U.S. patent application number 13/759588 was filed with the patent office on 2013-08-22 for golf ball.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD.. The applicant listed for this patent is BRIDGESTONE SPORTS CO., LTD.. Invention is credited to Atsushi KOMATSU, Hiroshi NASU, Yuichiro OZAWA.
Application Number | 20130217516 13/759588 |
Document ID | / |
Family ID | 48982696 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130217516 |
Kind Code |
A1 |
KOMATSU; Atsushi ; et
al. |
August 22, 2013 |
GOLF BALL
Abstract
A golf ball of the present invention includes: a core located in
the center of the golf ball; a cover which surrounds the outside of
the core and has a plurality of dimples on the surface thereof; and
a coating layer located between the core and the cover. The coating
layer is formed of a material having rubber elasticity. The .mu.
hardness of the golf ball is preferred to be approximately 3.0 or
more and the cover is preferred to have a hardness of approximately
50 or more in terms of Shore D hardness. The intermediate layer is
preferred to have a hardness of approximately 40 to approximately
65 in terms of Shore D hardness, and the hardness of the cover is
preferred to be higher than the hardness of the intermediate
layer.
Inventors: |
KOMATSU; Atsushi;
(Chichibu-shi, JP) ; OZAWA; Yuichiro;
(Chichibu-shi, JP) ; NASU; Hiroshi; (Shinagawa-ku,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BRIDGESTONE SPORTS CO., LTD.; |
|
|
US |
|
|
Assignee: |
BRIDGESTONE SPORTS CO.,
LTD.
Tokyo
JP
|
Family ID: |
48982696 |
Appl. No.: |
13/759588 |
Filed: |
February 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13328506 |
Dec 16, 2011 |
|
|
|
13759588 |
|
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|
Current U.S.
Class: |
473/374 |
Current CPC
Class: |
A63B 37/0003 20130101;
A63B 37/0033 20130101; A63B 37/0062 20130101; A63B 37/0075
20130101; A63B 37/0095 20130101; A63B 37/0074 20130101; A63B
37/0045 20130101; A63B 37/0092 20130101; A63B 37/0043 20130101;
A63B 37/0064 20130101; A63B 37/0031 20130101; A63B 37/0049
20130101; A63B 37/004 20130101 |
Class at
Publication: |
473/374 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Claims
1. A golf ball comprising: a core located in a center of the golf
ball; a cover that surrounds an outside of the core and has a
plurality of dimples on the surface thereof; and a coating layer
located between the core and the cover, the coating layer being
formed of a material having rubber elasticity.
2. The golf ball according to claim 1, further comprising an
intermediate layer located between the core and the cover, wherein
the coating layer is located between the core and the intermediate
layer or between the intermediate layer and the cover.
3. The golf ball according to claim 1, wherein the golf ball has a
.mu. hardness of at least 3.0, and wherein the cover has a hardness
of at least approximately 50 in terms of Shore D hardness.
4. The golf ball according to claim 2, wherein the intermediate
layer has a hardness of approximately 40 to 65 in terms of Shore D
hardness and the hardness of the cover is higher than the hardness
of the intermediate layer.
5. The golf ball according to claim 1, wherein the coating layer
has a thickness of approximately 10 to approximately 150 .mu.m.
6. The golf ball according to claim 1, wherein a material used for
forming the coating layer has a Young's modulus of approximately 70
MPa.
7. The golf ball according to claim 1, wherein the material used
for forming the coating layer has a Poisson's ratio of at least
approximately 0.45.
8. The golf ball according to claim 1, wherein the coating layer
has a hardness of at most approximately 70 in terms of JIS-C
hardness.
9. The golf ball according to claim 1, wherein the cover comprises
ionomer resin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims the benefits of U.S. patent
application Ser. No. 13/328,506 filed Dec. 16, 2011, U.S. patent
application Ser. No. 13/409,994 filed Mar. 1, 2012, and U.S. patent
application Ser. No. 13/410,012 filed Mar. 1, 2012.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a golf ball, and more
particularly, relates to a golf ball containing a soft coating
layer internally.
[0003] Usually, the surface of the golf ball is provided with a
coating layer. The coating layer is demanded to have performances
in appearance such as color tone, impact resistance and abrasion
resistance. Japanese Patent Application Publication No. 8-206255
has disclosed a golf ball having a coating layer formed of coating
material composition including acrylic polyol, polyester polyol and
hardening agent in order to improve its impact resistance and
abrasion resistance.
[0004] A high-performance golf ball has a small spin amount when it
is hit with a driver, thereby increasing a flying distance. When
the ball is hit for approach, its spin amount is increased to
secure an excellent controllability around the green. To improve
the above-described performance, Japanese Patent Application
Publication No. 9-276446 has disclosed an idea that by using two
coating layers, an inside layer is formed as a white coating film
of thermoplastic resin by dispersion coating, and the outside layer
is formed of transparent coating film of thermoplastic resin by
dispersion coating.
[0005] Furthermore, Japanese Patent Application Publication No.
2001-000585 has disclosed a golf ball having an adhesive layer
formed of epoxy resin adhesive, urethane resin adhesive, vinyl
resin adhesive or rubber adhesive, between an intermediate layer
and a cover. This publication has stated that the golf ball having
such adhesive layer ensures a high resilience property and the spin
performance in an iron shot is excellent.
[0006] Japanese Patent Application Publication No. 11-137725 has
disclosed a golf ball in which of its intermediate layer and cover,
one is formed of ionomer resin and the other is formed of urethane
resin and that an adhesive layer is formed between the inside layer
cover and the outside layer cover. This publication stated that the
golf ball having such a configuration has resistance to repeated
impacts and that it has a large spin amount when hit for approach
while the spin amount in a driver shot is small.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to improve the
above-described conventional technologies and provide a golf ball
capable of increasing the spin amount when hit with a driver while
holding the spin amount when hit for approach, this golf ball
ensuring an excellent durability.
[0008] The golf ball of the present invention includes: a core
located in the center of the golf ball; a cover which surrounds the
outside of the core and has a plurality of dimples on the surface
thereof; and a coating layer located between the core and the
cover, the coating layer being formed of a material having rubber
elasticity. The golf ball of the present invention may further
include an intermediate layer located between the core and the
cover and the coating layer is located between the core and the
intermediate layer or between the intermediate layer and the cover.
According to a simulation performed by the inventor of the present
invention, it has been found that provision of the coating layer
having rubber elasticity inside of the golf ball allows the spin
amount when the ball is hit with a driver to be increased while
maintaining the spin amount upon an approach shot on a current
level.
[0009] Generally, a golfer having a low head speed tends to apply a
low spin to the golf ball when it is hit with a driver so that
flight distance may be lost. The golfer having such a low head
speed tends to like soft balls. However, because the soft ball is
structured not to spin well when it is hit by an approach shot, the
ball is not spun even when it is hit with a driver. A .mu. hardness
of the ball of approximately 3.0 or more is in a range which makes
the ball to be spun low when it is hit with a driver, and amateur
golfers like such a hardness range. A ball of which Shore D
hardness is approximately 50 or more is structured to be spun low
when it is hit with a driver. However, golfers who wish to roll a
ball upon an approach shot like such a ball. Even the golf ball
having such a hardness is capable of increasing the spin amount
when it is hit with a driver by providing the coating layer of
material having rubber elasticity inside of the ball.
[0010] If any intermediate layer is provided, preferably, the
intermediate layer has a hardness of approximately 40 to 65 in
terms of Shore D hardness and the hardness of the cover is higher
than the hardness of the intermediate layer. Usually, although the
durability of the golf ball is determined by its cover, provision
of the coating layer having a low hardness and additionally the
intermediate layer under the cover relaxes a shock on the cover
thereby leading to improvement of the durability.
[0011] The coating layer may have a thickness of approximately 10
to approximately 150 .mu.m. The material for forming the coating
layer may have a Young's modulus of approximately 70 MPa. The
material for forming the coating layer may have a Poisson's ratio
of approximately 0.45 or more. The coating layer may have a
hardness of approximately 70 or less in terms of JIS-C hardness.
The cover may contain ionomer resin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan sectional view showing an embodiment of a
golf ball according to the present invention.
[0013] FIG. 2 is a plan sectional view showing another embodiment
of the golf ball according to the present invention.
[0014] FIG. 3 is a plan sectional view showing still another
embodiment of the golf ball according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Hereinafter, embodiments of a golf ball according to the
present invention will be described with reference to the
accompanying drawings. However, the present invention is not
restricted to these embodiments. In the meantime, the accompanying
drawings are drawn mainly to facilitate understanding of the
present invention, but they are not drawn to scale.
[0016] As shown in FIG. 1, the golf ball 1 of the present
embodiment mainly includes a core 10 located in the center of the
ball, a cover 30 surrounding the outside of the core and a coating
layer 40 located between the core and the cover. Plural dimples 32
are formed on the surface of the cover 30. The coating layer 40
covers the surface of the core 10 with a substantially equal
thickness.
[0017] In addition, the golf ball of the present invention is not
limited to the structure shown in FIG. 1, but may be as shown in
FIG. 2 or 3, it may have arbitrary freely chosen intermediate layer
20 between the cover 10 and the cover 30. Although in FIG. 1, the
coating layer 40 is formed to make direct contact with both the
core 10 and the cover 30, the coating layer 40 may be formed
between the core 10 and the intermediate layer 20 as shown in FIG.
2, or between the intermediate layer 20 and the cover 30, as shown
in FIG. 3.
[0018] The core 10 may be formed mainly of base rubber. As the base
rubber, a variety of rubbers (thermoplastic elastomer) may be used,
such as polybutadiene rubber (BR), styrene-butadiene rubber (SBR),
natural rubber (NR), polyisoprene rubber (IR), polyurethane rubber
(PU), butyl rubber (IIR), vinyl polybutadiene rubber (VBR),
ethylene-propylene rubber (EPDM), nitrile rubber (NBR), silicone
rubber; however the present invention is not restricted to these
materials. As the polybutadiene rubber (BR), for example,
1,2-polybutadiene, cis-1,4-polybutadiene and the like may be
used.
[0019] As well as the base rubber which is a main component, for
example, co-cross linking agent, cross linking agent, filler, age
resistor, isomerization agent, peptizing agent, sulfur and organic
sulfur compound may be added to the core 10. As the main component,
thermoplastic elastomer, ionomer resin or a mixture of these
components may be used instead of the base rubber.
[0020] As the co-cross linking agent, it is preferable to use, for
example, .alpha.,.beta.-unsaturated carboxylic acid or its metallic
salt, although it is not restricted to these materials. As the
.alpha.,.beta.-unsaturated carboxylic acid or its metallic salt,
for example, acrylic acid, methacrylic acid, and zinc salt,
magnesium salt and calcium salt of these substances are available.
Although the composition of the co-cross-linking agent is not
limited to this example, for example, assuming that the base rubber
is 100 parts by weight, it is preferred to be approximately 5 parts
or more by weight and is more preferred to be approximately 10
parts or more by weight. Furthermore, the composition of the
co-cross-linking agent is preferred to be approximately 70 parts or
less by weight and is more preferred to be approximately 50 parts
or less by weight.
[0021] As the cross-linking agent, it is preferred to use an
organic peroxide, although this is not restricted to this
substance. Assuming that the base rubber is 100 parts by weight,
the composition of an initiator is preferred to be approximately
0.10 parts by weight, is more preferred to be approximately 0.15
parts by weight, and is further preferred to be approximately 0.30
parts by weight, although it is not restricted to these values. The
composition of the initiator is preferred to be approximately 8
parts or less by weight and is more preferred to be approximately 6
parts or less by weight.
[0022] Although, as the filler, for example, silver, gold, cobalt,
chrome, copper, germanium, manganese, molybdenum, nickel, lead,
platinum, tin, titanium, tungsten, zinc, zirconium, barium sulfate,
zinc oxide, and manganese oxide may be used, it is not restricted
to these substances. The filler is preferred to be in a form of
powder. Assuming that the base rubber is 100 parts by weight, the
composition of the filler is preferred to be approximately 1 part
or more by weight, is more preferred to be approximately 2 parts or
more by weight and is further preferred to be approximately 3 parts
or more by weight. Furthermore, the composition of the filler is
preferred to be approximately 100 parts or less by weight, is more
preferred to be approximately 80 parts or less by weight, and is
further preferred to be approximately 70 parts or less by
weight.
[0023] The core 10 is substantially spherical. The outside diameter
of the core 10 is preferred to be approximately 42 mm or less, is
more preferred to be approximately 41 mm or less, and is further
preferred to be approximately 40 mm or less. Because if the outside
diameter of the core is too small, the resiliency of the golf ball
is decreased, it is preferred to be approximately 5 mm or more, is
more preferred to be approximately 15 mm or more, and is further
preferred to be approximately 25 mm or more. Although the core 10
shown in FIG. 1 is solid, the core is not restricted to this
example, but may be hollow. Although the core 10 shown in FIG. 1 is
of a single layer, the core is not restricted to this example, but
may be constituted of plural layers, which may include, for
example, a center core and surrounding layers.
[0024] As the forming method of the core 10, any known forming
method for the core of the golf ball may be adopted. For example,
the core may be obtained by kneading materials including the base
rubber with a kneading machine and vulcanizing the kneaded
materials under a pressure with a round mold. As a method for
forming a core having plural layers, it is permissible to adopt a
known forming method for the multi-layered solid-core. For example,
materials are kneaded with the kneading machine and then, the
center core is obtained by vulcanizing the kneaded materials under
a pressure with a round mold. After that, for the surrounding
layers, again, materials are kneaded with the kneading machine and
the kneaded materials are formed into a sheet. Then, the center
core is covered with this sheet and vulcanized under a pressure
with the round mold to obtain a multi-layered core.
[0025] The cover 30 may be formed using ionomer resin, polyurethane
thermoplastic elastomer, thermoplastic polyurethane or a mixture of
these substances although the material thereof is not restricted
thereto. Furthermore, as well as the aforementioned ionomer resin,
polyurethane thermoplastic elastomer, and thermoplastic
polyurethane which serve as a main component, other thermoplastic
elastomer, polyisocyanate compound, fatty acid or its derivative,
basic inorganic metal compound or filler may be added to the cover
30.
[0026] As the ionomer resin, following resins containing a
component (a) and/or a component (b) may be used as base resin,
although it is not restricted to these substances. Furthermore, a
following component (c) may be added to this base resin freely. The
component (a) is olefin-unsaturated carboxylic acid-unsaturated
carboxylic ester random terpolymer and/or its metallic salt. The
component (b) is olefin-unsaturated carboxylic acid random
copolymer and/or its metallic salt. The component (c) is
thermoplastic block copolymer having polyolefin crystalline block
and polyethylene/butylene random copolymer.
[0027] The thickness of the cover 30 is preferred to be
approximately 0.2 mm or more, and is more preferred to be
approximately 0.4 mm or more, although it is not restricted to
these values. Furthermore, the thickness of the cover 30 is
preferred to be approximately 4 mm or less, is more preferred to be
approximately 3 mm or less and is further preferred to be
approximately 2 mm or less. Plural dimples 32 are formed on the
surface of the cover 30. The size, shape and quantity of the
dimples 30 may be designed appropriately corresponding to a desired
aerodynamic characteristic of the golf ball 1.
[0028] The hardness of the cover 30 is preferred to be
approximately 50 or more in terms of Shore D hardness, and is more
preferred to be approximately 55, although it is not restricted to
this example. Additionally, the hardness of the cover 30 is
preferred to be approximately 75 or less, is more preferred to be
approximately 70 or less and is further preferred to be
approximately 65 or less.
[0029] To form the cover 30, any known forming method for the cover
of the golf ball may be adopted. For example, the cover 30 is
formed by injection-molding a material for the cover into a mold,
although the forming method is not restricted to any particular
one. The mold for forming the cover has cavities for molding the
cover, and this cavity has plural projections for forming the
dimples on the wall surface thereof. By disposing the core 10 in
the center of the cavity, the cover 30 is formed such that it
surrounds the core 10.
[0030] The coating layer 40 is formed of a material having rubber
elasticity. The Young's modulus of the material having rubber
elasticity is preferred to be approximately 0.1 MPa or more, is
more preferred to be approximately 1 MPa or more, and is further
preferred to be approximately 3 MPa or more, although the material
for use is not restricted to these materials. Furthermore, the
Young's modulus of the material is preferred to be approximately 70
MPa or less, is more preferred to be approximately 65 MPa or less,
and is further preferred to be approximately 60 MPa or less. The
Poisson's ratio of the material having rubber elasticity is
preferred to be approximately 0.45 or more, is more preferred to be
approximately 0.46 or more and is further preferred to be
approximately 0.47 or more, although the material for use is not
restricted to these materials. Furthermore, the Poisson's ratio of
the material is preferred to be approximately 0.60 or less, is more
preferred to be approximately 0.55 or less, and is further
preferred to be approximately 0.50 or less. Unless the Young's
modulus and the Poisson's ratio are within the above-mentioned
ranges, a coating layer 40 may not ensure a sufficient plasticity
or friction force.
[0031] Regarding a material having such rubber elasticity,
according to, for example, a classification of JIS K6397, as an
M-group (rubbers having polymethylene type saturated main chain),
ACM (acrylic rubber or rubber-like copolymer formed of ethyl
acrylate or other acrylic ester with a small amount of monomer
allowing vulcanization), AEM (rubber-like copolymer formed of ethyl
acrylate or acrylic ester with ethylene), ANM (rubber-like
copolymer formed of ethyl acrylate or acrylic ester with
acrylonitrile), CM (polyethylene chloride), CSM (chlorosulfonated
polyethylene, trade name: Hypalon), EPDM (rubber-like copolymer
formed of ethylene, propylene and diene. Called EPT also), EPM
(rubber-like copolymer formed of ethylene and propylene. Called EPR
also), and EVM (rubber-like copolymer formed of ethylene and vinyl
acetate) polymers may be used.
[0032] As an O group (rubber having carbon and oxygen as main
chain), polymers such as CO (called epichlorohydrin rubber or
polychloromethyl oxirane also) and ECO (rubber-like copolymer
formed of ethylene oxide and Epichlorohydrin) may be used.
[0033] As an R group (rubber having unsaturated carbon bonds in the
main chain), BR (butadiene rubber), CR (chloroprene rubber, Trade
name: neoprene), IIR (butyl rubber or rubber-like copolymer formed
of isobutene and isoprene), IR (synthetic natural rubber or
isoprene rubber), NBR (nitrile rubber or rubber-like copolymer
formed of acrylonitril and butadiene), NR (natural rubber), NOR
(polynorbornene rubber), SBR (rubber-like copolymer formed of
styrene and butadiene), E-SBR (rubber-like copolymer formed of
styrene and butadiene by emulsion polymerization), S-SBR
(rubber-like copolymer formed of styrene and butadiene by solution
polymerization), SIBR (rubber-like copolymer formed of styrene,
isoprene and butadiene), XBR (carboxylated butadiene rubber), XCR
(carboxylated chloroprene rubber), XNBR (carboxylated rubber-like
copolymer formed of acrylonitril and butadiene), XSBR (carboxylated
rubber-like copolymer formed of styrene and butadiene), BIIR
(brominated butyl rubber or rubber-like copolymer formed of
brominated isobutene and isoprene), CIIR (chlorinated butyl rubber
or rubber-like copolymer formed of chlorinated isobutene and
isoprene) may be used.
[0034] The thickness of the coating layer 40 is preferred to be
approximately 10 .mu.m or more and more preferred to be
approximately 30 .mu.m or more, and is further preferred to be
approximately 50 .mu.m or more, although it is not always
restricted to these values. Furthermore, the thickness of the
coating layer 40 is preferred to be approximately 150 .mu.m or less
and is more preferred to be approximately 120 .mu.m or less, and is
further preferred to be approximately 100 .mu.m. If the thickness
of the coating layer is too small, the spin amount upon a driver
shot cannot be increased sufficiently. If the thickness of the
coating layer is too great, the durability of the golf ball
sometimes can decline.
[0035] The hardness of the coating layer 40 is preferred to be
approximately 10 or more in terms of JIS-C hardness, is more
preferred to be approximately 20 or more, and is further preferred
to be approximately 30 or more, although it is not restricted to
these values. Furthermore, the hardness of the coating layer 40 is
preferred to be approximately 70 or less, is more preferred to be
approximately 60 or less, and is further preferred to be
approximately 50 or less. In particular, the hardness of the
coating layer 40 is preferred to be lower than that of the core 10.
Furthermore, the core 10 may be formed such that its hardness is
increased gradually from the center of the core to the surface of
the core. By forming a golf ball so that the hardness thereof
increases gradually from the core center toward the surface, the
driver spin can be reduced to increase the flying distance. Here,
the hardness of the coating layer 40 is preferred to be lower than
the hardness of the center of the core and more preferred to be
lower by approximately 10 or more. If the hardness of the coating
layer 40 is higher than the hardness of the center of the core, no
appropriate spin may be obtained.
[0036] The .mu. hardness of a golf ball product 1 is preferred to
be approximately 3.0 or more, more preferred to be approximately
3.2 or more, and is further preferred to be approximately 3.5 or
more. The upper limit thereof is preferred to be approximately 5.0
or less and is more preferred to be approximately 4.5 or less. The
.mu. hardness of the product refers to an amount of deflection
(deformation) when the golf ball product 1 is loaded with an
initial load of 98 N (10 kgf) up to 1,275 N (130 kgf) while the
unit is expressed in mm. If the .mu. hardness of the product is
increased too much, an amateur golfer's feeling upon hitting the
golf ball becomes too stiff, which may be undesirable.
[0037] As a formation method for the coating layer 40, any known
formation method for the coating layer of the golf ball may be
adopted even if the coating layer 40 is formed on the surface of
the core 10 or the intermediate layer 20. For example, for the
coating layer 40, a liquid coating material can be obtained by
diluting material having the above-described rubber elasticity with
solvent, although it is not restricted to any particular material.
As the solvent, n-pentane, gasoline, n-hexane, diethyl ether,
cyclohexane, isobutyl acetate, butyl acetate, isopropyl acetate,
methyl isopropyl ketone, xylene tetrachloride, methyl propyl
ketone, ethyl benzene, xylene, toluene, ethyl acetate,
tetrahydrofuran, benzene, chloroform, methyl ethyl ketone,
trichloroethylene, acetone, n-hexanol and the like may be used,
although this is not restricted to any particular type. The
dilution rate (concentration of coating polymer) may be
approximately 5% to approximately 100% although this is not
restricted to any particular value.
[0038] After coating the surface of the core 10 or the intermediate
layer 20 with this coating material, the coating layer 40 may be
formed by a cross-linking process. The coating method is not
restricted to any particular one, but any coating material may be
applied by a spraying method, dipping method, rolling method or
spin method. Although the cross-linking method is not restricted to
any particular type, it is preferable to add a cross-linking agent
or a hardening agent to the above-mentioned coating material, so
that, after the coating material is applied, cross-linking or
hardening is induced. As the cross-linking agent or the hardening
agent, cross-linking with, for example, peroxide, metal, amine,
oxime, resin, or sulfur is preferable to obtain the coating layer
40 having a sufficient impact resilience. Furthermore, as well as
the cross-linking agent and the hardening agent, a filler may be
freely added to the coating material. Even material difficult to
cross-link may be applied by dispersing the material having a long
molecular chain in solvent, and even if no cross-linking agent is
used, the molecular chains tangle with each other to produce
coating material having rubber elasticity.
[0039] A top coat (not shown) may be freely formed on the cover 30.
As the top coat material, any known material suitable for the top
coat of the golf ball may be used. As the material, polyester
polyol or acrylic polyol may be used and fixed with a hardening
agent. For example, two-liquid type curable urethane coating
material may be mentioned, and particularly, it is preferable to
use a non-yellowing type coating material. The thickness of the top
coat is preferred to be, for example, approximately 5 .mu.m or more
and is more preferred to be approximately 10 .mu.m or more.
Furthermore, the thickness of the top coat is preferred to be
approximately 100 .mu.m or less and is more preferred to be
approximately 60 .mu.m or less.
[0040] The intermediate layer 20 disposed between the core 10 and
the cover 30 is not indispensable, but it may be freely provided.
It is permissible to provide an intermediate layer which functions
as a core or a cover. Furthermore, it is also permissible to
provide plural intermediate layers, for example, plural
intermediate layers which function as the core or the cover, or a
first intermediate layer that functions as the core with a second
intermediate layer that functions as the cover.
[0041] For materials of the intermediate layer 20, the following
heated mixture is preferably used, as the main material, but the
materials are not limited thereto. Using the following mixture for
the intermediate layer can lower the spin rate of the hit ball, and
thus, long distance can be achieved.
(a) at least one of olefin-unsaturated carboxylic acid random
copolymer and a metal ion neutralizing material of
olefin-unsaturated carboxylic acid random copolymer, (b) at least
one of olefin-unsaturated carboxylic acid-unsaturated carboxylic
acid ester random terpolymer and a metal ion neutralizing material
of olefin-unsaturated carboxylic acid-unsaturated carboxylic acid
ester random terpolymer, (c) at least one of fatty acid having a
molecular weight of 228 to 1500 and its derivative, (d) basic
inorganic metallic compound capable of neutralizing an
unneutralized acid group in components (a) to (c), and (e)
non-ionomer thermoplastic elastomer, wherein a base resin contains
component (a) and component (b) which are mixed in a ratio of 100:0
to 0:100 by weight, wherein the base resin and component (e) are
mixed in a ratio of 100:0 to 50:50 by weight, and wherein 5 to 150
parts by weight of component (c) and 0.1 to 17 parts by weight of
component (d) are added to the resin component containing the base
resin and component (e) with respect to 100 parts by weight of the
resin component.
[0042] The "main material" mentioned here means a material which
has approximately 50 weight % or more with respect to the total
weight of the intermediate layer 20, preferably approximately 60
weight % or more and more preferably approximately 70 weight % or
more.
[0043] The hardness of the intermediate layer 20 is preferred to be
approximately 40 or more in terms of Shore D hardness, more
preferred to be approximately 45 or more and is further preferred
to be approximately 50 or more. The hardness of the intermediate
layer 20 is preferred to be lower than the hardness of the cover
30, and is particularly preferred to be approximately 65 or less in
terms of Shore D hardness and is more preferred to be approximately
60 or less.
[0044] The thickness of the intermediate layer 20 is preferred to
be approximately 0.5 mm or more and is more preferred to be
approximately 1 mm or more, although it is not restricted to these
values. Furthermore, the thickness of the intermediate layer 20 is
preferred to be approximately 10 mm or less, is more preferred to
be approximately 5 mm or less and is further preferred to be
approximately 3 mm or less. Although the intermediate layer 20 is
represented in a single layer in FIG. 1, it is not limited to this
example and it may be of plural layers, i.e., two layers or
more.
Example
[0045] Golf balls having each configuration shown in Table 1 were
manufactured, and then tests for measuring the spin performance of
each golf ball were performed. In each test case, five balls were
prepared and evaluated. Table 1 shows a test result indicating each
average of the five balls. Table 2 shows compositions A1 and A2 of
the core material shown in Table 1 (in parts by weight). Table 3
shows compositions B to D of the cover and intermediate layer
materials (in parts by weight). Table 4 shows a composition E of
the coating layer material (in parts by weight). In the meantime,
the coating layer was formed by diluting a material having a
predetermined composition by 30% to 50% using toluene and spraying
the diluted material.
TABLE-US-00001 TABLE 1 Example Comparative example 1 2 3 4 5 6 7 8
1 2 3 Core Outside diameter (mm) 37.1 37.1 37.3 37.1 37.1 37.3 37.1
37.1 37.3 37.3 37.1 Composition A1 A2 A2 A1 A2 A2 A2 A2 A1 A2 A2
Coating layer Thickness (.mu.m) -- -- -- 100 100 20 -- 100 -- -- --
Young's modulus (MPa) -- -- -- 12 12 12 -- 12 -- -- -- Composition
-- -- -- E E E -- E -- -- -- Intermediate Thickness (mm) 1.45 1.45
1.45 1.45 1.45 1.45 1.45 1.45 1.45 1.45 1.45 layer Shore D hardness
51 51 51 51 51 51 51 51 51 51 51 Composition D D D D D D D D D D D
Coating layer Thickness (.mu.m) 100 100 20 -- -- -- 100 -- -- -- --
Young's modulus (MPa) 12 12 12 -- -- -- 12 -- -- -- -- Composition
E E E -- -- -- E -- -- -- -- Cover Thickness (mm) 1.25 1.25 1.25
1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 Shore D hardness 63 63 63
63 63 63 58 58 63 63 58 Composition B B B B B B C C B B C Product
.mu. hardness 3.1 4.0 4.0 3.1 4.0 4.0 4.2 4.2 3.1 4.0 4.2 Spin
Driver 2220 2130 2080 2210 2110 2150 2420 2410 2080 1970 2300
performance Approach 4400 4600 4600 4400 4600 4600 5200 5200 4400
4600 5200 COR durability (times) 160 135 140 115 115 120 210 190
140 100 180
TABLE-US-00002 TABLE 2 Composition of core A1 A2 Polybutadiene 100
100 Zinc acrylate 21.0 15.0 Peroxide 1 0.6 0.6 Peroxide 2 0.6 0.6
Anti-aging agent 0.1 0.1 Zinc oxide 30.0 32.3 Core hardness Center
(JIS-C) 58 53 Surface (JIS-C) 72 65 Vulcanization Temperature (C.
.degree.) 155 155 method Time (h) 15 15
[0046] As polybutadiene, BR01 manufactured by JSR was used as base
rubber. As zinc acrylate, WN86 manufactured by Nippon Shokubai was
used. As peroxide 1, dicumylperoxide manufactured by NOF
Corporation was used, the product name of which is Percumyl D. As
peroxide 2, a mixture of 1,1 di(t-butylperoxy) cyclohexane and
silica, manufactured by NOF was used, the product name of which is
Perhexa C-40. This product was used as an initiator. As anti-aging
agent, 2,2'-methylenebis(4-methyl-6-t-butylphenol), manufactured by
Ouchi Shinko Kagaku was used, the product name of which is Nocrac
NS-6. As zinc oxide, a product manufactured by Sakai Kagaku Kogyo
was used, the product name of which is Zinc Oxide Grade 3.
TABLE-US-00003 TABLE 3 Composition of cover B C D Himilan 1557 --
42.5 -- Himilan 1605 40 -- -- Himilan 1706 50 -- -- Himilan 1601 10
42.5 -- AN4318 -- 15 AN4319 -- -- 100 Magnesium stearate -- -- 70
Magnesium oxide -- -- 1.9 TiO.sub.2 3 3 -- Blue 0.04 0.04 --
[0047] Himilan 1557 is an ionomer resin of Zn-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical.
Himilan 1605 is an ionomer resin of Na-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Himilan 1706 is an ionomer resin of Zn-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Himilan 1601 is an ionomer resin of Na-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. AN4318 is olefin-unsaturated carboxylic acid-unsaturated
carboxylic ester terpolymer manufactured by Mitsui DuPont Chemical.
AN4319 is olefin-unsaturated carboxylic acid-unsaturated carboxylic
ester terpolymer manufactured by Mitsui DuPont Chemical. TiO.sub.2
is Taipak R550 manufactured by ISHIHARA SANGYO KAISHA LTD. Blue is
a product EP-62 manufactured by Holiday Pigments.
TABLE-US-00004 TABLE 4 Composition of coating layer E Main material
Oil Proto 100 Young's modulus (MPa) 12 Poison's ratio 0.495
Hardness (JIS-C) 43.5
[0048] The Oil Proto is a product name of a Hagitec product, which
is produced of SBR resin as its main component. The detailed
composition thereof includes gasoline (naphtha) of 33 to 37%,
hexane of 13 to 16%, xylene of 15 to 19%, acetone of 8 to 10% and
SBR resin of 24 to 28%.
[0049] In tests for measurement of the spin performance shown in
Table 1, with a driver (Tour Stage X-Drive Type 455 9.5.degree.
manufactured by Bridgestone) and an approach wedge (Tour Stage
X-WEDGE 58.degree. manufactured by Bridgestone) mounted on a swing
robot (manufactured by Miyamae), a golf ball was hit at a head
speed of 45 m/s for the driver, and at a head speed of 25 m/s for
the approach, and the ball just after it was hit was photographed
with a high-speed camera to measure its spin amount (rpm).
[0050] In COR durability measurement test shown in Table 1, an ADC
ball COR Durability Tester Machine manufactured by Automated Design
Corporation in US was used to evaluate the durability of a golf
ball. This tester machine has a function of shooting a golf ball
with pneumatic pressure and striking it against two metallic sheets
placed in parallel. An average of times of shoots required until
the golf ball breaks is referred to as COR durability. In this
case, the average value mentioned here refers to an average of the
number of shoot times required until each of the prepared seven
balls of the same type breaks after being shot. The tester machine
type was a lateral COR type and an incident speed to the metallic
sheet was 43 m/s.
[0051] As for the measurement method of Young's Modulus in Table 4,
materials having each composition were formed into a sheet having a
thickness of 2 mm and stored under an environment of
23.+-.1.degree. C. for two weeks. They were processed into a
dumbbell-like No. 3 test pieces according to JIS K6251, and using
Tensilon Universal Tester RTG-1310 manufactured by A&D, their
tensile strengths (MPa) when the test piece was elongated by 10%
were measured at a test speed of 500 mm/min. Then, their Young's
Moduli were calculated from these measured tensile strengths. In
the meantime, three test pieces were prepared for each composition
and an average of those measured values was obtained to indicate
its measurement result.
[0052] As shown in Table 1, the comparative examples 1 and 2
provided with no coating layer have a .mu. hardness of more than 3
and a hard cover structure. The comparative example 3 has a large
product .mu. hardness. Thus, although these comparative examples
ensured a predetermined performance in the spin amount for an
approach, the spin amounts for a driver were very small.
[0053] On the other hand, in the examples 1 to 8, the coating layer
formed of a material having rubber elasticity was arranged between
the intermediate layer and the cover or between the core and the
intermediate layer. As a result, a shock was absorbed by the
coating layer and at the same time, the spin amount for a driver
shot increased greatly without a large increase in the spin amount
for approach.
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