Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1998-07-28
2001-03-27
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S072000, C525S452000, C525S453000, C525S454000, C473S354000, C473S355000, C473S357000, C473S365000, C473S372000, C473S373000, C473S385000
Reexamination Certificate
active
06207784
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to golf balls and, more particularly, to golf balls having covers, coatings, intermediate layers or cores which comprise an anionic polyurethane or polyurea ionomer and to methods for making the same. Preferably the anionic group(s) are based on carboxylic or sulfonic acid groups. Golf balls produced in accordance with the present invention are characterized by improved properties including increased resiliency, increased distance, abrasion-resistance, cut resistance, and durability.
BACKGROUND OF THE INVENTION
The covers of golf balls are generally made from a variety of materials, such as balata or ionomer resins such as SURLYN® and IOTEK®. Balata, which is a natural or synthetic trans-polyisoprene rubber, is the softest of these cover materials. Balata covered balls are favored by the more highly skilled golfers because the softness of the cover allows the player to achieve spin rates sufficient to more precisely control ball direction and distance, particularly on shorter shots.
However, balata covered balls are expensive and less durable as compared to the other cover materials. In particular, balata covered balls are subject to nicks or cuts as a result of a mis-swung golf club or due to landing on cart paths, etc. and/or contact with rocks, trees, etc. Such nicks or cuts detract from the flight characteristics of such balls, rendering them of little use. Accordingly, cover compositions have been developed in an attempt to provide balls with spin rates and a feel approaching those of balata covered balls, while also providing a golf ball with a higher durability and overall distance.
Ionomer resins have, to a large extent, replaced balata as a cover stock material. Chemically, ionomer resins are a copolymer of an olefin and an alpha, beta ethylenically-unsaturated carboxylic acid having 10-90% of the carboxylic acid groups neutralized by a metal ion. See U.S. Pat. No. 3,264,272. Commercially available ionomer resins include, for example, copolymers of ethylene and methacrylic or acrylic acid. These are sold by E.I. DuPont de Nemours and Co. under the trademark “SURLYN®” and by the Exxon Corporation under the trademark “ESCOR®” and the trademark “IOTEK®”. These ionomer resins are distinguished by the type of metal ion, the amount of acid, and the degree of neutralization. Also, Chevron Chemical Co. sells a family of ionomers produced from ethylene acrylate-based copolymers under the trademark “IMAC®”.
U.S. Pat. Nos. 3,454,280, 3,819,768, 4,323,247, 4,526,375, 4,884,814, and 4,911,451 all relate to the use of SURLYN®-type compositions in golf ball covers. However, while SURLYN® covered golf balls as described in the preceding patents possess virtually cutproof covers, they have inferior spin and feel properties as compared to balata covered balls.
In 1986, DuPont introduced two new classes of ionomer resins. One was a sodium and zinc ionomer resin having a low flexural modulus. DuPont suggested using and blending the same with other ionomer resins for making a golf ball cover. Golf ball covers made from these low flexural modulus ionomer resins have improved spin and feel characteristics but relatively low velocity. The other was a lithium ionomer resin which was a copolymer of ethylene and methacrylic acid. These lithium ionomer resins have a very high flexural modulus, typically about 60,000 psi (415 MPa). DuPont suggested that lithium ionomer resins could be used to produce a golf ball cover which would be more cut resistant and harder than a cover made with either sodium or zinc ionomer resins. DuPont also suggested that a golf ball having a cover made from a lithium ionomer resin would go farther, have a higher coefficient of restitution and be less prone to cutting (i.e., more durable) than a golf ball made from other known ionomer resins such as sodium and zinc ionomer resins and blends thereof. DuPont further suggested that lithium ionomer resins could be used in blends with other ionomer resins where they can impart better cut resistance to those other resins.
“The Rules of Golf” by the USGA dictates that no golf ball shall have an initial velocity that exceeds 255 feet (78 m) per second, i.e., 250 feet (76 m) per second with a 2% tolerance when impacted by the USGA test machine under specified conditions. Golf balls with covers made from ionomer resins with a low flexural modulus are significantly below this maximum and, as should be appreciated, all golf ball manufacturers strive to come as close as possible to this limit.
In various attempts to produce an ideal golf ball, the golf industry has blended hard ionomer resins (i.e., those ionomer resins having a hardness of about 60 to about 70 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 (see, e.g., U.S. Pat. No. 4,674,751 to Molitor et al.). 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.
In addition, various hard-soft ionomer blends, that is, mixtures of ionomer resins which are significantly different in hardness and/or flexural modulus, have been attempted. U.S. Pat. No. 4,884,814 discloses the blending of various hard methacrylic based ionomer resins with similar or larger quantities of one or more “soft” ionomer methacrylic acid based ionomer resins (i.e., those ionomer resins having a hardness from about 25 to 40 as measured on the Shore D scale) to produce relatively low modulus golf ball cover compositions that are not only softer than the prior art hard ionomer covers but also exhibit a sufficient degree of durability for repetitive play. These relatively low modulus cover compositions were generally comprised of from about 25 to 70% of hard ionomer resins and from about 30 to 75% of soft ionomer resins.
U.S. Pat. No. 5,324,783 discloses golf ball cover compositions comprising a blend of a relatively large amount, e.g., 70-90 wt. %, of hard ionomer resins with a relatively low amount, e.g., 10 to about 25-30 wt. %, of soft ionomers. The hard ionomers are sodium or zinc salts of a copolymer of an olefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from 3 to 8 carbon atoms. The soft ionomer is a sodium or a zinc salt of a terpolymer of an olefin having from 2 to 8 carbon atoms, methacrylic acid and an unsaturated monomer of the acrylate ester class having from 1 to 21 carbon atoms.
In order to approximate the characteristics of balata covered balls at lower cost, the art has developed balls having a variety of cover compositions. There are more than fifty commercial grades of ionomers available from DuPont and Exxon with a wide range of properties which vary according to the type and amount of metal cations, molecular weight, composition of the base resin (i.e., relative content of ethylene and methacrylic and/or acrylic acid groups) and additive ingredients such as reinforcements, etc. As noted above, these prior art compositions have a considerably higher cut resistance and durability as compared to balata covered balls. A great deal of research continues in order to develop golf ball cover compositions exhibiting not only improved impact resistance and carrying distance properties produced by the “hard” ionomeric resins, but also the playability (i.e. “spin”) characteristics previously associated with the “soft” balata covers, properties which are still desired by the more skilled golfer.
Polyurethane has also been recognized as a useful material for golf ball covers since as early as about 1960. U.S. Pat. No. 3,147,324, filed Oct. 20, 1960, is directed to a method of making a golf ball having a polyurethane cover. This patent disclosed an improved method of covering a golf ball with a liquid urethane polymer which could be applied, set and cured at room temperature or at a temperature that would not damage the tension
Acushnet Company
Buttner David J.
Pennie & Edmonds LLP
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