JP2000271248A - Multipiece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multipiece solid golf ball showing equal repulsiveness when hit at a high head speed and high repulsiveness when hit at a low head speed as compared with a two-piece golf ball. SOLUTION: In a multipiece solid golf ball comprising a core 5 made up of an inner layer core 1, an intermediate layer core 2 placed over the inner layer core, and an outer layer core 3 placed over the intermediate layer core and a cover 4 of one or more layers formed over the core, characteristically, the inner layer core has a JIS-C hardness of 60 to 85, the outer layer core has a JIS-C hardness of 60 to 85, the inner layer core has a 3 to 45 higher JIS-C hardness than the intermediate layer core, and the outer layer core has a 3 to 45 higher JIS-C hardness than the intermediate layer core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a multi-piece golf ball which has the same resilience performance when hit at a high head speed and excellent resilience performance when hit at a low head speed, as compared with a conventional two-piece golf ball. The present invention relates to a piece solid golf ball, that is, a multi-piece solid golf ball having a structure that is not disadvantageous to a golfer having a low head speed when hit.

[0002]

2. Description of the Related Art Conventionally, solid golf balls are roughly divided into two-piece golf balls and one-piece golf balls, and two-piece golf balls are mainly used for amateur player rounds. However, although the two-piece golf ball has an excellent flight distance, it has a disadvantage that the shot feeling is hard and poor. In addition, there is a dependence on the head speed at the time of hitting, and the flight distance is usually long when hitting at a high head speed, and short when hitting at a low head speed. However, when actually playing a round, a player with a low head speed and a player with a high head speed often play in the same group, and a golf ball that does not disadvantage a player with a low head speed is desired.

[0003] Various attempts have been made to improve the disadvantages of such solid golf balls. As a typical example, a three-piece solid golf ball having an intermediate layer provided between a core and a cover of a two-piece solid golf ball (for example, JP-A-4-244174,
No. 6-142228) and a four-piece solid golf ball having two intermediate layers (for example, see Japanese Patent Application Laid-Open No. 9-266959).
JP-A-10-179797, JP-A-10-179798, etc.) have been proposed.

JP-A-4-244174 and JP-A-6-1422
No. 28 describes a three-piece solid golf ball comprising a core formed of a rubber composition, an intermediate layer made of a thermoplastic resin, and a cover. Further, Japanese Patent Application Laid-Open No. 9-266959 describes a four-piece solid golf ball comprising a core having a three-layer structure formed of a rubber composition and a cover made of a thermoplastic resin. It is an object of the present invention to improve the flight distance and the shot feeling and controllability, particularly the shot feeling and controllability at the time of approach shot of an iron club. Further, JP-A-10-179797 discloses that a core formed of a rubber composition, an intermediate layer formed of a thermoplastic resin, an intermediate layer formed of a rubber composition, and an outer layer formed of a thermoplastic resin. A four-piece solid golf ball comprising a cover has been described, and JP-A-10-179798 discloses a core and an inner layer formed of a rubber composition, an outer layer formed of a thermoplastic resin, and a cover. Are described, and these two kinds of four-piece golf balls are designed for the purpose of increasing the launch angle and increasing the flight distance.

In these multi-piece solid golf balls, a variety of hardness distributions can be obtained as compared with a two-piece golf ball, and a golf ball excellent in shot feeling without impairing flight performance is provided. However, in these golf balls, no consideration has been given to the head speed dependence of the resilience performance.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional solid golf ball, has a small impact force, has an excellent hit feeling, and has a rebound performance at the time of hitting. It is an object of the present invention to provide a multi-piece solid golf ball that does not depend on speed and does not decrease rebound performance even when the head speed decreases.

[0007]

Means for Solving the Problems The inventors of the present invention have made a two-piece golf ball having a multi-layered core in order to solve the above-mentioned object, and made various changes in the hardness of each layer.
In a multi-piece solid golf ball comprising an inner core, an intermediate core and an outer core, and a cover formed on the core, the JIS-C hardness of the inner core and the outer core, and the inner core and By defining the hardness difference between the intermediate layer core and the hardness difference between the outer layer core and the intermediate layer core within a specific range, the impact force is small, the shot feeling is good, and the rebound performance is low when the head is hit. The present inventors have found that a multi-piece solid golf ball which does not depend on the speed and does not decrease the flight distance even when the head speed is reduced can be obtained, and have completed the present invention.

That is, the present invention comprises an inner core (1), an intermediate core (2) coated on the inner core, and an outer core (3) coated on the intermediate core. A multi-piece solid golf ball comprising a core (5), and one or more layers of a cover (4) formed on the core, wherein the inner layer core has a JIS-C hardness of 60 to 85, and the outer layer core has JIS-C hardness
60 to 85, the JIS-C hardness of the inner layer core is 3 to 45 greater than the JIS-C hardness of the intermediate layer core, and the JIS-C
The present invention relates to a multi-piece solid golf ball having a hardness that is 3 to 45 greater than the JIS-C hardness of the intermediate layer core.

In the golf ball of the present invention having the above-mentioned structure, when hit at a high head speed, the soft portion of the intermediate layer core having a small hardness is deformed, resulting in a large energy loss and a high head. The increase in flight distance due to impact at speed and the decrease in flight distance due to such energy loss are offset. Conversely, when hitting at low head speed, the deformation does not reach the middle layer core part, only the hard outer layer core and the hard part of the cover are deformed, so energy loss like hitting at high head speed is lost. It does not increase, it compensates for the decrease in flight distance due to hitting at low head speed,
It is considered that the flight distance of the golf ball of the present invention is almost equal without depending on the head speed.

With respect to the impact force, a method of softening the entire core is generally considered. In this method, the impact force is reduced, but at the same time, the energy given by the head of the golf club is not only the flight energy but also the ball. It is known that a large amount of energy is spent on the vibrational energy of the vehicle, which causes a reduction in flight distance. However, in the golf ball of the present invention, the vibration of the ball is suppressed as much as possible by adopting a structure in which the soft intermediate layer core is sandwiched between the hard inner layer and the outer layer core. Does not drop.

Hereinafter, the golf ball of the present invention will be described in more detail with reference to FIG. FIG. 1 is a schematic sectional view showing one embodiment of the golf ball of the present invention. As shown in FIG. 1, the golf ball of the present invention comprises an inner core (1), an intermediate core (2) coated on the inner core, and an outer core (3) coated on the intermediate core. Core composed of
(5), and one or more layers of the cover formed on the core (4)
Consists of However, in FIG. 1, a golf ball having a one-layer cover (4) is used for easy understanding.

The core (5) is an inner core (1) and an intermediate core.
Both (2) and the outer layer core (3) are preferably manufactured by heating and pressing a rubber composition in which polybutadiene is blended with a co-crosslinking agent, an organic peroxide and a filler as essential components. This is because, when all three layers are made of the same vulcanized rubber composition, the adhesive strength between the layers is high, the problem of peeling between the layers is unlikely to occur, and the high resilience, low impact force and high This is because durability can be maintained in a well-balanced manner. The polybutadiene may be any one which has been conventionally used in the core of a solid golf ball, and particularly has a cis-1,4-bond of at least 40% or more, preferably 80% or more, more preferably 90% or more. High cis polybutadiene rubber is preferred, and the above polybutadiene rubber optionally contains 0 to 50 parts by weight of natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM), etc. with respect to 100 parts by weight of polybutadiene. You may.

As the co-crosslinking agent, a monovalent or divalent metal salt such as a zinc or magnesium salt of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid; Functional monomers such as triethanolpropane trimethacrylate, and mixtures thereof, and the like are mentioned, and zinc acrylate which imparts high resilience is preferable. The amount is 5 parts per 100 parts by weight of polybutadiene.
5050 parts by weight, preferably 10-40 parts by weight. If the amount is more than 50 parts by weight, the ball becomes too hard and the shot feeling becomes poor. If the amount is less than 5 parts by weight, the amount of the organic peroxide must be increased in order to obtain an appropriate hardness, and the rebound is deteriorated and the flight distance is reduced. descend.

Examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,3
5-trimethylcyclohexane, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane, di-t-butyl peroxide and the like are mentioned, and dicumyl peroxide is preferred. The amount is based on 100 parts by weight of polybutadiene.
0.3 to 5.0 parts by weight, preferably 0.8 to 3.0 parts by weight. 0.
If the amount is less than 3 parts by weight, it becomes too soft, the rebound is deteriorated, and the flight distance is reduced. If the amount exceeds 5.0 parts by weight, the amount of the co-crosslinking agent must be reduced in order to obtain an appropriate hardness, so that the rebound is deteriorated and the flight distance is reduced.

The filler may be any one which is usually compounded in the core of a solid golf ball, and includes, for example, inorganic fillers, specifically, zinc oxide, barium sulfate, calcium carbonate and the like. It may be used in combination with a filler, for example, tungsten powder, molybdenum powder and the like, and a mixture thereof. The blending amount is 10 polybutadiene, respectively.
It is 3 to 50 parts by weight, preferably 10 to 30 parts by weight with respect to 0 parts by weight. If the amount is less than 3 parts by weight, it is difficult to adjust the weight, and if it exceeds 50 parts by weight, the weight fraction of the rubber becomes small and the rebound becomes too low.

Further, the core of the golf ball of the present invention may contain an antioxidant or a peptizer, an organic sulfur compound such as a sulfide or a thiol, or other components which can be generally used in the production of a solid golf ball core. You may mix. The blending amount is based on 100 parts by weight of polybutadiene.
It is preferable that the antioxidant is 0.1 to 1.0 part by weight, the peptizer is 0.1 to 5.0 parts by weight, and the organic sulfur compound is 0.1 to 5.0 parts by weight.

As described above, the inner layer core (1), the intermediate layer core (2) and the outer layer core (3) of the present invention are composed of the same components. The above-described desired hardness can be achieved by appropriately adjusting the compounding amount, vulcanization conditions, and the like.

A method for manufacturing a core used in the golf ball of the present invention will be described with reference to FIGS. FIG. 2 is a schematic cross-sectional view of one embodiment of a mold for a semi-vulcanized hemispherical shell-like molded product used for the golf ball of the present invention. FIG. 3 is a schematic cross-sectional view of one embodiment of a core molding die used in the golf ball of the present invention. First, the rubber composition for the inner layer core was kneaded, and placed in an upper and lower mold having a hemispherical cavity.
Heat press at 160 ° C for 10-60 minutes to produce a spherical vulcanized molded product for inner layer core. Next, the rubber composition for the intermediate layer core is kneaded, and the outer diameter of the core portion is equal to the diameter of the spherical vulcanized molded product for the inner layer core, in a mold (6, 7) as shown in FIG.
A half-vulcanized hemispherical shell-shaped molded product (8) for an intermediate layer core is prepared by hot pressing at 90 to 165 ° C for 20 seconds to 5 minutes. The vulcanized molded product (10) for the inner layer core is sandwiched between two semi-vulcanized hemispherical shell-shaped molded products (8) for the intermediate layer core produced as described above, and a mold as shown in FIG. 9) within 1 at 140-160 ° C
A two-layer core is prepared by hot pressing for 0 to 60 minutes.

Further, the rubber composition for the outer layer core is kneaded, and a mold (6, 7) as shown in FIG. 2 having a size such that the outer diameter of the core portion is equal to the diameter of the two-layer core is used. Except for the above, a semi-vulcanized hemispherical shell-shaped molded product (8) for the outer core is produced in the same manner as the semi-vulcanized hemispherical shell-shaped molded product for the intermediate layer core. 2 above
The layer core (10) is sandwiched between two half-vulcanized hemispherical shell-shaped molded products (8) for the outer layer core produced as described above, and is placed in a mold (9) as shown in FIG. The core (4) having a three-layer structure is prepared by hot pressing at 10 ° C. for 10 to 60 minutes.
The method of manufacturing the core is not limited to the above-described hot press method, but may be performed by rubber injection molding or the like. Also,
After vulcanizing the inner layer core, the two-layer core and the core (three-layer core),
Each surface can be polished to improve the adhesiveness between adjacent layers.

In the present invention, the inner layer core (1) has a JIS-C hardness of 6
Although it is 0 to 85, the hardness is preferably 63 or more, more preferably 65 or more, because if it is less than 60, it becomes too soft, the resilience performance is reduced, and the desired physical properties are not obtained because the resilience performance is reduced and the desired physical properties are not obtained. It is. Conversely, if it is larger than 85, the ball is too hard and the shot feeling is hard and poor, so the hardness is preferably 83 or less, more preferably 80 or less.

Further, in the present invention, it is required that the JIS-C hardness of the inner layer core (1) is larger by 3 to 45 than the JIS-C hardness of the intermediate layer core (2). In addition, since the effect of the present invention by sandwiching the soft layer between the two hard layers as described above cannot be sufficiently exhibited, the hardness difference is 5
The above is preferred. If the hardness difference is larger than 45, the resilience performance is reduced, or the hardness difference between the layers becomes too large, and the durability between the layers is reduced. Therefore, the hardness difference is preferably 40 or less. In the golf ball of the present invention, the intermediate layer core (2) has a JIS-C hardness of 30 to 80, preferably 40 to 75. If it is less than 30, it will be too soft, resulting in a decrease in resilience performance, and the concentration of stress will reduce the durability. Conversely, if it is larger than 80, it becomes too hard and cannot sufficiently fulfill the role of absorbing impact force.

The thickness of the intermediate layer core (2) of the present invention is 1.5 to 7.0 m.
m, preferably 2.0 to 5.0 mm, but if the thickness is less than 1.5 mm, even if the deformation reaches the middle layer core when hitting at a high head speed, the effect of lowering the resilience performance decreases, The effect of the present invention that the performance does not depend on the head speed cannot be sufficiently obtained. Conversely, if it is larger than 7.0 mm, the same effect cannot be sufficiently obtained because the middle layer is deformed even when hit at a low head speed. The intermediate layer core (2) of the present invention has a distance of 6.5 to 1 from the center of the core (5).
6.0 mm, preferably in the range of 8.0 to 16.0 mm. If the distance from the center is smaller than 6.5 mm, the deformation at the time of impact does not reach the middle layer core (2) at both low head speed and high head speed, so that the rebound performance does not depend on the head speed Is not obtained enough. Conversely, if the distance from the center is larger than 16.0 mm, the deformation at the time of impact reaches the middle layer core (2) at both low head speed and high head speed,
The effect that the resilience performance does not depend on the head speed cannot be sufficiently obtained. Therefore, the preferred structure of the three-layer core (5) of the present invention is such that the intermediate layer core (2) has a distance of 6.5 from the core center.
16.0 mm and a thickness of 1.5 to 7.0 mm.

In the present invention, the outer layer core (3) has a JIS-C hardness of 6
If it is less than 60, the shot feeling will be softer, but the resilience performance will be reduced and the flight performance will be reduced,
The hardness is preferably 63 or more, more preferably 65 or more, since the durability also decreases. vice versa,
If it is larger than 85, the shot feeling becomes too hard and the shot feeling becomes hard, and for a golf player with a low head speed expected to be effective in the present invention, the shot feeling becomes very hard and bad, so the hardness is preferably 83 or less, more preferably Is 80 or less. Furthermore, in the present invention, the JIS-C hardness of the outer layer core (3) is required to be larger than the JIS-C hardness of the intermediate layer core (2) by 3 to 45, but if this hardness difference is smaller than 3, Since the effect of the present invention by sandwiching the soft layer between the two hard layers as described above cannot be sufficiently exerted, the difference in hardness is preferably 5 or more. If the hardness difference is larger than 45, the resilience performance is reduced, or the hardness difference between the layers becomes too large, and the durability between the layers is reduced. Therefore, the hardness difference is preferably 40 or less. The hardness of the inner layer core, the intermediate layer core and the outer layer core means that the produced golf ball is usually cut into two equal parts, and at the cut surface, the inner layer core is the center, and the intermediate layer core and the outer layer core are the center in the thickness direction. Mean hardness measured at position.

The radius of the inner layer core (1) is t ₁ , and the intermediate layer core (2)
Is t ₂ , the thickness of the outer core 3 is t ₃ , and the radius of the core 5 is T, (t ₁ / T) is 0.3 to 0.85, and further 0.3 to 0.7.
5, (t ₂ / T) is 0.07 to 0.4, further 0.1 to 0.35, (t ₃ / T
T) is preferably 0.06 to 0.6, more preferably 0.1 to 0.5. If (t ₁ / T) is smaller than 0.3, the resilience performance decreases,
If it is larger than 0.85, the impact strength becomes large or other layers become thin, and productivity and durability decrease. (T ₂ / T)
Is smaller than 0.07, the effect of the present invention by sandwiching the soft layer between the two hard layers cannot be sufficiently exhibited. If it is larger than 0.4, the resilience performance decreases. (T ₃ /
When T) is less than 0.06, the resilience performance decreases, and when it is greater than 0.6, the impact force increases or the thickness of the intermediate layer core becomes thin, thereby lowering productivity and durability. The diameter of the core (5) is 3
4.0~41.0mm are preferred, also t ₁ is 6.5～14.5Mm, further
6.5~13.0mm, t ₂ is 1.5~7.0mm, further 2.0~6.0mm, t ₃
Is preferably 1.0 to 12.5 mm, more preferably 2.0 to 10.0 mm.

Next, the core (5) is covered with at least one cover (4). When the cover (4) of the present invention has a single-layer structure, it contains, as a base resin, a thermoplastic resin, particularly an ionomer resin which is usually used for a cover of a golf ball. Examples of the ionomer resin include an ionomer resin obtained by neutralizing a part of the carboxylic acid in a copolymer of an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, or a mixture thereof. Used. As the α-olefin in the ionomer resin, ethylene and propylene are preferable, and as the α, β-unsaturated carboxylic acid, acrylic acid, methacrylic acid and the like are preferable. Further, as the metal ions to be neutralized, alkali metal ions such as Na ion, K ion and Li ion; divalent metal ions such as Zn ion, Ca ion and Mg ion; trivalent metal ions such as Al ion; Nd ions and the like; and mixtures thereof, including Na ions, Zn ions,
Li ions and the like are often used because of their resilience and durability.
Specific examples of ionomer resins include, but are not limited to, Himilan 1555, 1557, 1605, 1706, 1707,
AM7315, AM7317 (manufactured by Mitsui Dupont Polychemical Co., Ltd.), Surlyn 7930, 8511, 8512 (manufactured by Dupont), IOTEC 701
0, 8000 (manufactured by Exxon) and the like. These ionomers may be used individually or as a mixture of two or more of the above examples.

Further, when the cover (4) of the present invention comprises two or more layers, preferred examples of the material include one selected from the group consisting of a thermoplastic resin and a thermoplastic elastomer.
Seeds may be used, or two or more kinds may be used in combination. Examples of the thermoplastic resin include ionomer resins similar to those described above. Specific examples of the thermoplastic elastomer include, for example, polyamides commercially available from Toray Industries, Inc. under the trade name “Pebax” (eg, “Pebax 2533”). -Based thermoplastic elastomer, commercially available from Toray Dupont under the trade name "Hytrel" (eg, "Hytrel 3548", "Hitrel 4047") polyester-based thermoplastic elastomer, trade name from Takeda Birdish Co., Ltd. "Elastoran" (for example, "Elastoran ET88
0 "), trade name" Pandex "from Dai Nippon Ink Co., Ltd.
(For example, “Pandex T-8180”) commercially available polyurethane-based thermoplastic elastomers.

To the cover used in the present invention, if necessary, various additives other than the above resins, for example, pigments such as titanium dioxide, dispersants, antioxidants, ultraviolet absorbers, light stabilizers and the like are added. May be.

The method of coating the cover (3) is not particularly limited, either, and can be performed by a usual method of coating a cover. The cover composition is preliminarily formed into a hemispherical shell-like half shell, and two cores are used to wrap the core and pressure-formed at 130 to 170 ° C. for 1 to 5 minutes, or the cover composition is directly cored. A method of wrapping the core by injection molding on it is used. Then, when forming the cover, if necessary, dimples are formed on the ball surface,
After the cover is formed, paint finishing, stamping and the like may be performed as necessary. In the present invention, the cover (4) has a total thickness of 1.0 to 4.5 mm, preferably 1.5 to 4.0 mm. 1.0mm
If it is smaller, the resilience and durability decrease, and if it is larger than 4.5 mm, the shot feeling is hard and poor.

The golf ball of the present invention has a compression deformation of 2.3 to 4.5 mm, preferably 2.4 to 4.2 mm, from a state where an initial load of 10 kgf is applied to a state where a final load of 130 kgf is applied to the ball.
Having. If the compression deformation amount is smaller than 2.3 mm, the shot feeling becomes hard and poor, and the impact force becomes large even when hitting at a low head speed. If it is larger than 4.5 mm, the shot feeling is soft but the resilience performance, that is, the flight distance is reduced.

According to the present invention, by realizing resilience performance having a small impact force and a good shot feeling and having no dependency on head speed, the resilience performance does not decrease even if the head speed at the time of impact is reduced. Provide multi-piece solid golf balls.

[0031]

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

(I) Production of spherical vulcanized molded product for inner layer core The rubber composition for the inner layer core having the composition shown in the following Tables 1 to 4 was kneaded, and the mixture was placed in an upper and lower mold having a hemispherical cavity at 130 to 1
It was heated and pressed at 60 ° C. for 10 to 60 minutes to obtain a spherical vulcanized molded product for the inner layer core having a radius shown in Tables 6 to 9.

(Ii) Production of Vulcanized Molding of Hemispherical Shell for Intermediate Layer Core A rubber composition for an intermediate layer core having the composition shown in Tables 1 to 4 below was kneaded, and the outer diameter of the core portion was (i) 2) A mold as shown in FIG. 2 having a diameter equal to the diameter of the spherical vulcanized molded product for the inner layer core.
In (6, 7), by half-pressing at 90 to 165 ° C for 20 seconds to 5 minutes, a semi-vulcanized hemispherical shell-shaped molded product for the intermediate layer core
(8) was obtained.

(Iii) Preparation of Two-Layer Core The vulcanized molded product (10) for the inner core prepared in the above (i) is replaced with (ii)
Semi-vulcanized hemispherical shells for two intermediate layer cores
(8), and in a mold (9) as shown in FIG.
A two-layer core was prepared by hot pressing at 10 ° C. for 10 to 60 minutes.

(Iv) Production of hemispherical shell vulcanized molded product for outer layer core The rubber composition for the outer layer core having the composition shown in Tables 1 to 4 below was kneaded, and the outer diameter of the core portion was (iii). A mold as shown in FIG. 2 having dimensions equal to the diameter of the manufactured two-layer core.
Except for using (6, 7), a semi-vulcanized hemispherical shell-shaped molded product (8) for an outer layer core was obtained in the same manner as (ii).

(V) Preparation of core The two-layer core (10) prepared in (iii) above is sandwiched between two semi-vulcanized hemispherical shell-shaped moldings (8) for outer layer core prepared in (iv).
A three-layer core having a diameter shown in Tables 6 to 9 was produced by hot pressing at 140 to 160 ° C. for 10 to 60 minutes in a mold (9) as shown in FIG.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4] (Note 1) High-cis polybutadiene rubber manufactured by JSR Corporation (1,4-cis-polybutadiene content: 97.1%) (Note 2) Asada Chemical Co., Ltd. (Note 3) Toho Zinc Co., Ltd. (Note 4) ) Commercially available from Nippon Yushi Co., Ltd. under the trade name “Park Mill D”, 175 ° C, half-life 1 minute

(Vi) Preparation of Cover Composition The materials having the formulations shown in Table 5 below were mixed with a twin-screw kneading extruder to prepare a pellet-shaped cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the compound was heated to 200 to 260 ° C. at the position of the die of the extruder.

[0042]

[Table 5]

(Note 5) Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui Dupont Polychemical Co., Ltd. (Note 6) Zinc ion neutralized ethylene-methacrylic acid manufactured by Mitsui Dupont Polychemical Co., Ltd. Copolymer ionomer resin

(Examples 1 to 15 and Comparative Examples 1 to 2, 4 to
7) The above-mentioned cover composition was prepared using the above-obtained 3
Form the cover layer (4) by directly injection molding on the core (5) having a layer structure, paint the surface,
Golf balls having a diameter of 42.8 mm and a weight of 45.0-45.4 g were prepared. The obtained golf ball is cut into two equal parts, the JIS-C hardness (a, b, and c) of each core layer is measured, and the radius of the inner layer core (h) indicating the position of the intermediate layer core is measured.
₁ ) and the radius (h ₂ ) of the inner layer core and the intermediate layer core were measured. The results are shown in Tables 6 to 9. Further, the compression, coefficient of restitution and impact force of the obtained golf ball were measured, and the results are shown in the same table. The test method was performed as follows.

(Test Method) JIS-C Hardness of the Core The produced golf ball is cut into two equal parts, and the cut surface is such that the inner layer core is at the center point, and the intermediate layer core and the outer layer core are at the center position in the thickness direction. It is measured using a spring type hardness tester type C specified in JIS K 6301.

Coefficient of Restitution A golf ball was hit with a 200-g aluminum cylinder at a speed of 35 m / s and 45 m / s, and the speeds of the cylinder and the golf ball before and after the collision were measured. Calculated. The measurement was performed five times for each golf ball, and the average value was used as the coefficient of restitution of each golf ball, and was expressed as an index when Comparative Example 1 was set to 100. The coefficient of restitution was A when the speed was 35 m / sec, and the coefficient of restitution B was 45 m / sec. The higher these indices are, the higher the resilience and the better.

Impact Force An acceleration pickup is attached to the side sole portion of the head of a wood head club (driver) made of a metal head, and the club is mounted on a swing robot manufactured by True Temper, and the head speed is 35 m / sec and 45 m / sec. Hit the golf ball in seconds. The acceleration generated in the direction opposite to the head traveling direction at the time of impact in the impact is measured, and the maximum value of this acceleration is calculated according to the following formula: F (force) = m (head weight: 210 g) × a (acceleration) The force for returning the head, that is, the impact force is calculated.
The measurement was performed five times for each golf ball, and the average value was described as the impact force (kgf) of each golf ball, and the index when Comparative Example 1 was set to 100 was also described. The index B was the impact force when hit at a head speed of 35 m / sec, and the index D was the impact force when hit at a head speed of 45 m / sec. The smaller the index, the smaller and better the impact.

[0048]

[Table 6]

[0049]

[Table 7]

[0050]

[Table 8]

[0051]

[Table 9] *: Commercial two-piece golf ball

From the above results, in the three-layer core composed of the inner core, the intermediate core and the outer core, the JIS-C hardness of the inner core and the outer core, and the The golf balls of the present invention of Examples 1 to 11 and 14 to 15 in which the hardness difference and the hardness difference between the outer layer core and the intermediate layer core are controlled within a specific range,
Compared with the golf ball of the comparative example, the impact force at the time of hitting is smaller and the shot feeling is excellent, and the hitting at a low head speed (35 m / s) is larger than that at the time of hitting at a high head speed (45 m / s) It was found to have a coefficient of restitution. Example 12 which is within the scope of the present invention except that the intermediate layer core is disposed inside a range of 6.5 to 16.0 mm from the center of the core also has a low head speed (35 m / sec). Has a higher coefficient of restitution than when hitting at high head speed (45m / s)
Although the impact force is almost the same as the golf ball of the comparative example, the coefficient of restitution at 35 m / sec is large. Example 13, which is within the scope of the present invention except that the intermediate layer core is disposed outside the range of 6.5 to 16.0 mm from the center of the core, has a coefficient of restitution almost equal to that of the golf ball of the comparative example. However, the impact force is very small and the shot feeling is excellent.

On the other hand, in the golf ball of Comparative Example 1, since the three layers of the core all have the same hardness, the effect of the present invention by sandwiching the soft layer between the two hard layers can be sufficiently exhibited. And the coefficient of restitution when hitting at low head speed (35m / s) is not large. In the golf ball of Comparative Example 2, the JIS-C hardness of the intermediate layer core in the core was conversely large, and the effects of the present invention as described above could not be sufficiently exhibited, and the impact force was large and the shot feeling was poor. , Low coefficient of restitution when hitting at low head speed (35m / s). Since the golf ball of Comparative Example 3 is a commercially available two-piece golf ball and has a single-layer core, the effect of the present invention cannot be sufficiently exerted similarly to the golf ball of Comparative Example 2, and the impact force is large and the shot feeling is large. Bad, low coefficient of restitution when hitting at low head speed (35m / sec).

The golf ball of Comparative Example 4 had an inner core JI
Due to the high S-C hardness, the impact force when hitting at low head speed (35 m / sec) is large, and the shot feeling is poor. The golf ball of Comparative Example 5 has a small JIS-C hardness of the inner layer core.
The coefficient of restitution is extremely small regardless of the head speed. In the golf ball of Comparative Example 6, since the outer layer core has a large JIS-C hardness, the impact force is large and the shot feeling is poor regardless of the head speed. The golf ball of Comparative Example 7 had an outer layer core of JI
Since the SC hardness is small, the coefficient of restitution is extremely small regardless of the head speed.

Further, at each head speed (35 m / sec and 45 m / s)
m / sec), the restitution coefficients A and C are
Table 6 shows the values of A / B and C / D divided by
-9. The larger the A / B and C / D values, the higher the resilience and the lower impact, which are the required characteristics of a golf ball, indicating that the golf ball is overall better. For example, if the impact force B is small even if the coefficient of restitution A is not so large,
It is useful as a golf ball having a soft feel at impact, and even if B is somewhat large, if A is large, it is useful as a high rebound golf ball.

As described above, the golf balls of Examples 1 to 11 and 14 to 15 of the present invention, in which the coefficient of restitution A (35 m / sec) was very large and excellent, had a higher A / A ratio than the golf ball of the comparative example.
The values of B and C / D are large, and both high rebound and low impact are provided, and they are excellent overall. In Examples 12 and 13, the values of A / B and C / D were both larger than the golf ball of the comparative example and were generally superior. In Example 13, particularly, the low head speed (35 m /
The characteristics when hitting in seconds) are very good.

On the other hand, the golf ball of Comparative Example 2 having a small coefficient of restitution A (35 m / sec) and a large impact force has an A / B
And the values of C / D are also very small. In the golf ball of Comparative Example 3 which is a commercially available two-piece golf ball, the values of A / B and C / D are almost the same as in Comparative Example 1, and are small. Comparative Example 4 having a large impact force at the time of impact at a low head speed (35 m / sec) has a small value of A / B. Restitution coefficient A at both head speeds (35m / s and 45m / s)
Comparative Example 5 having small C and C has small values of A / B and C / D. Comparative Example 6, which has a large impact force at the time of impact at both head speeds (35 m / sec and 45 m / sec), includes A / B and C /
The value of D is also very small. In Comparative Example 7, the values of A / B and C / D were large because the impact force was very small, but the coefficient of restitution was extremely small.

[0058]

According to the present invention, the core has a three-layer structure composed of an inner core, an intermediate core and an outer core, and the JIS-C hardness of the inner core and the outer core, and the above-mentioned inner core and the intermediate core. By defining the hardness difference between the outer layer core and the intermediate layer core within a specific range, the impact force is small, the ball has a good shot feeling, and the rebound performance does not have a head speed dependency. The present invention provides a multi-piece solid golf ball in which the resilience performance does not decrease even when the head speed at the time of hitting decreases.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of the golf ball of the present invention.

FIG. 2 is a schematic cross-sectional view of one embodiment of a mold for a hemispherical shell-shaped molded product for the intermediate layer core and the outer layer core of the golf ball of the present invention.

FIG. 3 is a schematic cross-sectional view of one embodiment of a mold for a spherical molded product coated with an intermediate layer core or an outer layer core of the golf ball of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inner core 2 ... Intermediate core 3 ... Outer core 4 ... Cover 5 ... Core 6 ... Hemispherical mold 7 ... Core mold 8 ... Semi-vulcanized hemispherical shell-shaped molding 9 ... Core molding mold 10 ... Spherical vulcanized molded product

Claims (5)

[Claims] A core (5) comprising an inner core (1), an intermediate core (2) coated on the inner core, and an outer core (3) coated on the intermediate core. ), And a multi-piece solid golf ball comprising at least one cover (4) formed on the core, wherein the inner layer core has a JIS-C hardness of 60 to 85, and the outer layer core has a JIS-C hardness of JIS-C.
-C hardness of 60 to 85, the JIS-C hardness of the inner layer core is 3 to 45 greater than the JIS-C hardness of the intermediate layer core, and the JIS-C hardness of the outer layer core is JIS of the intermediate layer core. A multi-piece solid golf ball characterized by being 3-45 greater than -C hardness. 2. The multi-piece solid golf ball according to claim 1, wherein the inner core, the intermediate core, and the outer core are made of a vulcanized rubber composition. 3. The intermediate layer core has a thickness of 1.5 to 7.0 mm, and the intermediate layer core is 6.5 to 16.0 m from the center of the core.
2. The multi-piece solid golf ball according to claim 1, wherein the golf ball is arranged within a range of m. 4. The inner layer core has a JIS-C hardness of 63 to 83, the intermediate layer core has a JIS-C hardness of 30 to 80, and the outer layer core has a JIS-C hardness of 30 to 80.
The multi-piece solid golf ball according to claim 1, having an IS-C hardness of 63 to 83. 5. The inner layer core has a JIS-C hardness of 65 to 80, the intermediate layer core has a JIS-C hardness of 40 to 75, and the outer layer core has a J-C hardness of 40 to 75.
The multi-piece solid golf ball according to claim 1, having an IS-C hardness of 65 to 80.