Solid golf ball
The invention provides a solid golf ball which has a core of at least one layer and a cover of at least one layer. At least one layer of the core is formed primarily of polybutadiene and includes at least 0.05 part by weight each of (I) a rubber powder obtained by granulating a rubber material containing acrylic acid or a metal salt of acrylic acid and (II) a polyurethane resin powder per 100 parts by weight of rubber component. At least one layer of the cover is formed primarily of polyurethane.
1. A solid golf ball comprising a core of at least one layer and a cover of at least one layer, wherein at least one layer of the core is a sphere formed primarily of polybutadiene and includes at least 0.05 part by weight each of (I) a rubber powder obtained by granulating a rubber material containing acrylic acid or a metal salt of acrylic acid and (II) a polyurethane resin powder per 100 parts by weight of rubber component, and at least one layer of the cover is formed primarily of polyurethane,
wherein, when A is the JIS-C hardness at a surface of the core, B is the JIS-C hardness at a position 2 mm inside the core surface, C is the JIS-C hardness at a position 5 mm inside the core surface, D is the JIS-C hardness at a position 10 mm inside the core surface, E is the JIS-C hardness at a position 15 mm inside the core surface, and F is the JIS-C hardness at the center of the core, the following hardness relationship is satisfied:
A>B<C≧D>E>F.
2. The solid golf ball of claim 1 , wherein the core layer which includes the polyurethane resin powder (II) adjoins the cover layer composed primarily of polyurethane.
3. The solid golf ball of claim 1 , wherein the core includes at least 5 parts by weight of methacrylic acid and/or a metal salt of methacrylic acid as a co-crosslinking agent per 100 parts by weight of rubber component.
4. The solid golf ball of claim 1 , wherein the polyurethane resin powder (II) is granulated by a granulator to an average particle size of not more than 1 mm.
5. The solid golf ball of claim 1 , wherein the polyurethane resin powder (II) is composed primarily of thermoplastic polyurethane and has a flow starting point of from 150 to 320° C.
6. The solid golf ball of claim 1 , wherein the core has a hardness designed so as to gradually increase from a center of the core toward a surface of the core.
7. The solid golf ball of claim 1 which has been produced by treating a surface of the core with a solution containing a haloisocyanuric acid and/or a metal salt thereof, then encasing the core in a cover layer.
8. The solid golf ball of claim 1 , wherein the value of A−C is from 0 to 8 and the value of A−F is not more than 19.
9. The solid golf ball of claim 1 , wherein the core has a diameter of from 38.9 to 42.1 mm.
10. The solid golf ball of claim 1 , which is a two-piece solid golf ball having a core and a cover.