Patent Publication Number: US-2011053707-A1

Title: Multilayer Solid Golf Ball

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/153,952, entitled “Multilayer Solid Golf Ball”, and filed on Feb. 19, 2009, which application is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to a golf ball and, more particularly, to a multilayer solid golf ball having a core that retains its performance characteristics after exposure to high temperature. 
     The history of golf ball development had gone very far from wound golf balls to solid two piece golf balls and multilayer golf balls. Rubber cores gradually replaced wound cores because of quality consistency and performance benefit such as reducing of driver spin for longer distance. 
     Multilayer golf balls with layers comprising a thermoplastic material such as ionomer materials brought golf ball technology to the next level. Typically, thin layers of different materials fused together added extra features such as lower spin off the tee but increasing spin around the green. For example, one of the layers may be a hard ionomer in a mantle layer while a soft elastomer material forms the layer for outer cover. Thin layers of ionomer layers were typically used because ionomer has relatively low resilience, particularly when compared to the rubbers typically used to form the core or the layers of the core. 
     However, highly neutralized ionomers, such as those developed by DuPont®, have resilience comparable to or even better than the resilience of rubber materials. These highly neutralized ionomers may represent the next step in innovation for golf ball cores. Golf ball cores comprising a thermoplastic material are more consistent in quality than thermoset rubber cores. One limitation on the use of thermoplastic resins, such as a highly neutralized ionomer, for a golf ball core is the effect that ambient temperature has on the shape and performance of the golf ball core. 
     Flying distance is an important index used to evaluate the performance of a golf ball. Flying distance is affected by three main factors: “initial velocity”, “spin rate”, and “launch angle”. Initial velocity is one of the primary physical properties affecting the flying distance of the golf ball. The coefficient of restitution (COR) is an alternate parameter of initial velocity of the golf ball, and the temperature will affect the COR. The COR is generally defined as the ratio of velocity of an object before and after an impact. A COR of 1 is a perfect elastic collision where no energy is lost due to the collision, and a COR of 0 is a perfect inelastic collision, where all of the energy is dissipated during the collision. Taking 24 degrees Celsius as the standard temperature at which the United States Golf Association (USGA) sets as a standard temperature for measuring golf ball physical properties and performance characteristics for adherence to USGA rules and regulations, the physical properties, including the COR, of the golf ball will be affected when the temperature is lower or higher than 24 degrees Celsius. For example, the COR is significantly positive relative to the ambient temperature, so the golf ball usually flies shorter in a cold weather. 
     Similarly, performance is affected by long-term exposure to high temperatures. Due to the habits of many golfers, golf balls may be routinely subjected to long-term exposure to high temperatures. For example, many golfers tend to leave their golf balls in their golf bags and in their car trunks. Golfers may live in areas where daytime, or even nighttime temperatures regularly exceed 30 degrees Celsius, particularly during daylight hours during the summer. Inside a car trunk, the temperature may reach 50 degrees Celsius for extended periods of time. 
     When exposed to relatively high ambient temperatures for extended periods, golf balls tend to lose their original performance characteristics. The material of the core or the cover layers may distort or lose their shape, particularly when the temperature cycles between relatively high ambient temperatures and relatively low ambient temperatures, such as the ambient temperature changes over the course of a day. This results in loss of distance and feel. 
     Therefore, there exists a need in the art for a golf ball that maintains its performance characteristics even after exposure to relatively high ambient temperatures. 
     SUMMARY 
     In one aspect, the invention provides a golf ball comprising a core, said core comprising a thermoplastic material; an intermediate layer enclosing said core to form an inner ball, said intermediate layer comprising a thermoset material; and a cover enclosing said inner ball, wherein said golf ball satisfies the following requirements: (1) said inner ball has a first deflection amount of 2.2 to 3.2 millimeters under a load of 10 to 130 kilograms when said inner ball is kept in an environment of 24 degrees Celsius for at least about eight hours, (2) said inner ball has a second deflection amount under a load of 10 to 130 kilograms when said inner ball is kept in an environment of about 50 degrees Celsius for at least about 8 hours, and wherein the ratio of the second deflection amount to the first deflection amount is between about 1.05 and about 1.15, and (3) said core has a coefficient of restitution at 40 meters per second falling between approximately 0.79 and 0.89 and higher than that of said golf ball. 
     In another aspect the invention provides a golf ball comprising a core, said core comprising a thermoplastic material; an intermediate layer enclosing said core to form an inner ball, said intermediate layer comprising a thermoset material; and a cover enclosing said inner ball and having a plurality of dimples on its outer surface, wherein said golf ball satisfies the following requirements: (1) said inner ball has a first deflection amount of 2.2 to 3.2 millimeters under a load of 10 to 130 kilograms when said inner ball is kept in an environment of 24 degrees Celsius for at least about 8 hours, (2) said inner ball has a second deflection amount under a load of 10 to 130 kilograms when said inner ball is kept in an environment of 50 degrees Celsius for at least about 8 hours, and the ratio of the second deflection amount to the first deflection amount is between about 1.05 and about 1.15, (3) said core has a coefficient of restitution at forty (40) meters per second falling between approximately 0.79 and 0.89 and higher than that of said golf ball, and (4) said dimples have a total volume of 550 cubic millimeters to 800 cubic millimeters. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a perspective view of a golf ball; 
         FIG. 2  is a cross-sectional view of a first embodiment of the golf ball shown in  FIG. 1 ; and 
         FIG. 3  is a cross-sectional view of a second embodiment of the golf ball shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective view of a solid golf ball  100  according to the invention. Golf ball  100  is generally spherical in shape with a plurality of dimples  102  disposed on the surface of golf ball  100 . Any number of dimples  102  may be provided on the surface of golf ball  100 . In some embodiments, the number of dimples  102  may range from about 250 to about 500. In some embodiments, the number of dimples  102  may range from about 300 to about 400. Dimples  102  may be arranged on the surface of golf ball  100  in any pattern. 
     Though shown as substantially hemispherical, dimples  102  may have any shape known in the art, such as elliptical, polygonal, or the like. While in some embodiments dimples  102  may be protrusions extending away from the surface of golf ball  100 , dimples  102  are typically indentations in the surface of golf ball  100 . Each indentation defines a volume. For example, if a dimple is a hemispherical indentation in the surface, the space carved out by the dimple and bounded by an imaginary line representing where the surface of golf ball  100  would be if no dimple were present has a volume of a hemisphere, or 2/3πr 3 , where r is the radius of the hemisphere. In some embodiments, all dimples  102  may have the same diameter or radius. In other embodiments, dimples  102  may be provided with different diameters or radii. In some embodiments, each dimples may have a diameter or radius selected from a preselected group of diameters/radii. In some embodiments, the number of different diameters/radii in the preselected group of diameters/radii ranges from three (3) to six (6). In some embodiments, the number of dimples  102  with the greatest diameter/radius is greater than the number of dimples with any other diameter/radius. In other words, in such an embodiment, there are more of the largest dimples than dimples of any other size. 
     The aggregate of the volumes of all of dimples  102  on the surface of golf ball  100  is a total dimple volume. In one embodiment, the total dimple volume is about 550 cubic millimeters to about 800 cubic millimeters. In some embodiments, the total dimple volume may range from about 600 cubic millimeters to about 800 cubic millimeters. 
     Internally, golf ball  100  is generally constructed as a multilayer solid golf ball. In other words, multiple layers of material are fused or compressed together to form the ball. As shown in  FIG. 2 , one embodiment of golf ball  100  includes a core  104 , a cover  108 , and an intermediate layer  106  sandwiched between core  104  and intermediate layer  106 . Together, core  104  and intermediate layer  106  may be considered to be an “inner ball”. 
     Core  104  may include any number of materials. In some embodiments, core  104  may include a thermoplastic material or a thermoset material. The thermoplastic material of core  104  may be an ionomer resin, a highly neutralized acid polymer composition, a polyamide resin, a polyester resin, a polyurethane resin, and combinations thereof. In one embodiment, core  104  comprises an ionomer resin. For example, core  104  may include HPF and Surlyn®, both commercially available from E.I. Dupont de Nemours and Company, and IOTEK®, commercially available from Exxon Corporation. To increase COR, one composition of core  104  includes HPF as the main composition with Surlyn® and/or IOTEK® as optional sub-compositions. Any sub-composition of core  104  may be in an amount of 0 to 40 parts by weight, or in some embodiments, 0 to 10 parts by weight, based on 100 parts by weight of the main composition of core  104 . 
     Core  104  may be made using any method known in the art, such as hot-press molding or injection molding. Core  104  of the present invention may be single layer or multilayer construction, and except for the aforementioned materials, any other materials may be also used to make core  104 . In some embodiments, the material of core  104  is selected to provide core  104  with a COR greater than 0.750. In some embodiments, core  104  has a COR at 40 meters per second ranging between about 0.79 and 0.89. In some embodiments, core  104  has a higher COR than that of golf ball  100  taken as a whole. 
     In some embodiments, a diameter of core  104  may be in a range between about 19.0 millimeters and about 37.0 millimeters. In some embodiments, the diameter of core  104  may range from about 19.0 millimeters and about 32 millimeters. In some embodiments, the diameter of core  104  may range between about 21.0 millimeters and about 35.0 millimeters. In some embodiments, the diameter of core  104  may range between about 23.0 millimeters and 32.0 millimeters. 
     In the embodiment shown in  FIG. 2 , intermediate layer  106  covers and substantially encloses core  104 . Intermediate layer  106  has an interior surface facing an exterior surface of core  104 . In the embodiment shown in  FIG. 2 , the exterior surface of intermediate layer  106  faces an interior surface of cover  108 . Intermediate layer  106  may have any thickness. In one embodiment, the thickness of intermediate layer  106  may range from about 3 millimeters to about 11 millimeters. In one embodiment, the thickness of intermediate layer  106  may range from about 4 millimeters to about 10 millimeters. 
     Intermediate layer  106  may include a thermoset material. In some embodiments, the thermoset material may be a rubber composition. In some embodiments, the base rubber of the rubber composition may include 1,4-cis-polybutadiene, polyisoprene, styrene-butadiene copolymers, natural rubber, and combinations thereof. To increase the resiliency of the inner ball, 1,4-cis-polybutadiene may be used as the base rubber of the rubber composition. Alternatively, 1,4-cis-polybutadiene can be used as the base material for intermediate layer  106 , with additional materials added to the base material. In some embodiments, the amount of 1,4-cis-polybutadiene is at least 50 parts by weight, based on 100 parts by weight of the rubber composition. 
     Additives, such as a crosslinking agent and a filler with a greater specific gravity may be added to the rubber composition. The suitable crosslinking agent can be selected from the group consisting of peroxide, zinc diacrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. To increase the resiliency of the rubber composition, zinc acrylate may be used. However, to increase the resistance to long-term exposure to relatively high ambient temperatures, peroxide may be used as the cross-linking agent. In particular, when core  104  is formed from a high resilient thermoplastic material, the performance of golf ball  100  is maintained in spite of long-term exposure to relatively high ambient temperatures when intermediate layer  106  is formed from a peroxide cross-linked polybutadiene material. 
     For example, when intermediate layer  106  is formed from a peroxide cross-linked polybutadiene material and core  104  may include a high resilient thermoplastic material, golf ball  100  may be stored at 24 degrees Celsius for at least about 8 hours. The inner ball (core  104  and intermediate layer  106 ) may have a first deflection amount of 2.2 millimeters to about 3.2 millimeters under a load of about 10 kilograms to about 130 kilograms when golf ball  100  is stored in an environment of about 24 degrees Celsius for at least about 8 hours. When the same ball is stored in an environment of about 50 degrees Celsius for at least about 8 hours, golf ball  100  may have a different deflection, the second deflection amount. The ratio of the second deflection amount to the first deflection amount is between about 1.5 and about 1.15. 
     In Table 1, various COR and deflection measurements are provided for various golf balls. An Example ball is made according to the invention. In the Example, core  104  includes HPF2000, a DuPont ionomer resin in which the MAA acid groups have been fully neutralized with magnesium ions. Intermediate layer  106  includes BR compound, a peroxide cross-linked polybutadiene material, the specific composition of which is shown in Table 2. The performance of the Example is compared with two conventional balls: 
     Comparative 1, where the entire inner ball includes HPF2000 and Comparative 2, where the entire inner ball comprises Surlyn8940, a Dupont ionomer resin-Ethylene/methacrylic acid (E/MAA) copolymer, in which the MAA acid groups have been partially neutralized with sodium ions. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Comparison of Example Ball Performance with Conventional Balls 
               
            
           
           
               
               
               
               
            
               
                   
                 Example 
                 Comparative 1 
                 Comparative 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Core 
                 HPF2000 
                 HPF2000 
                 Surlyn8940 
               
               
                 Intermediate layer 
                 BR 
               
               
                 Core diameter (mm) 
                 28.0 
               
               
                 Inner ball diameter (mm) 
                 39.3 
                 39.3 
                 39.3 
               
            
           
           
               
            
               
                 Compression Test (10-130 kg) 
               
            
           
           
               
               
               
               
            
               
                 Second Deflection Amount 
                 3.13 
                 3.27 
                 2.21 
               
               
                 after storage at 50 
               
               
                 degrees C. for 8 hrs (mm) 
               
               
                 First Deflection Amount 
                 2.84 
                 2.66 
                 1.54 
               
               
                 after storage at 24 
               
               
                 degrees C. for 8 hrs (mm) 
               
               
                 Ratio of Second Deflection 
                 1.10 
                 1.23 
                 1.44 
               
               
                 Amount to First Deflection 
               
               
                 Amount 
               
            
           
           
               
            
               
                 COR 
               
            
           
           
               
               
               
               
            
               
                   
                 0.838 
                 0.825 
                 0.726 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 BR Compound Composition 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 TAIPOL ™ BR0150 
                 100 
               
               
                   
                 Zinc diacrylate 
                 28 
               
               
                   
                 Zinc oxide 
                 6 
               
               
                   
                 Barium sulfate 
                 39.5 
               
               
                   
                 Peroxide 
                 1 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 1, the deflection performance of the Example ball is greater than that of Comparative 1 and Comparative 2 after exposure to high ambient temperatures. The ratio of the second deflection amount to the first deflection amount of the Example ball is about 1.1, while the other balls have a ratio of 1.23 and 1.44, respectively. This means that the Comparative balls are less capable of holding their shape and resisting compression after long exposure to high temperatures than the Example ball. Further the COR of the Example ball is greater than either of the Comparative balls. 
     To increase the specific gravity of intermediate layer  106 , a suitable filler may be added in the rubber composition, such as zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate, and in the present invention, zinc oxide is preferred. In addition, a metal powder with a greater specific gravity may also be used as the filler, such as tungsten. By means of adjusting the added amount of the filler, the specific gravity of intermediate layer  106  can reach the desired level. 
     In the embodiment shown in  FIG. 2 , an exterior surface of intermediate layer  106  faces an interior surface of cover  108 . The exterior surface of cover  108  is the exterior surface of golf ball  100 , which is shown in  FIG. 1 . Cover  108  may include any material known in the art. In some embodiments, cover  108  may include an ionomer resin, a highly neutralized ionomer resin, a polyamide resin, a polyester resin, a thermoplastic polyurethane resin, a thermoset polyurethane resin, or combinations of these compounds. 
     In the embodiment shown in  FIG. 3 , an additional cover layer is provided: inner cover layer  110 . In such an embodiment cover  108  may be considered to be an outer cover layer. Inner cover layer  110  may comprise the same material as that of outer cover layer  108 . 
     The thickness of inner cover layer  110  may range between about 0.5 millimeters and 11.0 millimeters. In some embodiments, the thickness of inner cover layer  110  may range between about 0.5 millimeters and about 8.5 millimeters. In some embodiments, the thickness of inner cover layer  110  may range between about 0.5 millimeters and about 3.0 millimeters. 
     Inner cover layer  110  has an interior surface that faces an exterior surface of intermediate layer  106 . Inner cover layer  110  covers and encloses intermediate layer  106 . Inner cover layer  110  has an exterior surface that faces an interior surface of outer cover layer  108 . 
     In some embodiments, the exterior surface of inner cover layer  110  has a higher hardness than the exterior surface of cover  108 . In some embodiments, an exterior surface of inner cover layer  110  may have a Shore D hardness of 45 to 65, while the exterior surface of outer cover layer  108  may have a Shore D hardness of 40 to 60. In some embodiments, the entirety of inner cover layer  110  has a higher hardness than the entirety of cover  108 . 
     While the balls described herein have compositions and layers selected to improve the performance of balls after exposure to high ambient temperatures, balls may also be designed to improve or maintain performance in other types of environments. For example, some types of golf balls may have reduced performance when cold. This problem is addressed in U.S. Pat. No. ______, currently U.S. patent application Ser. No. 12/230,272, entitled “Multilayer Solid Golf Ball”, and filed on Aug. 27, 2008, the entirety of which is incorporated herein by reference. 
     While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.