U.S. patent application number 10/453522 was filed with the patent office on 2003-12-18 for multi-piece solid golf ball.
Invention is credited to Moriyama, Keiji, Sasaki, Takashi.
Application Number | 20030232665 10/453522 |
Document ID | / |
Family ID | 29727576 |
Filed Date | 2003-12-18 |
United States Patent
Application |
20030232665 |
Kind Code |
A1 |
Sasaki, Takashi ; et
al. |
December 18, 2003 |
Multi-piece solid golf ball
Abstract
The present invention provides a multi-piece solid golf ball,
which is superior in flight distance, shot feel and
controllability. The present invention relates to a multi-piece
solid golf ball comprising a core consisting of a center and an
intermediate layer formed on the center, and a cover covering the
core, wherein the center has a deformation amount when applying
from an initial load of 98 N to a final load of 1275 N of 2.7 to
4.5 mm, the intermediate layer has a thickness of 0.5 to 2.0 mm and
a hardness in Shore D hardness of 65 to 85, and the cover has a
thickness of 0.3 to 1.5 mm and a hardness in Shore D hardness of 30
to 55.
Inventors: |
Sasaki, Takashi; (Kobe-shi,
JP) ; Moriyama, Keiji; (Kobe-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
29727576 |
Appl. No.: |
10/453522 |
Filed: |
June 4, 2003 |
Current U.S.
Class: |
473/371 ;
473/374; 473/378 |
Current CPC
Class: |
A63B 37/0033 20130101;
A63B 37/0043 20130101; A63B 37/0003 20130101; A63B 37/0031
20130101; A63B 37/0075 20130101; A63B 37/0045 20130101; A63B 37/02
20130101 |
Class at
Publication: |
473/371 ;
473/374; 473/378 |
International
Class: |
A63B 037/04; A63B
037/06; A63B 037/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 2002 |
JP |
2002-164734 |
Claims
What is claimed is:
1. A multi-piece solid golf ball comprising a core consisting of a
center and an intermediate layer formed on the center, and a cover
covering the core, wherein the center has a deformation amount when
applying from an initial load of 98 N to a final load of 1275 N of
2.7 to 4.5 mm, the intermediate layer has a thickness of 0.5 to 2.0
mm and a hardness in Shore D hardness of 65 to 85, and the cover
has a thickness of 0.3 to 1.5 mm and a hardness in Shore D hardness
of 30 to 55.
2. The multi-piece solid golf ball according to claim 1, wherein
the intermediate layer is formed from thermoplastic resin other
than ionomer resin as a main component.
3. The multi-piece solid golf ball according to claim 1, wherein
the cover is formed from polyurethane-based thermoplastic elastomer
as a main component.
4. The multi-piece solid golf ball according to claim 1, wherein
the polyurethane-based thermoplastic elastomer is formed by using
cycloaliphatic diisocyanate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a multi-piece solid golf
ball. More particularly, it relates to a multi-piece solid golf
ball, which is superior in flight distance, controllability and
shot feel.
BACKGROUND OF THE INVENTION
[0002] As golf balls having high spin performance at approach shot
and long flight distance, two-layer structured core type or
two-layer structured cover type golf balls, which comprise a center
formed from soft rubber, an intermediate layer formed on the center
and from rubber or resin that is relatively harder than the center
and a cover formed from soft material, have been proposed (Japanese
Patent No. 2910516, Japanese Patent Publication Nos. 151226/1998,
151320/1999 and the like).
[0003] In Japanese Patent No. 2910516, a multi-piece golf ball, of
which the center has a diameter of not less than 29 mm, the
intermediate layer has a JIS-C hardness of not less than 85, and
the specific gravity of the center is larger than that of the
intermediate layer, is described. However, since the cover has
large thickness, the rebound characteristics of the resulting golf
ball are poor, and the flight distance when hit by a driver is not
sufficiently obtained.
[0004] In Japanese Patent Publication No. 151226/1998, a
multi-piece golf ball, of which the center has a distortion of at
least 2.5 mm under a load of 100 kg, the hardness in Shore D
hardness of the intermediate layer is at least 13 degrees higher
than that of the cover, and the ball as a whole has an inertia
moment of at least 83 g-cm.sup.2, is described. However, since the
cover is soft and has large thickness, the rebound characteristics
of the resulting golf ball are poor and the spin amount is large,
and the flight distance when hit by a driver is not sufficiently
obtained.
[0005] In Japanese Patent Kokai Publication No. 151320/1999, a
three-piece solid golf ball which comprises a two-layer structured
core composed of an inner core (center) and outer core
(intermediate layer), and a cover is described. The inner core and
outer core are formed from rubber composition comprising
polybutadiene rubber as a main component, and the inner core has a
diameter of 15 to 22 mm and a hardness in Shore D hardness of 40 to
70. However, since the diameter of the inner core (center) is too
small, the rebound characteristics of the resulting golf ball are
poor, and the flight distance when hit by a driver is not
sufficiently obtained.
[0006] There has been no golf ball, which is superior in flight
distance, shot feel and controllability as described above.
OBJECTS OF THE INVENTION
[0007] A main object of the present invention is to provide a
multi-piece solid golf ball, which is superior in flight distance,
controllability and shot feel.
[0008] According to the present invention, the object described
above has been accomplished by providing a multi-piece solid golf
ball comprising a center, intermediate layer and cover, and by
adjusting the deformation amount under the load of the center, the
thickness and hardness of the intermediate layer, and the thickness
and hardness of the cover to specified ranges, thereby providing a
multi-piece solid golf ball, which is superior in flight distance,
controllability and shot feel.
[0009] This object as well as other objects and advantages of the
present invention will become apparent to those skilled in the art
from the following description with reference to the accompanying
drawings.
BRIEF EXPLANATION OF DRAWINGS
[0010] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0011] FIG. 1 is a schematic cross section illustrating one
embodiment of the golf ball of the present invention.
SUMMARY OF THE INVENTION
[0012] The present invention provides a multi-piece solid golf ball
comprising a core consisting of a center and an intermediate layer
formed on the center, and a cover covering the core, wherein
[0013] the center has a deformation amount when applying from an
initial load of 98 N to a final load of 1275 N of 2.7 to 4.5
mm,
[0014] the intermediate layer has a thickness of 0.5 to 2.0 mm and
a hardness in Shore D hardness of 65 to 85, and
[0015] the cover has a thickness of 0.3 to 1.5 mm and a hardness in
Shore D hardness of 30 to 55.
[0016] In order to put the present invention into a more suitable
practical application, it is desired that
[0017] the intermediate layer be formed from thermoplastic resin
other than ionomer resin as a main component;
[0018] the cover be formed from polyurethane-based thermoplastic
elastomer as a main component; and
[0019] the polyurethane-based thermoplastic elastomer be formed by
using cycloaliphatic diisocyanate.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The multi-piece solid golf ball of the present invention
will be explained with reference to the accompanying drawing in
detail. FIG. 1 is a schematic cross section illustrating one
embodiment of the multi-piece solid golf ball of the present
invention. As shown in FIG. 1, the golf ball of the present
invention comprises a core 4 consisting of a center 1 and an
intermediate layer 2 formed on the center 1, and a cover 3 covering
the core 4. The cover may have single-layer structure or
multi-layer structure, which has two or more layers. In FIG. 1, in
order to explain the golf ball of the present invention simply, a
golf ball having one layer of cover 3, that is, a three-piece solid
golf ball will be used hereinafter for explanation.
[0021] It is desired for the center 1 to comprise polybutadiene
rubber as a main component. The center is preferably obtained by
press-molding a rubber composition under applied heat. The rubber
composition essentially contains polybutadiene, a co-crosslinking
agent, an organic peroxide and a filler.
[0022] The polybutadiene used for the center 1 of the present
invention may be one, which has been conventionally used for cores
of solid golf balls. Preferred is high-cis polybutadiene rubber
containing a cis-1, 4 bond of not less than 40%, preferably not
less than 80%. The high-cis polybutadiene rubber may be optionally
mixed with natural rubber, polyisoprene rubber, styrene-butadiene
rubber, ethylene-propylene-diene rubber (EPDM) and the like.
[0023] The co-crosslinking agent can be a metal salt of
.alpha.,.beta.-unsaturated carboxylic acid, including mono or
divalent metal salts, such as zinc or magnesium salts of
.alpha.,.beta.-unsaturate- d carboxylic acids having 3 to 8 carbon
atoms (e.g. acrylic acid, methacrylic acid, etc.), or a functional
monomers (such as trimethylolpropane trimethacrylate, and the like)
and the like. The preferred co-crosslinking agent is a zinc salt of
.alpha.,.beta.-unsatura- ted carboxylic acid, particularly zinc
acrylate, because it imparts high rebound characteristics to the
resulting golf ball. The amount of the co-crosslinking agent is
from 10 to 60 parts by weight, preferably from 10 to 50 parts by
weight, more preferably from 20 to 40 parts by weight, based on 100
parts by weight of the polybutadiene. When the amount of the
co-crosslinking agent is larger than 60 parts by weight, the center
is too hard, and the shot feel of the resulting golf ball is poor.
On the other hand, when the amount of the co-crosslinking agent is
smaller than 10 parts by weight, it is required to increase an
amount of the organic peroxide in order to impart a desired
hardness to the center, and the rebound characteristics are
degraded, which reduces the flight distance.
[0024] The organic peroxide includes, for example, dicumyl
peroxide, 1,1-bis (t-butylperoxy)-3,3,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di(t-butylperoxy) hexane, di-t-butyl peroxide and
the like. The preferred organic peroxide is dicumyl peroxide. The
amount of the organic peroxide is from 0.3 to 4.0 parts by weight,
preferably 0.4 to 3.0 parts by weight, more preferably 0.5 to 2.0
parts by weight, based on 100 parts by weight of the polybutadiene.
When the amount of the organic peroxide is smaller than 0.3 parts
by weight, the center is too soft, and the rebound characteristics
of the resulting golf ball are degraded, which reduces the flight
distance. On the other hand, when the amount of the organic
peroxide is larger than 4.0 parts by weight, it is required to
decrease an amount of the co-crosslinking agent in order to impart
a desired hardness to the center, and the rebound characteristics
are degraded, which reduces the flight distance.
[0025] The filler, which can be typically used for the core of
solid golf ball, includes for example, inorganic filler (such as
zinc oxide, barium sulfate, calcium carbonate, magnesium oxide and
the like), high specific gravity metal powder filler (such as
tungsten powder, molybdenum powder and the like), and the mixture
thereof. The amount of the filler is from 5 to 30 parts by weight,
preferably from 5 to 25 parts by weight, based on 100 parts by
weight of the polybutadiene. When the amount of the filler is
smaller than 5 parts by weight, it is difficult to adjust the
weight of the resulting golf ball. On the other hand, when the
amount of the filler is larger than 30 parts by weight, the weight
ratio of the rubber component in the center is small, and the
rebound characteristics reduce too much.
[0026] The rubber compositions for the center of the golf ball of
the present invention can contain other components, which have been
conventionally used for preparing the core of solid golf balls,
such as organic sulfide compound or antioxidant. If used, it is
desired for the amount thereof to be 0.2 to 5.0 parts by weight,
preferably 0.3 to 4.0 parts by weight, more preferably 0.5 to 2.0
parts by weight, based on 100 parts by weight of the
polybutadiene.
[0027] The center 1 used for the golf ball of the present invention
is obtained by mixing the rubber composition, followed by
vulcanizing and press-molding the mixture in a mold. The
vulcanization condition is not limited, but the vulcanization may
be conducted at 140 to 180.degree. C. and 2.9 to 11.8 MPa for 10 to
60 minutes. The vulcanization may be conducted in two or more
stages of the temperature.
[0028] In the golf ball of the present invention, it is desired for
the center 1 to have a diameter of 37 to 41 mm, preferably 37 to 40
mm, more preferably 38 to 40 mm. When the diameter of the center is
smaller than 37 mm, the rebound characteristics of the resulting
golf ball are degraded, which reduces the flight distance. In
addition, the spin amount at the time of hitting of the resulting
golf ball is increased, and the hit golf ball creates blown-up
trajectory, which reduces the flight distance. On the other hand,
when the diameter of the center is larger than 41 mm, the thickness
of the intermediate layer or the cover is too small, and the
technical effects accomplished by the presence of the intermediate
layer or the cover are not sufficiently obtained.
[0029] In the golf ball of the present invention, it is required
for the center 1 to have a deformation amount when applying from an
initial load of 98 N to a final load of 1275 N of 2.7 to 4.5 mm,
preferably 2.8 to 4.2 mm, more preferably 3.0 to 4.0 mm. When the
deformation amount of the center is smaller than 2.7 mm, the center
is too hard, and the shot feel of the resulting golf ball is hard
and poor. On the other hand, when the deformation amount is larger
than 4.5 mm, the core is too soft, and the rebound characteristics
of the resulting golf ball are degraded, which reduces the flight
distance.
[0030] In the golf ball of the present invention, it is desired for
the center 1 to have a central point hardness in Shore D hardness
of 15 to 40, preferably 20 to 40, more preferably 20 to 35. When
the central point hardness is lower than 15, the center is too
soft, and the rebound characteristics of the resulting golf ball
are degraded, which reduces the flight distance. In addition, the
shot feel of the resulting golf ball is heavy and poor. On the
other hand, when the surface hardness is higher than 40, high
launch angle at the time of hitting is not sufficiently
accomplished, which reduces the flight distance. In addition, the
center is too hard, and the shot feel of the resulting golf ball is
poor such that the impact force at the time of hitting is
large.
[0031] In the golf ball of the present invention, it is desired for
the center 1 to have a surface hardness in Shore D hardness of 40
to 65, preferably 40 to 60, more preferably 45 to 60. When the
surface hardness is lower than 40, the center is too soft, and the
rebound characteristics of the resulting golf ball are degraded,
which reduces the flight distance. In addition, the shot feel is
heavy and poor. On the other hand, when the surface hardness is
higher than 65, the center is too hard, and the shot feel of the
resulting golf ball is hard and poor.
[0032] The term "a surface hardness of the center" as used herein
refers to the hardness, which is determined by measuring a hardness
at the surface of the center prepared by press molding as described
above, that is, at the surface of the center before covering with
the intermediate layer. The term "a central point hardness of the
center" as used herein refers to the hardness, which is determined
by cutting the resulting center into two equal parts and then
measuring a hardness at its central point in section. The
intermediate layer 2 is then formed on the center 1.
[0033] In the golf ball of the present invention, it is required
for the intermediate layer 2 to have a thickness of 0.5 to 2.0 mm,
preferably 0.5 to 1.6 mm, more preferably 0.7 to 1.4 mm. When the
thickness is smaller than 0.5 mm, the technical effect accomplished
by the hardness of the intermediate layer is not sufficiently
obtained, and the spin amount at the time of hitting can not be
sufficiently restrained. On the other hand, when the thickness is
not less than 2.0 mm, since the intermediate layer is formed from a
relatively hard material, the shot feel is hard and poor.
[0034] In the golf ball of the present invention, it is required
for the intermediate layer 2 to have a hardness in Shore D hardness
of 65 to 85, preferably 67 to 82, more preferably 70 to 80. When
the hardness is lower than 65, the rebound characteristics of the
resulting golf ball are degraded, which reduces the flight
distance. On the other hand, when the hardness is higher than 85,
the shot feel is hard and poor, or the durability is degraded. The
term "a hardness of the intermediate layer" as used herein refers
to the hardness, which is determined by measuring a hardness (slab
hardness) using a sample of a stack of the three or more heat and
press molded sheets having a thickness of about 2 mm from the
intermediate layer composition, which had been stored at 23.degree.
C. for 2 weeks.
[0035] In the golf ball of the present invention, it is desired
that the hardness of the intermediate layer 2 be higher than the
surface hardness of the center 1, and the hardness difference
between the intermediate layer and the surface of the center is 5
to 35, preferably 5 to 30, more preferably 10 to 25. When the
hardness difference is smaller than 5, the center is too hard, and
the shot feel of the resulting golf ball is hard and poor. On the
other hand, when the hardness difference is larger than 35, the
durability is degraded.
[0036] In the golf ball of the present invention, a material for
the intermediate layer 2 is not limited as long as it has
properties as described above, but it is desired for the
intermediate layer 2 to be formed from hard and high rebound
characteristics material, particularly thermoplastic resin other
than ionomer resin as a main component. Examples thereof include
thermoplastic elastomer, such as polyester-based thermoplastic
elastomer, polyamide-based thermoplastic elastomer and
polyurethane-based thermoplastic elastomer; polyamide resin,
polyacetal resin, polycarbonate resin, acrylic resin, polyolefin
resin and modified compounds thereof. Examples of the commercially
available materials for the intermediate layer include
polyester-based thermoplastic elastomer, which is commercially
available from Toray-Du Pont Co., Ltd. under the trade name of
"Hytrel" (such as "Hytrel 7247"); polyamide-based thermoplastic
elastomer, which is commercially available from Atofina Japan Co.,
Ltd. under the trade name of "Pebax" (such as "Pebax 7233");
polyurethane-based elastomer, which is commercially available from
BASF Polyurethane Elastomers Co., Ltd. under the trade name of
"Elastollan" (such as "Elastollan XHM76D"); and the like.
[0037] A method of covering the center 1 with the intermediate
layer 2 is not specifically limited, but may be conventional
methods, which have been known to the art and used for forming the
cover of the golf balls. For example, there can be used a method
comprising molding the intermediate layer composition into a
semi-spherical half-shell in advance, covering the core with the
two half-shells, followed by press molding at 130 to 170.degree. C.
for 1 to 5 minutes, or a method comprising injection molding the
intermediate layer composition directly on the center, which is
covered with the cover, to cover it. The intermediate layer 2 is
formed on the center 1 to form the core 4 having two-layered
structure by using the above method.
[0038] In the golf ball of the present invention, it is desired for
the core 4 to have a deformation amount when applying from an
initial load of 98 N to a final load of 1275 N of 2.0 to 3.7 mm,
preferably 2.2 to 3.5 mm, more preferably 2.5 to 3.3 mm. When the
deformation amount of the core is smaller than 2.0 mm, the core is
too hard, and the shot feel of the resulting golf ball is poor. On
the other hand, when the deformation amount is larger than 3.7 mm,
the core is too soft, the rebound characteristics of the resulting
golf ball are degraded, which reduces the flight distance.
[0039] At least one layer of cover 3 are then covered on the core
4. In the golf ball of the present invention, it is required for
the cover 3 to have a thickness of 0.3 to 1.5 mm, preferably 0.5 to
1.2 mm, more preferably 0.5 to 1.0 mm. When the thickness is
smaller than 0.3 mm, the technical effects accomplished by
softening the cover are not sufficiently obtained, and the spin
amount at short iron shot to approach shot is small, which degrades
the controllability. On the other hand, when the thickness of the
cover is larger than 1.5 mm, the rebound characteristics of the
resulting golf ball are degraded and the spin amount at the time of
hitting is increased, and the hit golf ball creates blown-up
trajectory, which reduces the flight distance.
[0040] In the golf ball of the present invention, it is required
for the cover 3 to have a hardness in Shore D hardness of 30 to 55,
preferably 33 to 52, more preferably 35 to 50. When the hardness of
the cover 3 is lower than 30, the spin amount when hit by a driver
or middle iron club is increased, which reduces the flight
distance. On the other hand, when the hardness of the cover is
higher than 55, the spin amount when hit by a short iron club is
decreased, and the controllability is degraded. In addition, the
shot feel is poor. The term "a hardness of the cover" as used
herein is determined by measuring a hardness (slab hardness) using
a sample of a stack of the three or more heat and press molded
sheets having a thickness of about 2 mm from the composition for
the cover, which had been stored at 23.degree. C. for 2 weeks.
[0041] In the golf ball of the present invention, it is desired
that the hardness in Shore D hardness of the intermediate layer 2
be higher than that of the cover 3, and the hardness difference
between the intermediate layer and cover is within the range of
preferably 10 to 50, more preferably 10 to 40, most preferably 15
to 30. When the hardness difference between the intermediate layer
and the cover is smaller than 10 or larger than 50, it is difficult
to adjust the hardness of each layer in the resulting golf ball to
specified ranges, which degrades the controllability or reduces the
flight distance.
[0042] In the golf ball of the present invention, a material for
the cover 3 is not limited as long as it has properties as
described above, but it is desired for the cover 3 to be formed
from polyurethane-based thermoplastic elastomer as a main component
in view of productivity and cost, more preferably
polyurethane-based thermoplastic elastomer formed by using
cycloaliphatic diisocyanate in view of yellowing resistance.
[0043] Examples of the cycloaliphatic diisocyanates include one or
combination of two or more selected from the group consisting of
4,4'-dicyclohexylmethane diisocyanate (H.sub.12MDI), which is
hydrogenated compound of 4,4'-diphenylmethane diisocyanate (MDI);
1,3-bis (isocyanatomethyl) cyclohexane (H.sub.6XDI), which is
hydrogenated compound of xylylene diisocyanate (XDI); isophorone
diisocyanate (IPDI); and trans-1,4-cyclohexane diisocyanate (CHDI).
Preferred is the H.sub.12MDI in view of general-purpose properties
and processability.
[0044] Concrete examples of the polyurethane-based thermoplastic
elastomers include polyurethane-based thermoplastic elastomer
formed by using the H.sub.12MDI, which is commercially available
from BASF Polyurethane Elastomers Co., Ltd. under the trade name
"Elastollan" (such as "Elastollan XNY90A", "Elastollan XNY97A",
"Elastollan XNY585" and the like) and the like.
[0045] As a suitable materials used in the cover 3 of the present
invention, the above polyurethane-based thermoplastic elastomer may
be used alone, but the polyurethane-based thermoplastic elastomer
may be used in combination with at least one of the other
thermoplastic elastomer, diene-based block copolymer, ionomer resin
and the like. Examples of the other thermoplastic elastomers
include the other polyurethane-based thermoplastic elastomer,
polyamide-based thermoplastic elastomer, polyester-based
thermoplastic elastomer, polystyrene-based thermoplastic elastomer,
polyolefin-based thermoplastic elastomer and the like. If used, it
is desired for the polyurethane-based thermoplastic elastomer to be
used in combination with polyamide-based thermoplastic elastomer in
view of the compatibility with the polyurethane-based thermoplastic
elastomer and the rebound characteristics. In addition, it is
desired that the weight ratio of the polyurethane-based
thermoplastic elastomer to the polyamide-based thermoplastic
elastomer be within the range of 95/5 to 70/30. The other
thermoplastic elastomer may have functional group, such as carboxyl
group, glycidyl group, sulfone group, epoxy group and the like.
[0046] Concrete examples of the other thermoplastic elastomers
include polyurethane-based elastomer, which is commercially
available from BASF Polyurethane Elastomers Co., Ltd. under the
trade name of "Elastollan" (such as "Elastollan ET880");
polyamide-based thermoplastic elastomer, which is commercially
available from Atofina Japan Co., Ltd. under the trade name of
"Pebax" (such as "Pebax 2533"); polyester-based thermoplastic
elastomer, which is commercially available from Toray-Du Pont Co.,
Ltd. under the trade name of "Hytrel" (such as "Hytrel 3548",
"Hytrel 4047"); styrene-based thermoplastic elastomer available
from Asahi Kasei Corporation under the trade name "Tuftec" (such as
"Tuftec H1051"); olefin-based thermoplastic elastomer available
from Mitsubishi Chemical Co., Ltd. under the trade name "Thermoran"
(such as "Thermoran 3981N"); polyolefin-based thermoplastic
elastomer, which is commercially available from Sumitomo Chemical
Co., Ltd. under the trade name of "Sumitomo TPE" (such as "Sumitomo
TPE3682" and "Sumitomo TPE9455"); and the like.
[0047] The diene-based block copolymer is a block copolymer or
partially hydrogenated block copolymer having double bond derived
from conjugated diene compound. The base bock copolymer is block
copolymer composed of block polymer block A mainly comprising at
least one aromatic vinyl compound and polymer block B mainly
comprising at least one conjugated diene compound. The partially
hydrogenated block copolymer is obtained by hydrogenating the block
copolymer. Examples of the aromatic vinyl compounds comprising the
block copolymer include styrene, .alpha.-methyl styrene, vinyl
toluene, p-t-butyl styrene, 1,1-diphenyl styrene and the like, or
mixtures thereof. Preferred is styrene. Examples of the conjugated
diene compounds include butadiene, isoprene, 1,3-pentadiene,
2,3-dimethyl-1,3-butadiene and the like, or mixtures thereof.
Preferred are butadiene, isoprene and combinations thereof.
Examples of the diene block copolymers include an SBS
(styrene-butadiene-styrene) block copolymer having polybutadiene
block with epoxy groups or SIS (styrene-isoprene-styrene) block
copolymer having polyisoprene block with epoxy groups and the like.
Concrete examples of the diene block copolymers include the diene
block copolymers, which are commercially available from Daicel
Chemical Industries, Ltd. under the trade name of "Epofriend" (such
as "Epofriend A1010"), the diene-based block copolymers, which are
commercially available from Kuraray Co., Ltd. under the trade name
of "Septon" (such as "Septon HG-252" and the like) and the
like.
[0048] The ionomer resin may be a copolymer of ethylene and
.alpha.,.beta.-unsaturated carboxylic acid, of which a portion of
carboxylic acid groups is neutralized with metal ion; or a
terpolymer of ethylene, .alpha.,.beta.-unsaturated carboxylic acid
and .alpha.,.beta.-unsaturated carboxylic acid ester, of which a
portion of carboxylic acid groups is neutralized with metal ion.
Examples of the .alpha.,.beta.-unsaturated carboxylic acid in the
ionomer include acrylic acid, methacrylic acid, fumaric acid,
maleic acid, crotonic acid and the like, and preferred are acrylic
acid and methacrylic acid. Examples of the
.alpha.,.beta.-unsaturated carboxylic acid ester in the ionomer
include methyl ester, ethyl ester, propyl ester, n-butyl ester and
isobutyl ester of acrylic acid, methacrylic acid, fumaric acid,
maleic acid, crotonic acid and the like. Preferred are acrylic acid
esters and methacrylic acid esters. The metal ion which neutralizes
a portion of carboxylic acid groups of the copolymer or terpolymer
includes sodium ion, potassium ion, lithium ion, magnesium ion,
calcium ion, zinc ion, barium ion, aluminum ion, tin ion, zirconium
ion, cadmium ion, and the like. Preferred are sodium ions, zinc
ions, magnesium ions and the like, in view of rebound
characteristics, durability and the like.
[0049] The ionomer resin is not limited, but examples thereof will
be shown by a trade name thereof. Examples of the ionomer resins,
which are commercially available from Du Pont-Mitsui Polychemicals
Co., Ltd. include Hi-milan 1555, Hi-milan 1557, Hi-milan 1605,
Hi-milan 1652, Hi-milan 1702, Hi-milan 1705, Hi-milan 1706,
Hi-milan 1707, Hi-milan 1855, Hi-milan 1856 and the like. Examples
of the ionomer resins, which are commercially available from Du
Pont Co., include Surlyn 8945, Surlyn 9945, Surlyn 6320 and the
like. Examples of the ionomer resins, which are commercially
available from Exxon Chemical Co., include Iotek 7010, Iotek 8000
and the like. These ionomer resins may be used alone or in
combination.
[0050] The composition for the cover 3 used in the present
invention may optionally contain pigments (such as titanium
dioxide, etc.) and the other additives such as a dispersant, an
antioxidant, a UV absorber, a photostabilizer and a fluorescent
agent or a fluorescent brightener, etc., in addition to the resin
component as long as the addition of the additives does not
deteriorate the desired performance of the golf ball cover. If
used, the amount of the pigment is preferably 0.1 to 5.0 parts by
weight, based on 100 parts by weight of the base resin for the
cover.
[0051] A method of covering the core 4 with the cover 3 is not
specifically limited, but may be a conventional method. For
example, there can be used a method comprising molding the cover
composition into a semi-spherical half-shell in advance, covering
the core with the two half-shells, followed by press molding at 130
to 170.degree. C. for 1 to 5 minutes, or a method comprising
injection molding the cover composition directly on the core, which
is covered with the cover, to cover it.
[0052] At the time of molding the cover, many depressions called
"dimples" are formed on the surface of the golf ball. Furthermore,
paint finishing or marking with a stamp may be optionally provided
after the cover is molded for commercial purposes.
[0053] The golf ball of the present invention is formed such that
it has a diameter of not less than 42.67 mm (preferably 42.67 to
42.82 mm) and a weight of not more than 45.93 g, in accordance with
the regulations for golf balls.
[0054] In the golf ball of the present invention, it is desired to
have a deformation amount when applying from an initial load of 98
N to a final load of 1275 N of 2.0 to 3.5 mm, preferably 2.2 to 3.2
mm, more preferably 2.4 to 3.0 mm. When the deformation amount is
smaller than 2.0 mm, the shot feel is hard and poor. On the other
hand, when the deformation amount is larger than 3.5 mm, the golf
ball is too soft, and the shot feel is heavy and poor, or the
flight distance is reduced.
[0055] The diameter of golf balls is limited to not less than 42.67
mm in accordance with the regulations for golf balls as described
above. Generally, when the diameter of the golf ball is large, air
resistance of the golf ball on a flight is large, which reduces the
flight distance. Therefore, most of golf balls commercially
available are designed to have a diameter of 42.67 to 42.82 mm. The
present invention is applicable to the golf balls having the
diameter. There are golf balls having large diameter in order to
improve the easiness of hitting. In addition, there are cases where
golf balls having a diameter out of the regulations for golf balls
are required depending on the demand and object of users.
Therefore, it can be considered for golf balls to have a diameter
of 42 to 44 mm, more widely 40 to 45 mm. The present invention is
also applicable to the golf balls having the diameter. In addition,
the golf ball of the present invention has a weight of 44 to 46 g,
preferably 45.00 to 45.93 g.
EXAMPLES
[0056] The following Examples and Comparative Examples further
illustrate the present invention in detail but are not to be
construed to limit the scope of the present invention.
Examples 1 to 6 and Comparative Examples 1 to 7
[0057] (i) Production of Center
[0058] The rubber compositions for the center having the
formulation shown in Table 1 (Examples) and Table 2 (Comparative
Examples) were mixed, and then vulcanized by press-molding in the
mold at 170.degree. C. for 15 minutes to obtain spherical centers.
The diameter, weight, deformation amount, central point hardness
and surface hardness of the resulting centers were measured. The
results are shown in Table 3 (Examples) and Table 4 (Comparative
Examples).
[0059] (ii) Preparation of Compositions for Intermediate Layer
[0060] The formulation materials for the intermediate layer shown
in Table 1 (Examples) and Table 2 (Comparative Examples) were mixed
using a kneading type twin-screw extruder to obtain pelletized
intermediate layer compositions. The extrusion condition was,
[0061] a screw diameter of 45 mm,
[0062] a screw speed of 200 rpm, and
[0063] a screw L/D of 35.
[0064] The formulation materials were heated at 160 to 260.degree.
C. at the die position of the extruder. The Shore D hardness were
measured, using a sample of a stack of the three or more heat and
press molded sheets having a thickness of about 2 mm from each
intermediate layer composition, which had been stored at 23.degree.
C. for 2 weeks. The results are shown in Table 3 (Examples) and
Table 4 (Comparative Examples) as the hardness of the intermediate
layer.
[0065] (iii) Production of Core
[0066] The compositions for the intermediate layer obtained in the
step (ii) were injection-molded to obtain semi-spherical
half-shells for the intermediate layer. The center produced in the
step (i) was covered with the two semi-spherical half-shells for
the intermediate layer into a concentric sphere, and then
press-molded in the mold at 150.degree. C. for 2 minutes to obtain
two-layer structured cores 4. The two-layer structured core 4 was
consisted of the center 1 and the intermediate layer 2 having the
thickness shown in Table 3 (Examples) and Table 4 (Comparative
Examples) covered on the center 1. The diameter, weight, and
deformation amount of the resulting two-layer structured core 4
were measured. The results are shown in Table 3 (Examples) and
Table 4 (Comparative Examples).
[0067] (iv) Preparation of Compositions for Cover
[0068] The formulation materials for the cover shown in Table 1
(Examples) and Table 2 (Comparative Examples) were mixed using a
kneading type twin-screw extruder to obtain pelletized cover
compositions. The extrusion condition was,
[0069] a screw diameter of 45 mm,
[0070] a screw speed of 200 rpm, and
[0071] a screw L/D of 35.
[0072] The formulation materials were heated at 160 to 260.degree.
C. at the die position of the extruder. The Shore D hardness were
measured, using a sample of a stack of the three or more heat and
press molded sheets having a thickness of about 2 mm from each
cover composition, which had been stored at 23.degree. C. for 2
weeks. The results are shown in Table 3 (Examples) and Table 4
(Comparative Examples) as the cover hardness.
1 TABLE 1 (parts by weight) Example No. Composition 1 2 3 4 5 6
(Center composition) BR11 *1 100 100 100 100 100 100 Zinc acrylate
35 35 35 30 35 35 Zinc oxide 6.0 6.0 6.0 8.3 4.0 18 Dicumyl
peroxide 0.8 0.8 0.8 0.8 0.8 0.8 Diphenyl disulfide 0.5 0.5 0.5 0.5
0.5 0.5 (Intermediate layer composition) Hytrel 7247 *2 100 100 100
100 100 -- Surlyn 8945 *3 -- -- -- -- -- -- Pebax 7233 *4 -- -- --
-- -- 100 (Cover composition) Elastollan XNY90A *5 -- -- 100 -- --
100 Elastollan XNY97A *6 100 80 -- 100 100 -- Pebax 5533 *7 -- 20
-- -- -- -- Surlyn 8945 *3 -- -- -- -- -- -- Surlyn 9945 *8 -- --
-- -- -- -- Titanium dioxide 4 4 4 4 4 4
[0073]
2 TABLE 2 (parts by weight) Comparative Example No. Composition 1 2
3 4 5 6 7 (Center composition) BR11 *1 100 100 100 100 100 100 100
Zinc acrylate 33 35 35 35 43 25 33 Zinc oxide 3.0 5.0 16.0 8.0 3.0
10.5 12.0 Dicumyl peroxide 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Diphenyl
disulfide 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (Intermediate layer
composition) Hytrel 7247 *2 100 100 -- 100 100 100 -- Surlyn 8945
*3 -- -- 100 -- -- -- Pebax 7233 *4 -- -- -- -- -- -- (Cover
composition) Elastollan XNY90A -- -- -- -- -- -- -- *5 Elastollan
XNY97A 100 100 100 -- 100 100 100 *6 Pebax 5533 *7 -- -- -- -- --
-- -- Surlyn 8945 *3 -- -- -- 50 -- -- -- Surlyn 9945 *8 -- -- --
50 -- -- -- Titanium dioxide 4 4 4 4 4 4 4 *1: BR-11 (trade name),
high-cis polybutadiene commercially available from JSR Co., Ltd.
(Content of 1,4-cis-polybutadiene: 96%) *2: Hytrel 7247 (trade
name), polyester-based thermoplastic elastomer, which is
commercially available from Toray-Du Pont Co., Ltd. *3: Surlyn 8945
(trade name), ethylene-methacrylic acid copolymer ionomer resin
obtained by neutralizing with sodium ion, manufactured by Du Pont
Co. *4: Pebax 7233 (trade name), polyamide-based thermoplastic
elastomer, which is commercially available from Atofina Japan Co.,
Ltd. *5: Elastollan XNY90A (trade name), polyurethane-based
thermoplastic elastomer formed by using 4,4'-dicyclohexylmethane
diisocyanate (H.sub.12MDI), commercially available from BASF
Polyurethane Elastomers Co., Ltd.; Shore A (JIS-A) hardness = 90
*6: Elastollan XNY97A (trade name), polyurethane-based
thermoplastic elastomer formed by using 4,4'-dicyclohexylmethane
diisocyanate (H.sub.12MDI), commercially available from BASF
Polyurethane Elastomers Co., Ltd.; Shore A (JIS-A) hardness = 97
*7: Pebax 5533 (trade name), polyamide-based thermoplastic
elastomer, which is commercially available from Atofina Japan Co.,
Ltd. *8: Surlyn 9945 (trade name), ethylene-methacrylic acid
copolymer ionomer resin obtained by neutralizing with zinc ion,
manufactured by Du Pont Co.
[0074] (v) Production of Golf Ball
[0075] The cover composition obtained in the step (iv) was
injection molded to obtain semi-spherical half-shell for the cover.
The two-layer structured core 4 produced in the step (iii) was
covered with the two semi-spherical half-shells for the cover into
a concentric sphere, and then press-molded in the mold at
150.degree. C. for 2 minutes to form a cover layer 3 having a
thickness shown in Table 3 (Examples) and Table 4 (Comparative
Examples). Then, clear paint was applied on the surface to produce
golf ball having a diameter of 42.7 mm and a weight of 45.3 g. With
respect to the resulting golf balls, the deformation amount,
coefficient of restitution, flight performance (spin amount and
flight distance), shot feel and controllability were measured or
evaluated. The results are shown in Table 5 (Examples) and Table 6
(Comparative Examples). The test methods are as follows.
[0076] (Test Method)
[0077] (1) Hardness of Center
[0078] The surface hardness of the center is determined by
measuring a Shore D hardness at the surface of the center prepared.
The central point hardness of the center is determined by measuring
a Shore D hardness at the central point of the center in section,
after the center is cut into two equal parts. Shore D hardness is
measured with a Shore D hardness meter according to ASTM-D
2240.
[0079] (2) Hardness of Intermediate Layer and Cover
[0080] The hardness of the intermediate layer and the hardness of
the cover are determined by measuring a hardness, using a sample of
a stack of the three or more heat and press molded sheets having a
thickness of about 2 mm from each intermediate layer composition
and each cover composition, which had been stored at 23.degree. C.
for 2 weeks, with a Shore D hardness meter according to ASTM
D-2240.
[0081] (3) Deformation Amount
[0082] The deformation amount of was determined by measuring a
deformation amount when applying from an initial load of 98 N to a
final load of 1275 N on the center, core or golf ball.
[0083] (4) Coefficient of Restitution
[0084] An aluminum cylinder having a weight of 200 g was struck at
a speed of 45 m/sec against a golf ball, and the velocity of the
cylinder and the golf ball after the strike were measured. The
coefficient of restitution of the golf ball was calculated from the
velocity and the weight of both the cylinder and golf ball before
and after strike.
[0085] (5) Flight Performance
[0086] After a No. 1 wood club (a driver, W#1; "XXIO" loft angle=10
degrees, S shaft, manufactured by Sumitomo Rubber Industries, Ltd.)
having metal head was mounted to a swing robot manufactured by Golf
Laboratory Co. and each golf ball was hit at head speed of 45
m/sec, the spin amount (backspin amount) immediately after hitting,
and flight distance were measured. As the flight distance, total
that is a distance to the stop point of the hit golf ball was
measured. The measurement was conducted 12 times for each golf ball
(n=12), and the average is shown as the result of the golf
ball.
[0087] (6) Shot Feel
[0088] The shot feel of the golf ball is evaluated by 10 golfers
according to a practical hitting test using a No. 1 wood club (W#1,
a driver) having a metal head. The evaluation criteria are as
follows. The results shown in the Tables below are based on the
fact that the most golfers evaluated with the same criterion about
shot feel.
[0089] Evaluation Criteria
[0090] .largecircle.: The golfers felt that the golf ball has good
shot feel such that the impact force is small and the rebound
characteristics are good.
[0091] .DELTA.: The golfers felt that the golf ball has fairly good
shot feel.
[0092] x: The golfers felt that the golf ball has hard and poor
shot feel such that the impact force is large, or heavy and poor
shot feel such that the rebound characteristics are poor.
[0093] (7) Controllability
[0094] The resulting golf balls were evaluated by 10 golfers
according to practical hitting test using a pitching wedge (PW).
The results shown in the Tables below are based on the fact that
the most golfers evaluated with the same criterion about shot feel.
The evaluation criteria are as follows.
[0095] Evaluation Criteria
[0096] .largecircle.: The golfers felt that it is easy to apply
spin on the golf ball, and the golf ball has good
controllability.
[0097] .DELTA.: The golfers felt that the golf ball has fairly good
controllability.
[0098] x: The golfers felt that it is difficult to apply spin on
the golf ball such that the golf ball slips on the face of golf
club, and the golf ball has poor controllability.
[0099] (Test Results)
3 TABLE 3 Example No. Test item 1 2 3 4 5 6 (Center) Diameter (mm)
38.5 38.5 38.5 38.5 36.7 38.5 Weight (g) 32.6 32.6 32.6 32.6 27.8
34.2 Deformation amount (mm) 3.2 3.2 3.2 3.8 3.25 3.2 Hardness
(Shore D) Central point hardness 34 34 34 31 33 33 Surface hardness
56 56 56 52 55 55 (Intermediate layer) Thickness (mm) 1.3 1.3 1.3
1.3 1.6 1.3 Hardness (Shore D) 72 72 72 72 72 72 (Core) Diameter
(mm) 41.1 41.1 41.1 41.1 39.9 41.1 Weight (g) 40.6 40.6 40.6 40.6
37.3 40.6 Deformation amount (mm) 2.8 2.8 2.8 3.2 2.7 2.9 (Cover)
Thickness (mm) 0.8 0.8 0.8 0.8 1.4 0.8 Hardness (Shore D) 47 47 42
47 47 42
[0100]
4 TABLE 4 Comparative Example No. Test item 1 2 3 4 5 6 7 (Center)
Diameter (mm) 36.4 36.4 38.5 38.5 38.5 38.5 41.1 Weight (g) 26.4
29.1 34.5 33.0 32.6 32.6 40.6 Deformation 3.4 3.3 3.2 3.2 2.4 5.1
3.1 amount (mm) Hardness (Shore D) Central point 32 34 35 34 40 26
33 hardness Surface hardness 54 55 56 56 63 47 57 (Intermediate
layer) Thickness (mm) 2.4 1.3 1.3 1.3 1.3 1.3 -- Hardness (Shore D)
72 72 61 72 72 72 (Core) Diameter (mm) 41.1 39.0 41.1 41.1 41.1
41.1 -- Weight (g) 40.6 34.6 40.6 41.2 40.6 40.6 Deformation 2.7
2.9 2.95 2.8 2.0 4.3 amount (mm) (Cover) Thickness (mm) 0.8 1.9 0.8
0.8 0.8 0.8 0.8 Hardness (Shore D) 47 47 42 47 47 42 47
[0101]
5 TABLE 5 Example No. Test item 1 2 3 4 5 6 Deformation 2.7 2.7
2.75 3.05 2.6 2.8 amount (mm) Coefficient of 0.765 0.766 0.764
0.759 0.761 0.763 restitution Flight performance (W#1; 45 m/sec)
Spin amount 2850 2820 2900 2770 2950 2870 (rpm) Total (m) 232.5
233.3 231.0 232.1 229.9 231.5 Shot feel .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .DELTA. .smallcircle. Controllability
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle.
[0102]
6TABLE 6 Comparative Example No. Test item 1 2 3 4 5 6 7
Deformation 2.6 2.7 2.8 2.5 1.95 4.1 2.9 amount (mm) Coefficient of
0.769 0.748 0.746 0.771 0.776 0.739 0.757 restitution Flight
performance (W#1; 45 m/sec) Spin amount 2800 3230 3180 2700 2720
2800 3300 (rpm) Total (m) 233.5 224.9 223.5 235.1 236.0 224.0 223.0
Shot feel x x .DELTA. x x x .DELTA. Controllability .smallcircle.
.smallcircle. .smallcircle. x .DELTA. .smallcircle.
.smallcircle.
[0103] As is apparent from the results of Tables 5 and 6, the golf
balls of the present invention of Examples 1 to 6, when compared
with the golf balls of Comparative Examples 1 to 7, are superior in
flight distance, shot feel and controllability.
[0104] On the other hand, in the golf balls of Comparative Example
1, since the thickness of the intermediate layer having high
hardness is large, the shot feel is poor. In the golf ball of
Comparative Example 2, since the thickness of the cover is too
large, the coefficient of restitution is small and the spin amount
at the time of hitting is large, which reduces the flight distance.
In addition, the shot feel is poor.
[0105] In the golf balls of Comparative Example 3, since the
intermediate layer is formed from ionomer resin and has low
hardness, and the coefficient of restitution is small, which
reduces the flight distance. In the golf balls of Comparative
Example 4, since the cover hardness is high, the spin amount is
small, and controllability is poor, or the shot feel is poor.
[0106] In the golf balls of Comparative Example 5, since the
deformation amount of the center is small, the center is too hard,
and the shot feel of the resulting golf ball is poor. In the golf
balls of Comparative Example 6, since the deformation amount of the
center is large, the center is too soft, and the coefficient of
restitution is small, which reduces the flight distance. In
addition, the shot feel is heavy and poor. In the golf balls of
Comparative Example 7, since the intermediate layer having high
hardness is not present, the spin amount is large, which reduces
the flight distance.
* * * * *