Golf ball cover material and golf ball using the same

Abstract

To provide a novel golf ball cover material from which a golf ball showing a high spin rate on short iron shots and a low spin rate on driver shots is obtained.SOLUTION: A golf ball cover material has a loss elastic modulus (E"-40) in a range from 6.50×107 Pa to 22.0×107 Pa at a measuring temperature of -40°C, and a loss elastic modulus (E"-20) in a range from 3.50×107 Pa to 7.10×107 Pa at a measuring temperature of -20°C, when measured using a dynamic viscoelasticity measuring apparatus under the following measuring conditions: <Measuring conditions> Measuring mode: tensile mode, Measuring temperature: -100°C to 100°C, Temperature rising rate: 4°C / minute, Oscillation frequency: 10 Hz, Measuring strain: 0.05%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a novel golf ball cover material and a golf ball using the same. [Background technology]

[0002] Ionomer resins and polyurethanes are used as resin components constituting the cover of a golf ball. Ionomer resins are widely used due to their excellent resilience, durability, and processability. However, it has been pointed out that covers using ionomer resins have problems such as poor shot feeling due to their high rigidity and hardness, insufficient spin performance, and poor controllability. On the other hand, it is known that when polyurethane is used as the resin component constituting the cover, the shot feeling and spin performance are improved compared to ionomer resins.

[0003] With regard to the spin performance of a golf ball, a high spin rate is preferable for approach shots, whereas a low spin rate is preferable for driver shots. Therefore, golf ball materials that exhibit the appropriate spin performance for each type of shot are being investigated.

[0004] For example, in Patent Document 1, a shear loss modulus G" measured in shear mode using a dynamic viscoelasticity device under measurement conditions of an excitation frequency of 10 Hz and a temperature of 0°C is 1.95 × 10 7 A golf ball cover material is described, which is characterized in that the elastic modulus E" measured in a tensile mode is equal to or less than Pa, and the ratio of the tensile loss modulus E" to the shear loss modulus G" (E" / G") is equal to or greater than 1.78 (see Patent Document 1 (Claim 1)). Furthermore, Patent Document 2 describes a golf ball cover material characterized in that the shear loss moduli G1" (Pa), G2" (Pa), and G3" (Pa) measured under specific measurement conditions using a dynamic viscoelasticity device satisfy logG1" ≦ 7.09, logG2" ≧ 7.17, and logG3" ≦ 7.14 (see Patent Document 2 (Claim 1)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-125438 A [Patent Document 2] JP 2012-45223 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a novel golf ball cover material which provides a golf ball with a high spin rate for shots with a short iron and a low spin rate for shots with a driver. [Means for solving the problem]

[0007] The golf ball cover material of the present invention, which has been able to solve the above problems, has a loss modulus (E") at a measurement temperature of -40°C, measured using a dynamic viscoelasticity device under the following measurement conditions. -40 ) is 6.50 × 10 7 Pa~22.0×10 7 Pa, and the loss modulus (E” -20 ) is 3.50 × 10 7 Pa ~ 7.10 x 10 7 It is characterized in that it is Pa. <Measurement conditions> Measurement mode: Tensile Measurement temperature: -100℃~100℃ Heating rate: 4℃ / min Excitation frequency: 10Hz Measurement distortion: 0.05% Effect of the Invention

[0008] By using the golf ball cover material of the present invention, the spin rate can be increased for shots with a short iron, and the spin rate can be reduced for shots with a driver. [Brief description of the drawings]

[0009] [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 PREFERRED EMBODIMENTS

[0010] [Golf ball cover materials] The golf ball cover material of the present invention has a loss modulus (E") at a measurement temperature of -40°C, measured using a dynamic viscoelasticity device under the following measurement conditions. -40 ) is 6.50 × 10 7 Pa~22.0×10 7 Pa, and the loss modulus (E” -20 ) is 3.50 × 10 7 Pa ~ 7.10 x 10 7 It is characterized in that it is Pa. <Measurement conditions> Measurement mode: Tensile Measurement temperature: -100℃~100℃ Heating rate: 4℃ / min Excitation frequency: 10Hz Measurement distortion: 0.05%

[0011] The loss modulus (E″) at the measurement temperature of -40°C -40 The loss modulus (E” -40 ) can reduce the amount of spin on driver shots. The loss modulus (E″ -40 ) is 6.50 x 10 7 Pa or more, and more preferably 6.60×10 7 Pa or more, more preferably 6.70×10 7 Pa or more, 22.0×10 7 Pa or less, and more preferably 21.0×10 7 Pa or less, more preferably 20.0×10 7 Pa or less. The loss modulus (E″ -40 ) is 6.50 x 10 7 If the ball is more than 22.0×10 Pa, the amount of spin on the driver shot is reduced. 7 If it is less than Pa, handling during the production process becomes easy.

[0012] The loss modulus (E″) at the measurement temperature of -20°C -20 The loss modulus (E” -20 ) can increase the amount of spin on short iron shots. The loss modulus (E″ -20 ) is 3.50 × 10 7 Pa or more, and more preferably 3.60×10 7 Pa or more, more preferably 3.70×10 7 Pa or more, 7.10 x 10 7 Pa or less, and more preferably 7.00×10 7 Pa or less, and more preferably 6.90×10 7 Pa or less. The loss modulus (E″ -20 ) is 3.50 × 10 7 If the spin rate is above 7.10 x 10 Pa, the spin rate of the iron shot increases. 7 If it is equal to or less than Pa, the decrease in the initial velocity of the ball on a driver shot is suppressed.

[0013] The slab hardness of the golf ball cover material is preferably 65 or more, more preferably 68 or more, and even more preferably 70 or more, and is preferably 95 or less, more preferably 93 or less, and even more preferably 92 or less, in Shore A hardness. If the slab hardness is 65 or more, handling during the production process becomes easy, and if it is 95 or less, the amount of spin on approach shots can be kept high.

[0014] The golf ball cover material preferably contains, as a resin component, polyurethane obtained by reacting a polyol with a polyisocyanate.

[0015] The polyol is a compound having two or more hydroxy groups in the molecule. The polyol may be used alone or in combination of two or more kinds.

[0016] The polyol constituting the polyurethane is preferably a polyol having a number average molecular weight of 200 or more and 6000 or less. The polyol having a number average molecular weight of 200 or more and 6000 or less forms a soft segment and imparts flexibility to the polyurethane. The number average molecular weight of the polyol constituting the polyurethane is preferably at least 200, more preferably at least 300, and even more preferably at least 1000, and is preferably at most 6000, more preferably at most 4000, and even more preferably at most 3000. If the number average molecular weight is at least 200 and at most 6000, the shot feeling of the golf ball is improved.

[0017] The polyol constituting the polyurethane is preferably at least one polymer polyol selected from the group consisting of polyether polyol, condensation polyester polyol, lactone polyester polyol, polycarbonate polyol and acrylic polyol. The polymer polyol is a polymer obtained by polymerizing a low molecular weight compound and has a plurality of hydroxyl groups. The polymer polyol may be derived from a petroleum resource or a biomass resource.

[0018] Examples of the polyether polyol include polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polytrimethylene ether glycol (PO3G), and polytetramethylene ether glycol (PTMG). Examples of the condensation polyester polyol include polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA). The lactone-based polyester polyols include poly-ε-caprolactone (PCL). The polycarbonate polyol may, for example, be polyhexamethylene carbonate.

[0019] The polymer polyol is preferably a polymer diol having two hydroxy groups. By using a polymer diol, a linear thermoplastic polyurethane is obtained, which makes it easy to mold the polyurethane into the components that constitute the golf ball.

[0020] The polyol constituting the polyurethane is preferably a polyether polyol. In particular, the content of the polyether polyol in 100% by mass of the polyol constituting the polyurethane is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. If the content of the polyether polyol is 50% by mass or more, the mechanical strength can be maintained for a long period of time. When the golf ball cover material contains two or more types of polyurethane, the content of the polyether polyol in 100% by mass of the polyol constituting each polyurethane is preferably within the above range.

[0021] The polyol constituting the polyurethane preferably contains a first polymer polyol and a second polymer polyol having a number average molecular weight greater than that of the first polymer polyol. By containing the first polymer polyol and the second polymer polyol, the spin rate upon iron shots can be further increased. Examples of the polyol constituting the polyurethane that contains a first polymer polyol and a second polymer polyol include a mode in which the polyol constituting one type of polyurethane contains the first polymer polyol and the second polymer polyol; and a mode in which a first polyurethane containing the first polymer polyol as a constituent component and a second polyurethane containing the second polymer polyol as a constituent component are used in combination.

[0022] When the polyol constituting the polyurethane contains a first polymer polyol and a second polymer polyol, the difference (Mm2-Mm1) between the number average molecular weight (Mm1) of the first polymer polyol and the number average molecular weight (Mm2) of the second polymer polyol is preferably 50 or more, more preferably 100 or more, and even more preferably 200 or more, and is preferably 1500 or less, more preferably 1200 or less, and even more preferably 1000 or less.

[0023] The number average molecular weight (Mm1) of the first polymer polyol is preferably 200 or more, more preferably 500 or more, and even more preferably 800 or more; it is preferably 3,000 or less, more preferably 2,000 or less, and even more preferably 1,500 or less. The number average molecular weight (Mm2) of the second polymer polyol is preferably 1000 or more, more preferably 1200 or more, and even more preferably 1400 or more, and is preferably 6000 or less, more preferably 4500 or less, and even more preferably 3000 or less.

[0024] The polyisocyanate constituting the polyurethane is not particularly limited as long as it has two or more isocyanate groups. The polyisocyanate may be used alone or in combination of two or more kinds. The polyisocyanate may be, for example, an aromatic polyisocyanate, an alicyclic polyisocyanate, or an aliphatic polyisocyanate. Examples of aromatic polyisocyanates include 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). Alicyclic or aliphatic polyisocyanates include 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI), hydrogenated xylylene diisocyanate (H 6 Examples of suitable isocyanates include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and norbornene diisocyanate (NBDI).

[0025] From the viewpoint of improving the abrasion resistance, it is preferable to use an aromatic polyisocyanate as the polyisocyanate constituting the polyurethane. By using an aromatic polyisocyanate, the mechanical properties of the resulting polyurethane are improved, and a cover having excellent abrasion resistance can be obtained. In addition, from the viewpoint of improving weather resistance, non-yellowing polyisocyanates (TMXDI, XDI, HDI, H) are used as the polyisocyanates that make up the polyurethane. 6 XDI, 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 improves the mechanical properties of the resulting polyurethane, resulting in a cover with excellent abrasion resistance.

[0026] The polyurethane may contain a chain extender as a constituent component, as long as the effect of the present invention is not impaired. As the chain extender component, low molecular weight polyol, low molecular weight polyamine, etc. can be used. Examples of low molecular weight polyols include diols such as ethylene glycol, diethylene glycol, triethylene glycol, propanediol (e.g., 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol), dipropylene glycol, butanediol (e.g., 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol), neopentyl glycol, pentanediol, hexanediol, heptanediol, octanediol, and 1,4-cyclohexanedimethylol; triols such as glycerin, trimethylolpropane, and hexanetriol; and tetraols or hexaols such as pentaerythritol and sorbitol.

[0027] Furthermore, the low molecular weight polyamine that can be used as the 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.

[0028] 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, where "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 having two or more amino groups 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.

[0029] Examples of the monocyclic aromatic polyamine include phenylenediamine, toluenediamine, diethyltoluenediamine, dimethylthiotoluenediamine, and other types in which an amino group is directly bonded to an aromatic ring; and xylylenediamine, and other 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.

[0030] The molecular weight of the chain extender is preferably 400 or less, more preferably 350 or less, even more preferably less than 200, and is preferably 30 or more, more preferably 40 or more, and even more preferably 45 or more. If the molecular weight is too large, it becomes difficult to distinguish it from the polyol that constitutes the soft segment of the polyurethane. The "low molecular weight polyols" and "low molecular weight polyamines" used as chain extenders are low molecular weight compounds that do not have a molecular weight distribution, and are therefore distinguished from polymer polyols having a number average molecular weight of 200 or more and 3,000 or less obtained by polymerizing low molecular weight compounds.

[0031] The configuration of the polyurethane is not particularly limited, but examples thereof include a configuration constituted by a polyisocyanate and a polyol having a number average molecular weight of 200 or more and 6000 or less; a configuration constituted by a polyisocyanate, a polyol having a number average molecular weight of 200 or more and 6000 or less, and a chain extender; and a configuration constituted by a polyisocyanate, a first polymer polyol having a number average molecular weight of 200 or more and 3000 or less, a second polymer polyol having a number average molecular weight of 1000 or more and 6000 or less and having a higher number average molecular weight than the first polymer polyol, and a chain extender component.

[0032] The polyurethane may be either a thermoplastic polyurethane or a thermosetting polyurethane. Thermoplastic polyurethane is a polyurethane that exhibits plasticity when heated, and generally means a polyurethane having a linear structure with a certain degree of high molecular weight. Thermosetting polyurethane is a polyurethane obtained by a curing reaction between a relatively low molecular weight prepolymer and a curing agent when used. Thermosetting polyurethane forms a three-dimensional crosslinked structure by controlling the number of functional groups of the prepolymer and curing agent used. The polyurethane is preferably a thermoplastic polyurethane. If it is a thermoplastic polyurethane, the cover can be easily molded.

[0033] The polyurethane can be synthesized by a one-shot method or a prepolymer method. The one-shot method is a method in which polyisocyanate, polyol, etc. are reacted at once. The prepolymer method is a method in which polyisocyanate, polyol, etc. are reacted in multiple stages, for example, by synthesizing a relatively low molecular weight urethane prepolymer and then further increasing the molecular weight.

[0034] As an example of an embodiment for producing polyurethane by the prepolymer method, an embodiment in which an isocyanate-terminated urethane prepolymer is synthesized and then polymerized with a chain extender will be described in detail below.

[0035] First, polyisocyanate and polymer polyol are reacted to synthesize an isocyanate group-terminated urethane prepolymer. At this time, the charge ratio of polyisocyanate to polymer polyol is preferably 1 or more, more preferably 1.2 or more, even more preferably 1.5 or more, and is preferably 10 or less, more preferably 9 or less, even more preferably 8 or less, in terms of the molar ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate to the hydroxyl group (OH) of the polymer polyol.

[0036] The temperature during the prepolymerization reaction is preferably 10°C or higher, more preferably 30°C or higher, and even more preferably 50°C or higher, and is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower. The reaction time is preferably 10 minutes or more, more preferably 1 hour or more, and even more preferably 3 hours or more, and is preferably 32 hours or less, more preferably 16 hours or less, and even more preferably 8 hours or less.

[0037] Next, the obtained isocyanate-terminated urethane prepolymer is subjected to a chain extension reaction with a chain extender to obtain a high molecular weight polyurethane. In this case, the charge ratio of the isocyanate-terminated urethane prepolymer and the chain extender is preferably set to a molar ratio (NCO / OH) of the isocyanate group (NCO) of the isocyanate-terminated urethane prepolymer to the hydroxyl group (OH) of the chain extender of 0.9 or more, more preferably 0.92 or more, even more preferably 0.95 or more, and is preferably 1.1 or less, more preferably 1.08 or less, even more preferably 1.05 or less.

[0038] The temperature at which the chain extension reaction is carried out is preferably 10°C or higher, more preferably 30°C or higher, and even more preferably 50°C or higher, and is preferably 220°C or lower, more preferably 170°C or lower, and even more preferably 120°C or lower. The reaction time is preferably 10 minutes or more, more preferably 30 minutes or more, and even more preferably 1 hour or more, and is preferably 20 days or less, more preferably 10 days or less, and even more preferably 5 days or less.

[0039] Both the prepolymerization reaction and the chain extension reaction are preferably carried out in a dry nitrogen atmosphere.

[0040] A known catalyst can be used for the synthesis of polyurethane. Examples of the catalyst include monoamines such as triethylamine and N,N-dimethylcyclohexylamine; polyamines such as N,N,N',N'-tetramethylethylenediamine and N,N,N',N",N"-pentamethyldiethylenetriamine; cyclic diamines such as 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) and triethylenediamine; and tin-based catalysts such as dibutyltin dilaurate and dibutyltin diacetate. These catalysts may be used alone or in combination of two or more. Among these, tin-based catalysts such as dibutyltin dilaurate and dibutyltin diacetate are preferred, and dibutyltin dilaurate is particularly preferred.

[0041] The content of polyurethane in 100% by mass of the resin component of the golf ball cover material is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The resin component may contain only polyurethane.

[0042] The golf ball cover material may contain one type of polyurethane or two or more types of polyurethane as a resin component. The golf ball cover material preferably contains a first polyurethane containing a first polymer polyol as a constituent component and a second polyurethane containing a second polymer polyol as a constituent component.

[0043] When the golf ball cover material contains a first polyurethane and a second polyurethane as resin components, the mass ratio thereof (first polyurethane / second polyurethane) is preferably 1 / 99 or more, more preferably 30 / 70 or more, and even more preferably 50 / 50 or more, and is preferably 99 / 1 or less, more preferably 98 / 2 or less, and even more preferably 95 / 5 or less.

[0044] The golf ball cover material preferably contains only polyurethane as the resin component, but may contain other resin components as long as the effect of the present invention is not impaired.

[0045] Examples of the other resin components include ionomer resins and thermoplastic elastomers. Examples of the ionomer resin include a copolymer of ethylene and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms in which at least a part of the carboxyl groups is neutralized with a metal ion, a ternary copolymer of ethylene, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid ester in which at least a part of the carboxyl groups is neutralized with a metal ion, or a mixture thereof. Specific examples of the ionomer resin include "Himilan (registered trademark)" manufactured by Mitsui Dow Polychemical, "Surlyn (registered trademark)" manufactured by DuPont, and "Iotec (registered trademark)" manufactured by ExxonMobil Chemical. Specific examples of the thermoplastic elastomer include thermoplastic polyurethane elastomers such as "Elastollan (registered trademark)" (e.g., "Elastollan XNY88A") manufactured by BASF Japan; thermoplastic polyamide elastomers such as "Pebax (registered trademark)" (e.g., "Pebax 2533") manufactured by Arkema; ​​thermoplastic polyester elastomers such as "Hytrel (registered trademark)" (e.g., "Hytrel 3548", "Hytrel 4047") manufactured by Toray DuPont; and thermoplastic polystyrene elastomers such as "Labalon (registered trademark)" manufactured by Mitsubishi Chemical.

[0046] The golf ball cover material may further contain pigment components such as titanium oxide and blue pigments, weight adjusters such as calcium carbonate and barium sulfate, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, or fluorescent brighteners, to the extent that the cover performance is not impaired.

[0047] The amount of the white pigment (titanium oxide) is preferably at least 0.5 parts by weight, more preferably at least 1 part by weight, and even more preferably at least 1.5 parts by weight, and is preferably no more than 10 parts by weight, more preferably no more than 8 parts by weight, and even more preferably no more than 6 parts by weight, per 100 parts by weight of the resin component. A white pigment amount of 0.5 parts by weight or more can impart hiding properties to the golf ball material, while a white pigment amount of 10 parts by weight or less can prevent a decrease in the durability of the golf ball material.

[0048] [Golf balls] The golf ball of the present invention comprises a spherical core and a cover enclosing the spherical core, the cover being formed from the golf ball cover material.

[0049] (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.

[0050] A known rubber composition (hereinafter, sometimes simply referred to as a "rubber composition for core") 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.

[0051] As the base rubber, it is preferable to use high-cis polybutadiene having cis bonds, which are particularly advantageous in terms of resilience, of 40% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0052] 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 acrylic acid or a metal salt thereof, methacrylic acid or a metal salt thereof are 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. When using an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent, it is preferable to blend a metal compound (for example, magnesium oxide).

[0053] 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, still more preferably 0.4 parts by mass or more with respect to 100 parts by mass of the base rubber, and preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less.

[0054] Further, the rubber composition for the core may further contain an organic sulfur compound. As the organic sulfur compound, diphenyldisulfides, thiophenols, and 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, still more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the base rubber, and preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 2.0 parts by mass or less.

[0055] 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 having 1 to 30 carbon atoms and / or a salt thereof. 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.

[0056] The core rubber composition may further contain, in addition to the base rubber, co-crosslinking agent, crosslinking initiator, and organic sulfur compound, a weight adjuster such as zinc oxide or barium sulfate, an antioxidant, color powder, and the like.

[0057] The hot press molding conditions for the core rubber composition may be appropriately set depending on the rubber composition, but it is usually 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 at 130°C to 150°C for 20 to 40 minutes, and then heat the core rubber composition at 160°C to 180°C for 5 to 15 minutes.

[0058] When the spherical core has an intermediate layer, examples of the intermediate layer material 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 products of rubber compositions. Examples of the ionomer resin include a copolymer of ethylene and α,β-unsaturated carboxylic acid in which at least a part of the carboxyl groups is neutralized with a metal ion, or a ternary copolymer of ethylene, α,β-unsaturated carboxylic acid, and α,β-unsaturated carboxylic acid ester in which at least a part of the carboxyl groups is neutralized with a metal ion. The intermediate layer may further contain weight adjusters such as barium sulfate and tungsten, antioxidants, pigments, and the like.

[0059] 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 pressure molded, or a method in which the intermediate layer composition is directly injection molded onto the sphere to encase the sphere.

[0060] 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 hold pin, inserting and holding the coated sphere, injecting the heated and molten intermediate layer composition, and cooling it.

[0061] When the intermediate layer is molded by compression molding, the molding of the half shell can be performed by either compression molding or injection molding, but compression molding is preferred. Conditions for compression molding the intermediate layer composition into the half shell include, for example, a pressure of 1 MPa or more and 20 MPa or less, and a molding temperature of -20°C or more and +70°C or less relative to the flow start temperature of the intermediate layer composition. By using the above molding conditions, a half shell having a uniform thickness can be molded. For example, a method for molding the intermediate layer using half shells includes a method of covering a sphere with two half shells and compression molding. Conditions for compression molding the half shells into the intermediate layer include, for example, a molding pressure of 0.5 MPa or more and 25 MPa or less, and a molding temperature of -20°C or more and +70°C or less relative to the flow start temperature of the intermediate layer composition. By using the above molding conditions, a middle layer having a uniform thickness can be molded.

[0062] The molding temperature means the maximum temperature that the surface of the recess in the lower die reaches during the period from mold clamping to mold opening. The flow start temperature of the composition was measured by subjecting a pelletized thermoplastic resin composition to a plunger area of ​​1 cm using a Shimadzu Corporation "Flow Tester CFT-500". 2The measurement can be performed under the conditions of DIE LENGTH: 1 mm, DIE DIA: 1 mm, load: 588.399 N, starting temperature: 30° C., and heating rate: 3° C. / min.

[0063] The central hardness Ho of the spherical core is preferably 40 or more, more preferably 45 or more, and even more preferably 50 or more, in Shore C hardness. When the central hardness Ho of the spherical core is 40 or more in Shore C hardness, the spherical core does not become too soft and good resilience is obtained. In addition, the central hardness Ho of the spherical core is preferably 75 or less in Shore C hardness, more preferably 70 or less, and even more preferably 65 or less. When the central hardness Ho of the spherical core is 75 or less in Shore C hardness, the spherical core does not become too hard and good shot feeling is obtained.

[0064] The surface hardness Hs of the spherical core is preferably 65 or more, more preferably 70 or more, even more preferably 75 or more, and is preferably 100 or less, more preferably 95 or less, even more preferably 90 or less, in Shore C hardness. If the surface hardness of the spherical core is 65 or more in Shore C hardness, the spherical core does not become too soft and good resilience is obtained. If the surface hardness of the spherical core is 100 or less in Shore C hardness, the spherical core does not become too hard and good shot feeling is obtained.

[0065] The difference in hardness (Hs-Ho) between the surface hardness Hs and the center hardness Ho of the spherical core is preferably at least 10, more preferably at least 12, and even more preferably at least 15 on the Shore C hardness scale, and is preferably at most 40, more preferably at most 35, and even more preferably at most 30. A large difference in hardness between the core surface and the core center results in a golf ball with a high launch angle and long flight distance with low spin.

[0066] The diameter of the spherical core is preferably 34.8 mm or more, more preferably 36.8 mm or more, even more preferably 38.8 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 thickness of the cover is not too thick, and the resilience is better. On the other hand, if the diameter of the spherical core is 42.2 mm or less, the cover is not too thin, and the function of the cover is more fully exhibited.

[0067] When the diameter of the spherical core is 34.8 mm to 42.2 mm, the amount of compressive deformation (the amount of shrinkage of the spherical core in the compressive direction) from when an initial load of 98 N is applied to when a final load of 1275 N is applied is preferably 2.0 mm or more, more preferably 2.4 mm or more, even more preferably 2.8 mm or more, and preferably 6.0 mm or less, more preferably 5.0 mm or less, even more preferably 4.5 mm or less. If the amount of compressive deformation is 2.0 mm or more, the hitting feeling becomes better, and if it is 6.0 mm or less, the resilience becomes better.

[0068] (Golf ball structure) The structure of the golf ball is not particularly limited as long as it has a spherical core and a cover that covers the spherical core. Examples of the golf ball structure include a two-piece golf ball having a single-layered spherical core and a cover that covers the spherical core; a three-piece golf ball having a spherical core consisting of a center and one intermediate layer that covers the center and a cover that covers the spherical core; a multi-piece golf ball having a spherical core consisting of a center and two or more intermediate layers that cover the center and a cover that covers the spherical core, etc.

[0069] The manner in which the cover is molded using the cover material is not particularly limited, but examples thereof include a manner in which the cover material is directly injection molded onto the spherical core, or a manner in which a hollow shell is molded from the cover material, the spherical core is covered with the shells, and compression molded (preferably, a method in which a hollow half shell is molded from the cover material, the spherical core is covered with two half shells, and compression molded). The golf ball body with the molded cover is removed from the mold, and is preferably subjected to surface treatment such as deburring, cleaning, and sandblasting as necessary. Also, a mark can be formed as desired.

[0070] The thickness of the cover 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 1.5 mm or less, and even more preferably 1.0 mm or less. If the thickness of the cover is 0.3 mm or more, molding of the cover becomes easier, and if it is 2.0 mm or less, the diameter of the core can be relatively large, improving the resilience performance of the golf ball.

[0071] The total number of dimples formed on the cover is preferably 200 to 500 inclusive. 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 may be a circle; a polygon such as an approximately triangular, approximately rectangular, approximately pentagonal, or approximately hexagonal; or other irregular shape; or may be used alone or in combination of two or more types.

[0072] The golf ball with the molded cover is preferably removed from the mold and, if necessary, subjected to surface treatment such as deburring, cleaning, and sandblasting. If desired, a coating film or markings can also be formed. 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. If the thickness is 5 μm or more, the coating film is unlikely to wear away even with continuous use, and if the thickness is 50 μm or less, the effect of the dimples can be fully exhibited.

[0073] The diameter of the golf ball is preferably 40 mm to 45 mm. From the viewpoint of meeting the standards of the United States Golf Association (USGA), the diameter is particularly preferably 42.67 mm or more. From the viewpoint of suppressing air resistance, the diameter is more preferably 44.00 mm or less, and particularly preferably 42.80 mm or less. In addition, 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 more preferably 44.00 g or more, and particularly preferably 45.00 g or more. From the viewpoint of meeting the standards of the USGA, the mass is particularly preferably 45.93 g or less.

[0074] In the golf ball of the present invention, when the diameter is 40mm to 45mm, the compressive deformation amount (the amount of shrinkage of the golf ball in the compressive direction) when a final load of 1275N is applied from an initial load of 98N is preferably 2.0mm or more, more preferably 2.4mm or more, and even more preferably 2.5mm or more, and is preferably 5.0mm or less, more preferably 4.5mm or less, and even more preferably 4.0mm or less. A golf ball with the compressive deformation amount of 2.0mm or more is not too hard and has a good shot feeling. On the other hand, by making the compressive deformation amount 5.0mm or less, the resilience is increased.

[0075] 1 is a partially cutaway cross-sectional view showing a golf ball 1 according to one embodiment of the present invention. Golf ball 1 has a spherical core 2 and a cover 3 disposed on the outside of this spherical core 2. A large number of dimples 31 are formed on the surface of the cover 3. The portions of the surface of the cover 3 other than the dimples 31 are lands 32. The cover 3 is formed from the cover material. EXAMPLES

[0076] 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.

[0077] [Evaluation method] (1) Number average molecular weight of polyol component The polyol was subjected to gel permeation chromatography measurement under the following measurement conditions. <Measurement conditions> Equipment: Tosoh Corporation, HLC-8120GPC Eluent: tetrahydrofuran (THF) Temperature: 40℃ Column: TSKgel SuperHM-M (Tosoh Corporation) Polyol concentration: 0.2% by mass (polyol / (polyol+THF)) Sample injection volume: 5μl Flow rate: 0.5ml / min Molecular weight standard: polystyrene (Tosoh Corporation, PStQuick Kit-H)

[0078] (2) Slab hardness (Shore A) of golf ball cover material A sheet of about 2 mm thickness was made by injection molding using the golf ball cover material and stored at 23°C for two weeks. The hardness was measured using an automatic hardness tester (Digitest II, manufactured by H. Burleith Co.) in a state where three or more sheets were stacked so as not to be affected by the measurement substrate, etc. The detector used was "Shore A".

[0079] (3) Slab hardness of the intermediate layer (Shore D hardness) Using the resin composition, a sheet with a thickness of about 2 mm was produced by injection molding and stored at 23°C for 2 weeks. With three or more of these sheets stacked so as not to be affected by the measurement substrate, etc., the hardness was measured using an automatic hardness tester (manufactured by H. Barless Co., Ltd., Digi Test II). The detector used was "Shore D".

[0080] (4) Loss modulus E” (Pa) The loss modulus E” (Pa) of the cover material was measured under the following conditions. Apparatus: Dynamic viscoelasticity measuring apparatus "Rheogel-E4000" manufactured by UBM Co., Ltd. Measurement sample: From the cover material, a sheet with a thickness of 0.5 mm was produced by hot press molding, and a sample piece was cut out from this sheet so that the width was 4 mm and the clamp distance was 20 mm. <Measurement conditions> Measurement mode: Tension Measurement temperature: -100°C to 100°C Temperature increase rate: 4°C / min Vibration frequency: 10 Hz Measurement strain: 0.05%

[0081] (5) Spin amount of the driver shot A driver equipped with a titanium head (manufactured by Sumitomo Rubber Industries, SRIXON (registered trademark) ZX7, loft 10.5°, hardness S) was attached to a swing robot M / C manufactured by Tru Temper Co., Ltd., and a golf ball was struck at a head speed of 50 m / s, and the spin speed of the golf ball immediately after the strike was measured. The measurement was performed 10 times for each golf ball, and the average value was taken as the measured value of that golf ball. The spin speed of the golf ball immediately after the strike was measured by continuously photographing the struck golf ball.

[0082] (6) Spin amount of the 8-iron shot An 8-iron with a titanium head (manufactured by Sumitomo Rubber Industries, SRIXON (registered trademark) ZX7, loft 36°, hardness S) was attached to a swing robot M / C manufactured by True Temper, and a golf ball was struck at a head speed of 39 m / sec, and the spin speed of the golf ball immediately after striking was measured. The measurement was performed 10 times for each golf ball, and the average value was taken as the measured value for that golf ball. The spin speed of the golf ball immediately after striking was measured by continuously photographing the struck golf ball.

[0083] [Polyurethane synthesis] Polyurethanes having the composition ratios shown in Table 1 were synthesized as follows. Dicyclohexylmethane diisocyanate (H 12 Polytetramethylene ether glycol (PTMG) heated to 80°C was added to the MDI, and the raw material (H 12 Dibutyltin dilaurate (manufactured by Aldrich, dibutyltin dilaurate) was added in an amount of 0.005% by mass of the total amount of MDI, PTMG and BD, and then the mixture was stirred at 80°C for 2 hours under a nitrogen stream. Next, butanediol (BD) heated to 80°C was added under a nitrogen stream, and then the mixture was stirred at 80°C for 1 minute. Thereafter, the reaction liquid was cooled and the pressure was reduced at room temperature for 1 minute to degas the system. The degassed reaction liquid was spread in a container and stored under a nitrogen atmosphere at 110°C for 6 hours to carry out a urethane reaction to obtain polyurethane.

[0084] [Table 1] PTMG650: Polytetramethylene ether glycol (number average molecular weight: 650) PTMG1000: Polytetramethylene ether glycol (number average molecular weight: 1000) PTMG1400: Polytetramethylene ether glycol (number average molecular weight: 1400) PTMG2000: Polytetramethylene ether glycol (number average molecular weight: 2000) PTMG3000: Polytetramethylene Ether Glycol (number average molecular weight: 3000) H 12 MDI: Dicyclohexylmethane Diisocyanate BD: 1,4-Butanediol

[0085] [Production of Golf Ball] (1) Production of Intermediate Layer-Coated Sphere The rubber composition for core with the formulation shown in Table 2 was kneaded and heat-pressed at 170 °C for 15 minutes in an upper and lower mold having a hemispherical cavity to obtain a spherical core (diameter 38.5 mm). Next, the intermediate layer material with the formulation shown in Table 3 was extruded using a twin-screw kneading extruder to prepare a pelletized composition for the intermediate layer. The extrusion was carried out with a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35. The formulation was heated to 150 - 230 °C at the die position of the extruder. The obtained composition for the intermediate layer was injection-molded onto the core obtained as described above so that the thickness became 1.6 mm to coat the core and produce an intermediate layer-coated sphere (diameter 41.7 mm).

[0086]

Table 2

[0087]

Table 3

[0088] (2) Forming the half shell As shown in the compounding recipe in Table 4, polyurethane and titanium oxide were dry blended and mixed by a twin-screw kneading extruder to obtain a pellet-shaped cover material. Extrusion was performed with a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D of 35. The compound was heated to 150 to 230°C at the die position of the extruder. The compression molding of the half shell was performed by putting the obtained pellet-shaped cover material into each recess of the lower mold of the half shell molding die, one by one, and pressing to mold the half shell. 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.

[0089] (3) Molding the cover The intermediate layer-covered sphere obtained in (1) was concentrically covered with the two half shells obtained in (2) and a cover was formed by compression molding. 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. The surface of the obtained golf ball body was sandblasted and marked, and then clear paint was applied and the paint was dried in an oven at 40°C to obtain a golf ball with a diameter of 42.7 mm and a mass of 45.3 g. The spin performance of the obtained golf ball was evaluated and the results are shown in Table 4.

[0090] [Table 4]

[0091] Golf balls No. 3 to 6 have covers with loss modulus (E -40 ) is 6.50 x 10 7 Pa~22.0×10 7 Pa, and loss modulus (E -20 ) is 3.50 × 10 7 Pa ~ 7.10 x 10 7 The golf ball cover is made of a golf ball cover material having a diameter of 100 mm. These golf balls No. 3 to 6 have a reduced spin amount in driver shots and an increased spin amount in iron shots.

[0092] Golf balls No. 1 and 2 have a cover made of a material for a golf ball cover with a loss elastic modulus (E” -40 ) of 6.50×10 7 Pa to 22.0×10 7 Pa, but the loss elastic modulus (E” -20 ) exceeds 7.10×10 7 Pa. Although these golf balls No. 1 and 2 have a reduced spin amount in driver shots, the spin amount in iron shots is low.

[0093] Golf ball No. 7 has a cover made of a material for a golf ball cover with a loss elastic modulus (E” -20 ) of 3.50×10 7 Pa to 7.10×10 7 Pa, but the loss elastic modulus (E” -40 ) is less than 6.50×10 7 Pa. This golf ball No. 7 has an increased spin amount in iron shots, but the spin amount in driver shots is also high.

[0094] The present invention (1) is a material for a golf ball cover, characterized in that the loss elastic modulus (E” -40 ) measured at a measurement temperature of -40°C under the following measurement conditions using a dynamic viscoelasticity apparatus is 6.50×10 7 Pa to 22.0×10 7 Pa, and the loss elastic modulus (E” -20 ) measured at a measurement temperature of -20°C is 3.50×10 7 Pa to 7.10×10 7 Pa. <Measurement Conditions> Measurement mode: Tension Measurement temperature: -100°C to 100°C Temperature rising rate: 4 °C / min Vibration frequency: 10 Hz Measured strain: 0.05%

[0095] The present invention (2) is a material for a golf ball cover according to the present invention (1), which contains polyurethane formed by reacting a polyol and a polyisocyanate as resin components.

[0096] The present invention (3) is a material for a golf ball cover according to the present invention (2), which contains at least one polymer polyol selected from the group consisting of polyether polyol, condensation polyester polyol, lactone polyester polyol, polycarbonate polyol, and acrylic polyol as the polyol constituting the polyurethane.

[0097] The present invention (4) is a material for a golf ball cover according to any one of the present invention (2) or (3), which contains a first polymer polyol and a second polymer polyol having a higher number average molecular weight than the first polymer polyol as the polyol constituting the polyurethane.

[0098] The present invention (5) is a material for a golf ball cover according to any one of the present invention (2) to (4), wherein the content of polyether polyol in 100% by mass of the polyol constituting the polyurethane is 50% by mass or more.

[0099] The present invention (6) is a golf ball having a spherical core and a cover covering the spherical core, wherein the cover is formed from the material for a golf ball cover according to any one of the present invention (1) to (5).

Explanation of symbols

[0100] 1; Golf ball, 2; Spherical core, 3; Cover, 31; Dimple, 32; Land

Claims

1. The loss modulus (E″) at a measurement temperature of −40° C. was measured using a dynamic viscoelasticity device under the following measurement conditions. -40 ) is 6.50 x 10 7 Pa ~ 22.0 x 10 7 Pa, and the loss modulus (E″) at a measurement temperature of −20° C. -20 ) is 3.50 x 10 7 Pa ~ 7.10 x 10 7 2. A golf ball cover material comprising: <Measurement conditions> Measurement mode: Tensile Measurement temperature: -100℃~100℃ Heating rate: 4°C / min Excitation frequency: 10Hz Measured distortion: 0.05%

2. 2. The golf ball cover material according to claim 1, further comprising, as the resin component, a polyurethane obtained by reacting a polyol with a polyisocyanate.

3. 3. The golf ball cover material according to claim 2, wherein the polyol constituting the polyurethane contains at least one polymer polyol selected from the group consisting of polyether polyol, condensation polyester polyol, lactone polyester polyol, polycarbonate polyol and acrylic polyol.

4. 4. The golf ball cover material according to claim 3, wherein the polyurethane comprises a first polymer polyol and a second polymer polyol having a number average molecular weight greater than that of the first polymer polyol.

5. 3. The golf ball cover material according to claim 2, wherein the content of the polyether polyol in 100% by weight of the polyol constituting the polyurethane is 50% by weight or more.

6. A spherical core and a cover that covers the spherical core, A golf ball, the cover of which is formed from the golf ball cover material according to any one of claims 1 to 5.

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