In a golf ball having a core and a cover consisting of a plurality of layers that encases the core, adhesion between adjoining cover layers is improved by judicious selection of the materials making up the cover layers, providing the ball with an improved durability to impact without diminishing the ball initial velocity.

An object of the present invention is to provide a golf ball exhibiting good shot feeling and excellent resilience. The present invention provides a golf ball comprising a spherical core and one or more cover layers disposed outside the spherical core, wherein at least one layer of the cover layers contains: (A) a base resin containing (a-1) an ionomer resin and having a material hardness of 59 or more in Shore D hardness; and (B) a polyrotaxane having a cyclodextrin with at least a part of hydroxyl groups of the cyclodextrin being modified with a caprolactone chain via OC.sub.3H.sub.6O group, a linear molecule piercing through a cyclic structure of the cyclodextrin, and blocking groups located at both terminals of the linear molecule to prevent disassociation of the cyclodextrin.

A golf ball 2 includes a core 4, a mid layer 6, a cover 8, and dimples 10. A Shore C hardness Hmc of the mid layer 6 is greater than a Shore C hardness Hs at a surface of the core 4. A Shore D hardness He of the cover 8 is less than a Shore D hardness Hm of the mid layer 6. Peak values and orders of maximum peaks of data constellations of the golf ball 2 are calculated. A minimum value of the peak values is not less than 95 mm. A minimum value of the orders is not less than 27, and a maximum value of the orders is not greater than 37. An average of the orders is not less than 30 and not greater than 34.

A golf ball includes a core, one or more mid layers, a cover, and dimples. A central hardness Ho and a surface hardness Hs of the core, a hardness Hm(min) of a layer having a lowest hardness among the mid layers, and a hardness Hc of the cover satisfy the following mathematical formulas (i) to (iv).

HsHo>15(i)

HcHm(min)>20(ii)

10<Hm(min)Ho<15(iii)

5<HcHs<20(iv)

A golf ball includes a spherical core, a mid layer, an inner cover, and an outer cover. A hardness Hm of the mid layer is greater than a hardness Hinc of the inner cover which is greater than a hardness Houc of the outer cover. A difference (HmHouc) is greater than 25. A volume Vm of the mid layer is greater than a volume Vinc of the inner cover which is greater than a volume Vouc of the outer cover. A ratio [(Vm+Vinc+Vouc)/V] of a sum (Vm+Vinc+Vouc) relative to a volume V of an entirety of the golf ball is less than 0.30. A ratio (Vm/Vouc) is greater than 1.50. A product (Vm*Hm) and a product (Vouc*Houc) meet the following relationship: [(Vm*Hm)/(Vouc*Houc)]>3.0.

In a multi-piece solid golf ball having a two-layer core with an inner core layer and an outer core layer, a cover, and at least one intermediate layer between the core and cover, the inner and outer core layers are formed of different rubber compositions, and the intermediate layer and the cover are formed of different resin compositions. The inner core layer diameter, the hardness relationship between the surface of the outer core layer and the center of the inner core layer, and the material hardness of the intermediate layer fall within specific ranges. Also, within the ball, the intermediate layer-encased sphere has a higher surface hardness than the cover-encased sphere. This golf ball has a larger spin rate-lowering effect on full shots with a driver, resulting in an increased distance, and also has an excellent spin performance on approach shots, thus providing the golfer with a competitive advantage.

A polyurethane coating for a golf ball that is based on polyol mixture containing acrylic polyol and BEPD based caprolcatone polyol is disclosed herein. The polyurethane coating comprises a part A component and a part B component, with the part A component comprising an acrylic polyol, a BEPD polyol, a 3-Oxazolidineethanol, a fluorosurfactant, a hindered amine light stabilizer, a UV-absorber, an optical brightener, a dibutyltin dilaurate catalyst, and an organic solvent, and the part B component comprising an aliphatic polyisocyanate and an organic solvent.

A golf ball includes a spherical core, and a cover covering the spherical core. The spherical core is formed from a rubber composition including a base rubber, a co-cross-linking agent, a cross-linking initiator, and an unsaturated fatty acid and/or a metal salt thereof, the co-cross-linking agent includes ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, the unsaturated fatty acid and/or metal salt thereof excludes an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof, an unsaturated aliphatic carboxylic acid that forms the unsaturated fatty acid and/or metal salt thereof has a functional group other than a carboxy group and a carbon-carbon unsaturated bond, and the rubber composition further includes a metal compound when the co-cross-linking agent is only an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms.

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.sub.1 that is greater than microhardness M.sub.2 of untreated region to define the outer cover layer positive microhardness gradient M=M.sub.1M.sub.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.

The present invention is directed to multi-layer golf balls including a layer formed from a composition comprising a relatively soft or low modulus HNP, a layer formed from a composition comprising a relatively hard or high modulus HNP, an inner cover layer formed from a thermoplastic composition, and an outer cover layer.