Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02320550 2000-09-25
P-5079 SLD 2177
CROSSLINKED FOAM AS FILLER IN AN INNER LAYER
OR CORE OF A MULTI-COMPONENT GOLF BALL
Crass References to Related Applications
This application is a continuation-in-part and claims priority from U.S.
Patent Application Serial No. 09/027,482, filed February 20, 1998, which
claims
priority from U.S. Provisional Application Serial No. 60/042,120, filed March
28,
1997; Provisional Application Serial No. 60!042,430, filed March 28, 1997; and
U.S.
Application Serial No. 081714,661, filed September 16, 1996.
o This application is also a continuation-in-part and claims priority from
U.S. Serial No. 081815,556 filed March 12, 1997.
Field of the Invention
This invention generally relates to golf balls, and more specifically, to
a multi-component golf ball. In particular, this invention relates to a golf
ball having
~s a core, at least one cover layer, and one or more interior mantle layers
disposed
betvreen the core and cover layer. Relatively small foam granules are
dispersed
throughout one or more of the mantle layers, the core, or both. The multi-
component golf balls of the present invention, having such a configuration and
using such foam granules, have been found to provide the distance and
durability
2o characteristics approaching that of a conventional two-piece ball while
also
providing the "click and feel" of a conventional three-piece or "wound" ball.
Background of the Invention
Conventional golf balls can be divided into two general types or
groups, two-piece balls or wound balls (also known as three-piece balls). The
2s difference in play characteristics resulting from these different types of
constructions can be quite significant.
Balls having a two-piece construction are generally most popular with
the average recreational golfer because they provide a very durable ball while
also
providing maximum distance. Two-piece balls are made with a single solid core,
3o usually made of a crosslinked rubber, which is encased by a cover material.
Typically, the solid core is made of polybutadiene which is chemically
crosslinked
with zinc diacrylate (ZDA) andlor similar crosslinking agents and is covered
by a
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tough, cut-proof blended cover. The cover is generally material such as
SURLYN~, which is a trademark for an ionomer resin produced by DuPont. The
combination of the core and cover materials provide a "hard" ball that is
virtually
indestructible by golfers. Further, such a combination imparts a high initial
velocity
s to the ball which results in improved distance. Because these materials are
very
rigid, two piece balls have a hard "feel" when struck with a club. Likewise,
due to
their hardness, these balls have a relatively low spin rate which makes them
difficult
to control, particularly in shorter approach shots. However, as golf ball
manufacturers continue to improve the spin and feel characteristics of the two-
piece
~o ball, it is likely that the two-piece ball will continue to grow in
popularity.
But, at the present time, the wound ball remains the preferred ball of
the more advanced players due to its superior spin and feel characteristics.
Wound
balls typically have either a solid rubber or liquid center core around which
many
yards of a stretched elastic thread or yarn are wound. The wound core is then
~ 5 covered with a durable cover material such as a SURLYN~ or similar
material or
a softer cover such as Balata. Wound balls are generally softer and provide
more
spin, which enables a skilled golfer to have more control over the ball's
flight.
However, wound higher spinning balls typically have a shorter distance as
compared to a two-piece ball. Moreover, as a result of their more complex
2o structure, wound balls generally require a longer time to manufacture and
are more
expensive to produce than a two-piece ball.
Consequently, a need exists for an improved ball which provides the
"click and feel" of a wound ball, while also providing the relative ease of
manufacturing, durability and distance of a two-piece ball.
2s Description of the Prior Art
Several patents have been issued which are directed toward
modifying the properties of a conventional two-piece ball by altering the
typical
single-layer core and single cover layer construction to provide a multi-layer
core.
The developments disclosed in the prior art patents are directed toward
improving
3o a variety of golf ball characteristics.
Several patents are directed toward improving the carry distance of
the ball. For example, U.S. Patent No. 4,863,167 relates to a three-piece
solid golf
' CA 02320550 2000-09-25
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ball having improved rebound characteristics in order to increase its flight
distance.
This golf ball has a center portion and an outer layer formed from a rubber
composition, preferably having a base rubber of polybutadiene, wherein the
outer
layer further contains a gravity filler such as tungsten or tungsten carbide
so as to
impart a higher specific gravity to the outer layer than that of the inner
layer. The
difference in specific gravity of the layers should be 0.15 - 0.8 for small
balls and
0.15 - 0.45 for large balls. Preferably, the outer layer is harder than the
center
portion.
U.S. Patent No. 5,184,828 relates to a solid three-piece golf ball
o having improved rebound characteristics and carry distance while maintaining
an
adequate spin rate. These characteristics are obtained by controlling the size
of
the inner core and outer layer as well as the specific gravity and hardness.
The
core and mantle layers are made from a rubber compound such as polybutadiene,
and have a Shore D hardness of 30-62 and 30-56, respectively. The key to
~5 obtaining the desired rebound characteristics is that the maximum hardness
(42-62)
must be located at the interface between the core and the mantle and the
hardness
must then decrease both inwardly and outwardly.
U.S. Patent No. 4,714,253 is also directed toward a three-piece golf
ball having an excellent rebound coefficient. This golf ball has a core with a
Shore
2o C hardness of 57-80 in its center, but not more than 83 at a distance
between 5-10
mm from its center and outer layer with a Shore C hardness of 70-83.
Additionally, there are a number of patents also directed toward
improving the spin, click or feel of solid balls while maintaining the
distance
provided by the solid construction. A variety of approaches to manipulating
the
25 core construction are described in the art. For example, U.S. Patent No.
5,072,944
discloses a three-piece solid golf ball having a center and outer layer which
are
prepared from a rubber composition, preferably having a base rubber of
polybutadiene. It is desirable that the center core is softer than the outer
layer,
each having a hardness (Shore C) of 25-50 and 70-90, respectively.
3o U.S. Patent No. 4,625,964 relates to a solid golf ball having a
polybutadiene rubber core of a diameter not more than 32 mm, and a
polybutadiene rubber intermediate layer having a specific gravity of lower
than that
of the core material, and a cover.
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U.S. Patent No. 4,650,193 is directed toward a solid golf ball having
a core comprising a central portion and an integral outer layer. Preferably,
the core
is a curable elastomer such as polybutadiene which is treated with a cure
altering
agent to soften an outer layer of the core, thereby producing a central layer
with a
hardness (Shore C) of greater than 75 and an outer layer with a hardness
(Shore
A) of less than 80.
U.S. Patent No. 4,848,770 discloses a non-wound, three-piece golf
-ball which includes a core of a highly filled synthetic rubber or polymeric
material,
an intermediate mantle of an unfilled synthetic rubber and a cover. The core
and
o intermediate mantle have a hardness of between 50-95.
U.S. Patent No. 5,002,281 is directed toward a three-piece solid golf
ball which has an inner core having a hardness of 25-70 (Shore C), an outer
shell
having a hardness of 80-95 (Shore C) and a cover. Further, the specific
gravity of
the inner core must be greater than 1.0, but less than or equal to that of the
outer
~5 shell, which must be less than 1.3.
U.S. Patent No. 5,253,871 concerns a golf ball having a three-piece
structure comprising an elastomer core, an intermediate layer of a
thermoplastic
material containing at least 10% of ether block copolymer, preferably blended
with
an ionomer and a thermoplastic cover.
2o Further, there are also several patents which are directed to golf balls
having multiple cover layers. For example, U.S. Patent No. 4,431,193 relates
to a
golf ball having a multi-layer cover wherein the inner layer is a hard, high
flexural
modulus ionomer resin and the outer layer is a soft, low flexural modulus
ionomer
resin, and wherein either or both layers may comprise a foamed ionomer resin.
25 U.S. Patent No. 5,314,187 also relates to golf balls having a multiple
layer cover, wherein the outer layer is molded over the inner layer and
comprises
a blend of balata and an elastomer and the inner layer is an ionomer resin.
U.S. Patent No. 4,919,434 is directed toward a golf ball having a
cover which comprises an inner layer and an outer layer each of which comprise
3o a thermoplastic resin. Preferably the layers comprise materials that are
capable of
fusion bonding with each other.
Prior artisans have attempted to incorporate metal layers or metal
filler particles in golf balls to alter the physical characteristics and
performance of
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the balls. For example, U.S. Patent No. 3,031,194 to Strayer is directed to
the use
of a spherical inner metal layer that is bonded or otherwise adhered to a
resilient
inner constituent within the ball. The ball utilizes a liquid filled core.
U.S. Patent
No. 4,863,167 to Matsuki, et al. describes golf balls containing a gravity
filler which
may be formed from one or more metals disposed within a solid rubber-based
core.
U.S. Patent Nos. 4,886,275 and 4,995,613, both to Walker, disclose golf balls
having a dense metal-containing core. U.S. Patent No. 4,943,055 to Corley is
directed to a weighted warmup ball having a metal center.
Prior artisans have also described golf balls having one or more
interior layers formed from a metal, and which feature a hollow center. Davis
disclosed a golf ball comprising a spherical steel shell having a hollow air-
filled
center in U.S. Patent No. 697,816. Kempshall received numerous patents
directed
to golf balls having metal inner layers and hollow interiors, such as 704,748;
704,838; 713,772; and 739,753. In U.S. Patent Nos. 1,182,604 and 1,182,605,
~5 Wadsworth described golf balls utilizing concentric spherical shells formed
from
tempered steel. U.S. Patent No. 1,568,514 to Lewis describes several
embodiments for a golf ball, one of which utilizes multiple steel shells
disposed
within the ball, and which provide a hollow center for the ball.
As to the incorporation of glass or vitreous materials in golf balls, U.S.
2o Patent No. 985,741 to Harvey discloses the use of a glass shell. Other
artisans
described incorporating glass microspheres within a golf ball such as in U.S.
Patent
No. 4,085,937 to Schenk.
In contrast, the use of polymeric materials in intermediate layers
within a golf ball, is more popular than, for instance, the use of glass or
other
25 vitreous material. Kempshall disclosed the use of an interior coating layer
of plastic
in U.S. Patent Nos. 696,887 and 701,741. Kempshall further described
incorporating a fabric layer in conjunction with a plastic layer in U.S.
Patent Nos.
696,891 and 700,656. Numerous subsequent approaches were patented in which
a plastic inner layer was incorporated in a golf ball. A thermoplastic outer
core
30 layer was disclosed in U.S. Patent No. 3,534,965 to Harrison. Inner
synthetic
polymeric layers are noted in U.S. Patent No. 4,431,193 to Nesbitt. An inner
layer
of thermoplastic material surrounding a core is described in U.S. Patent No.
4,919,434 to Saito. An intermediate layer of an amide block polyether
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thermoplastic is disclosed in U.S. Patent No. 5,253,871 to Viellaz. Golf balls
with
thermoplastic interior shell layers are described in U.S. Patent No. 5,480,155
to
Motitor, et al.
Although satisfactory in many respects, these patents are not
specifically directed to the use of a particular configuration of foamed
material
dispersed within a particular type of polymeric material as utilized in the
present
invention and described herein.
Prior artisans have attempted to incorporate various particles and filler
materials into golf ball cores and intermediate layers. U.S. Patent No.
3,218,075
o to Shakespeare discloses a core of fiberglass particles dispersed within an
epoxy
matrix. Similarly, U.S. Patent No. 3,671,477 to Nesbitt discloses an epoxy-
based
composition containing a wide array of fillers. A rubber intermediate layer
containing various metal fillers is noted in U.S. Patent 4,863,167 to Matsuki,
et al.
Similarly, a rubber inner layer having filler materials is noted in U.S.
Patent No.
~5 5,048,838 to Chikaraishi, et al. More recently, a golf ball with an inner
layer of
reinforced carbon graphite is disclosed in U.S. Patent No. 5,273,286 to Sun.
However, none of these patents disclose a multi-layer ball having the
materials and material property requirements as disclosed herein to provide
the
improved golf balls of the present invention.
2o In view of the ever increasing demands of the current golf industry,
there exists a need for yet another improved golf ball design and
construction.
Specifically, there is a need for a golf ball that exhibits a high initial
velocity or
coefficient of restitution (COR), may be driven relatively long distances in
regulation
play, and which may be readily and inexpensively manufactured. And, there is a
25 need for such a golf ball that further exhibits desirable "click and feel"
characteristics.
These and other objects and features of the invention will be apparent
from the following summary and description of the invention, the drawings, and
from the claims.
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Summaryr of the Invention
The present invention is directed toward, in a first aspect, a golf ball
comprising a core, a cover assembly disposed about the core, and a mantle
layer
disposed about the core, between the core and the cover layer. The mantle
layer
comprises a polymeric matrix material and a plurality of foam granules
dispersed
within the polymeric matrix material. The granules have a mean diameter of
from
about 0.001 inches to about 0.200 inches. The cover assembly may include one
or more cover layers.
In yet another aspect, the present invention provides a golf ball
o comprising a core, a cover layer disposed about the core, and an interior
mantle
layer surrounding the core and disposed between the core and the cover layer.
The mantle layer comprises a plurality of foam particles dispersed within a
polymeric matrix material. The particles comprise one or more materials
selected
from a specific set of materials. The cover may be of a single or multi-layer
~s configuration.
In yet a further aspect, the present invention provides a golf ball
comprising a core, a cover layer disposed about the core, and an interior
primary
mantle surrounding the core and disposed between the core and the cover layer.
The primary mantle includes a matrix material and a plurality of foam granules
2o dispersed within the matrix material. The weight ratio of the granules to
the matrix
material is in a range of from about 10 to 95% of the matrix material to about
5 to
90% of the granules. The cover may include one or more cover layers.
In another aspect, the present invention provides a golf ball
comprising a core, at least one cover layer disposed about the core, and a
plurality
25 of foam granules dispersed in the core. The foam granules have a mean
diameter
of from about 0.001 inches to about 0.200 inches.
In an additional aspect, the present invention provides a golf ball
comprising a core, at least one cover layer disposed about the core, an
interior
mantle layer surrounding the core and disposed between said core and said
cover,
3o and a plurality of foam particles dispersed within either or both the core
and the
mantle layer. The foam particles are formed from one or more specific classes
of
materials.
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~ 8
Brief Description of the Drawings
The above and other objects, features, and advantages of the present
invention will be better understood from the following description taken in
conjunction with the accompanying drawings as follows.
Fig. 1 is a cross-sectional view of a preferred embodiment golf ball
according to the present invention;
Fig. 2 is a view of the preferred embodiment golf ball according to the
present invention and illustrated in Fig. 1;
Fig. 3 is a detailed schematic view of a portion of a mantle layer of
o another preferred embodiment golf ball according to the present invention;
and
Fig. 4 is a cross-sectional view of yet another preferred embodiment
golf ball according to the present invention.
It will be appreciated that these drawings are not necessarily to scale,
and are schematic in nature, particularly Figs. 1, 3, and 4.
~5 Detailed Descri~,tion of the Preferred Embodiments
The present invention provides, in a particularly preferred aspect, a
golf ball comprising a plurality of foamed granules dispersed throughout a
polymeric
matrix material in one or more interior mantle layers, and/or a core within
the ball.
The foamed granules are relatively small and are preferably dispersed
throughout
2o a thermoplastic or thermoset matrix material.
Referring to Figs. 1 and 2, a preferred embodiment of the present
invention golf ball is illustrated as a multi-layer golf ball 1 which
comprises a core
2, at least one cover layer 3, and at least one primary mantle 4 disposed
therebetween. The preferred embodiment golf balls described herein all have
25 dimpled outer surfaces. These various components and other aspects of the
preferred embodiment golf balls are described in greater detail below.
Mantle and Foam Granules
The preferred embodiment golf balls comprise at least one interior
mantle layer that includes a plurality of foam particles or granules dispersed
3o throughout a polymeric matrix material. The term "foam granules" as
utilized herein
refers to granules or particles having the characteristics and properties
described
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_g_
herein, and having a structure characterized by a plurality of cells or
chambers,
defined throughout, or at least substantially so, the granule. The cells or
chambers
may range in size , e.g. have an average interior span, from about 0.00001
inches
to about 0.0001 inches. Preferably, the structure of the foam granules
resembles
that of a foam. All, a portion, or none of the cells or chambers may be
connected
to adjacent cells or chambers. All, a portion, or none of the cells or
chambers may
be filled with air, one or more other gases, or the matrix material. It is to
be
understood that the term foam granules does not imply or mean that the
granules
utilized in the present invention must be formed according to a foaming
process.
to That is, the foam granules may be produced by other methods such as
leaching or
erosion strategies.
The at least one interior mantle layer is referred to herein as a primary
mantle. Fig. 3 illustrates a preferred embodiment primary mantle 4 that
includes
foamed granules 6 dispersed within a polymeric matrix 5.
~5 The preferred foam granules range in size from a mean diameter of
about 0.001 to about 0.200 inches, and most preferably from about 0.0012
inches
to about 0.180 inches. The foam granules preferably have a specific gravity of
from
about 0.01 to about 0.8, and most preferably from about 0.1 to about 0.7.
The matrix and the granules may be formed from a wide array of
2o materials such as, but not limited to, ionomers, non-ionomeric polyolefins,
metallocene catalyzed polymer, polyethylene ethyl or methyl acrylate, styrene
butadiene elastomer, thermoplastic polyester, thermoplastic polyetherester,
thermoplastic polyetheramide, polyamide, polycarbonate, polyphenylene oxide,
thermoplastic or thermoset polyurethane, silicone elastomer, dynamically
2s vulcanized elastomer, or combinations or blends of the foregoing.
Additional
examples of materials suitable for the primary mantle are set forth below.
In all preferred embodiments described herein, it is significant that the
granules which are dispersed within and generally throughout one or more
mantle
layers andlor a core of a golf ball be formed from a material or composition
that is
3o different from the material or composition of the matrix constituting the
mantle
layers) and/or core. It is known in the prior art to form cellular or foamed
regions
in a layer of material having a constant composition throughout the layer. The
preferred embodiment golf balls are readily distinguishable in that they are
based
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upon, at least in part, the incorporation of foamed granules having a
composition
that is different than the composition of the matrix throughout which they are
dispersed.
The foam granules may be prepared according to a wide variety of
methods known in the art. Preferably, the granules are prepared by known
foaming
techniques. Conventional blowing agents may be used. Once foamed and after
sufficiently curing to a rigid solid form, the material is subjecting to a
sizing
operation such as a granulating process so that the foamed material is
processed
into fine particles preferably having the previously described mean diameters.
~o As previously noted, the foamed granules may utilize either an open
cell foam structure, a closed cell foam structure, or a hybrid structure that
includes
both open and closed cells.
A comprehensive description of foamed plastics and their production
is provided in Kirk Othmer Encyclopedia of Chemical Technology, under "Foamed
~s Plastics," Vol. 11, Fourth Edition, pages 730 to 783, herein incorporated
by
reference.
Preferably, the foam granules are crosslinked. Crosslinking of the
granules may be performed before, during, or after incorporation of the
granules
into the polymeric matrix described in greater detail herein.
2o The preferred overall thickness of the primary mantle layer is from
about 0.010 inches to about 0.500 inches, more preferably from about 0.020
inches
to abo~~~ 0.300 inches, and most preferably from about 0.050 inches to about
0.250
inches.
Preferably, the granules and matrix material are combined together
25 in a particular weight ratio, such as from about 10 to 95% matrix to about
5 to 90%
granules. More preferably, the granules and matrix material are combined in a
weight ratio of from about 25 to 90% matrix to about 10 to 75% granules, and
most
preferably, from about 50 to 85% matrix to about 15 to 50°r6 granules.
In addition to the previously described primary mantle layer
3o comprising foam granules dispersed in a matrix material, the preferred
embodiment
golf balls may further include one or more optional secondary mantle layers as
follows. The one or more secondary mantle layers are disposed at any region
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within a golf ball, between a core and a cover layer. Preferably, the one or
more
secondary mantle layers are disposed adjacent to the primary mantle layer.
The secondary mantle layer may comprise any of the materials noted
for use in the primary mantle. The secondary mantle preferably comprises
thermoplastic polyetherester, thermoplastic polyester, dynamically vulcanized
thermoplastic elastomer, functionalized styrene-butadiene elastomer;
thermoplastic
polyurethane or metallocene polymer or blends thereof.
In a preferred embodiment of the present invention, the secondary
mantle layer is a thermoplastic polyetherester. Suitable thermoplastic
o polyetheresters include Hytrel~ 3078, Hytrel~ G3548W and Hytrel~ G4078W
which are commercially available from DuPont. Hytrel~ 3078 is the most
preferred.
The mantle layer preferably has a specific gravity greater than 1 and less
than 1.2.
Suitable commercially available dynamically vulcanized thermoplastic
elastomers for use in the primary andlor secondary mantles, include
Santoprene~,
~s Sarlink~, Vyram~, Dyton~ and Vistaflex~. Santoprene~ is the trademark for a
dynamically vulcanized PPIEPDM. Santoprene~ 203-40 is an .example of a
preferred Santoprene0 and is commercially available from Advanced Elastomer
Systems. Examples of suitable functionalized styrene-butadiene elastomers
include Kraton FG-1901x, which is available from the Shell Corporation.
Examples
20 of suitable thermoplastic polyurethanes include Estane~ 58133, Estane~
58134
and Estane~ 58144, which are commercially available from the B.F.Goodrich
Company. Suitable metallocene polymers whose melting points are higher than
the
cover materials can also be employed in the primary and/or secondary mantle
layer
of the present invention golf balls. Further, the materials for the primary
andlor
25 secondary mantle layer described above may be in the form of a foamed
polymeric
material. For example, suitable metallocene polymers include foams of
thermoplastic elastomers based on metallocene single-site catalyst-based
foams.
Such metallocene-based foam resins are commercially available from Sentinel
Products of Hyannis, Massachusetts. In a preferred embodiment of the present
3o invention, the secondary mantle layer comprises Santoprene~, thermoplastic
polyurethane or blends thereof.
In another preferred embodiment of the present invention, the one or
more secondary mantle layers comprise a blend of a first and a second
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thermoplastic, wherein the first thermoplastic is a dynamically vulcanized
thermoplastic elastomer, a functionalized styrene-butadiene elastomer, a
thermoplastic polyurethane or a metallocene polymer and the second
thermoplastic
is a material such as a thermoplastic polyurethane, a thermoplastic
polyetherester
or polyetheramide, a thermoplastic ionomer resin, a thermoplastic polyester,
another dynamically vulcanized elastomer, another functionalized styrene-
butadiene elastomer, another metallocene polymer or blends thereof.
For this blended embodiment, suitable thermoplastic polyetheresters
include Hytrel~ 3078, Hytrel~ G3548W and Hytrel~ G4078W which are
~o commercially available from DuPont. Suitable thermoplastic polyetheramides
include Pebax~ 2533, Pebax~ 3533 and Pebax~ 4033 which are available from
Elf-Atochem. Suitable thermoplastic ionomer resins include any number of
olefinic
based ionomers including SURLYN~ and lotek~, which are commercially available
from DuPont and Exxon, respectively. The flexural moduli for these ionomers is
~s about 100 kpsi to about 200 kpsi. Suitable thermoplastic polyesters include
polybutylene terephthalate. Likewise, the dynamically vulcanized thermoplastic
elastomers, functionalized styrene-butadiene elastomers, thermoplastic
polyurethane or metallocene polymers identified above are also useful as the
second thermoplastic in such blends. Further, the materials of the second
2o thermoplastic described above may be in the form of a foamed polymeric
material.
Such thermoplastic blends comprise about 1 %. to about 99% by
weight of a first thermoplastic and about 99% to about 1 % by weight of a
second
thermoplastic. Preferably, the thermoplastic blend comprises about 5°~
to about
95% by weight of a first thermoplastic and about 5% to about 95% by weight of
a
25 second thermoplastic. In a preferred embodiment of the present invention,
the first
thermoplastic material of the blend is a dynamically vulcanized thermoplastic
elastomer, such as Santoprene4. It is contemplated that such a blended
configuration could also be utilized for the~matrix material of the primary
mantle.
It is contemplated that any of the previously noted materials suitable
for use in the secondary mantle may be employed in the primary mantle
comprising
the foam granules. It is also contemplated that the previously described foam
granules be dispersed in the secondary mantle. And furthermore, it is
contemplated that the mantle assembly comprises three or more discrete mantle
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layers. As described in greater detail herein, the foam granules may also be
incorporated in the golf ball core.
Core
The core of the preferred embodiment golf ball of the present
s invention may comprise a variety of materials, including those typically
employed
as golf ball cores. The conventional materials for such cores include core
compositions having a base rubber; a crosslinking agent, a filler and a co-
crosslinking agent. The base rubber typically includes natural or synthetic
rubbers.
A preferred base rubber is 1,4-polybutadiene having a cis-structure of at
least 40%.
o Natural rubber, polyisoprene rubber andlor styrene-butadiene rubber may be
optionally added to the 1,4-polybutadiene. The initiator included in the core
composition can be any known polymerization initiator which decomposes during
the cure cycle. The crosslinking agent includes a metal salt of an unsaturated
fatty
acid such as a zinc salt or a magnesium salt of an unsaturated fatty acid
having 3
~5 to 8 carbon atoms such as acrylic or methacrylic acid. The filler typically
includes
materials such as zinc oxide, barium sulfate, silica, calcium carbonate, zinc
carbonate and the like.
Preferably, the core is a cross-linked 1,4-polybutadiene having a
specific gravity greater than 1.1 and, more preferably, about 1.25. The high
specific
2o gravity of the core decreases the spin rate of the ball for a lower flight
path. Also,
the PGA compression of the core is preferably greater than 60 and, more
preferably, about 65.
In one embodiment of the present invention, the core comprises a
center which is liquid-filled or solid, around which an elastic thread is
wound. The
25 solid center is typically a homogenous mass of a resilient material such as
pofybutadiene or a natural rubber. The liquid-filled center is typically a
thin walled
sphere into which a liquid such as com syrup is injected by means of a
hypodermic
needle. The sphere is then sealed and frozen to make the center a solid mass.
The windings for either type of center are provided by an elastic thread which
is
3o stretched and wound about the center to a desired thickness. It will be
understood
that although the noted foam particles are generally used as an alternative to
a
wound core, both may be used together.
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Conventionally, the centers of wound cores have a diameter of about
1.0 to about 1.125 inches. The outer diameter of a conventional wound core is
about 92% of the overall diameter of the finished ball. However, the outer
diameter
of wound cores employed in this embodiment of the present invention have an
overall diameter of less than 90% of the overall diameter of the finished
ball.
Preferably, the wound cores have a diameter of about 75-90°r6 of the
overall
diameter of the finished ball. Most preferably, the wound cores of the present
invention have an overall diameter of about 85% of the diameter of the
finished ball.
It should be appreciated that a wide variety of materials can be
o utilized for the core including solid materials, gels, hot-melts, liquids,
and other
materials which at the time of their introduction into a shell, can be handled
as a
liquid. Examples of suitable gels include water gelatin gels, hydrogels, and
water/methyl cellulose gels. Hot-melts are materials that are heated to become
liquid and at or about normal room temperatures become solid. This property
~s allows their easy injection into the interior of the ball to form the core.
Examples of
suitable liquids include either solutions such as glycol/water, salt in water
or oils or
colloidal suspensions, such as clay, barytes, carbon black in water or other
liquid,
or salt in waterlglycol mixtures.
A preferred example of a suitable liquid core material is a solution of
2o inorganic salt in water. The inorganic salt is preferably calcium chloride.
Other
liquids that have been successfully used are conventional hydraulic oils.
The liquid material, which is inserted in the interior of the golf ball may
also be reactive liquid systems that combine to form a solid. Examples of
suitable
reactive liquids are silicate gels, agar gels, peroxide cured polyester
resins, two-
25 part epoxy resin systems and peroxide cured liquid polybutadiene rubber
compositions. It will be understood by those skilled in the art that other
reactive
liquid systems can likewise be utilized depending on the physical properties
of the
adjacent mantle and the physical properties desired in the resulting finished
golf
balls.
3o The core of all embodiments, whether remaining a solid, a liquid or
ultimately becoming a solid, should be unitary, that is, of a substantially
common
material throughout its entire extent or cross-section, with its exterior
surface in
contact with substantially the entire interior surface of its shell or inner
mantle. All
CA 02320550 2000-09-25
-15-
cores are also essentially substantially homogenous throughout, except for a
cellular or foamed embodiment described herein.
In the preferred embodiments, in order to provide a golf ball which has
similar physical properties and functional characteristics to conventional
golf balls,
preferably the core material will have a specific gravity greater than that of
the shell
or mantle (and the outer cover when such a cover is molded over the shell).
Specifically, the core material may have a specific gravity of between about
0.10
and about 3.9, preferably at about 1.05. Thus, it will be understood by those
skilled
in the art that the specific gravity of the core may be varied depending on
the
o physical dimensions and density of the outer shell and the diameter of the
finished
golf ball.
Solid cores are typically compression molded from a slug of uncured
or lightly cured elastomer composition comprising a high cis content
polybutadiene
and a metal salt of an a, (i, ethylenically unsaturated carboxylic acid such
as zinc
~5 mono or diacrylate or methacrylate. To achieve higher coefficients of
restitution in
the core, the formulator may include a small amount of a metal oxide such as
zinc
oxide. In addition, larger amounts of metal oxide than are needed to achieve
the
desired coefficient may be included in order to increase the core weight so
that the
finished ball more closely approaches the U.S.G.A. upper weight limit of 1.620
20 ounces. Other materials may be used in the core composition including
compatible
rubbers or ionomers, and low molecular weight fatty acids such as stearic
acid.
Free radical initiator catalysts such as peroxides are admixed with the core
composition so that on the application of heat and pressure, a complex curing
or
cross-linking reaction takes place.
25 The term "solid cores" as used herein refers not only to one piece
cores but also to those cores having a separate solids layer beneath the cover
and
above the core as in U.S. Patent No. 4,431,193, herein incorporated by
reference,
and other multi layer andlor non-wound cores.
Wound cores are generally produced by winding a very long elastic
3o thread around a solid or liquid filled balloon center. The elastic thread
is wound
around a frozen center to produce a finished core of about 1.4 to 1.7 inches
in
diameter, generally.
CA 02320550 2000-09-25
-1s-
The preferred embodiment golf ball may also comprise a cellular core
comprising a material having a porous or cellular configuration. Suitable
materials
for a cellular core include, but are not limited to, foamed elastomeric
materials such
as, for example, crosslinked polybutadiene2DA mixtures, polyurethanes,
polyolefins, ionomers, metallocenes, polycarbonates, nylons, polyesters, and
polystyrenes. Preferred materials include polybutadieneIZDA mixtures,
ionomers,
and metallocenes. The most preferred materials are foamed crosslinked
polybutadiene2DA mixtures.
If the cellular core is used in conjunction with a relatively dense
o mantle, the selection of the type of material for the mantle will determine
the size
and density for the cellular core. A hard, high modulus metal will require a
relatively
thin mantle so that ball compression is not too hard. If the mantle is
relatively thin,
the ball may be too light in weight so a cellular core will be required to add
weight
and, further, to add resistance to oil canning or deformation of the mantle.
~ 5 The weight of the cellular core can be controlled by the cellular
density. The cellular core typically has a specific gravity of from about 0.10
to
about 1Ø The coefficient of restitution of the cellular core should be at
least 0.500.
The structure of the cellular core may be either open or closed cell.
It is preferable to utilize a closed cell configuration with a solid surface
skin that can
2o be metalized or receive a conductive coating. The preferred cell size is
that
required to obtain an apparent specific gravity of from about 0.10 to about
1Ø
In a preferred method, a cellular core is fabricated and a metallic
cover applied over the core. The metallic cover may be deposited by providing
a
conductive coating or layer about the core and electroplating one or more
metals
25 on that coating to the required thickness. Alternatively, two metallic half
shells can
be welded together and a flowable cellular material, for example a foam, or a
cellular core material precursor, injected through an aperture in the metallic
sphere
using a two component liquid system that forms a semi-rigid or rigid material
or
foam. The fill hole in the mantle may be sealed to prevent the outer cover
stock
3o from entering into the cellular core during cover molding. Application of
these
techniques will be appreciated and may be similarly used if the mantle is
ceramic
or polymeric.
CA 02320550 2000-09-25
-17-
If the cellular core is prefoamed or otherwise foamed prior to applying
the metallic layer, the blowing agent may be one or more conventional agents
that
release a gas, such as nitrogen or carbon dioxide. Suitable blowing agents
include,
but are not limited to, azodicarbonamide, N,N-dinitros-opentamethylene-
tetramine,
4-4 oxybis (benzenesulfonyl-hydrazide), and sodium bicarbonate. The preferred
blowing agents are those that produce a fine closed cell structure forming a
skin on
the outer surface of the core.
A cellular core may be encapsulated or otherwise enclosed by the
mantle, for instance by affixing two hemispherical halves of a shell together
about
o a cellular core. It is also contemplated to introduce a foamable cellular
core
material precursor within a hollow spherical mantle and subsequently foaming
that
material in situ.
In a most preferred aspect of the present invention, it is desirable to
incorporate the previously described foam granules in the core or core
formulations.
~s The previously noted granule sizes and materials, and ratios of granules to
matrix
material are utilized for the granules incorporated in the cores andlor core
materials. Preferably, previously formed foam granules of desired size and
specific
gravity are incorporated into and dispersed within the material utilized in
forming the
core.
2o Fig. 4 is a cross-sectional view of another preferred embodiment golf
ball 10 according to the present invention. Golf ball 10 comprises a core 12
including a plurality of foam granules 16, as described herein, dispersed
throughout
a polymeric matrix 15. The golf ball 7 0 further comprises one or more mantles
14,
such as a primary or secondary mantle as previously described. The preferred
25 embodiment ball 10 also includes a mufti-layer cover including an inner
cover 17
and an outer cover 18. The one or more mantle layers 14 disposed about the
core
12, may also include the foam granules as previously described herein. The
inner
cover layer 17 preferably is disposed about the one or more mantle layers 14.
It
is contemplated that the golf ball 10 may include the foam granules 16 within
the
3o core 12, foam granules dispersed within one or more mantle layers 14, or
foam
granules 16 dispersed in both the core 12 and one or more mantle layers 14.
CA 02320550 2000-09-25
-18-
Cover
The cover layer of the preferred embodiment golf balls of the present
invention comprises at least one layer of a thermoplastic or thermoset
material.
Any number of a wide variety of cover materials may be used in the preferred
embodiments of the present invention. Among the preferred conventional cover
materials are ionomer resins and low modulus ionomers obtained by providing a
cross metallic bond to polymers of monoolefin with at least one member
selected
from the group consisting of unsaturated mono- or di-carboxylic acids having 3
to
12 carbon atoms and esters thereof (the polymer contains 1 to 50% by weight of
o the unsaturated mono- or di-carboxylic acid and/or ester thereof). More
particularly,
loW modulus ionomers, such as acid-containing ethylene copolymer ionomers,
include E/X copolymers where E is ethylene, X is a softening comonomer such as
acrylate or methacrylate present in 5-35 (preferably 10-35, most preferably 15-
20)
weight percent of the polymer, wherein the acid moiety is neutralized 1-90%
~s (preferably at least 40%, most preferably at least about 60%) to form an
ionomer
by a ration such as lithium, sodium, potassium, magnesium, calcium, barium,
lead,
tin, zinc or aluminum, or a combination of such rations. Preferably, rations
such
as lithium, sodium, magnesium, zinc andlor combinations are employed. Specific
acid-containing ethylene copolymers include ethylenelacryiic acid,
2o ethylenelmethacrylic acid, ethylenelacrylic acidln-butyl acrylate,
ethylenelmethacrylic acidln-butyl acrylate, ethylene/methacrylic acidliso-
butyl
acrylate, ethylenelacrylic acidrso-butyl acrylate, ethylene/methacrylic acidln-
butyl
methacrylate, ethylene/acrylic acid/methyl methacrylate, ethylenelacrylic
acidlmethyl acrylate, ethylenelmethacrylic acid/methyl acrylate,
25 ethylenelmethacrylic acidlmethy! methacrylate, and ethylenelacrylic acidln-
butyl
methacrylate. Preferred acid-containing ethylene copolymers include
ethylenelmethacrylic acid, ethylenelacrylic acid, ethylenelmethacrylic acid/n-
butyl
acrylate, ethylene/acrylic acidln-butyl acrylate, ethytenelmethacrylic
acidlmethyl
acrylate and ethylenelacrylic acidlmethyl acrylate copolymers. The most
preferred
3o acid-containing ethylene copolymers are ethylenelmethacrylic acid,
ethylene/acrylic
acid, ethylene/(meth) acrylic acid-n-butyl acrylate, ethylenel(meth)acrylic
acidlethyl
acrylate, and ethylene/(meth) acrylic acid/methyl acrylate copolymers.
CA 02320550 2000-09-25
-19-
The manner in which these ionomers are made is well known in the
art as described in, e.g., U.S. Patent No. 3,262,272, herein incorporated by
reference. Such ionomer resins are commercially available from DuPont Co.
under
the tradename SURLYN~. The presently preferred cover material is a 50150 blend
of SURLYN~ 8140 and SURLYN~ SEP671, which is a lithium SURLYN ~ having
about 19% methacrylic acid. This material has a flex modulus of about 105 ksi.
Preferably, the flex modulus of the cover is greater than 80 ksi. Still
further, the
preferred cover has a hardness of about 70 Shore D. The high flex modulus of
the
cover provides increased initial velocity and a low spin rate.
In another preferred embodiment of the present invention, the cover
layer comprises an inner layer and an outer layer. For instance, Fig. 4
illustrates
an inner cover layer 17 and an outermost cover layer 18. The inner layer of
the
cover is either a thermoplastic material such as a thermoplastic elastomer or
a
thermoplastic rubber, or a thermoset rubber or thermoset elastomer material.
~5 Some examples of materials suitable for use as the inner cover layer
include
polyether or polyester thermoplastic urethanes as well as thermoset
polyurethanes.
A preferable thermoset material is a rubber based, castable urethane. The
outer
layer of the cover is either a thermoplastic plastic material such as an
elastomer or
a thermoplastic rubber, or a thermosetting material.
2o Suitable materials for the outer layer include urethanes, ionomers with
a low modulus and other "dead" but durable materials such as EPDM and butyl
rubber. Additionally, the present invention also contemplates the use of a
polymeric foam material, such as the metallocene-based foamed resin described
above, as the material for either the outer cover layer or the inner cover
layer, but
2s preferably not both layers.
In another preferred embodiment of the present invention, it is
preferable that the thermoplastic or thermosetting materials of the outer
layer have
a melting point or heat of reaction (cure) temperature less than the melting
point or
heat of reaction (cure) temperature of the materials of the inner layer.
3o In yet another embodiment, the polymeric outer cover layer is
comprised of a low acid (less than about 16 weight percent acid) ionorner, a
high
acid (greater than about 16 weight percent acid) ionomer, an ionomer blend, a
non-
CA 02320550 2000-09-25
-20-
ionomeric elastomer, a thermoset material, or blends or combinations thereof.
In
some applications it may be desirable to provide an outer cover that is
relatively
soft and that has a low modulus (about 1,000 psi to about 10,000 psi). The non-
ionomeric elastomers are preferably thermoplastic elastomers such as, but not
limited to, a polyurethane, a polyester elastomer such as that marketed by
DuPont
under the trademark Hytrel~, a polyester amide such as that marketed by Elf
Atochem S.A. under the trademark Pebax~, or combinations thereof.
For outer cover compositions comprising a high acid ionomer, several
new metal ration neutralized high acid ionomer resins are particularly
preferred.
These high acid ionomers have been produced by neutralizing, to various
extents,
high acid copolymers of an alpha-olefin and an alpha, beta-unsaturated
carboxylic
acid with a wide variety of different metal ration salts. More particularly,
it has been
found that numerous new metal ration neutralized high acid ionomer resins can
be
obtained by reacting a high acid copolymer (i.e., a copolymer containing
greater
~s than about 16 percent by weight acid, preferably from about 17 to about 25
weight
percent acid, and more preferably about 20 weight percent acid), with a metal
ration salt capable of ionizing or neutralizing the copolymer to the extent
desired
(i.e., from about 10% to 90%).
The base copolymer is made up of greater than 16 percent by weight
20 of an alpha, beta-unsaturated carboxylic acid and alpha-olefin. Generally,
the
alpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene, and the
unsaturated carboxylic acid is a carboxylic acid having from about 3 to 8
carbons.
Examples of such acids include acrylic acid, methacrylic acid, ethacrylic
acid,
chloroacrylic acid, crotomic acid, malefic acid, fumaric acid, and itacomic
acid, with
25 acrylic acid being preferred.
Consequently, examples of a number of copolymers suitable for use
in the invention include, but are not limited to, high acid embodiments of an
ethylenelacrylic acid copolymer, an ethylenelmethacrylic acid copolymer, an
ethylenelitaconic acid copolymer, an ethylenelmaleic acid copolymer, etc. The
3o base copolymer broadly contains greater than 16 percent by weight
unsaturated
carboxylic acid, and less than 84 percent by weight alpha-olefin. Preferably,
the
copolymer contains about 20 percent by weight unsaturated carboxylic acid and
CA 02320550 2000-09-25
-21 -
about 80 percent by weight ethylene. Most preferably, the copolymer contains
about 20 percent acrylic acid with the remainder being ethylene.
Along these lines, examples of the preferred high acid base
copolymers which fulfill the criteria set forth above, are a series of
ethylene-acrylic
s copolymers which are commercially available from The Dow Chemical Company,
Midland, Michigan, under the "Primacor" designation. These high acid
copolymers
are described in greater detail in U.S. Patent Numbers 5,688,869 and
5,542,677,
both of which are herein incorporated by reference.
Alternatively, the outer layer may include a blend of hard and soft (low
~o acid) ionomer resins such as those described in U. S. Patent Nos. 4,884,814
and
5,120,791, both incorporated herein by reference. Specifically, a desirable
material
for use in molding the outer layer comprises a blend of a high modulus (hard)
ionomer with a low modulus (soft) ionomer to form a base ionomer mixture. A
high
modulus ionomer herein is one which measures from about 15,000 to about 70,000
~ s psi as measured in accordance with ASTM method D-790. The hardness may be
defined as at least 50 on the Shore D scale as measured in accordance with
ASTM
method D-2240. A low modulus ionomer suitable for use in the outer layer blend
has a flexural modulus measuring from about 1,000 to about 10,000 psi, with a
hardness of about 20 to about 40 on the Shore D scale.
2o The hard ionomer resins utilized to produce the outer cover layer
composition hard/soft blends include ionic copolymers which are the sodium,
zinc,
magnesium or lithium salts of the reaction product of an olefin having from 2
to 8
carbon atoms and an unsaturated monocarboxylic acid having from 3 to 8 carbon
atoms. The carboxylic acid groups of the copolymer may be totally or partially
(i.e.,
2s approximately 15-75 percent) neutralized.
The hard ionomeric resins are likely copolymers of ethylene and
either acrylic andlor methacrylic acid, with copolymers of ethylene and
acrylic acid
being the most preferred. Two or more types of hard ionomeric resins may be
blended into the outer cover layer compositions in order to produce the
desired
3o properties of the resulting golf balls.
The hard ionomeric resins developed by Exxon Corporation and
introduced under the designation EscorO and sold under the designation "lotek"
are
CA 02320550 2000-09-25
-22-
somewhat similar to the hard ionomeric resins developed by E.I. DuPont de
Nemours 8 Company and sold under the Surlyn~ trademark. However, since the
"lotek" ionomeric resins are sodium or zinc salts of polyethylene-acrylic
acid) and
the Surlyn~ resins are zinc or sodium salts of polyethylene-methacrylic acid)
some
distinct differences in properties exist. As more specifically indicated in
the data set
forth below, the hard "lotek" resins (i.e., the acrylic acid based hard
ionomer resins)
are the more preferred hard resins for use in formulating the outer cover
layer
blends for use in the present invention. In addition, various blends of
"lotek" and
Surlyn~ hard ionomeric resins, as well as other available ionomeric resins,
may be
o utilized in the present invention in a similar manner.
Examples of commercially available hard ionomeric resins which may
be used in the present invention in formulating the outer cover blends include
the
hard sodium ionic copolymer sold under the trademark Surlyn~8940 and the hard
zinc ionic copolymer sold under the trademark Surlyn~9910. Surlyn~8940 is a
~s copolymer of ethylene with methacrylic acid and about 15 weight percent
acid
which is about 29 percent neutralized with sodium ions. This resin has an
average
melt flow index of about 2.8. Surlyn09910 is a copolymer of ethylene and
methacrylic acid with about 15 weight percent acid which is about 58 percent
neutralized with zinc ions. The average melt flow index of Surlyn~9910 is
about
20 0.7. The typical properties of Surlyn~9910 and 8940 are set forth below in
Table
1:
CA 02320550 2000-09-25
-23
TABLE 1
Typical Properties of Commercially Available Hard
Surl~n~ Resins
Suitable
for Use in
the Outer
Layer Blends
of the Preferred
Embodiments
ASTM D 8940 9910 8920 8528 9970 9730
Cation Type Sodium Zinc Sodium Sodium Zinc Zinc
Mett flow
index,
gmsll0 min. D-1238 2.8 0.7 0.9 1.3 14.0 1.6
Specific Gravity,
glcm' D-792 0.95 0.97 0.95 0.94 0.95 0.95
htardness, 0-2240 66 64 66 60 62 63
Shore D
Tensile Strength,
(kps7, MPa D-638 (4.8) (3.6) (5.4) (4.2) (3.2) (4.1)
33.1 24.8 37.2 29.0 22.0 28.0
Elongation, D-638 470 290 350 450 460 460
%
Flexural Modulus,
(kps~ MPa D-790 (51) (48) (55) (32) (28) (30)
350 330 380 220 190 210
Tensile impact
(23C)
tWlm,(rt:Ibsln~0.t822S 1020 1020 865 1160 760 1240
(485) (485) (410) (550) (360) (590)
Vicat Temperature,O-1525 63 62 58 73 61 73
C
Examples of the more pertinent acrylic acid based
hard ionomer resin
suitable for
use in the
present outer
cover composition
sold under
the "lotek"
trade
name by the
Exxon Corporation
include lotek
4000, iotek
4010, lotek
8000, lotek
8020 and lotek
8030. The
typical properties
of these
and other
lotek hard
ionomers
suited for in formulating the outer layer cover composition
use are set forth below
in Table 2:
TABLE 2
3o Typical Properties of lotek lonomers
Resin ASTM
Properties Method Unts 4000 4010 8000 8020 8030
Canon type zrcx zinc sodium sodium sodium
Melt index D1238 g/10 min. 2.5 1.5 0.8 1.6 2.8
oensity o.l5os t~m~ 963 963 954 9so 9so
Melting PoirdD-3417 'C 90 90 90 87.5 87.5
CrystallizationD3417 C 62 64 56 53 55
Point
Vicat SofteningD.1525 C 62 63 61 64 67
Point
'Xe Weigh 16 11
Acrylic Acid
% of Add
Groups
canon neutralized30 40
Plaque ASTM
CA 02320550 2000-09-25
-24-
Method Units 4000 4010 8000 8020 8030
(3 mm thick
Tensile D~38 MPa 24 26 36 31.5 28
at txeak
S Yield point0638 MPa rune none 21 21 23
Elongation D-638 % 395 420 350 410 395
at break
1% Secarrt D-638 MPa 160 160 300 350 390
modulus
Shore Hardness02240 - 55 55 61 58 59
D
Film Properties
(50 micron
film 2.2:1
4000 4010 8000 8020 8030
Tensile MD D~82 MPa 41 39 42 52 47.4
at freak
TD D-882 MPa 37 38 38 38 40.5
Yield pointMD D~882 MPa 15 17 17 23 21.6
~ TD D-882 MPa 14 15 15 21 20.7
Etongatron
at freak
MD O-882 % 310 270 260 295 305
Tp o-gg2 % 360 340 260 340 345
1% Secant MD D-882 MPa 210 215 390 380 380
modulus
2o TD D-882 MPa 200 225 380 350 345
Dart Drop D-1709 g/micron
Impact 12.4 12.5
20.3
Resin ASTM
Properties Method Units 7010 7020 7030
Canon type zinc zinc zinc
25 Mettlndex D-1238 gIlO min. 0.8 1.5 2.5
Density D-1505 kglm' 960 960 960
Melting D-3417 ~C 90 90 90
Point
Crystallization
Point D-3417 oC - - -
3o Vicat Softening
Point D-1525 oC 60 63 62.5
%Weight - - -
Acrylic
Acid
% of Add
Groups
35 canon rJeutralized - - -
Plaque ASTM
Properties Method Units 7010 7020 7030
(3 mm thick,
corttpressbn
molded)
Tensile D.638 MPa 38 38 38
at Ixeak
Yield PointD~638 MPa nave rwne bone
Ekxigation D~63B % 500 420 395
at txeak
1 % Secant D~38 MPa - - -
modulus
Stxxe HardnessD-2240 - 57
D
45 Comparatively,soft ionomers are used in formulating
the hardlsoft
blends of
the outer
cover composition.
These ionomers
include
acrylic
acid based
soft ionomers.
They are
generally
characterized
as comprising
sodium
or zinc
salts
of a terpolymer
of an olefin
having
from about
2 to 8
carbon
atoms,
acrylic
acid, and
an unsaturated the acrylate ester class having from
monomer 1 to 27 carbon
of
CA 02320550 2000-09-25
-25-
atoms. The soft ionomer is preferably a zinc based ionomer made from an
acrylic
acid base polymer and an unsaturated monomer of the acrylate ester class. The
soft (low modulus) ionomers have a hardness from about 20 to about 40 as
measured on the Shore D scale and a flexural modulus from about 1,000 to about
10,000, as measured in accordance with ASTM method D-790.
Certain ethylene-acrylic acid based soft ionomer resins developed by
the Exxon Corporation under the designation "lotek 7520" (referred to
,experimentally by differences in neutralization and melt indexes as LDX 195,
LDX
196, LDX 218 and LDX 219) may be combined with known hard ionomers such as
those indicated above to produce the outer cover. The combination produces
higher COR's (coefficient of restitution) at equal or softer hardness, higher
melt flow
(which corresponds to improved, more efficient molding, i.e., fewer rejects)
as well
as significant cost savings versus the outer layer of multi-layer balls
produced by
other known hard-soft ionomer blends as a result of the lower overall caw
materials
~5 costs and improved yields.
While the exact chemical composition of the resins to be sold by
Exxon under the designation lotek 7520 is considered by Exxon to be
confidential
and proprietary information, Exxon's experimental product data sheet lists the
following physical properties of the ethylene acrylic acid zinc ionomer
developed
2o by Exxon:
TABLE 3
Physical Properties of lotek 7520
Property ASTM Method Units Typical Value
Melt Index D-1238 g110 min. 2
25 Density D-1505 kg/m3 0.962
Cation Zinc
Melting Point D-3417 °C 66
Crystallization
Point D-3417 °C 49
3o Vicat Softening
CA 02320550 2000-09-25
-26-
Point D-1525 ° C 42
Plaque Properties~2 mm thick Compression Molded Plaouesl
Tensile at Break D-638 MPa 10
Yield Point D-638 MPa None
Elongation at Break D-638 % 760
1 % Secant Modulus D-638 MPa 22
Shore D Hardness D-2240 32
Flexural Modulus D-790 MPa 26
Zwick Rebound ISO 4862 % 52
~o De Mattia Flex
Resistance D-430 Cycles >5000
In addition, test data collected by the inventor and others indicate that
lotek 7520 resins have Shore D hardnesses of about 32 to 36 (per ASTM D-2240),
melt flow indexes of 310.5 g/10 min (at 190°C. per ASTM D-1288), and a
flexural
~5 modulus of about 2500-3500 psi (per ASTM D-790). Furthermore, testing by an
independent testing laboratory by pyrolysis mass spectrometry indicates that
lotek
7520 resins are generally zinc salts of a terpolymer of ethylene, acrylic
acid, and
methyl acrylate.
Furthermore, the inventor has found that a newly developed grade of
2o an acrylic acid based soft ionomer available from the Exxon Corporation
under the
designation lotek 7510, is also effective, when combined with the hard
ionomers
indicated above in producing golf ball covers exhibiting higher COR values at
equal
or softer hardness than those produced by known hard-soft ionomer blends. In
this
regard, lotek 7510 has the advantages (i.e., improved flow, higher COR values
at
25 equal hardness, increased clarity, etc.) produced by the lotek 7520 resin
when
compared to the methacrylic acid base soft ionomers known in the art (such as
the
Surlyn 8625 and the Surlyn 8629 combinations disclosed in U.S. Patent No.
4,884,814).
CA 02320550 2000-09-25
- 27 -
In addition, lotek 7510, when compared to lotek 7520, produces
slightly higher COR values at equal softnesslhardness due to the lotek 7510's
higher hardness and neutralization. Similarly, lotek 7510 produces better
release
properties (from the mold cavities) due to its slightly higher stiffness and
lower flow
rate than lotek 7520. This is important in production where the soft covered
balls
tend to have lower yields caused by sticking in the molds and subsequent
punched
pin marks from the knockouts.
According to Exxon, lotek 7510 is of similar chemical composition as
lotek 7520 (i.e., a zinc salt of a terpolymer of ethylene, acrylic acid, and
methyl
o acrylate) but is more highly neutralized. Based upon FTIR analysis, lotek
7520 is
estimated to be about 30-40 weight percent neutralized and lotek 7510 is
estimated
to be about 40-60 weight percent neutralized. The typical properties of lotek
7510
in comparison with those of lotek 7520 are set forth below:
TABLE 4
~5 PhXsical Properties of lotek 7510
in Comparison to lotek 7520
IOTEK 7520 IOTEK 7510
MI, g/10 min 2.0 0.8
Density, g/cc 0.96 0.97
2o Melting Point, F 151 149
Vicat Softening Point, F 108 109
Flex Modulus, psi 3800 5300
Tensile Strength, psi 1450 1750
Elongation, % 760 690
25 Hardness, Shore D 32 35
It has been determined that when hardlsoft ionomer blends are used
for the outer cover layer, good results are achieved when the relative
combination
is in a range of about 90 to about 10 percent hard ionomer and about 10 to
about
90 percent soft ionomer. The results are improved by adjusting the range to
about
CA 02320550 2000-09-25
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75 to 25 percent hard ionomer and 25 to 75 percent soft ionomer. Even better
results are noted at relative ranges of about 60 to 90 percent hard ionomer
resin
.and about 40 to 60 percent soft ionomer resin.
Specific formulations which may be used in the cover composition are
included in the examples set forth in U.S. Patent Nos. 5,120,791 and
4,884,814,
both of which are herein incorporated by reference. The present invention is
in no
way limited to those examples. It will be understood that ionomer compositions
containing about 16 weight percent acid may be referred to as either low acid
or
high acid. However, for purposes herein, such compositions are generally
considered to be low acid.
Moreover, in alternative embodiments, the outer cover layer
formulation may also comprise a soft, low modulus non-ionomeric thermoplastic
elastomer including a polyester polyurethane such as B.F. Goodrich Company's
Estane~ polyester polyurethane X-4517. According to B.F. Goodrich, Estane~ X-
~5 4517 has the following properties:
TABLE 5
Properties of Estane~ X-4517
Tensile 1430
100% 815
2o 200% 1024
300% 1193
Elongation 641
Youngs Modulus 1826
Hardness AID 88139
25 Bayshore Rebound 59
Solubility in Water Insoluble
Melt processing temperature >350~F (>177~C)
Specific Gravity (H20=1) 1.1-1.3
Other soft, relatively low modulus non-ionomeric thermoplastic
3o elastomers may also be utilized to produce the outer cover layer as long as
the
non-ionomeric thermoplastic elastomers produce the playability and durability
characteristics desired without adversely effecting the enhanced travel
distance
characteristic produced by the high acid ionomer resin composition. These
include,
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but are not limited to thermoplastic polyurethanes such as: Texin
thermoplastic
polyurethanes from Mobay Chemical Co. and the Pellethane thermoplastic
polyurethanes from Dow Chemical Co.; lonomer/rubber blends such as those in
Spalding U.S. Patents 4,986,545; 5,098,105 and 5,187,013, all of which are
hereby
s incorporated by reference; and, Hytrel polyester elastomers from DuPont and
Pebax polyester amides from Elf Atochem S.A.
In addition, or instead of the following thermoplastics, one or more
thermoset polymeric materials may be utilized for the outer cover. Preferred
thermoset polymeric materials include, but are not limited to, polyurethanes,
o metallocenes, diene rubbers such as cis 1,4 polybutadiene, traps
polyisoprene
EDPM or EPR. It is also preferred that all thermoset materials be crosslinked.
Crosslinking may be achieved by chemical crosslinking and/or initiated by free
radicals generated from peroxides, gamma or election beam radiation.
The polymeric outer cover layer is about 0.020 inches to about 0.120
~ 5 inches in thickness. The outer cover layer is preferably about 0.050
inches to about
0.075 inches in thickness. Together, the mantle and the outer cover layer
combine
to form a ball having a diameter of 1.680 inches or more, the minimum diameter
permitted by the rules of the United States Golf Association and weighing
about
1.620 ounces.
2o The inner and outer cover layers of this embodiment of the invention
can be molded about the core and mantle layers through a variety of
conventional
molding methods. For example, the cover layers can be compression molded,
retractable pin injection molded, fixed pin injection molded, cast around the
core
and mantle or a combination thereof. However, it is important that the
materials of
2s the outer layer are characterized in that they have thermal properties such
that no
flow of the inner layer material occurs during the molding of the outer cover
layer
about the inner layer, regardless of the process employed to mold the layers.
The inner cover layer of this embodiment of the present invention has
a thickness of about 0.005 inches to about 0.040 inches. The outer cover layer
has
3o a thickness of about 0.010 inches to about 0.100 inches. Preferably, the
inner
cover layer has a thickness of about 0.010 inches to about 0.030 inches and
the
outer cover layer has a thickness of about 0.030 inches to about 0.090 inches.
CA 02320550 2000-09-25
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The present invention also contemplates the use of a variety of non-
conventional cover materials. In particular, the cover of the present
invention may
comprise thermoplastic or engineering plastics such as ethylene or propylene
based homopolymers and copolymers including functional monomers such as
acrylic and methacrylic acid and fully or partially neutralized ionomers and
their
blends, methyl acrylate, methyl methacrylate homopolymers and copolymers,
imidized, amino group containing polymers, polycarbonate, reinforced
polyamides,
polyphenylene oxide, high impact polystyrene, polyether ketone, polysulfone,
poly-
(phenylene sulfide), reinforced engineering plastics, aaylonitrile-butadiene,
acrylic-
styrene-acrylonitrile, polyethylene terephthalate), poly(butylene
terephthalate),
polyethylene-vinyl alcohol), poly(tetrafluoroethylene and their copolymers
including
functional comonomers and blends thereof. These polymers or copolymers can be
further reinforced by blending with a wide range of fillers and glass fibers
or
spheres or wood pulp.
~5 Other Aspects
Properties such as hardness, Bayshore resilience, modulus, core
diameter and mantle layer thickness of the golf balls of the present invention
have
been found to affect play characteristics such as spin, initial velocity and
feel of the
present invention golf balls.
2o In particular, the overall thickness of the primary and optional
secondary mantle layer of the preferred embodiment balls of the present
invention
is about 0.005 inches to about 0.6 inches. Preferably, the thickness of the
primary
and optional secondary mantle layer is about 0.04 inches to about 0.10 inches.
Most preferably, the thickness of the primary and secondary mantle layer is
about
25 0.06 inches. Similarly, the diameter of the core of the preferred
embodiment golf
balls of the present invention is about 1.25 inches to about 1.51 inches.
Preferably
the diameter of the core is about 1.30 inches to about 1.48 inches. Most
preferably, the diameter of the core is about 1.39 inches. The overall
diameter of
the core and the mantle layers) is about 84% to about 97% of the overall
diameter
30 of the finished ball, and is preferably about 1.51 inches.
~ 5 inches in thickness. The ou
CA 02320550 2000-09-25
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The present multi-layer golf ball can have an overall diameter of any
size. Although the United States Golf Association (USGA) specifications limit
the
minimum size of a competition golf ball to more than 1.680 inches in diameter,
there is no specification as to the maximum diameter. Moreover, golf balls of
any
size can be used for recreational play. The preferred diameter of the present
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. The most preferred
.diameter is about 1.680 inches to about 1.740 inches. However, oversized game
balls well in excess of 1.800 inches are also contemplated by the present
invention.
~o Several physical properties such as hardness, resilience and modulus
of the various layers of the golf balls of the present invention are believed
to impact
the playing characteristics of such golf balls. For example, the flexural
andlor
tensile moduli of the mantle layer are believed to have an effect on the
"feel" of the
golf balls of the present invention. Accordingly, it is preferable that the
golf balls of
~s the present invention have a mantle layer with a flexural modulus of about
500 psi
to about 50,000 psi in order to impart a softer "feel° to the golf
balls of the present
invention. Likewise, it is preferred that the one or more mantle layers) have
a
tensile modulus of about 500 psi to about 50,000 psi in order to impart a
softer
"feel" to the golf balls of the present invention. More preferably, the flex
modulus
2o and tensile modulus of the one or more mantle layers) are both less than
about
10,000 psi. Most preferably, the flex modulus of the mantle layers) is less
than
5000 psi.
Further, the core of the preferred embodiment golf balls of the present
invention has a Bayshore resilience of about 30 to about 80. Preferably the
core
25 has a Bayshore resilience of abut 40 to about 70. The one or more mantle
layers)
of the present invention have a Bayshore resilience of about 35 to about 75.
Preferably the mantle layers have a Bayshore resilience of about 60-70.
The preferred embodiment golf balls of the present invention have
mantle layers with a Shore D hardness of less than about 60. Preferably, the
Shore
3o D hardness of the mantle layers is about 20 to about 60. Most preferably,
the
mantle layer has a Shore D hardness of about 30 to provide the soft
"feel° desired.
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The core has a Shore D hardness of about 30 to about 65. Preferably, the core
has a Shore D hardness of about 35 to about 60.
In another preferred embodiment ball, the speck gravities of the ball
materials increase toward the center of the ball. In other words, the specific
gravity
of the core is greater than the specific gravity of the mantle layer(s), which
is
greater than the specific gravity of the cover. More particularly, the core
preferably
has a specific gravity greater than about 1.2, the mantle layers) has a
specific
gravity between about 1 and 1.2 and the cover has a specific gravity of less
than
about 1.1.
o The golf balls of the present invention can be made by any
conventional process employed in the golf ball art. For example, the solid
cores
can be either injection or compression molded. Similarly, the undersized wound
cores of the present invention are produced through conventional means. The
mantle layer is subsequently injection or compression molded about the core.
It is
~5 important that the mantle material be able to sustain the temperatures
applied
during the application of the cover layer. The cover layer or layers are then
injection or compression molded or cast about the mantle layer.
In the manufacturing of the ball, the core is compression molded. The
one or more primary and secondary mantle layers) is molded over the core using
2o a fixed-pin mold such that a plurality of apertures are formed in the
mantle layer.
Then the cover is molded over the mantle layer such that some of the cover
material flows into the apertures in the mantle layer, thereby forming a
mechanical
interlock.
Examples
25 A series of trials could be conducted in which golf ball primary
mantles are produced as set forth in Table 6 below:
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TABLE 6
- Example Matrix Material Foam Granule
1 10-95 wt % ionomer 90-5 wt % peroxide or radiation
cross-linked ionomer
2 10-95 wt k ionomer 90-5 wt % cross-linked metallocene
3 10-95 wt % ionomer 90-5 wt ~ cross-linked styrene-butadiene
block
copolymer
4 10-95 wt % ionomer 90-5 wt % cross-linked styrene-ethylene-
butadine-
styrene block copolymer
5 10-95 wt % ionomer Thermoplastic hytrel polyetherester
6 10-95 wt % ionomer Thermoplastic pebax polyetheramide
7 10-95 wt % ionomer Thermoplastic polyamide
8 10-95 wt % ionomer Thermoplastic polyurethane
9 10-95 wt % ionomer Thermosetting polyurethane
10 10-95 wt % ionomer Cross-linked PP, PE, LDPE, LLDPE,
HDPE, EEA, EMA
or other non-ionomeric olefinic
polymers
11 25-95 wt % thermosetting5-75 wt % cross-linked ionomer
PU (cast, RIM, etc.)
12 25-95 wt % thermosetting5-75 wt % cross-linked metallocene
PU (cast, RIM, etc.)
13 25-95 wt % thermosetting5-75 wt % polyamide
PU (cast, RIM, etc.)
14 25-95 wt ~ thermosetting5-75 wt % polyetherester
PU (cast, RIM, etc.)
15 25-95 wt .6 thermosetting5-75 wt % polyurethane
PU (cast, RIM, etc.)
16 25-95 wt ~ thermosetting5-75 wt % polyetheramide
PU (cast, RIM, etc.)
In each example 1-10 the cover or mantle layer, as compared to a
100% ionomer cover or mantle layer, would exhibit an improved soft feel with
minimal change in C.O.R. or durability (cut resistance or crack resistance),
and
ease of molding as compared to a cover or mantle layer comprising 100% foamed
material. In each example 11-16 the cover or mantle layer, as compared to a
cover
or mantle layer comprising a 100% thermosetting polyurethane, would exhibit an
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improved soft feel with minimal change in C.O.R. or durability and ease of
molding.
Because the foamed polymers in examples 5-8 and 13-16 melt at temperatures
above the processing or molding temperatures of the matrix material (ionomer)
it
is not necessary to crosslink the foam.
The invention has been described with reference to the preferred
embodiments. Obviously, modifications and alterations will occur to others
upon
a reading and understanding of the preceding detailed description. It is
intended
that the invention be construed as including all such alterations and
modifications
insofar as they come within the scope of the appended claims or the
equivalents
o thereof.
