JP2006009065A - Phosphate composite coated steel sheet having white rust resistance and coating characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphate composite coated steel sheet having white rust resistance and coating characteristics equivalent to those of chromate sealed material. <P>SOLUTION: The phosphate composite coated steel sheet has a phosphate film on the surface of a galvanized steel sheet, and a surface-treated film consisting of a surface treatment composition containing (a) a water dispersion of a resin obtained by reacting a polyalkylene glycol modified epoxy resin obtained by reacting a polyalkylene glycol of the specified number average molecular weight, a bisphenol type epoxy resin, an active hydrogen-containing compound and a polyisocyanate compound, an epoxy group containing resin, and an active hydrogen containing compound consisting of a hydrazine derivative partly or totally having active hydrogen, (b) a silane coupling agent, and (c) at least one kind selected from phosphoric acid, a water-soluble phosphate and a hexafluoro metallic acid, is formed on an upper layer thereof. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a surface-treated steel sheet suitable for use in automobiles, home appliances, building materials, etc., which is based on a phosphate-treated zinc-based plated steel sheet and is not subjected to sealing with hexavalent chromium. The present invention relates to a coated steel sheet.

  2. Description of the Related Art Conventionally, zinc-based plated steel sheets used for automobiles, home appliances, building materials, etc. have been subjected to zinc phosphate treatment for anticorrosion or painting. However, the conventional zinc phosphate treatment could not form a film excellent in all of bare corrosion resistance, corrosion resistance after coating, and paint adhesion. That is, in this zinc phosphate treatment, the corrosion resistance and paint adhesion after coating are excellent, but since the formed film is due to the dissolution reaction between phosphoric acid and the base metal (zinc), the dissolution reaction is insufficient. Holes in which no film is formed remain at such locations, and therefore the bare corrosion resistance is poor. For this reason, conventionally, in order to improve the white rust resistance of the zinc phosphate-treated steel sheet before coating, sealing treatment (sealing) with an aqueous chromic acid solution has been performed. However, since conventional sealing treatment uses hexavalent chromium, which is an environmentally regulated substance, there is a need for a zinc phosphate-treated steel sheet that provides excellent corrosion resistance without sealing, or a sealing treatment technology that does not use an environmentally regulated substance. ing.

In response to such a demand, for example, the following techniques have been proposed.
(1) A method of depositing one or more of Mg, Ni, Co, and Cu on a zinc phosphate coating (for example, Patent Document 1)
(2) A method of forming a film with a treatment liquid in which an organic resin, a thiocarbonyl group-containing compound, and a vanadic acid compound are blended (for example, Patent Document 2)
(3) A method for forming a chromate-free film containing a water-soluble resin and a titanium or zirconium compound (for example, Patent Document 3)

JP 2002-285346 A JP 2000-248367 A JP 2003-253464 A

However, in the method (1), although the corrosion resistance is improved by adding Mg, the effect of improving the corrosion resistance is negligible because no sealing treatment is performed, and the corrosion resistance is higher than that of the conventional chromate sealing treatment. Is inferior.
In addition, the methods (2) and (3) can be positioned as chromate-free sealing technology to develop the same level of corrosion resistance as chromate sealing treatment, but in order to obtain sufficient corrosion resistance, There is a disadvantage that the thickness has to be increased, and conversely the paintability deteriorates.
Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art and provide a phosphate composite coated steel sheet having white rust resistance and paintability equivalent to the sealing material without performing chromate sealing treatment. There is to do.

  As a result of the study by the present inventors, in order to remarkably improve the white rust resistance and paintability of the phosphate-treated zinc-based plated steel sheet, a specific modified epoxy resin is formed on the surface of the phosphate-treated zinc-based plated steel sheet. Surface obtained by mixing a silane coupling agent and a specific acid component (phosphoric acid, hexafluorometal acid or phosphate) with an aqueous epoxy resin dispersion of a resin obtained by reacting hydrazine derivatives having active hydrogen with hydrazine derivatives It has been found effective to form a coating with the treatment composition. In addition, this surface-treated film is formed by a single-layer process, but has a so-called pseudo two-layer structure in which a reaction layer is formed at the lower part of the film (plating side) and a resin concentrated layer is formed at the upper part of the film. And it turned out that the remarkable improvement effect of corrosion resistance and paintability is acquired by the synergistic effect of such a pseudo | simulation bilayer membrane | film | coat.

The present invention has been made based on the above findings, and the features thereof are as follows.
[1] A film formed by applying a surface treatment composition containing the following components (a) to (c) to a surface of a zinc-based plated steel sheet, and drying the coated film. A phosphate composite-coated steel sheet excellent in white rust resistance and paintability, characterized by having a surface-treated film having a thickness of 0.01 to 1 μm.
(A) A polyalkylene glycol-modified epoxy resin (A) obtained by reacting a polyalkylene glycol having a number average molecular weight of 400 to 20000, a bisphenol type epoxy resin, an active hydrogen-containing compound and a polyisocyanate compound, and the polyalkylene glycol-modified A resin obtained by reacting an epoxy group-containing resin (B) other than the epoxy resin (A) with an active hydrogen-containing compound comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is used in water. Dispersed aqueous epoxy resin dispersion (b) Silane coupling agent: 1 to 300 parts by mass (solid content) per 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion
(C) One or more selected from phosphoric acid, water-soluble phosphate, and hexafluorometal acid: 0.1 to 80 parts by mass (solid) with respect to 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion Min)

[2] In the phosphate composite coated steel sheet of [1], the surface treatment composition contains a silane coupling agent having an amino group as a reactive functional group, and has white rust resistance and paintability An excellent phosphate composite coated steel sheet.
[3] In the phosphate composite-coated steel sheet according to [1] or [2], the surface treatment composition has a molar ratio of the cation component to the P ₂ O ₅ component [cation] / [P ₂ O ₅ ] = 0. White rust resistance and paintability, characterized by containing a water-soluble phosphate which is 4 to 1.0 and whose cationic species is one or more selected from Mn, Mg, Al and Ni An excellent phosphate composite coated steel sheet.
[4] The phosphate composite-coated steel sheet according to any one of [1] to [3], wherein the surface treatment composition contains one or more elements selected from Ti, Si, and Zr. A phosphate composite coated steel sheet excellent in white rust resistance and paintability, characterized in that it contains.

  The phosphate composite-coated steel sheet of the present invention has excellent white rust resistance and paintability equivalent to the sealing material, although it is not subjected to chromate sealing.

The details of the present invention and the reasons for limitation will be described below.
There is no special restriction | limiting in the zinc plating steel plate used as the base of the phosphate composite coating steel plate of this invention, Any of a pure zinc plating steel plate and a zinc type alloy plating steel plate may be sufficient.
Specifically, galvanized steel sheet (electroplated steel sheet, hot dip galvanized steel sheet), Zn—Ni alloy plated steel sheet, Zn—Fe alloy plated steel sheet (electroplated steel sheet, galvannealed steel sheet), Zn—Cr alloy plated Steel sheet, Zn-Mn alloy plated steel sheet, Zn-Co alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet, Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al alloy plated steel sheet ( For example, Zn-5% Al alloy plated steel sheet, Zn-55% Al alloy plated steel sheet, Zn-Mg alloy plated steel sheet, Zn-Al-Mg plated steel sheet (for example, Zn-6% Al-3% Mg alloy plated steel sheet) Zn-11% Al-3% Mg alloy-plated steel sheet), and zinc-based composites in which metal oxides, polymers, etc. are dispersed in the plated film of these plated steel sheets Kki steel (e.g., Zn-SiO ₂ dispersion plating steel plate) or the like can be used.

Moreover, the multilayer plating steel plate which plated two or more layers of the same kind or different kind among the above plating can also be used.
Moreover, as a plated steel plate, the steel plate surface may be previously plated with lightness such as Ni, and various plating as described above may be performed thereon.
As a plating method, any feasible method among an electrolytic method (electrolysis in an aqueous solution or electrolysis in a nonaqueous solvent), a melting method, and a gas phase method can be adopted.
Furthermore, in order to prevent blackening of the plating, one or more trace elements of Ni, Co, Fe are deposited in the plating film at a concentration of about 1 to 2000 ppm, or Ni, Co, Fe are deposited on the surface of the plating film. These elements may be deposited by performing a surface conditioning treatment with an alkaline or acidic aqueous solution containing one or more of the above.

Although there is no special restriction | limiting in the kind of phosphate membrane | film | coat formed in the surface of the said zinc-plated steel plate, A zinc phosphate-type membrane | film | coat is especially preferable from points, such as corrosion resistance and coating property. Further, the zinc phosphate-based film may contain one or more selected from Mn, Ni, Co, and Mg.
The adhesion amount of the phosphate film is preferably 0.1 to 3 g / m ² . If the adhesion amount is less than 0.1 g / m ^{2, the} amount of phosphate crystals produced is small and sufficient anchoring effect cannot be obtained, so the paintability (paint adhesion) is poor, while the adhesion amount is 3 g / m ² . Even if it exceeds, the paintability (paint adhesion) tends to be inferior.

Next, the surface treatment film formed on the phosphate film and the surface treatment composition for forming this film will be described.
This surface treatment film is a surface treatment film formed by applying a surface treatment composition containing the following components (a) to (c) and drying. This surface treatment film does not contain any chromium.
(A) A polyalkylene glycol-modified epoxy resin (A) obtained by reacting a polyalkylene glycol having a number average molecular weight of 400 to 20000, a bisphenol type epoxy resin, an active hydrogen-containing compound and a polyisocyanate compound, and the polyalkylene glycol-modified A resin obtained by reacting an epoxy group-containing resin (B) other than the epoxy resin (A) with an active hydrogen-containing compound comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is used in water. Dispersed aqueous epoxy resin dispersion (b) Silane coupling agent: 1 to 300 parts by mass (solid content) per 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion
(C) One or more selected from phosphoric acid, water-soluble phosphate, and hexafluorometal acid: 0.1 to 80 parts by mass (solid) with respect to 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion Min)

First, the aqueous epoxy resin dispersion that is the component (a) will be described.
In this aqueous epoxy resin dispersion, a specific polyalkylene glycol-modified epoxy resin (A), an epoxy group-containing resin (B) other than the polyalkylene glycol-modified epoxy resin (A), and a part or all of the compounds are active. An active hydrogen-containing compound comprising a hydrazine derivative (C) having hydrogen (that is, a hydrazine derivative (C) having active hydrogen and, if necessary, an active hydrogen-containing compound (D) other than the hydrazine derivative (C)); A resin obtained by reacting (hereinafter also simply referred to as “water-dispersible resin”) is dispersed in water.

The polyalkylene glycol-modified epoxy resin (A) is obtained by reacting a polyalkylene glycol having a number average molecular weight of 400 to 20000, a bisphenol type epoxy resin, an active hydrogen-containing compound, and a polyisocyanate compound. .
As the polyalkylene glycol, for example, polyethylene glycol, polypropylene glycol, polybutylene glycol and the like can be used, and among them, polyethylene glycol is particularly preferable. The number average molecular weight of the polyalkylene glycol is suitably in the range of 400 to 20000, preferably 500 to 10,000, from the viewpoint of water dispersibility and storage properties of the resulting resin.
The bisphenol-type epoxy resin is a bisphenol compound having at least one epoxy group in one molecule, and in particular, a bisphenol diester obtained by a condensation reaction between a bisphenol compound and an epihalohydrin (for example, epichlorohydrin). Glycidyl ether is preferable because a film excellent in flexibility and corrosion resistance can be easily obtained.

Typical examples of bisphenol compounds that can be used for the preparation of bisphenol-type epoxy resins include bis (4-hydroxyphenyl) -2,2-propane, bis (4-hydroxyphenyl) -1,1-ethane, and bis. (4-hydroxyphenyl) -methane, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-3-t- Butylphenyl) -2,2-propane and the like. Of the epoxy resins prepared using such bisphenol-based compounds, bisphenol A type epoxy resins are particularly suitable in that a film excellent in flexibility and corrosion resistance can be obtained.
Further, the bisphenol type epoxy resin generally has a number average molecular weight of about 310 to 10,000, particularly preferably about 320 to 2,000, from the viewpoint of production stability during production of the polyalkylene glycol-modified epoxy resin. The epoxy equivalent is preferably in the range of about 155 to 5000, particularly desirably about 160 to 1000.

  The active hydrogen-containing compound is used for blocking isocyanate groups in the polyalkylene glycol-modified epoxy resin (A). Typical examples thereof include monohydric alcohols such as methanol, ethanol and diethylene glycol monobutyl ether; monovalent carboxylic acids such as acetic acid and propionic acid; monovalent thiols such as ethyl mercaptan. Other blocking agents (active hydrogen-containing compounds) include secondary amines such as diethylamine; one secondary amino group or hydroxyl group such as diethylenetriamine and monoethanolamine and one or more primary groups. A compound in which a primary amino group of an amine compound containing an amino group is modified to aldimine, ketimine, oxazoline or imidazoline by heating reaction with a ketone, aldehyde or carboxylic acid at a temperature of, for example, 100 to 230 ° C .; methyl ethyl ketoxime And oximes such as phenol; phenols such as phenol and nonylphenol; These compounds generally have a number average molecular weight in the range of 30 to 2000, particularly preferably 30 to 200.

  The polyisocyanate compound is a compound having 2 or more, preferably 2 or 3 isocyanate groups in one molecule, and those generally used for the production of polyurethane resins can be used in the same manner. Such polyisocyanate compounds include aliphatic, alicyclic and aromatic polyisocyanate compounds. Representative examples include aliphatic polyisocyanate compounds such as hexamethylene diisocyanate (HMDI), HMDI biuret compound, HMDI isocyanurate compound; isophorone diisocyanate (IPDI), IPDI biuret compound, IPDI isocyanurate compound, Examples thereof include alicyclic polyisocyanate compounds such as hydrogenated xylylene diisocyanate and hydrogenated 4,4′-diphenylmethane diisocyanate; aromatic polyisocyanate compounds such as tolylene diisocyanate and xylylene diisocyanate.

In general, the blending ratio of each component during the production of the polyalkylene glycol-modified epoxy resin (A) is suitably in the following range.
That is, the equivalent ratio of the hydroxyl group of the polyalkylene glycol and the isocyanate group of the polyisocyanate compound is 1 / 1.2 to 1/10, preferably 1 / 1.5 to 1/5, particularly preferably 1 / 1.5 to A value of 1/3 is appropriate. The equivalent ratio of the hydroxyl group of the active hydrogen-containing compound to the isocyanate group of the polyisocyanate compound is 1/2 to 1/100, preferably 1/3 to 1/50, particularly preferably 1/3 to 1/20. Is appropriate. Further, the equivalent ratio of the total amount of hydroxyl groups of the polyalkylene glycol, bisphenol type epoxy resin and active hydrogen-containing compound to the isocyanate group of the polyisocyanate compound is 1 / 1.5 or less, preferably 1 / 0.1 to 1/1. .5, particularly preferably 1 / 0.1 to 1 / 1.1.

The reaction of the polyalkylene glycol, the bisphenol type epoxy resin, the active hydrogen-containing compound and the polyisocyanate compound can be performed by a known method.
The polyalkylene glycol-modified epoxy resin (A) obtained above, an epoxy group-containing resin (B) other than the polyalkylene glycol-modified epoxy resin (A), a hydrazine derivative (C) having active hydrogen, and further necessary Accordingly, by reacting with the active hydrogen-containing compound (D) other than the hydrazine derivative (C), an epoxy resin that can be easily dispersed in water and has good adhesion to the material can be obtained. .

As the epoxy group-containing resin (B) other than the polyalkylene glycol-modified epoxy resin (A), a glycidyl group is introduced by reacting polyphenols such as bisphenol A, bisphenol F, and novolac phenol with an epihalohydrin such as epichlorohydrin. Or an aromatic epoxy resin obtained by further reacting this glycidyl group-introduced reaction product with a polyphenol to increase the molecular weight; and further, an aliphatic epoxy resin, an alicyclic epoxy resin, etc. One kind can be used alone, or two or more kinds can be mixed and used. These epoxy resins preferably have a number average molecular weight of 1500 or more, particularly when film formation at low temperatures is required.
Examples of the epoxy group-containing resin (B) include resins obtained by reacting various modifiers with epoxy groups or hydroxyl groups in the epoxy group-containing resin. For example, epoxy ester resins obtained by reacting a dry oil fatty acid. An epoxy acrylate resin modified with a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid; a urethane-modified epoxy resin reacted with an isocyanate compound;

Further, as the epoxy group-containing resin (B), an unsaturated monomer having an epoxy group and a polymerizable unsaturated monomer component essentially comprising an acrylic ester or a methacrylic ester are used as a solution polymerization method, emulsion polymerization method or suspension polymerization method. An acrylic copolymer resin copolymerized with an epoxy group-containing monomer synthesized by a method such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl ( Acrylic or methacrylic acid such as (meth) acrylate, n-, iso- or tert-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate C1-C24 Alkyl ester; acrylic acid, methacrylic acid, styrene, vinyl toluene, acrylamide, acrylonitrile, N-methylol (meth) acrylamide, C1-4 alkyl etherified product of N-methylol (meth) acrylamide; N, N-diethylaminoethyl methacrylate, etc. Can be mentioned. Moreover, as an unsaturated monomer which has an epoxy group, if it has an epoxy group and a polymerizable unsaturated group, such as glycidyl methacrylate, glycidyl acrylate, and 3,4 epoxy cyclohexyl-1-methyl (meth) acrylate, It is not limited.
The acrylic copolymer resin may be a resin modified with a polyester resin, an epoxy resin, a phenol resin, or the like.

上記化学構造式中、ｑは０〜５０の整数、好ましくは１〜４０の整数、特に好ましくは２〜２０の整数である。
このようなビスフェノールＡ型エポキシ樹脂は、当業界において広く知られた製造法により得ることができる。 Particularly preferable as the epoxy group-containing resin (B) is a resin represented by the following chemical structural formula, which is a reaction product of bisphenol A and epiparohydrin, and is particularly preferable because of its excellent corrosion resistance.

In said chemical structural formula, q is an integer of 0-50, Preferably it is an integer of 1-40, Most preferably, it is an integer of 2-20.
Such a bisphenol A type epoxy resin can be obtained by a production method widely known in the art.

Examples of the active hydrogen-containing compound that reacts with the epoxy group of the epoxy group-containing resin (B) include the following.
・ Hydrazine derivatives with active hydrogen ・ Primary or secondary amine compounds with active hydrogen ・ Organic acids such as ammonia and carboxylic acids ・ Hydrogen halides such as hydrogen chloride ・ Alcohols, thiols ・ Active hydrogen Quaternary chlorinating agent which is a mixture of hydrazine derivative or tertiary amine and acid which does not have

  In preparing the aqueous epoxy resin dispersion, one or more of these can be used, but in order to obtain excellent corrosion resistance, at least a part (preferably all) of the active hydrogen-containing compounds are active. It is necessary that the hydrazine derivative (C) has hydrogen. That is, among these, a hydrazine derivative (C) having active hydrogen is an essential component, and an active hydrogen-containing compound (D) other than the hydrazine derivative (C) is used as necessary.

The following can be mentioned as a typical example of the amine compound which has the said activated hydrogen.
(1) a primary amino group of an amine compound containing one secondary amino group and one or more primary amino groups, such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, etc .; A compound modified with aldimine, ketimine, oxazoline or imidazoline by heat reaction with aldehyde or carboxylic acid at a temperature of about 100 to 230 ° C., for example;
(2) Secondary monoamines such as diethylamine, diethanolamine, di-n- or -ios-propanolamine, N-methylethanolamine, N-ethylethanolamine;
(3) a secondary amine-containing compound obtained by adding a monoalkanolamine such as monoethanolamine and a dialkyl (meth) acrylamide by a Michael addition reaction;
(4) A compound obtained by modifying a primary amine group of an alkanolamine such as monoethanolamine, neopentanolamine, 2-aminopropanol, 3-aminopropanol, 2-hydroxy-2 ′ (aminopropoxy) ethyl ether to ketimine;

  The quaternary chlorinating agent which can be used as a part of the active hydrogen-containing compound (that is, as an active hydrogen-containing compound (D) other than the hydrazine derivative (C) having active hydrogen) is a hydrazine derivative or third compound having no active hydrogen. Since the secondary amines themselves are not reactive with epoxy groups, they are made into a mixture with acids in order to be able to react with the epoxy groups. The quaternary chlorinating agent reacts with an epoxy group in the presence of water as necessary to form a quaternary salt with the epoxy group-containing resin. The acid used to obtain the quaternary chlorinating agent may be any of organic acids such as acetic acid and lactic acid, and inorganic acids such as hydrochloric acid. Examples of the hydrazine derivative having no active hydrogen used for obtaining a quaternary chlorinating agent include 3,6-dichloropyridazine, and examples of the tertiary amine include dimethylethanolamine, triethylamine, Examples include trimethylamine, triisopropylamine, and methyldiethanolamine.

It is a hydrazine derivative having active hydrogen that exhibits the most useful and excellent corrosion resistance performance among the active hydrogen-containing compounds.
Specific examples of the hydrazine derivative having active hydrogen include the following.
(1) Carbohydrazide, propionic acid hydrazide, salicylic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, thiocarbohydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, benzophenone hydrazone, aminopolyacrylamide Hydrazide compounds such as;
(2) pyrazole compounds such as pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazolone, 3-amino-5-methylpyrazole;

 (3) 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 5-amino -3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole, 1H-benzotriazole, 1-hydroxybenzotriazole (monohydrate), 6- Triazole compounds such as methyl-8-hydroxytriazolopyridazine, 6-phenyl-8-hydroxytriazolopyridazine, 5-hydroxy-7-methyl-1,3,8-triazaindolizine;

(4) tetrazole compounds such as 5-phenyl-1,2,3,4-tetrazole and 5-mercapto-1-phenyl-1,2,3,4-tetrazole;
(5) thiadiazole compounds such as 5-amino-2-mercapto-1,3,4-thiadiazole and 2,5-dimercapto-1,3,4-thiadiazole;
(6) Maleic hydrazide, 6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone, 4,5-dibromo-3-pyridazone, 6-methyl-4,5-dihydro-3-pyridazone, etc. Pyridazine compounds;
Of these, pyrazole compounds and triazole compounds having a 5-membered or 6-membered ring structure and having a nitrogen atom in the ring structure are particularly suitable.
These hydrazine derivatives can be used individually by 1 type or in mixture of 2 or more types.

  A polyalkylene glycol-modified epoxy resin (A) as described above, an epoxy group-containing resin (B) other than the polyalkylene glycol-modified epoxy resin (A), a hydrazine derivative (C) having active hydrogen, and further necessary The active hydrogen-containing compound (D) other than the hydrazine derivative (C) is preferably reacted at a temperature of 10 to 300 ° C., more preferably 50 to 150 ° C. for about 1 to 8 hours. The aqueous epoxy resin dispersion described above can be obtained by dispersing the resin in water.

  The above reaction may be performed by adding an organic solvent, and the type of the organic solvent to be used is not particularly limited. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone, cyclohexanone; ethanol, butanol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether , Propylene glycol, propylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and other alcohols and ethers containing hydroxyl groups; ethyl acetate, butyl acetate, ethylene glycol monobutyl ether acetate and other esters; toluene, xylene Aromatic hydrocarbons, etc. Indicates possible, it is possible to use one or more of these. Of these, ketone-based or ether-based solvents are particularly preferable from the viewpoints of solubility with an epoxy resin, film formation, and the like.

The blending ratio of the polyalkylene glycol-modified epoxy resin (A), the epoxy group-containing resin (B) other than the polyalkylene glycol-modified epoxy resin (A), and the hydrazine derivative (C) having active hydrogen is polyalkylene glycol-modified. The equivalent ratio of active hydrogen groups in the hydrazine derivative (C) to the epoxy groups in the epoxy resin (A) and the epoxy group-containing resin (B) is 0.01 to 10, preferably 0.1 to 8, and more preferably 0. 2 to 4 is appropriate from the viewpoints of corrosion resistance and water dispersibility of the resin.
Further, a part of the hydrazine derivative (C) having active hydrogen can be replaced with the active hydrogen-containing compound (D), but the replacement amount is 90 mol% or less, preferably 70 mol% or less, more preferably 10 to 10 mol%. It is suitable from the viewpoint of anticorrosion and adhesion to be in the range of 60 mol%.

  Moreover, in order to form a dense barrier film, it is desirable to mix a curing agent in the water-dispersible resin and to heat and cure the film. The curing method for forming a film with the resin composition was selected from (1) a curing method using a urethanization reaction between an isocyanate and a hydroxyl group in a base resin, and (2) melamine, urea, and benzoguanamine. Etherification reaction between an alkyl etherified amino resin obtained by reacting one or more methylol compounds obtained by reacting formaldehyde with one or more monovalent alcohols having 1 to 5 carbon atoms and a hydroxyl group in the base resin. However, it is particularly preferable to use a urethanization reaction between an isocyanate and a hydroxyl group in the base resin as a main reaction.

The polyisocyanate compound as a curing agent that can be used in the curing method (1) is an aliphatic, alicyclic (including heterocyclic) or aromatic isocyanate compound having at least two isocyanate groups in one molecule. Or a compound obtained by partially reacting these compounds with a polyhydric alcohol. Examples of such polyisocyanate compounds include the following.
(a) m- or p-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, o- or p-xylylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate, isophorone diisocyanate
(b) Compound (a) above or a mixture thereof and polyhydric alcohols (dihydric alcohols such as ethylene glycol and propylene glycol; trihydric alcohols such as glycerin and trimethylolpropane; tetrahydric alcohols such as pentaerythritol; A compound obtained by reaction with a hexahydric alcohol such as sorbitol and dipentaerythritol), in which at least two isocyanates remain in one molecule. These polyisocyanate compounds may be used alone or in combination of two or more. Can be used in combination.

Moreover, as a protective agent (blocking agent) of a polyisocyanate compound, for example,
(A) Aliphatic monoalcohols such as methanol, ethanol, propanol, butanol, octyl alcohol;
(B) Ethylene glycol and / or diethylene glycol monoethers, for example, monoethers such as methyl, ethyl, propyl (n-, iso), butyl (n-, iso, sec);
(C) aromatic alcohols such as phenol and cresol;
(D) oximes such as acetooxime and methyl ethyl ketone oxime;
A polyisocyanate compound that is stably protected at least at room temperature can be obtained by reacting one or more of these with the polyisocyanate compound.

  Such a polyisocyanate compound (a2) has a curing agent of (a) / (a2) = 95/5 to 55/45 (nonvolatile) with respect to the aqueous epoxy resin dispersion (a) (the component (a)). (Mass ratio of minute), preferably (a) / (a2) = 90/10 to 65/35. The polyisocyanate compound has water absorption, and if it is blended in excess of (a) / (a2) = 55/45, the adhesion of the surface treatment film is deteriorated. Furthermore, when it coats on a surface treatment film | membrane, an unreacted polyisocyanate compound will move in a coating film, and will cause the hardening inhibition of a coating film and adhesiveness defect. From such a viewpoint, the blending amount of the polyisocyanate compound (a2) is preferably (a) / (a2) = 55/45 or less.

  The water-dispersible resin is sufficiently crosslinked by the addition of the crosslinking agent (curing agent) as described above, but it is desirable to use a known curing accelerating catalyst in order to further increase the low-temperature crosslinking property. Examples of the curing accelerating catalyst include N-ethylmorpholine, dibutyltin dilaurate, cobalt naphthenate, stannous chloride, zinc naphthenate, and bismuth nitrate. In addition, for the purpose of slightly improving physical properties such as adhesion, a known resin such as acrylic, alkyd, or polyester can be mixed and used together with the epoxy group-containing resin (B).

In order to disperse the reaction product of the polyalkylene glycol-modified epoxy resin (A), the epoxy group-containing resin (B) and the active hydrogen-containing compound comprising a hydrazine derivative (C) partly or entirely having active hydrogen, in water dispersion, For example, the following method can be employed.
(1) A tertiary amine as a neutralizing agent by reacting an epoxy group of an epoxy group-containing resin (that is, resin (A) or (B)) with a dibasic acid or secondary amine as an active hydrogen-containing compound. , Neutralization with water or acetic acid or phosphoric acid
(2) A method of dispersing in water using a modified epoxy resin obtained by reacting an epoxy resin with a terminal hydroxyl group-containing polyalkylene oxide such as polyethylene glycol or polypropylene glycol with an isocyanate.
(3) Method of using both (1) and (2) in combination In addition to the specific water-dispersible resin described above, other surface-dispersible resins and / or water-soluble resins include, for example, acrylic Resin, urethane resin, polyester resin, epoxy resin, ethylene resin, alkyd resin, phenol resin, olefin resin, etc. You may mix | blend as an upper limit.

Next, the silane coupling agent which is the said component (b) is demonstrated.
Examples of the silane coupling agent include vinyl methoxy silane, vinyl ethoxy silane, vinyl trichloro silane, vinyl trimethoxy silane, vinyl triethoxy silane, β- (3,4 epoxy cyclohexyl) ethyl trimethoxy silane, and γ-glycid. Xylpropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ -Aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-me Tacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, p-styryltrimethoxysilane, γ -Acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, γ-isocyanatopropyl Triethoxysilane, γ-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- (vinylbenzylamine) -β-aminoethyl-γ-aminopropyltri Etc. can be mentioned Tokishishiran, these one may be used alone or in combination of two or more.

The reason why the surface-treated film containing these silane coupling agents is excellent in corrosion resistance and paintability is that silanol groups (Si—OH) generated by hydrolysis of the silane coupling agent in the aqueous solution are phosphate films and hydrogen. This is considered to be for bonding and further providing excellent adhesion by a dehydration condensation reaction.
By blending the silane coupling agent in this way, it is possible to improve the adhesion between the phosphate film and the water-dispersible resin, but in the case of the present invention, the acid component contained in the surface treatment composition The phosphate film and the water-dispersible resin are activated by chemically activating both the phosphate film surface and the water-dispersible resin on which the inactive phosphate film surface is activated and the silane coupling agent is activated. Adhesion with can be greatly improved. And especially outstanding corrosion resistance and coating property are obtained by improving the adhesiveness of a phosphate membrane | film | coat and membrane | film | coat formation resin in this way.

  Among the silane coupling agents, a silane coupling agent having an amino group as a reactive functional group is particularly preferable from the viewpoint of having a functional group highly reactive with the water-dispersible resin of the component (a). preferable. Examples of such silane coupling agents include N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ. -Aminopropyltrimexysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc., specifically, “KBM-903” and “KBE-903” manufactured by Shin-Etsu Chemical Co., Ltd. , “KBM-603”, “KBE-602”, “KBE-603” (all are trade names), and the like.

  The compounding amount of the silane coupling agent is 1 to 300 parts by mass, preferably 5 to 100 parts by mass in terms of the solid content with respect to 100 parts by mass of the resin solid content of the aqueous epoxy resin dispersion as the component (a). More preferably, the content is 15 to 50 parts by mass. When the blending amount of the silane coupling agent is less than 1 part by mass, the corrosion resistance is inferior and the paintability (paint adhesion) is inferior due to insufficient adhesion, while when it exceeds 300 parts by mass, the barrier property of the water-dispersible resin is impaired. Therefore, the corrosion resistance decreases.

Next, phosphoric acid, water-soluble phosphate and hexafluorometal acid, which are the component (c), will be described.
These components have an action of acting on the surface of the inactive phosphate film to activate the surface. Then, the adhesion between the surface of the activated phosphate film and the water-dispersible resin is remarkably improved through the silane coupling agent. As a result, the corrosion resistance and paintability are remarkably improved. As the component (c), one or more selected from phosphoric acid, water-soluble phosphate and hexafluorometal acid are used.

The type of hexafluorometal acid is not particularly limited, but from the viewpoint of effectively forming the reaction layer of the pseudo-bilayer film described above, in particular, fluorinated titanic acid, fluorinated zirconic acid, silicofluoric acid, etc. Hexafluorometal acids containing one or more elements selected from Ti, Si, and Zr are preferred, and one or more of these can be used.
As the water-soluble phosphate, for example, one or more metal salts such as orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, and metaphosphoric acid can be used. Moreover, you may add 1 type, or 2 or more types of the salt (For example, phytic acid, phytate, phosphonic acid, phosphonate, and these metal salts) of organic phosphoric acid. Of these, the primary phosphate is preferable from the viewpoint of the stability of the surface treatment composition.

There are no particular limitations on the form of phosphate present in the film, and it may be crystalline or non-crystalline. There are no particular restrictions on the ionicity and solubility of the phosphate. However, from the viewpoint of obtaining particularly excellent corrosion resistance, Al, Mn, Ni, and Mg are particularly desirable as the cationic species of the water-soluble phosphate, and one or more elements selected from these are included. It is preferable to use a water-soluble phosphate. Examples of such water-soluble phosphates include primary aluminum phosphate, primary manganese phosphate, primary nickel phosphate, and primary magnesium phosphate. Further, it is preferable that the molar ratio of the cationic components and _P 2 _{O 5} component [cation] / _[P 2 _{O 5]} is 0.4 to 1.0. If the molar ratio [cation] / [P ₂ O ₅ ] is less than 0.4, the solubility of the film is impaired by the soluble phosphoric acid, and the corrosion resistance is lowered. On the other hand, if it exceeds 1.0, the stability of the processing solution is remarkably lost, which is not preferable.

The total blending amount of at least one selected from phosphoric acid, water-soluble phosphate, and hexafluorometal acid is based on 100 parts by mass of the resin solid content of the aqueous epoxy resin dispersion that is the component (a). The solid content is 0.1 to 80 parts by mass, preferably 1 to 60 parts by mass, more preferably 5 to 50 parts by mass. When the total blending amount is less than 0.1 parts by mass, the corrosion resistance is inferior. On the other hand, when it exceeds 80 parts by mass, the appearance unevenness after film formation tends to occur.
The film thickness of the surface treatment film is 0.01 to 1 μm. When the film thickness is less than 0.01 μm, the corrosion resistance is insufficient. On the other hand, when it exceeds 1 μm, the conductivity decreases.

Next, the manufacturing method of the phosphate composite covering steel plate of this invention is demonstrated.
First, after the above-described zinc-based plated steel sheet is degreased and washed with water, surface adjustment (pretreatment) is performed as necessary. Next, the surface of the plated steel sheet is subjected to a phosphate treatment to form a phosphate film having a predetermined adhesion amount. Although there is no special restriction | limiting in the kind of this phosphating, a zinc phosphate type | system | group processing is especially preferable from viewpoints, such as corrosion resistance and coating property. The zinc phosphate-based treatment liquid contains phosphate ions and Zn ions, but may further contain one or more selected from Mn ions, Co ions, Mg ions, and the like. The treatment liquid is brought into contact with the surface of the plated steel sheet (immersion method, spray method, etc.), washed with water and dried to form a phosphate film. It is also possible to add one or more of fluoride ions, nitrate ions, nitrite ions and the like to the treatment liquid.

Next, a surface treatment film is formed by applying the surface treatment composition (treatment liquid) having the above-described composition to the surface of the phosphate-treated zinc-based plated steel sheet so as to have a predetermined dry film thickness and drying. To do.
It is appropriate to adjust the surface treatment composition (treatment liquid) to pH 0.5 to 6, preferably 1 to 4. If the pH of the surface treatment composition is less than 0.5, the reactivity of the treatment liquid is too strong, resulting in uneven appearance. On the other hand, if the pH exceeds 6, the reactivity of the treatment liquid becomes low, and the bonding between the plating metal and the film is reduced. Becomes insufficient, and the corrosion resistance decreases.
As a method of coating the surface treatment composition on the phosphate-treated zinc-based plated steel sheet, any of a coating method, a dipping method, and a spray method may be used. As a coating treatment method, any method such as a roll coater (3-roll method, 2-roll method, etc.), a squeeze coater, or a die coater may be used. In addition, after the coating process, dipping process, and spraying process using a squeeze coater, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method.

  After coating the surface treatment composition, drying is performed without washing with water. As the heating and drying means, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace or the like can be used. It is appropriate to perform the heat treatment in the range of 30 ° C. to 300 ° C., preferably 40 ° C. to 250 ° C., at the ultimate plate temperature. If this heating temperature is less than 30 ° C., a large amount of moisture remains in the film, resulting in insufficient corrosion resistance and paintability. Moreover, if it exceeds 300 degreeC, it will not only be uneconomical, but a defect will arise in a membrane | film | coat and corrosion resistance will fall.

A water-soluble or water-dispersible epoxy resin shown in Table 2 is used as a resin composition for the surface treatment composition, and a silane coupling agent (Table 3), phosphoric acid or the like (Table 4) is appropriately blended therein, and ammonia is further added. After adjusting pH to 0.5-6 with water, nitric acid, acetic acid, sulfuric acid, etc., it stirred for the required time using the disperser for coating materials (sand grinder), and prepared the surface treatment composition.
The water-soluble or water-dispersible epoxy resin shown in Table 2 was produced as follows.

[Production Example 1] (Production of polyalkylene glycol-modified epoxy resin)
To a glass four-necked flask equipped with a thermometer, stirrer and condenser, 1688 g of polyethylene glycol having a number average molecular weight of 4000 and 539 g of methyl ethyl ketone were added and stirred and mixed at 60 ° C., and then 171 g of tolylene diisocyanate was added. In addition, after 2 hours of reaction, 1121 g of epoxy resin “Epicoat 834X90” (trade name, manufactured by Shell Japan, epoxy equivalent 250), 66 g of diethylene glycol ethyl ether and 1.1 g of 1% dibutyltin dilaurate solution were added, and 2 Reacted for hours. Thereafter, the temperature was raised to 80 ° C. and reacted for 3 hours to confirm that the isocyanate value became 0.6 or less. Thereafter, the temperature was raised to 90 ° C., and methyl ethyl ketone was removed by distillation under reduced pressure until the solid content concentration reached 81.7%. After removal, 659 g of propylene glycol monomethyl ether and 270 g of deionized water were added and diluted to obtain a polyalkylene glycol-modified epoxy resin solution A1 having a solid content concentration of 76%.

[Production Example 2] (Production of aqueous epoxy resin dispersion)
Epoxy resin “EP1004” (trade name, manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent 1000) 2029 g and propylene glycol monobutyl ether 697 g were charged into a four-necked flask, heated to 110 ° C., and completely cured in 1 hour. Dissolved. After 1180 g of the polyalkylene glycol-modified epoxy resin solution A1 obtained in Production Example 1 and 311.7 g of 3-amino-1,2,4-triazole (molecular weight 84) were added to this product and reacted at 100 ° C. for 5 hours. Then, 719.6 g of propylene glycol monobutyl ether was added to obtain a resin solution D1.
257.6 g of the resin solution D1 was mixed with 50 g of an isocyanate curing agent “MF-K60X” (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.) and 0.3 g of a curing catalyst “Scat24” (trade name), and then mixed with water 692. 0.1 g was dropped and mixed little by little to obtain an aqueous epoxy resin dispersion E1 (aqueous epoxy resin dispersion satisfying the conditions of the present invention).

[Production Example 3] (Aqueous epoxy resin dispersion containing no hydrazine derivative)
Epoxy resin “EP1004” (trade name, manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent 1000) 2029 g and propylene glycol monobutyl ether 697 g were charged into a four-necked flask, heated to 110 ° C., and completely cured in 1 hour. Dissolved. 1180 g of the polyalkylene glycol-modified epoxy resin solution A1 obtained in Production Example 1 and 527.0 g of propylene glycol monobutyl ether were added to this to obtain a resin solution D2.
257.6 g of the resin solution D2 was mixed with 50 g of an isocyanate curing agent “MF-K60X” (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.) and 0.3 g of a curing catalyst “Scat24” (trade name), and then mixed with water 692. 0.1 g was dropped and mixed little by little to obtain an aqueous epoxy resin dispersion E2 (aqueous epoxy resin dispersion not satisfying the conditions of the present invention).

The plated steel sheet shown in Table 1, which is a surface-treated steel sheet for home appliances, building materials, and automobile parts based on cold-rolled steel sheets, was used as a processing original sheet. Zinc phosphate treatment was performed by immersing these plated steel sheets in an aqueous solution diluted with 60 g / l of a zinc phosphate treatment solution “Palbond PB-3312” (trade name, manufactured by Nihon Parkerizing Co., Ltd.) for 2 to 8 seconds. . Then, it washed with water, apply | coated the surface treatment composition, and heat-dried at various temperature, without washing with water.
Tables 5 to 7 show the results of each test of the film composition and quality performance (film appearance, white rust resistance, paint adhesion) of the phosphate composite-coated steel sheet thus obtained. The quality performance was evaluated as follows.

(1) Film appearance For each sample, the uniformity of the film appearance (with or without unevenness) was visually evaluated. The evaluation criteria are as follows.
○: Uniform appearance with no unevenness Δ: Appearance with slightly unevenness ×: Appearance with unevenness (2) White rust resistance Each sample was subjected to a salt spray test (JIS-Z-2371), and after 120 hours The white rust generation area ratio was evaluated. The evaluation criteria are as follows.
◎: White rust occurrence area ratio less than 5% ○: White rust occurrence area ratio 5% or more and less than 10% ○-: White rust occurrence area ratio 10% or more and less than 25% △: White rust occurrence area ratio 25% or more Less than 50% x: White rust generation area ratio 50% or more

(3) Paint secondary adhesion For each sample, a melamine-based baked paint was applied (coating thickness 30 μm) and then immersed in boiling water for 2 hours. Immediately after the cross-cut (10 × 10, 1 mm interval) A cut was made, and adhesion / peeling with an adhesive tape was performed, and the peeled area ratio of the coating film was measured. The evaluation criteria are as follows.
◎: No peeling ○: Peeling area ratio less than 5% △: Peeling area ratio of 5% or more and less than 20% ×: Peeling area ratio of 20% or more

Claims (4)

The surface of the galvanized steel sheet has a phosphate film, and the film thickness formed by applying a surface treatment composition containing the following components (a) to (c) to the upper layer and drying is 0. A phosphate composite-coated steel sheet excellent in white rust resistance and paintability, characterized by having a surface treatment film of 0.01 to 1 μm.
(A) A polyalkylene glycol-modified epoxy resin (A) obtained by reacting a polyalkylene glycol having a number average molecular weight of 400 to 20000, a bisphenol type epoxy resin, an active hydrogen-containing compound and a polyisocyanate compound, and the polyalkylene glycol-modified A resin obtained by reacting an epoxy group-containing resin (B) other than the epoxy resin (A) with an active hydrogen-containing compound comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is used in water. Dispersed aqueous epoxy resin dispersion (b) Silane coupling agent: 1 to 300 parts by mass (solid content) per 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion
(C) One or more selected from phosphoric acid, water-soluble phosphate, and hexafluorometal acid: 0.1 to 80 parts by mass (solid) with respect to 100 parts by mass of resin solid content of the aqueous epoxy resin dispersion Min)   2. The phosphate composite-coated steel sheet excellent in white rust resistance and paintability according to claim 1, wherein the surface treatment composition contains a silane coupling agent having an amino group as a reactive functional group. The surface treatment composition has a molar ratio of the cation component to the P ₂ O ₅ component [cation] / [P ₂ O ₅ ] = 0.4 to 1.0, and the cation species are Mn, Mg, Al, Ni The phosphate composite-coated steel sheet excellent in white rust resistance and paintability according to claim 1 or 2, comprising one or more water-soluble phosphates selected from among the above.   The surface treatment composition contains hexafluorometal acid containing one or more elements selected from Ti, Si, and Zr, and the white rust resistance according to any one of claims 1 to 3, Phosphate composite coated steel sheet with excellent paintability.