JPH07252433A - Aqueous coating composition for surface treatment of steel plate - Google Patents

Abstract

PURPOSE:To obtain an aqueous coating composition for metal surface treatment useful for surface protection of a steel plate and improvement in corrosion resistance of the steel plate. CONSTITUTION:This aqueous coating composition consists of (D) an aqueous resin dispersant obtained by dispersing a resin obtained by copolymerizing (A) an epoxy resin acrylate, an epoxy resin methacrylate or its mixture with (B) an alpha, beta-unsaturated carboxylic acid and (C) at least one kind of polymerizable monomer selected from the group consisting of an acrylic acid ester, a methacrylic acid ester and a vinyl group-containing monomer into an alkaline aqueous solution and (E) a sol obtained by dispersing silica particles having >=100m<2>/g specific surface area into water or this aqueous coating composition consists of the component D, (F) an aqueous resin dispersant obtained by dispersing a carboxylated polyolefin resin into water and the sol (E).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is a water-based paint for metal surface treatment, which is useful for surface protection and improvement of corrosion resistance of phosphate-treated or chromate-treated steel sheets, galvanized steel sheets, galvannealed steel sheets and the like. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, a resin coating film is applied to the inner surface of a metal can made of aluminum or tin-plated steel plate. In addition, for household electric appliances, steel sheets used for automobile bodies, galvanized steel sheets, alloyed galvanized steel sheets, etc.,
For the purpose of improving corrosion resistance, protecting the surface, etc., rust-preventing oil coating treatment is carried out.
A resin thin film having a thickness of about 5 to 10 μm is provided to improve not only corrosion resistance but also more functions.

Many of the conventional paints for metal surface treatment are organic solvent solution type paints such as epoxy resin, and when the paints are applied, the organic solvent is volatilized in the working atmosphere, so that it is safe for the human body of the worker. Due to the problems of hygiene and the danger of fire, explosion, toxicity, air pollution, etc., in recent years, water-based paints that do not have these problems have been used. These water-based paints include not only conventionally used acrylic aqueous resin dispersions, vinyl acetate aqueous resin dispersions, low molecular weight epoxy resin aqueous dispersions, but also epoxy ester resins, alkyd / acrylic resins, and modified olefins. Aqueous resin dispersions such as resins, polyurethane resins and polyester resins have come to be used.

Examples of such an aqueous resin dispersion include a water-dispersible acrylic resin described in Japanese Patent Publication No. 54-34406, a coating comprising silane and fine particle silica, and a carboxylated polyethylene described in Japanese Patent Publication No. 61-36587. A coating comprising an aqueous resin dispersion of the above and fine particle silica, an epoxy resin is reacted with a copolymer of a monoethylenically unsaturated aliphatic carboxylic acid monomer described in Japanese Patent Publication No. 63-41934 and other monomers. A coating comprising an aqueous resin dispersion obtained by neutralizing the resin thus obtained with a base, JP-A-52-81344, JP-A-52-1
No. 14625 and JP-A No. 54-30249, after copolymerizing a polymerizable unsaturated carboxylic acid or the like in the presence of an epoxy alkyd resin or epoxy ester resin having a polymerizable unsaturated bond, and then neutralizing with an amine or the like. A coating consisting of an aqueous resin dispersion obtained by the addition, described in JP-A 1-110517, of an aqueous dispersion of an acrylated epoxy resin having an aqueous dispersion of a carboxyl group-containing polymer and a copolymerizable unsaturated bond. A paint comprising an aqueous resin dispersion obtained by polymerizing an acrylic ester, a vinyl monomer and the like in a mixture is disclosed.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Corrosion resistance on a flat plate of a coated steel sheet on which a resin thin film is formed, corrosion resistance of a coated steel sheet after press working, drawing, bending, etc. Improvement in corrosion resistance and the like after forming an electrodeposition coating film is required. Further, recently, as described in “Materials and Processes”, Vol. 5, p. 1693 (1992), when an iron-based member is present near a coated steel sheet, it is accompanied by the occurrence of iron rust from the iron-based member. It was pointed out that the corrosion resistance on the side of the coated steel sheet is extremely reduced. The reason for this is not necessarily clear, but it is considered that one reason is that the life of the coating film is shortened due to the increase in pH of corrosive agents such as salt water that accompanies the occurrence of iron rust. Further, particularly in the automobile field, etc., the resin thin film swells in the degreasing step with an alkaline solution performed to remove the coating oil applied for rust prevention and pressing on the surface of the coated steel sheet on which the resin thin film is formed. However, the resin thin film may be destroyed when the steel sheets are in contact with each other, and improvement thereof is also required. In addition to this, the sophistication of required performance related to substrate adhesion, required physical properties after electrodeposition coating, etc. has many problems that cannot be solved by conventional water-based resins. Therefore, various water-based paints have been proposed.

The paint described in Japanese Examined Patent Publication No. 54-34406 has the adhesion to the coating film, the impact resistance in a low temperature environment, the coated surface when the electrodeposition paint is applied on the coating film of the paint. The adhesiveness between the adhesive and the adhesive is not sufficient. In the paint described in JP-B-61-36587, the adhesion between the coating film of this paint and the electrodeposition paint applied thereon, the corrosion resistance after electrodeposition coating, etc. are not sufficient.

Further, Japanese Patent Publication No. 63-41934 and Japanese Patent Laid-Open No. 52-8
1344, JP-A-52-114625, JP-A-54-30249,
And in the paint described in JP-A 1-110517, the water resistance of the coating film, the alkali resistance is insufficient, further, since it does not contain fine particle silica, if there is an iron-based member in the vicinity of the coated steel sheet However, the corrosion resistance under the environment where iron rust is generated from the iron-based member is not sufficient, the coating film durability is not sufficient in the degreasing step with an alkaline solution, and the weldability of the coated steel sheet is also insufficient.

The present invention provides a metal surface of a steel sheet, a galvanized steel sheet, an alloyed galvanized steel sheet or the like, particularly a metal surface of a steel sheet or the like which has been subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment. A coated steel sheet with a film of about 10μ has high corrosion resistance, high alkali resistance, and high adhesion with adhesives and electrodeposition paints. Furthermore, this coated steel sheet is bent or electrocoated. It is intended to provide a water-based coating composition for metal surface treatment, which is excellent in corrosion resistance even when applied. In particular, when an iron-based member exists near the coated steel sheet, the corrosion resistance, surface protection, and chemical resistance in an environment accompanied by iron rust generation from the iron-based member are improved.

[0009]

According to the first aspect of the present invention, 30 to 90 parts by weight of an epoxy resin acrylate, an epoxy resin methacrylate or a mixture thereof (A) is used.
3 to 20 parts by weight of α, β-unsaturated carboxylic acid (B), and one or more kinds of polymerizable monomers selected from the group consisting of acrylic acid ester, methacrylic acid ester and vinyl group-containing monomer A resin obtained by copolymerizing 7 to 67 parts by weight of the body (C) is dispersed in an aqueous alkaline solution (D), and silica particles having a specific surface area of 100 m ² / g or more are dispersed in water. Made of sol (E), and
10 to 10 of the sol (E) as SiO ₂ with respect to 100 parts by weight of the solid content of the resin of the aqueous resin dispersion (D).
Metal surface treatment in which the content of the resin is 0 part by weight, and the solid content of the resin of the aqueous resin dispersion (D) and the SiO ₂ content of the sol (E) are 5 to 50% by weight in total. A water-based coating composition for use.

Furthermore, the second invention is that epoxy resin acrylate, epoxy resin methacrylate or a mixture thereof (A) 40 to 90 parts by weight, α, β-unsaturated carboxylic acid (B) 3 to 20 parts by weight, and acrylic acid. 1 to 2 or more polymerizable monomers (C) selected from the group consisting of ester, methacrylic acid ester and vinyl group-containing monomer 7 to
A resin obtained by copolymerizing 57 parts by weight of the resin is dispersed in an aqueous alkaline solution (D), an aqueous resin dispersion (F) in which a carboxylated polyolefin resin is dispersed in water, and 100 m ² / g. Silica particles having the above specific surface area are composed of a sol (E) dispersed in water, and b. 1 to 9 parts by weight of the solid content of the resin of the aqueous resin dispersion (D) with respect to 1 part by weight of the solid content of the resin of the aqueous resin dispersion (F); The sol (E) was added to SiO 2 with respect to 100 parts by weight of the total solid content of the resins of the aqueous resin dispersions (D) and (F).
₂ to 10 to 100 parts by weight, and the total solid content of the resins of the aqueous resin dispersions (D) and (F) and the SiO ₂ content of the sol (E) is 5 to 50% by weight.
It is an aqueous coating composition for metal surface treatment which is contained in a concentration.

The epoxy resin acrylate, the epoxy resin methacrylate or the mixture (A) thereof used in the present invention is obtained by reacting a bisphenol type epoxy resin having a molecular weight of 1000 to 9000 with acrylic acid, methacrylic acid or a mixture thereof. The resulting ester is preferred. The bisphenol type epoxy resin preferably has a molecular weight in the range of 1,000 to 9000, and particularly preferably 200.
The range of 0-8000 is good. Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin,
There is a bisphenol F type epoxy resin. They are resins obtained by reacting bisphenol A or bisphenol F with epichlorohydrin, and have at least one glycidyl group (epoxy ring) in the molecule, and particularly have a glycidyl group (epoxy ring) at the end of the molecular chain. Resins are preferred. For example, Yuka Shell Epoxy Co., Ltd.
Product name Epicoat 1055 (bisphenol A type epoxy resin: epoxy equivalent 800 to 900 g / eq, molecular weight is about 1350), Epicoat 1004 (bisphenol A type epoxy resin: epoxy equivalent 875 to 975 g / eq,
Molecular weight is about 1600), Epicoat 1007 (bisphenol A type epoxy resin: epoxy equivalent 1750-22
00g / eq, molecular weight is about 2900), Epikote 1009
(Bisphenol A type epoxy resin: Epoxy equivalent 24
00-3300 g / eq, molecular weight about 3750), Epicoat 1010 (bisphenol A type epoxy resin: epoxy equivalent 3000-5000 g / eq, molecular weight about 5500)
Etc. These bisphenol type epoxy resins can be used alone or in combination.

In the esterification reaction of the above-mentioned bisphenol type epoxy resin with acrylic acid, methacrylic acid or a mixture thereof, a carboxyl group derived from acrylic acid, methacrylic acid or a mixture thereof is added to the epoxy group in the bisphenol type epoxy resin. Undergoes an addition reaction to produce (A), which is an epoxy resin ester containing an acryloyloxy group [CH ₂ ═CHCOO-] or a methacryloyloxy group [CH ₂ ═C (CH ₃ ) COO-]. . The component (A) has at least one polymerizable unsaturated bond due to an acryloyloxy group or a methacryloyloxy group in the molecule. In particular, the epoxy group at one end of the bisphenol epoxy resin is a carboxyl group. An epoxy resin ester (A) which is esterified by the reaction with and has only one polymerizable unsaturated bond in the molecule by an acryloyloxy group or a methacryloyloxy group is preferable. In the component (A), the ratio of the resin having two or more polymerizable unsaturated bonds in the molecule is preferably 20 mol% or less. In order to produce such a component (A), a carboxyl group derived from acrylic acid, methacrylic acid or a mixture thereof is 0.8 to 1 equivalent of the epoxy group in the bisphenol type epoxy resin.
It is preferable to add 3 equivalents, preferably 1 to 2 equivalents. Then, as a result of excessive addition, unreacted acrylic acid or methacrylic acid can be distilled off by reprecipitation, drying or the like.

The above bisphenol type epoxy resin,
As the solvent used for the reaction with acrylic acid, methacrylic acid or a mixture thereof, any organic solvent can be used as long as it does not significantly inhibit the addition reaction of the epoxy group and the carboxyl group, but particularly methyl is used. Ketone solvents such as isobutyl ketone, ester solvents such as butyl acetate, ether solvents such as dioxane, alcohol solvents such as butanol, cellosolve solvents such as butyl cellosolve, carbitol solvents such as butyl carbitol, toluene, xylene. Aromatic hydrocarbon solvents such as
Amide solvents such as dimethylformamide and dimethylacetamide, sulfoxide solvents such as dimethylsulfoxide, and pyrrolidone solvents such as N-methylpyrrolidone are preferable. However, in an acidic atmosphere, water, lower alcohols such as ethanol and propanol, and lower cellosolves such as methyl cellosolve and ethyl cellosolve undergo an addition reaction to the epoxy group, and the addition reaction of these solvents is a side reaction. , Not preferable. Therefore, water, carbon number 4
The lower alcohol content, the lower cellosolve having less than 6 carbon atoms, and the lower carbitol having less than 8 carbon atoms are preferably 5% by weight or less in all the solvents. Furthermore, organic solvents containing primary amino groups and secondary amino groups are excluded because they significantly inhibit the addition reaction between the epoxy group and the carboxyl group. When this reaction is carried out under atmospheric pressure, the reaction temperature may be 60 to 200 ° C, preferably 80 to 150 ° C. When using a low boiling point solvent, use an autoclave or the like, and 2 to 100 kg /
The reaction can be carried out at a pressure of cm ² and a temperature of 100 to 200 ° C., preferably 110 to 150 ° C. The reaction time can be 30 minutes to 20 hours, but in the reaction for a longer time, when an epoxy resin having epoxy groups at both ends is used as a raw material, the epoxy groups at both ends are esterified. It is not preferable because the produced epoxy resin ester (A) is produced. The most preferred reaction time under the above temperature conditions is 1 to 10 hours.

A catalyst may be added to the reaction of the bisphenol type epoxy resin with acrylic acid, methacrylic acid or a mixture thereof. Examples of the catalyst include tertiary amine compounds such as N, N-dimethylbenzylamine, quaternary ammonium salt compounds such as tetraethylammonium bromide, tertiary phosphine compounds such as triphenylphosphine, and triphenylmonobenzylphosphonate. Quaternary phosphonium salt system such as niobium bromide, 2
Examples include imidazole-based compounds such as -ethyl-4-methylimidazole. The catalyst can be used in a ratio of 1 part by weight or less based on 100 parts by weight of the total weight of the bisphenol type epoxy resin and acrylic acid, methacrylic acid or a mixture thereof.

Examples of the α, β-unsaturated carboxylic acid (B) used in the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid and maleic anhydride, which may be used alone or in combination of two or more. Can be used as a mixture. In particular, it is preferably one or more selected from the group consisting of acrylic acid, methacrylic acid and maleic acid.

Acrylic acid ester used in the present invention,
One or more polymerizable monomers (C) selected from the group consisting of methacrylic acid esters and vinyl group-containing monomers
In the above, examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate. However, among them, n-butyl acrylate and 2-ethylhexyl acrylate are preferable. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate,
Examples thereof include glycidyl methacrylate and 2-hydroxyethyl methacrylate, but among them, methyl methacrylate,
Glycidyl methacrylate and 2-hydroxyethyl methacrylate are preferred. The vinyl group-containing monomer includes, for example, vinyl acetate, styrene, vinyl chloride, ethylene, propylene, isoprene, butadiene, acrylonitrile and vinyl pyridine, and among them, styrene, vinyl acetate and acrylonitrile are preferable.

Any of α, β-unsaturated carboxylic acids, acrylic acid esters, methacrylic acid esters and vinyl group-containing monomers other than those described above can be copolymerized with epoxy resin acrylate, epoxy resin methacrylate or a mixture thereof. Can be used if present. Further, as a crosslinking agent, an epoxy crosslinking agent, a blocked isocyanate crosslinking agent, or an aziridine crosslinking agent can be added.

The above-mentioned epoxy resin acrylate, epoxy resin methacrylate or a mixture thereof (A), α, β
In the composition of the first invention of the present application, the mixing ratio at the time of copolymerizing the unsaturated carboxylic acid (B) and the polymerizable monomer (C) is
Epoxy resin acrylate, epoxy resin methacrylate or a mixture (A) thereof is 30 to 90 parts by weight, preferably 40 to 80 parts by weight, and α, β-unsaturated carboxylic acid (B) is 3 to 20 parts by weight, preferably Is 5 to 15 parts by weight, and the polymerizable monomer (C) is 7 to 67 parts by weight, preferably 15 to 45 parts by weight. On the other hand, in the composition of the second invention of the present application, the epoxy resin acrylate, the epoxy resin methacrylate or a mixture thereof (A) is 40 to 90.
Parts by weight, preferably 40 to 80 parts by weight, α, β-
The unsaturated carboxylic acid (B) is 3 to 20 parts by weight, preferably 5 to 15 parts by weight, and the polymerizable monomer (C) is 7 to 57 parts by weight.
Parts by weight, preferably 15 to 45 parts by weight.

In the present invention, the copolymerization reaction of the epoxy resin acrylate, the epoxy resin methacrylate or the mixture thereof (A), the α, β-unsaturated carboxylic acid (B) and the polymerizable monomer (C) is an ionic polymerization. Radical polymerization, thermal polymerization, and photopolymerization using a photosensitive initiator can be used, but radical polymerization is preferable. Radical polymerization initiators used in the radical copolymerization reaction include, for example, azo-based initiators such as azobisisobutyronitrile, azobispropionitrile and azobisvaleronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydro. Organic peroxide-based initiators such as peroxides, or redox-based initiators obtained by combining the above organic peroxides with reducing agents such as naphthenates, ferrous salts, thiosulfates, and aromatic tertiary amines. An initiator is mentioned. In particular,
The above-mentioned azo-based initiators that are less likely to cause side reactions such as hydrogen abstraction reaction are preferred. The reaction temperature is 0 ° C to room temperature when the redox initiator is used, and 150 to 200 ° C when cumene hydroperoxide is used as the initiator. It is necessary to select the temperature requirement by selecting the polymerization initiator from When using azobisisobutyronitrile, 50 to 90 ° C
It is possible to carry out a copolymerization reaction with.

In the above radical copolymerization reaction, if necessary, a small amount of a chain transfer agent such as thiols such as dodecyl mercaptan and thioglycolic acid and halogenated hydrocarbons such as trichlorethylene can be used in combination. For the copolymerization reaction, polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization can be used, but solution polymerization is particularly preferable. As the organic solvent used for solution polymerization,
If the radical copolymerization reaction is not significantly hindered,
Any organic solvent can be used. Examples of the organic solvent include ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as tetrahydrofuran and dioxane, methyl cellosolve, cellosolve solvents such as ethyl cellosolve, and methyl carbi. Carbitol solvents such as Tol and ethylcarbitol, aromatic hydrocarbon solvents such as toluene and xylene, amide solvents such as dimethylformamide and dimethylacetamide, sulfoxide solvents such as dimethylsulfoxide, and pyrrolidone such as N-methylpyrrolidone. A system solvent or the like can be used. However, an amine solvent or a solvent containing a phenolic hydroxyl group is not preferable because it hinders the above copolymerization reaction.

The resin obtained by the above copolymerization reaction is
Weight average molecular weight of 2,000 to 300,000, preferably 5,000 to 100,000, more preferably 5,000.
Is in the range of up to 70,000. The resin obtained by this copolymerization reaction may be at room temperature to 100 by using an ordinary stirrer, mixer or the like, whether in a solid state obtained by removing the solvent and drying or in a state of being dissolved in an organic solvent. ℃
The aqueous resin dispersion (D) can be obtained by easily dispersing in an alkaline aqueous solution within the temperature range of. As the alkaline aqueous solution, an aqueous sodium hydroxide solution,
Examples thereof include an aqueous solution of an alkali metal hydroxide such as an aqueous solution of potassium hydroxide, an aqueous solution of ammonia, an aqueous solution of triethanolamine, and an aqueous solution of an organic amine such as an aqueous solution of tetramethylammonium hydroxide. These alkaline substances include α of the component (B), 0.5 to 10 equivalents, preferably 1 to 1 equivalent of the carboxyl group of the β-unsaturated carboxylic acid
It can be added at a ratio of about 5 equivalents to obtain an aqueous resin dispersion (D) in which the resin obtained by the above copolymerization is dispersed in an alkaline aqueous solution. Further, if necessary, a surfactant, a dispersant or the like can be used in combination. The aqueous resin dispersion (D) obtained by the above method has an alkaline p
It preferably has H, and particularly preferably has a pH of 8 to 12, and contains a resin solid content at a concentration of 70% by weight or less.

Silica aqueous sol (E) used in the present invention
Is easily obtained by a known method and obtained as a commercial product.
You can do it. The silica particles of the aqueous sol (E) are
At least 100m²It has a specific surface area of / g. This ratio
Surface area is measured by BET method (nitrogen gas adsorption method)
It The shape of the silica particles of the above aqueous sol (E) is spherical particles.
Children, particles with elongated structure, fine particles agglomerated
Examples include particles having a structure and particles having a porous structure.
It Specific surface area S (m ²/
g) to R₂= (2720 / S), a virtual spherical shape
Silica particle size R₂(Nm) can be calculated.

In the case of spherical silica particles, the particle diameter R ₂ measured by the BET method, the particle diameter determined by electron microscope observation, the particle diameter determined by the centrifugal sedimentation method, or US Cou
The particle diameters obtained by the dynamic scattering method using an N ₄ apparatus manufactured by Lter Co. are equal. The spherical silica particles used in the present invention,
The specific surface area S is 100 m ² / g or more, and the particle diameter thereof is preferably 27.2 nm or less. In particular, the specific surface area S is 110 to 500 m ² / g, and the particle diameter is
More preferably, it is 5.4 to 24 nm.

In the silica particles having an elongated structure, B
Particle size R measured by ET method ₂And the view of the electron microscope
Particle size obtained by observation, particle size obtained by centrifugal sedimentation method,
Alternatively, the difference between the particle size obtained by the dynamic scattering method and the value is large.
Yes. For example, the particle diameter R obtained by the dynamic scattering method₁(N
m) and the particle diameter R measured by the BET method₂(N
R with m)₁/ R₂The ratio is 3 or more. R in this case₁
/ R₂The ratio means the degree of elongation of silica particles. For the present invention
The silica particles that have an extended structure are
S is 100m²/ G or more, the above R₁/ R₂Ratio is 3
The above is the uniformity of 5 to 40 nm observed by an electron microscope.
Amorphous Amorphous with Uniform Thickness and Elongation Only in One Plane
Colloidal silica particles are preferred, especially the specific surface area S
Is 110-500m²/ G, R above₁/ R₂Ratio is 4 or more
Is more preferable.

The silica particles having a structure in which fine particles are aggregated have a particle diameter R ₂ measured by the BET method, a particle diameter determined by an electron microscope observation, a particle diameter determined by the centrifugal sedimentation method, or a dynamic scattering method. There is a large difference in the value with the particle size obtained by. For example, the particle diameter R ₁ (nm) obtained by the dynamic scattering method and the particle diameter R ₁ measured by the BET method
The R ₁ / R ₂ ratio with ₂ (nm) is 10 or more. The R ₁ / R ₂ ratio in this case means the degree of aggregation of the fine silica particles. The above-mentioned silica particles used in the present invention, as a result of electron microscope observation, are found to be silica particles having a structure in which fine silica particles are aggregated, and this particle has a high adsorption capacity for alkali metal ions and the like, and is porous. It is also a silica particle having a structure. The silica particles having a structure in which the fine particles are aggregated have a specific surface area S of 100 m ² / g or more,
The R ₁ / R ₂ ratio is preferably 10 or more, and in particular, the specific surface area S is 110 to 500 m ² / g and the R ₁ / R ₂ ratio is 1
It is more preferably 3 or more.

In particular, the silica particles of the aqueous sol (E) are preferably silica particles having a stretched structure, silica particles having a structure in which fine particles are aggregated, or a mixture thereof. The sol (E) in which the silica particles having the above particle structure are dispersed in water has a SiO ₂ concentration of 5 to 5.
It is preferably 50% by weight and stable.

The aqueous resin dispersion (F) obtained by dispersing the carboxylated polyolefin resin used in the present invention in water is
It is a dispersion of a carboxylated modified polyolefin resin in water. The carboxylated polyolefin resin is obtained by copolymerizing a carboxylic group-containing polymerizable monomer and an olefin. Examples of the polymerizable monomer containing a carboxyl group include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like, but acrylic acid, methacrylic acid, maleic acid are preferable, and among them,
Acrylic acid is most preferred. Examples of the olefin include ethylene, propylene and butene, but ethylene and propylene are preferable, and ethylene is most preferable. Examples of this copolymer include an irregular (random) copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. The weight average molecular weight of these copolymers is 5
000-200000, preferably 10,000-900
It is in the range of 00. These copolymers include, for example, a copolymer of ethylene and acrylic acid, a copolymer of propylene and maleic acid, a copolymer of propylene and methacrylic acid, a copolymer of ethylene and methacrylic acid, and particularly ethylene. And a copolymer of acrylic acid are preferred. In the carboxylated polyolefin resin, as the content of the carboxyl group increases, the hydrophilicity increases, and dispersion in water becomes easier, but as the content of the carboxyl group, the resin is dispersed in water, It is preferable to contain an amount that enables dissolution. Taking a copolymer of ethylene and acrylic acid as an example, a copolymer having an acrylic acid content of usually 2 to 30% by weight is available, and particularly 10 to 30% by weight.
Are preferred for the present invention. Incidentally, in order to disperse and dissolve in water, such a carboxyl group [-COOH] is usually used.
Can also be used in the form of a carboxylic acid salt [-COOM, where M is an alkali metal, ammonium, quaternary ammonium, amine]. Any carboxylic acid salt may be used as long as it can be dispersed and dissolved in water, but ammonium salts, sodium salts and potassium salts are particularly preferable. The ratio of the carboxyl group [-COOH] to the functional group [-COOM] in the form of the carboxylate salt may be any ratio, but the ratio of the carboxyl group [-COOH] to the carboxyl group Functional group in the form of acid salt [-C
OOM] is desirably 10 to 100 mol%, and 50 to 1
00 mol% is more desirable. The aqueous resin dispersion (F) has a solid content of the resin of 5 to 50% by weight,
Preferably, it is contained in a concentration of 10 to 40% by weight.

The mixing ratio of the aqueous resin dispersion (D) and the aqueous resin dispersion (F) is 1 part by weight of the resin solid content of the aqueous resin dispersion (F), and the aqueous resin dispersion ( The solid content of the resin D) is 1 to 9 parts by weight, preferably,
It is preferable to use it in a ratio of 1.5 to 6.0 parts by weight. In the composition of the first invention of the present application, the aqueous sol (E) is mixed with S based on 100 parts by weight of the resin solid content of the aqueous resin dispersion (D).
10 to 100 parts by weight, preferably 15 to 7 as iO _2.
Used at 0 parts by weight. Furthermore, in the composition of the second invention of the present application, the aqueous sol (for the total solid content of 100 parts by weight of the resin solid content of the aqueous resin dispersion (D) and the resin solid content of the aqueous resin dispersion (F) is 100 parts by weight). E) as SiO ₂ and 10 to 10
It is recommended to use 0 parts by weight, preferably 15 to 70 parts by weight.

The aqueous coating composition for metal surface treatment of the present invention comprises the total resin solid content of the aqueous resin dispersion (D) and the SiO ₂ content of the aqueous sol (E), or the aqueous resin dispersion (D). And resin solids of (F) and Si of the sol (E)
The total amount of O ₂ is 70% by weight or less, preferably 5
To 50 wt% concentration, more preferably 10 to 40 wt% concentration. Further, the water-based coating composition of the present invention has
It has a low viscosity of about 100 cps and is stable at room temperature for 6 months or more. Also, by using a thickener, 100
The viscosity can be adjusted up to 000 cps. As the thickener, polyacrylic acid type, polymethacrylic acid type, polyacrylic acid copolymer system, polymethacrylic acid copolymer system,
A cellulose-based or polyvinyl alcohol-based thickener can be used. Furthermore, a small amount of an antifoaming agent can be added as an optional component. For example, a silicone-based, amide-based, or ester-based defoaming agent can be used.

The water-based coating composition for metal surface treatment of the present invention comprises a roll coater coating method, a gravure coater coating method,
It can be applied to steel materials by spray coating or brush coating. Drying and curing are different depending on the apparatus, but it is preferable to carry out under the condition that the final temperature of the steel sheet reaches 60 to 200 ° C, which is 80 to 800 ° C as the temperature inside the furnace when a normal furnace is used. Is the temperature of. The time required for drying and curing is, for example, about 200 to 600 seconds when the temperature inside the furnace is 80 ° C, and about 3 to 10 seconds when the temperature inside the furnace is 800 ° C. 60-200
It is preferable to carry out under the line speed condition of becoming ° C. The water-based coating composition for metal surface treatment of the present invention applied on a metal substrate is treated with the above-mentioned drying and curing conditions so that
A film can be obtained with an arbitrary film thickness of 5 to 10 μm.

[0031]

In the present invention, when the component (A) uses an epoxy resin instead of the epoxy resin acrylate, the epoxy resin methacrylate, or a mixture thereof, the epoxy resin does not have an unsaturated bond, ,
The resin obtained when copolymerized with the component (C) is (B)
And (C) is a copolymer, and a homogeneous resin intended by the present invention cannot be obtained. Further, an aqueous resin dispersion prepared by dispersing the resin in an alkaline aqueous solution is a silica aqueous sol as a rust preventive agent. However, if such a water-based paint is used for a coated steel sheet, sufficient corrosion resistance cannot be obtained. When the component (A) is a resin obtained by reacting a bisphenol type epoxy resin with an unsaturated fatty acid such as linoleic acid, linolenic acid or oleic acid, an acrylyloxy group [CH ₂ = CH
COO-] or methacryloyloxy group [CH ₂ = C
Since (CH ₃ ) COO-] does not exist, good copolymerization with the components (B) and (C) cannot be carried out, and again there is a problem with the same compounding stability with the silica aqueous sol as described above. Or a coated steel sheet does not have sufficient corrosion resistance.

In the present invention, when a bisphenol type epoxy resin is reacted with acrylic acid, methacrylic acid or a mixture thereof to obtain an epoxy resin acrylate, an epoxy resin methacrylate or a mixture thereof (A),
The molecular weight of the above bisphenol type epoxy resin is 1000
When the ratio is less than the above, the ratio of the resin having both ends esterified (that is, the resin having an unsaturated bond at both ends) in the resulting epoxy resin ester (A) increases,
In the step of copolymerizing the component (B) and the component (C), crosslinking easily occurs, and the obtained copolymer resin is dispersed in an alkaline aqueous solution to form an aqueous resin dispersion (D). Absent. Further, when the molecular weight of the bisphenol type epoxy resin exceeds 9000, the ratio of unsaturated bonds contained in the obtained epoxy resin ester (A) becomes small, and the step of copolymerizing the (B) component and the (C) component However, the amount of unreacted epoxy resin ester (A) increases, which is not preferable.

When the above bisphenol type epoxy resin is reacted with acrylic acid, methacrylic acid or a mixture thereof, it is derived from acrylic acid, methacrylic acid or a mixture thereof with respect to 1 equivalent of epoxy group in the bisphenol type epoxy resin. When the charged amount of the carboxyl group is less than 0.5 equivalent, the ratio of unreacted epoxy groups increases, which is not preferable. Moreover, even if the carboxyl group is used in 3 equivalents or more,
No further effect can be expected.

In the composition of the present invention, maleic acid in the component (B) is a dibasic acid, but it was confirmed that it has the same action and effect as those of the monobasic acids acrylic acid and methacrylic acid. It was also found that the addition amount of these dibasic acids and monobasic acids had an effect in the same amount addition range.
In the ratio of the above-mentioned epoxy resin acrylate, epoxy resin methacrylate or a mixture thereof (A), α, β-unsaturated carboxylic acid (B) and polymerizable monomer (C),
When the ratio of the component (A) is less than 30 parts by weight in the first invention composition and less than 40 parts by weight in the second invention composition,
The coating film obtained from the coating composition lacks adhesion, corrosion resistance, adhesion with electrodeposition coating, etc., and conversely, when the proportion of component (A) exceeds 90 parts by weight, it becomes a coated steel sheet. Corrosion resistance after bending is reduced. When the ratio of the component (B) is less than 3 parts by weight, when the resin obtained in the subsequent copolymerization step is dispersed in an alkaline aqueous solution to form the aqueous resin dispersion (D) component, it can be sufficiently dispersed. No, on the contrary, (B)
When the proportion of the components exceeds 20 parts by weight, the resulting component (D) has an extremely high viscosity, and the carboxylated polyolefin resin is dispersed in water to prepare an aqueous resin dispersion (F) and a silica aqueous sol (E). When mixed with, gelation occurs. Further, if the ratio of the component (C) is less than 7 parts by weight, the corrosion resistance after bending the coated steel sheet decreases,
On the contrary, when the ratio of the component (C) exceeds 67 parts by weight in the first invention composition or exceeds 57 parts by weight in the second invention composition, the corrosion resistance of the coated steel sheet, the adhesive, and the electrodeposition coating composition The adhesiveness with

When the resin obtained by copolymerizing the above components (A), (B) and (C) is dispersed in an alkaline aqueous solution to obtain an aqueous resin dispersion (D), calcium hydroxide or the like is used. An aqueous solution of a polyvalent metal hydroxide is not preferable because it causes the resin to gel. The mixing ratio of the aqueous resin dispersion (D) and the aqueous resin dispersion (F) is such that the aqueous resin dispersion (D) is added to 1 part by weight of the resin solid content of the aqueous resin dispersion (F). If the solid content of the resin is less than 1 part by weight, the adhesion and adhesiveness with the electrodeposition coating composition will be reduced, and if it exceeds 9 parts by weight, the alkali resistance will be reduced, resulting in alkalinity. Sufficient coating strength cannot be obtained in solution.

Silica aqueous sol (E) used in the present invention
When the specific surface area of the silica particles is less than 100 m ² / g, the coating film obtained from the coating composition does not have sufficient corrosion resistance. Also, an aqueous resin dispersion (D)
100 parts by weight of the resin solid content or 100 parts by weight of the total solid content of the resins of the aqueous resin dispersions (D) and (F), silica particles having a specific surface area of 100 m ² / g or more are dispersed in water. When the amount of the sol (E) as SiO ₂ is less than 10 parts by weight, the coating film obtained from the coating composition does not have sufficient corrosion resistance. On the other hand, if it exceeds 100 parts by weight, the flexibility of the coating film is insufficient and the corrosion resistance after bending the coated steel sheet is deteriorated.

The aqueous coating composition for metal surface treatment of the present invention comprises the resin solid content of the aqueous resin dispersion (D) and the SiO ₂ content of the aqueous sol (E), or the aqueous resin dispersion (D).
If the total of the resin solid content of (F) and the SiO ₂ content of the sol (E) exceeds 50% by weight, 0.5 to 1
It is difficult to obtain a film thickness of about 0 μ, and when the concentration is less than 5% by weight, it takes a long time to dry and cure, and there is no sufficient corrosion resistance and adhesion with an adhesive or electrodeposition coating. Sufficient corrosion resistance cannot be obtained even when this coated steel sheet is bent or electrodeposited.

[0038]

【Example】

Example 1 As shown below, epoxy resin esters (A1) to (A
4), aqueous resin dispersions (D1) to (D6), and an aqueous resin dispersion (F1) in which a carboxylated polyolefin resin was dispersed in water were produced. Further, silica aqueous sol (E1)
(E3) and an aqueous dispersion (G1) of a crosslinking agent were prepared.

Production of Epoxy Resin Acrylate (A1) In a four-necked flask equipped with a stirrer, thermometer and cooling tube,
Bisphenol A type epoxy resin having a molecular weight of about 5500 (produced by Yuka Shell Epoxy Co., Ltd., trade name Epicoat 1010) 100 g (containing 0.027 equivalent of epoxy group) and 80 g of methyl isobutyl ketone were added, and the resin was added to about It melted at 100 ° C. Here, acrylic acid 3g
(Contains 0.040 equivalents of carboxylic acid group) Add 0.7 g of 10% methanol solution of tetramethylammonium hydroxide, raise the temperature, react at reflux temperature for 5 hours, then vacuum dry the contents. Then, methyl isobutyl ketone and excess acrylic acid were distilled off to obtain a solid epoxy resin acrylate (A1).

Production of Epoxy Resin Methacrylate (A2) In a four-necked flask equipped with a stirrer, a thermometer and a cooling tube,
About 100 g of a bisphenol A type epoxy resin (trade name Epicoat 1009 manufactured by Yuka Shell Epoxy Co., Ltd.) having a molecular weight of about 3750 (containing 0.034 equivalents of epoxy groups) and 80 g of methyl isobutyl ketone were added, and the resin was adjusted to about 100. It melted at ℃. Here, 3.5 g of methacrylic acid (including 0.040 equivalent of carboxylic acid group), 10
% Tetramethylammonium hydroxide methanol solution 0.8 g was added and the temperature was raised to 5 at the reflux temperature.
After reacting for a time, the content was vacuum dried to distill off methyl isobutyl ketone and excess methacrylic acid to obtain a solid epoxy resin methacrylate (A2).

Production of Epoxy Resin Acrylate (A3) In a four-necked flask equipped with a stirrer, thermometer and cooling tube,
Bisphenol A type epoxy resin having a molecular weight of about 2900 (trade name Epicoat 1007 manufactured by Yuka Shell Epoxy Co., Ltd.) (100 g (including 0.051 equivalent of epoxy group)) and 40 g of methyl isobutyl ketone were added, and the resin was added to about 100. It melted at ℃. Here, acrylic acid 7.
3 g (containing 0.101 equivalent of carboxylic acid group) and 0.1 g of tetramethylammonium chloride were added and the temperature was raised.
After reacting at 100 ° C. for 4 hours, the content was vacuum dried to distill off methyl isobutyl ketone and excess acrylic acid to obtain a solid epoxy resin acrylate (A3).

Production of Epoxy Resin Acrylate (A4) In a four-necked flask equipped with a stirrer, a thermometer and a cooling tube,
Bisphenol A type epoxy resin having a molecular weight of about 1600 (trade name Epicoat 1004 manufactured by Yuka Shell Epoxy Co., Ltd.) 100 g (including 0.11 equivalent of epoxy groups)
And 40 g of methyl isobutyl ketone were added, and the resin was melted at about 80 ° C. Here, 7.9 g of acrylic acid
(Containing 0.11 equivalent of carboxylic acid group), and 0.02 g of hydroquinone monomethyl ether to prevent radical polymerization at the time of addition reaction, heated to 90 ° C., reacted for 10 hours, and then vacuumed contents. After drying, methyl isobutyl ketone and excess acrylic acid were distilled off to obtain a solid epoxy resin acrylate (A4).

Production of Aqueous Resin Dispersion (D1) In a four-necked flask equipped with a stirrer, a thermometer and a cooling tube,
(A1) epoxy resin acrylate 45 g, methacrylic acid 15 g, n-butyl acrylate 35 g, styrene 5
g, 190 g of methyl ethyl ketone, 0.8 g of azobis 2,4-dimethylvaleronitrile, and 0.1 g of n-dodecyl mercaptan were added, and after reacting at 70 ° C. for 5 hours,
The internal temperature was raised to 80 ° C., and 10 g of methyl ethyl ketone,
0.2 g of azobis 2,4-dimethylvaleronitrile was additionally added, and the mixture was further reacted for 3 hours. After that, set the internal temperature to 6
The temperature was lowered to 0 ° C., 20 g of ammonia water and 100 g of ion-exchanged water were added thereto, and the mixture was stirred for 30 minutes to neutralize the copolymer. Further, 300 g of water was added and stirred for 1 hour to emulsify the content and cool the content to room temperature. This emulsion is decompressed by an aspirator and gradually raised in temperature,
Methyl ethyl ketone and a small amount of water were distilled off. Ion-exchanged water and a small amount of ammonia water were further added thereto to adjust the pH to 9 to 10 and the solid content to 20% by weight to obtain an aqueous resin dispersion (D1).

Production of Aqueous Resin Dispersion (D2) In a four-necked flask equipped with a stirrer, thermometer and cooling tube,
(A2) epoxy resin methacrylate 40 g, methacrylic acid 15 g, n-butyl acrylate 40 g, styrene 5 g, methyl ethyl ketone 100 g, n-butanol 9
Add 0 g and azobisisobutyronitrile 0.8 g,
After reacting at 5 ° C. for 3 hours, the internal temperature was raised to 80 ° C., 10 g of methyl ethyl ketone and 0.2 g of azobisisobutyronitrile were additionally added, and the mixture was further reacted for 2 hours. After that, the contents are vacuum dried to completely remove the solvent,
A solid acrylated epoxy resin was obtained. In a four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, 100 g of the acrylated epoxy resin, 25 g of ammonia water, and 375 g of ion-exchanged water were added and stirred, and the inner temperature was raised to 40 ° C. to 30 The mixture was stirred for a minute, then the inner temperature was raised to 60 ° C. and stirred for 30 minutes, and further the inner temperature was raised to 75 ° C. and stirred for 2 hours to emulsify the content. Then, the content was cooled to room temperature and adjusted to have a pH of 9 to 10 and a solid content of 20% by weight to obtain an aqueous resin dispersion (D2).

Production of Aqueous Resin Dispersion (D3) 52 g of epoxy resin methacrylate (A2), 5 g of acrylic acid, 23 g of methyl methacrylate, 2-acrylic acid
20 g of ethylhexyl, 200 g of methyl ethyl ketone,
Azobisisobutyronitrile (1.0 g) and n-dodecylmercaptan (0.2 g) were added, and the reaction was carried out at 70 ° C. for 10 hours. Thus, an aqueous resin dispersion (D3) having a solid content of 20% by weight was obtained.

Production of Aqueous Resin Dispersion (D4) 62 g of epoxy resin acrylate of (A4), 8 g of maleic acid, 22 g of n-butyl acrylate, 8 g of styrene,
After adding 150 g of methyl ethyl ketone and 0.6 g of azobis2,4-dimethylvaleronitrile and reacting at 75 ° C. for 3 hours, the internal temperature was raised to 80 ° C., 10 g of methyl ethyl ketone and azobis2,4-dimethylvaleronitrile. By the same method as the above-mentioned aqueous resin dispersion (D1) except that 0.2 g was additionally added and the reaction was continued for 3 hours, the pH was adjusted to 9
10. Aqueous resin dispersion having a solid content of 20% by weight (D4)
Got

Production of Aqueous Resin Dispersion (D5) 82 g of the epoxy resin acrylate of (A3), 7 g of acrylic acid, 11 g of n-butyl acrylate, 150 g of methyl ethyl ketone, 0.6 g of azobis2,4-dimethylvaleronitrile were added to give 75 After reacting at 0 ° C for 3 hours, the internal temperature was raised to 80 ° C, 10 g of methyl ethyl ketone and 0.2 g of azobis2,4-dimethylvaleronitrile were additionally added, and the reaction was continued for another 3 hours. By the same method as the resin dispersion (D1), pH 9 to 10, solid content 2
An aqueous resin dispersion (D5) having a concentration of 0% by weight was obtained.

Production of Aqueous Resin Dispersion (D6) 32 g of epoxy resin acrylate (A4), 10 g of methacrylic acid, 50 g of n-butyl acrylate, 8 styrene
g, 150 g of methyl ethyl ketone, 0.8 g of azobis 2,4-dimethylvaleronitrile, and 0.2 g of n-dodecyl mercaptan were added, and the mixture was reacted at 75 ° C. for 3 hours,
The internal temperature was raised to 80 ° C., and 10 g of methyl ethyl ketone,
Azobis 2,4-dimethylvaleronitrile (0.2 g) was additionally added, and the reaction was conducted for 3 hours, in the same manner as in the above aqueous resin dispersion (D1), pH 9 to 10, solid content 20% by weight. To obtain an aqueous resin dispersion (D6).

Aqueous resin dispersion of carboxylated polyolefin resin (F1) In an autoclave equipped with a stirrer, thermometer and cooling pipe,
Commercially available ethylene / acrylic acid copolymer containing 20% by weight of acrylic acid as monomer (weight average molecular weight of about 5
10,000) 100 g, ammonia water 20 g, ion-exchanged water 10
Charge 0 g, raise the temperature with stirring after nitrogen sealing, and
After stirring at 0 to 150 ° C. for 3 hours, the contents were taken out by cooling, and ion-exchanged water was added to adjust the pH to 9 to 10,
The solid content was adjusted to 20% by weight to obtain an aqueous resin dispersion (F1) of ethylene / acrylic acid copolymer.

Silica Aqueous Sol (E1) Spherical silica particles having a specific surface area according to the BET method of 200 m ² / g, a particle diameter calculated according to the BET method of 13.6 nm, and a particle diameter according to the electron microscope observation of 10 to 20 nm. A commercially available aqueous silica sol having a SiO ₂ concentration of 20 wt% (manufactured by Nissan Chemical Industries, Ltd., trade name Snowtex 20) was prepared.

Silica Aqueous Sol (E2) The specific surface area by the BET method is 250 m ² / g, the particle diameter R ₁ by the dynamic light scattering method (measured by N ₄ apparatus manufactured by Coulter, USA) is 50 nm, and it is calculated by the BET method. A commercially available aqueous silica sol having a particle diameter R ₂ of 10.9 nm and consisting of silica particles having an elongated shape with a diameter of 5 to 10 nm according to an electron microscope observation and having a SiO ₂ concentration of 20% by weight. (Nissan Chemical Industry Co., Ltd., trade name Snowtex UP) was prepared.

Silica Aqueous Sol (E3) The specific surface area according to the BET method is 150 m ² / g, the particle diameter R ₁ according to the dynamic light scattering method (measured by N ₄ apparatus manufactured by Coulter, USA) is 300 nm, and the particle diameter is calculated according to the BET method. A commercially available aqueous silica sol having a particle diameter R ₂ of 18.1 nm, silica particles having a porous structure formed by aggregating fine particles of 5 to 10 nm by electron microscope observation, and having a SiO ₂ concentration of 25% by weight ( Manufactured by Nissan Chemical Industries,
Ion-exchanged water is added to the product name PT3025)
₂ Concentration was adjusted to 20% by weight.

Preparation of Aqueous Dispersion of Crosslinking Agent (G1) A commercially available aziridine crosslinking agent consisting of an aqueous dispersion containing 25% by weight of diphenylmethane-bis-4,4'-diethyleneurea is diluted with ion-exchanged water. By 2
An aqueous dispersion of crosslinker (G1) having a concentration of 0% by weight was obtained. Comparative Example 1 Production of Epoxy Resin Acrylate (A5) In a four-necked flask equipped with a stirrer, a thermometer and a cooling tube,
Bisphenol A type epoxy resin having a molecular weight of about 900 (trade name: Epicoat 1001, manufactured by Yuka Shell Epoxy Co., Ltd.) 100 g (containing 0.21 equivalent of epoxy group)
And 40 g of methyl isobutyl ketone were added, and the resin was melted at about 80 ° C. 13 g of acrylic acid (containing 0.17 equivalents of carboxylic acid group) and 0.02 g of hydroquinone monomethyl ether for inhibiting radical polymerization at the time of addition reaction were added thereto and heated to react at reflux temperature for 6 hours. After that, the content was vacuum dried to distill off methyl isobutyl ketone and excess acrylic acid to obtain a solid epoxy resin acrylate (A5).

Unsaturated fatty acid ester of epoxy resin (A
Production of 6) In a four-necked flask equipped with a stirrer, a thermometer and a cooling tube,
Bisphenol A type epoxy resin having a molecular weight of about 1600 (produced by Yuka Shell Epoxy Co., Ltd., trade name Epicoat 1004) 100 g (containing 0.11 equivalent of epoxy group) and commercially available tall oil fatty acid (oleic acid and linoleic acid). 90% or more of unsaturated fatty acids, etc.)
After reacting at 5 ° C. for 5 hours, a highly viscous content was taken out, and this was cooled and solidified to obtain a solid unsaturated fatty acid ester (A6) of the epoxy resin.

Production of Aqueous Resin Dispersion (D7) 13 g of epoxy resin methacrylate (A2), 7 g of acrylic acid, 50 g of n-butyl acrylate, 25 g of methyl methacrylate, 5 g of styrene, 10 of methyl ethyl ketone.
0 g, azobisisobutyronitrile 1.0 g, and n-dodecyl mercaptan 0.1 g were added, and the reaction was carried out at 70 ° C. for 10 hours, except that the reaction was carried out at pH 9 in the same manner as in the above aqueous resin dispersion (D1). -10, an aqueous resin dispersion (D7) having a solid content of 20% by weight was obtained.

Production of Aqueous Resin Dispersion (D8) Unsaturated Fatty Acid Ester 70 of Epoxy Resin of (A6)
g, methacrylic acid 7 g, butyl acrylate 18 g, styrene 5 g, butanol 50 g, methyl ethyl ketone 50
g, benzoyl peroxide 0.6 g,
After reacting at ℃ for 3 hours, raise the internal temperature to 80 ℃,
The above aqueous resin dispersion (D1) except that 0.2 g of benzoyl peroxide was additionally added and the reaction was continued for 3 hours.
By the same method as described above, an aqueous resin dispersion (D8) having a pH of 9 to 10 and a solid content of 20% by weight was obtained.

Production of Aqueous Resin Dispersion (D9) 52 g of epoxy resin acrylate of (A5), 10 g of methacrylic acid, 30 g of n-butyl acrylate, 8 styrene
g, methyl ethyl ketone 150 g, azobisisobutyronitrile 0.8 g, n-dodecyl mercaptan 0.2 g
When the reaction was carried out at 75 ° C., about 1 hour after the start of the reaction, the viscosity was rapidly increased and finally gelled. Lower the internal temperature to 60 ° C, and add ammonia water 20
g and 375 g of water could not be emulsified.

Silica Aqueous Sol (E4) Spherical silica particles having a specific surface area of 62 m ² / g by the BET method, a particle size of 43.9 nm calculated by the BET method, and a particle size of 40-60 nm by the electron microscope observation. A commercially available aqueous silica sol having a SiO ₂ concentration of 20 wt% (manufactured by Nissan Chemical Industries, Ltd., trade name Snowtex 20L) was prepared.

Example 2 The above prepared aqueous resin dispersions (D1) to (D6), an aqueous resin dispersion of carboxylated polyolefin resin (F)
1), the silica aqueous sol (E1) to (E3) and the aqueous dispersion (G1) of the cross-linking agent are mixed in the weight ratios shown in Tables 1 and 2 to obtain water-based paints P1 to P13 and R1. It was

Comparative Example 2 Aqueous resin dispersions (D1) to (D2) and (D7) to (D8) prepared above, an aqueous resin dispersion of a carboxylated polyolefin resin (F1), an aqueous silica sol (E1).
To (E3) and (E4) and an aqueous dispersion (G1) of the same cross-linking agent as used in Example 2 at the weight ratios shown in Tables 1 and 2 to prepare water-based paints P14-P2.
Got 4.

[0061]

TABLE 1 Table 1 coating paint Ingredients (g) D1 D2 D3 D4 D5 D6 D7 D8 E1 E2 E3 E4 G1 P1 100 0 0 0 0 0 0 0 15 0 0 0 0 P2 0 100 0 0 0 0 0 0 0 15 0 0 10 P3 0 0 100 0 0 0 0 0 0 0 30 0 20 P4 0 0 0 100 0 0 0 0 40 0 0 0 5 P5 0 0 0 0 100 0 0 0 0 50 0 0 0 P6 0 0 0 0 0 100 0 0 0 0 50 0 0 P7 0 50 50 0 0 0 0 0 70 0 0 0 3 P14 0 0 0 0 0 0 100 0 50 0 0 0 0 P15 100 0 0 0 0 0 0 0 0 0 0 50 5 P16 100 0 0 0 0 0 0 0 0 0 0 0 0 P17 0 100 0 0 0 0 0 0 0 200 0 0 0 P18 0 0 0 0 0 0 0 0 100 50 0 0 0 0

[0062]

Table 2 Table 2 paint paint Ingredients (g) D1 D2 D3 D4 D5 D7 D8 F1 E1 E2 E3 E4 G1 P8 85 0 0 0 0 0 0 15 40 0 0 0 0 P9 0 90 0 0 0 0 0 10 0 70 0 0 10 P10 0 0 75 0 0 0 0 25 0 0 15 0 20 P11 0 0 0 70 0 0 0 30 50 0 0 0 0 P12 0 0 0 0 60 0 0 40 0 30 0 0 15 P13 0 0 0 65 0 0 0 35 0 0 20 0 0 P19 0 0 0 0 0 80 0 20 0 0 20 0 5 P20 0 0 0 0 0 0 80 20 25 0 0 0 3 P21 30 0 0 0 0 0 0 70 0 50 0 0 5 P22 80 0 0 0 0 0 0 20 0 0 0 50 5 P23 80 0 0 0 0 0 0 20 0 0 0 0 0 P24 0 80 0 0 0 0 0 20 0 200 0 0 0 R1 100 0 0 0 0 0 0 0 0 50 0 0 5 Stability Test of Water-Based Coating Composition (T1) The obtained water-based coatings P1 to P24 and R1 were sealed in a 500 ml bottle and placed in a constant temperature bath at 40 ° C. every 7 days. After re-stirring, the viscosity was measured at 20 ° C. Based on the viscosity value before carrying out this stability test, if the number of days required for the increase rate of the viscosity value to exceed 50% is within 7 days, (xx) mark, if 14 to 28 days (X) mark, 35-7
(△) mark for 7 days, (○) for 84-161 days
Indicated in Tables 3 and 4 with (⊚) when the mark was 168 days or more.

Example 3 A zinc-nickel alloy-plated steel sheet having a coating weight of 30 g / m ² and a chromate-treated steel surface was prepared. On this steel plate, P1 to P prepared in Example 2
After applying the water-based paints of Nos. 13 and R1 using a bar coater, the steel plate temperature was reached to 120 ° C. for 7 seconds and baked to form a coated steel plate having a film with a film thickness of 1 to 1.5 μm. did.

Comparative Example 3 The procedure of Example 3 was repeated except that the water-based paints P14 to P24 prepared in Comparative Example 2 were used, and the film thickness was 1 to 1.5 μm.
A coated steel sheet having a film of was prepared. Then, Example 3
And the coated steel sheet obtained in Comparative Example 3, the corrosion resistance, the corrosion resistance after bending, the corrosion resistance when the iron-based member is present in the vicinity of the coated steel sheet, the degreasing bath resistance, the adhesiveness, the electrodeposition coating property, Each test T2 to T9 of corrosion resistance after electrodeposition coating was performed. As a reference, the same chromate-treated zinc-nickel alloy-plated steel sheet, which was not coated with the above-mentioned water-based paint, was treated in the same manner by allowing the steel sheet temperature to reach 120 ° C over 7 seconds and baking it. The same test as described above was performed for the product. These test results are the third
The results are shown in Tables and 4. In addition, in the test T1 in Tables 3 and 4, the paint codes (P1) to (P24) and (R
1) shows the storage stability test results of the water-based coating compositions P1 to P24 and R1, and in Tests T2 to T9 in Tables 3 and 4, coating codes (P1) to (P2).
4) and (R1) show each test result of the steel sheets coated with the water-based paints P1 to P24 and R1.

Corrosion Resistance Test (T2) According to the method of JIS Z-2371, when the coated steel sheet is sprayed with salt water for 2000 hours, the occurrence of white rust and red rust on the steel sheet is observed. White rust area ratio is 50
% And the area ratio of red rust is 0% (◎)
When the white rust occurrence area ratio is 50% or more and the red rust occurrence area ratio is less than 5%, the mark (○) indicates the white rust occurrence area ratio is 50% or more and the red rust occurrence area ratio is 5%. When the area ratio of white rust is 50% or more, and when the area ratio of red rust exceeds 10%, it is shown in Table 3 when the ratio is 10% to 10%.
The results are shown in Table 4.

Corrosion resistance test after bending (T3) Using an Erichsen tester, the coated steel plate was deformed from the back side to deform the coated surface to a convex shape, and then bent to 7 mm, and then sprayed with salt water. After 2000 hours, the occurrence of white rust and red rust is observed. When the white rust occurrence area ratio is less than 50% and the red rust occurrence area ratio is 0%, the white rust occurrence area ratio is 50% or more and the red rust occurrence area ratio is less than 5%. (○) indicates that the white rust occurrence area ratio is 50% or more and the red rust occurrence area ratio is 5 to 10
When the percentage is (%), the white rust occurrence area ratio is 50% or more,
When the area ratio of red rust exceeds 10%, it is shown in Tables 3 and 4 by a mark (x).

Corrosion resistance test (T4) when an iron-based member is present near the coated steel sheet. A vinyl chloride resin case having a thickness of 4 mm and an inner dimension of 140 mm × 140 mm × 40 mm is used to coat the coated steel sheet and the untreated iron sheet with 140 mm × 140 mm. Insert the one cut into face to face so that it does not touch. Then, 392 g of a 5 wt% concentration saline solution is put therein and sealed. This case is placed in a constant temperature bath at 50 ° C. After 30 minutes, incline 90 °, then after 30 minutes, return 90 °. This operation is repeated for 10 days and the occurrence of red rust is observed. When the area ratio of red rust is less than 5%, it is shown in Table 3 and Table 4, when it is 5 to 10%, it is shown in triangle, and when it exceeds 10%, it is shown in Table 3 and Table 4.

Adhesion test (T5) 3 g / m²2 coated steel plates coated with rust preventive oil
prepare. Vinyl chloride adhesive (Henkel white
Water Co., Ltd. product name Macroplast PV5300C18)
Is applied to a thickness of 150μ, and the dimension of the adhesive surface is 25mm.
Stick another sheet so that it becomes × 12.5mm
It Then, the coated steel sheet thus laminated is heated at 160 ° C.
After heating for 10 minutes, the temperature is 23 ° C and the relative humidity is 50%.
Specimens are prepared by leaving them in the greenhouse for 1 day.
Tensile shear was applied to this test specimen at a tensile speed of 5 mm / min.
The breaking strength is measured. This strength is 40 kg / cm²To
When crossing over (○), 30-40 kg / cm²When
(△) mark, 30kg / cm ²When less than, mark with (x)
It is shown in Table 3 and Table 4.

Electrodeposition coatability test (T6) Epoxy resin / block isocyanate isocyanate cationic electrodeposition coating (manufactured by Nippon Paint Co., Ltd., trade name Power Top U-
52) prepare a bath, and at a bath temperature of 23 ° C. and a voltage of 200 V,
Electrodeposit the coated steel sheet for 2 minutes. The obtained steel plate having an electrodeposition coating film is baked at 170 ° C. for 20 minutes to prepare an electrodeposition coating plate having a film thickness of 20 μm. Observe the change in the appearance of this electrodeposition coated plate. When the number of pinholes and craters is 0 to 5 points (○), when it is 6 to 10 points (△), when it is 11 points or more (x), Table 3 and 4
Shown in the table.

Corrosion resistance test after electrodeposition coating (T7) The electrodeposition coated plate obtained in the same manner as above is cross-cut with a cutter knife. The electrodeposition coated plate having this cross cut is immersed in a 5% saline solution at 50 ° C. for 10 days, washed with water, dried, and then subjected to a peeling test with cellophane tape. The maximum peeling width from the cross-cut line was measured, and when the width was 0 to 1 mm, it was marked with (○), when it was 1 to 2 mm, it was marked with Δ, and when it was 2 mm or more, it was marked with ×, Table 3 Fourth
Shown in the table.

Degreasing Bath Resistance Test (T8) As an alkaline degreasing agent, an aqueous solution of Surf Cleaner SD270, trade name, manufactured by Nippon Paint Co., Ltd. was heated to 60 ° C., and the coated steel sheet was immersed in this for 2 minutes and washed with water. Then, the residual rate of the film after drying is measured. When the residual rate is 90 to 100%, it is marked (○), and when it is 80 to 90%, it is marked (△) and 80
When it is less than%, it is shown in Tables 3 and 4 by the mark (x).

Durability test of coating film after immersion in alkaline degreasing bath (T9) As an alkaline degreasing agent, an aqueous solution of Surf Cleaner SD270 under the trade name of Nippon Paint Co., Ltd. was prepared.
Put the above alkaline degreasing agent in a container, heat to 60 ° C., immerse the coated steel sheet for 2 minutes, take out the coated steel sheet from the container, and immediately remove the coated steel sheet from Jujo Kimberley Co., Ltd., trade name. The reciprocating coating surface is rubbed with a paper wiper in which Kimwipe S-200 is impregnated with the aqueous solution of Surf Cleaner SD270. Then, the residual rate of the film after washing with water and drying is measured. When the remaining rate is 90 to 100%, it is marked with (○), and when it is 80 to 90%, it is marked with (△) and 80%.
When it is less than, it is shown in Table 2 by the mark (x).

[0073]

[Table 3] Table 3 paint T1 T2 T3 T4 T5 T6 T7 T8 P1 ○ ○ ○ ○ ○ ○ ○ ○ P2 ○ ◎ ◎ ○ ○ ○ ○ ○ P3 ◎ ○ ○ ○ ○ ○ ○ ○ P4 ○ ○ ○ ○ ○ ○ ○ ○ P5 ○ ◎ ◎ ○ ○ ○ ○ ○ P6 ◎ ○ ○ ○ ○ ○ ○ ○ P7 ○ ○ ○ ○ ○ ○ ○ ○ P14 ○ ○ ○ × × × × △ P15 ○ × × △ ○ ○ × ○ P16 ◎ × × × ○ ○ × ○ P17 ○ ○ × △ ○ × ○ ○ P18 × × ○ × × ○ ○ ○ ×

[0074]

[Table 4] Table 4 paint T1 T2 T3 T4 T5 T6 T7 T9 P8 ○ ○ ○ ○ ○ ○ ○ ○ P9 ○ ◎ ◎ ○ ○ ○ ○ ○ P10 ◎ ○ ○ ○ ○ ○ ○ ○ P11 ○ ○ ○ ○ ○ ○ ○ ○ P12 ○ ◎ ◎ ○ ○ ○ ○ ○ P13 ◎ ○ ○ ○ ○ ○ ○ ○ P19 ◎ ○ ○ × × ○ × △ P20 × × × × × ○ ○ ○ △ P21 ○ ◎ ◎ ○ × × × ○ P22 ○ × × × ○ ○ ○ ○ P23 ◎ × × × ○ ○ ○ ○ P24 ○ ○ × ○ ○ ○ ○ × R1 ○ ◎ ◎ ○ ○ ○ ○ × See ─── × × × × × ○ × ── Table 3 From the results of Table 4, the paints P14 to P2 of Comparative Examples
4 is the corrosion resistance, the corrosion resistance after bending, the corrosion resistance when an iron-based member is present near the coated steel sheet, the degreasing bath resistance, the adhesiveness,
While the performance of any one of the electrodeposition coatability and the corrosion resistance after electrodeposition coating is not sufficient, all of the paints P1 to P13 and R1 of the examples show that they are excellent in all of these performances. . Further, it can be seen that the coating components P8 to P13 containing the carboxylated polyolefin resin have extremely excellent coating film durability particularly in the degreasing step.

[0075]

EFFECT OF THE INVENTION The aqueous coating composition for metal surface treatment of the present invention is subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment on a metal surface of a steel sheet, a galvanized steel sheet, an alloyed galvanized steel sheet or the like. Spray, brush, or
It can be applied using a roll or the like, dried and cured in a short time, and a coated steel sheet having a film of about 0.5 to 10 μm can be obtained. This coated steel sheet has high corrosion resistance and high adhesion with an adhesive or an electrodeposition coating, and further, even when the coated steel sheet is bent or subjected to electrodeposition coating, it has excellent corrosion resistance. In particular, when an iron-based member is present near the coated steel sheet, the corrosion resistance in an environment where iron rust is generated from the iron-based member is improved. Further, it has excellent surface protection and chemical resistance, and in particular, swelling of the coating film in the degreasing step with an alkaline solution does not easily occur, and even if the steel sheets come into contact with each other, the coating film is less likely to break. The aqueous coating composition for metal surface treatment of the present invention also has sufficient storage stability as a coating composition. Furthermore, the aqueous coating composition for metal surface treatment of the present invention,
As it has high adhesion and adhesion to base materials and high chemical resistance, it is not only used in the field of metal surface treatment, but also in fiber treatment, paper processing, wood processing, paint vehicles, concrete coating, and binders for pharmaceuticals and agricultural chemicals. It is also useful for applications such as plastic surface coating agents and ceramic coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Miyake 1 722, Tsuboi-cho, Funabashi-shi, Chiba Nissan Chemical Industry Co., Ltd. Central Research Laboratory

Claims (6)

[Claims] 1. An epoxy resin acrylate, an epoxy resin methacrylate or a mixture thereof (A) 30 to 90.
Parts by weight, 3 to 20 parts by weight of α, β-unsaturated carboxylic acid (B), and one or more polymerization selected from the group consisting of acrylic acid ester, methacrylic acid ester and vinyl group-containing monomer. Of an aqueous resin dispersion (D) obtained by dispersing a resin obtained by copolymerizing 7 to 67 parts by weight of a polymerizable monomer (C) in an alkaline aqueous solution, and silica particles having a specific surface area of 100 m ² / g or more. It is composed of a sol (E) dispersed in water and has a resin solid content of 1 in the above-mentioned aqueous resin dispersion (D).
The sol (E) is contained in an amount of 10 to 100 parts by weight as SiO ₂ with respect to 00 parts by weight, and the solid content of the resin of the aqueous resin dispersion (D) and the S of the sol (E).
Aqueous coating composition for metal surface treatment, containing 5 to 50% by weight of total iO ₂ content. 2. An epoxy resin acrylate, an epoxy resin methacrylate or a mixture thereof (A) 40 to 90.
Parts by weight, 3 to 20 parts by weight of α, β-unsaturated carboxylic acid (B), and one or more polymerization selected from the group consisting of acrylic acid ester, methacrylic acid ester and vinyl group-containing monomer. Aqueous resin dispersion (D) in which a resin obtained by copolymerizing 7 to 57 parts by weight of a polymerizable monomer (C) is dispersed in an alkaline aqueous solution, and an aqueous resin dispersion in which a carboxylated polyolefin resin is dispersed in water. (F) and 100m
Silica particles having a specific surface area of ² / g or more are formed of a sol (E) dispersed in water, and b. 1 to 9 parts by weight of the solid content of the resin of the aqueous resin dispersion (D) with respect to 1 part by weight of the solid content of the resin of the aqueous resin dispersion (F); The sol (E) was added to SiO 2 with respect to 100 parts by weight of the total solid content of the resins of the aqueous resin dispersions (D) and (F).
₂ to 10 to 100 parts by weight, and the total solid content of the resins of the aqueous resin dispersions (D) and (F) and the SiO ₂ content of the sol (E) is 5 to 50% by weight.
Aqueous coating composition for metal surface treatment, which is contained in a concentration. 3. A carboxylated polyolefin resin,
The aqueous coating composition for metal surface treatment according to claim 2, which is a copolymer of ethylene and acrylic acid. 4. An epoxy resin acrylate, an epoxy resin methacrylate or a mixture (A) thereof is 100
The bisphenol type epoxy resin having a molecular weight of 0 to 9,000 is an ester obtained by reacting acrylic acid, methacrylic acid, or a mixture thereof with each other, which is an ester. Aqueous coating composition for metal surface treatment. 5. The α, β-unsaturated carboxylic acid (B) is one or more selected from the group consisting of acrylic acid, methacrylic acid and maleic acid. The aqueous coating composition for metal surface treatment according to any one of claims 1 to 4. 6. The silica particles having a specific surface area of 100 m ² / g or more are silica particles having an elongated structure, silica particles having an agglomerated structure of fine particles, or a mixture thereof. Item 6. An aqueous coating composition for metal surface treatment according to any one of items 1 to 5.