Golf Ball Having Outer Cover With Low Flexural Modulus

Abstract

A golf ball having an outer cover layer with a lower flexural modulus than that of an inner core layer and/or an inner cover layer is disclosed. The lower flexural modulus of the outer cover layer may give the golf ball a good feel during short shots and putting. The inner cover layer may have a first flexural modulus and the outer cover layer may have a second flexural modulus. The first flexural modulus may be at least about 10 times greater than the second flexural modulus. The inner core layer may have a third flexural modulus. The third flexural modulus may be at least about 5 times greater than the second flexural modulus.

Description

[0001] This application claims priority under 35 U.S.C. .sctn.119(e) to U.S. Provisional Patent Application No. 61/526,557, entitled "Golf Ball Having Outer Cover With Low Flexural Modulus", and filed on Aug. 23, 2011, which application is hereby incorporated by reference.

BACKGROUND

[0002] The present invention relates generally to a golf ball having different play characteristics in different situations.

[0003] The game of golf is an increasingly popular sport at both amateur and professional levels. A wide range of technologies related to the manufacture and design of golf balls are known in the art. Such technologies have resulted in golf balls with a variety of play characteristics. For example, some golf balls have a better flight performance than other golf balls. Some golf balls with a good flight performance do not have a good feel when hit with a golf club. Thus, it would be advantageous to make a golf ball with a good flight performance that also has a good feel.

SUMMARY

[0004] A golf ball having an outer cover layer with a lower flexural modulus than that of an inner core layer and/or an inner cover layer is disclosed. The lower flexural modulus of the outer cover layer may give the golf ball a good feel during short shots and putting.

[0005] In one aspect, the disclosure provides a golf ball that may have an inner core layer, an outer core layer enclosing the inner core layer, an inner cover layer enclosing the outer core layer, and an outer cover layer enclosing the inner cover layer. The inner cover layer may have a first flexural modulus and the outer cover layer may have a second flexural modulus. The first flexural modulus may be at least 10 times greater than said second flexural modulus. The ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) may range from about 10 to about 30. The ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) may range from about 10 to about 30. The ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) may range from about 95 to about 250. The inner core layer may include a third flexural modulus and the ratio of third flexural modulus to second flexural modulus (third flexural modulus/second flexural modulus) may range from about 5 to about 10. The inner core layer may include a first highly neutralized acid polymer composition. The inner core layer may have a coefficient of restitution value ranging from about 0.775 to about 0.81. The inner core layer may have a coefficient of restitution value that is about 0.005 to about 0.02 greater than the coefficient of restitution value of the golf ball. The inner cover layer may have a Shore D hardness ranging from about 45 to about 55.

[0006] In one aspect, the disclosure provides a golf ball that may have an inner core layer, an outer core layer enclosing the inner core layer, an inner cover layer enclosing the outer core layer, and an outer cover layer enclosing the inner cover layer. The inner core may have a first flexural modulus and the outer cover layer may have a second flexural modulus. The first flexural modulus may be at least about 5 times greater than the second flexural modulus. The ratio of first flexural modulus to second flexural modulus (first flexural modulus/second flexural modulus) may range from about 5 to about 10. The inner cover layer may have a third flexural modulus and the ratio between the third flexural modulus and the second flexural modulus (third flexural modulus/second flexural modulus) may range from about 10 to about 30. The inner core layer may include a first highly neutralized acid polymer composition. The first highly neutralized acid polymer composition includes one of HPF 2000 and HPF AD 1035. The inner core layer may include a first highly neutralized acid polymer composition and a second highly neutralized acid polymer composition and the ratio of the first highly neutralized acid polymer composition to the second highly neutralized acid polymer composition may range from about 20:80 to about 80:20. The inner core layer may have a coefficient of restitution value that is about 0.005 to about 0.02 greater than the coefficient of restitution value of the golf ball.

[0007] In one aspect, the disclosure provides a golf ball that may have an inner core layer, an outer core layer enclosing the inner core layer, an inner cover layer enclosing the outer core layer, and an outer cover layer enclosing the inner cover layer. The inner cover layer may have a first flexural modulus and the outer cover layer may have a second flexural modulus. The first flexural modulus may be at least about 45,000 psi greater than the second flexural modulus. The first flexural modulus may be between about 60,000 psi and about 95,000 psi greater than the second flexural modulus. The inner core layer may include a third flexural modulus and the third flexural modulus may be between about 15,000 psi to 65,000 psi greater than the second flexural modulus.

[0008] 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

[0009] 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.

[0010] FIG. 1 illustrates the trajectory of a golf ball prepared according to the present disclosure compared with the trajectory of a different type of golf ball after being hit by a driver;

[0011] FIG. 2 illustrates the trajectory of a golf ball prepared according to the present disclosure after being hit by a pitching wedge; an

[0012] FIG. 3 is a golf ball according to the exemplary embodiment of FIGS. 1 and 2.

DETAILED DESCRIPTION

[0013] Generally, the present disclosure relates to a golf ball having a variable initial velocity associated with striking the golf ball with a driver having different head speeds. The structure of the disclosed golf ball may cause the golf ball to experience an initial velocity comparable to premium golf balls currently on the market when hit with a driver head speed less than 100 mph. However, the same golf ball may experience an initial velocity higher than premium golf balls currently on the market when hit with a driver head speed higher than 125 mph. As a result, the disclosed golf ball may have different initial velocities associated with different head speeds.

[0014] FIGS. 1-2 show an exemplary embodiment of a golf ball 100. In FIG. 1, a recreational golfer 142 has used a driver 144 to hit golf ball 100 and another type of golf ball, golf ball 182, off of a tee 146 located in a tee box 148. As a typical recreational golfer, golfer 142 hits golf ball 100 and golf ball 182 with a driver head speed of less than 100 mph. FIG. 1 demonstrates a comparison between a trajectory 150 of golf ball 100 and a trajectory 180 of golf ball 182 after each of the golf balls have been struck by driver 144. Each of the golf balls has a comparable trajectory length because each of the golf balls has a similar initial velocity associated with being hit by driver 144 with a driver head speed of less than 100 mph. Trajectory 150 extends about as long as trajectory 180 because golf ball 100 has a similar initial velocity as golf ball 182 after being struck by driver 144 with a driver head speed of less than 100 mph.

[0015] In FIG. 2, a professional golfer 152 has used a driver 144 to hit golf ball 100 and another type of golf ball, golf ball 182, off of a tee 146 located in a tee box 148. As a typical professional golfer, golfer 152 hits golf ball 100 and golf ball 182 with a driver head speed of more than 125 mph. FIG. 2 demonstrates a comparison between a trajectory 160 of golf ball 100 and a trajectory 162 of golf ball 182 after each of the golf balls have been struck by driver 144. Trajectory 160 is longer than trajectory 162 because golf ball 100 and golf ball 182 each have a different initial velocity associated with being hit by driver 144 with a driver head speed of more than 125 mph. When struck by driver 144 with a driver head speed of more than 125 mph, golf ball 100 has a higher initial velocity than that of golf ball 182 and, in turn, golf ball 100 flies further than golf ball 182.

[0016] Tables 3-6 show the results of tests performed on test balls, which include golf balls prepared according to the present disclosure and existing golf balls currently available on the market. The golf balls prepared according to the present disclosure includes Example 1, details of which are shown in Table 1. Materials A, B, C, and D are discussed in more detail with reference to Tables 8-11. The existing golf balls currently available on the market include Comparative Examples 1-4, details of which are shown in Table 2 (where PBR is polybutadiene rubber). The results shown in Tables 3-6 include initial velocity (IV) and launch angle (LA). All results for IV have an uncertainty of .+-.1 mph.

TABLE-US-00001 TABLE 1 Golf Ball Testing Data 1 Inner Core Layer Material A Diameter (mm) 24 Shore D Hardness 53 Compression 3.2 Deformation (mm) COR 0.83 Outer Core Layer Material B Thickness (mm) 7.25 Shore D Hardness 59 Inner Cover Layer Material C Thickness (mm) 1.0 Shore D Hardness 69 Flexural Modulus 77,000 (psi) Outer cover layer Material D Thickness (mm) 1.1 Shore D Hardness 53 Flexural 550 Modulus (psi) Entire Ball COR 0.785

TABLE-US-00002 TABLE 2 Comparative Test Balls Ball Name and Brand Ball Pieces Core Cover ProV1 by Titleist Comparative Five (5) PBR Urethane Example 1 Tour i(s) by Comparative Three (3) PBR Urethane Callaway Example 2 ONE Tour by Nike Comparative Three (3) PBR Urethane Golf Example 3 ONE Tour D by Comparative Three (3) PBR Urethane Nike Golf Example 4

[0017] The tests performed on the test balls were conducted as follows: a Nike SQ Dymo driver (loft angle: 10.5.degree.; shaft: Diamana by Mitsubishi Rayon; flex: X (extra stiff); grip: golf pride) was fixed to a swing robot manufactured by Miyamae Co., Ltd. and then swung at different head speeds from about 80 mph to about 125 mph. The clubface was oriented for a square hit. The forward/backward tee position was adjusted so that the tee was three inches in front of the point in the downswing where the club was vertical. The height of the tee and the toe-heel position of the club relative to the tee were adjusted such that the center of the impact mark was centered toe to heel across the face.

[0018] Table 3 shows the results of the 125 mph head speed test. The 125 mph head speed test involves hitting the test balls with a driver having a head speed of about 125 mph.+-.1 mph. The driver used in the test of Table 3 is described above. The calibration ball for the 125 mph head speed test is a ONE Tour D golf ball commercially available by Nike Golf. To calibrate the 125 mph head speed test, the conditions are set to cause the calibration ball to have an initial velocity of 171 mph.+-.1 mph when the calibration ball is hit with the driver having a head speed of about 125 mph.+-.1 mph.

[0019] The results show that, for the 125 mph head speed test, the Initial Velocity of golf balls prepared according to the present disclosure are higher than the Initial Velocity of the existing golf balls currently available on the market. For example, Comparative Example 2 has an Initial Velocity of about 171 mph. In contrast, Example 1 has a higher Initial Velocity of about 174 mph. The next highest Initial Velocity resulting from the 125 mph head speed test came from Comparative Example 1. At about 172.5 mph, this Initial Velocity is still less than the Initial Velocity of Example 1.

TABLE-US-00003 TABLE 3 125 MPH DRIVER Ball Name Initial Velocity (IV) (mph) and Brand Ball of Samples N/A Example 1 174 ProV1 by Comparative 172.5 Titleist Example 1 Tour i(s) by Comparative 171 Callaway Example 2a ONE Tour by Comparative 171.5 Nike Golf Example 3a ONE Tour D Comparative 171 by Nike Golf Example 4a

[0020] Table 4 shows the results of the 110 mph head speed test. The 110 mph head speed test involves hitting the test balls with a driver having a head speed of about 110 mph.+-.1 mph. The driver used in the test of Table 4 is described above. The calibration ball for the 110 mph head speed test is a ONE Tour D golf ball commercially available by Nike Golf. To calibrate the 110 mph head speed test, the conditions are set to cause the calibration ball to have an initial velocity of 159 mph.+-.1 mph when the calibration ball is hit with the driver having a head speed of about 110 mph.+-.1 mph.

[0021] The results show that, for the 110 mph head speed test, the Initial Velocity of golf balls prepared according to the present disclosure are comparable to the Initial Velocity of the existing golf balls currently available on the market. For example, Comparative Example 2 has an Initial Velocity of about 159 mph. Similarly, Example 1 has an Initial Velocity of about 159.5 mph. The Initial Velocities of the Comparative Examples resulting from the 110 mph head speed test were all within about 157 mph and about 159.5 mph.

TABLE-US-00004 TABLE 4 110 MPH DRIVER Ball Name Initial Velocity (IV) (mph) and Brand Ball of Samples N/A Example 1 159.5 ProV1 by Comparative Example 1 159 Titleist Tour i(s) by Comparative Example 2 157 Callaway ONE Tour by Comparative Example 3 159.5 Nike Golf ONE Tour D Comparative Example 4 159 by Nike Golf

[0022] Table 5 shows the results of the 95 mph head speed test. The 95 mph head speed test involves hitting the test balls with a driver having a head speed of about 95 mph.+-.1 mph. The driver used in the test of Table 5 is described above. The calibration ball for the 95 mph head speed test is a ONE Tour D golf ball commercially available by Nike Golf. To calibrate the 95 mph head speed test, the conditions are set to cause the calibration ball to have an initial velocity of 116.5 mph.+-.1 mph when the calibration ball is hit with the driver having a head speed of about 95 mph.+-.1 mph.

[0023] The results show that, for the 95 mph head speed test, the Initial Velocity of golf balls prepared according to the present disclosure are comparable to the Initial Velocity of the existing golf balls currently available on the market. For example, Comparative Example 1 has an Initial Velocity of about 116 mph. Similarly, Example 1 has an Initial Velocity of about 116 mph. The Initial Velocities of the Comparative Examples resulting from the 95 mph head speed test were all either about 116 mph or about 116.5 mph.

TABLE-US-00005 TABLE 5 95 MPH DRIVER Ball Name Initial Velocity (IV) (mph) and Brand Ball of Samples N/A Example 1 116 ProV1 by Comparative Example 1 116 Titleist Tour i(s) by Comparative Example 2 116.5 Callaway ONE Tour by Comparative Example 3 116 Nike Golf ONE Tour D Comparative Example 4 116.5 by Nike Golf

[0024] Table 6 shows the results of the 80 mph head speed test. The 80 mph head speed test involves hitting the test balls with a driver having a head speed of about 80 mph.+-.1 mph. The driver used in the test of Table 4 is described above. The calibration ball for the 80 mph head speed test is a ONE Tour D golf ball commercially available by Nike Golf. To calibrate the 80 mph head speed test, the conditions are set to cause the calibration ball to have an initial velocity of 89.5 mph.+-.1 mph when the calibration ball is hit with the driver having a head speed of about 80 mph.+-.1 mph.

[0025] The results show that, for the 80 mph head speed test, the Initial Velocity of golf balls prepared according to the present disclosure are comparable to the Initial Velocity of the existing golf balls currently available on the market. For example, Comparative Example 1 has an Initial Velocity of about 88 mph. Similarly, Example 1 has an Initial Velocity of about 88 mph. The Initial Velocities of the Comparative Examples resulting from the 80 mph head speed test were all within about 87.5 mph or about 89.5 mph.

TABLE-US-00006 TABLE 6 80 MPH DRIVER Ball Name Initial Velocity (IV) (mph) and Brand Ball of Samples N/A Example 1 88 ProV1 by Comparative Example 1 88 Titleist Tour i(s) by Comparative Example 2 87.5 Callaway ONE Tour by Comparative Example 3 89 Nike Golf ONE Tour D Comparative Example 4 89.5 by Nike Golf

[0026] Table 7 shows the differences between initial velocities resulting from striking the test balls with a driver under different head speeds.

TABLE-US-00007 TABLE 7 DIFFERENCES IN INITIAL VELOCITIES Difference in Difference in Initial Difference in Initial Velocities Velocities Resulting Initial Velocities Ball Name Resulting from 95 mph from 110 mph and Resulting from and Brand Ball and 80 mph 80 mph 125 mph and 80 mph N/A Example 1 28 mph 71.5 mph 86 mph ProV1 by Comparative 28 mph 71 mph 84.5 mph Titleist Example 1 Tour i(s) by Comparative 29 mph 69.5 mph 83.5 mph Callaway Example 2 ONE Tour by Comparative 27 mph 70.5 mph 82.5 mph Nike Golf Example 3 ONE Tour D Comparative 27 mph 69.5 mph 81.5 mph by Nike Golf Example 4

[0027] As used herein, unless otherwise stated, compression, hardness, COR, and flexural modulus are measured as follows:

[0028] Compression deformation: The compression deformation herein indicates the deformation amount of the ball under a force; specifically, when the force is increased to become 130 kg from 10 kg, the deformation amount of the ball under the force of 130 kg subtracts the deformation amount of the ball under the force of 10 kg to become the compression deformation value of the ball.

[0029] Hardness: Hardness of golf ball layer is measured generally in accordance with ASTM D-2240, but measured on the land area of a curved surface of a molded ball. For material hardness, it is measured in accordance with ASTM D-2240 (on a plaque).

[0030] Method of measuring COR: A golf ball for test is fired by an air cannon at an initial velocity of 40 m/sec, and a speed monitoring device is located over a distance of 0.6 to 0.9 meters from the cannon. When striking a steel plate positioned about 1.2 meters away from the air cannon, the golf ball rebounds through the speed-monitoring device. The return velocity divided by the initial velocity is the COR.

[0031] As shown in FIG. 3, golf ball 100 may include an inner core layer 110, an outer core layer 120, an inner cover layer 130, and an outer cover layer 140. While the exemplary embodiment of golf ball 100 has been described and illustrated as having four layers, other embodiments may include any number of layers. For example, in some embodiments, golf ball 100 may be a one-piece, two-piece, three-piece, or five-piece ball. In some embodiments, golf ball 100 may include more than five layers. The number of layers may be selected based on a variety of factors. For example, the number of layers may be selected based on the type of materials use to make the golf ball and/or the size of the golf ball.

[0032] The type of materials used to make the layers of the golf ball may be selected based on a variety of factors. For example, the type of materials used to make the layers of the golf ball may be selected based on the properties of the material and/or the processes used to form the layers. Exemplary materials are discussed below with respect to the individual layers of the exemplary embodiment. In some embodiments, one or more layers may be made from different materials. In some embodiments, one or more layers may be made from the same materials.

[0033] The golf ball may be made by any suitable process. The process of making the golf ball may be selected based on a variety of factors. For example, the process of making the golf ball may be selected based on the type of materials used and/or the number of layers included. Exemplary processes are discussed below with respect to the individual layers of the exemplary embodiment.

[0034] In some embodiments, inner core layer 110 may have a diameter ranging from 19 mm to 32 mm. In some embodiments, inner core layer 110 may have a diameter ranging from 20 mm to 30 mm. In some embodiments, inner core layer 110 may have a diameter ranging from 21 mm to 28 mm. In some embodiments, the diameter of inner core layer 110 may be at least three times greater than the thickness of outer core layer 120.

[0035] Inner core layer 110 may be made by any suitable process. For example, in some embodiments, inner core layer 110 may be made by an injection molding process. During injection molding process, the temperature of the injection machine may be set within a range of about 190.degree. C. to about 220.degree. C. In some embodiments, before the injection molding process, the at least two highly neutralized acid polymer compositions may be kept sealed in a moisture-resistant dryer capable of producing dry air. Drying conditions for the highly neutralized acid polymer composition may include 2 to 24 hours at a temperature below 50.degree. C. In some embodiments, inner core layer 110 may be made by a compression molding process. The process of making the inner core layer may be selected based on a variety of factors. For example, the process of making the inner core layer may be selected based on the type of material used to make the inner core layer and/or the process used to make the other layers.

[0036] In some embodiments, inner core layer 110 may include one or more highly neutralized acid polymer compositions. For example, in the exemplary embodiments, inner core layer 110 may include two highly neutralized acid polymer compositions. In some embodiments, the ratio of a first highly neutralized acid polymer composition to a second highly neutralized acid polymer composition may range from 20:80 to 80:20. In another embodiment, the same ratio may range from 30:70 to 70:30. In another embodiment, the same ratio may range from 40:60 to 60:40. In yet another embodiment, the same ratio same ratio may be 50:50. In some embodiments, two highly neutralized acid polymer compositions each having a flexural modulus of ranging from 20,000 psi to 35,000 psi may be used to make inner core layer 110. In some embodiments, two highly neutralized acid polymer compositions each having a Vicat softening temperature of from 50.degree. C. to 60.degree. C., or 52.degree. C. to 58.degree. C. may be used to make inner core layer 110. In some embodiments, suitable materials for the inner core layer may include the following highly neutralized acid polymer compositions: HPF resins such as HPF1000, HPF2000, HPF AD1024, HPF AD1027, HPF AD1030, HPF AD1035, HPF AD1040, all produced by E. I. Dupont de Nemours and Company.

[0037] Table 8 provides an example of materials used to make inner core layer 110, according to the exemplary embodiment. The amounts of the materials listed in Table 8 are shown in parts by weight (pbw).

TABLE-US-00008 TABLE 8 Inner Core Layer Materials Resin: A HPF 2000 66 HPF AD 1035 34

[0038] In some embodiments, the material used to form inner core layer 110 may include a highly neutralized acid polymer composition and optional additives, fillers, and/or melt flow modifiers. The acid polymer may be neutralized to 80% or higher, including up to 100%, with a suitable cation source, such as magnesium, sodium, zinc, or potassium. In the exemplary embodiment, the highly neutralized acid polymer compositions used to make the inner core layer may include the same cation source. Suitable additives and fillers may include, for example, blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nanofillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, acid copolymer wax, surfactants. Suitable fillers may also include inorganic fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay, silica, lead silicate. Suitable fillers may also include high specific gravity metal powder fillers, such as tungsten powder and molybdenum powder. Suitable melt flow modifiers may include, for example, fatty acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof.

[0039] In some embodiments, outer core layer 120 may be formed primarily of a thermoset material. For example, outer core layer 120 may be formed by crosslinking a polybutadiene rubber composition as described in U.S. patent application Ser. No. 12/827,360, entitled Golf Balls Including Crosslinked Thermoplastic Polyurethane, filed on Jun. 30, 2010, and applied for by Chien-Hsin Chou et al., the disclosure of which is hereby incorporated by reference in its entirety. When other rubber is used in combination with a polybutadiene, polybutadiene may be included as a principal component. For example, in some embodiments, a proportion of polybutadiene in the entire base rubber may be equal to or greater than 50% by weight. In some embodiments, a proportion of polybutadiene in the entire base rubber may be equal to or greater than 80% by weight. In some embodiments, a polybutadiene having a proportion of cis-1,4 bonds of equal to or greater than 60 mol %, and further, equal to or greater than 80 mol % may be used.

[0040] In some embodiments, cis-1,4-polybutadiene may be used as the base rubber and mixed with other ingredients to form outer core layer 120. In some embodiments, the amount of cis-1,4-polybutadiene may be at least 50 parts by weight, based on 100 parts by weight of the rubber compound. Various additives may be added to the base rubber to form a compound. The additives may include a cross-linking agent and a filler. In some embodiments, the cross-linking agent may be zinc diacrylate, magnesium acrylate, zinc methacrylate, or magnesium methacrylate. In some embodiments, zinc diacrylate may provide advantageous resilience properties. The filler may be used to increase the specific gravity of the material. The filler may include zinc oxide, barium sulfate, calcium carbonate, or magnesium carbonate. In some embodiments, zinc oxide may be selected for its advantageous properties. Metal powder, such as tungsten, may alternatively be used as a filler to achieve a desired specific gravity. In some embodiments, the specific gravity of outer core layer 120 may be from about 1.05 g/cm.sup.3 to about 1.45 g/cm.sup.3. In some embodiments, the specific gravity of outer core layer 120 may be from about 1.05 g/cm.sup.3 to about 1.35 g/cm.sup.3.

[0041] In some embodiments, a polybutadiene synthesized with a rare earth element catalyst may be used to form outer core layer 120. Such a polybutadiene may provide excellent resilience performance of golf ball 100. Examples of rare earth element catalysts include lanthanum series rare earth element compound, organoaluminum compound, and almoxane and halogen containing compounds. Polybutadiene obtained by using lanthanum rare earth-based catalysts usually employs a combination of a lanthanum rare earth (atomic number of 57 to 71) compound, such as a neodymium compound.

[0042] In some embodiments, a polybutadiene rubber composition having at least from about 0.5 parts by weight to about 5 parts by weight of a halogenated organosulfur compound may be used to form outer core layer 120. In some embodiments, the polybutadiene rubber composition may include at least from about 1 part by weight to about 4 parts by weight of a halogenated organosulfur compound. The halogenated organosulfur compound may be selected from the group consisting of pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol; pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol; pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol; 2,3,5,6-tetraiodothiophenol; pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol 4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol; 3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; and their zinc salts, the metal salts thereof and mixtures thereof.

[0043] Table 9 provides an example of materials used to make outer core layer 120, according to the exemplary embodiment. The amounts of the materials listed in Table 9 are shown in parts by weight (pbw). TAIPOL.TM. BR0150 is the trade name of a rubber produced by Taiwan Synthetic Rubber Corp.

TABLE-US-00009 TABLE 9 Outer Core Layer Material Rubber compound: B TAIPOL .TM. BR0150 100 Zinc diacrylate 29 Zinc oxide 9 Barium sulfate 11 Peroxide 1

[0044] Outer core layer 120 may be made by any suitable process. For example, in some embodiments, outer core layer 120 may be made by a compression molding process. The process of making the outer core layer may be selected based on a variety of factors. For example, the process of making the outer core layer may be selected based on the type of material used to make the outer core layer and/or the process used to make the other layers.

[0045] In some embodiments, outer core layer 120 may be made through a compression molding process including a vulcanization temperature ranging from 130.degree. C. to 190.degree. C. and a vulcanization time ranging from 5 to 20 minutes. In some embodiments, the vulcanization step may be divided into two stages: (1) the outer core layer material may be placed in an outer core layer-forming mold and subjected to an initial vulcanization so as to produce a pair of semi-vulcanized hemispherical cups and (2) a prefabricated inner core layer may be placed in one of the hemispherical cups and may be covered by the other hemispherical cup and vulcanization may be completed. In some embodiments, the surface of inner core layer 110 placed in the hemispherical cups may be roughened before the placement to increase adhesion between inner core layer 110 and outer core layer 120. In some embodiments, inner core surface may be pre-coated with an adhesive before placing inner core layer 110 in the hemispherical cups to enhance the durability of the golf ball and to enable a high rebound.

[0046] In some embodiments, inner core layer 110 may have a high resilience. Such a high resilience may cause golf ball 100 to have increased carry and distance. In some embodiments, inner core layer 110 may have a coefficient of restitution (COR) value ranging from 0.79 to 0.89. In some embodiments, inner core layer 110 may have a COR value ranging from 0.795 to 0.88. The COR value of inner core layer 110 may be greater than the COR value of golf ball 100. In some embodiments, the COR value of inner core layer 110 may be 0.005 to 0.02 greater than the COR value of golf ball 100.

[0047] In some embodiments, inner core layer 110 may have a compression deformation value ranging from 2.5 mm to 5 mm. In some embodiments, inner core layer 110 may have a compression deformation value ranging from 3.5 mm to 5 mm. Inner core layer 110 may have a surface Shore D hardness of from 40 to 60. In some embodiments, outer core layer 120 may have a surface Shore D hardness of from 50 to 60, which may be higher than the surface hardness of inner core layer 110. In some embodiments, outer core layer 120 may have a surface Shore D hardness of from 45 to 55.

[0048] In some embodiments, inner core layer 110 may have a Shore D cross-sectional hardness ranging from 40 to 60 at any single point on a cross-section obtained by cutting inner core layer 110 in half. In some embodiments, inner core layer 110 may have a Shore D cross-sectional hardness ranging from 45 to 55 at any single point on a cross-section obtained by cutting inner core layer 110 in half. In some embodiments, the difference in Shore D cross-sectional hardness at any two points on the same cross-section may be within .+-.6. In some embodiments, the difference in Shore D cross-sectional hardness at any two points on the same cross-section may be within .+-.3.

[0049] In some embodiments, inner core layer 110 may have a smaller specific gravity than outer layers. Such a difference in specific gravity may cause golf ball 100 to have a greater moment of inertia. In some embodiments, the specific gravity of inner core layer 110 may range from about 0.85 g/cm.sup.3 to about 1.1 g/cm.sup.3. In some embodiments, the specific gravity of inner core layer 110 may range from about 0.9 g/cm.sup.3 to about 1.1 g/cm.sup.3.

[0050] In some embodiments, inner cover layer 130 of golf ball 100 may have a thickness ranging from 0.5 mm to 1.5 mm. For example, inner cover layer 130 may have a thickness of 1 mm. In some embodiments, inner cover layer 130 may have a thickness ranging from 0.8 mm to 1 mm. For example, in some embodiments, inner cover layer 130 may have a thickness of 0.9 mm.

[0051] In some embodiments, outer cover layer 140 of golf ball 100 may have a thickness ranging from 0.5 mm to 2 mm. For example, outer cover layer 140 may have a thickness of 1 mm. In some embodiments, outer cover layer 140 may have a thickness ranging from 1 mm to 1.5 mm. For example, in some embodiments, inner cover layer 130 may have a thickness of 1.2 mm.

[0052] Outer cover layer 140 may have a thickness T1, inner cover layer may have a thickness T2, and outer core layer 120 may have a thickness T3. In some embodiments, T1 may be greater than T2. In some embodiments, T1 and T3 may have the following relationship: 5T1.ltoreq.T3.ltoreq.10T1.

[0053] In some embodiments, inner cover layer 130 may have a Shore D hardness, as measured on the curved surface, ranging from about 60 to 80. In some embodiments, outer cover layer 140 of golf ball 100 may have a Shore D hardness, as measured on the curved surface, ranging from 40 to 60. To have a low spin performance off the driver shot and good hitting feel, inner cover layer 130 may have a higher flexural modulus than outer cover layer 140. In some embodiments, inner cover layer 130 may have a flexural modulus ranging from 50,000 psi to 100,000 psi, or from 60,000 psi to 100,000 psi and outer cover layer 140 may have a flexural modulus ranging from 200 psi to 3,000 psi, or from 300 psi to 2,000 psi. In some embodiments, inner cover layer 130 may have a first flexural modulus and outer cover layer 140 may have a second flexural modulus, and a ratio of first flexural modulus to second flexural modulus (first flexural modulus/second flexural modulus) may range from 10 to 30. In some embodiments, ratio of first flexural modulus to second flexural modulus (first flexural modulus/second flexural modulus) may range from 25 to 100. In some embodiments, the ratio of first flexural modulus to second flexural modulus (first flexural modulus/second flexural modulus) may range from 95 to 250. In some embodiments, inner core layer 110 may have a third flexural modulus. In some embodiments, the ratio of first flexural modulus to third flexural modulus (third flexural modulus/second flexural modulus) may range from 5 to 10. Outer cover 140 having a lower flexural modulus than inner cover 130 and/or inner core layer 110 may provide golf ball 100 with a good feel in short shots and putting shots.

[0054] In some embodiments, inner cover layer 130 and/or outer cover layer 140 may be made from a thermoplastic material including at least one of an ionomer resin, a highly neutralized acid polymer composition, a polyamide resin, a polyester resin, and a polyurethane resin. In some embodiments, inner cover layer 130 may include the same type of material as outer cover layer 140. In some embodiments, inner cover layer 130 may include a different type of material from outer cover layer 140.

[0055] Table 10 provides an example of materials used to make inner cover layer 130, according to the exemplary embodiment. The amounts of the materials listed in Table 9 are shown in parts by weight (pbw) or percentages by weight. Neothane 6303D is the trade name of a thermoplastic polyurethane produced by Dongsung Highchem Co. LTD.

TABLE-US-00010 TABLE 10 Inner Cover Layer Material Resin: C Neothane 6303D 100

[0056] Table 11 provides an example of materials used to make outer cover layer 140, according to the exemplary embodiment. The amounts of the materials listed in Table 11 are shown in parts by weight (pbw) or percentages by weight, as indicated. "PTMEG" is polytetramethylene ether glycol, having a number average molecular weight of 2,000, and is commercially available from Invista, under the trade name of Terathane.RTM. 2000. "BG" is 1,4-butanediol, commercially available from BASF and other suppliers. "TMPME" is trimethylolpropane monoallylether, commercially available from Perstorp Specialty Chemicals AB. "DCP" is dicumyl peroxide, commercially available from LaPorte Chemicals Ltd. "MDI" is diphenylmethane diisocyanate, commercially available from Huntsman, under the trade name of Suprasec.RTM. 1100. Outer cover materials D may be formed by mixing PTMEG, BG, TMPME, DCP and MDI in the proportions shown in Table 11. Specifically, these materials may be prepared by mixing the components in a high agitated stir for one minute, starting at a temperature of about 70.degree. C., followed by a 10-hour post curing process at a temperature of about 100.degree. C. The post cured polyurethane elastomers may be ground into small chips.

TABLE-US-00011 TABLE 11 Outer Cover Layer Materials Polyurethane: D PTMEG (pbw) 100 BG (pbw) 15 TMPME (weight % to 10% total components) DCP (weight % to 0.5% total components) MDI (pbw) 87.8 (NCO index) 1.01

[0057] In some embodiments, golf ball 100 may have a moment of inertia between about 80 g/cm.sup.2 and about 90 g/cm.sup.2. Such a moment of inertia may produce a desirable distance and trajectory, particularly when golf ball 100 is struck with a driver or driven against the wind.

[0058] In some embodiments, golf ball 100 may include a ball compression deformation of 2.2 mm to 4 mm. In some embodiments, golf ball 100 may have compression deformation of 2.5 mm to 3.5 mm. In some embodiments, golf ball 100 may have compression deformation of 2.5 mm to 3 mm.

[0059] In some embodiments, the specific gravity of inner cover layer 130 or outer cover layer 140 may range from about 1.1 g/cm.sup.3 to about 1.45 g/cm.sup.3. In some embodiments, the specific gravity of inner cover layer 130 or outer cover layer 140 may range from about 1.1 g/cm.sup.3 to about 1.35 g/cm.sup.3. In some embodiments, the layers used to make golf ball 100 may have a specified relationship in terms of their respective physical properties. For example, to have greater moment of inertia, the golf ball layers may have a specific gravity gradient increased from inner core layer 110 to outer cover layer 140. In some embodiments, inner core layer 110 may have a first specific gravity, outer core layer 120 may have a second specific gravity greater than the first specific gravity by at least 0.01, and inner cover layer 130 may have a third specific gravity greater than the second specific gravity by at least 0.01. In some embodiments, golf ball 100 may have the following mathematical relationship for specific gravity of each layer: inner core layer 110 may have a specific gravity SG1; outer core layer 120 may have a specific gravity SG2; inner cover layer 130 may have a specific gravity SG3, and outer cover layer 140 may have a specific gravity SG4, wherein SG3>SG4>SG2>SG1.

[0060] In some embodiments, golf ball 100 may have 300 to 400 dimples on the outer surface of outer cover layer 140. In some embodiments, golf ball 100 may have 310 to 390 dimples on the outer surface of outer cover layer 140. In some embodiments, golf ball 100 may have 320 to 380 dimples on the outer surface of outer cover layer 140. When the total number of the dimples is smaller than 300, the resulting golf ball may create a blown-up trajectory, which reduces flight distance. On the other hand, when the total number of the dimples is greater than 400, the trajectory of the resulting golf ball may be easy to drop, which reduces the flight distance.

[0061] 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.

Claims

1. A golf ball comprising, an inner core layer; an outer core layer enclosing the inner core layer; an inner cover layer enclosing the outer core layer, the inner cover layer having a first flexural modulus; an outer cover layer enclosing the inner cover layer, the outer cover layer having a second flexural modulus; and wherein the first flexural modulus is at least 10 times greater than said second flexural modulus.

2. The golf ball according to claim 1, wherein the ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) ranges from about 10 to about 30.

3. The golf ball according to claim 1, wherein the ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) ranges from about 25 to about 100.

4. The golf ball according to claim 1, wherein the ratio between the first flexural modulus and the second flexural modulus (first flexural modulus/second flexural modulus) ranges from about 95 to about 250.

5. The golf ball according to claim 1, wherein the inner core layer includes a third flexural modulus and the ratio of third flexural modulus to second flexural modulus (third flexural modulus/second flexural modulus) ranges from about 5 to about 10.

6. The golf ball according to claim 5, wherein the inner core layer includes at least one highly neutralized acid polymer composition.

7. The golf ball according to claim 1, wherein the inner core layer has a coefficient of restitution value ranging from about 0.775 to about 0.81.

8. The golf ball according to claim 1, wherein the inner core layer has a coefficient of restitution value that is about 0.005 to about 0.02 greater than the coefficient of restitution value of the golf ball.

9. The golf ball according to claim 1, wherein the inner cover layer has a Shore D hardness ranging from about 45 to about 55.

10. A golf ball comprising, an inner core layer, the inner core layer having a first flexural modulus; an outer core layer enclosing the inner core layer; an inner cover layer enclosing the outer core layer; an outer cover layer enclosing the inner cover layer, the outer cover layer having a second flexural modulus; and wherein the first flexural modulus is at least 5 times the second flexural modulus.

11. The golf ball according to claim 10, wherein the ratio of first flexural modulus to second flexural modulus (first flexural modulus/second flexural modulus) ranges from about 5 to about 10.

12. The golf ball according to claim 11, wherein the inner cover layer has a third flexural modulus and the ratio between the third flexural modulus and the second flexural modulus (third flexural modulus/second flexural modulus) ranges from about 10 to about 30.

13. The golf ball according to claim 10, wherein the inner core layer includes a first highly neutralized acid polymer composition.

14. The golf ball according to claim 13, wherein the first highly neutralized acid polymer composition includes one of HPF 2000 and HPF AD 1035.

15. The golf ball according to claim 10, wherein the inner core layer includes a first highly neutralized acid polymer composition and a second highly neutralized acid polymer composition and the ratio of the first highly neutralized acid polymer composition to the second highly neutralized acid polymer composition ranges from about 20:80 to about 80:20.

16. The golf ball according to claim 10, wherein the inner core layer has a coefficient of restitution value that is about 0.005 to about 0.02 greater than the coefficient of restitution value of the golf ball.

17. A golf ball comprising, an inner core layer; an outer core layer enclosing the inner core layer; an inner cover layer enclosing the outer core layer, the inner cover layer having a first flexural modulus; an outer cover layer enclosing the inner cover layer, the outer cover layer having a second flexural modulus; wherein the first flexural modulus is at least about 45,000 psi greater than said second flexural modulus.

18. The golf ball according to claim 17, wherein the first flexural modulus is between about 45,000 psi and about 65,000 psi greater than the second flexural modulus.

19. The golf ball according to claim 17, wherein the first flexural modulus is between about 60,000 psi and about 95,000 psi greater than the second flexural modulus.

20. The golf ball according to claim 17, wherein the inner core layer includes a third flexural modulus and the third flexural modulus is between about 15,000 psi to 65,000 psi greater than the second flexural modulus.