Golf ball having reduced surface hardness

Abstract

A golf ball comprising a core and at least one cover layer disposed about the core, the core comprising a geometric center and an outer surface, the core further comprising an untreated region extending radially from the geometric center a predetermined distance DUTr and a treated region disposed about the untreated region and extending inward from the outer surface a predetermined depth DTr. The treated region has been exposed to and comprises a fatty acid and / or fatty acid salt composition wherein the treated region comprises a first hardness and the untreated region comprises a second hardness wherein the first hardness is greater than the second hardness. Additionally, the golf ball may comprise an intermediate untreated region disposed about the untreated region and adjacent the treated region wherein the intermediate untreated region comprises a third hardness and wherein the first hardness is greater than the second hardness and the third hardness. In another embodiment, the first hardness is greater than the second hardness and substantially similar to the third hardness. In yet another embodiment, the first hardness is less than the second hardness and the third hardness.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a division of co-pending U.S. patent application Ser. No. 12 / 695,579, filed Jan. 28, 2010, which is a continuation of co-pending U.S. patent application Ser. No. 12 / 695,379, filed Jan. 28, 2010, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 12 / 395,023, filed Feb. 27, 2009, now U.S. Pat. No. 7,819,760, which is a continuation of co-pending U.S. patent application Ser. No. 12 / 394,942, filed Feb. 27, 2009, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 12 / 056,457, filed Mar. 21, 2008, now U.S. Pat. No. 7,678,313, which is a continuation of co-pending U.S. patent application Ser. No. 12 / 048,665, filed Mar. 14, 2008, now U.S. Pat. No. 7,678,312, which is a continuation-in-part of U.S. patent application Ser. No. 11 / 772,903, filed Jul. 3, 2007, now U.S. Pat. No. 7,537,529. This application is also a continuation-in-part of co-pending U.S. patent application Ser...

AI Technical Summary

Benefits of technology

[0049]An advantage of the present invention is that a core is formed having a hardness gradient between the core treated outer surface comprising the fatty acid and / or fatty acid salt composition and the untreated regions within the core. The fatty acid and / or fatty acid salt composition becomes part of the resulting core surface following treatment of the core outer surface with the fatty acid and / or fatty acid salt composition. The fatty acid and / or fatty acid salt composition acts as a plasticizer to penetrate and soften the core surface and thereby create a gradient between the core outer surface and other core regions within the core. For example, a gradient is formed between the geometric center and the treated outer surface. The long hydrocarbon chains of the fatty acids and / or fatty acid salts increase the free volume between the polymer chains to soften the crosslinked network resulting in a lower hardness measurement.

[0050]The fatty acid and / or fatty acid salt compositions maintain plasticizer permanence within the core surface through several mechanisms. Fatty acid salts inherently have low volatility and permanence due to their ability to solidify and / or crystallize within the polymer network minimizing or eliminating migration. Although the fatty acid salts solidify and / or crystallize, they continue to reduce the hardness of the original crosslinked network. The fatty acids are highly compatible with the polymer network aiding in plasticizer permanence. Additionally, since the core formulations contain significant amounts of reactive metal oxides and / or metal salts, the fatty acids will react or coordinate with the various cation sources in the polymer matrix improving the thermal stability and permanence of the plasticizer. Furthermore, a free radical initiator can be used in conjunction with the fatty acids and / or fatty acid salts, especially when the fatty acids and / or fatty acid salts contain some unsaturation, to covalently bond the plasticizer to the polymer network further improving the plasticizer permanence.

Problems solved by technology

One drawback to this method of manufacture is the time-consuming process of creating first elastomer and then a second elastomer and then molding the two together.

However, since the interior portions of these cores are untreated, they have the similar hard surface to soft center gradient as conventional cores.

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