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 which accounts for at least 50 wt % of the resin composition, 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.

A golf ball can include a core, a mid layer, and a cover. The golf ball can satisfy the following mathematical formulas (1), (2), and (3):
C1≤(124.8−Hs)/11.5  (1)
C2−C1≥(−1/6*C1+(68−H2)/20+(5−Hd)/100)*T2   (2)
10≤H2*T2−H3*T3  (3), where C1 is an amount of compressive deformation (mm) of the core, C2 is an amount of compressive deformation (mm) of a sphere including the core and the mid layer, Hd is Hs−Ho, Ho is a hardness (Shore C) of a center the core, Hs is a hardness (Shore C) of a surface of the core, H2 is a hardness (Shore D) of the mid layer, H3 is a hardness (Shore D) of the cover, T2 is a thickness (mm) of the mid layer, and T3 is a thickness (mm) of the cover.

In a golf ball having a core, an envelope layer, an intermediate layer and a cover, the core, the envelope layer-encased sphere obtained by encasing the core with the envelope layer, the intermediate layer-encased sphere obtained by encasing the envelope layer-encased sphere with the intermediate layer and the ball obtained by encasing the intermediate layer-encased sphere with the cover have respective deflections when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which satisfy specific conditions. This ball achieves a good distance on shots with a utility club and with irons, is receptive to spin in the short game and has a soft feel at impact on all shots, making it useful to amateur golfers.

Golf ball comprising a core and a cover, wherein the core includes between 2 and 20 smaller spheres that are surrounded by a second core composition having at least one different physical property than the composition(s) forming the smaller spheres. The smaller spheres can be entirely surrounded by the second core composition; or, at least two smaller adjacent spheres may each be partially surrounded by the second core composition while also being in partial contact with each other.

A golf ball with a core comprising polybutadiene and graphene is disclosed herein. The golf ball has a single core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an inner core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an outer core comprising polybutadiene and graphene.

A golf ball 2 includes a core 4 and a cover 6 positioned outside the core 4. The cover 6 is formed in a mold having support pins by injection molding. A ratio (V/S) of a volume V (mm.sup.3) of the cover 6 to an amount of compressive deformation S (mm) of the core 4 is not less than 1000 and not greater than 1900. The cover 6 has a shore D hardness of not greater than 62. The golf ball 2 has a plurality of dimples 8 on a surface thereof. A total volume W of these dimples is not less than 490 mm.sup.3 and not greater than 620 mm.sup.3. A ratio (α/P) of a latitude α (degree) of each support pin to a total cross-sectional area P (mm.sup.2) of the support pins is not less than 0.35 and not greater than 0.60.

A method for manufacturing a golf ball having a core, an intermediate layer and a cover that is formed of a resin material composed primarily of a polyurethane resin and has a thickness of 0.1 mm to 0.7 mm by injection molding the cover using a vertically separating two-part injection mold having specific gate and support pin configurations. This method enables a relatively soft urethane resin cover that is thin and of high quality to be formed, and has a good golf ball productivity.

In a golf ball having a core, an intermediate layer and a cover, the core is formed primarily of a base rubber and has a diameter set in a specific range, and the intermediate layer and cover are each formed of resin materials. The core has an internal hardness such that, regarding the hardness at the core center, the hardnesses at positions located at 2 mm intervals from the core center outward up to 16 mm and the core surface hardness, the hardness differences therebetween are set within a specific range. The ball surface hardness is set so as to be higher than the surface hardness of the intermediate layer-encased sphere. This ball achieves a satisfactory distance on full shots not only with a driver, but also with a long iron or a middle iron, in addition to which it has an excellent durability to repeated impact.

In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the envelope layer is formed into two layers—an inner envelope layer and an outer envelope layer. The inner envelope layer-encased sphere, outer envelope layer-encased sphere, intermediate layer-encased sphere and ball have respective surface hardness that satisfy a specific relationship. The inner envelope layer or outer envelope layer is formed primarily of one or more elastomer, and further the core has a particular hardness profile. This ball has an excellent flight when struck by golfers whose head speeds are not that fast and has a good, soft feel at impact, thus making it highly suitable for amateur golfers.

In a golf ball having a core, envelope layer, intermediate layer and cover, the (core diameter)/(ball diameter) value falls within a particular range, the core has a specific hardness profile, and the Shore C hardness relationships among the core center and surface hardnesses and the surface hardnesses of the envelope layer-encased sphere, intermediate layer-encased sphere and ball satisfy the following conditions:
core surface hardness<surface hardness of envelope layer-encased sphere<surface hardness of intermediate layer-encased sphere>ball surface hardness,  (1)
(surface hardness of envelope layer-encased sphere)−(core center hardness)≥28.  (2) Also, the envelope layer, intermediate layer and cover have respective thicknesses which satisfy the condition:
cover thickness<intermediate layer thickness envelope layer thickness.  (3) This ball enables mid-level and skilled amateur golfers to achieve superior distances on driver shots and on iron shots, and moreover has a soft yet good feel at impact.