U.S. patent application number 09/725610 was filed with the patent office on 2001-12-27 for ultimate control, reduced slippage golf ball.
Invention is credited to Binette, Mark L., Kennedy, Thomas J. III, Nealon, John L., Sullivan, Michael J..
Application Number | 20010055997 09/725610 |
Document ID | / |
Family ID | 24915264 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010055997 |
Kind Code |
A1 |
Kennedy, Thomas J. III ; et
al. |
December 27, 2001 |
Ultimate control, reduced slippage golf ball
Abstract
The present invention is directed to an improved multi-layer
golf ball comprising a core, an inner cover layer and an outer
cover layer. The inner cover layer is comprised of a relatively
hard cover material. The outer cover layer is comprised of a soft,
very low modulus ionomer or ionomer blend, or a non-ionomeric
thermoplastic elastomer such as polyurethane, polyester or
polyesteramide. The outer cover layer exhibits a Shore D hardness
of less than 50D. The golf ball may further comprise an optional
mantle layer, which may include one or more filler materials.
Filler material may be incorporated in one or more of the core,
inner cover layer, or outer cover layer. The resulting
multi-layered golf ball of the present invention exhibits reduced
slippage between the ball and club face, and therefore, relatively
high spin rates.
Inventors: |
Kennedy, Thomas J. III;
(Wilbraham, MA) ; Nealon, John L.; (Springfield,
MA) ; Binette, Mark L.; (Ludlow, MA) ;
Sullivan, Michael J.; (Barrington, RI) |
Correspondence
Address: |
MICHELLE BUGBEE, ASSOCIATE PATENT COUNSEL
SPALDING SPORTS WORLDWIDE INC
425 MEADOW STREET
PO BOX 901
CHICOPEE
MA
01021-0901
US
|
Family ID: |
24915264 |
Appl. No.: |
09/725610 |
Filed: |
November 29, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09725610 |
Nov 29, 2000 |
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09523561 |
Mar 10, 2000 |
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09523561 |
Mar 10, 2000 |
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08920070 |
Aug 26, 1997 |
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6224498 |
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08920070 |
Aug 26, 1997 |
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08542793 |
Oct 13, 1995 |
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08542793 |
Oct 13, 1995 |
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08070510 |
Jun 1, 1993 |
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09725610 |
Nov 29, 2000 |
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09248016 |
Feb 10, 1999 |
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6258302 |
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09725610 |
Nov 29, 2000 |
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09226340 |
Jan 6, 1999 |
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09725610 |
Nov 29, 2000 |
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09226727 |
Jan 7, 1999 |
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60226251 |
Aug 17, 2000 |
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Current U.S.
Class: |
473/374 |
Current CPC
Class: |
C08L 9/00 20130101; A63B
37/02 20130101; B29K 2009/00 20130101; A63B 37/0075 20130101; C08L
53/00 20130101; B29C 48/388 20190201; C08L 75/04 20130101; C08K
5/098 20130101; B29C 48/12 20190201; A63B 37/0076 20130101; A63B
37/0054 20130101; C08K 3/08 20130101; A63B 37/0087 20130101; A63B
37/0003 20130101; B29C 48/08 20190201; B29L 2031/54 20130101; C08L
23/08 20130101; C08L 69/00 20130101; A63B 37/0034 20130101; A63B
37/0045 20130101; A63B 37/12 20130101; B29C 43/24 20130101; C08L
23/0876 20130101; B29C 48/35 20190201; A63B 37/0043 20130101; A63B
37/0031 20130101; A63B 37/0052 20130101; A63B 37/0033 20130101;
B29C 48/13 20190201; C08K 3/08 20130101; C08L 9/00 20130101; C08K
5/098 20130101; C08L 9/00 20130101; C08L 9/00 20130101; C08L
2666/08 20130101; C08L 23/08 20130101; C08L 2666/18 20130101; C08L
23/08 20130101; C08L 2666/02 20130101; C08L 23/08 20130101; C08L
2666/04 20130101 |
Class at
Publication: |
473/374 |
International
Class: |
A63B 037/12; A63B
037/02 |
Claims
We claim:
1. A multi-layer golf ball adapted for reduced slippage upon a golf
club face, said multi-layer golf ball comprising: a spherical core;
an inner cover layer disposed about said core, said inner cover
layer exhibiting a Shore D hardness of from about 40 to about 80;
and an outer cover layer defining a plurality of dimples along an
outer surface of said outer cover layer, said outer cover layer
disposed on said inner cover layer, said outer cover layer
exhibiting a Shore D hardness of less than 50, said multi-layer
golf ball exhibiting a PGA compression less than 100.
2. The multi-layer golf ball of claim 1 wherein said outer cover
exhibits a Shore D hardness of less than 45.
3. The multi-layer golf ball of claim 2 wherein said outer cover
exhibits a Shore D hardness of less than 40.
4. The multi-layer golf ball of claim 1 wherein said inner cover
layer exhibits a Shore D hardness of from about 50 to about 80.
5. The multi-layer golf ball of claim 1 wherein said inner cover
layer exhibits a Shore D hardness of from 70 to 80.
6. The multi-layer golf ball of claim 1 wherein said outer cover
layer has a thickness in the range of from about 0.07 to about 0.1
inches.
7. The multi-layer golf ball of claim 1 wherein said outer cover
layer has a thickness greater than 0.055 inches.
8. The multi-layer golf ball of claim 1 wherein said golf ball
exhibits a PGA compression of from about 50 to about 90.
9. The multi-layer golf ball of claim 8 wherein said golf ball
exhibits a PGA compression of from about 60 to about 80.
10. The multi-layer golf ball of claim 1 further comprising: a
mantle layer disposed between said core and said inner cover
layer.
11. The multi-layer golf ball of claim 10 wherein said mantle layer
has a thickness in the range of from about 0.020 to about 0.150
inches.
12. The multi-layer golf ball of claim 1 1 wherein said mantle
layer has a thickness in the range of from about 0.030 to about
0.060 inches.
13. The multi-layer golf ball of claim 10 wherein each of said
inner cover layer, said outer layer, and said mantle layer has a
thickness in the range of from about 0.02 to about 0.1 inches.
14. The multi-layer golf ball of claim 13 wherein each of said
inner cover layer, said outer cover layer, and said mantle layer
has a thickness in the range of from about 0.03 to about 0.07
inches.
15. The multi-layer golf ball of claim 13 wherein said outer cover
layer exhibits a Shore D hardness of less than 47.
16. The multi-layer golf ball of claim 1 wherein said core is a
core selected from the group consisting of a solid core, a liquid
core, a gel core, a wound core, and a multi-piece solid core.
17. The multi-layer golf ball of claim 1 wherein said core
comprises a metallic core component centrally disposed within said
core.
18. The multi-layer golf ball of claim 17 wherein said metallic
core component comprises a metal selected from the group consisting
of steel, bismuth, tungsten, and stainless steel.
19. The multi-layer golf ball of claim 10 wherein said mantle layer
comprises a particulate filler material dispersed throughout said
mantle layer.
20. A low slip multi-layer golf ball comprising: a core including a
polybutadiene having a Mooney viscosity of from about 65 to about
85; an inner cover layer disposed about said core, said inner cover
layer exhibiting a Shore D hardness of from about 50 to about 80;
and an outer cover layer disposed on said inner cover layer and
exhibiting a Shore D hardness of less than about 50.
21. The multi-layer golf ball of claim 20 wherein said outer cover
exhibits a Shore D hardness of less than 45.
22. The multi-layer golf ball of claim 21 wherein said outer cover
exhibits a Shore D hardness of less than 40.
23. The multi-layer golf ball of claim 20 wherein said inner cover
layer exhibits a Shore D hardness of at least 70.
24. The multi-layer golf ball of claim 20 wherein said outer cover
layer has a thickness in the range of from about 0.07 to about 0.1
inches.
25. The multi-layer golf ball of claim 20 wherein said outer cover
layer has a thickness greater than 0.055 inches.
26. The multi-layer golf ball of claim 20 wherein said golf ball
exhibits a PGA compression less than 100.
27. The multi-layer golf ball of claim 26 wherein said golf ball
exhibits a PGA compression of from about 50 to about 90.
28. The multi-layer golf ball of claim 20 further comprising: a
mantle layer disposed between said core and said inner cover
layer.
29. The multi-layer golf ball of claim 28 wherein said mantle layer
has a thickness in the range of from about 0.020 to about 0.150
inches.
30. The multi-layer golf ball of claim 29 wherein said mantle layer
has a thickness in the range of from about 0.030 to about 0.060
inches.
37. A multi-layer low slip golf ball adapted for improved control,
said golf ball comprising: a generally spherical core including (i)
a non-rubber material having a specific gravity of at least 1.5 and
(ii) polybutadiene; an inner cover layer disposed about said core;
and an outer cover layer disposed about said inner cover layer,
said outer cover layer having a Shore D hardness of less than
50.
38. The multi-layer golf ball of claim 37 wherein said outer cover
exhibits a Shore D hardness of less than 45.
39. The multi-layer golf ball of claim 38 wherein said outer cover
exhibits a Shore D hardness of less than 40.
40. The multi-layer golf ball of claim 37 wherein said inner cover
layer exhibits a Shore D hardness of from about 50 to about 80.
41. The multi-layer golf ball of claim 37 wherein said inner cover
layer exhibits a Shore D hardness of at least 70.
42. The multi-layer golf ball of claim 37 wherein said outer cover
layer has a thickness in the range of from about 0.07 to about 0.1
inches.
43. The multi-layer golf ball of claim 37 wherein said outer cover
layer has a thickness greater than 0.055 inches.
44. The multi-layer golf ball of claim 37 further comprising: a
mantle layer disposed between said core and said inner cover
layer.
45. The multi-layer golf ball of claim 44 wherein said mantle layer
has a thickness in the range of from about 0.020 to about 0.150
inches.
46. The multi-layer golf ball of claim 45 wherein said mantle layer
has a thickness in the range of from about 0.030 to about 0.060
inches.
47. The multi-layer golf ball of claim 44 wherein each of said
inner cover layer, said outer cover layer, and said mantle layer
has a thickness in the range of from about 0.02 to about 0.1
inches.
48. The multi-layer golf ball of claim 47 wherein each of said
inner cover layer, said outer cover layer, and said mantle layer
has a thickness in the range of from about 0.03 to about 0.07
inches.
49. The multi-layer golf ball of claim 47 wherein said outer cover
layer exhibits a Shore D hardness of less than 47.
50. The multi-layer golf ball of claim 44 wherein said mantle layer
comprises a particulate filler material dispersed throughout said
mantle layer.
51. The multi-layer golf ball of claim 37, said non-rubber material
in said core selected from the group consisting of steel, tungsten,
bismuth, stainless steel, and combinations thereof.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
U.S. application Ser. No. 09/523,561 filed on Mar. 10, 2000 which
is a continuation-in-part application of U.S. application Ser. No.
08/920,070 filed on Aug. 26, 1997 which in turn is a continuation
of U.S. application Ser. No. 08/542,793 filed Oct. 13,1995, now
abandoned, which is a continuation-in-part of U.S. application Ser.
No. 08/070,510 filed on Jun. 1, 1993, now abandoned. This
application is also a continuation-in-part of U.S. application Ser.
No. 09/248,016 filed on Feb. 10,1999; Ser. No. 09/226,340 filed on
Jan. 6, 1999; and Ser. No. 09/226,727 filed on Jan. 7, 1999.
Additionally, this application claims priority to U.S. Provisional
Application No. 60/226,251 filed on Aug. 17, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to golf balls and, more
particularly, to improved standard and oversized golf balls
comprising multi-layer covers which have a comparatively hard inner
layer and a relatively soft outer layer. The golf balls also
feature the use of improved core formulations. The improved
multi-layer golf balls exhibit reduced slippage between the ball
and the club face. The golf balls may also be configured to easily
and quickly deform against the club face. Accordingly, the golf
balls of the present invention exhibit relatively high spin
rates.
BACKGROUND OF THE INVENTION
[0003] Traditional golf ball covers have been comprised of balata
or blends of balata with elastomeric or plastic materials. The
traditional balata covers are relatively soft and flexible. Upon
impact, the soft balata covers compress against the surface of the
club producing high spin. Consequently, the soft and flexible
balata covers provide an experienced golfer with the ability to
apply a spin to control the ball in flight in order to produce a
draw or a fade, or a backspin which causes the ball to "bite" or
stop abruptly on contact with the green. Moreover, the soft balata
covers produce a soft "feel" to the low handicap player. Such
playability properties (workability, feel, etc.) are particularly
important in short iron play with low swing speeds and are
exploited significantly by relatively skilled players.
[0004] Despite all the benefits of balata, balata covered golf
balls are easily cut and/or damaged if mis-hit. Golf balls produced
with balata or balata-containing cover compositions therefore have
a relatively short lifespan.
[0005] As a result of this negative property, balata and its
synthetic substitutes, trans-polyisoprene and trans-polybutadiene,
have been essentially replaced as the cover materials of choice by
new cover materials comprising ionomeric resins.
[0006] Ionomeric resins are polymers containing interchain ionic
bonding. As a result of their toughness, durability and flight
characteristics, various ionomeric resins sold by E. I. DuPont de
Nemours & Company under the trademark "Surlyn.RTM." and more
recently, by the Exxon Corporation (see U.S. Pat. No. 4,911,451)
under the trademarks "Escor.RTM." and the trade name "lotek", have
become the materials of choice for the construction of golf ball
covers over the traditional "balata" (trans-polyisoprene, natural
or synthetic) rubbers. As stated, the softer balata covers,
although exhibiting enhanced playability properties, lack the
durability (cut and abrasion resistance, fatigue endurance, etc.)
properties required for repetitive play.
[0007] Ionomeric resins are generally ionic copolymers of an
olefin, such as ethylene, and a metal salt of an unsaturated
carboxylic acid, such as acrylic acid, methacrylic acid, or maleic
acid. Metal ions, such as sodium or zinc, are used to neutralize
some portion of the acidic group in the copolymer resulting in a
thermoplastic elastomer exhibiting enhanced properties, i.e.
durability, etc., for golf ball cover construction over balata.
However, some of the advantages gained in increased durability have
been offset to some degree by the decreases produced in
playability. This is because although the ionomeric resins are very
durable, they tend to be very hard when utilized for golf ball
cover construction, and thus lack the degree of softness required
to impart the spin necessary to control the ball in flight. Since
the ionomeric resins are harder than balata, the ionomeric resin
covers do not compress as much against the face of the club upon
impact, thereby producing less spin. In addition, the harder and
more durable ionomeric resins lack the "feel" characteristic
associated with the softer balata related covers.
[0008] As a result, while there are currently more than fifty (50)
commercial grades of ionomers available both from DuPont and Exxon,
with a wide range of properties which vary according to the type
and amount of metal cations, molecular weight, composition of the
base resin (i.e., relative content of ethylene and methacrylic
and/or acrylic acid groups) and additive ingredients such as
reinforcement agents, etc., a great deal of research continues in
order to develop a golf ball cover composition exhibiting not only
the improved impact resistance and carrying distance properties
produced by the "hard" ionomeric resins, but also the playability
(i.e., "spin", "feel", etc.) characteristics previously associated
with the "soft" balata covers, properties which are still desired
by the more skilled golfer.
[0009] Consequently, a number of two-piece (a solid resilient
center or core with a molded cover) and three-piece (a liquid or
solid center, elastomeric winding about the center, and a molded
cover) golf balls have been produced by the present inventors and
others to address these needs. The different types of materials
utilized to formulate the cores, covers, etc. of these balls
dramatically alter the balls' overall characteristics.
[0010] In addition, multi-layered covers containing one or more
ionomer resins have also been formulated in an attempt to produce a
golf ball having the overall distance, playability and durability
characteristics desired. For example, this was addressed by
Spalding Sports Worldwide, Inc., the assignee of the present
invention, in U.S. Pat. No. 4,431,193 where a multi-layered regular
sized, golf ball is disclosed.
[0011] In the '193 patent, a multi-layer golf ball is produced by
initially molding a first cover layer on a spherical core and then
adding a second layer. The first layer is comprised of a hard, high
flexural modulus resinous material such as type 1605 Surlyn.RTM.
(now designated Surlyn.RTM. 8940). Type 1605 Surlyn.RTM.
(Surlyn.RTM. 8940) is a sodium ion based low acid (less than or
equal to 15 weight percent methacrylic acid) ionomer resin having a
flexural modulus of about 51,000 psi. An outer layer of a
comparatively soft, low flexural modulus resinous material such as
type 1855 Surlyn.RTM. (now designated Surlyn.RTM. 9020) is molded
over the inner cover layer. Type 1855 Surlyn.RTM. (Surlyn.RTM.
9020) is a zinc ion based low acid (10 weight percent methacrylic
acid) ionomer resin having a flexural modulus of about 14,000
psi.
[0012] The '193 patent teaches that the hard, high flexural modulus
resin which comprises the first layer provides for a gain in
coefficient of restitution over the coefficient of restitution of
the core. The increase in the coefficient of restitution provides a
ball which serves to attain or approach the maximum initial
velocity limit of 255 feet per second as provided by the United
States Golf Association (U.S.G.A.) rules. The relatively soft, low
flexural modulus outer layer provides essentially no gain in the
coefficient of restitution but provides for the advantageous "feel"
and playing characteristics of a balata covered golf ball.
Unfortunately, however, while a ball of the '193 patent does
exhibit enhanced playability characteristics with improved distance
(i.e. enhanced C.O.R. values) over a number of other then known
multi-layered balls, the ball suffers from poor cut resistance and
relatively short distance (i.e. lower C.O.R. values) when compared
to two-piece, single cover layer balls commercially available
today. These undesirable properties make the ball produced in
accordance with the '193 patent unacceptable by today's
standards.
[0013] The present invention is directed to a new multi-layer golf
ball that readily deforms against a club face under virtually all
conditions. Specifically, the present invention golf balls exhibit
very little or reduced slippage of the ball on the club face,
particularly irons and more particularly short irons, upon
impact.
[0014] These and other objects and features of the invention will
be apparent from the following summary and description of the
invention, the drawings and from the claims.
SUMMARY OF THE INVENTION
[0015] In a first aspect, the present invention provides a golf
ball adapted for reduced slippage upon striking with a golf club.
The golf ball comprises a core, an inner cover layer disposed about
the core, and an outer cover layer disposed on the inner cover
layer. The inner cover layer exhibits a Shore D hardness of from
about 40 to about 80. The outer cover layer is very soft and
exhibits a Shore D hardness of less than 50. The golf ball exhibits
a PGA compression of less than 100.
[0016] In another aspect, the present invention provides a
multi-layer golf ball comprising a core including polybutadiene
having a Mooney viscosity of from about 65 to about 85, an inner
cover layer disposed about the core, and an outer cover layer
disposed on the inner cover layer. The inner cover layer exhibits a
Shore D hardness of from about 50 to about 80. And, the outer cover
layer exhibits a Shore D hardness of less than about 50.
[0017] In yet another aspect, the present invention provides a
multi-layer low slip golf ball comprising a generally spherical
core, an inner cover layer disposed about the core, and an outer
cover layer disposed about the inner cover layer. The core is
recited as including a non-rubber material having a specific
gravity of at least 1.5 and polybutadiene. The outer cover layer is
relatively soft, having a Shore D hardness of less than 50.
[0018] These and other objects and features of the invention will
be apparent from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view of a preferred embodiment
golf ball 2 according to the present invention illustrating a core
10 and a cover 12 consisting of an inner layer 14 and an outer
layer 16 having dimples 18;
[0020] FIG. 2 is another view of the preferred embodiment golf ball
illustrated in FIG. 1 having a core 10 and a cover 12 made of an
inner layer 14 and an outer layer 16 having dimples 18; and
[0021] FIG. 3 is a cross-sectional view of another preferred
embodiment golf ball 4 in accordance with the present invention
illustrating a core 20, a mantle 22, an inner cover layer 24, and
an outer cover layer 26 having dimples 28.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The present invention is directed to improved multi-layer
golf ball compositions and the resulting multi-layer golf balls
produced using the improved compositions. The present invention
includes a multi-layer golf ball that easily and quickly deforms
against a club face under virtually all conditions, and which
exhibits very little or reduced slippage of the ball on the club
face. This characteristic of minimal slippage is particularly
evident with irons, and more particularly with short irons, at
impact. The preferred embodiment golf balls utilize a very soft,
e.g., less than about 50D, and/or relatively thick outer cover
layers, with or without an unusually soft coating and one or more
mantle (or inner) cover layers that range in hardness from about 50
to about 80D. More preferably, the outer layer has a hardness of
Shore D 45 or less, and most preferably, less than about 40. More
preferably, the hardness of the mantle is greater than 70D.
Alternatively a mid-layer of medium hardness is included at a Shore
D of about 40 to about 60.
[0023] Two principal properties involved in golf ball performance
are resilience and hardness. Resilience is determined by the
coefficient of restitution (C.O.R.), the constant "e" which is the
ratio of the relative velocity of two elastic spheres 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
an elastic collision and 0 being equivalent to an inelastic
collision.
[0024] 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.
[0025] 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. Although both the core and the
cover contribute to the coefficient of restitution, the present
invention is directed to the enhanced coefficient of restitution
(and thus travel distance) which is affected by the cover
composition.
[0026] In this regard, the coefficient of restitution of a golf
ball is generally measured by propelling a ball at a given speed
against a hard surface and measuring the ball's incoming and
outgoing velocity electronically. As mentioned above, the
coefficient of restitution is the ratio of the outgoing velocity to
the incoming velocity. The coefficient of restitution must be
carefully controlled in all commercial golf balls in order for the
ball to be within the specifications regulated by the United States
Golf Association (U.S.G.A.). Along this line, the U.S.G.A.
standards indicate that a "regulation" ball cannot have an initial
velocity (i.e., the speed off the club) exceeding 255 feet per
second. Since the coefficient of restitution of a ball is related
to the ball's initial velocity, it is highly desirable to produce a
ball having sufficiently high coefficient of restitution to closely
approach the U.S.G.A. limit on initial velocity, while having an
ample degree of softness (i.e., hardness) to produce enhanced
playability (i.e., spin, etc.).
[0027] The hardness of the ball is the second principal property
involved in the performance of a golf ball. The hardness of the
ball can affect the playability of the ball on striking and the
sound or "click" produced. Hardness is determined by the
deformation (i.e., compression) of the ball under various load
conditions applied across the ball's diameter (i.e., the lower the
compression value, the harder the material). As indicated in U.S.
Pat. No. 4,674,751, softer covers permit the accomplished golfer to
impart proper spin. This is because the softer covers deform on
impact significantly more than balls having "harder" ionomeric
resin covers. As a result, the better player is allowed to impart
fade, draw or backspin to the ball thereby enhancing playability.
Such properties may be determined by various spin rate tests such
as the "nine iron" spin rate test described below in the
Examples.
[0028] Accordingly, the present invention is directed to an
improved multi-layer cover which produces, upon molding each layer
around a core (preferably a solid core) to formulate a multi-layer
cover, a golf ball exhibiting reducing slippage of the ball on the
club face without adversely affecting, and in many instances,
improving the ball's playability (hardness/softness) and/or
durability (i.e., cut resistance, fatigue resistance, etc.)
characteristics.
[0029] The present invention relates to improved multi-layer golf
balls, particularly a golf ball 2 as shown in FIGS. 1 and 2,
comprising a multi-layered cover 12 disposed over a solid core 10,
and methods for making same.
[0030] The present invention also provides multi-layer golf balls
having one or more mantle or interior layers such as golf ball 4
depicted in FIG. 3. The golf ball 4 comprises a core 20, a mantle
layer 22, an inner cover assembly 24, and an outer cover assembly
26 having a plurality of dimples 28.
[0031] Specifically, in a most preferred aspect of the present
invention, a multi-layer cover golf ball having a solid (one or
more layers of thermoplastic or thermoset polymer), liquid, hollow
or wound core and meeting U.S.G.A. specifications is provided.
[0032] The preferred embodiment golf ball has a PGA compression of
less than about 100 and preferably is from about 50 to about 90.
While a thicker outer cover is thought to be beneficial, the
present invention includes golf balls with covers having
thicknesses of from about 0.055 inches and thinner.
[0033] Other critical parameters, such as specific gravity of
various components, exact chemical compositions, wall thicknesses,
spin rates, etc. are described in greater detail herein.
[0034] Cover Assembly
[0035] Referring to the FIGS. 1 and 2 illustrating a preferred
embodiment golf ball 2, the multi-layered cover 12 comprises two
layers: a first or inner layer or ply 14 and a second or outer
layer or ply 16. The inner layer 14 may be comprised of a low acid
(i.e. 16 weight percent acid or less) ionomer blend. Preferably,
the inner layer is comprised of a blend of two or more low acid
(i.e. 16 weight percent acid or less) ionomer resins neutralized to
various extents by different metal cations. The inner cover layer
may or may not include a metal stearate (e.g., zinc stearate) or
other metal fatty acid salt. The purpose of the metal stearate or
other metal fatty acid salt is to lower the cost of production
without affecting the overall performance of the finished golf
ball.
[0036] The low acid ionomers which may be suitable for use in
formulating the inner layer compositions of the subject invention
are ionic copolymers which are the metal, i.e., sodium, zinc,
magnesium, etc., salts of the reaction product of an olefin having
from about 2 to 8 carbon atoms and an unsaturated monocarboxylic
acid having from about 3 to 8 carbon atoms. Preferably, the
ionomeric resins are copolymers of ethylene and either acrylic or
methacrylic acid. In some circumstances, an additional comonomer
such as an acrylate ester (i.e., iso- or n-butylacrylate, etc.) can
also be included to produce a softer terpolymer. The carboxylic
acid groups of the copolymer are partially neutralized (i.e.,
approximately 10-75%, preferably 30-70%) by the metal ions. Each of
the low acid ionomer resins which may be included in the inner
layer cover compositions of the invention contains 16% by weight or
less of a carboxylic acid.
[0037] The inner layer compositions include the low acid ionomers
such as those developed and sold by E. I. DuPont de Nemours &
Company under the trademark "Surlyn.RTM." and by Exxon Corporation
under the trademark "Escor.RTM." or trade name "lotek", or blends
thereof.
[0038] The low acid ionomeric resins available from Exxon under the
designation "Escor.RTM." and or "lotek", are somewhat similar to
the low acid ionomeric resins available under the "Surlyn.RTM."
trademark. However, since the Escor.RTM./lotek ionomeric resins are
sodium or zinc salts of poly(ethylene-acrylic acid) and the
"Surlyn.RTM." resins are zinc, sodium, magnesium, etc. salts of
poly(ethylene-methacrylic acid), distinct differences in properties
exist.
[0039] When utilized in the construction of the inner layer of a
multi-layered golf ball, it has been found that the low acid
ionomer blends extend the range of compression and spin rates
beyond that previously obtainable. More preferably, it has been
found that when two or more low acid ionomers, particularly blends
of sodium and zinc high acid ionomers, are processed to produce the
covers of multi-layered golf balls, (i.e., the inner cover layer
herein) the resulting golf balls will travel further and at an
enhanced spin rate than previously known multi-layered golf balls.
Such an improvement is particularly noticeable in enlarged or
oversized golf balls.
[0040] For example, the normal size, multi-layer golf ball taught
in U.S. Pat. No. 4,650,193 does not incorporate blends of low acid
ionomeric resins of the present invention in the inner cover layer.
In addition, the multi-layered ball disclosed in the '193 patent
suffers substantially in durability in comparison with the present
invention.
[0041] Furthermore, it has been discovered that use of a inner
layer formulated from blends of lower acid ionomers produces
multi-layer golf balls having enhanced compression and spin rates.
These are the properties desired by the more skilled golfer.
[0042] With respect to the outer layer, such as layer 16 shown in
FIGS. 1 and 2, of the multi-layered cover of the present invention,
the outer cover layer is comparatively softer than the low acid
ionomer blend based inner layer. The softness provides for the
enhanced feel and playability characteristics typically associated
with balata or balata-blend balls.
[0043] The outer cover material is comprised of ionomer,
polyurethane (cast, reaction injection molded (RIM), thermoplastic
polyurethane (TPU)), Pebax.RTM., Hytrel.RTM., metallocene, or any
other thermoplastic (or thermosetting) elastomer, or silicone that
has a Shore D hardness of less than or equal to about 50D.
[0044] More specifically, the outer layer or ply may be comprised
of a relatively soft, low modulus (about 1,000 psi to about 10,000
psi) and low acid (less than 16 weight percent acid) ionomer,
ionomer blend or a non-ionomeric thermoplastic elastomer such as,
but not limited to, a polyurethane, a polyester elastomer such as
that marketed by DuPont under the trademark Hytrel.RTM., or a
polyester amide such as that marketed by Elf Atochem S. A. under
the trademark Pebax.RTM.. The outer layer is fairly thin, but thick
enough to achieve desired playability characteristics while
minimizing expense.
[0045] Preferably, the outer layer includes a blend of hard and
soft (low acid) ionomer resins such as those described in U.S. Pat.
Nos. 4,884,814 and 5,120,791, both incorporated herein by
reference. Specifically, a desirable material for use in molding
the outer layer comprises a blend of a high modulus (hard), low
acid, ionomer with a low modulus (soft), low acid, ionomer to form
a base ionomer mixture. A high modulus ionomer herein is one which
measures from about 15,000 to about 70,000 psi as measured in
accordance with ASTM method D-790. The hardness may be defined as
at least 50 on the Shore D scale as measured in accordance with
ASTM method D-2240. All hardness values described herein, for cover
layers having dimples defined therein, are with regard to the land
area on the cover, extending between dimples.
[0046] A low modulus ionomer suitable for use in the outer layer
blend has a flexural modulus measuring from about 1,000 to about
10,000 psi, with a hardness of about 20 to about 40 on the Shore D
scale.
[0047] The hard ionomer resins utilized to produce the outer cover
layer composition hard/soft blends include ionic copolymers which
are the sodium, zinc, magnesium or lithium salts of the reaction
product of an olefin having from 2 to 8 carbon atoms and an
unsaturated monocarboxylic acid having from 3 to 8 carbon atoms.
The carboxylic acid groups of the copolymer may be totally or
partially (i.e. approximately 15-75 percent) neutralized.
[0048] The hard ionomeric resins are likely copolymers of ethylene
and either acrylic and/or methacrylic acid, with copolymers of
ethylene and acrylic acid being the most preferred. Two or more
types of hard ionomeric resins may be blended into the outer cover
layer compositions in order to produce the desired properties of
the resulting golf balls.
[0049] As discussed earlier herein, the hard ionomeric resins
introduced under the designation Escor.RTM. and sold under the
designation "lotek" are somewhat similar to the hard ionomeric
resins sold under the Surlyn.RTM. trademark. However, since the
"lotek" ionomeric resins are sodium or zinc salts of
poly(ethylene-acrylic acid) and the Surlyn.RTM. resins are zinc or
sodium salts of poly(ethylene-methacrylic acid) some distinct
differences in properties exist. As more specifically indicated in
the data set forth below, the hard "lotek" resins (i.e., the
acrylic acid based hard ionomer resins) are the more preferred hard
resins for use in formulating the outer layer blends for use in the
present invention. In addition, various blends of "lotek" and
Surlyn.RTM. hard ionomeric resins, as well as other available
ionomeric resins, may be utilized in the present invention in a
similar manner.
[0050] Examples of commercially available hard ionomeric resins
which may be used in the present invention in formulating the inner
and outer cover blends include the hard sodium ionic copolymer sold
under the trademark Surlyn.RTM. 8940 and the hard zinc ionic
copolymer sold under the trademark Surlyn.RTM. 9910. Surlyn.RTM.
8940 is a copolymer of ethylene with methacrylic acid and about 15
weight percent acid which is about 29 percent neutralized with
sodium ions. This resin has an average melt flow index of about
2.8. Surlyn.RTM. 9910 is a copolymer of ethylene and methacrylic
acid with about 15 weight percent acid which is about 58 percent
neutralized with zinc ions. The average melt flow index of
Surlyn.RTM. 9910 is about 0.7. The typical properties of
Surlyn.RTM. 9910 and 8940 are set forth below in Table 1:
1TABLE 1 Typical Properties of Commercially Available Hard Surlyn
.RTM. Resins Suitable for Use in the Inner and Outer Layer Blends
of the Present Invention ASTM D 8940 9910 8920 8528 9970 9730
Cation Type Sodium Zinc Sodium Sodium Zinc Zinc Melt flow index,
D-1238 2.8 0.7 0.9 1.3 14.0 1.6 gms/10 min. Specific Gravity, D-792
0.95 0.97 0.95 0.94 0.95 0.95 g/cm.sup.3 Hardness, Shore D D-2240
66 64 66 60 62 63 Tensile Strength, D-638 (4.8) (3.6) (5.4) (4.2)
(3.2) (4.1) (kpsi), MPa 33.1 24.8 37.2 29.0 22.0 28.0 Elongation, %
D-638 470 290 350 450 460 460 Flexural Modulus, D-790 (51) (48)
(55) (32) (28) (30) (kpsi) MPa 350 330 380 220 190 210 Tensile
Impact (23.degree. C.) D-1822S 1020 1020 865 1160 760 1240
KJ/m.sub.2 (ft.-lbs./in.sup.2) (485) (485) (410) (550) (360) (590)
Vicat Temperature, .degree. C. D-1525 63 62 58 73 61 73
[0051] Examples of the more pertinent acrylic acid based hard
ionomer resin suitable for use in the present inner and outer cover
composition sold under the "lotek" tradename by the Exxon
Corporation include lotek 4000, lotek 4010, lotek 8000, lotek 8020
and lotek 8030. The typical properties of these and other lotek
hard ionomers suited for use in formulating the inner and outer
layer cover compositions are set forth below in Table 2:
2TABLE 2 Typical Properties of Iotek Ionomers ASTM Method Units
4000 4010 8000 8020 8030 Resin Properties Cation type zinc zinc
sodium sodium sodium Melt index D-1238 g/10 min. 2.5 1.5 0.8 1.6
2.8 Density D-1505 kg/m.sup.3 963 963 954 960 960 Melting Point
D-3417 .degree. C. 90 90 90 87.5 87.5 Crystallization Point D-3417
.degree. C. 62 64 56 53 55 Vicat Softening Point D-1525 .degree. C.
62 63 61 64 67 % Weight Acrylic Acid 16 11 % of Acid Groups cation
neutralized 30 40 Plaque Properties (3 mm thick, compression
molded) Tensile at break D-638 MPa 24 26 36 31.5 28 Yield point
D-638 MPa none none 21 21 23 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 Part Drop Impact D-1709 g/micron 12.4 12.5 20.3 ASTM Method
Units 7010 7020 7030 Resin Properties Cation type zinc zinc zinc
Melt Index D-1238 g/10 min. 0.8 1.5 2.5 Density D-1505 kg/m.sup.3
960 960 960 Melting Point D-3417 .degree. C. 90 90 90
Crystallization D-3417 .degree. C. -- -- -- Point Vicat Softening
D-1525 .degree. C. 60 63 62.5 Point % Weight Acrylic Acid -- -- --
% of Acid Groups -- -- -- Cation Neutralized Plaque Properties (3
mm thick, compression molded) Tensile at break D-636 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
[0052] Comparatively, soft ionomers are used in formulating the
hard/soft blends of the inner and outer cover compositions. These
ionomers include acrylic acid based soft ionomers. They are
generally characterized as comprising sodium or zinc salts of a
terpolymer of an olefin having from about 2 to 8 carbon atoms,
acrylic acid, and an unsaturated monomer of the acrylate ester
class having from 1 to 21 carbon atoms. The soft ionomer is
preferably a zinc based ionomer made from an acrylic acid base
polymer in an unsaturated monomer of the acrylate ester class. The
soft (low modulus) ionomers have a hardness from about 20 to about
40 as measured on the Shore D scale and a flexural modulus from
about 1,000 to about 10,000, as measured in accordance with ASTM
method D-790.
[0053] Certain ethylene-acrylic acid based soft ionomer resins
developed by the Exxon Corporation under the designation "lotek
7520" (referred to experimentally by differences in neutralization
and melt indexes as LDX 195, LDX 196, LDX 218 and LDX 219) may be
combined with known hard ionomers such as those indicated above to
produce the inner and outer cover layers. The combination produces
higher C.O.R.s at equal or softer hardness, higher melt flow (which
corresponds to improved, more efficient molding, i.e., fewer
rejects) as well as significant cost savings versus the inner and
outer layers of multi-layer balls produced by other known hard-soft
ionomer blends as a result of the lower overall raw materials costs
and improved yields.
[0054] While the exact chemical composition of the resins to be
sold by Exxon under the designation lotek 7520 is considered by
Exxon to be confidential and proprietary information, Exxon's
experimental product data sheet lists the following physical
properties of the ethylene acrylic acid zinc ionomer developed by
Exxon:
3TABLE 3 Physical Properties of Iotek 7520 Property ASTM Method
Units Typical Value Melt Index D-1238 g/10 min. 2 Density D-1505
kg/m.sup.3 0.962 Cation Zinc Melting Point D-3417 .degree. C. 66
Crystallization D-3417 .degree. C. 49 Point Vicat Softening D-1525
.degree. C. 42 Point
[0055]
4 Plaque Properties (2 mm thick Compression Molded Plaques) Tensile
at Break D-638 MPa 10 Yield Point D-638 MPa None Elongation at
Break D-638 % 760 1% Secant Modulus D-638 MPa 22 Shore D Hardness
D-2240 32 Flexural Modulus D-790 MPa 26 Zwick Rebound ISO 4862 % 52
De Mattia Flex D-430 Cycles >5000 Resistance
[0056] In addition, test data indicates that lotek 7520 resins have
Shore D hardnesses of about 32 to 36 (per ASTM D-2240), melt flow
indexes of 3.+-.0.5 g/10 min (at 190.degree. C. per ASTM D-1288),
and a flexural modulus of about 2500-3500 psi (per ASTM D-790).
Furthermore, testing by an independent testing laboratory by
pyrolysis mass spectrometry indicates that lotek 7520 resins are
generally zinc salts of a terpolymer of ethylene, acrylic acid, and
methyl acrylate.
[0057] Furthermore, it has been found that a newly developed grade
of an acrylic acid based soft ionomer available from the Exxon
Corporation under the designation lotek 7510, is also effective,
when combined with the hard ionomers indicated above in producing
golf ball covers exhibiting higher C.O.R. values at equal or softer
hardness than those produced by known hard-soft ionomer blends. In
this regard, lotek 7510 has the advantages (i.e. improved flow,
higher C.O.R. values at equal hardness, increased clarity, etc.)
produced by the lotek 7520 resin when compared to the methacrylic
acid base soft ionomers known in the art (such as the Surlyn 8625
and the Surlyn 8629 combinations disclosed in U.S. Pat. No.
4,884,814).
[0058] In addition, lotek 7510, when compared to lotek 7520,
produces slightly higher C.O.R. values at equal softness/hardness
due to the lotek 7510's higher hardness and neutralization.
Similarly, lotek 7510 produces better release properties (from the
mold cavities) due to its slightly higher stiffness and lower flow
rate than lotek 7520. This is important in production where the
soft covered balls tend to have lower yields caused by sticking in
the molds and subsequent punched pin marks from the knockouts.
[0059] According to Exxon, lotek 7510 is of similar chemical
composition as lotek 7520 (i.e. a zinc salt of a terpolymer of
ethylene, acrylic acid, and methyl acrylate) but is more highly
neutralized. Based upon FTIR analysis, lotek 7520 is estimated to
be about 30-40 wt.-% neutralized and lotek 7510 is estimated to be
about 40-60 wt.-% neutralized. The typical properties of lotek 7510
in comparison of those of lotek 7520 are set forth below:
5TABLE 4 Physical Properties of Iotek 7510 in Comparison to Iotek
7520 IOTEK 7520 IOTEK 7510 MI, g/10 min 2.0 0.8 Density, g/cc 0.96
0.97 Melting Point, .degree. F. 151 149 Vicat Softening Point,
.degree. F. 108 109 Flex Modulus, psi 3800 5300 Tensile Strength,
psi 1450 1750 Elongation, % 760 690 Hardness, Shore D 32 35
[0060] It has been determined that when hard/soft ionomer blends
are used for the outer cover layer, good results are achieved when
the relative combination is in a range of about 90 to about 10
percent hard ionomer and about 10 to about 90 percent soft ionomer.
The results are improved by adjusting the range to about 75 to 25
percent hard ionomer and 25 to 75 percent soft ionomer. Even better
results are noted at relative ranges of about 60 to 90 percent hard
ionomer resin and about 40 to 10 percent soft ionomer resin.
However, as previously noted, it is preferred that the outer cover
layer have a Shore D hardness of 50 or less, more preferably less
than about 45, and most preferably less than about 40.
[0061] Specific formulations which may be used in the cover
composition are included in the examples set forth in U.S. Pat.
Nos. 5,120,791 and 4,884,814. The present invention is in no way
limited to those examples.
[0062] Moreover, in alternative embodiments, the outer cover layer
formulation may also comprise a soft, low modulus non-ionomeric
thermoplastic elastomer including a polyester polyurethane such as
B. F. Goodrich Company's Estane.RTM. polyester polyurethane X4517.
According to B. F. Goodrich, Estane.RTM. X-4517 has the following
properties set forth in Table 5:
6TABLE 5 Properties of Estane .RTM. X-4517 Tensile 1430 100% 815
200% 1024 300% 1193 Elongation 641 Youngs Modulus 1826 Hardness A/D
88/39 Dayshore Rebound 59 Solubility in Water Insoluble Melt
processing temperature >350.degree. F. (>177.degree. C.)
Specific Gravity (water equals 1.0) 1.1-1.3
[0063] Other soft, relatively low modulus non-ionomeric
thermoplastic elastomers may also be utilized to produce the outer
cover layer as long as the non-ionomeric thermoplastic elastomers
produce the playability and durability characteristics desired
without adversely effecting the enhanced spin characteristics
produced by the low acid ionomer resin compositions. These include,
but are not limited to, thermoplastic polyurethanes such as Texin
thermoplastic polyurethanes from Mobay Chemical Co. and the
Pellethane thermoplastic polyurethanes from Dow Chemical Co.;
ionomer/rubber blends such as those in Spalding U.S. Pat. Nos.
4,986,545; 5,098,105 and 5,187,013; and, Hytrel.RTM. polyester
elastomers from DuPont and Pebax.RTM. polyesteramides from Elf
Atochem S. A.
[0064] In a two-layer cover version of the present invention golf
ball, such as illustrated in FIGS. 1 and 2, the outermost cover
layer is preferably thicker than 0.055 inches, and is most
preferably from about 0.70 to about 0.100 inches thick. Preferably,
the outermost cover layer is made of nearly all lotek 7510 or
similar material disposed over a mantle of high acid ionomer at a
thickness of, or less than, about 0.50 inches. The core may be
somewhat harder and faster than current cores to achieve good
overall distance.
[0065] In a three-layer cover version, such as illustrated in FIG.
3, each layer has a thickness of from about 0.020 to about 0.100
inches and preferably from about 0.030 to about 0.070 inches.
Preferably, the outer cover exhibits a Shore D hardness of less
than 50D, and more preferably less than 47D. Furthermore, the outer
cover is mostly, if not all soft ionomer or polyurethane,
thermoplastic polyurethane, Pebax.RTM., Hytrel.RTM., or blends
thereof. The middle layer is preferably a medium hardness hard/soft
ionomer blend or any other material that exhibits a 40 to 60D
hardness. Preferably, the innermost layer exhibits a hardness of
more than 50D and preferably more than 70D and could be high acid
ionomer, or any other material that functions in a suitable
fashion.
[0066] In preparing golf balls in accordance with the present
invention, a hard inner cover layer is molded (by injection molding
or by compression molding) about a core (preferably a solid core).
A detailed description of other preferred cores is provided herein.
A comparatively softer outer layer is then molded over the inner
layer.
[0067] Preferably, together, the core, the inner cover layer and
the outer cover layer combine to form a ball having a diameter of
1.680 inches or more, the minimum diameter permitted by the rules
of the United States Golf Association and weighing about 1.620
ounces.
[0068] Additional materials may be added to the cover compositions
(both inner and outer cover layer) of the present invention
including dyes (for example, Ultramarine Blue sold by Whitaker,
Clark and Daniels of South Plainsfield, N.J.) (see U.S. Pat. No.
4,679,795); pigments such as titanium dioxide, zinc oxide, barium
sulfate and zinc sulfate; and UV absorbers; antioxidants;
antistatic agents; and stabilizers. Further, the cover compositions
of the present invention may also contain softening agents, such as
plasticizers, processing aids, etc. and reinforcing material such
as glass fibers and inorganic fillers, as long as the desired
properties produced by the golf ball covers are not impaired.
[0069] The various cover composition layers of the present
invention may be produced according to conventional melt blending
procedures. In the case of the outer cover layer, when a blend of
hard and soft, low acid ionomer resins are utilized, the hard
ionomer resins are blended with the soft ionomeric resins and with
a master batch containing the desired additives in a Banbury.RTM.
mixer, two-roll mill, or extruder prior to molding. The blended
composition is then formed into slabs and maintained in such a
state until molding is desired. Alternatively, a simple dry blend
of the pelletized or granulated resins and color master batch may
be prepared and fed directly into the injection molding machine
where homogenization occurs in the mixing section of the barrel
prior to injection into the mold. If necessary, further additives
such as an inorganic filler, etc., may be added and uniformly mixed
before initiation of the molding process. A similar process is
utilized to formulate the low acid ionomer resin compositions used
to produce the inner cover layer.
[0070] As previously noted, the preferred golf balls of the present
invention utilize improved dimple patterns. These are set forth in
detail in the following patents assigned to the same assignee as
the present invention, Spalding Sports Worldwide, Inc.: U.S. Pat.
Nos. Des. 401,986; Des. 401,979; U.S. Pat. Nos. 5,833,443;
5,772,532; 5,766,098; 5,735,756; 5,688,194; U.S. Pat. Nos. Des.
383,179; Des. 381,723; Des. 381,722; Des. 381,721; Des. 381,720;
Des. 377,816; U.S. Pat. No. 5,588,924; U.S. Pat. No. Des. 375,339;
U.S. Pat. Nos. 5,569,100; 5,507,493; 5,482,287; 5,482,286; and
5,470,075, all of which are hereby incorporated by reference.
[0071] Mantle Assembly and Filler Materials
[0072] The preferred embodiment golf ball may also comprise one or
more mantle layers disposed between the previously described cover
assembly and a core assembly described below. One such preferred
configuration is shown in FIG. 3.
[0073] The mantle preferably comprises high acid ionomer
(.gtoreq.16%) or low acid ionomer (.gtoreq.15%) or a hard/soft
blend, but preferably has a Shore D of from about 50 to about 80D
and is harder than the outer cover layer. The mantle thickness is
generally from about 0.020 inches to about 0.150 inches and
preferably from about 0.030 to about 0.060 inches.
[0074] Alternatively, the mantle and/or inner layers comprise
non-ionomeric materials of Shore D hardness greater than 50 such as
polyamide, AMODEL.TM., polycarbonate, silicone, polyolefinic,
polyester, Hytrel.RTM., etc.
[0075] As previously noted, FIG. 3 illustrates another preferred
embodiment golf ball 4 in accordance with the present invention.
That preferred ball 4 comprises a core 20, at least one mantle
layer 22 disposed about the core 20, an inner cover layer 24
disposed about the mantle layer 22, and an outer cover layer 26
disposed about the inner cover layer 24. The core 20 and cover
layers 24, 26 are as described herein.
[0076] More specifically, the mantle layer may be formed from a
wide array of materials including ionomers and/or non-ionomeric
materials. Examples of non-ionomeric materials which are suitable
for use in forming the mantle layer include, but are not limited
to, low density polyethylene, linear low density polyethylene, high
density polyethylene, polypropylene, rubber-toughened olefin
polymers, acid copolymers which do not become part of an ionomeric
copolymer when used in the inner cover layer, plastomers,
flexomers, and thermoplastic elastomers such as
styrene/butadiene/styrene (SBS) or
styrene/ethylene-butylene/styrene (SEBS) block copolymers,
including Kraton.RTM. (Shell), dynamically vulcanized elastomers
such as Santoprene.RTM. (Monsanto), ethylene vinyl acetates such as
Elvax.RTM. (DuPont), ethylene methyl acrylates such as Optema.RTM.
(Exxon), polyvinyl chloride resins, and other elastomeric materials
may be used. It is desirable that the polyolefin be a tough, low
density material. The non-ionomeric polyolefins can be mixed with
ionomers.
[0077] The cover, mantle, and/or core may include fillers which
include, but are not limited to, clay, talc, asbestos, graphite,
glass, mica, calcium metasilicate, 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, polystyrene, 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. Dark colored fillers generally are not
preferred for use at the outer surface of the ball if a white ball
is desired. 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.
[0078] Examples of various suitable heavy filler materials which
can be included in the present invention are set forth in Table 6
as follows:
7 TABLE 6 Spec. Grav. Filler Type graphite fibers 1.5-1.8
precipitated hydrated silica 2.0 clay 2.62 talc 2.85 asbestos 2.5
glass fibers 2.55 aramid fibers (Kevlar .RTM.) 1.44 mica 2.8
calcium metasilicate 2.9 barium sulfate 4.6 zinc sulfide 4.1
silicates 2.1 diatomaceous earth 2.3 calcium carbonate 2.71
magnesium carbonate 2.20 Metals and Alloys (powders) titanium 4.51
tungsten 19.35 aluminum 2.70 bismuth 9.78 nickel 8.90 molybdenum
10.2 iron 7.86 copper 8.94 brass 8.2-8.4 boron 2.364 bronze
8.70-8.74 cobalt 8.92 beryllium 1.84 zinc 7.14 tin 7.31 Metal
Oxides zinc oxide 5.57 iron oxide 5.1 aluminum oxide 4.0 titanium
dioxide 3.9-4.1 magnesium oxide 3.3-3.5 zircomium oxide 5.73 Metal
Stearates zinc stearate 1.09 calcium stearate 1.03 barium stearate
1.23 lithium stearate 1.01 magnesium stearate 1.03 Particulate
carbonaceous materials graphite 1.5-1.8 carbon black 1.8 natural
bitumen 1.2-1.4 cotton flock 1.3-1.4 cellulose flock 1.15-1.5
leather fiber 1.2-1.4
[0079] The amount and type of heavy weight filler material utilized
is dependent upon the overall characteristics of the multi-layered
golf ball desired. Generally, lesser amounts of high specific
gravity materials are necessary to produce an increase in the
moment of inertia in comparison to low specific gravity materials.
Furthermore, handling and processing conditions can also affect the
type of heavy weight filler material incorporated into cover
layers.
[0080] The most preferred ball construction uses a bronze filled
mantle to increase the Moment of Inertia (M.O.I.). This
construction utilizes a 19 parts per hundred (PPH) addition of
bronze powder to the mantle. This results in a specific gravity for
the mantle of about 1.12. It is possible to increase the amount of
bronze or other heavy metal. Another most preferred filler is
tungsten powder due to its very high specific gravity. Other heavy
fillers may be utilized to reduce the amount of weighting material
otherwise added to the core. The preferred minimum core specific
gravity is about 1.05.
[0081] Using the multi-layer construction described herein, the
mantle layer can be loaded with tungsten powder to produce a golf
ball weighing about 45.5 grams. A preferred set of specific
gravities for a preferred embodiment golf ball is set forth
below.
8 TABLE 7 Sp. Gr. Core 1.05 Mantle 1.63 Cover 0.96
[0082] A preferred mantle composition is as follows:
9 TABLE 8 PPH VOLUME % Ionomer 100.0 104 Tungsten 75.7 3.9
[0083] Using tungsten powder, only 3.9% by volume is required to
obtain a mantle specific gravity of 1.63. This greatly increases
the M.O.I., reduces spin decay and increases the total distance of
the resulting ball due to increased roll.
[0084] The calculated M.O.I. for this preferred construction is
0.4640 oz.-inch.sup.2. A typical 1.68 inch two-piece golf ball has
a M.O.I. of 0.445 oz.-inch.sup.2. Tungsten or other heavy metal can
also be added to the outer cover to further increase the M.O.I.
provided that the overall ball weight does not exceed the U.S.G.A.
maximum. Adding the powdered metal to the cover will make it
necessary to use a white pigmented paint to cover the dark color of
the molded cover.
[0085] Core Assembly
[0086] The core is solid, liquid, gel, wound, multi-piece solid,
and in at least one embodiment, is a solid diene rubber core
comprising a very heavy, essentially non-rubber inner core of a
heavy material (S.G..gtoreq.1.5) such as steel or tungsten.
[0087] Alternatively, the core may be a dual-core comprising a
stainless steel center. This would enable a golfer to impart very
high initial spin rates more readily than current
constructions.
[0088] Another type of core configuration encompassed by the
present invention utilizes a liquid centered wound core. Other
examples utilize a solid or gel-centered wound core. Still other
examples uses a "unique" hollow or liquid or gel filled sphere of
ionomer as a core.
[0089] The conventional solid core is about 1.545 inches in
diameter, although it can range from about 1.37 to about 1.575
inches. Conventional solid cores are typically compression molded
from a slug of uncured or lightly cured elastomer composition
comprising a high cis content polybutadiene and a metal salt of an
.alpha., .beta., ethylenically unsaturated carboxylic acid such as
zinc mono or diacrylate or methacrylate. To achieve higher
coefficients of restitution in the core, the manufacturer may
include fillers such as small amounts of a metal oxide such as zinc
oxide. In addition, larger amounts of metal oxide than those that
are needed to achieve the desired coefficient are often included in
conventional cores in order to increase the core weight so that the
finished ball more closely approaches the U.S.G.A. upper weight
limit of 1.620 ounces. Other materials may be used in the core
composition including compatible rubbers or ionomers, and low
molecular weight fatty acids such as stearic acid. Free radical
initiators such as peroxides are admixed with the core composition
so that on the application of heat and pressure, a complex curing
cross-linking reaction takes place.
[0090] The core compositions of the preferred embodiments of the
present invention may comprise one or more rubber or elastomeric
components and an array of non-rubber or non-elastomeric
components. The preferred rubber components of the core
compositions of the invention comprise a particular solid
polybutadiene having an ultra-high Mooney viscosity and certain
molecular weight characteristics described in detail below, and one
or more other optional polybutadienes. The non-rubber components of
the core compositions of the invention comprise one or more
crosslinking agents which preferably include an unsaturated
carboxylic acid component, a free radical initiator to promote
cross linking, one or more optional modifying agents, fillers such
as those previously described with respect to the mantle,
moldability additives, processing additives, and dispersing agents,
all of which are described in greater detail below.
[0091] The preferred polybutadiene resin for use in the present
invention composition has a relatively ultra high Mooney viscosity.
A "Mooney" unit is an arbitrary unit used to measure the plasticity
of raw, or unvulcanized rubber. The plasticity in Mooney units is
equal to the torque, measured on an arbitrary scale, on a disk in a
vessel that contains rubber at a temperature of 212.degree. F.
(100.degree. C.) and that rotates at two revolutions per
minute.
[0092] The measurement of Mooney viscosity, i.e. Mooney viscosity
(ML.sub.1+4 (100.degree. C.)), is defined according to the standard
ASTM D-1646, herein incorporated by reference. In ASTM D-1646, it
is stated that the Mooney viscosity is not a true viscosity, but a
measure of shearing torque over a range of shearing stresses.
Measurement of Mooney viscosity is also described in the Vanderbilt
Rubber Handbook, 13th Ed., (1990), pages 565-566, also herein
incorporated by reference. Generally, polybutadiene rubbers have
Mooney viscosities, measured at 212.degree. F., of from about 25 to
about 65. Instruments for measuring Mooney viscosities are
commercially available, such as a Monsanto Mooney Viscometer, Model
MV 2000. Another commercially available device is a Mooney
viscometer made by Shimadzu Seisakusho Ltd.
[0093] As will be understood by those skilled in the art, polymers
may be characterized according to various definitions of molecular
weight. The "number average molecular weight," M.sub.n, is defined
as: 1 M n = W i W i / M i
[0094] where W.sub.i is the molecular weight of a fraction or
sample of the polymer and M.sub.i is the total number of fractions
or samples.
[0095] "Weight average molecular weight," M.sub.W, is defined as: 2
M w = W i M i W i
[0096] where W.sub.i and M.sub.i have the same meanings as noted
above.
[0097] The "Z-average molecular weight," M.sub.Z, is defined as: 3
M z = W 1 M i 2 W i M i
[0098] where W.sub.i and M.sub.i also have the same meanings as
noted above.
[0099] "M.sub.peak" is the molecular weight of the most common
fraction or sample, i.e. having the greatest population.
[0100] Considering these various measures of molecular weight
provides an indication of the distribution or rather the "spread"
of molecular weights of the polymer under review.
[0101] A common indicator of the degree of molecular weight
distribution of a polymer is its "polydispersity,"P: 4 P = M w M
n
[0102] Polydispersity, or "dispersity" as sometimes referred to
herein, also provides an indication of the extent to which the
polymer chains share the same degree of polymerization. If the
polydispersity is 1.0, then all polymer chains must have the same
degree of polymerization. Since weight average molecular weight is
always equal to or greater than the number average molecular
weight, polydispersity, by definition, is equal to or greater than
1.0:
P.gtoreq.1.0
[0103] The particular polybutadiene for use in the preferred
embodiment compositions of the present invention (i) exhibits a
Mooney viscosity of from about 65 to about 85, and preferably from
about 70 to about 83; ii) has a number average molecular weight
M.sub.n of from about 90,000 to about 130,000; and preferably from
about 100,000 to about 120,000; iii) has a weight average molecular
weight M.sub.W of from about 250,000 to about 350,000; and
preferably from about 290,000 to about 310,000; iv) has a Z-average
molecular weight M.sub.Z of about 600,000 to about 750,000; and
preferably from about 660,000 to about 700,000; and, v) has a peak
molecular weight M.sub.peak of about 150,000 to about 200,000; and
preferably from about 170,000 to about 180,000.
[0104] The term "ultra high Mooney viscosity" used in reference to
the preferred polybutadienes, refers to such polybutadienes having
Mooney viscosities of from about 65 to about 85.
[0105] The polydispersity of the particular polybutadiene for use
in the preferred embodiment compositions typically ranges from
about 1.9 to about 3.9; and preferably from about 2.4 to about 3.1.
Most preferably, the polydispersity is about 2.7.
[0106] The particular polybutadiene for use in the preferred
embodiment compositions preferably contains a majority fraction of
polymer chains containing a cis-1, 4 bond, more preferably, having
a cis-1, 4 polybutadiene content of about 90%, and most preferably,
having a cis-1,4 polybutadiene content of at least about 95%. A
preferred polybutadiene, as described herein, is obtained by
utilizing a cobalt or cobalt-based catalyst. However,
polybutadienes exhibiting the foregoing characteristics, which are
obtained by using a lanthanum rare earth catalyst, nickel catalyst,
or mixtures thereof, are also encompassed by the present invention.
It is also envisioned that other catalysts could be utilized to
produce the particular preferred polybutadienes described herein.
Examples of such other catalysts include, but are not limited to,
aluminum, boron, lithium, neodymium, titanium, and combinations
thereof.
[0107] The polybutadiene utilized in the present invention is a
solid at room temperature. Consequently, the polybutadiene is
referenced as a "solid" polybutadiene, as opposed to a "liquid"
which means that the rubber is flowable at room temperature.
[0108] A commercially available polybutadiene corresponding to the
noted preferred ultra-high viscosity polybutadiene, and which is
suitable for use in the preferred embodiment compositions in
accordance with the present invention is available under the
designation Cariflex.RTM. BCP 820, from Shell Chimie of France. The
properties and characteristics of this preferred polybutadiene are
set forth below in Table 9.
10TABLE 9 Properties of Shell Chimie BCP 820 (Also known as
BR-1202J) Property Value Mooney Viscosity (approximate) 73-83
Volaties Content 0.5% maximum Ash Content 0.1% maximum Cis
1,4-polybutadiene Content 95.0% minimum Stabilizer Content 0.2 to
0.3% Polydispersity 2.7 Molecular Weight Data: Trial 1 Trial 2
M.sub.n 110,000 111,000 M.sub.w 300,000 304,000 M.sub.z 680,000
M.sub.peak 175,000
[0109] The compositions of the present invention may also utilize
other polybutadiene resins in addition to the noted particular
polybutadiene exhibiting an ultra-high Mooney viscosity, such as
the BCP 820 resin. For example, Cariflex.RTM. BR-1 220
polybutadiene available from Shell Chemical (see Table 10 below);
and Taktene.TM. 220 polybutadiene available from Bayer Corp. of
Orange, Tex. (see Tables 11 and 12 below) may be utilized as other
polybutadienes in combination with the particular ultra-high Mooney
viscosity polybutadiene component described herein. Generally,
these other polybutadienes have Mooney viscosities in the range of
about 25 to 65. It is also contemplated that a similar
polybutadiene resin, BCP 819, commercially available from Shell
Chimie, may be used in conjunction with BCP 820.
11TABLE 10 Properties of Cariflex .RTM. BR-1220 Polybutadiene
Physical Properties: Polybutadiene Rubber CIS 1,4 Content - 97%-99%
Min. Stabilizer Type - Non Staining Total Ash - 0.5% Max. Specific
Gravity - 0.90-0.92 Color - Transparent, clear, Lt. Amber Moisture
- 0.3% max. ASTM 1416.76 Hot Mill Method Polymer Mooney Viscosity -
(35-45 Cariflex .RTM.) (ML1 + @ 212.degree. F.) 90% Cure -
10.0-13.0 Polydispersity 2.75-3.0 Molecular Weight Data: Trial 1
Trial 2 M.sub.n 80,000 73,000 M.sub.w 220,000 220,000 M.sub.z
550,000 M.sub.peak 110,000
[0110]
12TABLE 11 Properties of Taktene .TM. 220 Polybutadiene Physical
Properties: Polybutadiene Rubber CIS 1,4 Content (%) - 98% Typical
Stabilizer Type - Non Staining 1.0-1.3% Total Ash - 0.25 Max. Raw
Polymer Mooney Visc. - 35-45 40 Typical (ML1 + 4' @ 212 Deg.
F./212.degree. F.) Specific Gravity - 0.91 Color - Transparent -
almost colorless (15 APHA Max.) Moisture % - 30% Max. ASTM 1416-76
Hot Mill Method
[0111]
13TABLE 12 Properties of Taktene .TM. 220 Polybutadiene Product A
low Mooney viscosity, non-staining, solution Description
polymerized, high cis-1,4-polybutadiene rubber. Raw Polymer
Properties Property Range Test Method Mooney viscosity 1 +
4(212.degree. F.) 40 .+-. 5 ASTM D 1646 Volatile matter (wt %) 0.3
max. ASTM D 1416 Total Ash (wt %) 0.25 max. ASTM D 1416
Polydispersity [need data] Cure.sup.(1)(2) Characteristics Minimum
torque M.sub.L (dN.m) 9.7 .+-. 2.2 ASTM D 2084 (lbf).in) 8.6 .+-.
1.9 ASTM D 2084 Maximum torque M.sub.H (dN.m) 35.7 .+-. 4.8 ASTM D
2084 (lbf.in) 31.6 .+-. 4.2 ASTM D 2084 t.sub.21 (min) 4 .+-. 1.1
ASTM D 2084 t'50 (min) 9.6 .+-. 2.5 ASTM D 2084 t'90 (min) 12.9
.+-. 3.1 ASTM D 2084 Other Product Property Typical Value Features
Specific gravity 0.91 Stabilizer type Non-staining (1) Monsanto
Rheometer at 160.degree. C., 1.7 Hz (100 cpm), 1 degree arc,
micro-die (2) Cure characteristics determined on ASTM D 3189 MIM
mixed compound: TAKTENE .TM. 220 100 (parts by mass) Zinc oxide 3
Stearic acid 2 IRB #6 black (N330) 60 Naphthenic oil 15 TBBS 0.9
Sulfur 1.5 *This specification refers to product manufactured by
Bayer Corp., Orange, Texas, U.S.A.
[0112] The preferred embodiment core compositions of the present
invention generally comprise from about 100 parts by weight of
elastomeric or rubber components, i.e. the noted ultra-high Mooney
viscosity polybutadiene, and from about 60 to about 80, or more,
parts by weight of non-rubber or non-elastomeric components.
Preferably, the core compositions comprise about 100 parts of
rubber components and from about 60 to about 80, or more, parts by
weight of non-rubber components. It will be understood that
depending upon the types and respective function of components
added to the non-rubber portion of the preferred embodiment core
compositions, that the non-rubber portion may constitute a
significantly greater proportion than the rubber portion. The
rubber components include the previously described ultra-high
Mooney viscosity polybutadiene. The non-rubber components are as
follows.
[0113] Preferably, the crosslinking agent of the core composition
is an unsaturated carboxylic acid component which is the reaction
product of a 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.
[0114] Exemplary of the unsaturated carboxylic acids which find
utility in the preferred 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 15 to about
50, and preferably from about 20 to about 35 parts by weight of the
carboxylic acid salt, such as zinc diacrylate (ZDA), is included
per 100 parts of the rubber components in the core composition. The
unsaturated carboxylic acids and metal salts thereof are generally
soluble in the elastomeric base, or are readily dispersible.
[0115] 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.
[0116] Exemplary of suitable peroxides for the purposes of the
present invention are dicumyl peroxide, n-butyl
4,4'-bis(buylperoxy) 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.
[0117] Examples of such commercial available peroxides are
Luperco.RTM. 230 or 231 XL, a peroxyketal manufactured and sold by
Atochem, Lucidol Division, Buffalo, N.Y., and Trigonox.RTM. 17/40
or 29/40, al, 1-di-(t-butylperoxy)-3,3,5-trimethyl cyclohexane sold
by Akzo Chemie America, Chicago, Ill. 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.
[0118] 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. For example, Papi 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.
[0119] 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.
[0120] 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. Exemplary fillers include mineral fillers such as
limestone, silica, mica barytes, calcium carbonate, or clays.
Limestone is ground calcium/magnesium carbonate and is used because
it is an inexpensive, heavy filler. Other heavy weight fillers
include metal particles, such as powdered tungsten. A wide array of
suitable fillers are noted herein with regard to the mantle.
[0121] As indicated, 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.
[0122] 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 about 10 to
about 40 carbon atoms, and preferably having from about 15 to about
20 carbon atoms, are used. Exemplary of suitable fatty acids are
stearic acid and linoleic acids, as well as mixtures thereof.
Exemplary of suitable metallic salts of fatty acids include zinc
stearate. When included in the core compositions, the fatty acid
component is 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).
[0123] 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.
[0124] Diisocyanates may also be optionally included in the core
compositions. When utilized, the diioscyanates 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 to the art.
[0125] Furthermore, the dialkyl tin difatty acids set forth in U.S.
Pat. No. 4,844,471, the dispersing agents disclosed in U.S. Pat.
No. 4,838,556, and the dithiocarbonates 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.
[0126] As indicated above, additional suitable and compatible
modifying agents such as 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
increase the weight of the ball as necessary in order to have the
ball reach or closely approach the U.S.G.A. weight limit of 1.620
ounces.
[0127] The second polybutadiene for use in the preferred embodiment
golf ball core compositions is a polybutadiene that is obtained or
synthesized by utilizing a neodymium or lanthanide series catalyst,
and that exhibits a Mooney viscosity of from about 30 to about 70,
preferably from about 35 to about 70, more preferably from about 40
to about 65, and most preferably from about 45 to about 60. While
the second polybutadiene provides covers exhibiting higher C.O.R.
values, it exhibits very poor cold flow properties and very high
die swell characteristics.
[0128] Examples of such second polybutadienes obtained by using a
neodymium-based catalyst include NEOCIS.TM. 40, NEOCIS.TM. 60 from
Enichem and CB-22, CB-23, and CB-24 from Bayer. The properties of
these polybutadienes are given below.
14TABLE 13 Properties of NEOCIS .TM. Properties of Raw Polymer
Microstructure 1,4 cis (typical) 97.5% 1,4 trans (typical) 1.7%
Vinyl (typical) 0.8% Volatile Matter (max) 0.75% Ash (max) 0.30%
Stabilizer (typical) 0.50% Mooney Viscosity, ML 1 + 4 at
100.degree. C. 38-48 and 60-66 Properties of compound (typical)
Vulcanization at 145.degree. C. Tensile strength, 35' cure, 16 MPa
Elongation, 35' cure, 440% 300% modulus, 35' cure, 9.5 MPa
[0129]
15TABLE 14 Properties of CB-22 TESTS RESULTS SPECIFICATIONS 1.
Mooney-Viscosity ML 1 + 4 100 Cel/ASTM-sheet ML 1 + 1 Minimum 58
MIN.58 ME Maximum 63 MAX.68 ME Median 60 58-68 ME 2. Content of ash
DIN 53568 Ash 0.1 MAX.0.5% 3. Volatile matter heating 3h/105 Cel
Loss in weight 0.11 MAX.0.5% 4. Organic acid Bayer Nr.18 Acid 0.33
MAX.1.0% 5. CIS-1,4 content IR-spectroscopy CIS 1,4 97.62 MIN.96.0%
6. Vulcanization behavior Monsanto MDR/160 Cel DIN 53529 Compound
after ts01 3.2 2.5-4.1 min t50 8.3 6.4-9.6 min t90 13.2 9.2-14.0
min s'min 4.2 3.4-4.4 dN.m s'max 21.5 17.5-21.5 dN.m 7. Informative
data Vulcanization 150 Cel 30 min Tensile ca. 15,0 Elongation at
break ca. 450 Stress at 300% elongation ca. 9,5
[0130]
16TABLE 15 Properties of CB-23 TESTS RESULTS SPECIFICATIONS 1.
Mooney-Viscosity ML 1 + 4 100 Cel/ ASTM-sheet ML 1 + 4 Minimum 50
MIN.46 ME Maximum 54 MAX.56 ME Median 51 46-56 ME 2. Content of ash
DIN 53568 0.09 MAX.0.5% Ash 3. Volatile matter DIN 53526 Loss in
weight 0.19 MAX.0.5% 4. Organic acid Bayer Nr.18 Acid 0.33 MAX.1.0%
5. CIS-1,4 content IR-spectroscopy CIS 1,4 97.09 MIN.96.0% 6.
Vulcanization behaviour Monsanto MDR/160 Cel DIN 53529 Compound
after MIN.96.0 ts01 3.4 2.4-4.0 min t50 8.7 5.8-9.0 min t90 13.5
8.7-13.5 min s'min 3.1 2.7-3.8 dN.m s'max 20.9 17.7-21.7 dN.m 7.
Vulcanization test with ring Informative data Tensile ca. 15,5
Elongation at break ca. 470 Stress at 300% elongation ca. 9,3
[0131]
17TABLE 16 Properties of CB-24 TESTS RESULTS SPECIFICATIONS 1.
Mooney-Viscosity ML 1 + 4 100 Cel/ASTM-sheet ML 1 + 4 Minimum 44
MIN.39 ME Maximum 46 MAX.49 ME Median 45 39-49 ME 2. Content of ash
DIN 53568 Ash 0.12 MAX.0.5% 3. Volatile matter DIN 53526 Loss in
weight 0.1 MAX.0.5% 4. Organic acid Bayer Nr.18 Acid 0.29 MAX.1.0%
5. CIS-1,4 content IR-spectroscopy CIS 1,4 96.73 MIN.96.0% 6.
Vulcanization behaviour Monsanto MDR/160 Cel DIN 53529 Compound
after masticator ts01 3.4 2.6-4.2 min t50 8.0 6,2-9,4 min t90 12.5
9,6-14,4 min s'min 2.8 2.0-3.0 dN.m s'max 19.2 16.3-20.3 dN.m 7.
Informative data Vulcanization 150 Cel 30 min Tesile ca 15,0
Elongation at break ca. 470 Stress at 300% elongation ca. 9,1
[0132] It has been found that when the first and second
polybutadienes are blended together within certain ranges, golf
ball cores can be produced without the individual processing
difficulties associated with each polybutadiene. In essence, a
synergistic effect is produced allowing the blends to produce golf
ball cores using conventional equipment exhibiting enhanced
resilience.
[0133] These preferred embodiment golf ball cores can be formed by
the techniques described in U.S. application Ser. No. 09/248,016,
filed Feb. 10, 1999, herein incorporated by reference.
[0134] 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 inner cover layer about wound or solid
molded cores to produce an intermediate golf ball having a diameter
of about 1.50 to 1.67 inches, and preferably about 1.620 inches.
The outer layer is subsequently molded over the inner layer to
produce a golf ball having a diameter of 1.680 inches or more.
Although either solid cores or wound cores can be used in the
present invention, as a result of their lower cost and superior
performance, solid molded cores are preferred over wound cores.
[0135] In compression molding, the inner cover composition is
formed via injection at about 380.degree. F. to about 450.degree.
F. into smooth surfaced hemispherical shells which are then
positioned around the core in a mold having the desired inner cover
thickness and subjected to compression molding at 200.degree. to
300.degree. F. for about 2 to 10 minutes, followed by cooling at
500 to 70.degree. F. for about 2 to 7 minutes to fuse the shells
together to form a unitary intermediate ball. In addition, the
intermediate balls may be produced by injection molding wherein the
inner cover layer is injected directly around the core placed at
the center of an intermediate ball mold for a period of time in a
mold temperature of from 50.degree. F. to about 100.degree. F.
Subsequently, the outer cover layer is molded about the core and
the inner layer by similar compression or injection molding
techniques to form a dimpled golf ball of a diameter of 1.680
inches or more.
[0136] After molding, the golf balls produced may undergo various
further processing steps such as buffing, painting and marking as
disclosed in U.S. Pat. No. 4,911,451.
[0137] The resulting golf ball produced from the low acid ionomer
resin inner layer and the relatively softer, low flexural modulus
outer layer provide for an improved multi-layer golf ball which
provides for desirable coefficient of restitution, compression,
spin and durability properties while at the same time offering the
feel characteristics associated with soft balata and balata-like
covers of the prior art.
[0138] The invention has been described with reference to the
preferred embodiments. Obviously, modifications and alterations
will occur to others upon reading and understanding the preceding
detailed description. It is intended that the invention be
construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *