JP2880688B2 - Three piece solid golf ball - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-piece solid golf ball in which a core having a two-layer structure comprising an inner core and an outer core is covered with a cover.

[0002]

2. Description of the Related Art Currently available golf balls are roughly classified into solid golf balls and thread-wound golf balls. Among them, solid golf balls include golf balls having a one-layer, two-layer or three-layer structure. Particularly, solid golf balls having a two-layer or three-layer structure tend to have a softer cover, especially a short iron. The development of a ball that emphasizes so-called controllability, which increases the spin rate at the time of hitting and easily stops at landing, is being actively promoted.

[0003]

However, simply softening the cover increases the spin rate, but lowers the ball's repulsion performance and reduces the flight distance.

Accordingly, it is an object of the present invention to provide a solid golf ball that satisfies both a flight distance and controllability. In other words, the object of the present invention is to develop a solid golf ball that has a long flight distance on a driver shot and a large spin rate on a short iron shot near the green and has a good controllability to stop immediately.

[0005]

According to the present invention, the core has a two-layer structure of an inner core and an outer core, and the diameter of the inner core is 25 to 37 m.
m, and the hardness at the center of the inner core is 60 to 85 as measured by a JIS-C hardness tester, the difference in hardness from the center of the inner core to the surface is 4 or less, and the hardness of the surface of the outer core is JIS. -By increasing the hardness measured by a C-type hardness meter to 75 to 90, the repulsion performance is enhanced to increase the flight distance,
Furthermore, the cover has a flexural rigidity of 1200 to 3600 kg /
By constituting the cover composition of cm ² , the controllability is improved, the long flight distance on driver shots and the good controllability on short iron shots are both achieved, and the above object has been achieved.

[0006] In the present invention, the diameter of the inner core is 25 to 3
7 mm, the hardness of the center of the inner core is 60 to 85 as measured by a JIS-C type hardness meter, and the hardness difference from the center of the inner core to the surface is 4 or less. This is due to the following reason. .

[0007] That is, when the diameter of the inner core is smaller than 25 mm, the ball becomes hard and the shot feeling is deteriorated. When the diameter of the inner core is larger than 37 mm, the outer core is formed around the inner core to produce a core. In addition, since the thickness of the outer core becomes thinner, it is very difficult to control the thickness of the outer core, so that the uniformity of the characteristics of the ball is impaired,
Flight performance becomes unstable. When the hardness at the center of the inner core is lower than 60 as measured by a JIS-C hardness tester, the core becomes soft and the rebound performance is reduced, so that the flight distance is reduced, and the hardness at the center of the inner core is JIS. If the hardness measured by a C-type hardness tester is higher than 85, it becomes too hard and brittle, so that the durability decreases. When the hardness difference from the center of the inner core to the surface is larger than 4, the energy loss at the time of hitting the ball becomes large, so that the repulsion performance is reduced and the flight distance is reduced.

In the present invention, the hardness of the surface of the outer core (the surface of the outer core corresponds to the surface of a core having a two-layer structure composed of an inner core and an outer core) is measured by a JIS-C type hardness meter. The hardness of the cover is 75 to 90, and the flexural modulus of the cover composition constituting the cover is 1200 to 3600 kg / cm.
It needs to be ² , for the following reasons:

That is, the hardness of the surface of the outer core is JIS-C
When the hardness measured by a mold hardness meter is lower than 75, the ball compression is reduced, so that the repulsion performance is reduced, the flight distance is reduced, and the hardness of the outer core surface is JIS-
If the hardness measured by a C-type hardness meter is higher than 90, the ball is too hard and the shot feeling (feel at the time of hitting the ball) deteriorates. And, the flexural rigidity of the cover composition is 1200 kg / cm.
^When it is lower than ² , the rebound performance is reduced, the flight distance is reduced, and the flexural modulus of the cover composition is 3600 kg /
If it is higher than cm ² , the spin rate on short iron shots will decrease and controllability will deteriorate.
In the present invention, the flexural rigidity of the cover is not determined,
The bending stiffness of the cover composition is used, but once the ball is formed, the current technology cannot measure the bending stiffness from the cover. This is because a test piece must be prepared from the composition. As described above, although the flexural rigidity cannot be measured from the cover of the golf ball, it is considered that the flexural rigidity of the cover is substantially the same as the flexural rigidity of the cover composition.

In the present invention, as described above, the hardness of the surface of the outer core is 75 as a hardness measured with a JIS-C type hardness meter.
It is particularly preferable that the hardness of the surface of the outer core is higher than the hardness of the surface of the inner core by at least 3 within the range, because all of the shot feeling, rebound performance and flight performance are improved.

The above-mentioned inner core is composed of a cross-linked molded article of a rubber composition. The rubber composition for producing the inner core is usually kneaded by mixing a rubber with a cross-linking agent, a cross-linking initiator, a filler and the like. It is prepared by If necessary, an antioxidant, a crosslinking regulator, a softener, and the like may be appropriately blended.

The cis-1,4 structure is preferably 8
Butadiene rubber containing 5% or more is preferable, but other rubbers such as natural rubber, isoprene rubber,
A material obtained by appropriately mixing styrene-butadiene rubber or the like may be used.

As the crosslinking agent, metal salts of α, β-unsaturated carboxylic acids are used. Examples of the metal salt of the α, β-unsaturated carboxylic acid include metal salts of acrylic acid such as zinc acrylate and magnesium acrylate, and metal salts of methacrylic acid such as zinc methacrylate and magnesium methacrylate. One or two or more are selected and used, and zinc acrylate and zinc methacrylate are particularly preferred. The amount of the metal salt of the α, β-unsaturated carboxylic acid as the crosslinking agent is not particularly limited, but is preferably 20 to 35 parts by weight based on 100 parts by weight of the rubber. The metal salt of the α, β-unsaturated carboxylic acid is compounded with the α, β-unsaturated carboxylic acid and the metal oxide at the time of compounding, and the kneaded rubber composition is mixed with the α, β-unsaturated carboxylic acid. A metal salt may be generated.

Examples of the crosslinking initiator include dicumyl peroxide and 1,1-bis (t-butylperoxy).
Organic peroxides such as -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and di-t-butyl peroxide are used. Mil peroxide is preferred. The amount of the crosslinking initiator is not particularly limited, but may be 0.5 to 100 parts by weight of the rubber.
2.5 parts by weight are preferred.

As the filler, for example, inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, barium carbonate and clay are mainly used. Although the amount of the filler is not particularly limited,
20 to 25 parts by weight relative to 0 parts by weight is preferred.

When a crosslinking modifier is blended, a sulfur compound such as morpholine disulfide, pentachlorothiophenol or diphenyl disulfide is used as the crosslinking modifier. It is preferred to add about 0.1 to 1.5 parts by weight per part.

The inner core is produced by crosslinking and molding the above rubber composition for the inner core by press molding or injection molding. In the case of the former press molding, the above rubber composition is filled in a mold, and usually at 140 to 180 ° C for 10 to 60.
By heating for a minute and performing cross-linking molding, an inner core is produced. In the case of the latter injection molding, the mold temperature is 135-1.
This is done by heating at 65 ° C. for 10-20 minutes. The inner core has a diameter of 25 to 37 mm. The inner core preferably has a diameter of 28 to 35 mm. Further, the heating at the time of the cross-linking molding may be performed in two or more steps.

The outer core is also produced by crosslinking and molding a rubber composition using the same material as the inner core. The hardness of the surface of the outer core was measured with a JIS-C type hardness meter as described above. To achieve a hardness of 75 to 90, the crosslinking agent α, β-
The compounding amount of the metal salt of the unsaturated carboxylic acid is preferably 25 to 35 parts by weight based on 100 parts by weight of rubber, and the compounding amount of the crosslinking initiator is 1 to 3 parts by weight based on 100 parts by weight of rubber. Is preferred.

The cross-linking molding for producing the outer core is performed by press molding or injection molding as in the case of the inner core. In the case of press molding, a pair of hemispherical shells is prepared from the rubber composition for the outer core, the inner core is put into the half shells, and the core is formed by crosslinking with a mold.
The conditions at the time of the cross-linking molding are usually 160 to 180
Heating at 10 ° C. for 10-40 minutes is employed. Also,
When using injection molding, simply mold and make a pair of half shells, put the inner core in it and finish it into a core by press molding, or make a pair of half shells in a semi-crosslinked shape by injection molding in advance Then, a method of putting an inner core therein and finishing the core by press molding is adopted. In the crosslinking of the outer core, heating may be performed in two or more stages.

The thickness of the outer core depends on the diameter of the inner core, but is usually preferably 1 to 7 mm.

Various types of covers can be used. For example, ionomers are mainly used, or polyamide, polyester, polyurethane,
A cover composition prepared by adding a synthetic resin containing polyethylene or the like as a main material and adding a pigment such as titanium dioxide or barium sulfate and, if necessary, an antioxidant is used.

Examples of the ionomer include Himilan 1605 (Na) and Himilan 1706 (Z
n), Himilan 1707 (Na), Himilan AM7
315 (Zn), Himilan AM7316 (Zn), Himilan AM7317 (Zn), Himilan AM731
8 (Na), Himilan MK7320 (K), Himilan 1555 (Na), Himilan 1557 (Zn) (all trade names, manufactured by Du Pont-Mitsui Polychemicals), Surlyn 8920 (Na), Surlyn 8940 (Na), Surlyn AD8512 (Na), Surlyn 7930 (L
i), Surlyn 7940 (Li), Surlyn 9910
(Zn), Surlyn AD8511 (Zn), Surlyn 9
650 (Zn) (all trade names, manufactured by DuPont, USA), Iotek 7010 (Zn), Iotek 8
000 (Na) (all are trade names, manufactured by Exxon Chemical Co.)
These ionomers are used alone or as a mixture of two or more. In addition, N described in parentheses (parentheses) after the trade name of the above ionomer
a, Zn, K, Li and the like indicate their neutralizing metal ion species.

In the present invention, the flexural rigidity of the cover composition is also an important characteristic for improving controllability, and the flexural rigidity of the cover composition is adjusted to 1200 to 3600 kg / cm ² as described above. To The bending stiffness of the cover composition as described above can be achieved by selecting the above ionomer or using two or more kinds in combination.

For forming the cover, for example, the cover composition as described above is preliminarily formed into a hemispherical shell half shell, and the two cores are used to wrap the core.
C. for 1 to 15 minutes, or a method in which the cover composition is directly injection-molded around the core to wrap the core.

The thickness of the cover is usually about 1 to 4 mm. The hardness of this cover is 59 in Shore D hardness.
It is preferably from 70 to 70. When the cover hardness is lower than 59 in Shore D hardness, the rebound performance tends to decrease and the flight distance tends to decrease. When the cover hardness is higher than 70 in Shore D hardness, the shot feeling and controllability deteriorate. Tend. Further, when forming the cover, dimples are formed on the ball surface as necessary, and after the cover is formed, paint finishing, stamping, and the like are performed as necessary.

Next, a three-piece solid golf ball of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically illustrating an example of a three-piece solid golf ball of the present invention. In the figure, reference numeral 1 denotes a core, and the core 1 includes an inner core 1a and an outer core 1b formed therearound. 2
Is a cover for covering the core 1.

The inner core 1a is made of a cross-linked molded article of a rubber composition, has a diameter of 25 to 37 mm, and has a center hardness of 60 to 85 as measured by a JIS-C type hardness meter. It is manufactured so that the hardness difference from the center to the surface is 4 or less. The outer core 1b is the inner core 1
It consists of a cross-linked molded article of the rubber composition formed around a, and has a surface hardness of 75 to 90 as measured by a JIS-C type hardness meter. The cover 2 is made of a cover composition having a flexural rigidity of 1200 to 3600 kg / cm ² , and includes the inner core 1 a and the outer core 1 b.
The periphery of the core 1 having a layer structure is covered, and the hardness of the cover 2 is preferably 59 to 70 in Shore D hardness.

Reference numeral 3 denotes a dimple.
Are provided on the cover 2 in an appropriate number and in an appropriate manner so as to obtain desired or desired characteristics. In addition, the three-piece solid golf ball is painted or marked on the ball surface as necessary.

[0029]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Examples 1 to 6 and Comparative Examples 1 to 6 A rubber composition for an inner core was prepared with the compounding composition shown in Tables 1 to 4,
The obtained rubber composition was filled in a mold for an inner core, and was subjected to cross-linking molding under the conditions shown in Tables 1 to 4 to produce an inner core.
The diameter and hardness of the obtained inner core were measured. The results are shown in Tables 1 to 4. In addition, the compounding quantity of each component in a table | surface is a part by weight, and this is the same also in the table | surface which shows the following compounding composition. The hardness of the inner core was measured with a JIS-C type hardness meter at the center of the inner core, at a position of 5 mm from the center to the surface, at a position of 10 mm from the center to the surface, at a position of 15 mm from the center to the surface, and at the surface. The hardness inside the inner core, such as the hardness at the center of the inner core, was measured at predetermined positions by cutting the inner core into two equal parts.

Table 1 shows the composition of the inner core, the diameter of the inner core, the crosslinking conditions and the hardness of the inner core of Examples 1 to 3, Table 2 shows those of Examples 4 to 6, and Table 3 shows those of Comparative Examples 1 to 6. 3 and Table 4 shows those of Comparative Examples 4 to 6. In addition,
The butadiene rubber used in the preparation of the rubber composition for the inner core is BR-11 (trade name) manufactured by Nippon Synthetic Rubber Co., Ltd.
The cis-1,4 structure content of this butadiene rubber is 96
%. The antioxidant used was Nocrack NS-6 (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. The two-stage cross-linking conditions indicate that the heating for cross-linking was performed in two stages. In addition, because the diameter of the inner core is small, if there is no hardness measurement point at the corresponding position, of course,
Does not show hardness.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

Next, a rubber composition for an outer core was prepared with the compounding composition shown in Tables 5 to 8, and a pair of half shells was formed from the obtained rubber composition. Cross-linking molding in the mold under the cross-linking conditions shown in Tables 5 to 8,
A core having a diameter of 39 mm was produced. The hardness of the surface of the obtained core (that is, the hardness of the surface of the outer core) is determined by JIS-
It was measured with a C-type hardness meter. The results are shown in Tables 5 to 8. In Comparative Example 4, the hardness of the core surface was not measured because the diameter of the inner core was too large, the thickness of the outer core was thin, and the thickness was uneven, so that proper characteristics could not be evaluated. Therefore, Table 8 does not show the measurement results of the hardness of the surface of the core of Comparative Example 4. The butadiene rubber and antioxidant used in preparing the rubber composition for the outer core are the same as those used in preparing the inner core.

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

[Table 8]

Next, cover compositions A to G were prepared with the composition shown in Tables 9 to 10, and the flexural rigidity and Shore D hardness of the obtained cover compositions were measured. The results are shown in Tables 9 to 10. For the measurement of the flexural rigidity, a cover-shaped composition was press-molded to prepare a flat test piece having a thickness of about 2 mm, and after standing at 23 ° C. and 50% relative humidity for 2 weeks according to ASTM D-747. The measurement was performed using a stiffness meter manufactured by Toyo Seiki. The measurement of Shore D hardness is
The composition for the cover was press-molded to produce a flat test piece having a thickness of about 2 mm, and the test piece was prepared according to ASTM D-2240.
After standing at 3 ° C. and a relative humidity of 50% for 2 weeks, the measurement was performed using a Shore D hardness meter. The hardness of the cover, other than the method of preparing a test piece from the cover composition as described above,
It can also be measured from a golf ball cover. Table 9
Shows the composition, flexural rigidity and hardness (Shore D hardness) of cover compositions A to D, and Table 10 shows the composition, flexural rigidity and hardness (Shore D hardness) of cover compositions E to G. ). Details of the components indicated by the trade names in the table are shown after Table 10.

[0042]

[Table 9]

[0043]

[Table 10]

* 1: Himilan 1855 (trade name) Ethylene-butyl acrylate-methacrylic acid terpolymer ionomer of zinc ion neutralizing type manufactured by Du Pont-Mitsui Polychemicals, flexural rigidity = about 900 kg / c
m ² * 2: Himilan 1555 (trade name) Ethylene-methacrylic acid copolymer ionomer of sodium ion neutralization type manufactured by Mitsui DuPont Polychemicals, flexural rigidity = 2100 kg / cm ² * 3: Himilan 1706 (trade name) Ethylene-methacrylic acid copolymer ionomer of zinc ion neutralization type manufactured by Mitsui Dupont Polychemical Co., Ltd., flexural rigidity = 2500 kg / cm ² * 4: Himilan 1557 (trade name) Zinc ion neutralization manufactured by Mitsui Dupont Polychemical Co., Ltd. Type ethylene-methacrylic acid copolymer ionomer, flexural rigidity = 2400 kg / cm ² * 5: Himilan 1605 (trade name) Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer manufactured by Mitsui Dupont Polychemicals, Flexural rigidity = about 3500 kg / cm ²

Next, the cover compositions A to G prepared as described above were injection-molded on the cores in the combinations shown in Tables 11 to 14 to form covers, and a three-piece solid golf having an outer diameter of 42.7 mm was formed. A ball was made. However,
In Tables 11 to 14, the types of cover compositions are indicated by the symbols, and the flexural rigidity and hardness (Shore D hardness) are additionally described. In Comparative Example 4, balls were not produced because the thickness was uneven at the time of formation of the outer core and valid characteristics could not be evaluated. Therefore, Table 14 shows the types of the cover composition and the flexural rigidity. And no characteristic values relating to Comparative Example 4 are shown.

The ball weight of the obtained golf ball, US
The ball compression, coefficient of restitution, flight distance (carry), spin rate, controllability, and shot feeling by the GA method were examined. The results are shown in Tables 11 to 14. In addition,
The methods for measuring or evaluating the above-mentioned coefficient of restitution, flight distance, spin amount, controllability and shot feeling are as follows.

Coefficient of restitution: Using an air gun of the same model as the air gun whose initial speed is measured by R & A (British Golf Association), the ball speed when a metal cylinder of 198.4 g collides with the ball at a speed of 45 m / s is measured. Then, it is calculated from the ball speed. The larger the value, the higher the resilience performance of the golf ball.

Flying distance: A driver (Wood No. 1 club) was attached to a swing robot manufactured by True Temper, and the ball was hit at a head speed of 45 m / s to measure the distance to the drop point.

Spin Amount: An iron No. 9 club was attached to a swing robot manufactured by True Temper, the ball was hit at a head speed of 34 m / s, and the hit ball was continuously photographed and examined.

Controllability: The golf ball was actually hit with a sand wedge by four professional golfers and six amateur golfers with a handicap of 10 or less. The evaluation criteria are as follows. When the evaluation results are displayed in the table, the same symbols are used. In this case, it is indicated that eight or more out of ten persons who have evaluated have made the same evaluation.

Evaluation criteria: ○: good △: normal ×: bad

Shot feel: A driver (wood No. 1 club) drives a ball by a total of 10 professional golfers and 6 amateur golfers with a handicap of 10 or less.
Evaluate by hitting it. The evaluation criteria are as follows. When the evaluation results are displayed in the table, the same symbols are used. In this case, it is indicated that eight or more out of ten persons who have evaluated have made the same evaluation.

Evaluation criteria: ○: good △: normal ×: bad

[0054]

[Table 11]

[0055]

[Table 12]

[0056]

[Table 13]

[0057]

[Table 14]

As is clear from the comparison between the ball characteristics of Examples 1 to 6 shown in Tables 11 to 12 and the ball characteristics of Comparative Examples 1 to 6 shown in Tables 13 and 14, Examples 1 to 6 showed the flight distance. Was large, the spin rate was large, the controllability was good, and the shot feeling was good. That is, Table 1
As shown in FIG. 2, the diameter of the inner core is in the range of 25 to 37 mm, and the hardness of the center of the inner core is in the range of 60 to 85 as measured by a JIS-C hardness tester. The hardness difference is 4 or less, and the hardness of the outer core surface is
As shown in the figure, the hardness measured by a JIS-C type hardness tester is 75
And the flexural modulus of the cover composition constituting the cover is 120 as shown in Tables 11-12.
Examples 1 to 6 in the range of 0 to 3600 kg / cm ²
Has a flight distance of 223 to 226 as shown in Tables 11 to 12.
It was large in yards, and the evaluation of controllability was good, the controllability was good, and the evaluation of shot feeling was also good, and the shot feeling was good.

On the other hand, in Comparative Example 1, as shown in Table 3, the hardness at the center of the inner core was low and the difference in hardness from the center of the inner core to the surface was large. As shown in the figure, the flight distance was short, and the controllability and feel at impact were not good. Comparative Example 2
As shown in Tables 3 and 7, the hardness of the center of the inner core and the hardness of the surface of the outer core were too low, so that the repulsion performance was reduced, and as shown in Table 13, the flight distance was reduced and the shot feeling was heavy. It was bad. In Comparative Example 3, since the diameter of the inner core was small as shown in Table 3, the ball was hardened.
As shown in the figure, the shot feeling was poor and the controllability was also poor.

As shown in Table 14, Comparative Example 5
Since the flexural rigidity of the cover composition constituting the cover is small, the rebound performance is reduced and the flight distance is reduced. In Comparative Example 6, the flexural rigidity of the cover composition constituting the cover is too large. Also, controllability and shot feeling were poor. In Comparative Example 4, as shown in Table 4, since the diameter of the inner core was too large, as described above, when the outer core was formed and the core was manufactured, the outer core was extremely uneven in thickness, and proper property evaluation was performed. No ball was made because it was not possible.

[0061]

As described above, according to the present invention, a three-piece solid golf ball having a large flight distance and good controllability, and satisfying both the flight distance and controllability can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a three-piece solid golf ball of the present invention.

[Explanation of symbols]

 1 core 1a inner core 1b outer core 2 cover

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kuniyasu Horiuchi 2-1-6-115, Jonai-dori, Nada-ku, Kobe-shi, Hyogo (56) References JP-A-7-194735 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) A63B 37/00 A63B 37/04 A63B 37/12

Claims (2)

(57) [Claims] 1. A three-piece solid golf ball in which a core having a two-layer structure consisting of an inner core and an outer core is covered with a cover, the inner core has a diameter of 25 to 37 mm, and the hardness of the center of the inner core is JIS-C type. 6 with hardness measured with a hardness meter
0 to 85, and the hardness difference from the center of the inner core to the surface is 4 or less, and the hardness of the surface of the outer core is 75 to 90 as measured by a JIS-C type hardness meter. Flexural rigidity of the constituent cover composition is 1200 to 3
A three-piece solid golf ball having a weight of 600 kg / cm ² . 2. The three-piece solid golf ball according to claim 1, wherein the hardness of the surface of the outer core is higher than the hardness of the surface of the inner core.