Golf ball

Abstract

To provide a novel golf ball excellent in a spin performance in approach shot.SOLUTION: A base material resin 4 forming an outermost layer of a golf ball coating film is a polyurethane obtained by reacting (A) a polyol composition including a polyol with a side chain and (B) a polyisocyanate composition, a loss elastic modulus (E") at -50°C obtained by measuring, in a specific condition, a dynamic visco-elasticity of the polyurethane is 2.0×108 Pa or greater, and a loss tangent (tanδ) has a peak in a range of -60°C or higher and -20°C or lower, and a height of the peak is 0.1 or greater and 0.5 or smaller.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a golf ball having a coating film.

Background Art

[0002] A coating film is provided on the surface of the golf ball body. It has been proposed to improve the characteristics of the golf ball by improving the coating film.

[0003] Patent Document 1 discloses a golf ball including a core, a cover located outside the core, and a paint layer located outside the cover, wherein the Shore D hardness of the cover is 61 or less, and the Martens hardness of the paint layer is 2.0 mgf / μm 2 or less.

[0004] Patent Document 2 discloses a golf ball having a golf ball body and a coating film provided on the surface of the golf ball body, wherein the coating film has a Martens hardness of 2.0 mgf / μm 2 or less, and the ratio of the 50% modulus to the 10% modulus (50% modulus / 10% modulus) is 1.6 or more.

[0005] Patent Document 3 discloses a golf ball having a golf ball body and a coating film provided on the surface of the golf ball body, wherein the coating film has a storage elastic modulus (E') in the temperature range of 120°C to 150°C measured under specific measurement conditions by a dynamic viscoelasticity apparatus of 1.00×10 7 dyn / cm 2 or more and 1.00×10 8 dyn / cm 2 or less, and the loss tangent (tanδ) at 10°C is 0.050 or more.

[0006] Patent Document 4 discloses a golf ball having a golf ball body and a coating film covering the golf ball body, wherein the peak temperature of the loss tangent tanδ obtained by measuring the dynamic viscoelasticity of the coating film is 50°C or lower, and the peak height is less than 0.8.

[0007] Patent Document 5 discloses a golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body, wherein the outermost layer coating film located on the outermost layer of the coating film contains a polyurethane formed by reacting (A) a polyisocyanate composition and (B) a polyol composition as a base resin, the (B) polyol composition contains a urethane polyol as a polyol component, and the outermost layer coating film has a peak temperature of the loss tangent (tanδ) measured under specific measurement conditions by a dynamic viscoelasticity device in the range of -40°C to 40°C.

[0008] Patent Document 6 discloses a golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body, wherein the base resin constituting the outermost layer of the coating film is a polyurethane formed by reacting (A) a polyol composition and (B) a polyisocyanate composition, and the loss elastic modulus (E") at -50°C obtained by measuring the dynamic viscoelasticity of the polyurethane under specific conditions is 1.00×10 8 Pa or more.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0010] Among approach shots, there is an approach shot hit from a place where the turf such as the green edge or fairway is cut under the condition that there is no water between the golf ball and the club face of the wedge (dry condition). This approach shot under dry conditions is easy to spin and easy to control the golf ball. On the other hand, there is an approach shot from the rough where the turf around the green is not cut. Since there is turf between the golf ball and the club face of the wedge in the approach shot from the rough, it is difficult to give the desired spin. Therefore, there is a problem that the controllability of the approach shot from the rough tends to decrease.

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel golf ball having excellent spin performance in an approach shot from the rough while maintaining the spin performance of the approach shot under dry conditions.

Means for Solving the Problems

[0012] The golf ball of the present invention is a golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body, The base resin constituting the outermost layer of the coating film is a polyurethane obtained by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition, and the loss elastic modulus (E") at -50 °C obtained by measuring the dynamic viscoelasticity of the polyurethane under the following conditions is 2.0×10 8It is Pa or higher, and the loss tangent (tanδ) has a peak in the range of -60°C or higher and -20°C or lower, and the peak height is 0.1 or higher and 0.5 or lower. The golf ball is characterized by this. <Measurement conditions> Measurement mode: Sinusoidal wave tension Measurement temperature range: -100°C to 100°C Temperature increase rate: 3°C / min Vibration frequency: 10 Hz Measured strain: 0.05%

[0013] When the hitting speed at the approach shot is 16 m / s and the unevenness of the face land portion of the wedge is several μm, the vibration received by the coating film of the golf ball at the approach shot is 10 7 Hz. The dynamic viscoelasticity of the coating film of this vibration at normal temperature of 10 7 Hz, when converted by time-temperature conversion measurement, corresponds to the dynamic viscoelasticity measured at a frequency of 10 Hz at -50°C. The inventors of the present invention have found that by controlling the loss elastic modulus, the peak temperature and the peak height of the loss tangent (tanδ) measured at a frequency of 10 Hz at -50°C, the spin performance of the approach shot is improved, and the present invention has been completed.

Effects of the invention

[0014] According to the present invention, a golf ball excellent in the spin performance of the approach shot can be obtained.

Brief description of the drawings

[0015]

Figure 1

Modes for carrying out the invention

[0016] The golf ball of the present invention is a golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body, The base resin constituting the outermost layer of the coating film is a polyurethane obtained by reacting (A) a polyol composition containing a polyol having a side chain with (B) a polyisocyanate composition. The loss elastic modulus (E") at -50 °C obtained by measuring the dynamic viscoelasticity of the polyurethane under the following conditions is 2.0×10 8 Pa or more, and the loss tangent (tanδ) has a peak in the range of -60 °C or more and -20 °C or less, and the peak height is 0.1 or more and 0.5 or less. A golf ball characterized by this. <Measurement conditions> Measurement mode: Sinusoidal wave tension Measurement temperature range: -100 °C to 100 °C Temperature increase rate: 3 °C / min Vibration frequency: 10 Hz Measurement strain: 0.05%

[0017] The polyurethane constituting the outermost layer of the coating film of the golf ball of the present invention has a loss elastic modulus (E") at -50 °C obtained by measuring the dynamic viscoelasticity under the above conditions of 2.0×10 8 Pa or more. From the viewpoint of enhancing the spin performance of the approach shot, the loss elastic modulus (E") is preferably 2.2×10 8 Pa or more, more preferably 2.3×10 8 Pa or more, preferably 1.0×10 9 Pa or less, more preferably 8.0×10 8 Pa or less, and even more preferably 6.0×10 8 Pa or less.

[0018] The polyurethane constituting the outermost layer of the coating film of the golf ball of the present invention has a loss tangent (tanδ) obtained by measuring the dynamic viscoelasticity under the above conditions and has a peak in the negative temperature region. It is preferable that the loss tangent (tanδ) further has a peak in the positive temperature region. In the following description, the peak in the negative temperature region is referred to as the first peak, and the peak in the positive temperature region is referred to as the second peak.

[0019] The loss tangent (tanδ) has a first peak in the range of -60°C or higher and -20°C or lower. The peak temperature of the first peak of the loss tangent (tanδ) is preferably -60°C or higher, more preferably -58°C or higher, still more preferably -55°C or higher, preferably -20°C or lower, more preferably -25°C or lower, and still more preferably -30°C or lower. This is because when the peak temperature of the first peak of the loss tangent (tanδ) is within the above range, the approach spin performance is improved.

[0020] The peak height of the first peak of the loss tangent (tanδ) is preferably 0.1 or higher, more preferably 0.12 or higher, still more preferably 0.15 or higher, preferably 0.5 or lower, more preferably 0.45 or lower, and still more preferably 0.4 or lower. This is because when the peak height of the first peak of the loss tangent (tanδ) is within the above range, the energy transfer efficiency is improved, resulting in an increase in shear force and good spin performance.

[0021] The polyurethane that constitutes the outermost layer of the coating film of the golf ball of the present invention has a storage elastic modulus (E') at 0°C obtained by measuring the dynamic viscoelasticity under the above conditions of 0.5×10 8 Pa or higher and 1.5×10 9 Pa or lower.

[0022] The contact time between the golf ball and the face of the wedge during an approach shot is about 500 μs. This corresponds to the coating film biting into the wedge's scoring line about 2000 times per second (=2000 Hz). The dynamic viscoelasticity of the coating film vibrating at 2000 Hz at room temperature, when converted by time-temperature conversion measurement, corresponds to the dynamic viscoelasticity measured at a frequency of 10 Hz at 0°C. Therefore, the present inventors focused on the storage elastic modulus (E') measured at a frequency of 10 Hz at 0°C. By using a polyurethane with the storage elastic modulus (E') within the above range, the biting of the coating film into the scoring line of the wedge is improved. As a result, the spin performance is enhanced.

[0023] From the viewpoint of enhancing the spin performance of an approach shot, the storage elastic modulus (E’) is preferably 1.0×10 8 Pa or more, more preferably 2.0×10 8 Pa or more, still more preferably 1.3×10 9 Pa or less, more preferably 9.0×10 8 Pa or less.

[0024] The 10% modulus of the coating film covering the golf ball body of the present invention is preferably 130 kgf / cm 2 (12.7 MPa) or less, more preferably 120 kgf / cm 2 (11.8 MPa) or less, still more preferably 110 kgf / cm 2 (10.8 MPa) or less. If the 10% modulus of the coating film is 130 kgf / cm 2 (12.7 MPa) or less, the coating film is soft, and the spin amount of the approach shot becomes high. The lower limit of the 10% modulus of the coating film is not particularly limited, but 2 kgf / cm 2 (0.2 MPa) is preferable, 4 kgf / cm 2 (0.4 MPa) is more preferable, 6 kgf / cm 2 (0.6 MPa) is still more preferable. This is because if the 10% modulus is too small, it becomes too soft, leaving a tacky feeling and deteriorating the feeling.

[0025] The base resin constituting the outermost layer of the coating film of the golf ball of the present invention is a polyurethane obtained by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition. The polyurethane is preferably a polymer having a plurality of urethane bonds in the main chain. First, the polyol composition and the polyisocyanate composition will be described.

[0026] The polyol composition contains a polyol having at least two or more hydroxy groups. Examples of the polyol include low molecular weight polyols having a molecular weight of less than 500 and high molecular weight polyols having an average molecular weight of 500 or more. Examples of the low molecular weight polyol include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol. Examples of the high molecular weight polyol include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), 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 urethane polyols, acrylic polyols, and the like. The polyol may be used alone or in combination of two or more.

[0027] The (A) polyol composition used in the present invention contains, as a polyol component, a polyol having a side chain. Examples of the polyol having a side chain include a high molecular weight polyol having a side chain and a low molecular weight polyol having a side chain.

[0028] The side chain of the polyol having a side chain is preferably a hydrocarbon group having 1 to 7 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and still more preferably a hydrocarbon group having 1 to 3 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group, and an alkyl group is more preferable. When the carbon number of the side chain is within the above range, the orientation of the molecular chain is inhibited by the steric hindrance of the side chain, so that the coating film can be softened and the spin performance becomes good.

[0029] The number average molecular weight of the high molecular weight polyol having a side chain is not particularly limited, but is preferably 1000 or more, more preferably 1200 or more, still more preferably 1500 or more, preferably 3000 or less, more preferably 2800 or less, and still more preferably 2500 or less.

[0030] Examples of the high molecular weight polyol having a side chain include a polyether polyol having a side chain and a polyester polyol having a side chain, and a polyether polyol having a side chain is preferred. The high molecular weight polyol having a side chain is preferably a high molecular weight diol having a side chain.

[0031] Examples of the polyether polyol having a side chain include polyoxypropylene glycol (PPG) and polyoxyethylene glycol (PEG)-polyoxypropylene glycol (PPG) block copolymers.

[0032] Examples of the polyester polyol having a side chain include polyester diols obtained by reacting a dicarboxylic acid with a diol, and at least one of the dicarboxylic acid and the diol preferably has a side chain.

[0033] As the diol having a side chain, an alkylene diol having a side chain is preferred. As the alkylene diol having a side chain, an alkylene diol having 3 to 18 carbon atoms is preferred, and an alkylene diol having 3 to 10 carbon atoms is more preferred.

[0034] Specific examples of the alkylene diol having a side chain include, for example, 1,2-propanediol (propylene glycol), 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol (2,2-dimethyl-1,3-propanediol), 1,4-pentanediol, 3-methyl-1,5-pentanediol, 2,5-hexanediol, 2-methyl-1,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,2,4-trimethyl-1,6-hexanediol, and the like.

[0035] As the dicarboxylic acid having a side chain, an alkylene dicarboxylic acid having a side chain is preferred. As the alkylene dicarboxylic acid having a side chain, an alkylene dicarboxylic acid having 3 to 18 carbon atoms is preferred, and an alkylene dicarboxylic acid having 3 to 10 carbon atoms is more preferred.

[0036] Specific examples of the alkylene dicarboxylic acid having a side chain include 2-methylmalonic acid, 2,2-dimethylmalonic acid, 2-methylsuccinic acid, 2,2,3,3-tetramethylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3,3-dimethylglutaric acid, 2,4-dimethylglutaric acid, 2,2,3-trimethylglutaric acid, 2,2,4-trimethylglutaric acid, 2,3,3-trimethylglutaric acid, 2,3,4-trimethylglutaric acid, and the like. In addition to these alkylene dicarboxylic acids, alkylene dicarboxylic acids obtained by oxidizing the alkylene diol having the side chain can be mentioned.

[0037] The polyol having a side chain used in the present invention does not include trimethylolpropane.

[0038] The (A) polyol composition used in the present invention preferably contains a urethane polyol. (A) The content of the urethane polyol in the polyols contained in the polyol composition is preferably 60% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more. (A) The polyol composition preferably contains only the urethane polyol as the polyol.

[0039] The urethane polyol is a compound having a plurality of urethane bonds in the molecule and having two or more hydroxy groups in one molecule. Examples of the urethane polyol include urethane prepolymers obtained by reacting a polyol and a polyisocyanate under conditions such that the hydroxy groups of the polyol are in excess with respect to the isocyanate groups of the polyisocyanate.

[0040] In the present invention, the polyol component that can constitute the urethane polyol preferably contains a high molecular weight polyol having a side chain, and more preferably contains polyoxypropylene glycol.

[0041] The number average molecular weight of the high molecular weight polyol that can constitute the urethane polyol is preferably 1000 or more, more preferably 1200 or more, and still more preferably 1500 or more, and preferably 3000 or less, more preferably 2800 or less, and still more preferably 2500 or less. If the number average molecular weight of the high molecular weight polyol is 1000 or more, the distance between crosslinking points in the coating film becomes long and the coating film becomes soft, so the spin performance is improved. If the number average molecular weight is 3000 or less, the distance between crosslinking points in the coating film does not become too long, and the stain resistance of the coating film is good. The number average molecular weight of the high molecular weight polyol component can be measured, for example, by gel permeation chromatography (GPC) using polystyrene as a standard substance, tetrahydrofuran as an eluent, and a column for organic solvent-based GPC (for example, "Shodex (registered trademark) KF series" manufactured by Showa Denko KK, etc.).

[0042] The polyol component of the urethane polyol can include a low molecular weight polyol component having a molecular weight of less than 500 and a high molecular weight polyol component having an average molecular weight of 500 or more, in addition to the polyol component having the side chain. Examples of the low molecular weight polyol component include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, and 1,6-hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol. Examples of the high molecular weight polyol component include linear polyether diols and linear polyester diols. The polyol components may be used alone or in combination of two or more.

[0043] The urethane polyol preferably contains a triol component and a high molecular weight diol component having a side chain as the polyol components. As the triol component, trimethylolpropane is preferable. As the high molecular weight diol component having a side chain, polyoxypropylene glycol (diol type) is preferable. The mixing ratio (triol component / high molecular weight diol component having a side chain) of the triol component and the high molecular weight diol component having a side chain is preferably 1.0 or more, more preferably 1.1 or more, still more preferably 1.2 or more, preferably 2.6 or less, more preferably 2.5 or less, and still more preferably 2.4 or less in terms of the molar ratio of OH groups.

[0044] The polyisocyanate component that can constitute the urethane polyol is not particularly limited as long as it has two or more isocyanate groups. For example, 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'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI); alicyclic polyisocyanates or aliphatic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), hydrogenated xylylene diisocyanate (H6XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), etc. These polyisocyanates may be used alone or in combination of two or more.

[0045] The content of the polyoxypropylene glycol having a number average molecular weight of 1000 to 3000 in the urethane polyol is preferably 55% by mass or more, more preferably 60% by mass or more, still more preferably 63% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less. The polyoxypropylene glycol having a number average molecular weight of 1000 to 3000 forms a soft segment in the coating film. Therefore, when the content of the polyoxypropylene glycol is 55% by mass or more, the spin performance of the obtained golf ball is further improved.

[0046] The urethane polyol preferably has a number average molecular weight of 5000 or more, more preferably 5300 or more, still more preferably 5500 or more, and preferably 20000 or less, more preferably 19800 or less, still more preferably 19600 or less. If the number average molecular weight of the urethane polyol is 5000 or more, the distance between crosslinking points in the coating film becomes longer, the coating film becomes softer, and the spin performance is improved. If the number average molecular weight is 20000 or less, the distance between crosslinking points in the coating film does not become too long, and the stain resistance of the coating film is good.

[0047] The hydroxyl value of the urethane polyol is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, still more preferably 20 mgKOH / g or more, and preferably 200 mgKOH / g or less, more preferably 190 mgKOH / g or less, still more preferably 180 mgKOH / g or less.

[0048] The hydroxyl value of the polyol contained in the polyol composition is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, still more preferably 20 mgKOH / g or more, and preferably 400 mgKOH / g or less, preferably 300 mgKOH / g or less, more preferably 200 mgKOH / g or less, still more preferably 170 mgKOH / g or less, and particularly preferably 160 mgKOH / g or less. This is because if the hydroxyl value of the polyol component is within the above range, the adhesion of the coating film to the golf ball body is improved. In the present invention, the hydroxyl value can be measured, for example, by the acetylation method in accordance with JIS K 1557-1.

[0049] Next, the polyisocyanate composition will be described. The polyisocyanate composition contains one or more polyisocyanates. Examples of the polyisocyanate include compounds having at least two isocyanate groups.

[0050] Examples of the polyisocyanate include aromatic diisocyanates 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'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI); alicyclic diisocyanates or aliphatic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), hydrogenated xylylene diisocyanate (H6XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and norbornene diisocyanate (NBDI); and triisocyanates such as allophanate, biuret, isocyanurate, and adduct forms of these diisocyanates.

[0051] The allophanate form is, for example, a triisocyanate obtained by further reacting a diisocyanate with a urethane bond formed by reacting a diisocyanate with a low molecular weight diol. The adduct form is a triisocyanate obtained by reacting a diisocyanate with a low molecular weight triol such as trimethylolpropane or glycerin. The biuret form is, for example, a triisocyanate having a biuret bond represented by the following formula (1). The isocyanurate form of the diisocyanate is, for example, a triisocyanate represented by the following formula (2).

[0052] [In formulas (1) and (2), R represents the residue obtained by removing the isocyanate group from the diisocyanate.]

[0053] ​The polyisocyanate composition preferably contains a triisocyanate. The content rate of the triisocyanate in the polyisocyanate contained in the polyisocyanate composition is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more. Most preferably, the polyisocyanate composition contains only a triisocyanate as the polyisocyanate.

[0054] The (B) polyisocyanate composition used in the present invention preferably contains an isocyanurate form of a diisocyanate as the polyisocyanate component, and more preferably contains an isocyanurate form of hexamethylene diisocyanate and / or an isocyanurate form of isophorone diisocyanate. This is because the loss modulus of the resulting polyurethane at -50°C becomes large.

[0055] The amount of isocyanate groups (NCO%) in the polyisocyanate contained in the polyisocyanate composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 2% by mass or more, preferably 45% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less. The amount of isocyanate groups (NCO%) in the polyisocyanate can be represented by 100×[the number of moles of isocyanate groups in the polyisocyanate × 42 (molecular weight of NCO)] / total mass (g) of the polyisocyanate.

[0056] Specific examples of the polyisocyanate include Vernoc D-800, Vernoc DN-950, Vernoc DN-955 manufactured by DIC Corporation; Desmodur N75MPA / X, Desmodur L75(C), Desmodur Z4470BA manufactured by Sumika Covestro Urethane Co., Ltd.; Sumidur N3300, Sumidur E21-1; Coronate HX, Coronate HK manufactured by Nippon Polyurethane Industry Co., Ltd.; Duranate 24A-100, Duranate 21S-75E, Duranate TPA-100, Duranate TKA-100 manufactured by Asahi Kasei Chemicals Corporation; VESTANAT T1890 manufactured by Degussa, etc.

[0057] The base resin constituting the outermost layer of the coating film of the golf ball of the present invention contains polyurethane obtained by reacting the polyol composition and the polyisocyanate composition. In the reaction between the polyol composition and the polyisocyanate composition, the molar ratio (NCO group / OH group) of the isocyanate group (NCO group) of the polyisocyanate composition to the hydroxy group (OH group) of the polyol composition is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 0.9 or more. When the molar ratio (NCO group / OH group) is 0.5 or more, the crosslinking density increases, and the stain resistance of the resulting coating film becomes better. Further, when the molar ratio (NCO group / OH group) becomes too large, the amount of isocyanate groups becomes excessive, and the resulting coating film becomes hard and brittle, and the appearance also deteriorates. Therefore, the molar ratio (NCO group / OH group) is preferably 3.5 or less, more preferably 3.0 or less, and even more preferably 2.5 or less. Incidentally, the reason why the appearance of the resulting coating film deteriorates when the amount of isocyanate groups in the paint becomes excessive is considered to be that when the amount of isocyanate groups becomes excessive, the reaction between the moisture in the air and the isocyanate groups increases, and a large amount of carbon dioxide gas is generated.

[0058] The coating film of the golf ball of the present invention is preferably formed from a paint containing a polyol composition and a polyisocyanate composition. Examples of the paint include so-called two-component curing paints composed of a first component containing a polyol composition and a second component containing a polyisocyanate composition. The paint may be either an aqueous paint having water as a main dispersion medium or a solvent-based paint having an organic solvent as a dispersion medium. In the case of a solvent-based paint, preferred solvents include toluene, isopropyl alcohol, xylene, methyl ethyl ketone, methyl ethyl isobutyl ketone, ethylene glycol monomethyl ether, ethylbenzene, propylene glycol monomethyl ether, isobutyl alcohol, ethyl acetate, butyl acetate, and the like.

[0059] In the case of the two-component curable coating, the total solid content of the first component and the second component is preferably 24% by mass or more, more preferably 26% by mass or more, still more preferably 28% by mass or more, and preferably 45% by mass or less, more preferably 44% by mass or less, still more preferably 43% by mass or less. If the solid content is 24% by mass or more, it becomes easier to apply the coating uniformly, the uniformity of the thickness of the coating film is further improved, and if it is 45% by mass or less, the leveling property of the coating is good, the unevenness on the surface of the coating film is reduced, and the appearance of the golf ball becomes better.

[0060] The coating may further contain additives that can generally be contained in coatings for golf balls, such as fillers, ultraviolet absorbers, antioxidants, light stabilizers, fluorescent brighteners, anti-blocking agents, leveling agents, slip agents, and viscosity modifiers, as required.

[0061] Next, the coating method of the curable coating of the present invention will be described. The coating method of the curable coating is not particularly limited, and a known method can be adopted. For example, spray coating, electrostatic coating, etc. can be mentioned.

[0062] In the case of spray coating using an air gun, the polyol component and the polyisocyanate component are each supplied by a pump and continuously mixed by a line mixer arranged immediately before the air gun, and the resulting mixture may be spray-coated, or the polyol and the polyisocyanate may be spray-coated separately using an air spray system equipped with a mixing ratio control mechanism. The coating may be spray-coated once or may be applied in multiple coats.

[0063] The curable coating applied to the golf ball body can form a coating film, for example, by drying at a temperature of 30°C to 70°C for 1 hour to 24 hours.

[0064] The golf ball of the present invention has a golf ball body and at least one layer of coating film provided on the surface of the golf ball body. The base resin constituting the outermost layer of the coating film is not particularly limited as long as it is a polyurethane formed by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition.

[0065] When the coating film is a single layer, the base resin of the single-layer coating film may be a polyurethane formed by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition.

[0066] When the coating film has a multi-layer structure of two or more layers, the base resin constituting the outermost layer of the coating film is not particularly limited as long as it is a polyurethane formed by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition. Examples of the base resin constituting the layers other than the outermost layer include, but are not particularly limited to, polyurethane, epoxy resin, acrylic resin, and the like.

[0067] In a more preferred embodiment of the present invention, the golf ball has a golf ball body and two layers of coating films provided on the surface of the golf ball body, and the base resin constituting the outer coating film is a polyurethane formed by reacting (A) a polyol composition containing a polyol having a side chain and (B) a polyisocyanate composition.

[0068] The film thickness of the coating film of the golf ball of the present invention 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. If the film thickness is less than 5 μm, the coating film tends to wear and disappear due to continuous use. In addition, since the amount of spin in the approach shot increases as the film thickness is increased, the film thickness of the coating film is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less. If the film thickness is greater than 50 μm, the effect of the dimples may decrease and the flight performance of the golf ball may deteriorate. The film thickness of the coating film can be measured, for example, by using a microscope (VHX-1000 manufactured by Keyence Corporation) to measure the cross-section of the golf ball. In the case where the paint has a multilayer structure, it is preferable that the thickness of the entire formed coating film is within the above range.

[0069] The golf ball of the present invention is not particularly limited as long as it is a golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body. The structure of the golf ball body is not particularly limited, and it may be a one-piece golf ball, a two-piece golf ball, a three-piece golf ball, a four-piece golf ball, a multi-piece golf ball of five pieces or more, or a wound golf ball. This is because the present invention can be preferably applied in any case.

[0070] FIG. 1 is a partially cut-away cross-sectional view showing a golf ball according to an embodiment of the present invention. The golf ball 1 has a spherical core 2, a cover 3 covering the spherical core 2, and a coating film 4 provided on the surface of the cover 3. A large number of dimples 31 are formed on the surface of the cover 3. Among the surface of the cover 3, the portion other than the dimples 31 is a land 32.

[0071] The golf ball body preferably has a core and a cover covering the core. The cover is preferably formed from a cover composition containing a resin component. The slab hardness of the cover composition is preferably set as appropriate according to the performance of the desired golf ball. For example, in the case of a distance-type golf ball that emphasizes flight distance, the slab hardness of the cover composition is preferably 50 or more, more preferably 55 or more, preferably 80 or less, and more preferably 70 or less in Shore D hardness. By setting the slab hardness of the cover composition to 50 or more, a golf ball with a high launch angle and low spin can be obtained in driver shots and iron shots, and the flight distance increases. Also, by setting the slab hardness of the cover composition to 80 or less, a golf ball with excellent durability can be obtained. Also, in the case of a spin-type golf ball that emphasizes controllability, the slab hardness of the cover composition is preferably less than 50, preferably 20 or more, and more preferably 25 or more in Shore D hardness. If the slab hardness of the cover composition is less than 50 in Shore D hardness, the spin amount of the approach shot increases. Also, by setting the slab hardness to 20 or more, the scratch resistance is improved.

[0072] The cover material constituting the cover is not particularly limited. For example, ionomer resin, polyester resin, urethane resin such as thermoplastic urethane resin or two-component curable urethane resin, various resins such as polyamide resin, thermoplastic polyamide elastomer commercially available under the trade name "Pebax (registered trademark) (for example, "Pebax 2533")" from Arkema Co., Ltd., thermoplastic polyester elastomer commercially available under the trade name "Hytrel (registered trademark) (for example, "Hytrel 3548", "Hytrel 4047")" from Toray DuPont Co., Ltd., thermoplastic polyurethane elastomer commercially available under the trade name "Estane (registered trademark) (for example, "Estane XNY97A")" from BASF Japan Ltd., thermoplastic styrene elastomer and thermoplastic polyester-based elastomer commercially available under the trade name "Tefabloc" from Mitsubishi Chemical Corporation, etc. can be mentioned. The cover material may be used alone or as a mixture of two or more.

[0073] In addition to the resin component described above, the cover may contain pigment components such as white pigments (e.g., titanium oxide), blue pigments, and red pigments, specific gravity adjusters such as calcium carbonate and barium sulfate, dispersants, anti-aging agents, ultraviolet absorbers, light stabilizers (e.g., bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate), fluorescent materials or fluorescent brighteners, etc., as long as the performance of the cover is not impaired.

[0074] The mode of forming the cover using the cover composition is not particularly limited, but examples include a mode of directly injection molding the cover composition onto the core, or a mode of forming a hollow shell-shaped shell from the cover composition and covering the core with a plurality of shells and compression molding (preferably, a method of forming a hollow shell-shaped half shell from the cover composition and covering the core with two half shells and compression molding). The golf ball body with the cover formed thereon is preferably taken out from the mold and, if necessary, subjected to surface treatments such as deburring, cleaning, and sandblasting. Also, if desired, marks can be formed.

[0075] The total number of dimples formed on the cover is preferably 200 or more and 500 or less. If the total number of dimples is less than 200, it is difficult to obtain the effect of the dimples. Also, if the total number of dimples exceeds 500, the size of each dimple becomes small, and it is difficult to obtain the effect of the dimples. The shape (shape in plan view) of the dimples to be formed is not particularly limited, and circular; polygons such as substantially triangular, substantially quadrangular, substantially pentagonal, and substantially hexagonal; other irregular shapes; may be used alone or in combination of two or more.

[0076] In the present invention, the ratio of the total area of all dimples to the surface area of a virtual sphere is referred to as the occupancy rate. The virtual sphere is a golf ball (sphere) when there are no dimples. In the golf ball of the present invention, the occupancy rate of the dimples is preferably 60% or more, more preferably 63% or more, still more preferably 66% or more, preferably 90% or less, more preferably 87% or less, and still more preferably 84% or less. If the occupancy rate becomes too high, the contribution of the coating film to the friction coefficient becomes small. On the other hand, if the occupancy rate is too small, the flight performance deteriorates.

[0077] Note that the area of a dimple is the area of the region surrounded by the contour line when viewing the center of the golf ball from infinity. In the case of a circular dimple, the area S is calculated by the following formula. S=(Di / 2) 2 ·π (Di: diameter of the dimple)

[0078] The diameter of the golf ball is preferably 40 mm to 45 mm. From the viewpoint of satisfying the standards of the United States Golf Association (USGA), the diameter is preferably 42.67 mm or more. From the viewpoint of air resistance, the diameter is preferably 44 mm or less, and more preferably 42.80 mm or less. The mass of the golf ball is preferably 40 g or more and 50 g or less. From the viewpoint of obtaining a large inertia, the mass is preferably 44 g or more, and more preferably 45.00 g or more. From the viewpoint of satisfying the USGA standards, the mass is preferably 45.93 g or less.

[0079] Next, the wound golf ball, the core used for two-piece to multi-piece golf balls, and the one-piece golf ball body will be described.

[0080] For the core and the one-piece golf ball body, a known rubber composition (hereinafter sometimes simply referred to as "rubber composition for core") can be used. For example, a rubber composition containing a base rubber, a co-crosslinking agent, and a crosslinking initiator can be heated and pressed to be molded.

[0081] As the base rubber, it is particularly preferable to use high-cis polybutadiene having a cis bond favorable for resilience of 40% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more. As the co-crosslinking agent, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof is preferable, and a metal salt of acrylic acid or a metal salt of methacrylic acid is more preferable. As the metal of the metal salt, zinc, magnesium, calcium, aluminum, and sodium are preferable, and zinc is more preferable. The amount of the co-crosslinking agent used is preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base rubber. As the crosslinking initiator, an organic peroxide is preferably used. Specifically, 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 can be mentioned, and among these, dicumyl peroxide is preferably used. The compounding amount of the crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 3 parts by mass or less, more preferably 2 parts by mass or less with respect to 100 parts by mass of the base rubber.

[0082] In addition, the rubber composition for the core may further contain an organic sulfur compound. As the organic sulfur compound, compounds belonging to diphenyldisulfides, thiophenols, or thionaphthols can be preferably used. The compounding amount of the organic sulfur compound is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less with respect to 100 parts by mass of the base rubber. The rubber composition for the core may further contain a carboxylic acid and / or a salt thereof. As the carboxylic acid and / or a salt thereof, a carboxylic acid having 1 to 30 carbon atoms and / or a salt thereof is preferable. The compounding amount of the carboxylic acid and / or a salt thereof is 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the base rubber.

[0083] In addition to the base rubber, co-crosslinking agent, crosslinking initiator, and organic sulfur compound, the rubber composition for the core may further be appropriately blended with a weight regulator such as zinc oxide or barium sulfate, an antioxidant, a color powder, and the like. The heat press molding conditions of the rubber composition for the core may be appropriately set according to the rubber composition. Usually, it is heated at 130°C to 200°C for 10 minutes to 60 minutes, or after heating at 130°C to 150°C for 20 minutes to 40 minutes, it is preferably heated in two stages at 160°C to 180°C for 5 minutes to 15 minutes.

[0084] When the golf ball of the present invention is a multi-piece golf ball such as a three-piece, four-piece golf ball, or five-piece golf ball or more, examples of the intermediate layer provided between the core and the outermost cover include thermoplastic resins such as polyurethane resin, ionomer resin, polyamide resin, and polyethylene; thermoplastic elastomers such as styrene elastomer, polyolefin elastomer, polyurethane elastomer, and polyester elastomer; cured products of rubber compositions, and the like. Here, examples of the ionomer resin include those in which at least a part of the carboxyl groups in the copolymer of ethylene and α,β-unsaturated carboxylic acid are neutralized with metal ions, or those in which at least a part of the carboxyl groups in the terpolymer of ethylene, α,β-unsaturated carboxylic acid, and α,β-unsaturated carboxylic acid ester are neutralized with metal ions. The intermediate layer may further be blended with a specific gravity regulator such as barium sulfate and tungsten, an antioxidant, a pigment, and the like. Note that the intermediate layer may be referred to as an inner cover layer or an outer core depending on the configuration of the golf ball.

Examples

[0085] Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and any changes and embodiments within the scope not departing from the spirit of the present invention are included in the scope of the present invention.

[0086] [Evaluation Method] (1) Measurement of Dynamic Viscoelasticity The storage elastic modulus E’, loss elastic modulus E” and loss tangent tanδ of the coating film were measured under the following conditions. Apparatus: Dynamic viscoelastic measuring apparatus Rheogel-E4000 manufactured by UBM Measurement sample: A paint containing a main agent and a curing agent was dried and cured at 40°C for 4 hours to prepare a coating film with a thickness of 0.11 - 0.14 mm. From this coating film, a specimen was cut out so that the width was 4 mm and the distance between clamps was 20 mm. Measurement mode: Sinusoidal wave tension Measurement temperature: -100°C to 100°C Temperature rising rate: 3°C / min Measurement data acquisition interval: 3°C Vibration frequency: 10 Hz Measurement strain: 0.05%

[0087] (2) 10% modulus of the coating film The tensile properties of the coating film were measured in accordance with JIS K7161 (2014). Specifically, a paint containing a polyisocyanate composition and a polyol composition was dried and cured at 40°C for 4 hours to prepare a coating film (thickness 0.05 mm). This coating film was punched out into a specimen type 2 (width of parallel part 10 mm, distance between gauge marks 50 mm) defined in JIS K7127 (1999). For this specimen, a tensile test was conducted using a precision universal testing machine (manufactured by Shimadzu Corporation, Autograph (registered trademark)). The test conditions were a distance between grips of 100 mm, a tensile speed of 50 mm / min, and a test temperature of 23°C. Then, the tensile stress (10% modulus) at 10% strain was recorded.

[0088] (3) Dry spin amount Sd (rpm) of the approach shot A sand wedge (RTX-3 (58°) manufactured by Cleveland Golf) was attached to a swing machine manufactured by Golf Laboratories, and a golf ball was hit at a head speed of 16 m / sec. The spin amount (rpm) was measured by continuously photographing the hit golf ball. The measurement was performed 8 times for each golf ball, and the average value was taken as the spin amount.

[0089] (4) Rough spin amount Sr (rpm) of the approach shot from the rough A sand wedge (RTX-3 (58°) manufactured by Cleveland Golf) was attached to a swing machine manufactured by Golf Laboratories, Inc. A golf ball with two blades of rough grass attached to its surface was used, and the golf ball was struck at a head speed of 16 m / s with the rough grass intervening between the face of the sand wedge and the golf ball, and the spin amount (rpm) was measured. The spin amount was measured by taking consecutive photographs of the struck golf ball. The rough grass was attached to the golf ball with cellophane tape so that the rough grass and the grooves of the face were perpendicular when the face of the sand wedge and the golf ball came into contact. For each golf ball, the average value of the data obtained by measuring eight times each was calculated respectively.

[0090] [Manufacture of golf ball] 1. Manufacture of the center The center rubber composition with the formulation shown in Table 1 was kneaded and heated and pressed at 170 °C for 20 minutes in an upper and lower mold having a hemispherical cavity to obtain a spherical center with a diameter of 39.7 mm. The compounding amount of barium sulfate was adjusted so that the mass of the golf ball would be 45.3 g.

[0091]

Table 1

[0092] 2. Preparation of the intermediate layer composition and the cover composition The materials with the formulations shown in Table 2 and Table 3 were mixed by a twin-screw kneading extruder to prepare a pelletized intermediate layer composition and a cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the formulation was heated to 200 - 260 °C at the die position of the extruder.

[0093]

Table 2

[0094]

Table 3

[0095] 3. Preparation of Spherical Core The intermediate layer composition obtained above was directly injection-molded onto the spherical center to form an intermediate layer with a thickness of 1.0 mm covering the center, thereby preparing a spherical core. The upper and lower molds for molding have a hemispherical cavity and a retractable hold pin for supporting the spherical center. During the molding of the intermediate layer, the above hold pin was protruded, the center was inserted and held, and the intermediate layer composition heated to 260 °C was injected into the mold clamped at a pressure of 80 tons in 0.3 seconds, cooled for 30 seconds, and the mold was opened to take out the spherical core.

[0096] 4. Molding of Half Shell The compression molding of the half-shells was carried out by charging one pellet-shaped cover composition into each recess of the lower mold of the half-shell molding die one by one and applying pressure to form the half-shells. The compression molding was performed under the conditions of a molding temperature of 170 °C, a molding time of 5 minutes, and a molding pressure of 2.94 MPa.

[0097] 5. Molding of the Cover The spherical core obtained above was concentrically coated with two half-shells, and a cover with a thickness of 0.5 mm was formed by compression molding. The compression molding was performed under the conditions of a molding temperature of 145 °C, a molding time of 2 minutes, and a molding pressure of 9.8 MPa.

[0098] 6. Preparation of the Coating Preparation of the First Agent (Polyol Composition) As the polyol component, polyoxytetramethylene glycol (PTMG) or polyoxypropylene glycol (PPG) and trimethylolpropane (TMP) were dissolved to a concentration of 50% by mass using a solvent (toluene / methyl ethyl ketone = 1 / 2, mass ratio). Here, dibutyltin laurate was added as a catalyst to a concentration of 0.1% by mass based on the solid content of the polyol component. While maintaining this polyol solution at 80 °C, isophorone diisocyanate (IPDI) as the polyisocyanate component was added dropwise and mixed. After the dropping, stirring was continued until the isocyanate disappeared, and then it was cooled to room temperature. A solvent (toluene / methyl ethyl ketone = 1 / 2, mass ratio) was added to prepare a urethane polyol (solid content: 30% by mass). The composition and the like of each urethane polyol are shown in Table 4.

[0099]

Table 4

[0100] The following were used as polyols. PPG1: Polyoxypropylene glycol (diol type, number average molecular weight 700) manufactured by FUJIFILM Wako Pure Chemical Corporation PPG2: Polyoxypropylene glycol (diol type, number average molecular weight 1000) manufactured by FUJIFILM Wako Pure Chemical Corporation PPG3: Polyoxypropylene glycol P2000 manufactured by Sigma-Aldrich (number average molecular weight 1513) PPG4: Polyoxypropylene glycol (diol type, number average molecular weight 2000) manufactured by FUJIFILM Wako Pure Chemical Corporation PTMG: Polyoxytetramethylene glycol (diol type, number average molecular weight 1000) manufactured by Mitsubishi Chemical Corporation

[0101] Preparation of the second agent (polyisocyanate composition) Polyisocyanate composition No.1: Isocyanurate of hexamethylene diisocyanate (manufactured by Sumika Covestro Urethane Co., Ltd., Sumidur N3300) Polyisocyanate composition No.2: A mixture of isocyanurate of hexamethylene diisocyanate (manufactured by Sumika Covestro Urethane Co., Ltd., Sumidur N3300) and isocyanurate of isophorone diisocyanate (manufactured by Sumika Covestro Urethane Co., Ltd., Desmodur Z4470) with a molar ratio of 1:1 To Polyisocyanate compositions No.1 - 2, a mixed solvent of methyl ethyl ketone, n-butyl acetate, and toluene was added as a solvent and adjusted so that the concentration of the polyisocyanate component became 60% by mass.

[0102] Preparation of the paint The second agent was blended with the first agent (urethane polyol) prepared above so that the NCO / OH ratio shown in Table 5 was obtained, and the paint was prepared.

[0103] 7. Formation of the paint film The surface of the golf ball body obtained above was sandblasted and marked, and then paint was applied with a spray gun. The paint was dried in an oven at 40°C for 24 hours to obtain a golf ball with a diameter of 42.7 mm and a mass of 45.3 g. The thickness of the paint film was 20 μm. For painting, the golf ball body was placed on a rotating body equipped with three prongs, the rotating body was rotated at 300 rpm, and the air gun was separated from the golf ball body by a spraying distance (7 cm) and moved vertically. The interval for each coat of overpainting was set to 1.0 second. The spraying conditions of the air gun were as follows: overpainting; 2 times, spraying air pressure; 0.15 MPa, pressure-feeding tank air pressure; 0.10 MPa, application time per time; 1 second, ambient temperature; 20°C to 27°C, ambient humidity; 65% or less. The evaluation results of the obtained golf balls are shown in Tables 5 and 6.

[0104]

Table 5

[0105] Golf balls No. 2 to No. 4 are golf balls having a golf ball body and at least one layer of paint film provided on the surface of the golf ball body. The base resin constituting the outermost layer of the paint film is a polyurethane obtained by reacting (A) a polyol composition containing a polyol having a side chain with (B) a polyisocyanate composition. The loss elastic modulus (E") at -50°C obtained by measuring the dynamic viscoelasticity of the polyurethane is 2.0×10 8 Pa or more, and the loss tangent (tanδ) has a peak in the range of -60°C or more and -20°C or less, and the peak height is 0.1 or more and 0.5 or less. It can be seen that golf balls No. 2 to 4 have a higher spin amount and spin retention rate in the approach shot from the rough than golf balls No. 1 and 5.

Industrial Applicability

[0106] The present invention can be suitably applied to painted golf balls.

Explanation of Reference Numerals

[0107] 1: Golf ball, 2: Spherical core, 3: Cover, 4: Coating film, 31: Dimple, 32: Land

Claims

1. A golf ball having a golf ball body and at least one layer of coating film provided on the surface of the golf ball body, wherein the base resin constituting the outermost layer of the coating film is a polyurethane obtained by reacting (A) a polyol composition containing a urethane polyol having a polyoxypropylene glycol with a number average molecular weight of 1000 to 3000 as a polyol having a side chain and (B) a polyisocyanate composition, the urethane polyol further contains trimethylolpropane and isophorone diisocyanate as constituent components, and the mixing ratio of trimethylolpropane to polyoxypropylene glycol (trimethylolpropane / polyoxypropylene glycol) having a number average molecular weight of 1000 to 3000 is 1.0 or more and 2.6 or less in terms of the molar ratio of OH groups, The loss modulus (E") at -50°C obtained by measuring the dynamic viscoelasticity of the polyurethane under the following conditions is 2.0×10 ８ Pa or more and 6.0×10 8 Pa or less, and the loss tangent (tanδ) has a peak in the range of -60°C or more and -20°C or less, and the peak height is 0.1 or more and 0.5 or less. A golf ball characterized by that. <Measurement conditions> Measurement mode: Sinusoidal tension Measurement temperature range: -100°C to 100°C Heating rate: 3°C / min Vibration frequency: 10 Hz Measurement strain: 0.05%

2. The storage modulus (E') at 0°C obtained by measuring the dynamic viscoelasticity of the polyurethane under the following conditions is 0.5 × 10 ８ Pa to 1.5 × 10 ９ Pa. The golf ball according to claim 1. <Measurement conditions> Measurement mode: Sinusoidal tension Measurement temperature range: -100°C to 100°C Heating rate: 3°C / min Vibration frequency: 10 Hz Measurement strain: 0.05%

3. The golf ball according to claim 1 or 2, wherein the content of the polyoxypropylene glycol having a number average molecular weight of 1000 to 3000 in the urethane polyol is 55% by mass or more and 90% by mass or less.

4. The golf ball according to any one of claims 1 to 3, wherein the number average molecular weight of the urethane polyol is 5000 or more and 20000 or less.

5. (B) The golf ball according to any one of claims 1 to 4, wherein the polyisocyanate composition contains an isocyanurate of diisocyanate as a polyisocyanate component.

6. The golf ball according to claim 5, wherein the diisocyanate is hexamethylene diisocyanate and / or isophorone diisocyanate.

7. The golf ball according to any one of claims 1 to 6, wherein the molar ratio (NCO group / OH group) of the isocyanate group (NCO group) of (B) the polyisocyanate composition to the hydroxy group (OH group) of (A) the polyol composition is 0.5 or more and 3.5 or less.

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