Golf ball compositions containing polymeric compatibilizers free of .alpha.,.beta.-ethylenically unsaturated carboxylic acids

A golf ball and a method of making a golf ball, having a cover and a core, wherein the golf ball has at least one layer formed of a compatibilized blend of about 4 percent to 95 percent of at least one ionomer resin; about 95 percent to 4 percent of at least one non-ionic polymer; and about 1 to 15 phr, based on 100 parts ionomer resin and non-ionic polymer, of at least one compatibilizer of a functionalized block and graft polymers and oligomers, wherein the compatibilizer is free of any monomers containing an .alpha.,.beta.-ethylenically unsaturated carboxylic acid, and wherein at least one portion of the non-carboxylic acid compatibilizer is miscible with the at least one ionomer and at least one portion of the non-carboxylic acid compatibilizer is miscible with the at least one non-ionic polymer.

TECHNICAL FIELD 
The present invention is directed to a method for producing an improved 
golf ball with improved materials properties by compatibilizing normally 
incompatible mixtures of polymeric materials used in forming, e.g., golf 
ball covers, cover layers, intermediate and mantle layers, and cores and 
core layers, and, more particularly, to a golf ball comprising 
compatibilized blends of otherwise incompatible ionomers and non-ionic 
thermoplastics. The incompatibility of the mixtures is overcome by the 
addition of at least one block, graft, or random polymer or oligomer that 
is substantially free of carboxylic acid groups as a compatibilizer to 
form a compatible blend. 
BACKGROUND OF THE INVENTION 
Three-piece, wound balls with balata (trans-polyisoprene) covers are 
typically preferred by professional and low handicap amateur golfers. 
These balls provide better golfers with a combination of distance, high 
spin rate, and control that is not available with an ionomer cover or in 
one-piece and two-piece balls. However, balata cuts easily, and lacks the 
durability required by the average golfer. 
Two-piece golf balls, which are used by the average amateur golfer, provide 
a combination of durability and maximum distance that is not available 
with balata covered balls. These balls comprise a core formed of a single 
solid sphere, which typically comprises a polybutadiene based compound, 
encased in an ionomer cover, such as SURLYN.RTM.. These balls are 
extremely durable, and are almost impossible to cut. However, the 
durability results from the hardness of the ionomer, which gives such 
balls a very hard "feel" when struck with a golf club that many golfers 
find unacceptable. 
Manufacturers have attempted to form blends of ionomers with other, softer 
polymers to soften the ball and improve the feel and the spin rate. 
Ionomers are ionic copolymers of an olefin and an unsaturated carboxylic 
acid in which at least a portion of the carboxylic acid groups have been 
neutralized with a metal ion. As a result, ionomers are immiscible with 
many other, softer polymers in the same manner as oil and water. A highly 
polar ionomer will not blend properly with either non-polar polymers or 
with polar, but non-ionic polymers that are sufficiently different 
chemically from ionomers that strong interactions between the polymers and 
the ionomers are not present in the mixture. 
A mixture of polymer components is immiscible unless strong interactions 
are present between the polymer components in the mixture, such as those 
that exist between polymers with similar polarities. It is only when these 
strong interactions are present between the polymer components in the 
mixture that the polymers are miscible. As a result, mixtures of ionomers 
and non-polar polymers or of ionomers and polar polymers that cannot form 
strong interactions are immiscible. 
A blend of miscible polymers is homogeneous on a microscopic scale, and 
consists of a single, continuous phase. In contrast, separate phases are 
formed in mixtures of immiscible polymers. Typically, the polymer that is 
present in the lower concentration forms a discontinuous or discrete 
phase, and the polymer that is present in the higher concentration forms a 
continuous phase. Mixtures of polymers that are highly immiscible are 
heterogeneous on a macroscopic scale, as well as on the microscopic scale. 
Golf balls formed with mixtures of polymers that are highly immiscible, 
such as prior art balls having a cover formed from a blend of an ionomer 
and a thermoplastic urethane, lack durability, and crack or split on 
impact. 
Polymers are not always totally miscible or totally immiscible. Blends of 
such polymers are heterogeneous on a microscopic scale, but may be 
homogeneous on a macroscopic scale. Immiscible blends that are homogeneous 
on a macroscopic scale are referred to as being compatible, and often 
provide commercially attractive polymer blends that frequently possess 
enhanced physical properties when compared to the constituent polymers. 
Compatible blends form two phases that do not have well-defined 
boundaries, as each polymer can partially penetrate the phase of the other 
polymer. This interfacial interaction results in the improved properties 
of the compatible blend. Immiscible blends can also be compatibilized by 
the addition of a molecule that is at least partially miscible in each of 
the two phases, so that the interfacial interaction between the polymers 
in the two phases is improved. 
Attempts have been made to overcome the deficiencies of blends of ionomers 
with other, softer polymers that would be expected to be immiscible or 
incompatible. For example, U.S. Pat. No. 5,397,840 to Sullivan et al. 
discloses blends of "ionic" and "non-ionic copolymers". Although it would 
be expected that blends of ionic and non-ionic polymers would be 
immiscible, both the "ionic copolymers" and "non-ionic copolymers" 
disclosed by Sullivan are highly polar, and, thus, strong interactions are 
present between the polymer components in the blend, which presumably 
result from "ion-hopping" during the blending stage. Therefore, the 
polymers in these blends are miscible, or at least compatible. The "ionic 
copolymers" are ionomers, consisting of a copolymer of an .alpha.-olefin 
and an .alpha.,.beta.-ethylenically unsaturated carboxylic acid, where at 
least part of the acid groups are neutralized by a metal derivative. The 
"non-ionic" copolymers are simply copolymers or terpolymers of ethylene 
and acrylic or methacrylic acid or propylene and acrylic acid, i.e., an 
.alpha.-olefin and an .alpha.,.beta.-ethylenically unsaturated carboxylic 
acid, in which the carboxylic acid groups are not neutralized. Blending 
such a "non-ionic" polymer with one or more ionomers would likely result 
in an exchange of acidic protons from the carboxylic acid groups of the 
"non-ionic" polymers and metal ions from the neutralized carboxylic acid 
groups in the ionomers, resulting in a blend of ionomers, which would be 
expected to be miscible. 
U.S. Pat. No. 5,359,000 to Hamada et al. describes a golf ball cover 
material formed from a heated mixture of an ionomer resin, a copolymer of 
maleic anhydride or a polymer modified with maleic anhydride, and a metal 
hydroxide, metal carbonate, or metal acetate. As with U.S. Pat. No. 
5,397,840, there are strong interactions between the components in the 
blend, so that the mixture of polymers appear to be miscible. 
U.S. Pat. Nos. 5,098,105 and 4,986,545 to Sullivan disclose golf ball 
covers that include blends of ionomers and thermoplastic rubber elastomers 
modified with a polar group, wherein the latter material is selected from 
the group consisting of a maleic anhydride modified ethylene propylene 
copolymer, a maleic anhydride modified styrenic block copolymer, and a 
maleic anhydride modified ethylene-vinyl acetate copolymer. 
European Patent Application 0 557 069 describes a golf ball cover 
containing a heated mixture of an ionomer resin and a polymer containing a 
glycidyl group. 
In each of the patents discussed above, one or more ionomers are blended 
with a non-ionic polymer, containing groups such as maleic anhydride and 
glycidyl methacrylate that provide strong interactions between the 
ionomeric and non-ionic polymer components in the mixture. Therefore, the 
ionomers and non-ionic polymers are at least partially miscible, and 
compatible blends can be formed without a compatibilizer. None of the 
patents discussed above discloses immiscible blends of ionomers and 
polymers that require a compatibilizer to produce useful golf ball core, 
cover, or mantle layer compositions. 
Gersappe et al., The Use of Graft Copolymers to Bind Immiscible Blends, 
Science, 265 (1994), describe copolymers with side chains that associate 
across boundaries between phase-separated regions in polymer blends to 
bind the regions together, and to enhance the structural integrity and 
mechanical properties of the resulting material. Normally incompatible 
mixtures of deuterated poly(ethyl acrylate) ("d-PEA") and deuterated 
poly(methyl methacrylate) ("d-PMMA"), compatibilized with PEA-polystyrene 
and PMMA-polystyrene are disclosed. There is no disclosure of 
compatibilized blends of ionomers and other, softer polymers that would 
normally be incompatible. 
U.S. Pat. No. 5,321,089 to Cadorniga et al. describes a golf ball cover, 
containing ethylene-methyl acrylate, blended with an ionomer resin and a 
compatibilizer. The compatibilizer consists of a copolymer or terpolymer 
containing 80 to 95 percent by weight of an olefin, preferably ethylene, 
20 to 5 percent by weight of an .alpha.,.beta.-ethylenically unsaturated 
carboxylic acid, preferably acrylic or methacrylic acid, and possibly 
containing a small amount of an n-alkyl acrylate, such as n-butyl 
acrylate. The disclosed balls had durability properties superior to balata 
covered balls, failing in a hit test after only 145 to 182 hits. This is 
significantly less durable than golf ball covers made from ionomer blends. 
None of these compositions provide the combination of durability and 
distance that is provided by two-piece balls with ionomer covers and the 
high spin rate and control that is available with a three-piece, wound 
balls with balata covers. Therefore, there remains a need for a method of 
making golf ball cores and covers that provides for the blending of 
thermoplastic ionomers with other, non-ionic polymers that are normally 
incompatible with ionomers to provide a one-piece, two-piece, or 
three-piece, wound golf ball with the durability and distance of a 
SURLYN.RTM. covered two-piece ball and the feel, click, and control of a 
balata covered three-piece ball. The present invention provides such a 
method, and produces such a product. 
SUMMARY OF THE INVENTION 
The present invention relates to golf balls, and, in particular, to golf 
balls having at least one layer comprising about 4 percent to 95 percent 
of at least one ionomer resin; about 95 percent to 4 percent of at least 
one non-ionic polymer; and about 1 to 15 parts per hundred ("phr"), based 
on 100 parts per weight of combined ionic and non-ionic polymers, of at 
least one non-carboxylic acid compatibilizer. The layer may be the cover, 
a layer in the cover, i.e., part of a multi-layer cover, an intermediate 
or mantle layer, or a layer in the core. 
Non-carboxylic acid compatibilizers useful in the invention include 
functionalized block and graft polymers, oligomers, and mixtures thereof, 
wherein at least one portion of the non-carboxylic acid compatibilizer is 
miscible with the at least one ionomer and at least one portion of the 
non-carboxylic acid compatibilizer is miscible with the at least one 
non-ionic polymer. Preferred non-carboxylic acid compatibilizers include 
olefinic block, random, and graft thermoplastic polymers and oligomers, 
which contain monomers and comonomers functionalized with groups selected 
from the group consisting of acids, esters, epoxies, isocyanates, 
hydroxys, anhydrides, amines, thiols; polyester-polyether block 
copolymers; polyamide-polyether block copolymers; polysiloxanes; 
silicones; styrene-butadiene and hydrogenated styrene-butadiene block 
co-polymers; and mixtures thereof. The styrene-butadiene and hydrogenated 
styrene-butadiene block co-polymers may be functionalized with acids, 
esters, epoxies, isocyanates, hydroxys, anhydrides, amines, oxazolines, 
and thiols. 
Non-ionic polymers useful in the invention include polyamides, 
polyurethanes, polyesters, poly(alkylacrylates), homopolymers and 
copolymers of fluoropolymers, siloxanes, and functionalized or 
unfunctionalized styrene-butadiene-isoprene polymers. Useful ionomers 
include olefinic, polyester, polyamide, polyether, polycarbonate, 
polyurethane, polyacrylate, and polyalkyl homopolymer and copolymer 
ionomers. Preferred ionomers are copolymers of from about 70 to 95 percent 
of an olefin and from about 30 to 5 percent of an 
.alpha.,.beta.-ethylenically unsaturated carboxylic acid, where at least a 
portion of the carboxylic acid groups are neutralized with a metal atom. 
The most preferred ionomers are copolymers of ethylene and acrylic or 
methacrylic acid, where at least a portion of the carboxylic acid groups 
are neutralized with zinc, sodium, magnesium, lithium, calcium, manganese, 
aluminum, or ammonium derivatives. 
Preferably, the golf ball of the invention includes at least one layer, 
typically the cover or a layer in a multi-layer cover, comprising about 4 
percent to 95 percent of at least one ionomer resin; about 95 percent to 4 
percent of at least one non-ionic copolymer of an olefin and an acrylate 
or methacrylate ester comonomer of formula HRC=CR'COOC.sub.n H.sub.2n+1, 
where R and R' are the same or different, and are hydrogen or methyl, and 
n is 1 or greater, preferably at least 3; and about 1 to 15 phr of at 
least one non-carboxylic acid compatibilizer selected from the group 
consisting of copolymers of an olefin and an alkyl acrylate or alkyl 
methacrylate, functionalized with maleic anhydride, terpolymers of an 
olefin, an alkyl acrylate or alkyl methacrylate, and carbon dioxide, 
functionalized with maleic anhydride, copolymers of an olefin and vinyl 
acetate, functionalized with maleic anhydride, copolymers of an olefin and 
an alkyl acrylate or alkyl methacrylate, functionalized with glycidyl 
acrylate or methacrylate, and copolymers of olefins with oxazoline or 
imide groups. 
The most preferred golf ball compositions of the invention comprise an 
ionomer, a copolymer of ethylene and n-butyl acrylate, and a 
non-carboxylic acid compatibilizer of a copolymer of ethylene and vinyl 
acetate, functionalized with about 0.01 percent to about 5 percent of 
maleic anhydride, a copolymer of ethylene and n-butyl acrylate, 
functionalized with about 0.01 percent to about 5 percent maleic 
anhydride, a terpolymer of ethylene, n-butyl acrylate and carbon monoxide, 
functionalized with about 0.01 percent to about 5 percent maleic 
anhydride, or a copolymer of ethylene and n-butyl acrylate, functionalized 
with about 0.1 percent to about 6 percent of glycidyl methacrylate or 
acrylate. 
The invention also relates to a method of making a golf ball, which 
comprises forming a golf ball core, forming a blend of at least one 
ionomer resin, at least one non-ionic polymer, and at least one 
non-carboxylic acid compatibilizer, and molding the blend around the golf 
ball core to form at least one layer in the golf ball, wherein the blend 
is any of the golf ball blends described above.

DETAILED DESCRIPTION OF THE INVENTION 
As used herein, the terms "non-carboxylic acid compatibilizer" and 
"non-carboxylic acid polymer" refer to polymers or oligomers that are 
substantially free of any monomers containing an 
.alpha.,.beta.-ethylenically unsaturated carboxylic acid. However, 
non-carboxylic acid polymers, oligomers, and compatibilizers may contain 
monomers comprising other acidic moieties. 
In addition, as used herein, a "compatibilized polymer blend" or a 
"compatible polymer blend" is a blend of two or more polymers that is 
heterogeneous on a microscopic scale, but homogeneous on a macroscopic 
scale, and has useful golf ball properties. An "incompatible polymer 
blend" is a mixture of at least two polymers that is heterogeneous on a 
macroscopic scale, in which useful golf ball properties, such as 
durability, are lacking. 
The term "layer" includes any generally spherical portion of a golf ball or 
golf ball core, cover, or mantle or intermediate layer, including 
one-piece cores and one-piece balls. A mantle is defined herein as a 
portion of the golf ball that occupies the volume between the cover and 
the core. Of course, as one of ordinary skill in the art would recognize, 
any of the core, cover, and mantle of the golf balls of the invention can 
be formed of one layer or a plurality of layers, as that term is defined 
herein. 
The present invention is directed to methods and compositions for use in 
the manufacture of golf balls, and, in particular, golf ball cores, 
mantles, and covers and any layer of a golf ball cover, core or mantle. 
The compositions of the present invention comprise compatibilized blends 
of ionomers and other, non-ionic polymers that are normally incompatible 
with ionomers, such as non-polar polymers and polar polymers that are 
sufficiently different chemically from ionomers to be incompatible with 
ionomers without the use of at least one non-carboxylic acid 
compatibilizer. Typically, the incompatibility is the result of large 
differences in the polarity of the ionomer and the other, non-ionic 
polymer. Although the non-ionic polymer may be polar, it may be 
sufficiently different chemically from an ionomer that the blend lacks the 
strong interactions that are required for the polymers to be miscible, so 
that two distinct phases form in the blend. The blends of the invention 
are compatibilized with non-carboxylic acid block, graft, or random 
polymers or oligomers, or mixtures thereof that are at least partially 
miscible with both components of what would otherwise be an incompatible 
mixture, i.e., an ionomer and a non-polar polymer or a polar, but 
chemically different polymer. The compatibilized blends can be used as 
golf ball covers for three-piece, wound golf balls and for two piece balls 
with liquid and solid cores, as well as in cores for two-piece balls, in 
unitary or one-piece balls, and in multi-core or multi-cover golf balls. 
The present invention is further directed to a method of making a 
composition for a golf ball core or cover or any layer in a golf ball that 
is part of the cover, core, or a mantle layer between the cover and the 
core, comprising compatibilizing an otherwise incompatible mixture of one 
or more ionomers and non-polar polymers or an otherwise incompatible 
mixture of one or more ionomers and a polar, but chemically different 
polymer, or mixtures thereof by forming a mixture of the incompatible 
polymers and a non-carboxylic acid compatibilizer of an appropriate block, 
graft, or random polymer or oligomer or mixture thereof that is miscible 
in both components of the otherwise incompatible mixture described above. 
Preferably, the blends are formed by combining the incompatible polymers 
in, for example, a twin-screw extruder, and then adding the non-carboxylic 
acid compatibilizer to produce a compatible blend of the otherwise 
incompatible polymers. Once the compatibilized blends are formed in the 
extruder or in other polymer processing equipment known in the art, 
conventional equipment used in the production of golf balls may be used to 
form the golf balls of the invention. 
Compatibilization of blends of two or more different and normally 
incompatible polymers dramatically improves the mechanical and thermal 
properties of the blends. Golf balls and, in particular, golf ball covers 
produced from incompatible polymer blends without non-carboxylic acid 
compatibilizers, lack durability, and crack or split into pieces when hit 
with a golf club. In contrast, the compatibilized blends of the invention, 
particularly when used in golf ball covers, provide golf balls having the 
durability and distance of ionomer covered two-piece balls and the feel, 
click and control of balata covered three-piece balls. 
The ionomers useful in the compositions of the invention are typically 
thermoplastic ionomers, and include olefinic, polyester, polyamide, 
polyether, polycarbonate, polyurethane, polyacrylate, and polyalkyl 
homopolymer and copolymer ionomers. Preferably, the ionomer is a copolymer 
of an olefin and an .alpha.,.beta.-ethylenically unsaturated carboxylic 
acid, where at least a portion of the carboxylic acid groups are 
neutralized with a metal derivative. The ionomer may also be a very low 
modulus ionomer ("VLMI"), i.e., a terpolymer of an olefin, an .alpha., 
.beta.-ethylenically unsaturated carboxylic acid, and an acrylate or 
methacrylate ester, typically n- or iso-butyl-acrylate, where at least a 
portion of the acid groups are neutralized with a metal derivative. 
Most preferably, the olefin is ethylene, and the 
.alpha.,.beta.-ethylenically unsaturated carboxylic acid is acrylic or 
methacrylic acid, where the metal derivative is a zinc, sodium, magnesium, 
lithium, calcium, manganese, aluminum, or ammonium derivative. 
Non-polar polymers useful in the present invention include polyethylene, 
polyisoprene, polybutadiene, ethylene-propylene, EPDM, vulcanized EPDM/PP, 
and styrene-butadiene-isoprene. The preferred non-ionic polymers are 
non-ionic copolymers of an olefin, preferably ethylene, and an acrylate or 
methacrylate ester of formula HRC.dbd.CR'COOC.sub.n H.sub.2n+1, where R 
and R' are the same or different and are hydrogen or methyl, and n is 1 or 
greater, but is preferably at least 3. The most preferred polymer is a 
copolymer of ethylene and n-butyl acrylate. 
The non-carboxylic acid compatibilizers of the present invention are chosen 
for their compatibility with both the ionomer and the non-polar polymer or 
polar, but chemically different polymer that is used in the blend. Simply 
put, one portion of the non-carboxylic acid compatibilizer is miscible 
with the ionomer, while a second portion is miscible with the other 
polymer in the blend. This increases the interfacial tension between the 
polymers, and produces an attraction between the polymers at the interface 
that does not exist without a non-carboxylic acid compatibilizer. Thus, 
the non-carboxylic acid compatibilizer acts as a "molecular zipper" that 
effectively binds the polymers of the compatibilized blend together, and 
produces a miscible blend of the ionomer, the otherwise incompatible 
polymer, and the non-carboxylic acid compatibilizer. 
Useful non-carboxylic acid compatibilizers include block, random, and graft 
thermoplastics and oligomers, such as block, random, and graft 
thermoplastics based on homopolymers and copolymers of olefinic monomers 
with comonomers containing functionalized groups that enable the 
non-carboxylic acid compatibilizer to be miscible with both the ionomer 
and the non-polar polymer or polar, but chemically different polymer. 
Functionalized polymers useful in the invention include copolymers of 
olefinic monomers with comonomers containing functionalized groups of 
acids, esters, epoxies, isocyanates, hydroxys, anhydrides, amines, and 
thiols, e.g., copolymers of ethylene with alkylacrylates or glycidyl 
acrylate. Useful non-carboxylic acid compatibilizers also include block 
copolymers such as copoly(ether ester), such as Du Pont's Hytrel, and 
copolyether-amide (Pebax). Other useful block copolymers include 
styrene-butadiene and hydrogenated styrene-butadiene block co-polymers. 
These block copolymers may also be functionalized with functional groups 
such as acids, esters, epoxies, isocyanates, hydroxys, anhydrides, amines, 
and thiols. Polysiloxanes and silicones are also useful. 
The most preferred non-carboxylic acid compatibilizers for this embodiment 
are copolymers of an olefin, preferably ethylene, and an alkyl acrylate or 
alkyl methacrylate, preferably n-butyl acrylate, functionalized with 
maleic anhydride, preferably about 0.01 percent to about 5 percent maleic 
anhydride; terpolymers of an olefin, preferably ethylene, an alkyl 
acrylate or alkyl methacrylate, preferably n-butyl acrylate, and carbon 
monoxide, functionalized with maleic anhydride, preferably about 0.01 
percent to about 5 percent maleic anhydride; copolymers of an olefin, 
preferably ethylene, and vinyl acetate, functionalized with maleic 
anhydride, preferably about 0.01 percent to about 5 percent of maleic 
anhydride; copolymers of an olefin, preferably ethylene, and an alkyl 
acrylate or alkyl methacrylate, preferably n-butyl acrylate, 
functionalized with glycidyl methacrylate or acrylate, preferably about 
0.1 percent to about 6 percent of glycidyl methacrylate or acrylate; and 
copolymers of olefins with oxazoline or imide comonomers. 
In a first embodiment, the compositions of the present invention comprise a 
blend of about 4 to about 95 weight percent of an olefinic ionomer, 
preferably about 40 to about 90 weight percent, about 95 to about 4 weight 
percent of a non-polar polymer, preferably 60 to about 10 weight percent, 
and about 1 to about 15 phr of a block, graft, or random polymer or 
oligomer, or mixture thereof, as a non-carboxylic acid compatibilizer. 
In an alternate embodiment, about 4 to about 95 weight percent of an 
ionomer, preferably about 40 to about 90 weight percent, is blended with 
about 95 to about 4 weight percent of a polar, but chemically different 
polymer, preferably about 60 to about 10 weight percent, and about 1 to 
about 15 phr of a non-carboxylic acid compatibilizer of a block, graft, or 
random polymer or oligomer or mixture thereof. 
Typical polar polymers include, but are not limited to, polyamides, 
polyurethane, polyesters, poly(alkylacrylate), fluoropolymers, siloxanes, 
and functionalized styrene-butadiene-isoprene polymers. 
Typically, the compositions of the invention comprise a compatibilized 
blend of a relatively hard ionomer and a softer, non-polar or polar, but 
chemically different, non-ionic polymer. However, useful blends according 
to the present invention also include compatibilized blends of a soft 
ionomer, typically a VLMI, and a harder, non-ionic polymer. The flexural 
modulus and hardness of the ionomer, non-polar or polar, but chemically 
different non-ionic polymer, and the compatibilizer can be selected to 
vary the flexural modulus and hardness of the layer, and to provide a 
desired set of golf ball properties. Therefore, the flexural modulus of 
the ionomer preferably ranges from about 1,000 to about 150,000 psi, more 
preferably from about 1,000 to about 120,000, most preferably from about 
2,000 to about 110,000, and the flexural modulus of the non-polar or 
polar, but chemically different non-ionic polymer preferably ranges from 
about 1,000 to about 500,000 psi, more preferably from about 1,000 to 
about 400,000, most preferably from about 2,000 to about 300,000. The 
flexural modulus of the non-carboxylic acid compatibilizer preferably 
ranges from about 1,000 to about 150,000 psi, more preferably from about 
1,000 to about 120,000, most preferably from about 2,000 to about 110,000. 
EXAMPLES 
The following non-limiting examples are merely illustrative of the 
preferred embodiments of the present invention, and are not to be 
construed as limiting the 10 invention, the scope of which is defined by 
the appended claims. 
Tests were performed to compare the durability of golf ball covers based on 
a blend of an ionomer and a non-ionic copolymer of ethylene-n-butyl 
acrylate incorporating a non-carboxylic acid compatibilizer of a 
functionalized polymer with golf ball covers based on a similar blend that 
lacked the non-carboxylic acid compatibilizer and with "standard" ball 
covers based on a blend of ionomer resins. The polymer blends are given in 
Table I, where the amount of each component is given in parts per hundred 
("phr"). 
Example 1 is representative of a commercially available ball, and 
incorporates a cover blend of a commercially available ionomer, believed 
to comprise about 13 to about 17 percent acid, and to be neutralized with 
lithium, and a commercially available very low modulus ionomer ("VLMI"), 
believed to comprise about 9 to about 12 percent acid, and to be 
neutralized with sodium. Example 2 incorporates a cover blend of a 
commercially available ionomer, believed to comprise about 13 to about 17 
percent acid, and to be neutralized with lithium, and a commercially 
available, non-ionic copolymer of ethylene and and about 17 to about 21 
percent n-butyl acrylate. Example 3 incorporates a non-carboxylic acid 
compatibilizer according to the invention of ethylene-vinyl acetate 
functionalized with 1 percent maleic anhydride into the blend of Example 
2. 
Golf balls incorporating the non-carboxylic acid compatibilizers of the 
invention show dramatically improved durability in hit tests. Example 3 
demonstrates that blends incorporating the present non-carboxylic acid 
compatibilizers can sustain 550 hits before the failure of a single ball, 
and 800 hits before 50 percent of the balls fail. In contrast, in Example 
2, blends of the lithium ionomer with the copolymer of ethylene with 19 
percent n-butyl acrylate, but lacking a non-carboxylic acid 
compatibilizer, only require about 100 hits before the first failure and 
250 hits before 50 percent failure. The golf balls produced in accordance 
with the present invention are also more durable than those made from 
blends incorporating acid compatibilizers, as disclosed in U.S. Pat. No. 
5,321,089 to Cadorniga et al. When compared to the ionomer blend balls, 
the balls of the invention provided a decrease in Shore D hardness for 
improved feel, comparable initial velocity, and equivalent or improved 
durability. 
TABLE I 
______________________________________ 
Ingredients 1 2 3 
______________________________________ 
Surlyn 7940.sup.1 
55 55 55 
Surlyn 8320.sup.2 
45 -- -- 
Quantum 719-009.sup.3 
-- 45 45 
Fusabond MG-197D.sup.4 
-- -- 10 
White Concentrate 
5 5 5 
Shore D Hardness 
64.3 62.4 60.9 
Initial Velocity-fps 
252.8 251.0 251.0 
Durability Test 
600 hits 100 hits 550 hits 
First Failure at 
Durability Test 
650 hits 250 hits 800 hits 
50% Failure at 
______________________________________ 
.sup.1 lithium ionomer containing about 12 to about 17% acid 
.sup.2 sodium ionomer containing about 9 to about 12% acid 
.sup.3 Ethylene 19% nbutyl acrylate from Quantum Chemical. 
.sup.4 Ethylenevinyl acetate functionalized with 1% maleic anhydride from 
Du Pont Canada. 
While it is apparent that the invention disclosed herein is well calculated 
to fulfill the objects stated above, it will be appreciated that numerous 
modifications and embodiments may be devised by those skilled in the art. 
Therefore, it is intended that the appended claims cover all such 
modifications and embodiments as falling within the true spirit and scope 
of the present invention.