JP2002322417A - Coating for golf ball and golf ball using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating for golf balls that can rapidly dry after coating without applying such a high temperature that the golf balls are not damaged with a drying heat, keeping the good adhesion to the surface of the ball, and provide the golf balls applied with the coating. SOLUTION: The objective coating for golf balls comprises the polyurethane and a photopolymerization initiator satisfying the followings (A), (B) and (C). (A) The contents of free isocyanate group is 0.3-3.0 mmol per one gram of the polyurethane. (B) The contents of the urethane bonds is 2.0-4.5 mmol per one gram of the polyurethane. (C) The contents of vinyl group is 1.0-3.0 mmol per one gram of the polyurethane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for reducing the curing time,
In addition, the present invention relates to a golf ball paint capable of providing a coating film having excellent adhesion to a ball body, particularly an ionomer cover, and a golf ball using the paint.

[0002]

2. Description of the Related Art To protect printed marks and numbers, or to improve the appearance by giving gloss, the golf ball surface is coated with a pigmented paint or clear paint. Painted.

[0003] Here, as a paint for golf balls, a paint excellent in impact resistance and scratch resistance is generally a two-pack curable polyurethane obtained by combining a polyol (main component) and a polyisocyanate (curing agent). Paints are commonly used. This coating material is applied with a mixture of a main agent and a curing agent, and is then usually baked to accelerate the curing reaction.

[0004] In recent years, multi-piece golf balls comprising a core and a cover covering the core have been mainly used as golf balls, and an ionomer resin is generally used as a cover material. When the ionomer resin is heated to a high temperature, the ionic bonding force is weakened. Therefore, when drying after coating is performed at a high temperature, both the elasticity and the hardness of the ionomer resin decrease. Therefore, it is conceivable to lower the drying temperature, but the curing reaction is slowed down, and the drying takes a long time, and the productivity is deteriorated. For example, Japanese Patent Application Laid-Open No. 8-182775 discloses a urethane paint which is blended in such a manner that the amount of hydroxyl groups of the polyol is excessive in the molar ratio with respect to the amount of isocyanate groups of the polyisocyanate as a paint having excellent adhesion to the cover. As disclosed, the urethane paint is 40-
Drying at a temperature of 50 ° C. takes 24 hours or more, resulting in poor productivity. Accordingly, golf ball paints having good drying properties have been studied.

On the other hand, Japanese Patent Publication No. 59334/1994 proposes the use of an ultraviolet-curable coating material containing substantially no solvent as a urethane coating material having a short drying time.

The ultraviolet-curable coating material disclosed herein is a combination of a vinyl polymerizable resin such as an unsaturated polyester or an acrylic resin and a photosensitizer such as benzoin ethers or acetophenones; an epoxy resin, diazonium and Lewis. Combinations of acid complex photosensitizers; amino
A combination of an alkyd resin and a trichloroacetophenone photosensitizer is disclosed. Such an ultraviolet-curable coating material is cured within a few seconds by irradiating with ultraviolet light after coating.

However, such UV-curable paints are
Because it has poor adhesion to the ball surface, it is only necessary to coat a small area such as the mark part or a mark to be printed on the ball surface or a coating of a small area part, but for a coating film that covers the entire ball body surface It is unsuitable for use in paints.

In particular, in the case of an ionomer cover, since the curing reaction of the ultraviolet-curable paint is a radical reaction that hardly contributes to the adhesion, the adhesion is particularly poor. Cracks easily occur.

The present invention has been made in view of such circumstances, and an object of the present invention is to maintain high adhesion to a ball surface layer while maintaining a high temperature at which the ball surface layer is affected. An object of the present invention is to provide a paint for a golf ball that has been dried quickly after coating without coating, and a golf ball using the paint.

[0010]

The golf ball coating of the present invention is characterized by containing a polyurethane satisfying the following conditions (A), (B) and (C) and a photopolymerization initiator. (A) The free isocyanate group content in 1 g of polyurethane is 0.3 to 3.0 mmol / g. (B) The urethane bond content in 1 g of polyurethane is 2.
0 to 4.5 mmol / g (C) The vinyl group content in 1 g of the polyurethane is 1.0 to
3.0 mmol / g In the polyurethane, it is preferable that a methacryloyl group or an acryloyl group be bonded to at least one of the molecular terminals, and the other molecular terminals be an isocyanate group.

The urethane bond of the polyurethane is preferably formed by a reaction between polytetramethylene ether glycol and an alicyclic polyisocyanate, and the polytetramethylene ether glycol has a number average molecular weight. It is preferably from 200 to 2500.

[0012] The golf ball paint of the present invention comprises a polyol and a polyisocyanate as the polyurethane.
The equivalent ratio (OH: NCO) of the hydroxyl group of the polyol to the isocyanate group of the polyisocyanate is 0.1: 1 to 1
After the reaction at a ratio of 0.6: 1, the hydroxyl group-containing vinyl monomer was converted to an equivalent ratio (OH: NCO) of the hydroxyl group of the hydroxyl group-containing vinyl monomer to the isocyanate group of the polyisocyanate of 0.2: 1 to 0.1. It is preferable to use a polyurethane obtained by adding and reacting at a ratio of 8: 1. In particular, N is obtained by using acrylate or methacrylate as the hydroxy group-containing vinyl monomer.
Preference is given to polyurethane acrylates containing CO groups or polyurethane methacrylates containing NCO groups.

Further, a polyurethane resin containing the polyurethane according to any one of claims 1 to 6 and a polymerizable vinyl monomer may be used in place of the polyurethane.

The golf ball of the present invention is obtained by coating the surface of an ionomer cover with the above-mentioned paint for a golf ball of the present invention.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The paint for golf balls of the present invention comprises:
An ultraviolet-curable paint containing a polyurethane satisfying the following requirements (A), (B) and (C) (hereinafter referred to as “ultraviolet-curable polyurethane”) and a photopolymerization initiator.

Condition (A): UV-curable polyurethane 1
g is 3.0 mmol / g or more, preferably 0.5 mmol / g or more, and is 3.0 mm / g.
ol / g or less, preferably 2.5 mmol / g or less.

The free isocyanate group in the ultraviolet-curable polyurethane molecule has the function of improving the adhesion to the surface layer of the ball, particularly to the cover made of an ionomer. To obtain such an effect, the isocyanate group content is 0.3 mmol.
/ G or more is required. On the other hand, the free isocyanate groups in the molecule do not participate in the polymerization or curing reaction caused by the irradiation of the ultraviolet rays, and therefore remain as free isocyanate groups at the molecular terminals even after the irradiation of the ultraviolet rays. For this reason, if there are many isocyanate groups, the number of unreacted molecular terminals increases, and this unreacted molecular terminal causes tack, so that it is necessary to be 3.0 mmol / g or less.

Condition (B): The content of urethane bonds in the ultraviolet-curable polyurethane is at least 2.0 mmol / g, preferably at least 2.5 mmol / g and 4.5 mmol / g.
Or less, preferably 4.0 mmol / g or less.

The urethane bond content is determined as a calculated value on the assumption that all the hydroxyl groups contained in the raw materials added for the synthesis of the ultraviolet-curable polyurethane react with the isocyanate groups to form urethane bonds.
The urethane binding portion acts as a hard segment of polyurethane, the other portion of polyurethane acts as a soft segment, and the balance of the hard segment and the soft segment allows the flexibility of the coating film to follow the deformation of the ball due to impact, Contributes to elasticity. Therefore,
If it is less than 2.0 mmol / g, the proportion in the formed polyurethane becomes too small, the elasticity becomes insufficient, and it becomes impossible to follow the deformation at the time of impact, and the coating film is easily peeled.
On the other hand, if it exceeds 4.5 mmol / g, the proportion of the hard segment in the polyurethane becomes too large, the elasticity and flexibility are reduced, cracks are easily generated, and the coating film is easily peeled off.

Condition (C): The content of the vinyl group in the ultraviolet-curable polyurethane is 1.0 mmol / g or more, preferably 1.5 mmol / g or more and 3.0 mmol / g or less, preferably 2.5 mmol / g. It is as follows.

The vinyl group in the ultraviolet-curable polyurethane has a function of performing vinyl polymerization by irradiating ultraviolet rays and curing a polymer chain having a urethane bond by increasing the molecular weight. Therefore, if the amount is less than 1.0 mmol / g, crosslinking and curing becomes insufficient, and tack remains even after ultraviolet curing. On the other hand, if it exceeds 3.0 mmol / g, the crosslinking density becomes too high, and the flexibility of the coating film is lost, so that the coating film cannot follow the deformation of the ball due to the impact, and the coating film is easily cracked.

The ultraviolet-curable polyurethane satisfying the above conditions (A), (B) and (C) is a polyurethane having an isocyanate group and a vinyl group at the molecular terminal, and preferably the vinyl group is an acryloyl group or a methacryloyl group. That is, a polyurethane (meth) acrylate having an NCO group at a terminal (hereinafter, referred to as “NCO group-containing polyurethane (meth) acrylate”) is particularly preferable.
Such UV-curable polyurethane is, specifically,
It is obtained by reacting a hydroxyl group-containing vinyl compound with an isocyanate-terminated polyurethane obtained by reacting a polyol and a polyisocyanate in excess of isocyanate.

As the above polyisocyanate compound,
Especially limited if it has two or more isocyanate groups
Without using hexamethylene diisocyanate (HD
I), xylylene diisocyanate (XDI), hydrogenated
Silylene diisocyanate (H ₆XDI), isophorone
Diisocyanate (IPDI), tetramethylxylylene
Diisocyanate (TMXDI), hydrogenated diphenylmeth
Tandiisocyanate (H₁₂MDI), norbornane
Aliphatic, alicyclic, aromatic, aromatic oils such as isocyanates
An aliphatic diisocyanate compound is exemplified. These
Non-yellowing polyisocyanates (aliphatic and alicyclic)
Polyisocyanate) is preferably used, and more preferably
Or isophorone diisocyanate. Paint of the present invention
Is initially cured by ultraviolet irradiation, as described below.
Things. UV irradiation excites oxygen in the air
Oxygen radicals are produced, and yellowish
Non-yellowing polyisocyanates (fat
Or alicyclic polyisocyanates) are preferably used.
You.

As the polyol, any low molecular weight compound or high molecular weight compound may be used as long as it has a plurality of hydroxyl groups. Examples of low molecular polyols include diols such as ethylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol; and glycerin. And triols such as trimethylolpropane and hexanetriol. As the high molecular polyol, a polyether polyol obtained by reacting an initiator having an active hydrogen atom with an alkylene oxide; a condensation polyester obtained by dehydration condensation of a dibasic acid such as adipic acid with glycol or triol Polyols; lactone-based polyester polyols obtained by ring-opening polymerization of lactams such as ε-caprolactam; polycarbonate diols synthesized using cyclic diols; acrylic polyols obtained by appropriately introducing a hydroxyl group into an acrylic copolymer; epoxy resin-based Polyol;
Silicone-based polyols; polyolefin polyols;
Polybutadiene polyol; and polymer polyols such as castor oil. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polyether ricinoleate.Examples of the condensation polyester polyol include polyethylene azide, and examples of the lactone polyester polyol include polyether. -Ε-caprolactone and the like. Examples of the acrylic polyol include S-acryl polyol. Among them, polyether polyol is preferably used, and more preferably polytetramethylene ether glycol.

As the polytetramethylene ether glycol, a polytetramethylene ether glycol having a number average molecular weight of about 200 to 2500 is particularly preferable. If the number average molecular weight is too large, the urethane group content of the coating film tends to be small and a soft coating film is formed, or the vinyl group content tends to be small and the curability tends to be low.

The polyurethane main chain portion of the ultraviolet-curable polyurethane used in the present invention is constituted by various combinations of the above polyols and polyisocyanates. The most preferable combination is polytetramethylene ether glycol and alicyclic polyisocyanate. Polyurethane obtained by reaction with isocyanate.

The polyol and the polyisocyanate are preferably used such that the equivalent ratio (OH: NCO) of the hydroxyl group to the isocyanate is 0.65: 1 to 0.95: 1. This is because the reaction at such a ratio can leave an isocyanate group at the molecular end so as to satisfy the condition (A) and form a polyurethane main chain portion satisfying the above condition (B).

The vinyl compound used for bonding to the terminal of the polyurethane main chain has a vinyl bond,
In addition, it is preferably a compound having a hydroxyl group (a hydroxyl group-containing vinyl monomer) so that it can react with an isocyanate terminal of the polyurethane to form a bond. Specifically, 2-hydroxyethyl (meth) acrylate,
3-hydroxypropyl (meth) acrylate, (meth)
Alcoholic hydroxyl such as "Placcel F" series (manufactured by Daicel Chemical Industries, Ltd.), which is a polycaprolactone modified product of 2-hydroxypropyl acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. Group-containing (meth) acrylates and the like. Of these, hydroxyethyl acrylate is particularly preferably used.

The vinyl compound is added to the previously synthesized polyurethane main chain as long as the condition (C) can be satisfied. First, a polyurethane main chain having isocyanate groups at both ends is first synthesized as a polyurethane main chain, and this is reacted with a hydroxyl group-containing vinyl compound to form an NCO.
In the case of synthesizing a group-containing polyurethane (meth) acrylate, a polyol and a polyisocyanate are used in an equivalent ratio (OH: NCO) of a hydroxyl group of the polyol and an isocyanate group of the polyisocyanate of 0.1: 1 to 0.6:
After the reaction in step 1, the hydroxyl group-containing vinyl monomer is converted to a hydroxyl group-containing vinyl monomer having an equivalent ratio (OH: NCO) of the isocyanate group of the polyisocyanate of 0.2: 1 to 0.8: 1. Add,
A polyurethane obtained by the reaction is preferably used.

Instead of the polyurethane satisfying the above conditions (A), (B) and (C), a polyurethane (preferably N
As the polyurethane resin containing a CO group-containing polyurethane (meth) acrylate and a polymerizable vinyl monomer, a resin that satisfies the above conditions (A), (B), and (C) can also be used. As the polymerizable vinyl monomer that can be used in this case, an unsaturated carboxylic acid ester such as acrylate or methacrylate is preferably used, and all of the alcoholic hydroxyl groups such as triethylene glycol diacrylate and trimethylolpropane triacrylate are used. It may be a vinyl polymerizable monomer that has been converted to an ester, or may be a hydroxy group-containing vinyl monomer having an alcoholic hydroxyl group remaining, such as pentaerythritol triacrylate and pentaerythritol diacrylate.

Next, the photopolymerization initiation curing agent used in the paint of the present invention will be described.

Examples of the photopolymerization initiator include benzoin such as benzoin, benzoin methyl ether and benzoin ethyl ether and alkyl ethers thereof; acetophenone such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone and 1,1-dichloroacetophenone. Anthraquinones such as 2-methylanthraquinone, 2-amylanthraquinone, 2-t-butylanthraquinone and 1-chloroanthraquinone; thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone and 2-chlorothioxanthone ;
Ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone; 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one and 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) -butanone-1; acylphosphine oxides and xanthones; a complex of diazonium and Lewis acid, and the like, which may be selected according to the type of ultraviolet-curable polyurethane. For example, when the UV-curable polyurethane is a (meth) acryloyloxy-containing polyurethane, 2-hydroxy-2-methyl-1-phenylpropan-1-one and 1-hydroxy-cyclohexyl-phenyl ketone are preferably used.

The golf ball paint of the present invention includes an ultraviolet-curable polyurethane or a polyurethane resin satisfying the conditions (A), (B) and (C) (hereinafter collectively referred to as "ultraviolet-curable polyurethane" unless otherwise specified). (Referred to as a resin) or a diluent in addition to the photopolymerization initiator. The diluent is added to uniformly disperse the ultraviolet-curable polyurethane (or resin) and the photopolymerization initiator so as to facilitate the coating operation. It is preferable to use an organic solvent as the diluent.

Examples of the organic solvent include hydrocarbons such as toluene and xylene; cellosolves such as cellosolve and butyl cellosolve; carbitols such as carbitol and butyl carbitol; cellosolve acetate, carbitol acetate, propylene glycol monomethyl ether acetate and the like. Esters; ketones such as methyl ethyl ketone; ethers such as diethylene glycol dimethyl ether; and the like, and two or more kinds thereof may be used in combination.

The organic solvent volatilizes to some extent at the time of coating, but remains even after polymerization by ultraviolet irradiation.
Since it gradually evaporates at room temperature curing, it is preferable to use an amount that does not cause tack after irradiation with ultraviolet rays.

The paint of the present invention may optionally contain
Furthermore, in order to improve the storage stability of the paint, a small amount of a polymerization inhibitor (for example, hydroquinones), an ultraviolet absorber, a light stabilizer,
A slip agent, a fluorescent whitening agent, another polymer or the like may be contained. As another polymer, a polyester polyol is preferably used.

The golf ball paint of the present invention having the above-described structure can be applied by a conventionally known coating method, spray coating, brush coating, paint gun, dipping, or the like.

After coating, the initial curing of the paint is completed by irradiating ultraviolet rays to cure the ultraviolet-curable polyurethane (or resin).

The ultraviolet light to be irradiated is 250 to 450 nm,
Preferably it is 340-460 nm. Specifically, a commercially available mercury lamp, arc lamp, xenon lamp, or the like can be used as the ultraviolet heat source.

The ultraviolet irradiation time may be any time as long as radical polymerization of the ultraviolet curable polyurethane can be caused, and specifically, is preferably about 0.2 to 10 seconds, more preferably 0.5 to 3 seconds. It is about. The ultraviolet curable polyurethane is cured by vinyl polymerization to such an extent that no tack remains, so that even when the crosslinking and curing of the polyurethane have hardly progressed, tackiness when touching a finger is eliminated. And, the free isocyanate of the ultraviolet curing type polyurethane, the ball body surface,
In particular, since it can show an affinity for the surface of the ionomer cover, necessary coating film adhesion can be maintained. Further, the free isocyanate in the ultraviolet curable polyurethane reacts with moisture in the air or a residual hydroxyl or a polyhydroxyl group-containing compound added to the resin, whereby the crosslinking and curing of the polyurethane progresses, and the adhesion of the coating film and Strength can be increased.

As described above, the paint of the present invention completes the initial curing of the coating film by the irradiation of ultraviolet rays, and the painted paint does not fall off the surface of the ball body. Therefore, the paint is transferred to the next step such as boxing work. And increase productivity.

The golf ball of the present invention is obtained by forming a cured film of the golf ball paint of the present invention having the above composition on the surface of a ball body.

In the case of a one-piece golf ball, the ball body used in the present invention is a sphere made of vulcanized rubber;
In the case of a multi-piece golf ball having at least one layer of a core and at least one layer of a cover, the core and the cover; in the case of a thread wound golf ball, a thread rubber is wound around a liquid center or a solid center, and one or more layers are wound thereon. Covered with a cover.

The material of the core constituting the ball body is not particularly limited. The cover may be made of a natural material such as balata, a synthetic resin such as an ionomer or an elastomer, or a blend thereof, but is preferably a material containing an ionomer. This is because the ionomer has a carboxyl group, has excellent affinity with the paint of the present invention, and has a large effect of improving the adhesion.

The above-mentioned ball body may be subjected to a surface roughening process known to those skilled in the art, such as a sand blasting process, a shot blasting process, and a buffing process, before applying the paint. Such a roughening treatment can physically improve the adhesion to the coating film.

The coating amount of the ball coating is preferably such that the thickness of the coating film formed is about 5 μm to 30 μm.

The coating method is not particularly limited, and conventionally known methods such as spray coating and dipping can be used.

[0048]

EXAMPLES [Evaluation and Measurement Methods] (1) Drying property A finger touch test was performed on the ball immediately after the irradiation with ultraviolet rays.
(Fingerprint remains on the ball coating), △ (feels tacky),
（(No tackiness was felt).

(2) Durability of Coating Film Peeling Test The ball was immersed in water for 3 days after irradiation with ultraviolet rays. The ball was hit 100 times with a driver-type club attached to a swing machine manufactured by True Temper. The ball after impact is visually observed, and depending on the degree of peeling of the coating film, ○ (no peeling), Δ (total peeling area 10 mm ²
Less than), × (total peeling area is 10 mm ² or more)
Was evaluated in three steps.

Crack The ball was immersed in water for 3 days after the irradiation with ultraviolet rays. The ball was hit 100 times with a driver-type club attached to a swing machine manufactured by True Temper. The ball after hitting is visually observed, and according to the degree of cracking, ○ (no crack), Δ (total crack area 10 mm)
² ) and x (the total area of cracks is 10 mm ² or more).

(3) Free isocyanate group content (mol / g) The isocyanate group content in 1 g of the solid content of the coating composition is determined such that all the hydroxyl groups react with the isocyanate groups on a one-to-one basis, and the excess isocyanate groups remain. It was calculated assuming that
Specifically, a value obtained by subtracting the number of hydroxyl groups from the number of added isocyanate groups was calculated as the number of isocyanate groups contained in urethane acrylate.

Based on the calculated isocyanate group calculation method, the number of moles of the isocyanate group contained in 1 g of the solid content of the paint was determined.

(4) Urethane bond content (mol / g) The number of moles of urethane bonds in 1 g of the solid content of the paint is calculated on the assumption that all hydroxyl groups in the added compound react with isocyanate groups to form urethane bonds. did.

(5) Vinyl Group Content (mol / g) The number of moles of vinyl group contained in 1 g of the solid content of the paint was calculated assuming that the vinyl group of the added vinyl compound was kept as it was.

[Preparation of paint] A paint having a composition shown in Table 1 was prepared using an ultraviolet-curable polyurethane resin prepared as follows.

[0056]

[Table 1]

In Table 1, as the photopolymerization initiator, "Darocur-" manufactured by Ciba Specialty Chemicals Co., Ltd. was used.
1173 "(trade name of 2-hydroxy-2-methyl-1-phenylpropan-1-one), and" Tinuvin 400 "manufactured by Ciba Specialty Chemicals Co., Ltd. was used as an ultraviolet absorber.

[Synthesis of UV-curable polyurethane resin]
A 500 cc flask equipped with a stirrer and a cooler was charged with a predetermined amount of isophorone diisocyanate (IPDI), 38.2 g of toluene, 80 g of methyl ethyl ketone, and 1.8 g of a 5% toluene solution of dibutyltin dilaurate. After heating and dropping a predetermined amount of a predetermined polyol (polytetramethylene ether glycol or butanediol) and reacting for 1 hour while maintaining at 80 ° C., a predetermined amount of 2-hydroxyethyl acrylate (2-HEA) and hydroquinone 0.1 g of a 1% toluene solution containing ethyl ether was added dropwise, and the mixture was further reacted for 2 hours.
o. 1-11 and 13-21 were obtained. No. With regard to No. 12, the reaction of isophorone diisocyanate, polytetramethylene ether glycol and 2-HEA
After synthesizing the O-group-containing polyurethane acrylate, Table 1
In preparing a coating having the composition shown in (1), trimethylolpropane triacrylate (TMP-A) was added. The isocyanate content, urethane bond content, and vinyl group content of the obtained ultraviolet-curable urethane resin are shown in Table.
2 and Table 3.

Incidentally, isophorone diisocyanate was manufactured by Sumitomo Bayer Urethane Co., Ltd., and polytetramethylene ether glycol was manufactured by BASF Corporation. Trimethylolpropane triacrylate (TMP-A)
Was manufactured by Kyoeisha Chemical Co., Ltd. Further, as polytetramethylene ether glycol, PTMG250
(Number average molecular weight 250), PTMG650 (Number average molecular weight 650), PTMG (Number average molecular weight 1000), and PTMG2000 (Number average molecular weight 2000) were used.

[Manufacture of Golf Ball] The paint No. 1 prepared above was coated on the surface of a two-piece golf ball having a diameter of 42 mm in which a rubber core was covered with an ionomer cover using an air gun. Nos. 1 to 21 and conventional two-component curable polyurethane paint Nos. No. 22 (a two-pack curing type using a polyether urethane prepolymer having a hydroxyl group at the end as a polyol and a modified HDI as an isocyanate) was applied to a coating amount of 120 mg.

No. With respect to 1 to 21, after coating, ultraviolet rays were irradiated for 1.5 seconds using a high-pressure mercury lamp to produce a coated golf ball. No. After coating, No. 22 was dried and cured at 40 ° C. for 1 hour.

With respect to the manufactured golf balls, the paint drying property and the durability of the coating film were evaluated based on the above evaluation methods. Tables 2 and 3 show the composition and evaluation results of the ultraviolet-curable polyurethane resin used for the paint.

[0063]

[Table 2]

[0064]

[Table 3]

No. As can be seen from 17, 20, and 21, when the isocyanate content of the ultraviolet-curable polyurethane is low, the adhesion of the coating film is reduced and the coating film is easily peeled. Conversely, if the free isocyanate content of the ultraviolet-curable polyurethane is too high, it becomes sticky and poor in dryness. On the other hand, if the vinyl bond content is low, the strength of the coating film is low, and the peelability is poor (No. 1)
3).

In addition, No. 14, 16 that the urethane bond content is too low or too high,
The coating film adhesion was poor. This is probably because the stretchability of the coating film was reduced.

When the vinyl bond content was low, the drying property was reduced, and the coating strength was lowered, so that the coating adhesion was poor (No. 18). On the other hand, if the vinyl bond content is too high, the rate of curing by irradiation with ultraviolet rays increases, so that peeling of the coating film and cracks tend to occur (No. 1).
5, 19).

On the other hand, no. Polyurethanes 1 to 11 are
The isocyanate group content, urethane bond content, and vinyl group content satisfy the requirements (A), (B), and (C) of the present invention, respectively, so that the drying property and the coating film durability can be satisfied. In addition, No. 3 and No. Compared with No. 12, the requirement (A) of the present invention can be obtained by adding a vinyl polymerizable monomer separately from the NCO group-containing polyurethane acrylate.
Even when (B) and (C) are satisfied, the drying property and the coating film durability can be similarly satisfied.

It should be noted that a conventional two-component cured polyurethane paint (N
o. Since 22) does not contain a vinyl bond, it does not cure even when irradiated with ultraviolet light, does not cure unless dried at 40 ° C. for about 1 hour, and has poor drying properties.

[0070]

The paint for golf balls of the present invention has been initially cured to the extent that it is not sticky by the irradiation of ultraviolet rays, so that it is possible to proceed to the next step immediately after the irradiation, and the productivity is good.
Further, since the free isocyanate group has an affinity for the ball body surface and can contribute to the crosslinking and curing of the coating film, the coating film adhesion and the coating film strength required for the coating film can be secured.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoto Maruoka 3-6-9, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Inside Sumitomo Rubber Industries, Ltd. (72) Inventor Masaaki Kikuchi, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture 3-6-9 Sumitomo Rubber Industries, Ltd. F-term (reference) 4J038 DG051 DG271 DG321 FA122 FA281 GA01 GA08 GA11 JA33 KA03 NA12 PA17 PB02

Claims (8)

[Claims] 1. A golf ball paint comprising a polyurethane satisfying the following conditions (A), (B) and (C) and a photopolymerization initiator. (A) The free isocyanate group content in 1 g of polyurethane is 0.3 to 3.0 mmol / g. (B) The urethane bond content in 1 g of polyurethane is 2.
0 to 4.5 mmol / g (C) The vinyl group content in 1 g of the polyurethane is 1.0 to
3.0 mmol / g 2. The golf ball paint according to claim 1, wherein the polyurethane has a methacryloyl group or an acryloyl group bonded to at least one molecular terminal, and the other molecular terminal is an isocyanate group. 3. The golf ball paint according to claim 1, wherein the urethane bond of the polyurethane is formed by a reaction between polytetramethylene ether glycol and an alicyclic polyisocyanate. 4. The coating for golf balls according to claim 3, wherein the polytetramethylene ether glycol has a number average molecular weight of 200 to 2500. 5. As the polyurethane, a polyol and a polyisocyanate are used in an equivalent ratio of hydroxyl group of the polyol to isocyanate group of the polyisocyanate (OH:
NCO) is reacted at 0.1: 1 to 0.6: 1, and then the hydroxyl group-containing vinyl monomer is converted into an equivalent ratio of hydroxyl group of the hydroxyl group-containing vinyl monomer to isocyanate group of the polyisocyanate (OH: NCO). Is 0.
The golf ball paint according to any one of claims 1 to 4, wherein the polyurethane is added and reacted in a range of 2: 1 to 0.8: 1. 6. The golf ball paint according to claim 5, wherein the polyurethane is an NCO group-containing polyurethane acrylate or an NCO group-containing polyurethane methacrylate obtained by using acrylate or methacrylate as the hydroxy group-containing vinyl monomer. 7. The method according to claim 1, wherein the polyurethane is used instead of the polyurethane.
6. A golf ball paint using the polyurethane resin containing the polyurethane according to any one of 6 and a polymerizable vinyl monomer. 8. A golf ball obtained by coating the surface of an ionomer cover with the paint according to claim 1.