Multi-piece golf balls containing a multi-layered core structure having layers with different hardness gradients and specific gravities are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity with metal material preferably dispersed in a first thermoset composition. The intermediate core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer ionomer resin; and the outer core layer is preferably formed from a second thermoset composition. The resulting ball has high resiliency and good spin control.

A golf ball 2 includes a spherical core 4, a mid layer 6, and a cover 8. The core 4 is obtained by crosslinking a rubber composition. The difference between: a hardness H(5.0) at a point which is located at a distance of 5 mm from the central point of the core 4; and a hardness Ho at the central point is 6.0 or greater. The difference between: a hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point; and the hardness H(5.0) is 4.0 or less. The difference between a hardness Hs at the surface of the core 4 and the hardness H(12.5) is 10.0 or greater. The difference between the hardness Hs and the hardness Ho is 22.0 or greater. There is no zone in which a hardness decreases from the central point to the surface. A Shore D hardness H3 of the cover is greater than a Shore D hardness H2 of the mid layer.

A golf ball is provided that has a spherical core exhibiting a stiffness from 400 MPa to 200 GPa. The stiffness of the core may be controlled by adjusting the materials of construction and the ratio of the materials. This results in a golf ball that is legal for play and capable of drive distances essentially equivalent to those of currently-available high performance golf balls, but also provides a golf ball that has less hook and slice during play.

A golf ball includes a relatively large polymer core and has a soft ball compression. The polymer is, in the illustrated embodiments, a highly neutralized acid polymer. The golf ball may, optionally, include an outer core made of a different material, such as a thermoset polybutadiene rubber. The golf ball may, optionally, include a mantle layer made of an ionomer material. The inner core having a diameter of between 24 mm and 40 mm, and in some designs, between 28 mm and 32 mm, yields increased iron initial velocity and lower iron spin while maintaining driver performance.

An object of the present invention is to provide a golf ball showing a low spin rate on driver shots and a high spin rate on approach shots. The present invention provides a golf ball having a low hardness part having a hardness in a range from 5 to 40 in Shore D hardness or a lowest hardness point in a core hardness distribution in a region located at a distance from 36.0% to 65.0% of a radius of the golf ball from a center point of the golf ball.

Multi-piece solid golf ball having a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and an outermost layer encasing the intermediate layer, the envelope layer-encased sphere, the intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, the intermediate layer and the cover have thicknesses which satisfy a specific relationship, and the core has a hardness profile in which the hardnesses at the core surface, core center, a position 5 mm from the core center, and a position midway between the core surface and center satisfy specific relationships.

In a multi-piece solid golf ball having a core, an intermediate layer encasing the core and a cover which encases the intermediate layer and has numerous dimples on an outside surface thereof, the intermediate layer is formed of a resin material, the cover is formed of a urethane resin material, the core has a diameter of at least 38.0 mm, the core has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) of at least 3.9 mm, the core has a center and a surface such that the value obtained by subtracting the JIS-C hardness at the core center from the JIS-C hardness at the core surface is at least 15, the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) has a surface hardness on the Shore D hardness scale of at least 69, the ball has a surface hardness on the Shore D hardness scale of 62 or less, and the (intermediate layer thickness)/(core diameter) value is from 0.025 to 0.043, the (cover thickness)/(core diameter) value is from 0.014 to 0.027.

In a golf ball having a core composed of one or more layer, the outermost layer of the core is formed of a rubber composition containing a base rubber and an α,β-unsaturated metal carboxylate, an envelope layer directly encasing the core is formed of a resin composition containing a thermoplastic resin having a structure that includes α,β-ethylenically unsaturated carboxylic acid copolymerization units, and a surface of the core outermost layer and the envelope layer adjoin each other through an intervening oxazoline group-containing substance. The golf ball has improved adhesion between the rubber-based core and the cover layer that directly encases the core and is formed of an ionomer resin or other α,β-ethylenically unsaturated carboxylic acid copolymer-containing resin material.

An object of the present invention is to provide a golf ball having an excellent flight performance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein a hardness difference D1 (H75−H0) between a hardness H75 at a point radially located at a distance of 75% from a center of the spherical core and a center hardness H0 of the spherical core is 10 or more and 27 or less in Shore C hardness, and a hardness difference D2 (Hs−H75) between a surface hardness Hs of the spherical core and the hardness H75 at the point radially located at the distance of 75% from the center of the spherical core is 0 or more and 6.5 or less in Shore C hardness.

A golf ball with improved durability is disclosed herein. The golf ball has a mantle layer comprising a blend of ionomers and methyl methacrylate, butadiene, styrene (MBS) with a weight percentage of MBS ranging from 5 to 15 weight percent of the mantle layer.