An object of the invention is to provide a golf ball excellent in the durability at the normal and low temperatures, flight distance, and shot feeling on the shots. Another object of the present invention is to provide a golf ball excellent in a direction stability on the shots. The present invention provides a golf ball comprising: a core consisting of at least one layer; and a cover covering the core and having a thickness ranging from 0.3 mm to 1.0 mm, wherein the cover is formed from a cover composition that contains as a resin component, (A) a highly elastic polyamide resin (B) a metal-neutralized product of binary copolymer and/or ternary copolymer, and (C) a resin having a polar functional group in a specific amount, and wherein the cover composition has a slab hardness ranging from 65 to 75 in Shore D hardness.
1. A golf ball comprising:
a core consisting of at least one layer;
an intermediate layer covering the core; and
a cover covering the intermediate layer and having a thickness ranging from 0.3 mm to 1.0 mm,
wherein the cover is formed from a cover composition that contains as a resin component
(A) a highly elastic polyamide resin having a flexural modulus in a range from 700 MPa to 5,000 MPa;
(B) a metal-neutralized product of ethylene-(meth)acrylic acid binary copolymer and/or a metal-neutralized product of ethylene-(meth)acrylic acid-(meth)acrylic acid ester ternary copolymer in an amount ratio ((A)/(B)) of (A) the highly elastic polyamide resin to (B) the metal-neutralized product of the binary copolymer and/or the ternary copolymer being (5 mass % to 80 mass %)/(95 mass % to 20 mass %) (the total is 100 mass %); and
(C) a resin having a polar functional group in an amount of 0.1 part by mass to 20 parts by mass with respect to 100 parts by mass of a sum of (A) the highly elastic polyamide resin and (B) the metal-neutralized product of the binary copolymer and/or the ternary copolymer, and
wherein the cover composition has a slab hardness ranging from 65 to 75 in Shore D hardness, and
wherein a surface hardness (H3) of the core and a slab hardness (H4) of the intermediate layer composition constituting the intermediate layer satisfy an equation H3>H4.
2. The golf ball according to claim 1 , wherein the intermediate layer has a density of 1.10 g/cm 3 or more.
3. The golf ball according to claim 1 , wherein regarding slab properties, the cover composition has a flexural modulus in a range from 300 MPa to 1,000 MPa, and a tensile modulus in a range from 400 MPa to 1,500 MPa.
4. The golf ball according to claim 1 , wherein (A) the highly elastic polyamide resin is at least one member selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide MST, polyamide 612 and a polyetherblock amide copolymer.
5. The golf ball according to claim 1 , wherein (C) the resin having a polar functional group is at least one member selected from a group consisting of an ethylene-glycidyl methacrylate copolymer, an ethylene-acrylic acid-glycidyl methacrylate copolymer, and a methyl methacrylate-glycidyl methacrylate copolymer.
6. The golf ball according to claim 1 , wherein the core has a diameter of 39.1 mm or more.
7. The golf ball according to claim 1 , wherein (A) the highly elastic polyamide resin has a brittle temperature of −20° C. or less.
8. The golf ball according to claim 1 , wherein a degree of neutralization of acidic groups contained in (B) the metal neutralized copolymer ranges from 20 mole % to 90 mole %.
9. The golf ball according to claim 1 , wherein (B) the metal neutralized copolymer has a flexural modulus ranging from 250 MPa to 1,000 MPa.
10. A golf ball comprising:
a core consisting of a center having a diameter of 35 mm or less and a surrounding layer covering the center;
at least one intermediate layer covering the core; and
a cover covering the intermediate layer and having a thickness ranging from 0.3 mm to 1.0 mm,
wherein the cover is formed from a cover composition that contains as a resin component
(A) a highly elastic polyamide resin having a flexural modulus in a range from 700 MPa to 5,000 MPa;
(B) a metal-neutralized product of ethylene-(meth)acrylic acid binary copolymer and/or a metal-neutralized product of ethylene-(meth)acrylic acid-(meth)acrylic acid ester ternary copolymer in an amount ratio ((A)/(B)) of (A) the highly elastic polyamide resin to (B) the metal-neutralized product of the binary copolymer and/or the ternary copolymer being (5 mass % to 80 mass %)/(95 mass % to 20 mass %) (the total is 100 mass %); and
(C) a resin having a polar functional group in an amount of 0.1 part by mass to 20 parts by mass with respect to 100 parts by mass of a sum of (A) the highly elastic polyamide resin and (B) the metal-neutralized product of the binary copolymer and/or the ternary copolymer, and
wherein the cover composition has a slab hardness ranging from 65 to 75 in Shore D hardness and a hardness difference (H3−H1) between a surface hardness (H3) of the core and a center hardness (H1) of the core is 10 or more in Shore D hardness.
11. The golf ball according to claim 10 , wherein the intermediate layer has a density of 1.10 g/cm 3 or more.
12. The golf ball according to claim 10 , wherein the cover composition has a flexural modulus in a range from 300 MPa to 1,000 MPa and a tensile strength in a range from 400 MPa to 1,500 MPa in Slab properties.
13. The golf ball according to claim 10 , wherein (A) the highly elastic polyamide resin is at least one member selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide MST, polyamide 612 and a polyetherblock amide copolymer.
14. The golf ball according to claim 10 , wherein (C) the resin having a polar functional group is at least one member selected from a group consisting of an ethylene-glycidyl methacrylate copolymer, an ethylene-acrylic acid-glycidyl methacrylate copolymer, and a methyl methacrylate-glycidyl methacrylate copolymer.
15. The golf ball according to claim 10 , wherein a center hardness (H1) of the core, a slab hardness (H4) of the intermediate layer, and a surface hardness (H3) of the core satisfy an equation H1<H4<H3.
16. The golf ball according to claim 10 , wherein a center composition for forming the center and a surrounding layer composition for forming the surrounding layer comprise a rubber component as a main component, and an intermediate layer composition for forming the intermediate layer comprises a thermoplastic material as a main component.
17. The golf ball according to claim 10 , wherein (A) the highly elastic polyamide resin has a brittle temperature of −20° C. or less.
18. The golf ball according to claim 10 , wherein a degree of neutralization of acidic groups contained in (B) the metal neutralized copolymer ranges from 20 mole % to 90 mole %.
19. The golf ball according to claim 10 , wherein (B) the metal neutralized copolymer has a flexural modulus ranging from 250 MPa to 1,000 MPa.