JPS6347473B2 - - Google Patents

Description

Claim 1: Consisting of a solid or wound core and a cover having a foam layer, the cover is formed from an ionic copolymer of an olefin having 2 to 5 carbon atoms and an unsaturated molar carboxylic acid metal salt. characterized in that at least one foam layer is formed inside the non-foamed outermost skin,
Golf ball. 2 The cover is an ionic copolymer of an olefin having 2 to 5 carbon atoms and a sodium salt of an unsaturated monocarboxylic acid having 2 to 8 carbon atoms, and 2 to 5 carbon atoms.
2. The golf ball of claim 1, wherein the golf ball is formed from an ionic copolymer selected from the group consisting of ionic copolymers of olefins containing olefins and zinc salts of unsaturated molar carboxylic acids having 2 to 8 carbon atoms. 3 The cover is an ionic copolymer of an olefin having 2 to 5 carbon atoms and a sodium salt of an unsaturated monocarboxylic acid having 2 to 8 carbon atoms, and 2 to 5 carbon atoms.
Claim 2, wherein the ionic copolymer is formed from a mixture of an ionic copolymer selected from the group consisting of an ionic copolymer of an olefin of Golf ball. 4 The cover is made of a copolymer of ethylene and a sodium salt of an unsaturated monocarboxylic acid having 3 to 8 carbon atoms.
75% to about 25% and a copolymer of ethylene and a zinc salt of an unsaturated monocarboxylic acid having 3 to 8 carbon atoms.
4. The golf ball of claim 3, wherein the golf ball is formed from a mixture comprising about 75%. BACKGROUND OF THE INVENTION Golf balls have traditionally included covers formed from polymeric materials. In this regard, traditional golf balls with covers formed from Balata rubber are notable. The physical properties and especially the feel of the loose rubber cover when struck with a golf club have become the standard in the industry.
In recent years, golf balls have begun to include covers formed from synthetic polymeric materials such as polyolefins and particularly ionic copolymers of polyethylene, polyurethane, and olefins. The above-mentioned olefin ionic copolymer was manufactured by DuPont (E, I.Du
It was marketed in the mid-1960s by Pont De Nemours & Co., Inc. (Wilmington, Del.) and sold under the trade name Surlyn. Cover compositions based on Surlyn resins have become very popular and are very advantageous in that the resulting covers have excellent cut and abrasion resistance. It is well known in the golf world that golf balls with Surlyn resin covers are more cut resistant than balls with balata covers. These Surlyn covered golf balls have received widespread consumer praise. Approximately 60% of golf balls sold in the United States in 1976 contained Surlyn covers. Golf balls containing Surlyn covers are generally described in US Pat. No. 3,454,280, issued July 8, 1969. Most of the Surlyn resins sold by DuPont contain zinc or sodium ions.
A variety of Surlyn resins with different physical properties are commercially available from DuPont. The physical properties of these various resins are described in readily available DuPont technical reports. The basic Surlyn resins useful as golf ball cover materials in this invention are Surlyn A1605 and Surlyn A1557. Mixtures of various Surlyn resins are likewise very advantageous as stock materials for the cover. A suitable mixture for use as a cover stock material is disclosed in U.S. Pat. No. 3,819,768 (issued June 25, 1974).
is described in detail. Although Surlyn resin is highly advantageous in its resistance to abrasion cutting, its use alone or in mixtures has significant disadvantages as a stock material for golf ball covers. The reason is that the feel of the ball when hit with a golf club is significantly different from the feel of a traditional balata covered golf ball. When you hit a golf ball with a golf club, it makes an audible sound. This sound is commonly referred to as a golf ball click.
Again, the click of a Surlyn covered golf ball is significantly different than the click of a Balata covered golf ball. For some golfers, and especially for those who have consistently used balata covered golf balls, the changes in click and feel in Surlyn covered golf balls are dissatisfying. Some advanced golfers are able to hit the golf ball in such a way as to put a significant amount of backspin on the ball and control the ball's flight. It is desirable for golfers to be able to control the flight of a golf ball and apply backspin to the ball in order to control the movement of the ball at the end of its flight. For example, if you apply backspin to the flight of the ball, you can stop it exactly when it hits the green (otherwise it would bounce forward). Whether backspin can be applied to a golf ball is related to the degree of deformation of the golf ball when it is hit with a golf club. Adding spin to these traditional balls is relatively easy since traditional balata covers are more deformable. On the other hand, Surlyn covered golf balls are not as easily deformed as balata covered golf balls due to the nature of the cover, making it more difficult to apply sufficient backspin to these balls. The advantages of such control will be explained in detail later. A standard commonly referred to as the coefficient of restitution is one of the criteria useful for determining the rebound characteristics of a golf ball. The properties of cover stock have a substantial relationship to the coefficient of restitution of a given golf ball. Utilizing the present invention, one skilled in the art can vary the coefficient of restitution of a given golf ball to a much greater degree than was possible using prior art covers. A detailed explanation of the results of the coefficient of restitution regarding the present invention will be provided later. Competitive advertising campaigns comparing Balata covered golf balls to Surlyn resin covered golf balls take advantage of the deficiencies of Surlyn resin covered golf balls discussed above. In particular, these advertising campaigns emphasize the difference in feel and the difficulty of applying spin to golf balls with Surlyn resin covers. Some advertising campaigns even go so far as to compare Surlyn resin-covered golf balls to stones. By incorporating the present invention into the construction of a golf ball, it is possible to first achieve and selectively vary cut resistance, abrasion resistance, coefficient of restitution, feel, click and the ability to impart backspin to the golf ball. can. Broadly speaking, by utilizing the present invention these physical properties can be altered to an optimal degree by varying the apparent density and distribution of pores in the golf ball cover. As a result of these changes, those skilled in the art can produce golf balls with the desirable qualities of both balata and Surlyn resin covered golf balls.

[Brief explanation of drawings]

FIG. 1 is a front view of a conventional golf ball. FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1 and shows the cover of the present invention on a solid core golf ball. FIG. 3 is an illustration showing a cover of the present invention on a wound core golf ball. FIG. 4 is a cross-sectional view of one embodiment of a cover of the present invention including a central foam layer sandwiched between non-foam shells. FIG. 5 is a micrograph showing a cross section of an actual cover of the present invention having the structure shown in FIG. FIG. 6 is a photomicrograph showing a cross section of an actual cover of the present invention, which is made entirely of a foamed layer except for the non-foamed outermost shell skin. FIG. 7 is an explanatory diagram showing the excellent high-speed impact characteristics of the golf ball according to the present invention. FIGS. 8 and 9 are explanatory diagrams showing the excellent low speed impact characteristics of the golf ball according to the present invention. FIG. 10 and FIG. 11 are cross-sectional views showing the relationship between the shape of the nozzle and the mold used for injection molding of the cover in the example. PREFERRED MODES FOR CARRYING OUT THE INVENTION In broad terms, the present invention is directed to the use of foam materials as the cover stock for conventional golf ball centers. As described later in the detailed description, the foamed cover stock of the present invention can have a uniform foamed cross-section, a variable foamed cross-section,
Four or more non-foam shells can be included at any time. The foam coverstock of the present invention can be formed from any foamable synthetic polymeric material. Such materials are known in the art and are generally formulated with blowing agents, nucleating materials, and other additives necessary to create the desired structure. Preferred polymeric materials for use according to the invention are:
DuPont De Nemours &
(Wilmington, Del.) under the trade name Surlyn, an ionic resin consisting of a copolymer of ethylene and an unsaturated molar carboxylic acid. According to a preferred embodiment of the invention, the intumescent cover in question is formed from either a zinc or sodium ionic copolymer of ethylene or a mixture thereof. The sodium copolymer is sold by DuPont under the trade name Surlyn 1605, and the zinc copolymer is sold under the trade name Surlyn 1557. The use of monoionic copolymer materials of polyethylene as cover stock for golf balls was introduced in 1969.
No. 3,454,280, issued July 8, 2006. The use of mixed Surlyn resins according to this preferred embodiment is described in the detailed description in US Pat. No. 3,819,768, issued June 25, 1974. Ionic copolymers of the type suitable for use in the present invention are further described in the detailed description in US Pat. No. 3,264,272, issued Aug. 2, 1966. Referring to the figures, it can be seen that FIG. 1 shows a standard golf ball construction 2 having a number of conventional dimples 4. The dimples 4 are molded into the cover material which is the subject of the invention. As used herein, golf ball 2 is generally meant to include golf balls having a solid center or a wound center. Referring to FIG. 2, golf ball 2 can be seen to have a solid center portion 6 which is in turn covered by a foam cover 8. Referring to FIG. Generally, the central part 6 consists of highly cross-linked polybutadiene spheres. The engineering of manufacturing solid cores such as core 6 is known in the prior art and does not form part of the present invention. Referring to FIG. 3, it can be seen that this exemplary golf ball 2 has a wound center portion 10 which is in turn covered by a foam cover 8. Referring to FIG. Generally central part 1
0 consists of a central sphere (not shown) wrapped with an elongated length of elastomeric polymer thread to create a sphere of constant size. Techniques for manufacturing balls of the type shown with wound center 10 are well known in the prior art and do not form part of the present invention. FIG. 4 shows a preferred embodiment of the invention for use in conjunction with a central portion 6 which may be of solid or wound type. In this embodiment, the cover 12
includes a central foam layer 14 sandwiched between non-foam shells 16 and 18. The non-foamed shells 16 and 18 are formed in-situ by various process parameters when molding the cover 12 over the center 6. Shells 16 and 18 may be varied and formed by a number of techniques. For example, the shells 16 and 18 are formed at various molding temperatures during the initial stages of the injection molding process, and at various other parameters such as melting temperature, injection time, injection rate, injection pressure, nozzle shape, gating, venting, It can be formed by controlling the holding pressure, holding time, injection amount, blowing agent concentration, core material concentration, polymerization composition, casting surface treatment, and casting smoothing. Figure 5 shows a cross-section of an actual cover with the structure shown in Figure 4, and Figure 6 shows a cross-section of an actual cover with the entire foam layer except for the non-foamed outermost skin. This is a microscopic photograph. As will be apparent to those skilled in the art, the apparent density of the foam layer is
Variations can be made by those skilled in the art by varying the process parameters described above when molding the cover onto the center. For purposes of this invention, when expressing density and specific gravity, they are expressed in terms of "apparent density" and "apparent specific gravity." These terms take into account the fact that the cover stock of the present invention is non-uniform, containing shells and various cell structures. These terms take into account such variables and indicate the actual density and specific gravity of the average structure. The solid core used in accordance with the present invention has a diameter of approximately
It is 1.50 inches. According to modern thinking, all golf balls are between 1.680 and 1.690 inches in diameter. Therefore, the thickness of the cover of the ball of the present invention is about half the difference between the center size and the finished ball size, or about 0.090 inch. This cover thickness has been found to be generally advantageous and functional when used with the present invention. Naturally, it is also possible to use a larger diameter center part to reduce the thickness of the cover. Generally, the thickness of the cover should not be reduced to the point beyond which functional foaming is no longer possible. Although not all parameters of cover thickness have been investigated, in general it appears that reducing cover thickness below 0.060 inch will result in no functional foaming. It is within the scope of the present invention to utilize a thicker cover than the standard of about 0.090 inches. Thicker covers utilized in this embodiment range from about 0.090 to about
0.125 inch is also acceptable. If a thicker cover is used, the diameter of the center will naturally be correspondingly smaller. As is well understood by those skilled in the art, the diameter of a wound core is typically larger than that of a solid core. During the process of applying the cover over the center, the wound center is compressed with mesh so that the effective size of the finished center is the same as the 1.50 inch size described above for the solid center. Additional substances can be added to the cover composition within the scope of the invention to the extent that they do not adversely affect the basic new properties of the cover according to the invention. Such substances include colorants, including dyes and pigments, excipients and similar additives.
Additives such as antioxidants, antistatic agents and stabilizers are also added. The upper limit for the amount of additive is usually about 5 percent by weight of the product. The golf ball cover material of the present invention can be applied to the center by any standard method. For example, the cover material can be injection molded directly around a pre-placed center, or two half shells of the cover can be made with the cover material of the invention. These half shells are then placed around the center and fused together to form the finished golf ball. The molding technique used to produce the finished golf ball is also not an essential part of the invention. However, the cover compositions of the present invention can utilize many standard manufacturing methods to create a finished golf ball. The technique utilized must, of course, provide sufficient physical conditions to allow foaming. As briefly mentioned above, the cover material of the present invention is applied in a conventional manner onto a standard center. Either solid or wound cores can be used in accordance with the present invention. Regarding the wound center part,
The thread-like material is wrapped around either a solid core or a liquid-filled spherical shell. The thread-like material wrapped around this small core is either thread-like or tape-like. Regarding balls with solid centers, these generally consist of a sphere whose center is made of a resilient polymeric material. Since this core material is not an essential part of the invention, a detailed description of the core material is not considered necessary. However, it can be said that the cover material of the present invention can be utilized in conjunction with any standard golf ball center. As mentioned above, the golf ball cover of the present invention can be used as a means of varying or adjusting the coefficient of restitution. Generally, the repulsion factor of a golf ball indicates the resiliency of the ball in question, and therefore the distance the ball will travel when struck with a golf club. Although both the center and the cover contribute to the coefficient of restitution, for the purposes of this invention we will only deal with the coefficient of restitution as influenced by the cover material. Coefficient of restitution is generally measured by hitting a completed golf ball against a hard surface at a constant speed. Measure again the velocity of the ball as it rebounds from that surface. The ratio of rebound speed to initial speed is the coefficient of restitution. The coefficient of restitution is directly related to the resiliency of a golf ball and how far it travels when struck with a golf club, holding other variables constant. The elasticity of a golf ball is generally determined by the United States Golf Association (United States Golf Association) through a test called the initial velocity test.
regulated by the States Golf Association. In this test, a golf ball is struck with a rotating club face. The peripheral speed of the face of a rotating club is approximately 146 feet/second. The velocity of a ball struck by the face of the club is measured as it passes through two screens of light located in front of the face of the club. The maximum allowable limit for a golf ball when measured in this manner is 225 feet per second at 75 feet. This upper standard value of 225 feet/second corresponds to a coefficient of restitution of approximately 0.795. The cover material of the invention is particularly advantageous with respect to the above-mentioned coefficient of restitution criteria, and using the invention
It is possible to make golf balls with solid centers that are very close to the maximum limit of 0.795. According to one embodiment of the invention, this objective is achieved by forming a center that exceeds the 0.795 limit and then covering said center in order to reduce the coefficient of restitution to 0.795. The ability and extent to which the coefficient of restitution can be varied will be shown in the Examples below. The data of these examples show that changing the stock material of the cover from a solid material to a foam material changes the coefficient of restitution of a given golf ball. It is true that it is desirable to approach the maximum value of the coefficient of restitution mentioned above without exceeding it, but
It is a matter of conjecture whether anything other than approaching the specified maximum limit is desirable.
The data in question sufficiently demonstrate that it is possible to vary the coefficient of restitution of a given golf ball using the present invention. While there may be design latitude in a golf ball system provided by use of the present invention, such design latitude did not exist in the prior art. The foam covers of the present invention are formed by foaming the polymeric material in situ during the operation of forming the cover over the core. A wide range of blowing agents can be used for this purpose. Examples of suitable organic blowing agents are azobisformamide, azobisisobutyronitrile, diazoaminobenzene, N,N-dimethyl-
N,N-dinitroterephthalamide, N,N-dinitrosopentamethylene-tetramine, benzenesulfonyl-hydrazide, benzene-1,3-disulfonylhydrazide, diphenylsulfone-
3,3-disulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, barium azodicarboxylate, butylamine nitrile, nitrourea, trihydrazino-triazine, phenylmethyl-urethane-p-sulfone hydrazide and inorganic Blowing agents such as ammonium bicarbonate and sodium bicarbonate. Blowing agents generally function by pyrolysis, which generates gas in situ, which is absorbed by the melt. When the pressure is removed, the melt expands and foams. In addition to this operation, it is commercially practiced to inject gases such as nitrogen, trichloromonofluoromethane, pentane, carbon dioxide, etc. into the melt under pressure. Gas is absorbed and the melt expands and foams when the pressure is removed again. A preferred embodiment of the invention uses a thermally decomposable, nitrogen-producing blowing agent. It will be appreciated that the proportion of blowing agent used in accordance with the present invention will vary depending on the physical and chemical properties of the blowing agent used and the desired apparent density of the resulting golf ball cover. According to a preferred embodiment of the invention, Ficel EPA is
Use in amounts of 0.1-0.5%. Ficel EPA is the trade name used for a blowing agent that is essentially an azodicarbonamide. Ficel EPA, Sobin Chemicals,
Inc. (Sobin Park, Boston, Massachusetts,
02201). The apparent density of foamed golf ball covers according to the present invention can also be varied by injection techniques.
The injection technology in question is well understood by those skilled in the art and includes a variety of variables, including ram advance time, injection speed, shot size, gate size, mold vent holes, injection pressure, holding pressure, and the like. Depending on the nature of the blowing agent used, the golf ball cover of the present invention can have a single cell structure or an interconnected cell structure, with a single cell structure being preferred. In either case, the outermost shell should be a non-foamed skin. As mentioned above, the golf ball cover of the present invention can be used in a number of ways with a suitable center. According to a preferred object of the invention, the golf ball cover is used on the core by injection molding. A preferred injection molding technique involves preparing a masterbatch of plastic molding powder of defined composition.
The masterbatch is dry mixed and contains one or more polymeric materials, colorants, antioxidants, blowing agents, and the like. Naturally, the blowing agent is incorporated into the polymeric material at a temperature below its decomposition temperature. Next, this masterbatch is made into pellets. Next, place the center of the golf ball into the mold.
The masterbatch pellets described above are placed in an injection molding machine and the resulting melt is injected into a mold, thus foaming the polymeric material and spreading the flow to adhere to the core. This molding process creates dimples on the cover. The resulting golf ball is cooled and the substantially completed golf ball is removed. Another important aspect of the present invention is that the use of foam cover stock material reduces the net cost of golf ball covers. Good quality polymeric materials suitable for use in golf ball cover stock materials are relatively expensive. For example, the cost of the Surlyn resin, including in-factory operations prior to injection molding to make golf ball cores, is at least 80 cents/lb.
The method of the present invention maximizes the utilization of golf ball cover stock material. That is, more golf ball covers can be made per pound of material.
If we look at the invention properly from a cost perspective, it is less expensive to make a golf ball cover from a foamed polymeric material where the cells include foaming gas than to make the cover from a non-foamed material. It is clear that the low cost feature is very advantageous when the cost of the polymeric material is taken into account. The synthetic golf ball cover provided by the present invention is also advantageous in that the apparent specific gravity of the cover stock is lower than the specific gravity of a ball covered with non-foamed material. According to a broad aspect of the invention, the synthetic cover stock including the non-foamed shell can have an apparent specific gravity of about 0.65 to about 1.50. The preferred range of this apparent specific gravity is about 0.65 to about 1.25,
The most preferred apparent specific gravity is about 0.75 to about 0.80. These specific gravity must be compared to the specific gravity of the non-foamed material to make a comparison. This variation in specific gravity can be obtained by changing the foam structure of the golf ball cover. It should be noted for reference that the Surlyn resin used in conventional golf balls is 0.940 ~
It has a specific gravity of 0.965. The physical and flight properties of a golf ball are influenced in part by the resulting weight distribution of the finished golf ball. In some instances, it is desirable to concentrate the weight as close as possible to the ball's center of gravity. Considering this fact, the present invention, which concentrates a greater proportion of the total weight in the center of the ball compared to conventional balls with non-foamed covers, is a natural advantage in ball design. . Additionally, and for the first time, the present invention shows that golf ball manufacturers can modify the dynamics and flight characteristics of the resulting golf ball by varying the density of the cover stock material. This weight distribution results in less rotational inertia to overcome and therefore allows more spin to be imparted when striking the golf ball with the club. Prior to the present invention, this kind of thinking did not hold true. In addition to the above-mentioned advantages resulting from the state of weight distribution, the present invention is significant in that the golf balls obtained by the present invention have different high- and low-velocity impact characteristics compared to similar balls with non-foamed covers. It's advantageous. At high velocity impact, the cover distorts and the cover contacts the club face over a substantially larger contact area than a ball with a non-foamed cover. The result is better control of the ball, allowing important ball maneuvers during play, such as backspin, drawing, and fading. The energy required to warp the cover at high speed is less than with conventional covers. This allows more energy to be applied directly to the inner core material at impact, increasing the flight of the golf ball. On the other hand, this same foam covered ball has different low-velocity impact characteristics, which is useful for puttying. At low-velocity impacts, foam covers produce the same dissipating effect as balata-covered balls, so at low-velocity impacts, foam-covered balls require greater impact force than conventional balls to move the same distance. It is well known that the more force required to move the ball a certain distance within the putting range, the greater the chance of failure in the putting attempt. Examples of these control characteristics in low velocity impacts are as follows. If a ball, for example a ball with a non-foamed Surlyn cover, bounces off the putterface, the chances of failure are very high. In contrast, failure is minimized in ball movements where more energy is required to impart motion to the ball. Another important advantage of this low velocity impact characteristic in puttering is that, as a result of the energy absorption discussed above, a golf ball that leaves the putter face begins to truly spin sooner than a ball with a non-foam cover. Balls with prior art non-foamed covers tend to skid before starting true rotation on the green because the cover is unable to absorb the energy at low velocity impact. It should be noted that the exact physical properties described above with respect to the present invention can be varied by adjusting the cell size, its distribution, cover thickness, and changes in the apparent density of the foam cover material. be. Because of the interaction described above between the ball and club face of the present invention, superior control and feel can be achieved. As a result of this control and feel, skilled players are able to draw and fade at will, and on approach to the green, have more backspin to help the ball bite into the grass and come to rest better. can. The controllability of the golf ball of the present invention when struck with a golf club is illustrated in FIGS. 7, 8, and 9 by its ability to provide desirable high and low velocity impact characteristics. do. In the tests described in FIGS. 7 and 8, the impact is performed by feeding a sample ball into a golf ball firing device that shoots the ball against a steel plate. To create a trace of the problem, cover the surface of the steel plate with carbon-type transfer paper. The purpose of the high speed impact tests in Figures 7 and 8 is the same. In Figure 7, trace C was made with ball A. Ball A is a Surlyn covered golf ball having a center section A as described below and a golf ball cover sold under the trade name TOP-FLITE. The cover for this ball is made according to the method of U.S. Pat. No. 3,819,768 (issued June 25, 1974). Trace D in Figure 7, created by ball B, is similar in all respects to ball A used to create trace C, except that the cover stock is foamed using Ficel EPA blowing agent 0.3%. It was made from balls that are almost identical. The resulting golf ball is similar to the ball described in Example 1 and illustrated in FIGS. 2 and 4. It is easy to see that trace D is larger than trace C. Trace C is 1.020 inches while trace D is 1.068 inches. Therefore, according to the above theory, the distortion of the surface of ball B due to the steel plate is much greater than the distortion of the surface of ball A. In addition to the distortion on the surface of ball B, which is larger than ball A, traces of the dimple pattern on ball B are also visible on ball A.
It can be seen that ball B is wetted out to a greater extent since it is not as clear as the trace of the dimple pattern. Therefore, you can convey greater control to the ball. In FIG. 8, balls "A" and "B" as described with respect to FIG. 7 are fired at 80 feet per second in accordance with the test procedure of FIG. Ball "B" forms a trace "E" 0.789 inches in diameter. Ball "A" forms a trace "F" 0.750 inch in diameter. As can be seen from the difference in diameter of these marks, ball "B" deformed more significantly than ball "A" during this test operation. FIG. 9 relates to the low speed impact characteristics of the golf ball of the present invention. As shown in this figure, balls "A" and "B" described above in connection with FIG. 7 were used in this test. Drop these balls from a height of 100 inches onto a steel plate. Ball “A” is the diameter
A trace "G" of 0.416 inches was formed. Ball "B" formed a trace "H" 0.422 inches in diameter. From these differences in diameter, it can be further seen that the ball "B" with the trace "H" is much more likely to wet out than the ball "A" with the trace "G".
In addition to the traces "G" and "H" regarding this test, it is also noted that in this test the rebound height of ball "A" is 76 inches and the rebound height of ball "B" is 73 inches. Should. This difference in rebound further indicates that the balls of the present invention have a softer feel on the face of a golf club. Think of this test as analogous to a putting shot on a golf course. Regarding the tests of FIGS. 7, 8, and 9, it should be noted that these tests were performed on balls with identical centers to achieve maximum uniformity. However, this is not possible or practical in the manufacture of commercially available balls. This is because in reality the cover for ball 'B' is significantly lighter than the cover for ball 'A'. From a practical standpoint, because of this difference in weight, the center weight of ball "B" is adjusted to be heavy enough to compensate for the difference in cover weight. If this adjustment is actually made, the difference in the traces of balls "A" and "B" in Figures 7, 8, and 9 will be because ball "B" has a larger mass. It is thought that the difference is greater than the difference mentioned above because it has a larger kinetic energy for impact. Table 1 below shows data from impact tests conducted on the balls of the present invention in comparison to standard commercially available balls. In the batting test, balls "C" were two standard commercially available balls sold under the trade name "Top Flite." Ball "B" according to the invention and generally as described in Example 1 below.
This is a ball made according to Ball "C" has a coefficient of restitution of 0.795. Ball “B” has a coefficient of repulsion
It is 0.782. Regarding the data in Table 1, ball "B", which is the ball of the present invention, is faster than ball "C" at 145 feet/second.
It has a more advantageous carry. At 160 feet/second, ball ``C'' has a slightly better carry than ball ``B''. The advantageous carry of ball ``B'' at 145 feet per second is considered to be particularly significant in view of the advantageous properties of the ball of the present invention listed above as a reflection of ball ``B''. Regarding the data in Table 1, it should be noted that a club speed of 145 feet per second is high for the average golfer's ability to hit a golf ball. A club speed of 145 feet per second corresponds to an advanced golfer, such as a 4 or 5 handicap golfer. On the other hand, in terms of relative importance, the 160 ft/sec test does not seem to be a meaningful comparison of the average golfer's abilities since most golfers do not reach club speeds of 160 ft/sec. . It is particularly noteworthy that ball "B" travels approximately the same distance as ball "C" since the coefficient of ball "B" is significantly less than that of ball "C." This fact is believed to demonstrate the particularly advantageous properties of the ball of the invention. This is because clearly more energy from the golf club head is transferred through the cover to the core and significantly less energy is absorbed by the cover. This advantage allows the United States Golf Association (USGA)
It would be possible to create a ball that travels farther while fully adhering to the specified coefficient of restitution of 0.795, which is correlated to the initial velocity determined by
It should be noted that the United States Golf Association recently added new rules regarding the total distance the ball can travel. According to this rule, a ball launched by a machine under specified conditions cannot travel farther than 280 yards plus 8%. This stipulated
This rule is not believed to be restrictive with respect to the balls of the present invention, since 280 yards is beyond the limits of what a human can hit a golf ball. I mention this rule because I want the above data to be evaluated from the correct perspective. Hit Method The test for total flight distance with a driver and a 5-iron is as follows. Balls ``B'' and ``C'', 6 each, are hit 3 times using a #1 driver at a club head speed of 145 feet/second.
Fire each time. Each ball is then fired three times using a 5-iron at 145 feet/second. Repeat this procedure at 160 feet/second.
The blow was made using a Tru-Temper striking device (product number 7) from Tru-Temper Corporation (1623 Euclid Avenue, Cleveland, Ohio).
I went there using Tests were conducted at 68-70〓 and wind speeds of 0-2 miles per hour. All distances are in yards.

【table】

[Table] As used in the claims and examples below to define golf ball components, the term ``consisting of'' refers to amounts of other ingredients in the composition described therein that substantially interfere with its properties and characteristics. It is meant to exclude the presence of , but to permit the presence of other components in amounts that do not adversely affect the aforementioned properties and characteristics. In this specification, the term "wet out" is used to describe the deformation of a golf ball when it comes into contact with a golf club. This refers to the extent to which a spherical golf ball deforms along a flatter, non-deformable golf club face. The present invention will be explained below with reference to examples. These examples are intended to illustrate the invention and are not intended to limit the invention. Examples In the examples described below, unless otherwise specified,
For golf balls with solid centers, all centers are approximately 1.50 inches in diameter. Three types of centers were used. The restitution coefficient of center A is 0.78
±0.010 and compression is 85±10PGA. Center B
has a coefficient of restitution of 0.765±0.010 and a compression of 60±10 PGA. The center C has a restitution coefficient of 0.790±0.010,
Compression is 100±10PGA. These cores consist (essentially) of highly crosslinked polybutadiene rubber where the main crosslinking agents are peroxides and heavy metal organic salts. In the example, when using the wound center part D,
The center has a diameter of 1.560±0.010 inches and a compression of 90±
It is 10PGA and has a coefficient of restitution of 0.825±0.015. The wound center is formed in the conventional manner by wrapping a rubbery thread containing high volume polyisoprene over a solid core of high modulus polybutadiene 1.125 inches in diameter until it is compressed and sized as described above. Manufacture. In all of the following examples, the covers are made using injection molding techniques (injecting the coverstock material into the mold by first placing the center in the mold and allowing the coverstock material to flow around the previously placed center). was applied to the center of each.
The temperature of the center and mold is approximately 70°C. The nozzle used for injection was a standard self-closing type. Nozzle 31 as shown in FIG.
When the cover stock material is applied to the mold 32, the valve 33 is opened and the cover stock material is injected into the mold 32 in the direction of the arrow. As shown in FIG.
2, the valve 33 automatically closes due to the pressure within the nozzle. The operating conditions such as nozzle temperature in each example are as follows.

[Table] The circulation time of the injection molding process is such that sufficient time is allowed for the material to harden around the previously placed center. Generally the circulation time is about 30-50 seconds depending on the mold cooling rate.
It will be appreciated by those skilled in the art that the circulation time will vary depending on the nature of the polymeric material used as the foam cover stock material and especially its melting point. Here, "compression" refers to the compression of the ball and ball components using the Riehle Model.
It was measured using a #501A-1/type device, and the deformation under constant impact under constant load was measured. Throughout these tests, the constant load was 200 pounds. The data obtained from the above test is then converted to PGA compression using a simple formula. In other words, if you subtract the Liele display from 160, you get the PGA display.
Here, "PGA compression" has the same meaning as is widely used as a standard in this industry. In this test one record is taken from each of the 12 samples and the average of the test is defined as its compression. To determine durability data for barrel tests, 12 balls are fired from a 100-round air cannon at 135 feet per second at room temperature into an octagonal steel container that measures 15 inches. First strike the corrugated metal plate across the iron to create a corrugated imitation on the top of the iron, then bounce off the remaining sides. To check the cold crack resistance of golf balls, 12 balls are fired five times from a mechanical air cannon with a coefficient of restitution as described below. The muzzle velocity of the ball being tested is 165 feet/second. The ball is fired at a steel plate placed perpendicular to its axis of flight. This steel plate is placed 10 feet from the muzzle. Set the ball to 0 before firing.
Condition for 16 hours. When determining the cutting test data, this test is carried out with the lower third of the ball held in a fixed position in a retaining cup, using a 1360 g ball with a blunt edge blade similar to the main edge of an iron club. Things
Free fall from a height of 36 inches. The coefficient of restitution data below was obtained by firing 12 balls from an air cannon at a muzzle velocity of 125 feet/second into a steel plate placed 10 feet from the muzzle, and calculating the initial velocity and rebound of the balls. This was obtained by measuring the speed at which the The ratio of the return speed to this initial speed is the determined coefficient of restitution. The results are reported as an average of the balls thus tested. When determining low velocity rebound data, drop the 12 balls being tested from a height of 100 inches onto a steel plate, measure the rebound height of the dropped golf balls, and report the average of the test results. In these data, parts are by weight unless otherwise specified. In the manufacture of the golf balls in question, the specified polymeric cover material was dry mixed with the specified blowing agent and poured into the extruder section of an injection molding process by conventional methods. Where specific data are available for results for a single ball, these data represent data for multiple balls tested according to each method of operation. The test results for these balls in question are TOP
- Compare to a standard Surlyn covered golf ball with a solid center sold under the trade name FLITE. This ball is PGA compressed
100, coefficient of restitution 0.90, low speed rebound is 74 inches, 12 out of 12 balls passed the cold crack and durability tests, and 12 out of 12 balls passed the cut test and 12 out of 12 balls passed the cut test and 12 out of 12 balls passed the cut test. 12 balls passed the barrel test. Test results are also provided by Acushnet Company,
Titleist Pro from New Bedford.Massachusetts
Also compared to a ball with a standard balata cover with a wound center sold under the trademark Trajectory. This ball has compression 64, hard hitting range
255 yards, 0.80 coefficient of restitution and slow rebound
It is 68 inches. 12 out of 12 balls failed the barrel test. 12 out of 12 balls passed the cold crack resistance test and 12 out of 12 failed the cut test. In the examples below, several ingredients are listed under the trade name under which they are marketed. The products in question, according to the best information available to the inventors, are as follows. In the cover stock formulas listed in the Examples, unless otherwise specified, titanium dioxide was added via masterbatch A having the following composition. 1 part Unitane0110 to 4 parts Surlyn A1557 Unless otherwise specified, blowing agents were added through Masterbatch B having the following composition: Ficel 4 parts EVA (ethylene/vinyl acetate copolymer) per 1 part EPA

[Table]
Example 1 In this example, center area A was used. The cover stock was made by dry mixing the ingredients in Table 2 below. Table 2 Part Surlyn 1605 88.00 Surlyn 1557 17.40 TiO ₂ Masterbatch A 35.20 Blowing Agent Masterbatch B 2.32 The compression of the resulting golf ball was 95. 12 out of 12 balls passed the barrel test. Six out of six balls passed the low temperature crack test.
Twelve out of twelve balls passed the cutting test, and the coefficient of restitution of these balls was 0.780. In the low-velocity rebound test, the ball rebounded 72 inches. Example 2 In this example, center area B was used. Cover stocks were made according to Table 3 below. Table 3 Part Surlyn 1605 88.00 Surlyn 1557 17.40 TiO ₂ Masterbatch A 35.20 Blowing Agent Masterbatch B 2.32 The compression of the resulting golf ball was 90. 12 out of 12 balls passed the barrel test, and 6 out of 6 balls passed the low temperature crack test. 12 out of 12 balls passed the cutting test. The coefficient of restitution of the ball was 0.780. In the low-velocity rebound test, the ball rebounded 72 inches. Example 3 In this example, center area C was used. Cover stocks were made according to Table 4 below. Table 4 Part Surlyn 1605 88.00 Surlyn 1577 17.40 TiO ₂ Masterbatch A 35.20 Blowing Agent Masterbatch B 2.32 The compression of the resulting golf ball was 110.
12 out of 12 balls passed the barrel test,
Six out of six balls passed the low temperature crack test.
12 out of 12 balls passed the cutting test. The coefficient of restitution of this ball was 0.785. In a low-velocity rebound test, the ball rebounded 70 inches. Example 4 In this example, center area D was used. Cover stock was made according to Table 5 below. Table 5 Part Surlyn 1605 88.00 Surlyn 1557 17.40 TiO ₂ Masterbatch A 35.20 Blowing Agent Masterbatch B 2.32 The compression of the resulting golf ball was 95. 12 out of 12 balls passed the barrel test, and 6 out of 6 balls passed the low temperature crack test.
12 out of 12 balls passed the cutting test. The coefficient of restitution of this ball was 0.770. In a low-velocity rebound test, the ball rebounded 73 inches. Example 5 The same procedure as Example 4 was repeated except using a center with the following physical properties. Its center is 1.550
inch diameter, a coefficient of restitution of 0.808, a weight of 37.0 grams, and a PGA compression of 75. A cover stock was made according to Example 4. Since the diameter of the center was larger, the cover was of course thinner. The compression of the resulting golf ball was 93. In the barrel test, all 12 balls passed. All 12 balls passed the low temperature crack test. A cut test was performed on 12 balls, which resulted in a slight dent in the cover. The coefficient of restitution of the ball was 0.781. In a low-velocity rebound test, this ball rebounded 73 inches. Example 6 Example 4 except using a center with the following physical properties
The same operation was repeated. Its center has a diameter of 1.540 inches, a coefficient of restitution of 0.800 and a weight of 36.7
g and the PGA compression is 83. A cover stock was made according to Example 4. Since this center was larger in diameter, the cover was of course thinner. The compression of the resulting golf ball was 97. All 12 balls passed the barrel test, and all 12 balls passed the low temperature crack test. A cut test was performed on 12 balls, and the cover was slightly dented. The coefficient of restitution of this ball is 0.775
, and in the low velocity rebound test the ball scored 73
The inch bounced back. Example 7 The same procedure as in Example 4 was repeated except that a center with the following physical properties was used. Its center is
It has a diameter of 1.530 inches, a coefficient of restitution of 0.802, a weight of 36.1 grams, and a PGA compression of 84.
A cover stock was made according to Example 4. Since this center was larger in diameter, its cover was of course thinner. The compression of the resulting golf ball was 99. The barrel test was performed on 12 balls, all of which passed. All 12 balls passed the low temperature crack test. A cut test was performed on 12 balls, but a slight dent was made in the cover. The coefficient of restitution of this ball was 0.772. In a low-velocity rebound test, the ball rebounded 71 inches.