Note: Descriptions are shown in the official language in which they were submitted.
21 ~ S 783
THREAD WOUND GOLF BALL
FIELD OF THE INVENTION
The present invention relates to a thread wound golf ball.
More particularly, it relates to a thread wound golf ball which keeps good
5 hit feeling inherently present in thread wound golf balls and attains long
flying distance.
BACKGROUND OF THE INVENTION
A thread wound golf ball is obtained by winding a thread
rubber on a solid or liquid rubber center to form a thread rubber layer and
10 covering on the thread rubber layer with a cover material (e.g. ionomer,
balata, etc.).
The thread wound golf ball is superior in hit feeling and
control properties to a two-piece solid golf ball using a solid core.
However, it can not attain long flying distance because a spin amount is
15 large and a launch angle is small in comparison with the two-piece solid
golf ball. Therefore, general amateur golfers tend to prefer the two-piece
solid golf ball which attains long flying distance in comparison with the
thread wound golf ball, and the two-piece solid golf ball have recently been
put on the market, exclusively.
OBJECTS OF THE INVENTION
The present invention has been accomplished in order to
solve a problem that the a conventional thread wound golf ball merely
attains relatively short flying distance, and the main object of the present
invention is to provide a thread wound golf ball which keeps good hit
21q~78~
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feeling inherently holding in thread wound golf balls and attains long flying
distance which is equal to that attained by the two-piece solid golf ball.
This object as well as other objects and advantages of the
present invention will become apparent to those skilled in the art from the
5 following description with reference to the accompanying drawing.
BRIEF EXPLANATION OF DRAWINGS
Fig. 1 is a schematic cross section illustrating one
embodiment of a thread wound golf ball of the present invention.
SUMMARY OF THE INVENTION
According to the present invention, the above object has
been accomplished by increasing a diameter of the center of the thread
wound golf ball and making the center hard to control an amount of spin to
be formed and increasing the launch angle to increase the flying distance.
That is, the present invention provides a thread wound golf
15 ball comprising a center composed of a vulcanized molded article of a
rubber composition, a thread rubber layer formed on said center and a
cover covering on said thread rubber layer, wherein said center has a
diameter of 30 to 35 mm and a strain amount formed between an initial
loading of 10 kg and a final loading of 30 kg is 1.2 to 2.5 mm.
DETAILED DESCRIPTION OF THE INVENTION
The center can be obtained, for example, by formulating 5 to
80 (preferably 15 to 50) parts by weight of a thermoplastic resin as a filler
for adjusting hardness, 2 to 12 (preferably 8 to 10) parts by weight of sulfur,
1 to 4 (preferably 1 to 2) parts by weight of a vulcanization accelerator and
21~5783
10 to 150 (preferably 50 to 120) parts by weight of a weight adjustor and, if
necessary, 3 to 10 (preferably 5 to 9) parts by weight of a vulcanization
auxiliary, based on 100 parts by weight of a rubber, to give a rubber
composition and subjecting the rubber composition to a vulcanization
5 molding.
In the present invention, the reason why large flying distance
of the thread wound golf ball can be attained while maintaining good hit
feeling by adjusting the diameter of the center at 30 to 35 mm and the
strain amount formed between initial loading (10 kg) and final loading (30
10 kg) at 1.2 to 2.5 mm is not clear at present, but is considered as follows.
It is considered that, by adjusting the diameter of the center at
30 to 35 mm and the strain amount formed between initial loading (10 kg)
and final loading (30 kg) at 1.2 to 2.5 mm, the deformation behavior of the
golf ball at the time of hitting becomes similar to that of the two-piece solid
15 golf ball and, as a result, the amount of spin to be formed at the time of
hitting is controlled and the launch angle becomes large, thereby
increasing the flying distance.
Further, the reason why the thread wound golf ball can keep
good hit feeling which is characteristics inherently holding in thread wound
20 golf balls regardless of improvement of the flying distance as described
above is considered that the tension of the thread rubber layer is small in
comparison with a conventional thread wound golf ball.
When the diameter of the center is smaller than 30 mm, the
thread rubber layer becomes thick and, as a result, the launch angle
25 becomes small and the spin amount becomes large. On the other hand,
when the diameter of the center is larger than 35 mm, the thread rubber
layer becomes thin and the thread rubber has already been wound before
- 4 21~783
the tension is formed so that a suitable hardness as the golf ball can not be
obtained.
Further, when the strain amount of the center is larger than
2.5 mm under the above condition, the thread rubber must be wound tightly
5 so as to obtain a proper ball hardness. As a result, the tension of the
thread rubber layer becomes large and the deformation at the time of
hitting is not easily arisen, thereby obtaining no desired technical effects.
On the other hand, when the strain amount of the center is smaller than 1.2
mm under the above condition, the hit feeling becomes inferior.
Further, it is preferred that the height of rebound of the center
is 120 cm or more, particularly 140 to 240 cm, when dropping it on a
concrete board from the height of 254 cm. That is, the fact that the center
has the large height of rebound shows that the impact resilience of the
center is large, and when the center has the large impact resilience, the
ball initial velocity at the time of hitting becomes large and, therefore, good
flying performances can be obtained. On the other hand, when the height
of rebound of the center is smaller than the above range, the ball initial
velocity becomes small and, therefore, long flying distance can not be
obtained easily.
As described above, the center is composed of the
vulcanized molded article of the rubber composition obtained by
formulating 5 to 80 (preferably 15 to 50) parts by weight of a thermoplastic
resin as a filler for adjusting hardness, 2 to 12 (preferably 8 to 10) parts by
weight of sulfur, 1 to 4 (preferably 1 to 2) parts by weight of a vulcanization
accelerator and 10 to 150 (preferably 50 to 120) parts by weight of a weight
adjustor and, if necessary, 3 to 10 (preferably 5 to 9) parts by weight of a
vulcanization auxiliary, based on 100 parts by weight of a rubber. The
5 21~S783
-
vulcanization is normally conducted by heating at 140 to 170C (preferably
150 to 160~C) under pressure for 5 to 30 minutes (preferably 10 to 20
minutes).
The rubber as the center is not specifically limited, and a
5 polybutadiene having high resilient performances (particularly high-cis
polybutadiene) is preferred. It is preferred that high-cis polybutadiene or a
rubber containing high-cis polybutadiene as a main component is used in
the preparation of the rubber composition for the center.
The thermoplastic resin is not specifically limited, and there
10 can be preferably used high-molecular weight polyolefins such as high-
styrene resin, high-molecular weight polyethylene, high-molecular weight
polypropylene, etc., or a mixture thereof.
The above rubber composition for center differs from a
conventional rubber composition for center in formulating the thermoplastic
15 resin as the filler for adjusting hardness.
The thermoplastic resin is used for adjusting the hardness of
the center and the amount is, as described above, 5 to 80 parts by weight,
preferably 15 to 50 parts by weight, based on 100 parts by weight of the
rubber. When the amount of the thermoplastic resin is smaller than the
20 above range, the hardness of the center can not be sufficiently increased.
Therefore, the hardness becomes the same as that of a conventional
center, thereby affording no desired effect. On the other hand, when the
amount of the thermoplastic resin is larger than the above range, the
hardness becomes too high and, therefore, the hit feeling becomes inferior
25 and the workability at the time of kneading of rubber also becomes inferior.
The amount of sulfur is, as described above, 2 to 12 parts by
weight, preferably 8 to 10 parts by weight, based on 100 parts by weight of
21~783
the rubber. When the amount of sulfur is smaller than the above range, the
vulcanization degree becomes low and, therefore, the desired hardness of
the center can not be obtained easily. On the other hand, when the
amount of sulfur is larger than the above range, the hardness of the center
5 becomes too high and, therefore, the desired effect can not be obtained.
Examples of the vulcanization auxiliary include metal oxides
(e.g. zinc oxide, magnesium oxide, etc.) and higher fatty acids (e.g. stearic
acid, palmitic acid, oleic acid, lauric acid, etc.). This vulcanization auxiliary
is preferably used for conducting the vulcanization smoothly, but is not
10 necessarily required.
The vulcanization accelerator may be any one which can be
used as the normal vulcanization accelerator of the sulfur vulcanization,
and typical examples thereof include thiazole vulcanization accelerators
such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, etc.; thiuram
15 vulcanization accelerators such as tetramethylthiuram monosulfide,
tetramethylthiuram disulfide, etc.; sulfenamide vulcanization accelerators
such as N-cyclohexyl-2-benzothiazyl sulfenamide, etc., but it is not limited
to those described above.
The vulcanization auxiliary and vulcanization accelerator may
20 be formulated according to the amount of sulfur to be formulated. The
amount of the vulcanization auxiliary is preferably 3 to 10 parts by weight,
particularly 5 to 9 parts by weight, based on 100 parts by weight of the
rubber, and the amount of the vulcanization accelerator is preferably 1 to 4
parts by weight, particularly 1 to 2 parts by weight, based on 100 parts by
25 weight of the rubber. When the amount of them is smaller than the above
range, the vulcanization due to sulfur can not be sufficiently conducted. On
the other hand, when the amount of them is larger than the above range,
2145783
_ 7
the hardness of the center becomes too high, which results in deterioration
of hit feeling.
Examples of the weight adjustor include barium sulfate, clay,
calcium carbonate, silica filler and the like, and the amount is, as described
above, preferably 10 to 150 parts by weight, particularly 50 to 120 parts by
weight, based on 100 parts by weight of the rubber.
When the amount of the weight adjustor is smaller than the
above range, the weight of the center becomes small and, the proper
weight as the golf ball can not be obtained. On the other hand, when the
10 amount of the weight adjustor is larger than the above range, the weight of
the center becomes large and, therefore, the ball weight exceeds the
standard value.
To the rubber composition for center, antioxidants, etc. may
be added, in addition to the above components.
2145783
The construction of the golf ball of the present invention will
be explained with reference to the accompanying drawing. Fig. 1 is a
schematic cross section illustrating one embodiment of the thread wound
golf ball of the present invention. In Fig. 1, 1 is a center, 2 is a thread
5 rubber layer and 3 is a cover.
The center 1 is composed of a vulcanized molded article of a
rubber composition and the diameter of the center is 30 to 35 mm. Further,
the strain amount of the center, which is formed between initial loading (10
kg) and final loading (30 kg), is within a range of 1.2 to 2.5 mm.
The thread rubber layer 2 is formed by winding a thread
rubber around the center 1, and a so-called thread wound core is
composed of the center 1 and thread rubber layer 2 constitute.
As the thread rubber used for forming the thread rubber layer
2, there can be used the same thread rubber which has hitherto been
used. For example, there c~an be used those obtained by vulcanizing a
rubber composition wherein sulfur, a vulcanization auxiliary, a
vulcanization accelerator, an antioxidant, etc. are formulated in a natural
rubber, or a natural rubber and a synthetic polyisoprene.
The thread rubber layer 2 is covered with the cover 3 and 3a
is a dimple provided on the cover 3 and, if necessary, a suitable number of
dimples 3a may be provided according to the desired characteristics.
As the cover 3, there can be used both ionomer cover
containing ionomer as a main material and balata cover, but the ionomer
cover is preferred in view of increase in flying distance.
A method of covering the core with cover is not specifically
limited, and the covering is conducted by a normal method. For example,
there can be used a method comprising molding two half-shells having a
Z1~57~3
_, g
semispherical shape in advance, covering a core using them and
subjecting to a pressure molding at 130 to 170C for 1 to 15 minutes, or a
method comprising injection-molding a composition for cover directly on a
core to cover the core. The thickness of the cover is normally about 1 to 4
mm. Then, a dimple may be optionally formed on the surface of the golf
ball at the time of cover molding. Further, paint finishing, stamping, etc.
may be optionally provided after cover molding.
According to the present invention, there could be provided a
thread wound golf ball which attains long flying distance while maintaining
a good hit feeling as a characteristic of the thread wound golf ball, by
increasing a diameter of the center and making the center hard in
comparison with a conventional thread wound golf ball.
EXAM PLES
The following Examples and Comparative Examples further
illustrate the present invention in detail but are not to be construed to limit
the scope thereof.
Examples 1 to 5 and Comparative Examples 1 to 7
A rubber composition for center having a formulation shown
in Tables 1 and 2, and the resulting rubber composition was charged in a
mold for center and subjected to compression molding/vulcanization at
1 55C for 20 minutes to give a center, respectively.
The diameter, the JIS-A hardness (hardness measured by a
JIS-A hardness tester), the strain amount, the height of rebound and the
weight of the resulting center are shown in Tables 1 and 2.
The amount of the respective formulation amount to be
formulated shown in Tables 1 and 2 is represented by parts by weight. The
diameter, the JIS-A hardness (hardness measured by a JIS-A hardness
Z~S783
tester), the strain amount, the height of rebound and the weight of the
resulting center are shown in Tables 1, in addition to the composition of
Examples 1 to 5. Those as to Comparative Examples 1 to 7 are shown in
Table 2.
Further, the measuring method of the strain amount and
height of rebound is as follows. The explanation of the formulation
component will be described the back of Table 2.
Strain amount:
The strain amount formed between initial loading (10 kg) and
final loading (30 kg) is measured.
Height of rebound:
The height of rebound of the center is measured when
dropping it on a concrete board from the height of 254 cm.
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1 1
Table 1
Example No.
2 3 4 5
BR11 3~1 100 100 100 100 100
Nippol 2007J ~2 30 30 30 40 0
MiperonXM-220 3~3 0 0 0 0 30
Sulfur 10 10 10 10 10
Vulcanization auxiliary39~4 7 7 7 7 7
Vulcanization accele,~ r3~5 1.5 1.5 1.5 1.5 1.5
Weightadjustor ~6 90 80 70 75 90
Center
Diameter (mm) 30.3 31.3 32.4 32.3 31.2
JIS-A hardness 86 87 87 90 86
Strain amount (mm) 1.95 1.98 2.00 1.78 1.90
Height of rebound (cm)200 198 196 190 210
Weight (9) 20.4 22.1 23.2 23.2 22.1
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12
Table 2
Comparative Example No.
2 3 4 5 6 7
BR11 ~1 100 100 100 100 100 100 100
Nippol2007J ~2 0 0 0 0 85 0 40
Sulfur 10 10 10 15 10 10
Vulcanization auxiliary 3~3 7 7 7 7 7 7 7
Vulcanization accelerator 3~4 1.5 1.5 1.5 1.5 1.5 1.5 1.5
Weight adjustor ~5 83 70 65 65 90 33 77
Center
Diameter (mm) 28.2 30.2 31.3 31.2 32.3 35.5 32.3
JIS-A hardness 76 75 74 85 99 73 84
- Strainamount(mm) 3.17 3.20 3.25 2.65 1.18 3.35 2.20
Heightofrebound(cm) 216 215 214 210 180 205 118
Weight(g) 17.5 20.5 22.0 22.0 23.2 29.1 23.1
~1: Trade name, high-cis polybutadiene (amount of 1,4-cis-
polybutadiene: 96%) manufactured by Nihon Gosei Gomu Co., Ltd.
~2: Trade name, high-styrene resin manufactured by Nihon Zeon Co.,
Ltd.
~3: Trade name, high-molecular weight polyethylene manufactured by
Mitsui Petroleum Chemical Industries Co., Ltd.
3~4: 5 Parts by weight of zinc white, GINREI R (trade name, manufactured
by Toho Aen Co., Ltd.) and 2 parts by weight of stearic acid
(manufactured by Nihon Yushi Co., Ltd.)
~5: 0.25 Parts by weight of Noxxelar TT (trade name, tetramethylthiuram
21~578~
13
disulfide, manufactured by Ohuchi Shinko Kagaku Kogyo Co., Ltd.)
and 1.25 parts by weight of Noxxelar CZ-G (trade name, N-
cyclohexyl-2-benzothiazyl sulfenamide, manufactured by Ohuchi
Shinko Kagaku Kogyo Co., Ltd.)
5 ~6: Barium sulfate (manufactured by Sakai Kagaku Kogyo Co., Ltd.
Next, a thread rubber comprising a natural rubber/low-cis
synthetic polyisoprene (50:50, weight ratio) [Shell IR-309 (trade name),
manufactured by Shell Kagaku Co., Ltd.] as the base rubber was wound
around each center thus obtained as described above to form a thread
10 rubber layer, thereby preparing a thread wound core of 39.5 mm in outer
diameter.
The above core was covered with pair of semispherical half-
shells molded from the composition for cover, followed by subjecting to a
press molding in a mold for ball at 150C for 3 minutes to give a thread
15 wound golf ball. The resulting golf ball was coated with a paint to finish a
golf ball of 42.7 mm in outer diameter. The composition for cover is
obtained by formulating 2 parts by weight of titanium dioxide in an ionomer
mixture of Hi-milane 1605 (trade name) and Hi-milane 1706 (trade name)
(50:50, weight ratio), which are ionomer neutralized with a sodium ion
20 manufactured by Mitsui Du Pont Polychemical Co., Ltd. and ionomer
neutralized with a zinc ion manufactured by Mitsui Du Pont Polychemical
Co., Ltd., respectively.
The weight, the compression, the flying performances and the hit
feeling of the resulting golf ball were examined. The flying performances
25 were examined as to the case when hitting with a No. 1 wood club (flying
performances 1) and the case when hitting with a No. 5 iron club (flying
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14
performances 2).
The evaluation results of the weight, the compression, the flying
performances 1 ) and 2) and the hit feeling of the golf balls of Examples 1 to
5 are shown in Table 3. Those of the golf balls of Comparative Examples 1
5 to 4 were shown in Table 4 and those of the golf balls of Comparative
Examples 5 to 7 are shown in Table 5.
Further, the measuring method of the compression, flying
performances 1 and flying performances 2 as well as the evaluation
method of the hit feeling and the evaluation criteria are as follows.
1 0 Compression:
An initial load (10 kg) is applied on the golf ball, and then the
load is gradually increased to the final load (130 kg). The amount of strain
formed between initial loading and final loading of the golf ball is
measured according to PGA system.
15 Flying performances 1:
A Swing robot manufactured by True Temper Co. is equipped
with a No. 1 wood club and the golf ball is hit at a head speed of about 45
m/second to measure the flying performances 1. The spin amount is
determined by taking a photograph of the golf ball to be hit. The carry is a
20 distance of the golf ball from the point where it was dropped. The total is atotal of the carry and a distance of the golf ball running from the point
where it was dropped.
Flying performances 2:
A Swing robot manufactured by True Temper Co. is equipped
25 with a No. 5 iron club and the golf ball is hit at a head speed of about 38
m/second to measure the flying performances 2.
Evaluation method of hit feeling and evaluation criteria:
21~578~
The golf ball is practically hit with No. 1 wood club by 10 top
professional golfers to evaluate the hit feeling. The evaluation criteria are
as follows. The results shown in Tables 3 to 5 are based on the fact that
not less than 8 out of 10 golfers evaluated with the same criterion.
5 0: Good hit feeling which is similar to that of a standard thread
wound golf ball using a balata cover
XH: Heavy and inferior
XS: Soft and heavy feeling, inferior
16 21~57~
Table 3
Example No.
2 3 4 5
Ball
Weight(g) 45.4 45 4 45 5 45 3 45 3
Compression 86 87 87 86 86
Flying performances 1 (No.1 wood club)
Launch angle (degree) 11.2 11.3 11.4 11.5 11.4
Spin (rpm) 3150 3130 3080 3050 3120
Carry (yard) 227.0 227.3 228.0 228.2 227.2
Total (yard) 233.5 233.9 234.5 234.7 234.0
Flying performances 2 (No.5 iron club)
Launch angle (degree) 14.7 14.8 15.0 15.2 14.9
Spin (rpm) 4800 4750 4730 4700 4730
Carry (yard) 187.3 187.5 187.9 188.0 187.6
Total (yard) 189.5 189.8 190.0 190.5 189.7
Hit feeling O O O O
21~S783
17
Table 4
Comparative Example No.
2 3 4
Ball
Weight(g) 45.4 45.4 45-4 45 3
Compression 86 86 86 87
Flying performances 1 (No.1 wood club)
Launch angle (degree) 10.7 11.0 10.9 11.1
Spin (rpm) 3400 3300 3310 3280
Carry (yard) 224.0 225.0 224.8 225.2
Total (yard) 229.5 230.2 230.0 230.4
Flying performances 2 (No.5 iron club)
Launch angle (degree) 14.0 14.5 14.4 14.5
Spin (rpm) 5150 5020 5030 5000
Carry (yard) 184.3 185.0 184.8 185.2
Total (yard) 186.5 187.3 187.0 187.2
Hit feeling xH xH xH xH
~1~5~83
18
Table 5
Comparative Example No.
6 7
Ball
Weight (9) 45.4 45.3 45.4
Compression 86 65 86
Flying performances 1 (No.1 wood club)
Launch angle (degree) 11.2 11.5 11.0
Spin (rpm) 3320 3100 3350
Carry (yard) 225.5 223.5222.5
Total (yard) 230.5 229.0228.0
Flying performances 2 (No.5 iron club)
Launch angle (degree) 14.3 15.0 14.1
Spin (rpm) 5030 4800 5100
Carry (yard) 184.7 184.0183.0
Total (yard) 187.1 187.5186.5
Hit feeling xH xS O
As is apparent from comparing the results shown in Tables 3,
4 and 5, regarding the golf balls of Examples 1 to 5, the spin amount was
small and the launch angle was large and, further the flying distance was
5 large in comparison with the golf balls of Comparative Examples 1 to 7.
The flying distance (carry) due to the No. 1 wood club of a standard two-
piece solid golf ball using a solid core is normally 225.0 to 235.0 yards
21~578~
19
and, therefore, it is understood that the flying distance of the golf balls of
Examples 1 to 5 is large, which is equal to that of a two-piece solid golf
ball. Further, in the evaluation of Examples 1 to 4 using the same
thermoplastic resin, as the diameter of the center becomes larger and the
5 center becomes harder, the spin tends to become small and the launch
angle tends to become large, which results in large flying distance.
To the contrary, regarding the golf balls of Comparative
Examples 1 to 3 and 6, the center was soft and its strain amount was
large and, therefore, large flying distance could not be attained. Also,
10 regarding the golf ball of Comparative Example 4, the strain amount of the
center was large and, therefore, large flying distance could not be
attained. Regarding the golf ball of Comparative Example 5, the center
was too hard and its strain amount was small and, therefore, large flying
distance could not be attained. Regarding the golf ball of Comparative
15 Example 7, the height of rebound was small and the impact resilient is
insufficient and, therefore, the initial velocity became small, thereby
attaining small flying distance.
Further, the golf balls of Comparative Examples 1 to 5
maintained a good hit feeling which is similar to that of a standard thread
20 wound golf ball using a balata cover, but some golf balls among the golf
balls of Comparative Examples 1 to 6 were too hard or soft and, therefore,
they were inferior.
