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.

An object of the present invention is to provide a golf ball striking a good balance between flight distance on driver shots and spin rate on approach shots, and excellent in stain resistance and shot feeling. The present invention provides a golf ball comprising a paint film, wherein a base resin of the paint film contains a polyurethane obtained by a reaction between a polyisocyanate composition and a polyol composition containing a urethane polyol having a polyether diol with a number average molecular weight in a range from 800 to 3,000 as a constituent component, and the following requirements are satisfied:
Mp≦200×X−75
Mp≦100
Minm−Moum>40
Moum−Mc<5
Tinm≧Toum>Tc>Tp
(Tinm×Minm)/(Toum×Moum)>2.0
(Toum×Moum)/(Tc×Mc)<3.0
(Tc×Mc)/(Tp×Mp)>10.0
[where Mp, Minm, Moum, and Mc represent a 10% elastic modulus (kgf/cm.sup.2) of the paint film, inner intermediate layer, outer intermediate layer and cover, respectively; Tp, Tinm, Toum, and Tc represent a thicknesses (mm) of the paint film, inner intermediate layer, outer intermediate layer and cover, respectively; and X represents a molar ratio (NCO/OH) of a NCO group in the polyisocyanate composition to a OH group in the polyol composition.].

An object of the present invention is to provide a golf ball having excellent durability and good shot feeling. The present invention provides a golf ball comprising a core, wherein a difference (crosslinking density at surface of core−crosslinking density at center of core) between a crosslinking density at a surface of the core and a crosslinking density at a center of the core is more than 1.0×10.sup.2 mol/m.sup.3 and less than 9.0×10.sup.2 mol/m.sup.3, and a hardness difference (Hs−Ho) between Hs and Ho is 13.0 or more and 30.0 or less, and the core satisfies H50−Ho>Hs−H50, wherein Hs (Shore C hardness) is a hardness at the surface of the core, Ho (Shore C hardness) is a hardness at the center of the core, and H50 (Shore C hardness) is a hardness at a midpoint between the center of the core and the surface of the core.

In a golf ball having a core, envelope layer, intermediate layer and cover, the (core diameter)/(ball diameter) value falls within a particular range, the core has a specific hardness profile, the intermediate layer is formed primarily of an ionomer resin material including a high-acid ionomer resin, and the Shore C hardness relationships among the core center and surface hardnesses and the surface hardnesses of the envelope layer-encased sphere, intermediate layer-encased sphere and ball satisfy the following conditions: (1) core surface hardness<surface hardness of envelope layer-encased sphere<surface hardness of intermediate layer-encased sphere>ball surface hardness, (2) (surface hardness of envelope layer-encased sphere)−(core center hardness)≥28.

Also, the intermediate layer and cover have respective thicknesses which satisfy the condition: (3) cover thickness<intermediate layer thickness.

This ball enables mid-level and skilled amateur golfers to achieve superior distances on driver shots and on iron shots, and moreover has a soil yet good feel at impact.

A golf ball comprising a core and a cover, wherein the core consists of: a solid inner core layer formed from an unfoamed thermoplastic composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H.sub.center) of 50 or less, one or more optional intermediate core layers, and an outer core layer formed from an unfoamed thermoset composition and having a thickness of 0.200 inches or greater and an outer surface Shore C hardness (H.sub.outer surface) of 70 or greater, wherein H.sub.outer surface>H.sub.center, and H.sub.outer surface−H.sub.center≧40.