| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a golf ball which suppresses inclusion of a large size particle or a foreign matter and is excellent in efficiency. SOLUTION: A coarsely crushed crosslinked rubber is introduced through a feed port 17 of a grinding mill 1 provided with an upper grindstone 5 and a lower grindstone 7 opposite to each other, the lower grindstone 7 rotating. The crosslinked rubber moves outward in the direction of the radius owing to a centrifugal force and rubs against the grinding surfaces of the upper grindstone 5 and the lower grindstone 7. Thus, the crosslinked rubber gradually moves outward in the direction of the radius while being gradually reduced in its size to give a finely powdered rubber. The average particle diameter of the finely powdered rubber is caused to be at most 1,500μm. This finely powdered rubber is compounded with a core material of a golf ball. The clearance between the upper grindstone 5 and the lower grindstone 7 is preferably at least 200μm and at most 1,200μm.
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