Rubber compositions comprising quinhydrones and the use thereof in golf balls

1. A golf ball comprising at least one layer formed from a rubber composition comprising:

(a) a base rubber;

(b) a free radical initiator; and

(c) a quinhydrone.

2. The golf ball of claim 1 , wherein the free radical initiator is present in the rubber composition in an amount of at least 0.05 parts by weight per 100 parts of the base rubber.

3. The golf ball of claim 2 , wherein the quinhydrone is present in the rubber composition in an amount of at least 0.05 parts by weight per 100 parts of the base rubber.

4. The golf ball of claim 3 , wherein a ratio (P QUINHYDRONE /P INITIATOR ) of the amount of the quinhydrone present in the rubber composition (P QUINHYDRONE ), measured in parts by weight per 100 parts of the base rubber, to the amount of free radical initiator present in the rubber composition (P INITIATOR ), measured in parts by weight per 100 parts of the base rubber, is from 0.05 to 2.

5. The golf ball of claim 4 , wherein P QUINHYDRONE /P INITIATOR is from 0.25 to 2.

6. The golf ball of claim 4 , wherein P QUINHYDRONE /P INITIATOR is at least 0.05 and less than 0.5.

7. The golf ball of claim 4 , wherein P QUINHYDRONE /P INITIATOR is at least 0.25 and less than 0.5.

8. The golf ball of claim 4 , wherein P QUINHYDRONE /P INITIATOR is from 0.25 to 0.45.

9. The golf ball of claim 1 , wherein the quinhydrone is a selected from compounds represented by the following formula, and hydrates thereof:

wherein each R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently selected from the group consisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group, a carboxyl group (—COOH) and metal salts thereof and esters thereof, an acetate group (—CH 2 COOH) and esters thereof, a formyl group (—CHO), an acyl group, an acetyl group (—COCH 3 ), a halogenated carbonyl group, a sulfo group (—SO 3 H) and esters thereof, a halogenated sulfonyl group, a sulfino group (—SO 2 H), an alkylsulfinyl group, a carbamoyl group (—CONH 2 ), a halogenated alkyl group, a cyano group (—CN), an alkoxy group, a hydroxy group (—OH) and metal salts thereof, an amino group (—NH 2 ), a nitro group (—NO 2 ), an aryl group, an aryloxy group, an arylalkyl group, a nitroso group (—NO), an acetamido group (—NHCOCH 3 ), and a vinyl group (—CH═CH 2 ).

10. The golf ball of claim 9 , wherein each R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is hydrogen.

11. The golf ball of claim 3 , wherein the rubber composition comprises one or more coagents selected from metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates, wherein the metal is selected from magnesium, calcium, zinc, aluminum, lithium, and nickel; and wherein the total amount of metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates present in the rubber composition is less than 20 parts per 100 parts of the base rubber.

12. The golf ball of claim 1 , wherein the rubber composition is substantially free of organosulfur compounds.

13. The golf ball of claim 1 , wherein the golf ball comprises a core and a cover, and wherein the core is a single layer formed from the rubber composition.

14. The golf ball of claim 1 , wherein the golf ball comprises an inner core layer, an outer core layer, and a cover, and where the inner core layer is formed from the rubber composition.

15. The golf ball of claim 1 , wherein the golf ball comprises an inner core layer, an outer core layer, and a cover, and wherein the outer core layer is formed from the rubber composition.

16. A golf ball comprising a core and a cover, wherein the core has at least one layer formed from a rubber composition comprising:

(a) a base rubber;

(b) at least 0.05 parts by weight of a free radical initiator per 100 parts of the base rubber; and

(c) at least 0.15 parts by weight of a quinhydrone per 100 parts of the base rubber.

17. The golf ball of claim 16 , wherein a ratio (P QUINHYDRONE /P INITIATOR ) of the amount of the quinhydrone present in the rubber composition (P QUINHYDRONE ), measured in parts by weight per 100 parts of the base rubber, to the amount of free radical initiator present in the rubber composition (P INITIATOR ), measured in parts by weight per 100 parts of the base rubber, is at least 0.05.

18. The golf ball of claim 16 , wherein the rubber composition is substantially free of organosulfur compounds.

19. A golf ball comprising a core and a cover, wherein the core has at least one layer formed from a rubber composition comprising:

(a) a base rubber;

(b) at least 0.05 parts by weight of a free radical initiator, per 100 parts of the base rubber; and

(c) at least 0.15 parts by weight of a quinhydrone, per 100 parts of the base rubber;

wherein the quinhydrone is selected from compounds represented by the following formula, and hydrates thereof:

wherein each R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently selected from the group consisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group, a carboxyl group (—COOH) and metal salts thereof and esters thereof, an acetate group (—CH 2 COOH) and esters thereof, a formyl group (—CHO), an acyl group, an acetyl group (—COCH 3 ), a halogenated carbonyl group, a sulfo group (—SO 3 H) and esters thereof, a halogenated sulfonyl group, a sulfino group (—SO 2 H), an alkylsulfinyl group, a carbamoyl group (—CONH 2 ), a halogenated alkyl group, a cyano group (—CN), an alkoxy group, a hydroxy group (—OH) and metal salts thereof, an amino group (—NH 2 ), a nitro group (—NO 2 ), an aryl group, an aryloxy group, an arylalkyl group, a nitroso group (—NO), an acetamido group (—NHCOCH 3 ), and a vinyl group (—CH═CH 2 );

wherein a ratio (P QUINHYDRONE /P INITIATOR ) of the amount of the quinhydrone present in the rubber composition (P QUINHYDRONE ), measured in parts by weight per 100 parts of the base rubber, to the amount of free radical initiator present in the rubber composition (P INITIATOR ), measured in parts by weight per 100 parts of the base rubber, is from 0.25 to 2; and

wherein the rubber composition is substantially free of organosulfur compounds.

20. The golf ball of claim 19 , wherein P QUINHYDRONE /P INITIATOR is at least 0.25 and less than 0.5.