Golf ball
An object of the present invention is to provide a golf ball having excellent shot feeling on driver shots. The present invention provides a golf ball comprising a core and at least one cover covering the core, wherein the core is formed from a core rubber composition containing (a) a base rubber containing a polybutadiene, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin.
1. A golf ball comprising a core and at least one cover covering the core, wherein
the core is formed from a core rubber composition containing (a) a base rubber containing a polybutadiene, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin; and wherein
a hardness difference (Hs−H75) between a hardness (H75) at a point located at a distance of 75% of a core radius from a center of the core and a surface hardness (Hs) of the core is less than 10 in Shore C hardness.
2. The golf ball according to claim 1 , wherein (d) the terpene-based resin is at least one member selected from the group consisting of a terpene polymer, a terpene-phenol copolymer, a terpene-styrene copolymer, a terpene-phenol-styrene copolymer, a hydrogenated terpene-phenol copolymer, a hydrogenated terpene-styrene copolymer, and a hydrogenated terpene-phenol-styrene copolymer.
3. The golf ball according to claim 1 , wherein the terpene-based resin is at least one member selected from the group consisting of compounds having a structure represented by the following formulae (1) to (4):
wherein in the formulae (1) to (4),
R 1 and R 2 each independently represent a divalent residue of a phenol-based compound and/or a styrene-based compound,
m 1 to m 4 each independently represent a natural number of 1 to 30, and
n 1 to n 2 each independently represent a natural number of 1 to 20.
4. The golf ball according to claim 1 , wherein (d) the terpene-based resin is at least one member selected from the group consisting of an α-pinene-phenol copolymer, an α-pinene-α-methylstyrene copolymer, an α-pinene-α-methylstyrene-phenol copolymer, a β-pinene-phenol copolymer, a β-pinene-α-methylstyrene copolymer, and a β-pinene-α-methylstyrene-phenol copolymer.
5. The golf ball according to claim 1 , wherein (d) the terpene-based resin has a softening point in a range of from 60° C. to 150° C.
6. The golf ball according to claim 1 , wherein the core rubber composition contains (d) the terpene-based resin in an amount of from 3 parts by mass to 20 parts by mass with respect to 100 parts by mass of (a) the base rubber.
7. The golf ball according to claim 1 , wherein a blending ratio (component (b)/component (d)) of the component (b) to the component (d) ranges from 2.0 to 15.0 in a mass ratio.
8. The golf ball according to claim 1 , wherein the polybutadiene is a high-cis polybutadiene having a cis-1,4 bond in an amount of 90 mass % or more.
9. The golf ball according to claim 1 , wherein a hardness (H75) at a point located at a distance of 75% of a core radius from a center of the core ranges from 55 to 80 in Shore C hardness.
10. The golf ball according to claim 1 , wherein a surface hardness (Hs) of the core ranges from 60 to 83 in Shore C hardness.
11. The golf ball according to claim 1 , wherein a central hardness (Ho) of the core ranges from 30 to 70 in Shore C hardness.
12. The golf ball according to claim 1 , wherein a hardness difference (Hs−Ho) between a surface hardness (Hs) of the core and a central hardness (Ho) of the core ranges from 5 to 35 in Shore C hardness.
13. The golf ball according to claim 1 , wherein a hardness difference (H75−Ho) between a hardness (H75) at a point located at a distance of 75% of a core radius from a center of the core and a central hardness (Ho) of the core ranges from 3 to 20 in Shore C hardness.
14. The golf ball according to claim 2 , wherein the terpene-phenol copolymer has an acid value in a range of from 10 mgKOH/g 300 mgKOH/g.
15. The golf ball according to claim 2 , wherein the terpene-phenol copolymer has a hydroxy value in a range of from 30 mgKOH/g to 150 mgKOH/g.
16. The golf ball according to claim 1 , wherein the core rubber composition contains (d) the terpene-based resin in an amount of from 3 parts by mass to 20 parts by mass with respect to 100 parts by mass of (a) the base rubber, and
the terpene-based resin is at least one member selected from the group consisting of compounds having a structure represented by the following formulae (1) to (4):
wherein in the formulae (1) to (4),
R 1 and R 2 each independently represent a divalent residue of a phenol-based compound and/or a styrene-based compound,
m 1 to m 4 each independently represent a natural number of 1 to 30, and
n 1 to n 2 each independently represent a natural number of 1 to 20.
17. A golf ball comprising a core and at least one cover covering the core, wherein
the core is formed from a core rubber composition containing (a) a base rubber containing a polybutadiene, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin; and wherein
(d) the terpene-based resin is at least one member selected from the group consisting of a terpene-phenol copolymer, a terpene-styrene copolymer, a terpene-phenol-styrene copolymer, a hydrogenated terpene-phenol copolymer, a hydrogenated terpene-styrene copolymer, and a hydrogenated terpene-phenol-styrene copolymer, and has a softening point in a range of from 110° C. to 150° C.
18. A golf ball comprising a core and at least one cover covering the core, wherein
the core is formed from a core rubber composition containing (a) a base rubber containing a polybutadiene, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin;
the core rubber composition contains (d) the terpene-based resin in an amount of from 3 parts by mass to 20 parts by mass with respect to 100 parts by mass of (a) the base rubber; and
(d) the terpene-based resin is at least one member selected from the group consisting of an α-pinene-phenol copolymer, an α-pinene-α-methylstyrene copolymer, an α-pinene-α-methylstyrene-phenol copolymer, a β-pinene-phenol copolymer, a β-pinene-α-methylstyrene copolymer, and a β-pinene-α-methylstyrene-phenol copolymer.
19. A golf ball comprising a core and at least one cover covering the core, wherein
the core is formed from a core rubber composition consisting of (a) a base rubber containing a polybutadiene, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, (d) a terpene-based resin, and optionally at least one component selected from the group consisting of
an organic sulfur compound,
a metal hydroxide,
a metal oxide selected from magnesium oxide, calcium oxide, zinc oxide, and copper oxide,
a metal carbonate, barium sulfate, tungsten powder, molybdenum powder,
a pigment,
an antioxidant,
a peptizing agent, and
a softening agent; and
(d) the terpene-based resin is at least one member selected from the group consisting of an α-pinene polymer, a β-pinene polymer, a limonene polymer, a dipentene polymer, a β-pinene/limonene polymer, a terpene-phenol copolymer, a terpene-styrene copolymer, a terpene-phenol-styrene copolymer, a hydrogenated terpene-phenol copolymer, a hydrogenated terpene-styrene copolymer, and a hydrogenated terpene-phenol-styrene copolymer, and has a softening point in a range of from 110° C. to 150° C.