Resin composition, golf ball shell, golf ball, and method for manufacturing golf ball

Abstract

To provide a resin composition for a golf ball hull excellent in weld growth, and excellent in strength; and to provide a golf ball hull, a golf ball and a manufacturing method of a golf ball.SOLUTION: A resin composition for a golf ball hull contains a 10-250 pts. mass partially cross-linked thermoplastic polyurethane resin to 100 pts. mass polyacetal resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition for a golf ball cover, a golf ball cover, a golf ball, and a method for manufacturing a golf ball. [Background technology]

[0002] Conventionally, golf balls generally comprise a core, an intermediate layer (sometimes called a mid layer or an intermediate layer), and a cover layer (see, for example, Patent Document 1 and Patent Document 2). The intermediate layer is generally an ionomer resin layer, and the cover layer is known to be a polyurethane resin layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-81554 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-12298 Summary of the Invention [Problem to be solved by the invention]

[0004] Golf balls are typically formed by injection molding, and if they do not have excellent weld elongation, they will crack. Naturally, they also require excellent strength. To achieve these properties, the ionomer resin layer and polyurethane resin layer described above are provided. If the ionomer layer and polyurethane layer could be combined into a single layer while maintaining the above properties, the number of manufacturing steps could be reduced, which would be beneficial. The present invention aims to solve these problems by providing a resin composition for a golf ball outer shell that has excellent weld elongation and strength, as well as a golf ball outer shell, a golf ball, and a method for manufacturing a golf ball that uses the resin composition. [Means for solving the problem]

[0005] In view of the above problems, the present inventors have conducted research and found that the above problems can be solved by blending a specific polyurethane resin with a polyacetal resin. Specifically, the above problems were solved by the following means. <1> A resin composition for a golf ball outer cover, comprising 100 parts by mass of a polyacetal resin and 10 to 250 parts by mass of a partially crosslinked thermoplastic polyurethane resin. <2> The resin composition is molded into a dumbbell test piece having an ASTM D638 Type I shape, in which molten resin is filled symmetrically from both ends to form weld lines, and when the dumbbell test piece is subjected to a tensile test at a rate of 10 mm / min, the break point is greater than the yield point. <1> The resin composition according to claim 1. <3> The partially crosslinked thermoplastic polyurethane resin is formed from a bifunctional polyol, a multifunctional polyol, a chain extender, and a diisocyanate. <1> or <2> The resin composition according to claim 1. <4> The average number of functional groups of the polyfunctional polyol (the number of hydroxy groups per molecule) is 2.01 to 3.0. <3> The resin composition according to claim 1. <5> the bifunctional polyol and the multifunctional polyol have a molar ratio (bifunctional polyol / multifunctional polyol) of 0.99 / 0.01 to 0.5 / 0.5; <3> or <4> The resin composition according to claim 1. <6> The chain extender is a bifunctional polyol. <3> ~ <5> The resin composition according to any one of the above. <7> The number average molecular weight of the bifunctional polyol is 500 to 3000, the number average molecular weight of the multifunctional polyol is 300 to 3000, and the molecular weight of the chain extender is 62 to 380. <3> ~ <6> The resin composition according to any one of the above. <8> a reaction molar ratio of the diisocyanate to the total of the bifunctional polyol, the multifunctional polyol, and the chain extender, [diisocyanate / (bifunctional polyol+multifunctional polyol+chain extender)], is 1.10 to 0.95; <3> ~ <7> The resin composition according to any one of the above. <9> <1> ~ <8> 10. A golf ball shell formed from the resin composition according to any one of claims 1 to 9. <10> <1> ~ <8> 1. A golf ball having an outer cover formed from the resin composition according to any one of claims 1 to 8. <11> The outer skin is provided on the surface of the core portion. <10> 2. The golf ball according to claim 1 . <12> <1> ~ <8> 10. A method for producing a golf ball, comprising injection molding the resin composition according to any one of the above items. [Effects of the Invention]

[0006] The present invention makes it possible to provide a resin composition for a golf ball shell that is excellent in weld elongation and strength, as well as a golf ball shell, a golf ball, and a method for manufacturing a golf ball. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a golf ball. [Figure 2] FIG. 2 is a diagram showing the relationship between the breaking point and the yield point when a tensile test is performed on a molded article having a weld. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified.

[0009] The resin composition for a golf ball shell of this embodiment (hereinafter sometimes simply referred to as "the resin composition of this embodiment") is characterized by containing 10 to 250 parts by mass of a partially crosslinked thermoplastic polyurethane resin per 100 parts by mass of a polyacetal resin. This configuration results in a resin composition for a golf ball shell that has high weld elongation and excellent strength. As a result, while golf balls have traditionally had two layers, an intermediate layer and a cover layer, formed on the surface of the core, it is now possible to form only the shell on the surface of the core. Furthermore, the shell of this golf ball can be manufactured by injection molding.

[0010] <Polyacetal resin> The resin composition of this embodiment contains a polyacetal resin, which can impart impact resistance while maintaining the hardness required of golf ball materials. The polyacetal resin is not particularly limited, and may be a homopolymer containing only divalent oxymethylene groups as constituent units, or a copolymer containing divalent oxymethylene groups and divalent oxyalkylene groups having 2 to 6 carbon atoms as constituent units.

[0011] Examples of the oxyalkylene group having 2 to 6 carbon atoms include an oxyethylene group, an oxypropylene group, and an oxybutylene group.

[0012] In the polyacetal resin, the proportion of oxyalkylene groups having 2 to 6 carbon atoms in the total number of moles of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms is not particularly limited, and may be 0.5 to 10 mol %.

[0013] To produce the polyacetal resin, trioxane is typically used as the main raw material. Furthermore, to introduce oxyalkylene groups having 2 to 6 carbon atoms into the polyacetal resin, cyclic formals or cyclic ethers can be used. Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, and 1,3,6-trioxocane. Specific examples of cyclic ethers include ethylene oxide, propylene oxide, and butylene oxide. To introduce oxyethylene groups into the polyacetal resin, 1,3-dioxolane can be used as the main raw material. To introduce oxypropylene groups, 1,3-dioxane can be used as the main raw material. To introduce oxybutylene groups, 1,3-dioxepane can be used as the main raw material. In addition, it is preferable that the amount of hemiformal terminal groups, formyl terminal groups, and terminal groups unstable to heat, acid, or base is small in polyacetal resins. Here, the hemiformal terminal group is represented by -OCHOH, and the formyl terminal group is represented by -CHO.

[0014] The melt index of the polyacetal resin (ASTM-D1238 standard: 190°C, 2.16 kg) is preferably 1.0 g / 10 minutes to 100 g / 10 minutes. The melting point of the polyacetal resin is preferably 180° C. or lower, and more preferably 175° C. or lower. The lower limit of the melting point is, for example, 160° C. or higher. The melting point in the present invention refers to the peak-top temperature of an endothermic peak observed by differential scanning calorimetry (DSC). The endothermic peak is the endothermic peak observed when a sample is heated and melted once to eliminate the influence of thermal history on crystallinity, and then heated again.

[0015] In addition to the above, the polyacetal resins that can be used include those described in paragraphs 0018 to 0043 of JP-A No. 2015-074724, the contents of which are incorporated herein by reference.

[0016] <Partially cross-linked thermoplastic polyurethane resin> The resin composition of this embodiment contains a partially crosslinked thermoplastic polyurethane resin, which effectively reduces tensile stress (modulus), increases elongation at break, thereby imparting flexibility, improving abrasion resistance, and increasing the coefficient of friction. The partially crosslinked thermoplastic polyurethane resin used in this embodiment is preferably formed from a bifunctional polyol, a multifunctional polyol, a chain extender, and a diisocyanate. By using such a partially crosslinked thermoplastic polyurethane resin, a shell having excellent weld elongation and strength can be obtained.

[0017] <<Bifunctional polyol>> The bifunctional polyol is a polyol having two hydroxy groups, and a wide variety of bifunctional polyols commonly used in the synthesis of polyurethane resins can be used. A linear polyether glycol having primary hydroxy groups at both ends is more preferred, and polytetramethylene glycol ether is even more preferred. The number average molecular weight of the bifunctional polyol is preferably 500 to 3000, more preferably 800 to 2500. The number average molecular weight is a value calculated in polystyrene equivalent terms according to GPC. The bifunctional polyol may be used alone or in combination of two or more kinds.

[0018] <<Multifunctional polyol>> The polyfunctional polyol is a compound having two or more hydroxyl groups at its terminals, and a wide range of polyols commonly used in the synthesis of polyurethane resins can be used. The upper limit of the number of hydroxyl groups in the polyfunctional polyol is preferably three or less. The average number of functional groups (the number of hydroxy groups per molecule) of the polyol used in this embodiment is preferably 2.01 to 3.0, and more preferably 2.1 to 2.5. By setting it within this range, flexibility according to the purpose and application can be imparted, and various physical properties can be more effectively improved. Specifically, examples of polyols used in the synthesis of polyurethane resins include polyether polyols, polymer polyols, and polyester polyols, with polyester polyols being preferred. The polyester polyol is more preferably a polyester obtained by polycondensation of an aliphatic bifunctional polyol and / or an aliphatic polyol (preferably an aliphatic triol) with a carboxylic acid. As the bifunctional polyol used as a raw material for polyester polyol, an aliphatic bifunctional polyol having 3 to 10 carbon atoms is preferred, and 1,4-butanediol is more preferred. As the polyol used as a raw material for polyester polyol, a triol and / or a tetraol is preferred, and an aliphatic triol having 3 to 12 carbon atoms is preferred, and trimethylolpropane is more preferred. As the dicarboxylic acid used as a raw material for polyester polyol, a dicarboxylic acid having 4 to 10 carbon atoms is preferred, and an aliphatic dicarboxylic acid having 4 to 10 carbon atoms is more preferred, and adipic acid and sebacic acid are even more preferred, and adipic acid is even more preferred.

[0019] The number average molecular weight of the polyfunctional polyol used in the synthesis of the polyurethane resin is preferably 300 to 3000, more preferably 500 to 2500. The number average molecular weight is a value calculated in polystyrene equivalent terms according to GPC. The polyfunctional polyol may be used alone or in combination of two or more kinds.

[0020] <<Chain extender>> The type of chain extender used in synthesizing the polyurethane resin is not particularly limited, and for example, a low molecular weight compound having two or more terminal hydroxy groups can be used, with a low molecular weight compound having two to three terminal hydroxy groups being preferred. Examples of chain extenders include bifunctional polyols having 2 to 10 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol. The molecular weight of the chain extender is preferably 62-380. The chain extender may be used alone or in combination of two or more. The amount of the chain extender to be added is preferably 20 to 30 moles per 100 moles of the total of the bifunctional polyol, the multifunctional polyol, and the diisocyanate.

[0021] <<Diisocyanate>> As the diisocyanate, a wide range of diisocyanates generally used in the synthesis of polyurethane resins can be used. The diisocyanate is not particularly limited, and examples thereof include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate (4,4'-methylene diphenyl diisocyanate) and 2,4-tolylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, and aliphatic diisocyanates such as hexamethylene diisocyanate. Aromatic diisocyanates are preferred, and 4,4'-diphenylmethane diisocyanate is more preferred. The diisocyanates may be used alone or in combination of two or more.

[0022] <<Polyurethane resin manufacturing method>> The method for producing a polyurethane resin used in this embodiment includes a step of reacting a bifunctional polyol, a multifunctional polyol, a chain extender, and a diisocyanate. After the bifunctional polyol, the multifunctional polyol, and the diisocyanate are reacted to obtain a prepolymer, the chain extender may be added. The bifunctional polyol and multifunctional polyol used as raw materials for the polyurethane resin preferably have a molar ratio (bifunctional polyol / multifunctional polyol) of 0.99 / 0.01 to 0.5 / 0.5. The effect of the present invention is that the hardness of the resin composition can be determined by changing the molar ratio according to the purpose and application. Furthermore, the reaction molar ratio of diisocyanate to the total of bifunctional polyol, multifunctional polyol, and chain extender as raw materials for the polyurethane resin, [diisocyanate / (bifunctional polyol + multifunctional polyol + chain extender)], is preferably 1.10 to 0.95, and more preferably 1.08 to 0.99. By setting it in this range, flexibility and physical properties according to the purpose and application can be more effectively exhibited.

[0023] <<Physical properties of polyurethane resin>> The polyurethane resin used in this embodiment preferably has a flow initiation temperature of 160°C or higher, more preferably 165°C or higher, even more preferably 170°C or higher, and even more preferably 175°C or higher. By setting the flow initiation temperature at or above the lower limit, dispersibility when compounded with a polyacetal resin tends to be improved. There is no particular upper limit to the flow initiation temperature, but an example is 190°C or lower. When two or more polyurethane resins are contained, the temperature is the temperature at which the mixture begins to flow. The flow initiation temperature is measured according to the method described in the Examples section below.

[0024] Meanwhile, the content of the partially crosslinked thermoplastic polyurethane resin in the resin composition of this embodiment is 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 60 parts by mass or more, even more preferably 65 parts by mass or more, and even more preferably 75 parts by mass or more, per 100 parts by mass of the polyacetal resin. By ensuring that the content is above the lower limit, impact resistance tends to be further improved. Furthermore, the content of the partially crosslinked thermoplastic polyurethane resin is 250 parts by mass or less, preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 120 parts by mass or less, even more preferably 95 parts by mass or less, and even more preferably 85 parts by mass or less, per 100 parts by mass of the polyacetal resin. By ensuring that the content is below the upper limit, the hardness and impact resistance required of golf ball materials can be further improved.

[0025] In the resin composition of this embodiment, the total content of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more, with the upper limit being 100% by mass. The resin composition of the present embodiment may contain only one polyacetal resin and one partially crosslinked thermoplastic polyurethane resin, or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0026] <Other ingredients> In addition to the above, the resin composition of this embodiment may contain other components within the scope of the present invention. Examples of other components include thermoplastic resins other than polyacetal resins, pigments, dispersants, antioxidants, antioxidants, UV absorbers, light stabilizers, weather stabilizers, antistatic agents, and fillers. When these additives are added, the amount of each additive is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 4 parts by mass or less, per 100 parts by mass of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin combined. The resin composition of the present embodiment may be configured to be substantially free of ionomer resin, which means that the amount of ionomer resin is 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin combined.

[0027] <Method of manufacturing resin composition> The resin composition of the present embodiment contains the above-mentioned essential components and, if necessary, the above-mentioned optional components, and can be produced by any method known in the art, by mixing and kneading these raw materials.

[0028] Examples of the kneading machine include a kneader, a Banbury mixer, an extruder, etc. There are no particular limitations on the various conditions and devices for mixing and kneading, and they may be appropriately selected from any conventionally known conditions. Kneading is preferably carried out at a temperature above the melting point of the polyacetal resin, specifically above the melting point of the polyacetal resin (generally 180°C or higher, preferably 210°C or lower).

[0029] <Physical properties of resin composition> The resin composition of this embodiment is preferably molded into an ASTM D638 Type I dumbbell test piece, in which molten resin is filled symmetrically from both ends to form a weld line, and the dumbbell test piece is subjected to a tensile test at a rate of 10 mm / min. When a polyacetal resin and a thermoplastic polyurethane resin are mixed, a dumbbell test piece with a weld line breaks before reaching the yield point due to poor adhesion at the weld. In this patent, the degree of adhesion at the weld line can be measured by determining whether the break point of the dumbbell test piece with a weld is greater than the yield point.

[0030] <Golf ball shell and golf ball> Next, the outer cover and the golf ball of this embodiment will be described. FIG. 1 is a schematic cross-sectional view of a golf ball, in which 1 indicates the golf ball, 2 indicates the outer shell of the golf ball, and 3 indicates the core of the golf ball. The outer shell of this embodiment is formed from the resin composition of this embodiment. By using such an outer shell, an outer shell that serves both as an intermediate layer and a cover layer can be obtained. In other words, while conventional golf balls have an intermediate layer and a cover layer formed on the surface of the core, the outer shell of this embodiment can be configured to serve both as an intermediate layer and a cover layer. In other words, a golf ball can be formed in which the outer shell of this embodiment is formed on the surface of the core. Here, the term "on the surface of the core" refers to a layer that replaces the conventional intermediate layer and cover layer, and includes a case in which a layer that was conventionally formed between the core and the outer shell is formed between the core and the outer shell. Furthermore, a decorative layer, such as a paint layer, may be formed on the surface of the outer shell. In addition, although the core portion is shown as one region in FIG. 1, it may be shown as two regions, an inner core portion and an outer core portion.

[0031] The golf ball can be manufactured by any known method, but is preferably manufactured by a method that includes injection molding the resin composition of the present embodiment. For details of the golf ball manufacturing method, see, for example, paragraphs

[0109] to

[0117] of JP 2013-81554 A, the contents of which are incorporated herein by reference. [Example]

[0032] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance.

[0033] 1. Raw materials Polyacetal resin POM1: Polyacetal resin (MI: 50 g / 10 min), an oxymethylene copolymer of trioxane and 1,3-dioxolane, containing 1.5 mol% of oxyethylene units (melt index (MI) is measured in accordance with ASTM-D1238 at 190°C under a load of 2.16 kg), melting point: 166°C

[0034] Tetramethylene glycol: Polytetramethylene glycol ether 1,4BG-adipate: Polycondensation product of 1,4-butanediol and adipic acid 1.4BG / TM adipate: Polycondensation product of 1,4-butanediol, trimethylolpropane and adipic acid Chain extender: 1,4-butanediol Diisocyanate: 4,4'-diphenylmethane diisocyanate (MDI)

[0035] <Polyurethane Synthesis Examples 1 and 2 and Comparative Synthesis Examples 1 and 2> The difunctional polyol, multifunctional polyol, and chain extender (1,4-butanediol) shown in Table 1 were sequentially added to a 2-liter reaction flask in the amounts shown in the table, and the mixture was stirred and mixed while heated to 100°C. Finally, 4,4'-diphenylmethane diisocyanate was added in the amount also shown in the table, and after stirring at high speed for 1 minute, the mixture was poured into a stainless steel tray coated with a silicone agent to provide mold release properties, and then reacted and aged for 12 hours at 90°C to 100°C. The reaction product was crushed into flakes, granulated in an extruder, and pelletized to obtain a thermoplastic polyurethane resin composition. The components shown in Table 1 were sequentially added to a 1-L reaction vessel and stirred. When the reaction polymer reached 100°C, the polymer was poured into a tray and formed into a plate. This plate was then heated and solidified in an oven at 100°C for approximately 10 minutes to obtain a thermoplastic polyurethane resin. The plate-shaped thermoplastic polyurethane resin was then crushed into flakes using a crusher. The resulting thermoplastic polyurethane resin flakes were extruded in a single-screw extruder at a molding temperature of 180°C to 210°C to produce pellets.

[0036] <Polyurethane flow temperature (℃)> The obtained pellets were used for measurement in accordance with JIS K7311.

[0037] <100% modulus of polyurethane (MPa)> The obtained pellets were used for measurement in accordance with JIS K7311.

[0038] <Tensile strength of polyurethane (MPa)> The obtained pellets were used for measurement in accordance with JIS K7311.

[0039] <Polyurethane elongation (%)> The obtained pellets were used for measurement in accordance with JIS K7311.

[0040] <Hardness of polyurethane (JISA)> The obtained pellets were used for measurement in accordance with JIS K7311.

[0041] [Table 1]

[0042] In Table 1 above, the molecular weights of the bifunctional polyols and polyols indicate number average molecular weights, which are values ​​calculated in terms of polystyrene according to GPC.

[0043] 2. Examples 1 and 2 and Comparative Examples 1 and 2 The polyacetal resin and polyurethane resin were pre-blended as shown in Table 2, and then the mixture was fed into the main feed port of a 26 mm diameter twin-screw extruder equipped with one vent port and melt-mixed (extrusion conditions: L / D = 48, extrusion temperature = 190°C, screw rotation speed = 200 rpm) to prepare a pellet-shaped resin composition. Next, the pellets were used to produce ISO dumbbells by injection molding, and notches with a notch radius of 0.25 mm and a depth of 2 mm were applied using a notching machine.Then, the Charpy impact strength was measured using a 1 J hammer in a Charpy impact tester. Similarly, the above pellets were used by injection molding to fill both ends of an ASTM Type I shaped dumbbell with molten resin, creating a dumbbell with a visible weld line in the center. The dumbbell was subjected to a tensile test at a speed of 10 mm / min to confirm the break point. The weld elongation was evaluated as A if the break point was larger than the yield point, and B if it was smaller. Materials with inelastic welds break before reaching the yield point. As shown in Figure 2, a material that does not break even after exceeding the yield point is an indicator of strong weld elongation.

[0044] [Table 2]

[0045] As is clear from the above results, the resin compositions of the present invention had high Charpy notched impact strength and strong weld elongation (Examples 1 and 2). In contrast, the resin compositions of the comparative examples had low Charpy notched impact strength and weak weld elongation (Comparative Examples 1 and 2). [Explanation of symbols]

[0046] 1 golf ball 2 Hull 3 Core

Claims

1. The composition contains 75 to 85 parts by mass of a partially crosslinked thermoplastic polyurethane resin relative to 100 parts by mass of a polyacetal resin, the partially crosslinked thermoplastic polyurethane resin is formed from a bifunctional polyol, a multifunctional polyol, a chain extender, and a diisocyanate; the average functionality of the polyfunctional polyol (the number of hydroxy groups per molecule) is 2.01 to 3.0; a golf ball having an outer shell formed from a resin composition in which the bifunctional polyol and the multifunctional polyol have a molar ratio (bifunctional polyol / multifunctional polyol) of 0.99 / 0.01 to 0.5 / 0.5; the total amount of the polyacetal resin and the partially crosslinked thermoplastic polyurethane resin in the resin composition is more than 99% by mass, The outer skin is provided on the surface of the core portion, the partially crosslinked thermoplastic polyurethane resin has a flow initiation temperature of 160°C or higher and 190°C or lower, as measured in accordance with JIS K7311; an ISO dumbbell formed from the resin composition is notched to a notch radius of 0.25 mm and a depth of 2 mm, and the Charpy impact strength measured using a 1 J hammer in a Charpy impact tester is 27 to 30 kJ / m 2 ; A molten resin composition is filled into both ends of an ASTM Type I dumbbell to produce a dumbbell with a weld line in the center. When the dumbbell is subjected to a tensile test at a rate of 10 mm / min, the break point is greater than the yield point. Golf ball.

2. 2. The golf ball of claim 1, wherein the chain extender is a difunctional polyol.

3. 3. The golf ball according to claim 1, wherein the bifunctional polyol has a number average molecular weight of 500 to 3,000, the multifunctional polyol has a number average molecular weight of 300 to 3,000, and the chain extender has a molecular weight of 62 to 380.

4. 4. The golf ball according to claim 1, wherein the reaction molar ratio of the diisocyanate to the total of the bifunctional polyol, the multifunctional polyol, and the chain extender, [diisocyanate / (bifunctional polyol+multifunctional polyol+chain extender)], is 1.10 to 0.

95.

5. The method for producing the golf ball according to any one of claims 1 to 4, comprising injection molding the resin composition.

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