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
2000-02-09
2002-05-21
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...
C525S072000, C525S196000, C525S201000, C525S221000, C521S134000, C473S355000, C473S365000, C473S371000, C473S372000, C473S373000, C473S378000, C473S385000
Reexamination Certificate
active
06391966
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls and, in particular, to golf balls having at least one layer comprising a blend of at least one saponified polymeric material and at least one polyolefin polymer produced using a single-site metallocene catalyst in the polymerization process. The metallocene catalyzed polymer may be unmodified, or may contain at least one pendant functional group that is grafted to the polymer chain by a post-polymerization reaction. The layer, which may be foamed or unfoamed, may be located in any of the cover or core of the ball or in a mantle layer located between the cover and the core.
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 may 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.
Many attempts have been made to produce a golf ball with the control and feel of a wound balata ball and the durability of a solid, two-piece ball, but none have succeeded totally. In various attempts to produce an ideal golf ball, the golfing industry has blended hard ionomer resins (i.e., those ionomer resins having a hardness of about 60 to 66 on the Shore D scale, as measured in accordance with ASTM method D-2240) with a number of softer polymeric materials, such as softer polyurethanes. However, the blends of the hard ionomer resins with the softer polymeric materials have generally been unsatisfactory in that these balls exhibit numerous processing problems. In addition, the balls produced by such a combination are usually short on distance.
While different blend combinations of species of one variety of polymer, such as prior art ionomers, i.e., copolymers of an olefin and an &agr;,&bgr;-unsaturated carboxylic acid, have been successfully used in the prior art, different polymers, such as carboxylic acid based ionomers and balata or other non-ionic polymers have not been successfully blended for use in golf ball covers. In general, prior art blends of polymer components are immiscible, i.e., heterogeneous on a microscopic scale, and incompatible, i.e., heterogeneous on a macroscopic scale, unless strong interactions are present between the polymer components in the mixture, such as those observed between carboxylic acid based ionomers and other polymers containing carboxylic acid groups. In particular, this lack of compatibility exists when an ionomer is blended with a polyolefin homopolymer, copolymer, or terpolymer that does not contain ionic, acidic, basic, or other polar pendant groups, and is not produced with a metallocene catalyst. These mixtures often have poor 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, cut resistance, and so on. In contrast, a compatible blend may be heterogeneous on a microscopic scale, but is homogeneous on a macroscopic scale, and, thus, has useful golf ball properties.
In this regard, U.S. Pat. No. 5,397,840 discloses golf ball covers including a blend of “ionic copolymers” and “non-ionic copolymers”. However, the “ionic copolymers” are defined as copolymers of an &agr;-olefin and a metal salt of an &agr;&bgr;-unsaturated carboxylic acid, and the “non-ionic copolymers” are copolymers or terpolymers containing ethylene or propylene and acrylic or methacrylic acid monomers. Therefore, strong interactions exist between the metal salts of the “ionic copolymers” and the acrylic or methacrylic acid monomers of the “non-ionic copolymers” that allow compatible blends to be formed. These interactions do not exist in prior art blends of ionomers and polymers that are truly non-ionic or nonpolar, in particular, those polymers produced with a process that does not involve the use of a metallocene catalyst.
The use of single-site metallocene catalysts in the polymerization of polyolefins produces polymers with a narrow molecular weight distribution and uniform molecular architecture, so that the order and orientation of the monomers in the polymer, and the amount and type of branching is essentially the same in each polymer chain. The narrow molecular weight distribution and uniform molecular architecture provides metallocene polymers with properties that are not available with conventional polymers, and allow polymers to be produced having unique properties that are specifically tailored to a particular application. The desired molecular weight distribution and the molecular architecture are obtained by the selection of the appropriate metallocene catalyst and polymerization conditions. The properties may than be further tailored to an application by grafting an appropriate functional group to the polymer chain using a post-polymerization reaction.
Grafted metallocene catalyzed polymers, which are available commercially, share the advantages of unmodified metallocene catalyzed polymers, including a narrow molecular weight distribution and uniform molecular architecture. The addition of functional groups to the metallocene catalyzed polymers by grafting allows polymers to be produced having properties that are not available with unfunctionalized metallocene catalyzed polymers or polymers formed without the use of metallocene catalysts.
As shown in co-pending patent application Ser. No. 08/482,514, metallocene catalyzed polymers and ionomers form compatible blends having useful golf ball properties. However, there is no known disclosure of golf balls comprising compatible blends of grafted or non-grafted metallocene catalyzed polymers, i.e., polymers produced using single-site metallocene catalysts, and ester based ionomeric polymers produced by carrying out a hydrolysis or saponification on copolymers containing pendant ester groups to form an ionomeric polymer that is less hydrophilic than typical carboxylic acid based ionomers.
Hydrolysis or saponification of alkyl acrylate units in a crosslinkable polymer chain is disclosed by Gross in U.S. Pat. No. 3,926,891. This is accomplished by dissolving the polymer in an aqueous alkali metal hydroxide solution and then heating. The product is recovered by coating the solution onto a substrate and evaporating the water or by extruding the solution into a non-solvent. 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. This emulsion can be used as such, partially dried to a paste or moist solid, or fully dried to solid form.
A different approach to hydrolysis or saponification 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. Typically, the copolymer would be molten when mixed with the aqueous solution.
All of these prior methods 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. Processes of this nature pose several disadvantages, however. First, it is difficult to remove water from the hydrolyzed or saponified polymer product. The polymer product is in the form of a salt that has
Acushnet Company
Buttner David J.
Swidler Berlin Shereff & Friedman, LLP
LandOfFree
Golf ball compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Golf ball compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Golf ball compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2872918