U.S. patent application number 13/330469 was filed with the patent office on 2012-06-28 for golf ball composition.
This patent application is currently assigned to Taylor Made Golf Company, Inc.. Invention is credited to Hong G. Jeon, Hyun J. Kim.
Application Number | 20120165122 13/330469 |
Document ID | / |
Family ID | 46317825 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120165122 |
Kind Code |
A1 |
Kim; Hyun J. ; et
al. |
June 28, 2012 |
GOLF BALL COMPOSITION
Abstract
The present invention relates to golf ball where at least one of
the outer cover layer and the intermediate layer (if present)
includes a blend composition of about 2 to about 40 wt % of a
polyamide and about 60 to about 98 wt % of one or more of either a
block copolymer, an acidic copolymer; an acidic terpolymer; an
ionomer, or a multi component blend composition ("MCBC"); and where
the polyamide has a melting point which is greater than about 5 and
less than about 200.degree. C. above the melting point of the other
blend component.
Inventors: |
Kim; Hyun J.; (Carlsbad,
CA) ; Jeon; Hong G.; (Carlsbad, CA) |
Assignee: |
Taylor Made Golf Company,
Inc.
|
Family ID: |
46317825 |
Appl. No.: |
13/330469 |
Filed: |
December 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61427769 |
Dec 28, 2010 |
|
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|
Current U.S.
Class: |
473/372 ;
473/371 |
Current CPC
Class: |
A63B 37/0024 20130101;
A63B 37/0039 20130101; C08L 23/0846 20130101; A63B 37/0092
20130101; A63B 37/0003 20130101; A63B 37/0076 20130101; C08L
23/0846 20130101; A63B 37/02 20130101; A63B 37/0078 20130101; C08L
77/00 20130101; A63B 45/00 20130101 |
Class at
Publication: |
473/372 ;
473/371 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Claims
1. A golf ball comprising; 1) a core comprising a center, 2) an
outer cover layer; and 3) one or more intermediate layers, wherein
at least one of the outer cover layer and the intermediate layer
comprises a blend composition of; (A) from about 2 to about 40 wt %
(based on the combined weight of Components A and B) of a
polyamide; and (B) from about 60 to about 98 wt % (based on the
combined weight of Components A and B) of a polymer selected from
the group consisting of; i) block copolymers; ii) acidic
copolymers; iii) acidic terpolymers; iv) ionomers, v) a multi
component blend composition ("MCBC"); and vi) any and all
combinations of i-v; and wherein said polyamide has a melting point
which is greater than about 5 and less than about 200.degree. C.
above the melting point of Component B.
2. The golf ball of claim 1 wherein; Component (A) is present in an
amount of from about 5 to about 30 wt % (based on the combined
weight of Components A and B) and comprises a polyamide selected
from the group consisting of homopolyamides, copolymers of
polyamide and polyesters, copolymers of polyamide and polyethers;
and any and all combinations thereof; Component (B) is present in
an amount of from about 70 to about 95 wt % (based on the combined
weight of Components A and B) and is selected from the group
consisting of i) block copolymers of an aromatic vinyl compound and
a conjugated diene; ii) unimodal ethylene/(meth)acrylic acid
copolymers; iii) unimodal ethylene/(meth)acrylic
acid/(meth)acrylate terpolymers; iv) bimodal ethylene/(meth)acrylic
acid copolymers v) bimodal ethylene/(meth)acrylic
acid/(meth)acrylate terpolymers; vi) unimodal ionomers; vii)
bimodal ionomers, viii) modified unimodal ionomers; ix) modified
bimodal ionomers; x) a multi component blend composition
comprising; a) an ethylene/(meth)acrylic acid copolymer or
ethylene/(meth)acrylic acid/(meth)acrylate terpolymer; b) a block
copolymer of an aromatic vinyl compound and a conjugated diene; and
c) a basic metal salt selected from the group consisting of metal
hydroxides, metal oxides, metal carbonates, metal acetates, metal
stearates, metal laureates, metal oleates, metal palmitates and any
and all combinations thereof; and xi) any and all combinations
thereof; and wherein Component A has a melting point which is
greater than about 10 and less than about 150.degree. C. above the
melting point of Component B.
3. The golf ball of claim 1 wherein; A) Component (A) is present in
an amount of from about 8 to about 20 wt % (based on the combined
weight of Components A and B) and comprises include polyamide 6;
polyamide 11; polyamide 12; polyamide 4,6; polyamide 6,6; polyamide
6,8; polyamide 6,9; polyamide 6,10; polyamide 6,12; or Polyamide
BMACM.12; (B) Component (B) is present in an amount of from about
80 to about 92 wt % (based on the combined weight of Components A
and B) and comprises a block copolymer comprising
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene/propylene-styrene (SEPS) or a multi
component blend composition comprising; a) an
ethylene/(meth)acrylic acid copolymer; b) a block copolymer of
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene/propylene-styrene (SEPS); and c) a zinc
oxide, zinc hydroxides, calcium stearates and all combinations
thereof; and wherein Component A has a melting point which is
greater than about 20 and less than about 10.degree. C. above the
melting point of Component B.
4. The golf ball according to claim 1, wherein the one or more of
the layers enclosing the golf ball core also include a polymer
selected from the group consisting of thermoplastic elastomer,
thermoset elastomer, synthetic rubber, thermoplastic vulcanizate,
copolymeric ionomer, terpolymeric ionomer, polycarbonate,
polyolefin, polyamide, copolymeric polyamide, polyesters, polyvinyl
alcohols, acrylonitrile-butadiene-styrene copolymers, polyarylate,
polyacrylate, polyphenylene ether, impact-modified polyphenylene
ether, high impact polystyrene, diallyl phthalate polymer,
metallocene catalyzed polymers functionalized styrenic copolymer,
functionalized styrenic terpolymer, styrenic terpolymer, cellulose
polymer, liquid crystal polymer (LCP), ethylene-propylene-diene
terpolymer (EPDM), ethylene-vinyl acetate copolymers (EVA),
ethylene-propylene copolymer, ethylene vinyl acetate, polyurea,
polysiloxane, and any metallocene-catalyzed polymers of these
species.
5. The golf ball according to claim 1, wherein the core or one or
more of the layers enclosing the golf ball core include a
nanofiller clay selected from the group consisting of hydrotalcite,
montmorillonite, phyllosilicate, saponite, hectorite, beidellite,
stevensite, vermiculite, halloysite, mica, micafluoride, and
ostosilicate and present in an amount between about 0.1% and about
20% by weight and said nanofiller is either is either intercalated
or exfoliated within the polymer.
6. A two piece golf ball having; 1) a core comprising a center, and
2) an outer cover layer; wherein the outer cover layer comprises a
blend composition of; (A) from about 2 to about 40 wt % (based on
the combined weight of Components A and B) of a polyamide; and (B)
from about 60 to about 98 wt % (based on the combined weight of
Components A and B) of a polymer selected from the group consisting
of; i) block copolymers; ii) acidic copolymers; iii) acidic
terpolymers; iv) ionomers, v) a multi component blend composition
("MCBC"); and vi) any and all combinations of i-v; and wherein said
polyamide has a melting point which is greater than about 5 and
less than about 200.degree. C. above the melting point of Component
B.
7. The golf ball of claim 6 wherein; A) Component (A) is present in
an amount of from about 5 to about 30 wt % (based on the combined
weight of Components A and B) and comprises a polyamide selected
from the group consisting of homopolyamides, copolymers of
polyamide and polyesters, copolymers of polyamide and polyethers;
and any and all combinations thereof; (B) Component (B) is present
in an amount of from about 70 to about 95 wt % (based on the
combined weight of Components A and B) and is selected from the
group consisting of i) block copolymers of an aromatic vinyl
compound and a conjugated diene; ii) unimodal
ethylene/(meth)acrylic acid copolymers; iii) unimodal
ethylene/(meth)acrylic acid/(meth)acrylate terpolymers; iv) bimodal
ethylene/(meth)acrylic acid copolymers v) bimodal
ethylene/(meth)acrylic acid/(meth)acrylate terpolymers; vi)
unimodal ionomers; vii) bimodal ionomers, viii) modified unimodal
ionomers; ix) modified bimodal ionomers; x) a multi component blend
composition comprising; a) an ethylene/(meth)acrylic acid copolymer
or ethylene/(meth)acrylic acid/(meth)acrylate terpolymer; b) a
block copolymer of an aromatic vinyl compound and a conjugated
diene; and c) a basic metal salt selected from the group consisting
of metal hydroxides, metal oxides, metal carbonates, metal
acetates, metal stearates, metal laureates, metal oleates, metal
palmitates and any and all combinations thereof; and xi) any and
all combinations thereof; and wherein Component A has a melting
point which is greater than about 10 and less than about
150.degree. C. above the melting point of Component B.
8. The golf ball of claim 6 wherein; A) Component (A) is present in
an amount of from about 8 to about 20 wt % (based on the combined
weight of Components A and B) and comprises include polyamide 6;
polyamide 11; polyamide 12; polyamide 4,6; polyamide 6,6; polyamide
6,8; polyamide 6,9; polyamide 6,10; polyamide 6,12; or Polyamide
BMACM.12; (B) Component (B) is present in an amount of from about
80 to about 92 wt % (based on the combined weight of Components A
and B) and comprises a block copolymer comprising
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene/propylene-styrene (SEPS), or a multi
component blend composition comprising; a) an
ethylene/(meth)acrylic acid copolymer; b) a block copolymer of
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene/propylene-styrene (SITS); and c) a zinc
oxide, zinc hydroxides, calcium stearates and all combinations
thereof; and wherein Component A has a melting point which is
greater than about 20 and less than about 10.degree. C. above the
melting point of Component B.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/427,769, which was filed on Dec. 28, 2010, and
is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to sports equipment in general
and more particularly to golf balls comprising a particular
composition suitable for use in golf ball manufacture. In one
embodiment, the present invention is used in the manufacture of a
golf ball comprising a core, a cover layer and, optionally, one or
more inner cover layers. In one preferred embodiment, a golf ball
is disclosed in which the cover layer comprises the novel
composition of the present invention. In another preferred
embodiment, a golf ball is disclosed in which at least one
intermediate layer comprises the novel composition of the present
invention.
DESCRIPTION OF RELATED ART
[0003] The application of synthetic polymer chemistry to the field
of sports equipment has revolutionized the performance of athletes
in many sports. One sport in which this is particularly true is
golf, especially as relates to advances in golf ball performance
and ease of manufacture. For instance, the earliest golf balls
consisted of a leather cover filled with wet feathers. These
"feathery" golf balls were subsequently replaced with a single
piece golf ball made from "gutta percha," a naturally occurring
rubber-like material. In the early 1900's, the wound rubber ball
was introduced, consisting of a solid rubber core around which
rubber thread was tightly wound with a gutta percha cover.
[0004] More modern golf balls can be classified as one-piece,
two-piece, three-piece or multi-layered golf balls. One-piece balls
are molded from a homogeneous mass of material with a dimple
pattern molded thereon. One-piece balls are inexpensive and very
durable, but do not provide great distance because of relatively
high spin and low velocity. Two-piece balls are made by molding a
cover around a solid rubber core. These are the most popular types
of balls in use today. In attempts to further modify the ball
performance especially in terms of the distance such balls travel
and the feel transmitted to the golfer through the club on striking
the ball, the basic two piece ball construction has been further
modified by the introduction of additional layers between the core
and outer cover layer. If one additional layer is introduced
between the core and outer cover layer a so called "three-piece
ball" results and similarly, if two additional layers are
introduced between the core and outer cover layer, a so called
"four-piece ball" results, and so on.
[0005] Golf ball covers were previously made from balata rubber
which was favored by some players because the softness of the cover
allows them to achieve spin rates sufficient to allow more
precisely control of ball direction and distance, particularly on
shorter approach shots. However balata-covered balls, although
exhibiting high spin and soft feel, were often deficient in terms
of the velocity of the ball when it leaves the club face which in
turn affects the distance the ball travels.
[0006] This distance is directly related to the coefficient of
restitution ("C.O.R.") of the ball. The coefficient of restitution
of a one-piece golf ball is a function of the ball's composition.
In a two-piece or a multi-layered golf ball, the coefficient of
restitution is a function of the properties of the core, the cover
and any additional layer. While there are no United States Golf
Association ("USGA") limitations on the coefficient of restitution
values of a golf ball, the USGA requires that the golf ball cannot
exceed an initial velocity of 255 feet/second. As a result, golf
ball manufacturers generally seek to maximize the coefficient of
restitution of a ball without violating the velocity
limitation.
[0007] Accordingly, a variety of golf ball constructions have been
developed in an attempt to provide spin rates and a feel
approaching those of balata covered balls, while also providing a
golf ball with a higher durability and overall distance. This has
resulted in the emergence of balls, which have a solid rubber core,
a cover, and one or more so called intermediate layers, as well as
the application of new materials to each of these components.
[0008] A material which has been often utilized in more modern golf
balls is the family of ionomer resins developed in the mid-1960's,
by E.I. DuPont de Nemours and Co., and sold under the trademark
SURLYN.RTM.. These ionomer resins have, to a large extent, replaced
balata as a golf ball cover stock material. Preparation of such
ionomers is well known, for example see U.S. Pat. No. 3,264,272
(the entire contents of which are herein incorporated by
reference). Generally speaking, commercial ionomers consist of a
polymer of a mono-olefin, e.g., an alkene, with an unsaturated
mono- or dicarboxylic acids having 3 to 12 carbon atoms. An
additional monomer in the form of a mono- or dicarboxylic acid
ester may also be incorporated in the formulation as a so-called
"softening comonomer." The acid groups in the polymer are then
neutralized to varying degrees by addition of a neutralizing agent
in the form of a basic metal salt.
[0009] Today, there are a wide variety of commercially available
ionomer resins based both on copolymers of ethylene and
(meth)acrylic acid or terpolymers of ethylene and (meth)acrylic
acid and (meth)acrylate, all of which many of which are be used as
a golf ball component. The properties of these ionomer resins can
vary widely due to variations in acid content, softening comonomer
content, the degree of neutralization, and the type of metal ion
used in the neutralization.
[0010] More recent developments in the field have attempted to
utilize the various types of ionomers, both singly and in blend
compositions to optimize the often conflicting golf ball
performance requirements of high C.O.R. and ball velocity, and
cover durability, with the need for a ball to spin and have a
so-called soft feel on shorter iron shots. However, the
incorporation of more acid in the ionomer and/or increasing its
degree of neutralization results in a material with increased
polarity, and hence one which is often less compatible with other
potential blend materials. Also increasing the acid content of the
ionomer while increasing C.O.R. may render the ball too hard and
brittle causing a loss of shot feel, control (i.e., the ability to
spin the ball) and may render the cover too brittle and prone to
premature failure. Finally, the incorporation of more acid in the
ionomer and/or increasing its degree of neutralization typically
results in an increase in melt viscosity which in turn greatly
decreases the processability of these resins. Attempts to mediate
these effects by adding softer terpolymeric ionomers to high acid
ionomer compositions to adjust the hardness and improve the shot
"feel" often result in concomitant loss of C.O.R. and hence
distance.
[0011] Another particular elastomeric material that provides for
good performance when used in making ball covers and intermediate
layers is a block copolymer having a first polymer block comprising
an aromatic vinyl compound, and a second polymer block comprising a
diene compound. However, it has been observed that covers
incorporating these copolymers can suffer from cracks after being
hit during play. During endurance testing of balls having covers
incorporating such block copolymers, crack initiation and
propagation was observed in the covers. This cracking leads to
substantial deterioration in ball performance and long-term
durability. These cracks also can initiate in an intermediate layer
and subsequently propagate to a cover. Additionally, shear-cut
resistance in the covers needs to be further improved for optimal
performance.
[0012] In view of the above, it is apparent that golf ball cover
and intermediate layers are needed that allow the optimization of
golf ball performance properties by incorporating ionomers or block
copolymers into the layers, while eliminating or reducing formation
of cracks in the covers and intermediate layers. The ball layers
also should provide little or no processing and preparation
difficulties beyond that provided by present layers. We have now
surprisingly found that addition of a solid polyamide to golf ball
compositions comprising a block copolymer, an ethylene/unsaturated
carboxylic acid copolymer or terpolymer, or an ionomer and any
combination thereof results in an improvement in the flex modulus
or hardness and shear cut resistance of the resulting golf ball
component, provided the polyamide melting point is above the
temperature of any processing steps used to fabricate the golf ball
component.
SUMMARY
[0013] Disclosed herein is a golf ball having a center core, an
outer cover layer; and one or more intermediate layers, where at
least one of the outer cover layer and the intermediate layer
includes a blend composition of about 2 to about 40 wt % of a
polyamide and about 60 to about 98 wt % of one or more of either a
block copolymer, an acidic copolymer; an acidic terpolymer; an
ionomer, or a multi component blend composition ("MCBC"); and where
the polyamide has a melting point which is greater than about 5 and
less than about 200.degree. C. above the melting point of the other
blend component.
[0014] According to another embodiment, there is disclosed herein a
two piece golf ball having a core including a center, and an outer
cover layer where the outer cover layer includes a blend
composition of about 2 to about 40 wt % of a polyamide and about 60
to about 98 wt % of one or more of either a block copolymer, an
acidic copolymer; an acidic terpolymer; an ionomer, or a multi
component blend composition ("MCBC"); and where the polyamide has a
melting point which is greater than about 5 and less than about
200.degree. C. above the melting point of the other blend
component.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 illustrates a three-piece golf ball 1 comprising a
solid center or core 2, an intermediate layer 3, and an outer cover
layer 4.
[0016] FIG. 2 illustrates a 4-piece golf ball 1 comprising a core
2, and an outer cover layer 5. an inner intermediate layer 3, and
an outer intermediate layer 4.
[0017] Although FIGS. 1 and 2 illustrate only three- and four-piece
golf ball constructions, golf balls of the present invention may
comprise from 1 to at least 5 intermediate layer(s), preferably
from 1 to 3 intermediate layer(s), more preferably from 1 to 2
intermediate layer(s).
DETAILED DESCRIPTION
[0018] Any numerical values recited herein include all values from
the lower value to the upper value in increments of one unit
provided that there is a separation of at least 2 units between any
lower value and any higher value. As an example, if it is stated
that the amount of a component or a value of a process variable is
from 1 to 90, preferably from 20 to 80, more preferably from 30 to
70, it is intended that values such as 15 to 85, 22 to 68, 43 to
51, 30 to 32 etc. are expressly enumerated in this specification.
For values, which have less than one unit difference, one unit is
considered to be 0.1, 0.01, 0.001, or 0.0001 as appropriate. Thus
all possible combinations of numerical values between the lowest
value and the highest value enumerated herein are said to be
expressly stated in this application.
[0019] The term "(meth)acrylic acid copolymers" is intended to mean
copolymers of methacrylic acid and/or acrylic acid.
[0020] The term "(meth)acrylate" is intended to mean an ester of
methacrylic acid and/or acrylic acid.
[0021] The term "partially neutralized" is intended to mean an
ionomer with a degree of neutralization of less than 100
percent.
[0022] The term "hydrocarbyl" is intended to mean any aliphatic,
cycloaliphatic, aromatic, aryl substituted aliphatic, aryl
substituted cycloaliphatic, aliphatic substituted aromatic, or
cycloaliphatic substituted aromatic groups. The aliphatic or
cycloaliphatic groups are preferably saturated. Likewise, the term
"hydrocarbyloxy" means a hydrocarbyl group having an oxygen linkage
between it and the carbon atom to which it is attached.
[0023] As used herein, the term "block copolymer" is intended to
mean a polymer comprising two or more homopolymer subunits linked
by covalent bonds. The union of the homopolymer subunits may
require an intermediate non-repeating subunit, known as a junction
block. Block copolymers with two or three distinct blocks are
called diblock copolymers and triblock copolymers, respectively. It
is a particular feature of the present invention that the block
copolymer contain no polar functionality including pendant or
terminal hydroxyl or acid groups.
[0024] As used herein, the term "core" is intended to mean the
elastic center of a golf ball. The core may have one or more "core
layers" of elastic material, which are usually made of rubbery
material such as diene rubbers.
[0025] The term "cover layer" is intended to mean the outermost
layer of the golf ball; this is the layer that is directly in
contact with paint and/or ink on the surface of the golf ball. If
the cover consists of two or more layers, only the outermost layer
is designated the cover layer, and the remaining layers (excluding
the outermost layer) are commonly designated intermediate layers as
herein defined. The term "outer cover layer" as used herein is used
interchangeably with the term "cover layer."
[0026] The term "intermediate layer" may be used interchangeably
herein with the terms "mantle layer" or "inner cover layer" and is
intended to mean any layer(s) in a golf ball disposed between the
core and the outer cover layer. Should a ball have more than one
intermediate layer, these may be distinguished as "inner
intermediate" or "inner mantle" layers which are used
interchangeably to refer to the intermediate layer nearer the core
and further from the outer cover, as opposed to the "outer
intermediate" or "outer mantle layer" which are also used
interchangeably to refer to the intermediate layer further from the
core and closer to the outer cover.
[0027] The term "prepolymer" as used herein is intended to mean any
material that can be further processed to form a final polymer
material of a manufactured golf ball, such as, by way of example
and not limitation, a polymerized or partially polymerized material
that can undergo additional processing, such as crosslinking.
[0028] A "thermoplastic" as used herein is intended to mean a
material that is capable of softening or melting when heated and of
hardening again when cooled. Thermoplastic polymer chains often are
not cross-linked or are lightly crosslinked using a chain extender,
but the term "thermoplastic" as used herein may refer to materials
that initially act as thermoplastics, such as during an initial
extrusion process or injection molding process, but which also may
be crosslinked, such as during a compression molding step to form a
final structure.
[0029] A "thermoset" as used herein is intended to mean a material
that crosslinks or cures via interaction with as crosslinking or
curing agent. Crosslinking may be induced by energy, such as heat
(generally above 200.degree. C.), through a chemical reaction (by
reaction with a curing agent), or by irradiation. The resulting
composition remains rigid when set, and does not soften with
heating. Thermosets have this property because the long-chain
polymer molecules cross-link with each other to give a rigid
structure. A thermoset material cannot be melted and re-molded
after it is cured. Thus thermosets do not lend themselves to
recycling unlike thermoplastics, which can be melted and
re-molded.
[0030] The term "thermoplastic polyurethane" as used herein is
intended to mean a material prepared by reaction of a prepared by
reaction of a diisocyanate with a polyol, and optionally addition
of a chain extender.
[0031] The term "thermoplastic polyurea" as used herein is intended
to mean a material prepared by reaction of a prepared by reaction
of a diisocyanate with a polyamine, with optionally addition of a
chain extender.
[0032] The term "thermoset polyurethane" as used herein is intended
to mean a material prepared by reaction of a diisocyanate with a
polyol, and a curing agent.
[0033] The term "thermoset polyurea" as used herein is intended to
mean a material prepared by reaction of a diisocyanate with a
polyamine, and a curing agent.
[0034] A "urethane prepolymer" as used herein is intended to mean
the reaction product of diisocyanate and a polyol.
[0035] A "urea prepolymer" as used herein is intended to mean the
reaction product of a diisocyanate and a polyamine.
[0036] The term "zwitterion" as used herein is intended to mean a
form of the compound having both an amine group and carboxylic acid
group, Component (B), where both are charged and where the net
charge on the compound is neutral.
[0037] The term "bimodal polymer" refers to a polymer comprising
two main fractions and more specifically to the form of the
polymers molecular weight distribution curve, i.e., the appearance
of the graph of the polymer weight fraction as function of its
molecular weight. When the molecular weight distribution curves
from these fractions are superimposed into the molecular weight
distribution curve for the total resulting polymer product, that
curve will show two maxima or at least be distinctly broadened in
comparison with the curves for the individual fractions. Such a
polymer product is called bimodal. It is to be noted here that also
the chemical compositions of the two fractions may be
different.
[0038] Similarly the term "unimodal polymer" refers to a polymer
comprising one main fraction and more specifically to the form of
the polymers molecular weight distribution curve, i.e., the
molecular weight distribution curve for the total polymer product
shows only a single maximum.
[0039] The term "sports equipment" refers to any item of sports
equipments such as sports clothing, boots, sneakers, clogs,
sandals, slip on sandals and shoes, golf shoes, tennis shoes,
running shoes, athletic shoes, hiking shoes, skis, ski masks, ski
boots, cycling shoes, soccer boots, golf clubs, golf bags, and the
like.
[0040] The present invention can be used in forming golf balls of
any desired size. "The Rules of Golf" by the USGA dictate that the
size of a competition golf ball must be at least 1.680 inches in
diameter; however, golf balls of any size can be used for leisure
golf play. The preferred diameter of the golf balls is from about
1.680 inches to about 1.800 inches. The more preferred diameter is
from about 1.680 inches to about 1.760 inches. A diameter of from
about 1.680 inches to about 1.740 inches is most preferred; however
diameters anywhere in the range of from 1.70 to about 2.0 inches
can be used. Oversize golf balls with diameters above about 1.760
inches to as big as 2.75 inches are also within the scope of the
invention.
[0041] In order to increase the flexural modulus or hardness and to
improve the shear cut resistance of compositions comprising
styrenic block copolymers or ionomeric polymers for use in golf
ball applications, we have surprisingly found that this can be
accomplished by the addition of a solid polyamide (in the form of a
powder, pellet or fiber) to either; 1) a styrenic block copolymer;
2) an ionomer; 3) an acidic polymer precursor of an ionomer
(followed by subsequent or in-situ neutralization); 4) a blend of
an ionomer and additional polymer components including styrenic
block copolymers, or 5) to a multi component blend composition
("MCBC") comprising an acidic polymer, a styrenic block copolymer
and a basic metal salt neutralizing agent.
[0042] The polyamide is chosen to have, among other properties, a
melting point in a specific range relative to the other blend
component(s). Although not wishing to be bound by any theory or
mechanism, it is believed that this melting point difference
induces the polyamide in a dispersed phase to deform into a fiber
under the shear force of the extrusion process which then results
in the observed improvements in flexural modulus or hardness shear
cut resistance of the resulting blend compositions. Depending on
their final properties the resulting polyamide reinforced polymer
compositions can be used to form one or more of a golf ball core,
cover or intermediate layer(s).
Polyamide Powder
[0043] The term "polyamide" as used herein includes both
homopolyamides and copolyamides. Illustrative homopolyamides for
use in the polyamide blend compositions include those obtained by:
(1) polycondensation of (a) a dicarboxylic acid, such as oxalic
acid, adipic acid, sebacic acid, terephthalic acid, isophthalic
acid, or 1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such
as ethylenediamine, tetramethylenediamine, pentamethylenediamine,
hexamethylenediamine, decamethylenediamine, 1,4-cyclohexyldiamine
or m-xylylenediamine; (2) a ring-opening polymerization of cyclic
lactam, such as .epsilon.-caprolactam or .omega.-laurolactam; (3)
polycondensation of an aminocarboxylic acid, such as 6-aminocaproic
acid, 9-aminononanoic acid, 11-aminoundecanoic acid or
12-aminododecanoic acid; (4) copolymerization of a cyclic lactam
with a dicarboxylic acid and a diamine; or any combination of
(1)-(4). In certain examples, the dicarboxylic acid may be an
aromatic dicarboxylic acid or a cycloaliphatic dicarboxylic acid.
In certain examples, the diamine may be an aromatic diamine or a
cycloaliphatic diamine. Specific examples of suitable polyamides
include polyamide 6; polyamide 11; polyamide 12; polyamide 4,6;
polyamide 6,6; polyamide 6,8; polyamide 6,9; polyamide 6,10;
polyamide 6,12; polyamide MXD6; PA12,CX; PA12, IT; PPA; PA6, IT;
and PA6/PPE.
[0044] One example of a group of suitable copolyamides are
thermoplastic polyamide elastomers. Thermoplastic polyamide
elastomers typically are copolymers of a polyamide and polyester or
polyether. For example, the thermoplastic polyamide elastomer can
contain a polyamide (Nylon 6, Nylon 66, Nylon 11, Nylon 12 and the
like) as a hard segment and a polyether or polyester as a soft
segment. In one specific example, the thermoplastic polyamides are
amorphous copolyamides based on polyamide (PA 12). Most referred
polyamides comprise aromatic, aliphatic and cycloaliphatic blocks
with aliphatic and cycloaliphatic blocks being more preferred. An
especially preferred thermoplastic polyamide is based on polyamide
12 including polyamides made by substantially equimolar mixing of
(bis(methyl-para-aminocyclohexyl)methane) (BMACM) and of
dodecanedioic acid. The polymer obtained, Polyamide BMACM.12, is
transparent, exhibits good mechanical properties and exhibits
stress crack resistance in the presence of alcohols. Its glass
transition temperature, measured by DSC, is 155.degree. C., and it
absorbs 3.0% by weight of water at 23.degree. C. Polyamide
BMACM.12, is commercially available from EMS Chemie under the
tradename TR90.
[0045] One class of copolyamide elastomers are polyether amide
elastomers. Illustrative examples of polyether amide elastomers are
those that result from the copolycondensation of polyamide blocks
having reactive chain ends with polyether blocks having reactive
chain ends, including:
[0046] (1) polyamide blocks of diamine chain ends with
polyoxyalkylene sequences of dicarboxylic chains;
[0047] (2) polyamide blocks of dicarboxylic chain ends with
polyoxyalkylene sequences of diamine chain ends obtained by
cyanoethylation and hydrogenation of polyoxyalkylene alpha-omega
dihydroxylated aliphatic sequences known as polyether diols;
and
[0048] (3) polyamide blocks of dicarboxylic chain ends with
polyether diols, the products obtained, in this particular case,
being polyetheresteramides.
[0049] More specifically, the polyamide elastomer can be prepared
by polycondensation of the components (i) a diamine and a
dicarboxylate, lactames or an amino dicarboxylic acid (PA
component), (ii) a polyoxyalkylene glycol such as polyoxyethylene
glycol, polyoxy propylene glycol (PG component) and (iii) a
dicarboxylic acid.
[0050] The polyamide blocks of dicarboxylic chain ends come, for
example, from the condensation of alpha-omega aminocarboxylic acids
of lactam or of carboxylic diacids and diamines in the presence of
a carboxylic diacid which limits the chain length. The molecular
weight of the polyamide sequences is preferably between about 300
and 15,000, and more preferably between about 600 and 5,000. The
molecular weight of the polyether sequences is preferably between
about 100 and 6,000, and more preferably between about 200 and
3,000.
[0051] The amide block polyethers may also comprise randomly
distributed units. These polymers may be prepared by the
simultaneous reaction of polyether and precursor of polyamide
blocks. For example, the polyether diol may react with a lactam (or
alpha-omega amino acid) and a diacid which limits the chain in the
presence of water. A polymer is obtained that has primarily
polyether blocks and/or polyamide blocks of very variable length,
but also the various reactive groups that have reacted in a random
manner and which are distributed statistically along the polymer
chain.
[0052] Suitable amide block polyethers include those as disclosed
in U.S. Pat. Nos. 4,331,786; 4,115,475; 4,195,015; 4,839,441;
4,864,014; 4,230,848 and 4,332,920, the contents of each of which
are herein incorporated by reference.
[0053] The polyether may be, for example, a polyethylene glycol
(PEG), a polypropylene glycol (PPG), or a polytetramethylene glycol
(PTMG), also designated as polytetrahydrofurane (PTHF). The
polyether blocks may be along the polymer chain in the form of
diols or diamines. However, for reasons of simplification, they are
designated PEG blocks, or PPG blocks, or also PTMG blocks.
[0054] The polyether block comprises different units such as units
which derive from ethylene glycol, propylene glycol, or
tetramethylene glycol.
[0055] The amide block polyether comprises at least one type of
polyamide block and one type of polyether block. Mixing of two or
more polymers with polyamide blocks and polyether blocks may also
be used. The amide block polyether also can comprise any amide
structure made from the method described on the above.
[0056] Preferably, the amide block polyether is such that it
represents the major component in weight, i.e., that the amount of
polyamide which is under the block configuration and that which is
eventually distributed statistically in the chain represents 50
weight percent or more of the amide block polyether.
Advantageously, the amount of polyamide and the amount of polyether
is in a ratio (polyamide/polyether) of 1/1 to 3/1.
[0057] One type of polyetherester amide elastomer is the family of
Pebax resins, which are available from Elf-Atochem Company.
Preferably, the choice can be made from among Pebax 2533, 3533,
4033, 1205, 7033 and 7233 and blends therefrom. Pebax 2533 has a
hardness of about 25 shore D (according to ASTM D-2240), a Flexural
Modulus of 2.1 kpsi (according to ASTM D-790), and a Bayshore
resilience of about 62% (according to ASTM D-2632). Pebax 3533 has
a hardness of about 35 shore D (according to ASTM D-2240), a
Flexural Modulus of 2.8 kpsi (according to ASTM D-790), and a
Bayshore resilience of about 59% (according to ASTM D-2632). Pebax
7033 has a hardness of about 69 shore D (according to ASTM D-2240)
and a Flexural Modulus of 67 kpsi (according to ASTM D-790). Pebax
7333 has a hardness of about 72 shore D (according to ASTM D-2240)
and a flexural modulus of 107 kpsi (according to ASTM D-790).
[0058] Other examples of suitable polyamides for use in the
compositions of the present invention include those commercially
available under the tradenames CRISTAMID and RILSAN marketed by
Atofina Chemicals of Philadelphia, Pa., GRIVORY and GRILAMID
marketed by EMS Chemie of Sumter, S.C., TROGAMID and VESTAMID
available from Degussa, LOMOD available from GE Plastics, and HYTRE
and ZYTEL, marketed by E.I. DuPont de Nemours & Co., of
Wilmington, Del. and SKYPEL available from SK Chemicals.
[0059] The polyamide may be used in solid form in the form of a
powder, pellet or fiber, and the type of polyamide is selected
based on the properties of the polymer component(s) to which it is
to be added. The melting point of the polyamide should be greater
than about 5 and less than about 200, preferably greater than about
10 and less than about 150 and more preferably greater than about
20 and less than about 100.degree. C. above the melting point of
the lowest melting polymer component to which it is added.
[0060] The polyamide is added in an amount of from about 2 to about
40, preferably from about 5 to about 30 and more preferably from
about 8 to about 20 wt % (based on the total weight of polyamide
and additional polymer component(s))
[0061] One preferred material to which the polyamide may be added
and which also may be used as a separate component of the cover
layer or intermediate layer of the golf balls of the present
invention is a block copolymer including di and triblock copolymers
incorporating a first polymer block having an aromatic vinyl
compound, and a second polymer block having an olefinic and/or
conjugated diene compound. Preferred aromatic vinyl compounds
include styrene, .alpha.-methylstyrene, o-, m- or p-methylstyrene,
4-propylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and
vinylanthracene. In particular, styrene and .alpha.-methylstyrene
are preferred. These aromatic vinyl compounds can each be used
alone, or can be used in combination of two or more kinds. The
aromatic vinyl compound is preferably contained in the block
copolymer (b) in an amount of from 5 to 75% by weight, and more
preferably from 10 to 65% by weight.
[0062] The conjugated diene compound, that constitutes another
polymer block in the block copolymer includes, e.g., 1,3-butadiene,
isoprene, 2,3-diemthyl-1,3-butadiene, 1,3-pentadiene and
1,3-hexadiene. In particular, isoprene and 1,3-butadiene are
preferred. These conjugated diene compounds can each be used alone,
or can be used in combination of two or more kinds. Preferred block
copolymers include the styrenic block copolymers such as
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene/propylene-styrene (SEPS). Commercial
examples include SEPTON marketed by Kuraray Company of Kurashiki,
Japan; TOPRENE by Kumho Petrochemical Co., Ltd and KRATON marketed
by Kraton Polymers. Also included are functionalized styrenic block
copolymers, including those where the block copolymer incorporates
a first polymer block having an aromatic vinyl compound, a second
polymer block having a conjugated diene compound and a hydroxyl
group located at a block copolymer, or its hydrogenation product. A
preferred functionalized styrenic block copolymer is SEPTON
HG-252.
[0063] Another preferred material to which the polyamide may be
added and which also may be used as a separate component of the
cover layer or intermediate layer of the golf balls of the present
invention is an acidic polymer that incorporates at least one type
of an acidic functional group. Examples of such polymers suitable
for use as include, but are not limited to, ethylene/(meth)acrylic
acid copolymers and ethylene/(meth)acrylic acid/alkyl
(meth)acrylate terpolymers, or ethylene and/or propylene maleic
anhydride copolymers and terpolymers. Examples of such polymers
which are commercially available include, but are not limited to,
the Escor.RTM. 5000, 5001, 5020, 5050, 5070, 5100, 5110 and 5200
series of ethylene-acrylic acid copolymers sold by Exxon Mobil, the
PRIMACOR.RTM. 1321, 1410, 1410-XT, 1420, 1430, 2912, 3150, 3330,
3340, 3440, 3460, 4311, 4608 and 5980 series of ethylene-acrylic
acid copolymers sold by The Dow Chemical Company, Midland, Mich.
and the ethylene-methacrylic acid copolymers such as Nucrel 599,
699, 0903, 0910, 925, 960, 2806, and 2906 sold by DuPont
[0064] Also included are the so called bimodal ethylene/carboxylic
acid polymers as described in U.S. Pat. No. 6,562,906, the contents
of which are incorporated herein by reference. These polymers
comprise a first component comprising an ethylene/.alpha.,
.beta.-ethylenically unsaturated C.sub.3-8 carboxylic acid high
copolymer, particularly ethylene (meth)acrylic acid copolymers and
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers,
having a weight average molecular weight, Mw, of about 80,000 to
about 500,000, and a second component comprising an
ethylene/.alpha., .beta.-ethylenically unsaturated C.sub.3-8
carboxylic acid copolymers, particularly ethylene/(meth)acrylic
acid copolymers having weight average molecular weight, Mw, of
about 2,000 to about 30,000.
[0065] Another preferred material to which the polyamide may be
added and which also may be used as a separate component of the
cover layer or intermediate layer of the golf balls of the present
invention is an ionomer resin. One family of such resins was
developed in the mid-1960's, by E.I. DuPont de Nemours and Co., and
is sold under the trademark SURLYN.RTM.. Preparation of such
ionomers is well known, for example see U.S. Pat. No. 3,264,272.
Generally speaking, most commercial ionomers are unimodal and
consist of a polymer of a mono-olefin, e.g., an alkene, with an
unsaturated mono- or dicarboxylic acids having 3 to 12 carbon
atoms. An additional monomer in the form of a mono- or dicarboxylic
acid ester may also be incorporated in the formulation as a
so-called "softening comonomer". The incorporated carboxylic acid
groups are then neutralized by a basic metal ion salt, to form the
ionomer. The metal cations of the basic metal ion salt used for
neutralization include Li.sup.+, Na.sup.+, K.sup.+, Zn.sup.2+,
Ca.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+, Pb.sup.2+, and
Mg.sup.2+, with the Li.sup.+, Na.sup.+, Ca.sup.2+, Zn.sup.2+, and
Mg.sup.2+ being preferred. The basic metal ion salts include those
of for example formic acid, acetic acid, nitric acid, and carbonic
acid, hydrogen carbonate salts, oxides, hydroxides, and
alkoxides.
[0066] The first commercially available ionomer resins contained up
to 16 weight percent acrylic or methacrylic acid, although it was
also well known at that time that, as a general rule, the hardness
of these cover materials could be increased with increasing acid
content. Hence, in Research Disclosure 29703, published in January
1989, DuPont disclosed ionomers based on ethylene/acrylic acid or
ethylene/methacrylic acid containing acid contents of greater than
15 weight percent. In this same disclosure, DuPont also taught that
such so called "high acid ionomers" had significantly improved
stiffness and hardness and thus could be advantageously used in
golf ball construction, when used either singly or in a blend with
other ionomers.
[0067] More recently, high acid ionomers can be ionomer resins with
acrylic or methacrylic acid units present from 16 wt. % to about 35
wt. % in the polymer. Generally, such a high acid ionomer will have
a flexural modulus from about 50,000 psi to about 125,000 psi.
[0068] Ionomer resins further comprising a softening comonomer,
present from about 10 wt. % to about 50 wt. % in the polymer, have
a flexural modulus from about 2,000 psi to about 10,000 psi, and
are sometimes referred to as "soft" or "very low modulus" ionomers.
Typical softening comonomers include n-butyl acrylate, iso-butyl
acrylate, n-butyl methacrylate, methyl acrylate and methyl
methacrylate.
[0069] Today, there are a wide variety of commercially available
ionomer resins based both on copolymers of ethylene and
(meth)acrylic acid or terpolymers of ethylene and (meth)acrylic
acid and (meth)acrylate, all of which many of which are be used as
a golf ball component. The properties of these ionomer resins can
vary widely due to variations in acid content, softening comonomer
content, the degree of neutralization, and the type of metal ion
used in the neutralization. The full range commercially available
typically includes ionomers of polymers of general formula, E/X/Y
polymer, wherein E is ethylene, X is a C.sub.3 to C.sub.8
.alpha.,.beta. ethylenically unsaturated carboxylic acid, such as
acrylic or methacrylic acid, and is present in an amount from about
2 to about 30 weight % of the E/X/Y copolymer, and Y is a softening
comonomer selected from the group consisting of alkyl acrylate and
alkyl methacrylate, such as methyl acrylate or methyl methacrylate,
and wherein the alkyl groups have from 1-8 carbon atoms, Y is in
the range of 0 to about 50 weight % of the E/X/Y copolymer, and
wherein the acid groups present in said ionomeric polymer are
partially neutralized with a metal selected from the group
consisting of lithium, sodium, potassium, magnesium, calcium,
barium, lead, tin, zinc or aluminum, or a combination of such
cations.
[0070] The ionomer may also be a so-called bimodal ionomer as
described in U.S. Pat. No. 6,562,906 (the entire contents of which
are herein incorporated by reference). These ionomers are bimodal
as they are prepared from blends comprising polymers of different
molecular weights. Specifically they include bimodal polymer blend
compositions comprising:
[0071] a) a high molecular weight component having a weight average
molecular weight, Mw, of about 80,000 to about 500,000 and
comprising one or more ethylene/.alpha., .beta.-ethylenically
unsaturated C.sub.3-8 carboxylic acid copolymers and/or one or more
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers;
said high molecular weight component being partially neutralized
with metal ions selected from the group consisting of lithium,
sodium, zinc, calcium, magnesium, and a mixture of any these;
and
[0072] b) a low molecular weight component having a weight average
molecular weight, Mw, of about from about 2,000 to about 30,000 and
comprising one or more ethylene/.alpha., .beta.-ethylenically
unsaturated C.sub.3-8 carboxylic acid copolymers and/or one or more
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers;
said low molecular weight component being partially neutralized
with metal ions selected from the group consisting of lithium,
sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or
aluminum, and a mixture of any these.
[0073] In addition to the unimodal and bimodal ionomers, also
included are the so-called "modified ionomers" examples of which
are described in U.S. Pat. Nos. 6,100,321, 6,329,458 and 6,616,552
and U.S. Patent Publication US 2003/0158312 A1, the entire contents
of all of which are herein incorporated by reference.
[0074] The modified unimodal ionomers may be prepared by
mixing:
[0075] a) an ionomeric polymer comprising ethylene, from 5 to 25
weight percent (meth)acrylic acid, and from 0 to 40 weight percent
of a (meth)acrylate monomer, said ionomeric polymer neutralized
with metal ions selected from the group consisting of lithium,
sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or
aluminum, and any and all mixtures thereof; and
[0076] b) from about 5 to about 40 weight percent (based on the
total weight of said modified ionomeric polymer) of one or more
fatty acids or metal salts of said fatty acid, the metal selected
from the group consisting of lithium, sodium, potassium, magnesium,
calcium, barium, lead, tin, zinc or aluminum, and any and all
mixtures thereof; and the fatty acid preferably being stearic
acid.
[0077] The modified bimodal ionomers, which are ionomers derived
from the earlier described bimodal ethylene/carboxylic acid
polymers (as described in U.S. Pat. No. 6,562,906, the entire
contents of which are herein incorporated by reference), are
prepared by mixing;
[0078] a) a high molecular weight component having a weight average
molecular weight, Mw, of about 80,000 to about 500,000 and
comprising one or more ethylene/.alpha., .beta.-ethylenically
unsaturated C.sub.3-8 carboxylic acid copolymers and/or one or more
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers;
said high molecular weight component being partially neutralized
with metal ions selected from the group consisting of lithium,
sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or
aluminum, and any and all mixtures thereof; and
[0079] b) a low molecular weight component having a weight average
molecular weight, Mw, of about from about 2,000 to about 30,000 and
comprising one or more ethylene/.alpha., .beta.-ethylenically
unsaturated C.sub.3-8 carboxylic acid copolymers and/or one or more
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers;
said low molecular weight component being partially neutralized
with metal ions selected from the group consisting of lithium,
sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or
aluminum, and any and all mixtures thereof; and
[0080] c) from about 5 to about 40 weight percent (based on the
total weight of said modified ionomeric polymer) of one or more
fatty acids or metal salts of said fatty acid, the metal selected
from the group consisting of lithium, sodium, potassium, magnesium,
calcium, barium, lead, tin, zinc or aluminum, and any and all
mixtures thereof; and the fatty acid preferably being stearic
acid.
[0081] The fatty or waxy acid salts utilized in the various
modified ionomers are composed of a chain of alkyl groups
containing from about 4 to 75 carbon atoms (usually even numbered)
and characterized by a --COOH terminal group. The generic formula
for all fatty and waxy acids above acetic acid is CH.sub.3
(CH.sub.2).sub.x COOH, wherein the carbon atom count includes the
carboxyl group (i.e. x=2-73). The fatty or waxy acids utilized to
produce the fatty or waxy acid salts modifiers may be saturated or
unsaturated, and they may be present in solid, semi-solid or liquid
form.
[0082] Examples of suitable saturated fatty acids, i.e., fatty
acids in which the carbon atoms of the alkyl chain are connected by
single bonds, include but are not limited to stearic acid
(C.sub.18, i.e., CH.sub.3 (CH.sub.2).sub.16 COOH), palmitic acid
(C.sub.16, i.e., CH.sub.3 (CH.sub.2).sub.14 COOH), pelargonic acid
(C.sub.9, i.e., CH.sub.3 (CH.sub.2).sub.7 COOH) and lauric acid
(C.sub.12, i.e., CH.sub.3 (CH.sub.2).sub.10 OCOOH). Examples of
suitable unsaturated fatty acids, i.e., a fatty acid in which there
are one or more double bonds between the carbon atoms in the alkyl
chain, include but are not limited to oleic acid (C.sub.13, i.e.,
CH.sub.3 (CH.sub.2).sub.7 CH:CH(CH.sub.2).sub.7 COOH).
[0083] The source of the metal ions used to produce the metal salts
of the fatty or waxy acid salts used in the various modified
ionomers are generally various metal salts which provide the metal
ions capable of neutralizing, to various extents, the carboxylic
acid groups of the fatty acids. These include the sulfate,
carbonate, acetate and hydroxylate salts of zinc, barium, calcium
and magnesium.
[0084] Since the fatty acid salts modifiers comprise various
combinations of fatty acids neutralized with a large number of
different metal ions, several different types of fatty acid salts
may be utilized in the invention, including metal stearates,
laureates, oleates, and palmitates, with calcium, zinc, sodium,
lithium, potassium and magnesium stearate being preferred, and
calcium and sodium stearate being most preferred.
[0085] The fatty or waxy acid or metal salt of said fatty or waxy
acid is present in the modified ionomeric polymers in an amount of
from about 5 to about 40, preferably from about 7 to about 35, more
preferably from about 8 to about 20 weight percent (based on the
total weight of said modified ionomeric polymer).
[0086] As a result of the addition of the one or more metal salts
of a fatty or waxy acid, from about 40 to 100, preferably from
about 50 to 100, more preferably from about 70 to 100 percent of
the acidic groups in the final modified ionomeric polymer
composition are neutralized by a metal ion.
[0087] An example of such a modified ionomer polymer is DuPont.RTM.
HPF-1000 available from E. I. DuPont de Nemours and Co. Inc.
[0088] Another preferred material to which the polyamide may be
added and which also may be used as a separate component of the
cover layer or intermediate layer of the golf balls of the present
invention is a multi component blend composition ("MCBC") prepared
by blending together at least three materials, identified as
Components A, B, and C, and melt-processing these components to
form in-situ, a polymer blend composition incorporating a
pseudo-crosslinked polymer network.
[0089] The first of these blend components (blend Component A)
include block copolymers including di and triblock copolymers,
incorporating a first polymer block having an aromatic vinyl
compound, and a second polymer block having an olefinic and/or
conjugated diene compound. Preferred aromatic vinyl compounds
include styrene, .alpha.-methylstyrene, o-, m- or p-methylstyrene,
4-propylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and
vinylanthracene. In particular, styrene and .alpha.-methylstyrene
are preferred. These aromatic vinyl compounds can each be used
alone, or can be used in combination of two or more kinds. The
aromatic vinyl compound is preferably contained in the block
copolymer (b) in an amount of from 5 to 75% by weight, and more
preferably from 10 to 65% by weight.
[0090] The conjugated diene compound, that constitutes the polymer
block B in the block copolymer (b), includes, e.g., 1,3-butadiene,
isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and
1,3-hexadiene. In particular, isoprene and 1,3-butadiene are
preferred. These conjugated diene compounds can each be used alone,
or can be used in combination of two or more kinds.
[0091] Preferred block copolymers include the styrenic block
copolymers such as styrene-butadiene-styrene (SBS),
styrene-ethylene-butylene-styrene, (SEBS) and
styrene-ethylene/propylene-styrene (SEES). Commercial examples
include SEPTON marketed by Kuraray Company of Kurashiki, Japan;
TOPRENE by Kumho Petrochemical Co., Ltd and KRATON marketed by
Kraton Polymers.
[0092] Also included are functionalized styrenic block copolymers,
including those where the block copolymer incorporates a first
polymer block having an aromatic vinyl compound, a second polymer
block having a conjugated diene compound and a hydroxyl group
located at a block copolymer, or its hydrogenation product. A
preferred functionalized styrenic block copolymer is SEPTON
HG-252.
[0093] The second blend component, Component B, is an acidic
polymer that incorporates at least one type of an acidic functional
group. Examples of such polymers suitable for use as include, but
are not limited to, ethylene/(meth)acrylic acid copolymers and
ethylene/(meth)acrylic acid/alkyl (meth)acrylate terpolymers, or
ethylene and/or propylene maleic anhydride copolymers and
terpolymers. Examples of such polymers which are commercially
available include, but are not limited to, the Escor.RTM. 5000,
5001, 5020, 5050, 5070, 5100, 5110 and 5200 series of
ethylene-acrylic acid copolymers sold by Exxon Mobil, the
PRIMACOR.RTM. 1321, 1410, 1410-XT, 1420, 1430, 2912, 3150, 3330,
3340, 3440, 3460, 4311, 4608 and 5980 series of ethylene-acrylic
acid copolymers sold by The Dow Chemical Company, Midland, Mich.
and the ethylene-methacrylic acid copolymers such as Nucrel 599,
699, 0903, 0910, 925, 960, 2806, and 2906 commercially available
from DuPont
[0094] Also included are the so called bimodal ethylene/carboxylic
acid polymers as described in U.S. Pat. No. 6,562,906, the contents
of which are incorporated herein by reference. These polymers
comprise a first component comprising an ethylene/.alpha.,
.beta.-ethylenically unsaturated C.sub.3-8 carboxylic acid high
copolymer, particularly ethylene (meth)acrylic acid copolymers and
ethylene, alkyl (meth)acrylate, (meth)acrylic acid terpolymers,
having a weight average molecular weight, Mw, of about 80,000 to
about 500,000, and a second component comprising an
ethylene/.alpha., .beta.-ethylenically unsaturated C.sub.3-8
carboxylic acid copolymers, particularly ethylene/(meth)acrylic
acid copolymers having weight average molecular weight, Mw, of
about 2,000 to about 30,000.
[0095] Component C is a base capable of neutralizing the acidic
functional group of Component B and typically is a base having a
metal cation. These metals are from groups IA, IB, IIA, IIB, IIIA,
IIIB, IVA, IVB, VA, VB, VIIA, VIIB, VIIB and VIIIB of the periodic
table. Examples of these metals include lithium, sodium, magnesium,
aluminum, potassium, calcium, manganese, tungsten, titanium, iron,
cobalt, nickel, hafnium, copper, zinc, barium, zirconium, and tin.
Suitable metal compounds for use as a source of Component C are,
for example, metal salts, preferably metal hydroxides, metal
oxides, metal carbonates, metal acetates, metal stearates, metal
laureates, metal oleates, metal palmitates and the like.
[0096] The MCBC composition preferably is prepared by mixing the
above materials into each other thoroughly, either by using a
dispersive mixing mechanism, a distributive mixing mechanism, or a
combination of these. These mixing methods are well known in the
manufacture of polymer blends. As a result of this mixing, the
acidic functional group of Component B is dispersed evenly
throughout the mixture in either their neutralized or
non-neutralized state. Most preferably, Components A and B are
melt-mixed together without Component C, with or without the
premixing discussed above, to produce a melt-mixture of the two
components. Then, Component C separately is mixed into the blend of
Components A and B. This mixture is melt-mixed to produce the
reaction product. This two-step mixing can be performed in a single
process, such as, for example, an extrusion process using a proper
barrel length or screw configuration, along with a multiple feeding
system.
[0097] The resulting MCBC compositions may be further modied by the
addition of an impact modifier, which can include copolymers or
terpolymers having a glycidyl group, hydroxyl group, maleic
anhydride group or carboxylic group, collectively referred to as
functionalized polymers. These copolymers and terpolymers may
comprise an .alpha.-olefin. Examples of suitable .alpha.-olefins
include ethylene, propylene, 1-butene, 1-pentene,
3-methyl-1-butene, 1-hexene, 4-methyl-1-petene, 3-methyl-1-pentene,
1-octene, 1-decene-, 1-dodecene, 1-tetradecene, 1-hexadecene,
1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene,
1-octacocene, and 1-triacontene. One or more of these
.alpha.-olefins may be used.
[0098] Examples of suitable glycidyl groups in copolymers or
terpolymers in the polymeric modifier include esters and ethers of
aliphatic glycidyl, such as allylglycidylether, vinylglycidylether,
glycidyl maleate and itaconatem glycidyl acrylate and methacrylate,
and also alicyclic glycidyl esters and ethers, such as
2-cyclohexene-1-glycidylether, cyclohexene-4,5
diglyxidylcarboxylate, cyclohexene-4-glycidyl carobxylate,
5-norboenene-2-methyl-2-glycidyl carboxylate, and
endocis-bicyclo(2,2,1)-5-heptene-2,3-diglycidyl dicarboxylate.
These polymers having a glycidyl group may comprise other monomers,
such as esters of unsaturated carboxylic acid, for example,
alkyl(meth)acrylates or vinyl esters of unsaturated carboxylic
acids. Polymers having a glycidyl group can be obtained by
copolymerization or graft polymerization with homopolymers or
copolymers.
[0099] Examples of suitable terpolymers having a glycidyl group
include LOTADER AX8900 and AX8920, marketed by Atofina Chemicals,
ELVALOY marketed by E.I. Du Pont de Nemours & Co., and REXPEARL
marketed by Nippon Petrochemicals Co., Ltd. Additional examples of
copolymers comprising epoxy monomers and which are suitable for use
within the scope of the present invention include
styrene-butadiene-styrene block copolymers in which the
polybutadiene block contains epoxy group, and
styrene-isoprene-styrene block copolymers in which the polyisoprene
block contains epoxy. Commercially available examples of these
epoxy functional copolymers include ESBS A1005, ESBS A1010, ESBS
A1020, ESBS AT018, and ESBS AT019, marketed by Daicel Chemical
Industries, Ltd.
[0100] Examples of polymers or terpolymers incorporating a maleic
anhydride group suitable for use within the scope of the present
invention include maleic anhydride-modified ethylene-propylene
copolymers, maleic anhydride-modified ethylene-propylene-diene
terpolymers, maleic anhydride-modified polyethylenes, maleic
anhydride-modified polypropylenes, ethylene-ethylacrylate-maleic
anhydride terpolymers, and maleic anhydride-indene-styrene-cumarone
polymers. Examples of commercially available copolymers
incorporating maleic anhydride include: BONDINE, marketed by
Sumitomo Chemical Co., such as BONDINE AX8390, an ethylene-ethyl
acrylate-maleic anhydride terpolymer having a combined ethylene
acrylate and maleic anhydride content of 32% by weight, and BONDINE
TX TX8030, an ethylene-ethyl acrylate-maleic anhydride terpolymer
having a combined ethylene acrylate and maleic anhydride content of
15% by weight and a maleic anhydride content of 1% to 4% by weight;
maleic anhydride-containing LOTADER 3200, 3210, 6200, 8200, 3300,
3400, 3410, 7500, 5500, 4720, and 4700, marketed by Atofina
Chemicals; EXXELOR VA1803, a maleic anyhydride-modified
ethylene-propylene copolymer having a maleic anyhydride content of
0.7% by weight, marketed by Exxon Chemical Co.; and KRATON FG
1901X, a maleic anhydride functionalized triblock copolymer having
polystyrene endblocks and poly(ethylene/butylene) midblocks,
marketed by Shell Chemical. Preferably the functional polymer
component is a maleic anhydride grafted polymers preferably maleic
anhydride grafted polyolefins (for example, Exxellor VA1803).
Additional Polymer Components
[0101] Other polymeric materials generally considered useful for
making golf balls may also be included as a component of the one or
more layers of the golf balls of the present invention. These
include, without limitation, synthetic and natural rubbers,
thermoset polymers such as other thermoset polyurethanes or
thermoset polyureas, as well as thermoplastic polymers including
thermoplastic elastomers such as metallocene catalyzed polymer,
unimodal ethylene/carboxylic acid copolymers, unimodal
ethylene/carboxylic acid/carboxylate terpolymers, bimodal
ethylene/carboxylic acid copolymers, bimodal ethylene/carboxylic
acid/carboxylate terpolymers, thermoplastic polyurethanes,
thermoplastic polyureas, polyamides, copolyamides, polyesters,
copolyesters, polycarbonates, polyolefins, halogenated (e.g.
chlorinated) polyolefins, halogenated polyalkylene compounds, such
as halogenated polyethylene [e.g. chlorinated polyethylene (CPE)],
polyalkenamer, polyphenylene oxides, polyphenylene sulfides,
diallyl phthalate polymers, polyimides, polyvinyl chlorides,
polyamide-ionomers, polyurethane-ionomers, polyvinyl alcohols,
polyarylates, polyacrylates, polyphenylene ethers, impact-modified
polyphenylene ethers, polystyrenes, high impact polystyrenes,
acrylonitrile-butadiene-styrene copolymers, styrene-acrylonitriles
(SAN), acrylonitrile-styrene-acrylonitriles, styrene-maleic
anhydride (S/MA) polymers, styrenic block copolymers including
styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene,
(SEBS) and styrene-ethylene-propylene-styrene (SEPS), styrenic
terpolymers, functionalized styrenic block copolymers including
hydroxylated, functionalized styrenic copolymers, and terpolymers,
cellulosic polymers, liquid crystal polymers (LCP),
ethylene-propylene-diene terpolymers (EPDM), ethylene-vinyl acetate
copolymers (EVA), ethylene-propylene copolymers, propylene
elastomers (such as those described in U.S. Pat. No. 6,525,157, to
Kim et al, the entire contents of which is hereby incorporated by
reference in its entirety), ethylene vinyl acetates, polyureas, and
polysiloxanes and any and all combinations thereof.
[0102] Another preferred material which may be used as a component
of the cover layer or intermediate layer(s) of the golf balls of
the present invention are the polyalkenamers which may be prepared
by ring opening metathesis polymerization of one or more
cycloalkenes in the presence of organometallic catalysts as
described in U.S. Pat. Nos. 3,492,245, and 3,804,803, the entire
contents of both of which are herein incorporated by reference.
Examples of suitable polyalkenamer rubbers are polypentenamer
rubber, polyheptenamer rubber, polyoctenamer rubber, polydecenamer
rubber and polydodecenamer rubber. For further details concerning
polyalkenamer rubber, see Rubber Chem. & Tech., Vol. 47, page
511-596, 1974, which is incorporated herein by reference.
Polyoctenamer rubbers are commercially available from Huls AG of
Marl, Germany, and through its distributor in the U.S., Creanova
Inc. of Somerset, N.J., and sold under the trademark
VESTENAMER.RTM.. Two grades of the VESTENAMER.RTM.
trans-polyoctenamer are commercially available: VESTENAMER 8012
designates a material having a trans-content of approximately 80%
(and a cis-content of 20%) with a melting point of approximately
54.degree. C.; and VESTENAMER 6213 designates a material having a
trans-content of approximately 60% (cis-content of 40%) with a
melting point of approximately 30.degree. C. Both of these polymers
have a double bond at every eighth carbon atom in the ring.
[0103] The polyalkenamer rubbers used in the present invention
exhibit excellent melt processability above their sharp melting
temperatures and exhibit high miscibility with various rubber
additives as a major component without deterioration of
crystallinity which in turn facilitates injection molding. Thus,
unlike synthetic rubbers typically used in golf ball preparation,
polyalkenamer-based compounds can be prepared which, are injection
moldable. The polyalkenamer rubbers may also be blended within
other polymers and an especially preferred blend is that of a
polyalkenamer and a polyamide. A more complete description of the
polyalkenamer rubbers and blends with polyamides is disclosed in
copending U.S. Application Ser. No. 11/335,070, filed on Jan. 18,
2006, in the name of Hyun Kim et al., the entire contents of which
are hereby incorporated by reference.
[0104] Another preferred material for either the outer cover and/or
one or intermediate layers of the golf balls of the present
invention is a blend of a homopolyamide or copolyamide modified
with a functional polymer modifier. Illustrative polyamides for use
in the polyamide blend compositions include those obtained by: (1)
polycondensation of (a) a dicarboxylic acid, such as oxalic acid,
adipic acid, sebacic acid, terephthalic acid, isophthalic acid, or
1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as
ethylenediamine, tetramethylenediamine, pentamethylenediamine,
hexamethylenediamine, decamethylenediamine, 1,4-cyclohexyldiamine
or m-xylylenediamine; (2) a ring-opening polymerization of cyclic
lactam, such as .epsilon.-caprolactam or .omega.-laurolactam; (3)
polycondensation of an aminocarboxylic acid, such as 6-aminocaproic
acid, 9-aminononanoic acid, 11-aminoundecanoic acid or
12-aminododecanoic acid; (4) copolymerization of a cyclic lactam
with a dicarboxylic acid and a diamine; or any combination of
(1)-(4). In certain examples, the dicarboxylic acid may be an
aromatic dicarboxylic acid or a cycloaliphatic dicarboxylic acid.
In certain examples, the diamine may be an aromatic diamine or a
cycloaliphatic diamine. Specific examples of suitable polyamides
include polyamide 6; polyamide 11; polyamide 12; polyamide 4,6;
polyamide 6,6; polyamide 6,9; polyamide 6,10; polyamide 6,12;
polyamide MXD6; PA12,CX; PA12, IT; PPA; PA6, IT; and PA6/PPE.
[0105] The functional polymer modifier of the polyamide used in the
ball covers or intermediate layers of the present invention can
include copolymers or terpolymers having a glycidyl group, hydroxyl
group, maleic anhydride group or carboxylic group, collectively
referred to as functionalized polymers. These copolymers and
terpolymers may comprise an .alpha.-olefin. Examples of suitable
.alpha.-olefins include ethylene, propylene, 1-butene, 1-pentene,
3-methyl-1-butene, 1-hexene, 4-methyl-1-petene, 3-methyl-1-pentene,
1-octene, 1-decene-, 1-dodecene, 1-tetradecene, 1-hexadecene,
1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene,
1-octacocene, and 1-triacontene. One or more of these
.alpha.-olefins may be used.
[0106] Examples of suitable glycidyl groups in copolymers or
terpolymers in the polymeric modifier include esters and ethers of
aliphatic glycidyl, such as allylglycidylether, vinylglycidylether,
glycidyl maleate and itaconatem glycidyl acrylate and methacrylate,
and also alicyclic glycidyl esters and ethers, such as
2-cyclohexene-1-glycidylether, cyclohexene-4,5
diglyxidylcarboxylate, cyclohexene-4-glycidyl carobxylate,
5-norboenene-2-methyl-2-glycidyl carboxylate, and
endocis-bicyclo(2,2,1)-5-heptene-2,3-diglycidyl dicarboxylate.
These polymers having a glycidyl group may comprise other monomers,
such as esters of unsaturated carboxylic acid, for example,
alkyl(meth)acrylates or vinyl esters of unsaturated carboxylic
acids. Polymers having a glycidyl group can be obtained by
copolymerization or graft polymerization with homopolymers or
copolymers.
[0107] Examples of suitable terpolymers having a glycidyl group
include LOTADER AX8900 and AX8920, marketed by Atofina Chemicals,
ELVALOY marketed by E.I. Du Pont de Nemours & Co., and REXPEARL
marketed by Nippon Petrochemicals Co., Ltd. Additional examples of
copolymers comprising epoxy monomers and which are suitable for use
within the scope of the present invention include
styrene-butadiene-styrene block copolymers in which the
polybutadiene block contains epoxy group, and
styrene-isoprene-styrene block copolymers in which the polyisoprene
block contains epoxy. Commercially available examples of these
epoxy functional copolymers include ESBS A1005, ESBS A1010, ESBS
A1020, ESBS AT018, and ESBS AT019, marketed by Daicel Chemical
Industries, Ltd.
[0108] Examples of polymers or terpolymers incorporating a maleic
anhydride group suitable for use within the scope of the present
invention include maleic anhydride-modified ethylene-propylene
copolymers, maleic anhydride-modified ethylene-propylene-diene
terpolymers, maleic anhydride-modified polyethylenes, maleic
anhydride-modified polypropylenes, ethylene-ethylacrylate-maleic
anhydride terpolymers, and maleic anhydride-indene-styrene-cumarone
polymers. Examples of commercially available copolymers
incorporating maleic anhydride include: BONDINE, marketed by
Sumitomo Chemical Co., such as BONDINE AX8390, an ethylene-ethyl
acrylate-maleic anhydride terpolymer having a combined ethylene
acrylate and maleic anhydride content of 32% by weight, and BONDINE
TX TX8030, an ethylene-ethyl acrylate-maleic anhydride terpolymer
having a combined ethylene acrylate and maleic anhydride content of
15% by weight and a maleic anhydride content of 1% to 4% by weight;
maleic anhydride-containing LOTADER 3200, 3210, 6200, 8200, 3300,
3400, 3410, 7500, 5500, 4720, and 4700, marketed by Atofina
Chemicals; EXXELOR VA1803, a maleic anyhydride-modified
ethylene-propylene copolymer having a maleic anyhydride content of
0.7% by weight, marketed by Exxon Chemical Co.; and KRATON FG
1901X, a maleic anhydride functionalized triblock copolymer having
polystyrene endblocks and poly(ethylene/butylene) midblocks,
marketed by Shell Chemical. Preferably the functional polymer
component is a maleic anhydride grafted polymers preferably maleic
anhydride grafted polyolefins (for example, Exxellor VA1803).
[0109] Another preferred material which may be used as a component
of the cover layer or intermediate layer of the golf balls of the
present invention is the family of polyurethanes or polyureas which
are typically are prepared by reacting a diisocyanate with a polyol
(in the case of polyurethanes) or with a polyamine (in the case of
a polyurea). Thermoplastic polyurethanes or polyureas may consist
solely of this initial mixture or may be further combined with a
chain extender to vary properties such as hardness of the
thermoplastic. Thermoset polyurethanes or polyureas typically are
formed by the reaction of a diisocyanate and a polyol or polyamine
respectively, and an additional crosslinking agent to crosslink or
cure the material to result in a thermoset.
[0110] In what is known as a one-shot process, the three reactants,
diisocyanate, polyol or polyamine, and optionally a chain extender
or a curing agent, are combined in one step. Alternatively, a
two-step process may occur in which the first step involves
reacting the diisocyanate and the polyol (in the case of
polyurethane) or the polyamine (in the case of a polyurea) to form
a so-called prepolymer, to which can then be added either the chain
extender or the curing agent. This procedure is known as the
prepolymer process.
[0111] In addition, although depicted as discrete component
packages as above, it is also possible to control the degree of
crosslinking, and hence the degree of thermoplastic or thermoset
properties in a final composition, by varying the stoichiometry not
only of the diisocyanate-to-chain extender or curing agent ratio,
but also the initial diisocyanate-to-polyol or polyamine ratio. Of
course in the prepolymer process, the initial
diisocyanate-to-polyol or polyamine ratio is fixed on selection of
the required prepolymer.
[0112] In addition to discrete thermoplastic or thermoset
materials, it also is possible to modify a thermoplastic
polyurethane or polyurea composition by introducing materials in
the composition that undergo subsequent curing after molding the
thermoplastic to provide properties similar to those of a
thermoset. For example, Kim in U.S. Pat. No. 6,924,337, the entire
contents of which are hereby incorporated by reference, discloses a
thermoplastic urethane or urea composition optionally comprising
chain extenders and further comprising a peroxide or peroxide
mixture, which can then undergo post curing to result in a
thermoset.
[0113] Also, Kim et al. in U.S. Pat. No. 6,939,924, the entire
contents of which are hereby incorporated by reference, discloses a
thermoplastic urethane or urea composition, optionally also
comprising chain extenders, that is prepared from a diisocyanate
and a modified or blocked diisocyanate which unblocks and induces
further cross linking post extrusion. The modified isocyanate
preferably is selected from the group consisting of: isophorone
diisocyanate (IPDI)-based uretdione-type crosslinker; a combination
of a uretdione adduct of IPDI and a partially
.epsilon.-caprolactam-modified IPDI; a combination of isocyanate
adducts modified by .epsilon.-caprolactam and a carboxylic acid
functional group; a caprolactam-modified Desmodur diisocyanate; a
Desmodur diisocyanate having a 3,5-dimethylpyrazole modified
isocyanate; or mixtures of these.
[0114] Finally, Kim et al. in U.S. Pat. No. 7,037,985 B2, the
entire contents of which are hereby incorporated by reference,
discloses thermoplastic urethane or urea compositions further
comprising a reaction product of a nitroso compound and a
diisocyanate or a polyisocyanate. The nitroso reaction product has
a characteristic temperature at which it decomposes to regenerate
the nitroso compound and diisocyanate or polyisocyanate. Thus, by
judicious choice of the post-processing temperature, further
crosslinking can be induced in the originally thermoplastic
composition to provide thermoset-like properties.
[0115] Any isocyanate available to one of ordinary skill in the art
is suitable for use according to the invention. Isocyanates for use
with the present invention include, but are not limited to,
aliphatic, cycloaliphatic, aromatic aliphatic, aromatic, any
derivatives thereof, and combinations of these compounds having two
or more isocyanate (NCO) groups per molecule. As used herein,
aromatic aliphatic compounds should be understood as those
containing an aromatic ring, wherein the isocyanate group is not
directly bonded to the ring. One example of an aromatic aliphatic
compound is a tetramethylene diisocyanate (TMXDI). The isocyanates
may be organic polyisocyanate-terminated prepolymers, low free
isocyanate prepolymer, and mixtures thereof. The
isocyanate-containing reactable component also may include any
isocyanate-functional monomer, dimer, trimer, or polymeric adduct
thereof, prepolymer, quasi-prepolymer, or mixtures thereof.
Isocyanate-functional compounds may include monoisocyanates or
polyisocyanates that include any isocyanate functionality of two or
more.
[0116] Suitable isocyanate-containing components include
diisocyanates having the generic structure:
O.dbd.C.dbd.N--R--N.dbd.C.dbd.O, where R preferably is a cyclic,
aromatic, or linear or branched hydrocarbon moiety containing from
about 1 to about 50 carbon atoms. The isocyanate also may contain
one or more cyclic groups or one or more phenyl groups. When
multiple cyclic or aromatic groups are present, linear and/or
branched hydrocarbons containing from about 1 to about 10 carbon
atoms can be present as spacers between the cyclic or aromatic
groups. In some cases, the cyclic or aromatic group(s) may be
substituted at the 2-, 3-, and/or 4-positions, or at the ortho-,
meta-, and/or para-positions, respectively. Substituted groups may
include, but are not limited to, halogens, primary, secondary, or
tertiary hydrocarbon groups, or a mixture thereof.
[0117] Examples of isocyanates that can be used with the present
invention include, but are not limited to, substituted and isomeric
mixtures including 2,2'-, 2,4'-, and 4,4'-diphenylmethane
diisocyanate (MDI); 3,3'-dimethyl-4,4'-biphenylene diisocyanate
(TODI); toluene diisocyanate (TDI); polymeric MDI;
carbodiimide-modified liquid 4,4'-diphenylmethane diisocyanate;
para-phenylene diisocyanate (PPDI); meta-phenylene diisocyanate
(MPDI); triphenyl methane-4,4'- and triphenyl
methane-4,4''-triisocyanate; naphthylene-1,5-diisocyanate; 2,4'-,
4,4'-, and 2,2-biphenyl diisocyanate; polyphenylene polymethylene
polyisocyanate (PMDI) (also known as polymeric PMDI); mixtures of
MDI and PMDI; mixtures of PMDI and TDI; ethylene diisocyanate;
propylene-1,2-diisocyanate; trimethylene diisocyanate; butylenes
diisocyanate; bitolylene diisocyanate; tolidine diisocyanate;
tetramethylene-1,2-diisocyanate; tetramethylene-1,3-diisocyanate;
tetramethylene-1,4-diisocyanate; pentamethylene diisocyanate;
1,6-hexamethylene diisocyanate (HDI); octamethylene diisocyanate;
decamethylene diisocyanate; 2,2,4-trimethylhexamethylene
diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate;
dodecane-1,12-diisocyanate; dicyclohexylmethane diisocyanate;
cyclobutane-1,3-diisocyanate; cyclohexane-1,2-diisocyanate;
cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;
diethylidene diisocyanate; methylcyclohexylene diisocyanate (HTDI);
2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane
diisocyanate; 4,4'-dicyclohexyl diisocyanate; 2,4'-dicyclohexyl
diisocyanate; 1,3,5-cyclohexane triisocyanate;
isocyanatomethylcyclohexane isocyanate;
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;
isocyanatoethylcyclohexane isocyanate;
bis(isocyanatomethyl)-cyclohexane diisocyanate;
4,4'-bis(isocyanatomethyl)dicyclohexane;
2,4'-bis(isocyanatomethyl)dicyclohexane; isophorone diisocyanate
(IPDI); dimeryl diisocyanate, dodecane-1,12-diisocyanate,
1,10-decamethylene diisocyanate, cyclohexylene-1,2-diisocyanate,
1,10-decamethylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate,
furfurylidene diisocyanate, 2,4,4-trimethyl hexamethylene
diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate,
dodecamethylene diisocyanate, 1,3-cyclopentane diisocyanate,
1,3-cyclohexane diisocyanate, 1,3-cyclobutane diisocyanate,
1,4-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl
isocyanate), 4,4'-methylenebis(phenyl isocyanate),
1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane
diisocyanate, 1,3-bis(isocyanato-methyl)cyclohexane,
1,6-diisocyanato-2,2,4,4-tetra-methylhexane,
1,6-diisocyanato-2,4,4-tetra-trimethylhexane,
trans-cyclohexane-1,4-diisocyanate,
3-isocyanato-methyl-3,5,5-trimethylcyclo-hexyl isocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane,
cyclohexyl isocyanate, dicyclohexylmethane 4,4'-diisocyanate,
1,4-bis(isocyanatomethyl)cyclohexane, m-phenylene diisocyanate,
m-xylylene diisocyanate, m-tetramethylxylylene diisocyanate,
p-phenylene diisocyanate, p,p'-biphenyl diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenylene diisocyanate,
3,3'-diphenyl-4,4'-biphenylene diisocyanate, 4,4'-biphenylene
diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate,
1,5-naphthalene diisocyanate, 4-chloro-1,3-phenylene diisocyanate,
1,5-tetrahydronaphthalene diisocyanate, metaxylene diisocyanate,
2,4-toluene diisocyanate, 2,4'-diphenylmethane diisocyanate,
2,4-chlorophenylene diisocyanate, 4,4'-diphenylmethane
diisocyanate, p,p'-diphenylmethane diisocyanate, 2,4-tolylene
diisocyanate, 2,6-tolylene diisocyanate,
2,2-diphenylpropane-4,4'-diisocyanate, 4,4'-toluidine diisocyanate,
dianidine diisocyanate, 4,4'-diphenyl ether diisocyanate,
1,3-xylylene diisocyanate, 1,4-naphthylene diisocyanate,
azobenzene-4,4'-diisocyanate, diphenyl sulfone-4,4'-diisocyanate,
triphenylmethane 4,4',4''-triisocyanate, isocyanatoethyl
methacrylate,
3-isopropenyl-.alpha.,.alpha.-dimethylbenzyl-isocyanate,
dichlorohexamethylene diisocyanate, .omega.,
.omega.'-diisocyanato-1,4-diethylbenzene, polymethylene
polyphenylene polyisocyanate, isocyanurate modified compounds, and
carbodiimide modified compounds, as well as biuret modified
compounds of the above polyisocyanates. These isocyanates may be
used either alone or in combination. These combination isocyanates
include triisocyanates, such as biuret of hexamethylene
diisocyanate and triphenylmethane triisocyanates, and
polyisocyanates, such as polymeric diphenylmethane
diisocyanate.triisocyanate of HDI; triisocyanate of
2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI);
4,4'-dicyclohexylmethane diisocyanate (H.sub.12MDI);
2,4-hexahydrotoluene diisocyanate; 2,6-hexahydrotoluene
diisocyanate; 1,2-, 1,3-, and 1,4-phenylene diisocyanate; aromatic
aliphatic isocyanate, such as 1,2-, 1,3-, and 1,4-xylene
diisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);
para-tetramethylxylene diisocyanate (p-TMXDI); trimerized
isocyanurate of any polyisocyanate, such as isocyanurate of toluene
diisocyanate, trimer of diphenylmethane diisocyanate, trimer of
tetramethylxylene diisocyanate, isocyanurate of hexamethylene
diisocyanate, and mixtures thereof, dimerized uretdione of any
polyisocyanate, such as uretdione of toluene diisocyanate,
uretdione of hexamethylene diisocyanate, and mixtures thereof;
modified polyisocyanate derived from the above isocyanates and
polyisocyanates; and mixtures thereof.
[0118] Any polyol now known or hereafater developed is suitable for
use according to the invention. Polyols suitable for use in the
present invention include, but are not limited to, polyester
polyols, polyether polyols, polycarbonate polyols and polydiene
polyols such as polybutadiene polyols.
[0119] Any polyamine available to one of ordinary skill in the
polyurethane art is suitable for use according to the invention.
Polyamines suitable for use in the compositions of the present
invention include, but are not limited to, amine-terminated
compounds typically are selected from amine-terminated
hydrocarbons, amine-terminated polyethers, amine-terminated
polyesters, amine-terminated polycaprolactones, amine-terminated
polycarbonates, amine-terminated polyamides, and mixtures thereof.
The amine-terminated compound may be a polyether amine selected
from polytetramethylene ether diamines, polyoxypropylene diamines,
poly(ethylene oxide capped oxypropylene) ether diamines,
triethyleneglycoldiamines, propylene oxide-based triamines,
trimethylolpropane-based triamines, glycerin-based triamines, and
mixtures thereof.
[0120] The diisocyanate and polyol or polyamine components may be
combined to form a prepolymer prior to reaction with a chain
extender or curing agent. Any such prepolymer combination is
suitable for use in the present invention.
[0121] One preferred prepolymer is a toluene diisocyanate
prepolymer with polypropylene glycol. Such polypropylene glycol
terminated toluene diisocyanate prepolymers are available from
Uniroyal Chemical Company of Middlebury, Conn., under the trade
name ADIPRENE.RTM.LFG963A and LFG640D. Most preferred prepolymers
are the polytetramethylene ether glycol terminated toluene
diisocyanate prepolymers including those available from Uniroyal
Chemical Company of Middlebury, Conn., under the trade name
ADIPRENE.RTM. LF930A, LF950A, LF601D, and LF751D.
[0122] In one embodiment, the number of free NCO groups in the
urethane or urea prepolymer may be less than about 14 percent.
Preferably the urethane or urea prepolymer has from about 3 percent
to about 11 percent, more preferably from about 4 to about 9.5
percent, and even more preferably from about 3 percent to about 9
percent, free NCO on an equivalent weight basis.
[0123] Polyol chain extenders or curing agents may be primary,
secondary, or tertiary polyols. Non-limiting examples of monomers
of these polyols include: trimethylolpropane (TMP), ethylene
glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, propylene glycol, dipropylene glycol,
1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-pentanediol,
2,3-pentanediol, 2,5-hexanediol, 2,4-hexanediol,
2-ethyl-1,3-hexanediol, cyclohexanediol, and
2-ethyl-2-(hydroxymethyl)-1,3-propanediol.
[0124] Diamines and other suitable polyamines may be added to the
compositions of the present invention to function as chain
extenders or curing agents. These include primary, secondary and
tertiary amines having two or more amines as functional groups.
Exemplary diamines include aliphatic diamines, such as
tetramethylenediamine, pentamethylenediamine, hexamethylenediamine;
alicyclic diamines, such as 3,3'-dimethyl-4,4'-diamino-dicyclohexyl
methane; or aromatic diamines, such as diethyl-2,4-toluenediamine,
4,4''-methylenebis-(3-chloro,2,6-diethyl)-aniline (available from
Air Products and Chemicals Inc., of Allentown, Pa., under the trade
name LONZACURE.RTM.), 3,3'-dichlorobenzidene;
3,3'-dichloro-4,4'-diaminodiphenyl methane (MOCA);
N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine,
3,5-dimethylthio-2,4-toluenediamine;
3,5-dimethylthio-2,6-toluenediamine; N,N'-dialkyldiamino diphenyl
methane; trimethylene-glycol-di-p-aminobenzoate;
polytetramethyleneoxide-di-p-aminobenzoate, 4,4'-methylene
bis-2-chloroaniline, 2,2',3,3'-tetrachloro-4,4'-diamino-phenyl
methane, p,p'-methylenedianiline, p-phenylenediamine or
4,4'-diaminodiphenyl; and
2,4,6-tris(dimethylaminomethyl)phenol.
[0125] Depending on their chemical structure, curing agents may be
slow- or fast-reacting polyamines or polyols. As described in U.S.
Pat. Nos. 6,793,864, 6,719,646 and copending U.S. Patent
Publication No. 2004/0201133 A1, (the contents of all of which are
hereby incorporated herein by reference), slow-reacting polyamines
are diamines having amine groups that are sterically and/or
electronically hindered by electron withdrawing groups or bulky
groups situated proximate to the amine reaction sites. The spacing
of the amine reaction sites will also affect the reactivity speed
of the polyamines.
[0126] Suitable curatives for use in the present invention are
selected from the slow-reacting polyamine group include, but are
not limited to, 3,5-dimethylthio-2,4-toluenediamine;
3,5-dimethylthio-2,6-toluenediamine; N,N'-dialkyldiamino diphenyl
methane; trimethylene-glycol-di-p-aminobenzoate;
polytetramethyleneoxide-di-p-aminobenzoate, and mixtures thereof.
Of these, 3,5-dimethylthio-2,4-toluenediamine and
3,5-dimethylthio-2,6-toluenediamine are isomers and are sold under
the trade name ETHACURE.RTM. 300 by Ethyl Corporation. Trimethylene
glycol-di-p-aminobenzoate is sold under the trade name POLACURE
740M and polytetramethyleneoxide-di-p-aminobenzoates are sold under
the trade name POLAMINES by Polaroid Corporation.
N,N'-dialkyldiamino diphenyl methane is sold under the trade name
UNILINK.RTM. by UOP.
[0127] Also included as a curing agent for use in the polyurethane
or polyurea compositions used in the present invention are the
family of dicyandiamides as described in copending application Ser.
No. 11/809,432 filed on May 31, 2007 by Kim et al., the entire
contents of which are hereby incorporated by reference
Core Composition
[0128] The cores of the golf balls of the present invention may
include the traditional rubber components used in golf ball
applications including, both natural and synthetic rubbers, such as
cis-1,4-polybutadiene, trans-1,4-polybutadiene, 1,2-polybutadiene,
cis-polyisoprene, trans-polyisoprene, polychloroprene,
polybutylene, styrene-butadiene rubber, styrene-butadiene-styrene
block copolymer and partially and fully hydrogenated equivalents,
styrene-isoprene-styrene block copolymer and partially and fully
hydrogenated equivalents, nitrile rubber, silicone rubber, and
polyurethane, as well as mixtures of these. Polybutadiene rubbers,
especially 1,4-polybutadiene rubbers containing at least 40 mol %,
and more preferably 80 to 100 mol % of cis-1,4 bonds, are preferred
because of their high rebound resilience, moldability, and high
strength after vulcanization. The polybutadiene component may be
synthesized by using rare earth-based catalysts, nickel-based
catalysts, or cobalt-based catalysts, conventionally used in this
field. Polybutadiene obtained by using lanthanum rare earth-based
catalysts usually employ a combination of a lanthanum rare earth
(atomic number of 57 to 71)-compound, but particularly preferred is
a neodymium compound.
[0129] The 1,4-polybutadiene rubbers have a molecular weight
distribution (Mw/Mn) of from about 1.2 to about 4.0, preferably
from about 1.7 to about 3.7, even more preferably from about 2.0 to
about 3.5, most preferably from about 2.2 to about 3.2. The
polybutadiene rubbers have a Mooney viscosity (ML.sub.1+4
(100.degree. C.)) of from about 20 to about 80, preferably from
about 30 to about 70, even more preferably from about 30 to about
60, most preferably from about 35 to about 50. The term "Mooney
viscosity" used herein refers in each case to an industrial index
of viscosity as measured with a Mooney viscometer, which is a type
of rotary plastometer (see JIS K6300). This value is represented by
the symbol ML.sub.1+4 (100.degree. C.), wherein "M" stands for
Mooney viscosity, "L" stands for large rotor (L-type), "1+4" stands
for a pre-heating time of 1 minute and a rotor rotation time of 4
minutes, and "100.degree. C." indicates that measurement was
carried out at a temperature of 100.degree. C. As readily
appreciated by one skilled in the art, blends of polybutadiene
rubbers may also be utilized in the golf balls of the present
invention, such blends may be prepared with any mixture of rare
earth-based catalysts, nickel-based catalysts, or cobalt-based
catalysts derived materials, and from materials having different
molecular weights, molecular weight distributions and Mooney
viscosity.
[0130] The cores of the golf balls of the present invention may
also include 1,2-polybutadienes having differing tacticity, all of
which are suitable as unsaturated polymers for use in the presently
disclosed compositions, are atactic 1,2-polybutadiene, isotactic
1,2-polybutadiene, and syndiotactic 1,2-polybutadiene. Syndiotactic
1,2-polybutadiene having crystallinity suitable for use as an
unsaturated polymer in the presently disclosed compositions are
polymerized from a 1,2-addition of butadiene. The presently
disclosed golf balls may include syndiotactic 1,2-polybutadiene
having crystallinity and greater than about 70% of 1,2-bonds, more
preferably greater than about 80% of 1,2-bonds, and most preferably
greater than about 90% of 1,2-bonds. Also, the 1,2-polybutadiene
may have a mean molecular weight between about 10,000 and about
350,000, more preferably between about 50,000 and about 300,000,
more preferably between about 80,000 and about 200,000, and most
preferably between about 10,000 and about 150,000. Examples of
suitable syndiotactic 1,2-polybutadienes having crystallinity
suitable for use in golf balls are sold under the trade names
RB810, RB820, and RB830 by JSR Corporation of Tokyo, Japan.
[0131] The cores of the golf balls of the present invention may
also include the polyalkenamer rubbers as previously described
herein and disclosed in copending U.S. application Ser. No.
11/335,070, filed on Jan. 18, 2006, in the name of Hyun Kim et al.,
the entire contents of which are hereby incorporated by
reference.
[0132] When synthetic rubbers such as the aforementioned
polybutadienes or polyalkenamers and their blends are used in the
golf balls of the present invention they may contain further
materials typically often used in rubber formulations including
crosslinking agents, co-crosslinking agents, peptizers and
accelerators.
[0133] Suitable cross-linking agents for use in the golf balls of
the present invention include peroxides, sulfur compounds, or other
known chemical cross-linking agents, as well as mixtures of these.
Non-limiting examples of suitable cross-linking agents include
primary, secondary, or tertiary aliphatic or aromatic organic
peroxides. Peroxides containing more than one peroxy group can be
used, such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and
1,4-di-(2-tert-butyl peroxyisopropyl)benzene. Both symmetrical and
asymmetrical peroxides can be used, for example, tert-butyl
perbenzoate and tert-butyl cumyl peroxide. Peroxides incorporating
carboxyl groups also are suitable. The decomposition of peroxides
used as cross-linking agents in the present invention can be
brought about by applying thermal energy, shear, irradiation,
reaction with other chemicals, or any combination of these. Both
homolytically and heterolytically decomposed peroxide can be used
in the present invention. Non-limiting examples of suitable
peroxides include: diacetyl peroxide; di-tert-butyl peroxide;
dibenzoyl peroxide; dicumyl peroxide;
2,5-dimethyl-2,5-di(benzoylperoxy)hexane;
1,4-bis-(t-butylperoxyisopropyl)benzene; t-butylperoxybenzoate;
2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, such as Trigonox
145-45B, marketed by Akrochem Corp. of Akron, Ohio;
1,1-bis(t-butylperoxy)-3,3,5 tri-methylcyclohexane, such as Varox
231-XL, marketed by R.T. Vanderbilt Co., Inc. of Norwalk, Conn.;
and di-(2,4-dichlorobenzoyl)peroxide. The cross-linking agents can
be blended in total amounts of about 0.05 part to about 5 parts,
more preferably about 0.2 part to about 3 parts, and most
preferably about 0.2 part to about 2 parts, by weight of the
cross-linking agents per 100 parts by weight of the unsaturated
polymer.
[0134] Each cross-linking agent has a characteristic decomposition
temperature at which 50% of the cross-linking agent has decomposed
when subjected to that temperature for a specified time period
(t.sub.1/2). For example,
1,1-bis-(t-butylperoxy)-3,3,5-tri-methylcyclohexane at
t.sub.1/2=0.1 hr has a decomposition temperature of 138.degree. C.
and 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3 at t.sub.112=0.1 hr
has a decomposition temperature of 182.degree. C. Two or more
cross-linking agents having different characteristic decomposition
temperatures at the same t.sub.112 may be blended in the
composition. For example, where at least one cross-linking agent
has a first characteristic decomposition temperature less than
150.degree. C., and at least one cross-linking agent has a second
characteristic decomposition temperature greater than 150.degree.
C., the composition weight ratio of the at least one cross-linking
agent having the first characteristic decomposition temperature to
the at least one cross-linking agent having the second
characteristic decomposition temperature can range from 5:95 to
95:5, or more preferably from 10:90 to 50:50.
[0135] Besides the use of chemical cross-linking agents, exposure
of the composition to radiation also can serve as a cross-linking
agent. Radiation can be applied to the unsaturated polymer mixture
by any known method, including using microwave or gamma radiation,
or an electron beam device. Additives may also be used to improve
radiation curing of the diene polymer.
[0136] The rubber and cross-linking agent may be blended with a
co-cross-linking agent, which may be a metal salt of an unsaturated
carboxylic acid. Examples of these include zinc and magnesium salts
of unsaturated fatty acids having 3 to 8 carbon atoms, such as
acrylic acid, methacrylic acid, maleic acid, and fumaric acid,
palmitic acid with the zinc salts of acrylic and methacrylic acid
being most preferred. The unsaturated carboxylic acid metal salt
can be blended in a rubber either as a preformed metal salt, or by
introducing an .alpha.,.beta.-unsaturated carboxylic acid and a
metal oxide or hydroxide into the rubber composition, and allowing
them to react in the rubber composition to form a metal salt. The
unsaturated carboxylic acid metal salt can be blended in any
desired amount, but preferably in amounts of about 10 parts to
about 60 parts by weight of the unsaturated carboxylic acid per 100
parts by weight of the synthetic rubber.
[0137] The core compositions used in the present invention may also
incorporate one or more of the so-called "peptizers". The peptizer
preferably comprises an organic sulfur compound and/or its metal or
non-metal salt. Examples of such organic sulfur compounds include
thiophenols, such as pentachlorothiophenol, 4-butyl-o-thiocresol, 4
t-butyl-p-thiocresol, and 2-benzamidothiophenol; thiocarboxylic
acids, such as thiobenzoic acid; 4,4' dithio dimorpholine; and,
sulfides, such as dixylyl disulfide, dibenzoyl disulfide;
dibenzothiazyl disulfide; di(pentachlorophenyl) disulfide;
dibenzamido diphenyldisulfide (DBDD), and alkylated phenol
sulfides, such as VULTAC marketed by Atofina Chemicals, Inc. of
Philadelphia, Pa. Preferred organic sulfur compounds include
pentachlorothiophenol, and dibenzamido diphenyldisulfide.
[0138] Examples of the metal salt of an organic sulfur compound
include sodium, potassium, lithium, magnesium calcium, barium,
cesium and zinc salts of the above-mentioned thiophenols and
thiocarboxylic acids, with the zinc salt of pentachlorothiophenol
being most preferred.
[0139] Examples of the non-metal salt of an organic sulfur compound
include ammonium salts of the above-mentioned thiophenols and
thiocarboxylic acids wherein the ammonium cation has the general
formula [NR.sup.1R.sup.2R.sup.3R.sup.4].sup.+ where R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 are selected from the group consisting
of hydrogen, a C.sub.1-C.sub.20 aliphatic, cycloaliphatic or
aromatic moiety, and any and all combinations thereof, with the
most preferred being the NH.sub.4.sup.+-salt of
pentachlorothiophenol.
[0140] Additional peptizers include aromatic or conjugated
peptizers comprising one or more heteroatoms, such as nitrogen,
oxygen and/or sulfur. More typically, such peptizers are heteroaryl
or heterocyclic compounds having at least one heteroatom, and
potentially plural heteroatoms, where the plural heteroatoms may be
the same or different. Such peptizers include peptizers such as an
indole peptizer, a quinoline peptizer, an isoquinoline peptizer, a
pyridine peptizer, purine peptizer, a pyrimidine peptizer, a
diazine peptizer, a pyrazine peptizer, a triazine peptizer, a
carbazole peptizer, or combinations of such peptizers.
[0141] Suitable peptizers also may include one or more additional
functional groups, such as halogens, particularly chlorine; a
sulfur-containing moiety exemplified by thiols, where the
functional group is sulfhydryl (--SH), thioethers, where the
functional group is --SR, disulfides, (R.sub.1S--SR.sub.2), etc.;
and combinations of functional groups. Such peptizers are more
fully disclosed in copending U.S. Application No. 60/752,475 filed
on Dec. 20, 2005 in the name of Hyun Kim et al, the entire contents
of which are herein incorporated by reference. A most preferred
example is 2,3,5,6-tetrachloro-4-pyridinethiol (TCPT).
[0142] The peptizer, if employed in the golf balls of the present
invention, is present in an amount up to about 10, from about 0.01
to about 10, preferably of from about 0.10 to about 7, more
preferably of from about 0.15 to about 5 parts by weight per 100
parts by weight of the synthetic rubber component.
[0143] The core compositions can also comprise one or more
accelerators of one or more classes. Accelerators are added to an
unsaturated polymer to increase the vulcanization rate and/or
decrease the vulcanization temperature. Accelerators can be of any
class known for rubber processing including mercapto-,
sulfenamide-, thiuram, dithiocarbamate, dithiocarbamyl-sulfenamide,
xanthate, guanidine, amine, thiourea, and dithiophosphate
accelerators. Specific commercial accelerators include
2-mercaptobenzothiazole and its metal or non-metal salts, such as
Vulkacit Mercapto C, Mercapto MGC, Mercapto ZM-5, and ZM marketed
by Bayer AG of Leverkusen, Germany, Nocceler M, Nocceler MZ, and
Nocceler M-60 marketed by Ouchisinko Chemical Industrial Company,
Ltd. of Tokyo, Japan, and MBT and ZMBT marketed by Akrochem
Corporation of Akron, Ohio. A more complete list of commercially
available accelerators is given in The Vanderbilt Rubber Handbook:
13.sup.th Edition (1990, R.T. Vanderbilt Co.), pp. 296-330, in
Encyclopedia of Polymer Science and Technology, Vol. 12 (1970, John
Wiley & Sons), pp. 258-259, and in Rubber Technology Handbook
(1980, Hanser/Gardner Publications), pp. 234-236. Preferred
accelerators include 2-mercaptobenzothiazole (MBT) and its salts.
The synthetic rubber composition can further incorporate from about
0.1 part to about 10 parts by weight of the accelerator per 100
parts by weight of the rubber. More preferably, the ball
composition can further incorporate from about 0.2 part to about 5
parts, and most preferably from about 0.5 part to about 1.5 parts,
by weight of the accelerator per 100 parts by weight of the
rubber.
Fillers
[0144] The various polymeric compositions used to prepare the golf
balls of the present invention also can incorporate one or more
fillers. Such fillers are typically in a finely divided form, for
example, in a size generally less than about 20 mesh, preferably
less than about 100 mesh U.S. standard size, except for fibers and
flock, which are generally elongated. Filler particle size will
depend upon desired effect, cost, ease of addition, and dusting
considerations. The appropriate amounts of filler required will
vary depending on the application but typically can be readily
determined without undue experimentation.
[0145] The filler preferably is selected from the group consisting
of precipitated hydrated silica, limestone, clay, talc, asbestos,
barytes, glass fibers, aramid fibers, mica, calcium metasilicate,
barium sulfate, zinc sulfide, lithopone, silicates, silicon
carbide, diatomaceous earth, carbonates such as calcium or
magnesium or barium carbonate, sulfates such as calcium or
magnesium or barium sulfate, metals, including tungsten, steel,
copper, cobalt or iron, metal alloys, tungsten carbide, metal
oxides, metal stearates, and other particulate carbonaceous
materials, and any and all combinations thereof. Preferred examples
of fillers include metal oxides, such as zinc oxide and magnesium
oxide. In another preferred aspect the filler comprises a
continuous or non-continuous fiber. In another preferred aspect the
filler comprises one or more so called nanofillers, as described in
U.S. Pat. No. 6,794,447 and copending U.S. patent application Ser.
No. 10/670,090 filed on Sep. 24, 2003 and copending U.S. patent
application Ser. No. 10/926,509 filed on Aug. 25, 2004, the entire
contents of each of which are incorporated herein by reference.
[0146] Inorganic nanofiller material generally is made of clay,
such as hydrotalcite, phyllosilicate, saponite, hectorite,
beidellite, stevensite, vermiculite, halloysite, mica,
montmorillonite, micafluoride, or octosilicate. To facilitate
incorporation of the nanofiller material into a polymer material,
either in preparing nanocomposite materials or in preparing
polymer-based golf ball compositions, the clay particles generally
are coated or treated by a suitable compatibilizing agent. The
compatibilizing agent allows for superior linkage between the
inorganic and organic material, and it also can account for the
hydrophilic nature of the inorganic nanofiller material and the
possibly hydrophobic nature of the polymer. Compatibilizing agents
may exhibit a variety of different structures depending upon the
nature of both the inorganic nanofiller material and the target
matrix polymer. Non-limiting examples include hydroxy-, thiol-,
amino-, epoxy-, carboxylic acid-, ester-, amide-, and siloxy-group
containing compounds, oligomers or polymers. The nanofiller
materials can be incorporated into the polymer either by dispersion
into the particular monomer or oligomer prior to polymerization, or
by melt compounding of the particles into the matrix polymer.
Examples of commercial nanofillers are various Cloisite grades
including 10A, 15A, 20A, 25A, 30B, and NA+ of Southern Clay
Products (Gonzales, Tex.) and the Nanomer grades including 1.24TL
and C.30EVA of Nanocor, Inc. (Arlington Heights, Ill.).
[0147] Nanofillers when added into a matrix polymer, such as the
polyalkenamer rubber, can be mixed in three ways. In one type of
mixing there is dispersion of the aggregate structures within the
matrix polymer, but on mixing no interaction of the matrix polymer
with the aggregate platelet structure occurs, and thus the stacked
platelet structure is essentially maintained. As used herein, this
type of mixing is defined as "undispersed".
[0148] However, if the nanofiller material is selected correctly,
the matrix polymer chains can penetrate into the aggregates and
separate the platelets, and thus when viewed by transmission
electron microscopy or x-ray diffraction, the aggregates of
platelets are expanded. At this point the nanofiller is said to be
substantially evenly dispersed within and reacted into the
structure of the matrix polymer. This level of expansion can occur
to differing degrees. If small amounts of the matrix polymer are
layered between the individual platelets then, as used herein, this
type of mixing is known as "intercalation".
[0149] In some circumstances, further penetration of the matrix
polymer chains into the aggregate structure separates the
platelets, and leads to a complete disruption of the platelet's
stacked structure in the aggregate. Thus, when viewed by
transmission electron microscopy (TEM), the individual platelets
are thoroughly mixed throughout the matrix polymer. As used herein,
this type of mixing is known as "exfoliated". An exfoliated
nanofiller has the platelets fully dispersed throughout the polymer
matrix; the platelets may be dispersed unevenly but preferably are
dispersed evenly.
[0150] While not wishing to be limited to any theory, one possible
explanation of the differing degrees of dispersion of such
nanofillers within the matrix polymer structure is the effect of
the compatibilizer surface coating on the interaction between the
nanofiller platelet structure and the matrix polymer. By careful
selection of the nanofiller it is possible to vary the penetration
of the matrix polymer into the platelet structure of the nanofiller
on mixing. Thus, the degree of interaction and intrusion of the
polymer matrix into the nanofiller controls the separation and
dispersion of the individual platelets of the nanofiller within the
polymer matrix. This interaction of the polymer matrix and the
platelet structure of the nanofiller is defined herein as the
nanofiller "reacting into the structure of the polymer" and the
subsequent dispersion of the platelets within the polymer matrix is
defined herein as the nanofiller "being substantially evenly
dispersed" within the structure of the polymer matrix.
[0151] If no compatibilizer is present on the surface of a filler
such as a clay, or if the coating of the clay is attempted after
its addition to the polymer matrix, then the penetration of the
matrix polymer into the nanofiller is much less efficient, very
little separation and no dispersion of the individual clay
platelets occurs within the matrix polymer.
[0152] Physical properties of the polymer will change with the
addition of nanofiller. The physical properties of the polymer are
expected to improve even more as the nanofiller is dispersed into
the polymer matrix to form a nanocomposite.
[0153] Materials incorporating nanofiller materials can provide
these property improvements at much lower densities than those
incorporating conventional fillers. For example, a nylon-6
nanocomposite material manufactured by RTP Corporation of Wichita,
Kans., uses a 3% to 5% clay loading and has a tensile strength of
11,800 psi and a specific gravity of 1.14, while a conventional 30%
mineral-filled material has a tensile strength of 8,000 psi and a
specific gravity of 1.36. Using nanocomposite materials with lower
inorganic materials loadings than conventional fillers provides the
same properties, and this allows products comprising nanocomposite
fillers to be lighter than those with conventional fillers, while
maintaining those same properties.
[0154] Nanocomposite materials are materials incorporating up to
about 20%, or from about 0.1% to about 20%, preferably from about
0.1% to about 15%, and most preferably from about 0.1% to about 10%
of nanofiller reacted into and substantially dispersed through
intercalation or exfoliation into the structure of an organic
material, such as a polymer, to provide strength, temperature
resistance, and other property improvements to the resulting
composite. Descriptions of particular nanocomposite materials and
their manufacture can be found in U.S. Pat. Nos. 5,962,553 to
Ellsworth, 5,385,776 to Maxfield et al., and 4,894,411 to Okada et
al. Examples of nanocomposite materials currently marketed include
M1030D, manufactured by Unitika Limited, of Osaka, Japan, and
1015C2, manufactured by UBE America of New York, N.Y.
[0155] When nanocomposites are blended with other polymer systems,
the nanocomposite may be considered a type of nanofiller
concentrate. However, a nanofiller concentrate may be more
generally a polymer into which nanofiller is mixed; a nanofiller
concentrate does not require that the nanofiller has reacted and/or
dispersed evenly into the carrier polymer.
[0156] The nanofiller material is added in an amount up to about 20
wt %, from about 0.1% to about 20%, preferably from about 0.1% to
about 15%, and most preferably from about 0.1% to about 10% by
weight (based on the final weight of the polymer matrix material)
of nanofiller reacted into and substantially dispersed through
intercalation or exfoliation into the structure of the polymer
matrix.
[0157] If desired, the various polymer compositions used to prepare
the golf balls of the present invention can additionally contain
other conventional additives such as plasticizers, pigments,
antioxidants, U.V. absorbers, optical brighteners, or any other
additives generally employed in plastics formulation or the
preparation of golf balls.
[0158] Another particularly well-suited additive for use in the
various polymer compositions used to prepare the golf balls of the
present invention includes compounds having the general
formula:
(R.sub.2N).sub.m--R'--(X(O).sub.nOR.sub.y).sub.m,
where R is hydrogen, or a C.sub.1-C.sub.20 aliphatic,
cycloaliphatic or aromatic systems; R' is a bridging group
comprising one or more C.sub.1-C.sub.20 straight chain or branched
aliphatic or alicyclic groups, or substituted straight chain or
branched aliphatic or alicyclic groups, or aromatic group, or an
oligomer of up to 12 repeating units including, but not limited to,
polypeptides derived from an amino acid sequence of up to 12 amino
acids; and X is C or S with the proviso that when X.dbd.C, n=1 and
y=1 and when X.dbd.S, n=2 and y=1. Also, m=1-3. These materials are
more fully described in copending U.S. patent application Ser. No.
11/182,170, filed on Jul. 14, 2005, the entire contents of which
are incorporated herein by reference.
[0159] Preferably the material is selected from the group
consisting of 4,4'-methylene-bis-(cyclohexylamine)carbamate
(commercially available from R.T. Vanderbilt Co., Norwalk Conn.
under the tradename Diak.RTM. 4), 11-aminoundecanoic acid,
12-aminododecanoic acid, epsilon-caprolactam; omega-caprolactam,
and any and all combinations thereof.
[0160] In an especially preferred aspect, a nanofiller additive
component in the golf ball of the present invention is surface
modified with a compatibilizing agent comprising the earlier
described compounds having the general formula:
(R.sub.2N).sub.m--R'--(X(O).sub.nOR.sub.y).sub.m,
A most preferred aspect would be a filler comprising a nanofiller
clay material surface modified with an amino acid including
12-aminododecanoic acid. Such fillers are available from Nanonocor
Co. under the tradename Nanomer 1.24TL.
[0161] The filler can be blended in variable effective amounts,
such as amounts of greater than 0 to at least about 80 parts, and
more typically from about 10 parts to about 80 parts, by weight per
100 parts by weight of the base rubber. If desired, the rubber
composition can additionally contain effective amounts of a
plasticizer, an antioxidant, and any other additives generally used
to make golf balls.
[0162] The various polymer compositions used to prepare the golf
balls of the present invention may also be further modified by
addition of a monomeric aliphatic and/or aromatic amide as
described in copending application Ser. No. 11/592,109 filed on
Nov. 1, 2006 in the name of Hyun Kim et al., the entire contents of
which are hereby incorporated by reference.
[0163] Golf balls within the scope of the present invention also
can include, in suitable amounts, one or more additional
ingredients generally employed in golf ball compositions. Agents
provided to achieve specific functions, such as additives and
stabilizers, can be present. Examplary suitable ingredients include
colorants, antioxidants, colorants, dispersants, mold releasing
agents, processing aids, fillers, and any and all combinations
thereof. Although not required, UV stabilizers, or photo
stabilizers such as substituted hydroxphenyl benzotriazoles may be
utilized in the present invention to enhance the UV stability of
the final compositions. An example of a commercially available UV
stabilizer is the stabilizer sold by Ciba Geigy Corporation under
the tradename TINUVIN.
[0164] The various formulations for the intermediate layer and/or
cover layer may be produced using a twin-screw extruder or may be
blended manually or mechanically prior to the addition to the
injection molder feed hopper. Finished golf balls may be prepared
by initially positioning the solid, preformed core in an
injection-molding cavity, followed by uniform injection of the
intermediate layer and/or cover layer composition sequentially over
the core. The cover formulations can be injection molded around the
cores to produce golf balls of the required diameter.
[0165] Alternatively, the cover layers may also be formed around
the core by first forming half shells by injection molding followed
by compression molding the half shells about the core to form the
final ball.
[0166] Covers may also be formed around the cores using compression
molding. Cover materials for compression molding may also be
extruded or blended resins or castable resins such as
polyurethane.
[0167] Typically the golf ball core is made by mixing together the
unsaturated polymer, cross-linking agents, and other additives with
or without melting them. Dry blending equipment, such as a tumbler
mixer, V blender, ribbon blender, or two-roll mill, can be used to
mix the compositions. The golf ball compositions can also be mixed
using a mill, internal mixer such as a Banbury or Farrel continuous
mixer, extruder or combinations of these, with or without
application of thermal energy to produce melting. The various core
components can be mixed together with the cross-linking agents, or
each additive can be added in an appropriate sequence to the milled
unsaturated polymer. In another method of manufacture the
cross-linking agents and other components can be added to the
unsaturated polymer as part of a concentrate using dry blending,
roll milling, or melt mixing. If radiation is a cross-linking
agent, then the mixture comprising the unsaturated polymer and
other additives can be irradiated following mixing, during forming
into a part such as the core of a ball, or after forming.
[0168] The resulting mixture can be subjected to, for example, a
compression or injection molding process, to obtain solid spheres
for the core. The polymer mixture is subjected to a molding cycle
in which heat and pressure are applied while the mixture is
confined within a mold. The cavity shape depends on the portion of
the golf ball being formed. The compression and heat liberates free
radicals by decomposing one or more peroxides, which initiate
cross-linking The temperature and duration of the molding cycle are
selected based upon the type of peroxide and peptizer selected. The
molding cycle may have a single step of molding the mixture at a
single temperature for fixed time duration.
[0169] For example, a preferred mode of preparation for the cores
used in the present invention is to first mix the core ingredients
on a two-roll mill, to form slugs of approximately 30-40 g, and
then compression-mold in a single step at a temperature between 150
to 180.degree. C., for a time duration between 5 and 12
minutes.
[0170] The various core components may also be combined to form a
golf ball by an injection molding process, which is also well known
to one of ordinary skill in the art. The curing time depends on the
various materials selected, and those of ordinary skill in the art
will be readily able to adjust the curing time upward or downward
based on the particular materials used and the discussion
herein.
[0171] The core of the balls may have a diameter of from about 0.5
to about 1.62, preferably from about 0.7 to about 1.60, more
preferably from about 1 to about 1.58, yet more preferably from
about 1.20 to about 1.54, and most preferably from about 1.40 to
about 1.50 in.
[0172] The core of the balls also may have a PGA compression of
less than about 140, preferably less than about 120, more
preferably less than about 100, yet more preferably less than about
90, and most preferably less than about 80.
[0173] The various core layers (including the center) may each
exhibit a different hardness. The difference between the center
hardness and that of the next adjacent layer, as well as the
difference in hardness between the various core layers may be
greater than 2, preferably greater than 5, most preferably greater
than 10 units of Shore D.
[0174] In one preferred aspect, the hardness of the center and each
sequential layer increases progressively outwards from the center
to outer core layer.
[0175] In another preferred aspect, the hardness of the center and
each sequential layer decreases progressively inwards from the
outer core layer to the center.
[0176] The one or more intermediate layers of the golf balls may
have a thickness of about 0.01 to about 0.50, preferably from about
0.01 to about 0.30, more preferably from about 0.02 to about 0.20
and most preferably from about 0.03 to about 0.10 in.
[0177] The one or more intermediate layers of the golf balls also
may have a hardness as measured on the ball of greater than about
25, preferably greater than about 30, more preferably greater than
about 40, and most preferably greater than about 50 Shore D
units.
[0178] The cover layer of the balls may have a thickness of about
0.01 to about 0.10, preferably from about 0.02 to about 0.08, more
preferably from about 0.03 to about 0.06 in.
[0179] The cover layer the balls may have a Shore D hardness as
measured on the ball from about 30 to about 75, preferably from
about 35 to about 70, more preferably from 38 to about 68 and most
preferably from about 40 to about 65.
[0180] The COR of the golf balls may be greater than about 0.700,
preferably greater than about 0.730, more preferably greater than
0.750, most preferably greater than 0.775, and especially greater
than 0.800 at 125 ft/sec inbound velocity.
[0181] The shear cut resistance of the golf balls of the present
invention is less than about 4, preferably less than about 3, even
more preferably less than about 2.
[0182] The polyamide blend compositions used in the golf balls of
the present invention may comprise from about 2 to about 40,
preferably from about 5 to about 30 and more preferably from about
8 to about 20 wt % of a polyamide and from about 60 to about 98,
preferably from about 70 to about 95 and more preferably from about
80 to about 92 wt % of on or more additional polymer components
(all wt % based on the total weight of polyamide and additional
polymer component(s)).
[0183] The polyamide blend composition may be used in the core,
intermediate layer(s), and/or cover layer of the golf ball. In
certain embodiments, the polyamide blend composition is the
majority ingredient of the material used to form at least one
structural component (e.g., the core, intermediate layer(s) or
cover layer) of the golf ball. As used herein "majority ingredient"
means that the polyamide blend composition is present in an amount
of at least about 50 wt %, particularly at least 60 wt %, and more
particularly at least 80 wt %, based on the total weight of all the
ingredients in the final material used to form at least one
structural component.
[0184] The polyamide may be used in solid form in the form of a
powder, pellet or fiber, and the type of polyamide is selected
based on the properties of the polymer component(s) to which it is
to be added. The polyamide should have a melting point greater than
about 5 and less than about 200, preferably greater than about 10
and less than about 150 and more preferably greater than about 20
and less than about 100.degree. C. above the melting point of the
lowest melting additional polymer component to which it is
added.
[0185] The additional polymer blend component may be unimodal
ionomer, a bimodal ionomer, a modified unimodal ionomer, a modified
bimodal ionomer, a polyalkenamer, a polyamide, a thermoplastic or
thermoset polyurethane, or a multicomponent blend composition
("MCBC"), the MCBC comprising (A) a block copolymer; and (B) one or
more acidic polymers; and (C) one or more basic metal salts present
in an amount to neutralize at greater than or equal to about 30
percent of the acid groups of Component (B); and any and all
combinations thereof.
[0186] The golf ball of the present invention may comprise from 0
to 5, preferably from 0 to 3, more preferably from 1 to 3, most
preferably 1 to 2 intermediate layer(s).
[0187] In one preferred aspect, at least one of the intermediate
layers comprises the polyamide blend compositions described
herein.
[0188] In one preferred aspect, the golf ball is a two-piece ball
with the polyamide blend composition used in the cover layer.
[0189] In another aspect the golf ball is a three-piece ball with
the polyamide blend composition used in the outer cover layer and
the intermediate or mantle layer comprises a thermoplastic
elastomer including a unimodal ionomer, a bimodal ionomer, a
modified unimodal ionomer, a modified bimodal ionomer, a
polyalkenamer, a polyamide, a thermoplastic or thermoset
polyurethane, or any and all combinations thereof.
[0190] In another aspect the golf ball is a four-piece ball with
the polyamide blend composition used in the outer cover layer and
the intermediate or mantle layer comprises a thermoplastic
elastomer including a unimodal ionomer, a bimodal ionomer, a
modified unimodal ionomer, a modified bimodal ionomer, a
polyalkenamer, a polyamide, a thermoplastic or thermoset
polyurethane, or any and all combinations thereof.
[0191] In another aspect the golf ball is a five-piece ball with
the polyamide blend composition used in the outer cover layer and
the intermediate or mantle layer comprises a thermoplastic
elastomer including a unimodal ionomer, a bimodal ionomer, a
modified unimodal ionomer, a modified bimodal ionomer, a
polyalkenamer, a polyamide, a thermoplastic or thermoset
polyurethane, or any and all combinations thereof.
[0192] The various test properties which may be used to measure the
properties of the golf balls of the present invention are described
below including any test methods as defined below.
[0193] Core or ball diameter may be determined by using standard
linear calipers or size gauge.
[0194] Compression may be measured by applying a spring-loaded
force to the golf ball center, golf ball core, or the golf ball to
be examined, with a manual instrument (an "Atti gauge")
manufactured by the Atti Engineering Company of Union City, N.J.
This machine, equipped with a Federal Dial Gauge, Model D81-C,
employs a calibrated spring under a known load. The sphere to be
tested is forced a distance of 0.2 inch (5 mm) against this spring.
If the spring, in turn, compresses 0.2 inch, the compression is
rated at 100; if the spring compresses 0.1 inch, the compression
value is rated as 0. Thus more compressible, softer materials will
have lower Atti gauge values than harder, less compressible
materials. Compression measured with this instrument is also
referred to as PGA compression. The approximate relationship that
exists between Atti or PGA compression and Riehle compression can
be expressed as:
(Atti or PGA compression)=(160-Riehle Compression).
Thus, a Riehle compression of 100 would be the same as an Atti
compression of 60.
[0195] COR may be measured using a golf ball or golf ball
subassembly, air cannon, and a stationary steel plate. The steel
plate provides an impact surface weighing about 100 pounds or about
45 kilograms. A pair of ballistic light screens, which measure ball
velocity, are spaced apart and located between the air cannon and
the steel plate. The ball is fired from the air cannon toward the
steel plate over a range of test velocities from 50 ft/s to 180
ft/sec (for the tests used herein the velocity was 125 ft/sec). As
the ball travels toward the steel plate, it activates each light
screen so that the time at each light screen is measured. This
provides an incoming time period proportional to the ball's
incoming velocity. The ball impacts the steel plate and rebounds
though the light screens, which again measure the time period
required to transit between the light screens. This provides an
outgoing transit time period proportional to the ball's outgoing
velocity. The coefficient of restitution can be calculated by the
ratio of the outgoing transit time period to the incoming transit
time period, COR=T.sub.out/T.sub.in.
[0196] A "Mooney" viscosity is a unit used to measure the
plasticity of raw or unvulcanized rubber. The plasticity in a
Mooney unit is equal to the torque, measured on an arbitrary scale,
on a disk in a vessel that contains rubber at a temperature of
100.degree. C. and rotates at two revolutions per minute. The
measurement of Mooney viscosity is defined according to ASTM
D-1646.
[0197] Shore D hardness may be measured in accordance with ASTM
Test D2240.
[0198] Melt flow index (12) may be measured in accordance with ASTM
D-1238, Condition 230.degree. C./2.16 kg.
[0199] Tensile strength, and tensile elongation may be measured in
accordance with ASTM standard D-638, and flexural modulus, using
ASTM standard D-790.
[0200] Shear cut resistance may be determined by examining the
balls after they were impacted by a pitching wedge at controlled
speed, classifying each numerically from 1 (excellent) to 5 (poor),
and averaging the results for a given ball type. Three samples of
each Example may be used for this testing. Each ball is hit twice,
to collect two impact data points per ball. Then, each ball is
assigned two numerical scores-one for each impact-from 1 (no
visible damage) to 5 (substantial material displaced). These scores
may be then averaged for each Example to produce the shear
resistance numbers. These numbers may be then directly compared
with the corresponding number for a commercially available ball,
having a similar construction including the same core and mantle
composition and cover thickness for comparison purposes.
* * * * *