A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The core is formed from a substantially homogenous rubber composition. The golf ball also includes an inner cover layer and an outer cover layer. The soft transition region has a thickness of up to 4 mm and a negative hardness gradient of about 5 Shore C to about 15 Shore C. The unitary core has an overall negative hardness gradient of up to 20 Shore C.

Multi-layer golf balls comprising a center, intermediate layer, and cover are disclosed. The center is formed from a highly-neutralized acid copolymer composition.

Golf ball incorporating polymer composition comprising: (i) a reaction mixture of ethylene-acid copolymer and C.sub.3-8 , -ethylenically unsaturated carboxylic acid(s); and (ii) poly-hydroxy crosslinking agent(s) such as polyvinyl alcohol, diols, glycols, sugar alcohols, and/or glycerols. Concentration of poly-hydroxy crosslinking agent(s) in polymer composition may be up to about 10% (or up to about 5%, or from 0.1% to about 2.5%, or from about 0.05% to 0.95%), by weight, based on 100% total weight of polymer composition. Reaction mixture may further comprise cation source and optionally organic acid(s) or salt thereof. Reaction mixture or polymer composition may include adjuvant(s). such as a silane compound, for example N-(2-aminoethyl-3 aminopropyl)trimethoxysilane and/or 3-glycidoxypropyl trimethoxysilane, in concentration of from 0.025% to 1.0% by weight, based on 100% total weight of reaction mixture or in concentration of up to 10% by weight, based on 100% total weight of the polymer composition.

A golf ball having an inner core layer, an outer core layer enclosing the inner core layer, and a cover layer enclosing the outer core layer. The inner core layer includes a blend of a first highly neutralized acid polymer having a first Vicat softening temperature and a first specific gravity, a second highly neutralized acid polymer having a second Vicat softening temperature and a second specific gravity, and an ionomer-based masterbatch comprising an additive and an ionomer resin having a third Vicat softening temperature and a third specific gravity. The absolute values of the differences among the Vicat softening temperatures is no more than about 15 C. and the absolute value of the difference between the specific gravities is no more than about 0.015. The cover layer may include an inner cover layer enclosing the outer core layer and an outer layer enclosing the inner cover layer.

An ultra-low compression golf ball is disclosed herein. The core preferably has a PGA compression less than 30. The mantle layer and cover have approximately the same thickness. The cover comprises a thermoplastic polyurethane material and has a specific gravity greater than the core and mantle layer. The golf ball has a PGA compression less than 75 and a COR of at least 0.780.

Golf balls having a very high positive gradient multilayer core are provided. The multilayer core includes an outer core layer and a very soft, low compression inner core layer. The inner core layer is formed from an unfoamed composition and has a center hardness that is at least 40 Shore C points less than the outer surface hardness of the outer core layer.

A golf ball and a method of forming a golf ball is disclosed herein. The golf ball includes an alignment aid or feature that is integrally formed with a core body of the golf ball. A cover is provided that allows the alignment aid to be visible from an exterior of the golf ball. The alignment aid can be formed as central spherical segment that fuses two spherical cap portions with each other to form the core body. Different material selections can be made for the spherical cap portions and the central spherical segment that can further provide variation in performance characteristics of the golf ball.

An ultra-low compression three-piece golf ball is disclosed herein. The core preferably has a PGA compression less than 30. The mantle layer and cover have approximately the same thickness. The cover comprises a thermoplastic polyurethane material and has a specific gravity greater than the core and mantle layer. The golf ball has a PGA compression less than 75 and a COR of at least 0.780.

A golf ball includes a core and a cover. The core has an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The soft transition region has a thickness of 4 mm or less, includes about 10 to 30% trans-polybutadiene isomer, and has a positive hardness gradient of about 10 Shore C or less. The cover layer has a hardness of about 50 Shore M or greater. The core has a positive hardness gradient of about 10 to 42 Shore C. A secondary gradient quotient, GQ, from about 2.2 to 9.5, GQ being defined by the equation:

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

where G is the core 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 of the core measured at an incoming velocity of 125 ft/s.

An object of the present invention is to provide a golf ball having an excellent initial velocity when being hit at a head speed of 50 m/sec and an improved initial velocity when being hit at a head speed of 40 m/sec. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a rebound equivalence energy ratio (R.sub.40) ranging from 65.50% to 99.0% at a deformation amount of 7%, and a rebound equivalence energy ratio (R.sub.50) ranging from 20.0% to 70.0% at a deformation amount of 19%, in a compression test (measurement temperature: 70 C., compression speed: 30 mm/min) applying a load to the golf ball along a radial direction of the golf ball.