U.S. patent application number 16/540618 was filed with the patent office on 2020-03-12 for golf ball.
This patent application is currently assigned to Bridgestone Sports Co., Ltd.. The applicant listed for this patent is Bridgestone Sports Co., Ltd.. Invention is credited to Katsunori Sato, Hideo Watanabe.
Application Number | 20200078643 16/540618 |
Document ID | / |
Family ID | 69721079 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200078643 |
Kind Code |
A1 |
Watanabe; Hideo ; et
al. |
March 12, 2020 |
GOLF BALL
Abstract
A golf ball for amateur golfers is endowed with both an
excellent flight and a good feel at impact that is soft and solid
when hit by the average golfer whose head speed is not very high.
The golf ball, which includes a core and a cover, has a compressive
deformation A when subjected to a final load of 5 kg from an
initial load of 0.2 kg that is 0.21 mm or less, a compressive
deformation B when subjected to a final load of 30 kg from an
initial load of 5 kg that is from 0.72 to 0.90 mm and a compressive
deformation C when subjected to a final load of 60 kg from an
initial load of 5 kg that is from 1.55 to 1.80 mm.
Inventors: |
Watanabe; Hideo;
(Chichibushi, JP) ; Sato; Katsunori; (Chichibushi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bridgestone Sports Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Bridgestone Sports Co.,
Ltd.
Tokyo
JP
|
Family ID: |
69721079 |
Appl. No.: |
16/540618 |
Filed: |
August 14, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 37/0031 20130101;
A63B 37/0063 20130101; A63B 37/0068 20130101; A63B 37/0087
20130101; A63B 37/0076 20130101; A63B 37/0032 20130101; A63B
2037/0079 20130101; A63B 37/0043 20130101; A63B 37/0084 20130101;
A63B 37/0044 20130101; A63B 37/0022 20130101; A63B 37/0062
20130101; A63B 37/0092 20130101 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2018 |
JP |
2018-169572 |
Claims
1. A golf ball comprising a core and a cover, wherein the ball has
an amount of compressive deformation such that the compressive
deformation A when the ball is subjected to a final load of 5 kg
from an initial load state of 0.2 kg is 0.21 mm or less, the
compressive deformation B when the ball is subjected to a final
load of 30 kg from an initial load state of 5 kg is from 0.72 to
0.90 mm and the compressive deformation C when the ball is
subjected to a final load of 60 kg from an initial load state of 5
kg is from 1.55 to 1.80 mm.
2. The golf ball of claim 1, wherein the compressive deformation D
when the ball is subjected to a final load of 130 kg from an
initial load state of 10 kg is from 2.80 to 3.40 mm.
3. The golf ball of claim 2, wherein the ratio D/C between
compressive deformation D and compressive deformation C is from
1.80 to 1.90.
4. The golf ball of claim 2, wherein the ratio D/B between
compressive deformation D and compressive deformation B is from
3.65 to 4.20.
5. The golf ball of claim 2, wherein the ratio D/A between
compressive deformation D and compressive deformation A is from
16.0 to 25.0.
6. The golf ball of claim 1, wherein the ball further comprises,
between the core and the cover, at least an envelope layer and an
intermediate layer, which golf ball has a construction of four or
more layers that includes a core, an envelope layer, an
intermediate layer and a cover.
7. The golf ball of claim 6 which satisfies the following surface
hardness relationship: (1) Shore D hardness at surface of
cover>Shore D hardness at surface of intermediate layer>Shore
D hardness at surface of envelope layer>Shore D hardness at
center of core.
8. The golf ball of claim 1 wherein, letting Cc be the Shore C
hardness at a center of the core and Cs be the Shore C hardness at
a surface of the core, the Shore D hardness difference between the
surface and center of the core (Cs-Cc) is 20 or more.
9. The golf ball of claim 1, wherein the cover has a paint film
layer formed on a surface thereof, which paint film layer has a
material hardness that is higher than the core center hardness
(Cc).
10. The golf ball of claim 6 which satisfies the following initial
velocity relationships (2), (3) and (4): (2) -0.8 m/s.ltoreq.(ball
initial velocity-core initial velocity).ltoreq.0 m/s, (3) -0.4
m/s.ltoreq.(ball initial velocity-initial velocity of intermediate
layer-encased sphere).ltoreq.0.4 m/s, and (4) 0 m/s.ltoreq.(initial
velocity of intermediate layer-encased sphere-initial velocity of
envelope layer-encased sphere).ltoreq.0.4 m/s.
11. A golf ball comprising a core and a cover, wherein the ball has
an amount of compressive deformation such that, letting A be the
compressive deformation when the ball is subjected to a final load
of 5 kg from an initial load state of 0.2 kg, B be the compressive
deformation when the ball is subjected to a final load of 30 kg
from an initial load state of 5 kg, C be the compressive
deformation when the ball is subjected to a final load of 60 kg
from an initial load state of 5 kg and D be the compressive
deformation when the ball is subjected to a final load of 130 kg
from an initial load state of 10 kg, D has a value of from 2.80 to
3.40 mm, the ratio D/C is from 1.80 to 1.90, the ratio D/B is from
3.65 to 4.20 and the ratio D/A is from 16.0 to 25.0.
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. 2018-169572 filed in
Japan on Sep. 11, 2018, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a golf ball which has a
core and a cover, and is intended for use by amateur golfers
lacking a fast head speed.
BACKGROUND ART
[0003] In the field of golf balls for amateur golfers, numerous
balls intended to satisfy amateur players in terms of flight
performance and feel have hitherto been developed. For example,
JP-A H08-280845 describes a golf ball wherein, using the amount of
compressive deformation when a final load of 5 kg is applied from
an initial load state of 0.2 kg as an indicator of the influence
exerted on the ball properties when a small impact force has acted
upon a golf ball, this value is set in the range of from 0.26 to
0.40 mm. However, this golf ball is a spin-type ball that is
targeted primarily at the spin on approach shots, and does not
fully satisfy the flight performance desired on shots with a
driver.
[0004] In addition, a variety of functional, multi-piece solid golf
balls in which the ball has a multilayer construction and the
surface hardnesses of the respective layers--i.e., the core,
envelope layer, intermediate layer and cover (outermost layer)--are
optimized have been described. These include the multi-piece solid
golf balls disclosed in JP-A 2014-132955, JP-A 2015-173860, JP-A
2016-16117 and JP-A 2016-179052. The golf balls disclosed in these
patent publications satisfy the following hardness relationship:
ball surface hardness>intermediate layer surface
hardness>envelope layer surface hardness<core surface
hardness, and impart an excellent flight performance even when used
by amateur golfers lacking a fast head speed. However, these
prior-art golf balls do not optimize the amount of compressive
deformation when subjected to a final load of 5 kg from an initial
load state of 0.2 kg and the amount of compressive deformation when
subjected to a final load of 30 kg from an initial load state of 5
kg. That is, no attention has been paid to how the golf ball
properties are affected by the magnitude of the impact force acting
on the ball, and so there remains room for improvement in obtaining
a good flight performance and a good feel at impact in golf ball
products for amateur golfers.
SUMMARY OF THE INVENTION
[0005] It is therefore an object of the present invention to
provide a golf ball for amateur golfers which has an excellent
flight when hit by the average golfer whose head speed is not that
high and which also has a good feel at impact that is both soft and
solid.
[0006] As a result of extensive investigations, we have focused on
the relationship, in golf balls having a core and a cover, between
the magnitude of the force of impact applied to the golf ball and
the ball characteristics of flight performance and feel. We have
discovered in particular that, in the amount of compressive
deformation by the golf ball, by specifying the following
respective compressive deformations: the compressive deformation A
when the ball is subjected to a final load of 5 kg from an initial
load state of 0.2 kg, the compressive deformation B when the ball
is subjected to a final load of 30 kg from an initial load state of
5 kg, the compressive deformation C when the ball is subjected to a
final load of 60 kg from an initial load state of 5 kg and the
compressive deformation D when the ball is subjected to a final
load of 130 kg from an initial load state of 10 kg, as well as the
ratios therebetween, a flight performance that is satisfactory when
the ball is hit with all golf clubs, including drivers (W #1) and
irons, can be fully obtained by golfers lacking a fast head speed,
in addition to which a feel that is both soft and solid can be
obtained.
[0007] Accordingly, in a first aspect, the invention provides a
golf ball that includes a core and a cover, wherein the ball has an
amount of compressive deformation such that the compressive
deformation A when the ball is subjected to a final load of 5 kg
from an initial load state of 0.2 kg is 0.21 mm or less, the
compressive deformation B when the ball is subjected to a final
load of 30 kg from an initial load state of 5 kg is from 0.72 to
0.90 mm, and the compressive deformation C when the ball is
subjected to a final load of 60 kg from an initial load state of 5
kg is from 1.55 to 1.80 mm.
[0008] In a preferred embodiment of the golf ball of the invention,
the compressive deformation D when the ball is subjected to a final
load of 130 kg from an initial load state of 10 kg is from 2.80 to
3.40 mm.
[0009] In another preferred embodiment of the inventive golf ball,
the ratio D/C between compressive deformation D and compressive
deformation C is from 1.80 to 1.90.
[0010] In yet another preferred embodiment, the ratio D/B between
compressive deformation D and compressive deformation B is from
3.65 to 4.20.
[0011] In still another preferred embodiment, the ratio D/A between
compressive deformation D and compressive deformation A is from
16.0 to 25.0.
[0012] In a further preferred embodiment, the ball additionally
includes, between the core and the cover, at least an envelope
layer and an intermediate layer, thus having a construction of four
or more layers that includes a core, an envelope layer, an
intermediate layer and a cover.
[0013] In a still further preferred embodiment, the golf ball
satisfies the following surface hardness relationship:
(1) Shore D hardness at surface of cover>Shore D hardness at
surface of intermediate layer>Shore D hardness at surface of
envelope layer>Shore D hardness at center of core.
[0014] In another preferred embodiment of the inventive golf ball,
letting Cc be the Shore C hardness at a center of the core and Cs
be the Shore C hardness at a surface of the core, the Shore C
hardness difference between the surface and center of the core
(Cs-Cc) is 20 or more.
[0015] In yet another preferred embodiment, the cover has a paint
film layer formed on a surface thereof, which paint film layer has
a material hardness that is higher than the core center hardness
(Cc).
[0016] In still another preferred embodiment, the golf ball
satisfies the following initial velocity relationships (2), (3) and
(4):
(2) -0.8 m/s.ltoreq.(ball initial velocity-core initial
velocity).ltoreq.0 m/s, (3) -0.4 m/s.ltoreq.(ball initial
velocity-initial velocity of intermediate layer-encased
sphere).ltoreq.0.4 m/s, and (4) 0 m/s.ltoreq.(initial velocity of
intermediate layer-encased sphere-initial velocity of envelope
layer-encased sphere).ltoreq.0.4 m/s.
[0017] In a second aspect, the invention provides a golf ball that
includes a core and a cover, wherein the ball has an amount of
compressive deformation such that, letting A be the compressive
deformation when the ball is subjected to a final load of 5 kg from
an initial load state of 0.2 kg, B be the compressive deformation
when the ball is subjected to a final load of 30 kg from an initial
load state of 5 kg, C be the compressive deformation when the ball
is subjected to a final load of 60 kg from an initial load state of
5 kg and D be the compressive deformation when the ball is
subjected to a final load of 130 kg from an initial load state of
10 kg, D has a value of from 2.80 to 3.40 mm, the ratio D/C is from
1.80 to 1.90, the ratio D/B is from 3.65 to 4.20 and the ratio D/A
is from 16.0 to 25.0.
Advantageous Effects of the Invention
[0018] The golf ball of the invention has an excellent flight
performance when hit by golfers whose head speeds are not that high
and also has a good feel at impact that is both soft and solid,
making it highly suitable for use by amateur golfers.
BRIEF DESCRIPTION OF THE DIAGRAMS
[0019] The FIGURE is a schematic cross-sectional view of a golf
ball having a four-layer construction according to one embodiment
of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The objects, features and advantages of the invention will
become more apparent from the following detailed description taken
in conjunction with the appended diagrams.
[0021] The golf ball of the invention has a core and a cover. In
this invention, the cover refers to the member positioned as the
outermost layer in the ball construction and typically is formed by
injection molding or the like. Numerous dimples are typically
formed on the outer surface of the cover at the same time that the
cover material is injection molded.
[0022] The core has a diameter of preferably at least 34.0 mm, more
preferably at least 34.5 mm, and even more preferably at least 35.0
mm. The upper limit is preferably not more than 37.0 mm, more
preferably not more than 36.5 mm, and even more preferably not more
than 36.0 mm. When the core diameter is too small, the spin rate on
shots with a driver (W #1) may become high, as a result of which it
may not be possible to achieve the desired distance. On the other
hand, when the core diameter is too large, the durability to
repeated impact may worsen or the feel at impact may worsen.
[0023] The core has an amount of compressive deformation (mm) when
subjected to 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 3.5 mm, and
even more preferably at least 4.0 mm. The upper limit is preferably
not more than 7.0 mm, more preferably not more than 6.0 mm, and
even more preferably not more than 5.0 mm. When the compressive
deformation of the core is too small, i.e., when the core is too
hard, the spin rate of the ball may rise excessively and a good
distance may not be achieved, or the feel at impact may be too
hard. On the other hand, when the compressive deformation of the
core is too large, i.e., when the core is too soft, the ball
rebound may become too low and a good distance may not be achieved,
the feel at impact may be too soft, or the durability to cracking
on repeated impact may worsen.
[0024] The core is formed of a single layer or a plurality of
layers of rubber material. A rubber composition can be prepared as
this core-forming rubber material by using a base rubber as the
chief component and including, together with this, other
ingredients such as a co-crosslinking agent, an organic peroxide,
an inert filler and an organosulfur compound. It is preferable to
use polybutadiene as the base rubber.
[0025] Commercial products may be used as the polybutadiene.
Illustrative examples include BR01, BR51 and BR730 (all products of
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.
[0026] Examples of co-crosslinking agents include unsaturated
carboxylic acids and metal salts of unsaturated carboxylic acids.
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.
[0027] 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 5 parts by weight, preferably at least
9 parts by weight, and more preferably at least 13 parts by weight.
The amount included is typically not more than 60 parts by weight,
preferably not more than 50 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.
[0028] 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, even more preferably at least 0.5 part by
weight, and most preferably at least 0.6 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.
[0029] Another compounding ingredient typically included with the
base rubber is an inert filler, preferred examples of which include
zinc oxide, barium sulfate and calcium carbonate. One of these may
be used alone, or two or more may be used together. The amount of
inert filler included per 100 parts by weight of the base rubber is
preferably at least 1 part by weight, and more preferably at least
5 parts by weight. The upper limit is preferably not more than 50
parts by weight, more preferably not more than 40 parts by weight,
and even more preferably not more than 35 parts by weight. Too much
or too little inert filler may make it impossible to obtain a
proper weight and a suitable rebound.
[0030] In addition, an antioxidant may be optionally included.
Illustrative examples of suitable commercial antioxidants include
Nocrac NS-6 and Nocrac NS-30 (both available from Ouchi Shinko
Chemical Industry Co., Ltd.), and Yoshinox 425 (available from
Yoshitomi Pharmaceutical Industries, Ltd.). One of these may be
used alone, or two or more may be used together.
[0031] The amount of antioxidant included per 100 parts by weight
of the base rubber is set to 0 part by weight or more, preferably
at least 0.05 part by weight, and more preferably at least 0.1 part
by weight. The upper limit is set to preferably not more than 3
parts by weight, more preferably not more than 2 parts by weight,
even more preferably not more than 1 part by weight, and most
preferably not more than 0.5 part by weight. Too much or too little
antioxidant may make it impossible to achieve a suitable ball
rebound and durability.
[0032] An organosulfur compound may be included in the core in
order to impart a good resilience. The organosulfur compound is not
particularly limited, provided it can enhance the rebound of the
golf ball. Exemplary organosulfur compounds include thiophenols,
thionaphthols, halogenated thiophenols, and metal salts of these.
Specific examples include pentachlorothiophenol,
pentafluorothiophenol, pentabromothiophenol, p-chlorothiophenol,
the zinc salt of pentachlorothiophenol, the zinc salt of
pentafluorothiophenol, the zinc salt of pentabromothiophenol, the
zinc salt of p-chlorothiophenol, and any of the following having 2
to 4 sulfur atoms: diphenylpolysulfides, dibenzylpolysulfides,
dibenzoylpolysulfides, dibenzothiazoylpolysulfides and
dithiobenzoylpolysulfides. The use of the zinc salt of
pentachlorothiophenol is especially preferred.
[0033] The amount of organosulfur compound included per 100 parts
by weight of the base rubber is 0 part by weight or more, and it is
recommended that the amount be preferably at least 0.1 part by
weight, and even more preferably at least 0.2 part by weight, and
that the upper limit be preferably not more than 5 parts by weight,
more preferably not more than 3 parts by weight, and even more
preferably not more than 2 parts by weight. Including too much
organosulfur compound may make a greater rebound-improving effect
(particularly on shots with a W #1) unlikely to be obtained, may
make the core too soft or may worsen the feel of the ball at
impact. On the other hand, including too little may make a
rebound-improving effect unlikely.
[0034] Decomposition of the organic peroxide within the core
formulation can be promoted by the direct addition of water (or a
water-containing material) to the core material. The decomposition
efficiency of the organic peroxide within the core-forming rubber
composition is known to change with temperature; starting at a
given temperature, the decomposition efficiency rises with
increasing temperature. If the temperature is too high, the amount
of decomposed radicals rises excessively, leading to recombination
between radicals and, ultimately, deactivation. As a result, fewer
radicals act effectively in crosslinking. Here, when a heat of
decomposition is generated by decomposition of the organic peroxide
at the time of core vulcanization, the vicinity of the core surface
remains at substantially the same temperature as the temperature of
the vulcanization mold, but the temperature near the core center,
due to the build-up of heat of decomposition by the organic
peroxide which has decomposed from the outside, becomes
considerably higher than the mold temperature. In cases where water
(or a water-containing material) is added directly to the core,
because the water acts to promote decomposition of the organic
peroxide, radical reactions like those described above can be made
to differ at the core center and core surface. That is,
decomposition of the organic peroxide is further promoted near the
center of the core, bringing about greater radical deactivation,
which leads to a further decrease in the amount of active radicals.
As a result, it is possible to obtain a core in which the crosslink
densities at the core center and the core surface differ markedly.
It is also possible to obtain a core having different dynamic
viscoelastic properties at the core center.
[0035] The water included in the core material is not particularly
limited, and may be distilled water or tap water. The use of
distilled water that is free of impurities is especially preferred.
The amount of water included per 100 parts by weight of the base
rubber is preferably at least 0.1 part by weight, and more
preferably at least 0.3 part by weight. The upper limit is
preferably not more than 5 parts by weight, and more preferably not
more than 4 parts by weight.
[0036] The core can be produced by vulcanizing and curing the
rubber composition containing the above ingredients. For example,
the core can be produced by using a Banbury mixer, roll mill or
other mixing apparatus to intensively mix the rubber composition,
subsequently compression molding or injection molding the mixture
in a core mold, and curing the resulting molded body by suitably
heating it under conditions sufficient to allow the organic
peroxide or co-crosslinking agent to act, such as at a temperature
of between 100 and 200.degree. C., preferably between 140 and
180.degree. C., for 10 to 40 minutes.
[0037] The core may consist of a single layer alone, or may be
formed as a two-layer core consisting of an inner core layer and an
outer core layer. When the core is formed as a two-layer core
consisting of an inner core layer and an outer core layer, the
inner core layer and outer core layer materials may each be
composed primarily of the above-described rubber material. Also,
the rubber material making up the outer core layer encasing the
inner core layer may be the same as or different from the inner
core layer material. The details here are the same as those given
above for the ingredients of the core-forming rubber material.
[0038] Next, the core hardness profile is described.
[0039] The core center has a hardness (Cc) which, expressed on the
Shore C hardness scale, is preferably at least 50, more preferably
at least 53, and even more preferably at least 55. The upper limit
is preferably not more than 65, more preferably not more than 62,
and even more preferably not more than 60. When this value is too
large, the feel at impact may become hard, 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 low, resulting in a poor distance, or the
durability to cracking on repeated impact may worsen. The Shore C
hardness is the hardness value measured with a Shore C durometer in
general accordance with ASTM D2240. Although, for example, the
timing of the read-off of measurements differs from that in the
technique used for measuring JIS-C hardness, the measured Shore C
hardness values do not differ much from and, in fact, are closely
similar to the JIS-C values.
[0040] Alternatively, the core center hardness (Cc) expressed on
the Shore D hardness scale is preferably at least 26, more
preferably at least 28, and even more preferably at least 30. The
upper limit is preferably not more than 40, more preferably not
more than 37, and even more preferably not more than 34.
[0041] The core surface has a hardness (Cs) which, expressed on the
Shore C hardness scale, is preferably at least 73, more preferably
at least 77, and even more preferably at least 80. The upper limit
is preferably not more than 89, more preferably not more than 87,
and even more preferably not more than 85. A value outside of this
range may lead to undesirable results similar to those described
above for the core center hardness (Cc).
[0042] Alternatively, the core surface hardness (Cs) expressed on
the Shore D hardness scale is preferably at least 40, more
preferably at least 43, and even more preferably at least 45. The
upper limit is preferably not more than 54, more preferably not
more than 52, and even more preferably not more than 50.
[0043] The difference between the core surface hardness (Cs) and
the core center hardness (Cc), expressed on the Shore C hardness
scale, is preferably at least 20, more preferably at least 22, and
even more preferably at least 24. The upper limit is preferably not
more than 32, and more preferably not more than 30. When this value
is too small, the ball spin rate-lowering effect on shots with a
driver may be inadequate, resulting in a poor distance. When this
value is too large, the initial velocity of the ball when struck
may decrease, resulting in a poor distance, or the durability to
cracking on repeated impact may worsen.
[0044] Next, the cover is described.
[0045] The cover has a material hardness on the Shore D scale
which, although not particularly limited, is preferably at least
55, more preferably at least 59, and even more preferably at least
61. The upper limit is preferably not more than 70, more preferably
not more than 68, and even more preferably not more than 65. The
surface hardness of the cover (also referred to herein as the "ball
surface hardness"), expressed on the Shore D scale, is preferably
at least 61, more preferably at least 65, and even more preferably
at least 67. The upper limit is preferably not more than 76, more
preferably not more than 74, and even more preferably not more than
71. When the material hardness of the cover and the ball surface
hardness are too much lower than the above respective ranges, the
spin rate of the ball on shots with a driver (W #1) may rise and
the ball initial velocity may decrease, as a result of which a good
distance may not be obtained. On the other hand, when the material
hardness of the cover and the ball surface hardness are too high,
the durability to cracking on repeated impact may worsen.
[0046] The cover has a thickness of preferably at least 0.6 mm,
more preferably at least 0.8 mm, and even more preferably at least
1.1 mm. The upper limit in the cover thickness is preferably not
more than 1.5 mm, more preferably not more than 1.4 mm, and even
more preferably not more than 1.3 mm. When the cover is too thin,
the durability to cracking on repeated impact may worsen. When the
cover is too thick, the spin rate of the ball on shots with a
driver (W #1) may rise excessively and a good distance may not be
obtained, or the feel at impact in the short game and on shots with
a putter may be too hard.
[0047] Various types of thermoplastic resins, particularly ionomer
resins, that are employed as cover stock in golf balls may be
suitably used as the cover material. Commercial products may be
used as the ionomer resin. Alternatively, the cover-forming resin
material that is used may be one obtained by blending, of
commercially available ionomer resins, a high-acid ionomer resin
having an acid content of at least 18 wt % into a conventional
ionomer resin. The high rebound and the spin rate-lowering effect
obtained with such a blend make it possible to achieve a good
distance on shots with a driver (W #1). The amount of such a
high-acid ionomer resin included per 100 parts by weight of the
resin material is preferably at least 10 wt %, more preferably at
least 30 wt %, and even more preferably at least 60 wt %. The upper
limit is generally up to 100 wt %, preferably up to 90 wt %, and
more preferably up to 80 wt %. When the content of this high-acid
ionomer resin is too low, the spin rate on shots with a driver (W
#1) may rise, resulting in a poor distance. On the other hand, when
the content of the high-acid ionomer resin is too high, the
durability to cracking on repeated impact may worsen.
[0048] The envelope layer and intermediate layer described below
may be provided between the core and cover. Suitable ball
constructions in the present invention are not limited to two-piece
golf balls having a core and a single-layer cover; three-piece golf
balls and four-piece golf balls may also be used. The use of golf
balls composed of four layers--a core, an envelope layer, an
intermediate layer and a cover--is especially suitable. Such golf
balls are exemplified by the golf ball G shown in the FIGURE. The
golf ball G in the FIGURE has a core 1, an envelope layer 2
encasing the core 1, an intermediate layer 3 encasing the envelope
layer 2, and a cover 4 encasing the intermediate layer 3. This
cover 4 is positioned as the outermost layer, aside from a paint
film layer, in the layer structure of the golf ball. The
intermediate layer and the envelope layer may each be either a
single layer or may be formed of two or more layers. Numerous
dimples D are generally formed on the surface of the cover
(outermost layer) 4 in order to enhance the aerodynamic properties.
In addition, a paint film layer 5 is formed on the surface of the
cover 4.
[0049] Next, the envelope layer is described.
[0050] The envelope layer has a material hardness on the Shore D
scale which, although not particularly limited, is preferably at
least 20, more preferably at least 23, and even more preferably at
least 27. The upper limit is preferably not more than 45, more
preferably not more than 42, and even more preferably not more than
40. The surface hardness of the sphere obtained by encasing the
core with the envelope layer (envelope layer-encased sphere),
expressed on the Shore D scale, is preferably at least 28, more
preferably at least 31, and even more preferably at least 35. The
upper limit is preferably not more than 53, more preferably not
more than 50, and even more preferably not more than 48. When the
material and surface hardnesses of the envelope layer are lower
than the above respective ranges, the spin rate of the ball on full
shots may rise excessively, resulting in a poor distance, or the
durability of the ball to repeated impact may worsen. On the other
hand, when the material and surface hardnesses are too high, the
durability to cracking on repeated impact may worsen or the spin
rate on full shots may rise, as a result of which, particularly on
low head speed shots, a good distance may not be achieved, and the
feel at impact may worsen.
[0051] The envelope layer has a thickness of 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 envelope layer thickness is
preferably not more than 1.5 mm, more preferably not more than 1.4
mm, and even more preferably not more than 1.3 mm. When this
envelope layer is too thin, the durability to cracking on repeated
impact may worsen or the feel at impact may worsen. When the
envelope layer is too thick, the spin rate of the ball on full
shots may rise and a good distance may not be achieved.
[0052] The envelope layer material is not particularly limited,
although various types of thermoplastic resin materials may be
suitably employed for this purpose. For example, use can be made of
ionomer resins, urethane, amide, ester, olefin or styrene-type
thermoplastic elastomers, and mixtures thereof. From the standpoint
of obtaining a good rebound in the desired hardness range, the use
of a thermoplastic polyether ester elastomer is especially
suitable.
[0053] The sphere obtained by encasing the core with the envelope
layer (envelope layer-encased sphere) has an amount of compressive
deformation (mm) when subjected to 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 3.4 mm, more
preferably at least 3.8 mm, and even more preferably at least 3.9
mm. The upper limit is preferably not more than 4.7 mm, more
preferably not more than 4.5 mm, and even more preferably not more
than 4.3 mm. When the compressive deformation of the sphere is too
small, that is, when the sphere is too hard, the ball spin rate may
rise excessively, resulting in a poor distance, or the feel at
impact may become too hard. On the other hand, when the compressive
deformation of the sphere is too large, that is, when the sphere is
too soft, the ball rebound may become too low, resulting in a poor
distance, the feel at impact may become too soft, or the durability
to cracking on repeated impact may worsen.
[0054] Next, the intermediate layer is described.
[0055] The intermediate layer has a material hardness on the Shore
D scale which, although not particularly limited, is preferably at
least 40, more preferably at least 45, and even more preferably at
least 50. The upper limit is preferably not more than 62, more
preferably not more than 60, and even more preferably not more than
58. The surface hardness of the sphere obtained by encasing the
envelope layer-encased sphere with the intermediate layer
(intermediate layer-encased sphere), expressed on the Shore D
scale, is preferably at least 46, more preferably at least 51, and
even more preferably at least 56. The upper limit is preferably not
more than 68, more preferably not more than 66, and even more
preferably not more than 64. When the material and surface
hardnesses of the intermediate layer are lower than the above
respective ranges, the spin rate of the ball on full shots may rise
excessively, resulting in a poor distance, or the ball may cease to
have a solid feel at impact. On the other hand, when the material
and surface hardnesses are too high, the durability to cracking on
repeated impact may worsen or the ball may cease to have a soft
feel at impact.
[0056] The intermediate layer has a thickness of 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 intermediate
layer thickness is preferably not more than 1.5 mm, more preferably
not more than 1.4 mm, and even more preferably not more than 1.35
mm. When the intermediate layer is too thin, the durability to
cracking on repeated impact may worsen or the feel at impact may
worsen. When the intermediate layer is too thick, the spin rate of
the ball on full shots may rise and a good distance may not be
obtained.
[0057] The intermediate layer-forming material is not particularly
limited and may be a known resin. Examples of preferred materials
include resin compositions containing as the essential
ingredients:
100 parts by weight of a resin component composed of, in
admixture,
[0058] (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
[0059] (B) a non-ionomeric thermoplastic elastomer in a weight
ratio between 100:0 and 50:50;
[0060] (C) from 5 to 80 parts by weight of a fatty acid and/or
fatty acid derivative having a molecular weight of from 228 to
1,500; and
[0061] (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.
[0062] 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.
[0063] A non-ionomeric thermoplastic elastomer may be included in
the intermediate layer material. The amount of non-ionomeric
thermoplastic elastomer included is preferably from 0 to 50 parts
by weight per 100 parts by weight of the total amount of the base
resin.
[0064] Exemplary non-ionomeric thermoplastic elastomers include
polyolefin elastomers (including polyolefin and metallocene
polyolefins), polystyrene elastomers, diene polymers, polyacrylate
polymers, polyamide elastomers, polyurethane elastomers, polyester
elastomers and polyacetals.
[0065] 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 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.
[0066] The sphere obtained by encasing the envelope-encased sphere
with the intermediate layer (intermediate layer-encased sphere) has
an amount of compressive deformation when subjected to 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 3.3 mm,
more preferably at least 3.45 mm, and even more preferably at least
3.6 mm. The upper limit is preferably not more than 4.2 mm, more
preferably not more than 4.0 mm, and even more preferably not more
than 3.8 mm. When the compressive deformation of the sphere is too
small, that is, when the sphere is too hard, the ball spin rate may
rise excessively, resulting in a poor distance, or the feel at
impact may become too hard. On the other hand, when the compressive
deformation of the sphere is too large, that is, when the sphere is
too soft, the ball rebound may become too low, resulting in a poor
distance, the feel at impact may become too soft, or the durability
to cracking on repeated impact may worsen.
[0067] The manufacture of multi-piece solid golf balls in which the
above-described core, 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 obtained by
successively injection-molding the envelope layer material and the
intermediate layer material over the core so as to obtain an
intermediate layer-encased sphere, and then injection-molding the
cover material 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.
[0068] The compressive deformation A of the inventive golf ball
when subjected to a final load of 5 kg from an initial load state
of 0.2 kg is 0.21 mm or less, preferably 0.19 mm or less, and more
preferably 0.17 mm or less. The lower limit is preferably at least
0.10 mm, and more preferably at least 0.12 mm. When this value
becomes smaller, in cases where this is attributable to the cover
hardness, the cover may be too hard and the durability of the ball
to cracking under repeated impact may worsen. Alternatively, when
this value becomes smaller owing to compression of an inner layer,
the feel of the ball on full shots may become too hard. On the
other hand, when the above value becomes larger, in cases where
this is attributable to the cover hardness, the spin rate of the
ball on full shots may end up rising, so that a good distance is
not achieved. Alternatively, when this value becomes larger owing
to compression of an inner layer, the ball may cease to have a
crisp feel on full shots and a good distance may not be
achieved.
[0069] The compressive deformation B of the inventive golf ball
when subjected to a final load of 30 kg from an initial load state
of 5 kg is preferably at least 0.72 mm, more preferably at least
0.73 mm, and even more preferably at least 0.74 mm. The upper limit
is preferably not more than 0.90 mm, more preferably not more than
0.88 mm, and even more preferably not more than 0.86 mm. If this
value is small, the ball may have too hard a feel when struck with
a utility club (also abbreviated below as "UT") or an iron. On the
other hand, if this value is large, the crisp feel of the ball when
struck with a utility club or an iron may diminish and a good
distance may not be achieved.
[0070] The compressive deformation C of the inventive golf ball
when subjected to a final load of 60 kg from an initial load state
of 5 kg is preferably at least 1.55 mm, more preferably at least
1.56 mm, and even more preferably at least 1.58 mm. The upper limit
is preferably not more than 1.80 mm, more preferably not more than
1.77 mm, and even more preferably not more than 1.74 mm. If this
value is small, the ball may have too hard a feel at impact when
struck with a utility club or an iron. On the other hand, if this
value is large, the crisp feel of the ball when struck with a
utility club or an iron may diminish and a good distance may not be
achieved.
[0071] The compressive deformation D of the inventive golf ball
when subjected to a final load of 130 kg from an initial load state
of 10 kg is preferably at least 2.80 mm, more preferably at least
2.90 mm, and even more preferably at least 2.95 mm. The upper limit
is preferably not more than 3.40 mm, more preferably not more than
3.30 mm, and even more preferably not more than 3.15 mm. If this
value is small, the spin rate of the ball may rise, resulting in a
poor distance, or the feel of the ball may become too hard. On the
other hand, if this value is large, the ball rebound may become too
low, resulting in a poor distance, the feel of the ball may become
too soft, or the durability to cracking under repeated impact may
worsen.
[0072] The ratio D/C between compressive deformation D and
compressive deformation C is preferably from 1.80 to 1.90. Outside
of this range, the solid feel of the ball may worsen and impact
conditions under which the distance falls may arise.
[0073] The ratio D/B between compressive deformation D and
compressive deformation B is preferably at least 3.65, more
preferably at least 3.67, and even more preferably at least 3.69.
The upper limit is preferably not more than 4.20, more preferably
not more than 4.15, and even more preferably not more than 4.10.
Outside of this range, the solid feel of the ball may worsen and
impact conditions under which the distance falls may arise.
[0074] The ratio D/A between compressive deformation D and
compressive deformation A is preferably at least 16.0, more
preferably at least 17.0, and even more preferably at least 17.5.
The upper limit is preferably not more than 25.0, more preferably
not more than 24.0, and even more preferably not more than 23.0.
Outside of this range, the ball may become too receptive to spin or
the initial velocity of the ball when struck may decrease and,
depending on the number of the golf club, the distance may
decrease.
Surface Hardness Relationships Among Layers
[0075] In this invention, it is desirable for the hardness
relationships among the layers to satisfy formula (1) below:
(1) Shore D hardness at cover surface>Shore D hardness at
intermediate layer surface>Shore D hardness at envelope layer
surface>Shore D hardness at core center.
[0076] Here, the hardness at the cover surface refers to the
surface hardness of the ball. The hardness at the intermediate
layer surface refers to the surface hardness of the intermediate
layer-encased sphere, and the hardness at the envelope layer
surface refers to the surface hardness of the envelope
layer-encased sphere.
[0077] When the above hardness relationship is not satisfied, a
good flight performance and a feel at impact that is both soft and
solid may not be obtained.
[0078] As indicated in the above formula, the cover surface
hardness is larger than the intermediate layer surface hardness.
The difference therebetween, i.e., the "cover surface
hardness-intermediate layer surface hardness" value, expressed on
the Shore D hardness scale, is preferably from 1 to 14, more
preferably from 3 to 10, and even more preferably from 5 to 8. When
this value is small, the spin rate of the ball on full shots may
end up rising, as a result of which a good distance may not be
achieved. On the other hand, when this value is large, the feel at
impact may worsen or the durability to cracking on repeated impact
may worsen.
[0079] As indicated in the above formula, the intermediate layer
surface hardness is larger than the envelope layer surface
hardness. The difference therebetween, i.e., the "intermediate
layer surface hardness-envelope layer surface hardness" value,
expressed on the Shore D hardness scale, is preferably from 10 to
28, more preferably from 13 to 26, and even more preferably from 15
to 24. When this value is small, the spin rate of the ball on full
shots may end up rising, as a result of which a good distance may
not be achieved. On the other hand, when this value is large, the
feel at impact may worsen or the durability to cracking on repeated
impact may worsen.
[0080] As indicated in the above formula, the envelope layer
surface hardness is larger than the core center hardness. The
difference therebetween, i.e., the "envelope layer surface
hardness-core center hardness" value, expressed on the Shore D
hardness scale, is preferably from 3 to 23, more preferably from 5
to 20, and even more preferably from 7 to 17. Also, the "envelope
layer surface hardness-core surface hardness" value, expressed on
the Shore D hardness scale, is preferably from -20 to 8, more
preferably from -15 to 5, and even more preferably from -10 to 2.
When these values are small, the spin rate of the ball on full
shots may end up rising, as a result of which a good distance may
not be achieved. On the other hand, when these values are large,
the feel at impact may worsen or the durability to cracking on
repeated impact may worsen.
[0081] Also, the "core surface hardness-ball surface hardness"
value, expressed on the Shore D hardness scale, is preferably from
-30 to -10, more preferably from -27 to -14, and even more
preferably from -24 to -17. When this value is small, the solid
feel of the ball at impact may be lost or the durability to
cracking on repeated impact may worsen. On the other hand, when
this value is large, impact conditions may emerge under which the
spin rate of the ball rises and a good distance is not
achieved.
Compressive Deformation Relationships among Encased Spheres
[0082] Letting P and Q be the respective compressive deformations
(mm) of the core and the envelope layer-encased sphere when
subjected to a final load of 1,275 N (130 kg) from an initial load
of 98 N (10 kgf), the value P-Q is preferably from 0 to 0.6 mm,
more preferably from 0.1 to 0.5 mm, and even more preferably from
0.2 to 0.4 mm. When this value is small, the feel at impact may
worsen or the durability to cracking under repeated impact may
worsen. When this value is large, the spin rate of the ball on full
shots may end up rising, as a result of which a good distance may
not be obtained.
[0083] Letting Q and R be the respective compressive deformations
(mm) of the envelope layer-encased sphere and the intermediate
layer-encased sphere when subjected to a final load of 1,275 N (130
kg) from an initial load of 98 N (10 kgf), the value Q-R is
preferably from 0.1 to 0.8 mm, more preferably from 0.2 to 0.7 mm,
and even more preferably from 0.3 to 0.6 mm. When this value is
small, the spin rate of the ball on full shots may end up rising,
as a result of which a good distance may not be achieved. On the
other hand, when this value is large, the feel at impact may worsen
or the durability to cracking on repeated impact may worsen.
[0084] Letting P and D be the respective compressive deformations
(mm) of the core and the ball when subjected to a final load of
1,275 N (130 kg) from an initial load of 98 N (10 kgf), the value
P-D is preferably from 1.0 to 1.7 mm, more preferably from 1.1 to
1.6 mm, and even more preferably from 1.2 to 1.5 mm. When this
value is small, the spin rate of the ball on full shots may end up
rising, as a result of which a good distance may not be achieved.
On the other hand, when this value is large, the solid feel at
impact may be lost or the durability to cracking on repeated impact
may worsen.
Initial Velocity Relationships Among Encased Spheres
[0085] The "ball initial velocity-core initial velocity" value is
preferably from -0.8 to 0 m/s, more preferably from -0.6 to -0.1
m/s, and even more preferably from -0.5 to -0.3 m/s. When this
value is too small, the rebound of the overall ball may become low
or the spin rate on full shots may rise excessively, as a result of
which a good distance may not be obtained. On the other hand, when
this value is too large, the cover may become hard and the
durability to cracking on repeated impact may worsen. As used
herein, "initial velocity" refers to the initial velocity of the
various spheres--i.e., the ball, the core, and the subsequently
described intermediate layer-encased sphere and envelope
layer-encased sphere--as measured by the method, set forth in the
Rules of Golf, for measuring the initial velocity of golf balls
using an initial velocity measuring apparatus of the same type as
the USGA drum rotation-type initial velocity instrument.
[0086] The "ball initial velocity-intermediate layer-encased sphere
initial velocity" value is preferably from -0.4 to 0.4 m/s, more
preferably from -0.3 to 0.3 m/s, and even more preferably from -0.2
to 0.1 m/s. When this value is too large, the spin rate-lowering
effect on full shots may be inadequate and a good distance may not
be achieved, or the cover may become hard, worsening the durability
to cracking on repeated impact. On the other hand, when this value
is too small, the cover may become soft, as a result of which the
spin rate on full shots may rise, resulting in a poor distance, or
a solid feel at impact may not be obtained.
[0087] The "intermediate layer-encased sphere initial
velocity-envelope layer-encased sphere initial velocity" value is
at least 0.0 m/s, preferably from 0.1 to 0.4 m/s, and more
preferably from 0.15 to 0.3 m/s. When this value is too small, the
spin rate-lowering effect on full shots may be inadequate and a
good distance may not be achieved. On the other hand, when this
value is too large, the intermediate layer material may become
brittle and the durability to cracking on repeated impact may
worsen.
[0088] Numerous dimples may be formed on the outside 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 250, more preferably at least 300, and even
more preferably at least 320. The upper limit is preferably not
more than 380, more preferably not more than 350, and even more
preferably not more than 340. When the number of dimples is higher
than this range, the ball trajectory may become lower, as a result
of which 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, as a result of which a good
distance may not be achieved.
[0089] 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.
[0090] 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 a 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 obtained and so the
ball may fail to travel a fully satisfactory distance.
[0091] To ensure a good ball appearance, it is preferable to apply
a clear coating onto the cover surface. The coating composition
used in clear coating is preferably one which uses two types of
polyester polyol as the base resin and uses a polyisocyanate as the
curing agent. In this case, various organic solvents can be admixed
depending on the intended coating conditions. Examples of organic
solvents that can be used 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-based solvents such as mineral spirits.
[0092] The paint film layer (coating layer) obtained by clear
coating has a hardness which, on the Shore C hardness scale, is
preferably from 40 to 80, more preferably from 47 to 72, and even
more preferably from 55 to 65. When the coating layer is too soft,
mud may tend to stick to the surface of the ball when used for
golfing. On the other hand, when the coating layer is too hard, it
may tend to peel off when the ball is struck.
[0093] The "core center hardness (Cc)-coating layer hardness" value
on the Shore C hardness scale is preferably from -15 to 5, more
preferably from -10 to 0, and even more preferably from -7 to -5.
When this value falls outside of the above range, the spin rate of
the ball on full shots may end up rising, as a result of which a
good distance may not be achieved.
[0094] The paint film layer (coating layer) has a thickness of
typically from 9 to 22 .mu.m, preferably from 11 to 20 .mu.m, and
more preferably from 13 to 18 .mu.m.
[0095] 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
[0096] The following Examples and Comparative Examples are provided
to illustrate the invention, and are not intended to limit the
scope thereof.
Examples 1 to 4, Comparative Examples 1 to 5
Formation of Core
[0097] Solid cores were produced by preparing rubber compositions
for the respective Examples and Comparative Examples shown in Table
1, and then molding/vulcanizing the compositions under
vulcanization conditions of 155.degree. C. and 15 minutes.
TABLE-US-00001 TABLE 1 Core formulation Example Comparative Example
(pbw) 1 2 3 4 1 2 3 4 5 Polybutadiene A 80 80 80 80 80 80 80 80 100
Polybutadiene B 20 20 20 20 20 20 20 20 Zinc acrylate 28.2 26.9
29.6 28.2 28.2 29.6 30.9 29.6 27.0 Organic peroxide (1) 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 0.6 Organic peroxide (2) 0.6 Water 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 Antioxidant 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Barium sulfate 27.4 27.9 26.8 27.4 27.4 26.8 26.3 26.8 24.3 Zinc
oxide 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Zinc salt of
pentachlorothiophenol 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Details on
the ingredients mentioned in Table 1 are given below. Polybutadiene
A: Available under the trade name "BR 01" from JSR Corporation
Polybutadiene B: Available under the trade name "BR 51" from JSR
Corporation Zinc acrylate: Available as "ZN-DA85S" from Nippon
Shokubai Co., Ltd. Organic Peroxide (1): Dicumyl peroxide,
available under the trade name "Percumyl D" from NOF Corporation
Organic Peroxide (2): A mixture of 1,1-di(t-butylperoxy)cyclohexane
and silica, available under the trade name "Perhexa C-40" from NOF
Corporation Water: Pure water (from Seiki Chemical Industrial Co.,
Ltd.) Antioxidant: 2,2'-Methylenebis(4-methyl-6-butylphenol),
available under the trade name "Nocrac NS-6" from Ouchi Shinko
Chemical Industry Co., Ltd. Barium sulfate: Baryte powder available
as "Barico #100" from Hakusui Tech Zinc oxide: Available as "Zinc
Oxide Grade 3" from Sakai Chemical Co., Ltd. Zinc salt of
pentachlorothiophenol: Available from Wako Pure Chemical
Industries, Ltd.
Formation of Envelope Layer and Intermediate Layer
[0098] Next, in each Example and Comparative Example other than
Comparative Example 5, an envelope layer was formed by injection
molding the envelope layer material formulated as shown in Table 2
over the core, following which the intermediate layer was formed by
injection molding the intermediate layer material formulated as
shown in the same table, thereby giving a sphere encased by an
envelope layer and an intermediate layer. In Comparative Example 5,
an intermediate layer was formed by injection molding the
intermediate layer material formulated as shown in Table 2 over the
core, thereby giving an intermediate layer-encased sphere.
Formation of Cover (Outermost Layer)
[0099] Next, in all of the Examples and Comparative Examples, a
cover (outermost layer) was formed by injection molding the cover
material formulated as shown in Table 2 over the intermediate
layer-encased sphere obtained as described above. 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-00002 TABLE 2 Resin composition (pbw) No. 1 No. 2 No. 3
No. 4 No. 5 No. 6 No. 7 No. 8 Hytrel 4001 100 Hytrel 3001 100 HPF
2000 100 HPF 1000 100 56 Himilan 1605 44 50 AM 7318 75 AM 7327 25
AM 7329 50 Surlyn 9320 70 AN 4221C 30 Magnesium 60 stearate
Magnesium 1.12 oxide Titanium oxide 4 4 Trade names of the chief
materials mentioned in the table are given below. Hytrel: Polyester
elastomers available from DuPont-Toray Co., Ltd. HPF 1000: DuPont
.TM. HPF1000 HPF 2000: DuPont .TM. HPF 2000 Himilan, AM7318,
AM7327, AM7329: Ionomers available from DuPont-Mitsui Polychemicals
Co., Ltd. Surlyn: An ionomer available from E.I. DuPont de Nemours
& Co. AN 4221C: Available under the trade name "Nucrel" from
DuPont-Mitsui Polychemicals Co., Ltd. Magnesium stearate: Available
as "Magnesium Stearate G" from NOF Corporation Magnesium oxide:
Available as "Kyowamag MF-150" from Kyowa Chemical Industry Co.,
Ltd. Titanium oxide: Available from Sakai Chemical Industry Co.,
Ltd.
Formation of Paint Film Layer (Coating Layer)
[0100] Next, the paint formulated as shown in Table 3 below was
applied with an air spray gun onto the surface of the cover
(outermost layer) on which numerous dimples had been formed,
thereby producing golf balls having a 15 .mu.m-thick paint film
layer formed thereon.
TABLE-US-00003 TABLE 3 Paint C Base resin Polyol 29.77 composition
Additive 0.22 (pbw) Solvent 70.01 Curing agent Isocyanate 42
Solvent 58 Paint film properties Shore C hardness 62.5 Thickness
(.mu.m) 15
[0101] A polyester polyol synthesized as follows was used as the
polyol in the base resin.
[0102] 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 temperature was
raised to between 200 and 240.degree. C. under stirring and the
reaction was effected by 5 hours of heating. This yielded a
polyester polyol having an acid value of 4, a hydroxyl value of 170
and a weight-average molecular weight (Mw) of 28,000. The additives
were water repellent additives. All the additives used were
commercial products. Products that were silicone-based additives,
stain resistance-improving silicone additives, or fluoropolymers
having an alkyl group chain length of 7 or less were added.
[0103] The isocyanate used in the curing agent was Duranate.TM.
TPA-100 (from Asahi Kasei Corporation; NCO content, 23.1%; 100%
nonvolatiles), an isocyanurate of hexamethylene diisocyanate
(HMDI).
[0104] Butyl acetate was used as the base resin solvent, and ethyl
acetate and butyl acetate were used as the curing agent solvents.
The Shore C hardness values in the table were obtained by preparing
sheets having a thickness of 2 mm, stacking together three such
sheets, and carrying out measurement with a Shore C durometer in
general accordance with ASTM D2240.
[0105] Various properties of the resulting golf balls, including
the core center and surface hardnesses, the diameters of the core
and the respective layer-encased spheres, the thickness and
material hardness of each layer, and the surface hardness, initial
velocity and compressive deformation under specific loading of the
respective layer-encased spheres were evaluated by the following
methods. The results are presented in Table 4.
Diameters of Core, Envelope Layer-Encased Sphere and Intermediate
Layer-Encased Sphere
[0106] 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 diameters for ten test specimens were
determined.
Diameter of Ball
[0107] The diameters at 15 random dimple-free areas on the surface
of a ball 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 ball, the average diameter for ten measured balls was
determined.
Compressive Deformations of Core, Envelope Layer-Encased Sphere,
Intermediate Layer-Encased Sphere and Ball
[0108] A core, envelope layer-encased sphere, intermediate
layer-encased sphere or ball was placed on a hard plate and the
compressive deformation A when subjected to a final load of 5 kgf
from an initial load of 0.2 kg, the compressive deformation B when
subjected to a final load of 30 kgf from an initial load of 5 kg,
the compressive deformation C when subjected to a final load of 60
kgf from an initial load of 5 kg and the compressive deformation D
when subjected to a final load of 130 kgf from an initial load of
10 kg were each measured. These compressive deformations refer in
each case to a measured value obtained after holding the test
specimen isothermally at 23.9.degree. C. The instrument used was a
high-load compression tester available from MU Instruments Trading
Corporation. Measurement was carried out with the pressing head
moving downward at a speed of 4.7 mm/sec.
Core Hardness Profile
[0109] The indenter of a durometer was set substantially
perpendicular to the spherical surface of the core, and the surface
hardness of the core on the Shore C hardness scale was measured in
accordance with ASTM D2240. The hardness at the center of the core
was measured by perpendicularly pressing the indenter of a
durometer against the center region of the flat cross-section
obtained by cutting the core into hemispheres. The measurement
results are indicated as Shore C hardness values.
Material Hardnesses (Shore D Hardnesses) of Envelope Layer,
Intermediate Layer and Cover
[0110] The resin materials for each of these layers were molded
into sheets having a thickness of 2 mm and left to stand for at
least two weeks, following which the Shore D hardnesses were
measured in accordance with ASTM D2240.
Surface Hardnesses (Shore D Hardnesses) of Envelope Layer-Encased
Sphere, Intermediate Layer-Encased Sphere and Ball
[0111] Measurements were taken by pressing the durometer indenter
perpendicularly against the surface of each sphere. The surface
hardness of the ball (cover) is the measured value obtained at
dimple-free places (lands) on the ball surface. The Shore D
hardnesses were measured with a type D durometer in accordance with
ASTM D2240.
Initial Velocities of Core, Envelope Layer-Encased Sphere,
Intermediate Layer-Encased Sphere and Ball
[0112] The initial velocity was measured using an initial velocity
measuring apparatus of the same type as the USGA drum rotation-type
initial velocity instrument approved by the R&A. The cores,
envelope layer-encased spheres, intermediate layer-encased spheres
and balls (referred to collectively below as the "test spheres")
were tested in a chamber at a room temperature of 23.9.+-.2.degree.
C. after being held isothermally in a 23.9.+-.1.degree. C.
environment for at least 3 hours. Each test sphere was hit using a
250-pound (113.4 kg) head (striking mass) at an impact velocity of
143.8 ft/s (43.83 m/s). One dozen test spheres were each hit four
times. The time taken for the test sphere to traverse a distance of
6.28 ft (1.91 m) was measured and used to compute the initial
velocity (m/s). This cycle was carried out over a period of about
15 minutes.
TABLE-US-00004 TABLE 4 Example Comparative Example 1 2 3 4 1 2 3 4
5 Construction 4-piece 4-piece 4-piece 4-piece 4-piece 4-piece
4-piece 4-piece 3-piece Core Diameter (mm) 35.17 35.18 35.23 35.17
35.17 35.23 35.18 35.23 37.29 Weight (g) 27.8 27.8 27.9 27.8 27.8
27.9 27.8 27.9 32.6 Compressive deformation P (mm) 4.4 4.6 4.2 4.4
4.4 4.2 4.0 4.2 3.2 Initial velocity (m/s) 77.6 77.5 77.5 77.6 77.6
77.5 77.6 77.5 77.0 Core Surface hardness (Cs) Shore C 83.2 80.8
84.3 83.2 83.2 84.3 85.0 84.3 83.9 hardness Center hardness (Cc)
55.9 55.6 57.2 55.9 55.9 57.2 57.4 57.2 66.5 profile Surface
hardness - Center hardness 27.3 25.2 27.1 27.3 27.3 27.1 27.6 27.1
17.4 (Cs - Cc) Surface hardness (Cs) Shore D 48.2 46.4 49.1 48.2
48.2 49.1 49.6 49.1 48.8 Center hardness (Cc) 31.7 31.5 32.4 31.7
31.7 32.4 32.5 32.4 37.3 Surface hardness - Center hardness 16.5
14.9 16.7 16.5 16.5 16.7 17.1 16.7 11.5 (Cs - Cc) Envelope Material
No. 1 No. 1 No. 2 No. 2 No. 2 No. 1 No. 2 No. 2 -- layer Thickness
(mm) 1.24 1.24 1.22 1.25 1.25 1.21 1.25 1.22 -- Material hardness
(sheet hardness: Shore D) 40 40 27 27 27 40 27 27 -- Envelope
Diameter (mm) 37.65 37.66 37.67 37.67 37.67 37.65 37.68 37.67 --
layer- Weight (g) 33.6 33.7 33.6 33.5 33.5 33.7 33.6 33.6 --
encased Compressive deformation Q (mm) 4.05 4.30 3.90 4.12 4.12
3.86 3.68 3.90 -- sphere Initial velocity (m/s) 77.0 77.0 76.9 77.0
77.0 77.0 76.8 76.9 -- Surface hardness Shore D 46 46 41 41 41 46
41 41 -- Envelope layer surface hardness - Core Shore D 14 14 9 9 9
14 9 9 -- center hardness Envelope layer surface hardness - Core
Shore D -2 0 -8 -7 -7 -3 -9 -8 -- surface hardness Difference in
compressive deformation between 0.38 0.29 0.33 0.31 0.31 0.36 0.33
0.33 -- core and envelope layer-encased sphere: P - Q (mm) Inter-
Material No. 5 No. 5 No. 5 No. 5 No. 6 No. 5 No. 3 No. 3 No. 4
mediate Thickness (mm) 1.31 1.30 1.29 1.30 1.28 1.31 1.29 1.29 1.36
layer Material hardness (sheet hardness: Shore D) 57 57 57 57 52 57
47 47 51 Inter- Diameter (mm) 40.27 40.27 40.26 40.28 40.24 40.28
40.26 40.26 40.00 mediate Weight (g) 39.57 39.53 39.35 39.38 39.41
39.57 39.44 39.45 38.7 layer- Compressive deformation R (mm) 3.61
3.78 3.58 3.76 3.76 3.44 3.49 3.71 3.01 encased Initial velocity
(m/s) 77.2 77.1 77.1 77.2 77.1 77.1 76.9 76.9 77.0 sphere Surface
hardness Shore D 63 63 63 63 60 63 53 53 58 Intermediate layer
surface hardness - Shore D 17 17 22 22 19 17 12 12 -- Envelope
layer surface hardness Difference in compressive deformation
between envelope 0.44 0.52 0.32 0.36 0.37 0.42 0.19 0.19 --
layer-encased sphere and intermediate layer-encased sphere: Q - R
(mm) Initial velocity of intermediate layer-encased sphere - 0.2
0.2 0.2 0.2 0.2 0.0 0.0 0.0 -- Initial velocity of envelope
layer-encased sphere (m/s) Cover Material No. 7 No. 7 No. 7 No. 7
No. 7 No. 7 No. 7 No. 7 No. 8 Thickness (mm) 1.23 1.22 1.23 1.22
1.25 1.22 1.23 1.23 1.34 Material hardness (sheet hardness: Shore
D) 62 62 62 62 62 62 62 62 64 Paint film Material Paint C Paint C
Paint C Paint C Paint C Paint C Paint C Paint C Paint C layer
Material hardness (sheet hardness) 62.5 62.5 62.5 62.5 62.5 62.5
62.5 62.5 62.5 Core center hardness - Material hardness of Shore C
-6.6 -6.9 -5.3 -6.6 -6.6 -5.3 -5.1 -5.3 4.0 paint film layer Ball
Diameter (mm) 42.73 42.72 42.72 42.72 42.73 42.72 42.73 42.73 42.67
Weight (g) 45.6 45.5 45.4 45.4 45.5 45.6 45.5 45.4 45.4 Compressive
deformation (A) under 0.2 to 5 kg 0.17 0.16 0.13 0.17 0.14 0.16
0.17 0.18 0.13 loading (mm) Compressive deformation (B) under 5 to
30 kg 0.74 0.78 0.75 0.84 0.86 0.71 0.98 0.98 0.72 loading (mm)
Compressive deformation (C) under 5 to 60 kg 1.58 1.68 1.66 1.72
1.81 1.53 1.86 1.93 1.40 loading (mm) Compressive deformation (D)
under 10 to 130 kg 2.98 3.12 3.01 3.10 3.24 2.89 3.20 3.31 2.64
loading (mm) Initial velocity (m/s) 77.2 77.1 77.1 77.1 77.3 77.1
77.0 77.1 77.3 Surface hardness Shore D 68 68 68 68 68 68 68 68 71
Core surface hardness - Ball surface hardness Shore D -20 -22 -19
-20 -20 -19 -18 -19 -22 Ball surface hardness - Intermediate layer
Shore D 5 5 5 5 8 5 15 15 13 surface hardness Difference in
compressive deformation between core and 1.45 1.47 1.22 1.33 1.18
1.33 0.81 0.92 0.56 ball: P - D (mm) Ball initial velocity - Core
initial velocity (m/s) -0.5 -0.4 -0.5 -0.5 -0.4 -0.4 -0.6 -0.5 0.3
Ball initial velocity - Intermediate layer-encased sphere initial
-0.1 0.0 0.0 0.0 0.1 0.1 0.2 0.2 0.3 velocity (m/s) Compressive
deformation ratio D/C 1.89 1.86 1.81 1.80 1.79 1.89 1.72 1.72 1.88
Compressive deformation ratio D/B 4.03 4.02 4.00 3.69 3.75 4.08
3.27 3.37 3.64 Compressive deformation ratio D/A 17.5 19.8 22.8
18.7 23.5 18.5 18.4 18.8 20.9
[0113] The flight performance and feel at impact of each golf ball
were evaluated by the following methods. The results are shown in
Table 6.
Flight Performance
[0114] Various clubs (W #1, UT #4, I #6) were mounted on a golf
swing robot and the distance traveled by the balls when struck
under the conditions shown in Table 5 below were measured and rated
according to the criteria in the table.
TABLE-US-00005 TABLE 5 Sum of W#1 W#1 UT#4 I#6 4 conditions
Clubused Product name PHYZ PHYZ PHYZ PHYZ Conditions HS, 40 m/s HS,
35 m/s HS, 35 m/s HS, 35 m/s Rating Good .gtoreq.205.0 m
.gtoreq.176.0 m .gtoreq.160.0 m .gtoreq.140.0 m .gtoreq.683.0 m
criteria NG .ltoreq.204.9 m .ltoreq.175.9 m .ltoreq.159.9 m
.ltoreq.139.9 m .ltoreq.682.9 m
[0115] Regarding the club name "PHYZ" in the above table, the PHYZ
Driver (loft angle, 10.5.degree.), PHYZ Utility U4 and PHYZ Iron I
#6, all manufactured by Bridgestone Sports Co., Ltd., were
used.
Feel
[0116] Sensory evaluations were carried out when the balls were hit
with a driver (W #1) by amateur golfers having head speeds of 30 to
40 m/s. Both the "soft feel" and "solid feel" of the balls were
rated according to the following criteria.
(1) Rating Criteria for "Soft Feel"
[0117] Good: Twelve or more out of 20 golfers rated the ball as
having a soft feel
[0118] Fair: From 7 to 11 out of 20 golfers rated the ball as
having a soft feel
[0119] NG: Six or fewer out of 20 golfers rated the ball as having
a soft feel
(2) Rating Criteria for "Solid Feel"
[0120] Good: Twelve or more out of 20 golfers rated the ball as
having a solid feel
[0121] Fair: From 7 to 11 out of 20 golfers rated the ball as
having a solid feel
[0122] NG: Six or fewer out of 20 golfers rated the ball as having
a solid feel
TABLE-US-00006 TABLE 6 Example Comparative Example 1 2 3 4 1 2 3 4
5 Flight W#1 Spin rate (rpm) 2,830 2,774 2,801 2,761 2,679 2,853
2,719 2,693 2,755 HS, 40 m/s Total distance (m) 206.5 205.6 205.3
206.1 205.4 205.8 206.0 205.3 205.9 Rating good good good good good
good good good good W#1 Spin rate (rpm) 2,968 2,891 2,996 2,906
2,870 3,031 2,853 2,824 2,946 HS, 35 m/s Total distance (m) 176.8
177.2 176.6 177.3 175.7 177.0 177.3 177.8 175.8 Rating good good
good good NG good good good NG UT#4 Spin rate (rpm) 4,389 4,355
4,442 4,372 4,316 4,481 4,405 4,328 4,247 Total distance (m) 161.5
162.0 160.7 161.3 161.1 160.9 159.0 159.5 158.8 Rating good good
good good good good NG NG NG I#6 Spin rate (rpm) 4,897 4,806 5,053
4,910 5,009 4,925 5,262 4,999 5,535 Total distance (m) 141.1 141.4
140.4 140.5 139.8 139.7 138.2 139.8 138.3 Rating good good good
good NG NG NG NG NG Sum of Total distance (m) 685.9 686.2 683.0
685.2 682.1 683.4 680.5 682.4 678.8 4 conditions Rating good good
good good NG good NG NG NG Feel Soft feel Rating good good good
good good fair good good NG Solid feel Rating good good good good
fair good fair fair good
[0123] As demonstrated by the results in Table 6, the golf balls of
Comparative Examples 1 to 5 were inferior in the following respects
to the golf balls according to the present invention that were
obtained in the Examples.
[0124] In Comparative Example 1, the compressive deformation C when
the ball was subjected to a final load of 60 kg from an initial
load state of 5 kg was a value larger than 1.80 mm. As a result,
the solid feel was inferior and the distances traveled by the ball
when hit with a driver (W #1) at a head speed of 35 m/s and when
hit with a number six iron (I #6) were inferior.
[0125] In Comparative Example 2, the compressive deformation B when
the ball was subjected to a final load of 30 kg from an initial
load state of 5 kg was a value smaller than 0.72 mm and the
compressive deformation C when the ball was subjected to a final
load of 60 kg from an initial load state of 5 kg was a value
smaller than 1.55 mm. As a result, the soft feel was inferior and
the distance traveled by the ball when hit with a number six iron
(I #6) was inferior.
[0126] In Comparative Example 3, the compressive deformation B was
a value larger than 0.90 mm and the compressive deformation C was a
value larger than 1.80. As a result, the solid feel was inferior
and the distances traveled by the ball when hit with a utility club
and a number six iron were inferior.
[0127] In Comparative Example 4, the compressive deformation B was
a value larger than 0.90 mm and the compressive deformation C was a
value larger than 1.80. As a result, the solid feel was inferior
and the distances traveled by the ball when hit with a utility club
and a number six iron were inferior.
[0128] In Comparative Example 5, the compressive deformation C was
a value smaller than 1.55 mm. As a result, the soft feel was
inferior and the distances traveled by the ball when hit with a W
#1 (HS=35 m/s), a utility club and a number six iron were
inferior.
Comparative Examples 6 to 8
[0129] Using other company's products, namely the XXIO Premium
(2018 model) from Sumitomo Rubber Industries, Ltd., the Titleist
VG3 (2018 model) from Acushnet Company and the CHROME SOFT (2018
model) from Callaway Golf Company as, respectively, Comparative
Example 6, Comparative Example 7 and Comparative Example 8, the
various compressive deformations of the golf balls in these
Comparative Examples were measured in the same way as in the above
Examples. The flight performance and feel of each of these golf
balls were evaluated in the same way as in the Examples. The
compressive deformations and ball properties are shown in Table 7.
Comparative Example 6 was a three-piece solid golf ball having a
single-layer core, an intermediate layer and a cover, Comparative
Example 7 was a three-piece solid golf ball having a two-layer core
and a cover, and Comparative Example 8 was a four-piece solid golf
ball having a two-layer core, an intermediate layer and a
cover.
TABLE-US-00007 TABLE 7 Comparative Example 6 7 8 Construction
3-piece 3-piece 4-piece Compressive Compressive deformation A under
0.23 0.22 0.23 deformations 0.2 to 5 kg loading (mm) of ball
Compressive deformation B under 1.08 0.96 0.82 5 to 30 kg loading
(mm) Compressive deformation C under 5 to 2.07 1.85 1.66 60 kg
loading (mm) Compressive deformation D under 10 to 3.55 3.28 3.05
130 kg loading (mm) Compressive deformation ratio D/C 1.72 1.78
1.84 Compressive deformation ratio D/B 3.29 3.41 3.72 Compressive
deformation ratio D/A 15.6 15.2 13.5 Flight W#1: HS, 40 m/s Spin
rate (rpm) 2,757 2,702 2,867 Total distance (m) 204.4 205.2 204.1
Rating NG good NG W#1: HS, 35 m/s Spin rate (rpm) 2,872 2,905 3,005
Total distance (m) 176.5 176.9 177.3 Rating good good good UT#4
Spin rate (rpm) 4,049 4,387 4,155 Total distance (m) 161.0 159.6
162.8 Rating good NG good I#6 Spin rate (rpm) 5,259 4,931 5,298
Total distance (m) 139.7 141.8 138.8 Rating NG good NG Sum of 4
conditions Total distance (m) 681.5 683.5 683.0 Rating NG good good
Feel Soft feel Rating good good good Solid feel Rating NG fair
fair
[0130] As demonstrated by the results in Table 7, the golf balls of
Comparative Examples 6 to 8 were inferior in the following respects
to the golf balls according to the present invention that were
obtained in the Examples.
[0131] In Comparative Example 6, the compressive deformation A was
a value larger than 0.21 mm, the compressive deformation B was a
value larger than 0.90 mm and the compressive deformation C was a
value larger than 1.80 mm. As a result, the solid feel was
inferior, and the distances traveled by the ball when hit with a W
#1 (HS=40 m/s) and a number six iron were inferior.
[0132] In Comparative Example 7, the compressive deformation A was
a value larger than 0.21 mm, the compressive deformation B was a
value larger than 0.90 mm and the compressive deformation C was a
value larger than 1.80 mm. As a result, the solid feel was inferior
and the distance traveled by the ball when hit with a utility club
was inferior.
[0133] In Comparative Example 8, the compressive deformation A was
a value larger than 0.21 mm. As a result, the solid feel was
inferior and the distances traveled by the ball when hit with a W
#1 (HS=40 m/s) and a number six iron were inferior.
[0134] Japanese Patent Application No. 2018-169572 is incorporated
herein by reference.
[0135] 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.
* * * * *