Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-30
2002-10-22
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S221000, C473S354000, C473S371000, C473S372000, C473S373000, C473S374000, C473S378000, C473S385000
Reexamination Certificate
active
06469105
ABSTRACT:
TECHNICAL FIELD
The present invention relates to golf balls and, in particular, to golf balls having at least one layer comprising at least one saponified polymeric material. The layer may be located in any of the core or the optional mantle layer located between the cover and the core of a golf ball.
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.
Golf balls having a non-wound intermediate layer between the cover and the core comprising an ionomer have been disclosed. For example, U.S. Pat. No. 5,253,871 to Viollaz discloses the use of at least 10 percent of a block copoly(amide-ether) elastomer, optionally blended with an ionomer, for use as the middle layer of a three-layer golf ball.
The USGA has promulgated a rule that no golf ball shall have an initial velocity that exceeds 255 feet per second, i.e., 250 feet per second with a 2% tolerance. Golf balls with covers made from ionomer resins with a low flexural modulus are woefully below this maximum and, as should be appreciated, all golf ball manufacturers strive to come as close as possible to this limit.
Consequently, a need exists for a golf ball composition that provides spin rates and a feel more closely approximating those of balata balls, while also providing the distance of an ionomer two-piece ball. This invention teaches a new route to produce polymers with ionomeric character by selectively carrying out hydrolysis or saponification on copolymers to produce core and intermediate layer compositions useful in golf balls
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 melt 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.
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 with desirable properties. The golf ball composition can be used for both solid and wound construction balls.
SUMMARY OF THE INVENTION
The invention relates to a golf ball comprising a cover, a core, and optionally, an intermediate layer positioned between the cover and the core, where at least one of the core, and the optional intermediate layer comprises at least one layer comprising a saponified polymer, and to a method of making such golf balls. The saponified polymer of the present invention is prepared by a process comprising the steps of forming a polymer comprising a first monomeric component comprising a first olefinic monomer having from 2 to 8 carbon atoms, a second monomeric component comprising an unsaturated carboxylic acid based acrylate class ester having from 4 to 22 carbon atoms; and, optionally, a third monomeric component comprising at least one monomer selected from the group consisting of carbon monoxide, sulfur dioxide, an anhydride monomer, an unsaturated monocarboxylic acid, a second olefin having from 2 to 8 carbon atoms, and a vinyl ester or a vinyl ether of an alkyl acid having from 4 to 21 carbon atoms. A sufficient amount of heat is applied to the polymer to convert the polymer to a substantially molten state, and a mixture is formed by adding an inorganic metal base to the molten polymer, such that the viscosity of the mixture remains substantially unchanged from the viscosity of the molten polymer, where a sufficient amount of the inorganic metal base is added to the molten polymer in forming the mixture to obtain a degree of saponification of the polymer ranging between about 1 and 50 percent. Little or no saponification occurs during this initial mixing step. The mixture is then saponified to produce a saponified polymer comprising a polymer salt adapted for forming improved golf ball layers. Preferably, a layer of a golf ball of the present invention has a flexural modulus of at least 500 to about 300,000 psi and a specific gravity of at least 0.7.
A golf ball comprising the present invention has an Atti compression of at least 50 and a coefficient of restitution of at least 0.7. Preferably, the Atti compression of the golf ball is at least 60 to about 100.
Golf balls in accordance with the invention preferably have a cover and a core diameter of at least 0.5 to about 1.63 inches. Where the golf ball of the present invention further comprises at least one optional mantle or intermediate layer, the mantle or intermediate layer has a thickness of at least 0.02 inches. Golf balls of the present invention have an intermediate layer hardness of at least 20 Shore D and a flexural modulus of about 500 to about 100,000 psi and a core layer hardness of at least 40 Shore A to about 70 Shore D and a flexural modulus of at least 500to about 150,000 psi. Any of the core or the center, or the at least one optional mantle or intermediate layer may comprise a density adjusting filler material to increase or decrease the density so that a ball's trajectory can be altered as necessary. The density adjusting filler materi
Acushnet Company
Buttner David J.
Swidler Berlin Shereff & Friedman, LLP
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