U.S. patent application number 11/874633 was filed with the patent office on 2008-02-14 for golf ball and thermoplastic material.
This patent application is currently assigned to CALLAWAY GOLF COMPANY. Invention is credited to MARK L. BINETTE, THOMAS J. III KENNEDY.
Application Number | 20080039235 11/874633 |
Document ID | / |
Family ID | 38119525 |
Filed Date | 2008-02-14 |
United States Patent
Application |
20080039235 |
Kind Code |
A1 |
KENNEDY; THOMAS J. III ; et
al. |
February 14, 2008 |
GOLF BALL AND THERMOPLASTIC MATERIAL
Abstract
Disclosed herein is novel thermoplastic material and a golf ball
utilizing the thermoplastic material of the invention. The golf
ball (10) preferably comprises a core (12), a cover (16) and,
optionally, a boundary layer (14). At least one of the core (12),
cover (16) or boundary layer (14) of the golf ball (10) comprises a
thermoplastic material according to the invention. The
thermoplastic material comprises a partially to highly neutralized
blend of acid and alkyl acrylate copolymers, which additionally
comprise a fatty acid or fatty acid salt. A golf ball comprising a
component that incorporates the thermoplastic material of the
invention has a soft feel and resilience that is maintained or
improved compared to a standard golf ball.
Inventors: |
KENNEDY; THOMAS J. III;
(WILBRAHAM, MA) ; BINETTE; MARK L.; (LUDLOW,
MA) |
Correspondence
Address: |
CALLAWAY GOLF C0MPANY
2180 RUTHERFORD ROAD
CARLSBAD
CA
92008-7328
US
|
Assignee: |
CALLAWAY GOLF COMPANY
2180 RUTHERFORD ROAD
CARLSBAD
CA
92008-7328
|
Family ID: |
38119525 |
Appl. No.: |
11/874633 |
Filed: |
October 18, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11673388 |
Feb 9, 2007 |
|
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|
11874633 |
Oct 18, 2007 |
|
|
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11276199 |
Feb 17, 2006 |
7175543 |
|
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11673388 |
Feb 9, 2007 |
|
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10905925 |
Jan 26, 2005 |
7156755 |
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11276199 |
Feb 17, 2006 |
|
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Current U.S.
Class: |
473/374 |
Current CPC
Class: |
C08L 23/0869 20130101;
A63B 37/0065 20130101; A63B 37/0033 20130101; C08K 5/098 20130101;
A63B 37/0031 20130101; A63B 37/0064 20130101; C08L 2205/02
20130101; C08L 23/0876 20130101; A63B 37/0043 20130101; A63B
37/0045 20130101; C08K 5/09 20130101; A63B 37/0003 20130101; A63B
37/0038 20130101; C08L 23/0876 20130101; C08K 5/09 20130101; C08L
2666/06 20130101; C08L 23/08 20130101 |
Class at
Publication: |
473/374 |
International
Class: |
A63B 37/06 20060101
A63B037/06 |
Claims
1. A golf ball comprising: a core having a diameter ranging from
1.35 inches to 1.64 inches; a boundary layer disposed over the
core, the boundary layer composed of a thermoplastic material
comprising a first copolymer comprising an alpha olefin and an
alpha, beta-unsaturated carboxylic acid, a second copolymer of an
alpha olefin and an alkyl acrylate, and a fatty acid or salt of a
fatty acid, wherein the thermoplastic material is partially to
highly neutralized; and a cover disposed over the boundary
layer.
2. The golf ball according to claim 1 wherein alpha-olefin of the
thermoplastic material the is ethylene.
3. The golf ball according to claim 1 wherein the thermoplastic
material is from about 10 to about 100 percent neutralized.
4. The golf ball according to claim 1 wherein the fatty acid or
fatty acid salt of the thermoplastic material comprises from about
10 to about 60 parts by weight of thermoplastic material.
5. The golf ball according to claim 1 wherein the fatty acid salt
of the thermoplastic material is a metal stearate.
6. The golf ball according to claim 1 wherein the metal stearate of
thermoplastic material is selected from the group consisting of
calcium stearate, magnesium stearate, zinc stearate, barium
stearate, aluminum stearate, lithium stearate and sodium
stearate.
7. The golf ball according to claim 1 wherein the thermoplastic
material further comprises a second fatty acid or fatty acid
salt.
8. A golf ball comprising: a core having a diameter ranging from
1.35 inches to 1.64 inches; a boundary layer disposed over the
core, the boundary layer composed of a thermoplastic material
comprising a first copolymer comprising an alpha olefin and an
alpha, beta-unsaturated carboxylic acid, a second copolymer of an
ethylene and an alkyl acrylate, and a fatty acid or salt of a fatty
acid, wherein the thermoplastic material is neutralized from 50% to
100%; and a cover disposed over the boundary layer.
9. The golf ball according to claim 8 wherein the thermoplastic
material comprises from about 10 to about 60 parts by weight fatty
acid or fatty acid salt.
10. The golf ball according to claim 8 wherein the fatty acid salt
is a metal stearate.
11. The golf ball according to claim 10 wherein the metal stearate
is selected from the group consisting of calcium stearate,
magnesium stearate, zinc stearate, barium stearate, aluminum
stearate, lithium stearate and sodium stearate.
12. A golf ball comprising: a core having a diameter ranging from
1.35 inches to 1.64 inches; a boundary layer disposed over the
core, the boundary layer composed of a thermoplastic material
comprising a first copolymer comprising an alpha olefin, an alpha,
beta-unsaturated carboxylic acid and a softening comonomer, a
second copolymer of an alpha olefin and an alkyl acrylate, and a
fatty acid or salt of a fatty acid, wherein the thermoplastic
material is partially to highly neutralized; and a cover disposed
over the boundary layer.
13. The golf ball according to claim 12 wherein the cover is
composed of a blend of ionomers and at least one of the ionomers is
a high acid ionomer.
14. The golf ball according to claim 12 wherein the cover is
composed of a polyurethane material.
15. The golf ball according to claim 12 wherein the core is filled
with a liquid.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The Present application is a continuation of U.S. patent
application Ser. No. 11/673,388, filed on Feb. 9, 2007, which is a
continuation of U.S. patent application Ser. No. 11/276,199 filed
on Feb. 17, 2006, now U.S. Pat. No. 7,175,543, which is a
continuation-in-part application of U.S. patent application Ser.
No. 10/905,925, filed on Jan. 26, 2005, now U.S. Pat. No.
7,156,755.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a thermoplastic material
and to its use in a golf ball.
[0005] 2. Description of the Related Art
[0006] Traditional golf ball covers have been comprised of balata
or blends of balata with elastomeric or plastic materials.
Balata-related covers, often referred to as soft balata covers, are
relatively soft and flexible. Upon impact, soft balata covers
compress against the surface of the club producing high spin.
Consequently, these soft and flexible covers provide an experienced
golfer with the ability to apply a spin to control the ball in
flight in order to produce a draw or a fade, or a backspin which
causes the ball to "bite" or stop abruptly on contact with the
green. Moreover, soft balata covers produce a soft "feel" to the
low handicap player. Such playability properties as, workability
and feel are particularly important in short iron play with low
swing speeds and are exploited significantly by relatively skilled
players.
[0007] Despite all the benefits of balata, balata-related golf ball
covers are easily cut and/or damaged if hit improperly. Golf balls
produced with balata or balata-containing cover compositions
therefore have a relatively short lifespan. As a result of this
negative property, balata and its synthetic substitutes,
trans-polybutadiene and trans-polyisoprene, have been essentially
replaced as the cover materials of choice by new cover materials
comprising ionomeric resins.
[0008] Ionomeric resins are polymers containing interchain ionic
bonding. As a result of their toughness, durability and flight
characteristics, various ionomeric resins sold by E.I. du Pont de
Nemours and Company (DuPont), under the trade name "Surlyn7"
(Surlyn7.TM.), and, more recently, by the ExxonMobil Corporation
(ExxonMobil) (see, for example, U.S. Pat. No. 4,911,451), under the
trade name "Iotek" (Iotek.TM.), have become the materials of choice
for the construction of golf ball covers over traditional balata
(trans-polyisoprene, natural or synthetic) rubbers.
[0009] Ionomeric resins are generally ionic copolymers of an olefin
(such as ethylene) and a metal salt of an unsaturated carboxylic
acid (such as acrylic acid, methacrylic acid or maleic acid). Metal
cations such as sodium or zinc are used to neutralize some portion
of the acidic group in the copolymer resulting in a thermoplastic
elastomer exhibiting enhanced properties such as durability for
golf ball cover construction over balata. However, some of the
advantages gained in increased durability have been offset to some
degree by decreases produced in playability. This is because
although ionomeric resins are very durable, they tend to be very
hard when utilized for golf ball cover construction and, thus, lack
the degree of softness required to impart the spin necessary to
control the ball in flight. Since the ionomeric resins are harder
than balata, the ionomeric resin covers do not compress as much
against the face of the club upon impact, thereby producing less
spin. In addition, the harder and more durable ionomeric resins
lack the feel characteristic associated with the softer
balata-related covers.
[0010] As a result, while there are many commercial grades of
ionomers available both from DuPont and ExxonMobil, with a wide
range of properties that vary according to the type and amount of
metal cations, molecular weight, composition of the base resin
(such as relative content of ethylene and methacrylic and/or
acrylic acid groups) and additive ingredients such as reinforcement
agents, or the like, a great deal of research continues in order to
develop a golf ball cover composition exhibiting not only the
improved impact resistance and carrying distance properties
produced by the "hard" ionomeric resins, but also the playability
(for example, "spin", "feel" and the like) characteristics
previously associated with soft balata-related covers, properties
that are still desired by the more skilled golfer.
[0011] Consequently, a number of golf balls have been produced to
address these needs. The different types of materials utilized to
formulate the cores, mantles and covers of these balls dramatically
alter the balls' overall characteristics. In addition,
multi-layered covers containing one or more ionomeric resins have
also been formulated in an attempt to produce a golf ball having
the overall distance, playability and durability characteristics
desired.
[0012] Such formulations are described in U.S. Pat. No. 4,431,193
('193), where a multi-layered golf ball is produced by initially
molding a first cover layer on a spherical core and then adding a
second layer. The first layer consists of a hard, high flexural
modulus resinous material such as Surlyn7.TM. 8940, a sodium ion
based low acid (less than or equal to 16 weight percent methacrylic
acid) ionomeric resin having a flexural modulus of about 51,000
psi. An outer layer of a comparatively soft, low flexural modulus
resinous material such Surlyn7.TM. 9020 is molded over the inner
cover layer. Surlyn7.TM. 9020 is a zinc ion based low acid (10
weight percent methacrylic acid) ionomeric resin having a flexural
modulus of about 14,000 psi.
[0013] The '193 patent also teaches that the hard, high flexural
modulus resin, which comprises the first layer, provides for a gain
in coefficient of restitution over the coefficient of restitution
of the core. The increase in the coefficient of restitution
provides a ball that attains or approaches the maximum initial
velocity limit of 255 feet per second, as provided by the United
States Golf Association (USGA) rules. The relatively soft, low
flexural modulus outer layer provides for the advantageous feel and
playing characteristics of a balata covered golf ball.
[0014] In various attempts to produce a durable, high spin golf
ball, the golfing industry has blended the hard ionomeric resins
with a number of softer ionomeric resins. For example, U.S. Pat.
Nos. 4,884,814 and 5,120,791 are directed to cover compositions
containing blends of hard and soft ionomeric resins. The hard
copolymers typically are made from an olefin and an unsaturated
carboxylic acid. The soft copolymers are generally made from an
olefin, an unsaturated carboxylic acid and an acrylate ester.
However, it has been found that golf ball covers formed from
hard-soft ionomer blends tend to become scuffed more readily than
covers made of a hard ionomeric resin alone. It would be useful to
develop a golf ball having a combination of softness and durability
that is better than the softness-durability combination of a golf
ball cover made from a hard-soft ionomer blend.
[0015] Most professional golfers and good amateur golfers desire a
golf ball that provides distance when hit off a driver, control and
stopping ability on full iron shots as well as high spin on short
"touch and feel" shots. Many conventional golf balls have
undesirable high spin rates on full shots. The excessive spin on
full shots is a sacrifice made in order to achieve more spin on the
shorter touch shots. It would be beneficial to provide a golf ball
that has high spin for touch shots, without generating excessive
spin on full shots, while maintaining or improving some of the
other properties of the golf ball.
BRIEF SUMMARY OF THE INVENTION
[0016] The present invention is directed to a novel thermoplastic
material and to its use in a golf ball as a core, cover or
intermediate layer. The thermoplastic material of the invention
includes a blend of two or more copolymers and fatty acids or salts
of fatty acids. The material of the invention is partially to
highly neutralized (preferably 50 to 100%), and has a greater
coefficient of restitution than other thermoplastic materials.
[0017] One embodiment of the present invention is a golf ball
comprising a core and a cover layer disposed on and, preferably,
covering the core, wherein at least one of the cover and the core
is formed from the thermoplastic material of the invention. The
thermoplastic material of the invention preferably comprises, as
part of the blend, (1) a copolymer comprising an alpha olefin and
an acid, such as ethylene/acrylic acid (an alpha, beta-unsaturated
carboxylic acid), and (2) a copolymer of an alpha olefin and an
alkyl acrylate, such as ethylene/butyl acrylate. Alternatively, the
first copolymer may include an alpha olefin, an acid and a
softening comonomer such as an alkyl acrylate (wherein the first
copolymer is also referred to as a terpolymer). A thermoplastic
material blend of the invention further comprises fatty acids or
fatty acid salts. Exemplary fatty acids or fatty acid salts can
include metal stearates or stearic acids. Other materials such as
metallocene-catalyzed plastomers, urethanes or other materials
known in the art may also be used for thermoplastic material blend
modification as desired.
[0018] In a particularly preferred form of the invention the
thermoplastic material of the invention comprises a blend of two or
more copolymers, wherein the first copolymer is formed from an
alpha olefin having 2 to 8 carbon atoms, and an acid which includes
at least one member selected from the group consisting of alpha,
beta-ethylenically unsaturated mono- or dicarboxylic acids with a
portion of the acid being neutralized with cations, and the second
copolymer is formed from an alpha olefin having 2 to 8 carbon
atoms, and an alkyl acrylate having from 1 to 8 carbon atoms in the
alkyl group. The optional softening comonomer that may be added to
the first copolymer is, preferably, an unsaturated monomer of the
acrylate ester class having from 1 to 21 carbon atoms.
[0019] Another embodiment of the present invention is a golf ball
having a core, boundary layer and cover. The core includes a
polybutadiene mixture, has a diameter ranging from 1.35 inches to
1.64 inches and has a PGA compression ranging from 50 to 90. The
boundary layer is formed over the core and is composed of a
thermoplastic material of the invention. The boundary layer has a
thickness ranging from 0.020 to 0.075 inches and a Shore D hardness
ranging from 50 to 70 as measured according to standard test method
D2240 of the American Society for Testing and Materials
(ASTM-D2240). The cover is formed over the boundary layer. The
cover is composed of a fast chemical reaction aliphatic
polyurethane material formed from reactants that comprise a
polyurethane prepolymer and a polyol. The polyurethane material has
a Shore D hardness ranging from 30 to 60 as measured according to
ASTM-D2240 and a thickness ranging from 0.015 to 0.044 inches. The
polyurethane material of the cover also provides for an aerodynamic
surface geometry.
[0020] Having briefly described the present invention, the above
and further objects, features and advantages thereof will be
recognized by those skilled in the pertinent art from the following
detailed description of the invention when taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0021] FIG. 1 illustrates a perspective view of a golf ball of the
present invention including a cut-away portion showing a core, a
boundary layer and a cover.
[0022] FIG. 2 illustrates a perspective view of a golf ball of the
present invention including a cut-away portion showing a core and a
cover.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention relates to a novel thermoplastic
material and to its use in golf equipment, particularly, a golf
ball 10. As shown in FIG. 1, a three-piece solid golf ball
comprises a core 12, a boundary 14 and a cover 16. As shown in FIG.
2, a two-piece golf ball comprises a core 12 and a cover 16. At
least one of the components of the golf ball comprises a
thermoplastic material of the invention.
[0024] More particularly, the invention provides a neutralized
thermoplastic material comprising a blend of (1) a copolymer
comprising an alpha olefin and an alpha, beta-unsaturated
carboxylic acid (an acid copolymer referred to as EX), (2) a
copolymer of an alpha olefin and an alkyl acrylate (an alkyl
acrylate copolymer referred to as EY) and 3) a fatty acid or salt
of a fatty acid. The first copolymer may also include a softening
comonomer such as an alkyl acrylate, which copolymer (or
terpolymer) is referred to as EXY. Other materials, including but
not limited to, urethanes and the like may be used to modify the
blend The acid copolymer of a thermoplastic material of the
invention may contain anywhere from 1 to 30% by weight acid. A high
acid copolymer containing greater than 16% by weight acid,
preferably, from about 17 to about 25 weight % acid and, more
preferably, about 20 weight % acid, or a low acid copolymer
containing 16% by weight acid or less may be used as desired. The
acid copolymer is neutralized with a metal cation of a salt (a
metal cation salt) capable of ionizing or neutralizing the
copolymer to the extent desired, generally from about 10 to 100%,
preferably, from 30 to 100% and, more preferably, from 40 to 90%.
The amount of metal cation salt needed varies with the extent of
neutralization desired.
[0025] The acid copolymer is preferably made up of from about 10 to
about 30% 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 alpha olefin has from 2
to 10 carbon atoms and is, preferably, ethylene. The unsaturated
carboxylic acid is an acid having from about 3 to 8 carbon atoms.
Examples of such acids include, but are not limited to, acrylic
acid, methacrylic acid, ethacrylic acid, chloroacrylic acid,
crotonic acid, maleic acid, fumaric acid and itaconic acid, with
acrylic acid and methacrylic acid being preferred. The optional
softening comonomer, such as an alkyl acrylate, has, e.g., from 1
to 8 carbon atoms in the alkyl group. The acid copolymer broadly
contains from 1 to about 30% by weight unsaturated carboxylic acid,
from about 70 to about 99% by weight ethylene and from 0 to about
40% by weight of a softening comonomer.
[0026] Examples of acid copolymers suitable for use in a
thermoplastic material of the invention include, but are not
limited to, an ethylene/acrylic acid copolymer, an
ethylene/methacrylic acid copolymer, an ethylene/itaconic acid
copolymer, an ethylene/maleic acid copolymer, an
ethylene/methacrylic acid/alkyl acrylate terpolymer, or an
ethylene/acrylic acid/alkyl acrylate terpolymer.
[0027] Acid copolymers are well known in the golf ball art.
Examples of acid copolymers that fulfill the criteria set forth
above include, but are not limited to, those sold under the trade
names Escor.TM. (ethylene/acrylic acid copolymers) and Iotek.TM.
(ethylene/acrylic acid/acrylate terpolymers) by ExxonMobil, namely,
Escor.TM.959, Escor.TM.960, Escor.TM. AT325 and Iotek.TM. 7510.
Other examples of acid copolymers include those sold under the
trade name Primacor.TM. (ethylene/acrylic acid copolymers) by Dow
Chemical Company, namely Primacor.TM. 5980I and Primacor.TM. 3340I.
Other acid copolymers that may be used include ethylene/methacrylic
acid copolymers such as sold under the trade names Surlyn.TM. and
Nucrel.TM. by DuPont. Surlyn.TM. copolymers are neutralized with
zinc, sodium or lithium ions. Nucrel.TM. copolymers are inherently
flexible like ethylene vinyl acetate (EVA) copolymers and offer
desirable performance characteristics similar to those of
Surlyn.TM.. Nucrel.TM. copolymers are produced by reacting ethylene
and methacrylic acid in the presence of free radical initiators. A
branched, random ethylene/methacrylic acid (EMAA) copolymer is
produced thereby. Carboxyl groups are distributed along the polymer
chain and interact with carboxyl groups on adjacent molecules to
form a weakly cross-linked network through hydrogen bonding.
Nucrel.TM. and Surlyn.TM. terpolymers are also available for use in
a thermoplastic material of the invention.
[0028] Acid copolymers of a thermoplastic material of the invention
are neutralized to a desired percentage through the use of metal
cation salts. The salts utilized are those that provide the metal
cations capable of neutralizing, to various extents, the carboxylic
acid groups of the acid copolymer. These salts include, for
example, acetate, oxide or hydroxide salts of lithium, calcium,
zinc, sodium, potassium, nickel, magnesium, aluminum, zirconium or
manganese.
[0029] Some examples of salts comprising lithium cations are
lithium hydroxide monohydrate, lithium hydroxide, lithium oxide and
lithium acetate. Salts comprising calcium cations include calcium
hydroxide, calcium acetate and calcium oxide. Suitable salts
comprising zinc cations are zinc acetate dihydrate, zinc acetate or
a blend of zinc oxide and acetic acid. Examples of salts comprising
sodium cations include sodium hydroxide and sodium acetate.
Similarly, salts comprising potassium cations include potassium
hydroxide and potassium acetate. Suitable salts comprising nickel
cations are nickel acetate, nickel oxide and nickel hydroxide.
Salts comprising magnesium cations include magnesium oxide,
magnesium hydroxide and magnesium acetate. Salts comprising
manganese cations include manganese acetate and manganese
oxide.
[0030] Additionally a wide variety of pre-neutralized acid polymers
are commercially available for a thermoplastic material of the
invention. These pre-neutralized acid polymers include both hard
and soft pre-neutralized ionomeric resins as well as both low and
high acid pre-neutralized ionomeric resins.
[0031] Hard (high modulus) pre-neutralized ionomeric resins include
those having a hardness greater than 50 on the Shore D scale as
measured in accordance with ASTM D-2240 and a flexural modulus from
about 15,000 to about 70,000 psi as measured in accordance with
ASTM standard test method D-790 (ASTM D-790).
[0032] Soft (low modulus) pre-neutralized ionomeric resins are
generally acrylic acid or methacrylic acid based. One example of a
soft pre-neutralized ionomer resin comprises a zinc based ionomer
made from an acrylic acid polymer and unsaturated monomers of the
acrylate ester class. The soft ionomeric resins generally have a
hardness from about 20 to about 50 or, preferably, from about 30 to
about 40 as measured on the Shore D scale and a flexural modulus
from about 2,000 to about 15,000 psi or, preferably, from about
3,000 to 10,000 psi as measured in accordance with ASTM D-790.
Examples of hard and soft ionomeric resins include those sold under
the Iotek.TM. and Surlyn.TM. trade names.
[0033] The golf ball 10 has at least one layer composed of the
thermoplastic material of the invention comprising about 10 to
about 95% by weight of at least one neutralized acid copolymer and,
preferably, from about 15 to about 90% acid copolymer.
[0034] Generally, ethylene/alkyl acrylate copolymers include
ethylene and acrylic or methacrylic esters of linear, branched or
cyclic alkanols. Preferably, the copolymers contain from about 1 to
about 35 weight % alkyl acrylate and from about 99 to about 65
weight % ethylene.
[0035] Examples of ethylene/alkyl acrylate copolymers that may be
used include, among others, ethylene/ethyl acrylate (EEA),
ethylene/methyl acrylate (EMA) and ethylene/butyl acrylate (EBA).
EEA copolymers are made by the polymerization of ethylene units
with randomly distributed ethylene acrylate (EA) monomer groups.
The copolymers contain up to about 30% by weight of EA. The
copolymers are tough and flexible having a relatively high
molecular weight. The copolymers have good flexural fatigue and low
temperature properties (down to -65.degree. C.). In addition, EEA
resists environmental stress cracking as well as ultraviolet (UV)
radiation. Examples of EEA copolymers include those sold under the
trade name Bakelite.TM. by the Union Carbide Corporation. EEA is
similar to ethylene vinyl acetate (EVA) in its density-property
relationships and high-temperature resistance. In addition, like
EVA, EEA is not resistant to aliphatic and aromatic
hydrocarbons.
[0036] EMA copolymers contain up to about 30% by weight of methyl
acrylate and yield blown films having rubberlike limpness and high
impact strength. These copolymers may be useful in coating and
laminating applications as a result of their good adhesion to
commonly used substrates. EMA also has good heat-seal
characteristics.
[0037] EMA copolymers are manufactured by reacting, at high
temperatures and pressures, methyl acrylate monomers with ethylene
and free radical initiators. Polymerization occurs such that the
methyl acrylate forms random pendant groups on the polyethylene
backbone. The acrylic functionality decreases polymer crystallinity
and increases polarity, enhancing polymer properties. These
properties depend on molecular weight (determined, for example, by
melt index) and percent crystallinity. Percent crystallinity is
determined by the extent of methyl acrylate comonomer
incorporation. As the methyl acrylate content increases, the film
becomes softer, tougher and easier to heat seal.
[0038] EMA films have low moduli (generally less than 10,000 psi),
low melting points and good impact strengths. In addition, EMA
copolymers are highly polar and, as a result, are compatible with
olefinic and other polymers. They adhere well to many substrates
including low density polyethylene (LDPE), linear low density
polyethylene (LLDPE) and EVA.
[0039] Examples of EMA copolymers for use in the golf ball
components of the present invention include those sold under the
trade names Optema.TM. or Escor.TM. by ExxonMobil. Optema.TM. and
Escor.TM. are thermally stable polymers that will accept up to 65%
or more fillers and pigments without losing their properties. These
copolymers are more thermally stable than EVA and can be extruded
or molded over a range of temperatures from 275 to 625.degree. F.
(compared to the limit of 450.degree. F. for EVA copolymers). EMA
copolymers are generally not corrosive as compared to EVA and EAA
copolymers.
[0040] EBA copolymers can also be included in a thermoplastic
material of the invention. These are generally similar to EMA
copolymers with improved low temperature impact strength and high
clarity. For example, the EBA copolymer sold under the trade name
EBAC.TM. by the Chevron Corporation is stable at high temperatures
and may be processed as high as 600.degree. F.
[0041] Metal cation salts may also be utilized to neutralize
ethylene/alkyl acrylate copolymers as a source of the corresponding
carboxylic acid. The salts to be used are those salts that provide
the metal cations capable of hydrolyzing and neutralizing, to
various extents, the carboxylic acid ester groups of the
copolymers. This converts the alkyl ester into a metal salt of the
acid. These metal cation salts include, but are not limited to,
oxide, carbonate or hydroxide salts of alkali metals such as
lithium, sodium, potassium or mixtures thereof. Some examples
hydroxide salts of alkali metals include, but are not limited to,
lithium hydroxide monohydrate, lithium hydroxide, lithium
carbonate, lithium oxide, sodium hydroxide, sodium oxide, sodium
carbonate, potassium hydroxide, potassium oxide and potassium
carbonate.
[0042] The amount of metal cation salt, preferably, an alkali metal
cation salt reacted with an ethylene/alkyl acrylate copolymer
varies depending upon such factors as the reactivity of the salt
and copolymer used, reaction conditions (such as temperature,
pressure, moisture content and the like) and the desired level of
conversion. Preferably, the reaction occurs through saponification,
wherein the carboxylic acid ester groups of the ethylene/alkyl
acrylate copolymer are converted by alkaline hydrolysis to form the
salt of the acid and alcohol. Examples of such reactions are set
forth in U.S. Pat. Nos. 3,970,626, 4,638,034 and 5,218,057, which
are incorporated herein by reference.
[0043] The products of the conversion reaction are an alkanol (the
alkyl group of which comes from the alkyl acrylate comonomer) and a
terpolymer of ethylene, alkyl acrylate, and an alkali metal salt of
the (meth) acrylic acid. The degree of conversion or saponification
is variable depending on the amount of alkali metal cation salt
used and the saponification conditions. Generally, from about 10 to
about 60% of the ester groups are converted during the
saponification reaction. The alkanol and other by products can be
removed by normal separation processes leaving the remaining metal
cation neutralized (or hydrolyzed) ester-based ionomer resin
reaction product.
[0044] Alternatively, the ethylene alkyl acrylate copolymer
included in the invention can be commercially obtained in a
pre-neutralized or saponified condition. For example, a number of
metal cation neutralized ester-based ionomer resins produced under
the saponification process of U.S. Pat. No. 5,218,057 are available
from the Chevron Corporation.
[0045] Additional examples of the preferred copolymers that fulfill
the criteria set forth above are a series of acrylate copolymers
that are commercially available from ExxonMobil, such as Optema.TM.
ethylene methyl acrylates and Enable.TM. ethylene butyl acrylates;
Elvaloy.TM. ethylene butyl acrylates available from DuPont, and
Lotryl.TM. ethylene butyl acrylic esters available from Atofina
Chemical.
[0046] The acrylate ester is preferably an unsaturated monomer
having from 1 to 21 carbon atoms, which serves as a softening
comonomer. The acrylate ester preferably is methyl, ethyl,
n-propyl, n-butyl, n-octyl, 2-ethylhexyl or 2-methoxyethyl
1-acrylate and most preferably is methyl acrylate or n-butyl
acrylate. Another suitable type of softening comonomer is an alkyl
vinyl ether selected from the group consisting of n-butyl, n-hexyl,
2-ethylhexyl and 2-methoxyethyl vinyl ethers.
[0047] The acrylate ester-containing ionic copolymer or copolymers
used in golf ball components can be obtained by neutralizing
commercially available acrylate ester-containing acid copolymers
such as poly(ethylene/methyl acrylate/acrylic acid) terpolymers
sold by ExxonMobil under the trade name Escor.TM. ATX or
poly(ethylene/butyl acrylate/methacrylic acid) terpolymers sold by
DuPont under the trade name Nucrel.TM.. The acid groups of these
materials and blends thereof are neutralized with one or more of
various metal cation salts that include zinc, sodium, magnesium,
lithium, potassium, calcium, manganese, nickel and the like. The
extent of neutralization can range from 10 to about 100%,
preferably from about 30 to about 100% or, more preferably, from
about 40 to about 90%. Generally, a higher degree of neutralization
results in a harder and tougher thermoplastic material.
[0048] The fatty acids and salts of fatty acids generally comprise
fatty acids neutralized with metal cations. The fatty acids can be
saturated or unsaturated fatty acids and are generally composed of
a chain of alkyl groups containing from about 2 to about 80 carbon
atoms, preferably from about 4 to about 30, usually an even number,
and terminate with a carboxyl (--COOH) group. The general formula
for fatty acids (except for acetic acid) is
CH.sub.3(CH.sub.2).sub.XCOOH, wherein the carbon atom count
includes the carboxyl group and X is from about 4 to about 30
carbon atoms. Examples of fatty acids suitable for use include, but
are not limited to, stearic acid, oleic acid, palmitic acid,
pelargonic acid, lauric acid, butyric acid, valeric acid, caproic
acid, caprylic acid, capric acid, myristic acid, margaric acid,
arachidic acid, behenic acid, lignoceric acid, cerotic acid,
carboceric acid, montanic acid and melissic acid. Such fatty acids
are preferably neutralized with metal cations such as zinc,
calcium, magnesium, barium, sodium, lithium, aluminum or
combinations thereof, although other metal cations may also be
used. The metal cations are generally from metal cation salts that
neutralize, to various extents, the carboxylic acid groups of the
fatty acids. Examples of metal cation salts include sulfate,
carbonate, acetate and hydroxylate salts of metals such as zinc,
calcium, magnesium and barium. Examples of the fatty acid salts
that may be utilized in a thermoplastic material of the invention
include, but are not limited to, metal stearates, laureates,
oleates, palmitates, pelargonates and the like such as zinc
stearate, calcium stearate, magnesium stearate, barium stearate and
so forth. Metal stearates are known in the art and are commercially
available from various manufacturers.
[0049] Highly neutralized blends of copolymers used to form the
golf ball components of the present invention can be produced by
reacting the two copolymers with various amounts of the metal
cation salts at a temperature above the crystalline melting point
of the copolymers, for example, from about 200 to about 500.degree.
F. and, preferably, from about 250 to about 425.degree. F. under
high shear conditions at a pressures of from about 100 to 10,000
psi. Other well known blending techniques in the art may also be
used. The amount of metal cation salt used to produce the highly
neutralized blend of copolymers is the quantity that provides a
sufficient amount of the metal cations to neutralize a desired
percentage of the carboxylic acid groups of the acid copolymer. The
copolymers can be blended before or after neutralization, or they
can be mixed and neutralized at the same time (that is, the
copolymers, metal cation salts and fatty acids or salts of fatty
acids are mixed together). The fatty acids or salts of fatty acids
are added in the desired amounts, generally from about 5 to about
100 parts by weight, preferably from about 10 to about 60 parts by
weight, more preferably from about 20 to about 50 parts by weight
and even more preferably from about 30 to about 40 parts by
weight.
[0050] The various compositions of the present invention may be
produced according to conventional melt blending procedures. In a
preferred embodiment, the copolymers are blended in a Banbury.TM.
type mixer, two-roll mill or extruder prior to neutralization.
After blending, neutralization then occurs as the polymers are in a
melt or molten state within the Banbury.TM. type mixer, two-roll
mill or extruder. The blended composition is then formed into
slabs, pellets or the like and maintained in such a state until
molding is desired. Alternatively, a simple dry blend of the
pelletized or granulated copolymers, which have previously been
neutralized to a desired extent (and colored masterbatch, if
desired) 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 inorganic fillers may be added and
uniformly mixed in before initiation of the molding process.
[0051] The compatibility of a metallocene-catalyzed copolymer with
an acid copolymer results in a thermoplastic material blend having
superior properties over standard ionomeric resin blends as shown
by the results provided in the Examples detailed below.
[0052] Additional materials may also be added to a thermoplastic
material of the invention when utilized for golf equipment so long
as such materials do not substantially reduce the playability
properties of the equipment. Exemplary materials include dyes such
as Ultramarine Blue.TM. sold by Whitaker, Clark& Daniels,
Incorporated (see U.S. Pat. No. 4,679,795), pigments such as
titanium dioxide, zinc oxide, barium sulfate and zinc sulfate, UV
absorbers, antioxidants, antistatic agents, and stabilizers.
Moreover, the ball cover compositions utilizing the thermoplastic
material of the invention may also contain softening agents such as
those disclosed in U.S. Pat. Nos. 5,312,857 and 5,306,760.
Exemplary softeners include plasticizers, processing acids, and the
like, and reinforcing materials such as glass fibers and inorganic
fillers, as long as the desired properties of the golf ball
produced are not impaired.
[0053] Various fillers may be added to golf ball compositions to
reduce manufacturing costs, to increase or decrease weight, to
reinforce the thermoplastic material, adjust ball layer density or
flex modulus, aid in ball mold release and/or adjust the melt flow
index of the thermoplastic material and the like. Examples of heavy
weight fillers include titanium, tungsten, aluminum, bismuth,
nickel, molybdenum, iron, steel, lead, copper, brass, boron, boron
carbide whiskers, bronze, cobalt, beryllium, zinc, tin, metal
oxides (such as zinc oxide, iron oxide, aluminum oxide, titanium
oxide, magnesium oxide, zirconium oxide) and metal stearates (such
as zinc stearate, calcium stearate, barium stearate, lithium
stearate and magnesium stearate). Other preferred fillers include
limestone (ground calcium or magnesium carbonate) and ground flash
filler.
[0054] Fillers that may be used in the layers of a golf ball (other
than the outer cover layer) are typically in a finely divided form
such as, for example, in a particle size generally less than about
20 U.S. standard mesh and, preferably, less than about 100 U.S.
standard mesh (except for fibers and flock, which are generally
elongated). Flock and fiber sizes should be small enough to
facilitate processing. Filler particle size will depend upon the
desired effect, cost, ease of addition and dusting considerations.
A filler for a golf ball layer preferably is selected from the
group consisting of precipitated hydrated silica, clay, talc,
asbestos, glass fibers, aramid fibers, mica, calcium metasilicate,
barium sulfate, zinc sulfide, lithopone, silicates, silicon
carbide, diatomaceous earth, polyvinyl chloride, carbonates,
metals, metal alloys, tungsten carbide, metal oxides, metal
stearates, particulate carbonaceous materials, micro-balloons and
combinations thereof. Non-limiting examples of suitable fillers,
their densities or specific gravities (spec. grav.) and preferred
uses are listed in Table 1: TABLE-US-00001 TABLE 1 FILLERS FILLER
TYPE SPEC. GRAV. COMMENT Precipitated hydrated silica 2.00 1, 2
Clay 2.62 1, 2 Talc 2.85 1, 2 Asbestos 2.50 1, 2 Glass fibers 2.55
1, 2 Aramid fibers (KEVLAR) 1.44 1, 2 Mica 2.80 1, 2 Calcium
metasilicate 2.90 1, 2 Barium sulfate 4.60 1, 2 Zinc sulfide 4.10
1, 2 Lithopone 4.2-4.3 1, 2 Silicates 2.10 1, 2 Silicon carbide
platelets 3.18 1, 2 Silicon carbide whiskers 3.20 1, 2 Tungsten
carbide 15.60 1 Diatomaceous earth 2.30 1, 2 Polyvinyl chloride
1.41 1, 2 CARBONATES Calcium carbonate 2.71 1, 2 Magnesium
carbonate 2.20 1, 2 METAL AND ALLOYS (POWDERS) Titanium 4.51 1
Tungsten 19.35 1 Aluminum 2.70 1 Bismuth 9.78 1 Nickel 8.90 1
Molybdenum 10.20 1 Iron 7.86 1 Steel 7.8-7.9 1 Lead 11.40 1, 2
Copper 8.94 1 Brass 8.2-8.4 1 Boron 2.34 1 Boron carbide whiskers
2.52 1, 2 Bronze 8.70-8.74 1 Cobalt 8.92 1 Beryllium 1.84 1 Zinc
7.14 1 Tin 7.31 1 METAL OXIDES Zinc oxide 5.57 1, 2 Iron oxide 5.10
1, 2 Aluminum oxide 4.00 Titanium oxide 3.9-4.1 1, 2 Magnesium
oxide 3.3-3.5 1, 2 Zirconium oxide 5.73 1, 2 METAL STEARATES Zinc
stearate 1.09 3, 4 Calcium stearate 1.03 3, 4 Barium stearate 1.23
3, 4 Lithium stearate 1.01 3, 4 Magnesium stearate 1.03 3, 4
PARTICULATE CARBONACEOUS Graphite 1.5-1.8 1, 2 Carbon black 1.80 1,
2 Natural bitumen 1.2-1.4 1, 2 Cotton flock 1.3-1.4 1, 2 Cellulose
flock 1.15-1.5 1, 2 Leather fiber 1.2-1.4 1, 2 MICRO BALLOONS Glass
0.15-1.1 1, 2 Ceramic 0.2-0.7 1, 2 Fly ash 0.6-0.8 1, 2 COUPLING
AGENTS Titanates 0.95-1.17 Zirconates 0.92-1.11 Silane 0.95-1.2
Comments: 1. Particularly useful for adjusting density of the cover
layer. 2. Particularly useful for adjusting flex modulus of the
cover layer. 3. Particularly useful for adjusting mold release of
the cover layer. 4. Particularly useful for increasing melt flow
index of the cover layer.
[0055] Most fillers except for metal stearates would be expected to
reduce the melt flow index of an injection molded golf ball cover
layer.
[0056] The amount of filler used in a golf ball layer is primarily
a function of the weight and distribution requirements of the
ball.
[0057] Fillers may be added to any or all layers of a golf ball.
Such fillers may be used to adjust the properties of a golf ball
layer, reinforce the layer or for any other purpose. In a
thermoplastic material blend of the invention, reinforcing fillers
may be used without detracting from or significantly reducing the
coefficient of restitution (COR) of the material in a golf ball
layer.
[0058] Together, the core 12 of the golf ball (and any optional
core layers) and its cover layer 16 or layers 14 preferably combine
to form a ball having a diameter of 1.680 inches or more, the
minimum diameter permitted by the rules of the USGA, and weighing
no more than 1.62 ounces for a regulation golf ball. Oversize golf
balls may also be produced, if desired, using a thermoplastic
material blend of the invention.
[0059] In another embodiment of the invention, the golf ball may be
a one-piece or unitary construction golf ball comprising the blend
of the invention. A thermoplastic material blend of the invention
provides for a very durable golf ball. Such a golf ball may be
painted or may have a clear coat or other markings if desired.
[0060] In a particularly preferred embodiment of the invention, the
golf ball has a dimple pattern that provides coverage of 65% or
more. The golf ball typically is coated with a durable,
abrasion-resistant and relatively non-yellowing finish coat.
[0061] A golf ball and its components can be produced by molding
processes that include, but are not limited to, those that are well
known in the art. For example, golf ball components can be produced
by injection molding, reaction injection molding, liquid injection
and/or compression molding the partially to highly neutralized
thermoplastic material blend of the invention as a golf ball core,
core layer, cover layer and so forth. One or more layers of a golf
ball may comprise the partially to highly neutralized blend
according to the invention. Other layers of a golf ball may be made
of the same or different materials and may comprise any suitable
material or blend thereof known in the art.
[0062] The thermoplastic material of the invention preferably has a
Shore D hardness of from about 30 to about 80 Shore D as desired.
Additionally, a golf ball core, intermediate ball or finished ball
may have a PGA compression of from about 0 to about 160.
[0063] After a golf ball has been molded, it may undergo various
further processing steps such as buffing, painting and marking as
disclosed in U.S. Pat. No. 4,911,451.
[0064] The present invention is further illustrated by the
following examples in which the parts of the specific ingredients
are by weight. It is to be understood that the present invention is
not limited to the examples as various changes and modifications
may be made to the invention without departing from the spirit and
scope thereof.
EXAMPLES
Example 1
[0065] Three different highly neutralized blends of
olefin/acid/acrylate terpolymers and olefin/acrylate copolymers
containing metal stearates were produced and formed into neat
spheres. The neat spheres were tested for compression and
coefficient of restitution. The terpolymer was an ethylene/acrylic
acid/methyl acrylate terpolymer, and the copolymer was an
ethylene/butyl acrylate copolymer. The terpolymer was used alone
and in a blend with the copolymer. A terpolymer control with no
metal stearate added was also produced. Each of the blends was
neutralized to 100% using Mg(OH).sub.2. Metal stearate (magnesium
stearate) was added to the terpolymer and the terpolymer-copolymer
blend. The results are shown in Table 2 below.
[0066] Coefficient of restitution (COR) was measured by firing a
resulting golf ball via an air cannon (at a velocity of 125 feet
per second) toward a steel plate positioned 12 feet from the muzzle
of the cannon. The rebound velocity was then measured. The rebound
velocity was divided by the velocity of the golf ball leaving the
air cannon to give the COR.
[0067] The term "compression" as used in the golf ball art
generally defines the overall deflection that a golf ball undergoes
when subjected to a compressive load. For example, compression
indicates the amount of change in a golf ball's shape upon
striking. The development of solid core technology in two-piece or
multi-piece solid balls has allowed for much more precise control
of compression in comparison to thread wound, three-piece balls.
This result is because in the manufacture of solid core golf balls,
the amount of deflection or deformation is precisely controlled by
the chemical formula used in making the core(s). This differs from
thread wound, three-piece golf balls in which compression is
controlled in part by the winding process of the elastic thread.
Thus, two- and multi-piece (or component) solid core golf balls
exhibit much more consistent compression readings than balls having
thread wound cores (e.g., thread wound three-piece golf balls). In
the past, PGA compression related to a scale of golf ball
compression from 0 to 200. The lower the PGA compression value, the
softer the feel of the ball upon striking. In practice, tournament
quality balls have PGA compression ratings around 40 to 110, and
preferably around 50 to 100.
[0068] In determining PGA compression using the 0 to 200 scale, a
standard force is applied to the external surface of the ball. A
ball that exhibits no deflection (0.0 inches of deflection) is
rated 200 and a ball that deflects 0.2 inches is rated 0. Every
change of 0.001 inch in deflection represents a 1 point drop in
compression value. Consequently, a ball that deflects 0.1 inches
(100.times.0.001 inches) has a PGA compression value of 100 and a
ball that deflects 0.110 inches (110.times.0.001 inches) has a PGA
compression value of 90.
[0069] In order to assist in the determination of PGA compression,
several devices have been employed in the art. For example, PGA
compression is determined by a golf ball compression tester
fashioned in the form of a press with an upper and lower anvil. The
upper anvil is at rest against a 200 pound (lbs) die spring, and
the lower anvil is movable through 0.300 inches by means of a crank
mechanism. In the open position, the gap between the anvils is
1.780 inches, allowing a clearance of 0.200 inches for insertion of
the ball. As the lower anvil is raised by the crank mechanism, it
compresses the ball against the upper anvil, with such compression
occurring during the last 0.200 inches of lower anvil stroke. The
golf ball then loads the upper anvil, which in turn loads the die
spring. The equilibrium point of the upper anvil is measured by a
dial micrometer. When the upper anvil is deflected by the golf ball
more than 0.100 in (a lesser extent of deflection is simply
regarded as zero compression), the reading on the micrometer dial
is referred to as the compression of the ball. In practice,
tournament quality golf balls have PGA compression ratings around
80 to 100, which means that the upper anvil was deflected a total
of 0.120 to 0.100 inches. When golf ball components (i.e., centers,
cores, mantled core, etc.) with diameters smaller than 1.680 inches
are utilized, metallic shims are included such that the combined
diameter of the shims and the component is 1.680 inches.
[0070] Determining golf ball compression can also be carried out
via a compression tester sold by OK Automation, formerly, Atti
Engineering Corporation. This golf ball compression tester is
calibrated against a calibration spring provided by OK Automation.
The compression value obtained by such a tester (referred to as
Atti compression) relates to an arbitrary value expressed by a
number that may range from 0 to 100 (a value of 200 can also be
measured by two revolutions of a dial indicator, which is described
below). Atti compression values that are obtained define the
deflection that a golf ball undergoes when subjected to compressive
loading. The golf ball compression tester consists of a lower
movable platform and an upper movable spring-loaded anvil. A dial
indicator of the compression tester is mounted such that it
measures the upward movement of the spring-loaded anvil. A golf
ball to be tested is placed in the lower platform, which is then
raised a fixed distance. The upper portion of the golf ball comes
in contact with and exerts a pressure on the spring-loaded anvil,
forcing the anvil upward against a spring.
[0071] Alternative devices, apparatuses or testers have also been
employed to determine golf ball compression. For example, a
modified Riehle compression device (Riehle Bros. Testing Machine
Company) can be used to evaluate the compression of various golf
ball components (i.e., cores, mantle cover balls, finished balls,
etc.). The modified Riehle compression device determines golf ball
deformation in thousandths of an inch via a load designed to
emulate the 200 lbs spring constant of other golf ball compression
testers such as those described above. With a modified Riehle
compression device, a Riehle compression value of 61 corresponds to
a load deflection of 0.061 in. Furthermore, additional golf ball
compression devices, apparatuses or testers may also be utilized to
monitor and evaluate ball compression. Such devices, apparatuses or
testers include a Whitney tester and Instron.TM. device, which can
correlate or correspond to, for example, PGA or Atti compression
values.
[0072] Compression was measured using an Instron.TM. device,
namely, model 5544. Compression of golf ball components were
measured based on the deflection (in inches) caused by a 200 lbs
load applied during a load control mode with a rate of 15
kilopounds per second (kips s.sup.-1), an approach speed of 20 in
per minute and a preload of 0.2 pound-force (lbf) (in addition to
device system compliance). TABLE-US-00002 TABLE 2 #1 #2 #3 Escor
.TM. AT325 (EXY) 100 100 50 Enable .TM. 33330 (EY) 0 0 50 % Acrylic
Acid 6 6 3 % Butyl Acrylate 0 0 16.25 % Methyl Acrylate 20 20 10 %
Neutralization 100 100 100 % Mg Stearate 0 28.6 28.6 Compression
(Instron) 0.141 0.105 0.118 COR 0.685 0.767 0.705 Nes Factor* 826
872 823
[0073] Nes factor is determined by taking the sum of the
compression and (COR) measurements and multiplying this value by
1,000. The Nes factor represents an optimal combination of softer
but more resilient golf ball cores.
[0074] As can be seen from the results of Example 1 (Table 2), the
blend of sample #3, comprising a blend of the acid terpolymer (EXY)
and the alkyl acrylate copolymer (EY), produced a sphere with a
higher COR than that comprising the terpolymer alone (sample #1),
while the highly neutralized terpolymer with the metal stearate had
a much higher COR than the terpolymer without the metal stearate.
The addition of the magnesium stearate, as shown above, in both
cases increased the COR and the Nes factor of the sample, producing
an enhanced combination of compression and resiliency
characteristics, as noted by the Nes factor parameter.
Example 2
[0075] Additional sample blends of highly neutralized materials
with metal stearates were produced and compared against other
blends that were not highly neutralized and had no metal stearates
added. The blends were made up of an olefin/acid copolymer and an
olefin/acrylate copolymer. The blends were further neutralized to
about 100% in a Banbury.TM. type mixer using Mg(OH).sub.2. Zinc
stearate was then added to the sample blend, and the blends were
extruded into pellets. The sample blends were subsequently
compression molded into neat spheres and tested as described in
Example 1. Comparative blends were also produced that were not
further neutralized and did not have metal stearates added (these
blends are labeled "C"). Results are shown in Table 3.
TABLE-US-00003 TABLE 3 Sample # # 4C # 5C #6C #4 #5 #6 Blend Type
Control EX/EY EX/EY Control EX/EY EX/EY Surlyn .TM. 6120 (EX) 100
50 50 100 48.2 48.2 Lotryl .TM. 29 MA03 (EY) 0 50 50 0 51.8 51.8
Fusabond .TM. MG423D 0 0 5 0 0 0 % Zn Stearate (approx) 0 0 0 33.3
19 29.5 % Neutralization* 40 40 40 100 100 100 % Methacrylic Acid
19 9.5 9 19 9.2 9.2 % Acrylate 0 15 14.5 0 15 15 Compression
(Instron) 0.049 0.078 0.098 0.065 0.089 0.090 COR 0.742 0.645 0.643
0.753 0.697 0.731 Nes Factor 791 723 741 818 786 821 *The percent
neutralization was estimated based on the metals analysis of the
material.
[0076] The results in Table 3 show that the COR increases along
with the level (amount) of metal stearate or fatty acid salt.
Additionally, highly neutralized thermoplastic material blends of
the invention (for example, EX/EY copolymers) that contain metal
stearates have a much higher COR (and are considerably softer) than
the comparative blends without metal stearates and sample blends
that are not as highly neutralized. Sample #6C shows that the
addition of a small amount of Fusabond.TM. produces a much softer
material with the same resiliency or COR.
Example 3
[0077] Further examples were produced using different starting
materials to compare an acid copolymer and acid terpolymer (EX/EXY)
blend against an acid copolymer and alkyl acrylate copolymer
(EX/EY) blend. Three different starting blends were produced as
follows: TABLE-US-00004 BLEND 1 (EX) BLEND 2 (EY) BLEND 3 (EXY)
Primacor .TM. 5980 Lotryl .TM. 29 MA03 Escor .TM. AT325 100 pbw 100
pbw 100 pbw Mg Stearate 66.7 pbw Mg Stearate 67 pbw Mg Stearate
66.7 pbw Mg Hydroxide Mg Hydroxide 2.43 pbw 8.28 pbw
[0078] Note: Primacor.TM. 5980 is an ethylene/acrylic acid
copolymer (EX) with approximately 20% acid; Lotryl.TM. 29 MA03 is
an ethylene/methyl acrylate copolymer (EY) with about 29% methyl
acrylate; and Escor AT325 is an ethylene/acrylic acid/methyl
acrylate terpolymer with about 6% acid and about 20% methyl
acrylate (EXY).
[0079] The blends were then mixed together in various combinations
and extruded. Neat spheres were produced in the same manner as
previously discussed. Results are shown in Table 4 below.
TABLE-US-00005 TABLE 4 Sample # #7 #8 #9 #10 #11 #12 Blend Type
EX/EXY EX/EY EX/EY EX/EY EX/EY EX/EY Blend 1 (EX) 25 46.3 46.3 46.3
37.04 37.04 Blend 2 (EY) 0 53.7 45.3 37 53.7 37 Blend 3 (EXY) 75 0
0 0 0 0 Primacor .TM. 5980 % 0 0 0 0 5.6 5.6 Fusabond .TM. MG-423D
% 0 0 5 10 0 10 % Acrylic Acid 9.5 9.5 9.5 9.5 9.5 9.5 % Methyl
Acrylate 15 15.6 13.1 10.73 15.6 10.73 % Neutralization 100 100 100
100 80 80 % Mg Stearate 40 40 36.6 40 40 40 Compression (Instron)
0.091 0.081 0.083 0.082 0.082 0.082 COR 0.782 0.809 0.797 0.804
0.805 0.805 Nes Factor 873 890 880 886 887 887 Shore C/D 82/59
81/59 81/59 81/59 81/59 86/60 Breaks/Cracks None 2 of 3 2 of 3 1
small 1 of 3 2 of 3 crack
[0080] The results in Table 4 show that the EX/EY blends have
superior COR and Nes Factor as compared to the control sample,
which is a blend of EX and EXY. The breaks in samples 8 to 12 were
the result of molding the spheres at too low of a temperature,
thereby forming knit lines that easily broke.
Example 4
[0081] Further examples were produced using different starting
materials to compare an acid copolymer and acid terpolymer blend
(EX/EXY) against an acid copolymer and alkyl acrylate copolymer
blend (EX/EY). The blends were mixed (dry blending) together in
various combinations and extruded in a Prism twin screw. Neat
spheres were produced in the same manner as previously discussed.
Results are shown in Table 5 below. TABLE-US-00006 TABLE 5 Sample #
#13 #14 #15 #16 #17 #18 #19 #20 #21 Blend Type EX/EXY EX/EXY EX/EXY
EX/EY EX/EY EX/EY EXY EXY EY Surlyn .TM. 9910 (EX) 45 45 45 46 46
46 0 0 0 Surlyn .TM. 8920 (EX) 30 30 30 39 39 39 0 0 0 Surlyn .TM.
8320 (EXY) 25 25 25 0 0 0 0 0 0 Lotryl .TM. 29MA03 0 0 0 15 15 15 0
0 100 (EY) HPF 1000 0 0 0 0 0 0 100 0 0 HPF 2000 0 0 0 0 0 0 0 100
0 % Mg Stearate 0 40 40 0 40 40 * * 0 % Neutralization NA NA
.about.90 NA NA .about.90 100 100 0 Comp. (Instron) 0.058 0.074
0.078 0.059 0.077 0.080 0.087 0.095 0.257 COR .702 0.783 0.803
0.726 0.787 0.797 0.819 0.841 0.528 Nes Factor 760 857 881 785 864
877 906 936 785 Shore D 64 60 59 65 59 59 54 51 27
[0082] Polymers sold under the trade names HPF.TM.1000 and HPF.TM.
2000 by DuPont, which are commercially available EXY materials
presumably produced using a fatty acids such as magnesium stearate
or magnesium oleate, were also used in the examples below. Such
polymers were used as purchased and without modification.
[0083] As used herein, the Shore D hardness of a golf ball cover
was measured in accordance with ASTM D-2240, although such
measurements were made on the curved surface of the molded cover
rather than on a plaque. Furthermore, the Shore D hardness of golf
ball covers were measured with the cover in place over the core of
the ball. When a hardness measurement is made on a dimpled or other
aerodynamic patterned cover, Shore D hardness is measured across a
land area of the cover.
[0084] Sample no. 13 was a control blend of an EX/EXY ionomeric
resin. Sample nos. 14 and 15 were blends based on sample no. 13
with magnesium stearate added at 40% level. Sample no. 15 was
additionally neutralized to about 90%. Sample no. 16 was an
unneutralized blend of acid copolymers and an alkyl acrylate
copolymer (EX/EY) without additional neutralization or fatty
acid/fatty acid salt. Samples nos. 17 and 18 were blends based on
sample no. 16 with magnesium stearate added at 40% level. Sample
no. 18 was additionally neutralized to about 90%. Sample nos. 19 to
21 consisted of commercially available EXY and EY polymers that
were extruded and molded into neat spheres to show the properties
of these materials.
[0085] The above results clearly show that the addition of fatty
acid salts increased compression, COR and Nes Factor values of both
the control EX/EXY blends as well as the EX/EY thermoplastic
material blends of the invention. The neutralization of these
blends with the fatty acid salts provided additional improvement in
their properties. Moreover, the EX/EY blends according to the
invention are generally softer and faster than any of the EX/EXY
blends known in the art.
Example 5
[0086] Further sample blends were produced using different starting
materials to compare an acid copolymer and acid terpolymer blend
(EX/EXY) against an acid copolymer and alkyl acrylate copolymer
blend (EX/EY) when each is used as a cover material on a two-piece
golf ball. The blends were mixed (dry blending) together in various
combinations and extruded in a Prism twin screw extruder. The golf
ball covers were molded over cores to produce a finished two-piece
golf ball. The cores used were standard cores (1.557 inches
diameter, 37.8 grams, Instrom Compression of 0.107, COR of 0.784,
and a Nes Factor of 891). Results are show in Table 6 below.
Amounts are in parts by weight unless otherwise stated.
TABLE-US-00007 TABLE 6 Sample # # 22 # 23 # 24 #25 #26 #27 #28 #29
Blend Type EX/EXY EX/EXY EX/EXY EX/EY EX/EY EX/EY EXY EXY Surlyn
.TM. 9910 (EX) 35.5 35.5 35.5 36.5 36.5 36.5 0 0 Surlyn .TM. 8920
(EX) 30 30 30 39 39 39 0 0 Surlyn .TM.8320 25 25 25 0 0 0 0 0 (EXY)
Lotryl .TM.29MA03 0 0 0 15 15 15 0 0 (EY) HPF 1000 (EXY) 0 0 0 0 0
0 97.5 0 HPF 2000 (EXY) 0 0 0 0 0 0 0 97.5 Mg Stearate 0 0 66.7 0
66.7 0 * * Ca Stearate 0 66.7 0 0 0 66.7 0 0 Masterbatch 9.5 9.5
9.5 9.5 9.5 9.5 0 0 TiO.sub.2 0 1.6 1.6 0 1.6 1.6 2.5 2.5 Comp.
(Instron) 0.100 0.099 0.102 0.100 0.100 0.099 0.105 0.105 COR 0.793
0.804 0.796 0.793 0.796 Broke 0.796 0.790 Nes Factor 893.6 902.7
897.2 893.6 895.7 NA 901.2 894.6 Shore D 65 67 63-64 65 62-63 66-67
60 54-55 *HPF 1000 and HPF 2000 are commercially available EXY
materials presumably produced using a fatty acid, such as magnesium
stearate or magnesium oleate. The HPF materials were used as
purchased.
[0087] Sample no. 22 was a control sample of a prior art EX/EXY
blend. Sample no. 25 was a control sample blend of EX/EY with no
fatty acid salt added to the blend. As shown in the above results,
sample blends of both EX/EXY and EX/EY that are modified with both
magnesium stearate and calcium stearate have increased COR and Nes
Factor values as compared to samples that are not modified with a
fatty acid. Magnesium stearate can lower the Shore D hardness
value, while calcium stearate generally increases the Shore D
hardness value. Therefore, depending on the desired final
properties of a golf ball cover (or mantle), different fatty acids
may be used.
[0088] In one embodiment, a golf ball 10 is constructed with a
cover 16 composed of a polyurethane material as set forth in U.S.
Pat. No. 6,117,024 from which pertinent parts are hereby
incorporated by reference. The golf ball 10 has a core 12, a
boundary layer 14 or both composed of a thermoplastic material of
the present invention. The golf ball 10 preferably has a COR at 143
feet per second greater than 0.7964 and a USGA initial velocity
less than 255.0 feet per second. The golf ball 10, more preferably,
has a COR of approximately 0.8152 at 143 feet per second, and an
initial velocity between 250 to 255 feet per second under USGA
initial velocity conditions. A more thorough description of a high
COR golf ball is disclosed in U.S. Pat. No. 6,443,858 from which
pertinent parts are hereby incorporated by reference.
[0089] Additionally, the core of a golf ball 10 may be solid,
hollow or filled with a fluid such as a gas or liquid. The golf
ball can also have a metal mantle. The cover 16 of the golf ball 10
may be any suitable material. A preferred cover for a three-piece
golf ball is composed of a thermoset polyurethane material.
Alternatively, the cover 16 is composed of a thermoplastic
polyurethane, ionomeric resin blend, ionomeric rubber blend,
ionomeric resin, thermoplastic polyurethane blend or like.
Alternatively, the golf ball 10 may have a thread layer. Those
skilled in the pertinent art will recognize that other cover
materials may be utilized without departing from the scope and
spirit of the present invention. The golf ball 10 may have a finish
of one or two base-coats and/or one or two top-coats.
[0090] In an alternative embodiment of a golf ball 10, the boundary
layer 14 or cover layer 16 is comprised of a high acid (i.e.,
greater than 16 weight % acid) ionomeric resin or high acid
ionomeric resin blend and the core 12 is composed of a
thermoplastic material of the present invention. Alternatively, if
the cover layer 16 is composed of a high acid ionomeric resin or a
high acid ionomeric resin blend, then the boundary layer 14 and/or
core 12 is composed of the thermoplastic material of the present
invention. More preferably, the boundary layer 14 is comprised of a
blend of two or more high acid (i.e., greater than 16 weight %
acid) ionomeric resins neutralized, to various extents, by
different metal cations.
[0091] In an alternative embodiment of a golf ball 10, the boundary
layer 14 or cover layer 16 is comprised of a low acid (i.e., 16
weight % acid or less) ionomeric resin or low acid ionomeric resin
blend. Preferably, the boundary layer 14 is comprised of a blend of
two or more low acid (i.e., 16 weight % acid or less) ionomeric
resins neutralized, to various extents, by different metal cations.
The boundary layer 14 compositions of the embodiments described
herein may include high acid ionomeric resins such as those
developed by DuPont under the trade name Surlyn.TM., and by
ExxonMobil under the Escor.TM. or Iotek.TM. trade names or blends
thereof. Examples of compositions that may be used as the boundary
layer 16 herein are set forth in detail in U.S. Pat. No. 5,688,869,
which is incorporated herein by reference. Of course, such high
acid ionomeric resin compositions are not limited in any way by
those compositions set forth in U.S. Pat. No. 5,688,869. The
compositions set forth in U.S. Pat. No. 5,688,869 are incorporated
herein by way of example only.
[0092] High acid ionomeric resins that may be suitable for use in
formulating the boundary layer 14 compositions are copolymers that
are the metal (such as sodium, zinc, magnesium, etc.) salts of the
reaction product of an olefin having from about 2 to 8 carbon atoms
and an unsaturated monocarboxylic acid having from about 3 to 8
carbon atoms. Preferably, the ionomeric resins are copolymers of
ethylene and either acrylic or methacrylic acid. In some
circumstances, an additional comonomer such as an acrylate ester
(for example, iso- or n-butylacrylate, etc.) can also be included
to produce a softer terpolymer. The carboxylic acid groups of the
acid copolymer are partially neutralized (for example,
approximately 10 to 100%, preferably, 30 to 70%) by the metal
cations. Each of the high acid ionomeric resins that may be
included in the inner layer components of a golf ball (components,
for example, composed in part of a thermoplastic material of the
invention) contains greater than 16% by weight of a carboxylic
acid, preferably from about 17 to about 25% by weight of a
carboxylic acid and, more preferably from about 18.5 to about 21.5%
by weight of a carboxylic acid. Examples of high acid methacrylic
acid ionomeric resins found suitable for use in accordance with the
present invention include, but are not limited to, Surlyn.TM. 8220
and 8240 (both formerly known as forms of Surlyn.TM. AD-8422),
Surlyn.TM. 9220 (zinc cation), Surlyn.TM. SEP-503-1 (zinc cation)
and Surlyn.TM. SEP-503-2 (magnesium cation). According to DuPont,
all of these ionomeric resins contain from about 18.5 to about
21.5% by weight methacrylic acid. Examples of high acid acrylic
acid ionomeric resins suitable for use in the present invention
also include, but are not limited to, the high acid
ethylene/acrylic acid copolymers produced by ExxonMobil such as
EX.TM. 1001, 1002, 959, 960, 989, 990, 1003, 1004, 993 and 994.
Moreover, Escor.TM. or Iotek.TM. 959 are also copolymers that can
be used with the present invention. According to ExxonMobil,
Iotek.TM. 959 and 960 contain from about 19.0 to about 21.0% by
weight acrylic acid with approximately 30 to about 70% of the acid
groups neutralized with sodium and zinc cations, respectively.
[0093] Furthermore, a number of high acid ionomeric resins or
ionomeric resin blends neutralized, to various extents, by several
different types of metal cations such as manganese, lithium,
potassium, calcium, sodium, zinc, magnesium and nickel cations are
also available for use in golf ball component production as
described herein. It has also been found that manganese, lithium,
potassium, calcium or nickel metal cations can neutralize high acid
ionomeric resin blends to produce boundary layer 16 compositions
exhibiting enhanced hardness and resiliency due to synergies that
occur during production. Consequently, high acid ionomeric resins
and ionomeric resin blends neutralized with manganese, lithium,
potassium, calcium or nickel cations can be blended to produce
substantially higher CORs than those yielded by low acid ionomeric
resin boundary layer 16 compositions that are commercially
available.
[0094] More particularly, several high acid ionomeric resins have
been produced by using a variety of metal cation salts to
neutralize, to various extents, polymers comprising an alpha olefin
and an alpha, beta-unsaturated carboxylic acid such as disclosed by
U.S. Pat. No. 5,688,869, which has been incorporated herein by
reference. It has also been found that numerous metal cation
neutralized, high acid ionomeric resins can be obtained by reacting
a high acid polymer (i.e., a polymer containing greater than 16% by
weight acid, preferably, from about 17 to about 25% by weight acid
and, more preferably, about 20% by weight percent acid) with a
metal cation salt capable of ionizing or neutralizing the polymer
to a desired extent (for example, from about 10 to 90%).
[0095] Such a copolymer can be 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 alpha olefin has from 2 to 10 carbon
atoms and, preferably, is ethylene. Preferably, the unsaturated
carboxylic acid is a carboxylic acid having from about 3 to 8
carbon atoms. 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.
[0096] A softening comonomer can be optionally included in the
boundary layer 14 of a golf ball as described herein. The softening
comonomer can be selected from the group consisting of vinyl esters
of aliphatic carboxylic acids having 2 to 10 carbon atoms, vinyl
ethers having alkyl groups that contain 1 to 10 carbon atoms and
alkyl acrylates or methacrylates in which 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.
[0097] Examples of a number of copolymers suitable for use in a
thermoplastic material of the present 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 ethylene/maleic acid
copolymer, an ethylene/methacrylic acid/vinyl acetate terpolymer,
an ethylene/acrylic acid/vinyl alcohol terpolymer, etc. The base
copolymer broadly contains greater than 16% by weight unsaturated
carboxylic acid, from about 39 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.
[0098] Boundary layer 14 compositions may also include low acid
ionomeric resins such as those developed and sold by DuPont under
the trade name Suryln.TM. and ExxonMobil under the trade names
Escor.TM. and Iotek.TM. as well as any blends thereof.
[0099] Another embodiment of a boundary layer 14 of a golf ball can
comprise non-ionomeric thermoplastic material or thermoset
materials. Suitable non-ionomeric materials include, but are not
limited to, metallocene-catalyzed polyolefins or polyamides,
metallocene-catalyzed polyamide/ionomeric resin blends,
polyphenylene ether/ionomeric resin blends, etc., which preferably
have a Shore D hardness of at least 60 (or a Shore C hardness of at
least about 90) and a flex modulus of greater than about 30,000
psi, preferably, greater than about 50,000 psi, or other hardness
and flex modulus values that are comparable to the properties of
the ionomeric resins described above. Other suitable materials
include, but are not limited to, thermoplastic or thermosetting
polyurethanes, thermoplastic block polyesters (for example, a
polyester elastomer such as that sold by DuPont under the trade
name Hytrel.TM.), or thermoplastic block polyamides (for example, a
polyether amide such as that sold by Elf Atochem S.A. under the
trade name Pebex.TM., a blend of two or more non-ionomeric
thermoplastic elastomers, or a blend of one or more ionomeric
resins and one or more non-ionomeric thermoplastic elastomers. Such
materials can be blended with the ionomeric resins described above
in order to reduce overall golf ball manufacturing costs.
[0100] Additional materials suitable for use in the boundary layer
14 or cover layer 16 of a golf ball as set forth herein include
polyurethanes, which are described in more detail below.
[0101] In one embodiment, the cover layer 16 is comprised of a
relatively soft, low flex modulus (about 500 to about 50,000 psi,
preferably about 1,000 to about 25,000 psi, and more preferably
about 5,000 to about 20,000 psi) material or blend of materials.
Preferably, the cover layer 16 comprises a polyurethane, a
polyurea, a blend of two or more polyurethanes/polyureas or a blend
of one or more ionomeric resins or non-ionomeric thermoplastic
materials with a polyurethane/polyurea. More preferably, the cover
layer comprises a thermoplastic polyurethane or a reaction
injection molded polyurethane/polyurea as described in more detail
below.
[0102] The cover layer 16 preferably has a thickness in the range
of 0.005 to about 0.15 inch, more preferably about 0.010 to about
0.050 inch and most preferably 0.015 to 0.025 inch. In one
embodiment, the cover layer 14 has a Shore D hardness of 60 or less
(or a Shore C hardness less than 90) and more preferably 55 or less
(or a Shore C hardness of about 80 or less). In another preferred
embodiment, the cover layer 16 is comparatively harder than the
boundary layer 14.
[0103] In one preferred embodiment, the cover layer 16 comprises a
polyurethane, a polyurea or a blend of polyurethanes/polyureas.
Polyurethanes are polymers that are used to form a broad range of
products. These polymers are generally formed by mixing two primary
ingredients during processing. For the most commonly used
polyurethanes, the two primary ingredients are a polyisocyanate
(for example, 4,4'-diphenylmethane diisocyanate monomer, MDI,
toluene diisocyanate, TDI, or derivatives thereof) and a polyol
(for example, a polyester polyol or a polyether polyol).
[0104] A wide range of combinations of polyisocyanates and polyols
(as well as other ingredients) are available for yielding
polyurethanes such as described above. Furthermore, the properties
of polyurethanes can be controlled by the types of ingredients
used. For example, a polyurethane can be a thermoset type (a
cross-linked molecular structure that is generally not flowable
with heat) or thermoplastic type (a linear molecular structure that
is generally flowable with heat).
[0105] Cross-linking of a thermoset polyurethane can occur between
isocyanate groups (NCO) and the hydroxyl end-groups of polyols.
Cross-linking will also occur between NH.sub.2 groups of the amines
and NCO groups of the isocyanates to form a polyurea. Additionally,
the characteristics of such polyurethanes as described above can
also be controlled by different types of reactive chemicals and
processing parameters. For example, catalysts can be used to
control polymerization rates. Depending on the processing method
employed, polymerization rates can be very quick (as in the case
for some reaction injection molding, RIM, systems) or may be on the
order of several hours (as in several coating systems such as a
cast system). Consequently, a great variety of polyurethanes are
suitable for different end-uses.
[0106] Polyurethanes are typically classified as thermosetting or
thermoplastic materials. A polyurethane becomes irreversibly "set"
when a polyurethane prepolymer is cross-linked with a
polyfunctional curing agent such as a polyamine or a polyol. The
prepolymer typically is made from polyether polyester. A prepolymer
is typically an isocyanate-terminated polymer that is produced by
reacting an isocyanate with a moiety that has active hydrogen
groups such as a polyester and/or polyether polyol. For example,
the moiety can be a hydroxyl group. Diisocyanate polyethers are the
preferred polyurethanes set forth herein because of their water
resistance.
[0107] The physical properties of thermoset polyurethanes are
controlled substantially by the degree of cross-linking and by the
content of hard and soft segments. Tightly cross-linked
polyurethanes are fairly rigid and strong. A lower amount of
cross-linking results in materials that are flexible and resilient.
Thermoplastic polyurethanes have some cross-linking, although such
cross-linking is primarily by physical means, for example, hydrogen
bonding. Cross-linking bonds of a thermoplastic polyurethane can be
reversibly broken by increasing temperatures such as during molding
or extrusion. In this regard, thermoplastic polyurethanes can be
injection molded and extruded as a sheet or blow film.
Thermoplastic polyurethanes can be used up to about 400.degree. F.
and are available in a wide range of hardnesses.
[0108] Polyurethane materials suitable for use with the present
invention may be formed by the reaction of a polyisocyanate, a
polyol and, optionally, one or more polymer chain extenders. The
polyol component can include any suitable polyether or polyester
polyol. Additionally, in an alternative embodiment, the polyol
component is polybutadiene diol. The polymer chain extenders
include, but are not limited to, diols, triols and amine extenders.
Any suitable polyisocyanate may be used to form a polyurethane as
set forth herein. The polyisocyanate is preferably selected from
the group of diisocyanates including, but not limited to, MDI,
2,4-TDI, m-xylylene diisocyanate (XDI), methylene bis-(4-cyclohexyl
isocyanate) (HMDI), hexamethylene diisocyanate (HDI),
naphthalene-1,5,-diisocyanate (NDI), 3,3'-dimethyl-4,4'-biphenyl
diisocyanate (TODI), 1,4-diisocyanate benzene (PPDI),
phenylene-1,4-diisocyanate and 2,2,4- or 2,4,4-trimethyl
hexamethylene diisocyanate (TMDI). Other less preferred
diisocyanates include, but are not limited to, isophorone
diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI),
diphenylether-4,4'-diisocyanate, p,p'-diphenyl diisocyanate, lysine
diisocyanate (LDI), 1,3-bis(isocyanato methyl)cyclohexane and
polymethylene polyphenyl isocyanate (PMDI).
[0109] One additional polyurethane component that can also be used
incorporates meta-tetramethylxylylene diisocyanate (TMXDI)
aliphatic isocyanate. Polyurethanes based on TMXDI aliphatic
isocyanate can provide improved gloss retention UV light stability,
thermal stability and hydrolytic stability. Additionally, TMXDI
aliphatic isocyanate has demonstrated favorable toxicological
properties. Furthermore, given that TMXDI aliphatic isocyanate has
a low viscosity, it is usable with a wider range of diols (to
polyurethane) and diamines (to polyureas). If TMXDI aliphatic
isocyanate is used, it typically (although not necessarily) can be
added as a direct replacement for some or all of the other
aliphatic isocyanates. Because of the slow reactivity of TMXDI
aliphatic isocyanate, it may be useful or necessary to use
catalysts in order to achieve practical demolding times. Hardness,
tensile strength and elongation can be adjusted by adding further
materials to such a polyurethane component.
[0110] For a soft cover layer 16 preferably comprises a
polyurethane with a Shore D hardness of from about 10 to about 55
(a Shore C hardness of about 15 to about 75), more preferably, from
about 25 to about 55 (a Shore C hardness of about 40 to about 75)
and, most preferably, from about 30 to about 55 (a Shore C hardness
of about 45 to about 75). Alternatively, for a hard cover layer 16
a Shore D hardness should be from about 20 to about 90, preferably,
from about 30 to about 80 and, more preferably, from about 40 to
about 70.
[0111] The polyurethane material preferably has a flex modulus from
about 1 to about 310 Kpsi, more preferably, from about 3 to about
100 Kpsi and most preferably from about 3 to about 40 Kpsi for a
soft cover layer. Alternatively, for a hard cover layer 14 the flex
modulus should be about 40 to 90 Kpsi.
[0112] Non-limiting examples of a polyurethane suitable for use in
the cover layer 16 (or boundary layer 14) include a thermoplastic
polyester polyurethane such as sold by Bayer Corporation under the
trade name Texin.TM. (for example, Texin.TM. DP7-1097 and Texin.TM.
285) and by B.F. Goodrich under the trade name Estane.TM. (for
example, Estane.TM. X-4517). The thermoplastic polyurethane
material may be blended with a soft ionomeric resin or other
non-ionomer. For example, polyamides blend well with soft ionomeric
resins.
[0113] Other soft, relatively low modulus non-ionomeric
thermoplastic or thermoset polyurethane materials may also be
utilized so as long as the materials can produce the desired
playability and durability characteristics. These materials
include, but are not limited to, thermoplastic polyurethanes such
as Pellethane.TM. as sold by Dow Chemical Company and non-ionomeric
thermoset polyurethanes such as disclosed in U.S. Pat. No.
5,334,673, which is incorporated herein by reference.
[0114] Typically, there are two classes of thermoplastic
polyurethane materials, namely, aliphatic polyurethanes and
aromatic polyurethanes. Aliphatic polyurethanes are produced from a
polyol or polyols and aliphatic isocyanates such as H.sub.12MDI or
HDI. Aromatic polyurethanes are produced from a polyol or polyols
and aromatic isocyanates such as MDI or TDI. Thermoplastic
polyurethane materials may also be produced from a blend of both
aliphatic and aromatic polyurethanes such as a blend of HDI and TDI
with a polyol or polyols.
[0115] Generally, aliphatic thermoplastic polyurethanes are
lightfast meaning that they do not yellow appreciably upon exposure
to ultraviolet (UV) light. Conversely, aromatic thermoplastic
polyurethanes tend to yellow upon exposure to UV light. One method
of stopping the yellowing of aromatic polyurethanes is to paint the
outer surface of a finished golf ball comprising such a
polyurethane with a coating containing a pigment, such as titanium
dioxide, so that the UV light is prevented from reaching the
surface of the ball. Another method is to add UV absorbers, optical
brighteners and stabilizers to a clear coating(s) on the outer
cover of the golf ball as well as to the thermoplastic polyurethane
material itself. By adding UV absorbers and stabilizers to the
thermoplastic polyurethane and the golf ball coatings, aromatic
polyurethanes can be effectively used in the outer cover layer of a
ball. This result is advantageous as aromatic polyurethanes
typically have better scuff resistance characteristics and cost
less than aliphatic polyurethanes.
[0116] Other suitable polyurethane materials for use golf balls as
set forth herein include reaction injection molded ("RIM")
polyurethanes. RIM is a process by which highly reactive liquids
are injected into a mold and mixed (usually by impingement and/or
mechanical mixing in an in-line device such as a "peanut mixer").
The reactive liquids polymerize primarily in the mold to form a
coherent, one-piece molded article. A RIM process usually involves
a rapid polymerization reaction between one or more reactive
components (such as a polyether or polyester polyol, polyamine or
other material with an active hydrogen) and one or more isocyanate
containing constituents. Often the reaction occurs in the presence
of a catalyst. The reactive liquids are stored in separate tanks
prior to molding and may be first mixed in a mix head, which is
upstream of the mold. After mixing, the liquids can be injected
into the mold. The liquid streams are metered in a desired
weight-to-weight ratio and fed into an impingement mix head, with
mixing occurring under high pressure, for example, 1,500 to 3,000
psi. The liquid streams impinge upon each other in the mixing
chamber of the mix head and the resulting mixture is injected into
the mold. One of the liquid streams typically contains a catalyst
for the polymerization reaction. The constituent liquids react
rapidly after mixing to gel and form polyurethane polymers.
Polyureas, epoxies and various unsaturated polyesters also can be
molded by RIM processes. Further descriptions of suitable RIM
systems are disclosed in U.S. Pat. No. 6,663,508 from which
pertinent parts are hereby incorporated by reference.
[0117] Non-limiting examples of suitable RIM materials for use as
set forth herein are Bayflex.TM., Baydur.TM. GS and Prism.TM.
materials sold by Bayer Corporation. Spectrim.TM. RIM materials
from Dow Chemical Company including Spectrim.TM. MM 373-A
(isocyanate) and 373-B (polyol) can also be used. In addition,
Elastolit.TM. SR RIM materials from BASF Corporation can also be
used. Preferred RIM materials include Bayflex.TM. MP-10000, MP-7500
and 110-50 (filled or unfilled). Further preferred examples are
polyols, polyamines and isocyanates formed by processes that
recycle polyurethanes and polyureas. Additionally, such processes
may be modified by incorporating a butadiene component in a diol
agent.
[0118] Another preferred embodiment is a golf ball in which at
least one of the boundary layer 14 and/or the cover layer 16
comprise a fast-chemical-reaction-produced component. This
component comprises at least one material selected from the group
consisting of polyurethane, polyurea, polyurethane ionomeric resin,
epoxy, and unsaturated polyesters, and preferably comprises
polyurethane, polyurea or a blend comprising polyurethanes and/or
other polymers. A particularly preferred form of the invention is a
golf ball with a cover comprising polyurethane or a polyurethane
blend.
[0119] Polyol components typically contain additives such as
stabilizers, flow modifiers, catalysts, combustion modifiers,
blowing agents, fillers, pigments, optical brighteners and release
agents to modify physical characteristics of the golf ball cover.
Also, polyurethane/polyurea constituent molecules derived from
recycled polyurethane can be added to the polyol component.
[0120] The surface geometry of a golf ball 10 is preferably a
conventional dimple pattern such as disclosed in U.S. Pat. No.
6,213,898 from which pertinent parts are hereby incorporated by
reference. Alternatively, the surface geometry of the golf ball 10
may have a non-dimple pattern such as disclosed in U.S. Pat. No.
6,290,615 from which pertinent parts are hereby incorporated by
reference.
[0121] From the foregoing it is believed that those skilled in the
pertinent art will recognize the meritorious advancement of this
invention and will readily understand that while the present
invention has been described in association with a preferred
embodiment thereof and other embodiments illustrated in the
accompanying drawings, numerous changes, modifications and
substitutions of equivalents may be made therein without departing
from the spirit and scope of this invention, which is intended to
be unlimited by the foregoing except as may appear in the following
appended claims. Therefore, the embodiments of the invention in
which an exclusive property or privilege is claimed are defined in
the following appended claims.
* * * * *