# US 9,751,272 B2 · Method for manufacturing a golf ball

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- Number: US 9,751,272 B2
- Document ID: US9751272B2
- Status: Granted
- Kind: B2
- Application number: 13/895,755
- Filed: 2013-05-16
- Published: 2013-11-21
- Granted: 2017-09-05
- Earliest claimed: 2012-05-17
- Assignees: Dunlop Sports Co. Ltd.
- Applicants: Dunlop Sports Co. Ltd.
- Inventors: Satoko Okabe; Masatoshi Yokota; Koichi Fujisawa; Yusuke Tanigawa
- Web page: https://patentgrep.com/patent/US9751272B2

## CPC

- B29D 99/0042: {Producing plain balls (hollow balls B29D22/04)}
- A63B 37/0003: {Golf balls}
- A63B 37/0022: {Coatings, e.g. paint films; Markings}
- A63B 37/0051: {Materials other than polybutadienes; Constructional details}
- A63B 37/00621: {Centre hardness}
- A63B 37/00622: {Surface hardness}
- A63B 37/0063: {Hardness gradient}
- 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 37/0096: {Spin rate}
- A63B 45/00: Apparatus or methods for manufacturing balls (working of plastics or substances in a plastic state B29)
- C08L 9/00: Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
- A63B 37/0031: {Hardness}
- A63B 37/0033: {Thickness}
- A63B 37/0043: {Hardness}
- A63B 37/0064: {Diameter}
- A63B 37/008: {Diameter}
- A63B 37/0087: {Deflection or compression}
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- 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

An object of the present invention is to provide a method for manufacturing a golf ball excellent in kneading workability when preparing a core rubber composition containing (d) a carboxylic acid and/or a salt thereof. The present invention provides a method for manufacturing a golf ball comprising the steps of blending (a) a base rubber and at least (b) a carboxylic acid and/or a salt thereof to prepare a first masterbatch; blending (a) a base rubber and at least (c) a crosslinking initiator to prepare a second masterbatch; blending the first masterbatch and second masterbatch to form a core rubber composition; molding the core rubber composition into a spherical core; and forming one or more cover layers covering the spherical core.

## Claims

### Claim 1

A method for manufacturing a golf ball that comprises a spherical core formed from a core rubber composition containing:
(a) a base rubber, (b) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a carboxylic acid and/or a salt thereof not including (b) the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, and at least one cover layer covering the spherical core,
comprising the steps of:
blending (a) the base rubber and at least (d) the carboxylic acid and/or the salt thereof to prepare a first masterbatch;
blending (a) the base rubber, and at least (b) the α, β-unsaturated carboxylic acid having 3to 8 carbon atoms and/or a metal salt thereof and (c) the crosslinking initiator to prepare a second masterbatch while adjusting a material temperature thereof to 95° C. or more;
blending the first masterbatch and the second masterbatch to prepare the core rubber composition while adjusting a material temperature thereof to 90° C. or less;
molding the core rubber composition into the spherical core; and
forming at least one cover layer covering the spherical core,
wherein the core rubber composition may further contain (e) a metal compound to neutralize the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, a weight adjusting agent to adjust the weight of the spherical core, a hardness adjusting agent to adjust the hardness of the spherical core, or an inorganic pigment.

### Claim 2 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein (a) the base rubber and at least (d) the carboxylic acid and/or the salt thereof are kneaded to prepare the first masterbatch while adjusting a material temperature thereof to 90° C. or less.

### Claim 3 (depends on 2)

The method for manufacturing the golf ball according to claim 2, wherein (d) the carboxylic acid and/or the salt thereof is blended in an amount of 25 parts by mass to 150parts by mass with respect to 100 parts by mass of (a) the base rubber in the step of preparing the first masterbatch.

### Claim 4 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein the first masterbatch is prepared in the presence of at least one kind of metal-containing components.

### Claim 5 (depends on 4)

The method for manufacturing the golf ball according to claim 4, wherein the first masterbatch is prepared in the presence of the metal salt of (b) the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms which is the co-crosslinking agent and/or (e) the metal compound as the metal-containing component.

### Claim 6 (depends on 4)

The method for manufacturing the golf ball according to claim 4, wherein the first masterbatch is prepared in the presence of a zinc compound as the metal-containing component.

### Claim 7 (depends on 4)

The method for manufacturing the golf ball according to claim 4, wherein the first masterbatch is prepared in the presence of (b) zinc acrylate and/or (e) zinc oxide as the metal-containing component.

### Claim 8 (depends on 4)

The method for manufacturing the golf ball according to claim 4, wherein the metal-containing component is contained in an amount of 10 parts by mass or more and less than 200 parts by mass with respect to 100 parts by mass of (a) the base rubber.

### Claim 9 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein (d) the carboxylic acid and/or the salt thereof is a carboxylic acid having 4 to 30 carbon atoms and/or a salt thereof.

### Claim 10 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein (d) the carboxylic acid and/or the salt thereof is a fatty acid and/or a salt thereof.

### Claim 11 (depends on 10)

The method for manufacturing the golf ball according to claim 10, wherein the fatty acid is a saturated fatty acid.

### Claim 12 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein the core rubber composition contains (d) the carboxylic acid and/or the salt thereof in an amount from 0.1 part by mass to 40.0 parts by mass with respect to 100 parts by mass of (a) the base rubber.

### Claim 13 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein the spherical core has a hardness distribution that R2 of a linear approximate curve determined by a least-squares method is 0.95 or more, when plotting if JIS-C hardness values are measured at the core center, the core surface and at intervals of 2.5 mm from the core center and plotted versus distances from the core center, then R2 of a linear approximate curve determined by the least-squares method is 0.95 or more.

### Claim 14 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein the spherical core has a hardness difference ranging from 18 to 80 in JIS-C hardness between a surface hardness Hs and a center hardness Ho thereof.

### Claim 15 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein (d) the carboxylic acid and/or the salt thereof is blended only in the step of preparing the first masterbatch.

### Claim 16 (depends on 1)

The method for manufacturing the golf ball according to claim 1, wherein the first masterbatch and the second masterbatch are blended while adjusting a material temperature thereof to 85° C. or less.