JP2002224244A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball excellent in a balance between an impact feeling and a flying distance, obtained a specified organic sulfur compound. SOLUTION: This solid golf ball includes a core consisting of base material rubber, α,β-unsaturated carboxylic acid and/or the metal salt, organic peroxide and inorganic metal salt thereof and the vulcanized matter of a rubber composition containing the disulfides expressed by the following general formula (1) or the multilayered core containing one or more layers consisting of this vulcanized matter and a cover of a single layer or multiple layers formed on the core: Formula 1 (In the formula, at least one among X1 to X5 and X1' to X5' are electron withdrawing substitutes.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball, and more particularly to a solid golf ball having improved rebound performance at hitting, flight performance, and hit feeling.

[0002]

2. Description of the Related Art A solid golf ball comprises a solid core made of vulcanized rubber and a cover covering the core.
The solid core is generally formed by spherical vulcanization of a rubber composition containing a polybutadiene-based rubber, a metal salt of an unsaturated carboxylic acid as a co-crosslinking agent, a crosslinking initiator such as dicumyl peroxide, a mass regulator, and other fillers. It is formed of a molded body. The metal salt of the unsaturated carboxylic acid contained in the composition,
By graft-bonding to the polybutadiene main chain by the action of a cross-linking initiator or by forming cross-links between the polybutadiene main chains, the core is imparted with appropriate hardness and durability and resilience is enhanced.

[0003] However, the demands of golf players for golf balls are very strong, and further improvement in flight performance is required. Generally, in order to improve the flight performance, it is conceivable to increase the degree of cross-linking of the vulcanized rubber by increasing the content of the co-crosslinking agent to increase the resilience. However, an increase in the degree of cross-linking due to an increase in the content of the co-crosslinking agent causes the core as a vulcanized body to be hard, so that the flight distance increases, but there is a problem that the hit feeling becomes hard. In other words, the fact that the hit feeling is hard increases the impact of the golfer upon hitting, which is not preferred by golfers.

[0004] For these reasons, research has been conducted on golf balls that increase the rebound resilience while suppressing the increase in hardness of the core and balance the flight performance and the hit feeling. For example, Japanese Patent No. 2778229 discloses that a rubber composition for a core contains one selected from a thiophenol, a thiocarboxylic acid, a sulfide, a zinc salt of a thiophenol and a zinc salt of a thiocarboxylic acid, thereby increasing the rebound resilience. At the same time, there has been proposed a golf ball in which the amount of deflection under a load of 100 kg corresponding to the hardness is limited to a relatively soft and constant range, thereby improving the rebound resilience while securing the hitting feeling.

[0005]

SUMMARY OF THE INVENTION In an improved technique for increasing the rebound resilience of a core while suppressing the hardness of the core by adding an organic sulfur compound to the rubber composition for the core, the degree of the rebound resilience is increased. The effect on hardness and hardness differs depending on the type of the organic sulfur compound contained in the rubber composition.

However, Japanese Patent No. 2779229 merely shows an example relating to a zinc salt of pentachlorothiophenol.

The present invention has been made in view of such circumstances, and a purpose of the present invention is to use a special organic sulfur compound to provide a golf ball having an excellent balance between a hit feeling and a flight distance. The goal is to provide the ball.

[0008]

The solid golf ball of the present invention comprises a base rubber, an α, β-unsaturated carboxylic acid and / or
Alternatively, a vulcanized core of a rubber composition containing a metal salt, an organic peroxide, an inorganic metal salt thereof, and a disulfide represented by the following formula (1), or a vulcanized layer,
It includes a multi-layer core including at least one layer, and a single-layer or multi-layer cover formed on the core.

[0009]

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(Wherein X ^{1 to} X ⁵ and X ^{1 ′ to} X ^{5 ′} are each at least one member selected from the group consisting of the following formulas (2), (3) and (4)). is there)

[0011]

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(In the formula, A is at least one selected from the group consisting of a hydrogen atom, a hydroxy group, an alkoxy group, an alkyl group, and a halogen.) The inorganic metal salt preferably contains zinc oxide.

A preferred embodiment of the solid golf ball of the present invention comprises: 100 parts by mass of a base rubber; 15 to 45 parts by mass of a metal salt of an α, β-unsaturated carboxylic acid;
5 parts by mass; zinc oxide 3 to 30 parts by mass; and an electron-withdrawing substituted disulfide represented by the above formula (1) 0.05 to 5 parts by mass.
A core composed of a vulcanized rubber composition containing 3.0 parts by mass, or a multilayer core including at least one layer composed of the vulcanized body, and a single-layer or multilayer cover formed on the core including.

Preferably, in the solid golf ball of the present invention, the core has an initial load of 98N and a load of 1275.
The amount of deformation of the core when increased to N is 2.5 to 5.5
mm.

When the core has a multilayer structure, the ratio of the volume V _S of the vulcanized product of the rubber composition to the volume V _C of the entire core (V _S / V _C ) is 0.5 or more, and Volume V
Ratio of volume V _S of the vulcanizate of the rubber composition to _B (V
_(S / V _B ) is preferably 0.3 or more.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The solid golf ball of the present invention has a core and a cover for covering the core, and a part of the core is composed of a base rubber, an α, β-unsaturated carboxylic acid and / or a metal thereof. It is characterized by being constituted by a vulcanizate of a rubber composition ("disulfide-containing rubber composition") containing a salt, an organic peroxide, an inorganic metal salt and a specific disulfide. Hereinafter, each component will be described in order.

First, as the base rubber, natural rubber or synthetic rubber conventionally used for solid golf balls can be used.
It is a so-called high cis polybutadiene rubber having 1,4-bonds of 40% or more, more preferably 80% or more, and optionally contains a proper amount of natural rubber, isoprene rubber, styrene butadiene rubber, ethylene propylene rubber or the like. Is also good. This is because polybutadiene having a higher content of cis-1,4-bond has higher resilience.

The α, β-unsaturated carboxylic acid and / or its metal salt is mainly blended as a co-crosslinking agent, and has 3 to 8 carbon atoms, such as acrylic acid or methacrylic acid. Carboxylic acids and / or metal salts thereof are preferably used. Further, as the metal salt, zinc, magnesium or the like may be used.
A trivalent metal salt is preferably used. Of these,
Particularly preferred for imparting excellent resilience to the core are zinc salts of acrylic acid or methacrylic acid.

The compounding amount of the metal salt of α, β-unsaturated carboxylic acid is preferably in the range of 15 to 45 parts by mass based on 100 parts by mass of the base rubber. On the other hand, if the repellency is poor, the flight distance tends to decrease. On the other hand, if it exceeds 45 parts by mass, the core becomes too hard, and the hit feeling and control performance tend to deteriorate. The more preferable lower limit of the metal salt of α, β-unsaturated carboxylic acid is 20 parts by mass, and the more preferable upper limit is 35 parts by mass.

The organic peroxide is a component compounded as a crosslinking initiator, and oxy radicals generated by dissociation can extract hydrogen at the allylic position of the base rubber and initiate a crosslinking reaction. As the organic peroxide used in the present invention, specifically, dicumyl peroxide,
Examples thereof include 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butyl peroxide and the like. Among them, dicumyl peroxide is highly versatile.

The compounding amount of the organic peroxide is preferably in the range of 0.2 to 5 parts by mass based on 100 parts by mass of the base rubber. If the amount is less than 0.2 parts by mass, the crosslinking will be insufficient and the resilience will decrease, making it difficult to sufficiently increase the flight distance. on the other hand,
If the content exceeds 5 parts by mass, the amount of the α, β-unsaturated carboxylic acid metal salt must be reduced to give the core an appropriate hardness, and the flight distance tends to decrease due to insufficient rebound. Because there is.

The disulfide compound used in the present invention is a disulfide compound represented by the following formula (1).

[0023]

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In the formula, at least one of X ^{1 to} X ⁵ and X ^{1 ′ to} X ^{5 ′} is one type selected from the group consisting of the following formulas (2), (3) and (4). . That is, a diphenyl disulfide compound substituted with a carbonyl group, a sulfonyl group, or a sulfinyl group having a high electron-withdrawing property (hereinafter referred to as “electron-withdrawing-substituted diphenyl disulfide compound”) is characterized. By containing such an electron-withdrawing substituted diphenyl disulfide compound, it is considered that a substituted thiophenyl radical is generated in the vulcanization reaction system, and that the radical participates in a rubber crosslinking system to form a highly resilient crosslinked form. .

[0025]

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A in each of the formulas (2) to (4) is a hydrogen atom, a hydroxy group, an alkoxy group, an alkyl group or a halogen. As the alkoxy group, a methoxy group having a small steric bulk is preferable.

Accordingly, the electron withdrawing substitution used in the present invention
Diphenyl disulfide compounds bind to phenyl groups
Substituent X¹~ X^FiveAt least one of X^{1 '}
~ X ^Five'At least any one of
Group (—COOH) or its alkyl ester (—C
OOR), formyl group (-CHO), acyl group (-CO
R), a carbonyl halide group (—COHal), a sulfo
Group (-SO_ThreeH) or its alkyl ester (—SO
_ThreeR), a sulfonyl halide group (—SO_TwoR), sulf
Ino group (-SO_TwoH), alkylsulfinyl group (-S
OR) and the like. As alkyl esters, steric bulk
Is preferred.

The electron-withdrawing substituted diphenyl disulfide compound used in the present invention may be a symmetrical disulfide compound in which the same substituent is substituted at the same position among the above-mentioned electron-withdrawing substituents, or may be the same. It may be a disulfide compound in which the groups are substituted at different positions and disulfides or different types of substituents are substituted at the same or different positions. Further, when the number of substituents on each benzene ring is 3 or less, it is preferable that each benzene ring is substituted at the o-position and the p-position so as to exhibit electron-withdrawing properties.

Therefore, the symmetric electron-withdrawing substituted diphenyldiphenyl
Specific examples of the sulfide compound include X¹~ X^Five, X^{1 '}~
X^Five'If at least one of each is a carboxyl group
And bis (4-carboxyphenyl) disulfide,
(2,6-dicarboxyphenyl) disulfide, bi
(2,4,6-tricarboxyphenyl) disulfite
, Bis (pentacarboxyphenyl) disulfide
Etc .; X¹~ X^Five, X^{1 '}~ X ^Five'At least one of each
Bis (4-methoxycarbonyl) which is a carbonyl group
Ruphenyl) disulfide, bis (2,4,6-trime
Toxylcarbonylphenyl) disulfide, bis (pen)
X, such as (tamethoxycarbonylphenyl) disulfide;¹
~ X^Five, X^{1 '}~ X^Five'At least one is a formyl group
Bis (4-formylphenyl) disulfide, bis
(2,4,6-triformylphenyl) disulfide,
Bis (pentaformylphenyl) disulfide and the like; X¹
~ X^Five, X ^{1 '}~ X^Five'At least one of each is an acyl group
Certain bis (4-acetylphenyl) disulfides, bis
(2,4,6-triacetylphenyl) disulfide,
Bis (pentaacetylphenyl) disulfide and the like; X¹
~ X^Five, X^{1 '}~ X^Five'At least one of each is halogenated
Bis (4-chlorocarbonylphenyl) which is a carbonyl group
Ru) disulfide, bis (2,4,6-tri (chloroca
Rubonyl) phenyl) disulfide, bis (penta (c
X, such as lolocarbonyl) phenyl) disulfide; ¹~
X^Five, X^{1 '}~ X^Five'At least one of each is a sulfo group
Bis (4-sulfophenyl) disulfide, bis
(2,4,6-trisulfophenyl) disulfide, bi
X (pentasulfophenyl) disulfide and the like; X¹~
X^Five, X^{1 '}~ X^Five'At least one of each is an alkoxys
Bis (4-methoxysulfonyl) in the case of a rufonyl group
Phenyl) disulfide, bis (2,4,6-trimeth
Xisulfonylphenyl) disulfide, bis (penta)
Methoxysulfonylphenyl) disulfide and the like; X¹~
X^Five, X^{1 '}~ X^Five'At least one of each is halogenated
Bis (4-chlorosulfonylphenyl) which is a ruphonyl group
Ru) disulfide, bis (2,4,6-trichlorosulfur)
Honylphenyl) disulfide, bis (pentatrichloro)
X such as (rosulfonylphenyl) disulfide;¹~ X^Five, X
^{1 '}~ X^Five'Wherein at least one of is a sulfino group
(4-sulfinophenyl) disulfide, bis (2,
4,6-trisulfinophenyl) disulfide, bis
(Pentasulfinophenyl) disulfide and the like; X¹~
X^Five, X^{1 '}~ X^Five'At least one of which is an alkyl sulfite
Bis (4-methylsulfinylphenyl) di
Sulfide, bis (2,4,6-trimethylsulfini
Ruphenyl) disulfide, bis (pentamethylsulfur)
(Inylphenyl) disulfide and the like.

The number of substituents on each benzene ring is not limited to one, but may be an electron-withdrawing diphenyldisulfide compound having two or more kinds of electron-withdrawing substituents represented by formulas (2) to (4). Good. For example, bis (4-acetyl, 2
-Carboxyphenyl) disulfide, bis (4-acetyl, 2-methoxycarbonylphenyl) disulfide, bis (4-acetyl, 2-formylphenyl) disulfide, bis (4-acetyl, 2-chlorocarbonylphenyl) disulfide, bis (4 -Acetyl, 2-sulfophenyl) disulfide, bis (4-acetyl, 2
-Methoxysulfonylphenyl) disulfide, bis (4-acetyl, 2-chlorosulfonylphenyl) disulfide, bis (4-acetyl, 2-sulfinophenyl) disulfide, bis (4-acetyl, 2-methylsulfinylphenyl) disulfide, etc. No.

Further, the electron-withdrawing substitution die used in the present invention is used.
The phenyl disulfide compound is represented by X ¹~ X^FiveAt least
One and X^{1 '}~ X^Five'At least one of the above-mentioned electron suction
If the substituent is a neutral substituent, the remaining substituents
Groups other than attractive groups, such as halogen, cyano group, nitro
Group, amino group, alkyl group, alkoxy group, hydroxy
Group, phenylthio group, carbamoyl group, halogenated al
It may be a kill group or the like. The combination of substituents is organic
There is no particular limitation except for difficulty in synthesis. So the example
For example, disulfides substituted with a halogen and an acyl group
Bis (4-chloro, 2-acetylphenyl) dis
Sulfide, bis (4-chloro, 2,6-diacetylfe
Nyl) disulfide and the like; substituted with a cyano group and an acyl group
Bis (4-cyano, 2-a) as a disulfide compound
Cetylphenyl) disulfide, bis (4-cyano,
2,6-diacetylphenyl) disulfide and the like; nitro
(4-nitro, 2-acetyl)
Tylphenyl) disulfide, bis (4-nitro, 2,2)
6-diacetylphenyl) disulfide and the like;
Bis (4-amino, 2-acetyl substituted with an acyl group
Phenyl) disulfide, bis (4-amino, 2,6-
Diacetylphenyl) disulfide, etc .;
Bis (4-methyl, 2-acetyl) substituted with a sil group
Enyl) disulfide, bis (4-methyl, 2,6-di
Acetylphenyl) disulfide, bis (4-t-butyi)
, 2-acetylphenyl) disulfide, bis (4-
t-butyl, 2,6-diacetylphenyl) disulfite
B; bis (4-methoxy) substituted with a methoxy group and an acyl group
Xy, 2-acetylphenyl) disulfide, bis (4
-Methoxy, 2,6-diacetylphenyl) disulfite
Bis (4-substituted with a hydroxy group and an acyl group)
(Hydroxy, 2-acetylphenyl) disulfide, bi
(4-hydroxy, 2,6-diacetylphenyl) di
Sulfide, etc .; substituted with phenylthio and acyl groups
Bis (4-phenylthio, 2-acetylphenyl) dis
Sulfide, bis (4-phenylthio, 2,6-diacetyl
Ruphenyl) disulfide, etc .; carbamoyl group and acyl
(4-carbamoyl, 2-acetyl substituted with a group
Phenyl) disulfide, bis (4-carbamoyl,
2,6-diacetylphenyl) disulfide and the like; halogen
Bis (4-tri) substituted with an alkylated alkyl group and an acyl group
Chloromethyl, 2-acetylphenyl) disulfide,
Bis (4-trichloromethyl, 2,6-diacetylfe
Nyl) disulfide and the like;
With any of the electron withdrawing groups represented by the formulas (2) to (4)
As a substituted disulfide compound, for example, bis (4
-Chloro, 2-carboxyphenyl) disulfide, bi
Di (4-chloro, 2-methoxycarbonylphenyl) di
Sulfide, bis (4-chloro, 2-formylphenyi)
L) disulfide, bis (4-chloro, 2-chlorocar
Bonylphenyl) disulfide, bis (4-chloro, 2
-Sulfophenyl) disulfide, bis (4-chloro,
2-methoxysulfonylphenyl) disulfide, bis
(4-chloro, 2-chlorosulfonylphenyl) disul
Fido, bis (4-chloro, 2-sulfinophenyl)
Disulfide, bis (4-chloro, 2-methylsulfide
Nylphenyl) disulfide and the like.

The above-mentioned electron-withdrawing-substituted diphenyl disulfide compound has a high resilience-improving effect, and has a higher rate of increase in the coefficient of restitution with respect to a reduction in the amount of flexure (higher hardness) than the conventionally used organic sulfur compounds. . Therefore, by containing the electron-withdrawing substituted disulfide compound represented by the above formula (1), it is possible to increase the rebound resilience and to increase the flight distance while securing the impact feeling.

In order to effectively exert the effect of adding the above-mentioned electron-withdrawing substituted diphenyl disulfide compound, it is necessary to add the compound to the base rubber in an amount of 0.05 part by mass or more, preferably 0.2 part by mass, based on 100 parts by mass of the base rubber. As described above, the amount is more preferably 0.5 part by mass or more, and the upper limit is 3 parts by mass or less, preferably 2 parts by mass or less, and more preferably 1 part by mass or less. When the amount is less than 0.05 parts by mass, the effect of increasing the repulsive force and the effect of improving the hit feeling are not effectively exhibited, and if the amount is too large, the compression becomes large and the hit feeling is improved.
This is because the resilience is slightly reduced.

The disulfide-containing rubber composition used in the present invention contains an inorganic metal salt in addition to the above compounds.
Examples of the inorganic metal salt include oxides, carbonates, sulfates and the like, and specifically, zinc oxide, barium sulfate, calcium carbonate and the like are preferably used. Among them, particularly preferred is zinc oxide, which also functions as a vulcanization aid in a vulcanization step described later. One kind of inorganic metal salt may be used alone, or two or more kinds may be used in combination. Zinc oxide generally belongs to a low-specific-gravity modifier, and may be used in combination with a metal such as tungsten, molybdenum, lead, nickel, or copper, or a high-specific-gravity filler such as an oxide, carbide, or nitride thereof. .

Since the inorganic metal salt is mainly blended as a component for adjusting the specific gravity of the golf ball obtained as the final product to the range of 1 to 1.5, its content depends on the kind of the material to be combined and the blending. Although it is appropriately selected depending on the ratio, particularly in the case of zinc oxide, it is desirable to positively mix it in the range of 3 to 30 parts by mass with respect to 100 parts by mass of the base rubber. Inorganic metal salt compounded as a specific gravity adjuster,
In particular, zinc oxide hardens the vulcanized rubber to increase the repulsion,
This is because it effectively works to increase the flight distance. But 30
If the amount is too large in excess of parts by mass, the amount of the α, β-unsaturated carboxylic acid metal salt must be reduced in order to secure an appropriate hardness, and the rebound as the core deteriorates, resulting in poor flight. This is because a tendency to adversely affect the distance occurs. On the other hand, if the amount is less than 3 parts by mass, the ratio of other inorganic metal salts used for adjusting the specific gravity is too high, and it is difficult to obtain the effect of zinc oxide blending. Therefore, from the viewpoint that the resilience can be increased without blending other inorganic metal salts for adjusting specific gravity, the blending amount of zinc oxide is 5 to 2
It is preferably 5 parts by mass, more preferably 10 to 25 parts by mass.

The disulfide-containing rubber composition contains, in addition to the above essential components, an antioxidant, a plasticizer, a dispersant, an ultraviolet absorber, a colorant, a peptizer, and the like, which are usually added to the core rubber composition. Can be appropriately compounded as needed.

The disulfide-containing rubber composition having the above composition is uniformly kneaded, and is heated and pressed in a mold and vulcanized. The vulcanization conditions are not particularly limited,
Usually 130-240 ° C, pressure 2.9-11.8MPa
For 15 to 60 minutes.

The entire core may be formed from the vulcanizate formed as described above, or in the case of a multilayer core, at least one layer is formed from the vulcanizate of the disulfide-containing rubber composition. I just need. When only a part of the multilayer core is formed of a vulcanizate of the disulfide-containing rubber composition,
Ratio of the volume V _S of the vulcanizates (V _S / V _C) is preferably 0.5 or more cores disulfides containing rubber composition in a total volume V _C, more preferably 0.60 or more, further 0.7 It is preferable that it is above. If the ratio is less than 0.5, the effect of the disulfide-containing composition cannot be sufficiently obtained. In the multilayer core, the core portion composed of a vulcanized product of a rubber composition other than the disulfide-containing rubber composition contains a disulfide compound other than the electron-withdrawing substituted diphenyl disulfide used in the present invention, such as diphenyl disulfide. It is preferable to comprise a vulcanizate of the rubber composition.

The ratio (V _S / V _B ) of the vulcanized product V _S of the disulfide-containing rubber composition to the ball volume V _B is preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0 or more. It is preferably at least 0.5, and the upper limit is preferably at most 0.95, more preferably at most 0.90, further preferably at most 0.85, particularly preferably at most 0.80. If it exceeds 0.95, the cover will be too thin,
This is because the durability of the cover cannot be ensured.

The outer diameter of the core is 32.8 to 40.8 m
m is preferable, and more preferably, 33.6 to 40.0 mm
It is about. If the outer diameter is too small, the excellent resilience performance based on the disulfide-containing rubber composition cannot be effectively utilized, and if the outer diameter is too large, the durability tends to deteriorate.

With respect to the core of the present invention, the compression indicated by the amount of compression deformation (mm) when a load of 1275 N is applied is 2.
It is preferably from 5 to 5.5 mm, more preferably from 2.8 to 4.5 mm, and still more preferably from 3.0 to 4.5.
mm. If it is less than 2.5 mm, the core becomes too hard, and the hit feeling of the obtained ball becomes poor,
If it exceeds 5.5 mm, the core becomes too soft, and the durability of the obtained golf ball decreases, the resilience deteriorates, and the flight distance decreases.

The solid golf ball of the present invention is obtained by covering a core having the above structure with a cover.

The cover may be made of a thermoplastic resin,
Preferably, an α-olefin and α, β- having 3 to 8 carbon atoms are used.
An ionomer resin in which a part of carboxyl groups in a copolymer with an unsaturated carboxylic acid is neutralized with a metal ion, or a mixture mainly composed of the ionomer resin; or a soft segment having a diene system such as polybutadiene and a hard segment having polyamide, A polymer composition mainly comprising a polyester or a thermoplastic elastomer which is a block copolymer to be a polyurethane, or a mixture thereof is used.

As the preferable α-olefin constituting the ionomer resin, ethylene and propylene are preferable, and as the α, β-unsaturated carboxylic acid, acrylic acid and methacrylic acid are preferable. Metal ions for neutralizing carboxyl groups include Na ion, K
Ions, alkali metal ions such as Li ions; divalent ions such as Zn ions, Ca ions, and Mg ions; trivalent ions such as Al ions; these can be used alone, or two or more kinds can be used in combination It is also possible. Among these metal ions, Na ions, Zn ions, and Mg ions are particularly preferable for enhancing the durability and repulsion performance of the cover.

When the cover material is a mixture of an ionomer and a thermoplastic elastomer, the content of the thermoplastic elastomer is preferably 60 parts by mass or less, more preferably 10 to 40 parts by mass, per 100 parts by mass of the polymer component. If the content of the thermoplastic elastomer is more than 60 parts by mass, the cover becomes too soft and the resilience is reduced, or the compatibility with the ionomer is reduced.

In the polymer composition for a cover, in addition to the above-mentioned polymer as a main component, a filler such as barium sulfate, a coloring agent such as titanium dioxide, a dispersant, an antioxidant, an ultraviolet absorber, An appropriate amount of a light stabilizer, a fluorescent agent, a fluorescent bleach or the like can be added.

The cover can be formed by a known method used for molding a cover of a solid golf ball. For example, a method in which a cover composition is formed in advance into a hemispherical shell half shell, the two are combined, a solid core is wrapped, and pressure molding is performed at about 130 to 170 ° C. for about 1 to 5 minutes. Examples include a method of injection molding the composition directly onto a solid core and molding the composition so as to enclose the core. A large number of depressions, usually called dimples, are formed on the surface during cover molding, and the product is made into a product by applying a paint finish, a marking stamp, or the like to enhance aesthetics and commercial value. The preferred thickness of the cover is 1.0-5.0 mm, more preferably 1.4-4.6.
mm. If the cover is too thin, the durability of the ball will be reduced, and if it is larger than 5.0 mm, the hit feeling will be poor.

The cover is not limited to a single layer, but may have a multilayer structure.

[0049]

EXAMPLES Next, examples of the present invention will be described. However, the present invention is not limited by the following examples, and the present invention can be practiced with appropriate modifications within a range that can conform to the spirit of the preceding and following examples. Of course, it is possible, and all of them are included in the technical scope of the present invention.

[Evaluation Method] First, the evaluation method used in the following examples will be described.

Based on the amount of deformation when a load of 98 N is applied to the compression core,
The amount of compressive deformation (mm) when the load was increased to 1275 N was measured. Generally, the smaller the deformation amount, the harder the ball.

Core Restitution Coefficient A metal cylinder of 198.4 g was caused to collide with the core at a speed of 40 m / sec, and the velocities of the cylinder and the ball before and after the collision were measured and calculated from the respective velocities and masses.

Hitting Feeling An actual hitting test was performed on the No. 1 wood club by 10 golfers.
"O": The impact is small and the impact is soft, "△": The impact is normal, "X": The impact is large and the impact is poor.
The ball with the highest score among the 0 players was determined to be the hitting feel of the ball.

Flying distance (m) A golf club W # 1 (head speed: 35 m / sec) was attached to a swing robot manufactured by True Temper.
The distance to the ball drop point when each golf ball was hit was measured.

[Manufacture of Golf Ball of Single Core Layer Type]
The core rubber compositions shown in Tables 2 and 3 were uniformly mixed,
A single-layer spherical core having a diameter of 38.2 mm was prepared by vulcanizing in a mold at 160 ° C. for 30 minutes. The coefficient of restitution and compression of the obtained core were measured. Next, the cover composition shown in Table 1 was injection-molded on each core, and the solid golf ball of Example No. 4 having an outer diameter of 42.8 mm was used. 1 to 11 and Comparative Example Solid Golf Ball Nos. 1 to 5 were produced. Here, in the golf ball of the present invention, bis (2-
Acetyl, 4-chlorophenyl) disulfide, bis (4-acetyl, 2-methylsulfinylphenyl) disulfide, bis (4-cyano, 2,6-diacetylphenyl) disulfide, bis (2,4,6-tri (methoxysulfonyl)) Phenyl) disulfide, bis (2,
Either (4,6-triformylphenyl) disulfide is incorporated in the core.

The hit feeling and the flight distance of each golf ball were measured. The results are shown in Table 2 (Example golf ball) and Table 3 (Comparative golf ball). Also,
Example No. Nos. 1 to 11 and Comparative Example Nos. FIG. 1 shows the relationship between the core compression of 1 to 5 and the coefficient of restitution. Figure 1
In the figure, “●” indicates an example, and “○” indicates a comparative example.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

In Table 1, as polybutadiene, JSR
BR-11 manufactured by KK was used. Himilan 170
6 is a zinc ion neutralized ethylene-methacrylic acid copolymer ionomer manufactured by Mitsui Dupont Polychemical Co., Ltd .; and Himilan 1707 is a zinc ion neutralized ethylene-methacrylic acid copolymer ionomer manufactured by Mitsui Dupont Polychemical Co., Ltd. .

Table 3 shows Comparative Example Nos. From the comparison of 1 to 3, it can be seen that the blending of an organic sulfur compound (diphenyl disulfide or pentachlorothiophenol) increases the flight distance. The flight distance was superior when using pentachlorothiophenol (No. 3) than when using diphenyl disulfide (No. 2). When using diphenyl disulfide,
The flight distance can be increased by increasing the amount of zinc acrylate, but the impact feeling is reduced (N
o. 4) When the amount of zinc acrylate was reduced to increase the amount of dicumyl peroxide, the flight distance could not be increased (No. 5).

On the other hand, Table 2 shows that the amount of zinc acrylate is 2
Example No. 8 in which the electron withdrawing substituted disulfide was blended in 8 parts by mass. Nos. 1, 6 to 11 are Comparative Example Nos. 2 (containing diphenyl disulfide) and Comparative Example No. It can be seen that the flight distance was longer than any of 3 (containing pentachlorothiophenol), and the hit feeling was excellent.

In the embodiment No. As can be seen from 1 to 5, by increasing the amount of zinc acrylate and decreasing the amount of dicumyl peroxide, compression (related to the hardness and softness of the core, and thus to the impact feeling) and the coefficient of restitution (to the flying distance) In addition, by adjusting the amount of zinc acrylate and dicumyl peroxide by blending an appropriate amount of electron-withdrawing disulfides, it is possible to adjust the amount of flight distance while securing the impact feeling. Increase can be achieved.

Therefore, as shown in FIG. 1, when the core compression is in the range of 2.5 to 5.5 mm, the golf ball of the present invention has a higher core restitution coefficient than a conventional ball having the same compression. That is, the golf ball of the present invention is more excellent in resilience when the hitting feeling is substantially the same.

[Manufacture of golf ball of two-layer core type]
The rubber composition for an inner layer core having the composition shown in Table 4 below was uniformly mixed and vulcanized in a mold at 160 ° C. for 25 minutes to produce an inner layer core having a diameter of 32.4 mm. On the other hand, two half-vulcanized half shells forming the outer layer core were formed by vulcanizing the rubber composition for the outer layer core at 160 ° C. for 2 minutes using a core mold. The two-layer core (diameter 38.2 m) is formed by vulcanizing the inner layer core at 160 ° C. for 25 minutes while being covered with the half shell.
m).

The coefficient of restitution and compression of the obtained core were measured. Next, a cover composition having the composition shown in Table 1 was injection-molded on each of the cores.
An 8-mm core two-layer solid golf ball was produced.

With respect to the manufactured golf balls, the flight distance and the hit feeling were measured based on the above evaluation methods. Table 4 shows the results.

[0068]

[Table 4]

From Table 4, it can be seen that the core volume fraction (V _S / V _C ) of the two-core type golf ball, that is, the vulcanized product of the rubber composition having the electron-withdrawing substituted disulfide, is 0.610.
Is inferior to the case where the core volume fraction is 1 (Example No. 1), but similar to the case where another type of electron-withdrawing substituted disulfide is used (Example No. 8). , Showed compression. That is, it is possible to show the same hit feeling and flight distance.

[0070]

The electron-withdrawing substituted disulfide used in the core of the solid golf ball of the present invention has an effect of increasing the coefficient of restitution without suppressing the increase in hardness and reducing the hitting feel, as compared with conventional organic sulfur compounds. high. Therefore, the golf ball of the present invention has an excellent balance between the hit feeling and the flight distance, and is more excellent in the hit feeling and the flight distance than before.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the core compression and the coefficient of restitution of golf balls of Examples and Comparative Examples.

Claims (5)

[Claims] 1. A rubber composition comprising a base rubber, an α, β-unsaturated carboxylic acid and / or a metal salt thereof, an organic peroxide, an inorganic metal salt, and a disulfide represented by the following formula (1): A solid golf ball comprising: a core formed of a vulcanized product; or a multilayer core including at least one layer formed of the vulcanized product; and a single-layer or multi-layer cover formed on the core. Embedded image (In the formula, at least one of X ^{1 to} X ⁵ and X ^{1 ′ to} X ^{5 ′} is at least one selected from the group consisting of the following formulas (2), (3) and (4)). Formula 2 (Where A is a hydrogen atom, a hydroxy group, an alkoxy group,
At least one selected from the group consisting of an alkyl group and a halogen) 2. The solid golf ball according to claim 1, wherein the inorganic metal salt contains zinc oxide. 3. Base rubber 100 parts by mass; metal salt of α, β-unsaturated carboxylic acid 15 to 45 parts by mass; organic peroxide 0.2 to 5 parts by mass; zinc oxide 3 to 30 parts by mass; Electron-withdrawing substituted disulfides represented by the following formula (1):
A core comprising a vulcanizate of a rubber composition containing from 0.05 to 3.0 parts by mass, or a multilayer core comprising at least one layer comprising the vulcanizate; a single layer or a multilayer formed on the core; A solid golf ball including a cover. Embedded image (In the formula, at least one of X ^{1 to} X ⁵ and X ^{1 ′ to} X ^{5 ′} is at least one selected from the group consisting of the following formulas (2), (3) and (4)). Formula 4 (Where A is a hydrogen atom, a hydroxy group, an alkoxy group,
At least one selected from the group consisting of an alkyl group and a halogen) 4. The method according to claim 1, wherein the core has an initial load of 98N.
The amount of deformation of the core when increased to 1275N is 2.5
The solid golf ball according to any one of claims 1 to 3, which has a diameter of from 5.5 mm. 5. The core is a multilayer, and a ratio (V _S / V _C ) of a volume V _S of a vulcanized product of the rubber composition to a volume V _C of the whole core is 0.5 or more, and the solid golf ball according to any one of claims 1 to 4 ratio of the volume V _S of the vulcanizates of the rubber composition of the whole ball to volume _{V B (V S / V B} ) is 0.3 or more.