golf ball

Abstract

To provide a golf ball which does not reduce resilience even using a hard cover material, achieves preferable hitting feeling, and is excellent in durability.SOLUTION: A golf ball has: a spherical core; and a cover of one or more layers arranged outside the spherical core. At least one layer of the cover includes: (A) a substrate resin; and (B) at least one kind selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and liquid polymer, wherein when an arithmetic average roughness in a cover surface is Sa, and an arithmetic average curvature on a crest part is Spc, Sa×Spc≥100 is satisfied.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to an improved technology for golf ball covers. [Background technology]

[0002] Thermoplastic resins such as ionomer resin and polyurethane are used as resin components in the cover and intermediate layer of golf balls. Ionomer resin has high rigidity, and when used as a component of a golf ball, it increases rebound and results in a golf ball with greater flight distance. For this reason, ionomer resin is widely used as a material for the intermediate layer and cover of golf balls.

[0003] Furthermore, golf balls are required to have not only distance performance, but also durability and feel upon impact.

[0004] Patent Document 1 describes a golf ball having a spherical core and one or more covers disposed on the outside of the spherical core, At least one layer of the cover contains (A) a base resin and (B) a polyrotaxane. (A) The base resin contains (a-1) an ionomer resin, (A) The material hardness of the base resin is 59 or higher on the Shore D hardness scale. (B) The golf ball disclosed is characterized in that the polyrotaxane has a cyclodextrin, a linear molecule that skeweres the cyclic structure of the cyclodextrin, and a sealing group located at both ends of the linear molecule that prevents the elimination of the cyclodextrin, and at least a portion of the hydroxyl groups of the cyclodextrin is modified by a caprolactone chain via an -O-C3H6-O- group.

[0005] Patent Document 2 describes a golf ball having a spherical core and one or more covers disposed on the outside of the spherical core, At least one layer of the cover contains (A) a base resin and (B) a polyrotaxane. (A) The base resin contains (a-1) an ionomer resin, (A) The material hardness of the base resin is 58 or less on the Shore D hardness scale. (B) The golf ball disclosed is characterized in that the polyrotaxane has a cyclodextrin, a linear molecule that skeweres the cyclic structure of the cyclodextrin, and a sealing group located at both ends of the linear molecule that prevents the elimination of the cyclodextrin, and at least a portion of the hydroxyl groups of the cyclodextrin is modified by a caprolactone chain via an -O-C3H6-O- group. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-102692 [Patent Document 2] Japanese Patent Publication No. 2018-102694 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The objective of this disclosure is to provide a golf ball that offers a good feel upon impact and excellent durability, without reducing rebound properties, even when using a hard cover material. [Means for solving the problem]

[0008] The golf ball of this disclosure, which has been able to solve the above problems, is a golf ball having a spherical core and one or more covers disposed on the outside of the spherical core, At least one layer of the cover comprises (A) a base resin and (B) at least one selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and liquid polymer, wherein the arithmetic mean roughness of the surface of the cut surface of the cover is Sa (μm) and the arithmetic mean curvature of the peak is Spc (mm -1When [condition], it is characterized in that Sa×Spc≧100.

Advantages of the Invention

[0009] According to the present disclosure, a golf ball with good hitting feeling and excellent durability can be obtained without reducing the resilience.

Brief Description of the Drawings

[0010] [Figure 1] An explanatory diagram for explaining the molecular structure of an example of the polyrotaxane used in the present disclosure. [Figure 2] A partially cut-away cross-sectional view showing a golf ball according to an embodiment of the present disclosure. [Figure 3] An electron micrograph of a cut surface of the cover of a golf ball according to an embodiment of the present disclosure. [Figure 4] An electron micrograph of a cut surface of the cover of a golf ball according to an embodiment of the present disclosure. [Figure 5] An electron micrograph of a cut surface of the cover of a golf ball according to an embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0011] The golf ball of the present disclosure is a golf ball having a spherical core and one or more covers disposed outside the spherical core, wherein at least one layer of the cover contains (A) a base resin and (B) at least one selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and a liquid polymer. When the arithmetic mean roughness on the surface of the cut surface of the cover is Sa (μm) and the arithmetic mean curvature of the peak points is Spc (mm -1 ) When [condition], it is characterized in that Sa×Spc≧100.

[0012] The golf ball of the present disclosure is a golf ball having a spherical core and one or more covers disposed outside the spherical core, wherein the arithmetic mean roughness on the surface of the cut surface of the cover is Sa (μm) and the arithmetic mean curvature of the peak points is Spc (mm -1When this is the case, Sa × Spc ≥ 100.

[0013] The arithmetic mean roughness Sa (μm) of the surface of the cut surface of the cover and the arithmetic mean curvature Spc (mm) of the peak -1 ) is determined by the measurement method described later.

[0014] The Sa×Spc (μm / mm) is preferably 100 or more, more preferably 150 or more, even more preferably 165 or more, preferably 1000 or less, more preferably 950 or less, and even more preferably 900 or less. This is because if the Sa×Spc (μm / mm) is within the above range, the stress is dispersed due to the fine dispersion of the additive (component (B)), and an effect of improving durability can be expected.

[0015] The arithmetic mean roughness Sa (μm) on the surface of the cut surface of the cover is preferably 0.06 or higher, more preferably 0.07 or higher, even more preferably 0.08 or higher, preferably 0.50 or lower, more preferably 0.45 or lower, and even more preferably 0.40 or lower. This is because if the arithmetic mean roughness Sa (μm) is within the above range, it indicates that the necessary amount of additive is dispersed.

[0016] The arithmetic mean curvature of the peaks on the surface of the cut surface of the cover, Spc(mm) -1 The arithmetic mean curvature of the peak is preferably 1300 or more, more preferably 1600 or more, even more preferably 2500 or more, preferably 10000 or less, more preferably 9000 or less, and even more preferably 8000 or less. -1 ) is within the aforementioned range because it indicates that the additive is more finely dispersed.

[0017] Preferably, at least one layer of the golf ball cover of this disclosure is formed from a cover composition containing, as a resin component, (A) a base resin and (B) at least one selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and liquid polymer. First, the base resin (A) used for the golf ball cover of this disclosure will be described.

[0018] [(A) Base resin] The base resin (A) is not particularly limited, but may be either a thermoplastic resin or a thermosetting resin, although a thermoplastic resin is preferred.

[0019] Examples of the (A) base resin include thermoplastic resins such as ionomer resins, polyurethanes, polyamides, and polyolefins; thermoplastic elastomers such as polyurethane elastomers, styrene elastomers, polyolefin elastomers, polyamide elastomers, and polyester elastomers; binary copolymers of olefins such as ethylene-(meth)acrylic acid copolymers and α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms; and terpolymers of olefins such as ethylene-(meth)acrylic acid-(meth)acrylic acid ester copolymers and α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms and α,β-unsaturated carboxylic acid esters.

[0020] The (A) base resin used in this disclosure is preferably relatively hard. The material hardness of the (A) base resin is preferably 59 or higher on the Shore D scale, more preferably 60 or higher, even more preferably 61 or higher, preferably 69 or lower, more preferably 68 or lower, and even more preferably 67 or lower. If the material hardness of the (A) base resin is 59 or higher on the Shore D scale, the rebound of the resulting golf ball will be further improved. Furthermore, if the material hardness of the (A) base resin is 69 or lower on the Shore D scale, the decrease in durability due to repeated impacts can be further suppressed. The material hardness of the base resin is the slab hardness measured after the base resin is molded into a sheet.

[0021] As the base resin (A), for example, ionomer resin and / or polyamide are more preferred.

[0022] Examples of the ionomer resin include: an ionomer resin consisting of a metal ion neutralized product of a binary copolymer of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; an ionomer resin consisting of a metal ion neutralized product of a terpolymer of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid ester; or mixtures thereof.

[0023] In this disclosure, "ionomer resins consisting of metal ion neutralized products of a binary copolymer of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms" may be simply referred to as "binary ionomer resins," and "ionomer resins consisting of metal ion neutralized products of a terpolymer of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid ester" may be simply referred to as "ternary ionomer resins."

[0024] The olefin is preferably an olefin having 2 to 8 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, etc., with ethylene being particularly preferred. The α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms is, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid, etc., with acrylic acid or methacrylic acid being particularly preferred. The α,β-unsaturated carboxylic acid ester is, for example, methyl, ethyl, propyl, n-butyl, isobutyl esters of acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc., and with acrylic acid ester or methacrylic acid ester being particularly preferred.

[0025] As the binary ionomer resin, a metal ion neutralized product of an ethylene-(meth)acrylic acid binary copolymer is preferred. As the ternary ionomer resin, a metal ion neutralized product of a ternary copolymer of ethylene, (meth)acrylic acid, and (meth)acrylic acid ester is preferred. Here, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0026] The content of the α,β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the binary ionomer resin is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 16% by mass or more, most preferably 17% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less. This is because if the content of the α,β-unsaturated carboxylic acid component having 3 to 8 carbon atoms is 5% by mass or more, it becomes easier to achieve the desired hardness in the resulting component. Furthermore, if the content of the α,β-unsaturated carboxylic acid component having 3 to 8 carbon atoms is 30% by mass or less, the resulting component does not become too hard, resulting in better durability and feel.

[0027] The degree of neutralization of the carboxyl groups in the binary ionomer resin is preferably 15 mol% or more, preferably 20 mol% or more, preferably 90 mol% or less, and more preferably 85 mol% or less. If the degree of neutralization is 15 mol% or more, the rebound and durability of the resulting golf ball will be better. On the other hand, if the degree of neutralization is 90 mol% or less, the fluidity of the cover material will be good (good moldability). The degree of neutralization of the carboxyl groups in the binary ionomer resin can be determined by the following formula.

[0028] Degree of neutralization of binary ionomer resin (mol%) = 100 × number of moles of neutralized carboxyl groups in the binary ionomer resin / total number of moles of carboxyl groups in the binary ionomer resin

[0029] Examples of metal ions that neutralize at least a portion of the carboxyl groups of the binary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; divalent metal ions such as magnesium, calcium, zinc, barium, and cadmium; trivalent metal ions such as aluminum; and other ions such as tin and zirconium. It is preferable to use a mixture of a binary ionomer resin neutralized with sodium and a binary ionomer resin neutralized with zinc as the binary ionomer resin. Using these mixtures further improves resilience and durability.

[0030] A specific example of the aforementioned binary ionomer resin, exemplified by its trade name, is "Himilan (registered trademark)" (for example, Himilan 1555 (Na), Himilan 1557 (Zn), Himilan 1605 (Na), Himilan 1702 (Zn), Himilan 1706 (Zn), Himilan 1707 (Na), Himilan AM7311 (Mg), Himilan AM7329 (Zn), Himilan AM7337 (Na), etc.), which is commercially available from Mitsui DuPont Polychemical Co., Ltd.

[0031] Furthermore, examples include "Surlyn" (registered trademark) (e.g., Surlyn 8945(Na), Surlyn 9945(Zn), Surlyn 8140(Na), Surlyn 8150(Na), Surlyn 9120(Zn), Surlyn 9150(Zn), Surlyn 6910(Mg), Surlyn 6120(Mg), Surlyn 7930(Li), Surlyn 7940(Li), Surlyn AD8546(Li)) which are commercially available from DuPont.

[0032] Other ionomer resins commercially available from ExxonMobil Chemicals, Inc. include "Iotek (registered trademark) (e.g., Iotek 8000 (Na), Iotek 8030 (Na), Iotek 7010 (Zn), Iotek 7030 (Zn))."

[0033] The binary ionomer resins described above may be used individually or as a mixture of two or more. The Na, Zn, Li, Mg, etc., listed in parentheses after the trade names indicate the metal species of the neutralizing metal ions.

[0034] The bending stiffness of the aforementioned binary ionomer resin is preferably 140 MPa or higher, more preferably 150 MPa or higher, even more preferably 160 MPa or higher, preferably 550 MPa or lower, more preferably 500 MPa or lower, and even more preferably 450 MPa or lower. If the bending stiffness is within the above range, the amount of spin on driver shots is optimized, resulting in excellent distance performance and good durability.

[0035] The melt flow rate (at 190°C, 2.16 kg load) of the binary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, even more preferably 1.0 g / 10 min or more, preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, and even more preferably 15 g / 10 min or less. If the melt flow rate (at 190°C, 2.16 kg load) of the binary ionomer resin is 0.1 g / 10 min or more, the fluidity of the cover material will be good, for example, it will be possible to make the resulting cover thinner. Furthermore, if the melt flow rate (at 190°C, 2.16 kg load) of the binary ionomer resin is 30 g / 10 min or less, the durability of the resulting golf ball will be better.

[0036] The content of the α,β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the ternary ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, preferably 30% by mass or less, and more preferably 25% by mass or less.

[0037] The degree of neutralization of the carboxyl groups in the ternary ionomer resin is preferably 20 mol% or more, more preferably 30 mol% or more, preferably 90 mol% or less, and more preferably 85 mol% or less. If the degree of neutralization is 20 mol% or more, the resulting golf ball will have good rebound and durability, and if it is 90 mol% or less, the fluidity of the cover material will be good (good moldability). The degree of neutralization of the carboxyl groups in the ionomer resin can be determined by the following formula. Degree of neutralization of ionomer resin (mol%) = 100 × number of moles of neutralized carboxyl groups in the ionomer resin / total number of moles of carboxyl groups in the ionomer resin

[0038] Examples of metal ions that neutralize at least a portion of the carboxyl groups in the aforementioned ternary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; divalent metal ions such as magnesium, calcium, zinc, barium, and cadmium; trivalent metal ions such as aluminum; and other ions such as tin and zirconium.

[0039] Specific examples of the aforementioned ternary ionomer resins include "Himilan" (registered trademark) (e.g., Himilan AM7327 (Zn), Himilan 1855 (Zn), Himilan 1856 (Na), Himilan AM7331 (Na)), etc.), which are commercially available from Mitsui DuPont Polychemical Co., Ltd. Furthermore, examples of ternary ionomer resins commercially available from DuPont include "Sarlin 6320 (Mg), Surlin 8120 (Na), Surlin 8320 (Na), Surlin 9320 (Zn), Surlin 9320W (Zn), etc.") And examples of ternary ionomer resins commercially available from ExxonMobil Chemicals, Ltd. include "IOTEC 7510 (Zn), IOTEC 7520 (Zn), etc." The Na, Zn, Mg, etc., listed in parentheses after the product names indicate the type of neutralizing metal ion. The ternary ionomer resins may be used individually or in combination of two or more types.

[0040] The bending stiffness of the ternary ionomer resin is preferably 10 MPa or higher, more preferably 11 MPa or higher, even more preferably 12 MPa or higher, preferably 100 MPa or lower, more preferably 97 MPa or lower, and even more preferably 95 MPa or lower. If the bending stiffness is within the above range, the amount of spin on driver shots is optimized, resulting in excellent distance performance and good durability.

[0041] The melt flow rate (at 190°C, 2.16 kg load) of the ternary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, even more preferably 0.5 g / 10 min or more, preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less. If the melt flow rate (at 190°C, 2.16 kg load) of the ternary ionomer resin is 0.1 g / 10 min or more, the fluidity of the cover material will be good, and it will be possible to mold thin components. Furthermore, if the melt flow rate (at 190°C, 2.16 kg load) of the ternary ionomer resin is 20 g / 10 min or less, the durability of the resulting golf ball will be even better.

[0042] The polyamide is not particularly limited as long as it is a thermoplastic resin having multiple amide bonds (-NH-CO-) in the main chain of the molecule. Examples include products in which amide bonds are formed within the molecule by ring-opening polymerization of lactam or by reacting a diamine component with a dicarboxylic acid component.

[0043] Examples of the polyamides include aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, and polyamide 612; and aromatic polyamides such as poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide. These may be used individually or in combination of two or more. Among these, aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 11, and polyamide 12 are preferred.

[0044] Specific examples of the aforementioned polyamides, shown by their trade names, include, for example, "Lilsan (registered trademark) B" (e.g., Lilsan BESN TL, Lilsan BESN P20 TL, Lilsan BESN P40 TL, Lilsan MB3610, Lilsan BMF O, Lilsan BMN O, Lilsan BMN O TLD, Lilsan BMN BK TLD, Lilsan BMN P20 D, Lilsan BMN P40 D, etc.) which are commercially available from Arkema.

[0045] Next, component (B) will be described. Component (B) contains at least one selected from the group consisting of (b1) polyrotaxane, (b2) polyethylene oxide, (b3) polypropylene oxide, (b4) polycaprolactone, and (b5) liquid polymer.

[0046] In this disclosure, it is preferable to use (b1) polyrotaxane and / or (b2) polyethylene oxide as component (B), and more preferably to use (b2) polyethylene oxide. (b2) polyethylene oxide is finely dispersed in the (A) base resin to further enhance the durability of the resulting golf ball.

[0047] [(b1) Polyrotaxane] (b1) The polyrotaxane comprises a cyclodextrin, a linear molecule that pierces the cyclic structure of the cyclodextrin, and chelating groups positioned at both ends of the linear molecule to prevent the detachment of the cyclic molecule. The polyrotaxane has viscoelastic properties because the cyclodextrin molecule that pierces the linear molecule is movable along the linear molecule (pulley effect), and even when tension is applied, this pulley effect allows the tension to be uniformly dispersed.

[0048] The term "cyclodextrin" refers to a general term for oligosaccharides having a cyclic structure. A cyclodextrin, for example, is formed by 6 to 8 D-glucopyranose residues linked cyclically by α-1,4-glucosidic bonds. Examples of cyclodextrins include α-cyclodextrin (6 glucose units), β-cyclodextrin (7 glucose units), and γ-cyclodextrin (8 glucose units), with α-cyclodextrin being preferred. The cyclodextrin may be used alone or in combination of two or more types.

[0049] The linear molecule is not particularly limited as long as it is a linear molecule that rotatably penetrates the cyclic structure of cyclodextrin in a skewer-like manner. Examples of the linear molecule include polyalkylene, polyester, polyether, and polyacrylic, among which polyether is preferred, and polyethylene glycol is particularly preferred. Polyethylene glycol has low steric hindrance and can penetrate the cyclic structure of cyclodextrin in a skewer-like manner.

[0050] The weight-average molecular weight of the linear molecule is preferably 5,000 or more, more preferably 6,000 or more, preferably 100,000 or less, and more preferably 80,000 or less.

[0051] The linear molecule is preferably one having functional groups at both ends. Having functional groups allows it to react easily with the chelating group. Examples of functional groups include hydroxyl groups, carboxyl groups, amino groups, and thiol groups.

[0052] The aforementioned blocking group is not particularly limited as long as it is positioned at both ends of the linear molecule and can prevent cyclodextrin from detaching from the linear molecule. Methods for preventing detachment include physically preventing detachment using a bulky blocking group, and electrostatically preventing detachment using an ionic blocking group. Examples of the bulky blocking group include cyclodextrin and adamantyl groups. The number of cyclodextrins that penetrate the linear molecule is preferably 0.06 to 0.61, more preferably 0.11 to 0.48, and even more preferably 0.24 to 0.41, with the maximum number being 1. Below 0.06, the pulley effect may not be observed, and above 0.61, the cyclodextrins may be too densely arranged, reducing their mobility.

[0053] The (b1) polyrotaxane used in this disclosure is preferably one in which at least a portion of the hydroxyl groups of the cyclodextrin are modified by caprolactone chains. This is because the modification by caprolactone increases the flexibility of the cover layer, resulting in a better feel when hitting the ball.

[0054] As for the aforementioned modification, for example, the hydroxyl group of cyclodextrin is treated with propylene oxide to hydroxypropylate it. Subsequently, ε-caprolactone is added and ring-opening polymerization is carried out. Through this modification, the caprolactone chain -(CO(CH2)5O)nH (where n is a natural number from 1 to 100) is bonded to the outside of the cyclic structure of cyclodextrin via an -O-C3H6-O- group. n represents the degree of polymerization and is preferably a natural number from 1 to 100, more preferably from 2 to 70, and even more preferably from 3 to 40. A hydroxyl group is formed at the other end of the caprolactone chain by ring-opening polymerization.

[0055] The proportion of hydroxyl groups modified by the caprolactone chain relative to the total hydroxyl groups (100 mol%) of the cyclodextrin before modification is preferably 2 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, preferably 50 mol% or less, more preferably 30 mol% or less, and even more preferably 20 mol% or less. This is because compatibility with the base resin is further improved when the proportion of hydroxyl groups modified by the caprolactone chain is within the above range.

[0056] Figure 1 is an explanatory diagram showing an example of the molecular structure of (b1) polyrotaxane. Polyrotaxane 10 has a cyclodextrin 12, a linear molecule 14 that pierces the cyclic structure of the cyclodextrin 12, and a chokeholding group 16 located at both ends of the linear molecule 14 that prevents the detachment of the cyclic molecule. A caprolactone chain 18 is bonded to the outside of the cyclic structure of the cyclodextrin via an -O-C3H6-O- group (not shown).

[0057] The hydroxyl value of the polyrotaxane (b1) is preferably 10 mg KOH / g or more, more preferably 15 mg KOH / g or more, even more preferably 20 mg KOH / g or more, preferably 400 mg KOH / g or less, more preferably 300 mg KOH / g or less, even more preferably 220 mg KOH / g or less, and particularly preferably 180 mg KOH / g or less. This is because the compatibility with the ionomer resin is further improved when the hydroxyl value of the polyrotaxane is within the above range. The hydroxyl value can be measured, for example, by the acetylation method in accordance with JIS K 1557-1.

[0058] The total molecular weight of the polyrotaxane (b1) is preferably 30,000 or more, more preferably 40,000 or more, even more preferably 50,000 or more, preferably 3,000,000 or less, more preferably 2,500,000 or less, and even more preferably 2,000,000 or less, as a weight-average molecular weight. This is because a weight-average molecular weight of 30,000 or more results in better elasticity of the cover composition, and a weight-average molecular weight of 3,000,000 or less improves the flexibility of the cover composition, resulting in a better feel when hitting the ball. The weight-average molecular weight can be measured, for example, by gel permeation chromatography (GPC) using polystyrene as the standard substance, tetrahydrofuran as the eluent, and an organic solvent-based GPC column (for example, Showa Denko's "Shodex® KF series").

[0059] Specific examples of polyrotaxanes modified with polycaprolactone include SELM® Superpolymer SH3400P, SH2400P, and SH1300P manufactured by Advanced Soft Materials.

[0060] [(b2) Polyethylene oxide (polyethylene glycol) and (b3) Polypropylene oxide (polypropylene glycol)]

[0061] (b2) Polyethylene oxide (polyethylene glycol) is a polymer having oxyethylene as a repeating unit. (b3) Polypropylene oxide (polypropylene glycol) is a polymer having oxypropylene as a repeating unit.

[0062] (b2) Polyethylene oxide (polyethylene glycol) and (b3) Polypropylene oxide (polypropylene glycol) include, for example, those obtained by addition polymerization of ethylene oxide or propylene oxide using one or more compounds having two or more active hydrogen atoms (-NH- or -OH) as initiators.

[0063] The initiator can be one or more types, and examples include compounds having two hydroxyl groups such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and bisphenol A; and compounds having three hydroxyl groups such as glycerin, trimethylolethane, and trimethylolpropane.

[0064] (b2) Polyethylene oxide (polyethylene glycol) is a polymer obtained by ring-opening polymerization of ethylene oxide, and preferably has hydroxyl groups at both ends. The polyethylene oxide (b2) used in this disclosure does not include polyethylene glycol having chelating groups at both ends to be used as the axial molecule of the polyrotaxane.

[0065] (b2) The number average molecular weight of polyethylene oxide (polyethylene glycol) and (b3) polypropylene oxide (polypropylene glycol) is preferably 400 or more, more preferably 700 or more, even more preferably 1000 or more, preferably 7 million or less, more preferably 6 million or less, and even more preferably 5 million or less.

[0066] [(b4) Polycaprolactone] Polycaprolactone can be obtained, for example, by ring-opening addition polymerization of a lactone monomer such as ε-caprolactone monomer in the presence of an initiator and catalyst having an active hydrogen group. The reaction temperature is, for example, 120 to 220°C, preferably 150 to 200°C, and can be obtained by reacting with stirring for several hours. The reaction is preferably carried out in an inert gas environment.

[0067] Examples of polymerization initiators include alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butylene glycol, pentamethylene glycol, and hexamethylene glycol; aromatic diols such as isophthalyl alcohol, terephthalyl alcohol, β,β'-bishydroxyethyl terephthalate, and β,β'-bishydroxyethyl isophthalate; alicyclic diols such as cyclohexane 1,4-diol and cyclohexane 1,4-dimethanol; and polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene adipate diol, polypropylene adipate diol, polybutylene adipate diol, polyethylene sebacate diol, polyethylene propylenediol, and polyethylene butylene adipate diol.

[0068] Examples of the catalysts include tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, dibutyltin oxide, dibutyltin laurate, tin octoate, and stannous chloride.

[0069] (b4) The number average molecular weight of polycaprolactone is preferably 1000 or more, more preferably 2000 or more, even more preferably 3000 or more, preferably 1,000,000 or less, more preferably 900,000 or less, and even more preferably 800,000 or less.

[0070] [(b5) Liquid polymer] Next, the (b5) liquid polymer used in this disclosure will be described. The (b5) liquid polymer is a polymer that is liquid at room temperature (23°C). Examples of the (b5) liquid polymer include liquid polybutene, liquid polyisoprene, liquid polybutadiene, liquid poly-α-olefin, liquid ethylene-α-olefin copolymer, liquid ethylene propylene copolymer, liquid ethylene butylene copolymer, and the like. Among these, liquid polybutene or liquid polybutadiene is preferred, and liquid polybutene is more preferred.

[0071] The liquid polybutene is not particularly limited as long as it is a polymer having butene as a main constituent. For example, polymers having 1-butene as a main constituent, polymers having isobutene as a main constituent (liquid polyisobutene), etc. can be mentioned. In the present disclosure, it is preferable to use liquid polyisobutene as the liquid polybutene.

[0072] The liquid polyisobutene is not particularly limited as long as it is a polymer having isobutene as a main constituent, and it may be a polymer having only isobutene as a constituent. As the liquid polyisobutene, for example, a copolymer having a molecular structure of a long-chain hydrocarbon obtained by using isobutene as a main component and further reacting normal butene (for example, polybutene HV manufactured by JXTG Energy Co., Ltd.) can be preferably used.

[0073] As the liquid polybutene, a hydrogenated product of the polybutene (hydrogenated liquid polybutene) can also be used.

[0074] (b5) Only one kind of the liquid polymer may be used, or two or more kinds may be used in combination.

[0075] (b5) The kinematic viscosity of the liquid polymer at 40°C is preferably 900 mm 2 / s or more, more preferably 2000 mm 2 / s or more, even more preferably 3000 mm 2 / s or more, and preferably 100000 mm 2 / s or less, more preferably 50000 mm 2 / s or less, and even more preferably 30000 mm 2 / s or less. If the kinematic viscosity at 40°C is within the above range, there is no bleed of low molecular weight components and no problems in the process, and good rubber can be obtained.

[0076] (b5) The kinematic viscosity of the liquid polymer at 100°C is preferably 50 mm 2 / s or more, more preferably 60 mm 2It is more preferable that it be 70mm or more / s. 2 It is even more preferable that it be 150 mm or more / s. 2 It is particularly preferable that the speed be 4000 mm or more. 2 Preferably, it is less than / s, and 3000mm 2 It is more preferable that it be less than or equal to / s, and 2000mm 2 It is even more preferable that the kinematic viscosity at 100°C is less than or equal to / s. If the kinematic viscosity at 100°C is within the above range, there will be no bleeding of low molecular weight components and no process problems.

[0077] (b5) The kinematic viscosity of the liquid polymer is measured in accordance with JIS K2283-2000 under conditions of 100°C and 40°C.

[0078] (b5) The number-average molecular weight of the liquid polymer is preferably 650 or more, more preferably 700 or more, even more preferably 750 or more, preferably 2800 or less, more preferably 2500 or less, and even more preferably 2000 or less. The number-average molecular weight was measured using gel permeation chromatography (HLC-8120GPC, manufactured by Tosoh Corporation) with a differential refractometer as the detector, under the conditions of column: GMHHXL (manufactured by Tosoh Corporation), column temperature: 40°C, mobile phase: tetrahydrofuran, and the value was calculated as a standard polystyrene equivalent.

[0079] At least one layer of the golf ball cover according to this disclosure is formed from a cover composition containing (A) a base resin and (B) component as resin components. The cover layer containing (A) a base resin and (B) component preferably contains 0.1 parts by mass or more of (B) component per 100 parts by mass of (A) base resin, more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, preferably 30 parts by mass or less, preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. This is because if the content of (B) component is 0.1 parts by mass or more, the rebound of the resulting golf ball is further improved, and if it is 30 parts by mass or less, it does not affect the release properties during golf ball molding.

[0080] If the golf ball of this disclosure has multiple covers, at least one layer of the covers may contain (A) a base resin and (B) a component, and the layers that do not contain (A) a base resin and (B) a component may contain other resin components. Examples of other resins include thermoplastic resins such as polyurethane, ionomer resin, polyamide, and polyethylene; and thermoplastic elastomers such as styrene elastomer, polyolefin elastomer, polyurethane elastomer, polyamide elastomer, and polyester elastomer.

[0081] Specific examples of the aforementioned other resins, exemplified by their trade names, include ionomer resins sold by Mitsui DuPont Polychemicals Co., Ltd. under the trade name "Himilan" (registered trademark), thermoplastic polyurethane elastomers sold by BASF Japan Ltd. under the trade name "Elastran" (registered trademark), thermoplastic polyamide elastomers sold by Arkema Inc. under the trade name "Pebax" (registered trademark), thermoplastic polyester elastomers sold by Toray DuPont Ltd. under the trade name "Hytrel" (registered trademark), and thermoplastic styrene elastomers or thermoplastic polyester elastomers sold by Mitsubishi Chemical Corporation under the trade name "Tefablock".

[0082] The total content of the base resin (A) and component (B) in the cover layer containing the base resin (A) and component (B) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This is because a total content of 60% by mass or more improves the rebound of the resulting golf ball. The upper limit of the total content is not particularly limited, but 100% by mass is preferred.

[0083] The golf ball cover of this disclosure may further contain pigment components such as white pigments (e.g., titanium dioxide), blue pigments, and red pigments, weight modifiers such as calcium carbonate and barium sulfate, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, or fluorescent whitening agents, to the extent that they do not impair the performance of the cover.

[0084] In this disclosure, the material hardness of the cover layer containing (A) the base resin and (B) component is preferably 59 or higher on the Shore D hardness scale, more preferably 60 or higher, even more preferably 61 or higher, preferably 69 or lower, more preferably 68 or lower, and even more preferably 67 or lower. This is because if the material hardness is 59 or higher on the Shore D hardness scale, the decrease in rebound of the resulting golf ball can be suppressed. Also, if the material hardness is 69 or lower on the Shore D hardness scale, the resulting golf ball will have a good feel when struck. The material hardness of the cover layer containing (A) the base resin and (B) component is the slab hardness measured after molding the cover composition containing (A) the base resin and (B) component into a sheet.

[0085] The spherical core of the golf ball according to this disclosure is preferably formed from a resin composition or a rubber composition, and more preferably from a rubber composition. The spherical core can be formed, for example, by heating and pressing a rubber composition (hereinafter sometimes simply referred to as "rubber composition for core") that includes a base rubber, a co-crosslinking agent and a crosslinking initiator.

[0086] As the base rubber, it is preferable to use a high-cis polybutadiene with 40% or more by mass, preferably 70% or more by mass, and more preferably 90% or more by mass, of which cis bonds are advantageous for rebound. As the cocrosslinking agent, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or its metal salt is preferred, and a metal salt of acrylic acid or a metal salt of methacrylic acid is more preferred. As the metal of the metal salt, zinc, magnesium, calcium, aluminum, and sodium are preferred, and zinc is more preferred. The amount of cocrosslinking agent used is preferably 15 parts by mass or more and 50 parts by mass or less per 100 parts by mass of base rubber. As the crosslinking initiator, an organic peroxide is preferably used. Specifically, examples of organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide, of which dicumyl peroxide is preferably used. The amount of crosslinking initiator added is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less, per 100 parts by mass of the base rubber.

[0087] Furthermore, the core rubber composition may also contain an organic sulfur compound. Examples of the organic sulfur compound include compounds belonging to the diphenyl disulfide group (diphenyl disulfide, bis(pentabromophenyl) disulfide, etc.), thiophenols, or thionaphthols. The amount of the organic sulfur compound is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, preferably 5.0 parts by mass or less, and more preferably 3.0 parts by mass or less, per 100 parts by mass of the base rubber. The core rubber composition may further contain a carboxylic acid and / or its salt. As the carboxylic acid and / or its salt, a carboxylic acid having 1 to 30 carbon atoms and / or its salt is preferred. As the carboxylic acid, either an aliphatic carboxylic acid (caprylic acid, etc.) or an aromatic carboxylic acid (benzoic acid, etc.) can be used. The amount of the carboxylic acid and / or its salt is preferably 1 part by mass or more and 40 parts by mass or less, per 100 parts by mass of the base rubber.

[0088] In addition to the base rubber, co-crosslinking agent, crosslinking initiator, and organic sulfur compound, the core rubber composition may also contain, as appropriate, weight adjusters such as zinc oxide and barium sulfate, antioxidants, colorants, and the like.

[0089] [Golf ball structure] The structure of the golf ball of this disclosure is not particularly limited as long as it has a spherical core and one or more covers covering the spherical core. For example, a two-piece golf ball comprising a single spherical core and a single cover covering the spherical core, wherein the single cover contains (A) a base resin and (B) a component; a three-piece golf ball comprising a single spherical core, an inner cover covering the spherical core, and an outer cover covering the inner cover, wherein either the inner cover or the outer cover, or both, contain (A) a base resin and (B) a component; a single spherical core, two or more inner covers covering the spherical core, and the inner cover Examples include a multi-piece golf ball (such as a four-piece golf ball or a five-piece golf ball) comprising a single spherical core, two or more inner covers covering the spherical core, and an outermost cover covering the inner covers, wherein at least one of the two or more inner covers contains (A) a base resin and (B) a component; and a multi-piece golf ball (such as a four-piece golf ball or a five-piece golf ball) comprising a single spherical core, two or more inner covers covering the spherical core, and an outermost cover covering the inner covers, wherein the outermost cover contains (A) a base resin and (B) a component.

[0090] A multi-piece golf ball (such as a four-piece golf ball or a five-piece golf ball) comprising a single spherical core, two or more inner layers covering the spherical core, and an outermost layer covering the inner layers, wherein at least one layer of the two or more inner layers contains (A) a base resin and (B) component, it is preferable that the outermost layer of the inner layers contains (A) a base resin and (B) component, and all layers of the inner layers may contain (A) a base resin and (B) component.

[0091] A multi-piece golf ball (such as a four-piece golf ball or a five-piece golf ball) comprising a single spherical core, two or more inner layers covering the spherical core, and an outermost layer covering the inner layers, wherein the outermost layer cover contains (A) a base resin and (B) a component, and further, at least one layer of the two or more inner layers cover may also contain (A) a base resin and (B) a component. In this case, it is preferable that the outermost layer of the inner layers cover contains (A) a base resin and (B) a component, and all layers of the inner layers cover may contain (A) a base resin and (B) a component.

[0092] The diameter of the spherical core of the golf ball disclosed herein is preferably 37.0 mm or more, more preferably 37.5 mm or more, even more preferably 38.0 mm or more, preferably 42.2 mm or less, more preferably 41.8 mm or less, even more preferably 41.5 mm or less, and most preferably 41 mm or less. If the diameter of the spherical core is 37.0 mm or more, the thickness of the cover will not become too thick, resulting in better rebound. On the other hand, if the diameter of the spherical core is 42.2 mm or less, the cover will not become too thin, allowing the cover to function better.

[0093] For the spherical core with a diameter of 37.0 mm to 42.2 mm, the amount of compressive deformation (the amount the center shrinks in the compression direction) from an initial load of 98 N to a final load of 1275 N is preferably 2.0 mm or more, more preferably 2.1 mm or more, even more preferably 2.2 mm or more, preferably 5.0 mm or less, more preferably 4.9 mm or less, and even more preferably 4.8 mm or less. If the amount of compressive deformation is 2.0 mm or more, the feel of hitting the ball will be better, and if it is 5.0 mm or less, the rebound performance will be better.

[0094] The thickness of the golf ball cover according to this disclosure is preferably 0.5 mm or more, more preferably 0.7 mm or more, even more preferably 0.9 mm or more, preferably 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.0 mm or less. This is because if the cover thickness is within the above range, the decrease in the durability and abrasion resistance of the cover can be further suppressed. If the cover has multiple layers, it is preferable that the total thickness of the multiple layers is within the above range.

[0095] If the golf ball of this disclosure has two or more inner layer covers and an outermost layer cover, the total thickness of the inner layer covers is preferably 0.5 mm or more, more preferably 0.6 mm or more, even more preferably 0.7 mm or more, preferably 4.0 mm or less, more preferably 3.5 mm or less, and even more preferably 3.0 mm or less. Furthermore, the thickness of each layer of the inner layer covers is preferably 0.3 mm or more, more preferably 0.4 mm or more, even more preferably 0.5 mm or more, preferably 2.0 mm or less, more preferably 1.8 mm or less, and even more preferably 1.6 mm or less.

[0096] The thickness of the outermost cover is preferably 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.0 mm or less. The thickness of the outermost cover is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.5 mm or more. This is because if the thickness of the outermost cover is within the above range, the resulting golf ball will have better rebound and feel.

[0097] The total number of dimples formed on the cover is preferably between 200 and 500. If the total number of dimples is less than 200, the effect of the dimples is difficult to obtain. Also, if the total number of dimples exceeds 500, the size of each dimple becomes smaller, making it difficult to obtain the effect of the dimples. The shape of the formed dimples (planar view shape) is not particularly limited, and may be a circle; a polygon such as a roughly triangular, roughly square, roughly pentagon, roughly hexagon; or other irregular shapes; used individually or in combination of two or more types.

[0098] The diameter of the golf ball in this disclosure is preferably 40 mm to 45 mm. From the viewpoint of meeting the standards of the United States Golf Association (USGA), a diameter of 42.67 mm or more is particularly preferred. From the viewpoint of suppressing air resistance, a diameter of 44 mm or less is more preferred, and 42.80 mm or less is particularly preferred. The mass of the golf ball is preferably 40 g to 50 g. From the viewpoint of obtaining a large inertia, a mass of 44 g or more is more preferred, and 45.00 g or more is particularly preferred. From the viewpoint of meeting the standards of the USGA, a mass of 45.93 g or less is particularly preferred.

[0099] In the golf balls of this disclosure, when the diameter is 40 mm to 45 mm, the amount of compression deformation (the amount the golf ball shrinks in the compression direction) when an initial load of 98 N is applied and a final load of 1275 N is applied is preferably 2.0 mm or more, more preferably 2.4 mm or more, even more preferably 2.5 mm or more, most preferably 2.8 mm or more, preferably 5.0 mm or less, and more preferably 4.5 mm or less. Golf balls with a compression deformation of 2.0 mm or more are not too hard and have a good feel when hit. On the other hand, by making the compression deformation amount 5.0 mm or less, the rebound performance is increased.

[0100] [How to manufacture Golball] The spherical core of the golf ball according to this disclosure can be formed, for example, by heating and pressing a rubber composition for spherical cores. The heating and pressing conditions for the rubber composition for the core can be set appropriately according to the rubber composition, but it is generally preferable to heat at 130°C to 200°C for 10 to 60 minutes, or to heat at 130°C to 150°C for 20 to 40 minutes, followed by heating in two stages at 160°C to 180°C for 5 to 15 minutes.

[0101] Methods for molding the golf ball cover according to this disclosure include, for example, a method of molding a hollow shell from the cover composition and then compression molding the core with multiple shells (preferably, a method of molding a hollow half-shell from the cover composition and then compression molding the spherical core with two half-shells), or a method of directly injection molding the cover composition onto the spherical core. The golf ball cover according to this disclosure is preferably molded by injection molding. This is because the cover can be produced more easily by employing injection molding.

[0102] When forming a cover by compression molding, the half-shell can be formed by either compression molding or injection molding, but compression molding is preferred. Conditions for compression molding the cover composition into a half-shell include, for example, a pressure of 1 MPa to 20 MPa and a molding temperature of -20°C to 70°C relative to the flow start temperature of the cover composition. By using these molding conditions, a half-shell with a uniform thickness can be formed. As a method for forming a cover using a half-shell, for example, a method of covering a spherical core with two half-shells and then compression molding can be used. Conditions for compression molding the half-shell into a cover include, for example, a molding pressure of 0.5 MPa to 25 MPa and a molding temperature of -20°C to 70°C relative to the flow start temperature of the cover composition. By using these molding conditions, a golf ball cover with a uniform cover thickness can be formed.

[0103] When forming a cover by injection molding of a cover composition, the cover composition may be injection molded using pelletized cover composition obtained by extrusion, or the cover material, such as base resin components and pigments, may be dry blended and directly injection molded. For the upper and lower molds used for cover molding, it is preferable to use molds having hemispherical cavities and pimples, with a portion of the pimples serving as movable hold pins. The cover can be formed by injection molding, for example, by protruding the hold pins, inserting and holding the core, injecting the cover composition, and then cooling. This is done by injecting the cover composition, heated to 200°C to 250°C, into a mold clamped at a pressure of 9 MPa to 15 MPa, in 0.5 to 5 seconds, cooling for 10 to 60 seconds, and then opening the mold.

[0104] When molding a cover using an injection molding machine having an injection device and a molding die, the temperature at the cylinder (barrel) portion of the injection device (the set temperature of the device) is preferably 200°C or higher, more preferably 210°C or higher, preferably 270°C or lower, and preferably 260°C or lower. By keeping the temperature at the cylinder (barrel) portion within the above range, the fluidity of the cover composition can be maintained.

[0105] The golf balls with molded covers are removed from the mold and, if necessary, subjected to surface treatments such as deburring, cleaning, and sandblasting. A coating or markings can also be formed as desired. The thickness of the coating is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. This is because a thickness of less than 5 μm makes the coating prone to wear and loss with continuous use, and a thickness exceeding 50 μm reduces the dimple effect, thus decreasing the golf ball's flight performance.

[0106] Figure 2 is a partially cutaway cross-sectional view showing a golf ball 1 according to one embodiment of the present disclosure. The golf ball 1 has a spherical core 2, an inner layer cover 3 disposed on the outside of the spherical core 2, and an outer layer cover 4 disposed on the outside of the inner layer cover 3. A number of dimples 41 are formed on the surface of the outer layer cover 4. The portion of the surface of the outer layer cover 4 other than the dimples 41 is a land 42. In a preferred embodiment of the present disclosure, the outer layer cover 4, the inner layer cover 3, or both the outer layer cover 4 and the inner layer cover 3 contain (A) a base resin and (B) a polyrotaxane. [Examples]

[0107] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the examples below, and any modifications and modes of implementation that do not depart from the spirit of the present disclosure are included within the scope of the present disclosure.

[0108] [Evaluation Method] (1) Analysis of the surface condition of the cover cross-section The surface properties of the cover's cross-section were analyzed using a Keyence Vk-X100 shape analysis laser microscope. Each material was mixed using a twin-screw compounding extruder according to the formulations shown in Table 2 to prepare pelletized cover compositions. The extrusion conditions for the cover compositions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D ratio of 35. The mixture was heated to 160-230°C at the extruder die position. The resulting cover compositions were heated and pressed at 170°C under vacuum for 10 minutes to produce slabs with a thickness of 2.0 mm, a length of 130 mm, and a width of 130 mm. The interior of these slabs was cut with a razor blade to create the surface. The resulting cross-sections were observed to determine the arithmetic mean roughness Sa and the arithmetic mean curvature Spc of the peaks. The arithmetic mean roughness Sa and arithmetic mean curvature Spc are shown as the average values ​​of three measurements. Measurement conditions: Magnification: Observe a smooth surface at 100x magnification. Image processing: De-wavy image Smoothing: Median size 3x3 Reference plane setting → Surface shape correction (Plane tilt correction → Wavy removal × 2 (strength 20))

[0109] (2) Compression deformation amount (mm) The amount of deformation in the compressive direction (the amount the core shrinks in the compressive direction) was measured from when an initial load of 98N was applied to the core until a final load of 1275N was applied.

[0110] (3) Material hardness (Shore D hardness) Using the cover composition, a sheet approximately 2 mm thick was fabricated by injection molding (cylinder temperature 230°C) and stored at 23°C for two weeks. The hardness of this sheet was measured using an automated hardness tester (H. Barleys, DigiTest II) with three or more sheets stacked to avoid interference from the measurement substrate. The detector used was "Shore D". Furthermore, when measuring the material hardness of the cover composition, measurements were taken using a composition in which a predetermined material (component (B), such as titanium dioxide) was blended with (A) the base resin.

[0111] (4) Feel at impact Ten amateur golfers (advanced level) conducted a practical test using drivers, and each person evaluated the feel of their swing according to the following criteria. The golf ball's feel was determined by the most frequent rating among the ten participants. Evaluation Criteria ○: Less impact and good feel. △: Average. ×: The impact is too strong and the feeling is poor.

[0112] (5) Coefficient of restitution A 198.4g metal cylinder was impacted against each golf ball at a speed of 40 m / s. The velocities of the cylinder and the golf ball were measured before and after the impact, and the coefficient of restitution for each golf ball was calculated from the respective velocities and masses. Twelve measurements were taken for each golf ball, and the average value was taken as the coefficient of restitution for that golf ball. The coefficient of restitution for each golf ball is shown as an indexed value, with the coefficient of restitution of golf ball No. 11 set to 100.

[0113] (6)Durability Using an air gun, each golf ball was struck against a metal plate 150 times at a speed of 45 m / s. This test was performed 12 times for each golf ball. Evaluation criteria: ◎: After 150 collisions without damage, the object was subjected to an additional 20 collisions, and no damage occurred. ○: Of the 12 golf balls, none were damaged. △: Of the 12 golf balls, one was damaged. ×: Two or more of the 12 golf balls were damaged.

[0114] (7) Analysis of the surface condition of the cover cross-section For golf balls No. 3, 7, and 11, each material was mixed using a twin-screw compounding extruder according to the formulations shown in Table 2 to prepare pelletized cover compositions. The extrusion conditions for the cover compositions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D ratio of 35. The mixture was heated to 160-230°C at the extruder die position. The resulting cover compositions for golf balls No. 3, 7, and 11 were heated and pressed at 170°C under vacuum for 10 minutes to produce slabs with a thickness of 2.0 mm, a length of 130 mm, and a width of 130 mm. The inside of these slabs was cut with a razor blade and the surfaces were smoothed. The resulting cut surfaces were observed using a Keyence Vk-X100 shape analysis laser microscope.

[0115] [Golf ball manufacturing] (1) Fabrication of spherical cores A rubber composition with the formulation shown in Table 1 was kneaded and heated and pressed in upper and lower molds having hemispherical cavities to obtain a spherical core. Barium sulfate was added in an appropriate amount so that the mass of the resulting golf ball was 45.6 g.

[0116] [Table 1]

[0117] Polybutadiene rubber: JSR Corporation, "BR730 (High-Sys Polybutadiene)" Zinc acrylate: Manufactured by Nichishoku Techno Fine Chemical Co., Ltd., "ZNDA-90S" Zinc oxide: Manufactured by Toho Zinc Co., Ltd., "Ginrei® (registered trademark)" Barium sulfate: "Barium Sulfate BD" manufactured by Sakai Chemical Co., Ltd. Dicumyl peroxide: Manufactured by NOF Corporation, "Percumyl (registered trademark) D" Diphenyl disulfide: Manufactured by Sumitomo Seika Co., Ltd.

[0118] (2) Making the cover Pellet-shaped cover compositions were prepared by mixing each material using a twin-screw extruder according to the formulations shown in Table 2. The extrusion conditions for the cover compositions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D ratio of 35. The mixture was heated to 160-230°C at the position of the extruder die.

[0119] During cover molding, a holding pin was extended, a spherical core was inserted and held in place, and the mold was clamped under 80 tons of pressure. A cover composition heated to 260°C was injected into the mold in 0.3 seconds, cooled for 30 seconds, and the mold was opened to remove the golf ball. The surface of the resulting golf ball was sandblasted, marked, and then clear paint was applied. The paint was dried in a 40°C oven to obtain a golf ball with a diameter of 42.7 mm and a mass of 45.6 g.

[0120] [Table 2]

[0121] Hymiran 1555: Manufactured by Mitsui DuPont Polychemicals, a sodium ion-neutralized ethylene-methacrylic acid binary copolymer ionomer resin (melt flow rate (190℃ × 2.16kg load): 10g / 10min, flexural stiffness: 240MPa, material hardness: 60 (Shore D)). Hymiran 1605: Manufactured by Mitsui DuPont Polychemicals, a sodium ion-neutralized ethylene-methacrylic acid binary copolymer ionomer resin (melt flow rate (190℃ × 2.16kg load): 3g / 10min, flexural stiffness: 320MPa, material hardness: 65 (Shore D)). Hymiran AM7329: Manufactured by Mitsui DuPont Polychemicals, zinc ion neutralized ethylene-methacrylic acid binary copolymer ionomer resin (melt flow rate (190℃ × 2.16kg load): 5g / 10min, flexural stiffness: 221MPa, material hardness: 64 (Shore D)) SH1300P: Polyrotaxane manufactured by Advanced Soft Materials, Inc., "Celm® Superpolymer SH1300P (a polyrotaxane in which at least a portion of the hydroxyl groups of cyclodextrin are modified by caprolactone chains via -O-C3H6-O- groups, linear molecule: polyethylene glycol, chelating group: adamantyl group, molecular weight of linear molecule: 11,000, hydroxyl value: 40 mgKOH / g, total molecular weight: weight-average molecular weight 190,000)." SH2400P: Polyrotaxane manufactured by Advanced Soft Materials, Inc., "Celm® Superpolymer SH2400P (a polyrotaxane in which at least a portion of the hydroxyl groups of cyclodextrin are modified by caprolactone chains via -O-C3H6-O- groups, linear molecule: polyethylene glycol, chelating group: adamantyl group, molecular weight of linear molecule: 20,000, hydroxyl value: 76 mgKOH / g, total molecular weight: weight-average molecular weight 400,000)." SH3400P: Polyrotaxane manufactured by Advanced Soft Materials, Inc., "Celm® Superpolymer SH3400P (a polyrotaxane in which at least a portion of the hydroxyl groups of cyclodextrin are modified by caprolactone chains via -O-C3H6-O- groups, linear molecule: polyethylene glycol, chelating group: adamantyl group, molecular weight of linear molecule: 35000, hydroxyl value: 72.0 mgKOH / g, total molecular weight: weight-average molecular weight 700,000)." Polyethylene oxide 3350: Manufactured by Sigma-Aldrich. Polyethylene Oxide 35000: Manufactured by Sigma-Aldrich Polyethylene oxide 300000: Manufactured by Sigma-Aldrich. Polyethylene oxide 2000000: Manufactured by Sigma-Aldrich Titanium dioxide: Ishihara Sangyo Co., Ltd., "A220"

[0122] Table 2 shows the results of the evaluation of the obtained golf balls. From the results in Table 2, it can be seen that the golf ball of this disclosure, having a spherical core and one or more covers disposed on the outside of the spherical core, wherein at least one of the covers comprises (A) a base resin and (B) at least one selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and liquid polymer, and where Sa × Spc ≥ 100 is the arithmetic mean roughness of the surface of the cross-section of the cover and Spc is the arithmetic mean curvature of the peak, the golf ball of this disclosure has good feel when hit and excellent durability without reducing rebound.

[0123] Figures 3 and 4 are electron microscope images of the surface of the cross-section of the covers of golf balls No. 3 and No. 7 of this disclosure. It can be seen that the additive component (B) is finely dispersed in the base resin (A). Figure 5 shows the case where the cover contains only the base resin (A) and does not contain the additive component (B) (golf ball No. 11), and no dispersion originating from component (B) was observed. [Industrial applicability]

[0124] The golf ball disclosed herein offers excellent feel and durability without a decrease in rebound. [Explanation of Symbols]

[0125] 1: Golf ball, 2: Spherical core, 3: Inner layer cover, 4: Outer layer cover, 41: Dimple, 42: Land, 10: Polyrotaxane, 12: Cyclodextrin, 14: Linear molecule, 16: Sealing group, 18: Caprolactone chain

[0126] The golf ball of this disclosure (1) is a golf ball having a spherical core and one or more covers disposed outside the spherical core, At least one layer of the cover comprises (A) a base resin and (B) at least one selected from the group consisting of polyrotaxane, polyethylene oxide, polypropylene oxide, polycaprolactone, and liquid polymer. The present invention is characterized in that, when Sa is the arithmetic mean roughness of the surface of the cover cross-section and Spc is the arithmetic mean curvature of the peak, Sa × Spc ≥ 100.

[0127] The golf ball of this disclosure (2) is the golf ball of this disclosure (1) wherein the amount of component (B) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the base resin (A).

[0128] The golf ball of this disclosure (3) is the golf ball of this disclosure (1) or (2), wherein the component (B) is polyrotaxane and / or polyethylene oxide.

[0129] The golf ball of this disclosure (4) is the golf ball described in any one of the items (1) to (3) of this disclosure, wherein the number average molecular weight of the polyethylene oxide is 400 or more and 7 million or less.

[0130] The golf ball of the present disclosure (5) is the golf ball of any one of the present disclosures (1) to (4), wherein the polyrotaxane has a cyclodextrin and a linear molecule that skeweres the cyclic structure of the cyclodextrin, and a sealing group located at both ends of the linear molecule that prevents the detachment of the cyclodextrin, and at least a portion of the hydroxyl groups of the cyclodextrin is modified by a caprolactone chain via an -O-C3H6-O- group.

[0131] The golf ball of this disclosure (6) is the golf ball according to any one of the claims (1) to (5) of this disclosure, wherein the polyrotaxane has a linear molecule which is polyethylene glycol and the choke group which is an adamantyl group.

[0132] The golf ball of this disclosure (7) is the golf ball of any one of the items (1) to (6) of this disclosure, wherein the material hardness of the cover layer containing the base resin (A) and component (B) is 59 to 69 on the Shore D hardness scale.

[0133] The golf ball of this disclosure (8) is the golf ball of any one of the items (1) to (7) of this disclosure, wherein the base resin (A) contains an ionomer resin.

Claims

1. A golf ball having a spherical core and one or more covers disposed on the outside of the spherical core, At least one layer of the cover comprises (A) a base resin and (B) polyrotaxane and / or polyethylene oxide. The arithmetic mean roughness of the surface of the cut surface of the cover is Sa (μm), and the arithmetic mean curvature of the peak is Spc (mm). －１ A golf ball characterized in that, when ), 117 ≤ Sa × Spc ≤ 752.

2. The golf ball according to claim 1, wherein the amount of component (B) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the base resin (A).

3. The golf ball according to claim 1 or 2, wherein the number-average molecular weight of the polyethylene oxide is 400 or more and 7 million or less.

4. The polyrotaxane has a cyclodextrin, a linear molecule that skeweres the cyclic structure of the cyclodextrin, and a sealing group positioned at both ends of the linear molecule to prevent the detachment of the cyclodextrin, wherein at least a portion of the hydroxyl groups of the cyclodextrin are -O-C ３ H ６ A golf ball according to any one of claims 1 to 3, which is a polyrotaxane modified by a caprolactone chain via an -O- group.

5. The golf ball according to claim 4, wherein the polyrotaxane has a linear molecule which is polyethylene glycol and the choke group which is an adamantyl group.

6. The golf ball according to any one of claims 1 to 5, wherein the material hardness of the cover layer containing the base resin (A) and component (B) is 59 to 69 on the Shore D hardness scale.

7. The golf ball according to any one of claims 1 to 6, wherein the (A) base resin contains an ionomer resin.

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