JP2012130676A - Multi-piece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve flight performance and obtain a good, solid feel on impact.SOLUTION: A multi-piece solid golf ball G has a core 1, at least one intermediate layer 2 coating the core, and a cover 3 of at least one layer coating the intermediate layer. The core is formed of a base rubber, and the intermediate layer and cover are each formed of a resin material. A ratio (a)/(b) is from 0.7 to 1.9, wherein the intermediate layer has a thickness (a) and the cover has a thickness (b). A ratio (c)/(a) is from 23 to 38, wherein the core has a diameter (c) and the above intermediate layer has the thickness (a). The intermediate layer has a material hardness (Shore D) of from 42 to 76, and the cover has a material hardness (Shore D) of from 41 to 69. The ball satisfies the following relationship: the cover material hardness is less than the intermediate layer material hardness, and the intermediate layer material hardness is more than the core surface hardness.

Description

  The present invention relates to a multi-piece solid golf ball formed by laminating a core, an intermediate layer, and a cover layer. More specifically, the present invention further improves flying performance and provides a firm and good feel. Related to a multi-piece solid golf ball.

  Conventionally, as a solid golf ball to meet the demands of professional golfers and amateur advanced players, an intermediate layer is interposed between the core and cover as described below, and a three-piece structure that defines the hardness and thickness of each layer Many golf balls have been proposed. Among these proposals, there are golf balls with improved spin, flight and durability.

  US Pat. No. 6,632,149 proposes a golf ball in which the intermediate layer / cover has a soft / hard hardness relationship and the intermediate layer is formed thin. Japanese Patent No. 4109778 proposes a golf ball in which the intermediate layer / cover has a soft / hard hardness relationship and the core hardness distribution is optimized. Japanese Patent No. 4045089 proposes a golf ball in which the intermediate layer / cover has a hard / soft hardness relationship and the intermediate layer has a thickness of less than 1 mm. Japanese Patent No. 4247030 proposes a golf ball in which the intermediate layer / cover has a soft / hard hardness relationship and polyurethane is used for the cover material. Japanese Patent No. 2910516 proposes a golf ball in which a cover is formed relatively thicker than an intermediate layer. Japanese Patent No. 3661812 proposes a golf ball in which the hardness difference between the core surface and the intermediate layer is optimized, the intermediate layer / cover has a hard / soft hardness relationship, and the dimple design is devised. Japanese Patent No. 3516125 proposes a golf ball in which the cover is made of polyurethane and the intermediate layer / cover has a hard / soft hardness relationship and the dimple design is devised. Japanese Patent No. 3601582 proposes a golf ball in which the deflection amount, intermediate layer hardness, and cover hardness at a predetermined load of the core are optimized and the dimple ballistic volume is optimized in quantity.

  However, the golf balls proposed above still have inadequate improvements, and a well-balanced improvement that achieves both low spin, increased W # 1 flight distance and good feel is desired. It is rare.

US Pat. No. 6,632,149 Japanese Patent No. 4109778 Japanese Patent No. 4045089 Japanese Patent No. 4247030 Japanese Patent No. 2910516 Japanese Patent No. 3661812 Japanese Patent No. 3516125 Japanese Patent No. 3601582

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-piece solid golf ball that sufficiently combines excellent flying and a solid good hit feeling.

  As a result of intensive studies to achieve the above object, the present inventor has formed the core with a base rubber in a multi-piece solid golf ball having an intermediate layer interposed between the core and the cover, and the intermediate layer And each layer of the cover is made of a resin material, the ratio (a) / (b) of the thickness (a) of the intermediate layer to the thickness (b) of the cover is within a predetermined range, and By setting the ratio (c) / (a) of the diameter (c) to the thickness (a) of the intermediate layer within a predetermined range, the material hardness of the intermediate layer and the material hardness of the cover are optimized. The rebound characteristics of the driver are improved, the effect of reducing the spin rate when hitting the driver is improved, the flight distance is expected to increase sufficiently, and furthermore, a solid and good hit feeling can be obtained when hitting by the driver. Heading, what led to the present invention A.

Accordingly, the present invention provides the following multi-piece solid golf ball.
[1] In a multi-piece solid golf ball comprising a core, at least one intermediate layer covering the core, and at least one cover covering the intermediate layer, the core is formed of a base rubber, Each layer of the intermediate layer and the cover is formed of a resin material, and a ratio (a) / (b) between the thickness (a) of the intermediate layer and the thickness (b) of the cover is 0.7 to 1. 0.9, and the ratio (c) / (a) of the core diameter (c) to the thickness (a) of the intermediate layer is 23 to 38, and the material hardness of the intermediate layer is Shore D A multi-piece solid golf ball characterized in that the material hardness of the cover is 41 to 69 for Shore D, and the cover material hardness <intermediate layer material hardness> core surface hardness is satisfied.
[2] The multi-piece solid golf ball according to [1], wherein a value obtained by subtracting the center hardness (Shore D hardness) from the surface hardness (Shore D hardness) of the core is 17 or less.
[3] The amount of deflection (mm) from when the initial load 98N (10 kgf) is applied to the ball to when the final load 490N (50 kgf) is applied is (A), and the initial load 98N ( (B) / (A) × 100 is 830 to 930, where (B) is the amount of deflection (mm) from when 10 kgf) is applied to when the final load is 5880 N (600 kgf). The multi-piece solid golf ball according to [1] or [2].
[4] When the deflection amount (B) of the ball is 7.0 to 10.0 mm, and the initial load of 98N (10 kgf) is applied to the core and the final load of 1275 N (130 kgf) is applied. The multi-piece solid golf ball according to [3], wherein the amount of deflection is 2.1 to 4.1 mm.
[5] The resin material of the cover is formed by injection molding a single resin composition mainly composed of (A) a thermoplastic polyurethane and (B) a polyisocyanate compound, and the resin composition The multi-component according to any one of [1] to [4], wherein a polyisocyanate compound in which all of the isocyanate groups in one molecule remain in an unreacted state is present at least partially. Peace solid golf ball.
[6] A large number of dimples are formed on the ball surface, the total number of dimples is 250 to 350, the dimple surface occupancy (SR) is 75% or more, and the Reynolds number is 70000 when the ball is hit. The multi-piece solid golf ball according to any one of [1] to [5], wherein the lift coefficient CL of the ball at a spin amount of 2000 rpm is 60% or more of the lift coefficient CL at a Reynolds number of 80000 and a spin amount of 2000 rpm.
[7] The multi-piece solid golf ball according to [6], wherein five or more kinds of dimples having different diameters and / or depths are used, and 6 to 30 small dimples having a diameter of 3.0 mm or less are included.

  The multi-piece solid golf ball of the present invention can further improve the flight performance and obtain a firm and good hit feeling.

It is a schematic sectional drawing of the multi-piece solid golf ball (three-layer structure) of this invention. The dimple pattern used with the ball | bowl of a present Example is represented, (A) is a front view, (B) is a side view.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1, the multi-piece solid golf ball of the present invention is a golf ball G that includes a core 1, an intermediate layer 2 that covers the core, and a cover 3 that covers the intermediate layer. In addition, a large number of dimples D are formed on the cover surface. The core 1, the intermediate layer 2, and the cover 3 are not limited to a single layer, but can be formed in a plurality of layers of two or more layers.

  In the present invention, the diameter of the core is not particularly limited, but is preferably 35.7 mm or more, more preferably 36.7 mm or more, and further preferably 37.7 mm or more. The upper limit of the diameter is not particularly limited, but is preferably 41.7 mm or less, more preferably 40.7 mm or less, and further preferably 39.7 mm or less. If the diameter of the core deviates from this range, the initial ball speed may be lowered or the feel at impact may be deteriorated.

  The central hardness of the core is not particularly limited, but is preferably Shore D hardness of 35 or more, more preferably 36 or more, and still more preferably 37 or more. The upper limit is not particularly limited, but is preferably 54 or less, more preferably 53 or less, and still more preferably 52 or less. If the above value is too small, there is a case where the rebound is not sufficient and the flight distance cannot be obtained. On the other hand, if the above value is too large, the amount of spin at the time of a full shot with the driver becomes too large, and as a result, the flight distance may not be obtained and the hit feeling may be hard.

  The surface hardness of the core is not particularly limited, but the Shore D hardness is preferably 45 or more, more preferably 50 or more, and further preferably 55 or more. The upper limit is not particularly limited, but is preferably 73 or less, more preferably 68 or less, and still more preferably 63 or less. If the above value is too small, the rebound is insufficient and the flight distance does not come out, and the crack durability when repeatedly hit may be deteriorated. On the other hand, if the above value is too large, the hit feeling at the time of a full shot will be hard, and the spin distance may increase so that the flight distance may not be obtained.

  The value obtained by subtracting the center hardness (Shore D hardness) from the core surface hardness (Shore D hardness) is not particularly limited, but is preferably 17 or less, more preferably 16 or less, and even more preferably 15 or less. is there. If this value is too large, the ball at the time of a full shot will be greatly deformed and an initial speed loss will occur, with the result that a sufficient flight distance may not be obtained.

  The amount of deflection when the core is loaded, that is, the amount of deflection (mm) from when the initial load of 98 N (10 kgf) is applied to when the final load of 1,275 N (130 kgf) is applied to the core, Although there is no restriction | limiting in particular, Preferably it is 2.1 mm or more, More preferably, it is 2.4 mm or more, More preferably, it is 2.7 mm or more. The upper limit is not particularly limited, but is preferably 4.1 mm or less, more preferably 3.8 mm or less, and still more preferably 3.5 mm or less. If this value is too small, the ball does not have sufficient rebound and the flight distance does not come out, and the crack durability when repeatedly hit may be deteriorated. On the other hand, if the above value is too large, the feeling of hitting at the time of full shot becomes hard, and the spin may be increased so that the flight distance may not be obtained.

  The core material having the desired physical properties is not particularly limited. For example, a rubber composition containing a co-crosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound, or the like is used. Can be formed. It is preferable to use polybutadiene as the base rubber of the rubber composition.

  The polybutadiene preferably has cis-1,4-bond in the polymer chain of 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 95% by mass or more. It is. If there are too few cis-1,4-bonds in the bonds in the molecule, the resilience may decrease.

  The content of 1,2-vinyl bond contained in the polybutadiene is usually 2% or less, preferably 1.7% or less, more preferably 1.5% or less in the polymer chain. If the content of 1,2-vinyl bond is too large, the resilience may be lowered.

  The polybutadiene is preferably synthesized from a rare earth element-based catalyst or a Group VIII metal compound catalyst from the viewpoint of obtaining a vulcanized molded product of a rubber composition that has a high resilience and increases a flight distance as a ball. In particular, those synthesized with a rare earth element-based catalyst are particularly preferable.

  Such a rare earth element-based catalyst is not particularly limited. For example, a catalyst obtained by combining a lanthanum series rare earth element compound with an organoaluminum compound, an alumoxane, a halogen-containing compound, and a Lewis base as necessary. Can be mentioned.

  Examples of the lanthanum series rare earth element compounds include metal halides having an atomic number of 57 to 71, carboxylates, alcoholates, thioalcolates, and amides.

  In particular, the use of a neodymium-based catalyst using a neodymium compound as a lanthanum-based rare earth element compound results in excellent polymerization activity of polybutadiene rubber having a high content of cis-1,4-bonds and a low content of 1,2-vinyl bonds. Specific examples of these rare earth element-based catalysts are preferably those described in JP-A-11-35633, JP-A-11-164912, and JP-A-2002-293996. be able to.

  The polybutadiene synthesized using a lanthanum series rare earth element compound-based catalyst is preferably contained in the rubber component in an amount of 10% by mass or more, preferably 20% by mass or more, particularly 40% by mass or more in order to improve resilience. .

  In addition to the polybutadiene, other rubber components can be blended with the rubber base material as long as the effects of the present invention are not impaired. Examples of the rubber component other than the polybutadiene include polybutadiene other than the polybutadiene, and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

  Examples of the co-crosslinking agent include unsaturated carboxylic acids and unsaturated carboxylic acid metal salts.

  Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Acrylic acid and methacrylic acid are particularly preferably used.

  Although it does not specifically limit as a metal salt of unsaturated carboxylic acid, For example, what neutralized the said unsaturated carboxylic acid with the desired metal ion is mentioned. Specific examples include zinc salts such as methacrylic acid and acrylic acid, magnesium salts, and the like. In particular, zinc acrylate is preferably used.

  The unsaturated carboxylic acid and / or metal salt thereof is usually 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and usually 60 parts by mass as an upper limit with respect to 100 parts by mass of the base rubber. Hereinafter, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and most preferably 40 parts by mass or less. If the blending amount is too large, it may become too hard and unbearable feel may occur, and if the blending amount is too small, the resilience may decrease.

  Commercially available products can be used as the organic peroxide. For example, Park Mill D (manufactured by NOF Corp.), Perhexa 3M (manufactured by NOF Corp.), Luperco 231XL (manufactured by Atchem Corp.) and the like can be suitably used. . These may be used alone or in combination of two or more.

  The organic peroxide is usually 0.1 parts by mass or more, preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and most preferably 0.7 parts by mass with respect to 100 parts by mass of the base rubber. The upper limit is usually 5 parts by mass or less, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 2 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain suitable feel, durability and resilience.

  As the inert filler, for example, zinc oxide, barium sulfate, calcium carbonate and the like can be suitably used. These may be used individually by 1 type and may use 2 or more types together.

  The compounding amount of the inert filler is usually 1 part by mass or more, preferably 5 parts by mass or more, and usually 50 parts by mass or less as an upper limit, preferably 40 parts by mass or less, more preferably 100 parts by mass of the base rubber. 30 parts by mass or less, most preferably 20 parts by mass or less. If the amount is too large or too small, it may not be possible to obtain an appropriate weight and suitable resilience.

  Furthermore, an anti-aging agent can be blended as necessary. For example, as a commercial product, Nocrack NS-6, NS-30 (manufactured by Ouchi Shinsei Chemical Co., Ltd.), Yoshinox 425 (Yoshitomi Pharmaceutical Co., Ltd.) )) And the like. These may be used individually by 1 type and may use 2 or more types together.

  The blending amount of the anti-aging agent is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, most preferably 0.2 parts by mass or more with respect to 100 parts by mass of the base rubber. It is not more than part by mass, preferably not more than 2 parts by mass, more preferably not more than 1 part by mass, most preferably not more than 0.5 parts by mass. If the amount is too large or too small, it may not be possible to obtain suitable resilience and durability.

  The core is preferably blended with an organic sulfur compound in order to improve the resilience of the golf ball and increase the initial velocity of the golf ball. Here, as the organic sulfur compound, for example, thiophenol, thionaphthol, halogenated thiophenol or a metal salt thereof is recommended. More specifically, pentachlorothiophenol, pentafluorothiophenol, Pentabromothiophenol, parachlorothiophenol, zinc salt of pentachlorothiophenol, diphenyl polysulfide having 2 to 4 sulfur, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide, etc. In particular, a zinc salt of pentachlorothiophenol and diphenyl disulfide can be preferably used.

  The organic sulfur compound is preferably added in an amount of 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably 0.2 parts by mass or more with respect to 100 parts by mass of the base rubber described above. preferable. If the blending amount is too small, the effect of improving the resilience cannot be expected. The upper limit of the amount of the organic sulfur compound is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 2.5 parts by mass or less, with respect to 100 parts by mass of the base rubber. If it is too high, the effect of improving the resilience (especially the impact by W # 1) can no longer be expected, and the core may become too soft or the feel may be poor.

  The core composition obtained by blending the above components is kneaded using an ordinary kneader, for example, a Banbury mixer, roll, etc., and compressed or injection molded into a core mold, and the molded product is crosslinked and co-crosslinked. The core is appropriately heated and cured at a temperature sufficient for the action of the material, usually about 130 to 170 ° C., particularly 150 to 160 ° C. for 10 to 40 minutes, particularly 12 to 20 minutes, to obtain a predetermined hardness distribution. It is desirable to manufacture.

Next, the intermediate layer will be described.
The material hardness of the intermediate layer is a value of Shore D hardness (measured by a type D durometer according to ASTM D2240. The same shall apply hereinafter), which is 42 or more, preferably 43 or more, more preferably 44 or more. 76 or less, preferably 73 or less, more preferably 70 or less. If the intermediate layer is too soft, the spin may be applied too much during a full shot and the flight distance may not be achieved. On the other hand, if the intermediate layer is too hard, the durability to cracking during repeated impacts may be deteriorated, or the feel at the time of performing a putter or a short approach may become too hard.

  The thickness of the intermediate layer is preferably 0.7 mm or more, more preferably 0.9 mm or more, further preferably 1.1 mm or more, and the upper limit is 1.7 mm or less, preferably 1.5 mm or less, Preferably it is 1.3 mm or less. If the thickness of the intermediate layer is greater than the above range, the low spin effect of the ball when hit with W # 1 may be insufficient and the flight distance may not be achieved. On the other hand, if the thickness of the intermediate layer is too thin, the durability against cracking during repeated hitting and the durability at low temperatures may deteriorate.

  The intermediate layer material is not particularly limited, and various thermoplastic resins and thermoplastic elastomers can be used. In particular, it is preferable to use a resin composition mainly composed of an ionomer. . Specifically, it is desirable that the resin composition is a mixture of a zinc ion neutralized ionomer and a sodium ion neutralized ionomer. The blending ratio (I) / (II) of the zinc ion neutralized ionomer (I) and the sodium ion neutralized ionomer (II) is a mass ratio, preferably 25/75 to 75/25, More preferably, it is 35 / 65-65 / 35, More preferably, it is 45 / 55-55 / 45. If the zinc-neutralized ionomer and sodium-neutralized ionomer are mixed out of the above range, the rebound of the entire ball becomes too low to obtain the desired jump, or at room temperature. The crack durability at the time of repeated hitting deteriorates, and further, the crack durability at low temperatures (below zero) may deteriorate.

  As will be described later, when polyurethane is employed as the cover material, it is desirable to polish the surface of the intermediate layer in order to improve adhesion to the urethane cover material. Furthermore, it is desirable to apply a primer to the surface of the intermediate layer after the polishing treatment or to add an adhesion reinforcing material to the intermediate layer material.

Regarding the ratio between the core diameter and the intermediate layer thickness In the present invention, it is desirable to optimize the ratio between the core diameter and the intermediate thickness within a predetermined range. Specifically, the ratio (c) / (a) of the core diameter (c) to the thickness (a) of the intermediate layer is 23 to 38, preferably 24 to 38, more preferably 25 to 38. is there. If the above value is too small, the feeling of hitting may become hard, or there may be insufficient rebound and a flight distance may not be obtained. On the other hand, if the above value is too large, the feeling of hitting may become stiff, or the spin may be applied too much and the flight distance may not be achieved.

  Next, the material hardness of the cover used in the present invention is Shore D hardness of 41 or more, preferably 42 or more, more preferably 43 or more, and the upper limit is 69 or less, preferably 66 or less, and more preferably 63. It is as follows. If the cover is too soft than the above range, the ball will be spun too much and the flight distance when hit with W # 1 may not be achieved. On the other hand, if the cover is too hard than the above range, the approach may not be spun, and even professionals and advanced players may lack control.

  The thickness of the cover is preferably 0.4 mm or more, more preferably 0.6 mm or more, further preferably 0.8 mm or more, and the upper limit is preferably 1.4 mm or less, more preferably 1.2 mm or less. More preferably, it is 1.0 mm or less. If the cover is thicker than the above range, the ball may be spun too much when hit with W # 1 and the flight distance may not be achieved. Conversely, if the cover is too thin than the above range, the spin may not be applied in a short game and the controllability may deteriorate.

  Although there is no restriction | limiting in particular about a cover material, Various thermoplastic resins and thermoplastic elastomers can be employ | adopted, and it forms especially using polyurethane as a main material. A thermoplastic polyurethane elastomer is preferred from the viewpoint of productivity.

  Specifically, it is preferable to use a specific thermoplastic polyurethane composition mainly composed of (A) a thermoplastic polyurethane and (B) a polyisocyanate compound. This resin blend will be described below.

  In order to exhibit the effect of the present invention sufficiently effectively, a necessary and sufficient amount of unreacted isocyanate groups may be present in the cover resin material. Specifically, the above components (A) and (B) Is recommended to be 60% or more of the total mass of the cover layer, and more preferably 70% or more. The components (A) and (B) will be described in detail below.

  When the thermoplastic polyurethane (A) is described, the structure of the thermoplastic polyurethane comprises a soft segment composed of a high-molecular polyol (polymeric glycol) which is a long-chain polyol, and a hard segment composed of a chain extender and a polyisocyanate compound. Including. Here, as the long-chain polyol as a raw material, any of those conventionally used in the technology relating to thermoplastic polyurethane can be used, and is not particularly limited. For example, polyester polyol, polyether polyol, polycarbonate polyol , Polyester polycarbonate polyol, polyolefin polyol, conjugated diene polymer polyol, castor oil polyol, silicone polyol, vinyl polymer polyol and the like. One kind of these long-chain polyols may be used, or two or more kinds may be used in combination. Of these, polyether polyols are preferred because they can synthesize thermoplastic polyurethanes having high impact resilience and excellent low-temperature properties.

  Examples of the polyether polyol include poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyltetramethylene glycol) and the like obtained by ring-opening polymerization of a cyclic ether. Can do. As the polyether polyol, one type may be used, or two or more types may be used in combination. Of these, poly (tetramethylene glycol) and / or poly (methyltetramethylene glycol) are preferred.

  The number average molecular weight of these long-chain polyols is preferably in the range of 1,500 to 5,000. By using a long-chain polyol having such a number average molecular weight, a golf ball made of a thermoplastic polyurethane composition excellent in various properties such as the resilience and productivity described above can be obtained with certainty. The number average molecular weight of the long-chain polyol is more preferably in the range of 1,700 to 4,000, and still more preferably in the range of 1,900 to 3,000.

  In addition, the number average molecular weight of said long chain polyol is the number average molecular weight computed based on the hydroxyl value measured based on JISK-1557.

  As the chain extender, those used in the conventional technology relating to thermoplastic polyurethane can be suitably used. For example, a low molecular weight of 400 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule. It is preferably a molecular compound. Examples of the chain extender include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. However, it is not limited to these. Of these, the chain extender is preferably an aliphatic diol having 2 to 12 carbon atoms, and more preferably 1,4-butylene glycol.

  As a polyisocyanate compound, what is used in the technique regarding the conventional thermoplastic polyurethane can be used suitably, and there is no restriction | limiting in particular. Specifically, 4,4′-diphenylmethane diisocyanate, 2,4- (or) 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated One type or two or more types selected from the group consisting of xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate can be used. However, some isocyanate species make it difficult to control the crosslinking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic diisocyanate, is most preferable from the viewpoint of the balance between the stability during production and the physical properties to be expressed.

  The most preferable thermoplastic polyurethane as the component (A) is a thermoplastic polyurethane synthesized using a polyether polyol as a long-chain polyol, an aliphatic diol as a chain extender, and an aromatic diisocyanate as a polyisocyanate compound. The polyether polyol is a polytetramethylene glycol having a number average molecular weight of 1,900 or more, the chain extender is 1,4-butylene glycol, and the aromatic diisocyanate is 4,4′-diphenylmethane diisocyanate, However, it is not limited to these.

  In addition, the active hydrogen atom: isocyanate group mixing ratio in the polyurethane forming reaction described above is a golf ball made of a thermoplastic polyurethane composition having various properties such as resilience, spin performance, scratch resistance and productivity as described above. Can be adjusted within a preferable range. Specifically, in producing a thermoplastic polyurethane by reacting the long-chain polyol, the polyisocyanate compound and the chain extender, with respect to 1 mol of active hydrogen atoms of the long-chain polyol and the chain extender, It is preferable to use each component in such a ratio that the isocyanate group contained in the polyisocyanate compound is 0.95 to 1.05 mol.

  The method for producing the thermoplastic polyurethane as the component (A) is not particularly limited, and a prepolymer method, a one-shot, using a long-chain polyol, a chain extender, and a polyisocyanate compound and utilizing a known urethanization reaction. It may be produced by any of the methods. Among them, it is preferable to perform melt polymerization in the substantial absence of a solvent, and it is particularly preferable to produce by continuous melt polymerization using a multi-screw extruder.

  As the specific thermoplastic polyurethane of component (A), commercially available products may be used, and examples thereof include Pandex T8295, T8290, and T8260 (all manufactured by DCI Bayer Polymer Co., Ltd.).

  Next, with respect to the polyisocyanate compound used as the component (B), at least a part of all the isocyanate groups remains unreacted in a single resin compound (pellet) before molding. It is necessary. That is, it is only necessary that a polyisocyanate compound having a completely free isocyanate group exists in one molecule. Even if such a polyisocyanate compound and a polyisocyanate compound having only one terminal free are present together. Good.

  Although there is no restriction | limiting in particular as this polyisocyanate compound, Various isocyanate can be employ | adopted, Specifically, 4,4'- diphenylmethane diisocyanate, 2, 4- (or) 2, 6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, 1 type (s) or 2 or more types selected from the group which consists of dimer acid diisocyanate can be used. Adoption of 4,4'-diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate among the above isocyanate groups affects the moldability due to an increase in viscosity associated with the reaction of the component (A) with the thermoplastic polyurethane. And a balance with the physical properties of the obtained golf ball cover material.

  In the present invention, although not an essential component, a thermoplastic elastomer other than the thermoplastic polyurethane can be blended as the component (C) in the components (A) and (B). By blending the component (C) with the resin blend, various physical properties required for a golf ball cover material such as further improvement in fluidity, resilience, and abrasion resistance of the resin blend can be enhanced. .

  In addition to the resin component, various additives can be blended in the cover resin material described above as necessary. Examples of such additives include pigments, dispersants, antioxidants, UV absorbers, UV stabilizers, mold release agents, plasticizers, inorganic fillers (such as zinc oxide, barium sulfate, and titanium dioxide). be able to.

Regarding the ratio between the intermediate layer thickness and the cover thickness, in the present invention, it is desirable to optimize the ratio between the intermediate layer thickness and the cover thickness within a predetermined range. Specifically, the ratio (a) / (b) of the thickness (a) of the intermediate layer to the thickness (b) of the cover is 0.7 to 1.9, preferably 0.8 to 1. .9, and more preferably in the range of 0.9 to 1.9. If the above value is too small, the feeling of hitting may become hard, or the spin may be applied too much and the flight distance may not be obtained. On the other hand, if the above value is too large, the rebound may not be sufficient and the flight distance may not be achieved.

Regarding the relationship between the intermediate layer material hardness, the cover material hardness and the core surface hardness In the present invention, the relationship between the intermediate layer material hardness, the cover material hardness and the core surface hardness is expressed by the following formula: Cover material hardness <interlayer material hardness> core surface Satisfaction of hardness is a condition. Thus, by setting the hardness of each layer so as to maintain the above relational expression, it is possible to further improve the flying performance and obtain a firm and good feel.

  In the present invention, a large number of dimples are formed on the cover surface. The dimples arranged on the cover surface are not particularly limited, but are preferably 250 or more, more preferably 300 or more, more preferably 318 or more, and the upper limit is preferably 350 or less, more preferably Is 328 or less. If the number of dimples exceeds the above range, the trajectory of the ball may be lowered and the flight distance may not be achieved. On the other hand, if the number of dimples is too smaller than the above range, the trajectory becomes high and the flight distance may not be extended.

  The shape of the dimple is not particularly limited, but can be appropriately used by combining one type or two or more types such as a circular shape, various polygonal shapes, a dew drop shape, and other elliptical shapes. For example, when circular dimples are used, dimples having a diameter of 2.5 to 6.0 mm or less can be appropriately selected. In addition, it is possible to cover a spherical surface with good balance by applying at least 3 to 5 or more types, preferably 5 or more types of dimples.

  There are no particular restrictions on the type of dimple, and dimples can be arranged according to a spherical polyhedron arrangement that is suitably applied in dimple arrangement, for example, a repeating pattern of unit polygons such as unit triangles and unit pentagons. It is possible to change the diameter of all the dimples little by little. In this case, the number of dimple types can be 20 or more. In addition, the ratio of the total dimple area defined by the surface edge of the plane surrounded by the edge of the dimple to the ball ball area assuming that there is no dimple is dimple because it can sufficiently exhibit aerodynamic characteristics. The surface occupancy (SR) is desirably 75% or more.

  Furthermore, it is preferable to contain 6 or more small dimples having a diameter of 3.0 mm or less, particularly preferably in the range of 6 to 30. In the present invention, an effect of increasing the CL value and decreasing the CD value in the first half of the ball trajectory can be obtained by increasing the surface occupancy by mixing large and small dimples. In order to improve the flight distance of the hit ball, it is not very effective to reduce only the drag or drag coefficient CD. When only the drag coefficient is reduced, the position of the highest point of the hit ball is extended, but the flying distance tends to be lost due to a drop due to insufficient lift in the low speed region after the highest point. Therefore, in the multi-piece solid golf ball of the present invention, when the Reynolds number is 180,000 immediately after the ball is hit and the spin rate is 2520 rpm, the drag coefficient CD is 0.225 or less, and when the ball is hit, the Reynolds number is 70000, It is preferable that the lift coefficient CL of the ball at a spin rate of 2000 rpm is maintained at 60% or more with respect to the lift coefficient CL at a Reynolds number of 80000 and a spin rate of 2000 rpm. Note that the Reynolds number of 180,000 immediately after hitting the hit ball is approximately 66 m / s at the ball speed, and in this case, the Reynolds numbers of 80000 and 70000 correspond to the speeds of approximately 30 m / s and 26 m / s, respectively.

  The golf ball of the present invention may be in compliance with golf regulations for competition purposes. The outer diameter of the ball does not pass through a ring with an inner diameter of 42.672 mm and is 42.80 mm or less, and the weight is usually 45.0. It is preferable to set it to -45.93g.

Regarding the deflection amount of the ball In the present invention, the deflection amount (mm) from the state in which an initial load of 98 N (10 kgf) is applied to the final load of 490 N (50 kgf) is applied to the ball (A), When the deflection (mm) from when the initial load 98N (10 kgf) is applied to when the final load 5880N (600 kgf) is applied is (B), the value of (B) / (A) × 100 is It is 830-930, Preferably it is 840-920, More preferably, it is 850-910. If the above value is too small, the driver may be spun too much and the flight distance may not be achieved. Conversely, if the above value is too large, the driver's initial speed may be insufficient and the flight distance may not be achieved.
Further, the value of the deflection amount (B) of the ball is not particularly limited, but is preferably 7.0 to 10.0 mm.

  The amount of deflection (mm) from when the initial load of 98 N (10 kgf) is applied to when the final load of 1,275 N (130 kgf) is applied to the ball is not particularly limited, but is preferably 2.1 mm. More preferably, it is 2.2 mm or more, and further preferably 2.3 mm or more. The upper limit is not particularly limited, but is preferably 2.9 mm or less, more preferably 2.8 mm or less, and still more preferably 2.7 mm or less.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1 to 3, Comparative Examples 1 and 2]
After adjusting the core composition according to the formulation shown in Table 1 below, a solid core was prepared by vulcanization molding at 155 ° C. for 13 minutes.

The details of the core material are as follows. In addition, the number in a table | surface shows a mass part.
“Polybutadiene A”: Product name “BR730” manufactured by JSR Corporation
“Polybutadiene B”: Product name “BR01” manufactured by JSR Corporation
“Peroxide”: 1,1-di (t-butylperoxy) cyclohexane and silica mixture Trade name “Perhexa C-40” (manufactured by NOF Corporation)
“Anti-aging agent”: 2,2′-methylenebis (4-methyl-6-tert-butylphenol) ”trade name“ NOCRACK NS-6 ”(manufactured by Ouchi Shinsei Chemical Co., Ltd.)
“Barium sulfate”: Trade name “Sedimentable Barium # 300” manufactured by Sakai Chemical Co., Ltd.

Formation of Intermediate Layer and Cover Next, around the core obtained above, No. 2 shown in Table 2 was formed. 1, no. 2 or No. 5 was obtained by sequentially forming the intermediate layer (one layer or two layers) by the injection molding method.

  Next, No. 2 shown in Table 2 was obtained. 3 or No. 4 raw materials (unit: part by mass) were kneaded in a nitrogen gas atmosphere by a twin screw extruder to obtain a cover resin composition. This resin blend was in the form of a pellet having a length of 3 mm and a diameter of 1 to 2 mm.

  The intermediate sphere was placed in an injection mold, and the cover material was injection molded around the sphere to obtain multi-piece solid golf balls of Examples and Comparative Examples. Regarding the cover physical properties, a sheet having a thickness of 2 mm obtained by injection molding was subjected to an annealing treatment at 100 ° C. for 8 hours, and further allowed to stand at room temperature for 1 week, and then the cover physical properties were measured.

  At this time, the common dimples shown in FIG. 2 were formed on the cover surfaces of the examples and comparative examples. Details of the dimples are shown in Table 3.

The trade names of the materials described in the above table are as follows.
“High Milan”: Ionomer “Surlin” manufactured by Mitsui DuPont Polychemical Co., Ltd .: Ionomer “Dynalon E6100P” manufactured by DuPont Co., Ltd .: Hydrogenated polymers “AN4319” and “AN4221C” manufactured by JSR Co., Ltd. ”
“Magnesium stearate”: Trade name “Magnesium stearate G” manufactured by NOF Corporation “Magnesium oxide”: “Kyowa Mag MF150” manufactured by Kyowa Chemical Industry Co., Ltd.
"Behenic acid": Trade name "NAA222-S (bead designation)" NOF Corporation "Calcium hydroxide": Shiraishi Kogyo Co., Ltd., trade name "CLS-B designation"
"T8925, T-8290, T8283": Trade name "Pandex" manufactured by DIC Bayer Polymer: MDI-PTMG type thermoplastic polyurethane "Polyethylene wax": Trade name "Sunwax 161P" (manufactured by Sanyo Kasei)
Isocyanate compound: 4,4'-diphenylmethane diisocyanate

Dimples Definition <br/> diameter: diameter depth flat plane circumscribed by an edge of the dimple: maximum depth of the dimple from the plane surrounded by the edge of the dimple V _0: under flat plane circumscribed by an edge of the dimple A value obtained by dividing the spatial volume of the dimple by a cylindrical volume having the plane as the bottom and the maximum depth of the dimple from the bottom as a height SR: Total dimple area defined by the plane surrounded by the edge of the dimple Is the percentage of the ball sphere area assuming no dimples (unit:%)

Aerodynamic characteristics (low speed CL ratio and high speed CD value)
The low speed CL ratio is the lift coefficient CL when the Reynolds number is 70000 with respect to the lift coefficient CL of the ball when the Reynolds number is 80000 and the spin amount is 2000 rpm from the ball on the trajectory immediately after launch using UBL (Ultra Ball Launcher). The ratio of was calculated. Similarly, the high-speed CD value is obtained by calculating a drag coefficient when a ball is hit at a Reynolds number of 180,000 and a spin rate of 2520 rpm.

  The above "UBL" is a device that launches the ball under desired conditions by installing two pairs of drums on the top and bottom, putting belts on the upper and lower drums, rotating them and inserting the balls between them. is there. UBL is made by Automated Design Corporation.

  For each of the obtained golf balls, various physical properties such as thickness, hardness, and deflection amount of each layer, flying performance and feel were evaluated by the following methods. The results are shown in Tables 4 and 5. In addition, all measured in 23 degreeC environment.

(1) Deflection amount of core and intermediate layer coated sphere (mm)
The core or intermediate layer coated sphere is compressed at a speed of 50 mm / min at a temperature of 23 ± 1 ° C., and the amount of deflection from when the initial load is 98 N (10 kgf) to when the final load is 1275 N (130 kgf). (Mm) was measured, and an average value of 10 measurement pieces was obtained.

(2) Core surface hardness The surface of the core is a spherical surface. Set the hardness meter needle so that the surface of the core is almost perpendicular to the surface of the core. Shore D hardness (according to ASTM D-2240 standard durometer "Type D" The average value of the values obtained by randomly measuring two points on the surface of the core.

(3) Material hardness of intermediate layer and cover (hardness of sheet-like molded product)
The material forming each layer was formed into a sheet having a thickness of 2 mm, stored at 23 ° C. for 2 weeks, and then measured by ASTM D-2240 standard durometer “Type D”, that is, “Shore D hardness”.

(4) Ball deflection amount (each deflection amount at 50 kgf load, 130 kgf load and 600 kgf load)
The ball is compressed at a speed of 500 mm / min at a temperature of 23 ± 1 ° C., and the amount of deflection (mm) from when the initial load is 98 N (10 kgf) to when the final load is 5880 N (600 kgf) is measured. Then, an average value of 10 balls measured was obtained.
Further, the ball is compressed at a temperature of 23 ± 1 ° C. at a speed of 500 mm / min, and the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 490 N (50 kgf). Was measured, and an average value of 10 measurement pieces was obtained.

(5) Flying performance by driver A golf hitting robot equipped with a driver (W # 1), Bridgestone Sports, "TourStage GR (2010 model)" (loft angle: 10.5 °), head speed (HS) 50m The flight distance when hitting at / s was measured and evaluated according to the following criteria. Similarly, the spin rate was measured with an initial condition measuring device for the ball immediately after hitting.
○: Total flight distance 245m or more
×: Total flight distance less than 245m

(6) Hit feeling head speed (HS) A golfer who places importance on a flight distance of 48 m / s or more was hit with a driver (W # 1) and subjected to sensory evaluation based on the following criteria.
The driver (W # 1) used was “TourStage GR (2010 model)” (loft angle: 10.5 °) manufactured by Bridgestone Sports, as in (5) above.
○: 7 or more out of 10 people feel good and feel good
X: 3 or less out of 10 people have good hit feeling and evaluation ("Good hit feeling" means a hit feeling that seems to fly with firm feeling, and hit feeling that is too soft or too hard is bad. It is a feeling.)

From Table 5, each Comparative Example was inferior to the present invention (Example) in the following points.
In Comparative Example 1, the ratio of the core diameter to the intermediate layer thickness is small, the initial speed at W # 1 is insufficient, and no carry occurs. Moreover, it is not sufficient that the hit feeling at W # 1 is too soft.
In Comparative Example 2, the ratio of the core diameter to the intermediate layer thickness is large, and the low spin rate at W # 1 is insufficient, and no carry occurs. Further, the hit feeling at W # 1 is too hard.

1 Core 2 Mid layer 3 Cover G Golf ball D Dimple

Claims (7)

  A multi-piece solid golf ball comprising a core, at least one intermediate layer covering the core, and at least one cover covering the intermediate layer, wherein the core is formed of a base rubber, and the intermediate layer And each layer of the cover is formed of a resin material, and the ratio (a) / (b) of the thickness (a) of the intermediate layer to the thickness (b) of the cover is 0.7 to 1.9. And the ratio (c) / (a) of the diameter (c) of the core to the thickness (a) of the intermediate layer is 23-38, and the material hardness of the intermediate layer is 42- The multi-piece solid golf ball according to claim 76, wherein the cover has a hardness of 41 to 69 on Shore D and satisfies the cover material hardness <interlayer material hardness> core surface hardness.   The multi-piece solid golf ball according to claim 1, wherein a value obtained by subtracting the center hardness (Shore D hardness) from the surface hardness (Shore D hardness) of the core is 17 or less.   The deflection amount (mm) from when the initial load 98N (10 kgf) is applied to the ball to when the final load 490N (50 kgf) is applied is (A), and the initial load 98N (10 kgf) is applied to the ball. The value of (B) / (A) × 100 is 830 to 930, where (B) is the amount of deflection (mm) from when the load is applied to when the final load is 5880 N (600 kgf). 2. A multi-piece solid golf ball according to 2.   The value of the deflection (B) of the ball is 7.0 to 10.0 mm, and the deflection from when the initial load 98N (10 kgf) is applied to when the final load 1275N (130 kgf) is applied to the core. The multi-piece solid golf ball according to claim 3, wherein the amount is 2.1 to 4.1 mm.   The resin material of the cover is formed by injection molding a single resin compound mainly composed of (A) a thermoplastic polyurethane and (B) a polyisocyanate compound. In the resin compound, 5. The multi-piece solid golf ball according to claim 1, wherein at least a part thereof is a polyisocyanate compound in which all isocyanate groups in one molecule remain in an unreacted state.   A large number of dimples are formed on the ball surface, the total number of dimples is 250 to 350, the dimple surface occupancy (SR) is 75% or more, and when the ball is hit, the Reynolds number is 70,000 and the spin rate is 2000 rpm. The multi-piece solid golf ball according to claim 1, wherein the lift coefficient CL of the ball is 60% or more of the lift coefficient CL at a Reynolds number of 80000 and a spin rate of 2000 rpm.   The multi-piece solid golf ball according to claim 6, wherein five or more kinds of dimples having different diameters and / or depths are used, and 6 to 30 small dimples having a diameter of 3.0 mm or less are included.

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