# US 9,873,024 B2 · Golf ball

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- Number: US 9,873,024 B2
- Document ID: US9873024B2
- Status: Granted
- Kind: B2
- Application number: 14/055,900
- Filed: 2013-10-17
- Published: 2014-04-10
- Granted: 2018-01-23
- Earliest claimed: 2012-05-01
- Assignees: Bridgestone Sports Co., Ltd.
- Applicants: Bridgestone Sports Co., Ltd.
- Inventors: Akira Kimura; Toru Ogawana; Ryota Nakamura; Tsuyoshi Nakajima
- Web page: https://patentgrep.com/patent/US9873024B2

## CPC

- A63B 37/0063: {Hardness gradient}
- A63B 37/0031: {Hardness}
- A63B 37/0035: {Density; Specific gravity}
- A63B 37/0043: {Hardness}
- A63B 37/006: {Physical properties}
- A63B 37/0064: {Diameter}
- A63B 37/0066: {Density; Specific gravity}
- A63B 37/0087: {Deflection or compression}
- A63B 37/0092: {Hardness distribution amongst different ball layers}
- C08L 9/00: Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
- A63B 37/0018: {Specified number of dimples}
- 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}
- A63B 37/0084: {Initial velocity}
- A63B 45/00: Apparatus or methods for manufacturing balls (working of plastics or substances in a plastic state B29)
- C08K 5/0025: {Crosslinking or vulcanising agents; including accelerators}
- C08K 5/098: Metal salts of carboxylic acids
- 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)
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)

## Abstract

The invention provides a golf ball having a core and a cover of at least one layer. The core has a cross-sectional hardness which, letting R (mm) be the radius of the core, A be the JIS-C hardness at a center of the core, B be the JIS-C hardness at a position R/3 mm from the core center, C be the JIS-C hardness at a position R/1.8 mm from the core center, D be the JIS-C hardness at a position R/1.3 mm from the core center, and E be the JIS-C hardness at a surface of the core, satisfies the formulas (1) D−C≧7, (2) C−B≦7, (3) (D−C)−(C−B)≧7, and (4) E−A≧16.

## Claims

### Claim 1

A golf ball comprising a core and a cover of at least one layer, wherein the core has a cross-sectional hardness which, letting R (mm) be a radius of the core, A be a JIS-C hardness at a center of the core, B be a JIS-C hardness at a position R/3 mm from the core center, C be a JIS-C hardness at a position R/1.8 mm from the core center, D be a JIS-C hardness at a position R/1.3 mm from the core center, and E be a JIS-C hardness at a surface of the core, satisfies formulas (1) to (4) below:
D−C≧7 (1)
C−B≦7 (2)
(D−C)−(C−B)≧7 (3)
E−A≧16, (4)
wherein the core is formed from a material molded under heat and is formed from a rubber composition comprising a base rubber, a crosslinking initiator, and water,
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, and
wherein the base rubber consists of polybutadiene synthesized with a rare-earth catalyst and/or a polybutadiene synthesized with a nickel catalyst.

### Claim 2 (depends on 1)

The golf ball of claim 1, wherein the ball has a deflection, when compressed under a final load of 5,880 N (600 kgf) from an initial load state of 98 N (10 kgf), of from 7 to 10 mm.

### Claim 3 (depends on 1)

The golf ball of claim 1, wherein the cover comprises an outermost layer and an intermediate layer interposed between the outermost layer and the core, and the ball has, at a surface of a sphere composed of the core covered by the intermediate layer, a JIS-C hardness of at least 90.

### Claim 4 (depends on 1)

The golf ball of claim 1, wherein the outermost layer of the cover contains a base resin comprising a polyurethane material having a Shore D hardness of from 40 to 60.

### Claim 5 (depends on 1)

The golf ball of claim 1, wherein the core has a diameter of from 32 to 41 mm.

### Claim 6 (depends on 1)

The golf ball of claim 1, wherein the core is composed of a single layer.

### Claim 7 (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 0.002.

### Claim 8 (depends on 1)

The golf ball of claim 1, wherein the amount of water per 100 parts by weight of the base rubber is from 0.1 to 5 parts by weight.

### Claim 9

A golf ball comprising a core, an envelope layer, an intermediate layer and an outermost layer, wherein the core has a cross-sectional hardness which, letting R (mm) be a radius of the core, A be a JIS-C hardness at a center of the core, B be a JIS-C hardness at a position R/3 mm from the core center, C be a JIS-C hardness at a position R/1.8 mm from the core center, D be a JIS-C hardness at a position R/1.3 mm from the core center, and E be a JIS-C hardness at a surface of the core, satisfies formulas (1) to (4) below:
D−C≧7 (1)
C−B≦2 (2)
(D−C)−(C−B)≧7 (3)
E−A≧16, and (4)
wherein the material hardness of the intermediate layer, expressed as the Shore D hardness, is from 62 to 70,
wherein the core is formed from a material molded under heat and is formed from a rubber composition comprising a base rubber, a crosslinking initiator, and water, and
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, and
wherein the base rubber consists of polybutadiene synthesized with a rare-earth catalyst and/or a polybutadiene synthesized with a nickel catalyst.

### Claim 10 (depends on 9)

The golf ball of claim 9, wherein the JIS-C hardness at the core center is from 63 to 70.

### Claim 11 (depends on 9)

The golf ball of claim 9, wherein the JIS-C hardness at the core surface is from 84 to 100.

### Claim 12 (depends on 9)

The golf ball of claim 9, wherein the material hardness of the envelope layer is from 40 to 51 at Shore D hardness.

### Claim 13 (depends on 9)

The golf ball of claim 9, wherein the material hardness of the outermost layer is from 34 to 47 at Shore D hardness.

### Claim 14 (depends on 9)

The golf ball of claim 9 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 0.002.

### Claim 15 (depends on 9)

The golf ball of claim 9, wherein the amount of water per 100 parts by weight of the base rubber is from 0.1 to 5 parts by weight.