U.S. patent application number 09/877835 was filed with the patent office on 2003-10-23 for multi-core, multi-layer cover golf ball.
Invention is credited to Nesbitt, R. Dennis.
Application Number | 20030199338 09/877835 |
Document ID | / |
Family ID | 25370823 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030199338 |
Kind Code |
A1 |
Nesbitt, R. Dennis |
October 23, 2003 |
Multi-core, multi-layer cover golf ball
Abstract
The present invention is directed to a golf ball comprising a
multi-layer core component. The multi-layer core comprises an
interior center component formed from a thermoset material, a
thermoplastic material, or combinations thereof. The multi-layer
core also comprises a core layer disposed about the center
component, formed from a thermoset material, a thermoplastic
material, or combinations thereof. The present invention golf ball
may further comprise an outer core layer that surrounds the
multi-layer core. The resulting multi-layered golf ball of the
present invention provides for enhanced distance without
sacrificing playability or durability when compared to known golf
balls.
Inventors: |
Nesbitt, R. Dennis;
(Westfield, MA) |
Correspondence
Address: |
Michelle Bugbee
Spalding Sports Worldwide, Inc.
425 Meadow Street
P.O. Box 901
Chicopee
MA
01021-0901
US
|
Family ID: |
25370823 |
Appl. No.: |
09/877835 |
Filed: |
June 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09877835 |
Jun 8, 2001 |
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09829708 |
Apr 10, 2001 |
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09829708 |
Apr 10, 2001 |
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09048701 |
Mar 26, 1998 |
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6213895 |
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09877835 |
Jun 8, 2001 |
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09394829 |
Sep 13, 1999 |
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6277034 |
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09877835 |
Jun 8, 2001 |
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09562773 |
May 2, 2000 |
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6495633 |
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09562773 |
May 2, 2000 |
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09049410 |
Mar 27, 1998 |
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6057403 |
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60042439 |
Mar 28, 1997 |
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Current U.S.
Class: |
473/374 |
Current CPC
Class: |
C08L 23/0876 20130101;
A63B 37/0075 20130101; A63B 37/0062 20130101; A63B 37/0003
20130101; A63B 37/12 20130101; A63B 37/0043 20130101; A63B 37/0076
20130101; A63B 37/0064 20130101; A63B 37/0031 20130101; A63B
37/0024 20130101; C08L 23/08 20130101; A63B 37/0045 20130101; A63B
37/04 20130101; C08L 23/08 20130101; C08L 2666/04 20130101 |
Class at
Publication: |
473/374 |
International
Class: |
A63B 037/02 |
Claims
What is claimed is:
1. A golf ball comprising: a multi-layer core comprising a center
component and a core layer disposed about said center component;
wherein said center component comprises a thermoset material and
said core layer comprises a thermoset material; and, a cover layer
disposed about said multi-layer core; wherein said cover layer
includes at least one of (i) a multi-layer cover comprising an
inner cover layer having a Shore D hardness of 65 or greater and an
outer cover layer having a Shore D hardness of 65 or less, said
inner cover layer being harder than said outer cover layer, (ii) a
multi-layer cover comprising an inner cover layer having a Shore D
hardness of 65 or less and an outer cover layer of 65 or greater,
wherein said inner cover layer is softer than said outer cover
layer, (iii) a single non-ionomeric outer cover layer having a
Shore D hardness of from about 40 to 80, and (iv) a single
ionomeric outer cover layer having a Shore D hardness of at least
56.
2. The golf ball of claim 1 wherein the outer cover layer is
selected from multi-layer cover (i) or multi-layer cover (ii).
3. The golf ball of claim 1 wherein said thermoset material
comprises a material selected from the group consisting of (i) a
diene-containing polymer, (ii) a metallocene catalyzed polyolefin
that is cross-linked, (iii) a polyurethane, (iv) a silicone, (v) a
polyamide, (vi) a polyurea, and (vii) combinations thereof; and
said thermoplastic material comprises a material selected from the
group consisting of (i) an ionomer, (ii) a polyurethane, (iii) an
elastomer, (iv) a polyetheramide, (v) a polyetherester, (vi) a
metallocene catalyzed polyolefin, (vii) a styrene butadiene block
copolymer, and (viii) combinations thereof.
4. The golf ball of claim 1 wherein said core layer comprises more
than one layer.
5. The golf ball of claim 1 wherein said center component thermoset
material comprises a polybutadiene rubber.
6. The golf ball of claim 5 wherein said thermoset polybutadiene
rubber further comprises zinc diacrylate (ZDA).
7. The golf ball of claim 1 wherein said core layer thermoset
material comprises polybutadiene rubber.
8. The golf ball of claim 7 wherein said polybutadiene rubber
further comprises zinc diacrylate (ZDA).
9. The golf ball of claim 1 wherein said center component of said
multi-layer core has an outer diameter of from about 1.340 inches
to about 1.400 inches, and said core layer of said multi-layer core
has an thickness of from about 0.020 to about 0.100 inches.
10. The golf ball of claim 1 wherein said center component of said
multi-layer core is softer relative to said core layer.
11. The golf ball of claim 10 wherein said core layer ha s a Shore
D hardness of at least 60.
12. The golf ball according to claim 1 wherein each layer in the
multi-layer cover (i) and multi-layer cover (ii) is independently
formed from a thermoplastic resin, a thermoset resin, or a blend
thereof.
13. The golf ball according to claim 2 wherein the multi-layer
cover (i) or multi-layer cover (ii) comprises at least one
ionomeric material.
14. A golf ball comprising: a multi-layer core comprising a center
component and a core layer disposed about said center component;
wherein said center component comprises a polybutadiene thermoset
material and said core layer comprises a polybutadiene thermoset
material; and, a cover layer disposed about said multi-layer core;
wherein said cover layer includes at least one of (i) a multi-layer
cover comprising an inner cover layer having a Shore D hardness of
65 or greater and an outer cover layer having a Shore D hardness of
65 or less, said inner cover layer being harder than said outer
cover layer, (ii) a multi-layer cover comprising an inner cover
layer having a Shore D hardness of 65 or less and an outer cover
layer of 65 or greater, wherein said inner cover layer is softer
than said outer cover layer, and (iii) a single non-ionomeric outer
cover layer having a Shore D hardness of from about 40 to 80, and
(iv) a single ionomeric outer cover layer having a Shore D hardness
of at least 56.
15. The golf ball according to claim 14 wherein the cover layer is
selected from multi-layer cover (i) or multi-layer cover (ii).
16. The golf ball of claim 14 wherein said thermoset material
further comprises zinc diacrylate (ZDA).
17. The golf ball of claim 14 wherein said core layer comprises
more than one layer.
18. The golf ball of claim 14 wherein said center component of said
dual core comprise is softer relative to said core layer.
19. The golf ball of claim 11 wherein said core layer has a Shore D
hardness of at least 60.
20. A golf ball comprising: a multi-layer core comprising a center
component and a core layer disposed about said center component;
wherein said center component comprises a polybutadiene/ZDA
thermoset material and said core layer comprises a
polybutadiene/ZDA thermoset material; and, a multi-layer, ionomeric
cover layer disposed about said dual core; wherein said cover layer
includes at least one of (i) a multi-layer cover comprising an
inner cover layer having a Shore D hardness of 65 or greater and an
outer cover layer having a Shore D hardness of 65 or less, said
inner cover layer being harder than said outer cover layer, and
(ii) a multi-layer cover comprising an inner cover layer having a
Shore D hardness of 65 or less and an outer cover layer of 65 or
greater, wherein said inner cover layer is softer than said outer
cover layer.
Description
[0001] CROSS REFERENCE TO RELATED APPLICATIONS
[0002] This application claims priority as a continuation-in-part
of U.S. Ser. No. 09/829,708, filed Apr. 10, 2001, which is a
continuation of U.S. Ser. No. 09/048,701; filed Mar. 26, 1998, now
U.S. Pat. No. 6,213,895 which claims priority to U.S. provisional
patent application serial No. 60/042,439 filed Mar. 28, 1997. This
application also claims priority as a continuation-in-part of U.S.
application Ser. No. 09/394,829; filed Sep. 13, 1999, and as a
continuation-in-part of U.S. application Ser. No. 09/562,773, filed
May 2, 2000, which is a continuation of U.S. Ser. No. 09/049,410,
filed Mar. 27, 1998 now U.S. Pat. No. 6,057,403.
FIELD OF THE INVENTION
[0003] The present invention relates generally to golf balls and,
more particularly, to improved golf balls comprising unique
multi-layer core and cover configurations. The improved golf balls
provide for enhanced distance and durability properties.
BACKGROUND OF THE INVENTION
[0004] A number of two-piece (a solid resilient center or core with
a molded cover) and three-piece (a liquid or solid center,
elastomeric winding about the center, and a molded cover) golf
balls have been produced. The different types of materials utilized
to formulate the cores, covers, etc. of these balls dramatically
alters the balls' overall characteristics. In addition,
multi-layered covers containing one or more ionomer resins have
also been formulated in an attempt to produce a golf ball
[0005] Despite the great number of materials and combinations of
materials utilized in prior art golf balls, there still remains a
need for an improved golf ball exhibiting superior properties.
[0006] 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.
SUMMARY OF THE INVENTION
[0007] The present invention relates to new and improved golf balls
which overcome the above referenced problems and others.
[0008] In one aspect, the present invention provides a golf ball
comprising a multi-layer core comprising a center component and at
least one core layer disposed about the center component. The
center component comprises a thermoset material and the core layer
comprises a thermoset material.
[0009] In yet another aspect, the present invention provides a golf
ball comprising a multi-layer core comprising a center component
and a core layer disposed about the center component. The center
component comprises a thermoplastic material and the core layer
comprises a thermoset material.
[0010] In yet another aspect, the present invention provides a
multi-layer golf ball comprising a multi-layer core component that
includes a center component and a core layer disposed about the
center component. The center component comprises a thermoset
material and the core layer comprises a thermoplastic material.
[0011] In yet another embodiment, the present invention provides a
multi-layer golf ball comprising a multi-layer core, having a
center component and a core layer, both of which comprise a
thermoplastic material.
[0012] In addition, for each of the above recited aspects, a cover
selected from multi-layer covers and single layer covers is
provided. The multi-layer covers comprise a relatively hard inner
layer and a relatively soft outer layer or, conversely, a
relatively soft inner layer and a relatively hard outer layer. The
components of the cover may be ionomeric, non-ionomeric, or in the
case of multi-layer covers, a combination thereof.
[0013] Other objects will be, in part, obvious and, in part,
pointed out in greater detail hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following is a brief description of the drawings which
are presented for the purpose of illustrationg the invention and
not for the purpose of limiting the same.
[0015] FIG. 1 is a cross-sectional view of a preferred embodiment
golf ball in accordance with the present invention comprising a
dual core component and a single layer cover;
[0016] FIG. 2 is a cross-sectional view of another preferred
embodiment golf ball in accordance with the present invention
comprising a dual core component and a multi-layer cover;
[0017] FIG. 3 is a cross-sectional view of another preferred
embodiment golf ball in accordance with the present invention
comprising a multi-layer core component including multiple core
layers;
[0018] FIG. 4 is a cross sectional view of yet another preferred
embodiment golf ball in accordance with the present invention
comprising a dual core component and a multi-layer cover;
[0019] FIG. 5 is a schematic view of an assembly used for molding a
preferred embodiment golf ball in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The present invention is directed to a golf ball comprising
a multi-layer core component. The present invention golf balls
preferably utilize a multi-layer cover. However, the golf balls may
instead utilize conventional cover materials such as balata or
blends of balata with elastomeric or plastic materials.
[0021] As mentioned, the golf balls of the present invention
utilize a unique multi-layer core configuration. Preferably, the
cores comprise (i) an interior spherical center component formed
from a thermoset material, a thermoplastic material, or
combinations thereof; and (ii) a core layer disposed about the
spherical center component, the core layer formed from a thermoset
material, a thermoplastic material, or combinations thereof. The
cores may further comprise (iii) an optional outer core layer
disposed about the core layer. The outer core layer may be formed
from a thermoset material, a thermoplastic material, or
combinations thereof.
[0022] Although the present invention is primarily directed to golf
balls comprising a multi-layer core component and preferably in
conjunction with a multi-layer cover as described herein, the
present invention also includes golf balls having a multi-layer
core component and conventional covers comprising balata, various
thermoplastic materials, cast polyurethanes, or any other known
cover material.
[0023] With respect to the multi-layer golf ball covers, these
covers include a first or inner layer or ply of a high acid
(greater than 16 weight percent acid) ionomer blend or, more
preferably, a low acid (16 weight percent acid or less) ionomer
blend and second or outer layer or ply comprised of a comparatively
softer, low modulus ionomer, ionomer blend or other non-ionomeric
thermoplastic or thermosetting elastomer such as polyurethane or
polyester elastomer. The multi-layer golf balls of the present
invention can be of standard or enlarged size. Preferably, the
inner layer or ply includes a blend of low acid ionomers and has a
Shore D hardness of 70 or greater and the outer cover layer
comprised of polyurethane and has a Shore D hardness of about 45
(i.e., Shore C hardness of about 65).
[0024] It has been found that multi-layer golf balls having inner
and outer cover layers exhibit higher C.O.R. values and have
greater travel distance in comparison with balls made from a single
cover layer. In addition, it has been found that use of an inner
cover layer constructed of a blend of low acid (i.e., 16 weight
percent acid or less) ionomer resins produces softer compression
and higher spin rates than inner cover layers constructed of high
acid ionomer resins. This is compounded by the fact that the softer
polyurethane outer layer adds to the desirable "feel" and high spin
rate while maintaining respectable resilience. The soft outer layer
allows the cover to deform more during impact and increases the
area of contact between the club face and the cover, thereby
imparting more spin on the ball. As a result, the soft polyurethane
cover provides the ball with a balata-like feel and playability
characteristics with improved distance and durability.
[0025] Consequently, the overall combination of the unique
multi-layer core configuration, described in greater detail herein,
and the multi-layer cover construction of inner and outer cover
layers made, for example, from blends of low acid ionomer resins
and polyurethane results in a standard size or oversized golf ball
having enhanced resilience (improved travel distance) and
durability (i.e. cut resistance, etc.) characteristics while
maintaining and in many instances, improving the ball's playability
properties.
[0026] The combination of a low acid ionomer blend inner cover
layer with a soft, relatively low modulus ionomer, polyurethane
based elastomer outer cover layer provides for good overall
coefficient of restitution (i.e., enhanced resilience) while at the
same time demonstrating improved compression and spin. The outer
cover layer generally contributes to a more desirable feel and
spin, particularly at lower swing speeds with highly lofted clubs
such as half wedge shots.
[0027] Accordingly, the present invention is directed to a golf
ball comprising a multi-layer core configuration and an improved
multi-layer cover which produces, upon molding each layer around a
core to formulate a multi-layer cover, a golf ball exhibiting
enhanced distance (i.e., resilience) without adversely affecting,
and in many instances, improving the ball's playability
(hardness/softness) and/or durability (i.e., cut resistance,
fatigue resistance, etc.) characteristics.
[0028] FIGS. 1 and 2 illustrate a preferred embodiment golf ball 10
and 20 in accordance with the present invention. It will be
understood that none of the referenced figures are to scale. And
so, the thicknesses and proportions of the various layers and the
diameter of the various core components are not necessarily as
depicted.
[0029] The golf ball 10 (FIG. 1) comprises a single layer cover 16
disposed about a core 12 and a core layer 14. The core 12 of the
golf ball can be formed of a solid, a wound, a liquid including
combinations thereof, or any other substances that may be utilized
to form the novel multi-layer core described herein.
[0030] The golf ball 20 (FIG. 2) comprises a multi-layer cover 26,
28, disposed about a core 22 and a core layer 24. The core 22 of
the golf ball can be formed of a solid, a liquid, a wound,
including combinations thereof, or any other substances that may be
utilized to form the novel multi-layer core described herein.
[0031] The multi-layered cover of golf ball 20 comprises two
layers: a first or inner layer or ply 26 and a second or outer
layer or ply 28. The inner layer 26 can be ionomer, ionomer blends,
non-ionomer, non-ionomer blends, or blends of ionomer and
non-ionomer. The outer layer 28 is softer than the inner layer and
can be ionomer, ionomer blends, non-ionomer, non-ionomer blends or
blends of ionomer and non-ionomer.
[0032] In a first preferred embodiment as shown in FIG. 2, the
inner cover layer 26 is comprised of a high acid (i.e., greater
than 16 weight percent acid) ionomer resin or a high acid ionomer
blend. Preferably, the inner cover layer 26 is comprised of a blend
of two or more high acid (i.e., at least 16 weight percent acid)
ionomer resins neutralized to various extents by different metal
cations.
[0033] The inner cover layer 26 may or may not include a metal
stearate (e.g., zinc stearate) or other metal fatty acid salt. The
purpose of the metal stearate or other metal fatty acid salt is to
lower the cost of production without affecting the overall
performance of the finished golf ball.
[0034] In a second embodiment, the inner layer 26 is comprised of a
low acid (i.e., 16 weight percent acid or less) ionomer blend.
Preferably, the inner cover layer 26 is comprised of a blend of two
or more low acid (i.e., 16 weight percent acid or less) ionomer
resins neutralized to various extents by different metal cations.
The inner cover layer 26 may or may not include a metal stearate
(e.g., zinc stearate) or other metal fatty acid salt.
[0035] Two principal properties involved in golf ball performance
are resilience and hardness. Resilience is determined by the
coefficient of restitution (C.O.R.), the constant "e" which is the
ratio of the relative velocity of an elastic sphere after direct
impact to that before impact. As a result, the coefficient of
restitution ("e") can vary from 0 to 1, with 1 being equivalent to
a perfectly or completely elastic collision and 0 being equivalent
to a perfectly or completely inelastic collision.
[0036] Resilience (C.O.R.), along with additional factors such as
club head speed, angle of trajectory and ball configuration (i.e.,
dimple pattern) generally determine the distance a ball will travel
when hit. Since club head speed and the angle of trajectory are
factors not easily controllable by a manufacturer, factors of
concern among manufacturers are the coefficient of restitution
(C.O.R.) and the surface configuration of the ball.
[0037] The coefficient of restitution (C.O.R.) in solid core balls
is a function of the composition of the molded core and of the
cover. In balls containing a dual core (i.e., balls comprising an
interior spherical center component, a core layer disposed about
the spherical center component, and a cover), the coefficient of
restitution is a function of not only the composition of the cover,
but also the composition and physical characteristics of the
interior spherical center component and the core layer. Both the
dual core and the cover contribute to the coefficient of
restitution in the golf balls of the present invention.
[0038] In this regard, the coefficient of restitution of a golf
ball is generally measured by propelling a ball at a given speed
against a hard surface and measuring the ball's incoming and
outgoing velocity electronically. As mentioned above, the
coefficient of restitution is the ratio of the outgoing velocity to
the incoming velocity. The coefficient of restitution must be
carefully controlled in all commercial golf balls in order for the
ball to be within the specifications regulated by the United States
Golf Association (U.S.G.A.). Along this line, the U.S.G.A.
standards indicate that a "regulation" ball cannot have an initial
velocity (i.e., the speed of the club) exceeding 255 feet per
second. Since the coefficient of restitution of a ball is related
to the ball's initial velocity, it is highly desirable to produce a
ball having sufficiently high coefficient of restitution to closely
approach the U.S.G.A. limit on initial velocity, while having an
ample degree of softness (i.e., hardness) to produce enhanced
playability (i.e., spin, etc.).
[0039] The hardness of the ball is the second principal property
involved in the performance of a golf ball. The hardness of the
ball can affect the playability of the ball on striking and the
sound or "click" produced. Hardness is determined by the
deformation (i.e., compression) of the ball under various load
conditions applied across the ball's diameter (i.e., the lower the
compression value, the harder the material). As indicated in U.S.
Pat. No. 4,674,751, softer covers permit the accomplished golfer to
impart increased spin. This is because the softer covers deform on
impact significantly more than balls having "harder" ionomeric
resin covers. As a result, the better player is allowed to impart
fade, draw or backspin to the ball thereby enhancing playability.
Such properties may be determined by various spin rate tests.
[0040] It has been found that a hard inner cover layer provides for
a substantial increase in resilience (i.e., enhanced distance) over
known multi-layer covered balls. The softer outer cover layer
provides for desirable "feel" and high spin rate while maintaining
respectable resiliency. The soft outer layer allows the cover to
deform more during impact and increases the area of contact between
the club face and the cover, thereby imparting more spin on the
ball. As a result, the soft cover provides the ball with a
balata-like feel and playability characteristics with improved
distance and durability.
[0041] In addition, the unique multi-layer core configuration, when
formed into a finished golf ball according to the present
invention, results in a golf ball having enhanced resilience
(improved travel distance), durablilty and feel characteristics
while maintaining and in many instances, improving the playability
properties of the ball.
[0042] The combination of a multi-layer core component and a hard
inner cover layer with a soft, relatively low modulus ionomer,
ionomer blend or other non-ionomeric thermoplastic elastomer outer
cover layer provides for excellent overall coefficient of
restitution (i.e., excellent resilience) because of the improved
resiliency produced by the inner cover layer. Moreover, the
configuration of, and the ability to select the materials used in,
the multi-layer core component enables the formulator to readily
tailor the end properties and characteristics of the resulting golf
ball. While some improvement in resiliency is also produced by the
outer cover layer, the outer cover layer generally provides for a
more desirable feel and high spin, particularly at lower swing
speeds with highly lofted clubs such as half wedge shots.
[0043] In an alternative embodiment, a soft inner cover layer is
provided which is covered by a relatively harder outer cover layer.
While some of the enhanced "feel" characteristics are sacrificed
compared to a soft over hard cover for a golf ball, enhanced
distance may be realized by the hard over soft covers.
A. The Core Layers
[0044] Multi-Layer Core
[0045] As noted, the present invention golf balls utilize a unique
dual core configuration. Preferably, the cores comprise (i) an
interior spherical center component formed from a thermoset
material, a thermoplastic material, or combinations thereof and
(ii) a core layer disposed about the spherical center component,
the core layer formed from a thermoset material, a thermoplastic
material, or combinations thereof. Most preferably, the core layer
is disposed immediately adjacent to, and in intimate contact with
the center component. The cores may further comprise (iii) an
optional outer core layer disposed about the core layer. Most
preferably, the outer core layer is disposed immediately adjacent
to, and in intimate contact with the core layer. The outer core
layer may be formed from a thermoset material, a thermoplastic
material, or combinations thereof.
[0046] The present invention provides several additionally
preferred embodiment golf balls utilizing the unique dual core
configuration and the previously described cover layers. Referring
to FIG. 2, a preferred embodiment golf ball 20 is illustrated
comprising a core 22 formed from a thermoset material surrounded by
a core layer 24 formed from a thermoset material. A multi-layer
cover 26, 28 surrounds the core 22 and the core layer 24.
[0047] FIG. 3 illustrates yet another preferred embodiment golf
ball 30 in accordance with the present invention. The preferred
embodiment golf ball 30 comprises a core 32 formed from a thermoset
material. A core layer 34 surrounds the core 32. The core layer 34
is formed form a thermoset material which may be the same as the
material utilized for the core 32, or one or mor other or different
thermoset materials. The preferred embodiment golf ball 30 utilizes
an optional outer core layer 35 that surrounds the core component
32 and the core layer 34. The outer core layer 35 is formed from a
thermoplastic or thermoset material. The thermoset material may be
the same or different than any of the thermoset materials utilized
for the core 32 and the core layer 34. The golf ball 30 further
comprises a multi-layer cover 36, 38.
[0048] FIG. 4 illustrates yet another preferred embodiment golf
ball 40 in accordance with the present invention is depicted. The
preferred embodiment golf ball 40 comprises a core 42 formed from a
thermoplastic, thermoset material, or any combination of a
thermoset and thermoplastic material. The core layer 44 is formed
from a thermoset or thermoplastic material. An additional
embodiment golf ball 40 also comprises an optical outer core layer
formed form a thermoplastic or thermoset materials as in the golf
ball of FIG. 3. A multi-layer cover 46, 48 is disposed about, and
generally surrounds, the core 42, the core layer 44 and, if
present, the optional outer core.
[0049] A wide array of thermoset materials can be utilized in the
present invention dual cores. Examples of suitable thermoset
materials include butadiene or any natural or synthetic elastomer,
including metallocene polyolefins, polyurethanes, silicones,
polyamides, polyureas, or virtually any irreversibly cross-linked
resin system. It is also contemplated that epoxy, phenolic, and an
array of unsaturated polyester resins could be utilized.
[0050] The thermoplastic materials utilized in the present
invention golf balls and, particularly their dual cores, may be
nearly any thermoplastic material. Examples of typical
thermoplastic materials for incorporation in the golf balls of the
present invention include, but are not limited to, ionomers,
polyurethane thermoplastic elastomers, and combinations thereof. It
is also contemplated that a wide array of other thermoplastic
materials could be utilized, such as polysulfones, fluoropolymers,
polyamide-imides, polyarylates, polyaryletherketones, polyaryl
sulfones/polyether sulfones, polybenzimidazoles, polyether-imides,
polyimides, liquid crystal polymers, polyphenylene sulfides; and
specialty high-performance resins, which would include
fluoropolymers, polybenzimidazole, and ultrahigh molecular weight
polyethylenes.
[0051] Additional examples of suitable thermoplastics include
metallocenes, polyvinyl chlorides,
acrylonitrile-butadiene-styrenes, acrylics, styrene-acrylonitriles,
styrene-maleic anhydrides, polyamides (nylons), polycarbonates,
polybutylene terephthalates, polyethylene terephthalates,
polyphenylene ethers/polyphenylene oxides, reinforced
polypropylenes, and high-impact polystyrenes.
[0052] Preferably, the thermoplastic materials have relatively high
melting points, such as a melting point of at least about
300.degree. F. Several examples of these preferred thermoplastic
materials and which are commercially available include, but are not
limited to, Capron (a blend of nylon and ionomer, available from
Allied Chemical), Lexan (a polycarbonate, available from General
Electric), Pebax (a polyether block amide, avaliable from Elf
Atochem), and Hytrel (a polyester elastomeric resin, available from
DuPont). The polymers or resin system may be cross-linked by a
variety of means such as by peroxide agents, sulphur agents,
radiation or other cross-linking techniques.
[0053] Any or all of the previously described components in the
cores of the golf balls of the present invention may be formed in
such a manner, or have suitable fillers added, so that their
resulting density is decreased or increased. For example, any of
the components in the multi-layer cores could be formed or
otherwise produced to be light in weight. For instance, the
components could be foamed, either separately or in-situ. Related
to this, a foamed light weight filler agent may be added. In
contrast, any of these components could be mixed with, or otherwise
receive, various high density filler agents or other weighting
components such as relatively high density fibers or particulate
agents in order to increase their mass or weight.
[0054] The following commercially available thermoplastic resins
are particularly preferred for use in the noted dual cores employed
in the golf balls of the present invention: Capron 8351 (a blend of
nylon and ionomer, available from Allied Signal Plastics), Lexan
ML5776 (a polycarbonate, available from General Electric), Pebax
3533 (a polyether block amide, available from Elf Atochem), and
Hytrel G4074 (a polyester elastomeric resin, available from
DuPont). Properties of these four preferred thermoplastics are set
forth below in Tables 1-4. When forming a golf ball in accordance
with the present invention, if the interior center component of the
dual core is to comprise a thermoplastic material, it is most
preferred to utilize Pebax thermoplastic resin.
1TABLE 1 CAPRON 8351 DAM 50% RH ASTM Test MECHANICAL Tensile
Strength, Yield, 7,800 (54) -- D-638 psi (MPa) Flexural Strength,
9,500 (65) -- D-790 psi (MPa) Flexural Modulus, 230,000 (1,585) --
D-790 psi (MPa) Ultimate Elongation, % 200 -- D-638 Notched Izod
Impact, No Break -- D-256 ft-lbs/in (J/M) Drop Weight Impact, 150
(200) -- D-3029 ft-lbs (J) Drop Weight Impact, @ 150 (200) --
D-3029 -40.degree. F., ft-lbs (J) PHYSICAL Specific Gravity 1.07 --
D-792 THERMAL Melting Point, .degree. F. (.degree. C.) 420 (215) --
D-789 Heat Deflection @ 264 psi 140 (60) -- D-648 .degree. F.
(.degree. C.)
[0055]
2TABLE 2 Lexan ML5776 PROPERTY TYPICAL DATA UNIT METHOD MECHANICAL
Tensile Strength, 8500 psi ASTM D 638 yield, Type I, 0.125" Tensile
Strength, 9500 psi ASTM D 638 break, Type I, 0.125" Tensile
Elongation, 110.0 % ASTM D 638 yield, Type I, 0.125" Flexural
Strength, 12000 psi ASTM D 790 yield, 0.125" Flexural Modulus,
310000 psi ASTM D 790 0.125" IMPACT Izod Impact, unnotched, 60.0
ft-lb/in ASTM D 4812 73 F. Izod Impact, notched, 15.5 ft-lb/in ASTM
D 256 73 F. Izod Impact, notches, 12.0 ft-lb/in ASTM D 256 73 F.,
0.250" Instrumented Impact 48.0 ft-lbs ASTM D 3763 Energy @ Peak,
73 F. THERMAL HDT, 264 psi, 0.250", 257 deg F. ASTM D 648
unannealed Thermal Index, 80 deg C. UL 7468 Elec Prop Thermal
Index, 80 deg C. UL 7468 Mech Prop with impact Thermal Index, 80
deg C. UL 7468 Mech Prop without impact PHYSICAL Specific Gravity,
solid 1.19 -- ASTM D 792 Water Absorption, 0.150 % ASTM D 570 24
hours @ 73 F. Mold shrinkage, 5.7 in/in ASTM D 955 flow, 0.125" E-3
Melt Flow Rate, nom'l, 7.5 g/10 ASTM D 1238 300 C./1.2 kgf (0) min
FLAME CHARACTERISTICS UL File Number, USA E121562 -- -- 94HB Rated
(tested 0.060 inch UL 94 thickness)
[0056]
3TABLE 3 PEBAX .RTM. 3533 RESIN ASTM PROPERTY TEST METHOD UNITS
3533 Specific Gravity D792 Water Absorption 0.5 Equilibrium (2000,
50% R.H.>) 24 Hr. Immersion D570 1.2 Hardness D2240 35D Tensile
Strength, D638 psi 5600 Ultimate Elongation, Ultimate D638 % 580
Flexural Modulus D790 psi 2800 Izod Impact, Notched D256 ft-lb./in.
20.degree. C. NB -40.degree. C. NB Abrasion Resistance D1044
Mg/1000 104 H18/1000 g Cycles Tear Resistance Notched D624C lb./in.
260 Melting Point D3418 .degree. F. 306 Vicat Softening Point D1525
.degree. F. 165 HDT 66 psi D648 .degree. F. 115 Compression Set
D395A % 54 (24 hr., 160.degree. F.)
[0057]
4TABLE 4 HYTREL G4074 Thermoplastic Elastomer PHYSICAL Sp Gr ASTM
D792 1.1800 Melt Flow ASTM D1238 5.20 g/10 min 190 C/2.16 kgf Wat
Abs ASTM D570 2.100% MECHANICAL Elong @ Brk ASTM D638 230.0% Flex
Mod ASTM D790 9500 psi TnStr @ Brk ASTM D638 2000 psi IMPACT Notch
Izod ASTM D256 No Break @ 73.0 F. @ 0.2500 inft-lb/in 0.50 @ -40.0
F. @ 0.2500 inft-lb/in HARDNESS Shore ASTM D2240 40 Shore D THERMAL
DTUL @ 66 ASTM D648 122 deg. F. Melt Point 338.0 deg. F. Vicat Soft
ASTM D1525 248 deg. F. Melt Point
[0058] The cores of the inventive golf balls typically have a
coefficient of restitution of about 0.750 or more, more preferably
0.770 or more and a PGA compression of about 90 or less, and more
preferably 70 or less. The cores have a weight of 25-40 grams and
preferably 30-40 grams. The core can be compression molded from a
slug of uncured or lightly cured elastomer composition comprising a
high cis content polybutadiene and a metal salt of an .alpha.,
.beta., ethylenically unsaturated carboxylic acid such as zinc
mono- or diacrylate or methacrylate. To achieve higher coefficients
of restitution and/or to increase hardness in the core, the
manufacturer 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 ounces.
Non-limiting examples of other materials which 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
curing or cross-linking reaction takes place.
[0059] Wound cores are generally produced by winding a very long
elastic thread around a solid or liquid filled balloon center. The
elastic thread is wound around the center to produce a finished
core of about 1.4 to 1.6 inches in diameter, generally. However,
the preferred embodiment golf balls of the present invention
preferably utilize a solid core, or rather a solid dual core
configuration, as opposed to a wound core.
B. The Cover Layer(s)
[0060] Inner Cover Layer
[0061] The inner cover layer is preferably harder than the outer
cover layer and generally has a thickness in the range of 0.01 to
0.10 inches, preferably 0.03 to 0.07 inches for a 1.68 inch ball
and 0.05 to 0.10 inches for a 1.72 inch (or more) ball. The core
and inner cover layer together form an inner ball having a
coefficient of restitution of 0.780 or more and more preferably
0.790 or more, and a diameter in the range of 1.45-1.66 inches for
a 1.68 inch ball and 1.50-1.70 inches for a 1.72 inch (or more)
ball. The inner cover layer has a Shore D hardness of 60 or more.
It is particularly advantageous if the golf balls of the invention
have an inner layer with a Shore D hardness of 65 or more. The
above-described characteristics of the inner cover layer provide an
inner ball having a PGA compression of 100 or less. It is found
that when the inner ball has a PGA compression of 90 or less,
excellent playability results.
[0062] The inner layer compositions include the high acid ionomers
such as those developed by E. I. DuPont de Nemours & Company
under the trademark "Surlyn.RTM." and by Exxon Corporation under
the trademark "Escor.RTM." or trade name "Iotek", or blends
thereof. Examples of compositions which may be used as the inner
layer herein are set forth in detail in a continuation of U.S.
application Ser. No. 08/174,765, which is a continuation of U.S.
application Ser. No. 07/776,803 filed Oct. 15, 1991, and Ser. No.
08/493,089, which is a continuation of Ser. No. 07/981,751, which
in turn is a continuation of Ser. No. 07/901,660 filed Jun. 19,
1992, all of which are incorporated herein by reference. Of course,
the inner layer high acid ionomer compositions are not limited in
any way to those compositions set forth in said applications.
[0063] The high acid ionomers which may be suitable for use in
formulating the inner layer compositions are ionic copolymers which
are the metal, i.e., sodium, zinc, magnesium, etc., salts of the
reaction product of an olefin having from about 2 to 8 carbon atoms
and an unsaturated monocarboxylic acid having from about 3 to 8
carbon atoms. Preferably, the ionomeric resins are copolymers of
ethylene and either acrylic or methacrylic acid. In some
circumstances, an additional comonomer such as an acrylate ester
(i.e., iso- or n-butylacrylate, etc.) can also be included to
produce a softer terpolymer. The carboxylic acid groups of the
copolymer are partially neutralized (i.e., approximately 10-100%,
preferably 30-70%) by the metal ions. Each of the high acid ionomer
resins which may be included in the inner layer cover compositions
of the invention contains greater than about 16% by weight of a
carboxylic acid, preferably from about 17% to about 25% by weight
of a carboxylic acid, more preferably from about 18.5% to about
21.5% by weight of a carboxylic acid.
[0064] Although the inner layer cover composition of several
embodiments of the present invention preferably includes a high
acid ionomeric resin, the scope of the patent embraces all known
high acid ionomeric resins falling within the parameters set forth
above. Only a relatively limited number of these high acid
ionomeric resins have recently become commercially available.
[0065] The high acid ionomeric resins available from Exxon under
the designation "Escor.RTM." and or "Iotek", are somewhat similar
to the high acid ionomeric resins available under the "Surlyn.RTM."
trademark. However, since the Escor.RTM./Iotek ionomeric resins are
sodium or zinc salts of poly(ethylene-acrylic acid) and the
"Surlyn.RTM." resins are zinc, sodium, magnesium, etc. salts of
poly(ethylene-methacrylic acid), distinct differences in properties
exist.
[0066] Examples of the high acid methacrylic acid based ionomers
found suitable for use in accordance with this invention include
Surlyn.RTM. 8220 and 8240 (both formerly known as forms of
Surlyn.RTM. AD-8422), Surlyn.RTM. 9220 (zinc cation), Surlyn.RTM.
SEP-503-1 (zinc cation), and Surlyn.RTM. SEP-503-2 (magnesium
cation). According to DuPont, all of these ionomers contain from
about 18.5 to about 21.5% by weight methacrylic acid.
[0067] More particularly, Surlyn.RTM. AD-8422 is currently
commercially available from DuPont in a number of different grades
(i.e., AD-8422-2, AD-8422-3, AD-8422-5, etc.) based upon
differences in melt index. According to DuPont, Surlyn.RTM. 8422,
which is believed recently to have been redesignated as 8220 and
8240, offers the following general properties when compared to
Surlyn.RTM. 8920, the stiffest, hardest of all on the low acid
grades (referred to as "hard" ionomers in U.S. Pat. No.
4,884,814):
5 LOW ACID HIGH ACID (15 wt % Acid) (>20 wt % Acid) SURLYN .RTM.
SURLYN .RTM. SURLYN .RTM. 8920 8422-2 8422-3 IONOMER Cation Na Na
Na Melt Index 1.2 2.8 1.0 Sodium, Wt % 2.3 1.9 2.4 Base Resin MI 60
60 60 MP.sup.1, .degree. C. 88 86 85 FP.sup.1, .degree. C. 47 48.5
45 COMPRESSION MOLDING.sup.2 Tensile Break, psi 4350 4190 5330
Yield, psi 2880 3670 3590 Elongation, % 315 263 289 Flex Mod, K psi
53.2 76.4 88.3 Shore D hardness 66 67 68 .sup.1DSC second heat,
10.degree. C./min heating rate. .sup.2Samples compression molded at
150.degree. C. annealed 24 hours at 60.degree. C. 8422-2, -3 were
homogenized at 190.degree. C. before molding.
[0068] In comparing Surlyn.RTM. 8920 to Surlyn.RTM. 8422-2 and
Surlyn.RTM. 8422-3, it is noted that the high acid Surlyn.RTM.
8422-2 and 8422-3 ionomers have a higher tensile yield, lower
elongation, slightly higher Shore D hardness and much higher
flexural modulus. Surlyn.RTM. 8920 contains 15 weight percent
methacrylic acid and is 59% neutralized with sodium.
[0069] In addition, Surlyn.RTM. SEP-503-1 (zinc cation) and
Surlyn.RTM. SEP-503-2 (magnesium cation) are high acid zinc and
magnesium versions of the Surlyn.RTM. AD 8422 high acid ionomers.
When compared to the Surlyn.RTM. AD 8422 high acid ionomers, the
Surlyn.RTM. SEP-503-1 and SEP-503-2 ionomers can be defined as
follows:
6 Surlyn .RTM. Ionomer Ion Melt Index Neutralization % AD 8422-3 Na
1.0 45 SEP 503-1 Zn 0.8 38 SEP 503-2 Mg 1.8 43
[0070] Further, Surlyn.RTM. 8162 is a zinc cation ionomer resin
containing approximately 20% by weight (i.e., 18.5-21.5% weight)
methacrylic acid copolymer that has been 30-70% neutralized.
Surlyn.RTM. 8162 is currently commercially available from
DuPont.
[0071] Examples of the high acid acrylic acid based ionomers
suitable for use in the present invention also include the
Escor.RTM. or Iotek high acid ethylene acrylic acid ionomers
produced by Exxon such as Ex 1001, 1002, 959, 960, 989, 990, 1003,
1004, 993, 994. In this regard, Escor.RTM. or Iotek 959 is a sodium
ion neutralized ethylene-acrylic neutralized ethylene-acrylic acid
copolymer. According to Exxon, Ioteks 959 and 960 contain from
about 19.0 to 21.0% by weight acrylic acid with approximately 30 to
about 70 percent of the acid groups neutralized with sodium and
zinc ions, respectively. The physical properties of these high acid
acrylic acid based ionomers are set forth in Tables 5 and 6 as
follows:
7TABLE 5 Physical Properties of Various Ionomers ESCOR .RTM. ESCOR
.RTM. Ex- (IOTEK) (IOTEK) PROPERTY 1001 Ex1002 959 Ex1003 Ex1004
960 Melt index, 1.0 1.8 2.0 1.1 2.0 1.8 g/10 mm Cation Na Na Na Zn
Zn Zn Melting 183 183 172 180 180.5 174 Point, .degree. F. Vicat
125 125 130 133 131 131 Softening Point, .degree.F. Tensile 34.4
22.5 4600 24.8 20.6 3500 @ Break MPa MPa psi MPa MPa psi Elongation
341 348 325 387 437 430 @ Break, % Hardness, 63 62 66 54 53 57
Shore D Flexural 365 380 66,000 147 130 27,000 Modulus MPa MPa psi
MPa MPa psi
[0072]
8TABLE 6 Physical Properties of Various Ionomers PROPERTY UNITS EX
989 EX 993 EX 994 EX 990 Melt index g/10 mm 1.30 1.25 1.32 1.24
Moisture ppm 482 214 997 654 Cation type -- Na Li K Zn M+ content
by AAS wt % 2.74 0.87 4.54 0 Zn content by AAS wt % 0 0 0 3.16
Density kg/m.sup.3 959 945 976 977 Vicat softening point .degree.
C. 52.5 51 50 55.0 Crystallization point .degree. C. 40.1 39.8 44.9
54.4 Melting point .degree. C. 82.6 81.0 80.4 81.0 Tensile at yield
MPa 23.8 24.6 22 16.5 Tensile at break MPa 32.3 31.1 29.7 23.8
Elongation at break % 330 260 340 357 1% secant modulus MPa 389 379
312 205 Flezural modulus MPa 340 368 303 183 Abrasion resistance mg
20.0 9.2 15.2 20.5 Hardness Shore D -- 62 62.5 61 56 Zwick Rebound
% 61 63 59 48
[0073] Furthermore, as a result of the development by the assignee
of this application of a number of new high acid ionomers
neutralized to various extents by several different types of metal
cations, such as by manganese, lithium, potassium, calcium and
nickel cations, several new high acid ionomers and/or high acid
ionomer blends besides sodium, zinc and magnesium high acid
ionomers or ionomer blends are now available for golf ball cover
production. It has been found that these new cation neutralized
high acid ionomer blends produce inner cover layer compositions
exhibiting enhanced hardness and resilience due to synergies which
occur during processing. Consequently, the metal cation neutralized
high acid ionomer resins recently produced can be blended to
produce substantially higher C.O.R.'s than those produced by the
low acid ionomer inner cover compositions presently commercially
available.
[0074] More particularly, several new metal cation neutralized high
acid ionomer resins have been produced by the inventors 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 cation salts. This discovery is the
subject matter of U.S. application Ser. No. 08/493,089,
incorporated herein by reference. It has been found that numerous
new metal cation neutralized high acid ionomer resins can be
obtained by reacting a high acid copolymer (i.e., a copolymer
containing greater than 16% by weight acid, preferably from about
17 to about 25 weight percent acid, and more preferably about 20
weight percent acid), with a metal cation salt capable of ionizing
or neutralizing the copolymer to the extent desired (i.e., from
about 10% to 90%).
[0075] The base copolymer is made up of greater than 16% by weight
of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin.
Optionally, a softening comonomer can be included in the copolymer.
Generally, the 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, crotonic acid, maleic acid, fumaric acid, and
itaconic acid, with acrylic acid being preferred.
[0076] The softening comonomer that can be optionally included in
the inner cover layer for the golf ball of the invention may be
selected from the group consisting of vinyl esters of aliphatic
carboxylic acids wherein the acids have 2 to 10 carbon atoms, vinyl
ethers wherein the alkyl groups contains 1 to 10 carbon atoms, and
alkyl acrylates or methacrylates wherein the alkyl group contains 1
to 10 carbon atoms. Suitable softening comonomers include vinyl
acetate, methyl acrylate, methyl methacrylate, ethyl acrylate,
ethyl methacrylate, butyl acrylate, butyl methacrylate, or the
like.
[0077] Consequently, examples of a number of copolymers suitable
for use to produce the high acid ionomers included in the present
invention include, but are not limited to, high acid embodiments of
an ethylene/acrylic acid copolymer, an ethylene/methacrylic acid
copolymer, an ethylene/itaconic acid copolymer, an ethylene/maleic
acid copolymer, an ethylene/methacrylic acid/vinyl acetate
copolymer, an ethylene/acrylic acid/vinyl alcohol copolymer, etc.
The base copolymer broadly contains greater than 16% by weight
unsaturated carboxylic acid, from about 39% to about 83% by weight
ethylene and from 0 to about 40% by weight of a softening
comonomer. Preferably, the copolymer contains about 20% by weight
unsaturated carboxylic acid and about 80% by weight ethylene. Most
preferably, the copolymer contains about 20% acrylic acid with the
remainder being ethylene.
[0078] Along these lines, examples of the preferred high acid base
copolymers which fulfill the criteria set forth above, are a series
of ethylene-acrylic copolymers which are commercially available
from The Dow Chemical Company, Midland, Mich., under the "Primacor"
designation. These high acid base copolymers exhibit the typical
properties set forth below in Table 7.
9TABLE 7 Typical Properties of Primacor Ethylene-Acrylic Acid
Copolymers MELT TENSILE FLEXURAL VICAT PERCENT DENSITY, INDEX, YD.
ST MODULUS SOFT PT SHORE D GRADE ACID glcc g/10 min (psi) (psi)
(.degree. C.) HARDNESS ASTM D-792 D-1238 D-638 D-790 D-1525 D-2240
5980 20.0 0.958 300.0 -- 4800 43 50 5990 20.0 0.955 1300.0 650 2600
40 42 5990 20.0 0.955 1300.0 650 3200 40 42 5981 20.0 0.960 300.0
900 3200 46 48 5981 20.0 0.960 300.0 900 3200 46 48 5983 20.0 0.958
500.0 850 3100 44 45 5991 20.0 0.953 2600.0 635 2600 38 40 'The
Melt Index values are obtained according to ASTM D-1238, at
190.degree. C.
[0079] Due to the high molecular weight of the Primacor 5981 grade
of the ethylene-acrylic acid copolymer, this copolymer is the more
preferred grade utilized in the invention.
[0080] The metal cation salts utilized in the invention are those
salts which provide the metal cations capable of neutralizing, to
various extents, the carboxylic acid groups of the high acid
copolymer. These include acetate, oxide or hydroxide salts of
lithium, calcium, zinc, sodium, potassium, nickel, magnesium, and
manganese.
[0081] Examples of such lithium ion sources are lithium hydroxide
monohydrate, lithium hydroxide, lithium oxide and lithium acetate.
Sources for the calcium ion include calcium hydroxide, calcium
acetate and calcium oxide. Suitable zinc ion sources are zinc
acetate dihydrate and zinc acetate, a blend of zinc oxide and
acetic acid. Examples of sodium ion sources are sodium hydroxide
and sodium acetate. Sources for the potassium ion include potassium
hydroxide and potassium acetate. Suitable nickel ion sources are
nickel acetate, nickel oxide and nickel hydroxide. Sources of
magnesium include magnesium oxide, magnesium hydroxide, magnesium
acetate. Sources of manganese include manganese acetate and
manganese oxide.
[0082] The new metal cation neutralized high acid ionomer resins
are produced by reacting the high acid base copolymer with various
amounts of the metal cation salts above the crystalline melting
point of the copolymer, such as at a temperature from about
200.degree. F. to about 500.degree. F., preferably from about
250.degree. F. to about 350.degree. F. under high shear conditions
at a pressure of from about 10 psi to 10,000 psi. Other well known
blending techniques may also be used. The amount of metal cation
salt utilized to produce the new metal cation neutralized high acid
based ionomer resins is the quantity which provides a sufficient
amount of the metal cations to neutralize the desired percentage of
the carboxylic acid groups in the high acid copolymer. The extent
of neutralization is generally from about 10% to about 90%.
[0083] As indicated below in Table 8 and more specifically in
Example 1 in U.S. application Ser. No. 08/493,089, a number of new
types of metal cation neutralized high acid ionomers can be
obtained from the above indicated process. These include new high
acid ionomer resins neutralized to various extents with manganese,
lithium, potassium, calcium and nickel cations. In addition, when a
high acid ethylene/acrylic acid copolymer is utilized as the base
copolymer component of the invention and this component is
subsequently neutralized to various extents with the metal cation
salts producing acrylic acid based high acid ionomer resins
neutralized with cations such as sodium, potassium, lithium, zinc,
magnesium, manganese, calcium and nickel, several new cation
neutralized acrylic acid based high acid ionomer resins are
produced.
10TABLE 8 Metal Cation Neutralized High Acid Ionomers Formulation
Wt- % Wt- % Melt Shore D No. Cation Salt Neutralization Index
C.O.R. Hardness 1(NaOH) 6.98 67.5 0.9 .804 71 2(NaOH) 5.66 54.0 2.4
.808 73 3(NaOH) 3.84 35.9 12.2 .812 69 4(NaOH) 2.91 27.0 17.5 .812
(brittle) 5(MnAc) 19.6 71.7 7.5 .809 73 6(MnAc) 23.1 88.3 3.5 .814
77 7(MnAc) 15.3 53.0 7.5 .810 72 8(MnAc) 26.5 106 0.7 .813
(brittle) 9(LiOH) 4.54 71.3 0.6 .810 74 10(LiOH) 3.38 52.5 4.2 .818
72 11(LiOH) 2.34 35.9 18.6 .815 72 12(KOH) 5.30 36.0 19.3 Broke 70
13(KOH) 8.26 57.9 7.18 .804 70 14(KOH) 10.7 77.0 4.3 .801 67
15(ZnAc) 17.9 71.5 0.2 .806 71 16(ZnAc) 13.9 53.0 0.9 .797 69
17(ZnAc) 9.91 36.1 3.4 .793 67 18(MgAc) 17.4 70.7 2.8 .814 74
19(MgAc) 20.6 87.1 1.5 .815 76 20(MgAc) 13.8 53.8 4.1 .814 74
21(CaAc) 13.2 69.2 1.1 .813 74 22(CaAc) 7.12 34.9 10.1 .808 70
23(MgO) 2.91 53.5 2.5 .813 24(MgO) 3.85 71.5 2.8 .808 25(MgO) 4.76
89.3 1.1 .809 26(MgO) 1.96 35.7 7.5 .815 27(NiAc) 13.04 61.1 0.2
.802 71 28(NiAc) 10.71 48.9 0.5 .799 72 29(NiAc) 8.26 36.7 1.8 .796
69 30(NiAc) 5.66 24.4 7.5 .786 64 Controls: 50/50 Blend of Ioteks
8000/7030 C.O.R. = .810/65 Shore D Hardness DuPont High Acid Surlyn
.RTM. 8422 (Na) C.O.R. = .811/70 Shore D Hardness DuPont High Acid
Surlyn .RTM. 8162 (Zn) C.O.R. = .807/65 Shore D Hardness Exxon High
Acid Iotek EX-960 (Zn) C.O.R. = .796/65 Shore D Hardness Control
for Formulations 23-26 is 50/50 Iotek 8000/7030, C.O.R. = .814,
Formulation 26 C.O.R. was normalized to that control accordingly
Control for Formulation Nos. 27-30 is 50/50 Iotek 8000/7030, C.O.R.
= .807
[0084] When compared to low acid versions of similar cation
neutralized ionomer resins, the new metal cation neutralized high
acid ionomer resins exhibit enhanced hardness, modulus and
resilience characteristics. These are properties that are
particularly desirable in a number of thermoplastic fields,
including the field of golf ball manufacturing.
[0085] When utilized in the construction of the inner layer of a
multi-layered golf ball, it has been found that the new acrylic
acid based high acid ionomers extend the range of hardness beyond
that previously obtainable while maintaining the beneficial
properties (i.e. durability, click, feel, etc.) of the softer low
acid ionomer covered balls, such as balls produced utilizing the
low acid ionomers disclosed in U.S. Pat. Nos. 4,884,814 and
4,911,451.
[0086] Moreover, as a result of the development of a number of new
acrylic acid based high acid ionomer resins neutralized to various
extents by several different types of metal cations, such as
manganese, lithium, potassium, calcium and nickel cations, several
new ionomers or ionomer blends are now available for production of
an inner cover layer of a multi-layered golf ball. By using these
high acid ionomer resins, harder, stiffer inner cover layers having
higher C.O.R.s, and thus longer distance, can be obtained.
[0087] More preferably, it has been found that when two or more of
the above-indicated high acid ionomers, particularly blends of
sodium and zinc high acid ionomers, are processed to produce the
covers of multi-layered golf balls, (i.e., the inner cover layer
herein) the resulting golf balls will travel further than
previously known multi-layered golf balls produced with low acid
ionomer resin covers due to the balls' enhanced coefficient of
restitution values.
[0088] The low acid ionomers which may be suitable for use in
formulating the inner layer compositions of several of the
embodiments of the subject invention are ionic copolymers which are
the metal, i.e., sodium, zinc, magnesium, etc., salts of the
reaction product of an olefin having from about 2 to 8 carbon atoms
and an unsaturated monocarboxylic acid having from about 3 to 8
carbon atoms. Preferably, the ionomeric resins are copolymers of
ethylene and either acrylic or methacrylic acid. In some
circumstances, an additional comonomer such as an acrylate ester
(i.e., iso- or n-butylacrylate, etc.) can also be included to
produce a softer terpolymer. The carboxylic acid groups of the
copolymer are partially neutralized (i.e., approximately 10-100%,
preferably 30-70%) by the metal ions. Each of the low acid ionomer
resins which may be included in the inner layer cover compositions
of the invention contains 16% by weight of less of a carboxylic
acid.
[0089] The inner layer compositions include the low acid ionomers
such as those developed and sold by E. I. DuPont de Nemours &
Company under the trademark "Surlyn.RTM." and by Exxon Corporation
under the trademark "Escor.RTM." or tradename "Iotek," or blends
thereof.
[0090] The low acid ionomer resins available from Exxon under the
designation "Escor.RTM." and/or "Iotek," are somewhat similar to
the low acid ionomeric resins available under the "Surlyn.RTM."
trademark. However, since the Escor.RTM./Iotek ionomeric resins are
sodium or zinc salts of poly(ethylene-acrylic acid) and the
"Surlyn.RTM." resins are zinc, sodium, magnesium, etc. salts of
poly(ethylene-methacrylic acid), distinct differences in properties
exist.
[0091] When utilized in the construction of the inner layer of a
multi-layered golf ball, it has been found that the low acid
ionomer blends extend the range of compression and spin rates
beyond that previously obtainable. More preferably, it has been
found that when two or more low acid ionomers, particularly blends
of sodium and zinc ionomers, are processed to produce the covers of
multi-layered golf balls, (i.e., the inner cover layer herein) the
resulting golf balls will travel further and at an enhanced spin
rate than previously known multi-layered golf balls. Such an
improvement is particularly noticeable in enlarged or oversized
golf balls.
[0092] The use of an inner layer formulated from blends of lower
acid ionomers produces multi-layer golf balls having enhanced
compression and spin rates. These are the properties desired by the
more skilled golfer.
[0093] In yet another embodiment of the inner cover layer, a blend
of high and low acid ionomer resins is used. These can be the
ionomer resins described above, combined in a weight ratio which
preferably is within the range of 10:90 to 90:10 parts of high and
low acid ionomer resins.
[0094] A further additional embodiment of the inner cover layer is
primarily based upon the use of a fully non-ionomeric thermoplastic
material. Suitable non-ionomeric materials include metallocene
catalyzed polyolefins or polyamides, polyamide/ionomer blends,
polyphenylene ether/ionomer blends, etc., which have a shore D
hardness of .gtoreq.60 and a flex modulus of greater than about
30,000 psi, or other hardness and flex modulus values which are
comparable to the properties of the ionomers described above. Other
suitable materials include, but are not limited to, thermoplastic
or thermosetting polyurethanes, a polyester elastomer such as that
marketed by DuPont under the trademark Hytrel.RTM., or a polyester
amide such as that marketed by Elf Atochem S.A. under the trademark
Pebax.RTM., a blend of two or more non-ionomeric thermoplastic
elastomers, or a blend of one or more ionomers and one or more
non-ionomeric thermoplastic elastomers. These materials can be
blended with the ionomers described above in order to reduce cost
relative to the use of higher quantities of ionomer.
[0095] Outer Cover Layer
[0096] While the multi-layer core component described above, and
the hard inner cover layer formed thereon, provide the multi-layer
golf ball with power and distance, the outer cover layer 28, as
shown in FIG. 2, is comparatively softer than the inner cover
layer. However, as noted previously, a hard outer cover over a
relatively softer inner cover is contemplated and within the scope
of the golf balls described herein. The softness provides for the
feel and playability characteristics typically associated with
balata or balata-blend balls. The outer cover layer or ply is
comprised of a relatively soft, low modulus (about 1,000 psi to
about 10,100 psi) and, in an alternate embodiment, low acid (less
than 16 weight percent acid) ionomer, an ionomer blend, a
non-ionomeric thermoplastic or thermosetting material such as, but
not limited to, a metallocene catalyzed polyolefin such as EXACT
material available from EXXON, a polyurethane, a polyester
elastomer such as that marketed by DuPont under the trademark
Hytrel.RTM., or a polyester amide such as that marketed by Elf
Atochem S.A. under the trademark Pebax.RTM., a blend of two or more
non-ionomeric thermoplastic or thermosetting materials, or a blend
of one or more ionomers and one or more non-ionomeric thermoplastic
materials. The outer layer is fairly thin (i.e. from about 0.010 to
about 0.10 inches in thickness, more desirably 0.03 to 0.06 inches
in thickness for a 1.680 inch ball and 0.04 to 0.07 inches in
thickness for a 1.72 inch or more ball), but thick enough to
achieve desired playability characteristics while minimizing
expense. Thickness is defined as the average thickness of the
non-dimpled areas of the outer cover layer. The outer cover layer,
such as layer 28, has a Shore D hardness of 55 or less, and more
preferably 50 or less.
[0097] In one embodiment, the outer cover layer preferably is
formed from an ionomer which constitutes at least 75 weight % of an
acrylate ester-containing ionic copolymer or blend of acrylate
ester-containing ionic copolymers. This type of outer cover layer
in combination with the multi-layer core and inner cover layer
described above results in golf ball covers having a favorable
combination of durability and spin rate. The one or more acrylate
ester-containing ionic copolymers each contain an olefin, an
acrylate ester, and an acid. In a blend of two or more acrylate
ester-containing ionic copolymers, each copolymer may contain the
same or a different olefin, acrylate ester and acid than are
contained in the other copolymers. Preferably, the acrylate
ester-containing ionic copolymer or copolymers are terpolymers, but
additional monomers can be combined into the copolymers if the
monomers do not substantially reduce the scuff resistance or other
good playability properties of the cover.
[0098] For a given copolymer, the olefin is selected from the group
consisting of olefins having 2 to 8 carbon atoms, including, as
non-limiting examples, ethylene, propylene, butene-1, hexene-1 and
the like. Preferably the olefin is ethylene.
[0099] The acrylate ester is an unsaturated monomer having from 1
to 21 carbon atoms which serves as a softening comonomer. The
acrylate ester preferably is methyl, ethyl, n-propyl, n-butyl,
n-octyl, 2-ethylhexyl, or 2-methoxyethyl 1-acrylate, and most
preferably is methyl acrylate or n-butyl acrylate. Another suitable
type of softening comonomer is an alkyl vinyl ether selected from
the group consisting of n-butyl, n-hexyl, 2-ethylhexyl, and
2-methoxyethyl vinyl ethers.
[0100] The acid is a mono- or dicarboxylic acid and preferably is
selected from the group consisting of methacrylic, acrylic,
ethacrylic, .alpha.-chloroacrylic, crotonic, maleic, fumaric, and
itaconic acid, or the like, and half esters of maleic, fumaric and
itaconic acid, or the like. The acid group of the copolymer is
10-100% neutralized with any suitable cation, for example, zinc,
sodium, magnesium, lithium, potassium, calcium, manganese, nickel,
chromium, tin, aluminum, or the like. It has been found that
particularly good results are obtained when the neutralization
level is about 50-100%.
[0101] The one or more acrylate ester-containing ionic copolymers
each has an individual Shore D hardness of about 5-64. The overall
Shore D hardness of the outer cover is 55 or less, and generally is
40-55. It is preferred that the overall Shore D hardness of the
outer cover is in the range of 40-50 in order to impart
particularly good playability characteristics to the ball.
[0102] The outer cover layer of the invention is formed over a core
to result in a golf ball having a coefficient of restitution of at
least 0.770, more preferably at least 0.780, and most preferably at
least 0.790. The coefficient of restitution of the ball will depend
upon the properties of both the core and the cover. The PGA
compression of the golf ball is 100 or less, and preferably is 90
or less.
[0103] The acrylate ester-containing ionic copolymer or copolymers
used in the outer cover layer can be obtained by neutralizing
commercially available acrylate ester-containing acid copolymers
such as polyethylene-methyl acrylate-acrylic acid terpolymers,
including ESCOR ATX (Exxon Chemical Company) or poly
(ethylene-butyl acrylate-methacrylic acid) terpolymers, including
NUCREL (DuPont Chemical Company). Particularly preferred
commercially available materials include ATX 320, ATX 325, ATX 310,
ATX 350, and blends of these materials with NUCREL 010 and NUCREL
035. The acid groups of these materials and blends are neutralized
with one or more of various cation salts including zinc, sodium,
magnesium, lithium, potassium, calcium, manganese, nickel, etc. The
degree of neutralization ranges from 10-100%. Generally, a higher
degree of neutralization results in a harder and tougher cover
material. The properties of non-limiting examples of commercially
available un-neutralized acid terpolymers which can be used to form
the golf ball outer cover layers of the invention are provided
below in Table 9.
11TABLE 9 Properties of Un-Neutralized Acid Terpolymers Melt Index
Flex dg/min Acid No. Modulus MPa Hardness Trade Name ASTM D 1238 %
KOH/g (ASTM D790) (Shore D) ATX 310 6 45 80 44 ATX 320 5 45 50 34
ATX 325 20 45 9 30 ATX 350 6 15 20 28 Nucrel 010 11 60 40 40 Nucrel
035 35 60 59 40
[0104] The ionomer resins used to form the outer cover layers can
be produced by reacting the acrylate ester-containing acid
copolymer with various amounts of the metal cation salts at a
temperature above the crystalline melting point of the copolymer,
such as a temperature from about 200.degree. F. to about
500.degree. F., preferably from about 250.degree. F. to about
350.degree. F., under high shear conditions at a pressure of from
about 100 psi to 10,000 psi. Other well known blending techniques
may also be used. The amount of metal cation salt utilized to
produce the neutralized ionic copolymers is the quantity which
provides a sufficient amount of the metal cations to neutralize the
desired percentage of the carboxylic acid groups in the high acid
copolymer. When two or more different copolymers are to be used,
the copolymers can be blended before or after neutralization.
Generally, it is preferable to blend the copolymers before they are
neutralized to provide for optimal mixing.
[0105] The compatibility of the acrylate ester-containing
copolymers with each other in a copolymer blend produces a golf
ball outer cover layer having a surprisingly good scuff resistance
for a given hardness of the outer cover layer. The golf ball
according to the invention has a scuff resistance of no higher than
3.0. It is preferred that the golf ball has a scuff resistance of
no higher than about 2.5 to ensure that the golf ball is scuff
resistant when used in conjunction with a variety of types of
clubs, including sharp-grooved irons, which are particularly
inclined to result in scuffing of golf ball covers. The best
results according to the invention are obtained when the outer
cover layer has a scuff resistance of no more than about 2.0.
[0106] Additional materials may also be added to the inner and
outer cover layer of the present invention as long as they do not
substantially reduce the playability properties of the ball. Such
materials include dyes (for example, Ultramarine Blue sold by
Whitaker, Clark, and Daniels of South Plainsfield, N.J.) (see U.S.
Pat. No. 4,679,795), pigments such as titanium dioxide, zinc oxide,
barium sulfate and zinc sulfate; UV absorbers; antioxidants;
antistatic agents; optical brighteners; and stabilizers. Moreover,
the cover compositions of the present invention may also contain
softening agents such as those disclosed in U.S. Pat. Nos.
5,312,857 and 5,306,760, including plasticizers, metal stearates,
processing acids, etc., and reinforcing materials such as glass
fibers and inorganic fillers, as long as the desired properties
produced by the golf ball covers of the invention are not
impaired.
[0107] The outer layer, in another embodiment of the invention,
includes a blend of a soft (low acid) ionomer resin with a small
amount of a hard (high acid) ionomer resin. 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. A high modulus ionomer
herein is one which measures from about 15,000 to about 70,000 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.
[0108] Soft ionomers primarily are used in formulating the
hard/soft blends of the cover compositions. These ionomers include
acrylic acid and methacrylic acid based soft ionomers. They are
generally characterized as comprising sodium, zinc, or other mono-
or divalent metal cation salts of a terpolymer of an olefin having
from about 2 to 8 carbon atoms, methacrylic acid, acrylic acid, or
another, .alpha., .beta.-unsaturated carboxylic acid, and an
unsaturated monomer of the acrylate ester class having from 1 to 21
carbon atoms. The soft ionomer is preferably made from an acrylic
acid base polymer is an unsaturated monomer of the acrylate ester
class.
[0109] Certain ethylene-acrylic acid based soft ionomer resins
developed by the Exxon Corporation under the designation "Iotek
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 inner and outer cover layers. The combination produces
higher C.O.R.s 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 raw materials cost and
improved yields.
[0110] While the exact chemical composition of the resins to be
sold by Exxon under the designation Iotek 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 by
Exxon:
12TABLE 10 Physical Properties of Iotek 7520 ASTM Typical Property
Method Units Value Melt Index D-1238 g/10 min. 2 Density D-1505
kg/m.sup.3 0.962 Cation Zinc Melting Point D-3417 .degree. C. 66
Crystallization Point D-3417 .degree. C. 49 Vicat Softening Point
D-1525 .degree. C. 42 Plaque Properties (2 mm thick Compression
Molded Plaques) 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 De Mattia Flex Resistance D-430 Cycles
>5000
[0111] In addition, test data collected by the inventors indicates
that Iotek 7520 resins have Shore D hardnesses of about 32 to 36
(per ASTM D-2240), melt flow indexes of 3.+-.0.5 g/10 min (at
190.degree. C. per ASTM D-1288), and a flexural modulus of about
2500-3500 psi (per ASTM D-790). Furthermore, testing by an
independent testing laboratory by pyrolysis mass spectrometry
indicates that Iotek 7520 resins are generally zinc salts of a
terpolymer of ethylene, acrylic acid, and methyl acrylate.
[0112] Furthermore, the inventors have found that a newly developed
grade of an acrylic acid based soft ionomer available from the
Exxon Corporation under the designation Iotek 7510 is also
effective when combined with the hard ionomers indicated above in
producing golf ball covers exhibiting higher C.O.R. values at equal
or softer hardness than those produced by known hard-soft ionomer
blends. In this regard, Iotek 7510 has the advantages (i.e.
improved flow, higher C.O.R. values at equal hardness, increased
clarity, etc.) produced by the Iotek 7520 resin when compared to
the methacrylic acid base soft ionomers known in the art (such as
the Surlyn.RTM. 8625 and Surlyn.RTM. 8629 combinations disclosed in
U.S. Pat. No. 4,8884,814).
[0113] In addition, Iotek 7510, when compared to Iotek 7520,
produces slightly higher C.O.R. values at equal softness/hardness
due to the Iotek 7510's higher hardness and neutralization.
Similarly, Iotek 7510 produces better release properties (from the
mold cavities) due to its slightly higher stiffness and lower flow
rate than Iotek 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.
[0114] According to Exxon, Iotek 7510 is of similar chemical
composition as Iotek 7520 (i.e. a zinc salt of a terpolymer of
ethylene, acrylic acid, and methyl acrylate) but is more highly
neutralized. Based upon FTIR analysis, Iotek 7520 is estimated to
be about 30-40 wt. % neutralized and Iotek 7510 is estimated to be
about 40-60 wt. % neutralized. The typical properties of Iotek 7510
in comparison of those of Iotek 7520 in comparison of those of
Iotek 7520 are set forth below:
13TABLE 11 Physical Properties of Iotek 7510 in Comparison to Iotek
7520 IOTEK 7520 IOTEK 7510 MI, g/10 min 2.0 0.8 Density, g/cc 0.96
0.97 Melting Point, .degree. F. 151 149 Vicat Softening Point,
.degree. F. 108 109 Flex Modulus, psi 3800 5300 Tensile Strength,
psi 1450 1750 Elongation, % 760 690 Hardness, Shore D 32 35
[0115] The hard ionomer resins utilized to produce the outer cover
layer composition hard/soft blends include ionic copolymers which
are the sodium, zinc, magnesium, lithium, etc. 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. approximately 15-75 percent) neutralized.
[0116] The hard ionomeric resins are likely copolymers of ethylene
and acrylic and/or 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 properties of the
resulting golf balls.
[0117] As discussed earlier herein, the hard ionomeric resins
introduced under the designation Escor.RTM. and sold under the
designation "Iotek" are somewhat similar to the hard ionomeric
resins sold under the Surlyn.RTM. trademark. However, since the
"Iotek" ionomeric resins are sodium or zinc salts of
poly(ethylene-acrylic acid) and the Surlyn.RTM. resins are zinc or
sodium salts of poly(ethylene-methacrylic acid) some distinct
differences in properties exist. As more specifically indicated in
the data set forth below, the hard "Iotek" resins (i.e., the
acrylic acid based hard ionomer resins) are the more preferred hard
resins for use in formulating the outer layer blends for use in the
present invention. In addition, various blends of "Iotek" and
Surlyn.RTM. hard ionomeric resins, as well as other available
ionomeric resins, may be utilized in the present invention in a
similar manner.
[0118] Examples of commercially available hard Monomeric 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.RTM. 8940 and the hard zinc ionic copolymer sold
under the trademark Surlyn.RTM. 9910. Surlyn.RTM. 8940 is a
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.
Surlyn.RTM. 9910 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.RTM. 9910 is about 0.7. The typical properties of
Surlyn.RTM. 9910 and 8940 are set forth below in Table 12:
14TABLE 12 Typical Properties of Commercially Available Hard Surlvn
.RTM. Resins Suitable for Use in the Outer Layer Blends of the
Present Invention ASTM D 8940 9910 8920 8528 9970 9730 Cation Type
Sodium Zinc Sodium Sodium Zinc Zinc Melt flow index, D-1238 2.8 0.7
0.9 1.3 14.0 1.6 gms/10 min. Specific Gravity, D-792 0.95 0.97 0.95
0.94 0.95 0.95 g/cm.sup.3 Hardness, Shore D D-2240 66 64 66 60 62
63 Tensile Strength, D-638 (4.8) (3.6) (5.4) (4.2) (3.2) (4.1)
(kpsi), MPa 33.1 24.8 37.2 29.0 22.0 28.0 Elongation, % D-638 470
290 350 450 460 460 Flexural Modulus, D-790 (51) (48) (55) (32)
(28) (30) (kpsi) MPa 350 330 380 220 190 210 Tensile Impact
(23.degree. C.) D-1822S 1020 1020 865 1160 760 1240 KJ/m.sup.2 (ft.
- lbs./in.sup.2) (485) (485) (410) (550) (360) (590) Vicat
Temperature, .degree. C. D-1525 63 62 58 73 61 73
[0119] Examples of the more pertinent acrylic acid based hard
ionomer resin suitable for use in the present outer cover
composition sold under the "Iotek" trade name by the Exxon
Corporation include Iotek 8000, 8010, 8020, 8030, 7030, 7010, 7020,
1002, 1003, 959 and 960. The physical properties of Iotek 959 and
960 are shown above. The typical properties of the remainder of
these and other Iotek hard ionomers suited for use in formulating
the outer layer cover composition are set forth below in Table
13:
15TABLE 13 Typical Properties of Iotek Ionomers ASTM Method Units
4000 4010 8000 8020 8030 7010 7020 7030 Resin Properties Cation
type zinc zinc sodium sodium sodium zinc zinc zinc Melt index
D-1238 g/10 min. 2.5 1.5 0.8 1.6 2.8 0.8 1.5 2.5 Density D-1505
kg/m.sup.3 963 963 954 960 960 960 960 960 Melting Point D-3417
.degree. C. 90 90 90 87.5 87.5 90 90 90 Crystallization Point
D-3417 .degree. C. 62 64 56 53 55 -- -- -- Vicat Softening Point
D-1525 .degree. C. 62 63 61 64 67 60 63 62.5 % Weight Acrylic Acid
16 11 -- -- -- % of Acid Groups 30 40 -- -- -- cation neutralized
Plaque Properties (3 mm thick, compression molded) Tensile at break
D-638 MPa 24 26 36 31.5 28 38 38 38 Yield point D-638 MPa none none
21 21 23 none none none Elongation at break D-638 % 395 420 350 410
395 500 420 395 1% Secant modulus D-638 MPa 160 160 300 350 390 --
-- -- Shore Hardness D D-2240 -- 55 55 61 58 59 57 55 55 Film
Properties (50 micron film 2.2:1 Blow-up ratio) Tensile at Break MD
D-882 MPa 41 39 42 52 47.4 TD D-882 MPa 37 38 38 38 40.5 Yield
point MD D-882 MPa 15 17 17 23 21.6 TD D-882 MPa 14 15 15 21 20.7
Elongation at Break MD D-882 % 310 270 260 295 305 TD D-882 % 360
340 280 340 345 1% Secant modulus MD D-882 MPa 210 215 390 380 380
TD D-882 MPa 200 225 380 350 345 Dart Drop Impact D-1709 g/micron
12.4 12.5 20.3
[0120] It has been determined that when hard/soft ionomer blends
are used for the outer cover layer, good results are achieved when
the relative combination is in a range of about 3-25 percent hard
ionomer and about 75-97 percent soft ionomer.
[0121] Additionally, it is contemplated that the above described
hard ionomers may be utilized as the outer cover layer over a
relatively softer ionomeric material as the inner cover layer.
[0122] Moreover, in alternative embodiments, the outer cover layer
formulation may also comprise up to 100 wt % of a soft, low modulus
non-ionomeric thermoplastic material including a polyester
polyurethane such as B. F. Goodrich Company's Estane.RTM. polyester
polyurethane X-4517. The non-ionomeric thermoplastic material may
be blended with a soft ionomer. For example, polyamides blend well
with soft ionomer. According to B. F. Goodrich, Estane.RTM. X-4517
has the following properties:
16 Properties of Estane .RTM. X-4517 Tensile 1430 100% 815 200%
1024 300% 1193 Elongation 641 Youngs Modulus 1826 Hardness A/D
88/39 Bayshore Rebound 59 Solubility in Water Insoluble Melt
processing temperature >350.degree. F. (>177.degree. C.)
Specific Gravity (H.sub.2O = 1) 1.1-1.3
[0123] Other soft, relatively low modulus non-ionomeric
thermoplastic 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, 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.; non-ionomeric thermoset polyurethanes including but not
limited to those disclosed in U.S. Pat. No. 5,334,673; cross-linked
metallocene catalyzed polyolefins; ionomer/rubber blends such as
those in Spalding U.S. Pat. Nos. 4,986,545; 5,098,105 and
5,187,013; and, Hytrel polyester elastomers from DuPont and Pebax
polyesteramides from Elf Atochem S.A.
C. Method of Making Golf Balls
[0124] In preparing preferred embodiment golf balls in accordance
with the present invention, a hard inner cover layer is molded (by
injection molding or by compression molding) about a core
(preferably a multi-layer, solid core). A comparatively softer
outer layer is molded over the inner cover layer. This may,
however, be reversed (hard outer over soft inner) wherein maximum
distances can be achieved.
[0125] The dual cores of the present invention are preferably
formed by compression molding techniques. However, it is fully
contemplated that liquid injection molding or transfer molding
techniques could be utilized.
[0126] For purposes of example, a preferred method of making a golf
ball according to the invention as follows. Specifically, a
thermoset material, i.e. a core layer, is formed about an inner
core component comprising a thermoplastic material as follows.
Referring to FIG. 5, preforms 55 of a thermoset material, i.e.
utilized to form the core layer 24, are preheated in an oven for
one-half hour at 170.degree. F. and placed in the bottom 53 of a
molding assembly 50. A Teflon-coated plate 56 with two hemispheres
57 and 58, each about 0.840 inches in diameter, is placed on top of
the preforms. Additional preforms, preheated as described above,
are placed in the corresponding cavities of a top mold 52. The
bottom mold 53 is engaged with the top mold 52 and the assembly
flipped or otherwise inverted. The bottom one half of the mold
assembly 50 then becomes the top one half of the mold assembly. The
mold assembly 50 is then placed in a press and cold formed at room
temperature using approximately 10 tons of pressure in a steam
press. The molding assembly 50 is closed for approximately two
minutes and pressure released. The molding assembly 50 is then
opened and the Teflon plate 56 is removed thereby leaving one or
more essentially perfectly formed one-half shells or cavities in
the thermoset material. Previously formed thermoplastic core
centers are then placed in the bottom cavities and the top portion
52 of the molding assembly 50 is placed on the bottom 53 and the
materials disposed therebetween cured. The golf ball produced by
this method had an inner core diameter of 0.840 inches in diameter.
The outer core diameter had a final diameter of 1.470 inches, and a
pre-mold diameter of 1.490 inches. A relatively hard inner cover
layer is then molded about the resulting dual core component. The
diameter of the inner cover was 1.570 inches. A comparatively
softer outer cover layer is then molded about the inner cover
layer. The outer cover diameter was 1.680 inches. Details of
molding the inner and outer covers are set forth below.
[0127] Most preferably, the resulting golf balls in accordance with
the present invention have the following dimensions:
17 Size Specifications: Preferred Most Preferred Inner Core Max.
1.250" 1.00" Min. 0.500" 0.70" Outer Core Max. 1.600" 1.570" Min.
1.500" 1.550" Cover Thickness (Total) Max. 0.090" 0.065" Min.
0.040" 0.055"
[0128] In a particularly preferred embodiment of the invention, the
golf ball has a dimple pattern which provides coverage of 65% or
more. The golf ball typically is coated with a durable,
abrasion-resistant, relatively non-yellowing finish coat.
[0129] The various cover composition layers of the present
invention may be produced according to conventional melt blending
procedures. Generally, the copolymer resins are blended in a
Banbury type mixer, two-roll mill, or extruder prior to
neutralization. After blending, neutralization then occurs in the
melt or molten states in the Banbury mixer. Mixing problems are
minimal because preferably more than 75 wt %, and more preferably
at least 80 wt % of the ionic copolymers in the mixture contain
acrylate esters and, in this respect, most of the polymer chains in
the mixture are similar to each other. The blended composition is
then formed into slabs, pellets, etc., and maintained in such a
state until molding is desired. Alternatively, a simple dry blend
of the pelletized or granulated resins which have previously been
neutralized to a desired extent and colored master batch may be
prepared and fed directly into the injection molding machine where
homogenization occurs in the mixing section of the barrel prior to
injection into the mold. If necessary, further additives such as an
inorganic filler, etc., may be added and uniformly mixed before
initiation of the molding process. A similar process is utilized to
formulate the high acid ionomer resin compositions used to produce
the inner cover layer. In one embodiment of the invention, a master
batch of non-acrylate ester-containing ionomer with pigments and
other additives incorporated therein is mixed with the acrylate
ester-containing copolymers in a ratio of about 1-7 weight % master
batch and 93-99 weight % acrylate ester-containing copolymer.
[0130] The golf balls of the present invention can be produced by
molding processes which include but are not limited to those which
are currently well known in the golf ball art. For example, the
golf balls can be produced by injection molding or compression
molding the novel cover compositions around a wound or solid molded
core to produce an inner ball which typically has a diameter of
about 1.50 to 1.67 inches. The core, preferably of a dual core
configuration, may be formed as previously described. The outer
layer is subsequently molded over the inner layer to produce a golf
ball having a diameter of 1.620 inches or more, preferably about
1.680 inches or more. Although either solid cores or wound cores
can be used in the present invention, as a result of their lower
cost and superior performance solid molded cores are preferred over
wound cores. The standards for both the minimum diameter and
maximum weight of the balls are established by the United States
Golf Association (U.S.G.A.).
[0131] In compression molding, the inner cover composition is
formed via injection at about 380.degree. F. to about 450.degree.
F. into smooth surfaced hemispherical shells which are then
positioned around the core in a mold having the desired inner cover
thickness and subjected to compression molding at 200.degree. to
300.degree. F. for about 2 to 10 minutes, followed by cooling at
50.degree.to 70.degree. F. for about 2 to 7 minutes to fuse the
shells together to form a unitary intermediate ball. In addition,
the intermediate balls may be produced by injection molding wherein
the inner cover layer is injected directly around the core placed
at the center of an intermediate ball mold for a period of time in
a mold temperature of from 50.degree. to about 100.degree. F.
Subsequently, the outer cover layer is molded around the core and
the inner layer by similar compression or injection molding
techniques to form a dimpled golf ball of a diameter of 1.680
inches or more.
[0132] After molding, the golf balls produced may undergo various
further processing steps such as buffing, painting and marking as
disclosed in U.S. Pat. No. 4,911,451.
[0133] The resulting golf ball produced from the hard inner layer
and the relatively softer, low flexural modulus outer layer provide
for an improved multi-layer golf ball having a unique dual core
configuration which provides for desirable coefficient of
restitution and durability properties while at the same time
offering the feel and spin characteristics associated with soft
balata and balata-like covers of the prior art.
EXAMPLES
[0134] Four (4) golf balls in accordance with the present invention
were formed, each using a preferred and commercially available high
melting point thermoplastic material as an inner core component. In
this regard, Capron 8351 is a blend of nylon and ionomer,
(available from Allied Signal Plastics), Lexan ML5776 is a
polycarbonate, (available from General Electric), Pebax 3533 is a
polyether block amide, (available from Elf Atochem), and Hytrel
G4074 is a polyester elastomeric resin, (available from DuPont).
Table 14, set forth below, summarizes these balls.
18TABLE 14 Example 1 Example 2 Example 3 Example 4 Example 5 Capron
Lexan Pebax Hytrel Control 8351 ML 5776-7539 3533 G-4074 (Single
Core) Inner Core size (inches) 0.835 0.854 0.840 0.831 -- weight
(grams) 5.33 6.14 5.08 5.81 -- rebound % (100") 78 83 65 61 --
Shore C (surface) -- -- 57 73 -- Shore D (surface) 75 83 36 47 --
Outer Core Cis 1,4 Polybutadiene 100 100 100 100 100 Formulation
Zinc oxide 27 26 28 21 25 Zinc stearate 16 16 16 16 15 Zinc
diacrylate 20 20 24 24 18 231 XL.sup.1 0.9 0.9 0.9 0.9 0.9 163.9
162.9 168.9 161.9 158.9 Double Core size (inches) 1.561 1.560 1.562
1.563 1.562 Properties weight (grams) 37.7 37.8 37.8 37.5 37.8
compression (Riehle) 79 80 99 93 114 COR .689 .603 .756 .729 .761
Molded Ball size (inches 1.685 1.683 1.682 1.683 1.685 Properties
weight (grams) 45.3 45.5 45.5 45.2 45.4 compression (Riehle) 78 80
89 87 102 COR .750 .667 .785 .761 .788 Cover Stock Surlyn 8940 22
(used on all Surlyn 9910 54.5 above balls) Surlyn 8320 10 Surlyn
8120 4 T.G. MB.sup.2 9.5 100.0 .sup.1231 XL is a peroxy ketal
manufactured by Attochem. .sup.2T.G. MB is as follows: Iotek 7030
75.35% Unitane 0-110 23.90% Ultra Marine Blue 0.46% Eastonbrite
OB-1 0.26% Santonox R 0.03% 100.00
[0135] Generally, the inner cover layer which is molded over the
core, or preferably a dual core component, is about 0.01 inches to
about 0.10 inches in thickness, preferably about 0.03-0.07 inches
thick. The inner ball which includes the core and inner cover layer
preferably has a diameter in the range of 1.25 to 1.60 inches. The
outer cover layer is about 0.01 inches to about 0.10 inches in
thickness. Together, the core, the inner cover layer 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 no more than 1.62
ounces.
[0136] In a similar fashion to that described above, a golf ball
according to FIG. 2, for example, having a thermoset core 22 and a
thermoset core layer 24 can be formed. Typically, the thermoset
core 22 will have a diameter of about 1.340 to about 1.400 inches.
The thermoset core layer 24 typically will have a thickness of
about 0.020 inches to about 0.100 inches. The outer diameter of the
multi-layer core will typically have a diameter of about 1.440
inches to about 1.500 inches. about 0.020 inches to about 0.100
inches. A cover layer is then formed on the multi-layer core. The
cover layer has an inner layer and an outer layer. The inner layer
is typically formed from a relatively hard material (compared to
the outer layer) while the outer layer is typically formed from a
relatively softer material. However, a softer inner layer with a
harder outer layer is also contemplated depending upon the desired
final properties of the golf ball. The inner cover will typically
have a thickness of about 0.020 inches to about 0.080 inches while
the outer cover will typically have a thickness of about 0.040
inches to about 0.090 inches. The diameter of the golf ball with
the inner cover formed thereon is typically about 1.540 inches to
about 1.600 inches. The diameter of the golf ball with the outer
cover formed thereon is about 1.680 inches to about 1.720 inches.
Typically, the inner core will have a Shore C hardness value of
about 50 to about 85 while the core layer which is harder than the
inner core will have a Shore D hardness value of about 40 to about
80. The specific gravity of each of the inner core and outer core
layers is typically .gtoreq.0.1.
[0137] The following in Table 15, describes a multi-layer golf ball
core with a thermoset inner core and a thermoset core layer in
accordance with the present invention.
19TABLE 15 Example 6 Inner Core Core Layer Cariflex BR-1220.sup.1
70 70 Taktene 220.sup.2 30 30 ZnO 32.8 7 T.G. Regrind 16 Zn
Stearate 16 16 ZDA 19 55 231 XL.sup.3 0.9 0.9 184.7 178.9 Diameter
1.370" 1.470" Specific Gravity 1.215 1.212 .sup.1Cariflex BR-1220
is a high molecular weight, cobalt catalyzed polybutadiene
available from Shell Chemical. .sup.2Taktene 220 is a cobalt
catalyzed polybutadiene. .sup.3231 XL is a peroxy ketal
manufactured by Attochem.
[0138] The above multi-layer core is then covered with a relatively
hard, high acid (i.e. >16% acid) ionomer resin mantle (0.05" in
thickness) which is then covered with a relatively softer ionomeric
resin material to form a golf ball having a diameter of 1.680".
Example 7
[0139]
20 Inner Core Core Layer Cariflex BR-1220 70 70 Taktene 220 30 30
ZnO 6 6 Zn Stearate 15 15 ZDA 20 23 Tungsten Powder 114 231 XL 0.9
0.9 255.9 144.9 Diameter .840" 1.50" Specific Gravity 1.842
1.079
[0140] The above inner core and core layer are formed into golf
ball dual core having the following properties:
Dual Core from Example 7 Inner Core and Core Layer
[0141]
21 Size 1.470" Weight 32.8 g Compression (Riehle) 113 (PGA 47)
C.O.R. .766
[0142] The above dual core is then covered with a multi-layer
ionomeric cover having a relatively hard inner layer and a
relatively soft cover layer. This is the same type of cover
currently used in the Top Flite.RTM. Strata golf ball. The finished
golf balls had the following properties:
Finished Dual Core/Dual Cover Golf Balls
[0143]
22 Size 1.685" Weight 45.78 g Compression (Riehle) 89 (PGA 71)
C.O.R. .779
[0144] Five finished balls according to the above description were
tested to 300 blows with no fractures resulting. In addition, the
following results were obtained by comparing distance of a STRATA
golf ball with the golf balls prepared according to Example 7. Each
Example represents an average for 12 (twelve)balls hit.
23 Diff.* Trajectory Carry* Roll* Total Dist.* Total Distance
Comparison (TFT 5 iron @ 126.6 fps) STRATA 90 24.4.degree. 175.8
4.5 180.2 -4.10 Example 7 ball 24.9.degree. 179.5 4.8 184.3 0.00
(dual core/ dual cover) Distance Comparison (10.degree. Striker @
135 fps) STRATA 90 15.0.degree. 250.7 5.2 255.8 -2.50 Example 7
ball 15.4.degree. 252.8 5.4 258.3 0.00 (dual core/ dual cover) *all
distances are in yards
[0145] As can be seen from the above results, an increase in
distance can be realized from the dual core golf ball according to
the invention over a single core golf ball having essentially the
same cover (i.e. the STRATA 90).
[0146] Further, the spin rate of the dual core/dual cover golf
balls according to Example 7 were tested and compared to the STRATA
90 golf balls. The spin tests were conducted with a Miya driving
machine set up with a Top Flite Tour 9 iron.
Spin Test Comparison
[0147]
24 STRATA 90 (125 fps) 23.9 139.7 9273 Example 7 (125 fps) 24.6
139.9 9038 STRATA 90 (60 fps) 27.5 57.7 5397 0.444 Example 7 (60
fps) 28.0 57.8 5367 0.421
[0148] As can be seen from the above test, distance can be
increased from the dual core/dual cover golf ball compared to the
single core/dual cover STRATA 90 golf ball with little sacrifice in
spin rate. This results in an increased distance golf ball which
has the desired control and feel of a high spin golf ball.
[0149] The invention has been described with reference to the
preferred embodiments. Obviously, modifications and alterations
will occur to others upon a reading and understanding the preceding
detailed description. It is intended that the invention be
construed as including all such modifications and alterations in so
far as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *