The present invention provides a golf ball comprising a golf ball body and a paint film formed on a surface of the golf ball body, wherein the paint film has a storage modulus (E′) in a temperature range from 120° C. to 150° C. measured under the specific measurement conditions using a dynamic viscoelasticity measuring apparatus of 1.00×10 7 dyn/cm 2 or more and 1.00×10 8 dyn/cm 2 or less and a loss tangent (tan δ) at the temperature of 10° C. of 0.050 or more.
1. A golf ball comprising a golf ball body and a paint film formed on a surface of the golf ball body, wherein
the paint film includes a base resin that is a polyurethane obtained by a reaction between a polyol and two or more polyisocyanates,
the two or more polyisocyanates include a derivative of hexamethylene diisocyanate and a derivative of isophorone diisocyanate,
a mixing ratio of the derivative of hexamethylene diisocyanate and the derivative of isophorone diisocyanate (HDI derivative/IPDI derivative) ranges from 80/20 to 50/50 in a mass ratio,
the derivative of hexamethylene diisocyanate includes a biuret-modified product of hexamethylene diisocyanate and an isocyanurate of hexamethylene diisocyanate,
the derivative of isophorone diisocyanate includes an isocyanurate of isophorone diisocyanate,
the isocyanate groups (NCO) of the polyisocyanates and hydroxyl groups (OH) of the polyol have a molar ratio (NCO/OH) of 0.1 or more and 0.8 or less in the reaction between the polyisocyanates and the polyol, and
the paint film has a storage modulus (E′) in a temperature range from 120° C. to 150° C. of 1.00×10 7 dyn/cm 2 or more and 1.00×10 8 dyn/cm 2 or less, and a loss tangent (tan δ) at a temperature of 10° C. of 0.050 or more when measured in a tensile mode using a dynamic viscoelasticity measuring apparatus at a measuring temperature of −50° C. to 150° C., a temperature increase rate of 4° C./min, an oscillation frequency of 10 Hz, and a measuring strain of 0.1%.
2. The golf ball according to claim 1 , wherein an absolute value (|E′ 120 -E′ 150 |) of a difference between a storage modulus (E′ 120 ) at the temperature of 120° C. and a storage modulus (E′ 150 ) at the temperature of 150° C. is 2.00×10 7 dyn/cm 2 or less.
3. The golf ball according to claim 1 , wherein the polyol includes a urethane polyol obtained by a reaction between a first polyol component and a first polyisocyanate component.
4. The golf ball according to claim 3 , wherein the first polyol component used to make the urethane polyol includes a triol component and a diol component, and a mixing ratio (triol component/diol component) of the triol component to the diol component is 0.2 or more and 6.0 or less in a mass ratio.
5. The golf ball according to claim 1 , wherein the paint film has a 10% elastic modulus of 2 kgf/cm 2 or more and 160 kgf/cm 2 or less.
6. The golf ball according to claim 1 , wherein the paint film has a 10% elastic modulus of 2 kgf/cm 2 or more and 130 kgf/cm 2 or less.
7. The golf ball according to claim 1 , wherein the paint film has a coefficient of friction calculated using a contact force tester of 0.35 or more and 0.60 or less.
8. The golf ball according to claim 1 , wherein the paint film has a thickness of 10 μm or more and 50 μm or less.
9. The golf ball according to claim 1 , wherein the golf ball body has a core and at least one cover layer enclosing the core, and the cover layer has a slab hardness in a range from 10 to 75 in Shore D hardness.
10. The golf ball according to claim 9 , wherein the cover has a slab hardness of 10 or more and less than 55 in Shore D hardness.
11. The golf ball according to claim 9 , wherein the cover has a slab hardness of 55 or more and 75 or less in Shore D hardness.
12. The golf ball according to claim 1 , wherein the golf ball has a compression deformation amount in a range from 1.7 mm to 4.5 mm when applying a load from an initial load of 98N to a final load of 1275 N.
13. The golf ball according to claim 12 , wherein a product of the loss tangent (tan δ) at the temperature of 10° C. and the compression deformation amount ranges from 0.14 to 0.68.
14. The golf ball according to claim 1 , wherein the golf ball has a compression deformation amount of 1.7 mm or more and less than 3.0 mm when applying a load from an initial load of 98N to a final load of 1275 N.
15. The golf ball according to claim 14 , wherein a product of the loss tangent (tan δ) at the temperature of 10° C. and the compression deformation amount ranges from 0.14 to 0.65.
16. The golf ball according to claim 1 , wherein the golf ball has a compression deformation amount in a range from 3.0 mm to 4.5 mm when applying a load from an initial load of 98N to a final load of 1275 N.
17. The golf ball according to claim 16 , wherein a product of the loss tangent (tan δ) at the temperature of 10° C. and the compression deformation amount ranges from 0.23 to 0.68.
18. The golf ball according to claim 1 , wherein the golf ball body has a plurality of dimples on a surface thereof and an occupation ratio Y of all the dimples of 60% or more and 95% or less.
19. The golf ball according to claim 18 , wherein the golf ball body has the occupation ratio Y of 60% or more and less than 75%.
20. The golf ball according to claim 19 , wherein the loss tangent (tan δ) and the occupation ratio Y satisfy the following equation:
4.28≦(tan δ)( Y )≦17.59.
21. The golf ball according to claim 18 , wherein the golf ball body has the occupation ratio Y of 75% or more and 95% or less.
22. The golf ball according to claim 21 , wherein the loss tangent (tan δ) and the occupation ratio Y satisfy the following equation:
5.44≦(tan δ)( Y )≦21.4.
23. The golf ball according to claim 1 , wherein a mixing ratio (biuret-modified product/isocyanurate) of the biuret-modified product of hexamethylene diisocyanate to the isocyanurate of hexamethylene diisocyanate ranges from 20/40 to 40/20 in a mass ratio.