US20120064998A1

US20120064998A1 - Golf Ball Having High Initial Velocity

Info

Publication number: US20120064998A1
Application number: US13/198,554
Authority: US
Inventors: Hideyuki Ishii; Arthur Molinari
Original assignee: Nike Inc
Current assignee: Nike Inc
Priority date: 2010-08-20
Filing date: 2011-08-04
Publication date: 2012-03-15
Also published as: JP5779445B2; JP2012040383A; CN202654631U; KR101211295B1; AU2011213701A1; CN102371053B; EP2420297A2; KR20120018099A; EP2420297B1; AU2011213701B2; CN102371053A; TW201223594A; TWI457160B; EP2420297A3

Abstract

A multi-layer ball includes a core made of a high energy material such as a highly neutralized polymer and a cover made of a deadening material. A specified relationship exists between the compression and coefficient of restitution of the core and of the ball. The initial velocity of the ball is higher than what would be expected based on the coefficient of restitution of the ball compared to prior balls. The use of the deadening material allows the coefficient of restitution of the ball to be relatively low, which can yield improved spinnability in the half wedge shots while maintaining driver distance.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/375,775, entitled “Golf Ball Having High Initial Velocity”, and filed on Aug. 20, 2010, which application is hereby incorporated by reference.

FIELD

The present disclosure relates generally to a golf ball that has a plurality of layers. The layers are designed to have a specified relationship of coefficient of restitution and compression in order to achieve a high initial velocity.

BACKGROUND

It is standard in the industry to manufacture golf balls having a plurality of layers. Individual designers in the industry may feel that certain characteristics are more important than others, and may design a golf ball to optimize certain characteristics. Individual golfers may also feel that certain characteristics are more important or desirable than others.
In many cases, golfers desire golf balls that provide as long a drive as possible. Drive length is governed by many factors out of the golfer's control, such as the relative height of the tee box and the fairway, obstacles on or adjacent the fairway, wind speed, weather, and the like. Drive length is also governed by the golfer's swing parameters, such as his or her club head speed, his or her form, and the club he or she chooses to use for a particular drive. Drive length is also governed by the initial velocity at which the ball comes off the driver.
In other cases, such as in the short game, golfers desire golf balls that have a good feel and good spin/spinnability when hit. The feel of a golf ball is often governed by the material from which the cover layer or layers are made. The choice of cover material may also be based on durability, scuff resistance, color, and the like.
Many golfers desire a balance between the length of the ball trajectory and the feel of the ball. While some golfers want one or the other exclusively, it is more likely that a golfer will want a balance of these features.
It is desirable, therefore, to develop a ball that includes a combination of the features of a good feel and a maximum initial velocity. This combination of features is generally deemed desirable by a golfer in playing a ball.

SUMMARY

In one embodiment, a golf ball is provided. The golf ball may have a core and a cover surrounding the core. The core may comprise a highly neutralized polymer. The cover may comprise a deadening material. The core may have a first coefficient of restitution and the ball may have a second coefficient of restitution. The difference between the first coefficient of restitution and the second coefficient of restitution is less than about 0.032.
In another embodiment, a golf ball is provided. The golf ball may have a core and a cover surrounding the core. The core may have a compression x. The coefficient of restitution of the ball may be given by the equation 0.6511−0.024x²+0.1165x. The coefficient of restitution of the core may be given by the equation 0.7951−0.0121x²+0.416x. The coefficient of restitution for any ball made according to this trend line may be capped to produce a conforming ball. Using the deadening material as the cover may allow a designer to produce a conforming ball using a high energy core.
A golf ball can be designed with a particular relationship between compression, coefficient of restitution, and initial velocity. The material for and coefficient of restitution of the core can be devised to create a higher than expected initial velocity of a ball and/or spinnability of a ball. The material for and compression of the core can be devised to create a different coefficient of restitution for the ball as a whole than expected. In particular, balls made according to the invention will tend to have a higher initial velocity than expected for a given coefficient of restitution. This means that a golfer can have sufficient initial velocity to obtain a good driver distance while having increased spinnability due to the low coefficient of restitution in the short game, particularly on half wedge shots.
Balls that include high energy materials in the core, such as a highly neutralized polymer, and deadening or dampening materials in the cover, such as thermoplastic polyurethane, can achieve these benefits. A ball with a given high energy core can give a designer more cover choices in order to achieve desired ball performance parameters.
Other systems, methods, features and advantages of the embodiments 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 disclosure, 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 side view of a golf ball according to the present disclosure;

FIG. 2 is a cross-sectional view of an embodiment of a ball according to the present disclosure;

FIG. 3 is a cross-sectional view of another embodiment of a ball according to the present disclosure;

FIG. 4 is a cross-sectional view of another embodiment of a ball according to the present disclosure;

FIG. 5 is a chart comparing initial velocity when tested with a driver and the coefficient of restitution of the ball;

FIG. 6 is a chart comparing the coefficient of restitution and the compression for two balls and their corresponding cores; and

FIG. 7 is a chart showing various trend lines for the various cores from FIGS. 5 and 6.

DETAILED DESCRIPTION

A multi-layered ball is disclosed. Although the embodiments discussed herein are limited to golf balls, the invention is not intended to be so limited. The technology described herein may be applicable to any layered article, particularly a projectile, ball, recreational device, or component thereof.
FIG. 1 is a side view of a ball 100 that may be manufactured in accordance with the technology disclosed herein. FIGS. 1-4 show a generic dimple pattern applied to an outer surface 102 of ball 100. While the dimple pattern on ball 100 may affect the flight path of ball 100, no specific dimple pattern is critical to the use of the disclosed embodiments. A designer may select from any appropriate dimple pattern to be applied to ball 100.
FIG. 2 is a cross-sectional view of a first embodiment of ball 100 taken along line 2-2 of FIG. 1. As shown in FIG. 2, a ball 200 may have two layers. Ball 200 may include a core 204 and a cover 206 surrounding core 204. Any of the embodiments of golf balls described herein may be made according to any known technique, such as compression and/or injection molding the core, injection molding any outer layers, optionally adhering the layers of the golf ball together with an adhesive, and painting or coating the ball such as by spraying, brushing, dipping, and pad printing.
Core 204 may be made of a highly energy efficient material. A highly energy efficient material is one that tends to collide in a highly elastic manner. Core 204 may, in some embodiments, be made primarily or entirely from a highly neutralized polymer. In some embodiments, the highly neutralized polymer may be HPF 1000 or HPF 2000, available from E.I. DuPont de Nemours and Company. In some embodiments, core 204 may have a diameter between about 38 and about 41 mm. Cover 206 may, in some embodiments, be made of a less energy efficient or deadening material. A less energy efficient material is one that tends to collide in a less elastic manner. In some embodiments, cover 206 may be made primarily or entirely of a thermoplastic urethane resin. In some embodiments, cover 206 may have a thickness of at least 2.1 mm.
In some embodiments, one or more additional outer layers may be included but are not illustrated in FIG. 2 or any of the remaining FIGS. External to cover 206 in FIG. 2 may be a top coat. The top coat may be a coat applied to improve or adjust the appearance of ball 200. For example, the top coat may be applied to change the color of ball 200 or to change the degree of sheen on ball 200. In another embodiment, an additional coat may take the form of the application of a logo or other printing on exterior surface 202 of ball 200. Other additional coats may also be applied external to cover 206. It will be understood by a person having ordinary skill in the art that such external coats may be applied to any of the embodiments described herein, and accordingly, this optional coating will not be further described in connection with the following embodiments. It should be noted that golf balls are typically coated. All of the tested balls discussed in this application were provided with coatings, such as paint and protective coatings. While the coatings may have some impact on the coefficient of restitution of the ball, it is believed that this impact is negligible for the considerations of the present embodiments. However, if the coatings are made sufficiently thick or from a very hard or very soft material, this impact may be significant for design purposes of embodiments according to the present disclosure.
FIG. 3 is a cross sectional view of a second embodiment of ball 100 taken along line 2-2 of FIG. 1. As shown in FIG. 3, a ball 300 may have three layers. Ball 300 may include a core 304, an inner cover layer 308 surrounding core 304, and an outer cover layer 310 surrounding inner cover layer 308.
Core 304 may be made of a highly energy efficient material. Core 304 may, in some embodiments, be made primarily or entirely from a highly neutralized polymer. In some embodiments, the highly neutralized polymer may be HPF 1000 or HPF 2000, available from E.I. DuPont de Nemours and Company. Core 304 may have a diameter between about 38 mm and about 41 mm. In some embodiments any layer other than the cover layer(s) may include a highly neutralized ionomer. In some embodiments, all of the layers other than the cover layer(s) may aggregate to a size between about 38 mm and 41 mm. In some embodiments, all of the layers other than the cover layer(s) may aggregate to about 38.6 mm.
Inner cover layer 308 and outer cover layer 310 may, in some embodiments, be made of one or more less energy efficient or deadening materials. In some embodiments, inner cover layer 308, outer cover layer 310, or both, may be made primarily or entirely of a thermoplastic urethane resin or a thermoplastic polyurethane resin. In other embodiments, inner cover layer 308, outer cover layer 310, or both, may be made primarily or entirely of an ionomeric resin. In some embodiments, the ionomeric resin may be SURLYN®, commercially available from E.I. DuPont de Nemours and Company. In some embodiments, the combined thickness of inner cover layer 308 and outer cover layer 310 may be about 2.1 mm.
FIG. 4 is a cross-sectional view of ball 100 taken along line 2-2 of FIG. 1. As shown in FIG. 4, a ball 400 may have four layers. A first layer 412 may be an inner core layer. A second layer 414 may be an outer core layer and may surround first layer 412. A third layer 416 may be an inner cover layer and may surround second layer 414. A fourth layer 418 may be an outer cover layer and may surround third layer 416. First or inner core layer 412 and second or outer core layer 414 may together be considered and referred to as core 420. Third or inner cover layer 416 and fourth or outer cover layer 418 may together be considered and referred to as cover 422.
Core 420 may be made of one or more highly efficient materials, and each of first layer 412 and second layer 414 may be made of a different formulation of highly efficient material. At least one layer of core 420 may, in some embodiments, be made primarily or entirely from a highly neutralized polymer. In some embodiments, the highly neutralized polymer may be HPF 1000 or HPF 2000, available from E.I. DuPont de Nemours and Company. Cover 422 may be made of a less efficient or deadening material. In some embodiments, third layer 416, fourth layer 418, or both, may be made primarily or entirely of a thermoplastic urethane resin. In other embodiments, third layer 416, fourth layer 418, or both, may be made primarily or entirely of an ionomeric resin. In some embodiments, the ionomeric resin may be SURLYN®, commercially available from E.I. DuPont de Nemours and Company. In some embodiments, the combined thickness of inner cover layer 416 and outer cover layer 418 may be about 2.1 mm. In some embodiments any layer other than the cover layer(s) may include a highly neutralized ionomer. In some embodiments, all of the layers other than the cover layer(s) may aggregate to a size between about 38 mm and 41 mm. In some embodiments, all of the layers other than the cover layer(s) may aggregate to about 38.6 mm.
In FIG. 4, ball 400 has been described and illustrated as having a plurality of layers. In some embodiments, an additional layer may be added. For example, in some embodiments, a mantle layer may be added between core 420 and cover 422. In other embodiments, an intermediate cover layer may be inserted between inner cover layer 416 and outer cover layer 418. In other embodiments, an intermediate core layer may be inserted between inner core layer 412 and outer core layer 414.
It will also be apparent to a person having ordinary skill in the art that similar modifications may be made to any of the embodiments, based on the specific desires of a designer without departing from the intention of the present embodiments. For example, a four layer ball could include an inner core layer, an intermediate core layer, an outer core layer, and a single cover layer. Likewise, a ball four layer ball could include a single core layer and an inner cover layer, an intermediate cover layer, and an outer cover layer. Balls having other numbers of intermediate layers would also be apparent to a person having ordinary skill in the art. The embodiments illustrated, therefore, are exemplary in nature, rather than intended to be limiting.
Turning now to FIG. 5, there is shown a chart that demonstrates a difference between the disclosed embodiments and balls currently commercially available. These balls are described in greater detail below. The values on the left side y-axis are the initial velocity of the ball when tested with a driver. Each ball was hit with the same condition (head speed, angle of attack, etc.) with a 9.5 loft angle Nike SQ driver.
The initial velocity is shown in the chart by the height of each bar on the bar graph. The initial velocity as shown in the bar chart is shown in miles per hour. An initial velocity of 150 miles per hour equates to about 220 feet per second. An initial velocity of about 170 miles per hour equates to about 250 feet per second.
The values on the right side of the chart reflect the coefficient of restitution (coefficient of restitution) of the ball as a whole. In order to measure the coefficient of restitution of an object, the object is fired by an air cannon at an initial velocity of about 40 meters per second. A steel plate is positioned about 1.2 meters from the cannon, and a speed monitoring device is located at a distance of about 0.6 to about 0.9 meters from the cannon. The object is fired from the air cannon, passes through the speed monitoring device to determine an initial velocity. The object then strikes the steel plate and rebounds back through the speed monitoring device to determine the return velocity. The coefficient of restitution is the ratio of the return velocity over the initial velocity. The coefficient of restitution for each ball is shown by the line 544 that appears on the chart.
The x-axis identifies the balls tested. Each ball tested was tested for initial velocity and coefficient of restitution. The first nine balls (numbered 1-9) are commercially available golf balls. Each of these golf balls has a core made of a butadiene rubber compound that has a diameter about 40 mm. For each ball, the precise formulation of the core is slightly different. The core of each ball is made of butadiene rubber with different additives or different sizes that create different compressions and coefficient of restitution. It is believed that there is a correlation, potentially a strong correlation, between coefficient of restitution and core size, so that minor variations in core size may have a non-negligible impact on coefficient of restitution. The cover of each of the balls is about 1.4 mm thick and is made primarily of SURLYN®.
The ball labeled 10, on the other hand, is a ball made according to the present embodiments. The ball labeled ball 10 instead has a core made of primarily of a highly neutralized polymer resin that is about 38 mm in diameter. The diameter of the core may be as large as about 41 mm. The cover of the ball is about 2.1 mm thick, but may be as thin as about 0.9 mm thick. If desired, a mantle layer may be included to ensure that the ball conforms to minimum USGA size regulations of 42.67 mm (1.680 inches).
In comparing the relationship of initial velocity and coefficient of restitution, it is noted that for balls 1-9, there is a general correlation between coefficient of restitution and initial velocity. For example, for balls 1, 2, 4, and 5, where the coefficient of restitution is below 0.795, the initial velocity drops to below about 150.2. For balls 3, 6, 7, and 8, where the coefficient of restitution is above 0.800, the initial velocity is above about 150.8. For ball 9, where the coefficient of restitution is about 0.800, the initial velocity is about 150.5. The chart, therefore, shows a general correlation between the coefficient of restitution and the initial velocity.
However, the chart shown in FIG. 5 indicates that the initial velocity of ball 10 deviates from the anticipated initial velocity of a conventional ball with a coefficient of restitution of 0.774. For ball 10, the coefficient of restitution has a value of about 0.774. Instead of the initial velocity being under 150 miles per hour, as would be predicted from conventional balls 1-9, the initial velocity of ball 10 remains at 150.8, which is almost as high as the initial velocity of balls having a coefficient of restitution that is much higher than ball 10. Accordingly, by using the ball structure indicated above, the ball coefficient of restitution can remain relatively low for better feel and spinnability in the short game, while maintaining an adequately high initial velocity for longer distance with a driver.
This is especially important for the half wedge shots. With a lower coefficient of restitution ball, the golfer will tend to hit the ball harder, i.e., with a higher club head speed, to achieve the same distance as a ball with higher coefficient of restitution. The harder hit (higher club head speed) imparts more spin to the ball. Therefore, a golfer can have a lower coefficient of restitution ball with good initial velocity and driver distance, but increased spinnability in the short game.
An additional feature that may be compared between existing balls and the ball of the present disclosures may be seen in FIG. 6. FIG. 6 is a chart showing the relationship between compression and coefficient of restitution for various balls and ball cores. The values on the x-axis represent the compression of the inner core layer of the ball. The compression is determined in a manner well-known in the art. The spherical core and/or ball is placed under an initial load of 10 kg. A measurement of the diameter of the ball, typically in millimeters, is taken at one or more points, such as at the pole(s), the seam, or a random point. Either a single value or the average of the values is recorded. The load is increased to 130 kg and a second measurement of the diameter of the ball, also in millimeters, is taken at the same point or points. The single value or the average of the values under the greater load is recorded. The difference between the recorded values, in millimeters, is the compression.
The values on the y-axis represent the coefficient of restitution (coefficient of restitution) for each of the four items considered. Line 650 represents the relationship between the compression and coefficient of restitution for a core that is about 38 mm in diameter and that is made of a butadiene rubber compound. The equation for this rubber core trend line is given by
y=0.7531−0.0128x ²+0.055x Eq. 1
where x is the inner core compression and y is the corresponding coefficient of restitution.
Line 660 represents the relationship between the compression and coefficient of restitution for a ball that includes a cover that covers the core shown in line 650. The equation for this line is given by
y=0.6794−0.0179x ²+0.0831x Eq. 2
where x is the compression of the core and y is the coefficient of restitution of the ball as a whole. The difference between the relative coefficient of restitution of the core and the coefficient of restitution of the ball ranges between about 0.035 and about 0.037.
However, a comparison of the relative coefficient of restitution for the ball including a core made primarily or entirely of a highly neutralized polymer shows a distinct difference. Line 670 represents the relationship between the compression and coefficient of restitution for a core that is about 38 mm in diameter and that is made primarily or entirely of a highly neutralized polymer. The equation for this line is given by
y=0.7951−0.0121x ²+0.0416x Eq. 3
where x is the compression of the core and y is the corresponding coefficient of restitution.
Line 680 represents the relationship between the compression and coefficient of restitution for a ball that includes a cover that covers the core shown in line 670. The cover is the same cover structure as the cover of the ball governed by line 650. The equation for this line is given by
y=0.6511−0.024x ²+0.1165x Eq. 4
where x is the compression of the core and y is the coefficient of restitution of the ball as a whole. The difference between the relative coefficient of restitution of the core and the coefficient of restitution of the ball ranges between about 0.026 and 0.031.
As is clearly shown in FIG. 6, therefore, for a given inner core compression, a ball with a rubber core will have a lower coefficient of restitution than a ball with an HNP core. Also, to maximize the effects of the deadening material, the difference between the coefficient of restitution of the core and the coefficient of restitution of the ball should be at least 0.026, but may be significantly higher, such as 0.037, 0.05, 0.1 or even higher. The lower the coefficient of restitution of the ball, the more spinnable the ball may be, so a ball with a higher coefficient of restitution difference, such as at least 0.037 or at least 0.05, may be desirable. The relatively high coefficient of restitution of the cores made according to the invention as discussed above allows for significant flexibility in selecting cover materials, as the coefficient of restitution of the ball as a whole may still be within top performance ranges when provided with a deadening cover.
These benefits are shown more simply in FIG. 7, where rubber core trend line 762 shows a consistently lower inner core compression for a given coefficient of restitution than HNP core trend line 760. HNP core ball trend line 764 (the trend line for a full ball with an HNP core) is shown for reference.
Accordingly, substituting a resin core with a specified coefficient of restitution for a rubber core with the same specified coefficient of restitution allows for a dramatic difference in the relative coefficient of restitution of the ball and the core. This is particularly true when the resin core coefficient of restitution exceeds the coefficient of restitution given by the rubber core trend line and where the ball has a coefficient of restitution less than the coefficient of restitution given by the equation
y=−0.0103x+0.8419 Eq. 5
where y is the coefficient of restitution and x is an inner core compression.
This can typically be achieved by making at least one interior/non-cover layer from a highly neutralized ionomer/polymer. The properties of the cover need not change between the butadiene rubber core and the highly neutralized polymer core. However, the difference in coefficient of restitution between the core and the ball is at least about 0.004 less when the highly neutralized polymer core is used. This allows for a ball with a higher coefficient of restitution to be made with the same cover materials.
When following the coefficient of restitution trend lines discussed above for highly neutralized polymer cores and balls made with highly neutralized polymer cores, other limitations may need to be observed. For example, a conforming ball will have a coefficient of restitution which is lower than the trend given by Eq. 5 or, more conservatively, by the equation
y=−0.0103x+0.8299 Eq. 6
where y is the coefficient of restitution and x is an inner core compression. Therefore, a designer may want to cap the coefficient of restitution of a ball which follows Eq. 4 so that the coefficient of restitution does not exceed the coefficient of restitution given by Eq. 6.
A ball made within the scope of the disclosure above is believed to have improved properties. Such a ball is believed to have a higher initial velocity than may be expected. Such a ball may also allow for a greater variety of cover materials, particularly including those that have a lower cost. Such a ball may provide a golfer with a less expensive ball that has a longer trajectory than other balls.
Alternate constructions of the layered article may also be possible to enhance these benefits. For example, a golf ball may be made according to the teaching of both this disclosure and the article described in U.S. Pat. No. ______, currently U.S. application Ser. No. 12/860,785, entitled “Golf Ball Having Layers with Specified Moduli and Hardnesses”, and filed on Aug. 20, 2010, which disclosure is incorporated herein by reference in its entirety.
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 disclosure. Accordingly, the disclosure 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

What is claimed is:

1. A ball, comprising:

a core comprising a highly neutralized polymer; and

a cover comprising a deadening material, wherein the cover is disposed radially outward of and surrounds the core;

wherein the core has a first coefficient of restitution and the ball has a second coefficient of restitution; and

wherein the difference between the first coefficient of restitution and the second coefficient of restitution is greater than about 0.026.

2. The ball according to claim 1, wherein the first coefficient of restitution is greater than 0.78.

3. The ball according to claim 1, wherein the second coefficient of restitution is less than 0.79.

4. The ball according to claim 3, wherein the second coefficient of restitution is about 0.774.

5. The ball according to claim 1, wherein the core has at least two layers, at least one layer comprising a highly neutralized polymer, and wherein the cover has at least two layers, at least one layer comprising thermoplastic urethane.

6. The ball according to claim 1, wherein the ball has a higher initial velocity than a rubber core ball with substantially similar non-core layers.

7. A ball, comprising:

a core having a compression “x”; and

a cover surrounding the core;

wherein the coefficient of restitution of the ball is given by: 0.6511−0.024x²+0.1165×; and

wherein the coefficient of restitution of the core is given by: 0.7951−0.0121x²+0.416x.

8. The ball according to claim 7, wherein the coefficient of restitution of the core is greater than 0.78.

9. The ball according to claim 7, wherein the coefficient of restitution of the ball is less than 0.79.

10. The ball according to claim 7, wherein the core has at least one layer comprising a highly neutralized polymer.

11. The ball according to claim 7, wherein the cover has at least one layer comprising thermoplastic urethane.

12. The ball according to claim 7, wherein the coefficient of restitution of the ball is less than the coefficient of restitution given by: −0.0103x+0.8419.

13. A ball comprising:

a core comprising one or more layers;

a cover comprising one or more layers, wherein the cover is positioned radially outward of and surrounds the core;

wherein the core has a diameter of at least 38 mm;

wherein at least of the core layers comprises a highly neutralized ionomer; and

wherein the core has a coefficient of restitution greater than a rubber core trend line coefficient of restitution, wherein the rubber core trend line coefficient of restitution is given by the equation: y=−0.0128x2+0.055x+0.7531, wherein “y” is the coefficient of restitution and “x” is an inner core compression.

14. The ball of claim 13, wherein the ball has a higher initial velocity than a rubber core ball with substantially similar non-core layers.

15. The ball of claim 13, wherein the ball has a coefficient of restitution less than the coefficient of restitution given by the equation: y=−0.0103x+0.8419.

16. The ball of claim 13, wherein the core comprises a highly neutralized polymer.

17. The ball of claim 16, wherein the cover comprises thermoplastic polyurethane.

18. The ball of claim 13, wherein the core consists of two layers, wherein at least one of the layers consists of a highly neutralized polymer.

19. The ball of claim 13, wherein the cover consists of two layers, wherein at least one of the layers consists of thermoplastic polyurethane.

20. The ball of claim 13, wherein the coefficient of restitution of the ball is less than the coefficient of restitution given by the equation: y=−0.0103x+0.8299.