# US 2017/0282016 A1 · Golf ball

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- Number: US 2017/0282016 A1
- Document ID: US20170282016A1
- Status: Published application
- Kind: A1
- Application number: 15/624,476
- Filed: 2017-06-15
- Published: 2017-10-05
- Earliest claimed: 2013-09-03
- Assignees: Bridgestone Sports Co., Ltd.
- Applicants: Bridgestone Sports Co., Ltd.
- Inventors: Tsuyoshi NAKAJIMA; Yuichiro OZAWA
- Web page: https://patentgrep.com/patent/US20170282016A1

## CPC

- A63B 37/0051: {Materials other than polybutadienes; Constructional details}
- A63B 37/006: {Physical properties}
- A63B 37/0063: {Hardness gradient}
- A63B 37/0065: {Deflection or compression}
- A63B 37/0066: {Density; Specific gravity}
- A63B 37/0068: {Initial velocity}
- A63B 37/0074: {Two piece balls, i.e. cover and core}
- A63B 37/0075: {Three piece balls, i.e. cover, intermediate layer and core}
- A63B 37/0076: {Multi-piece balls, i.e. having two or more intermediate layers}
- C08L 21/00: Compositions of unspecified rubbers
- A63B: APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT (apparatus for passive exercising, massage A61H)
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, the core being formed of a material molded under heat from a rubber composition which includes (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate. The product P×E of the difference P (mol/m3) in crosslink density between the core surface and the core center, as measured based on a toluene swelling test, multiplied by the deflection E (mm) of the core when compressed under a final load of 1,275 N (130 kgf) from an initial load state of 98 N (10 kgf) is at least 28×102 mol/m3·mm.

## Claims

### Claim 1

A golf ball comprising a core and a cover of one layer or a plurality of layers, wherein the core is formed of a material molded under heat from a rubber composition comprising the following components (A) to (C):
(A) a base rubber,
(B) an organic peroxide, and
(C) (C-I) water and/or (C-II) a metal monocarboxylate and a metal dicarboxylate;
wherein the difference between the crosslink density at the core surface and the crosslink density at the core center, both of which are crosslink densities measured based on a toluene swelling test, is at least 9×102 mol/m3.

### Claim 2 (depends on 1)

The golf ball of claim 1, wherein the product P×E of the difference P (mol/m3) in crosslink density between a surface of the core and a center of the core, as measured based on a toluene swelling test, multiplied by the deflection E (mm) of the core when compressed under a final load of 1,275 N (130 kgf) from an initial load state of 98 N (10 kgf) is a least 28×102 mol/m3·mm.

### Claim 3 (depends on 1)

The golf ball of claim 1, wherein the rubber composition before vulcanization has a moisture content of at least 1,000 ppm.

### Claim 4 (depends on 1)

The golf ball of claim 1, wherein the core after vulcanization has a higher moisture content at the core center than at the core surface.

### Claim 5 (depends on 1)

The golf ball of claim 1, wherein the rubber composition includes from 0.1 to 5 parts by weight of an organosulfur compound per 100 parts by weight of the base rubber.

### Claim 6 (depends on 1)

The golf ball of claim 1, wherein the core of the golf ball after molding of the cover has an initial velocity V0, as measured after peeling away the cover, of at least 77.0 m/s and not more than 78.5 m/s.

### Claim 7 (depends on 1)

The golf ball of claim 1 which satisfies the relationship V0−V60<0.7, wherein V0 is the initial velocity of the core in the golf ball after molding of the cover, as measured after peeling away the cover, and V60 is the initial velocity of the core 60 days after measuring V0.

### Claim 8 (depends on 1)

The golf ball of claim 1 wherein, when the loss tangent of the core center is measured at a temperature of −12° C. and a frequency of 15 Hz, letting tan δ1 be the loss tangent at a dynamic strain of 1% and tan δ10 be the loss tangent at a dynamic strain of 10%, the slope of these tan δ values, expressed as [(tan δ10−tan δ1)/(10%−1%)], is not more than 0.003.

### Claim 9 (depends on 1)

The golf ball of claim 1, wherein the JIS-C hardness difference obtained by subtracting a core center hardness from a core surface hardness is at least 20 and not more than 40.