In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer, and a cover with a plurality of dimples thereon, the core is a two-layer core consisting of an inner core layer and an outer core layer each formed primarily of a base rubber, the envelope layer, the intermediate layer and the cover layer are each composed of at least one layer and formed primarily of a synthetic resin material, and the initial velocities and surface hardnesses of the core, the envelope layer-encased sphere and the intermediate layer-encased sphere are designed within specific ranges. This golf ball satisfies at a very high level the flight and control performances expected for use by professional golfers and skilled amateurs, has the ability to move forward on a straight path particularly on full shots, and also has an excellent scuff resistance.

A golf ball including a dual core comprising an inner core having a first outer surface, a geometric center, and a soft transition region adjacent to the outer surface, and an outer core layer having a second outer surface disposed about the inner core. An inner cover layer and an outer cover layer are formed over the core. The second outer surface is greater than the first outer surface to define a dual core overall positive hardness gradient of about 25 Shore C to 35 Shore C and has a secondary gradient quotient, GQ, defined by the equation:

[00001]$6\frac{G^{}+T}{10\mathrm{COR}}7$

where G is the overall positive hardness gradient in Shore C, T is the percent of trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution measured at an incoming velocity of 125 ft/s.

A golf ball includes a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The soft transition region has a thickness of about 4 mm or less and includes about 2 to 10 percent of a trans-polybutadiene isomer. An outer cover layer has a hardness of about 50 Shore M or greater. The core outer surface hardness is greater than the hardness at the geometric center to define a positive hardness gradient of about 10 to 48 Shore C. The core has a secondary gradient quotient, GQ, of 1.5 to 7.25, GQ being defined by the equation:

[00001]$\frac{G^{}+T}{10\mathrm{COR}}$

where G is the positive hardness gradient in Shore C, T is the percent trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.

A golf ball includes a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The soft transition region has a thickness of about 4 mm or less and includes about 10 to 45 percent of a trans-polybutadiene isomer. An outer cover layer has a hardness of about 50 Shore M or greater. The core outer surface hardness is greater than the hardness at the geometric center to define a positive hardness gradient of about 12 to 68 Shore C. The core has a secondary gradient quotient, GQ, of 4 to 13, GQ being defined by the equation:

[00001]$\frac{G^{}+T}{10\mathrm{COR}}$

where G is the positive hardness gradient in Shore C, T is the percent trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/.

Golf balls comprising a multi-layer core and a cover are disclosed. The multi-layer core comprises a layer formed from a highly neutralized polymer composition, a layer formed from an additional thermoplastic composition, and an outermost layer formed from a thermoset rubber.

A golf ball includes a core, an intermediate layer, and a cover, in which an initial velocity is not more than 76.0 m/s, a deflection when the ball is compressed under a specific load is at least 2.8 mm, and letting a value of (initial velocity of coreweight of core) be Ciw, a value of [(initial velocity of intermediate layer-encased sphereinitial velocity of core)(weight of intermediate layer-encased sphereweight of core)] be Miw, and a value of [(initial velocity of ballinitial velocity of intermediate layer-encased sphere)(weight of ballweight of intermediate layer-encased sphere)] be CViw, the condition is of Ciw+Miw+CViw2,550 is satisfied, thereby to be capable of making a distance for reducing a distance on shots with a driver and an iron by average hitters smaller.

In a golf ball having a core, a cover and at least one intermediate layer formed therebetween, the core, intermediate layer and cover have respective specific gravities with a standard deviation of not more than 0.07 or less, the cover has a material hardness on the Shore D hardness scale of 52 or less, and the ball has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which is 2.8 mm or less. The amount of deviation in the ball center of gravity is exceedingly small, increasing the straightness with which the ball rolls on putts with a putter.

Golf balls comprising a multi-layer core and a cover are disclosed. The multi-layer core comprises a layer formed from a highly neutralized polymer composition and a layer formed from a thermoset rubber.

A golf ball includes a core and a cover, in which the core is formed in a single layer of a rubber composition, the cover is formed of a resin composition, a hardness profile of the core has a specific cross-sectional hardness profile, and letting a deflection (mm) when the core is compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) be C (mm), a Shore C hardness at a core center be Cc, and a Shore C hardness at a core surface be Cs, the following condition is satisfied:

[00001]$C\left(\mathrm{Cs}-\mathrm{Cc}\right)132.0.$

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) made from a foam or metal-containing composition, or it has a hollow shell construction, and the outer core layer is made of a thermoplastic composition. Preferably, the thermoplastic composition 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 core assembly preferably may have a positive hardness gradient extending across the entire assembly. The core structure and resulting ball have relatively good resiliency at given compressions.