US20070270242A1

US20070270242A1 - Polybutadiene diols for unique polyurethane

Info

Publication number: US20070270242A1
Application number: US11/749,307
Authority: US
Inventors: Viktor Keller; Thomas J. Kennedy; William M. Risen
Original assignee: Callaway Golf Co
Current assignee: Topgolf Callaway Brands Corp
Priority date: 2006-05-17
Filing date: 2007-05-16
Publication date: 2007-11-22

Abstract

Disclosed herein is a golf ball comprising a polyurethane material formed by the reaction of a diisocyanate and polybutadiene diol. In a multi-piece golf ball any of a core, a cover, and optionally one or more mantle layers disposed therebetween, comprises a polyurethane formed by the reaction of a diisocyanate and polybutadiene diol. One preferred form of the invention is a golf ball having a cover layer comprising a polybutadiene diol-based polyurethane. Another preferred form of the invention is a golf ball comprising a polybutadiene diol-based polyurethane that is formed by reaction injection molding.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

The Present application claims priority to U.S. Provisional Patent Application No. 60/747,447, filed on May 17, 2006.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a golf ball.
2. Description of the Related Art
Golf balls may be classified in generally three types of classes. The first type is a wound ball wherein a vulcanized rubber thread is wound under tension around a solid or semi-solid core, and thereafter enclosed in a single or multi-layer covering of a tough, protective material.
A second type of golf ball is a one-piece ball formed from a solid mass of moldable resilient material which has been cured to develop the necessary degree of hardness. One-piece molded balls do not have an enclosing cover.
A third type of ball is a multi-piece (two or more pieces) non-wound ball which includes a solid or liquid core and a cover having one or more layers formed over the core. One or more additional layers may optionally be disposed between the core and the cover.
Golf ball covers have been made of ionomers, balata, and slow-reacting, thermoset polyurethane. When covers are made from conventional polyurethanes and formed by conventional methods, such as by casting, a substantial amount of time and energy are required, thus resulting in relatively high costs. Furthermore, a variety of inefficiencies exist stemming from the use of currently known polyurethanes.
Accordingly, it would be useful to identify a polyurethane that could be used in the production of golf ball components, especially covers, that would provide a wide range of desirable properties and which was formed via a fast-chemical-reaction.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to produce a golf ball having a polyurethane material, the polyurethane being formed from the reaction of an isocyanate and a polyol.
Another object of the invention is to produce a golf ball having a core and a cover, wherein at least the cover includes a polyurethane formed by the reaction of a diisocyanate and polybutadiene diol.
Yet another object of the invention is to produce a golf ball having a polybutadiene diol-based polyurethane cover.
Still another object of the invention is to produce a golf ball having a polybutadiene diol-based polyurethane cover formed by reaction injection molding.
A further object of the invention is to produce a golf ball having a polybutadiene diol-based polyurethane component.
A further object of the invention is to produce a golf ball having a polybutadiene diol-based polyurethane component formed by reaction injection molding.
Another object of the invention is to provide a golf ball comprising a polyurethane material in which the polyurethane material is a reaction product of a diisocyanate and a polybutadiene diol.
Still another object of the invention is to produce a multi-piece golf ball comprising a generally spherical core, an intermediate layer disposed about the core, and a cover layer disposed about the intermediate layer, in which at least one of the intermediate layer and the cover layer comprises a polyurethane material which is a reaction product of diisocyanate and a polybutadiene diol.
Yet another object of the invention is to provide a golf ball comprising a core and a cover in which the cover includes a polyurethane and is a reaction product of a diisocyanate and a polybutadiene diol in which the polybutadiene diol has a molecular weight of from about 100 to 10,000 and the resulting polyurethane exhibits a Shore D hardness in the range of from about 10 to about 95 and flexural modulus in the range from about 1 to about 310 Kpsi.
Another object of the invention is to provide a method for forming a golf ball having components that include a polybutadiene diol-based polyurethane, in which the method comprises providing a mold adapted for forming a golf ball that defines a molding cavity and an inlet for introducing the material into the molding cavity, providing a polybutadiene diol-based polyurethane, administering the polybutadiene diol-based polyurethane through the inlet and into the mold cavity and partially curing the polybutadiene diol-based polyurethane to form the golf ball component.
Still another object of the invention is to provide a method for forming a golf ball having a core including a polybutadiene diol-based polyurethane, in which the method comprises providing a mold adapted for forming a golf ball core that defines a molding cavity and an inlet for introducing the material into the molding cavity, providing a polybutadiene diol-based polyurethane, introducing the polybutadiene diol-based polyurethane into the inlet and flowing the polyurethane into the molding cavity, and at least partially curing the polybutadiene diol-based polyurethane to form the golf ball core.
A further object of the invention is to provide a method for producing a golf ball component formed from a polybutadiene diol-based polyurethane in which the method comprises providing a mold adapted for forming a golf ball component that defines a mold cavity and at least one port for introducing material into the cavity, providing a polybutadiene diol, providing a diisocyanate, and administering the polybutadiene diol and the diisocyanate through the at least one port and into the molding cavity, whereby the polybutadiene diol and the diisocyanate react within the molding cavity to form a polybutadiene diol-based polyurethane golf ball component.
Another object of the invention is to provide a method for forming a golf ball component including a polybutadiene diol-based polyurethane in which the method is performed by employing a mold adapted for forming a golf ball component, defining a molding cavity, wherein the method includes administering the polybutadiene diol-based polyurethane into the molding cavity to form the golf ball component.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a first embodiment of a golf ball formed according to a reaction injection molded (RIM) process according to the invention.

FIG. 2 is a second embodiment of a golf ball formed according to a reaction injection molded (RIM) process according to the invention.

FIG. 3 is a third embodiment of a golf ball formed according to a reaction injection molded (RIM) process according to the invention.

FIG. 4 is a process flow diagram which schematically depicts a reaction injection molding process according to the invention.

FIG. 5 schematically shows a mold for reaction injection molding a golf ball cover according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a golf ball in which at least one cover or core layer of the ball comprises a polyurethane/polyurea material having polybutadiene diol as its diol component. The polyurethane material may be formed by reacting polybutadiene diol with various polyisocyanates and optionally other chain extending diols, triols or amines.
A preferred form of the invention is a golf ball in which at least one cover layer, intermediate mantle layer, or core layer comprises a fast-chemical-reaction-produced component. This component comprises at least one material selected from the group consisting of polyurethane, polyurea, polyurethane ionomer, epoxy, and unsaturated polyesters, and preferably comprises polyurethane. The invention also includes a method of producing a golf ball which contains a fast-chemical-reaction-produced component. Particularly preferred forms of the invention also provide for a golf ball with a fast-chemical-reaction-produced cover having good scuff resistance and cut resistance. As used herein, “polyurethane and/or polyurea” is expressed as “polyurethane/polyurea.”
A particularly preferred form of the invention is a golf ball with a cover comprising polyurethane. The preferred cover includes from about 5 to about 100 weight percent of polyurethane formed from recycled polyurethane.
The method of the invention is particularly useful in forming golf balls because it can be practiced at relatively low temperatures and pressures. The preferred temperature range for the method of the invention is from about 90 to about 180° F. when the component being produced contains polyurethane. Preferred pressures for practicing the invention using polyurethane-containing materials are 200 psi or less and more preferably 100 psi or less. The method of the present invention offers numerous advantages over conventional slow-reactive process compression molding of golf ball covers. The method of the present invention results in molded covers in a demold time of 10 minutes or less, preferably 2 minutes or less, and most preferably in 1 minute or less. The method of the present invention results in the formation of a reaction product formed by mixing two or more reactants together, that exhibits a reaction time of about 2 minutes or less, preferably one minute or less, and most preferably about 30 seconds or less. The term fast-chemical-reaction-produced component as used herein refers to such reaction products. An excellent finish can be produced on the ball utilizing these components and molding techniques.
The term “demold time” generally refers to the mold release time, which is the time span from the mixing of the components until the earliest possible removal of the finished part, sometimes referred to in the industry as “green strength.” The term “reaction time” generally refers to the setting time or curing time, which is the time span form the beginning of mixing until a point is reached where the polyaddition product no longer flows. Further description of the terms “setting time” and “mold release time” are provided in the “Polyurethane Handbook,” Edited by Gunter Oertel, Second Edition, ISBN 1-56990-157-0, herein incorporated by reference.
The method of the invention also is particularly effective when recycled polyurethane or other polymer resin, or materials derived by recycling polyurethane or other polymer resin, is incorporated into the product. The process may include the step of recycling at least a portion of the reaction product, preferably by glycolysis. That is, 5-100% of the polyurethane/polyurea formed from the reactants used to form particular components is obtained from recycled polyurethane/polyurea.
As indicated above, the fast-chemical-reaction-produced component can be utilized in one or more cover, mantle, and/or core layers or components of the ball. When a polyurethane cover is formed according to the invention, and then covered with a polyurethane top coat, excellent adhesion can be obtained. The adhesion in this case is better than adhesion of a polyurethane coating to an ionomeric cover. This improved adhesion can result in the use of a thinner top coat, the elimination of a primer coat, and the use of a greater variety of golf ball printing inks beneath the top coat. These include but are not limited to typical inks such as one component polyurethane inks and two component polyurethane inks.
Polyurethanes are polymers which are used to form a broad range of products. They are generally formed by mixing two primary ingredients during processing. For the most commonly used polyurethanes, the two primary ingredients are a polyisocyanate (for example, diphenylmethane diisocyanate monomer (“MDI”) and toluene diisocyanate (“TDI”) and their derivatives) and a polyol (for example, a polyester polyol or a polyether polyol).
A wide range of combinations of polyisocyanates and polyols, as well as other ingredients, are available. Furthermore, the end-use properties of polyurethanes can be controlled by the type of polyurethane utilized, i.e., whether the material is thermoset (cross linked molecular structure) or thermoplastic (linear molecular structure).
Cross linking occurs between the isocyanate groups (—NCO) and the polyol's hydroxyl end-groups (—OH). Additionally, the end-use characteristics of polyurethanes can also be controlled by different types of reactive chemicals and processing parameters. For example, catalysts are utilized to control polymerization rates. Depending upon the processing method, reaction rates can be very quick (as in the case for some reaction injection molding systems (i.e., “RIM”) or may be on the order of several hours or longer (as in several coating systems). Consequently, a great variety of polyurethanes are suitable for different end-users.
Polyurethanes are typically classified as thermosetting or thermoplastic. A polyurethane becomes irreversibly “set” when a polyurethane prepolymer is cross linked with a polyfunctional curing agent, such as a polyamine or a polyol. The prepolymer typically is made from polyether or polyester. Diisocyanate polyethers are preferred because of their water resistance.
The physical properties of thermoset polyurethanes are controlled substantially by the degree of cross linking. Tightly cross linked polyurethanes are fairly rigid and strong. A lower amount of cross linking results in materials that are flexible and resilient. Thermoplastic polyurethanes have some cross linking, but primarily by physical means. The crosslinkings bonds can be reversibly broken by increasing temperature, as occurs during molding or extrusion. In this regard, thermoplastic polyurethanes can be injection molded, and extruded as sheet and blow film. They can be used up to about 350° F. and are available in a wide range of hardnesses.
Golf balls according to the present invention are based on a discovery by the present inventors of utilizing polybutadiene diol as the polyol component in a polyurethane composition in the ball. A wide range of properties and characteristics are obtainable. These features lead to golf balls exhibiting superior performance characteristics.
Polybutadiene diol-based polyurethanes exhibit characteristics of both polybutadiene rubber and polyurethanes. Additionally, polybutadiene diol polyurethanes exhibit good elasticity, good characteristics at low temperatures, and low moisture permeability. Polybutadiene diol polyurethanes also exhibit good adhesive properties.
Polybutadiene diol, as used herein, also refers to hydroxyl terminated polybutadiene (HTPB) and/or hydrogenated polybutadiene diol.
Physical properties of polybutadiene diol polyurethanes depend on a variety of factors, including the molecular weight of the polybutadiene diol, the concentration of urethane linkages, the amount of unreacted polybutadiene diol present in the polyurethane, and the degree of cross linking and/or vulcanization.
In general, properties of polybutadiene diol-based polyurethanes, such as tensile strength, flex modulus, and hardness increase as the molecular weight of the polybutadiene diol component decreases. Additionally, vulcanizing the unreacted polybutadiene diol improves the above-listed properties. A more detailed discussion on the effects of various structure characteristics on the mechanical properties of polybutadiene diol polyurethanes is provided in “Effects of Number-Average Molecular Weight of Liquid Hydroxl-Terminated Polybutadiene on Physical Properties of the Elastomer,” Ono et al., Journal of Applied Polymer Science, Vol. 21, 3223-3235 (1977), incorporated herein by reference.
Accordingly, by forming polybutadiene diol-based polyurethanes employing polybutadiene diols of a selected molecular weight, properties of the polybutadiene diol-based polyurethane material can be modified and selected as desired. Consequently, when polybutadiene diol-based polyurethane materials are utilized for forming golf balls and/or golf ball components, golf balls and/or golf ball components having a wide rage of properties may be produced.
The molecular weight of the polybutadiene diol used to form the polyurethane depends on the desired characteristics of the golf ball component. Polybutadiene diols suitable for forming a polyurethane material according to the present invention preferably have a molecular weight from about 100 to about 10,000, more preferably from about 300 to about 5,000 and most preferably from about 600 to about 1,000. Lower molecular weight polybutadiene diols yield polyurethanes, and subsequently golf ball components, having larger hardness and flex modulus values (compared to polyurethanes with higher molecular weight polybutadiene diols)
Double bonds along the chain of the polyurethane, provided by the butadiene chain of polybutadiene diol, provide sites in the polyurethane which can undergo further reactions. These sites may be used to form crosslinks, serve as the site of addition reactions and/or also be cured by vulcanization. For example, polybutadiene diols can undergo addition reactions with unsaturated compounds such as zinc diacrylate. Such reactions lead to improved adhesion at interfaces of components comprising polybutadiene diol-based polyurethanes.
Polyurethane materials formed using polybutadiene diol are readily crosslinkable by radiation, allowing for a wide range of property modifications. Crosslinking typically increases the hardness of a polyurethane material. Consequently, the degree of crosslinking affects the physical properties of the material and the golf ball component.
Polyurethane materials suitable for the present invention are formed by the reaction of a polyisocyanate, polybutadiene diol, and optionally one or more chain extenders. The chain extenders include, but are not limited, to diols, triols and amine extenders. Any suitable polyisocyanate may be used to form a polyurethane according to the present invention. The polyisocyanate is preferably selected from the group of diisocyanates including, but not limited, to 4,4′-diphenylmethane diisocyanate (“MDI”); 2,4-toluene diisocyanate (“TDI”); m-xylylene diisocyanate (“XDI”); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamthylene diisocyanate (HDI); naphthalene-1,5,-diisocyanate (“NDI”); 3,3′-dimethyl-4,4′-biphenyl diisocyanate (“TODI”); 1,4-diisocyanate benzene (“PPDI”); phenylene-1,4-diisocyanate; and
2,2,4- or 2,4,4-trimethyl hexamethylene diisocyanate (“TMDI”).
Other less preferred diisocyanates include, but are not limited to, isophorone diisocyanate (“IPDI”); 1,4-cyclohexyl diisocyanate (“CHDI”); diphenylether-4,4′-diisocyanate; p,p′-diphenyl diisocyanate; lysine diisocyanate (“LDI”); 1,3-bis(isocyanato methyl)cyclohexane; and polymethylene polyphenyl isocyanate (“PMDI”).
One polyurethane component which can be used in the present invention incorporates TMXDI (“META”) aliphatic isocyanate (Cytec Industries, West Paterson, N.J.). Polyurethanes based on meta-tetramethylxylylene diisocyanate (TMXDI) can provide improved gloss retention UV light stability, thermal stability, and hydrolytic stability. Additionally, TMXDI (“META”) aliphatic isocyanate has demonstrated favorable toxicological properties. Furthermore, because it has a low viscosity, it is usable with a wider range of diols (to polyurethane) and diamines (to polyureas). If TMXDI is used, it typically, but not necessarily, is added as a direct replacement for some or all of the other aliphatic isocyanates in accordance with the suggestions of the supplier. Because of slow reactivity of TMXDI, it may be useful or necessary to use catalysts to have practical demolding times. Hardness, tensile strength and elongation can be adjusted by adding further materials in accordance with the supplier's instructions.
Suitable glycol chain extenders include, but are not limited to ethylene glycol; propane glycol; butane glycol; pentane glycol; hexane glycol; benzene glycol; xylenene glycol; 1,4-butane diol; 1,3-butane diol; 2,3-dimethyl-2,3-butane diol; and dipropylene glycol.
Suitable amine extenders include, but are not limited to, tetramethyl-ethylenediamine; dimethylbenzylamine; diethylbenzylamine; pentamethyldiethylenetriamine; dimethyl cyclohexylamine; tetramethyl-1,3-butanediamine; 1,2-dimethylimidazole; 2-methylimidazole; pentamethyldipropylenetriamine; and bis-(dismethylaminoethylether).
Numerous ways are known to induce cross linking in a polymer by free radical initiation, including peroxide initiation and irradiation. The golf ball covers of the present invention may be cross linked by irradiation, preferably by light rays such as gamma or UV irradiation. Furthermore, other forms of particle irradiation, including electron beam also can be used. Gamma radiation is preferred as golf balls or game balls can be irradiated in bulk. Gamma penetrates relatively deep into the material undergoing irradiation, but also increases cross linking of the inner core. Accordingly, the compression of the core has to be adjusted to allow for the increase in hardness stemming from the cross linking.
Electron beam techniques are faster but cannot be used for treating in bulk as the electron beam does not sufficiently penetrate into the material and the product typically needs to be rotated to obtain an even or uniform crosslink density.
The type of irradiation to be used will depend in part upon the underlying layers. For example, certain types of irradiation may degrade windings in a wound golf ball. On the other hand, balls with a solid core would not be subject to the same concerns. However, with any type of core, certain types of irradiation will tend to crosslink and thus harden the core. Depending upon whether this type of effect is sought or is to be avoided, the appropriate type of irradiation can be selected.
The level of radiation employed depends upon the desired end characteristics of the final golf ball component. However, generally a wide range of dosage levels may be used. For example, total dosages of up to about 12.5 or even 15 Mrads may be employed. Preferably, radiation delivery levels are controlled so that the game ball is not heated above about 80° C. (176° F.) while being cross linked.
Polyurethane compositions of the present invention are especially desirable as materials in forming golf balls. Polyurethanes according to the invention, are suitable materials for any of a core layer, a mantle layer, and a cover layer. Most preferably, the polyurethane materials are used to form a cover layer.
Golf balls according to the present invention utilize polyurethane compositions described herein as any of the core, mantle and cover layer. Accordingly, golf balls according to the present invention, may be formed as two-piece, or multi-layer balls having either a wound core or a solid, non-wound core. In a preferred form golf balls utilizing a polyurethane composition described herein are solid, i.e., non-wound, multi-layer golf balls comprising a solid non-wound core, a cover formed from the present invention polyurethane, and one or more intermediate layers disposed between the cover and the core.
The golf balls of the present invention can be produced, at least in part, by molding processes currently known in the golf ball art. Specifically, multi-layer golf balls can be produced by injection molding or compression molding a mantle layer about wound or solid molded cores to produce an intermediate golf ball having a diameter of about 1.50 to 1.67 inches, preferably about 1.620 inches. The cover layer is subsequently molded over the mantle layer to produce a golf ball having a diameter of 1.680 inches or more. Although either solid cores or wound cores can be used in the present invention, as a result of their lower cost and superior performance, solid molded cores are preferred over wound cores.
In compression molding, the mantle layer composition is formed via injection at about 380° F. to about 450° F. into smooth surfaced hemispherical shells which are then positioned around the core in a mold having the desired mantle layer thickness and subjected to compression molding at 200° F. to 300° F. for about 2 to 10 minutes, followed by cooling at 50° F. to 70° F. for about 2 to 7 minutes to fuse the shells together to form a unitary intermediate ball. In addition, the intermediate balls may be produced by injection molding wherein the mantle layer is injected directly around the core placed at the center of an intermediate ball mold for a period of time in a mold temperature of from 50° F. to about 100° F. Subsequently, the cover layer is molded about the core and the inner layer by similar compression or injection molding techniques to form a dimpled golf ball of a diameter of 1.680 inches or more.
A preferred method of forming a golf ball according to the present invention is forming one or more layers via a fast-chemical-reaction process.
Specifically, the preferred method of forming a fast-chemical-reaction-produced component for a golf ball according to the invention is by reaction inj ection molding (“RIM”). RIM is a process by which highly reactive liquids are inj ected into a closed mold, mixed usually by impingement and/or mechanical mixing in an in-line device such as a “peanut mixer,” where they polymerize primarily in the mold to form a coherent, one-piece molded article. The RIM process usually involves a rapid reaction between one or more reactive components such as polyether—or polyester-polyol, polyamine, or other material with an active hydrogen, and one or more isocyanate-containing constituents, often in the presence of a catalyst. The constituents are stored in separate tanks prior to molding and may be first mixed in a mix head upstream of a mold and then injected into the mold. The liquid streams are metered in the desired weight to weight ratio and fed into an impingement mix head, with mixing occurring under high pressure, e.g., 1,500 to 3,000 psi. The liquid streams impinge upon each other in the mixing chamber of the mix head and the mixture is injected into the mold. One of the liquid streams typically contains a catalyst for the reaction. The constituents react rapidly after mixing to gel and form polyurethane polymers. Polyureas, epoxies, and various unsaturated polyesters also can be molded by RIM.
RIM differs from non-reaction injection molding in a number of ways. The main distinction is that in RIM a chemical reaction takes place in the mold to transform a monomer or adducts to polymers and the components are in liquid form. Thus, a RIM mold need not be made to withstand the pressures which occur in a conventional injection molding. In contrast, injection molding is conducted at high molding pressures in the mold cavity by melting a solid resin and conveying it into a mold, with the molten resin often being at about 150 to about 350° C. At this elevated temperature, the viscosity of the molten resin usually is in the range of about 50,000 to about 1,000,000 centipoise, and is typically around 200,000 centipoise. In an injection molding process, the solidification of the resins occurs after about 10 to about 90 seconds, depending upon the size of the molded product, the temperature and heat transfer conditions, and the hardness of the injection molded material. Subsequently, the molded product is removed from the mold. There is no significant chemical reaction taking place in an injection molding process when the thermoplastic resin is introduced into the mold. In contrast, in a RIM process, the chemical reaction causes the material to set in less than about 5 minutes, often in less than 2 minutes, preferably in less than one minute, more preferably in less than 30 seconds, and in many cases in about 10 seconds or less.
If plastic products are produced by combining components that are preformed to some extent, subsequent failure can occur at a location on the cover which is along the seam or parting line of the mold. Failure can occur at this location because this interfacial region is intrinsically different from the remainder of the cover layer and can be weaker or more stressed. The present invention is believed to provide for improved durability of a golf ball cover layer by providing a uniform or “seamless” cover in which the properties of the cover material in the region along the parting line are generally the same as the properties of the cover material at other locations on the cover, including at the poles. The improvement in durability is believed to be a result of the fact that the reaction mixture is distributed uniformly into a closed mold. This uniform distribution of the injected materials eliminates knit-lines and other molding deficiencies which can be caused by temperature difference and/or reaction difference in the injected materials. The process of the invention results in generally uniform molecular structure, density and stress distribution as compared to conventional injection-molding processes.
The polybutadiene diol-based polyurethane component has a flex modulus from about 1 to about 310 Kpsi, more preferably from about 5 to about 100 Kpsi, and most preferably from about 5 to about 80 Kpsi. The subject component can be a cover with a flex modulus which is higher than that of the centermost component of the cores, as in a liquid center core and some solid center cores. Furthermore, the polybutadiene diol-based polyurethane component can be a cover with a flex modulus that is higher than that of the immediately underlying layer, as in the case of a wound core. The core can be one piece or multi-layer, each layer can be either foamed or unfoamed, and density adjusting fillers, including metals, can be used. The cover of the ball can be harder or softer than any particular core layer.
The polybutadiene diol-based polyurethane component can incorporate or be utilized in combination with suitable additives and/or fillers. When the component is an outer cover layer, pigments or dyes, accelerators and UV stabilizers can be added. Examples of suitable optical brighteners which probably can be used include Uvitex and Eastobrite OB-1. An example of a suitable white pigment is titanium dioxide. Examples of suitable and UV light stabilizers are provided in commonly assigned U.S. Pat. No. 5,494,291. Fillers which can be incorporated into the fast-chemical-reaction-produced cover or core component include those listed herein. Furthermore, compatible polymeric materials can be added. For example, when the component comprises polyurethane and/or polyurea, such polymeric materials include polyurethane ionomers, polyamides, etc.
A golf ball core layer formed from a polybutadiene diol-based polyurethane material according to the present invention typically contains from about 0 to about 20 weight percent of such filler material, and more preferably about 1 to about 15 weight percent. When the polybutadiene diol-based polyurethane component is a core, the additives typically are selected to control the density, hardness and/or COR.
A golf ball inner cover layer formed from a polybutadiene diol-based polyurethane material according to the present invention typically contains from about 0 to about 60 weight percent of filler material, more preferably from about 1 to about 30 weight percent, and most preferably from about 1 to about 20 weight percent.
A golf ball outer cover layer formed from a polybutadiene diol-based polyurethane material according to the present invention typically contains from about 0 to about 20 weight percent of filler material, more preferably from about 1 to about 10 weight percent, and most preferably from about 1 to about 5 weight percent.
Catalysts can be added to the RIM polyurethane system starting materials as long as the catalysts generally do not react with the constituent with which they are combined. Suitable catalysts include those which are known to be useful with polyurethanes and polyureas.
The reaction mixture viscosity should be sufficiently low to ensure that the empty space in the mold is completely filled. The reactant materials generally are preheated to 90° F. to 150° F. before they are mixed. In most cases it is necessary to preheat the mold to, e.g., 100 to 180° F., to ensure proper injection viscosity.
As indicated above, one or more cover layers of a golf ball can be formed from a polybutadiene diol-based polyurethane material according to the present invention.
Referring now to the drawings, and first to FIG. 1, a golf ball having a cover comprising a polybutadiene diol-based polyurethane is shown. The golf ball 10 includes a polybutadiene core 12 and a polybutadiene diol-based polyurethane cover 14. In a preferred embodiment, cover 14 is formed by RIM.
Referring now to FIG. 2, a golf ball having a core comprising a polybutadiene diol-based polyurethane is shown. The golf ball 20 has a polybutadiene diol-based polyurethane core 22, and a RIM polyurethane cover 24. Core 22 is optionally formed by RIM.
Referring to FIG. 3, a multi-layer golf ball 30 is shown with a solid core 32 containing recycled RIM polyurethane, a mantle cover layer 34 comprising polybutadiene diol-based polyurethane and an outer cover layer 36 comprising ionomer or another conventional golf ball cover material. Such conventional golf ball materials typically contain titanium dioxide utilized to make the cover white in appearance. Non-limiting examples of multi-layer golf balls according to the invention with two cover layers include those with RIM polyurethane mantles having a thickness from about 0.01 to about 0.20 inches and a Shore D hardness from about 10 to about 95, covered with ionomeric or non-ionomeric thermoplastic, balata or other covers having a Shore D hardness from about 10 to about 95 and a thickness of from about 0.020 to about 0.20 inches.
Referring next to FIG. 4, a process flow diagram for forming a RIM cover of polyurethane is shown. Isocyanate from bulk storage is fed through line 80 to an isocyanate tank 100. The isocyanate is heated to the desired temperature, e.g., 90° F. to about 150° F., by circulating it through heat exchanger 82 via lines 84 and 86. Polyol, polyamine, or another compound with an active hydrogen atom is conveyed from bulk storage to a polyol tank 108 via line 88. The polyol is heated to the desired temperature, e.g., 90° F. to about 150° F., by circulating it through heat exchanger 90 via lines 92 and 94. Dry nitrogen gas is fed from nitrogen tank 96 to isocyanate tank 100 via line 97 and to polyol tank 108 via line 98.
Isocyanate is fed from isocyanate tank 100 via line 102 through a metering cylinder or metering pump 104 into recirculation mix head inlet line 106. Polyol is fed from polyol tank 108 via line 110 through a metering cylinder or metering pump 112 into a recirculation mix head inlet line 114. The recirculation mix head 116 receives isocyanate and polyol, mixes them, and provides for them to be fed through nozzle 118 into injection mold 120. The injection mold 120 has a top mold 122 and a bottom mold 124. Coolant flows through cooling lines 126 in the top mold 122 and lines 128 in the bottom mold 124. The materials are kept under controlled temperature conditions to insure that the desired reaction profile is maintained.
The polyol component typically contains additives, such as stabilizers, flow modifiers, catalysts, combustion modifiers, blowing agents, fillers, pigments, optical brighteners, and release agents to modify physical characteristics of the cover. Recycled polyurethane/polyurea also can be added to the core. Polyurethane/polyurea constituent molecules that were derived from recycled polyurethane can be added in the polyol component.
Inside the mix head 116, injector nozzles impinge the isocyanate and polyol at ultra-high velocity to provide excellent mixing. Additional mixing preferably is conducted using an after mixer 130, which typically is constructed inside the mold between the mix head and the mold cavity.
As is shown in FIG. 5, the mold includes a golf ball cavity chamber 132 in which a spherical golf ball mold 134 with a dimpled, spherical mold cavity 136 is defined. The after mixer 130 can be a peanut after mixer, as is shown in FIG. 5, or in some cases another suitable type, such as a heart, harp or dipper. An overflow channel 138 receives overflow material from the golf ball mold 134 through a shallow vent 142. Heating/ cooling passages 126 and 140, which preferably are in a parallel flow arrangement, carry heat transfer fluids such as water, oil, etc. through the top mold 122 and the bottom mold 124.
The mold cavity contains retractable pins and is generally constructed in the same manner as a mold cavity used to injection mold a thermoplastic, e.g., ionomeric golf ball cover. However, a few differences when RIM is used are that tighter pin tolerances generally are required and a lower injection pressure is used. Also, the molds can be produced from lower strength material such as aluminum. The golf balls formed according to the present invention can be coated using a conventional two-component spray coating or can be coated during the RIM process, i.e., using an in-mold coating process.
One of the significant advantages of the RIM process according to the invention is that polyurethane or other cover material can be recycled and used in golf ball cores. Recycling can be conducted by, e.g., glycolysis. Typically, 10 to 90% of the material which is injection molded actually becomes part of the cover. The remaining 10 to 90% is recycled.
Recycling of polyurethanes by glycolysis is known from, for example, RIM Part and Mold Design—Polyurethanes, 1995, Bayer Corp., Pittsburgh, Pa. Another significant advantage of the present invention is that because reaction injection molding occurs at low temperatures and pressures, i.e., 90 to 180° F. and 50 to 200 psi, this process is particularly beneficial when a cover is to be molded over a very soft core. When higher pressures are used for molding over soft cores, the cores “shut off,” i.e., deform and impede the flow of material causing uneven distribution of cover material.
Golf ball cores also can be made using the materials and processes of the invention. To make a golf ball core using RIM polyurethane, the same processing conditions are used as are described above with respect to covers. One difference is that no retractor pins are needed in the mold. Furthermore, an undimpled, smaller mold is used. If, however, a one piece ball is desired, a dimpled mold would be used. Polyurethanes also can be used for cores.
Golf balls typically have indicia and/or logos stamped or formed thereon. Such indicia can be applied by printing using a material or a source of energetic particles after the ball core and/or cover have been reaction-injection-molded according to the present invention. Printed indicia can be formed from a material such as ink, foil (for use in foil transfer), etc. Indicia print using a source of energetic particles or radiation can be applied by burning with a laser, burning with heat, directed electrons, or light, phototransformations of, e.g., UV ink, impingement by particles, impingement by electromagnetic radiation etc. Furthermore, the indicia can be applied in the same manner as an in-mold coating, i.e., by applying to the indicia to the surface of the mold prior to molding of the cover.
The polyurethane which is selected for use as a golf ball cover preferably has a Shore D hardness of from about 10 to about 95, more preferably from about 30 to about 75, and most preferably from about 30 to about 50 for a soft cover layer and from about 50 to about 75 for a hard cover layer. The polyurethane which is to be used for a cover layer preferably has a flex modulus from about 1 to about 310 Kpsi, more preferably from about 5 to about 100 Kpsi, and most preferably from about 5 to about 20 Kpsi for a soft cover layer and 30 to 70 Kpsi for a hard cover layer. Accordingly, covers comprising these materials exhibit similar properties.
Non-limiting examples of suitable RIM systems for use in the present invention are Bayflex® elastomeric polyurethane RIM systems, Baydur® GS solid polyurethane RIM systems, Prism® solid polyurethane RIM systems, all from Bayer Corp. (Pittsburgh, Pa.), SPECTRIM reaction moldable polyurethane and polyurea systems from Dow Chemical USA (Midland, Mich.), including SPECTRIM MM 373-A (isocyanate) and 373-B (polyol), and Elastolit SR systems from BASF (Parsippany, N.J.). Preferred RIM systems include Bayflex® MP-10000 and Bayflex® 110-50, filled and unfilled. Further preferred examples are polyols, polyamines and isocyanates formed by processes for recycling polyurethanes and polyureas. In accordance with the present invention, these various systems are modified by incorporating a butadiene component in the diol agent.
It is contemplated that KRASOL LBH 3000, sold by Kaucuk of the Czech Republic, would be suitable as the polybutadiene diol component in accordance with the present invention.
A wide array of materials may be used for the cores and mantle layer(s) of the present invention golf balls. For instance, the core and mantle or interior layer materials disclosed in U.S. Pat. Nos. 5,833,533; 5,830,087; 5,820,489; and 5,820,488, all of which are hereby incorporated by reference, may be employed. In particular, it is preferred to utilize the cores described in U.S. application Ser. No. 09/226,340, filed Jan. 6, 1999; and Ser. No. 09/226,727, filed Jan. 7, 1999, both of which are hereby incorporated by reference.
In a particularly preferred form of the invention, at least one layer of the golf ball contains at least one part by weight of a filler. Fillers preferably are used to adjust the density, flex modulus, mold release, and/or melt flow index of a layer or component used in the ball. More preferably, at least when the filler is for adjustment of density or flex modulus of a layer, it is present in an amount of at least five parts by weight based upon 100 parts by weight of the layer composition. With some fillers, up to about 200 parts by weight probably can be used.
A density adjusting filler according to the invention preferably is a filler which has a specific gravity which is at least 0.05 and more preferably at least 0.1 higher or lower than the specific gravity of the layer composition. Particularly preferred density adjusting fillers have specific gravities which are higher than the specific gravity of the resin composition by 0.2 or more, even more preferably by 2.0 or more.
A flex modulus adjusting filler according to the invention is a filler which e.g., when used in an amount of, 1 to 100 parts by weight based upon 100 parts by weight of resin composition, will raise or lower the flex modulus (ASTM D-790) of the resin composition by at least 1% and preferably at least 5% as compared to the flex modulus of the resin composition without the inclusion of the flex modulus adjusting filler.
A mold release adjusting filler is a filler which allows for the easier removal of a part from a mold, and eliminates or reduces the need for external release agents which otherwise could be applied to the mold. A mold release adjusting filler typically is used in an amount of up to about 2 weight percent based upon the total weight of the layer.
A melt flow index adjusting filler is a filler which increases or decreases the melt flow, or ease of processing of the composition.
The layers may contain coupling agents that increase adhesion of materials within a particular layer, e.g., to couple a filler to a resin composition, or between adjacent layers. Non-limiting examples of coupling agents include titanate, zirconates and silanes. Coupling agents typically are used in amounts of 0.1 to 2 weight percent based upon the total weight of the composition in which the coupling agent is included.
A density adjusting filler is used to control the moment of inertia, and thus the initial spin rate of the ball and spin decay. The addition in one or more layers, and particularly in the outer cover layer of a filler with a lower specific gravity than the resin composition results in a decrease in moment of inertia and a higher initial spin rate than would result if no filler were used. The addition in one or more of the cover layers, and particularly in the outer cover layer of a filler with a higher specific gravity than the resin composition, results in an increase in moment of inertia and a lower initial spin rate. High specific gravity fillers are preferred as less volume is used to achieve the desired inner cover total weight. Nonreinforcing fillers are also preferred as they have minimal effect on COR. Preferably, the filler does not chemically react with the resin composition to a substantial degree, although some reaction may occur when, for example, zinc oxide is used in a shell layer which contains some ionomer.
The density-increasing fillers for use in the invention preferably have a specific gravity in the range of from about 1.0 to about 20. The density-reducing fillers for use in the invention preferably have a specific gravity of from about 0.06 to about 1.4, and more preferably from about 0.06 to about 0.90. The flex modulus increasing fillers have a reinforcing or stiffening effect due to their morphology, their interaction with the resin, or their inherent physical properties. The flex modulus reducing fillers have an opposite effect due to their relatively flexible properties compared to the matrix resin. The melt flow index increasing fillers have a flow enhancing effect due to their relatively high melt flow versus the matrix. The melt flow index decreasing fillers have an opposite effect due to their relatively low melt flow index versus the matrix.
Fillers which may be employed in layers other than the outer cover layer may be or are typically in a finely divided form, for example, in a size generally less than about 20 mesh, preferably less than about 100 mesh U.S. standard size, except for fibers and flock, which are generally elongated. Flock and fiber sizes should be small enough to facilitate processing. Filler particle size will depend upon desired effect, cost, ease of addition, and dusting considerations. The filler preferably is selected from the group consisting of precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide, metal oxides, metal stearates, particulate carbonaceous materials, micro balloons, and combinations thereof. Non-limiting examples of suitable fillers, their densities, and their preferred uses are as follows:

Filler Table

Filler Type	Spec. Grav.	Comments

Precipitated hydrated silica	2.00	1, 2
Clay	2.62	1, 2
Talc	2.85	1, 2
Asbestos	2.50	1, 2
Glass fibers	2.55	1, 2
Aramid fibers (KEVLAR ®)	1.44	1, 2
Mica	2.80	1, 2
Calcium metasilicate	2.90	1, 2
Barium sulfate	4.60	1, 2
Zinc sulfide	4.10	1, 2
Lithopone	4.2-4.3	1, 2
Silicates	2.10	1, 2
Silicon carbide platelets	3.18	1, 2
Silicon carbide whiskers	3.20	1, 2
Tungsten carbide	15.60	1
Diatomaceous earth	2.30	1, 2
Polyvinyl chloride	1.41	1, 2
Carbonates
Calcium carbonate	2.71	1, 2
Magnesium carbonate	2.20	1, 2
Metals and Alloys (Powders)
Titanium	4.51	1
Tungsten	19.35	1
Aluminum	2.70	1
Bismuth	9.78	1
Nickel	8.90	1
Molybdenum	10.20	1
Iron	7.86	1
Steel	7.8-7.9	1
Lead	11.40	1, 2
Copper	8.94	1
Brass	8.2-8.4	1
Boron	2.34	1
Boron carbide whiskers	2.52	1, 2
Bronze	8.70-8.74	1
Cobalt	8.92	1
Beryllium	1.84	1
Zinc	7.14	1
Tin	7.31	1
Metal Oxides
Zinc oxide	5.57	1, 2
Iron oxide	5.10	1, 2
Aluminum oxide	4.00
Titanium oxide	3.9-4.1	1, 2
Magnesium oxide	3.3-3.5	1, 2
Zirconium oxide	5.73	1, 2
Metal Stearates
Zinc stearate	1.09	3, 4
Calcium stearate	1.03	3, 4
Barium stearate	1.23	3, 4
Lithium stearate	1.01	3, 4
Magnesium stearate	1.03	3, 4
Particulate Carbonaceous Materials
Graphite	1.5-1.8	1, 2
Carbon black	1.80	1, 2
Natural bitumen	1.2-1.4	1, 2
Cotton flock	1.3-1.4	1, 2
Cellulose flock	1.15-1.5	1, 2
Leather fiber	1.2-1.4	1, 2
Micro Balloons
Glass	0.15-1.1	1, 2
Ceramic	0.2-0.7	1, 2
Fly ash	0.6-0.8	1, 2
Coupling Agents Adhesion Promoters
Titanate	0.95-1.17
Zirconates	0.92-1.11
Silane	0.95-1.2

Comments:
1. Particularly useful for adjusting density of the cover layer.
2. Particularly useful for adjusting flex modulus of the cover layer.
3. Particularly useful for adjusting mold release of the cover layer.
4. Particularly useful for increasing melt flow index of the cover layer.

The amount of filler employed is primarily a function of weight requirements and distribution.

Shore D Hardness

As used herein, “Shore D hardness” of a cover is measured generally in accordance with ASTM D-2240, except the measurements are made on a land area of the curved surface of a molded cover, rather than on a plaque. Furthermore, the Shore D hardness of the cover is measured while the cover remains over the core. When a hardness measurement is made on a dimpled cover, Shore D hardness is measured at a land area of the dimpled cover.

Coefficient of Restitution

The resilience or coefficient of restitution (COR) of a golf ball is the constant “e,” which is the ratio of the relative velocity of an elastic sphere after direct impact to that before impact. As a result, the COR (“e”) can vary from 0 to 1, with 1 being equivalent to a perfectly or completely elastic collision and 0 being equivalent to a perfectly or completely inelastic collision.
COR, along with additional factors such as club head speed, club head mass, ball weight, ball size and density, spin rate, angle of trajectory and surface configuration (i.e., dimple pattern and area of dimple coverage) as well as environmental conditions (e.g., temperature, moisture, atmospheric pressure, wind, etc.) generally determine the distance a ball will travel when hit. Along this line, the distance a golf ball will travel under controlled environmental conditions is a function of the speed and mass of the club and size, density and resilience (COR) of the ball and other factors. The initial velocity of the club, the mass of the club and the angle of the ball's departure are essentially provided by the golfer upon striking. Since club head, club head mass, the angle of trajectory and environmental conditions are not determinants controllable by golf ball producers and the ball size and weight are set by the U.S.G.A., these are not factors of concern among golf ball manufacturers. The factors or determinants of interest with respect to improved distance are generally the coefficient of restitution (COR) and the surface configuration (dimple pattern, ratio of land area to dimple area, etc.) of the ball.
The COR in solid core balls is a function of the composition of the molded core and of the cover. The molded core and/or cover may be comprised of one or more layers such as in multi-layered balls. In balls containing a wound core (i.e., balls comprising a liquid or solid center, elastic windings, and a cover), the coefficient of restitution is a function of not only the composition of the center and cover, but also the composition and tension of the elastomeric windings. As in the solid core balls, the center and cover of a wound core ball may also consist of one or more layers.
The coefficient of restitution is the ratio of the outgoing velocity to the incoming velocity. In the examples of this application, the coefficient of restitution of a golf ball was measured by propelling a ball horizontally at a speed of 125±5 feet per second (fps) and corrected to 125 fps against a generally vertical, hard, flat steel plate and measuring the ball's incoming and outgoing velocity electronically. Speeds were measured with a pair of Oehler Mark 55 ballistic screens available from Oehler Research, Inc., P.O. Box 9135, Austin, Tex. 78766, which provide a timing pulse when an object passes through them. The screens were separated by 36″ and are located 25.25″ and 61.25″ from the rebound wall. The ball speed was measured by timing the pulses from screen 1 to screen 2 on the way into the rebound wall (as the average speed of the ball over 36″), and then the exit speed was timed from screen 2 to screen 1 over the same distance. The rebound wall was tilted 2 degrees from a vertical plane to allow the ball to rebound slightly downward in order to miss the edge of the cannon that fired it. The rebound wall is solid steel 2.0 inches thick.
As indicated above, the incoming speed should be 125±5 fps but corrected to 125 fps. The correlation between COR and forward or incoming speed has been studied and a correction has been made over the ±5 fps range so that the COR is reported as if the ball had an incoming speed of exactly 125.0 fps.
The coefficient of restitution must be carefully controlled in all commercial golf balls if the ball is to be within the specifications regulated by the United States Golf Association (U.S.G.A.). As mentioned to some degree above, the U.S.G.A. standards indicate that a “regulation” ball cannot have an initial velocity exceeding 255 feet per second in an atmosphere of 75° F., when tested on a U.S.G.A. machine. Since the coefficient of restitution of a ball is related to the ball's initial velocity, it is highly desirable to produce a ball having sufficiently high coefficient of restitution to closely approach the U.S.G.A. limit on initial velocity, while having an ample degree of softness (i.e., hardness) to produce enhanced playability (i.e., spin, etc.).

Compression

PGA compression is another important property involved in the performance of a golf ball. The compression of the ball can affect the playability of the ball on striking and the sound or “click” produced. Similarly, compression can affect the “feel” of the ball (i.e., hard or soft responsive feel), particularly in chipping and putting.
Moreover, while compression itself has little bearing on the distance performance of a ball, compression can affect the playability of the ball on striking. The degree of compression of a ball against the club face and the softness of the cover strongly influences the resultant spin rate. Typically, a softer cover will produce a higher spin rate than a harder cover. Additionally, a harder core will produce a higher spin rate than a softer core. This is because at impact a hard core serves to compress the cover of the ball against the face of the club to a much greater degree than a soft core thereby resulting in more “grab” of the ball on the clubface and subsequent higher spin rates. In effect the cover is squeezed between the relatively incompressible core and clubhead. When a softer core is used, the cover is under much less compressive stress than when a harder core is used and therefore does not contact the clubface as intimately. This results in lower spin rates.
The term “compression” utilized in the golf ball trade generally defines the overall deflection that a golf ball undergoes when subjected to a compressive load. For example, PGA compression indicates the amount of change in golf ball's shape upon striking. The development of solid core technology in two-piece balls has allowed for much more precise control of compression in comparison to thread wound three-piece balls. This is because in the manufacture of solid core balls, the amount of deflection or deformation is precisely controlled by the chemical formula used in making the cores. This differs from wound three-piece balls wherein compression is controlled in part by the winding process of the elastic thread. Thus, two-piece and multi-layer solid core balls exhibit much more consistent compression readings than balls having wound cores such as the thread wound three-piece balls.
In the past, PGA compression related to a scale of from 0 to 200 given to a golf ball. The lower the PGA compression value, the softer the feel of the ball upon striking. In practice, tournament quality balls have compression ratings around 70 to 110, preferably around 80 to 100.
In determining PGA compression using the 0 to 200 scale, a standard force is applied to the external surface of the ball. A ball which exhibits no deflection (0.0 inches in deflection) is rated 200 and a ball which deflects 2/10th of an inch (0.2 inches) is rated 0. Every change of 0.001 of an inch in deflection represents a 1 point drop in compression. Consequently, a ball which deflects 0.1 inches (100×0.001 inches) has aPGA compression value of 100 (i.e.,200 to 100) and a ball which deflects 0.110 inches (110×0.001 inches) has a PGA compression of 90 (i.e., 200 to 110).
In order to assist in the determination of compression, several devices have been employed by the industry. For example, PGA compression is determined by an apparatus fashioned in the form of a small press with an upper and lower anvil. The upper anvil is at rest against a 200-pound die spring, and the lower anvil is movable through 0.300 inches by means of a crank mechanism. In its open position the gap between the anvils is 1.780 inches allowing a clearance of 0.100 inches for insertion of the ball. As the lower anvil is raised by the crank, it compresses the ball against the upper anvil, such compression occurring during the last 0.200 inches of stroke of the lower anvil, the ball then loading the upper anvil which in turn loads the spring. The equilibrium point of the upper anvil is measured by a dial micrometer if the anvil is deflected by the ball more than 0.100 inches (less deflection is simply regarded as zero compression) and the reading on the micrometer dial is referred to as the compression of the ball. In practice, tournament quality balls have compression ratings around 80 to 100 which means that the upper anvil was deflected a total of 0.120 to 0.100 inches.
An example to determine PGA compression can be shown by utilizing a golf ball compression tester produced by Atti Engineering Corporation of Newark, N.J. The value obtained by this tester relates to an arbitrary value expressed by a number which may range from 0 to 100, although a value of 200 can be measured as indicated by two revolutions of the dial indicator on the apparatus. The value obtained defines the deflection that a golf ball undergoes when subjected to compressive loading. The Atti test apparatus consists of a lower movable platform and an upper movable spring-loaded anvil. The dial indicator is mounted such that it measures the upward movement of the spring loaded anvil. The golf ball to be tested is placed in the lower platform, which is then raised a fixed distance. The upper portion of the golf ball comes in contact with and exerts a pressure on the spring loaded anvil. Depending upon the distance of the golf ball to be compressed, the upper anvil is forced upward against the spring.
Alternative devices have also been employed to determine compression. For example, Applicant also utilizes a modified Riehle Compression Machine originally produced byRiehle Bros. Testing Machine Company, Phil., Pa. to evaluate compression of the various components (i.e., cores, mantle cover balls, finished balls, etc.) of the golf balls. The Riehle compression device determines deformation in thousandths of an inch under a load designed to emulate the 200 pound spring constant of the Atti or PGA compression testers. Using such a device, a Riehle compression of 61 corresponds to a deflection under load of 0.061 inches.
Additionally, an approximate relationship between Riehle compression and PGA compression exists for balls of the same size. It has been determined by Applicant that Riehle compression corresponds to PGA compression by the general formula PGA compression=160−Riehle compression. Consequently, 80 Riehle compression corresponds to 80 PGA compression, 70 Riehle compression corresponds to 90 PGA compression, and 60 Riehle compression corresponds to 100 PGA compression. For reporting purposes, Applicant's compression values are usually measured as Riehle compression and converted to PGA compression.
Furthermore, additional compression devices may also be utilized to monitor golf ball compression so long as the correlation to PGA compression is known. These devices have been designed, such as a Whitney Tester, to correlate or correspond to PGA compression through a set relationship or formula.
The RIM process used in forming components of a multi-layered golf ball disclosed herein is substantially different from, and advantageous over, the conventional injection and compression molding techniques.
First, during the RIM process of the present application, the chemical reaction, i.e., the mixture of isocyanate from the isocyanate tank and polyol from the polyol tank, occurs during the molding process. Specifically, the mixing of the reactants occurs in the recirculation mix head and the after mixer, both of which are connected directly to the injection mold. The reactants are simultaneously mixed and injected into the mold, forming the desired component.
Typically, prior art techniques utilize mixing of reactants to occur before the molding process. Mixing under either compression or injection molding occurs in a mixer that is not connected to the molding apparatus. Thus, the reactants must first be mixed in a mixer separate from the molding apparatus, then added into the apparatus. Such a process causes the mixed reactants to first solidify, then later melt in order to properly mold.
Second, the RIM process requires lower temperatures and pressures during molding than does injection or compression molding. Under the RIM process, the molding temperature is maintained at about 100° F. to about 120° F. in order to ensure proper injection viscosity. Compression molding is typically completed at a higher molding temperature of about 320° F. (160° C.). Injection molding is completed at even a higher temperature range of from about 392° F. to about 482° F. (200 to 250° C.). Molding at a lower temperature is beneficial when, for example, the cover is molded over a very soft core so that the very soft core does not melt or decompose during the molding process.
Third, the RIM process creates more favorable durability properties in a golf ball than does conventional injection or compression molding. The preferred process of the present invention provides improved durability for a golf ball cover by providing a uniform or “seamless” cover in which the properties of the cover material in the region along the parting line are generally the same as the properties of the cover material at other locations on the cover, including at the poles. The improvement in durability is due to the fact that the reaction mixture is distributed uniformly into a closed mold. This uniform distribution of the injected materials eliminates knit-lines and other molding deficiencies which can be caused by temperature difference and/or reaction difference in the injected materials. The RIM process of the present invention results in generally uniform molecular structure, density and stress distribution as compared to conventional injection molding processes, where failure along the parting line or seam of the mold can occur because the interfacial region is intrinsically different from the remainder of the cover layer and, thus, can be weaker or more stressed.
Fourth, the RIM process is relatively faster than the conventional injection and compression molding techniques. In the RIM process, the chemical reaction takes place in under 5 minutes, typically in less than two minutes, preferably in under one minute and, in many cases, in about 30 seconds or less. The demolding time of the present application is 10 minutes or less. The molding process alone for the conventional methods typically takes about 15 minutes. Thus, the overall speed of the RIM process makes it advantageous over the injection and compression molding methods.
The present invention also provides a method of forming a golf ball or golf ball component that contains a polybutadiene diol-based polyurethane.
In one preferred form the method includes providing a mold that is adapted for forming a golf ball or golf ball component. The mold defines a molding cavity and an inlet for introducing material into the molding cavity. The molding cavity is especially suited for forming a golf ball component such as a cover, a mantle layer, and/or a core. A polybutadiene diol-based polyurethane is provided and administered through the inlet and into the molding cavity. The polybutadiene diol-based polyurethane, as previously described herein, is the reaction product of a diisocyanate and polybutadiene diol. Preferably, the polybutadiene diol-based polyurethane is allowed to partially cure to form a golf ball component.
In a particularly preferred form, a core component is provided and positioned in the molding cavity prior to introduction of the polybutadiene diol-based polyurethane. The polybutadiene diol-based polyurethane is administered into the molding cavity and forms a layer over the core component. The layer formed about the core may be any of a mantle layer or a cover layer.
The present invention also provides a method for forming a golf ball having a core that includes a polybutadiene diol-based polyurethane. A mold adapted for forming a golf ball core is provided and defines a mold cavity and an inlet for introducing material into the molding cavity. A polybutadiene diol-based polyurethane is provided and introduced into the inlet, whereby the polyurethane flows through the inlet and into the molding cavity. A golf ball core is formed by allowing the polybutadiene diol-based polyurethane to partially cure.
A most preferred method according to the present invention includes forming a golf ball component having a polybutadiene diol-based polyurethane by providing a mold adapted for forming a golf ball component that defines a molding cavity in at least one port for introducing material into the molding cavity. A polybutadiene diol component and a diisocyanate component are provided and separately administered through the at least one port and into the molding cavity. The reaction of the polybutadiene diol and the diisocyanate occurs within the molding cavity to produce a polyurethane and subsequently a polybutadiene diol-based polyurethane golf ball component.
From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.

Claims

1. A golf ball comprising:

a core; and

a layer disposed over the core, the layer composed of a polyurethane material formed from the reaction product of a diisocyanate and a polybutadiene diol having a molecular weight of from about 300 to about 5,000, the polyurethane material having a Shore D hardness ranging from 30 to 75 and a flexural modulus ranging from 30 to 70 Kpsi, the layer having a thickness ranging from 0.010 inch to 0.20 inch;

wherein the golf ball has a diameter of at least 1.680 inches.

2. The golf ball according to claim 1 wherein the core is selected from the group consisting of a solid core, a multi-layer core, a wound core, a liquid core, a metal filled core and a foamed core.

3. The golf ball according to claim 1 wherein the layer is a cover layer.

4. The golf ball according to claim 1 wherein the layer is an intermediate layer, and the golf ball further comprises a cover disposed over the intermediate layer.

5. The golf ball according to claim 1 wherein said diisocyanate is selected from the group consisting of 4,4′-diphenylmethane diisocyanate; 2,4-toluene diisocyanate; m-xylylene diisocyanate; methylene bis-(4-cyclohexyl isocyanate); hexamethylene diisocyanate; meta-tetramethylxylylene diisocyanate; naphthalene-1,5-diisocyanate; 3,3′-dimethyl-4,4′ biphenyl diisocyanate; 1,4-diisocyanate benzene; phenylene-1,4, diisocyanate; 2,2,4-trimethyl hexamethylene diisocyanate; 2,4,4-trimethyl hexamethylene diisocyanate; and combinations thereof.

6. A method of forming a golf ball component including a polybutadiene diol-based polyurethane, said method comprising:

providing a mold adapted for forming a golf ball component, said mold defining a molding cavity and an inlet for introducing material into the molding cavity;

providing a polybutadiene diol-based polyurethane;

administering the polybutadiene diol-based polyurethane through said inlet and into the molding cavity; and

at least partially curing the polybutadiene diol-based polyurethane, thereby forming the golf ball component.

7. The method according to claim 6 wherein said diisocyanate is selected from the group consisting of 4,4′-diphenylmethane diisocyanate; 2,4-toluene diisocyanate; m-xylylene diisocyanate; methylene bis-(4-cyclohexyl isocyanate); hexamethylene diisocyanate; meta-tetramethylxylylene diisocyanate; naphthalene-1,5-diisocyanate; 3,3′-dimethyl-4,4′ biphenyl diisocyanate; 1,4-diisocyanate benzene; phenylene-1,4, diisocyanate; 2,2,4-trimethyl hexamethylene diisocyanate; 2,4,4-trimethyl hexamethylene diisocyanate; and combinations thereof.

8. The method of claim 6 further comprising:

providing a core component;

positioning said core component in said molding cavity prior to the introduction of the polybutadiene diol-based polyurethane;

wherein said polybutadiene diol-based polyurethane is administered into said molding cavity and forms a layer about the core component.

9. The method according to claim 8 wherein said layer formed from said polybutadiene diol-based polyurethane is a cover layer.