Golf ball
In a golf ball for professional golfers and skilled amateurs which has a single-layer core, a cover and at least one intermediate layer therebetween, the intermediate layer has a specific gravity of at least 1.05, the sphere the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) and the ball have a surface hardness relationship which satisfies the condition: (surface hardness of intermediate layer-encased sphere)>(surface hardness of ball). The core has a diameter of from 35.5 to 39.5 mm and a distinctive hardness profile that satisfies specific conditions. The ball is endowed with both an excellent flight performance and excellent durability to repeated impact.
1. A golf ball comprising a single-layer core, a cover and at least one intermediate layer interposed between the core and the cover, wherein the intermediate layer has a specific gravity of at least 1.05, the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) and the ball have a surface hardness relationship therebetween which satisfies the condition:
(surface hardness of intermediate layer-encased sphere)>(surface hardness of ball);
the core has a diameter of from 35.5 to 39.5 mm and a corresponding radius; and the core has a hardness profile which satisfies the following conditions:
( H 75 −H 50)>( H 25 −H 0)
( H 100 −H 87.5)>( H 50 −H 25)
30.0≥( H 100 −H 0)≥20.0
absolute value of( H 87.5 −H 0)/( H 50 −H 0)≥3.0,
4.0≤( H 75− H 50)≤9.0
where H100 is the Shore C hardness at a surface of the core, H87.5 is the Shore C hardness at a position 87.5% of the core radius outward from a center of the core, H75 is the Shore C hardness at a position 75% of the core radius outward from the core center, H62.5 is the Shore C hardness at a position 62.5% of the core radius outward from the core center, H50 is the Shore C hardness at a position 50% of the core radius outward from the core center, H37.5 is the Shore C hardness at a position 37.5% of the core radius outward from the core center, H25 is the Shore C hardness at a position 25% of the core radius outward from the core center, H12.5 is the Shore C hardness at a position 12.5% of the core radius outward from the core center and H0 is the Shore C hardness at the core center.
2. The golf ball of claim 1 which satisfies the condition:
0≤( H 100 −H 87.5)≤3.0.
3. The golf ball of claim 1 which satisfies the condition:
3.0≤( H 25− H 0)≤6.0.
4. The golf ball of claim 1 which satisfies the condition:
( H 75− H 50)>( H 25− H 0)>( H 100− H 87.5)>( H 50− H 25).
5. The golf ball of claim 1 which satisfies the condition:
23.0≥( H 87.5− H 0)≥17.0.
6. The golf ball of claim 1 which satisfies the condition:
70≥ H 0≥62.
7. The golf ball of claim 1 , wherein the core has a deflection of from 2.5 to 3.5 mm when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) and the ball has a deflection of from 2.1 to 2.8 mm when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf).
8. The golf ball of claim 1 wherein, letting CLI be the coefficient of lift measured at a Reynolds number of 80,000 and a spin rate of 2,000 rpm and CL2 be the coefficient of lift measured at a Reynolds number of 70,000 and a spin rate of 1,900, CL1 and CL2 satisfy the condition:
0.900≤ CL 2/ CL 1.
9. The golf ball of claim 1 wherein, letting CL3 be the coefficient of lift measured at a Reynolds number of 200,000 and a spin rate of 2,500 rpm and CL4 be the coefficient of lift measured at a Reynolds number of 120,000 and a spin rate of 2,250, CL3 and CL4 satisfy the condition:
1.250≤ CL 4/ CL 3≤1.300.
10. The golf ball of claim 1 , wherein the core is a material molded under heat from a rubber composition comprising:
(A) a base rubber,
(B) an organic peroxide,
(C) water or a metal monocarboxylate or both, and
(D) sulfur.
11. The golf ball of claim 10 , wherein components (C) and (D) have a weight ratio (D)/(C) therebetween which is from 0.02 to 0.20.
12. The golf ball of claim 1 , wherein the intermediate layer comprises an ionomer resin as a base resin and an inorganic granular filler.
13. A golf ball comprising a single-layer core, a cover and at least one intermediate layer interposed between the core and the cover, wherein the intermediate layer has a specific gravity of at least 1.05, the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) and the ball have a surface hardness relationship therebetween which satisfies the condition:
(surface hardness of intermediate layer-encased sphere)>(surface hardness of ball);
the core has a diameter of from 35.5 to 39.5 mm and a corresponding radius; and the core has a hardness profile which satisfies the following conditions:
( H 75− H 50)>( H 25− H 0)
( H 100− H 87.5)>( H 50− H 25)
0≥( H 100 −H 0)≥20.0
absolute value of( H 87.5− H 0)/( H 50− H 0)≥3.0,
−1.0≤( H 50 −H 25)≤1.0
where H100 is the Shore C hardness at a surface of the core, H87.5 is the Shore C hardness at a position 87.5% of the core radius outward from a center of the core, H75 is the Shore C hardness at a position 75% of the core radius outward from the core center, H62.5 is the Shore C hardness at a position 62.5% of the core radius outward from the core center, H50 is the Shore C hardness at a position 50% of the core radius outward from the core center, H37.5 is the Shore C hardness at a position 37.5% of the core radius outward from the core center, H25 is the Shore C hardness at a position 25% of the core radius outward from the core center, H12.5 is the Shore C hardness at a position 12.5% of the core radius outward from the core center and H0 is the Shore C hardness at the core center.
14. The golf ball of claim 13 which satisfies the condition:
0≤( H 100 −H 87.5)≤3.0.
15. The golf ball of claim 13 which satisfies the condition:
3.0≤( H 25 −H 0)≤6.0.
16. The golf ball of claim 13 which satisfies the condition:
( H 75− H 50)>( H 25− H 0)>( H 100− H 87.5)>( H 50− H 25).
17. The golf ball of claim 13 which satisfies the condition:
23.0≥( H 87.5 −H 0)≥17.0.
18. The golf ball of claim 13 which satisfies the condition:
70≥ H 0≥62.
19. The golf ball of claim 13 , wherein the core has a deflection of from 2.5 to 3.5 mm when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) and the ball has a deflection of from 2.1 to 2.8 mm when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf).
20. The golf ball of claim 13 wherein, letting CLI be the coefficient of lift measured at a Reynolds number of 80,000 and a spin rate of 2,000 rpm and CL2 be the coefficient of lift measured at a Reynolds number of 70,000 and a spin rate of 1,900, CL1 and CL2 satisfy the condition:
0.900≤ CL 2/ CL 1.
21. The golf ball of claim 13 wherein, letting CL3 be the coefficient of lift measured at a Reynolds number of 200,000 and a spin rate of 2,500 rpm and CL4 be the coefficient of lift measured at a Reynolds number of 120,000 and a spin rate of 2,250, CL3 and CL4 satisfy the condition:
1.250≤ CL 4/ CL 3≤1.300.
22. The golf ball of claim 13 , wherein the core is a material molded under heat from a rubber composition comprising:
(A) a base rubber,
(B) an organic peroxide,
(C) water or a metal monocarboxylate or both, and
(D) sulfur.
23. The golf ball of claim 22 , wherein components (C) and (D) have a weight ratio (D)/(C) therebetween which is from 0.02 to 0.20.
24. The golf ball of claim 13 , wherein the intermediate layer comprises an ionomer resin as a base resin and an inorganic granular filler.