U.S. patent application number 09/777595 was filed with the patent office on 2002-10-10 for golf ball having very thin outermost cover layer for improved scuff resistance.
This patent application is currently assigned to SPALDING SPORTS WORLDWIDE, INC.. Invention is credited to Binette, Mark L., Sullivan, Michael J..
Application Number | 20020147057 09/777595 |
Document ID | / |
Family ID | 25110688 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020147057 |
Kind Code |
A1 |
Binette, Mark L. ; et
al. |
October 10, 2002 |
Golf ball having very thin outermost cover layer for improved scuff
resistance
Abstract
A golf ball having a core and cover, the cover including an
outermost cover layer, is disclosed. The outermost cover layer is
relatively thin and provides resistance to scratching and scuffing
of the ball's cover layer, while maintaining desirable playability
characteristics. The outermost cover layer is formed from a
thermoplastic material, has a Shore D hardness of at least 56, and
a Shore D hardness at least as hard as a layer disposed between the
outermost layer and the core.
Inventors: |
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
|
Assignee: |
SPALDING SPORTS WORLDWIDE,
INC.
|
Family ID: |
25110688 |
Appl. No.: |
09/777595 |
Filed: |
February 6, 2001 |
Current U.S.
Class: |
473/378 |
Current CPC
Class: |
A63B 37/12 20130101;
A63B 37/0075 20130101; A63B 37/0003 20130101; A63B 37/0076
20130101; A63B 37/0043 20130101; A63B 37/0045 20130101; A63B
37/0031 20130101; A63B 37/0033 20130101; A63B 37/0024 20130101 |
Class at
Publication: |
473/378 |
International
Class: |
A63B 037/12 |
Claims
Having thus described the preferred embodiment, the invention is
now claimed to be:
1. A golf ball comprising: a core; and a cover enclosing said core,
wherein said cover includes at least one layer comprising an
outermost layer having a thermoplastic material, a thickness of
less than about 0.040 inches, a Shore D hardness of at least about
56 and a Shore D hardness at least as hard as a layer disposed
between said outermost layer and said core.
2. The golf ball according to claim 1, wherein said golf ball
further comprises a mantle layer disposed between said core and
said cover.
3. The golf ball according to claim 1, wherein said outermost layer
comprises an ionomer.
4. The golf ball according to claim 1, wherein said outermost layer
comprises a high acid ionomer consisting of (i) an olefin having 2
to 8 carbon atoms, and (ii) an unsaturated monocarboxylic acid
having 3 to 8 carbon atoms.
5. The golf ball according to claim 1, wherein said outermost layer
has a Shore D hardness of at least about 60.
6. The golf ball according to claim 1, wherein said outermost layer
has a Shore D hardness of at least about 62.
7. The golf ball according to claim 1, wherein said outermost layer
has a thickness of less than about 0.025 inches.
8. The golf ball according to claim 1, wherein said outermost layer
has a thickness of less than about 0.020 inches.
9. The golf ball according to claim 1, wherein said cover further
includes an inner layer and said outermost layer is disposed about
said inner layer.
10. A golf ball comprising: a core; and a cover comprising an inner
layer and an outermost layer disposed about said inner layer, said
outermost layer comprising a thermoplastic material, having a
thickness of less than about 0.040 inches, a Shore D hardness of at
least 56 and a Shore D hardness at least as hard as said inner
layer.
11. The golf ball according to claim 10, wherein said golf ball
further comprises a mantle layer disposed between said core and
said cover.
12. The golf ball according to claim 10, wherein said outermost
layer comprises an ionomer.
13. The golf ball according to claim 10, wherein said outermost
layer comprises a high acid ionomer consisting of (i) an olefin
having 2 to 8 carbon atoms, and (ii) an unsaturated monocarboxylic
acid having 3 to 8 carbon atoms.
14. The golf ball according to claim 10, wherein said outermost
layer has a Shore D hardness of at least about 60.
15. The golf ball according to claim 10, wherein said outermost
layer has a Shore D hardness of at least about 62.
16. The golf ball according to claim 10, wherein said outermost
cover layer has a thickness of less than about 0.025 inches.
17. The golf ball according to claim 10, wherein said outer cover
layer has a thickness of less than about 0.020 inches.
18. A golf ball comprising: a core; a wound layer; and a cover,
wherein said cover includes an outermost layer that comprises a
thermoplastic material, said outermost layer having a thickness
less than about 0.040 inches, a Shore D hardness at least about 56
and a Shore D hardness at least as hard as a layer disposed between
said outermost layer and said core.
19. The golf ball according to claim 18, wherein said golf ball
comprises a mantle layer disposed between said core and said
cover.
20. The golf ball according to claim 19, wherein said mantle layer
is disposed between said core and said wound layer.
21. The golf ball according to claim 18, wherein said outermost
layer comprises an ionomer.
22. The golf ball according to claim 18, wherein said outermost
layer comprises a high acid ionomer consisting of (i) an olefin
having 2 to 8 carbon atoms, and (ii) an unsaturated monocarboxylic
acid having 3 to 8 carbon atoms.
23. The golf ball according to claim 18, wherein said outermost
layer has a Shore D hardness of at least about 60.
24. The golf ball according to claim 18, wherein said outermost
layer has a Shore D hardness of at least about 62.
25. The golf ball according to claim 18, wherein said outermost
layer has a thickness less than about 0.025 inches.
26. The golf ball according to claim 18, wherein said outermost
layer has a thickness less than about 0.020 inches.
27. The golf ball according to claim 18, wherein said cover further
includes an inner layer disposed immediately adjacent to said
outermost layer and between said core and said outermost layer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a golf ball, and particularly, a
multi-layer golf ball having a very thin outermost cover layer that
improves resistance to scuffing and scratching of the ball.
BACKGROUND OF THE INVENTION
[0002] There has been a longstanding trade-off in golf ball
technology between playability (a ball's spin, click, feel, etc.)
and durability (scuff, cut, marking, and abrasion resistance,
fatigue endurance, etc.). Generally, a thicker and harder golf ball
cover is more durable than a thinner and softer cover. A golf ball
with a thick, hard cover gives the ball maximal durability and
would be beneficial to the less experienced golfer. However, a
thick, hard cover greatly sacrifices a golf ball's playability, a
quality experienced golfers desire. Thus, over the years, various
types of golf balls have been developed in an attempt to resolve
this dilemma.
[0003] Traditionally, golf balls have been categorized in three
different groups: one-piece balls, multi-piece (two or more pieces)
solid balls, and wound (three-piece) balls. The one-piece ball is
typically formed from a solid mass of moldable material, which has
been cured to develop the necessary degree of hardness. It
possesses no significant difference in composition between the
interior and exterior of the ball. These balls do not have an
enclosing cover. One-piece balls are described, for example, in
U.S. Pat. Nos. 3,313,545, 3,373,123, and 3,384,612.
[0004] The wound ball is frequently referred to as a three-piece
ball since it is made with a vulcanized rubber thread wound under
tension around a solid or semi-solid core and thereafter enclosed
in a single or multi-layer covering of tough protective material.
While for many years the wound ball satisfied the standards of both
the U.S.G.A. and most golfers, it has several disadvantages. For
example, a wound ball is difficult to manufacture due to the number
of production steps required and the careful control, which must be
exercised in each stage of manufacture to achieve suitable
roundness, velocity, rebound, click, feel, and the like.
[0005] The three-piece wound ball typically has a balata cover,
which is relatively soft and flexible. Upon impact, it compresses
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 backs pin, which causes the
ball to "bite" or stop abruptly on contact with the green.
Moreover, the soft balata cover produces a soft "feel" to the low
handicap player. Such playability properties of workability, feel,
etc. are particularly important in short iron play with low swing
speeds and are exploited significantly by relatively skilled
players.
[0006] Despite all the benefits of balata covered balls, they are
easily cut and/or damaged if hit incorrectly. Thus, golf balls
produced with balata or balata containing cover compositions have a
relatively short life span. As a result of this negative property,
balata and its synthetic substitute, transpolyisoprene and resin
blends, have been essentially replaced as the cover materials of
choice by new cover materials comprising ionomeric resins.
[0007] One important development in balancing the
playability-durability dilemma found in one-piece and wound balls
has been the multi-layered golf ball. Generally, multi-layered golf
balls have cores designed for "driver distance", mid-layers
designed for full iron shots, and covers designed for maximal
"feel" and spin in half-shots, chips, and putts.
[0008] U.S. Pat. Nos. 4,431,193 and 4,919,434 disclose multi-layer
golf balls. Multi-layered golf balls attempt to achieve playability
with a "soft"-type solid or liquid core, while the multiple layers
of the molded covers attempt to maximize the protection of the ball
from cutting and scuffing. Solid cores are generally made of
polybutadiene, while molded covers are generally made from natural
balata, synthetic balata, or ionomeric resins.
[0009] Ionomeric resins are polymers containing interchain ionic
bonding. Ionomeric resins are known to have superior toughness,
durability, and flight characteristics, and as a result of these
characteristics, various ionomeric resins sold by E. I. DuPont de
Nemours & Company under trademark "Surlynt.RTM." and by the
Exxon Corporation (see U.S. Pat. No. 4,911,451) under trademarks
"Escor.RTM." and the trade name "Iotek", have become the materials
of choice for the construction of golf ball covers over the
traditional "balata" (transpolyisoprene, natural or synthetic)
rubbers. The softer balata covers, although exhibiting enhanced
playability properties, lack the durability (cut and abrasion
resistance, fatigue endurance, etc.) properties that ionomer resins
possess which are required for repetitive play or for use by less
experienced golfers.
[0010] 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.
[0011] Currently, more than fifty (50) commercial grades of
ionomers are available both from Exxon and DuPont, 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. A great deal of research continues in developing ionomeric
materials for golf balls exhibiting the desired combination of the
properties of both playability and durability.
[0012] Various non-ionomeric thermoplastic materials have been used
for golf ball covers in order to increase playability, but have
been found inferior to ionomers in achieving good cut resistance
and travel distance. It would be useful to obtain a golf ball
having a cover which incorporates non-ionomeric materials creating
favorable playability characteristics, while achieving favorable
durability characteristics of a ball having a cover which primarily
contains ionomers.
[0013] Recently, several patents have been issued which attempt to
achieve favorable playability and durability characteristics. For
example, U.S. Pat. No. 4,431,193 discloses a multi-layer ball with
a hard ionomeric inner cover layer and a soft outer cover layer.
U.S. Pat. No. 4,919,434 discloses a golf ball with a 0.4-2.2 mm
thick cover made from two thermoplastic cover layers.
[0014] U.S. Pat. No. 5,628,699 discloses a wound golf ball with an
inner layer having a higher Shore D hardness than the outer layer.
The outer layer has a thickness of 0.4 to 3.3 mm and has a Shore D
hardness of 40 to 55. The inner layer is formed of a different
ionomer resin from the outer layer and has a Shore D hardness of 55
to 68.
[0015] U.S. Pat. No. 5,674,137 discloses a wound golf ball with a
cover having a multi-layered structure having a total thickness of
1.0 to 4.0 mm. The outer layer has a thickness of 0.4 to 3.0 mm and
a particular first hardness. The inner layer has a second hardness
higher than the first hardness. The outer layer is formed of a
first ionomer or balata rubber resin having a Shore D hardness of
40 to 55, and the inner layer is formed of a second ionomer or
balata rubber resin having a Shore D hardness of 55 to 68. The
difference in hardness between the first and second resins is at
least 5 in Shore D hardness.
[0016] U.S. Pat. No. 5,779,562 discloses a multi-core, multi-cover
golf ball. The cover includes an inner cover layer and an outer
cover layer enclosing the inner cover layer. The outer cover layer
has a Shore D hardness of no more than 55, and the outer cover
layer has a Shore D hardness less than the inner cover 15
layer.
[0017] U.S. Pat. No. 5,803,831 discloses a multi-layered golf ball
having a soft outer cover. The golf ball has a thermoplastic inner
cover layer with a preferable Shore D hardness of at least 65, and
an outer cover layer with a Shore D hardness of 55 or less.
[0018] Unfortunately, the durability of the multi-layered golf
balls described above suffer with a softer outer layer which
increases the likelihood of scuffing, cutting, and scratching. Each
of the above noted patents disclose an outer layer having a Shore D
hardness no greater than 55. Also, the above noted patents also
disclose that the Shore D hardness of the outer layer is less than
the inner cover layer. The durability of such golf balls would
suffer as less experienced golfers are more prone to scuffs, cuts,
and scratches. Therefore, it would be advantageous to have a golf
ball with the playability of the golf balls described in the above
noted patents while having improved durability, namely scuff,
cutting, and scratching resistance.
SUMMARY OF THE INVENTION
[0019] The present invention is directed toward a golf ball with a
very thin outermost cover layer that provides the ball durability
characteristics such as scuff, cutting, and scratch resistance
while maintaining desirable playability characteristics when struck
with golf clubs.
[0020] The present invention is further directed toward a golf ball
which comprises a core and a cover including a very thin outermost
cover layer, wherein the outermost cover layer comprises a
thermoplastic material, has a thickness of less than about 0.040
inches, a Shore D hardness of at least 56, and a Shore D hardness
at least as hard as a layer between the outermost layer and
core.
[0021] In another aspect, the present invention is further directed
toward a golf ball which comprises a core and a cover including a
very thin outermost cover layer disposed about an inner cover
layer, wherein the outermost cover layer comprises a thermoplastic
material, has a thickness of less than about 0.040 inches, a Shore
D hardness of at least 56, and a Shore D hardness at least as hard
as the layer below it.
[0022] In yet another aspect, the present invention provides a golf
ball comprising a core, at least one mantle layer including a woven
elastomer thread, and a cover including a very thin outermost cover
layer, wherein the outermost cover layer comprises a thermoplastic
material, has a thickness of less than about 0.040 inches, a Shore
D hardness of at least 56, and a Shore D hardness at least as hard
as the layer below it.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a partial sectional view of a preferred embodiment
golf ball in accordance with the present invention;
[0024] FIG. 2 is a partial sectional view of another preferred
embodiment golf ball in accordance with the present invention;
[0025] FIG. 3 is a partial sectional view of another preferred
embodiment golf ball in accordance with the present invention;
and
[0026] FIG. 4 is a partial sectional view of yet another preferred
embodiment golf ball in accordance with the present invention.
[0027] It will be appreciated that these drawings are not
necessarily to scale and are schematic in nature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The present invention provides a golf ball, and preferably a
multi-layer golf ball, comprising a very thin outermost cover layer
that imparts improved scuff or scratch resistance properties to the
ball.
[0029] As described in greater detail herein, in a preferred
embodiment, the present invention golf ball comprises a core,
optional mantle layer, optional wound layer and/or wound core
layer, a cover or cover layer, and an outermost protective layer.
In a particularly preferred embodiment, a multi-layer cover
assembly is used for the cover of the present invention golf ball,
wherein the outer cover layer of that assembly is formed and
provided as described herein, and serves as the outer protective
layer. In another particularly preferred embodiment, a multi-layer
cover assembly is formed and provided as described herein, and upon
which is disposed, an outer protective layer as described herein.
The present invention also includes golf ball embodiments utilizing
outermost protective layers formed or otherwise disposed upon
single cover layers and cover layer assemblies of three or more
cover layers.
[0030] Referring to FIG. 1, the present invention is particularly
directed toward a multi-layer golf ball 1 which comprises a core 2,
at least one cover layer 3 comprising an outermost cover layer and
at least one mantle layer 4 disposed therebetween.
[0031] In another preferred embodiment of the present invention,
illustrated in FIG. 2, a golf ball 10 is shown having an inner
cover layer 16 and an outer cover layer 18 which comprises an
outermost cover layer, disposed about a mantle 14 and core 12.
[0032] In another preferred embodiment, the present invention
provides a golf ball comprising a wound interior layer, such as
shown in FIGS. 3 and 4. Specifically, FIG. 3 illustrates a
preferred embodiment golf ball 20 comprising a core 22, a wound
layer 24 disposed about and immediately adjacent to the core 22, a
mantle layer 26, and a cover 28 comprising an outermost cover
layer. The cover 28 may include an inner and outer cover layer as
previously described with regard to the preferred embodiment golf
ball 10 depicted in FIG. 2.
[0033] FIG. 4 illustrates yet another preferred embodiment golf
ball 30 comprising a core 32, a mantle layer 34 disposed about and
immediately adjacent to the core 32, a wound layer 36 disposed
about the mantle and core, and a cover 38. The cover 38 may include
inner and outer cover layers as previously described with regard to
the preferred embodiment golf ball 10.
[0034] Before addressing the characteristics and features of the
preferred embodiment scuff resistant outermost layer, it is
instructive to address the other components of the preferred
embodiment golf balls in accordance with the present invention.
Core
[0035] The core of the present invention golf ball may comprise a
variety of materials, including those conventionally employed as
golf ball cores. Typical materials for such cores include core
compositions having a base rubber, a crosslinking agent, a filler,
and a co-crosslinking agent. The base rubber typically includes
natural or synthetic rubbers. A preferred base rubber is
1,4-polybutadiene having a cis-structure of at least 40%. Natural
rubber, polyisoprene rubber and/or styrene-butadiene rubber may be
optionally added to the 1,4-polybutadiene. The initiator included
in the core composition can be any known polymerization initiator
which decomposes during the cure cycle. The crosslinking agent
includes a metal salt such as a zinc salt or a magnesium salt from
an unsaturated fatty acid having 3 to 8 carbon atoms such as
acrylic or methacrylic acid. The filler typically includes
materials such as zinc oxide, barium sulfate, silica, calcium
carbonate, zinc carbonate and the like.
[0036] In a preferred aspect, the core is a cross-linked
1,4-polybutadiene having a specific gravity greater than 1.2, and,
more preferably, about 1.25. The high specific gravity of the core
decreases the spin rate of the ball for a lower flight path. Also,
the PGA compression of the core is preferably greater than 60, and,
more preferably, about 65.
[0037] In another preferred aspect, the core of the golf ball is
made of a crosslinked unsaturated elastomer and preferably
comprises a thermoset rubber such as polybutadiene, but can also be
made of other core materials which would provide a sufficient
coefficient of restitution (COR). The core imparts upon the
finished golf ball a COR of at least 0.780, and preferably at least
0.790.
[0038] The diameter of the core is determined based upon the
desired overall ball diameter, minus the combined thicknesses of
the inner and outer cover layers. The core typically has a diameter
of about 1.0-1.6 inches, preferably 1.4-1.6 inches, a PGA
compression of 80-100, and a COR in the range of 0.770-0.830.
[0039] 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 di-acrylate or methacrylate. To achieve a higher COR
in the core, the manufacturer may include filler such as small
amounts of a metal oxide, e.g., zinc oxide. In addition, larger
amounts of metal oxide other than those that are needed to achieve
the desired COR 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.
[0040] 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. The core, such as core 2 in FIG. 1, core 12
in FIG. 2, core 22 in FIG. 3, and core 32 in FIG. 4, may be
composed of any one or more of the materials herein described.
[0041] In one embodiment of the present invention, the core
comprises a center which is liquid-filled or solid around which an
elastic thread is wound such as core 22 in FIG. 3, and core 32 in
FIG. 4. The solid center is typically a homogenous mass of a
resilient material such as polybutadiene or a natural rubber. The
liquid-filled center is typically a thin-walled sphere into which a
liquid such as corn syrup is injected by means of a hypodermic
needle. The sphere is then sealed and frozen to make the center a
solid mass. The windings for either type of center are provided by
an elastic thread, which is stretched and wound about the center to
a desired thickness.
[0042] Conventionally, the centers of wound cores have a diameter
of about 1.000 to about 1.125 inches. Typically, the outer diameter
of a conventional wound core is about 92% of the overall diameter
of the finished ball. However, the outer diameter of wound cores
employed in this embodiment of the present invention have an
overall diameter of less than 90% of the overall diameter of the
finished ball. Preferably, the wound cores have a diameter of about
75-90% of the overall diameter of the finished ball. Most
preferably, the wound cores of the present invention have an
overall diameter of about 85% of the overall diameter of the
finished ball.
[0043] In another embodiment, the core may comprise more than one
layer, i.e., the core may be multi-layered. At least one layer is
disposed about the core. Also, the multi-layered core may
optionally be wound with an elastic thread.
[0044] An extensive discussion of suitable materials and processes
for forming golf ball cores for use in the present invention is
found in U.S. Pat. Nos. 5,833,553; 5,830,087; 5,827,167; 5,820,489;
5,820,488; 5,803,831; 5,779,562; and 5,480,155, all of which are
hereby incorporated by reference.
Optional Mantle Layer(s)
[0045] The mantle layer such as layer 4 in FIG. 1, layer 14 in FIG.
2, layer 26 in FIG. 3, and layer 34 in FIG. 4, comprises a wide
array of materials such as thermoplastic polyester, thermoplastic
polyetherester, dynamically vulcanized thermoplastic elastomer,
functionalized styrene-butadiene elastomer, thermoplastic
polyurethane or metallocene polymer, or blends thereof.
[0046] In a preferred embodiment of the present invention, the
mantle layer is a thermoplastic polyetherester. Suitable
thermoplastic polyetheresters include Hytrel.RTM. 3078, Hytrel.RTM.
G3548W, and Hytrel.RTM. G4078W, which are commercially available
from DuPont. Hytrel.RTM. 3078 is the most preferred. The mantle
layer preferably has a specific gravity greater than 1 and less
than 1.2.
[0047] Suitable dynamically vulcanized thermoplastic elastomers
include Santoprene.RTM., Sarlink.RTM., Vyram.RTM., Dytron.RTM., and
Vistaflex.RTM.. Santoprene.RTM. is the trademark for a dynamically
vulcanized PP/EPDM. Santoprene.RTM. 203-40 is an example of a
preferred Santoprene.RTM. and is commercially available from
Advanced Elastomer Systems.
[0048] Examples of suitable functionalized styrene-butadiene
elastomers include Kraton.RTM. FG-1901x and FG-1921x, which are
available from the Shell Corporation.
[0049] Examples of suitable thermoplastic polyurethane include
Estane.RTM. 58133, Estane.RTM. 58134, and Estane.RTM. 58144, which
are commercially available from the B. F. Goodrich Company.
[0050] Suitable metallocene polymers whose melting points are
higher than the cover materials can also be employed in the mantle
layer of the present invention.
[0051] Further, the materials for the mantle layer described above
may be in the form of a foamed polymeric material. For example,
suitable metallocene polymers include foams of thermoplastic
elastomers based on metallocene single-site catalyst-based foams.
Such metallocene-based foam resins are commercially available from
Sentinel Products located in Hyannis, Mass.
[0052] The mantle layer may comprise up to 100% by weight a
dynamically vulcanized thermoplastic elastomer, a functionalized
styrene-butadiene elastomer, a thermoplastic polyurethane, a
metallocene polymer, or blends thereof. In a preferred embodiment
of the present invention, the mantle layer comprises
Santoprene.RTM., thermoplastic polyurethane, or blends thereof.
[0053] In another preferred embodiment of the present invention,
the mantle layer is a blend of a first and a second thermoplastic
polymer, wherein the first thermoplastic polymer is a dynamically
vulcanized thermoplastic elastomer, a functionalized
styrene-butadiene elastomer, a thermoplastic polyurethane or a
metallocene polymer, and the second thermoplastic is a material
such as a thermoplastic polyurethane, a thermoplastic
polyetherester or polyetheramide, a thermoplastic ionomer resin, a
thermoplastic polyester, another dynamically vulcanized elastomer,
another functionalized styrene-butadiene elastomer, another
metallocene polymer, or blends thereof.
[0054] Suitable thermoplastic polyetheresters for use in this
blended embodiment include Hytrel.RTM. 3078, Hytrel.RTM. G3548W,
and Hytrel.RTM. G4078W, which are commercially available from
DuPont. Suitable thermoplastic polyetheramides include Pebax.RTM.
2533, Pebax.RTM. 3533, and Pebax.RTM. 4033, which are available
from Elf-Atochem. Suitable thermoplastic ionomer resins include any
number of olefinic based ionomers including SURLYN.RTM. and
Iotek.RTM.), which are commercially available from DuPont and
Exxon, respectively. The flexural moduli for these ionomers is
about 100 kpsi to about 200 kpsi. Suitable thermoplastic polyesters
include polybutylene terephthalate. Likewise, the dynamically
vulcanized thermoplastic elastomers, functionalized
styrene-butadiene elastomers, thermoplastic polyurethane, or
metallocene polymers identified above are also useful as the second
thermoplastic in such blends. Further, the materials of the second
thermoplastic described above may be in the form of a foamed
polymeric material.
[0055] Such thermoplastic blends comprise about 1% to about 99% by
weight of a first thermoplastic material, and about 99% to about 1%
by weight of a second thermoplastic material. Preferably, the
thermoplastic blend comprises about 5% to about 95% by weight of a
first thermoplastic material, and about 5% to about 95% by weight
of a second thermoplastic material. In a preferred embodiment of
the present invention, the first thermoplastic material of the
blend is a dynamically vulcanized thermoplastic elastomer, such as
Santoprene.RTM..
[0056] Alternative embodiments of the present invention golf ball
include a ball with more than one mantle layer. If more than one
mantle layer is used, the mantle layers do not have to be in
contact with one another, i.e., the mantle layers may be disposed
between various layers of the golf ball without touching one
another.
[0057] Other suitable materials and descriptions for forming
mantles in the present invention golf balls are found in U.S. Pat.
Nos. 5,833,554; 5,779,562; 5,733,206; and 5,480,155, all of which
are hereby incorporated by reference.
Cover
[0058] The cover layer of the present invention golf balls
comprises at least one layer of a thermoplastic or thermosetting
material. The cover layer is shown in FIG. 1 as layer 3, in FIG. 2,
as layers 16 and 18, in FIG. 3 as layer 28, and in FIG. 4 as layer
38. Any number of a wide variety of cover materials may be used in
the present invention golf balls. Among the preferred conventional
cover materials are ionomer resins and low modulus ionomers
obtained by providing a cross metallic bond to polymers of
monoolefins with at least one member selected from the group
consisting of unsaturated mono- or di-carboxylic acids having 3 to
12 carbon atoms and esters thereof. The polymers contain 1 to 50%
by weight of the unsaturated mono- or di-carboxylic acid and/or
ester thereof. More particularly, low modulus ionomers, such as
acid-containing ethylene copolymer ionomers, include E/X/Y
copolymers. E is ethylene. X is a softening comonomer such as
acrylate or methacrylate present in 0-50, preferably 0-25, and most
preferably 0-2, weight percent of the polymer. Y is acrylic or
methacrylic acid present in 5-35, preferably 10-35, and most
preferably 15-20, weight percent of the polymer, wherein the acid
moiety is neutralized 1-90%, preferably at least 40%, and most
preferably at least about 60%, to form an ionomer by a cation.
Examples of suitable cations include lithium, sodium, potassium,
magnesium, calcium, barium, lead, tin, zinc or aluminum, or a
combination of such cations. Preferred cations include lithium,
sodium, magnesium, and zinc. Specific acid-containing ethylene
copolymers include ethylene/acrylic acid, ethylene/methacrylic
acid, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic
acid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl
acrylate, ethylene/acrylic acid/iso-butyl acrylate,
ethylene/methacrylic acid,n-butyl methacrylate, ethylene/acrylic
acid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,
ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylic
acid/methyl methacrylate, and ethylene/acrylic acid/n-butyl
methacrylate. Preferred acid-containing ethylene copolymers include
ethylene/methacrylic acid, ethylene/acrylic acid,
ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylic
acid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate
and ethylene/acrylic acid/methyl acrylate copolymers. The most
preferred acid-containing ethylene copolymers are
ethylene/methacrylic acid, ethylene/acrylic acid, ethylene/(meth)
acrylic acid/n-butyl acrylate, ethylene/(meth) acrylic acid/ethyl
acrylate, and ethylenel(meth) acrylic acid/methyl acrylate
copolymers.
[0059] The manner in which these ionomers are made is well known in
the art as described in, e.g., U.S. Pat. No. 3,264,272, hereby
incorporated by reference. Such ionomer resins are commercially
available from DuPont Co. under the tradename SURLYN.RTM.. The
presently preferred cover material is a 50/50 blend of SURLYN.RTM.
8140 and SURLYN.RTM. 7940, which are high acid sodium and standard
lithium SURLYN.RTM., respectively. This cover material has a flex
modulus of about 85 kpsi and a specific gravity of about 0.95.
Another preferred cover is comprised of a 50/50 blend of
SURLYN.RTM. 8140 and SURLYN.RTM. SEP671, which is a lithium
SURLYN.RTM. having about 19% methacrylic acid. This material has a
flex modulus of about 105 kpsi. Preferably, the flex modulus of the
cover is greater than 80 kpsi. Still further, the preferred cover
has a hardness of about 70 Shore D. The high flex modulus of the
cover provides increased initial velocity and a low spin rate.
[0060] In a preferred aspect, a multi-layer cover is utilized, such
as shown in FIG. 2. Preferably, the inner layer 16 of the cover is
either a thermoplastic material such as a thermoplastic elastomer,
a thermoplastic rubber, a thermoset rubber, or a thermoset
elastomer material. Additional examples of materials suitable for
use as the inner cover layer include polyether or polyester
thermoplastic urethanes as well as thermoset polyurethanes. A
preferable thermoplastic material is a thermoplastic urethane with
a melting point of about 178.degree. to about 205.degree. F. A
preferable thermoset material is a rubber-based, castable urethane.
Preferably, the outer layer 18 of the cover is either a
thermoplastic plastic material such as an elastomer or a
thermoplastic rubber, or a thermosetting material. Suitable
materials is for the outer layer include urethanes, ionomers with a
low modulus and other "dead" but durable materials such as EPDM and
butyl rubber. Additionally, the present invention also contemplates
the use of a polymeric foam material, such as the metallocene-based
foamed resin described above, as the material for either the outer
cover layer or the inner cover layer, but preferably not both
layers.
[0061] In one embodiment of the present invention, it is preferable
that the thermoplastic or thermosetting materials of the outer
layer have a melting point or heat of reaction (cure) temperature
less than the melting point or heat of reaction (cure) temperature
of the materials of the inner layer.
[0062] The inner and outer cover layers of this embodiment of the
invention can be molded about the core and mantle layers through a
variety of conventional molding methods. For example, the cover
layers can be compression molded, retractable pin injection molded,
fixed pin injection molded, cast around the core and mantle or a
combination thereof. However, it is important that the materials of
the outer layer are characterized in that they have thermal
properties such that no flow of the inner layer material occurs
during the molding of the outer cover layer about the inner layer,
regardless of the process employed to mold the layers.
[0063] The present invention also contemplates the use of a variety
of non-conventional cover materials. In particular, the covers of
the present invention golf balls may comprise thermoplastic or
engineering plastics such as ethylene or propylene based
homopolymers and copolymers including functional monomers such as
acrylic and methacrylic acid and fully or partially neutralized
ionomers and their blends, methyl acrylate, methyl methacrylate
homopolymers and copolymers, imidized, amino group containing
polymers, polycarbonate, reinforced polyamides, polyphenylene
oxide, high impact polystyrene, polyether ketone, polysulfone,
poly(phenylene sulfide), reinforced engineering plastics,
acrylonitrile-butadiene, acrylic-styrene-acrylonitrile,
poly(ethylene terephthalate), poly(butylene terephthalate), poly
(ethylene-vinyl alcohol), poly(tetrafluorethylene) and their
copolymers including functional comonomers and blends thereof.
These polymers or copolymers can be further reinforced by blending
with a wide range of fillers and glass fibers, spheres, or wood
pulp.
[0064] In a preferred form of the invention, the inner cover layer
comprises an ionomer with an average weight percent (wt %) acid
content of about 15 or less which is at least 10% neutralized. In a
particularly preferred form of the invention, the inner cover
layer, such as layer 16 shown in FIG. 2 constitutes a blend of two
types of ionomers in which one component of the blend is an
ethylene-acrylic acid or ethylene-methacrylic acid copolymer
containing at least 15 wt % acid groups which are at least
partially neutralized with a cation, and the other type of ionomer
is a terpolymer of ethylene, acrylic acid or methacrylic acid and a
softening termonomer such as butyl acrylate or methyl acrylate,
resulting in an overall wt % acid content of about 15 or less.
[0065] The outer cover layer may also comprise an ionomer. The
outer layer, such as layer 18 in FIG. 2, can contain a single type
of ionomer or a blend of two or more types of ionomers.
Furthermore, a hardening and/or softening modifier can be added.
The outer cover layer is harder than the inner cover layer, and has
a Shore D hardness of about 60 or more, more preferably 65 or more
and most preferably 68 or more (ASTM D-2240). In a particularly
preferred form of the invention, the outer cover layer contains an
ionomer having at least 16 weight % acid groups, which are at least
partially neutralized.
[0066] As described in greater detail herein, for golf ball
embodiments in which an outermost cover layer is formed or
otherwise disposed on a multi-layer cover assembly, and thus, the
outer cover layer of the cover assembly is not designed to serve as
this protective layer, the thicknesses for the inner and outer
cover layers are as follows. The inner and outer layers together
form a cover having a thickness of about 0.090 to about 0.250
inches, more preferably about 0.10 to about 0.20 inches, and most
preferably about 0.11 to about 0.15 inches. Preferably, the inner
cover layer has a thickness of about 0.025 to about 0.200 inches,
and more preferably from about 0.050 to about 0.100 inches. The
outer cover layer preferably has a thickness of about 0.025 to
0.200 inches, or more preferably from about 0.050 to about 0.100
inches. The ratio of the diameter of the ball to the thickness of
the cover, i.e., the sum of the thickness of the inner cover layer
and the outer cover layer, is no more than about 19:1, preferably
no more than about 17:1, and more preferably no more than about
15:1.
[0067] The hardness of the inner and outer cover layers, and the
compositions and thicknesses of these layers are appropriate to
result in a golf ball having a COR of at least 0.780, more
preferably at least 0.790 and most preferably at least 0.800. The
golf ball of the invention has an overall PGA compression of from
about 30 to about 110, more preferably from about 50 to about 107,
and most preferably from about 60 to about 90.
[0068] Preferably, the spin rate of the golf balls is no more than
about 8000 revolutions per minute (rpm) when struck with a 9-iron
under conditions of launch angle, ball speed and tee position which
produce a spin rate of about 7100 rpm for a two-piece hard covered
ball (1994 Top-Flite XL) and a spin rate of about 9700 rpm for a
thread wound balata covered ball (1994 Titleist Tour 100) using the
same club. This relatively low spin rate provides the advantage of
less sideways spin for improved accuracy and less backspin for
improved rolling distance.
[0069] More particularly, the inner cover layer preferably
comprises an ionomer having an average wt % acid content of about
15 or less which is at least 10% neutralized. Preferably, the inner
cover layer such as layer 16 in FIG. 2, includes a blend of hard
and soft ionomer resins including but not limited to those
described in U.S. Pat. Nos. 4,884,814 and 5,120,791, both of which
are incorporated herein by reference. For example, a blend of a
high modulus ionomer (i.e., a hard ionomer) and a low modulus
ionomer (i.e., a soft ionomer) in a mixture can be used. A high
modulus ionomer is one which has a flexural modulus of about
15,000-70,000 psi or more as measured under ASTM method D-790. The
hardness of this type of ionomer is at least 50 on the Shore D
scale as measured in accordance with ASTM method D-2240. A low
modulus ionomer which can be blended with the high modulus ionomer
to form an inner layer, should have a flexural modulus of about
1,000 to about 15,000 psi (ASTM D-790), and a hardness of about 20
to about 40 on the Shore D scale (ASTM D-2240).
[0070] The hard ionomer resins used in blends to form the inner
cover layer include ionic copolymers which are the, e.g., sodium,
zinc, magnesium, calcium, manganese, nickel, potassium or lithium,
etc., salt, or blend thereof, 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 and which result in a ball
having the desired combination of COR, compression, and inner cover
layer hardness. The carboxylic acid groups of the copolymer may be
totally or partially, that is from about 10 to about 100%,
neutralized. The hard ionomeric resins typically are copolymers of
ethylene with acrylic and/or methacrylic acid. Two or more hard
ionomer resins can be blended.
[0071] The metal cation salts utilized in the invention are
preferably 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, e.g., lithium, calcium, zinc, sodium, potassium, nickel,
magnesium, and manganese, etc.
[0072] 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.
[0073] The metal cation neutralized high acid ionomer resins can be
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%.
[0074] Examples of commercially available hard ionomeric resins
which can be used in a blend to form the inner cover layer 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 % 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 % acid which is
about 58% neutralized with zinc ions. The average melt flow index
of SURLYN.RTM. 9910 is about 0.7. Additional examples include Iotek
4000, Iotek 4010, Iotek 8000, Iotek 8020, Iotek 8030, Iotek 7010
and Iotek 7030 which are sold by Exxon Corporation. It is to be
understood that the above examples are for illustrative purposes
and are by no means intended to be limiting.
[0075] Non-limiting examples of soft ionomers to be blended with
the above-described hard ionomers to form the inner cover layer of
the inventive golf ball comprise sodium, zinc magnesium, calcium,
manganese, nickel, potassium or lithium, etc. salts of a terpolymer
of an olefin having from about 2 to 8 carbon atoms, acrylic acid or
methacrylic acid, and a softening comonomer which is an unsaturated
monomer of the acrylate ester class having from 1 to 21 carbon
atoms. The soft ionomer is preferably an ionomer made from an
acrylic acid-based polymer and an unsaturated monomer of the
acrylate ester class. The soft (low modulus) ionomers have a
hardness from about 20 to 40 as measured on the Shore D scale and a
flexural modulus from about 1,000 to about 15,000, as measured in
accordance with ASTM method D-790.
[0076] Certain ethylene-acrylic acid-based soft ionomer resins
developed by he Exxon Corporation under the designation "Iotek
7510" may be combined with known hard ionomers such as those
indicated above to produce the inner cover. The combination
produces higher CORs at equal or lower levels of hardness, higher
melt flow (which corresponds to improved, more efficient molding,
i.e., fewer rejects) as well as significant cost savings versus the
outer layer of multi-layer balls produced by other known hard-soft
ionomer blends as a result of the lower overall raw materials costs
and improved yields. Furthermore, Iotek 7520, SURLYN.RTM. 8320 and
SURLYN.RTM. 8120 also can be used.
[0077] It has been determined that when hard-soft ionomer blends
are used for the inner cover layer, good results are achieved when
the relative combination is in a range of about 90 to about 10%
hard ionomer and about 10 to about 90% soft ionomer. The results
are improved by adjusting the range to about 75 to 25% hard ionomer
and 25 to 75% soft ionomer. Even better results are noted at
relative ranges of about 60 to 40% hard ionomer resin and about 40
to 60% soft ionomer resin.
[0078] 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, both patents of which are herein
incorporated by reference. The present invention is in no way
limited to those examples.
[0079] The outer cover layer such as layer 18 shown in FIG. 2 of
the golf ball is harder than the inner cover layer, such as inner
cover layer 16 of FIG. 2, and generally, but not necessarily, has a
different chemical composition than the inner cover layer. The
outer cover layer preferably comprises a high acid ionomer resin or
high acid ionomer blend in which more than 10 weight % of the acid
groups are neutralized. Preferably, the outer cover layer is formed
from a blend of two or more high acid ionomer resins that are
neutralized to different extents using different metal cations.
Softening modifiers can be used to achieve the desired Shore D
hardness of the outer cover layer.
[0080] The preferred high acid ionomers which can be used in
formulating the outer cover layer of the golf ball are ionic
copolymers which are the metal 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. As
nonlimiting examples, sodium, zinc, magnesium, manganese,
potassium, calcium, nickel and lithium can be used as the
neutralizing cation. Preferably, the ionomeric resins are
copolymers of ethylene with either acrylic or methacrylic acid. In
some circumstances, an additional comonomer such as an acrylate
ester, e.g., iso-n-butylacrylate, etc. can also be used to produce
a somewhat softer terpolymer. The carboxylic acid groups of the
copolymer are partially neutralized by the metal ions, i.e., from
about 10 to about 75% or more preferably from about 30 to about
70%. Each of the high acid ionomer resins which may be included in
the outer cover layer composition preferably contains more than 16%
by weight of a carboxylic acid, preferably 17 to about 25% by
weight of a carboxylic acid, and most preferably from about 18.5 to
about 21.5% by weight of a carboxylic acid. Examples of
commercially available high acid methacrylic acid-based ionomers
which can be used in accordance with the invention include
SURLYN.RTM. AD-8422 (sodium cation), SURLYN.RTM. 8162 (zinc
cation), SURLYN.RTM. SEP-513-1 (zinc cation), and SURLYN.RTM.
SEP-503-2 (magnesium cation). According to DuPont, all of these
ionomers contain from about 18.5 to about 21% by weight methacrylic
acid.
[0081] Examples of high acid acrylic acid-based ionomers which can
be used in the present invention also include the Escor.RTM. or
Iotek High Acid Ethylene Ionomers produced by Exxon, including
Iotek Ex-959 and Iotek EX-960. Furthermore, a number of other high
acid ionomers neutralized to various extent by different types of
metal cations, including manganese, lithium, potassium, calcium and
nickel and several new high acid ionomers and/or high acid ionomer
blends other than sodium, zinc and magnesium are now available for
golf ball cover production.
[0082] As indicated above, softening comonomers can be included in
the ionomeric inner and/or outer cover layers. Non-limiting
examples of a softening comonomer include vinyl esters of aliphatic
carboxylic acids wherein the acids have 2 to 10 carbon atoms, vinyl
ethers wherein the alkyl group 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.
[0083] Examples of a number of copolymers suitable for use to
produce the high acid ionomers used 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, an
ethylene/acrylic acid/vinyl alcohol copolymer, etc. The base
copolymer broadly contains greater than 16% by weight unsaturated
carboxylic acid, from about 30 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.
[0084] As indicated above, the inner cover layer and/or outer cover
layer optionally may include hardening or softening modifiers,
non-limiting examples of which include a metal stearate, such as
zinc stearate, or another fatty acid salt, as described in commonly
assigned U.S. Pat. Nos. 5,306,760 and 5,312,857, both of which are
herein incorporated by reference. One purpose of the metal stearate
or other fatty acid salt is to reduce the cost of production of the
ball without affecting overall performance of the finished ball.
Furthermore, polar-group modified rubbers can be blended with
ionomers as described, for example, in commonly assigned U.S. Pat.
Nos. 4,986,545; 5,098,105; 5,187,013; 5,330,837 and 5,338,610, all
of which are herein incorporated by reference. Examples of
thermoplastic elastomers which act as hardening or softening
agents, include polyurethane, a polyester elastomer such as that
sold by DuPont as Hytrel.RTM., a polyester polyurethane such as B.
F. Goodrich Company's Estane.RTM. polyester polyurethane X-4517,
and a polyether amide such as that sold by Elf Atochem S. A. under
the name Pebax.RTM.. A plastomer such as that sold by Exxon under
the name Exact.TM., e.g., Exact.TM. 4049 can be included. Various
plasticizers and processing aids also can be used. It may also be
preferred to apply a conventional clear coat on the cover
layer.
[0085] When the golf ball of the invention has more than two cover
layers, the inner cover layer as defined in this application can be
formed from two or more layers which, taken together, meet the
requirements of softness, thickness and compression of the layer or
layers which are defined herein as the inner cover layer.
Similarly, the outer cover layer can be formed from two or more
layers which, taken together, meet the requirements of hardness,
thickness and compression of the layer or layers which are defined
herein as the outer cover layer. Furthermore, one or more
additional, very thin ionomeric or non-ionomeric layers can be
added on either side of the inner cover layer as long as the
objectives of the invention are achieved.
[0086] An extensive discussion of compositions, materials,
processes and equipment for forming covers for the preferred
embodiment golf balls of the present invention is set forth in U.S.
Pat. Nos. 5,833,443; 5,830,087; 5,827,167; 5,820,489; 5,820,488;
5,803,831; 5,800,284; 5,779,562; 5,779,561; and 5,733,207, all of
which are hereby incorporated by reference.
Outermost Cover Layer
[0087] In accordance with the present invention, a thin outermost
cover layer of a scuff resistant and/or scratch resistant material
is disposed on the outer surface of a golf ball.
[0088] In a preferred embodiment of the present invention, this
thin outermost cover layer is disposed on the outer surface of the
cover 3 of the golf ball 1 illustrated in FIG. 1; on the outer
surface of the outer cover layer 18 of the golf ball 10 of FIG. 2;
on the outer layer 28 of the golf ball 20 of FIG. 3; and on the
outer layer of the cover 38 of the golf ball 30 of FIG. 4.
[0089] In another preferred embodiment of the present invention,
the outer layer of a multi-layer cover assembly is formed, as
described herein, to serve as the outermost protective layer. For
example, the outer cover layer 18 of the multi-layer cover assembly
illustrated in FIG. 2, may be formed to serve as the outermost
protective layer.
[0090] The noted very thin protective outermost layer has a maximum
thickness such that the layer does not detract from the
playability, i.e., spin, feel, etc., of the golf ball, as compared
to the ball if not having this layer. The thickness of this
outermost layer is preferably less than about 0.040 inches, more
preferably less than about 0.025 inches, and most preferably less
than about 0.020 inches. The minimum thickness for this outermost
cover layer is that thickness at which the layer provides an
effective degree of scuff and/or scratch resistance for the golf
ball.
[0091] A wide array of materials may be used for this very thin
outermost cover layer. Preferred compositions include ionomer
blends such as Spalding Blends No. 1 and 2, set forth below.
1 Materials wt % Spalding Blend No. 1 Surlyn .RTM. 8320 17.4 Surlyn
.RTM. 8120 7.6 Surlyn .RTM. 9910 49.0 Surlyn .RTM. 8940 16.4 2832-2
9.6 White MB -- Spalding Blend No. 2 Surlyn .RTM. 8320 10.0 Surlyn
.RTM. 8120 4.0 Surlyn .RTM. 9910 54.5 Surlyn .RTM. 8940 22.0 2832-2
9.5 White MB --
[0092] Other preferred materials include harder materials such as
high acid blends, thermoplastic polyurethane, thermoset
polyurethane, and combinations thereof. Additional materials
contemplated for use in the outer layer include polyamide, SEBS,
PPE, metallocenes, and combinations thereof. Moreover, the
compositions and combinations of materials described in the
disclosure for the cover above can be used to form the outermost
cover layer as long as the objectives of the present invention are
met. The properties of the outer layer may be further improved by
electron beam or gamma radiation treatment, as described in U.S.
Pat. No. 5,891,973, herein incorporated by reference.
[0093] The hardness of the outermost cover layer also dictates the
golf ball's durability and playability. In a preferred embodiment
of this invention, the Shore D hardness of the outer cover layer is
at least 56, more preferably at least 60, and most preferably at
least 62. The maximal Shore D hardness is one which provides
maximum durability without decreasing the playability properties of
the golf ball. Preferably, the Shore D hardness of the outermost
cover layer is greater than the Shore D hardness of the layer below
it.
EXAMPLES
[0094] Having generally described the invention, the following
examples are included for purposes of illustration so that the
invention may be more readily understood and are in no way intended
to limit the scope of the invention unless otherwise specifically
indicated.
Comparative Example 1
[0095] About 2 dozen thermoset polybutadiene golf ball cores having
a conventional composition, a PGA compression of 93, a COR of 0.782
and a diameter of 1.47 inches were molded in a conventional manner.
An inner cover layer of a first ionomer formed from a blend of a
soft acrylic acid based ionomer containing a softening comonomer
and a hard acrylic acid based ionomer, designated as ionomer 1,
having a thickness of 0.050 inches, and a Shore D hardness of 55
was injection molded over the cores. The resulting covered cores
had a PGA compression of 94 and a COR of 0.789.
[0096] An outer layer formed from a blend of two hard acrylic acid
based ionomers and designated as ionomer 2 was injection molded
over the inner layer. The outer layer had a thickness of 0.055
inches and a Shore D hardness of 68. The balls were primed and
clear coated in a uniform manner. The balls with the two-part cover
had an average PGA compression of about 99, and a COR of about
0.803. The spin rate of the balls was determined by striking the
balls with a 9-iron under conditions of launch angle, ball speed,
and tee position, which produced a spin rate of about 7100 rpm for
a two-piece hard covered ball (1994 Top-Flite XL), and a spin rate
of about 9700 rpm for a thread wound balata covered ball (1994
Titleist Tour 100) using the same club. The properties of the ball
are shown in Table 1.
Example 1
[0097] Same as Comparative Example 1 except that the outer cover
layer was 0.025 inches thick instead of 0.055 inches. The resulting
ball is predicted to have a PGA compression of about 90 (softened),
a COR of 0.803 (unchanged), a spin rate of 8000 (increased), and a
scuff resistance that is excellent and at least as good as compared
to the thicker cover version.
Comparative Examples 2-4
[0098] The procedure of Comparative Example 1 was repeated using
three different combinations of inner and outer cover layer
materials at the same cover layer thicknesses. The results are
shown on Table 1.
Example 2
[0099] The ball configuration was the same as Comparative Example 3
except that the outer cover layer thickness was reduced to 0.025
inches. The resulting ball is predicted to have a PGA compression
of 90 (softer feel), a COR of 0.809 (unchanged), a spin rate of
7000, and excellent cut and scuff resistance that is at least as
good as compared to the thicker cover version.
2 TABLE 1 Core Hardness (Shore D) Inner Cover Layer Example Size
COMP (if readily Thickness COMP.sup.2 Hardness No. (inches) (PGA)
available) COR.sup.1 Material (inches) (PGA) COR.sup.1 3 (Shore D)
Comp. 1 1.47 93 782 Ionomer 1 0.050 94 789 55 1 1.47 93 782 Ionomer
1 0.050 94 789 55 Comp. 2 1.47 93 782 Ionomer 3 0.050 94 795 63
Comp. 3 1.47 93 782 Ionomer 1 0.050 94 789 55 Comp. 4 1.47 93 782
Ionomer 3 0.050 94 795 63 2 1.47 93 782 Ionomer 1 0.050 94 789 55
Outer Cover Layer Ball Example Thickness Hardness COMP SPIN No.
Material (inches) (Shore D) (PGA) COR.sup.1 (RPM) Comp. 1 Ionomer 2
0.055 68 99 803 7508 1 Ionomer 2 0.025 68 .sup. 90.sup.4 .sup.
803.sup.4 .sup. 8000.sup.4 Comp. 2 Ionomer 2 0.055 68 102 809 7650
Comp. 3 Ionomer 4 0.055 73 101 809 6626 Comp. 4 Ionomer 4 0.055 73
107 816 6358 2 Ionomer 4 0.025 73 .sup. 90.sup.4 .sup. 809.sup.4
.sup. 7000.sup.4 .sup.1Actual COR valuess have been multiplied by
1000 .sup.2COMP of inner cover layer and core .sup.3COR of inner
cover layer and core .sup.4Estimated values
Comparative Example 5
[0100] A golf ball core made of a blend of polybutadiene, zinc
diacrylate, zinc dimethacrylate, and conventional additives, and
having a diameter of 1.43 inches was obtained. The core had a COR
of 0.763. The core was coated with a polyolefin material in a
thickness of 0.058 inches. The polyolefin material was a butene
comonomer with a melt index of 4.5 dg/min and is available under
the unregistered trademark EXACT.TM. 4049 (Exxon Chemical Company,
Houston, Tex.).
[0101] An outer cover layer formed from a blend of ionomers
designated as ionomer 1 was used for the cover of the ball and was
injection molded over the inner cover layer in a thickness of 0.090
inches. The outer cover layer had a Shore D hardness of 68 (ASTM
D-2240).
[0102] The resulting golf ball was primed and top coated using
conventional materials. The resulting ball had a coefficient of
restitution of 0.796, and a PGA compression 79. The properties of
the core, cover layers, and overall golf ball are shown on Table
2.
Comparative Examples 6-9
[0103] The procedure of Comparative Example 5 was repeated using
different combinations of inner cover layer thickness and core size
and composition. The same types of inner and outer cover layer
materials were used in Comparative Examples 6-9 as were used in
Comparative Example 5. The results are shown on Table 2.
[0104] As shown by Comparative Examples 5-9, golf balls having a
good coefficient of restitution and soft compression can be
obtained even when the inner cover layer is not an ionomer or
balata. Surprisingly, the relative thicknesses of the inner cover
layer and outer cover layer had little impact on COR. The balls of
Comparative Example 9 exhibited a high COR, while having a thick
inner cover layer and a soft compression. The balls of Comparative
Example 7 have a relatively high COR in combination with a soft
inner cover layer and a low spin rate.
3 TABLE 2 Outer Inner Cover Layer Cover Core Thick- Layer Ball
Example Mater- Size COMP COR ness COMP COR Hardness Thickness COMP
COR Weight SPIN No. ial (inches) (PGA) (.times.1000) Material
(inches) (PGA) (.times.1000) (Shore D) (inches) (PGA) (.times.1000)
(g) (RPM) Comp. 5 PBD 1.43 .sup. --.sup.2 763 Polyol- 0.058 58 763
30 0.090 79 796 45.9 -- .sup. BL1.sup.1 efin Comp. 6 PBD 1.43 --
763 Polyol- 0.070 55 761 30 0.075 78 794 43.8 7945 BL1 efin Comp. 7
PBD 1.47 90 789 Polyol- 0.050 82 787 30 0.0765 93 806 44.9 7736
.sup. BL2.sup.3 efin Comp. 8 PBD 1.43 -- 788 Polyol- 0.058 75 785
30 0.090 89 807 44 8039 BL2 efin Comp. 9 PBD 1.43 -- 788 Polyol-
0.070 70 784 30 0.075 83 803 45.8 -- BL2 efin 3 PBD 1.43 -- 763
Polyol- 0.070 55 761 30 0.025 65.sup.4 .sup. 794.sup.4 -- .sup.
8500.sup.4 BL1 efin 4 PBD 1.43 -- 788 Polyol- 0.058 75 785 30 0.025
75.sup.4 807 -- .sup. 8500.sup.4 BL2 efin .sup.1Polybuatdiene blend
1 .sup.2"--" indicates that no measurement was made due to small
core size .sup.3Polybutadiene blend 2 .sup.4Estimated values
Example 3
[0105] The ball configuration was the same as Comparative Example 8
except that the outer cover layer thickness was reduced to 0.025
inches. The PGA compression softened to 65, the COR relatively
unchanged at 0.794, the spin rate increased to 8500, and the cut
and scuff resistance remained excellent.
Example 4
[0106] The ball configuration was the same as Comparative Example 9
except that the outer cover layer thickness is reduced to 0.025
inches. The PGA compression softened to 75, the COR unchanged at
0.807, the spin rate increased to 8500, and the cut and scuff
resistance remained excellent.
Comparative Examples 10-12
[0107] Three golf balls, labeled Comparative Examples 10, 11, and
12, respectively, were formed with the same core composition. The
three golf balls contained no mantle layer. Each ball was molded
with a different cover.
[0108] The outer cover layer of Comparative Example 10 was made
from 90.6 parts by weight Iotek 7510 and 9.4 parts White MB. The
outer cover layer of Comparative Example 11 was made from 57.6
parts Iotek 7510, 33 parts Iotek 8000, and 9.4 parts White MB. The
outer cover layer of Comparative Example 12 was made from 35 parts
Surlyn.RTM. 8140, 57.5 parts Surlyn.RTM. 6120, and 12.5 parts White
MB.
[0109] A "Guillotine Cut Test" was performed on the golf balls by
holding the ball firmly in a cavity to expose the top half of the
ball. A guillotine blade weighing 5 pounds and having inner and
outer blade edge angles of 900 and 600, respectively, and a cutting
edge of three sixty-fourths inch radius was dropped from a height
of 3.5 feet to strike the ball at a point one-half inch off the top
center point. The guillotine blade was guided during the drop by
means of a substantially friction-free vertical track. The drops
were repeated until ball failure occurred, ball failure defined as
permanent damage evidenced by a crack or by removal of a segment
from the ball surface.
Example 5
[0110] A multi-layered golf ball was made with the same core as the
golf balls found in Comparative Examples 10-12. The inner cover
layer of the multi-layered ball is constructed by molding Iotek
7510, having a Shore D hardness of about 45, over the core using a
1.68" injection mold. The composition of the mantle layer of the
multi-layered golf ball is the same as the outer cover layer of
Comparative Example 10 except for the addition of White MB to the
outer cover layer composition of Comparative Example 10. The core
and inner cover were glebarred to a size of approximately 1.645",
thus leaving a mantle thickness of about 0.050". Alternatively, the
mantle could have been molded either by compression or injection
molding in the proper size cavities to yield the desired mantle
size and thickness.
[0111] After glebar, a very thin, hard layer of ionomer made from
35 parts by weight Surlyn.RTM. 8140, 57.5 parts Surlyn.RTM. 6120,
and 12.5 parts White MB, having a Shore D hardness of 70-71, was
compression molded over the soft mantle. The outer cover layer of
the multi-layered golf ball was the same composition as the outer
cover layer of Comparative Example 12. The outer cover thickness
for the multi-layered golf ball is about 0.020". A Guillotine Cut
Test was then performed on the ball.
[0112] The outer cover layer of the multi-layered golf ball has a
Shore D hardness of 70, while the inner cover layer has a Shore D
hardness of about 45. The overall Shore D hardness measured on the
ball was 57, roughly in between the Shore D hardness measurements
of the inner and outer cover layers.
[0113] The multi-layered golf ball was faster and better for cut
resistance compared to Comparative Examples 10 and 11. Comparative
Example 12 did have a higher guillotine resistance than the
multi-layered golf ball, but this result was expected due to the
high cover hardness and compression as well as greater overall
thickness of the outer cover layer.
Example 6
[0114] The configuration for the multi-layered golf ball was the
same as Example 5 except that the inner cover layer was made from
60 parts by weight Iotek 7510, 33 parts Iotek 8000, and 7 parts
7030. The Shore D hardness of the outer cover layer was 70, while
the Shore D hardness of the inner cover layer was about 54. The
overall Shore D hardness of the cover was about 60, roughly halfway
between the inner and outer cover layer hardness. The guillotine
results of the multi-layered ball were much better than those found
in Comparative Examples 10 and 11.
4TABLE 3 CORE MANTLE LAYER Example Size Weight Mater- Thick- Weight
No. (inches) (g) COMP COR ial Size ness (g) Comp COR Comp. 1.542"
36.8 85 0.779 None -- -- -- -- -- 10 Comp. 1.542" 36.8 85 0.779
None -- -- -- -- -- 11 Comp. 1.542" 36.8 85 0.779 None -- -- -- --
-- 12 Comp. 5 1.542" 36.8 85 0.779 A.sup.1 1.645" 0.052" 43.3 85
0.780 Comp. 6 1.542" 36.8 85 0.779 B.sup.2 1.645" 0.052" 43.2 81
0.785 OUTER COVER LAYER Example Shore Cover Thick- Weight Shore
Guillotine No. C/D Material ness (g) Comp COR C/D (rank) Comp. --
.sup. C.sup.3 0.070" 45.4 86 0.780 70/45 1.5 5th 10 Comp. -- .sup.
D.sup.4 0.070" 45.3 81 0.787 84/56 1.5 4th 11 Comp. -- .sup.
E.sup.5 0.070" 45.4 66 0.811 97/71 1 1st 12 Comp. 5 70/45 E 0.021"
45.6 80 0.790 85/57 1 2nd Comp. 6 84/54 E 0.021" 45.6 75 0.794
91/60 1 3rd A.sup.1 = 100 pts. lotek 7510 B.sup.2 = 60 pts lotek
7510; 33 pts lotek 8000; 7 pts lotek 7030 C.sup.3 = 90.6 pts lotek
7510; 9.4 pts White MB D.sup.4 = 57.6 pts lotek 7510; 33 pts lotek
8000; 9.4 pts White MB E.sup.5 35 pts Suryln .RTM. 8140; 57.5 pts
Surlyn .RTM. 6120; 12.5 pts White MB
[0115] While certain representative embodiments and details of the
present invention have been shown for the purposes of illustrating
the invention, it will be apparent to those skilled in the art that
various changes and modifications may be made therein without
departing from the spirit or scope of the invention.
* * * * *