golf balls

Abstract

SOLUTION: A golf ball provided by the present invention includes at least one layer of rubber core and at least one layer of cover covering the core, wherein at least one layer of the cover is formed by a resin composition containing the following (I) and (II) components, and HMa and HMb satisfy the following formula (1), here, the Martens hardness of the resin material of the component (I) is HMa[N / mm2], and that of the cover layer formed by the resin composition containing the components (I) and (II) is HMb[N / mm2]. (I) Polyurethane or polyurea. (II) (Meth)acrylic block copolymer. 1.020≤HMa / HMb≤1.500 (1).EFFECT: The golf balls of the present invention have excellent controllability during approach shots and maintain good abrasion resistance and moldability.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a golf ball having at least one core layer and at least one cover layer. [Background technology]

[0002] The main characteristic required for a golf ball is increased flight distance, but other requirements include the ability to stop the ball well on approach shots and abrasion resistance. To date, many golf balls have been developed that fly well on driver shots and generate favorable backspin on approach shots. Recently, golf balls targeting professionals and advanced players have increasingly adopted urethane resin materials as an alternative to ionomer resin materials.

[0003] Several polymer blend cover materials have been proposed, in which a urethane resin material is used as the base resin and other resin materials are mixed in. The present inventor previously proposed, in JP 2019-107401 A (Patent Document 1), the use of an acrylic or methacrylic resin as the main material for the cover as a polymer blend of the urethane resin material. While this technology provides a golf ball that achieves high initial velocities on driver shots and low initial velocities on approach shots, acrylic or methacrylic resins are essentially hard resin materials, and therefore, approach controllability was not fully satisfactory. Approach controllability is one factor in the maneuverability of the club on the approach shot, and the quality of the club's maneuverability is influenced not only by the amount of spin on the ball but also by the length of contact time between the ball and the club face due to the club's low resilience. A longer contact time improves maneuverability, while a shorter contact time reduces maneuverability. In other words, there was a need for an improved golf ball with even better approach controllability than the golf ball described in Patent Document 1.

[0004] Furthermore, the resin material for the cover described in Patent Document 1 requires a higher molding temperature because the urethane resin material has an increased melt viscosity and poor flowability due to the addition of acrylic resin. This can result in defects such as burns on the entire surface of the cover after molding, leaving room for improvement in the moldability and abrasion resistance of the golf ball.

[0005] Additionally, Japanese Patent Laid-Open Publication 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 with a special core-shell chemical structure, and Patent Document 1 does not disclose that blending this acrylic copolymer with a urethane resin material results in sufficiently excellent approach controllability, abrasion resistance, and moldability. Therefore, it is difficult to say that this technology can solve the above-mentioned problems of the present invention. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-107401 [Patent Document 2] Japanese Patent Application Publication No. 2019-88770 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances, and its object is to provide a golf ball that has excellent controllability on approach shots and is also fully satisfactory in abrasion resistance and moldability compared to golf balls with conventional urethane covers. [Means for solving the problem]

[0008] In order to achieve the above object, the present inventors have developed a golf ball having a core and a cover, which uses a (meth)acrylic block copolymer as a polymer blend of a resin material containing polyurethane or polyurea as a main component, and which has a Martens hardness of HMa [N / mm 2 ], and the Martens hardness of the cover layer formed from a resin composition obtained by blending the polyurethane or polyurea with a (meth)acrylic block copolymer is HMb [N / mm 2 ], HMa and HMb are expressed by the following formula (1) 1.020≦HMa / HMb≦1.500 (1) The present inventors have fabricated a golf ball having a cover molded from the above resin composition so as to satisfy the above requirements. They have found that this golf ball has excellent controllability on approach shots, as well as good abrasion resistance and moldability, which has led to the creation of the present invention. Specifically, the present invention provides a resin composition using polyurethane or polyurea as the main component, by adding a (meth)acrylic block copolymer having a relatively low Shore D hardness and a relatively low impact resilience as an added resin, thereby achieving sufficiently high controllability on approach shots. Furthermore, since the melt viscosity does not increase during molding when the above (meth)acrylic block copolymer is mixed with a main material such as polyurethane, there is no problem with moldability (productivity), and a golf ball that is fully satisfactory in terms of abrasion resistance and moldability can be obtained, thereby solving the problems of the present invention.

[0009] Accordingly, the present invention provides the following golf balls. 1. A golf ball having at least one rubber core layer and at least one cover layer covering the core, wherein at least one layer of the cover contains the following components (I) and (II): (I) Polyurethane or Polyurea (II) (Meth)acrylic block copolymer The resin composition is formed from a resin composition containing The block copolymer of the component (II) has two or more blocks constituting hard segments and one or more blocks constituting soft segments, the hard segments being mainly composed of methyl methacrylate units, and the soft segments being mainly composed of n-butyl acrylate units, and the blending amount of the component (II) is 3 to 15 parts by mass per 100 parts by mass of the component (I). At the same time, the Martens hardness of the resin material of the above component (I) is HMa [N / mm 2], and the Martens hardness of the cover layer formed from the resin composition containing the components (I) and (II) is HMb [N / mm 2 ], HMa and HMb are expressed by the following formula (1) 1.020≦HMa / HMb≦1.500 (1) A golf ball characterized by satisfying the following: 2 The material hardness of the component (II) is 40 or less in Shore D hardness. 1 The golf ball described herein. 3 The above component (II) has a rebound resilience of 50% or less as measured according to JIS-K 6255. 1 or 2 The golf ball described herein. 4 The weight average molecular weight of the component (II) is 10,000 or more. 3 1. The golf ball according to claim 1, 5 1. The cover has a Shore D hardness of 48 or less. 4 1. The golf ball according to claim 1, 6 The resin composition further contains (III) a thermoplastic polyester elastomer. 5 1. The golf ball according to claim 1, 7 The material hardness of the component (III) is 20 to 50 in Shore D hardness. 6 The golf ball described herein. 8 The above component (III) has a rebound resilience of 50 to 80% as measured according to JIS-K 6255. 6 or 7 The golf ball described herein. 9 The melt viscosity of the above component (III) at 200°C and a shear rate of 243 (1 / sec) is 0.3 x 10 4 ~1.5×10 4 (dPa·s) 6~8 1. The golf ball according to claim 1, 10When the elastic work recovery rate of the cover layer formed from the resin composition containing the above components (I) and (II) is ηItb [%], ηItb and HMb are calculated by the following formula (2): 5.00≦ηItb / HMb≦8.00 (2) 10. The golf ball according to any one of the above items 1 to 9, which satisfies the above conditions. 11 When the elastic work recovery rate of the resin material of the above component (I) is ηIta [%], the following formula (3) is obtained. 0.97≦ηIta / ηItb≦1.12 (3) Satisfy the above 10 The golf ball described herein. 12.Furthermore, the following formula (4) 0.70≦(ηIta·HMb) / (ηItb·HMa)≦1.06 ···(4) Satisfy the above 11 The golf ball described herein. [Effects of the Invention]

[0010] The golf ball of the present invention has superior controllability on approach shots, maintains good abrasion resistance, and is easily moldable, compared to golf balls having conventional urethane covers. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] The golf ball of the present invention is a golf ball in which a core made of at least one layer is covered with at least one cover layer, that is, a single-layer or multi-layer cover.

[0013] The core can be formed using a known rubber material as a base material. Known natural or synthetic rubbers can be used as the base rubber. More specifically, polybutadiene, particularly cis-1,4-polybutadiene having at least 40% or more cis structures, is recommended as the primary base material. Furthermore, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. can be used in combination with the polybutadiene in the base rubber, if desired.

[0014] Polybutadiene can also be synthesized using a metal catalyst such as a rare earth element catalyst such as a Nd catalyst, a cobalt catalyst, or a nickel catalyst.

[0015] The base rubber may contain co-crosslinking agents such as unsaturated carboxylic acids and their metal salts, inorganic fillers such as zinc oxide, barium sulfate, and calcium carbonate, and organic peroxides such as dicumyl peroxide and 1,1-bis(t-butylperoxy)cyclohexane. Commercially available antioxidants may also be added as needed.

[0016] The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, the core can be produced by kneading the rubber composition using a kneader such as a Banbury mixer or a roll, compression molding or injection molding using a core mold, and curing the molded product by appropriately heating the molded product at a temperature sufficient for the organic peroxide and co-crosslinking agent to act, 100 to 200°C, preferably 140 to 180°C, for 10 to 40 minutes.

[0017] The golf ball of the present invention has a core surrounded by a single-layer or multi-layer cover. Examples of such golf balls include a golf ball having a core surrounded by a single-layer cover, and a golf ball having a core, an intermediate layer surrounding the core, and an outermost layer surrounding the intermediate layer.

[0018] In the present invention, the resin material for at least one layer of the cover contains the following components (I) and (II): (I) Polyurethane or Polyurea (II) (Meth)acrylic block copolymer It is formed from a resin composition containing

[0019] (I) Polyurethane or Polyurea Polyurethane or polyurea can be the main or base resin of the cover material (resin composition). Details of this component, polyurethane (Ia) or polyurea (Ib), are as follows:

[0020] (Ia) Polyurethane The polyurethane structure consists of a soft segment made of a long-chain polyol (polymeric glycol), and a hard segment made of a chain extender and polyisocyanate. The polymeric polyol used as the raw material can be any of those conventionally used in polyurethane material technology, and is not particularly limited. 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 polyols include adipate polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polybutadiene adipate glycol, and polyhexamethylene adipate glycol, as well as lactone polyols such as polycaprolactone polyols. Examples of polyether polyols include poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene glycol), and poly(methyltetramethylene glycol). These may be used alone or in combination of two or more.

[0021] As the polymer polyol, it is preferable to use a polyether polyol.

[0022] 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, golf balls made from polyurethane compositions having various excellent properties such as the above-mentioned resilience and productivity can be reliably obtained. The number-average molecular weight of the long-chain polyol is more preferably within the range of 1,500 to 4,000, and even more preferably within the range of 1,700 to 3,500.

[0023] The number average molecular weight mentioned above is a number average molecular weight calculated based on the hydroxyl value measured in accordance with JIS-K1557 (the same applies hereinafter).

[0024] The chain extender may be any of those used in conventional polyurethane-related technologies, and is not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms in the molecule that can react with an isocyanate group and a molecular weight of 2,000 or less may be used, and among these, an aliphatic diol having 2 to 12 carbon atoms may be preferably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, and 2,2-dimethyl-1,3-propanediol, and among these, 1,4-butylene glycol may be particularly preferably used.

[0025] The polyisocyanate may be any of those used in conventional polyurethane-related technologies, and is not particularly limited. Specifically, one or more selected from the group consisting of 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, and dimer acid diisocyanate may be used. However, depending on the isocyanate, it may be difficult to control the crosslinking reaction during injection molding.

[0026] The ratio of active hydrogen atoms to isocyanate groups in the polyurethane-forming reaction can be adjusted within a suitable range. Specifically, when the long-chain polyol, polyisocyanate compound, and chain extender are reacted to produce polyurethane, it is preferable to use the components in such a ratio that the amount of isocyanate groups contained in the polyisocyanate compound is 0.95 to 1.05 moles per mole of active hydrogen atoms contained in the long-chain polyol and chain extender.

[0027] The method for producing polyurethane is not particularly limited, and polyurethane may be produced by either a prepolymer method or a one-shot method using a long-chain polyol, a chain extender, and a polyisocyanate compound, utilizing a known urethane reaction. Among these methods, melt polymerization in the substantial absence of a solvent is preferred, and continuous melt polymerization using a multi-screw extruder is particularly preferred.

[0028] As the polyurethane, it is preferable to use a thermoplastic polyurethane material, and particularly an ether-based thermoplastic polyurethane material. As the thermoplastic polyurethane material, commercially available products can be suitably used, such as "Pandex" manufactured by DIC Covestropolymer Co., Ltd. and "Rezamin" manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.

[0029] (Ib) Polyurea Polyurea is a resin composition primarily composed of urea bonds formed by the reaction of (i) isocyanate with (ii) an amine-terminated compound. This resin composition is described in detail below.

[0030] (i) Isocyanate The isocyanate can be suitably any isocyanate used in conventional polyurethane-related techniques, and is not particularly limited, and the same isocyanates as those explained above for the polyurethane material can be used.

[0031] (ii) Amine-terminated compounds The amine-terminated compound is a compound having an amino group at the end of the molecular chain, and in the present invention, the long-chain polyamine and / or amine-based curing agent shown below can be used.

[0032] The long-chain polyamine is an amine compound having two or more amino groups in the molecule that can react with isocyanate groups and 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 to 4,000, and even more preferably 1,900 to 3,000. Specific examples of the long-chain polyamine include, but are not limited to, amine-terminated hydrocarbons, amine-terminated polyethers, amine-terminated polyesters, amine-terminated polycarbonates, amine-terminated polycaprolactones, and mixtures thereof. These long-chain polyamines may be used alone or in combination.

[0033] On the other hand, the amine curing agent is an amine compound having two or more amino groups capable of reacting with isocyanate groups in the 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, and even more preferably less than 600.Specific examples of the amine-based 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, di Ethanolamine, 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.These amine-based curing agents may be used alone or in combination of two or more.

[0034] (iii) Polyol Although not essential, polyurea can further contain a polyol in addition to the above-mentioned components (i) and (ii). As this polyol, those used in conventional polyurethane-related technologies can be suitably used without any particular limitation, but specific examples include the long-chain polyols and / or polyol-based curing agents shown below.

[0035] The long-chain polyol may be any of those conventionally used in polyurethane-related technologies, and is not particularly limited, but examples thereof include polyester polyols, polyether polyols, polycarbonate polyols, polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols, castor oil polyols, silicone polyols, vinyl polymer polyols, etc. These long-chain polyols may be used alone or in combination of two or more.

[0036] The number average molecular weight of the long chain polyol is preferably 1,000 to 5,000, and more preferably 1,700 to 3,500. If the number average molecular weight is within this range, the resilience, productivity, etc. will be even more excellent.

[0037] The polyol-based curing agent can be suitably one used in conventional polyurethane-related technologies, and is not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms in the molecule capable of reacting with an isocyanate group and a molecular weight of less than 1,000 can be used, and among these, aliphatic diols having 2 to 12 carbon atoms can be suitably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, and 2,2-dimethyl-1,3-propanediol, and among these, 1,4-butylene glycol is particularly suitable. Furthermore, the number-average molecular weight of the polyol-based curing agent is preferably less than 800, more preferably less than 600.

[0038] The polyurea can be produced by any known method, such as a prepolymer method or a one-shot method.

[0039] From the viewpoint of spin characteristics and abrasion resistance of the resulting golf ball, the material hardness of component (I) is preferably not more than 52 Shore D hardness, more preferably not more than 50 Shore D hardness, and even more preferably not more than 48. From the viewpoint of moldability, the lower limit is preferably not less than 38 Shore D hardness, more preferably not less than 40 Shore D hardness.

[0040] The rebound resilience of the component (I) is preferably 55% or more, more preferably 57% or more, and even more preferably 59% or more, from the viewpoint of improving the approach spin rate. The rebound resilience is measured in accordance with JIS-K 6255:2013.

[0041] The above component (I) is the main material of the resin composition, and in order to provide sufficient abrasion resistance that urethane resins possess, it accounts for 50% by mass or more of the resin composition, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and most preferably 90% by mass or more.

[0042] In the present invention, by blending component (II), which will be described in detail below, with component (I) above, the controllability on approach shots, abrasion resistance and moldability are excellent.

[0043] (II) (Meth)acrylic block copolymer The (meth)acrylic block copolymer of component (II) is preferably a block copolymer having two or more blocks constituting hard segments and one or more blocks constituting soft segments. 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 an AB or ABA chemical structure. Note that the (meth)acrylic block copolymer used in the present invention has a different chemical structure from general core-shell acrylic copolymers such as those described in Patent Document 2.

[0044] Block polymer A is a moiety that constitutes a hard segment, and specific examples of the monomer unit include methacrylate esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and 2-hydroxyethyl methacrylate, with methyl methacrylate (MMA) being preferred as the main component. Block polymer A can be constructed using any one of the above monomer units or two or more of them in combination.

[0045] On the other hand, block polymer B is a moiety that constitutes a soft segment, and specific examples of monomer units include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate, and 2-methoxyethyl acrylate, with n-butyl acrylate (nBA) being preferred as the main component. Block polymer B can be constructed using one or more of the above monomer units.

[0046] The glass transition temperature (Tg) of the block polymer A showing 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 block polymer B showing the soft segment is preferably -80 to -20°C, more preferably -60 to -40°C.

[0047] In the (meth)acrylic block copolymer, the ratio of the hard segment to the soft segment, expressed as a mass ratio, is preferably 5:95 to 40:60, and more preferably 10:90 to 30:70. As the proportion of the soft segment increases, it is expected that the resin composition will be softened and the desired approach controllability will be obtained, but if the proportion of the hard segment is too low, compatibility with the base material, such as a polyurethane resin, will decrease, and moldability may deteriorate.

[0048] The (meth)acrylic block copolymer can be obtained by polymerizing the above-mentioned monomer units, and examples of the polymerization method include radical polymerization, living anionic polymerization, living radical polymerization, etc. Examples of the polymerization form include solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, etc.

[0049] The weight-average molecular weight of the (meth)acrylic block copolymer is not particularly limited, but is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 45,000 or more, with the upper limit being preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less. The higher the weight-average molecular weight, the higher the spin rate and the better the controllability on approach shots, while maintaining the effect of low resilience. The weight-average molecular weight can be measured by gel permeation chromatography (GPC).

[0050] The (meth)acrylic block copolymer used in the present invention is preferably 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. Such a (meth)acrylic block copolymer can be a commercially available product, such as "CLARITY" manufactured by Kuraray Co., Ltd., specifically, examples thereof include trade names "CLARITY LA2140," "CLARITY LA2250," "CLARITY LA2270," and "CLARITY LA2330."

[0051] With regard to the material hardness of the component (II), from the viewpoint of improving the approach spin rate, it is preferable that the Shore D hardness is 38 or less, more preferably 35 or less, and even more preferably 32 or less. The lower limit of the Shore D hardness is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more.

[0052] The rebound resilience of component (II) is preferably 50% or less, more preferably 45% or less, and even more preferably 42% or less, in order to maintain the approach spin rate and reduce the rebound on approach shots to obtain controllability. 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 in accordance with JIS-K 6255:2013.

[0053] The amount of component (II) blended is 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 12 parts by mass or less, per 100 parts by mass of component (I). If this amount exceeds this value, abrasion resistance may decrease. The lower limit of the blended amount 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).

[0054] The resin composition containing the above components (I) and (II) may further contain a thermoplastic polyester elastomer (III), which will be described below.

[0055] (III) Thermoplastic polyester elastomer To achieve the desired effects of the present invention and further improve the feel on impact, a specific thermoplastic polyester elastomer can be blended into the resin composition. Specifically, this specific thermoplastic polyester elastomer imparts a certain level of resilience to the resin composition, which, in combination with this resilience, maintains a certain level of spin rate on approach shots. Furthermore, blending the specific thermoplastic polyester elastomer into the resin composition improves compatibility with the base resin, component (I), thereby imparting good abrasion resistance. Furthermore, blending the specific thermoplastic polyester elastomer into the resin composition provides a certain level of melt viscosity, thereby imparting solidification properties to the resin composition after molding. This prevents a decrease in the overall viscosity of the resin composition due to the softness of the base resin, component (I), thereby preventing a decrease in moldability (productivity), an increase in poor appearance of the molded golf ball, and an increase in production costs due to increased cooling time. Such thermoplastic polyester elastomers are described below.

[0056] The thermoplastic polyester elastomer of component (III) is The resin composition comprises (b-1) a polyester block copolymer and (b-2) a hard resin. The (b-1) component further comprises (b-1-1) a high-melting-point crystalline polymer segment and (b-1-2) a low-melting-point polymer segment.

[0057] The (b-1-1) high-melting point crystalline polymer segment constituting the polyester block copolymer of the component (b-1) is a polyester formed from one or more members selected from the group consisting of aromatic dicarboxylic acids or their ester-forming derivatives, and diols or their ester-forming derivatives.

[0058] Specific examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, and sodium 3-sulfoisophthalate. In the present invention, aromatic dicarboxylic acids are primarily used, but if necessary, a portion of these aromatic dicarboxylic acids may be substituted with aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, and 4,4'-dicyclohexyldicarboxylic acid, or adipic acid, succinic acid, oxalic acid, sebacic acid, dodecanedioic acid, and dimer acid. Specific examples of ester-forming derivatives of dicarboxylic acids include lower alkyl esters, aryl esters, carbonate esters, and acid halides of the above-mentioned dicarboxylic acids.

[0059] Next, as the diol, a diol having a molecular weight of 400 or less can be suitably used. Specific examples include aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, and decamethylene glycol, alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, and tricyclodecanedimethanol, and aromatic diols such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxy)diphenylpropane, 2,2′-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4′-dihydroxy-p-terphenyl, and 4,4′-dihydroxy-p-quaterphenyl. Specific examples of the ester-forming derivatives of diols include acetylated forms and alkali metal salts of the above-mentioned diols.

[0060] The above aromatic dicarboxylic acids, diols, and derivatives thereof may be used alone or in combination of two or more.

[0061] As the component (b-1-1), particularly, those comprising polybutylene terephthalate units derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol, those comprising polybutylene terephthalate units derived from isophthalic acid and / or dimethyl isophthalate and 1,4-butanediol, and further copolymers of these two can be suitably used.

[0062] The (b-1-2) low-melting point polymer segment is an aliphatic polyether and / or an aliphatic polyester.

[0063] Examples of aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide addition polymers of poly(propylene oxide) glycol, and copolymer glycols of ethylene oxide and tetrahydrofuran. Examples of aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprolactone, polybutylene adipate, and polyethylene adipate. In the present invention, from the viewpoint of elastic properties, poly(tetramethylene oxide) glycol, ethylene oxide addition products of poly(propylene oxide) glycol, copolymer glycols of ethylene oxide and tetrahydrofuran, poly(ε-caprolactone), polybutylene adipate, and polyethylene adipate can be preferably used. Among these, it is particularly recommended to use poly(tetramethylene oxide) glycol, an ethylene oxide adduct of poly(propylene oxide) glycol, and a copolymer glycol of ethylene oxide and tetrahydrofuran.The number average molecular weight of these segments in the copolymerized state is preferably about 300 to 6,000.

[0064] The component (b-1) can be produced by a known method, such as a method of transesterifying a lower alcohol diester of a dicarboxylic acid, an excess amount of a low-molecular-weight glycol, and a low-melting-point polymer segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product, or a method of esterifying a dicarboxylic acid, an excess amount of a glycol, and a low-melting-point polymer segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product.

[0065] The proportion of the (b-1) component accounted for by the (b-1-2) component is 30 to 60 mass%. In this case, the preferred lower limit can be 35 mass% or more, and the preferred upper limit can be 55 mass% or less. If the proportion of the (b-1-2) component is too low, impact resistance (especially at low temperatures) and compatibility may be insufficient. On the other hand, if the proportion of the (b-1-2) component is too high, the rigidity of the resin composition (and molded article) may be insufficient.

[0066] The hard resin of component (b-2) is not particularly limited, but may be, for example, one or more selected from the group consisting of polycarbonate, acrylic resin, styrene resin such as ABS resin or polystyrene, polyester resin, polyamide resin, polyvinyl chloride, and modified polyphenylene ether. In the present invention, polyester resin is preferably used from the viewpoint of compatibility, and it is more preferable to use polybutylene terephthalate and / or polybutylene naphthalate.

[0067] The blending ratio ((b-1):(b-2)) of the above-mentioned components (b-1) and (b-2) is not particularly limited, but is preferably 50:50 to 90:10 by mass, and more preferably 55:45 to 80:20. If the proportion of component (b-1) is too low, the impact resistance (at low temperatures) may be insufficient. On the other hand, if the proportion of component (b-1) is too high, the rigidity and moldability of the composition (and molded article) may be insufficient.

[0068] As such (III) polyester elastomer, commercially available products can be used, and a specific example is "Hytrel" manufactured by Toray DuPont Co., Ltd.

[0069] With regard to the material hardness of the component (III), from the viewpoint of improving the approach spin rate, the Shore D hardness is preferably not more than 50, more preferably not more than 43. The lower limit is preferably not less than 20, more preferably not less than 30.

[0070] From the viewpoint of improving the approach spin rate, the rebound resilience of component (III) is preferably 50% or more, more preferably 60% or more, and the upper limit is preferably 80% or less, more preferably 70% or less. The rebound resilience is measured in accordance with JIS-K 6255:2013.

[0071] The melt viscosity of component (III) is 0.3 x 10 4 It is preferably dPa·s or more, and more preferably 0.4×10 4 dPa·s or more, and the upper limit is preferably 1.5×10 4 dPa·s or less, and more preferably 1.0×10 4 The melt viscosity is dPa·s or less. This melt viscosity imparts solidification properties to the resin composition after molding, preventing a decrease in moldability (productivity). This melt viscosity is measured at a shear rate of 243 (1 / sec) using a capillograph at a temperature of 200°C in accordance with ISO 11443:1995.

[0072] The blending ratio of component (III) is 30 parts by mass or less, preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, based on 100 parts by mass of the resin composition. The lower limit is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass. If the amount exceeds this value, moldability and abrasion resistance may be reduced.

[0073] The resin composition containing the above-mentioned components (I), (II), and optionally (III) may contain other resin materials in addition to the resin components described above, in order to further improve the flowability of the golf ball resin composition and enhance its physical properties such as resilience and crack resistance.

[0074] The other resin material may be selected from polyamide elastomer, ionomer resin, ethylene-ethylene-butylene-ethylene block copolymer or modified product thereof, polyacetal, polyethylene, nylon resin, styrene resin, polyvinyl chloride, polycarbonate, polyphenylene ether, polyarylate, polysulfone, polyethersulfone, polyetherimide, and polyamideimide, and one or more of these may be used.

[0075] The resin composition may further contain an active isocyanate compound, which reacts with the polyurethane or polyurea that is the main component to further improve the abrasion resistance of the entire resin composition, and also improves the flowability and moldability due to the plasticizing effect of the isocyanate.

[0076] The isocyanate compound can be any isocyanate compound commonly used in polyurethanes. Examples of aromatic isocyanate compounds include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of these, 4,4-diphenylmethane diisocyanate, m-phenylene diisocyanate, and 4,4'-biphenyl diisocyanate. Hydrogenated versions of these aromatic isocyanate compounds, such as dicyclohexylmethane diisocyanate, can also be used. Other examples include aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), and octamethylene diisocyanate, and alicyclic diisocyanates such as xylene diisocyanate. Other examples include blocked isocyanate compounds obtained by reacting the isocyanate groups of a compound having two or more terminal isocyanate groups with a compound having active hydrogen, and uretidione compounds obtained by dimerization of isocyanates.

[0077] The amount of the isocyanate compound is preferably at least 0.1 parts by mass, more preferably at least 0.5 parts by mass, per 100 parts by mass of the polyurethane or polyurea resin (component (I)). The upper limit is preferably no more than 30 parts by mass, more preferably no more than 20 parts by mass. If this amount is too small, a sufficient crosslinking reaction may not be achieved, and improvement in physical properties may not be observed. On the other hand, if this amount is too large, problems such as significant discoloration over time due to heat or ultraviolet rays, loss of thermoplasticity, or reduced resilience may occur.

[0078] Furthermore, any additives can be appropriately blended into the resin composition depending on the application. For example, when the golf ball material of the present invention is used as a cover material, various additives such as fillers (inorganic fillers), short organic fibers, reinforcing agents, crosslinking agents, pigments, dispersants, antioxidants, UV absorbers, and light stabilizers can be added to the above components. When these additives are blended, the amount of the additives blended is preferably at least 0.1 parts by weight, more preferably at least 0.5 parts by weight, and preferably no more than 10 parts by weight, more preferably no more than 4 parts by weight, per 100 parts by weight of the base resin.

[0079] In order to improve low resilience and approach spin rate, the resin composition needs to have a rebound resilience of 48% or more as measured in accordance with JIS-K 6255:2013, preferably 50% or more, and more preferably 52% or more, with the upper limit being 72% or less, preferably 70% or less, and more preferably 68% or less.

[0080] Furthermore, from the viewpoint of abrasion resistance and imparting an appropriate amount of spin on approach shots, the material hardness of the resin composition is preferably 50 or less in Shore D hardness, more preferably 48 or less, and even more preferably 45 or less in Shore D hardness. From the viewpoint of moldability, the lower limit is preferably 30 or more in Shore D hardness, more preferably 35 or more, and even more preferably 37 or more.

[0081] The components of the resin composition can be prepared by mixing them using various kneaders such as a kneading type (single-screw or) twin-screw extruder, a Banbury mixer, a kneader, a Labo Plastomill, etc. Alternatively, the components may be mixed by dry blending during injection molding of the resin composition. Furthermore, when the active isocyanate compound is used, it may be added during resin mixing using various kneaders, or a masterbatch containing the active isocyanate compound and other components may be separately prepared and dry blended during injection molding of the resin composition to mix the components.

[0082] For example, the cover can be molded from the resin composition by feeding the resin composition into an injection molding machine and injecting the molten resin composition around the core to form the cover. In this case, the molding temperature varies depending on the type of main component (I), such as polyurethane or polyurea, but is usually in the range of 150 to 270°C.

[0083] In the present invention, the Martens hardness of the resin material of component (I) is defined as HMa [N / mm 2 ], and the Martens hardness of the cover layer formed from the resin composition containing the components (I) and (II) is HMb [N / mm 2 ], in order to improve the controllability at the time of approach while maintaining the abrasion resistance, it is necessary to satisfy the following formula (1). 1.020≦HMa / HMb≦1.500 (1)

[0084] The lower limit of the formula (1) is 1.020 or more, preferably 1.050 or more, more preferably 1.100 or more, and the lower limit is 1.500 or less, preferably 1.400 or less, more preferably 1.300 or less. If the value of the formula (1) is too large, the abrasion resistance will be reduced, while if the value of the formula (1) is too small, the approach controllability may be reduced.

[0085] The Martens hardness HMa of the resin material of component (I) is preferably 10.00 N / mm2 More preferably, it is 11.00 N / mm 2 The upper limit is preferably 30.00 N / mm 2 or less, more preferably 25.00 N / mm 2 The following is the result.

[0086] The cover layer formed from the resin composition containing the components (I) and (II) preferably has a lower limit of Martens hardness HMb of 8.00 N / mm 2 More preferably, 9.00 N / mm 2 The upper limit is preferably 28.00 N / mm 2 Less than or equal to 23.00 N / mm 2 The following is the result.

[0087] The Martens hardness HMa and HMb can be measured using an ultra-microhardness tester based on ISO 14577:2002 "Metallic materials - Instrumented indentation test for hardness and materials parameters." In other words, they are physical property values ​​determined by pressing an indenter into a measurement object while applying a load, and are expressed as the ratio of the pressing force [N] to the area of ​​the pressure-receiving part [mm 2 The Martens hardness can be measured using, for example, an ultra-microhardness testing system called "Fischerscope HM2000" (manufactured by Fischer Instruments). This measuring device can measure the hardness of the cover by continuously applying a load in steps, and the setting conditions are that the applied load is set to 50 mN for 10 seconds at room temperature.

[0088] Furthermore, when measuring the surface of the cover, if a coating or the like is formed on the surface of the cover, it is difficult to identify the coating or the like. Furthermore, if the hardness is measured deep from the surface of the cover toward the center of the ball, the hardness will be affected by the hardness of the adjacent layer. Therefore, it is desirable to measure the Martens hardness at a point approximately 0.3 mm from the surface of the cover toward the center of the ball, as this will provide a stable measurement of the cover's inherent Martens hardness.

[0089] In the present invention, when the elastic work recovery rate of the cover layer formed from the resin composition containing the above components (I) and (II) is defined as ηItb [%], it is preferable that the following formula (2) is satisfied: 5.00≦ηItb / HMb≦8.00 (2)

[0090] The lower limit of the above formula (2) is preferably 5.00 or more, more preferably 5.30 or more, and more preferably 5.80 or more, and the lower limit is preferably 8.00 or less, more preferably 7.50 or less, and even more preferably 7.20 or less. If the value of the above formula (2) is too large or too small, the abrasion resistance may deteriorate.

[0091] The lower limit of the elastic work recovery rate ηItb of the cover layer is preferably 50% or more, more preferably 55% or more, and the upper limit is preferably 85% or less, more preferably 80% or less.

[0092] Furthermore, when the elastic work recovery rate of the resin material of the component (I) is ηIta [%], it is preferable that the following formula (3) is satisfied. 0.97≦ηIta / ηItb≦1.12 (3)

[0093] The lower limit of the above formula (2) is preferably 0.97 or more, more preferably 0.98 or more, and even more preferably 0.99 or more, and the lower limit is preferably 1.12 or less, more preferably 1.05 or less, and even more preferably 1.03 or less. If the value of the above formula (3) is too large, the abrasion resistance or durability may deteriorate. On the other hand, if the value of the above formula (3) is too small, the controllability on the approach may deteriorate.

[0094] The elastic work recovery rate ηIta of the resin material of component (I) is preferably 45% or more as a lower limit, more preferably 50% or more, and is preferably 80% or less as an upper limit, more preferably 75% or less.

[0095] When the elastic work recovery rates ηIta and ηItb are within the above ranges, the cover formed on the surface of the golf ball maintains a certain level of hardness and elasticity while enhancing its self-repairing function, contributing to the ball's excellent durability and abrasion resistance. Even if the Martens hardness is low, if the elastic work recovery rate is too low, the ball will have good spin performance on approaches but poor abrasion resistance. The method for measuring the elastic work recovery rate will be described later.

[0096] The elastic work recovery rate is a parameter of the nanoindentation method, which evaluates the physical properties of a golf ball cover. This method uses an ultra-microhardness test to control the indentation load on the order of micronewtons (μN) and track the indenter depth during indentation with nanometer (nm) accuracy. Conventional methods can only measure the size of the deformation mark (plastic deformation mark) corresponding to the maximum load. However, the nanoindentation method automatically and continuously measures the relationship between the indentation load and the indentation depth. This allows for reliable and highly accurate evaluation of the cover's physical properties, without the individual variability that occurs when visually measuring deformation marks with an optical microscope. Therefore, since golf ball covers are significantly affected by impacts from drivers and various clubs and have a significant impact on the various physical properties of a golf ball, measuring the cover with the ultra-microhardness test method, with higher accuracy than conventional methods, is a highly effective evaluation method.

[0097] Furthermore, in order to enhance the desired effects of the present invention, it is preferable that the following formula (4) is satisfied. 0.70≦(ηIta·HMb) / (ηItb·HMa)≦1.06 ···(4)

[0098] The lower limit of the above formula (4) is preferably 0.70 or more, more preferably 0.75 or more, and even more preferably 0.78 or more, and the lower limit is preferably 1.06 or less, more preferably 1.00 or less, and even more preferably 0.90 or less. If the value of the above formula (4) is too large, the approach spin rate may decrease, and if it is too small, the abrasion resistance and durability may decrease.

[0099] The cover thickness is preferably at least 0.4 mm, more preferably at least 0.5 mm, and even more preferably at least 0.6 mm, and is preferably at most 3.0 mm, and more preferably at most 2.0 mm.

[0100] When at least one intermediate layer is interposed between the core and the core, the intermediate layer is preferably made of a thermoplastic resin, particularly an ionomer resin, used in golf ball cover materials. Commercially available ionomer resins can be used. In this case, the thickness of the intermediate layer can be set within the same range as the thickness of the cover.

[0101] The golf ball of the present invention has a large number of dimples on the surface of the outermost layer from the viewpoint of aerodynamic performance. There are no particular restrictions on the number of dimples formed on the surface of the outermost layer, but from the viewpoint of improving aerodynamic performance and increasing flight distance, the number is preferably at least 250, more preferably at least 270, even more preferably at least 290, and most preferably at least 300, with the upper limit being preferably at most 400, more preferably at most 380, and even more preferably at most 360.

[0102] In the present invention, a coating film layer is formed on the surface of the cover. As the coating material for forming this coating film layer, a two-component curing urethane coating material is preferably used. Specifically, in this case, the two-component curing urethane coating material contains a base agent whose main component is a polyol resin and a curing agent whose main component is polyisocyanate.

[0103] The method for applying the above-mentioned paint to the cover surface to form a coating film layer is not particularly limited, and any known method can be used, such as air gun coating or electrostatic coating, as desired.

[0104] The thickness of the coating layer is not particularly limited, but is usually 8 to 22 μm, preferably 10 to 20 μm.

[0105] The golf ball of the present invention can be made to conform to the Rules of Golf for competitive use, and can be formed to have an outer diameter of 42.80 mm or less so as not to pass through a ring with an inner diameter of 42.672 mm, and a mass of preferably 45.0 to 45.93 g. [Example]

[0106] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0107] [Examples 1 to 12, Comparative Examples 1 to 5] Common Core A rubber composition for the core common to all examples was prepared using the formulation shown in Table 1, and a core having a diameter of 38.6 mm was fabricated by vulcanization molding.

[0108] [Table 1]

[0109] Details of the core material are as follows: "cis-1,4-Polybutadiene" manufactured by JSR Corporation, product 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. "Anti-aging agent" product name "Nocrac NS6" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) "Organic peroxide (1)" Dicumyl peroxide, trade name "Percumyl D" (manufactured by NOF Corporation) "Organic peroxide (2)": A mixture of 1,1-di(tert-butylperoxy)cyclohexane and silica, trade name "Perhexa C-40" (manufactured by NOF Corporation) "Zinc stearate" manufactured by NOF Corporation

[0110] A common middle class The resin material for the intermediate layer was injection molded around a 38.6 mm diameter core to produce an intermediate layer-coated sphere with a 1.25 mm thick intermediate layer. The resin material for the intermediate layer was a blend of 50 parts by weight of a sodium-neutralized ethylene-unsaturated carboxylic acid copolymer with an acid content of 18% by weight and 50 parts by weight of a zinc-neutralized ethylene-unsaturated carboxylic acid copolymer with an acid content of 15% by weight, totaling 100 parts by weight.

[0111] Cover (outermost layer) Next, for Examples 1-4, 6-8, 10-12 and Comparative Example 1, the outermost layer cover material shown in Table 2 below was injection molded around the above-mentioned mid layer-covered sphere to produce three-piece golf balls with a diameter of 42.7 mm and an outermost layer thickness of 0.8 mm. In this process, common dimples were formed on the surface of the cover in each Example and Comparative Example, although not specifically shown. The resin composition of the cover was designed to contain the components in the amounts shown in Tables 2 and 3 below, and the cover was injection molded at a molding temperature of 200-250°C. Furthermore, in Examples 5 and 9 and Comparative Examples 2 to 5, the components were designed to be blended in the amounts shown in Tables 2 and 3, and three-piece golf balls were produced in the same manner as above.

[0112] Details of the components contained in the compositions shown in Table 2 below are as follows: "TPU (1)": DIC Covestro Polymers' trade name "Pandex", an ether-type thermoplastic polyurethane (Shore D hardness "43"). "(Meth)acrylic block copolymer 1" Kuraray's product name "Clarity LA2250" acrylic block copolymer (hard segment PMMA / soft segment PBA), Shore D hardness "22" "(Meth)acrylic block copolymer 2" Kuraray's product name "Clarity LA2270" acrylic block copolymer (hard segment PMMA / soft segment PBA), Shore D hardness "31" "(Meth)acrylic block copolymer 1" Kuraray's product name "Clarity LA2140" acrylic block copolymer (hard segment PMMA / soft segment PBA), Shore D hardness "7" "(Meth)acrylic block copolymer 2" Kuraray's product name "Clarity LA2330" acrylic block copolymer (hard segment PMMA / soft segment PBA), Shore D hardness "6" "PMMA1" Kuraray's product name "Parapet Soft Acrylic SA-NW201" methacrylic resin (Shore D hardness "40") "PMMA2" Kuraray's product name "Parapet GF" methacrylic resin (Shore D hardness "87") "Hydrogenated styrene elastomer (1)" manufactured by Asahi Kasei Corporation, product name "Tuftec H1051" (Shore D hardness: 45) "Hydrogenated styrene elastomer (2)" manufactured by Asahi Kasei Corporation, product name "Tuftec H1517" (Shore D hardness: 47) Thermoplastic polyester elastomer: Hytrel 2401, a thermoplastic polyether ester elastomer (Shore D hardness 40) manufactured by Toray DuPont.

[0113] Physical properties of the cover resin composition (1) Shore D hardness The resin material was molded into a 2 mm thick sheet and left at a temperature of 23 ± 2°C for two weeks. Three sheets were stacked together during measurement. The hardness of the resin material was measured using a Shore D hardness tester in accordance with the ASTM D2240 standard. To measure the hardness, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd., equipped with a Shore D hardness tester, was used. (2) Rebound elasticity The impact resilience of the resin composition measured based on JIS-K 6255:2013 standard is shown in Tables 2 and 3. (3) Melt viscosity Tables 2 and 3 show the melt viscosity at a shear rate of 243 (1 / sec) measured with a capillograph at a temperature of 200°C in accordance with ISO 11443:1995.

[0114] The Martens hardness (HMa) and elastic work recovery (ηIta) of the polyurethane resin "TPU1" used in each Example and Comparative Example were measured by the following methods. The Martens hardness (HMb) and elastic work recovery (ηItb) of the resin composition of the cover layer (outermost layer) used in each Example and Comparative Example were also measured. Next, the following three relationship equations for these parameters were used: Formula (1): HMa / HMb, Equation (2): ηItb / HMb, Equation (3) ηIta / ηItb, and Equation (4)(ηIta·HMb) / (ηItb·HMa) These calculated values ​​are shown in Tables 2 and 3.

[0115] Martens hardness (HMb) of the outermost layer (cover layer) For each golf ball, the ball was cut in half, and a point 0.3 mm from the surface of the cover toward the center of the ball was identified on the cross section of the ball. The Martens hardness HMa [N / mm 2 The hardness was measured using a Fischerscope HM2000 ultra-microhardness tester manufactured by Fischer Instruments, Inc. The hardness was measured at room temperature under an applied load of 50 mN / 10 s.

[0116] Martens hardness (HMa) of resin materials The Martens hardness (HMa) of the polyurethane resin "TPU1" is as follows: The Martens hardness measurement device and measurement conditions for this resin are the same as those described above. Martens hardness (HMa) of TPU1: 14.3N / mm 2

[0117] Elastic work recovery rate of the cover layer (outermost layer) The elastic work recovery rate of the cover layer was measured using an ultra-microhardness tester, Fischerscope HM2000, manufactured by Fischer Instruments. The measurement conditions were: at room temperature, under an applied load of 50 mN / 10 s, the indentation work W due to the return deformation of the cover. elast (Nm) and mechanical pushing work W total Based on this, the elastic work recovery rate is calculated using the following formula: Elastic work recovery rate = W elast / W total × 100(%)

[0118] Elastic work recovery rate of resin materials The elastic work recovery rate (%) of the polyurethane resin "TPU1" is as follows: The measuring device and conditions for the elastic work recovery rate of this resin are the same as those described above. Elastic work recovery rate of TPU1: 72%

[0119] The spin performance, initial velocity performance, approach controllability, abrasion resistance, and moldability of each golf ball were evaluated by the following methods. The results are shown in Tables 2 and 3.

[0120] Initial speed 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 the ball at a head speed (HS) of 20 m / s are measured using an initial condition measuring device.

[0121] Controllability In addition, a sensory evaluation of the controllability of the ball during approach was conducted using the following method. The club used was the same sand wedge (SW) as above, product name "Bridgestone Tour Stage TW-03 (loft angle 57°)", and golfers evaluated the actual shots using the following criteria. [Judgment evaluation] ◎ ··· Extremely easy to operate. 〇 ··· Excellent operability. △ ··· Slightly inferior in operability. × ··· Poor operability. In addition to the amount of spin on the ball, the length of contact time between the ball and the club face, which is caused by low resilience, also affects whether or not the controllability is excellent. A long contact time improves controllability, while a short contact time reduces controllability. Here, we evaluate controllability (controllability) including the amount of spin and the length of contact time.

[0122] Evaluation of abrasion resistance The balls are kept warm at 23°C, and using a swing robot machine, five balls of each type are hit at a head speed of 33 m / s using a pitching wedge (PW) club, and the damage caused by the impact is visually evaluated according to the following criteria. 〇 ··· Slightly damaged or barely noticeable damage. × The dimple has been completely removed.

[0123] Evaluation of moldability (removal) The balls of each example were evaluated for ease of release from the mold after the cover was injection molded, according to the following criteria. ◎ No external damage such as broken runners or pins being stuck occurs when demolding. 〇 ··· When demolding, external damage such as broken runners and pins may occur, but this does not affect molding. △ ··· When demolding, external damage such as runner breakage or pin sticking may occur, and the molding temperature must be increased due to increased viscosity.

[0124] [Table 2]

[0125] [Table 3]

[0126] As shown in the results in Tables 2 and 3, the golf balls of Comparative Examples 1 to 5 are inferior to the products of the present invention (Examples) in the following respects. In Comparative Example 1, the component (II) was not blended into the resin composition, and the controllability during approach was poor. In Comparative Example 2, the resin composition does not contain component (II) but instead contains PMMA, but this increases the melt viscosity and reduces fluidity, necessitating a higher molding temperature, resulting in defects such as burns on the entire cover surface and poor moldability. In Comparative Example 3, the resin composition contains PMMA, which increases the melt viscosity and reduces fluidity, necessitating a higher molding temperature, resulting in defects such as burns on the entire cover surface and poor moldability. Furthermore, the high hardness of PMMA reduces approach spin and reduces controllability on approach shots. In Comparative Example 4, the HMa / HMb ratio is smaller than the lower limit of "1.020" in the formula (1), and as a result, the controllability during approach is poor. In Comparative Example 5, the HMa / HMb ratio is smaller than the lower limit of "1.020" in the formula (1), and as a result, the controllability during approach is poor.

Claims

1. A golf ball having at least one rubber core layer and at least one cover layer covering the core, wherein at least one layer of the cover comprises the following components (I) and (II): (I) Polyurethane or Polyurea (II) (Meth)acrylic block copolymer The block copolymer of the component (II) has two or more blocks constituting a hard segment and one or more blocks constituting a soft segment, the hard segment being mainly composed of methyl methacrylate units, and the soft segment being mainly composed of n-butyl acrylate units. The amount of the component (II) blended is 3 to 15 parts by mass per 100 parts by mass of the component (I), and 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 from the resin composition containing the components (I) and (II) is HMb [N / mm 2 ], HMa and HMb are expressed by the following formula (1): 1.020≦HMa / HMb≦1.500 (1) A golf ball characterized by satisfying the following:

2. 2. The golf ball of claim 1, wherein the material hardness of component (II) is 40 or less in Shore D hardness.

3. 3. The golf ball of claim 1, wherein component (II) has a rebound resilience of 50% or less as measured according to JIS-K 6255.

4. 4. The golf ball of claim 1, wherein component (II) has a weight average molecular weight of 10,000 or greater.

5. 5. The golf ball according to claim 1, wherein the cover has a Shore D hardness of 48 or less.

6. 6. The golf ball according to claim 1, wherein the resin composition further contains (III) a thermoplastic polyester elastomer.

7. 7. The golf ball of claim 6, wherein the material hardness of component (III) is 20 to 50 in Shore D hardness.

8. 8. The golf ball according to claim 6, wherein the component (III) has a rebound resilience of 50 to 80% as measured according to JIS-K 6255.

9. The melt viscosity of the component (III) at 200°C and a shear rate of 243 (1 / sec) is 0.3 x 10 4 ~1.5 x 10 4 9. The golf ball of claim 6, wherein the viscosity is (dPa·s).

10. When the elastic work recovery rate of the cover layer formed from the resin composition containing the components (I) and (II) is ηItb [%], ηItb and HMb can be calculated by the following formula (2): 5.00≦ηItb / HMb≦8.00 (2) 10. The golf ball according to claim 1, which satisfies the following:

11. When the elastic work recovery rate of the resin material of the component (I) is ηIta [%], the following formula (3) can be obtained. 0.97≦ηIta / ηItb≦1.12 (3) 11. The golf ball according to claim 10, which satisfies the following:

12. Furthermore, the following formula (4) 0.70≦(ηIta・HMb) / (ηItb・HMa)≦1.06 (4) 12. The golf ball according to claim 11, which satisfies the following:

Images