JP2002085590A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multipiece solid golf ball which is improved in flying performance and ball hitting feel. SOLUTION: This multipiece solid golf ball consists of a core (4) which is composed of a center (1) and an intermediate layer (2) formed around this center and >=1 layer of covers (3) covering the core. The center (1) has a diameter of 20 to 35 mm and central hardness of 10 to 70 by Shore A hardness and the intermediate layer (2) has a thickness of 2.5 to 10.0 mm and surface hardness of 4 to 65 by Shore A hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-piece solid golf ball which has a very low center hardness compared to a conventional golf ball, has a soft and good shot feeling, and has an improved flight distance. .

[0002]

2. Description of the Related Art Conventionally, most amateur golfers have a strong tendency to emphasize flight distance, and therefore have good resilience performance and prefer to use solid golf balls such as two-piece golf balls with a small amount of spin. I have. On the other hand, the performances required by professional golfers and advanced golfers are firstly controllability, and then soft and good shot feeling and flight performance. As described above, since the controllability is emphasized, and since the golf ball has a soft and good shot feeling, thread-wound golf balls have conventionally been the mainstream. However, since the golf ball has a structure that easily spins, there is a drawback that the spin amount is large and the flight performance is inferior even if any golf club is used. In view of this, many solid golf balls have been proposed which have good controllability and improved flight performance and shot feeling (Japanese Patent Application Laid-Open Nos. 8-332247 and 9-313643).

In such a golf ball, an intermediate layer is provided between the core and the cover of the two-piece solid golf ball to form a three-piece, and a more various hardness distribution is obtained as compared with the two-piece solid golf ball, so that flight performance and hitting ball are improved. At the same time, this slip-piece structure is the mainstream.

Japanese Patent Application Laid-Open No. 8-332247 discloses a three-piece solid golf ball having a two-layer structure core having an inner core and an outer core and a cover, wherein the inner core has a diameter of 25 to 37 mm and a JIS-C of the inner core. The center hardness according to the hardness is 60 to 85, the hardness difference from the center of the inner core to the surface is 4 or less,
A three-piece solid golf ball in which the outer core has a surface hardness of 75 to 90 according to JIS-C hardness and the cover has a flexural rigidity of 1200 to 3600 kg / cm ² is disclosed. However,
In this golf ball, the thickness of the intermediate layer is large,
When hitting with a short iron club from a middle iron, there is a problem that it is difficult to obtain sufficient rebound characteristics and a high launch angle.

Japanese Patent Application Laid-Open No. 9-313643 discloses a three-piece solid golf ball having an intermediate layer between a core and a cover, wherein the core has a core hardness of 75 or less according to JIS-C hardness, A three-piece solid golf ball having a hardness of 85 or less, a core surface hardness of 5 to 25 higher than the center hardness, an intermediate layer hardness of less than 10 higher than the core surface hardness, and a cover hardness higher than the intermediate layer hardness is disclosed.
However, in this golf ball, there is a problem that the intermediate layer portion is made of a thermoplastic resin, the rebound characteristics are inferior, and the shot feeling is hard and poor.

[0006] Therefore, there is an increasing demand for a golf ball which improves the above-mentioned drawbacks of the golf ball, and has more excellent flight performance and good hit feeling, regardless of whether it is a professional golfer or an amateur golfer.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-piece solid golf ball which solves the above-mentioned problems of the conventional solid golf ball and has improved flight performance and shot feel. And

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a core comprising a center and an intermediate layer and one or more layers of covers formed on the core are provided. By defining the diameter and center hardness of the center, and the thickness and surface hardness of the intermediate layer in a specific range,
We found that we could improve flight performance and feel at impact,
The present invention has been completed.

That is, the present invention provides a core comprising a center (1) and an intermediate layer (2) formed around the center.
(4) and a multi-piece solid golf ball comprising at least one cover (3) covering the core, wherein the center (1) has a diameter of 20 to 35 mm and a center hardness of 10 to 70 by Shore A hardness. And the intermediate layer (2) has a thickness of 2.5 to 10.0 mm and a surface hardness of 40 to 65 in Shore D hardness.

In the present invention, the center hardness is 10 to 70 in Shore A hardness as compared with the conventional golf ball described above.
By making it extremely low (with a Shore D hardness of 45 or less), the shot feeling is soft and good, and the spin amount at the time of hitting can be suppressed, so that the flight distance can be improved. is there.

Further, in order to suitably carry out the present invention, it is desirable that the cover (3) has a Shore D hardness of 45 to 60.

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 a core (4) comprising a center (1) and an intermediate layer (2) formed on the center,
And one or more layers of cover (3) covering the core. However, in FIG. 1, a golf ball having a one-layer cover (3) is used for easy understanding.

In the golf ball of the present invention, the center (1) is a cross-linked molded product mainly composed of a silicone rubber composition from which a soft rubber is easily obtained, or a vulcanized molded product of a rubber composition containing an oily substance. Is preferably used. In particular,
Silicone rubber, which is easy to obtain a soft and highly resilient rubber, is preferable.

The silicone rubber composition is obtained by uniformly dispersing a filler, a vulcanizing agent and the like in silicone raw rubber.
The above-mentioned silicone raw rubber is a colorless elastic body having a dimethylsiloxane unit [(CH ₃ ) ₂ SiO] as a main component and having a slight fluidity at room temperature, and has an average of 10 ³ diorganosiloxanes per molecule. consists unit, average molecular weight is about ^{105 to 106.} The above-mentioned silicone raw rubber can be produced by subjecting cyclic dimethylsiloxane produced by hydrolysis of dimethyldichlorosilane to ring-opening polymerization with an acid or alkali by heating, for example, dimethylsilicone raw rubber, methylvinylsilicone raw rubber, methylphenylvinylsilicone raw rubber, etc. Can be used.

As specific examples of the above, examples of the dimethyl silicone raw rubber include, for example, Shin-Etsu Chemical Co., Ltd.
"KE-76" manufactured by Toshiba Silicone Co., Ltd.
959 "and" Sil "manufactured by Dow Corning (DC).
asic 400 "," Siastic 401 ",
"SE-7" manufactured by General Electric (GE)
6 ”, manufactured by Union Carbide (UCC).
-95 ". Examples of the above-mentioned methyl vinyl silicone raw rubber include, for example, “KE manufactured by Shin-Etsu Chemical Co., Ltd.
-77 "and" TS-959 "manufactured by Toshiba Silicone Co., Ltd.
B "," SH-430 "manufactured by Toray Silicone Co., Ltd.," Silastic 4 "manufactured by Dow Corning (DC).
10, "Silastic 430", "SE-31" manufactured by General Electric (GE), "W-96" manufactured by Union Carbide (UCC), and the like. As an example of the above methylphenylvinylsilicone raw rubber, for example, "KE-7" manufactured by Shin-Etsu Chemical Co., Ltd.
9 "," Silas "manufactured by Dow Corning (DC)
tic 440 ", General Electric (GE)
SE-31 manufactured by Union Carbide (U.S.A.).
C.C.) and the like.

When a vulcanized molded product of only silicone raw rubber is used, the tensile strength tends to be low, so that a filler can be used to improve the strength of the silicone rubber. As a filler, a reinforcing filler for the purpose of reinforcement,
A non-reinforcing filler for the purpose of increasing the amount can be used. However, it is necessary to use a material which has excellent heat resistance and does not adversely affect the silicone rubber at high temperatures. Examples of the reinforcing filler include, for example, surface-treated silica, high-purity fumed silica, silica airgel, and precipitated silica.

Examples of the non-reinforcing filler include calcined diatomaceous earth silica, precipitated calcium carbonate, ground silica, quartz powder, titanium oxide, zinc oxide and the like.

As a method for vulcanizing silicone rubber, there are methods using an organic peroxide, a fatty acid azo compound, radiation and the like, but generally, an organic peroxide is used as a vulcanizing agent. Examples of the organic peroxide include benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-t-butyl peroxide, and the like. The compounding amount of the vulcanizing agent is preferably 0.2 to 8.0 parts by weight based on 100 parts by weight of the base rubber, and if less than 0.2 part by weight, the vulcanization is not completely performed, the hardness is low, and the resilience is low. When the content is more than 8.0 parts by weight, the center becomes hard, and as a result, the spin amount increases and the flight distance decreases.

The crosslink of the silicone rubber may be a heat crosslinkable type in which the crosslink is performed by heating.
A room temperature cross-linking type, which is allowed to stand at room temperature for cross-linking, may be used. As a room temperature crosslinking type, a one-pack type, which is filled in a cartridge or tube in a state where a crosslinking agent is already blended and crosslinks by a condensation reaction when exposed to air, is mixed with a catalyst at the time of use. And a two-pack type that is crosslinked.

As the silicone rubber, as described above,
Dimethyl silicone rubber, methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber can be used, but their copolymers can also be used. It is preferable to use a heat-curable silicone rubber containing dimethyl silicone rubber as a main component and a small amount of methylvinylsiloxane copolymerized thereon because of its good rebound resilience. The content of the vinyl group is 0.1
It is preferably from 10 to 10 mol%, more preferably from 0.15 to 0.8 mol%.

In the above cross-linked molded product, the silicone rubber is suitably compounded in an amount of 70 parts by weight or more, preferably 80 parts by weight or more based on 100 parts by weight of the base rubber. If the amount of the silicone rubber is less than 70 parts by weight, a good spin retention cannot be obtained. Examples of the rubber that can be used in combination with the silicone rubber include butadiene rubber (BR), ethylene propylene rubber (EPDM), acrylonitrile butadiene rubber (NBR), acrylonitrile rubber, and polynorbornene rubber.

The above silicone rubber composition is used as a center (1)
In the case of preparing the silicone rubber, 100 parts by weight of silicone rubber, 0.5 to 5 parts by weight of a vulcanizing agent, and a desired amount of a weight adjusting agent are kneaded with a Banbury mixer or a roll,
It is obtained by vulcanization molding at 150 to 170 ° C for 10 to 20 minutes.
The vulcanizing agent and the weight adjusting agent may be any of those commonly used, but as the weight adjusting agent, the rubber fraction of the solid center is increased, and the specific gravity is large to obtain low hardness. Those which are suitable include, for example, barium sulfate, calcium carbonate, clay filler, silica filler and the like.

When the center (1) is prepared from the rubber composition containing the above oily substance, 100 to 500 parts by weight of the oily substance and 0.5 parts by weight of sulfur are added to 100 parts by weight of the base rubber.
~ 5 parts by weight, vulcanization aid 3 ~ 10 parts by weight, vulcanization accelerator 1 ~
5 parts by weight and a desired weight controlling agent are kneaded with a Banbury mixer or a roll,
It is obtained by vulcanization molding for 0 to 20 minutes.

The base rubber is not particularly restricted but includes, for example, butadiene rubber (BR), natural rubber (NR), ethylene propylene rubber (EPDM), polynorbornene rubber and the like. A preferred base rubber is polynorbornene rubber. The above-mentioned polynorbornene rubber can be filled with an oily substance at a high level, and a soft rubber can be easily obtained.

The oily substance used in the rubber composition is not particularly limited.
Ester plasticizers such as naphthenic oils, paraffinic oils, aromatic oils, DOA and DOS are suitable. Among them, a naphthenic oil or an alkylbenzene-based oil, which hardly causes bloom even when added in a large amount and has high repulsion, is suitable.

The vulcanization aid, vulcanization accelerator and weight adjuster may be any of those commonly used. The weight adjusters may be the same as those used for the silicone rubber composition. Things can be used.

Next, an intermediate layer (2) is formed around the center (1). In the golf ball of the present invention,
The intermediate layer (2) is produced by heating and pressing a rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, a filler, an antioxidant, and the like. As the base rubber, natural rubber and / or conventionally used for solid golf balls are used.
Alternatively, a synthetic rubber is used, and in particular, a so-called high cis polybutadiene rubber having at least 40% or more, preferably 80% or more of cis-1,4-bonds is preferable. If desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM), and the like may be blended with the polybutadiene rubber.

Examples of the co-crosslinking agent include monovalent or divalent metal salts such as zinc and magnesium salts of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. Alternatively, blends thereof with acrylic esters or methacrylic esters may be mentioned, but zinc acrylate which imparts high resilience is preferred. The amount is 25 to 40 parts by weight, preferably 27 parts by weight, based on 100 parts by weight of the base rubber.
~ 35 parts by weight. If it is more than 40 parts by weight, the golf ball becomes too hard and the feel at impact deteriorates, and if it is less than 25 parts by weight, the resilience deteriorates and the flight distance decreases, and the golf ball obtained by using soft rubber for the center becomes soft. It becomes too bad and has a bad shot feeling without rebound.

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 compounding amount is 0.5 to 2 per 100 parts by weight of the base rubber.
Parts by weight, preferably 0.8 to 1.5 parts by weight. If it is less than 0.5 parts by weight, it becomes too soft and rebound becomes worse, resulting in a shorter flight distance. If it exceeds 2 parts by weight, the ball becomes too hard and the shot feeling becomes poor.

The filler may be any one which is usually compounded in the core of a solid golf ball, and examples thereof include inorganic fillers, specifically, zinc oxide, barium sulfate, calcium carbonate, magnesium oxide and the like. High specific gravity metal fillers such as tungsten powder, molybdenum powder and the like and mixtures thereof may be used. The compounding amount is 5 to 50 parts by weight, preferably 8 to 40 parts by weight, based on 100 parts by weight of the base rubber. If it is less than 5 parts by weight, it is necessary to mix a large amount of filler in the center in order to obtain a proper ball weight. As a result, the resilience of the center decreases, and if it exceeds 50 parts by weight, the weight of the core becomes too large. It is difficult to properly adjust the weight.

Further, the center of the golf ball of the present invention (1)
And the middle layer (2), an antioxidant or a peptizer,
In addition, components that can be generally used for manufacturing a core of a solid golf ball may be appropriately compounded. The compounding amount is base rubber 10
The antioxidant is preferably 0.2 to 0.5 part by weight, and the peptizer is preferably 0.2 to 5 parts by weight, based on 0 part by weight.

A method for manufacturing a core used in the golf ball of the present invention will be described with reference to FIGS. FIG. 2 shows a mold 1 for forming an intermediate layer used in the golf ball of the present invention.
FIG. 4 is a schematic sectional view of one embodiment. 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 center rubber composition is heated and pressed in a mold at, for example, 150 to 170 ° C. for 10 to 20 minutes to form a spherical vulcanizing center. Next, a hemispherical mold having a hemispherical cavity as shown in FIG.
Using (5) and a core mold (6) having a hemispherical convex portion having the same shape as the center, the rubber composition for the intermediate layer is pressed to form an unvulcanized hemispherical shell-like intermediate layer (7). I do. Subsequently, using two upper and lower core molds (8) as shown in FIG. 3, the vulcanization center (9) is sandwiched between the two hemispherical shell-like intermediate layers (7), for example, 140 to 180. Vulcanization molding at 10 ° C for 10 to 60 minutes, center (1)
And an intermediate layer (2) formed on the center
Form (4).

In the golf ball of the present invention, the center
(1) is required to have a diameter of 20 to 35 mm, preferably 22 to 33 mm, more preferably 25 to
32 mm. If the diameter is smaller than 20 mm, the spin rate at the time of hitting increases and the flight distance decreases. If the diameter is larger than 35 mm, the ball compression becomes large and becomes too soft, resulting in a poor shot feeling without rebound.

In the golf ball of the present invention, the center
It is required that (1) has a center hardness of 10 to 70 based on Shore A hardness, but it is preferably 15 to 65, more preferably 30 to 60. The center hardness of the above center is 1
If the value is lower than 0, the resilience of the obtained golf ball is reduced and the flight distance is reduced. Becomes smaller. The center hardness of the center means the Shore A hardness measured at the center of the cut surface by cutting the center obtained by vulcanization molding into two equal parts.

In the golf ball of the present invention, the intermediate layer
(2) is required to have a thickness of 2.5 to 10.0 mm, preferably 3.0 to 9.5 mm, and more preferably 3.5 to 7.5 mm. If the thickness is smaller than 2.5 mm, the ball compression becomes large and becomes too soft, resulting in a poor shot feeling without rebound.
If it is larger than 0 mm, not only does the spin amount increase and the flight distance decreases, but also the shot feeling deteriorates.

In the golf ball of the present invention, the intermediate layer
(2) is required to have a surface hardness of 40 to 65 based on Shore D hardness, but is preferably 42 to 60, and more preferably 44 to 60 mm. If the surface hardness of the intermediate layer is lower than 40, the obtained golf ball becomes too soft, and the rebound resilience is reduced to reduce the flight distance, and if the surface hardness is higher than 65, the golf ball becomes too hard and the shot feeling is deteriorated,
The amount of spin when hit by the driver also increases, and the flight distance decreases. The surface hardness of the intermediate layer is defined as the center hardness.
It means the Shore D hardness measured on the outer surface of a core (4) having a two-layer structure formed by integrally vulcanizing and forming an intermediate layer (2) on (1).

Next, the core (4) is covered with one or more covers (3). In the golf ball of the present invention, the cover (3) has a thickness of 1.0 to 4.0 mm, preferably 1.5 to 4.0 mm.
It is desirable to have 3.8 mm, more preferably 2.0 to 3.5 mm, but if it is smaller than 1.0 mm, sufficient controllability will not be obtained, and if it is larger than 4.0 mm, sufficient flight distance will not be obtained. . The cover of the golf ball of the present invention may have a single-layer structure or a multilayer structure of two or more layers. When the cover has a multilayer structure of two or more layers, the total thickness of the cover is in the above range. If it is inside.

In the golf ball of the present invention, the cover
(3) has a Shore D hardness of 45 to 60, preferably 47 to 5
8, more preferably 48-57, most preferably 50-
It is desirable to have 55. If the cover hardness is lower than 45, the spin rate at the time of hitting by a driver increases and the flight distance decreases, and if the cover hardness is higher than 60, it becomes too hard and the shot feeling is deteriorated, and the spin rate in approach shots etc. It becomes low and controllability deteriorates. When the cover has a multilayer structure of two or more layers,
It is sufficient that the outermost layer cover has the above hardness. still,
The cover hardness means the Shore D hardness measured on the outer surface of a golf ball having the cover (3) covered around the core (4).

The cover (3) of the present invention contains, as a base resin, a thermoplastic resin, particularly an ionomer resin generally used for a cover of a golf ball. Examples of the ionomer resin include those obtained by neutralizing at least a part of the carboxyl groups in a copolymer of ethylene and α, β-unsaturated carboxylic acid with metal ions, or ethylene and α, β-unsaturated carboxylic acid. It is obtained by neutralizing at least a part of carboxyl groups in a terpolymer with an α, β-unsaturated carboxylic acid ester with a metal ion. Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like, and acrylic acid and methacrylic acid are particularly preferable. Examples of α, β-unsaturated carboxylic acid ester metal salts include, for example, methyl such as acrylic acid, methacrylic acid, fumaric acid, and maleic acid.
Ethyl, propyl, n-butyl, isobutyl esters and the like are used, and acrylates and methacrylates are particularly preferred. Carboxyl groups in the above-mentioned copolymers of ethylene and α, β-unsaturated carboxylic acid or in terpolymers of ethylene, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester Examples of metal ions that neutralize at least a part of sodium, potassium, lithium, magnesium, calcium, zinc, barium, aluminum, tin, zirconium, cadmium ions, etc., and particularly sodium, zinc, and magnesium ions are repelled. Often used and preferred from the viewpoints of properties, durability and the like.

Specific examples of the ionomer resin include:
Without limitation, Hi-Milan 155
5, High Milan 1557, High Milan 1605, High Milan 165
2, High Milan 1702, High Milan 1705, High Milan 170
6, High Milan 1707, High Milan 1855, High Milan 1856
(Manufactured by DuPont Mitsui Polychemicals), Surlyn
8945, Surlyn 9945, Surlyn 6320 (manufactured by DuPont),
Examples include Iotek 7010 and 8000 (manufactured by Exxon). As these ionomers, the above-mentioned examples may be used alone or as a mixture of two or more.

Further, as an example of a preferable material of the cover (3) of the present invention, only the ionomer resin as described above may be used, but the ionomer resin may be used in combination with a thermoplastic elastomer or a diene block copolymer. You may use in combination with more than one kind. Specific examples of the above thermoplastic elastomer include, for example, a polyamide thermoplastic elastomer commercially available from Toray Industries, Inc. under the trade name “Pebax” (eg, “Pebax 2533”), and a trade name “Hytrel” from Toray Dupont Co., Ltd. (E.g., "Hytrel 3548", "Hytrel 4047"), a polyester-based thermoplastic elastomer, commercially available from Takeda Verdish K.K. under the trade name "Elastolane ET880". ") Polyurethane-based thermoplastic elastomers and the like.

The diene-based block copolymer has a double bond derived from a conjugated diene compound of a block copolymer or a partially hydrogenated block copolymer. The base block copolymer is a block copolymer comprising at least one polymer block A mainly composed of a vinyl aromatic compound and at least one polymer block B mainly composed of a conjugated diene compound. It is. In addition, the partially hydrogenated block copolymer is obtained by hydrogenating the above block copolymer. Examples of the vinyl aromatic compound constituting the block copolymer include styrene,
One or more of α-methylstyrene, vinyltoluene, pt-butylstyrene, 1,1-diphenylstyrene and the like can be selected, and styrene is preferred. As the conjugated diene compound, for example, butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-
One or more of 1,3-butadiene and the like can be selected, butadiene, isoprene and a combination thereof are preferred. Specific examples of the diene-based block copolymer include, for example, those commercially available from Daicel Chemical Industries, Ltd. under the trade name “Epo Friend” (for example,
"Epo Friend A1010"), which is commercially available from Kuraray Co., Ltd. under the trade name "Septon" (for example, "Septon HG
-252).

The amount of the above-mentioned thermoplastic elastomer, diene-based block copolymer or the like is adjusted according to the amount of the base resin 100 for the cover.
It is 1 to 60 parts by weight, preferably 1 to 35 parts by weight based on parts by weight. If the amount is less than 1 part by weight, the effect of lowering the impact at the time of hitting by combining them becomes insufficient, and if it is more than 60 parts by weight, the cover becomes too soft and the resilience decreases, and the compatibility with the ionomer And the durability tends to decrease.

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

The method for coating the cover (3) is not particularly limited, either, and can be performed by a usual method for 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. And 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.

According to the present invention, there is provided a multi-piece solid golf ball having a soft and good shot feeling and an improved flight distance since the center has a very low hardness as compared with a conventional golf ball.

[0047]

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 a spherical vulcanized molded product for a center A rubber composition for a center having the composition shown in Table 1 below was kneaded, and heated and pressed in a mold at 160 ° C. for 20 minutes. Was obtained. The diameter, center hardness and specific gravity of the obtained center were measured, and the results are shown in Table 3.

(Ii) Preparation of a semi-spherical shell-shaped unvulcanized molded product for the intermediate layer A rubber composition for an intermediate layer having the composition shown in Table 1 below was kneaded, and the molds (5, 6) shown in FIG. By pressing in), a hemispherical shell-shaped unvulcanized molded product (7) for the intermediate layer was obtained.

(Iii) Preparation of core The vulcanized molded product for center (9) prepared in (i) above was replaced with (ii)
3 between the two hemispherical shell-shaped unvulcanized molded products (7) for the intermediate layer prepared in the above (2) in a mold (8) as shown in FIG.
The core (4) having a two-layer structure having a diameter of 39.0 mm was produced by heating and pressing for 0 minutes. The surface hardness, thickness and specific gravity of the obtained core (4) were measured, and the results are shown in Table 3. However, the surface hardness of the core is the Shore D of the intermediate layer.
The table shows the surface hardness according to the hardness.

[0051]

[Table 1]

(Note 1) High-cis polybutadiene rubber (manufactured by JSR Corporation, content of 1,4-cis-polybutadiene: 96%) (Note 2) Trade name “Nocrack NS-” from Ouchi Shinko Chemical Co., Ltd.
2,5-t-butyl hydroquinone commercially available under "6" (Note 3) Silicone compound manufactured by Shin-Etsu Chemical Co., Ltd. (Note 4) Silicone compound manufactured by Shin-Etsu Chemical Co., Ltd. (Note 5) Shin-Etsu Chemical Co., Ltd. (Note 6) Vulcanization accelerator manufactured by Shin-Etsu Chemical Co., Ltd.

(Iv) Preparation of Cover Composition The materials having the formulations shown in Table 2 below were mixed by 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 150 to 260 ° C. at the position of the die of the extruder.

[0054]

[Table 2]

(Note 7) Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemicals, Shore D hardness = 61, flexural rigidity =
Approx. 310 MPa (Note 8) Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui Dupont Polychemical Co., Ltd., Shore D hardness = 60, Flexural rigidity = about 260 MPa (Note 9) Mitsui Dupont Polychemical ( Zinc ion neutralized ethylene-methacrylic acid-isobutyl acrylate terpolymer copolymer ionomer resin, Shore D hardness = 54, flexural rigidity = about 90 MPa (Note 10) Zinc ion neutralized ethylene-methacrylic manufactured by DuPont Acid copolymer type ionomer resin, Shore D hardness = 5
9. Flexural rigidity = approx. 220MPa (Note 11) Sodium ion neutralized ethylene manufactured by DuPont
Methacrylic acid copolymer type ionomer resin, Shore D hardness = 61, flexural rigidity = about 270 MPa (Note 12) Magnesium ion neutralized ethylene-methacrylic acid-n-butyl acrylate terpolymer ionomer resin manufactured by DuPont, Shore D hardness = 44, flexural rigidity =
Approximately 35 MPa (Note 13) Glycidyl methacrylate adduct of styrene-butadiene-styrene block copolymer hydrogenated product manufactured by Asahi Kasei Kogyo Co., Ltd., JIS-A hardness = 65, styrene content about 20% by weight,
Butadiene hydrogenated product content about 80% by weight, glycidyl methacrylate content about 1% by weight, (Note 14) Ethylene-ethyl acrylate-maleic anhydride terpolymer manufactured by Sumitomo Chemical Co., Ltd., MI = 7.0, Shore D hardness = 14, ethyl acrylate + maleic anhydride content = 32% (including maleic anhydride 1 to 4%) (Note 15) Styrene-butadiene having an epoxy group-containing polybutadiene block manufactured by Daicel Chemical Industries, Ltd. -
Styrene (SBS) block copolymer, JIS-A hardness = 67, styrene / butadiene = 40/60 (weight ratio), epoxy content about 1.5-1.7% by weight (Note 16) Terminal OH manufactured by Kuraray Co., Ltd. Group-added hydrogenated styrene
-Isoprene-styrene (SIS) block copolymer, JIS-
A hardness = 80, styrene content = about 40% by weight

(Examples 1 to 4 and Comparative Examples 1 to 3) The above-mentioned cover composition was directly injection-molded on the core (4) having a two-layer structure obtained as described above. 3
A cover layer (3) having a Shore D hardness as shown in FIG.
Was produced. The resulting golf ball was measured or evaluated for initial ball speed, spin rate, flight distance (total), and feel at impact, and the results are shown in Table 3.
The test method was performed as follows.

(Test Method) Hardness (i) Center Hardness The center hardness was obtained by cutting a center obtained by vulcanization molding into two equal parts, and JIS-K6253 at the center of the cut surface.
A was measured using a Shore A type spring hardness tester specified in A. (ii) Intermediate layer hardness Intermediate layer hardness is determined by ASTM- on the outer surface of a core having a two-layer structure formed by integrally vulcanizing an intermediate layer on a center.
Spring type hardness tester Shore D specified in D 2240-68
It was measured using a mold. (iii) Cover Hardness The cover hardness is determined by measuring the hardness of the outer surface of a golf ball having a cover around the core (4) by ASTM-D.
It was measured in an environment of 23 ° C. using a Shore D type spring hardness meter specified in 2240-68.

Flight Performance (1) A golf club swinging robot was fitted with a No. 1 wood club (W # 1, driver), and the golf ball was hit at a head speed of 45 m / sec. The flight distance was measured. The total (distance to the stop point) was measured as the flight distance. The measurement was performed 12 times (n = 12) with each golf ball, and the average was calculated to obtain the result of each golf ball.

(2) Attach a sand wedge (SW) to a swing robot manufactured by Golf Laboratory, strike a golf ball at a head speed of 21 m / sec, and take continuous shots of the hit golf ball to obtain a spin amount. I asked. The measurement was performed 12 times (n = 12) with each golf ball, and the average was calculated to obtain the result of each golf ball.

Hitting Feeling An actual hit test was performed with a metal head No. 1 wood club (W # 1, driver) by ten golfers, and the magnitude of impact at the time of hitting and the presence / absence of rebound were evaluated. The evaluation was the result of the golf ball. The evaluation criteria are as follows. Evaluation Criteria (Impact) ○… The impact is small and the shot feeling is good △… Normal ×… The impact is large and the shot feel is poor Evaluation Criteria (Rebound) ○… There is a rebound and the shot feel is good △… Normal ×… There is no feeling of rebound and it is a heavy shot feeling and bad

(Test results)

[0062]

[Table 3]

From the above results, the golf balls of the present invention of Examples 1 to 4 have a longer flight distance when hit by a driver, a smaller impact and a resilience as compared with the golf balls of Comparative Examples 1 to 3. It was found that the golf ball had a good shot feeling.

The golf ball of Example 4 which is the golf ball of the present invention is superior in both the flight distance and the shot feeling to the golf ball of the comparative example, but has a high cover hardness, so that the spin amount when hit with a sand wedge is low. ing. In low iron count clubs such as sand wedges, controllability is emphasized. For example, the spin amount when hit by a sand wedge is 5500 rpm or more, preferably 6950 rpm.
pm or more. Since the golf ball of Example 4 has a high cover hardness, the golf ball of the other examples has a lower spin rate when hit with a sand wedge and is poor in controllability.

On the other hand, the golf ball of Comparative Example 1 has a small center diameter, so that the spin rate at the time of hitting is high and the flight distance is short, and the golf ball of the comparative example 1 is high in spin rate because of the large thickness of the intermediate layer. Not only is the distance reduced, but the impact is large and the shot feel is bad.

The golf ball of Comparative Example 2 had a large center diameter, so that the golf ball became too soft, resulting in a poor hitting feeling without rebound, and the small thickness of the intermediate layer became too soft, giving a poor hitting feeling without rebound. I have.

The golf ball of Comparative Example 3 has a large center hardness, so that the golf ball becomes too hard, resulting in a poor shot feeling and a high spin rate when hit by a driver, resulting in a short flight distance.

[0068]

According to the multi-piece solid golf ball of the present invention, the center diameter and the center hardness, and the thickness and the surface hardness of the intermediate layer are defined in specific ranges, so that the center has a very low hardness and softness. And has a good feel at impact and excellent flight performance.

[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 molding an intermediate layer of a golf ball of the present invention.

FIG. 3 shows a mold 1 for molding a core of a golf ball of the present invention.
FIG. 4 is a schematic sectional view of one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Center 2 ... Intermediate layer 3 ... Cover 4 ... Core 5 ... Hemispherical mold 6 ... Core mold 7 ... Hemispherical shell-like intermediate layer 8 ... Core molding die 9 ... Vulcanization center

Claims (4)

[Claims] 1. A multi-layer comprising a core (4) comprising a center (1) and an intermediate layer (2) formed around the center, and one or more covers (3) covering the core. A piece solid golf ball, wherein the center (1) has a diameter of 20 to 35 mm and a center hardness of 10 to 70 by Shore A hardness, and the intermediate layer
(2) A multi-piece solid golf ball having a thickness of 2.5 to 10.0 mm and a surface hardness of 40 to 65 according to Shore D hardness. 2. The cover (3) having a Shore D hardness of 45 to 6
2. The multi-piece solid golf ball according to claim 1, having a value of zero. 3. The multi-piece solid golf ball according to claim 1, wherein said center (1) is formed from a cross-linked molded product mainly comprising a silicone rubber composition. 4. The multi-piece solid golf ball according to claim 1, wherein the cover (3) has one layer.