A golf ball 2 has a hollow center 8 , a mid layer 10 , an inner cover 12 and an outer cover 14 . The center 8 is formed by crosslinking a rubber composition. The rubber composition contains a natural rubber as a base polymer. The rubber composition contains sulfur. The mid layer 10 is formed by crosslinking a rubber composition. This rubber composition includes butadiene as a principal component of the base polymer. The center 8 has an inside diameter of 2 mm or greater and 13 mm or less. The center 8 has an outside diameter of 5 mm or greater and 15 mm or less. The center 8 has a surface JIS-C hardness H 2 of 25 or greater and 55 or less. A difference (H 4 −H 3 ) between a surface JIS-C hardness H 4 of the mid layer 10 and a JIS-C hardness H 3 of an innermost part of the mid layer is equal to or greater than 10.
1. A golf ball comprising a core and a cover positioned outside the core, wherein;
the core has a center and a mid layer positioned outside the center, and a hollow space is located within the center,
the center has an inside diameter of 2 mm or greater and 13 mm or less,
the center has an outside diameter of 5 mm or greater and 15 mm or less,
a JIS-C hardness H 2 of a surface of the center is 25 or greater and 55 or less, and
a difference (H 4 −H 3 ) between a JIS-C hardness H 4 of a surface of the core and a JIS-C hardness H 3 of an innermost part of the mid layer is equal to or greater than 10.
2. The golf ball according to claim 1 , wherein a difference (H 2 −H 1 ) between the hardness H 2 and a hardness H 1 of an innermost part of the center is 1 or greater and 15 or less.
3. The golf ball according to claim 1 , wherein a difference (H 3 −H 2 ) between the hardness H 3 and the hardness H 2 is equal to or less than 35.
4. The golf ball according to claim 1 , wherein a difference (H 4 −H 2 ) between the hardness H 4 and the hardness H 2 is equal to or greater than 40.
5. The golf ball according to claim 1 , wherein the JIS-C hardness H 1 of an innermost part of the center is equal to or less than 35.
6. The golf ball according to claim 1 , wherein the hardness H 3 is 45 or greater and 75 or less.
7. The golf ball according to claim 1 , wherein the hardness H 4 is 65 or greater and 90 or less.
8. The golf ball according to claim 1 , wherein;
the center is formed by crosslinking a rubber composition, and
the rubber composition contains sulfur as a crosslinking agent.
9. The golf ball according to claim 8 , wherein the rubber composition contains 100 parts by weight of a base rubber and 2.0 parts by weight or greater and 10.0 parts by weight or less of the sulfur.
10. The golf ball according to claim 8 , wherein the rubber composition contains 100 parts by weight of the base rubber and 0.5 parts by weight or greater and 7.0 parts by weight or less of a vulcanization accelerator agent.
11. The golf ball according to claim 8 , wherein the rubber composition contains 100 parts by weight of the base rubber and 3 parts by weight or greater and 20 parts by weight or less of silica.
12. The golf ball according to claim 1 , wherein the rubber composition for the center contains a natural rubber.
13. The golf ball according to claim 1 , wherein;
the mild layer is formed by crosslinking a rubber composition, and
a base rubber of the rubber composition contains polybutadiene as a principal component.
14. The golf ball according to claim 13 , wherein the rubber composition contains 0.1 parts by weight or greater and 1.5 parts by weight or less of an organic sulfur compound per 100 parts by weight of the base rubber.
15. The golf ball according to claim 1 , wherein the mid layer has a thickness of 10 mm or greater and 20 mm or less.
16. The golf ball according to claim 1 , wherein;
the cover includes an inner cover and an outer cover, and
a Shore D hardness H 5 of the inner cover is smaller than a Shore D hardness H 6 of the outer cover.
17. The golf ball according to claim 16 , wherein a difference (H 6 −H 5 ) between the hardness H 6 and the hardness H 5 is equal to or greater than 10.
18. The golf ball according to claim 16 , wherein the hardness H 5 is 20 or greater and 50 or less.
19. The golf ball according to claim 16 , wherein the hardness H 6 is equal to or greater than 57.
20. The golf ball according to claim 16 , wherein;
the inner cover is made of a thermoplastic resin composition, and
the outer cover is made of a thermoplastic resin composition.