Golf ball having a polyurethane cover

A golf ball having a polyurethane cover composed of a blend of polyurethane prepolymers is disclosed herein. The blend may be a dual blend with a TDI-based polyurethane prepolymer blended with a second diisocyanate polyurethane prepolymer, typically a PPDI-based polyurethane prepolymer. The blend may also be a tri-blend with a TDI-based polyurethane prepolymer blended with two other diisocyanate polyurethane prepolymers, typically two different PPDI-based polyurethane prepolymers. The golf ball has a durability of at least 3.5 on a shear test rating of the cover. The golf ball of the present invention also demonstrates tremendous distance using a BIG BERTHA.RTM. HAWKEYE.RTM. driver.

CROSS REFERENCES TO RELATED APPLICATIONS
 Not Applicable
 STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 Not Applicable
 BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a cover for a golf ball. More
 specifically, the present invention relates to a golf ball cover layer
 composed of a polyurethane formed from a blend of diisocyanate
 prepolymers.
 2. Description of the Related Art
 Conventionally golf balls are made by molding a cover around a core. The
 core may be wound or solid. A wound core typically comprises elastic
 thread wound about a solid or liquid center. Unlike wound cores, solid
 cores do not include a wound elastic thread layer. Solid cores typically
 may comprise a single solid piece center or a solid center covered by one
 or more mantle or boundary layers of material.
 The cover may be injection molded, compression molded, or cast over the
 core. Injection molding typically requires a mold having at least one pair
 of mold cavities, e.g., a first mold cavity and a second mold cavity,
 which mate to form a spherical recess. In addition, a mold may include
 more than one mold cavity pair.
 In one exemplary injection molding process each mold cavity may also
 include retractable positioning pins to hold the core in the spherical
 center of the mold cavity pair. Once the core is positioned in the first
 mold cavity, the respective second mold cavity is mated to the first to
 close the mold. A cover material is then injected into the closed mold.
 The positioning pins are retracted while the cover material is flowable to
 allow the material to fill in any holes caused by the pins. When the
 material is at least partially cured, the covered core is removed from the
 mold.
 As with injection molding, compression molds typically include multiple
 pairs of mold cavities, each pair comprising first and second mold
 cavities that mate to form a spherical recess. In one exemplary
 compression molding process, a cover material is pre-formed into
 half-shells, which are placed into a respective pair of compression mold
 cavities. The core is placed between the cover material half-shells and
 the mold is closed. The core and cover combination is then exposed to heat
 and pressure, which cause the cover half-shells to combine and form a full
 cover.
 As with the above-referenced processes, a casting process also utilizes
 pairs of mold cavities. In a casting process, a cover material is
 introduced into a first mold cavity of each pair. Then, a core is held in
 position (e.g. by an overhanging vacuum or suction apparatus) to contact
 the cover material in what will be the spherical center of the mold cavity
 pair. Once the cover material is at least partially cured (e.g., a point
 where the core will not substantially move), the core is released, the
 cover material is introduced into a second mold cavity of each pair, and
 the mold is closed. The closed mold is then subjected to heat and pressure
 to cure the cover material thereby forming a cover on the core. With
 injection molding, compression molding, and casting, the molding cavities
 typically include a negative dimple pattern to impart a dimple pattern on
 the cover during the molding process.
 Materials previously used as golf ball covers include balata (natural or
 synthetic), gutta-percha, ionomeric resins (e.g., DuPont's SURLYN.RTM.),
 and polyurethanes. Balata is the benchmark cover material with respect to
 sound (i.e. the sound made when the ball is hit by a golf club) and feel
 (i.e. the sensation imparted to the golfer when hitting the ball). Natural
 balata is derived from the Bully Gun tree, while synthetic balata is
 derived from a petroleum compound. Balata is expensive compared to other
 cover materials, and golf balls covered with balata tend to have poor
 durability (i.e. poor cut and shear resistance). Gutta percha is derived
 from the Malaysian sapodilla tree. A golf ball covered with gutta percha
 is considered to have a harsh sound and feel as compared to balata covered
 golf balls.
 Ionomeric resins, as compared to balata, are typically less expensive and
 tend to have good durability. However, golf balls having ionomeric resin
 covers typically have inferior sound and feel, especially as compared to
 balata covers.
 A golf ball with a polyurethane cover generally has greater durability than
 a golf ball with a balata cover. The polyurethane covered golf ball
 generally has a better sound and feel than a golf ball with an ionomeric
 resin cover. Polyurethanes may be thermoset or thermoplastic.
 Polyurethanes are formed by reacting a prepolymer with a polyfunctional
 curing agent, such as a polyamine or a polyol. The polyurethane prepolymer
 is the reaction product of, for example, a diisocyanate and a polyol such
 as a polyether or a polyester. Several patents describe the use of
 polyurethanes in golf balls. However, golf balls with polyurethane covers
 usually do not have the distance of other golf balls such as those with
 covers composed of SURLYN.RTM. materials.
 Gallagher, U.S. Pat. No. 3,034,791 discloses a polyurethane golf ball cover
 prepared from the reaction product of poly(tetramethylene ether) glycol
 and toluene-2,4-diisocyanates (TDI), either pure TDI or an isomeric
 mixture.
 Isaac, U.S. Pat. No. 3,989,568 ("the '568 patent) discloses a polyurethane
 golf ball cover prepared from prepolymers and curing agents that have
 different rates of reaction so a partial cure can be made. The '568 patent
 explains that "the minimum number of reactants is three." Specifically, in
 '568 patent, two or more polyurethane prepolymers are reacted with at
 least one curing agent, or at least one polyurethane prepolymer is reacted
 with two or more curing agents as long as the curing agents have different
 rates of reaction. The '568 patent also explains that "[o]ne of the great
 advantages of polyurethane covers made in accordance with the instant
 invention is that they may be made very thin. . . . ", and "[t]here is no
 limitation on how thick the cover of the present invention may be but it
 is generally preferred . . . that the cover is no more than about 0.6
 inches in thickness." The examples in the '568 patent only disclose golf
 balls having covers that are about 0.025 inches thick.
 Dusbiber, U.S. Pat. No. 4,123,061 ("the '061 patent")discloses a
 polyurethane golf ball cover prepared from the reaction product of a
 polyether, a diisocyanate and a curing agent. The '061 patent discloses
 that the polyether may be polyalkylene ether glycol or polytetramethylene
 ether glycol. The '061 patent also discloses that the diisocyanate may be
 TDI, 4,4'-diphenylmethane diisocyanate ("MDI"), and
 3,3'-dimethyl-4,4'-biphenylene diisocyanate ("TODI"). Additionally, the
 '061 patent discloses that the curing agent may be either a polyol (either
 tri- or tetra-functional and not di-functional) such as triisopropanol
 amine ("TIPA") or trimethoylol propane ("TMP"), or an amine-type having at
 least two reactive amine groups such as: 3,3' dichlorobenzidene; 3,3'
 dichloro 4,4' diamino diphenyl methane ("MOCA"); N,N,N',N' tetrakis
 (2-hydroxy propyl) ethylene diamine; or Uniroyal's Curalon L which is an
 aromatic diamine mixture.
 Hewitt, et al., U.S. Pat. No. 4,248,432 ("the '432 patent") discloses a
 thermoplastic polyesterurethane golf ball cover formed from a reaction
 product of a polyester glycol (molecular weight of 800-1500) (aliphatic
 diol and an aliphatic dicarboxylic acid) with a para-phenylene
 diisocyanate ("PPDI") or cyclohexane diisocyanate in the substantial
 absence of curing or crosslinking agents. The '432 patent teaches against
 the use of chain extenders in making polyurethanes. The '432 patent
 states, "when small amounts of butanediol-1,4 are mixed with a polyester .
 . . the addition results in polyurethanes that do not have the desired
 balance of properties to provide good golf ball covers. Similarly, the use
 of curing or crosslinking agents is not desired. . . . "
 Holloway, U.S. Pat. No. 4,349,657 ("the '657 patent") discloses a method
 for preparing polyester urethanes with PPDI by reacting a polyester (e.g.
 prepared from aliphatic glycols having 2-8 carbons reacted with aliphatic
 dicarboxylic acids having 4-10 carbons) with a molar excess of PPDI to
 obtain an isocyanate-terminated polyester urethane (in liquid form and
 stable at reaction temperatures), and then reacting the polyester urethane
 with additional polyester. The '657 patent claims that the benefit of this
 new process is the fact that a continuous commercial process is possible
 without stability problems. The '657 patent further describes a suitable
 use for the resultant material to be golf ball covers.
 Wu, U.S. Pat. No. 5,334,673 ("the '673 patent") discloses a polyurethane
 prepolymer cured with a slow-reacting curing agent selected from
 slow-reacting polyamine curing agents and difunctional glycols (i.e.,
 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine,
 N,N'-dialkyldiamino diphenyl methane,
 trimethyleneglycol-di-p-aminobenzoate,
 polytetramethyleneoxide-di-p-aminobenzoate, 1,4-butanediol,
 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, ethylene glycol, and mixtures
 of the same). The polyurethane prepolymer in the '673 patent is disclosed
 as made from a polyol (e.g., polyether, polyester, or polylactone) and a
 diisocyanate such as MDI or TODI. The polyether polyols disclosed in the
 '673 patent are polytetramethylene ether glycol, poly(oxypropylene)
 glycol, and polybutadiene glycol. The polyester polyols disclosed in the
 '673 patent are polyethylene adipate glycol, polyethylene propylene
 adipate glycol, and polybutylene adipate glycol. The polylactone polyols
 disclosed in the '673 patent are diethylene glycol initiated caprolactone,
 1,4-butanediol initiated caprolactone, trimethylol propane initiated
 caprolactone, and neopentyl glycol initiated caprolactone.
 Cavallaro, et al., U.S. Pat. No. 5,688,191 discloses a golf ball having
 core, mantle layer and cover, wherein the mantle layer is either a
 vulcanized thermoplastic elastomer, functionalized styrene-butadiene
 elastomer, thermoplastic polyurethane, metallocene polymer or blends of
 the same and thermoset materials.
 Wu, et al., U.S. Pat. No. 5,692,974 discloses golf balls having covers and
 cores that incorporate urethane ionomers (i.e. using an alkylating agent
 to introduce ionic interactions in the polyurethane and thereby produce
 cationic type ionomers).
 Sullivan, et al., U.S. Pat. No. 5,803,831 ("the '831 patent") discloses a
 golf ball having a multi-layer cover wherein the inner cover layer has a
 hardness of at least 65 Shore D and the outer cover layer has a hardness
 of 55 Shore D or less, and more preferably 48 Shore D or less. The '831
 patent explains that this dual layer construction provides a golf ball
 having soft feel and high spin on short shots, and good distance and
 average spin on long shots. The '831 patent provides that the inner cover
 layer can be made from high or low acid ionomers such as SURLYN.RTM.,
 ESCOR.RTM. or IOTEK.RTM., or blends of the same, nonionomeric
 thermoplastic material such as metallocene catalyzed polyolefins or
 polyamides, polyamide/ionomer blends, polyphenylene ether/ionomer blends,
 etc., (having a Shore D hardness of at least 60 and a flex modulus of more
 than 30000 psi), thermoplastic or thermosetting polyurethanes, polyester
 elastomers (e.g. HYTREL.RTM.), or polyether block amides (e.g.
 PEBAX.RTM.), or blends of these materials. The '831 patent also provides
 that the outer cover layer can be made from soft low modulus (i.e.
 1000-10000 psi) material such as low-acid ionomers, ionomeric blends,
 non-ionomeric thermoplastic or thermosetting materials such as
 polyolefins, polyurethane (e.g. thermoplastic polyurethanes like
 TEXIN.RTM., PELETHANE.RTM., and thermoset polyurethanes like those
 disclosed in Wu, U.S. Pat. No. 5,334,673), polyester elastomer (e.g.
 HYTREL.RTM.), or polyether block amide (e.g. PEBAX.RTM.), or a blend of
 these materials.
 Hebert, et al., U.S. Pat. No. 5,885,172 ("the '172 patent") discloses a
 multilayer golf ball giving a "progressive performance" (i.e. different
 performance characteristics when struck with different clubs at different
 head speeds and loft angles) and having an outer cover layer formed of a
 thermoset material with a thickness of less than 0.05 inches and an inner
 cover layer formed of a high flexural modulus material. The '172 patent
 provides that the outer cover is made from polyurethane ionomers as
 described in Wu, et al., U.S. Pat. No. 5,692,974, or thermoset
 polyurethanes such as TDI or methylenebis-(4-cyclohexyl isocyanate)
 ("HMDI"), or a polyol cured with a polyamine (e.g. methylenedianiline
 (MDA)), or with a trifinctional glycol (e.g.,
 N,N,N',N'-tetrakis(2-hydroxpropyl)ethylenediamine). The '172 also provides
 that the inner cover has a Shore D hardness of 65-80, a flexural modulus
 of at least about 65,000 psi, and a thickness of about 0.020-0.045 inches.
 Exemplary materials for the inner cover are ionomers, polyurethanes,
 polyetheresters (e.g. HYTREL.RTM.), polyetheramides (e.g., PEBAX.RTM.),
 polyesters, dynamically vulcanized elastomers, functionalized
 styrene-butadiene elastomer, metallocene polymer, blends of these
 materials, nylon or acrylonitrile-butadiene-styrene copolymer.
 Wu, U.S. Pat. No. 5,484,870 ("the '870 patent") discloses golf balls having
 covers composed of a polyurea composition. The polyurea composition
 disclosed in the '870 patent is a reaction product of an organic
 isocyanate having at least two functional groups and an organic amine
 having at least two functional groups. One of the organic isocyanates
 disclosed by the '870 patent is PPDI.
 Although the prior art has disclosed golf ball covers composed of many
 different materials, none of these golf balls have proven completely
 satisfactory. Dissatisfaction, for example, remains with processing and
 manufacturing the balls, and with the balls' durability and performance.
 Specifically, with respect to processing, prior materials are not user
 friendly because certain starting materials may be unhealthful, such as
 diamines and isocyanides. In addition, prior balls using such materials
 are generally wound balls. Wound balls have tolerances that are more
 difficult to control due to core sizes and/or windings sizes, and
 therefore, require thicker cover layers to account for the manufacturing
 tolerances. With respect to durability problems, prior polyurethane
 covered balls, because they are wound balls, tend to lose compression and
 initial velocity due to the windings relaxing over time and use. With
 respect to performance problems, prior balls, as a general rule, tend to
 have smaller cores that result in shorter flight distances. Although many
 golf balls having a polyurethane cover have been provided by the prior
 art, these golf balls have failed to capture the sound and feel of balata
 while providing a golf ball with the durability of an ionomer.
 BRIEF SUMMARY OF THE INVENTION
 The present invention provides a golf ball that demonstrates the best
 overall durability and distance as yet put forth by the golf industry
 while adhering to all of the rules for golf balls as set forth by the USGA
 and The Royal & Ancient Golf Club of Saint Andrews. The golf ball of the
 present invention is able to accomplish this by providing a cover composed
 of a blend of polyurethane prepolymers.
 One aspect of the present invention is a golf ball that includes a core and
 a polyurethane cover formed from reactants including a toluene
 diisocyanate based polyurethane prepolymer, a second diisocyanate
 polyurethane prepolymer and at least one curing agent. The toluene
 diisocyanate based polyurethane prepolymer of the golf ball may include
 toluene diisocyanate and polyether polyol. The golf ball may include at
 least one boundary layer disposed between the core and the polyurethane
 cover. The second diisocyanate polyurethane prepolymer of the golf ball is
 different from the toluene diisocyanate based polyurethane prepolymer and
 may be a p-phenylene diisocyanate based polyurethane prepolymer. The
 p-phenylene diisocyanate based polyurethane prepolymer may include
 p-phenylene diisocyanate and one or more polyester polyols, polyether
 polyols or a mixture thereof The p-phenylene diisocyanate based
 polyurethane prepolymer of the golf ball may include p-phenylene
 diisocyanate and polycaprolactone polyol.
 Another aspect of the present invention is golf ball including a core, a
 boundary layer and a thermoset polyurethane cover. The core includes a
 polybutadiene. The boundary layer encompasses the core and includes at
 least one ionomer. The boundary layer has a shore D hardness in the range
 of 50 to 70. The thermoset polyurethane cover encompasses the boundary
 layer. The thermoset polyurethane cover has a Shore D hardness in the
 range of 40 to 55, and a thickness in the range of 0.02 to 0.05 inches.
 The golf ball has a durability of at least 3.5 on a scale of 1 to 5 based
 on a cover shear test.
 The golf ball may have the thermoset polyurethane cover formed from a
 p-phenylene diisocyanate terminated polyether prepolymer, a toluene
 diisocyanate terminated polyether prepolymer and at least one other
 component. Alternatively, the golf ball may have the thermoset
 polyurethane cover formed from a p-phenylene diisocyanate terminated
 polyester prepolymer, a toluene diisocyanate terminated polyether
 prepolymer and at least one other component. Yet further, the golf ball
 may have the thermoset polyurethane cover formed from a p-phenylene
 diisocyanate terminated polyether prepolymer, a p-phenylene diisocyanate
 terminated polyester prepolymer, a toluene diisocyanate terminated
 polyether prepolymer and at least one other component. The at least one
 other component may be a blend of a diamine curing agent and a diol curing
 agent.
 Yet another aspect of the present invention is a golf ball including a
 core, a boundary layer and a polyurethane cover formed from 0 to 90 parts
 of a p-phenylene diisocyanate terminated polyester prepolymer, 0 to 90
 parts of a p-phenylene diisocyanate terminated polyether prepolymer, 10 to
 40 parts of a toluene diisocyanate polyurethane prepolymer, and at least
 one curing agent. The at least one curing agent may be a blend of a
 diamine curing agent and a diol curing agent. More specifically, the
 diamine curing agent may be diethyl 2,4-toluenediamine, and the diol
 curing agent may be a 1,4 butane diol and glycol.
 The polyurethane cover may have a hardness of between about 45-60 Shore D,
 a flexural modulus of between about 12,000-35,000 psi, a Bayshore
 resilience of between about 50-70, and a tensile strength of between about
 5900-7500 psi. More specifically, the polyurethane cover may be formed
 from 20 parts of a p-phenylene diisocyanate terminated polyester
 prepolymer, 50 parts of a p-phenylene diisocyanate terminated polyether
 prepolymer, and 30 parts of a toluene diisocyanate polyurethane
 prepolymer. Alternatively, the polyurethane cover may be formed from 70 to
 80 parts of a p-phenylene diisocyanate terminated polyether prepolymer,
 and 30 to 20 parts of a toluene diisocyanate polyurethane prepolymer.
 Yet another aspect of the present invention is a method of fabricating a
 golf ball. The method generally includes cast molding a polyurethane cover
 over a golf ball precursor product. The golf ball precursor product may be
 a core, or a core and boundary layer. The polyurethane cover is formed
 from a toluene diisocyanate based polyurethane prepolymer, a second
 diisocyanate based polyurethane prepolymer and an agent. The agent is
 selected from the group consisting of a curative, a chain extender, a
 cross-linking agent and a mixture thereof.
 The method may also include heating the tolune diisocyanate based
 polyurethane prepolymer and second diisocyanate based polyurethane
 prepolymer to a predetermined temperature. The method may also include
 heating the agent to a predetermined temperature. The method may also
 include mixing the toluene diisocyanate based polyurethane prepolymer and
 second diisocyanate based polyurethane prepolymer with the agent to form a
 common mixture prior to cast molding the cover over the golf ball
 precursor product.
 The cast molding step may include placing the golf ball precursor product
 in a first half of a mold containing the mixture of toluene diisocyanate
 based polyurethane prepolymer, the second diisocyanate based polyurethane
 prepolymer and the agent. The cast molding step may also include curing
 the mixture of toluene diisocyanate based polyurethane prepolymer, the
 second diisocyanate based polyurethane prepolymer and the agent for a
 predetermined time period. The cast molding step may also include mating
 the first half of the mold with a second half of the mold. The second half
 of the mold would contain the mixture of toluene diisocyanate based
 polyurethane prepolymer, the second diisocyanate based polyurethane
 prepolymer and the agent. The cast molding step may also include pressing
 the first half of the mold and the second half of the mold together for a
 predetermined time period.
 The method may include adding a third diisocyanate based polyurethane
 prepolymer to the prepolymer mixture. The second diisocyanate based
 polyurethane prepolymer may be a p-phenylene terminated polyether
 prepolymer and the third diisocyanate based polyurethane prepolymer may be
 a p-phenylene terminated polyester prepolymer.
 Another aspect of the present invention is a polyurethane system. The
 polyurethane system is formed from reactants comprising 0 to 90 parts of a
 p-phenylene diisocyanate terminated polyester prepolymer, 0 to 90 parts of
 a p-phenylene diisocyanate terminated polyether prepolymer, 10 to 40 parts
 of a toluene diisocyanate polyurethane prepolymer, and at least one curing
 agent.
 Another aspect of the present invention is a method for forming a
 polyurethane system. The method includes blending a tolune diisocyanate
 based polyurethane prepolymer with a second diisocyanate based
 polyurethane prepolymer to form a polyurethane prepolymer blend. The
 method also includes heating the prepolymer blend to a predetermined
 temperature, and then mixing the polyurethane prepolymer blend with a
 curing agent to form the polyurethane system.
 Having briefly described the present invention, the above and further
 objects, features and advantages thereof will be recognized by those
 skilled in the pertinent art from the following detailed description of
 the invention when taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION
 As illustrated in FIG. 1, the golf ball of the present invention is
 generally indicated as 10. The golf ball 10 includes a core 12, a boundary
 layer 14 and a cover 16. Alternatively, as shown in FIG. 2, the golf ball
 10 may only include a core 12 and a cover 16.
 The cover 16 is a polyurethane cover having a predetermined hardness and a
 predetermined durability as measured on a cover strike plate drop test as
 further described below. The polyurethane cover 16 is composed of a
 polyurethane material formed from a blend of diisocyanate prepolymers. The
 blend of diisocyanate prepolymers includes at least one TDI-based
 polyurethane prepolymer and at least one other diisocyanate-based
 polyurethane prepolymer. In a preferred embodiment, the blend of
 diisocyanate prepolymers includes at least one PPDI-based polyurethane
 prepolymer and at least one TDI-based polyurethane prepolymer. Alternative
 embodiments have a blend which includes at least two different PPDI-based
 polyurethane prepolymer and at least one TDI-based polyurethane
 prepolymer. Yet further embodiments may include at least one TDI-based
 polyurethane prepolymer and at least one MDI-based polyurethane
 prepolymer. Those skilled in the pertinent art will recognize that
 multiple variations of diisocyanate prepolymers may be utilized without
 departing from the scope and spirit of the present invention.
 The polyurethane cover 16 encompasses a boundary layer 14, as shown in FIG.
 1, or alternatively the cover 16 may encompass the core 12 as shown in
 FIG. 2. The boundary layer 14 is composed of a thermoplastic material that
 has a predetermined hardness. The boundary layer 14 will encompass the
 core 12. Each component of the golf ball 10 of the present invention will
 be described below in greater detail.
 The most important feature of the present invention is the durability of
 the cover. As shown in FIG. 3, the golf ball 10 is subjected to tremendous
 forces when impacted with a golf club 20 during a "golf shot." The golf
 ball 10 of the present is capable of enduring, more than polyurethane
 covered golf balls of the prior art, slices or other incorrect hits by
 golfers. The unique polyurethane formulation for the cover 16 of the
 present invention provides this enhanced durability. Durability as defined
 herein is objectively measured through comparative testing of available
 golf balls versus the golf ball 10 of the present invention. The testing
 methods and results will be described below.
 The polyurethane utilized in the present invention is composed of blend of
 a TDI-based prepolymer, a second diisocyanate-based polyurethane
 prepolymer and a curing agent. The TDI-based prepolymer is preferably
 formed from TDI and a polyether polyol. The second diisocyanate-based
 polyurethane prepolymer is preferably a PPDI-based prepolymer formed from
 PPDI and a polyester polyol, preferably a polycaprolactone. The prepolymer
 blend is cured with a curing agent. The curing agent, or curative, may be
 a diol (e.g., 1,4 butane diol, trimethylpropanol), a mixture of diols
 (e.g., 1,4 butane diol and ethylene glycol, or other suitable glycols), a
 hydroquinone, a mixture of hydroquinones, a triol, a mixture of triols, a
 diamine, a mixture of diamines, an oligomeric diamine, a triamine, or a
 blend of some or all of these materials. Preferably, the curing agent is a
 blend of a diamine and a mixture of diols.
 In an alternative embodiment, the blend of prepolymers includes three
 diisocyanate-based polyurethane prepolymers. In this embodiment, the
 TDI-based prepolymer is preferably formed from TDI and a polyether polyol.
 The second diisocyanate-based polyurethane prepolymer is preferably a
 PPDI-based prepolymer formed from PPDI and a polyester polyol, preferably
 a polycaprolactone. The third diisocyanate-based polyurethane prepolymer
 is a PPDI-based prepolymer formed from PPDI and a polyether polyol.
 Preferably, the curing agent is a blend of a diamine and a mixture of
 diols. As mentioned above, alternative embodiments may have variations of
 the dual blend or the tri-blend, and may use a TDI-based polyurethane
 prepolymer with other non-PPDI-based polyurethane prepolymers.
 TDI PPDI
 As previously set forth in this Assignee's co-pending U.S. patent
 application Ser. No. 09/295,635, entitled Golf Ball With Polyurethane
 Cover, filed on Apr. 20, 1999, which is hereby incorporated by reference
 in its entirety, a PPDI-based polyurethane prepolymer provides a
 polyurethane with a higher rebound at a lower hardness, greater durability
 and improved sound and feel. However, although the use of only a
 PPDI-based polyurethane prepolymer provides greater durability for a
 polyurethane cover, the polyurethane cover 16 of the present invention
 formed from a blend of prepolymers provides even greater durability.
 The blending of a TDI-based prepolymer with other diisocyanate-based
 polyurethane prepolymers lowers the viscosity of the mixture, lowers the
 temperature of the exothermic reaction that occurs when the prepolymers
 are reacted with the curing agent, and increases the durability. The
 TDI-based prepolymer may range from 10 to 40 percent of the polyurethane
 prepolymer blend. Preferably, the TDI-based prepolymer is 30 percent of
 the polyurethane prepolymer blend. A preferred TDI based prepolymer is a
 TDI terminated polyether prepolymer available from Uniroyal Chemical
 Company of Middlebury, Conn., under the tradename ADIPRENE.RTM. LF950.
 The dual blend and tri-blend formulations will preferably contain a PPDI
 terminated polyester prepolymer and/or a PPDI terminated polyether
 prepolymer. A preferred PPDI terminated polyester prepolymer is available
 from Uniroyal Chemical under the tradename ADIPRENE.RTM. LFPX 2950. A
 preferred PPDI terminated polyether prepolymer is available from Uniroyal
 Chemical under the tradename ADIPRENE.RTM. LFPX 950.
 The polyurethane prepolymer blend may have 10 to 40 parts of a TDI
 terminated polyether prepolymer blended with 60 to 90 parts of a PPDI
 terminated polyether prepolymer. Alternatively, the polyurethane
 prepolymer blend may have 10 to 40 parts of a TDI terminated polyether
 prepolymer blended with 60 to 90 parts of a PPDI terminated polyester
 prepolymer. Further, the polyurethane prepolymer blend may have 10 to 40
 parts of a TDI terminated polyether prepolymer blended with 5 to 90 parts
 of a PPDI terminated polyether prepolymer and 5 to 90 parts of a PPDI
 terminated polyester prepolymer. More specific blend formulations are set
 forth in the Examples below.
 The cover 16 of the golf ball 10 of the present invention is most
 preferably composed of a polyurethane formed from a polyurethane
 prepolymer blend composed of a TDI-based polyurethane prepolymer and a
 PPDI-based polyurethane prepolymer, and cured with a mixture of curing
 agents such as a diamine and a blend of 1,4 butane diol and glycols. A
 suitable blend of diol and glycols is available from Uniroyal Chemical
 under the tradename VIBRACURE.RTM. A250. A suitable diamine is toluene
 ethylene diamine available from Albemarle Corporation of Baton Rouge, La.
 under the tradename ETHACURE.RTM. 100. Other agents which may be utilized
 during the curing process include dimethylthio-2,4-toluenediamine (such as
 EHTACURE.RTM. 300 available from Albemarle Corporation); trimethyl glycol
 di-p-aminobenzoate (such as VERSALINK.RTM. 740M available from Air
 Products and Chemicals, Inc., Allentown, Pa.); cyclohexane dimethanol;
 hydroquinone-bis-hydroxyethyl ether; phenyldiethanol amine mixture (such
 as VIBRACURE.RTM. A931 available from Uniroyal Chemical); methylene
 dianiline sodium chloride complex (such as CAYTOR.RTM. 31 available from
 Uniroyal Chemical); and/or prionene amine. This list of preferred agents
 (including chain extenders, cross-linkers and curing agents) is not meant
 to be exhaustive, as any suitable (preferably polyfunctional) chain
 extender, cross-linker, or curing agent may be used.
 The curing agent mixture for the cover 16 of the present invention may have
 numerous variations. In a preferred embodiment, the curing agent is
 composed of 30 to 70 parts of a diol blend such as VIBRACURE.RTM. 250 to
 70 to 30 parts of a diamine such as ETHACURE.RTM. 300. Alternatively, the
 diamine component may be a blend of different diamines such as a blend of
 EHTACURE.RTM. 100 with ETHACURE.RTM. 300.
 The ratio of the polyurethane prepolymer blend to curing agent is
 determined by the nitrogen-carbon-oxygen group ("NCO") content of the
 polyurethane prepolymer blend. For example, the NCO content of the
 TDI-terminated polyether or TDI-terminated polyester is preferably in the
 range of 4.0% to 9.0%, while the NCO content of the PPDI-terminated
 polyether is preferably in the range of 5.0% to 8.0%. The NCO content of
 the PPDI-terminated polyester is preferably in the range of 2.0% to 6.0%.
 The NCO content of the polyurethane prepolymer blend ranges from 2% to 8%
 of the polyurethane prepolymer blend. The amount of curing agent should
 correspond to 90% to 110% of the mol equivalence of the NCO content of the
 polyurethane prepolymer blend. The weight ratio of the polyurethane
 prepolymer blend to the curing agent is preferably in the range of about
 10:1 to about 30:1.
 Prior to curing, the polyurethane prepolymer blend and curing agent are
 preferably stored separately. The polyurethane is formed by first heating
 and mixing the polyurethane prepolymer blend with the curing agent in a
 mold, and then curing the mixture by applying heat and pressure for a
 predetermined time period. Additionally, a catalyst (e.g. dibutyl tin
 dilaurate, a tertiary amine, etc.) may be added to the mixture to expedite
 the casting process. Specific suitable catalysts include TEDA dissolved in
 di propylene glycol (such as TEDA L33 available from Witco Corp.
 Greenwich, Conn., and DABCO 33 LV available from Air Products and
 Chemicals Inc.,) which may be added in amounts of 2-5%, and more
 preferably TEDA dissolved in 1,4-butane diol which may be added in amounts
 of 2-5%. Another suitable catalyst includes a blend of 0.5% 33LV or TEDA
 L33 (above) with 0.1% dibutyl tin dilaurate (available from Witco Corp. or
 Air Products and Chemicals, Inc.) which is added to a curative such as
 VIBRACURE.RTM. A250. Furthermore, additives such as colorants may also be
 added to the mixture.
 The polyurethane prepolymer blend material is preferably degassed and
 warmed in a first holding container prior to processing of the cover 16.
 The processing temperature for the polyurethane prepolymer blend is
 preferably in the range of about 100-220.degree. F., and most preferably
 in the range of about 120-200.degree. F. The polyurethane prepolymer blend
 is preferably flowable from the first holding container to a mixing
 chamber in a range of about 200-1100 grams of material per minute, or as
 needed for processing. In addition, the polyurethane prepolymer blend
 material may be agitated in the first holding container, in the range of
 0-250 rpm, to maintain a more even distribution of material and to
 eliminate crystallization.
 In the preferred embodiment, the curing agent is a blend of a diamine such
 as ETHACURE.RTM. 300 and a 1,4 butane diol and glycol such as
 VIBRACURE.RTM. A250. As previously mentioned, other curatives may also be
 utilized in forming the cover 16 of the golf ball 10 of the present
 invention. The curing agent is preferably degassed and warmed in a second
 holding container prior to processing of the cover 16. The processing
 temperature for the curative is preferably in the range of about
 50-230.degree. F., and most preferably in the range of about
 80-200.degree. F. The curing agent is preferably flowable from the second
 holding container to the mixing chamber in the range of about 15-75 grams
 of material per minute, or as needed. If a catalyst is used for processing
 the cover 16, then the catalyst is added to the curing agent in the second
 holding container to form a curative mixture. Suitable catalyst are
 described above. The curing agent and catalyst are agitated, in the range
 of about 0 to 250 rpm, to maintain an even distribution of catalyst in the
 curative mixture in the second holding container. It is preferred that the
 catalyst is added in an amount in the range of about 0.25-5% by weight of
 the combined polyurethane prepolymer blend and curing agent. Additives may
 be added to the curative mixture as desired. It was discovered that
 hydrolytic instability of the polyurethane polymer may be avoided by the
 addition of a stabilizer such as STABOXYL.RTM. (available from
 Rheinchemie, Trenton, N.J.), in amounts of about 0.25-5% of the
 polyurethane.
 The polyurethane prepolymer blend and curative mixture are preferably added
 to the common mixing chamber at a temperature in the range of about
 160-220.degree. F. A colorant material, such as, for example, titanium
 dioxide, barium sulfate, and/or zinc oxide in a glycol or castor oil
 carrier, and/or other additive material(s) as are well known in the art,
 may be added to the common mixing chamber. The amount of colorant material
 added is preferably in the range of about 0-10% by weight of the combined
 polyurethane prepolymer blend and curative materials, and more preferably
 in the range of about 2-8%. Other additives, such as, for example, polymer
 fillers, metallic fillers, and/or organic and inorganic fillers (e.g.
 polymers, balata, ionomers, etc.) may be added as well to increase the
 specific gravity of the polyurethane cover 16 of the present invention. It
 was discovered that the addition of barytes (barium sulfate) or a blend of
 barytes and titanium dioxide (preferably added in a carrier glycol and/or
 castor oil) to the mixture, in the amounts of about 0.01-30%, may add
 sufficient weight to the polyurethane cover 16. The added weight to the
 cover 16 allows for a lower specific gravity for the core 12 thereby
 allowing for an increased resiliency of the core 12. The entire mixture is
 preferably agitated in the mixing chamber in the range of about 1 to 250
 rpm prior to molding. A more detailed explanation of the process is set
 forth in this Assignee's co-pending U.S. patent application Ser. No.
 09/296,197, entitled Golf Balls And Methods Of Manufacturing The Same,
 filed on Apr. 20, 1999, which is hereby incorporated by reference in its
 entirety.
 The core 12 of the golf ball 10 is the "engine" for the golf ball 10 such
 that the inherent properties of the core 12 will strongly determine the
 initial velocity and distance of the golf ball 10. A higher initial
 velocity will usually result in a greater overall distance for a golf
 ball. In this regard, the Rules of Golf, approved by the United States
 Golf Association ("USGA") and The Royal and Ancient Golf Club of Saint
 Andrews, limits the initial velocity of a golf ball to 250 feet (76.2m)
 per second (a two percent maximum tolerance allows for an initial velocity
 of 255 per second) and the overall distance to 280 yards (256m) plus a six
 percent tolerance for a total distance of 296.8 yards (the six percent
 tolerance may be lowered to four percent). A complete description of the
 Rules of Golf are available on the USGA web page at www.usga.org. Thus,
 the initial velocity and overall distance of a golf ball must not exceed
 these limits in order to conform to the Rules of Golf. Therefore, the core
 12 for a USGA approved golf ball is constructed to enable the golf ball 10
 to meet, yet not exceed, these limits.
 The coefficient of restitution ("COR") is a measure of the resilience of a
 golf ball. The COR is a measure of the ratio of the relative velocity of
 the golf ball after direct impact with a hard surface to the relative
 velocity before impact with the hard surface. The COR may vary from 0 to
 1, with 1 equivalent to a completely elastic collision and 0 equivalent to
 a completely inelastic collision. A golf ball having a COR value closer to
 1 will generally correspond to a golf ball having a higher initial
 velocity and a greater overall distance. The effect of a higher COR value
 is illustrated in FIG. 3 in which a golf club 20 strikes the golf ball 10.
 The force of the club 20 during a swing is transferred to the golf ball
 10. If the golf ball has a high COR (more elastic), then the initial
 velocity of the golf ball will be greater than if the golf ball had a low
 COR. In general, a higher compression core will result in a higher COR
 value.
 The core 12 of the golf ball 10 is generally composed of a blend of a base
 rubber, a cross-linking agent, a free radical initiator, and one or more
 fillers or processing aids. A preferred base rubber is a polybutadiene
 having a cis-1,4 content above 90%, and more preferably 98% or above.
 The use of cross-linking agents in a golf ball core is well known, and
 metal acrylate salts are examples of such cross-linking agents. For
 example, metal salt diacrylates, dimethacrylates, or mono(meth)acrylates
 are preferred for use in the golf ball cores of the present invention, and
 zinc diacrylate is a particularly preferred cross-linking agent. A
 commercially available suitable zinc diacrylate is SR-416 available from
 Sartomer Co., Inc., Exton, Pa. Other metal salt di- or
 mono-(meth)acrylates suitable for use in the present invention include
 those in which the metal is calcium or magnesium. In the manufacturing
 process it may be beneficial to pre-mix some cross-linking agent(s), such
 as, e.g., zinc diacrylate, with the polybutadiene in a master batch prior
 to blending with other core components.
 Free radical initiators are used to promote cross-linking of the base
 rubber and the cross-linking agent. Suitable free radical initiators for
 use in the golf ball core 12 of the present invention include peroxides
 such as dicumyl peroxide, bis-(t-butyl peroxy) diisopropyl benzene,
 t-butyl perbenzoate, di-t-butyl peroxide,
 2,5-dimethyl-2,5-di-5-butylperoxy-hexane, 1,1-di(t-butylperoxy)
 3,3,5-trimethyl cyclohexane, and the like, all of which are readily
 commercially available.
 Zinc oxide is also preferably included in the core formulation. Zinc oxide
 may primarily be used as a weight adjusting filler, and is also believed
 to participate in the cross-linking of the other components of the core
 (e.g. as a coagent). Additional processing aids such as dispersants and
 activators may optionally be included. In particular, zinc stearate may be
 added as a processing aid (e.g. as an activator). Any of a number of
 specific gravity adjusting fillers may be included to obtain a preferred
 total weight of the core 12. Examples of such fillers include tungsten and
 barium sulfate. All such processing aids and fillers are readily
 commercially available. The present inventors have found a particularly
 useful tungsten filler is WP102 Tungsten (having a 3 micron particle size)
 available from Atlantic Equipment Engineers (a division of Micron Metals,
 Inc.), Bergenfield, N.J.
 Table 1 below provides the ranges of materials included in the preferred
 core formulations of the present invention.
 TABLE 1
 Core Formulations
 Component Preferred Range Most Preferred Range
 Polybutadiene 100 parts 100 parts
 Zinc diacrylate 20-35 phr 25-30 phr
 Zinc oxide 0-50 phr 5-15 phr
 Zinc stearate 0-15 phr 1-10 phr
 Peroxide 0.2-2.5 phr 0.5-1.5 phr
 Filler As desired As desired
 (e.g. tungsten) (e.g. 2-10 phr) (e.g. 2-10 phr)
 In the present invention, the core components are mixed and compression
 molded in a conventional manner known to those skilled in the art. In a
 preferred form, the finished core 12 has a diameter of about 1.35 to about
 1.64 inches for a golf ball 10 having an outer diameter of 1.68 inches.
 The core weight is preferably maintained in the range of about 32 to about
 40 g. The core PGA compression is preferably maintained in the range of
 about 50 to 90, and most preferably about 55 to 80.
 As used herein, the term "PGA compression" is defined as follows:
EQU PGA compression value=180-Riehle compression value
 The Riehle compression value is the amount of deformation of a golf ball in
 inches under a static load of 200 pounds, multiplied by 1000. Accordingly,
 for a deformation of 0.095 inches under a load of 200 pounds, the Riehle
 compression value is 95 and the PGA compression value is 85.
 As is described above, the present invention preferably includes at least
 one boundary layer 14 that preferably is composed of a thermoplastic (e.g.
 thermoplastic or thermoplastic elastomer) or a blend of thermoplastics
 (e.g. metal containing, non-metal containing or both). However, the golf
 ball 10 may have several boundary layers 14 disposed between the core 12
 and the cover 16. Most preferably the boundary layer 14 is composed of at
 least one thermoplastic that contains organic chain molecules and metal
 ions. The metal ion may be, for example, sodium, zinc, magnesium, lithium,
 potassium, cesium, or any polar metal ion that serves as a reversible
 cross-linking site and results in high levels of resilience and impact
 resistance. Suitable commercially available thermoplastics are ionomers
 based on ethylene copolymers and containing carboxylic acid groups with
 metal ions such as described above. The acid levels in such suitable
 ionomers may be neutralized to control resiliency, impact resistance and
 other like properties. In addition, other fillers with ionomer carriers
 may be used to modify (e.g. preferably increase) the specific gravity of
 the thermoplastic blend to control the moment of inertia and other like
 properties. Exemplary commercially available thermoplastic materials
 suitable for use in a boundary layer 14 of a golf ball 10 of the present
 invention include, for example, the following materials and/or blends of
 the following materials: HYTREL.RTM. and/or HYLENE.RTM. products from
 DuPont, Wilmington, Del., PEBAX.RTM. products from Elf Atochem,
 Philadelphia, Pa., SURLYN.RTM. products from DuPont, and/or ESCOR.RTM. or
 IOTEK.RTM. products from Exxon Chemical, Houston, Tex.
 The Shore D hardness of the boundary layer 14 should be about 65 or less.
 It is preferred that the boundary layer 14 have a hardness of between
 about 50-65 Shore D. In a preferred embodiment, the boundary layer 14 has
 a Shore D hardness in the range of about 57-65. One reason for preferring
 a boundary layer 14 with a Shore D hardness of 65 or lower is to improve
 the feel of the resultant golf ball. It is also preferred that the
 boundary layer 14 is composed of a blend of SURLYN.RTM. ionomer resins.
 SURLYN.RTM. 8150, 9150, and 6320 are, respectively, an ionomer resin
 composed of a sodium neutralized ethylene/methacrylic acid, an ionomer
 resin composed of a zinc neutralized ethylene/methacrylic acid, and an
 ionomer resin composed of a terpolymer of ethylene, methacrylic acid and
 n-butyl acrylate partially neutralized with magnesium, all of which are
 available from DuPont, Polymer Products, Wilmington, Del.
 The boundary layer 14 may include a predetermined amount of a baryte
 mixture. The baryte mixture is included as 8 or 9 parts per hundred parts
 of the ionomer resins. One preferred baryte mixture is composed of 80%
 barytes and 20% of an ionomer, and is available from Americhem, Inc.,
 Cuyahoga Falls, Ohio, under the trade designation 38534X1. The Shore D
 hardness provided in Table Three below was determined according to ASTM
 D2240.
 EXAMPLES
 Twelve golf balls of the present invention were compared to a Maxfli
 REVOLUTION, a Titlelist PROFESSIONAL, a Titlelist DT-2, and a Bridgestone
 PRECEPT. All of the golf balls were subjected to a durability test to
 determine the durability of the golf balls in an objective manner. The
 durability tests were conducted on a cover shear apparatus as illustrated
 in FIGS. 4, 4A and 4B. The apparatus 30 includes a ten pound metal block
 32 with a strike plate 34 on its bottom, mounted on a frame 36. A golf
 ball 10 is placed within a holder 38 and held by a set of pins 40. The
 strike plate 34 is angled at 54 degrees from vertical. The strike plate 34
 is dropped from six inches above the golf ball 10.
 The golf balls are measured on a cover shear criteria. The scale for each
 is from 1 to 5, with 1 being poor, 2 being below average, 3 being average,
 4 being above average and 5 being excellent. The cover shear criteria is
 as follows: 1-portion of the cover has been completely sheared off and
 dimples have been greatly reduced or removed; 2-the cover material has
 been sheared to the extent that the flaps of the cover are visible, and
 severe bunching or peeling back of the cover material is evident; 3-there
 is moderate cutting of the cover material to the extent that internal
 portions of the cover are exposed, but the cover is intact; 4-indentations
 in the cover are evident, but there is no bunching of the cover material;
 5-groove marks are difficult to see and slight score marks may or may not
 be visible, and there is no deformation of the cover material.
 Table Three below sets forth physical data for suitable boundary layers 14
 that were manufactured and incorporated into specific embodiments of
 twelve example golf balls of the present invention. As is shown in Table 3
 below, each of the boundary layers 14 were composed of an ionomer blend
 and the specific percentages are provided. The thickness of each of the
 boundary layers 14 varies from 0.0525 and 0.058 inches. The shore D
 hardness varies between 58 and 62.
 TABLE THREE
 Ball SURLYN .RTM. Thickness Shore D
 Ex. No. % 8150 % 9150 % 6320 (inches) Hardness
 1 40 40 20 0.058 58
 2 45 45 10 0.0525 62
 3 45 45 10 0.0525 62
 4 40 40 20 0.058 60
 5 40 40 20 0.058 60
 6 40 40 20 0.058 60
 7 45 45 20 0.0525 62
 8 45 45 20 0.0525 62
 9 45 45 10 0.0525 62
 10 45 45 10 0.0525 62
 11 45 45 10 0.0525 62
 12 45 45 10 0.0525 62
 Table Four sets forth data for each of the twelve overall golf balls 10 and
 each of the cores 12. The weight of each of the golf balls 10 varies from
 45.65 grams to 45.92 grams. The PGA compression of each of the golf balls
 10 varies from 92 to 101. The average diameter of each of the golf balls
 10 is consistently 1.684 inches. The core diameter of each of the cores 12
 is 1.489 inches or 1.515 inches. The PGA compression of each of the cores
 12 varies between 60 and 75 points.
 TABLE FOUR
 Ball Ball Average Core Core
 Weight Compression Diameter Diameter Compression
 Ball (grams) (points) (inches) (inches) (points)
 1 45.65 92 1.684 1.489 60
 2 45.86 98 1.684 1.515 70
 3 45.92 101 1.684 1.515 75
 4 45.82 94 1.684 1.489 60
 5 45.83 99 1.684 1.489 65
 6 45.90 99 1.684 1.489 65
 7 45.86 96 1.684 1.515 70
 8 45.84 100 1.684 1.515 75
 9 45.84 101 1.684 1.515 75
 10 45.89 98 1.684 1.515 65
 11 45.83 95 1.682 1.515 65
 12 45.84 97 1.681 1.515 69
 TABLE FIVE
 Thick- Shore D
 Ball Polyurethane prepolymer ness Hard-
 Ex. No. TDI PPDI-1 PPDI-2 PPDI-3 PPDI-4 (inches) ness
 1 30 70 0.0375 47
 2 30 20 50 0.0300 53
 3 30 70 0.0300 47
 4 30 70 0.0375 47
 5 30 50 20 0.0375 47
 6 30 70 0.0375 47
 7 30 50 20 0.0300 47
 8 30 20 50 0.0300 53
 9 30 70 0.0300 53
 10 20 80 0.0300 47
 11 30 70 0.0300 47
 12 30 70 0.0300 47
 Table Five sets forth the properties of each of the cover layers 16 for
 each of the twelve golf balls 10. The number of parts of each polyurethane
 prepolymer for each of the cover layers 16 is provided in columns 2
 through 6. Column 2 includes the number of parts of the TDI-terminated
 polyether prepolymer, ADIPRENE.RTM. LF950. Column 3 includes the number of
 parts of the PPDI terminated polyether prepolymer, ADIPRENE.RTM. LFPX950.
 Column 4 includes the number of parts of the PPDI terminated polyester
 (polycaprolactone) prepolymer, ADIPRENE.RTM. LFPX2950. Column 5 includes
 the number of parts of the PPDI terminated polyether prepolymer,
 ADIPRENE.RTM. LFPX590. The difference between LFPX590 and LFPX950 is the
 NCO content and the molecular weight of the polyol (ether) backbone, with
 LFPX950 having a NCO content in the range of approximately 5.45% to
 approximately 5.75%, and LFPX590 having a NCO content in the range of
 approximately 5.6% to approximately 6.2%. Column 6 includes the number of
 parts of the PPDI terminated polyester (polycaprolactone) prepolymer,
 ADIPRENE.RTM. LFPX2952. The difference between LFPX2950 and LFPX2952 is
 the NCO content, with LFPX2950 having a NCO content in the range of
 approximately 3.55% to approximately 3.85%, and LFPX2952 having a NCO
 content in the range of approximately 4.45% to approximately 5.05%. Each
 of the polyurethane prepolymer blends for examples 1-9 and 11-12 were
 cured with a blend of curing agents. The blend of curing agents was
 composed of 50 parts ETHACURE 300 (a diamine curing agent) and 50 parts
 VIBRACURE A250 (a blend of a 1,4 butane diol and glycol). Example 10 of
 the golf balls 10 of the present invention was cured with a blend of 70
 parts ETHACURE 300 and 30 parts VIBRACURE A250. The thickness of the cover
 layer 16 for each of the twelve golf balls 10 of present invention is
 either 0.0300 inches or 0.0375 inches. The shore D hardness of the cover
 layer 16 for each of the twelve golf balls 10 of present invention is
 either 47 degrees or 53 degrees.
 TABLE SIX
 110 mph Driver 90 mph Driver 79 mph 5-Iron
 Shear Carry Total Carry Total Carry
 Ball (1-5) (yds) (yds) (yds) (yds) (yds)
 Revolution 5 251.5 269.6 194.5 218.6 158.1
 Precept EV 4 253.1 270.6 196.2 220.4 162.7
 Professional 4 248.2 266.1 190.3 216.0 158.4
 DT 2-piece 1 256.1 274.7 197.1 222.8 164.8
 1 4.25 253.9 271.1 195.7 220.6 161.2
 2 4.0 255.5 274.1 196.7 222.4 163.2
 3 4.0 257.3 272.2 199.2 221.8 162.0
 4 4.0 253.9 269.7 197.0 220.4 160.4
 5 4.0 254.3 274.1 198.2 220.4 159.1
 6 4.25 254.4 269.4 197.4 220.6 160.1
 7 4.25 255.9 271.4 198.3 221.9 161.6
 8 3.75 257.2 273.2 198.2 222.7 163.6
 9 3.75 256.8 273.6 197.2 222.7 163.8
 10 3.75 256.7 275.5 197.5 222.6 161.3
 11 4.5 255.5 273.3 196.8 222.5 160.9
 12 4.5 257.3 274.2 196.8 221.5 161.1
 Table Six illustrates the comparison testing between the twelve sample golf
 balls 10 of the present invention, and the four well-known and well-played
 golf balls. All of the golf balls in Table Six were subjected to the
 afore-mentioned shear test and rated. The golf balls were also subject to
 a standard robot swing test at 110 miles per hour ("mph") using a BIG
 BERTHA.RTM. HAWKEYE.RTM. driver, at 90 mph using a BIG BERTHA.RTM.
 HAWKEYE.RTM. driver, and at 79 mph using a BIG BERTHA.RTM. X-12.RTM. five
 iron. Although the REVOLUTION.RTM. had the best shear rating, its carry
 and total distance was only better than the Titlelist PROFESSIONAL.RTM..
 Example 12 of the golf balls 10 of the present invention had a durability
 rating of 4.5, and it had a carry six yards better than the REVOLUTION at
 110 mph using a BIG BERTHA.RTM. HAWKEYE.RTM. driver. The best distance at
 110 mph using a BIG BERTHA.RTM. HAWKEYE.RTM. driver was example 10 of the
 golf balls 10 of the present invention which had a carry yardage of 256.7
 yards and a total distance of 275.5 yards with a durability of 3.75. The
 next closest golf ball in distance was the DT-2, however, it only had a
 durability of 1. Table Six demonstrates that the golf ball 10 of the
 present invention provides objectively the best overall durability with
 the best overall distance.
 The above examples demonstrate the efficacy of the golf ball 10 of the
 present invention and are not intended to limit the scope or spirit of the
 present invention.
 From the foregoing it is believed that those skilled in the pertinent art
 will recognize the meritorious advancement of this invention and will
 readily understand that while the present invention has been described in
 association with a preferred embodiment thereof, and other embodiments
 illustrated in the accompanying drawings, numerous changes, modifications
 and substitutions of equivalents may be made therein without departing
 from the spirit and scope of this invention which is intended to be
 unlimited by the foregoing except as may appear in the following appended
 claims. Therefore, the embodiments of the invention in which an exclusive
 property or privilege is claimed are defined in the following appended
 claims.