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Golf ball compositions comprising elastic proteins

Golf ball compositions comprising elastic proteins description/claims

The present invention relates to compositions comprising elastic proteins and the use thereof in golf balls.

Elastic proteins are a class of materials which includes, for example, resilin, titin, elastin, abductin, collagen, and spider silks. Recent developments in genetic engineering have made possible the replication of partial genomes of various organisms to synthetically produce elastic proteins. For example, in a recent publication, “Synthesis and properties of crosslinked recombinant pro-resilin,” Nature, vol. 437, pages 999-1002 (2005), a method for producing crosslinked synthetic resilin is disclosed. The publication describes synthetic resilin as having superior resilience relative to high-resilience polybutadiene. The publication also describes synthetic resilin as being useful for industrial and biomedical applications, but its use in golf ball applications is not disclosed.

Conventional golf balls can be divided into two general classes: solid and wound. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material, and a cover. Resilience in wound golf balls is provided by the tensioned elastomeric material, e.g., isoprene rubber.

Wound golf balls have been replaced by solid golf balls, in both the marketplace and among the game's most accomplished players, as a result of the formulation of high-resilience synthetic rubbers, particularly polybutadiene, which provide for resilience in solid golf balls that is comparable to or exceeds that of wound golf balls. This development has led to design opportunities in multi-layer golf balls, wherein layers of different materials are used to provide various combinations of ball characteristics. For example, ionomer cover layers have been used to lower the spin and improve the durability of solid golf balls. Also, intermediate layers have been used to create balls that spin and, therefore, perform differently for different kinds of golf shots or for different types of players. Thus, the selection of various materials for use in cover, core, and intermediate layer(s) is of principal significance in modern golf ball design.

Despite the growth in design variation, polybutadiene remains the primary source of resilience in solid golf balls, because other materials that are used to form golf ball layers do not have the resilience of polybutadiene and/or lack the desired softness. For example, while some ionomers have good resilience, they can also have undesirable hardness.

In addition to the limited choice of suitable materials, golf ball design is also limited by diameter. Larger diameter adversely affects the aerodynamic performance of a golf ball. Therefore, with each added design element, e.g., an added layer or an added thickness to an existing layer, the volume of polybutadiene in the overall product may be reduced, which can lead to a reduction in resiliency. Several proposed solutions include the use of softer, high-resilience thermoplastic polymers and formulations of polybutadiene having higher resilience. However, these materials have not yet been formulated such that they can replace conventional polybutadiene as the primary source of resilience in golf balls.

Thus, there is a need in the golf ball industry for novel high-resilience, soft materials. Such materials may enable the incorporation into golf balls of soft centers, fluid-filled or hollow centers, and/or soft covers. The present invention describes such compositions and their use in a variety of golf ball core, cover, and intermediate layers.

In one embodiment, the present invention is directed to a golf ball having at least one layer formed from a composition comprising an elastic protein.

In another embodiment, the present invention is directed to a golf ball having at least one layer formed from a composition comprising an elastic protein, wherein the golf ball has a coefficient of restitution of at least 0.815 and an Atti compression of 90 or less.

Golf balls of the present invention include one-piece, two-piece (i.e., a core and a cover), multi-layer (i.e., a core of one or more layers and a cover of one or more layers), and wound golf balls, having a variety of core structures, intermediate layers, covers, and coatings. Golf ball cores may consist of a single, unitary layer, comprising the entire core from the center of the core to its outer periphery, or they may consist of a center surrounded by at least one outer core layer. The center, innermost portion of the core may be solid, hollow or liquid-, gel-, or gas-filled. The outer core layer may be solid, or it may be a wound layer formed of a tensioned elastomeric material. Golf ball covers may also contain one or more layers, such as a double cover having an inner and outer cover layer. Additional layers may optionally be disposed between the core and cover in the golf balls of the present invention, at least one layer is formed from a composition comprising an elastic protein as described below.

The elastic protein of the present invention may be any naturally occurring or engineered protein, peptide, or polypeptide that has resilience properties suitable for use in golf ball compositions. Such proteins may have particularly suitable resilience properties when crosslinked. In one embodiment, the elastic protein of the present invention is selected from resilin, titin, elastin, fibrillin, gluten, gliadin, abductin, byssus, spectrin, collagen, and spider silks.

In a particular embodiment of the invention, the elastic protein comprises crosslinked recombinant resilin. The following procedure is suitable for preparing crosslinked recombinant resilin. The first exon of the Drosophila melanogaster CG15920 gene, which encodes an amino-terminal domain in the native protein comprising 17 copies of the putative elastic repeat motif, GGRPSDSYGAPGGGN, is cloned and expressed as a soluble protein in Escherichia coli. The resulting soluble resilin protein is then crosslinked by establishing conditions for the formation of dityrosine crosslinks between soluble proteins to produce a solid material. A non-limiting example of such crosslinking method is Ru(II)-mediated photocrosslinking, which provides a rapid, quantitative and controllable conversion of the soluble monomer to a high molecular weight polymeric material. For a more detailed description of the cloning, expression, and crosslinking of recombinant resilin, reference is made to “Synthesis and properties of crosslinked recombinant pro-resilin,” Nature, vol. 437, pages 999-1002 and Supplementary Information pages 1-17 (2005), the entire disclosure of which is hereby incorporated herein by reference.

In a particular embodiment, the elastic protein has a resilience of greater than 80%, or at least 85%, or at least 90%, or at least 92%, or at least 95%. In another particular embodiment, the elastic protein has a modulus at 100% of less than 7 kPa, preferably 6 kPa or less, more preferably 5 kPa or less, more preferably from 1 kPa to 5 kPa, more preferably from 1 kPa to 3 kPa, and even more preferably 2 kPa. Resilience and modulus, as used herein, are measured on samples in buffer on an Instron Tensile Tester (model 4500) at a rate of 5 mm/min at a temperature of 21° C. Swollen strip samples (7 mm×1 mm), having a gauge length of 5 mm, are cycled initially up to a strain of about 200%. The maximum strain is increased successively in steps of 25-50% until failure occurs. Resilience is calculated from the ratio of the area under the retraction curve to the area under the extension curve. The stress at 100% strain on the extension curve is taken as the secant modulus at 100%.

In another particular embodiment, a sphere formed from the elastic protein has a coefficient of restitution (“COR”) of at least 0.810, or at least 0.815, or at least 0.820, or at least 0.850, or at least 0.900, or at least 0.910, or at least 0.920, or at least 0.930, or at least 0.940, or at least 0.950. As used herein, COR is defined as the ratio of the rebound velocity to the inbound velocity when balls are fired into a rigid plate. In determining COR, the inbound velocity is understood to be 125 ft/s.

In another particular embodiment, the elastic protein is a crosslinked material comprising a plasticizer, such as water, in an amount of at least 75 wt %, preferably at least 80 wt %. In yet another particular embodiment, the elastic protein has a density of less than 1.50 g/cm3, preferably less than 1.40 g/cm3, more preferably less than 1.35 g/cm3, and even more preferably 1.33 g/cm3.

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