U.S. patent application number 09/840312 was filed with the patent office on 2002-04-04 for golf ball with multi-layer cover utilizing polyurethane materials.
This patent application is currently assigned to SPALDING SPORTS WORLDWIDE, INC.. Invention is credited to Binette, Mark L., Keller, Viktor, Kennedy, Thomas J. III, Risen, William M. JR., Sullivan, Michael J., Tzivanis, Michael John.
Application Number | 20020039936 09/840312 |
Document ID | / |
Family ID | 25281999 |
Filed Date | 2002-04-04 |
United States Patent
Application |
20020039936 |
Kind Code |
A1 |
Binette, Mark L. ; et
al. |
April 4, 2002 |
Golf ball with multi-layer cover utilizing polyurethane
materials
Abstract
A golf ball is described having a core with a multi-layer cover
that includes one or more polyurethane materials and which exhibits
a Shore D hardness of at least 60. The one or more polyurethane
materials may be utilized in one, all, or in only some of the
individual cover layers that form the multi-layer cover.
Inventors: |
Binette, Mark L.; (Ludlow,
MA) ; Sullivan, Michael J.; (Barrington, RI) ;
Kennedy, Thomas J. III; (Wilbraham, MA) ; Tzivanis,
Michael John; (Chicopee, MA) ; Keller, Viktor;
(Enfield, CT) ; Risen, William M. JR.; (Rumford,
RI) |
Correspondence
Address: |
MICHELLE BUGBEE, ASSOCIATE PATENT COUNSEL
SPALDING SPORTS WORLDWIDE INC
425 MEADOW STREET
PO BOX 901
CHICOPEE
MA
01021-0901
US
|
Assignee: |
SPALDING SPORTS WORLDWIDE,
INC.
|
Family ID: |
25281999 |
Appl. No.: |
09/840312 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09840312 |
Apr 23, 2001 |
|
|
|
09335302 |
Jun 17, 1999 |
|
|
|
6220972 |
|
|
|
|
09335302 |
Jun 17, 1999 |
|
|
|
08743579 |
Nov 4, 1996 |
|
|
|
5833553 |
|
|
|
|
08743579 |
Nov 4, 1996 |
|
|
|
08240259 |
May 10, 1994 |
|
|
|
08240259 |
May 10, 1994 |
|
|
|
08054406 |
Apr 28, 1993 |
|
|
|
5368304 |
|
|
|
|
Current U.S.
Class: |
473/374 |
Current CPC
Class: |
C08L 23/025 20130101;
C08L 23/0876 20130101; C08L 2205/02 20130101; A63B 37/0076
20130101; A63B 37/0027 20130101; A63B 37/0031 20130101; C08L 23/08
20130101; C08L 23/025 20130101; A63B 37/0043 20130101; A63B 37/0003
20130101; A63B 37/12 20130101; C08L 23/08 20130101; A63B 37/0065
20130101; C08L 2666/04 20130101; C08L 2666/04 20130101 |
Class at
Publication: |
473/374 |
International
Class: |
A63B 037/06 |
Claims
We claim:
1. A golf ball comprising: a core; a first cover layer disposed
about said core, said first cover layer comprising a majority
proportion by weight of a composition selected from the group
consisting of polyurethane, polyureas and blends thereof, said
first cover layer exhibiting a Shore D hardness of less than 60;
and a second outermost cover layer disposed on said first cover
layer, said second cover layer comprising a majority proportion by
weight of a polyurethane, said second cover layer exhibiting a
Shore D hardness of less than 60.
2. The golf ball of claim 1 wherein said first cover layer and said
second cover layer each exhibit a Shore D hardness less than
55.
3. The golf ball of claim 2 wherein said first cover layer and said
second cover layer each exhibit a Shore D hardness less than
50.
4. The golf ball of claim 1 wherein said core exhibits a PGA
compression of from 20 to 85.
5. The golf ball of claim 4 wherein said core exhibits a PGA
compression of from 40 to 60.
6. The golf ball of claim 1 wherein said polyurethane is the
product of a polyisocyanate and a polyol.
7. The golf ball of claim 6 wherein said polyisocyanate is selected
from the group consisting of diphenylmethane diisocyanate,
hexamethylene diisocyanate, cyclohexane diisocyanate, toluene
diisocyanate, bitolylene diisocyanate, p-phenylene diisocyanate,
dicyclohexylmethane diisocyanate,
3-isocyanato-methyl-3,5,5-trimethylcyclo-hexyl isocyanate,
trans-cyclohexane-1,4-diisocyanate, m-tetramethyl-xylylene,
1,5-naphthalene diisocyanate, polymethylene polyphenyl isocyanate
and combinations thereof.
8. The golf ball of claim 6 wherein said polyol is selected from
the group consisting of polyester polyol, polyether polyol, and
combinations thereof.
9. The golf ball of claim 1 wherein said polyurethane is a
thermoset.
10. The golf ball of claim 1 wherein said polyurethane is a
thermoplastic.
11. The golf ball of claim 1 further comprising a third cover layer
disposed between said first cover layer and said second cover
layer.
12. The golf ball of claim 1 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 5.
13. The golf ball of claim 1 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 2.
14. A golf ball comprising: a core; a first cover layer disposed
about said core, said first cover layer comprising a majority
proportion by weight of a composition selected from the group
consisting of polyurethane, polyureas and blends thereof, said
first cover layer exhibiting a Shore D hardness less than 60; and a
second outermost cover layer disposed on said first cover layer,
said second cover layer exhibiting a Shore D hardness of less than
60.
15. The golf ball of claim 14 wherein said first cover layer and
said second cover layer each exhibit a Shore D hardness less than
55.
16. The golf ball of claim 15 wherein said first cover layer and
said second cover layer each exhibit a Shore D hardness less than
50.
17. The golf ball of claim 14 wherein said core exhibits a PGA
compression of from 20 to 85.
18. The golf ball of claim 17 wherein said core exhibits a PGA
compression of from 40 to 60.
19. The golf ball of claim 14 wherein said polyurethane is the
product of a polyisocyanate and a polyol.
20. The golf ball of claim 19 wherein said polyisocyanate is
selected from the group consisting of diphenylmethane diisocyanate,
hexamethylene diisocyanate, cyclohexane diisocyanate, toluene
diisocyanate, bitolylene diisocyanate, p-phenylene diisocyanate,
dicyclohexylmethane diisocyanate,
3-isocyanato-methyl-3,5,5-trimethylcyclo-hexyl isocyanate,
trans-cyclohexane-1,4-diisocyanate, m-tetramethyl-xylylene,
1,5-naphthalene diisocyanate, polymethylene polyphenyl isocyanate
and combinations thereof.
21. The golf ball of claim 19 wherein said polyol is selected from
the group consisting of polyester polyol, polyether polyol, and
combinations thereof.
22. The golf ball of claim 14 wherein said polyurethane is a
thermoset.
23. The golf ball of claim 14 wherein said polyurethane is a
thermoplastic.
24. The golf ball of claim 14 further comprising a third cover
layer disposed between said first cover layer and said second cover
layer.
25. The golf ball of claim 14 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 5.
26. The golf ball of claim 14 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 2.
27. A golf ball comprising: a core; a first cover layer disposed on
said core, said first cover layer exhibiting a Shore D hardness of
less than 60; and a second outermost cover layer disposed on said
first cover layer, said second cover layer comprising a majority
proportion by weight of a composition selected from the group
consisting of polyurethane, polyureas and blends thereof, said
second cover layer exhibiting a Shore D hardness of less than
60.
28. The golf ball of claim 27 wherein said first cover layer and
said second cover layer each exhibit a Shore D hardness less than
55.
29. The golf ball of claim 28 wherein said first cover layer and
said second cover layer each exhibit a Shore D hardness less than
50.
30. The golf ball of claim 27 wherein said core exhibits a PGA
compression of from 20 to 85.
31. The golf ball of claim 30 wherein said core exhibits a PGA
compression of from 40 to 60.
32. The golf ball of claim 27 wherein said polyurethane is the
product of a polyisocyanate and a polyol.
33. The golf ball of claim 32 wherein said polyisocyanate is
selected from the group consisting of diphenylmethane diisocyanate,
hexamethylene diisocyanate, cyclohexane diisocyanate, toluene
diisocyanate, and combinations thereof.
34. The golf ball of claim 32 wherein said polyol is selected from
the group consisting of polyester polyol, polyether polyol, and
combinations thereof.
35. The golf ball of claim 27 wherein said polyurethane is a
thermoset.
36. The golf ball of claim 27 wherein said polyurethane is a
thermoplastic.
37. The golf ball of claim 27 further comprising a third cover
layer disposed between said first cover layer and said second cover
layer.
38. The golf ball of claim 27 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 5.
39. The golf ball of claim 27 wherein the difference between the
Shore D hardness of said first layer and the Shore D hardness of
said second layer is less than 2.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. application Ser. No.
09/335,302 filed Jun. 17, 1999, which is a continuation-in-part of
U.S. application Ser. No. 08/743,579 filed Nov. 4, 1996 and issued
as U.S. Pat. No. 5,833,553, which is a continuation-in-part of U.S.
application Ser. No. 08/240,259 filed May 10, 1994 now abandoned,
which in turn is a continuation-in-part of U.S. application Ser.
No. 08/054,406, filed Apr. 28, 1993, which issued as U.S. Pat. No.
5,368,304.
FIELD OF THE INVENTION
[0002] The present invention relates generally to golf balls, and
more particularly to golf balls having multi-layer covers that
utilize one or more polyurethane materials. Preferably, the cover
layers exhibit hardnesses less than 60 as measured on the Shore D
hardness scale. In a further aspect, the present invention relates
to golf balls having multi-layer covers in which each of the
individual cover layers have the same, or similar, hardness.
BACKGROUND OF THE INVENTION
[0003] Top grade golf balls sold in the United States generally
comprise a central core with one or more cover layers formed
thereover. A golf ball cover is particularly influential in
effecting the compression (feel) and durability (i.e., impact
resistance, etc.) of the resulting ball. Various cover compositions
have been developed in order to optimize desired properties of the
resulting golf balls.
[0004] FIGS. 1 and 2 illustrate a conventional golf ball 10 having
a single cover layer 14 molded about a golf ball core 16. FIG. 2
illustrates (in an exaggerated view) stress lines 12 extending
partially, or entirely across the thickness of the cover layer 14.
Stress lines 12 typically result in a crack or fracture across the
thickness of the golf ball cover. FIGS. 1 and 2 illustrate one
problem that may occur when a very thick, single layer cover is
formed about a golf ball core.
[0005] Although not wishing to be bound to any particular theory,
it is believed that stress lines in a golf ball cover, such as
stress lines 12 in cover 14, result from repeated strikes with a
golf club, particularly drivers, and temperature effects. Stress
lines often serve as initiation sites for crack or fracture
propagation in a golf ball cover material. Such cracks or
fractures, and their related stress lines, are undesirable in golf
ball covers. Moreover, it is particularly undesirable for such
stress lines and the resulting cracks or fractures to extend across
the entire thickness of a golf ball cover since such damage
significantly impairs golf ball performance. And, such cracks or
fractures greatly reduce the durability of a golf ball cover.
[0006] When a multi-layer cover is employed, each cover layer
traditionally has had a significantly different Shore D hardness
than an adjacent cover layer in order to impart to the golf ball a
particular desired combination of spin and distance
characteristics. Although the use of a multi-layer cover
configuration reduces the tendency of stress lines, and thus cracks
and fractures, propagating across the entire thickness of the
cover, such multi-layer arrangement of cover materials, each having
its own particular set of properties and characteristics, has
associated design and manufacturing problems.
[0007] For instance, in order to produce a multiple cover layer
golf ball that exhibits a desired set of performance
characteristics, it is necessary to design and anticipate an
overall performance profile for the set of cover layers. This
involves analyzing each of the individual cover layers and any and
all effects between the individual cover layers. Even if such
daunting design analysis is performed, the increased number of
variables may lead to unanticipated difficulties in manufacturing
or with the final product golf ball.
[0008] In addition, although, once again, not wishing to be bound
to any particular theory, it is believed that although a multiple
cover layer configuration may reduce the tendency for cracks or
fractures that extend through the entire thickness of the cover,
such configuration may lead to an increase in the number or
frequency of fractures, particularly in applications in which the
various cover layers constituting the multi-layer cover each have
different physical properties such as hardness and flexural
characteristics.
[0009] Accordingly, there is a need for an improved golf ball which
is less susceptible to cracking or fracturing across the thickness
of the cover than currently known single cover layer golf balls.
And, there is a need for an improved multiple cover layer golf ball
that is simpler to design and manufacture, and which is less
susceptible to cracking or fracturing of one or more of the
individual cover layers that constitute the multiple cover layer of
the ball.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention relates to new and improved golf balls
which overcome the above-referenced problems and others. In a first
aspect, the present invention provides a golf ball comprising a
core, a first cover layer disposed about the core, and a second
outermost cover layer disposed on the first cover layer. The first
inner cover layer comprises a majority proportion by weight of a
polyurethane. The first cover layer exhibits a Shore D hardness of
less than 60. The second outermost cover layer comprises a majority
proportion by weight of a polyurethane, and exhibits a Shore D
hardness of less than 60.
[0011] In another aspect, the present invention provides a golf
ball comprising a core, a first cover layer disposed about the
core, and a second outermost cover layer disposed on the first
cover layer. The first inner cover layer comprises a majority
proportion by weight of a polyurethane and exhibits a Shore D
hardness less than 60. The second outermost cover layer exhibits a
Shore D hardness less than 60.
[0012] In yet another aspect, the present invention provides a golf
ball comprising a core, a first cover layer disposed about the
core, and a second outermost cover layer disposed on the first
inner cover layer. The inner cover layer exhibits a Shore D
hardness of less than 60. And, the second outermost cover layer
exhibits a Shore D hardness of less than 60. Furthermore, the
second outermost cover layer comprises a majority proportion by
weight of a polyurethane.
[0013] Other features and objectives of the present invention will
be pointed out in more detail hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following is a brief description of the drawings which
are presented for the purposes of illustrating the invention and
not for the purposes of limiting the same.
[0015] FIG. 1 is a perspective view of a conventional single cover
layer golf ball.
[0016] FIG. 2 is a partial cross sectional view of the golf ball
depicted in FIG. 1, taken across line 2-2, illustrating stress
lines extending partially or entirely across the thickness of the
golf ball cover.
[0017] FIG. 3 is a partial cross section of a preferred embodiment
solid golf ball with a dual layer cover according to the present
invention.
[0018] FIG. 4 is a partial cross section of a preferred embodiment
solid golf ball with a three layer cover according to an
alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] The present invention generally provides a golf ball having
a multiple layer cover in which one or more properties of each of
the individual cover layers are matched so that certain desired
properties are the same, or substantially so. In several of the
preferred embodiments described herein, the individual cover layers
all have the same, or nearly the same, Shore D hardness. The
present invention includes matching of one or more further
properties or characteristics of individual cover layers in a
multiple cover layer assembly utilized in a golf ball. The present
invention is embodied in golf balls having multi-layer cover
assemblies comprising two, three, or more cover layers.
[0020] In a particularly preferred aspect, the golf ball of the
present invention has a solid core having a coefficient of
restitution (COR) of at least about 0.650 in combination with a
thick, relatively soft cover assembly which is formed from two or
more layers. Each cover layer has a Shore D hardness within 5
points, and preferably within 2 points, of the Shore D hardness of
all other cover layers.
[0021] Referring to the drawings and particularly to FIG. 3, a
first preferred embodiment of a golf ball according to the present
invention is shown and is designated as 20. The golf ball 20 has a
core 26. The core 26 can consist of a solid or wound core and can
consist of one or more layers.
[0022] A multi-layer cover surrounds the core 26. The multi-layer
cover includes a non-dimpled inner cover layer 24 and a dimpled
outer cover layer 22. The outer cover layer 22 defines a plurality
of dimples 27 and an outer surface 28 to form an unfinished golf
ball.
[0023] A thin primer coat (not shown) is preferably applied to the
outer surface of cover layer 22. A thin top coat (not shown) also
preferably surrounds the primer coat to form a finished ball.
Optionally, one or more pigmented paint coat(s) can be substituted
for the primer coat and/or top coat. In one preferred embodiment,
the core 26 is relatively soft, with a PGA compression of about 85
or less, preferably about 20 to 85, and more preferably about 40 to
60. PGA compression is described and defined herein below.
[0024] The multi-layer cover has an overall cover thickness of at
least about 3.6 mm (0.142 inches). It is particularly preferred
that the cover thickness be at least 3.8 mm (0.150 inches).
Particularly good results are obtained when the cover has a
thickness of at least 4.0 mm (0.157 inches). In certain
circumstances, such as when a harder compression and harder feel
may be desired, it is useful to employ a cover having a thickness
of at least 4.5 mm (0.177 inches). The thickness of the individual
cover layers may vary depending upon the thicknesses of the other
cover layers and the desired overall cover layer thickness. It may,
in some applications, be desirable to form the outermost cover
layer to be relatively thick due to the presence of the
dimples.
[0025] As used herein, "overall cover thickness" is the thickness
of the multi-layer cover as measured from the inner diameter of the
innermost cover to the outer surface of the outermost or exterior
cover at a land (i.e. non-dimpled) area. The "cover layer
thickness" of any particular cover layer is the thickness of the
layer from its inner diameter to its outer surface. If the outer
surface of the layer is dimpled, the measurement is made to a land
area of the cover layer.
[0026] The preferred golf ball of the present invention preferably
exhibits a difference between the coefficient of restitution of the
ball and the coefficient of restitution of the core of at least
about 0.025, preferably at least 0.035, and more preferably at
least 0.045. The golf balls exhibit an unexpectedly long distance
upon impact or drives given their coefficient of restitution.
[0027] In one preferred embodiment, each layer of the multi-layer
cover assembly has a Shore D hardness of less than 60, more
preferably less than 55, and most preferably less than 50.
[0028] The golf balls of the present invention can be produced by
molding processes currently well known in the golf ball art.
Specifically, the golf balls can be produced by injection molding
or compression molding the cover compositions described herein
about wound or solid molded cores to produce a golf ball having a
diameter of about 1.680 to about 1.800 inches and weighing about
1.620 ounces. The standards for both the minimum diameter and
maximum weight of the balls have been established by the United
States Golf Association (U.S.G.A.).
[0029] Although both solid core and wound cores can be utilized in
the present invention, as a result their lower cost and superior
performance, solid molded cores are preferred over wound cores.
[0030] The term "solid cores" as used herein refers not only to one
piece cores but also to those cores having a separate solid layer
beneath the cover and above the core as in U.S. Pat. No. 4,431,193,
and other multi-layer and/or non-wound cores. The compositions of
suitable cores that can be incorporated into the present invention
are presented in more detail below.
[0031] The layers of the multi-layer cover may be formed from
generally the same resin composition, or may be formed from
different resin compositions with similar hardnesses. For example,
one cover layer may be formed from an ionomeric resin of ethylene
and methacrylic acid, while another layer is formed from an ionomer
of ethylene and acrylic acid. One or more cover layers may contain
polyamides or polyamide-nylon copolymers or intimate blends
thereof. Furthermore, polyurethanes, Pebax.RTM. polyetheramides,
Hytrel.RTM. polyesters, and/or thermosetting polyurethanes can be
used. In order to visibly distinguish the layers, various
colorants, metallic flakes, phosphorous, florescent dyes,
florescent pigments, etc. can be incorporated in the resin.
Preferably, the various cover layers that comprise ionomer are made
of at least 50 weight % ionomer based upon 100 parts by weight of
resin composition, and more preferably 75 or more weight % ionomer.
However, as explained in greater detail herein, it is preferred
that at least one of the cover layers of the multi-layer cover
comprise a polyurethane, and most preferably, at least 50% by
weight. Additional description and details of suitable materials
for cover layers are provided herein.
[0032] Preferable cover materials for use as inner or outer cover
layers include, for example, zinc, sodium and lithium ionomers, and
blends of ionomers with harder non-ionic polymers such as nylon,
polyphenylene oxide, metallocene catalyzed polyolefins, and other
compatible thermoplastics. A wide array of nylon materials or
blends thereof can be incorporated in the present invention golf
ball covers. This is described in greater detail herein. Moreover,
various suitable ionomers are further described below. Furthermore,
examples of cover compositions which may be used are set forth in
detail in copending U.S. application Ser. No. 08/596,690, which is
a continuation of U.S. application Ser. No. 08/174,765 now
abandoned, which in turn is a continuation of U.S. Ser. No.
07/776,803 filed Oct. 15, 1991 now abandoned, and U.S. application
Ser. No. 08/493,089 issued as U.S. Pat. No. 5,688,869, which is a
continuation of Ser. No. 07/981,751 now abandoned, which in turn is
a continuation of U.S. application Ser. No. 07/901,660 filed Jun.
19, 1992 now abandoned, all of which are incorporated herein by
reference. The cover compositions are not limited in any way to the
compositions set forth in said copending applications.
[0033] A further embodiment of a golf ball according to the present
invention is shown in FIG. 4, and is designated as golf ball 30.
The ball 30 has a core 38, as is illustrated in FIG. 3. The core 38
preferably has a PGA compression of about 85 or less, preferably 20
to 85, and more preferably 40 to 60.
[0034] A multi-layer cover having three layers is formed over the
core 38 to produce an unfinished golf ball. In the embodiment
shown, the cover includes an inner cover layer 36, an intermediate
inner cover layer 34 and an outer cover layer 32. Again, as in the
embodiment illustrated in FIG. 3, further finished coat(s) (not
shown) can be included to produce a finished golf ball. The inner,
intermediate, and outer cover layers 36, 34 and 32 respectively,
preferably exhibit substantially the same Shore D hardness.
Restated, the difference between the Shore D hardness of any two of
these cover layers is preferably 5 or less, and most preferably is
2 or less. Preferably, each of the cover layers 36, 34 and 32 has a
Shore D hardness of less than 60, more preferably less than 55, and
most preferably less than 50.
[0035] The overall thickness of the multi-layer cover assembly
shown in FIG. 4 can be the same as the thickness of the multi-layer
cover assembly of the embodiment of FIG. 3. The thickness of the
individual cover layers may vary depending upon the thicknesses of
the other cover layers and the desired overall cover layer
thickness. It may, in some applications, be desirable to form the
outermost cover layer to be relatively thick due to the presence of
the dimples. The three cover layers 36, 34 and 32 can be formed
from the same or different resin compositions, and preferably
comprise ionomer, ionomer blends, polyurethanes, polyureas,
polyurethane blends, etc.
[0036] A detailed description of the various components and
materials utilized in the present invention golf balls is set forth
below after a description of various golf ball properties and their
measurement. Moreover, further multiple cover layers are also
included as being within the scope of the present invention.
[0037] As used herein, "Shore D hardness" of a cover is measured
generally in accordance with ASTM D-2240, except the measurements
are made on the curved surface of a molded cover, rather than on a
plaque. Furthermore, the Shore D hardness of the cover is measured
while the cover remains over the core. When a hardness measurement
is made on a dimpled cover, Shore D hardness is measured at a land
area of the dimpled cover.
[0038] Two principal properties involved in golf ball performance
are resilience and PGA compression. Resilience is determined by the
coefficient of restitution (C.O.R.), i.e. 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.
[0039] 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.
[0040] 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 wound core (i.e., balls comprising a
liquid or solid center, elastic windings, and a cover), the
coefficient of restitution is a function of not only the
composition of the center and cover, but also the composition and
tension of the elastomeric windings.
[0041] The coefficient of restitution is the ratio of the outgoing
velocity to the incoming velocity. In the examples of this
application, the coefficient of restitution of a golf ball was
measured by propelling a ball horizontally at a speed of 125.+-.1
feet per second (fps) against a generally vertical, hard, flat
steel plate and measuring the ball's incoming and outgoing velocity
electronically. Speeds were measured with a pair of Ohler Mark 55
ballistic screens, which provide a timing pulse when an object
passes through them. The screens are separated by 36 inches and are
located 25.25 inches and 61.25 inches from the rebound wall. The
ball speed was measured by timing the pulses from screen 1 to
screen 2 on the way into the rebound wall (as the average speed of
the ball over 36 inches), and then the exit speed was timed from
screen 2 to screen 1 over the same distance. The rebound wall was
tilted 2 degrees from a vertical plane to allow the ball to rebound
slightly downward in order to miss the edge of the cannon that
fired it.
[0042] As indicated above, the incoming speed should be 125+/-1
fps. Furthermore, the correlation between COR and forward or
incoming speed has been studied and a correction has been made over
the +/-1 fps range so that the COR is reported as if the ball had
an incoming speed of exactly 125.0 fps.
[0043] The coefficient of restitution must be carefully controlled
in all commercial golf balls if the ball is 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
off the club) exceeding 255 feet per second in an atmosphere of
75.degree. F. when tested on a U.S.G.A. machine. 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.).
[0044] As indicated above, PGA compression is another important
property involved in the performance of a golf ball. The
compression of the ball can affect the playability of the ball on
striking and the sound or "click" produced. Similarly, compression
can effect the "feel" of the ball (i.e., hard or soft responsive
feel), particularly in chipping and putting.
[0045] Moreover, while compression itself has little bearing on the
distance performance of a ball, compression can affect the
playability of the ball on striking. The degree of compression of a
ball against the club face and the softness of the cover strongly
influences the resultant spin rate. Typically, a softer cover will
produce a higher spin rate than a harder cover. Additionally, a
harder core will produce a higher spin rate than a softer core.
This is because at impact a hard core serves to compress the cover
of the ball against the face of the club to a much greater degree
than a soft core thereby resulting in more "grab" of the ball on
the clubface and subsequent higher spin rates. In effect the cover
is squeezed between the relatively incompressible core and
clubhead. When a softer core is used, the cover is under much less
compressive stress than when a harder core is used and therefore
does not contact the clubface as intimately. This results in lower
spin rates.
[0046] The term "compression" utilized in the golf ball trade
generally defines the overall deflection that a golf ball undergoes
when subjected to a compressive load. For example, PGA compression
indicates the amount of change in golf ball's shape upon striking.
The development of solid core technology in two-piece balls has
allowed for much more precise control of compression in comparison
to thread wound three-piece balls. This is because in the
manufacture of solid core balls, the amount of deflection or
deformation is precisely controlled by the chemical formula used in
making the cores. This differs from wound three-piece balls wherein
compression is controlled in part by the winding process of the
elastic thread. Thus, two-piece and multi-layer solid core balls
exhibit much more consistent compression readings than balls having
wound cores such as the thread wound three-piece balls.
[0047] In the past, PGA compression related to a scale of from 0 to
200 given to a golf ball. The lower the PGA compression value, the
softer the feel of the ball upon striking. In practice, tournament
quality balls have compression ratings around 50 to 110, and
preferably around 80 to 100.
[0048] In determining PGA compression using the 0 to 200 scale, a
standard force is applied to the external surface of the ball. A
ball which exhibits no deflection (0.0 inches in deflection) is
rated 200 and a ball which deflects {fraction (2/10)}th of an inch
(0.2 inches) is rated 0. Every change of 0.001 of an inch in
deflection represents a 1 point drop in compression. Consequently,
a ball which deflects 0.1 inches (100.times.0.001 inches) has a PGA
compression value of 100 (i.e., 200 to 100) and a ball which
deflects 0.110 inches (110.times.0.001 inches) has a PGA
compression of 90 (i.e., 200 to 110).
[0049] In order to assist in the determination of compression,
several devices have been employed by the industry. For example,
PGA compression is determined by an apparatus fashioned in the form
of a small press with an upper and lower anvil. The upper anvil is
at rest against a 200-pound die spring, and the lower anvil is
movable through 0.300 inches by means of a crank mechanism. In its
open position the gap between the anvils is 1.780 inches allowing a
clearance of 0.100 inches for insertion of the ball. As the lower
anvil is raised by the crank, it compresses the ball against the
upper anvil, such compression occurring during the last 0.200
inches of stroke of the lower anvil, the ball then loading the
upper anvil which in turn loads the spring. The equilibrium point
of the upper anvil is measured by a dial micrometer if the anvil is
deflected by the ball more than 0.100 inches (less deflection is
simply regarded as zero compression) and the reading on the
micrometer dial is referred to as the compression of the ball. In
practice, tournament quality balls have compression ratings around
80 to 100 which means that the upper anvil was deflected a total of
0.120 to 0.100 inches.
[0050] An example to determine PGA compression can be shown by
utilizing a golf ball compression tester produced by Atti
Engineering Corporation of Newark, N.J. The value obtained by this
tester relates to an arbitrary value expressed by a number which
may range from 0 to 100, although a value of 200 can be measured as
indicated by two revolutions of the dial indicator on the
apparatus. The value obtained defines the deflection that a golf
ball undergoes when subjected to compressive loading. The Atti test
apparatus consists of a lower movable platform and an upper movable
spring-loaded anvil. The dial indicator is mounted such that it
measures the upward movement of the spring-loaded anvil. The golf
ball to be tested is placed in the lower platform, which is then
raised a fixed distance. The upper portion of the golf ball comes
in contact with and exerts a pressure on the spring-loaded anvil.
Depending upon the distance of the golf ball to be compressed, the
upper anvil is forced upward against the spring.
[0051] Alternative devices have also been employed to determine
compression. For example, Applicant also utilizes a modified Riehle
Compression Machine originally produced by Riehle Bros. Testing
Machine Company, Philadelphia, Pa. to evaluate compression of the
various components (i.e., cores, mantle cover balls, finished
balls, etc.) of the golf balls. The Riehle compression device
determines deformation in thousandths of an inch under a load
designed to emulate the 200 pound spring constant of the Atti or
PGA compression testers. Using such a device, a Riehle compression
of 61 corresponds to a deflection under load of 0.061 inches.
[0052] Additionally, an approximate relationship between Riehle
compression and PGA compression exists for balls of the same size.
It has been determined by Applicant that Riehle compression
corresponds to PGA compression by the general formula PGA
compression equals 160 minus Riehle compression. Consequently, 80
Riehle compression corresponds to 80 PGA compression, 70 Riehle
compression corresponds to 90 PGA compression, and 60 Riehle
compression corresponds to 100 PGA compression. For reporting
purposes, Applicant's compression values are usually measured as
Riehle compression and converted to PGA compression.
[0053] Furthermore, additional compression devices may also be
utilized to monitor golf ball compression so long as the
correlation to PGA compression is known. These devices have been
designed, such as a Whitney Tester, to correlate or correspond to
PGA compression through a set relationship or formula.
Core
[0054] The core which is used to form the golf balls of the present
invention can be solid, foamed, wound, hollow or liquid. The core
can be unitary, or can have two or more core layers. A solid core
or solid layer of a multi-layer core can be thermosetting or
thermoplastic. Preferably, the core is solid and is formed from a
thermoset material.
[0055] Solid cores of the more preferred embodiment of the present
invention can be manufactured using relatively conventional
techniques. In this regard, the core compositions of the invention
may be based on polybutadiene, natural rubber, metallocene
catalyzed polyolefins such as Exact.RTM. (Exxon Chem. Co.) and
Engage.RTM. (Dow Chem. Co.), polyurethanes, other thermoplastic or
thermoset elastomers, and mixtures of one or more of the above
materials with each other and/or with other elastomers. The core
may be formed from a uniform composition or may be a dual or
multi-layer core. The core may be foamed or unfoamed.
[0056] It is preferred that the base elastomer have a relatively
high molecular weight. Polybutadiene has been found to be
particularly useful because it imparts to the golf balls a
relatively high coefficient of restitution. Polybutadiene can be
cured using a free radical initiator such as a peroxide, or can be
sulfur cured. A broad range for the molecular weight of preferred
base elastomers is from about 50,000 to about 500,000. A more
preferred range for the molecular weight of the base elastomer is
from about 100,000 to about 500,000. As a base elastomer for the
core composition, cis-1-4-polybutadiene is preferably employed, or
a blend of cis-1-4-polybutadiene with other elastomers may also be
utilized. Most preferably, cis-1-4-polybutadiene having a
weight-average molecular weight of from about 100,000 to about
500,000 is employed. Along this line, it has been found that the
high cis-1-4-polybutadienes manufactured and sold by Bayer Corp.,
Germany, under the trade name Taktene.RTM. 220 or 1220 are
particularly preferred. Furthermore, the core may be comprised of a
crosslinked natural rubber, EPDM, metallocene catalyzed polyolefin,
or another crosslinkable elastomer.
[0057] When polybutadiene is used for golf ball cores, it commonly
is crosslinked with an unsaturated carboxylic acid co-crosslinking
agent. The unsaturated carboxylic acid component of the core
composition typically is the reaction product of the selected
carboxylic acid or acids and an oxide or carbonate of a metal such
as zinc, magnesium, barium, calcium, lithium, sodium, potassium,
cadmium, lead, tin, and the like. Preferably, the oxides of
polyvalent metals such as zinc, magnesium and cadmium are used, and
most preferably, the oxide is zinc oxide.
[0058] Exemplary of the unsaturated carboxylic acids which find
utility in the core compositions are acrylic acid, methacrylic
acid, itaconic acid, crotonic acid, sorbic acid, and the like, and
mixtures thereof. Preferably, the acid component is either acrylic
or methacrylic acid. Usually, from about 5 to about 40, and
preferably from about 15 to about 30 parts by weight of the
carboxylic acid salt, such as zinc diacrylate, is included in the
core composition. The unsaturated carboxylic acids and metal salts
thereof are generally soluble in the elastomeric base, or are
readily dispersible.
[0059] The free radical initiator included in the core composition
is any known polymerization initiator (a co-crosslinking agent)
which decomposes during the cure cycle. The term "free radical
initiator" as used herein refers to a chemical which, when added to
a mixture of the elastomeric blend and a metal salt of an
unsaturated, carboxylic acid, promotes crosslinking of the
elastomers by the metal salt of the unsaturated carboxylic acid.
The amount of the selected initiator present is dictated only by
the requirements of catalytic activity as a polymerization
initiator. Suitable initiators include peroxides, persulfates, azo
compounds and hydrazides. Peroxides which are readily commercially
available are conveniently used in the present invention, generally
in amounts of from about 0.1 to about 10.0 and preferably in
amounts of from about 0.3 to about 3.0 parts by weight per each 100
parts of elastomer.
[0060] Exemplary of suitable peroxides for the purposes of the
present invention are dicumyl peroxide, n-butyl 4,4'-bis
(butylperoxy) valerate, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl
cyclohexane, di-t-butyl peroxide and 2,5-di-(t-butylperoxy)-2,5
dimethyl hexane and the like, as well as mixtures thereof. It will
be understood that the total amount of initiators used will vary
depending on the specific end product desired and the particular
initiators employed.
[0061] Examples of such commercially available peroxides are
Luperco.RTM. 230 or 231 XL sold by Atochem, Lucidol Division,
Buffalo, N.Y., and Trigonox.RTM. 17/40 or 29/40 sold by Akzo
Chemicals, America, Chicago, Ill. In this regard Luperco.RTM. 230
XL and Trigonox.RTM. 29/40 are comprised of
1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane. The one hour
half life of Luperco.RTM. 231 XL is about 112.degree. C., and the
one hour half life of Trigonox.RTM. 29/40 is about 129.degree.
C.
[0062] The core compositions of the present invention may
additionally contain any other suitable and compatible modifying
ingredients including, but not limited to, metal oxides, fatty
acids, and diisocyanates and polypropylene powder resin. For
example, Papi.RTM. 94, a polymeric diisocyanate, commonly available
from Dow Chemical Co., Midland, Mich., is an optional component in
the rubber compositions. It can range from about 0 to 5 parts by
weight per 100 parts by weight rubber (phr) component, and acts as
a moisture scavenger. In addition, it has been found that the
addition of a polypropylene powder resin results in a core which is
hard (i.e. exhibits high PGA compression) and thus allows for a
reduction in the amount of crosslinking co-agent utilized to soften
the core to a normal or below normal compression.
[0063] Furthermore, because polypropylene powder resin can be added
to a core composition without an increase in weight of the molded
core upon curing, the addition of the polypropylene powder allows
for the addition of higher specific gravity fillers, such as
mineral fillers. Since the crosslinking agents utilized in the
polybutadiene core compositions are expensive and/or the higher
specific gravity fillers are relatively inexpensive, the addition
of the polypropylene powder resin substantially lowers the cost of
the golf ball cores while maintaining, or lowering, weight and
compression.
[0064] The polypropylene (C.sub.3H.sub.5) powder suitable for use
in the present invention has a specific gravity of about 0.90
g/cm.sup.3, a melt flow rate of about 4 to about 12 and a particle
size distribution of greater than 99% through a 20 mesh screen.
Examples of such polypropylene powder resins include those sold by
the Amoco Chemical Co., Chicago, Ill., under the designations "6400
P", "7000 P" and "7200 P". Generally, from 0 to about 25 parts by
weight polypropylene powder per each 100 parts of elastomer are
included in the present invention.
[0065] Various activators may also be included in the compositions
of the present invention. For example, zinc oxide and/or magnesium
oxide are activators for the polybutadiene. The activator can range
from about 2 to about 30 parts by weight per 100 parts by weight of
the rubbers (phr) component.
[0066] Moreover, reinforcement agents may be added to the core
compositions of the present invention. Since the specific gravity
of polypropylene powder is very low, and when compounded, the
polypropylene powder produces a lighter molded core, when
polypropylene is incorporated in the core compositions, relatively
large amounts of higher specific gravity fillers may be added so
long as the specific core weight limitations are met. As indicated
above, additional benefits may be obtained by the incorporation of
relatively large amounts of higher specific gravity, inexpensive
mineral fillers such as calcium carbonate. Such fillers as are
incorporated into the core compositions should be in finely divided
form, as for example, in a size generally less than about 30 mesh
and preferably less than about 100 mesh U.S. standard size. The
amount of additional filler included in the core composition is
primarily dictated by weight restrictions and preferably is
included in amounts of from about 10 to about 100 parts by weight
per 100 parts rubber.
[0067] The preferred fillers are relatively inexpensive and heavy
and serve to lower the cost of the ball and to increase the weight
of the ball to closely approach the U.S.G.A. weight limit of 1.620
ounces. However, if thicker cover compositions are to be applied to
the core to produce larger than normal (i.e. greater than 1.680
inches in diameter) balls, use of such fillers and modifying agents
will be limited in order to meet the U.S.G.A. maximum weight
limitations of 1.620 ounces. Limestone is ground calcium/magnesium
carbonate and is used because it is an inexpensive, heavy filler.
Ground flash filler may be incorporated and is preferably 20 mesh
ground up center stock from the excess flash from compression
molding. It lowers the cost and may increase the hardness of the
ball.
[0068] Fatty acids or metallic salts of fatty acids may also be
included in the compositions, functioning to improve moldability
and processing. Generally, free fatty acids having from abut 10 to
about 40 carbon atoms, and preferably having from about 15 to about
10 carbon atoms, are used. Exemplary of suitable fatty acids are
stearic acid and linoleic acids, as well as mixtures thereof. An
example of a suitable metallic salt of a fatty acid is zinc
stearate. When included in the core compositions, the metallic
salts of fatty acids are present in amounts of from about 1 to
about 25, preferably in amounts from about 2 to about 15 parts by
weight based on 100 parts rubber (elastomer). It is preferred that
the core compositions include stearic acid as the fatty acid
adjunct in an amount of from about 2 to about 5 parts by weight per
100 parts of rubber.
[0069] Diisocyanates may also be optionally included in the core
compositions. When utilized, the diisocyanates are included in
amounts of from about 0.2 to about 5.0 parts by weight based on 100
parts rubber. Exemplary of suitable diisocyanates is
4,4'-diphenylmethane diisocyanate and other polyfunctional
isocyanates known in the art.
[0070] Furthermore, the dialkyl tin difatty acids set forth in U.S.
Pat. No. 4,844,471, the dispensing agents disclosed in U.S. Pat.
No. 4,838,556, and the dithiocarbamates set forth in U.S. Pat. No.
4,852,884 may also be incorporated into the polybutadiene
compositions of the present invention. The specific types and
amounts of such additives are set forth in the above identified
patents, which are incorporated herein by reference.
[0071] The core compositions of the invention which contain
polybutadiene are generally comprised of 100 parts by weight of a
base elastomer (or rubber) selected from polybutadiene and mixtures
of polybutadiene with other elastomers, 15 to 25 parts by weight of
at least one metallic salt of an unsaturated carboxylic acid, and
0.5 to 10 parts by weight of a free radical initiator.
[0072] As indicated above, additional suitable and compatible
modifying agents such as particulate polypropylene resin, fatty
acids, and secondary additives such as pecan shell flour, ground
flash (i.e. grindings from previously manufactured cores of
substantially identical construction), barium sulfate, zinc oxide,
etc. may be added to the core compositions to adjust the weight of
the ball as necessary in order to have the finished molded ball
(core, cover and coatings) to closely approach the U.S.G.A. weight
limit of 1.620 ounces.
[0073] In producing solid golf ball cores utilizing the present
compositions, the ingredients may be intimately mixed using, for
example, two roll mills or an internal mixer until the composition
is uniform, usually over a period of from about 5 to about 20
minutes. The sequence of addition of components is not critical. A
preferred blending sequence is as follows.
[0074] The elastomer, polypropylene powder resin (if desired),
fillers, zinc salt, metal oxide, fatty acid, and the metallic
dithiocarbamate (if desired), surfactant (if desired), and tin
difatty acid (if desired), are blended for about 7 minutes in an
internal mixer such as a Banbury.RTM. (Farrel Corp.) mixer. As a
result of shear during mixing, the temperature rises to about
200.degree. F. The initiator and diisocyanate are then added and
the mixing continued until the temperature reaches about
220.degree. F. whereupon the batch is discharged onto a two roll
mill, mixed for about one minute and sheeted out.
[0075] The sheet is rolled into a "pig" and then placed in a
Barwell.TM. preformer and slugs are produced. The slugs are then
subjected to compression molding at about 320.degree. F. for about
14 minutes. After molding, the molded cores are cooled, the cooling
effected at room temperature for about 4 hours or in cold water for
about one hour. The molded cores can be subjected to a centerless
grinding operation whereby a thin layer of the molded core is
removed to produce a round core having a diameter of 1.2 to 1.5
inches. Alternatively, the cores are used in the as-molded state
with no grinding needed to achieve roundness.
[0076] The mixing is desirably conducted in such a manner that the
composition does not reach incipient polymerization temperatures
during the blending of the various components.
[0077] Usually the curable component of the composition will be
cured by heating the composition at elevated temperatures on the
order of from about 275.degree. F. to about 350.degree. F.,
preferably and usually from about 290.degree. F. to about
325.degree. F., with molding of the composition effected
simultaneously with the curing thereof. The composition can be
formed into a core structure by any one of a variety of molding
techniques, e.g. injection, compression, or transfer molding. When
the composition is cured by heating, the time required for heating
will normally be short, generally from about 10 to about 20
minutes, depending upon the particular curing agent used. Those of
ordinary skill in the art relating to free radical curing agents
for polymers are conversant with adjustments of cure times and
temperatures required to effect optimum results with any specific
free radical agent.
[0078] After molding, the core is removed from the mold and the
surface thereof optionally is treated to facilitate adhesion
thereof to the covering materials. Surface treatment can be
effected by any of the several techniques known in the art, such as
corona discharge, ozone treatment, sand blasting, and the like.
Preferably, surface treatment is effected by grinding with an
abrasive wheel.
[0079] In addition to using solid molded cores, wound cores may
also be incorporated in the golf balls of the present invention.
Such wound cores would include a generally spherical center and a
rubber thread layer, or windings, enclosing the outer surface of
the center.
[0080] In this regard, the generally spherical center of the wound
cores may be a solid center or a liquid center. The solid center
can consist of one or more layers. For example, the solid center
can comprise a molded polybutadiene rubber sphere which, although
smaller in size, is of similar construction to the molded cores in
the two-piece molded golf balls described above.
[0081] Suitable solid centers used in the invention are not
particularly limited to, but include those made of vulcanized
rubber. Such solid centers may be prepared by adding to butadiene
rubber, additives such as vulcanizing agents, accelerators,
activating agents, fillers, modifiers and aids and then subjecting
the mixture to vulcanization and molding.
[0082] The solid center (whether of single unitary construction or
of multi-layers) generally is from 1 to 1.5 inches in diameter,
preferably 1.0625 to 1.42 inches, with a weight of 15 grams to 36
grams, preferably 16.5 to 30 grams.
[0083] Alternatively, a liquid center can be incorporated into the
wound core of the present invention. The liquid center consists of
a hollow spherical bag or sack of conventional vulcanized rubber
filled with a liquid, paste or gel. Examples of such a liquid
include water, glycerin, sugar-water solutions, corn-syrup, saline
solutions, oils, etc. and/or combinations thereof. Examples of
pastes can be produced by adding clay, sodium sulfate, barytes,
barium sulfate to a minor amount of ethylene glycol in water.
Examples of suitable gels include hydrogels, cellulose gels, water
gels, etc. The specific gravity of the liquid is, in general, 0.6
to 3 and the specific gravity of the paste is from 0.6 to 3 and the
gels from 0.6 to 3. The bag or sack is, in general, from 0.05 to
0.150 inches in thickness, preferably 0.08 to 0.105 inches in
thickness.
[0084] The liquid center generally is from 1 to 1.25 inches in
diameter, preferably 1.0625 to 1.14 inches, with a weight of 5.5 to
25.5 grams, preferably 15 to 21 grams.
[0085] The wound core is formed by winding conventional thread
rubber around the outer periphery of the solid or liquid center.
The thread rubber may include, for example, those prepared by
subjecting natural rubber, or a blend of natural rubber and
polyisoprene rubber to vulcanization and molding. The winding
process is under high tension to produce a threaded layer over the
solid or liquid center. Conventional techniques may be employed in
winding the thread rubber and known compositions may be used.
Although the thread rubber is not limited with respect to specific
gravity, dimension and gage, it usually has a specific gravity of
0.9 to 1.1, a width of 0.047 to 0.094 and a gage of 0.012 to
0.026.
[0086] The rubber thread layer has a radial thickness of 0.10 to
0.315 inches and comprises a wound core having an outer diameter of
1.52 to 1.63 inches. The overall weight of the wound core is 33 to
44 grams, preferably 35 to 39 grams.
Multi-Layer Covers
[0087] As indicated above, cover layers of the present invention
golf ball preferably but not necessarily comprise an ionomer resin.
High or low acid ionomers, or ionomer blends can be used, along
with polyurethane, polyurea and blends thereof. The high acid
ionomers which may be suitable for use in formulating the cover
compositions are ionic copolymers which are the metal, i.e.,
sodium, zinc, magnesium, lithium, 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 at
least partially neutralized (i.e., approximately 10% to 100%, and
preferably 30% to 70%) by the metal ions. Each of the high acid
ionomer resins contains greater than about 16% by weight of a
carboxylic acid, and preferably from about 17% to about 25% by
weight of a carboxylic acid, and more preferably from about 18.5%
to about 21.5% by weight of a carboxylic acid.
[0088] The high acid ionomeric resins available from Exxon under
the designation lotek.RTM., are somewhat similar to the high acid
ionomeric resins available under the Surlyn.RTM. trademark.
However, since the lotek.RTM. ionomeric resins are sodium, lithium
or zinc salts of poly(ethylene-acrylic acid) and the Surlyn.RTM.
resins are zinc, sodium, lithium, etc. salts of
poly(ethylene-methacrylic acid), distinct differences in properties
exist.
[0089] Non-limiting examples of the high acid methacrylic acid
based ionomers suitable for use in accordance with this invention
include Surlyn.RTM. 8140(Na), 8220 (Na), 8240 (Na), 9120 (Zn), 9220
(Zn), AD8181 (Li), AD8530 (Zn), AD8531 (Na) and SEP 671 (Li). Table
1, set forth below, lists properties for two of these
materials.
1TABLE 1 Surlyn .RTM. Resins SURLYN .RTM. 8140 SURLYN .RTM. 120 (19
wt % acid) (19 wt % acid) IONOMER Cation Na Zn Melt Flow Index,
g/10 min. 2.60 1.30 Specific gravity 0.96 0.97 MP, C. 88 85 FP, C.
49 50 MECHANICAL PROPERTIES Tensile Strength, kpsi (MPa) 5.0 (34.5)
3.8 (26.2) Yield Strength, kpsi (MPa) 2.8 (19.3) 2.4 (16.6)
Elongation, % 340 280 Flex Mod, kpsi (MPa) 71 (490) 84 (440) Shore
D Hardness 70 69
[0090] Examples of the high acid acrylic acid based ionomers
suitable for use in the present invention also include lotek.RTM.
high acid ethylene acrylic acid ionomers produced by Exxon such as
1001, 1002, 959, 960, 989, 990, 1003, 1004, 993, and 994. In this
regard, lotek.RTM. 959 is a sodium ion neutralized ethylene-acrylic
acid copolymer. According to Exxon, lotek.RTM. 959 and 960 contain
from about 19.0 to about 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 and other high acid acrylic acid based ionomers are set forth
in Table 2 as follows:
2TABLE 2 Iotek .RTM. Resins PROPERTY 1001 1002 959 1003 1004 960
Melt index, 1.00 1.60 2.00 1.10 2.00 1.80 g/10 min. Cation Na Na Na
Zn Zn Zn Melting 183.0 183.0 172.0 180.0 180.5 174.0 point, F.
Crystalliza- 107.0 110.0 106.0 125.0 126.5 120.0 tion point, F.
Vicat 125.0 125.0 130.0 133.0 131.0 131.0 Softening Point, F.
Tensile @@ 34.4 31.7 4600 24.8 20.6 3500 Break MPa MPa psi MPa MPa
psi Tensile @@ 21.8 22.5 -- 14.9 14.0 -- Yield MPa MPa MPa MPa 1%
Secant 356 418 350 145 128 140 Modulus MPa MPa MPa MPa MPa MPa
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 Density .9558 .9557 .968 .9715 .9691 .980
g/cm.sup.3 g/cm.sup.3 g/cm.sup.3 g/cm.sup.3 g/cm.sup.3 g/cm.sup.3
EX 989 EX 993 EX 994 EX 990 Melt index g/10 min 1.30 1.25 1.32 1.24
Moisture ppm 482 214 997 654 Cation Type -- Na Li K Zn M+ content
wt % 2.74 0.87 4.54 0.00 by AAS Zn content wt % 0.00 0.00 0.00 3.16
by AAS Density kg/m3 959 945 976 977 Vicat soften- C. 52.5 51.0
50.0 55.0 ing point Crystalliza- C. 40.1 39.8 44.9 54.4 tion point
Melting C. 82.6 81.0 80.4 81.0 point Tensile at MPa 23.8 24.6 22.0
16.5 yield Tensile at MPa 32.3 31.1 29.7 23.8 break Elongation at %
330 260 340 357 break 1% secant MPa 389 379 312 205 modulus
Flexural MPa 340 368 303 183 modulus Abrasion mg 20.0 9.2 15.2 20.5
resistance Hardness -- 62 62.5 61 56 Shore D Zwick % 61 63 59 48
rebound
[0091] Furthermore, as a result of the development by the assignee
of this application of a number of new ionomers neutralized to
various extents by several different types of metal cations, such
as by manganese, lithium, potassium, calcium and nickel cations,
several new ionomers and/or ionomer blends besides sodium, zinc and
magnesium high acid ionomers or ionomer blends are now available
for golf ball cover production. In particular it has been found
that 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.
[0092] More particularly, several new metal cation neutralized high
acid ionomer resins have been produced by the inventor 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. 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%).
[0093] The base copolymer is made up of greater than 16% by weight
of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin.
As indicated above, 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.
[0094] 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.
[0095] 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.
[0096] 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 Dow Chemical Company, Midland, Michigan, under the
Primacor.RTM. designation. These high acid base copolymers exhibit
the typical properties set forth below in Table 3.
3TABLE 3 Typical Properties of Primacor .RTM. Ethylene-Acrylic Acid
Copolymers MELT INDEX, g/10 TENSILE FLEXURAL VICAT DENSITY, min YD.
ST MODULUS SOFT PT SHORE D GRADE PERCENT g/cc D-1238, (psi) (psi)
(C.) HARDNESS ASTM ACID D-792 190 C. D-638 D-790 D-1525 D-2240 5980
20 0.96 300 -- 4800 43 50 5990 20 0.96 1300 650 2600 40 42 5981 20
0.96 300 900 3200 46 48 5983 20 0.96 500 850 3100 44 45 5991 20
0.95 2600 635 2600 38 40
[0097] Due to the high molecular weight of the Primacor.RTM. 5981
grade of the ethylene-acrylic acid copolymer, this copolymer is the
more preferred grade utilized in the invention.
[0098] The metal cation salts utilized in the present 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.
[0099] 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, and
magnesium acetate. Sources of manganese include manganese acetate
and manganese oxide.
[0100] 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 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%.
[0101] When the acid groups of copolymers of acrylic acid and
ethylene sold by Dow Chemical Co. (Midland, Mich.) and designated
as Primacor.RTM. 5981 were neutralized to various weight
percentages using a number of different cations, a number of
different high acid ionomer resins were produced. Due to
differences in the nature of the cation salts, the amount of cation
salts utilized, etc., the new high acid ionomer resins produced
differed substantially in the extent of neutralization and in melt
indices, as well as in resilience (i.e. C.O.R.) and hardness
values.
[0102] For the purpose of determining the weight percent of
neutralization of the carboxylic acid groups in the acrylic
acid/ethylene copolymer after reacting with various cation salts,
it was assumed that one mole of sodium (Na.sup.+), potassium
(K.sup.+), and lithium (Li.sup.+) neutralized one mole of acrylic
acid, and that one mole of zinc (Zn.sup.2+), magnesium (Mg.sup.2+),
manganese (Mn.sup.2+), calcium (Ca.sup.2+) and nickel (Ni.sup.2+)
neutralized two moles of acrylic acid. The calculations of
neutralization were based upon an acrylic acid molecular weight of
79 g/m, giving 0.2778 moles per 100 grams of copolymer.
[0103] As indicated below in Table 4, the various cation salts were
added in variable amounts to the 20 weight percent acrylic
acid/ethylene copolymer in order to determine the optimal level of
neutralization for each of the cations. In Table 4, NaOH refers to
sodium hydroxide (formula weight of 40). MnAc refers to manganese
acetate tetrahydrate having a formula weight of 245. LiOH is
lithium hydroxide, fwt=24. KOH is potassium hydroxide, fwt=56. ZnAc
is zinc acetate dihydrate, fwt=219.5. MgAc is magnesium acetate
tetrahydrate, fwt=214.4. CaAc is calcium acetate, fwt=158. MgO is
magnesium oxide, fwt=40.3. NiAc is nickel acetate, fwt=176.8. All
of these cation salts are solids at room temperature.
[0104] The specific cation salts were added in differing amounts
with the 20 weight percent acrylic acid/ethylene copolymer (i.e.
the Primacor.RTM. 5981) to an internal mixer (Banbury.RTM. type)
for the neutralization reaction. The only exception was calcium
acetate, which, due to problems encountered in solid form, was
added as a 30 wt % solution in water.
[0105] In the neutralization reaction, the cation salts solubilized
in the Primacor.RTM. 5981 acrylic acid/ethylene copolymer above the
melting point of the copolymer and a vigorous reaction took place
with a great deal of foaming occurring as the cation reacted with
the carboxylic acid groups of the acrylic acid/ethylene copolymer
and the volatile by-products of water (in the case of oxides or
hydroxides) or acetic acid (when acetates are used) were
evaporated. The reaction was continued until foaming ceased (i.e.
about 30-45 minutes at 250 to 350.degree. F.), and the batch was
removed from the Banbury.RTM. mixer. Mixing continued of the batch
obtained from the mixer on a hot two-roll mill (175 to 250.degree.
F.) to complete the neutralization reaction. The extent of the
reaction was monitored by measuring melt flow index according to
ASTM D-1238-E. As indicated below, the neutralized products
exhibited different properties depending upon the nature and amount
of the cation salts utilized.
4TABLE 4 Wt % Wt % Formulation Cation Neutral- Melt Shore D No.
Salt ization Index C.O.R. Hardness 1(NaOH) 6.98 67.50 0.90 0.80 71
2(NaOH) 5.66 54.00 2.40 0.81 73 3(NaOH) 3.84 35.90 12.20 0.81 69
4(NaOH) 2.91 27.00 17.50 0.81 (brittle) 5(MnAc) 19.60 71.70 7.50
0.81 73 6(MnAc) 23.10 88.30 3.50 0.81 77 7(MnAc) 15.30 53.00 7.50
0.81 72 8(MnAc) 26.50 106.00 0.70 0.81 (brittle) 9(LiOH) 4.54 71.30
0.60 0.81 74 10(LiOH) 3.38 52.50 4.20 0.82 72 11(LiOH) 2.34 35.90
18.60 0.81 72 12(KOH) 5.30 36.00 19.30 Broke 70 13(KOH) 8.26 57.90
7.18 0.80 70 14(KOH) 10.70 77.00 4.30 0.80 67 15(ZnAc) 17.90 71.50
0.20 0.81 71 16(ZnAc) 13.90 53.00 0.90 0.80 69 17(ZnAc) 9.91 36.10
3.40 0.79 67 18(MgAc) 17.40 70.70 2.80 0.81 74 19(MgAc) 20.60 87.10
1.50 0.81 76 20(MgAc) 13.80 53.80 4.10 0.81 74 21(CaAc) 13.20 69.20
1.10 0.81 74 22(CaAc) 7.12 34.90 10.10 0.81 70 Controls: 50/50
Blend of Ioteks .RTM. 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 .RTM. EX-960 (Zn) C.O.R. =
.796/65 Shore D Hardness Wt % Formulation Cation Wt % Melt No. Salt
Neutralization Index C.O.R. 23(MgO) 2.91 53.50 2.50 0.81 24(MgO)
3.85 71.50 2.80 0.81 25(MgO) 4.76 89.30 1.10 0.81 26(MgO) 1.96
35.70 7.50 0.81 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. Wt % Formulation Cation Wt % Melt Shore D
No. Salt Neutralization Index C.O.R. Hardness 27(NiAc) 13.04 61.10
0.20 0.80 71 28(NiAc) 10.71 48.90 0.50 0.80 72 29(NiAc) 8.26 36.70
1.80 0.80 69 30(NiAc) 5.66 24.40 7.50 0.79 64 Control for
formulation No. 27-30 is 50/50 Iotek 8000/7030, C.O.R. = .807
[0106] 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.
[0107] As will be further noted in the examples below, either or
both high and low acid ionomer resins may be used in the cover
compositions so long as the molded cover layers have a Shore D
hardness of 60 or more, and more preferably 55 or more.
[0108] For example, one or more low acid (i.e. 16 weight % and/or
less) hard ionomers may be included in the present invention. The
hard (high modulus) ionomers suitable for use in the present
invention include those ionomers having a hardness greater than 50
on the Shore D scale as measured in accordance with ASTM method
D-2240, and a flexural modulus from about 15,000 to about 70,000
psi as measured in accordance with ASTM method D-790.
[0109] The hard ionomer resins utilized to produce the cover
compositions are ionic copolymers which are the sodium, zinc,
magnesium or lithium salts of the reaction product of an olefin
having from 2 to 8 carbon atoms and an unsaturated monocarboxylic
acid having from 3 to 8 carbon atoms. The carboxylic acid groups of
the copolymer may be totally or partially (i.e. approximately 15-75
percent) neutralized.
[0110] Preferably, the hard ionomeric resins are copolymers of
ethylene and either acrylic and/or methacrylic acid, with
copolymers of ethylene and acrylic acid the most preferred. In
addition, two or more types of hard ionomeric resins may be blended
into the cover compositions in order to produce the desired
properties of the resulting golf balls.
[0111] Examples of commercially available hard ionomeric resins
which may be utilized in the present invention 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 with about 15 weight percent acid which is about
29% 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% 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.
5TABLE 5 Typical Properties of Commercially Available Hard Surlyn
.RTM. Resins Suitable for Use in the Present Invention ASTM D 8940
9910 8920 8528 9970 9730 Cation Type Sodi- Zinc Sodi- Sodi- Zinc
Zinc um um um Melt flow index, D01238 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-2240 66 64 66 60 62 63 D 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 D-790 (51) (48) (55) (32) (28) (30) Modulus,
(kpsi) 350 330 380 220 190 210 MPa Tensile Impact D-18225 1020 1020
865 1160 760 1240 (23.degree. C.) (485) (485) (410) (550) (360)
(590) KJ/m.sub.2 (ft.-lbs./ in.sup.2) Vicat Tempera- D-1525 63 62
58 73 61 73 ture, .degree. C.
[0112] In addition, examples of the more pertinent acrylic acid
based hard ionomer resins suitable for use in the present invention
sold under the lotek.RTM. trademark by the Exxon Corporation
include lotek.RTM. 4000 (formerly Escor.RTM. 4000), lotek.RTM.
4010, lotek.RTM. 8000 (formerly Escor.RTM. 900), lotek.RTM. 8020,
and lotek.RTM. 8030. The typical properties of the lotek.RTM. hard
ionomers are set forth below in Table 6.
6TABLE 6 Typical Properties of Iotek .RTM. Ionomers ASTM Method
Units 4000 4010 8000 8020 8030 Resin Properties Cation Type zinc
zinc sodium sodium sodium Melt Index D-1238 g/10 2.50 1.50 0.80
1.60 2.80 min. Density D-1505 kg/m.sup.3 963.00 963.00 954.00
960.00 960.00 Melting Point D-3417 C. 90.0 90.0 90.0 87.5 87.5
Crystallization Point D-3417 C. 62 64 56 53 55 Vicat Softening
Point D-1525 C. 62 63 61 64 67 % Wt Acrylic Acid 16 11 % of Acid
Groups 30 40 cation neutralized Plaque Properties (3 mm thick,
compression molded) Tensile at break D-638 MPa 24.0 26.0 36.0 31.5
28.0 Yield point D-638 MPa none none 21.0 21.0 23.0 Elongation at
break D-638 % 395 420 350 410 395 1% Secant modulus D-638 MPa 160
160 300 350 390 Shore Hardness D D-2240 -- 55 55 61 58 59 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/ 12.40
12.50 20.30 micron ASTM Method Units 7010 7020 7030 Resin
Properties Cation type zinc zinc zinc Melt Index D-1238 g/10 min.
0.80 1.50 2.50 Density D-1505 kg/m.sup.3 960 960 960 Melting Point
D-3417 C. 90 90 90 Crystallization Point D-3417 C. -- -- -- Vicat
Softening Point D-1525 C. 60 63 62.5 % Wt Acrylic Acid -- -- -- %
of Acid Groups -- -- -- cation neutralized Plaque Properties (3 mm
thick, compression molded) Tensile at break D-638 MPa 38 38 38
Yield Point D-638 MPa none none none Elongation at break D-638 %
500 420 395 1% Secant modulus D-638 MPa -- -- -- Shore Hardness D
D-2240 -- 57 55 55
[0113] In addition to the above, non-ionomeric materials can also
be blended with the ionomers, or used separately, to produce the
cover layer of the invention. Non-limiting examples of materials
that can be utilized include ethylene-ethyl acrylate,
ethylene-methyl acrylate, ethylene-vinyl acetate, low density
polyethylene, linear low density polyethylene, metallocene
catalyzed polyolefins such as Engage.RTM. polyolefins available
from Dow Chemical and Exact.RTM. polyolefins available from Exxon,
non-ionomeric acid copolymers such as Primacor.RTM., available from
Dow Chemical, and Nucrel.RTM., available from DuPont, and a variety
of thermoplastic elastomers, including Kraton.RTM., available from
Shell, Santoprene.RTM., available from Monsanto, and Hytrel.RTM.,
available from DuPont, etc. Furthermore functionalized EPDM, such
as maleated EPDM, nylon, and nylon-ionomer graft copolymers.
[0114] A wide array of nylon-containing or nylon-based materials
may be incorporated into the various cover layers of the present
invention golf ball. Preferred nylon materials for utilizing in the
present invention golf ball are described in U.S. Pat. No.
5,886,103 herein incorporated by reference.
[0115] Moreover, a wide array of polyurethane materials can be
utilized in one or more cover layers of the present invention golf
balls. Before turning attention to the specifics of such materials,
it is instructive to review the features and terminology associated
with polyurethanes.
[0116] Polyurethanes are polymers which are used to form a broad
range of products. They are generally formed by mixing two primary
ingredients during processing. For the most commonly used
polyurethanes, the two primary ingredients are a polyisocyanate
(for example, diphenylmethane diisocyanate monomer ("MDI") and
toluene diisocyanate ("TDI") and their derivatives) and a polyol
(for example, a polyester polyol or a polyether polyol).
[0117] A wide range of combinations of polyisocyanates and polyols,
as well as other ingredients, are available. Furthermore, the
end-use properties of polyurethanes can be controlled by the type
of polyurethane utilized, i.e., whether the material is thermoset
(cross linked molecular structure) or thermoplastic (linear
molecular structure).
[0118] Crosslinking occurs between the isocyanate groups (--NCO)
and the polyol's hydroxyl end-groups (--OH). Additionally, the
end-use characteristics of polyurethanes can also be controlled by
different types of reactive chemicals and processing parameters.
For example, catalysts are utilized to control polymerization
rates. Depending upon the processing method, reaction rates can be
very quick (as in the case for some reaction injection molding
systems (i.e., "RIM")) or may be on the order of several hours or
longer (as in several coating systems). Consequently, a great
variety of polyurethanes are suitable for different end-users.
[0119] Polyurethane has been used for golf balls and other game
balls as a cover material. Polyurethanes are typically classified
as thermosetting or thermoplastic. Commercially available
polyurethane golf balls have been made of thermoset polyurethanes.
A polyurethane becomes irreversibly "set" when a polyurethane
prepolymer is crosslinked with a polyfunctional curing agent, such
as polyamine and polyol. The prepolymer typically is made from
polyether or polyester. Diisocyanate polyethers are preferred
because of their water resistance.
[0120] The physical properties of thermoset polyurethanes are
controlled substantially by the degree of crosslinking. Tightly
crosslinked polyurethanes are fairly rigid and strong. A lower
amount of crosslinking results in materials that are flexible and
resilient. Thermoplastic polyurethanes have some crosslinking, but
purely by physical means. The crosslinking bonds can be reversibly
broken by increasing temperature, as occurs during molding or
extrusion. In this regard, thermoplastic polyurethanes can be
injection molded, and extruded as sheet and blown film. They can be
used to up to about 350.degree. F. and are available in a wide
range of hardnesses.
[0121] U.S. Pat. No. 5,006,297 indicates that while thermoplastic
and thermosetting polyurethanes are known, thermosets have been
found to produce better cover stocks for golf balls. Additionally,
while thermoplastic polyurethanes can be used to form game balls,
they lack the scuff and cut resistance of a crosslinked
polyurethane. Similarly, thermoplastic polyurethanes do not readily
crosslink.
[0122] Polyurethanes typically are formed by reacting a polyol with
a polyisocyanate. In some cases, the polyisocyanate is in the form
of a polyurethane prepolymer formed from a polyether or polyester
and a polyisocyanate. The polyol or polyamine is typically referred
to as a "curing" agent. Examples of reactants used to form
polyurethanes by this technique are discussed in U.S. Pat. No.
5,006,297, herein incorporated by reference. In other cases a
polyester or acrylic polyol is reacted with a polyisocyanate.
[0123] Two types of polyisocyanates are predominantly used to make
polyurethanes, diphenylmethane diisocyanate monomer (MDI) and its
derivatives, and toluene diisocyanate (TDI) and its
derivatives.
[0124] MDI is the most widely used polyisocyanate. Both rigid and
flexible foams, reaction injection moldings, elastomers, coatings,
and casting compounds are made from MDI. There are three basic
grades of MDI: polymeric MDI, pure MDI, and pure MDI
derivatives.
[0125] Polymeric MDI is used in both cellular and non-cellular
products. However, because of the high thermal insulation
properties possible with polymeric MDI, its main use is in
closed-cell, rigid foam insulation for the construction and
refrigeration industries. Other uses are high-resilience (HR)
flexible foam, carpet backing, and binders.
[0126] Pure MDI, which is produced from polymeric MDI, is a
low-melting-temperature (about 100.degree. F.) solid. Its primary
use is in thermoplastic and cast elastomers. It also is used as an
additive for synthetic fibers to achieve high fiber tenacity and
elongation.
[0127] Pure MDI derivatives are tailored to provide specific
processing and reaction characteristics. A major use for these
solvent-free liquids is in reaction injection molding (RIM), but
they also find application in integral skin moldings, semi-flexible
moldings, and cast elastomers.
[0128] Toluene diisocyanate, TDI, is used almost exclusively to
make flexible foam. TDI, however, also finds some use in
elastomers, sealants, and coatings. TDI's generally are water-white
liquids which have much higher isocyanate (--NCO) contents than any
MDI, but lower molecular weights.
[0129] MDI and TDI also are blended, particularly for producing
flexible molded foams. The free-flowing, brown liquid blends have
nearly as high isocyanate contents as TDI.
[0130] Urethanes obtained from aromatic diisocyanates undergo slow
oxidation in the presence of air and light, causing discoloration,
which is unacceptable in some applications. Polyurethanes obtained
from aliphatic diisocyanates are color-stable, although it is
necessary to add antioxidants and uv-stabilizers to the formulation
to maintain the physical properties with time. The least costly
aliphatic diisocyanate is hexamethylene diisocyanate (HDI), which
is obtained by phosgenating the nylon intermediate
hexamethylenediamine. Because of its low boiling point, HDI is
mostly used in form of its derivatives, such as biurets,
allophanates, dimers, or trimers. It is contemplated that
isophorone diisocyanate (IPDI) and its derivatives; and
hydrogenated MDI (HMDI) and cyclohexame diisocyanate (CHDI) may be
used in the formulations described herein.
[0131] A wide array of isocyanates may be used in forming
polyurethanes for use in the present invention, such as p-phenylene
diisocyanate (PPDI) (CAS Registry No. 104-49-4); toluene
diisocyanate (TDI) (CAS Registry No. 1321-38-6);
4,4'-methylenebis-(phenylisocyanate) (MDI) (CAS Registry No.
101-68-8); polymethylene polyphenyl isocyanate (PMDI) (CAS Registry
No. 9016-87-9); 1,5-naphthalene diisocyanate (NDI) (CAS Registry
No. 3173-72-6); bitolylene diisocyanate (TODI) (CAS Registry No.
91-97-4); m-xylylene diisocyanate (XDI) (CAS Registry No.
3634-83-1); m-tetramethyl-xylylene (TMXDI) (CAS Registry No.
58067-42-8); hexamethylene diisocyanate (HDI) (CAS Registry No.
822-06-0); 1,6-diisocyanato-2,2,4,4-tetra-methylhexane (TMDI) (CAS
Registry No. 83748-30-5); 1,6-diisocyanato-2,4,4-trimethylhexane
(TMDI) (CAS Registry No. 15646-96-5);
trans-cyclohexane-1,4-diisocyanate (CHDI) (CAS Registry No.
2556-36-7); 1,3-bis(isocyanato-methyl)cyclohexane (HXDI) (CAS
Registry No. 38661-72-2);
3-isocyanato-methyl-3,5,5-trimethylcyclo-hexyl isocyanate (IPDI)
(CAS Registry No. 4098-171-9); dicyclohexylmethane diisocyanate
(HMDI) (CAS Registry No. 5124-30-1).
[0132] Two basic types of polyols are used in polyurethanes
systems: polyesters and polyethers. Polyethers are the most widely
used.
[0133] Often in referring to polyols, their functionality is
specified. The functionality pertains to the number of reactive
sites, which in turn, controls crosslinking. The more crosslinked
(higher functionality), the more rigid will be the polyurethane.
Functionality is controlled by the initiator used to manufacture
the polyol. Glycerine, for example, is commonly used to initiate
triol (3 functional) polyols. To this initiator is added an oxide
such as propylene oxide, ethylene oxide, or a combination, to
extend the molecular chain and tailor final processing and
performance characteristics of the polyol. Triols typically are
used to produce flexible foams; diols are used for elastomers,
coatings, and sealants; and tetrols typically are used for rigid
foams.
[0134] Polyether-based polyols have greater resistance to
hydrolysis. Polyether polyols can be modified by the in-situ
polymerization of acrylonitrile/styrene monomers. The resulting
graft polyols generally produce flexible foams with improved
load-bearing properties as well as greater tensile and tear
strengths. Depending on the backbone on which these vinyl monomers
are grafted, a wide range of performance characteristics can be
developed.
[0135] Polyether polyols are high molecular weight polymers that
range from viscous liquids to waxy solids, depending on structure
and molecular weight. Most commercial polyether polyols are based
on the less expensive ethylene or propylene oxide or on a
combination of the two. Block copolymers are manufactured first by
the reaction of propylene glycol with propylene oxide to form a
homopolymer. This polymer upon further reaction with ethylene oxide
to form the block copolymer. Because primary hydroxyl groups,
resulting from the polymerization of the ethylene oxide, are more
reactive than secondary hydroxyl groups, the polyols produced in
this manner are more reactive. Random copolymers are obtained by
polymerizing mixtures of propylene oxide and ethylene oxide. The
viscosity of polyether polyols increases with hydroxyl equivalent
weight. The higher molecular weight polyether polyols are soluble
in organic solvents. Poly(propylene oxide) is soluble in water up
to a molecular weight of 760, and copolymerization with ethylene
oxide expands the range of water solubility.
[0136] Polyester polyols yield polyurethanes with greater strength
properties, wear resistance, and thermal stability than polyether
polyurethanes, and they can absorb more energy. These materials,
however, are generally more expensive than polyethers.
[0137] Polyester polyols are based on saturated aliphatic or
aromatic carboxylic acids and diols or mixtures of diols. The
carboxylic acid of choice is adipic acid because of its favorable
cost/performance ratio. For elastomers, linear polyester polyols of
about 2000 mol wt are preferred. Branched polyester polyols,
formulated from higher functional glycols, are used for foam and
coatings applications. Phthalates and terephthalates are also
used.
[0138] Polyester polyols are typically classed by molecular weight.
Low molecular weight polyols (less than 1500) are used in coatings,
casting compounds, and rigid foams. Medium molecular weight polyols
(1550 to 2500) are used in elastomers. And, high molecular weight
polyols (greater than 2500) are used in flexible foams.
[0139] Thermoset polyurethanes are typically crosslinked and cannot
be repeatedly thermoformed. On the other hand, thermoplastic
polyurethanes are similar to other thermoplastics in that they can
be repeatedly plasticized by the influence of temperature and
pressure.
[0140] The crosslinkable thermoplastic polyurethane used to form a
game ball according to the present invention is initially a
thermoplastic, and in this state can be melted and solidified
repeatedly. However, the material can be readily crosslinked,
thereby increasing its hardness and providing that it cannot be
reversibly melted without thermal degradation.
[0141] The melt viscosity of a thermoplastic polyurethane (TPU)
depends on the weight-average molecular weight and is influenced by
chain length and branching. TPUs are viscoelastic materials, which
behave like a glassy, brittle solid, an elastic rubber, or a
viscous liquid, depending on temperature and time scale of
measurement. With increasing temperature, the material becomes
rubbery because of the onset of molecular motion. At higher
temperatures a free-flowing liquid forms.
[0142] The melt temperature of a polyurethane is important for
processibility. Melting should occur well below the decomposition
temperature. Below the glass-transition temperature (T.sub.g), the
molecular motion is frozen, and the material is only able to
undergo small-scale elastic deformations. For amorphous
polyurethane elastomers, the T.sub.g of the soft segment is about
-50 to -60.degree. C., whereas for the amorphous hard segment,
T.sub.g is in the 20-100.degree. C. range.
[0143] The choice of macrodiol influences the low temperature
performance, whereas the modulus, i.e. hardness, stiffness, and
load-bearing properties, increases with increasing hard-segment
content.
[0144] A wide array of crosslinkable thermoplastic polyurethanes
can be used in the present invention. For example, EBXL-TPU is a
thermoplastic polyurethane recently made available from Zylon
Polymers, 23 Mountain Avenue, Monsey, N.Y. 10952. EBXL-TPU is a
pelletized, medical grade, polyether or polyester based
thermoplastic polyurethane, reactor modified to allow crosslinking
by ionizing radiation. It is a low melt index material suitable for
extrusion into profiles, film and sheet, or injection molding. Once
crosslinked, the material combines the ease of processing and
toughness of TPU with the improved resistance to water, solvents
and elevated temperatures characteristic of thermoset materials.
Table 7 below, sets forth details of this preferred material.
7TABLE 7 EBXL-TPU Typical Physical Properties PROPERTY VALUE UNITS
Radiation 12.5-15 MegaRads Shore Hardness 80 Shore A Specific
Gravity 1.04 gr/cc Tensile Strength 5000 psi Ultimate Elongation
425 % Compression set, 50 % 70 hrs @ 100 deg C. Melt Flow Index 2
gms/10 min FLUID RESISTANCES Water, no effect 24 hrs @ 23 C.
Isopropyl Alcohol, no effect 100% 24 hrs @ 23 C. Tetrahydrofuran,
swells, does not dissolve 24 hrs @ 23 C.
[0145] A further preferred class of crosslinkable thermoplastic
polyurethanes is a commercially available polyurethane from BASF,
designated as Elastollan.RTM.. Properties of several specific
formulations of Elastollan.RTM. polyurethanes are set forth in
Table 8 below.
8TABLE 8 Physical ASTM properties.sup.1 Units Method 1175AW.sup.3
1180A 1185A 1190A 1195A 1154D 1160D 1164D 1174D Specific gravity
gr/cc D-792 1.14 1.11 1.12 1.13 1.14 1.16 1.17 1.18 1.19 Hardness
Shore D-224 A 76 .+-. 2 80 .+-. 2 86 .+-. 2 91 .+-. 2 95 .+-. 2 --
-- -- -- D -- -- -- 42 .+-. 2 47 .+-. 2 53 .+-. 2 60 .+-. 2 64 .+-.
2 73 .+-. 2 Tensile strength MPa D-412 30 32 33 37 36 40 40 41 45
psi 4500 4700 4800 5300 5200 5800 5800 6000 6500 Tensile stress
D-412 @ 100% elongation MPa 4.3 5.5 7.6 10 12 20 22 25 32 psi 620
800 1100 1500 1750 2900 3200 3600 4600 @ 300% elongation MPa 8.3 10
12 17 21 30 33 33 38 psi 1180 1500 1750 2500 3000 4300 4800 4800
5500 Elongation @ brk. % D-412 740 600 640 575 490 460 415 425 350
Tensile set @ brk. % D-412 -- 45 70 75 65 70 60 90 80 Tear strength
kN/m D-624 80 90 105 125 140 180 205 220 255 pli DIE C 460 515 600
715 800 1025 1170 1250 1450 Abrasion resistance mg D-1044.sup.2 25
30 45 55 75 50 55 75 (loss) (Taber) NOTE: .sup.1Test samples were
cured 20 hours @ 100.degree. C. before testing. .sup.2H-18 wheel,
1000 gm weight and 1000 cycles. .sup.3Contains proprietary
plasticizer.
[0146] Elastollan.RTM. 1100 series of products are polyether-based
thermoplastic polyurethanes. They exhibit excellent low temperature
properties, hydrolysis resistance and fungus resistance. These
products can be injection and blow molded and extruded.
[0147] BASF indicates that Elastollan.RTM. 1175AW, 80A, 90A and 95A
are suitable for extrusion. And, Elastollan.RTM. 1175AW to 1174D
are suitable for injection molding. BASF further provides that a
grade should be dried before processing. Elastollan.RTM. can be
stored for up to 1 year in its original sealed container.
Containers should be stored in a cool, dry area. Elastollan.RTM.
TPU's from BASF are commercial TPU's but will not crosslink using
irradiation unless a particular reactive co-agent such as
Liquiflex.TM. H, described below, is added. Nearly any other
commercially available TPU such as Urepan.RTM., Pellethane.RTM.,
Morthane.RTM., Desmopan.RTM., etc. can be used provided it is
compounded with a co-agent that readily crosslinks with
radiation.
[0148] Liquiflex.TM. is a commercially available hydroxyl
terminated polybutadiene (HTPB), from Petroflex. It is believed
that this co-agent enables the thermoplastic polyurethane to
crosslink upon exposure to radiation. It is believed that the
previously noted thermoplastic polyurethane EBXL-TPU from Zylon
contains a co-agent similar to Liquiflex.TM..
[0149] In accordance with the present invention, it is most
preferred that at least one of the cover layers of a multi-layer
assembly comprise a polyurethane. More preferably, the one or more
cover layers comprise a majority proportion, by weight, of a
polyurethane.
[0150] As indicated above, numerous ways are known to induce
crosslinking in a polymer by free radical initiation, including
peroxide initiation and irradiation. The golf ball covers of the
present invention preferably are crosslinked by irradiation, and
more preferably light rays such as gamma or UV irradiation.
Furthermore, other forms of particle irradiation, including
electron beam also can be used. Gamma radiation is preferred as
golf balls or game balls can be irradiated in bulk. Gamma
penetrates very deep but also increases crosslinking of the inner
core and the compression of the core has to be adjusted to allow
for the increase in hardness.
[0151] Electron beam techniques are faster but cannot be used for
treating in bulk as the electron beam does not penetrate very deep
and the product needs to be rotated to obtain an even crosslink
density.
[0152] The type of irradiation to be used will depend in part upon
the underlying layers. For example, certain types of irradiation
may degrade windings in a wound golf ball. On the other hand, balls
with a solid core would not be subject to the same concerns.
However, with any type of core, certain types of irradiation will
tend to crosslink and thus harden the core. Depending upon whether
this type of effect is sought or is to be avoided, the appropriate
type of irradiation can be selected.
[0153] The level of radiation employed depends upon the desired end
characteristics of the final game ball, e.g. golf ball, cover.
However, generally a wide range of dosage levels may be used. For
example, total dosages of up to about 12.5, or even 15 Mrads may be
employed. Preferably, radiation delivery levels are controlled so
that the game ball is not heated above about 80.degree. C.
(176.degree. F.) while being crosslinked.
[0154] The layers of the cover may be formed from generally the
same resin composition, or may be formed from different resin
compositions with similar hardnesses. For example, one cover layer
may be formed from an ionomeric resin of ethylene and methacrylic
acid, while another layer is formed from an ionomer of ethylene and
acrylic acid. One or more cover layers may contain polyamides or
polyamide-nylon copolymers or intimate blends. Furthermore,
polyurethanes, pebax, or thermosetting polyurethane can be
used.
[0155] In order to visibly distinguish the layers, a wide variety
of agents such as phosphorous, florescent dies, florescent
pigments, etc. can be used.
[0156] Additional materials may also be added to the cover (or
inner and outer cover layers) 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.TM. sold by Whitaker, Clark, and Daniels of South Plainsfield,
N.J.) (see U.S. Pat. No. 4,679,795), optical brighteners, pigments
such as titanium dioxide, zinc oxide, barium sulfate and zinc
sulfate; UV absorbers; antioxidants; antistatic agents; 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, both of which are herein
incorporated by reference, including plasticizers, metal stearates,
processing acids, etc., as long as the desired properties produced
by the golf ball covers of the invention are not impaired.
[0157] Moreover, since there are various hues of white, i.e. blue
white, yellow white, etc., trace amounts of blue pigment may be
added to the cover stock composition to impart a blue white
appearance thereto. However, if different hues of the color white
are desired, different pigments can be added to the cover
composition at the amounts necessary to produce the color
desired.
[0158] In addition, it is within the purview of this invention to
add to the cover compositions of this invention compatible
materials such as antioxidants (i.e. Santonox.RTM. R), antistatic
agents, stabilizers and processing aids. The cover compositions of
the present invention may also contain softening agents, such as
plasticizers, 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.
[0159] In one preferred form of the invention, the inner cover
layer or inner cover layers contain filler materials. More
particularly, filler materials are included in order to affect
moment of inertia and spin of the golf ball, for example. Suitable
filler materials for the inner cover layer or layers of the golf
ball include, but are not limited to, clay, talc, asbestos,
graphite, glass, mica, calcium metal silicate, barium sulfate, zinc
sulfide, aluminum hydroxide, silicates, diatomaceous earth,
carbonates such as calcium carbonate, magnesium carbonate and the
like, metals such as titanium, tungsten, aluminum, bismuth, nickel,
molybdenum, iron, copper, brass, boron, bronze, cobalt and
beryllium, and alloys of the above metals, metal oxides such as
zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium
oxide, zirconium oxide and the like, particulate synthetic plastic
such as high molecular weight polyethylene, polystryene,
polyethylene ionomer resins and the like, particulate carbonaceous
materials such as carbon black, natural bitumen and the like, as
well as cotton flock, cellulose flock, and leather fiber.
[0160] Dark colored fillers generally are not preferred for use at
the outer surface of the ball if a white ball is desired. Thus, a
two-layer cover in which a non-white filler is only present in the
inner cover layer can be employed.
[0161] The amount of filler employed is primarily a function of
weight restrictions. For example, weight may be removed from the
core and placed in the inner and/or outer cover. This added weight
will change the moment of inertia of the ball thereby potentially
altering performance. Whereas typically the specific gravity of the
cover layer or layers is about 0.95-1.00, it may be desirable to
increase the specific gravity of one or more of the cover layers to
greater than 1.0, preferably 1.1-2.0.
[0162] Furthermore, optical brighteners, such as those disclosed in
U.S. Pat. No. 4,679,795, herein incorporated by reference, may also
be included in the cover composition of the invention. Examples of
suitable optical brighteners which can be used in accordance with
this invention are Uvitex.RTM. OB as sold by the Ciba-Geigy
Chemical Company, Ardsley, N.Y. Uvitex.RTM. OB thought to be
2,5-Bis(5-tert-butyl-2-benzoxazoyl)-thi- ophene. Examples of other
optical brighteners suitable for use in accordance with this
invention include Leucopure.RTM. EGM as sold by Sandoz, East
Hanover, N.J. 07936. Leucopure.RTM. EGM is thought to be
7-(2n-naphthol(1,2-d)-triazol-2yl)3-phenyl-coumarin. Phorwhite.RTM.
K-20G2 is sold by Mobay Chemical Corporation, P.O. Box 385, Union
Metro Park, Union, N.J. 07083, and is thought to be a pyrazoline
derivative. Eastobrite.RTM. OB-1 is
2,2'(1,2-ethenediyldi-4,1-phenylene)bisbenzoxazol- e and is
available from Eastman Chemical Company.
[0163] Moreover, since many optical brighteners are colored, the
percentage of optical brighteners utilized must not be excessive in
order to prevent the optical brightener from functioning as a
pigment or dye in its own right.
[0164] The percentage of optical brighteners which can be used in
accordance with this invention is from about 0.01% to about 0.5% as
based on the weight of the polymer used as a cover stock. A more
preferred range is from about 0.05% to about 0.25% with the most
preferred range from about 0.10% to about 0.20% depending on the
optical properties of the particular optical brightener used and
the polymeric environment in which it is a part.
[0165] Generally, the additives are admixed with an ionomer to be
used in the cover composition to provide a masterbatch (M.B.) of
desired concentration and an amount of the masterbatch sufficient
to provide the desired amounts of additive is then admixed with the
copolymer blends.
[0166] The above cover layer compositions, when combined with soft
cores at the cover layer thicknesses described herein, produce golf
balls having a relatively low spin in combination with good click
and feel.
[0167] The cover compositions and molded balls of the present
invention may be produced according to conventional melt blending
procedures. In this regard, the ionomeric resins are blended along
with the masterbatch containing the desired additives in a
Banbury.RTM. type mixer, two-roll mill, or extruded prior to
molding. The blended composition is then formed into slabs or
pellets, etc. and maintained in such a state until molding is
desired. Alternatively a simple dry blend of the pelletized or
granulated resins and color masterbatch 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. Additives such as the fillers, etc., are added and
uniformly mixed before initiation of the molding process.
[0168] The golf balls of the present invention can be produced by
molding processes currently well known in the golf ball art.
Specifically, the golf balls can be produced by conventional
molding techniques, such as by injection molding or compression
molding the novel cover compositions over the soft polybutadiene
cores to produce a golf ball having a diameter of about 1.680
inches or greater, preferably at least 1.70 inches, and weighing
about 1.620 ounces. Larger molds are utilized to produce the
thicker covered oversized golf balls. For injection-molded cover
layers having a thickness of up to about 3.0 mm, it may be
preferable to mold the cover in a single step. For covers and for
cover layers of 3.0 mm or more, it generally is preferable for
reasons of both processability and uniformity to mold the cover in
two layers. In compression molding, it may be appropriate to mold a
thicker cover in a single layer. In compression molding, the 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 dimpled golf ball
mold and subjected to compression molding at 200 to 300.degree. F.
for 2 to 10 minutes, followed by cooling at 50 to about 70.degree.
F. for 2 to 10 minutes, to fuse the shells together to form an
unitary ball. In addition, the golf balls may be produced by
injection molding, wherein the cover composition is injected
directly around the core placed in the center of a golf ball mold
for a period of time at a mold temperature of from 50 to about
100.degree. F. After molding the golf balls produced may undergo
various further finishing steps such as flash trimming, priming,
marking, finish coating and the like as is well known and is
disclosed, for example in U.S. Pat. No. 4,911,451, herein
incorporated by reference.
[0169] A preferred method of forming a golf ball according to the
present invention is forming one or more layers via a
fast-chemical-reaction process.
[0170] Specifically, the preferred method of forming a
fast-chemical-reaction-produced component for a golf ball according
to the invention is by reaction injection molding ("RIM"). RIM is a
process by which highly reactive liquids are injected into a closed
mold, mixed usually by impingement and/or mechanical mixing in an
in-line device such as a "peanut mixer," where they polymerize
primarily in the mold to form a coherent, one-piece molded article.
The RIM process usually involves a rapid reaction between one or
more reactive components such as polyether= or polyester-polyol,
polyamine, or other material with an active hydrogen, and one or
more isocyanate-containing constituents, often in the presence of a
catalyst. The constituents are stored in separate tanks prior to
molding and may be first mixed in a mix head upstream of a mold and
then injected into the mold. The liquid streams are metered in the
desired weight to weight ratio and fed into an impingement mix
head, with mixing occurring under high pressure, e.g., 1,500 to
3,000 psi. The liquid streams impinge upon each other in the mixing
chamber of the mix head and the mixture is injected into the mold.
One of the liquid streams typically contains a catalyst for the
reaction. The constituents react rapidly after mixing to gel and
form polyurethane polymers. Polyureas, epoxies, and various
unsaturated polyesters also can be molded by RIM.
[0171] RIM differs from non-reaction injection molding in a number
of ways. The main distinction is that in RIM a chemical reaction
takes place in the mold to transform a monomer or adducts to
polymers and the components are in liquid form. Thus, a RIM mold
need not be made to withstand the pressures which occur in a
conventional injection molding. In contrast, injection molding is
conducted at high molding pressures in the mold cavity by melting a
solid resin and conveying it into a mold, with the molten resin
often being at about 150 to about 350.degree. C. At this elevated
temperature, the viscosity of the molten resin usually is in the
range of about 50,000 to about 1,000,000 centipoise, and is
typically around 200,000 centipoise. In an injection molding
process, the solidification of the resins occurs after about 10 to
about 90 seconds, depending upon the size of the molded product,
the temperature and heat transfer conditions, and the hardness of
the injection molded material. Subsequently, the molded product is
removed from the mold. There is no significant chemical reaction
taking place in an injection molding process when the thermoplastic
resin is introduced into the mold. In contrast, in a RIM process,
the chemical reaction causes the material to set in less than about
5 minutes, often in less than 2 minutes, preferably in less than
one minute, more preferably in less than 30 seconds, and in many
cases in about 10 seconds or less.
[0172] If plastic products are produced by combining components
that are preformed to some extent, subsequent failure can occur at
a location on the cover which is along the seam or parting line of
the mold. Failure can occur at this location because this
interfacial region is intrinsically different from the remainder of
the cover layer and can be weaker or more stressed. The present
invention is believed to provide for improved durability of a golf
ball cover layer by providing a uniform or "seamless" cover in
which the properties of the cover material in the region along the
parting line are generally the same as the properties of the cover
material at other locations on the cover, including at the poles.
The improvement in durability is believed to be a result of the
fact that the reaction mixture is distributed uniformly into a
closed mold. This uniform distribution of the injected materials
eliminates knit-lines and other molding deficiencies which can be
caused by temperature difference and/or reaction difference in the
injected materials. The process of the invention results in
generally uniform molecular structure, density and stress
distribution as compared to conventional injection-molding
processes.
[0173] The RIM process used in forming components of a
multi-layered golf ball disclosed herein is substantially different
from, and advantageous over, the conventional injection and
compression molding techniques.
[0174] First, during the RIM process of the present application,
the chemical reaction, i.e., the mixture of isocyanate from the
isocyanate tank and polyol from the polyol tank, occurs during the
molding process. Specifically, the mixing of the reactants occurs
in the recirculation mix head and the after mixer, both of which
are connected directly to the injection mold. The reactants are
simultaneously mixed and injected into the mold, forming the
desired component.
[0175] Typically, prior art techniques utilize mixing of reactants
to occur before the molding process. Mixing under either
compression or injection molding occurs in a mixer that is not
connected to the molding apparatus. Thus, the reactants must first
be mixed in a mixer separate from the molding apparatus, then added
into the apparatus. Such a process causes the mixed reactants to
first solidify, then later melt in order to properly mold.
[0176] Second, the RIM process requires lower temperatures and
pressures during molding than does injection or compression
molding. Under the RIM process, the molding temperature is
maintained at about 100.degree. F. to about 120.degree. F. in order
to ensure proper injection viscosity. Compression molding is
typically completed at a higher molding temperature of about
320.degree. F. (160.degree. C.). Injection molding is completed at
even a higher temperature range of from about 392.degree. F. to
about 482.degree. F. (200 to 250.degree. C.). Molding at a lower
temperature is beneficial when, for example, the cover is molded
over a very soft core so that the very soft core does not melt or
decompose during the molding process.
[0177] Third, the RIM process creates more favorable durability
properties in a golf ball than does conventional injection or
compression molding. The preferred process of the present invention
provides improved durability for a golf ball cover by providing a
uniform or "seamless" cover in which the properties of the cover
material in the region along the parting line are generally the
same as the properties of the cover material at other locations on
the cover, including at the poles. The improvement in durability is
due to the fact that the reaction mixture is distributed uniformly
into a closed mold. This uniform distribution of the injected
materials eliminates knit-lines and other molding deficiencies
which can be caused by temperature difference and/or reaction
difference in the injected materials. The RIM process of the
present invention results in generally uniform molecular structure,
density and stress distribution as compared to conventional
injection molding processes, where failure along the parting line
or seam of the mold can occur because the interfacial region is
intrinsically different from the remainder of the cover layer and,
thus, can be weaker or more stressed.
[0178] Fourth, the RIM process is relatively faster than the
conventional injection and compression molding techniques. In the
RIM process, the chemical reaction takes place in under 5 minutes,
typically in less than two minutes, preferably in under one minute
and, in many cases, in about 30 seconds or less. The demolding time
of the present application is 10 minutes or less. The molding
process alone for the conventional methods typically takes about 15
minutes. Thus, the overall speed of the RIM process makes it
advantageous over the injection and compression molding
methods.
[0179] The present invention is further illustrated by the
following examples in which the parts of the specific ingredients
are by weight (pbw). It is to be understood that the present
invention is not limited to the examples, and various changes and
modifications may be made in the invention without departing from
the spirit and scope thereof.
EXAMPLES
Example 1
Thick, Single Cover Oversize Balls
[0180] A number of golf ball cores having Formulation A, shown
below, were prepared.
9 Core Formulation A Parts by Material Weight SMR-CV 60.sup.1 25.00
Taktene .RTM. 220.sup.2 73.50 Hi-Sil .TM. 234 LD.sup.3 6.00 Zinc
Oxide.sup.4 5.00 Barytes #22.sup.5 80.00 Stearic Acid.sup.6 1.60
Agerite Superlite .TM..sup.7 1.60 TiO.sub.2 Rutile 2020.sup.8 3.00
Circolite .TM. Oil.sup.9 5.00 Red pigment.sup.10 3.00 Sulfur
(insol).sup.11 3.14 Santocure .TM. N.S..sup.12 1.28 Methyl
Zimate.sup.13 0.27 D.P.G..sup.14 0.68 206.07 .sup.1Natural rubber,
Muehlstein, Norwalk, CT .sup.2Synthetic polybutadiene, Bayer Corp.,
Akron, OH .sup.3Precipitated hydrated silica, PPG Industries,
Pittsburgh, PA .sup.4Zinc Corp. of America, Monaca, PA
.sup.5Harwick Chemical, Akron, OH .sup.6Harwick Chemical, Akron, OH
.sup.7R. T. Vanderbilt, Norwalk, CT .sup.8Harwick Chemical, Akron,
OH .sup.9Sun Oil, Philadelphia, PA .sup.10Stauffer Chemical,
Westport, CT .sup.11Stauffer Chemical, Westport, CT .sup.12R. T.
Vanderbilt, Norwalk, CT .sup.13R. T. Vanderbilt, Norwalk, CT
.sup.141,3-Diphenylguanidine (accelerator) R. T. Vanderbilt,
Norwalk, CT
[0181] One to two dozen cores were made having an average diameter
of 36.3 mm (1.430 inches) (Example 1-1). One to two dozen cores
having an average diameter of 37.3 mm (1.470 inches) also were made
(Example 1-2). The 36.3 mm diameter cores were cured at 320.degree.
F. for 12 minutes, followed by six minutes of cooling using cold
water. The cores having a 37.3 mm diameter were cured at
320.degree. F. for 12 minutes, followed by six minutes of cooling
using cold water.
[0182] The cores were covered with a thick, single layer of an
ionomeric cover material to produce an unfinished golf ball 43.7 mm
(1.72 inches) in diameter. The ionomeric cover material consisted
of Cover Formulation W, shown below:
10 Cover Formulation W Parts by weight White Masterbatch - Parts by
weight Iotek .RTM. 8000 70.6 Iotek .RTM. 7030 100. Iotek .RTM. 7010
19.9 Unitane .RTM. 0-110 31.72 White MasterBatch 9.5 Ultra Marine
Blue .TM. 0.6 Eastobrite .RTM. OB-1 0.35 Santonox .RTM. R 0.05
[0183] As shown in Table 9 below, the golf balls with a 36.3 mm
average core diameter had an overall average weight of 43.5 grams,
an average cover thickness of 3.68 mm (0.145 inches), an average
PGA compression of 78, and an average coefficient of restitution
(C.O.R.) of 0.744 (Example 1-1). The golf balls with 37.3 mm (1.470
inch) average core diameters had an average weight of 44.4 grams,
an average cover thickness of 3.18 mm (0.125 inches), an average
PGA compression of 48, and an average coefficient of restitution of
0.732 (Example 1-2). These thick covered, two piece oversized golf
balls have excellent feel due to the combination of a hard cover
and a very soft core, and could be used (due to their low average
C.O.R.'s) as restricted flight golf balls.
[0184] A number of golf ball cores having Core Formulation B, shown
below, were formed.
11 Core Formulation B Parts by Material Weight Cariflex .RTM.
BR-1220.sup.1 67.35 Taktene .RTM. 220.sup.2 27.50 Natsyn .TM.
2200.sup.3 5.15 Zinc Oxide.sup.4 6.53 Limestone.sup.5 8.25 Poly Pro
.TM. 20 Mesh.sup.6 6.19 Regrind.sup.7 19.59 Zinc Stearate.sup.8
14.78 Zinc Diacrylate.sup.9 19.24 Luperco .RTM. 230XL or Trigonox
.RTM. 17/40.sup.10 1.48 .sup.1Polybutadiene Muehlstein, Norwalk, CT
.sup.2Synthetic Polybutadiene Bayer Corp., Akron, OH (internal
source) .sup.3Natural Rubber Muehlstein, Norwalk, CT .sup.4Zinc
Corp of America, Monaca, PA .sup.5Lee Lime, Lee, MA .sup.6Amoco
Chemical, .sup.7golf ball core regrind .sup.8Synpro, Cleveland, OH
.sup.9Rockland React Rite, Rockland, GA .sup.10Peroxide, R. T.
Vanderbilt, Norwalk, CT
[0185] The cores were cured for 15 minutes at 310.degree. F.
followed by 7 minutes of cooling using cooling water. Cores having
average diameters of 36.3 mm (1.430 inches) (Example 1-4) and of
37.3 mm (1.470 inches) were formed (Example 1-3).
[0186] Cores having an average diameter of 39.2 mm (1.545 inches)
also were formed (Example 1-C1) as a control. These cores are
representative of the size of cores in standard size, oversized
golf balls.
[0187] The cores of Examples 1-3, 1-4 and 1-C1 were covered with a
single layer of the same ionomeric cover material as was used in
Examples 1-1 and 1-2. The 36.3 mm and 37.3 mm diameter cores
resulted in thick covered, oversized golf balls having an overall
diameter of 43.7 mm (1.72 inches) (Examples 1-3 and 1-4).
Similarly, the 39.2 mm cores were used to form golf balls having a
diameter of 43.8 mm (1.725 inches) (Example 1-C1).
[0188] The golf balls made from 36.3 mm cores (Example 1-4) had a
final weight of 44.5 grams, a cover thickness of 3.68 mm (0.145
inches), a PGA compression of 112 and a coefficient of restitution
of 0.811. The balls made from 37.3 mm cores (Example 1-3) had a
weight of 45.1 grams, a cover thickness of 3.18 mm (0.124 inches),
a PGA compression of 105, and a coefficient of restitution of
0.809. The normal cover thickness control balls having 39.2 mm
cores (Example 1-C1) had an overall weight of 46.0 grams, a cover
thickness of 2.29 mm (0.090 inches), a PGA compression of 93, and a
coefficient of restitution of 0.812.
Example 2
Thick Covered Multi-Layer Golf Balls, Standard Size
[0189] A number of 32.8 mm (1.29 inch) average diameter golf ball
cores were made using Core Formulation C, shown below. The curing
process was the same as the sulfur curing process described above
in Example 1. The cores were used to make four different types of
golf balls having the cover compositions and thicknesses shown in
Table 9 as Examples 2-1 to 2-4. The lotek.RTM. 959/960 cover
formulation (Cover Formulation X utilized) also is shown below.
12 Core Formulation C Cover Formulation X Parts by Parts by Weight
Weight Cariflex .RTM. BR 1220 80 Iotek .RTM. 959 45.3 SMR CV 60 20
Iotek .RTM. 960 45.3 Zinc Oxide 5 White MasterBatch 9.4 Limestone
110 (see formulation in Ex. 1) Stearic Acid 1.6 Agerite Superlite
.TM. 1.6 Circolite .TM. Oil 5 Sulfur 3.14 Santocure .RTM. N.S. 1.28
Methyl Zimate 0.28 D.P.G. 0.68 228.58
[0190] The resulting average PGA compression and coefficient of
restitution of the golf balls also is shown in Table 9. A control
example using a standard size, two piece ball core, i.e. 39.2 mm
(1.545 inch) core, having Core Formulation I, shown below, and a
single cover layer with a thickness of 1.78 mm (0.070 inches) also
was formed. The physical properties of the resulting balls are
shown in Table 9 as 2-C1.
13 Core Formulation I Parts by Weight Cariflex .RTM. BR-1220 70.80
Taktene .RTM. 220 29.20 Zinc Oxide 6.93 Limestone 18.98 Poly Pro
.TM. 20 Mesh 2.55 Regrind 20.07 Zinc Stearate 20.07 ZDA 30.29 Blue
masterbatch 0.01 Luperco .RTM. 231-XL or Trigonox .RTM. 29/40.sup.2
0.90 .sup.2peroxide, R. T. Vanderbilt, Norwalk, CT
[0191] The very thick covered balls (2-1 to 2-4) had the same, or
substantially the same, overall compression (i.e. 105-116 PGA) as
the thin covered control (i.e., 2-C1, 105 PGA) even though the
thick covers were more than double, and in some instances nearly
triple, the thickness of the control.
Example 3
Thick Covered Multi-Layer Balls, Standard Size
[0192] A number of sulfur-cured golf ball cores having an average
diameter of 32.5 mm (1.28 inches) and the formulation shown below
were formed:
14 Core Fomulation D Materials phr Cariflex .RTM. BR-1220 80 SMR
CV-60 20 Zinc Oxide 5 Limestone 20 Stearic Acid 1.6 Circolite .TM.
oil 5 Sulfur 3.14 Santocure .TM. N.S. 1.28 Methyl Zimate 0.28
D.P.G. 0.68 Agerite White .TM..sup.1 0.8 .sup.1R.T. Vanderbilt,
Norwalk, CT
[0193] The cores were cured for 12 minutes at 320.degree. F.,
followed by cooling for six minutes with cooling water. The
sulfur-cured cores (Examples 3-3, 3-4, 3-7 and 3-8) had an average
surface Shore A hardness of 71, an average surface Shore C hardness
of 35 and an average surface Shore D hardness of 21.
[0194] A number of peroxide-cured cores having an average diameter
of 32.5 mm (1.28 inches) and Core Formulation B, shown above were
formed. The cores were cured for 15 minutes at 310.degree. F.,
followed by cooling for seven minutes using cooling water. The
cores (Examples 3-1, 3-2, 3-5 and 3-6) had the PGA compression and
COR values shown in Table 6.
[0195] A number of standard size "control" cores were made having a
diameter of 39.2 mm (1.545 inches) and having Core Formulation F,
shown below, were formed (Examples 3-C1 and 3-C2).
15 Core Fomulation F Parts by Weight Cariflex .RTM. BR-1220 70.37
Taktene .RTM. 220 29.63 Zinc Oxide 6.67 Limestone 24.07 Poly Pro
.TM. 20 Mesh 8.89 Regrind 17.04 Zinc Stearate 18.52 Zinc Diacrylate
27.41 Luperco .RTM. 231-XL or Trigonox .RTM. 17/40 0.9
[0196] Furthermore, a number of "control" cores having a diameter
of 39.2 mm (1.545 inches) and having Core Formulation G, shown
below, were formed (Examples 3-C3 and 3-C4).
16 Core Fomulation G Parts by Weight Cariflex .RTM. BR-1220 73.33
Taktene .RTM. 220 26.67 Zinc Oxide 22.33 Regrind 10 Zinc Stearate
20 Zinc Diacrylate 26 Luperco .RTM. 231-XL or Trigonox .RTM. 17/40
0.9
[0197] The 32.5 mm cores were covered with a thick multi-layer
cover, i.e. 3.35 mm (0.132 inch) thick layer of ionomer followed by
a 1.78 mm (0.070 inch) thick layer of the same or a different
ionomer. The covers had a "422 tri" dimple pattern, which is the
same dimple pattern as is used on the Top-Flite.RTM. Hot XL (1995),
tour trajectory ball. The compression and coefficient of the cores,
balls having the first cover layer, and balls having the second
cover layer, as well as the finished balls, was obtained and is
shown in Table 9. The control cores were covered with a single
layer of ionomer having a thickness of 1.78 mm (0.070 inches).
[0198] The results demonstrate that thick covered multi-layer golf
balls can be produced having comparable compression and C.O.R.
values as existing multi-layer golf balls.
Example 4
[0199] A number of thermoplastic golf ball cores containing 100
parts by weight Exact.RTM. 4049 (Exxon Chemical Co.), a metallocene
catalyzed polyolefin and 60 parts by weight of tungsten powder were
formed (Core Formulation H, Examples 4-1, 4-2, 4-5 and 4-6). The
cores were cured for 5 minutes at 320.degree. F. followed by
cooling using cooling water for 7 minutes. The cores had an average
weight of 23.3 grams and an average diameter of 32.5 mm (1.28
inches). The cores were covered with a 3.35 mm (0.132 inch) thick
layer of ionomer, followed by a second cover having a thickness of
about 1.78 mm (0.070 inches). The inner and outer cover layers had
the formulations Y and Z as shown in Table 9. Cover formulation Y
is as follows:
17 Cover Formulation Y Parts by Weight Iotek .RTM. 1002 45.3 Iotek
.RTM. 1003 45.3 White MasterBatch 9.4 (see formulation in Ex.
1)
[0200] Cover Formulation Z is as follows:
18 Cover Formulation Z Parts by Weight Iotek .RTM. 8000 70.6 Iotek
.RTM. 7010 19.9 White MasterBatch 9.5 (see formulation in Ex.
1)
[0201] A number of crosslinked cores were made using 100 parts by
weight of Exact.RTM. 4049 (Exxon Chemical Co., Houston, Tex.),
which is a metallocene catalyzed polyolefin, 60 parts by weight of
tungsten powder and 5 parts by weight Trigonox.RTM. 17/40 (Core
Formulation J, Examples 4-3, 4-4 and 4-7). The cores were cured for
14 minutes at 320.degree. F. followed by cooling with cooling water
for 7 minutes. The cores had a weight of 23.6 grams. The cores had
a diameter of 32.5 mm (1.28 inches), and were covered with the same
types and thicknesses of cover materials as were used for the
thermoplastic cores. The cover materials are shown in Table 9. The
outer covers of Example 4 employed a "422 Hex" dimple pattern,
which is the same dimple pattern as is used on the Top-Flite.RTM.
XL (1996), regular trajectory ball.
[0202] The compression and coefficient values for the balls having
a single cover layer, both cover layers, and finished products were
determined and are shown in Table 9. As shown by the results, the
thick covered balls, having metallocene catalyzed polyolefin cores,
give relatively soft compression versus the thick covered balls
having polybutadiene cores, and demonstrate the variety of
properties which are possible with the novel constructions of the
invention. The balls of this Example which have cores made of
metallocene catalyzed polyolefin would be useful as range or
practice balls, as they have a soft feel and high spin, as well as
a very durable, hard cover.
19 TABLE 9 CORE INNER COVER OUTER COVER FINISHED BALL COR Thick-
COR Thick- COR COR SPIN EX. Size Comp (.times. ness Comp (.times.
ness Comp (.times. Weight Comp (.times. Revs/ # Type.sup.1 mm (PGA)
1000) Type.sup.2 mm (PGA) 1000) Type.sup.2 mm (PGA) 1000) (g) (PGA)
1000) min 1-1 A 36.32 -- -- W 3.68 43.50 78 744 -- 1-2 A 37.34 --
-- W 3.18 44.40 48 732 -- 1-3 B 37.34 -- -- W 3.18 45.10 105 809 --
1-4 B 36.32 -- -- W 3.68 44.50 112 811 -- 1-C1 B 39.24 -- -- W 2.29
46.00 93 812 -- 2-1 C 32.77 -- -- W 3.18 -- -- W 1.78 106 753 --
2-2 C 32.77 -- -- W 3.56 -- -- W 1.40 105 752 -- 2-3 C 32.77 -- --
X 3.18 -- -- X 1.78 116 746 -- 2-4 C 32.77 -- -- X 3.56 -- -- X
1.40 114 770 -- 2-C1 I 39.24 -- -- -- -- -- -- W 1.78 105 803 --
3-1 B 32.51 71 759 X 3.35 115 786 X 1.78 122 791 130 806 6314 3-2 B
32.51 71 759 X 3.35 115 786 W 1.78 118 778 126 796 6095 3-3 D 32.51
X 3.35 75 768 X 1.78 110 769 117 790 -- 3-4 D 32.51 X 3.35 75 768 W
1.78 102 764 114 778 -- 3-5 B 32.51 71 759 W 3.35 110 772 X 1.78
120 788 128 801 -- 3-6 B 32.51 71 759 W 3.35 110 772 W 1.78 118 775
126 791.00 -- 3-7 D 32.51 W 3.35 69 749 X 1.78 108 771 116 776 7999
3-8 D 32.51 W 3.35 69 749 W 1.78 102 758 111 764 -- 3-C1 F 39.24 98
752 -- -- -- -- X 1.78 105 790 108 797 -- 3-C2 F 39.24 96 762 -- --
-- -- W 1.78 102 789 106 791 -- 3-C3 G 39.24 87 767 -- -- -- -- X
1.78 98 800 102 807 -- 3-C4 G 39.24 87 787 -- -- -- -- W 1.78 95
789 100 799 -- 4-1 H 32.51 Y 3.35 79 731 Y 1.78 103 742 45.40 106
749 8497 4-2 H 32.51 Z 3.35 77 737 Y 1.78 101 746 45.30 105 753
8081 4-3 J 32.51 Y 3.35 80 740 Y 1.78 105 757 46.00 107 763 8337
4-4 J 32.51 Z 3.35 78 741 Y 1.78 103 759 46.20 105 763 8642 4-5 H
32.51 Y 3.35 79 731 Z 1.78 102 736 45.40 105 743 8226 4-6 H 32.51 Z
3.35 77 737 Z 1.78 99 747 45.20 103 751 8758 4-7 J 32.51 Z 3.35 78
741 Z 1.78 99 751 45.90 104 759 -- .sup.1A = sulphur cured core of
Ex. 1 .sup. B = polybutadiene peroxide cured core of Ex. 1 and Ex.
3-1, 3-2, 3-5 and 3-6 .sup. C = sulphur cured core of Ex 2 .sup. D
= sulphur cured core of Ex. 3-3 and 3-4 .sup. F = polybutadiene
peroxide cured core of Ex. 3-C1 and 3-C2 .sup. G = polybutadiene
peroxide cured core of Ex. 3-C3 and 3-C4 .sup. H = thermoplastic
EXACT .RTM. core of Ex 4 .sup. I = blue core of Ex. 2 .sup. J =
thermoset EXACT core of Ex 4 .sup.2W = Iotek .RTM. 8000/7030
formulation of Ex. 1-3 .sup. X = Iotek .RTM. 959/960 formulation of
Ex 2-3 .sup. Y = Iotek .RTM. 1002/1003 formulation of Ex. 4 .sup. Z
= Iotek .RTM. 8000/7010 formulation of Ex. 4
Example 5A
[0203] The balls of Examples 3-1, 3-2, 3-7, and 4-1 to 4-6 were
spin tested under the following conditions:
[0204] Miyamae Driving Machine
[0205] Club: Top-Flite.RTM. Custom 9 iron
[0206] Club Head Speed: 105 fps
[0207] The results are shown in Table 6 above.
[0208] The balls of Examples 3-1, 3-2, 3-7, 4-5 and 4-6 were
distance tested and were compared with the 1995 Top-Flite.RTM. Hot
XL golf balls. The distance test conditions are provided below:
[0209] Club Name: Top-Flite Tour 10.5
[0210] Club Head Speed: 160 ft/sec
[0211] Launch Angle--degrees: 9.5
[0212] The distance test results are shown below in Table 10.
20TABLE 10 Flight Carry Time Carry Diff Ctr Dev.sup.1 Roll Total
Dist Total Diff Ball Traj deg. sec yds yds yds yds yds yds 3-1
12.50 10.00 244.40 0.00 -2.25 11.30 255.60 0.00 3-7 12.80 10.00
237.70 -6.60 -1.75 9.40 247.10 -8.50 3-2 12.10 10.00 227.40 -17.00
-3.04 19.20 246.60 -9.10 4-5 10.90 10.00 225.50 -18.90 -6.54 10.20
235.70 -20.00 4-6 11.30 9.90 226.80 -17.50 -6.71 11.70 238.50
-17.10 Hot XL 11.70 10.00 237.80 -6.60 -4.75 13.10 250.90 -4.80
(1995) .sup.1Deviation from center
[0213] The longest ball is that of Example 3-1. This result is
surprising, particularly in view of the fact that this ball has a
COR of 0.806, while the 1995 Top-Flite.RTM. Hot XL ball has a COR
of 0.812.+-.0.003. The ball of Example 3-2 also had a surprisingly
long total distance given its low COR of 0.1796.
Example 5B
[0214] Distance tests were conducted for the balls of Examples 3-1,
3-2 and 4-1 to 4-4 under slightly different conditions, which were
the following:
[0215] Club Name: Top-Flite.RTM. Tour 10.5
[0216] Club Head Speed: 155ft/sec
[0217] Launch Angle--degrees: 9.6
[0218] The distance test results are shown below in Table 11.
21TABLE 11 Flight Carry Time Carry Diff Ctr Dev Roll Total Dist
Total Diff Ball Traj deg. sec yds yds yds yds yds yds 4-1 11.50
9.90 227.10 -12.20 2.08 13.10 240.20 -12.90 4-2 11.90 10.00 226.10
-13.10 1.96 13.40 239.50 -13.60 4-3 11.80 10.00 228.00 -11.30 2.54
12.10 240.10 -13.00 4-4 11.80 10.00 227.40 -11.90 0.63 11.10 238.50
-14.60 3-1 12.00 10.00 239.30 0.00 2.10 13.80 253.10 0.00 3-2 12.00
10.00 233.40 -5.90 2.79 11.10 244.50 -8.60 Hot XL 12.40 10.00
239.00 -0.20 2.46 13.80 252.90 -0.20 (1995)
[0219] Once again, the ball of Example 3-1 is the longest. The ball
of Example 3-2 again had a surprisingly long total distance given
its low COR.
Example 6
[0220] A number of standard size, control golf ball cores having an
average diameter of 39.2 mm (1.545 inches) and a weight of 36.7 g
were formed using Core Formulation K, shown below.
22 Core Fomulation K Parts by Weight Cariflex .RTM. 1220 70 Taktene
.RTM. 220 30 Zinc Oxide 6.7 Zinc diacrylate 27.4 Zinc Stearate 18.5
Limestone 24 Poly Pro .TM. 20 Mesh 8.9 Regrind 17 Trigonox .RTM.
17/40 0.9
[0221] The cores were cured for 111/2 minutes at 320.degree. F.,
and were then cooled using cooling water for about 7 minutes. The
cores had a PGA compression of 95 and a COR of 0.770.
[0222] A number of golf ball cores having Core Formulation L (shown
below) and average diameters of 34.8 mm (1.37 inches) and 39.9 mm
(1.57 inches) were formed. The cores were cured for 12 minutes at
320.degree. F., followed by cooling using cooling water for about 6
minutes.
23 Core Formulation L Parts by Weight Cariflex .RTM. 1220 100
Stearic Acid 2 Zinc Oxide 4 Barytes 52 Hi-Sil .TM. 233.sup.1 7.5
Vanox .TM. 1290.sup.2 1 Sulfur 5.25 Durax .TM..sup.3 1.75
DOTG.sup.4 1 Bismate .TM..sup.5 2.8 .sup.1P.P.G. Industries
.sup.2R.T. Vanderbilt .sup.3R.T. Vanderbilt .sup.4R.T. Vanderbilt
.sup.5R.T. Vanderbilt
[0223] The cores of control Examples 6-C1, 6-C2 and 6-C3 were
covered with a single cover layer having a thickness of 1.78 mm
(0.07 inches). The control cores were covered with the cover
formulations shown in Table 12, which are the same as cover
formulations W-Z in Examples 1-4. The cores of Examples 6-1 through
6-10 were covered with inner and outer covers having the cover
formulations and thicknesses shown in Table 12. All of the balls of
the present invention and the control balls were distance tested
using a 5-iron at 128 feet per second and a driver at 160 feet per
second.
[0224] As shown in Table 12, while the thick covered balls of the
present invention had substantially lower coefficients of
restitution than the control balls, their distance was only
slightly shorter. Thus, the golf balls of the invention provide a
greater distance per point of COR as compared to the control
balls.
24 TABLE 12 Inner Cover Outer Cover 5 Iron @ Driver @ Thick- Thick-
Finished Ball 128 fps 160 fps Core Dia. ness Wgt. PGA COR .times.
ness Wgt. PGA COR .times. Carry Total Carry Total Ex. # Type
Material mm mm g Comp 1000 Material mm g Comp 1000 yds yds yds yds
6-C1 K N.A. N.A. N.A. N.A. N.A. N.A. Z 1.78 45.40 104 792 170 172
249 256 6-1 L W 39.20 3.50 35.80 70 742 Z 1.78 44.60 105 764 167
170 242 248 6-2 L Y 39.20 3.50 35.80 74 744 Z 1.78 44.80 108 759
166 168 241 246 6-3 L X 39.20 3.50 36.30 88 766 Z 1.78 45.00 114
771 Not Not Tested Tested 6-4 L W 39.90 3.81 37.10 77 748 Y 1.40
45.00 107 766 164 167 242 247 6-5 L Y 39.90 3.81 37.20 82 756 Y
1.40 45.00 109 765 165 169 243 247 6-6 L W 39.20 3.50 35.80 70 742
Y 1.78 44.90 107 757 166 167 243 247 6-C2 K N.A. N.A. N.A. N.A.
N.A. N.A. Y 1.78 45.70 106 804 167 171 251 256 6-C3 K N.A. N.A.
N.A. N.A. N.A. N.A. X 1.78 45.80 109 807 168 174 252 257 6-7 L Y
39.20 3.50 35.80 78 744 X 1.78 45.20 111 779 169 171 245 250 6-8 L
X 39.20 3.50 36.30 88 766 X 1.78 45.40 116 783 170 170 244 249 6-9
L W 39.90 3.81 37.10 77 748 X 1.40 45.30 112 772 171 171 242 248
6-10 L X 39.90 3.81 37.50 92 768 X 1.40 45.20 118 774 172 172 245
250
[0225] The foregoing description is, at present, considered to
describe the preferred embodiments of the present invention.
However, it is contemplated that various changes and modifications
apparent to those skilled in the art, may be made without departing
from the present invention. Therefore, the foregoing description is
intended to cover all such changes and modifications encompassed
within the spirit and scope of the present invention, including all
equivalent aspects.
* * * * *