A golf ball 2 includes a core 4, a mid layer 6, and a cover 10. The core 4 includes a center 16, a first envelope layer 18, and a second envelope layer 20. The first envelope layer 18 is formed by a first rubber composition being crosslinked. The second envelope layer 20 is formed by a second rubber composition being crosslinked. The first rubber composition and/or the second rubber composition include: a base rubber; a co-crosslinking agent; a crosslinking initiator; and an acid and/or a salt. The co-crosslinking agent is (1) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; and/or (2) a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms.
A golf ball 2 includes a core 4, a first mid layer 6, a second mid layer 8, and a cover 12. The core 4 includes a center 18 and an envelope layer 20. The center 18 is formed by crosslinking a first rubber composition, and the envelope layer 20 is formed by crosslinking a second rubber composition. The first rubber composition or the second rubber composition includes a base rubber, a co-crosslinking agent, a crosslinking initiator, and an acid and/or a salt. The co-crosslinking agent is:
(1) an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms; and/or
(2) a metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms.
A hardness Hm2 of the second mid layer 8 is greater than a hardness Hm1 of the first mid layer 6. The hardness Hm2 is greater than a hardness Hc of the cover 12.
The present invention provides a solid golf ball having exceptional rebound characteristics and flight performance, as well as good shot feel. The present invention relates to a solid golf ball comprising at least one layer of a core, and at least one layer of a cover formed on the core, wherein at least one layer including the inmost layer of the core is formed by vulcanizing a rubber composition comprising a base rubber, a co-crosslinking agent, a vulcanization initiator and a filler, the core has a center hardness in JIS-C hardness of 40 to 60, a surface hardness in JIS-C hardness of 80 to 95 and a hardness difference (B−A) between a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) and the center hardness (A) of not less than 1 to less than 10.
An object of the present invention is to provide a golf ball comprising a core formed from a rubber composition containing (d) a carboxylic acid and/or a salt thereof and traveling a great flight distance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (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 carboxylic acid and/or a salt thereof and two or more kinds of (e) organic sulfur compounds, provided that the rubber composition further contains (f) a metal compound in case of containing only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent.