AU697628B2 - High acid ionomers and golf ball cover compositions comprising same - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int, Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: *099 4.

.4 *4*e 9 4 9* 9 0 4*c* *9 .9 4 4.4.

4. *4 9 9 a 999* 9 Name of Applicant: Lisco, Inc.

Actual Inventor(s): Michael L. Sullivan Addross for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: HIGH ACID IONOMIERS AND GOLF BALL COVE R COMPRISING SAME

COMPOSITIONS

Our Ref 467263 POF Code: 76477/162278 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1I- 1A HIGH ACID IONOMERS AND GOLF BALL COVER COMPOSITIONS COMPRISING SAME The present application is a divisional application from Australian patent number 670559, the entire disclosure of which is incorporated herein by reference.

Field of the Invention The present invention relates to metal cation neutralized high acid ionomer resins and to improved golf ball covers made from these resins. The improved golf ball covers are useful for producing golf balls, particularly multipiece balls, exhibiting enhanced travel distance while maintaining the playability and/or durability characteristics necessary for repetitive play.

Background of the Invention lonomeric resins are polymers containing interchain ionic bonding. As a result of their toughness, durability, and flight characteristics, various ionomeric resins sold by E.I. DuPont do Nemours Company under the trademark "Surlyn®" and more recently, by the Exxon Corporation (see U.S.

Patent No. 4,911,451) under the trademarks "Escor®" and the tradename "lotek", have become the materials of choice for the construction of golf ball covers over the traditional "balata" (trans polyisoprene, natural or synthetic) rubbers. The softer balata covers, although exhibiting enhanced playability properties, lack the durability properties required for repetitive play.

lonomeric resins are generally ionic copolymers of an olefin, such as e'hylene, and a metal salt of an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid or maleic acid. In some instances, an additional softening comonomer such as an acrylate can also be included to form a terpolymer. The pendent ionic groups in the ionomeric resins interact to form ion-rich aggregates contained in a non-polar polymer matrix. The metal ions, such as sodium, zinc, magnesium, lithium, potassium, calcium, etc are used to neutralize some portion of the acid groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties, i e. improved durability, etc. for golf ball construction over balata.

Broadly, the ionic copolymers comprise one or more alpha-olefins and from about 9 to about 20 weight percent of alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid, the basic copolymer neutralized with metal ions to the extent desired. Usually, at least 20% of the carboxylic acid groups of the copolymer are neutralized the metal ions (such as sodium, zinc and magnesium), and exist in the ionic state.

Suitable olefins for use in preparing the ionomeric resins include ethylene, propylene, butene-1, hexene-1, and the like. Unsaturated carboxylic acids include acrylic, r,(ethacrylic, ethacrylic, co-chloroacrylic,crotonic, maleic, fumaric, itaconic acids, and the like. The ionomeric resins utilized in the golf ball industry are generally copolymers of ethylene with acrylic Escor®) and/or methacrylic (i e. Surlyn®) acid.

Along this line, the properties of the cover compositions and/or the ionomeric resins utilized in the golf ball industry vary according to the type and amount of the metal cation, the molecular weight, the composition of the base resin the nature and the relative content of the olefin, the unsaturated carboxylic acid groups, etc.), the amount of acid, the degree of neutralization Sand 9 I I 3 whether additional ingredients such as reinforcement agents or additives are utilized. Consequently, the properties of the ionomer resins can be controlled and varied in order to produce golf balls having different playing characteristics, such as differences in hardness, playability e. spin, feel, click, etc.), durability impact and/or cut resistance), and resilience (i.e.

coefficient of restitution).

However, while there are currently more than fifty commercial grades of ionomers available from DuPont and Exxon with a wide range of properties which vary according to the type and amount of metal cations, molecular weight, composition of the base resin relative content of ethylene and methacrylic and/or acrylic acid groups) the degree of neutralization and additive ingredients such as reinforcement agents, etc. a great deal of research continues in order to develop golf ball cover compositions exhibiting not only the playability characteristics previously associated with the balata cover, but also the improved impact resistance and carrying distance properties produced by the ionomeric resins. Thus, an object of the present invention is to provide golf ball cover compositions which, when utilized in golf ball construction, produce balls exhibiting improved travel distance while maintaining satisfactory playability and durability properties.

0:6* ht In enhancing the distance a golf ball will travel when 6 hitthere are a variety of factors which are considered.

The coefficient of restitution, along with ball size, 30 weight and additional factors such as club head speed, angle of trajectory, and ball aerodynamics diii.pite pattern) generally determine the distance a ball will travel, when hit. Since club head speed and the angle of 1: 4. 0: rajectory are not factors easily controllable, particularly by golf ball manufacturers, the factors of S. 0 concern among manufacturers are the coefficient of restitution and the surface dimple pattern of the ball.

A golf ball's coefficient of restitution is the ratio of the relative velocity of the ball after direct impact to that before impact. One way to measure the coefficient of restitution is to propel a ball at a given speed against a hard massive surface, and measure its incoming velocity and outgoing velocity. The coefficient of restitution is defined as the ratio of the outgoing velocity to incoming velocity of a rebounding ball and is expressed as a decimal. As a result, the coefficient of restitution can vary from zero to one, with one being equivalent to an elastic collision and zero being equivalent to an inelastic collision, The coefficient of restitution of a one-piece golf ball is a function of the ball's composition. In a two-piece or a multi-layered golf ball, the coefficient of restitution is a function of the core, the cover and any additional layer. While there are no United States Golf Association limitations on the coefficient of restitution values of a golf ball, the U.S.G.A requires that the golf ball cannot exceed an initial velocity of 255 feet/second. As a result, golf ball manufacturers generally seek to maximize the coefficient of restitution of a ball without violating the velocity limitation.

In various attempts to produce a high coefficient of restitution golf ball exhibiting the enhanced travel distance desired, the golfing industry has blended various ionomeric resins. However, many of these blends do not .4: exhibit the durability and playability characteristics necessary for repetitive play *e 44 and/or the enhanced travel distance desired, 25 Until relatively recently, all of the ionomer resins commercially available o contained at most 15 to 16 weight percent carboxylic acid. In 1989, DuPont introduced a number of new high acid ionomers and suggested that these new ionomers may have some use in previously known low acid ionomer applications such as the production of shoe soles, box toes, bowling pins, golf balls, ski boots, auto trim, etc.

4 st Furthermore, DuPont suggested in a research disclosure DuPont de Nemours Co., Research Disclosure No. 297,003) that ionomers produced from polymers of ethylene acrylic acid or methacrylic acid containing greater than 15 weight percent acid can be melt processed to produce articles (i e. golf balls, foot wear, ski boots, cosmetic bottle cap closures and so on) with good properties improved stiffness, hardness and clarity) when compared with ionomers with lower acid levels.

However, not only has little information been provided concerning the acid levels and types of effective ionomers, particularly with respect to the art of golf ball manufacturing, it has been found that many cover compositions produced from polymers of ethylene/acrylic acid or ethylene/methacrylic acid containing greater than 15 weight percent acid have been dissatisfactory in that these compositions exhibit processing problems or are generally short on distance and/or durability and thus, are not particularly commercially viable.

Similar poor results have been produced with covers composed of blends of high and low acid ethylene/acrylic acid or ethylene/methacrylic acid polymers and/or covers produced from single high acid ionomers.

However, notwithstanding the above difficulties, it has been discovered that improved golf ball covers can be produced from specific blends of high acid ionomers ionomer resins containing greater than 16 weight percent acid, preferably from about 17 to about 25 weight percent acid, and more preferably from about 18.5 to about 21.5 weight percent acid) which do not exhibit the processing, distance and/or durability limitations demonstrated by the prior art.

25 In this regard, it has been found that blends of specific high acid Sionomer resins, particularly blends of sodium and zinc high acid ionomers, as well as blends of sodium and magnesium high acid ionomers, extend, when utilized in golf ball cover construction, the range of hardness beyond that previously obtainable while maintaining the beneficial properties durability, click, feel, etc.) of the softer low acid ionomers disclosed in U.S. Patent Nos.

4,884,814 and 4,911,451. These blends produce harder, stiffer golf balls I C WVINtWORDUACKIENODELETEAL'670$59SPC -i having higher C.O.R.s, and thus longer distance. This discovery is the subject matter of U.S. Patent No. 5,688,869.

The present invention is directed to the development of specific blends of high acid ionomers, particularly metal cation neutralized acrylic acid based high acid ionomer resins, which exhibit, when utilized for golf ball cover construction, cover compositions having further improved hardness and resilience properties. These blends of metal cation neutralized acrylic acid based high acid ionomer resin are particularly valuable in the field of golf ball production.

These and other objects and features of the invention will be apparent from the following description and from the claims.

Summary of the Invention In one aspect, the present invention is directed to a golf ball comprising a core and a cover, wherein the cover is a blend of two or more metal cation neutralized high acid ionomer resins, each ionomer resin comprised of about 20% by weight of acrylic acid and the remainder ethylene, of which about to about 90% of the carboxyl groups of each ionomer resin are neutralized with a metal cation. The metal cation of each resin is a cation selected from the co. ~20 group consisting of sodium, zinc and magnesium. In this regard, diblends consisting of sodium/zinc and sodium/magnesium, are the more preferred blends which comprise the cover component of the invention.

Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter, however, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.

Y- g Detailed Description of the Invention The present invention relates to the development of specific metal cation neutralized high acid ionomers and blends thereof. In addition, the present invention re!ates to the use of these metal cation neutralized high acid ionomers, and/or blends thereof, for the purpose of producing golf ball covers exhibiting enhanced resilience and/or hardness characteristics.

In this regard, several new metal cation neutralized high acid ionomer resins have been produced by neutralizing, to various extents, high acid copolymers of an alpha-olefin and an alpha, beta-unsaturated carboxylic acid with a variety of different metal cation salts. Mcre particularly, it has been found that numerous new metal cation neutralized high acid ionomer resins can be obtained by reacting a high acid copolymer a copolymer containing greater than 16% by weight acid, preferably from about 17 to about 25 weight percent acid, and more preferably about 20 weight percent acid), with a metal cation salt capable of ionizing or neutralizing the copolymer to the extent desired from about 10% to The base copolymer is made up of greater than 16% by weight of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin. Optionally, a softening comonomer can be included in the copolymer. Generally, the alphaolefin has from 2 to 10 carbon atoms and is preferably ethylene, and the unsaturated carboxylic acid is a carboxylic acid having from about 3 to 8 carbons. Examples of such acids include acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, with acrylic acid being preferred 0 V. 4 J C1WNWOtDU\ACKIENODELUE B1E7Ul559IPC Ld PB Y I The softening comonomer that can be optionally included in the invention may be selected from the group consisting of vinyl esters of aliphatic carboxylic acids wherein the acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkyl groups contains 1 to 10 carbon atoms, and alkyl aczylates or methacrylates wherein the alkyl group contains 1 to 10 carbon atoms. Suitable softening comonomers include vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, or the like.

Consequently, examples of a number of copolymers suitable for use in the invention include, but are not limited to, high acid embodiments of an ethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer, an ethylene/itaconic acid copolymer, an cthylene/maleic acid copolymer, an ethylene/methacrylic acid/vinyl acetate copolymer, an ethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymer broadly contains greater than 16% by weight unsaturated carboxylic acid, from about 30 to about 83% by weight ethylene and from 0 to about 40% by weight of a softening comonomer. Preferably, the copolymer contains about 20% by weight unsaturated carboxylic acid and about 80% by weight ethylene. Most preferably, the copolymer contains about 20% acrylic acid with the remainder being ethylene.

Along these lines, examples of the preferred high acid :base copolymers which fulfill the criteria set forth above, are a series of ethylene-acrylic copolymers which are commercially available from The Dow Chemical Company, Midland, Michigan, under the "Primacor" designation. These high acid base copolymers exhibit the typical properties set forth below in Table 1.

.6 TABLE I Typical Properties of Primacor Ethylene-Acrylic Acid Copolymers Grade PERCENT DENSITY MELT TENSILE FLEXURAL VICAT SHORE D ACID gicc INDEX YD. ST MODULUS SOFTPT HARDNESS g/lomin (psi) (psi) (o C) ASTM D-792 D-1238 D-638 D-790 D-1525 D-2240 5980 20.0 0.958 300.0 4800 43 5990 20.0 0.955 1300.0 650 2600 40 42 5990 20.0 0.955 1300.0 650 3200 40 42 5981 20.0 0.960 300.0 900 3200 46 48 5981 20,0 0,960 300,0 900 3200 46 48 5983 20.0 0.958 500.0 850 3100 44 5991 20.0 0.953 2600.0 635 2600 38 1 The Helt Index values are obtained according to ASTH D-1238, at 190'C Due to the high molecular weight of the Primacor 5981 grade of the ethylene-acrylic acid copolymer, this copolymer is the more preferred grade utilized in the invention.

The metal cation salts utilized in the invention are those salts wnich provide the metal cations capable of neutralizing, to various extents, the carboxylic acid groups of the high acid copolymer. These include acetate, oxide or hydroxide salts of magnesium, sodium and zinc.

Suitable zinc ion sources are zinc acetate dihydrate and zinc acetate, a Sblend of zinc oxide and acetic acid. Examples of sodium ion sources are sodium hydroxide and sodium acetate. Source of the magnesium include magnesium oxide, magnesium hydroxide, magnesium acetate.

of* 20 The new metal cation neutralized high acid ionomer resins of the invention are produced by reacting the high acid base copolymer with various amounts of the metal cation salts above the crystalline melting point of the .copolymer, such as at a temperature from about 2000 F to about 500* F, preferably from about 2500 F to about 350° F under high shear conditions at a pressure of from about 100 psi to 10,000 psi. Other well known blending techniques may also be used. The amount of metal cation salt utilized to produce the new metal cation neutralized high acid based ionomer resins is the quantity which provides a sufficient amount of the metal cations to neutralize the desired percentage of the carboxylic acid groups in the hign acid copolymer. The extent of neutralization is generally from about 10% to about As indicated more specifically in Example 1 below, when a high acid ethylene/acrylic acid copolymer is utilized as the base copolymer component of the invention and this component is subsequently neutralized to various extents with the metal cation salts producing acrylic acid based high acid ionomer resins neutralized with cations such as sodium, zinc and magnesium, several new cation neutralized acrylic acid based high acid ionomer resins are produced.

When compared to low acid versions of similar cation neutralized ionomer resins, the new metal cation neutralized high acid ionomer resins exhibit enhanced hardness, modulus and resilience characteristics. These are properties that are particularly desirable in a number of thermoplastic fields, including the field golf ball manufacturing S 20 When utilized in golf ball cover construction, it has been found that the new acrylic acid based high acid ionomer blends extend the range of hardness beyond that previously obtainable while maintaining the beneficial properties o durability, click, feel, etc of the softer low acid ionomer covered balls, such as balls produced utilizing the low acid ionomers disclosed in U.S. Patent Nos. 4,884,814,and 4,911,451, and the recently produced high acid blends disclosed in U.S. Patent No. 5,688,869.

Examples of existing high acid methacrylic acid based ionomers include Surlyn@ AD-8422 (sodium cation), Surlyn® 8162 (zinc cation), Surlyn@ SEP- 503-1 (an experimental zinc cation), and Surlyn® SEP-503-2 (an experimental magnesium cation). According to DuPont, all of these ionomers contain from 1Aj 4 about 18.5% to about 21.5% by weight methacrylic acid.

P I More particularly, Surlyn@ AD-8422, is currently commercially available from DuPont in a number of different grades AD-8422-2, AD-8422-3, AD- 8422-5, etc.) based upon differences in melt index. According to DuPont, Surlyno AD-3422 offers the following general properties when compared to Surlyn@ 8920 the stiffest, hardest of all of the low acid grades (referred to as "hard" lonomers in U S Patent No. 4,884,814): 9400 MI C XWNWORW'ACKlNO *LUMhAU6?59 SFC TABLE 2 LOW ACID HIGH ACID wt% Acid) (>20 wt% Acid) SURLYN® SURLYN® SURLYN® 8920 8422-2 8422-3

IONOMER

Cation Na Na Na Melt Index 1.2 2.8 Sodium, Wt% 2.3 1.9 2.4 Base Resin MI 60 60 MP', 0 C 88 86 FP', oC 47 48.5 COMPRESSION MOLDING 2 Tensile Break, psi 4350 4190 5330 Yield, psi 2880 3670 3590 Elongation, 315 263 289 Flex Mod, K psi 53-2 76.4 88.3 Shore D hardness 66 67 68 DSC second heat, 10°C/min heating rate.

2 Samples compression molded at 150 0 C annealed 24 hours at 60 0 8422-2, 8422-3 were homogenized at 190°C before molding.

In comparing Surlyn® 8920 to Surlyn® 8422-2 and 25 Surlyn® 8422-3, it is noted that the high acid Surlyn® 8422-2 and 8422-3 ionomers have a higher tensile yield, lower elongation, slightly higher Shore D hardness and much higher flexural modulus. Surlyn® 8920 contains 15 weight percent methacrylic acid and is 59% neutralized with sodium.

In addition, Surlyn® SEP-503-1 (an experimental zinc cation neutralized high acid methacrylic acid based ionomer resin) and Surlyn® SEP-503-2 an experimental magnesium cation neutralized high acid methacrylic acid based ionomer to 35 resin) are high acid zinc and magnesium versions of the Surlyn® AD 8422 high acid ionomers. When compared to the 13 Surlyn® AD 8422 high acid ionomers, the Surlyn® SEP-503-1 and SEP-503-2 ionorers can be defined as follows: TABLE 3 Surlyrn Ionomer Ion Melt index NeutralizPtion AD 8422-3 Na 1.0 SEP 503-1 Zn 0.8 38 SEP 503-2 Mg 1.8 43 Furthermore, Surlyn® 8162 is a zinc cation neutralized methacrylic acid based high acid ionomer resin containing approximately 20% by weight 18.5- 21.5% weight) methacrylic acid copolymer that has been 30-70% neutralized.

Surlyn® 8162 is currently commercially available from DuPont, TO For comparison purposes, examples of commercially available low acid methacrylic acid based ionomer resins are set forth below. These are many of hs "hard" ionomers utilized in the cover composition disclosed in U.S. Patent No.

4,884,8-14 Along this line, the low acid ionomer resin cover compositions disclosed in the '814 patent are generally considered to be among the best prior 15 art methacrylic acid based cover compositions currently available from Spalding Evenflo Companies, Inc., the assignee of the present application and U.S. Patent No. 5,688,869.

*o 0 fto a c 0* o o*o* o> -u 11 NEW TABLE 4 ASTM D 8940 sodium 0-1238 2.8 Cation Type Melt flow index, gms/10 min Specific Gravity, g/cm Hardness, Shore D Tensile Strength, (kpsi), HPa Elongation, X Flexural Modulus, (kpsi) HPa Tensile lapact (23*C) KJ/mU, (ft.-Lbs,/in') Vicat Temperature, *C Ueight Methacrylic acid (MAA) X of Acid Groups Cation Neutralized 9910 Zinc 0.7 0-792 0.95 0.97 D-2240 66 0-638 (4.8) 33.1 0-638 470 0-190 (51) 350 0-18225 1020 (485) D-1525 63 15 64 (3.6) 24.8 290 (48) 330 1020 (485) 62 15 29 58 8920 Sodiun 0.9 0.95 66 (5.4) 37.2 350 380 865 (410) 58 59 9730 Zinc 1.6 0.95 63 (4.1) 28.0 460 210 1240 (590) 73 12 38 s a 0 0 *ad# eo m Cation Type Melt flow index, min Specific Gravity, glcmm Hardnless, Shore 0 Tensile Strength, (kpsi), HPa Elongation, Flexural Modulus, (kpsi) HPa Tensile impact (23'C) KJ/m, (ft.-bs./in) Vicat Temperature, 'C X Weight Hethacrylic acid (MAA) X of Acid Groups Cation Neutralized

ASTMH

0-1238 0-792 0.94 0-2240 60 0-638 (4.2) 29.0 D-638 450 D-790 (32) 220 0-18225 1160 (550) 0-1525 73 10 8528 Sodiun 1.3 9970 Zinc 14.0 0.95 62 (3.2) 22.0 460 (28) 190 760 (360) 61 15 54 22 40 Examples of existing high acid acrylic acid based ionomer resins include the Escor® or the Iotek acrylic acid based high acid ionomers recently experimentally produced CC pi by Exxon. In this regard, Escor®, or Iotek, 959 is a sodium ion neutralized ethylene-acrylic acid copolymer and Escore), or Iotek, 960 is a zinc neutralized ethyleneacrylic acid copolymer. According to Exxon, Ioteks 959 and 960 contain from about 19.0 to about 21.0 by weight acrylic acid with approximately 30 to about 70 percent of the acid groups neutralized with sodium and zinc ions respectfully. The physical properties of these high acid acrylic acid based ionomers are as follows:

PROPERTY

Melt Index, g/10 rin Cation Melting Point, OF Vicat Softening Point, OF Tensile Q Break, psi Elongation Break, Hardness, Shore D Flexural Modulus, psi TABLE ESCOR" (IOTEK) 959 2.0 Sodium 172 130 4600 325 66 66,000 ESCOR DIoK) 960 1.8 Zinc 174 131 3500 430 57 27,000 For comparison purposes, examples of commercially available low acid acrylic acid based ionomer resins, such as these utilized in U.S. Patent No. 4,911,451 are set forth below.

C C C 9* C o S.

C

CC*C

TABLE 6 Tvoical Pronerties of Low Acid Escor (lotek) lonomers Resin Properties Cation type Melt index Density Melting Point Crystallization Point Vicat Softening Point Weight Acrylic Acid of Acid Groups Cation Neutralized

ASTM

Method Units D-1238 g/10 min.

D-1505 kg/m' D-3417 °C D-3417 °C D-1525 °C 4000 zinc 2.5 963 90 62 62 16 30 4010 8000 zinc sodium 1.5 0.8 963 954 90 90 64 56 63 61 11 8020 sodium 1.6 960 87.5 53 64 a a a.

a.

a. a a a Plaque Properties (3 mm thick, compression molded) Tensile at Break Yield point Elongation at break 1% Secant modulus Shore Hardness D Resin Prooerties Cation type Melt index Density Melting Point Crystallization Point Vicat Softening Point Weight Acrylic Acid of Acid Groups Cation Neutralized D-638 D-638 D-638 D-638 D-2240 AS'i Method D-1238 D-1505 D-3417 D-3417 D-1525 MPa 1Pa MPa Units g/10 min.

kg/m' oC oC 0C

ASTIM

Method Units 4000 4010 8000 8G20 24 26 36 31.5 none none 21 21 395 420 350 410 160 160 300 350 55 55 61 58 8030 7010 7020 7030 sodium zinc zinc zinc 2.8 0.8 1.5 960 960 960 960 87.5 90 90 55 67 60 63 62.5 Plaque ASTM Properties Method Units 8030 7010 7020 7030 (3 mm thick, compression molded) Tensile at Break D-638 MIPa 28 38 38 38 Yield point D-638 IdPa 23 none none none Elo;igation at break D-638 I- 395 500 420 395 Secant modulus D-638 MPa 390 Shore Hardness D D-2240 59 57 55 According to the present invention, it has been found that when the above indicated new metal cation neutralize acrylic acid based high acid ionomers, are processed according to the parameters set forth below to produce the covers of multi-layered golf balls, the resulting golf balls will travel further than previously known low acid ionomer resin covers and/or covers produced from high acid ionomers and/or high acid/low acid ionomer blends due to the balls' enhanced coefficient of restitution values.

This is particularly important in that an improvement of .001 in C.O.R. generally relates to our improvement of about 0.2 to 0.5 yards in travel distance. In addition, the resulting golf balls maintain the playability and .*.*odurability characteristics exhibited by known low-acid ionomer resin covered balls.

25 When blends of two of the above indicated metal cation neutralized acrylic acid high acid ionomers are used (i.e.

"dibends"), the ratio of one type of metal cation neutralized acrylic acid high acid ionomer to another is "generally from about 75% to about 25% and from about 25% to about 75%. In addition, "triblends" can also be formulated utilizing the new metal cation neutralized acrylic acid based high acid ionomers of the present invention. The general ratio for such "t.iblends" is 33 33%/33.33%/33.33% •9 by waight.

Additional compatible additive materials may also be added to the compositions of the present invention, such as I L1 -I dyes (for example, Ultramarine Blue sold by Whitaker, Clark, and Daniels of South Painsfield, NJ), and pigments, i.e. white pigments such as titanium dioxide (for example Unitane 0-110) zinc oxide, and zinc sulfate, as well as fluorescent pigments. As indicated in U.S. Patent 4,884,814, the amount of pigment and/or dye used in conjunction with the polymeric cover composition depends on the particular base ionomer mixture utilized and the particular pigment and/or dye utilized. The concentration of the pigment in the polymeric cover composition can be from about 1% to about 10% as based on the weight of the base ionomer mixture. A more preferred range is from about 1% to about 5% as based on the weight of the base ionomer mixture. The most preferred range is from about 1% to about 3% as based on the weight of the base ionomer mixture. The most preferred pigment for use in accordance with this invention is titanium dioxide.

Moreover, since these are various hues of white, i.e.

blue white, yellow white, etc., trace amounts of blie pigment may be added to the cover stock composition to impart a blue white appearance thereto. However, if Goo* different hues of the color white are desired, different pigments can be added to the cover composition at the amounts necessary to produce the color desired.

25 In addition, it is within the purview of this o invention to add to the cover compositions of this invention compatible materials which do not affect the S4* basic novel characteristics of the composition of this invention. Among such materials are antioxidants (i.e.

Santonox antistatic agents, stabilizers and processing aids. The cover compositions of the present invention may also contain softening agents, such as plasticizers, etc., and reinforcing materials such as glass fibers and inorganic fillers, as long as the desired properties 35 produced by the golf ball covers of the invention are not impaired.

I r ~sl rn~ Furthermore, optical brighteners, such as those disclosed in U.S. Patent No. 4,679,795, may also be included in the cover composition of the invention.

Examples of suitable optical brighteners which can be used in accordance with this invention are Uvitex OB as sold by the Ciba-Geigy Chemical Company, Ardaley, N.Y. Uvitex OB is thought to be 2,5-Bis(5-tert-butyl-2-benzoxazoly) thiopene.

Examples of other optical brighteners suitable for use in accordance with this invention are as follows: Leucopure EGM as sold by Sandoz, East Hanover, N.J. 07936. Leucopure EGM is thought to be 7-(2h-naphthol(l,2-d)-triazol-2yl) 3phenyl-coumarin. Phorwhite X-20G2 is sold by Mobay Chemical Corporation, P.O. Box 385, Union Metro Park, Union, N.J. 07083, and is thought to be a pyrazoline derivative, Eastobrite OB-1 as sold by Eastman Chemical Products, Inc. Kingsport, Tenn., is thought to be 4,4-Bis(benzoxaczoly)stilbene. The above-mentioned Uvite., and Eastobrite OB-1 are preferred optical brighteners w in accordance with this invention.

Moreover, since many optical brighteners are colored, the percentage of optical brighteners utilized must not be excessive in order to prevent the optical brightener from *Pee functioning as a pigment or dye in its own right.

V. The percentage of optical brighteners which can be 25 used in accordance with this invention is from about 0.01% to about 0.5% as based on the weight of the polymer used as a cover stock. A more preferred range is from about 0.05% to about 0.25% with the most preferred range from about 0.10% to about .020% depending on the optical properties of the particular optical brightener used and the polymeric S.o*4" environment in which it is a part.

o Generally, the additives are admixed with a ionomer to be used in the cover composition to provide a masterbatch of desired concentration and an amount of the masterbatch sufficient to provide th desired amounts of additive is then admixed with the -,opolymer blends.

The cover compositions of the present invention may be produced according to conventional melt blending procedures. In this regard, the above indicated high acid ionomeric resins are blended along with the masterbatch containing the desired additives in a Banbury type mixer, two-roll mill, or extruded prior to molding. The blended composition is then formed into slabs or pellets, etc. and maintained in such a state until molding is desired.

Alternatively a simple dry blend of the pelletized or granulated resins and color masterbatch may be prepared and fed directly into the injection molding machine where homogenization occurs in the mixing section of the barrel prior to injection into the mold. If necessary, further additives such as an inorganic filler, etc., may be added and uniformly mixed before initiation of the molding process.

Moreover, golf balls of the present invention can be produced by molding processes currently well known in thi Sgolf ball art. Specifically, the golf balls can be produced by injection molding or compression molding the novel cover compositions about wound or soli': Toia o :-es to produce a golf ball having a diameter of iQOut 1.680 inches or greater and weighing about 1.620 ounces. The standards for both the diameter and weight of the balls are established by the United States Golf Association Although both solid core and wound cores can be utilized in the present invention, as a result of their lower cost and superior performance, solid molded cores are t.o. preferred over wound cores.

Conventional solid cores are typically compression molded from a slug of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an o, 3, ethylenically unsaturated carboxylic acid such as zinc mono or diacrylate or methacrylate. To achieve higher coefficients of restitution in the core, the manufacturer may include a

LL

small amount of a metal oxide such as zinc oxide. In addition, larger amounts of metal oxide than those that are needed to achieve the desired coefficient may be included in order to increase the core weight so that the fin, ,shed ball more closely approaches the U.S.G.A. uppE.- weight limit of 1.620 ounces. Other materials may be used in the core composition including compatible rubbers or ionomers, and low molecular weight fatty acids such as stearic acid.

Free radical initiator catalysts such as peroxides are admixed with the core composition so that on the application of heat and pressure, a complex curing or cross-linking reaction takes place.

The term "solid cores" as useO herein refers not only to one piece cores but *Ito to those cores having a separate solid layer beneath the co-rer and above the core as in U.S. Patent No. 4,43-L,193, and other multilayer and/or non-wound cores (such s those desc-ribed in U.S.

Patent No. 4,848,770).

.**Wound cores are generally produced by winding a very large elastic thread around a solid or liquid filled balloon center. The elastic thread is wound around the *center to produce a finished core of about 1. 4 to 1.6G inches in diameter, generally. Since the core material is not an integral part of the present invention, a detailed discussion concerning the specific types of core materials which may be utilized with the cover compositions of the S...,.invention are not specifically set forth herein. In this regard, the cover compositions of the invention may be used in conjunction with any standard golf ball core.

30 As indicated, the golf balls of the present invention may be produced by forming covers consisting of the compositions of the invention around cores by conventional molding processes. For example, in comprc~sion molding, the cover composition is formed via injection at about 380OF to about 450OF into smooth surfaced hemispherical shells which are then positioned around the core in a :*foe* too** 0.0.S dimpled golf ball mold and subjected to compression molding at 200-3001F for 2-10 minutes, followed b L ,oling at S0for ~'0minutes, to fuse the shells together to form an unita.L.. ball. In addition, the golf balls may be produced by injection molding, wherein the cover composition is injected directly around the core placed in the center of a golf ball mold for a period of time at a mold temperature of from 50%' to about 1000F. After molding the golf ball produced may undergo various further finishing steps SUCh7 as buff ing, painting, and marking as disclosed in U.S. Patent No. 4,911,451.

The present invention is further illustrated by the following examples in which the parts of the specific ingredients are by weight (pbw) it is to be understood that the present invention is not limited to the examples, and various changes arnd modifications may be made in the invention without departing from the spirit and scope thereof.

EXAMPLES

By blending the ingredients set forth in the Tables below, a series of new metal cation neutralized high acid ionomer resins and golf ball cover formulations containing these resins were produced. Finished golf balls were prepared using the cover compositions of the present invention, controls and comparative cover compositions by positioning a so,-lid preformed cross-linked polybutadiene core in an injection molding cavity in such a manner to permit the uniform injection of the selected cover composition over each core. Along this line, the cover formulations were injection molded at about 400OF around identical solid type cores having a finished diameter of 1.545 inches to produce golf balls approximately .680 inches in diameter ha-vin,,x a normal cover thickness of 0. 0675 inches.- All materials were molded under essentially identical conditions. The properties off coefficient of restitution of the molded and finished balls, Shore D hardness, cold crack resistance, spin rates, etc.

for the cover compositions were then determined.

In conducting the comparative prior art testing, Escor® 4000/7030 and Escor' 900/8000 ionomers were utilized. In this regard, blends of EscorO~ 4000/7030 and Escor®9 900/8000 the subject of U.S. Patent No.

4,911,451) are considered by the inventors to be generally among the best prior art cover compositions concerning ethylene -acrylic acid ionomer (low acid) blends.

The data for each example represents the average data for one dozen balls produced according to the desired manner. The properties were measured according to the following parameters: Coefficient of restitution was measured by firing the resulting golf ball in an air cannon at a velocity of 125 feet per second against a steel plate which is positioned 12 feet from the muzzle of the cannon. The rebound velocity was then measured. The rebound velocity was divided by the forward velocity to give the coef ficient of restitution- Shore hardness was measured in accordance with ASTM' Test D-2240.

Cold cracking resistance was measured by firing balls from an air cannon, 5 blows at 165 f eet/sec 1 af ter the balls had been conditioned for 24 hours at -10 0 P. After allowing the balls to equilibrate to room temperature the balls are inspected for cover cracking.

The spin rate of the golf ball was measured by striking the resulting golf balls with a pitching wedge or 9-iron wherein the club-head speed is about 80 feet per second and the ball is launched at an angle of 26 to 34 degrees with an initial velocity of about 110-115 feet per second. The spin rate was measured by observing the rotation of the ball in flight using stop action Strobe photography.

EXAMPLE 1 Preparation of Acrylic Acid Based Hicrh Acid lonomers A number of new cation neutralized acrylic acid based high acid ionomer resins were prepared utilizing as the copolymer of an olefin and an alpha, beta-unsaturated carboxylic acid, a 20 weight percent acrylic acid/ethylene copolymer produced by The Dow Chemical Company, Midland, Michigan under the designation 'Primacor 5981." According to The Dow Chemical Company, Primacor 5981 has a melt index (at 190 0 C, 2150 g) of 300 g/10 min. The carboxylic acid groups present in the 20 weight percent acrylic acid/ethylene copolymer were neutralized to various weight percentages by a number of different metal cation salts resulting in the production of several new thermoplastLic elastomers exhibiting enhanced properties for golf ball cover production. Due to differences in the nature of the cation salts, the amount of catioii salts utilized, etc., the new high acid ionomer resins produced differed 20 substantially in the extent of neutralization and in melt indices, as well as in resilience and hardness values.

For the purpose of determining the weight percent of neutralization of the carboxylic acid groups in the acrylic acid/ethylene copolymer after reacting with various cation salts, it was assumed that 1 mole of sodium (Na potassium and lithiuii neutralized one mole of acrylic acid, and that one mole of zinc (Zn 2 magnesium (Mg 2 manganese (Mn 2 calcium (Ca 2 and nickel (Ni 2 neutralized two moles of acrylic acid, The calculations of neutralization were based upon an acrylic acid molecular weight of 79 g/m, giving 0.2778 moles per 100 grams of copolymer.

As indicated below in Table 7, the various cation salts were added in variable amounts to the 20 weight percent acrylic acid/v Ohylene copolymer in order to determine the optimal level of neutralization for each of the cations. In Table 7, NaOH refers to sodium hydroxide (formula weight of 40). MnlAc refers to manganese acetate tetrahydrate having a formula weight of 245. LiOH is lihium hydroxide, fwt=24. KOH is potassium hydroxide, fwt=56. ZnAc is zinc acetate dihydrate, fwt=219.5. MgAc is magnesium acetate tetrahydrate, fwt=214.4. CaAc is calciwan acetate, fwt=158. MgO is magnesium oxide, fwt=40.3. NiAc is nickel acetate, fwt=176.8. All of these cation salts are solids at room temperature.

The specific cation salts were added in differing amounts with the 20 weight percent acrylic acid/ethylene copolymer the Primacor 5981) to an internal mixer (Banbury type) for the neutralization reaction. The only exception was calcium acetate, which, due to problems encountered in solid form, was added as a 30 wt-% solution in water.

~In the neutralization reaction, the cation salts S solubilized in the Primacor 5981 acrylic acid/ethylene w S 20 copolymer above the melting point of the copolymer and a vigorous reaction took place with a great deal of foaming occurring as the cation reacted with the carboxylic acid groups of the acrylic acid/ethylene copolymer and the volatile by-products of water (in the case of oxides or hydroxides) or acetic acid (when acetates are used) were evaporated. The reaction was continued until foaming ceased about 30-45 minutes at 250-350°F), and the batch was removed from the Banbury mixer. Mixing continued of the batch obtained from the mixer on a hot two-roll mill (175-250°F) to complete the neutralization reaction. The extent of the reaction was monitored by measuring melt flow index according to ASTM D-1238-E. As indicated below, the neutralized products exhibited drastically different properties depending upon the nature and amount of the cation salts utilized.

TABLE 7 Formulation No.

1 (NaOH) 2(NaOH) 3(NaOH) 4(NaOH) 6(ZnAc) 7(ZnAc) 8(MgAc) 9(MgAc) I 0(MgAc) Wt% Cation Salt 6.98 5.66 3,84 2.01 17.9 13,9 a., 17,4 20.6 13.8 Wt% Neutralization 67.5 54,0 35.9, 27,0 71.5 53.0 36.1 70,7 87,1 53.8 Melt Index .804 .808 .81 2 .812 .806 .797 .793 .814 .8,15 .814 Shore D Hardness 71 73 69 (brittle) 71 69 67 74 76 74 11 (MgO) 1 2(MgO) I 3(Mg0) 14(MgO) 2.91 3.85 4.76 I 19 53.5 71.5 89.3 35.7 .813 .808 .809 .815 te 4i 4 6 0*a* C~qntrol: 50/50 13!snds of loteks 8000/7030 C.R .810/65 Shore D Hardness DuPont High Acid Surlyn@ 8422 (Na) =.81 1/70 Shore D Hardness DuPont High Acid Surlyn® 8162 (Zn) C.O.R, 807/65 Shore D Hardness DuPont High Acid lotek Ex-960 (Zn) C.0.R. 807/65 Shore D Hardness Control for Formulations 11 -14 is 50/50 lotek 800(17. 330, C.O.R. .814, Formulation 26 C.O. was normaliked to that control accordingly.

As indicasted in Table 7, a number of the new cation neutralized acrylic acid based high acid ionomer resins exhibited C.O.R. and Shore D hardness values greater than that exhibited by a 50/50 blend of the lotek low acid acrylic acid based hard ionomer resins, such as the lotek 8000/7030 blend utilized in 1S the cover compositions disclosed in U.S. Patent No. 4,911,451. Moreover, included in new acrylic acid based high acid ionomer resins were numerous cation neutralized high acid ionomer resins previously not available, such as 1) CAW1N WOWfl ACr.ILODELMT t241r'i9 SPC those acrylic acid based high acid ionomer resins neutralized to various degrees by the manganese, lithium, potassium, magnesium, calcium and nickel salts. Furthermore, the new cation neutralized acrylic acid based high acid ionomers produced C.O.R. and hardness values greater than those shown by the methacrylic acid based high acid ionomer resins recently produced by DuPont Surlyn® 8422 (Na) and Surlyn® 8162 and the acrylic acid based high acid resins experimentally produced by Exxon (i.e.

lotek EX-959 and Ex-960 collectively referred to as "the controls." In addition, the results produced by Formulation Nos. 1 through 3 directed to the sodium ion neutralized ethylene-acrylic acid copolymers and Formulation Nos. 5 through 7 directed to the zinc ion neutralized ethyleneacrylic acid copolymers in comparison to the new lotek high acid ethylene acrylic acid ionomers were also of interest. As indicated above, Escor® or lotek Ex-959 is a sodium ion neutralized ethylene-acrylic acid copolymer and Escore or lotek Ex-960 is a zinc neutralized ethylene-acrylic acid copolymer.

According to Exxon, loteks 959 and 960 contain from about 19.0 to about 21.0% by weight acrylic acid with approximately 30 to about 70 percent of the acid groups neutralized with sodium and zinc ions, respectfully.

Formulation No. 2 5.66 wt% sodium salt, 54 wt-% neutralization, 2.4 melt index, .808 C.O.R. and 73 Shore D hardness) is somewhat similar to lotek 959 and Formulation No. 16 13.9 wt-% zinc salt, 53 wt-% neutralization, 0.9 melt index, .797 C.O.R. and 69 Shore D hardness) is Ssomewhat similar to lotek 960.

Since the new sodium or zinc neutralized high acid ionomers produced improved properties over those produced by the existing available sodium or zinc high acid ionomers, a number of new cover compositions can be produced having enhanced characteristics.

Along this line, several of the cation neutralized acrylic acid based high acid ionomer resins produced above which exhibited enhanced C.O.R. and Shore D hardness values were blended together and evaluated for the JI C.I\NWO RDACKItCOE'OEIIEBAWT.U67U1 SPC II s~ 9 C C

C.

C

p.

6 tee.

CCZ

C

purpose of determining whether any synergistic effects were produced particularly with respect to enhanced C.O.R. values.

Specifically, from each group of the different cation neutralized high acid ionomer resins set forth in Table 7, the best overall ionomer (based upon melt index and Shore D hardness) was utilized to produce a number of blends ("diblends") and processed to produce the cover component of multilayered golf balls. The "diblends" consisted of 50/50 mixtures.

With respect to the blends set forth in Table 8, Na refers to Formulation No. 3, C.O.R. (molded/finished) of .812/817; Zn refers to Formulation No. 6, C.O.R. (molded/finished) of .797/.796; Mg refers to Formulation No. 8, C.O.R.

(molded/finished) of .814/.820; and 50/50 lotek 8000/7030 refers to control of 50/50 blend of lotek 8000/7030, C.O.R. (molded/finished) o .810/.812.

The C.O.R. values of the "diblends" were then evaluated after molding with a center stock having the following composition: MATERIAL WEIGHT (phr; BR-1220 1 70.70 Taktene 2202 29.30 React Rite ZDA 3 31.14 Zinc Oxide 6.23 Zinc Stearate 20.15 Limestone 17.58 Ground Flash (20-40 mesh) 20.15 Blue Masterbatch .012 Luperco 231XL4 .89 or Trigonox 29/405 Papi 946 'BR-1220 is high cis-polybutadiene from Shell Chemical Co., Houston Texas.

2 Taktene is high cis-polybutadiene from Polysar Chemic a!, 3 ZDA is zinc diacrylate.

4 Luperco 231XL is a peroxide-free radical initiator manufactured and sold by Atochem, Buffalo, New York.

Trigonox 29/40 is peroxide-free radical initiator manufactured and sold by Akzo Chemie America, Chicago, Illinois.

6 Papi 94 is a polymeric diisocyanate available from Dow Chemical Co., Midland, Michigan.

IJ C. tWIN WORDUACKIE\NODLLEIEIAU67Oi SPC 29 In addition, the molded balls were coated and finished according to the procedure mentioned above. The C.O.R. values of the finished balls were determined in order to evaluate whether any improvement in resilience was produced. Generally, it is typical to observe a .002 to .003 point pick up in C.O.R. values of the finished balls in comparison to the molded balls. The results are set forth in Tables 8A and 8B below.

TABLE 8A Diblends (50/50 Blends) C.O.R.

(Molded/Finished) Values Formulation No. Blend C.O.R. (Molded/Finished) Na/Zn .811/.818 16 Na/Mg .813/.819 17 Zn/Mg .807L814 18 lotek 959/960 .811/.818 19 Control .809/NA 20 Control .806/NA

C.

a 4*s* 4* a a..

a.

d~ei an.

*i D Controls are Formulation No. 18, a 50/50 blend of loek 959/960; Formulation No, 19 a 75/25 blend of Surlyn 8162/8422; and Formulation No. 20 a 50/50 blend of lotek 8000/7030 a. CC a a a rae.

C

JJ CWVINWORfUACKIE NODEL~ \AU67O559 SPC u IP~-il a. a a a a.

a.

a. a a a. at.

a. a a *a a a. .8.

o a. a a TABLE 8B Synergy Values of the DiBlends f(COR) exp Final Final Final Formulation No Salt 1 Salt 2 J(car) Caic j(COR) exp (COR) caic (COR) calc (car) exp (COR) Duff.

804..5 813.0 805.5 811.0 813.0 807.0 806.5 818.5 808.0 818.0 819.0 814.0 11.5 A1 CWINWORD1AOUIE%ODELEIZAU6O559 WS2 In Table 8B above, the C.O.R. synergy values are based upon the data from Table 7 of the various metal cation neutralized high acid acrylic acid based ionomer resins and the following calculations: (COR)calc coefficient calculated as weighted average of as-molded COR's for polymers of salts 1 and 2 (COR) exp experimental as-molded COR for blend FINAL (COR)calc coefficient calculated as weighted average of finished COR's for polymers of salts 1 and 2 FINAL (COR) exp experimental finished COR for blend 15 FINAL (COR) diff difference between FINAL (COR) exp and FINAL (COR) (calc) As noted in Table 8B, positive synergy in resilience is observed for nearly all of the finished (final) blends, with substantial synergy being produced 20 in Formulation Nos. 15 and 17.

Moreover, the diblends were also evaluated against a control Formulation No. 18 (see Table 8A), a 50/50 blend of lotek 959/960, the best available high acid blends, with respect to improved C.O.R. values (i.e.

811/.818). Similar or enhanced C,O.R. values (molded/finished) were observed in Formulation Nos. 15 (Na/Zn) and 16 (Na/Mg).

Furthermore, when reviewed for cold cracking, with the exception of Formulation No 16, all of the diblends tested exhibited resistance to breaking With respect to Formulation No. 16, some breakage did occur with 2 out of the 12 balls tested exhibiting breakage.

JJ C \WINWORDJACKl'.NODIET~AU.67059 SPC 1 L Consequently, not only are a number of new cation neutralized acrylic acid based high acid ionomers now available for golf ball cover construction, these new cation neutralized acrylic acid based high acid ionomers may be blended together in various combinations to produce cover compositions exhibiting enhanced resilience distance) due to the synergies noted above.

The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of the preceding detailed description. It is intended that the invention bc construed as including all such alterations and modifications insofar as they come within the scope of the appended claims or the equivalents thereof.

C* **4 S D1 C WINWORDJACKIE NODFO'EU.TAV67OSS9 SPC I I

Claims (9)

1. A golf ball comprising a core and a cover, wherein said cover is a blend of two or more metal cation neutralized high acid ionomer resins, each ionomer resin comprising greater than 16% by weight of acrylic acid and the remainder ethylene, of which 10 to 90% of the carboxyl groups of each ionomer resin are neutralized with a metal cation selected from the group consisting of sodium, zinc and magnesium.

2. A golf ball according to claim 1, wherein each ionomer resin comprises from 17% to 25% by weight of acrylic acid and the remainder ethylene,

3, A golf ball according to claim 1, wherein each ionomer resin comprises from 18.5 to 21.5 by weight of acrylic acid and the remainder ethylene,

4. A golf ball according to claim 1, wherein each ionomer resin comprises about 20% by weight of acrylic acid and the remainder ethylene.

5. The golf ball of any one of claims 1 to 4 wherein said metal cation is 20 magnesium. V.

6. The golf ball of any one of claims 1 to 4 wherein one ionomer resin is neutralized with sodium and another ionomer resin is neutralized with zinc.

7. The golf ball of any one of claims 1 to 4 wherein one ionomer resin is neutralized with sodium and another ionomer resin is neutralized with magnesium,

8. The golf ball of any one of claims 1 to 4 wherein the cover further comprises one or more additional ingredients selected from the group consisting of pigments, dyes, U.V. absorbers and optical brighteners. I -W 34

9. The golf ball of any one of claims I to 4 wherein the core is a solid core. DATED 2 October, 1996 PHILLIPS ORMONDE FITZPATRICK Attorneys for: LISCO, INC. hou~~ 0see *4 0 0*& *0 a 11 CAW IN4WORDUACKIEONQDItLEUAU6,70559 SPC ABSTRACT A golf ball comprising a core and a cover, wherein said cover is a blend of two or more metal cation neutralized high acid ionomer resins, each ionomer resin comprising greater than 16% by weight of acrylic acid and the remainder ethylene, of which 10 to 90% of the carboxyl groups of the copolymer are neutralized with a metal cation selected from the group consisting of sodium, zinc and magnesium. a• e*S S* 6 'a. Sa I: t R J VANIIB'JIt'-l OELLnTI' "Wl)Z, i