U.S. patent application number 13/866073 was filed with the patent office on 2013-12-05 for golf ball.
This patent application is currently assigned to Dunlop Sports Co. Ltd.. The applicant listed for this patent is DUNLOP SPORTS CO. LTD.. Invention is credited to Kazuhiko ISOGAWA, Kosuke TACHIBANA.
Application Number | 20130324315 13/866073 |
Document ID | / |
Family ID | 48139824 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130324315 |
Kind Code |
A1 |
TACHIBANA; Kosuke ; et
al. |
December 5, 2013 |
GOLF BALL
Abstract
A golf ball 2 includes a core 4, amid layer 6, and a cover 10.
The core 4 includes a center 16, a first envelope layer 18, and a
second envelope layer 20. The first envelope layer 18 is formed by
a first rubber composition being crosslinked. The second envelope
layer 20 is formed by a second rubber composition being
crosslinked. The first rubber composition and/or the second rubber
composition include: a base rubber; a co-crosslinking agent; a
crosslinking initiator; and an acid and/or a salt. The
co-crosslinking agent is (1) an .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 8 carbon atoms; and/or (2) a metal salt
of an .alpha.,.beta.-unsaturated carboxylic acid having 3 to 8
carbon atoms.
Inventors: |
TACHIBANA; Kosuke;
(Kobe-shi, JP) ; ISOGAWA; Kazuhiko; (Kobe-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DUNLOP SPORTS CO. LTD. |
Kobe-shi |
|
JP |
|
|
Assignee: |
Dunlop Sports Co. Ltd.
Kobe-shi
JP
|
Family ID: |
48139824 |
Appl. No.: |
13/866073 |
Filed: |
April 19, 2013 |
Current U.S.
Class: |
473/373 |
Current CPC
Class: |
A63B 37/0063 20130101;
A63B 37/0003 20130101; C08K 5/0025 20130101; A63B 37/0064 20130101;
A63B 37/0092 20130101; A63B 37/0076 20130101; A63B 37/0039
20130101; A63B 37/0054 20130101; C08K 5/098 20130101; C08L 21/00
20130101; C08L 21/00 20130101; C08K 5/098 20130101; A63B 37/0051
20130101; C08K 5/0025 20130101 |
Class at
Publication: |
473/373 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2012 |
JP |
2012-124406 |
Claims
1. A golf ball comprising a core, a mid layer positioned outside
the core, and a cover positioned outside the mid layer, wherein the
core comprises a center, a first envelope layer positioned outside
the center, and a second envelope layer positioned outside the
first envelope layer, the first envelope layer is formed by a first
rubber composition being crosslinked, the second envelope layer is
formed by a second rubber composition being crosslinked, the first
rubber composition and/or the second rubber composition include:
(a) a base rubber; (b) a co-crosslinking agent; (c) a crosslinking
initiator; and (d) an acid and/or a salt, and the co-crosslinking
agent (b) is: (b-1) an .alpha.,.beta.-unsaturated carboxylic acid
having 3 to 8 carbon atoms; and/or (b-2) a metal salt of an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms.
2. The golf ball according to claim 1, wherein an amount of the
acid and/or the salt (d) is equal to or greater than 0.5 parts by
weight but equal to or less than 45 parts by weight, per 100 parts
by weight of the base rubber (a).
3. The golf ball according to claim 1, wherein the acid and/or the
salt (d) is a carboxylic acid and/or a salt thereof (d-1).
4. The golf ball according to claim 3, wherein a carbon number of a
carboxylic acid component of the carboxylic acid and/or the salt
thereof (d-1) is equal to or greater than 1 but equal to or less
than 30.
5. The golf ball according to claim 3, wherein the carboxylic acid
and/or the salt thereof (d-1) is a fatty acid and/or a salt
thereof.
6. The golf ball according to claim 3, wherein the carboxylic acid
and/or the salt thereof (d-1) is a zinc salt of a carboxylic
acid.
7. The golf ball according to claim 6, wherein the zinc salt of the
carboxylic acid is one or more members selected from the group
consisting of zinc octoate, zinc laurate, zinc myristate, and zinc
stearate.
8. The golf ball according to claim 1, wherein the first rubber
composition and/or the second rubber composition further include an
organic sulfur compound (e).
9. The golf ball according to claim 8, wherein the organic sulfur
compound (e) is at least one member selected from the group
consisting of thiophenols, diphenyl disulfides, thionaphthols,
thiuram disulfides, and metal salts thereof.
10. The golf ball according to claim 8, wherein the organic sulfur
compound (e) is one or more members selected from the group
consisting of 2-thionaphthol, bis(pentabromophenyl)disulfide, and
2,6-dichlorothiophenol.
11. The golf ball according to claim 8, wherein an amount of the
organic sulfur compound (e) is equal to or greater than 0.05 parts
by weight but equal to or less than 5.0 parts by weight, per 100
parts by weight of the base rubber (a).
12. The golf ball according to claim 1, wherein an amount of the
co-crosslinking agent (b) is equal to or greater than 15 parts by
weight but equal to or less than 50 parts by weight, per 100 parts
by weight of the base rubber (a).
13. The golf ball according to claim 1, wherein an amount of the
crosslinking initiator (c) is equal to or greater than 0.2 parts by
weight but equal to or less than 5.0 parts by weight, per 100 parts
by weight of the base rubber (a).
14. The golf ball according to claim 1, wherein the first rubber
composition and/or the second rubber composition include the
.alpha.,.beta.-unsaturated carboxylic acid (b-1), and the first
rubber composition and/or the second rubber composition further
include a metal compound (f).
15. The golf ball according to claim 1, wherein a JIS-C hardness
H(0) at a central point of the core is equal to or greater than 40
but equal to or less than 70, and a JIS-C hardness H(100) at a
surface of the core is equal to or greater than 78 but equal to or
less than 96.
16. The golf ball according to claim 15, wherein a difference
(H(100)-H(0)) between the hardness H(100) and the hardness H(0) is
equal to or greater than 15.
17. The golf ball according to claim 1, wherein a Shore D hardness
Hm of the mid layer is greater than a Shore D hardness Hc of the
cover.
18. The golf ball according to claim 17, wherein a difference
(Hm-Hc) between the hardness Hm and the hardness Hc is equal to or
greater than 18.
19. The golf ball according to claim 1, wherein a JIS-C hardness
H(39) at a point whose ratio of a distance from a central point of
the core to a radius of the core is 39% is greater than a JIS-C
hardness H(36) at a point whose ratio of a distance from the
central point of the core to the radius of the core is 36%.
20. The golf ball according to claim 1, wherein a JIS-C hardness
H(76) at a point whose ratio of a distance from a central point of
the core to a radius of the core is 76% is greater than a JIS-C
hardness H(75) at a point whose ratio of a distance from the
central point of the core to the radius of the core is 75%.
21. The golf ball according to claim 1, wherein a JIS-C hardness
H(100) at a surface of the core is greater than a JIS-C hardness
H(75) at a point whose ratio of a distance from a central point of
the core to a radius of the core is 75%.
22. The golf ball according to claim 21, wherein a difference
(H(100)-H(75)) between the hardness H(100) and the hardness H(75)
is equal to or greater than 4.
23. The golf ball according to claim 1, wherein the mid layer is
formed from a resin composition, the cover is formed from a resin
composition whose base resin is different from a base resin of the
mid layer, and the golf ball further comprises a reinforcing layer
between the mid layer and the cover.
24. The golf ball according to claim 1, wherein a diameter of the
center is equal to or greater than 10 mm but equal to or less than
20 mm.
Description
[0001] This application claims priority on Patent Application No.
2012-124406 filed in JAPAN on May 31, 2012. The entire contents of
this Japanese Patent Application are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to golf balls. Specifically,
the present invention relates to golf balls that include a core
having a three-layer structure, amid layer, and a cover.
[0004] 2. Description of the Related Art
[0005] Golf players' foremost requirement for golf balls is flight
performance. In particular, golf players place importance on flight
performance upon a shot with a driver. Flight performance
correlates with the resilience performance of a golf ball. When a
golf ball having excellent resilience performance is hit, the golf
ball flies at a high speed, thereby achieving a large flight
distance. Golf balls that include a core having excellent
resilience performance are disclosed in JP61-37178, JP2008-212681
(US2008/0214324), JP2008-523952 (US2006/0135287 and
US2007/0173607), and JP2009-119256 (US2009/0124757).
[0006] The core disclosed in JP61-37178 is obtained from a rubber
composition that includes a co-crosslinking agent and a
crosslinking activator. This publication discloses'palmitic acid,
stearic acid, and myristic acid as the crosslinking activator.
[0007] The core disclosed in JP2008-212681 is obtained from a
rubber composition that includes an organic peroxide, a metal salt
of an .alpha.,.beta.-unsaturated carboxylic acid, and a copper salt
of a fatty acid.
[0008] The core disclosed in JP2008-523952 is obtained from a
rubber composition that includes a metal salt of an unsaturated
monocarboxylic acid, a free radical initiator, and a non-conjugated
diene monomer.
[0009] The core disclosed in JP2009-119256 is obtained from a
rubber composition that includes a polybutadiene whose vinyl
content is equal to or less than 2%, whose cis 1,4-bond content is
equal to or greater than 80%, and which has an active end modified
with an alkoxysilane compound.
[0010] An appropriate trajectory height is required in order to
achieve a large flight distance. A trajectory height depends on a
spin rate and a launch angle. With a golf ball that achieves a high
trajectory by a high spin rate, a flight distance is insufficient.
With a golf ball that achieves a high trajectory by a high launch
angle, a large flight distance is obtained. Use of an
outer-hard/inner-soft structure in a golf ball can achieve a low
spin rate and a high launch angle. Modifications regarding a
hardness distribution of a core are disclosed in JP6-154357 (U.S.
Pat. No. 5,403,010), JP2008-194471 (U.S. Pat. No. 7,344,455,
US2008/0194358, US2008/0194359, and US2008/0214325), and
JP2008-194473 (US2008/0194357 and US2008/0312008).
[0011] In the core disclosed in JP6-154357, a JIS-C hardness H1 at
the central point of the core is 58 to 73, a JIS-C hardness H2 in a
region that extends over a distance range from equal to or greater
than 5 mm to equal to or less than 10 mm from the central point is
equal to or greater than 65 but equal to or less than 75, a JIS-C
hardness H3 at a point located at a distance of 15 mm from the
central point is equal to or greater than 74 but equal to or less
than 82, and a JIS-C hardness H4 at the surface of the core is
equal to or greater than 76 but equal to or less than 84. The
hardness H2 is greater than the hardness H1, the hardness H3 is
greater than the hardness H2, and the hardness H4 is equal to or
greater than the hardness H3.
[0012] In the core disclosed in JP2008-194471, a Shore D hardness
at the central point of the core is equal to or greater than 30 but
equal to or less than 48, a Shore D hardness at a point located at
a distance of 4 mm from the central point is equal to or greater
than 34 but equal to or less than 52, a Shore D hardness at a point
located at a distance of 8 mm from the central point is equal to or
greater than 40 but equal to or less than 58, a Shore D hardness at
a point located at a distance of 12 mm from the central point is
equal to or greater than 43 but equal to or less than 61, a Shore D
hardness in a region that extends over a distance range from equal
to or greater than 2 mm to equal to or less than 3 mm from the
surface of the core is equal to or greater than 36 but equal to or
less than 54, and a Shore D hardness at the surface is equal to or
greater than 41 but equal to or less than 59.
[0013] In the core disclosed in JP2008-194473, a Shore D hardness
at the central point of the core is equal to or greater than 25 but
equal to or less than 45, a Shore D hardness in a region that
extends over a distance range from equal to or greater than 5 mm to
equal to or less than 10 mm from the central point is equal to or
greater than 39 but equal to or less than 58, a Shore D hardness at
a point located at a distance of 15 mm from the central point is
equal to or greater than 36 but equal to or less than 55, and a
Shore D hardness at the surface of the core is equal to or greater
than 55 but equal to or less than 75.
[0014] JP2010-253268 (US2010/0273575) discloses a golf ball that
includes a core, an envelope layer, a mid layer, and a cover. In
the core, the hardness gradually increases from the central point
of the core to the surface of the core. The difference between a
JIS-C hardness at the surface and a JIS-C hardness at the central
point is equal to or greater than 15. The hardness of the cover is
greater than the hardness of the mid layer, and the hardness of the
mid layer is greater than the hardness of the envelope layer.
[0015] Golf players also place importance on spin performance of
golf balls. When a backspin rate is high, the run is short. It is
easy for golf players to cause a golf ball, to which backspin is
easily provided, to stop at a target point. When a sidespin rate is
high, the golf ball tends to curve. It is easy for golf players to
intentionally cause a golf ball, to which sidespin is easily
provided, to curve. A golf ball to which spin is easily provided
has excellent controllability. In particular, advanced golf players
place importance on controllability upon a shot with a short
iron.
[0016] Golf players' requirements for flight distance have been
escalated more than ever. An object of the present invention is to
provide a golf ball having excellent flight performance.
SUMMARY OF THE INVENTION
[0017] A golf ball according to the present invention includes a
core, a mid layer positioned outside the core, and a cover
positioned outside the mid layer. The core includes a center, a
first envelope layer positioned outside the center, and a second
envelope layer positioned outside the first envelope layer. The
first envelope layer is formed by a first rubber composition being
crosslinked. The second envelope layer is formed by a second rubber
composition being crosslinked. The first rubber composition and/or
the second rubber composition include: [0018] (a) a base rubber;
[0019] (b) a co-crosslinking agent; [0020] (c) a crosslinking
initiator; and [0021] (d) an acid and/or a salt. The
co-crosslinking agent (b) is:
[0022] (b-1) an .alpha.,.beta.-unsaturated carboxylic acid having 3
to 8 carbon atoms; and/or
[0023] (b-2) a metal salt of an .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 8 carbon atoms.
[0024] Preferably, an amount of the acid and/or the salt (d) is
equal to or greater than 0.5 parts by weight but equal to or less
than 45 parts by weight, per 100 parts by weight of the base rubber
(a).
[0025] Preferably, the acid and/or the salt (d) is a carboxylic
acid and/or a salt thereof (d-1).
[0026] Preferably, a carbon number of a carboxylic acid component
of the carboxylic acid and/or the salt thereof (d-1) is equal to or
greater than 1 but equal to or less than 30. Preferably, the
carboxylic acid and/or the salt thereof (d-1) is a fatty acid
and/or a salt thereof. Preferably, the carboxylic acid and/or the
salt thereof (d-1) is a zinc salt of a carboxylic acid. Preferable
examples of the zinc salt of the carboxylic acid include zinc
octoate, zinc laurate, zinc myristate, and zinc stearate.
[0027] Preferably, the first rubber composition and/or the second
rubber composition further include an organic sulfur compound (e).
Preferable examples of the organic sulfur compound (e) include
thiophenols, diphenyl disulfides, thionaphthols, thiuram
disulfides, and metal salts thereof. Preferable examples of the
organic sulfur compound (e) include 2-thionaphthol,
bis(pentabromophenyl)disulfide, and 2,6-dichlorothiophenol.
Preferably, an amount of the organic sulfur compound (e) is equal
to or greater than 0.05 parts by weight but equal to or less than
5.0 parts by weight, per 100 parts by weight of the base rubber
(a).
[0028] Preferably, an amount of the co-crosslinking agent (b) is
equal to or greater than 15 parts by weight but equal to or less
than 50 parts by weight, per 100 parts by weight of the base rubber
(a). Preferably, an amount of the crosslinking initiator (c) is
equal to or greater than 0.2 parts by weight but equal to or less
than 5.0 parts by weight, per 100 parts by weight of the base
rubber (a).
[0029] Preferably, the first rubber composition and/or the second
rubber composition include the .alpha.,.beta.-unsaturated
carboxylic acid (b-1). The first rubber composition and/or the
second rubber composition further include a metal compound (f).
[0030] Preferably, a JIS-C hardness H(0) at a central point of the
core is equal to or greater than 40 but equal to or less than 70,
and a JIS-C hardness H(100) at a surface of the core is equal to or
greater than 78 but equal to or less than 96.
[0031] Preferably, a difference (H(100)-H(0)) between the hardness
H(100) and the hardness H(0) is equal to or greater than 15.
[0032] Preferably, a Shore D hardness Hm of the mid layer is
greater than a Shore D hardness Hc of the cover. More preferably, a
difference (Hm-Hc) between the hardness Hm and the hardness Hc is
equal to or greater than 18.
[0033] Preferably, a JIS-C hardness H(39) at a point whose ratio of
a distance from a central point of the core to a radius of the core
is 39% is greater than a JIS-C hardness H(36) at a point whose
ratio of a distance from the central point of the core to the
radius of the core is 36%. Preferably, a JIS-C hardness H(76) at a
point whose ratio of a distance from a central point of the core to
a radius of the core is 76% is greater than a JIS-C hardness H(75)
at a point whose ratio of a distance from the central point of the
core to the radius of the core is 75%.
[0034] Preferably, a JIS-C hardness H(100) at a surface of the core
is greater than a JIS-C hardness H(75) at a point whose ratio of a
distance from a central point of the core to a radius of the core
is 75%. More preferably, a difference (H(100)-H(75)) between the
hardness H(100) and the hardness H(75) is equal to or greater than
4.
[0035] Preferably, the mid layer may be formed from a resin
composition, and the cover may be formed from a resin composition
whose base resin is different from a base resin of the mid layer.
Preferably, the golf ball further includes a reinforcing layer
between the mid layer and the cover.
[0036] Preferably, a diameter of the center is equal to or greater
than 10 mm but equal to or less than 20 mm.
[0037] In the golf ball according to the present invention, a
hardness distribution is appropriate. In the golf ball, the energy
loss is low when the golf ball is hit. When the golf ball is hit
with a driver, the spin rate is low. The low spin rate achieves a
large flight distance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a partially cutaway cross-sectional view of a golf
ball according to one embodiment of the present invention;
[0039] FIG. 2 is a line graph showing a hardness distribution of a
first envelope layer of the golf ball in FIG. 1; and
[0040] FIG. 3 is a line graph showing a hardness distribution of a
second envelope layer of the golf ball in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] The following will describe in detail the present invention,
based on preferred embodiments with reference to the accompanying
drawings.
[0042] A golf ball 2 shown in FIG. 1 includes a spherical core 4, a
mid layer 6 positioned outside the core 4, a reinforcing layer 8
positioned outside the mid layer 6, and a cover 10 positioned
outside the reinforcing layer 8. On the surface of the cover 10, a
large number of dimples 12 are formed. Of the surface of the golf
ball 2, a part other than the dimples 12 is a land 14. The golf
ball 2 includes a paint layer and a mark layer on the external side
of the cover 10, but these layers are not shown in the drawing.
[0043] The golf ball 2 has a diameter of 40 mm or greater but 45 mm
or less. From the standpoint of conformity to the rules established
by the United States Golf Association (USGA), the diameter is
preferably equal to or greater than 42.67 mm. In light of
suppression of air resistance, the diameter is preferably equal to
or less than 44 mm and more preferably equal to or less than 42.80
mm. The golf ball 2 has a weight of 40 g or greater but 50 g or
less. In light of attainment of great inertia, the weight is
preferably equal to or greater than 44 g and more preferably equal
to or greater than 45.00 g. From the standpoint of conformity to
the rules established by the USGA, the weight is preferably equal
to or less than 45.93 g.
[0044] The core 4 preferably has a diameter of 35.0 mm or greater
but 42.0 mm or less. The core 4 having a diameter of 35.0 mm or
greater can achieve excellent resilience performance of the golf
ball 2. In this respect, the diameter is more preferably equal to
or greater than 37.0 mm and particularly preferably equal to or
greater than 38.0 mm. In the golf ball 2 that includes the core 4
having a diameter of 42.0 mm or less, the mid layer 6 and the cover
10 can have sufficient thicknesses. The golf ball 2 that includes
the mid layer 6 and the cover 10 which have large thicknesses has
excellent durability. In this respect, the diameter is more
preferably equal to or less than 41.0 mm and particularly
preferably equal to or less than 40.0 mm.
[0045] In the golf ball 2, the core 4 includes a spherical center
16, a first envelope layer 18, and a second envelope layer 20. The
first envelope layer 18 is positioned outside the center 16. The
second envelope layer 20 is positioned outside the first envelope
layer 18.
[0046] In the golf ball 2, the center 16 is more flexible than the
first envelope layer 18 and the second envelope layer 20. The
center 16 can suppress spin. The center 16 preferably has a
diameter of 10 mm or greater but 20 mm or less. In the golf ball 2
that includes the center 16 having a diameter of 10 mm or greater,
spin can be suppressed. In this respect, the diameter is more
preferably equal to or greater than 12 mm and particularly
preferably equal to or greater than 14 mm. The golf ball 2 that
includes the center 16 having a diameter of 20 mm or less has
excellent resilience performance. In this respect, the diameter is
more preferably equal to or less than 18 mm and particularly
preferably equal to or less than 16 mm.
[0047] In the golf ball 2, the ratio of the radius of the center 16
to the radius of the core 4 is preferably less than 39%. The golf
ball 2 has excellent resilience performance. In this respect, the
ratio is more preferably equal to or less than 38%. The ratio is
preferably equal to or greater than 20%. Thus, the center 16 can
effectively contribute to suppression of spin. In this respect, the
ratio is more preferably equal to or greater than 25%. When the
golf ball 2 is hit with a driver, the flight distance is large.
[0048] The first envelope layer 18 is harder than the center 16.
When the golf ball 2 is hit with a driver, the energy loss is low
in the first envelope layer 18. The first envelope layer 18 can
contribute to the resilience performance of the golf ball 2. When
the golf ball 2 is hit with a driver, the flight distance is
large.
[0049] The second envelope layer 20 is harder than the first
envelope layer 18. When the golf ball 2 is hit with a driver, the
energy loss is low in the second envelope layer 20. The second
envelope layer 20 can contribute to the resilience performance of
the golf ball 2. When the golf ball 2 is hit with a driver, the
flight distance is large.
[0050] The first envelope layer 18 preferably has a thickness of 3
mm or greater but 10 mm or less. In the golf ball 2 that includes
the first envelope layer 18 having a thickness of 3 mm or greater,
the spin suppression effect is great. In this respect, the
thickness is more preferably equal to or greater than 4 mm. The
golf ball 2 that includes the first envelope layer 18 having a
thickness of 10 mm or less has excellent resilience performance. In
this respect, the thickness is more preferably equal to or less
than 9 mm.
[0051] The second envelope layer 20 preferably has a thickness of
2.5 mm or greater but 10 mm or less. In the golf ball 2 that
includes the second envelope layer 20 having a thickness of 2.5 mm
or greater has excellent durability. In this respect, the thickness
is more preferably equal to or greater than 3.5 mm. The golf ball 2
that includes the second envelope layer 20 having a thickness of 10
mm or less has excellent resilience performance. In this respect,
the thickness is more preferably equal to or less than 9 mm.
[0052] In the golf ball 2, the ratio of the radius of a sphere
consisting of the center 16 and the first envelope layer 18 to the
radius of the core 4 is preferably less than 76%. The golf ball 2
has excellent resilience performance. In this respect, the ratio is
more preferably equal to or less than 75%. The ratio is preferably
equal to or greater than 65%. Thus, the center 16 having a
sufficient thickness can be obtained. In the golf ball 2, spin can
be effectively suppressed. In this respect, the ratio is more
preferably equal to or greater than 70%. When the golf ball 2 is
hit with a driver, the flight distance is large.
[0053] In the present invention, JIS-C hardnesses are measured at
eleven measuring points obtained by dividing a region from the
central point of the core 4 to the surface of the core 4 into ten
sections. The ratio of the distance from the central point of the
core 4 to each of these measuring points to the radius of the core
4 is as follows. In the golf ball 2, the first to third points are
included in the center 16. The fourth to seventh points are
included in the first envelope layer 18. The eighth to eleventh
points are included in the second envelope layer 20. [0054] First
point: 0.0% (central point) [0055] Second point: 18.0% [0056] Third
point: 36.0% [0057] Fourth point: 39.0% [0058] Fifth point: 51.0%
[0059] Sixth point: 63.0% [0060] Seventh point: 75.0% [0061] Eighth
point: 76.0% [0062] Ninth point: 84.0% [0063] Tenth point: 92.0%
[0064] Eleventh point: 100.0% (surface) Hardnesses at the first to
tenth points are measured by pressing a JIS-C type hardness scale
against a cut plane of the core 4 that has been cut into two
halves. A hardness at the eleventh point is measured by pressing
the JIS-C type hardness scale against the surface of the spherical
core 4. For the measurement, an automated rubber hardness
measurement machine (trade name "P1", manufactured by Kobunshi
Keiki Co., Ltd.), to which this hardness scale is mounted, is
used.
[0065] FIG. 2 is a line graph showing a hardness distribution of
the first envelope layer 18 of the golf ball 2 in FIG. 1. The
horizontal axis of the graph indicates the ratio (%) of a distance
from the central point of the core 4 to the radius of the core 4.
The vertical axis of the graph indicates a JIS-C hardness. In the
graph, among the first to eleventh points, the points included in
the first envelope layer 18 are plotted. In the present embodiment,
four points including the fourth to seventh points are plotted in
the graph.
[0066] FIG. 2 also shows a linear approximation curve obtained by a
least-square method on the basis of the ratios and the hardnesses
of the four measuring points. The linear approximation curve is
indicated by a dotted line. In FIG. 2, the broken line does not
greatly deviate from the linear approximation curve. In other
words, the broken line has a shape close to the linear
approximation curve. In the first envelope layer 18, the hardness
linearly increases from its inside toward its outside. When the
golf ball 2 is hit with a driver, the energy loss is low in the
first envelope layer 18. The golf ball 2 has excellent resilience
performance. When the golf ball 2 is hit with a driver, the flight
distance is large. When the golf ball 2 is hit with a golf club,
stress concentration does not occur. Thus, the golf ball 2 has
excellent durability.
[0067] R.sup.2 of the linear approximation curve for the first
envelope layer 18 which is obtained by the least-square method is
preferably equal to or greater than 0.95. R.sup.2 is an index
indicating the linearity of the broken line. For the first envelope
layer 18 for which R.sup.2 is equal to or greater than 0.95, the
shape of the broken line of the hardness distribution is close to a
straight line. The golf ball 2 that includes the first envelope
layer 18 for which R.sup.2 is equal to or greater than 0.95 has
excellent resilience performance. R.sup.2 is more preferably equal
to or greater than 0.96 and particularly preferably equal to or
greater than 0.97. R.sup.2 is calculated by squaring a correlation
coefficient R. The correlation coefficient R is calculated by
dividing the covariance of the distance (%) from the central point
and the hardness (JIS-C) by the standard deviation of the distance
(%) from the central point and the standard deviation of the
hardness (JIS-C).
[0068] In light of suppression of spin, the gradient al of the
linear approximation curve is preferably equal to or greater than
0.70 and more preferably equal to or greater than 0.82. The
gradient .alpha.1 is preferably equal to or less than 1.18 and more
preferably equal to or less than 1.04.
[0069] FIG. 3 is a line graph showing a hardness distribution of
the second envelope layer 20 of the golf ball 2 in FIG. 1. The
horizontal axis of the graph indicates the ratio (%) of a distance
from the central point of the core 4 to the radius of the core 4.
The vertical axis of the graph indicates a JIS-C hardness. In the
graph, among the first to eleventh points, the points included in
the second envelope layer 20 are plotted. In the present
embodiment, four points including the eighth to eleventh points are
plotted in the graph.
[0070] FIG. 3 also shows a linear approximation curve obtained by a
least-square method on the basis of the ratios and the hardnesses
of the four measuring points. The linear approximation curve is
indicated by a dotted line. In FIG. 3, the broken line does not
greatly deviate from the linear approximation curve. In other
words, the broken line has a shape close to the linear
approximation curve. In the second envelope layer 20, the hardness
linearly increases from its inside toward its outside. When the
golf ball 2 is hit with a driver, the energy loss is low in the
second envelope layer 20. The golf ball 2 has excellent resilience
performance. When the golf ball 2 is hit with a driver, the flight
distance is large. When the golf ball 2 is hit with a golf club,
stress concentration does not occur. Thus, the golf ball 2 has
excellent durability.
[0071] R.sup.2 of the linear approximation curve for the second
envelope layer 20 which is obtained by the least-square method is
preferably equal to or greater than 0.95. For the second envelope
layer 20 for which R.sup.2 is equal to or greater than 0.95, the
shape of the broken line of the hardness distribution is close to a
straight line. The golf ball 2 that includes the second envelope
layer 20 for which R.sup.2 is equal to or greater than 0.95 has
excellent resilience performance. R.sup.2 is more preferably equal
to or greater than 0.96 and particularly preferably equal to or
greater than 0.97. R.sup.2 is calculated in the same manner as that
for the above first envelope layer.
[0072] In light of suppression of spin, the gradient .alpha.2 of
the linear approximation curve is preferably equal to or greater
than 0.30 and more preferably equal to or greater than 0.77. The
gradient .alpha.2 is preferably equal to or less than 1.40 and more
preferably equal to or less than 1.35.
[0073] The center 16 is formed by crosslinking a rubber
composition. Examples of base rubbers for use in the rubber
composition include polybutadienes, polyisoprenes,
styrene-butadiene copolymers, ethylene-propylene-diene copolymers,
and natural rubbers. Two or more rubbers may be used in
combination. In light of resilience performance, polybutadienes are
preferred, and high-cis polybutadienes are particularly
preferred.
[0074] Preferably, the rubber composition of the center 16 includes
a co-crosslinking agent. Examples of preferable co-crosslinking
agents in light of resilience performance include zinc acrylate,
magnesium acrylate, zinc methacrylate, and magnesium methacrylate.
Preferably, the rubber composition includes an organic peroxide
together with a co-crosslinking agent. Examples of preferable
organic peroxides 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.
Preferably, the rubber composition includes a sulfur compound.
[0075] According to need, various additives such as a filler,
sulfur, a vulcanization accelerator, an anti-aging agent, a
coloring agent, a plasticizer, a dispersant, and the like are
included in the rubber composition of the center 16 in an adequate
amount. Synthetic resin powder or crosslinked rubber powder may
also be included in the rubber composition.
[0076] The first envelope layer 18 is formed by crosslinking a
first rubber composition. The first rubber composition includes:
[0077] (1a) a base rubber; [0078] (1b) a co-crosslinking agent;
[0079] (1c) a crosslinking initiator; and [0080] (1d) an acid
and/or a salt.
[0081] Examples of the base rubber (1a) include polybutadienes,
polyisoprenes, styrene-butadiene copolymers,
ethylene-propylene-diene copolymers, and natural rubbers. In light
of resilience performance, polybutadienes are preferred. When a
polybutadiene and another rubber are used in combination, it is
preferred that the polybutadiene is included as a principal
component. Specifically, the proportion of the polybutadiene to the
entire base rubber is preferably equal to or greater than 50% by
weight and more preferably equal to or greater than 80% by weight.
The proportion of cis-1,4 bonds in the polybutadiene is preferably
equal to or greater than 40% by weight and more preferably equal to
or greater than 80% by weight.
[0082] A polybutadiene in which the proportion of 1,2-vinyl bonds
is equal to or less than 2.0% by weight is preferred. The
polybutadiene can contribute to the resilience performance of the
golf ball 2. In this respect, the proportion of 1,2-vinyl bonds is
preferably equal to or less than 1.7% by weight and particularly
preferably equal to or less than 1.5% by weight.
[0083] From the standpoint that a polybutadiene having a low
proportion of 1,2-vinyl bonds and excellent polymerization activity
is obtained, a rare-earth-element-containing catalyst is preferably
used for synthesis of a polybutadiene. In particular, a
polybutadiene synthesized with a catalyst containing neodymium,
which is a lanthanum-series rare earth element compound, is
preferred.
[0084] The polybutadiene has a Mooney viscosity (ML.sub.1+4
(100.degree. C.)) of preferably 30 or greater, more preferably 32
or greater, and particularly preferably 35 or greater. The Mooney
viscosity (ML.sub.1+4(100.degree. C.)) is preferably equal to or
less than 140, more preferably equal to or less than 120, even more
preferably equal to or less than 100, and particularly preferably
equal to or less than 80. The Mooney viscosity
(ML.sub.1+4(100.degree. C.)) is measured according to the standards
of "JIS K6300". The measurement conditions are as follows. [0085]
Rotor: L rotor [0086] Preheating time: 1 minute [0087] Rotating
time of rotor: 4 minutes [0088] Temperature: 100.degree. C.
[0089] In light of workability, the polybutadiene has a molecular
weight distribution (Mw/Mn) of preferably 2.0 or greater, more
preferably 2.2 or greater, even more preferably 2.4 or greater, and
particularly preferably 2.6 or greater. In light of resilience
performance, the molecular weight distribution (Mw/Mn) is
preferably equal to or less than 6.0, more preferably equal to or
less than 5.0, even more preferably equal to or less than 4.0, and
particularly preferably equal to or less than 3.4. The molecular
weight distribution (Mw/Mn) is calculated by dividing the weight
average molecular weight Mw by the number average molecular weight
Mn.
[0090] The molecular weight distribution is measured by gel
permeation chromatography ("HLC-8120GPC" manufactured by Tosoh
Corporation). The measurement conditions are as follows. [0091]
Detector: differential refractometer [0092] Column: GMHHXL
(manufactured by Tosoh Corporation) [0093] Column temperature:
40.degree. C. [0094] Mobile phase: tetrahydrofuran The molecular
weight distribution is calculated as a value obtained by conversion
using polystyrene standard.
[0095] The co-crosslinking agent (1b) is:
[0096] (1b-1) an .alpha.,.beta.-unsaturated carboxylic acid having
3 to 8 carbon atoms; and/or
[0097] (1b-2) a metal salt of an .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 8 carbon atoms.
[0098] The first rubber composition may include only the
.alpha.,.beta.-unsaturated carboxylic acid (1b-1) or only the metal
salt (1b-2) of the .alpha.,.beta.-unsaturated carboxylic acid as
the co-crosslinking agent (1b). The first rubber composition may
include both the .alpha.,.beta.-unsaturated carboxylic acid (1b-1)
and the metal salt (1b-2) of the .alpha.,.beta.-unsaturated
carboxylic acid as the co-crosslinking agent (1b).
[0099] The metal salt (1b-2) of the .alpha.,.beta.-unsaturated
carboxylic acid graft-polymerizes with the molecular chain of the
base rubber, thereby crosslinking the rubber molecules. When the
first rubber composition includes the .alpha.,.beta.-unsaturated
carboxylic acid (1b-1), the first rubber composition preferably
further includes a metal compound (1f). The metal compound (1f)
reacts with the .alpha.,.beta.-unsaturated carboxylic acid (1b-1)
in the first rubber composition. A salt obtained by this reaction
graft-polymerizes with the molecular chain of the base rubber.
[0100] Examples of the metal compound (1f) include metal hydroxides
such as magnesium hydroxide, zinc hydroxide, calcium hydroxide,
sodium hydroxide, lithium hydroxide, potassium hydroxide, and
copper hydroxide; metal oxides such as magnesium oxide, calcium
oxide, zinc oxide, and copper oxide; and metal carbonates such as
magnesium carbonate, zinc carbonate, calcium carbonate, sodium
carbonate, lithium carbonate, and potassium carbonate. A compound
that includes a bivalent metal is preferred. The compound that
includes the bivalent metal reacts with the co-crosslinking agent
(1b) to form metal crosslinks. The metal compound (1f) is
particularly preferably a zinc compound. Two or more metal
compounds may be used in combination.
[0101] Examples of the .alpha.,.beta.-unsaturated carboxylic acids
include acrylic acid, methacrylic acid, fumaric acid, maleic acid,
and crotonic acid. Examples of the metal component in the metal
salt (1b-2) of the .alpha.,.beta.-unsaturated carboxylic acid
include sodium ion, potassium ion, lithium ion, magnesium ion,
calcium ion, zinc ion, barium ion, cadmium ion, aluminum ion, tin
ion, and zirconium ion. The metal salt (1b-2) of the
.alpha.,.beta.-unsaturated carboxylic acid may include two or more
types of ions. From the standpoint that metal crosslinks are likely
to occur between the rubber molecules, bivalent metal ions such as
magnesium ion, calcium ion, zinc ion, barium ion, and cadmium ion
are preferred. The metal salt (1b-2) of the
.alpha.,.beta.-unsaturated carboxylic acid is particularly
preferably zinc acrylate.
[0102] In light of resilience performance of the golf ball 2, the
amount of the co-crosslinking agent (1b) is preferably equal to or
greater than 15 parts by weight and particularly preferably equal
to or greater than 20 parts by weight, per 100 parts by weight of
the base rubber. In light of feel at impact, the amount is
preferably equal to or less than 50 parts by weight, more
preferably equal to or less than 45 parts by weight, and
particularly preferably equal to or less than 40 parts by weight,
per 100 parts by weight of the base rubber.
[0103] The crosslinking initiator (1c) is preferably an organic
peroxide. The organic peroxide contributes to the resilience
performance of the golf ball 2. Examples of preferable organic
peroxides 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.
In light of versatility, dicumyl peroxide is preferred.
[0104] In light of resilience performance of the golf ball 2, the
amount of the crosslinking initiator (1c) is preferably equal to or
greater than 0.2 parts by weight and particularly preferably equal
to or greater than 0.5 parts by weight, per 100 parts by weight of
the base rubber. In light of feel at impact and durability of the
golf ball 2, the amount is preferably equal to or less than 5.0
parts by weight and particularly preferably equal to or less than
2.5 parts by weight, per 100 parts by weight of the base
rubber.
[0105] In the present invention, the co-crosslinking agent (1b) is
not included in the concept of the acid and/or the salt (1d). It is
inferred that as described later, during heating and forming of the
core 4, the acid and/or the salt (1d) breaks the metal crosslinks
by the co-crosslinking agent (1b).
[0106] Examples of the acid and/or the salt (1d) include oxo acids,
such as carboxylic acids, sulfonic acids, and phosphoric acid, and
salts thereof; and hydroacids, such as hydrochloric acid and
hydrofluoric acid, and salts thereof. Oxo acids and salts thereof
are preferred. A carboxylic acid and/or a salt thereof (1d-1) is
preferred. Carboxylates are particularly preferred.
[0107] The carboxylic acid component of the carboxylic acid and/or
the salt thereof (1d-1) has a carboxyl group. The carboxylic acid
component reacts with the co-crosslinking agent (1b). It is
inferred that by this reaction, metal crosslinks are broken.
[0108] The carbon number of the carboxylic acid component of the
carboxylic acid and/or the salt thereof (1d-1) is preferably equal
to or greater than 1 but equal to or less than 30, more preferably
equal to or greater than 3 but equal to or less than 30, and even
more preferably equal to or greater than 5 but equal to or less
than 28. Examples of the carboxylic acid include aliphatic
carboxylic acids (fatty acids) and aromatic carboxylic acids. A
fatty acid and/or a salt thereof is preferred. The carbon number of
the fatty acid component of the fatty acid and/or the salt thereof
is preferably equal to or greater than 1 but equal to or less than
30.
[0109] The first rubber composition may include a saturated fatty
acid and/or a salt thereof, or may include an unsaturated fatty
acid and/or a salt thereof. The saturated fatty acid and/or the
salt thereof are preferred.
[0110] Examples of fatty acids include butyric acid (C4), valeric
acid (C5), caproic acid (C6), enanthic acid (C7), caprylic acid
(octanoic acid) (C8), pelargonic acid (C9), capric acid (decanoic
acid) (C10), lauric acid (C12), myristic acid (C14), myristoleic
acid (C14), pentadecylic acid (C15), palmitic acid (C16),
palmitoleic acid (C16), margaric acid (C17), stearic acid (C18),
elaidic acid (C18), vaccenic acid (C18), oleic acid (C18), linolic
acid (C18), linolenic acid (C18), 12-hydroxystearic acid (C18),
arachidic acid (C20), gadoleic acid (C20), arachidonic acid (C20),
eicosenoic acid (C20), behenic acid (C22), erucic acid (C22),
lignoceric acid (C24), nervonic acid (C24), cerotic acid (C26),
montanic acid (C28), and melissic acid (C30). Two or more fatty
acids may be used in combination. Octanoic acid, lauric acid,
myristic acid, palmitic acid, stearic acid, oleic acid, and behenic
acid are preferred.
[0111] An aromatic carboxylic acid has an aromatic ring and a
carboxyl group. Examples of aromatic carboxylic acids include
benzoic acid, phthalic acid, isophthalic acid, terephthalic acid,
hemimellitic acid (benzene-1,2,3-tricarboxylic acid), trimellitic
acid (benzene-1,2,4-tricarboxylic acid), trimesic acid
(benzene-1,3,5-tricarboxylic acid), mellophanic acid
(benzene-1,2,3,4-tetracarboxylic acid), prehnitic acid
(benzene-1,2,3,5-tetracarboxylic acid), pyromellitic acid
(benzene-1,2,4,5-tetracarboxylic acid), mellitic acid (benzene
hexacarboxylic acid), diphenic acid (biphenyl-2,2'-dicarboxylic
acid), toluic acid (methylbenzoic acid), xylic acid, prehnitylic
acid (2,3,4-trimethylbenzoic acid), .gamma.-isodurylic acid
(2,3,5-trimethylbenzoic acid), durylic acid (2,4,5-trimethylbenzoic
acid), .beta.-isodurylic acid (2,4,6-trimethylbenzoic acid),
.alpha.-isodurylic acid (3,4,5-trimethylbenzoic acid), cuminic acid
(4-isopropylbenzoic acid), uvitic acid (5-methylisophthalic acid),
.alpha.-toluic acid (phenylacetic acid), hydratropic acid
(2-phenylpropanoic acid), and hydrocinnamic acid (3-phenylpropanoic
acid).
[0112] The first rubber composition may include an aromatic
carboxylate substituted with a hydroxyl group, an alkoxy group, or
an oxo group. Examples of this carboxylic acid can include
salicylic acid (2-hydroxybenzoic acid), anisic acid (methoxybenzoic
acid), cresotinic acid (hydroxy(methyl)benzoic acid),
o-homosalicylic acid (2-hydroxy-3-methylbenzoic acid),
m-homosalicylic acid (2-hydroxy-4-methylbenzoic acid),
p-homosalicylic acid (2-hydroxy-5-methylbenzoic acid),
o-pyrocatechuic acid (2,3-dihydroxybenzoic acid), .beta.-resorcylic
acid (2,4-dihydroxybenzoic acid), .gamma.-resorcylic acid [0113]
(2,6-dihydroxybenzoic acid), protocatechuic acid [0114]
(3,4-dihydroxybenzoic acid), .alpha.-resorcylic acid [0115]
(3,5-dihydroxybenzoic acid), vanillic acid [0116]
(4-hydroxy-3-methoxybenzoic acid), isovanillic acid [0117]
(3-hydroxy-4-methoxybenzoic acid), veratric acid [0118]
(3,4-dimethoxybenzoic acid), o-veratric acid [0119]
(2,3-dimethoxybenzoic acid), orsellinic acid [0120]
(2,4-dihydroxy-6-methylbenzoic acid), m-hemipinic acid [0121]
(4,5-dimethoxyphthalic acid), gallic acid [0122]
(3,4,5-trihydroxybenzoic acid), syringic acid [0123]
(4-hydroxy-3,5-dimethoxybenzoic acid), asaronic acid [0124]
(2,4,5-trimethoxybenzoic acid), mandelic acid [0125]
(hydroxy(phenyl)acetic acid), vanillylmandelic acid [0126]
(hydroxy(4-hydroxy-3-methoxyphenyl)acetic acid), homoanisic acid
((4-methoxyphenyl)acetic acid), homogentisic acid [0127]
((2,5-dihydroxyphenyl)acetic acid), homoprotocatechuic acid [0128]
((3,4-dihydroxyphenyl)acetic acid), homovanillic acid [0129]
((4-hydroxy-3-methoxyphenyl)acetic acid), homoisovanillic acid
((3-hydroxy-4-methoxyphenyl)acetic acid), homoveratric acid
((3,4-dimethoxyphenyl)acetic acid), o-homoveratric acid [0130]
((2,3-dimethoxyphenyl)acetic acid), homophthalic acid [0131]
(2-(carboxymethyl)benzoic acid), homoisophthalic acid [0132]
(3-(carboxymethyl)benzoic acid), homoterephthalic acid [0133]
(4-(carboxymethyl)benzoic acid), phthalonic acid [0134]
(2-(carboxycarbonyl)benzoic acid), isophthalonic acid [0135]
(3-(carboxycarbonyl)benzoic acid), terephthalonic acid [0136]
(4-(carboxycarbonyl)benzoic acid), benzilic acid [0137]
(hydroxydiphenylacetic acid), atrolactic acid [0138]
(2-hydroxy-2-phenylpropanoic acid), tropic acid [0139]
(3-hydroxy-2-phenylpropanoic acid), melilotic acid [0140]
(3-(2-hydroxyphenyl)propanoic acid), phloretic acid [0141]
(3-(4-hydroxyphenyl)propanoic acid), hydrocaffeic acid [0142]
(3-(3,4-dihydroxyphenyl)propanoic acid), hydroferulic acid [0143]
(3-(4-hydroxy-3-methoxyphenyl)propanoic acid), hydroisoferulic acid
(3-(3-hydroxy-4-methoxyphenyl)propanoic acid), p-coumaric acid
(3-(4-hydroxyphenyl)acrylic acid), umbellic acid
(3-(2,4-dihydroxyphenyl)acrylic acid), caffeic acid
(3-(3,4-dihydroxyphenyl)acrylic acid), ferulic acid
(3-(4-hydroxy-3-methoxyphenyl)acrylic acid), isoferulic acid
(3-(3-hydroxy-4-methoxyphenyl) acrylic acid), and sinapic acid
(3-(4-hydroxy-3,5-dimethoxyphenyl)acrylic acid).
[0144] The cationic component of the carboxylate is a metal ion or
an organic cation. Examples of the metal ion include sodium ion,
potassium ion, lithium ion, silver ion, magnesium ion, calcium ion,
zinc ion, barium ion, cadmium ion, copper ion, cobalt ion, nickel
ion, manganese ion, aluminum ion, iron ion, tin ion, zirconium ion,
and titanium ion. Two or more types of ions may be used in
combination.
[0145] The organic cation is a cation having a carbon chain.
Examples of the organic cation include organic ammonium ions.
Examples of organic ammonium ions include primary ammonium ions
such as stearylammonium ion, hexylammonium ion, octylammonium ion,
and 2-ethylhexylammonium ion; secondary ammonium ions such as
dodecyl (lauryl) ammoniumion, and octadecyl (stearyl) ammonium ion;
tertiary ammonium ions such as trioctylammonium ion; and quaternary
ammonium ions such as dioctyldimethylammonium ion, and
distearyldimethylammonium ion. Two or more types of organic cations
may be used in combination.
[0146] Examples of preferable carboxylates include a potassium
salt, a magnesium salt, an aluminum salt, a zinc salt, an iron
salt, a copper salt, a nickel salt, or a cobalt salt of octanoic
acid, lauric acid, myristic acid, palmitic acid, stearic acid,
oleic acid, or behenic acid. Zinc salts of carboxylic acids are
particularly preferred. Specific examples of preferable
carboxylates include zinc octoate, zinc laurate, zinc myristate,
and zinc stearate. A particularly preferable carboxylate is zinc
octoate.
[0147] In light of linearity of the hardness distribution of the
core 4, the amount of the acid and/or the salt (1d) is preferably
equal to or greater than 0.5 parts by weight, more preferably equal
to or greater than 1.0 parts by weight, and particularly preferably
equal to or greater than 2.0 parts by weight, per 100 parts by
weight of the base rubber. In light of resilience performance, the
amount is preferably equal to or less than 45 parts by weight, more
preferably equal to or less than 40 parts by weight, and
particularly preferably equal to or less than 30 parts by weight,
per 100 parts by weight of the base rubber.
[0148] The weight ratio of the co-crosslinking agent (1b) and the
acid and/or the salt (1d) in the first rubber composition is
preferably equal to or greater than 3/7 but equal to or less than
9/1. From the first rubber composition in which this weight ratio
is within the above range, the first envelope layer 18 whose
hardness linearly increases from its inside toward its outside can
be obtained.
[0149] As the co-crosslinking agent (1b), zinc acrylate is
preferably used. Zinc acrylate whose surface is coated with stearic
acid or zinc stearate for the purpose of improving dispersibility
to rubber is present. In the present invention, when the first
rubber composition includes this zinc acrylate, this coating
material is not included in the concept of the acid and/or the salt
(1d).
[0150] Preferably, the first rubber composition further includes an
organic sulfur compound (1e). The organic sulfur compound (1e)
increases the linearity of the hardness distribution of the first
envelope layer 18. In addition, the organic sulfur compound (1e)
increases the degree of an outer-hard/inner-soft structure.
[0151] An example of the organic sulfur compound (1e) is an organic
compound having a thiol group or a polysulfide linkage having 2 to
4 sulfur atoms. A metal salt of this organic compound is also
included in the organic sulfur compound (1e). Examples of the
organic sulfur compound (1e) include aliphatic compounds such as
aliphatic thiols, aliphatic thiocarboxylic acids, aliphatic
dithiocarboxylic acids, and aliphatic polysulfides; heterocyclic
compounds; alicyclic compounds such as alicyclic thiols, alicyclic
thiocarboxylic acids, alicyclic dithiocarboxylic acids, and
alicyclic polysulfides; and aromatic compounds. Specific examples
of the organic sulfur compound (1e) include thiophenols,
thionaphthols, polysulfides, thiocarboxylic acids, dithiocarboxylic
acids, sulfenamides, thiurams, dithiocarbamates, and thiazoles.
Preferable organic sulfur compounds (1e) are thiophenols, diphenyl
disulfides, thionaphthols, thiuram disulfides, and metal salts
thereof.
[0152] Specific examples of the organic sulfur compound (1e) are
represented by the following chemical formulas (1) to (4).
##STR00001##
[0153] In the chemical formula (1), R1 to R5 each represent H or a
substituent.
##STR00002##
[0154] In the chemical formula (2), R1 to R10 each represent H or a
substituent.
##STR00003##
[0155] In the chemical formula (3), R1 to R5 each represent H or a
substituent, and M1 represents a monovalent metal atom.
##STR00004##
[0156] In the chemical formula (4), R1 to R10 each represent H or a
substituent, and M2 represents a bivalent metal atom.
[0157] In the formulas (1) to (4), each substituent is at least one
group selected from the group consisting of a halogen group (F, Cl,
Br, I), an alkyl group, a carboxyl group (--COOH), an ester
(--COOR) of a carboxyl group, a formyl group (--CHO), an acyl group
(--COR), a carbonyl halide group (--COX), a sulfo group
(--SO.sub.3H), an ester (--SO.sub.3R) of a sulfo group, a sulfonyl
halide group (--SO.sub.2X), a sulfino group (--SO.sub.2H), an
alkylsulfinyl group (--SOR), a carbamoyl group (--CONH.sub.2), an
alkyl halide group, a cyano group (--CN), and an alkoxy group
(--OR).
[0158] Examples of the organic sulfur compound (1e) represented by
the chemical formula (1) include thiophenol; thiophenols
substituted with halogen groups, such as 4-fluorothiophenol, [0159]
2,5-difluorothiophenol, 2,4,5-trifluorothiophenol, [0160]
2,4,5,6-tetrafluorothiophenol, pentafluorothiophenol, [0161]
2-chlorothiophenol, 4-chlorothiophenol, [0162]
2,4-dichlorothiophenol, 2,5-dichlorothiophenol, [0163]
2,6-dichlorothiophenol, 2,4,5-trichlorothiophenol, [0164]
2,4,5,6-tetrachlorothiophenol, pentachlorothiophenol, [0165]
4-bromothiophenol, 2,5-dibromothiophenol, [0166]
2,4,5-tribromothiophenol, 2,4,5,6-tetrabromothiophenol, [0167]
pentabromothiophenol, 4-iodothiophenol, [0168]
2,5-diiodothiophenol, 2,4,5-triiodothiophenol, [0169]
2,4,5,6-tetraiodothiophenol, and pentaiodothiophenol; thiophenols
substituted with alkyl groups, such as 4-methylthiophenol,
2,4,5-trimethylthiophenol, pentamethylthiophenol,
4-t-butylthiophenol, 2,4,5-tri-t-butylthiophenol, and
penta-t-butylthiophenol; thiophenols substituted with carboxyl
groups, such as 4-carboxythiophenol, 2,4,6-tricarboxythiophenol,
and pentacarboxythiophenol; thiophenols substituted with
alkoxycarbonyl groups, such as 4-methoxycarbonylthiophenol,
2,4,6-trimethoxycarbonylthiophenol, and
pentamethoxycarbonylthiophenol; thiophenols substituted with formyl
groups, such as 4-formylthiophenol, 2,4,6-triformylthiophenol, and
pentaformylthiophenol; thiophenols substituted with acyl groups,
such as 4-acetylthiophenol, 2,4,6-triacetylthiophenol, and
pentaacetylthiophenol; thiophenols substituted with carbonyl halide
groups, such as 4-chlorocarbonylthiophenol,
2,4,6-tri(chlorocarbonyl)thiophenol, and
penta(chlorocarbonyl)thiophenol; thiophenols substituted with sulfo
groups, such as 4-sulfothiophenol, 2,4,6-trisulfothiophenol, and
pentasulfothiophenol; thiophenols substituted with alkoxysulfonyl
groups, such as 4-methoxysulfonylthiophenol,
2,4,6-trimethoxysulfonylthiophenol, and
pentamethoxysulfonylthiophenol; thiophenols substituted with
sulfonyl halide groups, such as 4-chlorosulfonylthiophenol,
2,4,6-tri(chlorosulfonyl)thiophenol, and
penta(chlorosulfonyl)thiophenol; thio phenols substituted with
sulfino groups, such as 4-sulfinothiophenol,
2,4,6-trisulfinothiophenol, and pentasulfinothiophenol; thiophenols
substituted with alkylsulfinyl groups, such as
4-methylsulfinylthiophenol, 2,4,6-tri(methylsulfinyl)thiophenol,
and penta(methylsulfinyl)thiophenol; thiophenols substituted with
carbamoyl groups, such as 4-carbamoylthiophenol,
2,4,6-tricarbamoylthiophenol, and pentacarbamoylthiophenol;
thiophenols substituted with alkyl halide groups, such as
4-trichloromethylthiophenol, 2,4,6-tri(trichloromethyl)thiophenol,
and penta(trichloromethyl)thiophenol; thiophenols substituted with
cyano groups, such as 4-cyanothiophenol, 2,4,6-tricyanothiophenol,
and pentacyanothiophenol; and thiophenols substituted with alkoxy
groups, such as 4-methoxythiophenol, 2,4,6-trimethoxythiophenol,
and pentamethoxythiophenol. Each of these thiophenols is
substituted with one type of substituent.
[0170] Another example of the organic sulfur compound (1e)
represented by the chemical formula (1) is a compound substituted
with at least one type of the above substituents and another
substituent. Examples of the other substituent include a nitro
group (--NO.sub.2), an amino group (--NH.sub.2), a hydroxyl group
(--OH), and a phenylthio group (--SPh). Specific examples of the
compound include 4-chloro-2-nitrothiophenol, [0171]
4-chloro-2-aminothiophenol, 4-chloro-2-hydroxythiophenol, [0172]
4-chloro-2-phenylthiothiophenol, [0173] 4-methyl-2-nitrothiophenol,
4-methyl-2-aminothiophenol, [0174] 4-methyl-2-hydroxythiophenol,
[0175] 4-methyl-2-phenylthiothiophenol, [0176]
4-carboxy-2-nitrothiophenol, 4-carboxy-2-aminothiophenol, [0177]
4-carboxy-2-hydroxythiophenol, [0178]
4-carboxy-2-phenylthiothiophenol, [0179]
4-methoxycarbonyl-2-nitrothiophenol, [0180]
4-methoxycarbonyl-2-aminothiophenol, [0181]
4-methoxycarbonyl-2-hydroxythiophenol, [0182]
4-methoxycarbonyl-2-phenylthiothiophenol, [0183]
4-formyl-2-nitrothiophenol, 4-formyl-2-aminothiophenol, [0184]
4-formyl-2-hydroxythiophenol, [0185]
4-formyl-2-phenylthiothiophenol, [0186] 4-acetyl-2-nitrothiophenol,
4-acetyl-2-aminothiophenol, [0187] 4-acetyl-2-hydroxythiophenol,
[0188] 4-acetyl-2-phenylthiothiophenol, [0189]
4-chlorocarbonyl-2-nitrothiophenol, [0190]
4-chlorocarbonyl-2-aminothiophenol, [0191]
4-chlorocarbonyl-2-hydroxythiophenol, [0192]
4-chlorocarbonyl-2-phenylthiothiophenol, [0193]
4-sulfo-2-nitrothiophenol, 4-sulfo-2-aminothiophenol, [0194]
4-sulfo-2-hydroxythiophenol, [0195] 4-sulfo-2-phenylthiothiophenol,
[0196] 4-methoxysulfonyl-2-nitrothiophenol, [0197]
4-methoxysulfonyl-2-aminothiophenol, [0198]
4-methoxysulfonyl-2-hydroxythiophenol, [0199]
4-methoxysulfonyl-2-phenylthiothiophenol, [0200]
4-chlorosulfonyl-2-nitrothiophenol, [0201]
4-chlorosulfonyl-2-aminothiophenol, [0202]
4-chlorosulfonyl-2-hydroxythiophenol, [0203]
4-chlorosulfonyl-2-phenylthiothiophenol, [0204]
4-sulfino-2-nitrothiophenol, 4-sulfino-2-aminothiophenol, [0205]
4-sulfino-2-hydroxythiophenol, [0206]
4-sulfino-2-phenylthiothiophenol, [0207]
4-methylsulfinyl-2-nitrothiophenol, [0208]
4-methylsulfinyl-2-aminothiophenol, [0209]
4-methylsulfinyl-2-hydroxythiophenol, [0210]
4-methylsulfinyl-2-phenylthiothiophenol, [0211]
4-carbamoyl-2-nitrothiophenol, [0212]
4-carbamoyl-2-aminothiophenol, [0213]
4-carbamoyl-2-hydroxythiophenol, [0214]
4-carbamoyl-2-phenylthiothiophenol, [0215]
4-trichloromethyl-2-nitrothiophenol, [0216]
4-trichloromethyl-2-aminothiophenol, [0217]
4-trichloromethyl-2-hydroxythiophenol, [0218]
4-trichloromethyl-2-phenylthiothiophenol, [0219]
4-cyano-2-nitrothiophenol, 4-cyano-2-aminothiophenol, [0220]
4-cyano-2-hydroxythiophenol, [0221] 4-cyano-2-phenylthiothiophenol,
[0222] 4-methoxy-2-nitrothiophenol, 4-methoxy-2-aminothiophenol,
[0223] 4-methoxy-2-hydroxythiophenol, and [0224]
4-methoxy-2-phenylthiothiophenol.
[0225] Still another example of the organic sulfur compound (1e)
represented by the chemical formula (1) is a compound substituted
with two or more types of substituents. Specific examples of the
compound include 4-acetyl-2-chlorothiophenol, [0226]
4-acetyl-2-methylthiophenol, 4-acetyl-2-carboxythiophenol, [0227]
4-acetyl-2-methoxycarbonylthiophenol, [0228]
4-acetyl-2-formylthiophenol, [0229]
4-acetyl-2-chlorocarbonylthiophenol, [0230]
4-acetyl-2-sulfothiophenol, [0231]
4-acetyl-2-methoxysulfonylthiophenol, [0232]
4-acetyl-2-chlorosulfonylthiophenol, [0233]
4-acetyl-2-sulfinothiophenol, [0234]
4-acetyl-2-methylsulfinylthiophenol, [0235]
4-acetyl-2-carbamoylthiophenol, [0236]
4-acetyl-2-trichloromethylthiophenol, [0237]
4-acetyl-2-cyanothiophenol, and [0238]
4-acetyl-2-methoxythiophenol.
[0239] Examples of the organic sulfur compound (1e) represented by
the chemical formula (2) include diphenyl disulfide; diphenyl
disulfides substituted with halogen groups, such as [0240]
bis(4-fluorophenyl)disulfide, [0241]
bis(2,5-difluorophenyl)disulfide, [0242]
bis(2,4,5-trifluorophenyl)disulfide, [0243]
bis(2,4,5,6-tetrafluorophenyl)disulfide, [0244]
bis(pentafluorophenyl)disulfide, [0245]
bis(4-chlorophenyl)disulfide, [0246]
bis(2,5-dichlorophenyl)disulfide, [0247]
bis(2,4,5-trichlorophenyl)disulfide, [0248]
bis(2,4,5,6-tetrachlorophenyl)disulfide, [0249]
bis(pentachlorophenyl)disulfide, [0250]
bis(4-bromophenyl)disulfide, [0251]
bis(2,5-dibromophenyl)disulfide, [0252]
bis(2,4,5-tribromophenyl)disulfide, [0253]
bis(2,4,5,6-tetrabromophenyl)disulfide, [0254]
bis(pentabromophenyl)disulfide, bis(4-iodophenyl)disulfide, [0255]
bis(2,5-diiodophenyl)disulfide, [0256]
bis(2,4,5-triiodophenyl)disulfide, [0257]
bis(2,4,5,6-tetraiodophenyl)disulfide, and [0258]
bis(pentaiodophenyl)disulfide; diphenyl disulfides substituted with
alkyl groups, such as [0259] bis(4-methylphenyl)disulfide, [0260]
bis(2,4,5-trimethylphenyl)disulfide, [0261]
bis(pentamethylphenyl)disulfide, [0262]
bis(4-t-butylphenyl)disulfide, [0263]
bis(2,4,5-tri-t-butylphenyl)disulfide, and [0264]
bis(penta-t-butylphenyl)disulfide; diphenyl disulfides substituted
with carboxyl groups, such as [0265] bis(4-carboxyphenyl)disulfide,
[0266] bis(2,4,6-tricarboxyphenyl)disulfide, and [0267]
bis(pentacarboxyphenyl)disulfide; diphenyl disulfides substituted
with alkoxycarbonyl groups, such as [0268]
bis(4-methoxycarbonylphenyl)disulfide, [0269]
bis(2,4,6-trimethoxycarbonylphenyl)disulfide, and
bis(pentamethoxycarbonylphenyl)disulfide; diphenyl disulfides
substituted with formyl groups, such as [0270]
bis(4-formylphenyl)disulfide, [0271]
bis(2,4,6-triformylphenyl)disulfide, and
bis(pentaformylphenyl)disulfide; diphenyl disulfides substituted
with acyl groups, such as [0272] bis(4-acetylphenyl)disulfide,
[0273] bis(2,4,6-triacetylphenyl)disulfide, and [0274]
bis(pentaacetylphenyl)disulfide; diphenyl disulfides substituted
with carbonyl halide groups, such as [0275]
bis(4-chlorocarbonylphenyl)disulfide, [0276]
bis(2,4,6-tri(chlorocarbonyl)phenyl)disulfide, and [0277]
bis(penta(chlorocarbonyl)phenyl)disulfide; diphenyl disulfides
substituted with sulfo groups, such as [0278]
bis(4-sulfophenyl)disulfide, [0279]
bis(2,4,6-trisulfophenyl)disulfide, and [0280]
bis(pentasulfophenyl)disulfide; diphenyl disulfides substituted
with alkoxysulfonyl groups, such as [0281]
bis(4-methoxysulfonylphenyl)disulfide, [0282]
bis(2,4,6-trimethoxysulfonylphenyl)disulfide, and [0283]
bis(pentamethoxysulfonylphenyl)disulfide; diphenyl disulfides
substituted with sulfonyl halide groups, such as [0284]
bis(4-chlorosulfonylphenyl)disulfide, [0285]
bis(2,4,6-tri(chlorosulfonyl)phenyl)disulfide, and [0286]
bis(penta(chlorosulfonyl)phenyl)disulfide; diphenyl disulfides
substituted with sulfino groups, such as [0287]
bis(4-sulfinophenyl)disulfide, [0288]
bis(2,4,6-trisulfinophenyl)disulfide, and [0289]
bis(pentasulfinophenyl)disulfide; diphenyl disulfides substituted
with alkylsulfinyl groups, such as [0290]
bis(4-methylsulfinylphenyl)disulfide, [0291]
bis(2,4,6-tri(methylsulfinyl)phenyl)disulfide, and [0292]
bis(penta(methylsulfinyl)phenyl)disulfide; diphenyl disulfides
substituted with carbamoyl groups, such as [0293]
bis(4-carbamoylphenyl)disulfide, [0294]
bis(2,4,6-tricarbamoylphenyl)disulfide, and [0295]
bis(pentacarbamoylphenyl)disulfide; diphenyl disulfides substituted
with alkyl halide groups, such as [0296]
bis(4-trichloromethylphenyl)disulfide, [0297]
bis(2,4,6-tri(trichloromethyl)phenyl)disulfide, and [0298]
bis(penta(trichloromethyl)phenyl)disulfide; diphenyl disulfides
substituted with cyano groups, such as [0299]
bis(4-cyanophenyl)disulfide, [0300]
bis(2,4,6-tricyanophenyl)disulfide, and [0301]
bis(pentacyanophenyl)disulfide; and diphenyl disulfides substituted
with alkoxy groups, such as [0302] bis(4-methoxyphenyl)disulfide,
[0303] bis(2,4,6-trimethoxyphenyl)disulfide, and [0304]
bis(pentamethoxyphenyl)disulfide. Each of these diphenyl disulfides
is substituted with one type of substituent.
[0305] Another example of the organic sulfur compound (1e)
represented by the chemical formula (2) is a compound substituted
with at least one type of the above substituents and another
substituent. Examples of the other substituent include a nitro
group (--NO.sub.2), an amino group (--NH.sub.2), a hydroxyl group
(--OH), and a phenylthio group (--SPh). Specific examples of the
compound include bis(4-chloro-2-nitrophenyl)disulfide, [0306]
bis(4-chloro-2-aminophenyl)disulfide, [0307]
bis(4-chloro-2-hydroxyphenyl)disulfide, [0308]
bis(4-chloro-2-phenylthiophenyl)disulfide, [0309]
bis(4-methyl-2-nitrophenyl)disulfide, [0310]
bis(4-methyl-2-aminophenyl)disulfide, [0311]
bis(4-methyl-2-hydroxyphenyl)disulfide, [0312]
bis(4-methyl-2-phenylthiophenyl)disulfide, [0313]
bis(4-carboxy-2-nitrophenyl)disulfide, [0314]
bis(4-carboxy-2-aminophenyl)disulfide, [0315]
bis(4-carboxy-2-hydroxyphenyl)disulfide, [0316]
bis(4-carboxy-2-phenylthiophenyl)disulfide, [0317]
bis(4-methoxycarbonyl-2-nitrophenyl)disulfide, [0318]
bis(4-methoxycarbonyl-2-aminophenyl)disulfide, [0319]
bis(4-methoxycarbonyl-2-hydroxyphenyl)disulfide, [0320]
bis(4-methoxycarbonyl-2-phenylthiophenyl)disulfide, [0321]
bis(4-formyl-2-nitrophenyl)disulfide, [0322]
bis(4-formyl-2-aminophenyl)disulfide, [0323]
bis(4-formyl-2-hydroxyphenyl)disulfide, [0324]
bis(4-formyl-2-phenylthiophenyl)disulfide, [0325]
bis(4-acetyl-2-nitrophenyl)disulfide, [0326]
bis(4-acetyl-2-aminophenyl)disulfide, [0327]
bis(4-acetyl-2-hydroxyphenyl)disulfide, [0328]
bis(4-acetyl-2-phenylthiophenyl)disulfide, [0329]
bis(4-chlorocarbonyl-2-nitrophenyl)disulfide, [0330]
bis(4-chlorocarbonyl-2-aminophenyl)disulfide, [0331]
bis(4-chlorocarbonyl-2-hydroxyphenyl)disulfide, [0332]
bis(4-chlorocarbonyl-2-phenylthiophenyl)disulfide, [0333]
bis(4-sulfo-2-nitrophenyl)disulfide, [0334]
bis(4-sulfo-2-aminophenyl)disulfide, [0335]
bis(4-sulfo-2-hydroxyphenyl)disulfide, [0336]
bis(4-sulfo-2-phenylthiophenyl)disulfide, [0337]
bis(4-methoxysulfonyl-2-nitrophenyl)disulfide, [0338]
bis(4-methoxysulfonyl-2-aminophenyl)disulfide, [0339]
bis(4-methoxysulfonyl-2-hydroxyphenyl)disulfide, [0340]
bis(4-methoxysulfonyl-2-phenylthiophenyl)disulfide, [0341]
bis(4-chlorosulfonyl-2-nitrophenyl)disulfide, [0342]
bis(4-chlorosulfonyl-2-aminophenyl)disulfide, [0343]
bis(4-chlorosulfonyl-2-hydroxyphenyl)disulfide, [0344]
bis(4-chlorosulfonyl-2-phenylthiophenyl)disulfide, [0345]
bis(4-sulfino-2-nitrophenyl)disulfide, [0346]
bis(4-sulfino-2-aminophenyl)disulfide, [0347]
bis(4-sulfino-2-hydroxyphenyl)disulfide, [0348]
bis(4-sulfino-2-phenylthiophenyl)disulfide, [0349]
bis(4-methylsulfinyl-2-nitrophenyl)disulfide, [0350]
bis(4-methylsulfinyl-2-aminophenyl)disulfide, [0351]
bis(4-methylsulfinyl-2-hydroxyphenyl)disulfide, [0352]
bis(4-methylsulfinyl-2-phenylthiophenyl)disulfide, [0353]
bis(4-carbamoyl-2-nitrophenyl)disulfide, [0354]
bis(4-carbamoyl-2-aminophenyl)disulfide, [0355]
bis(4-carbamoyl-2-hydroxyphenyl)disulfide, [0356]
bis(4-carbamoyl-2-phenylthiophenyl)disulfide, [0357]
bis(4-trichloromethyl-2-nitrophenyl)disulfide, [0358]
bis(4-trichloromethyl-2-aminophenyl)disulfide, [0359]
bis(4-trichloromethyl-2-hydroxyphenyl)disulfide, [0360]
bis(4-trichloromethyl-2-phenylthiophenyl)disulfide, [0361]
bis(4-cyano-2-nitrophenyl)disulfide, [0362]
bis(4-cyano-2-aminophenyl)disulfide, [0363]
bis(4-cyano-2-hydroxyphenyl)disulfide, [0364]
bis(4-cyano-2-phenylthiophenyl)disulfide, [0365]
bis(4-methoxy-2-nitrophenyl)disulfide, [0366]
bis(4-methoxy-2-aminophenyl)disulfide, [0367]
bis(4-methoxy-2-hydroxyphenyl)disulfide, and [0368]
bis(4-methoxy-2-phenylthiophenyl)disulfide.
[0369] Still another example of the organic sulfur compound (1e)
represented by the chemical formula (2) is a compound substituted
with two or more types of substituents. Specific examples of the
compound include bis(4-acetyl-2-chlorophenyl)disulfide, [0370]
bis(4-acetyl-2-methylphenyl)disulfide, [0371]
bis(4-acetyl-2-carboxyphenyl)disulfide, [0372]
bis(4-acetyl-2-methoxycarbonylphenyl)disulfide, [0373]
bis(4-acetyl-2-formylphenyl)disulfide, [0374]
bis(4-acetyl-2-chlorocarbonylphenyl)disulfide, [0375]
bis(4-acetyl-2-sulfophenyl)disulfide, [0376]
bis(4-acetyl-2-methoxysulfonylphenyl)disulfide, [0377]
bis(4-acetyl-2-chlorosulfonylphenyl)disulfide, [0378]
bis(4-acetyl-2-sulfinophenyl)disulfide, [0379]
bis(4-acetyl-2-methylsulfinylphenyl)disulfide, [0380]
bis(4-acetyl-2-carbamoylphenyl)disulfide, [0381]
bis(4-acetyl-2-trichloromethylphenyl)disulfide, [0382]
bis(4-acetyl-2-cyanophenyl)disulfide, and [0383]
bis(4-acetyl-2-methoxyphenyl)disulfide.
[0384] Examples of the organic sulfur compound (1e) represented by
the chemical formula (3) include thiophenol sodium salt; thiophenol
sodium salts substituted with halogen groups, such as
4-fluorothiophenol sodium salt, 2,5-difluorothiophenol sodium salt,
2,4,5-trifluorothiophenol sodium salt,
2,4,5,6-tetrafluorothiophenol sodium salt, pentafluorothiophenol
sodium salt, 4-chlorothiophenol sodium salt, 2,5-dichlorothiophenol
sodium salt, 2,4,5-trichlorothiophenol sodium salt,
2,4,5,6-tetrachlorothiophenol sodium salt, pentachlorothiophenol
sodium salt, 4-bromothiophenol sodium salt, 2,5-dibromothiophenol
sodium salt, 2,4,5-tribromothiophenol sodium salt,
2,4,5,6-tetrabromothiophenol sodium salt, pentabromothiophenol
sodium salt, 4-iodothiophenol sodium salt, 2,5-diiodothiophenol
sodium salt, 2,4,5-triiodothiophenol sodium salt,
2,4,5,6-tetraiodothiophenol sodium salt, and pentaiodothiophenol
sodium salt; thiophenol sodium salts substituted with alkyl groups,
such as 4-methylthiophenol sodium salt, 2,4,5-trimethylthiophenol
sodium salt, pentamethylthiophenol sodium salt, 4-t-butylthiophenol
sodium salt, 2,4,5-tri-t-butylthiophenol sodium salt, and
penta(t-butyl)thiophenol sodium salt; thiophenol sodium salts
substituted with carboxyl groups, such as 4-carboxythiophenol
sodium salt, 2,4,6-tricarboxythiophenol sodium salt, and
pentacarboxythiophenol sodium salt; thiophenol sodium salts
substituted with alkoxycarbonyl groups, such as
4-methoxycarbonylthiophenol sodium salt,
2,4,6-trimethoxycarbonylthiophenol sodium salt, and
pentamethoxycarbonylthiophenol sodium salt; thiophenol sodium salts
substituted with formyl groups, such as 4-formylthiophenol sodium
salt, 2,4,6-triformylthiophenol sodium salt, and
pentaformylthiophenol sodium salt; thiophenol sodium salts
substituted with acyl groups, such as 4-acetylthiophenol sodium
salt, 2,4,6-triacetylthiophenol sodium salt, and
pentaacetylthiophenol sodium salt; thiophenol sodium salts
substituted with carbonyl halide groups, such as
4-chlorocarbonylthiophenol sodium salt,
2,4,6-tri(chlorocarbonyl)thiophenol sodium salt, and
penta(chlorocarbonyl)thiophenol sodium salt; thiophenol sodium
salts substituted with sulfo groups, such as 4-sulfothiophenol
sodium salt, 2,4,6-trisulfothiophenol sodium salt, and
pentasulfothiophenol sodium salt; thiophenol sodium salts
substituted with alkoxysulfonyl groups, such as
4-methoxysulfonylthiophenol sodium salt,
2,4,6-trimethoxysulfonylthiophenol sodium salt, and
pentamethoxysulfonylthiophenol sodium salt; thiophenol sodium salts
substituted with sulfonyl halide groups, such as
4-chlorosulfonylthiophenol sodium salt,
2,4,6-tri(chlorosulfonyl)thiophenol sodium salt, and
penta(chlorosulfonyl)thiophenol sodium salt; thiophenol sodium
salts substituted with sulfino groups, such as 4-sulfinothiophenol
sodium salt, 2,4,6-trisulfinothiophenol sodium salt, and
pentasulfinothiophenol sodium salt; thiophenol sodium salts
substituted with alkylsulfinyl groups, such as
4-methylsulfinylthiophenol sodium salt,
2,4,6-tri(methylsulfinyl)thiophenol sodium salt, and
penta(methylsulfinyl)thiophenol sodium salt; thiophenol sodium
salts substituted with carbamoyl groups, such as
4-carbamoylthiophenol sodium salt, 2,4,6-tricarbamoylthiophenol
sodium salt, and pentacarbamoylthiophenol sodium salt; thiophenol
sodium salts substituted with alkyl halide groups, such as
4-trichloromethylthiophenol sodium salt,
2,4,6-tri(trichloromethyl)thiophenol sodium salt, and
penta(trichloromethyl)thiophenol sodium salt; thiophenol sodium
salts substituted with cyano groups, such as 4-cyanothiophenol
sodium salt, 2,4,6-tricyanothiophenol sodium salt, and
pentacyanothiophenol sodium salt; and thiophenol sodium salts
substituted with alkoxy groups, such as 4-methoxythiophenol sodium
salt, 2,4,6-trimethoxythiophenol sodium salt, and
pentamethoxythiophenol sodium salt. Each of these thiophenol sodium
salts is substituted with one type of substituent.
[0385] Another example of the organic sulfur compound (1e)
represented by the chemical formula (3) is a compound substituted
with at least one type of the above substituents and another
substituent. Examples of the other substituent include a nitro
group (--NO.sub.2), an amino group (--NH.sub.2), a hydroxyl group
(--OH), and a phenylthio group (--SPh). Specific examples of the
compound include 4-chloro-2-nitrothiophenol sodium salt, [0386]
4-chloro-2-aminothiophenol sodium salt, [0387]
4-chloro-2-hydroxythiophenol sodium salt, [0388]
4-chloro-2-phenylthiothiophenol sodium salt, [0389]
4-methyl-2-nitrothiophenol sodium salt, [0390]
4-methyl-2-aminothiophenol sodium salt, [0391]
4-methyl-2-hydroxythiophenol sodium salt, [0392]
4-methyl-2-phenylthiothiophenol sodium salt, [0393]
4-carboxy-2-nitrothiophenol sodium salt, [0394]
4-carboxy-2-aminothiophenol sodium salt, [0395]
4-carboxy-2-hydroxythiophenol sodium salt, [0396]
4-carboxy-2-phenylthiothiophenol sodium salt, [0397]
4-methoxycarbonyl-2-nitrothiophenol sodium salt, [0398]
4-methoxycarbonyl-2-aminothiophenol sodium salt, [0399]
4-methoxycarbonyl-2-hydroxythiophenol sodium salt, [0400]
4-methoxycarbonyl-2-phenylthiothiophenol sodium salt, [0401]
4-formyl-2-nitrothiophenol sodium salt, [0402]
4-formyl-2-aminothiophenol sodium salt, [0403]
4-formyl-2-hydroxythiophenol sodium salt, [0404]
4-formyl-2-phenylthiothiophenol sodium salt, [0405]
4-acetyl-2-nitrothiophenol sodium salt, [0406]
4-acetyl-2-aminothiophenol sodium salt, [0407]
4-acetyl-2-hydroxythiophenol sodium salt, [0408]
4-acetyl-2-phenylthiothiophenol sodium salt, [0409]
4-chlorocarbonyl-2-nitrothiophenol sodium salt, [0410]
4-chlorocarbonyl-2-aminothiophenol sodium salt, [0411]
4-chlorocarbonyl-2-hydroxythiophenol sodium salt, [0412]
4-chlorocarbonyl-2-phenylthiothiophenol sodium salt, [0413]
4-sulfo-2-nitrothiophenol sodium salt, [0414]
4-sulfo-2-aminothiophenol sodium salt, [0415]
4-sulfo-2-hydroxythiophenol sodium salt, [0416]
4-sulfo-2-phenylthiothiophenol sodium salt, [0417]
4-methoxysulfonyl-2-nitrothiophenol sodium salt, [0418]
4-methoxysulfonyl-2-aminothiophenol sodium salt, [0419]
4-methoxysulfonyl-2-hydroxythiophenol sodium salt, [0420]
4-methoxysulfonyl-2-phenylthiothiophenol sodium salt, [0421]
4-chlorosulfonyl-2-nitrothiophenol sodium salt, [0422]
4-chlorosulfonyl-2-aminothiophenol sodium salt, [0423]
4-chlorosulfonyl-2-hydroxythiophenol sodium salt, [0424]
4-chlorosulfonyl-2-phenylthiothiophenol sodium salt, [0425]
4-sulfino-2-nitrothiophenol sodium salt, [0426]
4-sulfino-2-aminothiophenol sodium salt, [0427]
4-sulfino-2-hydroxythiophenol sodium salt, [0428]
4-sulfino-2-phenylthiothiophenol sodium salt, [0429]
4-methylsulfinyl-2-nitrothiophenol sodium salt, [0430]
4-methylsulfinyl-2-aminothiophenol sodium salt, [0431]
4-methylsulfinyl-2-hydroxythiophenol sodium salt, [0432]
4-methylsulfinyl-2-phenylthiothiophenol sodium salt, [0433]
4-carbamoyl-2-nitrothiophenol sodium salt, [0434]
4-carbamoyl-2-aminothiophenol sodium salt, [0435]
4-carbamoyl-2-hydroxythiophenol sodium salt, [0436]
4-carbamoyl-2-phenylthiothiophenol sodium salt, [0437]
4-trichloromethyl-2-nitrothiophenol sodium salt, [0438]
4-trichloromethyl-2-aminothiophenol sodium salt, [0439]
4-trichloromethyl-2-hydroxythiophenol sodium salt, [0440]
4-trichloromethyl-2-phenylthiothiophenol sodium salt, [0441]
4-cyano-2-nitrothiophenol sodium salt, [0442]
4-cyano-2-aminothiophenol sodium salt, [0443]
4-cyano-2-hydroxythiophenol sodium salt, [0444]
4-cyano-2-phenylthiothiophenol sodium salt, [0445]
4-methoxy-2-nitrothiophenol sodium salt, [0446]
4-methoxy-2-aminothiophenol sodium salt, [0447]
4-methoxy-2-hydroxythiophenol sodium salt, and [0448]
4-methoxy-2-phenylthiothiophenol sodium salt.
[0449] Still another example of the organic sulfur compound (1e)
represented by the chemical formula (3) is a compound substituted
with two or more types of substituents. Specific examples of the
compound include 4-acetyl-2-chlorothiophenol sodium salt, [0450]
4-acetyl-2-methylthiophenol sodium salt, [0451]
4-acetyl-2-carboxythiophenol sodium salt, [0452]
4-acetyl-2-methoxycarbonylthiophenol sodium salt, [0453]
4-acetyl-2-formylthiophenol sodium salt, [0454]
4-acetyl-2-chlorocarbonylthiophenol sodium salt, [0455]
4-acetyl-2-sulfothiophenol sodium salt, [0456]
4-acetyl-2-methoxysulfonylthiophenol sodium salt, [0457]
4-acetyl-2-chlorosulfonylthiophenol sodium salt, [0458]
4-acetyl-2-sulfinothiophenol sodium salt, [0459]
4-acetyl-2-methylsulfinylthiophenol sodium salt, [0460]
4-acetyl-2-carbamoylthiophenol sodium salt, [0461]
4-acetyl-2-trichloromethylthiophenol sodium salt, [0462]
4-acetyl-2-cyanothiophenol sodium salt, and [0463]
4-acetyl-2-methoxythiophenol sodium salt. Examples of the
monovalent metal represented by M1 in the chemical formula (3)
include sodium, lithium, potassium, copper (I), and silver (I).
[0464] Examples of the organic sulfur compound (1e) represented by
the chemical formula (4) include thiophenol zinc salt; thiophenol
zinc salts substituted with halogen groups, such as
4-fluorothiophenol zinc salt, 2,5-difluorothiophenol zinc salt,
2,4,5-trifluorothiophenol zinc salt, 2,4,5,6-tetrafluorothiophenol
zinc salt, pentafluorothiophenol zinc salt, 4-chlorothiophenol zinc
salt, 2,5-dichlorothiophenol zinc salt, 2,4,5-trichlorothiophenol
zinc salt, 2,4,5,6-tetrachlorothiophenol zinc salt,
pentachlorothiophenol zinc salt, 4-bromothiophenol zinc salt,
2,5-dibromothiophenol zinc salt, 2,4,5-tribromothiophenol zinc
salt, 2,4,5,6-tetrabromothiophenol zinc salt, pentabromothiophenol
zinc salt, 4-iodothiophenol zinc salt, 2,5-diiodothiophenol zinc
salt, 2,4,5-triiodothiophenol zinc salt,
2,4,5,6-tetraiodothiophenol zinc salt, and pentaiodothiophenol zinc
salt; thiophenol zinc salts substituted with alkyl groups, such as
4-methylthiophenol zinc salt, 2,4,5-trimethylthiophenol zinc salt,
pentamethylthiophenol zinc salt, 4-t-butylthiophenol zinc salt,
2,4,5-tri-t-butylthiophenol zinc salt, and penta-t-butylthiophenol
zinc salt; thiophenol zinc salts substituted with carboxyl groups,
such as 4-carboxythiophenol zinc salt, 2,4,6-tricarboxythiophenol
zinc salt, and pentacarboxythiophenol zinc salt; thiophenol zinc
salts substituted with alkoxycarbonyl groups, such as
4-methoxycarbonylthiophenol zinc salt,
2,4,6-trimethoxycarbonylthiophenol zinc salt, and
pentamethoxycarbonylthiophenol zinc salt; thiophenol zinc salts
substituted with formyl groups, such as 4-formylthiophenol zinc
salt, 2,4,6-triformylthiophenol zinc salt, and
pentaformylthiophenol zinc salt; thiophenol zinc salts substituted
with acyl groups, such as 4-acetylthiophenol zinc salt,
2,4,6-triacetylthiophenol zinc salt, and pentaacetylthiophenol zinc
salt; thiophenol zinc salts substituted with carbonyl halide
groups, such as 4-chlorocarbonylthiophenol zinc salt,
2,4,6-tri(chlorocarbonyl)thiophenol zinc salt, and
penta(chlorocarbonyl)thiophenol zinc salt; thiophenol zinc salts
substituted with sulfo groups, such as 4-sulfothiophenol zinc salt,
2,4,6-trisulfothiophenol zinc salt, and pentasulfothiophenol zinc
salt; thiophenol zinc salts substituted with alkoxysulfonyl groups,
such as 4-methoxysulfonylthiophenol zinc salt,
2,4,6-trimethoxysulfonylthiophenol zinc salt, and
pentamethoxysulfonylthiophenol zinc salt; thiophenol zinc salts
substituted with sulfonyl halide groups, such as
4-chlorosulfonylthiophenol zinc salt,
2,4,6-tri(chlorosulfonyl)thiophenol zinc salt, and
penta(chlorosulfonyl)thiophenol zinc salt; thiophenol zinc salts
substituted with sulfino groups, such as 4-sulfinothiophenolzine
salt, 2,4,6-trisulfinothiophenol zinc salt, and
pentasulfinothiophenol zinc salt; thiophenol zinc salts substituted
with alkylsulfinyl groups, such as 4-methylsulfinylthiophenol zinc
salt, 2,4,6-tri(methylsulfinyl)thiophenol zinc salt, and
penta(methylsulfinyl)thiophenol zinc salt; thiophenol zinc salts
substituted with carbamoyl groups, such as 4-carbamoylthiophenol
zinc salt, 2,4,6-tricarbamoylthiophenol zinc salt, and
pentacarbamoylthiophenol zinc salt; thiophenol zinc salts
substituted with alkyl halide groups, such as
4-trichloromethylthiophenol zinc salt,
2,4,6-tri(trichloromethyl)thiophenol zinc salt, and
penta(trichloromethyl)thiophenol zinc salt; thiophenol zinc salts
substituted with cyano groups, such as 4-cyanothiophenol zinc salt,
2,4,6-tricyanothiophenol zinc salt, and pentacyanothiophenol zinc
salt; and thiophenol zinc salts substituted with alkoxy groups,
such as 4-methoxythiophenol zinc salt, 2,4,6-trimethoxythiophenol
zinc salt, and pentamethoxythiophenol zinc salt. Each of these
thiophenol zinc salts is substituted with one type of
substituent.
[0465] Another example of the organic sulfur compound (1e)
represented by the chemical formula (4) is a compound substituted
with at least one type of the above substituents and another
substituent. Examples of the other substituent include a nitro
group (--NO.sub.2), an amino group (--NH.sub.2), a hydroxyl group
(--OH), and a phenylthio group (--SPh). Specific examples of the
compound include 4-chloro-2-nitrothiophenol zinc salt, [0466]
4-chloro-2-aminothiophenol zinc salt, [0467]
4-chloro-2-hydroxythiophenol zinc salt, [0468]
4-chloro-2-phenylthiothiophenol zinc salt, [0469]
4-methyl-2-nitrothiophenol zinc salt, [0470]
4-methyl-2-aminothiophenol zinc salt, [0471]
4-methyl-2-hydroxythiophenol zinc salt, [0472]
4-methyl-2-phenylthiothiophenol zinc salt, [0473]
4-carboxy-2-nitrothiophenol zinc salt, [0474]
4-carboxy-2-aminothiophenol zinc salt, [0475]
4-carboxy-2-hydroxythiophenol zinc salt, [0476]
4-carboxy-2-phenylthiothiophenol zinc salt, [0477]
4-methoxycarbonyl-2-nitrothiophenol zinc salt, [0478]
4-methoxycarbonyl-2-aminothiophenol zinc salt, [0479]
4-methoxycarbonyl-2-hydroxythiophenol zinc salt, [0480]
4-methoxycarbonyl-2-phenylthiothiophenol zinc salt, [0481]
4-formyl-2-nitrothiophenol zinc salt, [0482]
4-formyl-2-aminothiophenol zinc salt, [0483]
4-formyl-2-hydroxythiophenol zinc salt, [0484]
4-formyl-2-phenylthiothiophenol zinc salt, [0485]
4-acetyl-2-nitrothiophenol zinc salt, [0486]
4-acetyl-2-aminothiophenol zinc salt, [0487]
4-acetyl-2-hydroxythiophenol zinc salt, [0488]
4-acetyl-2-phenylthiothiophenol zinc salt, [0489]
4-chlorocarbonyl-2-nitrothiophenol zinc salt, [0490]
4-chlorocarbonyl-2-aminothiophenol zinc salt, [0491]
4-chlorocarbonyl-2-hydroxythiophenol zinc salt, [0492]
4-chlorocarbonyl-2-phenylthiothiophenol zinc salt, [0493]
4-sulfo-2-nitrothiophenol zinc salt, [0494]
4-sulfo-2-aminothiophenol zinc salt, [0495]
4-sulfo-2-hydroxythiophenol zinc salt, [0496]
4-sulfo-2-phenylthiothiophenol zinc salt, [0497]
4-methoxysulfonyl-2-nitrothiophenol zinc salt, [0498]
4-methoxysulfonyl-2-aminothiophenol zinc salt, [0499]
4-methoxysulfonyl-2-hydroxythiophenol zinc salt, [0500]
4-methoxysulfonyl-2-phenylthiothiophenol zinc salt, [0501]
4-chlorosulfonyl-2-nitrothiophenol zinc salt, [0502]
4-chlorosulfonyl-2-aminothiophenol zinc salt, [0503]
4-chlorosulfonyl-2-hydroxythiophenol zinc salt, [0504]
4-chlorosulfonyl-2-phenylthiothiophenol zinc salt, [0505]
4-sulfino-2-nitrothiophenol zinc salt, [0506]
4-sulfino-2-aminothiophenol zinc salt, [0507]
4-sulfino-2-hydroxythiophenol zinc salt, [0508]
4-sulfino-2-phenylthiothiophenol zinc salt, [0509]
4-methylsulfinyl-2-nitrothiophenol zinc salt, [0510]
4-methylsulfinyl-2-aminothiophenol zinc salt, [0511]
4-methylsulfinyl-2-hydroxythiophenol zinc salt, [0512]
4-methylsulfinyl-2-phenylthiothiophenol zinc salt, [0513]
4-carbamoyl-2-nitrothiophenol zinc salt, [0514]
4-carbamoyl-2-aminothiophenol zinc salt, [0515]
4-carbamoyl-2-hydroxythiophenol zinc salt, [0516]
4-carbamoyl-2-phenylthiothiophenol zinc salt, [0517]
4-trichloromethyl-2-nitrothiophenol zinc salt, [0518]
4-trichloromethyl-2-aminothiophenol zinc salt, [0519]
4-trichloromethyl-2-hydroxythiophenol zinc salt, [0520]
4-trichloromethyl-2-phenylthiothiophenol zinc salt, [0521]
4-cyano-2-nitrothiophenol zinc salt, [0522]
4-cyano-2-aminothiophenol zinc salt, [0523]
4-cyano-2-hydroxythiophenol zinc salt, [0524]
4-cyano-2-phenylthiothiophenol zinc salt, [0525]
4-methoxy-2-nitrothiophenol zinc salt, [0526]
4-methoxy-2-aminothiophenol zinc salt, [0527]
4-methoxy-2-hydroxythiophenol zinc salt, and [0528]
4-methoxy-2-phenylthiothiophenol zinc salt.
[0529] Still another example of the organic sulfur compound (1e)
represented by the chemical formula (4) is a compound substituted
with two or more types of substituents. Specific examples of the
compound include 4-acetyl-2-chlorothiophenol zinc salt, [0530]
4-acetyl-2-methylthiophenol zinc salt, [0531]
4-acetyl-2-carboxythiophenol zinc salt, [0532]
4-acetyl-2-methoxycarbonylthiophenol zinc salt, [0533]
4-acetyl-2-formylthiophenol zinc salt, [0534]
4-acetyl-2-chlorocarbonylthiophenol zinc salt, [0535]
4-acetyl-2-sulfothiophenol zinc salt, [0536]
4-acetyl-2-methoxysulfonylthiophenol zinc salt, [0537]
4-acetyl-2-chlorosulfonylthiophenol zinc salt, [0538]
4-acetyl-2-sulfinothiophenol zinc salt, [0539]
4-acetyl-2-methylsulfinylthiophenol zinc salt, [0540]
4-acetyl-2-carbamoylthiophenol zinc salt, [0541]
4-acetyl-2-trichloromethylthiophenol zinc salt, [0542]
4-acetyl-2-cyanothiophenol zinc salt, and [0543]
4-acetyl-2-methoxythiophenol zinc salt. Examples of the bivalent
metal represented by M2 in the chemical formula (4) include zinc,
magnesium, calcium, strontium, barium, titanium (II), manganese
(II), iron (II), cobalt (II), nickel (II), zirconium (II), and tin
(II).
[0544] Examples of thionaphthols include 2-thionaphthol, [0545]
1-thionaphthol, 2-chloro-1-thionaphthol, [0546]
2-bromo-1-thionaphthol, 2-fluoro-1-thionaphthol, [0547]
2-cyano-1-thionaphthol, 2-acetyl-1-thionaphthol, [0548]
1-chloro-2-thionaphthol, 1-bromo-2-thionaphthol, [0549]
1-fluoro-2-thionaphthol, 1-cyano-2-thionaphthol, [0550]
1-acetyl-2-thionaphthol, and metal salts thereof. [0551]
1-thionaphthol, 2-thionaphthol, and zinc salts thereof are
preferred.
[0552] Examples of sulfenamide type organic sulfur compounds (1e)
include N-cyclohexyl-2-benzothiazole sulfenamide,
N-oxydiethylene-2-benzothiazole sulfenamide, and
N-t-butyl-2-benzothiazole sulfenamide. Examples of thiuram type
organic sulfur compounds include tetramethylthiuram monosulfide,
tetramethylthiuram disulfide, tetraethylthiuram disulfide,
tetrabutylthiuram disulfide, and dipentamethylenethiuram
tetrasulfide. Examples of dithiocarbamates include zinc
dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc
dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, sodium
dimethyldithiocarbamate, sodium diethyldithiocarbamate, copper (II)
dimethyldithiocarbamate, iron (III) dimethyldithiocarbamate,
selenium diethyldithiocarbamate, and tellurium
diethyldithiocarbamate. Examples of thiazole type organic sulfur
compounds include 2-mercaptobenzothiazole (MBT); dibenzothiazyl
disulfide (MBTS); a sodium salt, a zinc salt, a copper salt, or a
cyclohexylamine salt of 2-mercaptobenzothiazole; [0553]
2-(2,4-dinitrophenyl)mercaptobenzothiazole; and [0554]
2-(2,6-diethyl-4-morpholinothio)benzothiazole.
[0555] Preferable organic sulfur compounds (1e) from the standpoint
that an outer-hard/inner-soft structure is easily obtained are
2-thionaphthol, bis(pentabromophenyl)disulfide, and
2,6-dichlorothiophenol. A more preferable organic sulfur compound
(1e) is 2-thionaphthol.
[0556] From the standpoint that an outer-hard/inner-soft structure
is easily obtained, the amount of the organic sulfur compound (1e)
is preferably equal to or greater than 0.05 parts by weight, more
preferably equal to or greater than 0.1 parts by weight, and
particularly preferably equal to or greater than 0.2 parts by
weight, per 100 parts by weight of the base rubber. In light of
resilience performance, the amount is preferably equal to or less
than 5.0 parts by weight, more preferably equal to or less than 3.0
parts by weight, and particularly preferably equal to or less than
1.0 parts by weight, per 100 parts by weight of the base
rubber.
[0557] For the purpose of adjusting specific gravity and the like,
a filler may be included in the first envelope layer 18. Examples
of suitable fillers include zinc oxide, barium sulfate, calcium
carbonate, and magnesium carbonate. The amount of the filler is
determined as appropriate so that the intended specific gravity of
the core 4 is accomplished. A particularly preferable filler is
zinc oxide. Zinc oxide serves not only as a specific gravity
adjuster but also as a crosslinking activator.
[0558] According to need, an anti-aging agent, a coloring agent, a
plasticizer, a dispersant, sulfur, a vulcanization accelerator, and
the like are added to the first rubber composition of the first
envelope layer 18. Crosslinked rubber powder or synthetic resin
powder may also be dispersed in the first rubber composition.
[0559] The second envelope layer 20 is formed by crosslinking a
second rubber composition. The second rubber composition
includes:
[0560] (2a) a base rubber;
[0561] (2b) a co-crosslinking agent;
[0562] (2c) a crosslinking initiator; and [0563] (2d) an acid
and/or a salt.
[0564] Examples of the base rubber (2a) include polybutadienes,
polyisoprenes, styrene-butadiene copolymers,
ethylene-propylene-diene copolymers, and natural rubbers. In light
of resilience performance, polybutadienes are preferred. When a
polybutadiene and another rubber are used in combination, it is
preferred that the polybutadiene is included as a principal
component. Specifically, the proportion of the polybutadiene to the
entire base rubber is preferably equal to or greater than 50% by
weight and more preferably equal to or greater than 80% by weight.
The proportion of cis-1,4 bonds in the polybutadiene is preferably
equal to or greater than 40% by weight and more preferably equal to
or greater than 80% by weight.
[0565] A polybutadiene in which the proportion of 1,2-vinyl bonds
is equal to or less than 2.0% by weight is preferred. The
polybutadiene can contribute to the resilience performance of the
golf ball 2. In this respect, the proportion of 1,2-vinyl bonds is
preferably equal to or less than 1.7% by weight and particularly
preferably equal to or less than 1.5% by weight.
[0566] From the standpoint that a polybutadiene having a low
proportion of 1,2-vinyl bonds and excellent polymerization activity
is obtained, a rare-earth-element-containing catalyst is preferably
used for synthesis of a polybutadiene. In particular, a
polybutadiene synthesized with a catalyst containing neodymium,
which is a lanthanum-series rare earth element compound, is
preferred.
[0567] The polybutadiene has a Mooney viscosity (ML.sub.1+4
(100.degree. C.)) of preferably 30 or greater, more preferably 32
or greater, and particularly preferably 35 or greater. The Mooney
viscosity (ML.sub.1+4 (100.degree. C.)) is preferably equal to or
less than 140, more preferably equal to or less than 120, even more
preferably equal to or less than 100, and particularly preferably
equal to or less than 80. The Mooney viscosity (ML.sub.1+4
(100.degree. C.)) is measured according to the standards of "JIS
K6300". The measurement conditions are as follows. [0568] Rotor: L
rotor [0569] Preheating time: 1 minute [0570] Rotating time of
rotor: 4 minutes [0571] Temperature: 100.degree. C.
[0572] In light of workability, the polybutadiene has a molecular
weight distribution (Mw/Mn) of preferably 2.0 or greater, more
preferably 2.2 or greater, even more preferably 2.4 or greater, and
particularly preferably 2.6 or greater. In light of resilience
performance, the molecular weight distribution (Mw/Mn) is
preferably equal to or less than 6.0, more preferably equal to or
less than 5.0, even more preferably equal to or less than 4.0, and
particularly preferably equal to or less than 3.4. The molecular
weight distribution (Mw/Mn) is calculated by dividing the weight
average molecular weight Mw by the number average molecular weight
Mn.
[0573] The molecular weight distribution is measured by gel
permeation chromatography ("HLC-8120GPC" manufactured by Tosoh
Corporation). The measurement conditions are as follows. [0574]
Detector: differential refractometer [0575] Column: GMHHXL
(manufactured by Tosoh Corporation) [0576] Column temperature:
40.degree. C. [0577] Mobile phase: tetrahydrofuran The molecular
weight distribution is calculated as a value obtained by conversion
using polystyrene standard.
[0578] The co-crosslinking agent (2b) is:
[0579] (2b-1) an .alpha.,.beta.-unsaturated carboxylic acid having
3 to 8 carbon atoms; and/or
[0580] (2b-2) a metal salt of an .alpha.,.beta.-unsaturated
carboxylic acid having 3 to 8 carbon atoms.
[0581] The second rubber composition may include only the
.alpha.,.beta.-unsaturated carboxylic acid (2b-1) or only the metal
salt (2b-2) of the .alpha.,.beta.-unsaturated carboxylic acid as
the co-crosslinking agent (2b). The second rubber composition may
include both the .alpha.,.beta.-unsaturated carboxylic acid (2b-1)
and the metal salt (2b-2) of the .alpha.,.beta.-unsaturated
carboxylic acid as the co-crosslinking agent (2b).
[0582] The metal salt (2b-2) of the .alpha.,.beta.-unsaturated
carboxylic acid graft-polymerizes with the molecular chain of the
base rubber, thereby crosslinking the rubber molecules. When the
second rubber composition includes the .alpha.,.beta.-unsaturated
carboxylic acid (2b-1), the second rubber composition preferably
further includes a metal compound (2f). The metal compound (2f)
reacts with the .alpha.,.beta.-unsaturated carboxylic acid (2b-1)
in the second rubber composition. A salt obtained by this reaction
graft-polymerizes with the molecular chain of the base rubber.
[0583] Examples of the metal compound (2f) include metal hydroxides
such as magnesium hydroxide, zinc hydroxide, calcium hydroxide,
sodium hydroxide, lithium hydroxide, potassium hydroxide, and
copper hydroxide; metal oxides such as magnesium oxide, calcium
oxide, zinc oxide, and copper oxide; and metal carbonates such as
magnesium carbonate, zinc carbonate, calcium carbonate, sodium
carbonate, lithium carbonate, and potassium carbonate. A compound
that includes a bivalent metal is preferred. The compound that
includes the bivalent metal reacts with the co-crosslinking agent
(2b) to form metal crosslinks. The metal compound (2f) is
particularly preferably a zinc compound. Two or more metal
compounds may be used in combination.
[0584] Examples of the .alpha.,.beta.-unsaturated carboxylic acids
include acrylic acid, methacrylic acid, fumaric acid, maleic acid,
and crotonic acid. Examples of the metal component in the metal
salt (2b-2) of the .alpha.,.beta.-unsaturated carboxylic acid
include sodium ion, potassium ion, lithium ion, magnesium ion,
calcium ion, zinc ion, barium ion, cadmium ion, aluminum ion, tin
ion, and zirconium ion. The metal salt (2b-2) of the
.alpha.,.beta.-unsaturated carboxylic acid may include two or more
types of ions. From the standpoint that metal crosslinks are likely
to occur between the rubber molecules, bivalent metal ions such as
magnesium ion, calcium ion, zinc ion, barium ion, and cadmium ion
are preferred. The metal salt (2b-2) of the
.alpha.,.beta.-unsaturated carboxylic acid is particularly
preferably zinc acrylate.
[0585] In light of resilience performance of the golf ball 2, the
amount of the co-crosslinking agent (2b) is preferably equal to or
greater than 15 parts by weight and particularly preferably equal
to or greater than 20 parts by weight, per 100 parts by weight of
the base rubber. In light of feel at impact, the amount is
preferably equal to or less than 50 parts by weight, more
preferably equal to or less than 45 parts by weight, and
particularly preferably equal to or less than 40 parts by weight,
per 100 parts by weight of the base rubber.
[0586] In the golf ball 2, the amount of the co-crosslinking agent
(2b) in the second envelope layer 20 is preferably equal to the
amount of the co-crosslinking agent (1b) in the first envelope
layer 18, or greater than the amount of the co-crosslinking agent
(1b) in the first envelope layer 18. Thus, the degree of the
outer-hard/inner-soft structure of the core 4 is increased. In this
respect, the difference between the amount of the co-crosslinking
agent (2b) in the second envelope layer 20 and the amount of the
co-crosslinking agent (1b) in the first envelope layer 18 is
preferably equal to or greater than 0 parts by weight and more
preferably equal to or greater than 1 parts by weight. From the
standpoint that the core 4 whose hardness linearly increases from
its central point toward its surface is obtained, the difference of
the amount is preferably equal to or less than 20 parts by weight
and more preferably equal to or less than 15 parts by weight. In
the golf ball 2, spin is effectively suppressed when the golf ball
2 is hit with a driver. The golf ball 2 has excellent flight
performance.
[0587] The crosslinking initiator (2c) is preferably an organic
peroxide. The organic peroxide contributes to the resilience
performance of the golf ball 2. Examples of preferable organic
peroxides 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.
In light of versatility, dicumyl peroxide is preferred.
[0588] In light of resilience performance of the golf ball 2, the
amount of the crosslinking initiator (2c) is preferably equal to or
greater than 0.2 parts by weight and particularly preferably equal
to or greater than 0.5 parts by weight, per 100 parts by weight of
the base rubber. In light of feel at impact and durability of the
golf ball 2, the amount is preferably equal to or less than 5.0
parts by weight and particularly preferably equal to or less than
2.5 parts by weight, per 100 parts by weight of the base
rubber.
[0589] In the present invention, the co-crosslinking agent (2b) is
not included in the concept of the acid and/or the salt (2d). It is
inferred that as described later, during heating and forming of the
core 4, the acid and/or the salt (2d) breaks the metal crosslinks
by the co-crosslinking agent (2b).
[0590] Examples of the acid and/or the salt (2d) include oxo acids,
such as carboxylic acids, sulfonic acids, and phosphoric acid, and
salts thereof; and hydroacids, such as hydrochloric acid and
hydrofluoric acid, and salts thereof. Oxo acids and salts thereof
are preferred. A carboxylic acid and/or a salt thereof (2d-1) is
preferred. Carboxylates are particularly preferred.
[0591] The carboxylic acid component of the carboxylic acid and/or
the salt thereof (2d-1) has a carboxyl group. The carboxylic acid
component reacts with the co-crosslinking agent (2b). It is
inferred that by this reaction, metal crosslinks are broken.
[0592] The carbon number of the carboxylic acid component of the
carboxylic acid and/or the salt thereof (2d-1) is preferably equal
to or greater than 1 but equal to or less than 30, more preferably
equal to or greater than 3 but equal to or less than 30, and even
more preferably equal to or greater than 5 but equal to or less
than 28. Examples of the carboxylic acid include aliphatic
carboxylic acids (fatty acids) and aromatic carboxylic acids. A
fatty acid and/or a salt thereof is preferred. The carbon number of
the fatty acid component of the fatty acid and/or the salt thereof
is preferably equal to or greater than 1 but equal to or less than
30.
[0593] The second rubber composition may include a saturated fatty
acid and/or a salt thereof, or may include an unsaturated fatty
acid and/or a salt thereof. The saturated fatty acid and/or the
salt thereof are preferred.
[0594] Examples of fatty acids include butyric acid (C4), valeric
acid (C5), caproic acid (C6), enanthic acid (C7), caprylic acid
(octanoic acid) (C8), pelargonic acid (C9), capric acid (decanoic
acid) (C10), lauric acid (C12), myristic acid (C14), myristoleic
acid (C14), pentadecylic acid (C15), palmitic acid (C16),
palmitoleic acid (C16), margaric acid (C17), stearic acid (C18),
elaidic acid (C18), vaccenic acid (C18), oleic acid (C18), linolic
acid (C18), linolenic acid (C18), 12-hydroxystearic acid (C18),
arachidic acid (C20), gadoleic acid (C20), arachidonic acid (C20),
eicosenoic acid (C20), behenic acid (C22), erucic acid (C22),
lignoceric acid (C24), nervonic acid (C24), cerotic acid (C26),
montanic acid (C28), and melissic acid (C30). Two or more fatty
acids may be used in combination. Octanoic acid, lauric acid,
myristic acid, palmitic acid, stearic acid, oleic acid, and behenic
acid are preferred.
[0595] An aromatic carboxylic acid has an aromatic ring and a
carboxyl group. Examples of aromatic carboxylic acids include
benzoic acid, phthalic acid, isophthalic acid, terephthalic acid,
hemimellitic acid (benzene-1,2,3-tricarboxylic acid), trimellitic
acid (benzene-1,2,4-tricarboxylic acid), trimesic acid
(benzene-1,3,5-tricarboxylic acid), mellophanic acid [0596]
(benzene-1,2,3,4-tetracarboxylic acid), prehnitic acid [0597]
(benzene-1,2,3,5-tetracarboxylic acid), pyromellitic acid [0598]
(benzene-1,2,4,5-tetracarboxylicacid), melliticacid (benzene
hexacarboxylic acid), diphenic acid [0599]
(biphenyl-2,2'-dicarboxylic acid), toluic acid (methylbenzoic
acid), xylic acid, prehnitylic acid (2,3,4-trimethylbenzoic acid),
.gamma.-isodurylic acid (2,3,5-trimethylbenzoic acid), durylic acid
(2,4,5-trimethylbenzoic acid), .beta.-isodurylic acid [0600]
(2,4,6-trimethylbenzoic acid), .alpha.-isodurylic acid [0601]
(3,4,5-trimethylbenzoic acid), cuminic acid [0602]
(4-isopropylbenzoic acid), uvitic acid (5-methylisophthalic acid),
.alpha.-toluic acid (phenylacetic acid), hydratropic acid [0603]
(2-phenylpropanoic acid), and hydrocinnamic acid [0604]
(3-phenylpropanoic acid).
[0605] The second rubber composition may include an aromatic
carboxylate substituted with a hydroxyl group, an alkoxy group, or
an oxo group. Examples of this carboxylic acid can include
salicylic acid (2-hydroxybenzoic acid), anisic acid (methoxybenzoic
acid), cresotinic acid (hydroxy(methyl)benzoic acid),
o-homosalicylic acid (2-hydroxy-3-methylbenzoic acid),
m-homosalicylic acid (2-hydroxy-4-methylbenzoic acid),
p-homosalicylic acid (2-hydroxy-5-methylbenzoic acid),
o-pyrocatechuic acid (2,3-dihydroxybenzoic acid), .beta.-resorcylic
acid (2,4-dihydroxybenzoic acid), .gamma.-resorcylic acid [0606]
(2,6-dihydroxybenzoic acid), protocatechuic acid [0607]
(3,4-dihydroxybenzoic acid), .alpha.-resorcylic acid [0608]
(3,5-dihydroxybenzoic acid), vanillic acid [0609]
(4-hydroxy-3-methoxybenzoic acid), isovanillic acid [0610]
(3-hydroxy-4-methoxybenzoic acid), veratric acid [0611]
(3,4-dimethoxybenzoic acid), o-veratric acid [0612]
(2,3-dimethoxybenzoic acid), orsellinic acid [0613]
(2,4-dihydroxy-6-methylbenzoic acid), m-hemipinic acid [0614]
(4,5-dimethoxyphthalic acid), gallic acid [0615]
(3,4,5-trihydroxybenzoic acid), syringic acid [0616]
(4-hydroxy-3,5-dimethoxybenzoic acid), asaronic acid [0617]
(2,4,5-trimethoxybenzoic acid), mandelic acid [0618]
(hydroxy(phenyl)acetic acid), vanillylmandelic acid [0619]
(hydroxy(4-hydroxy-3-methoxyphenyl)acetic acid), homoanisic acid
((4-methoxyphenyl)acetic acid), homogentisic acid [0620]
((2,5-dihydroxyphenyl)acetic acid), homoprotocatechuic acid [0621]
((3,4-dihydroxyphenyl)acetic acid), homovanillic acid [0622]
((4-hydroxy-3-methoxyphenyl)acetic acid), homoisovanillic acid
((3-hydroxy-4-methoxyphenyl)acetic acid), homoveratric acid
((3,4-dimethoxyphenyl)acetic acid), o-homoveratric acid [0623]
((2,3-dimethoxyphenyl)acetic acid), homophthalic acid [0624]
(2-(carboxymethyl)benzoic acid), homoisophthalic acid [0625]
(3-(carboxymethyl)benzoic acid), homoterephthalic acid [0626]
(4-(carboxymethyl)benzoic acid), phthalonic acid [0627]
(2-(carboxycarbonyl)benzoic acid), isophthalonic acid [0628]
(3-(carboxycarbonyl)benzoic acid), terephthalonic acid [0629]
(4-(carboxycarbonyl)benzoic acid), benzilic acid
(hydroxydiphenylacetic acid), atrolactic acid [0630]
(2-hydroxy-2-phenylpropanoic acid), tropic acid [0631]
(3-hydroxy-2-phenylpropanoic acid), melilotic acid [0632]
(3-(2-hydroxyphenyl)propanoic acid), phloretic acid [0633]
(3-(4-hydroxyphenyl)propanoic acid), hydrocaffeic acid [0634]
(3-(3,4-dihydroxyphenyl)propanoic acid), hydroferulic acid [0635]
(3-(4-hydroxy-3-methoxyphenyl)propanoic acid), hydroisoferulic acid
(3-(3-hydroxy-4-methoxyphenyl)propanoic acid), p-coumaric acid
(3-(4-hydroxyphenyl)acrylic acid), umbellic acid
(3-(2,4-dihydroxyphenyl)acrylic acid), caffeic acid
(3-(3,4-dihydroxyphenyl)acrylic acid), ferulic acid [0636]
(3-(4-hydroxy-3-methoxyphenyl)acrylic acid), isoferulic acid [0637]
(3-(3-hydroxy-4-methoxyphenyl)acrylic acid), and sinapic acid
[0638] (3-(4-hydroxy-3,5-dimethoxyphenyl)acrylic acid).
[0639] The cationic component of the carboxylate is a metal ion or
an organic cation. Examples of the metal ion include sodium ion,
potassium ion, lithium ion, silver ion, magnesium ion, calcium ion,
zinc ion, barium ion, cadmium ion, copper ion, cobalt ion, nickel
ion, manganese ion, aluminum ion, iron ion, tin ion, zirconium ion,
and titanium ion. Two or more types of ions may be used in
combination.
[0640] The organic cation is a cation having a carbon chain.
Examples of the organic cation include organic ammonium ions.
Examples of organic ammonium ions include primary ammonium ions
such as stearylammonium ion, hexylammonium ion, octylammonium ion,
and 2-ethylhexylammonium ion; secondary ammonium ions such as
dodecyl (lauryl) ammonium ion, and octadecyl (stearyl) ammonium
ion; tertiary ammonium ions such as trioctylammonium ion; and
quaternary ammonium ions such as dioctyldimethylammonium ion, and
distearyldimethylammonium ion. Two or more types of organic cations
may be used in combination.
[0641] Examples of preferable carboxylates include a potassium
salt, a magnesium salt, an aluminum salt, a zinc salt, an iron
salt, a copper salt, a nickel salt, or a cobalt salt of octanoic
acid, lauric acid, myristic acid, palmitic acid, stearic acid,
oleic acid, or behenic acid. Zinc salts of carboxylic acids are
particularly preferred. Specific examples of preferable
carboxylates include zinc octoate, zinc laurate, zinc myristate,
and zinc stearate. A particularly preferable carboxylate is zinc
octoate.
[0642] In light of linearity of the hardness distribution of the
core 4, the amount of the acid and/or the salt (2d) is preferably
equal to or greater than 0.5 parts by weight, more preferably equal
to or greater than 1.0 parts by weight, and particularly preferably
equal to or greater than 2.0 parts by weight, per 100 parts by
weight of the base rubber. In light of resilience performance, the
amount is preferably equal to or less than 45 parts by weight, more
preferably equal to or less than 40 parts by weight, and
particularly preferably equal to or less than 30 parts by weight,
per 100 parts by weight of the base rubber.
[0643] The weight ratio of the co-crosslinking agent (2b) and the
acid and/or the salt (2d) in the second rubber composition is
preferably equal to or greater than 3/7 but equal to or less than
9/1. From the second rubber composition in which this weight ratio
is within the above range, the second envelope layer 20 whose
hardness linearly increases from its inside toward its outside can
be obtained.
[0644] As the co-crosslinking agent (2b), zinc acrylate is
preferably used. Zinc acrylate whose surface is coated with stearic
acid or zinc stearate for the purpose of improving dispersibility
to rubber is present. In the present invention, when the second
rubber composition includes this zinc acrylate, this coating
material is not included in the concept of the acid and/or the salt
(2d).
[0645] Preferably, the second rubber composition further includes
an organic sulfur compound (2e). The organic sulfur compound (2e)
increases the linearity of the hardness distribution of the core 4.
In addition, the organic sulfur compound (2e) increases the degree
of the outer-hard/inner-soft structure.
[0646] In the golf ball 2, the same compounds as those described
above for the organic sulfur compound (1e) in the first rubber
composition can be used for the organic sulfur compound (2e).
Therefore, preferable organic sulfur compounds (2e) are
thiophenols, diphenyl disulfides, thionaphthols, thiuram
disulfides, and metal salts thereof. Preferable organic sulfur
compounds (2e) are 2-thionaphthol, bis(pentabromophenyl)disulfide,
and 2,6-dichlorothiophenol. A more preferable organic sulfur
compound (2e) is 2-thionaphthol.
[0647] From the standpoint that an outer-hard/inner-soft structure
is easily obtained, the amount of the organic sulfur compound (2e)
is preferably equal to or greater than 0.05 parts by weight, more
preferably equal to or greater than 0.1 parts by weight, and
particularly preferably equal to or greater than 0.2 parts by
weight, per 100 parts by weight of the base rubber. In light of
resilience performance, the amount is preferably equal to or less
than 5.0 parts by weight, more preferably equal to or less than 3.0
parts by weight, and particularly preferably equal to or less than
1.0 parts by weight, per 100 parts by weight of the base
rubber.
[0648] For the purpose of adjusting specific gravity and the like,
a filler may be included in the second envelope layer 20. Examples
of suitable fillers include zinc oxide, barium sulfate, calcium
carbonate, and magnesium carbonate. The amount of the filler is
determined as appropriate so that the intended specific gravity of
the core 4 is accomplished. A particularly preferable filler is
zinc oxide. Zinc oxide serves not only as a specific gravity
adjuster but also as a crosslinking activator.
[0649] According to need, an anti-aging agent, a coloring agent, a
plasticizer, a dispersant, sulfur, a vulcanization accelerator, and
the like are added to the second rubber composition of the second
envelope layer 20. Crosslinked rubber powder or synthetic resin
powder may also be dispersed in the second rubber composition.
[0650] During heating and forming of the core 4, the base rubber
(1a) is crosslinked by the co-crosslinking agent (1b). The base
rubber (2a) is crosslinked by the co-crosslinking agent (2b). The
heat of these crosslinking reactions remains near the central point
of the core 4. Thus, during heating and forming of the core 4, the
temperature at the central portion is high. The temperature
gradually decreases from the central point toward the surface. In
the first rubber composition which forms the first envelope layer
18 of the core 4, the acid reacts with the metal salt of the
co-crosslinking agent (1b) to bond to cation. The salt reacts with
the metal salt of the co-crosslinking agent (1b) to exchange
cation. By the bonding and the exchange, metal crosslinks are
broken. In the second rubber composition which forms the second
envelope layer 20 of the core 4, the acid reacts with the metal
salt of the co-crosslinking agent (2b) to bond to cation. The salt
reacts with the metal salt of the co-crosslinking agent (2b) to
exchange cation. By the bonding and the exchange, metal crosslinks
are broken. This breaking of the metal crosslinks in the core 4 is
likely to occur near the innermost portion of the first envelope
layer 18, and is unlikely to occur near the surface of the second
envelope layer 20. As a result, the crosslinking density of the
core 4 increases from its central point toward its surface. In the
core 4, an outer-hard/inner-soft structure can be achieved.
Further, since the first rubber composition includes the organic
sulfur compound (1e) together with the acid and/or the salt (1d),
and/or the second rubber composition includes the organic sulfur
compound (2e) together with the acid and/or the salt (2d), the
gradient of the hardness distribution can be controlled, and the
degree of the outer-hard/inner-soft structure of the core 4 can be
increased. In light of ease of controlling the gradient of the
hardness distribution, the first rubber composition preferably
includes the organic sulfur compound (1e) together with the acid
and/or the salt (1d), and the second rubber composition preferably
includes the organic sulfur compound (2e) together with the acid
and/or the salt (2d). When the golf ball 2 that includes the core 4
is hit with a driver, the spin rate is low. In the golf ball 2,
excellent flight performance is achieved upon a shot with a
driver.
[0651] In the golf ball 2, when the first rubber composition of the
first envelope layer 18 includes the acid and/or the salt (1d), the
second rubber composition of the second envelope layer 20 may not
include the acid and/or the salt (2d). When the second rubber
composition of the second envelope layer 20 includes the acid
and/or the salt (2d), the first rubber composition of the first
envelope layer 18 may not include the acid and/or the salt (1d).
From the standpoint that the gradient of the hardness distribution
can be effectively controlled and the degree of the
outer-hard/inner-soft structure of the core 4 can be further
increased, the first rubber composition of the first envelope layer
18 preferably includes the acid and/or the salt (1d), and the
second rubber composition of the second envelope layer 20
preferably includes the acid and/or the salt (2d).
[0652] For the mid layer 6, a resin composition is suitably used.
Examples of the base polymer of the resin composition include
ionomer resins, polystyrenes, polyesters, polyamides, and
polyolefins.
[0653] Particularly preferable base polymers are ionomer resins.
The golf ball 2 that includes the mid layer 6 including an ionomer
resin has excellent resilience performance. An ionomer resin and
another resin may be used in combination for the mid layer 6. In
this case, the principal component of the base polymer is
preferably the ionomer resin. Specifically, the proportion of the
ionomer resin to the entire base polymer is preferably equal to or
greater than 50% by weight, more preferably equal to or greater
than 60% by weight, and particularly preferably equal to or greater
than 70% by weight.
[0654] Examples of preferable ionomer resins include binary
copolymers formed with an .alpha.-olefin and an
.alpha.,.beta.-unsaturated carboxylic acid having 3 to 8 carbon
atoms. A preferable binary copolymer includes 80% by weight or
greater but 90% by weight or less of an .alpha.-olefin, and 10% by
weight or greater but 20% by weight or less of an
.alpha.,.beta.-unsaturated carboxylic acid. The binary copolymer
has excellent resilience performance. Examples of other preferable
ionomer resins include ternary copolymers formed with: an
.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. A preferable ternary
copolymer includes 70% by weight or greater but 85% by weight or
less of an .alpha.-olefin, 5% by weight or greater but 30% by
weight or less of an .alpha.,.beta.-unsaturated carboxylic acid,
and 1% by weight or greater but 25% by weight or less of an
.alpha.,.beta.-unsaturated carboxylate ester. The ternary copolymer
has excellent resilience performance. For the binary copolymers and
the ternary copolymers, preferable .alpha.-olefins are ethylene and
propylene, while preferable .alpha.,.beta.-unsaturated carboxylic
acids are acrylic acid and methacrylic acid. A particularly
preferable ionomer resin is a copolymer formed with ethylene and
acrylic acid or methacrylic acid.
[0655] In the binary copolymers and the ternary copolymers, some of
the carboxyl groups are neutralized with metal ions. Examples of
metal ions for use in 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 types of metal ions. Particularly suitable metal ions
in light of resilience performance and durability of the golf ball
2 are sodium ion, zinc ion, lithium ion, and magnesium ion.
[0656] Specific examples of ionomer resins include trade names
"Himilan 1555", "Himilan 1557", "Himilan 1605", "Himilan 1706",
"Himilan 1707", "Himilan 1856", "Himilan 1855", "Himilan AM7311",
"Himilan AM7315", "Himilan AM7317", "Himilan AM7318", "Himilan
AM7329", "Himilan MK7320", and "Himilan MK7329", manufactured by Du
Pont-MITSUI POLYCHEMICALS Co., Ltd.; trade names "Surlyn 6120",
"Surlyn 6910", "Surlyn 7930", "Surlyn 7940", "Surlyn 8140", "Surlyn
8150", "Surlyn 8940", "Surlyn 8945", "Surlyn 9120", "Surlyn 9150",
"Surlyn 9910", "Surlyn 9945", "Surlyn AD8546", "HPF1000", and
"HPF2000", manufactured by E.I. du Pont de Nemours and Company; and
trade names "IOTEK 7010", "IOTEK 7030", "IOTEK 7510", "IOTEK 7520",
"IOTEK 8000", and "IOTEK 8030", manufactured by ExxonMobil Chemical
Company.
[0657] Two or more ionomer resins may be used in combination for
the mid layer 6. An ionomer resin neutralized with a monovalent
metal ion, and an ionomer resin neutralized with a bivalent metal
ion may be used in combination.
[0658] A preferable resin that can be used in combination with an
ionomer resin is a styrene block-containing thermoplastic
elastomer. The styrene block-containing thermoplastic elastomer has
excellent compatibility with ionomer resins. A resin composition
including the styrene block-containing thermoplastic elastomer has
excellent fluidity.
[0659] The styrene block-containing thermoplastic elastomer
includes a polystyrene block as a hard segment, and a soft segment.
A typical soft segment is a diene block. Examples of compounds 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.
[0660] Examples of styrene block-containing thermoplastic
elastomers include styrene-butadiene-styrene block copolymers
(SBS), styrene-isoprene-styrene block copolymers (SIS),
styrene-isoprene-butadiene-styrene block copolymers (SIBS),
hydrogenated SBS, hydrogenated SIS, and hydrogenated SIBS. Examples
of hydrogenated SBS include styrene-ethylene-butylene-styrene block
copolymers (SEGS). Examples of hydrogenated SIS include
styrene-ethylene-propylene-styrene block copolymers (SEPS).
Examples of hydrogenated SIBS include
styrene-ethylene-ethylene-propylene-styrene block copolymers
(SEEPS).
[0661] In light of resilience performance of the golf ball 2, the
content of the styrene component in the styrene block-containing
thermoplastic elastomer is preferably equal to or greater than 10%
by weight, more preferably equal to or greater than 12% by weight,
and particularly preferably equal to or greater than 15% by weight.
In light of feel at impact of the golf ball 2, the content is
preferably equal to or less than 50% by weight, more preferably
equal to or less than 47% by weight, and particularly preferably
equal to or less than 45% by weight.
[0662] In the present invention, styrene block-containing
thermoplastic elastomers include an alloy of an olefin and one or
more members selected from the group consisting of SBS, SIS, SIBS,
SEBS, SEPS, and SEEPS. The olefin component in the alloy is
presumed to contribute to improvement of compatibility with ionomer
resins. Use of this alloy improves the resilience performance of
the golf ball 2. An olefin having 2 to 10 carbon atoms is
preferably used. Examples of suitable olefins include ethylene,
propylene, butene, and pentene. Ethylene and propylene are
particularly preferred.
[0663] Specific examples of polymer alloys include trade names
"RabalonT3221C", "RabalonT3339C", "RabalonSJ4400N", "Rabalon
SJ5400N", "Rabalon SJ6400N", "Rabalon SJ7400N", "Rabalon SJ8400N",
"Rabalon SJ9400N", and "Rabalon SR04", manufactured by Mitsubishi
Chemical Corporation. Other specific examples of styrene
block-containing thermoplastic elastomers include trade name
"Epofriend A1010" manufactured by Daicel Chemical Industries, Ltd.,
and trade name "Septon HG-252" manufactured by Kuraray Co.,
Ltd.
[0664] The mid layer 6 may include a highly elastic resin as the
base polymer. The highly elastic resin contributes to high rigidity
of the mid layer 6. Specific examples of the highly elastic resin
include polyamides.
[0665] According to need, a coloring agent such as titanium
dioxide, a filler such as barium sulfate, a dispersant, an
antioxidant, an ultraviolet absorber, a light stabilizer, a
fluorescent material, a fluorescent brightener, and the like are
included in the resin composition of the mid layer 6 in an adequate
amount.
[0666] From the standpoint that an outer-hard/inner-soft structure
can be achieved in the sphere consisting of the core 4 and the mid
layer 6, the mid layer 6 has a hardness Hm of preferably 30 or
greater and more preferably 40 or greater. In light of
controllability, the hardness Hm is preferably equal to or less
than 75 and more preferably equal to or less than 73. The hardness
Hm is measured according to the standards of "ASTM-D 2240-68" with
a Shore D type hardness scale mounted to an automated rubber
hardness measurement machine (trade name "P1", manufactured by
Kobunshi Keiki Co., Ltd.). For the measurement, a slab that is
formed by hot press and that has a thickness of about 2 mm is used.
A slab kept at 23.degree. C. for two weeks is used for the
measurement. At the measurement, three slabs are stacked. A slab
formed from the same resin composition as the resin composition of
the mid layer 6 is used.
[0667] The mid layer 6 preferably has a thickness Tm of 0.5 mm or
greater but 1.6 mm or less. The mid layer 6 having a thickness Tm
of 0.5 mm or greater can contribute to the durability of the golf
ball 2. In this respect, the thickness Tm is particularly
preferably equal to or greater than 0.7 mm. The golf ball 2 that
includes the mid layer 6 having a thickness Tm of 1.6 mm or less
can include a large core 4. The large core 4 can contribute to the
resilience performance of the golf ball 2. In this respect, the
thickness Tm is particularly preferably equal to or less than 1.4
mm.
[0668] For forming the mid layer 6, known methods such as injection
molding, compression molding, and the like can be used. The golf
ball 2 may have two or more layers as the mid layer 6.
[0669] For the cover 10, a resin composition is suitably used. A
preferable base polymer of the resin composition is a polyurethane.
The polyurethane is flexible. When the golf ball 2 that includes
the cover 10 formed from the resin composition that includes the
polyurethane is hit with a short iron, the spin rate is high. The
cover 10 formed from this resin composition contributes to
controllability upon a shot with a short iron. Furthermore, the
polyurethane can also contribute to excellent feel at impact when
the golf ball 2 is hit with a putter or a short iron.
[0670] In light of ease of forming the cover 10, a preferable base
polymer is a thermoplastic polyurethane elastomer. The
thermoplastic polyurethane elastomer includes a polyurethane
component as a hard segment, and a polyester component or a
polyether component as a soft segment. Examples of isocyanates for
the polyurethane component include alicyclic diisocyanates,
aromatic diisocyanates, and aliphatic diisocyanates. Two or more
diisocyanates may be used in combination.
[0671] Examples of alicyclic diisocyanates 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.
[0672] Examples of aromatic diisocyanates include
4,4'-diphenylmethane diisocyanate (MDI) and toluene diisocyanate
(TDI). Examples of aliphatic diisocyanates include hexamethylene
diisocyanate (HDI).
[0673] Specific examples of thermoplastic polyurethane elastomers
include trade names "Elastollan NY80A", "Elastollan NY82A",
"Elastollan NY84A", "Elastollan NY85A", "Elastollan NY88A",
"Elastollan NY90A", "Elastollan NY97A", "Elastollan NY585", and
"Elastollan XKP016N", manufactured by BASF Japan Ltd.; and trade
names "RESAMINE P4585LS" and "RESAMINE PS62490", manufactured by
Dainichiseika Color & Chemicals Mfg. Co., Ltd.
[0674] From the standpoint that a low hardness of the cover 10 can
be achieved, particularly preferable thermoplastic polyurethane
elastomers are "Elastollan NY80A", "Elastollan NY82A",
"ElastollanNY84A", "ElastollanNY85A", and"Elastollan NY90A".
[0675] A thermoplastic polyurethane elastomer and another resin may
be used in combination. Examples of the resin that can be used in
combination include thermoplastic polyester elastomers,
thermoplastic polyamide elastomers, thermoplastic polyolefin
elastomers, styrene block-containing thermoplastic elastomers, and
ionomer resins. When a thermoplastic polyurethane elastomer and
another resin are used in combination, the thermoplastic
polyurethane elastomer is included as the principal component of
the base polymer, in light of spin performance. The proportion of
the thermoplastic polyurethane elastomer to the entire base polymer
is preferably equal to or greater than 50% by weight, more
preferably equal to or greater than 70% by weight, and particularly
preferably equal to or greater than 85% by weight.
[0676] According to need, a coloring agent such as titanium dioxide
and a fluorescent pigment, a filler such as barium sulfate, a
dispersant, an antioxidant, an ultraviolet absorber, a light
stabilizer, a fluorescent material, a fluorescent brightener, and
the like are included in the cover 10 in an adequate amount.
[0677] The cover 10 preferably has a Shore D hardness Hc of 55 or
less. The golf ball 2 that includes the cover 10 having a hardness
Hc of 55 or less has excellent controllability. In this respect,
the hardness Hc is more preferably equal to or less than 50 and
particularly preferably equal to or less than 48. In light of
flight distance upon a shot with a driver, the hardness Hc is
preferably equal to or greater than 10. The hardness Hc is measured
by the same measurement method as that for the hardness Hm.
[0678] The cover 10 preferably has a thickness Tc of 1.1 mm or
less. The golf ball 2 having a thickness Tc of 1.1 mm or less has
excellent resilience performance. In this respect, the thickness Tc
is more preferably equal to or less than 1.0 mm and particularly
preferably equal to or less than 0.8 mm. In light of
controllability, the thickness Tc is preferably equal to or greater
than 0.1 mm.
[0679] For forming the cover 10, known methods such as injection
molding, compression molding, and the like can be used. When
forming the cover 10, the dimples 12 are formed by pimples formed
on the cavity face of a mold.
[0680] In the present invention, a JIS-C hardness at a measuring
point whose ratio of the distance from the central point of the
core 4 to the radius of the core 4 is x % is represented by H (x).
For example, the hardness at the first point described above, i.e.,
the hardness at the central point of the core 4 is represented by
H(0), and the hardness at the eleventh point described above, i.e.,
the surface hardness of the core 4 is represented by H(100).
[0681] In the golf ball 2, the difference (H(100)-H(0)) between the
surface hardness H(100) and the central hardness H (0) is
preferably equal to or greater than 15. The core 4 in which the
difference (H(100)-H(0)) is equal to or greater than 15 has an
outer-hard/inner-soft structure. When the golf ball 2 is hit with a
driver, the recoil (torsional return) in the core 4 is great, and
thus spin is suppressed. The core 4 contributes to the flight
performance of the golf ball 2. In light of flight performance, the
difference (H(100)-H(0)) is more preferably equal to or greater
than 23 and particularly preferably equal to or greater than 24.
From the standpoint that the core 4 can easily be formed, the
difference (H(100)-H(0)) is preferably equal to or less than 50. In
the core 4, the hardness gradually increases from its central point
toward its surface.
[0682] The central hardness H(0) is preferably equal to or greater
than 40 but equal to or less than 70. The golf ball 2 having a
hardness H(0) of 40 or greater has excellent resilience
performance. In this respect, the hardness H(0) is more preferably
equal to or greater than 45 and particularly preferably equal to or
greater than 50. In the core 4 having a hardness H(0) of 70 or
less, an outer-hard/inner-soft structure can be achieved. In the
golf ball 2 that includes the core 4, spin can be suppressed. In
this respect, the hardness H(0) is more preferably equal to or less
than 65 and particularly preferably equal to or less than 60.
[0683] The surface hardness H(100) is preferably equal to or
greater than 78 but equal to or less than 96. In the core 4 having
a hardness H(100) of 78 or greater, an outer-hard/inner-soft
structure can be achieved. In the golf ball 2 that includes the
core 4, spin can be suppressed. In this respect, the hardness
H(100) is more preferably equal to or greater than 82 and
particularly preferably equal to or greater than 84. The golf ball
2 having a hardness H(100) of 96 or less has excellent durability.
In this respect, the hardness H(100) is more preferably equal to or
less than 94 and particularly preferably equal to or less than
92.
[0684] Preferably, in the golf ball 2, a JIS-C hardness H(36) at
the third point whose ratio of the distance from the central point
of the core 4 to the radius of the core 4 is 36% and a JIS-C
hardness H(39) at the fourth point whose ratio of the distance from
the central point of the core 4 to the radius of the core 4 is 39%
meet the relationship of the following mathematical formula.
H(39)>H(36)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0685] In light of flight performance, the difference (H(39)-H(36))
between the hardness H(39) and the hardness H(36) is preferably
equal to or greater than 0.5 and more preferably equal to or
greater than 2. In light of durability, the difference
(H(39)-H(36)) is preferably equal to or less than 10 and more
preferably equal to or less than 8.
[0686] Preferably, in the golf ball 2, a JIS-C hardness H(75) at
the seventh point whose ratio of the distance from the central
point of the core 4 to the radius of the core 4 is 75% and a JIS-C
hardness H(76) at the eighth point whose ratio of the distance from
the central point of the core 4 to the radius of the core 4 is 76%
meet the relationship of the following mathematical formula.
H(76)>H(75)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0687] In light of flight performance, the difference (H(76)-H(75))
between the hardness H(76) and the hardness H(75) is preferably
equal to or greater than 1 and more preferably equal to or greater
than 2. In light of durability, the difference (H(76)-H(75)) is
preferably equal to or less than 10 and more preferably equal to or
less than 8.
[0688] In the golf ball 2, the hardness H(75) and the surface
hardness H(100) meet the relationship of the following mathematical
formula.
H(100)>H(75)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0689] In light of flight performance, the difference
(H(100)-H(75)) between the hardness H(100) and the hardness H(75)
is preferably equal to or greater than 4 and more preferably equal
to or greater than 10. In light of durability, the difference
(H(100)-H(75)) is preferably equal to or less than 25 and more
preferably equal to or less than 20.
[0690] In the golf ball 2, the hardness H(36) and the surface
hardness H(100) meet the relationship of the following mathematical
formula.
H(100)>H(36)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0691] In light of flight performance, the difference
(H(100)-H(36)) between the hardness H(100) and the hardness H(36)
is preferably equal to or greater than 15 and more preferably equal
to or greater than 20. In light of durability, the difference
(H(100)-H(36)) is preferably equal to or less than 30 and more
preferably equal to or less than 28.
[0692] In the golf ball 2, the hardness H(39) and the surface
hardness H(100) meet the relationship of the following mathematical
formula.
H(100)>H(39)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0693] In light of flight performance, the difference
(H(100)-H(39)) between the hardness H(100) and the hardness H(39)
is preferably equal to or greater than 12 and more preferably equal
to or greater than 15. In light of durability, the difference
(H(100)-H(39)) is preferably equal to or less than 30 and more
preferably equal to or less than 28.
[0694] In the golf ball 2, the hardness H(76) and the surface
hardness H(100) meet the relationship of the following mathematical
formula.
H(100)>H(76)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0695] In light of flight performance, the difference
(H(100)-H(76)) between the hardness H(100) and the hardness H(76)
is preferably equal to or greater than 1 and more preferably equal
to or greater than 5. In light of durability, the difference
(H(100)-H(76)) is preferably equal to or less than 8 and more
preferably equal to or less than 7.
[0696] In the golf ball 2, the hardness H(39) and the hardness
H(75) meet the relationship of the following mathematical
formula.
H(75)>H(39)
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0697] In light of flight performance, the difference (H(75)-H(39))
between the hardness H(75) and the hardness H(39) is preferably
equal to or greater than 5 and more preferably equal to or greater
than 6. In light of durability, the difference (H(75)-H(39)) is
preferably equal to or less than 10 and more preferably equal to or
less than 9.
[0698] In the golf ball 2, an average hardness H1 of the hardness
H(39), the hardness H(51), the hardness H(63), and the hardness
H(75), and an average hardness H2 of the hardness H(76), the
hardness H(84), the hardness H(92), and the hardness H(100) meet
the relationship of the following mathematical formula.
H2>H1
When the golf ball 2 is hit with a driver, the core 4 becomes
significantly distorted since the head speed is high. Since the
core 4 has an outer-hard/inner-soft structure, the spin rate is
suppressed. The hardnesses of the first envelope layer 18 and/or
the second envelope layer 20 linearly change. Thus, the golf ball 2
is launched at a high speed due to deformation and restoration of
the core 4. The suppression of the spin rate and the high launch
speed achieve a large flight distance.
[0699] In light of flight performance, the difference (H2-H1)
between the average hardness H2 and the average hardness H1 is
preferably equal to or greater than 6 and more preferably equal to
or greater than 8. In light of durability, the difference (H2-H1)
is preferably equal to or less than 25 and more preferably equal to
or less than 20.
[0700] Preferably, in the golf ball 2, the hardness Hm of the mid
layer 6 and the hardness Hc of the cover 10 meet the relationship
of the following mathematical formula.
Hm>Hc
When the golf ball 2 is hit with a driver, the sphere consisting of
the core 4 and the mid layer 6 becomes significantly distorted
since the head speed is high. Since the sphere has an
outer-hard/inner-soft structure, the spin rate is suppressed. The
hardnesses of the first envelope layer 18 and/or the second
envelope layer 20 linearly change. Thus, the golf ball 2 is
launched at a high speed due to deformation and restoration of this
sphere. The suppression of the spin rate and the high launch speed
achieve a large flight distance. When the golf ball 2 is hit with a
short iron, this sphere becomes less distorted since the head speed
is low. When the golf ball 2 is hit with a short iron, the behavior
of the golf ball 2 depends on the cover 10. Since the cover 10 is
flexible, a slip between the golf ball 2 and a club face is
suppressed. Due to the suppression of the slip, a high spin rate is
obtained. The high spin rate achieves excellent controllability. In
the golf ball 2, both desired flight performance upon a shot with a
driver and desired controllability upon a shot with a short iron
can be achieved.
[0701] When the golf ball 2 is hit, the cover 10 absorbs the shock.
This absorption achieves soft feel at impact. Particularly, when
the golf ball 2 is hit with a short iron or a putter, the cover 10
achieves excellent feel at impact.
[0702] In light of achievement of both desired flight performance
and desired controllability, the difference (Hm-Hc) between the
hardness Hm and the hardness Hc is preferably equal to or greater
than 18 and more preferably equal to or greater than 20. The
difference (Hm-Hc) is preferably equal to or less than 60.
[0703] The reinforcing layer 8 is positioned between the mid layer
6 and the cover 10. The reinforcing layer 8 firmly adheres to the
mid layer 6 and also to the cover 10. The reinforcing layer 8
suppresses separation of the cover 10 from the mid layer 6. In the
golf ball 2, when the mid layer 6 is formed from a resin
composition and the cover 10 is formed from a resin composition
whose base resin is different from the base resin of the mid layer
6, the reinforcing layer 8 effectively suppresses separation of the
cover 10 from the mid layer 6.
[0704] As the base polymer of the reinforcing layer 8, a
two-component curing type thermosetting resin is suitably used.
Specific examples of two-component curing type thermosetting resins
include epoxy resins, urethane resins, acrylic resins, polyester
resins, and cellulose resins. In light of strength and durability
of the reinforcing layer 8, two-component curing type epoxy resins
and two-component curing type urethane resins are preferred.
[0705] A two-component curing type epoxy resin is obtained by
curing an epoxy resin with a polyamide type curing agent. Examples
of epoxy resins used in two-component curing type epoxy resins
include bisphenol A type epoxy resins, bisphenol F type epoxy
resins, and bisphenol AD type epoxy resins. A bisphenol A type
epoxy resin is obtained by a reaction of bisphenol A and an epoxy
group-containing compound such as epichlorohydrin or the like. A
bisphenol F type epoxy resin is obtained by a reaction of bisphenol
F and an epoxy group-containing compound. A bisphenol AD type epoxy
resin is obtained by a reaction of bisphenol AD and an epoxy
group-containing compound. In light of balance among flexibility,
chemical resistance, heat resistance, and toughness, bisphenol A
type epoxy resins are preferred.
[0706] The polyamide type curing agent has a plurality of amino
groups and one or more amide groups. The amino groups can react
with epoxy groups. Specific examples of the polyamide type curing
agent include polyamide amine curing agents and modified products
thereof. A polyamide amine curing agent is obtained by a
condensation reaction of a polymerized fatty acid and a polyamine.
A typical polymerized fatty acid is obtained by heating and
combining natural fatty acids including a large amount of
unsaturated fatty acids, such as linoleic acid, linolenic acid, and
the like, in the presence of a catalyst. Specific examples of
unsaturated fatty acids include tall oil, soybean oil, linseed oil,
and fish oil. A hydrogenated polymerized fatty acid having a dimer
content of 90% by weight or greater and a trimer content of 10% by
weight or less is preferred. Examples of preferable polyamines
include polyethylene diamines, polyoxyalkylene diamines, and
derivatives thereof.
[0707] In a mixture of an epoxy resin and a polyamide type curing
agent, the ratio of the epoxy equivalent of the epoxy resin to the
amine active hydrogen equivalent of the polyamide type curing agent
is preferably equal to or greater than 1.0/1.4 but equal to or less
than 1.0/1.0.
[0708] A two-component curing type urethane resin is obtained by a
reaction of a base material and a curing agent. A two-component
curing type urethane resin obtained by a reaction of a base
material containing a polyol component and a curing agent
containing a polyisocyanate or a derivative thereof, and a
two-component curing type urethane resin obtained by a reaction of
a base material containing an isocyanate group-terminated urethane
prepolymer and a curing agent having active hydrogen, can be used.
Particularly, a two-component curing type urethane resin obtained
by a reaction of a base material containing a polyol component and
a curing agent containing a polyisocyanate or a derivative thereof,
is preferred.
[0709] As the polyol component of the base material, a urethane
polyol is preferably used. The urethane polyol has urethane bonds
and at least two or more hydroxyl groups. Preferably, the urethane
polyol has hydroxyl groups at its ends. The urethane polyol can be
obtained by causing a reaction of a polyol and a polyisocyanate at
such a ratio that the hydroxyl groups of the polyol component are
excessive in mole ratio with respect to the isocyanate groups of
the polyisocyanate.
[0710] The polyol used for producing the urethane polyol has a
plurality of hydroxyl groups. Polyols having a weight average
molecular weight of 50 or greater but 2000 or less are preferred,
and polyols having a weight average molecular weight of 100 or
greater but 1000 or less are particularly preferred. Examples of
low-molecular-weight polyols include diols and triols. Specific
examples of diols include ethylene glycol, diethylene glycol,
triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl
glycol, and 1,6-hexanediol. Specific examples of triols include
trimethylol propane and hexanetriol. Examples of
high-molecular-weight polyols 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 (PHMA); lactone polyester polyols such as
poly-s-caprolactone (PCL); polycarbonate polyols such as
polyhexamethylene carbonate; and acrylic polyols. Two or more
polyols may be used in combination.
[0711] The polyisocyanate used for producing the urethane polyol
has a plurality of isocyanate groups. Specific examples of the
polyisocyanate include aromatic polyisocyanates such as 2,4-toluene
diisocyanate, 2,6-toluene diisocyanate, a mixture (TDI) of
2,4-toluene diisocyanate and 2,6-toluene diisocyanate,
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), and
isophorone diisocyanate (IPDI); and aliphatic polyisocyanates such
as hexamethylene diisocyanate (HDI). Two or more of these
polyisocyanates may be used in combination. In light of weather
resistance, TMXDI, XDI, HDI, H.sub.6XDI, IPDI, and H.sub.12MDI are
preferred.
[0712] In the reaction of the polyol and the polyisocyanate for
producing the urethane polyol, a known catalyst can be used. A
typical catalyst is dibutyl tin dilaurate.
[0713] In light of strength of the reinforcing layer 8, the
proportion of the urethane bonds included in the urethane polyol is
preferably equal to or greater than 0.1 mmol/g. In light of
followability of the reinforcing layer 8 to the cover 10, the
proportion of the urethane bonds included in the urethane polyol is
preferably equal to or less than 5 mmol/g. The proportion of the
urethane bonds can be adjusted by adjusting the molecular weight of
the polyol, which is the material for the urethane polyol, and
adjusting the blending ratio of the polyol and the
polyisocyanate.
[0714] From the standpoint that the time taken for the reaction of
the base material and the curing agent is short, the weight average
molecular weight of the urethane polyol is preferably equal to or
greater than 4000 and particularly preferably equal to or greater
than 4500. In light of adhesion of the reinforcing layer 8, the
weight average molecular weight of the urethane polyol is
preferably equal to or less than 10000 and particularly preferably
equal to or less than 9000.
[0715] In light of adhesion of the reinforcing layer 8, the
hydroxyl value (mg KOH/g) of the urethane polyol is preferably
equal to or greater than 15 and particularly preferably equal to or
greater than 73. From the standpoint that the time taken for the
reaction of the base material and the curing agent is short, the
hydroxyl value of the urethane polyol is preferably equal to or
less than 130 and particularly preferably equal to or less than
120.
[0716] The base material may contain, together with a urethane
polyol, a polyol that does not have any urethane bond. The
aforementioned polyol that is the material for the urethane polyol
can be used in the base material. Polyols compatible with the
urethane polyol are preferred. From the standpoint that the time
taken for the reaction of the base material and the curing agent is
short, the proportion of the urethane polyol in the base material
on the solid content basis is preferably equal to or greater than
50% by weight and particularly preferably equal to or greater than
80% by weight. Ideally, the proportion is 100% by weight.
[0717] The curing agent contains a polyisocyanate or a derivative
thereof. The aforementioned polyisocyanate that is the material for
the urethane polyol can be used in the curing agent.
[0718] The reinforcing layer 8 may include additives such as a
coloring agent (typically, titanium dioxide), a phosphate-based
stabilizer, an antioxidant, a light stabilizer, a fluorescent
brightener, an ultraviolet absorber, an anti-blocking agent, and
the like. The additives may be added to the base material of the
two-component curing type thermosetting resin, or may be added to
the curing agent of the two-component curing type thermosetting
resin.
[0719] The reinforcing layer 8 is obtained by applying, to the
surface of the mid layer 6, a liquid that is prepared by dissolving
or dispersing the base material and the curing agent in a solvent.
In light of workability, application with a spray gun is preferred.
After the application, the solvent is volatilized to permit a
reaction of the base material with the curing agent, thereby
forming the reinforcing layer 8. Examples of preferable solvents
include toluene, isopropyl alcohol, xylene, methyl ethylketone,
methylisobutylketone, ethylene glycol monomethyl ether,
ethylbenzene, propylene glycol monomethyl ether, isobutyl alcohol,
and ethyl acetate.
[0720] In light of feel at impact, the golf ball 2 has an amount of
compressive deformation (comp'n) of preferably 2.3 mm or greater,
more preferably 2.5 mm or greater, and particularly preferably 2.7
mm or greater. In light of resilience performance, the amount of
compressive deformation is preferably equal to or less than 3.5 mm,
more preferably equal to or less than 3.3 mm, and particularly
preferably equal to or less than 3.1 mm.
[0721] For measurement of the amount of compressive deformation, a
YAMADA type compression tester is used. In the tester, the golf
ball 2 is placed on a hard plate made of metal. Next, a cylinder
made of metal gradually descends toward the golf ball 2. The golf
ball 2, squeezed between the bottom face of the cylinder and the
hard plate, becomes deformed. A migration distance of the cylinder,
starting from the state in which an initial load of 98 N is applied
to the golf ball 2 up to the state in which a final load of 1274 N
is applied thereto, is measured.
EXAMPLES
Example 1
[0722] A rubber composition was obtained by kneading 100 parts by
weight of a high-cis polybutadiene (trade name "BR-730",
manufactured by JSR Corporation), 23 parts by weight of zinc
diacrylate (trade name "Sanceler SR", manufactured by SANSHIN
CHEMICAL INDUSTRY CO., LTD.), 5 parts by weight of zinc oxide, an
appropriate amount of barium sulfate, 0.3 parts by weight of
bis(pentabromophenyl)disulfide, and 0.8 parts by weight of dicumyl
peroxide. This rubber composition was placed into a mold including
upper and lower mold halves each having a hemispherical cavity, and
heated at 170.degree. C. for 25 minutes to obtain a center with a
diameter of 15.0 mm.
[0723] A first rubber composition was obtained by kneading 100
parts by weight of a high-cis polybutadiene (the aforementioned
"BR-730"), 25 parts by weight of zinc diacrylate (the
aforementioned "Sanceler SR"), 5 parts by weight of zinc oxide, an
appropriate amount of barium sulfate, 0.2 parts by weight of
2-thionaphthol, 0.8 parts by weight of dicumyl peroxide, and 5.0
parts by weight of zinc octoate. Half shells were formed from this
first rubber composition. The center was covered with two of these
half shells. The center and the half shells were placed into a mold
including upper and lower mold halves each having a hemispherical
cavity, and heated at 170.degree. C. for 25 minutes to obtain a
sphere with a diameter of 30.0 mm. A first envelope layer was
formed from the first rubber composition.
[0724] A second rubber composition was obtained by kneading 100
parts by weight of a high-cis polybutadiene (the aforementioned
"BR-730"), 35 parts by weight of zinc diacrylate (the
aforementioned "Sanceler SR"), 5 parts by weight of zinc oxide, an
appropriate amount of barium sulfate, 0.2 parts by weight of
2-thionaphthol, 0.8 parts by weight of dicumyl peroxide, and 5.0
parts by weight of zinc octoate. Half shells were formed from this
second rubber composition. The sphere was covered with two of these
half shells. The sphere and the half shells were placed into a mold
including upper and lower mold halves each having a hemispherical
cavity, and heated at 170.degree. C. for 25 minutes to obtain a
core with a diameter of 39.7 mm. A second envelope layer was formed
from the second rubber composition. The amount of barium sulfate
was adjusted such that the specific gravity of each of the first
envelope layer and the second envelope layer is equal to the
specific gravity of the center, and the weight of a golf ball is
45.4 g.
[0725] A resin composition was obtained by kneading 55 parts by
weight of an ionomer resin (the aforementioned "Surlyn 8945"), 45
parts by weight of another ionomer resin (the aforementioned
"Himilan AM7329"), and 3 parts by weight of titanium dioxide with a
twin-screw kneading extruder. The core was placed into a mold. The
resin composition was injected around the core by injection molding
to form a mid layer with a thickness Tm of 1.0 mm.
[0726] A paint composition (trade name "POLIN 750LE", manufactured
by SHINTO PAINT CO., LTD.) including a two-component curing type
epoxy resin as a base polymer was prepared. The base material
liquid of this paint composition includes 30 parts by weight of a
bisphenol A type solid epoxy resin and 70 parts by weight of a
solvent. The curing agent liquid of this paint composition includes
40 parts by weight of a modified polyamide amine, 55 parts by
weight of a solvent, and 5 parts by weight of titanium dioxide. The
weight ratio of the base material liquid to the curing agent liquid
is 1/1. This paint composition was applied to the surface of the
mid layer with a spray gun, and kept at 23.degree. C. for 12 hours
to obtain a reinforcing layer with a thickness of 10 .mu.m.
[0727] A resin composition was obtained by kneading 100 parts by
weight of a thermoplastic polyurethane elastomer (the
aforementioned "Elastollan NY82A"), 0.2 parts by weight of a
hindered amine light stabilizer (trade name "TINUVIN 770",
manufactured by Ciba Japan K.K.), 4 parts by weight of titanium
dioxide, and 0.04 parts by weight of ultramarine blue with a
twin-screw kneading extruder. Half shells were formed from this
resin composition by compression molding. The sphere consisting of
the core, the mid layer, and the reinforcing layer was covered with
two of these half shells. The sphere and the half shells were
placed into a mold including upper and lower mold halves each
having a hemispherical cavity. A cover was obtained from the half
shells by compression molding. The thickness Tc of the cover was
0.5 mm. Dimples having a shape that is the inverted shape of
pimples were formed on the cover. A clear paint including a
two-component curing type polyurethane as a base material was
applied to this cover to obtain a golf ball of Example 1 with a
diameter of 42.7 mm.
Examples 2 to 17 and Comparative Example 2
[0728] Golf balls of Examples 2 to 17 and Comparative Example 2
were obtained in the same manner as Example 1, except the
specifications of the center, the first envelope layer, the second
envelope layer, the mid layer, and the cover were as shown in
Tables 12 to 15 below. The compositions of the center and the
second envelope layer are shown in detail in Tables 1 and 2 below.
The composition of the first envelope layer is shown in detail in
Tables 3 to 6 below. A hardness distribution of the core is shown
in Tables 8 to 11 below. The compositions of the mid layer and the
cover are shown in detail in Table 7 below.
Comparative Example 1
[0729] A rubber composition (corresponding to composition F1 in
Table 1) was obtained by kneading 100 parts by weight of a high-cis
polybutadiene (the aforementioned "BR-730"), 23 parts by weight of
zinc diacrylate (the aforementioned "Sanceler SR"), 5 parts by
weight of zinc oxide, an appropriate amount of barium sulfate, 0.3
parts by weight of bis(pentabromophenyl)disulfide, and 0.8 parts by
weight of dicumyl peroxide. This rubber composition was placed into
a mold including upper and lower mold halves each having a
hemispherical cavity, and heated at 170.degree. C. for 25 minutes
to obtain a center with a diameter of 15.0 mm.
[0730] A rubber composition (corresponding to composition F2 in
Table 1) was obtained by kneading 100 parts by weight of a high-cis
polybutadiene (the aforementioned "BR-730"), 35 parts by weight of
zinc diacrylate (the aforementioned "Sanceler SR"), 5 parts by
weight of zinc oxide, an appropriate amount of barium sulfate, 0.2
parts by weight of 2-thionaphthol, 0.8 parts by weight of dicumyl
peroxide, and 5.0 parts by weight of zinc octoate. Half shells were
formed from this rubber composition. The center was covered with
two of these half shells. The center and the half shells were
placed into a mold including upper and lower mold halves each
having a hemispherical cavity, and heated at 170.degree. C. for 25
minutes to obtain a core with a diameter of 39.7 mm. An envelope
layer was formed from the rubber composition. The amount of barium
sulfate was adjusted such that the specific gravity of the envelope
layer is equal to the specific gravity of the center, and the
weight of a golf ball is 45.4 g.
[0731] A resin composition (corresponding to composition Min Table
7) was obtained by kneading 55 parts by weight of an ionomer resin
(the aforementioned "Surlyn 8945"), 45 parts by weight of another
ionomer resin (the aforementioned "Himilan AM7329"), and 3 parts by
weight of titanium dioxide with a twin-screw kneading extruder. The
core was placed into a mold. The resin composition was injected
around the core by injection molding to form a mid layer with a
thickness Tm of 1.0 mm.
[0732] A paint composition (the aforementioned "POLIN 750LE")
including a two-component curing type epoxy resin as a base polymer
was prepared. The base material liquid of this paint composition
includes 30 parts by weight of a bisphenol A type solid epoxy resin
and 70 parts by weight of a solvent. The curing agent liquid of
this paint composition includes 40 parts by weight of a modified
polyamide amine, 55 parts by weight of a solvent, and 5 parts by
weight of titanium dioxide. The weight ratio of the base material
liquid to the curing agent liquid is 1/1. This paint composition
was applied to the surface of the mid layer with a spray gun, and
kept at 23.degree. C. for 12 hours to obtain a reinforcing layer
with a thickness of 10 .mu.m.
[0733] A resin composition (corresponding to composition C in Table
7) was obtained by kneading 100 parts by weight of a thermoplastic
polyurethane elastomer (the aforementioned "Elastollan NY82A"), 0.2
parts by weight of a hindered amine light stabilizer (the
aforementioned "TINUVIN 770"), 4 parts by weight of titanium
dioxide, and 0.04 parts by weight of ultramarine blue with a
twin-screw kneading extruder. Half shells were formed from this
resin composition by compression molding. The sphere consisting of
the core, the mid layer, and the reinforcing layer was covered with
two of these half shells. The sphere and the half shells were
placed into a mold including upper and lower mold halves each
having a hemispherical cavity. A cover was obtained from the half
shells by compression molding. The thickness Tc of the cover was
0.5 mm. Dimples having a shape that is the inverted shape of
pimples were formed on the cover. A clear paint including a
two-component curing type polyurethane as a base material was
applied to this cover to obtain a golf ball of Comparative Example
1 with a diameter of 42.7 mm. A hardness distribution of the core
of Comparative Example 1 is shown in Table 9 below.
[0734] [Hit with Driver (W#1)]
[0735] A driver with a titanium head (trade name "XXIO",
manufactured by DUNLOP SPORTS CO. LTD., shaft hardness: S, loft
angle: 10.0.degree.) was attached to a swing machine manufactured
by True Temper Co. A golf ball was hit under the condition of a
head speed of 45 m/sec. The spin rate was measured immediately
after the hit. Furthermore, the distance from the launch point to
the stop point was measured. The average value of data obtained by
10 measurements is shown in Tables 12 to 15 below.
TABLE-US-00001 TABLE 1 Compositions of Center and Second Envelop
Layer (parts by weight) F1 F2 F3 BR-730 100 100 100 Sanceler SR 23
35 32 ZN-DA90S Zinc oxide 5 5 5 Barium sulfate * * * 2-thionaphthol
0.2 0.2 Bis(pentabromophenyl)disulfide 0.3 2,6-dichlorothiophenol
Dicumyl peroxide 0.8 0.8 0.8 Zinc octoate 5 Zinc stearate Total
amount of acid and/or salt 0.0 5.0 0.0 * Appropriate amount
TABLE-US-00002 TABLE 2 Compositions of Center and Second Envelop
Layer (parts by weight) F4 F5 BR-730 100 100 Sanceler SR 33 40
ZN-DA90S Zinc oxide 5 5 Barium sulfate * * 2-thionaphthol 0.2 0.2
Bis(pentabromophenyl)disulfide 2,6-dichlorothiophenol Dicumyl
peroxide 0.8 0.8 Zinc octoate 0.5 45 Zinc stearate Total amount of
acid and/or salt 0.5 45.0 * Appropriate amount
TABLE-US-00003 TABLE 3 Composition of First Envelop Layer (parts by
weight) S1 S2 S3 S4 BR-730 100 100 100 100 Sanceler SR 25 24 27 24
ZN-DA90S Zinc oxide 5 5 5 5 Barium sulfate * * * * 2-thionaphthol
0.2 0.2 0.2 0.2 Bis(pentabromophenyl)disulfide
2,6-dichlorothiophenol Dicumyl peroxide 0.8 0.8 0.8 0.8 Zinc
octoate 5 2 12 Zinc stearate 5 Total amount of acid and/or salt 5.0
2.0 12.0 5.0 * Appropriate amount
TABLE-US-00004 TABLE 4 Composition of First Envelop Layer (parts by
weight) S5 S6 S7 S8 BR-730 100 100 100 100 Sanceler SR 28 26 26
ZN-DA90S 25 Zinc oxide 5 5 5 5 Barium sulfate * * * *
2-thionaphthol 0.2 0.2 Bis(pentabromophenyl)disulfide 0.3
2,6-dichlorothiophenol 0.1 Dicumyl peroxide 0.8 0.8 0.8 0.8 Zinc
octoate 5 5 5 5 Zinc stearate Total amount of acid and/or salt 5.0
5.0 5.0 5.0 * Appropriate amount
TABLE-US-00005 TABLE 5 Composition of First Envelop Layer (parts by
weight) S9 S10 S11 S12 BR-730 100 100 100 100 Sanceler SR 22 23 30
15 ZN-DA90S Zinc oxide 5 5 5 5 Barium sulfate * * * *
2-thionaphthol 0.2 0.2 0.2 0.2 Bis(pentabromophenyl)disulfide
2,6-dichlorothiophenol Dicumyl peroxide 0.8 0.8 0.8 0.8 Zinc
octoate 0.5 45 5 Zinc stearate Total amount of acid and/or salt 0.0
0.5 45.0 5.0 * Appropriate amount
TABLE-US-00006 TABLE 6 Composition of First Envelop Layer (parts by
weight) S13 S14 S15 BR-730 100 100 100 Sanceler SR 35 20 32
ZN-DA90S Zinc oxide 5 5 5 Barium sulfate * * * 2-thionaphthol 0.2
0.2 0.2 Bis(pentabromophenyl)disulfide 2,6-dichlorothiophenol
Dicumyl peroxide 0.8 0.8 0.8 Zinc octoate 5 5 5 Zinc stearate Total
amount of acid and/or salt 5.0 5.0 5.0 * Appropriate amount
[0736] The details of the compounds listed in Tables 1 to 6 are as
follows.
[0737] BR-730: a high-cis polybutadiene manufactured by JSR
Corporation (cis-1,4-bond content: 96% by weight, 1,2-vinyl bond
content: 1.3% by weight, Mooney viscosity (ML.sub.1+4 (100.degree.
C.)): 55, molecular weight distribution (Mw/Mn): 3)
[0738] Sanceler SR: zinc diacrylate manufactured by SANSHIN
CHEMICAL INDUSTRY CO., LTD. (a product coated with 10% by weight of
stearic acid)
[0739] ZN-DA90S: zinc diacrylate manufactured by Nihon Jyoryu Kogyo
Co., Ltd. (a product coated with 10% by weight of zinc
stearate)
[0740] Zinc oxide: trade name "Ginrei R" manufactured by Toho Zinc
Co., Ltd.
[0741] Barium sulfate: trade name "Barium Sulfate BD" manufactured
by Sakai Chemical Industry Co., Ltd.
[0742] 2-thionaphthol: a product of Tokyo Chemical Industry Co.,
Ltd.
[0743] Bis(pentabromophenyl)disulfide: a product of Kawaguchi
Chemical Industry Co., LTD.
[0744] 2,6-dichlorothiophenol: a product of Tokyo Chemical Industry
Co., Ltd.
[0745] Dicumyl peroxide: trade name "Percumyl D" manufactured by
NOF Corporation
[0746] Zinc octoate: a product of Mitsuwa Chemicals Co., Ltd.
[0747] Zinc stearate: a product of Wako Pure Chemical Industries,
Ltd.
TABLE-US-00007 TABLE 7 Compositions of Mid Layer and Cover (parts
by weight) M C Surlyn 8945 55 -- Himilan AM7329 45 -- Rabalon
T3221C -- -- Elastollan NY82A -- 100 TINUVIN 770 -- 0.2 Titanium
dioxide 3 4 Ultramarine blue -- 0.04 Hardness (Shore D) 65 29
TABLE-US-00008 TABLE 8 Hardness Distribution of Core Ex. 1 Ex. 2
Ex. 3 Ex. 4 Ex. 5 Ex. 6 H(0) 62.0 62.0 62.0 62.0 62.0 62.0 H(18)
63.0 63.0 63.0 63.0 63.0 63.0 H(36) 63.5 63.5 63.5 63.5 63.5 63.5
H(39) 67.0 68.5 66.5 67.0 66.0 67.0 H(51) 71.0 71.5 70.0 71.0 70.0
71.0 H(63) 73.0 72.5 71.0 73.0 72.5 73.0 H(75) 75.0 74.0 73.0 74.5
75.0 75.0 H(76) 81.0 81.0 81.0 81.0 81.0 81.0 H(84) 82.5 82.5 82.5
82.5 82.5 82.5 H(92) 84.5 84.5 84.5 84.5 84.5 84.5 H(100) 87.5 87.5
87.5 87.5 87.5 87.5 H(100) - H(0) 25.5 25.5 25.5 25.5 25.5 25.5
H(100) - H(36) 24.0 24.0 24.0 24.0 24.0 24.0 H(100) - H(39) 20.5
19.0 21.0 20.5 21.5 20.5 H(100) - H(75) 12.5 13.5 14.5 13.0 12.5
12.5 H(39) - H(36) 3.5 5.0 3.0 3.5 2.5 3.5 H(76) - H(75) 6.0 7.0
8.0 6.5 6.0 6.0 H(75) - H(39) 8.0 5.5 6.5 7.5 9.0 8.0 H(100) -
H(76) 6.5 6.5 6.5 6.5 6.5 6.5 H2 - H1 12.4 12.3 13.8 12.5 13.0
12.4
TABLE-US-00009 TABLE 9 Hardness Distribution of Core Comp. Comp.
Ex. 7 Ex. 8 Ex. 1 Ex. 2 Ex. 9 Ex. 10 H(0) 62.0 62.0 62.0 62.0 62.0
62.0 H(18) 63.0 63.0 63.0 63.0 63.0 63.0 H(36) 63.5 63.5 63.5 63.5
63.5 63.5 H(39) 67.0 67.5 67.0 68.5 68.5 68.0 H(51) 71.0 71.5 68.5
72.0 72.0 71.0 H(63) 73.0 73.5 72.0 73.0 73.0 73.0 H(75) 75.0 75.5
81.0 74.0 74.0 74.0 H(76) 81.0 81.0 81.0 82.5 81.0 81.0 H(84) 82.5
82.5 83.5 83.5 82.5 82.5 H(92) 84.5 84.5 85.5 84.0 84.5 84.5 H(100)
87.5 87.5 87.5 86.0 87.5 87.5 H(100) - H(0) 25.5 25.5 25.5 24.0
25.5 25.5 H(100) - H(36) 24.0 24.0 24.0 22.5 24.0 24.0 H(100) -
H(39) 20.5 20.0 20.5 17.5 19.0 19.5 H(100) - H(75) 12.5 12.0 6.5
12.0 13.5 13.5 H(39) - H(36) 3.5 4.0 3.5 5.0 5.0 4.5 H(76) - H(75)
6.0 5.5 0.0 8.5 7.0 7.0 H(75) - H(39) 8.0 8.0 14.0 5.5 5.5 6.0
H(100) - H(76) 6.5 6.5 6.5 3.5 6.5 6.5 H2 - H1 12.4 11.9 12.3 12.1
12.0 12.4
TABLE-US-00010 TABLE 10 Hardness Distribution of Core Ex. 11 Ex. 12
Ex. 13 Ex. 14 Ex. 15 H(0) 62.0 62.0 62.0 62.0 62.0 H(18) 63.0 63.0
63.0 63.0 63.0 H(36) 63.5 63.5 63.5 63.5 63.5 H(39) 64.0 72.0 67.0
67.0 67.0 H(51) 67.0 76.0 71.0 71.0 71.0 H(63) 68.0 78.0 73.0 73.0
73.0 H(75) 69.5 80.0 75.0 75.0 75.0 H(76) 81.0 81.0 82.5 82.0 77.5
H(84) 82.5 82.5 83.5 83.5 78.2 H(92) 84.5 84.5 84.0 84.0 78.5
H(100) 87.5 87.5 86.0 86.0 79.0 H(100) - H(0) 25.5 25.5 24.0 24.0
17.0 H(100) - H(36) 24.0 24.0 22.5 22.5 15.5 H(100) - H(39) 23.5
15.5 19.0 19.0 12.0 H(100) - H(75) 18.0 7.5 11.0 11.0 4.0 H(39) -
H(36) 0.5 8.5 3.5 3.5 3.5 H(76) - H(75) 11.5 1.0 7.5 7.0 2.5 H(75)
- H(39) 5.5 8.0 8.0 8.0 8.0 H(100) - H(76) 6.5 6.5 3.5 4.0 1.5 H2 -
H1 16.8 7.4 12.5 12.4 6.8
TABLE-US-00011 TABLE 11 Hardness Distribution of Core Ex. 16 Ex. 17
H(0) 62.0 62.0 H(18) 63.0 63.0 H(36) 63.5 63.5 H(39) 64.0 71.0
H(51) 68.0 75.0 H(63) 70.0 77.0 H(75) 72.0 79.0 H(76) 81.0 80.0
H(84) 82.5 82.5 H(92) 84.5 84.5 H(100) 87.5 87.5 H(100) - H(0) 25.5
25.5 H(100) - H(36) 24.0 24.0 H(100) - H(39) 23.5 16.5 H(100) -
H(75) 15.5 8.5 H(39) - H(36) 0.5 7.5 H(76) - H(75) 9.0 1.0 H(75) -
H(39) 8.0 8.0 H(100) - H(76) 6.5 7.5 H2 - H1 15.4 8.1
TABLE-US-00012 TABLE 12 Results of Evaluation Ex. 1 Ex. 2 Ex. 3 Ex.
4 Ex. 5 Ex. 6 Center Composition F1 F1 F1 F1 F1 F1 Acid and/or salt
(phr) 0.0 0.0 0.0 0.0 0.0 0.0 Diameter (mm) 15.0 15.0 15.0 15.0
15.0 15.0 First envelope layer Composition S1 S2 S3 S4 S5 S6 Acid
and/or salt (phr) 5.0 2.0 12.0 5.0 5.0 5.0 Diameter (mm) 30.0 30.0
30.0 30.0 30.0 30.0 R.sup.2 0.97 0.95 0.95 0.95 0.98 0.97 Gradient
.alpha.1 1.04 0.70 0.82 0.98 1.18 1.04 Second envelop layer
Composition F2 F2 F2 F2 F2 F2 Acid and/or salt (phr) 5.0 5.0 5.0
5.0 5.0 5.0 Diameter (mm) 39.7 39.7 39.7 39.7 39.7 39.7 R.sup.2
0.98 0.98 0.98 0.98 0.98 0.98 Gradient .alpha.2 1.33 1.33 1.33 1.33
1.33 1.33 Mid layer Composition M M M M M M Hardness Hm (Shore D)
65.0 65.0 65.0 65.0 65.0 65.0 Thickness Tm (mm) 1.0 1.0 1.0 1.0 1.0
1.0 Cover Composition C C C C C C Hardness Hc (Shore D) 29.0 29.0
29.0 29.0 29.0 29.0 Thickness Tc (mm) 0.5 0.5 0.5 0.5 0.5 0.5 Ball
Hm - Hc 36.0 36.0 36.0 36.0 36.0 36.0 Deformation amount Db(mm) 2.6
2.6 2.6 2.6 2.6 2.6 W#1 spin rate (rpm) 2800 2900 2700 2800 2750
2800 W#1 flight distance (m) 246 244 248 246 247 246
TABLE-US-00013 TABLE 13 Results of Evaluation Comp. Comp. Ex. 7 Ex.
8 Ex. 1 Ex. 2 Ex. 9 Ex. 10 Center Composition F1 F1 F1 F1 F1 F1
Acid and/or salt (phr) 0.0 0.0 0.0 0.0 0.0 0.0 Diameter (mm) 15.0
15.0 15.0 15.0 15.0 15.0 First envelope layer Composition S7 S8 --
S9 S9 S10 Acid and/or salt (phr) 7.5 5.0 -- 0.0 0.0 0.5 Diameter
(mm) 30.0 30.0 -- 30.0 30.0 30.0 R.sup.2 0.97 0.97 -- 0.89 0.89
0.95 Gradient .alpha.1 1.04 1.04 -- 0.73 0.73 0.80 Second envelop
layer Composition F2 F2 -- F3 F2 F2 Acid and/or salt (phr) 5.0 5.0
-- 0.0 5.0 5.0 Diameter (mm) 39.7 39.7 -- 39.7 39.7 39.7 R.sup.2
0.98 0.98 -- 0.93 0.98 0.98 Gradient .alpha.2 1.33 1.33 -- 0.68
1.33 1.33 Mid layer Composition M M M M M M Hardness Hm (Shore D)
65.0 65.0 65.0 65.0 65.0 65.0 Thickness Tm (mm) 1.0 1.0 1.0 1.0 1.0
1.0 Cover Composition C C C C C C Hardness Hc (Shore D) 29.0 29.0
29.0 29.0 29.0 29.0 Thickness Tc (mm) 0.5 0.5 0.5 0.5 0.5 0.5 Ball
Hm - Hc 36.0 36.0 36.0 36.0 36.0 36.0 Deformation amount Db (mm)
2.6 2.6 2.6 2.6 2.6 2.6 W#1 spin rate (rpm) 2800 2900 3000 3100
2950 2950 W#1 flight distance (m) 246 244 241 240 243 243
TABLE-US-00014 TABLE 14 Results of Evaluation Ex. 11 Ex. 12 Ex. 13
Ex. 14 Ex. 15 Center Composition F1 F1 F1 F1 F1 Acid and/or salt
(phr) 0.0 0.0 0.0 0.0 0.0 Diameter (mm) 15.0 15.0 15.0 15.0 15.0
First envelope layer Composition S11 S13 S1 S1 S1 Acid and/or salt
(phr) 45.0 5.0 5.0 5.0 5.0 Diameter (mm) 30.0 30.0 30.0 30.0 30.0
R.sup.2 0.95 0.97 0.97 0.97 0.97 Gradient .alpha.1 0.70 1.04 1.04
1.04 1.04 Second envelop layer Composition F2 F2 F3 F4 F5 Acid
and/or salt (phr) 5.0 5.0 0.0 0.5 45.0 Diameter (mm) 39.7 39.7 39.7
39.7 39.7 R.sup.2 0.98 0.98 0.93 0.95 0.98 Gradient .alpha.2 1.33
1.33 0.68 0.77 0.30 Mid layer Composition M M M M M Hardness Hm
(Shore D) 65.0 65.0 65.0 65.0 65.0 Thickness Tm (mm) 1.0 1.0 1.0
1.0 1.0 Cover Composition C C C C C Hardness Hc (Shore D) 29.0 29.0
29.0 29.0 29.0 Thickness Tc (mm) 0.5 0.5 0.5 0.5 0.5 Ball Hm - Hc
36.0 36.0 36.0 36.0 36.0 Deformation amount Db 2.6 2.6 2.6 2.6 2.6
(mm) W#1 spin rate (rpm) 2700 2970 2950 2950 2980 W#1 flight
distance (m) 248 242 243 243 242
TABLE-US-00015 TABLE 15 Results of Evaluation Ex. 16 Ex. 17 Center
Composition F1 F1 Acid and/or salt (phr) 0.0 0.0 Diameter (mm) 15.0
15.0 First envelope layer Composition S14 S15 Acid and/or salt
(phr) 5.0 5.0 Diameter (mm) 30.0 30.0 R.sup.2 0.97 0.97 Gradient
.alpha.1 1.04 1.04 Second envelop layer Composition F2 F2 Acid
and/or salt (phr) 5.0 5.0 Diameter (mm) 39.7 39.7 R.sup.2 0.98 0.98
Gradient .alpha.2 1.33 1.33 Mid layer Composition M M Hardness Hm
(Shore D) 65.0 65.0 Thickness Tm (mm) 1.0 1.0 Cover Composition C C
Hardness Hc (Shore D) 29.0 29.0 Thickness Tc (mm) 0.5 0.5 Ball Hm -
Hc 36.0 36.0 Deformation amount Db 2.6 2.6 (mm) W#1 spin rate (rpm)
2750 2950 W#1 flight distance (m) 247 243
[0748] As shown in Tables 12 to 15, the golf balls according to
Examples are excellent in various performance characteristics. From
the results of evaluation, advantages of the present invention are
clear.
[0749] The golf ball according to the present invention can be used
for playing golf on golf courses and practicing at driving ranges.
The above descriptions are merely for illustrative examples, and
various modifications can be made without departing from the
principles of the present invention.
* * * * *