JP2008149059A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball that has a cover excellent in durability and repulsion and, at the same time, can acquire a soft shot feeling. <P>SOLUTION: The golf ball 10 has a solid core 12 and the cover 14 that wraps this solid core 12. This cover 14 contains a reactant which is generated when carboxyl group of ethylene-(meta) acrylic acid copolymer-based resin and terminal isocyanate group which exists at the terminal ends of the main chain of polyurethane forms amide bond. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a golf ball, and more particularly to a golf ball including a reaction product generated by forming an amide bond between an ethylene- (meth) acrylic acid copolymer resin and polyurethane in a cover.

  In recent years, so-called multi-piece solid golf balls having one or more cores and one or more covers covering the cores are widely used. The cover of this type of golf ball is generally formed from an ionomer resin.

  In the ionomer resin, for example, an acidic group of an ionic copolymer of ethylene and an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid is partially neutralized with a metal ion such as sodium or zinc. There are advantages such as excellent durability and good resilience. However, since the ionomer resin is relatively hard, when a golf ball having a cover made of this resin is hit, a problem that the shot feeling is hard has become obvious.

  In order to solve this problem, Patent Document 1 discloses that a relatively flexible ethylene- (meth) acrylic acid- (meth) acrylic ester terpolymer is an ethylene- (meth) acrylic acid copolymer ionomer resin. It has been proposed to mix in.

  In addition, it has been proposed to form a cover with polyurethane (see, for example, Patent Document 2). However, in this case, the resilience is smaller than that of the ionomer resin, and thus the golf ball has a short flight distance. Therefore, Patent Document 3 proposes that the cover has a two-layer structure, the inner cover is an ionomer resin, and the outer cover is a mixed composition of an ionomer resin and a polyurethane resin.

  Further, in Patent Document 4, after a golf ball is molded, a polyisocyanate is infiltrated from the outer surface of a cover made of a thermoplastic resin such as a polyurethane-based resin, and both compounds are reacted to thereby modify the surface layer of the cover. And thereby improving various physical properties of the cover.

JP-A-1-308577 U.S. Pat. No. 4,123,061 JP 2003-49028 A International Publication No. WO 98/28048 Pamphlet

  When the mixture composition of an ionomer resin and a polyurethane resin is used as the outermost layer (cover) as described in Patent Document 3, if the ratio of the polyurethane resin is excessively large, both resins cause phase separation. When such a situation occurs, the cover tends to fluff during polishing, and even a golf ball tends to crack when hit.

  On the other hand, in the technique described in Patent Document 4, since polyisocyanate is infiltrated from the outer surface of the cover, complicated work steps increase and only the surface layer of the cover is modified. There is a bug. In order to avoid this, if an attempt is made to form the cover after reacting the thermoplastic resin and the polyisocyanate, the reaction product is a crosslinked product, which causes a disadvantage that processing (injection molding) becomes extremely difficult.

  The present invention has been made to solve the above-described problems, and provides a golf ball having a cover that has excellent resilience, has a soft feel at impact when hit, and does not require a complicated work process at the time of formation. The purpose is to provide.

In order to achieve the above object, the present invention provides a golf ball having at least a core and a cover,
The cover contains a reaction product formed by forming an amide bond between a carboxyl group of an ethylene- (meth) acrylic acid copolymer resin and a terminal isocyanate group present at the terminal of the main chain of the polyurethane. Features. The core in the present invention includes a solid core and a thread wound core.

  In this cover, polyurethane is present. Due to the presence of this polyurethane, the durability of the cover is improved and a soft shot feeling can be obtained at the time of hitting. In addition, since the cover also contains an ethylene- (meth) acrylic acid copolymer resin, rebound is ensured.

  In addition, in the present invention, since the ethylene- (meth) acrylic acid copolymer resin and the polyurethane are chemically bonded via an amide bond, the occurrence of phase separation between the two is remarkably suppressed. Accordingly, the uneven distribution of polyurethane can be avoided, and therefore fluffing can be avoided during surface polishing and cracking can be avoided during impact.

  The reaction between the ethylene- (meth) acrylic acid copolymer resin and polyurethane can be performed before the cover is formed. This is because the produced reaction product is not a cross-linked product, and is therefore flexible and plastic and easy to injection mold. Therefore, it is possible to avoid an increase in the number of steps required for forming the cover.

Preferable examples of polyurethane include a reaction product of a polymer diol compound, a monomolecular chain extender, and a diisocyanate. In this case, it is preferable that the molar ratio between the isocyanate group and the hydroxyl group satisfies the following formula (1).

  By setting the value of isocyanate group / hydroxyl group within the range of 1 to 2, the reaction product exhibiting sufficient plasticity can be reliably obtained.

  On the other hand, an ionomer resin can be mentioned as a suitable example of ethylene- (meth) acrylic acid copolymer resin.

  Here, it is preferable that the ratio of the polyurethane in a cover is 5-50 mass parts with respect to 100 mass parts of ethylene- (meth) acrylic acid copolymer resin. As a result, a golf ball having both excellent resilience and a soft feel at impact can be reliably configured.

  According to the present invention, the reaction product generated by forming an amide bond between the carboxyl group of the ethylene- (meth) acrylic acid copolymer resin and the terminal isocyanate group present at the terminal of the main chain of the polyurethane is used as the base material. Since the cover is formed as a golf ball, it is possible to obtain a golf ball having a cover showing excellent resilience and having a soft feel at impact.

  In addition, since the ethylene- (meth) acrylic acid copolymer resin and the polyurethane are chemically bonded, the occurrence of phase separation between the two is remarkably suppressed. For this reason, it is also possible to avoid the occurrence of fuzz during surface polishing and the generation of cracks during impact.

  Hereinafter, preferred embodiments of the golf ball according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic overall cross-sectional view along the diameter direction of a golf ball 10 according to the present embodiment. The golf ball 10 includes a solid core 12 and a cover 14 that covers the solid core 12.

  In the present embodiment, the solid core 12 is formed from a rubber composition in which a co-crosslinking agent, a crosslinking initiator, a filler, and the like are blended with a base rubber such as natural rubber or synthetic rubber.

  Preferable examples of the base rubber include polybutadiene containing 80% or more of cis-1,4 structure. Examples of the co-crosslinking agent for crosslinking such a base rubber include zinc salts of unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and examples of the crosslinking initiator include dicumyl peroxide, 1,1. -Bis (t-butylperoxy) 3,3,5-trimethylcyclohexane and the like are exemplified. Examples of the filler include zinc oxide and barium sulfate. You may mix | blend an anti-aging agent, a coloring agent, etc. further as needed.

  The diameter of the solid core 12 is preferably set to 30 mm or more. If it is less than 30 mm, the resilience of the golf ball 10 may be poor. A more preferable diameter of the solid core 12 is 35 mm or more.

  One cover 14 contains a reaction product of an ethylene- (meth) acrylic acid copolymer resin and polyurethane. This reaction product was produced by forming an amide bond between the carboxyl group of the ethylene- (meth) acrylic acid copolymer resin and the terminal isocyanate group present at the end of the main chain of the polyurethane. is there.

  Preferable examples of the ethylene- (meth) acrylic acid copolymer resin include a binary copolymer of ethylene and an α, β-unsaturated carboxylic acid, and other repetitions of the binary copolymer. Examples include multi-component copolymers in which units are bonded.

  The α, β-unsaturated carboxylic acid is not particularly limited, and preferable examples include acrylic acid, methacrylic acid, fumaric acid, and itaconic acid. In the case of a multi-component copolymer, preferred examples of other repeating units include methyl α, β-unsaturated carboxylate, ethyl α, β-unsaturated carboxylate, α, β-unsaturated carboxylic acid. Examples include α, β-unsaturated carboxylic acid esters such as butyl, vinyl esters such as vinyl acetate, and α-olefins. In any case, the proportion of α, β-unsaturated carboxylic acid is usually in the range of 0.5 to 15 mol%, with the majority being 1 to 8 mol%.

The ethylene- (meth) acrylic acid copolymer resin may be an ionomer resin in which the above-described copolymer is neutralized with metal ions. Examples of metal ions include Li ⁺ , Na ⁺ , K ⁺ , Zn ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Pb ²⁺ , and Mg ²⁺ . Li ⁺ , Na ⁺ , Zn ²⁺ Mg ²⁺ is particularly preferred. These metal ions can be introduced using compounds such as formate, acetate, nitrate, carbonate, bicarbonate, oxide, hydroxide, and alkoxide.

  Such an ethylene- (meth) acrylic acid copolymer resin is available as a commercial product.

  Typical commercial products include Nukurel AN4214C, Nukurel N0903H, Nukurel N410, Nukurel N1560, Nukurel AN4228C, High Milan AM7315, High Milan AM7317, High Milan AM7318, High Milan 1706, High Milan 1555, High Milan 1557 (all manufactured by Mitsui DuPont Polychemical Co., Ltd.) These can be used alone or in combination.

  On the other hand, polyurethane contains a soft segment made of a polymer diol compound, a hard segment made of a monomolecular chain extender, and diisocyanate.

  Preferable examples of the polymer diol compound that is a soft segment include polyester diols, polyether diols, polycarbonate diols, and the like. Specific examples of the polyester diol include polycaprolactone diol, poly (ethylene-1,4-adipate) glycol, poly (butylene-1,4-adipate) glycol, and the like. Specific examples of the polyether diol Examples thereof include polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol and the like. Examples of the polycarbonate diol include poly (hexanediol-1,6-carbonate) glycol.

  The number average molecular weight of the polymer diol compound as described above is usually 500 or more, but the number average molecular weight is preferably 1000 or more. The number average molecular weight is preferably 5000 or less, more preferably 3000 or less, in order to facilitate injection molding described later.

  As the monomolecular chain extender that is a hard segment, a known monomolecular chain extender may be employed. Representative examples thereof include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-propylene glycol, 1,6-hexyl glycol, 1,3-butylene glycol, 2-ethyl-1, Examples include glycols such as 3-hexanediol.

  The diisocyanate may be a known diisocyanate, but it is preferable to employ an aliphatic isocyanate or an alicyclic diisocyanate. This is because the yellowing resistance of the cover 14 is good in this case. That is, hexamethylene diisocyanate, 2,2,4- (2,4,4) -trimethylhexamethylene diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and the like are preferable.

In the polyurethane containing the soft segment, the hard segment and the diisocyanate as described above, it is preferable that the molar ratio of the isocyanate group to the hydroxyl group satisfies the following formula (1).

  When the value of isocyanate group / hydroxyl group is less than 1, since the number of isocyanates that can be bonded to the carboxyl group of the ethylene- (meth) acrylic acid copolymer resin is small, the ethylene- (meth) acrylic acid copolymer resin and It is not easy to obtain a reaction product with polyurethane. On the other hand, when the value of isocyanate group / hydroxyl group exceeds 2, crosslinking between the ethylene- (meth) acrylic acid copolymer resin and polyurethane occurs, and as a result, thermoplasticity may be lost.

  In the cover 14, the ratio of the ethylene- (meth) acrylic acid copolymer resin and the polyurethane is preferably 100: 5 to 50 by mass ratio. In other words, the polyurethane is preferably 5 to 50 parts by mass with respect to 100 parts by mass of the ethylene- (meth) acrylic acid copolymer resin. When the polyurethane is less than 5 parts by mass, the effect of obtaining a soft shot feeling derived from polyurethane is poor. Moreover, when it exceeds 50 mass parts, the resilience of the cover 14 may fall.

  The cover 14 is obtained by copolymerizing a polymer diol compound, a monomolecular chain extender, and diisocyanate to synthesize polyurethane, and then melt-mixing the polyurethane and ethylene- (meth) acrylic acid copolymer resin to form a molten mixture. Further, it can be formed by injection molding so as to cover the solid core 12 using the molten mixture.

  Alternatively, a prepolymer of a polymer diol compound and diisocyanate, a monomolecular chain extender, and an ethylene- (meth) acrylic acid copolymer resin may be melt-mixed, or a polymer diol compound and diisocyanate. The monomolecular chain extender may be simultaneously added to the ethylene- (meth) acrylic acid copolymer resin. Furthermore, the polymer diol compound and the monomolecular chain extender may be added to the ethylene- (meth) acrylic acid copolymer resin first, and the diisocyanate may be added after a predetermined time has elapsed.

  In addition, if only diisocyanate is added to the ethylene- (meth) acrylic acid copolymer resin first, a crosslinked product of the diisocyanate and the ethylene- (meth) acrylic acid copolymer resin is generated. Since this crosslinked body is relatively hard, it is difficult to flow, and therefore, it is not easy to form the cover 14.

  What is necessary is just to implement melt-mixing by a general method. That is, for example, an ethylene- (meth) acrylic acid copolymer resin is heated to a molten resin in a reaction vessel in an inert gas atmosphere, and polyurethane is added while stirring the resin.

  As described above, instead of polyurethane, a prepolymer of a polymer diol compound and diisocyanate and a monomolecular chain extender may be added, or the polymer diol compound, diisocyanate and monomolecular chain extender may be added simultaneously. You may make it add. Further, a polymer diol compound and a monomolecular chain extender may be added, and the diisocyanate may be added after a predetermined time has elapsed.

  By melt mixing, the carboxylic acid of the ethylene- (meth) acrylic acid copolymer resin and the isocyanate group present at the terminal of the polyurethane form an amide bond, thereby producing a reactant having the amide bond. When a polymer or monomer containing a polyurethane repeating unit is added, a polyurethane is first formed, and then this polyurethane is chemically bonded to an ethylene- (meth) acrylic acid copolymer resin.

  The reaction temperature at this time is preferably set to a range where the ethylene- (meth) acrylic acid copolymer resin is sufficiently melted while the polyurethane does not undergo thermal decomposition, specifically, 100 to 250 ° C.

  The reaction vessel may be a reactor having a stirrer or a kneader. As the kneader, a biaxial kneader or a triaxial kneader is suitable.

  When the ethylene- (meth) acrylic acid copolymer resin and the polyurethane are chemically bonded by such melt mixing, the cover 14 is formed by performing the same operation as that for forming the cover from an ionomer resin or the like. can do. That is, the cover forming process does not increase.

  In addition, although a formation process increases, after providing a pre-cover from the resin composition containing ethylene- (meth) acrylic acid copolymer resin, the polyurethane is brought into contact with the pre-cover, whereby ethylene- (meth) You may make it form the cover 14 containing the reaction material of acrylic acid copolymer system resin and a polyurethane.

  In addition to performing injection molding as described above, the pre-cover or cover 14 is also formed by providing two hemispherical half cups, covering the solid core 12 with these half cups, and then performing pressure heating molding. It is possible. Further, after the cover 14 is formed, surface polishing, stamping, painting, and the like are performed.

  In any case, in addition to the reaction product of ethylene- (meth) acrylic acid copolymer resin and polyurethane, the cover 14 includes an antioxidant, a colorant, a filler, a light stabilizer, an ultraviolet absorber, an ultraviolet ray, Stabilizers, fluorescent brighteners, dispersants, antistatic agents, and the like may be blended as necessary.

  Since the golf ball 10 having the cover 14 configured as described above has polyurethane in the cover 14, a soft feel at impact can be obtained when hit. In addition, since ethylene- (meth) acrylic acid copolymer resin such as ionomer resin and polyurethane are bonded via an amide bond, ethylene- (meth) acrylic acid copolymer resin and polyurethane are phase separated. Occurrence is significantly suppressed. Therefore, it is possible to avoid the occurrence of fluff during polishing. In addition, it is possible to avoid the occurrence of cracks when hitting, which ultimately improves the hit durability.

  Moreover, since it is derived from the ethylene- (meth) acrylic acid copolymer resin present in the cover 14 and exhibits high resilience, flight distance performance is also ensured.

  Furthermore, when hitting with a short iron or the like, the spin increases and the green is easily stopped. In other words, the golf ball 10 can be easily stopped at a position according to the player's intention and has excellent controllability.

  In the above-described embodiment, the single-layer solid core 12 has been described as an example of the core. However, a multi-layer solid core in which two or more layers are stacked may be used. Of course, the core may be a thread wound core.

  In any case, an inner cover may be further provided between the solid core 12 and the cover 14. An example of a suitable material for the inner cover is ionomer resin.

  A rubber composition was obtained by kneading cis-1,4-polybutadiene, zinc acrylate, zinc oxide, an antioxidant, and dicumyl peroxide at a mass ratio of 100: 30: 18: 0.3: 1. This rubber composition was put in a mold and vulcanized by performing heat treatment at 150 ° C. and 10 MPa for 20 minutes to produce a solid core. The obtained solid core had a diameter of 38.5 mm, a weight of 34.2 g, a specific gravity of 1.18, and a surface JIS-C hardness of 80.

  On the other hand, 100 g of each of High Milan 1555 and High Milan 1557 was introduced while circulating nitrogen gas through the separable glass flask, and then the temperature of the oil bath was raised to 150 ° C. to melt them.

  Then, while stirring the melt, 11.2 g of hexamethylene diisocyanate (HDI), 16.7 g of polypropylene glycol (PPG1000: number average molecular weight = 1000, 2 hydroxyl groups / 1000 g), 4.9 g of 2-ethyl-1 , 3-hexanediol (EHD) and 0.01 g di-n-butyltin dilaurate as catalyst were added simultaneously. Stirring was continued for another 20 minutes while maintaining the temperature to obtain a reaction product.

  After the reaction product was cooled, it was pulverized into pellets with a pulverizer to obtain a pulverized product. Further, this pulverized product was used for injection molding so as to cover the solid core, thereby forming a cover. Furthermore, the surface was polished and painted on the cover to produce a two-piece solid golf ball. This is Example 1.

  For comparison, the reaction was carried out according to Example 1 except that only HDI was first added to the mixture of Himilan 1555 and Himilan 1557, and PPG1000, HDI and di-n-butyltin dilaurate were added 5 minutes later. A product was obtained (Comparative Example 1). However, this product did not melt even when heated and could not be injection molded. Therefore, a cover could not be obtained.

  In addition, PPG1000, 4.9 g of EHD was replaced with polyethylene glycol (PEG1000: number average molecular weight = 1000, 2 hydroxyl groups / 1000 g), and 3.9 g of 1,6-hexanediol (HXD) was used. In accordance with 1, a two-piece solid golf ball was produced. This is Example 2.

  Further, in a separable glass flask in which nitrogen gas was circulated, 62.2 g of HDI, 234 g of polypropylene glycol (PPG3000: number average molecular weight = 3000, 2.34 hydroxyl groups / 3000 g), 23.7 g of HXD, 0.003. 1 g of di-n-butyltin dilaurate was mixed and the polymerization reaction was started after a slight induction period. The oil bath temperature was 70 ° C.

  After 12 hours, the mixture was cooled to obtain a polyurethane having an isocyanate group at the end. This was pulverized into pellets with a pulverizer to obtain a pulverized product, and a mixture in which the pulverized product, HiMilan 1555 and HiMilan 1557 were mixed at a mass ratio of 0.32: 1: 1 was kneaded with a biaxial kneader. . The produced reaction product was injection-molded so as to cover the solid core to form a cover. Furthermore, the surface was polished and painted on the cover to produce a two-piece solid golf ball. This is Example 3.

  In addition, after dissolving 50 g of Nucrel 1560 in a separable glass flask in which nitrogen gas was circulated, 25 g of HDI and 27.3 g of PPG 1000 were added. After 5 minutes, 10.5 g EHD and 0.01 g di-n-butyltin dilaurate were added and reacted. The oil bath temperature was 120 ° C.

  After completion of cooling, the product was pulverized into a pulverized product by a pulverizer, and 100 g of High Milan 1555 and High Milan 1557 were added and mixed while heating 82 g of the pulverized product. The produced reaction product was injection-molded so as to cover the solid core to form a cover. Furthermore, the surface was polished and painted on the cover to produce a two-piece solid golf ball. This is Example 4.

  In a separable glass flask in which nitrogen gas was circulated, 100.2 g of 4,4′-diphenylmethane diisocyanate (PMDI), 256 g of PPG3000, 23.6 g of HXD, 0.2 g of di-n-butyltin Dilaurate was mixed and reacted at 70 ° C. with stirring.

  After 12 hours, the mixture was cooled to obtain a polyurethane having an isocyanate group at the end. This was pulverized into pellets with a pulverizer to obtain a pulverized product, and a mixture in which the pulverized product, HiMilan 1555 and HiMilan 1557 were mixed at a mass ratio of 0.2: 1: 1 was kneaded with a biaxial kneader. . The produced reaction product was injection-molded so as to cover the solid core to form a cover. Furthermore, the surface was polished and painted on the cover to produce a two-piece solid golf ball. This is Example 5.

  For comparison, a two-piece solid golf ball was produced in accordance with Example 1 except that the amount of EHD was 7.3 g. This is referred to as Comparative Example 2.

  Further, a two-piece solid golf ball was manufactured by forming a cover from a mixed ionomer resin in which HiMilan 1555 and HiMilan 1557 are in a mass ratio of 1: 1. This is referred to as Comparative Example 3.

  The physical properties of the cover were evaluated for the two-piece solid golf balls of Examples 1 to 5 and Comparative Examples 2 and 3 described above. That is, while measuring the Shore D hardness of the cover, the raw material of the cover was placed on the substrate and heated to check whether it was melted to evaluate the thermal meltability. Furthermore, according to JISK7210, the melt flow rate in 190 degreeC and load 21.18N was measured, and the moldability was evaluated.

  Furthermore, while evaluating hit durability using each two-piece solid golf ball, the initial velocity at the time of hitting was measured. In terms of durability to impact, each ball was fired under the action of compressed air and repeatedly hit with a golf club head positioned and fixed, and whether or not damage occurred within 50 times was examined. On the other hand, the initial velocity is a result of measurement according to the measurement method specified by USGA. Higher initial speed means greater resilience.

  Furthermore, five players hit each golf ball with a driver and a putter to evaluate the hit feeling.

  The above physical properties and results of evaluation are also shown in FIG. From FIG. 2, it is clear that each of the two-piece solid golf balls of Examples 1 to 5 has excellent durability and good resilience, and a soft feel at impact can be obtained.

1 is a schematic overall cross-sectional view of a golf ball according to an embodiment. It is a table | surface which shows the composition ratio of each component of the raw material for covers in Examples 1-5 and Comparative Examples 1-3, the physical property of a cover, and the evaluation result of a ball | bowl.

Explanation of symbols

10 ... Golf ball 12 ... Solid core 14 ... Cover

Claims (4)

A golf ball having at least a core and a cover,
The cover contains a reaction product formed by forming an amide bond between a carboxyl group of an ethylene- (meth) acrylic acid copolymer resin and a terminal isocyanate group present at the terminal of the main chain of the polyurethane. A featured golf ball. The ball according to claim 1, wherein the polyurethane is a reaction product of a polymer diol compound, a monomolecular chain extender, and a diisocyanate, and a molar ratio of an isocyanate group to a hydroxyl group is represented by the following formula (1): A golf ball characterized by satisfaction.

  3. The golf ball according to claim 1, wherein the ethylene- (meth) acrylic acid copolymer resin is an ionomer resin.   The ball | bowl of any one of Claims 1-3 WHEREIN: The ratio of the said polyurethane in the said cover is 5-50 mass parts with respect to 100 mass parts of said ethylene- (meth) acrylic acid copolymer resin. A golf ball characterized by being.

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