JP4977272B2 - Solid golf balls - Google Patents

Description

The present invention relates to a solid golf ball.

As a golf ball, a solid golf ball excellent in durability and flight distance is known, and a two-piece golf ball having a core covered with a cover, a golf having a multilayer structure in which one or more intermediate layers are interposed between the core and the cover. A ball is used. As a rubber material used for the core of a solid golf ball, emphasizing the resilience characteristics, high base polybutadiene (BR) as a base rubber and metal salt of α, β-unsaturated carboxylic acid such as zinc acrylate (co-crosslinking) Agents), vulcanized moldings of rubber compositions containing organic peroxides and the like are widely used.

It is known that the rebound performance is improved by adding a very small amount of organic sulfur compound (disulfide type (SS), thiol type (SH)) to this compounding system, and golf having a core to which an organic sulfur compound is added Some balls are also in practical use. However, details of the mechanism of the performance improvement have not yet been clarified.

Patent Document 1 discloses a compound in which a substituent of a benzene ring is identified as a thiol-type or sulfide-type organic sulfur compound using a numerical value called a substituent constant indicating electronegativity, and the substituent constant is generally large. There is a tendency for the rebound to increase as the object increases. However, here, as the sulfide-type sulfur compound, a symmetric compound such as bis (2,3,5,6-tetraacetylphenyl) disulfide or bis (pentabromophenyl) disulfide (bonded to the S atom of the sulfide). A compound in which two aromatic hydrocarbon groups are identical is only substantially shown. There is also a demand for further improvement in resilience performance.

In addition, the rebound performance is enhanced by increasing the amount of sulfur compound added within a certain range, but if the amount exceeds a certain amount, the resilience performance tends to deteriorate and the hardness tends to decrease. It becomes difficult to adjust the hardness which affects the performance of the resin. Generally, it is possible to adjust the hardness (increase the hardness) by increasing the amount of initiator or the amount of co-crosslinking agent, but there is a limit to adjusting the hardness with the initiator. It tends to be lower and has its limits as well.

Furthermore, although improvement of the resilience performance by mixing a plurality of sulfur compounds has been tried conventionally, the physical properties of a compound with inferior performance are often manifested. For example, chlorobenzenethiol having 1 substituent and 5 substituents When pentachlorobenzenethiol is mixed, it becomes slightly smaller than the average of the resilience performance of both compounds, and the effect of mixing cannot be expressed.

As described above, even if a conventionally known organic sulfur compound is used for the core, it is difficult to further improve the resilience performance (flight performance) while having the hardness required for a golf ball. It has been desired to provide a solid golf ball having a good feel at impact.

Japanese Patent No. 3554526

An object of the present invention is to solve the above-mentioned problems and to provide a solid golf ball having high resilience performance and flight performance and having a good shot feeling.

The present invention is a solid golf ball comprising one or more cores and one or more cover layers formed on the core, wherein at least one layer of the core comprises (a) a base rubber, (b ) Co-crosslinking agent, (c) organic peroxide, (d) filler, and (e) the following formula (I);
R ¹ —S—S—R ² (I)
(In Formula (I), R ¹ and R ² are an aromatic hydrocarbon group, an aliphatic hydrocarbon group having 2 or more carbon atoms, a heterocyclic hydrocarbon group or an alicyclic hydrocarbon which may have a substituent. Represents a group, and R ¹ and R ² are different groups.)
The present invention relates to a solid golf ball obtained by vulcanization molding of a rubber composition containing a disulfide-type sulfur compound represented by the formula:

In the disulfide-type sulfur compound, R ¹ is an aromatic hydrocarbon group which may have a substituent, R ² is an aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent, and The R ¹ and R ² are preferably different groups. Further, R ¹ is an aromatic hydrocarbon group having a substituent, R ² is an aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent, and R ¹ and R ² are different groups. It is more preferable that

In the disulfide-type sulfur compound, R ¹ and R ² are preferably aromatic hydrocarbon groups which may have a substituent, and R ¹ and R ² are preferably different groups. More preferably, R ¹ and R ² are aromatic hydrocarbon groups having a substituent, and R ¹ and R ² are different groups.

Furthermore, in the disulfide-type sulfur compound, the substituent is preferably a group containing a halogen atom.

In the solid golf ball of the present invention, since a specific asymmetric disulfide type sulfur compound is used as an additive for the core material, the resilience performance can be further enhanced while having a desired hardness. Therefore, it is possible to provide a solid golf ball having high resilience performance and flight performance and having a good shot feeling.

It is a graph showing the relationship between the amount of compressive deformation (X axis) and the coefficient of restitution (Y axis) of the solid golf ball core listed in Tables 2-3. 6 is a graph showing the relationship between the amount of compressive deformation (X axis) and the coefficient of restitution (Y axis) of a solid golf ball core listed in Tables 4 to 5. FIG.

The solid golf ball of the present invention comprises one or more cores and one or more cover layers formed on the core, and at least one layer of the core comprises (a) a base rubber and (b) A rubber composition containing a crosslinking agent, (c) an organic peroxide, (d) a filler, and (e) a disulfide-type sulfur compound represented by the above formula (I) is vulcanized and molded.

In the solid golf ball of the present invention, one or more layers of a cover are formed on one or more layers of a core. The core basically uses a rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, a filler, a disulfide-type sulfur compound represented by the above formula (I), etc. for a normal solid core. It is obtained by heat compression vulcanization using the method and conditions obtained.

As the base rubber used in the present invention, natural rubber and / or synthetic rubber conventionally used for solid golf balls can be used. Particularly, cis-1,4-bond is at least 40% or more, preferably 80%. So-called high-cis polybutadiene rubber having the above is preferable, and natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) or the like may be blended with the polybutadiene rubber as desired.

Examples of the co-crosslinking agent include C3-C8 α, β-unsaturated carboxylic acids such as acrylic acid and methacrylic acid, or monovalent or divalent metal salts such as zinc and magnesium salts thereof. Among these, zinc acrylate that imparts high resilience is preferable. The compounding amount of the co-crosslinking agent is preferably 15 to 45 parts by mass, more preferably 20 to 35 parts by mass with respect to 100 parts by mass of the base rubber. If it is less than 15 parts by mass, it is necessary to increase the blending amount of the organic peroxide in order to obtain an appropriate hardness, and high resilience cannot be obtained. If it exceeds 45 parts by mass, it becomes too hard and the ball is hit. There is a risk of feeling bad.

The organic peroxide acts as a crosslinking agent or a curing agent, for example, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl- 2,5-di (t-butylperoxy) hexane and di-t-butyl peroxide are mentioned, and dicumyl peroxide is preferable. The compounding amount of the organic peroxide is preferably 0.2 to 5.0 parts by mass, more preferably 1.0 to 2.5 parts by mass with respect to 100 parts by mass of the base rubber. If it is less than 0.2 parts by mass, it becomes too soft and high resilience cannot be obtained, and if it exceeds 5.0 parts by mass, it is necessary to reduce the blending amount of the co-crosslinking agent in order to obtain appropriate hardness. There is a possibility that high resilience cannot be obtained. The organic peroxide is decomposed by heat to generate radicals, and increases the degree of crosslinking between the co-crosslinking agent and the base rubber to improve resilience.

The filler is mainly blended as a specific gravity adjusting agent for adjusting the specific gravity of the golf ball obtained as a final product to a range of 1.0 to 1.5, but is usually blended in the core of the golf ball. For example, inorganic fillers (specifically, zinc oxide, barium sulfate, calcium carbonate, etc.), high specific gravity metal powders (eg, tungsten powder, molybdenum powder, etc.) and mixtures thereof can be mentioned. Particularly preferred is zinc oxide that also functions as a vulcanization aid. When using zinc oxide, the compounding amount is preferably 3 to 30 parts by mass, more preferably 10 to 25 parts by mass with respect to 100 parts by mass of the base rubber. If it is less than 3 parts by mass, it is difficult to adjust the specific gravity as described above, and the ball weight may be too small. When it exceeds 30 parts by mass, it is necessary to reduce the blending amount of the co-crosslinking agent such as zinc polyacrylate in order to obtain an appropriate hardness, and high resilience may not be obtained.

In the present invention, a disulfide-type sulfur compound represented by the following formula (I) is blended as the organic sulfur compound.
R ¹ —S—S—R ² (I)
(In Formula (I), R ¹ and R ² are an aromatic hydrocarbon group, an aliphatic hydrocarbon group having 2 or more carbon atoms, a heterocyclic hydrocarbon group or an alicyclic hydrocarbon which may have a substituent. Represents a group, and R ¹ and R ² are different groups.)

In the present invention, a disulfide-type sulfur compound in which R ¹ and R ² are different hydrocarbon groups, that is, an asymmetric disulfide-type sulfur compound in which two hydrocarbon groups bonded to sulfide are different is blended. For this reason, excellent repulsion compared with symmetrical organic sulfur compounds (disulfide-type sulfur compounds (for example, bis (pentabromophenyl) disulfide) in which R ¹ and R ^{2 in} formula (I) are the same hydrocarbon group). Performance (at least equal or better) can be obtained. At the same time, appropriate hardness as a golf ball can be obtained. Therefore, it is possible to obtain excellent flight performance and feel at impact in the obtained solid golf ball.

A disulfide-type sulfur compound having high left-right symmetry has high crystallinity and low solubility. However, in the present invention, reversing performance can be improved because the crystallinity is lowered and the solubility is increased by making the left-right asymmetry. It is guessed.

Examples of the aromatic hydrocarbon group for R ¹ and R ² include groups having 6 to 18 carbon atoms, which may have a substituent. Specifically, aryl groups such as phenyl group, tolyl group, xylyl group, biphenyl group, o-terphenyl group, naphthyl group, anthryl group, phenanthryl group; aralkyl groups such as benzyl group, phenethyl group, etc. You may have a substituent on an aromatic ring. In addition, examples of the aliphatic hydrocarbon group having 2 or more carbon atoms include groups having 2 to 20 carbon atoms, which may have a substituent, and may be linear or branched. Specifically, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group Alkyl groups having 2 to 20 carbon atoms such as decyl group, undecyl group and dodecyl group; alkenyl groups having 2 to 20 carbon atoms such as vinyl group, propenyl group, allyl group, hexenyl group and octenyl group. , May have a substituent. Moreover, as a heterocyclic hydrocarbon group, C3-C18 group is mentioned, You may have a substituent. Specific examples include a furyl group, a thienyl group, a thiazolyl group, a benzofuryl group, a benzothiophenyl group, a benzothiazolyl group, a benzoxazolyl group, a pyridyl group, and a quinolyl group, which may have a substituent. Furthermore, examples of the alicyclic hydrocarbon group include groups having 3 to 14 carbon atoms and may have a substituent. Specific examples include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclopentenyl group, and a cyclohexenyl group. Of these, an aromatic hydrocarbon group which may have a substituent and an aliphatic hydrocarbon group having 2 or more carbon atoms are preferred from the viewpoint of resilience performance.

Among the disulfide-type sulfur compounds, R ¹ is an aromatic hydrocarbon group that may have a substituent, R ² is an aliphatic hydrocarbon group having 2 or more carbon atoms that may have a substituent, and An asymmetric compound in which R ¹ and R ² are different groups is preferable, R ¹ is an aromatic hydrocarbon group having a substituent, and R ² is an aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent. And an asymmetric compound in which R ¹ and R ² are different groups is more preferable. In this case, resilience performance can be enhanced while obtaining a desired hardness.

As such an asymmetric disulfide type sulfur compound, for example, a compound represented by the following formula (II) is preferably used.

（式（ＩＩ）中、Ｒ^１−ｉ〜Ｒ^１−ｖは、同一若しくは異なって、Ｈ又は置換基を表し、該Ｒ^１−ｉ〜Ｒ^１−ｖの少なくとも１つは置換基である。Ｒ^２−ｉは、置換基を有してもよい炭素数２以上の脂肪族炭化水素基を表す。）

(In formula (II), R ^{1-i to} R ^1-v are the same or different and represent H or a substituent, and at least one of the R ^{1-i to} R ^1-v is a substituent. R ^2-i represents an aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent.

Examples of the substituents R ^{1-i to} R ^{1-v in the} above formula (II) include electron-withdrawing substituents. The electron withdrawing substituent is a substituent having a Hammett's rule substituent constant σ value exceeding 0, such as a halogen group (chloro group, bromo group, iodo group, fluoro group, etc.) and trihalo. Groups containing halogen atoms such as methyl groups (trifluoromethyl group, tribromomethyl group, trichloromethyl group, etc.), carboxylic acid groups, carboxylic acid ester groups, cyano groups, amide groups, nitro groups, acetyl groups, formyl groups, etc. Can be mentioned. These substituents may be introduced alone or in combination of two or more. From the viewpoint of resilience performance, a halogen group, a trihalomethyl group, a carboxylate group, a cyano group, an acetyl group, and more preferably a halogen group and a trihalomethyl group are preferred. Moreover, the organic sulfur compound substituted with a halogen group or a trihalomethyl group and having a large number of substituents can effectively improve the resilience performance.
In addition, as the aliphatic hydrocarbon group having 2 or more carbon atoms which may have a substituent represented by R ^2-i in the above formula (II), the above-mentioned aliphatic hydrocarbon group of R ¹ and R ² and The same thing is mentioned.

Specific examples of the disulfide-type sulfur compound represented by the above formula (II) include 2-chlorophenyl-ethyl-disulfide, 3-chlorophenyl-ethyl-disulfide, 4-chlorophenyl-ethyl-disulfide, 2-bromophenyl-ethyl- Monohalophenyl-ethyl-disulfides such as disulfide, 3-bromophenyl-ethyl-disulfide, 4-bromophenyl-ethyl-disulfide; 2,4-dichlorophenyl-ethyl-disulfide, 3,5-dichlorophenyl-ethyl-disulfide, 2 , 4-dibromophenyl-ethyl-disulfide, 3,5-dibromophenyl-ethyl-disulfide, (2-chloro-4-bromophenyl) -ethyl-disulfide, (3-chloro-5-bromophenyl) -ethyl-disulfide Dihalophenyl-ethyl-disulfide; 2,4,6-trichlorophenyl-ethyl-disulfide, 2,4,6-tribromophenyl-ethyl-disulfide, (2,6-dichloro-4-bromophenyl) -ethyl-disulfide Trihalophenyl-ethyl-disulfide such as 2,3,5,6-tetrachlorophenyl-ethyl-disulfide, 2,3,5,6-tetrabromophenyl-ethyl-disulfide, (2,6-dichloro-3,5 Tetrahalophenyl-ethyl-disulfides such as -dibromophenyl) -ethyl-disulfide; 2,3,4,5,6-pentachlorophenyl-ethyl-disulfide, 2,3,4,5,6-pentabromophenyl-ethyl Disulfide, (2,4,6-trichloro-3,5-dibromopheny ) - ethyl - ethyl - - penta-halophenyl, such as disulfide disulfide and the like. Also included are halophenyl-alkyl-disulfides such as halophenyl-propyl-disulfide, halophenyl-butyl-disulfide, halophenyl-pentyl-disulfide, halophenyl-hexyl-disulfide, halophenyl-heptyl-disulfide, and the like corresponding to the compounds mentioned here. It is done.

Examples of the compound represented by the above formula (I), R ¹ and R ² represents an aromatic hydrocarbon group which may have a substituent group, and the asymmetric compound wherein R ¹ and R ² are different groups may An asymmetric compound which is preferably used and R ¹ and R ² are aromatic hydrocarbon groups having a substituent and R ¹ and R ² are different groups is more preferable. In this case, resilience performance can be enhanced while obtaining a desired hardness.

As such an asymmetric disulfide type sulfur compound, for example, a compound represented by the following formula (III) is preferably used.

（式（ＩＩＩ）中、Ｒ^１−ｖｉ〜Ｒ^１−ｘは、同一若しくは異なって、Ｈ又は置換基を表し、該Ｒ^１−ｖｉ〜Ｒ^１−ｘの少なくとも１つは置換基である。Ｒ^２−ｖｉ〜Ｒ^２−ｘは、同一若しくは異なって、Ｈ又は置換基を表し、該Ｒ^２−ｖｉ〜Ｒ^２−ｘの少なくとも１つは置換基である。置換基Ｒ^１−ｖｉ〜Ｒ^１−ｘを持つフェニル基及び置換基Ｒ^２−ｖｉ〜Ｒ^２−ｘを持つフェニル基は異なる基である。）

(In formula (III), R ^{1 -vi to} R ^{1 -x} are the same or different and represent H or a substituent, and at least one of the R ^{1 -vi to} R ^{1 -x} is a substituent. ^{R 2-vi} ~R ^2-x are the same or different, represent H or a substituent, at least one of the ^{R 2-vi ~R 2-x} is a substituent. substituents ^{R 1-vi} ~ The phenyl group having R ^1-x and the phenyl group having substituents R ^{2-vi to} R ^2-x are different groups.)

Examples of the substituents R ^{1 -vi to} R ^{1 -x} and R ^{2 -vi to} R ^{2 -x in the} above formula (III) include the same as the substituents R ^{1 -i to} R ^{1 -v} .

Specific examples of the disulfide-type sulfur compound represented by the above formula (III) include 2-chlorophenyl-pentachlorophenyl-disulfide, 3-chlorophenyl-pentachlorophenyl-disulfide, 4-chlorophenyl-pentachlorophenyl-disulfide, and 2-bromophenyl. Monohalophenyl-2,3,4,5,6-pentachlorophenyl-disulfide such as pentachlorophenyl-disulfide, 3-bromophenyl-pentachlorophenyl-disulfide, 4-bromophenyl-pentachlorophenyl-disulfide; Dichlorophenyl-pentachlorophenyl-disulfide, 3,5-dichlorophenyl-pentachlorophenyl-disulfide, 2,4-dibromophenyl-pentachlorophenyl-disulfide, , 5-dibromophenyl-pentachlorophenyl-disulfide, (2-chloro-4-bromophenyl) -pentachlorophenyl-disulfide, (3-chloro-5-bromophenyl) -pentachlorophenyl-disulfide and the like dihalophenyl-2,3, 4,5,6-pentachlorophenyl-disulfide; 2,4,6-trichlorophenyl-pentachlorophenyl-disulfide, 2,4,6-tribromophenyl-pentachlorophenyl-disulfide, (2,6-dichloro-4-bromo Phenyl) -pentachlorophenyl-disulfide and the like trihalophenyl-2,3,4,5,6-pentachlorophenyl-disulfide; 2,3,5,6-tetrachlorophenyl-pentachlorophenyl-disulfide, 2,3,5,6 -Tetra Tetrahalophenyl-2,3,4,5,6-pentachlorophenyl-disulfide such as lomophenyl-pentachlorophenyl-disulfide, (2,6-dichloro-3,5-dibromophenyl) -pentachlorophenyl-disulfide; Pentahalophenyl-2,3,4,5,6-pentachlorophenyl-disulfide (asymmetric) such as pentachlorophenyl-disulfide, (2,4,6-trichloro-3,5-dibromophenyl) -pentachlorophenyl-disulfide And so on. Also included are halophenyl-2,3,4,5,6-pentabromophenyl-disulfide and the like corresponding to the compounds mentioned here. Furthermore, 2-chlorophenyl- (2,4,6-trichloro-3,5-dibromophenyl) -disulfide, 2,4-dichlorophenyl- (2,4,6-trichloro-3,5-dibromophenyl) -disulfide, And other asymmetric compounds. The said disulfide type | mold sulfur compound may be used independently and may use 2 or more types together.

Conventionally, when synthesizing a new SS-type compound, a method of modifying a substituent using a compound having an SS-type skeleton (for example, diphenyl disulfide) as a raw material in advance has been used. There is a limit to the new synthesis of SS bodies having groups and structures. The asymmetric disulfide-type sulfur compound in the present invention can be synthesized using a method in which the sulfur compound represented by the above formula (I) is changed to the SS type by oxidizing the SH-type sulfur compound in the presence of iodine, and the like. Various combinations of SS-type sulfur compounds can be prepared.

Specifically, for example, it can be synthesized and separated by the following production method.
Two different thiol-type compounds are dissolved in a methanol solution and stirred thoroughly. A 20% by mass KI / I ₂ aqueous solution prepared separately is added dropwise thereto while stirring, and the addition is continued until the brown color of iodine is not visible. After completion of the reaction, it is separated by filtration. The separated solid sample (SS body) is applied to a column, re-separated, only the target substance is taken out, and a predetermined amount is blended with the rubber composition.

The blending amount of the disulfide type sulfur compound represented by the above formula (I) is preferably 0.05 to 3.0 parts by mass, more preferably 0.1 to 2.0 parts per 100 parts by mass of the base rubber. Part by mass. There exists a possibility that the effect which improves resilience cannot fully be exhibited as it is less than 0.05 mass part. If it exceeds 3.0 parts by mass, the amount of compressive deformation becomes large and the resilience may be lowered.

Furthermore, the golf ball core of the present invention may be appropriately blended with an anti-aging agent, a peptizer, and other components that can be normally used in the production of a solid golf ball core. The anti-aging agent is preferably 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the base rubber.

The core can be obtained by uniformly kneading the above rubber composition using an appropriate kneader such as a kneading roll and vulcanizing and molding in a mold. Although the conditions in this case are not particularly limited, it is usually performed at 130 to 240 ° C., pressure 2.9 to 11.8 MPa, and 15 to 60 minutes.

The core of the golf ball of the present invention preferably has a deformation amount of 2.0 to 6.0 mm, more preferably 2.8 to 4.5 mm, from a state where an initial load of 98 N is applied to a case where a final load of 1275 N is applied. It is desirable to have. If it is smaller than 2.0 mm, the core becomes too hard and the shot feeling of the obtained golf ball is deteriorated. If it is larger than 6.0 mm, the core becomes too soft and the durability of the obtained golf ball is lowered. In addition, the repulsion may be worsened and the flight distance may be reduced.

In the present invention, the diameter of the core is preferably 32.8 to 40.8 mm, more preferably 33.6 to 40.0 mm. If it is smaller than 32.8 mm, the resilience is lowered and the flight distance is lowered, and if it is larger than 40.8 mm, the cover becomes too thin and the durability may be lowered.

The core used in the golf ball of the present invention may have a single layer structure or a multilayer structure of two or more layers, but the volume of the core part having the above composition is 30% or more of the entire core, It is preferably set to be 50% or more, more preferably 70% or more, and still more preferably 100%. A cover is then coated on the core obtained as described above.

The cover used for the golf ball of the present invention may have a single layer structure or a multilayer structure of two or more layers. The cover preferably contains a thermoplastic resin, particularly an ionomer resin usually used for a golf ball cover, as a base resin. Examples of the ionomer resin include those obtained by neutralizing at least a part of carboxyl groups in a copolymer of ethylene and α, β-unsaturated carboxylic acid with metal ions, or ethylene and α, β-unsaturated carboxylic acid. Examples include those 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, and crotonic acid. Acrylic acid and methacrylic acid are particularly preferable. As the α, β-unsaturated carboxylic acid ester metal salt, for example, methyl, ethyl, propyl, n-butyl, isobutyl ester, etc. such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc. are used. Acid esters and methacrylic acid esters are preferred. Carboxyl group in the copolymer of ethylene and α, β-unsaturated carboxylic acid or in the terpolymer 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 these include sodium, potassium, lithium, magnesium, calcium, zinc, barium, aluminum, tin, zirconium, and cadmium ions. It is often used because of its properties and durability.

Furthermore, as an example of a preferable material for the cover, only the ionomer resin as described above may be used, but the ionomer resin may be used in combination with one or more of a thermoplastic elastomer, a diene block copolymer and the like. Good. Examples of the thermoplastic elastomer include polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and the like. The diene block copolymer has a double bond derived from a conjugated diene compound of a block copolymer or a partially hydrogenated block copolymer.

For the cover used in the present invention, in addition to the above resin, if necessary, the same filler as used for the core, various additives, for example, pigments such as titanium dioxide, dispersants, anti-aging agents, An ultraviolet absorber, a light stabilizer, etc. may be added.

The method for covering the cover is not particularly limited, and can be performed by a method for covering a normal cover. The cover composition is pre-molded into a hemispherical half-shell, and the two cores are used to wrap the core and pressure-molded at 130-170 ° C. for 1-5 minutes, or the cover composition is directly cored A method of wrapping the core by injection molding is used.

The thickness of the cover is preferably 1.0 to 5.0 mm, more preferably 1.4 to 4.6 mm, and still more preferably 1.4 to 2.5 mm. If it is smaller than 1.0 mm, it becomes too thin and the durability is lowered, and the resilience performance is also lowered. If it is larger than 5.0 mm, the shot feeling may be deteriorated.

When forming the cover, dimples may be formed on the ball surface as necessary, and after the cover is formed, paint finishing, stamping, and the like may be applied as necessary.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[Test method]
(1) Core compression deformation (mm)
The amount of deformation in the compression direction (the amount of contraction in the compression direction) from when the initial load 98N was applied to the core to when the final load 1275N was applied was measured. In addition, an indexized value is also shown with the amount of deformation of the blend A-1 of the comparative example as 100.

(2) Core restitution coefficient 198.4 g of a metal cylinder collided with each core at a speed of 40 m / sec, and the speed of the cylinder and core before and after the collision were measured. The coefficient of restitution was calculated. The measurement was performed 12 pieces for each core, and the average value was used as the restitution coefficient of each core. In addition, an indexed value was also shown with the coefficient of restitution of Formulation A-1 of Comparative Example as 100.

(3) 10 hitting golf players conduct a hit test using Wood No. 1 club (driver, W # 1, New Breed Tour Forged, Sumitomo Rubber Industries, Ltd., loft angle 8.5 °). The golf ball was evaluated by the magnitude of impact at the time of hitting, and the most evaluated value was the shot feeling of each golf ball. The judgment criteria were as follows.
Judgment criteria ◎… Impact at impact is very small and feels very soft and good ○… Impact at impact is small and feel is soft and good △… Impact at impact is normal ×… The impact at the time of hitting is large and the shot feeling is bad

(Preparation 1 of asymmetric disulfide-type sulfur compound (formula (II)))
2,3,4,5,6-pentachlorobenzenethiol and 1-hexylthiol were dissolved in a methanol solution and sufficiently stirred. A 20% by mass KI / I ₂ aqueous solution prepared separately was added dropwise thereto while stirring, and the addition was continued until the brown color of iodine was not visible. After completion of the reaction, the product was separated by filtration. The separated solid sample (SS form) was applied to a column and re-separated to obtain 2,3,4,5,6-pentachlorophenyl-hexyl-disulfide.

(Preparation 2 of asymmetric disulfide-type sulfur compound (formula (III)))
4-Chlorobenzenethiol and 2,3,4,5,6-pentachlorobenzenethiol were dissolved in a methanol solution and sufficiently stirred. A 20% by mass KI / I ₂ aqueous solution prepared separately was added dropwise thereto while stirring, and the addition was continued until the brown color of iodine was not visible. After completion of the reaction, the product was separated by filtration. The separated solid sample (SS form) was applied to a column and re-separated to obtain 4-chlorophenyl-2,3,4,5,6-pentachlorophenyl-disulfide.

(Examples and Comparative Examples)
(1) Preparation of cover composition Next, a cover material having the composition shown in Table 1 below was 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 speed of 200 rpm, and a screw L / D = 35, and the blend was heated to 150-230 ° C. at the die position of the extruder.

The resin materials used for the cover are as follows.
High Milan 1706: Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. High Milan 1707: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. High Milan 1605: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd.

(2) Preparation of core Rubber composition for core by kneading the compounding ingredients shown in Table 2 (Example) and Table 3 (Comparative Example) below, and Table 4 (Example) and Table 5 (Comparative Example) below Was then placed in a mold and press molded at 170 ° C. within 200 minutes to obtain a core having a diameter of 40.4 mm.
The amount of compression deformation and the coefficient of restitution of the obtained core were measured, and the results are shown in Tables 2-3 and Tables 4-5.

The butadiene rubber used in the core rubber composition is a high cis polybutadiene rubber (BR730, cis content of 96% or more) manufactured by JSR, and the zinc acrylate is Suncellor SR (Zinc acrylate manufactured by Sanshin Chemical Co., Ltd.). , 90% product), DCP is dicumyl peroxide manufactured by NOF Corporation.

(3) Production of Golf Ball Main Body Next, the cover composition is injection molded on the core obtained above to form a cover layer, and a paint is applied to the surface to have an outer diameter of 42.7 mm. A two-piece solid golf ball was obtained.
The hit feeling of the obtained golf ball was evaluated, and the results are shown in Table 2 (Example) and Table 3 (Comparative Example), and Table 4 (Example) and Table 5 (Comparative Example).

The relationship between the amount of compression deformation (index) and the resilience characteristics (index) of the cores shown in Tables 2 and 3 is shown in a graph in FIG. 1. Indicates that the golf ball is excellent. The rebound characteristics of golf balls can be generally compared by the coefficient of restitution at the same amount of compressive deformation. Examples 1-1 to 1- 1 using pentachlorophenyl-hexyl-disulfide which is an asymmetric disulfide-type sulfur compound In the compounding system of 3, the resilience performance is higher than the blends B-1 to B-3 and C-1 to C-3 of Comparative Examples using dihexyl disulfide or bis (pentachlorophenyl) disulfide which are symmetrical compounds. found. Moreover, the mixing effect was not seen also by the mixing | blending D-1 to D-3 of the comparative example which mixed 2 types of symmetrical compounds.

In addition, the feel at impact of the golf balls of the examples was good. Furthermore, since the resilience performance is high, an excellent flight distance can be expected.

FIG. 2 is a graph showing the relationship between the amount of compression deformation (index) and the rebound characteristics (index) of the cores in Tables 4 to 5.
When 4-chlorophenyl-pentachlorophenyl-disulfide was used as the asymmetric disulfide-type sulfur compound, high resilience performance was exhibited as in FIG. In addition, the feel at impact was also good, and an excellent flight distance could be expected.

Claims (1)

A solid golf ball comprising one or more cores and one or more cover layers formed on the cores,
At least one layer of the core comprises (a) a base rubber, (b) a co-crosslinking agent, (c) an organic peroxide, (d) a filler, and (e) the following formula (III):

(In formula (III), R ^{1 -vi to} R ^{1 -x} are the same or different and each represents H or a substituent, and at least one of the R ^{1 -vi to} R ^{1 -x} is a substituent, At least one of the substituents is a halogen group or a trihalomethyl group, R ^{2-vi to} R ^2-x are the same or different and each represents H or a substituent, and each of R ^{2-vi to} R ^2-x At least one is a substituent, and at least one of the substituents is a halogen group or a trihalomethyl group, a phenyl group having substituents R ^{1 -vi to} R ^{1 -x} and a substituent R ^{2 -vi to} R ^{2. (The} phenyl group having ^-x is a different group.)
A solid golf ball obtained by vulcanizing and molding a rubber composition containing a disulfide-type sulfur compound represented by the formula:

Images