WO1999008756A1 - Compositions for golf ball covers, and golf balls with improved covers - Google Patents

Abstract

A golf ball cover composition. This composition includes an amide block copolymer having a hardness less than or equal to 40 shore D, and an ionomer having a hardness greater than the hardness of the amide block copolymer. The respective amounts by weight of the amide block copolymer and the ionomer depend upon the desired cover hardness.

Description

Description Compositions for Golf Ball Covers, and Golf Balls with Improved Covers Cross-Reference to Related Applications

This application is a continuation-in-part of U.S. Patent Application No. 08/915,081, filed on August 20, 1997, entitled "Golf Ball with an Improved Cover", the inventors of which are Dean Snell and Benoit Vincent. Priority from U.S. Patent Application No. 08/915,081 is claimed under 35 U.S.C. § 120. This application also claims the benefit of U.S. Provisional Patent Application No. 60/070,497, filed on January 5, 1998, entitled "Composition for Golf Ball Cover", the inventors of which are Hyun Kim, Dean Snell, Philippe Renard, and Benoit Vincent. Priority from U.S. Provisional Patent Application No. 60/070,497 is claimed under 35 U.S.C. § 119(e). The disclosures of both U.S. Patent Application No. 08/915,081 and U.S. Provisional Patent Application No. 60/070,497 are hereby incorporated herein in their entireties, by reference thereto.

Technical Field

The present invention relates generally to golf balls and, more particularly, to golf balls having an improved cover layer. The present application also relates to thermoplastic compositions suitable for golf ball covers. The invention further relates to two piece golf balls, to wound golf balls, and to multi-piece solid golf balls as well. Yet additionally, the invention relates to compositions suitable for two-piece golf balls, wound golf balls, and multi-piece solid golf balls, as well.

Background Art and Other Information

The modern golf ball generally comprises a cover including layers made of ionomeric resins, in a pure form or in a blend. Ionomeric resins are polymers containing ionic groups or ionic salts in a polymer structure. More particularly, the ionomers are intended to be the ionomeric resins obtained by providing a cross-metallic bond to polymers of monoolefms with at least one member selected from the group consisting of unsaturated mono- or di-carboxylic acids having at least 3 to 12 atoms, and esters thereof. The ionomeric resins are distinguished by the type of metal ion, the acid content, and the degree of neutralization. There is currently a wide choice of commercial ionomers available both from E. I. DuPont de Nemours & Company, Wilmington, Delaware, under the trademark name "Surlyn", and from Exxon, under the trademark name "Iotek", with a wide range of properties (such as flexural modulus and hardness, for example) which vary according to the type and amount of metal cations, molecular weight, composition of the base resin and additive ingredients, such as reinforcement agents.

Among the family of ionomer resins, the high acid-ionomers, which have been recently developed, have a very high flexural modulus due to the high acid content and they provide a high level of resilience. The resilience imparts to the ball an increased initial velocity. Therefore, the ball travels a greater distance than a ball having a lower initial velocity. On the other hand, the main disadvantage of these covers made of pure high acid ionomers is their extremely great hardness (68 shore D and higher). Therefore, balls made of high acid covers have a very "hard" feel and a low spin rate, which renders it difficult to control the distance of the ball with short irons. High acid ionomer covers also have a tendency to crack after multiple hits with a driver or similar long club. For those reasons, UK-A-2,278,609 proposes to use a high acid ionomer as an inner cover layer and a softer polymeric material of low flex modulus ionomer resin and non-ionomeric thermoplastic elastomer for the outer cover layer to compensate for the hard feel of the high acid ionomer resin.

Other ionomers known as VLMI (Very Low Modulus Ionomers) have the properties of being very low in stiffness and hardness but, as a consequence, they have the drawback of providing a very poor resilience. VLMI are described in U.S. Patent No.

4,690,981. They are known as being "slow materials" with respect to the initial velocity.

Therefore, a pure VLMI cover does not impart a sufficient rebound to the ball. A pure

VLMI cover also has a very poor cut and shear durability. In consequence, it has been common to blend the VLMI with other higher flex modulus ionomers to produce a desired range of hardness for the cover. However, the gain in performance, in particular in distance, has not been proven to be particularly significant. Examples of VLMI include Surlyn 8120 (sodium cation), 8320 (sodium cation), and 9320 (zinc cation). Among the VLMI family, Surlyn 8320 has the lowest value of Flexural Modulus (2.8 kpsi or 19.3 MPa).

Other families of thermoplastic materials having interesting properties are also known, particularly the amide block copolyethers known commercially as Pebax^® of Elf- Atochem Company, Paris, France. The use of these materials in golf balls is described for the first time in U.S. Patent No. 4,234,184 to make a golf ball cover. However, a pure Pebax cover experiences the same disadvantages as VLMI except for the cut durability and abrasion for the high grades of Pebax. On the other hand, the higher the hardness of Pebax, the lower the impact resilience becomes. A cover made entirely of Pebax with a certain level of hardness to resist cutting, shearing and abrasion will provide to the ball, in counterpart, a low velocity.

U.S. Patent No. 5,253,871 to Viollaz is directed to a multi-piece golf ball having an intermediate mantle between the cover and the core which comprises at least 10% by weight of amide block copolyether. In the mantle, this material is protected from cutting and peeling by the cover and, therefore, the ball has a good durability. The remarkable property of this material is that, in contrast with the ionomeric resins, the lower the hardness and modulus, the higher becomes the impact resilience. Like the ionomer resins, the amide block copolyethers are available in a wide range of hardness and flex modulii. U.S. Patent No. 5,253,871 also proposes a relatively wide choice of materials for the cover. Among the preferred materials are cited ionomers, amide block copolymers of the type used for the mantle but with greater hardness, ionomer and amide block copolymer compounds, thermoplastic polyurethanes, as well as combinations of these materials. However, at the time of the Viollaz patent, the high acid ionomers were unknown to the public. As explained below, the present invention pertains to all types of golf balls, including two-piece balls, three-piece solid balls, and wound balls. Despite a crowded state of the art, there still exists a need which has not yet been met to have a cover composition which provides a spin rate and a sensation more closely approximating balata-covered balls, while also proving to impart more distance to the ball than previous cover compositions.

With respect to this need, the purpose of U.S. Application Number 08/915,081, filed on August 20, 1997, which is incorporated herein in its entirety by reference thereto, is to propose a new composition for a cover comprising a soft amide block copolymer and a harder ionomer. This composition indeed has been found to achieve high values of spin rate for a better control, to improve the feel, and further has been found to increase the distance of the ball.

However, it has been determined that a cover made of such a composition would exhibit a lower shear resistance than a conventional ionomer cover. For example, the results of tests which have been conducted, and are discussed herein, have shown that the cover may be easily cut or its surface damaged when the ball is hit with a short iron golf club which transfers a high spin rate to the golf ball. It has also been ascertained that there are durability problems which result in the cracking of the cover after only a few number of shots. Problems of delamination have yet additionally been noticed after injection of the cover around the rest of the inner spherical structure.

A study on the morphology of the composition by microscopic analysis has established that these problems were related to a poor degree of compatibilization between the polyamide elastomer and the ionomer in the composition. In particular, the composition shows cryogenic fractures and delamination at the interface between the ionomer and the polyamide elastomer. A heterogeneous dispersion of the mixed polymers has been also observed.

It appears - though this is provided only as a possible explanation, and is not to be taken as binding or limiting - that the main problem occurs during the mixing of the ionomeric resin and the polyamide elastomer which have a limited compatibility. The ionomeric resin comprises long linear polyethylene chains that have little or no polarity except for several carboxylic groups. The polyamide block elastomer comprises numerous polar amide groups which have no chemical affinity with the ethylene chains.

U.S. Patent No. 5,155,157 to E.I. DuPont de Nemours & Company, discloses thermoplastic compositions comprising: a thermoplastic polymer selected from copolyetheramides and copolyetheresters; an epoxy-containing compound; and an acid- containing ethylene copolymer ionomer. The composition provides improved features of durability which make it suitable for use in a center of a wound golf ball, a core of a two- piece solid golf ball, or a one-piece golf ball for use in driving ranges. This patent further discloses that where the composition has a flex modulus of about 14,000-30,000 psi (ASTM D790. procedure B), preferably without filler, it may also be employed for golf ball cover materials. However, due to the large percentage of copolyetherester or copolyetheramide, such a composition has certain disadvantages for use as a golf ball cover and, more particularly, for use as the outermost layer of the cover. Indeed, where the relative proportions of thermoplastic elastomer and ionomer are such that the amount of the thermoplastic elastomer is so much greater than that of the ionomer, the cover is rendered too soft, causing loss of distance and ballooning trajectory due to an abnormally high spin rate. Poor cutting resistance would also be expected even in presence of the epoxy-containing compound.

Furthermore, it has also surprisingly been discovered, by experimentation, that a compatibilizing agent comprising a functional group such as epoxy would have little effect on the improvement of the tensile strength and elongation properties, when the elastomer comprises too high a proportion of the composition. On the contrary, these mechanical properties would be dramatically improved where the amount of elastomer remains under a predetermined level. Tensile strength and elongation properties are parameters which indicate the amount of energy the material can withstand; they are therefore closely related to the durability of the golf ball. Disclosure of Invention

The present invention is directed to a golf ball and, more particularly, to a cover composition for a golf ball that provides for the ball improved spin and feel characteristics, but at the same time, that shows an unattended increase in distance.

To that end, in a first embodiment the invention is directed to a compound for a golf ball cover which comprises:

(a) an amide block copolymer whose hardness is less than or equal to 40 shore D; and (b) an ionomer whose hardness is greater than the hardness of the amide block copolymer; wherein the amount by weight of each depends upon the desired cover hardness to be achieved.

Further in this first embodiment, the invention is directed to a cover which includes at least one thermoplastic layer made of the foregoing compound. Yet additionally in this first embodiment, the invention is directed to a golf ball which includes a core and this cover.

It has been discovered that the combination of an amide block copolymer, particularly a soft or even a very soft amide block copolymer, and a harder ionomer, gives a surprisingly remarkable increase in the spin rate that has been never achieved until now for ionomer-based blends. More precisely, the combination allows the achievement of high values of spin rate for a better feel and control, which further proves to also increase the distance of the ball. The primary reason is that due to a higher spin rate, the flight of the golf ball is improved and the velocity decreases less rapidly; thus, the ball travels a greater distance than a conventional ball with a cover of ionomer, more particularly one made of a blend of VLMI/high flexural ionomer. In addition, the invention enables the adjustment of the cover hardness to a determined value in order to control the feel and spin rate of the golf ball as precisely as desired. In other words, the invention is directed to maintaining a cover with a high resilience when blending a "fast" material, which is the hard ionomer, with a softer but resilient material to obtain a desired cover hardness, a high spin for both control and distance and a good feel.

In the blend, the soft amide block copolymer has the function of lowering the hardness to the desired value without sacrificing significant loss in resilience. Furthermore, it results surprisingly from the softening of the hard ionomer by the soft amide block copolymer that the spin rate of the ball increases significantly in comparison with a high flex ionomer softened by a VLMI, for example. Therefore, the soft amide block copolymer, which replaces the VLMI in the context particularly of this first embodiment of the present invention, plays a key role in the increase of the spin to the golf ball, and more generally to the performance of the golf ball. It appears that due to its rubbery properties, the amide block copolymer offers to the cover a tendency (1) to deform elastically under the momentum forces applied by the club face at impact and (2) to release more energy transformed into spin to the ball just after impact. The harder ionomer in the blend gives the properties of high resilience to have a high velocity imparted to the ball. The ionomer also increases high shear resistance which confers more durability of the cover. For example, the applicant has noted that despite the fact that amide block copolymer is commercially available in a wide range of hardnesses, a cover made purely of this material would not provide sufficient peeling and cut resistance.

Further in this first embodiment of the invention, the cover can comprise a layer having:

(a) from 10 to 90 weight percent (wt %) of an amide block copolymer whose hardness is less than or equal to 40 shore D; and (b) from 90 to 10 wt % of an ionomer whose hardness is greater than or equal to 65 shore D; whereby a hardness of between 45 to 65 shore D is conferred to the layer.

It has been noted that the cover hardness must remain in the given range to reach an acceptable rate of spin. When the hardness of the cover is greater than 65 shore D, the spin rate has been found to decrease dramatically.

On the contrary, when the hardness is too low and, particularly, lower than 45 shore D, a loss of distance can be measured. The only way to compensate this loss of distance would be to have a stiffer core with a high level of compression. This is undesirable because it causes the golf ball to feel very hard. It has also been found that under 45 shore

D, the cover also experiences a weakness in cut and shear resistance.

Yet additionally in this first embodiment, the invention is directed to a compound for a golf ball cover which comprises:

(a) a polyamide elastomer whose hardness is less than or equal to 40 shore D;

(b) at least one high acid ionomer whose hardness is greater than 65 shore D.

The present invention is also directed to a cover which includes at least one thermoplastic layer made of the foregoing compound. Still further, the invention is directed to a golf ball which includes a core and this cover.

Preferably, the polyamide elastomer is very soft and has a hardness of 35 shore D or less. Preferably, the polyamide elastomer is a soft amide block copolymer. More preferably, the amide block copolymer is a polyetheresteramide.

The high acid ionomer is intended to be an ionomer including at least 16 weight percent, or about 18-19 weight percent, or at least 19 weight percent, of an alpha, beta- unsaturated carboxylic acid. More preferably, the high acid ionomer comprises acid groups partially neutralized by lithium. The high acid ionomer neutralized with lithium is the ionomer which provides the highest impact resilience when tested with respect to other high acid ionomers neutralized with different cations such as zinc, magnesium, sodium, etc. Particularly in the case of high acid ionomers for which neutralization is effected by magnesium cations, these ionomers preferably include about 18-19 weight percent, or at least 19 weight percent, of an alpha, beta-unsaturated carboxylic acid.

The present invention further is directed to a golf ball cover composition that provides exceptional mechanical properties and reasonable softness - i.e., an increase of the tensile and elongation properties - while at the same time providing a high level of cutting resistance and durability, which makes it suitable for directly contacting the club striking face.

In this regard, in a second embodiment the present invention is directed to a composition for a golf ball cover which comprises:

(a) about 60 wt % or less of an elastomer, particularly a soft elastomer, comprising at least one member selected from the group consisting of polyamide elastomers and polyester elastomers;

(b) about 0.3 to 10 wt % - or, alternatively, 10 wt % or less - of a compatibilizer, or compatibilizing agent. This agent comprises a copolymer which comprises at least one monomer, with this at least one monomer comprising at least one functional group selected from the group consisting of cyclic functional groups and noncyclic functional groups. Particularly, the indicated at least one monomer can comprise at least one cyclic functional group and/or at least one noncyclic functional group. Further, the copolymer can comprise one or more monomers comprising at least one cyclic functional group, and also one or more monomers comprising at least one noncyclic functional group. In a preferred aspect of this second embodiment of the invention, the composition of the invention comprises about 0.3 to 10 wt % of the compatibilizer, with the compatibilizer

- 9 - SUBST1TUTE SHEET (RULE 26) comprising a copolymer which comprises at least one monomer comprising a cyclic functional group. In another preferred aspect, the composition of the invention comprises 10 wt % or less, or less than 10 wt %, of the compatibilizer, with the compatibilizer comprising a copolymer which comprises at least one monomer comprising a noncyclic functional group; and

(c) a remainder comprising at least one ionomeric polymer, or ionomer, having a hardness greater than the hardness of the elastomer;

wherein the functional group interacts physically and/or chemically, with one or both of the elastomer and the ionomer, to reduce the interfacial tension, which helps bring about a homogenous mixing of these polymers.

Further in this second embodiment, the invention is directed to a cover which includes the foregoing composition - particularly, to a cover which includes at least one thermoplastic layer made of the foregoing composition. Yet additionally in this second embodiment, the invention is directed to a golf ball which includes a core and this cover.

As a matter of preference, the indicated golf ball cover composition of this second embodiment is in the form of a discontinuous phase dispersed within a matrix or continuous phase, with the elastomer and ionomer providing different phases. In this regard, the matter of which phase is formed by elastomer and which by ionomer depends upon a multiplicity of factors, including the relative proportions of elastomer and ionomer, their respective identities, and their respective properties. Considering the foregoing, the continuous phase is accordingly understood as comprising the amount of continuous phase polymer, relative to the amount of discontinuous phase polymer, so that the former is maintained as the continuous phase, with the latter dispersed therein as the discontinuous phase.

- 10 - SUBST1TUTE SHEET (RULE 26) Further as to the disposition of the phases, the dispersed phase can comprise clusters randomly distributed within the continuous phase. These clusters can be significantly smaller than would be the case if the compatibilizer were absent from the composition.

In this regard, the compatibilizing agent can act in the composition to reduce interfacial tension. Accordingly, the presence of compatibilizer can lead to a decrease in the size of clusters. In turn, this improved morphology can cause a directly related improvement in the mechanical properties of the composition.

Yet additionally regarding the compatibilizer, the presence of this agent can serve to maintain the stability of the developed morphology of the blend of elastomer and ionomer. In this manner, the compatibilizer helps to maintain the material performance of the composition.

However, the compatibilizer also has a disadvantageous effect on the composition of the invention, in that it decreases the velocity of a golf ball having a cover prepared from the composition; this agent therefore lessens the distance which can be obtained with the ball. Moreover, the greater the amount of compatibilizer which is present in the composition, the greater is the adverse effect on velocity, and therefore on distance.

Accordingly, it is desirable that the composition of the invention include as little as possible of the compatibilizer. The preferred amount of this component is that which is the minimum necessary to develop the desired morphology of the elastomer and the ionomer in their blended state.

In a preferred aspect of this second embodiment of the invention, the elastomer represents about 50 wt % or less, more preferably about 40 wt % or less, of the golf ball cover composition. This allows the use of a wide range of ionomers, including low acid and/or high acid ionomers. Beyond this limit, if low acid ionomer is the only ionomer which is used, the golf ball may lose a significant amount of velocity, have too much spin rate, and the cover may be more sensitive to shear resistance due to the softness of the elastomer in combination with the properties of the low acid ionomer. In addition, it has surprisingly been found that for a composition which includes compatibilizing agent, the mechanical properties, such as tensile strength and elongation, may be substantially lower than for the same composition without compatibilizing agent.

In another aspect of this second embodiment of the invention, component (c) comprises at least one high acid ionomer including at least 16 weight percent, or about 18- 19 weight percent, or at least 19 weight percent, of an alpha, beta-unsaturated carboxylic acid. Preferably, the alpha, beta-unsaturated carboxylic acid comprises at least one member selected from the group consisting of acrylic acid and methacrylate.

The high acid ionomer has improved mechanical properties such as a higher flexural modulus than conventional hard and low acid ionomers. This allows the cover to maintain a high resilience and shear resistance, especially when the amount of the elastomer is greater than 40 wt % but still less than the maximum recommended limit.

Preferably, component (c) comprises both a first high acid ionomer and a second high acid ionomer, each including at least 16 weight percent, or about 18-19 weight percent, or at least 19 weight percent, of an alpha, beta-unsaturated carboxylic acid. More preferably, the first high acid ionomer has acid groups neutralized by sodium ions and the second high acid ionomer has acid groups neutralized by zinc ions. A combination of two ionomers or more in the composition, especially these two high acid ionomers as indicated, shows unexpected improved results - specifically, an increase of velocity without sacrificing spin rate.

Also as a matter of preference, component (c) comprises a high acid ionomer including about 18-19 weight percent, or at least 19 weight percent, of an alpha, beta- unsaturated carboxylic acid, with this high acid ionomer comprising acid groups neutralized by magnesium ions As a matter of particular preference, this high acid ionomer with neutralization by magnesium ions can be used as a substitute for the above discussed combination of sodium-neutralized and zinc-neutrahzed ionomers, that is, for a composition including specific amounts of the sodium-neutralized and zinc-neutrahzed ionomers, instead there can be used an amount of magnesium-neutralized ionomer which is equal, or about equal, to the sum of the weight percents of the sodium and zinc ionomers

In yet a third embodiment the present invention is directed to a composition for a golf ball cover which comprises

(a) an elastomer, particularly a soft elastomer, comprising at least one member selected from the group consisting of polyamide elastomers and polyester elastomers, and

(b) at least one ionomeric polymer, or ionomer, which

(0 has a hardness greater than the hardness of the elastomer, (n) includes about 18 weight percent, or about 18-19 weight percent, or about 19 weight percent, or at least 19 weight percent, of an alpha, beta-unsaturated carboxylic acid, and (in) comprises acid groups neutralized by magnesium ions

Preferably with regard to relative proportions of the elastomer and ionomer, this composition of the third embodiment comprises about 60 weight percent or less of the elastomer Also as a matter of preference, this composition comprises the elastomer, and a remainder of the at least one ionomer Yet additionally as a matter of preference, the elastomer and ionomer are present in relative proportions which provide the desired cover hardness

Further in this third embodiment, the invention is directed to a cover which includes the foregoing composition - particularly, to a cover which includes at least one thermoplastic layer made of the foregoing composition. Yet additionally in this third embodiment, the invention is directed to a golf ball which includes a core and this cover.

A two-piece golf ball, according to the invention, has a core made of rubber, e.g., and a single-layer cover. The combination of the core and cover materials provide a "hard" ball that is generally very rigid and confers a "hard" feel when the ball is struck with the club.

A wound golf ball, according to the invention, generally has a thread wound core covered by a cover made of one or more thermoplastic layers.

A multi-piece golf ball, according to the invention, has a solid core, made of rubber, e.g., covered by more than one thermoplastic layer. According to the invention, such multi-piece ball has a variety of improved characteristics. For example, a multi-piece ball can be constructed according to the invention which has properties similar to a wound ball but with more durability and with improved performance and greater distance.

The present invention also relates to a golf ball including a core and a cover and further at least one mantle layer disposed between the core and the cover, wherein the mantle includes at least one layer that has a material selected from the group consisting of a thermoplastic polyetherester, polyamide based copolymer, an ionomer resin, thermoplastic polyurethane, metallocene polymer, and mixtures thereof.

In a preferred example, the core is a solid rubber core that has a PGA compression which varies as a function of the core size, in the following manner: between 70 to 95, for a core diameter comprised between 1.56 to 1.60 inches; between 50 to 80, for a core diameter comprised 1.43 to 1.56 inches; and between 35 to 70, for a core diameter comprised between 1.39 to 1.43 inches. In this range of compression values, the golf ball maintains a good feel at impact with, in particular, the long clubs. It is important to note that the excellent properties of the cover of the invention renders possible the use of such a core.

Having been briefly summarized, the invention is hereinafter described in detail by reference to the following detailed description, including non-limiting examples.

Brief Description of Drawings

Figs. 1-7 are Scanning Electron Microscope (SEM) micrographs of compositions of the invention, at a magnification of 1 ,000.

Fig. 8 is a cross sectional view of a golf ball according to the present invention.

Fig. 9 is a cross sectional view of a multi-piece golf ball according to the present invention.

Best Mode for Carrying Out the Invention

Copolymers, as discussed herein, are understood as including both those polymers incorporating two different monomeric units, as well as polymers incorporating three or more different monomeric units, e.g., terpolymers, etc.

A first embodiment of the invention pertains to a blend, particularly to a thermoplastic blend, having two main components: a relatively soft amide block copolymer; and an ionomer which has a hardness higher than the hardness of the amide block copolymer. This first embodiment also pertains to a golf ball cover layer which includes this blend. Yet additionally, this first embodiment pertains to a golf ball comprising a core and a cover which comprises this blend.

The amide block copolymer is chosen from among the soft grades of hardness, i.e., less than or equal to 40 shore D (according to ASTM D-2240). Preferably, the amide block copolymer has a hardness of about 25 shore D (according to ASTM D-2240). The choice of a low hardness of amide block copolymer enables a relatively wide range of hardness of the final cover to be encompassed, while simultaneously not affecting the properties of resilience of the final cover.

The polyamide-based copolymer of the invention comprises or consists preferably of a polyether block amide (PEBA). The structure consists of a regular linear chain of rigid polyamide segments interspaced with flexible polyether segments. The polyamide segments are linked to an adjacent polyether segment by an ester group to form a polyetheresteramide.

Suitable thermoplastic polyetheramides are chosen from among the family of Pebax, which are available from Elf-Atochem Company. Preferably, the choice can be made from among Pebax 2533, 3533, 4033 and 1205. Blends or combinations of Pebax 2533, 3533 4033 and 1205 can also be prepared, as well. Pebax 2533 has a hardness of about 25 shore D (according to ASTM D-2240), a Flexural Modulus of 2.1 Kpsi (according to ASTM D-790), and a Bayshore resilience of about 62% (according to ASTM D-2632). Pebax 3533 has a hardness of about 35 shore D (according to ASTM D-2240), a Flexural Modulus of 2.8 Kpsi (according to ASTM D-790), and a Bayshore resilience of about 59%) (according to ASTM D-2632). Pebax has the remarkable and probably unique property of increasing in resilience while decreasing in hardness. Pebax 4033 has a hardness of about 40 shore D (according to ASTM D-2240), a Flexural Modulus of 13 Kpsi (according to ASTM D-790), and a Bayshore resilience of about 51 %, (according to ASTM D-2632). Pebax 1205 also has a hardness of about 40 shore D (according to ASTM D-2240) and a Flexural Modulus of 1.13 Kpsi (according to ASTM D-790). Where Pebax 4033 and/or Pebax 1205 are used, it is preferable that they be employed in small amounts. Particularly, a small amount of Pebax 4033 or 1205 and other Pebax of lower hardness is suitable as long as the total hardness remains in the determined limits. It is noted that the shore hardness of Pebax varies little with the temperature between -40°C and +80°C. The given values are determined at room temperature, between about 18 and 23 °C.

The second main component of the blend, in this first embodiment of the invention, is an ionomer or a mixture of ionomers. The ionomer or mixture of ionomers must have a hardness value which is greater than the hardness value of the first main component. More preferably, the hardness of the second main component must be at least 65 shore D. Among the preferred ionomers suitable to reach these properties are the high flexural ionomers with a flexural modulus of at least 60,000 psi. More precisely, these ionomers are chosen among the acid ionomers, particularly the high acid ionomers.

These high acid ionomers are designated as ionic copolymers which are the metal, e.g., sodium, zinc, lithium, magnesium, etc., salts of the reaction product of an olefin having about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from about 3 to 8 carbons atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%) by the metal ions. The high acid ionomer must contain at least 16%>, or about 18%), or about 18-19%), or about 19%, or at least 19%), by weight of the carboxylic acid.

The high acid ionomers include high acid ionomers such as those developed by E.I. DuPont de Nemours & Company under the trademark "Surlyn^®" and by Exxon Corporation under the trademarks ΕscoX' or "lotek", or a blend thereof. Among the high acid ionomers which can be used for the invention are Surlyn^® 9120, 8140, AD8546 and AD8552 (Surlyn^® AD8552 currently being commercially available as Surlyn 6^®120). These grades can be used alone or in a mixture thereof

According to DuPont, the aforementioned grades offer the following characteristics and properties: 1) Surlyn 9120: Cation type: Zn

Melt flow index: 1.3 g/10 min (ASTM D-1238) Specific gravity: 0.97 (ASTM D-792) Tensile Strength: 3.8 kpsi (ASTM D-638) Yield Strength: 2.4 kpsi (ASTM D-638) Elongation: 280 % (ASTM D-638) Hardness: 69 shore D (ASTM D-2240) Flexural Modulus: 64 kpsi (ASTM D-790) Bayshore Resilience: 64 % (ASTM D-2632)

2) Surlvn 8140:

Cation type: Na

Melt flow index: 2.6 (ASTM D-1238) Specific gravity: 0.96 (ASTM D-792)

Tensile Strength: 5.0 kpsi (ASTM D-638) Yield Strength: 2.8 kpsi (ASTM D-638) Elongation: 340 % (ASTM D-638) Hardness: 70 shore D (ASTM D-2240) Flexural Modulus: 71 kpsi (ASTM D-790) Bayshore Resilience: 58 % (ASTM D-2632)

3) Surlvn AD8546: Cation type: Li Melt flow index: 1.1 (ASTM D-1238) Specific gravity: 0.95 (ASTM D-792) Tensile Strength: 5.4 kpsi (ASTM D-638) Yield Strength: 2.86 kpsi (ASTM D-638) Elongation: 275 % (ASTM D-638) Hardness: 66 shore D (ASTM D-2240) Flexural Modulus: 74 kpsi (ASTM D-790) Bayshore Resilience: 64 % (ASTM D-2632)

4) Surlvn AD8552: Cation type: Mg

Melt flow index: 1.3 (ASTM D-1238) Specific gravity: 0.95 (ASTM D-792) Tensile Strength: 5.2 kpsi (ASTM D-638) Yield Strength: 2.9 kpsi (ASTM D-638) Elongation: 270 % (ASTM D-638)

Hardness: 67 shore D (ASTM D-2240) Flexural Modulus: 75 kpsi (ASTM D-790) Bayshore Resilience: 59 % (ASTM D-2632).

Bayshore Resilience is measured with a Bayshore resiliometer after a sample of material is placed into the base of the test fixture. A plunger is dropped down from a controlled height of 17V_ inches. The plunger hits the test slab and rebounds back toward its original position. This rebound is measured at its highest point and is recorded as a function of the percentage rebound.

As it appears from the aforementioned characteristics, the high acid ionomers are very stiff and hard materials. A cover made of pure high acid ionomer is felt as extremely hard and it imparts a very low spin rate to the ball, which causes difficulty in controlling the ball at the approach to the green. Also, it cannot withstand multiple impacts against a long club such as a driver and the like.

In a preferred aspect of the first embodiment, the high acid ionomer comprises groups partially neutralized by lithium. Ionomer with lithium gives a maximum of rebound at impact in comparison with other high acid ionomers. The compound of which the cover is compπsed can advantageously include other mateπals to ensure proper blending and mixing between the amide block copolyether and the ionomer and to achieve the optimized mechanical and physical properties of the cover.

According to the invention, the range of hardness for the cover can be fitted at a desired value between 40 and 65 shore D, while the Bayshore resilience remains at very high value in comparison with the VLMI/high acid ionomer composition.

Illustrated in the following table (Table 1) are a number of batch formulations for several cover compositions of the present invention as well as specific characteπstics of these formulations These five examples are designated as PB-10 to PB-90 As shown in the table, the examples PB-10 to PB-90 comprise different covers made of a mixture of a

Pebax 2533 and a high acid ionomer AD8546

For the purpose of compaπson, five comparative examples VM-10 to VM-90 of balls have been made and measured for covers made of a blend of Surlyn 8320 and Surlyn AD8546 In these five examples, the Surlyn 8320 is a VLMI which replaces in the same amount the part of Pebax 2533 in the blend.

The general and mechanical characteristics of Surlyn 8320 are as follows:

Cation Type Na

Melt Flow Index. 1.0 g/10 mm (ASTM D-1238) Specific Gravity- 0 94 (ASTM D-792) Tensile Strength : 3.1 kpsi (ASTM D-638) Elongation: 770 % (ASTM D-638) Hardness. 35 D (ASTM D-2240) Flexural Modulus: 2.8 kpsi (ASTM D-790) Tensile Impact (23 °C): 213 ft- lb/in² (ASTM D-18225) Bayshore Resilience: 36 % (ASTM D-2632).

Regarding preparation of the examples PB-10 to PB-90 and comparative examples VM-10 to VM-90, formulation components were mixed at room temperature in a tumbler mixer for 30 minutes. The covers were injection molded around the core at a temperature of injection between 250 and 500 °F, depending upon the blend injected.

In each case, the two-piece ball comprises a cover having a single layer and a polybutadiene core of 1.55 inches and PGA compression of 70. The external diameter of the ball is between 1.680 to 1.686 inches, in conformance with the USGA rules.

A comparative example is also given with a ball having a cover made from balata available in the market under the name "Tour Balata" from Acushnet Company.

Table

c co in

=J

H

C -I rπ

CΛ

I m m

H to

^"3 t-J c I" m t

From the results of Table 1, it can be noted that, for the same amount m weight of Surlyn AD8546 in the blend, the examples of the invention with Pebax generally show a lower initial velocity than the comparative examples with VLMI However, it is very surprising to note that the distance traveled by the golf balls of the invention is always greater than the comparative examples (still for the same amount in weight of high flexural modulus lonomer Surlyn AD8545) The pπmary reason for that unexpected phenomenon comes from the larger amount of spin imparted to the ball in the case of the invention, as can be seen in the table It seems that a lower velocity combined with a higher spin prevents "ballooning" or "upshootmg" and, therefore, allows longer distances

It is particularly interesting to compare example PB-50 of the invention with the comparative example VM-70, since the hardness of the cover is equal to 50 shore D in the two cases In particular, the example PB-50 shows an increase of about 5% of the spin rate when the ball is hit by a dπver, which mainly results in a benefit of about 2 7% in distance with lespect to example VM-70 Furthermore, the improvement in spin rate is of about 7%o when the ball is hit with an 8-ιron All the examples of the invention can be regarded as having a relatively soft feel, close to that of a balata ball The reason is pπmaπly due to the relatively low compression chosen for the core and also the range of hardness chosen for the cover

As a matter of compaπson, the following table (Table 2) gives test results for three examples of golf balls, 1 e , examples PB-A, PB-B, PB-C, which have covers made of pure

Pebax It is readily observable that the balls experience lower spin rates as well as lower initial velocity values with respect to the examples of the present invention which have comparable values of cover hardness For the driver test, a Taylor Made titanium 8.5 ° loft driver was used to launch the test control ball (Pinnacle Gold) at 160 mph; a 9.0° initial starting angle; and 3000 rpm of backspin, i.e., similar to that of the USGA distance test set-up procedure.

The 8-iron test was set up with a Taylor Made "Burner" iron, tested at a swing speed of 88 mph. Backspin is measured initially as the ball leaves the club face.

Table 2

For the golf ball cover composition of the second embodiment of the present invention, the (a) elastomer, (b) compatibilizing agent, and (c) ionomer are hereinafter discussed

The at least one ionomeric polymer, or ionomer, of component (c) is understood as encompassing the copolymers of an alpha-olefin and an unsaturated - particularly, an alpha, beta-unsaturated - carboxylic acid whose carboxylic functions are partly neutralized by a metal ion This polymer may also include another monomer such as an alkyl

(meth)acrylate

Further as to the lonomenc polymers of the present invention, these are understood as including acid ionomers such as high acid ionomers and low acid ionomers Moreover, the high acid ionomers are understood as comprising at least 16 wt %, or about 18 wt %, or about 18-19 wt %, or about 19 wt %, or at least 19 wt %, carboxylic acid - particularly unsaturated carboxylic acid, and more particularly alpha, beta-unsaturated carboxylic acid - and the low acid ionomers are understood as compπsing less than 16 wt % carboxylic acid

Still additionally as to the ionomers of the invention, they are understood as including ionomers having a flexural modulus of about 20,000 to 60,000 psi (according to ASTM D-790), and also as including ionomers having a flexural modulus of about 60,000 psi or greater (according to ASTM D-790) The former of these ionomers are understood as including the low acid ionomers, and the latter are understood as including the high acid ionomers

Suitable ionomeric resins include those as disclosed in the International Publications Nos WO 96/40377 and WO 97/02318, and in U S Patent No 5,591,803, the disclosures of which are hereby incorporated herein in their entireties by reference thereto Appropriate alpha-olefins include ethylene, propylene, 1-butene, and 1-hexene. Among the suitable unsaturated carboxylic acids are acrylic acid, and also methacrylic, ethacrylic, alphachloroacrylic, crotonic, maleic, fumaric and itaconic acid.

Preferably, the ionomeric polymer of the invention is a copolymer of ethylene comprising about 0 to 25 wt %, preferably about 0 to 2 wt % of alkyl (meth)acrylate, and about 5 to 35 wt %>, preferably about 15 to 35 wt % of (meth)acrylic acid, in which about 1 to 90 % of the carboxylic groups are neutralized to form an ionomer with a cation such as, for example, lithium, sodium, potassium, magnesium, calcium, barium, lead, zinc, tin, aluminum, or a combination of two or more of these cations. The proportion of acid is preferably at least about 16 wt %, or about 18 wt %>, or about 18-19 wt %, or about 19 wt %, or at least about 19 wt %..

In accordance with the foregoing, ionomers with at least 16 wt %> of acid are known as the "high acid" ionomers and they are prefeπed in the present invention since they confer more speed to the golf ball without sacrificing the spin properties of the ball. It has also been found out that synergistic properties result from including more than one high acid ionomer in the composition. Preferably, two high acid ionomers are preferred. More preferably, a combination of a zinc high acid ionomer and a sodium high acid ionomer has given the best results. The alkyl group of the alkyl (meth)acrylate may comprise up to 18 carbon atoms.

As examples, suitable alkyl (meth)acrylates include methyl, ethyl, n-butyl and isobutyl (meth)acrylate. These resins preferably have a flexural modulus of between about 500 and 150,000 psi (according to ASTM D-790). Their hardness may be between about 20 and 80 shore D (according to ASTM D-2240). Their Melt Flow Index may be between about 0.2 and 10 g/10 min (ASTM D-1238). In instances where magnesium high acid ionomer is employed, the proportion of acid m the ionomer is preferably about 18 weight percent, or about 18-19 weight percent, or about 19 weight percent, or at least 19 weight percent For compositions of the invention where the ionomer component compπses a combination of zmc and sodium high acid ionomers, a magnesium high ionomer can be used their place Where this substitution is employed, preferably the amount of the magnesium high ionomer is equal, or about equal, to the total amount of the zinc and sodium high ionomers that have been replaced A particular substitution which can be made is that of Surlyn AD8552 for the Surlyn 9120/Surlyn 8140 combination

Replacement of the zmc/sodium ionomer combination with magnesium ionomer improves shear resistance, without adversely affecting compression, hardness, Coefficient of Restitution (COR), or 8-ιron spin In fact, substitution of the magnesium ionomer results in better shear resistance, even if no compatibilizer is present, than is obtained from using the zinc/sodium ionomer combination with compatibilizer However, it is preferred that compatibilizer be included with the magnesium ionomer, because the presence of the compatibilizer provides even greater shear resistance than is achieved using magnesium ionomer without compatibilizer Actually, inclusion of compatibilizer with the magnesium lonomer generally improves mechanical properties over those exhibited by the magnesium ionomer without the compatibilizer For instance, greater reduction of surface tension and interfacial tension, and improvements in tensile strength and elongation, are all realized where the compatibilizer is also present.

The ionomer or mixture of ionomers preferably have a hardness value which is greater than the hardness value of the elastomer component The hardness of the ionomer or mixture of ionomers more preferably is at least about 65 shore D (according to ASTM D-2240) Among the prefeπed ionomers suitable to reach these properties are the high flexural ionomers with a flexural modulus of at least about 60,000 psi (according to ASTM D-790) More precisely, these ionomers are chosen from among the acid ionomers, particularly the high acid ionomers.

The acid ionomers, including the high acid ionomers, are designated as ionic copolymers which are the metal - e.g., one, or two or more in combination, of sodium, zinc, lithium, potassium, magnesium, calcium, barium, lead, tin, aluminum, etc. - salts of the reaction product of an olefin having about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having about 3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%) by the metal ions. As noted herein, the high acid ionomer contains 16% or more, preferably about 18- 19 %, or 19%) or more, by weight of the carboxylic acid, and the low acid ionomer contains less than \6% by weight of the carboxylic acid.

The high acid ionomers include high acid ionomers such as those developed by E.I.

DuPont de Nemours & Company under the trademark "Surlyn" and by Exxon Corporation under the trademarks "Escor" or "lotek", or a blend thereof Among the high acid ionomers which can be used for the invention are Surlyn 9120, 8140, AD8546 and AD8552. These grades can be used alone or in a mixture thereof.

Further as to the second embodiment of the present invention, the elastomer component may include one or more polyamide elastomers, and/or one or more polyester elastomers. Preferred polyamide and polyester elastomers of the invention include the soft polyamide and soft polyester elastomers. For the purpose of the present invention, it is understood that the soft elastomers are preferably those having a hardness of about 35-40 shore D or less, more preferably 25-35 Shore D (according to ASTM D-2240). Preferred polyamide elastomers of the invention include the block amide polyethers which result from the copolycondensation of polyamide blocks having reactive chain ends with polyether blocks having reactive chain ends, including:

1) polyamide blocks of diamine chain ends with polyoxyalkylene sequences of dicarboxylic chain ends;

2) polyamide blocks of dicarboxylic chain ends with polyoxyalkylene sequences of diamine chain ends obtained by cyanoethylation and hydrogenation of polyoxyalkylene alpha-omega dihydroxylated aliphatic sequences known as polyether diols; and

3) polyamide blocks of dicarboxylic chain ends with polyether diols, the products obtained, in this particular case, being polyetheresteramides.

The polyamide blocks of dicarboxylic chain ends come, for example, from the condensation of alpha-omega aminocarboxylic acids of lactam or of carboxylic diacids and diamines in the presence of a carboxylic diacid which limits the chain length. Preferably, the polyamide blocks are polyamide- 12.

The molecular weight of the polyamide sequences is preferably between about 300 and 15,000, and more preferably between about 600 and 5,000. The molecular weight of the polyether sequences is preferably between about 100 and 6,000, and more preferably between about 200 and 3,000.

The amide block polyethers may also comprise randomly distributed units. These polymers may be prepared by the simultaneous reaction of polyether and precursor of polyamide blocks. For example, the polyether diol may react with a lactam (or alpha-omega ammo acid) and a diacid which limits the chain m the presence of water There is obtained a polymer having mamly, polyether blocks, polyamide blocks of very vanable length, but also the various reactive groups having reacted in a random manner and which are distributed statistically along the polymer chain

Suitable amide block polyethers include those as disclosed in U S Patents Nos 4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014, 4,230,838, and 4,332,920 These patents are incorporated herein in their entireties, by reference thereto

The polyether may be, for example, a polyethylene glycol (PEG), a polypropylene glycol (PPG), or a polytetramethylene glycol (PTMG), also designated as polytetrahydrofurane (PTHF)

The polyether blocks may be along the polymer chain in the form of diols or diamines However, for reasons of simplification, they are designated PEG blocks, or PPG blocks, or also PTMG blocks

It is also within the scope of the invention that the polyether block comprises different units such as units which derive from ethylene glycol, propylene glycol, or tetramethylene glycol

Preferably, the amide block polyether compπses only one type of polyamide block and one type of polyether block Mixing of two or more polymers with polyamide blocks and polyether blocks may also be used

Preferably, the amide block polyether is such that it represents the major component in weight, l e , that the amount of polyamide which is under the block configuration and that which is eventually distributed statistically in the chain represents 50 weight percent or more of the amide block polyether. Advantageously, the amount of polyamide and the amount of polyether is in a ratio (polyamide/polyether) of 1/1 to 3/1.

Also prefeπed as polyamide elastomers of the invention are the polyetheramide elastomers. These include the suitable thermoplastic polyetheramides as discussed herein.

Suitable polyester elastomers of the invention include polyetherester elastomers and polyesterester elastomers. Of these, the polyetherester elastomers are prefeπed.

Commercially available polyetherester elastomers which may be used are SKYPEL

G130D, G135D, and G140D from Sunkyong Industries, Seoul, Korea, and HYTREL G3078, G3548, and G4074 from DuPont.

Component (b), in the second embodiment of the invention, may include one, or two or more, compatibilizing agents. Correspondingly, the indicated at least one monomer can comprise one or more cyclic functional groups, and/or one or more noncyclic functional groups.

In a prefeπed aspect of this second embodiment, the compatibilizing agent comprises a copolymer which comprises at least one monomer comprising a cyclic functional group, or two or more cyclic functional groups. Also in this embodiment, the compatibilizing agent preferably comprises about 0.3 to 10 wt % of the composition of the invention.

Further as to the at least one monomer comprising one or more cyclic functional groups, this monomer may comprise one or more of an epoxy monomer, maleic anhydride, norbornene, norbornadiene, dicyclopentadiene, and oxazoline. As a matter of preference, this monomer comprises an epoxy monomer. As a matter of particular preference, the epoxy group of the epoxy monomer comprises an unsaturated epoxy group which shows very good chemical activity with terminal point of unsaturation capable of undergoing polymerization reactions with the other components in the composition and particularly the ionomer and the elastomer previously defined.

As stated herein, the functional group undergoes one or both of physical reaction and chemical reaction, with the elastomer and or with the ionomer, to reduce the interfacial tension. Where the copolymer comprises an epoxy monomer which includes an unsaturated epoxy group, it is prefeπed that the different components be chosen so that the interaction which occurs includes reaction of the epoxy group with free carboxyl groups in the ionomer, and also with amide groups in the polyamide elastomer or with the ester groups in the polyester elastomer, to bring uniform or homogenous dispersion of the elastomer when the ionomer comprises the matrix or continuous phase. This dispersion improves the desirable mechanical properties of a golf ball cover.

The copolymer also preferably comprises an alphaolefin having 30 carbon atoms. Suitable alphaolefins include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-l -butene, 1 -hexene, 4-methyl-l-pentene, 3-methyl-l-pentene, 1-octene, 1-decene, 1-dodecene, 1- tetradecene, 1 -hexadecene, 1-octadecene, 1 -eicocene, 1 -dococene, 1 -tetracocene, 1- hexacocene, 1 -octacocene, and 1-triacontene. These alphaolefins may be used alone or in blend of two or more alphaolefins.

The functional monomer preferably comprises an epoxy group. Prefeπed embodiments include the following:

- esters and ethers of aliphatic glycidyl such as allylglycidylether, vinylglycidylether, glycidyl maleate and itaconate, glycidyl acrylate and methacrylate, and - alicyclic glycidyl ester and ether such as the 2-cyclohexene-l-glycidylether, the cyclohexene-4.5-diglycidylcarboxylate, the cyclohexene-4-glycidyl carboxylate, the 5- norbornene-2-methyl-2-glycidyl carboxylate, and the endocis-bicyclo(2,2, 1 )-5-heptene-2,3- diglycidyl dicarboxylate.

Component (b) may yet additionally comprise other monomers. Those which are suitable include esters of unsaturated carboxylic acid, for example, alkyl (meth)acrylates or vinylic esters of unsaturated carboxylic acids.

The functional monomer may be copolymerized with the alphaolefin, and eventually with other monomers, or may be grafted with homo- or copolymers. Polyolefin intends to cover polymers having at least one unit of alphaolefin among those cited herein below, for example:

- high density polyethylene (HDPE);

- low density polyethylene (LDPE);

- linear low density polyethylene (LLDPE);

- very low density polyethylene (VLDPE); and

- polyethylene obtained by metallocene catalysis, i.e., polymers obtained by copolymerization of ethylene and alphaolefin such as propylene, butene, hexene or octene in the presence of a monosite catalyst constituted generally of a zirconium or titanium atom and two alkyl cyclic molecules bonded to the metal. More specifically, the metallocene catalysts are usually composed of two cyclopentadiene cyclic groups bonded to the metal atom. These catalysts are frequently used with aluminoxanes such as cocatalysts or activators, preferably the methylaluminoxane (MAO). The hafnium may also be used as a metal on which the cyclopentadiene is bonded. Other metallocene catalysts may include transition metals of the groups IV A, V A, and VI A. Metals of the series of the lanthamides may also be used.

Other examples of alphaolefins are:

- homo or copolymers of polypropylene;

- EPR elastomers (ethylene-propylene-rubber);

- EPDM elastomers (ethylene-propylene-diene);

- blends of polyethylene with an EPR or an EPDM;

- copolymers of ethylene- alkyl (meth)acrylate containing up to about 60 wt %, and preferably about 2 to 40 wt %, of (meth)acrylate; and

- copolymers of ethylene-vinyl acetate.

Various known processes may be used to graft the functional monomer to the polyolefin.

For example, this grafting can be effected by heating the polymers at a high temperature, from around 150° C to 300° C, optionally in the presence of a solvent with or without free radicals. Suitable solvents which may be used in this reaction are benzene, toluene, xylene, chlorobenzene, cumene, etc. Suitable free radicals which may be used include t-butyl-hydroperoxide, di-t-butyl-peroxide, t-butyl-cumyl-peroxide, dicumyl- peroxide, l,3-bis-(t-butylperoxy-isopropyl)benzene, acetyl-peroxide, benzoyl-peroxide, iso-butyryl-peroxide, bis-3,5,5-trimethyl-hexanoyl-peroxide, and methyl-ethyl-cetone- peroxide.

In the grafted polyolefin, the amount of grafted monomer may be chosen in an appropriate manner but preferably is about 0.01 to 10%, more preferably about 0.1 to 5 wt %, with respect to the weight of the grafted polyolefin.

Advantageously, the following terpolymers are obtained by direct copolymerization by opposition to grafted copolymers:

- unsaturated epoxy-ethylene copolymers;

- unsaturated epoxy-alkyl (meth)acrylate-ethylene; and

- unsaturated epoxy-saturated carboxylic acid vinyl ester-ethylene.

Preferably, the unsaturated epoxy is the glycidyl (meth)acrylate. The amount of epoxy may comprise about 1 to 15 wt %, preferably 10 wt % or less of component (b).

The amount of alkyl (meth)acrylate or vinylic ester may comprise about 5 to 40 wt % of component (b).

The alkyl (meth)acrylate may be chosen from among the (meth)acrylates previously cited for the ionomer of component (c).

Terpolymers comprising epoxy monomers - specifically, containing epoxy functional groups - and which are suitable for the invention, may include LOTADER® AX 8900, AX 8840, and AX 8920, sold commercially by Elf-Atochem Company, ELVALOY, sold commercially by DuPont, IGETABOND (formerly sold as BONDFAST), sold commercially by Sumitomo Chemical Co , and REXPEARL, sold commercially by Nippon Petrochemicals Co , Ltd

The viny c ester is preferably vinyl acetate

Additional examples of copolymers comprising epoxy monomers - specifically, epoxy functional copolymers - and which are suitable for the invention include the following

- styrene-butadiene-styrene block copolymers in which the polybutadiene block contains epoxy groups, and

- styrene-isoprene-styrene block copolymers in which the polyisoprene block contains epoxy groups

Commercially available examples of these epoxy functional copolymers include ESBS A1005, ESBS A1010, ESBS A1020, ESBS AT018, and ESBS AT019 All of these are available from Daicel Chemical Industries, Ltd

As stated herein for the copolymer used as a compatibilizer, the indicated at least one monomer comprising one or more cyclic functional groups may comprise maleic anhydride Suitable maleic anhydride copolymers include maleic anhydride-modified ethylene-propylene copolymers, maleic anhydπde-modified ethylene-propylene-diene monomer teφolymers, maleic anhydride-modified polyethylenes, maleic anhydnde- modified polypropylenes, ethylene-ethyl acrylate-maleic anhydπde teφolymers, and maleic anhydπde-indene-styrene-cumarone copolymers Commercially available copolymers which are suitable for the invention, and which contain maleic anhydride, include the following:

- BONDINE, sold commercially by Sumitomo Chemical Co., including BONDINE AX8390, which is an ethylene-ethyl acrylate-maleic anhydride teφolymer having an ethylene acrylate + maleic anhydride content of 32 wt %, and BONDINE TX8030, which is an ethylene-ethyl acrylate-maleic anhydride teφolymer having an ethylene acrylate + maleic anhydride content of 15 wt % and a maleic anhydride content of 1-4 wt %;

- maleic anhydride-containing LOTADER 3200, 3210, 6200, 8200, 3300, 3410, 7500, 5500, 4720, and 4700, sold commercially by Elf-Atochem;

- EXXELOR VA1803, which is sold commercially by Exxon Chemical Co., and which is a maleic anhydride-modified ethylene-propylene copolymer, with a maleic anhydride content of 0.7 wt %; and

- KRATON FG 190 IX, sold commercially by Shell Chemical, which is a maleic anhydride functionalized triblock copolymer having polystyrene endblocks and poly(ethylene/butylene) midblocks.

With regard to the maleic anhydride-containing LOTADER and BONDINE resins, polarity and branching of the acrylic ester improves wettability and flexibility, and lowers crystallinity. In addition, polarity and reactivity of the maleic anhydride result in chemical adhesion.

Further with respect to the copolymer used as a compatibilizer, the indicated at least one monomer comprising one or more cyclic functional groups may comprise oxazoline. The oxazoline copolymers include two types of thermoplastic resins containing oxazoline groups - polymers which have oxazoline groups situated at the surface of the polymer particles, and polymers wherein the oxazoline groups are added to the polymer backbone, both of these types are suitable for the present invention Each of these two types of oxazoline polymers includes polystyrenes, acrylonitπle-styrene copolymers, acrylic acid- styrene copolymers, polymethyl methacrylates, polyethyl methacrylates, polybutyl methacrylates, polymethyl acrylates, and polybutyl acrylates

Commercially available copolymers which are suitable for the invention, and which contain oxazoline, include the following, all commercially available from Nippon Shokubai Kagaku Kogyo K K

- EPICROSS RASIOOI , which is an acrylonitπle-styrene copolymer comprising oxazoline groups, and which has a weight average molecular weight of about 120,000 and a polyfunctional group (oxazoline group) equivalent molecular weight of about 2,200,

- EPICROSS RPS1001 , which is a polystyrene comprising oxazoline groups, and which has a w eight average molecular weight of about 120,000 and a polyfunctional group (oxazoline group) equivalent molecular weight of about 1 1 ,000, and

- EPICROSS RPS1005, which is a polystyrene comprising oxazoline groups, and which has a weight average molecular weight of about 140,000 and a polyfunctional group (oxazoline group) equivalent molecular weight of about 2,200

In another prefeπed aspect of this second embodiment of the invention, the compatibilizing agent comprises a copolymer which compπses at least one monomer comprising a noncyclic functional group, or two or more noncyclic functional groups Suitable noncyclic functional groups include carboxylic acid groups and ammo groups Also in this embodiment, the compatibilizing agent preferably comprises 10 wt % or less, or less than 10 wt %, of the composition of the invention.

For the golf ball cover composition, of the third embodiment of the invention, the elastomer component of the second embodiment is suitable. Ionomers which are appropriate for the third embodiment include particularly the magnesium ionomers of the second embodiment which comprise about 18 wt %, or about 18-19 wt %, or about 19 wt %>, or at least 19 wt %, carboxylic acid - particularly unsaturated carboxylic acid, and more particularly alpha, beta-unsaturated carboxylic acid. The third embodiment composition may include compatibilizing agent, as discussed for the second embodiment; however, preferably compatibilizing agent is absent, or essentially absent or substantially absent, from the composition of the third embodiment of the invention.

Further according to the invention, particularly for cover compositions of the second and third embodiments, the amount of the polyamide elastomer and/or polyester elastomer preferably remains at or under about 50 wt %, more preferably between about 30 and 40 wt %. Also as a matter of preference, the amount of elastomer is at least that which is sufficient so that the composition is in the form of a discontinuous phase dispersed within a matrix or continuous phase, with the elastomer and ionomer providing different phases.

Above about 40 wt %, if a low acid ionomer is used alone, the presence of the polyamide elastomer and/or polyester elastomer is too preponderant in the composition. This would cause a loss of the initial velocity, too much spin, and ballooning trajectories instead of straight trajectories.

The polyamide elastomer and/or polyester elastomer have the property of increasing in resilience while decreasing in hardness. Therefore, the polyamide elastomer and/or polyester elastomer have also to be chosen from among the soft grades to confer to the composition remarkable properties of both softness and resilience. Preferably, the hardness of component (a) is about 35 shore D or lower (according to ASTM D-2240).

The ionomeric polymer of component (c) has a hardness greater than that of the amide block polyether, to compensate for its softness and to take advantage of the high resilience of the high grades of ionomers. Preferably, the hardness of component (c) is about 65 shore D or higher (according to ASTM D-2240).

The hardness of the composition, and particularly the hardness of a golf ball cover provided from the composition, preferably is targeted to be between about 50 and 65 shore D (according to ASTM D-2240), so that it confers sufficient properties of control and a good feel, as well as performance in distance and initial velocity. A prefeπed means of achieving a hardness value within this range is to utilize elastomer and ionomer components having the appropriate relative hardness values, and in the necessary relative proportions, so as to provide the desired hardness value for the composition.

Accordingly, where the intended range for the hardness value is between about 50 and 65 shore D (according to ASTM D-2240), preferably the ionomer which is used has a hardness value of about 65 shore D or greater (according to ASTM D-2240). Also as a matter of preference in this instance, the elastomer has a hardness value of about 35 shore

D or less (according to ASTM D-2240).

The invention is further illustrated by the following additional Examples. These are provided for the puφose of representation, and are not to be construed as limiting the scope of the invention. ADDITIONAL EXAMPLES

The materials as set forth hereinafter have been employed in the following Examples.

SURLYN 9120 is an ionomer resin as discussed herein.

LOTADER AX 8900 identifies a teφolymer of ethylene, n-butyl acrylate, and glycidyl methacrylate produced by Elf-Atochem Co.

PEBAX 2533 identifies an amide block polyether having a hardness of 25 shore D (according to ASTM D-2240), a flexural modulus of 2.1 kpsi (according to ASTM D-790), and a Bayshore resilience of about 62 % (according to ASTM D-2632).

EXAMPLES B l TO B10:

In each of the following experimental trials numbered Bl to B10, a lesser amount of component (a) (soft amide block polyether) of the composition has been mixed with a comparatively greater amount of component (c) (the ionomer), according to a prefeπed embodiment of the invention. Bl and B6 are comparative examples which do not include the epoxy compound of component (b). B2 to B5 show various blends of the invention, each having a different amount of the epoxy compound for the given relative proportions of PEBAX 2533/Surlyn 9120. B7 to B10 show other various blends of the invention, again with each blend having a different amount of the epoxy compound, but in this case for another choice of relative proportions of PEBAX 2533/Surlyn 9120.

Five (5) lbs of blend were dry blended in a tumbler mixer for about 30 minutes at room temperature. Then, the blend was compounded by a 25 mm twin screw extruder to achieve good mixing. The processing from feeder to die was as follows: T_REAR = 190° C; T_{CE TER} = 205 ° C; T_FR0NT = 180° C; T_DIE = 190° C.

The use of a twin screw extruder is prefeπed, and has shown much improved mechanical results, in particular with regard to the resulting golf balls' durability against cracking. The use of a twin screw for extrusion is highly recommended to obtain a homogeneous compound with optimal mechanical properties.

In addition to twin screw extrusion, the polymer mixtures or blends can also be made by dry blending or by other internal mixers, such as a single screw extruder, a kneader, or a Banbury mixer.

The relative amounts of the ingredients for each batch Bl to B10 are set forth in Table 3. Numerical data given in this Table are presented as parts per hundred (phr).

TABLE 3

* B l and B6 are comparative examples

EXAMPLES B l 1 TO B20 (Comparative): These blends were prepared as comparative examples with the relative amount of

PEBAX 2533 (component (a)) being greater than the prefeπed relative amount for the present invention.

B 1 1 and B 16 are reference blends without compatibilizer or epoxy compound. B 12 to B15 are for comparison to Bl 1 with variation of the amount of the compatibilizer for a particular proportional ratio of PEBAX/Surlyn. B17 to B20 are for comparison to B16 for a different proportional ratio of PEBAX/Surlyn.

Each blend was dry blended and twin screw extruded in the same conditions as set forth in EXAMPLE Bl to B10: T_REAR = 180= C; T_CENTER = 200° C; T_FRONT = 175 ° C; T_DIE = 180°C. The relative amount of the ingredients for each batch Bl 1 to B20 are set forth in Table 4 As with Table 3, numerical data given in Table 4 are presented as parts per hundred (phr)

TABLE 4 (Comparative)

* Bl l and B 16 are comparative examples

From the resin composition obtained for each batch Bl to B20, test specimens ("dog bones" complying with ASTM D-638) were prepared, using an injection molding machine comprising a baπel with heating sections and a nozzle connected to a mold

The specific molding conditions are set forth below

REAR 160° C, T_{C EVrER} - 165 ° C, T_FRONT - 170° C, T _0ZZLE - 170° C, T_M0LD - 30° C

Back pressure = 150 psi and injection pressure = 1000 psi

Then, a tensile test was earned out using an "Instron" type universal tensile meter at a crosshead speed of 2"/mιnute to measure the tensile strength (in psi) The measurement of the tensile strength was regarded as an indication of the mechanical strength The test was carried out at room temperature. The maximum of elongation was also measured for each test piece.

The results are shown in Table 5 as follows:

TABLE 5

The results from the tensile and elongation tests demonstrate that the compositions of the invention experienced a significant improvement of their mechanical characteristics when compatibilizer of the epoxy type is added to the blend. In particular, the compatibilizer seems to have some effect on the tensile strength and/or elongation. The results from the tests also show that the mechanical properties are not improved, and even would rather decrease slightly when the amount of amide block copolymer is higher than the prefeπed relative amount according to the invention. In other words, the compatibilizer or teφolymer with epoxy functional group has no significant effect on the improvement of the mechanical properties of the composition (tensile strength and elongation), when the relative amount of the amide block polymer is higher than the prefeπed amount of the invention. These results were not expected in an 'a priori approach', and appeared to be very siiφrising.

In addition to these mechanical tests on specimens, golf balls were produced to carry out a shear resistance test and confirm the improvement in shear resistance of a cover made in accordance with the present invention. Two golf balls for each cover composition were shot twice with a sand wedge type iron "Taylor Made Tour 55", having the following physical characteristics: Lie: 64°; Loft: 55 °; bounce: 8°; club length: 35 inches. A visual evaluation was made according to the following criteria:

Rank: Criterion:

1 Excellent (no paint or cover damage)

2 Good (paint damage only)

3 Average (minor cover damage) 4 Fair (Moderate cover damage, slight material removed)

5 Poor (Major cover damage, moderate material removed) The tests results are displayed in the following table:

INVENTION COMPARATIVE

Cover Formulation A B C D

PEBAX 2533 (wt %) 10 30 10 30

SURLYN 9120 (wt %) 85 65 90 70

LOTADER AX8900 (wt %) 5 5 — —

Shear resistance 3.5 3.5

The results show a significant improvement of the shear resistance when the cover formulation comprises a certain amount of Lotader.

An impact durability test was also conducted which consisted of firing a golf ball via an air cannon at 125 feet/second inbound velocity into a stationary steel plate (Conventional test machine usually used to measure golf ball coefficient of restitution (COR)). The balls strike the wall at simulated "driver" conditions, then they are periodically checked for cracks. Twelve golf balls are used for one reference, and failure is based on cracks on 50 % of the balls.

The results are reported herein below:

INVENTION COMPARATIVE

Cover Formulation Al Cl C2

PEBAX 2533 (wt %) 40 40 ~ SURLYN 8140 (wt %) 30 30 50 SURLYN 9120 (wt %) 25 30 50 LOTADER AX8900 (wt %) 5

Durability Results

50% FAILURE (hits) 210 30 200

The foregoing results show that without compatibilizer, the composition experiences a very poor durability. In addition, the foregoing results show that with compatibilizer, the composition of the present invention experiences very good durability, comparable to that of a conventional blend of Surlyn.

The following tests, as performed, and with the results reported in the following Tables 6 and 7, show the benefit of using high acid ionomers in the composition of the invention, versus the use of a conventional hard low acid ionomer in the composition. The

Examples A2, A2', and A3, respectively, show significant improvement of the coefficient of restitution (COR) while the spin rate remains substantially stable when compared to the results obtained with Examples A4 and A5, respectively. Example C is given for comparative puφoses. The tested golf balls were 3-piece balls comprising a core, a thermoplastic mantle and a cover. However, the invention may apply, as well, to a 2-piece golf ball consisting of a core and a cover.

Particularly with regard to Table 6, Examples AT and A2' differ from Examples

Al and A2, respectively, by the substitution of 65 weight percent Surlyn AD 8552 ( Mg ionomer) for the 32.5 weight percent Surlyn 9120 (Zn ionomer) and 32.5 weight percent Surlyn 8140 (Na ionomer) in the cover. In Table 7, Examples A1-A5 and C are the same as the corresponding Examples A1-A5 and C of Table 6, except that for each of the Table 7 Examples, the mantle has 30 weight percent Surlyn AD 8552, instead of the 15 weight percent Surlyn 9120 and 15 weight percent Surlyn 8140 specified for each Example in Table 6. In each of these instances, the amount of Surlyn AD8552 is equal to the total amount of Surlyn 9120 and Surlyn 8140 which is replaced.

The data set forth in Tables 6 and 7 demonstrate that substitution of Surlyn AD 8552 for an equal weight proportion of the Surlyn 9120/Surlyn 8140 combination, either in the cover or in the mantle, does not change the values of compression, hardness, COR, and 8-iron spin exhibited by the golf balls of the relevant Examples. In fact, even if the substitution is effected in both cover and mantle, the compression, hardness, COR, and 8- iron spin values will still be the same.

And even though the foregoing properties are not changed, using Surlyn AD 8552 in place of Surlyn 9120 and Surlyn 8140 in the cover provides improved shear resistance, even if the Lotader is absent, over the shear resistance afforded by the Surlyn 9120/Surlyn 8140 with the Lotader being present Notwithstanding the foregoing, preferably the Lotader is included with the Surlyn AD8552, because inclusion of the Lotader with Surlyn AD8552 in the cover results in even greater shear resistance than is obtained from using Surlyn AD8552 without the Lotader Actually, inclusion of the Lotader with the Surlyn AD8552 generally improves mechanical properties over those exhibited by the Surlyn AD8552 without the Lotader For instance, greater reduction of surface tension and mterfacial tension, and improvements in tensile strength and elongation, are all realized where the Lotader is also present

TABLE 6

Al A A2 A2' A: A4 A5 c

Core

Diameter (in inches) 1.48 1.48 1.48 1.48 .48 .48 .48 .48

Compression 65 65 65 65 65 65 65 65

Mantle

Thickness (in inches) 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

Hardness (Shore D) 46 46 46 46 46 46 46 46

Pebax 2533 (wt %) 70 70 70 70 70 70 70 70

<n Surlyn 9120 (wt %) 15 15 15 15 15 15 15 15 c

DJ Surlyn 8140 (wt %) 15 15 15 15 15 15 15 CO

•H

H Cover

C Hardness (Shore D) 54 54 48 48 46 47 45 55 H πi Pebax 2533 (wt %) 30 30 40 40 50 40 50 co Surlyn AD8552* (wt %) — 65 55 x Surlyn 7930** (wt %) — 55 45 50 m Surlyn 9120*** (wt %) 32.5 27.5 22.5 H Surlyn 8140**** (wt %) 32.5 27.5 22.5

Surlyn 9320***** (wt %) — c 50 r Lotader AX8900 (wt %) 5 ΠI κ_ en Ball Features

Diameter (in.) 1.685 1.685 1.685 1.685 1.685 1.685 1.685 1.685

COR 0.796 0.796 0.792 0.792 0.790 0.787 0.785 0.784

8-Iron spin (φm) 7700 7700 8500 8500 9100 8600 9150 8000

* Surlyn AD8552 is a high acid ionomer with a flex modulus of 75kpsi and 1 wt % acid. ** Surlyn 7930 is a hard ionomer with a flex modulus of 462 MPa and 16 wt % acid. *** Surlyn 9120 is a high acid ionomer with a flex modulus of 440 MPa and 19 wt % acid. **** Surlyn 8140 is a high acid ionomer with a flex modulus of 545 MPa and 19 wt % acid. Surlyn 9320 is a VLMI having a flex modulus of 26 Mpa.

ΓABLE 7

A l A2 A3 A4 A5 C

Core

Diameter (in inches) 1 .48 1 .48 1 .48 1.48 1.48 1.48

Compression 65 65 65 65 65 65

Mantle

Thickness (in inches) 0.05 0.05 0.05 0.05 0.05 0.05 co Hardness (Shore D) 46 46 46 46 46 46

OJ Pebax 2533 (wt %) 70 70 70 70 70 70 CO

H Surlyn AD8552* (wt %) 30 30 30 30 30 30

H

C H Cover rπ Hardness (Shore D) 54 48 46 47 45 55 jg 2 Pebax 2533 (wt %) 30 40 50 40 50 — m ¹ Surlyn 7930** (wt %) — — — 55 45 50

H Surlyn 9120*** (wt %) 32.5 27.5 22.5 — -- —

30 Surlyn 8140**** (wt %) 32.5 27.5 22.5 — — — r Surlyn 9320***** (wt %) - - - - - 50

_" Lotader AX8900 (wt %) 5 5 5 5 5 -

Ball Features

Diameter (in.) 1 .685 1.685 1.685 1.685 1.685 1.685

COR 0.796 0.792 0.790 0.787 0.785 0.784

8-Iron spin (rpm) 7700 8500 9100 8600 9150 8000

* Surlyn AD8552 is a high acid ionomer with a flex modulus of 75kpsi and 19 wt % acid.

** Surlyn 7930 is a hard ionomer with a flex modulus of 462 MPa and 16 wt % acid.

*** Surlyn 9120 is a high acid ionomer with a flex modulus of 440 MPa and 19 wt % acid.

**** Surlyn 8140 is a high acid ionomer with a flex modulus of 545 MPa and 19 wt % acid.

***** Surlyn 9320 is a VLMI having a flex modulus of 26 MPa.

The following tests demonstrate the differences in blends of the invention, resulting from the presence of progressively greater proportions of compatibilizer with the elastomer and ionomer

Five compositions were prepared, one from each of Batches Nos 1-5 The relative amounts of Pebax 2533 elastomer, Surlyn AD8552 ionomer, and Lotader AX900 compatibilizing agent, for the five batches, are set forth in the following table Numerical data given in this table are presented as parts per hundred (phr)

Batch No Pebax 2533 Surlyn AD8552 Lotader AX8900

1 40 60 0

2 40 60 2 5

3 40 60 5

4 40 60 7 5

5 40 60 10

In prepanng each composition from its respective batch, the polymers, each m pellet form, w ere dry blended in a tumbler mixer for 30 minutes at room temperature The resulting dry blend was compounded by a twin screw extruder and pelletized

The SEM micrographs provided herein as Figs 1-5 were prepared from Batches

Nos 1-5, respectively, with a JEOL scanning electron microscope (Model JSM-6400) using 15KeV Injection molded test bars produced from these batches were immersed in liquid nitrogen and fractured The fractured surfaces were sputter coated with Au/Pd to provide a conductive path A magnification of 1000X was employed

Figs 1-5 provide particularly direct evidence, of the compatibihzation and decrease in discontinuous or dispersed phase size, resulting from the presence of compatibilizing agent In this regard, all of Figs 1-5 exhibit ductile fractured surfaces However, Fig 1, showing a blend without compatibilizer, displays gross phase separation with an obvious shear line development, in the form of fiber-like structures along the shear With the addition of a compatibilizer, Lotader AX8900, Figs 2-5 depict less obvious fiber-like structures and smaller dispersed minor phases - in fact, less than 1 μm in size, which is significantly smaller than what is shown in Fig 1

Polymer blends form a multiphase system with a defoπnable minor phase When processed in the melt, an in situ moφhology can be developed, e g , an optimally dispersed phase size and adequate mteφhase adhesion, which are directly related to useful mechanical properties Depending on the size and shape of the dispersed minor phase, many properties, such as impact strength, tensile strength, and impermeability to solvent, can be improved The addition of a proper mterfacial agent (compatibilizer) lowers the mterfacial tension between the phases formed by the components, and yields smaller dispersed phase sizes, thereby improving mechanical properties

Accordingly, the compositions of the foregoing batches, as demonstrated by pioperties e\ ident fiom their SEM miciographs, show the development of a desirable in situ moφhology m Pebax/Surlyn polymer blend systems provided by twin screw extrusion, in the presence of a compatibilizer

Two additional compositions were prepared, one from each of Batches Nos 7 and 8 The relative amounts of Pebax 2533 elastomer, Surlyn AD8552 ionomer, and Lotader AX8900 compatibilizing agent, for the two batches, are set forth in the following table Numerical data given in this table are presented as parts per hundred (phr)

ch No Pebax 2533 Surlyn AD8552 Lotader AX8900

6 20 80 0

7 20 80 5

As can be seen from this table, these batches coπespond to the previously discussed

Batches Nos 1 -5, except that rather than 40 and 60 phr proportions of Pebax 2533 and Surlyn AD8552, respectively, they include 20 and 80 phr of these polymers Blends and test bars were provided from these two batches in the same manner as for Batches Nos 1 -

5 The SEM micrographs prepared from Batches Nos 6 and 7 are presented herein as Figs

6 and 7, respectively, and coπespondingly were obtained according to the same procedure, and with the same equipment, as Figs 1-5

Like Figs 1-5, Figs 6 and 7 also provide particularly direct evidence, of the compatibihzation and decrease in discontinuous or dispersed phase size, resulting from the presence of compatibilizing agent

Particularly with respect to the relative proportions of compatibilizer and elastomer, the former is preferably provided in the range of about 10% to about 15%, more preferably about 12%) to about 12 5%, of the latter As a particularly prefeπed proportion, the compatibilizer is present in an amount of about 10% of the elastomer As another particularly prefeπed proportion, the compatibilizer is present in an amount of about 12.5% of the elastomer. These proportions are determined as parts per hundred of the compatibilizer to parts per hundred of the elastomer.

There is a potential disadvantage in employing a ratio of compatibilizer to elastomer which is higher than the indicated ranges. Specifically, the presence of too much compatibilizer, relative to elastomer, raises a possibility that crosslinking might occur between the elastomer and the ionomer. This crosslinking, if it takes place, can decrease melt flow index.

FIG. 8 shows a golf ball of the invention having a core 20 and a cover 22 having a single layer.

The core 20 is preferably a solid piece having a spherical configuration circumscribed by a cover 22 of determined thickness. Generally, the core is formed of a rubber composition of a base rubber blended with a co-crosslinking agent, a peroxide and a filler by a compression process including heating, pressing and shaping procedure. The rubber core can also be produced by the method of injection molding.

A prefeπed base rubber is 1 ,4-polybutadiene having a cis structure of at least 40 wt %. More preferably, the cis structure represents at least 90 wt % of the 1,4- polybutadiene. Other various rubbers including natural and synthetic rubbers can be added to the 1,4-polybutadiene. The crosslinking agent includes a metal salt of an unsaturated fatty acid such

as zmc salt, a magnesium salt of unsaturated fatty acid such as methacry c acid, acrylic acid and ester compounds

Polybutadiene rubber is prepared with a rare earth element catalyst, such as neodymium (Nd) This polymer has a higher amount of 1,4-polybutadιene than the conventional polybutadiene rubbers The consequence is an improvement of the values of compression of the core and an improvement of the ball initial velocity

Preferably, the core has a specific gravity of 1 05 and higher and a PGA compression which varies depending upon the size of the core so as to confer a soft feel to the ball More precisely, the PGA compression of the core is compnsed between 70 to 95, for a core diameter between 1 56 to 1 60 inches, between 50 to 80, for a core diameter between 1 43 to 1 56 inches, and between 35 to 70, for a core diameter between 1 39 to 1 43 inches.

The PGA compressions of core are measured with an ATTI compression gauge known by one skilled in the art

FIG 9 shows a multi-piece ball of the invention The golf ball compnses a core

20, a cover 22, and an intermediate mantle 21 between the core and the cover

The material chosen for the mantle can be made from among a wide variety of thermoplastic or vulcanized mateπals However, it is prefeπed that the mantle comprises at least one layer that includes a material selected from the group consisting of thermoplastic polyetheresters, polyamide elastomers, ionomer resins, thermoplastic polyurethanes, metallocene polymers, vulcanized elastomers, and mixtures thereof. Among the polyamide elastomers are prefeπed the polyetheresteramides. Suitable mantle compositions include those of the Examples shown in Tables 6 and 7 herein.

The cover compositions of the invention can also include, in suitable amounts, one or more additional ingredients generally employed in golf ball cover compositions. Agents provided to achieve specific functions, such as additives and stabilizers, can be present. Ingredients which are suitable include UV stabilizers, photostabilizers, antioxidants, pigments, dispersants, mold releasing agents, and processing aids. For example, inorganic fillers can be added such as titanium dioxide (Ti0₂), calcium carbonate, zinc sulfide or zinc oxide for coloring piiφoses. Additional fillers can be chosen to impart additional density to blends of the cover or any other part of the ball, such as zinc oxide or barium sulfate, tungsten carbite or lead powder.

Any conventional technique may be used for covering the solid core with the cover and additionally with an intermediate mantle. For example, the layers can be directly applied by injection molding over the core at a temperature of 250 to 500°F for 30 to 120 seconds.

Another method comprises forming the layers into half-cups and then fitting the cups around the core, followed by compression fonriing. In compression molding, the half-cups are preformed by injection molding into a conventional half-shell mold at 250 to 500 °F for a short time, between 30 to 60 seconds. Then, the half-cups are positioned around a core in a conventional compression molding device. Pressure and heat are applied for approximately 1 to 3 minutes. The ball is allowed to cool in the mold until the cover is hard solid enough to be removed without deforming.

In the examples, the core is a solid rubber core, but the invention is not limited to such a core. The core may also be a wound threaded structure. Additionally, the core may be manufactured as a combination of solid material for the center, such as rubber, suπounded by wound thread, or may alternatively consist of a liquid or paste filled core suπounded by wound thread. Conventionally, the diameter of the central part of the wound core is about 1.0 to 1.125 inches and the total wound diameter is about 1.54 to 1.60 inches.

In the case of a wound core, it is prefeπed to use the method of compression molding for assembling the parts of the cover around the core. Indeed, the heat of the injection molding around a wound core causes the thread to snap during molding.

Finally, the golf ball undergoes conventional operations such as buffing, painting and stamping. In order to facilitate the buffing operation, the golf ball can be prefrozen.

Although the prefeπed embodiments have been described in detail hereinabove, certain modifications may be envisioned by one of ordinary skill in the art, without departing from the scope of the invention that is encompassed by the claims which follow.

Claims

Claims

1 A golf ball comprising a core and a cover, said cover including at least one thermoplastic layer made of a compound comprising (a) an amide block copolymer having a hardness less than or equal to 40 shore D, and

(b) an ionomer having a hardness greater than said hardness of said amide block copolymer, each of said amide block copolymer and said ionomer having a respective amount by weight depending upon a desired cover hardness

2 A golf ball according to claim 1, wherein said thermoplastic layer compπses

(a) from 10 to 90 weight percent of said amide block copolymer having a hardness less than or equal to 35 shore D and, (b) from 90 to 10 weight percent of said hard ionomer having a hardness greater than or equal to 65 shore D, so as to confer to said layer a hardness of between 40 to 60 shore D

3 A golf ball according to claim 2, wherein said hard ionomer has a flexural modulus greater than 60,000 psi

4 A golf ball according to claim 3, wherein said hard ionomer is an acid ionomer including at least 19 weight percent of an alpha, beta-unsaturated carboxylic acid

5. A golf ball according to claim 1, wherein: said core has a PGA compression of between 70 to 95 and a core diameter from 1.56 to 1.60 inches.

6. A golf ball according to claim 1, wherein: said core has a PGA compression of between 50 to 80 and a core diameter from

1.43 to 1.56 inches.

7. A golf ball according to claim 1, wherein: said core has a PGA compression of between 35 to 70 and a core diameter from 1.39 to 1.43 inches.

8. A golf ball according to claim 1, wherein: said core is a solid rubber of 1,4-polybutadiene with at least 40 weight percent of cis structure.

9. A golf ball according to claim 1, wherein: said core is a solid rubber of 1,4-polybutadiene with a weight percent of cis structure greater than 90.

10. A golf ball according to claim 1 , further comprising: an intermediate mantle between said core and said cover, said mantle comprising at least one layer of a material selected from the group consisting of thermoplastic

polyetheresters, polyamide elastomers, ionomer resins, thermoplastic polyurethanes, metallocene polymers, vulcanized elastomers, and mixtures thereof.

11. A golf ball comprising: a core and a cover, said cover including at least one thermoplastic layer made of a compound comprising:

(a) a polyamide elastomer having a hardness less than or equal to 40 shore D;

(b) at least one high acid ionomer having a hardness greater than 65 shore D.

12. A golf ball according to claim 1 1, wherein: said polyamide elastomer is an amide block copolymer.

13. A golf ball according to claim 12, wherein: said amide block copolymer is a polyetheresteramide.

14. A golf ball according to claim 11, wherein: said high acid ionomer includes at least 19 weight percent of an alpha, beta- unsaturated carboxylic acid.

15. A golf ball according to claim 14, wherein: said high acid ionomer comprises acid groups partially neutralized by lithium.

16. A golf ball cover composition for a golf ball cover comprising:

(a) about 60 wt % or less of an elastomer comprising at least one member selected from the group consisting of polyamide elastomers and polyester elastomers;

(b) about 0.3 to 10 wt % of a compatibilizing agent, comprising a copolymer which comprises at least one monomer comprising a cyclic functional group; and

(c) a remainder comprising at least one ionomer having a hardness greater than the hardness of the elastomer;

- the golf ball cover composition further comprising a continuous phase and a discontinuous phase dispersed within the continuous phase, with one of the continuous phase and the discontinuous phase comprising the elastomer, and the other of the continuous phase and the discontinuous phase comprising the ionomer;

- wherein the cyclic functional group interacts with at least one of the elastomer and the ionomer, by at least one of physical reaction and chemical reaction, to reduce interfacial tension to improve compatibility.

17. The golf ball cover composition of claim 16, wherein the discontinuous phase comprises clusters randomly distributed within the continuous phase, and wherein the clusters are smaller in size than the clusters would be in the absence of the compatibilizing agent.

18. The golf ball cover composition of claim 16, wherein the elastomer comprises about 40 wt % or less of the composition.

19. The golf ball cover composition of claim 16, wherein the at least one ionomer comprises at least one acid ionomer which includes at least 16 wt %> of an alpha, beta- unsaturated carboxylic acid.

20. The golf ball cover composition of claim 19, wherein the alpha, beta- unsaturated carboxylic acid comprises at least one member selected from the group consisting of acrylic acid and methacrylate.

21. The golf ball cover composition of claim 16, wherein the at least one ionomer comprises a first acid ionomer and a second acid ionomer, each of the first acid ionomer and the second acid ionomer including at least 19 wt % of an alpha, beta-unsaturated carboxylic acid.

22. The golf ball cover composition of claim 21, wherein the first acid ionomer comprises acid groups neutralized by sodium ions and the second acid ionomer comprises acid groups neutralized by zinc ions.

23. The golf ball cover composition of claim 22, wherein the compatibilizing agent comprises a member selected from the group consisting of the following copolymers:

-unsaturated epoxy-ethylene copolymers;

-unsaturated epoxy-alkyl(meth)acrylate-ethylene copolymers; and

-unsaturated epoxy-carboxylic acid vinyl ester-ethylene copolymers.

24. The golf ball cover composition of claim 22, wherein the compatibilizing agent comprises about 2.5 to 7.5 wt % of the composition.

25. The golf ball cover composition of claim 16, wherein the at least one ionomer comprises at least one acid ionomer which includes about 19 wt % of an alpha, beta- unsaturated carboxylic acid, the at least one acid ionomer comprising acid groups neutralized by magnesium ions.

26. The golf ball cover composition of claim 16, wherein the at least one monomer comprises at least one member selected from the group consisting of an epoxy monomer, maleic anhydride, norbornene, norbornadiene, dicyclopentadiene, and oxazoline.

27. The golf ball cover composition of claim 26, wherein the at least one monomer comprises an epoxy monomer.

28. The golf ball cover composition of claim 26, wherein the at least one monomer comprises maleic anhydride.

29. The golf ball cover composition of claim 16, wherein the ionomer has a hardness of about 65 shore D or greater, according to ASTM D-2240, so as to provide a golf ball cover having a hardness of about 50 to 65 shore D, according to ASTM D-2240.

30. The golf ball cover composition of claim 29, wherein:

- the elastomer has a hardness of about 35 shore D or less, according to ASTM D- 2240, and

- the lonomer has a hardness of about 65 shore D or greater, according to ASTM D-2240, so as to provide a golf ball cover having a hardness of about 50 to 65 shore D, according to ASTM D-2240

31 The golf ball cover composition of claim 16, wherein the elastomer has a hardness of about 35 shore D or less, according to ASTM D-2240

32 The golf ball cover composition of claim 16, wherein the elastomer compπses an amide block copolymer resulting from copolycondensation of polyamide blocks having reactive chain ends and polyether blocks having reactive chain ends

33 A golf ball cover composition for a golf ball cover comprising

(a) about 60 wt % or less of an elastomer compnsing at least one member selected from the group consisting of polyamide elastomers and polyester elastomers, (b) less than 10 wt % of a compatibilizing agent, comprising a copolymer which comprises at least one monomer comprising a noncyclic functional group, and

(c) a remainder compnsing at least one ionomer having a hardness greater than the hardness of the elastomer,

- the golf ball cover composition further comprising a continuous phase and a discontinuous phase dispersed within the continuous phase, with one of the continuous phase

and the discontinuous phase comprising the elastomer, and the other of the continuous phase and the discontinuous phase comprising the ionomer;

- wherein the noncyclic functional group interacts with at least one of the elastomer and the ionomer, by at least one of physical reaction and chemical reaction, to reduce interfacial tension to improve compatibility.

34. The golf ball cover composition of claim 33, wherein the noncyclic functional group comprises at least one member selected from the group consisting of carboxylic acid groups and amino groups.

35. A golf ball cover composition for a golf ball cover comprising: (a) an elastomer comprising at least one member selected from the group consisting of polyamide elastomers and polyester elastomers; and (b) at least one acid ionomer:

(i) having a hardness greater than the hardness of the elastomer; (ii) including about 19 wt % of an alpha, beta-unsaturated carboxylic acid; and

(iii) comprising acid groups neutralized by magnesium ions.

36. The golf ball cover composition of claim 35, comprising about 60 wt % or less of the elastomer.

37. The golf ball cover composition of claim 36, comprising a remainder comprising the at least one acid ionomer.