A golf ball with a center core comprising 1,4 polybutadiene with a cis content more than 50% and containing a metal salt of acrylate, wherein the 1,4 polybutadiene has 5 to 60 weight percent of a metal salt of acrylate, is disclosed herein. The metal salt of acrylate is preferably selected from zinc, magnesium, sodium, and calcium.

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.

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 multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the envelope layer is formed into two layersan 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 hardnesses that satisfy a specific relationship. The inner envelope layer or outer envelope layer is formed primarily of one or more thermoplastic elastomer selected from the group consisting of polyester elastomers, polyamide elastomers, polyurethane elastomers, olefin elastomers and styrene elastomers. 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 two-layer core consisting of an inner core layer and an outer core layer, one or more intermediate layer, and a cover serving as an outermost layer, the inner core layer and outer core layer are each formed primarily of a base rubber, the inner core layer has a diameter of at least 19 mm, the intermediate layer and the cover are each formed primarily of a resin material, and the overall core has a specific hardness profile. The golf ball has a high initial velocity while holding down the spin rate on full shots with a driver or long iron, thus enabling a good distance to be achieved. The ball also has a high controllability in the short game.

A golf ball includes a core, a mid layer, and a cover. A ratio R1 calculated by mathematical formula (1): R1=(Df1Df2)/(Df2Df3) is not less than 5.00. A ratio R2 calculated by mathematical formula (2): R2=(T2*H2)/H3 is not less than 2.00. A ratio R3 calculated by mathematical formula (3): R3=D1/T3 is not less than 50. In mathematical formulas (1) to (3), Df1 represents an amount of compressive deformation of the core, Df2 represents an amount of compressive deformation of a sphere including the core and the mid layer, Df3 represents an amount of compressive deformation of the golf ball, T2 represents a thickness of the mid layer, H2 represents a hardness of the mid layer, H3 represents a hardness of the cover, D1 represents a diameter of the core, and T3 represents a thickness of the cover.

Golf balls having a multi-layered core made of a foamed composition are provided. The core preferably has a foam inner core (center) and surrounding thermoset or thermoplastic outer core layer. Preferably, a polyurethane foam composition is used to form the foam center. The foam inner core preferably includes a fully-foamed center region and a partially or completely-collapsed foam outer region. The hardness of the fully-foamed region is different than the hardness of the collapsed foam region. Non-foamed thermoset or thermoplastic materials such as polybutadiene rubbers or ethylene acid copolymer ionomer may be used to form the outer core layer. The ball further includes a cover that may be multi-layered. The foam cores have good resiliency.

In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer, an intermediate layer consisting of at least one layer and a cover of one or more layer, the inner core layer and outer core layer are each formed of a rubber composition made up primarily of a base rubber, the inner core layer has a diameter of not more than 30 mm; and the core has specific hardness ratios (JIS-C hardness/Shore D hardness) at specific points on the cross-section thereof and the surface and center of the two-layer core has a specific hardness difference. This golf ball has a reduced spin rate on full shots with a driver and middle irons, thus imparting an excellent flight performance, and moreover has a good controllability in the short game on approach shots, making it ideal as a golf ball for professional golfers and mid- and high-level amateur golfers.

Multi-layered golf balls having at least one layer made from silicone (polysiloxane) elastomers; silicone (polysiloxane) elastomer/polyurethane blends; polycarbonate-polysiloxane blends and copolymers; and polycarbonate-polysiloxane/polyurethane blends are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The polysiloxane compositions have good thermal stability and durability without sacrificing resiliency. The polysiloxane compositions also 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.

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 sphere obtained by encasing the core with the intermediate layer has a surface hardness on the Shore D hardness scale of at least 69, the cover has a material hardness on the Shore D hardness scale of 55 or less, 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, and the sphere obtained by encasing the core with the intermediate layer has an initial velocity A and the core has an initial velocity B which together satisfy the condition AB0 m/s.