An object of the present invention is to provide a golf ball comprising a core and a cover, wherein the cover is made from a cover composition containing, as a resin component, a thermoplastic polyurethane (A) and a polyisocyanate mixture (B) in which a polyisocyanate (b-1) having at least three isocyanate groups is dispersed in a thermoplastic resin (b-2) which does not substantially react with an isocyanate group; and wherein the cover composition has a slab hardness of more than 60 and not more than 75 in Shore D hardness, and the cover has the thickness of 2.5 mm or less.
1. A golf ball comprising a core and a cover covering the core,
wherein the cover is made from a cover composition containing, as a resin component,
a thermoplastic polyurethane (A) and
a polyisocyanate mixture (B) in which a polyisocyanate (b-1) having at least three isocyanate groups is dispersed in a thermoplastic resin (b-2) which does not substantially react with an isocyanate group; and
wherein the polyisocyanate (b-1) is an isocyanurate of a diisocyanate, the cover composition has a slab hardness of more than 60 and not more than 75 in Shore D hardness, and the cover has a thickness of 2.5 mm or less.
2. The golf ball according to claim 1 , wherein the polyisocyanate mixture (B) has NCO content (NCO %) of 5.0 mass % to 30.0 mass %.
3. The golf ball according to claim 1 , wherein the polyisocyanate (b-1) has NCO content (NCO %) of 1.5 mass % to 30.0 mass %.
4. The golf ball according to claim 1 , wherein the thermoplastic resin (b-2) which does not substantially react with the isocyanate group is at least one kind selected from the group consisting of a polyester elastomer, an acrylic elastomer, a styrene elastomer, an olefin elastomer, and a vinyl chloride elastomer.
5. The golf ball according to claim 1 , wherein the cover composition contains the polyisocyanate mixture (B) in an amount of 1 part by mass to 50 parts by mass relative to 100 parts by mass of the thermoplastic polyurethane (A).
6. The golf ball according to claim 1 , wherein the polyisocyanate (b-1) and the thermoplastic resin (b-2) are blended in the polyisocyanate mixture (B) (a total of 100 mass %) in a ratio of the polyisocyanate (b-1)/thermoplastic resin (b-2)=5 mass % to 50 mass %/50 mass % to 95 mass %.
7. The golf ball according to claim 1 , wherein the polyisocyanate (b-1) is an isocyanurate of isophorone diisocyanate, hexamethylene diisocyanate, or hydrogenated xylylene diisocyanate.
8. The golf ball according to claim 1 , wherein the polyisocyanate mixture (B) contains an isocyanurate of isophorone diisocyanate as a polyisocyanate (b-1) and a polyester elastomer as the thermoplastic resin (b-2).
9. The golf ball according to claim 1 , wherein the polyisocyanate mixture (B) contains an isocyanurate of hexamethylene diisocyanate as a polyisocyanate (b-1) and a polyester elastomer as the thermoplastic resin (b-2).
10. The golf ball according to claim 1 , wherein the core has a surface hardness lager than the center hardness in Shore D hardness.
11. The golf ball according to claim 1 , wherein the polyisocyanate mixture (B) has NCO content (NCO %) of 5.0 mass % to 30.0 mass %, and the polyisocyanate (b-1) has NCO content (NCO %) of 1.5 mass % to 30.0 mass %.
12. The golf ball according to claim 11 , wherein the thermoplastic resin (b-2) which does not substantially react with the isocyanate group is at least one kind selected from the group consisting of a polyester elastomer, an acrylic elastomer, a styrene elastomer, an olefin elastomer, and a vinyl chloride elastomer.
13. The golf ball according to claim 12 , wherein the cover composition contains the polyisocyanate mixture (B) in an amount of 1 part by mass to 50 parts by mass relative to 100 parts by mass of the thermoplastic polyurethane (A).
14. The golf ball according to claim 13 , wherein the polyisocyanate (b-1) and the thermoplastic resin (b-2) are blended in the polyisocyanate mixture (B) (a total of 100 mass %) in a ratio of the polyisocyanate (b-1)/thermoplastic resin (b-2)=5 mass % to 50 mass %/50 mass % to 95 mass %.
15. The golf ball according to claim 14 , wherein the polyisocyanate (b-1) is an isocyanurate of isophorone diisocyanate, hexamethylene diisocyanate, or hydrogenated xylylene diisocyanate.
16. The golf ball according to claim 14 , wherein the polyisocyanate mixture (B) contains an isocyanurate of isophorone diisocyanate as a polyisocyanate (b-1) and a polyester elastomer as the thermoplastic resin (b-2).
17. The golf ball according to claim 14 , wherein the polyisocyanate mixture (B) contains an isocyanurate of hexamethylene diisocyanate as a polyisocyanate (b-1) and a polyester elastomer as the thermoplastic resin (b-2).
18. The golf ball according to claim 15 , wherein the core has a surface hardness larger than the center hardness in Shore D hardness.