Golf ball having at least three layers comprising an ionomeric and/or HNP composition, wherein for each two adjacent layers, a relationship is established between a ratio of the volumes of the two adjacent layers and a ratio of the percent neutralizations of those two layers such that the volumes and % neutralizations of all layers are interrelated and interdependent to produce unique and desirable playing characteristics. In one embodiment, each of T layers, wherein T≧3, has a different volume “V” and comprises an ionomeric/HNP composition having a different % neutralization “N”; and wherein each of n inner layers of the T layers (n<T) has an adjacent surrounding layer n+1 such that a volume V.sub.n and a % neutralization N.sub.n of each inner layer and a volume V.sub.(n+1) and % neutralization N.sub.(n+1) of each adjacent surrounding layer n+1 satisfy the relationship (V.sub.(n+1)−V.sub.n)/V.sub.(n+1)≦(N.sub.(n+1)−N.sub.n)/N.sub.n.

Multi-layered golf balls having at least one layer made of a foamed silicone composition are provided. Multi-layered golf balls having at least one layer made of non-foamed silicone elastomer composition also are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The foamed silicones have good thermal stability and durability without sacrificing resiliency. The non-foamed silicone elastomers have high elongation, tensile strength, chemical/fluid-resistance, and weatherability properties. These compositions can be used to form any layer, for example, core, intermediate, or cover, in the golf ball.

A rubber composition for a golf ball core includes (a) a conjugated diene polymer, (b) a copolymer of a conjugated diene compound and a non-conjugated olefin, and (c) an organic peroxide. Golf balls having at least one core layer formed of such a rubber composition and a cover of one or more layers encasing the core exhibit improved durability to cracking on repeated impact while maintaining the basic properties required of golf balls, such as flight and spin controllability on approach shots.

An object of the present invention is to provide a golf ball having excellent durability. The present invention provides a golf ball comprising a core and at least one cover layer covering the core, wherein the core is formed from a core rubber composition containing (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a hindered phenol compound, and (b) the co-crosslinking agent and (d) the hindered phenol compound are blended in the core rubber composition such that the following expression (1) is satisfied:
0.04≤HF/B≤0.35  (1) in the formula (1), HF=a number of OH functional group in one molecule of (d) the hindered phenol compound×an amount of (d) the hindered phenol compound (mole) with respect to 100 parts by mass of (a) the base rubber, and B=an amount of (b) the co-crosslinking agent (mole) with respect to 100 parts by mass of (a) the base rubber.

A golf ball 2 includes a core 4, an inner cover 6 positioned outside the core 4, and an outer cover 8 positioned outside the inner cover 6. The core 4 has a capsule 14, a plurality of separators 16, an electronic unit 18, and a plurality of fillings 20. The capsule 14 has a melting point of not lower than 100° C. A ratio P1 of a volume Vr of the capsule 14 to a volume Vc of the core 4 is not less than 25% and not greater than 75%. The electronic unit 18 is housed in the capsule 14. The electronic unit 18 detects behavior of the golf ball 2.

A method for forming a golf ball with a graphene core disclosed herein. The method includes mixing a graphene masterbatch material with a polybutadiene material to form a core mixture, wherein the graphene masterbatch material comprises graphene in an amount from 0.1 to 80.0 weight percent of the graphene masterbatch material mixed with a carrier polymer in an amount from 99.9 to 20 weight percent of the graphene masterbatch material.

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.

An object of the present disclosure is to provide a golf ball having an increased spin rate when being hit with an 8-iron while suppressing rise in a spin rate when being hit with a driver. The present disclosure provides a golf ball comprising a spherical core having an inner core and an outer core, and a cover positioned outside the spherical core, wherein A×a is 12,200 or less and B×b is 20,400 or more, where “a” represents an average hardness (Shore C) of a hardness (H2.5) at a point of 2.5 mm from a center of the spherical core and a hardness (H5) at a point of 5 mm from the center of the spherical core, “b” represents an average hardness (Shore C) of a hardness (H7.5) at a point of 7.5 mm from the center of the spherical core and a hardness (H9) at a point of 9 mm from the center of the spherical core, “A” represents an impulse difference (kN.Math..Math.s) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with a driver, and “B” represents an impulse difference (kN.Math..Math.s) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with an 8-iron.

A method for forming a golf ball core with a nanofiller masterbatch is disclosed herein. The method includes mixing the nanofiller masterbatch, a graphene masterbatch material with other materials to form a core mixture, wherein the masterbatch preferably comprises 1-80% by weight of nanofillers and 20-99% by weight of a carrier polymer.

A golf ball according to the present invention includes: a module including an electronic circuit and its power source; a protective layer that surrounds an outer periphery of the module and is formed from a material having a Shore D hardness of at least 60; a core that surrounds an outer periphery of the protective layer; and a cover that surrounds an outer periphery of the core. A weight may be arranged on a surface of the protective layer. A difference between a value MOImax of the moment of inertia in a direction in which the moment of inertia of the golf ball is maximum and a value MOImin of the moment of inertia in a direction in which the moment of inertia of the golf ball is minimum is at most 1.0 g.Math.cm.sup.2.