JP2023054502A - Golf ball - Google Patents

Abstract

SOLUTION: In a golf ball having a rubber core of at least one layer and a cover of at least one layer encasing the core, at least one layer of the cover is formed from a resin composition that includes (I) a polyurethane or a polyurea and (II) a (meth)acrylic block copolymer, the (meth)acrylic block copolymer as the component (II) being included in an amount of 20 pts.wt. or less relative to 100 pts.wt. of the component (I).EFFECT: A golf ball has excellent controllability on approach shots and is able to maintain good scuff resistance and moldability.SELECTED DRAWING: None

Description

The present invention relates to golf balls having at least one layer of core and at least one layer of cover.

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. Recently, urethane resin materials are increasingly used as substitutes for ionomer resin materials for professionals and advanced users.

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. The inventor of the present invention previously proposed in Japanese Patent Application Laid-Open No. 2019-107401 (Patent Document 1) to adopt an acrylic resin or a methacrylic resin as a polymer blend of a urethane resin material and use it as the main material of the cover. . This technology provides a golf ball that can achieve a high initial velocity on driver shots and a low initial velocity on approach shots. It cannot be said that the approach controllability is sufficiently satisfactory. Approach controllability is one of the factors in club operability when approaching, and club operability is determined not only by the spin rate of the ball, but also by the relationship between the ball and the club face due to low resilience. The length of contact time has an effect. When the contact time is long, the operability is improved, and when it is short, the operability is deteriorated. That is, it has been desired to improve a golf ball that is even more excellent in approach controllability than the golf ball described in Patent Document 1.

Further, in the resin material for the cover described in Patent Document 1, the melt viscosity of the urethane resin material increases due to the mixing of the acrylic resin, and the flowability deteriorates, so the molding temperature must be raised. Therefore, after molding, the entire surface of the cover may suffer from defects such as burning, and there is room for improvement in terms of moldability and scratch resistance of the golf ball.

Japanese Patent Application Laid-Open No. 2019-88770 (Patent Document 2) discloses a golf ball resin material formed from a mixture containing a thermoplastic polymer and an acrylic copolymer (MMA copolymer). However, the acrylic copolymer described in Patent Document 2 is a polymer having a special core-shell type chemical structure, and when this acrylic copolymer is blended with a urethane resin material, the approach controllability is improved. Patent Document 1 does not disclose that it is sufficiently excellent, and that it is excellent in scratch resistance and moldability, and it is difficult to say that it is a technique that can solve the above problems of the present invention.

JP 2019-107401 A JP 2019-88770 A

The present invention has been devised in view of the above circumstances, and provides a golf ball that is superior in controllability on approach shots, as well as sufficiently satisfactory in scuff resistance and moldability, as compared with conventional golf balls having a urethane cover. intended to provide

In order to achieve the above objects, the present inventors have developed a golf ball comprising a core and a cover. By blending the copolymer within a predetermined range, a golf ball having a cover made of a molded resin composition composed of these material components was produced. The inventors have found that both scratch resistance and moldability are good, and have completed the present invention. That is, the present invention uses a (meth)acrylic block copolymer having a relatively low Shore D hardness and a relatively low impact resilience as a resin to be added to a resin composition using polyurethane or polyurea as a main component. By adopting it, the controllability at the time of approach is sufficiently high. In addition, even if the above (meth)acrylic block copolymer is mixed with the main material such as polyurethane, the melt viscosity does not increase during molding, so there is no problem with moldability (productivity), scratch resistance and moldability. A golf ball which is sufficiently satisfactory in terms of properties can be obtained, and the problems of the present invention can be solved.

Accordingly, the present invention provides the following golf balls.
1. In a golf ball comprising at least one layer of rubber core and at least one layer of cover covering said core, at least one layer of said cover comprises the following components (I) and (II): (I) polyurethane or polyurea ( II) Formed from a resin composition containing a (meth)acrylic block copolymer. A golf ball characterized by containing 20 parts by mass or less.
2. 2. The golf ball of item 1, wherein the block copolymer of component (II) has two or more blocks forming the hard segment and one or more blocks forming the soft segment.
3. 3. The golf ball of 1 or 2 above, wherein the material hardness of component (II) is 35 or less in Shore D hardness.
4. 4. The golf ball of any one of 1 to 3 above, wherein the rebound resilience of component (II) is 40% or less as measured according to JIS-K 6255 standards.
5. 5. The golf ball of any one of items 1 to 4, wherein component (II) is added in an amount of 15 parts by mass or less per 100 parts by mass of component (I).
6. 6. The golf ball according to any one of items 1 to 5, wherein in the block copolymer of component (II), the hard segment is mainly composed of methyl methacrylate units.
7. 6. The golf ball of any one of items 1 to 5, wherein in the block copolymer of component (II), the soft segment is mainly composed of n-butyl acrylate units.
8. 8. The golf ball of any one of 1 to 7, wherein the cover has a Shore D hardness of 48 or less.

The golf ball of the present invention has much better controllability on approach shots, maintains good scratch resistance, and has good moldability as compared to golf balls having a conventional urethane cover.

The present invention will be described in more detail below.
In this specification, the term "(meth)acrylic block copolymer" is used to mean both acrylic block copolymers and methacrylic block copolymers.

The golf ball of the present invention is a golf ball in which a core consisting of at least one layer is covered with at least one cover layer, that is, a single-layer or multi-layer cover.

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 golf ball of the present invention, the core is covered with a single-layer or multiple-layer cover. Examples of such golf balls include a golf ball having a core with a single-layer cover, and a golf ball having a core, an intermediate layer covering the core, and an outermost layer covering the intermediate layer. be done.

In the present invention, at least one layer of the resin material of the cover is formed of a resin composition containing the following components (I) and (II): (I) polyurethane or polyurea (II) (meth)acrylic block copolymer be done.

(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 preferable 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 1000 can be used. 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 52 or less, more preferably 50 or less, and even more preferably 50 or less in Shore D hardness, from the viewpoint of the spin characteristics and scratch resistance of the golf ball. is 48 or less. The lower limit thereof is preferably 38 or more in Shore D hardness, more preferably 40 or more in Shore D hardness, from the standpoint of moldability.

The impact resilience of component (I) is preferably 55% or more, more preferably 57% or more, and still more preferably 59% or more, from the viewpoint of improving the spin rate on approach. The rebound resilience is measured according to JIS-K 6255:2013 standard.

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.

In the present invention, by blending the component (II) described in detail below with the component (I), controllability, scratch resistance and moldability on approach shots are excellent.

(II) (Meth)acrylic block copolymer The (meth)acrylic block copolymer of component (II) has two or more blocks constituting hard segments and one or more blocks constituting soft segments. Block copolymers are preferred. That is, the (meth)acrylic block copolymer used in the present invention is a polymer containing block polymers A and B, and can be represented by a chemical structure of AB or ABA. The (meth)acrylic block copolymer used in the present invention has a chemical structure different from that of a general core-shell type acrylic copolymer as described in Patent Document 2.

Block polymer A is a site constituting a hard segment, and specific monomer units include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, and methacrylic acid. Examples include methacrylic acid esters such as cyclohexyl acid, isobornyl methacrylate, phenyl methacrylate, and 2-hydroxyethyl methacrylate, and it is preferable to use methyl methacrylate (MMA) as the main component. The block polymer A can be composed of the above monomer units singly or in combination of two or more.

On the other hand, block polymer B is a site constituting a soft segment, and specific monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate. , sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate, 2-methoxyethyl acrylate and the like, and it is preferable to use n-butyl acrylate (nBA) as a main component. The block polymer B can be composed of the above monomer units singly or in combination of two or more.

The glass transition temperature (Tg) of the block polymer A representing the hard segment is preferably 80 to 140°C, more preferably 100 to 120°C. On the other hand, the glass transition temperature (Tg) of the above block polymer B representing the soft segment is preferably -80 to -20°C, more preferably -60 to -40°C and 100 to 120°C.

In the (meth)acrylic block copolymer, the content ratio of the hard segment and the soft segment is preferably 5:95 to 40:60, more preferably 10:90 to 30, by mass. :70. As the proportion of the soft segment increases, it can be expected that the desired approach controllability can be obtained by softening the resin composition. It may decrease and the moldability may deteriorate.

The (meth)acrylic block copolymer can be obtained by polymerizing each of the monomer units described above, and examples of the polymerization method include radical polymerization, living anion polymerization, and living radical polymerization. Examples of the form of polymerization include a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and the like.

Although the weight average molecular weight of the (meth)acrylic block copolymer is not particularly limited, it is preferably in the range of 20,000 to 700,000, more preferably in terms of moldability and plasticity. is in the range of 50,000 to 200,000. Weight average molecular weight can be measured by gel permeation chromatography (GPC).

The (meth)acrylic block copolymer used in the present invention is a polymer in which the hard segment is mainly composed of methyl methacrylate units and the soft segment is mainly composed of n-butyl acrylate units. It is preferable to have Such a (meth)acrylic block copolymer can be a commercially available product, for example, "Clarity" manufactured by Kuraray Co., Ltd. Specifically, the product name is "Clarity LA2250" or "Clarity LA2270" can be exemplified.

Regarding the material hardness of the component (II), from the viewpoint of improving the spin rate on approach, the Shore D hardness is preferably 38 or less, more preferably 35 or less, and even more preferably 32 or less. be. The lower limit of the Shore D hardness is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more.

The modulus of rebound resilience of component (II) is preferably 40% or less, more preferably 35% or less, and still more preferably 35% or less, in order to maintain the spin rate on approach and keep the rebound on approach low to obtain controllability. is 30% or less. Also, the lower limit of the rebound resilience is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. The rebound resilience is measured according to JIS-K 6255:2013 standard.

The amount of component (II) is 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 12 parts by mass per 100 parts by mass of component (I). , there is a possibility that the abrasion resistance is lowered. The lower limit of the amount to be blended is 0.5 parts by mass or more, preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of component (I). is.

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 resistance to cracking.

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, styrene-based resins, polychlorinated It is selected from vinyl, 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 above isocyanate compound 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 as component (I). The value 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.

The rebound resilience of the resin composition is required to be 48% or more, preferably 50% or more, as measured according to the JIS-K 6255:2013 standard in order to improve low resilience and approach spin rate. , More preferably 52% or more, the upper limit is 72% or less, preferably 70% or less, more preferably 68% or less.

Regarding the material hardness of the resin composition, the Shore D hardness is preferably 50 or less, more preferably 48 or less, more preferably 48 or less, from the viewpoint of imparting scratch resistance and an appropriate approach spin rate. Shore D hardness is 45 or less. From the standpoint of moldability, the lower limit of the Shore D hardness is preferably 30 or more, more preferably 35 or more, and still more preferably 37 or more.

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 with the above resin composition, for example, the above resin composition may be supplied to an injection molding machine, and the cover may be molded by injecting the melted resin composition around the core. can. 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.

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. .

When at least one intermediate layer is interposed between the core and the above, the material of the intermediate layer is preferably selected from various thermoplastic resins used in golf ball cover materials, particularly ionomer resins. and a commercial product can be used as the ionomer resin. In this case, the thickness of the intermediate layer can be set within the same range as the thickness of the cover.

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 8, Comparative Examples 1 to 4]
common core
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

A resin material for the intermediate layer was injection-molded around a core having a common intermediate layer diameter of 38.6 mm to produce an intermediate layer-covered sphere having an intermediate layer with a thickness of 1.25 mm. The resin material for the intermediate layer has a resin formulation common to all examples, and includes 50 parts by mass of an ethylene-unsaturated carboxylic acid copolymer neutralized with sodium having an acid content of 18% by mass and 50 parts by mass of an acid content of 15% by mass. and 50 parts by weight of zinc-neutralized ethylene-unsaturated carboxylic acid copolymer to make a total of 100 parts by weight.

Cover (outermost layer)
Next, for Examples 2, 4, 6, 8 and Comparative Example 1, the cover material for the outermost layer shown in Table 2 below was injection-molded around the intermediate layer-covered sphere, and the outermost cover material having a thickness of 0.8 mm was formed. A three-piece golf ball with an outer layer and 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. The resin composition of the cover was designed to have the blending amount of each component shown in Table 2 below, and was injection molded at a molding temperature of 200 to 250°C.
For Examples 1, 3, 5 and 7 and Comparative Examples 2, 3 and 4, three-piece golf balls were produced in the same manner as described above.

The details of the ingredients in the composition in Table 2 below are as follows.
・"TPU (1)" Trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., ether type thermoplastic polyurethane (Shore D hardness "43", rebound resilience modulus "61%")
・"(Meth)acrylic block copolymer 1"Kuraray's trade name "Clarity LA2250" acrylic block copolymer (hard segment PMMA/soft segment PBA), Shore D hardness "22", rebound resilience modulus "28"%”
・"(Meth)acrylic block copolymer 2"Kuraray's trade name "Clarity LA2270" acrylic block copolymer (hard segment PMMA/soft segment PBA), Shore D hardness "31", rebound resilience modulus "26"%”
・"PMMA1"Kuraray's product name "Parapet Soft Acrylic SA-NW201" methacrylic resin (Shore D hardness "40", rebound resilience "23%"
・"PMMA2"Kuraray's product name "Parapet GF" methacrylic resin (Shore D hardness "87", impact resilience "31%")

Physical Properties of Resin Composition (1) Shore D Hardness A resin material was formed into a sheet having a thickness of 2 mm and left at a temperature of 23±2° C. for 2 weeks. Three sheets are superimposed during the measurement. The material hardness of the resin was measured with a Shore D hardness tester conforming to the ASTM D2240 standard. For hardness measurement, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore D type hardness tester is used.
(2) Rebound resilience Table 2 shows the rebound resilience of the resin composition measured according to JIS-K 6255:2013.

Spin performance, initial speed performance, approach controllability, scratch resistance and moldability of each golf ball are evaluated by the following methods. Table 2 shows the results.

Initial Velocity and Spin Performance During Approach A sand wedge (SW) is attached to a golf hitting robot, and the initial velocity and backspin amount immediately after hitting at a head speed (HS) of 20 m/s are measured by an initial condition measuring device.

Controllability Sensory evaluation of controllability of the ball during approach was carried out by the following method. The club used was a sand wedge (SW) product name "Bridgestone Tour Stage TW-03 (loft angle 57°)" similar to the above.
[Judgment evaluation]
(double-circle) ... Very excellent in operability.
O: Excellent in operability.
Δ: Slightly inferior in operability.
x: Inferior in operability.
In addition to the spin rate of the ball, the length of contact time between the ball and the club face due to the low resilience affects the determination of whether or not the maneuverability is excellent. When the contact time is long, the operability is improved, and when it is short, the operability is deteriorated. Here, the controllability (operability) including the amount of spin and the length of contact time is determined.

Scratch resistance evaluation The balls were kept warm at 23°C, and a pitching wedge (PW) was used to hit each ball five times at a head speed of 33 m/s using a swing robot machine. is visually evaluated according to the following criteria.
◯: Slightly scratched or almost unnoticeable.
× . . . Dimples are completely scraped off.

Evaluation of moldability (demoldability) The ball of each example was evaluated for demoldability from the mold after injection molding of the cover according to the following criteria.
◯: No external injuries such as broken runners or sticking of pins occur during demolding.
Δ: Damage such as broken runners or sticking of pins occurs during demolding, and molding temperature must be raised due to increased viscosity.

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.
Comparative Example 1 does not contain the component (II) in the resin composition, and is inferior in controllability during approach.
In Comparative Example 2, the blending amount of the component (II) of the resin composition is large, so the controllability at the time of approach is excellent, but the scratch resistance and the moldability are inferior.
In Comparative Example 3, since PMMA was blended into the resin composition, the melt viscosity increased and the flowability deteriorated, so the molding temperature had to be increased. Poor moldability.
In Comparative Example 4, since PMMA was blended into the resin composition, the melt viscosity increased and the fluidity deteriorated. Therefore, it was necessary to raise the molding temperature. Poor moldability. In addition, since PMMA has a high hardness, the spin rate on approach decreases, resulting in poor controllability during approach.

Claims (8)

In a golf ball comprising at least one layer of rubber core and at least one layer of cover covering said core, at least one layer of said cover comprises the following components (I) and (II): (I) polyurethane or polyurea ( II) Formed from a resin composition containing a (meth)acrylic block copolymer. A golf ball characterized by containing 20 parts by mass or less. 2. The golf ball of claim 1, wherein the block copolymer of component (II) has two or more blocks constituting hard segments and one or more blocks constituting soft segments. 3. The golf ball of claim 1, wherein the material hardness of component (II) is 35 or less in Shore D hardness. The golf ball of any one of claims 1 to 3, wherein component (II) has a modulus of impact resilience of 40% or less as measured according to JIS-K 6255 standards. The golf ball of any one of claims 1 to 4, wherein component (II) is added in an amount of 15 parts by mass or less per 100 parts by mass of component (I). 6. The golf ball of claim 1, wherein in the block copolymer of component (II), the hard segment is mainly composed of methyl methacrylate units. 6. The golf ball of claim 1, wherein in the block copolymer of component (II), the soft segment is mainly composed of n-butyl acrylate units. 8. The golf ball of claim 1, wherein the cover has a Shore D hardness of 48 or less.