JP5661002B2 - Cationic electrodeposition coating composition - Google Patents

Description

  The present invention relates to a cationic electrodeposition coating composition that is excellent in corrosion resistance, in particular, corrosion resistance and moisture resistance adhesion on an untreated steel sheet.

  Cationic electrodeposition paints are used in a wide range of applications including undercoating for automobiles because of their excellent throwing power and low environmental pollution. Conventionally, cationic electrodeposition coating compositions containing lead compounds such as lead chromate, basic lead silicate, strontium chromate, chromium compounds and the like have been proposed.

  However, in recent years, the use of harmful compounds such as lead compounds and chromium compounds has been restricted due to pollution problems, and they are non-toxic or excellent in anticorrosion properties even without such harmful compounds. Cationic electrodeposition paints using low-toxic rust preventive pigments have been developed and put to practical use.

  On the other hand, the cationic electrodeposition paint exhibits excellent corrosion resistance when subjected to chemical conversion treatment, but the corrosion resistance of the portion not subjected to chemical conversion treatment is insufficient. In particular, since the shape of the vehicle body has become complicated in recent years, there has been a portion that is not sufficiently subjected to chemical conversion treatment, and an improvement in corrosion resistance in that portion has been required.

  In addition, it is attempted to perform electrodeposition coating on an untreated steel sheet without performing chemical conversion treatment for the purpose of shortening the rust prevention process, but the adhesion between the steel sheet and the organic component that has been subjected to chemical conversion treatment. And the corrosion resistance was insufficient.

  For example, Patent Document 1 contains (A) a cationic amine-modified epoxy resin, (B) a blocked polyisocyanate, and (C) a divalent or trivalent metal salt of phosphorous acid, and has lead-free corrosion resistance. A cationic electrodeposition coating composition for the purpose of improving the above is disclosed.

  In addition, Patent Document 2 discloses a cationic electrodeposition coating that contains a zirconium compound and is lead-free and excellent in corrosion resistance. Patent Document 3 discloses a xylene formaldehyde resin-modified amino group-containing epoxy resin obtained by reacting an xylene formaldehyde resin (B) and an amino group-containing compound (C) with an epoxy resin (A) having an epoxy equivalent of 180 to 2500. A cationic coating composition is disclosed in which the obtained coating film is lead-free and has the purpose of improving corrosion resistance.

  However, in the inventions described in Patent Documents 1 to 3, although the coating film formed on the steel sheet subjected to the chemical conversion treatment can provide corrosion resistance without containing harmful substances such as lead compounds and chromium compounds, the chemical conversion treatment In the electrodeposition coating film formed on the untreated steel sheet not subjected to the above, the corrosion resistance and the moisture-resistant adhesion were insufficient.

In addition, as a surface treatment liquid used in the case of chemical conversion treatment as a pretreatment of the cationic electrodeposition coating, it contains In, Zr, and other metals, and the ratio of In / Zr to other metals is specified, and the pH is 3 A surface treatment liquid of 0.0 to 4.4 is disclosed (Patent Document 4). However, the coating of only the surface treatment solution has insufficient anticorrosion and moisture resistance even when formed on an untreated steel sheet not subjected to chemical conversion treatment.
From such a background, a cationic electrodeposition coating composition having excellent corrosion resistance and moisture resistance adhesion on an untreated steel sheet has been demanded.

Japanese Patent Laid-Open No. 9-241546 JP 2000-290542 A JP 2003-221547 A International Publication No. 2008/105052 Pamphlet

  An object of the present invention is to find a cationic electrodeposition coating composition that is excellent in corrosion resistance, in particular, corrosion resistance and moisture resistance adhesion on an untreated steel sheet.

  As a result of intensive studies to solve the above problems, the present inventors have at least selected from the group consisting of a cationic resin (A), a blocked polyisocyanate (B), a water-soluble zirconium compound, and a water-soluble titanium compound. The present inventors have found that the above problems can be solved by a cationic electrodeposition coating composition containing one metal compound (C) and an indium compound (D), and have completed the present invention.

That is, the present invention
1. At least one metal compound (C) selected from the group consisting of a cationic resin (A), a blocked polyisocyanate curing agent (B), a water-soluble zirconium compound and a water-soluble titanium compound, and an indium compound (D) A cationic electrodeposition coating composition containing:
10 to 5,000 ppm in terms of the mass of the metal element in the metal compound (C), 10 to 5,000 ppm in terms of the mass of In and 10 to 5,000 ppm in terms of the mass of the cationic electrodeposition coating composition. The cationic electrodeposition coating composition whose mass ratio of a compound (C) and an indium compound (D) is the mass of the metal element in the metal compound (C) / mass of In = 1-70.

  2. The cationic electrodeposition coating composition according to item 1, which contains methanesulfonic acid.

  3. 3. The cationic electrodeposition coating composition according to item 1 or 2, wherein the pH of the cationic electrodeposition coating composition bath is 2.3 to 5.0.

4.1 A coated article obtained by electrodepositing and immersing a metal coating in the cationic electrodeposition coating composition according to any one of items 1 to 3 as an electrodeposition coating bath,
About.

  According to the cationic electrodeposition coating composition of the present invention, a coated article of an electrodeposition coating film excellent in corrosion resistance and moisture resistance adhesion on an untreated steel sheet without containing harmful metals such as lead compounds and chromium compounds. Can be obtained.

The reason is that a deposited layer in which at least one metal compound (C) selected from zirconium and titanium and an indium compound (D) are deposited on the surface of the material by electrodeposition coating using the cationic electrodeposition coating composition. Can be formed. This deposited layer improves the adhesion with the organic film deposited thereafter.
According to the present invention, a deposited layer can be formed on the surface of a material only with at least one metal compound (C) selected from zirconium and titanium, but the inhomogeneity of the film is insufficient by blending the indium compound (D). The insufficiency of corrosion resistance and moisture adhesion due to the fact that the

  The present invention provides at least one metal compound (C) selected from the group consisting of a cationic resin (A), a blocked polyisocyanate (B), a water-soluble zirconium compound and a water-soluble titanium compound, and an indium compound (D ) Containing a cationic electrodeposition coating composition. Details will be described below.

Cationic resin (A)
The cationic resin (A) used in the present invention is a resin having a cationizable group such as an amino group, ammonium base, sulfonium base, phosphonium base, etc. in the molecule. Examples of such resins that are commonly used include epoxy resins, acrylic resins, polybutadiene resins, alkyd resins, and polyester resins. In particular, an amine-added epoxy resin obtained by addition reaction of an amino group-containing compound with an epoxy resin is suitable from the viewpoint of both corrosion resistance and suitability for electrodeposition coating on an alloyed hot-dip steel sheet.

As the above-mentioned amine-added epoxy resin, for example,
(1) Adducts of epoxy resins with primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines (see, for example, US Pat. No. 3,984,299);
(2) Adducts of epoxy resins with secondary mono- and polyamines having primary amino groups ketiminated (see, for example, US Pat. No. 4,017,438);
(3) A reaction product obtained by etherification of an epoxy resin and a ketiminated hydroxy compound having a primary amino group (see, for example, JP-A-59-43013) can be exemplified.

  The epoxy resin used for the production of the amine-added epoxy resin is a compound having at least one, preferably two or more epoxy groups in one molecule, at least 200, preferably 400 to 4,000, more preferably. Are suitable having a [number average molecular weight] in the range of 800 to 2,500 and an epoxy equivalent weight in the range of at least 160, preferably 180 to 2,500, more preferably 400 to 1,500. Those obtained by the reaction of a polyphenol compound and epihalohydrin are preferred.

  Here, the “number average molecular weight” is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured with a gel permeation chromatograph according to the method described in JIS K 0124-83. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: under the conditions of RI.

  Examples of the polyphenol compound used for forming the epoxy resin include bis (4-hydroxyphenyl) -2,2-propane [bisphenol A], bis (4-hydroxyphenyl) methane [bisphenol F], bis ( 4-hydroxycyclohexyl) methane [hydrogenated bisphenol F], 2,2-bis (4-hydroxycyclohexyl) propane [hydrogenated bisphenol A], 4,4′-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1, 1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-2 or 3-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, Tetra (4-hydroxyphenyl) -1,1,2,2-ethane 4,4'-dihydroxydiphenyl sulfone, phenol novolak, mention may be made of cresol novolac. The said polyphenol compound can be used individually by 1 type or in combination of 2 or more types.

  Moreover, as an epoxy resin obtained by reaction of a polyphenol compound and epichlorohydrin, especially following formula (1) induced | guided | derived from bisphenol A is mentioned.

[N = 0-8]
Those represented by are preferred.

  Examples of such commercially available epoxy resins include those sold by Japan Epoxy Resins Co., Ltd. under the trade names jER828EL, jER1002, jER1004, and jER1007. The said epoxy resin can be used individually by 1 type or in combination of 2 or more types.

  Moreover, as an epoxy resin used for manufacture of an amine addition epoxy resin, by making the epoxy resin represented by the said Formula (1), the epoxy compound represented by following formula (2), and the above-mentioned polyphenol compound react. Mention may be made of the resulting epoxy resins:

[Wherein, R ² is the same or different and represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, X represents an integer of 1 to 9, and Y represents an integer of 1 to 50].

  Examples of the diepoxy compound represented by the above formula (2) include Denacol EX-850, EX-821, EX-830, EX-841, EX-861, EX-941, EX-920, EX-931 (Nagase Chem). (Tex Co., Ltd.). The said diepoxy compound can be used individually by 1 type or in combination of 2 or more types.

  Examples of the polyphenol compound to be reacted with the epoxy resin of the formula (1) and the diepoxy compound of the formula (2) include the polyphenol compounds used for the formation of the epoxy resin described above, and preferably bisphenol A is used. Can do.

  In the embodiment, the blending ratio of each component of the epoxy resin represented by the formula (1), the diepoxy compound represented by the formula (2) and the polyphenol compound is not particularly limited. For example, the total solid content of these three components The epoxy resin (solid content) represented by the formula (1) is 10 to 80% by mass, preferably 15 to 75% by mass, and the diepoxy compound (solid content) represented by the formula (2) based on the mass. It is preferable that it is 1-35 mass%, Preferably it is 2-30 mass%, and a bisphenol compound is 10-60 mass%, Preferably it is 15-50 mass%.

  The epoxy resin may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate compound or the like, and further, a lactone such as ε-caprolactone, An acrylic monomer or the like may be graft polymerized.

  Examples of the primary mono- and polyamines, secondary mono- and polyamines, and primary and secondary mixed polyamines used in the production of the amine-added epoxy resin of (1) above include monomethylamine, dimethylamine, and monoamine. Mono- or di-alkylamines such as ethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono (2-hydroxypropyl) amine, monomethylaminoethanol; ethylenediamine And alkylene polyamines such as propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine.

  Examples of the secondary mono- and polyamines having a ketimized primary amino group used in the production of the amine-added epoxy resin (2) include, for example, the production of the amine-added epoxy resin (1). Among the primary and secondary mixed polyamines used, there can be mentioned, for example, ketimine compounds obtained by reacting a ketone compound with diethylenetriamine or the like.

  Examples of the hydroxy compound having a ketiminated primary amino group used in the production of the amine-added epoxy resin (3) include, for example, a first compound used in the production of the amine-added epoxy resin (1). Of primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines, compounds having a primary amino group and a hydroxyl group, such as monoethanolamine, mono (2-hydroxypropyl) amine And the like, and a hydroxyl group-containing ketimine compound obtained by reacting a ketone compound with the above. The said hydroxy compound can be used individually by 1 type or in combination of 2 or more types.

  The above addition reaction is usually carried out in a suitable solvent at a temperature of 80 to 170 ° C., preferably 90 to 150 ° C., for 1 to 6 hours, preferably 1 to 5 hours. Examples of the solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane and n-hexane; ester solvents such as methyl acetate, ethyl acetate and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone. Ketone solvents; amide solvents such as dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, n-propanol and iso-propanol; or a mixture thereof. The said solvent can be used individually by 1 type or in combination of 2 or more types.

  When the cationic epoxy resin has an amino group as a cationizable group, it should be neutralized with an organic carboxylic acid such as formic acid, acetic acid, propionic acid or lactic acid; a sulfonic acid compound such as methanesulfonic acid. Can be water-soluble or water-dispersed.

  In particular, by containing a sulfonic acid compound such as methanesulfonic acid as a neutralizing agent, the lower metal oxide film can be uniformly deposited. Thereby, the corrosion resistance of an untreated steel plate can be improved.

  Specific examples of such sulfonic acid compounds include, for example, alkane sulfonic acids such as methanesulfonic acid and ethanesulfonic acid, aromatics such as benzenesulfonic acid, sulfanilic acid (p-aminobenzenesulfonic acid), and p-toluenesulfonic acid. Examples thereof include sulfocarboxylic acids such as sulfonic acid, 2-aminoethanesulfonic acid (taurine), sulfoacetic acid and sulfobenzoic acid, hydroxysulfoxalate, and 2-hydroxyethanesulfonic acid (isethionic acid). Among these, methanesulfonic acid is preferable from the viewpoint of the temporal stability of the paint. The said sulfonic acid compound can be used individually by 1 type or in combination of 2 or more types.

  The blending ratio of the cationic resin (A) is not particularly limited, but is, for example, 50 to 90% by mass, preferably 60 to 85% by mass with respect to the mass of the cationic electrodeposition coating composition of the present invention in terms of solid content. It can be set within the range.

Blocked polyisocyanate (B)
The cationic electrodeposition coating composition of the present invention can be made into a thermosetting cationic electrodeposition coating by using a combination of the aforementioned cationic resin (A) and blocked polyisocyanate (B).

  The blocked polyisocyanate (B) is an addition reaction product of a polyisocyanate compound and an isocyanate blocking agent in an approximately chemical theoretical amount. As the polyisocyanate compound used in the blocked polyisocyanate (B), known compounds can be used. For example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2′-diisocyanate, diphenylmethane- Aromatics such as 2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, crude MDI [polymethylene polyphenyl isocyanate], bis (isocyanate methyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate , Aliphatic or alicyclic polyisocyanate compounds; cyclized polymers or biurets of these polyisocyanate compounds Or it may be combinations thereof.

  In particular, aromatic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI and the like are more preferable for corrosion resistance.

  On the other hand, the isocyanate blocking agent is added and blocked to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition is stable at room temperature, but the coating baking temperature (usually 100 to When heated to 200 ° C., it is desirable that the blocking agent dissociates to regenerate free isocyanate groups.

  Examples of the blocking agent used in the blocked polyisocyanate (B) include oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; n-butanol, 2- Aliphatic alcohols such as ethyl hexanol; Aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; Ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; ε-caprolactam, γ-butyrolactam, etc. Lactam compounds; and the like. The said blocking agent can be used individually by 1 type or in combination of 2 or more types.

  The blending ratio of the blocked polyisocyanate (B) is not particularly limited, but is, for example, 10 to 50% by mass, preferably 15 to 40% by mass with respect to the mass of the cationic electrodeposition coating composition of the present invention in solid content ratio. % Can be set.

Metal compound (C)
The cationic electrodeposition coating composition of the present invention contains at least one metal compound (C) selected from a water-soluble zirconium compound and a water-soluble titanium compound.

  Here, the water-soluble zirconium compound is zirconium chloride, zirconyl chloride, zirconium sulfate, zirconyl sulfate, zirconium nitrate, zirconyl nitrate, zirconium hydrofluoric acid, zirconyl fluoride salt, zirconyl bromide, zirconyl acetate, zirconyl carbonate, etc. Is mentioned. The said water-soluble zirconium compound can be used individually by 1 type or in combination of 2 or more types.

  Examples of the water-soluble titanium compound include titanium chloride, titanium sulfate, titanyl sulfate, titanium nitrate, titanyl nitrate, titanium hydrofluoric acid, and a salt of fluorinated titanic acid. The said water-soluble titanium compound can be used individually by 1 type or in combination of 2 or more types.

  Among these, zirconium hydrofluoric acid and a salt of fluorinated zirconic acid are suitable because they have a high effect of improving the corrosion resistance of an untreated steel sheet when blended with a sulfonic acid compound.

  The concentration of the metal compound (C) used in the present invention is 10 in terms of the mass of the metal element with respect to the mass of the cationic electrodeposition coating composition (including moisture) in order to improve the corrosion resistance on the untreated steel plate. ˜5,000 ppm, preferably 150˜4,000 ppm.

  When the mass of the metal element in the metal compound (C) is less than 10 ppm, the corrosion resistance of the electrodeposition coating film formed on the untreated steel sheet, in particular, the corrosion resistance and moisture resistant adhesion on the untreated steel sheet is improved. It becomes difficult. Moreover, when the mass of the metal element is larger than 5,000 ppm with respect to the mass of the cationic electrodeposition coating composition, coating workability and / or coating stability may be impaired, which is not preferable.

Indium compound (D)
The cationic electrodeposition coating composition of the present invention contains an indium compound (D).
Examples of the indium compound (D) include indium nitrate, indium sulfate, indium methanesulfonate, indium sulfamate, indium fluoride, indium oxide, and indium hydroxide. The said indium nitrate can be used individually by 1 type or in combination of 2 or more types.

  The concentration of the indium compound (D) used in the present invention is 10 in terms of the mass of the metal element with respect to the mass of the cationic electrodeposition coating composition (including moisture) in order to improve the corrosion resistance on the untreated steel sheet. ˜5,000 ppm, preferably 30˜4,000 ppm.

  When the mass of the metal element in the indium compound (D) is less than 10 ppm, the corrosion resistance of the electrodeposition coating film formed on the untreated steel sheet, particularly the corrosion resistance and moisture resistance adhesion on the untreated steel sheet is improved. It becomes difficult.

  Moreover, when the mass of the metal element is larger than 5,000 ppm with respect to the mass of the cationic electrodeposition coating composition, coating workability and / or coating stability may be impaired, which is not preferable.

  Furthermore, the metal compound (C) and the indium compound (D) have a mass of the metal element / the mass of the indium metal element in the metal compound (C) = 1 to 70, preferably 2 to 50.

  Outside this range, the deposited layer of the metal compound (C) and the indium compound (D) cannot be easily formed on the object to be coated, and the corrosion resistance, in particular, the corrosion resistance and moisture resistance adhesion on the untreated steel sheet. Either of sex becomes insufficient.

  Moreover, the cationic electrodeposition coating composition of this invention can contain a nitrogen oxide ion as needed. Nitrogen oxide ion is a general term for nitrate ion, nitrite ion, etc., and by adding a compound that generates or contains nitrogen oxide ion in the cationic electrodeposition paint, the nitrogen oxide ion is contained in the cationic electrodeposition paint. Nitric acid, metal nitrate, metal nitrite and the like which can be contained in

  Specific examples of nitric acid, metal nitrate and metal nitrite include nitric acid, nitrous acid, zinc nitrate, indium nitrate, aluminum nitrate, ytterbium nitrate, yttrium nitrate, indium nitrate, molybdenum nitrate chloride, potassium nitrate, calcium nitrate, silver nitrate, Cobalt nitrate, zirconium nitrate, zirconyl nitrate, strontium nitrate, cesium nitrate, cerium nitrate, titanyl nitrate, titanium nitrate, iron nitrate, copper nitrate, samarium nitrate, neodymium nitrate, praseodymium nitrate, ruthenium nitrate, lanthanum nitrate, ruthenium nitrate, cobalt nitrate , Copper nitrate, bismuth nitrate, magnesium nitrate, zinc nitrite, potassium nitrite, calcium nitrite, cerium nitrite, cupric nitrite, copper nitrite, barium nitrite, nickel nitrite, magnesium nitrite, etc. . The nitric acid, metal nitrate and metal nitrite can be used singly or in combination of two or more.

  By blending at least one of the above nitric acid and / or metal nitrate, nitrogen oxide ions can be contained in the cationic electrodeposition coating. The content of nitrogen oxide ions in the bath of the cationic electrodeposition coating composition of the present invention is preferably 0 to 10,000 ppm, preferably 0 to 10,000 ppm, based on the mass of the cationic electrodeposition coating composition (bath). Is preferably 50 to 8,000 ppm. This range can promote the precipitation of the metal compound (C) and the indium compound (D) at the interface between the object to be coated and the film (the object to be coated), and can form a dense film. For this reason, the corrosion resistance of the electrodeposition coating film formed on an untreated steel plate, especially the warm salt-water immersion property under high temperature can be improved.

  Furthermore, in the cationic electrodeposition coating composition of the present invention, if necessary, other additives such as pigments, catalysts, organic solvents, pigment dispersants, surface conditioners, surfactants and the like are usually used in the paint field. It can contain with the compounding quantity currently used.

  Examples of the pigment and catalyst include coloring pigments such as titanium white and carbon black; extender pigments such as clay, talc and barita; rust preventive pigments such as aluminum dihydrogen phosphate and aluminum phosphomolybdate; bismuth oxide Bismuth compounds such as bismuth hydroxide and bismuth lactate; organic tin compounds such as dibutyltin oxide and dioctyltin oxide; dialkyls such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin dibenzoate, and dibutyltin dibenzoate Tin compounds such as tin aliphatic or aromatic carboxylates may be mentioned. The said pigment and catalyst can be used individually by 1 type or in combination of 2 or more types.

  Specifically, the cationic electrodeposition coating composition of the present invention can be adjusted by methods (1) to (3) described below.

  Method (1): The cationic resin (A), the blocked polyisocyanate (B), and optionally other additives are combined together and mixed thoroughly to form a dissolution varnish, and a neutralizing agent is added and water is added. The method of mix | blending the emulsion which mix | blended the metal compound (C), the indium compound (D), and the nitrogen oxide ion as needed with the emulsion formed by dispersion | distribution, and a pigment dispersion paste.

  Method (2): A metal compound (C), an indium compound (D), nitrogen oxide ions are blended as necessary, and a pigment component, a neutralizing agent, a catalyst, other additives, and water are added and dispersed. A method of preparing a pigment dispersion paste and blending the pigment dispersion paste into an emulsion containing the cationic resin (A) and the blocked polyisocyanate (B).

  Method (3): A metal electrode (C), an indium compound (D), a neutralizing agent, and a bath of a cationic electrodeposition coating material (cationic resin (A), blocked polyisocyanate (B)) prepared in advance. And a method of blending nitrogen oxide ions.

  The cationic electrodeposition coating composition can be produced by at least one method selected from the above methods (1) to (3).

  The cationic electrodeposition coating composition is prepared by adjusting the emulsion and the pigment dispersion paste with deionized water or the like, so that the bath solid content concentration is usually 5 to 40% by mass, preferably 8 to 25% by mass, and the pH is 2. It can be carried out so that it falls within the range of 0 to 7.0, preferably 2.3 to 5.0.

  The coating film formation using the cationic electrodeposition coating composition of the present invention can be carried out by a conventionally known method without any particular limitation, and specifically, energization immediately after the object to be coated is immersed in the bath of the cationic electrodeposition coating. Then, a method of forming a coating film (so-called “one-step method”), or immersion or electrodeposition of an object to be coated in a cationic electrodeposition paint bath for a certain period of time (perform electrodeposition coating at a low voltage) Then, a method of forming a coating film by so-called electrodeposition coating (so-called “two-step method”) can be mentioned.

  Examples of the object to be coated include an automobile body, a two-wheeled vehicle part, a household device, and other devices. Examples of metal steel plates to be coated include cold-rolled steel plates, galvannealed steel plates, electrogalvanized steel plates, electrogalvanized steel double-layer plated steel plates, organic composite plated steel plates, Al materials, Mg materials, and these metals. The surface of the plate may be subjected to surface treatment such as phosphate chemical conversion after cleaning the surface such as alkali degreasing as required.

  In the above two methods, the object to be coated is immersed in a cationic electrodeposition paint bath for a certain period of time (step 1) and then electrodeposited (step 2). Since a film can be formed, it is more preferable from the viewpoint of improving corrosion resistance.

  In the above-mentioned “method by two steps”, specifically, the cationic electrodeposition coating composition is placed in a bath to form a bath, and the metal coating is immersed at a bath temperature of 15 to 55 ° C., preferably 20 to 50 ° C. Thus, a film can be formed. As the immersion time, a dense passivated film can be formed on the object to be coated by immersing the object to be coated for 10 to 600 seconds, preferably 30 to 480 seconds (Step 1).

  Next, a coating film is deposited on the object to be coated by applying current for 60 to 600 seconds, preferably 80 to 400 seconds at a coating voltage of 50 to 400 V, preferably 75 to 370 V, using a metal substrate as a cathode (step 2). be able to.

  In addition, as a bath temperature of a cationic electrodeposition coating-material composition, the deposit film with few defects can be formed uniformly within the range of 10-55 degreeC normally, Preferably it is 20-50 degreeC. It is also possible to take out the object to be dipped in the metal object from the tank, and further immerse the metal object again and apply electrodeposition.

  Continuously forming a second layer (upper layer) having a composition with a resin component and a pigment as main components on the first layer (lower layer) by the above-described two-step coating film forming method. As a result, it is possible to form a multilayered film structure with better corrosion resistance and finish.

  The deposition mechanism of the film using the cationic electrodeposition coating is such that when the step 1 is performed by immersion, the metal coating is first an etching action of acid and nitrogen oxide ions contained in the cationic electrodeposition coating composition. As a result, the pH in the vicinity of the object to be coated is increased, and then the metal ion species (for example, zirconium hexafluoride ion, indium ion) undergo a hydrolysis reaction to form a slightly soluble first layer (lower layer) (mainly In addition, for example, zirconium oxide and indium oxide) are deposited on the object to be coated. Thereafter, a second film (upper layer) is deposited.

  The baking temperature of the film thus obtained is 100 to 200 ° C., preferably 120 to 180 ° C. on the surface of the object to be coated, and the baking time is 5 to 90 minutes, preferably 10 Can be up to 50 minutes.

  Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, “parts” indicates mass parts, and “%” indicates mass%.

Production of amine-modified epoxy resin (A)
Production Example 1 Production Example of Amino Group-Containing Epoxy Resin Solution In a separable flask having an internal volume of 2 liters equipped with a thermometer, reflux condenser and stirrer, 638.9 parts of jER828EL (Note 1) (solid content 638.9 parts) , Denacol EX821 (Note 2) 300.0 parts (solid content 300.0 parts), bisphenol A 404.2 parts (solid content 404.2 parts) and dimethylbenzylamine 0.2 parts, and epoxy equivalent at 130 ° C The reaction was continued until 900.

  Next, after adding 156.9 parts of diethanolamine and making it react at 120 degreeC for 4 hours, 375.0 parts of ethylene glycol monobutyl ether was added, and the amino group containing epoxy resin solution of 80 mass% of resin solid content was obtained.

The amino group-containing epoxy resin had an amine value of 56 mgKOH / g and a number average molecular weight of 2,000.
(Note 1) jER828EL: manufactured by Japan Epoxy Resin Co., Ltd., trade name, epoxy resin, epoxy equivalent 190, number average molecular weight 380
(Note 2) Denacol EX821: manufactured by Nagase ChemteX Corporation, trade name, epoxy resin, epoxy equivalent 185. Corresponds to the diepoxy compound represented by the above formula (2) (R2 = hydrogen atom, X = 1, Y = 4)
Production of blocked polyisocyanate (B)
Production example 2 Production example of curing agent 270 parts of Cosmonate M-200 (Note 3) and 127 parts of methyl isobutyl ketone were added to the reaction vessel, and the temperature was raised to 70C. In this, 236 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, and then heated to 100 ° C., sampled over time while maintaining this temperature, and measured for unreacted isocyanate groups by infrared absorption spectrum measurement. After confirming that absorption was lost, a curing agent having a resin solid content of 80% was obtained.
(Note 3) Cosmonate M-200: Trade name, manufactured by Mitsui Chemicals, Crude MDI.

Production Example 3 Production Example of Resin for Dispersing Pigment jER828EL (see Note 1) 1,010 parts, 390 parts of bisphenol A, 240 parts of Plaxel 212 (Note 4) and 0.2 part of dimethylbenzylamine were added at 130 ° C. The reaction was continued until the epoxy equivalent was about 1,090.

Next, 134 parts of dimethylethanolamine and 150 parts of a 90% aqueous lactic acid solution were added and reacted at 120 ° C. for 4 hours. Next, methyl isobutyl ketone was added to adjust the solid content, and an ammonium salt resin-based pigment dispersion resin having a solid content of 60% was obtained. The ammonium salt concentration of the dispersing resin was 0.78 mmol / g.
(Note 4) Plaxel 212: polycaprolactone diol, Daicel Chemical Industries, Ltd., trade name, weight average molecular weight of about 1,250.

Production Example 4 Production Example of Pigment Dispersion Paste 8.3 parts of pigment dispersion resin 60% solid content obtained in Production Example 3 (5 parts solids), 14.5 parts titanium oxide, 7.0 parts refined clay, carbon 0.3 parts of black, 1 part of dioctyl tin oxide, 1 part of bismuth hydroxide and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste having a solid content of 55%.

Emulsion production
Production Example 5 Emulsion No. 87.5 parts of an amino group-containing epoxy resin obtained in 1 of Preparation Example Preparation Example 1 (solid content 70 parts), mixing 37.5 parts of a curing agent obtained in Production Example 2 (solid content 30 parts) Further, 30.8 parts of 10% methanesulfonic acid was added and stirred uniformly, and then 138.2 parts of deionized water was added dropwise over about 15 minutes with vigorous stirring to obtain a solid content of 34%. Emulsion No. 1 was obtained.

Production Examples 6 to 7 Emulsion No. 2-No. 3 Production Example Emulsion No. 5 was prepared in the same manner as in Production Example 5 except that the contents of Table 1 were used. 2-No. 3 was obtained.

Production of cationic electrodeposition paints
Example 1
Emulsion No. 1 part 294 parts (solid content 100 parts), 55 parts pigment dispersion paste obtained in Production Example 4 52.4 parts (solid content 28.8 parts), deionized water 653.6 parts and 1,000 parts The bath. Subsequently, 14.0 parts of 10% zirconium hydrofluoric acid (1.4 parts of solid content) and 3.0 parts (0.3 parts) of 10% indium nitrate were added thereto to add cationic electrodeposition paint No. 1 was obtained.

Examples 2-7
A cationic electrodeposition paint No. 1 was prepared in the same manner as in Example 1 except that the formulation shown in Table 2 below was used. 2-No. 7 was obtained.

Comparative Examples 1-6
A cationic electrodeposition paint No. 1 was prepared in the same manner as in Example 1 except that the formulation shown in Table 3 below was used. 8-No. 13 was obtained.

A cold-rolled steel sheet (70 mm × 150 mm × 0.8 mm) that has not been subjected to chemical conversion treatment on the object to be coated is immersed in an ultrasonic cleaner containing toluene and subjected to ultrasonic degreasing for 30 minutes. did.

Preparation and evaluation of cationic electrodeposition coating plate Each cationic electrodeposition coating No. 1-No. 13 baths were adjusted to 30 ° C., the “coating material” was immersed for 120 seconds (step 1), then the energization time was adjusted at 200 V and electrodeposition was applied (step 2), and baked at 170 ° C. for 20 minutes. Each test plate having a dry film thickness of 15 μm was prepared. Each test plate was evaluated according to the following conditions. Table 4 shows the results of the examples and Table 5 shows the results of the comparative examples.

(Note 5) Salt spray resistance:
A cross-cut wound was made with a knife so as to reach the base of the electrodeposition coating film obtained in Step 1 of each Example and Comparative Example, and this was subjected to a salt water spray test for 840 hours in accordance with JIS Z-2371. Evaluation based on the following criteria based on rust and blister width from:
◎ indicates that the maximum width of rust and blisters is less than 1.5mm from the cut part (one side)
○: The maximum width of rust and blisters is 1.5 mm or more and less than 2.5 mm (one side) from the cut part.
△ indicates that the maximum width of rust and blisters is 2.5 mm or more and less than 3.5 mm from the cut part (one side)
X: The maximum width of rust and blisters is 3.5 mm or more (one side) from the cut part.

(Note 6) Moisture resistant adhesion:
After spray-coating WP-300 (trade name, aqueous intermediate coating material, manufactured by Kansai Paint Co., Ltd.) on the test plate so that the cured film thickness is 25 μm, it is baked at 140 ° C. for 30 minutes with an electric hot air dryer. Was done. Furthermore, after spray-coating Neo Amirac 6000 (manufactured by Kansai Paint Co., Ltd., trade name, top coat) on the intermediate coating film so as to have a cured film thickness of 35 μm, an electric hot air dryer is used at 140 ° C. for 30 minutes. A test plate was prepared by baking for a minute.

Next, after putting it in a 50 ° C blister box for 240 hours, cut it with a cutter so that it reaches the substrate, make 100 2mm wide goblet eyes, stick an adhesive tape on the surface, and peel off abruptly at 20 ° C Observed the number of remaining coatings;
◎: remaining number / total number = 100/100, no missing edges ○: remaining number / total number = 100/100, no edges missing Δ: remaining number / total number = 99 to 90 / 100 pieces x: remaining number / total number = 89 or less / 100 pieces.

Comprehensive evaluation In the field of electrodeposition coating of metal objects to which the present invention belongs, it is important to form a coating film having both high corrosion resistance and moisture resistance adhesion. Therefore, a comprehensive evaluation was performed according to the following criteria:
A: Both salt spray resistance and moisture adhesion resistance are A.
○: The above two test results are ◎ or ○, and at least one is ○.
Δ: The above two test results are ◎, ○ or Δ, and at least one is Δ.
X: At least one of the above two test results is x.

  It is possible to provide a coated article excellent in corrosion resistance on an untreated steel sheet, in particular, warm salt water immersion resistance at high temperatures and electrodeposition coating suitability in an alloyed hot-dip galvanized steel sheet.

Claims (3)

At least one metal compound (C) selected from the group consisting of a cationic resin (A), a blocked polyisocyanate curing agent (B), a water-soluble zirconium compound and a water-soluble titanium compound, and an indium compound (D) A cationic electrodeposition coating composition containing:
10 to 5,000 ppm in terms of the mass of the metal element in the metal compound (C), 10 to 5,000 ppm in terms of the mass of In and 10 to 5,000 ppm in terms of the mass of the cationic electrodeposition coating composition. A cationic electrodeposition coating composition in which the mass ratio of the compound (C) and the indium compound (D) is the mass of the metal element in the metal compound (C) / the mass of In = 1 to 70 ,
A cationic electrodeposition coating composition containing methanesulfonic acid . The cationic electrodeposition coating composition according to claim 1, wherein the pH of the bath of the cationic electrodeposition coating composition is 2.3 to 5.0. A coated article obtained by subjecting the cationic electrodeposition coating composition according to claim 1 or 2 to an electrodeposition coating bath, immersing a metal coating in the electrodeposition coating bath, and performing electrodeposition coating.