JP4676889B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly to an improvement of a urethane cover using thermoplastic polyurethane as a base resin.

As the base resin constituting the cover of the golf ball, ionomer resin or polyurethane is used. Covers made of ionomer resin are widely used because of their excellent resilience, durability, and workability. However, they have high rigidity and hardness, so that the shot feel is poor and the spin performance is sufficient. Has been pointed out, such as poor controllability. On the other hand, polyurethane is used as the base resin constituting the cover because the shot feeling and spin characteristics are improved as compared with the ionomer resin. For example, Patent Documents 1 to 3 disclose that a thermosetting polyurethane is used for the cover, and Patent Documents 4 and 5 disclose that a thermoplastic polyurethane is used for the cover. However, when thermosetting polyurethane is used for the cover, a golf ball having excellent scratch resistance can be obtained, but the manufacturing process of the golf ball is complicated. Further, golf balls using thermoplastic polyurethane as a cover are not sufficient in scuff resistance, feel at impact and resilience compared to the case where thermosetting polyurethane is used.
Japanese Patent Laid-Open No. 51-74726 Japanese Patent No. 2,662,909 U.S. Pat. No. 4,123,061 U.S. Pat. No. 3,395,109 U.S. Pat. No. 4,248,432

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball having a novel urethane cover excellent in resilience and scratch resistance.

  The golf ball of the present invention that has solved the above problems is a golf ball having a cover, wherein the resin component constituting the cover contains polyurethane having an imide bond. By using a polyurethane having an imide bond introduced into the main chain, the resilience and scratch resistance of the resulting cover are improved. The polyurethane having an imide bond includes, for example, an acid anhydride as a constituent component, and the imide bond is formed by a reaction between an acid anhydride and an isocyanate group or an amino group when the polyurethane is synthesized. It is desirable. The polyurethane having an imide bond is preferably one obtained by reacting an isocyanate group-terminated urethane prepolymer with a chain extender containing tetracarboxylic acid / dianhydride. The chain extender may further include a chain extender such as a low molecular weight polyol or polyamine. As the tetracarboxylic acid dianhydride, for example, pyromellitic acid dianhydride is preferable.

  According to the present invention, a golf ball excellent in resilience, scratch resistance, and durability can be obtained.

  The golf ball of the present invention is a golf ball having a cover, wherein the resin component constituting the cover contains polyurethane having an imide bond. First, the polyurethane having an imide bond used in the present invention will be described.

  The polyurethane having an imide bond used in the present invention is not particularly limited as long as it has a plurality of polyurethane bonds and imide bonds in the molecule. For example, a chain extender containing a polyisocyanate, a polyol and an acid anhydride is used. The product in which a urethane bond and an imide bond are formed in the main chain can be mentioned by reacting with.

The polyisocyanate component constituting the polyurethane having an imide bond is not particularly limited as long as it has two or more isocyanate groups. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4- Mixture of toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3′-bitrylene-4,4′-diisocyanate Aromatic polyisocyanates such as (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI); 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), hydrogenated xylylene diisocyanate (H ₆ XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), etc. Or a mixture of two or more.

From the viewpoint of improving the scratch resistance, it is preferable to use an aromatic polyisocyanate as the polyisocyanate component of the polyurethane. By using the aromatic polyisocyanate, the mechanical properties of the resulting polyurethane are improved, and a cover having excellent scratch resistance can be obtained. From the viewpoint of improving weather resistance, non-yellowing polyisocyanates (TMXDI, XDI, HDI, H ₆ XDI, IPDI, H ₁₂ MDI, NBDI, etc.) may be used as the polyisocyanate component of polyurethane. Preferably, more preferably 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI) is used. This is because 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI) has a rigid structure, the mechanical properties of the resulting polyurethane are improved, and a cover having excellent scratch resistance can be obtained.

  The polyol component constituting the polyurethane having an imide bond is not particularly limited as long as it has a plurality of hydroxyl groups, and examples thereof include a low molecular weight polyol and a high molecular weight polyol. Examples of the low molecular weight polyol include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol; glycerin, trimethylol Examples include triols such as propane and hexanetriol. Examples of the high molecular weight polyol include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA), condensation type polyester polyols such as polyhexamethylene adipate (PHMA); lactone type polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols A mixture of at least two of the above-described polyols may be used.

  Although the average molecular weight of a high molecular weight polyol is not specifically limited, For example, it is preferable that it is 400 or more, More preferably, it is 1,000 or more. This is because if the average molecular weight of the high molecular weight polyol becomes too small, the resulting polyurethane becomes hard and the feel at impact of the golf ball decreases. The upper limit of the average molecular weight of the high molecular weight polyol is not particularly limited, but is 10,000 or less, more preferably 8,000 or less.

  In the present invention, the imide bond means a bond represented by the following formula (1), and is preferably formed by a reaction between an acid anhydride and an isocyanate group or an amino group. In formula (1), an allophanate bond formed by the reaction of a urethane bond and an isocyanate group and a burette bond formed by a reaction of a urea bond and an isocyanate group are included in the imide bond in the present invention. Make it not exist.

  Introduction of an imide bond into the polyurethane main chain can be performed, for example, by using a chain extender containing an acid anhydride. For example, as shown in the following formula (2), an imide bond is introduced into the polyurethane main chain by reacting an isocyanate group-terminated urethane prepolymer with a chain extender containing tetracarboxylic acid / dianhydride. be able to. In addition, you may introduce | transduce an imide bond by reaction of an acid anhydride and a polyamine like following formula (3).

  As the acid anhydride that can be used in the present invention, for example, a monoanhydride or dianhydride of a compound having at least three carboxyl groups is preferable, and a tetracarboxylic acid / dianhydride is more preferable. In particular, if an acid anhydride is selected so that the number of functional groups with respect to an isocyanate group is 2, such as tricarboxylic acid / monoanhydride or tetracarboxylic acid / dianhydride, a thermoplastic polyurethane can be produced.

  Examples of the tricarboxylic acid anhydride include trimellitic acid / monoanhydride, nitrilotriacetic acid / monoanhydride, and the like. In addition, when using tricarboxylic acid and monoanhydride, one imide bond and one amide bond are produced | generated by reaction with an isocyanate group.

  Examples of the tetracarboxylic acid dianhydride include aromatic dianhydrides of aromatic tetracarboxylic acids and non-aromatic tetracarboxylic acids. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic acid dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid dianhydride, 4,4′-oxydiphthalic acid, Dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid dianhydride, 2,2-bis [4 -(3,4-dicarboxyphenoxy) phenyl] propanoic acid dianhydride, naphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid And dianhydrides.

  Examples of the non-aromatic tetracarboxylic acid include diethylenetriaminetetraacetic acid / dianhydride, diethylenetriaminepentaacetic acid / dianhydride, butane-1,2,3,4-tetracarboxylic acid / dianhydride, pentane-1, 2,4,5-tetracarboxylic acid dianhydride, cyclobutane tetracarboxylic acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride, cyclohexane-1,2,4 5-tetracarboxylic acid dianhydride, cyclohex-1-ene-2,3,5,6-tetracarboxylic acid dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic acid dianhydride, 1-methyl-3-ethylcyclohexane-3- (1,2), 5,6-tetracarboxylic acid dianhydride, 1-methyl-3-ethylcyclohexa − -Ene-3- (1,2), 5,6-tetracarboxylic acid dianhydride, 1-ethylcyclohexane-1- (1,2), 3,4-tetracarboxylic acid dianhydride, 1- Propylcyclohexane-1- (2,3), 3,4-tetracarboxylic acid dianhydride, 1,3-dipropylcyclohexane-1- (2,3), 3- (2,3) -tetracarboxylic acid Dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid dianhydride 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic acid dianhydride, 1,3-dipropylcyclohexane-1- (2,3), 3- (2,3)- Tetracarboxylic acid dianhydride, dicyclohexyl-3,4,3 ′, 4 ′ Tetracarboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo [2.2.2] octane-2,3,5 Examples include 6-tetracarboxylic acid / dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid / dianhydride, and the like. The said acid anhydride may be used independently and may use 2 or more types together. In the present invention, it is particularly preferable to use pyromellitic acid / dianhydride.

  The content of the acid dianhydride in the polyurethane having an imide bond is not particularly limited, but the molar ratio of the functional group of the acid dianhydride to the isocyanate group of the polyisocyanate constituting the polyurethane (O = C -O-C = O / NCO) is preferably 0.05 or more, more preferably 0.1 or more, preferably 0.8 or less, and more preferably 0.6 or less. By making the molar ratio of the acid dianhydride / isocyanate group functional group (O═C—O—C═O / NCO) to be 0.05 or more, a substantial improvement effect is obtained by introducing an imide bond. Because it is. On the other hand, when the molar ratio exceeds 0.8, the imide bond is excessively increased, and the obtained cover is hardened and the scratch resistance may be lowered.

  In the present invention, a chain extender containing a low molecular weight polyol or polyamine can be used in addition to the acid anhydride. This is because by using a low molecular weight polyol or polyamine in combination, it is easy to adjust the hardness of the resulting polyurethane having an imide bond. The low molecular weight polyol is not particularly limited as long as it has a molecular weight of less than about 400. For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl Diols such as glycol and 1,6-hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol.

  The polyamine is not particularly limited as long as it has at least two amino groups, for example, aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, and alicyclic such as isophoronediamine and piperazine. System polyamines and aromatic polyamines.

  The aromatic polyamine is not particularly limited as long as at least two amino groups are directly or indirectly bonded to the aromatic ring. Here, being indirectly bonded means that the amino group is bonded to the aromatic ring via, for example, a lower alkylene group. The aromatic polyamine may be, for example, a monocyclic aromatic polyamine in which two or more amino groups are bonded to one aromatic ring, or an amino in which at least one amino group is bonded to one aromatic ring. It may be a polycyclic aromatic polyamine containing two or more phenyl groups.

  Examples of the monocyclic aromatic polyamine include a type in which an amino group such as phenylenediamine, toluenediamine, diethyltoluenediamine, and dimethylthiotoluenediamine is directly bonded to an aromatic ring; and an amino group such as xylylenediamine. Examples include a type bonded to an aromatic ring via a lower alkylene group. The polycyclic aromatic polyamine may be poly (aminobenzene) in which at least two aminophenyl groups are directly bonded, or at least two aminophenyl groups intervene with a lower alkylene group or an alkylene oxide group. May be combined. Of these, diaminodiphenylalkanes in which two aminophenyl groups are bonded via a lower alkylene group are preferred, and 4,4′-diaminodiphenylmethane and derivatives thereof are particularly preferred.

  In the present invention, the golf ball cover is not particularly limited as long as it contains the polyurethane having the imide bond as a base resin component, and the polyurethane having the imide bond in the resin component constituting the cover. The content of is desirably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. Furthermore, it is also a preferable aspect that the resin component constituting the cover is substantially made only of polyurethane having an imide bond.

  The synthesis of the polyurethane having an imide bond used in the present invention includes, for example, an isocyanate group-terminated urethane prepolymer and a chain extender containing a tetracarboxylic acid / dianhydride in a dry nitrogen atmosphere at 50 ° C. or higher. The reaction may be performed at 180 ° C. or lower (more preferably 60 ° C. or higher and 150 ° C. or lower) for 30 minutes to 600 minutes (more preferably 60 minutes to 300 minutes). In addition, the synthesis | combination of an isocyanate group terminal urethane prepolymer can employ | adopt a method well-known to those skilled in the art.

  The slab hardness of the polyurethane having an imide bond is Shore D hardness, preferably 25 or more, more preferably 30 or more, preferably 55 or less, and more preferably 50 or less. This is because when the slab hardness of the polyurethane having an imide bond is less than 25, the resilience of the obtained golf ball is lowered and the flight distance may be lowered. On the other hand, when the hardness of the polyurethane having an imide bond exceeds 55, the durability of the obtained golf ball may be lowered. The slab hardness of the polyurethane having an imide bond can be controlled by appropriately selecting the content ratio of polyisocyanate, polyol, acid anhydride and the like constituting the polyurethane, the kind of polyol, and the like.

  The polyurethane having an imide bond contained in the resin component of the golf ball cover of the present invention may be so-called thermoplastic polyurethane or thermosetting polyurethane. In any case, a golf ball having excellent scratch resistance, durability, and resilience can be obtained. The thermoplastic polyurethane is a polyurethane that exhibits plasticity when heated, and generally means a polyurethane having a linear structure that has been polymerized to some extent. On the other hand, thermosetting polyurethane (two-part curable polyurethane) is a high-strength polyurethane by reacting the prepolymer with a chain extender (curing agent) just before placing a low molecular weight urethane prepolymer and molding the cover. It is a polyurethane obtained by molecular weight. The thermosetting polyurethane includes a polyurethane having a linear structure and a polyurethane having a three-dimensional crosslinked structure by controlling the number of functional groups of a prepolymer and a chain extender (curing agent) to be used. In the present invention, since it is easy to mold the cover, it is preferable to use a thermoplastic polyurethane having an imide bond.

  In the present invention, in addition to the polyurethane having an imide bond as the cover material, examples of the resin component that can be used further include thermoplastic resins, thermoplastic elastomers, and diene block copolymers. Examples of the thermoplastic resin include an ionomer resin. Examples of the ionomer resin include at least a carboxyl group in a copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Some of the carboxyl groups in a terpolymer of a part of which is neutralized with a metal ion, ethylene, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester The thing which neutralized at least one part with the metal ion, or a mixture thereof can be mentioned. Specific examples of the ionomer resin include Hi Milan, which is commercially available from Mitsui DuPont Polychemical Co., Ltd., Surlyn, which is commercially available from DuPont, and Iotech, which is commercially available from ExxonMobil Chemical Co., Ltd. be able to.

  Specific examples of the thermoplastic elastomer include thermoplastic polyamide elastomer commercially available from Arkema Co., Ltd. under the trade name “Pebax (eg,“ Pebax 2533 ”), and trade name“ Hytrel ”from Toray DuPont Co., Ltd. (For example, “Hytrel 3548”, “Hytrel 4047”) ”, a thermoplastic polyester elastomer commercially available under the trade name“ Lavalon ”from Mitsubishi Chemical Corporation, and the like. Of these, thermoplastic polystyrene elastomer is preferred. Examples of the thermoplastic polystyrene elastomer include a polystyrene-diene block copolymer having a polystyrene block component as a hard segment and a diene block component such as polybutadiene, isoprene, hydrogenated polybutadiene, hydrogenated polyisoprene as a soft segment. be able to. The polystyrene-diene block copolymer has a double bond derived from a conjugated diene compound of a block copolymer or a partially hydrogenated block copolymer. Examples of the polystyrene-diene block copolymer include a block copolymer having an SBS (styrene-butadiene-styrene) structure having a polybutadiene block, or a block copolymer having an SIS (styrene-isoprene-styrene) structure. Is mentioned.

  The cover of the golf ball of the present invention includes, in addition to the resin component described above, a pigment component such as a white pigment (titanium oxide) and a blue pigment, a specific gravity adjusting agent such as calcium carbonate and barium sulfate, a dispersant, an anti-aging agent, and an ultraviolet absorption An agent, a light stabilizer, a fluorescent material, a fluorescent whitening agent, or the like may be contained as long as the performance of the cover is not impaired.

  The content of the white pigment (titanium oxide) is 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, with respect to 100 parts by mass of the resin component constituting the cover. Is desirably 8 parts by mass or less. By setting the content of the white pigment to 0.5 parts by mass or more, the cover can be concealed. Moreover, it is because durability of the cover obtained may fall when content of a white pigment exceeds 10 mass parts.

  The cover of the golf ball of the present invention is produced by molding using the cover composition containing the cover material described above. As a method of forming the cover, for example, a method of forming a hollow shell-shaped shell from the cover composition, and covering and compressing the core with a plurality of shells (preferably, forming the cover from the cover composition into a hollow shell-shaped shell). A method of molding a half shell, covering the core with two half shells and compression molding), and a method of injection molding the cover composition directly onto the core, and preferably a compression molding method is employed. . This is because by employing the compression molding method, the scuff resistance and durability of the obtained cover are further improved.

  The half shell can be molded by either compression molding or injection molding, but compression molding is preferred.

  The conditions for compression-molding the cover composition into a half shell include, for example, a pressure of 1 MPa or more and 20 MPa or less, and −20 ° C. or more and 70 ° C. or less with respect to the flow start temperature of the cover composition. A molding temperature can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method for forming a cover using a half shell, for example, a method in which a core is covered with two half shells and compression-molded can be mentioned. The conditions for forming the half shell into a cover by compression molding are, for example, from −20 ° C. to 70 ° C. with respect to the flow start temperature of the cover composition at a molding pressure of 0.5 MPa or more and 25 MPa or less. A molding temperature can be mentioned. By setting the molding conditions, a golf ball cover having a uniform cover thickness can be molded.

  In the present invention, the cover may be formed by directly injection-molding the cover composition onto the core. In this case, as the upper and lower molds for molding the cover, it is preferable to use a cover having a hemispherical cavity, with pimples and also serving as a hold pin in which a part of the pimples can be advanced and retracted. The cover can be formed by injection molding by projecting the hold pin, inserting and holding the core, injecting the cover composition, and cooling the cover, for example, 9 MPa to 15 MPa. The cover composition heated to 200 ° C. to 250 ° C. is poured into the mold clamped at a pressure of 0.5 to 5 seconds, cooled for 10 to 60 seconds, and opened.

  The golf ball formed with the cover is preferably removed from the mold and subjected to surface treatment such as deburring, washing, and sand blasting as necessary. Moreover, a paint layer and a mark can also be formed if desired.

  In the present invention, the thickness of the golf ball cover is preferably 2.0 mm or less, more preferably 1.6 mm or less, and even more preferably 1.0 mm or less. This is because when the thickness is 2.0 mm or less, the resilience of the golf ball is increased and the total flight distance is increased. Although the minimum of the thickness of a cover is not specifically limited, For example, it is 0.1 mm. This is because if the thickness is less than 0.1 mm, it may be difficult to mold the cover.

  The slab hardness of the golf ball cover of the present invention is 20 or more in Shore D hardness, more preferably 25 or more, further preferably 30 or more, 60 or less, and more preferably 55 or less. Yes, more preferably 50 or less. By setting the slab hardness of the cover to 20 or more, the rigidity of the obtained cover is increased, and a golf ball having excellent resilience (flying distance) can be obtained. On the other hand, by setting the slab hardness to 60 or less, the feel at impact when the golf ball is hit is improved. Here, the slab hardness of the cover is a hardness measured by molding the cover composition into a sheet shape, and is measured by a measurement method described later.

  The structure of the golf ball of the present invention is not particularly limited as long as it has a cover. A two-piece golf ball having a core and a cover covering the core, an intermediate layer covering the core and the core, and the intermediate layer A three-piece golf ball having a cover covering the core, a multi-piece golf ball having a core and a cover, and having at least two intermediate layers between the core and the cover, or a bobbin having a thread-wound core and a cover A golf ball may be used. This is because the present invention can be preferably applied in any case. In the structure of a golf ball, a core and an intermediate layer may be combined to form a multilayer core, and a cover and the intermediate layer may be combined to form a multilayer cover.

  The core in the case where the golf ball of the present invention has a core such as a thread wound golf ball, a two-piece golf ball, and a multi-piece golf ball will be described. For the core, a conventionally known rubber composition (hereinafter sometimes simply referred to as “core rubber composition”) may be employed. For example, a diene rubber as a base rubber, a co-crosslinking agent, And a rubber composition containing a crosslinking initiator can be molded by hot pressing.

  As the diene rubber, it is particularly preferable to use a high-cis polybutadiene having a cis bond advantageous for rebound of 40% or more, preferably 70% or more, more preferably 90% or more. As the co-crosslinking agent, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof, preferably a metal salt of acrylic acid or methacrylic acid is used. Aluminum and sodium are preferably used, and zinc is more preferably used. The amount of the co-crosslinking agent used is preferably 20 to 50 parts by mass per 100 parts by mass of the base rubber. As the crosslinking initiator, an organic peroxide is preferably used. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, Examples thereof include organic peroxides such as di-t-butyl peroxide, among which dicumyl peroxide is preferably used. The compounding amount of the organic peroxide is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 1.5 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, it is 1.0 mass part or less. The rubber composition for core may further contain diphenyl disulfides. The compounding amount of diphenyl disulfides is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5.0 parts by mass or less, with respect to 100 parts by mass of the base rubber. Preferably it is 3.0 mass parts or less.

  Examples of the diphenyl disulfides include diphenyl disulfide, bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, and bis (4- Mono-substituted products such as fluorophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (4-cyanophenyl) disulfide; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, bis ( 2,6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide, bis (2-cyano- -Disubstituted products such as bromophenyl) disulfide; trisubstituted products such as bis (2,4,6-trichlorophenyl) disulfide and bis (2-cyano-4-chloro-6-bromophenyl) disulfide; Tetra-substituted products such as 3,5,6-tetrachlorophenyl) disulfide; bis (2,3,4,5,6-pentachlorophenyl) disulfide, bis (2,3,4,5,6-pentabromophenyl) disulfide And the like, and the like. These diphenyl disulfides have some influence on the vulcanized state of the rubber vulcanizate and can improve the resilience. Among these, it is preferable to use diphenyl disulfide and bis (pentabromophenyl) disulfide from the viewpoint that a highly repulsive golf ball can be obtained.

  In addition to the base rubber, co-crosslinking agent, cross-linking initiator, diphenyl disulfides, the core rubber composition further includes specific gravity adjusters such as zinc oxide and barium sulfate, anti-aging agents, and color powders as appropriate. Can be blended. The hot-press molding conditions for the core rubber composition may be appropriately set according to the rubber composition, but are usually heated at 130 ° C. to 200 ° C. for 10 to 60 minutes, or at 130 ° C. to 150 ° C. for 20 to 20 ° C. After heating for 40 minutes, it is preferable to heat at 160 ° C. to 180 ° C. for 5 to 15 minutes in two steps.

  When the golf ball of the present invention is a three-piece or multi-piece golf ball, examples of the intermediate layer include thermoplastic resins such as polyurethane resin, ionomer resin, nylon, and polyethylene; polystyrene-based elastomer and polyolefin-based elastomer And thermoplastic elastomers such as polyurethane elastomers and polyester elastomers, and ionomer resins are preferred.

  Examples of the ionomer resin include an ionomer resin obtained by neutralizing at least a part of a carboxyl group in a copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, ethylene and carbon. What neutralized at least one part of the carboxyl group in the ternary copolymer of several 3-8 alpha, beta-unsaturated carboxylic acid and alpha, beta-unsaturated carboxylic acid ester with a metal ion, or Mention may be made of these mixtures.

  Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid, and acrylic acid or methacrylic acid is particularly preferable. Examples of the α, β-unsaturated carboxylic acid ester include methyl, ethyl, propyl, n-butyl, isobutyl ester and the like such as acrylic acid, methacrylic acid, fumaric acid and maleic acid. Methacrylic acid esters are preferred. The copolymer of ethylene and α, β-unsaturated carboxylic acid, or the carboxyl group 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 include alkali metal ions such as sodium, potassium, and lithium; divalent metal ions such as magnesium, calcium, zinc, barium, and cadmium; trivalent metal ions such as aluminum; tin Other ions such as zirconium and the like can be mentioned, and sodium, zinc and magnesium ions are particularly preferably used from the viewpoint of resilience and durability.

  In addition to the resin component, the intermediate layer may further contain a specific gravity adjusting agent such as barium sulfate or tungsten, an antiaging agent, a pigment, and the like.

  When the golf ball of the present invention is a thread wound golf ball, a thread wound core may be used as the core. In such a case, as the thread wound core, for example, a thread core composed of a center formed by curing the core rubber composition described above and a thread rubber layer formed by winding the thread rubber around the center in a stretched state is used. do it. The thread rubber wound on the center may be the same as that conventionally used for the thread wound layer of a thread wound golf ball, for example, natural rubber or natural rubber and synthetic polyisoprene with sulfur, You may use what was obtained by vulcanizing the rubber composition which mix | blended the vulcanization adjuvant, the vulcanization accelerator, the anti-aging agent, etc. The thread rubber is stretched about 10 times on the center and wound to form a thread wound core.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments without departing from the gist of the present invention are not limited thereto. Included in range.

[Evaluation methods]
(1) Scratch resistance A commercially available pitching wedge was attached to a swing robot manufactured by Golf Laboratories, and each ball was hit once at a head speed of 36 m / sec. .
Evaluation criteria A: There is almost no scratch on the surface of the golf ball.
○: Slight scratches occur on the surface of the golf ball.
Δ: The surface of the golf ball is slightly shaved and fluffing occurs.
X: The surface of the golf ball is considerably shaved and the fuzz is conspicuous.

(2) Durability A metal head # W1 driver was attached to a swing robot manufactured by True Temper, and each golf ball was hit at a head speed of 45 m / sec to collide with a collision plate. This was repeated to measure the number of hits until the golf ball was broken. The durability of each golf ball is determined according to the golf ball no. The number of hits of 9 is assumed to be 100, and the number of hits for each golf ball is shown as an index value. The larger the indexed value, the more excellent the golf ball is.

(3) Slab hardness (Shore D hardness)
A sheet having a thickness of about 2 mm was produced by hot press molding using the cover composition or polyurethane, and stored at 23 ° C. for 2 weeks. An automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness tester Shore D type as defined in ASTM-D2240 in a state where three or more sheets are stacked so as not to affect the measurement substrate or the like. It measured using.

(4) Golf ball restitution coefficient 200 g of an aluminum cylinder collides with each golf ball at a speed of 45 m / second, and the speeds of the cylinder and the golf ball before and after the collision are measured. The coefficient of restitution of the ball was calculated. The measurement was performed five times for each golf ball, and the average value was used as the coefficient of restitution of the golf ball. The coefficient of restitution is the golf ball no. The value obtained by indexing with the value of 9 as 100 is shown. A larger index value means better resilience.

[Synthesis of polyurethane]
(1) Synthesis of polyurethanes A to H having an imide bond The polyisocyanate shown in Table 1, a polyol, and 1,4-butanediol as a chain extender were reacted at 80 ° C. for 2 hours in a nitrogen atmosphere. Thus, an isocyanate group-terminated urethane prepolymer was obtained. The obtained isocyanate group-terminated urethane prepolymer was dissolved in 1000 g of N-methyl-2-pyrrolidone (NMP), and the tetracarboxylic acid / dianhydride shown in Table 1 was added as a chain extender at 150 ° C. The reaction was performed for 2 hours. The obtained polyurethaneimide solution was formed into a sheet with a centrifugal molding machine for 1 hour, and the obtained sheet was dried under reduced pressure (200 ° C./2 to 3 mmHg) for 4 hours to obtain a polyurethane having an imide bond. The obtained polyurethane having an imide bond was pulverized to obtain a cover material.

(2) Synthesis of polyurethanes I and J containing no imide bond Polyisocyanate shown in Table 1, a polyol, and 1,4-butanediol as a chain extender, N-methyl-2-pyrrolidone (NMP) It melt | dissolved in 1000g and made it react under nitrogen atmosphere at 80 degreeC for 2 hours. The obtained polyurethane solution was made into a sheet with a centrifugal molding machine for 1 hour, and the obtained sheet was dried under reduced pressure (200 ° C./2 to 3 mmHg) for 4 hours to obtain polyurethane. The obtained polyurethane was pulverized to obtain a cover material.

MDI: 4,4'-diphenylmethane diisocyanate manufactured by Tokyo Chemical Industry Co., Ltd. H12 MDI: dicyclohexylmethane 4,4'-diisocyanate PTMG1000 manufactured by Tokyo Chemical Industry Co., Ltd. Polyoxytetramethylene glycol (average molecular weight 1000) manufactured by Mitsubishi Chemical Corporation
PTMG2000: Polyoxytetramethylene glycol manufactured by Mitsubishi Chemical Corporation (average molecular weight 2000)
1,4-BD: Tokyo Chemical Co., Ltd. 1,4-butanediol PMDA: Tokyo Chemical Industries pyromellitic acid dianhydride BPDA: Tokyo Chemical Industry Co., Ltd. 3,3 ′, 4,4′-benzophenone tetracarboxylic acid Dianhydride

[Production of golf balls]
(1) Production of Center A rubber composition for a center having the composition shown in Table 2 was kneaded and heated and pressed at 170 ° C. for 15 minutes in an upper and lower mold having hemispherical cavities to obtain a diameter of 38.5 mm and a mass of 34.9 g. Obtained a spherical center.

Polybutadiene rubber: BR730 (high cis polybutadiene) manufactured by JSR Corporation
Zinc acrylate: ZNDA-90S manufactured by Nippon Distilled
Zinc Oxide: Toho Zinc Gin R
Dicumyl peroxide: Park Mill D made by NOF
Diphenyl disulfide: manufactured by Sumitomo Seika

(2) Blending of intermediate layer material Next, the intermediate layer material having the composition shown in Table 3 was mixed by a twin-screw kneading extruder to prepare a pellet-shaped intermediate layer composition. Extrusion was performed with a screw diameter of 45 mm, a screw speed of 200 rpm, and a screw L / D = 35. The blend was heated to 150-230 ° C. at the die position of the extruder.

“Himiran 1605”: sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. “Himiran AM7329”: zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. The obtained intermediate layer composition was injection-molded on the center obtained as described above to produce a core having a center and an intermediate layer (thickness 1.6 mm) covering the center.

(3) Preparation of cover composition and molding of half shell As shown in Table 4, the polyurethane obtained as described above was mixed by a twin-screw kneading extruder to form a pellet-shaped cover composition. Was prepared. 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 200-260 ° C. at the die position of the extruder. The obtained pellet-like composition for a cover was put into each of the concave portions of the lower mold of the half shell molding die, and pressed to form a half shell. The compression molding was performed at a molding temperature of 170 ° C., a molding time of 5 minutes, and a molding pressure of 2.94 MPa.

(4) Molding of cover The core obtained in (2) was covered concentrically with the two half shells obtained in (3), and a cover (thickness 0.5 mm) was molded by compression molding. The compression molding was performed at a molding temperature of 150 ° C., a molding time of 2 minutes, and a molding pressure of 9.8 MPa.

  The surface of the obtained golf ball body is subjected to sand blasting and marking, and then a clear paint is applied, and the paint is dried in an oven at 40 ° C. to obtain a golf ball having a diameter of 42.7 mm and a mass of 45.3 g. Obtained. Table 4 shows the results of evaluating the scratch resistance, durability, and resilience of the obtained golf ball.

ET890, XNY97A: Thermoplastic polyurethane elastomer manufactured by BASF Japan

  Golf ball no. 1-No. 8 is a golf ball having a cover, in which the resin component constituting the cover contains polyurethane having an imide bond. In either case, golf ball No. 1 using a conventional thermoplastic polyurethane containing no imide bond as a cover is used. 9-No. Compared to 12, it was excellent in scratch resistance, durability, and resilience.

  The golf ball of the present invention is excellent in scuff resistance, durability, and resilience.

Claims (5)

A golf ball having a cover,
The resin component constituting the cover contains 50% by mass or more of polyurethane having an imide bond,
The golf ball according to claim 1, wherein the slab hardness of the polyurethane having an imide bond is 30 to 55 in Shore D hardness.   The golf ball according to claim 1, wherein the polyurethane having an imide bond has an acid anhydride as a constituent component.   3. The golf ball according to claim 1, wherein the polyurethane having an imide bond is obtained by reacting an isocyanate group-terminated urethane prepolymer with a chain extender containing tetracarboxylic acid / dianhydride.   The golf ball according to claim 3, wherein the chain extender further contains a low molecular weight polyol or polyamine.   4. The golf ball according to claim 2, wherein the acid anhydride is pyromellitic acid / dianhydride.