In a multi-piece solid golf ball having a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and an outermost layer encasing the intermediate layer, the envelope layer-encased sphere, the intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, the intermediate layer and the cover have thicknesses which satisfy a specific relationship, and the core has a hardness profile in which the hardnesses at the core surface, core center, a position 5 mm from the core center, and a position midway between the core surface and center satisfy specific relationships. This golf ball satisfies at a high level the flight and control performances desired for use by professional golfers and skilled amateurs. In particular, it holds down the spin rate on full shots and follows a straight trajectory, thus having a superior flight performance, and moreover is endowed with an excellent scuff resistance.

A golf ball is provided which suppresses twisting due to external forces while maintaining sufficient deflection at the time of impact, reduces the spin rate without lowering ball rebound, and is thus able to effectively increase the distance traveled by the ball, particularly on shots with a driver. In the golf ball, which includes a core and a cover, the core has a core body made of a first polybutadiene rubber and having a surface with a plurality of groves or holes thereon, which grooves or holes are filled with a second polybutadiene rubber of a differing composition from the first polybutadiene rubber. The polybutadiene rubber-filled groove portions or hole portions have a higher surface hardness than the core body.

A golf ball including a thermoplastic inner core layer that has a geometric center hardness greater than its surface hardness to define a negative hardness gradient. An outer core layer is disposed about the inner core and is formed from a thermoplastic material and has an inner surface hardness substantially less than its outer surface hardness to define a positive hardness gradient. An inner cover layer is disposed about the outer core layer and an outer cover layer is disposed about the inner cover layer.

A golf ball comprising a core and a cover layer, wherein at least one of the core or cover layer comprises a plasticized polyurethane composition comprising at least one polyurethane and at least one plasticizer.

An object of the present invention is to provide a golf ball traveling a great distance on driver shots and on iron shots. The present invention provides a golf ball comprising a spherical core including an inner layer and an outer layer, and a cover, wherein a difference (H.sub.X+1−H.sub.X−1) between a hardness (H.sub.X+1) at a point outwardly away in a radial direction from a boundary between the inner layer and the outer layer of the spherical core by 1 mm and a hardness (H.sub.X−1) at a point inwardly away in the radial direction from the boundary between the inner layer and the outer layer of the spherical core by 1 mm is 0 or more in Shore C hardness, a surface hardness (H.sub.X+Y) of the spherical core is more than 65 in Shore C hardness, an angle α of a hardness gradient of the inner layer is 0° or more, a difference (α−β) between the angle α and an angle β of a hardness gradient of the outer layer is 0° or more, a thickness of the cover is 3 mm or less, a difference (Hc−H.sub.x+y) between a hardness (Hc) of the cover and the surface hardness (H.sub.X+Y) of the spherical core is 2 or more in Shore C hardness, and the cover has a highest hardness among the constituent members of the golf ball.

Multi-piece golf balls containing a dual-layered core and dual-layered cover are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, and a surrounding outer core layer. The core layers may have different hardness gradients. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and combinations and alloys thereof preferably dispersed in a thermoplastic polymeric matrix. The outer core layer is preferably formed from a thermoset composition such as polybutadiene. The multi-layered cores and covers have selective specific gravity relationships between the different layers. This helps provide the ball with good flight distance and spin control. The resulting balls have good resiliency and other playing performance properties.

Multi-piece golf balls containing a multi-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, an intermediate core layer, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. In one preferred embodiment, each core layer has a positive hardness gradient. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof. The intermediate core layer is preferably formed from a first thermoset composition such as polybutadiene rubber, and the outer core layer is preferably formed from a second thermoset composition. The resulting ball has high resiliency and good spin control.

Multi-piece golf balls having a solid core and cover are provided. The ball contains a small, heavy inner core and surrounding outer core layer. The inner core preferably contains metal powder such as copper, steel, brass, tungsten, titanium, nickel, iron, tin, and bronze particles dispersed in a thermoset or thermoplastic polymeric matrix. For example, a polybutadiene rubber matrix may be used. In one preferred embodiment, the inner core contains elemental iron powder. Preferably, the particles have a weight average size in the range of about 10 μm to about 450 μm. In one embodiment, the outer surface of the inner core has a structure with projecting members. For example, the outer surface may contain multiple projecting ribs with gaps located between the ribs. The ball includes a cover surrounding the core structure. The cover may be multi-layered.

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

Golf balls comprising a multi-layer core and a cover are disclosed. The multi-layer core comprises a zero or positive hardness gradient center that is hard relative to an intermediate core layer.