JP4937026B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly, to improvement of scuff resistance and durability of a golf ball having a urethane cover.

  As the base resin constituting the cover of the golf ball, ionomer resin or polyurethane is used. Covers made of ionomer resin are widely used because of their excellent resilience, durability, and workability. However, they have a high rigidity and hardness, resulting in poor shot feel and sufficient spin performance. Has been pointed out, such as poor control and poor control. On the other hand, polyurethane is used as the base resin constituting the cover because the shot feeling and spin characteristics are improved as compared with the ionomer resin. For example, Patent Documents 1 to 3 disclose that a thermosetting polyurethane is used for the cover, and Patent Documents 4 and 5 disclose that a thermoplastic polyurethane is used for the cover. However, when thermosetting polyurethane is used for the cover, a golf ball having excellent scratch resistance can be obtained, but the manufacturing process of the golf ball is complicated. Further, golf balls using thermoplastic polyurethane as a cover are not sufficient in scuff resistance and durability compared to the case where thermosetting polyurethane is used.

  For example, Patent Documents 6 to 10 are known as techniques for improving a cover using thermoplastic polyurethane. In Patent Document 6, in a solid golf ball in which a solid core and a cover are coated on the solid core, the resin component forming the cover is mainly composed of a reaction product of a thermoplastic polyurethane elastomer and blocked isocyanate. A golf ball characterized in that is disclosed. Patent Documents 7 to 9 disclose an isocyanate in which a thermoplastic polyurethane material and an isocyanate compound having two or more isocyanate groups as functional groups in one molecule are dispersed in a thermoplastic resin that does not substantially react with isocyanate. A golf ball having a cover formed of a composition containing the mixture is disclosed.

Patent Document 10 discloses that a thermoplastic resin composition selected from the group consisting of a thermoplastic block copolymer, a polyester elastomer, a polyamide elastomer, and a polyolefin modified with a functional group having reactivity with isocyanate, an isocyanate compound or A golf ball having a cover as a main component is a mixture of an isocyanate mixture having two or more isocyanate groups as functional groups in one molecule and a thermoplastic polyurethane elastomer.
Japanese Patent Laid-Open No. 51-74726 Japanese Patent No. 2662909 U.S. Pat. No. 4,123,061 U.S. Pat. No. 3,395,109 U.S. Pat. No. 4,248,432 Japanese Patent Laid-Open No. 11-178949 JP 2002-336378 A JP 2002-363380 A JP 2002-336386 A JP 2005-253962 A

  However, as disclosed in Patent Documents 6 to 10, when a low molecular weight polyisocyanate is used, the cover obtained by crosslinking becomes hard, so that the effect of improving the scratch resistance and durability is small. was there. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball having excellent abrasion resistance and durability.

  A golf ball that has solved the above-described problems is a golf ball having a core and a cover, and the cover includes, as a resin component, a thermoplastic polyurethane (A) and a urethane prepolymer having at least two isocyanate groups. It is formed with the composition for a cover containing the polyisocyanate mixture (B) which disperse | distributed the polymer (b-1) in the thermoplastic resin (b-2) which does not react with an isocyanate group substantially. Features.

  That is, in this invention, compared with the low molecular weight polyisocyanate compound, the urethane prepolymer (b-1) having a large molecular weight was dispersed in the thermoplastic resin (b-2) that does not substantially react with the isocyanate group. Since the thermoplastic polyurethane (A) is crosslinked using the polyisocyanate mixture (B), the resulting cover does not become too hard, and the effect of improving the scratch resistance and durability is great.

  According to the present invention, the scratch resistance and durability of the obtained golf ball can be improved.

  The golf ball of the present invention is a golf ball having a core and a cover, and the cover includes, as a resin component, a thermoplastic polyurethane (A) and a urethane prepolymer (b-1) having at least two isocyanate groups. And a polyisocyanate mixture (B) dispersed in a thermoplastic resin (b-2) that does not substantially react with isocyanate groups. Hereinafter, the present invention will be described in detail.

  First, the thermoplastic polyurethane (A) will be described. The thermoplastic polyurethane (A) used in the present invention is not particularly limited as long as it has a plurality of urethane bonds in the molecule and exhibits thermoplasticity. For example, urethane can be obtained by reacting polyisocyanate and polyol. The product is a product in which a bond is formed in the molecule, and can be obtained by a chain extension reaction with a low molecular weight polyol or polyamine, if necessary.

The polyisocyanate component constituting the thermoplastic polyurethane (A) is not particularly limited as long as it has two or more isocyanate groups. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4 -Mixture of toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitrylene-4,4'- diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), aromatic polyisocyanates such as p-phenylene diisocyanate (PPDI); 4,4'-dicyclohexylmethane diisocyanate (H ₂ MDI), hydrogenated xylylene diisocyanate _(H 6 XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1 of cycloaliphatic polyisocyanates or aliphatic polyisocyanates such as norbornene diisocyanate (NBDI) Seeds or a mixture of two or more.

From the viewpoint of improving the scratch resistance, it is preferable to use an aromatic polyisocyanate as the polyisocyanate component of the thermoplastic polyurethane (A). By using the aromatic polyisocyanate, the mechanical properties of the resulting polyurethane are improved, and a cover having excellent scratch resistance can be obtained. From the viewpoint of improving weather resistance, non-yellowing polyisocyanate (TMXDI, XDI, HDI, H ₆ XDI, IPDI, H ₁₂ MDI, NBDI, etc.) is used as the polyisocyanate component of the thermoplastic polyurethane (A). It is preferable to use 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI). This is because 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI) has a rigid structure, the mechanical properties of the resulting polyurethane are improved, and a cover having excellent scratch resistance can be obtained.

  The polyol component constituting the thermoplastic polyurethane (A) is not particularly limited as long as it has a plurality of hydroxyl groups, and examples thereof include a low molecular weight polyol and a high molecular weight polyol. Examples of the low molecular weight polyol include ethylene glycol, diethylene glycol, triethylene glycol, propanediol (eg, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, etc.), Dipropylene glycol, butanediol (eg, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, etc. ), Diols such as neopentyl glycol, pentanediol, hexanediol, heptanediol, octanediol, 1,6-cyclohexanedimethylol, aniline diol, bisphenol A diol; glycerol, trimethylolpropane, hexanetriol, etc. bird Lumpur; pentaerythritol, tetraol or a hexanol such as sorbitol. Examples of the high molecular weight polyol include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA) ), Condensation-type polyester polyols such as polyhexamethylene adipate (PHMA); lactone-type polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols, etc. It may be a mixture of at least two kinds of polyols.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 400 or more, and more preferably 1,000 or more, for example. This is because if the number average molecular weight of the high molecular weight polyol is too small, the resulting polyurethane becomes hard and the feel at impact of the golf ball is lowered. The upper limit of the number average molecular weight of the high molecular weight polyol is not particularly limited, but is 10,000, more preferably 8,000.

  Moreover, the polyamine which comprises the said thermoplastic polyurethane as needed is not specifically limited if it has at least 2 or more amino groups. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine and hexamethylenediamine, alicyclic polyamines such as isophoronediamine and piperazine, and aromatic polyamines.

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

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

  Although it does not specifically limit as a structural aspect of the said thermoplastic polyurethane (A), For example, the aspect comprised by the polyisocyanate component and the high molecular weight polyol component; Polyisocyanate component, high molecular weight polyol component, and low molecular weight An embodiment constituted by a polyol component; an embodiment constituted by a polyisocyanate component, a high molecular weight polyol component, a low molecular weight polyol component and a polyamine component; and constituted by a polyisocyanate component, a high molecular weight polyol component and a polyamine component An aspect etc. can be mentioned.

  Next, the polyisocyanate mixture (B) in which the urethane prepolymer (b-1) having at least two isocyanate groups is dispersed in the thermoplastic resin (b-2) that does not substantially react with the isocyanate groups will be described. To do.

  The urethane prepolymer (b-1) is a compound having a plurality of urethane bonds in the molecule and having two or more isocyanate groups, and having a lower molecular weight than the thermoplastic polyurethane (A). For example, an isocyanate group-terminated urethane prepolymer in which a urethane bond is formed in a molecule can be exemplified by reacting a polyisocyanate component and a polyol component under conditions where the polyisocyanate component is excessive. . The mixing ratio of the polyisocyanate component and the polyol component is preferably such that the molar ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate component to the hydroxyl group (OH) of the polyol component is 1.1 or more. More preferably, it is 1.3 or more, More preferably, it is 1.5 or more, It is preferable to set it as 3.0 or less, More preferably, it is 2.5 or less, More preferably, it is 2.0 or less.

  The polyisocyanate component used as a raw material for the urethane prepolymer (b-1) is not particularly limited as long as it has two or more isocyanate groups. For example, the polyisocyanate component constituting the thermoplastic polyurethane (A) Can be mentioned as examples. The polyol component used as a raw material for the urethane prepolymer (b-1) is not particularly limited as long as it has a plurality of hydroxyl groups, and is exemplified as the polyol component constituting the thermoplastic polyurethane (A). Examples thereof include a low molecular weight polyol and a high molecular weight polyol.

Examples of the isocyanate group-terminated urethane prepolymer used as the urethane prepolymer (b-1) include TDI urethane prepolymers; MDI urethane prepolymers; H ₁₂ MDI urethane prepolymers, and the like. Prepolymer: H ₁₂ MDI urethane prepolymer is preferably used. Here, the TDI-based urethane prepolymer refers to an isocyanate group-terminated urethane prepolymer obtained by reacting TDI or a polyisocyanate compound containing this as a main component with a polyol (preferably PTMG). The MDI urethane prepolymer refers to an isocyanate group-terminated urethane prepolymer obtained by reacting MDI or a polyisocyanate compound containing this as a main component with a polyol (preferably PTMG), and is an H ₁₂ MDI urethane. The prepolymer refers to an isocyanate group-terminated urethane prepolymer obtained by reacting H ₁₂ MDI or a polyisocyanate compound containing this as a main component with a polyol (preferably PTMG).

  When the polyisocyanate component and the polyol component are reacted, a conventionally known catalyst used in the urethane reaction can be used. Examples of the catalyst include monoamines such as triethylamine and N, N-dimethylcyclohexylamine; N, N, N ′, N′-tetramethylethylenediamine, N, N, N ″, N ″ -pentamethyldiethylenetriamine and the like 1,8-diazabicyclo [5,4,0] -7-undecene (DBU), cyclic diamines such as triethylenediamine; tin-based catalysts such as dibutyltin dilaurate and dibutyltin diacetate; azelaic acid, olein Examples thereof include organic carboxylic acids such as acid and adipic acid.

  The isocyanate group amount (NCO%) of the urethane prepolymer (b-1) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more. 0 mass% or less is preferable, 7.0 mass% or less is more preferable, and 5.0 mass% or less is still more preferable. If the isocyanate group amount (NCO%) of the urethane prepolymer (b-1) is too low, there is no crosslinking effect and the scratch resistance may be deteriorated. If it is too high, the viscosity of the cover composition will increase excessively. There is a possibility that the moldability is deteriorated. In addition, the isocyanate group amount (NCO%) of the urethane prepolymer (b-1) is (the number of moles of isocyanate groups in the urethane prepolymer (b-1) × 42 (molecular weight of NCO)) / urethane prepolymer (b -1) total amount (g) × 100.

  The number average molecular weight of the urethane prepolymer (b-1) is, for example, preferably 1000 or more, more preferably 1500 or more, further preferably 2000 or more, preferably 30000 or less, more preferably 20000 or less, and further preferably 10,000 or less. preferable. By setting the number average molecular weight to 1000 or more, the distance between cross-linking points during the cross-linking reaction is increased, and the resulting polyurethane cover is not excessively hard and durability is improved. On the other hand, when the number average molecular weight exceeds 30000, the crosslinking point density is lowered, and the scuff resistance of the obtained cover may be lowered.

  The polyisocyanate component and polyol component constituting the urethane prepolymer can be appropriately selected from those described above as the components constituting the thermoplastic polyurethane (A).

  The number average molecular weight of the polyol component constituting the urethane prepolymer is preferably 650 or more, more preferably 700 or more, still more preferably 800 or more, preferably 10,000 or less, more preferably 5000 or less, and still more preferably 3000 or less. . By setting the number average molecular weight to 650 or more, the distance between cross-linking points during the cross-linking reaction is increased, and the resulting polyurethane cover is not excessively hard and durability is improved. On the other hand, when the number average molecular weight exceeds 10,000, the crosslinking point density is lowered, and the scuff resistance of the obtained cover may be lowered. The number average molecular weights of the urethane prepolymer (b-1) and the polyol component are determined by, for example, gel permeation chromatography (GPC), polystyrene as a standard substance, tetrahydrofuran as an eluent, and TSK-GEL SUPERH 2500 (manufactured by Tosoh Corporation). ) Measurement may be performed using two.

  The number of functional groups of the isocyanate group of the urethane prepolymer (b-1) used in the present invention is not particularly limited as long as it is 2 or more. For example, it may be trifunctional or tetrafunctional. A trifunctional or higher polyfunctional urethane prepolymer can be obtained by using a trifunctional or higher functional polyol or polyisocyanate constituting the urethane prepolymer.

  Examples of the trifunctional or higher functional polyisocyanate include polymeric MDI, triphenylmethane triisocyanate, tris (isocyanate phenyl) thiophosphate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, and 1,8-diisocyanate-4. -Trifunctional isocyanate such as isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate; isocyanurate of diisocyanate; obtained by reacting diisocyanate with low molecular weight triol such as trimethylolpropane or glycerin Adducts (preferably free diisocyanate has been removed); allophanate modified; burette modified etc. That. The allophanate-modified product is, for example, a trifunctional polyisocyanate obtained by further reacting a diisocyanate with a urethane bond formed by a reaction between a diisocyanate and a low molecular weight diol. The burette-modified product is, for example, a diisocyanate. It is a trifunctional polyisocyanate obtained by further reacting a diisocyanate with a urea bond formed by reaction with a low molecular weight diamine.

Among these, in this invention, it is a preferable aspect to use the bifunctional isocyanate group terminal urethane prepolymer shown by following formula (1).
Polyisocyanate- (polyol-polyisocyanate) n (1)

  In the formula (1), the number of connections n is preferably 1 or more and 10 or less, more preferably 5 or less, further preferably 4 or less, and further preferably 3 or less. By setting the number of connections n to 1 or more, the distance between cross-linking points during the cross-linking reaction is increased, and the resulting polyurethane cover is not excessively hard and durability is improved. On the other hand, when the number of connections n exceeds 10, the crosslinking point density is lowered, and the scuff resistance of the obtained cover may be lowered.

  The thermoplastic resin (b-2) that does not substantially react with the isocyanate group is substantially inactive with respect to the isocyanate group (those that have substantially no active hydrogen with respect to the isocyanate group). If there is, it is not particularly limited, for example, polystyrene resin, polyvinyl chloride resin, acrylic resin, ABS resin, ester rubber, polycarbonate resin, polyester resin (preferably polyethylene terephthalate), polyolefin, polyacetal, difluoride resin , Tetrafluoride resin, ionomer resin and the like. Among these, as the thermoplastic resin (b-2), a thermoplastic elastomer having rubber elasticity is preferable. For example, a group consisting of a polyester elastomer, an acrylic elastomer, a styrene elastomer, an olefin elastomer, and a vinyl chloride elastomer. It is preferable to use at least one selected from Examples of the polyester elastomer include “Hytrel (registered trademark)” (for example, “Hytrel 3046”, “Hytrel 3548”, “Hytrel 4047”, etc.) manufactured by Toray DuPont Co., Ltd.), and the styrene. Examples of the elastomer include “Lavalon (registered trademark)” manufactured by Mitsubishi Chemical Corporation.

  The blending ratio (total 100% by mass) of the urethane prepolymer (b-1) and the thermoplastic resin (b-2) in the polyisocyanate mixture (B) is urethane prepolymer (b-1) / thermoplastic resin. (B-2) = 5% by mass to 50% by mass / 50% by mass to 95% by mass is preferable, more preferably 10% by mass to 50% by mass / 50% by mass to 90% by mass, and still more preferably 20% by mass. % To 45 mass% / 55 mass% to 80 mass%. If the blending ratio is outside the above range, the desired crosslinked structure may not be obtained, or the crosslinking density may become too high, resulting in impaired durability.

  The amount of isocyanate groups (NCO%) in the polyisocyanate mixture (B) is the amount of isocyanate groups (NCO%) in the urethane prepolymer (b-1) in the polyisocyanate mixture (B) × the amount in the polyisocyanate mixture (B). It can be expressed by mass (g) of urethane prepolymer (b-1) / total amount (g) of polyisocyanate mixture (B). The isocyanate group amount (NCO%) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, and preferably 10.0% by mass or less. 7.0 mass% or less is more preferable, and 5.0 mass% or less is still more preferable.

  If the amount of isocyanate groups (NCO%) in the polyisocyanate mixture (B) is too low, crosslinking may be reduced, and the effect of scuff resistance may be lost. If it is too high, the viscosity of the cover composition increases and the moldability is increased. May get worse.

  In the cover composition used in the present invention, the polyisocyanate mixture (B) is 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass with respect to 100 parts by mass of the thermoplastic polyurethane (A). The content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less. This is because if the polyisocyanate mixture (B) is outside the above range, a sufficient cross-linked structure may not be obtained, or the cross-linking density may become too high, thereby impairing durability.

  The cover composition used in the present invention substantially reacts with the isocyanate group, as a base resin component, the thermoplastic polyurethane (A) and the urethane prepolymer (b-1) having at least two isocyanate groups. It is preferable to contain the polyisocyanate mixture (B) dispersed in the thermoplastic resin (b-2) not to be used. Here, the base resin component is a component having a blending ratio of 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more, based on all resin components contained in the cover composition. Means that. Further, the cover composition used in the present invention is substantially composed of a thermoplastic polyurethane (A) and a urethane prepolymer (b-1) having at least two isocyanate groups as a base resin component. It is also a preferable aspect to contain only the polyisocyanate mixture (B) dispersed in the thermoplastic resin (b-2) that does not react with the resin.

  Examples of other resin components that can be used as long as the effects of the present invention are not impaired as the resin component of the cover composition in the present invention include ionomer resins and thermoplastic elastomers. Examples of the ionomer resin include those obtained by neutralizing at least part of carboxyl groups in a copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, ethylene and carbon number. What neutralized at least one part of the carboxyl group in the terpolymer of 3-8 alpha, beta-unsaturated carboxylic acid and alpha, beta-unsaturated carboxylic acid ester with a metal ion, or these Can be mentioned. Specific examples of the ionomer resin include “High Milan (registered trademark)” commercially available from Mitsui DuPont Polychemical Co., Ltd., and “Surlin (registered trademark)” commercially available from DuPont Co., Ltd., ExxonMobil Chemical. Examples include “Iotech (registered trademark)” commercially available from Co., Ltd. Specific examples of the thermoplastic elastomer include, for example, a thermoplastic polyamide elastomer commercially available from Arkema Co., Ltd. under the trade name “Pebax (registered trademark)” (for example, “Pebax 2533”), Toray DuPont Co., Ltd. Thermoplastic polyester elastomer marketed under the trade name “Hytrel® (for example,“ Hytrel 3548 ”,“ Hytrel 4047 ”)”, marketed under the trade name “Lavalon®” from Mitsubishi Chemical Corporation. And thermoplastic polystyrene elastomer.

  The cover composition used in the present invention includes the above-described resin components, pigment components such as titanium oxide and blue pigment, specific gravity adjusting agents such as calcium carbonate and barium sulfate, dispersants, anti-aging agents, and UV absorbers. Further, a light stabilizer, a fluorescent material, or a fluorescent brightening agent may be contained within a range not impairing the performance of the cover.

  The content of the white pigment (titanium oxide) is 0.5 parts by mass or more, more preferably 1 part by mass or more, and more preferably 10 parts by mass or less, with respect to 100 parts by mass of the resin component constituting the cover. Is desirably 8 parts by mass or less. By setting the content of the white pigment to 0.5 parts by mass or more, the cover can be concealed. Moreover, it is because durability of the cover obtained may fall when content of a white pigment exceeds 10 mass parts.

  In the golf ball production method of the present invention, a polyisocyanate in which a thermoplastic polyurethane (A) and a urethane prepolymer (b-1) are dispersed in a thermoplastic resin (b-2) that does not substantially react with an isocyanate group. A cover composition is obtained by blending the mixture (B). For the blending of the composition for the cover, for example, a mixer capable of blending pellet-shaped raw materials is preferably used, and a tumbler mixer is more preferably used. As an aspect of blending the cover composition, for example, thermoplastic polyurethane (A) is mixed with a cover additive such as titanium oxide and extruded to prepare white pellets in advance, and the white pellet and polyisocyanate mixture are mixed. A mode in which the pellets of (B) are dry blended; a mode in which the thermoplastic polyurethane (A) and the polyisocyanate mixture (B) are mixed with a cover additive such as titanium oxide and extruded to prepare white pellets in advance. (B) A polyisocyanate mixture and a cover additive such as titanium oxide are mixed and extruded to prepare white pellets in advance, and the white pellets and the thermoplastic polyurethane (A) pellets are dry blended. An aspect etc. can be mentioned.

  Although the aspect which shape | molds a cover using the composition for a cover is not specifically limited, the aspect which directly inject-molds the composition for a cover on a core, or shape | molds a hollow shell-like shell from a composition for a cover, and a core And a method of compression molding by coating with a plurality of shells (preferably a method of molding a hollow shell-shaped half shell from a cover composition and coating a core with two half shells) Can do. When forming a cover by injection molding the cover composition onto the core, the upper and lower molds for cover molding have hemispherical cavities, with pimples, which also serve as hold pins that allow part of the pimples to advance and retract. It is preferable to use what is. The cover can be molded by injection molding by protruding the hold pin, inserting the core and holding it, and then injecting the heat-melted composition for the cover and cooling, for example, The cover composition heated and melted at 150 ° C. to 230 ° C. is injected in a mold clamped at a pressure of 980 Kpa to 1,500 KPa in 0.1 seconds to 1 second, and cooled for 15 seconds to 60 seconds. This is done by opening the mold. Further, the crosslinking can be further promoted by post-curing the golf ball with the cover formed at 40 ° C. or higher for 4 hours to 96 hours.

  Here, the golf ball of the present invention uses the thermoplastic polyurethane (A) and the polyisocyanate mixture (B) to suppress the crosslinking reaction at the time of cover molding, and to advance the crosslinking reaction after the cover molding, The scuff resistance of the cover is improved without reducing the productivity of the golf ball. Whether or not the cover is cross-linked after molding the cover can be confirmed, for example, as follows.

  The thermoplastic polyurethane (A) crosslinked by the polyisocyanate mixture (B) exhibits insolubility in a solvent that dissolves the linear thermoplastic polyurethane (A). Examples of the solvent that dissolves the linear thermoplastic polyurethane (A) include N, N-dimethylformamide (DMF), tetrahydrofuran (THF), and the like. That is, the uncrosslinked thermoplastic polyurethane (A) dissolves easily in the solution, but when crosslinked by the polyisocyanate mixture (B), it becomes insoluble in the solution. can do.

  The thermoplastic polyurethane (A) crosslinked with the polyisocyanate mixture (B) is formed with allohanate bonds or burette bonds. These bonds are urethane bonds constituting the main chain of the thermoplastic polyurethane. Weak compared to urea bonds. Therefore, for example, the allophanate bond and the burette bond that form a crosslinked structure can be cleaved by treatment with a DMF solution of n-butylamine or heat treatment.

  The concentration of the n-butylamine DMF solution is preferably 0.01 mol / l to 0.25 mol / l, and more preferably 0.05 mol / l DMG solution. For example, the heat treatment is preferably performed at 130 ° C. to 150 ° C. for about 2 hours to 4 hours.

  In addition, what kind of polyisocyanate mixture the thermoplastic polyurethane is cross-linked is determined by gel permeation chromatography (GPC) measurement, Fourier transform infrared spectrophotometer (DPC solution of n-butylamine or heat-treated object) It can be confirmed by analyzing with FT-IR), nuclear magnetic resonance apparatus (NMR) or the like.

  The golf ball body in which the cover is molded is preferably taken out from the mold and subjected to surface treatment such as deburring, washing, and sandblasting as necessary. Moreover, a paint layer and a mark can also be formed if desired.

  In the present invention, the thickness of the golf ball cover is preferably 2.0 mm or less, more preferably 1.6 mm or less, and even more preferably 1.0 mm or less. This is because when the thickness is 2.0 mm or less, the resilience of the golf ball is increased and the total flight distance is increased. Although the minimum of the thickness of a cover is not specifically limited, For example, it is 0.1 mm. This is because if the thickness is less than 0.1 mm, it may be difficult to mold the cover.

  The slab hardness of the golf ball cover of the present invention is 20 or more in Shore D hardness, more preferably 25 or more, further preferably 30 or more, 60 or less, and more preferably 55 or less. Yes, more preferably 50 or less. By setting the slab hardness of the cover to 20 or more, a golf ball having excellent resilience (flying distance) and spin performance can be obtained. On the other hand, by setting the slab hardness to 60 or less, the feel at impact when the golf ball is hit is improved. Here, the slab hardness of the cover is a hardness measured by molding the cover composition into a sheet shape, and is measured by a measurement method described later.

  Next, a preferred embodiment of the core of the golf ball of the present invention will be described.

  Examples of the structure of the core of the golf ball of the present invention include a single-layer core, a core composed of a center and a single-layer intermediate layer covering the center, and a plurality of or multiple intermediate layers covering the center and the center. And a core composed of The core shape is preferably spherical. When the core shape is not spherical, the thickness of the cover is not uniform. As a result, a part in which the cover performance is partially reduced occurs. On the other hand, the shape of the center is generally spherical, but a ridge may be provided so as to divide the surface of the spherical center, for example, the ridge so as to divide the surface of the spherical center equally. May be provided. As an aspect which provides the said protrusion, the aspect which provides a protrusion integrally with a center on the surface of a spherical center, the aspect which provides the intermediate | middle layer of a protrusion on the surface of a spherical center, etc. can be mentioned, for example.

  For example, when the spherical center is regarded as the earth, the ridge is preferably provided along an equator and an arbitrary meridian that equally divides the surface of the spherical center. For example, when the spherical center surface is divided into 8 parts, 90 degrees east longitude, 90 degrees west longitude, and east longitude (west longitude) with reference to the equator, an arbitrary meridian (longitude 0 degrees), and the meridian of such longitude 0 degrees It may be provided along the meridian of 180 degrees. When providing the ridge, the concave portion partitioned by the ridge is filled with a plurality of intermediate layers or a single intermediate layer covering each of the concave portions, and the core shape is made spherical. It is preferable to do so. The shape of the protrusion is not particularly limited, and examples thereof include an arc shape or a substantially arc shape (for example, a shape in which cut portions are provided at portions that intersect or perpendicular to each other).

  For the core or center of the golf ball of the present invention, a conventionally known rubber composition (hereinafter may be simply referred to as “core rubber composition”) may be employed. A rubber composition containing an agent, a co-crosslinking agent, and a filler can be molded by hot pressing. The shape of the core is preferably spherical. When the core shape is not spherical, the thickness of the cover is not uniform. As a result, a part in which the cover performance is partially reduced occurs.

  As the base rubber, natural rubber and / or synthetic rubber can be used. For example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like can be used. Among these, it is particularly preferable to use a high-cis polybutadiene having a cis bond advantageous for repulsion of 40% or more, preferably 70% or more, more preferably 90% or more.

  The said crosslinking initiator is mix | blended in order to bridge | crosslink a base rubber component. As the crosslinking initiator, an organic peroxide is suitable. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, Examples thereof include organic peroxides such as di-t-butyl peroxide, among which dicumyl peroxide is preferably used. The amount of the crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 3 parts by mass or less, more preferably 100 parts by mass of the base rubber. 2 parts by mass or less. If it is less than 0.2 parts by mass, the core tends to be too soft and the resilience tends to decrease. If it exceeds 3 parts by mass, it is necessary to increase the amount of co-crosslinking agent used in order to obtain an appropriate hardness. There is a lack of resilience.

  The co-crosslinking agent is not particularly limited as long as it has a function of crosslinking rubber molecules by graft polymerization to a base rubber molecular chain. For example, α, β- having 3 to 8 carbon atoms. Unsaturated carboxylic acid or its metal salt can be used, Preferably, acrylic acid, methacrylic acid, or these metal salts can be mentioned. Examples of the metal constituting the metal salt include zinc, magnesium, calcium, aluminum, sodium and the like, and zinc is preferably used because resilience increases. The amount of the co-crosslinking agent used is 10 parts by mass or more, more preferably 20 parts by mass or more, and 50 parts by mass or less, more preferably 40 parts by mass or less with respect to 100 parts by mass of the base rubber. desirable. When the amount of the co-crosslinking agent used is less than 10 parts by mass, the amount of the crosslinking initiator must be increased in order to obtain an appropriate hardness, and the resilience tends to decrease. On the other hand, when the usage-amount of a co-crosslinking agent exceeds 50 mass parts, a core may become hard too much and there exists a possibility that a shot feeling may fall.

  The filler contained in the core rubber composition is mainly blended as a specific gravity adjusting agent for adjusting the specific gravity of the golf ball obtained as a final product to a range of 1.0 to 1.5. What is necessary is just to mix | blend as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The blending amount of the filler is 2 parts by mass or more, more preferably 3 parts by mass or more, and 50 parts by mass or less, more preferably 35 parts by mass or less with respect to 100 parts by mass of the base rubber. desirable. If the blending amount of the filler is less than 2 parts by mass, it is difficult to adjust the weight, and if it exceeds 50 parts by mass, the weight fraction of the rubber component tends to decrease and the resilience tends to decrease.

  In addition to the base rubber, the crosslinking initiator, the co-crosslinking agent, and the filler, the core rubber composition further contains an organic sulfur compound, an antiaging agent, a peptizer, or the like as appropriate. Can do.

  As the organic sulfur compound, diphenyl disulfides can be preferably used. Examples of the diphenyl disulfides include diphenyl disulfide; bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, bis (4- Mono-substituted products such as fluorophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (4-cyanophenyl) disulfide; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, bis ( 2,6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide, bis (2-cyano- -Disubstituted products such as bromophenyl) disulfide; trisubstituted products such as bis (2,4,6-trichlorophenyl) disulfide and bis (2-cyano-4-chloro-6-bromophenyl) disulfide; Tetra-substituted products such as 3,5,6-tetrachlorophenyl) disulfide; bis (2,3,4,5,6-pentachlorophenyl) disulfide, bis (2,3,4,5,6-pentabromophenyl) disulfide And the like, and the like. These diphenyl disulfides have some influence on the vulcanized state of the rubber vulcanizate and can improve the resilience. Among these, it is preferable to use diphenyl disulfide and bis (pentabromophenyl) disulfide from the viewpoint that a highly repulsive golf ball can be obtained. The compounding amount of diphenyl disulfides is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5.0 parts by mass or less, with respect to 100 parts by mass of the base rubber. Preferably it is 3.0 mass parts or less.

  The blending amount of the anti-aging agent is preferably 0.1 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the base rubber. The content of the peptizer is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.

  The hot-press molding conditions for the core rubber composition may be appropriately set according to the rubber composition, but are usually heated at 130 to 200 ° C. for 10 to 60 minutes, or at 130 to 150 ° C. for 20 to 40 minutes. After heating, it is preferable to heat at 160 to 180 ° C. for 2 to 5 minutes.

  The diameter of the core of the golf ball of the present invention is preferably 39.0 mm or more, more preferably 39.5 mm or more, and further preferably 40.8 mm or more. This is because if the core diameter is less than 39.0 mm, the cover becomes too thick and the resilience decreases. The upper limit of the core diameter is not particularly limited, but is preferably 42.2 mm, more preferably 42.0 mm, and further preferably 41.8 mm. This is because if the core diameter exceeds 42.2 mm, the cover becomes relatively thin, and the protective effect by the cover cannot be sufficiently obtained.

  The core preferably has a compressive deformation amount of 2.50 mm or more, more preferably 2.60 mm or more, and even more preferably 2 when a final load of 1275 N is applied from a state in which an initial load of 98 N is applied. .70 mm or more. When the amount of deformation is too small, the core becomes hard and the feel at impact tends to decrease. On the other hand, the upper limit of the amount of compressive deformation when a final load of 1275N is applied from a state in which an initial load of 98N is applied is not particularly limited, but is preferably 3.20 mm, more preferably 3.10 mm, and even more preferably. Is 3.00 mm. If the amount of deformation is too large, it may become too soft and the feel at impact may be felt heavy.

  As a core of the golf ball of the present invention, it is also a preferable aspect to use a core having a surface hardness larger than the center hardness. For example, by adopting a multilayer core structure, the surface hardness of the core can be easily made larger than the center hardness. The difference in hardness between the surface hardness and the center hardness of the core is preferably 20 or more and more preferably 25 or more in Shore D hardness. By making the surface hardness of the core greater than the center hardness, the launch angle is increased, the spin rate is decreased, and the flight distance is improved. Further, the upper limit of the Shore D hardness difference between the surface hardness and the center hardness of the core is not particularly limited, but is preferably 40, more preferably 35. This is because if the hardness difference becomes too large, the durability may be lowered.

  Furthermore, the center hardness of the core is preferably 30 or more in Shore D hardness, more preferably 32 or more, and further preferably 35 or more. If the center hardness of the core is less than 30 in Shore D hardness, the core may become too soft and the resilience may decrease. Further, the center hardness of the core is preferably 50 or less in Shore D hardness, more preferably 48 or less, and further preferably 45 or less. This is because if the center hardness exceeds 50 in Shore D hardness, the hardness becomes too hard and the shot feeling tends to decrease. In the present invention, the center hardness of the core means a hardness measured by a spring type hardness tester Shore D type at a center point of the cut surface by cutting the core into two equal parts.

  The surface hardness of the core of the golf ball of the present invention is preferably 45 or more in Shore D hardness, more preferably 50 or more, and further preferably 55 or more. If the surface hardness is less than 45, the surface hardness may be too soft and the resilience may be reduced. The surface hardness of the core is preferably 65 or less in Shore D hardness, more preferably 62 or less, and still more preferably 60 or less. This is because if the surface hardness is more than 65 in Shore D hardness, the core becomes too hard and the feel at impact may be lowered.

  The golf ball core of the present invention preferably has a PGA compression of 65 or more, more preferably 70 or more. When the PGA compression is less than 65, the resilience decreases. Moreover, it is because it becomes too soft and a hit feeling becomes heavy. Although the upper limit of PGA compression is not specifically limited, 115 is preferable and 110 is more preferable. This is because if the PGA compression exceeds 115, it becomes too hard and the feel at impact is reduced.

  The structure of the golf ball of the present invention is not particularly limited as long as it has a core and a cover. The two-piece golf ball having a single-layer core and a cover covering the core, and the center and the center are covered. A three-piece golf ball having a core composed of a single intermediate layer and a cover covering the core, a core composed of a center and a plurality of or multiple intermediate layers covering the center, and a cover covering the core It may be a multi-piece golf ball or a thread-wound golf ball having a thread-core and a cover. This is because the present invention can be preferably applied in any case. Among these, the present invention can be suitably applied to a two-piece golf ball having a single-layer core and a cover covering the core.

  When the golf ball of the present invention is a three-piece or multi-piece golf ball, examples of the material constituting the intermediate layer include thermoplastic resins such as polyurethane resin, ionomer resin, nylon and polyethylene; polystyrene elastomer And thermoplastic elastomers such as polyolefin elastomers, polyurethane elastomers and polyester elastomers, and ionomer resins are preferred.

  Examples of the ionomer resin include an ionomer resin obtained by neutralizing at least a part of a carboxyl group in a copolymer of ethylene and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion, ethylene and carbon. What neutralized at least one part of the carboxyl group in the ternary copolymer of several 3-8 alpha, beta-unsaturated carboxylic acid and alpha, beta-unsaturated carboxylic acid ester with a metal ion, or Mention may be made of these mixtures.

  Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid, and acrylic acid or methacrylic acid is particularly preferable. Examples of the α, β-unsaturated carboxylic acid ester include methyl, ethyl, propyl, n-butyl, isobutyl ester and the like such as acrylic acid, methacrylic acid, fumaric acid and maleic acid. Methacrylic acid esters are preferred. The copolymer of ethylene and α, β-unsaturated carboxylic acid, or the carboxyl group in the terpolymer of ethylene, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester. Examples of metal ions that neutralize at least a part include alkali 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; tin Other ions such as zirconium and the like can be mentioned, and sodium, zinc and magnesium ions are particularly preferably used from the viewpoint of resilience and durability.

  In addition to the resin component, the intermediate layer may further contain a specific gravity adjusting agent such as barium sulfate or tungsten, an antiaging agent, a pigment, and the like.

  When the golf ball of the present invention is a thread wound golf ball, a thread wound core may be used as the core. In such a case, as the thread wound core, for example, a thread core composed of a center formed by curing the core rubber composition described above and a thread rubber layer formed by winding the thread rubber around the center in a stretched state is used. do it. The thread rubber wound on the center may be the same as that conventionally used for the thread wound layer of a thread wound golf ball, for example, natural rubber or natural rubber and synthetic polyisoprene with sulfur, You may use what was obtained by vulcanizing the rubber composition which mix | blended the vulcanization adjuvant, the vulcanization accelerator, the anti-aging agent, etc. The thread rubber is stretched about 10 times on the center and wound to form a thread wound core.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments without departing from the gist of the present invention are not limited thereto. Included in range.

[Evaluation methods]
(1) Scratch resistance A commercially available pitching wedge was attached to a swing robot manufactured by Golf Laboratories, and each ball was hit once at a head speed of 36 m / sec. .
Evaluation criteria A: There is almost no scratch on the surface of the golf ball.
○: Slight scratches occur on the surface of the golf ball.
(Triangle | delta): The surface of the golf ball is shaved a little and fuzz has arisen.
X: The surface of the golf ball is considerably shaved and the fuzz is conspicuous.

(2) Durability A metal head # W1 driver was attached to a swing robot manufactured by True Temper, and each golf ball was hit at a head speed of 45 m / sec to collide with a collision plate. This was repeated to measure the number of hits until the golf ball was broken. The durability of each golf ball is determined according to the golf ball no. The number of hits for 15 golf balls is set to 100, and the number of hits for each golf ball is shown as an index value. The larger the indexed value, the more excellent the golf ball is.

(3) Slab hardness (Shore D hardness)
Using the cover composition, a sheet having a thickness of about 2 mm was produced by hot press molding and stored at 23 ° C. for 2 weeks. An automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness tester Shore D type as defined in ASTM-D2240 in a state where three or more sheets are stacked so as not to affect the measurement substrate or the like. It measured using.

(4) Spherical core hardness Shore D hardness measured on the surface portion of the spherical core using an automatic rubber hardness meter P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness meter Shore D type as defined in ASTM-D2240. The surface hardness of the spherical core was taken, the spherical core was cut into a hemisphere, and the Shore D hardness measured at the center of the cut surface was taken as the center hardness of the spherical core.

(5) Compression deformation (mm)
The amount of deformation in the compression direction (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98N was applied to the golf ball or spherical core to when the final load 1275N was applied was measured.

[Preparation of polyisocyanate mixture (B)]
A predetermined amount of polyisocyanate and polyol shown in Table 1 were used and reacted in a dry nitrogen atmosphere at 80 ° C. for 2 hours to obtain an isocyanate group-terminated urethane prepolymer (b-1).

MDI: 4,4′-diphenylmethane diisocyanate H ₁₂ manufactured by Tokyo Chemical Industry Co., Ltd. MDI: 4,4′-dicyclohexylmethane diisocyanate HDI isocyanurate manufactured by Tokyo Chemical Industry Co., Ltd .: Takenate D-170N manufactured by Mitsui Chemicals Polyurethanes
PTMG1000: polyoxytetramethylene glycol manufactured by Mitsubishi Chemical Corporation, number average molecular weight 1000
PTMG2000: polyoxytetramethylene glycol manufactured by Mitsubishi Chemical Corporation, number average molecular weight 2000

  Next, as a thermoplastic resin that does not substantially react with an isocyanate group, a thermoplastic polyester elastomer (“Hytrel 3046” manufactured by Toray DuPont) was previously dried to remove water (b-2). . The isocyanate group-terminated urethane prepolymer (b-1) obtained above and the thermoplastic polyester elastomer (b-2) are blended so as to have a mass ratio of 1: 2, and the mixing roll is used at 120 ° C. to It knead | mixed for 5 to 10 minutes at 180 degreeC. The obtained kneaded material was taken out and pulverized to obtain pellets of the polyisocyanate mixture (B).

[Production of two-piece golf balls]
(1) Production of core A rubber composition for a core having the composition shown in Table 2 was kneaded and heated and pressed in an upper and lower mold having hemispherical cavities at 160 ° C. for 13 minutes to have a diameter of 40.7 mm and a mass of 43.2 g. A spherical core was obtained.

Polybutadiene rubber: BR730 (high cis polybutadiene) manufactured by JSR Corporation
Zinc acrylate: ZNDA-90S manufactured by Nippon Distilled
Zinc Oxide: Toho Zinc Gin R
Barium sulfate: Sakai Chemical's barium sulfate BD
Dicumyl peroxide: Park Mill D made by NOF
Diphenyl disulfide: manufactured by Sumitomo Seika

(2) Preparation of cover composition and preparation of golf ball body (A) pellets of thermoplastic polyurethane (Elastollan XNY97A, ET890 manufactured by BASF) and (B) pellets of polyisocyanate mixture shown in Tables 3 and 4 Then, the cover additive (titanium oxide) was dry blended using a tumbler mixer to prepare a cover composition. The blending ratio of (B) polyisocyanate mixture to (A) thermoplastic polyurethane (Elastollan XNY97A, ET890 manufactured by BASF) is such that the amount of isocyanate groups relative to 100 parts by mass of (A) thermoplastic polyurethane is substantially the same. did.

(2-1) In the case of injection molding A cover was formed by directly injection-molding the obtained composition for a cover onto a core. The upper and lower molds for cover molding have hemispherical cavities, are attached with pimples, and also serve as hold pins in which a part of the pimples can advance and retract. The hold pin is protruded, the core is inserted and then held, and a resin heated to 210 ° C. is injected into a mold clamped at a pressure of 80 tons in 0.3 seconds, cooled for 30 seconds, and the mold is opened to open a golf ball The main body was taken out.

(2-2) In the case of compression molding The obtained pellet-shaped composition for a cover was put into each of the concave portions of the lower mold of the half shell molding die, and pressed to form a half shell. The compression molding was performed at a molding temperature of 170 ° C., a molding time of 5 minutes, and a molding pressure of 2.94 MPa.

  The core obtained above was concentrically covered with two half shells, and a cover (thickness 0.5 mm) was formed by compression molding. The compression molding was performed at a molding temperature of 150 ° C., a molding time of 2 minutes, and a molding pressure of 9.8 MPa to obtain a golf ball body.

(3) The surface of the obtained golf ball body is sandblasted and marked, and then a clear paint is applied, the paint is dried in an oven at 40 ° C. for 4 hours, a diameter of 42.7 mm, and a mass of 45.4 g. Got a golf ball.

  Table 3 and Table 4 show the results of evaluating the scratch resistance and durability of the obtained golf balls.

  Golf ball no. 1-No. 11 is (A) a thermoplastic polyurethane and a polyisocyanate mixture (B) in which a urethane prepolymer (b-1) is dispersed in a thermoplastic resin (b-2) that does not substantially react with an isocyanate group. A golf ball in which a cover is formed using the contained cover composition. As the polyisocyanate mixture (B), a golf ball No. 1 in which an isocyanate monomer is dispersed in a thermoplastic resin that does not substantially react with an isocyanate group is used. 12 and no. It can be seen that the scratch resistance and durability are remarkably improved as compared with 13. Golf ball no. 14 and no. 15 is a case where the cover was molded without crosslinking the thermoplastic polyurethane. 1-No. It can be seen that the scratch resistance and durability are reduced compared to 11.

  The present invention is suitable for a golf ball having excellent scratch resistance and durability.

Claims (7)

A golf ball having a core and a cover,
The cover is a resin component,
Thermoplastic polyurethane (A);
A polyisocyanate mixture (B) in which a urethane prepolymer (b-1) having at least two isocyanate groups is dispersed in a thermoplastic resin (b-2) that does not substantially react with the isocyanate groups ,
A golf ball characterized in that the urethane prepolymer (b-1) is formed of a cover composition having an isocyanate group amount (NCO%) of 0.1% by mass to 10.0% by mass .   The thermoplastic resin (b-2) that does not substantially react with the isocyanate group is at least one selected from the group consisting of polyester elastomers, acrylic elastomers, styrene elastomers, olefin elastomers, and vinyl chloride elastomers. The golf ball according to claim 1. The cover composition is
For 100 parts by mass of thermoplastic polyurethane (A),
The golf ball according to claim 1, wherein the golf ball contains 1 to 50 parts by mass of the polyisocyanate mixture (B).   The golf ball according to claim 1, wherein an amount of isocyanate groups (NCO%) of the polyisocyanate mixture (B) is 0.1% by mass or more and 10.0% by mass or less.   The blending ratio (total 100 mass%) of the urethane prepolymer (b-1) and the thermoplastic resin (b-2) in the polyisocyanate mixture (B) is urethane prepolymer (b-1) / thermoplastic resin ( The golf ball according to claim 1, wherein b-2) = 5% by mass to 50% by mass / 50% by mass to 95% by mass.   The golf ball according to claim 1, wherein the number average molecular weight of the polyol component constituting the urethane prepolymer (b-1) is 650 or more.   The golf ball according to any one of claims 1 to 6, wherein the cover has a Shore D hardness of 20 to 60.