JPH08332247A - Three-piece solid golf ball - Google Patents

Abstract

(57) [Summary] [Objective] To provide a three-piece solid golf ball having a long flight distance and good controllability. [Structure] The core has a two-layer structure of an inner core and an outer core, the inner core has a diameter of 25 to 37 mm, and the center hardness of the inner core is 60 to 85 in terms of hardness 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, and the hardness of the surface of the outer core is 75 to 90 as measured by JIS-C type hardness tester, and the bending rigidity of the cover is 1200 to 3600 kg / cm. ^A three-piece solid golf ball is formed by forming the cover composition of ² .

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 having a two-layer core composed of an inner core and an outer core covered with a cover.

[0002]

2. Description of the Related Art Golf balls currently on the market are roughly classified into solid golf balls and wound golf balls. Among them, solid golf balls include golf balls having a one-layer, two-layer, or three-layer structure. Particularly, in the solid golf balls having a two-layer or three-layer structure, the recent tendency is to soften the cover, especially for short irons. The development of a ball that emphasizes so-called controllability, which increases the amount of spin when hit and easily stops when landing, is being actively pursued.

[0003]

However, if the cover is simply softened, the spin amount is increased, but the resilience performance of the ball is lowered and the flight distance is reduced.

Therefore, an object of the present invention is to provide a solid golf ball satisfying both flight distance and controllability. In other words, the objective is to develop a solid golf ball that has a good flight distance on driver shots and a high spin rate on short iron shots near the green, which results in a good stop.

[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, the hardness of the center of the inner core is 60 to 85 as measured by JIS-C type 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 setting the hardness measured with a C-type hardness meter to 75 to 90, the resilience performance is enhanced and the flight distance is increased,
Furthermore, the bending rigidity of the cover is 1200 to 3600 kg /
By comprising a cover composition of cm ² , the controllability is improved, and a large flight distance on driver shots and good controllability on short iron shots are both achieved, achieving the above object.

In the present invention, the diameter of the inner core is 25 to 3
The hardness of the center of the inner core is set to 60 to 85 by the hardness measured by JIS-C type hardness tester, and the hardness difference from the center to the surface of the inner core is set to 4 or less, for the following reason. .

That is, when the diameter of the inner core is smaller than 25 mm, the ball becomes hard and the shot feeling is deteriorated, and when the diameter of the inner core is larger than 37 mm, the outer core is formed around the inner core to produce the core. In addition, since the thickness of the outer core becomes thin, it is very difficult to control the thickness, which impairs the homogeneity of the ball characteristics,
Flight performance becomes unstable. When the hardness of the center of the inner core is lower than 60 as measured by the JIS-C type hardness tester, the core becomes soft and the resilience performance is lowered, so that the flight distance is reduced and the hardness of the center of the inner core is JIS. If the hardness measured by a C-type hardness meter is higher than 85, the hardness becomes too hard and brittle, and the durability is lowered. 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 the resilience performance is deteriorated and the flight distance is shortened.

In the present invention, the hardness of the outer core (the surface of the outer core corresponds to the surface of the core having a two-layer structure consisting of the inner core and the outer core) is measured by the JIS-C type hardness tester. The hardness measured by the above method is 75 to 90, and the bending rigidity of the cover composition constituting the cover is 1200 to 3600 kg / cm.
It is necessary to be ² , because of the following reasons.

That is, the hardness of the outer core surface is JIS-C.
When the hardness measured by a mold hardness tester is lower than 75, the ball compression becomes small, the resilience performance deteriorates, the flight distance becomes short, and the hardness of the surface of the outer core is JIS-
If the hardness measured by a C-type hardness tester is higher than 90, it is too hard and the shot feeling (feeling at the time of hitting) deteriorates. The bending rigidity of the cover composition is 1200 kg / cm.
^When it is lower than ² , the resilience performance is lowered, the flight distance is shortened, and the bending rigidity of the cover composition is 3600 kg /
When it is higher than cm ² , the spin amount on short iron shots becomes small and the controllability deteriorates.
In the present invention, the bending rigidity of the cover is not used,
The bending rigidity of the composition for the cover is used, but once the ball is molded, the bending rigidity cannot be measured from the cover with the current technology. 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 the hardness measured by the JIS-C type hardness meter.
However, if the hardness of the surface of the outer core is higher than the hardness of the surface of the inner core by 3 or more, the shot feeling, the resilience performance and the flight performance are all improved.

The inner core is composed of a crosslinked molded body of a rubber composition, and the rubber composition for preparing the inner core is usually compounded with a crosslinking agent, a crosslinking initiator, a filler and the like and kneaded. It is prepared by In addition, if necessary, an antioxidant, a cross-linking modifier, a softening agent and the like may be appropriately blended.

The rubber has a cis-1,4 structure of 8
Butadiene rubber containing 5% or more is preferable, but other rubbers such as natural rubber, isoprene rubber,
It may be a mixture of styrene-butadiene rubber and the like.

As the cross-linking agent, a metal salt of α, β-unsaturated carboxylic acid is used. Examples of the metal salt of 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 kind or two or more kinds are selected and used, and zinc acrylate and zinc methacrylate are particularly preferable. The amount of the metal salt of α, β-unsaturated carboxylic acid as the cross-linking agent is not particularly limited, but is preferably 20 to 35 parts by weight with respect to 100 parts by weight of the rubber. Further, the metal salt of the α, β-unsaturated carboxylic acid is blended with the α, β-unsaturated carboxylic acid and the metal oxide at the time of compounding, and the α, β-unsaturated carboxylic acid of the α, β-unsaturated carboxylic acid is mixed during the kneading of the rubber composition. A metal salt may be produced.

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-butylperoxide are used. Mill peroxide is preferred. The amount of the crosslinking initiator compounded is not particularly limited, but is 0.5 to 100 parts by weight of the rubber.
2.5 parts by weight is preferred.

As the filler, for example, inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, barium carbonate and clay are mainly used. The compounding amount of this filler is not particularly limited, but rubber 10
20 to 25 parts by weight is preferable with respect to 0 parts by weight.

When a cross-linking modifier is blended, sulfur compounds such as morpholine disulfite, pentachlorothiophenol, diphenyl disulfite are used as the cross-linking modifier, and these sulfur compounds are 100 parts by weight of rubber. It is preferable to add about 0.1 to 1.5 parts by weight to parts by weight.

The inner core is produced by cross-linking the above rubber composition for inner core by press molding, injection molding or the like. In the case of the former press molding, the above rubber composition is filled in a mold and usually 10 to 60 at 140 to 180 ° C.
The inner core is produced by heating for a minute and crosslinking and molding. In the case of the latter injection molding, the mold temperature is 135 to 1
It is carried out by heating at 65 ° C. for 10 to 20 minutes. The diameter of the inner core is 25 to 37 mm, and the diameter of the inner core is preferably 28 to 35 mm. Further, the heating during 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, and the hardness of the surface of the outer core was measured by the JIS-C type hardness meter as described above. To make the hardness 75-90, the cross-linking agent α, β-
The amount of the metal salt of unsaturated carboxylic acid is preferably 25 to 35 parts by weight with respect to 100 parts by weight of rubber, and the amount of the crosslinking initiator is 1 to 3 parts by weight with respect to 100 parts by weight of rubber. Preferably.

The cross-linking molding for producing the outer core is also carried out by press molding or injection molding as in the case of the inner core. In the case of press molding, a pair of hemispherical shell-shaped half shells are prepared from the rubber composition for the outer core, the inner core is put therein, and the core is prepared by crosslinking molding with a mold.
The conditions for the cross-linking molding are usually 160 to 180.
Heating at 0 ° C for 10-40 minutes is employed. Also,
When using injection molding, simply mold to make a pair of half shells, insert the inner core into them to finish the core by press molding, or make a pair of half shells in a semi-crosslinked shape beforehand by injection molding. Then, a method of putting the inner core into it and finishing the core by press molding is adopted. Also, in the crosslinking and molding of the outer core, the heating may be performed in two or more steps.

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

Various kinds of materials can be used for the cover. For example, an ionomer is used as a main material, or an ionomer is made of polyamide, polyester, polyurethane, or the like.
A cover composition prepared by using, as a main material, a synthetic resin to which polyethylene or the like is added and adding pigments such as titanium dioxide and barium sulfate, and if necessary, an antioxidant and the like is used.

As the above-mentioned ionomer, for example, high milan 1605 (Na) and high milan 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 are trade names, manufactured by Mitsui DuPont Polychemical Co., Ltd.), 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) (both are trade names, manufactured by DuPont, USA), Iotech 7010 (Zn), Iotech 8
000 (Na) (both are trade names, manufactured by Exxon Chemical Co., Ltd.)
Etc., and these ionomers are used alone or as a mixture of two or more kinds. In addition, N described in parentheses (parentheses) after the product name of the above ionomer
a, Zn, K, Li and the like represent those neutralizing metal ion species.

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

The cover is molded, for example, by molding the above-mentioned cover composition into a half-shell-shaped half shell in advance, wrapping the core with two pieces of the half shell, and applying 130 to 170.
It can be carried out by pressure molding at 1 ° C. for 1 to 15 minutes, or by directly injection molding the cover composition around the core to wrap the core.

The cover usually has a thickness of about 1 to 4 mm. And the hardness of this cover is 59 Shore D hardness.
It is preferably about 70. When the hardness of the cover is less than 59 in Shore D hardness, the resilience performance is lowered and the flight distance tends to be short, and when the hardness of the cover is more than 70 in Shore D hardness, the shot feeling and controllability are deteriorated. Tend. Further, when the cover is molded, dimples are formed on the surface of the ball, if necessary, and after the cover is molded, paint finishing, stamping and the like are also performed as necessary.

Next, the 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 showing an example of the three-piece solid golf ball of the present invention, in which 1 is a core, and the core 1 comprises an inner core 1a and an outer core 1b formed around the inner core 1a, Two
Is a cover for covering the core 1.

The inner core 1a is made of a crosslinked molded product 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 hardness meter, and 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 is composed of a cross-linked molded body of the rubber composition formed around a, and the hardness of the surface thereof is 75 to 90 in hardness measured by 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 is composed of the inner core 1a and the outer core 1b.
It is preferable that the periphery of the core 1 having a layered structure is covered, and the hardness of the cover 2 is 59 to 70 in Shore D hardness.

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

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to only those examples.

Examples 1 to 6 and Comparative Examples 1 to 6 Rubber compositions for inner core were prepared with the compounding compositions shown in Tables 1 to 4,
The obtained rubber composition was filled in a mold for an inner core, and cross-linked and molded under the conditions shown in Tables 1 to 4 to prepare an inner core.
The diameter and hardness of the obtained inner core were measured. The results are shown in Tables 1 to 4. The blending amount of each component in the table is based on parts by weight, and this is the same in the tables showing the blending composition hereinafter. The hardness of the inner core was measured with a JIS-C type hardness meter at the center of the inner core, a position of 5 mm from the center to the surface, a position of 10 mm from the center to the surface, a position of 15 mm from the center to the surface, and the surface. The hardness of the inside of the inner core, such as the hardness of 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 cores of Examples 1 to 3, the diameter of the inner cores, the crosslinking conditions and the hardness of the inner cores, Table 2 shows those of Examples 4 to 6, and Table 3 shows Comparative Examples 1 to 1. 3 of them, and Table 4 shows those of Comparative Examples 4-6. In addition,
The butadiene rubber used in the preparation of the rubber composition for the inner core is BR-11 (trade name) manufactured by Japan Synthetic Rubber Co., Ltd.
The content of cis-1,4 structure of this butadiene rubber is 96
%. The antiaging agent used is Nocrac NS-6 (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. When the crosslinking conditions are described in two stages, it indicates that the heating for crosslinking molding is performed in two stages. Also, since the diameter of the inner core is small, for those that do not have a hardness measurement point at the corresponding position, of course,
It does not show hardness.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

Next, a rubber composition for the outer core was prepared with the compounding compositions shown in Tables 5 to 8, and a pair of half shells were molded from the obtained rubber composition respectively. Crosslinking and molding in the mold under the crosslinking conditions shown in Tables 5-8,
A core having a diameter of 39 mm was produced. Then, 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 5-8. In Comparative Example 4, since the diameter of the inner core is too large, the thickness of the outer core becomes thin and the uneven thickness becomes severe, and proper characteristics cannot be evaluated. Therefore, the hardness of the surface of the core is not measured. 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 the antioxidant used for preparing the rubber composition for the outer core are the same as those used for 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 compounding compositions shown in Tables 9 to 10, and the bending rigidity and Shore D hardness of the obtained cover compositions were measured. The results are shown in Tables 9-10. The flexural modulus was measured by press-molding the cover composition to prepare a plate-shaped test piece having a thickness of about 2 mm, which was allowed to stand for 2 weeks at 23 ° C. and 50% relative humidity according to ASTM D-747. The measurement was performed using a stiff meter manufactured by Toyo Seiki. Further, the Shore D hardness is measured by
The cover composition is press-molded to form a flat plate-shaped test piece having a thickness of about 2 mm, which is 2 in accordance with ASTM D-2240.
After standing for 2 weeks at 3 ° C. and 50% relative humidity, the hardness was measured using a Shore D hardness meter. Incidentally, the hardness of the cover, in addition to the method for producing a test piece from the composition for a cover as described above,
It can also be measured from the cover of a golf ball. Table 9
Shows the composition, flexural rigidity and hardness (Shore D hardness) of the cover compositions A to D, and Table 10 shows the composition, flexural rigidity and hardness (Shore D hardness) of the cover compositions E to G. ) Is shown. Details of the components indicated by trade names in the table are shown after Table 10.

[0042]

[Table 9]

[0043]

[Table 10]

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

Next, the cover compositions A to G prepared as described above were injection-molded on the core with the combinations shown in Tables 11 to 14 to form a cover, and a three-piece solid golf ball having an outer diameter of 42.7 mm was formed. A ball was made. However,
In Tables 11 to 14, the type of the cover composition is indicated by its symbol, and its bending rigidity and hardness (Shore D hardness) are also added. In Comparative Example 4, balls were not manufactured because the uneven thickness during formation of the outer core was too great to perform proper property evaluation. Therefore, in Table 14, the types of cover compositions and the flexural rigidity are shown in Table 14. In addition, no characteristic value for Comparative Example 4 is shown.

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

Coefficient of Repulsion: Using an air gun of the same type as the one used by R & A (British Golf Association) to measure the initial velocity, the ball velocity was measured when the metal cylinder of 198.4 g was made to collide with the ball at a velocity of 45 m / s. And calculated from the ball speed. The larger this value, the higher the resilience performance of the golf ball.

Flying distance: A swing robot manufactured by True Temper Co., Ltd. is equipped with a driver (Wood No. 1 club), and the ball is hit at a head speed of 45 m / s to measure the distance to the falling point.

Spin amount: A swing robot manufactured by Trutemper Co., Ltd. was equipped with an iron 9 club, the ball was hit at a head speed of 34 m / s, and the hit ball was continuously photographed and examined.

Controllability: Evaluation is made by hitting the ball with a sand wedge by a total of 10 professional golfers and 6 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, but in this case, 8 or more out of 10 people who were evaluated have the same evaluation.

Evaluation Criteria: ○: Good △: Normal ×: Poor

Feeling at Hit: The ball was driven by a total of 10 professional golfers and 6 amateur golfers with a handicap of 10 or less (Wood No. 1 club).
Hit with and evaluate. The evaluation criteria are as follows. When the evaluation results are displayed in the table, the same symbols are used, but in this case, 8 or more out of 10 people who were evaluated have the same evaluation.

Evaluation Criteria: ○: Good △: Normal ×: Poor

[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 to 14, Examples 1 to 6 have different flight distances. And the spin rate was large, the controllability was good, and the shot feeling was good. That is, Table 1
As shown in 2, the diameter of the inner core is in the range of 25 to 37 mm, the hardness of the center of the inner core is in the range of 60 to 85 in the hardness measured by JIS-C type hardness tester, and from the center of the inner core to the surface. The hardness difference is 4 or less, and the hardness of the outer core surface is shown in Tables 5 to 6.
As shown in, the hardness measured by JIS-C type hardness tester is 75
To 90, and the flexural modulus of the cover composition constituting the cover is 120 as shown in Tables 11 to 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 as large as a yard, and the controllability evaluation was good, and the controllability was good, and the shot feeling was good, and the shot feeling was good.

On the other hand, in Comparative Example 1, as shown in Table 3, the hardness of the center of the inner core is low, and the hardness difference from the center of the inner core to the surface is large. As shown in (3), the flight distance was reduced, and the controllability and shot feeling were not good. Comparative Example 2
As shown in Tables 3 and 7, since the hardness of the center of the inner core and the hardness of the surface of the outer core are too low, the resilience performance deteriorates, and as shown in Table 13, the flight distance becomes short and the shot feeling is heavy. It was bad. Further, in Comparative Example 3, since the diameter of the inner core is small as shown in Table 3, the ball becomes hard and
As shown in, the shot feeling was poor and the controllability was poor.

Further, as shown in Table 14, in Comparative Example 5,
Since the cover composition constituting the cover has a small flexural rigidity, the resilience performance is lowered and the flight distance is reduced. In Comparative Example 6, the cover composition constituting the cover has a too large flexural rigidity. The controllability and shot feeling were poor. In Comparative Example 4, since the diameter of the inner core is too large as shown in Table 4, as described above, when the outer core is formed to form the core, the outer core has a large uneven thickness, and a proper characteristic evaluation is performed. Therefore, no balls were made.

[0061]

As described above, according to the present invention, it is possible to provide a three-piece solid golf ball which has a long flight distance and good controllability and which can satisfy both the flight distance and the controllability.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an 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

Claims (2)

[Claims] 1. A three-piece solid golf ball comprising a cover having a two-layered core composed of an inner core and an outer core, the inner core having a diameter of 25 to 37 mm, and the center of the inner core having a JIS-C type hardness. The hardness measured by the hardness meter is 6
0 to 85, the hardness difference from the center of the inner core to the surface is 4 or less, the hardness of the outer core surface is 75 to 90 as measured by JIS-C type hardness tester, and the cover is The bending rigidity of the constituent composition for the cover 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 of claim 1, wherein the hardness of the surface of the outer core is higher than the hardness of the surface of the inner core.