Golf ball and method of manufacture

Patent metadata

Field	Value
Publication number	US-10173104-B2
Application number	US-201715806506-A
Country	US
Kind code	B2
Filing date	Nov 8, 2017
Priority date	Jun 23, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the core is formed of a rubber composition that includes a base rubber, a co-crosslinking agent and an organic peroxide. The core has a center portion and a surface portion that are unfoamed regions, and has an intermediate portion that contains a foamed region. A method of manufacturing such a golf ball is also provided.

First claim

The invention claimed is:

1. A golf ball comprising a core and a cover of one or more layer encasing the core, wherein the core is formed of a rubber composition comprising a base rubber, a co-crosslinking agent and an organic peroxide, has a center portion and a surface portion that are unfoamed regions, and has an intermediate portion that contains a foamed region.

2. The golf ball of claim 1 , wherein a gas generated by thermal decomposition of the organic peroxide creates a foamed region.

3. The golf ball of claim 1 , wherein the organic peroxide comprises a first organic peroxide having a first decomposition temperature and a second organic peroxide having a second decomposition temperature, wherein the one-minute half-life temperature of the first organic peroxide is lower than the one-minute half-life temperature of the second organic peroxide.

4. The golf ball of claim 1 , wherein when the core is cut hemispherically and the core cross-section is viewed from the center to the surface of the core, the foamed region appears as a concentric ring centered on a center of the core.

5. The golf ball of claim 1 , wherein the foamed region is formed to a position centered at a distance of 30 to 90% of the core radius from a center of the core as the origin.

6. The golf ball of claim 1 , wherein the specific gravity of the foamed region is at least 5% lower than the specific gravity of the unfoamed regions.

7. The golf ball of claim 1 , wherein the material in the foamed region has an average pore size of less than 500 μm.

8. A method of manufacturing a golf ball having a core and a cover of one or more layer encasing the core, which core is a cured and molded material produced using a first curing mold and a second curing mold, the first curing mold having a cavity with an inside diameter ϕ1 and the second curing mold having a cavity with an inside diameter ϕ2 such that ϕ1<ϕ2, the method comprising:
a first curing step of charging a rubber composition containing an organic peroxide into the first curing mold and applying heat and pressure under given temperature and time conditions; and
a second curing step of removing the molded rubber material in a semi-cured state from the first mold following the first curing step, transferring the semi-cured material to the second curing mold and applying heat and pressure under given temperature and time conditions,
wherein the cured and molded material has a center portion and a surface portion that are unfoamed regions and has an intermediate portion that contains a foamed region.

9. The golf ball manufacturing method of claim 8 , wherein the curing time in the first curing step is in the range of 33 to 60% of the sum of the curing time in the first curing step and the curing time in the second curing step.

Assignees

• Bridgestone Sports Co Ltd

Inventors

• Shindo Jun
• Nakajima Tsuyoshi

Classifications

• B29C44/08

  using several expanding {or moulding} steps · CPC title

• B29C45/14819

  the inserts being completely encapsulated · CPC title

• B29K2509/02

  Ceramics · CPC title

• B29K2105/16

  Fillers · CPC title

• B29K2009/00

  Use of rubber derived from conjugated dienes, as moulding material · CPC title