U.S. patent application number 10/178267 was filed with the patent office on 2003-01-02 for golf ball cover containing a blend of ionomer and plastomer, and method of making same.
This patent application is currently assigned to Spalding Sports Worldwide, Inc.. Invention is credited to Kaltenbacher, Edward J., Sullivan, Michael J..
Application Number | 20030004274 10/178267 |
Document ID | / |
Family ID | 25206575 |
Filed Date | 2003-01-02 |
United States Patent
Application |
20030004274 |
Kind Code |
A1 |
Sullivan, Michael J. ; et
al. |
January 2, 2003 |
Golf ball cover containing a blend of ionomer and plastomer, and
method of making same
Abstract
Disclosed herein is a golf ball having a core and a cover
comprising a blend of ionomer and plastomers. The golf ball has an
impact resistance and cut resistance comparable to a ball having a
non-plastomer cover and containing higher quantities of
ionomer.
Inventors: |
Sullivan, Michael J.;
(Barrington, RI) ; Kaltenbacher, Edward J.;
(Humble, TX) |
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.
Chicopee
MA
|
Family ID: |
25206575 |
Appl. No.: |
10/178267 |
Filed: |
June 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10178267 |
Jun 24, 2002 |
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09223450 |
Dec 30, 1998 |
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09223450 |
Dec 30, 1998 |
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08811447 |
Mar 3, 1997 |
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Current U.S.
Class: |
525/221 |
Current CPC
Class: |
C08L 23/0815 20130101;
C08L 53/02 20130101; C08L 23/08 20130101; A63B 37/12 20130101; C08L
23/0876 20130101; A63B 37/0003 20130101; A63B 37/0036 20130101;
C08L 23/0815 20130101; C08L 23/08 20130101; A63B 37/0034 20130101;
C08L 23/0815 20130101; C08L 23/08 20130101; C08L 2666/04 20130101;
C08L 2666/24 20130101; C08L 2666/04 20130101; C08L 2666/24
20130101 |
Class at
Publication: |
525/221 |
International
Class: |
C08L 033/02 |
Claims
We claim:
1. A golf ball having a core and a cover wherein said cover
comprises an at least partially miscible blend of at least one
ionomer resin and at least one metallocene catalyzed polyolefin
resin.
2. The golf ball according to claim 1, wherein the ionomer resin
comprises ethylene and methacrylic or acrylic acid.
3. The golf ball according to claim 2, wherein the ionomer resin is
a terpolymer.
4. The golf ball according to claim 1, wherein the metallocene
catalyzed polyolefin resin comprises a copolymer of ethylene and at
least one olefin comonomer selected from the group consisting of
propylene, butene, hexene, octene, pentene and norbornene.
5. The golf ball according to claim 1, wherein the cover comprises
from about 90-10 percent ionomer resin and from about 10-90 percent
metallocene catalyzed polyolefin resin.
6. The golf ball according to claim 1, wherein the cover comprises
from about 80-50 percent ionomer resin and from about 20-50 percent
metallocene catalyzed polyolefin resin.
7. A golf ball comprising a cover and a core according to claim 1,
wherein the golf ball has a diameter of from about 1.68 to about
1.75 inches.
8. A golf ball having a core and a cover wherein said cover
comprises from about 90 to 10 percent of at least one ionomer resin
selected from the group consisting of ethylene-methacrylic acid and
ethylene-acrylic acid copolymers neutralized by mono, di or
tri-valent metallic derivatives; and from about 10 to 90 percent of
at least one non-ionic metallocene catalyzed copolymer of an olefin
with a lower alkyl substituent having from about 1 to about 18
carbon atoms.
9. A golf ball according to claim 8 wherein the cover comprises
from about 80-50 percent ionomer resin and from about 20-50 percent
non-ionic metallocene catalyzed copolymer.
10. A golf ball comprising a cover and a core according to claim 8,
wherein the golf ball has a diameter of from about 1.68 to about
1.75 inches.
11. A golf ball comprising a cover and a core wherein the cover
comprises an at least partially miscible blend of at least one
ionomer and at least one metallocene catalyzed polymer having the
formula: 1wherein R.sub.1 is hydrogen; R.sub.2 is hydrogen or lower
alkyl selected from the group consisting of CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9, and
C.sub.5H.sub.11; R.sub.3 is hydrogen or lower alkyl selected from
the group consisting of CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7,
C.sub.4H.sub.9, and C.sub.5H.sub.11; R.sub.4 is selected from the
group consisting of CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7,
C.sub.4H.sub.9, C.sub.5H.sub.11, C.sub.6H.sub.13, C.sub.7H.sub.15,
C.sub.8H.sub.17, C.sub.9H.sub.19, C.sub.10H.sub.21, and phenyl, in
which from 0 to 5 H within R.sub.4 can be replaced by substituents
selected from the group consisting of COOH, SO.sub.3H, NH.sub.2, F,
Cl, Br, I, OH, SH, silicone, lower alkyl esters and lower alkyl
ethers, with the proviso that R.sub.3 and R.sub.4 can be combined
to form a bicyclic ring; R.sub.5 is hydrogen, lower alkyl including
C.sub.1-C.sub.5, carbocycilc, aromatic or heterocyclic; R.sub.6 is
hydrogen, lower alkyl including C.sub.1-C.sub.5 carbocyclic,
aromatic or heterocyclic; and wherein x ranges from 99 to 50 weight
per cent of the polymer, y ranges from 1 to 50 weight per cent of
the polymer and z ranges from 0 to 49 weight per cent of the
polymer.
12. A golf ball comprising a core and a cover according to claim 11
wherein R.sub.2 is hydrogen.
13. A golf ball composing a cover and a core according to claim 11
wherein the golf ball core has a diameter of about 1.58 inches.
14. A golf ball comprising a cover and a core according to claim 11
wherein the golf ball has a diameter from about 1.68 to about 1.80
inches.
15. A golf ball comprising a cover and a core according to claim 11
wherein the golf ball has a diameter of from about 1.710 to about
1.730 inches.
16. A golf ball comprising a cover and a core according to claim 11
wherein the core is a single piece of material.
17. A golf ball comprising a cover and a core according to claim 11
wherein the core is a solid or liquid center at least partially
covered with a wound thread.
18. A golf ball having a core and a cover, said cover comprising a
blend of two or more ionomer resins with one or more non-ionic
copolymers and an olefin with attached lower alkyl groups having
from about 1 to about 18 carbon atoms said olefin comonomer
produced using a metallocene catalyst.
19. A golf ball according to claim 18 having multiple cover or core
layers.
20. A golf ball having a core and a cover wherein said cover
comprises one or more ionomer resins having a flexural modulus of
from about 50 psi to about 150,000 psi and a non-ionic metallocene
catalyzed copolymer of an olefin having a flexural modulus of from
about 500 psi to 200,000 psi.
21. A golf ball having a core and a cover wherein said cover
comprises an at least partially miscible blend of at least one
ionomer resin and at least one polyolefin resin, wherein the
polyolefin resin is formed with a metallocene catalyst.
22. A golf ball having a core and a cover wherein said cover
comprises from about 99 to 1 phr of at least one ionomer resin
chosen from the group consisting of ethylene-methacrylic acid and
ethylene-acrylic acid copolymers neutralized by mono, di or
tri-valent metallic derivatives; and from about 1 to 99 phr of at
least one non-ionic metallocene catalyzed copolymer of an olefin
with a lower alkyl substituent having from about 1 to about 18
carbon atoms.
23. A golf ball having improved spin comprising a core and a cover
wherein said cover comprises from about 95 to 5 phr of at least one
ionomer resin chosen from the group consisting of
ethylene-methacrylic acid and ethylene-acrylic acid copolymers
neutralized by mono, di or tri-valent metallic derivatives; and
from about 5 to 95 phr of at least one non-ionic metallocene
catalyzed copolymer of an olefin with a lower alkyl substituent
having from about 1 to about 18 carbon atoms.
24. A golf ball according to claim 22 wherein the cover comprises
from about 95-30 percent ionomer and from about 5-70 percent
metallocene catalyzed copolymer.
25. A golf ball according to claim 22 wherein the cover comprises
from about 95-50 percent ionomer and from about 5-50 percent
metallocene catalyzed copolymer.
26. A golf ball according to claim 22 wherein the olefin has a
flexural modulus between about 500 psi and about 150,000 psi.
27. A golf ball according to claim 22 wherein the olefinic polymer
is a copolymer in which the monomers are selected from the group
consisting of butene, hexene, and octene.
28. A golf ball according to claim 22 wherein the olefinic polymer
is a copolymer of butene, hexene, or norbornene.
29. A golf ball according to claim 22 wherein the olefinic polymer
is a copolymer of ethylene and butene.
30. A golf ball according to claim 22 wherein the olefinic polymer
is a copolymer of butene and hexene.
31. A golf ball according to claim 22 wherein the olefinic polymer
is a copolymer of ethylene and octene.
32. A golf ball according to claim 23 wherein the olefinic polymer
is a copolymer of ethylene and norbornene.
33. A golf ball according to claim 23 wherein the olefinic polymer
is a polymer of ethylene and propylene and diene monomer.
34. The golf ball according to claim 11 wherein the ionomer
comprises ethylene and methacrylic or acrylic acid.
35. The golf ball according to claim 34 wherein the ionomer is a
terpolymer.
36. The golf ball according to claim 18 wherein the ionomers
comprise ethylene and methacrylic or acrylic acid.
37. The golf ball according to claim 36 wherein the ionomer is a
terpolymer.
38. The golf ball according to claim 21 wherein the ionomer
comprises ethylene and methacrylic or acrylic acid.
39. The golf ball according to claim 38 wherein the ionomer is a
terpolymer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to golf balls, and
more particularly to golf balls having covers containing blends of
ionomer and plastomer.
BACKGROUND OF THE INVENTION
[0002] Traditional golf ball covers were comprised of balata or
blends of balata with elastomeric or plastic materials. Balata
covered balls provide an experienced golfer with the ability to
apply a spin to control the ball in flight. Moreover, the soft
balata covers produce a soft "feel" to the low handicap player.
However, despite the benefits of balata, balata-covered golf balls
are easily cut and/or damaged if mis-hit; thus, balata and its
synthetic substitutes, trans-polybutadiene and trans-polyisoprene
have been essentially replaced by covers made of ionomers.
[0003] Ionomers are partial metal salts of acid containing
polymers, such as ethylene based polymers. These include the
partial metal salts of copolymers of ethylene and an
ethylene-copolymerizable unsaturated carboxylic acid, such as
acrylic acid, methacrylic acid, or maleic acid. Metal ions, such as
sodium, zinc, lithium, magnesium, and the like are used to
neutralize a portion of the acidic group in the copolymer resulting
in a thermoplastically reversible crosslinked polymer exhibiting
enhanced properties, i.e. durability, etc., for golf ball cover
construction as compared to balata-covered balls.
[0004] Several attempts have been made to match or improve the
performance of an ionomer golf ball by adding non-ionic and
non-ionizable polymers thereto. For example, U.S. Pat. No.
4,567,219 is directed to a cover composition for golf balls with
improved impact resistance. The cover comprises a blend of ionomer
resin and 1-15 parts by weight of a linear, low-density
polyethylene per 100 parts by weight of the ionomer resin. U.S.
Pat. No. 5,019,320 discloses a golf ball composition comprising an
ionomer resin and a low molecular weight polyethylene wax. This
blend also is alleged to provide improved impact resistance. The
polyethylene wax is present in a quantity of 0.1 to 6 parts by
weight based upon 100 parts by weight of ionomer resin. It would be
useful to develop a golf ball cover containing a blend of an
ionomer and a non-ionic or non-ionizable polymer in which
substantial quantities of the non-ionic and/or non-ionizable
polymers can be used while achieving playability properties
comparable to those which are obtained using known ionomeric golf
ball cover materials.
SUMMARY OF THE INVENTION
[0005] An object of the invention is to provide a golf ball having
the playability properties of an ionomeric covered ball while
containing reduced quantities of ionomer,
[0006] Another object of the invention is to provide a golf ball
having a durable cover.
[0007] Yet another object of the invention is to provide a golf
ball which can be produced in an efficient and economical
manner.
[0008] A further object of the invention is to provide a method for
making a golf ball having the characteristics described above.
[0009] Other objects will be in part obvious and in part pointed
out more in detail hereafter.
[0010] The invention in a preferred form is a golf ball having a
core and one or more cover layers, wherein the cover layer contains
a blend of ionomer and plastomer. The plastomer is comprised of
catalytically polymerized, random copolymers of ethylene and one or
more olefin comonomers characterized by a narrow or controlled
composition distribution. The plastomer preferably has a dispersion
index (M.sub.W/M.sub.M), i.e. the ratio of weight average molecular
weight to number average molecular weight, of about 1.5 to 4. The
olefin comonomer or comonomers are present in amounts of about
10-35 wt % based upon the overall weight of the plastomer.
[0011] In a particularly preferred form of the invention, the cover
layer contains 10-90, and preferably 20-60, parts of plastomer
based upon 100 parts by weight of ionomer. The golf ball has a cut
resistance of at least 3 and a Shore D hardness in the range of
40-80.
[0012] Another preferred form of the invention is a method of
making a golf ball comprising the steps of (1) obtaining a core and
(2) forming a cover over the core, the cover comprising a blend of
ionomer and plastomer.
[0013] The invention accordingly comprises the several steps and
the relation of one or more of such steps with respect to each of
the others and the article possessing the features, properties, and
the relation of elements exemplified in the following detailed
disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The golf balls of the invention have covers which comprise
blends of ionomers and non-ionic and/or non-ionizable olefin
copolymers which have a uniform, narrow molecular weight, a high
comonomer content, and an even distribution of plastomer. The
dispersion index of the plastomers generally is about 1.5-4,
preferably 1.5-3.5 and more preferably 1.5-2.4. The density is
typically in the range of 0.85-0.93 g/cc if unfoamed and 0.10-0.90
g/cc if foamed. The comonomer content typically is in the range of
10-35%, and preferably 15-30%. The melt index (MI) of the plastomer
generally is less than 30 with the lower melt index materials
providing blends with better low temperature impact. Accordingly a
melt index less than about 20 is typical with a melt index of less
than 10 being preferred and one of less than 5 being most
preferred. The composition distribution breadth index generally is
greater than 30%, preferably is at least 45%, and more preferably
is at least 50%. Preferably the golf balls also include a curing
agent for the plastomer.
[0015] The term "copolymer" includes olefin copolymers made from
ethylene and one or other olefin monomers. Examples of olefin
monomers include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl
pentene-1, 1,4-hexadiene, norbornene, norbornadiene, vinyl
norbornene, ethylidene norbornene, etc. The compositions of the
invention further may include additives and fillers as well as a
co-agent that can react with the curing agent to aid in
crosslinking the plastomer and/or ionomer or to improve
processability. Co-agents which have been used for that purpose
include triallyl cyanurates, ethylene glycol di(meth)acrylate,
tri(meth)acrylates, divinyl benzene and other multifunctional
chemicals.
[0016] The "composition distribution breadth index" (CDBI) is
defined as the weight percent of the plastomer molecules which have
a comonomer content between 50 percent and 125 percent of the
median comonomer content (on a mole basis) of the sample. For
example the CDBI of a sample which had a butene content of 8 mole
percent would be the weight percent of the molecules which had
butene contents between 6 and 10 mole percent.
[0017] The plastomers employed are polyolefin copolymers developed
using metallocene single-site catalyst technology. Polyethylene
plastomers generally have better impact resistance than
polyethylenes made with Ziegler-Natta catalysts. Plastomers exhibit
both thermoplastic and elastomeric characteristics. In addition to
being comprised of a polyolefin such as ethylene, plastomers
contain up to about 35 wt % comonomer. Plastomers include but are
not limited to ethylene-butene copolymers, ethylene-octene
copolymers, ethylene-hexene copolymers, and ethylene-hexene-butene
terpolymers, as well as mixtures thereof.
[0018] The golf ball covers of the invention contain a blend of
plastomer and ionomer in a ratio of 10:90 to 90:10, and more
preferably 20:80 to 50:50. It has been found that the golf ball
cover properties of high impact resistance, good durability and
playability are particularly favorable when the ratio of
plastomer:ionomer is in the range of 10:90 to 50:50. Other
additives such as coloring agents, optical brighteners, processing
aids and fillers typically are added in an amount of up to about 10
parts by weight based upon 100 parts by weight of the
plastomer-ionomer blend.
[0019] The plastomers employed in the invention preferably are
formed by a single site metallocene catalyst such as those
disclosed in EP 29368, U.S. Pat. No. 4,752,597, U.S. Pat. No.
4,808,561, and U.S. Pat. No. 4,937,299, the teachings of which are
incorporated herein by reference. Blends of plastomers can be used.
As is known in the art, plastomers can be produced by solution,
slurry and gas phase accesses but the preferred materials are
produced by metallocene catalysis using a high pressure process by
polymerizing ethylene in combination with other olefin monomers,
such as butene-1, hexene-1, octene-1 and 4-methyl-1-pentene in the
presence of catalyst system comprising a
cyclopentadienyl-transition metal compound and an alumoxane.
[0020] Plastomers found especially useful in the invention are
those sold by Exxon Chemical under the trademark "EXACT" and
include linear ethylene-butene copolymers such as EXACT 3024 having
a density of about 0.905 g/cc (ASTM D-1505) and a melt index of
about 4.5 g/10 min. (ASTM D-2839); EXACT 3025 having a density of
about 0.910 g/cc (ASTM D-1505) and a melt index of about 1.2 g/10
min. (ASTM D-2839); EXACT 3027 having a density of about 0.900 g/cc
(ASTM D-1505) and a melt index of about 3.5 g/10 min. (ASTM
D-2839). Other useful plastomers include but are not limited to
ethylene-hexene copolymers such as EXACT 3031 having a density of
about 0.900 g/cc (ASTM D-1505) and a melt index of about 3.5 g/10
min. (ASTM D-2839), as well as EXACT 4049, which is an
ethylene-butene copolymer having a density of about 0.873 g/cc
(ASTM D-1505) and a melt index of about 4.5 g/10 min. (ASTM
D-2839). All of the above EXACT series plastomers are available
from EXXON Chemical Co.
[0021] EXACT plastomers typically have a dispersion index
(M.sub.w/M.sub.n where M.sub.w is weight average molecular weight
and M.sub.n is number average molecular weight) of about 1.5 to
4.0, preferably 1.5-2.4, a density of about 0.86 to about 0.93
g/cc, preferably about 0.87 g/cc to about 0.91 g/cc, a melting
point of about 140-220.degree. F., and a melt index (MI) above
about 0.5 g/10 mins, preferably about 1-10 g/10 mins as determined
by ASTM D-1238, condition E. Plastomers which may be employed in
the invention include copolymers of ethylene and at least one
C.sub.3-C.sub.20 .alpha.-olefin, preferably a C.sub.4-C.sub.8
.alpha.-olefin present in an amount of about 5 to about 32 wt %,
preferably about 7 to about 22 wt %, more preferably about 9-18 wt
%. These plastomers are believed to have a composition distribution
breadth index of about 45% or more.
[0022] Plastomers such as those sold by Dow Chemical Co. under the
trade name ENGAGE also may be employed in the invention. These
plastomers are believed to be produced in accordance with U.S. Pat.
No. 5,272,236, the teachings of which are incorporated herein by
reference. These plastomers are substantially linear polymers
having a density of about 0.85 g/cc to about 0.93 g/cc measured in
accordance with ASTM D-792, a melt index (MI) of less than 30 g/10
minutes, a melt flow ratio (I.sub.10/I.sub.2) of about 7 to about
20, where I.sub.10 is measured in accordance with ASTM D-1238
(190/10) and I.sub.2 is measured in accordance with ASTM D-1238
(190/2.16), and a dispersion index M.sub.w/M.sub.n which preferably
is less than 5, and more preferably is less than about 3.5 and most
preferably is from about 1.5 to about 2.5. These plastomers include
homopolymers of C.sub.2-C.sub.20 olefins such as ethylene,
propylene, 4-methyl-1-pentene, and the like, or they can be
interpolymers of ethylene with at least one C.sub.3-C.sub.20
.alpha.-olefin and/or C.sub.2-C.sub.20 acetylenically unsaturated
monomer and/or C.sub.4-C.sub.18 diolefins. These plastomers have a
polymer backbone that is either unsubstituted or substituted with
up to 3 long chain branches/1000 carbons. As used herein, long
chain branching means a chain length of at least about 6 carbons,
above which the length cannot be distinguished using .sup.13C
nuclear magnetic resonance spectroscopy. The preferred ENGAGE
plastomers are characterized by a saturated ethylene-octene
backbone and a narrow dispersion index M.sub.w/M.sub.n of about
2.
[0023] These plastomers also are compatible with many conventional
plasticizers and fillers. The fillers 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. Thus, a two-layer cover in which a non-white filler is
only present in the inner cover layer can be employed. 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.
Various commercially available plastomers may be useful in the
invention, including those manufactured by Mitsui.
[0024] The dispersion index M.sub.w/M.sub.n of plastomers made in
accordance with U.S. Pat. No. 5,272,236 most preferably is about
2.0. Non-limiting examples of these plastomers include ENGAGE CL
8001 having a density of about 0.868 g/cc, a melt index of about
0.5 g/10 mins, and a Shore A hardness of about 75; ENGAGE CL 8002
having a density of about 0.87 g/cc, a melt index of about 1 gms/10
min, Shore A hardness of about 75; ENGAGE CL 8003 having a density
of about 0.885 g/cc, melt index of about 1.0 gms/10 min, and a
Shore A hardness of about 86; ENGAGE EG 8100 having a density of
about 0.87 g/cc, a melt index of about 1 gms/10 min., and a Shore A
hardness of about 87; ENGAGE 8150 having a density of about 0.868
g/cc, a melt index of about 0.5 gms/10 min, and a Shore A hardness
of about 75; ENGAGE 8200 having a density of about 0.87 g/cc, a
melt index of about 5 g/10 min., and a Shore A hardness of about
75; and ENGAGE EP 8500 having a density of about 0.87 gms/cc, a
melt index of about 5 g/10 min., and a Shore A hardness of about
75.
[0025] The ionomers which are blended with plastomer preferably are
various commercially available ionomers sold under the trade name
lotek, such as lotek 8000, lotek 8020, lotek 8030 or lotek 7000,
lotek 7010, lotek 7020 or lotek 7030. Blends of ionomers can be
used, however hard ionomers are preferred.
[0026] Coloring pigments and optical brighteners also may be
included in the compositions of the invention. Useful coloring
pigments include, for example, titanium dioxide, the presence of
which simplifies the surface painting operation of the finished
ball. In some cases, coloring pigments eliminate the need for
painting, such as, for example, where the ball is intended for use
on driving ranges.
[0027] The golf balls of the invention have a coefficient of
restitution of at least 0.650, and more preferably at least 0.700,
a PGA compression of about 60-110 and preferably 80-90, a ball size
of 1.68"-1.75", and a ball weight of 45.93 grams or less.
[0028] To form a golf ball according to the invention, a solid,
liquid or wound golf ball center is obtained. The center optionally
may be covered with one or more non-plastomer inner cover layers
prior to application of the plastomer cover layer or layers. If
necessary, the center can be surface treated to facilitate adhesion
thereof to a cover composition. Surface treatment can be performed
by techniques known in the art, such as corona discharge, ozone
treatment, sand blasting, grinding and the like. Non-limiting
examples of useful non-plastomer cover compositions include blends
of ethylene-acrylic acid or ethylene-methacrylic acid, as well as
copolymers neutralized with mono-or divalent metals such as sodium,
potassium, lithium, calcium, zinc or magnesium. Such compositions
are shown in U.S. Pat. No. 5,368,304, the disclosure of which is
incorporated herein in its entirety by reference. The plastomer
cover layer or layers are then formed over the core using a
conventional molding technique, such as compression molding or
injection molding. The golf ball is finished by applying an indicia
and a thin top coat with or without the use of a primer coat.
[0029] The plastomer and ionomer typically are subject to intensive
mixing such as in a Banbury mixer, two roll mill, or the like. When
the plastomer cover is made by compression molding, the golf ball
center is placed between two half-shells and the ball is molded for
about 1-3 minutes at 200-300.degree. F. and 100 p.s.i.
Subsequently, the molded ball is cooled for about 10 minutes. When
the plastomer cover is made by injection molding, the cover
material is heated to 300-400.degree. F. and injection molded into
a cold mold where it is maintained for about 20-60 seconds.
[0030] Coefficient of restitution (COR) is measured by firing a
golf ball from an air cannon at about 125 feet per second against a
steel plate positioned 12 feet from the muzzle of the cannon. The
rebound velocity then is measured. The rebound velocity is divided
by the initial velocity of 125 feet per second to give the COR
[0031] Riehle compression is a measurement of the deformation of a
golf ball in inches under a load. Riehle compression can be
converted to PGA compression by subtracting Riehle compression
values from 160.
[0032] The "Guillotine Cut Test" employed to measure cut resistance
is performed by holding an unfinished 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 90.degree.
and 60.degree. relative to the horizontal, respectively, and a
blunt cutting edge of three sixty-fourths inch radius which is
designed to simulate the leading edge of an iron is dropped from a
height of three feet to strike the ball at a point one-half inch
off the top center point. The guillotine blade is guided during the
drop by means of a substantially friction-free vertical track.
Optionally, but not necessarily, the test can be repeated on the
same or on different sections of the ball. Ball failure is defined
as permanent damage evidenced by a crack or by removal of a segment
from the ball surface. A rating of 1 is excellent and a rating of 4
is poor. The cut-off for a commercially acceptable ball is a rating
of 3.
[0033] 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. In the examples, Shore C and Shore D hardness values
generally were measured in accordance with ASTM D-2240, except that
measurements were made on the curved surface of a golf ball.
EXAMPLES
[0034] A number of golf ball cores were formed primarily from
polybutadiene, zinc diacrylate, and free radical initiator having a
weight of 36.8 grams, a Riehle compression of 81 (PGA compression
of 79), and a coefficient of restitution (COR) of 0.786. The cores
had a diameter of 1.55 inches. About 12 of the cores were covered
with each of the cover formulation shown below on Table 1. One set
of controls was covered with the 1995 Top Flite Z balata cover
formulation. The remaining cores were covered with one of four
different cover formulations comprising an ionomer-plastomer blend.
The covers had a thickness of 0.067 inches. Properties of the
molded balls were measured, and are also shown on Table 1 below.
All of the cover formulations were mixed in an internal
Banbury.RTM.-type mixer at an elevated temperature.
[0035] As shown on Table 1, Example 3 had a coefficient of
restitution 10 points higher than control Example C-1 with a Shore
D hardness comparable to that of control Example C-1.
[0036] As will be apparent to persons skilled in the art, various
modifications and adaptations of the composition and structure
above described will become readily apparent without departure from
the spirit and scope of the invention.
1TABLE 2 Golf Balls With Covers Formed From Blends of lonomer and
Plastomer Material (pbw) C1 C2 1 2 3 4 1995 Z-Balata X -- -- -- --
-- lotek 8000 -- 600 560 560 560 -- lotek 7030 -- 448 408 408 408
-- lotek 3110 -- -- -- -- -- 1120 GLS 6703 -- 400 240 -- -- --
EXACT 4049 -- -- 240 240 480 160 Kraton FG 1901 X -- -- -- 240 --
160 Masterbatch -- 152 152 152 152 152 Weight (g) 45.2 45.1 44.9
45.1 44.9 45.0 Comp (Riehle) 84 81 80 78 78 79 Comp (PGA) 76 79 80
82 82 81 COR .791 .795 .796 .800 .801 .793 Shore D (ASTM D-2240) 55
53 53 58 55-56 57 Shore C (ASTM D-2240) 86 85 89 87 Guillotine Cut
Test 1.5 15 15 15 1.5
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