U.S. patent application number 12/846185 was filed with the patent office on 2011-03-03 for golf ball.
Invention is credited to Seiichiro Endo, Kazuhiko Isoagawa, Yoshiko Matsuyama, Keiji Ohama.
Application Number | 20110053708 12/846185 |
Document ID | / |
Family ID | 43625715 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110053708 |
Kind Code |
A1 |
Isoagawa; Kazuhiko ; et
al. |
March 3, 2011 |
GOLF BALL
Abstract
Golf ball 2 has spherical core 4, cover 6 situated on the
external side of the core 4, and paint layer 8 situated on the
external side of the cover 6. The cover 6 has a Shore D hardness of
no greater than 61. The paint layer 8 has a Martens hardness of no
greater than 2.0 mgf/.mu.m.sup.2. The base polymer of the paint
layer 8 is a polyurethane obtained by a reaction of a polyol with a
polyisocyanate. The polyisocyanate contains a buret-modified form
of hexamethylene diisocyanate. The cover 6 has a thickness of 0.3
mm or greater and 1.0 mm or less. The paint layer 8 has a thickness
of 5 .mu.m or greater and 40 .mu.m or less.
Inventors: |
Isoagawa; Kazuhiko;
(Kobe-shi, JP) ; Ohama; Keiji; (Kobe-shi, JP)
; Matsuyama; Yoshiko; (Kobe-shi, JP) ; Endo;
Seiichiro; (Kobe-shi, JP) |
Family ID: |
43625715 |
Appl. No.: |
12/846185 |
Filed: |
July 29, 2010 |
Current U.S.
Class: |
473/376 ;
473/378 |
Current CPC
Class: |
A63B 37/0023 20130101;
C08G 59/54 20130101; A63B 37/0031 20130101; A63B 37/0033 20130101;
A63B 37/0022 20130101; A63B 37/0067 20130101; A63B 37/0075
20130101; A63B 37/0043 20130101; A63B 37/0087 20130101; A63B
37/0065 20130101; C08G 18/7831 20130101; C09D 175/06 20130101; A63B
37/0045 20130101; A63B 37/0062 20130101; A63B 2037/0079 20130101;
C09D 163/00 20130101; A63B 37/0064 20130101 |
Class at
Publication: |
473/376 ;
473/378 |
International
Class: |
A63B 37/02 20060101
A63B037/02; A63B 37/12 20060101 A63B037/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2009 |
JP |
2009-194918 |
Mar 30, 2010 |
JP |
2010-076562 |
Claims
1. A golf ball comprising a core, a cover situated on the external
side of the core, and a paint layer situated on the external side
of the cover, wherein the cover has a Shore D hardness of no
greater than 61, and the paint layer has a Martens hardness of no
greater than 2.0 mgf/.mu.m.sup.2.
2. The golf ball according to claim 1, wherein the base polymer of
the paint layer is a polyurethane obtained by a reaction of a
polyol with a polyisocyanate, and the polyisocyanate contains a
buret-modified form of hexamethylene diisocyanate.
3. The golf ball according to claim 2, wherein the percentage of
the buret-modified form relative to the total amount of the
polyisocyanate is no less than 20% by weight.
4. The golf ball according to claim 1, wherein the base polymer of
the paint layer is a polyurethane obtained by a reaction of a
polyol with a polyisocyanate, and the NCO/OH ratio in the
polyurethane is 1.0/1.0 or greater and 1.4/1.0 or less.
5. The golf ball according to claim 1, wherein the base polymer of
the paint layer is a polyurethane obtained by a reaction of a
polyol with a polyisocyanate, and the polyol has a weight average
molecular weight of 50 or greater and 2,000 or less.
6. The golf ball according to claim 1, wherein the paint layer has
a thickness of 5 .mu.m or greater and 40 .mu.m or less.
7. The golf ball according to claim 1, wherein the base polymer of
the cover is at least one selected from the group consisting of a
polyurethane, an ionomer resin, a polyamide, a polyester, a
polystyrene and a polyolefin.
8. The golf ball according to claim 1, wherein the cover has a
Shore D hardness of no greater than 55.
9. The golf ball according to claim 1, wherein the cover has a
thickness of 0.3 mm or greater and 1.0 mm or less.
10. The golf ball according to claim 1, wherein the amount of
compressive deformation of the core is 1.8 mm or greater and 4.0 mm
or less as measured under a condition in which the initial load is
98 N and the final load is 1,274 N.
11. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the surface of the center has a JIS-C hardness of 60 or greater
and 95 or less.
12. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the amount of compressive deformation of the center is 1.5 mm
or greater and 5.0 mm or less as measured under a condition in
which the initial load is 98 N and the final load is 1,274 N.
13. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the center has a diameter of 30 mm or greater and 41.5 mm or
less.
14. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the center has a weight of 25 g or greater and 42 g or
less.
15. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the base polymer of the mid layer is at least one selected from
the group consisting of an ionomer resin, a styrene
block-containing thermoplastic elastomer, a thermoplastic polyester
elastomer, a thermoplastic polyamide elastomer, a thermoplastic
polyurethane elastomer and a thermoplastic polyolefin
elastomer.
16. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the mid layer has a Shore D hardness of 40 or greater and 75 or
less.
17. The golf ball according to claim 1, wherein the core has a
center and a mid layer situated on the external side of the center,
and the mid layer has a thickness of 0.3 mm or greater and 2.5 mm
or less.
18. The golf ball according to claim 1 having an amount of
compressive deformation of 2.0 mm or greater and 3.5 mm or less as
measured under a condition in which the initial load is 98 N and
the final load is 1,274 N.
Description
[0001] This application claims priority on Patent Application No.
2009-194918 filed in Japan on Aug. 26, 2009, and Patent Application
No. 2010-76562 filed in Japan on Mar. 30, 2010. The entire contents
of these Japanese Patent Applications are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to golf balls. More
particularly, the present invention relates to a golf ball having a
core, a cover and a paint layer.
[0004] 2. Description of the Related Art
[0005] General golf balls have a core, a cover situated on the
external side of this core, and a paint layer situated on the
external side of this cover. The paint layer protects the cover and
a mark layer. The paint layer is also responsible for aesthetic
appearance of the golf ball. In addition, the paint layer is also
responsible for antifouling property of the golf ball. Japanese
Unexamined Patent Application Publication No. 2000-84116 (US
2001/003717) discloses a paint layer containing a polyurethane
obtained by a reaction of an isocyanate with a certain polyol. This
paint layer is excellent in adhesiveness with the cover. Japanese
Unexamined Patent Application Publication No. 2000-230147 discloses
a paint composition for golf balls containing a polyurethane having
a specified viscosity. A layer obtained with this paint composition
is excellent in adhesiveness with the cover.
[0006] Top concern to golf players for golf balls is their flight
performances. The golf players particularly place great importance
on travel distance attained by shots with a driver. The golf
players also place great importance on travel distance on shots
with a long iron and a middle iron.
[0007] Golf players place great importance also on spin
performances of golf balls. Great back spin rate results in small
run. For golf players, golf balls which are liable to be spun
backwards are apt to be rendered to stop at a target position.
Great side spin rate results in easily curved trajectory of the
golf ball. For golf players, golf balls which are liable to be spun
sidewise are apt to allow their trajectory to curve intentionally.
The golf balls that are excellent in spin performances are
excellent in control performances. High-level golf players
particularly place great importance on control performances on
shots with a short iron.
[0008] Japanese Unexamined Patent Application Publication No.
2004-8404 (US 2003/232665) discloses a golf ball provided with a
cover having a Shore D hardness of 30 to 55. This cover is
responsible for spin performances of the golf ball. Japanese
Unexamined Patent Application Publication No. 2006-34740 (US
2006/025238) discloses a golf ball provided with a cover having a
small volume. The base material of this cover is a polyurethane.
This cover is responsible for spin performances of the golf ball.
This cover does not impair the flight performances on shots with a
driver.
[0009] When a golf ball placed on rough is hit, turfgrass will be
interposed between the club face and the golf ball. Owing to this
turfgrass, slipping of the golf ball occurs on the club face. A
shot accompanied by slipping results in reduced spin rate. This
phenomenon is referred to as a "flyer". The flyer also occurs when
water is interposed between the club face and the golf ball in case
of rain.
[0010] When a flyer shot is made, the golf ball falls at a point
farther than the point intended by the golf player. The flyer makes
it difficult to predict the point of fall by the golf player. Golf
balls that are likely to result in a flyer are inferior in control
performances. Golf players expect golf balls less likely to result
in a flyer. In other words, golf players expect golf balls that are
superior in stability of the spin rate.
[0011] As described above, a soft cover can achieve excellent spin
performances. However, a soft cover is greatly deformed upon shots.
When a cover is deformed, the paint layer is also deformed
following the deformation of the cover. When a cover is excessively
deformed, a crack is generated on the paint layer. Abrasion of the
paint layer from the cover may be also caused.
[0012] An object of the present invention is to provide a golf ball
that is excellent in spin performances, stability of the spin rate
and durability of the paint layer.
SUMMARY OF THE INVENTION
[0013] The golf ball according to the present invention has a core,
a cover situated on the external side of the core, and a paint
layer situated on the external side of the cover. The cover has a
Shore D hardness of no greater than 61. The paint layer has a
Martens hardness of no greater than 2.0 mgf/.mu.m.sup.2.
[0014] In the golf ball according to the present invention, the
cover and the paint layer are soft. These cover and paint layer are
responsible for spin performances. When this golf ball is hit with
a short iron, a great spin rate is attained. This paint layer
suppresses slipping of the golf ball on the club face. In other
words, this paint layer is responsible for stability of the spin
rate. This paint layer suppresses a flyer. When the golf ball is
hit, the paint layer follows the cover as deformed. This paint
layer is excellent in durability.
[0015] As the base polymer of the paint layer, a polyurethane
obtained by a reaction of a polyol with a polyisocyanate may be
used. Preferably, the polyisocyanate contains a buret-modified form
of hexamethylene diisocyanate. The percentage of the buret-modified
form relative to the total amount of the polyisocyanate is no less
than 20% by weight. Preferably, the NCO/OH ratio in the
polyurethane is 1.0/1.0 or greater and 1.4/1.0 or less. Preferably,
the polyol has a weight average molecular weight of 50 or greater
and 2,000 or less. Preferably, the paint layer has a thickness of 5
.mu.m or greater and 40 .mu.m or less.
[0016] Preferably, the base polymer of the cover is at least one
selected from the group consisting of a polyurethane, an ionomer
resin, a polyamide, a polyester, a polystyrene and a polyolefin.
Preferably, the cover has a Shore D hardness of no greater than 55.
Preferably, the cover has a thickness of 0.3 mm or greater and 1.0
mm or less.
[0017] Preferably, the amount of compressive deformation of the
core is 1.8 mm or greater and 4.0 mm or less as measured under a
condition in which the initial load is 98 N and the final load is
1,274 N.
[0018] The core may have a center and a mid layer situated on the
external side of the center. Preferably, the amount of compressive
deformation of the center is 1.5 mm or greater and 5.0 mm or less
as measured under a condition in which the initial load is 98 N and
the final load is 1,274 N. Preferably, the center has a diameter of
30 mm or greater and 41.5 mm or less. Preferably, the center has a
weight of 25 g or greater and 42 g or less. Preferably, the base
polymer of the mid layer is at least one selected from the group
consisting of an ionomer resin, a styrene block-containing
thermoplastic elastomer, a thermoplastic polyester elastomer, a
thermoplastic polyamide elastomer, a thermoplastic polyurethane
elastomer and a thermoplastic polyolefin elastomer. Preferably, the
mid layer has a Shore D hardness of 40 or greater and 75 or less.
Preferably, the mid layer has a thickness of 0.3 mm or greater and
2.5 mm or less.
[0019] Preferably, the amount of compressive deformation of the
golf ball is 2.0 mm or greater and 3.5 mm or less as measured under
a condition in which the initial load is 98 N and the final load is
1,274 N.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows a partially cut off cross-sectional view
illustrating a golf ball according to one embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereinafter, the present invention will be described in
detail according to the preferred embodiments with appropriate
references to the accompanying drawing.
[0022] Golf ball 2 shown in FIG. 1 has spherical core 4, cover 6
situated on the external side of the core 4, and paint layer 8
situated on the external side of the cover 6. The core 4 has
spherical center 10, and mid layer 12 situated on the external side
of the center 10. A large number of dimples 14 are formed on the
surface of the cover 6. Of the surface of the cover 6, a part other
than the dimples 14 is land 16. The golf ball may have a core not
having the mid layer 12. The golf ball may have an inner cover
situated on the internal side of the cover 6.
[0023] This golf ball 2 has a diameter of from 40 mm to 45 mm. From
the standpoint of conformity to a rule defined by United States
Golf Association (USGA), the diameter is preferably no less than
42.67 mm. In light of suppression of the air resistance, the
diameter is preferably no greater than 44 mm, and more preferably
no greater than 42.80 mm. The weight of this golf ball 2 is 40 g or
greater and 50 g or less. In light of attainment of great inertia,
the weight is preferably no less than 44 g, and more preferably no
less than 45.00 g. From the standpoint of conformity to a rule
defined by USGA, the weight is preferably no greater than 45.93
g.
[0024] The center 10 is obtained through crosslinking of a rubber
composition. Examples of preferable base rubber include
polybutadienes, polyisoprenes, styrene-butadiene copolymers,
ethylene-propylene-diene copolymers and natural rubbers. In light
of the resilience performance, polybutadienes are preferred. When
other rubber is used in combination with polybutadiene, it is
preferred that the polybutadiene is included as a principal
component. Specifically, it is preferred that the percentage of
polybutadiene occupying the entire base rubber is no less than 50%
by weight, and particularly no less than 80% by weight. In
particular, polybutadienes having a percentage of cis-1,4 bonds of
no less than 40% by mole, and particularly no less than 80% by mole
are preferred.
[0025] For crosslinking of the center 10, a co-crosslinking agent
is used. Preferable examples of the co-crosslinking agent in light
of the resilience performance include monovalent or bivalent metal
salts of an .alpha.,.beta.-unsaturated carboxylic acid having 2 to
8 carbon atoms. Specific examples of the preferable co-crosslinking
agent include zinc acrylate, magnesium acrylate, zinc methacrylate
and magnesium methacrylate. Zinc acrylate and zinc methacrylate are
particularly preferred on the grounds that a high resilience
performance can be achieved.
[0026] The amount of the co-crosslinking agent is preferably 10
parts by weight or greater and 50 parts by weight or less relative
to 100 parts by weight of the base rubber. The center 10 including
the co-crosslinking agent in an amount of no less than 10 parts by
weight can achieve excellent resilience performance of the golf
ball 2. In this respect, the amount is more preferably no less than
15 parts by weight. The center 10 including the co-crosslinking
agent in an amount of no greater than 50 parts by weight enables
excellent feel at impact of the golf ball 2 to be achieved. In this
respect, the amount is more preferably no greater than 45 parts by
weight.
[0027] Into the rubber composition of the center 10, an organic
peroxide may be preferably blended together with the
co-crosslinking agent. The organic peroxide serves as a
crosslinking initiator. The organic peroxide is responsible for the
resilience performance. Examples of suitable organic peroxide
include dicumyl peroxide,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane and di-t-butyl peroxide.
Particularly versatile organic peroxide is dicumyl peroxide.
[0028] The amount of the organic peroxide is preferably 0.1 parts
by weight or greater and 3.0 parts by weight or less relative to
100 parts by weight of the base rubber. The center 10 including the
organic peroxide in an amount of no less than 0.1 parts by weight
can achieve excellent resilience performance of the golf ball 2. In
this respect, the amount is more preferably no less than 0.3 parts
by weight, and particularly preferably no less than 0.5 parts by
weight. The center 10 including the organic peroxide in an amount
of no greater than 3.0 parts by weight enables excellent feel at
impact of the golf ball 2 to be achieved. In this respect, the
amount is more preferably no greater than 2.5 parts by weight.
[0029] Into the center 10 may be blended a filler for the purpose
of adjusting specific gravity and the like. Illustrative examples
of suitable filler include zinc oxide, barium sulfate, calcium
carbonate and magnesium carbonate. Powders of a highly dense metal
may be blended as a filler. Specific examples of the highly dense
metal include tungsten and molybdenum. The amount of the filler is
determined ad libitum so that the intended specific gravity of the
center 10 can be accomplished. Particularly preferable filler is
zinc oxide. Zinc oxide serves not only to merely adjust the
specific gravity but also as a crosslinking activator. Various
kinds of additives such as sulfur, a sulfur compound, an anti-aging
agent, a coloring agent, a plasticizer, a dispersant and the like
may be blended in an adequate amount in the center 10 as needed.
Into the center 10 may be also blended crosslinked rubber powders
or synthetic resin powders.
[0030] The center 10 has a surface hardness H1 of preferably 60 or
greater and 95 or less. As described later, this golf ball 2 has a
soft cover 6. Upon hitting of this golf ball 2, the center 10 is
greatly deformed resulting from the cover 6 being soft. The center
10 having a surface hardness H1 of no less than 60 can achieve
excellent resilience performance of the golf ball 2. In this
respect, the surface hardness H1 is more preferably no less than
70, and particularly preferably no less than 75. The center 10
having a surface hardness H1 of no greater than 95 does not impair
the feel at impact of the golf ball 2. In this respect, the surface
hardness H1 is more preferably no greater than 90, and particularly
preferably no greater than 85. The surface hardness is measured by
pushing a JIS-C hardness scale on the surface of the center 10. For
the measurement, an automated rubber hardness scale ("P1", trade
name, available from Koubunshi Keiki Co., Ltd.) which is equipped
with this hardness scale is used.
[0031] The amount of compressive deformation of the center 10 is
preferably 1.5 mm or greater and 5.0 mm or less. The center 10
having an amount of compressive deformation of no less than 1.5 mm
does not impair the feel at impact of the golf ball 2. In this
respect, the amount of compressive deformation is more preferably
no less than 2.0 mm. The center 10 having an amount of compressive
deformation of no greater than 5.0 mm can achieve excellent
resilience performance of the golf ball 2. In this respect, the
amount of compressive deformation is more preferably no greater
than 4.5 mm, and particularly preferably no greater than 4.0
mm.
[0032] Upon measurement of the amount of compressive deformation,
the spherical body (center 10, core 4 or golf ball 2) is first
placed on a hard plate made of metal. Next, a cylinder made of
metal gradually descends toward the spherical body. The spherical
body interposed between the bottom face of the cylinder and the
hard plate is deformed. A migration distance of the cylinder,
starting from the state in which an initial load of 98 N is applied
to the spherical body up to the state in which a final load of
1,274 N is applied thereto is the amount of compressive
deformation.
[0033] The center 10 has a diameter of preferably 30 mm or greater
and 41.5 mm or less. The center 10 has a weight of preferably 25 g
or greater and 42 g or less. The crosslinking temperature of the
center 10 is usually 140.degree. C. or higher and 180.degree. C. or
lower. The crosslinking time of the center 10 is usually 10 min or
longer and 60 min or shorter. The center may be formed with two or
more layers. The center may have a rib on the surface thereof. The
golf ball may have a hollow center.
[0034] For the mid layer 12, a thermoplastic resin composition is
suitably used. Examples of the base polymer of the resin
composition include ionomer resins, styrene block-containing
thermoplastic elastomers, thermoplastic polyester elastomers,
thermoplastic polyamide elastomers, thermoplastic polyurethane
elastomers and thermoplastic polyolefin elastomers. In particular,
ionomer resins are preferred. The ionomer resins are highly
elastic. As described later, this golf ball 2 has a soft cover 6.
Upon hitting of this golf ball 2, the mid layer 12 is greatly
deformed resulting from the cover 6 being soft. The mid layer 12
including the ionomer resin is responsible for the resilience
performance.
[0035] An ionomer resin and other resin may be used in combination.
When these are used in combination, the ionomer resin is included
as the principal component of the base polymer, in light of the
resilience performance. The percentage of the ionomer resin in the
entire base polymer is preferably no less than 50% by weight, more
preferably no less than 60% by weight, and particularly preferably
no less than 65%.
[0036] Examples of preferred ionomer resin include binary
copolymers formed with .alpha.-olefin and an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms. Preferable binary copolymer comprises 80% by weight or more
and 90% by weight or less .alpha.-olefin, and 10% by weight or more
and 20% by weight or less .alpha.,.beta.-unsaturated carboxylic
acid. This binary copolymer provides excellent resilience
performance. Examples of other ionomer resin preferred include
ternary copolymers formed with .alpha.-olefin, an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms, and an .alpha.,.beta.-unsaturated carboxylate ester having 2
to 22 carbon atoms. Preferable ternary copolymer comprises 70% by
weight or more and 85% by weight or less .alpha.-olefin, 5% by
weight or more and 30% by weight or less .alpha.,.beta.-unsaturated
carboxylic acid, and 1% by weight or more and 25% by weight or less
.alpha.,.beta.-unsaturated carboxylate ester. This ternary
copolymer provides excellent resilience performance. In the binary
copolymer and ternary copolymer, preferable .alpha.-olefin is
ethylene and propylene, and preferable .alpha.,.beta.-unsaturated
carboxylic acid is acrylic acid and methacrylic acid. Particularly
preferred ionomer resin is a copolymer formed with ethylene, and
acrylic acid or methacrylic acid.
[0037] In the binary copolymer and ternary copolymer, a part of the
carboxyl groups may be neutralized with a metal ion. Illustrative
examples of the metal ion for use in the neutralization include
sodium ion, potassium ion, lithium ion, zinc ion, calcium ion,
magnesium ion, aluminum ion and neodymium ion. The neutralization
may be carried out with two or more kinds of metal ions.
Particularly suitable metal ion in light of the resilience
performance and durability of the golf ball 2 is sodium ion, zinc
ion, lithium ion and magnesium ion.
[0038] Specific examples of the ionomer resin include "Himilan.RTM.
1555", "Himilan.RTM. 1557", "Himilan.RTM. 1605", "Himilan.RTM.
1706", "Himilan.RTM. 1707", "Himilan.RTM. 1856", "Himilan.RTM.
1855", "Himilan.RTM. AM7311", "Himilan.RTM. AM7315", "Himilan.RTM.
AM7317", "Himilan.RTM. AM7318", "Himilan.RTM. MK7320" and
"Himilan.RTM. MK7329", trade names, available from Du Pont-MITSUI
POLYCHEMICALS Co., Ltd.; "Surlyn.RTM. 6120", "Surlyn.RTM. 6320",
"Surlyn.RTM. 6910", "Surlyn.RTM. 7930", "Surlyn.RTM. 7940",
"Surlyn.RTM. 8140", "Surlyn.RTM. 8150", "Surlyn.RTM. 8940",
"Surlyn.RTM. 8945", "Surlyn.RTM. 9120", "Surlyn.RTM. 9150",
"Surlyn.RTM. 9910", "Surlyn.RTM. 9945", "Surlyn.RTM. AD8546", "HPF
1000" and "HPF 2000", trade names, available from Du Pont Kabushiki
Kaisha; and "IOTEK 7010", "IOTEK 7030", "IOTEK 7510", "IOTEK 7520",
"IOTEK 8000" and "IOTEK 8030", trade names, available from EXXON
Mobil Chemical Corporation. Two or more kinds of the ionomer resins
may be used in combination.
[0039] Preferable resin which may be used in combination with the
ionomer resin is a styrene block-containing thermoplastic
elastomer. The styrene block-containing thermoplastic elastomer
includes a polystyrene block as a hard segment, and a soft segment.
Typical soft segment is a diene block. Illustrative examples of the
compound for the diene block include butadiene, isoprene,
1,3-pentadiene and 2,3-dimethyl-1,3-butadiene. Butadiene and
isoprene are preferred. Two or more compounds may be used in
combination.
[0040] The styrene block-containing thermoplastic elastomer may
include a styrene-butadiene-styrene block copolymer (SBS), a
styrene-isoprene-styrene block copolymer (SIS), a
styrene-isoprene-butadiene-styrene block copolymer (SIBS), a
hydrogenated product of SBS, a hydrogenated product of SIS or a
hydrogenated product of SIBS. Exemplary hydrogenated product of SBS
includes a styrene-ethylene-butylene-styrene block copolymer
(SEBS). Exemplary hydrogenated product of SIS includes a
styrene-ethylene-propylene-styrene block copolymer (SEPS).
Exemplary hydrogenated product of SIBS includes a
styrene-ethylene-ethylene-propylene-styrene block copolymer
(SEEPS).
[0041] In light of the resilience performance of the golf ball 2,
the content of the styrene component in the thermoplastic elastomer
is preferably no less than 10% by weight, more preferably no less
than 12% by weight, and particularly preferably no less than 15% by
weight. In light of the feel at impact of the golf ball 2, the
content is preferably no greater than 50% by weight, more
preferably no greater than 47% by weight, and particularly
preferably no greater than 45% by weight.
[0042] In the present invention, the styrene block-containing
thermoplastic elastomer includes an alloy of olefin with one or
more selected from the group consisting of SBS, SIS, SIBS, SEBS,
SEPS and SEEPS, and hydrogenated products thereof. The olefin
component in this alloy is speculated to contribute to improvement
of the compatibility with other base polymer. When this alloy is
used, the resilience performance of the golf ball 2 is improved.
Preferably, olefin having 2 to 10 carbon atoms may be used.
Illustrative examples of suitable olefin include ethylene,
propylene, butene and pentene. Ethylene and propylene are
particularly preferred.
[0043] Specific examples of the polymer alloy include "Rabalon.RTM.
T3221C", "Rabalon.RTM. T3339C", "Rabalon.RTM. SJ4400N",
"Rabalon.RTM. SJ5400N", "Rabalon.RTM. SJ6400N", "Rabalon.RTM.
SJ7400N", "Rabalon.RTM. SJ8400N", "Rabalon.RTM. SJ9400N" and
"Rabalon.RTM. SR04", trade names, available from Mitsubishi
Chemical Corporation. Other specific examples of the styrene
block-containing thermoplastic elastomer include "Epofriend A1010",
trade name, available from Daicel Chemical Industries; and "Septon
HG-252", trade name, available from Kuraray Co., Ltd.
[0044] Into the resin composition of the mid layer 12 may be
blended a filler for the purpose of adjusting specific gravity and
the like. Illustrative examples of suitable filler include zinc
oxide, barium sulfate, calcium carbonate and magnesium carbonate.
Powders of a highly dense metal may be blended as a filler.
Specific examples of the highly dense metal include tungsten and
molybdenum. The amount of the filler is determined ad libitum so
that an intended specific gravity of the mid layer 12 can be
attained. Into the mid layer 12 may be also blended a coloring
agent, crosslinked rubber powders or synthetic resin powders.
[0045] The mid layer 12 has a hardness H2 of 40 or greater and 75
or less. The mid layer 12 having a hardness H2 of no less than 40
can achieve excellent resilience performance of the golf ball 2. In
addition, with the mid layer 12 having a hardness H2 of no less
than 40, a core 4 having energy growing gradient can be attained.
This core 4 is responsible for suppression of the spin upon a shot
with a driver. In these respects, the hardness H2 is more
preferably no less than 45, and particularly preferably no less
than 48. The mid layer 12 having a outer-hard/inner-soft structure
H2 of no greater than 75 enables excellent feel at impact to be
achieved. In this respect, the hardness H2 is more preferably no
greater than 70, and particularly preferably no greater than
65.
[0046] The hardness H2 of the mid layer 12 and the hardness H3 of
the cover 6 may be measured in accordance with a standard of
"ASTM-D 2240-68". For the measurement, an automated rubber hardness
scale which is equipped with a Shore D type hardness scale ("P1",
trade name, available from Koubunshi Keiki Co., Ltd.) is used. For
the measurement, a sheet which was formed by hot press is used
having a thickness of about 2 mm and consisting of the same
material as that of the mid layer 12 (or the cover 6). Prior to the
measurement, the sheet is stored at a temperature of 23.degree. C.
for two weeks. When the measurement is carried out, three sheets
are overlaid.
[0047] The mid layer 12 has a thickness of preferably 0.3 mm or
greater and 2.5 mm or less. The mid layer 12 having a thickness of
no less than 0.3 mm can achieve excellent resilience performance of
the golf ball 2. In this respect, the thickness is more preferably
no less than 0.5 mm, and particularly preferably no less than 0.7
mm. The mid layer 12 having a thickness of no greater than 2.5 mm
does not impair the feel at impact of the golf ball 2. In this
respect, the thickness Tm is more preferably no greater than 2.0
mm.
[0048] The amount of compressive deformation of the core 4 is
preferably 1.8 mm or greater and 4.0 mm or less. The core 4 having
the amount of compressive deformation of no less than 1.8 mm
enables excellent feel at impact of the golf ball 2 to be achieved.
In this respect, the amount of compressive deformation is more
preferably no less than 2.0 mm, and particularly preferably no less
than 2.2 mm. As described later, this golf ball 2 has a soft cover
6. Upon hitting of the golf ball 2, the core 4 is greatly deformed
resulting from the cover 6 being soft. The core 4 having the amount
of compressive deformation of no greater than 4.0 mm can achieve
excellent resilience performance of the golf ball 2. In this
respect, the amount of compressive deformation is more preferably
no greater than 3.7 mm, and particularly preferably no greater than
3.4 mm.
[0049] The cover 6 is constituted with a resin composition.
Illustrative examples of the base resin for the resin composition
include polyurethanes, ionomer resins, polyamides, polyesters,
polystyrenes and polyolefins. Two or more polymers may be used in
combination.
[0050] A polymer suited for the cover 6 is a thermoplastic
polyurethane elastomer. The thermoplastic polyurethane elastomers
are soft. The thermoplastic polyurethane elastomer suppresses
slipping of the golf ball 2 on the club face. When golf ball 2
having a cover 6 constituted with a thermoplastic polyurethane
elastomer is hit with a short iron, a great spin rate is attained.
The cover 6 constituted with a thermoplastic polyurethane elastomer
is responsible for the control performance on a shot with a short
iron. The thermoplastic polyurethane elastomer is also responsible
for the scuff resistance performance of the cover 6. Moreover, due
to the thermoplastic polyurethane elastomer, excellent feel at
impact can be achieved upon hitting with a putter or short
iron.
[0051] Other resin may be also used in combination with the
thermoplastic polyurethane elastomer. In light of the control
performance, the thermoplastic polyurethane elastomer is included
in the base polymer as a principal component in the case of use in
combination. The percentage of the thermoplastic polyurethane
elastomer occupying the entire base polymer is preferably no less
than 50% by weight, more preferably no less than 70% by weight, and
particularly preferably no less than 85% by weight.
[0052] The thermoplastic polyurethane elastomer includes a
polyurethane component as a hard segment, and a polyester component
or a polyether component as a soft segment. Illustrative examples
of the curing agent for the polyurethane component include an
alicyclic diisocyanate, an aromatic diisocyanate and an aliphatic
diisocyanate. Illustrative examples of the alicyclic diisocyanate
include 4,4'-dicyclohexylmethane diisocyanate (H.sub.12MDI),
1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), isophorone
diisocyanate (IPDI) and trans-1,4-cyclohexane diisocyanate (CHDI).
In light of versatility and processability, H.sub.12MDI is
preferred. Illustrative examples of the aromatic diisocyanate
include 4,4'-diphenylmethane diisocyanate (MDI) and toluene
diisocyanate (TDI). Illustrative examples of the aliphatic
diisocyanate include hexamethylene diisocyanate (HDI). Two or more
kinds of the diisocyanate may be used in combination.
[0053] In particular, an alicyclic diisocyanate is preferred. Since
the alicyclic diisocyanate has no double bond in the main chain,
yellowing of the cover 6 can be suppressed. In addition, since an
alicyclic diisocyanate is excellent in strength, the cover 6 can be
prevented from being scuffed.
[0054] Thermoplastic polyurethane elastomers having a material
hardness of no greater than 42, and still further no greater than
are particularly preferred. Such an elastomer enables the cover 6
to have a small hardness H3. For the measurement of the material
hardness, a sheet consisting of the polymer alone may be used. The
measuring method is the same as the measuring method of the
hardness H2 of the mid layer 12.
[0055] Specific examples of the thermoplastic polyurethane
elastomer include "Elastollan.RTM. XNY80A", "Elastollan.RTM.
XNY85A", "Elastollan.RTM. XNY90A", "Elastollan.RTM. XNY97A",
"Elastollan.RTM. XNY585", "Elastollan.RTM. XKP016N" and
"Elastollan.RTM. ET858D", trade names, available from BASF Japan
Ltd; and "Rezamin P4585LS" and "Rezamin PS62490", trade names,
available from Dainichiseika Color & Chemicals Mfg. Co.,
Ltd.
[0056] Other resin suited for use in the cover 6 is an ionomer
resin. The ionomer resin similar to those described above in
connection with the mid layer 12 can be used for the cover 6. The
ionomer resin may be used in combination with a styrene
block-containing thermoplastic elastomer. The ionomer resin may be
used in combination with an ethylene-methacrylic acid copolymer.
Specific examples of the ethylene-methacrylic acid copolymer
include "Nucrel.RTM. 1050H", trade name, available from Du
Pont-MITSUI POLYCHEMICALS Co., Ltd.
[0057] Into the cover 6 may be blended a coloring agent such as
titanium dioxide, a filler such as barium sulfate, a dispersant, an
antioxidant, an ultraviolet absorbent, a light stabilizer, a
fluorescent agent, a fluorescent brightening agent and the like as
needed.
[0058] The cover 6 has a hardness H3 of no greater than 61. In
other words, the cover 6 is soft. This cover 6 enables a great spin
rate to be attained upon a shot with a short iron. This golf ball 2
is excellent in the control performance.
[0059] When the base material of the cover 6 is a polyurethane, the
hardness H3 is preferably no greater than 55, more preferably no
greater than 45, and particularly preferably no greater than 40.
The hardness H3 is preferably no less than 20, more preferably no
less than 25, and particularly preferably no less than 30.
[0060] When the base material of the cover 6 is an ionomer resin,
the hardness H3 is preferably no greater than 61, more preferably
no greater than 60, and particularly preferably no greater than 58.
The hardness H3 is preferably no less than 40, more preferably no
less than 44, and particularly preferably no less than 48.
[0061] The cover 6 has a thickness of preferably no greater than
1.0 mm. As described above, the cover 6 is soft. The soft cover 6
is disadvantageous in terms of the resilience coefficient of the
golf ball 2. On a shot with a driver, both the mid layer 12 and the
center 10 of the golf ball 2 are also deformed greatly. The cover 6
having a thickness of no greater than 1.0 mm does not adversely
affect the resilience coefficient to a large extent on a shot with
a driver, even when the cover 6 is soft. In light of the flight
performance, the thickness is more preferably no greater than 0.9
mm, and particularly preferably no greater than 0.8 mm. In light of
the spin performance, the thickness is preferably no less than 0.3
mm.
[0062] A reinforcing layer may be provided between the mid layer 12
and the cover 6. The reinforcing layer improves adhesion between
the mid layer 12 and the cover 6. For the base polymer of the
reinforcing layer, a two-component cured thermosetting resin may be
suitably used. Specific examples of the two-component cured
thermosetting resin include epoxy resins, urethane resins, acrylic
resins, polyester based resins and cellulose based resins.
[0063] Particularly preferable polymer is a resin obtained by
curing a bisphenol A type epoxy with a polyamide based curing
agent. The bisphenol A type epoxy is obtained by a reaction of
bisphenol A with an epoxy group-containing compound such as
epichlorohydrin. The polyamide based curing agent has multiple
amino groups, and one or more amide groups. This amino group can
react with an epoxy group. Specific examples of the polyamide based
curing agent include polyamide-amine curing agents and modified
products of the same. Upon mixing of the epoxy and the polyamide
based curing agent, the ratio of the epoxy equivalent, and the
amine active hydrogen equivalent of the polyamide based curing
agent is preferably 1.0/1.4 or greater and 1.0/1.0 or less.
[0064] The two-component cured urethane resin is also suited for
the reinforcing layer. The two-component cured urethane resin is
obtained by a reaction of a base material with a curing agent. A
two-component cured urethane resin obtained by a reaction of a base
material containing a polyol with a curing agent containing a
polyisocyanate or a derivative thereof, or a two-component cured
urethane resin obtained by a reaction of a base material containing
an isocyanate group-ended urethane prepolymer with a curing agent
having active hydrogen may be used. In particular, two-component
cured urethane resins obtained by a reaction of a base material
containing a polyol component with a curing agent containing a
polyisocyanate or a derivative thereof are preferred.
[0065] The reinforcing layer particularly exerts its effect in the
golf ball 2 in which the base material of the mid layer 12 is an
ionomer resin, and the base material of the cover 6 is
polyurethane. The reinforcing layer exerts its effect also in the
golf ball 2 in which the base material of the mid layer 12 is a
polyurethane, and the base material of the cover 6 is an ionomer
resin.
[0066] The paint layer 8 has a Martens hardness H4 of no greater
than 2.0 mgf/.mu.m.sup.2. This paint layer 8 is soft. This paint
layer 8 suppresses slipping of the golf ball 2 on the club face. A
great spin rate is attained upon hitting of the golf ball 2 with a
short iron.
[0067] The paint layer 8 suppresses the slipping even when
turfgrass is interposed between the club face and the golf ball 2.
This paint layer 8 suppresses slipping even when water is
interposed between the club face and the golf ball 2. This paint
layer 8 is responsible for stability of the spin rate. This paint
layer 8 suppresses the flyer. Golf players can easily let the golf
ball drop at an intended position. This golf ball 2 is excellent in
the control performance.
[0068] As described above, the cover 6 is soft. Upon hitting of
this golf ball 2, the cover 6 is greatly deformed. Since the paint
layer 8 is also soft, the paint layer 8 is deformed following the
deformation of the cover 6. Even though the golf ball 2 is
repeatedly hit, the paint layer 8 is less likely to be cracked.
Even though the golf ball 2 is repeatedly hit, this paint layer 8
is less likely to be abraded from the cover 6.
[0069] In light of the control performance and durability, the
paint layer 8 has a Martens hardness H4 of no greater than 1.4
mgf/.mu.m.sup.2, more preferably no greater than 1.0
mgf/.mu.m.sup.2, and particularly preferably no greater than 0.18
mgf/.mu.m.sup.2. The Martens hardness H4 is preferably no greater
than 0.01 mgf/.mu.m.sup.2.
[0070] For the measurement of the Martens hardness H4, a
nanoindenter "ENT-2100" available from Elionix Inc., is used. The
measurement conditions are as in the following.
[0071] Load F: 20 mgf
[0072] Angle .alpha. of Berkovich indenter: 65.03.degree.
[0073] Material of Berkovich indenter: SiO.sub.2
The area As (h) is calculated based on the penetration depth h and
the angle .alpha. of the indenter, according to the following
formula:
As(h)=3*31/2*tan .alpha./cos .alpha.*h.sup.2
The Martens hardness H4 is calculated based on the load F and the
area As (h), according to the following formula:
H4=F/As(h)
The measurement is carried out on a paint film sheet having a
thickness of 100 .mu.m.
[0074] The paint layer 8 is constituted with a resin composition.
Preferable base resin of this resin composition is a two-component
cured polyurethane. The two-component cured polyurethane is
obtained by a reaction of a base material containing a polyol with
a curing agent containing a polyisocyanate or a derivative thereof.
The paint layer 8 including the two-component cured polyurethane is
soft.
[0075] As the polyol for the base material, a polyol having a low
molecular weight and a polyol having a high molecular weight may be
used. Examples of the polyol having a low molecular weight include
diols and triols. Specific examples of the diol include ethylene
glycol, diethylene glycol, triethylene glycol, 1,3-butanediol,
1,4-butanediol, neopentyl glycol and 1,6-hexanediol. Specific
examples of the triol include trimethylolpropane and hexanetriol.
Examples of the polyol having a high molecular weight include
polyether polyols such as polyoxyethylene glycol (PEG),
polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol
(PTMG); condensed polyester polyols such as polyethylene adipate
(PEA), polybutylene adipate (PBA) and polyhexamethylene adipate
(PH2A); lactone based polyester polyols such as
poly-.epsilon.-caprolactone (PCL); polycarbonate polyols such as
polyhexamethylene carbonate; and acrylic polyols. Polyols having a
weight average molecular weight of 50 or greater and 2,000 or less,
and particularly 100 or greater and 1,000 or less are preferred.
Two or more kinds of the polyols may be used in combination.
[0076] Urethane polyol may be used for the base material. The
urethane polyol has a urethane bond, and at least two or more
hydroxyl groups. Preferably, the urethane polyol has hydroxyl
groups at its end. The urethane polyol may be obtained by allowing
a polyol and a polyisocyanate to react at a ratio by which an
excess molar ratio of the hydroxyl groups of the polyol to the
isocyanate groups of the polyisocyanate is provided. By using the
urethane polyol as the base material, the reaction of the base
material with the curing agent can be completed within a short
period of time. The base material may contain urethane polyol, and
a polyol not having any urethane bond.
[0077] Specific examples of the polyisocyanate used for producing
the urethane polyol include aromatic polyisocyanates such as
2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of
2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI),
4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene
diisocyanate (NDI), 3,3'-bitolylene-4,4'-diisocyanate (TODI),
xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate
(TMXDI) and paraphenylene diisocyanate (PPDI); alicyclic
polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate
(H.sub.12MDI), hydrogenated xylylene diisocyanate (H.sub.6XDI),
hexamethylene diisocyanate (HDI) and isophorone diisocyanate
(IPDI); and aliphatic polyisocyanates. Two or more polyisocyanates
may be used in combination.
[0078] As described above, the curing agent contains a
polyisocyanate or a derivative thereof. The aforementioned
polyisocyanate as a raw material of the urethane polyol may be used
in the curing agent.
[0079] The polyisocyanate particularly suited for the curing agent
is a buret-modified form of hexamethylene diisocyanate. This
buret-modified form has a buret bond represented by the following
chemical formula. This buret bond can be provided by a reaction of
an urea bond with an excess isocyanate group. This buret-modified
form has a three-dimensional structure. The polyurethane obtained
with the curing agent containing this buret-modified form has a
weak restraining force among molecules. The paint layer 8
constituted with this polyurethane has a small Martens hardness H4.
This paint layer 8 is also excellent in weather resistance.
##STR00001##
[0080] The curing agent may also contain other polyisocyanate in
addition to the buret-modified form of hexamethylene diisocyanate.
The percentage of this buret-modified form relative to the total
amount of the polyisocyanate is preferably no less than 20% by
weight, and particularly preferably no less than 50% by weight.
[0081] The NCO/OH ratio in the resin composition of the paint layer
8 is preferably 1.0/1.0 or greater and 1.4/1.0 or less, and
particularly preferably 1.1/1.0 or greater and 1.3/1.0 or less.
[0082] The resin composition of the paint layer 8 may include
additives such as a coloring agent (typically, titanium dioxide),
an antioxidant, a light stabilizer, a fluorescent whitening agent,
an ultraviolet ray absorbing agent and the like. The additive may
be added either to the base material, or to the curing agent.
[0083] The paint layer 8 has a thickness of 5 .mu.m or greater and
40 .mu.m or less. The paint layer 8 having a thickness of no less
than 5 .mu.m can be responsible for spin performance and stability
of the spin rate. In this respect, the thickness is more preferably
no less than 6 .mu.m, and particularly preferably no less than 10
.mu.m. The paint layer 8 having a thickness of no greater than 40
.mu.m does not lead to excessive spin upon a shot with a driver. In
this respect, the thickness is more preferably no greater than 38
.mu.m, and particularly preferably no greater than 30 .mu.m.
[0084] The paint layer 8 is obtained by coating a liquid, which is
prepared by dissolving or dispersing the base material and the
curing agent in a solvent, on the surface of the cover 6. The
coating may be carried out by electrostatic coating, spray coating
or the like. The solvent is volatilized after the coating to permit
a reaction of the base material with the curing agent thereby
forming the paint layer 8. Illustrative examples of preferred
solvent include toluene, isopropyl alcohol, xylene, methyl ethyl
ketone, methyl isobutyl ketone, ethylene glycol monomethyl ether,
ethylbenzene, propylene glycol monomethyl ether, isobutyl alcohol
and ethyl acetate.
[0085] The golf ball may also have other paint layer on the
internal side or the external side of the paint layer 8. The other
paint layer preferably has a Martens hardness of no greater than
2.0 mgf/.mu.m.sup.2. Alternatively, the other paint layer may have
a Martens hardness of greater than 2.0 mgf/.mu.m.sup.2.
[0086] It is preferred that the golf ball 2 has an amount of
compressive deformation of 2.0 mm or greater and 3.5 mm or less.
When the golf ball 2 having an amount of compressive deformation of
no less than 2.0 mm is hit with a driver, excessive spin is not
generated. In this respect, the amount of compressive deformation
is more preferably no less than 2.1 mm, and particularly preferably
no less than 2.2 mm. The golf ball 2 having an amount of
compressive deformation of no greater than 3.5 mm is excellent in
the resilience performance. In this respect, the amount of
compressive deformation is more preferably no greater than 3.4 mm,
and particularly preferably no greater than 3.3 mm.
EXAMPLES
Example 1
[0087] A rubber composition (1) was obtained by kneading 100 parts
by weight of polybutadiene ("BR-730", trade name, available from
JSR Corporation), 38 parts by weight of zinc diacrylate, 5 parts by
weight of zinc oxide, an adequate amount of barium sulfate, 0.5
parts by weight of diphenyl disulfide (Sumitomo Seika Chemicals
Co., Ltd.) and 0.9 parts by weight of dicumyl peroxide (NOF
Corporation). The amount of barium sulfate was adjusted such that
the golf ball had a weight of 45.6 g. This rubber composition (1)
was placed into a mold having upper and lower mold half each having
a hemispherical cavity, and heated under a temperature of
170.degree. C. for 20 minutes to obtain a center having a diameter
of 39.7 mm.
[0088] A resin composition (a) was obtained by kneading 55 parts by
weight of an ionomer resin (Surlyn.RTM. 8945, supra), 45 parts by
weight of other ionomer resin (Himilan.RTM. AM7329, supra) and 4
parts by weight of titanium dioxide in a biaxial kneading extruder.
This resin composition (a) was rendered to cover around the center
by injection molding to obtain a mid layer. The mid layer had a
thickness of 1.0 mm.
[0089] A paint composition containing a two-component cured epoxy
resin as a base polymer ("POLIN 750LE", trade name, available from
Shinto Paint Co., Ltd.) was prepared. The base material of this
paint composition consists of 30 parts by weight of a bisphenol A
type solid epoxy resin and 70 parts by weight of a solvent. The
curing agent of this paint composition consists of 40 parts by
weight of denatured polyamide amine, 55 parts by weight of a
solvent and 5 parts by weight of titanium dioxide. The weight ratio
of the base material and the curing agent was 1/1. This paint
composition was coated on the surface of the mid layer with a spray
gun, and kept in an atmosphere of 23.degree. C. for 12 hrs to give
a reinforcing layer.
[0090] A resin composition (c) was obtained by kneading 100 parts
by weight of a thermoplastic polyurethane elastomer
(Elastollan.RTM. XNY90A, supra) and 3 parts by weight of titanium
dioxide in a biaxial kneading extruder. Half shells were obtained
from this resin composition (c) with compression molding. A sphere
comprising the center, the mid layer and the reinforcing layer was
covered by two pieces of the half shell. The sphere and half shells
were placed into a mold having upper and lower mold half each
having a hemispherical cavity to obtain a cover with compression
molding. The cover had a thickness of 0.5 mm.
[0091] A polyester polyol, and a polyisocyanate containing a
buret-modified form of hexamethylene diisocyanate were mixed to
obtain a paint composition (VII). This composition had a NCO/OH
ratio of 1.2:1.0. This paint composition (VII) was coated on the
cover with a spray gun, and kept in an atmosphere at 40.degree. C.
for 24 hrs to obtain a paint layer. This golf ball had a diameter
of 42.7 mm, and a weight of 45.6 g.
Examples 2 to 16, and Comparative Examples 1 to 2
[0092] Golf balls of Examples 2 to 16, and Comparative Examples 1
to were obtained in a similar manner to Example 1 except that
specifications of the center, the mid layer, the cover and the
paint layer were as listed in Tables 4 and 5 below. The
compositions of the center are presented in Table 1 below. The
compositions of the mid layer and the cover are presented in Table
2 below. The compositions of the paint layer are presented in Table
3 below.
Example 17
[0093] A rubber composition (3) was obtained by kneading 100 parts
by weight of polybutadiene (BR-730, supra), 31 parts by weight of
zinc diacrylate, 5 parts by weight of zinc oxide, an adequate
amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide
(Sumitomo Seika Chemicals Co., Ltd.) and 0.9 parts by weight of
dicumyl peroxide (NOF Corporation). The amount of barium sulfate
was adjusted such that the golf ball had a weight of 45.6 g. This
rubber composition (3) was placed into a mold having upper and
lower mold half each having a hemispherical cavity, and heated
under a temperature of 170.degree. C. for 20 minutes to obtain a
center having a diameter of 38.9 mm.
[0094] A resin composition (b) was obtained by kneading 35 parts by
weight of an ionomer resin (Surlyn.RTM. 8945, supra), 34 parts by
weight of other ionomer resin (Himilan.RTM. AM7329, supra), 31
parts by weight of a styrene block-containing thermoplastic
elastomer (Rabalon.RTM. T3221C, supra) and 3 parts by weight of
titanium dioxide in a biaxial kneading extruder. This resin
composition (b) was rendered to cover around the center by
injection molding to obtain a mid layer. The mid layer had a
thickness of 1.0 mm.
[0095] A resin composition (i) was obtained by kneading 22 parts by
weight of an ionomer resin (Surlyn.RTM. 8945, supra), 50 parts by
weight of other ionomer resin (Himilan.RTM. AM7329, supra), 20
parts by weight of an ethylene-methacrylic acid copolymer
(Nucrel.RTM. 1050H, supra), 8 parts by weight of a styrene
block-containing thermoplastic elastomer (Rabalon.RTM. T3221C,
supra) and 3 parts by weight of titanium dioxide in a biaxial
kneading extruder. This resin composition (i) was rendered to cover
around the mid layer by injection molding to obtain a cover. The
cover had a thickness of 1.0 mm.
[0096] The aforementioned paint composition (VII) was coated on the
cover, and kept in an atmosphere at 40.degree. C. for 24 hrs to
obtain a paint layer. This golf ball had a diameter of 42.7 mm, and
a weight of 45.6 g.
Examples 18 to 28, and Comparative Examples 3 to 5
[0097] Golf balls of Examples 18 to 28, and Comparative Examples 3
to 5 were obtained in a similar manner to Example 17 except that
specifications of the center, the mid layer, the cover and the
paint layer were as listed in Tables 6 and 7 below. The
compositions of the center are presented in Table 1 below. The
compositions of the mid layer and the cover are presented in Table
2 below. The compositions of the paint layer are presented in Table
3 below.
[Shot with Driver]
[0098] A driver with a titanium head was attached to a swing
machine available from True Temper Co. Then the golf ball was hit
under a condition to give the head speed of 45 m/sec, and the spin
rate immediately after the hitting, and the travel distance (i.e.,
the distance from the launching point to the point where the ball
stopped) were measured. Mean values of 10 times measurements are
shown in Tables 4 to 7 below.
[Shot with Sand Wedge]
[0099] A sand wedge was attached to a swing machine available from
True Temper Co. Then the golf ball was hit under a condition to
give the head speed of 21 m/sec, and the spin rate immediately
after the hitting was measured. Mean values of the spin rates Sd of
10 times measurements were determined. Furthermore, water was
applied on the golf ball and the club face, and the golf balls were
hit with the club. Thus, the spin rate immediately after the
hitting was measured. Mean values of the spin rates Sw of 10 times
measurements were determined. Spin retention rate Rs was calculated
based on the spin rate Sd in the dry state and the spin rate Sw in
the wet state, according to the following formula:
Rs=(Sw/Sd)*100
The results are shown in Tables 4 to 7 below.
[Durability of Paint Film]
[0100] A driver with a titanium head was attached to a swing
machine available from True Temper Co. Then the golf ball was hit
150 times under a condition to give the head speed of 45 m/sec. The
golf ball was visually observed, and rating was performed based on
the following criteria.
[0101] A: Abrasion not found;
[0102] B: Percentage area of abraded portion being no greater than
5%;
[0103] C: Percentage area of abraded portion being greater than 5%
and 25% or less
[0104] D: Percentage area of abraded portion exceeding 25%
The results are shown in Tables 4 to 7 below.
TABLE-US-00001 TABLE 1 Composition of Center (parts by weight) (1)
(2) (3) (4) BR-730 100 100 100 100 Zinc diacrylate 38 33 31 30 Zinc
oxide 5 5 5 5 Barium sulfate adequate adequate adequate adequate
amount amount amount amount Diphenyl disulfide 0.5 0.5 0.5 0.5
Dicumyl peroxide 0.9 0.9 0.9 0.9
TABLE-US-00002 TABLE 2 Composition of Mid Layer and Cover (parts by
weight) (a) (b) (c) (d) (e) (f) (g) (h) (i) Surlyn .RTM. 8945 55 35
-- -- -- -- 40 30 22 Himilan .RTM. AM7329 45 34 -- -- -- -- 50 50
50 Nucrel .RTM. 1050H -- -- -- -- -- 10 20 20 Rabalon .RTM. T3221C
-- 31 -- -- -- -- -- -- 8 Elastollan .RTM. XNY90A -- -- 100 55 --
10 -- -- -- Elastollan .RTM. XNY80A -- -- -- -- 100 -- -- -- --
Elastollan .RTM. ET858D -- -- -- 45 -- 90 -- -- -- Titanium dioxide
4 3 3 3 3 3 3 3 -- Ultramarine blue -- -- 0.04 0.04 0.04 0.04 0.04
0.04 -- Hardness (Shore D) 65 48 38 47 26 56 62 60 56
TABLE-US-00003 TABLE 3 Composition of Paint Layer (NCO/OH ratio)
(I) (II) (III) (IV) (V) (VI) (VII) Polyol *1 1.00 1.00 1.00 1.00
1.00 1.00 -- Polyol *2 -- -- -- -- -- -- 1.00 Nurate form of 0.84
-- -- -- -- -- -- hexamethylene diisocyanate Buret-modified -- 1.20
0.84 0.60 0.24 0.18 1.20 product of hexamethylene diisocyanate
Isophorone 0.36 -- 0.36 0.60 0.96 1.02 -- diisocyanate Martens
hardness 4.2 0.18 1.4 1.7 2.0 2.2 0.12 (mgf/.mu.m.sup.2) *1:
Mixture of polyether polyol and polyester polyol Hydroxyl value: 82
mgKOH/g *2: Polyester polyol Hydroxyl value: 170 mgKOH/g
TABLE-US-00004 TABLE 4 Evaluation Results Com. Com. Exa. 1 Exa. 2
Exa. 3 Exa. 4 Exa. 5 Exa. 2 Exa. 1 Center Composition (1) (1) (1)
(1) (1) (1) (1) Diameter (mm) 39.7 39.7 39.7 39.7 39.7 39.7 39.7
Surface hardness H1 (JIS-C) 84 84 84 84 84 84 84 Mid Composition
(a) (a) (a) (a) (a) (a) (a) layer Hardness H2 (Shore D) 65 65 65 65
65 65 65 Diameter (mm) 41.7 41.7 41.7 41.7 41.7 41.7 41.7 Thickness
(mm) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Cover Composition (c) (c) (c) (c)
(c) (c) (c) Hardness H3 (Shore D) 38 38 38 38 38 38 38 Thickness
(mm) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Paint Composition (I) (II) (III)
(IV) (V) (VI) (VII) layer Thickness (.mu.m) 18 18 18 18 18 18 18
Hardness H4 (mgf/.mu.m.sup.2) 4.2 0.18 1.4 1.7 2.0 2.2 0.12 Ball
Compressive Deformation (mm) 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Driver
Spin rate (rpm) 2900 2920 2920 2900 2900 2900 2950 Travel distance
(m) 240 240 240 240 240 240 239 Sand Spin rate Sd (rpm) 6800 6860
6850 6840 6830 6810 6900 wedge Spin rate Sw (rpm) 4500 5500 5000
4900 4800 4600 5600 Rate Rs (%) 66 80 73 72 70 68 81 Durability of
paint film D A B B B D A
TABLE-US-00005 TABLE 5 Evaluation Results Exa. Exa. Exa. 6 Exa. 7
Exa. 8 Exa. 9 10 11 Center Composition (1) (1) (1) (1) (1) (1)
Diameter (mm) 39.7 39.7 39.7 39.7 39.7 39.7 Surface hardness 84 84
84 84 84 84 H1 (JIS-C) Mid Composition (a) (a) (a) (a) (a) (a)
layer Hardness 65 65 65 65 65 65 H2 (Shore D) Diameter (mm) 41.7
41.7 41.7 41.7 41.7 41.7 Thickness (mm) 1.0 1.0 1.0 1.0 1.0 1.0
Cover Composition (c) (c) (c) (c) (e) (d) Hardness 38 38 38 38 26
47 H3 (Shore D) Thickness (mm) 0.5 0.5 0.5 0.5 0.5 0.5 Paint
Composition (VII) (VII) (VII) (VII) (VII) (VII) layer Thickness
(.mu.m) 4 6 38 45 18 18 Hardness 0.12 0.12 0.12 0.12 0.12 0.12 H4
(mgf/.mu.m.sup.2) Ball Compressive 2.3 2.3 2.3 2.3 2.4 2.3
Deformation (mm) Driver Spin rate (rpm) 2900 2930 2980 3000 3000
2850 Travel distance (m) 240 239 238 237 237 241 Sand Spin rate Sd
(rpm) 6820 6850 6950 7000 7150 6500 wedge Spin rate Sw (rpm) 4950
5250 5800 5900 5900 5100 Rate Rs (%) 73 77 83 84 83 78 Durability
of paint film A A A A A A Exa. Exa. Exa. Exa. Exa. 12 13 14 15 16
Center Composition (1) (1) (1) (1) (2) Diameter (mm) 39.7 40.1 38.9
38.3 39.7 Surface hardness 84 84 84 84 82 H1 (JIS-C) Mid
Composition (a) (a) (a) (a) (a) layer Hardness 65 65 65 65 65 H2
(Shore D) Diameter (mm) 41.7 42.1 40.9 40.3 41.7 Thickness (mm) 1.0
1.0 1.0 1.0 1.0 Cover Composition (f) (c) (c) (c) (c) Hardness 56
38 38 38 38 H3 (Shore D) Thickness (mm) 0.5 0.3 0.9 1.2 0.5 Paint
Composition (VII) (VII) (VII) (VII) (VII) layer Thickness (.mu.m)
18 18 18 18 18 Hardness 0.12 0.12 0.12 0.12 0.12 H4
(mgf/.mu.m.sup.2) Ball Compressive 2.2 2.2 2.3 2.2 2.9 Deformation
(mm) Driver Spin rate (rpm) 2750 2850 3050 3200 2850 Travel
distance (m) 242 241 236 234 238 Sand Spin rate Sd (rpm) 6000 6400
7200 7400 6800 wedge Spin rate Sw (rpm) 4300 5000 5800 6000 5500
Rate Rs (%) 72 78 81 81 81 Durability of paint film A A A A A
TABLE-US-00006 TABLE 6 Evaluation Results Com. Exa. Exa. Exa. Exa.
Com. Exa. Exa. 3 18 19 20 21 Exa. 4 17 Center Composition (3) (3)
(3) (3) (3) (3) (3) Diameter (mm) 38.9 38.9 38.9 38.9 38.9 38.9
38.9 Surface hardness H1 (JIS-C) 81 81 81 81 81 81 81 Mid
Composition (b) (b) (b) (b) (b) (b) (b) layer Hardness H2 (Shore D)
48 48 48 48 48 48 48 Diameter (mm) 40.9 40.9 40.9 40.9 40.9 40.9
40.9 Thickness (mm) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Cover Composition
(i) (i) (i) (i) (i) (i) (i) Hardness H3 (Shore D) 56 56 56 56 56 56
56 Thickness (mm) 0.9 0.9 0.9 0.9 0.9 0.9 0.9 Paint Composition (I)
(II) (III) (IV) (V) (VI) (VII) layer Thickness (.mu.m) 18 18 18 18
18 18 18 Hardness H4 (mgf/.mu.m.sup.2) 4.2 0.18 1.4 1.7 2.0 2.2
0.12 Ball Compressive Deformation (mm) 3.2 3.2 3.2 3.2 3.2 3.2 3.2
Driver Spin rate (rpm) 2500 2540 2530 2520 2520 2520 2550 Travel
distance (m) 242 241 242 242 242 242 241 Sand Spin rate Sd (rpm)
6300 6380 6350 6330 6320 6310 6400 wedge Spin rate Sw (rpm) 4000
4800 4500 4400 4300 4050 5000 Rate Rs (%) 63 75 71 70 68 64 78
Durability of paint film A A A A A A A
TABLE-US-00007 TABLE 7 Evaluation Results Exa. Exa. Exa. Exa. Exa.
Com. Exa. Exa. 22 23 24 25 26 Exa. 5 27 28 Center Composition (3)
(3) (3) (3) (3) (4) (3) (3) Diameter (mm) 38.9 38.9 38.9 38.9 38.9
38.9 39.7 38.3 Surface hardness H1 (JIS-C) 81 81 81 81 81 81 81 81
Mid Composition (b) (b) (b) (b) (b) (b) (b) (b) layer Hardness H2
(Shore D) 48 48 48 48 48 48 48 48 Diameter (mm) 40.9 40.9 40.9 40.9
40.9 40.9 41.7 40.3 Thickness (mm) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Cover Composition (i) (i) (i) (i) (h) (g) (i) (i) Hardness H3
(Shore D) 56 56 56 56 60 62 56 56 Thickness (mm) 0.9 0.9 0.9 0.9
0.9 0.9 0.5 1.2 Paint Composition (VII) (VII) (VII) (VII) (VII)
(VII) (VII) (VII) layer Thickness (.mu.m) 4 6 38 45 18 18 18 18
Hardness H4 (mgf/.mu.m.sup.2) 0.12 0.12 0.12 0.12 0.12 0.12 0.12
0.12 Ball Compressive Deformation (mm) 3.2 3.2 3.2 3.2 3.1 3.2 3.3
3.2 Driver Spin rate (rpm) 2500 2530 2580 2650 2420 2350 2650 2550
Travel distance (m) 242 241 240 238 244 245 239 238 Sand Spin rate
Sd (rpm) 6300 6330 6470 6550 6000 5400 6450 6000 wedge Spin rate Sw
(rpm) 4500 4700 5050 5200 4200 3650 5200 4500 Rate Rs (%) 71 74 78
79 70 68 81 75 Durability of paint film A A A A A A A A
[0105] As shown in Tables 4 to 7, the golf ball of each Example is
excellent in a variety of performances. Therefore, advantages of
the present invention are clearly suggested by these results of
evaluation.
[0106] The golf ball according to the present invention is
particularly suited for use in golf tournaments. The foregoing
description is just for illustrative examples; therefore, various
modifications can be made in the scope without departing from the
principles of the present invention.
* * * * *