JP2005230454A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball which is excellent in durability, repulsion, and abrasion resistance. <P>SOLUTION: The golf ball includes a cover where a composition for the cover constituting the cover contains a crystalline thermoplastic resin and an organic nucleating agent where a melting point is ≥250°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a golf ball having a cover.

Golf balls are required to have resilience (flying distance), durability, feel at impact, controllability, scratch resistance, and the like. It has been proposed to improve. For example, Patent Document 1 discloses a golf having a cover in which organic short fibers are mixed with a polymer component mainly composed of a thermoplastic elastomer for the purpose of improving controllability and cut resistance while maintaining resilience. A ball is disclosed. Patent Document 2 discloses a golf ball in which a core is covered with a cover in which a crystal nucleating agent is blended with 100 parts by mass of an ionomer resin.
JP 2002-136618 A Japanese Patent Application Laid-Open No. 60-14878

  In recent years, in order to improve controllability and resilience, the diameter of the core / thinning of the cover is progressing, and the level of resilience, durability, scratch resistance, etc. required for the cover is further increased. However, the following problems have been pointed out in the proposal as described above, for example. In the method of blending organic short fibers or inorganic fibers as disclosed in Patent Document 1 into the cover composition, it is difficult to uniformly disperse the fibers in the cover composition, and durability is improved. In order to improve, it is necessary to mix | blend in large quantities. However, when a large amount of the fiber is added to the cover composition, the resilience tends to decrease. Patent Document 2 discloses that triphenyl phosphate is blended in the cover composition as an organic crystal nucleating agent, but the organic crystal nucleating agent generally has a low melting point and blends the cover composition. Since it melts at the same time, it is difficult to uniformly disperse it in the cover composition. As a result, there is a problem that the improvement effect obtained is reduced. In addition, triphenyl phosphate is recognized as a harmful substance that exhibits neurotoxicity, and problems in health and safety have been pointed out.

  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 cover that is excellent in durability and resilience and excellent in scuff resistance.

  The golf ball of the present invention that has solved the above problems is a golf ball having a cover, wherein the cover composition constituting the cover is made of an organic structure having a crystalline thermoplastic resin and a melting point of 250 ° C. or higher. It contains a nucleating agent.

  As a result of repeated studies by the present inventors, when a thermoplastic resin having crystallinity and an organic nucleating agent having a melting point of 250 ° C. or more are blended in the cover composition constituting the cover, durability and repulsion are obtained. It has been found that a golf ball having improved properties and excellent scratch resistance can be obtained. The reason why durability and resilience are improved by using the organic nucleating agent is not clear, but is considered to be as follows. That is, in the present invention, since an organic nucleating agent is used, an excellent effect can be obtained with a relatively small addition amount, and a large amount such as an inorganic nucleating agent or an inorganic reinforcing material is blended. It is not necessary, and the characteristics of the crystalline thermoplastic resin that is the base material of the cover composition can be fully utilized. In addition, since an organic nucleating agent having a melting point of 250 ° C. or higher is used as a temperature higher than the temperature at which the cover is molded, the organic nucleating agent is uniformly dispersed in the cover composition without melting. Therefore, the crystallinity of the thermoplastic resin having crystallinity can be increased uniformly. In the present invention, it is considered that a golf ball excellent in durability, resilience, and abrasion resistance can be obtained by utilizing these characteristics.

  Preferred as the organic nucleating agent having a melting point of 250 ° C. or higher for use in the present invention is a phosphate metal salt. This is because the phosphoric acid ester metal salt often has a melting point of 250 ° C. or higher, and is known to have a nucleating action on the crystalline thermoplastic resin. The phosphoric acid ester metal salt is a sodium salt of phosphoric acid (tert-butylphenyl) ester, and more preferably 2,2-methylenebis (4,6-di-tert-phosphate) having a melting point of 400 ° C. or higher. -Butylphenyl) sodium or bis (4-tert-butylphenyl) sodium phosphate having a melting point of 300 ° C. or higher. This is because the sodium salt of phosphoric acid (tert-butylphenyl) ester has an excellent nucleating action. As the cover composition, for example, it is preferable to use a composition containing 0.01 to 0.4 parts by mass of the organic nucleating agent with respect to 100 parts by mass of the crystalline thermoplastic resin component. .

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

  The golf ball of the present invention is a golf ball having a cover, wherein the cover composition constituting the cover contains a crystalline thermoplastic resin and an organic nucleating agent having a melting point of 250 ° C. or higher. Features. First, the organic nucleating agent having a melting point of 250 ° C. or higher used in the present invention will be described. An organic nucleating agent, for example, has an action of regulating the crystal formation process, such as shortening the crystallization when added to a crystalline polymer, or refining the produced crystal. If it is, it will not be specifically limited. In the present invention, the organic nucleating agent having a melting point of 250 ° C. or higher is used for the following reason. The molding of the cover is usually performed at about 150 ° C to 240 ° C. If an organic nucleating agent having a melting point higher than the molding temperature of the cover is used, the organic nucleating agent is not melted and uniformly dispersed in the cover composition when the cover is molded. be able to. As a result, the crystallinity of the crystalline thermoplastic resin that becomes the base material of the cover can be increased uniformly.

  The melting point of the organic nucleating agent used in the present invention is preferably 280 ° C. or higher, more preferably 300 ° C. or higher. The upper limit of the melting point is not particularly limited, but is preferably about 1000 ° C., more preferably 900 ° C., and still more preferably 800 ° C. The melting point of the organic nucleating agent can be measured according to a known method, for example, JISK6201.

  In addition, the organic nucleating agent used in the present invention is granular, and an average particle size thereof is 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1.0 μm or more. desirable. By setting the average particle size to 0.1 μm or more, the dispersibility in the cover composition can be enhanced. The upper limit of the average particle diameter is not particularly limited, but is preferably 100 μm, more preferably 50 μm, and still more preferably 20 μm. This is because if the average particle size becomes too large, the durability may be lowered. The average particle size of the organic nucleating agent can be measured by a laser diffraction / scattering particle size distribution measuring apparatus “LA-920” manufactured by HORIBA based on the Mie scattering theory as a measurement principle.

  The content of the organic nucleating agent in the cover composition is not particularly limited, but is 0.01 parts by mass or more with respect to 100 parts by mass of the thermoplastic resin component having crystallinity. Is more preferably 0.02 parts by mass or more, and still more preferably 0.04 parts by mass or more. This is because when the content is 0.01 parts by mass or more, the addition effect of the organic nucleating agent becomes clear. The upper limit of the content of the organic nucleating agent in the rubber composition is not particularly limited, but is preferably 0.4 parts by mass, more preferably 0.3 parts by mass. More preferably, it is 0.2 parts by mass. This is because the effect of adding the organic nucleating agent can be increased by setting the content to 0.4 parts by mass or less.

  Examples of the organic nucleating agent having a melting point of 250 ° C. or higher used in the present invention include phosphate ester metal salts and carboxylic acid esters having a melting point of 250 ° C. or higher. Preference is given to using phosphate ester metal salts. This is because the phosphoric acid ester metal salt has a high melting point and exhibits an excellent nucleating action with respect to the crystalline thermoplastic resin. Examples of the metal type of the metal salt include alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, and metals such as aluminum and zinc.

  The phosphoric acid ester metal salt is preferably a sodium salt of phosphoric acid (tert-butylphenyl) ester. For example, 2,2-methylenebisphosphate having a melting point of 400 ° C. or higher manufactured by Asahi Denka Kogyo Co., Ltd. 4,6-di-tert-butylphenyl) sodium (Adekastab NA-11, decomposition temperature 452 ° C.), bis (4-tert-butylphenyl) sodium phosphate (Adekastab NA-10, decomposition having a melting point of 300 ° C. or higher) A temperature of 393 ° C.) can be preferably used.

  The cover composition used in the present invention contains, in addition to the organic nucleating agent, a crystalline thermoplastic resin that serves as a base material for the cover. The crystalline thermoplastic resin used in the present invention is not particularly limited as long as it has crystallinity and thermoplasticity. In the present invention, the thermoplastic resin having crystallinity means having a regularly oriented molecular chain structure (crystal structure) in at least a part, for example, X-ray diffraction, light scattering, X-ray small angle scattering. The presence / absence, form, etc. of the crystal structure can be confirmed by observation with an electron microscope.

  Examples of the crystalline thermoplastic resin include a urethane resin, an ionomer resin, a polyester resin, a polyamide resin, a diene block copolymer, and the like, or a mixture of at least two of these. An ionomer resin is preferred. This is because a cover having excellent durability can be obtained by using an ionomer resin.

  Examples of the crystalline thermoplastic ionomer resin include those obtained by neutralizing at least one part of a carboxyl group in a copolymer of ethylene and an α, β-unsaturated carboxylic acid with a metal ion, or ethylene and α, β- Examples thereof include those obtained by neutralizing at least a part of carboxyl groups in a terpolymer of an unsaturated carboxylic acid and an α, β-unsaturated carboxylic acid ester with a metal ion.

  Examples of the metal ions for neutralization include monovalent metal ions such as sodium ion, potassium ion and lithium ion; divalent metal ions such as zinc ion, calcium ion, magnesium ion, copper ion and manganese ion; aluminum ion and neodymium Examples include trivalent metal ions such as ions. Zinc ions are particularly preferable because they have a high binding force of metal ion aggregates and a small decrease in mechanical strength due to dispersion of crosslinked diene rubber particles. Specific examples of the thermoplastic ionomer resin having crystallinity include Himilan 1605 (trade name of sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin) manufactured by Mitsui DuPont Polychemical Co., Ltd., Himiran 1707 (in sodium ion) Japanese ethylene-methacrylic acid copolymer ionomer resin trade name), Himiran 1706 (zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin trade name), Himiran AM7315 (zinc ion neutralized ethylene-methacrylic acid copolymer system) Product name of ionomer resin), Himiran AM7317 (product name of zinc ion neutralized ethylene-methacrylic acid copolymer system ion), Himiran 1555 (sodium ion neutralized ethylene-methacrylic acid copolymer system iono) -Product name of resin), Himiran 1557 (product name of zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Iontech 8000 (sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin) manufactured by Exxon Chemical Co., Ltd. Product name), Iotech 7010 (product name of zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Surlyn 7930 manufactured by DuPont (product name of lithium ion neutralized ethylene-methacrylic acid copolymer ionomer resin) Surlyn 9945 (trade name of zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Surlyn 8945 (trade name of sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin), and the like.

  Other crystalline thermoplastic resins that can be used in the present invention are commercially available from Toray Industries, Inc. under the trade name “Pebax” (for example, “Pebax 2533”), a thermoplastic polyamide resin from Toray DuPont Co., Ltd. A thermoplastic polyester resin marketed under the trade name “Hytrel” (for example, “Hytrel 3548”, “Hytrel 4047”), and commercially available under the trade name “Elastollan” from BASF Japan (for example, “Elastollan ET880”). ") Thermoplastic polyurethane resin etc. are mentioned.

  The diene block copolymer that can be used as a crystalline thermoplastic resin has a double bond derived from a conjugated diene compound of a block copolymer or a partially hydrogenated block copolymer. The block copolymer as the substrate is a block copolymer comprising a polymer block A mainly composed of at least one vinyl aromatic compound and a polymer block B mainly composed of at least one conjugated diene compound. It is. The partially hydrogenated block copolymer is obtained by hydrogenating the block copolymer. Examples of the vinyl aromatic compound constituting the block copolymer include one or two or more of styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, 1,1-diphenylstyrene, and the like. Styrene is preferred. Moreover, as a conjugated diene compound, 1 type (s) or 2 or more types can be selected from butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc., for example, Isoprene and combinations thereof are preferred. Examples of a preferred diene block copolymer include a block copolymer having an SBS (styrene-butadiene-styrene) structure having a polybutadiene block containing an epoxy group, or a SIS (styrene-isoprene-styrene) having an epoxy group. Examples thereof include a block copolymer having a structure. Specific examples of the diene block copolymer include “Epofriend A1010” manufactured by Daicel Chemical Industries, Ltd. and “Septon HG-252” manufactured by Kuraray Co., Ltd.

  The cover composition used in the present invention includes, in addition to the above-described crystalline thermoplastic resin and organic nucleating agent having a melting point of 250 ° C. or more, pigment components such as oil, zinc, titanium oxide, and blue pigment, Specific gravity adjusting agents such as calcium carbonate and barium sulfate, dispersants, anti-aging agents, ultraviolet absorbers, light stabilizers, fluorescent materials or fluorescent brighteners may be contained within a range that does not impair the performance of the cover.

  The hardness (slab hardness) of the cover of the golf ball of the present invention is preferably 45 or more in Shore D hardness, more preferably 46 or more, and further preferably 47 or more. This is because if the cover is too soft, the spin rate may increase and the flight distance may decrease. The cover hardness is preferably 66 or less in Shore D hardness, more preferably 65 or less, and further preferably 64 or less. This is because if the cover hardness is too high, the spin rate tends to decrease and the controllability tends to decrease.

  Moreover, the thickness of the cover of the golf ball of the present invention is not particularly limited, but is preferably 0.4 mm or more, more preferably 0.5 mm or more, and further preferably 0.6 mm or more. By setting the cover thickness to 0.4 mm or more, the cover can be easily formed. This is because if the cover thickness is too thin, the moldability of the cover becomes difficult and the productivity is lowered. Moreover, it is preferable that the thickness of a cover is 1.9 mm or less, More preferably, it is 1.8 mm or less, More preferably, it is 1.6 mm or less. If the cover is too thick, the spin rate may increase and the flight performance of the golf ball may be reduced.

  The present invention is not particularly limited as long as it is a golf ball having a cover formed from the above-described crystalline thermoplastic resin and a cover composition containing an organic nucleating agent having a melting point of 250 ° C. or higher. The present invention can be applied to any aspect of a ball, a two-piece golf ball, or a three-piece or more multi-piece golf ball. This is because, in any embodiment, by applying the present invention, a golf ball having a cover excellent in durability, resilience, and scratch resistance can be obtained.

  Hereinafter, although the method of manufacturing the golf ball of the present invention will be described based on the aspect of the two-piece golf ball, the present invention is not limited to such a manufacturing method. As a core of a two-piece golf ball, a conventionally known core can be used. For example, a core rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, and a filler is heated and pressed. It is preferable to use what was done.

  As the base rubber, natural rubber and / or synthetic rubber can be used. For example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like can be used. Among these, it is particularly preferable to use a high-cis polybutadiene having a cis bond advantageous for repulsion of 40% or more, preferably 70% or more, more preferably 90% or more.

  The co-crosslinking agent is not particularly limited as long as it has a function of crosslinking rubber molecules by graft polymerization to rubber molecular chains. For example, α, β-unsaturated carboxylic acid and / or metal salt thereof is used. Can be mentioned. Examples of the α, β-unsaturated carboxylic acid and / or metal salt thereof include, for example, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and / or a metal salt thereof, and more preferably acrylic. Examples thereof include acid, methacrylic acid, zinc acrylate, and zinc methacrylate. In particular, it is also preferable to use a zinc salt or a magnesium salt as the metal salt, and the resilience of the resulting golf ball can be increased. The content of the co-crosslinking agent in the core rubber composition is preferably 15 parts by mass or more, more preferably 18 parts by mass or more with respect to 100 parts by mass of the base rubber component. By setting it as 15 mass parts or more, the hardness of the obtained molded object can be made moderate. This is because if the molded body becomes too soft, the amount of deformation at the time of impact increases, and the adhesion of the coating film may decrease. Moreover, it is preferable that content of the said co-crosslinking agent in a rubber composition is 45 mass parts or less with respect to 100 mass parts of base rubber components, More preferably, it is 38 mass parts or less. By setting it to 45 parts by mass or less, a suitable shot feeling can be obtained.

  The organic peroxide is blended to crosslink the base rubber component, and is 0.2 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the base rubber component. It is desirable that 5 parts by mass or less, more preferably 3 parts by mass or less is blended. If it is less than 0.2 parts by mass, the core tends to be too soft and the resilience tends to decrease. If it exceeds 5 parts by mass, it is necessary to increase the amount of co-crosslinking agent used in order to obtain an appropriate hardness. There is a lack of resilience. Examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxide). Oxy) hexane, di-t-butyl peroxide, etc. are mentioned, and it is preferable to use dicumyl peroxide.

  Examples of the filler contained in the core rubber composition include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The blending amount of the filler is 2 parts by mass or more, more preferably 3 parts by mass or more, and 50 parts by mass or less, more preferably 35 parts by mass or less with respect to 100 parts by mass of the base rubber. desirable. If the blending amount of the filler is less than 2 parts by mass, it is difficult to adjust the weight, and if it exceeds 50 parts by mass, the weight fraction of the rubber component tends to decrease and the resilience tends to decrease.

  In addition to the base rubber, co-crosslinking agent, organic peroxide, and filler, the core rubber composition further contains an organic sulfur compound, an antioxidant, a peptizer, or the like as appropriate. be able to. The blending amount of the anti-aging agent is preferably 0.1 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the base rubber. Moreover, it is preferable that a peptizer is 0.1 to 5 mass parts with respect to 100 mass parts of base rubber.

  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 to 200 ° C. for 10 to 60 minutes, or at 130 to 150 ° C. for 20 to 40 minutes. After heating, it is preferable to heat at 160 to 180 ° C. for 2 to 5 minutes.

  In the present invention, the core molded as described above is coated with a cover composition containing the above-described crystalline thermoplastic resin, an organic nucleating agent having a melting point of 250 ° C. or higher, and the like to produce a golf ball body. . As a method for molding the cover, for example, first, the cover composition is formed in advance into a hemispherical half shell, the core is wrapped with two of them, and pressure molded at 130 to 170 ° C. for 1 to 5 minutes. Method: A method of injection molding the cover composition so as to cover the core is applied.

  Further, when a golf ball body is manufactured by covering a cover, a depression called dimple is usually formed on the surface. Further, the surface of the golf ball body may be subjected to a polishing process such as a sand blast process. The golf ball of the present invention is also preferably subjected to normal paint finish, marking stamp, etc. in order to enhance aesthetics and commercial value.

  In the above-described manufacturing method, the description has been made based on the mode of the two-piece golf ball. For example, in the case of a thread-wound golf ball, a thread-wound core may be used. At least one or more intermediate layers can be provided therebetween.

  The thread winding core includes a center and a thread rubber layer formed by winding a thread rubber around the center in a stretched state, and a conventionally known one can be used. As the center, either a liquid system (liquid center) or a rubber system (solid center) may be used. The thread rubber wound on the center can 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 | curing the rubber composition which mix | blended the vulcanization | cure adjuvant, the vulcanization accelerator, anti-aging agent, etc. The thread rubber is stretched about 10 times on the center and wound to form a thread wound core.

  Further, as an intermediate layer of a multi-piece golf ball having three or more pieces, the same ones that can be used as the thermoplastic resin constituting the cover can be used. For example, the above-described thermoplastic ionomer resin and thermoplastic polyamide resin can be used. Further, thermoplastic resins such as thermoplastic polyester resins and thermoplastic urethane resins, diene block copolymers, and the like can be used. The intermediate layer may further contain a specific gravity adjusting agent such as barium sulfate or tungsten, an anti-aging agent, or a pigment.

  The method for forming the intermediate layer is not particularly limited. For example, the intermediate layer forming material is previously formed into a hemispherical half-shell, and the two are used to wrap the solid center and press-mold, Alternatively, a method of wrapping the solid center by injection molding the intermediate layer material directly on the solid center can be employed.

  When the present invention is applied to a two-piece golf ball or a multi-piece golf ball, the diameter of the core (excluding the cover constituting the outermost layer) is preferably 38.0 mm or more, more preferably 39.5 mm or more, More preferably, it is 40.8 mm or more. This is because if the core diameter is less than 38.0 mm, the cover becomes too thick and the resilience is lowered. The upper limit of the core diameter is not particularly limited, but is preferably 42.2 mm, more preferably 42.0 mm, and further preferably 41.8 mm. This is because if the core diameter exceeds 42.2 mm, the cover becomes relatively thin, and the protective effect by the cover cannot be sufficiently obtained.

  The core preferably has a compressive deformation amount of 2.50 mm or more, more preferably 2.60 mm or more, and even more preferably 2 when a final load of 1275 N is applied from a state in which an initial load of 98 N is applied. .70 mm or more. When the amount of deformation is too small, the core becomes hard and the feel at impact tends to decrease. On the other hand, the upper limit of the amount of compressive deformation when a final load of 1275N is applied from a state in which an initial load of 98N is applied is not particularly limited, but is preferably 4.50 mm, more preferably 4.30 mm, and even more preferably. Is 4.00 mm. If the amount of deformation is too large, it may become too soft and the feel at impact may be felt heavy.

  The golf ball of the present invention preferably has an amount of compressive deformation of 2.1 mm or more, more preferably 2.3 mm or more, and more preferably 2.3 mm or more when a final load of 1275 N is applied from a state where an initial load of 98 N is applied. Is 2.5 mm or more. This is because if the amount of deformation is too small, the feel at impact is hardened and reduced. On the other hand, the upper limit of the amount of compressive deformation when the final load 1275N is applied from the state in which the initial load 98N is applied is not particularly limited, but is preferably 4.0 mm, more preferably 3.8 mm, and still more preferably. Is 3.5 mm. If the amount of deformation is too large, it may become too soft and the feel at impact may be felt heavy.

  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) Golf ball restitution coefficient In an environment of 23 ° C. and 50% RH, 200 g of an aluminum cylinder is caused to collide with each golf ball at a speed of 45 m / sec, and the speed of the cylinder and the golf ball before and after the collision is determined. Measurement was made, and the coefficient of restitution of each golf ball was calculated from the respective speeds and masses. The measurement was performed five times for each golf ball, and the average value was used as the restitution coefficient of each golf ball.

  The coefficient of restitution is the golf ball no. The value of 7 is taken as 100, and is shown as an indexed value. The larger the coefficient of restitution, the better the golf ball.

(2) Durability of golf balls A metal head # 1 driver is attached to a swing robot manufactured by Trutemper, the head speed is set to 45 m / s, and 12 golf balls are struck for each golf ball. The collision was evaluated. As the evaluation criteria, the number of repeated hits until the golf ball was broken was measured, the average of 12 golf balls was calculated, and the evaluation result of each golf ball was used. Durability is determined according to golf ball no. The value of 7 is shown as an indexed value with 100, and the larger the value, the better the durability.

(3) Golf ball scuff resistance A commercially available pitching wedge (PW) is attached to a swing robot manufactured by True Temper, and the head speed is set to 36 m / s. The hit | damage part of the location was observed visually and evaluated by the following evaluation criteria.
○: Scratches may remain on the ball surface, but there is no fuzz △: Scratches remain clearly on the ball surface and a little fuzz is seen ×: The ball surface is considerably shaved and fuzz is conspicuous

(4) Compression deformation (mm)
The amount of deformation in the compression direction (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98N was applied to the golf ball or core to when the final load 1275N was applied was measured.

(5) Cover hardness (slab hardness)
The cover composition was formed into a sheet having a thickness of about 2 mm by hot press molding and stored at 23 ° C. for 2 weeks. This sheet was measured using a spring type hardness meter Shore D type defined in ASTM-D2240 in a state where three or more sheets were stacked so that the measurement substrate or the like was not affected.

[Create two-piece golf ball body]
(1) Production of core A rubber composition for a core having the composition shown in Table 1 is kneaded and heated and pressed at 170 ° C. for 15 minutes in an upper and lower mold having hemispherical cavities to obtain a spherical core having a diameter of 41.2 mm. It was. The amount of compressive deformation of the obtained spherical core was 2.95 mm.

Polybutadiene rubber: BR18 manufactured by JSR (cis content 96% or more)
Zinc acrylate: ZNDA-90S manufactured by Nippon Distilled
Zinc Oxide: Toho Zinc Gin R
Diphenyl disulfide: Dicumyl peroxide manufactured by Sumitomo Seika Co., Ltd .: Park mill D manufactured by NOF Corporation

(2) Production of Cover The cover material shown in Table 2 was mixed with 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 170-240 ° C. at the die position of the extruder. The obtained cover composition was coated on the core by injection molding, and then the golf ball body was taken out of the mold, deburred, and then painted with a clear paint on the surface to have a diameter of 42.8 mm and a weight of 45 .4 g of a golf ball was obtained.

High Milan 1605: Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. High Milan 1706: Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui Du Pont Polychemical Co., Ltd. ADK STAB NA-10: Bis (4-tert-butylphenyl) sodium phosphate having a melting point of 300 ° C. or higher ADK STAB NA-11: 2,2-methylene bis (4,6-diphosphate) having a melting point of 400 ° C. or higher -Tert-butylphenyl) sodium triphenyl phosphate: melting point 49 ° C., L-100 manufactured by Fuji Talc
Organic short fiber: nylon short fiber reinforced polymer LA1060 manufactured by Ube Industries, Ltd.
Aluminum borate whisker: melting point 1440 ° C., Shikoku Kasei Kogyo Arbolex Y3A (surface-treated with aminosilane coupling agent)

  The results of evaluating the two-piece golf ball obtained as described above are shown together in Table 2.

  Table 2 shows that the two-piece golf ball No. 1 has a cover formed of a cover composition containing a crystalline thermoplastic resin and an organic nucleating agent having a melting point of 250 ° C. or higher. 1-No. No. 6 is excellent in resilience, durability, and scratch resistance. In particular, golf ball no. 1-No. 4 is compared, by increasing the content of the organic nucleating agent with respect to 100 parts by mass of the crystalline thermoplastic resin component in the cover composition, the resilience, durability, and scratch resistance are increased. It can be seen that it is improved. On the other hand, golf ball No. From the result of 5, it was found that even if the content of the organic nucleating agent is excessively increased, the improvement effect is reduced. From these results, by setting the content of the organic nucleating agent to 0.01 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the crystalline thermoplastic resin component in the cover composition. It can be seen that a two-piece golf ball having excellent resilience, durability, and scratch resistance can be obtained.

  Golf ball no. 8 and no. 9 is a case where the cover composition uses triphenyl phosphate having a melting point of 49 ° C. as a crystal nucleating agent, but the dispersibility in the cover composition is poor, the resilience, the scratch resistance, etc. Decreased. Golf ball no. No. 10 is a case where the cover composition contains organic short fibers, and there was a tendency that all of resilience, durability, and scratch resistance were lowered. Golf ball no. 11 is a case containing an aluminum borate whisker, and the resilience was remarkably lowered.

  The present invention is applicable to a golf ball having a cover, and is suitable for, for example, a thread wound golf ball, a two-piece golf ball, a multi-piece golf ball, and the like.

Claims (5)

  A golf ball having a cover, wherein the cover composition constituting the cover contains a crystalline thermoplastic resin and an organic nucleating agent having a melting point of 250 ° C. or higher.   The golf ball according to claim 1, wherein the organic nucleating agent is a phosphate metal salt.   The golf ball according to claim 1, wherein the organic nucleating agent is a sodium salt of phosphoric acid (tert-butylphenyl) ester.   The organic nucleating agent is sodium 2,2-methylenebis (4,6-di-tert-butylphenyl) phosphate having a melting point of 400 ° C. or higher, or bis (4 (4) phosphate having a melting point of 300 ° C. or higher. The golf ball according to claim 1, which is -tert-butylphenyl) sodium.   The said composition for covers contains 0.01-0.4 mass part of said organic nucleating agents with respect to 100 mass parts of said thermoplastic resins. Golf ball.