Background of the Invention

The present invention relates generally to plastic materials having phosphorescent or luminescent properties. More specifically, the present invention relates to a golf ball cover material having a highly visible color pigment and a phosphorescent or luminescent material impregnated therein, a golf ball made therewith and a molding process for making objects, specifically, golf balls, of plastic having highly visible color and phosphorescent or luminescent properties. Many sports and athletic events are played with balls. Some sports, such as golf, have play limited to daylight hours because of the expense in lighting a golf course or due to lack of suitable equipment to permit visualization of the sports equipment, such as the ball, during twilight or nighttime hours. The game of golf is enjoying expanding popularity. Most golf facilities are currently limited to use during the approximately ten hours of daylight, and the demand for course time is exceeding its availability. With the "graying" population migrating to the sunbelt during the winter months, the peak demand for course time occurs simultaneously with the shortest daylight hours. As competition for the available facilities increases, both golfers and course operators must seek alternative methods maximizing the existing capital investment without creating new courses. This may be accomplished by extending playing times through lighting the course, which is impractical and expensive, or by providing the player with equipment optimized for twilight and night use.

The most cost effective solution is develop a way to facilitate visualization of the sports equipment, e. g. , golf balls, golf tees, clubs, hole cups, hole flags, etc.. Many pieces of sporting equipment, including, without limitation, golf balls, golf tees, clubs, hole cups and hole flags, are or can be made of plastic materials. Attempts have been made

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to make one or more pieces of golf equipment with phosphorescent, luminescent or "glow-in-the-dark" properties. Examples of such attempts are illustrated in U.S. Patent Nos. 4,695,055, 4,878,674 and 4,957,297 which disclose a golf ball made of translucent solid plastic having a diametrically extending hole and a chemiluminescent light stick which is inserted into the hole after activation; U.S. Patent No. 1,622,421 which discloses a golf ball having a radium or other luminescent paint material applied into the dimples in the outer cover of the ball; U.S. Patent No. 5,007,647, issued April 16, 1991 to James D. Gulick which discloses a glow-in-the-dark golf ball having the glowing means continuously disposed on and around the inner core of a golf ball and being visible through a transparent cover; U.S. Patent No. 3,649,029 which discloses a golf practice apparatus which employs a luminescent material disposed on an adhesive backing attached to a club head, a putting target, a golfer's shoes, or gloves, in conjunction with an ultra¬ violet light source to provide an energy source for the luminescent material; or U.S. Patent No. 3,918,719 which discloses the use of balls, flags, hole cups, etc., made of a fluorescent material of the type which gives off light and does not require any light to activate it, for playing golf. Additionally, U.S. Patent No. 4,927,015 discloses a light box and luminous golf ball combination to facilitate night play. This patent teaches that it is known to mix a radiant color pigment with a luminous substance to form the ball cover, such that of the total constituents of the cover, the radiant color pigment/luminous substance mix constitutes about 0.001- 0.01 percent of the total cover constituents. Similarly, U.S. Patent No. 3,565,815 discloses the addition of a phosphor to polystyrene, at 420° F, at about 0.01 percent of specific "P ₁ - P ₃₀ type phosphors which include the sulfide and oxide phosphors" of the polystryrene to create an object having light radiant properties. This reference also teaches various conventional "types of phosphors that may be used are those such as CaSrSrBi; ZnCdS:Cu:Mg; Si0 ₂ :Mg; CdS.Cu; ZnO;

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ZnS:Ni:Mn; ZnS:Cu:Mn; ZnS:Cu:Ag; (Zn, Cd) S:Ag. Finally, U.S. Patent No. 3,445,551, discloses the manufacture of an inflatable pearlescent and phosphorescent ball, in which the preferred quantity of the phosphorescent pigment is 4% by weight of the plastic mixture.

The balls described in the foregoing patents all exhibit light emitting characteristics, but all have certain deficiencies, including, without limitation, poor image quality, poor image retention, poor play utility, safety concerns, or non-conformity with United States Golf Association (USGA) specifications, which prohibit their use in tournament play. None of the balls described in the foregoing patents exhibit optimum visible coloration, which permits effective daylight visibility, when combined with optimum phosphorescent or glowing capability, which permits effective night or low-light visibility for sufficient duration.

Golf balls have traditionally been made by bonding a cover about a resilient core. The cover is either compression molded from two half shells or is injection molded about the resilient core. Until about the mid-1960's, most golf ball covers were usually made of balata, a natural resin. However, since that time a golf ball cover material made of a synthetic ionomeric resin sold under the trademark SURLYN by E. I. DuPont de Nemours has captured the vast majority of the market.

Today, golf balls are typically made with a cover material molded about a core, as mentioned, with the core consisting either of a wound core or a solid core. Irrespective of the golf ball construction or the composition of the cover, it is customary in the art to apply a finish to the surface of the golf ball cover. The finishing process is an elaborate, complicated and highly developed process. A customary painting operation involves using an abrasive to prepare the cover surface, washing, drying, and then in successive steps, applying a primer, drying the primer, applying a first white coat, drying the first coat, applying

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a second white coat, drying the second white coat, stamping a trademark and numbers, and then finishing with a clear finish coat.

A myriad of different schemes have been developed to enhance the color brightness to achieve maximum visual appearance of the golf ball. U.S. Patent No. 4,798,386 discloses a translucent cover including an admixed fluorescent color pigment present in 2-6% by weight of the cover and fluorescent dyes present in 0.04 - 0.4% by weight of the cover. U.S. Patent No. 4,679,795 discloses the use of optical brighteners, present about 1-10% of a white pigment with about 0.01-0.5% of a compatible optical brightener, to enhance the cover color in the blue light spectrum to give the cover material a whiter appearance. While the fluorescent-colored and optically enhanced white golf balls increase visibility of the golf ball during daylight play, these enhanced-color cover materials do not affect the visibility of the ball during twilight or nighttime hours. Thus, a need exists for a golf ball, and process for making a golf ball, which conforms to USGA ball specifications, and which has a phosphorescent luminescence sufficient to permit and/or enhance the ability to play golf under low light conditions.

Summary of the Invention

Accordingly, it is a broad object of the present invention to provide a plastic material which may be molded, such as by injection molding, into a desired shape, to impart a light-emitting property to the material under low-light environmental conditions and have high color saturation to facilitate daylight visibility. More specifically, the present invention provides a golf ball of conventional construction, i.e., a solid or wound core bounded by a cover material, in which the cover material has color pigment, a phosphorescent or luminescent material admixed with the plastic cover material during the manufacture of the ball. The phosphorescent or luminescent material is activated by

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exposure to any source of ultraviolet radiation, such as an ordinary white light, e.g., a flashlight, incandescent light bulb, or from the sun, and emits light energy for several hours, and at least 3-5 hours, after activation. In accordance with the method of the invention, there is also provided a molding process which employs special mixing techniques to maintain an admixture of a phosphorescent pigment with a synthetic resin cover material during the molding process. These and other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the following more detailed description of the preferred embodiments thereof, taken with reference to the accompanying figures.

Brief Description of the Drawings

Fig. 1 is a cross-sectional view of a golf ball in accordance with the present invention having a solid core, a cover material having a phosphorescent pigment admixed therein and a transparent coating on top of the cover.

Fig. 2 is a schematic diagram of an injection molding process for making the golf ball of the present invention.

Detailed Description of the Preferred Embodiments Turning to Fig. 1, there is shown a golf ball 10 having a cover 14 provided about a solid core 16. A clear lacquer top coat 20 is provided about the cover 14 and is transparent as is well known in the art. The cover 14 contains a phosphorescent pigment to impart a phosphorescent or luminescent property under low-light conditions.

In accordance with the preferred embodiment of the present invention in the best mode of the invention, the core 16 may be either a solid or wound material. The cover 14 is made of a synthetic polymeric material which is capable of being admixed with both a color pigment and a phosphorescent material. The material for cover 14 will preferably be a thermoplastic material, which has the characteristics of,

without limitation, good flowability, moderate stiffness, high abrasion resistance, high tear strength, high resilience and good mold release. Preferred materials for use in accordance with this invention are ionic copolymers of ethylene and unsaturated monocarboxylic acid, such as ethylene-methacrylic acid polymers, sold under the trademark SURLYN from E.I. DuPont De Nemours & Company of Wilmington, Delaware. In addition to the preferred SURYLN resins, natural polymeric materials may be used in accordance with this invention. Balata and gutta percha are examples of natural polymeric materials adapted for use in accordance with the invention. A range of synthetic polymeric materials, other that the SURLYN resins, may also be used in the invention. Suitable homopolymeric and copolymeric materials which may be adapted for use in this invention are as follows:

1. Vinyl resins formed by the polymerization of vinyl chloride, or by copolymerization of vinyl chloride with vinyl acetate, acrylic esters and vinylidene chloride; 2. Polyolefins, such as polyethylene, polypropylene, polybutylene and copolymers such as polyethylene methylacrylate, polyethylene ethylacrylate, polyethylene vinyl acetate, polyethylene methacrylic or acrylic acid, or anhydride modified polyolefins; 3. Polyurethanes, such as prepared from polyols and diisocyanates or polyisocyanates;

4. Polyamides such as poly(hexamethylene adipamide) and those prepared from diamines and dibasic acids, from a ino acids, such as polycaprolactam, and blends of polyamides with SURLYN, polyethylene, ethylene copolymers, etc. ;

5. Acrylic resins, such as copolymers of meth lmethacrylate, acrylonitrile, styrene, maleic anhydride, or blends of these resins with poly vinyl chloride, elastomers or the like;

6. Thermoplastic rubbers such as the urethanes, olefinic thermoplastic rubbers such as blends of polyolefins

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with EPDM, block copolymers of styrene and butadiene, isoprene or ethylene-butylene rubber;

7. Polyphenylene oxide resins, or blends of polyphenylene oxide with high impact polystyrene; 8. Thermoplastic polyesters, such as polyethylene terephthalate (PET) , polybutylene terephthalate (PBT) , and polyethylene terephthalate/glycol modified (PETG) ; or

9. Blends and alloys, including polycarbonate with acrylonitrile butadiene styrene (ABS) , polybutylene terephthalate (PBT) , polyethylene terephthalate (PET) , styrene maleic anhydride (SMA) , polyethylene or elastomers, and polyvinyl chloride (PVC) with ABS or ethylene vinyl acetate (EVA) or other elastomers. Blends of thermoplastic rubbers with polyethylene, polypropylene, polyacetal, nylon, polyesters, cellulose esters or the like.

The foregoing list is not intended to be exhaustive nor limiting of the scope of the invention, but is illustrative of the wide range of polymeric materials which may be employed in the present invention. The addition of standard cover compositions, such as antioxidants, antistatic agents and stabilizers is regarded as within the purview of one skilled in the art.

The coloration and phosphorescence of the golf ball cover is formed by admixing a colored phosphorescent pigment with a polymeric material, which may be selected from the foregoing list of examples. Phosphorescent materials are available as pigmented powders, liquids, inks or as polystyrene, polyethylene or compatible-process injection molding pellets. Commercial suppliers of such phosphorescent materials include:

1. MoonGlow, Inc., Reynolds, Missouri

2. Per a-Glo Industries, Inc., San Diego, California

3. Shannon Luminous Materials, Inc., Santa Ana, California 4. United Mineral & Chemical Corporation, New York, New York

5. Natmar, Inc., Cincinnati, Ohio

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6. American Phosphor Works, Toledo, Ohio A wide variance exists in the specific gravity of the phosphorescent materials relative to ionomeric resins, such as SURLYN. Additionally, in order to achieve optimum phosphorescence and coloration, different amounts of phosphorescent pigment powder are required for different colors. Thus, it is necessary to produce a substantially homogeneous admixture of the phosphorescent pigment with the polymeric material when molding the cover, to produce a substantially uniform color and phosphorescence.

The preferred method for making the colored phosphorescent materials of the invention, including golf balls, is illustrated in Fig. 2 and represented by the examples set forth below. In accordance with the preferred method of the invention, separate hoppers are provided for the polymeric plastic 32, for the phosphorescent material 34 and for the color pigment 36. Dual mixing augers 35 are employed to feed specific metered amounts of the polymeric material 32 and the phosphorescent pigment 36 into an injection molding screw mechanism 37. The augers may be oriented in opposing position or may be perpendicularly oriented relative to each other. Use of the double auger injection system assures an adequate suspension of the phosphorescent/color pigment admixture within the polymeric matrix and in the injection molding screw mechanism 37. The screw mechanism 37 conveys the phosphorescent/color pigment/polymeric plastic admixture to the ^' mold barrel 38, which then meters and injects the admixture into the mold 40. A plurality of controls 42, as are known in the art, may be provided as discrete units or as a single control for all molding functions, are provided.

EXAMPLE I

A solid core was used for the golf ball. The solid core was white in appearance and was from a commercially available golf ball. The cover composition was prepared by admixing

76% by volume SURLYN with 24% by volume MoonGlow, Inc. Lunar

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Green phosphorescent pigment powder. Volume percentage mixture was accomplished via linear vibrator which meters and dispenses the correct percentage into the SURLYN matrix. The admixture was injection molded into a hexahedron 398 dimple pattern golf ball mold around the solid core. Injection molding was performed under the following parameters:

Barrel 225' Ball Core 65° F Temperature Temperature

Back Pressure 100 lbs Primary 1500 lbs Pressure Screw Speed 45 RPM Primary Time 5 sec.

Injection 1 in/sec Secondary 1100 lbs Speed Pressure

Cure Time 45 sec. Secondary 20 sec. Time

Cavity 85° F. Shot Size Cavity Temperature Dependent

The resulting golf ball had good color saturation and, after exposure to a light source, exhibited good phosphorescence under low light conditions for more than three hours, which did not substantially diminish for over five hours, and excellent visible color saturation.

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EXAMPLE II

Example I is repeated, except that MoonGlow, Inc. Lunar

Hot Pink phosphorescent pigment powder was employed at 26% by volume in 74% by volume SURLYN. A comparable golf ball was obtained.

EXAMPLE III

Example I is repeated, except that MoonGlow, Inc. Lunar Orange phosphorescent pigment powder was employed at 30% by volume in 70% by volume SURLYN. A comparable golf ball was obtained.

EXAMPLE IV Example I is repeated, except that MoonGlow, Inc. Lunar Yellow phosphorescent pigment powder was employed at 24% by volume in 76% by volume SURLYN. A comparable golf ball was again obtained.

EXAMPLE V Example I is repeated, except that phosphorescent pigment polyethylene pellets are metered into the mixing hopper at 30% weight by volume of the SURLYN. The molding pellets are blended at elevated temperature in a mixing hopper and injection molded around a wound core. The resulting golf ball exhibits good color saturation and good phosphorescence under low light conditions.

EXAMPLE VI

Example I is repeated, except that the molding parameters are varied as follows:

Barrel 80-500' Ball Core 65° F - Temperature Temperature Ambient

Back Pressure 50-100 lbs Primary 500-1500 lbs Pressure

Screw Speed >45 RPM Primary Time 5-10 sec.

Injection 1-5 in/sec Secondary 500-1500 lbs Speed Pressure

Cure Time 25-45 sec. Secondary 12-20 sec. Time

Cavity >85° F.- Shot Size Cavity Temperature <500° F Dependent

Those skilled in the art will understand that the cure time is dependent upon part size, i.e., a larger part will require a longer cure time, that the secondary time is dependent upon the mold gate size, and that the cavity temperature is dependent upon the stock temperature and the cure time. It has been found that the phosphorescent material begins to degrade at a molding temperature of 225° F and is extinguished at 500° F. Accordingly, lower molding temperatures will facilitate longer glowing characteristics, and are preferred.

The foregoing examples are presented and intended to illustrate representative processing parameters which have been found to yield golf balls with covers having optimum visible coloration and phosphorescent or luminous characteristics. Variations on molding parameters for

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different types of articles are deemed to be within the ordinary skill of the artisan.

Thus, in accordance with the preferred embodiment and best mode contemplated for the invention, the phosphorescent material is admixed with a color pigment, such that the phosphorescent material is present in the range of about 0.001 to about 2%, by volume, of the color pigment, this color/phosphorescent admixture is then be admixed with the polymeric cover material in a mixture of about 10% to about 40% by volume, preferably about 20% to about 35%, in the polymeric material. Conversion from volume percent to weight percent of SURLYN yields a preferred weight percent range of about 5% to about 10% by weight of the color/phosphorescent admixture in the polymeric cover material. Those skilled in the art will understand and appreciate that the claims appended hereto cover all changes and modifications to the preferred embodiment of the invention disclosed herein for the purpose of illustration which do not constitute departures from the scope and spirit of the invention.

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