Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-06-30
2002-11-26
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S440000, C525S066000, C525S179000, C525S183000, C473S354000, C473S355000, C473S365000, C473S373000, C473S374000, C473S377000, C473S385000
Reexamination Certificate
active
06486250
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to methods and compositions for forming at least one layer in a golf ball, and to golf balls, which comprise such a layer, having improved properties. In particular, the invention is directed to golf balls having a cover, a core, and, optionally, at least one intermediate layer situated between the cover and the core, where at least one of the cover or the core or the optional intermediate layer comprises a blend of at least one saponified polymer and at least one polyamide-containing polymer, and to methods of forming such golf balls.
BACKGROUND OF THE INVENTION
Three-piece, wound golf balls with balata covers are preferred by most expert golfers. These balls provide a combination of distance, high spin rate and control that is not available with other types of golf balls. However, balata is easily damaged in normal play and, thus, lacks the durability required by the average golfer. In contrast, amateur golfers typically prefer a solid, two-piece ball with an ionomer cover, which provides a combination of distance and durability. Because of the hard ionomer cover, these balls are almost impossible to cut, but also have a very hard “feel”, which many golfers find unacceptable, and a lower spin rate, making these balls more difficult to draw or fade. The differences in the spin rate can be attributed to the differences in the composition and construction of both the cover and the core.
Consequently, a need exists for a golf ball composition which provides spin rates and a feel more closely approximating those of balata covered balls, while also providing as high or a higher degree of durability than that provided by the balls presently available or disclosed in the prior art. Golf ball manufacturers have attempted to produce golf ball covers that provide the spin rate of balata with the cut resistance of an ionomer by forming blends consisting essentially of hard ionomers with softer, nonionomer polymers to soften the golf ball and improve its feel and spin rate. However, this approach has proven to be difficult because the ionic character of ionomers imparts a highly polar nature to these materials. Therefore, ionomers and other non-ionic polymers, such as balata and polyolefin homopolymers, copolymers or terpolymers that do not contain ionic, acidic, basic or other polar pendant groups, have not been successfully blended for use in golf ball covers. These mixtures often have poor mechanical properties such as inferior tensile strength, impact strength and the like. Hence, the golf balls produced from these incompatible mixtures will have inferior golf ball properties such as poor durability and cut resistance on impact.
Saponification or hydrolysis of alkyl acrylate units in a crosslinkable polymer chain is disclosed by Gross in U.S. Pat. No. 3,926,891. In U.S. Pat. No. 3,970,626, Hurst discloses heating a mixture of an alkali metal hydroxide, a thermoplastic ethylene-alkyl acrylate copolymer and water to saponify the acrylate units and form an aqueous emulsion.
A different approach to saponification or hydrolysis of an ethylene-alkyl acrylate copolymer is disclosed by Kurkov in U.S. Pat. No. 5,218,057, in which the copolymer is mixed with an aqueous solution of an inorganic alkali metal base at a temperature sufficient for saponification to take place and at which the copolymer undergoes a phase change.
All of the prior saponification methods discussed above require that the polymer component be in contact with water, either by conducting the reaction in an aqueous medium or by adding an aqueous solution to the polymer. However, nonaqueous inorganic alkali metal base solutions, e.g., containing an alcohol or polyethylene glycol solvent, are disclosed by U.S. Pat. No. 5,554,698 to Wang et al., although aqueous solutions are disclosed to be preferred.
McClain, in U.S. Pat. No. 4,638,034, discloses a process whereby ethylene-acrylic acid copolymers or their ionomers are prepared from ethylene-alkyl acrylate copolymers by saponifying the latter in the melt with metal hydroxides to form an ionomer and a by-product, i.e., alkanol, then optionally acidifying the ionomer to form the free acid copolymer.
The processes disclosed by the Kurkov, McClain and Wang references, in particular, are incapable of providing optimal product quality since blending and saponifying in a single operation as taught by the subject references leads to rapid saponification, with a concurrent rapid increase in melt viscosity. Due to this rapid increase in viscosity, the resultant mixture is non-uniform and therefore the material properties of products made from this material are not consistent throughout the product. U.S. Pat. No. 5,869,578 to Rajagopalan, a patent that issued from one of the parent applications of the present invention, overcame the above deficiencies.
It is known that saponified polymers may be blended with ionomers. For example, U.S. Pat. No. 5,508,351 to Horiuchi et al. discloses a golf ball cover comprising a resin composition containing 10 to 80 wt. % of a partially saponified olefin/acrylate ester copolymer with the balance consisting of an ionomer. However, this reference does not disclose or even suggest the use of saponified polymer being blended with polyamide for a golf ball cover or intermediate or core layer compositions.
Saponified polymers of the present invention differ from prior art ionomers, inter alia, in that any pendant groups that are not modified by the saponification process are ester groups in contrast to the pendant carboxylic acid groups that remain after neutralization in prior art ionomers. The new composition can contain binary, ternary, or multi-component blends of metal cations used to neutralize the polymer. Such blends may be further combined with other polymers, such as SURLYN®, IOTEK® and IMAC® ionomers, to produce golf balls and golf ball covers with desirable properties. The golf ball composition can be used for both solid and wound construction balls.
It is also known that saponified polymers may be blended with polyamides. For example, U.S. Pat. No. 5,554,698 to Wang et al. discloses low-haze films and peelable seals formed from saponified &agr;-olefin/&agr;,&bgr;-ethylenically-unsaturated carboxylic acid ester copolymers which, optionally, may contain polyamide. However, this reference does not disclose or even suggest the use of saponified polymer/polyamide blends in golf balls, or that such blends could provide golf balls having improved properties.
U.S. Pat. No. 5,981,654 to Rajagopalan is directed to compositions and methods for making golf balls, wherein the composition comprises a substantially optical brightener-free nonionomer/polyamide polymer blend. U.S. Pat. No. 5,886,103 to Bellinger et al. discloses a golf ball with covers having a composition comprising a polyamide and an ionomer. Both the Rajagopalan '654 and the Bellinger '103 patents do not disclose the saponified polymer/polyamide blends of the present invention.
Numerous attempts have been made to replicate the performance of balata covered balls, some using polyamides as a component of a golf ball composition. Despite these numerous attempts, the golf ball compositions of the prior art generally suffer from low spin rates which makes them difficult to control near the greens. Further, such balls tend to have relatively poor “feel” as compared to the balata covered balls. Additionally, many of the prior art golf ball compositions are made with low flexural modulus ionomer resins which have improved spin and feel characteristics, but relatively low velocity, which results in shorter overall distance.
A need exists in the golf ball art for highly durable golf balls, which have improved performance, and may be tailored to have virtually any combination of feel and spin rate. The present invention provides such a golf ball.
SUMMARY OF THE INVENTION
The present invention is directed to a golf ball having at least one layer, where the layer is formed of a saponified polymer/polyamide blend, comprising from about 1 to about
Acushnet Company
Buttner David J.
Swidler Berlin Shereff & Friedman, LLP
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