US20100267468A1

US20100267468A1 - Golf ball covers made from polyureas based on polycaprolactones

Info

Publication number: US20100267468A1
Application number: US12/426,579
Authority: US
Inventors: Shawn Ricci; Michael Michalewich; Brain Comeau
Original assignee: Acushnet Co
Current assignee: Acushnet Co
Priority date: 2009-04-20
Filing date: 2009-04-20
Publication date: 2010-10-21
Also published as: JP2010246930A

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 ionomer resin, and an outer cover layer made of the polyurea composition. The polyurea composition is the reaction product of an isocyanate, amine-terminated polycaprolactone, and amine-terminated curing agent. The resulting cover material has many advantageous properties including improved durability, toughness, abrasion-resistance, and moisture-resistance.

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 an isocyanate, amine-terminated polycaprolactone, and amine-terminated curing agent. The resulting cover material has many advantages including improved durability, toughness, abrasion-resistance, and moisture-resistance.
2. Brief Review of the Related Art
In recent years, manufacturers of golf balls have expanded their research efforts to develop golf ball cover materials having more desirable properties and performance characteristics. In particular, the golf industry has looked to develop cover materials having improved “hard” properties while maintaining optimum “soft” properties. Improved durability, toughness, and abrasion-resistance are some of the desired hard properties. The soft properties provide the player with a better “feel” when he/she strikes the ball with a golf club. The player senses more control over the ball as the club face makes impact. The hard properties of the ball help players achieve greater flight distance with their shots. While the softer feel of the ball cover allows players to place a spin on the ball and better control its flight pattern.
In the past, natural or synthetic rubber covered golf balls were commonly used. For example, balata covered balls were once very popular, because they provided good flight distance with a soft feel. Golf players experienced a pleasant sensation when striking the relatively soft balata ball and were able to better control the ball's flight pattern. The players could hear a “clicking” sound as the club face struck the ball. One disadvantage with using such balata covered balls, however, was the covers tended to wear away after repeated play. The balata balls generally did not have high durability, cut/shear-resistance, or impact-resistance. In turn, the golf industry looked to ionomer resins to make more durable covers. These cross-linked polymers contain interchain ionic bonding as well as covalent bonding. The ionomer resins include, for example, a copolymer of ethylene and a vinyl comonomer with an acid group such as methacrylic or acrylic acid. Metal ions such as sodium, lithium, zinc, and magnesium are used to neutralize the acid groups in the polymer. Commercially available ionomer resins are known in the industry and include numerous resins sold under the trademarks, Surlyn® (DuPont) and Escor® and Iotek® (Exxon). The ionomer resins are available in various grades and are identified based on the type of base resin, molecular weight, type of metal ion, amount of acid, degree of neutralization, additives, and other properties. Ball covers made with such ionomer resins show excellent, durability, mechanical strength, and cut/shear-resistance. However, at the same time, these ball covers have a hard surface and players may experience a loss in feel and comfort when making shots with these balls.
More recently, the golf industry has looked at making golf ball covers from polyurea compositions. 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 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.
Although some conventional polyurea cover materials have been somewhat effective, there is still a need for improved golf ball coverings. Particularly, it would be desirable to have a polyurea cover material that could provide enhanced durability, toughness, and abrasion-resistance to the golf ball but without sacrificing playing performance properties such as feel, softness, spin control, and the like. The present invention provides such golf balls. It also would be desirable to have a cover material that showed high weather and moisture-resistance. Such a ball covering would prevent the ball from gaining water and increasing in size and weight. The present invention provides such a ball covering having these properties as well as other advantageous features and benefits.

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, amine-terminated polycaprolactone, and amine-terminated curing agent. The resulting polyurea cover material has many advantages including improved durability, toughness, abrasion-resistance, and moisture-resistance. 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.
Golf balls made in accordance with this invention may have various constructions. In one embodiment, the golf ball core has a diameter of about 1.26 to about 1.60 inches; the intermediate layer has a thickness of about 0.015 to about 0.120 inches; and the cover has a thickness of about 0.015 to about 0.090 inches. The components constituting the golf ball may be of different hardness levels. For example, in one version, the golf ball core has a hardness in the range of about 35 to about 60 Shore D; the intermediate layer has a hardness in the range of about 30 to about 75 Shore D, and the cover has a material hardness of about 30 to about 65 Shore D.

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 made in accordance with the present invention;

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

FIG. 3 is a cross-sectional view of a multi-layered, four-piece golf ball including a two-piece core made in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to golf balls having a cover material made from a polyurea composition. In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group with an amine group. The chain length of the polyurea is extended by reacting the polymer with an amine-terminated 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, formed from the polyamines, are relatively flexible and mobile, while the hard, high-melting point segments, formed from the isocyanate and chain extenders, are relatively stiff and immobile. The phase separation of the hard and soft segments provides the polymer with its elastomeric resiliency. When amine-terminated compounds are used as the curing agent, the resulting polymer only contains urea linkages.
However, if a hydroxyl-terminated curing agent is used, any excess isocyanate groups in the polymer will react with the hydroxyl groups in the curing agent and create urethane linkages. That is, a polyurea/urethane hybrid composition is produced, which is distinct from a pure polyurea composition. It also should be understood that polyurethanes and polyureas are significantly different materials. Polyurethanes contain urethane linkages formed by reacting an isocyanate group with a hydroxyl group. Commercial polyurethane materials are produced by the reaction of an isocyanate with a polyalcohol (polyol) in the presence of a catalyst and other additives. The chain length of the polyurethane is extended by reacting the polymer with a hydroxyl or amine-terminated curing agent.
Any suitable isocyanate known in the art can be used to produce the polyurea compositions in accordance with this invention. Such isocyanates include, for example, aliphatic, cycloaliphatic, aromatic aliphatic, aromatic, any derivatives thereof, and combinations of these compounds having two or more isocyanate (—N═C═O) groups per molecule. The isocyanates may be organic polyisocyanate-terminated prepolymers, low free isocyanate prepolymers, and mixtures thereof. The isocyanate-containing reactable component may also include any isocyanate-functional monomer, dimer, trimer, or polymeric adduct thereof, prepolymer, quasi-prepolymer, or mixtures thereof. Isocyanate-functional compounds may include monoisocyanates or polyisocyanates that include any isocyanate functionality of two or more.
Preferred isocyanates include diisocyanates (having two NCO groups per molecule), biurets thereof, dimerized uretdiones thereof, trimerized isocyanurates thereof, and polyfunctional isocyanates such as monomeric triisocyanates. Diisocyanates typically have the generic structure of OCN—R—NCO. Exemplary diisocyanates include, but are not limited to, unsaturated isocyanates such as: p-phenylene diisocyanate (“PPDI,” i.e., 1,4-phenylene diisocyanate), m-phenylene diisocyanate (“MPDI,” i.e., 1,3-phenylene diisocyanate), o-phenylene diisocyanate (i.e., 1,2-phenylene diisocyanate), 4-chloro-1,3-phenylene diisocyanate, toluene diisocyanate (“TDI”), m-tetramethylxylene diisocyanate (“m-TMXDI”), p-tetramethylxylene diisocyanate (“p-TMXDI”), 1,2-, 1,3-, and 1,4-xylene diisocyanates, 2,2′-, 2,4′-, and 4,4′-biphenylene diisocyanates, 3,3′-dimethyl-4,4′-biphenylene diisocyanate (“TODI”), 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanates (“MDI”), 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, carbodiimide-modified MDI, polyphenylene polymethylene polyisocyanate (“PMDI,” i.e., polymeric MDI), 1,5-naphthalene diisocyanate (“NDI”), 1,5-tetrahydronaphththalene diisocyanate, anthracene diisocyanate, tetracene diisocyanate; and saturated isocyanates such as: 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (“HDI”) and isomers thereof, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanates, 1,7-heptamethylene diisocyanate and isomers thereof, 1,8-octamethylene diisocyanate and isomers thereof, 1,9-novamethylene diisocyanate and isomers thereof, 1,10-decamethylene diisocyanate and isomers thereof, 1,12-dodecane diisocyanate and isomer thereof, 1,3-cyclobutane diisocyanate, 1,2-, 1,3-, and 1,4-cyclohexane diisocyanates, 2,4- and 2,6-methylcyclohexane diisocyanates (“HTDI”), isophorone diisocyanate (“IPDI”), isocyanatomethylcyclohexane isocyanate, isocyanatoethylcyclohexane isocyanate, bis(isocyanatomethyl)cyclohexane (i.e., 1,4-cyclohexane-bis(methylene isocyanate)), 4,4′-dicyclohexylmethane diisocyanate (“H₁₂MDI,” i.e., bis(4-isocyanatocyclohexyl)-methane), 2,4′- and 4,4′-dicyclohexane diisocyanates, 2,4′- and 4,4′-bis(isocyanatomethyl) dicyclohexanes. Dimerized uretdiones of diisocyanates and polyisocyanates include, for example, unsaturated isocyanates such as uretdiones of toluene diisocyanates, uretdiones of diphenylmethane diisocyanates; and saturated isocyanates such as uretdiones of hexamethylene diisocyanates. Trimerized isocyanurates of diisocyanates and polyisocyanates include, for example, unsaturated isocyanates such as trimers of diphenylmethane diisocyanate, trimers of tetramethylxylene diisocyanate, isocyanurates of toluene diisocyanates; and saturated isocyanates such as isocyanurates of isophorone diisocyanate, isocyanurates of hexamethylene diisocyanate, isocyanurates of trimethyl hexamethylene diisocyanates. Monomeric triisocyanates include, for example, unsaturated isocyanates such as 2,4,4′-diphenylene triisocyanate, 2,4,4′-diphenylmethane triisocyanate, 4,4′,4″-triphenylmethane triisocyanate; and saturated isocyanates such as: 1,3,5-cyclohexane triisocyanate. Preferably, the isocyanate is selected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers and mixtures thereof.
As discussed above, polyurea is an elastomeric material that is the reaction product of an isocyanate component and amine-terminated polymer resin. As described further below, of the many possible amine-terminated compounds that can be used in the reaction process, it was found that amine-terminated polycaprolactones can be reacted with the isocyanate to provide a polyurea composition having the most desirable properties for purposes of this invention. In general, caprolactone is a cyclic ester compound having the following generic structure:
Methods for making amine-terminated polycaprolactone compounds are known in the art and described in such references as Carr et al., (Solvay) published PCT International Application WO 2006/040355 A1, the disclosure of which is hereby incorporated by reference. In the method described in the '355 PCT Publication, the lactone ring is opened using a polycarboxylic acid initiator to produce a polycaprolactone polymer having carboxylic acid groups located at its terminal ends. In turn, this product is reacted with a polyamine at a temperature above 50° C. to produce an amine-terminated polycaprolactone polymer having the following generic structure:
The molecular weight of the amine-terminated polycaprolactone is generally in the range of about 1000 to about 10,000.
It has been found that the amine-terminated polycaprolactones of this invention can be reacted with isocyanates to produce polyureas having high mechanical strength and integrity. Moreover, the amine-terminated polycaprolactones have enhanced hydrolytic stability, and it is believed this contributes to the resulting polyurea composition having enhanced moisture-resistance. There are less ester linkages along the carbon chain of the amine-terminated polycaprolactone and consequently less moisture attack sites. Furthermore, the distance between respective ester linkages is relatively long and this helps improve hydrolytic stability. Moisture is prevented from attacking the ester linkages and breaking-up the polymer chain into smaller, weaker chains. Thus, the polymers have good weather resistance. The polymers show high resistance to the effects of water and heat exposure as well as enhanced ultraviolet (UV) light-stability.
There are two basic techniques that can be used to make the polyurea elastomers 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 polycaprolactone, 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 a 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.
In a preferred embodiment, a pure polyurea composition 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/urethane hybrid composition may be prepared in accordance with this invention in some instances. Such a hybrid composition could be obtained if the polyurea prepolymer were 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/urethane hybrid composition contains both urea and urethane linkages.
Suitable amine-terminated 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′-dimethyl-4,4′-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-trioxamidecane-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), trimethylolpropane-based triamines, 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). It is also recognized that the amine-terminated polycaprolactone material of this invention can be used as the amine curing agent in some instances.
As discussed above, in some instances, it may be desirable to form a polyurea/polyurethane hybrid composition. In such circumstances, the curing agent used in the reaction of the polyurea prepolymer may be selected from the group consisting of hydroxy-terminated curing agents and mixtures of amine-terminated and hydroxyl-terminated curing agents.
The hydroxy-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 polyurea compositions. 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, ultraviolet (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. Antioxidants, stabilizers, softening agents, plasticizers, including internal and external plasticizers, impact modifiers, foaming agents, density-adjusting fillers, reinforcing materials, and compatibilizers also may be added to the composition in amounts known in the art. 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.
A catalyst may also be employed to promote the reaction between the prepolymer and the curing agent to make the polyurea composition. Suitable catalysts include, but are not limited to bismuth catalyst; zinc octoate; stannous octoate; tin catalysts such as bis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin (II) chloride, tin (IV) chloride, bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts such as triethylenediamine, triethylamine, and tributylamine; organic acids such as oleic acid and acetic acid; delayed catalysts; and mixtures thereof. The catalyst is preferably added in an amount sufficient to catalyze the reaction of the components in the reactive mixture. In one embodiment, the catalyst is present in an amount from about 0.001 percent to about 5 percent by weight of the composition.
Preferably, the polymer matrix constituting the ball covering is a pure polyurea composition. That is, the polymer composition contains only urea linkages having the following general structure:
However, as discussed above, it is recognized that a polyurea/urethane hybrid composition also may be prepared in accordance with this invention. This occurs if the polyurea prepolymer is cured with hydroxyl-terminated curing agents. Any excess isocyanate in the polyurea prepolymer reacts with the hydroxyl groups in the curing agent and forms urethane linkages. The resulting polyurea/polyurethane composition contains both urea linkages (as described above) and urethane linkages having the following general structure:
In one 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 is a blend of about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of another polymer or other material such as vinyl resins, polyesters, polyamides, or polyolefins.
The 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, two-piece, three-piece, and four-piece designs. The core, intermediate casing, and cover portions making up the golf ball each can be single or multi-layered. Referring to FIG. 1, a single layered (two-piece) golf ball (10) having a solid core (12) and polyurea cover (14) of this invention is shown. FIG. 2 shows a multi-layered (three-piece) golf ball (20) that can be made in accordance with this invention. In this version, the ball (20) includes a solid core (22), an intermediate casing layer (24), and polyurea cover (26).
The core portions (12, 22) in the golf balls (10, 20) shown in FIGS. 1 and 2, respectively are typically made from compositions containing a base rubber, filler, initiator agent, and cross-linking agent. The base rubber normally is a 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 may also function as cis-to-trans catalyst to convert some cis-1,4 bonds in the polybutadiene into trans 1,4 bonds. Fillers, which may be used to modify such properties as the specific gravity (density-modifying materials), hardness, weight, modulus, resiliency, compression, and the like may be added to the core composition. Normally, the fillers are inorganic, and suitable fillers include numerous metals or metal oxides, such as zinc oxide and tin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate, barium carbonate, clay, tungsten, tungsten carbide, silica, and mixtures thereof.
The intermediate layer (24), as shown in the golf ball (20) of FIG. 2, 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, including homopolymers and copolymers thereof, as well as their derivatives that are compatibilized with at least one grafted or copolymerized functional group, such as maleic anhydride, amine, epoxy, isocyanate, hydroxyl, sulfonate, phosphonate, and the like: 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 casing 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 additives and filler materials described above may be added to the intermediate layer composition to modify such properties as the specific gravity (density-modifying materials), hardness, weight, modulus, resiliency, compression, and the like.
The ionomeric resins can 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.
Referring back to FIGS. 1 and 2, the core portions (12, 22) are shown as single-piece structures made from a natural or synthetic rubber composition such as polybutadiene. In other instances, a multi-piece core may be constructed; that is, there may be two or more core portions or layers. For example, in FIG. 3, a golf ball (28) having a two-piece solid core (30, 32), intermediate layer (34), and a cover layer (36) made in accordance with this invention is shown. The intermediate layer (34) may be made of the above-described ionomer resins, and the cover may be made of the polyurea composition of this invention. The multi-layered core (constituting inner and outer core layers (30, 32)) may be referred to as the “center” of the ball. The inner core portion (30) may be made of a first base rubber material and the outer core layer (32), which surrounds the inner core (30), may be made of a second base rubber material. The respective core pieces (30, 32) 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 of each core piece.
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 portion 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. 1-3, the core portions 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 3, which show golf balls having intermediate layers (24, 34) respectively, 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. 1-3 and described above, the cover material (14, 26, and 36) is made of the polyurea composition of this invention. The polyurea cover provides the ball with good mechanical strength and durability as well as playing performance properties. The thickness of the polyurea cover 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) of the present invention may also 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 discussed above, suitable core materials include thermoset materials, such as, for example, rubber, styrene butadiene, polybutadiene, isoprene, polyisoprene, trans-isoprene, as well as thermoplastics such as, for example, ionomer resins, polyamides or polyesters. The intermediate casing layer, which may be made of ionomer resins or other polymer materials, may be formed using known methods such as, for example, retractable pin injection molding or compression molding.
This intermediate casing layer is then 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 ball cover materials made with the polyurea compositions of this invention have several advantageous properties and benefits including the following. First, the cover materials show good moisture resistance. While not wishing to be bound by any theory, it is believed the hydrophobic backbone of the amine-terminated polycaprolactones used to produce the polyurea composition, as described above, significantly contributes to this enhanced moisture resistance. Secondly, the polyurea cover materials have high durability and abrasion resistance. The polyurea cover materials maintain their original appearance and aesthetics over time.
Test Methods
Hardness: The surface hardness of a golf ball layer (or other spherical surface) is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface of the golf ball layer, care must be taken to ensure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated digital durometer, capable of reading to 0.1 hardness units, is used for all hardness measurements and is set to take hardness readings at 1 second after the maximum reading is obtained. The digital durometer must be attached to and its foot made parallel to the base of an automatic stand. The weight on the durometer and attack rate conforms to ASTM D-2240. It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” For purposes of the present invention, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Surface hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. The difference in “surface hardness” and “material hardness” values is due to several factors including, but not limited to, ball construction (that is, core type, number of cores and/or cover layers, and the like); ball (or sphere) diameter; and the material composition of adjacent layers. It also should be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other.
It is understood that the golf balls having a polyurea cover 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 isocyanate, amine-terminated polycaprolactone, and amine-terminated cross-linking agent.

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

3. The golf ball of claim 1, wherein the isocyanate is selected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers and mixtures thereof.

4. 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.

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

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

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

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

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

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

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

12. The golf ball of claim 11, wherein the cover has a material hardness of about 35 to about 55 Shore D.

13. A golf ball, comprising:

a core;

an intermediate casing layer overlying the core; and

a polyurea cover material produced by a reaction of ingredients comprising isocyanate, amine-terminated polycaprolactone, and amine-terminated cross-linking agent, the cover material overlying the casing layer.

14. The golf ball of claim 13, wherein the core comprises polybutadiene.

15. The golf ball of claim 13, wherein the casing layer comprises ionomeric resin.

16. The golf ball of claim 13, wherein the casing layer comprises a blend of ionomeric resin and non-ionomeric resin.

17. The golf ball of claim 13, wherein the isocyanate is selected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers and mixtures thereof.

18. The golf ball of claim 13, 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.

19. The golf ball of claim 13, wherein the polyurea cover material further comprises pigments and fillers.

20. The golf ball of claim 13, wherein the core has a diameter of about 1.26 to about 1.60 inches.

21. The golf ball of claim 13, wherein the intermediate casing layer has a thickness of about 0.015 to about 0.120 inches.

22. The golf ball of claim 21, wherein the intermediate casing layer has a thickness of about 0.020 to about 0.060 inches.

23. The golf ball of claim 13, wherein the cover has a thickness of about 0.015 to about 0.090 inches.

24. The golf ball of claim 23, wherein the cover has a thickness of about 0.020 to about 0.050 inches.

25. The golf ball of claim 23, wherein the cover has a thickness of about 0.020 to about 0.035 inches.