JP2021084026A - Coating composition for golf balls and golf ball - Google Patents

Abstract

SOLUTION: A coating composition for golf balls is predominantly composed of a urethane coating comprising polyol as a main agent and polyisocyanate as a curing agent. The polyisocyanate contains two of an isocyanurate body and an adduct body of hexamethylene diisocyanate, and the composition has an elastic work recovery rate of 70% or more. There is also provided a golf ball.EFFECT: A coating composition for golf balls has a high self-repairing function and has high quality as a coating for golf balls. A golf ball coated with the coating composition can keep its durability satisfactorily and exhibits excellent wear resistance and a good ball appearance.SELECTED DRAWING: None

Description

The present invention relates to a coating composition for a golf ball and a golf ball using the coating composition.

The surface portion of a golf ball is often coated with a coating composition for the purpose of protecting the surface of the golf ball or for the purpose of maintaining a good aesthetic appearance. As such a paint composition for golf balls, a two-component curable polyurethane paint in which a polyol and a polyisocyanate are mixed immediately before use is preferably used because it can withstand large deformation, impact, and friction. (For example, Patent Document 1).

What is often seen in the recent development of golf balls is to further reduce the spin at the time of a full shot by the driver, and due to the trend of such low spin, the cover which is the outermost layer tends to be softened. is there.

In addition, many golf balls include a core, a cover located outside the core, and a coating film layer located outside the cover. By making the coating film layer soft, it often has certain effects such as contributing to the stability of the spin speed of the golf ball and improving the durability (for example, Patent Document 2).

Further, a paint for golf balls using one kind of polyester polyol alone as a polyol component has also been developed.

However, the wear resistance on the surface of the coating film layer is not good, and there is room for further improvement.

Japanese Unexamined Patent Publication No. 2003-253201 Japanese Unexamined Patent Publication No. 2011-67595 Japanese Unexamined Patent Publication No. 2002-53799

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating composition for a golf ball capable of improving the wear resistance of a coating film and a golf ball using the same.

As a result of diligent studies to achieve the above object, the present inventor has obtained an isocyanurate form of hexamethylene diisocyanate as the polyisocyanate in a coating composition containing a urethane coating material composed of a polyol and a polyisocyanate as a main component. By using two types of the adduct body and preparing the coating composition so that the elastic work recovery rate of the above composition is 70% or more, the coating film obtained by this coating composition is resistant to yellowing and yellowing. It has become excellent in flexibility, and in particular, it has been found that high spin performance can be obtained by using two types of an adduct body having excellent flexibility and an isocyanurate body having relatively toughness, which led to the present invention. Is.

Therefore, the present invention provides the following paint composition for golf balls and golf balls.
1. 1. A paint composition for golf balls containing a urethane paint composed of a polyol as a main agent and a polyisocyanate as a curing agent as a main component, wherein the polyisocyanate is an isocyanurate form of hexamethylene diisocyanate and an adduct form. A paint composition for a golf ball, which comprises a variety and has an elastic work recovery rate of 70% or more.
2. The coating composition for a golf ball according to 1 above, wherein the elastic work recovery rate of the composition is 80% or more.
3. 3. The golf ball according to 1 or 2 above, wherein the mixing ratio (A) / (B) of the isocyanurate form (A) and the adduct form (B) of the hexamethylene diisocyanate is 95/5 to 40/60 in terms of mass ratio. Paint composition for.
4. The coating composition for a golf ball according to any one of 1 to 3 above, wherein the polyol contains one kind or two or more kinds of polyester polyols.
5. A golf ball having a core and a cover composed of one layer or two or more layers covering the core, and the outermost layer of the cover is formed of the coating composition according to any one of 1 to 4 above. A golf ball characterized by having a paint layer.
6. The golf ball according to 5 above, wherein each layer of the cover is formed of a resin composition, and the elastic work recovery rate of the resin composition is 35% or more.
7. 5. The golf ball according to 5 or 6 above, wherein the value of W1-W2 is 50% or less in relation to the elastic work recovery rate (W1) of the coating composition and the elastic work recovery rate (W2) of each cover layer.

The paint composition for golf balls of the present invention has a high self-healing function, high abrasion resistance, excellent yellowing resistance and flexibility, and further has high spin performance. A golf ball coated with the above coating composition can improve various performances.

Hereinafter, the present invention will be described in more detail.
The paint for golf balls of the present invention is mainly composed of a urethane paint composed of a polyol and a polyisocyanate.

The polyol is not particularly limited, but it is preferable to use one kind or two or more kinds of polyester polyols. In particular, it is preferable to use two types of polyester polyols, a polyester polyol (A) and a polyester polyol (B), as a main agent. These two types of polyester polyols have different weight average molecular weights (Mw), and the weight average molecular weight (Mw) of the component (A) is 20,000 to 30,000, and the weight average molecular weight (Mw) of the component (B) is It is preferable that the weight average molecular weight (Mw) is 800 to 1,500. The weight average molecular weight (Mw) of the component (A) is more preferably 22,000 to 29,000, and even more preferably 23,000 to 28,000. On the other hand, the weight average molecular weight (Mw) of the component (B) is more preferably 900 to 1200, and even more preferably 1,000 to 1,100.

The above two types of polyester polyols are obtained by polycondensation of the polyol and a polybasic acid. Examples of this polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and diethylene glycol. , Dipropylene glycol, hexylene glycol, dimethylol heptane, polyethylene glycol, polypropylene glycol and other diols, triol, tetraol, and polyols having an alicyclic structure. Examples of the polybasic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid and dimer acid, aliphatic unsaturated dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid and citraconic acid, and phthalic acid. Aromatic polyvalent carboxylic acids such as acids, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, endo Examples thereof include a dicarboxylic acid having an alicyclic structure such as methylenetetrahydrophthalic acid and tris-2-carboxyethyl isocyanurate. In particular, as the polyester polyol of the component (A), a polyester polyol having a cyclic structure introduced into the resin skeleton can be adopted. For example, the weight of a polyol having an alicyclic structure such as cyclohexanedimethanol and a polybasic acid. Examples thereof include polyester polyols obtained by condensation or polycondensation of a polyol having an alicyclic structure and diols or a triol and a polybasic acid. On the other hand, as the polyester polyol of the component (B), a polyester polyol having a multi-branched structure can be adopted, and examples thereof include a polyester polyol having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

The total weight average molecular weight (Mw) of the main agent composed of the above two types of polyester polyols is preferably 13,000 to 23,000, more preferably 15,000 to 22,000. The total number average molecular weight (Mw) of the main agent composed of the above two types of polyester polyols is preferably 1,100 to 2,000, and more preferably 1,300 to 1,850. If these average molecular weights (Mw and Mn) deviate from the above range, the wear resistance of the coating film may decrease. The weight average molecular weight (Mw) and the number average molecular weight (Mn) are measured values (polystyrene conversion values) measured by gel permeation chromatography (hereinafter abbreviated as GPC) by detecting a differential refractometer.

The blending amount of the above two types of polyester polyols (A) and (B) is not particularly limited, but the blending amount of the component (A) is 20 to 30% by mass with respect to the total amount of the main agent, and (B). The blending amount of the components is preferably 2 to 18% by mass with respect to the total amount of the main agent.

When only one type of the above-mentioned polyol is used, it is preferable to use the above-mentioned polyester polyol (A).

On the other hand, the polyisocyanate used in the present invention includes two types, an isocyanurate form of hexamethylene diisocyanate and an adduct form. Generally, isocyanate prepolymers are divided into three types of structures (adduct, burette, and isocyanurate). The adduct refers to an adduct of diisocyanate and trimethylolpropane. The isocyanurate form is a trimer of diisocyanate.

The hexamethylene diisocyanate also contains a modified product thereof. Examples of the modified hexamethylene diisocyanate include a polyester modified product and a urethane modified product of hexamethylene diisocyanate.

The mixing ratio (A) / (B) of the isocyanurate form (A) and the adduct form (B) of the hexamethylene diisocyanate is preferably 95/5 to 40/60, preferably 80/20 to 55. / 45 is more preferable. If the ratio of the adduct body (B) increases within the above range of the mixing ratio, the damage property and spin property tend to improve, but if the ratio of the adduct body (B) increases outside the above range, contamination occurs. There is a risk of reduced sex.

Examples of the nurate form of hexamethylene diisocyanate (HMDI) include the trade names "Coronate 2357" (manufactured by Tosoh Corporation), "Sumijour N3300" (manufactured by Sumika Covestro Urethane Co., Ltd.), and "Duranate TPA-100" (Asahi Kasei Co., Ltd.). , "Takenate D170N", "Takenate D177N" (all manufactured by Mitsui Chemicals, Inc.), "Bernock DN-980" (manufactured by DIC Corporation). One of these can be used alone or in combination of two or more.

Examples of the hexamethylene diisocyanate (HMDI) adduct body include the trade names "Coronate HL" (manufactured by Tosoh Corporation), "Takenate D160N" (manufactured by Mitsui Chemicals Co., Ltd.), "Duranate E402-80B", and "Duranate E405-". Examples include "70B" (all manufactured by Asahi Kasei Corporation), "Bernock DN-955", and "Bernock DN-955S" (all manufactured by DIC Corporation). One of these can be used alone or in combination of two or more.

The molar ratio (NCO group / OH group) of the hydroxyl group (OH group) of the polyester polyol used in the present invention to the isocyanate group (NCO group) of the polyisocyanate is preferably 0.6 or more, more preferably 0. It is .65 or more, and the upper limit is preferably 1.5 or less, more preferably 1.0 or less, and further preferably 0.9 or less. If this molar ratio is less than 0.6, unreacted hydroxyl groups remain, which may deteriorate the performance and water resistance of the golf ball coating film. On the other hand, if it exceeds 1.5, the isocyanate group becomes excessive, so that a urea group (brittle) is generated by the reaction with water, and as a result, the performance of the golf ball coating film may deteriorate.

As the curing catalyst (organic metal compound), an amine-based catalyst or an organometallic catalyst can be used, and as the organometallic compound, conventional two-component curing such as metal soaps such as aluminum, nickel, zinc, and tin can be used. Those compounded as a curing agent for the type urethane paint can be preferably used.

A known paint compounding component may be added to the golf ball paint composition, if necessary. Specifically, an appropriate amount of a thickener, an ultraviolet absorber, a fluorescent whitening agent, a slipping agent, a pigment and the like can be blended.

Further, the elastic work recovery rate of the golf ball coating composition needs to be 70% or more, preferably 80% or more. If the elastic work recovery rate of this paint deviates from the above range, the wear resistance may deteriorate. As described above, in the present invention, since the coating film formed on the surface of the golf ball has a high elastic force, it has a high self-healing function and is extremely excellent in wear resistance. In addition, various performances of the golf ball coated with the above coating composition can be improved. The method for measuring the elastic work recovery rate of the golf ball coating composition will be described later.

The above elastic work recovery rate is an ultra-micro hardness test method in which the indentation load is controlled on the order of micronewton (μN) and the indenter depth at the time of indentation is tracked with an accuracy of nanometer (nm). It is one of the parameters of the nanoindentation method for evaluating the physical properties of. With the conventional method, only the size of the deformation mark (plastic deformation mark) corresponding to the maximum load can be measured, but with the nanoindentation method, the relationship between the indentation load and the indentation depth is measured by measuring automatically and continuously. Can be obtained. Therefore, it is considered that the physical properties of the coating film can be evaluated with high accuracy without individual differences as in the case of visually measuring the deformation marks with an optical microscope as in the conventional case. Since the coating film on the surface of a golf ball is greatly affected by the impact of a driver or various clubs, and the effect of the coating film on the physical characteristics of the golf ball is not small, the coating film for golf balls is subjected to an ultrafine hardness test method. It is a very effective evaluation method to measure with and perform with higher accuracy than before.

When the above coating composition is used, the coating composition of the present invention is adjusted at the time of coating on a golf ball manufactured by a known method, applied to the surface by adopting a normal coating process, and dried. A coating layer can be formed on the surface of the ball. In this case, as the coating method, a spray coating method, an electrostatic coating method, a dipping method and the like can be preferably adopted, and there is no particular limitation.

As described above, the above-mentioned paint composition for golf balls uses a polyester polyol as a main agent and a polyisocyanate as a curing agent, and various organic solvents can be mixed depending on the coating conditions. Examples of such an organic solvent include aromatic solvents such as toluene, xylene and ethylbenzene, ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate and propylene glycol methyl ether propionate, acetone and methyl ethyl ketone. , Methylisobutylketone, ketone solvents such as cyclohexanone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirits, etc. Petroleum hydrocarbon solvents etc. can be used.

The above drying step may be the same as that of a known two-component curable urethane paint, and the coating composition of the present invention has a drying temperature of about 40 ° C. or higher, particularly 40 to 60 ° C., and a drying time of 20 to 20 to. It can be 90 minutes, especially 40-50 minutes.

The thickness of the coating layer is not particularly limited, but is preferably 3 to 50 μm, more preferably 5 to 20 μm.

The coating composition is a one-piece golf ball, a two-piece solid golf ball composed of a core and a cover covering the core, or a multi-piece solid golf ball composed of one or more layers of cores and a multi-layer cover covering the cores. Etc., any golf ball can be used.

Further, the present invention is a golf ball having a core and a cover composed of one layer or two or more layers covering the core, and the outermost layer of the cover is a coating material formed of the above-mentioned coating composition. A golf ball having a layer is provided.

The cover is a member that covers the core and has at least one layer, and examples thereof include a two-layer cover and a three-layer cover. In the case of a two-layer cover, each layer may be referred to as an intermediate layer on the inside and an outermost layer on the outside. Further, in the case of a three-layer cover, each layer may be referred to as a surrounding layer, an intermediate layer and an outermost layer in order from the inside. In addition, a large number of dimples are usually formed on the outer surface of the outermost layer in order to improve the aerodynamic characteristics.

The material of each layer of the cover is not particularly limited, and may be formed of, for example, an ionomer resin, a polyester resin, a polyamide resin, or a polyurethane resin. For example, the intermediate layer can be formed of an ionomer resin or a highly neutralized ionomer resin, and the outermost layer can be formed of a polyurethane resin.

The resin composition forming each layer of the cover preferably has an elastic work recovery rate of 35% or more, more preferably 43% or more. If the elastic work recovery rate of this resin composition deviates from the above range, the damage property of the cover material or the coating film may deteriorate. The elastic work recovery rate described above is one parameter of the nanoindentation method for evaluating the physical properties of the cover (each layer), and the measuring method is the same as the measuring method of the elastic work recovery rate of the coating composition described above.

Further, assuming that the elastic work recovery rate of the coating composition is W1 and the elastic work recovery rate of each cover layer is W2, regarding these relationships, if the difference is too large, the adhesiveness between the coating film and the cover deteriorates and the coating is applied. The value of W1-W2 is preferably 50% or less, more preferably 40% or less, still more preferably 30% or less, from the viewpoint that the film is easily peeled off.

The core can be formed using a known rubber material as a base material. As the base rubber, a known base rubber of natural rubber or synthetic rubber can be used, and more specifically, polybutadiene, particularly cis-1,4-polybutadiene having at least 40% of cis structure is mainly used. It is recommended to use for. Further, in the base rubber, natural rubber, polyisoprene rubber, styrene-butadiene rubber and the like can be used in combination with the above-mentioned polybutadiene, if desired. Further, polybutadiene can be synthesized by a Ziegler-based catalyst such as titanium-based, cobalt-based, nickel-based, or neodium-based catalyst, or a metal catalyst such as cobalt and nickel.

The above-mentioned base material rubber includes co-crosslinkers such as unsaturated carboxylic acid and its metal salt, inorganic fillers such as zinc oxide, barium sulfate and calcium carbonate, dicumyl peroxide and 1,1-bis (t-butyl). Peroxy) Organic peroxides such as cyclohexane can be blended. Further, if necessary, a commercially available anti-aging agent or the like can be appropriately added.

As described above, the coating film formed of the above coating composition has excellent wear resistance, and the golf ball coated with the coating composition is repeatedly hit by the golf club. Performance can be improved, such as preventing a significant decrease in spin performance.

Hereinafter, the present invention will be described in more detail with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 5, Comparative Examples 1 to 3]
A rubber composition for a core was prepared according to the formulation shown in Table 1, and then vulcanized at 155 ° C. for 15 minutes to prepare a core having a diameter of 36.3 mm. Next, the surrounding layer and the intermediate layer were sequentially coated by the injection molding method with various resin materials shown in the same table. The thickness of the surrounding layer is 1.3 mm, the material hardness is 52 on the shore D hardness, the thickness of the intermediate layer is 1.1 mm, and the material hardness is 62 on the shore D hardness.

The details of the core material are as follows. The numbers in the table indicate parts by mass.
"Polybutadiene A": Product name "BR01" JSR "Polybutadiene B": Product name "BR51" JSR "Organic peroxide": Dikmyl peroxide, Product name "Parkmill D" Nikko "Sulfuric acid" Barium: Product name "Varico # 100" Hakusui Tech Co., Ltd. "Zinc oxide": Product name "Zinc oxide 3 types" Sakai Chemical Industry Co., Ltd. "Zinc acrylate": Nippon Catalyst Co., Ltd. "Water": Distilled water, Jun Wako "Pentachlorothiophenol zinc salt" manufactured by Yaku Kogyo Co., Ltd .: Wako Pure Yaku Kogyo Co., Ltd.

Details of the material of the cover (surrounding layer and intermediate layer) are as follows. The numbers in the table indicate parts by mass.
"HPF1000": DuPont ionomer "Himilan 1605": Na-based ionomer, Mitsui-Dow Polychemical "Himilan 1557": Zn-based ionomer, Mitsui-Dow Polychemical "Himilan 1706": Zn-based ionomer, Made by Mitsui Dow Polychemical Co., Ltd.

Next, the outermost layer having a thickness of 0.8 mm was coated by injection molding using the resin materials I to IV of the outermost layer shown in Table 2 below. The Shore D hardness of each resin material I to IV is shown in the same table. Although not shown in particular, a large number of dimples were formed on the outer surface of the outermost layer at the same time as injection molding.

The details of the material of the cover (outermost layer) are as follows. The numbers in the table indicate parts by mass. “Himilan” has the same description as in Table 1.
"TPU1""TPU2": Product name "Pandex" manufactured by DIC Cobestropolymer, Ether type thermoplastic polyurethane "Nucrel": Ethylene copolymer "AM7329" manufactured by Mitsui Dow Polychemical Co., Ltd .: Mitsui Dow Ionomer resin manufactured by Polychemical

Elastic work recovery rate of the cover (outermost layer) To measure the elastic work recovery rate of the outermost layer, a flat plate with the same composition as the cover material and thickness is used as a sample, and as a measuring device, Toyo Technica's ultra-fine hardness tester " G200 ”was used. The measurement conditions are as follows.
・ Indenter: Berkovich indenter (material: diamond, angle α: 130.06 °)
・ Load F: 100mN
・ Loading time: 15 seconds ・ Holding time: 20 seconds ・ Unloading time: 15 seconds Based on the pushing work amount Elastic (Nm) and the mechanical pushing work amount Wtotal (Nm) due to the return deformation of the coating film, the following formula The elastic work recovery rate is calculated by.
Elastic work recovery rate = Welast / Wtotal x 100 (%)

Formation of paint layer (coating film) Next, in the paint formulation shown in Table 3 below, the above paint was applied to the surface of the outermost layer on which a large number of dimples were formed with an air spray gun, and a paint layer (coating film) having a thickness of 15 μm was applied. ) Was formed, and the golf balls of each example were produced.

Elastic work recovery rate of the paint layer The elastic work recovery rate of the paint layer is measured using a coating film sheet having a thickness of 50 μm. As the measuring device, an ultra-micro hardness tester "ENT-2100" manufactured by Elionix Inc. is used, and the measurement conditions are as follows.
・ Indenter: Berkovich indenter (material: diamond, angle α: 65.03 °)
・ Load F: 0.2mN
・ Load time: 10 seconds ・ Holding time: 1 second ・ Unloading time: 10 seconds Based on the pushing work amount Elastic (Nm) and the mechanical pushing work amount Wtotal (Nm) due to the return deformation of the coating film, the following formula The elastic work recovery rate is calculated by.
Elastic work recovery rate = Welast / Wtotal x 100 (%)

[Synthesis example of polyester polyol (A)]
A reactor equipped with a reflux condenser, a dropping funnel, a gas introduction tube and a thermometer was provided with 140 parts by mass of trimethylolpropane, 95 parts by mass of ethylene glycol, 157 parts by mass of adipic acid, and 58 parts by mass of 1,4-cyclohexanedimethanol. The temperature was raised to 200 to 240 ° C. with stirring, and the mixture was heated (reacted) for 5 hours. Then, a "polyester polyol (A)" having an acid value of 4, a hydroxyl value of 170 and a weight average molecular weight (Mw) of 28,000 was obtained.

In Examples 1 to 5 and Comparative Examples 1 and 2, the above "polyester polyol (B)" was not mixed, and as shown in Table 3, only "polyester polyol (A)" was dissolved in butyl acetate as the main agent. .. This solution had a non-volatile content of 27.5% by mass.

In Comparative Example 3, 3 parts by mass of "polyester polyol (B)" ("NIPPOLAN 800" manufactured by Tosoh Corporation, 100% solid content) and an organic solvent (butyl acetate) were added to 27 parts by mass of the polyester polyol solution. ) And used as the main ingredient. This mixture had a non-volatile content of 30.0% by mass.

[Measurement of molecular weight (Mw and Mn)]
The molecular weight was measured by the following device.
Equipment: High-speed GPC equipment HLC-8220 manufactured by Tosoh Corporation
Column: Two connected columns of "TSK-GEL G2000H _XL " and "TSK-GEL G4000H _XL " manufactured by Tosoh Corporation. Column temperature: 40 ° C.
Detector: Differential Refractometer Eluent: THF
Column flow rate: 0.6 ml / min

Next, as the isocyanate of the curing agent, in Examples 1 to 5 and Comparative Examples 1 and 2, "Duranate TPA-100" (NCO content) manufactured by Asahi Kasei Corporation, which is an isocyanurate form of hexamethylene diisocyanate (HMDI). 23.1%, non-volatile content 100%) and "Duranate E402-80B" (NCO content 7.6%, non-volatile content 80%) manufactured by Asahi Kasei Corporation, which is an adduct body of HMDI, were used. In Comparative Example 3, only the HMDI nurate body was used as the isocyanate of the curing agent. The mixing ratio (mass%) of the nurate body and the adduct body in each Example / Comparative Example is as shown in Table 3. Ethyl acetate and butyl acetate were added as organic solvents, and the blending amount (concentration) of isocyanate was adjusted to the values shown in the table with respect to the total amount of the curing agent including the solvent to prepare a coating material.

Then, the appearance of the coating film of the golf balls of each Example and Comparative Example was evaluated according to the following criteria. The results are shown in Table 4.

Appearance evaluation of ball surface after sand wear test About 4 kg of sand having a size of about 5 mm was put into a pot mill having an outer diameter of 210 mm, and 15 balls were put into the pot mill. Then, the mixture was stirred in a ball mill at a rotation speed of 50 to 60 rpm for 120 minutes. Then, the ball was taken out from the pot mill, and the appearance of the ball was evaluated according to the following criteria.
[Criteria]
◎: No noticeable damage such as peeling or dirt on the ball surface ○: Small scratches or dirt can be seen on the ball surface ×: The ball surface is peeled off due to large scratches or wear, or dirt or gloss is reduced Etc. stand out

Appearance evaluation of ball surface after sandwater wear test About 4 kg of sand and water having a size of about 5 mm were put into a pot mill having an outer diameter of 210 mm, and 15 balls were put into the pot mill. Then, the mixture was stirred in a ball mill at a rotation speed of 50 to 60 rpm for 120 minutes. Then, the ball was taken out from the pot mill, and the appearance of the ball was evaluated according to the following criteria.
[Criteria]
◎: No noticeable damage such as peeling or dirt on the ball surface ○: Small scratches or dirt can be seen on the ball surface ×: Large peeling due to large scratches or wear on the ball surface, or deterioration of dirt or luster Etc. stand out

From the results of the physical characteristics of the golf ball in Table 4, the following can be considered.
It can be seen that the golf balls of Examples 1 to 5 all have good results in the sand wear test and the sand water wear test, and the appearance of the coating film is good.
On the other hand, in Comparative Example 1 and Comparative Example 2, the ball surface in the sand wear test is good, but the ball surface in the sand water wear test is conspicuously peeled off due to wear, or the stain or gloss is reduced. In Comparative Example 3, the surface of the ball in the sand water wear test is good, but the surface of the ball in the sand wear test is conspicuously peeled off due to wear, or has a decrease in dirt and luster.

Claims (7)

A paint composition for golf balls containing a urethane paint composed of a polyol as a main agent and a polyisocyanate as a curing agent as a main component, wherein the polyisocyanate is a hexamethylene diisocyanate isocyanurate and an adduct. A paint composition for a golf ball, which comprises a variety and has an elastic work recovery rate of 70% or more. The coating composition for a golf ball according to claim 1, wherein the elastic work recovery rate of the composition is 80% or more. The golf according to claim 1 or 2, wherein the mixing ratio (A) / (B) of the isocyanurate form (A) and the adduct form (B) of the hexamethylene diisocyanate is 95/5 to 40/60 in terms of mass ratio. Paint composition for balls. The coating composition for a golf ball according to any one of claims 1 to 3, wherein the polyol contains one kind or two or more kinds of polyester polyols. A golf ball having a core and a cover including one layer or two or more layers covering the core, and the outermost layer of the cover is the coating composition according to any one of claims 1 to 4. A golf ball characterized by having a formed paint layer. The golf ball according to claim 5, wherein each layer of the cover is formed of a resin composition, and the elastic work recovery rate of the resin composition is 35% or more. The golf ball according to claim 5 or 6, wherein the value of W1-W2 is 50% or less in relation to the elastic work recovery rate (W1) of the coating composition and the elastic work recovery rate (W2) of each cover layer.