Golf ball having CoR of at least 0.810, specific gravity SG.sub.B of less than 1.00 g/cc, and initial velocity of at least 250 ft/s and comprising a first layer L.sub.1, a second layer L.sub.2 surrounding L.sub.1, and a third layer L.sub.3 surrounding L.sub.2. L.sub.1 is formed from at least one highly neutralized polymer and has first specific gravity SG.sub.1; L.sub.2 is formed from at least one partially neutralized polymer and has second specific gravity SG.sub.2; and L.sub.3 is formed from at least one of a thermoset or thermoplastic composition and has third specific gravity SG.sub.3. At least two of SG.sub.1, SG.sub.2, and SG.sub.3 is less than 1.13 g/cc. SG.sub.1 may be less than 1.13 g/cc, or less than 1.0 g/cc. The thermoset or thermoplastic composition may comprise polyurethane(s), polyurea(s), polyurethane(s)/polyurea(s) hybrids, and/or ionomers such as at least partially neutralized polymers and/or HNPs.

A golf ball 2 includes a core 4, a mid layer 6, a cover 8 and a paint layer 10. The core 4 includes a center 12 and an envelope layer 14. The golf ball 2 satisfies the following mathematical formulas. In the mathematical formulas, Tm represents a thickness of the mid layer, Tcmin represents a minimum thickness of the cover, Tcmax represents a maximum thickness of the cover, and Tp represents a thickness of the paint layer. The golf ball 2 has a large number of dimples 16 on a surface thereof. The number of planes that can divide a pattern of the dimples so that divided patterns are mirror symmetry to each other is one.
Tm>TcmaxTcmin>Tp
(TcmaxTcmin)0.15 mm
0.15(Tp/Tcmin)0.04

A golf ball can include a core, a mid layer, and a cover. An amount P(Na) of a sodium ion-neutralized ionomer resin in abase resin of the cover can be not greater than 5 parts by mass. The golf ball can satisfy the following mathematical formulas (1) and (2):

[00001]$\begin{array}{cc}\mathrm{Fm}/\left(\mathrm{Hm}*\mathrm{Tm}\right)-\mathrm{Fc}/\left(\mathrm{Hc}*\mathrm{Tc}\right)3.,\mathrm{and}& \left(1\right)\end{array}$$\begin{array}{cc}\mathrm{Mc}*\mathrm{Tc}10.,& \left(2\right)\end{array}$

where Hm: hardness (Shore D) of the mid layer, Tm: thickness (mm) of the mid layer, Fm: bending stiffness (MPa) of the mid layer, Tc: thickness (mm) of the cover, Fc: bending stiffness (MPa) of the cover, and Mc: melt flow rate (g/10 min) of the cover at a temperature of 190 C. under a load of 2.16 Kg.

An object of the present invention is to provide a golf ball traveling a great flight distance. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a ratio (t2/t1) of a time (t2) to a time (t1) of 1.05 or more in a hitting test using a driver (at a head speed of 40 m/sec), wherein the time (t1) is a time taken from a moment that the driver begins to contact with the golf ball to a moment that the golf ball reaches a maximum deformation amount, and the time (t2) is a time taken from the moment that the golf ball reaches the maximum deformation amount to a moment that the golf ball leaves the driver.

The present invention is directed to multi-layer golf balls including a layer formed from a relatively soft or low modulus HNP composition and a layer formed from a relatively hard or high modulus HNP composition. Optionally, the soft (or low modulus) HNP composition and/or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.

The present invention is directed to multi-layer golf balls including a layer formed from a composition comprising a relatively soft or low modulus HNP, a layer formed from a composition comprising a relatively hard or high modulus HNP, an inner cover layer formed from a thermoplastic composition, and an outer cover layer.

The present invention is directed to multi-layer golf balls including a layer formed from a relatively soft or low modulus HNP composition and a layer formed from a relatively hard or high modulus HNP composition. Optionally, the soft (or low modulus) HNP composition and/or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.

Multi-piece golf balls having a solid core of at least one layer and cover of at least one layer are provided. Thermoplastic ethylene acid copolymer ionomer compositions are used to form the core layers. Preferably, the ball contains a dual-core having an inner core and surrounding outer core layer. Low modulus and high modulus ionomer compositions may be used in the core structure. In one embodiment, a first ionomer composition is used to form the inner core and a second ionomer composition is used to form the outer core, and the flex modulus of the first composition is greater than the flex modulus of the second composition. The ionomer compositions have varying levels of hardness. The resulting ball has high resiliency and rebounding properties.

A golf ball includes an inner core layer formed from a thermoset rubber composition. The inner core layer has a first outer surface Shore D hardness and an outer diameter of about 0.8 to 1.40 inches. A thermoplastic outer core layer is formed around the inner core layer, has a second outer surface Shore D hardness, and is formed from a copolymer of ethylene and an ,-unsaturated carboxylic acid, a metal salt of an organic acid, and sufficient cation source to neutralize about 90% to about 100% of acid groups of the copolymer. The golf ball includes an inner cover layer and an outer cover layer. The first outer surface Shore D hardness is greater than the second outer surface Shore D hardness and the outer core layer has a thickness of about 0.01 inches to 0.05 inches.

A golf ball comprising at least one layer comprised of a neutralized acid polymer composition consisting of a mixture of: (a) at least one low molecular weight acid-containing wax; (b) at least one non-acid-polymer; (c) at least one organic acid or salt thereof; and (d) at least one plasticizer. Each low molecular weight acid-containing wax may have a molecular weight of from about 500 to about 7000, and in some embodiments, the molecular weight may be considered low up to 30,000. Interactions between components (a), (b), (c) and (d) as disclosed herein advantageously produce a layer of ionomeric material having desirable physical properties, such as heat stability, and processability (excellent melt flow) and softer feel without the need for blending high and low molecular weight acid-containing polymer(s)