U.S. patent application number 09/917539 was filed with the patent office on 2002-02-21 for low spin golf ball comprising a metal, ceramic, or composite mantle or inner layer.
This patent application is currently assigned to SPALDING SPORTS WORLDWIDE, INC.. Invention is credited to Nesbitt, R. Dennis, Sullivan, Michael J..
Application Number | 20020022537 09/917539 |
Document ID | / |
Family ID | 27574133 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022537 |
Kind Code |
A1 |
Nesbitt, R. Dennis ; et
al. |
February 21, 2002 |
Low spin golf ball comprising a metal, ceramic, or composite mantle
or inner layer
Abstract
The present invention is directed to a golf ball comprising a
soft core and a hard cover such that the golf ball, when struck
such as during play, exhibits a reduced spin rate. The golf ball
may comprise one or more mantle layers including one or more
metals, ceramic, or composite materials. The golf ball may also
comprise an optional polymeric spherical substrate disposed within
the interior of the ball. The golf balls according to the present
invention exhibit improved spin, feel, and acoustic properties. The
golf ball of the present invention may also have an enlarged
diameter which serves to further reduce spin rate. The resulting
golf ball exhibits properties of reduced spin without sacrificing
durability, playability and resilience.
Inventors: |
Nesbitt, R. Dennis;
(Westfield, 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.
Chicopee
MA
010121-0901
|
Family ID: |
27574133 |
Appl. No.: |
09/917539 |
Filed: |
July 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09917539 |
Jul 27, 2001 |
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09248860 |
Feb 11, 1999 |
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09248860 |
Feb 11, 1999 |
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08716016 |
Sep 19, 1996 |
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5820489 |
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08716016 |
Sep 19, 1996 |
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08255442 |
Jun 8, 1994 |
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08255442 |
Jun 8, 1994 |
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08054406 |
Apr 28, 1993 |
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5368304 |
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08255442 |
Jun 8, 1994 |
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09027482 |
Feb 20, 1998 |
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6142887 |
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08255442 |
Jun 8, 1994 |
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08714661 |
Sep 16, 1996 |
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60042120 |
Mar 28, 1997 |
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60042430 |
Mar 28, 1997 |
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Current U.S.
Class: |
473/378 ;
473/371; 473/373; 473/374 |
Current CPC
Class: |
A63B 37/00 20130101;
C08L 2205/02 20130101; C08L 23/025 20130101; A63B 37/0075 20130101;
A63B 43/00 20130101; C08L 23/025 20130101; A63B 37/0033 20130101;
C08L 2666/04 20130101; C08L 2666/04 20130101; A63B 37/0024
20130101; C08L 23/08 20130101; A63B 37/12 20130101; A63B 37/0034
20130101; A63B 37/0064 20130101; A63B 45/00 20130101; A63B 37/0003
20130101; A63B 2037/085 20130101; A63B 37/0031 20130101; A63B
37/0076 20130101; A63B 37/08 20130101; C08L 23/0876 20130101; A63B
37/0065 20130101; A63B 2209/08 20130101; C08L 23/08 20130101; A63B
37/0096 20130101 |
Class at
Publication: |
473/378 ;
473/371; 473/373; 473/374 |
International
Class: |
A63B 037/12; A63B
037/04; A63B 037/14; A63B 037/06 |
Claims
Having thus described the invention, we claim:
1. A low spin golf ball comprising: a core including a core
component and a spherical mantle encompassing said core component,
said mantle comprising (i) a polymeric material, and (ii) a
reinforcing material dispersed throughout said polymeric material,
said core having a Riehle compression of at least about 75; and a
polymeric outer cover disposed about said core, said polymeric
cover comprising a material selected from the group consisting of a
high acid ionomer, a low acid ionomer, an ionomer blend, a
non-ionomeric elastomer, a thermoset material, and combinations
thereof, said polymeric cover having a Shore D hardness of at least
about 65.
2. The golf ball of claim I wherein said polymeric material of said
mantle is selected from the group consisting of epoxy-based
materials, thermoset materials, nylon-based materials, styrene
materials, thermoplastic materials, and combinations thereof.
3. The golf ball of claim 2 wherein said thermoset material is
selected from the group consisting of a polyimide thermoset, a
silicone thermoset, a vinyl ester thermoset, a polyester thermoset,
a melamine thermoset, and combinations thereof.
4. The golf ball of claim 2 wherein said nylon-based material is
selected from the group consisting of nylon 6, nylon 6/10, nylon
6/6, nylon 11, and combinations thereof.
5. The golf ball of claim 2 wherein said styrene material is
selected from the group consisting of acrylonitrile-butadiene
styrene, polystyrene, styrene-acrylonitrile, styrene-maleic
anhydride, and combinations thereof.
6. The golf ball of claim 2 wherein said thermoplastic material is
selected from the group consisting of acetal copolymer,
polycarbonate, liquid crystal polymer, polyethylene, polypropylene,
polybutylene terephthalate, polyethylene terephthalate,
polyphenylene, polyaryl, polyether, and combinations thereof.
7. The golf ball of claim 1 wherein said reinforcing material is
selected from the group consisting of silicon carbide, glass,
carbon, boron carbide, aramid materials, cotton, flax, jute, hemp,
silk, and combinations thereof.
8. The golf ball of claim 1 wherein said mantle has a thickness
ranging from about 0.001 inch to about 0.100 inch.
9. The golf ball of claim 8 wherein said mantle has a thickness
ranging from about 0.010 inch to about 0.030 inch.
10. The golf ball of claim 1 wherein said cover comprises at least
one high acid ionomer resin comprising a copolymer of greater than
16% by weight of an alpha, beta-unsaturated carboxylic acid, and an
alpha olefin of which about 10 to about 90% of the carboxyl groups
of the copolymer are neutralized with a metal cation.
11. The golf ball of claim 10, wherein said cover is comprised of
at least one high acid ionomer resin comprising a copolymer of
about 17% to about 25% by weight of an alpha, beta-unsaturated
carboxylic acid, and an alpha olefin of which about 10 to about 90%
of the carboxyl groups of the copolymer are neutralized with a
metal cation.
12. The golf ball of claim 11, wherein said cover is comprised of
at least one high acid ionomer resin comprising from about 18.5% to
about 21.5% by weight of an alpha, beta-unsaturated carboxylic
acid, and an alpha olefin of which about 10 to about 90% of the
carboxyl groups of the copolymer are neutralized with a metal
cation.
13. The golf ball of claim 1, wherein the cover has a thickness
greater than 0.0675 inches.
14. The golf ball of claim 13, wherein the cover has a thickness
greater than 0.0675 inches to 0.130.
15. The golf ball of claim 1, wherein the golf ball has a diameter
of about 1.680 to 1.800 inches.
16. The golf ball of claim 15, wherein the golf ball has a diameter
of about 1.700-1.800 inches.
17. The golf ball of claim 16, wherein the golf ball has a diameter
of about 1.710-1.730 inches.
18. The golf ball claim 17, wherein the golf ball has a diameter of
about 1.717-1.720 inches.
19. A golf ball comprising: a core including a core component and a
vitreous mantle enclosing said core component, said core having a
Riehle compression of from about 75 to about 115; and a polymeric
outer cover disposed about said mantle, said cover having a Shore D
hardness of at least about 65.
20. The golf ball of claim 19 wherein said vitreous mantle
comprises a ceramic selected from the group consisting of silica,
soda lime, lead silicate, borosilicate, aluminoborosilicate,
aluminosilicate, and combinations thereof.
21. The golf ball of claim 19 wherein said vitreous mantle
comprises a reinforcing material dispersed within said mantle.
22. The golf ball of claim 21 wherein said reinforcing material is
selected from the group consisting of silicon carbide, glass,
carbon, boron carbide, aramid materials, cotton, flax, jute, hemp,
silk, and combinations thereof.
23. The golf ball of claim 19 wherein said polymeric outer cover
comprises a high acid ionomer of greater than about 16 weight
percent acid.
24. The golf ball of claim 19, wherein said core has a Riehle
compression of 80 to 90, and a diameter of about 1.540 to about
1.545 inches.
25. The golf ball of claim 19, wherein said golf ball has a
diameter of about 1.70 to about 1.80 inches.
26. The golf ball of claim 25, wherein said golf ball has a
diameter of about 1.710 to about 1.730 inches.
27. The golf ball of claim 26, wherein said golf ball has a
diameter of about 1.717 to about 1.720 inches.
28. A low spin golf ball comprising: a generally spherical core
having an interior core component, and a mantle layer disposed
about said core component, said mantle layer including at least one
metal, said core exhibiting a Riehle compression of from about 75
to about 115; and a polymeric outer cover disposed about said core,
said cover exhibiting a Shore D hardness of at least about 65.
29. The golf ball of claim 28 wherein said metal in said mantle is
selected from the group consisting of steel, titanium, chromium,
nickel, and alloy thereof.
30. The golf ball of claim 28 wherein said cover has a thickness
between about 0.0675 inches to about 0.130 inches.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 09/248,860 filed Feb. 11, 1999, which is a
continuation-in-part application of U.S. application Ser. No.
08/716,016 filed Sep. 19, 1996, which is a divisional of U.S.
application Ser. No. 08/255,442 filed Jun. 8, 1994, which is a
continuation of U.S. application Ser. No. 08/054,406 filed Apr. 28,
1993. This application is also a continuation-in-part application
of U.S. application Ser. No. 09/027,482 filed Feb. 20, 1998 which
claims priority from U.S. Provisional Application Serial No.
60/042,120 filed Mar. 27, 1997; and U.S. Provisional Application
60/042,430 filed Mar. 28, 1997; and is a continuation-in-part
application of U.S. application Ser. No. 08/714,661 filed Sep. 16,
1996.
FIELD OF THE INVENTION
[0002] The present invention relates to golf balls and, more
particularly, to improved golf balls having low spin rates. The
improvement in the golf balls results from a combination of a
relatively soft core, and a hard cover made from blends of one or
more specific hard, high stiffness ionomers. The combination of a
soft core and a hard cover leads to an improved golf ball having a
lower than anticipated spin rate while maintaining the resilience
and durability characteristics necessary for repetitive play.
[0003] In a particularly preferred embodiment, the present
invention relates to golf balls comprising one or more mantle
layers formed from a metal, ceramic, or a composite material. The
golf balls may comprise an optional polymeric outer cover and/or an
inner polymeric hollow sphere substrate.
[0004] In an additional embodiment of the invention, the spin rate
is further reduced by decreasing the weight of the soft core while
maintaining core size and by increasing the thickness of the cover.
The larger, less dense finished ball exhibits lower spin rates
after club impact than conventional balls.
BACKGROUND OF THE INVENTION
[0005] Spin rate is an important golf ball characteristic for both
the skilled and unskilled golfer. High spin rates allow for the
more skilled golfer, such as PGA professionals and low handicap
players, to maximize control of the golf ball. This is particularly
beneficial to the more skilled golfer when hitting an approach shot
to a green. The ability to intentionally produce "back spin",
thereby stopping the ball quickly on the green, and/or "side spin"
to draw or fade the ball, substantially improves the golfer's
control over the ball. Thus, the more skilled golfer generally
prefers a golf ball exhibiting high spin rate properties.
[0006] However, a high spin golf ball is not desirous by all
golfers, particularly high handicap players who cannot
intentionally control the spin of the ball. In this regard, less
skilled golfers, have, among others, two substantial obstacles to
improving their game: slicing and hooking. When a club head meets a
ball, an unintentional side spin is often imparted which sends the
ball off its intended course. The side spin reduces one's control
over the ball as well as the distance the ball will travel. As a
result, unwanted strokes are added to the game.
[0007] Consequently, while the more skilled golfer desires a high
spin golf ball, a more efficient ball for the less skilled player
is a golf ball that exhibits low spin properties. The low spin ball
reduces slicing and hooking and enhances roll distance for the
amateur golfer.
[0008] The present inventors have addressed the need for developing
a golf ball having a reduced spin rate after club impact, while at
the same time maintaining the durability, playability and
resiliency characteristics needed for repetitive use. The reduced
spin rate golf ball of the present invention meets the rules and
regulations established by the United States Golf Association
(U.S.G.A.).
[0009] Along these lines, the U.S.G.A. has set forth five (5)
specific regulations to which a golf ball must conform. The
U.S.G.A. rules require that a ball be no smaller than 1.680 inches
in diameter. However, notwithstanding this restriction, there is no
specific limitation as to the maximum permissible diameter of a
golf ball. As a result, a golf ball can be as large as desired so
long as it is larger than 1.680 inches in diameter and so long as
the other four (4) specific regulations are met.
[0010] The U.S.G.A. rules also require that balls weigh no more
than 1.620 ounces, and that their initial velocity may not exceed
250 feet per second with a maximum tolerance of 2%, or up to 255
ft./sec. Further, the U.S.G.A. rules state that a ball may not
travel a distance greater than 280 yards with a test tolerance of
6% when hit by the U.S.G.A. outdoor driving machine under specific
conditions.
[0011] It has been determined by the present inventors that the
combination of a relatively soft core (i.e. an overall core Riehle
compression of about 75 to 160) and a hard cover (i.e. Shore D
hardness of 65 or more) significantly reduces the overall spin rate
of the resulting golf ball. The inventors have also learned that an
increase in cover thickness, thereby increasing the overall
diameter of the resulting golf ball, further reduces spin rate.
[0012] Top-grade golf balls sold in the United States may be
generally classified as one of two types: two-piece or three-piece
balls. The two-piece ball, exemplified by the balls sold by
Spalding & Evenflo Companies, Inc. (the assignee of the present
invention through its wholly owned subsidiary, Lisco, Inc.) under
the trademark TOP-FLITE, consists of a solid polymeric core and a
separately formed outer cover. The so-called three-piece balls,
exemplified by the balls sold under the trademark TITLEIST by the
Acushnet Company, consist of a liquid (e.g., TITLEIST TOUR 384) or
solid (e.g., TITLEIST DT) center, elastomeric thread windings about
the center, and a cover.
[0013] Spalding's two-piece golf balls are produced by molding a
natural (balata) or synthetic (i.e. thermoplastic resin such as an
ionomer resin) polymeric cover composition around a preformed
polybutadiene (rubber) core. During the molding process, the
desired dimple pattern is molded into the cover material. In order
to reduce the number of coating steps involved in the finishing of
the golf balls, a color pigment or dye and, in many instances, an
optical brightener, are added directly to the generally "off white"
colored polymeric cover composition prior to molding By
incorporating the pigment and/or optical brightener in the cover
composition molded onto the golf ball core, this process eliminates
the need for a supplemental pigmented painting step in order to
produce a white or colored (notably orange, pink and yellow) golf
ball.
[0014] With respect to multi-layered golf balls, Spalding is the
leading manufacturer of two-piece golf balls in the world. Spalding
manufactures over sixty (60) different types of two-piece balls
which vary distinctly in such properties as playability (i.e. spin
rate, compression, feel, etc.), travel distance (initial velocity,
C.O.R., etc.), durability (impact, cut and weather resistance) and
appearance (i.e. whiteness, reflectance, yellowness, etc.)
depending upon the ball's core, cover and coating materials, as
well as the ball's surface configuration (i.e. dimple pattern).
Consequently, Spalding's two-piece golf balls offer both the
amateur and professional golfer a variety of performance
characteristics to suit an individual's game.
[0015] In regard to the specific components of a golf ball,
although the nature of the cover can, in certain instances, make a
significant contribution to the overall feel, spin (control),
coefficient of restitution (C.O.R.) and initial velocity of a ball
(see, for example, U.S. Pat. No. 3,819,768 to Molitor), the initial
velocity of two-piece and three-piece balls is determined mainly by
the coefficient of restitution of the core. The coefficient of
restitution of the core of wound (i.e. three-piece) balls can be
controlled within limits by regulating the winding tension and the
thread and center composition. With respect to two-piece balls, the
coefficient of restitution of the core is a function of the
properties of the elastomer composition from which it is made. The
cover component of a golf ball is particularly influential in
affecting the compression (feel), spin rates (control), distance
(C.O.R.), and durability (i.e. impact resistance, etc.) of the
resulting ball. Various cover compositions have been developed by
Spalding and others in order to optimize the desired properties of
the resulting golf balls.
[0016] Over the last twenty (20) years, improvements in cover and
core material formulations and changes in dimple patterns have more
or less continually improved golf ball distance. Top-grade golf
balls, however, must meet several other important design criteria.
To successfully compete in today's golf ball market, a golf ball
should be resistant to cutting and must be finished well; it should
hold a line in putting and should have good click and feel. In
addition, the ball should exhibit spin and control properties
dictated by the skill and experience of the end user. Prior
artisans have attempted to incorporate metal layers or metal filler
particles in golf balls to alter the physical characteristics and
performance of the balls. For example, U.S. Pat. No. 3,031,194 to
Strayer is directed to the use of a spherical inner metal layer
that is bonded or otherwise adhered to a resilient inner
constituent within the ball. The ball utilizes a liquid filled
core. U.S. Pat. No. 4,863,167 to Matsuki, et al. describes golf
balls containing a gravity filler which may be formed from one or
more metals disposed within a solid rubber-based core. U.S. Pat.
Nos. 4,886,275 and 4,995,613, both to Walker, disclose golf balls
having a dense metal-containing core. U.S. Pat. No. 4,943,055 to
Corley is directed to a weighted warmup ball having a metal
center.
[0017] Prior artisans have also described golf balls having one or
more interior layers formed from a metal, and which feature a
hollow center. Davis disclosed a golf ball comprising a spherical
steel shell having a hollow air-filled center in U.S. Pat. No.
697,816. Kempshall received numerous patents directed to golf balls
having metal inner layers and hollow interiors, such as Pat. Nos.
704,748; 704,838; 713,772; and 739,753. In U.S. Pat. Nos. 1,182,604
and 1,182,605, Wadsworth described golf balls utilizing concentric
spherical shells formed from tempered steel. U.S. Pat. No.
1,568,514 to Lewis describes several embodiments for a golf ball,
one of which utilizes multiple steel shells disposed within the
ball, and which provide a hollow center for the ball.
[0018] As to the incorporation of glass or vitreous materials in
golf balls, U.S. Pat. No. 985,741 to Harvey discloses the use of a
glass shell. Other artisans described incorporating glass
microspheres within a golf ball such as in U.S. Pat. No. 4,085,937
to Schenk.
[0019] In contrast, the use of polymeric materials in intermediate
layers within a golf ball, is more popular than, for instance, the
use of glass or other vitreous material. Kempshall disclosed the
use of an interior coating layer of plastic in U.S. Pat. Nos.
696,887 and 701,741. Kempshall further described incorporating a
fabric layer in conjunction with a plastic layer in U.S. Pat. Nos.
696,891 and 700,656. Numerous subsequent approaches were patented
in which a plastic inner layer was incorporated in a golf ball. A
thermoplastic outer core layer was disclosed in U.S. Pat. No.
3,534,965 to Harrison. Inner synthetic polymeric layers are noted
in U.S. Pat. No. 4,431,193 to Nesbitt. An inner layer of
thermoplastic material surrounding a core is described in U.S. Pat.
No. 4,919,434 to Saito. An intermediate layer of an amide block
polyether thermoplastic is disclosed in U.S. Pat. No. 5,253,871 to
Viellaz. Golf balls with thermoplastic interior shell layers are
described in U.S. Pat. No. 5,480,155 to Molitor, et al. Although
satisfactory in many respects, these patents are not specifically
directed to the use of reinforcement fibers or particles dispersed
within a polymeric inner layer.
[0020] Prior artisans have attempted to incorporate various
particles and filler materials into golf ball cores and
intermediate layers. U.S. Pat. No. 3,218,075 to Shakespeare
discloses a core of fiberglass particles dispersed within an epoxy
matrix. Similarly, U.S. Pat. No. 3,671,477 to Nesbitt discloses an
epoxy-based composition containing a wide array of fillers. A
rubber intermediate layer containing various metal fillers is noted
in U.S. Pat. No. 4,863,167 to Matsuki, et al. Similarly, a rubber
inner layer having filler materials is noted in U.S. Pat. No.
5,048,838 to Chikaraishi, et al. More recently, a golf ball with an
inner layer of reinforced carbon graphite is disclosed in U.S. Pat.
No. 5,273,286 to Sun.
[0021] In view of the ever increasing demands of the current golf
industry, there exists a need for yet another improved golf ball
design and construction. Specifically, there is a need for a low
spin golf ball that exhibits a high initial velocity or coefficient
of restitution (COR), may be driven relatively long distances in
regulation play, and which may be readily and inexpensively
manufactured.
[0022] As previously noted, in an alternative embodiment, the spin
rate of the ball is further reduced by increasing the thickness of
the cover and/or decreasing the weight and softness of the core. By
increasing the cover thickness and/or the overall diameter of the
resulting molded golf ball, enhanced reduction in spin rate is
observed.
[0023] With respect to the increased size of the ball, over the
years golf ball manufacturers have generally produced golf balls at
or around the minimum size and maximum weight specifications set
forth by the U.S.G.A. There have, however, been exceptions,
particularly in connection with the manufacture of golf balls for
teaching aids. For example, oversized, overweight (and thus
unauthorized) golf balls have been on sale for use as golf teaching
aids (see U.S. Pat. No. 3,201,384 to Barber).
[0024] Oversized golf balls are also disclosed in New Zealand
Patent No. 192,618 dated Jan. 1, 1980, issued to a predecessor of
the present assignee. This patent teaches an oversize golf ball
having a diameter between 1.700 and 1.730 inches and an oversized
core of resilient material (i.e. about 1.585 to 1.595 inches in
diameter) so as to increase the coefficient of restitution.
Additionally, the patent discloses that the ball should include a
cover having a thickness less than the cover thickness of
conventional balls (i.e. a cover thickness of about 0.050 inches as
opposed to 0.090 inches for conventional two-piece balls).
[0025] In addition, it is also noted that golf balls made by
Spalding in 1915 were of a diameter ranging from 1.630 inches to
1.710 inches. As the diameter of the ball increased, the weight of
the ball also increased. These balls were comprised of covers made
up of balata/gutta percha and cores made from solid rubber or
liquid sacs and wound with elastic thread.
[0026] Golf balls known as the LYNX JUMBO were also commercially
available by Lynx in October, 1979. These balls had a diameter of
1.76 to 1.80 inches. The LYNX JUMBO balls met with little or no
commercial success. The balls consisted of a core comprised of
wound core and a cover comprised of natural or synthetic
balata.
[0027] However, notwithstanding the enhanced diameters of these
prior golf balls, none of these balls produced the enhanced spin
reduction characteristics and overall playability, distance and
durability properties of the present invention and/or fall within
the regulations set forth by the U.S.G.A. An object of the present
invention is to produce a U.S.G.A. regulation golf ball having
improved low spin properties while maintaining the resilience and
durability characteristics necessary for repetitive play.
[0028] These and other objects and features of the invention will
be apparent from the following summary and description of the
invention and from the claims.
SUMMARY OF THE INVENTION
[0029] The present invention is directed to improved golf balls
having a low rate of spin upon club impact. The golf balls comprise
a soft core and a hard cover. The hard cover may be sized to be
larger than conventional diameters. The low spin rate enables the
ball to travel a greater distance. In addition, the low spin rate
provides the less skilled golfer with more control. This is because
the low spin rate decreases undesirable side spin which leads to
slicing and hooking. The combination of a hard cover and a soft
core provides for a ball having a lower than anticipated spin rate
while maintaining high resilience and good durability.
[0030] In a first aspect, the present invention provides a low spin
golf ball comprising a core that includes a core component and a
spherical mantle encompassing the core component. The mantle
comprises a polymeric material and a reinforcing material dispersed
throughout the polymeric material. The core exhibits a Riehle
compression of at least about 75. The golf ball further comprises a
polymeric outer cover disposed about the core. The cover may be
formed from an array of different materials, but exhibits a Shore D
hardness of at least about 65.
[0031] In another aspect, the present invention provides a golf
ball comprising a core including a core component and a vitrous
mantle enclosing the core component. The core has a Riehle
compression of from about 75 to about 115. The low spin golf ball
further comprises a polymeric outer cover disposed about the
mantle. The cover has a Shore D hardness of at least about 65.
[0032] In another aspect, the present invention provides a low spin
golf ball comprising a generally spherical core having an interior
core component and a mantle layer disposed around the core
component. The mantle layer is formed from a metal and the
resulting core exhibits a Riehle compression of from about 75 to
about 115. The golf ball further comprises a polymeric outer cover
disposed about the core The cover exhibits a Shore D hardness of at
least about 65.
[0033] Through the use of the softer cores and the hard cover,
overall finished balls of the invention exhibit significantly lower
spin rates than conventional balls of equal size and weight.
Further, reduction in spin is also produced by increasing the
thickness of the cover and by decreasing the weight of the softened
core.
[0034] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a partial cross-sectional view of a first
preferred embodiment low spin golf ball in accordance with the
present invention, comprising a polymeric outer cover, one or more
mantle layers, an optional polymeric hollow sphere substrate, and
core material;
[0036] FIG. 2 is a partial cross-sectional view of a second
preferred embodiment low spin golf ball in accordance with the
present invention, the golf ball comprising a polymeric outer
cover, one or more mantle layers, and a core material;
[0037] FIG. 3 is a partial cross-sectional view of a third
preferred embodiment low spin golf ball in accordance with the
present invention, the golf ball comprising one or more mantle
layers and a core material;
[0038] FIG. 4 is a partial cross-sectional view of a fourth
preferred embodiment low spin golf ball in accordance with the
present invention, the golf ball comprising one or more mantle
layers, an optional polymeric hollow sphere substrate, and a core
material;
[0039] FIG. 5 is a partial cross-sectional view of a fifth
preferred embodiment low spin golf ball in accordance with the
present invention, the golf ball comprising a polymeric outer
cover, a first mantle layer, a second mantle layer, and a core
material; and
[0040] FIG. 6 is a partial cross-sectional view of a sixth
preferred embodiment low spin golf ball in accordance with the
present invention, the golf ball comprising a polymeric outer
cover, a first and a second mantle layer in an alternate
arrangement as compared to the embodiment illustrated in FIG. 5,
and a core material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] The present invention relates to the development of a golf
ball having a low spin rate as a result of combining a relatively
soft core and a hard cover. The present invention low spin golf
balls feature a relatively soft interior core or core component.
That is, the core and any interior mantle layers, collectively,
exhibit a Riehle compression of at least about 75 and preferably
from about 75 to about 160. Most preferably, the Riehle compression
of the core is from about 80 to about 90. The present invention low
spin golf balls also feature a relatively hard cover. That is, the
cover exhibits a Shore D hardness of at least about 65. A lower
spin rate after club impact contributes to straighter shots when
the ball is mis-hit, greater efficiency in flight, and a lesser
degree of energy loss on impact with the ground, adding increased
roll or distance.
[0042] In addition, by increasing the diameter of the overall ball
of the present invention beyond the U.S.G.A. minimum of 1.680
inches, the spin rate is still further decreased. In this
embodiment of the invention, the ball, even though of larger
diameter, uses substantially the same size core as a standard golf
ball, the difference in size is provided by the additional
thickness in the cover of the ball. This larger, low spin ball
produces even greater control and flight efficiency than the
standard size ball embodiment of the present invention.
[0043] In all the preferred embodiments noted herein, the golf
balls preferably utilize a solid core or core component. It will be
understood that the low spin golf balls may instead feature a
hollow interior or hollow core. In addition, all preferred
embodiment golf balls comprise one or more mantle layers that
comprise one or more metals, ceramics, or composite materials.
Details of the materials, configuration, and construction of each
component in the preferred embodiment golf balls are set forth
below.
[0044] FIG. 1 illustrates a first preferred embodiment low spin
golf ball 100 in accordance with the present invention. It will be
understood that the referenced drawings are not necessarily to
scale. The first preferred embodiment golf ball 100 comprises an
outermost polymeric outer cover 10, one or more mantle layers 20,
an innermost polymeric hollow sphere substrate 30 and a core
material 40. the golf ball 100 provides a plurality of dimples 104
defined along an outer surface 102 of the golf ball 100.
[0045] FIG. 2 illustrates a second preferred embodiment low spin
golf ball 200 in accordance with the present invention. The golf
ball 200 comprises an outermost polymeric outer cover 10 and one or
more mantle layers 20 and a core material 40. The second preferred
embodiment golf ball 200 provides a plurality of dimples 204
defined along the outer surface 202 of the ball.
[0046] FIG. 3 illustrates a third preferred embodiment low spin
golf ball 300 in accordance with the present invention. The golf
ball 300 comprises one or more mantle layers 20 and a core material
40. The golf ball 300 provides a plurality of dimples 304 defined
along the outer surface 302 of the golf ball 300.
[0047] FIG. 4 illustrates a fourth preferred embodiment low spin
golf ball 400 in accordance with the present invention. The golf
ball 400 comprises one or more mantle layers 20, an optional
polymeric hollow sphere substrate 30, and a core material 40. The
golf ball 400 provides a plurality of dimples 404 defined along the
outer surface 402 of the golf ball 400.
[0048] FIG. 5 illustrates a fifth preferred embodiment low spin
golf ball 500 in accordance with the present invention. The golf
ball 500 comprises one or more mantle layers 20, one or more mantle
layers 50 of a material different than that in the mantle layers
20, a cover 10, and a core material 40. The golf ball 500 has
corresponding dimples as illustrated in FIGS. 14.
[0049] FIG. 6 illustrates a sixth preferred embodiment low spin
golf ball 600 in accordance with the present invention. The golf
ball 600 is similar to the golf ball 500, however, the mantle
layers 20 and 50 are reversed.
[0050] In all the foregoing noted preferred embodiments, i.e. golf
balls 100, 200, 300, 400, 500, and 600 the golf balls utilize a
core or core component, such as core material 40. It will be
understood that all preferred embodiment golf balls may instead
feature a hollow interior or hollow core. In addition, all
preferred embodiment golf balls comprise one or more mantle layers,
such as 20 and 50, that comprise one or more metals, ceramics, or
composite materials. And, it will be understood that all covers
such as cover 10, may be of a single or a multiple layer
construction. Details of the materials, configuration, and
construction of each component in the preferred embodiment golf
balls are set forth below.
[0051] Riehle compression is a measurement of the deformation in
thousandths of inches under a fixed static load of 200 pounds (a
Riehle compression of 47 corresponds to a deflection under load of
0.047 inches).
[0052] PGA compression is determined by a force applied to a spring
(i.e. 80 PGA=80 Riehle; 90 PGA=70 Riehle; and 100 PGA=60 Riehle)
manufactured by Atti Engineering, Union City, N.J.
[0053] Coefficient of restitution (C.O.R.) is measured by firing
the resulting golf ball in an air cannon at a velocity of 125 feet
per second against a steel plate which is positioned 12 feet from
the muzzle of the cannon. The rebound velocity is then measured.
The rebound velocity is divided by the forward velocity to give the
coefficient of restitution.
[0054] Shore D hardness is measured in accordance with ASTM Test
D-2240.
Core
[0055] In one aspect, the core used in the present invention golf
ball is a specially produced softened polybutadiene elastomeric
solid core having a conventional diameter of about 1.540 to 1.545
inches. The core is produced from a composition comprising a base
elastomer selected from polybutadiene and mixtures of polybutadiene
with other elastomers, at least one metallic salt of an unsaturated
carboxylic acid (a co-crosslinking agent), and free radical
initiator (a co-crosslinking agent). In addition, a suitable and
compatible modifying ingredient including, but not limited to metal
activators, fatty acids, fillers, polypropylene powder and other
additives may be included.
[0056] Of particular concern, only a limited amount of the metallic
salt of an unsaturated carboxylic acid is included in the core
compositions in order to produce the degree of core softness and
weight desired. In this regard, it is understood that when a larger
overall ball is desired, the composition of the core is adjusted so
that the molded finished ball falls within the weight parameters
set forth by the U.S.G.A. Since the finished golf balls must still
meet the U.S.G.A. weight limitation of 1.620 ounces, the core
component of the larger and thicker covered balls are designed to
be not only softer, but also lighter in weight.
[0057] In such circumstances, the specific gravity of the core is
less than that of a standard core since the larger ball must weigh
the same as a standard ball. The core generally weighs about 36 to
37 grams for a standard sized finished ball and about 33 to 34
grams for an oversized finished ball.
[0058] The core composition produces a softer molded core which
still maintains the resilience (C.O.R.), compression (hardness) and
durability characteristics required. The overall core has a PGA
compression of about 0 to 85, and preferably in the range of about
10 to about 70. Its Riehle compression is about 75 or more,
preferably in the range of about 75 to about 160, and the
resilience of the core is about 0.760 to 0.780.
[0059] The specially produced core compositions and resulting
molded cores of the present invention are manufactured using
relatively conventional techniques. In this regard, the core
compositions of the invention may be based on polybutadiene, and
mixtures of polybutadiene with other elastomers. It is preferred
that the base elastomer have a relatively high molecular weight.
The broad range for the molecular weight of suitable base
elastomers is from about 50,000 to about 500,000. A more preferred
range for the molecular weight of the base elastomer is from about
100,000 to about 500,000. As a base elastomer for the core
composition, cis-polybutadiene is preferably employed, or a blend
of cis-polybutadiene with other elastomers may also be utilized.
Most preferably, cis-polybutadiene having a weight-average
molecular weight of from about 100,000 to about 500,000 is
employed. Along this line, it has been found that the high
cispolybutadiene manufactured and sold by Shell Chemical Co,
Houston, Tex., under the tradename Cariflex BR-1220, and the
polyisoprene available from Muehistein, H & Co., Greenwich,
Conn. under the designation "SKI 35" are particularly well
suited.
[0060] The unsaturated carboxylic acid component of the core
composition (a co-crosslinking agent) is the reaction product of
the selected carboxylic acid or acids and an oxide or carbonate of
a metal such as zinc, magnesium, barium, calcium, lithium, sodium,
potassium, cadmium, lead, tin, and the like. Preferably, the oxides
of polyvalent metals such as zinc, magnesium and cadmium are used,
and most preferably, the oxide is zinc oxide.
[0061] Exemplary of the unsaturated carboxylic acids which find
utility in the present core compositions are acrylic acid,
methacrylic acid, itaconic acid, crotonic acid, sorbic acid, and
the like, and mixtures thereof. Preferably, the acid component is
either acrylic or methacrylic acid. Usually, from about 15 to about
25, and preferably from about 17 to about 21 parts by weight of the
carboxylic acid salt, such as zinc diacrylate, is included in the
core composition. The unsaturated carboxylic acids and metal salts
thereof are generally soluble in the elastomeric base, or are
readily dispersible.
[0062] The free radical initiator included in the core composition
is any known polymerization initiator (a co-crosslinking agent)
which decomposes during the cure cycle. The term "free radical
initiator" as used herein refers to a chemical which, when added to
a mixture of the elastomeric blend and a metal salt of an
unsaturated, carboxylic acid, promotes crosslinking of the
elastomers by the metal salt of the unsaturated carboxylic acid.
The amount of the selected initiator present is dictated only by
the requirements of catalytic activity as a polymerization
initiator. Suitable initiators include peroxides, persulfates, azo
compounds and hydrazides. Peroxides which are readily commercially
available are conveniently used in the present invention, generally
in amounts of from about 0.1 to about 10.0 and preferably in
amounts of from about 0.3 to about 3.0 parts by weight per each 100
parts of elastomer.
[0063] Exemplary of suitable peroxides for the purposes of the
present invention are dicumyl peroxide, n-butyl 4,4'-bis
(butylperoxy) valerate, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl
cyclohexane, di-t-butyl peroxide and 2,5-di-(t-butylperoxy)-2,5
dimethyl hexane and the like, as well as mixtures thereof. It will
be understood that the total amount of initiators used will vary
depending on the specific end product desired and the particular
initiators employed.
[0064] Examples of such commercially available peroxides are
Luperco 230 or 231 XL sold by Atochem, Lucidol Division, Buffalo,
N.Y., and Trigonox 17/40 or 29/40 sold by Akzo Chemie America,
Chicago, Ill. In this regard Luperco 230 XL and Trigonox 17/40 are
comprised of n-butyl 4,4-bis (butylperoxy) valerate; and, Luperco
231 XL and Trigonox 29/40 are comprised of
1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane. The one hour
half life of Luperco 231 XL and Trigonox 29/40 is about 112.degree.
C., and the one hour half life of Luperco 230 XL and Trigonox 17/40
is about 129.degree. C.
[0065] The core compositions of the present invention may
additionally contain any other suitable and compatible modifying
ingredients including, but not limited to, metal oxides, fatty
acids, and diisocyanates and polypropylene powder resin. For
example, Papi 94, a polymeric diisocyanate, commonly available from
Dow Chemical Co., Midland, Mich., is an optional component in the
rubber compositions. It can range from about 0 to 5 parts by weight
per 100 parts by weight rubber (phr) component, and acts as a
moisture scavenger. In addition, it has been found that the
addition of a polypropylene powder resin results in a core which is
too hard (i.e. exhibits low compression) and thus allows for a
reduction in the amount of crosslinking agent utilized to soften
the core to a normal or below normal compression.
[0066] Furthermore, because polypropylene powder resin can be added
to the core composition without an increase in weight of the molded
core upon curing, the addition of the polypropylene powder allows
for the addition of higher specific gravity fillers, such as
mineral fillers. Since the crosslinking agents utilized in the
polybutadiene core compositions are expensive and/or the higher
specific gravity fillers are relatively inexpensive, the addition
of the polypropylene powder resin substantially lowers the cost of
the golf ball cores while maintaining, or lowering, weight and
compression.
[0067] The polypropylene (C.sub.3H.sub.5) powder suitable for use
in the present invention has a specific gravity of about 0.90
g/cm.sup.3, a melt flow rate of about 4 to about 12 and a particle
size distribution of greater than 99% through a 20 mesh screen.
Examples of such polypropylene powder resins include those sold by
the Amoco Chemical Co., Chicago, Ill., under the designations "6400
P", "7000 P" and "7200 P". Generally, from 0 to about 25 parts by
weight polypropylene powder per each 100 parts of elastomer are
included in the present invention.
[0068] Various activators may also be included in the compositions
of the present invention. For example, zinc oxide and/or magnesium
oxide are activators for the polybutadiene. The activator can range
from about 2 to about 30 parts by weight per 100 parts by weight of
the rubber (phr) component.
[0069] Moreover, filler-reinforcement agents may be added to the
core composition of the present invention. Since the specific
gravity of polypropylene powder is very low, and when compounded,
the polypropylene powder produces a lighter molded core, when
polypropylene is incorporated in the core compositions, relatively
large amounts of higher gravity fillers may be added so long as the
specific core weight limitations are met. Additional benefits may
be obtained by the incorporation of relatively large amounts of
higher specific gravity, inexpensive mineral fillers such as
calcium carbonate. Such fillers as are incorporated into the core
compositions should be in finely divided form, as for example, in a
size generally less than about 30 mesh and preferably less than
about 100 mesh U.S. standard size. The amount of additional filler
included in the core composition is primarily dictated by weight
restrictions and preferably is included in amounts of from about 10
to about 100 parts by weight per 100 parts rubber.
[0070] The preferred fillers are relatively inexpensive and heavy
and serve to lower the cost of the ball and to increase the weight
of the ball to closely approach the U.S.G.A. weight limit of 1.620
ounces. However, if thicker cover compositions are to be applied to
the core to produce larger than normal (i.e. greater than 1.680
inches in diameter) balls, use of such fillers and modifying agents
will be limited in order to meet the U.S.G.A. maximum weight
limitations of 1.620 ounces. Exemplary fillers include mineral
fillers such as limestone, silica, micabarytes, calcium carbonate,
or clays. Limestone is ground calcium/magnesium carbonate and is
used because it is an inexpensive, heavy filler.
[0071] As indicated, ground flash filler may be incorporated and is
preferably 20 mesh ground up center stock from the excess flash
from compression molding. The use of such filler lowers the cost
and may increase the hardness of the ball.
[0072] Fatty acids or metallic salts of fatty acids may also be
included in the core compositions, functioning to improve
moldability and processing. Generally, free fatty acids having from
about 10 to about 40 carbon atoms, and preferably having from about
15 to about 20 carbon atoms, are used. Exemplary of suitable fatty
acids are stearic acid and linoleic acids, as well as mixtures
thereof. Exemplary of suitable metallic salts of fatty acids
include zinc stearate. When included in the core compositions, the
fatty acid component is present in amounts of from about 1 to about
25, preferably in amounts from about 2 to about 15 parts by weight
based on 100 parts rubber (elastomer).
[0073] It is preferred that the core compositions include stearic
acid as the fatty acid adjunct in an amount of from about 2 to
about 5 parts by weight per 100 parts of rubber.
[0074] Diisocyanates may also be optionally included in the core
compositions when utilized, the diioscyanates are included in
amounts of from about 0.2 to about 5.0 parts by weight based on 100
parts rubber. Exemplary of suitable diisocyanates is
4,4'-diphenylmethane diisocyanate and other polyfunctional
isocyanates know to the art.
[0075] Furthermore, the dialkyl tin difatty acids set forth in U.S.
Pat. No. 4,844,471, the dispersing agents disclosed in U.S. Pat.
No. 4,838,556, and the dithiocarbamates set forth in U.S. Pat. No.
4,852,884 may also be incorporated into the polybutadiene
compositions of the present invention. The specific types and
amounts of such additives are set forth in the above identified
patents, which are incorporated herein by reference.
[0076] The core compositions of the invention are generally
comprised of 100 parts by weight of a base elastomer (or rubber)
selected from polybutadiene and mixtures of polybutadiene with
other elastomers, 15 to 25 parts by weight of at least one metallic
salt of an unsaturated carboxylic acid, and 1 to 10 parts by weight
of a free radical initiator.
[0077] As indicated above, additional suitable and compatible
modifying agents such as particulate polypropylene resin, fatty
acids, and secondary additives such as Pecan shell flour, ground
flash (i.e. grindings from previously manufactured cores of
substantially identical construction), barium sulfate, zinc oxide,
etc. may be added to the core compositions to adjust the weight of
the ball as necessary in order to have the finished molded ball
(core, cover and coatings) to closely approach the U.S.G.A. weight
limit of 1.620 ounces.
[0078] In producing golf ball cores utilizing the present
compositions, the ingredients may be intimately mixed using, for
example, two roll mills or a Banbury mixer until the composition 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
blending sequence is as follows.
[0079] The elastomer, polypropylene powder resin (if desired),
fillers, zinc salt, metal oxide, fatty acid, and the metallic
dithiocarbamate (if desired), surfactant (if desired), and tin
difatty acid (if desired), are blended for about 7 minutes in an
internal mixer such as a Banbury mixer. As a result of shear during
mixing, the temperature rises to about 200.degree. F. The initiator
and diisocyanate are then added and the mixing continued until the
temperature reaches about 220.degree. F. whereupon the batch is
discharged onto a two roll mill, mixed for about one minute and
sheeted out.
[0080] The sheet is rolled into a "pig" and then placed in a
Barwell preformer and slugs are produced. The slugs are then
subjected to compression molding at about 320.degree. F. for about
14 minutes. After molding, the molded cores are cooled, the cooling
effected at room temperature for about 4 hours or in cold water for
about one hour. The molded cores are subjected to a centerless
grinding operation whereby a thin layer of the molded core is
removed to produce a round core having a diameter of 1.540 to 1.545
inches. Alternatively, the cores are used in the as-molded state
with no grinding needed to achieve roundness.
[0081] The mixing is desirably conducted in such a manner that the
composition does not reach incipient polymerization temperatures
during the blending of the various components.
[0082] Usually the curable component of the composition will be
cured by heating the composition at elevated temperatures on the
order of from about 275.degree. F. to about 350.degree. F.,
preferably and usually from about 290.degree. F. to about
325.degree. F., with molding of the composition effected
simultaneously with the curing thereof. The composition can be
formed into a core structure by any one of a variety of molding
techniques, e.g. injection, compression, or transfer molding. When
the composition is cured by heating, the time required for heating
will normally be short, generally from about 10 to about 20
minutes, depending upon the particular curing agent used. Those of
ordinary skill in the art relating to free radical curing agents
for polymers are conversant with adjustments of cure times and
temperatures required to effect optimum results with any specific
free radical agent.
[0083] After molding, the core is removed from the mold and the
surface thereof, preferably treated to facilitate adhesion thereof
to the covering materials. Surface treatment can be effected by any
of the several techniques known in the art, such as corona
discharge, ozone treatment, sand blasting, and the like.
Preferably, surface treatment is effected by grinding with an
abrasive wheel.
[0084] The core is converted into a golf ball by providing at least
one layer of covering material thereon, ranging in thickness from
about 0.070 to about 0.130 inches and preferably from about 0.0675
to about 0.1275 inches.
[0085] In another aspect, the present invention golf ball may
utilize a wound core as known in the art. Descriptions of wound
cores and their manufacture are found in the following U.S. Pat.
Nos.: 5,792,008; 5,755,628; 5,685,785; 5,630,562; 5,609,532;
5,007,594; 4,846,910; and 4,272,079; all of which are herein
incorporated by reference.
Mantle
[0086] The preferred embodiment low spin golf balls of the present
invention comprise one or more mantle layers disposed inwardly and
proximate to, and preferably adjacent to, the outer cover layer
which is described in greater detail herein. The mantle layer(s)
may be formed from metal, ceramic, or composite materials.
Regarding metals, a wide array of metals can be used in the mantle
layers or shells as described herein. Table 1, set forth below,
lists suitable metals for use in the preferred embodiment golf
balls.
1TABLE 1 Metals for Use in Mantle Layer(s) Young's Bulk Shear
Poisson's modulus, modulus, modulus, ratio, Metal E, 10.sup.6 psi
K, 10.sup.6 psi G, 10.sup.6 psi v Aluminum 102 109 380 0345 Brass,
30 Zn 146 16.2 541 0.350 Chromium 405 232 167 0.210 Copper 188 200
701 0.343 Iron (soft) 307 246 118 0.293 (cast) 221 15.9 8.7 0.27
Lead 234 664 0.811 0.44 Magnesium 648 516 251 0.291 Molybdenum 471
379 182 0293 Nickel (soft) 289 257 11.0 0312 (hard) 318 272 12.2
0306 Nickel-silver, 192 191 497 0333 55Cu-18Ni-27Zn Niobium 152 247
544 0397 Silver 120 150 439 0367 Steel, mild 307 245 119 0291
Steel, 0.75 C 305 245 11.8 0.293 Steel, 0 75 C, hardened 292 239
11.3 0296 Steel, tool 307 240 11.9 0.287 Steel, tool, hardened 295
240 11.4 0.295 Steel, stainless, 312 241 122 0.283 2Ni-18Cr
Tantalum 269 28.5 10.0 0.342 Tin 724 8.44 2.67 0.357 Titanium 174
15.7 6.61 0.361 Titanium/Nickel alloy Tungsten 596 451 233 0.280
Vanadium 185 22.9 6.77 0.365 Zinc 152 101 608 0.249
[0087] Preferably, the metals used in the one or more mantle layers
are steel, titanium, chromium, nickel, or alloys thereof.
Generally, it is preferred that the metal selected for use in the
mantle be relatively stiff, hard, dense, and have a relatively high
modulus of elasticity.
[0088] The thickness of the metal mantle layer depends upon several
factors, such as the density of the metals used in that layer, or
if a plurality of metal mantle layers are used, the densities of
those metals in other layers within the mantle. Typically, the
thickness of the mantle ranges from about 0.001 inches to about
0.050 inches. The preferred thickness for the mantle is from about
0.005 inches to about 0.050 inches. The most preferred range is
from about 0.005 inches to about 0.010 inches. It is preferred that
the thickness of the mantle be uniform and constant at all points
across the mantle.
[0089] As noted, the thickness of the metal mantle depends upon the
density of the metal(s) utilized in the one or more mantle layers.
Table 2, set forth below, lists typical densities for the preferred
metals for use in the mantle.
2 TABLE 2 Metal Density (grams per cubic centimeter) Chromium 6.46
Nickel 7.90 Steel (approximate) 7.70 Titanium 4.13
[0090] There are at least two approaches in forming a metal mantle
utilized in the preferred embodiment golf balls. In a first
embodiment, two metal half shells are stamped from metal sheet
stock. The two half shells are then arc welded together and heat
treated to stress relieve. It is preferred to heat treat the
resulting assembly since welding will typically anneal and soften
the resulting hollow sphere resulting in "oil canning," i.e.
deformation of the metal sphere after impact, such as may occur
during play.
[0091] In a second embodiment, a metal mantle is formed via
electroplating over a thin hollow polymeric sphere, described in
greater detail below. This polymeric sphere may correspond to an
optional polymeric hollow sphere substrate described in greater
detail herein. There are several preferred techniques by which a
metallic mantle layer may be deposited upon a non-metallic
substrate. In a first category of techniques, an electrically
conductive layer is formed or deposited upon the polymeric or
non-metallic sphere. Electroplating may be used to fully deposit a
metal layer after a conductive salt solution is applied onto the
surface of the non-metallic substrate. Alternatively, or in
addition, a thin electrically conducting metallic surface can be
formed by flash vacuum metallization of a metal agent, such as
aluminum, onto the substrate of interest. Such surfaces are
typically about 3.times.10.sup.-6 of an inch thick. Once deposited,
electroplating can be utilized to form the metal layer(s) of
interest. It is contemplated that vacuum metallization could be
employed to fully deposit the desired metal layer(s). Yet another
technique for forming an electrically conductive metal base layer
is chemical deposition. Copper, nickel, or silver, for example, may
be readily deposited upon a non-metallic surface. Yet another
technique for imparting electrical conductivity to the surface of a
non-metallic substrate is to incorporate an effective amount of
electrically conductive particles in the substrate, such as carbon
black, prior to molding. Once having formed an electrically
conductive surface, electroplating processes can be used to form
the desired metal mantle layers.
[0092] Alternatively, or in addition, various thermal spray coating
techniques can be utilized to form one or more metal mantle layers
onto a spherical substrate. Thermal spray is a generic term
generally used to refer to processes for depositing metallic and
non-metallic coatings, sometimes known as metallizing, that
comprise the plasma arc spray, electric arc spray, and flame spray
processes. Coatings can be sprayed from rod or wire stock, or from
powdered material.
[0093] A typical plasma arc spray system utilizes a plasma arc
spray gun at which one or more gasses are energized to a highly
energized state, i.e. a plasma, and are then discharged typically
under high pressures toward the substrate of interest. The power
level, pressure, and flow of the arc gasses, and the rate of flow
of powder and carrier gas are typically control variables.
[0094] The electric arc spray process preferably utilizes metal in
wire form. This process differs from the other thermal spray
processes in that there is no external heat source, such as from a
gas flame or electrically induced plasma. Heating and melting occur
when two electrically opposed charged wires, comprising the spray
material, are fed together in such a manner that a controlled arc
occurs at the intersection. The molten metal is atomized and
propelled onto a prepared substrate by a stream of compressed air
or gas.
[0095] The flame spray process utilizes combustible gas as a heat
source to melt the coating material. Flame spray guns are available
to spray materials in rod, wire, or powder form. Most flame spray
guns can be adapted for use with several combinations of gases.
Acetylene, propane, mapp gas, and oxygen-hydrogen are commonly used
flame spray gases.
[0096] Another process or technique for depositing a metal mantle
layer onto a spherical substrate in the preferred embodiment golf
balls is chemical vapor deposition (CVD). In the CVD process, a
reactant atmosphere is fed into a processing chamber where it
decomposes at the surface of the substrate of interest, liberating
one material for either absorption by or accumulation on the work
piece or substrate. A second material is liberated in gas form and
is removed from the processing chamber, along with excess
atmosphere gas, as a mixture referred to as off-gas.
[0097] The reactant atmosphere that is typically used in CVD
includes chlorides, fluorides, bromides and iodides, as well as
carbonyls, organometallics, hydrides and hydrocarbons. Hydrogen is
often included as a reducing agent. The reactant atmosphere must be
reasonably stable until it reaches the substrate, where reaction
occurs with reasonably efficient conversion of the reactant.
Sometimes it is necessary to heat the reactant to produce the
gaseous atmosphere. A few reactions for deposition occur at
substrate temperatures below 200 degrees C. Some organometallic
compounds deposit at temperatures of 600 degrees C. Most reactions
and reaction products require temperatures above 800 degrees C.
[0098] Common CVD coatings include nickel, tungsten, chromium, and
titanium carbide. CVD nickel is generally separated from a nickel
carbonyl, Ni(CO).sub.4, atmosphere. The properties of the deposited
nickel are equivalent to those of sulfonate nickel deposited
electrolytically. Tungsten is deposited by thermal decomposition of
tungsten carbonyl at 300 to 600 degrees C, or may be deposited by
hydrogen reduction of tungsten hexachloride at 700 to 900 degrees
C. The most convenient and most widely used reaction is the
hydrogen reduction of tungsten hexafluoride. If depositing chromium
upon an existing metal layer, this may be done by pack cementation,
a process similar to pack carbonizing, or by a dynamic,
flow-through CVD process. Titanium carbide coatings may be formed
by the hydrogen reduction of titanium tetrafluoride in the presence
of methane or some other hydrocarbon. The substrate temperatures
typically range from 900 to 1010 degrees C, depending on the
substrate.
[0099] Surface preparation for CVD coatings generally involve
degreasing or grit blasting. In addition, a CVD pre-coating
treatment may be given. The rate of deposition from CVD reactions
generally increases with temperature in a manner specific to each
reaction. Deposition at the highest possible rate is preferable,
however, there are limitations which require a processing
compromise.
[0100] Vacuum coating is another category of processes for
depositing metals and metal compounds from a source in a high
vacuum environment onto a substrate, such as the spherical
substrate used in several of the preferred embodiment golf balls.
Three principal techniques are used to accomplish such deposition:
evaporation, ion plating, and sputtering. In each technique, the
transport of vapor is carried out in an evacuated, controlled
environment chamber and, typically, at a residual air pressure of 1
to 10.sup.-5 Pascals.
[0101] In the evaporation process, vapor is generated by heating a
source material to a temperature such that the vapor pressure
significantly exceeds the ambient chamber pressure and produces
sufficient vapor for practical deposition. To coat the entire
surface of a substrate, such as the inner spherical substrate
utilized in the preferred embodiment golf balls, it must be rotated
and translated over the vapor source. Deposits made on substrates
positioned at low angles to the vapor source generally result in
fibrous, poorly bonded structures. Deposits resulting from
excessive gas scattering are poorly adherent, amorphous, and
generally dark in color. The highest quality deposits are made on
surfaces nearly normal or perpendicular to the vapor flux. Such
deposits faithfully reproduce the substrate surface texture. Highly
polished substrates produce lustrous deposits, and the bulk
properties of the deposits are maximized for the given deposition
conditions.
[0102] For most deposition rates, source material should be heated
to a temperature so that its vapor pressure is at least 1 Pascal or
higher. Deposition rates for evaporating bulk vacuum coatings can
be very high. Commercial coating equipment can deposit up to
500,000 angstroms of material thickness per minute using large
ingot material sources and high powered electron beam heating
techniques.
[0103] As indicated, the directionality of evaporating atoms from a
vapor source generally requires the substrate to be articulated
within the vapor cloud. To obtain a specific film distribution on a
substrate, the shape of the object, the arrangement of the vapor
source relative to the component surfaces, and the nature of the
evaporation source may be controlled.
[0104] Concerning evaporation sources, most elemental metals,
semi-conductors, compounds, and many alloys can be directly
evaporated in vacuum. The simplest sources are resistance wires and
metal foils. They are generally constructed of refractory metals,
such as tungsten, molybdenum, and tantalum The filaments serve the
dual function of heating and holding the material for evaporation
Some elements serve as sublimation sources such as chromium,
palladium, molybdenum, vanadium, iron, and silicon, since they can
be evaporated directly from the solid phase. Crucible sources
comprise the greatest applications in high volume production for
evaporating refractory metals and compounds. The crucible materials
are usually refractory metals, oxides, and nitrides, and carbon.
Heating can be accomplished by radiation from a second refractory
heating element, by a combination of radiation and conduction, and
by radial frequency induction heating.
[0105] Several techniques are known for achieving evaporation of
the evaporation source. Electron beam heating provides a flexible
heating method that can concentrate heat on the evaporant. Portions
of the evaporant next to the container can be kept at low
temperatures, thus minimizing interaction. Two principal electron
guns in use are the linear focusing gun, which uses magnetic and
electrostatic focusing methods, and the bent-beam magnetically
focused gun. Another technique for achieving evaporation is
continuous feed high rate evaporation methods High rate evaporation
of alloys to form film thicknesses of 100 to 150 micrometers
requires electron beam heating sources in large quantities of
evaporant. Electron beams of 45 kilowatts or higher are used to
melt evaporants in water cooled copper hearths up to 150 by 400
millimeters in cross section.
[0106] Concerning the substrate material of the spherical shell
upon which one or more metal layers are formed in the preferred
embodiment golf balls, the primary requirement of the material to
be coated is that it be stable in vacuum. It must not evolve gas or
vapor when exposed to the metal vapor. Gas evolution may result
from release of gas absorbed on the surface, release of gas trapped
in the pores of a porous substrate, evolution of a material such as
plasticizers used in plastics, or actual vaporization of an
ingredient in the substrate material.
[0107] In addition to the foregoing methods, sputtering may be used
to deposit one or more metal layers onto, for instance, an inner
hollow sphere substrate such as substrate 30 utilized in the
preferred embodiment golf balls. Sputtering is a process wherein
material is ejected from the surface of a solid or liquid because
of a momentum exchange associated with bombardment by energetic
particles. The bombarding species are generally ions of a heavy
inert gas. Argon is most commonly used. The source of ions may be
an ion beam or a plasma discharge into which the material can be
bombarded is immersed.
[0108] In the plasma-discharge sputter coating process, a source of
coating material called a target is placed in a vacuum chamber
which is evacuated and then back filled with a working gas, such as
Argon, to a pressure adequate to sustain the plasma discharge. A
negative bias is then applied to the target so that it is bombarded
by positive ions from the plasma.
[0109] Sputter coating chambers are typically evacuated to
pressures ranging from 0.001 to 0.00001 Pascals before back filling
with Argon to pressures of 0.1 to 10 Pascals. The intensity of the
plasma discharge, and thus the ion flux and sputtering rate that
can be achieved, depends on the shape of the cathode electrode, and
on the effective use of a magnetic field to confine the plasma
electrons. The deposition rate in sputtering depends on the target
sputtering rate and the apparatus geometry. It also depends on the
working gas pressure, since high pressures limit the passage of
sputtered flux to the substrates.
[0110] Ion plating may also be used to form one or more metal
mantle layers in the golf balls of the present invention. Ion
plating is a generic term applied to atomistic film deposition
processes in which the substrate surface and/or the depositing film
is subjected to a flux of high energy particles (usually gas ions)
sufficient to cause changes in the interfacial region or film
properties. Such changes may be in the film adhesion to the
substrate, film morphology, film density, film stress, or surface
coverage by the depositing film material.
[0111] Ion plating is typically done in an inert gas discharge
system similar to that used in sputtering deposition except that
the substrate is the sputtering cathode and the bombarded surface
often has a complex geometry. Basically, the ion plating apparatus
is comprised of a vacuum chamber and a pumping system, which is
typical of any conventional vacuum deposition unit. There is also a
film atom vapor source and an inert gas inlet. For a conductive
sample, the work piece is the high voltage electrode, which is
insulated from the surrounding system. In the more generalized
situation, a work piece holder is the high voltage electrode and
either conductive or non-conductive materials for plating are
attached to it. Once the specimen to be plated is attached to the
high voltage electrode or holder and the filament vaporization
source is loaded with the coating material, the system is closed
and the chamber is pumped down to a pressure in the range of 0.001
to 0.0001 Pascals. When a desirable vacuum has been achieved, the
chamber is back filled with Argon to a pressure of approximately 1
to 0.1 Pascals. An electrical potential of -3 to -5 kilovolts is
then introduced across the high voltage electrode, that is the
specimen or specimen holder, and the ground for the system. Glow
discharge occurs between the electrodes which results in the
specimen being bombarded by the high energy Argon ions produced in
the discharge, which is equivalent to direct current sputtering.
The coating source is then energized and the coating material is
vaporized into the glow discharge.
[0112] Another class of materials, contemplated for use in forming
the one or more metal mantle layers is nickel titanium alloys.
These alloys are known to have super elastic properties and are
approximately 50 percent (atomic) nickel and 50 percent titanium.
When stressed, a super elastic nickel titanium alloy can
accommodate strain deformations of up to 8 percent. When the stress
is later released, the super elastic component returns to its
original shape. Other shape memory alloys can also be utilized
including alloys of copper zinc aluminum, and copper aluminum
nickel. Table 3 set forth below presents various physical,
mechanical, and transformation properties of these three preferred
shape memory alloys
3TABLE 3 Properties of Shape Memory Alloys for Use in Mantle
Layer(s) PHYSICAL PROPERTIES Cu--Zn--Al Cu--Al--Ni Ni--Ti Density
(g/cm) 7 64 7 12 6 5 Resistivity (.mu..OMEGA.-cm) 85-97 11-13
80-100 Thermal Conductivity 120 30-43 10 (J/m-s-K) Heat Capacity
(J/Kg-K) 400 373-574 390 MECHANICAL PROPERTIES Cu--Zn--al
Cu--Al--Ni Ni--Ti Young's Modulus (GPa) .beta.-Phase 72 85 83
Martensile 70 80 34 Yield Strength (MPa) .beta.-Phase 350 400 690
Martensile 80 130 70-150 Ultimate Tensile 600 500-800 900 Strength
(MPa) TRANSFORMATION PROPERTIES Cu--Zn--Al Cu--Al--Ni Ni--Ti Heat
of Transformation (J/mole) Martensile 160-440 310-470 R-Phase 55
Hysteresis (K) Martensile 10-25 15-20 30-40 R-Phase 2-5 Recoverable
Strain (%) One-Way (Martensile) 4 4 8 One-Way (R-Phase 0 5-1
Two-Way (Martensile) 2 2 3
[0113] As noted, the previously-described mantle may also comprise
one or more ceramic or vitreous materials. Preferred ceramics
include, but are not limited to, silica, soda lime, lead silicate,
borosilicate, aluminoborosilicate, aluminosilicate, and various
glass ceramics. Specifically, a wide array of ceramic materials can
be utilized in the ceramic mantle layer. Table 4 set forth below
provides a listing of suitable ceramic materials.
4TABLE 4 Ceramics for Use in Mantle Layer(s) Modulus of rupture,
Material MPa aluminum oxide crystals 345-1034 sintered alumina (ca
5% porosity) 207-345 alumina porcelain (90-95% Al.sub.2O.sub.3) 345
sintered beryllia (ca 5% porosity) 138-276 hot-pressed boron
nitride (ca 5% porosity) 48-103 hot-pressed boron carbide (ca 5%
porosity) 345 sintered magnesia (ca 5% porosity) 103 sintered
molybdenum silicide (ca 5% porosity) 690 sintered spinel (ca 5%
porosity) 90 dense silicon carbide (ca 5% porosity) 172 sintered
titanium carbide (ca 5% porosity) 1100 sintered stabilized zirconia
(ca 5% porosity) 83 silica glass 107 vycor glass 69 pyrex glass 69
mullite porcelain 69 steatite porcelain 138 superduty fire-clay
brick 5.2 magnesite brick 27.6 bonded silicon carbide (ca 20%
porosity) 13.8 1090.degree. C. insulating firebrick (80-85%
porosity) 0.28 1430.degree. C. insulating firebrick (ca 75%
porosity) 1.17 1650.degree. C. insulating firebrick (ca 60%
porosity) 2.0
[0114] It is also preferred to utilize a ceramic matrix composite
material such as, for example, various ceramics that are reinforced
with silicon carbide fibers or whiskers. Table 5, set forth below,
lists properties of typical silicon carbide reinforced
ceramics.
5TABLE 5 SiC Reinforced Ceramics for Use in Mantle Layer(s)
Fracture Flexural toughness strength Matrix Reinforcement/vol %
(ksi inches)1/2 (ksi) Barium Osumilite SiC whiskers/25 41 50-60
Corning 1723 Glass SiC whiskers/25 19-31 30-50 Cordierite SiC
whiskers/20 34 40 MoSi.sub.2 SiC whiskers/20 75 45 Mullite SiC
whiskers/20 42 65 Si.sub.3N.sub.4 SiC whiskers/10 59-86 60-75
Si.sub.3N.sub.4 SiC whiskers/30 68-91 50-65 Spinel SiC whiskers/30
-- 60 Toughened Al.sub.2O.sub.3 SiC whiskers/20 77-123 100-130
[0115] It is also preferred to provide a ceramic matrix of aluminum
oxide, Al.sub.2O.sub.3, reinforced with silicon carbide fibers or
whiskers. Typical properties of such a reinforced matrix are set
forth below in Table 6.
6TABLE 6 SiC Reinforced Al.sub.2O.sub.3 Ceramics for Use in Mantle
Layer(s) Fracture Fracture strength toughness Test
Reinforcement/vol % (ksi) (ksi inches)1/2 temperature SiC
whiskers/10 65 6.5 RT SiC whiskers/10 45 -- 1830.degree. F. SiC
whiskers/20 95 6.8-6.2 RT SiC whiskers/20 85 6.4-7.3 1830.degree.
F. SiC whiskers/40 120 55 RT SiC whiskers/40 96 5.6 1830.degree.
F.
[0116] Yet another preferred embodiment for the ceramic composite
mantle is the use of a multidirectional continuous ceramic fiber
dispersed within a ceramic composite. Typical properties of such
substrates are set forth in Table 7 below.
7TABLE 7 Multidirectional Continuous Ceramic Fibers in Ceramic
Composite for Use in Mantle Layer(s) Material/properties
SiO.sub.2/SiO.sub.23-D Al.sub.2O.sub.3/Al.sub.2O.sub.33-D
Al.sub.2O.sub.3/SiO.sub.23-D BN/Bn3-D Reinforcement/(vol
%)(10.sup.3 psi) StO.sub.2/50 Al.sub.2O.sub.3/30 Al.sub.2O.sub.2/30
BN/40 Tensile strength 3.87 10.3 108 3.8 Tensile modulus (10.sup.6
psi) 2.26 5.26 490 223 Compressive strength (10.sup.3 psi) 21.0
32.6 -- 5.29 Compressive modulus (10.sup.4 psi) 3.18 4.55 -- 4.23
Thermal conductivity (BTU/hr/ft.sup.2/.degree. F./in) 46 11.2 47
624 Density (g/cm.sup.3) 1.6 19 20 1.6
[0117] In forming the ceramic mantle, two approaches are primarily
used. In a first preferred method, two ceramic half shells are
formed. Each half shell utilizes a tongue and groove area along its
bond interface region to improve bond strength. The shells are then
adhesively bonded to one another by the use of one or more suitable
adhesives known in the art.
[0118] In a second preferred method, a ceramic mantle layer is
deposited over a core or hollow spherical substrate, both of which
are described in greater detail below, by one of several deposition
techniques. If a composite matrix utilizing fibers is to be formed,
the fibers, if continuous, can be applied by winding the single or
multi-strands onto the core or hollow spherical substrate, in
either a wet or dry state. Using the wet method, the strand or
strands pass through an epoxy resin bath prior to their winding
around the core of the golf ball to a specific diameter. Either
during or subsequent to winding, the wound core is compression
molded using heat and moderate pressure in smooth spherical
cavities. After de-molding, a dimpled cover is molded around the
wound center using compression, injection, or transfer molding
techniques. The ball is then trimmed, surface treated, stamped, and
clear coated.
[0119] If the ceramic mantle layer is formed by a dry technique,
the epoxy resin, such as in the dipping bath if the previously
described wet method is used, can be impregnated into the fibers
and molded as described above.
[0120] If the fiber is discontinuous, it can be applied to the core
by simultaneously spraying a chopped fiber and a liquid epoxy resin
to a revolving core or spherical substrate. The wet, wound center
is then cured by molding as previously described.
[0121] With regard to the use of discontinuous fibers, the critical
factors are the length to diameter ratio of the fiber, the shear
strength of the bond between the fiber and the matrix, and the
amount of fiber. All of these variables effect the overall strength
of the composite mantle.
[0122] The thickness of the ceramic mantle typically ranges from
about 0.001 inch to about 0.070 inch. The preferred thickness
ranges from about 0.005 inch to about 0.040 inch. The most
preferred range is from about 0.010 inch to about 0.020 inch.
[0123] As the thickness of the ceramic layer increases, the weight
and stiffness generally increases, and therefore, the PGA
compression will also increase. This is typically the limiting
factor, that is the PGA compression. Ball compressions over 110 PGA
are generally undesirable. PGA compressions under 40 PGA are
typically too soft. The overall bali compression can be adjusted by
modifying or tailoring the core compression, i.e., a soft core
requires a relatively thick mantle and a hard core requires a thin
mantle but within the thicknesses described previously.
[0124] As noted, the mantle may comprise a ceramic composite
material. In addition to dispersing glass and/or carbon fibers
within various matrix materials, such as ceramics, epoxy,
thermoset, and thermoplastics, other preferred fibers include boron
carbide. It is also contemplated to utilize aramid (Kevlar),
cotton, flax, jute, hemp, and silk fibers. The most preferred
non-ceramic fibers are carbon, glass, and aramid fibers.
[0125] Typical properties for fibers suitable for forming
reinforced materials are set forth below in Tables 8 and 9.
8TABLE 8 Reinforced Composite Materials for Use in Mantle Layer(s)
Density Tensile strength Tensile modulus Fiber (g/cm.sup.2) GPa ksi
GPa 10.sup.4 psi E-Glass 2.58 3.45 500 72.5 105 A-Glass 2.50 3.04
440 69.0 10.0 ECR- 2.62 3.63 525 72.5 105 Glass S-Glass 2.48 4.59
665 86.0 12.5
[0126]
9TABLE 9 Reinforced Composite Materials for Use in Mantle Layer(s)
Precursor Density Tensile strength Tensile modulus Fiber type
(g/cm.sup.3) GPa ksi GPa 10.sup.6 psi AS-4 PAN 1.78 4.0 580 231
33.5 AS-6 PAN 1.82 4.5 652 245 35.5 IM-6 PAN 1.74 4.8 696 296 42.9
T300 PAN 1.75 3.31 480 228 32.1 T500 PAN 1.78 3.65 530 234 34.0
1700 PAN 1.80 4.48 650 248 36.0 T-40 PAN 1.74 4.50 652 296 42.9
Celion PAN 1.77 3.55 515 234 34.0 Celion ST PAN 1.78 4.34 630 234
34.0 XAS PAN 1.84 3.45 500 234 34.0 HMS-4 PAN 1.78 3.10 450 338
49.0 PAN 50 PAN 1.81 2.41 355 393 57.0 HMS PAN 1.91 1.52 220 341
49.4 G-50 PAN 1.78 2.48 360 359 52.0 GY-70 PAN 1.96 1.52 220 483
70.0 P-55 Pitch 2.0 1.73 250 379 55.0 P-75 Pitch 2.0 2.07 300 517
75.0 P-100 Pitch 2.15 2.24 325 724 100 HMG-50 Rayon 1.9 2.07 300
345 50.0 Thornel 75 Rayon 1.9 2.52 365 517 75.0
[0127] It is to be understood that one or more of these fibers
could be utilized in a ceramic, epoxy, thermoset, and/or
thermoplastic matrix material in forming the mantle layer(s).
Details of suitable epoxy, thermoset, and thermoplastic materials
are set forth below.
[0128] The composite mantle may also be formed from various epoxy
molding compounds including, for example, carbon or glass fibers
dispersed within an epoxy matrix. Table 10, set forth below, lists
typical properties of such epoxy molding compounds.
10TABLE 10 Reinforced Epoxy Based Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix Epoxy Epoxy Epoxy Epoxy
Epoxy Reinforcement/(vol %) Glass/60 Carbon/60 HS carbon/60 HM
carbon/60 Shortglass/60 Density (g/cm.sup.3) 1.86-1.92 1.48-1.54
1.48-1.54 1.48-1.54 1.78-1.83 Tensile strength 35 30 32 18 11
(10.sup.3 psi) Tensile modulus -- -- -- -- -- (10.sup.6 psi)
Flexural strength 85 54 58 53 18 (10.sup.3 psi) Flexural modulus
4.2 7.2 8.2 11.8 2.0 (10.sup.8 psi) Compressive strength 42 36 44
31 28 (10.sup.3 psi) Izod Impact notched 45 20 25 15 0.70 (ft
lb/in.) Coeff thermal expansion 14 1.0 1.0 1.0 27
(10.sup.-6/.degree. F.) Conductivity 0.02 -- -- -- 0.02
(BTU/hr/ft.sup.2/.degree. F./in.) Heat deflection temp 264 250 250
250 250 154 psi (.degree. F.) Flammability rating, UL -- -- -- --
94 V-1 Volume resisitivity (ohm-cm) 7.5 .times. 10.sup.14 -- -- --
9 .times. 10.sup.16 Water absorption, 24 hr 0.10 0.20 0.20 0.20
0.10 (%)
[0129] The composite mantle layer may also be formed from a
composite material of glass fibers dispersed within a thermoset
matrix wherein the thermoset matrix is, for example, a polyimide
material, silicone, vinyl ester, polyester, or melamine. Table 11,
set forth below, lists typical properties of such composite
thermoset molding materials.
11TABLE 11 Reinforced Thermoset Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix Polyimide Silicone Vinyl
Poly- Mela- ester ester mine Reinforcement/ Glass/ Glass/ Glass/
Glass/ Glass/ (vol %) 60 60 60 60 60 Density (g/cm.sup.3) 1.95-2.00
2.00- 1.84- 1.84- 1.79- 2.05 1.90 1.90 1.84 Tensile strength 21 4.0
39 0 8.0 8.0 (10.sup.3 psi) Tensile modulus.sub.area -- -- -- -- --
(10.sup.6 psi) Flexural strength 37 10 70 20 14 (10.sup.3 psi)
Flexural modulus 3.1 2.0 2.8 2.2 2.2 (10.sup.6 psi) Compressive
strength 32 11 42 20 42 (10.sup.3 psi) Izod impact notched 22 5.0
40 12 0.50 (ft lb/in.) Coeff thermal expan- 10 7.0 10 -- 20 sion
(10.sup.-6/.degree. F.) Conductivity 0.018 0.011 -- -- 0.022
(BTU/hr/ft.sup.2/.degree. F./in.) Heat deflection temp 500 500 430
480 320 264 psi (.degree. F.) Flammability rating, -- 94V-0 -- --
94V-0 UL Volume resistivity 2.5 .times. 10.sup.16 -- -- -- --
(ohm-cm) Water absorption, 0.30 0.15 0.15 0.15 0.15 24 hr (%)
[0130] The preferred embodiment composite mantle layer may also be
formed from various nylon molding compounds including, for example,
glass or carbon fibers dispersed within a nylon matrix. Table 12
lists typical properties of such composite nylon mantles.
12TABLE 12 Reinforced Nylon Composite Materials for use in Mantle
Layer(s) Material/Properties Matrix Nylon 6 Nylon 6 Nylon Nylon
Nylon Nylon 6/6 6/10 6/10 11 Reinforcement/ Glass/ Glass/ Glass/
Carbon/ Glass/ Glass/ (vol %) 20 40 40 40 40 20 Density 1 27 1 46 1
46 1 33 1.40 1 18 (g/cm.sup.3) Tensile 20 25 32 36 26.5 14 strength
(10.sup.3 psi) Tensile 0 98 1 4 1.9 4 2 1 5 0 75 modulus (10.sup.6
psi) Flexural 23 31 40 52 38 17 strength (10.sup.3 psi) Flexural
0.70 1.3 1.7 3 4 1.3 0 53 modulus (10.sup.6 psi) Compressive 21 23
23 25 25 12.5 strength (10.sup.3 psi) Izod impact 1.3 2.5 2.6 1.6
3.3 1 4 notched (ft lb/in.) Coeff thermal 23 13 19 8.0 11 40
expansion (10.sup.-6/.degree. F.) Conductivity 3.0 3 6 3.6 8.0 3.8
2 6 (BTU/hr/ft.sup.2/ .degree. F./in.) Heat deflection 390 400 480
500 420 340 temp 264 psi (.degree. F.) Flammability HB HB HB HB HB
HB rating, UL Volume 10.sup.14 10.sup.14 10.sup.14 30 10.sup.12
10.sup.13 resistivity (ohm-cm) Water absorp- 1.3 1.0 0.7 0.4 0.23
0.19 tion 24 hr (%)
[0131] The composite mantle layer may also be formed from a
styrenic molding material, such as comprising glass or carbon
fibers dispersed within a styrene material including, for example,
an acrylonitrile-butadiene-styrene (ABS), polystyrene (PS),
styrene-acrylonitrile (SAN), or styrene-maleic anhydride (SMA).
Table 13, set forth below, lists typical properties for such
materials.
13TABLE 13 Reinforced Styrene-Based Composite Materials for Use in
Mantle Layer(s) Matl/Propertles Matrix ABS ABS ABS PS SAN SMA
Reinforcement/ Glass/ Glass/ Carbon/ Glass/ Glass/ Glass/ (vol %) 2
0 40 40 40 40 40 Density 1.18 1.38 1.24 1.38 1.40 1.40 (g/cm.sup.3)
Tensile 13 18 17 14 20 14 strength (10.sup.3 psi) Tensile 0.88 1 5
3.1 2 0 2 0 1 67 modulus (10.sup.6 psi) Flexural 17 21 25 19 24
22.5 strength (10.sup.3 psi) Flexural 0 80 1 3 2.8 1 6 1 8 1 37
modulus (10.sup.6 psi) Compressive 13 5 19 19 17 5 22.0 -- strength
(10.sup.3 psi) Izod impact 1.4 1.2 1.0 1.1 1.1 1.5 notched (ft
lb/in.) Coeff thermal 20 13 12 17 15.5 -- expansion
(10.sup.-6/.degree. F.) Conductivity 1.4 1.6 3.8 2.2 2.1 --
(BTU/hr/ft.sup.2/ .degree. F./in.) Heat deflection 220 240 240 210
217 250 temp 264 psi (.degree. F.) Flammability HB HB HB HB HB HB
rating, UL Volume 10.sup.15 10.sup.15 30 10.sup.16 10.sup.16 --
resistivity (ohm-cm) Water absorp- 0.18 0.12 0.14 0.05 0 1 0.1
tion, 24 hr (%)
[0132] The preferred composite mantle may also be formed from a
reinforced thermoplastic material, such as comprising glass fibers
dispersed within acetal copolymer (AC), polycarbonate (PC), and/or
liquid crystal polymer (LCP). Table 14, set forth below, lists
typical properties for such materials.
14TABLE 14 Reinforced Thermoplastic Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix AC AC PC LCP
Reinforcement/(vol %) Glass/20 Glass/40 Glass/40 Glass/30 Density
(g/cm.sup.3) 1.55 1.74 1.52 1.57 Tensile strength 12 13 21 16-29
(10.sup.3 psi) Tensile modulus 1.2 1.6 1.7 2.5-2.6 (10.sup.6 psi)
Flexural strength 16.5 17.0 26.0 25-36 (10.sup.3 psi) Flexural
modulus 0 9 1.3 1 4 2 1-2.5 (10.sup.6 psi) Compressive strength 12
11 22 -- (10.sup.3 psi) Izod impact notched 0.9 0.9 2.2 1.0-2.5 (ft
lb/in.) Coeff thermal 25 18 9.5 -- expansion (10.sup.-6/.degree.
F.) Conductivity 2.0 2.3 2.4 -- (BTU/hr/ft.sup.2/.degree. F./in.)
Heat deflection temp 325 328 300 445-600 264 psi (.degree. F.)
Flammability rating, UL HB HB V1 -- Volume resistivity 10.sup.14
10.sup.14 10.sup.16 10.sup.16 (ohm-cm) Water absorption, 24 hr 0.5
1.0 0.07 -- (%)
[0133] The preferred embodiment composite material may also be
formed from one or more thermoplastic molding compounds such as,
for example, high density polyethylene (HDPE), polypropylene (PP),
polybutylene terephthalate (PBT), or polyethylene terephthalate
(PET) and including fibers of mica or glass. Table 15, set forth
below, lists typical properties for such materials.
15TABLE 15 Reinforced Thermoplastic Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix HDPE HDPE PP PP PBT PET
Reinforcement/ Glass/ Glass/ Glass/ Mica/ Glass/ Glass/ (vol %) 20
40 40 40 40 55 Density 1.10 1.28 1.23 1.26 1.63 1.80 (g/cm.sup.3)
Tensile 7.0 10 16 5.6 21.5 28.5 strength (10.sup.3 psi) Tensile 0.6
1.25 1.3 1.1 2.0 3.0 modulus (10.sup.6 psi) Flexural 9.0 12 19 9 30
43 strength (10.sup.3 psi) Flexural 0.55 1.0 0.9 1 0 1.5 2.6
modulus (10.sup.6 psi) Compressive 5 0 7 5 13.0 7 0 20 0 28.5
strength (10.sup.3 psi) Izod impact 1 2 1 4 2.0 0 5 1 8 1 9 notched
(ft lb/in.) Coeff thermal 28 25 17.5 22 12 10 expansion
(10.sup.-6/.degree. F.) Conductivity 2.3 2.7 2.45 2.2 1.5 2.3
(BTU/hr/ft.sup.2/ .degree. F./in) Heat deflection 240 250 300 230
415 450 temp 264 psi (.degree. F.) Flammability HB HB HB HB HB HB
rating, UL Volume 10.sup.16 10.sup.16 10.sup.15 10.sup.15 10.sup.16
10.sup.16 resistivity (ohm-cm) Water absorp- 0.01 0.022 0.06 0.03
0.08 0 04 tion, 24 hr (%)
[0134] The preferred embodiment composite mantle layer may also be
formed from thermoplastic materials including various
polyphenylenes such as polyphenylene ether (PPE), polyphenylene
oxide (PPO), or polyphenylene sulfide (PPS) within which are
dispersed fibers of glass or graphite. Typical properties of these
materials are set forth below in Table 16.
16TABLE 16 Reinforced Thermoplastic Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix PPE- PPE- PPO PPO PPS
PPS PPS Reinforcement/ Glass/ Gra- Glass/ Glass/ Gra- (vol %) 20
phite/20 20 40 phite/40 Density (g/cm.sup.3) 1.21 1.20 1.49 1 67
1.46 Tensile strength 13.5 15.0 14.5 20.0 26.0 (10.sup.3 psi)
Tensile modulus 1.0 1.0 1.3 2.0 4.8 (10.sup.6 psi) Flexural
strength 17.5 20.0 19.0 30.0 40 0 (10.sup.3 psi) Flexural modulus
0.75 0.98 1.3 1.6 4.1 (10.sup.6 psi) Compressive strength -- 17.0
22.5 25.0 27.0 (10.sup.3 psi) Izod Impact notched 2.0 1.6 1 4 1 4
1.2 (ft lb/in.) Coeff thermal expansion 20 12 16 12 8 0
(10.sup.-6/.degree. F.) Conductivity 1 1 -- 2 1 2 2 3.3
(BTU/hr/ft.sup.2/.degree. F./in.) Heat deflection temp 264 285 235
500 500 500 psi (.degree. F.) Flammability rating, UL HB -- VO VO
VO Volume resistivity (ohm- 10.sup.17 13.0 10.sup.16 10.sup.16 30
cm) Water absorption, 24 hr 0.06 -- 0.02 0.02 0 02 (%)
[0135] Also preferred for the composite material are various
polyaryl thermoplastic materials reinforced with glass fibers or
carbon fibers. Table 17, set forth below, lists typical properties
for such composite materials. It is to be noted that PAS is
polyarylsulfone, PSF is Polysulfone, and PES is
Polyethersulfone.
17TABLE 17 Reinforced Polyaryl Thermoplastic Materials for Use in
Mantle Layer(s) Material/Properties Matrix PAS PSF PSF PSF PES PES
Reinforcement/ Glass/ Glass/ Glass/ Carbon/ Glass/ Carbon/ (vol %)
20 20 40 40 40 40 Density 1.51 1.38 1.56 1.42 1.68 1.52
(g/cm.sup.3) Tensile 19 15 19 26 23 31 strength (10.sup.3 psi)
Tensile 1.0 0.88 1.7 3.0 2.0 3.5 modulus (10.sup.6 psi) Flexural 27
20 25 35 31 42 strength (10.sup.3 psi) Flexural 0.9 0.7 1.2 2.4 1.6
3.2 modulus (10.sup.6 psi) Compressive -- 19 24 -- 22 -- strength
(10.sup.3 psi) Izod impact 1.1 1.1 1.6 1.3 1.5 1.4 notched (ft
lb/in.) Coeff thermal -- 17 13 -- 14 -- expansion
(10.sup.-6/.degree. F.) Conductivity -- 2.1 2.6 -- 2.6 --
(BTU/hr/ft.sup.2/ .degree. F./in.) Heat deflection 405 360 365 365
420 420 temp 264 psi (.degree. F.) Flammability V0 V1 V0 V1 V0 V0
rating, UL Volume 10.sup.16 10.sup.16 10.sup.15 30 10.sup.16 30
resistivity (ohm-cm) Water absorp- 0 4 0.24 0.25 0.25 0.30 0.30
tion, 24 hr (%)
[0136] Other thermoplastic materials may be used for the composite
mantle including reinforced polyetherimide (PEI), or polyether
etherketone (PEEK), reinforced with glass or carbon fibers. Table
18, set forth below, lists typical properties for such
materials.
18TABLE 18 Reinforced Thermoplastic Composite Materials for Use in
Mantle Layer(s) Material/Properties Matrix PEI PEI PEI PEEK PEEK
Reinforcement/ Glass/ Glass/ Carbon/ Glass/ Carbon/ (vol %) 20 40
40 20 40 Density (g/cm.sup.3) 1.41 1.59 1.44 1.46 1.46 Tensile
strength 23 31 34 23 39 (10.sup.3 psi) Tensile modulus 1.1 1.9 4.1
2.0 4.4 (10.sup.6 psi) Flexural strength 32 43 46 36 54 (10.sup.3
psi) Flexural modulus 0.95 1.6 3.2 1.1 3.2 (10.sup.6 psi)
Compressive strength 24 24.5 -- -- -- (10.sup.3 psi) Izod impact
notched 1.6 2.1 1.2 1.5 1.7 (ft lb/in.) Coeff thermal expansion 15
11 -- 14 -- (10.sup.-6/.degree. F.) Conductivity 1.7 1.6 -- -- --
(BTU/hr/ft.sup.2/.degree. F./in.) Heat deflection temp 264 410 410
410 550 550 psi (.degree. F.) Flammability rating, UL VO VO VO VO
VO Volume resistivity (ohm- 10.sup.16 10.sup.16 10.sup.12 10.sup.16
30 cm) Water absorption, 24 hr 0.21 0.18 0 18 0 12 0 12 (%)
[0137] The thickness of a composite polymeric material based mantle
generally ranges from about 0.001 inch to about 0.100 inch. The
most preferred range is from about 0.010 inch to about 0.030
inch.
[0138] In forming the mantle from a polymeric material, two
approaches are primarily used. In a first preferred method, two
rigid polymeric half shells are formed. Each half shell utilizes a
tongue and groove area along its bond interface region to improve
bond strength. The shells are then adhesively bonded to one another
by the use of one or more suitable adhesives known in the art.
[0139] In a second preferred method, a polymeric mantle layer is
deposited over a core or hollow spherical substrate, both of which
are described in greater detail herein, by one of several
deposition techniques. If a composite matrix utilizing fibers is to
be formed, the fibers, if continuous, can be applied by winding the
single or multi-strands onto the core or hollow spherical
substrate, in either a wet or dry state. Using the wet method, the
strand or strands pass through an epoxy or other suitable resin
bath prior to their winding around the core of the golf ball to a
specific diameter. Either during or subsequent to winding, the
wound core is compression molded using heat and moderate pressure
in smooth spherical cavities. After de-molding, a dimpled cover is
molded around the wound center using compression, injection, or
transfer molding techniques. The ball is then trimmed, surface
treated, stamped, and clear coated.
[0140] If the polymeric mantle layer is formed by a dry technique,
the epoxy resin, such as in the dipping bath if the previously
described wet method is used, can be impregnated into the fibers
and molded as described above.
[0141] If the fiber is discontinuous, it can be applied to the core
by simultaneously spraying a chopped fiber and a liquid resin to a
revolving core or spherical substrate. The wet, wound center is
then cured by molding as previously described.
[0142] With regard to the use of discontinuous fibers, the critical
factors are the length to diameter ratio of the fiber, the shear
strength of the bond between the fiber and the matrix, and the
amount of fiber. All of these variables effect the overall strength
of the composite mantle.
[0143] In preparing the preferred embodiment golf balls, the
polymeric outer cover layer, if utilized, may be molded (for
instance, by injection molding or by compression molding) about the
mantle.
Polymeric Hollow Sphere
[0144] As noted, in another aspect, the present invention also
provides a golf ball that optionally comprises a polymeric hollow
sphere immediately adjacent to the mantle. The sphere may be
disposed inward of the mantle, or be disposed outward of the
mantle, relative to the center of the ball. The sphere may also be
disposed immediately adjacent to the mantle, or have one or more
layers of other materials separating it from the mantle. The
polymeric hollow sphere can be formed from nearly any relatively
strong plastic material. The thickness of the hollow sphere ranges
from about 0.005 inches to about 0.010 inches. The hollow inner
sphere can be formed using two half shells joined together via spin
bonding, solvent welding, or other techniques known to those in the
plastics processing arts. Alternatively, the hollow polymeric
sphere may be formed via blow molding.
[0145] A wide array of polymeric materials can be utilized to form
the polymeric hollow sphere. Thermoplastic materials are generally
preferred for use as materials for the shell. Typically, such
materials should exhibit good flowability, moderate stiffness, high
abrasion resistance, high tear strength, high resilience, and good
mold release, among others.
[0146] Synthetic polymeric materials which may be used in
accordance with the present invention include homopolymeric and
copolymer materials which may include: (1) Vinyl resins formed by
the polymerization of vinyl chloride, or by the copolymerization of
vinyl chloride with vinyl acetate, acrylic esters or vinylidene
chloride; (2) Polyoldefins such as polyethylene, polypropylene,
polybutylene, and copolymers such as polyethylene methylacrylate,
polyethylene ethylacrylate, polyethylene vinyl acetate,
polyethylene methacrylic or polyethylene acrylic acid or
polypropylene acrylic acid or terpolymers made from these and
acrylate esters and their metal ionomers, polypropylene/EPDM
grafted with acrylic acid or anhydride modified polyolefins; (3)
Polyurethanes, such as are prepared from polyols and diisocyanates
or polyisocyanates; (4) Polyamides such as poly(hexamethylene
adipamide) and others prepared from diamines and dibasic acids, as
well as those from amino acid such as poly(caprolactam), and blends
of polyamides with SURLYN, polyethylene, ethylene copolymers, EDPA,
etc; (5) Acrylic resins and blends of these resins with polyvinyl
chloride, elastomers, etc.; (6) Thermoplastic rubbers such as the
urethanes, olefinic thermoplastic rubbers such as blends of
polyolefins with EPDM, block copolymers of styrene and butadiene,
or isoprene or ethylene-butylene rubber, polyether block amides;
(7) Polyphenylene oxide resins, or blends of polyphenylene oxide
with high impact polystyrene; (8) Thermoplastic polyesters, such as
PET, PBT, PETG, and elastomers sold under the trademark HYTREL by
E. I. DuPont De Nemours & Company of Wilmington, Del.; (9)
Blends and alloys including polycarbonate with ABS, PBT, PET, SMA,
PE elastomers, etc. and PVC with ABS or EVA or other elastomers;
and (10) Blends of thermoplastic rubbers with polyethylene,
polypropylene, polyacetal, nylon, polyesters, cellulose esters,
etc.
[0147] It is also within the purview of this invention to add to
the polymeric spherical substrate compositions of this invention
materials which do not affect the basic novel characteristics of
the composition. Among such materials are antioxidants, antistatic
agents, and stabilizers.
Cover
[0148] The cover is preferably comprised of a hard, high-stiffness
ionomer resin, most preferably a metal cation neutralized high acid
ionomer resin containing more than 16% carboxylic acid by weight,
or blend thereof. The cover has a Shore D hardness of about 65 or
greater. The cover may be in the form of a single, unitary layer,
or may utilize multiple cover layers.
[0149] With respect to the ionomeric cover composition of the
invention, ionomeric resins are polymers containing interchain
ionic bonding. As a result of their toughness, durability, and
flight characteristics, various ionomeric resins sold by E. I.
DuPont de Nemours & Company under the trademark "Surlyn.RTM."
and more recently, by the Exxon Corporation (see U.S. Pat. No.
4,911,451) under the trademark "Escor.RTM." and the tradename
"lotek", have become the materials of choice for the construction
of golf ball covers over the traditional "balata"
(trans-polyisoprene, natural or synthetic) rubbers.
[0150] 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. In some instances, an additional softening comonomer such as
an acrylate can also be included to form a terpolymer. The pendent
ionic groups in the ionomeric resins interact to form ion-rich
aggregates contained in a non-polar polymer matrix. The metal ions,
such as sodium, zinc, magnesium, lithium, potassium, calcium, etc.
are used to neutralize some portion of the acid groups in the
copolymer resulting in a thermoplastic elastomer exhibiting
enhanced properties, i.e., improved durability, etc. for golf ball
construction over balata.
[0151] The ionomeric resins utilized to produce cover compositions
can be formulated according to known procedures such as those set
forth in U.S. Pat. No. 3,421,766 or British Patent No. 963,380,
with neutralization effected according to procedures disclosed in
Canadian Patent Nos. 674,595 and 713,631, wherein the ionomer is
produced by copolymerizing the olefin and carboxylic acid to
produce a copolymer having the acid units randomly distributed
along the polymer chain. Broadly, the ionic copolymer generally
comprises one or more .alpha.-olefins and from about 9 to about 20
weight percent of .alpha.,.beta.-ethylenically unsaturated mono- or
dicarboxylic acid, the basic copolymer neutralized with metal ions
to the extent desired.
[0152] At least about 20% of the carboxylic acid groups of the
copolymer are neutralized by the metal ions (such as sodium,
potassium, zinc, calcium, magnesium, and the like) and exist in the
ionic state. Suitable olefins for use in preparing the ionomeric
resins include ethylene, propylene, butene-1, hexene-1 and the
like. Unsaturated carboxylic acids include acrylic, methacrylic,
ethacrylic, .alpha.-chloroacrylic, crotonic, maleic, fumaric,
itaconic acids, and the like. The ionomeric resins utilized in the
golf ball industry are generally copolymers of ethylene with
acrylic (i.e., Escor.RTM.) and/or methacrylic (i.e., Surlyn.RTM.)
acid. In addition, two or more types of ionomeric resins may be
blended in to the cover compositions in order to produce the
desired properties of the resulting golf balls.
[0153] The cover compositions which may be used in making the golf
balls of the present invention are set forth in detail but not
limited to those in copending U.S. Ser. No. 07/776,803 filed Oct.
15, 1991, and Ser. No. 07/901,660 filed Jun. 19, 1992, both
incorporated herein by reference. In short, the cover material is
comprised of hard, high stiffness ionomer resins, preferably
containing relatively high amounts of acid (i.e., greater than 16
weight percent acid, preferably from about 17 to about 25 weight
percent acid, and more preferably from about 18.5 to about 21.5
weight percent) and at least partially neutralized with metal ions
(such as sodium, zinc, potassium, calcium, magnesium and the like).
The high acid resins are blended and melt processed to produce
compositions exhibiting enhanced hardness and coefficient of
restitution values when compared to low acid ionomers, or blends of
low acid ionomer resins containing 16 weight percent acid or
less.
[0154] The preferred cover compositions are made from specific
blends of two or more high acid ionomers with other cover additives
which do not exhibit the processing, playability, distance and/or
durability limitations demonstrated by the prior art. However, as
more particularly indicated below, the cover composition can also
be comprised of one or more low acid ionomers so long as the molded
covers exhibit a hardness of 65 or more on the Shore D scale.
[0155] The cover has a Shore D hardness of 65 or greater. Its
composition includes a hard, high stiffness preferably high acid
ionomer such as that sold by E. I. DuPont de Nemours & Company
under the trademark "Surlyn.RTM." and by Exxon Corporation under
the trademark "Escor.RTM." or tradename "lotek", or blends thereof.
In addition to the Surlyn.RTM. and Escor.RTM. or lotek ionomers,
the cover may comprise any ionomer which either alone or in
combination with other ionomers produces a molded cover having a
Shore D hardness of at least 65. These include lithium ionomers or
blends of ionomers with harder non-ionic polymers such as nylon,
polyphenylene oxide and other compatible thermoplastics. As briefly
mentioned above, examples of cover compositions which may be used
are set forth in detail in U.S. Pat. No. 5,688,869 incorporated
herein by reference. Of course, the cover compositions are not
limited in any way to those compositions set forth in said
copending applications. The high acid ionomers suitable for use in
the present invention are ionic copolymers which are the metal,
i.e., sodium, zinc, magnesium, etc., salts of the reaction product
of an olefin having from about 2 to 8 carbon atoms and an
unsaturated monocarboxylic acid having from about 3 to 8 carbon
atoms. Preferably, the ionomeric resins are copolymers of ethylene
and either acrylic or methacrylic acid. In some circumstances, an
additional comonomer such as an acrylate ester (i.e., iso- or
n-butylacrylate, etc.) can also be included to produce a softer
terpolymer. The carboxylic acid groups of the copolymer are
partially neutralized (i.e., approximately 10-75%, preferably
30-70%) by the metal ions. Each of the high acid ionomer resins
included in the cover compositions of the invention contains
greater than about 16% by weight of a carboxylic acid, preferably
from about 17% to about 25% by weight of a carboxylic acid, more
preferably from about 18.5% to about 21.5% by weight of a
carboxylic acid.
[0156] Although the cover composition preferably includes a high
acid ionomeric resin and the scope of the patent embraces all known
high acid ionomeric resins falling within the parameters set forth
above, only a relatively limited number of these high acid
ionomeric resins are currently available. In this regard, the high
acid ionomeric resins available from E. I. DuPont de Nemours
Company under the trademark "Surlyn.RTM.", and the high acid
ionomer resins available from Exxon Corporation under the trademark
"Escor.RTM." or tradename "lotek" are examples of available high
acid ionomeric resins which may be utilized in the present
invention.
[0157] The high acid ionomeric resins available from Exxon under
the designation "Escor.RTM." and or "lotek", are somewhat similar
to the high acid ionomeric resins available under the "Surlyn.RTM."
trademark. However, since the Escor.RTM./lotek ionomeric resins are
sodium or zinc salts of poly(ethylene acrylic acid) and the
"Surlyn.RTM." resins are zinc, sodium, magnesium, etc. salts of
poly(ethylene methacrylic acid), distinct differences in properties
exist.
[0158] Examples of the high acid methacrylic acid based ionomers
found suitable for use in accordance with this invention include
Surlyn.RTM. AD-8422 (sodium cation), Surlyn.RTM. 8162 (zinc
cation), Surlyn.RTM. SEP-503-1 (zinc cation), and Surlyn.RTM.
SEP-503-2 (magnesium cation). According to DuPont, all of these
ionomers contain from about 18.5 to about 21.5% by weight
methacrylic acid.
[0159] More particularly, Surlyn.RTM. AD-8422 is currently
commercially available from DuPont in a number of different grades
(i.e., AD-8422-2, AD-8422-3, AD-8422-5, etc.) based upon
differences in melt index. According to DuPont, Surlyn.RTM. AD-8422
offers the following general properties when compared to
Surlyn.RTM. 8920 the stiffest, hardest of all on the low acid
grades (referred to as "hard" ionomers in U.S. Pat. No.
4,884,814):
19 TABLE 19 LOW ACID HIGH ACID (15 wt % Acid) (>20 wt % Acid)
SURLYN .RTM. SURLYN .RTM. SURLYN .RTM. 8920 8422-2 8422-3 IONOMER
Cation Na Na Na Melt Index 1.2 2.8 1.0 Sodium, Wt % 2.3 1.9 2.4
Base Resin MI 60 60 60 MP.sup.1, .degree. C. 88 86 85 FP, .degree.
C. 47 48.5 45 COMPRESSION MOLDING.sup.2 Tensile Break, 4350 4190
5330 psi Yield, psi 2880 3670 3590 Elongation, % 315 263 289 Flex
Mod, 53.2 76.4 88.3 K psi Shore D 66 67 68 hardness .sup.1DSC
second heat, 10.degree. C./min heating rate. .sup.2samples
compression molded at 150.degree. C. annealed 24 hours at
60.degree. C. 8422-2, -3 were homogenized at 190.degree. C. before
molding.
[0160] In comparing Surlyn.RTM. 8920 to Surlyn.RTM. 8422-2 and
Surlyn.RTM. 8422-3, it is noted that the high acid Surlyn.RTM.
8422-2 and 8422-3 ionomers have a higher tensile yield, lower
elongation, slightly higher Shore D hardness and much higher
flexural modulus. Surlyn.RTM. 8920 contains 15 weight percent
methacrylic acid and is 59% neutralized with sodium.
[0161] In addition, Surlyn.RTM. SEP-503-1 (zinc cation) and
Surlyn.RTM. SEP-503-2 (magnesium cation) are high acid zinc and
magnesium versions of the Surlyn.RTM. AD 8422 high acid ionomers.
When compared to the Surlyn.RTM. AD 8422 high acid ionomers, the
Surlyn SEP-503-1 and SEP-503-2 ionomers can be defined as
follows:
20 TABLE 20 Surlyn .RTM. Ionomer Ion Melt Index Neutralization % AD
8422-3 Na 1.0 45 SEP 503-1 Zn 0.8 38 SEP 503-2 Mg 1.8 43
[0162] Furthermore, Surlyn.RTM. 8162 is a zinc cation ionomer resin
containing approximately 20% by weight (i.e. 18.5 -21.5% weight)
methacrylic acid copolymer that has been 30-70% neutralized.
Surlyn.RTM. 8162 is currently commercially available from
DuPont.
[0163] Examples of the high acid acrylic acid based ionomers
suitable for use in the present invention include the Escor.RTM. or
lotek high acid ethylene acrylic acid ionomers produced by Exxon.
In this regard, Escor.RTM. or lotek 959 is a sodium ion neutralized
ethylene-acrylic acid copolymer. According to Exxon, loteks 959 and
960 contain from about 19.0 to about 21.0% by weight acrylic acid
with approximately 30 to about 70 percent of the acid groups
neutralized with sodium and zinc ions, respectively. The physical
properties of these high acid acrylic acid based ionomers are as
follows:
21 TABLE 21 ESCOR .RTM. ESCOR .RTM. PROPERTY (IOTEK) 959 (IOTEK)
960 Melt Index, g/10 min 2.0 1.8 Cation Sodium Zinc Melting Point,
.degree. F. 172 174 Vicat Softening Point, .degree. F. 130 131
Tensile @ Break, psi 4600 3500 Elongation @ Break, % 325 430
Hardness, Shore D 66 57 Flexural Modulus, psi 66,000 27,000
[0164] Furthermore, as a result of the development by the inventors
of a number of new high acid ionomers neutralized to various
extents by several different types of metal cations, such as by
manganese, lithium, potassium, calcium and nickel cations, several
new high acid ionomers and/or high acid ionomer blends besides
sodium, zinc and magnesium high acid ionomers or ionomer blends are
now available for golf ball cover production. It has been found
that these new cation neutralized high acid ionomer blends produce
cover compositions exhibiting enhanced hardness and resilience due
to synergies which occur during processing. Consequently, the metal
cation neutralized high acid ionomer resins recently produced can
be blended to produce substantially harder covered golf balls
having higher C.O.R.'s than those produced by the low acid ionomer
covers presently commercially available.
[0165] More particularly, several new metal cation neutralized high
acid ionomer resins have been produced by the inventors by
neutralizing, to various extents, high acid copolymers of an
alpha-olefin and an alpha, beta-unsaturated carboxylic acid with a
wide variety of different metal cation salts. This discovery is the
subject matter of U.S. application Ser. No. 901,680, incorporated
herein by reference. It has been found that numerous new metal
cation neutralized high acid ionomer resins can be obtained by
reacting a high acid copolymer (i.e. a copolymer containing greater
than 16% by weight acid, preferably from about 17 to about 25
weight percent acid, and more preferably about 20 weight percent
acid), with a metal cation salt capable of ionizing or neutralizing
the copolymer to the extent desired (i.e. from about 10% to
90%).
[0166] The base copolymer is made up of greater than 16% by weight
of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin.
Optionally, a softening comonomer can be included in the copolymer.
Generally, the alpha-olefin has from 2 to 10 carbon atoms and is
preferably ethylene, and the unsaturated carboxylic acid is a
carboxylic acid having from about 3 to 8 carbons. Examples of such
acids include acrylic acid, methacrylic acid, ethacrylic acid,
chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and
itaconic acid, with acrylic acid being preferred.
[0167] The softening comonomer that can be optionally included in
the invention may be selected from the group consisting of vinyl
esters of aliphatic carboxylic acids wherein the acids have 2 to 10
carbon atoms, vinyl ethers wherein the alkyl groups 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.
[0168] Consequently, examples of a number of copolymers suitable
for use to produce the high acid ionomers included 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, 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.
[0169] Along these lines, examples of the preferred high acid base
copolymers which fulfill the criteria set forth above, are a series
of ethyleneacrylic copolymers which are commercially available from
The Dow Chemical Company, Midland, Mich., under the "Primacor"
designation. These high acid base copolymers exhibit the typical
properties set forth below in Table 22.
22TABLE 22 Typical Properties of Primacor Ethylene-Acrylic Acid
Copolymers MELT TENSILE FLEXURAL VICAT PERCENT DENSITY, INDEX, YD.
ST MODULUS SOFT PT SHORE D GRADE ACID glcc g/10 min (psi) (psi)
(.degree. C.) HARDNESS ASTM D-792 D-1238 D-638 D-790 D-1525 D-2240
5980 20.0 0.958 300.0 -- 4800 43 50 5990 20.0 0.955 1300.0 650 2600
40 42 5990 20.0 0.955 1300.0 650 3200 40 42 5981 20.0 0.960 300.0
900 3200 46 48 5981 20.0 0.960 300.0 900 3200 46 48 5983 20.0 0.958
500.0 850 3100 44 45 5991 20.0 0.953 2600.0 635 2600 38 40
.sup.1The Melt Index values are obtained according to ASTM D-1238,
at 190.degree. C.
[0170] Due to the high molecular weight of the Primacor 5981 grade
of the ethylene-acrylic acid copolymer, this copolymer is the more
preferred grade utilized in the invention.
[0171] The metal cation salts utilized in the invention are 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
lithium, calcium, zinc, sodium, potassium, nickel, magnesium, and
manganese.
[0172] 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, magnesium
acetate. Sources of manganese include manganese acetate and
manganese oxide.
[0173] The new metal cation neutralized high acid ionomer resins
are 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 well known
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%.
[0174] As indicated below in Table 23, more specifically in Example
1 in U.S. application Ser. No. 901,680, a number of new types of
metal cation neutralized high acid ionomers can be obtained from
the above indicated process. These include new high acid ionomer
resins neutralized to various extents with manganese, lithium,
potassium, calcium and nickel cations. In addition, when a high
acid ethylene/acrylic acid copolymer is utilized as the base
copolymer component of the invention and this component is
subsequently neutralized to various extents with the metal cation
salts producing acrylic acid based high acid ionomer resins
neutralized with cations such as sodium, potassium, lithium, zinc,
magnesium, manganese, calcium and nickel, several new cation
neutralized acrylic acid based high acid ionomer resins are
produced.
23TABLE 23 Formulation Wt-% Wt-% Melt Shore D No. Cation Salt
Neutralization Index C.O.R. Hardness 1(NaOH) 6.98 67.5 0.9 .804 71
2(NaOH) 5.66 54.0 2.4 .808 73 3(NaOH) 3.84 35.9 12.2 .812 69
4(NaOH) 2.91 27.0 17.5 .812 (brittle) 5(MnAc) 19.6 71.7 7.5 .809 73
6(MnAc) 23.1 88.3 3.5 .814 77 7(MnAc) 15.3 53.0 7.5 .810 72 8(MnAc)
26.5 106 0.7 .813 (brittle) 9(LiOH) 4.54 71.3 0.6 .810 74 10(LiOH)
3.38 52.5 4.2 .818 72 11(LiOH) 2.34 35.9 18.6 .815 72 12(KOH) 5.30
36.0 19.3 Broke 70 13(KOH) 8.26 57.9 7.18 .804 70 14(KOH) 10.7 77.0
4.3 .801 67 15(ZnAc) 17.9 71.5 0.2 .806 71 16(ZnAc) 13.9 53.0 0.9
.797 69 17(ZnAc) 9.91 36.1 3.4 .793 67 18(MgAc) 17.4 70.7 2.8 .814
74 19(MgAc) 20.6 87.1 1.5 .815 76 20(MgAc) 13.8 53.8 4.1 .814 74
21(CaAc) 13.2 69.2 1.1 .813 74 22(CaAc) 7.12 34.9 10.1 .808 70
Controls: 50/50 Blend of Ioteks 8000/7030 C.O.R. = .810/65 Shore D
Hardness DuPont High Acid Surlyn .RTM. 8422 (Na) C.O.R. = .811/70
Shore D Hardness DuPont High Acid Surlyn .RTM. 8162 (Zn) C.O.R. =
.807/65 Shore D Hardness Exxon High Acid Iotek EX-960 (Zn) C.O.R. =
.796/65 Shore D Hardness Wt-% Wt-% Melt Formulation No. Cation Salt
Neutralization Index C.O.R. 23(MgO) 2.91 53.5 2.5 .813 24(MgO) 3.85
71.5 2.8 .808 25(MgO) 4.76 89.3 1.1 .809 26(MgO) 1.96 35.7 7.5 .815
Control for Formulations 23-26 is 50/50 Iotek 8000/7030, C.O.R. =
.814, Formulation 26 C.O.R. was normalized to that control
accordingly Formulation Wt-% Wt-% Melt Shore D No. Cation Salt
Neutralization Index C.O.R. Hardness 27(NiAc) 13.04 61.1 0.2 .802
71 28(NiAc) 10.71 48.9 0.5 .799 72 29(NiAc) 8.26 36.7 1.8 .796 69
30(NiAc) 5.66 24.4 7.5 .786 64 Control for Formulation Nos. 27-30
is 50/50 Iotek 8000/7030, C.O.R. = .807
[0175] When compared to low acid versions of similar cation
neutralized ionomer resins, the new metal cation neutralized high
acid ionomer resins exhibit enhanced hardness, modulus and
resilience characteristics. These are properties that are
particularly desirable in a number of thermoplastic fields,
including the field of golf ball manufacturing.
[0176] When utilized in golf ball cover construction, it has been
found that the new acrylic acid based high acid ionomers extend the
range of hardness beyond that previously obtainable while
maintaining the beneficial properties (i.e. durability, click,
feel, etc.) of the softer low acid ionomer covered balls, such as
balls produced utilizing the low acid ionomers disclosed in U.S.
Pat. Nos. 4,884,814 and 4,911,451, and the recently produced high
acid blends disclosed in U.S. Pat. No. 5,688,869. Moreover, as a
result of the development of a number of new acrylic acid based
high acid ionomer resins neutralized to various extents by several
different types of metal cations, such as manganese, lithium,
potassium, calcium and nickel cations, several new ionomers or
ionomer blends are now available for golf ball production. By using
these high acid ionomer resins harder, stiffer golf balls having
higher C.O.R.s, and thus longer distance, can be obtained.
[0177] As will be further noted in the Examples below, other
ionomer resins may be used in the cover compositions, such as low
acid ionomer resins, so long as the molded cover produces a Shore D
hardness of 65 or more. Properties of some of these low acid
ionomer resins are provided in the following Table 24:
24TABLE 24 Typical Properties of Low Acid Escor .RTM. (Iotek)
Ionomers Resin ASTM Properties Method Units 4000 4010 8000 8020
Cation type zinc zinc sodium sodium Melt index D-1238 g/ 2.5 1.5
0.8 1.6 10 min. Density D-1505 kg/m.sup.3 963 963 954 960 Melting
Point D-3417 .degree. C. 90 90 90 87.5 Crystallization D-3417
.degree. C. 62 64 56 53 Point Vicat Softening D-1525 .degree. C. 62
63 61 64 Point % Weight 16 -- 11 -- Acrylic Acid % of Acid 30 -- 40
-- Groups Cation Neutralized Plaque Properties (3 mm thick,
compression ASTM molded) Method Units 4000 4010 8000 8020 Tensile
at D-638 MPa 24 26 36 31.5 Break Yield point D-638 MPa none none 21
21 Elongation at D-638 % 395 420 350 410 break 1% Secant D-638 MPa
160 160 300 350 modulus Shore D-2240 -- 55 55 61 58 Hardness D
Resin ASTM Properties Method Units 8030 7010 7020 7030 Cation type
sodium zinc zinc zinc Melt Index D-1238 g/ 2.8 0.8 1.5 2.5 10 min.
Density D-1505 kg/m.sup.3 960 960 960 960 Melting Point D-3417
.degree. C. 87.5 90 90 90 Crystallization D-3417 .degree. C. 55 --
-- -- Point Vicat Softening D-1525 .degree. C. 67 60 63 62.5 Point
% Weight -- -- -- -- Acrylic Acid % of Acid -- -- -- -- Groups
Cation Neutralized Plaque Properties (3 mm thick, compression ASTM
molded) Method Units 8030 7010 7020 7030 Tensile at D-638 MPa 28 38
38 38 Break Yield Point D-638 MPa 23 none none Elongation at D-638
% 395 500 420 395 Break 1% Secant D-638 MPa 390 -- -- -- modulus
Shore Hardness D-2240 -- 59 57 55 55 D
[0178] In addition to the above noted ionomers, compatible additive
materials may also be added to produce the cover compositions of
the present invention. These additive materials include dyes (for
example, Ultramarine Blue sold by Whitaker, Clark, and Daniels of
South Painsfield, N.J.), and pigments, i.e. white pigments such as
titanium dioxide (for example Unitane 0-110) zinc oxide, and zinc
sulfate, as well as fluorescent pigments. As indicated in U.S. Pat.
4,884,814, the amount of pigment and/or dye used in conjunction
with the polymeric cover composition depends on the particular base
ionomer mixture utilized and the particular pigment and/or dye
utilized. The concentration of the pigment in the polymeric cover
composition can be from about 1% to about 10% as based on the
weight of the base ionomer mixture. A more preferred range is from
about 1% to about 5% as based on the weight of the base ionomer
mixture. The most preferred range is from about 1% to about 3% as
based on the weight of the base ionomer mixture. The most preferred
pigment for use in accordance with this invention is titanium
dioxide.
[0179] Moreover, since there are various hues of white, i.e. blue
white, yellow white, etc., trace amounts of blue pigment may be
added to the cover stock composition to impart a blue white
appearance thereto. However, if different hues of the color white
are desired, different pigments can be added to the cover
composition at the amounts necessary to produce the color
desired.
[0180] In addition, it is within the purview of this invention to
add to the cover compositions of this invention compatible
materials which do not affect the basic novel characteristics of
the composition of this invention. Among such materials are
antioxidants (i.e. Santonox R), antistatic agents, stabilizers and
processing aids. The cover compositions of the present invention
may also contain softening agents, such as plasticizers, etc., and
reinforcing materials such as glass fibers and inorganic fillers,
as long as the desired properties produced by the golf ball covers
of the invention are not impaired.
[0181] Furthermore, optical brighteners, such as those disclosed in
U.S. Pat. No. 4,679,795, may also be included in the cover
composition of the invention. Examples of suitable optical
brighteners which can be used in accordance with this invention are
Uvitex OB as sold by the Ciba-Geigy Chemical Company, Ardsley, N.Y.
Uvitex OB is thought to be
2,5-Bis(5-tert-butyl-2-benzoxazoly)thiophene. Examples of other
optical brighteners suitable for use in accordance with this
invention are as follows: Leucopure EGM as sold by Sandoz, East
Hanover, N.J. 07936. Leucopure EGM is thought to be
7-(2n-naphthol(1,2-d)-triazol-2yl)-3phenyl- -coumarin. Phorwhite
K-20G2 is sold by Mobay Chemical Corporation, P.O. Box 385, Union
Metro Park, Union, N.J. 07083, and is thought to be a pyrazoline
derivative, Eastobrite OB-1 as sold by Eastman Chemical Products,
Inc. Kingsport, Tenn., is thought to be 4,4-Bis(-benzoxaczoly)s-
tilbene. The above-mentioned Uvitex and Eastobrite OB-1 are
preferred optical brighteners for use in accordance with this
invention.
[0182] Moreover, since many optical brighteners are colored, the
percentage of optical brighteners utilized must not be excessive in
order to prevent the optical brightener from functioning as a
pigment or dye in its own right.
[0183] The percentage of optical brighteners which can be used in
accordance with this invention is from about 0.01% to about 0.5% as
based on the weight of the polymer used as a cover stock. A more
preferred range is from about 0.05% to about 0.25% with the most
preferred range from about 0.10% to about 0.020% depending on the
optical properties of the particular optical brightener used and
the polymeric environment in which it is a part.
[0184] Generally, the additives are admixed with a ionomer to be
used in the cover composition to provide a masterbatch (M.B.) of
desired concentration and an amount of the masterbatch sufficient
to provide the desired amounts of additive is then admixed with the
copolymer blends.
[0185] The above cover compositions, when processed according to
the parameters set forth below and combined with soft cores at
thicknesses defined herein to produce covers having a Shore D
hardness of 65, provide golf balls with reduced spin rates. It is
noted, however, that the high acid ionomer resins provide for more
significant reduction in spin rate than that observed for the low
acid ionomer resins.
[0186] The cover compositions and molded balls of the present
invention may be produced according to conventional melt blending
procedures. In this regard, the ionomeric resins are blended along
with the masterbatch containing the desired additives in a Banbury
type mixer, two-roll mill, or extruded prior to molding. The
blended composition is then formed into slabs or pellets, etc. and
maintained in such a state until molding is desired. Alternatively
a simple dry blend of the pelletized or granulated resins and color
masterbatch may be prepared and fed directly into the injection
molding machine where homogenization occurs in the mixing section
of the barrel prior to injection into the mold. If necessary,
further additives such as an inorganic filler, etc., may be added
and uniformly mixed before initiation of the molding process.
[0187] Moreover, golf balls of the present invention can be
produced by molding processes currently well known in the golf ball
art. Specifically, the golf balls can be produced by injection
molding or compression molding the novel cover compositions about
the soft polybutadiene cores to produce a golf ball having a
diameter of about 1.680 inches or greater and weighing about 1.620
ounces. In an additional embodiment of the invention, larger molds
are utilized to produce the thicker covered oversized golf balls.
As indicated, the golf balls of the present invention can be
produced by forming covers consisting of the compositions of the
invention around the softer polybutadiene cores by conventional
molding processes. For example, in compression molding, the cover
composition is formed via injection at about 380.degree. F. to
about 450.degree. F. into smooth surfaced hemispherical shells
which are then positioned around the core in a dimpled golf ball
mold and subjected to compression molding at 200-300.degree. F. for
2-10 minutes, followed by cooling at 50-70.degree. F. for 2-10
minutes, to fuse the shells together to form an unitary ball. In
addition, the golf balls may be produced by injection molding,
wherein the cover composition is injected directly around the core
placed in the center of a golf ball mold for a period of time at a
mold temperature of from 50.degree. F. to about 100.degree. F.
After molding the golf balls produced may undergo various further
finishing steps such as buffing, painting, and marking as disclosed
in U.S. Pat. No. 4,911,451.
[0188] The invention has been described with reference to the
preferred embodiment. Obviously, modifications and alterations will
occur to others upon a reading and understanding of the preceding
detailed description. It is intended that the invention be
construed as including all such alterations and modifications
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *