US20100304896A1

US20100304896A1 - Polyurea covers for golf balls based on cycloaliphatic isocyanates

Info

Publication number: US20100304896A1
Application number: US12/472,685
Authority: US
Inventors: Michael Michalewich; Shawn Ricci; Brian Comeau
Original assignee: Acushnet Co
Current assignee: Acushnet Co
Priority date: 2009-05-27
Filing date: 2009-05-27
Publication date: 2010-12-02
Also published as: JP2010274115A

Abstract

A golf ball having a cover material made from a polyurea composition is provided. In one version, the golf ball includes a polybutadiene core and surrounding cover layer made of a polyurea composition. In another version, the golf ball includes a polybutadiene core, an intermediate casing layer made of an ionomer resin, and outer cover layer made of the polyurea composition. The polyurea composition is the reaction product of a cycloaliphatic isocyanate and amine compound. The diisocyanate is selected from 1,3-bis(isocyanatomethyl)cyclohexane; 1,4-bis(isocyanatomethyl)cyclohexane; and mixtures thereof. The resulting cover material has many advantages including improved durability, toughness, and light-stability.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to a golf ball having a cover material made from a polyurea composition. More particularly, the polyurea composition is the reaction product of a cycloaliphatic isocyanate, amine-terminated compound, and amine curing agent. The resulting cover material has many advantages including improved durability, toughness, and light-stability.
2. Brief Review of the Related Art
Golf ball covers made from polyurethane and polyurea compositions are generally known in the industry. In recent years, polyurethane and polyurea cover materials have become more popular, because they provide the golf balls with a desirable combination of “hardness” and “softness.” The “hardness” of the golf ball cover protects the ball from being cut, abraded, and otherwise damaged. In addition, hard-covered golf balls generally reach a higher velocity when struck by a club. As a result, such golf balls tend to travel a greater distance, which is particularly important for driver shots off the tee. Meanwhile, the “softness” of the golf ball provides the player with a better “feel” when he/she strikes the ball with the club face. The player senses more control over the ball as the club face makes impact. The softness allows players to place a spin on the ball and better control its flight pattern, which is particularly important for approach shots.
Basically, polyurethane compositions contain urethane linkages formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). Polyurethanes are produced by the reaction of a polyisocyanate with a polyalcohol(polyol) in the presence of a catalyst and other additives. The chain length of the polyurethane prepolymer is extended by reacting it with a hydroxyl-terminated curing agent compound.
Polyurea compositions, which are distinct from the above-described polyurethanes, also can be formed. In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group (—N═C═O) with an amine group (NH or NH₂). The chain length of the polyurea prepolymer is extended by reacting the prepolymer with an amine curing agent.
Polyurethane and polyurea covered golf balls are described in the patent literature. For example, Wu, U.S. Pat. No. 5,484,870 discloses a polyurea composition suitable for molding golf ball covers. The polyurea composition is the reaction product of an organic compound having at least two isocyanate functional groups and an amine curing agent. The mole equivalent ratio of amine groups to isocyanate groups may vary over a wide range. Additional materials such as colorants, ultraviolet light absorbers, plasticizers, and the like may be included in the compositions. Bulpett et al., U.S. Pat. No. 6,964,621 also discloses polyurea compositions that can be used in the construction of golf balls. The compositions are prepared from a polyurea prepolymer and a curing agent. According to the '621 Patent, the resulting golf ball has improved cut and shear-resistance.
As discussed above, isocyanates with two or more functional groups are essential components in producing polyurethane and polyurea polymers. Aromatic isocyanates are normally used for several reasons including their high reactivity and cost benefits. Examples of aromatic isocyanates include, but are not limited to, toluene 2,4-diisocyanate (TDI), toluene 2,6-diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI), 2,4′-methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (PMDI), p-phenylene diisocyanate (PDI), m-phenylene diisocyanate (PDI), naphthalene 1,5-diisocynate (NDI), naphthalene 2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and the like. The aromatic isocyanates are able to react with the hydroxyl or amine compound and form a durable and tough polymer having a high melting point. The resulting polyurethane or polyurea generally has good mechanical strength and cut/shear resistance. However, one disadvantage with using aromatic isocyanates is the polymeric reaction product tends to have poor light stability and may discolor upon exposure to light, particularly ultraviolet (UV) light. Because aromatic isocyanates are used as a reactant, some aromatic structures may be found in the reaction product. UV light rays can cause quinoidation of the benzene rings resulting in yellow discoloration. Hence, UV light stabilizers are commonly added to the formulation, but the covers may still develop a yellowish appearance over prolonged exposure to sunlight. Thus, golf balls are normally painted with a white paint and then covered with a transparent coating to protect the ball's appearance.
In a second approach, aliphatic isocyanates are used to form the prepolymer. Examples of aliphatic isocyanates include, but are not limited to, isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), and the like. These aliphatic isocyanates can provide polymers having good light stability but such polymers tend to have decreased mechanical strength and cut/shear-resistance.
It also is known to use cycloaliphatic isocyanates to prepare polyurethane formulations. Argyropoulos, US Patent Application Publication 2007/0265388 discloses polyurethane dispersions produced from the reaction of a polyisocyanate with a polyol. The cycloaliphatic diisocyanates used to produce the polyurethane are selected from: (i) trans- 1,4-bis(isocyanatomethyl)cyclohexane or (ii) an isomeric mixture of two or more of cis-1,3-bis(isocyanatomethyl)cyclohexane, trans-1,3-bis(isocyanatomethyl)cyclohexane, cis-1,4-bis(isocyanatomethyl)cyclohexane and trans-1,4-bis(isocyanatomethyl)cyclohexane. The isomeric mixture contains at least about 5 weight percent of the trans-1,4-bis(isocyanatomethyl) cyclohexane. The '388 Publication discloses that the polyurethane dispersion can be used for coating various materials including wood, textiles, plastics, metal, glass, fibers, medical applications, automotive interiors, and leather as well as for adhesive applications such as shoe soles, wood and glass.
Slagel et al., US Patent Application Publication 2009/0105013 discloses a polyurethane/polyurea hybrid composition that can be cured to form the outer layer and/or inner layer of a golf ball. In one embodiment, the prepolymer is the reaction product of polycaprolactone glycol with 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane or a combination thereof. The prepolymer may be cured using one or more isomers of diethyltoluene diamine as the curing agent. The '013 Publication does not disclose synthesizing a pure polyurea composition using the reactants, 1,3-bis(isocyanatomethyl)cyclohexane and/or 1,4-bis(isocyanatomethyl)cyclohexane.
There is a continuing need for polyurethane and polyurea golf ball cover materials having good mechanical strength and cut/shear-resistance as well as light-stability. Particularly, it would be advantageous to use isocyanate components that could provide the polymers with such properties. The present invention provides such golf ball cover materials having high mechanical strength, cut/shear-resistance, and light-stability.

SUMMARY OF THE INVENTION

The present invention provides a golf ball having a cover material made from a polyurea composition, which is the reaction product of an isocyanate selected from the group consisting of 1,3-bis(isocyanatomethyl)cyclohexane; cis-1,4-bis(isocyanatomethyl)cyclohexane; and mixtures thereof; an amine-terminated compound; and amine curing agent. The resulting polyurea cover material has many advantages including improved durability, toughness, cut/shear-resistance, and light-stability. In one version, the golf ball includes a polybutadiene core and surrounding cover layer made of the polyurea composition. In another version, the golf ball includes a polybutadiene core, an intermediate casing layer made of an ionomer resin, and an outer cover layer made of the polyurea composition that surrounds the casing layer. Golf balls made in accordance with this invention may have various constructions. In one embodiment, the core has a diameter of about 1.26 to about 1.60 inches, the intermediate layer has a thickness in the range of about 0.015 to about 0.120 inches, and the cover has a thickness of about 0.020 inches to about 0.050 inches.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention are set forth in the appended claims. However, the preferred embodiments of the invention, together with further objects and attendant advantages, are best understood by reference to the following detailed description in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a single layered, two-piece golf ball having a polyurethane cover made in accordance with the present invention;

FIG. 1A is a cross-sectional view of a single layered, two-piece golf ball having a polyurea cover made in accordance with the present invention;

FIG. 2 is a cross-sectional view of a multi-layered, three-piece golf ball having a polyurethane cover made in accordance with the present invention; and

FIG. 2A is a cross-sectional view of a multi-layered, three-piece golf ball having a polyurethane cover made in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates generally to golf balls having a cover material made from a polyurethane, or a hybrid polyurethane/polyurea, or a polyurea, or a hybrid polyurea/polyurethane composition.

Polyurethane Compositions

In general, polyurethane compositions contain urethane linkages that are formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). Commercial polyurethanes are produced by the reaction of a polyisocyanate with a polyalcohol (polyol) in the presence of a catalyst and other additives. The chain length of the polyurethane prepolymer is extended by reacting it with a hydroxyl-terminated curing agent. The resulting polyurethane polymer has elastomeric properties based on phase separation of its soft and hard segments. The soft segments, which are formed from the polyols, are generally flexible and mobile, while the hard segments, which are formed from the isocyanate and chain extenders, are generally stiff and immobile. The polyurethane composition contains urethane linkages having the following general structure:
Polyurethane/Polyurea Hybrid Compositions
A polyurethane/polyurea hybrid composition is produced when the polyurethane prepolymer is chain-extended using an amine-terminated curing agent. Any excess isocyanate groups in the prepolymer will react with the amine groups in the curing agent and create urea linkages. That is, a polyurethane/polyurea hybrid containing both urethane and urea linkages is produced. A polyurethane/polyurea hybrid composition also can be produced when water is reacted with the isocyanate. The isocyanate can be reacted with the polyol prior to reaction with the water, or the isocyanate can be reacted with the water prior to reaction with the polyol. The water reacts with the isocyanate group to produce carbamic acid. In turn, the relatively unstable carbamic acid decomposes to form carbon dioxide and an amine. The amine then reacts with an isocyanate group to produce a urea linkage.
Polyurea Compositions
In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group (—N═C═O) with an amine group (NH or NH₂). The chain length of the polyurea prepolymer is extended by reacting the prepolymer with an amine curing agent. The resulting polyurea has elastomeric properties, because of its “hard” and “soft” segments, which are covalently bonded together. The soft, amorphous, low-melting point segments, which are formed from the polyamines, are relatively flexible and mobile, while the hard, high-melting point segments, which are formed from the isocyanate and chain extenders, are relatively stiff and immobile. The phase separation of the hard and soft segments provides the polyurea with its elastomeric resiliency. The polyurea composition contains urea linkages having the following general structure:
Polyurea/Polyurethane Hybrid Compositions
A polyurea/polyurethane hybrid composition is produced when the polyurea prepolymer (as described above) is chain-extended using a hydroxyl-terminated curing agent. Any excess isocyanate groups in the prepolymer will react with the hydroxyl groups in the curing agent and create urethane linkages. That is, a polyurea/polyurethane hybrid composition is produced.
In a preferred embodiment, a pure polyurea composition, as described above, is prepared. That is, the composition contains only urea linkages. An amine-terminated curing agent is used in the reaction to produce the pure polyurea composition. However, it should be understood that a polyurea/polyurethane hybrid composition also may be prepared in accordance with this invention as discussed above. Such a hybrid composition can be formed if the polyurea prepolymer is cured with a hydroxyl-terminated curing agent. Any excess isocyanate in the polyurea prepolymer reacts with the hydroxyl groups in the curing agent and forms urethane linkages. The resulting polyurea/polyurethane hybrid composition contains both urea and urethane linkages.
More particularly, in one preferred version of the ball covering, the polymer matrix constituting the ball covering consists of 100% by weight of the polyurea composition of this invention. In another version, the polymer matrix of the ball covering is a polyurea/polyurethane hybrid blend. The blend contains about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of a polyurethane composition. In yet another embodiment, the polymer matrix of the ball covering consists of 100% by weight of the polyurethane composition of this invention. A polymer matrix containing a polyurea/polyurethane hybrid blend also can be prepared. The blend may contain about 10 to about 90% by weight of the polyurethane composition and about 90% to about 10% of a polyurea composition. Alternatively, the ball covering may be made of a blend of about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of another polymer such as vinyl resins, polyesters, polyamides, and polyolefins.
Isocyanate Compounds
As discussed above, a polyurea compositions is an elastomeric material that is the reaction product of an isocyanate component and amine-terminated polymer resin. There are many isocyanate compounds known in the art. Surprisingly, it has been found that isocyanate compound selected from the group consisting of 1,3-bis(isocyanatomethyl)cyclohexane; 1,4-bis(isocyanatomethyl)cyclohexane; and mixtures thereof provides the resulting polyurea composition with the most desirable properties for purposes of this invention. The diisocyanate compounds have the following generic structures:
It has been found that the isocyanate compounds of this invention can be reacted with amine-terminated compounds to produce polyureas having high mechanical strength and integrity. Moreover, the isocyanate compounds provide polyurea compositions having improved light stability. The isocyanate compounds are able to provide polymers having advantageous mechanical properties that are found in polymers normally produced using aromatic isocyanate compounds. At the same time, the polymers have good light-stability properties which are characteristic of polymers produced using aliphatic isocyanates.
Amine-Terminated Compounds
When forming a polyurea prepolymer per this invention, any suitable amine-terminated compound may be reacted with the above-described isocyanate compounds in accordance with this invention. Such amine-terminated compounds include, for example, amine-terminated hydrocarbons, amine-terminated polyethers, amine-terminated polyesters, amine-terminated polycarbonates, amine-terminated polycaprolactones, and mixtures thereof. The molecular weight of the amine-terminated compound is generally in the range of about 100 to about 10,000. Suitable polyether amines include, but are not limited to, methyldiethanolamine; polyoxyalkylenediamines such as, polytetramethylene ether diamines, polyoxypropylenetriamine, polyoxyethylene diamines, and polyoxypropylene diamines; poly(ethylene oxide capped oxypropylene) ether diamines; propylene oxide-based triamines; triethyleneglycoldiamines; glycerin-based triamines; and mixtures thereof. In one embodiment, the polyether amine used to form the prepolymer is Jeffamine D2000 (Huntsman Corp.). Additional amine-terminated compounds also may be useful in forming the polyurea prepolymers of the present invention including, but not limited to, poly(acrylonitrile-co-butadiene); poly(1,4-butanediol) bis(4-aminobenzoate) in liquid or waxy solid form; linear and branched polyethylene imine; low and high molecular weight polyethylene imine having an average molecular weight of about 500 to about 30,000; poly(propylene glycol) bis(2-aminopropyl ether) having an average molecular weight of about 200 to about 5,000; polytetrahydrofuran bis (3-aminopropyl) terminated having an average molecular weight of about 200 to about 2000; and mixtures thereof (Aldrich Co.). Preferably, the amine-terminated compound is a copolymer of polytetramethylene oxide and polypropylene oxide (Huntsman Corp.)
Polyol Compounds
When forming a polyurethane prepolymer, any suitable polyol compound may be reacted with the above-described isocyanate compounds in accordance with this invention. Exemplary polyols include, but are not limited to, polyether polyols, hydroxyl-terminated polybutadiene (including partially/fully hydrogenated derivatives), polyester polyols, polycaprolactone polyols, and polycarbonate polyols. Particularly preferred are polytetramethylene ether glycol (“PTMEG”), polyethylene propylene glycol, polyoxypropylene glycol, and combinations thereof. The hydrocarbon chain can have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups. Preferably, the polyol of the present invention includes PTMEG. Suitable polyester polyols include, but are not limited to, polyethylene adipate glycol, polybutylene adipate glycol, polyethylene propylene adipate glycol, ortho-phthalate-1,6-hexanediol, and combinations thereof. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups. Suitable polycaprolactone polyols include, but are not limited to, 1,6-hexanediol-initiated polycaprolactone, diethylene glycol-initiated polycaprolactone, trimethylol propane-initiated polycaprolactone, neopentyl glycol-initiated polycaprolactone, 1,4-butanediol-initiated polycaprolactone, and combinations thereof. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups. Suitable polycarbonates include polyphthalate carbonate. The hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups.
Manufacturing Processes
There are two basic techniques that can be used to make the polyurea compositions of this invention: a) one-shot technique, and b) prepolymer technique. In the one-shot technique, the isocyanate, amine-terminated compound, and amine-terminated curing agent are reacted in one step. Meanwhile, the prepolymer technique involves a first reaction between the isocyanate and amine-terminated compound to produce a polyurea prepolymer, and a subsequent reaction between the prepolymer and amine-terminated curing agent. As a result of the reaction between the isocyanate and amine-terminated compound, there will be some unreacted NCO groups in the polyurea prepolymer. The prepolymer should have less than 14% unreacted NCO groups. Preferably, the prepolymer has no greater than 8.5% unreacted NCO groups, more preferably from 2.5% to 8%, and most preferably from 5.0% to 8.0% unreacted NCO groups. As the weight percent of unreacted isocyanate groups increases, the hardness of the composition also generally increases. Either the one-shot or prepolymer method may be employed to produce the polyurea compositions of the invention; however, the prepolymer technique is preferred because it provides better control of the chemical reaction. The prepolymer method provides a more homogeneous mixture resulting in a more consistent polymer composition. The one-shot method results in a mixture that is inhomogeneous (more random) and affords the manufacturer less control over the molecular structure of the resultant composition.
In the casting process, the polyurea composition can be formed by chain-extending the polyurea prepolymer with a single curing agent or blend of curing agents as described further below. The compositions of the present invention may be selected from among both castable thermoplastic and thermoset materials. Thermoplastic polyurea compositions are typically formed by reacting the isocyanate and amine-terminated compound, each having two (or less) functional groups, at a 1:1 stoichiometric ratio. For example, a prepolymer may be cured with a secondary diamine to make the non-cross-linked thermoplastic composition. Thermoset compositions, on the other hand, are cross-linked polymers and are typically produced from the reaction of an isocyanate and amine-terminated compound, wherein each component has two (or greater) functional groups, at normally a 1.05:1 stoichiometric ratio. For example, a prepolymer may be cured with a primary or secondary diamine to make the cross-linked thermoset polyureas. In general, thermoset polyurea compositions are easier to prepare than thermoplastic polyureas.
Suitable amine curing agents that can be used in chain-extending the polyurea prepolymer of this invention include, but are not limited to, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-dianiline or “MDA”), m-phenylenediamine, p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-)toluenediamine or “DETDA”, 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane, 3,3′-diethyl-5,5′-dimethyl4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)), 3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-chloroaniline) or “MOCA”), 3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaniline), 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”), 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”), 3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane, 3,3′-dichloro-4,4′-diamino-diphenylmethane, 4,4′-methylene-bis(2,3-dichloroaniline) (i.e., 2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”), 4,4′-bis(sec-butylamino)-diphenylmethane, N,N′-dialkylamino-diphenylmethane, trimethyleneglycol-di(p-aminobenzoate), polyethyleneglycol-di(p-aminobenzoate), polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such as ethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine), imido-bis(propylamine), methylimino-bis(propylamine) (i.e., N-(3-aminopropyl)-N-methyl-1,3-propanediamine), 1,4-bis(3-aminopropoxy)butane (i.e., 3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine), diethyleneglycol-bis(propylamine) (i.e., diethyleneglycol-di(aminopropyl)ether), 4,7,10-trioxatridecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene) diamines, 1,3- or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or 1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophorone diamine, 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines, 3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane, polyoxypropylene diamines, 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane, polytetramethylene ether diamines, 3,3′,5,5 ′-tetraethyl-4,4′-diamino-dicyclohexylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaminocyclohexane)), 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane, (ethylene oxide)-capped polyoxypropylene ether diamines, 2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane, 4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such as diethylene triamine, dipropylene triamine, (propylene oxide)-based triamines (i.e., polyoxypropylene triamines), N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine), glycerin-based triamines, (all saturated); tetramines such as N,N′-bis(3-aminopropyl)ethylene diamine (i.e., N₄-amine) (both saturated), triethylene tetramine; and other polyamines such as tetraethylene pentamine (also saturated). The amine curing agents used as chain extenders normally have a cyclic structure and a low molecular weight (250 or less).
As discussed above, in some instances, it may be desirable to form a polyurea/polyurethane hybrid composition. In such circumstances, the curing agent used to chain extend the polyurethane prepolymer may be selected from the group consisting of hydroxyl-terminated curing agents and mixtures of amine-terminated and hydroxyl-terminated curing agents. The chain extender or cross-linker extends the chain length of the prepolymer and builds-up its molecular weight.
The hydroxyl-terminated curing agents are preferably selected from the group consisting of ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; monoethanolamine; diethanolamine; triethanolamine; monoisopropanolamine; diisopropanolamine; dipropylene glycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; trimethylolpropane; cyclohexyldimethylol; triisopropanolamine; N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycol bis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol; 1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol; 1,3-bis-[2-(2-hydroxyethoxy) ethoxy]cyclohexane; 1,3-bis- {2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; trimethylolpropane; polytetramethylene ether glycol, preferably having a molecular weight from about 250 to about 3900; and mixtures thereof.
Additional materials, as known in the art, may be added to the polyurethane and polyurea compositions of this invention. These additional materials include, but are not limited to, catalysts, wetting agents, coloring agents, optical brighteners, cross-linking agents, whitening agents such as titanium dioxide and zinc oxide, UV light absorbers, hindered amine light stabilizers, defoaming agents, processing aids, surfactants, and other conventional additives. For example, wetting additives may be added to more effectively disperse the pigments. Other suitable additives include antioxidants, stabilizers, softening agents, plasticizers, including internal and external plasticizers, impact modifiers, foaming agents, density-adjusting fillers, reinforcing materials, compatibilizers, and the like. Density-adjusting fillers can be added to modify the modulus, tensile strength, and other properties of the compositions. Examples of useful fillers include zinc oxide, zinc sulfate, barium carbonate, barium sulfate, calcium oxide, calcium carbonate, clay, tungsten, tungsten carbide, silica, and mixtures thereof. Regrind (recycled core material) high-Mooney-viscosity rubber regrind, and polymeric, ceramic, metal, and glass microspheres also may be used. Generally, the additives will be present in the composition in an amount between about 1 and about 70 weight percent based on the total weight of the composition depending upon the desired properties.
Ball Construction
The polyurethane and polyurea cover materials of this invention may be used with any type of ball construction known in the art. Such golf ball designs include, for example, single piece, two- piece, three-piece, and four-piece designs. The core, intermediate casing, and cover can be single or multi-layered. Referring to FIG. 1, a multilayered (two-piece) golf ball (20) having a solid core (22) and polyurethane cover (24) of this invention is shown. FIG. 1A shows another version of a multilayered (two-piece) golf ball (20 a) having a solid core (22 a) and polyurethane cover (24 a). In FIGS. 1 and 1A, the cover material (24, 24 a) surrounds and encapsulates the core segments (22, 22 a), respectively. In FIGS. 2 and 2A, multilayered (three-piece) golf balls (30, 30 a) are shown. In FIG. 2, the ball (30) includes a solid core (32), an intermediate layer (34), and polyurethane cover (36). Meanwhile, in FIG. 2A, the ball (30 a) is made with a polyurea cover (34). The ball (30 a) in FIG. 2A includes a solid core (32 a) and surrounding intermediate casing layer (34 a) made of an ionomer resin.
Core Segment
The core of the golf ball may be solid, semi-solid, fluid-filled, or hollow, and the core may have a single-piece or multi-piece structure. As shown in FIGS. 1-2A, the cores (22, 22 a, 32, and 32 a) have a solid construction. A variety of materials, known in the art, may be used to make the core including thermoset compositions such as rubber, styrene butadiene, polybutadiene, isoprene, polyisoprene, trans-isoprene; thermoplastics such as ionomer resins, polyamides or polyesters; and thermoplastic and thermoset polyurethane and polyurea elastomers. In one embodiment, the core is a single-piece made from a natural or synthetic rubber composition such as polybutadiene. More particularly, materials for solid cores typically include compositions having a base rubber, a filler, an initiator agent, and a cross-linking agent. The base rubber typically includes natural or synthetic rubber, such as polybutadiene rubber. In one embodiment, the base rubber is 1,4-polybutadiene having a cis-structure of at least 40%. The polybutadiene can be blended with other elastomers such as natural rubber, polyisoprene rubber, styrene-butadiene rubber, and/or other polybutadienes. Another suitable rubber that may be used in the core is trans-polybutadiene. This polybutadiene isomer is formed by converting the cis-isomer of the polybutadiene to the trans-isomer during a molding cycle. A soft and fast agent such as pentachlorothiophenol (PCTP) or ZnPCTP can be blended with the polybutadiene. These compounds also may function as cis-to-trans catalysts to convert some cis-1,4 bonds in the polybutadiene into trans 1,4 bonds. The above-described filler materials may be added to the core composition to modify such properties as specific gravity, density, hardness, weight, modulus, resiliency, compression, and the like. It is recognized that a multi-piece core (not shown) may be constructed if desired; that is, there may be two or more core portions or pieces. The inner core portion may be made of a first base rubber material and the outer core portion, which surrounds the inner core, may be made of a second base rubber material. The respective core pieces may be made of the same or different rubber materials as described above. Cross-linking agents and fillers may be added to the rubber materials constituting each core piece.
Intermediate Layer
Referring to FIGS. 2 and 2A, the golf balls (30, 30 a) may include an intermediate or casing layer (34, 34 a), positioned between the inner core (32, 32 a) and outer cover (36, 36 a). The overlying intermediate layer (34, 34 a) surrounds and envelopes the core (32, 32 a). The intermediate layer may be made of any suitable material known in the art including thermoplastic and thermosetting materials. Suitable thermoplastic compositions for forming the intermediate core layer include, but are not limited to, partially- and fully-neutralized ionomers, graft copolymers of ionomer and polyamide, and the following non-ionomeric polymers: polyesters; polyamides; polyamide-ethers, and polyamide-esters; polyurethanes, polyureas, and polyurethane-polyurea hybrids; fluoropolymers; non-ionomeric acid polymers, such as E/Y- and E/X/Y-type copolymers, wherein E is an olefin (e.g., ethylene), Y is a carboxylic acid, and X is a softening comonomer such as vinyl esters of aliphatic carboxylic acids, and alkyl alkylacrylates; metallocene-catalyzed polymers; polystyrenes; polypropylenes and polyethylenes; polyvinyl chlorides and grafted polyvinyl chlorides; polyvinyl acetates; polycarbonates including polycarbonate/acrylonitrile-butadiene-styrene blends, polycarbonate/polyurethane blends, and polycarbonate/polyester blends; polyvinyl alcohols; polyethers; polyimides, polyetherketones, polyamideimides; and mixtures of any two or more of the above thermoplastic polymers. Examples of commercially available thermoplastics suitable for forming the intermediate core layer include, but are not limited to, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc.; Surlyn® ionomer resins, Hytrel® thermoplastic polyester elastomers, and ionomeric materials sold under the trade names DuPont® HPF 1000 and HPF 2000, all of which are commercially available from E. I. du Pont de Nemours and Company; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylic acid copolymers, commercially available from The Dow Chemical Company; Clarix® ionomer resins, commercially available from A. Schulman Inc.; Elastollan® polyurethane-based thermoplastic elastomers, commercially available from BASF; and Xylex® polycarbonate/polyester blends, commercially available from SABIC Innovative Plastics. The foregoing filler materials may be added to the intermediate layer composition to modify such properties as the specific gravity, density, hardness, weight, modulus, resiliency, compression, and the like.
The ionomeric resins may be blended with non-ionic thermoplastic resins. Examples of suitable non-ionic thermoplastic resins include, but are not limited to, polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea, thermoplastic polyether block amides (e.g., Pebax® block copolymers, commercially available from Arkema Inc.), styrene-butadiene-styrene block copolymers, styrene(ethylene-butylene)-styrene block copolymers, polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene-(meth)acrylate, polyethylene-(meth)acrylic acid, functionalized polymers with maleic anhydride grafting, Fusabond® functionalized polymers commercially available from E. I. du Pont de Nemours and Company, functionalized polymers with epoxidation, elastomers (e.g., ethylene propylene diene monomer rubber, metallocene-catalyzed polyolefin) and ground powders of thermoset elastomers.
Golf balls made in accordance with this invention can be of any size, although the USGA requires that golf ball used in competition have a diameter of at least 1.68 inches and a weight of no greater than 1.62 ounces. For play outside of USGA competition, the golf balls can have smaller diameters and be heavier. Preferably, the diameter of the golf ball is in the range of about 1.68 to about 1.80 inches. The core generally will have a diameter in the range of about 1.26 to about 1.60 inches. In one preferred version, the single-piece core has a diameter of about 1.57 inches. The hardness of the core may vary depending upon the desired properties of the ball. In general, core hardness is in the range of about 30 to about 65 Shore D and more preferably in the range of about 35 to about 60 Shore D. The compression of the core segment is generally in the range of about 70 to about 110 and more preferably in the range of about 80 to about 100. As shown in FIGS. 1-2A, the core segment generally makes up a substantial portion of the ball, for example, the core may constitute at least 95% or greater of the ball structure.
Referring to FIGS. 2 and 2A, which show golf balls having intermediate casing layers (34, 34 a), the range of thicknesses for the intermediate layer can vary because different materials can be used. In general, however, the thickness of the intermediate layer will be in the range of about 0.015 to about 0.120 inches and preferably about 0.020 to about 0.060 inches. Multiple intermediate layers may be disposed between the inner core and outer cover. Preferably, the overall diameter of the core and all intermediate layers is about 90 percent to about 98 percent of the overall diameter of the finished ball. As shown in FIGS. 1 and 2, and described above, the cover material (24, 36) may be made of the polyurethane composition of this invention. In FIGS. 1A and 2A, the cover (24 a, 36 a) is made of the polyurea material of this invention. The polyurethane and polyurea covers provide the balls with good mechanical strength and durability as well as desirable playing performance properties. The thickness of the cover layers may vary, but it is generally in the range of about 0.015 to about 0.090 inches, preferably about 0.020 to about 0.050 inches, and more preferably about 0.020 inches to about 0.035 inches.
The golf balls of this invention may contain layers having the same hardness or different hardness values. Surface hardness and material hardness are important properties considered in ball design and construction. The test methods for measuring surface hardness and material hardness are described in further detail below. There can be uniform hardness throughout the different layers of the ball or there can be hardness gradients across the layers. For example, the hardness of the core may vary, but it is generally in the range of about 30 to about 65 Shore D and more preferably in the range of about 35 to about 60 Shore D. The intermediate layer(s) also may vary in hardness depending on the specific construction of the ball. In one embodiment, the hardness of the intermediate layer is about 30 to about 75 Shore D. Like the core and intermediate layers, the hardness of the cover may vary, but it is generally in the range of about 30 to about 65 Shore D. In some instances, the core is intended to be softer than the intermediate layers. For example, the core may have a hardness in the range of about 40 to about 55 Shore D, and the intermediate layer may have a hardness in the range of about 60 to about 75 Shore D. Furthermore, in some instances, the outer cover layer is intended to be softer than the intermediate layer. Thus, if the intermediate layer has a hardness in the range of about 60 to about 75 Shore D, the cover material may have a hardness of about 20 to about 55 Shore D.
The golf balls of this invention may be constructed using any suitable technique known in the art. These methods generally include compression molding, flip molding, injection molding, retractable pin injection molding, reaction injection molding (RIM), liquid injection molding (LIM), casting, vacuum forming, powder coating, flow coating, spin coating, dipping, spraying, and the like.
More particularly, the core of the golf ball may be formed using compression molding or injection molding. As described above, suitable core materials include thermoset materials, such as rubber, styrene butadiene, polybutadiene, isoprene, polyisoprene, trans-isoprene, as well as thermoplastics such as ionomer resins, polyamides or polyesters. The intermediate layer also may be formed using known methods such as, for example, retractable pin injection molding or compression molding. The intermediate layer can be made of commercially-available ionomer resins as described above.
This intermediate layer is covered with a cover layer using either reaction injection molding or a casting process. In a casting process, the polyurea mixture is dispensed into the cavity of an upper mold member. This first mold-half has a hemispherical structure. Then, the cavity of a corresponding lower mold member is filled with the polyurea mixture. This second mold-half also has a hemispherical structure. The cavities are typically heated beforehand. A ball cup holds the golf ball (core and overlying casing layer) under vacuum. After the polyurea mixture in the first mold-half has reached a semi-gelled or gelled sate, the pressure is removed and the golf ball is lowered into the upper mold-half containing the polyurea mixture. Then, the first mold-half is inverted and mated with the second mold-half containing polyurea mixture which also has reached a semi-gelled or gelled state. The polyurea mixtures, contained in the mold members that are mated together, form the golf ball cover. The mated first and second mold-halves containing the polyurea mixture and golf ball center may be next heated so that the mixture cures and hardens. Then, the golf ball is removed from the mold. The ball may be heated and cooled as needed.
The polyurethane and polyurea compositions of this invention provide the golf ball cover with many advantageous properties and features. Particularly, the cover materials have good mechanical strength and cut/shear-resistance as well as light-stability. The polyurethane and polyurea cover materials help enhance the weatherability of the golf balls. It is anticipated that the golf balls of this invention will show high resistance to yellowing and other discoloration as opposed to golf balls that are not constructed with the polyurethane and polyurea cover materials of this invention.
It is understood that the golf balls described and illustrated herein represent only presently preferred embodiments of the invention. It is appreciated by those skilled in the art that various changes and additions can be made to such golf balls without departing from the spirit and scope of this invention. It is intended that all such embodiments be covered by the appended claims.

Claims

1. A golf ball, comprising:

a core; and

a polyurea cover material produced by a reaction of ingredients comprising an isocyanate selected from the group consisting of 1,3-bis(isocyanatomethyl)cyclohexane; 1,4-bis(isocyanatomethyl)cyclohexane; and mixtures thereof; an amine-terminated compound; and amine cross-linking agent.

2. The golf ball of claim 1, wherein the isocyanate is 1,3-bis(isocyanatomethyl)cyclohexane.

3. The golf ball of claim 1, wherein the isocyanate is 1,4-bis(isocyanatomethyl)cyclohexane.

4. The golf ball of claim 1, wherein the core comprises polybutadiene.

5. The golf ball of claim 1, wherein the curing agent is an amine-terminated curing agent selected from the group consisting of 4,4′-diamino-diphenylmethane; 3,5-diethyl-(2,4- or 2,6-)toluenediamine; 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine; 3,5-diethylthio-(2,4- or 2,6-)toluenediamine: 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane; polytetramethyleneglycol-di(p-aminobenzoate); 4,4′-bis(sec-butylamino)-dicyclohexylmethane; and mixtures thereof.

6. The golf ball of claim 1, wherein the polyurea cover material further comprises pigments and fillers.

7. The golf ball of claim 1, wherein the core has a diameter of about 1.26 to about 1.60 inches.

8. The golf ball of claim 1, wherein the cover has a thickness of about 0.015 to about 0.090 inches.

9. The golf ball of claim 7, wherein the cover has a thickness of about 0.020 to about 0.050 inches.

10. The golf ball of claim 8, wherein the cover has a thickness of about 0.020 to about 0.035 inches.

11. The golf ball of claim 1, wherein the core has a surface hardness in the range of about 30 to about 65 Shore D.

12. The golf ball of claim 1, wherein the cover has a material hardness of about 30 to about 65 Shore D.

13. The golf ball of claim 12, wherein the cover has a material hardness of about 35 to about 55 Shore D.

14. A golf ball, comprising:

a core;

an intermediate casing layer overlying the core; and

15. The golf ball of claim 14, wherein the isocyanate is 1,3-bis(isocyanatomethyl)cyclohexane.

16. The golf ball of claim 14, wherein the isocyanate is 1,4-bis(isocyanatomethyl)cyclohexane.

17. The golf ball of claim 14, wherein the core comprises polybutadiene.

18. The golf ball of claim 14, wherein the polyurea cover material further comprises pigments and fillers.

19. The golf ball of claim 14, wherein the intermediate layer comprises an ionomer resin.

20. The golf ball of claim 14, wherein the intermediate layer comprises a blend of ionomer and non-ionomer resins.