Note: Descriptions are shown in the official language in which they were submitted.
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ONE-PIECE GOLF BALL
FIELD OF THE INVENTION
This invention relates to a novel composition of matter and to a golf ball
made therefrom.
BACKGROUND OF THE INVENTION
Prior art golf balls comprise, in general, three types. The first type is the
three piece
wound ball wherein a vulcanized rubber string is wound under tension around a
solid or
semi-solid core, and thereafter enclosed in a sheath or covering of tough;
protective material. A
second prior art golf ball is a one-piece ball formed from a solid mass of
moldable resilient
material which has been cured to develop the necessary degree of hardness to
provide utility.
One-piece molded balls do not have an enclosing cover. A third prior art ball
is the two-piece
1 S ball that includes a solid core and a cover thereon.
The one-piece ball is formed from a combination of materials such as
elastomers,
fillers and curing agents which are molded under high pressure and temperature
to provide a ball
of suitable hardness and resilience. One-piece balls are described, for
example, in U.S. Patent
No. 3,313,545, U.S. Patent No. 3,373,123 and U.S. Patent No. 3,384,612.
While the wound ball has for many years satisfied both the standards of 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 or rebound, "click" and the like. "Click" is the term
applied to the
sound produced by the ball when dropped on a hard surface or when struck with
a golf
club. In addition, the cover material for the wound ball has not provided the
optimum in
adhesion to the wound core and is susceptible to cutting when struck by a golf
club.
One-piece and two-piece golf balls, in contrast to wound golf balls, can be
produced with an essentially perfect center of gravity and thus, exhibit
excellent
aerodynamic properties, superior roll and trueness of flight. Such golf balls
are highly
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resistant to cutting and are practically indestructible during use in normal
play. These
balls return to round even when severely distorted and maintain their superior
flight
characteristics after extended use. Further, one and two-piece unitary golf
balls can be
manufactured with better quality than conventional wound balls. One-piece
balls also
maintain their playing characteristics throughout wide temperature ranges,
possess an excellent
shelf life, and do not water log. Moreover, if paint on one-piece golf balls
becomes worn or
damaged, the one-piece balls may be reclaimed by removing or stripping off the
old paint and
repainting. In contrast, wound balls seldom last long enough to allow
repainting.
Although one-piece balls have several distinct advantages, they have not had
satisfactory
durability due to brittleness. Most one-piece balls do not survive more
than~about 1000 hits. A
need therefore exists for one-piece balls which have high hardness but yet
possess improved
durability and flexibility to minimize cracking.
SUMMARY OF THE INVENTION
In accordance with the invention, a novel, cured composition and golf balls of
improved durability are provided. The composition includes an elastomer, a
polymerization agent, a co-agent for the polymerization agent, and an
unsaturated polycarboxylic
acid. The elastomer preferably is cis 1,4-polybutadiene, the unsaturated
polycarboxylic acid
preferably is fumaric acid, the polymerization agent preferably is dicumyl
peroxide, and the
coagent preferably is zinc diacrylate ("ZDA"). The compositions of the
invention further may
include a filler material. The compositions of the invention advantageously
avoid zinc oxide that
is employed in prior art compositions. Golf balls such as one-piece golf balls
formed from the
compositions of the invention have high flexibility and high durability.
Further scope of the applicability of the present invention will become
apparent
from the detailed description given hereinafter. It should, however, be
understood that the
detailed description and specific examples, while indicating preferred
embodiments of the
invention, are given by way of illustration only, since various changes and
modifications within
the spirit and scope of the invention will become apparent to those skilled in
the art.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention provides a novel, cured composition, as well as a golf ball
formed
of that composition. The composition includes an elastomer, a polymerization
agent and a
co-agent for cross-linking the elastomer, and an unsaturated polycarboxylic
acid. Preferably, the
compositions employed are free of alkaline oxides and alkaline earth oxides
such as ZnO, MgO,
Ca0 and the like. However, the above compositions which are substantially free
of these
alkaline oxides and alkaline earth oxides, i.e., compositions which have up to
about 0.5 parts of
alkaline oxides and alkaline earth oxides per about 100 parts elastomer, also
may be employed.
Elastomers which may be used in the compositions of the invention include
olefins
which can be crosslinked by peroxide polymerization agents. Preferably, the
elastomer is
cis 1,4 polybutadiene because of its very high resiliency and low hysteresis.
The molecular
weight of the cis 1,4 polybutadiene is from about 50,000 weight average to
about 500,000 weight
average, preferably about 100,000 weight average to about 500,000 weight
average. Other
elastomers which may be used include, for example, ethylene, polypropylene,
butene-1,
1 S hexene-I, polyisoprene, ethylene/propylene/non-conjugated diolefin
terpolymers,
styrene/butadiene rubbers, natural rubber, ethylene propylene copolymers,
ethylene propylene
rubber, synthetic natural rubber and mixtures thereof.
Peroxide polymerization agents useful in the compositions of the invention
include, for
example, di-tertbutyl peroxide, dicumyl peroxide, benzoyl peroxide, 2,4-
dichlorobenzol
peroxide, t-butyl-cumyl peroxide, t-butyl perbenzoate, t-butyl peroxide, t-
butylperoxy
(2-ethylhexanoate), 2,5-dimethyl-2,5-di(benzoylperoxy)-hexane, benzoyl
peroxide,
2,5-dimethyl 2,5-(t-butyl peroxy)-hexane, 1,1-ditert-butyl peroxy-3,3,5-
trimethyl cyclohexane,
4,4-ditert-butyl peroxy n-butyl valerate, preferably dicumyl peroxide at a
concentration of about
40%. The above polymerization agents are commercially available.
Co-agents which can be used with the above peroxide polymerization agents
include zinc
diacrylate, zinc dimethacrylate, trimethlol propane triacrylate, and
trimethloyl propane
trimethacrylate, preferably zinc diacrylate. Other co-agents which may be
employed include
vinyl, allyl, methallyl, fiu-furyl, crotyl and cinnamyl esters of the
following acids: oxatic, maionic,
succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, malefic,
itaconic, citraconic,
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mesaconic, fumaric, aconitic, phthalic, isophthalic, terephthalic,
naphthalene, dicarboxylic,
mellitic, pyromellitic, trimesic, acrylic, methacrylic, cennamic, and
crotonic. Polyamine amides
and imides of the following acids: malefic, itaconic, acrylic, methacrylic
crotonic, citaconic,
aconitic and cinnamic; polyol esters and anhydrides of acrylic, methacrylic,
crotonic and
cinnamic acids also may be used as co-agents. Other co-agents which may be
employed include
di- and triallyl cyanurate; di- and triallylmelamine, divinyl benzene; diallyl
benzene; diallyl
amine; allyl ether; allyl gycolates; di-, tri and tetravinyl and allyl
silanes. All of these co-agents
are commercially available.
Unsaturated polycarboxylic acids which may be employed in the compositions of
the
invention include malefic acid, fumaric acid, itaconic acid and the like,
preferably fumaric acid.
Use of fumaric acid in compositions including polybutadiene and epoxy resins
is shown in U.S.
Patent No. 3,671,477.
In addition to the foregoing, filler materials can be employed in the
compositions
of the invention to control the weight of the ball without affecting ball
resilience. Fillers
which are incorporated into the compositions should be in finely divided form,
typically in a size
generally less than about 20 mesh, preferably less than about 100 mesh U.S.
standard size.
Preferably, the filler is a precipitated hydrated silica such as that sold
under the trademark HiSil
by the Pittsburgh Plate Glass Company. Other fillers which may be employed
include, for
example, silica, clay, talc, mica, asbestos, glass, glass fibers,
Barytes(barium sulfate), limestone,
Lithopone(zinc sulphide-barium sulfate), titanium dioxide, zinc sulphide,
calcium metasilicate,
silicon carbide, diatomaceous earth, particulate carbonaceous materials, micro
balloons, arimid
fibers, particulate synthetic plastics such as high molecular weight
polyethylene, polystyrene,
polyethylene, ionomer resins and the like, as well as cotton flock, cellulose
flock and leather
fiber. Powdered metals such as titanium, tungsten, aluminum, bismuth, nickel,
molybdenum,
copper, brass and their alloys also may be used as fillers. The amount of
filler employed is
primarily a function of weight restrictions on the weight of a golf ball made
from those
compositions.
The compositions of the invention also may include various processing aids
known
in the rubber and molding arts such as fatty acids. Generally, free fatty
acids having from
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about 10 carbon atoms to about 40 carbon atoms, preferably having from about
15 carbon atoms
to about 20 carbon atoms, may be used. Fatty acids which may be used include
stearic acid and
linoleic acids, as well as mixtures thereof. When included in the compositions
of the invention,
the fatty acid component is present in amounts of from about 1 part by weight
per 100 parts
elastomer to about 15 parts by weight per 100 parts elastomer, preferably in
amounts of from
about 2 parts by weight per 100 parts elastomer to about 5 parts by weight per
100 parts
elastomer. Examples of processing aids which may be employed include, for
example, calcium
stearate, barium stearate, zinc stearate, lead stearate, basic lead sulfite,
dibasic lead phosphite,
dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin mercaptide, as well as
dioctyltin and
stannane diol derivatives.
Coloring pigments 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.
The compositions of the invention typically include, based on the total weight
of the
composition, about 100 parts by weight of cis 1,4 polybutadiene to about 175
parts by weight of
cis 1,4 polybutadiene, preferably about 100 parts by weight of cis 1,4
polybutadiene, zinc
diacrylate in an amount of up to about 40 parts by weight, preferably from
about 5 parts by
weight of zinc diacrylate to about 30 parts by weight of zinc diacrylate,
about 4 parts by weight
of dicumyl peroxide at 40% concentration to about 7 parts by weight of dicumyl
peroxide at 40%
concentration, preferably about 4 parts by weight of dicumyl peroxide at 40%
concentration to
about 5 parts by weight of dicumyl peroxide at 40% concentration, and about 20
parts by weight
fiunaric acid to about 50 parts by weight fumaric acid, preferably about 20
parts by weight
fumaric acid to about 40 parts by weight fumaric acid.
The amount of filler which can be employed in the compositions is primarily a
function
of restrictions on the weight of a golf ball formed from the compositions. The
filler is included
in amounts of from about S parts by weight per 100 parts elastomer to about
100 parts by weight
per 100 parts elastomer. Processing aids such as fatty acids, metal stearates
and the like may be
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employed in amounts of from about 1 part by weight per 100 parts elastomer to
about 15 parts by
weight per I 00 parts elastomer, preferably in amounts of from about 2 parts
by weight per 100
parts elastomer to about 5 parts by weight per 100 parts elastomer.
Wide latitude may be taken in the production of balls from the compositions of
the
invention to provide balls of various compressions suitable for every type of
golfer. Low
compression balls, generally preferred by the "soft" hitters or lady golfers,
may be made
by increasing the proportion of the elastomer component in the composition.
Medium
compression balls, preferred by the average golfers, may be made by balancing
the amounts of
the elastomer, co-agent, peroxide polymerization agent, and fumaric acid. High
compression
balls preferred by the "hard" hitters may be made by increasing the
proportions of unsaturated
polycarboxylic acid, co-agent, and peroxide polymerization agent initiator.
In producing one-piece golf balls from the present compositions, the
components of the
compositions are intimately mixed, using, for example, two roll mills or a
Banbury mixer until
the mixture is uniform, usually over a period of from about 5 to about 20
minutes. The sequence
of addition of components is not critical.
A preferred mixing sequence is one wherein cis-1,4 polybutadiene, zinc
diacrylate, filler
and fumaric acid are blended for about 5 minutes in a Banbury mixer. The
peroxide
polymerization agent is then added and the mixing continued for about one
minute. The mixed
batch then is discharged onto a two roll mill, mixed for about one additional
minute and formed
into a sheet. The temperature of the mixing is not critical, but should, of
course, be below the
curing temperature. Mixing is generally done at room temperature, although,
through friction, the
ingredients may be slightly warmed.
A golf ball formed from compositions of the invention may be made by
conventional mixing and compounding procedures used in the rubber industry.
Typically,
a golf ball is produced by placing uncured, preformed portions or slugs of the
compositions of the invention between two halves of a conventional press mold
that has
dimpled golf ball cavities therein. Thereafter, pressure is applied to close
the two halves
of the mold during the curing process. The volume of the preformed portions
placed in
the mold cavities is slightly in excess of the actual volume of the ball
cavities to enable
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the cavities to be completely filled when the mold is closed. Thus, an
extrudate or flash
of excess composition typically is formed at the mating surfaces of the closed
cavities.
The compositions of the invention can be formed into one-piece golf balls by
any one of a
variety of known molding techniques, e.g. injection molding, compression
molding or transfer
molding. Typically the molded balls are cured by heating at about 275°F
to about 350°F under a
pressure of about 100 PSI-500 PSI, preferably about 500 PSI per ball. The time
required for
curing is normally about 10 minutes to about 20 minutes depending upon the
amount and activity
of the selected peroxide polymerization agent and co-agent. Preferably, curing
of the
compositions is between about 300°F and about 340°F for about 10
minutes to about 30
minutes, more preferably, about 320°F for about 20 minutes.
After curing, the resulting balls are cooled for about 10 minutes in the mold
by
circulating cold water through the mold. The molded balls, with dimples, are
trimmed to remove
the flash line and the ball surface is treated to facilitate good paint
adhesion. Surface treatment
of the dimpled ball can be performed by several techniques known in the art,
such as corona
discharge, ozone treatment, chlorination, sand blasting, etc. the ball is then
given one coat of
paint, stamped and clear coated.
If a two-piece ball is desired, the core is surface treated to facilitate
adhesion
to covering compositions. Surface treatment of the core can be performed by
several
techniques known in the art, such as corona discharge, ozone treatment, sand
blasting, brush
tumbling, and the like. Preferably, surface treatment is effected by grinding
with an abrasive
wheel. A cover then can be applied in accordance with known procedures. Useful
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 disclosed in U.S.
Patent No.
5,368,304, the disclosure of which is incorporated herein by the entirety by
reference.
Examples 1-22 shown in Table I show one-piece golf balls prepared from various
compositions, molding pressures and curing conditions to yield one-piece golf
balls of from
about 60 PGA compression to about 100 PGA compression. The balls produced in
accordance
with the invention have increased durability and flexibility. These
characteristics make them
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especially suited for use as range balls. For example, balls such as those
formed from examples
8, 9, 14-16, 21 and 22 which do not employ Zn0 and which are subjected to the
"Guillotine Cut
Test" pass that test.
Example 23 shown in Table II shows the negative effect of adding Zn0 as the
ball has a
PGA compression of only 2. The same formulation without Zn0 shown as example 1
in Table I
has a PGA compression of 65-70 and is very durable.
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a .'1~w p w E."J~a
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CA 02393563 2002-06-04
WO 01/39843 PCT/US00/33025
Table II
Example 23 / Value
Component
Cariflex Br-1220' 100 parts by wt.
DiCup 40Cz 4 parts by wt.
Fumaric Acid SO parts by wt.
ZDA' 10 parts by wt.
Zn0 5 parts by wt.
Mold Temp. 320 F
Cure Time 20 minutes
Weight 46.4 gm
Compression 2 PGA
1. cis 1,4 polybutadiene from Shell Chemical Co.
2. Dicumyl peroxide, 40% concentration from Hercules Chemical Co.
3. Zinc diacrylate
The "Guillotine Cut Test" is performed 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 90° and 60°, respectively, and a
cutting edge of three sixty
fourths inch radius is dropped from a height of 3.5 feet to strike the ball at
one
half inch ofI'the top center point. The guillotine blade is guided during the
drop by means
of a substantially friction-free vertical track. Ball failure is defined as
permanent damage
evidenced by a crack or by removal of a segment from the ball surface.
The present invention relates most particularly to the use of a novel
composition of matter in a golf ball. Other extensive applications, however,
may also be
mentioned. These include, for example, the manufacture of printing plates,
coverings for rolls or
the manufacture of rolls per se, protective bumpers, bowling balls,
insulators, floor tiles, shoe
soles and heels, battery boxes, solid tired and the like. Other applications
are possible for
the compositions of the invention where properties of resilience, toughness
and high impact
resistance are required.
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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.
11
