Golf balls having cores with increased hardness gradients are provided. The cores have an increased positive hardness gradient (or a hard-to-soft hardness) where the outer surface of the core is harder than the center. The increased positive hardness gradient can be achieved by introducing a water-releasing agent into the core rubber formulation during the curing process. The resulting golf balls have reduced spin and sufficient impact durability.

Multi-layered golf balls having a dual-layered core and cover of at least one layer are provided. The dual-core construction includes a non-foamed inner core (center) made of a thermoplastic or thermoset composition such as polybutadiene rubber. An outer core layer comprising a foamed composition, such as polyurethane foam, is disposed about the inner core. In one version, the foamed outer core layer is made of a relatively soft foam composition having low flex modulus and density. The foamed outer core layer may specific gravity gradient within the layer, wherein the outer surface specific gravity is greater than the midpoint specific gravity. A cover may be disposed about the core structure. For example, an inner cover made of ethylene acid copolymer ionomer and outer cover made of polyurethane may be used.

Golf ball comprising at least one layer consisting of a double network cross-linked composition comprising a mixture of a base thermoset polymer composition and a double network polymer composition. The double network polymer composition comprises a plurality of particulates of a polymer composition that is elongated from 10% to 200%, or at least 50%, or at least 100% or at least 150% or 200% or greater during a partial cure state.

Golf ball comprising at least one layer consisting of a double network cross-linked composition comprising a mixture of a base thermoplastic polymer composition and a double network polymer composition. The double network polymer composition comprises a plurality of particulates of a polymer composition that is elongated from 10% to 200%, or at least 50%, or at least 100% or at least 150% or 200% or greater during a partial cure state.

An object of the present invention is to provide a golf ball exhibiting good shot feeling and excellent resilience. The present invention provides a golf ball comprising a spherical core and one or more cover layers disposed outside the spherical core, wherein at least one layer of the cover layers contains: (A) a base resin containing (a-1) an ionomer resin and having a material hardness of 59 or more in Shore D hardness; and (B) a polyrotaxane having a cyclodextrin with at least a part of hydroxyl groups of the cyclodextrin being modified with a caprolactone chain having a carboxyl group at a terminal of the caprolactone chain, a linear molecule piercing through a cyclic structure of the cyclodextrin, and blocking groups located at both terminals of the linear molecule to prevent disassociation of the cyclodextrin.

Golf balls having an inner core made of a foamed composition are provided. The core assembly preferably includes a foam inner core (center) and surrounding outer core layer. A cross-linked thermoplastic, preferably an ethylene acid copolymer ionomer, is used to form the foam composition. The core layers have different hardness gradients and specific gravity values. The ethylene acid copolymer is reacted with a metallic acrylate salt and peroxide free-radical initiator to form the cross-linked polymer. The foamed, cross-linked composition helps provide the inner core with good resiliency, thermal stability, and durability. Non-foamed thermoplastics or thermosets such as polybutadiene rubber may be used to form the outer core layer. The ball further includes a cover that may be multi-layered.

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.

Multi-piece golf balls having a multi-layered solid core and multi-layered cover are provided.

A golf ball includes a core having an outer surface and a geometric center. The core is formed from a substantially homogenous rubber composition. An ionomeric inner cover layer is formed about the core and has a material hardness of about 60 Shore D or greater. The golf ball includes an outer cover layer formed from a polyurea or a polyurethane and having a material hardness of about 60 Shore D or less. The outer surface of the core has a trans content of about 12% or less and a hardness of about 71 to 88 Shore C. The geometric center of the core has a trans content of about 10% or less and a hardness of about 60 to 80 Shore C. The core has an outer surface hardness greater than a geometric center hardness by about 5 to 19 Shore C to define a positive hardness gradient.

A golf ball a core, one or more intermediate layers, and one or more cover layers. The core may comprise an inner portion and an outer portion. One or more layers of the golf ball may be formed by the application of ultrasonic welding on two half shells to form. One or more of the layers may be formed by a number of different chemical compositions, and may have varying thicknesses, hardnesses, coefficients of restitution, and PGA compression. The golf ball itself may have varying coefficient of restitution and PGA compression, depending on the layers.