An object of the present disclosure is to provide a golf ball having excellent durability and flight distance and good shot feeling for an average golfer who hits a golf ball at a slow head speed. The present disclosure provides a golf ball comprising a spherical core and at least two cover layers covering the spherical core, wherein a difference between a core surface crosslinking density and a core center crosslinking density is more than 1.0×10.sup.2 mol/m.sup.3 and less than 9.0×10.sup.2 mol/m.sup.3, a hardness difference between a core surface hardness Cs (Shore C hardness) and a core center hardness Co (Shore C hardness) is 13.0 or more and 30.0 or less, a compression deformation amount of the core when applying a load from an initial load of 98 N to a final load of 1275 N to the core is less than 3.8 mm, and the at least two cover layers include a first cover layer and a second cover layer positioned closer to the spherical core than the first cover layer, an average hardness Dave=(Ti×Hi+To×Ho)/(Ti+To) of the first cover layer and the second cover layer is 55 or more, wherein To (mm) is a thickness of the first cover layer, Ho (Shore D) is a slab hardness of the first cover layer, Ti (mm) is a thickness of the second cover layer, and Hi (Shore D) is a slab hardness of the second cover layer.

Golf balls of the invention include at least one core layer comprised or consisting of a homogenous rubber-based core composition with a plurality of functionalized inorganic aluminosilicate ceramic microspheres dispersed throughout without agglomerating to create a relatively higher cross-link density of the core layer material. In golf balls of the invention, cross-link density gradients may be created between core layers by pre-electing the presence/absence, amount, type, and degree of functionalization of the plurality of functionalized inorganic aluminosilicate ceramic microspheres in two given core layers to target important properties such as resilience/CoR and desired playing characteristics such as distance.

A golf ball comprising layers that have from 0.05% to 70% by weight of a radio-opaque filler, and wherein the concentration of the radio-opaque filler is measurably different in each layer is disclosed herein. The radio-opaque filler is preferably a compound based on barium, bismuth, tungsten, iodine, or reduced iron.

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.

Provided are novel ethylene acid copolymers, their ionomers and their use in various articles, including packaging films and injection molded articles. The ethylene acid copolymers comprise copolymerized units of ethylene, about 10 to about 30 wt % of copolymerized units of a first α,β-unsaturated carboxylic acid having 3 to 10 carbon atoms; and about 5 to about 15 wt % of copolymerized units of a derivative of a second α,β-unsaturated carboxylic acid having 3 to 10 carbon atoms. Preferred derivatives include esters, and in particular alkyl esters. These ethylene acid copolymers and ionomers have improved optical properties when compared to conventional ethylene acrylic or methacrylic acid copolymers and their ionomers.

A golf ball includes: a radio frequency identification (RFID) tag including an IC chip and an antenna; a protection layer surrounding the outer periphery of the RFID tag; a relaxation layer surrounding the outer periphery of the protection layer; a core surrounding the outer periphery of the relaxation layer; and a cover surrounding the outer periphery of the core. The curing temperature of the protection layer is 60° C. or less, and the protection layer is formed with a material having a hardness of Shore D 60 or more. The relaxation layer is formed with a thermoplastic elastomer-based material having a hardness with a difference from a hardness of a surface of the core on a side contacting the relaxation layer of Shore D 20 or less.

In a golf ball having a core and a cover of at least one layer encasing the core, the core is a product molded under heat from a rubber composition which includes (A) a base rubber, (B) an unsaturated carboxylic acid and/or a metal salt thereof, and (C) an organic peroxide. Letting the content of component (B) in the rubber composition per 100 parts by weight of component (A) be X parts by weight and the concentration of volatile substances from component (B) within the core be A wt %, the value A/X is 0.0123 or less. This golf ball has a low energy loss, enabling a high initial velocity to be obtained.

A rubber composition for golf balls includes (A) a base rubber, (B) two different metal salts of α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms, (C) a metal salt in which at least one bonding site is a fatty acid of 9 or more carbon atoms, and (D) a crosslinking initiator. Letting component (B) include (B-1) an unsaturated metal carboxylate in a high compounding weight and (B-2) an unsaturated metal carboxylate in a low compounding weight, the ratio (B-2)/(B-1) is from 4 to 20 wt % and the ratio (B-2)/(C) is from 20 to 115 wt %. By using this rubber composition in a golf ball core, the golf ball can be endowed with both good spin properties and good durability on impact.

A golf ball includes a core having an outer surface and a geometric center; an inner cover layer, and an outer cover layer. The inner cover layer includes an ionomeric material and has a material hardness of about 60 Shore D or greater. The outer cover layer is formed from a polyurea or polyurethane and has a material hardness of about 60 Shore M or greater. The outer surface of the core has a hardness of about 68 to 92 Shore C. The geometric center of the core has a hardness of about 45 to 85 Shore C. The core outer surface hardness is greater than the geometric center hardness by about 5 to 21 Shore C to define a positive hardness gradient. The core also has a volume weighted average hardness, H.sub.V, of about 70 to 80, where

[00001]${\stackrel{\_}{H}}_V=\frac{I_V}{V_c}.$

A method of manufacturing golf balls having a core and a cover of at least one layer encasing the core includes the steps of producing a core by molding and vulcanizing a rubber composition containing (A) a base rubber, (B) an α,β-unsaturated carboxylic acid and/or a metal salt thereof, and (C) an organic peroxide; and heat-treating the core for 1 to 24 hours at between 175 and 300° C. Golf balls which undergo little energy loss and have a high initial velocity can be obtained by this method.