Golf ball

Abstract

To provide a golf ball including a cover containing polyurethane as a resin component, improving moldability of the cover while suppressing deterioration in scratch resistance of the cover, and enhancing golf ball productivity.SOLUTION: A golf ball comprises a spherical core and a cover for covering the spherical core, where the cover is formed from a cover composition including, as resin components, (A) a thermoplastic polyurethane, and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, where the content of (A) the thermoplastic polyurethane in the resin components is at least 50 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to golf balls, and more particularly to improving the moldability of polyurethane covers. [Background technology]

[0002] Conventionally, ionomer resins and polyurethanes have been used as resin components for golf ball covers. Covers using ionomer resins tend to have excellent resilience, durability, and processability. Covers using polyurethanes tend to have improved shot feel and spin performance. Cover materials that combine these ionomer resins and polyurethanes have also been proposed.

[0003] For example, Patent Document 1 describes a golf ball cover material containing a thermoplastic polyurethane elastomer, an ethylene-acrylic acid ester-glycidyl methacrylate terpolymer, and magnesium stearate (see Patent Document 1 (Table 1)). Patent Document 2 describes a cover composition containing, as the main components, a heated mixture of (a) 60 to 95% by weight of a polyurethane-based thermoplastic elastomer and (b) 5 to 40% by weight of an ethylene-(meth)acrylic acid-(meth)acrylic acid ester-based terpolymer ionomer resin (see Patent Document 2 (Table 2)).

[0004] Patent Document 3 also describes a golf ball whose cover is formed from a cover material whose main components are a heated mixture of: (A) 60 to 90% by mass of a metal ion-neutralized product of an olefin-unsaturated carboxylic acid copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic ester copolymer (wherein 40 to 80% by mass of the (A) component is an ionomer neutralized with an alkali metal ion); (B) 5 to 20% by mass of at least one olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic ester copolymer; and (C) 2 to 30% by mass of a thermoplastic polyurethane elastomer (see Patent Document 3 (Table 3)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-128402 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-180878 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-125377 Summary of the Invention [Problem to be solved by the invention]

[0006] When polyurethane is used as the primary resin component of a cover composition, the fluidity of the cover composition tends to decrease, making it difficult to mold the cover. Adding an ionomer resin to a polyurethane-containing cover composition can improve the fluidity of the cover composition. However, adding an ionomer resin to polyurethane reduces the scratch resistance of the resulting cover.

[0007] The present invention was made in consideration of the above circumstances, and aims to improve the moldability of a cover and increase the productivity of golf balls having a cover containing polyurethane as a resin component, while suppressing a decrease in the scratch resistance of the cover. [Means for solving the problem]

[0008] The golf ball of the present invention, which has solved the above-mentioned problems, has a spherical core and a cover enclosing the spherical core, and is characterized in that the cover is formed from a cover composition containing, as resin components, (A) a thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, wherein the content of (A) the thermoplastic polyurethane in the resin components is 50 mass% or more. [Effects of the Invention]

[0009] According to the present invention, for a golf ball having a cover containing polyurethane as a resin component, it is possible to improve the moldability of the cover while suppressing a decrease in the scratch resistance of the cover, thereby increasing the productivity of the golf ball. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a partially cutaway cross-sectional view showing a golf ball according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] The golf ball of the present invention has a spherical core and a cover enclosing the spherical core, and is characterized in that the cover is formed from a cover composition containing, as resin components, (A) a thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, with the resin components containing 50 mass% or more of (A) thermoplastic polyurethane.

[0012] By blending (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer with (A) a thermoplastic polyurethane, the flow initiation temperature of the cover composition can be lowered, and the melt viscosity can be reduced, thereby improving the moldability of the cover composition. Furthermore, (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer does not easily impair the flexibility of (A) a thermoplastic polyurethane, thereby preventing a decrease in the scratch resistance of the resulting cover.

[0013] [Cover composition] The cover composition used in the present invention will now be described. The cover composition contains, as resin components, (A) a thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer.

[0014] ((A) Thermoplastic polyurethane) The cover composition contains (A) a thermoplastic polyurethane as a resin component. The thermoplastic polyurethane (A) has a plurality of urethane bonds in the molecule and exhibits thermoplasticity. Thermoplastic polyurethane is a polyurethane that exhibits plasticity upon heating, and generally refers to a polyurethane having a linear structure with a high molecular weight to some extent. Examples of the thermoplastic polyurethane (A) include products in which urethane bonds are formed in the molecule by reacting polyisocyanate with polyol.

[0015] The polyisocyanate constituting the thermoplastic polyurethane (A) is not particularly limited as long as it is a compound having two or more isocyanate groups in the molecule. The polyisocyanate may be used alone or in combination of two or more. The polyisocyanate is preferably a diisocyanate having two isocyanate groups in the molecule.

[0016] Examples of the polyisocyanate include aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitrylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI); 4,4'-dicyclohexylmethane diisocyanate (H 12Examples of suitable polyisocyanates include alicyclic or aliphatic polyisocyanates such as cyclohexane (HDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trans-1,4-cyclohexane diisocyanate (CHDI), and norbornene diisocyanate (NBDI). Among these, alicyclic diisocyanates and / or aromatic diisocyanates are preferred as polyisocyanates. The use of alicyclic diisocyanates and / or aromatic diisocyanates improves the mechanical properties of the resulting polyurethane, further improving the scratch resistance of the resulting cover.

[0017] The polyisocyanate of the thermoplastic polyurethane (A) is 4,4'-dicyclohexylmethane diisocyanate (H 12 Particularly preferred is at least one diisocyanate selected from the group consisting of cyclohexane (MDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), isophorone diisocyanate (IPDI), trans-1,4-cyclohexane diisocyanate (CHDI), 4,4'-diphenylmethane diisocyanate (MDI), and toluene diisocyanate (TDI). Use of these diisocyanates improves the mechanical properties of the resulting polyurethane and further improves the scratch resistance of the resulting cover.

[0018] In addition, from the viewpoint of improving the weather resistance of the cover, (A) as the polyisocyanate of thermoplastic polyurethane, non-yellowing polyisocyanate (TMXDI, XDI, HDI, H6XDI, IPDI, H 12 It is preferable to use 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI) is used. 4,4'-Dicyclohexylmethane diisocyanate (H 12 MDI) has a rigid structure, which further improves the mechanical properties of the resulting polyurethane.

[0019] The polyol constituting the thermoplastic polyurethane (A) is not particularly limited as long as it is a compound having two or more hydroxy groups in the molecule, and examples thereof include high molecular weight polyols. The high molecular weight polyols may be used alone or in combination of two or more. The polyol is preferably a diol having two hydroxy groups in the molecule.

[0020] Examples of the high molecular weight polyol include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polytrimethylene ether glycol (PO3G), and polyoxytetramethylene glycol (PTMG); condensation polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols. The high molecular weight polyol may be derived from petroleum resources or biomass resources.

[0021] The number average molecular weight of the high molecular weight polyol is not particularly limited, but is, for example, preferably 400 or more, more preferably 1,000 or more, and is preferably 10,000 or less, more preferably 8,000 or less.

[0022] The thermoplastic polyurethane (A) may contain a chain extender as a constituent component, and examples of the chain extender include low-molecular-weight polyols and low-molecular-weight polyamines.

[0023] Examples of the low molecular weight polyol include diols such as ethylene glycol, diethylene glycol, triethylene glycol, propanediol (e.g., 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, etc.), dipropylene glycol, butanediol (e.g., 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, etc.), neopentyl glycol, pentanediol, hexanediol, heptanediol, octanediol, 1,6-cyclohexanedimethylol, aniline-based diols, and bisphenol A-based diols; triols such as glycerin, trimethylolpropane, and hexanetriol; and tetraols or hexaols such as pentaerythritol and sorbitol.

[0024] The low-molecular-weight polyamine used as a chain extender component is not particularly limited as long as it has at least two amino groups. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine; alicyclic polyamines such as isophoronediamine and piperazine; and aromatic polyamines.

[0025] The aromatic polyamine is not particularly limited as long as at least two or more amino groups are directly or indirectly bonded to an aromatic ring. Here, "indirectly bonded" means that the amino group is bonded to the aromatic ring via, for example, a lower alkylene group. The aromatic polyamine may be, for example, a monocyclic aromatic polyamine in which two or more amino groups are bonded to one aromatic ring, or a polycyclic aromatic polyamine containing two or more aminophenyl groups in which at least one amino group is bonded to one aromatic ring.

[0026] Examples of the monocyclic aromatic polyamine include phenylenediamine, toluenediamine, diethyltoluenediamine, and dimethylthiotoluenediamine, which are types in which an amino group is directly bonded to an aromatic ring; and xylylenediamine, which is types in which an amino group is bonded to an aromatic ring via a lower alkylene group. The polycyclic aromatic polyamine may be a poly(aminobenzene) in which at least two aminophenyl groups are directly bonded, or may be a poly(aminobenzene) in which at least two aminophenyl groups are bonded via a lower alkylene group or an alkylene oxide group. Among these, diaminodiphenylalkanes in which two aminophenyl groups are bonded via a lower alkylene group are preferred, and 4,4'-diaminodiphenylmethane and its derivatives are particularly preferred.

[0027] The molecular weight of the chain extender is preferably less than 400, more preferably 350 or less, and even more preferably 200 or less, and is preferably 30 or more, more preferably 40 or more, and even more preferably 45 or more.

[0028] The constituent form of the (A) thermoplastic polyurethane is not particularly limited, but examples thereof include a form constituted by a polyisocyanate and a high molecular weight polyol, a form constituted by a polyisocyanate, a high molecular weight polyol, and a low molecular weight polyol, a form constituted by a polyisocyanate, a high molecular weight polyol, a low molecular weight polyol, and a polyamine, and a form constituted by a polyisocyanate, a high molecular weight polyol, and a polyamine. As the constituent form of the (A) thermoplastic polyurethane, a form constituted by a diisocyanate and a diol is particularly preferred, and a form constituted by a diisocyanate, a high molecular weight diol, and a low molecular weight diol is more preferred.

[0029] The content of polyol in 100% by mass of the (A) thermoplastic polyurethane is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The content of polyisocyanate in 100% by mass of the (A) thermoplastic polyurethane is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0030] The slab hardness of the thermoplastic polyurethane (A) is preferably 25 or more, more preferably 26 or more, even more preferably 28 or more, in Shore D hardness, and is preferably 40 or less, more preferably 39 or less, even more preferably 38 or less. If the thermoplastic polyurethane (A) has a Shore D hardness of 25 or more, the spin rate on driver shots can be reduced, and if it is 40 or less, the spin rate on approach shots can be increased.

[0031] The content of the thermoplastic polyurethane (A) in the resin component is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, and is preferably 99.9% by mass or less, more preferably 99% by mass or less, even more preferably 98% by mass or less, and most preferably 95% by mass or less. If the content of the component (A) is 50% by mass or more, the scratch resistance of the cover will be improved, and if it is 99.9% by mass or less, the moldability of the cover composition will be improved.

[0032] ((B) Olefin-Unsaturated Carboxylic Acid Copolymer and / or Olefin-Unsaturated Carboxylic Acid-Unsaturated Carboxylic Acid Ester Copolymer) The cover composition contains, as a resin component, (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. The (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer may be used alone or in combination of two or more.

[0033] The olefin-unsaturated carboxylic acid copolymer is a binary copolymer of an olefin and an unsaturated carboxylic acid (hereinafter, sometimes referred to as "(B1) binary copolymer"). The olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer is a terpolymer of an olefin, an unsaturated carboxylic acid, and an unsaturated carboxylic acid ester (hereinafter, sometimes referred to as "(B2) terpolymer"). The (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer may consist solely of the (B1) binary copolymer or the (B2) terpolymer. Alternatively, the (B1) binary copolymer and the (B2) terpolymer may be used in combination.

[0034] The olefin is preferably an olefin having a carbon number of 2 to 8, more preferably an olefin having a carbon number of 2 to 4. Examples of the olefin include ethylene, propylene, butene, pentene, hexene, heptene, and octene, with ethylene being particularly preferred.

[0035] The unsaturated carboxylic acid is preferably an α,β-unsaturated carboxylic acid, more preferably an α,β-unsaturated carboxylic acid having a carbon number of 3 to 8. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid, with acrylic acid or methacrylic acid being particularly preferred.

[0036] The unsaturated carboxylic acid ester is preferably an α,β-unsaturated carboxylic acid ester, more preferably an alkyl ester of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. The unsaturated carboxylic acid ester is more preferably an alkyl ester of acrylic acid, methacrylic acid, fumaric acid, or maleic acid, and is particularly preferably an alkyl acrylate or alkyl methacrylate. Examples of the alkyl group constituting the ester include a methyl group, an ethyl group, a propyl group, an n-butyl group, and an isobutyl group. The unsaturated carboxylic acid ester is preferably methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, or isobutyl (meth)acrylate. In this specification, (meth)acrylic acid refers to acrylic acid and / or methacrylic acid.

[0037] The (B1) binary copolymer is preferably a binary copolymer of ethylene and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and more preferably an ethylene-(meth)acrylic acid binary copolymer. The (B2) terpolymer is preferably a terpolymer of ethylene, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an alkyl ester of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and more preferably an ethylene-(meth)acrylic acid-(meth)acrylic acid alkyl ester terpolymer.

[0038] The content of the unsaturated carboxylic acid component in the (B1) binary copolymer is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. If the content of the unsaturated carboxylic acid component is within the above range, the compatibility with the (A) thermoplastic polyurethane will be even better.

[0039] The content of the unsaturated carboxylic acid component in the (B2) terpolymer is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. If the content of the unsaturated carboxylic acid component is within the above range, the compatibility with the (A) thermoplastic polyurethane will be even better.

[0040] The melt flow rate (MFR) (190°C, 2.16 kg load) of the (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer is preferably 10 g / 10 min or more, more preferably 15 g / 10 min or more, and even more preferably 25 g / 10 min or more, and is preferably 1000 g / 10 min or less, more preferably 900 g / 10 min or less, and even more preferably 800 g / 10 min or less. When the (B) component's MFR (190°C, 2.16 kg load) is 10 g / 10 min or more, the fluidity of the cover composition is improved. Furthermore, when the (B) component's MFR (190°C, 2.16 kg load) is 1000 g / 10 min or less, the resulting cover's impact durability is improved. The MFR is measured using a flow tester in accordance with JIS K7210. When multiple types of component (B) are used in combination, the MFR of a mixture of these is measured.

[0041] The melting point of the (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer is preferably 120° C. or lower, more preferably 118° C. or lower, and even more preferably 115° C. or lower. The melting point of the (B) component is preferably 75° C. or higher.

[0042] Examples of the component (B) include Nucrel (registered trademark) N2050H, N2060, N1050H, N1560, N1525, AN4221C, AN4213C, N1110H, AN4229C, N11081C, N1108C, N1035, N035C, N0908C, AN42012C, N0903HC, N0823, AN42115C, AN4228C, AN4214C, N0200H, and AN4233C (manufactured by Mitsui Dow Polychemicals); and Primacol (registered trademark) 1321, 1410, 1430, 3002, 3003, 3004, 3330, 3340, 3440, and 3460 (manufactured by SK Geo Centric).

[0043] The content of (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, particularly preferably 3% by mass or more, and most preferably 5% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 20% by mass or less. If the content of (B) component is 0.1% by mass or more, the moldability of the cover composition is further improved, and if it is 50% by mass or less, the deterioration of the scratch resistance of the resulting cover can be further suppressed.

[0044] The mass ratio ((A) / (B)) of the (A) thermoplastic polyurethane to the (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is preferably 50.0 / 50.0 or more, more preferably 55.0 / 45.0 or more, and even more preferably 60.0 / 40.0 or more, and is preferably 99.9 / 0.1 or less, more preferably 99.0 / 1.0 or less, and even more preferably 98.0 / 2.0 or less. If the mass ratio ((A) / (B)) is 50.0 / 50.0 or more, the deterioration of the scratch resistance of the resulting cover can be further suppressed, and if it is 99.9 / 0.1 or less, the moldability of the cover composition can be further improved.

[0045] (Other resin components) The cover composition may contain only (A) thermoplastic polyurethane and (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer as resin components, or may contain other resin components in addition to these.

[0046] Examples of the other resin components include thermoplastic elastomers.

[0047] Specific examples of the thermoplastic elastomer include thermoplastic polyamide elastomers such as "Pebax (registered trademark)" manufactured by Arkema (e.g., "Pebax 2533"), thermoplastic polyester elastomers such as "Hytrel (registered trademark)" manufactured by Toray Celanese (e.g., "Hytrel 3548" and "Hytrel 4047"), thermoplastic polystyrene elastomers such as "Tefabloc (registered trademark)" manufactured by Mitsubishi Chemical Corporation, and the like.

[0048] When resin components other than the (A) component and the (B) component are blended as the resin components, the total content of the (A) component and the (B) component in the resin components is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0049] (additives) The cover composition may further contain additives such as pigment components such as titanium oxide or blue pigment, weight adjusters such as calcium carbonate or barium sulfate, dispersants, antioxidants, UV absorbers, light stabilizers, fluorescent materials, or fluorescent brighteners, within the range that does not impair the performance of the cover. The content of the resin component in the cover composition is preferably 90% by mass or more, more preferably 92% by mass or more, and even more preferably 94% by mass or more.

[0050] The content of the white pigment (titanium oxide) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the resin component. If the content of the white pigment is 0.5 parts by mass or more, it is possible to impart hiding properties to the cover, and if it is 10 parts by mass or less, it is possible to prevent a decrease in the durability of the cover.

[0051] The cover composition preferably does not contain a basic metal compound that neutralizes the carboxy groups of the (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. Metals contained in the basic metal compound include lithium, sodium, potassium, calcium, magnesium, zinc, aluminum, nickel, iron, copper, manganese, tin, lead, and cobalt. Examples of the basic metal compound include magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, sodium hydroxide, sodium carbonate, calcium oxide, calcium hydroxide, lithium hydroxide, lithium carbonate, and magnesium stearate.

[0052] The cover composition can be obtained, for example, by dry-blending component (A), component (B), and, if necessary, other additives. Alternatively, the dry-blended mixture can be extruded and pelletized. For dry-blending, a mixer capable of blending pelletized raw materials is preferably used, and a tumbler mixer is more preferably used. For extrusion, a known extruder such as a single-screw extruder, a twin-screw extruder, or a twin-screw / single-screw extruder can be used.

[0053] The cover composition preferably has a slab hardness of at least 25, more preferably at least 26, and even more preferably at least 28, in Shore D hardness, and preferably has a slab hardness of at most 40, more preferably at most 39, and even more preferably at most 38. If the slab hardness is at least 25, in Shore D hardness, the spin rate on driver shots can be reduced, and if it is at most 40, the spin rate on approach shots can be increased.

[0054] The melt viscosity (190°C) of the cover composition is preferably less than 3850 Pa·s, more preferably less than 3500 Pa·s. If the melt viscosity (190°C) is less than 3850 Pa·s, the moldability of the cover composition is further improved. Although there is no particular lower limit for the melt viscosity (190°C), the melt viscosity (190°C) is preferably 10 Pa·s or higher. The method for measuring the melt viscosity (190°C) will be described later.

[0055] The flow initiation temperature of the cover composition is preferably less than 110°C, more preferably less than 109°C. If the flow initiation temperature is less than 110°C, the moldability of the cover composition is further improved. Although there is no particular restriction on the lower limit of the flow initiation temperature, the flow initiation temperature is preferably 70°C or higher. The method for measuring the flow initiation temperature will be described later.

[0056] [Golf balls] The golf ball of the present invention has a spherical core and a cover enclosing the spherical core, the cover being formed from the cover composition. The cover constitutes the outermost layer of the golf ball body. Note that the present invention relates to the moldability and scratch resistance of the cover, and the configuration of the spherical core is not limited.

[0057] (spherical core) Examples of the spherical core include a single-layer spherical core, a spherical core consisting of a center and one intermediate layer covering the center, and a spherical core consisting of a center and two or more intermediate layers covering the center.

[0058] A known rubber composition (hereinafter, sometimes simply referred to as a "core rubber composition") can be used for the spherical core or center. For example, a rubber composition containing a base rubber, a co-crosslinking agent, and a crosslinking initiator can be molded by hot pressing.

[0059] As the base rubber, it is preferable to use high-cis polybutadiene having cis bonds of 40% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, which are particularly advantageous for resilience.

[0060] The co-crosslinking agent is preferably an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof, more preferably acrylic acid or a metal salt thereof, or methacrylic acid or a metal salt thereof. The metal in the metal salt is preferably zinc, magnesium, calcium, aluminum, or sodium, more preferably zinc. The amount of the co-crosslinking agent used is preferably 20 to 50 parts by weight per 100 parts by weight of the base rubber. When an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms is used as the co-crosslinking agent, it is preferable to incorporate a metal compound (e.g., magnesium oxide).

[0061] As the crosslinking initiator, an organic peroxide is preferably used. Specific examples include organic peroxides such as dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. Of these, dicumyl peroxide is preferably used. The amount of crosslinking initiator added is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, per 100 parts by mass of base rubber; and is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less.

[0062] The core rubber composition may further contain an organic sulfur compound. Suitable examples of the organic sulfur compound include diphenyl disulfides, thiophenols, and thionaphthols. The amount of the organic sulfur compound is preferably at least 0.1 parts by weight, more preferably at least 0.3 parts by weight, and even more preferably at least 0.5 parts by weight, per 100 parts by weight of the base rubber. The amount is preferably at most 5.0 parts by weight, more preferably at most 4.0 parts by weight, and even more preferably at most 2.0 parts by weight.

[0063] The core rubber composition may further contain a carboxylic acid and / or a salt thereof. The carboxylic acid and / or a salt thereof is preferably a carboxylic acid and / or a salt thereof having 1 to 30 carbon atoms. The carboxylic acid may be either an aliphatic carboxylic acid or an aromatic carboxylic acid (such as benzoic acid). The amount of the carboxylic acid and / or a salt thereof is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the base rubber.

[0064] In addition to the base rubber, co-crosslinking agent, crosslinking initiator, and organic sulfur compound, the core rubber composition may further contain, as appropriate, a weight adjuster such as zinc oxide or barium sulfate, an antioxidant, a color powder, and the like.

[0065] The conditions for hot press molding the core rubber composition may be set appropriately depending on the rubber composition, but it is generally preferable to heat the core rubber composition at 130°C to 200°C for 10 to 60 minutes, or to heat the core rubber composition in two stages: at 130°C to 150°C for 20 to 40 minutes, and then at 160°C to 180°C for 5 to 15 minutes.

[0066] When the spherical core has an intermediate layer, examples of intermediate layer materials include thermoplastic resins such as polyurethane resins, ionomer resins, polyamide resins, and polyethylene; thermoplastic elastomers such as styrene elastomers, polyolefin elastomers, polyurethane elastomers, polyamide elastomers, and polyester elastomers; and cured rubber compositions. Examples of ionomer resins include copolymers of ethylene and α,β-unsaturated carboxylic acids in which at least a portion of the carboxyl groups has been neutralized with metal ions, and terpolymers of ethylene, α,β-unsaturated carboxylic acids, and α,β-unsaturated carboxylic acid esters in which at least a portion of the carboxyl groups has been neutralized with metal ions. The intermediate layer may further contain weight adjusters such as barium sulfate and tungsten, antioxidants, pigments, and the like.

[0067] The method for forming the intermediate layer is not particularly limited, but examples include a method in which the intermediate layer composition is first molded into a hemispherical half shell, and then two of these are used to encase a sphere and then pressure-molded, or a method in which the intermediate layer composition is directly injection molded onto the sphere to encase the sphere.

[0068] When the intermediate layer is formed by injection molding the intermediate layer composition onto a sphere, it is preferable to use upper and lower molds having hemispherical cavities. The intermediate layer can be formed by injection molding by protruding a holding pin, inserting and holding the coated sphere, injecting the heated and molten intermediate layer composition, and cooling it.

[0069] When the intermediate layer is formed by compression molding, the half shells can be formed by either compression molding or injection molding, but compression molding is preferred. Conditions for compression molding the intermediate layer composition into half shells include, for example, a pressure of 1 MPa to 20 MPa and a molding temperature of -20°C to +70°C relative to the flow initiation temperature of the intermediate layer composition. By using these molding conditions, half shells with a uniform thickness can be formed. For example, a method for forming the intermediate layer using half shells includes a method in which a sphere is covered with two half shells and compression molded. Conditions for compression molding the half shells into the intermediate layer include, for example, a molding pressure of 0.5 MPa to 25 MPa and a molding temperature of -20°C to +70°C relative to the flow initiation temperature of the intermediate layer composition. By using these molding conditions, an intermediate layer with a uniform thickness can be formed.

[0070] The molding temperature refers to the maximum temperature that the surface of the recess in the lower mold reaches during the period from mold clamping to mold opening. The flow starting temperature of the composition was measured by measuring the flow rate of the thermoplastic resin composition in pellet form at a plunger area of ​​1 cm using a Shimadzu Flow Tester CFT-500. 2 Measurement can be performed under the conditions of die length: 1 mm, die diameter: 1 mm, load: 588.399 N, starting temperature: 30°C, and temperature rise rate: 3°C / min.

[0071] The diameter of the spherical core is preferably 34.8 mm or more, more preferably 35.7 mm or more, even more preferably 36.6 mm or more, and is preferably 42.2 mm or less, more preferably 41.8 mm or less, even more preferably 41.2 mm or less, and most preferably 40.8 mm or less. If the diameter of the spherical core is 34.8 mm or more, the cover will not be too thick, resulting in better resilience. On the other hand, if the diameter of the spherical core is 42.2 mm or less, the cover will not be too thin, resulting in better cover functionality.

[0072] (Golf ball structure) The structure of the golf ball is not particularly limited as long as it has a spherical core and a cover enclosing the spherical core. Examples of golf ball structures include a two-piece golf ball having a single-layer spherical core and a cover enclosing the spherical core, a three-piece golf ball having a spherical core consisting of a center and one intermediate layer enclosing the center and a cover enclosing the spherical core, and a multi-piece golf ball having a spherical core consisting of a center and two or more intermediate layers enclosing the center and a cover enclosing the spherical core.

[0073] The manner in which the cover composition is used to form the cover is not particularly limited, but examples include a manner in which the cover composition is directly injection-molded onto a spherical core, or a manner in which a hollow shell is molded from the cover composition, the spherical core is coated with multiple shells, and then compression-molded (preferably, a method in which a hollow half shell is molded from the cover composition, the spherical core is coated with two half shells, and then compression-molded). The golf ball body with the molded cover is preferably removed from the mold and, as necessary, subjected to surface treatment such as deburring, cleaning, and sandblasting. Furthermore, marks can also be formed, if desired.

[0074] The cover thickness is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.5 mm or more, and is preferably 2.0 mm or less, more preferably 1.8 mm or less, and even more preferably 1.6 mm or less. A cover thickness of 0.3 mm or more makes it easier to mold the cover, while a cover thickness of 2.0 mm or less allows the core diameter to be relatively large, improving the resilience performance of the golf ball.

[0075] The total number of dimples formed on the cover is preferably 200 to 500. If the total number of dimples is less than 200, the effect of the dimples is difficult to obtain. If the total number of dimples is more than 500, the size of each dimple becomes small, making it difficult to obtain the effect of the dimples. The shape (shape in plan view) of the dimples formed is not particularly limited, and the following may be used alone or in combination: circle; polygon such as approximately triangle, approximately square, approximately pentagon, approximately hexagon; or other irregular shape.

[0076] The golf ball with the molded cover is preferably removed from the mold and, if necessary, subjected to surface treatments such as deburring, cleaning, and sandblasting. A coating film or markings can also be formed as desired. The thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. A coating film thickness of 5 μm or more is less likely to wear away even with continuous use, while a coating film thickness of 50 μm or less allows the dimples to fully exert their effects.

[0077] The diameter of the golf ball is preferably 40 mm to 45 mm. From the viewpoint of meeting the United States Golf Association (USGA) standards, a diameter of 42.67 mm or more is particularly preferred. From the viewpoint of reducing air resistance, a diameter of 44.00 mm or less is more preferred, and 42.80 mm or less is particularly preferred. The mass of the golf ball is preferably 40 g or more and 50 g or less. From the viewpoint of obtaining high inertia, a mass of 44.00 g or more is more preferred, and 45.00 g or more is particularly preferred. From the viewpoint of meeting the USGA standards, a mass of 45.93 g or less is particularly preferred.

[0078] When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the compressive deformation (the amount the golf ball shrinks in the compression direction) when an initial load of 98 N is applied and a final load of 1275 N is applied is preferably 2.0 mm or more, more preferably 2.4 mm or more, and even more preferably 2.5 mm or more, and is preferably 5.0 mm or less, more preferably 4.5 mm or less, and even more preferably 4.0 mm or less. A golf ball with a compressive deformation of 2.0 mm or more is not too hard and has a good feel at impact. On the other hand, by setting the compressive deformation to 5.0 mm or less, the resilience is improved.

[0079] An example of a golf ball of the present invention is shown in Figure 1. Figure 1 is a partially cutaway cross-sectional view showing golf ball 1 according to one embodiment of the present invention. Golf ball 1 has a spherical core 2 composed of a center 21 and a mid layer 22 encasing center 21, and a cover 3 encasing spherical core 2. A large number of dimples 31 are formed on the surface of cover 3. The portion of the surface of this golf ball other than dimples 31 is land 32. This golf ball 1 has a paint layer and a mark layer on the outside of cover 3, but these layers are not shown in the figure. [Example]

[0080] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples, and all modifications and embodiments that do not deviate from the spirit of the present invention are included within the scope of the present invention.

[0081] [Evaluation method] (1) Slab hardness (Shore D hardness) The intermediate layer composition, thermoplastic polyurethane, and cover composition were injection molded into sheets approximately 2 mm thick and stored at 23°C for two weeks. Three or more of these sheets were stacked to avoid the influence of the measurement substrate, and their hardness was measured using an automatic hardness tester (DigiTest II, manufactured by H. Burleith Co.). A Shore D detector was used.

[0082] (2) Melt viscosity The melt viscosity of a pelletized sample was measured using a flow property evaluation device (Shimadzu Corporation, Flow Tester CFT-500D) and evaluated according to the following criteria: Measurement conditions: die length: 10 mm, die hole diameter: 1 mm, cylinder pressure: 3 MPa, temperature: 190°C. ◎: Less than 3500 Pa·s ○: 3500 Pa·s or more, less than 3850 Pa·s ×:3850Pa·s or more

[0083] (3) Flow start temperature The flow initiation temperature was measured for a pellet-shaped sample using a flow characteristic evaluation device (Shimadzu Corporation, Flow Tester CFT-500D) and evaluated according to the following criteria. Measurement conditions were: plunger area: 1 cm 2 , DIELENGTH: 1 mm, load: 588.399 N, starting temperature: 30°C, heating rate: 3°C / min. ◎: Less than 109℃ ○: 109℃ or higher, less than 110℃ ×: 110℃ or higher

[0084] (4) Scratch resistance A commercially available pitching wedge was attached to a swing robot, and a golf ball was hit twice, once at each point, at a head speed of 36 m / s. The two impacted points were visually observed and rated on a 5-point scale based on the following criteria, with the worse score being the evaluation result. If a cover of the required thickness could not be molded and scratch resistance could not be evaluated, an "X" was recorded. 5 points: Virtually no flaws observed. 4 points: No visible scratches, but slight scratches are visible when picked up and looked at closely. 3 points: There are visible scratches. 2 points: noticeable scratches. 1 point: Scratched to the point that it cannot be reused.

[0085] [Manufacturing golf balls] (1) Preparation of rubber composition The raw materials were kneaded with a kneading roll so as to obtain the composition shown in Table 1, thereby obtaining a rubber composition.

[0086] [Table 1]

[0087] The materials used in Table 1 are as follows: BR730: High cis polybutadiene rubber (cis-1,4-bond content = 95 mass%, 1,2-vinyl bond content = 1.3 mass%, Mooney viscosity (ML 1+4 (100℃)=55, molecular weight distribution (Mw / Mn)=3) ZN-DA90S: Zinc acrylate (containing 10% zinc stearate) manufactured by Nisshoku Techno Fine Chemicals Zinc oxide: "Ginrei R" manufactured by Toho Zinc Barium sulfate: Sakai Chemical Industry's "Barium Sulfate BD" PBDS: Kawaguchi Chemical Industry Co., Ltd., bis(pentabromophenyl) disulfide Dicumyl peroxide: manufactured by Tokyo Chemical Industry Co., Ltd.

[0088] (2) Preparation of intermediate layer composition The raw materials were extruded using a twin-screw kneading extruder so as to have the composition shown in Table 2, to prepare pellets of a composition for an intermediate layer.

[0089] [Table 2] Surlyn® 8150: Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin, manufactured by Dow Himilan® AM7329: Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin, manufactured by Mitsui Dow Polychemicals Titanium dioxide: Ishihara Sangyo Kaisha, A-220

[0090] (3) Preparation of Cover Composition Thermoplastic polyurethane was synthesized as follows: Dicyclohexylmethane diisocyanate (H 12 Polytetramethylene ether glycol (PTMG (number average molecular weight 1400)) heated to 80°C was added to MDI, and raw material (H 12 Dibutyltin dilaurate (MDI, PTMG and BD) was added in a total amount of 0.005% by mass, and the mixture was stirred at 80°C for 2 hours under a nitrogen stream. Subsequently, butanediol (BD) heated to 80°C was added under a nitrogen stream, and the mixture was stirred at 80°C for 1 minute. Thereafter, the reaction solution was cooled and the system was degassed by reducing the pressure at room temperature for 1 minute. The degassed reaction solution was spread in a container and stored under a nitrogen atmosphere at 110°C for 6 hours to carry out a urethane reaction and obtain a thermoplastic polyurethane. Note that PTMG, H 12 The molar ratio of MDI and BD was PTMG:H 12 The ratio of MDI to BD was 1:3.81:2.81. The slab hardness of the resulting thermoplastic polyurethane was 31 in Shore D hardness.

[0091] Next, the thermoplastic polyurethane obtained above was used to extrude raw materials in the formulations shown in Tables 3 to 6 using a twin-screw kneading extruder to prepare pelletized cover compositions.

[0092] (4) Golf ball manufacturing Golf balls No. 1-32 The rubber composition was hot-pressed in upper and lower molds with hemispherical cavities to obtain centers with diameters of 38.5 mm or 37.9 mm. Barium sulfate was added in an amount to give a golf ball with a mass of 45.6 g. The intermediate layer composition was injection molded onto the center to obtain a spherical core. The intermediate layer had a thickness of 1.6 mm. The spherical core was then placed in a final mold with numerous dimples on the cavity surface. Half shells were obtained from the cover composition by compression molding. Two half shells were placed in a final mold to cover a spherical core, resulting in a golf ball with a cover that had numerous dimples in the shape of the inverse of the dimples on the cavity surface. The evaluation results of the resulting golf balls are shown in Tables 3 and 4.

[0093] Golf ball No. 33~63 The rubber composition was hot-pressed in upper and lower molds with hemispherical cavities to obtain centers with diameters of 37.2 mm or 36.6 mm. Barium sulfate was added in an amount sufficient to give a golf ball with a mass of 45.6 g. The intermediate layer composition was injection molded onto a center to obtain a spherical core. The intermediate layer had a thickness of 1.6 mm. The obtained spherical core was placed in a final mold with numerous dimples on the cavity surface. The cover composition was injection molded onto the spherical core to obtain a golf ball with numerous dimples on the cover that were the inverse of the dimples on the cavity surface. The evaluation results of the obtained golf balls are shown in Tables 5 and 6.

[0094] [Table 3]

[0095] [Table 4]

[0096] [Table 5]

[0097] [Table 6] The materials used in Tables 3 to 6 are as follows: N2050H: Nucrel® N2050H manufactured by Mitsui Dow Polychemicals (acid content: 20% by mass, MFR (190°C, 2.16 kg): 500 g / 10 min, melting point: 75°C to 115°C) N2060: Nucrel N2060 manufactured by Mitsui Dow Polychemicals (acid content: 20% by mass, MFR (190°C, 2.16 kg): 60 g / 10 min, melting point: 75°C to 115°C) N1050H: Nucrel N1050H manufactured by Mitsui Dow Polychemicals (acid content: 10% by mass, MFR (190°C, 2.16 kg): 500 g / 10 min, melting point: 75°C to 115°C) Himilan® 1605: Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui Dow Polychemicals Himilan AM7329: Manufactured by Mitsui Dow Polychemicals, zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin Titanium dioxide: Ishihara Sangyo Kaisha, A-220

[0098] Golf balls Nos. 1 to 13, 17 to 29, 33 to 44, and 48 to 60 have covers formed from cover compositions Nos. 1 to 13, which contain, as resin components, (A) thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, and the content of (A) thermoplastic polyurethane in the resin components is 50 mass% or more.

[0099] Golf balls Nos. 14, 30, 45, and 61 have covers formed from cover composition No. 14, which contains (A) thermoplastic polyurethane as a resin component and does not contain (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. Golf balls Nos. 15, 16, 31, 32, 46, 47, 62, and 63 are formed from cover composition No. 15 or 16, which contains (A) a thermoplastic polyurethane and an ionomer resin (a metal-neutralized product of an olefin-unsaturated carboxylic acid copolymer or a metal-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer).

[0100] Golf balls Nos. 1 to 32 are balls in which half shells were produced from the cover composition by compression molding, and covers were formed using these half shells. Cover compositions Nos. 1 to 13 forming the covers of golf balls Nos. 1 to 13 and 17 to 29 have lower melt viscosities and lower flow-initiation temperatures than cover composition No. 14 forming the covers of golf balls Nos. 14 and 30. Therefore, these golf balls Nos. 1 to 13 and 17 to 29 have improved cover moldability. In addition, golf balls Nos. 1 to 13 and 17 to 29 have covers with higher scratch resistance than golf balls Nos. 15 and 31, and the use of (B) olefin-unsaturated carboxylic acid copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer has prevented the deterioration of scratch resistance.

[0101] Golf balls Nos. 33 to 47 have covers with a thickness of 1.15 mm formed from the cover composition by injection molding. Cover compositions Nos. 1 to 13 forming the covers of golf balls Nos. 33 to 44 have lower melt viscosities and lower flow-initiation temperatures than cover composition No. 14 forming the cover of golf ball No. 45. Therefore, these golf balls Nos. 33 to 44 have improved cover moldability. In addition, golf balls Nos. 33 to 44 have covers with higher scratch resistance than golf ball No. 46, and the use of (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer prevents a decrease in scratch resistance.

[0102] Golf balls Nos. 48 to 63 have covers with a thickness of 1.45 mm formed from the cover composition by injection molding. Cover compositions Nos. 1 to 13 forming the covers of golf balls Nos. 48 to 60 have lower melt viscosities and lower flow-initiation temperatures than cover composition No. 14 forming the cover of golf ball No. 61. Therefore, these golf balls Nos. 48 to 60 have improved cover moldability. In addition, golf balls Nos. 48 to 60 have covers with higher scratch resistance than golf ball No. 62, and the use of (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer prevents a decrease in scratch resistance.

[0103] The present invention (1) is a golf ball having a spherical core and a cover enclosing the spherical core, characterized in that the cover is formed from a cover composition containing, as resin components, (A) a thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, and the content of (A) thermoplastic polyurethane in the resin components is 50 mass% or more.

[0104] The present invention (2) is the golf ball according to the present invention (1), wherein the mass ratio ((A) / (B)) of the (A) thermoplastic polyurethane to the (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is 50.0 / 50.0 to 99.9 / 0.1.

[0105] The present invention (3) is the golf ball according to the present invention (1), wherein the mass ratio ((A) / (B)) of the (A) thermoplastic polyurethane to the (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is 60.0 / 40.0 to 99.0 / 1.0.

[0106] The present invention (4) is the golf ball according to any one of the present inventions (1) to (3), wherein the thermoplastic polyurethane (A) contains an alicyclic diisocyanate and / or an aromatic diisocyanate as the polyisocyanate.

[0107] The present invention (5) is a golf ball according to the present invention (4), wherein the polyisocyanate is at least one diisocyanate selected from the group consisting of 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, trans-1,4-cyclohexane diisocyanate, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate. [Explanation of symbols]

[0108] 1; golf ball; 2; spherical core; 21; center; 22; mid layer; 3; cover; 31; dimples; 32; land

Claims

1. A golf ball having a spherical core and a cover enclosing the spherical core, the cover contains, as resin components, (A) a thermoplastic polyurethane and (B) an olefin-unsaturated carboxylic acid copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer; A golf ball formed from a cover composition in which the resin component (A) contains 50% by mass or more of thermoplastic polyurethane.

2. 2. The golf ball according to claim 1, wherein the mass ratio ((A) / (B)) of the (A) thermoplastic polyurethane to the (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is 50.0 / 50.0 to 99.9 / 0.

1.

3. 2. The golf ball according to claim 1, wherein the mass ratio ((A) / (B)) of the (A) thermoplastic polyurethane to the (B) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer in the resin component is 60.0 / 40.0 to 99.0 / 1.

0.

4. 2. The golf ball according to claim 1, wherein the thermoplastic polyurethane (A) contains an alicyclic diisocyanate and / or an aromatic diisocyanate as the polyisocyanate constituting the thermoplastic polyurethane (A).

5. 5. The golf ball according to claim 4, wherein the polyisocyanate is at least one diisocyanate selected from the group consisting of 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, trans-1,4-cyclohexane diisocyanate, 4,4'-diphenylmethane diisocyanate, and toluene diisocyanate.

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