JP7255391B2 - Golf ball - Google Patents

Description

The present invention relates to a two-piece or more multi-layer golf ball comprising a core and a cover, and more particularly, to a golf ball having excellent spin performance on approach shots and excellent scuff resistance.

A major requirement for golf balls is an increase in flight distance. Other than that, the ball needs to stop well on approach shots and is scratch resistant. That is, until now, many golf balls have been developed that fly well when hit with a driver and give favorable backspin on approach shots. Furthermore, as a cover material for golf balls, materials with high resilience and good scratch resistance have been developed.

As such cover materials, urethane resin materials are increasingly being used as substitutes for ionomer resin materials, especially for professionals and advanced players. However, professional golfers and advanced golfers are demanding golf balls that are easier to control when approaching. It is required to be able to control. Therefore, there is a demand for further improvements in cover materials that use urethane resin as a base resin.

Several polymer blend cover materials have been proposed in which a urethane resin material is used as a base resin and other resin materials are mixed. For example, Japanese Patent Application Laid-Open No. 11-9721 proposes to use a blend of thermoplastic polyurethane and styrene base block copolymer as the main material of the cover in order to improve the scratch resistance of the cover. However, this blend cover was unsatisfactory in rebound resilience and scratch resistance.

Recently, various physical properties of thermoplastic urethane elastomers have been upgraded, one of which is improved scratch resistance. Therefore, when other resin materials are blended, it is desired that the scuff resistance inherent in the thermoplastic urethane elastomer is not lowered by appropriately adjusting the type and blending amount of the resin.

Moreover, when blending a urethane resin material with other resin materials for the purpose of lowering the hardness, it is also desirable to avoid changes in impact resilience and deterioration of moldability as much as possible.

JP-A-11-9721

SUMMARY OF THE INVENTION It is an object of the present invention to provide a golf ball that maintains excellent controllability on approach shots without reducing flight distance on driver shots and maintains good scuff resistance. and

The inventors of the present invention have made intensive studies to achieve the above objects, and as a result, have found that, in a golf ball comprising a core and a cover, a resin material that uses polyurethane or polyurea as the main component for the cover has been further improved. In order to achieve this, a resin composition in which an aromatic vinyl elastomer is blended with the polyurethane or polyurea is used, the Martens hardness of the polyurethane or polyurea is HMa [N/mm ² ], and the aromatic vinyl elastomer is added to the polyurethane or polyurea. When the Martens hardness of the cover layer formed from the blended resin composition is HMb [N/mm ² ], and the elastic work recovery rate of the cover layer is ηItb [%], HMa, HMb and ηItb are expressed by the following formulas: (1) and formula (2)
1.005≦HMa/HMb≦1.450 (1)
2.00≦ηItb/HMb≦7.00 (2)
The golf ball was produced to satisfy the above, and found that this golf ball had a low initial ball velocity on approach, but had a high spin rate and excellent controllability, as well as being able to maintain good scuff resistance. This is what has led to the present invention.

That is, when the outermost layer of the cover is formed of a resin composition using polyurethane or polyurea as a main component, the softer the resin used, such as polyurethane, the better the spin performance under approach conditions. The initial velocity tends to be high, making it difficult to control performance when approaching, but by adding an arbitrary amount of aromatic vinyl elastomer, the initial velocity controllability is improved while maintaining spin rate and scratch resistance. (maintaining good controllability on approach by keeping the initial velocity low), and defined the Martens hardness and elastic work recovery rate of such a low-resilience cover layer as above. is.

Accordingly, the present invention provides the following golf balls.
1. A golf ball comprising a core consisting of at least one layer and a single-layer or multiple-layer cover, wherein at least one layer of the cover comprises the following components (I) and (II): polyurethane or polyurea (II). ) Formed from a resin composition containing an aromatic vinyl elastomer, the Martens hardness of the resin material of component (I) is HMa [N/mm ² ], and components (I) and (II) are contained. When the Martens hardness of the cover layer formed of the resin composition is HMb [N/mm ² ] and the elastic work recovery rate of the cover layer is ηItb [%], HMa, HMb and ηItb are expressed by the following formula (1). and equation (2)
1.005≦HMa/HMb≦1.450 (1)
2.00≦ηItb/HMb≦7.00 (2)
A golf ball characterized by satisfying
2. 2. The golf ball of item 1, wherein the value of HMa/HMb in formula (1) has a lower limit of 1.007 and an upper limit of 1.400.
3. 2. The golf ball of 1 above, wherein the value of ηItb/HMb in the formula (2) has a lower limit of 2.50 and an upper limit of 6.50.
4. When the elastic work recovery rate of the resin material of the component (I) is ηIta [%], the following formula (3)
1.001≤ηIta/ηItb≤1.070 (3)
4. The golf ball according to any one of 1 to 3 above, which satisfies
5. 5. The golf ball of any one of items 1 to 4, wherein component (II) is added in an amount of 50 parts by mass or less per 100 parts by mass of component (I).
6. 6. The golf ball of any one of 1 to 5 above, wherein the component (II) is a hydrogenated aromatic vinyl elastomer.
7. The component (II) is an elastomer obtained by hydrogenating a polymer consisting of a polymer block mainly composed of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. 7. The golf ball according to any one of 1 to 6 above.
8. Component (II) is a polymer consisting of a styrene polymer block and a random copolymer block of styrene and butadiene, having polymer blocks of styrene at both ends and a random copolymer block in the middle. 8. The golf ball of any one of 1 to 7 above, which is a hydrogenated aromatic vinyl elastomer obtained by hydrogenating

The golf ball of the present invention has excellent controllability on approach and can maintain good scratch resistance.

1 is a schematic cross-sectional view of a golf ball that is an embodiment of the present invention; FIG.

The present invention will be described in more detail below.
The golf ball of the present invention is a golf ball in which a core consisting of at least one layer is covered with a single-layer or multiple-layer cover. For example, as shown in FIG. 1, it has a core 1, an intermediate layer (inner cover layer) 2 covering the core 1, and an outermost layer (outer cover layer) 3 covering the intermediate layer. A multi-piece solid golf ball G may be mentioned. The cover layer (outermost layer) 3 is the outermost layer in the layered structure of the golf ball, excluding the coating layer. A large number of dimples D are usually formed on the surface of the cover layer (outermost layer) 3 to improve aerodynamic characteristics. A coating layer is usually formed on the surface of the cover layer 3, although not shown.

The core can be formed using a known rubber material as a base material. As the base rubber, known base rubbers such as natural rubber or synthetic rubber can be used. recommended to be used for Further, in the base rubber, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. can be used in combination with the polybutadiene described above, if desired.

Moreover, polybutadiene can be synthesized using a metal catalyst such as a rare earth element-based catalyst such as an Nd catalyst, a cobalt catalyst, or a nickel catalyst.

Co-crosslinking agents such as unsaturated carboxylic acids and metal salts thereof, inorganic fillers such as zinc oxide, barium sulfate and calcium carbonate, dicumyl peroxide and 1,1-bis(t-butyl Organic peroxides such as peroxy)cyclohexane and the like can be blended. In addition, if necessary, a commercially available anti-aging agent or the like can be added as appropriate.

The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, it is kneaded using a kneader such as a Banbury mixer or a roll, compression molded or injection molded using a core mold, and the temperature is 100 to 100 as a temperature sufficient for the organic peroxide or co-crosslinking agent to act. By appropriately heating the molded article under conditions of 200° C., preferably 140 to 180° C., for 10 to 40 minutes, the molded article can be cured and produced.

In the present invention, at least one layer of the cover is formed of a resin composition containing the following (I) and (II) components (I) polyurethane or polyurea (II) aromatic vinyl elastomer. The components (I) and (II) are described in detail below.

(I) Polyurethane or Polyurea Polyurethane or polyurea can be the main material or base resin of the cover material (resin composition). The details of this component, polyurethane (Ia) or polyurea (Ib), are as follows.

(Ia) Polyurethane The structure of polyurethane is composed of a soft segment composed of a high-molecular-weight polyol (polymeric glycol), which is a long-chain polyol, and a chain extender and polyisocyanate constituting a hard segment. Here, as the polymer polyol used as a raw material, any of those conventionally used in techniques related to polyurethane materials can be used, and there is no particular limitation. Examples include polyester polyols, polyether polyols, polycarbonate polyols, polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols, castor oil polyols, silicone polyols, and vinyl polymer polyols. Specific examples of polyester-based polyols that can be used include adipate-based polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polybutadiene adipate glycol, and polyhexamethylene adipate glycol, and lactone-based polyols such as polycaprolactone polyol. Polyether polyols include poly(ethylene glycol), poly(propylene glycol) and poly(tetramethylene glycol), poly(methyltetramethylene glycol) and the like. These may be used individually by 1 type, and may use 2 or more types together.

As the polymer polyol, it is preferable to use a polyether-based polyol.

The number average molecular weight of the long-chain polyol is preferably within the range of 1,000 to 5,000. By using a long-chain polyol having such a number-average molecular weight, it is possible to reliably obtain a golf ball made of a polyurethane composition that is excellent in various properties such as resilience and productivity. The number average molecular weight of the long-chain polyol is more preferably in the range of 1,500 to 4,000, even more preferably in the range of 1,700 to 3,500.

The number average molecular weight mentioned above is the number average molecular weight calculated based on the hydroxyl value measured according to JIS-K1557 (hereinafter the same).

As the chain extender, those used in conventional polyurethane technology can be suitably used, and are not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule and having a molecular weight of 2,000 or less can be used. Group diols can be preferably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Among them, 1,4-butylene glycol can be preferably used.

As the polyisocyanate, those used in conventional polyurethane technology can be suitably used, and there is no particular limitation. Specifically, 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenation 1 selected from the group consisting of xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, dimer acid diisocyanate A species or two or more species can be used. However, with some isocyanate species, it is difficult to control the cross-linking reaction during injection molding.

In addition, the compounding ratio of active hydrogen atoms to isocyanate groups in the polyurethane-forming reaction can be appropriately adjusted within a preferred range. Specifically, in producing polyurethane by reacting the long-chain polyol, the polyisocyanate compound and the chain extender, the polyisocyanate compound is It is preferable to use each component in such a proportion that the isocyanate group contained in is 0.95 to 1.05 mol.

The method for producing polyurethane is not particularly limited, and a long-chain polyol, a chain extender, and a polyisocyanate compound can be used, and a known urethanization reaction can be used to produce the polyurethane by either the prepolymer method or the one-shot method. good. Among them, it is preferable to carry out melt polymerization in the absence of a solvent, and it is particularly preferable to carry out continuous melt polymerization using a multi-screw extruder.

A thermoplastic polyurethane material is preferably used as the polyurethane described above, and an ether-based thermoplastic polyurethane material is particularly preferable. As the thermoplastic polyurethane material, commercially available products can be suitably used. be able to.

(Ib) Polyurea Polyurea is a resin composition mainly composed of urea bonds produced by the reaction of (i) isocyanate and (ii) amine-terminated compounds. This resin composition will be described in detail below.

(i) Isocyanate As the isocyanate, those used in the conventional techniques related to polyurethane can be suitably used, and there are no particular restrictions, and the same isocyanate as explained for the polyurethane material can be used.

(ii) Amine-terminated compound The amine-terminated compound is a compound having an amino group at the end of the molecular chain, and in the present invention, the following long-chain polyamines and/or amine-based curing agents can be used.

A long-chain polyamine is an amine compound having two or more amino groups capable of reacting with an isocyanate group in its molecule and having a number average molecular weight of 1,000 to 5,000. In the present invention, the number average molecular weight is more preferably 1,500-4,000, more preferably 1,900-3,000. Specific examples of the long-chain polyamine include amine-terminated hydrocarbons, amine-terminated polyethers, amine-terminated polyesters, amine-terminated polycarbonates, amine-terminated polycaprolactones, and mixtures thereof. can be, but are not limited to: One of these long-chain polyamines may be used alone, or two or more thereof may be used in combination.

On the other hand, an amine-based curing agent is an amine compound having two or more amino groups capable of reacting with an isocyanate group in its molecule and having a number average molecular weight of less than 1,000. In the present invention, the number average molecular weight is more preferably less than 800, more preferably less than 600. Specific examples of the amine curing agent include ethylenediamine, hexamethylenediamine, 1-methyl-2,6-cyclohexyldiamine, tetrahydroxypropyleneethylenediamine, 2,2,4- and 2,4,4-trimethyl-1, 6-hexanediamine, 4,4′-bis-(sec-butylamino)-dicyclohexylmethane, 1,4-bis-(sec-butylamino)-cyclohexane, 1,2-bis-(sec-butylamino)- Cyclohexane, derivatives of 4,4′-bis-(sec-butylamino)-dicyclohexylmethane, 4,4′-dicyclohexylmethanediamine, 1,4-cyclohexane-bis-(methylamine), 1,3-cyclohexane-bis -(methylamine), diethylene glycol di-(aminopropyl) ether, 2-methylpentamethylenediamine, diaminocyclohexane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, propylenediamine, 1,3-diaminopropane, dimethylaminopropylamine , diethylaminopropylamine, dipropylenetriamine, imido-bis-propylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, isophoronediamine, 4,4'-methylenebis-(2-chloroaniline) , 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine, 3,5-diethylthio-2,4-toluenediamine, 3,5-diethylthio-2,6- toluenediamine, 4,4'-bis-(sec-butylamino)-diphenylmethane and its derivatives, 1,4-bis-(sec-butylamino)-benzene, 1,2-bis-(sec-butylamino)- Benzene, N,N'-dialkylamino-diphenylmethane, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p -aminobenzoate, 4,4'-methylenebis-(3-chloro-2,6-diethyleneaniline), 4,4'-methylenebis-(2,6-diethylaniline), m-phenylenediamine, p-phenylenediamine, and mixtures thereof, without limitation. These amine-based curing agents may be used singly or in combination of two or more.

(iii) Polyol Polyurea may contain a polyol in addition to the above components (i) and (ii), although it is not an essential component. As this polyol, those used in conventional polyurethane technology can be suitably used, and there is no particular limitation. Specific examples include the following long-chain polyols and/or polyol-based curing agents. can.

As the long-chain polyol, any one conventionally used in polyurethane technology can be used, and there is no particular limitation. Examples include polyester polyol, polyether polyol, polycarbonate polyol, polyester polycarbonate polyol, and polyolefin polyol. , conjugated diene polymer-based polyols, castor oil-based polyols, silicone-based polyols, vinyl polymer-based polyols, and the like. One of these long-chain polyols may be used alone, or two or more thereof may be used in combination.

The number average molecular weight of the long-chain polyol is preferably 1,000 to 5,000, more preferably 1,700 to 3,500. Within this number-average molecular weight range, the resilience, productivity and the like are further improved.

As the polyol-based curing agent, those used in conventional polyurethane technology can be suitably used, and are not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule and having a molecular weight of less than 1,000 can be used. Group diols can be preferably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Among them, 1,4-butylene glycol can be preferably used. The number average molecular weight of the polyol-based curing agent is preferably less than 800, more preferably less than 600.

As for the method for producing the polyurea, a known method can be adopted, and a known method such as a prepolymer method or a one-shot method can be appropriately selected.

Regarding the material hardness of component (I), the Shore D hardness is preferably 65 or less, more preferably 60 or less, still more preferably 60 or less, in terms of the spin characteristics and scratch resistance of the golf ball. is 55 or less. The lower limit thereof is preferably 25 or more in Shore D hardness, more preferably 30 or more in Shore D hardness, from the standpoint of moldability.

The above component (I) is the main component of the resin composition, and from the viewpoint of sufficiently imparting the scratch resistance of the urethane resin, it is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass of the resin composition. % by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more.

(II) Aromatic Vinyl Elastomer Next, the (II) aromatic vinyl elastomer will be described.
An aromatic vinyl-based elastomer is a polymer (elastomer) composed of a polymer block mainly composed of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. That is, aromatic vinyl-based elastomers generally have blocks composed of aromatic vinyl compound components as hard segments at both ends, and blocks composed of conjugated diene compound components as soft segments, as typified by SEBS. have in the middle. Recent studies have also reported a polymer in which, in addition to a conjugated diene compound component, an aromatic vinyl-based component is randomly incorporated in the midblock. In general, the hardness of aromatic vinyl elastomers decreases as the content of the aromatic vinyl that forms the hard segment decreases, and the impact resilience increases due to the increase in the soft segment component. On the other hand, when the aromatic vinyl component is randomly incorporated into the soft component of the mid-block, the impact resilience is lowered without significantly increasing the hardness. A similar effect can also be obtained by using a conjugated diene compound exhibiting a high Tg instead of the aromatic vinyl compound randomly incorporated in the intermediate block. In particular, in the present invention, it is preferable to use a hydrogenated polymer (elastomer) as the component (II) in order to sufficiently exhibit the above-mentioned effects.

Examples of aromatic vinyl compounds in the polymer include styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, N, Examples include N-diethyl-p-aminoethylstyrene. These may be used alone or in combination of two or more. Among these groups, styrene is preferred.

Examples of the conjugated diene compound in the polymer include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. etc. These may be used alone or in combination of two or more. Among these groups, butadiene and isoprene are preferred, and butadiene is more preferred.

Units derived from the conjugated diene compound, for example, units derived from butadiene, become ethylene units or butylene units by hydrogenation. For example, a styrene-butadiene-styrene block copolymer (SBS) is hydrogenated to give a styrene-ethylene-butylene-styrene block copolymer (SEBS).

As the aromatic vinyl elastomer as the component (II), as described above, it is preferable to employ a hydrogenated aromatic vinyl elastomer, that is, a hydrogenated aromatic vinyl elastomer. The hydrogenated aromatic vinyl elastomer is obtained by hydrogenating a polymer block composed mainly of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. Elastomers are preferred, and elastomers obtained by hydrogenating a polymer consisting of a polymer block mainly composed of styrene and a random copolymer block of styrene and butadiene are more preferred. A polymer consisting of a random copolymer block with butadiene, in particular, a polymer block mainly composed of styrene at both ends (especially a polymer block consisting only of styrene at both ends) and a random copolymer block in the middle Elastomers obtained by addition are preferred. By using a copolymer having this structure, it has both low hardness and low resilience, and because it has a fast solidification speed after molding, it has little tack, and is compatible with (I) polyurethane or polyurea, which is the main component. It is thought that deterioration of physical properties due to blending can be minimized due to excellent compatibility.

Specific examples of the hydrogenated aromatic vinyl elastomer include styrene-ethylene/butylene-styrene block copolymer (SEBS), styrene-isobutylene-styrene block copolymer (SIBS), and styrene-isoprene-styrene block. copolymer (SIS), styrene-isobutylene block copolymer (SIB), styrene-ethylene/propylene-styrene block copolymer (SEPS), styrene-ethylene/ethylene/propylene-styrene block copolymer (SEEPS), Styrene-butadiene/butylene-styrene block copolymer (SBBS), styrene-ethylene-propylene block copolymer (SEP), and the like.

In the aromatic vinyl-based elastomer, the ratio of units derived from the aromatic vinyl compound in the copolymer (that is, the content of the aromatic vinyl compound, preferably the content of styrene) is 30% by mass or more. is preferred, more preferably 40% by mass or more, still more preferably 50% by mass or more, and most preferably 60% by mass or more. Thus, by setting the aromatic vinyl compound content, preferably the styrene content, to a large amount, the compatibility with polyurethane or polyurea, which is the component (I), is improved, and the desired hardness and moldability are deteriorated. can be prevented. The content of units derived from the aromatic vinyl compound (preferably the styrene content) can be calculated by H ¹ -NMR measurement.

In addition, in the aromatic vinyl elastomer, the glass transition temperature (Tg) indicated by the tan δ peak temperature obtained by dynamic viscoelasticity measurement (DMA) is preferably -20 to 50°C, more preferably 0°C. 5° C. or higher, more preferably 5° C. or higher. That is, by having the tan δ peak temperature near the temperature at which golf balls are normally used, the impact resilience of the entire resin composition is kept low in the temperature range at which golf balls are normally used, and the desired effect of the present invention can be achieved. can be increased.

Commercially available products can be used as the aromatic vinyl-based elastomer that is the component (II). For example, commercially available products include “S.O.E. "Dick Styrene" manufactured by DIC Corporation can be mentioned.

The rebound resilience of component (II) is preferably 40% or less, more preferably 30% or less, still more preferably 25% or less as measured according to JIS-K 6255 standard. By keeping the modulus of rebound resilience very low in this way, it is possible to reduce the initial velocity of the ball on approach shots without adversely affecting the physical properties of the golf ball with a small addition amount. However, the lower limit of the modulus of rebound resilience is preferably 20% or more in order to minimize the impact on the reduction in rebound on driver shots and the reduction in flight distance.

The blending amount of component (II) is preferably 50 parts by mass or less per 100 parts by mass of component (I). In addition, the lower limit of the blending amount is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.5 parts by mass or more. If the blending amount of component (II) is too large, the scratch resistance and moldability may deteriorate. On the other hand, if the blending amount of component (II) is too small, the cover resin material may not have low hardness and desired rebound resilience, and the effect of lowering the ball's initial velocity on approach shots may be reduced.

The resin composition containing the above (I) and (II) may contain other resin materials in addition to the resin components described above. The purpose is to further improve the fluidity of the resin composition for golf balls and improve various physical properties such as resilience and scratch resistance.

Specific examples of other resin materials include polyester elastomers, polyamide elastomers, ionomer resins, ethylene-ethylene/butylene-ethylene block copolymers or modified products thereof, polyacetal, polyethylene, nylon resins, methacrylic resins, and polyvinyl chloride. , polycarbonate, polyphenylene ether, polyarylate, polysulfone, polyethersulfone, polyetherimide and polyamideimide, and one or more of them can be used.

In addition, the resin composition can further contain an active isocyanate compound. This active isocyanate compound reacts with polyurethane or polyurea, which is the main component, to further improve the scratch resistance of the entire resin composition. can be improved.

As the above isocyanate compound, any isocyanate compound that is commonly used in polyurethane can be used without particular limitation. Mixtures of these two, 4,4-diphenylmethane diisocyanate, m-phenylene diisocyanate, 4,4'-biphenyl diisocyanate, etc., and hydrogenated products of these aromatic isocyanate compounds, such as dicyclohexylmethane diisocyanate, can also be used. Aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI) and octamethylene diisocyanate, and alicyclic diisocyanates such as xylene diisocyanate are also included. Furthermore, a blocked isocyanate compound obtained by reacting an isocyanate group of a compound having two or more isocyanate groups at its end with a compound having an active hydrogen, and a uretidione compound obtained by dimerization of isocyanate may be mentioned.

The amount of the isocyanate compound compounded is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyurethane or polyurea resin that is the main material. is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. If this amount is too small, a sufficient cross-linking reaction may not be obtained, and no improvement in physical properties may be observed. On the other hand, if the blending amount is too large, problems such as discoloration due to heat or ultraviolet rays over time, loss of thermoplasticity, and a decrease in resilience may occur.

Furthermore, any additive can be appropriately added to the resin composition according to the application. For example, when the golf ball material of the present invention is used as a cover material, the above ingredients include a filler (inorganic filler), organic staple fiber, reinforcing agent, cross-linking agent, pigment, dispersant, anti-aging agent, ultraviolet absorber, Various additives such as light stabilizers can be added. When these additives are blended, the blending amount is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the base resin, and the upper limit is preferably 10 parts by mass. parts or less, more preferably 4 parts by mass or less.

Regarding the rebound resilience of the above resin composition, if this value is too high, it will have the effect of increasing flight distance on driver shots, but the ball's initial velocity on approach shots will also increase, making it difficult to control. Therefore, it is preferably 65% or less as measured according to the JIS-K 6255 standard. However, the lower limit of the modulus of rebound resilience is preferably 30% or more in order to suppress as much as possible the reduction in rebound and reduction in flight distance on driver shots.

The material hardness of the resin composition is preferably 60 or less in Shore D hardness, more preferably 55 or less in Shore D hardness, and still more preferably 55 or less in Shore D hardness, in view of the spin characteristics and scratch resistance of the golf ball. It is preferably 50 or less, most preferably 45 or less. The lower limit thereof is preferably 20 or more in Shore D hardness, more preferably 30 or more in Shore D hardness, from the standpoint of moldability.

Regarding the method of preparing each component of the resin composition, for example, it is possible to mix using various kneaders such as a kneading type (single-screw or) twin-screw extruder, Banbury, kneader, labo plastomill, or Each component may be mixed by dry blending during injection molding of the resin composition. Furthermore, when using the above-mentioned active isocyanate compound, it may be contained at the time of resin mixing using various kneaders, or a master batch containing the active isocyanate compound and other components is prepared separately in advance, and the resin composition The components may be mixed by dry blending during injection molding of the article.

For example, as a method of molding the cover layer from the above resin composition, for example, the above resin composition is supplied to an injection molding machine, and the melted resin composition is injected around the core to mold the cover layer. be able to. In this case, the molding temperature is usually in the range of 150 to 270° C., depending on the type of the main component (I) polyurethane or polyurea.

In the present invention, the Martens hardness of the resin material of the component (I) is HMa [N/mm ² ], and the Martens hardness of the cover layer formed of the resin composition containing the components (I) and (II) is HMb. When [N/mm ² ], it is necessary to satisfy the following formula (1) from the viewpoint of improving the control performance during approach while maintaining the scratch resistance.
1.005≦HMa/HMb≦1.450 (1)

The lower limit of the formula (1) is 1.005 or more, preferably 1.007 or more, more preferably 1.009 or more, and the lower limit is 1.450 or less, preferably 1.400. 1.350 or less, more preferably 1.350 or less. If the value of formula (1) is too large, the scratch resistance will be low, while if the value of formula (1) is too small, approach controllability may be low.

The lower limit of the Martens hardness HMa of the resin material of component (I) is preferably 10.00 N/mm ² or more, more preferably 11.00 N/mm ² or more. The upper limit is preferably 30.00 N/mm ² or less, more preferably 25.00 N/mm ² or less.

The lower limit of the Martens hardness HMb of the cover layer formed from the resin composition containing the components (I) and (II) is preferably 8.00 N/mm ² or more, more preferably 9.0 N/mm 2 . 00 N/mm ² or more. The upper limit is preferably 28.00 N/mm ² or less, more preferably 23.00 N/mm ² or less.

The above Martens hardness HMa and HMb can be measured with an ultra-micro hardness tester based on ISO 14577:2002 "Metallic materials - Instrumented indentation test for hardness and materials parameters". That is, it is a physical property value obtained by pushing the indenter into the object to be measured while applying a load, and is obtained by pressing force [N]/area of pressure receiving portion [mm ² ]. The measurement of Martens hardness can be performed using, for example, an ultra-micro hardness test system "Fischerscope HM2000" (manufactured by Fisher Instruments). For example, this measuring device can measure the hardness of the cover while continuously applying a load stepwise, and as a setting condition, the applied load can be set to 50 mN for 10 seconds at room temperature.

Also, when measuring the surface of the cover, it is difficult to identify if a coating film or the like is formed on the surface of the cover. Since it is affected by hardness, the Martens hardness inherent in the cover can be stably obtained at a point approximately 0.3 mm from the surface of the cover toward the center of the ball, so the Martens hardness is measured at the above position. is desirable.

Further, in the present invention, when the elastic work recovery rate of the cover layer is ηItb [%], the following formula ( 2) must be satisfied.
2.00≦ηItb/HMb≦7.00 (2)

The lower limit of the formula (2) is 2.00 or more, preferably 2.50 or more, more preferably 2.70 or more, and the lower limit is 7.00 or less, preferably 6.50. Below, more preferably below 6.30. If the value of formula (2) is too large or too small, the scratch resistance may deteriorate.

The lower limit of the elastic work recovery rate ηItb of the cover layer is preferably 50% or more, more preferably 55% or more. The upper limit is preferably 85% or less, more preferably 80% or less.

Further, when the elastic work recovery rate of the resin material of component (I) is ηIta [%], it is preferable that the following formula (3) is satisfied.
1.001≤ηIta/ηItb≤1.070 (3)

The lower limit of the elastic work recovery rate ηIta of the resin material of component (I) is preferably 45% or more, more preferably 50% or more. The upper limit is preferably 80% or less, more preferably 75% or less.

The above elastic work recovery rates ηIta and ηItb are such that the cover formed on the surface of the golf ball maintains a certain level of hardness and elasticity while enhancing the self-healing recovery function, thereby providing the ball with excellent durability and scratch resistance. can contribute to Even if the Martens hardness is low, if the elastic work recovery rate is too low, the spin performance on approach is good, but the scuff resistance is poor. A method for measuring the elastic work recovery rate will be described later.

The above elastic work recovery rate is an ultra-micro hardness test method that controls the indentation load on the order of micro Newtons (μN) and tracks the indenter depth during indentation with nanometer (nm) accuracy. is one parameter of the nanoindentation method for evaluating Conventional methods could only measure the size of the deformation mark (plastic deformation mark) corresponding to the maximum load, but the nanoindentation method automatically and continuously measures the relationship between the indentation load and the indentation depth. can be obtained. Therefore, it is believed that the physical properties of the cover can be evaluated reliably and with high precision without the individual differences that occur when visually measuring deformation marks with an optical microscope. For this reason, the cover of a golf ball is greatly affected by the impact of a driver or various clubs, and the impact of the cover on various physical properties of the golf ball is not small. Measuring with higher accuracy than before is a very effective evaluation method.

The thickness of the cover is preferably 0.4 mm or more, more preferably 0.5 mm or more, still more preferably 0.6 mm or more, and the upper limit is preferably 3.0 mm or less, more preferably 2.0 mm or less. .

At least one intermediate layer may be interposed between the core and the above. In this case, as the material for the intermediate layer, it is preferable to employ various thermoplastic resins, particularly ionomer resins, which are used in golf ball cover materials, and commercially available ionomer resins can be used.

In terms of aerodynamic performance, the golf ball of the present invention is provided with a large number of dimples on the surface of the outermost layer. The number of dimples formed on the surface of the outermost layer is not particularly limited, but is preferably 250 or more, more preferably 270 or more, still more preferably 270 or more, from the viewpoint of enhancing aerodynamic performance and increasing flight distance. The number is 290 or more, most preferably 300 or more, and the upper limit is preferably 400 or less, more preferably 380 or less, still more preferably 360 or less.

In the present invention, a coating film layer is formed on the surface of the cover. As the paint for forming this coating layer, it is preferable to employ a two-liquid curable urethane paint. Specifically, in this case, the two-liquid curing type urethane paint contains a main component having a polyol resin as a main component and a curing agent having a polyisocyanate as a main component.

The method for forming the coating film layer by coating the above-mentioned paint on the surface of the cover is not particularly limited, and any known method can be used, and a desired method such as an air gun coating method or an electrostatic coating method can be used. can be done.

The thickness of the coating layer is not particularly limited, but is usually 8-22 μm, preferably 10-20 μm.

The golf ball of the present invention may conform to the Rules of Golf for use in competitions, and has an outer diameter of 42.672 mm or less, which does not pass through a ring with an inner diameter of 42.672 mm, and a weight of 45.0 mm or less. ˜45.93 g.

EXAMPLES Hereinafter, the present invention will be specifically described by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 12, Comparative Examples 1 to 5]
A core having a diameter of 38.6 mm was produced by preparing and vulcanizing a core rubber composition common to all examples according to the formulation shown in Table 1.

Details of the core material are as follows.
・"cis-1,4-Polybutadiene" manufactured by JSR, trade name "BR01"
・"Zinc acrylate" manufactured by Nippon Shokubai Co., Ltd. ・"Zinc oxide" manufactured by Sakai Chemical Industry Co., Ltd. ・"Barium sulfate" manufactured by Sakai Chemical Industry Co., Ltd. )
・ “Organic peroxide (1)” dicumyl peroxide, trade name “Percumyl D” (manufactured by NOF Corporation)
・ “Organic peroxide (2)” 1,1-di(tert-butylperoxy)cyclohexane and silica mixture, trade name “Perhexa C-40” (manufactured by NOF Corporation)
・"Zinc stearate" manufactured by NOF Corporation

Next, an intermediate layer resin material common to all examples was compounded. This intermediate layer resin material is composed of 50 parts by mass of a neutralized sodium product of an ethylene-unsaturated carboxylic acid copolymer having an acid content of 18% by mass and an ethylene-unsaturated carboxylic acid copolymer having an acid content of 15% by mass in zinc. It is a blended product with 50 parts by mass of the soda to make a total of 100 parts by mass. This resin material was injection molded around the 38.6 mm diameter core obtained above to produce an intermediate layer-covered sphere having an intermediate layer with a thickness of 1.25 mm.

Next, the cover materials shown in Tables 2 and 3 below were injection-molded around the intermediate layer-covered spheres in the amounts shown in the same tables to form a cover layer (outermost layer) having a thickness of 0.8 mm. A three-piece golf ball with a diameter of 42.7 mm was produced. At this time, common dimples were formed on the cover surface of each example and comparative example, although not shown.

Preparation of resin composition for the cover (outermost layer) The resin composition was mixed by dry blending in the components and blending amounts shown in Tables 2 and 3 below, and injection molded at a molding temperature of 210 to 250°C.

The details of the ingredients in the compositions in Tables 2 and 3 below are as follows.
- "TPU1": trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., aromatic ether type thermoplastic polyurethane (Shore D hardness: 43)
- "TPU2": Trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., aromatic ether type thermoplastic polyurethane (Shore D hardness: 47)
- "TPU3": Trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., aromatic ether type thermoplastic polyurethane (Shore D hardness: 56)
・ “SOE S1611”: Hydrogenated aromatic vinyl elastomer manufactured by Asahi Kasei Corporation (styrene content: 60 wt%, Shore D hardness: 23, and impact resilience: 20%)
・ “Hytrel 4001”: Polyester elastomer manufactured by DuPont Toray Co., Ltd. (Shore D hardness: 37)

The Martens hardness (HMa) and elastic work recovery rate (ηIta) of the polyurethane resins (“TPU1” to “TPU3”) used in each example and each comparative example were measured by the following methods. In addition, Martens hardness (HMb) and elastic work recovery rate (ηItb) were measured for the resin composition of the cover layer (outermost layer) used in each example and each comparative example. Next, the following three relational expressions (1) of these parameters: HMa/HMb,
Equation (2): ηItb/HMb and Equation (3) ηIta/ηItb
was calculated. These calculated values are shown in Tables 2 and 3.

Martens hardness (HMb) of outermost layer (cover layer)
The golf ball of each example was cut in half, and a point of 0.3 mm from the surface of the cover toward the center of the ball was specified from the cross section of the ball ^. was measured using an ultra-micro hardness tester manufactured by Fisher Instruments under the trade name of "Fischerscope HM2000". The hardness measurement was performed at room temperature under an applied load of 50 mN/10 s.

Martens hardness (HMa) of resin material
The Martens hardness (HMa) of each resin of polyurethane (“TPU1” to “TPU3”) is as follows. The apparatus and conditions for measuring the Martens hardness of these resins are the same as those described above.
・ Martens hardness (HMa) of TPU1: 14.3 N/mm ²
・TPU2 Martens hardness (HMa) 22.1 N/mm ²
・ Martens hardness (HMa) of TPU3 is 40.3 N/mm ²

Elastic Work Recovery Rate of Cover Layer (Outermost Layer) The elastic work recovery rate of the cover layer was measured using an ultra-micro hardness tester under the trade name "Fischerscope HM2000" manufactured by Fisher Instruments. The measurement conditions are as follows: under the applied load of 50 mN/10 s at room temperature, the elastic work is calculated by the following formula based on the indentation work W _elast (Nm) due to the return deformation of the cover and the mechanical indentation work W _total (Nm). A recovery rate is calculated.
Elastic work recovery rate = W _elast / W _total x 100 (%)

Elastic Work Recovery Rate of Resin Material The elastic work recovery rate (%) of each resin of polyurethane (“TPU1” to “TPU3”) is as follows. The apparatus and conditions for measuring the elastic work recovery rate of these resins are the same as described above.
・ Elastic work recovery rate of TPU1: 72%
・ Elastic work recovery rate of TPU2: 57%
・ Elastic work recovery rate of TPU3: 40%

Physical Properties of Balls on Approach Shots Regarding the obtained golf balls of Examples and Comparative Examples, a sand wedge (SW) was attached to a golf hitting robot, and the initial velocity of the ball immediately after hitting at a head speed (HS) of 20 m/s. and the amount of backspin was measured by an initial condition measurement device. Regarding the initial velocity on approach shots, the initial velocity difference was examined for Examples 1 to 7 with Comparative Example 1 as the reference, and the initial velocity difference for Examples 8 to 12 was examined with Comparative Example 5 as the reference. Tables 2 and 3 show these measured and calculated values.

Further, a sensory evaluation of the operability of the club during approach was carried out by the following method.
[Judgment evaluation]
(double-circle) ... Very excellent in operability.
O: Excellent in operability.
x: Inferior in operability.

Scratch Resistance Evaluation Balls were kept warm at 23° C., and hit five balls each at a head speed of 33 m/s using a swing robot machine and a pitching wedge as the club. It was visually evaluated according to the standard.
[Judgment evaluation]
A: Slightly scratched or almost unnoticeable.
◯: The surface is slightly fuzzy, or the dimples are slightly lacking.
× . . . Dimples are completely scraped off.

As shown in Table 2, the golf balls of Comparative Examples 1 to 4 are inferior to the products of the present invention (Examples) in the following points.
In Comparative Example 1, the cover material did not contain the aromatic vinyl elastomer, which is the component (II) of the present invention. not sexual enough.
In Comparative Example 2, the cover material contained the aromatic vinyl elastomer as component (II) of the present invention, but the value of ηItb/HMb was less than 2.00, resulting in poor scratch resistance. .
In Comparative Example 3, the cover material contained the aromatic vinyl elastomer, which is the component (II) of the present invention, but the value of HMa/HMb was greater than 1.450 and the value of ηItb/HMb was 7. 00, resulting in poor scratch resistance.
In Comparative Example 4, the value of HMa/HMb is less than 1.005, resulting in insufficient controllability during approach.

As shown in Table 3, in Comparative Example 5, the cover material did not contain the aromatic vinyl elastomer, which is the component (II) of the present invention. Although the amount is large, the initial velocity is high and the controllability is not sufficient.

Claims (8)

A golf ball comprising a core consisting of at least one layer and a single-layer or multiple-layer cover, wherein at least one layer of the cover comprises the following components (I) and (II): polyurethane or polyurea (II). ) Formed from a resin composition containing an aromatic vinyl elastomer, the Martens hardness of the resin material of component (I) is HMa [N/mm ² ], and components (I) and (II) are contained. When the Martens hardness of the cover layer formed of the resin composition is HMb [N/mm ² ] and the elastic work recovery rate of the cover layer is ηItb [%], HMa, HMb and ηItb are expressed by the following formula (1). and equation (2)
1.005≦HMa/HMb≦1.450 (1)
2.00≦ηItb/HMb≦7.00 (2)
A golf ball characterized by satisfying 2. The golf ball of claim 1, wherein the value of HMa/HMb in formula (1) has a lower limit of 1.007 and an upper limit of 1.400. 2. The golf ball of claim 1, wherein the value of ηItb/HMb in formula (2) has a lower limit of 2.50 and an upper limit of 6.50. When the elastic work recovery rate of the resin material of the component (I) is ηIta [%], the following formula (3)
1.001≤ηIta/ηItb≤1.070 (3)
4. The golf ball according to any one of claims 1 to 3, which satisfies: The golf ball of any one of claims 1 to 4, wherein component (II) is added in an amount of 50 parts by mass or less per 100 parts by mass of component (I). The golf ball of any one of claims 1 to 5, wherein component (II) is a hydrogenated aromatic vinyl elastomer. The component (II) is an elastomer obtained by hydrogenating a polymer consisting of a polymer block mainly composed of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. The golf ball according to any one of Claims 1-6. Component (II) is a polymer consisting of a styrene polymer block and a random copolymer block of styrene and butadiene, having polymer blocks of styrene at both ends and a random copolymer block in the middle. The golf ball according to any one of claims 1 to 7, wherein the hydrogenated aromatic vinyl elastomer is obtained by hydrogenating the

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