Golf ball incorporating positive hardness gradient thermoset polyurethane outer cover layer
Golf ball comprising a positive hardness gradient core and an outer cover layer having a microhardness gradient and being formed from a thermoset polyurethane material throughout, and having: i) a treated region that is contacted with a thermoset polyurethane microhardness-increasing solution consisting of an isocyanate portion and at least one non-aqueous solvent; and ii) an untreated region that is not contacted with the thermoset polyurethane microhardness-increasing solution. The treated region comprises the isocyanate portion, whereas the untreated region does not comprise the isocyanate portion. Treated region has a microhardness M 1 that is greater than microhardness M 2 of untreated region to define the outer cover layer positive microhardness gradient ΔM=M 1 −M 2 . The treated region may have a depth Dtr that extends inward from the cover outer surface and in some embodiments is less than a thickness of the untreated region. Treated region may alternatively extend from the inner surface toward outer surface.
1. A golf ball comprising:
a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, the soft transition region having a thickness of about 4 mm or less and comprising about 10 percent to about 45 percent of a trans-polybutadiene isomer; and
wherein the core has an outer surface hardness greater than a hardness at the geometric center to define a positive hardness gradient of about 12 Shore C to 68 Shore C; and a secondary gradient quotient, GQ′, from about 4 to 13, GQ′ being defined by the equation:
G
′
+
T
10
×
COR
where G′ is the core positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s; and
an outer cover layer formed from a thermoset polyurethane material throughout and having a treated region including at least a cover outer surface and an untreated region extending from a cover inner surface to the treated region;
wherein the treated region is contacted with a thermoset polyurethane microhardness-increasing solution consisting of an isocyanate portion and at least one non-aqueous solvent;
wherein the treated region comprises the isocyanate portion and has a microhardness M 1 that is greater than a microhardness M 2 of the untreated region, wherein the untreated region is not contacted with the thermoset polyurethane microhardness-increasing solution and does not comprise the isocyanate portion.
2. The golf ball of claim 1 , wherein the outer cover layer has a positive microhardness gradient ΔM=M 1 −M 2 , wherein M 1 is greater than M 2 by up to 1 Shore M hardness point.
3. The golf ball of claim 1 , wherein the outer cover layer has a positive microhardness gradient ΔM=M 1 −M 2 , wherein M 1 is greater than M 2 by up to about 10 Shore M hardness points.
4. The golf ball of claim 1 , wherein the outer cover layer has a positive microhardness gradient ΔM=M 1 −M 2 , wherein M 1 is greater than M 2 by greater than 10 Shore M hardness points.
5. The golf ball of claim 1 , wherein the treated region extends inward from the cover outer surface a depth Dtr that is less than a thickness of the outer cover layer.
6. The golf ball of claim 1 , wherein the treated region extends inward from the cover outer surface a depth Dtr that is less than a thickness of the untreated region.
7. The golf ball of claim 6 , wherein depth Dtr is from about 10 μm to about 350 μm.
8. The golf ball of claim 1 , wherein the isocyanate portion consists of at least one of tolylene-2,6-diisocyanate, tolylene-2,4-diisocyanate, 2,2′ diphenylmethanediisocyanate, 2,4′ diphenylmethanediisocyanate, 4,4′-diphenylmethanediisocyanate, polymethylene polyphenyl polyisocyanate, 1,5-diisocyanatonaphthalene, isophorone diisocyanate (including isomer mixtures), 4,4′-dicyclohexylmethane diisocyanate, hexamethylene-1,6-diisocyanate, m-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, tolidine diisocyanate, norbornene diisocyanate, derivatives thereof, and combinations thereof.
9. The golf ball of claim 8 , wherein the solvent is selected from ketones, acetates, alcohols, acetic acid and acetic anhydride, aromatic hydrocarbons, esters, polyesters, polyethers, and combinations thereof.
10. The golf ball of claim 9 , wherein the ketone is acetone.
11. The golf ball of claim 10 , wherein the treated outer surface is crosslinked by a reaction between active hydrogen functionality of the molded thermoset polyurethane material and isocyanates of the isocyanate portion.
12. The golf ball of claim 11 , wherein the treated outer surface is exposed to a catalyst solution comprising an organometallic compound and a non-aqueous solvent and wherein the treated region comprises the organometallic compound.
13. The golf ball of claim 5 , wherein the molded thermoset polyurethane material is formed from an isocyanate-containing prepolymer and at least one chain extender in an amount sufficient to provide an isocyanate index of at least about 115.
14. The golf ball of claim 5 , wherein the molded thermoset polyurethane material is formed from an isocyanate-containing prepolymer and at least one chain extender in an amount sufficient to provide an isocyanate index of 95 or less.
15. The golf ball of claim 14 , wherein the at least one chain extender comprises multifunctional polyols, polyamines, polyamides, polymercaptans, polyacids, polyester-based polyols, polybutadiene-based polyols, diamines, diacids and mixtures thereof.
16. The golf ball of claim 5 , wherein the outer cover surface is exposed to and contains at least one excess hydroxyl-functional group-containing ingredient prior to contacting the thermoset polyurethane microhardness-increasing solution and comprising the isocyanate portion.
17. The golf ball of claim 16 , wherein the hydroxyl-functional group-containing ingredient is butane diol.
18. The golf ball of claim 5 , wherein the isocyanate portion comprises at least one isocyanate that is different than each isocyanate of the thermoset polyurethane material of the cover.
19. The golf ball of claim 5 , wherein the positive hardness gradient of the core is about 12 Shore C to 45 Shore C and M 1 is greater than 50 Shore M.
20. The golf ball of claim 5 , wherein the positive hardness gradient of the core is about 12 Shore C to 45 Shore C and M 1 is from 70 Shore M to 90 Shore M.
21. The golf ball of claim 5 , wherein the positive hardness gradient of the core is about 12 Shore C to 45 Shore C and M 1 is greater than 90 Shore M.
22. The golf ball of claim 21 , wherein the secondary gradient quotient, GQ′, is about 3.75 to about 12.75.
23. A golf ball comprising:
a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface, the soft transition region having a thickness of about 4 mm or less and comprising about 2 percent to about 10 percent of a trans-polybutadiene isomer; and
wherein the core has an outer surface hardness greater than a hardness at the geometric center to define a positive hardness gradient of about 10 Shore C to 48 Shore C; and a secondary gradient quotient, GQ′, from about 1.5 to 7.25, GQ′ being defined by the equation:
G
′
+
T
10
×
COR
where G′ is the core positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s; and
an outer cover layer formed from a thermoset polyurethane material throughout and having a treated region including at least a cover outer surface and an untreated region extending from a cover inner surface to the treated region;
wherein the treated region is contacted with a thermoset polyurethane microhardness-increasing solution consisting of an isocyanate portion and at least one non-aqueous solvent;
wherein the treated region comprises the isocyanate portion and has a microhardness M 1 that is greater than a microhardness M 2 of the untreated region, wherein the untreated region is not contacted with the thermoset polyurethane microhardness-increasing solution and does not comprise the isocyanate portion.
24. The golf ball of claim 23 , wherein the treated region extends inward from the cover outer surface a depth Dtr that is less than a thickness of the untreated region.
25. The golf ball of claim 24 , wherein depth Dtr is from about 10 μm to about 350 μm.
26. The golf ball of claim 25 , wherein the secondary gradient quotient, GQ′, is about 3.75 to about 12.75.
27. A golf ball comprising:
a core having a first outer surface and a geometric center;
wherein the first outer surface has a hardness of about 68 Shore C to 92 Shore C, the geometric center has a hardness of about 45 Shore C to 85 Shore C, and the first outer surface hardness is greater than the geometric center hardness by about 5 to 21 Shore C to define a positive hardness gradient;
an inner cover layer, the inner cover layer comprising an ionomeric material and having a material hardness of about 60 Shore D or greater; and
an outer cover layer comprising a polyurea or a polyurethane composition throughout and having a treated region including at least a cover outer surface and an untreated region extending from a cover inner surface to the treated region and having a material hardness of about 60 Shore M or greater;
wherein the treated region is contacted with a thermoset polyurethane microhardness-increasing solution consisting of an isocyanate portion and at least one non-aqueous solvent;
wherein the treated region comprises the isocyanate portion and has a microhardness M 1 that is greater than the material hardness of the untreated region, wherein the untreated region is not contacted with the thermoset polyurethane microhardness-increasing solution and does not comprise the isocyanate portion.
28. The golf ball of claim 27 , wherein the treated region extends inward from the cover outer surface a depth Dtr that is less than a thickness of the untreated region.
29. The golf ball of claim 28 , wherein depth Dtr is from about 10 μm to about 350 μm.
30. The golf ball of claim 29 , wherein the secondary gradient quotient, GQ′, is about 3.75 to about 12.75.