JP2008264570A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball, having durability and attaining compatibility between controllability in approach shot and carrying performance in driver shot. <P>SOLUTION: This golf ball includes: a solid core formed of one or two layers; and a cover covering the solid core, wherein base material resin forming the cover is made of two-pack curable polyurethane resin, the thickness (T) of the cover is 0.2-0.8 mm, the Shore hardness (S) of the cover is 34-50, and the T and S satisfy the relation of 30T + 16≤S≤30T+32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a golf ball, and more particularly, to a golf ball excellent in controllability, flight performance, and durability.

  The spin rate of a golf ball is an important characteristic that governs the flight performance and control performance of the ball. For example, in a shot that gives priority to a flight distance such as a driver shot, the backspin that rotates in the reverse direction with respect to the propulsion direction of the ball not only reduces air resistance but also acts as lift to raise the ball. However, if the amount of spin is too large, the trajectory will rise and the flight distance will tend to decrease. In addition, an increase in the amount of side spin that rotates laterally with respect to the propulsion direction of the ball may result in slicing or hooking the ball, and the ball may not jump in the direction intended by the golfer. Therefore, the smaller the spin rate is preferred for driver shots.

  On the other hand, in the approach shot from the green side, if the amount of spin is small, the distance that the ball rolls after it has landed becomes long, making it difficult to stop the ball at the intended location. Liked.

  Under these circumstances, it has been proposed to soften the cover of the golf ball in order to increase the spin rate mainly for the purpose of improving the controllability at the approach shot.

  For example, Patent Document 1 proposes a cover made of an ionomer resin using a mixture of a hard ionomer and a soft ionomer in order to improve the shot feeling and controllability of the ionomer cover. By blending soft ionomer resin, golf ball feel can be softened and controllability can be improved, but there is a problem that the resilience and durability (scratch resistance) inherently possessed by ionomer cover are reduced. Arise.

A technology that uses a polyurethane cover instead of an ionomer cover has also been proposed. Since the polyurethane cover is softer than the ionomer cover, the spin rate can be increased. However, the softening of the cover increases not only the approach shot but also the spin rate at the driver shot. Further, since the resilience is lowered by the softening of the cover, there remains a problem that it is difficult to obtain a flight distance. That is, there is a limit to improving the golf ball characteristics (controllability, flight distance performance, etc.) by optimizing the cover material.
Japanese Patent No. 2709950

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a golf ball that is durable and has both controllability on approach shots and flight performance on driver shots. Is to provide.

  The golf ball of the present invention is a golf ball including a solid core composed of one layer or a plurality of layers and a cover that covers the solid core, and the base resin constituting the cover is a two-component curable polyurethane resin. The thickness (T) of the cover is 0.2 to 0.8 mm, the Shore D hardness (S) of the cover is 34 to 50, and the T and S satisfy the following relational expression. It is what has.

30T + 16 ≦ S ≦ 30T + 32
Here, the Shore D hardness (S) of the cover means the hardness when the cover material is formed into a sheet shape and measured, and represents the surface hardness of the cover. The present inventors have found that the spin rate upon hitting a golf ball has the following relationship between the cover hardness and the thickness.

  That is, if the hardness of the cover is softened, the controllability at the approach shot can be improved, but the spin amount increases and the rebound is lowered, so that the flight distance cannot be obtained at the driver shot. Therefore, if the cover thickness is reduced in order to suppress a reduction in resilience, the durability of the cover cannot be obtained. From these findings, in the present invention, the golf ball cover is designed so that the Shore D hardness (S) of the golf ball cover and the thickness (T) of the cover satisfy the relational expression 30T + 16 ≦ S ≦ 30T + 32. Compatibility between flight performance and flight performance. Furthermore, it is preferable that the Shore D hardness of the cover satisfies 30T + 20 ≦ S ≦ 30T + 28 because a ball having good controllability and flight performance can be stably obtained. Moreover, the thickness (T) of the cover is 0.2 to 0.8 mm, more preferably 0.3 to 0.6 mm, and the Shore D hardness (S) of the cover is 34 to 50, more preferably 34 to 46. Thus, durability can be ensured.

  Moreover, it is preferable that the said cover contains 3-5 mass parts of titanium oxide with respect to 100 mass parts of base resin which comprises this cover. This is because even when the cover is relatively thin, an appropriate hardness can be ensured, and a decrease in durability due to the thinning of the cover can be suppressed.

  Further, in the case where dimples are provided on the surface of the cover, the film thickness of the cover can be made uniform if irregularities corresponding to the dimples are formed on the surface of the solid core. In some cases, a decrease in durability can be suppressed, which is desirable.

  The golf ball of the present invention has an excellent balance of flight performance and controllability because the spin amount can be increased by softening the cover and the rebound of the core can be effectively utilized by making the cover thinner. Also, since the hardness and thickness of the golf ball cover are designed to satisfy the relationship represented by a specific relational expression, even a ball having an extremely thin and extremely low hardness cover impairs durability. Therefore, it was possible to provide a ball having excellent controllability and flight performance.

  The golf ball of the present invention is a golf ball including a solid core composed of one or more layers and a cover that covers the solid core, and the base resin constituting the cover is made of a two-component curable polyurethane resin. The thickness (T) of the cover is 0.2 mm or more and 0.8 mm or less, the Shore D hardness (S) of the cover is 34 or more and less than 50, and T and S have the following relationship: It has characteristics where it meets.

30T + 16 ≦ S ≦ 30T + 32
The spin when hitting a golf ball is more likely to occur as the cover of the golf ball is softer. However, the softening of the cover hardness also leads to a decrease in resilience as the amount of spin increases, making it difficult to obtain a flight distance on driver shots. There is. In addition, in order to secure a shot feeling during shots and durability during use, it is necessary to give the cover a certain degree of hardness, and in order to ensure the flight distance during driver shots, the resilience of the core is wasted. It is effective to reduce the thickness of the cover so that it can be used without any problems. Based on these findings, the present inventors have conducted experiments on the relationship between the cover characteristics (thickness and hardness) and the spin rate at the time of hitting the ball in order to realize a golf ball with an excellent balance between controllability and flight distance performance. We proceeded with the examination.

  As a result, a golf ball whose cover hardness and cover thickness satisfy the above relational expression has durability, and has a spin amount that can satisfy both controllability on approach shots and flight performance on driver shots. The headline and the present invention were completed.

  When the Shore D hardness (S) of the cover obtained from the above relational expression is smaller than 30T + 16, it means that the cover is too soft with respect to the cover thickness. Accordingly, the amount of spin increases due to the softening of the cover, and the resilience decreases. Therefore, it is difficult to obtain a flight distance during a driver shot. On the other hand, when the value of Shore D hardness (S) is larger than 30T + 32, the cover becomes hard with respect to the cover thickness, so that the spin rate is reduced and the control performance at the approach shot is lowered. Furthermore, if the Shore D hardness (S) satisfies 30T + 20 ≦ S ≦ 30T + 28, it is preferable because the spin rate can be controlled more stably and a golf ball having both control performance and flight distance performance can be obtained stably.

  The golf ball cover according to the present invention preferably has a thickness (T) of 0.2 mm or more and 0.8 mm or less. More preferably, it is 0.3 mm or more and 0.6 mm or less. This is because if the thickness (T) is less than 0.2 mm, the cover is too thin and difficult to form, and in addition, the following problems are generally associated with the dimples provided on the cover surface. That is, the maximum depth of dimples usually provided on the surface of the cover is about 0.2 mm. Therefore, if the cover is less than 0.2 mm thick, the core may be exposed at the bottom of the dimple. Even if it is not exposed, the cover that is too thin is likely to be peeled off due to deformation of the ball at the time of hitting. Because it is inferior. On the other hand, if it exceeds 0.8 mm, the cover becomes thick and the resilience is lowered, making it difficult to obtain a flight distance.

  The Shore D hardness (S) of the cover is preferably 34 or more and 50 or less (more preferably 46 or less). This is because if the Shore D hardness is less than 34, the cover is too soft and the durability is lowered, and if it exceeds 50, the spin amount is reduced and it becomes difficult to control the ball at the approach shot. In addition, the Shore D hardness in this invention means the value when shape | molding a cover material in a sheet form and measuring Shore D hardness.

  Hereinafter, the golf ball of the present invention will be described in more detail.

  The structure of the golf ball of the present invention is not particularly limited, but includes a two-piece golf ball in which a solid core made of a rubber composition is covered with a cover material, a center made of a rubber composition, and at least one intermediate layer covering the center. And a multi-piece golf ball having a solid core covered with a cover material.

  First, the cover according to the golf ball of the present invention will be described.

  The cover material that can be used in the present invention is not limited, and a thermoplastic resin composition such as ionomer resin, polyethylene, polypropylene, polystyrene, ABS resin, methacrylic resin, polyamide resin, urethane-based thermoplastic resin, ester-based thermoplastic resin, Examples thereof include thermoplastic resin compositions such as amide-based thermoplastic resins, styrene-based thermoplastic resins, and olefin-based thermoplastic resins, and two-component curable resins such as polyurethane and polyurea. Among these, it is preferable to use a thermoplastic urethane resin or a two-component curable urethane resin because of its excellent durability. In addition, it is preferable to use a two-component curable urethane resin from the viewpoint that a thin cover can be formed.

  As the two-component curable urethane resin, for example, it is preferable to use a composition containing an isocyanate group-terminated urethane prepolymer (main agent) having an isocyanate component and a polyol component, and a polyamine (curing agent). .

  The isocyanate group-terminated urethane prepolymer has at least two isocyanate groups in the urethane prepolymer molecular chain. The position of the isocyanate group in the urethane prepolymer molecular chain is not limited, and may be at the end of the urethane prepolymer molecular chain main chain or at the side chain end.

  The isocyanate group-terminated urethane prepolymer is obtained by reacting a polyol and a polyisocyanate. In addition, it is preferable to perform the said reaction in the state which made the molar ratio of the isocyanate group of the polyisocyanate with respect to the hydroxyl group of a polyol excessive.

  Further, after the reaction, the content of unreacted polyisocyanate (residual polyisocyanate monomer) remaining in the isocyanate group-terminated urethane prepolymer is reduced to 0.5% by mass or less using a thin film distillation apparatus or the like. It is preferable to leave. More preferably, it is 0.1 mass% or less. Here, the content of the residual polyisocyanate monomer is defined by (mass of polyisocyanate monomer remaining in isocyanate group-terminated urethane prepolymer / total mass of isocyanate group-terminated urethane prepolymer) × 100. The value obtained by analyzing the product obtained by the above reaction by gas chromatography.

  When the content of the residual polyisocyanate monomer exceeds 0.5% by mass, the reaction between the residual polyisocyanate monomer and the polyamine as the curing agent takes place preferentially, and the resulting isocyanate group-terminated urethane prepolymer Properties such as resilience and durability may be reduced. In addition, since the speed of the reaction is high, the viscosity of the reaction solution may be rapidly increased to reduce workability. In addition, restraining the residual isocyanate content to a low level also reduces the harm given to the worker by suppressing the vaporization amount of the residual polyisocyanate monomer while preventing the above disadvantages, and also improving the environmental safety. It is valid.

  The polyisocyanate used as a raw material for the isocyanate group-terminated urethane prepolymer is not particularly limited. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used. Mixture of diisocyanates (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3′-bitrylene-4,4′-diisocyanate (TODI), xylylene diisocyanate Aromatic diisocyanates such as (XDI) and paraphenylene diisocyanate (PPDI); 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate One or a mixture of two or more of the alicyclic diisocyanate or aliphatic diisocyanate such as sulfonate (IPDI) and the like. Of these, TDI, MDI, PPDI, hydrogenated MDI, or a combination thereof is preferably used from the viewpoints of mechanical properties of the obtained polyurethane cover and good resilience, weather resistance, and water resistance of the golf ball.

  The polyol used as a raw material for the isocyanate group-terminated urethane prepolymer may be either a low molecular weight compound or a high molecular weight compound as long as it has a plurality of hydroxyl groups. Examples of the low molecular weight polyol include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol; glycerin, trimethylol Examples include triols such as propane and hexanetriol.

  Polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polyoxytetramethylene glycol (PTMG) and their copolymer polyols; polyethylene adipate (PEA) Polycondensation polyester polyols such as polydiethylene adipate, polypropylene adipate, polybutylene adipate (PBA), polyneopentyl adipate, polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); Polycarbonate polyols such as hexamethylene carbonate; and polybutadiene polyols and acrylic polyols. Among these, polyether polyol is preferable from the viewpoint of excellent resilience and water resistance, and polyoxytetramethylene glycol (PTMG) is particularly preferably used.

  The polyamine which is a curing agent to be reacted with the isocyanate group-terminated urethane prepolymer may be any one having at least two amino groups, and may be appropriately determined according to the type of isocyanate to be used. Examples thereof include aliphatic polyamines and alicyclic polyamines in which an amino group is bonded to an alkyl group, and aromatic polyamines in which an amino group is bonded to an aromatic ring. In particular, it is a preferred embodiment to use an aromatic polyamine as the polyamine. This is because the aromatic polyamine can provide a cured product of a two-component curable urethane resin having excellent mechanical properties, and can further improve the durability of the cover.

  The aromatic polyamine may be a phenylenediamine type in which two or more amino groups are bonded to one aromatic ring, or two or more aminophenyl groups in which one amino group is bonded to one aromatic ring. In the case of the polyaminopolyphenyl type, two aminophenyl groups may be directly bonded, or the two aminophenyl groups may be bonded via a lower alkylene group, a sulfide group or an alkylene oxide group. It may be bonded.

  Examples of the phenylenediamine type include dimethylthiotoluenediamine and diethyltoluenediamine. Examples of the polyaminopolyphenyl type include 4,4′-diaminodiphenylmethane and derivatives thereof. Specifically, 4,4′-methylenebis- (3-chloro-2,6-diethylaniline) and 4,4 Examples include '-diamino-3,3'-diethyl-5,5'-dimethylphenylmethane and 4,4'-diamino-3,3'-dimethyldiphenylmethane.

The content ratio of the isocyanate group-terminated urethane prepolymer and the polyamine in the two-component curable urethane resin composition is a molar ratio of amino group to the isocyanate group (NH ₂ / NCO), preferably 0.70 or more, more preferably It is 0.80 or more, More preferably, it is 0.85 or more, Preferably it is 1.2 or less, More preferably, it is 1.05 or less, More preferably, it is 1.00 or less. If it is less than 0.70, the amount of the isocyanate group-terminated urethane prepolymer with respect to the polyamine becomes excessive, the formation reaction of allophanate and burette is likely to occur, and the flexibility of the finally obtained polyurethane becomes insufficient. On the other hand, if it exceeds 1.20, the isocyanate group is insufficient, so that allophanate and burette cross-linking reactions are less likely to occur, and as a result, the number of three-dimensional cross-linking points becomes too small and the strength of the resulting polyurethane decreases. .

  The cover composition preferably contains titanium oxide in addition to the isocyanate group-terminated urethane prepolymer and the polyamine constituting the two-component curable polyurethane. The titanium oxide content is preferably 3 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base resin constituting the cover. The golf ball of the present invention employs a relatively thin cover in order to effectively utilize the resilience of the core. Therefore, even when the cover is thin, it is good by including titanium oxide within the above range. Golf ball appearance can be achieved.

  The cover composition further includes a conventionally known catalyst used in the urethane reaction, for example, a tertiary amine such as triethylamine, a tin-based catalyst such as dilauryltin dilaurate, or a fat such as oleic acid or lauric acid. A group carboxylic acid or the like may be added. In addition, a filler such as barium sulfate, an anti-aging agent, an ultraviolet absorber, a light stabilizer, and a fluorescent brightening agent may be added to the cover composition as long as the properties of the polyurethane cover are not impaired. An agent may be blended.

  Although the curing conditions of the curable urethane resin composition depend on the type of isocyanate group-terminated urethane prepolymer and polyamine to be used, it is generally preferable to set the temperature from room temperature to 140 ° C. for about 1 to 60 minutes. This is because, if cured under such conditions, there is little influence on the rubber molded body (core) during cover molding, and the productivity and workability are good. By curing under such conditions, a cured product suitable as a cover material can be obtained.

  The method for manufacturing the cover is not particularly limited, but for example, the following method is preferably used. After injecting the cover composition into a hemispherical mold and heating to gel, the half-cup-shaped gel cover overlaid on the core held in another core mold is heated and pressed. Then, an intermediate molded body in which the hemispherical portion of the core is covered with the cover is formed. Next, the cover composition is injected into the second mold, and when the cover composition is in a gel state, the gel cover is overlaid on the uncovered hemisphere of the previous intermediate molded body, and hot press molding is performed. Cover the other half of the core.

  In addition, it is preferable that a plurality of dimples are recessed in the cover surface. In this case, a mold having a plurality of protrusions corresponding to dimples may be used as the cover mold.

  Next, the core will be described.

  The solid core used in the present invention may have a single-layer structure or a multilayer structure having a center and one or more intermediate layers covering the center. In order to impart various performances to the golf ball, it is preferable that the coating layer (intermediate layer) has two or more layers, more preferably 3 to 7 layers. When a plurality of intermediate layers are provided, it is preferable to increase the value of the complex elastic modulus as the layer is closer to the core surface. This is because the amount of spin during a driver shot can be reduced.

  The center of the solid core of the single layer structure and the solid core of the multilayer structure is not particularly limited, but is a vulcanized molded body of a rubber composition containing a diene rubber, a co-crosslinking agent, a crosslinking initiator and the like as a base rubber. Is preferred.

  As the diene rubber, it is preferable to use a high-cis polybutadiene having a cis bond advantageous for rebound of 40% or more, preferably 70% or more, more preferably 90% or more. Further, other rubber may be blended with the high-cis polybutadiene rubber, and examples thereof include natural rubber, styrene butadiene rubber (SBR), isoprene rubber (IR), and ethylene propylene rubber.

  Examples of the co-crosslinking agent include an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof, preferably acrylic acid, methacrylic acid or a metal salt thereof. As said metal, zinc, magnesium, calcium, aluminum, and sodium are used preferably, More preferably, zinc is used. Such a co-crosslinking agent is preferably blended in an amount of 20 to 50 parts by mass with respect to 100 parts by mass of the base rubber.

  Examples of the crosslinking initiator include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxide). Examples thereof include organic peroxides such as oxy) hexane and di-t-butyl peroxide. Among these, dicumyl peroxide is preferably used. The blending amount of the crosslinking initiator is preferably 0.2 to 5 parts by mass, more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the base rubber.

  In addition to the base rubber, co-crosslinking agent, and crosslinking initiator described above, an organic sulfur compound is preferably added to the rubber composition in order to increase resilience. Specific examples of the organic sulfur compound include diphenyl disulfide derivatives such as diphenyl disulfide and dipentachlorodiphenyl disulfide. Further, the rubber composition may further contain an inorganic filler such as zinc oxide, barium sulfate, calcium carbonate, clay, an anti-aging agent, and colored powder as appropriate.

  The solid core or center having a single layer structure can be obtained by vulcanizing and molding a rubber composition as described above into a spherical shape. The vulcanization conditions may be appropriately set according to the rubber composition, but it is usually desirable to heat at 130 to 200 ° C. for 10 to 60 minutes, preferably at 150 to 175 ° C. for 10 to 40 minutes.

  When the solid core has a multilayer structure, at least one intermediate layer covering the center is not particularly limited, but in addition to the rubber composition described above, a thermoplastic resin such as an ionomer, a thermosetting resin, or the like is used. Is preferred. Examples of the thermoplastic resin include thermoplastic resins such as ionomer resins (Mitsui DuPont High Milan, DuPont Surlyn, Exxon Iotech, etc.), polyethylene, polypropylene, polystyrene, ABS resin, methacrylic resin, and polyamide. Examples of plastic elastomers include polyester elastomers (such as Toray DuPont Hytrel), polyurethane elastomers (such as BASF elastollan), polystyrene elastomers (such as Kuraray Septon), polyamide elastomers (such as Pevacs), and olefinic thermoplastic elastomers. And two-component curable resins such as polyurethane and polyurea. Among these, since the coefficient of friction (fc) can be increased and the resilience and durability are excellent, ionomer resins, polyamides, urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers are used as the intermediate layer. It is preferable to do this.

  Examples of the ionomer resin include those obtained by neutralizing a binary copolymer of an olefin and an unsaturated carboxylic acid with a metal ion, or a ternary of an olefin, an unsaturated carboxylic acid, and an ester of an unsaturated carboxylic acid. Examples include those obtained by neutralizing a copolymer with metal ions, and may be a mixture of these so as to have desired elasticity, rigidity, and the like. Examples of the metal to be neutralized include alkali metals such as sodium and lithium, alkaline earth metals such as magnesium and calcium, and divalent transition metals such as zinc and copper.

  In addition to the rubber composition and thermoplastic resin as the base material, the intermediate layer contains organic short fibers such as nylon fibers, acrylic fibers, polyester fibers, aramid fibers, etc. in order to increase the coefficient of friction (fc). In order to obtain desired properties, colorants such as titanium oxide, inorganic fillers such as barium sulfate and calcium carbonate, specific gravity adjusters such as tungsten, other anti-aging agents, ultraviolet absorbers, fluorescent enhancement You may add additives, such as a whitening agent.

  The thickness of the intermediate layer is preferably 0.3 mm or more and 5 mm or less, more preferably 0.3 mm or more and 3 mm or less, and particularly preferably 0.5 mm or more and 1.5 mm or less. This is because if the thickness is less than 0.3 mm, the resilience is low, and if it exceeds 5 mm, the feel at impact is reduced.

  The method for coating the center of the intermediate layer is not particularly limited, but in the case of a thermoplastic resin, the injection method or the compression method can be used to coat the thermoplastic resin on the center, and the rubber composition In the case of a product, an unvulcanized rubber composition is coated on the center and then vulcanized.

  In the golf ball of the present invention, when the cover is provided with dimples, particularly when the thickness of the cover is 0.5 mm or less, the surface of the solid core corresponding to the position of the dimples provided on the cover, It is preferable that irregularities (dimples) corresponding to the dimples of the cover are provided. In the case where the core is composed of a center and an intermediate layer covering the center, dimples are recessed on the surface of the intermediate layer.

  The depth of the dimple is generally about 0.1 to 0.2 mm. The cover of the present invention is so thin that the cover is extremely thin at the bottom of the dimple and in severe cases the core can even be exposed. Even if the cover is formed, the durability of the cover decreases, such as peeling or cracking of the cover from an extremely thinned portion. Accordingly, a dimple having the same shape as the dimple is recessed in the core surface corresponding to the dimple position of the cover, so that the thickness of the cover becomes uniform, and a cover thickness of 0.2 mm or more is secured even at the bottom of the dimple. Therefore, the durability of the cover can be ensured.

  When providing dimples in the core, a mold in which irregularities having the same shape as the dimples are provided in the core mold may be used. At this time, if a positioning projection is attached to the core and cover molds, and the core molded in the cover mold is set together with the positioning projections, the cover dimples are formed on the dimples formed on the core surface. Can be molded as is.

  The solid core used in the present invention preferably has a diameter of 41 mm or more and 42.4 mm or less. When the initial load of 98N to final load of 1275N is applied to the solid core, the deformation amount of the solid core is not less than 2.30 mm, preferably not less than 2.4 mm, not more than 3.30 mm, preferably not more than 3.20 mm. Is desirable. If it is less than 2.30 mm, it is too hard and the impact received by the golfer is too great. If it exceeds 3.30 mm, it is too soft and the resilience is lowered, and the ball feels heavy when it is hit.

  The solid core has a Shore D hardness of 25 to 45, preferably 30 to 40. If it is less than 25, it is too soft and the resilience is lowered and the flight distance cannot be obtained, and if it exceeds 45, the spin rate is increased and the flight distance cannot be obtained during a driver shot.

  The solid core has a Shore D hardness of 60 to 80, preferably 65 to 75. This is because if it is less than 60, the amount of spin increases and the flight distance during a driver shot cannot be obtained. On the other hand, if it exceeds 80, it will become too hard and the feeling at the time of hitting will worsen.

  The golf ball of the present invention obtained by covering the above core with the above-mentioned core has a deformation amount of 2.30 mm or more, preferably 2.50 mm or more and 3.30 mm when an initial load of 98N to a final load of 1275N is applied. Hereinafter, it is preferably 3.10 mm or less. If it is less than 2.30 mm, it is too hard and the shot feeling is hard, and if it exceeds 3.30 mm, it is too soft and the resilience is lowered, and the ball feels heavier when hitting, and the flight distance cannot be obtained.

  The golf ball of the present invention is put on the market with a paint finish, a marking stamp, etc. on the cover surface in order to increase the beauty and the commercial value.

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 within the scope not departing from the gist of the present invention are not limited thereto. Included in range.
[Measurement and evaluation methods]
(1) Compression deformation (mm)
The amount of deformation (mm) from the state in which an initial load of 10 kgf (98 N) was applied to the golf ball or core to the time when a final load of 130 kgf (1275 N) was applied was measured.
(2) Shore hardness (slab hardness) of the cover composition
The cover composition was poured into a mold and heated and cured in the mold to prepare a sheet having a thickness of about 2 mm and stored at 23 ° C. for 2 weeks. This sheet was measured by using a spring type hardness meter Shore D type defined in ASTM-D2240 in a state where three sheets were stacked so that the measurement substrate and the like were not affected.
(3) Rebound performance Each golf ball was impacted with 198.4 g of an aluminum cylinder at a speed of 45 m / sec, and the speed of the cylinder and the golf ball before and after the collision was measured. The coefficient of restitution of the golf ball was calculated.

The value of the coefficient of restitution is (comparative example) golf ball No. 11 is a numerical value obtained by indexing with a restitution coefficient of 11 as 100.
(4) Spin amount (rpm)
The spin amount (rpm) was measured by attaching a sand wedge (SW) to a true temper swing robot, setting the head speed to 20 m / sec, and continuously shooting the hit golf ball.
(5) Flight distance (carry) (m)
A titanium driver (W # 1) was attached to a true temper swing robot, the head speed was struck at 45 m / sec, and the distance (m) from the impact point to the fall point was measured.
(6) Durability A No. 5 iron was attached to a Truetemper swing robot, hit at a head speed of 38 m / sec, and the state of the ball after hitting 30 times and 50 times was visually observed. “◎” if the cover does not change even after 50 hits, no problem after 30 hits, but “50” if the cover is peeled or torn after 50 hits. The case where the cover was completely torn after 30 hits was evaluated as “x”.

[Manufacture of golf balls]
(1) Production of Core A rubber composition having the composition shown in Table 1 was heat compression molded at 170 ° C. for 15 minutes to produce a spherical solid center having a diameter of 38.7 to 40.5 mm.

BR18: High cis polybutadiene made by JSR (cis content 96% or more)
Zinc acrylate: ZNDA-90S manufactured by Nippon Distilled
Zinc Oxide: Toho Zinc Gin R
Dicumyl peroxide: Park Mill D made by NOF
Diphenyl disulfide: manufactured by Sumitomo Seika Co., Ltd. The intermediate layer composition shown in Table 2 was injection-molded at 240 ° C into the obtained solid center to form an intermediate layer having a thickness of 1 mm, and a solid core having a diameter of 40.7 to 42.5 mm Got. Golf ball no. The surface of the intermediate layer mold used for manufacturing 1 to 35 is provided with unevenness similar to dimples, and the obtained solid core has unevenness on the surface. Table 3 shows the diameter and load deformation of the obtained solid core.

Surlyn 8945: Sodium-neutralized ionomer resin made by DuPont Surlyn 9945: Zinc-neutralized ionomer resin made by DuPont

(2) Production of Ball The cover polymer composition having the composition shown in Table 4 was mixed and stirred to obtain a viscous liquid cover composition. Immediately injecting this into a hemispherical mold (with dimples), together with the mold holding the prepared solid core, heated at 80 ° C. for 2 minutes to produce an intermediate molded body half-coated with the solid core, Further, the cover composition was poured into the other hemispherical mold, and the intermediate molded body on the side not covered with the cover was overlaid thereon, and cured by heating and pressing at 80 ° C. for 10 minutes. The resulting ball was taken out of the mold and deburred, and then painted with white paint on the surface and further with clear paint to produce a golf ball having a diameter of 42.7 mm and a weight of 45.2 to 45.7 g. .

  Based on the above evaluation method, the amount of compressive deformation, coefficient of restitution, durability, carry and spin amount of the manufactured ball were measured. The measurement results are shown in Tables 4-7. In Tables 4 to 7, “C” indicates that the Shore D hardness (S) value of the cover satisfies the relational expression [30T + 16 ≦ S ≦ 30T + 32] of the present invention, and “X” indicates that the value does not satisfy the relational expression. FIG. 1 is a graph showing the relationship between the cover hardness and thickness of the golf ball obtained in the example and the formula of the present invention. In FIG. 1, ● represents an example satisfying the provisions of the present invention, and ▲ represents an example not satisfying the provisions of the present invention.

Adiprene LF800A: manufactured by Uniroyal Corporation, TDI-PTMG-based prepolymer, NCO content = 2.9%, free TDI is 0.1% or less Adiprene LF900A: manufactured by Uniroyal Corporation, TDI-PTMG-based prepolymer, NCO content = 3.8%, free TDI is 0.1% or less Adiprene LF930A: manufactured by Uniroyal, TDI-PTMG prepolymer, NCO content = 5.1%, free TDI is 0.1% or lessAdiprene LF950D: Uni Royal Co., Ltd., TDI-PTMG prepolymer, NCO content = 6.1%, free TDI is 0.1% or less Lonza Cure M-CDEA: Lonza 4,4′-methylenebis- (3-chloro-2, 6-diethylaniline), amine value 297 mg KOH / g

  Ball No. 21, 22, 24, 25, 28, 29 to 33, 35 are examples in which the Shore D hardness and thickness of the cover do not satisfy the relational expression of the present invention. Ball No. In 30, 32, 33, and 35, the cover was soft with respect to the thickness and the spin amount was large, so the flight distance was small. Ball No. Since 21, 22, 22, 24, 25, 28, 29, and 31 had a hard cover with respect to the thickness, the spin amount decreased.

  Ball No. 20, 23, 26, 27, 34, 36 and 37, the cover thickness and hardness satisfy the relational expression of the present invention, but the cover hardness (34-50) and / or cover thickness (0.2-0. 8 mm) is an example that does not satisfy the provisions of the present invention. Ball No. No. 20 was inferior in durability because the cover was thin and soft. Ball No. For 23, 26, and 27, the cover was soft and the durability was poor. Ball No. In No. 35, the cover was hard and the spin amount was small. Ball No. In No. 36, the cover was thick and the spin rate and flight distance could not be obtained. Ball No. In 37, the cover was thick and hard, so the spin amount was small and the flight distance could not be obtained.

  For these balls, ball no. As for Nos. 1 to 17, the thickness and hardness of the cover are controlled within an appropriate range, satisfy the above-mentioned relational expression, and the Shore D hardness with respect to the cover thickness is within the appropriate range. The golf ball has both the flight distance performance required at the time of driver shot. Ball No. Nos. 18 and 19 are ball numbers. 6 (18), ball no. A golf ball using a core having the same composition and size as that of No. 10 (19). Both the spin amount and the flight distance were sufficiently obtained, but none of them had dimples on the core surface. The durability was slightly inferior to the ball. In particular, ball no. In 3, 4, 6, 7, 9, 13, and 14, the relationship between the spin amount, the cover thickness, and the hardness is controlled in a more preferable range, so that the ball characteristics are stably obtained.

It is a graph which shows the relationship between the thickness of the cover of the golf ball obtained by the Example, Shore D hardness, and the relational expression of this invention.

Claims (3)

A golf ball comprising a solid core consisting of one or more layers and a cover covering the solid core,
The base resin constituting the cover is made of a two-component curable polyurethane resin,
The thickness (T) of the cover is 0.2 to 0.8 mm,
Shore D hardness (S) of the cover is 34-50,
The golf ball characterized in that T and S satisfy the following relational expression.
30T + 16 ≦ S ≦ 30T + 32 The thickness (T) of the cover is 0.3 to 0.6 mm, the Shore D hardness (S) of the cover is 34 to 46, and the T and S satisfy the following relational expression. Item 10. A golf ball according to Item 1.
30T + 20 ≦ S ≦ 30T + 28 The golf ball according to claim 1, wherein the cover includes 3 to 5 parts by mass of titanium oxide with respect to 100 parts by mass of the base resin constituting the cover.

Images