JP3310645B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous coating composition. More specifically, the present invention relates to aqueous acrylic
Urethane copolymer, a composition containing an aqueous emulsion of an acrylic resin and an aqueous emulsion of a polycarbodiimide-based resin, the surface of wood, metal, plastic, paper, leather, fiber, concrete, weather resistance, water resistance, The present invention relates to an aqueous coating composition capable of forming a film having excellent alkali resistance and the like.

[0002]

2. Description of the Related Art Organic solvent-based compositions have been mainly used in the field of various coating agents such as adhesives, paints and printing inks. However, in recent years, it has been replaced with an aqueous composition using water as a medium because of problems such as air pollution and improvement of working environment. As an aqueous coating composition, an acrylic copolymer aqueous dispersion has been used in a wide range of fields such as building interior, leather, metal, and wooden floor because of its low cost and excellent weather resistance and toughness. In recent years, with the sophistication of quality, diversification of coating base materials, application to new applications, etc., demands for aqueous coating compositions have become more sophisticated.For example, in the civil engineering and construction fields, outer walls, roofs, buildings, etc. In the field of concrete painting, stricter durability performance is required. However, with acrylic resin alone, it is difficult to achieve both hardness and softness.
In general, hard materials are inferior in water resistance and alkali resistance, and hard materials are inferior in film-forming properties and crack resistance. Therefore, modification with other aqueous resins is required. Aqueous polyurethane paints are mainly used as coating materials for woodwork products and flooring materials because of their excellent elasticity, gloss and abrasion resistance. However, the film of the aqueous polyurethane paint is required to be further improved in water resistance, durability, and solvent resistance. In order to improve such disadvantages, an aqueous emulsion of an acrylic resin and an aqueous urethane resin are blended, complexed, or copolymerized to have both the advantageous properties of the urethane resin and the acrylic resin. Various aqueous resins having higher durability have been developed. For example, Japanese Patent Application Laid-Open No. 59-138211 discloses a method for producing an aqueous polyurethane acrylic resin having particularly excellent film performance, in which a prepolymer obtained by reacting an organic diisocyanate with a polyol having a molecular weight of 200 to 4,000 is used for urethane. A method has been proposed in which a solution of a polymerizable ethylenically unsaturated compound of polyurethane crosslinked with a chain extender is dispersed in water and then emulsion-polymerized. According to this method, the resulting film is excellent in transparency and hardness, but poor in water resistance, alkali resistance, and weather resistance, and cannot be applied to severe use conditions.

[0003]

DISCLOSURE OF THE INVENTION The present invention has good compatibility, weather resistance, water resistance, alkali resistance, solvent resistance, etc., in a wide range of mixing ratios of acrylic and urethane, and is useful for wood, metal, plastic, A highly durable film can be formed on the surface of paper, leather, fiber, concrete, etc.
An object of the present invention is to provide an aqueous coating composition which can sufficiently withstand exterior wall paints, especially concrete paints which require particularly severe conditions.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, (A) neutralized product of isocyanate group-terminated prepolymer obtained from a specific component, An aqueous acrylic-urethane copolymer obtained by chain elongation in water, an aqueous emulsion of (B) an aqueous emulsion of an acrylic resin having a specific monomer unit and (C) an aqueous emulsion of a polycarbodiimide-based resin in a specific ratio The inventors have found that a film formed from the coating composition has excellent water resistance, alkali resistance, and weather resistance, and have completed the present invention based on this finding. That is, the present invention provides (1) (A) (a) an organic polyisocyanate compound,
(b) a high molecular weight polyol, (c) a compound having an anionic hydrophilic group and two or more active hydrogens and optionally a (d) neutralized product of an isocyanate group-terminated prepolymer obtained from a chain extender, e) an aqueous acrylic-urethane copolymer obtained by chain extension in water using one or more chain extenders selected from water-soluble polyamines, hydrazines and derivatives thereof, wherein (b) the high molecular weight polyol is glass Transition temperature -50 to 100 ° C, hydroxyl value 5-2
Aqueous acrylic-urethane copolymer containing 5 to 60% by weight of an acrylic polyol of 00 mg KOH / g and 1 to 40% by weight of dimer diol, (B) (f) alkyl methacrylate having alkyl group having 1 to 12 carbon atoms Ester units and
(g) an aqueous coating composition obtained by mixing an aqueous emulsion of an acrylic resin having an acrylic acid alkyl ester unit having 1 to 8 carbon atoms in an alkyl group, and (C) an aqueous emulsion of a polycarbodiimide resin. So,
Component (A), component (B), and component (C) are composed of (A) 4 to 98% by weight, (B) 1 to 95% by weight and
(C) an aqueous coating composition containing 1 to 10% by weight, (2) (a) an organic polyisocyanate compound selected from an aliphatic diisocyanate compound and an alicyclic diisocyanate compound. 2. The aqueous coating composition according to claim 1, which is at least one kind, wherein (3) (b) the high molecular weight polyol contains a polyester polyol, a polycarbonate polyol or a polyether polyol in addition to the acrylic polyol and the dimer diol. 2. The aqueous coating composition according to item 1, wherein (4) (c) the anionic hydrophilic group of the compound having an anionic hydrophilic group and two or more active hydrogens is a carboxyl group, and the content of the carboxyl group is 0.3-acryl-urethane copolymer
2.5% by weight of the aqueous coating composition according to item 1, wherein the acrylic resin of the aqueous emulsion of the component (B) is (h) a monomer unit having a carboxyl group. % Of the composition.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous coating composition of the present invention comprises
The composition is obtained by mixing (A) an aqueous acrylic-urethane copolymer, (B) an aqueous emulsion of an acrylic resin, and (C) an aqueous emulsion of a polycarbodiimide resin. (A) aqueous acrylic-urethane copolymer used in the aqueous coating composition of the present invention is (a) an organic polyisocyanate compound,
(b) a high molecular weight polyol, (c) a compound having an anionic hydrophilic group and two or more active hydrogens and optionally a (d) neutralized product of an isocyanate group-terminated prepolymer obtained from a chain extender, e) a water-soluble polyamine, hydrazine or an aqueous acrylic-urethane copolymer obtained by chain extension in water using one or more chain extenders selected from hydrazine or derivatives thereof, wherein (b) the high molecular weight polyol is glass Transition temperature -50 to 100 ° C, hydroxyl value 5-2
It is an aqueous acrylic-urethane copolymer containing 5 to 60% by weight of an acrylic polyol of 00 mg KOH / g and 1 to 40% by weight of a dimer diol. There is no particular limitation on the (a) organic polyisocyanate compound used in the present invention. Alicyclic diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, and xylylene diisocyanate. One of these organic polyisocyanate compounds can be used alone, or two or more can be used in combination. Among these,
Aliphatic diisocyanate compounds and alicyclic diisocyanate compounds can be suitably used because they give a non-yellowing film, and hexamethylene diisocyanate, isophorone diisocyanate and norbornane diisocyanate can be particularly preferably used.

The high molecular weight polyol (b) used in the present invention contains 5 to 60% by weight of an acrylic polyol having a glass transition temperature of -50 to 100 ° C., a hydroxyl value of 5 to 200 mg KOH / g, and 1 to 40% by weight of a dimer diol. .
The acrylic polyol is a homopolymer or a copolymer obtained from a monomer having one ethylenically unsaturated group and a hydroxyl group by a bulk polymerization method, a solution polymerization method, or the like. Examples of the monomer having one ethylenically unsaturated group and a hydroxyl group include, for example, 2-hydroxyethyl acrylate, 3-chloro-2-hydroxybutyl acrylate, 2-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, -Hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
6-hydroxyhexyl methacrylate, 5,6-dihydroxyhexyl methacrylate and the like can be mentioned. One of these monomers can be used alone, or two or more thereof can be used in combination. As a monomer copolymerizable with a monomer having one ethylenically unsaturated group and a hydroxyl group, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
n-propyl (meth) acrylate, isopropyl (meth)
Acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n
-Hexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate,
Cinnamyl (meth) acrylate, 2-ethoxyethyl
(Meth) acrylate, 2-methoxybutyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-
n-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, tetrahydrofurfuryl
(Meth) acrylate, furfuryl (meth) acrylate,
Trifluoroethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, hexafluoroisopropyl
(Meth) acrylate, 2-nitro-2-methylpropyl
(Meth) acrylate, tetrapyranyl (meth) acrylate, acrylic monomers such as (meth) acrylic acid, acrylonitrile, vinyl acetate, vinylpyridine, vinylpyrrolidone, methylcrotonate, maleic anhydride, styrene, α-methylstyrene, etc. And the like. In addition, (meth) acrylate means acrylate and methacrylate, and (meth) acrylic acid means acrylic acid and methacrylic acid. One of these copolymerizable monomers can be used alone, or two or more can be used in combination. Acrylic polyols can also be obtained by polymerizing the above monomers in (b) polyester polyols of high molecular weight polyols, polycarbonate polyols, polyether polyols and the like.

In the present invention, the acrylic polyol contained in the (b) high molecular weight polyol has a glass transition temperature (Tg) of -50 to 100 ° C. and a hydroxyl value of 5-2.
00 mg KOH / g, more preferably a glass transition temperature of -40 to 50 ° C. and a hydroxyl value of 30 to 70 mg KO
H / g. If the glass transition temperature is lower than -50 ° C, the water resistance and alkali resistance of the film may be insufficient. If the glass transition temperature exceeds 100 ° C., the film-forming properties and crack resistance may be insufficient. Also,
When the hydroxyl value is less than 5 mgKOH / g, the number of bonding points between the acrylic resin and the urethane resin decreases, and the performance as a copolymer may not be sufficiently exhibited. If the hydroxyl value exceeds 200 mgKOH / g, gelation may proceed due to an increase in crosslink density during synthesis of the isocyanate group-terminated prepolymer, and production may be difficult. The acrylic polyol used in the present invention has a weight average molecular weight of 1,000.
Preferably from 0 to 100,000, from 5,000 to
50,000, more preferably 8,000-3
More preferably, it is 0.000. The dimer diol used in the present invention is mainly composed of a diol obtained by reducing a dimer acid obtained by dimerizing an unsaturated fatty acid. Examples of the dimer acid include unsaturated fatty acids having 18 carbon atoms such as oleic acid, linoleic acid, and linolenic acid, drying oil fatty acids, semi-dry oil fatty acids, and lower alcohol esters of these fatty acids in the presence or absence of a catalyst. Diels-Alder-type bimolecular polymerization reaction can be mentioned. As the dimer acid, various types of compounds are commercially available. Typical examples are 0 to 5% by weight of a monocarboxylic acid having 18 carbon atoms, 70 to 98% by weight of a dimer acid having 36 carbon atoms, and There is a compound consisting of 0 to 30% by weight of the trimer acid having the number 54.

The high molecular weight polyol (b) used in the present invention is 5 to 60% by weight, more preferably 7 to 50% by weight, even more preferably 10 to 30% by weight of the above acrylic polyol.
% By weight. If the content of the acrylic polyol is less than 5% by weight, advantageous properties of the acrylic resin, for example, light resistance, weather resistance, high non-volatile content, toughness, and the like may be insufficient. ) The compatibility of the acrylic resin with the aqueous emulsion composition may be reduced. When the content of the acrylic polyol is more than 60% by weight, advantageous properties of the urethane resin, for example, mechanical resistance, chemical resistance, gloss, abrasion resistance, and particularly, elasticity may be insufficient. In addition, it is preferable that the monomer composition of the acrylic polyol and the monomer composition of the aqueous emulsion of the acrylic resin be as close as possible in order to improve the compatibility between the two. The high molecular weight polyol (b) used in the present invention is 1 to 40% by weight of dimer diol, more preferably 2 to 30% by weight, further preferably 5 to 2% by weight.
Contains 0% by weight. When the content of the dimer diol is less than 1% by weight, the expression of water resistance, which is considered to be caused by the effect of inhibiting hydrolysis, may be insufficient due to the fatty acid chain derived from the dimer diol. When the content of the dimer diol exceeds 40% by weight, there is a possibility that the urethane resin may exhibit insufficient advantageous properties such as elasticity and abrasion resistance. In the present invention, (b) the high molecular weight polyol can contain other polyols in addition to the acrylic polyol and the dimer diol. The other polyol to be contained is not particularly limited, but polyester polyol, polycarbonate polyol, and polyether polyol can be suitably used. As the polyester polyol, for example, polyethylene adipate, polybutylene adipate, polyethylene butylene adipate, polyhexamethylene isophthalate adipate, polyethylene succinate, polybutylene succinate, polyethylene sebacate, polybutylene sebacate, poly-ε-caprolactone, poly Examples thereof include polyols such as (3-methyl-1,5-pentylene adipate), a polycondensate of 1,6-hexanediol and dimer acid. Examples of the polycarbonate polyol include polytetramethylene carbonate diol and polyhexamethylene carbonate diol. Examples of the polyether polyol include a homopolymer, a block copolymer, and a random copolymer of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Further, a polyetherester polyol obtained by combining a polyether polyol and a polyester polyol can also be used. These other polyols
One kind may be used alone, or two or more kinds may be used in combination.

The (c) anionic hydrophilic group used in the present invention and 2
As the compound having two or more active hydrogens, for example,
2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and the like can be mentioned. One of these compounds can be used alone, or two or more of them can be used in combination. In the present invention, the anionic hydrophilic group and the anionic hydrophilic group of the compound having two or more active hydrogens, before or after the preparation of isocyanate group-terminated prepolymer, trimethylamine, triethylamine, tri-n-propylamine, tributylamine, Neutralize with amines such as N-methyl-diethanolamine, N, N-dimethylmonoethanolamine, triethanolamine, potassium hydroxide, sodium hydroxide, ammonia and the like. In the present invention, the neutralized product of the isocyanate group-terminated prepolymer is, before or after the preparation of the isocyanate group-terminated prepolymer, (c) an anionic hydrophilic group and an anionic hydrophilic group of a compound having two or more active hydrogens. Is obtained by neutralizing In the aqueous coating composition of the present invention, (c) the anionic hydrophilic group and the anionic hydrophilic group of the compound having two or more active hydrogens are preferably carboxyl groups, and the content of the carboxyl group is preferably aqueous. The acrylic-urethane copolymer, which is a nonvolatile component of the acrylic-urethane copolymer, has a concentration of 0.3 to
It is preferably 2.5% by weight, more preferably 0.5 to 1.5% by weight. If the content of the carboxyl group is less than 0.3% by weight of the acryl-urethane copolymer, it may be difficult to emulsify the acryl-urethane copolymer or the emulsion stability may be insufficient. The content of a carboxyl group in the acrylic-urethane copolymer is 2.
If it exceeds 5% by weight, the water resistance of the film may be reduced. In the present invention, when adjusting the isocyanate group-terminated prepolymer, a chain extender (d) can be used, if necessary. As chain extenders, for example, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, low molecular weight polyhydric alcohols such as sorbitol, ethylenediamine, propylenediamine, hexamethylenediamine, Diaminocyclohexylmethane, piperazine, 2-methylpiperazine, isophoronediamine,
Examples thereof include low molecular weight polyamines such as diethylenetriamine and triethylenetetramine. One of these chain extenders can be used alone, or two or more can be used in combination.

In the present invention, component (a), component (b),
A prepolymer having a terminal isocyanate group is prepared using the component (c) and, if necessary, the component (d). The prepolymer can be prepared, for example, by a one-shot method (one-stage method) or a multi-stage isocyanate polyaddition reaction method at a reaction temperature of 40 to 150 ° C. At this time, if necessary, dibutyltin dilaurate, stannas octoate, dibutyltin-2-ethylhexanoate,
A reaction catalyst such as triethylamine, triethylenediamine, N-methylmorpholine can be added. During or after the reaction, an organic solvent that does not react with the isocyanate group can be added. Examples of the organic solvent include acetone, methyl ethyl ketone, toluene, tetrahydrofuran, dioxane, dimethylformamide, N-methylpyrrolidone, and the like. Next, the neutralized product of the obtained isocyanate group-terminated prepolymer is subjected to chain extension in water. (C) in the prepolymer
When the anionic hydrophilic group and the anionic hydrophilic group of the compound unit having two or more active hydrogens are not neutralized, after neutralizing the anionic hydrophilic group, emulsified and dispersed in water,
(e) The molecular weight is increased using one or more chain extenders selected from water-soluble polyamines, hydrazines and derivatives thereof. Examples of the water-soluble polyamine used as a chain extender include:
For example, ethylenediamine, propylenediamine, hexamethylenediamine, diaminocyclohexylmethane,
Examples thereof include piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, and triethylenetetramine. Examples of the water-soluble amine derivative used as a chain extender include an amidoamine derived from a diprimary amine and a monocarboxylic acid, and a monoketimine of a diprimary amine. As the hydrazine derivative used as a chain extender, for example,
Compounds having at least two hydrazino groups in the molecule can be mentioned, and dicarboxylic acid hydrazide having 2 to 10 carbon atoms and aliphatic water-soluble dihydrazine having 2 to 4 carbon atoms are preferable. Examples of the dihydrazide of a dicarboxylic acid having 2 to 10 carbon atoms include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and itaconic dihydrazide. And the like. Examples of the aliphatic water-soluble dihydrazine having 2 to 4 carbon atoms used as a chain extender include 1,1′-ethylenedihydrazine, 1,1′-trimethylenedihydrazine,
1 '-(1,4-butylene) dihydrazine and the like can be mentioned. One of these chain extenders can be used alone, or two or more can be used in combination. In the present invention, when an isocyanate group-terminated prepolymer is synthesized using a solvent, for example,
After completion of the chain elongation reaction, the solvent is preferably removed by distillation under reduced pressure or the like. Surfactants, for example, anionic surfactants such as higher fatty acids, resin acids, acidic fatty alcohols, sulfates, higher alkyl sulfonates, alkyl allyl sulfonates, sulfonated castor oil, sulfosuccinates, ethylene oxide and long chain fats The emulsifiability can also be maintained by using a nonionic surfactant such as a reaction product with an aliphatic alcohol or a phenol.

The aqueous emulsion of the acrylic resin (B) used in the aqueous coating composition of the present invention comprises (f) an alkyl methacrylate unit having 1 to 12 carbon atoms.
(g) An aqueous emulsion of an acrylic resin having alkyl acrylate units having 1 to 8 carbon atoms in the alkyl group. The alkyl group of the methacrylic acid alkyl ester and the acrylic acid alkyl ester may be an alkyl group substituted by a hydroxyl group. The glass transition temperature of the acrylic resin is preferably -50 to 70C, more preferably -40 to 50C. Examples of the methacrylate having 1 to 12 carbon atoms in the alkyl group include methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate,
-Hydroxypropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-hydroxybutyl methacrylate, t-butyl methacrylate,
Cyclohexyl methacrylate and the like can be mentioned. By copolymerizing an alkyl methacrylate having 1 to 12 carbon atoms of the alkyl group, hardness and toughness can be imparted to the film. Alkyl group having 1 to 8 carbon atoms
Examples of the acrylate include ethyl acrylate, 2-hydroxyethyl acrylate, n-propyl acrylate, isopropyl acrylate, 2-hydroxypropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, and 2-hydroxybutyl acrylate. , N-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 6-hydroxyhexyl acrylate, 2
-Ethyl butyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and the like. By copolymerizing an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, flexibility and elasticity can be imparted to the film.

The acrylic resin of the aqueous emulsion (B) used in the present invention may have (h) a monomer unit having a carboxyl group. The content of the monomer unit having a carboxyl group is preferably not more than 2.5% by weight, more preferably from 0.3 to 2.0% by weight, based on all the monomer units of the acrylic resin. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid.
By having a monomer unit having a carboxyl group, the polymerization stability and pigment dispersibility of an aqueous emulsion of an acrylic resin can be improved. If the amount of the monomer unit having a carboxyl group exceeds 2.5% by weight of the total monomer units, when (C) an aqueous emulsion of a polycarbodiimide resin is mixed, an aggregate is generated or gelation occurs. There is a risk. The acrylic resin of the aqueous emulsion (B) used in the present invention may have other copolymerizable monomer units. As copolymerizable monomers,
For example, acrylonitrile, acrylamide, methacrylamide, styrene, vinyl acetate, α-methylstyrene, ethylene, vinyl chloride and the like can be mentioned.
By having these copolymerizable monomer units,
The minimum film forming temperature and physical properties of the film can be adjusted. In the present invention, (b) the acrylic monomer unit in the high molecular weight polyol and (B) the acrylic monomer unit in the acrylic resin of the aqueous emulsion are preferably the same or similar. By making the acrylic monomer units the same or similar, the compatibility can be improved and the transparency of the film can be improved.

The aqueous emulsion of the acrylic resin (B) used in the present invention can be produced by emulsion polymerization.
As the emulsifier used in the emulsion polymerization, for example, sodium dodecylbenzene sulfate, sodium dodecylbenzenesulfonate, anionic emulsifier such as alkylaryl polyether sulfate, polyoxyethylene lauryl ether, polyoxyethylene nonyl phenyl ether,
Examples include nonionic emulsifiers such as polyoxyethylene-polyoxypropylene block copolymers, and cationic emulsifiers such as cetyltrimethylammonium bromide and laurylpyridinium chloride. Also,
A water-soluble polymer such as polyvinyl alcohol and hydroxyethyl cellulose or a water-soluble oligomer thereof can be used in combination with an emulsifier. The total amount of the emulsifier, the water-soluble oligomer, and the water-soluble polymer is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the monomer. If the amount is less than 0.5% by weight based on 100 parts by weight of the monomer, the stability of emulsion polymerization and the stability of the obtained emulsion may be reduced. When the amount used is monomer 10
If the amount exceeds 10 parts by weight with respect to 0 parts by weight, the water resistance of the film may be reduced. Examples of the radical polymerization initiator for performing the emulsion polymerization include potassium persulfate and ammonium persulfate. Organic peroxides such as cumene hydroperoxide and t-butyl hydroperoxide can also be used as needed. Further, these persulfates or peroxides and iron
A redox initiator combining a reducing agent such as a metal ion such as (II) ion, sodium sulfoxylate, formaldehyde, sodium pyrosulfite, or L-ascorbic acid can also be used. The concentration of the monomer in the emulsion polymerization is preferably a concentration at which the nonvolatile content of the obtained aqueous emulsion of the acrylic resin is 25 to 65% by weight. The addition of the monomer and the polymerization initiator to the reaction system,
Any method such as batch charging, continuous dropping, and divisional addition can be used. The polymerization temperature is preferably from 40 to 100 ° C., and the polymerization reaction is usually completed in 2 to 4 hours.

The (C) polycarbodiimide resin aqueous emulsion used in the aqueous coating composition of the present invention is prepared by mixing an organic polyisocyanate compound and a monofunctional water-soluble or water-dispersible organic compound, and adding a carbodiimidation catalyst. , 1
It can be obtained by heating to 50 to 200 ° C. and advancing a carbodiimidation reaction accompanied by removal of carbon dioxide. The end of the reaction was determined by infrared absorption spectrum measurement.
It can be confirmed by disappearance of the absorption of the isocyanate group at 200 to 2,300 cm ^-1 . Examples of the organic polyisocyanate compound include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, norbornane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethyl xylylene diisocyanate, and isophorone diisocyanate. One of these organic polyisocyanate compounds can be used alone, or two or more can be used in combination. The monofunctional water-soluble or water-dispersible organic compound is a compound having one functional group capable of reacting with an isocyanate group, for example, a hydroxyl group, an amino group, etc., and being soluble or dispersible in water. Examples thereof include monoalkyl ethers of glycols and monoalkyl ethers of random or block copolymers of polyethylene glycol-polypropylene glycol. As the carbodiimidization catalyst, an organic phosphorus compound is preferable, and a phosphorene oxide is particularly preferable in terms of activity. Such organic phosphorus compounds include, for example, 3-methyl-1-phenyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-phospholene-1-oxide, and 1,3-dimethyl- 2-phospholene-1-oxide, 1-phenyl-2-phospholene-
1-oxide, 1-ethyl-2-phospholene-1-oxide, 1-methyl-1-phenyl-2-phospholene-1
-Oxides and double bond isomers thereof. Among these, 3-methyl-1-phenyl-
2-phospholene-1-oxide is readily available,
It can be suitably used. The amount of the carbodiimidation catalyst to be added is not particularly limited, but is usually 0.1 to the total amount.
-10% by weight, preferably 0.5-5% by weight
Is more preferable.

The aqueous coating composition of the present invention comprises the above (A)
An aqueous acrylic-urethane copolymer, an aqueous emulsion of (B) an acrylic resin, and an aqueous emulsion of a polycarbodiimide resin (C) were prepared by mixing (A) 4 to 9
8% by weight, (B) 1 to 95% by weight and (C) 1 to 10% by weight
In the proportion of If the content of the component (A) is less than 4% by weight, the film-forming properties and crack resistance may decrease. When the content of the component (A) exceeds 98% by weight, water resistance and weather resistance may be reduced. When the content of the component (B) is less than 1% by weight, water resistance and weather resistance may be reduced. When the content of the component (B) exceeds 95% by weight, the film-forming properties and crack resistance may decrease.
When the content of the component (C) is less than 1% by weight, water resistance and alkali resistance may be reduced. If the content of the component (C) exceeds 10% by weight, the film-forming properties and weather resistance may decrease. The film formed from the aqueous coating composition of the present invention has a good balance between hardness and softness, has excellent water resistance, alkali resistance, and weather resistance, and is suitable for applications such as adhesives, paints, and printing inks. Can be used. The reason that a film having excellent physical properties can be obtained from the aqueous coating composition of the present invention is that an aqueous acrylic composition obtained from a specific composition is used.
The urethane copolymer is a completely uniform copolymer in which the acrylic resin component is incorporated in the urethane resin, has good compatibility with the aqueous emulsion of the acrylic resin, and has each advantageous property. It is considered possible. In addition, a hydrophobic component derived from dimer diol covers the molecular surface, and the carboxyl group, which is an emulsifying component, is blocked by a carbodiimide group, and the crosslink density increases, resulting in a film having excellent water resistance and alkali resistance. It is thought that it is possible.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In Examples and Comparative Examples, the properties of the coating film were evaluated by the following methods. (1) Preparation of coating film As an adherend, an aqueous coating composition having a film thickness of 1 was used using an oak plate, a stainless steel plate, a glass plate and a concrete plate.
The coating is performed so as to have a thickness of 00 μm, and left at 25 ° C. for one week to perform a test. (2) Adhesion In accordance with JIS K 5400 8.5.2, a checkerboard-shaped grid 1 with a gap of 1 mm was applied to the coating film using a cutter knife.
Then, cellophane adhesive tape [Nichiban Co., Ltd.] was adhered to the square, and the appearance of the coating film when rapidly peeled off at an angle of 60 ° was observed, and evaluated according to the following criteria. ：: 95% or more of the coating film remains on the adherend side. Δ: 50% to less than 95% of the coating film remains on the adherend side. ×: Less than 50% of the coating film remains on the adherend side. (3) Appearance of coating film The transparency of the coating film prepared on a glass plate is visually evaluated. (4) Water resistance The coating film prepared on a concrete board is
After immersion for 8 hours, the whitening state of the coating film is visually evaluated. ：: No whitening was observed. Δ: slightly whitened X: Remarkable whitening has occurred. (5) Alcohol resistance On a coating film prepared on a glass plate, isopropyl alcohol is dropped at 20 ° C., and blistering and abnormal appearance of the coating film are visually evaluated. ：: No abnormality occurs. Δ: Mild abnormality was observed. X: A remarkable abnormality is observed. (6) Weather resistance The coating film prepared on the concrete plate is irradiated for 5,000 hours with a sunshine weatherometer to evaluate changes in appearance. ：: No whitening was observed. Δ: slightly whitened X: Remarkable whitening has occurred. (7) Pencil hardness Measured according to JIS K 5400 8.4.2.

Synthesis Example 1 (Acrylic polyol A) A flask equipped with a thermometer, a stirrer, two dropping funnels, a gas inlet tube and a reflux condenser was charged with 50 parts by weight of toluene, and the flask was stirred with nitrogen. The gas was replaced, and the mixture was heated to 100 ° C. under a nitrogen gas stream. Next, while maintaining the temperature at 100 ° C. under a nitrogen gas stream, 40 parts by weight of methyl methacrylate, 20 parts by weight of stearyl methacrylate, 31 parts by weight of butyl acrylate,
9 parts by weight of hydroxyethyl acrylate and 5 parts of toluene
A monomer mixture solution consisting of 0 parts by weight was added dropwise over 120 minutes. At the same time, a polymerization initiator solution consisting of 5 parts by weight of azobisisobutyronitrile and 50 parts by weight of toluene was added from the other dropping funnel over 180 minutes. It was dropped. After the completion of the dropwise addition, the polymerization was maintained at 100 ° C. for 60 minutes to complete the polymerization. Thereafter, toluene was distilled off under reduced pressure to obtain an acrylic polyol solution having a nonvolatile content of about 50% by weight. This acrylic polyol has a glass transition temperature of 22 ° C., a hydroxyl value of about 20 mg KOH / g, and a weight average molecular weight of 40,000.
Met. This acrylic polyol solution is referred to as acrylic polyol A. Synthesis Example 2 (Aqueous acrylic-urethane copolymer A) Acrylic polyol [Dainippon Ink Chemical Industry Co., Ltd., Acrylic Co., Ltd.] was placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube. Dick A-808T, nonvolatile content: about 50% by weight, glass transition temperature: 97 ° C., hydroxyl value: about 20 mg KOH / g] 56 parts by weight, polyhexamethylene carbonate diol [number average molecular weight: 1,000] 6
0 parts by weight, dimer diol [Toagosei Co., Ltd., Pespol HP-1000, weight average molecular weight 538] 10.8 parts by weight, 0.9 parts by weight of 1,4-butanediol, 2,2-dimethylolpropionic acid 6 0.7 parts by weight, 0.001 parts by weight of dibutyltin dilaurate and methyl ethyl ketone 60
Parts by weight and uniformly mixed. Then, 52.4 parts by weight of dicyclohexylmethane diisocyanate was added, and 80 parts by weight were added.
The reaction was carried out at a temperature of 2 ° C. for 2 hours to obtain a urethane prepolymer solution in methyl ethyl ketone having a free isocyanate group content of 1.7% by weight based on the nonvolatile content. The solution was cooled to 30 ° C., neutralized by adding 5 parts by weight of triethylamine, and then gradually added to 350 parts by weight of water to emulsify and disperse. Then, 15 parts by weight of a 20% by weight aqueous solution of ethylenediamine was added.
Stirring was continued for 2 hours. Then 6 hours under reduced pressure for 2 hours.
The solvent was removed while the temperature was raised to 0 ° C. to obtain an aqueous acrylic-urethane copolymer having a nonvolatile content of 35% by weight. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in the acrylic-urethane copolymer is 1.4% by weight. This aqueous acrylic-urethane copolymer is referred to as an aqueous acrylic-urethane copolymer A.

Synthesis Example 3 (Aqueous Acrylic-Urethane Copolymer B) Acrylic polyol [Dainippon Ink Chemical Industry Co., Ltd., Acridic A-809,
Non-volatile content: about 50% by weight, glass transition temperature: 61 ° C., hydroxyl value: about 20 mg KOH / g] 112 parts by weight, polybutylene adipate diol [number average molecular weight: 1,700] 68
Parts by weight, polyethylene glycol [number average molecular weight 1,0
00] 10 parts by weight, dimer diol [Toagosei Co., Ltd.
Pespol HP-1000, weight average molecular weight 538] 1
6 parts by weight and 7.4 parts by weight of 2,2-dimethylolbutanoic acid are dissolved in 30 parts by weight of methyl ethyl ketone, neutralized by adding 5 parts by weight of trimethylamine, and then 0.001 part by weight of dibutyltin dilaurate and 3 parts by weight of methyl ethyl ketone 3
After adding 0 parts by weight and uniformly mixing, 44.6 parts by weight of isophorone diisocyanate was added and reacted at 80 ° C. for 2 hours. A solution of a urethane prepolymer having a free isocyanate group content of 1.9% by weight based on the nonvolatile matter in methyl ethyl ketone was added. I got The solution was cooled to 30 ° C.
0 parts by weight was gradually added to emulsify and disperse, 15 parts by weight of a 20% by weight aqueous solution of ethylenediamine was added, and stirring was continued for 2 hours. Next, the solvent was removed while heating to 60 ° C. over 2 hours under reduced pressure to obtain an aqueous acrylic-urethane copolymer having a nonvolatile content of 35% by weight. The content of carboxyl groups derived from 2,2-dimethylolbutanoic acid in this acrylic-urethane copolymer is 1.1% by weight. This aqueous acrylic-urethane copolymer is referred to as aqueous acrylic-urethane copolymer B. Synthesis Example 4 (Aqueous Acrylic-Urethane Copolymer C) An acrylic polyol [Dainippon Ink Chemical Industry Co., Ltd., Acridic A-811,
Non-volatile content: about 50% by weight, glass transition temperature: 59 ° C, hydroxyl value: about 17 mgKOH / g] 64 parts by weight, poly-ε-caprolactone diol [number average molecular weight: 2,000] 80
Parts by weight, 16 parts by weight of dimer diol [Toagosei Co., Ltd., Pespol HP-1000, weight average molecular weight 538]
6.7 parts by weight of 2,2-dimethylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone were charged and uniformly mixed, and 52.4 parts by weight of dicyclohexylmethane diisocyanate was added. The reaction was conducted for 2 hours to obtain a urethane prepolymer solution in methyl ethyl ketone having a free isocyanate group content of 1.5% by weight based on the nonvolatile content. Add this solution to 30
After cooling to 5 ° C. and neutralizing by adding 5 parts by weight of triethylamine, 350 parts by weight of water was gradually added to emulsify and disperse, 4 parts by weight of a 60% by weight aqueous solution of hydrazine was added, and stirring was continued for 2 hours. Was. Next, the solvent was removed while raising the temperature to 60 ° C. over 2 hours under reduced pressure.
By weight, an aqueous acrylic-urethane copolymer was obtained. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in the acrylic-urethane copolymer is 1.2% by weight. This aqueous acrylic-urethane copolymer is referred to as aqueous acrylic-urethane copolymer C.

Synthesis Example 5 (Aqueous Acrylic-Urethane Copolymer D) An acrylic polyol [Dainippon Ink Chemical Industry Co., Ltd., Acrydic 44-19] was placed in the same reaction vessel as in Synthesis Example 2.
8, nonvolatile content of about 50% by weight, glass transition temperature of 70 ° C., hydroxyl value of about 20 mgKOH / g] 56 parts by weight, poly (3-
Methyl-1,5-pentylene adipate) diol [number average molecular weight 1,000] 50 parts by weight, polypropylene glycol [number average molecular weight 1,000] 10 parts by weight, dimer diol [Toagosei Co., Ltd., Vespol HP-100]
0, weight average molecular weight 538] 16 parts by weight, 6.7 parts by weight of 2,2-dimethylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone are charged and uniformly mixed, and then mixed with dicyclohexylmethane diisocyanate. 52.4 parts by weight, 80 ° C
For 2 hours to obtain a solution of a urethane prepolymer in methyl ethyl ketone having a free isocyanate group content of 1.6% by weight based on the nonvolatile content. The solution was cooled to 30 ° C. and neutralized by adding 5 parts by weight of triethylamine.
350 parts by weight of water was gradually added to emulsify and disperse, 15 parts by weight of a 20% by weight aqueous solution of ethylenediamine was added, and stirring was continued for 2 hours. Then, at 60 ° C. under reduced pressure for 2 hours.
The solvent was removed while elevating the temperature to obtain an aqueous acrylic-urethane copolymer having a nonvolatile content of 35% by weight. The carboxy group content derived from 2,2-dimethylolpropionic acid in this acrylic-urethane copolymer is 1.4% by weight.
This aqueous acrylic-urethane copolymer is referred to as aqueous acrylic-urethane copolymer D. Synthesis Example 6 (Aqueous acrylic-urethane copolymer E) In the same reaction vessel as in Synthesis Example 2, the acrylic polyol A obtained in Synthesis Example 1 [nonvolatile content: about 50% by weight, glass transition temperature: 22 ° C, hydroxyl value: about 20 mgKOH / g] 64 parts by weight, poly-ε-caprolactone diol [number average molecular weight 2,000] 80 parts by weight, dimer diol [Toagosei Co., Ltd., Pespol HP-1000, weight average molecular weight 5]
38] 16 parts by weight, 6.7 parts by weight of 2,2-dimethylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone were mixed and uniformly mixed, and then 52.4 parts by weight of dicyclohexylmethane diisocyanate. And reacted at 80 ° C. for 2 hours to obtain a free isocyanate group content of 1.5% by weight based on the nonvolatile content.
To obtain a solution of the urethane prepolymer in methyl ethyl ketone. The solution was cooled to 30 ° C. and triethylamine 5
After neutralization by adding a weight part, 350 parts by weight of water was gradually added to emulsify and disperse, 4 parts by weight of a 60% by weight aqueous solution of hydrazine was added, and stirring was continued for 2 hours. Then
The solvent was removed while elevating the temperature to 60 ° C. over about 2 hours under reduced pressure to obtain an aqueous acrylic-urethane copolymer having a nonvolatile content of 35% by weight. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in this acryl-urethane copolymer is 1.2% by weight. This water-based acrylic
The urethane copolymer is referred to as an aqueous acrylic-urethane copolymer E.

Comparative Synthesis Example 1 (Aqueous Acrylic-Urethane Copolymer F) An acrylic polyol [Dainippon Ink Chemical Industry Co., Ltd., Acridic A-809,
Non-volatile content: about 50% by weight, glass transition temperature: 61 ° C., hydroxyl value: about 20 mg KOH / g] 112 parts by weight, polybutylene adipate diol [number average molecular weight: 1,700] 68
Parts by weight, 1,6-hexanediol 2.4 parts by weight, 2,2
-6.7 parts by weight of dimethylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone were charged and uniformly mixed, and then 52.4 parts by weight of dicyclohexylmethane diisocyanate was added.
The reaction was carried out at 80 ° C. for 2 hours to obtain a urethane prepolymer solution in methyl ethyl ketone having a free isocyanate group content of 1.7% by weight based on the nonvolatile components. The solution was cooled to 30 ° C., neutralized by adding 5 parts by weight of triethylamine, and gradually added to 350 parts by weight of water to emulsify and disperse. 18 parts by weight of a 20% by weight aqueous solution of ethylenediamine was added thereto, followed by stirring for 2 hours. Continued. Next, the solvent was removed while raising the temperature to 60 ° C. over 2 hours under reduced pressure.
By weight, an aqueous acrylic-urethane copolymer was obtained. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in this acryl-urethane copolymer is 1.2% by weight. This aqueous acrylic-urethane copolymer is
This is referred to as an aqueous acrylic-urethane copolymer F. Comparative Synthesis Example 2 (Aqueous Urethane Resin G) In a reaction vessel similar to Synthesis Example 2, 70 parts by weight of polyhexamethylene carbonate diol [number average molecular weight 1,000], 1.2 parts by weight of ethylene glycol, 2,2-diene 6.7 parts by weight of methylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone were charged and uniformly mixed, and 52.4 parts by weight of dicyclohexylmethane diisocyanate was added.
The reaction was carried out for a period of time to obtain a urethane prepolymer solution in methyl ethyl ketone having a free isocyanate group content of 2.7% by weight based on the nonvolatile content. Cool the solution to 30 ° C.
After neutralization by adding 5 parts by weight of triethylamine, water 3
50 parts by weight were gradually added to emulsify and disperse, 18 parts by weight of a 20% by weight aqueous solution of ethylenediamine was added, and stirring was continued for 2 hours. Next, the solvent was removed while heating to 60 ° C. over 2 hours under reduced pressure to obtain an aqueous urethane resin having a nonvolatile content of 35% by weight. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in this urethane resin is 3.3% by weight. This aqueous urethane resin is referred to as an aqueous urethane resin G. Comparative Synthesis Example 3 (Aqueous Urethane Resin H) In a reaction vessel similar to Synthesis Example 2, 100 parts by weight of poly-ε-caprolactone diol [number average molecular weight 2,000] was added.
2.4 parts by weight of 1,6-hexanediol, 6.7 parts by weight of 2,2-dimethylolpropionic acid, 0.001 part by weight of dibutyltin dilaurate and 60 parts by weight of methyl ethyl ketone are charged and uniformly mixed, and then mixed with dicyclohexylmethane. 52.4 parts by weight of diisocyanate was added and reacted at 80 ° C. for 2 hours to obtain a solution of urethane prepolymer in methyl ethyl ketone having a free isocyanate group content of 1.9% by weight based on nonvolatile components. The solution was cooled to 30 ° C. and neutralized by adding 5 parts by weight of triethylamine.
350 parts by weight of water was gradually added to emulsify and disperse, 4 parts by weight of a 60% by weight aqueous solution of hydrazine hydrate was added, and stirring was continued for 2 hours. Next, the solvent was removed while heating to 60 ° C. over 2 hours under reduced pressure to obtain an aqueous urethane resin having a nonvolatile content of 35% by weight. The content of carboxyl groups derived from 2,2-dimethylolpropionic acid in this urethane resin is 1.3% by weight. This aqueous urethane resin is referred to as an aqueous urethane resin H.

Synthesis Example 7 (Aqueous Emulsion A of Acrylic Resin) Temperature Controller, Irritation Stirrer, Reflux Cooler, Supply Container,
In a reaction vessel equipped with a thermometer and a nitrogen gas introduction pipe, water 20
0 parts by weight, 5 parts by weight of a 35% by weight aqueous solution of an anionic emulsifier (sodium salt of sulfuric acid half ester of 20 moles of ethylene oxide adduct of p-nonylphenol) and a nonionic emulsifier (ethylene oxide 2 of p-nonylphenol ethylene oxide 2)
20 parts by weight of a 20% by weight aqueous solution of a 5 mol adduct) were charged, and the inside of the reaction vessel was replaced with nitrogen gas. In a reaction vessel, 20 parts by weight of water, 2.5 parts by weight of a 35% by weight aqueous solution of the above-mentioned anionic emulsifier, 23.6 parts by weight of methyl methacrylate, 16 parts by weight of n-butyl acrylate and 0.4 part of acrylic acid
The monomer mixture containing parts by weight was added and heated to 90 ° C.
Next, an aqueous initiator solution in which 0.25 parts by weight of potassium persulfate was dissolved in 8.5 parts by weight of water was added. Then, 180 parts by weight of water and a 35% by weight aqueous solution of the above anionic emulsifier 2
2.5 parts by weight, 212.4 parts by weight of methyl methacrylate, 144 parts by weight of n-butyl acrylate and 3.
A monomer mixture containing 6 parts by weight and an aqueous initiator solution obtained by dissolving 2.25 parts by weight of potassium persulfate in 76.5 parts by weight of water are supplied into a container maintained at 90 ° C. over 3.5 hours. After the completion of the supply, polymerization was carried out at 90 ° C. for another 2 hours to obtain an aqueous emulsion of an acrylic resin. The glass transition temperature of this acrylic resin was about 20 ° C.
This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion A. Synthesis Example 8 (Aqueous Emulsion B of Acrylic Resin) In a reaction vessel similar to that of Synthesis Example 7, 200 parts by weight of water and anionic emulsifier (sodium salt of sulfuric acid half ester of ethylene oxide 20 mol adduct of p-nonylphenol) were added.
5 parts by weight of a 5% by weight aqueous solution and 20 parts by weight of a 20% by weight aqueous solution of a nonionic emulsifier (addition product of 25 mol of ethylene oxide of p-nonylphenol) were charged, and the inside of the reaction vessel was replaced with nitrogen gas. In a reaction vessel, 20 parts by weight of water, 2.5 parts by weight of a 35% by weight aqueous solution of the above anionic emulsifier, 15.6 parts by weight of styrene, 12 parts by weight of methyl methacrylate, 12 parts by weight of n-butyl acrylate and acrylic A monomer mixture containing 0.4 parts by weight of acid was added and heated to 90 ° C. Next, an aqueous initiator solution in which 0.25 parts by weight of potassium persulfate was dissolved in 8.5 parts by weight of water was added. Then water 1
80 parts by weight, 22.5 parts by weight of a 35% by weight aqueous solution of the anionic emulsifier, 140.4 parts by weight of styrene, 108 parts by weight of methyl methacrylate, n-butyl acrylate 10
A monomer mixture containing 8 parts by weight and 3.6 parts by weight of acrylic acid and an aqueous solution of an initiator obtained by dissolving 2.25 parts by weight of potassium persulfate in 76.5 parts by weight of water were mixed with each other for 90 hours over 3.5 hours. And supply it in a container maintained at ℃.
Polymerization was carried out at 90 ° C. for a time to obtain an aqueous emulsion of an acrylic resin. The glass transition temperature of this acrylic resin was about 36 ° C. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion B. Synthesis Example 9 (Aqueous Emulsion C of Acrylic Resin) In a reaction vessel similar to that of Synthesis Example 7, 200 parts by weight of water and anionic emulsifier (sodium salt of sulfuric acid half-ester of 20 mol adduct of ethylene oxide with p-nonylphenol) were added.
5 parts by weight of a 5% by weight aqueous solution and 20 parts by weight of a 20% by weight aqueous solution of a nonionic emulsifier (addition product of 25 mol of ethylene oxide of p-nonylphenol) were charged, and the inside of the reaction vessel was replaced with nitrogen gas. In a reaction vessel, 20 parts by weight of water, 2.5 parts by weight of a 35% by weight aqueous solution of the above anionic emulsifier, 4 parts by weight of styrene, 4 parts by weight of methyl methacrylate, 31.6 parts by weight of n-butyl acrylate and 31.6 parts by weight of methacryl Acid 0.4
The monomer mixture containing parts by weight was added and heated to 90 ° C.
Next, an aqueous initiator solution in which 0.25 parts by weight of potassium persulfate was dissolved in 8.5 parts by weight of water was added. Then, 180 parts by weight of water and a 35% by weight aqueous solution of the above anionic emulsifier 2
A monomer mixture containing 2.5 parts by weight, 36 parts by weight of styrene, 36 parts by weight of methyl methacrylate, 284.4 parts by weight of n-butyl acrylate and 3.6 parts by weight of methacrylic acid, and 76.5 parts by weight of water Of an aqueous initiator solution in which 2.25 parts by weight of potassium persulfate was dissolved in 9 parts by weight over 9 hours.
The mixture was supplied into a container maintained at 0 ° C., and after completion of the supply, polymerization was carried out at 90 ° C. for another 2 hours to obtain an aqueous emulsion of acrylic resin. The glass transition temperature of this acrylic resin was about -23 ° C. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion C. Table 1 shows the monomer composition of the aqueous emulsion of acrylic resin produced in Synthesis Examples 7 to 9 and the glass transition temperature of the obtained acrylic resin.

[0022]

[Table 1]

Synthesis Example 10 (Aqueous emulsion D of acrylic resin) First, the monomer composition of the monomer mixture added to the reaction vessel was
19.75 parts by weight of methyl methacrylate, acrylic acid-n
-Butyl 20 parts by weight and acrylic acid 0.25 parts by weight, the monomer composition of the monomer mixture fed to the reaction vessel over 3.5 hours was 177.75 parts by weight of methyl methacrylate, acrylic acid-n An aqueous emulsion of an acrylic resin was obtained in the same manner as in Synthesis Example 7 except that 180 parts by weight of butyl and 2.25 parts by weight of acrylic acid were used. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion D. Synthesis Example 11 (Aqueous emulsion E of acrylic resin) First, the monomer composition of the monomer mixture added to the reaction vessel was
19.25 parts by weight of methyl methacrylate, acrylic acid-n
-Butyl 20 parts by weight and acrylic acid 0.75 parts by weight, the monomer composition of the monomer mixture supplied to the reaction vessel over 3.5 hours was 173.25 parts by weight of methyl methacrylate, acrylic acid-n An aqueous emulsion of an acrylic resin was obtained in the same manner as in Synthesis Example 7 except that 180 parts by weight of -butyl and 6.75 parts by weight of acrylic acid were used. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion E. Synthesis Example 12 (Aqueous emulsion F of acrylic resin) First, the monomer composition of the monomer mixture added to the reaction vessel was
The monomer composition of the monomer mixture supplied to the reaction vessel over 3.5 hours was 19 parts by weight of methyl methacrylate, 20 parts by weight of n-butyl acrylate and 1 part by weight of acrylic acid. Parts by weight, acrylic acid-n
An aqueous emulsion of an acrylic resin was obtained in the same manner as in Synthesis Example 7 except that 180 parts by weight of -butyl and 9 parts by weight of acrylic acid were used. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion F. Synthesis Example 13 (Aqueous emulsion G of acrylic resin) First, the monomer composition of the monomer mixture added to the reaction vessel was
18.5 parts by weight of methyl methacrylate, acrylic acid-n-
20 parts by weight of butyl and 1.5 parts by weight of 2-hydroxyethyl methacrylate, the monomer composition of the monomer mixture supplied to the reaction vessel over 3.5 hours was 166.5 parts by weight of methyl methacrylate, An aqueous emulsion of an acrylic resin was obtained in the same manner as in Synthesis Example 7 except that 180 parts by weight of n-butyl acrylate and 13.5 parts by weight of 2-hydroxyethyl methacrylate were used. This aqueous emulsion of acrylic resin is referred to as an aqueous emulsion G of acrylic resin. Comparative Synthesis Example 4 (Aqueous emulsion H of acrylic resin) First, the monomer composition of the monomer mixture added to the reaction vessel was
18.5 parts by weight of methyl methacrylate, acrylic acid-n-
20 parts by weight of butyl and 1.5 parts by weight of acrylic acid;
The monomer composition of the monomer mixture supplied to the reaction vessel over 5 hours was determined to be 166.5 parts by weight of methyl methacrylate, 180 parts by weight of n-butyl acrylate, and 13.5 parts of acrylic acid.
An aqueous acrylic resin emulsion was obtained in the same manner as in Synthesis Example 7 except that the amount was changed to parts by weight. This acrylic resin aqueous emulsion is referred to as an acrylic resin aqueous emulsion H.

Example 1 (Stability of Aqueous Coating Composition) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
To 200 g, 94 g of the acrylic resin aqueous emulsion G obtained in Synthesis Example 13 and a polycarbodiimide-based resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01,
Non-volatile content 40% by weight] was mixed to prepare an aqueous coating composition, left for 2 hours, and then filtered using a 325 mesh wire mesh. No aggregates were observed. Example 2 (Stability of aqueous coating composition) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
In 200 g, 94 g of the acrylic resin aqueous emulsion D obtained in Synthesis Example 10 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01,
Non-volatile content 40% by weight] was mixed to prepare an aqueous coating composition, left for 2 hours, and then filtered using a 325 mesh wire mesh. Aggregates remaining on the wire mesh were collected, dried and weighed to find that they were 0.5 mg or less and the amount of aggregates generated was 5 ppm or less. Example 3 (Stability of aqueous coating composition) The procedure of Example 3 was repeated except that the aqueous emulsion E of the acrylic resin obtained in Synthesis Example 11 was used instead of the aqueous emulsion D of the acrylic resin obtained in Synthesis Example 10. The same operation as in Example 2 was repeated. The weight of the dried aggregates was 0.5 mg or less, and the amount of aggregates generated was 5 ppm or less. Example 4 (Stability of aqueous coating composition) The procedure of Example 4 was repeated, except that the aqueous emulsion F of the acrylic resin obtained in Synthesis Example 12 was used instead of the aqueous emulsion D of the acrylic resin obtained in Synthesis Example 10. The same operation as in Example 2 was repeated. The weight of the dried aggregate was 5.6 mg, and the amount of the generated aggregate was 50 ppm. Comparative Example 1 (Stability of Aqueous Coating Composition) Instead of using the acrylic resin aqueous emulsion D obtained in Synthesis Example 10, the acrylic resin aqueous emulsion H obtained in Comparative Synthesis Example 4 was used. The same operation as in Example 2 was repeated. Gelation occurred and a large amount of gel remained on the wire mesh. Monomer compositions of aqueous emulsions of acrylic resins produced in Synthesis Examples 10 to 13 and Comparative Synthesis Example 4,
Table 2 shows the results of Examples 1 to 4 and Comparative Example 1.

[0025]

[Table 2]

As can be seen from Table 2, when the amount of acrylic acid in the monomer mixture, which is the raw material of the aqueous emulsion of acrylic resin, exceeds 2.5% by weight, the amount of aggregates generated increases. When the amount of acrylic acid reaches 3.75% by weight, clear gelation occurs. It can be seen that in order for the aqueous coating composition to have stability, the amount of acrylic acid in the monomer mixture is preferably 2.5% by weight or less. Example 5 (Preparation of aqueous coating composition and evaluation of physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
70 parts by weight, 25 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 and a polycarbodiimide-based resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, a nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was B. Example 6 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
50 parts by weight, 47 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was H. Example 7 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
30 parts by weight, 67 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7, and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 2H.

Example 8 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
10 parts by weight, 87 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7, and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
Except that two squares of the coating on the concrete board were peeled off,
The coating remained on the adherend side. No whitening was observed in the water resistance test. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 3H. Example 9 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer B obtained in Synthesis Example 3
30 parts by weight, 65 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, a nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 2H. Example 10 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer C obtained in Synthesis Example 4
30 parts by weight, 65 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, a nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 2H. Example 11 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer D obtained in Synthesis Example 5
30 parts by weight, 65 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, a nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 2H.

Example 12 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer E obtained in Synthesis Example 6
50 parts by weight, 47 parts by weight of the acrylic resin aqueous emulsion B obtained in Synthesis Example 8 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was smooth and transparent. In the adhesion test, all the coating films remained on the adherend side. No whitening was observed in the water resistance test. No abnormality was observed in the alcohol resistance test. In the weather resistance test,
No whitening was observed. The pencil hardness was 2H. Example 13 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
50 parts by weight, 47 parts by weight of the acrylic resin aqueous emulsion B obtained in Synthesis Example 8 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test,
All of the coating remained on the adherend side. In the water resistance test,
No whitening was observed. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was 2H. Example 14 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
50 parts by weight, 47 parts by weight of the acrylic resin aqueous emulsion C obtained in Synthesis Example 9 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-0
1, non-volatile content 40% by weight] to prepare an aqueous coating composition. The coating film made from this aqueous coating composition was cloudy. In the adhesion test, all the coating films remained on the adherend side. No whitening was observed in the water resistance test. No abnormality was observed in the alcohol resistance test. No whitening was observed in the weather resistance test. The pencil hardness was HB. Example 15 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
30 parts by weight, 65 parts by weight of the acrylic resin aqueous emulsion G obtained in Synthesis Example 13 and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-
01, a nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was slightly turbid. In the adhesion test, all the coating films remained on the adherend side. No whitening was observed in the water resistance test. No abnormality was observed in the alcohol resistance test. In the weather resistance test,
No whitening was observed. The pencil hardness was 2H.

Comparative Example 2 (Evaluation of aqueous coating composition and physical properties of coating film) 30 parts by weight of aqueous acrylic-urethane copolymer F obtained in Comparative Synthetic Example 1 and an aqueous emulsion of acrylic resin obtained in Synthetic Example 7 A65 parts by weight and a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E
-01, nonvolatile content of 40% by weight] to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was smooth and transparent. In the adhesion test, the coating films formed on the oak plate, the stainless steel plate, and the glass plate all remained on the adherend side, but 28 squares of the coating film formed on the concrete plate were peeled off. In the water resistance test, slight whitening occurred. In the alcohol resistance test, the coating film showed slight blistering and whitening. In the weather resistance test, slight whitening occurred. Pencil hardness is 2H
Met. Comparative Example 3 (Evaluation of aqueous coating composition and physical properties of coating film) 30 parts by weight of aqueous urethane resin G obtained in Comparative Synthesis Example 2, 65 parts by weight of aqueous emulsion A of acrylic resin obtained in Synthesis Example 7, and polycarbodiimide-based An aqueous coating composition was prepared by mixing 5 parts by weight of a resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01, nonvolatile content of 40% by weight]. The coating film made from this aqueous coating composition was cloudy. In the adhesion test, all of the coating films made on the oak plate and the glass plate remained on the adherend side, but three squares of the coating film made on the stainless steel plate and the coating film made on the concrete plate 58 squares were peeled off.
In the water resistance test, significant whitening occurred. In the alcohol resistance test, noticeable blistering and whitening occurred in the coating film. In the weather resistance test, noticeable whitening occurred. The pencil hardness was 2H. Comparative Example 4 (Evaluation of aqueous coating composition and physical properties of coating film) 30 parts by weight of aqueous urethane resin H obtained in Comparative Synthesis Example 3, 65 parts by weight of aqueous emulsion A of acrylic resin obtained in Synthesis Example 7, and polycarbodiimide-based An aqueous coating composition was prepared by mixing 5 parts by weight of a resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01, nonvolatile content of 40% by weight]. The coating film made from this aqueous coating composition was cloudy. In the adhesion test, all of the coatings formed on the oak plate remained on the adherend side, but three squares of the coating formed on the stainless steel plate and three squares of the coating formed on the glass plate Two pieces and 71 squares of the coating film formed on the concrete plate were peeled off. In the water resistance test,
Significant whitening occurred. In the alcohol resistance test, noticeable blistering and whitening occurred in the coating film. In the weather resistance test, noticeable whitening occurred. The pencil hardness was 2H.

Comparative Example 5 (Evaluation of Aqueous Coating Composition and Film Properties) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
An aqueous coating composition was prepared by blending 95 parts by weight and 5 parts by weight of a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01, nonvolatile content 40% by weight]. The coating film produced from this aqueous coating composition was smooth and transparent. In the adhesion test, all of the coatings formed on the oak plate remained on the adherend side, but four squares of the coating formed on the stainless steel plate and four squares of the coating formed on the glass plate Two pieces and 41 squares of the coating film formed on the concrete plate were peeled off. No whitening was observed in the water resistance test. In the alcohol resistance test, noticeable blistering and whitening occurred in the coating film. In the weather resistance test, noticeable whitening occurred. The pencil hardness was 5B. Comparative Example 6 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous emulsion A of acrylic resin obtained in Synthesis Example 7
An aqueous coating composition was prepared by blending 95 parts by weight and 5 parts by weight of a polycarbodiimide resin aqueous emulsion [Nisshinbo Co., Ltd., Carbodilite E-01, nonvolatile content 40% by weight]. The coating film produced from this aqueous coating composition had cracks. In the adhesion test, one square of the coating film formed on the oak plate, 34 squares of the coating film formed on the stainless steel plate, 22 squares of the coating film formed on the glass plate, and concrete Three squares of the coating film formed on the plate were peeled off. In the water resistance test, slight whitening was observed. In the alcohol resistance test, noticeable blistering and whitening occurred in the coating film. In the weather resistance test,
Significant whitening occurred. The pencil hardness was 4H. Comparative Example 7 (Evaluation of aqueous coating composition and physical properties of coating film) Aqueous acrylic-urethane copolymer A obtained in Synthesis Example 2
70 parts by weight and 95 parts by weight of the acrylic resin aqueous emulsion A obtained in Synthesis Example 7 were mixed to prepare an aqueous coating composition. The coating film produced from this aqueous coating composition was smooth and transparent. In the adhesion test, all the coating films remained on the adherend side. In the water resistance test, significant whitening occurred. In the alcohol resistance test, noticeable blistering and whitening occurred in the coating film. In the weather resistance test, noticeable whitening occurred. The pencil hardness was B. Example 5
Table 3 shows the results of No. 15 and Comparative Examples 2 to 7.

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

As can be seen from Table 3, the coating films of Examples 5 to 15 produced using the aqueous coating composition of the present invention were:
Although slight turbidity is generally recognized, adhesion is good including the concrete plate, and water resistance, alcohol resistance, and weather resistance are also excellent. Further, the pencil hardness is almost 2H, which is sufficient for practical use. On the other hand, the coating film produced using the aqueous coating composition of Comparative Example 2 in which the high molecular weight polyol used for producing the aqueous acrylic-urethane copolymer does not contain dimer diol is smooth and transparent, Adhesion to concrete plate, water resistance, alcohol resistance, weather resistance is slightly poor, the aqueous coating composition of Comparative Example 3 and Comparative Example 4 using an aqueous urethane resin instead of an aqueous acrylic-urethane copolymer. The coating film produced using the method has a turbid appearance and poor adhesion to a concrete plate, water resistance, alcohol resistance, and weather resistance. Further, a coating film produced using the aqueous coating composition of Comparative Examples 5, 6 and 7 lacking either the aqueous acrylic-urethane copolymer, the aqueous emulsion of the acrylic resin, or the aqueous polycarbodiimide emulsion. All have poor physical properties.

[0035]

The coating film obtained from the aqueous coating composition of the present invention has excellent water resistance, alkali resistance and weather resistance,
Excellent performance not only in various coating agents such as adhesives, paints, printing inks, etc. but also in coating fields where strict required performance such as weather resistance, light resistance, abrasion resistance, water resistance, alkali resistance, alcohol resistance are required. It can be used for a wide range of applications as an aqueous coating agent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09D 5/00 C09D 5/00 Z 175/04 175/04 179/00 179/00 (72) Inventor Takaki Ishii Yokkaichi, Mie Prefecture No. 1-4, Toue-cho, Urethane, Japan Urethane Giken Kogyo Co., Ltd. (72) Inventor Taichiro Kato 5-12-31 201 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, Japan (56) References JP-A-4-81447 (JP, A JP-A-4-103680 (JP, A) JP-A-9-235508 (JP, A) JP-A-6-508160 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 5/00-201/10 C08L 23/00-101/16

Claims (5)

(57) [Claims] (1) (A) (a) an organic polyisocyanate compound, (b) a high molecular weight polyol, (c) a compound having an anionic hydrophilic group and two or more active hydrogens, and (d) chain extension optionally used. Aqueous acrylic obtained by subjecting a neutralized isocyanate group-terminated prepolymer obtained from the agent to chain extension in water using (e) one or more chain extenders selected from water-soluble polyamines, hydrazines and derivatives thereof. -In the urethane copolymer, (b) the high molecular weight polyol is an acrylic polyol 5 having a glass transition temperature of -50 to 100 ° C and a hydroxyl value of 5 to 200 mgKOH / g.
Aqueous acrylic-urethane copolymer containing 重量 60% by weight and 1-40% by weight of dimer diol, (B) (f)
An alkyl methacrylate unit having 1 to 12 carbon atoms, and (g) an alkyl group having 1 to 8 carbon atoms.
An aqueous coating composition obtained by mixing an aqueous emulsion of an acrylic resin having an acrylic acid alkyl ester unit, and an aqueous emulsion of a polycarbodiimide resin (C), wherein the components (A) and (B) And (C) component in a non-volatile content weight ratio of (A) 4-98% by weight, (B)
An aqueous coating composition comprising 1 to 95% by weight and (C) 1 to 10% by weight. 2. The method according to claim 1, wherein (a) the organic polyisocyanate compound is
The aqueous coating composition according to claim 1, which is at least one selected from an aliphatic diisocyanate compound and an alicyclic diisocyanate compound. 3. The aqueous coating composition according to claim 1, wherein (b) the high molecular weight polyol contains a polyester polyol, a polycarbonate polyol or a polyether polyol in addition to the acrylic polyol and the dimer diol. (C) a compound having an anionic hydrophilic group and two or more active hydrogens, wherein the anionic hydrophilic group is a carboxyl group, and the content of the carboxyl group is acryl-based;
The amount of the urethane copolymer is 0.3 to 2.5% by weight.
An aqueous coating composition as described in the above. 5. The acrylic resin of the aqueous emulsion of the component (B) comprises (h) a monomer unit having a carboxyl group.
2. The aqueous coating composition according to claim 1, having less than 5% by weight.