JP2003183574A - Aqueous one-portion coating material and coating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous one-portion coating material which excels in storage stability, is environment-friendly, adheres to a substrate in a short period, and has a good appearance of a coated film, and a coating method having excellent workability. <P>SOLUTION: The aqueous one-portion coating material contains a thermosetting aqueous resin emulsion which is obtained by dispersing an organic polyisocyanate modified with a silane coupling agent into water or dispersing the organic polyisocyanate into an aqueous resin emulsion having a silane coupling agent structure to react the isocyanate groups with water until free isocyanate groups do not exist. The coating method comprises coating the aqueous one-portion coating material on the substrate at <80°C, and then is heat-cured at 80-300°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous one-component coating agent and a coating method using the same.

[0002]

2. Description of the Related Art A coating agent containing a large amount of an organic solvent has a harmful effect on the human body, safety and health problems such as explosion and fire,
It also has pollution problems such as air pollution. Therefore, in order to improve these problems, aqueous system development has been actively conducted in recent years. On the other hand, urethane coating agents
Shows good adhesion to various substrates. Therefore, the conventional water-based urethane coating agent is a two-component type composed of (a) a main agent having an active hydrogen group and a polyisocyanate curing agent, and (b) a main agent having an active hydrogen group in which a block isocyanate is preliminarily blended. One-liquid type,
(C) It is roughly classified into a one-pack type composed of a resin having an isocyanate group.

As the type (a), Japanese Patent Laid-Open No. 11-13
No. 1016 discloses a water-based coating agent using a specific water-based acrylic resin as a main agent and a water-dispersible polyisocyanate composition as a curing agent. As the type (b), Japanese Patent Application Laid-Open No. 8-4891
No. 3, which discloses a main component in which a specific hydrophobic polymer is dispersed in water with a surfactant, and an aqueous coating agent using blocked isocyanate as a curing agent. As the type (c), there is JP-A-7-48.
No. 429, which discloses a coating agent using a self-emulsifying polyisocyanate dispersed in water.

However, the type (a) type coating agent has a problem in that the main agent and the curing agent must be compounded immediately before use, so that the composition may be erroneous and a storage place may be secured. Further, after the main agent and the curing agent have been mixed, they must be used up immediately, and it is very difficult to store the once mixed. In the type (b), the blocking agent that has not been dissociated during curing gradually dissociates, which causes a problem such as a decrease in adhesion. The type (c) has problems such as carbon dioxide gas generated during the reaction between water and isocyanate groups (damage of the container during storage, poor state of the coating).

[0005]

DISCLOSURE OF THE INVENTION The present invention is an aqueous one-component solution which has excellent storage stability, is safe in consideration of the environment, exhibits adhesiveness to a substrate in a short time, and has a good film appearance. It is an object to provide a coating agent and a coating method having excellent workability.

As a result of intensive studies, the present inventors have found that an aqueous one-component coating agent using a specific aqueous dispersion can solve the above problems, and have completed the present invention.

That is, the present invention provides the following (1) to (6):
Is shown in. (1) Using a silane coupling agent having at least an organic diisocyanate and an isocyanate-reactive group,
An organic polyisocyanate obtained by directly reacting an isocyanate group and an isocyanate-reactive group is dispersed in water, and the isocyanate group and water are reacted until substantially no free isocyanate group is present, and substantially An aqueous one-component coating agent comprising a one-component thermosetting aqueous resin emulsion that does not have free isocyanate groups.

(2) An organic polyisocyanate obtained by directly or indirectly reacting isocyanate groups with at least an organic diisocyanate and a silane coupling agent having an isocyanate group is dispersed in water to form an isocyanate group. An aqueous one-component composition obtained by reacting water until substantially no free isocyanate groups are present, and containing a one-component thermosetting aqueous resin emulsion having substantially no free isocyanate groups. Coating agent.

(3) Obtained by mixing an organic polyisocyanate and a silane coupling agent having an isocyanate group, dispersing the mixture in water, and reacting the isocyanate group with water until substantially no free isocyanate group is present. And a one-component thermosetting water-based resin emulsion having substantially no free isocyanate group, an aqueous one-component coating agent.

(4) Obtained by dispersing an organic polyisocyanate in an aqueous resin emulsion in which a silane coupling agent is introduced into the molecular skeleton, and reacting an isocyanate group with water until substantially no free isocyanate group is present, An aqueous one-component coating agent comprising a one-component thermosetting aqueous resin emulsion having substantially no free isocyanate group.

(5) The aqueous one-component coating agent according to any one of (1) to (4) above, wherein the organic polyisocyanate is a self-emulsifying polyisocyanate.

(6) The aqueous one-pack coating agent according to any one of (1) to (5) is applied to a substrate at a temperature of less than 80 ° C. and then heat cured at 80 to 300 ° C. And coating method.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The aqueous one-component coating agent of the present invention is obtained from an organic polyisocyanate, a silane coupling agent component, and water, and contains a one-component thermosetting aqueous resin emulsion having substantially no free isocyanate group. Is characterized by. In addition, "one-component thermosetting" means that it is cured by heating it alone without using a curing agent or a crosslinking agent. Further, "curing" means that when a film is formed, it becomes a film having at least solvent resistance.

The organic polyisocyanate used in the present invention has (a) a silane coupling agent structure in the molecular skeleton and (b) a silane coupling agent structure in the molecular skeleton before the water dispersion. Not classified.

The organic polyisocyanate of (a) above is
(A-1) A product obtained by directly reacting an organic diisocyanate with a silane coupling agent having an isocyanate-reactive group, and (a-2) directly or indirectly using a silane coupling agent having an organic diisocyanate and an isocyanate group. There is something that can be obtained by reacting dynamically. Here, "directly" means not through a compound that acts as an intermediary, but means that the compound that acts as an "indirect" mediates. Specifically, it is as shown in the following formula.

[Chemical 1]

[Chemical 2]

[Chemical 3] (R ₁ and R ₂ represent a divalent hydrocarbon group, R ₃ represents a monovalent hydrocarbon group, and R ₄ represents a trivalent hydrocarbon group.)

That is, in the case of the formulas (1) and (2), it means that the organic diisocyanate and the silane coupling agent are reacted “directly” without the presence of any intervening compound. In the case of the formula (3), the organic diisocyanate and the silane coupling agent are "indirectly" reacted through the mediating compound.

The above-mentioned organic polyisocyanate (b) is
Initially, it does not have a silane coupling agent structure in the molecular skeleton, but after water dispersion / reaction, it has a silane coupling agent structure in the molecular skeleton.

The isocyanate content of the organic polyisocyanate used in the present invention is preferably 1 to 30% by mass, and particularly preferably 1 to 25% by mass. The viscosity at 25 ° C is preferably 5,000 mPa · s or less, and particularly preferably 4,500 mPa · s or less. Moreover, 2-5 are preferable and, as for the average number of functional groups, 2-4 are especially preferable.

The organic polyisocyanate is preferably a uretdione modified product, a carbodiimide modified product, an isocyanurate modified product, or a uretonimine modified product of an organic diisocyanate. As this organic diisocyanate,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4,4'-
Diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,
4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,
Aroma such as 4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate Group diisocyanates, polyphenylene polymethylene polyisocyanates, aromatic polyisocyanates such as crude tolylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, aliphatic diisocyanates such as lysine diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogen Added xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, tetrame Alicyclic diisocyanates such as Le xylene diisocyanate. In addition, a part of the organic diisocyanate may be replaced with an isocyanate group-containing silane coupling agent such as γ-isocyanatopropyltriethoxysilane.

Further, an isocyanate group-terminated prepolymer obtained by reacting the above organic diisocyanate with a silane coupling agent having an active hydrogen group-containing compound and / or an isocyanate-reactive group, and the prepolymer is further biuret-modified, allophanate-modified, carbodiimide. Degeneration,
A polyisocyanate obtained by uretonimine modification, uretdione modification, isocyanurate modification, or a combination of these modifications can also be preferably used. The "isocyanate-reactive group" is a concept including a group having active hydrogen such as a hydroxyl group, an amino group and a mercapto group, as well as an epoxy group.

Specific examples of the active hydrogen group-containing compound include water, a low molecular weight polyol having a (number average) molecular weight of 62 to less than 500, a low molecular weight polyamine, a low molecular weight amino alcohol, and a high number average molecular weight of 500 to 10,000. A molecular polyol etc. are mentioned. Any of these active hydrogen group-containing compounds may be used alone or in combination of two or more.

The low molecular weight polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and 1,5. -Pentanediol, 1,6-hexanediol, 2-methyl-1,
5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, decamethylene glycol, diethylene glycol, dipropylene glycol, 2,2-diethyl- 1,3-propanediol, 2
-N-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-n-
Hexadecane-1,2-ethylene glycol, 2-n-
Eicosane-1,2-ethylene glycol, 2-n-octacosane-1,2-ethylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, 3-hydroxy-2,2-dimethylpropyl- 3-hydroxy-2,2-dimethylpropionate, dimer acid diol, bisphenol A, hydrogenated bisphenol A, ethylene oxide or propylene oxide adduct of bisphenol A, ethylene oxide or propylene oxide adduct of hydrogenated bisphenol A, tri Low molecular weight polyols having no ionic polar group such as methylolpropane, glycerin, hexanetriol, quadrol, pentaerythritol, sorbitol, 2,2-dimethylolpropionic acid,
-COOH-containing low molecular weight polyols such as 2,2-dimethylolbutanoic acid, salts of -COOH-containing low molecular weight polyols with ammonia, organic amines, alkali metals, alkaline earth metals, etc., 2-sulfo-1,3 -Sulfonic acid group-containing low molecular weight polyols such as propanediol and 2-sulfo-1,4-butanediol, and salts of sulfonic acid group-containing low molecular weight polyols with ammonia, organic amines, alkali metals, alkaline earth metals, etc. Etc. Also,
A reaction product obtained by reacting an isocyanate group-containing silane coupling agent such as γ-isocyanatopropyltriethoxysilane with a low-molecular polyol under conditions of excess hydroxyl groups can also be used.

As the low molecular weight polyamine, ethylenediamine, hexamethylenediamine, isophoronediamine,
Mensendiamine, 4,4'-diphenylmethanediamine, 4,4'-diaminodiphenylsulfone, metaxylenediamine, piperazine and the like can be mentioned.

Examples of low molecular weight amino alcohols include monoalkanolamines such as monoethanolamine, monopropanolamine, diethanolamine and dipropanolamine, and dialkanolamines.

Examples of the polymer polyol include polyester polyol, polyamide ester polyol, polycarbonate polyol, polyether polyol, polyether ester polyol, polyolefin polyol, animal / plant type polyol and the like.

As the polyester polyol, phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, curtaconic acid, azelaic acid, sebacic acid, succinic acid, Adipic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,
β-diethylsuccinic acid, maleic acid, fumaric acid, trimellitic acid, pyromellitic acid, and other polycarboxylic acids having no cationic group, and sulfonic acid group-containing polycarboxylic acids such as 5-sulfo-isophthalic acid and their sulfones. Reaction of a salt of an acid group-containing polycarboxylic acid with ammonia, an organic amine, an alkali metal, an alkaline earth metal, etc., one or more of these acid anhydrides, acid halides, dialkyl esters, etc., and the aforementioned low-molecular polyol And the like can be mentioned. Furthermore, using the above-mentioned low molecular weight polyol as an initiator, ε-caprolactone, alkyl-substituted ε-
Caprolactone, δ-valerolactone, alkyl-substituted δ
Examples thereof include lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as valerolactone. Further, a polyamide ester polyol obtained by using a low molecular weight polyamine such as hexamethylenediamine, isophoronediamine, monoethanolamine or the like and a low molecular weight amino alcohol in place of a part of the low molecular weight polyol can be mentioned.

Examples of the polycarbonate polyols include those obtained by dealcoholation reaction and dephenolation reaction of one or more kinds of the above-mentioned low molecular weight polyols with ethylene carbonate, diethyl carbonate and diphenyl carbonate.

As the polyether polyol, the above-mentioned low molecular weight polyol, low molecular weight polyamine or low molecular weight amino alcohol is used as an initiator to open an alkylene oxide such as ethylene oxide or propylene oxide, or a cyclic ether such as tetrahydrofuran, or a mixture thereof. The thing obtained by superposing | polymerizing is mentioned.

Examples of the polyether ester polyol include the above-mentioned polyether polyol and the above-mentioned copolyol obtained from dicarboxylic acid and the like. Also,
Examples thereof include those obtained by reacting the above-mentioned polyester or polycarbonate with alkylene oxide or cyclic ether.

Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, and chlorinated products thereof.

Examples of animal and plant polyols include castor oil-based polyols and silk fibroin.

In addition to dimer acid type polyols and hydrogenated dimer acid type polyols, epoxy resins having a number average molecular weight of 500 or more and having an average of 1 or more active hydrogen groups in one molecule are also used. , Polyamide resin,
Resins containing active hydrogen groups such as polyester resin, acrylic resin, rosin resin, urea resin, melamine resin, phenol resin, coumarone resin, polyvinyl alcohol and the like can also be used.

Examples of the silane coupling agent having an isocyanate-reactive group include epoxysilane compounds such as β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, and γ-amino. Propyltriethoxysilane, N-β
Examples thereof include aminosilane compounds such as -aminoethyl-γ-aminopropylmethyldimethoxysilane and mercaptosilane compounds such as γ-mercaptopropyltrimethoxysilane.

When an ethylenically unsaturated bond- and active hydrogen group-containing compound is used, a vinylsilane compound such as γ-methacryloxypropyltrimethoxysilane or vinyltriethoxysilane can be used.

The temperature in the reaction between the isocyanate group and the active hydrogen group is preferably 0 to 100 ° C., more preferably 20 to 100 ° C.
80 ° C. is preferred. The molar ratio of the isocyanate group to the active hydrogen group at this time is preferably isocyanate group / active hydrogen group = 1.1 / 1 to 100/1. In order to accelerate the reaction, a metal catalyst commonly used in the production of polyurethane or polyurea such as dibutyltin dilaurate or a tertiary amine catalyst such as triethylamine may be used as the catalyst.

Further, the reaction may be further advanced to form allophanate or biuret. The reaction temperature at this time is preferably 80 to 150 ° C. As the catalyst at this time,
Mention may be made of metal salts of carboxylic acids.

The carbodiimidization (uretonimine conversion) modification of an organic diisocyanate or an isocyanate group-terminated prepolymer is carried out at a reaction temperature of 100 to 200 ° C. in the presence of a known carbodiimidization catalyst. Further, these uretdione modification and isocyanurate modification are carried out at a reaction temperature of 0 to 100 ° C. in the presence of a known uretdione catalyst and isocyanurate catalyst. At this time, a known cocatalyst may be used.

The reaction apparatus at this time may be any apparatus as long as the above reaction can be achieved, and examples thereof include a reaction kettle equipped with a stirrer, a kneader, and a mixing and kneading apparatus such as a single-screw or multi-screw extrusion reactor.

In the present invention, the preferred organic polyisocyanate is preferably an isocyanurate / urethane-modified polyisocyanate from the viewpoints of adhesion and durability of the coating film. Polyisocyanates that do not have self-emulsifying properties can be used because they can be used as a one-component thermosetting aqueous resin emulsion by using a surfactant during dispersion in water and reaction between isocyanate groups and water. is there. The amount of surfactant in this case is 1 with respect to the non-self-emulsifying polyisocyanate.
The amount is preferably about 20% by mass. “Self-emulsifying”
That is, it has the property of dispersing in water by itself without using a surfactant or an emulsifier.

In the present invention, the organic polyisocyanate is
Self-emulsifying polyisocyanates that do not require a surfactant are preferred. This is because it is considered that the surfactant may bleed out of the coating, resulting in poor appearance and reduced coating strength.

Further, as a particularly preferred organic polyisocyanate, isocyanurate / urethane-modified polyisocyanate is modified with a compound having a hydrophilic polar group and an active hydrogen group (hydrophilic modifier) from the viewpoint of adhesion and durability of the coating film. This is a self-emulsifying polyisocyanate obtained.

The hydrophilic polar group in the hydrophilic modifier may be any of a cationic hydrophilic polar group, an anionic hydrophilic polar group and a nonionic hydrophilic polar group, but the self-emulsifying polyisocyanate itself is stable in storage. In consideration of properties and the like, a nonionic hydrophilic polar group is preferable. A particularly preferred modifier is obtained by ring-opening addition of an alkylene oxide using a monol having 1 to 10 carbon atoms as an initiator, contains 50 mass% or more of an oxyethylene group, and has a number average molecular weight of 200 to 10 It is a polyether monool which is 1,000.

In the above self-emulsifying polyisocyanate, the content of the nonionic modifier is 0.1 to 20% by mass.
Is preferable, and 0.5-18 mass% is especially preferable. This is because when the amount of the nonionic modifier is too large, the mechanical strength and durability of the coating film tend to be insufficient. On the other hand, if the amount is too small, the resulting polyisocyanate tends to be difficult to self-emulsify.

The self-emulsifying polyisocyanate can be reacted with a hydrophobic and monofunctional active hydrogen group-containing compound in consideration of the adhesiveness of the coating film. As the active hydrogen group-containing compound, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, benzyl alcohol, Low molecular weight monools such as cyclohexanol and alkylene glycol monoalkyl ether, low molecular weight primary monoamines such as ethylamine, butylamine and aniline, low molecular weight secondary monoamines such as diethylamine, dibutylamine and methylaniline, active hydrogen group included C6 or more, such as polyester, active hydrogen group-containing polyether having less than 50 mol% of ethylene oxide units, active hydrogen group-containing polycarbonate, active hydrogen group-containing polyolefin, ricinoleic acid, etc. Include hydroxy higher fatty acid or its esters and the like.

In the present invention, the preferred organic polyisocyanate is an isocyanurate / urethane-modified polyisocyanate (urethanation and isocyanate) obtained from hexamethylene diisocyanate and a low molecular weight polyol in consideration of the weather resistance, heat resistance and adhesion of the coating. Nuration may be performed simultaneously or sequentially), and a number average molecular weight of 300 to 2,000 obtained by using a monol having 1 to 5 carbon atoms as an initiator.
It is a self-emulsifying polyisocyanate obtained by reacting 0 (particularly preferably 350 to 800) alkoxypolyethylene glycol.

When the silane coupling agent structure is introduced, the organic polyisocyanate is dispersed in an aqueous resin emulsion having the silane coupling agent introduced in the molecular skeleton so that an isocyanate group and water are substantially free. A one-component thermosetting aqueous resin emulsion obtained by reacting until it does not exist and having substantially no free isocyanate group may be used. Also in this case, as a result, the silane coupling agent is introduced into the organic polyisocyanate inside the obtained coating film.

Here, the "aqueous resin emulsion having a silane coupling agent structure" is obtained by using the above-mentioned silane coupling agent as a raw material when producing an aqueous resin emulsion, and has a silane coupling agent structure. And an aqueous acrylic emulsion having a silane coupling agent structure, an aqueous polyester emulsion having a silane coupling agent structure, and the like.

The silane coupling agent has a resin solid content of 0.
1 to 10 mass% is preferable, and 0.5 to 5 mass% is particularly preferable. This is because when the silane coupling agent is too much, the mechanical strength, durability, etc. of the coating tend to be insufficient. On the other hand, if it is too small, the adhesiveness of the coating tends to be insufficient.

For water dispersion / reaction, water, an organic polyisocyanate (and, in some cases, a silane coupling agent or an aqueous resin emulsion having a silane coupling agent structure) are charged in a reactor equipped with a stirrer and stirred. To emulsify and disperse. It is essential that the reactor is not sealed.
This is because if a closed reactor is used, the carbon dioxide gas generated may increase the internal pressure and damage the reactor itself. When the organic polyisocyanate used is non-self-emulsifying, it is emulsified and dispersed in water using a surfactant. From the middle of the dispersion, the reaction between the isocyanate group and water gradually progresses. At this time, it is important that the stirring is not stopped. This is because if the stirring is stopped, the particles will agglomerate and a uniform dispersion will not be obtained. The average particle size of the particles in the dispersion liquid is the stirring speed, the introduction amount and type of the hydrophilic polar group to be introduced when the self-emulsifying polyisocyanate is used, and the surfactant when the non-self-emulsifying polyisocyanate is used. It can be controlled by the amount and type of introduction. The stirring speed is preferably 200 times or more per minute. The end of the reaction is when no isocyanate group remains. The reaction temperature at this time is preferably 0 to 100 ° C, particularly preferably 10 to 80 ° C. The solid content in the reaction system is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass.

The average particle size of the one-component thermosetting aqueous resin emulsion thus obtained is preferably 10 to 1,000 nm, particularly preferably 20 to 500 nm. If the average particle size is too small, an emulsion may not be formed and the viscosity may increase. If the average particle size is too large,
Particles may settle over time. The average particle diameter in the present invention is a value measured by the dynamic light scattering method and analyzed by the cumulant method.

In the present invention, a resin emulsion other than the above aqueous resin emulsion may be blended and used. For example, polyurethane emulsion, acrylic emulsion, polyester emulsion, polyolefin emulsion, vinyl acetate emulsion, polyvinyl chloride emulsion, ethylene-vinyl acetate emulsion, vinylidene chloride emulsion, latex and the like.

If necessary, additives and auxiliaries can be added to the obtained emulsion. As additives and auxiliaries, pigments, dyes, viscosity modifiers, leveling agents, anti-gelling agents, light stabilizers, antioxidants, ultraviolet absorbers, heat resistance improvers, inorganic and organic fillers, plasticizers, Lubricants, antistatic agents, reinforcing materials, catalysts, thixotropic agents, surfactants,
Examples include emulsifiers and the like.

The aqueous one-pack coating agent thus obtained is substantially free of free isocyanate groups. When substantially free isocyanate groups are present, "blister", "foam",
"Peeling" etc. occurs and the appearance tends to be poor. In addition, since carbon dioxide gas is generated by the reaction between the isocyanate group and water during storage, the internal pressure of the container rises and the container is easily damaged.

Next, a specific coating procedure will be described. The coating temperature of the coating agent on the substrate is less than 80 ° C., preferably room temperature, in order to prevent dripping and rapid evaporation of water. The coating amount of the coating agent is 1 to 100 g / m ² , preferably ² to 80 g in terms of solid content of 100% by mass.
/ M ² . As a coating method, known methods such as a brush, a bar coater, a doctor blade, a reverse roll, a gravure roll, a spinner coat and an extruder are used.

The substrate in the coating method of the present invention is required to have heat resistance since it is heated after the coating agent is applied. The most suitable substrate for the coating method of the present invention is a metal-based substrate.

After applying the coating agent, 80 to 30
It is heat-cured at 0 ° C, preferably 120 to 280 ° C.
The heating time is preferably 30 seconds to 120 minutes, and particularly preferably 5 to 60 minutes. Since the present invention makes it possible to obtain a coating having excellent physical properties in a short time, too long heating time not only wastes energy but also gives the coating an unnecessary heat history. Before heat-curing, the temperature is lower than 80 ° C., preferably 70 ° C. or lower,
The water is preferably allowed to evaporate for 60 minutes.

In the present invention, the curing mechanism of the aqueous one-component coating agent is unknown, but for example, between amino groups and urethane groups, between amino groups and urea groups, between urea groups, between urethane groups, between urethane groups and urea groups. It is thought that it is cured by the exchange reaction of. Furthermore, it is considered that the emulsion particles were integrated by thermal fusion and the coating became strong.

In the coating method of the present invention, since the aqueous one-component coating agent containing the one-component thermosetting aqueous resin emulsion having substantially no isocyanate group is used alone, a two-component type aqueous coating agent is obtained. In comparison, it has the advantage of good workability.

[0059]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition,
In the following examples, "%" means mass% unless otherwise specified.

[Production of Self-Emulsifying Polyisocyanate] Production Example 1 Capacity equipped with stirrer, thermometer, nitrogen seal tube, and cooler:
After purging the inside of the reactor of 500 ml with nitrogen, 300.0 g of hexamethylene diisocyanate (HDI) was added.
2.4 g of -butanediol (1,3-BD) was charged, and a urethanization reaction was carried out at 80 ° C for 2 hours while stirring. When the isocyanate content of the reaction solution was measured, it was 4
It was 8.8%. Next, 0.06 g of potassium caprate as a catalyst and 0.3 g of phenol as a cocatalyst were added, and an isocyanurate-forming reaction was carried out at 60 ° C. for 4.5 hours. To this reaction solution, 0.042 g of phosphoric acid was added as a terminating agent, and the mixture was stirred at 60 ° C. for 1 hour, and then free HDI was removed by thin film distillation (conditions: 120 ° C., 1.3 Pa) to obtain polyisocyanate precursor A-1. Got A-1 is isocyanurate / urethane-modified polyisocyanate A-1, a light yellow transparent liquid, having an isocyanate content of 21.1.
%, Viscosity at 25 ° C .: 2,200 mPa, free HDI content: 0.4%, and presence of isocyanate group, isocyanurate group and urethane group was confirmed by FT-IR and ¹³ C-NMR. After replacing the inside of another reactor similar to the above reactor with nitrogen, 100.0 g of A-1 and methoxypolyethylene glycol (MPEG) having a number average molecular weight of 400 were used.
-400, trade name: methoxy PEG # 400, manufactured by Toho Chiba Chemical Co., Ltd.) was charged therein, and reacted at 75 ° C. for 3 hours to obtain an isocyanate content: 16.9% and a viscosity at 25 ° C .:
A self-emulsifying polyisocyanate NCO-A having a light yellow transparent liquid of 2,410 mPa and an average number of functional groups of 3.5 was obtained.

Production Example 2 Capacity equipped with stirrer, thermometer, nitrogen seal tube, and condenser:
In a 1,000 ml reactor, 300.0 g of HDI, 2
11.9 g of -n-butyl-2-ethyl-1,3-propanediol (DMH) and 12.0 of MPEG-400.
g and 4.0 g of methyl ricinoleate were added, the inside of the reactor was replaced with nitrogen, and a urethanization reaction was carried out at 75 ° C. for 3 hours while stirring. The isocyanate content of this reaction solution was measured and found to be 43.2%. Next, an isocyanurate-forming reaction was performed at 60 ° C. for 4.5 hours using 0.06 g of potassium propionate, 0.3 g of phenol and 0.072 g of phosphoric acid as catalysts. 0.042 g of phosphoric acid was added to this reaction solution as a terminating agent, and the mixture was stirred at the reaction temperature for 1 hour.
Thin film distillation of free HDI (conditions: 120 ° C, 1.3 Pa)
To obtain a polyisocyanate precursor B-1. B-1 is an isocyanurate / urethane modified polyisocyanate having an isocyanate content of 20.9.
%, Viscosity at 25 ° C. 650 mPas, free HDI content:
It was a pale yellow transparent liquid with 0.4% and an average number of functional groups of 2.9. FT-IR and ¹³ C-NMR measurements confirmed the presence of an isocyanate group, an isocyanurate group and a urethane group. After replacing the inside of another reactor similar to the above reactor with nitrogen, 99.0 g of B-1 and 1.0 g of γ-mercaptopropyltrimethoxysilane (trade name: A-189, manufactured by Nippon Unicar) were charged, The reaction was carried out at 75 ° C. for 3 hours to obtain a light yellow transparent liquid self-emulsifying polyisocyanate NCO-B having an isocyanate content of 20.5%, a viscosity of 25 ° C. of 660 mPas, and an average number of functional groups of 2.9.

Production Example 3 Capacity equipped with stirrer, thermometer, nitrogen seal tube and cooler:
After purging the inside of the 500 ml reactor with nitrogen, A-1 was added to 10
0.0g, polyoxyethylene nonylphenyl ether phosphate ester as a surfactant (trade name: Newcol 565-PS, acidic phosphate ester manufactured by Nippon Emulsifier)
16.0 g of the neutralized triethylamine salt of
After mixing for 1 hour, the isocyanate content: 14.3
%, Viscosity at 25 ° C. 2,820 mPas, average number of functional groups:
3.5 Light yellow transparent self-emulsifying polyisocyanate N
CO-C was obtained.

Production Example 4 Capacity equipped with stirrer, thermometer, nitrogen seal tube, and cooler:
After purging the inside of the 500 ml reactor with nitrogen, HDI was adjusted to 30
Charge 0.0 g and 2.3 g of DMH, and stir 7
The reaction was carried out at 0 ° C for 3 hours. At this time, the isocyanate content of the reaction solution was measured and found to be 49.1%. Next, 2.0 g of γ-glycidoxypropyltriethoxysilane (trade name: A-187, manufactured by Nippon Unicar) was charged,
Further, as a catalyst, tetramethylammonium iodide 0.5
g was added, the oxazolidone-forming reaction was carried out at 150 ° C. for 3 hours, the mixture was cooled to 60 ° C., and the isocyanurate-forming reaction was carried out for 8 hours. 0.33 g of methyl paratoluenesulfonate was added to this reaction solution to stop the reaction, and then free HDI was removed by thin-film distillation (conditions: 120 ° C., 1.3 Pa) to obtain polyisocyanate precursor D-1. Obtained. D-1
Is an isocyanurate / oxazolidone / urethane-modified polyisocyanate having an isocyanate content of 2
2.3%, viscosity at 25 ° C: 100.0 mPa, free HD
It was a pale yellow transparent liquid having an I content of 0.4% and an average number of functional groups of 2.3, and was subjected to FT-IR and ¹³ C-NMR measurements to find that it had an isocyanate group, an isocyanurate group, an oxazolidone group, and a urethane group. Existence was confirmed. After replacing the inside of another reactor similar to the above reactor with nitrogen, D-1
70.0 g, isocyanurate-modified polyisocyanate of isophorone diisocyanate (trade name: Vestanat T-1890, NCO content 17.0%, manufactured by Hüls) 30.0 g, MPEG-400 16.0 g, and at 75 ° C. After reacting for 3 hours, the isocyanate content:
A light yellow transparent liquid self-emulsifying polyisocyanate NCO-D having a viscosity of 16.4%, a viscosity at 25 ° C. of 810 mPas, and an average number of functional groups of 2.4 was obtained.

Production Example 5 Capacity equipped with stirrer, thermometer, nitrogen seal tube, and condenser:
After replacing the inside of the 500 ml reactor with nitrogen, γ-isocyanatopropyltriethoxysilane (trade name: A-13
10, a product of Nippon Unicar) and a reaction product of glycerin (A-1
310 / glycerin = 1/3, mass ratio) 4.0 g, H
300.0 g of DI was charged, and a urethane reaction was carried out at 80 ° C. for 2 hours while stirring. The isocyanate content of the reaction solution was measured and found to be 48.0%. Next, 0.06 g of potassium caprate as a catalyst and 0.3 g of phenol as a cocatalyst were added, and an isocyanurate-forming reaction was carried out at 60 ° C. for 4.5 hours. To this reaction solution, 0.042 g of phosphoric acid was added as a terminating agent, and the mixture was stirred at 60 ° C for 1 hour.
DI was removed by thin film distillation (conditions: 120 ° C., 1.3 Pa) to obtain polyisocyanate precursor E-1. E
-1 is an isocyanurate / urethane modified polyisocyanate, a pale yellow transparent liquid, having an isocyanate content of 21.3%, a viscosity at 25 ° C. of 2,400 mPas, a free HDI content of 0.3%, and FT -IR and ¹³ C
-The presence of isocyanate group, isocyanurate group and urethane group was confirmed by NMR. After replacing the inside of another reactor similar to the above reactor with nitrogen, E-1 was added to 100.0
g, MPEG-400 16.0g was charged, and 3 at 75 ℃
After reacting for a time, isocyanate content: 16.9%, 2
Viscosity at 5 ° C .: 2,800 mPa, average number of functional groups: 3.6
Light yellow transparent liquid self-emulsifying polyisocyanate NC
O-E was obtained.

Production Example 6 Capacity equipped with stirrer, thermometer, nitrogen seal tube and cooler:
After purging the inside of the 500 ml reactor with nitrogen, HDI was adjusted to 30
0.0 g, 2.4 g of 1,3-BD and 1.0 g of A-1310 were charged, and a urethanization reaction was carried out at 80 ° C. for 2 hours while stirring. The isocyanate content of the reaction solution was measured and found to be 48.9%. Next, 0.06 g of potassium caprate as a catalyst and 0.3 g of phenol as a cocatalyst were added, and an isocyanurate-forming reaction was carried out at 60 ° C. for 4.5 hours. To this reaction solution, 0.042 g of phosphoric acid was added as a terminating agent, and the mixture was stirred at 60 ° C. for 1 hour and then free HDI
Was removed by thin film distillation (conditions: 120 ° C., 1.3 Pa) to obtain a polyisocyanate precursor F-1. F-1
Is an isocyanurate / urethane modified polyisocyanate, which is a pale yellow transparent liquid and has an isocyanate content of 2
1.1%, viscosity at 25 ° C: 2,200 mPa, free HD
I content: 0.4%, FT-IR and ¹³ C-NM
From R, the presence of an isocyanate group, an isocyanurate group and a urethane group was confirmed. After replacing the inside of another reactor similar to the above reactor with nitrogen, 100.0 g of F-1 and MP
16.0 g of EG-400 was charged and reacted at 75 ° C. for 3 hours to self-emulsify a pale yellow transparent liquid having an isocyanate content: 17.0%, a viscosity at 25 ° C .: 2,150 mPas, and an average number of functional groups: 3.4. A polyisocyanate NCO-F was obtained.

[Production of One-Liquid Thermosetting Aqueous Resin Emulsion, Storage Stability] Example 1 Capacity equipped with stirrer, thermometer, gas release valve, and cooler:
In a 2,000 ml reactor, 297.0 g of self-emulsifying polyisocyanate NCO-A, 3.0 g of γ-aminopropyltriethoxysilane (trade name: A-1100, manufactured by Nippon Unicar), and 700 g of ion-exchanged water. 0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. Then, the stirring speed was reduced, and the reaction was carried out at room temperature until the absorption peak of the isocyanate group of FT-IR was not confirmed, to obtain a one-pack thermosetting aqueous resin emulsion EM-1. The average particle size of EM-1 was 160 nm. When EM-1 was placed in a closed container and stored in a cool dark place for 3 months, no change in appearance was observed.

Example 2 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 200.0 g of self-emulsifying polyisocyanate NCO-B and 80 of ion-exchanged water are added.
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. afterwards,
Decrease the stirring speed and react at room temperature until the absorption peak of the isocyanate group of FT-IR is no longer confirmed,
One-component thermosetting aqueous resin emulsion EM-2 was obtained. E
The average particle size of M-2 was 150 nm. When EM-2 was placed in a closed container and stored in a cool dark place for 3 months,
No change in appearance was observed.

Example 3 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 96.0 g of self-emulsifying polyisocyanate NCO-C and 4.0 of A-1310 were added.
g, ion-exchanged water 900.0g, 2,000r
It was rapidly stirred at pm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. After that, the stirring speed is reduced and F is maintained at room temperature.
The reaction was carried out until the absorption peak of the isocyanate group of T-IR was not confirmed, to obtain a one-pack thermosetting aqueous resin emulsion EM-3. The average particle size of EM-3 is 120 nm
Met. When EM-3 was placed in a closed container and stored in a cool dark place for 3 months, no change in appearance was observed.

Example 4 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 200.0 g of self-emulsifying polyisocyanate NCO-D and 80 of ion-exchanged water are used.
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. afterwards,
Decrease the stirring speed and react at room temperature until the absorption peak of the isocyanate group of FT-IR is no longer confirmed,
One-component thermosetting aqueous resin emulsion EM-4 was obtained. E
The average particle size of M-4 was 220 nm. When EM-4 was placed in a closed container and stored in a cool dark place for 3 months,
No change in appearance was observed.

Example 5 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 200.0 g of self-emulsifying polyisocyanate NCO-E and 80 of ion-exchanged water
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. afterwards,
Decrease the stirring speed and react at room temperature until the absorption peak of the isocyanate group of FT-IR is no longer confirmed,
One-component thermosetting aqueous resin emulsion EM-5 was obtained. E
The average particle size of M-5 was 180 nm. When EM-5 was placed in a closed container and stored in a cool dark place for 3 months,
No change in appearance was observed.

Example 6 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 300.0 g of self-emulsifying polyisocyanate NCO-F and 70% of ion-exchanged water were added.
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. afterwards,
Decrease the stirring speed and react at room temperature until the absorption peak of the isocyanate group of FT-IR is no longer confirmed,
One-component thermosetting aqueous resin emulsion EM-6 was obtained. E
The average particle size of M-6 was 150 nm. When EM-6 was placed in a closed container and stored in a cool dark place for 3 months,
No change in appearance was observed.

Example 7 Volume equipped with stirrer, thermometer, gas release valve, cooler:
Aqueous acrylic emulsion AE-1 (solid content: 50%, viscosity at 25 ° C .: 300 mPa, trade name: W
A-1015ND, manufactured by Asia Kogyo) 800.0 g, E
500.0 g (NCO-D / water = 2/8) of M-4 was charged and mixed at room temperature for 1 hour to obtain a one-pack thermosetting aqueous resin emulsion EM-7. The average particle size of EM-7 is 230.
was nm. Place EM-7 in a closed container and cool in a dark place.
When stored for a month, no change in appearance was observed.

Example 8 Volume with stirrer, thermometer, dropping funnel, condenser: 1,
In a 000 ml reactor, 3.0 g of sodium dodecylbenzenesulfonate, 20.0 g of p-nonylphenol reacted with 40 mol of ethylene oxide, 1.0 g of potassium persulfate and 542.0 g of ion-exchanged water were charged, and nitrogen substitution was performed. After that, the mixture was stirred at 70 ° C. Butyl acrylate 225.0 g, 2-hydroxyethyl methacrylate 194.0 g, and γ-methacryloxypropyltriethoxysilane (trade name: KBE50) adjusted in advance in the same reactor.
3, Shin-Etsu Chemical Co., Ltd.) 10.0 g, acrylic acid 5.0 g
The mixed solution of was added dropwise over 4 hours. After completion of dropping 1.
The mixture was kept at 70 ° C. for 5 hours for emulsion polymerization and then cooled to obtain an aqueous acrylic emulsion AE-2. Next, the capacity with a stirrer, thermometer, gas release valve, and cooler: 2,000 m
In a reactor of 1 l, self-emulsifying polyisocyanate NCO-
225.0 g of A, 275.0 g of ion-exchanged water, and 500.0 g of an aqueous acrylic emulsion AE-2,
It was rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. Then, the stirring speed was reduced, and the reaction was carried out at room temperature until the absorption peak of the isocyanate group of FT-IR was no longer confirmed, to obtain a one-pack thermosetting aqueous resin emulsion EM-8. The average particle size of EM-8 was 170 nm. When EM-8 was placed in a closed container and stored in a cool dark place for 3 months, no change in appearance was observed.

Comparative Example 1 Capacity equipped with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 300.0 g of self-emulsifying polyisocyanate NCO-A and 70% of ion-exchanged water were added.
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion EM-9 of polyisocyanate.
When EM-9 immediately after dispersion was put in a closed container and stored in a cool dark place, the container was broken the next day, and the liquid inside was spilled.

Comparative Example 2 Capacity with stirrer, thermometer, gas release valve, cooler:
In a 2,000 ml reactor, 300.0 g of self-emulsifying polyisocyanate NCO-A and 70% of ion-exchanged water were added.
0.0g was charged and rapidly stirred at 2,000 rpm for 30 seconds to obtain an aqueous dispersion of polyisocyanate. afterwards,
Decrease the stirring speed and react at room temperature until the absorption peak of the isocyanate group of FT-IR is no longer confirmed,
One-component thermosetting aqueous resin emulsion EM-10 was obtained.
The average particle size of EM-10 was 160 nm. EM-8
When placed in a closed container and stored in a cool dark place for 3 months, no change in appearance was observed.

Comparative Example 3 The aqueous acrylic emulsion AE-2 itself used in Example 7 was designated as EM-10. The average particle size of EM-11 is 1
It was 40 nm. When EM-11 was placed in a closed container and stored in a cool dark place for 3 months, no change in appearance was observed.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

[0080]

[Table 4]

[0081] In Production Examples 1 to 6 and Tables 1 to 4, HDI: Hexamethylene diisocyanate 1,3-BD: 1,3-butanediol DMH: 2-n-butyl-2-ethyl-1,3-propane                             Diol A-189: γ-mercaptopropyltrimethoxysilane                             Product name: A-189                             Made by Nippon Unicar A-187: γ-glycidoxypropyltriethoxysilane                             Product name: A-187                             Made by Nippon Unicar A-1310: γ-isocyanatopropyltriethoxysilane                             Product name: A-1310                             Made by Nippon Unicar MPEG-400: Methoxy polyethylene glycol                             Number average molecular weight = 400                             Product name: Methoxy PEG # 400                             Toho Chiba Chemical T-1890: isocyanurate of isophorone diisocyanate                             Modified polyisocyanate                             Product name: Vestanat T-1890                             NCO content = 17.0%                             Made by Hüls Newcol 565-PS salt: polyoxyethylene nonyl phenyl ether phosphorus                             Acid ester (trade name: Newcol 565-PS                             Triethyl ester of acid phosphate made by Nippon Emulsifier                             Luamine neutralized salt

Examples 9 to 24, Comparative Examples 4 to 5 EM-1 to 11 just after production and EM-1 to 8 stored for 3 months in a cool and dark place were used as they were as an aqueous one-component coating agent for evaluation. The coating agent was applied to an aluminum plate and cured by heating to obtain a film. Immediately after curing, the performance of the coating was tested. The results are shown in Table 5 (immediately after production) and Table 6.
(3 months elapsed). Note that EM-9 had a significantly poor coating appearance (foam and peeling did not occur over the entire coating and did not have a uniform film thickness), and thus other evaluations were omitted.

[Coating and Curing Conditions] Substrate: Aluminum plate (50 mm × 25 mm × 0.5 mm) Degreased with absorbent cotton soaked with methyl ethyl ketone on the surface coated with the coating agent. Coating amount: 50 g / m ² Coating temperature: 20 ° C. Curing condition: Coating drying condition; 70 ° C. × 20 minutes Curing time; 30 minutes Curing temperature; See Tables 5 and 6 [Performance test] Coating appearance: Visual inspection of coating surface Evaluation. Rubbing test: rubbing absorbent cotton with xylene soaked 100 times, and observing changes in the appearance of the film. Flex resistance: Measured according to JIS K5400. Use a mandrel with a diameter of 2 mm. Adhesion: Measured according to JIS K5400, cross-cut tape method

[0084]

[Table 5]

[0085]

[Table 6]

[Evaluation Criteria] appearance ◯: No crack or peeling is observed on the coating ×: Cracks and peeling are recognized in the coating XX: Significant cracking or peeling of the coating Rubbing test ◯: Almost no scratches can be confirmed on the coating △: Some scratches can be confirmed on the coating X: Significant scratches, etc. can be confirmed on the film Flex resistance ◯: No crack or peeling is observed on the coating ×: Cracks and peeling are recognized in the coating Adhesion ◯: The film remaining rate is 80% or more Δ: coating residual rate is 50% or more and less than 80% X: The residual film rate is less than 50%

From Tables 5 and 6, the aqueous one-component coating agent of the present invention showed good performance. On the other hand, EM-10
Since there was no coupling agent, the adhesiveness was somewhat insufficient, and since EM-11 could not have a crosslinked structure, the physical properties as a coating were insufficient.

[0088]

As described above, according to the present invention, it is possible to provide, for the first time, an aqueous one-component coating agent capable of exhibiting excellent adhesion and a good film in a short time, and a coating method excellent in workability. Became.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4D075 BB22Y BB23Y BB26Z BB93Y                       BB93Z CA13 CA44 DA06                       DB07 EA06 EA13 EA19 EB08                       EB13 EB15 EB19 EB22 EB32                       EB33 EB35 EB37 EB38 EB39                       EB42 EC45                 4J034 BA08 CA04 CA15 CA36 CB01                       CB03 CC03 CC12 CD01 CD04                       CD08 DA01 DA05 DC02 DF01                       DF02 DF11 DF21 DG02 DH02                       HA07 HC03 HC12 HC17 HC64                       RA19                 4J038 DG091 DG141 GA15 MA08                       MA10 NA12 PA19 PA20

Claims (6)

[Claims] 1. An organic polyisocyanate obtained by directly reacting an isocyanate group with an isocyanate-reactive group using at least an organic diisocyanate and a silane coupling agent having an isocyanate-reactive group is dispersed in water to obtain an isocyanate. An aqueous solution characterized by containing a one-pack thermosetting aqueous resin emulsion obtained by reacting a group and water until substantially no free isocyanate group is present, and containing substantially no free isocyanate group. One-part coating agent. 2. Using at least an organic diisocyanate and a silane coupling agent having an isocyanate group,
An organic polyisocyanate obtained by directly or indirectly reacting between isocyanate groups is dispersed in water, and the isocyanate group and water are reacted until substantially no free isocyanate group is present, and the organic polyisocyanate is substantially obtained. An aqueous one-component coating agent comprising a one-component thermosetting aqueous resin emulsion having no free isocyanate group in the above. 3. An organic polyisocyanate and a silane coupling agent having an isocyanate group are mixed and then dispersed in water, and the isocyanate group and water are reacted until substantially no free isocyanate group is present.
An aqueous one-component coating agent comprising a one-component thermosetting aqueous resin emulsion having substantially no free isocyanate group. 4. An organic polyisocyanate is dispersed in an aqueous resin emulsion in which a silane coupling agent is introduced into the molecular skeleton, and the isocyanate group is reacted with water until substantially no free isocyanate group is present.
An aqueous one-component coating agent comprising a one-component thermosetting aqueous resin emulsion having substantially no free isocyanate group. 5. The aqueous one-component coating agent according to any one of claims 1 to 4, wherein the organic polyisocyanate is a self-emulsifying polyisocyanate. 6. The aqueous one-component coating agent according to claim 1 is applied to a substrate at a temperature of less than 80 ° C. and then heat-cured at 80 to 300 ° C. Coating method.