Golf balls having a single or dual-layered solid core are provided. In one embodiment, the golf ball has dimensions and properties that do not conform to the rules of the United States Golf Association (USGA). For example, the ball weight; ball size; ball spherical symmetry; ball initial velocity; and/or ball overall distance may fall outside of the USGA standards. The dual-layered core can have an inner core comprising a thermoplastic composition and surrounding outer core comprising a thermoset composition. In another embodiment, the dual-layered core has an inner core comprising a thermoplastic composition and outer core comprising a thermoset composition. The thermoplastic composition preferably comprises an ethylene acid copolymer ionomer and plasticizer. The thermoset composition preferably comprises polybutadiene rubber. The ball further includes a cover of at least one layer.

Golf ball having a core and a cover of one or more layers, the core being formed of a material molded under heat from a rubber composition including a base rubber, an organic peroxide, and water and/or a metal monocarboxylate. Defining the tan slope as (tan .sub.10tan .sub.1)/(10%1%), where tan .sub.1 and tan .sub.10 are the loss tangents at dynamic strains of, respectively, 1% and 10% when the loss tangents of the core center and the core surface are measured at 12 C. and 15 Hz, the difference between the tan slopes at the core surface and the core center is larger than 0.002. Because a core material which undergoes little decrease in resilience over time and experiences little energy loss can be obtained, the golf ball maintains a good rebound, has a reduced spin rate and thus is able to achieve an increased distance.

Low compression, multi-piece golf balls containing a solid core and two or three-layered cover assemblies are provided. Preferably, the ball has a compression of less than 60 and more preferably less than 50. At least one cover layer is made of a plasticized thermoplastic composition. For example, two-layered and three-layered covers may be made. Preferably, the plasticized thermoplastic composition comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate or butyl oleate is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.

The invention provides a golf ball that is a one-piece golf ball or a golf ball having a core and a cover of one layer or a plurality of layers, wherein the one-piece golf ball or core is formed of a material molded under heat from a rubber composition containing: (A) a base rubber, (B) an organic peroxide, (C) water, (D) a metal methacrylate and (E) zinc oxide. The content of component (D) per 100 parts by weight of component (A) is from 30 to 45 parts by weight. The molar ratio (C)/(D) between components (C) and (D) satisfies the formula
0.9<(C)/(D)<1.1. The core has an initial velocity V.sub.0 of at least 72.0 m/s and up to 75.0 m/s.

Methods for making golf balls and golf ball components using three-dimensional (3D) additive manufacturing systems are provided. The golf ball includes at least one three-dimensional piece. Preferably, a continuous liquid interface printing method is used to make the three-dimensional structure. Ultraviolet (UV)-light polymerizable materials are used in the method. The method may be used to make single-piece or multi-piece balls. For example, the ball may include an inner core produced by the liquid interface printing method. An outer core layer may be disposed about the inner core, and a cover comprising inner and outer cover layers may encapsulate the core assembly to form the finished golf ball. The outer core and cover layers may be made using conventional molding technologies or methods of this invention.

Multi-layered golf balls containing a two or three-layered cover assembly are provided. In one embodiment, the cover assembly includes a relatively hard inner cover and relatively soft outer cover. Alternatively, the cover assembly may include a relatively soft inner cover with a relatively hard outer cover. Three-layered covers comprising an inner cover, intermediate cover, and outer cover layer also may be prepared. Preferably, at least one of the layers is formed from a thermoplastic composition that preferably comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.

Multi-piece golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed thermoset composition such as polybutadiene rubber. The inner and outer core layers can have different hardness gradients. Preferably, the specific gravity (density) of the foam inner core is less than the density of the outer core layer. The ball further includes a cover of at least one layer and may include at least one casing layer. The core structure and resulting ball have relatively good resiliency.

Multi-layered golf balls containing a two or three-layered cover assembly are provided. In one embodiment, the cover assembly includes a relatively hard inner cover and relatively soft outer cover. Alternatively, the cover assembly may include a relatively soft inner cover with a relatively hard outer cover. Three-layered covers comprising an inner cover, intermediate cover, and outer cover layer also may be prepared. Preferably, at least one of the layers is formed from a thermoplastic composition that preferably comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.

In a golf ball having a core, an outermost layer and an intermediate layer therebetween, the intermediate layer is formed of a thermoplastic resin composition that includes (A) an ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer, (B) a nonionic olefin-acrylic acid copolymer, (C) an organic acid or a metal salt thereof, and (D) a basic inorganic metal compound, and the outermost layer is formed of a thermoplastic resin composition that includes (a) a specific ionic olefin-unsaturated to carboxylic acid copolymer and (h) a specific ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. The ratio (tan ) between the tensile storage modulus (E) and the tensile loss modulus (E) in a dynamic viscoelasticity test on the outermost layer-forming resin composition conducted under specific conditions is not more than 0.150. This combination of intermediate layer and outermost layer materials has is a large spin rate-lowering effect on the ball, enabling the ball to travel further.

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed composition selected from thermoset compositions and thermoplastic compositions. The core layers have different hardness and specific gravity levels. The specific gravity (density) of the foam inner core is preferably less than the density of the outer core layer.