JP7438078B2 - Water-based coating agent for steel materials, film, coating method for steel materials, and steel materials - Google Patents

Description

The present invention relates to a water-based coating agent for steel, a coating, a method for coating steel, and steel.

Chromate treatment is conventionally known as a treatment for imparting corrosion resistance to steel materials and plated steel materials. Chromate treatment gives the steel surface a yellow tinge while maintaining its metallic luster. On the other hand, since hexavalent chromium used in chromate treatment is toxic, non-chromium treatment that does not contain chromium has also been used in recent years (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2004-190121

The surface of a steel material subjected to non-chromium treatment is colorless and transparent, unlike chromate treatment, so it is difficult to visually determine whether or not the treatment has been applied. In order to confirm the presence or absence of treatment, there is a method of analyzing the surface of the steel material or using a marking device, but there is a problem of increased costs due to additional steps.

For this reason, it is conceivable to color the surface of the steel material that has been subjected to chromium-free treatment. At this time, it is preferable to be able to give the surface of the steel material an appearance with a bright color tone and excellent design while maintaining the metallic luster characteristic of the steel material. However, simply adding a pigment to the treatment agent to color the steel material during the chromium-free treatment poses a problem in that the performance of the formed film, such as corrosion resistance and weather resistance, deteriorates. Further, there was a problem in that the pigments aggregated in the coating film, resulting in unclear color development and an appearance lacking in metallic luster.

The present invention has been made in view of the above, and provides a water-based coating agent for steel materials, a coating film, and a method for coating steel materials, which can maintain the corrosion resistance and weather resistance of the formed coating film and impart a desirable design to the metal surface. , and steel materials.
Another object of the present invention is to provide a coating for steel materials, a method for coating steel materials, and steel materials that can maintain corrosion resistance and weather resistance and impart a desirable design to the metal surface.

(1) The present invention provides polyurethane resin particles (A-1) and ethylenically unsaturated carboxylic acid particles each having a median diameter of 20 to 100 nm and having at least one of a silanol group and an alkoxysilyl group. Polymer resin particles (A-2), silicon oxide particles (B) having a mode diameter of 5 to 20 nm, an organic titanium compound (C), and a phthalocyanine coated with at least one of a resin and a surfactant. It has a pigment (F) and at least one rust preventive agent (G) selected from the group consisting of a phosphoric acid compound, a thiocarbonyl compound, a niobium oxide, and a guanidine compound, and the phthalocyanine pigment (F). The content is 0.01 to 10 parts by mass based on a total of 100 parts by mass of the polyurethane resin particles (A-1) and the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2). The present invention relates to an aqueous coating agent for steel materials having a primary particle size of 0.01 to 1.0 μm.

According to the invention (1), it is possible to provide a water-based coating agent for steel that maintains the corrosion resistance and weather resistance of the formed coating and can impart a desirable design to the metal surface.

(2) The phthalocyanine in the phthalocyanine pigment (F) is at least one of metal phthalocyanine and metal-free phthalocyanine, and the metal of the metal phthalocyanine is Ca, Ba, Cd, Na, Cu, Ni, Co, Fe, The aqueous coating agent for steel materials according to (1), which is any one of Mg, Zn, Al, Mn, V, Ti, and Sn.

According to the invention (2), the effect of maintaining the corrosion resistance and weather resistance of the formed film can be more preferably obtained, and the preferable design imparted to the metal surface can be maintained.

(3) The aqueous coating agent for steel materials according to (1) or (2), which has a 20°C viscosity of 100 mPa·s or less.

According to the invention (3), preferable coating properties of the water-based coating agent for steel materials can be obtained, coating unevenness can be eliminated, and preferable design properties can be imparted to the metal surface.

(4) The mass ratio of the polyurethane resin particles (A-1) to the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2) is (A-1):(A-2)=20: The aqueous coating agent for steel materials according to any one of (1) to (3), which has a ratio of 80 to 90:10.

According to the invention (4), a film having excellent solvent resistance and alkali resistance can be formed.

(5) The aqueous coating agent for steel materials according to any one of (1) to (4), further comprising silicon oxide particles (E) having a mode diameter of 70 to 200 nm.

According to the invention (5), the hardness of the formed film can be improved and the coefficient of friction can be adjusted to a suitable range, so that the abrasion resistance of the film can be improved.

(6) The content of the rust preventive agent (G) is based on a total of 100 parts by mass of the polyurethane resin particles (A-1) and the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2). , respectively,
The phosphoric acid compound is 0.01 to 5 parts by mass in terms of phosphate radical,
The thiocarbonyl compound is 0.1 to 10 parts by mass,
The niobium oxide is 0.1 to 5 parts by mass in terms of Nb ₂ O ₅ ,
The aqueous coating agent for steel materials according to any one of (1) to (5), wherein the guanidine compound is 0.1 to 5 parts by mass.
( 7 ) A coating formed from the water-based coating agent for steel materials according to any one of (1) to ( 6 ), and having a chroma C ^* of 2.0 or more and 50 or less.

According to the invention ( 7 ), a preferable design can be imparted to steel materials by the coating formed by the aqueous coating agent for steel materials.

( 8 ) A method for coating steel materials, comprising applying the aqueous coating agent for steel materials according to any one of (1) to ( 6 ) to the surface of steel materials to form a film.

According to the invention ( 8 ), it is possible to form a film on the surface of a steel material that maintains corrosion resistance and weather resistance and can impart a desirable design to the metal surface.

( 9 ) A steel material on the surface of which a film is formed with the aqueous coating agent for steel material according to any one of (1) to ( 6 ), and has a 60° glossiness of 50% or more.

According to the invention (9), it is possible to provide a steel material that has a desirable design.

( 10 ) The steel material according to ( 9 ), wherein the steel material is either hot dip galvanized steel or aluminum-containing galvanized steel.

According to the invention ( 10 ), it is possible to provide a steel material that has a desirable design.

An embodiment of the present invention will be described below. The present invention is not limited to the following embodiments.

<Water-based coating agent for steel materials>
The aqueous coating agent for steel materials according to the present embodiment includes polyurethane resin particles (A-1) (hereinafter sometimes simply referred to as "resin particles (A-1)") and an ethylene-unsaturated carboxylic acid copolymer. Resin particles (A-2) (hereinafter sometimes simply referred to as "resin particles (A-2)"), silicon oxide particles (B), organic titanium compound (C), and phthalocyanine pigment (F) and has. Moreover, wax particles (D) and silicon oxide particles (E) may be included.

The polyurethane resin particles (A-1) have a median diameter of 20 to 100 nm, and have at least one of a silanol group and an alkoxysilyl group. The resin particles (A-1) are not particularly limited, but polycarbonate polyurethane, for example, is preferable because it has excellent solvent resistance and alkali resistance. The polycarbonate-based polyurethane resin particles can be obtained, for example, by the following method. First, a polyurethane prepolymer is produced by reacting an isocyanate group-containing compound, a polycarbonate polyol, a low molecular weight polyol, and a compound having an active hydrogen group and a hydrophilic group. Next, the above hydrophilic group is neutralized with a neutralizing agent. Next, the above-mentioned neutralized prepolymer is dispersed in water containing an alkoxysilane containing an active hydrogen group and an amine, and by chain-extending the neutralized prepolymer, at least one of a silanol group and an alkoxysilyl group is dispersed. Polycarbonate-based polyurethane resin particles having the following properties are obtained.

The isocyanate group-containing compound is not particularly limited, but includes, for example, aliphatic diisocyanates such as hexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), methyl-2,4- Alicyclic diisocyanates such as cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, m-phenylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, 4,4- Aromatic diisocyanates such as diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, and 4,4-toluidine diisocyanate are exemplified.

The polycarbonate polyol is not particularly limited, but examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl - selected from the group consisting of 1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol-A, and hydrogenated bisphenol-A, Examples include those obtained by reacting one or more glycols with dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene, and the like.

The above-mentioned low-molecular polyols are not particularly limited, but examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol. , 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, glycols, glycerin, trimethylolpropane, pentaerythritol and the like.

The compound having an active hydrogen group and a hydrophilic group is not particularly limited, but includes, for example, a sulfonic acid group-containing compound such as 2-hydroxyethanesulfonic acid, or a derivative thereof, or 2,2-dimethylolpropionic acid. , carboxy group-containing compounds such as 2,2-dimethylolbutyric acid, or derivatives thereof. When producing the polyurethane resin particles, these compounds may be used alone or in combination of two or more. The hydrophilic groups such as the carboxy group or sulfonic acid group are preferably neutralized using a neutralizing agent in order to disperse the polyurethane prepolymer well in water.

Examples of the neutralizing agent include, but are not limited to, ammonia, tertiary amines such as triethylamine and dimethylethanolamine, and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. These may be used alone or in combination of two or more.

The alkoxysilanes containing an active hydrogen group are not particularly limited, but examples include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, γ- Amino group-containing silanes such as (2-aminoethyl)aminopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, Examples include mercapto group-containing silanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropylmethyldiethoxysilane.

The amines used for the chain extension are not particularly limited, but examples include diamines such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, etc. Examples include polyamines, hydrazines, and the like. These may be used alone or in combination of two or more.

The reaction for obtaining a polyurethane prepolymer from the above-mentioned isocyanate group-containing compound and an active hydrogen compound such as a polyol is preferably carried out at a reaction temperature of 30 to 100°C, for example. The above reaction may be performed in the presence or absence of an organic solvent. The organic solvent is preferably an organic solvent with relatively high solubility in water, such as acetone, methyl ethyl ketone, acetonitrile, N-methylpyrrolidone, and the like.

The method for dispersing the neutralized prepolymer in water is not particularly limited, and examples thereof include methods using a homogenizer, mixer, and the like. The temperature at this time is preferably about room temperature or higher and 70° C. or lower, for example.

When an organic solvent is used during the reaction to obtain the polyurethane prepolymer, the organic solvent may be removed by distillation under reduced pressure, if necessary.

The ethylene-unsaturated carboxylic acid copolymer resin particles (A-2) have a median diameter of 20 to 100 nm and have at least one of a silanol group and an alkoxysilyl group. The resin particles (A-2) are not particularly limited, but for example, ethylene-methacrylic acid copolymer resin is neutralized and water-dispersed with at least one of alkali metal hydroxide, ammonia, and amine. Resin particles obtained by reacting an epoxy group-containing alkoxysilane with a resin solution are preferable because they are fine particles and can form a high-performance coating.

The ethylene-methacrylic acid copolymer resin is not particularly limited, but preferably has an ethylene content of 70 to 90% by mass and a methacrylic acid content of 10 to 30% by mass. The ethylene-methacrylic acid copolymer resin may contain monomers other than ethylene and methacrylic acid, but the content of the other monomers is preferably 10% by mass or less. . The method for producing the ethylene-methacrylic acid copolymer resin is not particularly limited, and may be produced by a known method such as polymerization using a high-pressure low-density polyethylene production apparatus.

The epoxy group-containing alkoxysilanes are not particularly limited, but examples include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltriethoxysilane, and γ-glycidoxysilane. Examples include oxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like. These may be used alone or in combination of two or more.

The epoxy group-containing alkoxysilane is preferably reacted in an amount of 0.1 to 20 parts by mass, and 1 to 20 parts by mass, based on 100 parts by mass of the solid content of the water-dispersed ethylene-methacrylic acid copolymer resin. It is more preferable to use 10 parts by mass. When less than 0.1 part by mass of the above-mentioned epoxy group-containing alkoxysilanes is used, the alkali resistance of the coating formed on the surface of the steel material and the adhesion to a curable resin such as a paint are reduced. Similarly, if it is used in an amount exceeding 20 parts by mass, the bath stability of the aqueous coating agent for steel materials may decrease.

When reacting the water-dispersed ethylene-methacrylic acid copolymer resin with the epoxy group-containing alkoxysilane, a polyfunctional epoxy compound may be used in combination. The polyfunctional epoxy compound is not particularly limited, but includes, for example, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, propylene glycol diglycidyl ether, triglycidyl tris(2 -hydroxyethyl) isocyanurate, bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and the like. These may be used alone or in combination of two or more.

The reaction between the water-dispersed ethylene-methacrylic acid copolymer resin, the epoxy group-containing alkoxysilane, and the polyfunctional epoxy compound is carried out at a temperature of 50 to 100°C for 0.5 to 12 hours. It is preferable.

The mass ratio of resin particles (A-1) to resin particles (A-2) is preferably (A-1):(A-2)=20:80 to 90:10. When the amount of resin particles (A-1) is less than 20 parts by mass with respect to the total of 100 parts by mass of resin particles (A-1) and resin particles (A-2), the hydrophobicity of the coating becomes high and the resistance There may be a decrease in tape removability or a decrease in solvent resistance to highly hydrophobic solvents such as white gasoline. When the resin particles (A-1) exceed 90 parts by mass, the hydrophilicity of the coating increases, resulting in decreased alkali resistance, decreased solvent resistance to highly hydrophilic solvents such as ethanol, or processing due to the coating becoming brittle. Deterioration of corrosion resistance may occur in some cases.

Since the resin particles (A-1) and the resin particles (A-2) have at least one of a silanol group and an alkoxysilyl group, the resin particles (A-1) and the resin particles (A-2) have at least one of a silanol group and an alkoxysilyl group. , a composite coating is formed. Thereby, the solvent resistance, alkali resistance, etc. of the coating formed with the water-based coating agent for steel materials can be improved.

The particle diameters of the resin particles (A-1) and the resin particles (A-2) are both 20 to 100 nm. The above particle size is the median diameter (D50) measured by dynamic light scattering. If the particle size is less than 20 nm, the viscosity of the aqueous steel coating agent becomes high or the bath stability decreases, resulting in a decrease in coating workability. When the particle size exceeds 100 nm, the tape peeling resistance and solvent resistance of the coating formed with the aqueous coating agent for steel materials decrease.

The particle diameter of the resin particles (A-1) is determined by the amount of hydrophilic functional groups, such as carboxy groups and sulfonic acid groups, introduced to obtain water dispersibility, and the amount of hydrophilic functional groups to be introduced to obtain water dispersibility, and the amount of hydrophilic functional groups to be used to neutralize the hydrophilic functional groups. It can be adjusted by changing the type and amount of Japanese additives. The particle size of the resin particles (A-2) is adjusted by changing the type of neutralizing agent, water dispersion conditions, type and amount of epoxy group-containing alkoxysilanes, and type and amount of polyfunctional epoxy compound. be able to.

The silicon oxide particles (B) have a particle size of 5 to 20 nm. The above particle diameter is a mode diameter (most frequent particle diameter) measured by a dynamic light scattering method. When the particle size is within this range, light is transmitted, so that desirable design properties (gloss and chroma) can be obtained. Although the silicon oxide particles (B) are not particularly limited, for example, colloidal silica, fumed silica, etc. can be used. Specific examples include Snowtex N, Snowtex C (Nissan Chemical Industries), Adelite AT-20N, AT-20A (Asahi Denka Kogyo), Cataloid S-20L, Cataloid SA (Catalyst Chemical Industry), and the like. These may be used alone or in combination of two or more.

The content of silicon oxide particles (B) is preferably 5 to 100 parts by mass, and 10 to 50 parts by mass, based on the total of 100 parts by mass of resin particles (A-1) and resin particles (A-2). Parts by mass are more preferable. When the content of silicon oxide particles (B) is less than 5 parts by mass, the hardness and corrosion resistance of the coating formed by the aqueous coating material for steel materials may decrease. If it exceeds 100 parts by mass, the film forming properties and water resistance of the coating may deteriorate.

The organic titanium compound (C) is not particularly limited, but includes, for example, dipropoxybis(triethanolamimato)titanium, dipropoxybis(diethanolamimato)titanium, dibutoxybis(triethanolamimato)titanium, dibutoxybis(diethanolamimato)titanium. , dipropoxybis(acetylacetonato)titanium, dibutoxybis(acetylacetonato)titanium, dihydroxybis(lactato)titanium monoammonium salt, dihydroxybis(lactato)titanium diammonium salt, propanedioxytitanium bis(ethylacetoacetate), oxo Examples include titanium bis(monoammonium oxalate). These may be used alone or in combination of two or more.

The content of the organic titanium compound (C) shall be 0.05 to 3 parts by mass in terms of titanium atoms, based on the total of 100 parts by mass of the resin particles (A-1) and resin particles (A-2). The amount is preferably 0.1 to 2 parts by mass, and more preferably 0.1 to 2 parts by mass. If the content of the organic titanium compound (C) is less than 0.05 parts by mass, the various components in the coating formed by the aqueous coating agent for steel materials may not be sufficiently composited, and the performance of the coating may deteriorate. be. If the amount exceeds 3 parts by mass, the hydrophilicity of the coating may become too high, resulting in a decrease in the performance of the coating and a decrease in bath stability of the aqueous coating agent for steel materials.

Wax particles (D) may be added in order to reduce the coefficient of dynamic friction of the coating formed by the aqueous coating agent for steel materials and improve the lubricity of the coating surface. In that case, it is preferable that the particle size is 0.5 to 4 μm and the softening point is 100 to 140°C. The wax particles (D) are not particularly limited, but polyolefin wax particles (D) are preferred from the viewpoint of improving the design (gloss and chroma). Examples of the polyolefin wax particles (D) include, but are not limited to, paraffin, microcrystalline, hydrocarbon waxes such as polyethylene, and derivatives thereof. The above-mentioned derivatives include, but are not particularly limited to, carboxylated polyolefins, chlorinated polyolefins, and the like.

When the wax particles (D) are added to an aqueous coating agent for steel materials, the particle size is not particularly limited, but is preferably 0.5 to 4 μm. The above particle size is the median diameter (D50) measured by dynamic light scattering. When the particle size is less than 0.5 μm, the lubricity of the formed film may be insufficient. When the particle size exceeds 4 μm, problems such as non-uniform distribution of wax particles (D) and falling off from the coating may occur.

In addition to silicon oxide particles (B) with a particle diameter (mode diameter) of 5 to 20 nm, the aqueous coating agent for steel materials of this embodiment contains silicon oxide particles (E) with a particle diameter (mode diameter) of 70 to 200 nm. It may be included. The above particle diameter is a mode diameter (most frequent particle diameter) measured by a dynamic light scattering method. By containing silicon oxide particles (E) in the aqueous coating agent for steel materials, the hardness of the coating can be improved and the coefficient of friction can be adjusted to a suitable range. Therefore, the abrasion resistance of the coating can be improved, and the handling properties of the coated steel can be improved, such as preventing the coil of the coated steel on which the coating has been formed from collapsing and the cutting plate from collapsing.

By setting the particle diameter of the silicon oxide particles (E) to 70 nm or more, the hardness and friction coefficient of the coating can be improved. Further, by setting the particle size to 200 nm or less, the silicon oxide particles (E) are less likely to settle in the aqueous coating agent for steel materials, and dispersibility can be ensured.

The silicon oxide particles (E) have a larger particle diameter (mode diameter) than the silicon oxide particles (B). The silicon oxide particles (E) are not particularly limited, and known ones can be used. Examples include ST-ZL, MP-1040 (manufactured by Nissan Chemical Industries, Ltd.), PL-7 (manufactured by Fuso Chemical Industries, Ltd.), and SI-80P (manufactured by Catalysts Chemical Industries, Ltd.). These may be used alone or in combination of two or more.

The content of silicon oxide particles (E) is preferably 1 to 20 parts by mass, and 1 to 10 parts by mass, based on a total of 100 parts by mass of resin particles (A-1) and resin particles (A-2). More preferably, it is parts by mass. If the content of silicon oxide particles (E) is less than 1 part by mass, it is difficult to obtain the effect of adjusting the friction coefficient, so it is preferable to contain 1 part by mass or more. Moreover, if the content of the silicon oxide particles (E) exceeds 20 parts by mass, there is a possibility that the film-forming properties and water resistance of the film will be reduced.

The phthalocyanine pigment (F) imparts preferable chroma C ^* to the formed film while maintaining the gloss of the coated steel material. The phthalocyanine in the phthalocyanine pigment (F) is preferably at least one of metal phthalocyanine and metal-free phthalocyanine. The metal of the metal phthalocyanine is preferably one of Ca, Ba, Cd, Na, Cu, Ni, Co, Fe, Mg, Zn, Al, Mn, V, Ti, and Sn, for example. The above-mentioned phthalocyanine is more preferably a metal phthalocyanine in which the metal is either Cu or Sn. The crystal structure of phthalocyanine is not particularly limited, and the commonly used α-type and β-type may be used, or those having other crystal structures may be used.

The method for obtaining the above-mentioned phthalocyanine is not particularly limited, but for example, the method for obtaining copper phthalocyanine is to heat-react phthalic acid or its derivative, urea or its derivative in an organic solvent in the presence of a copper compound and a catalyst. Examples of known methods include the Weiler method, the phthalodinitrile method in which phthalodinitrile is heated and reacted in an organic solvent in the presence of a copper compound, and the like.

Since the phthalocyanine obtained by the above manufacturing method forms aggregates of fine pigments, the primary particle size can be reduced to a very small size using known methods such as acid pasting and solvent salt milling. It is possible to obtain phthalocyanine particles that are fine, have a narrow distribution width, and have a sharp particle size distribution. Furthermore, a resin and/or a surfactant may be added to prevent reaggregation of phthalocyanine particles. After coating, a phthalocyanine dispersion is obtained.

The method for coating the phthalocyanine with a resin or surfactant is not particularly limited, but for example, in a solvent salt milling method, the phthalocyanine, resin and/or surfactant, water-soluble inorganic salt, and water-soluble organic solvent are kneaded. By kneading using an extruder or the like, the phthalocyanine can be made fine and the surface of the phthalocyanine can be uniformly coated with the resin or surfactant. When pulverizing phthalocyanine by a method other than the above, a resin and/or surfactant may be added to cover the phthalocyanine surface, or a resin and/or surfactant may be added after pulverization. The phthalocyanine surface may also be coated. As a result, preferable dispersibility of phthalocyanine (F) in the aqueous coating agent for steel materials can be obtained, and as a result, preferable saturation and gloss of the coating formed by the aqueous coating agent for steel materials and the steel materials coated with the above coating. is obtained.

The above-mentioned resin has a pigment affinity site that has the property of adsorbing to the pigment and a site that is compatible with the colorant carrier, and has a function of adsorbing to the pigment and stabilizing the dispersion of the pigment in the colorant carrier. It is something that does. There are no particular limitations, and natural resins, modified natural resins, synthetic resins such as acrylic resins, synthetic resins modified with natural resins, and the like can be used. Rosin is a typical natural resin, and rosin derivatives, cellulose derivatives, rubber derivatives, protein derivatives, and oligomers thereof are used as modified natural resins. Examples of the synthetic resin include epoxy resin, acrylic resin, maleic acid resin, butyral resin, polyester resin, melamine resin, phenol resin, polyurethane resin, and polyamide resin. Examples of synthetic resins modified with natural resins include rosin-modified maleic acid resins, rosin-modified fumaric acid resins, and rosin-modified phenol resins.

Specifically, polycarboxylic acid esters such as polyurethane and polyacrylate, unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, Oil-based dispersants such as chain polyaminoamide phosphates, hydroxyl group-containing polycarboxylic acid esters, modified products thereof, amides formed by the reaction of poly(lower alkylene imine) with polyesters having free carboxyl groups, and their salts. Water-soluble resins and highly water-soluble resins such as (meth)acrylic acid-styrene copolymer, (meth)acrylic acid-(meth)acrylic acid ester copolymer, styrene-maleic acid copolymer, polyvinyl alcohol, polyvinylpyrrolidone, etc.; Molecular compounds, polyesters, modified polyacrylates, ethylene oxide/propylene oxide adducts, phosphoric esters, etc. are used, and these can be used alone or in combination of two or more.

The surfactant is not particularly limited, and conventionally known anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and the like can be used.

Specifically, examples of anionic surfactants include sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate, sodium dodecylbenzenesulfonate, alkali salts of styrene-acrylic acid copolymers, sodium stearate, and alkylnaphthalene sulfonic acids. Sodium, sodium alkyldiphenyl ether disulfonate, monoethanolamine lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, monoethanolamine stearate, sodium stearate, sodium lauryl sulfate, monoethanolamine of styrene-acrylic acid copolymer, poly Examples include oxyethylene alkyl ether phosphate. Examples of nonionic surfactants include polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether phosphate, polyoxyethylene sorbitan monostearate, polyethylene glycol monolaurate, Examples include acetylene glycol and polyoxyethylene acetylene glycol. Examples of cationic surfactants include alkyl quaternary ammonium salts and ethylene oxide adducts thereof. Examples of amphoteric surfactants include alkyl betaines such as alkyldimethylaminoacetic acid betaines, alkylimidazolines, and the like. These can be used alone or in combination of two or more.

The content of the phthalocyanine pigment (F) is 0.01 to 10 parts by mass based on the total of 100 parts by mass of the resin particles (A-1) and the resin particles (A-2). The content of the phthalocyanine pigment (F) is preferably 0.05 to 5 parts by mass. When the content of the phthalocyanine pigment (F) is less than 0.01 parts by mass, the formed film may not have a preferable chroma. If it exceeds 10 parts by mass, the glossiness of the steel material on which the coating is formed may decrease.

The particle size of the phthalocyanine pigment (F) is 0.01 to 1.0 μm. The above particle size is a primary particle size measured by an electron microscope. The primary particle diameter is preferably 0.05 to 1.0 μm. When the primary particle size of the phthalocyanine pigment (F) is less than 0.01 μm, preferred dispersibility in the aqueous coating agent for steel materials may not be obtained, and chroma and gloss may not be obtained. When the primary particle diameter exceeds 1.0 μm, diffuse reflection of light occurs in the coating, and a desirable saturation of the coating may not be obtained. Further, the preferable glossiness of the steel material on which the film is formed may not be obtained in some cases.

Preferably, the aqueous coating agent for steel according to the present embodiment further contains at least one rust preventive agent selected from the group consisting of phosphoric acid compounds, thiocarbonyl compounds, niobium oxides, and guanidine compounds. As a result, excellent corrosion resistance of the steel material on which the coating is formed can be obtained.

Examples of the above phosphoric acid compounds include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid, triammonium phosphate, diammonium hydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, etc. Examples include phosphates, etc. These may be used alone or in combination of two or more. By using the above phosphoric acid compound, phosphate ions form a phosphate layer on the surface of the steel material to passivate it, thereby improving the rust prevention properties of the steel material.

The content of the phosphoric acid compound is preferably 0.01 to 5 parts by mass in terms of phosphate radicals, based on 100 parts by mass in total of resin particles (A-1) and resin particles (A-2). , more preferably 0.05 to 3 parts by mass. If it is less than 0.01 parts by mass, corrosion resistance will be insufficient, and if it exceeds 5 parts by mass, it may gel and become unapplyable depending on the aqueous dispersion resin used.

The above-mentioned thiocarbonyl compounds, niobium oxides, and guanidine compounds are particularly effective in preventing white rust on zinc steel materials and the like, similar to chromium compounds that have been conventionally used to impart corrosion resistance. The thiocarbonyl compound is a compound having a thiocarbonyl group, and is represented by the following general formula (1), for example.

In the above formula (1), X and Y are H, OH, SH, or NH ₂ , those having OH, SH, or NH ₂ as a substituent, or -O-, -NH-, -S- as a substituent , -CO- or -CS-, and represents a hydrocarbon group having 1 to 15 carbon atoms. X and Y may be combined to form a ring. The thiocarbonyl compound represented by the above formula (1) preferably has a nitrogen atom or an oxygen atom.

In addition to the above, the thiocarbonyl compound may be a compound capable of forming a thiocarbonyl group-containing compound in an aqueous solution or in the presence of an acid or an alkali. For example, thiourea and its derivatives, such as methylthiourea, dimethylthiourea, trimethylthiourea, ethylthiourea, diethylthiourea, 1,3-dibutylthiourea, phenylthiourea, diphenylthiourea, 1,3-bis(dimethylaminopropyl) -2-thiourea, ethylenethiourea, propylenethiourea and the like.

As the thiocarbonyl compound, in addition to the above, carbothio acids and salts thereof may be used. For example, thioacetic acid, thiobenzoic acid, dithioacetic acid, sodium methyldithiocarbamate, sodium dimethyldithiocarbamate, triethylamine dimethyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, pipecoline salt of pipecolyldithiocarbamate, o- Examples include potassium ethylxanthate.

These thiocarbonyl compounds may be used alone or in combination of two or more. Note that among the above-mentioned thiocarbonyl compounds, those having low solubility in water can be dissolved in a solvent such as an alkaline solution and then blended into the aqueous coating agent for steel materials.

The content of the thiocarbonyl compound is preferably 0.1 to 10 parts by mass, and 0.2 parts by mass based on 100 parts by mass in total of resin particles (A-1) and resin particles (A-2). More preferably, the amount is 5 parts by mass. If the amount is less than 0.1 part by mass, corrosion resistance will be insufficient, and if it exceeds 10 parts by mass, not only will the corrosion resistance become saturated and become uneconomical, but depending on the aqueous dispersion resin used, it may gel and become unapplyable. There is.

Preferably, the niobium oxide is colloidal niobium oxide particles. Thereby, the corrosion resistance of the formed film can be further improved. The above-mentioned niobium oxide colloid particles preferably have a particle diameter of 100 nm or less in order to form a more stable and dense niobium oxide-containing film and stably impart rust prevention to the object to be treated. preferable. The above particle diameter is a mode diameter (most frequent particle diameter) measured by a dynamic light scattering method. The particle size is more preferably from 2 to 50 nm, even more preferably from 2 to 20 nm.

The niobium oxide colloid particles are particles of niobium oxide dispersed in water in the form of fine particles. The above includes, for example, those in which strictly speaking niobium oxide is not formed, but are in an amorphous state intermediate between niobium hydroxide and niobium oxide. The niobium oxide colloid particles are not particularly limited, and niobium oxide sol produced by a known method can be used.

The content of the niobium oxide is preferably 0.1 to 5 parts by mass in terms of Nb ₂ O ₅ based on 100 parts by mass of the resin particles (A-1) and resin particles (A-2). The amount is preferably 0.2 to 3 parts by mass, and more preferably 0.2 to 3 parts by mass. If it is less than 0.1 part by mass, sufficient rust prevention properties cannot be obtained, which is not preferable. Even if it exceeds 5% by mass, no improvement in the effect will be seen and it may be uneconomical.

The above-mentioned guanidine compound is not particularly limited, and examples thereof include guanidine, aminoguanidine, guanylthiourea, 1,3-di-o-tolylguanidine, 1-o-tolyl biguanide, and 1,3-diphenylguanidine. The above guanidine compounds may be used alone or in combination of two or more.

The content of the guanidine compound is preferably 0.1 to 5 parts by mass, and preferably 0.2 to 5 parts by mass, based on a total of 100 parts by mass of resin particles (A-1) and resin particles (A-2). More preferably, it is 3 parts by mass. If the amount is less than 0.1 part by mass, corrosion resistance will be insufficient, and if it exceeds 5 parts by mass, not only will the corrosion resistance become saturated and become uneconomical, but depending on the aqueous dispersion resin used, it will gel and become unapplyable. There is.

The aqueous coating agent for steel materials according to the present embodiment may contain components other than those described above within a range that does not impede the effects of the present invention. For example, antifoaming agents, organic solvents, leveling agents, etc. may be included. The organic solvent is not particularly limited as long as it is commonly used in paints, and examples thereof include alcohol-based, ketone-based, ester-based, and ether-based hydrophilic solvents. The leveling agent is not particularly limited, and includes, for example, silicone-based, fluorine-based, etc. leveling agents.

As the solvent for the aqueous coating agent for steel materials according to this embodiment, water, a mixture of water, and various alcohols, etc. can be used.

It is preferable that the aqueous coating agent for steel according to this embodiment has a 20°C viscosity of 100 mPa·s or less. When the viscosity at 20° C. exceeds 100 mPa·s, for example, during coating, the coating agent transferred from the coating roll to the object to be coated tends to form stringy droplets, which tends to cause uneven coating. The viscosity of the aqueous coating agent for steel materials is more preferably 50 mPa·s or less. The lower limit of the viscosity of the aqueous coating agent for steel materials is not particularly limited, but may be, for example, 3 mPa·s or more, or 5 mPa·s or more.

<Coating formed with water-based coating agent for steel>
The film formed by the water-based coating agent for steel materials according to the present embodiment (hereinafter, sometimes simply referred to as "film") is made of a composite resin in which the above-mentioned components are composited. That is, the functional groups of each component form bonds and are in a complex state. The above-mentioned bonds mainly include at least one of the Si-OH group and Si-OR group of the resin particles (A-1) and (A-2), the Si-OH group on the surface of the silicon oxide particle (B), and (E). This is a bond formed by the reaction of at least one of the Ti--OH and Ti--OR' groups of the organic titanium compound (C). The above bond is considered to be, for example, a Si--O--Si bond, a Si--O--Ti--O--Si bond, and the organic resin particles and inorganic particles form a chemically strong bond.

The film of the present embodiment contains a resin including polyurethane resin particles and ethylene-unsaturated carboxylic acid copolymer resin particles, silicon oxide particles, Ti, and a phthalocyanine pigment, and the content of the phthalocyanine pigment is equal to the amount of the polyurethane resin particles. and the ethylene-unsaturated carboxylic acid copolymer resin particles, the amount is 0.01 to 10 parts by mass, and the particle size (primary particle size) of the phthalocyanine pigment is 0.01 to 1.0 μm. It is a certain coating. The silicon oxide particles include those having a particle diameter (mode diameter) of 5 to 20 nm, and may further include silicon oxide particles having a particle diameter (mode diameter) of 70 to 200 nm. Ti is derived from the above-mentioned organic titanium compound (C). That is, the film of this embodiment contains Ti as an element. Moreover, the content of the phthalocyanine pigment can be confirmed by confirming that the phthalocyanine is contained in the coating. Furthermore, the coating may contain the above-mentioned rust preventive agent and other additive components.

The film has a chroma C ^* of 2.0 or more and 50 or less. It is preferable that the chroma C ^* of the coating is 2.0 or more because the coating has a clear color tone and good color development. It is more preferable that the saturation C ^* is 5.0 or more. Further, the saturation C ^* is set to 50 or less. More preferably, the saturation C ^* is less than 50. If the saturation C ^* is less than 2.0, the color development of the film may be poor. The chroma C ^* can be measured using a commercially available color difference meter, for example, a spectrophotometer SE6000 manufactured by Nippon Denshoku Industries, Ltd. The saturation C ^* is calculated using the following formula. In the following formula, a ^* and b ^* are the hue in the L ^* a ^* b ^* color system, where a ^* is the red direction, -a ^* is the green direction, b ^* is the yellow direction, and -b ^* is the blue direction. show.

The coating amount of the coating is preferably 0.5 to 3 g/m ² , more preferably 0.5 to 2 g/m ² . If the coating amount is less than 0.5 g/m ² , corrosion resistance and alkali resistance may decrease. On the other hand, if the amount of coating is too large, not only will the adhesion to the substrate deteriorate, but it will also be uneconomical.

<Method of coating steel>

The method for coating steel materials is to apply the water-based coating agent for steel materials onto a metal surface to form a film, and includes a coating step and a heat curing step.

In the coating process, the water-based coating agent for steel is uniformly applied to the metal surface. The coating method is not particularly limited, and commonly used methods such as roll coating, air spray, airless spray, and dipping can be appropriately employed. In order to increase the hardenability of the coating, the steel material to be coated may be heated in advance.

In the heat curing step, the steel material coated with the water-based coating agent for steel material is heated to form a film on the surface of the steel material. The heating temperature of the steel material to be coated is 50 to 250°C, preferably 70 to 220°C. If the heating temperature is less than 50° C., the rate of moisture evaporation is slow and sufficient film-forming properties cannot be obtained, resulting in a decrease in solvent resistance and alkali resistance. On the other hand, if the temperature exceeds 250° C., thermal decomposition of the resin occurs, resulting in a decrease in the physical properties of the coating, leading to deterioration in various performances, and deterioration in appearance such as yellowing. The heat curing time is preferably 1 second to 5 minutes.

In addition to the above, the method for coating steel materials may also include a top coating step of applying a top coat onto the film. Examples of the top coating used in the top coating process include coatings made of acrylic resin, acrylic modified alkyd resin, epoxy resin, urethane resin, melamine resin, phthalic acid resin, amino resin, polyester resin, vinyl chloride resin, etc. It will be done. The film thickness of the top coat is appropriately determined depending on the purpose of the rust-preventing metal product, the type of top coat used, etc., and is not particularly limited. Usually, it is about 5 to 300 μm, more preferably about 10 to 200 μm. The coating film of the top coat can be formed by applying the top coat on the film formed by the above-mentioned water-based coating agent for steel materials, and drying and curing it by heating. The heating temperature can be, for example, 50 to 250°C, and the heating time can be 5 minutes to 1 hour.

<Steel coated with water-based coating material for steel>
The steel material according to this embodiment includes a steel material (base material), a plating layer disposed on the steel material (base material), and a coating disposed on the surface of the plating layer. As described above, the coating contains a resin including polyurethane resin particles and ethylene-unsaturated carboxylic acid copolymer resin particles, silicon oxide particles, Ti, and a phthalocyanine pigment. The content of the phthalocyanine pigment is 0.01 to 10 parts by mass based on the total of 100 parts by mass of the polyurethane resin particles and the ethylene-unsaturated carboxylic acid copolymer resin particles. Further, the primary particle size of the phthalocyanine pigment is 0.01 to 1.0 μm.

Steel materials whose surfaces are coated with the water-based coating agent for steel materials according to the present embodiment are not particularly limited, but include, for example, aluminum-containing galvanized steel materials, galvanized steel materials, zinc-nickel plated steel materials, and zinc-iron plated steel materials. , zinc-based plated steel such as zinc-chromium plated steel, zinc-titanium plated steel, zinc-magnesium plated steel, zinc-manganese plated steel, zinc-aluminum-magnesium plated steel, zinc-aluminum-magnesium-silicon plated steel, and These plating layers contain small amounts of dissimilar metal elements or impurities such as cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic, etc. This includes those in which inorganic substances such as silica, alumina, and titania are dispersed. Furthermore, it is also applicable to multilayer plating in which the above plating is combined with other types of plating, such as iron plating, iron-phosphorus plating, nickel plating, cobalt plating, etc. Furthermore, it is also applicable to aluminum or aluminum alloy plating. The plating method is not particularly limited, and any known method such as electroplating, hot-dip plating, vapor deposition plating, dispersion plating, vacuum plating, etc. may be used. The steel material is preferably aluminum-containing galvanized steel material.

It is preferable that the steel material on the surface of which the coating according to the present embodiment is formed has a 60° glossiness of 50% or more. The 60° glossiness is more preferably from 50 to 200%, even more preferably from 60 to 150%. When the 60° glossiness is less than 50%, a desirable appearance of the steel material cannot be obtained. Furthermore, from the upper limit of the 60° glossiness of general plated steel materials, the more preferable 60° glossiness was set to 200% or less. However, by applying a special manufacturing method or post-manufacturing polishing to the steel material, it is possible to exceed 200%, and it may even exceed 200%. The 60° glossiness can be measured based on the method specified in JIS Z 8741, for example, using a commercially available glossmeter (such as VG2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

The steel material with the coating film according to the present embodiment formed on the surface maintains corrosion resistance and accelerated weathering resistance, has preferable glossiness and chroma, and has an appearance with excellent design.

Hereinafter, the content of the present invention will be explained in more detail based on Examples. The content of the present invention is not limited to the description of the following examples.

<Production of aqueous dispersion of resin particles (A-1)>
(Manufacturing example 1)
A reaction vessel was charged with 4,4-methylenebis(cyclohexyl isocyanate), polycarbonate diol with a molecular weight of 2000, neopentyl glycol, dimethylolpropionic acid, and N-methylpyrrolidone as a solvent, and after stirring at 80°C for 6 hours, dimethylethanolamine was added. A polyurethane prepolymer solution was obtained by neutralization. Next, by dispersing the polyurethane prepolymer solution obtained by the above reaction in water containing hydrazine and γ-(2-aminoethyl)aminopropyltriethoxysilane using a homodisper, silanol groups and/or An aqueous dispersion of polycarbonate-based polyurethane resin particles containing ethoxysilyl groups was obtained. The solid content concentration was 30% by mass, and the median diameter measured by dynamic light scattering was 39 nm.

(Manufacturing example 2)
The polyurethane prepolymer obtained by the above reaction was added to water containing hydrazine and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane using a homodisper. By dispersing the prepolymer solution using a homodisper, an aqueous dispersion of polycarbonate-based polyurethane resin particles containing silanol groups and/or ethoxysilyl groups was obtained. The solid content concentration was 30% by mass, and the median diameter measured by dynamic light scattering was 20 nm.

(Manufacturing example 3)
4,4-methylenebis(cyclohexyl isocyanate), dimethylolpropionic acid, and acetone were added to the reaction vessel and heated to 50°C with stirring to react, and then adipic acid, neopentyl glycol and ethylene glycol were added. A polyester polyol having a molecular weight of 2000 obtained by the reaction was added and reacted to obtain a polyurethane prepolymer solution. Next, the polyurethane prepolymer solution obtained by the above reaction was homodispersed in water containing dimethylethanolamine, γ-(2-aminoethyl)aminopropyltriethoxysilane, and 2-(2-aminoethylamino)ethanol. An aqueous dispersion of polyester-based polyurethane resin particles containing a silanol group and/or an ethoxysilyl group was obtained by dispersing the particles and distilling off acetone while heating. The solid content concentration was 30% by mass, and the median diameter was 32 nm.

<Production of aqueous dispersion of resin particles (A-2)>
(Manufacturing example 4)
Add ethylene-methacrylic acid copolymer resin (methacrylic acid content is 20% by mass), sodium hydroxide and deionized water equivalent to 5.6% by mass based on the resin into a reaction container, and stir at 95°C for 6 hours. As a result, a water-dispersed resin liquid having a solid content of 20% by mass was obtained. By further adding 0.8% by mass of γ-glycidoxypropyltrimethoxysilane and 0.8% by mass of glycerol polyglycidyl ether to this water-dispersed resin liquid, and reacting at 85°C for 2 hours, An aqueous dispersion of ethylene-methacrylic acid copolymer resin particles having silanol groups and/or methoxysilyl groups was obtained. The solid content concentration was 21% by mass, and the median diameter was 50 nm.

(Manufacturing example 5)
An ethylene-methacrylic acid copolymer resin (methacrylic acid content: 20% by mass), 3.7% by mass of sodium hydroxide, 6.3% by mass of aqueous ammonia, and deionized water were placed in a reaction vessel. In addition, by stirring at 95° C. for 6 hours, a water-dispersed resin liquid with a solid content of 20% by mass was obtained. To this water-dispersed resin liquid, 1.2% by mass of γ-glycidoxypropyltriethoxysilane and 0.6% by mass of pentaerythritol polyglycidyl ether were further added, and the mixture was reacted at 85°C for 2 hours. An aqueous dispersion of ethylene-methacrylic acid copolymer resin particles having silanol groups and/or methoxysilyl groups was obtained. The solid content concentration was 21% by mass, and the median diameter was 100 nm.

(Manufacturing example 6)
Add ethylene-methacrylic acid copolymer resin (methacrylic acid content is 20% by mass), sodium hydroxide equivalent to 4.7% by mass based on the resin, and deionized water to a reaction container, and stir at 95°C for 2 hours. As a result, a water-dispersed resin liquid having a solid content of 20% by mass was obtained. To this water-dispersed resin liquid, further add 1.2% by mass of γ-glycidoxypropyltrimethoxysilane and 1.2% by mass of hydrogenated bisphenol A diglycidyl ether, and react at 85°C for 2 hours. An aqueous dispersion of ethylene-methacrylic acid copolymer resin particles having silanol groups and/or methoxysilyl groups was obtained. The solid content concentration was 21% by mass, and the median diameter was 70 nm.

(Manufacturing example 7)
Add ethylene-methacrylic acid copolymer resin (methacrylic acid content is 20% by mass), aqueous ammonia of 21.0% by mass based on the resin, and deionized water to a reaction container, and stir at 95°C for 2 hours. A water-dispersed resin liquid having a solid content of 20% by mass was obtained. To this water-dispersed resin liquid, further add 1.2% by mass of γ-glycidoxypropyltrimethoxysilane and 1.2% by mass of hydrogenated bisphenol A diglycidyl ether, and react at 85°C for 2 hours. An aqueous dispersion of ethylene-methacrylic acid copolymer resin particles having silanol groups and/or methoxysilyl groups was obtained. The solid content concentration was 21% by mass, and the median diameter was 150 nm.

(Production example 8)
By adding ethylene-methacrylic acid copolymer resin (methacrylic acid content is 27% by mass), ammonia water and deionized water at 28.0% by mass based on the resin into a reaction container, and stirring at 95°C for 2 hours. A water-dispersed resin liquid with a solid content of 20% by mass was obtained. To this water-dispersed resin liquid, further add 1.6% by mass of γ-glycidoxypropyltrimethoxysilane and 1.6% by mass of hydrogenated bisphenol A diglycidyl ether, and react at 85°C for 2 hours. An aqueous dispersion of ethylene-methacrylic acid copolymer resin particles having silanol groups and/or methoxysilyl groups was obtained. The solid content concentration was 21% by mass, and the median diameter was 14 nm.

(Manufacturing example 9)
30 parts by mass of diethanolamine and 110 parts by mass of propylene glycol monomethyl ether acetate were added to 190 parts by mass of bisphenol F epichlorohydrin type epoxy resin with an epoxy equivalent of 190 in a reaction vessel, and the mixture was reacted at 100°C for 2 hours to obtain a modified epoxy resin with a solid content concentration of 70%. I got it. In a reaction vessel, 100 parts by mass of 2,4-toluene diisocyanate prepolymer of trimethylolpropane with 13.3% NCO and 75% nonvolatile content, 44 parts by mass of nonylphenol, 5 parts by mass of dimethylbenzylamine, and 65 parts by mass of propylene glycol monomethyl ether acetate were added. Parts by mass were mixed and reacted for 3 hours at 80° C. under a nitrogen atmosphere to obtain a half-blocked polyisocyanate having a solid content concentration of 70% and an NCO% of 20%. After mixing 70 parts by mass of the modified epoxy resin and 30 parts by mass of the half-blocked polyisocyanate and stirring at 80°C for 4 hours to react, it was confirmed by infrared spectroscopy that the absorption of NCO groups was completely eliminated. . Thereafter, it was diluted with ion-exchanged water to obtain a water-based epoxy resin. The solid content concentration was 25% by mass, and the median diameter was 600 nm.

<Preparation of water-based coating agent for steel materials according to Examples and Comparative Examples>
(Example 1)
80 parts by mass of the aqueous dispersion of the resin particles (A-1) of the above Production Example 1 in terms of solid content, and 20 parts by mass of the aqueous dispersion of the resin particles (A-2) of the above Production Example 4 in terms of the solid content. Using. As the silicon oxide particles (B), those having a particle diameter (mode diameter) of 15 nm were used. Dipropoxybis(triethanolaminato)titanium was used as the organic titanium compound (C). As the wax particles (D), polyethylene particles having a particle diameter (median diameter) of 1.0 μm and a softening point of 115° C. were used. As the silicon oxide particles (E), those having a particle diameter (mode diameter) of 100 nm were used. As the phthalocyanine pigment (F), Cu phthalocyanine (primary particle size 0.26 μm) using a surfactant as a coating agent was used. Phosphate and thiourea were used as the rust preventive agent (G). The content of each component is the amount shown in Table 6 as parts by mass based on the total of 100 parts by mass of resin particles (A-1) and resin particles (A-2). A drug was prepared. Note that the content of the organic titanium compound (C) shown in Table 6 is parts by mass in terms of titanium atoms.

(Examples 2 to 18 and Comparative Examples 1 to 21)
Coating conditioners for steel materials according to Examples 2 to 18 and Comparative Examples 1 to 20 were prepared in the same manner as in Example 1, except that the raw materials shown in Table 6 were used. Moreover, Comparative Example 21 was prepared by aging Comparative Example 12 at 60° C. and adjusting it to a high viscosity. In addition, the types of silicon oxide particles (B), organic titanium compounds (C), silicon oxide particles (E), phthalocyanine pigments (F), and rust inhibitors (G) shown in Table 6 and the symbols shown in Table 6 The correspondence is shown in Tables 1 to 5 below.

The details of the phthalocyanine pigment (F) shown in Table 4 are as follows.
Type K: “SA Blue 5204” manufactured by Mikuni Shiki Co., Ltd.
Type l: “LIOFAST SF670 Blue” manufactured by Toyo Color Co., Ltd.
Type m: “SA Blue 5205” manufactured by Mikuni Shiki Co., Ltd.
Type n: "DP Color 1737 Blue" manufactured by Dainichiseika Kagyo Co., Ltd.
Type o: "DP Color 1534 Blue" manufactured by Dainichiseika Kagyo Co., Ltd.
Type p: “DP-1957 Yellow” manufactured by Dainichiseika Kagyo Co., Ltd.
Type q: “NAF Color NAF1032 Red” manufactured by Dainichiseika Kagyo Co., Ltd.
Type r: Toyocolor Co., Ltd. "LIOFAST BLUE G227"
Type s: “EMF BLUE HG” manufactured by Toyocolor Co., Ltd.
Type t: “PSM Sky Blue FG” manufactured by Mikuni Shiki Co., Ltd.
Type u: “TB Color TB-700 Blue GA” manufactured by Dainichiseika Kagyo Co., Ltd.

<Creation of coated steel plate for evaluation>
Samples for evaluation were prepared by forming coatings on the surfaces of hot-dip galvanized steel sheets and aluminum-containing galvanized steel materials using the water-based steel coating agents of Examples 1 to 18 and Comparative Examples 1 to 21. The water-based coating material for steel was applied using a bar coater to give a dry coating amount of 1 g/m ² , and a test plate was prepared by baking it in a hot air drying oven at an ambient temperature of 500°C to a final plate temperature of 150°C. .

<Evaluation>
Using the test plates according to the Examples and Comparative Examples prepared above, the following conditions were met for alkali resistance, solvent resistance, abrasion resistance, plane corrosion resistance, weather resistance (chroma change amount), glossiness, saturation, and paintability. The evaluation was carried out. The results are shown in Table 7.

(alkali resistance)
After immersing the test plate in a 2% by mass aqueous solution (pH 12.5) of an alkaline degreaser (Surf Cleaner 53, manufactured by Nippon Paint Co., Ltd.) at 55°C for 2 minutes with stirring, the edges and back of the test plate were sealed with tape, and then soaked in salt water. A spray test (JIS-Z-2371) was conducted. The appearance of white rust after 72 hours was observed and evaluated based on the following criteria, and 3 was considered a pass. The results are shown in Table 7.
3: Almost no white rust 2: Less than 30% white rust area 1: 30% or more white rust area

(Solvent resistance)
After setting the test plate on a rubbing tester, rub absorbent cotton impregnated with ethanol, methyl ethyl ketone (MEK) or white gasoline 5 times (back and forth) at a load of 0.5 kgf/ ^cm2 , then rub the edges and back of the test plate. It was sealed with tape and subjected to a salt spray test (JIS-Z-2371). The appearance of white rust after 72 hours was observed and evaluated based on the following criteria, and 3 was considered a pass. The results are shown in Table 7.
3: Almost no white rust 2: Less than 30% white rust area 1: 30% or more white rust area

(Abrasion resistance [slidability])
A load of 10 g/cm ² was applied to the test plate through corrugated paper, and an elliptical motion was applied at a rate of 360 times/min to generate abrasion (abrasion scars) on the sliding portion. After conducting the test for 10 minutes, the state of the test plate surface was observed and evaluated according to the following criteria, and a score of 3 was considered to be a pass. The results are shown in Table 7.
3: Almost no blackening 2: Less than 50% of the area of the sliding part is blackened 1: More than 50% of the area of the sliding part is blackened

(Flat part corrosion resistance)
The edges and back of the test plate were sealed with tape, and a salt spray test SST (JIS-Z-2371) was conducted. The occurrence of white rust was observed after 72 hours for the hot-dip galvanized test piece and after 120 hours for the aluminum-containing galvanized test piece, and evaluated based on the following criteria, and 3 was considered a pass. The results are shown in Table 7.
3: Almost no white rust 2: Less than 30% white rust area 1: 30% or more white rust area

(Weathering resistance [amount of change in saturation])
The test plate was placed in a Sunshine Weather Meter tester, an accelerated weathering test was conducted for 500 hours, and the initial value and the amount of change in saturation after the test were measured. The chroma was calculated as chroma C ^* using the same method as the chroma measurement described below. The amount of change in saturation C ^* was calculated using the following formula (2), and evaluation was performed based on the following criteria, and 3 was considered to be a pass. The testing machine used was a Sunshine Weather Meter manufactured by Suga Test Instruments Co., Ltd. The results are shown in Table 7.
Amount of change (%) = Post-test chroma C ^* / Initial value chroma C ^* × 100 ... (2)
3: Amount of change (%) = 95% to 100%
2: Amount of change (%) = 90% to less than 95% 1: Amount of change (%) = 80% to less than 90%

(Glossiness [Design])
Using a gloss meter (VG2000, manufactured by Nippon Denshoku Industries Co., Ltd.), the 60° glossiness (%) of the test plate surface was measured based on the method specified in JIS Z 8741. Evaluation was performed based on the following criteria, and 2 was considered a pass. The results are shown in Table 7.
2:50-200%
1: less than 50%

(Saturation [Design])
The L ^* a ^* b ^* value on the surface of the test plate was measured using a spectrophotometer (SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.), and the chroma C ^* was calculated using the following formula. Evaluation was performed based on the following criteria, and a score of 3 was considered a pass. The results are shown in Table 7.
3:C ^* =2.0~50
2: C ^* = more than 50, less than 100 1: C ^* = less than 2.0

(Paintability)
A water-based coating agent for steel materials was applied using an automatic bar coater (No. 542-AB manufactured by Yasuda Seiki Seisakusho), and the coating appearance unevenness was evaluated according to the following criteria, and a score of 2 was considered a pass. The results are shown in Table 7.
2: No unevenness 1: There is unevenness

From the results in Table 7 above, it can be seen that the steel sheets coated with the water-based steel coating agents of Examples 1 to 18 have a higher gloss than the steel plates coated with the water-based steel coating agents of Comparative Examples 1 to 21. It was confirmed that both brightness and saturation were excellent, and the design was excellent. In addition, the steel sheets coated with the water-based steel coating materials of Examples 1 to 18 exhibited excellent alkali resistance, solvent resistance, sliding properties, corrosion resistance on flat surfaces, weather resistance, and paintability. Ta.

Claims (10)

Polyurethane resin particles (A-1) and ethylene-unsaturated carboxylic acid copolymer resin particles (A-2) each having a median diameter of 20 to 100 nm and having at least one of a silanol group and an alkoxysilyl group. )and,
silicon oxide particles (B) having a mode diameter of 5 to 20 nm;
an organic titanium compound (C);
A phthalocyanine pigment (F) coated with at least one of a resin and a surfactant;
At least one rust preventive agent (G) selected from the group consisting of phosphoric acid compounds, thiocarbonyl compounds, niobium oxides and guanidine compounds,
The content of the phthalocyanine pigment (F) is 0.0 parts by mass based on the total of 100 parts by mass of the polyurethane resin particles (A-1) and the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2). 01 to 10 parts by mass, and the primary particle size is 0.01 to 1.0 μm. The phthalocyanine in the phthalocyanine pigment (F) is at least one of metal phthalocyanine and metal-free phthalocyanine,
The steel material according to claim 1, wherein the metal of the metal phthalocyanine is any one of Ca, Ba, Cd, Na, Cu, Ni, Co, Fe, Mg, Zn, Al, Mn, V, Ti, and Sn. Water-based coating. The aqueous coating agent for steel materials according to claim 1 or 2, having a 20°C viscosity of 100 mPa·s or less. The mass ratio of the polyurethane resin particles (A-1) and the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2) is (A-1):(A-2)=20:80 to 90. :10. The aqueous coating agent for steel materials according to any one of claims 1 to 3. The aqueous coating agent for steel materials according to any one of claims 1 to 4, further comprising silicon oxide particles (E) having a mode diameter of 70 to 200 nm. The content of the rust preventive agent (G) is based on a total of 100 parts by mass of the polyurethane resin particles (A-1) and the ethylene-unsaturated carboxylic acid copolymer resin particles (A-2), respectively. ,
The phosphoric acid compound is 0.01 to 5 parts by mass in terms of phosphate radical,
The thiocarbonyl compound is 0.1 to 10 parts by mass,
The niobium oxide is Nb ₂ O ₅ It is 0.1 to 5 parts by mass in terms of
The aqueous coating agent for steel materials according to any one of claims 1 to 5, wherein the guanidine compound is 0.1 to 5 parts by mass. A coating formed from the aqueous coating agent for steel materials according to any one of claims 1 to 6 , and having a chroma C ^* of 2.0 or more and 50 or less. A method for coating steel materials, comprising applying the water-based coating agent for steel materials according to any one of claims 1 to 6 onto the surface of the steel materials to form a film. A steel material having a 60° glossiness of 50% or more, the surface of which is coated with the aqueous coating agent for steel material according to any one of claims 1 to 6 . The steel material according to claim 9 , wherein the steel material is either hot-dip galvanized steel or aluminum-containing galvanized steel.