U.S. patent application number 13/328506 was filed with the patent office on 2013-06-20 for golf ball.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD.. The applicant listed for this patent is Atsushi KOMATSU, Hiroshi NASU, Yuichiro OZAWA. Invention is credited to Atsushi KOMATSU, Hiroshi NASU, Yuichiro OZAWA.
Application Number | 20130157782 13/328506 |
Document ID | / |
Family ID | 48610673 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130157782 |
Kind Code |
A1 |
KOMATSU; Atsushi ; et
al. |
June 20, 2013 |
GOLF BALL
Abstract
A golf ball of the present invention includes: a core located in
the center of the golf ball; a cover surrounding the outside of the
core and having plural dimples on the surface thereof; and a paint
layer surrounding the outside of the cover. The paint layer is
formed of a material having rubber elasticity. The paint layer may
have a thickness of at most approximately 100 .mu.m. The paint
layer may have a hardness of at most approximately 70 in terms of
JIS-C hardness. The cover may contain ionomer resin. The cover may
have a hardness of at least 40 in terms of Shore D hardness.
Inventors: |
KOMATSU; Atsushi;
(Chichibu-shi, JP) ; OZAWA; Yuichiro;
(Chichibu-shi, JP) ; NASU; Hiroshi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOMATSU; Atsushi
OZAWA; Yuichiro
NASU; Hiroshi |
Chichibu-shi
Chichibu-shi
Tokyo |
|
JP
JP
JP |
|
|
Assignee: |
BRIDGESTONE SPORTS CO.,
LTD.
Tokyo
JP
|
Family ID: |
48610673 |
Appl. No.: |
13/328506 |
Filed: |
December 16, 2011 |
Current U.S.
Class: |
473/378 |
Current CPC
Class: |
A63B 37/0074 20130101;
A63B 37/0004 20130101; A63B 37/0064 20130101; A63B 37/0075
20130101; A63B 37/0031 20130101; A63B 37/0092 20130101; C08G
18/4063 20130101; C08G 18/4288 20130101; A63B 37/0023 20130101;
A63B 37/0022 20130101; A63B 45/00 20130101; C08G 18/73 20130101;
A63B 37/0003 20130101 |
Class at
Publication: |
473/378 |
International
Class: |
A63B 37/14 20060101
A63B037/14 |
Claims
1. A golf ball comprising: a core located in a center of the golf
ball; a cover surrounding an outside of the core and having plural
dimples on a surface thereof; and a paint layer surrounding an
outside of the cover, the paint layer formed of a material having
rubber elasticity.
2. The golf ball according to claim 1, wherein the paint layer has
a thickness of at most approximately 100 .mu.m.
3. The golf ball according to claim 1, wherein the paint layer has
a hardness of at most approximately 70 in terms of JIS-C
hardness.
4. The golf ball according to claim 1, wherein a material used for
forming the paint layer has a Young's Modulus of at most
approximately 70 MPa.
5. The golf ball according to claim 1, wherein the material for
forming the paint layer has a Poisson's ratio of at least
approximately 0.45.
6. The golf ball according to claim 1, wherein the cover contains
ionomer resin.
7. The golf ball according to claim 1, wherein the cover has a
hardness of at least 40 in terms of Shore D hardness.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a golf ball, and more
particularly, relates to a golf ball having an improved painted
layer.
[0002] The surface of a golf ball is usually covered with a painted
layer. This painted layer is demanded to have characteristics in
appearance such as color tone, impact resistance, and abrasion
resistance. Japanese Patent Application Publication No. 8-206255
discloses a golf ball including a paint layer formed of a coating
composition containing acrylic polyol, polyester polyol and a
hardening agent in order to improve its impact resistance and
abrasion resistance.
[0003] Generally, a high-performance golf ball has a low spin rate
when it is hit with a driver, thereby increasing distance. When the
ball is hit for approach, its spin rate is increased to secure an
excellent controllability around the green. To aim at improving the
above-described performance, Japanese Patent Application
Publication No. 9-276446 discloses an idea that by using two paint
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.
SUMMARY OF THE INVENTION
[0004] Due to development of simulation technology, mechanisms of
generation of spin in the golf ball have been investigated.
Consequently, it has been made evident that the larger the friction
between the golf club and the golf ball in both hitting with a
driver and hitting for approach, the better the spin performance of
the golf ball becomes.
[0005] Although Japanese Patent Application Publication No.
8-206255 has stated that increasing the friction force of the
surface of the golf ball improves the impact resistance and the
abrasion resistance of the golf ball, the spin performance of the
golf ball cannot be improved sufficiently by the friction force to
such an extent as described in this publication.
[0006] According to Japanese Patent Application No. 9-276446, the
two-layer coating film is formed into a thick paint layer of 700
.mu.m or less, and dimples are formed not in the cover but in the
paint layer. Thus, a too thick paint layer complicates the
manufacturing process, thereby affecting manufacturing
efficiency.
[0007] Accordingly, the present invention aims at providing a golf
ball in which the paint layer of the golf ball is improved to
increase a friction force with respect to a golf club, thereby
improving spin performance.
[0008] To achieve the above-described object, a golf ball of the
present invention comprises: a core located in the center of the
golf ball; a cover which surrounds the outside of the core and has
plural dimples on the surface thereof; and a paint layer which
surrounds the outside of the cover, wherein the paint layer is
formed of a material having rubber elasticity.
[0009] By forming the paint layer of a material having the rubber
elasticity, the thin paint layer on the surface of the golf ball
can be softened and consequently, the friction force with respect
to the golf ball can be increased so as to improve the spin
performance. According to simulations by the inventors, it has been
found that by increasing the coefficient of friction on the surface
of a ball, when the ball is struck with a driver, the spin rate is
neither decreased nor increased, but when the ball is struck for
approach, the spin rate is increased.
[0010] The paint layer may have a thickness of approximately 100
.mu.m or less. The paint layer may have a hardness of approximately
70 or less in terms of JIS-C hardness. A material for forming the
paint layer may a Young's modulus of approximately 70 MPa or less.
A material for forming the paint layer may have a Poisson's ratio
of approximately 0.45 or more. A ratio Sp of the JIS-C hardness of
the paint layer with respect to the .mu. hardness of the golf ball
may be approximately 15 or less.
[0011] The cover may contain ionomer resin. The cover may have a
hardness of 40 or more in terms of Shore D hardness. A ratio Sc of
the Shore D hardness of the cover with respect to the .mu. hardness
of the golf ball may be approximately 25 or less. A material for
forming the paint layer may have a first loss tangent, a material
for forming the cover may have a second loss tangent, and a
difference Td between the first loss tangent and the second loss
tangent may be approximately 0.05 or more.
[0012] The golf ball may include a top coat for further surrounding
the outside of the paint layer. The top coat may have a thickness
of approximately 60 .mu.m or less.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a sectional plan view showing a golf ball
according to an embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Hereinafter, an embodiment of a golf ball according to the
present invention will be described with reference to the
accompanying drawings, but the present invention is not restricted
to the present embodiment. In the meantime, the accompanying
drawings are drawn mainly to make the present invention easier to
understand, but they are not drawn to scale.
[0015] As shown in FIG. 1, the golf ball 1 of the present
embodiment mainly includes a core 1 located in the center of the
ball, a cover 30 surrounding the outside of the core and a paint
layer 40 surrounding the outside of the cover. Plural dimples are
formed on the surface of the cover 30. The paint layer 40 covers
the surface of the cover 30 along dents of the dimples 32 with a
substantially equal thickness.
[0016] Although the golf ball 1 can include an intermediate layer
20 between the core 10 and the cover 30 freely as shown in FIG. 1,
the present invention is not restricted to the present example, and
it is permissible to form the ball so that the cover 30 is in
direct contact with the core 10 without any provision of the
intermediate layer 20.
[0017] The core 10 can 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), and silicon
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.
[0018] As well as the base rubber for the 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.
[0019] 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
restricted 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 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 more preferred to be approximately 50 parts or
less by weight.
[0020] As the cross-linking agent, it is preferred to use organic
peroxide, although it 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,
more preferred to be approximately 0.15 parts by weight, and
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.
[0021] 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 the form of a
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, more preferred to be approximately 2 parts or
more by weight and 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.
[0022] 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 restitutive performance of
the golf ball is decreased, it is preferred to be approximately 5
mm or more, more preferred to be approximately 15 mm or more, and
further preferred to be approximately 25 mm or more. Although the
core 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, for example, a center core and
surrounding layers.
[0023] As the forming method of the core 10, any known forming
method for the core for a 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 pressure with a spherical 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 a kneading machine and then, the center
core is obtained by vulcanizing the kneaded materials under a
pressure with a spherical 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 pressure with
the spherical mold to obtain a multi-layered core.
[0024] The cover 30 may be formed using ionomer, 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 main components of
thermoplastic polyurethane, other thermoplastic elastomer,
polyisocyanate compound, fatty acid or its derivative, basic
inorganic metal compound or filler may be added to the core 30.
[0025] As the ionomer resin, the following resins containing at
least one of a component (a) and a component (b) may be used as the
base resin, although it is not restricted to these substances.
Furthermore, the following component (c) may be freely added to
this base resin. The component (a) is at least one of an
olefin-unsaturated carboxylic acid-unsaturated carboxylic ester
random terpolymer and a metallic salt thereof. The component (b) is
at least one of an olefin-unsaturated carboxylic acid random
copolymer and a metallic salt thereof. The component (c) is
thermoplastic block copolymer having polyolefin crystalline block
and at least one of a polyethylene and a butylene random
copolymer.
[0026] The thickness of the cover 30 is preferred to be
approximately 0.2 mm or more, and 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.
[0027] The hardness of the cover 30 is preferred to be
approximately 40 or more in terms of Shore hardness, more preferred
to be approximately 50 or more, and further preferred to be
approximately 55 or more. Additionally, the hardness of the cover
30 is preferred to be approximately 75 or less, more preferred to
be approximately 70 or less, and further preferred to be
approximately 65 or less.
[0028] To form the cover 30, known forming methods of 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.
[0029] The paint layer 40 is formed of material having rubber
elasticity. The Young's modulus of the material having rubber
elasticity is preferred to be approximately 0.1 MPa or more, more
preferred to be approximately 1 MPa or more, and 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 or the
Poisson's ratio is within the above-mentioned range, a paint layer
40 may not ensure sufficient plasticity or friction force.
[0030] Regarding a material having such rubber elasticity,
according to, for example, a classification of JIS K 6397, 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) polymer may be used.
[0031] As an O group (rubber having carbon and oxygen in the 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.
[0032] As an R group (rubber having unsaturated carbon bond 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.
[0033] The thickness of the paint layer 40 is preferred to be
approximately 5 .mu.m or more and more preferred to be
approximately 10 .mu.m or more, although it is not always
restricted to these values. Furthermore, the thickness of the paint
layer 40 is preferred to be approximately 100 .mu.m or less and
more preferred to be approximately 60 .mu.m or less. If the coating
is too thin, not only cannot sufficient friction be secured, but
also the coating may become easy to peel, thereby leading to
inferior performance in terms of function and durability.
Furthermore, conversely, if the coating is too thick, the driver
spin is increased so that sufficient distance may not be
secured.
[0034] As a material applied to the paint layer 40, a material
having a large loss tangent (tan .delta.), i.e., a material having
a low coefficient of restitution, is preferable. As a result, the
deformation amount of the material can be increased, and
consequently, the friction force can be increased. The loss tangent
tan .delta. is preferred to be approximately 0.05 or more, is more
preferred to be approximately 0.10 or more, is further preferred to
be approximately 0.15 or more, and is most preferred to be
approximately 0.20 or more. Furthermore, the upper limit of the
loss tangent tan .delta. is preferred to be approximately 0.30, or
less and is more preferred to be approximately 0.28 or less,
although it is not restricted to any particular value. In
particular, to reduce the driver spin and intensify the approach
spin, preferably, the loss tangent tan .delta. of the cover 30 is
set to a small value while the value tan .delta. of the paint layer
40 is set to a large value. Thus, as the material of the paint
layer 40, it is preferable to use a material having a larger tan
.delta. than the material of the cover 30. Td=tan .delta.-tan
.delta. of the cover of the paint layer is preferred to be
approximately 0.05 or more, is more preferred to be approximately
0.07 or more, and is further preferred to be approximately 0.10 or
more.
[0035] In addition, the loss tangent (tan .delta.) is expressed as
a value obtained by dividing loss elastic modulus by storage
elastic modulus, and is also called the dynamic viscoelastic
modulus. This loss tangent (tan .delta.) can be measured with a
commercially available measuring device, for example, a dynamic
viscoelasitc modulus measuring device (DMA Q800) manufactured by TA
Instrument. As a measuring condition, a specimen is prepared in
dimensions of 3 mm in width, 1 mm in thickness and 20 mm in length
(this length is that of a portion actually measured and does not
include both-end portions nipped). Assume that its initial
distortion is 0.1 N, the amplitude is 1% and the frequency is 15
Hz. The measurement is performed in a temperature range of
-100.degree. C. to 80.degree. C. with a rate of temperature rise of
3.degree. C./minute and then, a measured value at -10.degree. C. is
adopted.
[0036] The hardness of the paint layer 40 is preferred to be
approximately 10 or more in terms of JIS-C hardness, more preferred
to be approximately 20 or more, and further preferred to be
approximately 30 or more, although it is not restricted to these
values. Furthermore, the hardness of the paint 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 paint
layer 40 is preferred to be lower than that of the core 10. By
forming a golf ball so that the hardness thereof is increased
gradually from the core center toward the surface, the driver spin
can be reduced to increase the distance. As a consequence, by
disposing the softest material thinly in the vicinity of the
surface of the golf ball, often an appropriate spin can be obtained
in approach.
[0037] The harder the cover 30 serving as a foundation of the paint
layer 40, the more easily the approach spin is applied. When the
hardness of a golf ball product 1 is increased, in case of the hard
cover 30, the amount of deformation which occurs when the ball is
hit is reduced so that its contact area becomes short. As a
consequence, slip phenomenon occurs to decrease in the approach
spin. Thus, if the hardness of the golf ball product 1 is high, it
is preferable to intensify the hardness of the cover 30 as much as
possible within a range which does not cause the slip. For example,
as for a relationship between the .mu. hardness of the golf ball
product 1 and the Shore D hardness of the cover 30, Shore D
hardness of the cover/.mu. hardness of the golf ball product=Sc is
preferred to be approximately 25 or less and more preferred to be
approximately 23 or less. Although the lower limit of this hardness
ratio Sc is not restricted to any particular value, it is preferred
to be approximately 5 or more, is more preferred to be
approximately 10 or more and is further preferred to be
approximately 14 or more. In the meantime, the .mu. hardness refers
to the amount of flexure (deformation) when a load is applied to
the golf ball product 1 from its initial load of 98 N (10 kgf) up
to 1,275 N (130 kgf) and is expressed in the unit of mm.
[0038] Due to the same reason as the relationship between the
hardness of the golf ball product 1 and the hardness of the cover
30, when the hardness of the golf ball product 1 is intensified,
the amount of deformation when it is hit is decreased, so that the
contact area becomes short, thereby causing the slip phenomenon to
reduce the spin for approach. Thus, if the hardness of the golf
ball product 1 is high, it is preferable to increase the friction
force of the paint layer 40 in order to prevent occurrence of the
slip, that is, to lower the hardness. For example, as for the
relationship between the .mu. hardness of the golf ball product 1
and the JIS-C hardness of the paint layer 40, Sp=JIS-C hardness of
the paint layer/.mu. hardness of the golf ball product is preferred
to be approximately 15 or less, and is more preferred to be
approximately 13 or less. Although the lower limit of this hardness
ratio Sp is not restricted to any particular value, it is preferred
to be approximately 2 or more, is more preferred to be
approximately 5 or more, and is further preferred to be
approximately 7 or more.
[0039] As a formation method of the paint layer 40, any known
formation method of the paint layer of the golf ball may be
adopted. For example, for the paint 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, tetrahydrofurany, benzene, chloroform,
methyl ethyl ketone, trichloroethylene, acetone, n-hexanol and the
like are available, although it is not restricted to any particular
type. The dilution rate (concentration of coating polymer) may be
approximately 5% to approximately 100%, although it is not
restricted to any particular value.
[0040] After coating the surface of the cover 30 with this coating
material, the paint layer 40 can 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 spinning 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 paint layer 40 having a sufficient impact
resilience. Furthermore, as well as the cross-linking agent and the
hardening agent, a filler may be added freely to the coating
material. Even a material difficult to cross-link can 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 a coating material having rubber
elasticity.
[0041] A top coat (not shown) for covering the paint layer 40 can
be freely formed on the paint layer 40. 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 hardening agent. For example, two-liquid type
curable urethane coating material can be mentioned, and in
particular, it is preferable to use no-yellowing type coating
material. The thickness of the top coat is preferred to be, for
example, approximately 5 .mu.m or more and 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.
[0042] The intermediate layer 20 disposed between the core 10 and
the cover 30 is not indispensable but may be provided freely. 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 which functions as the core and a second intermediate layer
which functions as the cover.
[0043] 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. [0044] (a) at least one of
olefin-unsaturated carboxylic acid random copolymer and a metal ion
neutralizing material of olefin-unsaturated carboxylic acid random
copolymer, [0045] (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, [0046]
(c) at least one of fatty acid having a molecular weight of 228 to
1500 and its derivative, [0047] (d) basic inorganic metallic
compound capable of neutralizing an unneutralized acid group in
components (a) to (c), and [0048] (e) non-ionomer thermoplastic
elastomer, [0049] 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.
[0050] 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.
[0051] 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, 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. In the meantime, although the
intermediate layer 20 is expressed in a single layer in FIG. 1, it
is limited to this example but may be formed of two or more
layers.
EXAMPLE
[0052] Golf balls having a configuration shown in Table 1 were
manufactured and then, tests for measuring the spin performance of
the golf balls were performed. In each example, five balls were
prepared and evaluated. Table 1 shows a test result indicating each
average of the five balls. Table 2 shows mixtures A to C of the
materials shown in Table 1 of the core (in parts by weight). Table
3 shows mixtures E to G of the materials of the cover (in parts by
weight). Table 4 shows mixtures H to K of the materials of the
paint layer and the top coat (in parts by weight). In the meantime,
the paint layer is formed by diluting a material having a
predetermined mixture with toluene 30% to 50% and then spraying the
material.
TABLE-US-00001 TABLE 1 Examples 1 2 3 4 5 6 7 8 9 Core Outer
diameter (mm) 39.3 39.3 39.3 39.3 39.3 39.3 39.3 39.3 39.3 Mixture
A B B B B B B C A Cover Thickness (mm) 1.7 1.7 1.7 1.7 1.7 1.7 1.7
1.7 1.7 Shore D hardness 63 63 63 63 63 63 63 60 63 Mixture E E E E
E E E F E tan .delta. 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.1 0.12
Paint Thickness (.mu.m) 20 20 20 20 40 60 100 20 20 layer JIS-C
hardness 40 40 50 60 40 40 40 40 40 Mixture H H I J H H H H H tan
.delta. 0.25 0.25 0.26 0.27 0.25 0.25 0.25 0.25 0.25 Top coat
Thickness (.mu.m) -- -- -- -- -- -- -- -- 10 Mixture -- -- -- -- --
-- -- -- K Product .mu. hardness (mm) 3.0 4.0 4.0 4.0 4.0 4.0 4.0
2.7 3.0 Hardness ratio Sc 21.0 15.8 15.8 15.8 15.8 15.8 15.8 22.2
21.0 Hardness ratio Sp 13.3 10.0 12.5 15.0 10.0 10.0 10.0 14.8 13.3
tan .delta. difference Td 0.13 0.13 0.14 0.15 0.13 0.13 0.13 0.15
0.13 Spin performance Driver 2550 2490 2500 2510 2540 2560 2580
2520 2580 (rpm) Approach 5800 5700 5600 5500 5650 5630 5630 5720
5650 Anti-abrasion 23.degree. C. A A A A A A A A S performance
13.degree. C. B A A A A A A B S 0.degree. C. B B B B B B B B A
Examples 10 11 12 13 14 15 16 Core Outer diameter (mm) 39.3 39.3
39.3 39.3 39.3 39.3 39.3 Mixture B C A A B B B Cover Thickness (mm)
1.7 1.7 2.5 1.7 1.7 1.7 1.7 Shore D hardness 63 60 63 61 63 63 63
Mixture E F E G E E E tan .delta. 0.12 0.10 0.12 0.21 0.12 0.12
0.12 Paint Thickness (.mu.m) 150 20 20 20 60 -- 20 layer JIS-C
hardness 40 60 40 40 40 -- 72 Mixture H J H H H -- K tan .delta.
0.25 0.27 0.25 0.25 0.25 -- 0.20 Top coat Thickness (.mu.m) -- --
-- -- 100 -- -- Mixture -- -- -- -- K -- -- Product .mu. hardness
(mm) 4.0 2.7 3.0 3.1 4.0 4.0 4.0 Hardness ratio Sc 16.0 22.2 21.0
19.7 15.8 15.8 16.0 Hardness ratio Sp 10.0 22.2 13.3 12.9 10.0 --
18.0 tan .delta. difference Td 0.13 0.17 0.13 0.04 0.13 -- 0.08
Spin performance Driver 2650 2540 2530 2720 2600 2480 2600 (rpm)
Approach 5550 5200 4950 5800 5200 3500 4800 Anti-abrasion
23.degree. C. A A A A S A A performance 13.degree. C. A B A B S A A
0.degree. C. B B B B A B B
TABLE-US-00002 TABLE 2 Composition of core A B C Polybutadiene 100
100 100 Zinc acrylate 27.5 18.5 29.8 Peroxide 1 0.6 0.6 0.6
Peroxide 2 0.6 0.6 0.6 Anti-aging agent 0.1 0.1 0.1 Zinc oxide 21.3
25.0 20.4 Organic sulfur compound 0.2 0.2 0.2 Vulcanization
Temperature (.degree. C.) 155 155 155 method Time (h) 15 15 15
[0053] As polybutadiene, BR01 manufactured by JSR was used for base
rubber. As zinc acrylate, WN86 manufactured by Nippon Shokubai was
used. Percumyl D, which is the trade name of dicumylperoxide
manufactured by NOF Corporation, was used as peroxide 1. Perhexa
C-40, which is the trade name of a mixture of 1,1di(t-butylperoxy)
cyclohexane and silica manufactured by NOF was used as peroxide 2.
This product was used as an initiator. Nocrac NS-6, which is the
trade name of 2,2'-methylenebis(4-methyl-6-t-butylphenol)
manufactured by Ouchi Shinko Chemical Industry, was used as
anti-aging agent. Zinc Oxide Grade 3, which is a trade name
available from Sakai Chemical Industry, was used as zinc oxide.
Pentachlorothiophenol zinc salt was used as the organic sulfur
compound.
TABLE-US-00003 TABLE 3 Composition of cover E F G Himilan 1557 --
50 -- Himilan 1605 40 -- -- Himilan 1706 50 -- -- Himilan 1601 10
50 -- Pandex T8260 -- -- 100 polyisocyanate compound -- -- 7.5
Hytrel 4001 -- -- 11 Polyethylene wax -- -- 1 TiO.sub.2 3 3 3
[0054] Himilan 1557 is ionomer resin of Zn-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Himilan 1605 is ionomer resin of Na-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Himilan 1706 is ionomer resin of Zn-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Himilan 1601 is ionomer resin of Na-ion neutralizing
ethylene-methacrylate copolymer manufactured by Mitsui DuPont
Chemical. Pandex T8260 is MDI-PTMG type thermoplastic polyurethane
material manufactured by DIC Bayer Polymer, with Durometer D type
resin hardness of 56 and modulus of repulsion elasticity of 45%.
Polyisocyanate compound is 4,4'-diphenyl methane di-isocyanate.
Hytrel 4001 is thermoplastic polyether ester elastomer manufactured
by Toray-DuPont Co., Ltd. TiO.sub.2 is Tipaque R550 manufactured by
Ishihara Sangyo Ltd.
TABLE-US-00004 TABLE 4 Composition of paint layer H I J K Main Oil
Proto 100 100 100 -- material Polyester polyol -- -- -- 50 Acrylic
polyol -- -- -- 50 Filler Sedimentation -- 20 40 -- barium sulfate
Hardening agent -- -- -- 50 Young's modulus (MPa) 12 32 53 71
Poison's ratio 0.495 0.488 0.482 0.464
[0055] The Oil Proto is a product name of Hagitec's product, which
is produced of SBR resin as its main component. Its detailed
composition 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%. The polyester polyol is modified with recinolic acid
which is a vegetable oil fatty acid having a carbon number of 18,
and polyester polyol has a total molecular weight of 1500 and
hydroxyl number of 135. The acrylic polyol is ACRYDIC 801 (hydroxyl
number of 100) manufactured by Dai Nippon Ink. The sedimentation
barium sulfate is Sedimentation Barium Sulfate #100 in its product
name, manufactured by Sakai Chemical Industry. The hardening agent
used here is hexamethylene diisocyanate
[0056] In the tests for measurement of the spinning 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 Mieyama), 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 rate
(rpm).
[0057] For tests for measurement of the anti-abrasion performance
shown in Table 1, balls were warmed at 23.degree. C., 13.degree.
C., 0.degree. C. respectively assuming an actual usage condition
and the balls were hit with a swing robot equipped with a
non-plated pitching wedge at a head speed of 33 m/s. By recognizing
impact marks on the balls with naked eyes, balls which seven raters
or more of ten judged to be still usable were rated "S" and balls
which four to six raters judged to be still usable were rated "A",
and balls which three raters or less judged to be still usable were
rated "B".
[0058] As for the measurement method of Young's Modulus in Table 4,
the materials having each composition were formed into a sheet
having a thickness of 2 mm and stored under an temperature
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) at a time of 10% elongation
were measured at a test speed of 500 mm/min. Then, the Young's
Moduli were calculated from these measured tensile strengths. In
addition, three test pieces were prepared for each composition, and
an average value was adopted as a measurement value of this
test.
[0059] Because Example 15 having no paint layer provides the
surface of a golf ball with little friction force as shown in Table
1, the spin rate at the time of the approach was very small,
although the driver used here had a predetermined performance in
terms of the spin rate. Example 16 having a paint layer formed of
hard resin indicated a small friction force on the surface of the
golf ball. Thus, although this example indicates an increased spin
rate compared to Example 15, Example 16 did not reach a desired
performance.
[0060] On the other hand, because each of the paint layers in
Examples 1 to 14 was formed of the material having rubber
elasticity, the spin rate for approach was increased while the spin
rate when the ball was hit with a driver was not increased. As
shown in Example 10, when the paint layer was too thick, the
friction force was large, so that the spin rate for approach could
be greatly increased. However, an influence of the softness of the
paint layer emerges when the ball is hit with a driver, thereby
sometimes leading to an increase in the spin rate at the time.
[0061] In Example 11, the .mu. hardness of the golf ball is
intensified by the composition of the core, so that the ratio Sp of
the hardness of the paint layer with respect to the product .mu.
hardness is intensified. In this case, neither appropriate friction
nor contact area can be secured. As a consequence, when the ball is
hit, the ball sometimes slips on a club, thereby producing a
tendency that the friction force cannot be used effectively for
approach. In Example 12 in which the thickness of the cover was
intensified, the cover layer was thick, thereby the deformation
amount of the cover being short. As a consequence, the contact area
between the club and the ball was decreased. Consequently, a
sufficient friction force could not be obtained, thereby producing
a tendency that no sufficient spin for approach could be obtained.
In Example 13 in which the difference Td in tan .delta. between the
paint layer and the cover was set to be small, energy loss could
occur, thereby producing a tendency that the spin rate when the
ball is hit with a driver was increased.
[0062] However, in Example 9 provided with the top coat, no large
influence was given to the spin performance, when the thickness of
the top coat was too large in Example 14, the friction force was
reduced so that the spin rate for the approach was greatly
decreased.
* * * * *