with ASTM D-1646-96) that is required for the ML1+4 value to decrease 80%, of 3.5 or less, (b) an unsaturated carboxylic acid and/or a metal salt thereof, and (c) an organic peroxide; the intermediate layer has a thickness of from 0.5 to 2.5 mm and is made primarily of a resin material obtained by blending together (I) a sodium ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer with (II) a magnesium ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer and having a Shore D hardness of from 55 to 70; and the outermost cover layer has a thickness of from 0.5 to 2.0 mm and is made primarily of a non-ionomeric resin material having a Shore D hardness of from 35 to 60.

### Claim 2 (depends on 1)

The golf ball of claim 1, wherein the rubber composition further comprises (d) an organosulfur compound.

### Claim 3 (depends on 1)

The golf ball of claim 1, wherein the polybutadiene having a stress relaxation time (T80) of 3.5 or less accounts for at least 40 wt % of the base rubber.

### Claim 4 (depends on 1)

The golf ball of claim 1, wherein the polybutadiene having a stress relaxation time (T80) of 3.5 or less is a polybutadiene prepared using a rare-earth catalyst.

### Claim 5 (depends on 1)

The golf ball of claim 1, wherein the polybutadiene having a stress relaxation time (T80) of 3.5 or less is a polybutadiene prepared by polymerization using a rare-earth catalyst, followed by terminal modification.

### Claim 6 (depends on 1)

The golf ball of claim 1, wherein the intermediate layer-forming material contains material (I) and material (II) in a mixing ratio by weight of from 20/80 to 80/20.

### Claim 7 (depends on 1)

The golf ball of claim 1, wherein the non-ionomeric resin material in the outermost cover layer is a thermoplastic polyurethane elastomer.