JP2008081785A - Coated zinc based plated steel sheet treated with chromium-free water base rust preventive coating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rust prevention treated coated zinc based plated steel sheet using a chromium-free water base rust preventive coating agent having excellent adhesion of a coating film after coating, particularly having excellent adhesion in severe bending. <P>SOLUTION: The water base rust preventive coating agent composition comprises: (a) internally gelled hard polymer particles with the average particle diameter of 0.4 to 0.6 μm; (b) water dispersible silica; (c) a glycidoxyalkyltrialkoxysilane; (d) an organic vanadium compound; (e) a water dispersible urethane resin; (f) a zirconium compound; and (g) diammonium hydrogen phosphate. The coated zinc based plated steel sheet is obtained by being treated with the water base rust preventive coating agent composition in which the content ratios of the above respective components satisfy: (a) 18 to 30 pts.mass; (b) 18 to 30 pts.mass; (c) 22 to 37 pts.mass; (d) 0.4 to 1.7 pts.mass; (e) 8.3 to 13.8 pts.mass; (f) 8.6 to 14.3 pts.mass; and (g) 0.4 to 6.7 pts.mass. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention requires coated zinc-coated steel sheets such as coated galvanized steel sheets and coated galvanium steel sheets (zinc-aluminum alloy plating) treated with a water-based anti-corrosion coating, particularly high-level processing such as pressing and bending after coating. The present invention relates to rust-proof coated zinc-based plated steel sheets for home appliances and building materials.

As a rust preventive coating agent used for rust preventive treatment of coated steel sheets, a reaction type chromate treatment agent or a coating type chromate treatment agent is usually used. For example, Patent Document 1 discloses a rust preventive treatment method for a coating base in which a chromate treatment solution is applied and then an organic polymer resin aqueous solution is applied. However, according to the trend of environmental regulations in recent years, its use is restricted due to the toxicity and carcinogenicity of chromate.
In order to treat the metal surface with a chromium-free treatment agent, various methods of treating with a chromium-free water-based anticorrosion coating agent have been proposed. The actual situation is that a rust-preventive coating having a high level of demand for rust and having the same performance as a chromate film has not yet been developed.
For example, Patent Document 2 describes a method of forming a phosphate film on a zinc-based plated steel sheet, but in applications that require severe bending after coating, the adhesion with the top coat film is insufficient. You can only get

  Further, Patent Document 3 describes an aqueous rust preventive coating that contains specific phosphorus-containing ions, sulfur-containing compounds, water-dispersible silica, and the like without containing chromium. However, in order to ensure sufficient rust prevention, it is necessary to use a large amount of water-dispersible silica. The water-resistant secondary adhesion was not sufficient.

JP-A-62-202084 Japanese Patent Publication No.59-31593 JP 2001-73162 A

  An object of the present invention is to provide a rust-proof coated zinc-based plated steel sheet using a chromium-free aqueous rust-proof coating agent that is excellent in adhesion of a coated film after coating, particularly in tight bending. .

  The present invention provides an internal gelled hard polymer particle having a specific average particle diameter, a zinc-based plated steel sheet, water-dispersible silica, glycidoxyalkyltrialkoxysilane, an organic vanadium compound, a water-dispersible urethane resin, and a zirconium compound. And a coated zinc-based plated steel sheet treated with an aqueous rust-proof coating composition containing diammonium hydrogen phosphate in a specific ratio.

（式中Ａは水素原子又はメチル基、Ｒは炭素数２〜４の置換もしくは非置換アルキレン基、およびＸは酸素原子、リン原子及び硫黄原子の少なくとも１個を有する官能基を表す）で示される親水性単量体の群から選ばれた少なくとも１種との共重合体を乳化剤として、分子内に２個以上のラジカル重合可能なエチレン性不飽和結合を有する多官能性単量体とα，β−モノエチレン系不飽和単量体とを、後者単量体１００質量部に対し上記乳化剤を固形分で５〜１００質量部の割合で使用して、乳化重合させることで得られたものである上記（１）の塗装亜鉛系メッキ鋼板；
（３）有機バナジウム化合物（ｄ）がバナジウムアセチルアセトネートである上記（１）又は（２）の塗装亜鉛系メッキ鋼板；
（４）グリシドキシアルキルトリアルコキシシランがグリシドキシプロピルトリメトキシシラン及び／又はグリシドキシプロピルトリエトキシシランである上記（１）〜（３）のいずれかの塗装亜鉛系メッキ鋼板；
を提供する。 That is, the present invention
(1) Zinc-based plated steel sheet has internal gelled hard polymer particles (a) having an average particle diameter of 0.4 to 0.6 μm, water-dispersible silica (b), glycidoxyalkyltrialkoxysilane (c) , An organic vanadium compound (d), a water-dispersible urethane resin (e), a zirconium compound (f), and a diammonium hydrogen phosphate (g) aqueous rust-proof coating composition comprising: Content ratio is (a) 18-30 mass parts, (b) 18-30 mass parts, (c) 22-37 mass parts, (d) 0.4-1.7 mass parts, (e) 8.3. -13.8 parts by mass, (f) 8.6 to 14.3 parts by mass, (g) coated zinc that has been treated with an aqueous rust-proof coating composition that is 0.4 to 6.7 parts by mass Plated steel sheet;
(2) Internal gelled hard polymer particles (a) are polyacrylic acid and / or acrylic acid and methacrylic acid, acrylamides, methacrylamides and general formula (I)

(Wherein A represents a hydrogen atom or a methyl group, R represents a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, and X represents a functional group having at least one of an oxygen atom, a phosphorus atom and a sulfur atom) A polyfunctional monomer having at least two radically polymerizable ethylenically unsaturated bonds in the molecule and α as a copolymer with at least one selected from the group of hydrophilic monomers , Β-monoethylenically unsaturated monomer obtained by emulsion polymerization using the above emulsifier in a proportion of 5 to 100 parts by mass with respect to 100 parts by mass of the latter monomer The coated zinc-based plated steel sheet of (1) above;
(3) The coated zinc-based plated steel sheet according to the above (1) or (2), wherein the organic vanadium compound (d) is vanadium acetylacetonate;
(4) The coated zinc-based plated steel sheet according to any one of (1) to (3) above, wherein the glycidoxyalkyltrialkoxysilane is glycidoxypropyltrimethoxysilane and / or glycidoxypropyltriethoxysilane;
I will provide a.

  The coated zinc-based plated steel sheet of the present invention is characterized by containing internal gelled hard polymer particles having a specific average particle diameter, and water-dispersible silica, silane coupling agent, organic vanadium compound, water-dispersibility Treated with a chromium-free water-based rust-proof coating containing urethane resin, zirconium compound and diammonium hydrogen phosphate in specific ratios. It has adhesiveness.

  The coated galvanized steel sheet of the present invention is a galvanized steel sheet such as a galvanized steel sheet or a galvanium steel sheet (zinc-aluminum alloy plating), which has been coated with a specific chromium-free aqueous rust-proof coating. It is.

The chromium-free aqueous rust preventive coating used in the present invention will be described in detail below.
An important constituent of the rust preventive coating is internal gelled hard polymer particles (a) having an average particle size of 0.4 to 0.6 μm. When hard resin particles having such a particle diameter (the calculated glass transition temperature of the monomer composition excluding the polyfunctional monomer is about 80 to 110 ° C.) are scattered in the rust preventive film. Good processing adhesion can be obtained due to the stress relaxation effect of the resin particles forming fine irregularities.
Such internal gelled hard polymer particles have an α, β-monoethylenically unsaturated monomer and two or more radically polymerizable ethylenically unsaturated groups in the molecule in the presence of a specific water-soluble polymer. It can be suitably produced by emulsion polymerization of a monomer (hereinafter referred to as a polyfunctional monomer).

  The water-soluble polymer includes polyacrylic acid and / or acrylic acid and methacrylic acid, acrylamides (for example, acrylamide and N-methylolacrylamide), methacrylamides (for example, methacrylamide and N-methylolmethacrylamide), and the above general formula ( I)) (for example, a monomer in the case where X is a functional group having an oxygen atom, 2-hydroxyethyl acrylate, 3-hydroxybutyl acrylate, 2,2-bis (hydroxy) acrylate Methyl) ethyl, 2,3-dihydroxypropyl methacrylate, 3-hydroxybutyl methacrylate and the like; mono (2-hydroxyethyl methacrylate) acid phosphate and mono (2) as a monomer when X is a functional group having a phosphorus atom 3-chloro- 2-hydroxypropyl methacrylate) acid phosphate and the like; and a copolymer with at least one selected from sulfonylethyl methacrylate and the like as a monomer when X is a functional group having a sulfur atom, Used in seeds or mixtures of two or more.

  The proportion of acrylic acid and other hydrophilic monomer in the above copolymer is usually 50% by mass or more in acrylic acid content in all monomers from the viewpoint of stability of emulsion system and adhesion to metal substrate. Preferably, it is appropriately selected so as to be 60% by mass or more.

  Examples of α, β-monoethylenically unsaturated monomers used in emulsion polymerization include acrylic acid esters (methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate). , -Decyl acrylate, isooctyl acrylate, 2-ethylbutyl acrylate, octyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, 3-ethoxypropyl acrylate, etc.), methacrylates (methyl methacrylate, methacrylic acid) Ethyl, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, decyloctyl methacrylate, stearyl methacrylate, 2-methylhexyl methacrylate, methacrylate Lysidyl, 2-ethoxyethyl methacrylate, cetyl methacrylate, benzyl methacrylate, 3-methoxybutyl methacrylate, etc.), acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinyl ketone, vinyl toluene and styrene. It is used by 1 type or a mixture of 2 or more types. These α, β-monoethylenically unsaturated monomers include hard polymer particles (the calculated glass transition temperature of the monomer composition excluding the polyfunctional monomer is about 80 to 110 ° C.) In order to obtain the above, it is preferable to use methyl methacrylate and / or styrene as main components.

In addition to these, acrylamides and methacrylamides which are constituent monomers of the above-mentioned water-soluble copolymer and a small amount of the hydrophilic monomer represented by the general formula (I) may be added.
In particular, by adding a monomer having a hydroxyl group such as 2-hydroxyethyl methacrylate, the emulsion polymer can react with the carboxyl group in the emulsifier, so that the formed base film has adhesion to the metal substrate. Can be expected further.

The polyfunctional monomer used in the emulsion polymerization is substituted with a polymerizable unsaturated monocarboxylic acid ester of a polyhydric alcohol, a polymerizable unsaturated alcohol ester of a polybasic acid, and two or more vinyl groups. There are aromatic compounds, and typical examples include the following.
Ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,4-butanedioldi Acrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol di Methacrylate, glycero Diacrylate, glycerol allyloxy dimethacrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylethane dimethacrylate, 1, 1,1-trishydroxymethylethane trimethacrylate, 1,1,1-trishydroxymethylpropane diacrylate, 1,1,1-trishydroxymethylpropane triacrylate, 1,1,1-trishydroxymethylpropane dimethacrylate, 1,1,1-trishydroxymethylpropanetrimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate and divinyl Benzene.

  The amount of the polyfunctional monomer is not particularly limited as long as the internal gelled polymer particles are obtained, but for the purpose of the present invention, 0.01 to 20% by mass of the total monomers. Particularly preferably, it may be selected within the range of 0.1 to 10% by mass.

  The usage-amount of the said water-soluble copolymer as an emulsifier is selected within the range of 5-100 mass parts by solid content with respect to 100 mass parts of (alpha), (beta) -monoethylenically unsaturated monomer.

Emulsion polymerization is carried out in an aqueous medium, for example, in the presence of a polymerization initiator such as ammonium persulfate and 2,2-azobis- (2-amidinopropane) hydrochloride, under ordinary conditions and techniques.
In addition, the optimal conditions for making the average particle diameter of the emulsion particle | grains obtained by this emulsion polymerization means in the range of 0.4-0.6 micrometer can be suitably selected by those skilled in the art.

  The content of the internal gelling hard polymer particles (a) (solid content of the internal gelling hard polymer particle emulsion) in the anticorrosive coating agent used in the present invention is the addition amount of the following other additional components. The relative amount is 18 to 30 parts by mass. When the content is 18 parts by mass or less, the adhesion of the coating film is lowered, and when it is 30 parts by mass or more, the bath stability (stability of the aqueous rust preventive coating) is lowered.

The water-dispersible silica (b) is added to the rust-proof coating agent used in the present invention as a rust-proof additive. Addition of water-dispersible silica can improve drying properties, coating film adhesion, and corrosion resistance.
The water-dispersible silica is not particularly limited as long as it has few impurities such as sodium and is weakly alkaline. For example, commercially available silica gel such as “Snowtex N”, “Snowtex UP”, “Snowtex PS” (all manufactured by Nissan Chemical Industries), “Adelite AT-20N” (manufactured by Asahi Denka Kogyo Co., Ltd.) as wet silica Alternatively, “Aerosil 200” manufactured by Nippon Aerosil Co., Ltd. or the like can be used as commercially available dry silica.
The content of the water-dispersible silica (b) in the rust-proof coating agent (also referred to as silica solid content in the case of wet silica) is 18 to 30 parts by mass relative to other additive components. . When the content of the water-dispersible silica is less than 18 parts by mass, the adhesion of the coating film decreases. On the other hand, when the content exceeds 30 parts by mass, the water-dispersible silica tends to settle and Workability may be reduced.

The rust preventive coating agent used in the present invention further contains glycidoxyalkyltrialkoxysilane (c) as a silane coupling agent. By blending glycidoxyalkyltrialkoxysilane, the adhesion between the rust preventive coating film and the coating film coated thereon can be improved. A well-known thing is used suitably as said glycidoxyalkyl trialkoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (Brand name "KBM-303", the Shin-Etsu Chemical Co., Ltd. make), 3 -Glycidoxypropyltrimethoxysilane (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.), 3-glycidoxypropylmethyldiethoxysilane (trade name "KBE-403", manufactured by Shin-Etsu Chemical Co., Ltd.), etc. Is exemplified. In particular, glycidoxypropyltrimethoxysilane and / or glycidoxypropyltriethoxysilane can be preferably used.
Content of the glycidoxyalkyl trialkoxysilane (c) in a rust preventive coating agent is 22-37 mass parts as a relative quantity with another additive component. When the content of glycidoxyalkyltrialkoxysilane is less than 22 parts by mass, the adhesion of the coating film decreases, and when it exceeds 37 parts by mass, the corrosion resistance of the coating film decreases.

The organic vanadium compound (d) is mix | blended with the antirust coating agent used by this invention as an antirust agent. Examples of organic vanadium compounds include alkoxides such as triethoxyvanadyl, pentaethoxyvanadium, triamyloxyvanadyl, triisopropoxyvanadyl; bisacetylacetonate vanadyl, vanadium acetylacetonate, vanadylacetylacetonate, vanadiumoxyacetylacetonate And organic acid salts such as vanadium stearate, vanadium pivalate, and vanadium acetate. Especially as an organic vanadium compound, vanadium acetylacetonate can be used conveniently.
Content of the organic vanadium compound (d) in an antirust coating agent is 0.4-1.7 mass parts as a relative quantity with another additive component. When the content of the organic vanadium compound is less than 0.4 parts by mass, the corrosion resistance decreases, and when it exceeds 1.7 parts by mass, the secondary adhesion of the coating film decreases.

A water dispersible polyurethane (e) is blended in the rust preventive coating agent used in the present invention. The film formed of this water-dispersible polyurethane can improve the adhesion between the coated zinc-based plated steel sheet as the base material and the top coat film, corrosion resistance, and the like.
The water-dispersible polyurethane is a polyurethane having a hydrophilic group such as a carboxyl group, and is dispersed in water by adding a basic compound or the like. The polyurethane is prepared by polymerizing a component containing a polyfunctional isocyanate, a polyhydric alcohol, a bifunctional active hydrogen-containing compound having an acidic group and the like by a conventionally known method.
When the resin component is a polyurethane having a carboxyl group, the acid value is preferably 5 to 40 mgKOH / g, and ammonia, a lower alkylamine, or the like can be added to obtain a water-dispersible polyurethane.

  It does not specifically limit as said polyvalent isocyanate, The thing conventionally known as a polyurethane emulsion synthesis raw material can be used, For example, ethylene diisocyanate, 1, 6-hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1,4 -Diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, p-xylylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4 ' -Diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, 1,5-naphthylene diisocyanate, etc. can be mentioned. Furthermore, mixtures of these can be used. In addition, urethane, allophanate, urea, burette, carboimide, urethane imine, bifunctional isocyanate modified with isocyanurate residue, and the like can also be used.

  The polyhydric alcohol is not particularly limited, and those conventionally known as polyurethane emulsion synthesis raw materials can be used. For example, polyester polyol, polyester polyamide polyol, polyether polyol, polythioether polyol, polycarbonate polyol, Polyacetal polyols, polyolefin polyols, polysiloxane polyols and the like can be mentioned, and those having a molecular weight of 500 to 5,000 are preferred. Moreover, you may mix a low molecular-weight polyhydric alcohol as needed. Examples of the mixed polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, pentaerythritol and the like. be able to.

  The bifunctional active hydrogen-containing compound having an acidic group is not particularly limited, and those conventionally known as synthetic raw materials for anionic polyurethane emulsions can be used. For example, 2,2-dimethylolpropanoic acid can be used. 2,2-dimethylolbutanoic acid, lysine cystine, 3,5-diaminobenzoic acid and the like.

The water-dispersible polyurethane preferably has a glass transition temperature (Tg) of −20 ° C. to 50 ° C., more preferably −10 ° C. to 40 ° C., and −10 ° C. to 30 ° C. from the viewpoints of film formability and corrosion resistance. Most preferably.
Content of the said water dispersible polyurethane (e) in a rust preventive coating agent is 8.3 to 13.8 mass parts as a relative quantity with another additive component. When the content of the water-dispersible polyurethane is less than 8.3 parts by mass, the corrosion resistance decreases, and when it exceeds 13.8 parts by mass, the adhesion decreases.

Zirconium compound (f) is added to the rust preventive coating used in the present invention. The zirconium compound acts as a crosslinking agent or chemical conversion film forming agent for water-dispersible polyurethane, and improves the corrosion resistance and chemical resistance of the coating film after coating by forming the formed crosslinked polyurethane or chemical conversion film.
The zirconium compound is not particularly limited, and examples thereof include zircon hydrofluoric acid (H ₂ ZrF ₆ ); zircon hydrofluoric acid salts such as ammonium, lithium, sodium and potassium; ammonium oxycarbonate zirconate ( (NH ₄ ) ₂ ZrO (CO ₃ ) ₂ ); zirconium salt compounds such as zirconium hydroxide, zirconium carbonate, zirconium borate, zirconium oxalate, zirconium sulfate, zirconium nitrate, zirconyl nitrate, and zirconium fluoride; dibutylzirconium dilaurate And organic zirconium compounds such as dibutylzirconium dioctate, zirconium naphthenate, zirconium octylate, and acetylacetone zirconium; or a mixture thereof.
Content of the said zirconium compound (f) in a rust preventive coating agent is 8.6-14.3 mass parts as a relative quantity with another additive component. When the content of the zirconium compound is less than 8.6 parts by mass, the corrosion resistance decreases, and when it exceeds 14.3 parts by mass, the adhesion decreases.

Further, diammonium hydrogen phosphate (g) is added to the rust preventive coating used in the present invention. In diammonium hydrogen phosphate, phosphoric acid is generated by volatilization of ammonia when the film is dried, and surface modification is caused by reaction with the surface of the galvanized surface. Further, the generated phosphoric acid aggregates the film components to form a denser rust preventive film structure. By these, the adhesiveness and corrosion resistance of a rust preventive film can be improved more.
Content of the said diammonium hydrogenphosphate (g) in an antirust coating agent is 0.4-6.7 mass parts as a relative quantity with another additive component. When the content of diammonium hydrogen phosphate is less than 0.4 parts by mass, the adhesiveness decreases, and when it exceeds 6.7 parts by mass, the bath stability decreases.

  The aqueous rust preventive coating used in the present invention can be prepared by blending the above components together with water and mixing and stirring them in a conventional manner. Since the base material is a coated galvanized steel sheet, the treating agent thus obtained should not have too strong acidity or alkalinity. Therefore, the pH is preferably adjusted to 2 to 12, more preferably 4 to 11, and most preferably 7 to 11.

In the present invention, the object to be treated with the aqueous rust-proof coating is a coated zinc-based plated steel sheet.
The treatment of the coated galvanized steel sheet with the rust preventive coating in the present invention may be a method in which the rust preventive coating is applied to the base material, and this is heated and dried after the application. A method of applying this rust preventive coating agent and drying using residual heat may be used.

  The heating temperature is from room temperature to 250 ° C. in any of the above methods. If it is less than room temperature, drying takes time and it becomes uneconomical. On the other hand, if it exceeds 250 ° C., there is a risk of causing thermal decomposition of the anticorrosive film. Preferably it is 50-180 degreeC. The drying time when the substrate is dried by heating after coating is preferably from 1.0 second to 10 minutes.

In the above treatment, the coating amount of the rust preventive coating is preferably such that the dry film thickness is 10 mg / m ² or more and 1000 mg / m ² or less. When it is less than 10 mg / m ² , the rust prevention power is insufficient. On the other hand, when the coating amount exceeds 1000 mg / m ² or less, the treatment method is uneconomical and disadvantages such as a decrease in adhesion to the top coat film occur, and therefore, the amount is more preferably 10 to 500 mg / m ² .

  In the above treatment, the method for applying the rust-preventing coating is not particularly limited, and any commonly used method such as roll coating, air spray, airless spray, bar coater, flow coating, and dipping may be used. What is necessary is just to contact with a material.

Hereinafter, the present invention will be described more specifically with reference to examples. “Parts” and “%” mean “parts by mass” and “% by mass”.
Reference Example 1 (Synthesis of Internal Gelled Hard Polymer Particle Emulsion (A))
Obtained by copolymerizing 150 parts of deionized water and acrylic acid and 2-hydroxyethyl methacrylate in a weight ratio of 8: 2 in a flask equipped with a stirrer, reflux condenser, thermometer and two dropping funnels. 120 parts of a water-soluble copolymer (25% aqueous solution, molecular weight MW = 66000) is added, and the temperature is raised to 80 ° C. to 85 ° C. with stirring. Next, a monomer mixture consisting of 50 parts of methyl methacrylate, 27 parts of styrene, 10 parts of 2-hydroxyethyl methacrylate, 10 parts of n-butyl methacrylate and 3 parts of ethylene glycol dimethacrylate was introduced from one funnel and ammonium persulfate. A catalyst solution consisting of 2 parts and 50 parts deionized water was added dropwise from the other funnel over 3 hours. After the dropwise addition, aging was carried out at 80 ° C. to 85 ° C. for about 2 hours in order to complete the polymerization reaction. The obtained hard polymer particle emulsion (A) was a uniform and stable emulsion having a solid content of 30.0%, a pH of 1.6 and an average particle size of 0.55 μm, and these emulsion particles were not dissolved in xylene. The calculated glass transition temperature of the polymer particles in the monomer mixture excluding the polyfunctional monomer was about 94 ° C.

Example 1
In water, the internal gelled hard polymer particle emulsion (A) prepared in Reference Example 1 was used as a solid content of 18 parts (0.6 g / L in aqueous rust preventive coating), water-dispersible silica (trade name “Aerosil 200”). "Dry type: Nippon Aerosil Co., Ltd.) 25 parts (0.8 g / L), silane coupling agent glycidoxypropyltrimethoxysilane (trade name" KBM-403 "; Shin-Etsu Chemical Co., Ltd.) 30 parts (1 g / L), urethane resin emulsion (trade name “F-8372DB” solid content 30%; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as solid content 10 parts (0.375 g / L), and vanadium acetyl as organic vanadium compound 0.6 parts (0.02 g / L) of acetonate (trade name “Narsem vanadium” dry type; manufactured by Nippon Kagaku Sangyo Co., Ltd.), ammonium zirconium carbonate (trade name “Jill” 12 parts (0.4 g / L) of sol AC-7 "solid content 13%; Nippon Rare Element Co., Ltd.) as a solid content and 0 phosphoric acid compound (trade name" Nimmonium hydrogen phosphate "manufactured by Wako Pure Chemical Industries, Ltd.) .4 parts (0.013 g / L) were dissolved to obtain a chromium-free aqueous rust-proof coating agent.
On the other hand, a hot dip galvanized steel sheet (GI 60/60 basis weight; 0.8 mmt; YS = 138, TS = 285, EL = 50, r value = 1.86 mechanical property value) manufactured by Sumitomo Metal Construction Materials Co., Ltd. After degreasing at 65 ° C. for 5 seconds with a cleaner (trade name “Surf Cleaner 75N-4”; manufactured by Nippon Paint Co., Ltd.) and then washing with water, a surface conditioner (trade name “NP Conditioner 700”; Nippon Paint Co., Ltd.) Manufactured) was immersed at 65 ° C. for 5 seconds, washed with water and hot water, and dried. To this, the treatment agent prepared above was applied to a dry weight of 40 mg / m ² using a bar coater # 3, and dried at 120 ° C. for 30 seconds. A primer (trade name “PB10P”; manufactured by Nippon Fine Coatings Co., Ltd.) was applied to the obtained coated ground-treated galvanized steel sheet so as to have a film thickness of 10 μm, and dried at 210 ° C. at the plate arrival temperature. Next, a top coating (trade name “IPT206”; manufactured by Nihon Fine Coatings Co., Ltd.) is applied from above to a film thickness of 15 μm and dried at a plate temperature of 230 ° C. Obtained. Also on the back surface, the primer and overcoat film thicknesses were 3 μm and 7 μm, respectively, to obtain a coated galvanized steel sheet.

Examples 2-5
Various chromium-free water-based anticorrosive coating agents of the present invention having the compositions shown in Table 1 were obtained, and a ground-treated galvanized steel sheet was produced in the same manner as in Example 1, and finally a coated galvanized steel sheet was obtained.

Comparative Examples 1-5
Using a water-based anticorrosive coating agent having the composition shown in Table 1, a ground-treated galvanized steel sheet was produced in the same manner as in Example 1, and finally a coated galvanized steel sheet was obtained.

  The following methods are used for the coating / coating adhesion of coated galvanized steel sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 5 / bending adhesion, post-coating corrosion resistance, and stability of aqueous rust-proof coatings. It was evaluated by. The results are shown in Table 1.

Test method and evaluation 1) Workability of coated steel sheet (1T, 2T):
The galvanized steel sheet was subjected to a workability test by the following method and evaluated according to the following criteria.
A circular blank with a blank diameter of φ112.5 mm was punched out of a coated galvanized steel sheet, and was drawn to a height of 40 mm with an extrusion load (BHF) of 1.5 ton using a die with a die diameter of φ52.4 mm and a punch diameter of φ50.0 mm. (The front surface is the die surface). The drawn side walls were cut out and subjected to 1T and 2T bending tests (the front surface was the outside) at room temperature.
〔Evaluation criteria〕
A: No cracking, B: Small cracking, B: During cracking, B: Peeling

2) Corrosion resistance after painting:
The coated galvanized steel sheet was cross-cut to the iron surface with a cutter and subjected to a salt spray test for 240 hours, and then the presence or absence of blisters in the cross-cut part or the width of the blister part was evaluated.
〔Evaluation criteria〕
5 points: blister width 0 mm, 4 points: blister width 1 mm or less, 3 points: blister width 3 mm or less, 2 points: blister width 5 mm or less, 1 point: blister width over 5 mm.

3) Stability of aqueous rust preventive coating (bath stability):
The treatment liquid sample (aqueous rust preventive coating agent) was placed in a 40 ° C. furan container for one month, and the appearance was visually evaluated.
〔Evaluation criteria〕
○: No problem, Δ: Precipitate exists.

Claims (4)

  Zinc-based plated steel sheet has internal gelled hard polymer particles (a) having an average particle size of 0.4 to 0.6 μm, water-dispersible silica (b), glycidoxyalkyltrialkoxysilane (c), organic vanadium An aqueous rust-proof coating composition containing a compound (d), a water-dispersible urethane resin (e), a zirconium compound (f), and diammonium hydrogen phosphate (g), wherein the content ratio of these components is (A) 18-30 mass parts, (b) 18-30 mass parts, (c) 22-37 mass parts, (d) 0.4-1.7 mass parts, (e) 8.3-13. Coated galvanized steel sheet treated with a water-based anticorrosive coating composition of 8 parts by mass, (f) 8.6 to 14.3 parts by mass, and (g) 0.4 to 6.7 parts by mass . The internal gelling hard polymer particles (a) are polyacrylic acid and / or acrylic acid and methacrylic acid, acrylamides, methacrylamides and general formula (I)

(Wherein A represents a hydrogen atom or a methyl group, R represents a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, and X represents a functional group having at least one of an oxygen atom, a phosphorus atom and a sulfur atom) A polyfunctional monomer having at least two radically polymerizable ethylenically unsaturated bonds in the molecule and α as a copolymer with at least one selected from the group of hydrophilic monomers , Β-monoethylenically unsaturated monomer obtained by emulsion polymerization using the above emulsifier in a proportion of 5 to 100 parts by mass with respect to 100 parts by mass of the latter monomer The coated galvanized steel sheet according to claim 1.   The coated zinc-based plated steel sheet according to claim 1 or 2, wherein the organic vanadium compound (d) is vanadium acetylacetonate.   The coated galvanized steel sheet according to any one of claims 1 to 3, wherein the glycidoxyalkyltrialkoxysilane is glycidoxypropyltrimethoxysilane and / or glycidoxypropyltriethoxysilane.