Thin-layer-covered multilayer golf ball

Abstract

A golf ball includes a core formed of an inner core and at least one outer core layer disposed about the inner core, one of which includes a surface amount of trans-polybutadiene and an interior amount of trans-polybutadiene at least 6 percent less than the surface amount. A cover containing an inner cover layer and an outer cover layer is formed over the core. The inner cover layer includes a block copolymer of styrene and butadiene, isoprene, or ethylene-butylene rubber and has a material hardness of about 60 to 70 Shore D. The outer cover layer is formed from a castable polyurethane or polyurea and having a material hardness of 55 Shore D or less. The inner core has an interior hardness and a surface hardness differing from the interior hardness by greater than 20 percent.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of co-pending U.S. patent application Ser. No. 11 / 421,956, filed Jun. 2, 2006, which is a continuation of co-pending U.S. patent application Ser. No. 10 / 956,329, filed Oct. 1, 2004 and now abandoned, which is a continuation of co-pending U.S. Pat. No. 6,913,547, filed Feb. 13, 2001, which is a continuation-in-part of U.S. Pat. No. 7,090,798, filed Mar. 22, 1999, which is a continuation-in-part of U.S. Pat. No. 5,885,172; and also a continuation-in-part of U.S. Pat. No. 6,486,261, filed Nov. 27, 2000, which is a continuation-in-part of U.S. Pat. No. 6,210,294, filed May 14, 1999, and U.S. Pat. No. 6,465,578, filed Dec. 16, 1999, each of which is incorporated herein in its entirety by reference.FIELD OF THE INVENTION[0002]This invention relates generally to golf balls, and more specifically, to multilayer golf balls. In particular, this invention relates to a golf ball having a core comprising a center and...

AI Technical Summary

Benefits of technology

[0034]In one embodiment, the outer cover layer has a material hardness less than about 55 shore D and, preferably, the outer cover layer has a material hardness less than about 50 shore D. The inner cover layer should have a material hardness between about 60 and about 70 Shore D and, more preferably, between about 60 and about 65 Shore D.

[0035]In yet another embodiment, the ball has a moment of inertia of less than about 83 g·cm2. Additionally, the center preferably has a first hardness, the outer core layer has a second hardness greater than the first, and the inner cover layer has a third hardness greater than the second. In a preferred embodiment, the outer cover layer has a fourth hardness less than the third hardness.

[0036]In one embodiment, the center has a first specific gravity and the outer core layer has a second specific gravity that differ by less than about 0.1. In a preferred embodiment, the center is solid. The center may also be liquid, hollow, or air-filled.

[0037]The present invention is also directed to a golf ball comprising a core and a cover disposed about the core, wherein the core comprises a solid center and an outer core layer adjacent the center, and the cover comprises an inner cover layer and an outer cover layer; wherein the center has an outer diameter from about 0.375 in to about 1.4 in and deflection of greater t

Problems solved by technology

Solid golf balls include one-piece balls, which are easy to construct and relatively inexpensive, but have poor playing characteristics and are thus generally limited for use as range balls.

These balls are generally easy to manufacture, but are regarded as having limited playing characteristics.

Wound balls generally are more difficult and expensive to manufacture than solid two-piece balls.

The amount of trans-polybutadiene structure present after vulcanization is 10 to 30 percent, as amounts over 30 percent are alleged to detrimentally result in cores that are too soft with deteriorated resilience performance, and to cause a decrease in golf ball performance.

Additionally, conventional polymers that have a high percentage of the trans-polybutadiene conformation, such as DIENE 35NF, from Firestone Corp., that has 40 percent cis-isomer and 50 percent trans-polybutadiene isomer, and mixtures of high-cis- and high-trans-polybutadiene isomers, such as CARIFLEX BR1220, from Shell Corporation, and FUREN 88, from Asahi Chemical Co., respectively, typically do not yield high resilience values and therefore are not desirable.

However, golf ball covers made from polyurethane have not, to date, fully matched SURLYN®-covered golf balls with respect to resilience or the rebound that is a function of the initial velocity of a golf ball after impact with a golf club.

With full shots, the ball's inner construction greatly affects the ball's spin rate.

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