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.