JP2002533178A - Low spin golf ball - Google Patents

Abstract

(57) A golf ball comprising a core having a Riehle compression ratio of at least 0.075 and a cover having a Shore D hardness of at least 65, wherein the cover has an α, β- The above-described golf club, comprising at least one high acid ionomer resin comprising a copolymer of an unsaturated carboxylic acid and an α-olefin, wherein about 10% to about 90% of the carboxyl groups of the copolymer are neutralized with metal cations. ball.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] This application is a continuation-in-part of co-pending US patent application Ser. No. 09 / 102,342, filed on Jun. 22, 1998, which is incorporated by reference in its entirety. 08 / 716,01
No. 6,820,489 filed on Jun. 8, 1994, which is a divisional application of U.S. Patent Application No. 08 / 255,442, filed on June 8, 1994. No. 5,368,304, which is a continuation of US patent application Ser. No. 08 / 054,406.

FIELD OF THE INVENTION The present invention relates to golf balls, and more particularly, to improved golf balls having low spin rates (such as two-piece, thread-wound three-piece, etc.). These golf ball improvements are the result of combining a soft core with a hard cover made of one or more specific hard, high-rigidity ionomers. The combination of a soft core and a hard cover, while maintaining properties such as elasticity and durability required for repetitive play, results in an improved golf ball with a lower spin rate than expected.

In a further embodiment of the present invention, the spin speed is further reduced by reducing the weight of the soft core and / or increasing the thickness of the cover.
Background of the Invention

[0004] For both skilled and unskilled golfers, spin speed is one of the important properties of golf balls. High spin rates allow more skilled golfers, such as PGA pros and less handicapped players, to have maximum control over the golf ball. Such a high spin rate is particularly effective when a skilled golfer hits an approach shot on the green. The ability to intentionally generate a "backspin" to stop the ball quickly on the green, and / or to generate a "sidespin" to hit the ball into a draw or fade, would provide the golfer's ball control. Substantially improve. Thus, skilled golfers generally prefer golf balls with high spin rates.

[0005] However, not all golfers desire a golf ball with a high spin rate, especially a player with a high handicap who cannot intentionally control the spin of the ball. In this regard, unskilled golfers have two essential obstacles to improving their play, especially slicing and hooking. When the club head comes into contact with the ball, often unexpected side spins occur, causing the ball to deviate from the target course. Side spin reduces the golfer's ball control as well as the ball's flight distance. As a result, unnecessary strokes are repeated in play.

[0006] For this reason, while a skilled golfer desires a golf ball having a high spin rate, a golf ball that is more effective for an unskilled player is a ball having a characteristic of a low spin rate. For amateur golfers, a low spin rate ball reduces slicing and hooking and increases the distance the ball rolls.

[0007] The present inventors have reduced the spin rate after club impact while maintaining the properties of golf balls such as durability, playability and resilience required for repeated use. The need for the development of golf balls has been addressed. The low spin rate golf ball of the present invention conforms to the rules and regulations established by the United States Golf Association (USGA).

[0008] In line with these regulations, the USGA has established five special rules that golf balls must meet. According to USGA rules, golf balls have a diameter of 1.68
Must be at least 0 inches. However, despite these limitations, there are no specific restrictions on the maximum diameter allowed for a golf ball. As a result, golf balls can be as large as desired, as long as the diameter is greater than or equal to 1.680 inches, and as long as they meet the other four special rules.

[0009] Also, according to USGA regulations, the ball must weigh no more than 1.620 ounces, and the initial velocity may not exceed 250 feet / second with a maximum tolerance of 2%, or up to 255 feet / second. In addition, USGA rules state that golf balls can be used under certain conditions.
When hit with a USGA outdoor driving machine, the ball is not required to fly more than 280 yards with a 6% test tolerance.

The present inventors have found that combining a relatively soft core (ie, a Riehle compression ratio of about 0.075-0.115) and a hard cover (ie, a Shore D hardness of 65 or greater) results in a golf ball of the resulting golf ball. It revealed that the overall spin rate was significantly reduced. The inventors have further learned that increasing the cover thickness and / or increasing the overall diameter of the formed golf ball further reduces the spin rate of the ball.

[0011] The finest golf balls sold in the United States are generally classified as one of two types: either two-piece balls or three-piece balls. Two-pieces represented by golf balls sold by Spalding & Evenflo Companies, Inc. (through the wholly owned subsidiary Lisco, Inc. of this invention) under the registered trademark of TOP-FLITE The ball consists of a solid polymer core and a separately formed outer cover. A so-called three-piece ball, represented by a golf ball sold by Acushnet Company under the registered trademark of TITLEIST, is a liquid center (for example, TITLEIST TOUR 384) or a solid center (for example, TITLEIST DT), or an elastomeric yarn wound around the center. It consists of a winding and a cover.

Spalding's two-piece golf balls are formed by molding a natural (balata) or synthetic (such as a thermoplastic resin such as an ionomer resin) polymer cover composition around a preformed polybutadiene (rubber) core. Manufactured. In the forming step, a desired dimple (dent) pattern is formed in the cover material. Dyes and dyes, and often optical brighteners, are added directly to the typical "off-white" pigmented polymer cover composition prior to molding to reduce the number of coating steps involved in golf ball finishing. Dyes and / or optical brighteners are added to the cover composition to form the golf ball core to supplement the dyes to produce white or colored (especially orange, pink and yellow) golf balls. The step of applying is not required.

[0013] Spalding is the world's leading manufacturer of two-piece golf balls for multilayer golf balls. Spalding manufactures over 60 different two-piece balls, but these golf balls depend on the ball core, cover, coating material, and ball surface structure (ie, dimple pattern).
Competitiveness (ie, spin speed, compressibility, feel, etc.), flight distance (initial speed, COR
Etc.), durability (impact resistance, cut resistance and weather resistance), and appearance (ie, whiteness, reflectance, yellowish color, etc.) are extremely diverse. For this reason, Sp
Alding's two-piece golf balls offer both amateur and professional golfers a wide variety of performance characteristics suitable for personal play.

With respect to the specific components of a golf ball, the properties of the cover may, in some cases, affect overall feel, spin (control), coefficient of restitution (COR), and initial velocity of the ball (
By way of example, although it may make a significant contribution to Molitor US Pat. No. 3,819,768), the initial velocity of two-piece and three-piece balls is determined primarily by the coefficient of restitution of the core. The coefficient of restitution of the core of a wound (ie, three-piece) ball can be adjusted within certain limits by adjusting the winding tension and the composition of the yarn and center. Speaking of two-piece balls,
The coefficient of restitution of the core is one of the functions of the properties of the elastomer composition from which the core is made.

[0015] The cover component of a golf ball has a particularly large effect on providing the obtained ball with compressibility (feel), spin speed (control), flight distance (restitution coefficient COR) and durability (that is, impact resistance, etc.). are doing. Spalding and others have developed various cover compositions to optimize the properties desired for golf balls.

Over the past two decades, improvements in cover and core material formulations and changes in dimple patterns have almost continuously increased the flight distance of golf balls. However, the finest golf balls must meet some other important design standards. To compete successfully in today's golf ball market,
Golf balls must be resistant to cutting and have a good finish.
In other words, when putting, you must draw a straight line and have a good click sound and feel. Furthermore, golf balls must have the spin and control characteristics required by the skills and experience of the end user. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improved top-grade golf balls (two-piece and three-piece) with reduced spin rates. The improved golf ball provides less control to an unskilled golfer on shots and allows greater flight distance.

In another embodiment, the spin rate of the golf ball is further reduced by increasing the thickness of the cover and / or reducing the weight and softness of the core. By increasing the cover thickness and / or the overall diameter of the molded golf ball,
A further decrease in spin rate is observed.

With respect to increasing the size of golf balls, for many years golf ball manufacturers have generally manufactured golf balls at or near the minimum size and maximum weight of the USGA standards. However, there were exceptions, particularly with respect to the manufacture of teaching golf balls. For example, oversized, overweight (and therefore unapproved) golf balls have been sold for use in golf teaching purposes (see US Pat. No. 3,201,384 to Barber).

The large golf ball was issued to the previous owner of the Assignee, January 1, 1980.
It is also disclosed in the New Zealand Patent No. 192,618 dated. This patent discloses a large golf ball with a diameter of 1.700 to 1.730 inches and a large core of resilience material (ie, a diameter of about 1.585 to 1.595 inches) to increase the coefficient of restitution.
Is taught. The patent further discloses that the golf ball has a cover that is thinner than the thickness of the conventional ball cover (i.e., the conventional two-piece ball has a cover thickness of 0.090 inches, while , The cover thickness of this ball is about 0.050 inch).

It is also notable that the golf balls manufactured by Spalding in 1915 had a diameter of 1.630 to 1.710 inches. As the diameter of the ball increases, the weight of the ball also increases. These balls consist of a cover made of balata / gutta percha, a core made of solid rubber or liquid sack, and a wound of elastic yarn.

A golf ball known as LYNX JUMBO was also marketed by Lynx in October 1979. The diameter of the ball was 1.76 to 1.80 inches. This ball has had little or no commercial success. The LYNX JUMBO ball was composed of a core made of a wound core and a cover made of natural or synthetic balata.

However, despite increasing the diameter of the balls, none of these golf balls exceed the spin reduction characteristics of the present invention, as well as the overall playability, distance and durability. , And / or USGA stipulations. One of the objects of the present invention is to improve the low spin characteristics while maintaining the characteristics such as resilience and durability required for repetitive play.
To manufacture golf balls in accordance with the GA rules.

[0023] These and other objects and features of the invention will be apparent from the following summary and detailed description of the invention, and from the claims.

SUMMARY OF THE INVENTION The present invention relates to an improved golf ball having a low spin rate at impact with a club. The golf ball comprises a soft core and a hard cover. The hard cover can be larger than a normal diameter. If the spin speed is low, it is possible to extend the flight distance of the ball. If the spin rate is low, golfers with insufficient skills can control the golf ball easily. The reason for this is that the low spin rate reduces unwanted side spins that cause slices and hooks. The combination of a hard cover and a soft core provides a ball with a lower spin rate than expected while maintaining high resilience and excellent durability.

The golf ball of the present invention comprises a core and a cover. The core (which may be of the molded or wound type) has a Riehle compressibility of at least 0.075, preferably 0.
075 to about 0.115, and the PGA compression ratio is about 45 to 85. The Shore D hardness of the cover is at least 65.

In another embodiment, the resulting ball is larger than a standard 1.680 inch golf ball. Its diameter ranges from about 1.680 to 1.800 inches, more suitably about 1.700 to 1.800 inches, preferably 1.710 to 1.730 inches, and most preferably about 1.71 inches.
It is in the range of 7 to 1.720 inches.

In a further embodiment, the cover thickness of the ball can be varied. The cover thickness is greater than standard 0.0675 inches and up to about 0.130 inches, preferably in the range of about 0.0675 to about 0.1275 inches, more preferably about 0.0825 to 0.0925 inches, and most preferably about 0.0860 to 0.0890 inches. is there. The core is preferably of standard size and is approximately between about 1.540 and 1.545 inches. In one embodiment, the core used in the present invention is a specially manufactured softened polybutadiene elastic solid core having a typical diameter of about 1.540 to 1.545 inches. The core comprises a base elastomer selected from polybutadiene and a mixture of polybutadiene and another elastomer, at least one metal salt of an unsaturated carboxylic acid (heterocrosslinker), and a free radical initiator (heterocrosslinker) Produced from the composition. In addition, it is possible to incorporate suitable and compatible modifying components such as, but not limited to, metal activators, fatty acids, fillers, polypropylene powder and other additives.

Of particular importance is that the amount of metal salt of unsaturated carboxylic acid incorporated into the core composition is limited in order to obtain the desired core softness and weight. In this regard, when trying to enlarge the entire ball, the finished ball after molding is
It is understood that the core composition is adjusted so that it falls within the weight parameters specified by the above. Because the finished golf ball must meet the USGA weight limit (1.620 ounces), the core component of a large ball with a thick cover is designed to be not only flexible but also light in weight.

In such a case, since the large ball must have the same weight as the standard ball, the specific gravity of the core is made smaller than that of the standard core. The core usually weighs about 36-37 g for standard finished size balls and 33-34 g for larger finished size balls.

The core composition produces a soft molded core that still maintains the required resilience (COR), compressibility (hardness) and durability properties. Also, in a further embodiment, a wound core may be used. PGA compression ratio of the whole core is about 45-85,
Preferably it is in the range of about 70-80. Riehle compression ratio is about 0.075 or more, preferably 0.0
It ranges from 75 to 0.115, and the resilience of the core is about 0.760 to 0.780.

The cover is preferably composed of a rigid, high-rigidity ionomer resin, most preferably a high acid ionomer resin, or a blend thereof, neutralized with a metal cation containing more than 16% by weight of a carboxylic acid. The Shore D hardness of the cover is about 65 or more.

For the cover composition comprising the ionomer resin of the present invention, the ionomer resin is a polymer containing interchain ionic crosslinks. Due to its toughness, durability and flight characteristics, the EI DuPont de Nemours & Company under the trade name `` Surlyn® '' and more recently the Exxon Corporation (see U.S. Pat. (Trademark)) and various ionomer resins sold under the trade names Iotek
It has become the material of choice for golf ball covers over balata (trans-polyisoprene, natural or synthetic) rubber.

The ionomer resin is generally an ionic copolymer composed of an olefin such as ethylene and a metal salt of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid. In some cases, a terpolymer may be formed by further blending a softening comonomer such as an acrylate. The interaction of the ionic side groups of the ionomer resin results in the formation of ion-enriched aggregates in the non-polar polymer matrix. Neutralizing some of the acid groups in the copolymer with metal ions such as sodium, zinc, magnesium, lithium, potassium, calcium, etc., enhanced the properties required for golf ball construction as compared to balata ( That is, a thermoplastic elastomer having improved durability and the like is obtained.

The ionomer resin used to make the cover composition is disclosed in US Pat. No. 3,421,
No. 766 or British Patent No. 963,380, etc., and are compounded according to known procedures, and neutralization is performed according to the procedures disclosed in Canadian Patent Nos. 674,595 and 713,631. The ionomer is prepared by copolymerizing an olefin and a carboxylic acid to form a copolymer having a random distribution of acid units along the polymer chain. In general, ionic copolymers usually comprise one or more α-olefins and from about 9% to about 20% by weight of an α, β-ethylenically unsaturated mono- or dicarboxylic acid to reduce the original copolymer to the required extent. Neutralized with metal ions.

[0035] At least about 20% of the carboxylic acid groups of the copolymer are neutralized with metal ions (sodium, potassium, zinc, calcium, magnesium, etc.) to an ionic state. Suitable olefins for use in preparing ionomer resins include ethylene, propylene, butene-1, hexene-1 and the like. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Ionomer resins used in the golf ball industry are typically copolymers of ethylene and acrylic acid (i.e., E
scor®) and / or copolymers of ethylene and methacrylic acid (ie,
Surlyn (registered trademark)). Further, two or more ionomer resins may be incorporated into the cover composition to bring out the desired properties of the resulting golf ball.

Cover compositions that can be used to make the golf balls of the present invention include, but are not limited to, co-pending US patent application Ser. Nos. 07 / 776,803 (filed Oct. 15, 1991) and US Pat.
No. 07 / 901,660 (filed June 19, 1992) (both patent applications are incorporated herein by reference). Briefly, the cover material is composed of a rigid and highly rigid ionomer resin, which preferably comprises a relatively high amount of acid (
That is, it contains more than 16% by weight of an acid, preferably about 17% to about 25% by weight of the acid, more preferably about 18.5% to about 21.5% by weight of the acid, and contains metal ions (sodium, zinc, potassium). , Calcium, magnesium, etc.). The high acid resin is compounded and melt processed to produce a composition having improved hardness and coefficient of restitution values compared to low acid ionomers or blends of low acid ionomer resins containing up to 16% by weight of acid.

[0037] Suitable cover compositions are made from specific blends of two or more high acid ionomers and other cover additives and are processable, competitive, distance and / or as noted by the prior art. It does not show any limit regarding durability. However, as described in detail below, it is also possible for the cover composition to be comprised of one or more low acid ionomers, provided that the molded cover exhibits a hardness of 65 or more on the Shore D scale.

By using a more flexible core and a hard cover, the finished inventive ball as a whole exhibits a significantly lower spin rate than a conventional ball of the same size and weight. Furthermore, increasing the cover thickness or reducing the weight of the soft core also reduces the spin.

As is apparent from the above description, the two main properties involved in golf ball performance are resilience and PGA compression. The resilience or coefficient of restitution (COR) of a golf ball is a constant "e", which is the ratio of the relative velocities of an elastic sphere before and after having a direct impact. Therefore, COR ("e") can vary from 0 to 1, where 1 corresponds to a completely elastic collision and 0 corresponds to a completely inelastic collision.

In general, besides COR, club head speed, club head mass,
Additional factors of ball weight, ball size and density, spin rate, trajectory angle, and surface shape (i.e., dimple pattern and dimple coverage), and environmental conditions (e.g., temperature, humidity, atmospheric pressure, wind, etc.) The distance at the time of hitting is determined by the distance. Along this line, the flight distance of a golf ball under controlled environmental conditions is a function of club speed and mass, ball size and density and resilience (COR), and other factors. The initial speed of the club, the mass of the club, and the launch angle of the ball are essentially those provided by the golfer at the time of the shot. Club head, club head mass, trajectory angle and environmental conditions are not determinants that can be controlled by the golf ball manufacturer, and ball size and weight
These are not significant factors among golf ball manufacturers, as set by the USGA. In general, factors to be considered for the improvement of the flight distance and determinants are a ball restitution coefficient (COR) and a surface shape (a dimple pattern, a ratio of a dimple-free area to a dimple-containing area, and the like).

The COR of a solid core ball is a function of the core composition and the cover composition. The core and / or cover may be composed of one or more layers, such as a multilayer ball.
For a ball containing a wound core (i.e., a ball covered with a rubber thread wound around a liquid or solid center), the coefficient of restitution is a function of the rubber composition and tension, as well as the composition of the center and cover. Become. As with the solid core ball, the center and cover of the wound core ball may also consist of one or more layers. The COR of the golf balls of the present invention is a function of the composition and physical properties of the core and cover layer materials, such as flexural modulus, hardness, and, in particular, resilience (ie, the ability to quickly recover from deformation due to high impact).

The coefficient of restitution is the ratio of the reflection speed to the incident speed. In an embodiment of the present application, the coefficient of restitution of a golf ball is determined by projecting the ball horizontally at a speed of 125 ± 5 feet per second (fps) (corrected to 125 fps) toward a substantially vertical hard steel plate, Was measured by electronically determining the incidence and reflection velocities. A pair of Oehler Mark
55 Ballistic Screen (Oehler Research, Inc, PO Box 9135, Austin, Texas 7876
(Available from 6). The screen emits a timing pulse when an object passes through the screen. The screens were placed at a distance of 36 inches from each other and 25.25 inches and 61.25 inches from the reflective wall. In the direction of the reflecting wall, the ball speed is measured by emitting a timing pulse from the screen 1 to the screen 2 (measured as the average speed of the ball per 36 inches), and then the reflection speed is measured from the screen 2 to the screen 1 by the same distance. Was measured against. To prevent the ball from hitting the edge of the barrel that fired the ball, set the reflective wall at 2 ° from the vertical.
The ball was tilted so that it rebounded slightly downward. The reflective wall is a 2.0 inch thick solid steel.

As described above, although the incident speed is corrected to 125 fps, it must be 125 ± 5 fps. The correlation between COR and forward or incident velocity has been studied and is ± 5f
COR is reported as if the ball had an incident speed of exactly 125.0 fps, since the correlation was found within the range of ps.

If the ball is to be kept within the United States Golf Association (USGA) standards, the coefficient of restitution must be carefully managed for all commercially available golf balls. As mentioned earlier, the USGA rules include USG
When tested on equipment approved by A., the initial speed of a "certified" ball is 2 in air at 75 ° F.
It is specified that it must not exceed 55 feet per second. Since the coefficient of restitution of the ball is related to the initial velocity of the ball, it has a sufficiently high coefficient of restitution approaching the upper limit of the USGA for the initial velocity, while having sufficient softness (i.e., spinning) to improve playability (i.e. spin) That is, it is highly desirable to produce a ball having hardness).

PGA compression is another important property involved in golf ball performance.
The compression ratio of the ball affects the playability of the ball at the time of a shot, and produces a sound and a “click sound”. Similarly, compressibility also affects the "feel" of the ball (i.e., a hard or soft response feel), particularly the feel during chipping and putting.

Furthermore, although the compression ratio itself hardly affects the flight distance characteristics of the ball, the compression ratio may affect the ball's playability at the time of a shot. The degree of compression of the ball against the club face and the softness of the cover strongly influence the spin rate obtained. Typically, a soft cover will provide a higher spin rate than a hard cover.
In addition, a hard core can obtain a higher spin speed than a soft core. The reason for this is that, at impact, the hard core acts to compress the ball's cover against the club face to a greater extent than with the soft core, thereby making it easier to "trap" the ball on the club face, This is because a high spin speed is generated. In effect, the cover is squashed between the relatively less compressible core and the club head. When a soft core is used, the cover is subjected to much lower compressive stress than when a hard core is used, and thus does not make enough contact with the club face. Therefore, the spin speed becomes low. The term "compression (rate)" as used in the golf ball industry generally defines the overall deformation that a golf ball experiences when subjected to a compressive load. For example, the PGA compression ratio indicates the amount of change in the shape of a golf ball during a shot.

Conventionally, the PGA compression ratio has been represented on a scale of 0 to 200 for golf balls. The lower the PGA compression ratio value, the softer the ball feel when shot. In fact, the compression ratio of tournament quality balls is around 70-110, preferably 80-1
It is around 00.

When determining PGA compression using a scale of 0 to 200, a standard force is applied to the outer surface of the ball. Undeformed (deformed 0.0 inch) ball is 200, 2/10 inch
(0.2 inch) The deformed ball is set to 0. Each time the deformation changes by 0.001 inch, the compression ratio is reduced by one point. Thus, the PGA compression ratio value of a 0.1 inch (100 × 0.001 inch) deformed ball is 100 (i.e., 200-100), and the PGA compression ratio of a 0.110 inch (110 × 0.001) inch deformed ball is 90 ( That is, 200-110).

[0049] To facilitate the measurement of the compressibility, several devices are used industrially. For example, the PGA compression ratio is measured by a small press-type device having upper and lower anvils. The upper anvil is stationary against a 200 pound die spring and the lower anvil is movable up to 0.300 inches by a crank mechanism. In the open position, the gap between the anvils is 1.780 inches and 0.100 for ball insertion.
There is room for inches. The ball is compressed against the upper anvil to crank the lower anvil. Such compression occurs at the final 0.200 inch of the lower anvil stroke, transferring the load from the ball to the upper anvil and then from the upper anvil to the spring. Upper anvil is 0.100 with ball
When deformed by more than inch (deformation less than 0.100 inch is simply regarded as zero compression)
Then, the equilibrium point of the upper anvil is measured with a dial-type micrometer, and the dial of the micrometer is read to obtain the ball compression ratio. In fact, a tournament quality ball has a compression ratio of around 80-100, meaning that the upper anvil has deformed a total of 0.120-0.100 inches.

An example of measuring the PGA compressibility using a golf ball compressibility test device manufactured by Atti Engineering Corporation (Newark, NJ) can be shown. The value obtained with this test apparatus is an arbitrary unit value represented by a number from 0 to 100, but a value of 200 can be measured by rotating the dial gauge twice on the apparatus. The obtained value defines the deformation that the golf ball experiences when a compressive load is applied. The Atti test rig consists of a lower mobile platform and an upper mobile spring-loaded anvil. A dial gauge is installed to measure upward movement of the spring-loaded anvil. After placing the golf ball to be tested on the lower platform, it is raised a certain distance. The upper portion of the golf ball contacts and applies pressure to the spring-loaded anvil. Depending on the distance of the golf ball being compressed, the upper anvil is pushed upward against the spring.

Another device has been used to measure compression ratio. For example, Applicants have developed an improved Riehle compression device (originally manufactured by Riehle Bros. Testing Machine Company, Phil., PA).
) Is used to evaluate the compressibility of various components of the golf ball (ie, core, mantle cover ball, finished ball, etc.). The Riehle compression device measures one thousandth of an inch deformation under a constant initial load of 200 pounds. With such a device, a Riehle compression ratio 61 corresponds to a deformation under load of 0.061 inches.

Further, for balls of the same size, an approximate relationship holds between the Riehle compression ratio and the PGA compression ratio. The present applicant has determined that the Riehle compression ratio corresponds to the PGA compression ratio by the general formula [PGA compression ratio = 160−Riehle compression ratio]. Therefore, the Riehle compression ratio 80 corresponds to the PGA compression ratio 80, the Riehle compression ratio 70 corresponds to the PGA compression ratio 90, and the PGA compression ratio 60 corresponds to the PGA compression ratio 100. For reporting purposes, the applicant's compression ratio value is usually
Measure as Riehle compression rate and convert to PGA compression rate.

Further, as long as the correlation with the PGA compression ratio is known, the compression ratio of the golf ball may be monitored using another compression device. Such devices are, for example, Whitne
Like y Tester, it is designed to correlate or correspond to the PGA compression ratio by a predetermined relationship or equation.

As used herein, the “Shore D hardness” of a cover is usually measured according to ASTM D-2240, except that it is measured on a curved surface of a molded cover rather than on a plaque. Further, the Shore D hardness of the cover is measured while leaving the cover on the core. In the case where the hardness is measured with a cover subjected to dimple processing, the Shore D hardness is measured in a region of the cover where no dimple is arranged.

In describing the components of the golf balls of interest herein, the term “spherical” is used with respect to the shell (center). One of ordinary skill in the art, when referring to golf balls and their components, refers to the term `` spherical '' in terms of surfaces that may result in slight and insubstantial deviations from a perfect and ideal geometrical spherical shape. It is clear that shapes are included. Also, placing dimples on the outer surface of the shell to impart aerodynamic properties does not detract from the "spherical" shape of the present invention or in the art. In addition, intentionally designed patterns may also be placed on the inner surface of the shell as well as on the core, and may be considered "spherical" within the scope of the present invention.

The moment of inertia of a golf ball is the resistance to a change in spin of the ball, and is conventionally measured using an “Inertia Dynamics Moment of Inertia Measuring Instrument”.

Further applicability of the present invention will become apparent from the detailed description provided hereinafter. However, while the detailed description and specific examples illustrate preferred embodiments of the invention, various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. It should be understood that this is merely an example.

BRIEF DESCRIPTION OF THE DRAWINGS The brief description of the drawings will be described later, but the drawings are only for illustrating the present invention and do not limit the present invention.

DETAILED DESCRIPTION The present invention relates to the development of a golf ball having a reduced spin rate by combining a relatively soft core and a hard cover. If the spin rate is so low after a club impact, the shot will be closer to a straight line even when the ball is miss-hit, increasing flight efficiency and reducing the degree of energy loss when hitting the ground. , Rotation or flight distance increases.

In yet another embodiment, the overall ball diameter of the present invention is the minimum of the USGA,
If the spin speed is further reduced to about 500 rpm or more by making it longer than 1.680 inches, it will fly at 105 feet per second (fps) when hitting with a No. 9 iron. In this embodiment of the invention, even though the ball has a longer diameter, it uses a core of substantially the same size as a standard golf ball, so the size will vary as the ball cover thickness adds thickness. This larger, lower spin ball even provides better control and flight efficiency than the standard size ball embodiment of the present invention.

Although the overall size of various embodiments of the invention is different, the core of the invention is relatively soft,
They have similar sizes. This core has a Riehle compression ratio of about 0.075 or more, preferably about 0.075.
It has a PGA compression of about 75 to about 0.115, and a relatively low PGA compression of about 40 to 85, preferably about 70 to 80.

[0062] The specially produced core compositions of the present invention and the cores formed therefrom are manufactured using relatively conventional techniques. That is, the core composition of the present invention comprises polybutadiene,
And a mixture of polybutadiene and another elastomer may be the main component.
It is preferred that the main component elastomer has a relatively high molecular weight. Suitable elastomers as the major component have a wide molecular weight range, from about 50,000 to about 500,000. A more preferred molecular weight range for the main elastomer is from about 100,000 to about 500,000. As the elastomer as a main component of the core composition, cis-polybutadiene is preferably used,
Alternatively, a blend of cis-polybutadiene and another elastomer may be used. Most preferably, cis-polybutadiene having a weight average molecular weight of about 100,000 to about 500,000 is used. In line with this policy, Shell Chemical
high cis-polybutadiene manufactured and sold by Emical Co., Houston, Texas, under the trade name Cariflex BR-1220, and Muehls
Polyisoprene available as “SKI 35” from tein, H & Co., Greenwich, Connecticut) is particularly well suited.

The unsaturated carboxylic acid component (heterocrosslinking agent) of the core composition is selected carboxylic acid (s) and zinc, magnesium, barium, calcium, lithium, sodium, potassium, cadmium, lead, tin, etc. Reaction product with the metal oxide or carbonate. Preferably, oxides of polyvalent metals such as zinc, magnesium and cadmium are used. The most preferred oxide is zinc oxide.

Specific examples of the unsaturated carboxylic acid used in the core composition include acrylic acid,
Examples include methacrylic acid, itaconic acid, crotonic acid, sorbic acid, and the like, and further, mixtures thereof. The preferred acid component is either acrylic acid or methacrylic acid. Typically, about 15 to about 25, preferably about 17 to about 21 parts by weight of a carboxylate, such as zinc diacrylate, is included in the core composition. Unsaturated carboxylic acids and their metal salts are usually soluble in the elastomeric base or are easily dispersible.

The free radical initiator included in the core composition can be any known polymerization initiator (heterocrosslinker) that decomposes during the cure cycle. The term "free-radical initiator" as used herein, when added to a blend of a blend of an elastomer and a metal salt of an unsaturated carboxylic acid, promotes crosslinking of the elastomer by the metal salt of the unsaturated carboxylic acid. Is a chemical substance. The amount of initiator selected is determined only by the required amount of catalytic activity as a polymerization initiator. Suitable initiators include peroxides, persulfates, azo compounds and hydrazides. Peroxides which are readily available from the market are conveniently used in the present invention and are generally present in amounts of about 0.1 to about 10.0, preferably about 0.3 to about 3.0 parts by weight per 100 parts by weight of elastomer. is there.

Specific examples of peroxides suitable for the purposes of the present invention include dicumyl peroxide, n-
Butyl 4,4'-bis (butylperoxy) valerate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, di-t-butylperoxide and 2,5-
Examples thereof include di- (t-butylperoxy) -2,5-dimethylhexane and a mixture thereof. The total amount of initiator used will, of course, vary depending on the particular desired end product and the particular initiator.

Examples of commercially available peroxides include Atochem, Lucidol Divis
Luperco230 or 231XL from Ion, Buffalo, NY and Trigonox 1 from Akzo Chemie America, Chicago, Illionois.
7/40 or 29/40. This Luperco 230XL and Trigonox17 / 40 are n-
It consists of butyl 4,4-bis (butylperoxy) valerate, Luperco 231XL and Trigonox29 / 40 consist of 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane. Luperco231XL has a 1 hour half-life of about 112 ° C, and Trigonox29
In the case of / 40, it is about 129 ° C.

The core composition of the present invention may further include other suitable and compatible modifying components, such as, but not limited to, metal oxides, fatty acids and diisocyanates, and polypropylene. Powder resin. For example, Papi94, a polymeric diisocyanate, usually available from Dow Chemical Co., Midland, MI. Is an optional component in the rubber composition. This component is rubber (phr
) Per 100 parts by weight of component can range from about 0 to 5 parts by weight;
Acts as a sture scavenger). Furthermore, the addition of the polypropylene powder resin makes it possible to reduce the amount of cross-linking agent used to soften the core to a standard or lower compression ratio, since the core becomes too hard (ie, exhibits a low compression ratio). ing.

Further, since the polypropylene powder resin can be added to the core composition without increasing the weight of the molded core at the time of curing, a filler having a higher specific gravity such as a mineral filler can be added by adding the polypropylene powder. Since the crosslinker used in the polybutadiene core composition is expensive and / or the higher specific gravity filler is relatively inexpensive, the addition of a polypropylene powder resin can reduce the weight and compressibility while maintaining or reducing the golf ball core's core. Substantially lower costs.

A polypropylene (C ₃ H ₅ ) powder suitable for use in the present invention has a specific gravity of about 0.90 g / cm ³ , a melt flow index of about 4 to about 12, and a particle size distribution of 20 mesh screen. More than 99%. Examples of such a polypropylene powder resin include “6400P” and “7000P” by Amoco Chemical Co., Chicago, Illinois.
And "7200P". Usually 100 elastomers each
From 0 to about 25 parts by weight of polypropylene powder per part by weight are included in the present invention.

Various active agents may also be included in the compositions of the present invention. For example, zinc oxide and / or magnesium oxide are activators of polybutadiene. The activator is rubber (phr
) It can range from about 2 to about 30 parts by weight per 100 parts by weight of the components.

In addition, filler-enhancing agents may be added to the compositions of the present invention. The specific gravity of the polypropylene powder is very low, and when mixed, the polypropylene powder produces a lighter molded core, so when incorporating the polypropylene into the core composition, a relatively large amount may be used as long as it meets the weight limitations of the particular core. Higher specific gravity fillers may be added. Incorporating relatively large amounts of cheaper mineral fillers with higher specific gravity, such as calcium carbonate,
More useful. Such fillers to be incorporated into the core composition should be in a finely divided form, for example, usually less than about 30 mesh, and preferably less than about 100 mesh of US standard size. The amount of additional filler included in the core composition is determined primarily by weight limitations, and preferably is from about 10 to about 100 parts by weight per 100 parts by weight of rubber.

Preferred fillers are relatively inexpensive and heavy, contribute to lower ball costs, and
Increase ball weight to a value very close to the SGA weight limit of 1.620 oz. However, when a thicker cover composition is applied to the core to produce balls larger than a normal ball (i.e., larger than 1.680 inches in diameter), such a size is required to meet the USGA maximum weight limit of 1.620 oz. The use of fillers and modifiers is limited. Specific examples of the filler include mineral fillers such as limestone, silica, mica, barlite, calcium carbonate, and clay. Since limestone is an inexpensive and heavy filler, crushed calcium carbonate / magnesium is used.

Thus, the pulverized flash filler may be taken up, preferably pulverizing the center stock from excess flash during compression molding to 20 mesh. As a result, the cost can be reduced and the hardness of the ball can be increased.

A fatty acid or a metal salt of a fatty acid that functions to improve formability and processing may also be included in the composition. Generally, free fatty acids having about 10 to about 40 carbon atoms, and preferably about 15 to about 20 carbon atoms, are used. Specific examples of suitable fatty acids include stearic acid and linoleic acid and mixtures thereof. Specific examples of suitable metal salts of fatty acids include zinc stearate. The amount of fatty acid component present when included in the core composition is about 1 to 100 parts by weight of rubber (elastomer).
It is about 25, preferably about 2 to about 15 parts by weight.

[0076] Preferably, the core composition contains from about 2 to about 5 parts by weight of stearic acid as a fatty acid additive based on 100 parts by weight of rubber.

A diisocyanate may also optionally be included in the core composition. When used, the diisocyanate comprises from about 0.2 to about 5.0 parts by weight per 100 parts by weight of rubber. Specific examples of suitable diisocyanates include 4,4'-diphenylmethane diisocyanate and other polyfunctional isocyanates known in the art.

Further, dialkyl tin difatty acids described in US Pat. No. 4,844,471
difatty acids), the dispersants disclosed in U.S. Pat. No. 4,838,556, and the dithiocarbamates described in U.S. Pat. No. 4,852,884 may also be included in the polybutadiene compositions of the present invention. Specific types and amounts of such additives are described in the aforementioned patents, which are incorporated herein by reference.

The core composition of the present invention is usually an elastomer (or rubber) as a main component selected from polybutadiene and a mixture of polybutadiene and another elastomer.
Consists of 100 parts by weight, 15 to 25 parts by weight of at least one metal salt of an unsaturated carboxylic acid, and 0.1 to 10 parts by weight of a free radical initiator.

As mentioned above, to obtain finished molded balls (cores, covers and coatings) very close to the USGA weight limit of 1.620 oz, the particulate polypropylene resin, fatty acids and pecan flour, milled flash (ie, A suitable and compatible modifier such as a secondary additive such as barium sulfate or zinc oxide is further added to the core composition to obtain a ball weight. May be adjusted to the required amount.

In producing a golf ball core using the present composition, the ingredients may be mixed using, for example, a two-roll mill or Banbury mixer until the composition is uniform, usually for about 5 to 20 minutes. It may be mixed homogeneously. The order of addition of the components is not important. The preferred mixing order is as follows.

Elastomers, polypropylene powder resin (if desired), fillers, zinc salts,
Mix the metal oxide, fatty acid, and metal dithiocarbamate (if desired), surfactant (if desired), and tin difatty acid (if desired) for about 7 minutes in an internal mixer such as a Banbury mixer. . Due to shearing during mixing, the temperature is about 200
° F. Next, the initiator and diisocyanate are added and the temperature is about 220
Continue mixing until ° F. Here, the batch is placed in a two-roll mill, mixed for about 1 minute, and then formed into a sheet.

The sheet is wound into a “pig” and placed in a Barwell preformer to form a slug. The slug is then compression molded at about 320 ° F for about 14 minutes. After molding, the molded core is cooled. This cooling is performed at room temperature for about 4 hours or in cold water for about 1 hour. The formed core is subjected to a coreless grinding operation, which removes a thin layer of the formed core and forms a round core having a diameter of 1.540 to 1.545 inches. Alternatively, the core is used as it is. In this case, grinding for rounding is unnecessary.

The mixing desirably occurs during the blending of the various components such that the composition does not reach the initial polymerization temperature.

[0085] Typically, the curable component of the composition comprises from about 275 ° F to about 350 ° F, preferably about 29 ° F.
The composition is cured by heating the composition at an elevated temperature on the order of 0 ° F to about 325 ° F. At this time, the molding of the composition is performed simultaneously with the curing. The composition can be formed into a core structure by any of a variety of molding methods, such as, for example, injection, compression or transfer molding. When the composition is cured by heating, the time required for heating depends on the particular curing agent used, but is usually short, usually about 10 to 20 minutes. Conventional techniques in the art of free radical curing agents for polymers can adjust the cure time and temperature required for optimal results using any of the particular free radical agents.

[0086] After molding, the core is removed from the mold and its surface, and is preferably treated to promote adhesion to the cover material. The surface treatment can be performed by any method known in the art, such as corona discharge, ozone treatment, and sand blasting. Preferably, it is ground using a grinding stone and subjected to surface treatment.

In addition to utilizing a molded solid core, a wound core may also be incorporated into the golf balls of the present invention. Such wound cores typically include a spherical center and a layer of rubber thread or windings surrounding the outer surface of the center.

Here, the generally spherical center of the wound core may be a solid or liquid center. A solid center can consist of one or more layers.
For example, the solid center comprises a molded polybutadiene rubber sphere, which is smaller in size than the molded core in the two-piece molded golf ball described above, but has a similar structure.

A solid center suitable for use in the present invention is not particularly limited, and examples thereof include those made of vulcanized rubber. Such solid centers may be prepared by adding additives such as butadiene rubber, vulcanizing agents, accelerators, activators, fillers, modifiers, and auxiliaries, and then vulcanizing and molding the mixture. .

The solid center (whether single unitary construction or multiple layers) usually has a diameter of 1 to 1.5 inches, preferably 1.0625 to 1.42 inches, and a weight of 15 to 36 g, preferably 16.5 to 30 g. It is.

[0091] Alternatively, a liquid center can be incorporated into the wound core of the present invention. The liquid center consists of a conventional vulcanized rubber spherical bag or sack with a cavity filling the contents with a liquid, paste or gel. Examples of such liquids include water, glycerin, sugar-water solutions, corn syrup, saline, oils and the like and / or combinations thereof. Examples of pastes can be made by adding clay, sodium sulfate, barite, barium sulfate and a small amount of an aqueous solution of ethylene glycol. Examples of suitable gels include hydrogels, cellulose gels, water gels, and the like. Usually, the specific gravity of the liquid is 0.6-3, the specific gravity of the paste is 0.6-3, and the specific gravity of the gel is 0.6-3. Bags or sacks typically have a thickness of 0.05 to 0.150 inches, preferably 0.08 to 0.105 inches.

The liquid center usually has a diameter of 1 to 1.25 inches, preferably 1.0625 to 1.14 inches, and a weight of 5.5 to 25.5 g, preferably 15 to 21 g.

The wound core is formed by winding a conventional rubber thread around the outside of a solid or liquid center. Rubber yarns may include, for example, those prepared by vulcanizing or molding natural rubber or a blend of natural rubber and polyisoprene rubber. The winding step is performed under high tension to form a wound layer on a solid or liquid center. Conventional methods may be used to wind the rubber thread, and a known composition may be used. Rubber thread is not limited with respect to specific gravity, dimensions and gauge, but usually has specific gravity of 0.
9-1.1, width 0.047-0.094, and gauge 0.012-0.026 inch.

The rubber thread layer is composed of a wound core having a radial thickness of 0.010 to 0.315 inches and an outer diameter of 1.52 to 1.63 inches. The total weight of the wound core is 33-44 g, preferably 35
From 39g.

The ball is covered with at least one layer of cover material to convert the core into a golf ball. This layer thickness ranges from about 0.070 to about 0.130 inches, preferably from about 0.0675 to about 0.1275 inches.

The Shore D hardness of the cover is 65 or more. Preferably those sold by EI DuPont de Nemours & Company under the trademark "Surlyn Ò" and by Exxon Corporation under the trademark "Escor Ò" or trade name "Iotek" Or a high acid ionomer of high rigidity, such as, or a blend thereof, is included in the composition. In addition to Surlyn Ò, Escor Ò or Iotek ionomers, any ionomer that forms a molded cover having a Shore D hardness of at least 65, alone or in combination with other ionomers, may be included in the cover. Good. Such ionomers include lithium ionomers or blends of ionomers with harder non-ionic polymers such as nylon, polyphenylene oxide and other compatible thermoplastics. As briefly described above, for examples of cover compositions that may be used, see co-pending US patent application Ser. No. 07 / 776,803 (1).
(Filed October 15, 991) and US Patent Application No. 07 / 901,660 (filed June 19, 1992), both of which are incorporated herein by reference. Of course, the cover composition is not in any way limited to the compositions described in this co-pending application.

[0097] Suitable high acid ionomers for use in the present invention are ionic copolymers, which are olefins having about 2-8 carbon atoms and unsaturated mono-monomers having about 3-8 carbon atoms. It is a salt of a metal such as sodium, zinc, magnesium, etc., of a reaction product with a carboxylic acid. Preferably, the ionomer resin is a copolymer of ethylene and either acrylic or methacrylic acid. In some cases, additional comonomers such as acrylates (eg, iso- or n-butylacrylic acid) can be included to form a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized with metal ions (eg, about 10-75%, preferably 30-70%).
). Each high acid ionomer resin included in the cover composition of the present invention contains about 16 wt.
% Or more, preferably about 17 wt% to about 25 wt% or more, more preferably about 18.5 wt% to about 21 wt%.
It contains more than .5wt%.

The cover composition preferably comprises a high acid ionomer resin and all known high acid ionomer resins falling within the above parameters are included within the scope of the present invention, but those currently available with such high acid ionomer resins Are relatively limited in number. Regarding this, EI DuPont de Nemours & Company has announced that
rlyn Ò"is a trademark of Exxon Corporation and" Escor Ò"
Alternatively, high acid ionomer resins available under the trade name "Iotek" may be used in the present invention and are examples of available high acid ionomer resins.

[0099] The high acid ionomer resin available from Exxon as "Escor" or "Iotek" is somewhat similar to that available under the trademark "Surlyn". However, Escor Ò / Iotek ionomer resin is a sodium or zinc salt of poly (ethylene acrylic acid), and Surlyn Ò resin is a salt of poly (ethylene methacrylic acid) such as zinc, sodium and magnesium. There are distinct differences.

Examples of ionomers based on high acid methacrylic acid have been found to be suitable for use in accordance with the present invention, such as Surlyn Ò AD-8422 (sodium cation), Surlyn
lyn Ò 8162 (zinc cation), Surlyn Ò SEP-503-1 (zinc cation), and Surlyn Ò SEP-503-2 (magnesium cation). According to DuPont, all of these ionomers contain about 18.5 to about 21.5 wt% methacrylic acid.

In particular, Surlyn Ò AD-8422 is available in a number of different grades (eg, AD-8422-2, AD-8422-3, AD-8422-5, etc.) based on differences in melt index. Things are currently available from DuPont. According to DuPont, of all low acid grades (referred to as "hard" ionomers in U.S. Pat. No. 4,884,814), Surlyn Ò 8422 has the following general properties:

[0102]

Compared to Surlyn Ò 8422-2 and Surlyn Ò 8422-3, the high acid Surlyn Ò 8422-2 and Surlyn Ò 8422-3 ionomers were tensile yield It is noted that the hardness is high, the elongation is low, the Shore D hardness is slightly high, and the flexural modulus is quite high. Surlyn Ò 8920 contains 15 wt% methacrylic acid, 59% of which is neutralized with sodium.

Further, Surlyn Ò SEP-503-1 (zinc cation) and Surlyn Ò SEP-503
-2 (magnesium cation) is a high acid zinc and high acid version of Surlyn Ò AD8422 high acid ionomer. Compared to Surlyn Ò AD8422 high acid ionomer, Surlyn Ò SEP-503-1 and SEP-503-2 ionomers can be defined as follows.

[0105]

Further, Surlyn Ò 8162 is a zinc cation ionomer resin containing about 20 wt% (eg, 18.5 to 21.5 wt%) of a methacrylic acid copolymer whose 30% to 70% is neutralized. Surlyn Ò 8162 is currently available from Dupont.

Examples of ionomers based on high acid acrylic acid that are suitable for use in the present invention include Escor ' 210 or Iotek high acid ethylene acrylate ionomers produced by Exxon. Escor <210; or Iotek959 is a sodium ion neutralized ethylene-acrylic acid copolymer. According to Exxon, Iotek 959 and 960 contain about 19.0 to about 21.0 wt% acrylic acid, and about 30% to about 70% acid groups neutralized with sodium and zinc ions, respectively. The physical properties of these ionomers containing high acid acrylic acid as the main component are as follows.

[0108]

Furthermore, as a result of the present inventors having developed a large number of new high acid ionomers neutralized to various degrees with several different metal cations such as manganese, lithium, potassium, calcium and nickel cations, In addition to high acid ionomers or blends of ionomers of sodium, zinc and magnesium, several new high acid ionomers and / or blends of high acid ionomers can now be used in the manufacture of golf ball covers. . It has been found that when a cover composition is made with a blend of new high acid ionomers that are neutralized with these cations, the synergistic effects that occur during the processing step show an increase in hardness and resilience. As a result, mixing a recently produced high acid ionomer resin that is neutralized with metal cations has a substantially higher hardness, having a higher COR than golf balls made with low acid ionomer covers currently on the market. A golf ball with an increased cover can be manufactured.

More specifically, the inventors have found that neutralizing a high acid copolymer of an α-olefin and an α, β-unsaturated carboxylic acid to varying degrees with a variety of different metal cation salts provides several degrees of neutralization. To produce a new high acid ionomer resin that has been neutralized with a metal cation. This discovery is the subject of U.S. Patent Application No. 901,680, which is incorporated herein by reference. Many of the new high acid ionomer resins that have been neutralized with metal cations have high acid copolymers (i.e., 16% by weight, preferably about 17-
25% by weight, more preferably about 20% by weight of a copolymer containing an acid)
It has been found that it is obtained by reacting with a metal cation salt which can be ionized or neutralized to the desired extent (i.e. about 10-90%).

The base copolymer is composed of more than 16% by weight of α, β-unsaturated carboxylic acids and α-olefins. If desired, softening comonomers may be included in the copolymer. Generally, the α-olefin has from 2 to 10 carbon atoms and is preferably ethylene. Unsaturated carboxylic acids are carboxylic acids having about 3 to 8 carbons. Examples of such carboxylic acids are acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid, with acrylic acid being preferred.

Softening comonomers which may optionally be included in the present invention include vinyl esters of aliphatic carboxylic acids having 2 to 10 carbon atoms, vinyl ethers in which the alkyl group contains 1 to 10 carbon atoms, alkyl groups Can be selected from the group consisting of alkyl acrylates or alkyl methacrylates containing 1 to 10 carbon atoms. Examples of suitable softening comonomers include vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, and the like.

Thus, some examples of copolymers suitable for use in producing the high acid ionomers included in the present invention include ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, ethylene / itaconic acid copolymers, ethylene / itaconic acid copolymers. Specific examples of high acid such as maleic acid copolymer, ethylene / methacrylic acid / vinyl acetate copolymer, ethylene / acrylic acid / vinyl alcohol copolymer, but are not limited thereto. The base copolymer comprises more than 16% by weight of an unsaturated carboxylic acid,
Broadly includes about 30-83% by weight ethylene and 0 to about 40% by weight softening comonomer. Preferably, the copolymer contains about 20% by weight unsaturated carboxylic acid and about 80% by weight ethylene. Most preferably, the copolymer contains about 20% acrylic acid, the balance being ethylene.

In these respects, examples of preferred base high acid copolymers that meet the above criteria include the series of ethylene-acrylic copolymers marketed under the name “Primacor” by Dow Chemical Company (Midland, Michigan). No. These base high acid copolymers exhibit the standard properties noted in Table 1 below.

Table 1

Because of the high molecular weight of the ethylene-acrylic acid copolymer “Primacor 5981”, this copolymer is a preferred grade for use in the present invention.

The metal cation salt used in the present invention is a salt that provides a metal cation capable of neutralizing the carboxylic acid groups of the high acid copolymer to various degrees. Examples include lithium, calcium, zinc, sodium, potassium, nickel, magnesium and manganese acetates, oxides or hydroxides.

[0118] Such lithium ion sources include lithium hydroxide monohydrate, lithium hydroxide, lithium oxide and lithium acetate. Examples of calcium ion sources are calcium hydroxide, calcium acetate and calcium oxide. Examples of suitable zinc ion sources are zinc acetate dihydrate and zinc acetate, a blend of zinc oxide and acetic acid. Examples of sodium ion sources are sodium hydroxide and sodium acetate. Examples of potassium ion sources are potassium hydroxide and potassium acetate. Suitable sources of nickel ions are nickel acetate, nickel oxide and nickel hydroxide. Examples of magnesium sources are magnesium oxide, magnesium hydroxide, magnesium acetate. Examples of manganese sources are manganese acetate and manganese oxide.

The new high acid ionomer resins that have been neutralized with metal cations have a temperature above the crystal melting point of the copolymer, for example, between about 200 ° F. and 500 ° F., preferably between about 250 ° F. and 350 ° F.
At high temperatures of about 10 psi to 10,000 psi and by reacting the base high acid copolymer with varying amounts of metal cation salts. Other known mixing techniques may be used. The amount of metal cation salt used to make the new high acid based ionomer resin that is neutralized with metal cations is sufficient to neutralize the desired proportion of carboxylic acid groups in the high acid copolymer. An amount that provides a sufficient amount of metal cation. The degree of neutralization is usually about 10-90%.

As shown in Table 2 below, and more particularly in Example 1 of US Patent Application No. 901 680, a new high acid ionomer neutralized with multiple metal cations can be obtained by the method described above. . Examples include new high acid ionomer resins that have been neutralized to varying degrees with manganese, lithium, potassium, calcium and nickel cations. In addition, high acid ethylene / acrylic acid copolymers are used as the composition of the base copolymer of the present invention, and when the composition is neutralized to various degrees with metal cation salts, sodium, potassium, lithium, Acrylic-based high acid ionomer resin neutralized with cations such as zinc, magnesium, manganese, calcium and nickel is produced, and a new acrylic acid-based high acid neutralized with several types of cations An ionomer resin is produced.

Table 2

Compared to similar ionomer resins neutralized with cations and low acid,
The new high acid ionomer resins neutralized with metal cations show improved hardness, modulus and resilience properties. These are properties that are particularly desired in many thermoplastic fields, including golf ball manufacturing.

When used in the construction of golf ball covers, the new acrylic acid based high acid ionomers are the low acid ionomers described in US Pat. Nos. 4,884,814 and 4,911,451 and the recent acid described in US Pat. Maintains the beneficial properties (i.e., durability, click, feel, etc.) of balls covered with more flexible low acid ionomers, such as balls made using the manufactured high acid blends However, it was found that the range of the hardness was expanded beyond the hardness obtained so far.

In addition, a number of new acrylic acid-based high acid ionomer resins have been developed that are neutralized to varying degrees by several different metal cations, such as manganese, lithium, potassium, calcium and nickel cations. As a result, several new ionomers or blends of ionomers are now available for use in making golf balls. By using these high acid ionomer resins, COR
And a golf ball having higher hardness and a longer flight distance can be obtained.

As will be described in more detail in the examples below, the molded cover has a Shore of 65 or more.
Other ionomer resins, such as low acid ionomers, may be used in the cover composition as long as they provide D hardness. The properties of some of these low acid ionomer resins are shown in the following table:

[0126]

[0127]

In addition to the ionomers described above, compatible additives can be added to form the cover compositions of the present invention. These additives include dyes (e.g., Ultramarine Blue, marketed by Whitaker, Clark, and Daniel of South Painsfield, NJ), and pigments, i.e., titanium dioxide (e.g., Unitane). ) 0-110), zinc oxide and zinc sulfate, and fluorescent pigments. As described in U.S. Pat. No. 4,884,814, the amount of pigment and / or dye used with the polymeric cover composition depends on the particular base ionomer mixture used and / or the dye used. different. The concentration of the dye in the polymeric cover composition may be from about 1% to about 10%, based on the weight of the base ionomer mixture. A more preferred concentration range is
From about 1% to about 5% by weight of the base ionomer mixture. The most preferred concentration range is from about 1% to about 3%, based on the weight of the base ionomer mixture. The most preferred pigment for use in accordance with the present invention is titanium dioxide.

Further, since white has various hues (ie, bluish white, yellowish white, etc.), a trace amount of blue pigment is added to the raw material composition of the cover, and the bluish white Appearance can also be imparted. However, if a different hue of white is desired, it is also possible to add the necessary amount of another pigment to the cover composition to produce the desired color.

It is also possible within the scope of the present invention to add to the cover composition according to the invention, compatible materials which do not affect the basic novel characteristics of the composition according to the invention. Such materials include antioxidants (ie, Santonox®), antistatic agents, stabilizers and processing aids. The cover composition of the present invention may also include a softener such as a plasticizer, and a reinforcing material such as glass fiber or an inorganic filler, as long as the desired properties provided by the golf ball cover of the present invention are not impaired.

In addition, optical brighteners such as those disclosed in US Pat. No. 4,679,795 may be added to the cover compositions of the present invention. An example of a suitable optical brightener that can be used in accordance with the present invention is Uvitex OB marketed by Ciba-Geigy Chemical Company of Ardsley, NY. Ubitex OB is 2,
It is believed to be 5-bis (5-tert-butyl-2-benzoxazoly) thiophene. Examples of other optical brighteners suitable for use in the present invention include the following: Sand
Leucopure EGM marketed by oz (East Hanover, NJ). Leukopure EGM is believed to be 7- (2n-naphthol (1,2-d) -triazol-2-yl) -3phenyl-coumarin. Hoa White (Phorwh)
ite) K-20G2 is from Mobay Chemical (PO Box 385, Union Metro Park, Union,
NJ 07083) and is considered a pyrazoline derivative. Eastman Chemic
Estobrite OB-1 marketed by al Products (Kingsport, TN) is considered a 4,4-bis (-benzoxaxoli) stilbene. Ubitex and Eastbright OB-1 described above are preferred optical brighteners for use according to the present invention.

Further, since many optical brighteners are colored, the percentage of the optical brightener used must not be excessive so that the optical brightener itself does not function as a pigment or dye.

The percentage of optical brighteners that can be used according to the invention is from about 0.01% to about 0.5%, based on the weight of the polymer used as cover stock. A more preferred range is about 0.05
% To about 0.25%, the most preferred range is from about 0.10% to about 0.20%, and the ratio is
It depends on the optical properties of the particular optical brightener and the environment of the polymer in which it is contained.

Generally, by mixing the above additives with the ionomer used in the cover composition, a masterbatch (MB) of the desired concentration is obtained, and then sufficient to provide the desired amount of the additive. An amount of the masterbatch is mixed with the copolymer blend. The cover composition was processed according to the parameters described below and combined with a soft core at the thickness specified herein to produce a cover with a Shore D hardness of 65, thereby reducing the spin ratio. A golf ball is obtained. However, it should be noted that the high acid ionomer resin provides a more significant spin rate reduction than the low acid ionomer resin.

[0135] The cover composition and the ball of the present invention can be prepared by a conventional melt blending method.
Can be manufactured. In this regard, the ionomer resin is blended or extruded with a masterbatch containing the desired additives in a Banbury mixer or a two-roll mill, followed by molding. Next, the blended composition is formed into a shape such as a slab or a pellet, and is maintained in that state until the molding is attempted. Alternatively, a simple dry blend of pelletized or granulated resin and a colored masterbatch are provided and fed directly to an injection molding machine to achieve homogenization in the mixing section of the barrel before injection into a mold. . If necessary, an additive such as an inorganic filler may be added before the start of the molding step and may be mixed homogeneously.

Further, the golf ball of the present invention can be manufactured by a molding method which is well known in the technical field of golf balls. In particular, a golf ball is obtained by injection molding or compression molding a novel cover composition around a soft core to produce a golf ball having a diameter of about 1.680 inches or more and weighing about 1.620 ounces. Can be. In another embodiment of the invention, a larger mold is used to produce an oversized golf ball covered with a thicker cover. As already mentioned,
The golf ball of the present invention can be manufactured by forming a cover made of the composition of the present invention around a softer core using a conventional molding method. For example, in compression molding, the cover composition is injected at about 380 ° F. to 450 ° F. into a hemispherical shell with a smooth surface and the shell is placed around a core in a recessed golf ball mold. After compression molding at 200-300 ° F for 2-10 minutes, 50-70 °
Cool for 2-10 minutes at F and fuse the shells to form a single ball. Further, it is possible to produce golf balls by injection molding, in which case the cover composition is placed around a core located at the center of the golf ball mold by 50%.
Inject directly at mold temperature of ~ 100 ° F for a predetermined time. After molding, the manufactured golf ball is further subjected to various finishing steps such as buffing, painting and marking as described in U.S. Pat. No. 4,911,451.

The following examples illustrate the invention in more detail. In these examples,
Parts for specific components are parts by weight (pbw). The present invention is not limited to these embodiments, and various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention.

[0138]

EXAMPLE 1 A golf ball core having a finished diameter of about 1.540 to about 1.545 inches is manufactured by compression molding using the components shown in the following table and then removing the surface layer by grinding. Each core is compounded using 100 parts of elastomer (rubber). The amount of the remaining ingredients in the formulation, expressed in parts by weight, achieved weight, coefficient of restitution and compressibility
The (compression) (both Riehle and PGA) is described below. The data for these examples is the average of the 12 cores produced in each example. The properties of the molded cores made from each formulation were measured according to the parameters described above.

The following core formulations were prepared according to the method described above: 1: BR-1220 is a polybutadiene manufactured and sold by Shell Chemical (Houston, TX). 2: 6400 polypropylene is a powdered polypropylene available from Amco Chemical Company (Chicago, Illinois). 3: Trigonox 17/40 is a peroxide manufactured and sold by Akzo Chemie (Chicago, Ill.) With a half-life at 129 ° C. of 1 hour. 4: Papi 94 is a polymeric diisocyanate available from Dow Chemical (Midland, MI).

As can be seen from the data presented above, core formulations A and B produce softer cores. Formulation A is suitable for molded balls having an overall diameter of about 1.720 inches (ie, 1.717 "), which has less filler and therefore a lower specific gravity than Formulation B. Suitable for smaller balls, ie, balls having a diameter of about 1.680 inches.Formulations C and D are conventional hard cores.Formulation C is slightly heavier and is used for balls having a diameter of about 1.680 inches. Formulation D is used to make balls about 1.720 inches (1.717 ") in diameter.

Example 2 A cover composition was prepared by blending the following components: 1: Iotek 7520 is a relatively soft, low acid ionomer resin produced by Exxon. 2: MB = 74.9% by weight IOTEC 7030, 23.8% by weight TiO ₂ , 0.01% by weight Unitex O
B, 0.002 wt% Ultramarine Blue and 300 ppm Santonox
) R.

[0142] Of the three cover formulations listed above, Formulation 2 is the hardest. this is,
It is composed of two hard and high acid ionomer resins. Iotek 959 has an acid content of about 19-21%, and Iotek 960 also has an acid content of about 19-21%.

Formulation 3 is the softest of the three cover formulations and is substantially similar to the formulation used in the TOP-FLITE TOUR EDITION 90 golf ball . Formulation 3 contains Iotek 8000 in the amounts listed in the table above.
And Iotek 7030 (both hard and low acid ionomers) and Iotek 7520, a soft and low acid ionomer.

Formulation 1 provided an intermediate hardness and provided TOP FLITE XL II balls (
Substantially the same formulation used in US Pat. No. 4,911,481).

Example 3 The cover formulation described in Example 2 was injection molded at about 400 ° F. around the cores of Formulations AD described in Example 1. At that time, the selected cover composition was uniformly injected into each core. Each of the cores is equivalent to a finished diameter of about 1.541 to 1.543 inches, so that a golf ball having a diameter of about 1.720 (1.717) inches (cores AD) or about 1.680 inches (cores B and C) is obtained. produced. The cover thickness was between about 0.069 to about 0.088 inches. All materials were molded under substantially the same conditions. Reel compression ratio, PGA compression ratio, coefficient of restitution (COR),
The properties of barrel durability (100 hits), cover hardness and spin speed were measured.
The results are shown in Table 3 below.

The data for each example represents the average data for a dozen balls manufactured according to the desired method. Properties were measured according to the following parameters: Coefficient of restitution (COR) and Shore D hardness were measured as described above. In the barrel test or barrel durability test, a golf ball is placed in a 5-sided container at 135f.
Consists of shooting at t / s (72 ° F). The wall of the container is a steel plate, in which a groove simulating the surface of a golf club is cut. The balls were subjected to 100-300 hits and were inspected at regular intervals for breaks (i.e., cracking or delamination of the cover). NB = no break.

The spin rate of the golf ball was measured by hitting the manufactured golf ball with a 9-iron. At that time, the club head speed is about 105 feet / second, and the ball is hit at an initial velocity of about 110 to 115 feet / second from an angle of 26 to 34 °. The spin speed was measured by observing the spin of the ball during flight using a stop operation strobe photograph.

[0148]

For the comparisons presented, the results of the same test are shown for a well-known existing golf ball.

From the results of the spin speed test of the molded balls, the combination of the soft core (cores A and B) and the hard cover (cover formulations 1 and 2) showed that the spin speed was the minimum despite the different ball sizes. It turns out that it becomes. Harder core (core C
Even with and D), the golf ball with the hardest cover formulation tested (Formulation 2) provided the golf ball with the lowest spin rate.

The combination of the soft cores (Cores A and B) and the hardest cover (Cover Formulation 2) further reduced the spin rate, indicating that the softest core (Core A) and the hardest cover (Cover Composition 2) The maximum reduction of the spin rate was observed by the combination of ()).

It should further be noted that as the diameter increases, the spin rate decreases. Comparing the balls A, 1-3 and the corresponding balls B, 1-3, the larger diameter balls (A, 1-3) have lower spin speeds than the balls B, 1-3, respectively. COR and compressibility are controlled primarily by the core formulation, with a hard and fast core providing a harder and faster ball. As the thickness of the cover increases,
Because the ball diameter increases (the core diameter remains the same), the thicker cover (0.
0888 vs. 0.0690) provides a significant COR pickup from the center to the ball.
Further, as the cover thickness increases, there is a reduction in the spin rate found on the larger ball.

Further attention is paid to the results described in the table, and the combination of the soft core and the hard cover
The lowest spin rate is provided. Comparing the balls A, 2 with the balls D, 2 (both having a diameter of 1.72 inches), the softer core A contributes to a lower spin rate. Combination A, 2 (the softer core, the hardest cover)
Provides the lowest spin rate. The same is true for smaller balls. That is, the balls B and 2 have slower spins than the balls C and 2. Ball B, 2
Has the slowest spin of a 1.68 inch ball, and its spin rate is not as low as ball A, which has a larger diameter. This is thought to be due to the difference in cover thickness.

Example 4 A series of wound three-piece golf balls (both solid and liquid center) having low spin properties were produced. Specifically, balls having the following characteristics were manufactured.

A) Solid center, thread wound, three-piece golf ball (4SS97) i) Solid center A solid center having a diameter of 1.4 inches was manufactured using the following components: Califlex BR-1220 70 Taktene 220 30 Zinc oxide 40.5 Regrind 16 Zinc stearate 16 Zinc diacrylate 22 231 XL 0.9 195.4

After molding, the solid center exhibited the following characteristics: center size = 1.4 inch diameter center weight = 29.40 g center elastic rebound (100 inch drop) = 81 inch center hardness = about 47 D (peak) center Compression ratio = 73 PGA (87 reels) Center COR (125 feet / second) = 0.768

[0157] ii) yarn thickness 0.024 inches × width 1/16 inches, P / N 1511, was coated a solid center winding of elastomeric yarn. This elastomeric yarn is available from Fulflex, Middletown, RI. The wound core exhibited the following characteristics: bobbin core size = 1.56 inch diameter bobbin core weight = 35.51 grams bobbin core compressibility = 82 PGA (78 reel) bobbin core COR (125 ft / sec) = 0.813

Iii) Cover The above wound core was coated with a cover composition having the following formulation: Finest White Masterbatch Materials Department Iotek 7030 100 Unitein 0-110 31.3 East Bright OB-1 0.34 Ultra Marine Blue 0.605 Santo Knox R 0.05

Finished cover compounding material section IOTEC 1002 38 IOTEC 1003 52.6 TG masterbatch (combined with the above) 9.4

[0160] These balls have the following properties. Ball size, pole = 1.682 inch Ball size, equator = 1.683 inch Ball compression ratio = 88 PGA Ball weight = 45.01 g Ball COR (125 ft / sec) = 0.802 Ball elastic rebound (100 inch drop) = 79.4 inch Ball inertia moment = .42675 02.-in.2 Cover hardness = about 70 Shore D (peak) Cover thickness = 0.06 inch (based on a 1.56 inch diameter wound core) Indentation pattern = deformed tetrakaidecahedron (D335)
C-Hogan pattern) Number of depressions = 428

B) Liquid Center, thread wound, three-piece golf ball (8L957) i) Liquid Center Liquid center (11/8 inch diameter) P / N 65 obtained from Abott Labs (Chicago, Ill.) With the following characteristics: W 155L used: Center size = 1/8 inch diameter Center weight = 18.39 grams Liquid center volume = 6.57 cm ³ Center bag thickness = 0.105 inch Liquid composition = Water / glycerin based formulation center owned by Abbott Specific gravity = 0.98 Bag composition = Vulcanized rubber compound (Abbott's proprietary compound) Bag spatial gravity = 2.1

[0162] ii) yarn thickness 0.024 inches × width 1/16 inch elastomeric yarn, was coated with liquid center in the winding consisting of PN 15111. This elastomeric yarn is available from Fulflex, Middletown, RI. The wound liquid center exhibited the following general characteristics: Wound core size = 1.56 inch diameter Wound core weight = 34.46 grams Wound core compression ratio = 76 PGA (84 reels) Wound core COR (125 feet / second) ) = 0.813

Iii) Cover The wound core was covered with the same cover composition as used for the solid center described above. The coated ball exhibited the following characteristics: ball size, pole = 1.682 inches ball size, equator = 1.658 inches ball compressibility = 80 PGA ball weight = 44.53 grams ball COR (125 feet / second) = 0.785 ball rebound (100 inch drop) = 76 inch Ball moment of inertia = .39688 oz.-in.2 Cover hardness = about 70 Shore D (peak) Cover thickness = 0.06 inch (based on a 1.56 inch diameter winding core) Indentation pattern = Deformed tetrakaidecahedron (D335
C-Hogan pattern) Number of depressions = 428

C) Spin Test Solid Center (Top-Flite (R) Dot 4SS97) and Liquid Center (Top-Flite (R) Dot 8L957)
A spin test was performed on a wound three-piece golf ball, and Spalding's Top-Flite (registered trademark) XL and Titleist (registered trademark) Tour Balata 100 golf ball were used. And compared. The results are shown below: Controls: Top-Flite (TM) XL normal orbit, Titleist (TM) Tour Balata 100; Top-Flite (TM) custom-made 9 iron True Temper Driving, mechanically tuned

[0165] The solid center wound three-piece golf ball (ie, Top-Flite (R) Dot 4SS97) is a solid center two-piece golf ball, Top-Flite (R) XL, The spin was practically slow. Similarly, a liquid center wound three-piece golf ball (i.e., Top-Flite (registered trademark DST 8L 957)) has a higher spin than a Titleist (registered trademark) Tour Balata 100 golf ball. From the data obtained, it was found that the use of a hard high acid ionomer resin on the soft wound core enabled low spinning properties to be achieved.

The invention has been described with reference to the preferred embodiments. Obviously, other changes and modifications may occur to the interpretation and understanding of the above detailed description. All such variations and modifications are intended to be included herein within the scope of the appended claims or their equivalents.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of an improved golf ball of the present invention. D is the diameter of the ball, C is the distance of the core, and T is the thickness of the cover.

[Procedure for Amendment] Submission of translation of Article 19 Amendment of the Patent Cooperation Treaty

[Submission date] January 25, 2001 (2001.1.25)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

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[Claims]

7. A three-piece golf ball comprising a wound core and a cover, wherein the wound core has a Riehle compression ratio of about 0.75 to about 0.115, the cover has a Shore D hardness of at least 65, and a thickness of at least 65. About 0.050-0.160 inch,
The golf ball of at least one ionomer resin comprising at least 16% by weight of a carboxylic acid and an α-olefin, wherein about 10% to about 90% of the carboxyl groups of the copolymer are neutralized with metal cations.

[Procedure amendment]

[Submission date] July 4, 2001 (2001.7.4)

[Procedure amendment 1]

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[Correction target item name] 0102

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[Table 1]

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[0164]

Claims (13)

[Claims] 1. A golf ball comprising: a wound core having a Riehle compression ratio of at least 0.075; and a cover having a Shore D hardness of at least 65, wherein the cover has more than 16% by weight of α, β- The golf ball of claim 1, comprising at least one high acid ionomer resin comprising a copolymer of a saturated carboxylic acid and an α-olefin, wherein about 10% to about 90% of the carboxyl groups of the copolymer are neutralized with metal cations. . 2. The cover comprises at least one high acid ionomer resin comprising from about 17% to about 25% by weight of a copolymer of an α, β-unsaturated carboxylic acid and an α-olefin, wherein the copolymer comprises at least one high acid ionomer resin. The golf ball of claim 1, wherein about 10% to about 90% of the carboxyl groups are neutralized with a metal cation. 3. The cover is comprised of at least one high acid ionomer resin comprising from about 18.5% to about 21.5% by weight of an α, β-unsaturated carboxylic acid and an α-olefin, wherein the carboxyl group of the copolymer is The golf ball of claim 1, wherein about 10% to about 90% are neutralized with metal cations. 4. The golf ball according to claim 1, wherein the wound core comprises a solid center. 5. The golf ball according to claim 1, wherein the wound core comprises a liquid center. 6. The golf ball of claim 1, wherein the thickness of the cover is greater than 0.050 inches and up to 0.160 inches. 7. A three-piece golf ball comprising a wound core and a cover, wherein the wound core has a Riehle compression ratio of about 0.075 to about 0.115, the cover has a Shore D hardness of at least 65, and a thickness of at least 65. About 0.050-0.160 inch,
The golf ball of at least one ionomer resin comprising at least 16% by weight of a carboxylic acid and an α-olefin, wherein about 10% to about 90% of the carboxyl groups of the copolymer are neutralized with metal cations. 8. The golf ball according to claim 7, wherein the Riehle compression ratio of the wound core is 0.078 or more, and the Shore D hardness of the cover is 70 or more. 9. The golf ball according to claim 7, wherein the Riehle compression ratio of the wound core is 0.084 or more, and the Shore D hardness of the cover is 70 or more. 10. The golf ball according to claim 7, wherein the Riehle compression ratio of the completed golf ball is 0.078 or less. 11. The golf ball according to claim 7, wherein said wound core comprises a solid center. 12. The golf ball according to claim 7, wherein the wound core comprises a liquid center. 13. A wound core having a Riehle compression ratio of at least about 0.075 and a diameter of about 1.56 inches, and about 17% to about 25% by weight of an α, β-unsaturated carboxylic acid and an α-olefin. A three-piece wound golf ball comprising a cover composed of at least one ionomer resin comprising a copolymer of the formula: wherein the carboxyl groups of the copolymer are neutralized with metal cations from about 10% to about 90% of the copolymer. The cover is about 0 in thickness.
The golf ball of any of the preceding claims, having a Shore D hardness of at least about 65, between 050 and 0.160 inches.