Note: Descriptions are shown in the official language in which they were submitted.
2149968
GOLF BALL COVER
BACKGROUND OF THE INVENTION
This invention relates in general to golf balls and, more
particularly, to a golf ball having an improved cover material.
The assembly of a golf ball generally involves molding a
cover around a solid or wound core. Golf balls with wound cores
are typically referred to as "three piece" balls because they
consist of three basic components: (1) a solid or liquid-filled
center; (2) rubber winding around the center, and (3) the cover.
Similarly, solid cores are referred to as having a "two piece"
construction, since they consist solely of a solid core and a
cover. A third type of ball, known as a "one-piece" ball is also
known in the art. As the name suggests, one piece balls are
solid balls of homogeneous construction made by any conventional
molding method suitable for the purpose. The present invention
relates particularly to two piece golf balls.
The majority of modern golf balls use a two piece
construction with covers made of a durable synthetic
thermoplastic resin such as Surlyn, a product of E. I. DuPont-de
Nemours Company, Incorporated. Synthetic thermoplastic cover
materials have been used with limited success. They are durable
and produce satisfactory flight distance. It is desirable,
however, to utilize a synthetic cover material for improved
process manufacturing and to increase durability and resilience
performance.
Ionomer resins are olefin polymers in which the linkage is
ionic. They are popular for use in golf balls because they
provide toughness and resilience.
Typically, for golf ball covers, there are two kinds of
ionomer resins that are most commonly used commercially. One is
an ionomer resin in which carboxyl groups are neutralized with
sodium (hereinafter sodium neutralized ionomer resin) and the
other is an ionomer resin in which carboxyl groups are
neutralized with zinc (hereinafter zinc neutralized ionomer
resin). It has been found that the sodium neutralized ionomer
21~9968
resin is superior in impact resistance to the zinc neutralized
one, but is inferior in low temperature durability. Certain
mixtures of these two neutralized ionomer resins have not been
found to overcome the problems in physical properties of the
resulting covers made from either resin alone.
U.S. Pat. No. 4,526,375 teaches that an oxide of zinc or
magnesium be formulated into the sodium neutralized ionomer resin
to neutralize r~m~ining free~carboxyl groups of the sodium
neutralized ionomer resin with zinc or magnesium. The resulting
ionomer resin has improved low temperature durability without
sacrifice of impact resilience properties. There is still a
need, however, to improve impact resilience and ambient
temperature durability.
U.S. Pat. No. 4,984,804 describes a golf ball cover material
prepared by mixing three ionomer resins in specific amount
ratios. The three ionomer resins are a sodium neutralized
ionomer resin, a zinc or magnesium neutralized ionomer resin and
a sodium and zinc or magnesium neutralized ionomer resin. As
described in that reference, the cover material blend will be a
sodium/sodium/zinc blend of ionomer resins or a
sodium/sodium/magnesium blend. All physical properties of a
cover produced from this blend are not optimized.
Accordingly, it is an object of the present invention to
provide a golf ball having a synthetic cover material.
Another object of the present invention is to provide an
improved synthetic cover material for a golf ball.
It is another object of the present invention to provide a
golf ball having a synthetic cover material that achieves the
click, feel, playability, impact resilience and flight
performance qualities of a high performance golf ball.
A further object of the present invention is to provide a
golf ball having a cover material that has improved process
manufacturing as well as ambient and cold pound temperature
durability.
SUMMARY OF THE INVENTION
The present invention is a cover material for a golf ball,
2149968
especially a two piece golf ball. The cover material includes
a blend of ionomer resins, including magnesium neutralized
ionomer(s), zinc ion neutralized ionomer(s) and sodium ion
neutralized ionomer(s). The result is a golf ball cover with
cover hardness and feel comparable to high performance golf balls
and yielding improved COR/initial velocity, improved impact
resilience, durability and cut resistance.
These and other objects and features of the present
invention will be apparent from a reading of the following
detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The cover composition of the present invention includes, in
its broadest form, a blend of ionomers, magnesium ion neutralized
ionomer(s), zinc ion neutralized ionomer(s) and sodium ion
neutralized ionomer(s).
For the purposes of the present invention, the term
"magnesium ionomer" shall be defined as a copolymer having 80-85%
by weight of an olefin, and 15-20% by weight of an a,
ethylenically unsaturated carboxylic acid, with 10-90% of the
carboxylic acid groups being neutralized with magnesium metal
ions. The magnesium ionomer shall have a melt index of 0.5 to
5.0 g/10 min, Shore "D" hardness of 60 or greater, and a flexural
modulus of 30,000-60,000 psi.
The term "zinc ionomer" shall be defined as a copolymer
having 80-85% by weight of an olefin, and 15-20% by weight of an
a, ~ ethylenically unsaturated carboxylic acid, with 10-90% of
the carboxylic acid groups being neutralized with zinc metal
ions. The zinc ionomer shall have a melt index of 0.5 to 5.0
g/10 min, Shore "D" hardness of 60 or greater, and a flexural
modulus of 30,000-60,000 psi.
Additionally, the term "sodium ionomer" shall be defined as
a copolymer having 80-85~ by weight of an.olefin, and 15-20% by
weight of an a, ~ ethylenically unsaturated carboxylic acid. with
10-90~ of the carboxylic acid groups being neutralized with
sodium metal ions. The sodium ionomer shall have a melt index
of 0.S to 5.0 g/10 min, Shore "D" hardness of 65 or greater, and
2l~9968
a flexural modulus of 40,000-80,000 psi.
For each of the above ionomers, the preferred olefin shall
be ethylene and the preferred carboxylic acids shall be acrylic
acid, methacrylic acids and combinations of acrylic and
methacrylic acids.
Suitable ionomer resins for use in the present invention are
listed below, along with the relevant physical properties. These
ionomers are listed for illustrative purposes.
Flexural Shore
Material Ion TYPe % Acid Modulus D
Surlyn AD8172 Mg 15 44,000 61
Surlyn SEP 503-2 Mg 20 50,000 66
Surlyn 8240 Na 20 75,000 75
Surlyn 9220 Zn 20 45,000 67
Accordingly, the present invention is a cover material for
a golf ball including 10-45% of one or more magnesium ionomers,
each of said magnesium ionomers having 80-85% by weight of
ethylene, and 15-20% by weight of a carboxylic acid, 10-90% of
which are neutralized with magnesium metal ions, having a melt
index of 0.5 to 5.0 g/10 min, Shore "D" of 60 or greater, and
flexural modulus of 30,000-60,000 psi;
10-50% of one or more zinc ionomers, each of said zinc
ionomers having 80-85% by weight of ethylene and 15-20% by weight
of a carboxylic acid, 10-90% of which are neutralized with zinc
metal ions, having a melt index of 0.5 to 5.0 g/10 min, Shore "D"
hardness of 60 or greater, and flexural modulus of 30,000-60,000
psi; and
30-80% of one or more sodium ionomers, each of said sodium
ionomers having 80-85% by weight of ethylene, and 15-20% by
weight of a carboxylic acid, 10-90% of which are neutralized with
sodium metal ions, having a melt index of 0.5 to 5.0 g/10 min,
Shore "D" hardness of 65 or greater, and a flexural modulus of
40,000-80,000 psi.
It may be desirable for the cover material of the present
invention to include a colorant. The colorant may be present in
the composition in an amount up to 5 parts per hundred polymer
(p.h.p.) of the composition. Typically, the colorant will
2I~9968
consist of titanium dioxide, ultramarine blue, ultramarine violet
and an ionomeric carrier. A suitable colorant is available from
AMERICHEM Inc. of Cuyahuga, Ohio.
The blends are made and produced into a golf ball cover by
processes known in the art for producing golf ball covers,
processes such as extrusion molding or injection molding. It is
within the skill of those in the field to produce a blend from
the components of the present invention.
Golf balls are typically designed and manufactured to yield
PGA Compression values of over 120 to attain initial velocity
that will approach 255 ft/sec. The preferred range of PGA
Compression, however, is 90 to 110, so as to obtain the benefit
of the desirable sensation during club and ball impact by the
player, that is, a soft feel. The present invention offers a
range of PGA Compression that will provide the desired soft feel,
and still maximize the initial velocity that is very important
in providing the maximum flight distance performances of the golf
ball.
Balls manufactured with covers of the material of the
present invention exhibit superior COR/initial velocity, softer
PGA Compression and Shore D Hardness, with excellent cold pound
properties. COR represents the coefficient of restitution and
is taken as a measure of the rebound velocity versus the forward
velocity. The test balls are launched by hitting or propelling
it at certain impact velocity from a club or blank shell driven
pneumatically. The ball velocity is measured immediately after
impact. Under current USGA standards, the ball must not exceed
255 ft/sec initial velocity. PGA Compression measures
deformation under a fixed static load of 200 lbs. Shore D =
Shore D hardness, ASTM 2240.
Golf balls produced according to the present invention will
have COR values ranging from 0.738-0.740, PGA Compression values
from 105-115 and Shore "D" hardness values from 68-70.
For purposes of the present invention, low temperature
durability and ambient temperature durability are tested with an
impact tester, as known in the art. Low temperature durability
was determined in a "cold pound testn, in which six (6) balls are
2lq9968
conditioned to -20CF for 24 hours and placed at the impact tester
to hit once. If the balls does not split or crack, it was
returned to the freezer and hit again after 24 hours. This cycle
was repeated for up to 10 days or 10 hits.
Ambient temperature durability was tested in an impact
durability test. Twelve (12) balls are conditioned to 72F for
24 hours and placed at the impact tester to hit continuously up
to 100 hits, which is a minimum requirement of the industry.
Golf balls produced according to the present invention exhibited
superior ambient temperature durability and low temperature
durability.
The present invention will be described by way of the
following examples, which are provided for illustration, but are
not to be considered as limiting.
Ion1 2 3 4
Surlyn 8240 Na33 40 40 50
Surlyn 9220 Zn33 50 30 10
Surlyn SEP 503-2B Mg33 10 30 40
Surlyn AD8172 Mg -- -- -- --
Ball ProPerties:
COR 0.738 0.739 0.739 0.739
PGA Compression 111 111 110 111
Shore "D" 69 70 69 70
Cold Pound Test 10+ 10+ 10+ 10+
Impact Durability 150+ 150+ 150+ 150+
Ion5 6 7 8
Surlyn 8240 Na80 60 30 100
Surlyn 9220 Zn10 20 35 --
Surlyn SEP 503-2B Mg10 20 -- --
Surlyn AD8172 Mg -- -- 35 --
Ball ProPerties:
COR 0.739 0.740 0.738 0.737
PGA Compression 112 111 106 114
Shore "D" 70 70 68 73
Cold Pound Test 10+ 10+ 10+
Impact Durability 150+ 150+ 150+ 28
21~9968
Ion 9 10 11 12
Surlyn 8240 Na -- --
Surlyn 9220 Zn 100 -- 50 --
Surlyn SEP 503-2B Mg -- 100 50 50
Surlyn AD8172 Mg -- -- -- --
Ball ProPerties:
COR 0.725 0.7260.728 0.736
PGA Compression 106 110 110 113
Shore "D" 69 69 68 70
Cold Pound Test 5 3 3 3
Impact Durability 120 122 110 110
Examples 1-7 shown in Table I represent different
embodiments of the present invention. The results of testing of
physical properties of all examples indicates that a cover made
with a blend of the three specified ionomers is superior to those
made in other ratios.
The golf balls of Examples 1-7 show superior cold pound and
impact durability testing properties to the remaining Examples
8-12, examples of golf balls having cover blends known in the
art. Additionally, a golf ball with a cover made according to
the present invention exhibits consistently higher COR, even with
lower PGA compression. Currently, in this field, it is expected
that COR will reduce once the PGA compression reduces.
Accordingly, the discovery with the present invention represents
a true breakthrough in the general trend previously known.
The golf balls of Examples 8-12 have covers of ionomer that
are known in the art. Examples 8 and 12 show suitable COR
properties to perform competitively, but lack the cold pound and
impact durability resistance required for an acceptable golf
ball. Examples 9-11 show cover materials that lack the COR to
perform competitively, as well as the cold pound properties
required of a high performance golf ball.
Additionally, golf balls utilizing cover materials as
described in the present invention have been tested to determine
their playability. A 20 player testing has shown that the golf
balls of Examples 1-7 provide a softer feel and a "click" during
club/ball impact, making it a much more desirable golf ball than
2l~9968
balls containing cover blends known in the art, and currently
used in the game.
In short, the compositions of the present invention produce
a cover for a golf ball that is cost effective to produce, and
yet yields the playability and flight performance qualities of
a high performance ball.
It will be appreciated that the instant specification and
claims are set forth by way of illustration and not limitation
and that various changes and modifications may be made without
departing from the spirit and scope of the present invention.
