U.S. patent application number 17/678298 was filed with the patent office on 2022-09-08 for multi-piece solid golf ball.
This patent application is currently assigned to Bridgestone Sports Co., Ltd.. The applicant listed for this patent is Bridgestone Sports Co., Ltd.. Invention is credited to Hideo WATANABE.
Application Number | 20220280840 17/678298 |
Document ID | / |
Family ID | 1000006212596 |
Filed Date | 2022-09-08 |
United States Patent
Application |
20220280840 |
Kind Code |
A1 |
WATANABE; Hideo |
September 8, 2022 |
MULTI-PIECE SOLID GOLF BALL
Abstract
In a multi-piece solid golf ball having a core, envelope layer,
intermediate layer and cover, the core is formed primarily of a
base rubber, the core has a diameter of at least 30 mm, the
envelope layer is formed as two layers--an inner layer and an outer
layer, and the intermediate layer and the cover are each formed as
single layers of a resin material. The core and the respective
layer-encased spheres have surface hardnesses which satisfy
specific relationships, the Shore C hardness value obtained by
subtracting the core center hardness from the core surface hardness
is 16 or more, and certain layers have respective thicknesses which
satisfy specific conditions. This ball achieves a good distance on
full shots both with a driver and with irons, is superior in the
short game, and moreover has a good feel at impact and an excellent
scuff resistance.
Inventors: |
WATANABE; Hideo;
(Chichibushi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bridgestone Sports Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Bridgestone Sports Co.,
Ltd.
Tokyo
JP
|
Family ID: |
1000006212596 |
Appl. No.: |
17/678298 |
Filed: |
February 23, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 37/0096 20130101;
A63B 37/0018 20130101; A63B 37/009 20130101; A63B 37/0076 20130101;
A63B 37/0063 20130101; A63B 37/0092 20130101; A63B 37/0064
20130101 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2021 |
JP |
2021-035283 |
Claims
1. A multi-piece solid golf ball comprising a core, an envelope
layer, an intermediate layer and a cover, wherein the core is
formed primarily of a base rubber as one or more layer; the core as
a whole has a diameter of at least 30 mm; the envelope layer is
formed as two layers--an inner envelope layer and an outer envelope
layer; the intermediate layer and the cover are each formed as
single layers of a resin material; the core has a surface hardness,
the sphere obtained by encasing the core with the inner envelope
layer (inner envelope layer-encased sphere) has a surface hardness,
the sphere obtained by encasing the inner envelope layer-encased
sphere with the outer envelope layer (outer envelope layer-encased
sphere) has a surface hardness, the sphere obtained by encasing the
outer envelope layer-encased sphere with the intermediate layer
(intermediate layer-encased sphere) has a surface hardness and the
ball has a surface hardness which together satisfy the following
condition in which the hardnesses are Shore C hardness values: core
surface hardness<surface hardness of inner envelope
layer-encased sphere<surface hardness of outer envelope
layer-encased sphere<surface hardness of intermediate
layer-encased sphere>ball surface hardness; the Shore C hardness
value obtained by subtracting the core center hardness from the
core surface hardness is 16 or more; and the envelope layer, the
intermediate layer and the cover have respective thicknesses which
satisfy the following two conditions: cover
thickness<intermediate layer thickness, and outer envelope layer
thickness<inner envelope layer thickness.
2. The golf ball of claim 1, wherein the core center hardness (Cc),
core surface hardness (Cs) and the hardness at a midpoint between
the core surface and the core center (Cm) satisfy the condition:
(Cs-Cm)/(Cm-Cc).gtoreq.1.5.
3. The golf ball of claim 1 which satisfies the condition:
0.4.ltoreq.(OE vh+IE vh)/Core vh.ltoreq.1.1, wherein Core vh is the
volume (mm.sup.3) of the core multiplied by the Shore C hardness at
a midpoint between the core surface and the core center (Cm), IE vh
is the volume (mm.sup.3) of the inner envelope layer multiplied by
the Shore C hardness at the surface of the inner envelope
layer-encased sphere, and OE vh is the volume (mm.sup.3) of the
outer envelope layer multiplied by the Shore C hardness at the
surface of the outer envelope layer-encased sphere.
4. The golf ball of claim 1 wherein, letting CL1 be the coefficient
of lift at a Reynolds number of 80,000 and a spin rate of 2,000 rpm
and CL2 be the coefficient of lift at a Reynolds number of 70,000
and a spin rate of 1,900 rpm, the ball satisfies the following
condition: 0.900.ltoreq.CL2/CL1.
5. The golf ball of claim 1 wherein, letting CL3 be the coefficient
of lift at a Reynolds number of 200,000 and a spin rate of 2,500
rpm and CL4 be the coefficient of lift at a Reynolds number of
120,000 and a spin rate of 2,250 rpm, the ball satisfies the
following condition: 1.250.ltoreq.CL4/CL3.ltoreq.1.300.
6. The golf ball of claim 1, wherein the cover has a surface with
from 323 to 380 dimples arranged thereon.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn. 119(a) on Patent Application No. 2021-035283 filed in
Japan on Mar. 5, 2021, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a multi-piece solid golf
ball composed of five or more layers, including a core, an inner
envelope layer, an outer envelope layer, an intermediate layer and
a cover.
BACKGROUND ART
[0003] A variety of golf balls have hitherto been developed for
professional golfers and skilled amateurs. Of these, multi-piece
solid golf balls having an optimized hardness relationship among
the layers encasing the core are in widespread use because they
provide both a superior distance performance in the high head-speed
range and also a good controllability on iron shots and approach
shots. Given that not only the flight performance but also the feel
of the ball at impact and the spin rate of the ball after being
struck by a club strongly influence control of the ball, optimizing
the thicknesses and hardnesses of the golf ball layers in order to
achieve the best possible feel and spin rate is also an important
topic in golf ball development. In addition, because there exists a
desire for golf balls, when repeatedly hit with various clubs, to
have a good durability to repeated impact and for the scuffing
observed at the ball surface to be suppressed (increased scuff
resistance), maximal protection of the ball from external factors
is yet another important topic in golf ball development.
[0004] Examples of such literature include JP-A 2008-149131, JP-A
2009-095358, JP-A 2009-095364, JP-A 2009-095365, JP-A 2009-095369,
JP-A 2016-101254, JP-A 2016-101256, U.S. Published Patent
Application No. 2009/0170634, U.S. Published Patent Application No.
2012/0129630, U.S. Published Patent Application No. 2013/0012338,
U.S. Published Patent Application No. 2015/0251058, U.S. Published
Patent Application No. 2015/0314169, U.S. Published Patent
Application No. 2016/0317873, U.S. Published Patent Application No.
2017/0340925, U.S. Published Patent Application No. 2017/0361171,
U.S. Published Patent Application No. 2018/0015332, U.S. Published
Patent Application No. 2018/0008867, U.S. Published Patent
Application No. 2018/0078826, U.S. Published Patent Application No.
2019/0344127, and U.S. Published Patent Application No.
2020/0086177. These disclosures, all of which relate to golf balls
having a multilayer construction of four or more layers, focus on,
for example, the surface hardnesses of the respective
layers--namely, the core, the envelope layer, the intermediate
layer and the cover (outermost layer), the relationship between the
ball diameter and the core diameter, and the core hardness profile.
Moreover, some of the foregoing disclosures relate to golf balls
which have a ball construction of five layers wherein the core is
encased by four layers--an inner envelope layer, an outer envelope
layer, an intermediate layer and a cover (outermost layer), and
which have specifically defined hardness relationships and
thickness relationships among these layers.
[0005] However, there remains room for improvement in optimizing
the core hardness profile and the thickness relationships among the
various layers in these prior-art golf balls. That is, when these
golf balls are played by amateur golfers whose head speeds are not
high, a fully satisfactory distance cannot be achieved,
particularly on full shots taken with a utility club or an iron.
Moreover, with some of these prior-art golf balls, when an attempt
is made to achieve a superior distance performance even on iron
shots, a sufficiently high spin rate cannot be obtained on approach
shots, resulting in a ball that lacks a high playability or that
has a poor feel at impact on full shots. Accordingly, there exists
a desire for the development of a golf ball for amateur golfers
which has an improved flight on full shots with a utility club or
an iron, has a soft and good feel on all full shots, and also has a
high playability in the short game.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the present invention to
provide a multi-piece solid golf ball which, along with achieving a
satisfactory distance on full shots not only with a driver (W#1)
but also with long and middle irons, is highly receptive to spin on
approach shots and thus superior in the short game, and also has a
good feel at impact and an excellent scuff resistance.
[0007] As a result of intensive investigations, I have discovered,
with regard to golf balls having a core, an envelope layer, an
intermediate layer and a cover, that certain desirable effects can
be achieved by fabricating multi-piece solid golf balls in which
the core is formed primarily of a base rubber as one or more layer;
the core as a whole has a diameter of at least 30 mm; the envelope
layer is formed as two layers--an inner envelope layer and an outer
envelope layer; the intermediate layer and the cover are both
formed as single layers of a resin material; the core and the
respective layer-encased spheres have surface hardnesses which
together satisfy the following condition in which the hardnesses
are Shore C hardness values: [0008] core surface
hardness<surface hardness of inner envelope layer-encased
sphere<surface hardness of outer envelope layer-encased
sphere<surface hardness of intermediate layer-encased
sphere>ball surface hardness; the Shore C hardness value
obtained by subtracting the core center hardness from the core
surface hardness is 16 or more; and the envelope layer, the
intermediate layer and the cover have respective thicknesses which
satisfy the following two conditions: [0009] cover
thickness<intermediate layer thickness, and [0010] outer
envelope layer thickness<inner envelope layer thickness. That
is, an even further reduction in the spin rate on shots with a
driver (W#1) and with various irons can be achieved while
maintaining a high initial velocity when hit, as a result of which
a good distance can be attained. In addition, the spin rate on
approach shots in the short game is optimized, providing a higher
controllability, and a good scuff resistance can be obtained.
[0011] Accordingly, the invention provides a multi-piece solid golf
ball having a core, an envelope layer, an intermediate layer and a
cover, the core being formed primarily of a base rubber as one or
more layer, the core as a whole having a diameter of at least 30
mm, the envelope layer being formed as two layers--an inner
envelope layer and an outer envelope layer, and the intermediate
layer and the cover each being formed as single layers of a resin
material. In the golf ball of the invention, the core has a surface
hardness, the sphere obtained by encasing the core with the inner
envelope layer (inner envelope layer-encased sphere) has a surface
hardness, the sphere obtained by encasing the inner envelope
layer-encased sphere with the outer envelope layer (outer envelope
layer-encased sphere) has a surface hardness, the sphere obtained
by encasing the outer envelope layer-encased sphere with the
intermediate layer (intermediate layer-encased sphere) has a
surface hardness and the ball has a surface hardness which together
satisfy the following condition in which the hardnesses are Shore C
hardness values: [0012] core surface hardness<surface hardness
of inner envelope layer-encased sphere<surface hardness of outer
envelope layer-encased sphere<surface hardness of intermediate
layer-encased sphere>ball surface hardness. Also, the Shore C
hardness value obtained by subtracting the core center hardness
from the core surface hardness is 16 or more. In addition, the
envelope layer, the intermediate layer and the cover have
respective thicknesses which satisfy the following two conditions:
[0013] cover thickness<intermediate layer thickness, and [0014]
outer envelope layer thickness<inner envelope layer
thickness.
[0015] In a preferred embodiment of the golf ball according to the
present invention, the core center hardness (Cc), core surface
hardness (Cs) and the hardness at a midpoint between the core
surface and the core center (Cm) satisfy the condition:
(Cs-Cm)/(Cm-Cc).gtoreq.1.5.
[0016] In another preferred embodiment, the golf ball satisfies the
condition:
0.4.ltoreq.(OE vh+IE vh)/Core vh.ltoreq.1.1,
wherein Core vh is the volume (mm.sup.3) of the core multiplied by
the Shore C hardness at a midpoint between the core surface and the
core center (Cm), IE vh is the volume (mm.sup.3) of the inner
envelope layer multiplied by the Shore C hardness at the surface of
the inner envelope layer-encased sphere, and OE vh is the volume
(mm.sup.3) of the outer envelope layer multiplied by the Shore C
hardness at the surface of the outer envelope layer-encased
sphere.
[0017] In yet another preferred embodiment, letting CL1 be the
coefficient of lift at a Reynolds number of 80,000 and a spin rate
of 2,000 rpm and CL2 be the coefficient of lift at a Reynolds
number of 70,000 and a spin rate of 1,900 rpm, the ball satisfies
the following condition:
0.900.ltoreq.CL2/CL1.
[0018] In still another preferred embodiment, letting CL3 be the
coefficient of lift at a Reynolds number of 200,000 and a spin rate
of 2,500 rpm and CL4 be the coefficient of lift at a Reynolds
number of 120,000 and a spin rate of 2,250 rpm, the ball satisfies
the following condition:
1.250.ltoreq.CL4/CL3.ltoreq.1.300.
[0019] In a further preferred embodiment, the cover has a surface
with from 323 to 380 dimples arranged thereon.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0020] The multi-piece solid golf ball of the invention, along with
achieving a satisfactory distance on full shots not only with a
driver (W#1) but also with various irons, is highly receptive to
spin on approach shots and thus superior in the short game.
Moreover, it has a good feel at impact and an excellent scuff
resistance. Such qualities make this ball highly useful as a golf
ball for professional golfers and skilled amateurs.
BRIEF DESCRIPTION OF THE DIAGRAMS
[0021] FIG. 1 is a schematic cross-sectional view of the
multi-piece solid golf ball (5-layer structure) according to the
invention.
[0022] FIGS. 2A and 2B are, respectively, a top view and a side
view of the exterior of a golf ball showing the arrangement
(pattern) of dimples common to all of the Examples and Comparative
Examples described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The objects, features and advantages of the invention will
become more apparent from the following detailed description taken
in conjunction with the appended diagrams.
[0024] Referring to FIG. 1, the multi-piece solid golf ball of the
invention is a golf ball G having five or more layers, including a
core 1, an envelope layer 2 made of two layers (inner envelope
layer 2a and outer envelope layer 2b) that encases the core 1, an
intermediate layer 3 that encases the envelope layers, and a cover
4 that encases the intermediate layer 3. Numerous dimples D are
generally formed on the surface of the cover 4. Although not shown
in the diagram, a coating layer is generally applied onto the
surface of the cover 4. Apart from the coating layer, the cover 4
is positioned as the outermost layer in the layered structure of
the golf ball. The core 1 is not limited to a single layer and may
be formed of a plurality of two or more layers.
[0025] The core has a diameter of at least 30.0 mm. The diameter is
preferably at least 31.4 mm, and more preferably at least 32.0 mm.
The diameter upper limit is preferably not more than 35.0 mm, more
preferably not more than 34.2 mm, and even more preferably not more
than 33.5 mm. When the core diameter is too large, the spin rate on
full shots with a driver (W#1) or an iron may rise, as a result of
which the desired distance may not be achieved. On the other hand,
when the core diameter is too small, the initial velocity of the
ball may decrease, as a result of which a good distance may not be
achieved.
[0026] The core has a deflection when compressed under a final load
of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which,
although not particularly limited, is preferably at least 3.0 mm,
more preferably at least 3.2 mm, and even more preferably at least
3.5 mm. The core deflection upper limit is preferably 5.5 mm or
less, more preferably 5.3 mm or less, and even more preferably 5.0
mm or less. When the core deflection is too small, i.e., when the
core is too hard, the spin rate of the ball may rise excessively,
resulting in a poor distance, or the feel at impact may be too
hard. On the other hand, when the core deflection is too large,
i.e., when the core is too soft, the ball rebound may be too low,
resulting in a poor distance, the feel at impact may be too soft,
or the durability to cracking on repeated impact may worsen.
[0027] The core consists of one or more layer of a vulcanized
rubber composition made up primarily of a rubber material, and is
preferably formed of a single layer. If the core material is not a
rubber material, the rebound may be too low and the ball may fail
to travel a good distance. Also, when the core is composed of a
plurality of layers, upon repeated impact, the ball may end up
cracking early from the core interface. The rubber composition of
the core is typically obtained by using a base rubber as the
primary ingredient and compounding with this a co-crosslinking
agent, a crosslinking initiator, an inert filler, an organosulfur
compound and the like.
[0028] It is preferable to use a polybutadiene as the base rubber.
Commercial products may be used as the polybutadiene. Illustrative
examples include BR01, BR51 and BR730 (from JSR Corporation). The
proportion of polybutadiene within the base rubber is preferably at
least 60 wt %, and more preferably at least 80 wt %. Rubber
ingredients other than the above polybutadienes may be included in
the base rubber, provided that doing so does not detract from the
advantageous effects of the invention. Examples of rubber
ingredients other than the above polybutadienes include other
polybutadienes and also other diene rubbers, such as
styrene-butadiene rubbers, natural rubbers, isoprene rubbers and
ethylene-propylene-diene rubbers.
[0029] The co-crosslinking agent is an .alpha.,.beta.-unsaturated
carboxylic acid and/or a metal salt thereof. Specific examples of
unsaturated carboxylic acids include acrylic acid, methacrylic
acid, maleic acid and fumaric acid. The use of acrylic acid or
methacrylic acid is especially preferred. Metal salts of
unsaturated carboxylic acids are exemplified by, without particular
limitation, the above unsaturated carboxylic acids that have been
neutralized with desired metal ions. Specific examples include the
zinc salts and magnesium salts of methacrylic acid and acrylic
acid. The use of zinc acrylate is especially preferred.
[0030] The unsaturated carboxylic acid and/or metal salt thereof is
included in an amount, per 100 parts by weight of the base rubber,
which is typically at least 15 parts by weight, preferably at least
20 parts by weight, and more preferably at least 25 parts by
weight. The amount included is typically not more than 50 parts by
weight, preferably not more than 45 parts by weight, and more
preferably not more than 40 parts by weight. Too much may make the
core too hard, giving the ball an unpleasant feel at impact,
whereas too little may lower the rebound.
[0031] It is preferable to use an organic peroxide as the
crosslinking initiator. Commercial products may be used as the
organic peroxide. Examples of such products that may be suitably
used include Percumyl D, Perhexa C-40 and Perhexa 3M (all from NOF
Corporation), and Luperco 231XL (from AtoChem Co.). One of these
may be used alone, or two or more may be used together. The amount
of organic peroxide included per 100 parts by weight of the base
rubber is preferably at least 0.1 part by weight, more preferably
at least 0.3 part by weight, and even more preferably at least 0.5
part by weight. The upper limit is preferably not more than 5 parts
by weight, more preferably not more than 4 parts by weight, even
more preferably not more than 3 parts by weight, and most
preferably not more than 2.5 parts by weight. When too much or too
little is included, it may not be possible to obtain a ball having
a good feel, durability and rebound.
[0032] Fillers that may be suitably used include zinc oxide, barium
sulfate and calcium carbonate. These may be used singly or two or
more may be used in combination. The amount of filler included per
100 parts by weight of the base rubber may be set to preferably at
least 4 parts by weight, more preferably at least 5 parts by
weight, and even more preferably at least 7 parts by weight. The
upper limit in the amount of filler included per 100 parts by
weight of the base rubber may be set to preferably not more than
100 parts by weight, more preferably not more than 75 parts by
weight, and even more preferably not more than 50 parts by weight.
At a filler content which is too high or too low, a proper weight
and a suitable rebound may be impossible to obtain.
[0033] Commercial products such as Nocrac NS-6, Nocrac NS-30,
Nocrac 200 and Nocrac MB (all products of Ouchi Shinko Chemical
Industry Co., Ltd.) may be used as antioxidants. These may be used
singly, or two or more may be used in combination.
[0034] The amount of antioxidant included per 100 parts by weight
of the base rubber, although not particularly limited, is
preferably at least 0.05 part by weight, and more preferably at
least 0.1 part by weight. The upper limit is preferably not more
than 1.0 part by weight, more preferably not more than 0.7 part by
weight, and even more preferably not more than 0.5 part by weight.
When the antioxidant content is too high or too low, a suitable
core hardness gradient may not be obtained, as a result of which it
may not be possible to obtain a good rebound, a good durability and
a good spin rate-lowering effect on full shots.
[0035] In addition, an organosulfur compound may be included in the
rubber composition so as to impart an excellent rebound.
Thiophenols, thionaphthols, halogenated thiophenols, and metal
salts thereof are recommended for this purpose. Illustrative
examples include pentachlorothiophenol, pentafluorothiophenol,
pentabromothiophenol, p-chlorothiophenol, and the zinc salt of
pentachlorothiophenol; and also diphenylpolysulfides,
dibenzylpolysulfides, dibenzoylpolysulfides,
dibenzothiazoylpolysulfides and dithiobenzoylpolysulfides having 2
to 4 sulfurs. The use of diphenyldisulfide or the zinc salt of
pentachlorothiophenol is especially preferred.
[0036] The amount of the organosulfur compound included per 100
parts by weight of the base rubber is at least 0.05 part by weight,
preferably at least 0.07 part by weight, and more preferably at
least 0.1 part by weight. The upper limit is not more than 5 parts
by weight, preferably not more than 4 parts by weight, more
preferably not more than 3 parts by weight, and most preferably not
more than 2 parts by weight. Including too much organosulfur
compound may excessively lower the hardness, whereas including too
little is unlikely to improve the rebound.
[0037] The core can be produced by vulcanizing/curing the rubber
composition containing the above respective ingredients. For
example, production may be carried out by kneading the composition
using a mixer such as a Banbury mixer or a roll mill, compression
molding or injection molding the kneaded composition using a core
mold, and curing the molded material by suitably heating it at a
temperature sufficient for the organic peroxide or co-crosslinking
agent to act, i.e., between 100.degree. C. and 200.degree. C.,
preferably between 140.degree. C. and 180.degree. C., for 10 to 40
minutes.
[0038] Next, the hardness profile of the core is described. The
hardness of the core refers hereinafter to the Shore C hardness.
This Shore C hardness is a hardness value measured with a Shore C
durometer in accordance with ASTM D2240.
[0039] The core has a center hardness (Cc) which is preferably at
least 54, more preferably at least 57, and even more preferably at
least 60. The upper limit is preferably not more than 69, more
preferably not more than 67, and even more preferably not more than
65. When this value is too large, the feel at impact may harden, or
the spin rate on full shots may rise, as a result of which the
intended distance may not be achieved. On the other hand, when this
value is too small, the rebound may become lower and so a good
distance may not be obtained, or the durability to cracking under
repeated impact may worsen.
[0040] The core has a surface hardness (Cs) which is preferably at
least 70, more preferably at least 74, and even more preferably at
least 77. The upper limit is preferably not more than 90, more
preferably not more than 87, and even more preferably not more than
85. A core surface hardness outside of this range may lead to
undesirable results similar to those described above for the core
center hardness (Cc).
[0041] The core has a hardness Cm at the midpoint between the core
surface and core center which, although not particularly limited,
may be set to preferably at least 58, more preferably at least 61,
and even more preferably at least 64. The upper limit value is
preferably not more than 75, more preferably not more than 74, and
even more preferably not more than 72. A hardness that deviates
from these values may lead to undesirable results similar to those
described above for the core center hardness (Cc).
[0042] The Shore C hardness value obtained by subtracting the core
center hardness (Cc) from the core surface hardness (Cs) is 16 or
more, preferably 17 or more, and more preferably 18 or more. The
upper limit value is preferably not more than 25, more preferably
not more than 22, and even more preferably not more than 21. When
this value is too small, the spin rate on full shots with a driver
becomes high, as a result of which the desired distance may not be
attainable. When this hardness difference is larger than the above
range, the durability of the ball to cracking on repeated impact
may worsen or the initial velocity on shots may decrease, as a
result of which the intended distance may not be attainable. In
cases where the above hardness difference is smaller than the above
range on account of a large core deflection hardness, the initial
velocity of the ball on full shots with a driver is low, as a
result of which the desired distance may not be attainable.
[0043] With regard to the interior hardness of the core, the value
expressed as (Cs-Cm)/(Cm-Cc) is preferably at least 1.5, more
preferably at least 1.7, and even more preferably at least 1.9. The
upper limit is preferably 10.0 or less, more preferably 8.0 or
less, and even more preferably 5.0 or less. When this value is too
large, the durability to cracking on repeated impact may worsen or
the initial velocity on shots may become low, as a result of which
the intended distance may not be attainable. On the other hand,
when this value is too small, the spin rate on full shots may rise,
as a result of which the intended distance may not be
attainable.
[0044] Letting the core volume (mm.sup.3) multiplied by the Shore C
hardness at the midpoint between the core surface and core center
be Core vh, the value of Core vh is preferably at least 800, more
preferably at least 900, and even more preferably at least 1,000;
the upper limit value is preferably 1,540 or less, more preferably
1,480 or less, and even more preferably 1,430 or less. When the
Core vh value is too small, the ball initial velocity may decrease
and a good distance may not be obtained. On the other hand, when
the Core vh value is too large, the spin rate on full shots with an
iron may rise and the intended distance may not be attainable.
[0045] Next, the envelope layer is described.
[0046] In this invention, the envelope layer is formed of two
layers: an inner layer and an outer layer. These are referred to
as, respectively, the inner envelope layer and the outer envelope
layer.
[0047] The inner envelope layer has a material hardness on the
Shore C hardness scale which, although not particularly limited, is
preferably at least 67, more preferably at least 70, and even more
preferably at least 72. The upper limit is preferably not more than
90, more preferably not more than 89, and even more preferably not
more than 88. The material hardness of the inner envelope layer on
the Shore D hardness scale is preferably at least 43, more
preferably at least 45, and even more preferably at least 47. The
upper limit is preferably not more than 60, more preferably not
more than 56, and even more preferably not more than 54.
[0048] The sphere obtained by encasing the core with the inner
envelope layer (inner envelope layer-encased sphere) has a surface
hardness which, on the Shore C hardness scale, is preferably at
least 75, more preferably at least 78, and even more preferably at
least 80. The upper limit is preferably not more than 94, more
preferably not more than 92, and even more preferably not more than
90. The surface hardness on the Shore D hardness scale is
preferably at least 49, more preferably at least 51, and even more
preferably at least 53. The upper limit is preferably not more than
66, more preferably not more than 62, and even more preferably not
more than 60.
[0049] When the material hardness and the surface hardness of the
inner envelope layer are lower than the above ranges, the ball may
be too receptive to spin on full shots or the initial velocity may
decline, as a result of which a good distance may not be achieved.
On the other hand, when the material hardness and the surface
hardness are too high, the feel at impact may become hard, the
durability to cracking on repeated impact may worsen, or the spin
rate on full shots may rise, as a result of which a good distance
may not be achieved.
[0050] The surface hardness of the inner envelope layer-encased
sphere is higher than the surface hardness of the core. When this
is not the case, the spin rate on full shots rises and the intended
distance cannot be attained.
[0051] The inner envelope layer has a thickness that is preferably
at least 0.8 mm, more preferably at least 1.0 mm, and even more
preferably at least 1.2 mm. The upper limit in the thickness of the
inner envelope layer is preferably 1.8 mm or less, more preferably
1.7 mm or less, and even more preferably 1.6 mm or less. When the
inner envelope layer thickness falls outside of this range, the
spin rate lowering effect on full shots may be inadequate and a
good distance may not be achieved. Also, when the inner envelope
layer is too thin, the durability to cracking on repeated impact
and the low-temperature durability may worsen.
[0052] Letting IE vh be the inner envelope layer volume (mm.sup.3)
multiplied by the Shore C surface hardness of the inner envelope
layer-encased sphere, the value of IE vh is preferably at least
380, more preferably at least 410, and even more preferably at
least 440. The upper limit value is preferably 520 or less, more
preferably 500 or less, and even more preferably 480 or less. When
the IE vh value falls outside of the above range, the spin
rate-lowering effect on full shots may be inadequate, as a result
of which a good distance may not be achieved.
[0053] The value of (OE vh+IE vh)/Core vh, where OE vh and Core vh
are as defined below, is preferably at least 0.4, more preferably
at least 0.5, and even more preferably at least 0.6. The upper
limit is preferably 1.1 or less, more preferably 1.0 or less, and
even more preferably 0.9 or less. When this value is too small, the
initial velocity on shots may decrease, as a result of which a good
distance may not be achieved. On the other hand, when this value is
too large, the initial velocity may decrease or the spin rate on
full shots may rise, as a result of which the intended distance may
not be achieved.
[0054] The outer envelope layer has a material hardness on the
Shore C hardness scale which is preferably at least 75, more
preferably at least 78, and even more preferably at least 80. The
upper limit is preferably not more than 95, more preferably not
more than 92, and even more preferably not more than 90. The
surface hardness of the outer envelope layer on the Shore D
hardness scale is preferably at least 46, more preferably at least
48, and even more preferably at least 50. The upper limit is
preferably not more than 63, more preferably not more than 59, and
even more preferably not more than 57.
[0055] The sphere obtained by encasing the inner envelope
layer-encased sphere with the outer envelope layer (outer envelope
layer-encased sphere) has a surface hardness on the Shore C
hardness scale which is preferably at least 83, more preferably at
least 86, and even more preferably at least 88. The upper limit is
preferably not more than 95, more preferably not more than 93, and
even more preferably not more than 92. The surface hardness on the
Shore D hardness scale is preferably at least 52, more preferably
at least 54, and even more preferably at least 56. The upper limit
is preferably not more than 69, more preferably not more than 65,
and even more preferably not more than 63.
[0056] When the material hardness and the surface hardness of the
outer envelope layer are lower than the above ranges, the ball may
take on too much spin on full shots or the initial velocity may
decrease, as a result of which a good distance may not be achieved.
On the other hand, when the material hardness and the surface
hardness are too high, the feel at impact may become too hard, the
durability to cracking on repeated impact may worsen, or the spin
rate on full shots may rise, as a result of which a good distance
may not be achieved.
[0057] The outer envelope layer has a thickness which is preferably
at least 0.7 mm, more preferably at least 0.9 mm, and even more
preferably at least 1.1 mm. The upper limit in the thickness of the
outer envelope layer is preferably 1.7 mm or less, more preferably
1.6 mm or less, and even more preferably 1.5 mm or less. When the
outer envelope layer thickness falls outside of this range, the
spin rate-lowering effect on full shots may be inadequate and a
good distance may not be achieved. Also, when the outer envelope
layer is too thin, the durability to cracking on repeated impact
and the low-temperature durability may worsen.
[0058] To lower the spin rate of the ball on full shots and
increase the distance traveled by the ball, it is critical for the
outer envelope layer to have a smaller thickness than the inner
envelope layer. The value obtained by subtracting the outer
envelope layer thickness from the inner envelope layer thickness is
larger than 0 mm, preferably at least 0.1 mm, and more preferably
at least 0.2 mm. The upper limit value is generally 0.5 mm or less,
preferably 0.4 mm or less, and more preferably 0.3 mm or less. When
this value falls outside of the above range, the spin rate on full
shots may rise and a good distance may not be achieved.
[0059] Letting OE vh the outer envelope layer volume (mm.sup.3)
multiplied by the Shore C surface hardness of the outer envelope
layer-encased sphere, the value of OE vh is preferably at least
380, more preferably at least 410, and even more preferably at
least 440. The upper limit value is preferably 600 or less, more
preferably 540 or less, and even more preferably 480 or less. When
the OE vh value falls outside of the above range, the spin
rate-lowering effect on full shots may be inadequate and so a good
distance may not be achieved.
[0060] The total thickness of the envelope layer is preferably at
least 2.0 mm, more preferably at least 2.2 mm, and even more
preferably at least 2.4 mm. The upper limit value is preferably not
more than 4.0 mm, more preferably not more than 3.5 mm, and even
more preferably not more than 3.0 mm. When the total thickness of
the envelope layer is too large, the initial velocity may decrease
and a good distance may not be achieved. When the overall thickness
of the envelope layer is too low, the spin rate-lowering effect may
be insufficient and a good distance may not be achieved on full
shots with an iron.
[0061] The materials making up the inner envelope layer and the
outer envelope layer are not particularly limited; known resins may
be used for this purpose. Examples of preferred materials include
resin compositions containing as the essential ingredients: 100
parts by weight of a resin component composed of, in admixture,
[0062] (A) a base resin of (a-1) an olefin-unsaturated carboxylic
acid random copolymer and/or a metal ion neutralization product of
an olefin-unsaturated carboxylic acid random copolymer mixed with
(a-2) an olefin-unsaturated carboxylic acid-unsaturated carboxylic
acid ester random terpolymer and/or a metal ion neutralization
product of an olefin-unsaturated carboxylic acid-unsaturated
carboxylic acid ester random terpolymer in a weight ratio between
100:0 and 0:100, and
[0063] (B) a non-ionomeric thermoplastic elastomer in a weight
ratio between 100:0 and 50:50;
[0064] (C) from 5 to 120 parts by weight of a fatty acid and/or
fatty acid derivative having a molecular weight of from 228 to
1,500; and
[0065] (D) from 0.1 to 17 parts by weight of a basic inorganic
metal compound capable of neutralizing un-neutralized acid groups
in components A and C.
[0066] Components A to D in the intermediate layer-forming resin
material described in, for example, JP-A 2010-253268 may be
advantageously used as above components A to D.
[0067] The resin materials that form the inner envelope layer and
the outer envelope layer may be mutually like or unlike. As
subsequently described, in this invention, the outer envelope
layer-encased sphere has a higher surface hardness than the inner
envelope layer-encased sphere. One way to have the resin material
of the outer envelope layer be harder than the resin material of
the inner envelope layer is to mix a suitable amount of a
relatively hard ionomer resin together with the resin material
composed of components (A) to (D) above, thereby forming a resin
material for the outer envelope layer which differs from the resin
material for the inner envelope layer.
[0068] A non-ionomeric thermoplastic elastomer may be included in
the respective materials for the inner envelope layer and the outer
envelope layer. The non-ionomeric thermoplastic elastomer is
preferably included in an amount of from 0 to 50 parts by weight
per 100 parts by weight of the total amount of the base resin.
[0069] Exemplary non-ionomeric thermoplastic elastomers include
polyolefin elastomers (including polyolefins and metallocene
polyolefins), polystyrene elastomers, diene polymers, polyacrylate
polymers, polyamide elastomers, polyurethane elastomers, polyester
elastomers and polyacetals.
[0070] Depending on the intended use, optional additives may be
suitably included in the above resin materials. For example,
pigments, dispersants, antioxidants, ultraviolet absorbers and
light stabilizers may be added. When these additives are included,
the amount added per 100 parts by weight of the overall base resin
is preferably at least 0.1 part by weight, and more preferably at
least 0.5 part by weight. The upper limit is preferably not more
than 10 parts by weight, and more preferably not more than 4 parts
by weight.
[0071] Next, the intermediate layer is described.
[0072] The intermediate layer has a material hardness on the Shore
D hardness scale which, although not particularly limited, is
preferably at least 58, more preferably at least 60, and even more
preferably at least 63. The upper limit is preferably not more than
70, more preferably not more than 68, and even more preferably not
more than 65. The material hardness on the Shore C hardness scale
is preferably at least 87, more preferably at least 89, and even
more preferably at least 93. The upper limit is preferably not more
than 100, more preferably not more than 98, and even more
preferably not more than 96.
[0073] The sphere obtained by encasing the outer envelope
layer-encased sphere with the intermediate layer (intermediate
layer-encased sphere) has a surface hardness on the Shore D
hardness scale which is preferably at least 64, more preferably at
least 66, and even more preferably at least 69. The upper limit is
preferably not more than 76, more preferably not more than 74, and
even more preferably not more than 71. The surface hardness on the
Shore C hardness scale is preferably at least 90, more preferably
at least 93, and even more preferably at least 96. The upper limit
is preferably not more than 100, more preferably not more than 99,
and even more preferably not more than 98.
[0074] When the material hardness and surface hardness of the
intermediate layer are lower than the above respective ranges, the
ball may take on too much spin on full shots, or the initial
velocity may decrease, resulting in a poor distance. On the other
hand, when the material hardness and surface hardness are too high,
the durability of the ball to cracking on repeated impact may
worsen or the feel at impact on shots with a putter and on short
approaches may be too hard.
[0075] The surface hardness of the intermediate layer-encased
sphere is set to a higher value than the surface hardness of the
ball and the surface hardness of the outer envelope layer-encased
sphere. When this is not the case, the spin rate on full shots will
rise, preventing a good distance from being achieved, or the
controllability of the ball in the short game will worsen.
[0076] The intermediate layer has a thickness of preferably at
least 0.7 mm, more preferably at least 0.8 mm, and even more
preferably at least 1.0 mm. The upper limit in the intermediate
layer thickness is preferably 1.8 mm or less, more preferably 1.4
mm or less, and even more preferably 1.2 mm or less.
[0077] The intermediate layer has a greater thickness than the
subsequently described cover (outermost layer). The value obtained
by subtracting the cover thickness from the intermediate layer
thickness is preferably at least 0.04 mm, and more preferably at
least 0.08 mm. The upper limit value is preferably 1.5 mm or less,
more preferably 1.0 mm or less, and even more preferably 0.6 mm or
less. When the cover is thicker than the intermediate layer, the
spin rate on full shots may rise or the initial velocity may
decrease, which may result in a poor distance. On the other hand,
when this value is too large, the ball may not be receptive to spin
in the short game or the cover may cut easily when the ball is
topped with a wedge.
[0078] The intermediate layer material may be suitably selected
from among various types of thermoplastic resins that are used as
golf ball materials, with the use of the highly neutralized resin
material containing components (a) to (c) described above in
connection with the envelope layer materials or the use of an
ionomer resin being preferred.
[0079] Specific examples of ionomer resin materials include
high-acid ionomers having an acid content of at least 16 wt %,
sodium-neutralized ionomer resins and zinc-neutralized ionomer
resins. These may be used singly or two or more may be used
together.
[0080] An embodiment that uses in admixture a zinc-neutralized
ionomer resin and a sodium-neutralized ionomer resin as the chief
materials is especially preferred. The blending ratio therebetween,
expressed as the weight ratio (zinc-neutralized
ionomer)/(sodium-neutralized ionomer), is from 25/75 to 75/25,
preferably from 35/65 to 65/35, and more preferably from 45/55 to
55/45. When the zinc-neutralized ionomer and sodium-neutralized
ionomer are not included in a ratio within this range, the rebound
may become too low, as a result of which the desired distance may
not be achieved, the durability to cracking on repeated impact at
normal temperatures may worsen, or the durability to cracking at
low temperatures (subzero Centigrade) may worsen.
[0081] Depending on the intended use, optional additives may be
suitably included in the intermediate layer material. For example,
pigments, dispersants, antioxidants, ultraviolet absorbers and
light stabilizers may be added. When these additives are included,
the amount added per 100 parts by weight of the base resin is
preferably at least 0.1 part by weight, and more preferably at
least 0.5 part by weight. The upper limit is preferably not more
than 10 parts by weight, and more preferably not more than 4 parts
by weight.
[0082] It is desirable to abrade the surface of the intermediate
layer in order to increase adhesion of the intermediate layer
material with the polyurethane that is preferably used in the
subsequently described cover material. In addition, it is desirable
to apply a primer (adhesive) to the surface of the intermediate
layer following such abrasion treatment or to add an adhesion
reinforcing agent to the intermediate layer material.
[0083] The intermediate layer material has a specific gravity which
is typically less than 1.1, preferably between 0.90 and 1.05, and
more preferably between 0.93 and 0.99. Outside of this range, the
rebound of the overall ball may decrease and a good distance may
not be obtained, or the durability of the ball to cracking on
repeated impact may worsen.
[0084] Next, the cover (outermost layer) is described.
[0085] The cover has a material hardness on the Shore D hardness
scale which, although not particularly limited, is preferably at
least 35, more preferably at least 40, and even more preferably at
least 45. The upper limit is preferably not more than 60, more
preferably not more than 55, and even more preferably not more than
50. On the Shore C hardness scale, the material hardness is
preferably at least 57, more preferably at least 63, and even more
preferably at least 70. The upper limit is preferably not more than
89, more preferably not more than 83, and even more preferably not
more than 76.
[0086] The surface hardness of the sphere obtained by encasing the
intermediate layer-encased sphere with the cover (i.e., the ball),
expressed on the Shore D hardness scale, is preferably at least 50,
more preferably at least 53, and even more preferably at least 56.
The upper limit is preferably not more than 70, more preferably not
more than 67, and even more preferably not more than 64. On the
Shore C hardness scale, the surface hardness is preferably at least
75, more preferably at least 80, and even more preferably at least
85. The upper limit is preferably not more than 95, more preferably
not more than 92, and even more preferably not more than 90.
[0087] When the material hardness of the cover and the surface
hardness of the ball are too much lower than the above respective
ranges, the spin rate of the ball on full shots with an iron may
rise and a good distance may not be achieved. On the other hand,
when the material hardness of the cover and the surface hardness of
the ball are too high, the ball may not be receptive to spin on
approach shots or the scuff resistance may worsen.
[0088] The cover has a thickness of preferably at least 0.3 mm,
more preferably at least 0.45 mm, and even more preferably at least
0.6 mm. The upper limit in the cover thickness is preferably not
more than 1.2 mm, more preferably not more than 1.15 mm, and even
more preferably not more than 1.0 mm. The cover thickness is
preferably lower than the intermediate layer thickness. When the
cover thickness falls outside of the above range or is greater than
the intermediate layer thickness, the ball rebound on full shots
with an iron may be inadequate or the spin rate may rise, as a
result of which a good distance may not be achieved. On the other
hand, when the cover is too thin, the scuff resistance may worsen,
or the ball may not be receptive to spin on approach shots,
resulting in an inadequate controllability.
[0089] Various types of thermoplastic resins and thermoset resins
employed as cover stock in golf balls may be used as the cover
material. For reasons having to do with ball controllability and
scuff resistance, preferred use can be made of a urethane resin. In
particular, from the standpoint of the mass productivity of the
manufactured balls, it is preferable to use a material that is
composed primarily of a thermoplastic polyurethane, and especially
preferable to form the cover of a resin blend in which the main
components are (I) a thermoplastic urethane and (II) a
polyisocyanate compound.
[0090] It is recommended that the total weight of components (I)
and (II) combined be at least 60%, and preferably at least 70%, of
the overall amount of the cover-forming resin blend. Components (I)
and (II) are described below.
[0091] The thermoplastic polyurethane (I) has a structure which
includes soft segments composed of a polymeric polyol (polymeric
glycol) that is a long-chain polyol, and hard segments composed of
a chain extender and a polyisocyanate compound. Here, the
long-chain polyol serving as a starting material may be any that
has hitherto been used in the art relating to thermoplastic
polyurethanes, and is not particularly limited. Illustrative
examples include polyester polyols, polyether polyols,
polycarbonate polyols, polyester polycarbonate polyols, polyolefin
polyols, conjugated diene polymer-based polyols, castor oil-based
polyols, silicone-based polyols and vinyl polymer-based polyols.
These long-chain polyols may be used singly, or two or more may be
used in combination. Of these, in terms of being able to synthesize
a thermoplastic polyurethane having a high rebound resilience and
excellent low-temperature properties, a polyether polyol is
preferred.
[0092] Any chain extender that has hitherto been employed in the
art relating to thermoplastic polyurethanes may be suitably used as
the chain extender. For example, low-molecular-weight compounds
with a molecular weight of 400 or less which have on the molecule
two or more active hydrogen atoms capable of reacting with
isocyanate groups are preferred. Illustrative, non-limiting,
examples of the chain extender include 1,4-butylene glycol,
1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol and
2,2-dimethyl-1,3-propanediol. Of these, the chain extender is
preferably an aliphatic diol having 2 to 12 carbon atoms, and more
preferably 1,4-butylene glycol.
[0093] Any polyisocyanate compound hitherto employed in the art
relating to thermoplastic polyurethanes may be suitably used
without particular limitation as the polyisocyanate compound. For
example, use may be made of one or more selected from the group
consisting of 4,4'-diphenylmethane diisocyanate, 2,4-toluene
diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate,
xylylene diisocyanate, 1,5-naphthylene diisocyanate,
tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate,
dicyclohexylmethane diisocyanate, tetramethylene diisocyanate,
hexamethylene diisocyanate, isophorone diisocyanate, norbornene
diisocyanate, trimethylhexamethylene diisocyanate and dimer acid
diisocyanate. However, depending on the type of isocyanate, the
crosslinking reactions during injection molding may be difficult to
control. In the practice of the invention, to provide a balance
between stability at the time of production and the properties that
are manifested, it is most preferable to use the following aromatic
diisocyanate: 4,4'-diphenylmethane diisocyanate.
[0094] Commercially available products may be used as the
thermoplastic polyurethane serving as component (I). Illustrative
examples include Pandex T-8295, Pandex T-8290 and Pandex T-8260
(all from DIC Covestro Polymer, Ltd.).
[0095] A thermoplastic elastomer other than the above thermoplastic
polyurethanes may also be optionally included as a separate
component, i.e., component (III), together with above components
(I) and (II). By including this component (III) in the above resin
blend, the flowability of the resin blend can be further improved
and properties required of the golf ball cover material, such as
resilience and scuff resistance, can be increased.
[0096] The compositional ratio of above components (I), (II) and
(III) is not particularly limited. However, to fully elicit the
advantageous effects of the invention, the compositional ratio
(I):(II):(III) is preferably in the weight ratio range of from
100:2:50 to 100:50:0, and more preferably from 100:2:50 to
100:30:8.
[0097] In addition, various additives other than the ingredients
making up the above thermoplastic polyurethane may be optionally
included in this resin blend. For example, pigments, dispersants,
antioxidants, light stabilizers, ultraviolet absorbers and internal
mold lubricants may be suitably included.
[0098] The manufacture of multi-piece solid golf balls in which the
above-described core, inner envelope layer, outer envelope layer,
intermediate layer and cover (outermost layer) are formed as
successive layers may be carried out by a customary method such as
a known injection molding process. For example, a multi-piece golf
ball can be produced by successively injection-molding the
respective materials for the inner envelope layer, outer envelope
layer and intermediate layer over the core in injection molds for
each layer so as to obtain the respective layer-encased spheres and
then, last of all, injection-molding the material for the cover
serving as the outermost layer over the intermediate layer-encased
sphere. Alternatively, the encasing layers may each be formed by
enclosing the sphere to be encased within two half-cups that have
been pre-molded into hemispherical shapes and then molding under
applied heat and pressure.
[0099] The golf ball has a deflection when compressed under a final
load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf)
which is preferably at least 1.8 mm, more preferably at least 2.0
mm, and even more preferably at least 2.2 mm. The upper limit value
is preferably not more than 3.0 mm, more preferably not more than
2.7 mm, and even more preferably not more than 2.5 mm. When the
ball deflection is too small, i.e., when the ball is too hard, the
spin rate of the ball may rise excessively so that the ball does
not achieve a good distance, or the feel at impact may be too hard.
On the other hand, when the ball deflection is too large, i.e.,
when the ball is too soft, the ball rebound may become so low that
the ball does not achieve a good distance, the feel at impact may
be too soft, or the durability to cracking under repeated impact
may worsen.
[0100] Hardness Relationships Among Layers
[0101] In this invention, it is critical for the surface hardness
of the core, the surface hardness of the sphere obtained by
encasing the core with the inner envelope layer (inner envelope
layer-encased sphere), the surface hardness of the sphere obtained
by encasing the inner envelope layer-encased sphere with the outer
envelope layer (outer envelope layer-encased sphere), the surface
hardness of the sphere obtained by encasing the outer envelope
layer-encased sphere with the intermediate layer (intermediate
layer-encased sphere) and the surface hardness of the ball to
satisfy the following relationship in which the hardnesses are
Shore C hardness values: [0102] core surface hardness<surface
hardness of inner envelope layer-encased sphere<surface hardness
of outer envelope layer-encased sphere<surface hardness of
intermediate layer-encased sphere>ball surface hardness. By
satisfying this hardness relationship, a satisfactory distance can
be achieved on full shots with a driver (W#1) or an iron, in
addition to which the ball is highly receptive to spin on approach
shots and thus superior in the short game.
[0103] The Shore C hardness value obtained by subtracting the core
surface hardness from the surface hardness of the inner envelope
layer-encased sphere is more than 0, preferably 2 or more, and more
preferably 4 or more. The upper limit is preferably not more than
20, more preferably not more than 16, and even more preferably not
more than 13. When this value is too small, the initial velocity of
the ball is low and a good distance is not achieved. When this
value is too large, the durability to cracking on repeated impact
may worsen.
[0104] The Shore C hardness value obtained by subtracting the core
center hardness from the surface hardness of the outer envelope
layer-encased sphere is preferably 23 or more, more preferably 25
or more, and even more preferably 27 or more. The upper limit is
preferably not more than 40, more preferably not more than 35, and
even more preferably not more than 32. When this value is too
small, the spin rate on full shots may rise and a good distance may
not be achieved. When this value is too large, the initial velocity
on shots may decrease and a good distance may not be achieved, or
the durability to cracking under repeated impact may worsen.
[0105] The Shore C hardness value obtained by subtracting the core
surface hardness from the surface hardness of the outer envelope
layer-encased sphere is preferably 5 or more, more preferably 6 or
more, and even more preferably 7 or more. The upper limit is
preferably not more than 28, more preferably not more than 23, and
even more preferably not more than 20. When this value is too
small, the spin rate on full shots may rise and a good distance may
not be achieved. When this value is too large, the initial velocity
on shots may decrease and a good distance may not be achieved, or
the durability to cracking under repeated impact may worsen.
[0106] The Shore C hardness value obtained by subtracting the
surface hardness of the inner envelope layer-encased sphere from
the surface hardness of the outer envelope layer-encased sphere is
more than 0, preferably 2 or more, and more preferably 3 or more.
The upper limit is preferably not more than 16, more preferably not
more than 14, and even more preferably not more than 12. When this
value is too small, the spin rate on full shots rises and a good
distance cannot be achieved. When this value is too large, the
initial velocity on shots may become low and a good distance may
not be achieved.
[0107] The Shore C hardness value obtained by subtracting the
surface hardness of the outer envelope layer-encased sphere from
the surface hardness of the intermediate layer-encased sphere is
more than 0, preferably 2 or more, and more preferably 4 or more.
The upper limit is preferably not more than 18, more preferably not
more than 15, and even more preferably not more than 12. When this
value is too small, the spin rate on full shots rises and a good
distance cannot be achieved. When this value is too large, the
initial velocity on shots may become low and a good distance may
not be achieved.
[0108] The Shore C hardness value obtained by subtracting the core
center hardness from the surface hardness of the intermediate
layer-encased sphere is preferably 30 or more, more preferably 32
or more, and even more preferably 34 or more. The upper limit is
preferably not more than 45, more preferably not more than 43, and
even more preferably not more than 40. When this value is too
small, the spin rate on full shots may rise and a good distance may
not be achieved. When this value is too large, the initial velocity
on shots may decrease and a good distance may not be achieved, or
the durability to cracking on repeated impact may worsen.
[0109] The Shore C hardness value obtained by subtracting the ball
surface hardness from the surface hardness of the intermediate
layer-encased sphere is more than 0, preferably 2 or more, and more
preferably 4 or more. The upper limit is preferably not more than
20, more preferably not more than 17, and even more preferably not
more than 14. When this value is too small, i.e., when the ball
surface is harder than the intermediate layer surface, the ball is
not sufficiently receptive to spin in the short game (this being
the case especially when the cover is hard) or the spin rate on
full shots rises, as a result of which a good distance is not
achieved (this being the case especially when the intermediate
layer is soft). On the other hand, when the above value is too
large, the spin rate on full shots may rise, as a result of which a
good distance is not achieved (this being the case especially when
the cover is too soft) or the durability to cracking on repeated
impact may worsen (this being the case especially when the
intermediate layer is too hard).
[0110] Other Relationships Among Layers
[0111] The value obtained by dividing the overall thickness of the
envelope layer by the combined thickness of the cover and the
intermediate layer, which value is expressed as [(overall thickness
of envelope layer)/(intermediate layer thickness+cover thickness)],
is preferably at least 0.8, more preferably at least 0.9, and even
more preferably at least 1.0. The upper limit value is preferably
1.6 or less, more preferably 1.4 or less, and even more preferably
1.2 or less. When this value is too large, the initial velocity may
decrease, as a result of which a good distance may not be achieved,
or the durability to cracking on repeated impact may worsen. On the
other hand, when this value is too small, the spin rate-lowering
effect may be inadequate, as a result of which a good distance may
not be achieved.
[0112] The core diameter/ball diameter value is preferably at least
0.702, more preferably at least 0.735, and even more preferably at
least 0.749. The upper limit value is preferably 0.821 or less,
more preferably 0.802 or less, and even more preferably 0.785 or
less. When this value is too small, the initial velocity of the
ball may decrease, as a result of which a good distance may not be
achieved. On the other hand, when this value is too large, the spin
rate on full shots with an iron may rise, as a result of which the
intended distance may not be achieved.
[0113] Letting S and B the deflections in millimeters of,
respectively, the core and the ball when compressed under a final
load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf),
the value B-S, although not particularly limited, is preferably at
least 0.8 mm, more preferably at least 0.9 mm, and even more
preferably at least 1.0 mm. The upper limit value is preferably 3.3
mm or less, more preferably 2.7 mm or less, and even more
preferably 2.2 mm or less. When this value is too small, the spin
rate on full shots may rise and so a good distance may not be
achieved. On the other hand, when this value is too large, the
initial velocity on shots may be low and so a good distance may not
be achieved, or the durability to cracking on repeated impact may
worsen.
[0114] Numerous dimples may be formed on the surface of the cover
serving as the outermost layer. The number of dimples arranged on
the cover surface, although not particularly limited, is preferably
at least 323, more preferably at least 326, and even more
preferably at least 330. The upper limit is preferably not more
than 380, more preferably not more than 360, and even more
preferably not more than 350. When the number of dimples is higher
than this range, the ball trajectory may become lower and the
distance traveled by the ball may decrease. On the other hand, when
the number of dimples is lower that this range, the ball trajectory
may become higher and a good distance may not be achieved.
[0115] The dimple shapes used may be of one type or may be a
combination of two or more types suitably selected from among, for
example, circular shapes, various polygonal shapes, dewdrop shapes
and oval shapes. When circular dimples are used, the dimple
diameter may be set to at least about 2.5 mm and up to about 6.5
mm, and the dimple depth may be set to at least 0.08 mm and up to
0.30 mm.
[0116] In order for the aerodynamic properties to be fully
manifested, it is desirable for the dimple coverage ratio on the
spherical surface of the golf ball, i.e., the dimple surface
coverage SR, which is the sum of the individual dimple surface
areas, each defined by the flat plane circumscribed by the edge of
a dimple, as a percentage of the spherical surface area of the ball
were the ball to have no dimples thereon, to be set to at least 70%
and not more than 90%. Also, to optimize the ball trajectory, it is
desirable for the value V.sub.0, defined as the spatial volume of
the individual dimples below the flat plane circumscribed by the
dimple edge, divided by the volume of the cylinder whose base is
the flat plane and whose height is the maximum depth of the dimple
from the base, to be set to at least 0.35 and not more than 0.80.
Moreover, it is preferable for the ratio VR of the sum of the
volumes of the individual dimples, each formed below the flat plane
circumscribed by the edge of the dimple, with respect to the volume
of the ball sphere were the ball surface to have no dimples
thereon, to be set to at least 0.6% and not more than 1.0%. Outside
of the above ranges in these respective values, the resulting
trajectory may not enable a good distance to be achieved and so the
ball may fail to travel a fully satisfactory distance.
[0117] It is desirable for the golf ball of the invention to
optimize the ratios CL2/CL1 and CL4/CL3, where CL1 is the
coefficient of lift at a Reynolds number of 80,000 and a spin rate
of 2,000 rpm, CL2 is the coefficient of lift at a Reynolds number
of 70,000 and a spin rate of 1,900 rpm, CL3 is the coefficient of
lift at a Reynolds number of 200,000 and a spin rate of 2,500 rpm
and CL4 is the coefficient of lift at a Reynolds number of 120,000
and a spin rate of 2,250 rpm.
[0118] In this Specification, the coefficients of lift (CL1, CL2,
CL3 and CL4) are measured in conformity with the Indoor Test Range
(ITR) method established by the United States Golf Association
(USGA). The coefficient of lift can be adjusted by adjusting the
golf ball dimple configuration (arrangement, diameter, depth,
volume, number, shape, etc.). The coefficient of lift does not
depend on the internal construction of the golf ball. The Reynolds
number (Re) is a dimensionless number used in the field of fluid
dynamics, and is computed using formula (I) below.
Re=.rho.vL/.mu. (I)
[0119] In formula (I), .rho. represents the density of a fluid, v
is the relative average velocity of an object relative to flow by
the fluid, L is a characteristic length, and .mu. is the
coefficient of viscosity of the fluid.
[0120] The conditions under which the coefficient of lift CL1 is
measured, i.e., a Reynolds number of 80,000 and a spin rate of
2,000 rpm, generally correspond approximately to the state at the
time that the coefficient of lift begins to decrease and, in turn,
the golf ball begins to fall after having reached its highest point
following launch. The conditions under which the coefficient of
lift CL2 is measured, i.e., a Reynolds number of 70,000 and a spin
rate of 1,900 rpm, generally correspond approximately to the state
just before the golf ball falls to the ground after having reached
its highest point following launch. The above is particularly true
in cases where the golf ball is launched under high-velocity
conditions (e.g., an initial velocity of 66 m/s, a spin rate of
2,600 rpm, and a launch angle of 11.degree.). These high-velocity
conditions generally correspond to the launch conditions when the
ball is hit with a driver by an amateur golfer.
[0121] The ratio CL2/CL1 has a value of preferably at least 0.900,
more preferably at least 0.970, and even more preferably at least
0.990. By satisfying the above range, the decrease in lift as the
golf ball falls can be suppressed, which in turn makes it easier
for the flight distance (i.e., the carry) to be extended as the
ball falls and for the run to be extended. Hence, the total
distance can be increased. When CL2/CL1 is too low, the golf ball
tends to fall more abruptly, making it difficult to satisfactorily
increase the carry and run. A higher CL2/CL1 is better from the
standpoint of increasing the total distance. However, when this
value is too high, the carry is extended but the run decreases, as
a result of which the total distance may not exceed the optimal
value. Therefore, the upper limit value for CL2/CL1 is 1.100 or
less, preferably 1.018 or less, more preferably 0.999 or less, and
even more preferably 0.995 or less.
[0122] The conditions under which the coefficient of lift CL3 is
measured, i.e. a Reynolds number of 200,000 and a spin rate of
2,500 rpm, generally correspond approximately to the state just
after the golf ball has been launched under high-velocity
conditions (e.g., an initial velocity of 72 m/s, a spin rate of
2,500 rpm and a launch angle of 10.degree.). The conditions under
which the coefficient of lift CL4 is measured, i.e. a Reynolds
number of 120,000 and a spin rate of 2,250 rpm, generally
correspond approximately to the state when approximately 2 seconds
have elapsed as the ball rises after being launched under
high-velocity conditions (e.g., an initial velocity of 72 m/s, a
spin rate of 2,500 rpm and a launch angle of 10.degree.).
[0123] The ratio CL4/CL3 has a value of preferably at least 1.250,
more preferably at least 1.252, and even more preferably at least
1.255. The upper limit is preferably not more than 1.300, more
preferably not more than 1.295, and even more preferably not more
than 1.290. By setting the ratio in this range, when the golf ball
has been launched under high-velocity conditions (e.g., when hit
with a driver), the amount of rise by the golf ball can be kept
from becoming excessive (i.e., the ball can be kept from climbing
too steeply), making it possible to increase the resistance of the
ball to wind and thus enabling the carry to be increased. In
addition, the run can be increased. This enables the total distance
traveled by the ball to be increased.
[0124] From the standpoint of increasing the distance traveled by
the ball, the coefficient of lift CL1 is preferably at least 0.230.
Also, CL1 is preferably not more than 0.240. From the same
standpoint, the coefficient of lift CL2 is preferably at least
0.230. Also, CL2 is preferably not more than 0.240. From the same
standpoint, the coefficient of lift CL3 is preferably at least
0.145. Also, CL3 is preferably not more than 0.155. From the same
standpoint, the coefficient of lift CL4 is preferably at least
0.185. Also, CL4 is preferably not more than 0.195.
[0125] A coating layer may be formed on the surface of the cover.
This coating layer can be formed by applying various types of
coating materials. Because the coating layer must be capable of
enduring the harsh conditions of golf ball use, it is desirable to
use a coating composition in which the chief component is a
urethane coating material composed of a polyol and a
polyisocyanate.
[0126] The polyol component is exemplified by acrylic polyols and
polyester polyols. These polyols include modified polyols. To
further increase workability, other polyols may also be added.
[0127] It is suitable to use two types of polyester polyol together
as the polyol component. In this case, letting the two types of
polyester polyol be component (a) and component (b), a polyester
polyol in which a cyclic structure has been introduced onto the
resin skeleton may be used as the polyester polyol of component
(a). Examples include polyester polyols obtained by the
polycondensation of a polyol having an alicyclic structure, such as
cyclohexane dimethanol, with a polybasic acid; and polyester
polyols obtained by the polycondensation of a polyol having an
alicyclic structure with a diol or triol and a polybasic acid. A
polyester polyol having a branched structure may be used as the
polyester polyol of component (b). Examples include polyester
polyols having a branched structure, such as NIPPOLAN 800, from
Tosoh Corporation.
[0128] The polyisocyanate is exemplified without particular
limitation by commonly used aromatic, aliphatic, alicyclic and
other polyisocyanates. Specific examples include tolylene
diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate,
tetramethylene diisocyanate, hexamethylene diisocyanate, lysine
diisocyanate, isophorone diisocyanate, 1,4-cyclohexylene
diisocyanate, naphthalene diisocyanate, trimethylhexamethylene
diisocyanate, dicyclohexylmethane diisocyanate and
1-isocyanato-3,3,5-trimethyl-4-isocyanatomethylcyclohexane. These
may be used singly or in admixture.
[0129] Depending on the coating conditions, various types of
organic solvents may be mixed into the coating composition.
Examples of such organic solvents include aromatic solvents such as
toluene, xylene and ethylbenzene; ester solvents such as ethyl
acetate, butyl acetate, propylene glycol methyl ether acetate and
propylene glycol methyl ether propionate; ketone solvents such as
acetone, methyl ethyl ketone, methyl isobutyl ketone and
cyclohexanone; ether solvents such as diethylene glycol dimethyl
ether, diethylene glycol diethyl ether and dipropylene glycol
dimethyl ether; alicyclic hydrocarbon solvents such as cyclohexane,
methyl cyclohexane and ethyl cyclohexane; and petroleum hydrocarbon
solvents such as mineral spirits.
[0130] The thickness of the coating layer made of the coating
composition, although not particularly limited, is typically from 5
to 40 .mu.m, and preferably from 10 to 20 .mu.m. As used herein,
"coating layer thickness" refers to the coating thickness obtained
by averaging the measurements taken at a total of three places: the
center of a dimple and two places located at positions between the
dimple center and the dimple edge.
[0131] In this invention, the coating layer composed of the above
coating composition has an elastic work recovery that is preferably
at least 60%, and more preferably at least 80%. At a coating layer
elastic work recovery in this range, the coating layer has a high
elasticity and so the self-repairing ability is high, resulting in
an outstanding abrasion resistance. Moreover, the performance
attributes of golf balls coated with this coating composition can
be improved. The method of measuring the elastic work recovery is
described below.
[0132] The elastic work recovery is one parameter of the
nanoindentation method for evaluating the physical properties of
coating layers, this being a nanohardness test method that controls
the indentation load on a micro-newton (.mu.N) order and tracks the
indenter depth during indentation to a nanometer (nm) precision. In
prior methods, only the size of the deformation (plastic
deformation) mark corresponding to the maximum load could be
measured. However, in the nanoindentation method, the relationship
between the indentation load and the indentation depth can be
obtained by continuous automated measurement. Hence, unlike in the
past, there are no individual differences between observers when
visually measuring a deformation mark under an optical microscope,
and so it is thought that the physical properties of the coating
layer can be precisely evaluated. Given that the coating layer on
the ball surface is strongly affected by the impact of drivers and
various other types of clubs, and has a not inconsiderable
influence on various golf ball properties, measuring the coating
layer by the nanohardness test method and carrying out such
measurement to a higher precision than in the past is a very
effective method of evaluation.
[0133] The hardness of the coating layer, as expressed on the Shore
M hardness scale, is preferably at least 40, and more preferably at
least 60. The upper limit is preferably not more than 95, and more
preferably not more than 85. This Shore M hardness is obtained in
accordance with ASTM D2240. The hardness of the coating layer, as
expressed on the Shore C hardness scale, is preferably at least 40,
and more preferably at least 50; the upper limit is preferably not
more than 80, and more preferably not more than 70. This Shore C
hardness is obtained in accordance with ASTM D2240. At coating
layer hardnesses that are higher than these ranges, the coating may
become brittle when the ball is repeatedly struck, which may make
it incapable of protecting the cover layer. On the other hand,
coating layer hardnesses that are lower than the above range are
undesirable because the ball surface is more easily damaged when
striking a hard object.
[0134] When the above coating composition is used, the formation of
a coating layer on the surface of golf balls manufactured by a
known method can be carried out via the steps of preparing the
coating composition at the time of application, applying the
composition onto the golf ball surface by a conventional coating
operation, and drying the applied composition. The coating
technique is not particularly limited. For example, spray painting,
electrostatic painting or dipping may be suitably used.
[0135] The multi-piece solid golf ball of the invention can be made
to conform to the Rules of Golf for play. The inventive ball may be
formed to a diameter which is such that the ball does not pass
through a ring having an inner diameter of 42.672 mm and is not
more than 42.80 mm, and to a weight which is preferably between
45.0 and 45.93 g.
EXAMPLES
[0136] The following Examples and Comparative Examples are provided
to illustrate the invention, and are not intended to limit the
scope thereof.
[0137] Of Examples 1 to 4 according to the invention and
Comparative Examples 1 to 18 below, Comparative Examples 7 to 14
are predictive data that can be inferred from measured values
obtained in the other Examples of the invention and Comparative
Examples and are not Examples that were actually carried out. These
Comparative Examples 7 to 14 are treated below in the same way as
the other Examples and Comparative Examples.
Examples 1 to 4, Comparative Examples 1 to 18
[0138] Formation of Core
[0139] Solid cores were produced by preparing rubber compositions
for the respective Examples and Comparative Examples shown in
Tables 1 and 2, and then vulcanizing the compositions for 15
minutes at 155.degree. C.
TABLE-US-00001 TABLE 1 Core formulation Example Comparative Example
(pbw) 1 2 3 4 1 2 3 4 5 6 Polybutadiene (I) 100 100 100 100 100 100
100 100 100 100 Zinc acrylate 38.0 34.0 31.0 28.0 31.5 26.0 21.0
31.5 26.0 21.0 Organic peroxide 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2
1.2 Sulfur Zinc stearate 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Antioxidant 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Zinc oxide 32.5
33.9 35.0 47.9 76.2 77.1 78.1 76.2 77.1 78.1 Zinc salt of 2.0 2.0
2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 pentachlorothiophenol
TABLE-US-00002 TABLE 2 Core formulation Comparative Example (pbw) 7
8 9 10 11 12 13 14 15 16 17 18 Polybutadiene (I) 100 100 100 100
100 100 100 100 100 100 100 80 Polybutadiene (II) 20 Zinc acrylate
33.0 23.0 31.0 21.0 28.0 33.0 33.0 39.0 41.0 37.0 32.0 35.0 Organic
peroxide 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 3.0 Sulfur 0.1
Zinc stearate 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Antioxidant 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0 Zinc
oxide 46.3 49.4 35.1 50.0 58.2 46.3 46.3 44.6 25.8 27.3 29.3 21.9
Zinc salt of 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.5
pentachlorothiophenol
[0140] Details on the ingredients mentioned in Tables 1 and 2 are
given below. [0141] Polybutadiene (I): Available under the trade
name "BR 730" from JSR Corporation [0142] Polybutadiene (II):
Available under the trade name "BR 51" from JSR Corporation [0143]
Zinc acrylate: "ZN-DA85S" from Nippon Shokubai Co., Ltd. [0144]
Organic Peroxide: A mixture of 1,1-Di(t-butylperoxy)cyclohexane and
silica, available under the trade name "Perhexa C-40" from NOF
Corporation [0145] Zinc stearate: Available as "Zinc Stearate G"
from NOF Corporation [0146] Antioxidant:
2,2'-Methylenebis(4-methyl-6-butylphenol), available under the
trade name "Nocrac NS-6" from Ouchi Shinko Chemical Industry Co.,
Ltd. [0147] Zinc oxide: Available as "Grade 3 Zinc Oxide" from
Sakai Chemical Co., Ltd. [0148] Zinc salt of pentachlorothiophenol:
Available from Wako Pure Chemical Industries, Ltd.
[0149] Formation of Inner and Outer Envelope Layers
[0150] Next, in each Example and Comparative Example, an inner
envelope layer was formed by injection-molding the inner envelope
layer material shown in Table 3 over the core, following which an
outer envelope layer was formed by injection-molding the outer
envelope layer material shown in the same table over the inner
envelope layer. In Comparative Examples 15 to 17, the material of
formulation No. 2 in Table 3 was injection-molded over the core to
form a single envelope layer (the details are provided in the
"Outer envelope layer" section in the table). No envelope layer was
formed in Comparative Example 18.
[0151] Formation of Intermediate Layer and Cover (Outermost
Layer)
[0152] Next, in all of the working Examples and Comparative
Examples except for Comparative Example 18, an intermediate layer
was formed by injection-molding the intermediate layer material
shown in Table 3 over the envelope layer-encased sphere obtained
above. A cover (outermost layer) was then formed by
injection-molding the cover material shown in the same table over
the resulting intermediate layer-encased sphere. A plurality of
given dimples common to all the Examples and Comparative Examples
were formed at this time on the surface of the cover.
TABLE-US-00003 TABLE 3 Resin composition (pbw) No. 1 No. 2 No. 3
No. 4 No. 5 No. 6 HPF 1000 100 Himilan 1601 50 Himilan 1605 68.75
50 Himilan 1557 50 15 Himilan 1706 35 AM 7315 50 AM 7318 50 Dynaron
6100P 31.25 Behenic acid 18 20 Calcium hydroxide 2.3 2.8 Calcium
stearate 0.15 Zinc stearate 0.15 Trimethylolpropane 1.1 Polytail H
2 Titanium oxide 4 TPU 100
[0153] Trade names for the materials in the above table are given
below. [0154] HPF 1000: Available under the trademark Dow.TM. from
The Dow Chemical Company [0155] Himilan: Ionomers available from
Dow-Mitsui Polychemicals Co., Ltd. [0156] AM 7315, AM 7318:
Ionomers available from Dow-Mitsui Polychemicals Co., Ltd. [0157]
Dynaron 6100P: A hydrogenated polymer available from JSR
Corporation [0158] Behenic acid: NAA222-S (beads) from NOF
Corporation [0159] Calcium hydroxide: Available as "CLS-B" from
Shiraishi Calcium Kaisha, Ltd. [0160] Trimethylolpropane (TMP):
Available from Tokyo Chemical Industry Co., Ltd. [0161]
Polytail.TM. H: Product name for a polyhydroxy hydrocarbon polymer
from Mitsubishi Chemical Corporation [0162] TPU: An ether-type
thermoplastic polyurethane (Shore D hardness of material, 48)
available as Pandex.RTM. from DIC Covestro Polymer, Ltd.
[0163] Eight types of circular dimples were used as the dimples D.
Details on the dimples are shown in Table 4 below, and the dimple
pattern is shown in FIG. 2. FIG. 2A is a top view of a golf ball on
the surface of which the dimples D have been formed, and FIG. 2B is
a side view of the same.
TABLE-US-00004 TABLE 4 Dimples Diameter Depth Volume Cylinder SR VR
D Number (mm) (mm) (mm.sup.3) volume ratio (%) (%) D-1 12 4.6 0.123
1.116 0.546 82.30 0.775 D-2 198 4.45 0.122 1.036 0.546 D-3 36 3.85
0.119 0.757 0.546 D-4 12 2.75 0.090 0.288 0.539 D-5 36 4.45 0.136
1.120 0.530 D-6 24 3.85 0.133 0.820 0.530 D-7 6 3.4 0.118 0.563
0.526 D-8 6 3.3 0.118 0.530 0.525 Total 330
[0164] Dimple Definitions [0165] Edge: Highest place in
cross-section passing through center of dimple. [0166] Diameter:
Diameter of flat plane circumscribed by edge of dimple. [0167]
Depth: Maximum depth of dimple from flat plane circumscribed by
edge of dimple. [0168] SR: Sum of individual dimple surface areas,
each defined by flat plane circumscribed by edge of dimple, as a
percentage of spherical surface area of ball were it to have no
dimples thereon. [0169] Dimple volume: Dimple volume below flat
plane circumscribed by edge of dimple. [0170] Cylinder volume
ratio: Ratio of dimple volume to volume of cylinder having same
diameter and depth as dimple. [0171] VR: Sum of volumes of
individual dimples formed below flat plane circumscribed by edge of
dimple, as a percentage of volume of ball sphere were it to have no
dimples thereon.
[0172] For the golf balls having Dimples D formed on the surface of
the cover, the coefficient of lift CL1 measured at a Reynolds
number of 80,000 and a spin rate of 2,000 rpm, the coefficient of
lift CL2 measured at a Reynolds number of 70,000 and a spin rate of
1,900 rpm, the coefficient of lift CL3 measured at a Reynolds
number of 200,000 and a spin rate of 2,500 rpm, the coefficient of
lift CL4 measured at a Reynolds number of 120,000 and a spin rate
of 2,250 rpm, and the values of the ratios CL2/CL1 and CL4/CL3 are
shown in Table 5 below. These coefficients of lift were measured in
conformity with the Indoor Test Range (ITR) method established by
the United States Golf Association (USGA).
TABLE-US-00005 TABLE 5 CL1 CL2 CL3 CL4 CL2/CL1 CL4/CL3 Dimples D
0.234 0.238 0.148 0.186 1.018 1.262
[0173] Formation of Coating Layer
[0174] Next, using Coating Composition C shown in Table 6 below as
a coating composition common to all of the Examples and Comparative
Examples, the coating was applied with an air spray gun onto the
surface of the cover (outermost layer) having numerous dimples
formed thereon, producing golf balls with a 15 .mu.m-thick coating
layer on top.
TABLE-US-00006 TABLE 6 Coating composition Base resin Polyester
polyol (A) 23 (parts by weight) Polyester polyol (B) 15 Organic
solvent 62 Curing agent Isocyanate (HMDI 42 isocyanurate) Solvent
58 Molar blending ratio (NCO/OH) 0.89 Coating properties Elastic
work recovery (%) 84 Shore M hardness 84 Shore C hardness 63
Thickness (.mu.m) 15
[0175] Synthesis of Polyester Polyol (A)
[0176] A reactor equipped with a reflux condenser, a dropping
funnel, a gas inlet and a thermometer was charged with 140 parts by
weight of trimethylolpropane, 95 parts by weight of ethylene
glycol, 157 parts by weight of adipic acid and 58 parts by weight
of 1,4-cyclohexanedimethanol, following which the reaction was
effected by raising the temperature to between 200 and 240.degree.
C. under stirring and heating for 5 hours. This yielded Polyester
Polyol (A) having an acid value of 4, a hydroxyl value of 170 and a
weight-average molecular weight (Mw) of 28,000.
[0177] The Polyester Polyol (A) thus synthesized was then dissolved
in butyl acetate, thereby preparing a varnish having a nonvolatiles
content of 70 wt %.
[0178] The base resin for the coating composition in Table 6 was
prepared by mixing together 23 parts by weight of the above
polyester polyol solution, 15 parts by weight of Polyester Polyol
(B) (the saturated aliphatic polyester polyol NIPPOLAN 800 from
Tosoh Corporation; weight-average molecular weight (Mw), 1,000;
100% solids) and the organic solvent. This mixture had a
nonvolatiles content of 38.0 wt %.
[0179] Elastic Work Recovery
[0180] The elastic work recovery of the coating material was
measured using a coating sheet having a thickness of 50 .mu.m. The
ENT-2100 nanohardness tester from Erionix Inc. was used as the
measurement apparatus, and the measurement conditions were as
follows. [0181] Indenter: Berkovich indenter (material: diamond;
angle .alpha.: 65.03.degree.) [0182] Load F: 0.2 mN [0183] Loading
time: 10 seconds [0184] Holding time: 1 second [0185] Unloading
time: 10 seconds
[0186] The elastic work recovery was calculated as follows, based
on the indentation work W.sub.elast (Nm) due to spring-back
deformation of the coating and on the mechanical indentation work
W.sub.total (Nm).
Elastic work recovery=W.sub.elast/W.sub.total.times.100 (%)
[0187] Shore C Hardness and Shore M Hardness
[0188] The Shore C hardness and Shore M hardness in Table 6 above
were determined by forming the material being tested into 2 mm
thick sheets and stacking three such sheets together to give test
specimens. Measurements were taken using a Shore C durometer and a
Shore M durometer in accordance with ASTM D2240.
[0189] Various properties of the resulting golf balls, including
the internal hardnesses of the core at various positions, the
diameters of the core and each layer-encased sphere, the thickness
and material hardness of each layer, and the surface hardness of
each layer-encased sphere, were evaluated by the following methods.
The results are presented in Tables 7 to 10.
[0190] Diameters of Core, Inner Envelope Layer-Encased Sphere,
Outer Envelope Layer-Encased Sphere, and Intermediate Layer-Encased
Sphere
[0191] The diameters at five random places on the surface were
measured at a temperature of 23.9.+-.1.degree. C. and, using the
average of these measurements as the measured value for a single
core, envelope layer-encased sphere or intermediate layer-encased
sphere, the average diameter for ten such spheres were
determined.
[0192] Ball Diameter
[0193] The diameter at 15 random dimple-free areas was measured at
a temperature of 23.9.+-.1.degree. C. and, using the average of
these measurements as the measured value for a single ball, the
average diameter for ten balls was determined.
[0194] Deflections of Core, Inner Envelope Layer-Encased Sphere,
Outer Envelope Layer-Encased Sphere, Intermediate Laver-Encased
Sphere and Ball
[0195] The sphere to be measured (i.e., a core, inner envelope
layer-encased sphere, outer envelope layer-encased sphere,
intermediate layer-encased sphere or ball) was placed on a hard
plate and the amount of deflection when compressed under a final
load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) was
measured. The amount of deflection refers in each case to the
measured value obtained after holding the core isothermally at
23.9.degree. C.
[0196] Core Hardness Profile
[0197] The indenter of a durometer was set substantially
perpendicular to the spherical surface of the core, and the surface
hardness on the Shore C hardness scale was measured in accordance
with ASTM D2240. The P2 Automatic Rubber Hardness Tester (Kobunshi
Keiki Co., Ltd.) equipped with a Shore C durometer can be used for
measuring the hardness. The maximum value is read off as the
hardness value. Measurements were all carried out in a
23.+-.2.degree. C. environment. The core center hardness Cc and the
hardness Cm at the midpoint between the core center and core
surface were measured by perpendicularly pressing the indenter of a
durometer against the positions to be measured on the flat
cross-section obtained by cutting the core into hemispheres. The
results are indicated as Shore C hardness values.
[0198] Material Hardnesses (Shore C and Shore D) of Inner Envelope
Layer, Outer Envelope Layer, Intermediate Layer and Cover
[0199] The resin material for each layer was molded into a sheet
having a thickness of 2 mm and left to stand for at least two weeks
at a temperature of 23.+-.2.degree. C. Three sheets were stacked
together at the time of measurement. The Shore C hardness and Shore
D hardness of each material were measured with a Shore C durometer
and a Shore D durometer in accordance with ASTM D2240. The P2
Automatic Rubber Hardness Tester (Kobunshi Keiki Co., Ltd.) having
a Shore C durometer or Shoe D durometer mounted thereon can be used
for measuring the hardness. The maximum value is read off as the
hardness value.
[0200] Surface Hardnesses (Shore C and Shore D) of Inner Envelope
Layer-Encased Sphere, Outer Envelope Layer-Encased Sphere,
Intermediate Layer-Encased Sphere and Ball
[0201] These hardnesses were measured by perpendicularly pressing
an indenter against the surfaces of the respective spheres. The
surface hardness of a ball (cover) is the value measured at a
dimple-free area (land) on the surface of the ball. The P2
Automatic Rubber Hardness Tester (Kobunshi Keiki Co., Ltd.) having
a Shore C durometer or Shore D durometer mounted thereon can be
used for measuring the hardness. The maximum value is read off as
the hardness value.
TABLE-US-00007 TABLE 7 Example Comparative Example 1 2 3 4 1
Construction (piece) 5P 5P 5P 5P 5P Core Diameter (mm) 33.50 33.42
33.53 31.43 27.76 Weight (g) 24.55 24.30 24.70 21.33 16.59 Volume
(mm.sup.3) 19.68 19.55 19.74 16.26 11.20 Deflection (mm) 3.2 3.6
4.1 4.4 3.9 Hardness Core surface hardness: Cs 85 83 79 77 81
profile Hardness at midpoint between 72 70 67 65 68 (Shore C) core
surface and center: Cm Core center hardness: Cc 65 63 61 60 62 Core
surface hardness - 20 19 18 17 19 Core center hardness (Cs -
Cm)/(Cm - Cc) 1.9 1.9 2.0 2.0 1.9 Core volume .times. 1421 1370
1330 1065 765 Hardness at midpoint between core surface and center
Inner Material No. 1 No. 1 No. 1 No. 1 No. 1 envelope Thickness
(mm) 1.37 1.40 1.35 1.46 2.26 layer Volume (mm.sup.3) 5.24 5.34
5.17 4.98 6.41 Material hardness (Shore C) 84 84 84 84 84 Material
hardness (Shore D) 52 52 52 52 52 Inner Diameter (mm) 36.24 36.22
36.24 34.36 32.28 envelope Weight (g) 29.62 29.51 29.60 26.18 22.47
layer-encased Deflection (mm) 2.9 3.3 3.8 4.1 3.1 sphere Surface
hardness (Shore C) 89 89 89 89 89 Surface hardness (Shore D) 57 57
57 57 57 Surface hardness of inner envelope layer - 4 6 10 12 8
Core surface hardness (Shore C) Volume of inner envelope layer
.times. Surface hardness of 466 475 460 444 570 inner envelope
layer-encased sphere (Shore C) Outer Material No. 2 No. 2 No. 2 No.
2 No. 2 envelope Thickness (mm) 1.10 1.10 1.10 1.37 1.94 layer
Volume (mm.sup.3) 4.80 4.81 4.81 5.52 7.16 Material hardness (Shore
C) 87 87 87 87 87 Material hardness (Shore D) 56 56 56 56 56
Overall thickness of envelope layer (mm) 2.47 2.50 2.45 2.84 4.20
Inner envelope layer thickness - 0.27 0.30 0.25 0.09 0.32 Outer
envelope layer thickness (mm) Outer Diameter (mm) 38.43 38.42 38.44
37.11 36.16 envelope Weight (g) 34.08 34.02 34.12 31.28 29.29
layer-encased Deflection (mm) 2.7 3.0 3.4 3.6 3.0 sphere Material
hardness (Shore C) 92 92 92 92 92 Material hardness (Shore D) 62 62
62 62 62 Outer envelope layer surface hardness - 27 29 31 32 30
Core center hardness (Shore C) Outer envelope layer hardness - 7 9
13 15 11 Core surface hardness (Shore C) Outer envelope layer
surface hardness - 3 3 3 3 3 Inner envelope layer surface hardness
(Shore C) Outer envelope layer volume .times. Surface hardness 442
443 443 508 658 of outer envelope layer-encased sphere (Shore C)
Comparative Example 2 3 4 5 6 Construction (piece) 5P 5P 5P 5P 5P
Core Diameter (mm) 27.71 27.70 27.76 27.71 27.70 Weight (g) 16.56
16.58 16.59 16.56 16.58 Volume (mm.sup.3) 11.14 11.13 11.20 11.14
11.13 Deflection (mm) 4.6 5.5 3.9 4.6 5.5 Hardness Core surface
hardness: Cs 75 70 81 75 70 profile Hardness at midpoint between 64
59 68 64 59 (Shore C) core surface and center: Cm Core center
hardness: Cc 59 55 62 59 55 Core surface hardness - 17 15 19 17 15
Core center hardness (Cs - Cm)/(Cm - Cc) 2.0 2.2 1.9 2.0 2.2 Core
volume .times. 715 660 765 715 660 Hardness at midpoint between
core surface and center Inner Material No. 1 No. 1 No. 2 No. 2 No.
2 envelope Thickness (mm) 2.28 2.29 2.24 2.27 2.28 layer Volume
(mm.sup.3) 6.46 6.47 6.35 6.42 6.44 Material hardness (Shore C) 84
84 87 87 87 Material hardness (Shore D) 52 52 56 56 56 Inner
Diameter (mm) 32.28 32.28 32.24 32.25 32.26 envelope Weight (g)
22.48 22.48 22.57 22.57 22.59 layer-encased Deflection (mm) 3.7 4.4
3.5 4.2 5.0 sphere Surface hardness (Shore C) 89 89 92 92 92
Surface hardness (Shore D) 57 57 62 62 62 Surface hardness of inner
envelope layer - 14 19 11 17 22 Core surface hardness (Shore C)
Volume of inner envelope layer .times. Surface hardness of 575 576
584 591 592 inner envelope layer-encased sphere (Shore C) Outer
Material No. 2 No. 2 No. 3 No. 3 No. 3 envelope Thickness (mm) 1.95
1.95 1.96 1.96 1.96 layer Volume (mm.sup.3) 7.20 7.18 7.22 7.20
7.22 Material hardness (Shore C) 87 87 91 91 91 Material hardness
(Shore D) 56 56 60 60 60 Overall thickness of envelope layer (mm)
4.24 4.23 4.21 4.23 4.24 Inner envelope layer thickness - 0.33 0.34
0.28 0.32 0.31 Outer envelope layer thickness (mm) Outer Diameter
(mm) 36.18 36.17 36.17 36.16 36.18 envelope Weight (g) 29.31 29.30
29.31 29.35 29.33 layer-encased Deflection (mm) 3.4 3.9 2.3 2.6 2.9
sphere Material hardness (Shore C) 92 92 95 95 95 Material hardness
(Shore D) 62 62 66 66 66 Outer envelope layer surface hardness - 33
37 33 36 40 Core center hardness (Shore C) Outer envelope layer
hardness - 17 22 14 20 25 Core surface hardness (Shore C) Outer
envelope layer surface hardness - 3 3 3 3 3 Inner envelope layer
surface hardness (Shore C) Outer envelope layer volume .times.
Surface hardness 662 660 686 684 686 of outer envelope
layer-encased sphere (Shore C)
TABLE-US-00008 TABLE 8 Comparative Example 7 8 9 10 11 12
Construction (piece) 5P 5P 5P 5P 5P 5P Core Diameter (mm) 31.42
31.43 33.14 31.43 31.43 31.42 Weight (g) 21.38 21.45 23.89 21.45
22.23 21.38 Volume (mm.sup.3) 16.24 16.25 19.06 16.25 16.26 16.24
Deflection (mm) 3.7 5.3 4.1 5.8 4.4 3.7 Hardness Core surface
hardness: Cs 82 71 79 67 77 82 profile Hardness at midpoint between
69 60 67 58 65 69 (Shore C) core surface and center: Cm Core center
hardness: Cc 63 55 61 53 60 63 Core surface hardness - 19 15 18 14
17 19 Core center hardness (Cs - Cm)/(Cm - Cc) 1.9 2.2 2.0 2.3 2.0
1.9 Core volume .times. 1125 978 1284 936 1065 1125 Hardness at
midpoint between core surface and center Inner Material No. 1 No. 1
No. 1 No. 1 No. 1 No. 1 envelope Thickness (mm) 1.38 1.38 1.35 1.47
1.46 1.47 layer Volume (mm.sup.3) 4.65 4.66 5.06 4.99 4.98 5.02
Material hardness (Shore C) 84 84 84 84 84 84 Material hardness
(Shore D) 52 52 52 52 52 52 Inner Diameter (mm) 34.17 34.18 35.85
34.36 34.36 34.37 envelope Weight (g) 25.69 25.75 28.67 26.20 27.08
26.18 layer-encased Deflection (mm) 3.5 5.2 3.8 5.6 4.1 3.4 sphere
Surface hardness (Shore C) 89 89 89 89 89 89 Surface hardness
(Shore D) 57 57 57 57 57 57 Surface hardness of inner envelope
layer - 7 18 10 22 12 7 Core surface hardness (Shore C) Volume of
inner envelope layer .times. Surface hardness of 414 415 450 444
444 446 inner envelope layer-encased sphere (Shore C) Outer
Material No. 2 No. 2 No. 2 No. 2 No. 2 No. 4 envelope Thickness
(mm) 1.47 1.47 1.10 1.38 1.37 1.38 layer Volume (mm.sup.3) 5.89
5.86 4.71 5.53 5.52 5.53 Material hardness (Shore C) 87 87 87 87 87
92 Material hardness (Shore D) 56 56 56 56 56 62 Overall thickness
of envelope layer (mm) 2.85 2.84 2.45 2.84 2.84 2.85 Inner envelope
layer thickness - -0.10 -0.09 0.25 0.09 0.09 0.10 Outer envelope
layer thickness (mm) Outer Diameter (mm) 37.12 37.11 38.04 37.11
37.11 37.12 envelope Weight (g) 31.29 31.31 33.10 31.31 32.18 31.29
layer-encased Deflection (mm) 3.0 4.2 3.4 4.7 3.6 3.0 sphere
Material hardness (Shore C) 92 92 92 92 92 95 Material hardness
(Shore D) 62 62 62 62 62 64 Outer envelope layer surface hardness -
29 37 31 39 32 32 Core center hardness (Shore C) Outer envelope
layer hardness - 10 21 13 25 15 13 Core surface hardness (Shore C)
Outer envelope layer surface hardness - 3 3 3 3 3 6 Inner envelope
layer surface hardness (Shore C) Outer envelope layer volume
.times. Surface hardness 542 539 434 509 508 525 of outer envelope
layer-encased sphere (Shore C) Comparative Example 13 14 15 16 17
18 Construction (piece) 5P 5P 4P 4P 4P 3P Core Diameter (mm) 31.42
31.42 35.08 35.07 35.12 37.18 Weight (g) 21.38 21.38 27.57 27.42
27.72 31.67 Volume (mm.sup.3) 16.24 16.24 22.60 22.58 22.68 26.91
Deflection (mm) 3.7 2.7 3.1 3.4 3.9 3.7 Hardness Core surface
hardness: Cs 82 89 86 84 80 84 profile Hardness at midpoint between
69 75 73 71 68 71 (Shore C) core surface and center: Cm Core center
hardness: Cc 63 67 66 64 62 62 Core surface hardness - 19 21 20 20
18 22 Core center hardness (Cs - Cm)/(Cm - Cc) 1.9 1.8 1.9 1.9 1.9
1.4 Core volume .times. 1125 1218 1641 1608 1544 1921 Hardness at
midpoint between core surface and center Inner Material No. 2 No. 1
envelope Thickness (mm) 1.47 1.47 layer Volume (mm.sup.3) 5.02 5.02
Material hardness (Shore C) 87 84 Material hardness (Shore D) 56 52
Inner Diameter (mm) 34.37 34.37 envelope Weight (g) 26.18 26.18
layer-encased Deflection (mm) 3.3 2.4 sphere Surface hardness
(Shore C) 87 89 Surface hardness (Shore D) 56 57 Surface hardness
of inner envelope layer - 5 0 Core surface hardness (Shore C)
Volume of inner envelope layer .times. Surface hardness of 436 446
inner envelope layer-encased sphere (Shore C) Outer Material No. 1
No. 2 No. 2 No. 2 No. 2 envelope Thickness (mm) 1.38 1.38 1.59 1.59
1.57 layer Volume (mm.sup.3) 5.53 5.53 6.73 6.73 6.62 Material
hardness (Shore C) 84 87 87 87 87 Material hardness (Shore D) 52 56
56 56 56 Overall thickness of envelope layer (mm) 2.85 2.85 1.59
1.59 1.57 Inner envelope layer thickness - 0.10 0.10 -- -- -- Outer
envelope layer thickness (mm) Outer Diameter (mm) 37.12 37.12 38.26
38.25 38.25 envelope Weight (g) 31.29 31.29 33.85 33.79 33.90
layer-encased Deflection (mm) 3.1 2.6 2.8 2.9 3.4 sphere Material
hardness (Shore C) 84 92 92 92 92 Material hardness (Shore D) 52 62
62 62 62 Outer envelope layer surface hardness - 21 25 26 28 30
Core center hardness (Shore C) Outer envelope layer hardness - 2 3
6 8 12 Core surface hardness (Shore C) Outer envelope layer surface
hardness - -3 3 -- -- -- Inner envelope layer surface hardness
(Shore C) Outer envelope layer volume .times. Surface hardness 462
509 620 619 609 of outer envelope layer-encased sphere (Shore
C)
TABLE-US-00009 TABLE 9 Example Comparative Example 1 2 3 4 1 2 3 4
5 6 Intermediate Material No. 4 No. 4 No. 4 No. 4 No. 4 No. 4 No. 4
No. 4 No. 4 No. 4 layer Thickness (mm) 1.09 1.12 1.11 1.78 2.24
2.22 2.23 2.23 2.23 2.22 Material hardness (Shore C) 95 95 95 95 95
95 95 95 95 95 Material hardness (Shore D) 64 64 64 64 64 64 64 64
64 64 Intermediate Diameter (mm) 40.62 40.67 40.65 40.67 40.64
40.62 40.62 40.63 40.63 40.62 layer-encased Weight (g) 39.14 39.16
39.20 39.29 39.11 39.04 39.05 39.12 39.12 39.09 sphere Deflection
(mm) 2.4 2.6 2.8 2.6 2.0 2.2 2.4 1.6 1.7 1.8 Surface hardness
(Shore C) 97 97 97 97 97 97 97 97 97 97 Surface hardness (Shore D)
70 70 70 70 70 70 70 70 70 70 Intermediate layer surface hardness -
5 5 5 5 5 5 5 2 2 2 Outer envelope layer surface hardness (Shore C)
Intermediate layer surface hardness - 32 34 36 37 35 38 42 35 38 42
Core center hardness (Shore C) Cover Material No. 5 No. 5 No. 5 No.
5 No. 5 No. 5 No. 5 No. 5 No. 5 No. 5 Thickness (mm) 1.01 0.99 1.00
0.99 1.01 1.02 1.02 1.02 1.01 1.01 Material hardness (Shore C) 74
74 74 74 74 74 74 74 74 74 Material hardness (Shore D) 48 48 48 48
48 48 48 48 48 48 Coating Material C C C C C C C C C C Material
hardness (Shore C) 63 63 63 63 63 63 63 63 63 63 Dimples Type D D D
D D D D D D D Number 330 330 330 330 330 330 330 330 330 330 Ball
Diameter (mm) 42.65 42.65 42.66 42.65 42.66 42.66 42.67 42.67 42.66
42.65 Weight (g) 45.11 45.07 45.20 45.17 45.08 45.04 45.06 45.06
45.03 45.05 Deflection (mm) 2.2 2.3 2.5 2.3 1.8 1.9 2.0 1.5 1.6 1.6
Surface hardness (Shore C) 90 90 90 90 90 90 90 90 90 90 Surface
hardness (Shore D) 59 59 59 59 59 59 59 59 59 59 Intermediate layer
thickness - Cover thickness (mm) 0.08 0.13 0.10 0.79 1.22 1.20 1.20
1.21 1.22 1.21 Overall thickness of envelope layer/ 1.17 1.18 1.16
1.02 1.29 1.31 1.30 1.29 1.30 1.31 (Cover thickness + Intermediate
layer thickness) Core diameter/Ball diameter 0.785 0.784 0.786
0.737 0.651 0.650 0.649 0.651 0.650 0.650 Intermediate layer
surface hardness - 7 7 7 7 7 7 7 7 7 7 Ball surface hardness (Shore
C) Core deflection - Ball deflection (mm) 1.0 1.3 1.5 2.1 2.1 2.7
3.5 2.4 3.1 3.9 (OE vh + IE vh)/Core vh 0.64 0.67 0.68 0.89 1.61
1.73 1.87 1.66 1.78 1.94
TABLE-US-00010 TABLE 10 Comparative Example 7 8 9 10 11 12
Intermediate Material No. 4 No. 4 No. 4 No. 4 No. 4 No. 2 layer
Thickness (mm) 1.74 1.78 1.11 1.78 1.78 1.74 Material hardness
(Shore C) 95 95 95 95 95 92 Material hardness (Shore D) 64 64 64 64
64 62 Intermediate Diameter (mm) 40.61 40.68 40.26 40.68 40.67
40.61 layer-encased Weight (g) 39.14 39.37 38.13 39.37 40.19 39.14
sphere Deflection (mm) 2.3 2.8 2.8 3.1 2.6 2.4 Surface hardness
(Shore C) 97 97 97 97 97 92 Surface hardness (Shore D) 70 70 70 70
70 62 Intermediate layer surface hardness - 5 5 5 5 5 -3 Outer
envelope layer surface hardness (Shore C) Intermediate layer
surface hardness - 34 42 36 44 37 29 Core center hardness (Shore C)
Cover Material No. 5 No. 5 No. 5 No. 5 No. 6 No. 5 Thickness (mm)
1.02 0.99 1.20 0.99 0.99 1.02 Material hardness (Shore C) 74 74 74
74 98 74 Material hardness (Shore D) 48 48 48 48 68 48 Coating
Material C C C C C C Material hardness (Shore C) 63 63 63 63 63 63
Dimples Type D D D D D D Number 330 330 330 330 330 330 Ball
Diameter (mm) 42.65 42.66 42.66 42.66 42.65 42.65 Weight (g) 45.17
45.18 45.20 45.18 45.20 45.17 Deflection (mm) 2.1 2.5 2.5 2.6 1.9
2.2 Surface hardness (Shore C) 90 90 90 90 100 90 Surface hardness
(Shore D) 59 59 58 59 74 58 Intermediate layer thickness - 0.73
0.79 -0.09 0.79 0.79 0.72 Cover thickness (mm) Overall thickness of
envelope layer/ 1.03 1.03 1.06 1.03 1.03 1.03 (Cover thickness +
Intermediate layer thickness) Core diameter/Ball diameter 0.737
0.737 0.777 0.737 0.737 0.737 Intermediate layer surface hardness -
7 7 7 7 -3 2 Ball surface hardness (Shore C) Core deflection - Ball
deflection (mm) 1.6 2.8 1.5 3.2 2.5 1.6 (OE vh + IE vh)/Core vh
0.85 0.98 0.69 1.02 0.89 0.86 Comparative Example 13 14 15 16 17 18
Intermediate Material No. 4 No. 4 No. 4 No. 4 No. 4 No. 4 layer
Thickness (mm) 1.74 1.74 1.20 1.20 1.21 1.74 Material hardness
(Shore C) 95 95 95 95 95 95 Material hardness (Shore D) 64 64 64 64
64 64 Intermediate Diameter (mm) 40.61 40.61 40.67 40.65 40.68
40.66 layer-encased Weight (g) 39.14 39.14 39.41 39.25 39.47 39.50
sphere Deflection (mm) 2.4 2.2 2.3 2.5 2.9 2.9 Surface hardness
(Shore C) 97 97 97 97 97 97 Surface hardness (Shore D) 70 70 70 70
70. 70 Intermediate layer surface hardness - 13 5 5 5 5 -- Outer
envelope layer surface hardness (Shore C) Intermediate layer
surface hardness - 34 30 31 33 35 35 Core center hardness (Shore C)
Cover Material No. 5 No. 5 No. 5 No. 5 No. 5 No. 5 Thickness (mm)
1.02 1.02 1.00 1.01 0.99 1.01 Material hardness (Shore C) 74 74 74
74 74 74 Material hardness (Shore D) 48 48 48 48 48 48 Coating
Material C C C C C C Material hardness (Shore C) 63 63 63 63 63 63
Dimples Type D D D D D D Number 330 330 330 330 330 330 Ball
Diameter (mm) 42.65 42.65 42.68 42.67 42.66 42.67 Weight (g) 45.17
45.17 45.28 45.20 45.30 45.40 Deflection (mm) 2.1 1.9 2.1 2.2 2.5
2.6 Surface hardness (Shore C) 90 90 90 90 90 90 Surface hardness
(Shore D) 59 59 59 59 59 59 Intermediate layer thickness - 0.73
0.73 0.20 0.19 0.22 0.73 Cover thickness (mm) Overall thickness of
envelope layer/ 1.03 1.03 0.72 0.72 0.71 -- (Cover thickness +
Intermediate layer thickness) Core diameter/Ball diameter 0.737
0.737 0.822 0.822 0.823 0.871 Intermediate layer surface hardness -
7 7 7 7 7 7 Ball surface hardness (Shore C) Core deflection - Ball
deflection (mm) 1.6 0.9 1.0 1.1 1.4 1.1 (OE vh + IE vh)/Core vh
0.80 0.78 0.38 0.38 0.39 --
[0202] The flight performance of each golf ball on shots with a
driver (W#1) and on shots with a number six iron (I#6) and the spin
rate on approach shots were evaluated by the following methods. The
results are shown in Tables 11 and 12.
[0203] Flight Performance (W#1) [0204] (1) A driver (W#1) was
mounted on a golf swing robot and the distance traveled by the ball
when struck at a head speed of 47 m/s was measured and rated
according to the criteria shown below. The club used was the TOUR B
XD-5 (loft angle, 9.5.degree.) manufactured by Bridgestone Sports
Co., Ltd. In addition, the spin rate was measured with a launch
monitor immediately after the ball was similarly struck. [0205]
Rating Criteria [0206] Good: Total distance was at least 233.0 m
[0207] NG: Total distance was less than 233.0 m [0208] (2) The
distance traveled by the ball when struck by a similar driver at a
head speed of 42 m/s was measured and rated according to the
criteria shown below. [0209] Rating Criteria [0210] Good: Total
distance was at least 208.0 m [0211] NG: Total distance was less
than 208.0 m
[0212] Flight Performance (I#6) [0213] (1) A middle iron (I#6) was
mounted on a golf swing robot and the distance traveled by the ball
when struck at a head speed of 43 m/s was measured and rated
according to the criteria shown below. The club used was the TOUR B
X-CB manufactured by Bridgestone Sports Co., Ltd. In addition, the
spin rate was measured with a launch monitor immediately after the
ball was similarly struck. [0214] Rating Criteria [0215] Good:
Total distance was at least 164.0 m [0216] NG: Total distance was
less than 164.0 m
[0217] Evaluation of Spin Rate on Approach Shots
[0218] A sand wedge (SW) was mounted on a golf swing robot and the
amount of spin by the ball when struck at a head speed of 16 m/s
was rated according to the criteria shown below. The spin rate was
measured with a launch monitor immediately after the ball was
struck. The sand wedge used was the Tour B XW-1 manufactured by
Bridgestone Sports Co., Ltd. [0219] Rating Criteria: [0220] Good:
Spin rate was 5,300 rpm or more [0221] NG: Spin rate was less than
5,300 rpm
TABLE-US-00011 [0221] TABLE 11 Example Comparative Example 1 2 3 4
1 Flight (W#1) Spin rate (rpm) 2,851 2,777 2,671 2,749 2,981 HS =
47 m/s Total distance (m) 235.0 236.1 235.9 233.8 233.6 Rating good
good good good good Flight (W#1) Spin rate (rpm) 2,612 2,535 2,467
2,591 2,755 HS = 42 m/s Total distance (m) 210.3 211.8 209.5 209.4
203.4 Rating good good good good NG Flight (I#6) Spin rate (rpm)
6,421 6,223 5,875 6,091 6,780 HS = 43 m/s Total distance (m) 164.4
165.6 165.5 166.0 160.7 Rating good good good good NG
Controllability Spin rate (rpm) 5,616 5,540 5,453 5,625 5,694 on
approach Rating good good good good good shots Comparative Example
2 3 4 5 6 Flight (W#1) Spin rate (rpm) 2,911 2,864 3,133 3,050
3,052 HS = 47 m/s Total distance (m) 232.1 232.3 230.5 229.0 228.9
Rating NG NG NG NG NG Flight (W#1) Spin rate (rpm) 2,660 2,703
2,889 2,865 2,817 HS = 42 m/s Total distance (m) 204.8 204.0 203.9
205.8 202.4 Rating NG NG NG NG NG Flight (I#6) Spin rate (rpm)
6,482 6,396 7,125 6,931 6,885 HS = 43 m/s Total distance (m) 159.9
160.9 156.3 156.5 158.9 Rating NG NG NG NG NG Controllability Spin
rate (rpm) 5,694 5,717 5,874 5,785 5,811 on approach Rating good
good good good good shots
TABLE-US-00012 TABLE 12 Comparative Example 7 8 9 10 11 12 Flight
(W#1) Spin rate (rpm) 2,894 2,670 2,719 2,585 2,560 2,864 HS = 47
m/s Total distance (m) 234.3 232.9 232.9 232.8 237.1 234.7 Rating
good NG NG NG good good Flight (W#1) Spin rate (rpm) 2,676 2,458
2,522 2,384 2,411 2,646 HS = 42 m/s Total distance (m) 207.8 206.1
207.5 205.7 213.2 207.9 Rating NG NG NG NG good NG Flight (I#6)
Spin rate (rpm) 6,402 5,803 5,878 5,675 5,661 6,398 HS = 43 m/s
Total distance (m) 160.1 166.4 165.0 166.9 172.0 160.5 Rating NG
good good good good NG Controllability Spin rate (rpm) 5,633 5,544
5,465 5,528 4,650 5,622 on Approach Rating good good good good NG
good shots Comparative Example 13 14 15 16 17 18 Flight (W#1) Spin
rate (rpm) 2,874 2,994 2,857 2,755 2,631 2,569 HS = 47 m/s Total
distance (m) 234.5 235.4 235.0 235.3 235.0 232.4 Rating good good
good good good NG Flight (W#1) Spin rate (rpm) 2,651 2,799 2,623
2,619 2,507 2,482 HS = 42 m/s Total distance (m) 208.2 210.1 207.3
206.0 206.5 207.5 Rating good good NG NG NG NG Flight (I#6) Spin
rate (rpm) 6,413 6,749 6,418 6,246 5,808 5,817 HS = 43 m/s Total
distance (m) 160.0 157.7 165.9 163.3 167.4 165.9 Rating NG NG good
NG good good Controllability Spin rate (rpm) 5,635 5,701 5,564
5,537 5,503 5,394 on Approach Rating good good good good good good
shots
[0222] As demonstrated by the results in the above tables, the golf
balls of Comparative Examples 1 to 18 are inferior in the following
respects to the golf balls according to the present invention that
are obtained in Examples 1 to 4.
[0223] In Comparative Example 1, the core diameter is smaller than
30 mm and the ball initial velocity is low. As a result, the
distances traveled by the ball on full shots with a driver (W#1)
and with an iron are both poor.
[0224] In Comparative Example 2, the core diameter is smaller than
30 mm and the ball initial velocity is low. As a result, the
distances traveled by the ball on full shots with a driver (W#1)
and with an iron are both poor.
[0225] In Comparative Example 3, the core diameter is smaller than
30 mm and the ball initial velocity is low, in addition to which
the Shore C hardness value obtained by subtracting the core center
hardness from the core surface hardness is smaller than 16. As a
result, the distances traveled by the ball on full shots with a
driver (W#1) and with an iron are both poor.
[0226] In Comparative Example 4, the core diameter is smaller than
30 mm and the ball initial velocity is low. As a result, the
distances traveled by the ball on full shots with a driver (W#1)
and with an iron are both poor.
[0227] In Comparative Example 5, the core diameter is smaller than
30 mm and the ball initial velocity is low. As a result, the
distances traveled by the ball on full shots with a driver (W#1)
and with an iron are both poor.
[0228] In Comparative Example 6, the core diameter is smaller than
30 mm and the ball initial velocity is low, in addition to which
the Shore C hardness value obtained by subtracting the core center
hardness from the core surface hardness is smaller than 16. As a
result, the distances traveled by the ball on full shots with a
driver (W#1) and with an iron are both poor.
[0229] In Comparative Example 7, (thickness of outer envelope
layer).gtoreq.(thickness of inner envelope layer). As a result, the
spin rate of the ball is high and the distances traveled by the
ball on full shots with a driver (W#1) and with an iron are both
poor.
[0230] In Comparative Example 8, (thickness of outer envelope
layer) (thickness of inner envelope layer). As a result, the
initial velocity of the ball when struck is low and the distance
traveled by the ball on shots with a driver (W#1) is poor.
[0231] In Comparative Example 9, (cover
thickness).gtoreq.(intermediate layer thickness). As a result, the
spin rate of the ball is high and the ball has a low initial
velocity, resulting in a poor distance on shots with a driver
(W#1).
[0232] In Comparative Example 10, the Shore C hardness value
obtained by subtracting the core center hardness from the core
surface hardness is lower than 16 and the ball has a low initial
velocity when struck. As a result, the distance traveled by the
ball on shots with a driver (W#1) is poor.
[0233] In Comparative Example 11, (surface hardness of
ball).gtoreq.(surface hardness of intermediate layer-encased
sphere). As a result, the spin rate on approach shots in the short
game is insufficient.
[0234] In Comparative Example 12, (surface hardness of intermediate
layer-encased sphere) (surface hardness of outer envelope
layer-encased sphere). As a result, the spin rate on full shots is
high and the distances traveled on shots with a driver (W#1) and an
iron are poor.
[0235] In Comparative Example 13, (surface hardness of outer
envelope layer-encased sphere).ltoreq.(surface hardness of inner
envelope layer-encased sphere). As a result, the spin rate on full
shots with an iron is high and the distance traveled is poor.
[0236] In Comparative Example 14, (surface hardness of inner
envelope layer-encased sphere).ltoreq.(surface hardness of core).
As a result, the spin rate on full shots is high and the distance
traveled on shots with an iron is poor.
[0237] The ball in Comparative Example 15 is a four-piece ball
(4-layer construction). As a result, the initial velocity when
struck is low and the distance traveled by the ball on shots with a
driver (W#1) is poor.
[0238] The ball in Comparative Example 16 is a four-piece ball
(4-layer construction). As a result, the initial velocity when
struck is low and the distance traveled by the ball on shots with a
driver (W#1) is poor.
[0239] The ball in Comparative Example 17 is a four-piece ball
(4-layer construction). As a result, the initial velocity when
struck is low and the distance traveled by the ball on shots with a
driver (W#1) is poor. The ball in Comparative Example 18 is a
three-piece ball (3-layer construction).
[0240] As a result, the initial velocity when struck is low and the
distance traveled by the ball on shots with a driver (W#1) is
poor.
[0241] Japanese Patent Application No. 2021-035283 is incorporated
herein by reference.
[0242] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *