Method for the production of golf ball

1. A method of the production of a golf ball which comprises:

reinforcing layer formation step in which a reinforcing layer comprising a thermosetting resin composition is formed on the surface of a core having a mantle layer comprising a thermoplastic resin composition on the outer side thereof to obtain a spherical body;

placing step in which two pieces of a substantially semi-spherical half shell comprising another thermoplastic resin composition, and said spherical body covered by said half shells are placed into a mold having upper and lower mold half each having a hemispherical cavity in the state of said mold open;

clamping step in which said mold is clamped at a velocity of 0.01 mm/sec or greater and 1.0 mm/sec or less whereby the thermoplastic resin composition of the half shell being heated while being compressed in the spherical cavity, accompanied by outflow of excess thermoplastic resin composition from the spherical cavity; and

hardening step in which the thermoplastic resin composition of said half shell is hardened to give a cover having a thickness of 0.1 mm or greater and less than 0.7 mm,

with the difference (T−Fc) between the molding temperature T and the incipient fluidization temperature Fc of the thermoplastic resin composition of the cover being 0° C. or greater and 25° C. or less.

2. The method of the production according to claim l wherein compressive force Fl in said clamping step is 130 kgf or greater and 1900 kgf or less.

3. The method of the production according to claim l, further comprising a high pressure step between said clamping step and said hardening step, in which the thermoplastic resin composition of the half shell is compressed in said spherical cavity with a compressive force F 2 that is greater than the compressive force F 1 in the clamping step.

4. The method of the production according to claim 3 , wherein ratio (F 2 /F 1 ) of the compressive force F 2 in said high pressure step to the compressive force F 1 in said clamping step is 1.5 or greater and 30.0 or less.

5. The method of the production according to claim 1 wherein base polymer of the thermoplastic resin composition of said mantle layer comprises an ionomer resin as the principal component, and base polymer of the thermoplastic resin composition of the cover comprises a thermoplastic polyurethane elastomer as the principal component.

6. The method of the production according to claim 1 , wherein incipient fluidization temperature Fm of the thermoplastic resin composition of said mantle layer is lower than the incipient fluidization temperature Fc of the thermoplastic resin composition of the cover.

7. A method of the production of a golf ball which comprises:

reinforcing layer formation step in which a reinforcing layer comprising a thermosetting resin composition is formed on the surface of a core having a mantle layer comprising a thermoplastic resin composition on the outer side thereof to obtain a spherical body;

placing step in which two pieces of a half shell comprising another thermoplastic resin composition, and said spherical body covered by said half shells are placed into a mold having upper and lower mold half each having a hemispherical cavity in the state of said mold open;

clamping step in which said mold is clamped at a velocity of 0.01 mm/sec or greater and 1.0 mm/sec or less whereby the thermoplastic resin composition of the half shell being heated while being compressed in the spherical cavity, accompanied by outflow of excess thermoplastic resin composition from the spherical cavity; and

hardening step in which the thermoplastic resin composition of said half shell is hardened to give a cover having a thickness of 0.1 mm or greater and less than 0.7 mm,

with the difference (T−Fc) between the molding temperature T and the incipient fluidization temperature Fc of the thermoplastic resin composition of the cover being 0° C. or greater and 25° C. or less.

8. The method of the production according to claim 7 , wherein compressive force F 1 in said clamping step is 130 kgf or greater and 1900 kgf or less.

9. The method of the production according to claim 7 , further comprising a high pressure step between said clamping step and said hardening step, in which the thermoplastic resin composition of the half shell is compressed in said spherical cavity with a compressive force F 2 that is greater than the compressive force F 1 in the clamping step.

10. The method of the production according to claim 9 , wherein ratio (F 2 /F 1 ) of the compressive force F 2 in said high pressure step to the compressive force F 1 in said clamping step is 1.5 or greater and 30.0 or less.

11. The method of the production according to claim 7 , wherein base polymer of the thermoplastic resin composition of said mantle layer comprises an ionomer resin as the principal component, and base polymer of the thermoplastic resin composition of the cover comprises a thermoplastic polyurethane elastomer as the principal component.

12. The method of the production according to claim 7 , wherein incipient fluidization temperature Fm of the thermoplastic resin composition of said mantle layer is lower than the incipient fluidization temperature Fc of the thermoplastic resin composition of the cover.

13. The method of the production according to claim 1 , further comprising:

forming step in which the half shell is formed by a pellet.

14. The method of the production according to claim 7 , further comprising:

forming step in which the half shell is formed by a pellet.