JP6085499B2 - Electrodeposition painting method - Google Patents

Description

  The present invention relates to an electrodeposition coating method capable of forming an electrodeposition coating film having excellent corrosion resistance.

  Electrodeposition coating can be applied to the details even if the workpiece has a complicated shape, and can be applied automatically and continuously, especially in large and complex shapes such as automobile bodies. It has been widely put into practical use as an undercoating method for articles to be coated. Cationic electrodeposition coating is widely used as such electrodeposition coating. Cationic electrodeposition coating is a coating method performed by immersing an object to be coated as a cathode in a cationic electrodeposition coating composition and applying a voltage.

  Before the cationic electrodeposition coating, the article to be coated is often subjected to a chemical conversion treatment such as a zinc phosphate chemical conversion treatment. By performing this chemical conversion treatment, corrosion resistance and adhesion can be improved. However, since the chemical conversion composition used in the zinc phosphate chemical conversion treatment has a high metal ion concentration and is very reactive, it is not preferable from the viewpoints of economy and workability, such as costly wastewater treatment. Further, in the chemical conversion treatment using the zinc phosphate-based chemical conversion treatment composition, water-insoluble salts are generated along with the metal surface treatment, and are deposited as precipitates in the chemical conversion treatment tank. Such precipitates are generally called sludge, and the generation of costs associated with the removal and disposal of sludge is regarded as a problem. In addition, phosphate ions may cause environmental load such as eutrophication of rivers and oceans. In addition, in the surface treatment with the zinc phosphate-based chemical conversion treatment composition, it is necessary to prepare the surface in advance, and there is a problem in production efficiency that the surface treatment process becomes complicated and long.

  In place of such a zinc phosphate-based chemical conversion treatment composition, methods using a zirconium-based chemical conversion treatment composition are being studied. However, since the chemical conversion film formed from the zirconium-based chemical conversion treatment composition is thinner than the chemical conversion film formed from the zinc phosphate-based chemical conversion treatment composition, the surface current becomes non-uniform during electrodeposition. , Paint appearance and throwing power will decrease. Zirconium-based chemical conversion treatment compositions can produce less sludge than zinc phosphate-based chemical conversion treatment compositions, but sludge generation is unavoidable due to the deposition principle of forming a film by etching the coating. .

JP2011-84729A (Patent Document 1) and JP2011-84723A (Patent Document 2) related to Patent Document 1 include zirconium, titanium, cobalt, vanadium, and a cationic electrodeposition coating composition. Compounding at least one metal selected from tungsten, molybdenum, copper, indium, zinc, aluminum, bismuth, yttrium, lanthanoid metal, alkali metal and alkaline earth metal, in the presence of nitrogen oxide ions, It describes that electrodeposition coating is performed after a metal to be coated is immersed for a predetermined time. This method describes a method in which electrodeposition coating is carried out after forming a passivated film on the surface of an object to be coated by immersing it directly in an electrodeposition bath without subjecting it to a chemical conversion treatment. However, the metal types actually used in the examples are all only one metal, there is no example of using two or more types, and a combination of zinc and another metal is not described.
In addition, the formation of a passivated film by immersion in an electrodeposition bath inevitably generates sludge because of the reaction of the chemical conversion film that etches the substrate. Another problem is a decrease in paintability due to an increase in conductivity due to the eluted iron ions.

  In Japanese translations of PCT publication No. 2008-538383 (Patent Document 3), a rare earth metal compound is blended in an electrodeposition coating, and the object to be coated is treated at a voltage of less than 50 V, and then electrodeposition is applied at a voltage of 50 to 450 V. A method for forming a multilayer coating film is described. This method also omits the chemical conversion treatment by immersing it directly in the electrodeposition bath without subjecting it to chemical conversion treatment, and performing electrodeposition in two steps of a weak voltage and a strong voltage. The method of not applying is not described. This is not practical because the corrosion resistance is inferior to that in the case of pretreatment, and it is substantially very difficult to uniformly control the potential of a structure such as an automobile body.

JP 2011-84729 A JP 2011-84723 A Special table 2008-538383 gazette

  The present invention eliminates the chemical conversion treatment of the object to be coated, and in the method of direct electrodeposition coating, the electrodeposition coating having high corrosion resistance and high adhesion is formed by the simplified treatment, and at the same time, a structure in which a potential difference occurs. An electrodeposition coating method that maintains the same quality as that before the chemical conversion treatment and does not generate sludge is also provided.

In the present invention, an electrodeposition film is formed by applying a voltage after immersing an object to be coated that has not been subjected to chemical conversion treatment in an electrodeposition coating composition for 0 to 30 seconds without applying a voltage. An electrodeposition coating method comprising a step and a step of heat-curing the electrodeposition coating to form an electrodeposition coating,
The electrodeposition coating composition is
A dissolved zinc compound (A1) and a dissolved zirconium compound (A2), an aminated resin (B), a curing agent (C), and a metal nitrite (D), the aminated resin (B) The number average molecular weight is 1,000 to 5,000, the amine value is 20 to 100 mgKOH / g, the hydroxyl value is 50 to 400 mgKOH / g, and
The curing agent (C) is a blocked isocyanate curing agent,
Electrodeposition characterized by having a theoretical residual hydroxyl value of 50 to 350 mgKOH / g when the aminated resin (B) and the blocked isocyanate curing agent react in a heat-cured state in an electrodeposition coating film It provides a painting method.

The present invention further provides the following aspects:
The electrodeposition coating composition is further a chelating acid (which is at least one selected from the group consisting of sulfonic acid, organic phosphonic acid, organic carboxylic acid, amino acid, aminocarboxylic acid, sugar acid and carboxyl group-containing vinyl resin) Including E).
The electrodeposition coating composition further contains an aminosilane compound (F).
The electrodeposition coating composition further contains a plasticizer.

  According to the electrodeposition coating method of the present invention, even if the object to be coated is not subjected to zinc phosphate chemical conversion treatment or zirconium chemical conversion treatment, it has good corrosion resistance simply by dipping the object to be coated and performing electrodeposition coating. An electrodeposition coating can be obtained. By using the electrodeposition coating method of the present invention, it is possible to omit the zirconium chemical conversion treatment and the zinc phosphate chemical conversion treatment step on the object to be coated, and reduce the cost and labor required for the maintenance management accompanying the chemical conversion treatment. can do. Furthermore, since no chemical conversion treatment is performed, the problem of sludge that always occurs in the chemical conversion treatment does not occur. Needless to say, the electrodeposition coating method of the present invention can form an effective film even on an object subjected to zirconium chemical conversion treatment or zinc phosphate chemical conversion treatment.

  In the electrodeposition coating method of the present invention, when a specific electrodeposition coating composition containing a dissolved zinc compound and a dissolved zirconium compound and containing a metal nitrite is used, an electrodeposition coating film having corrosion resistance and adhesion can be obtained. Can do. When the object to be coated is immersed in the electrodeposition coating composition, an inorganic layer composed of a composite of zinc and zirconium is immediately deposited on the object to be coated. Therefore, after immersion for 0 to 30 seconds without applying a voltage, When a step of forming an electrodeposition film by applying a voltage is performed, the inorganic layer is formed on the object to be coated, and the electrode layer is a resin film mainly composed of a resin contained in the electrodeposition coating composition. A deposit is formed.

As is well known, zinc is a readily available metal species, and in combination with zirconium and in combination with a metal nitrite, the inorganic layer formed on the object to be coated becomes uniform and dense. As a result, it is considered that the corrosion resistance and adhesion are improved.

Definition of Terms In the present specification, “substantially not chemically treated” refers to a chemical treatment performed before dipping the coated material in an electrodeposition coating bath, such as a zinc phosphate chemical treatment or the like. This means that zirconium conversion treatment is not performed, but other treatments such as degreasing treatment are performed.

Electrodeposition Paint Composition The electrodeposition paint composition used in the electrodeposition coating method of the present invention comprises a dissolved zinc compound (A1) and a dissolved zirconium compound (A2), which are dissolved metal compounds, an aminated resin (B), and a curing agent. (C) and metal nitrite (D). Hereinafter, each component will be described in detail.

Dissolved zinc compounds (A1) and dissolved zirconium compounds (A2) which are dissolved metal compounds
The electrodeposition coating composition used in the electrodeposition coating method of the present invention contains dissolved zinc compound (A1) and dissolved zirconium compound (A2), which are dissolved metal compounds, as essential components. In the present specification, the dissolved metal compound is one in which 0.1% by mass or more in terms of metal is dissolved in water at 20 ° C. adjusted to pH 4 with nitric acid. This dissolved metal compound has the above-described properties, and therefore exists in a state where all of the dissolved metal compound is dissolved in the electrodeposition coating composition, or a part thereof is dissolved and the rest is dispersed. Here, dissolution refers to a state in which it is dissolved in a solvent and is uniform and a state in which it is finely dispersed. Specifically, it means a state in which precipitation does not occur when centrifugation is performed at 12,000 rpm for 30 minutes. When this dissolved metal compound is partly dissolved but is dispersed in the electrodeposition coating composition, the volume average particle diameter D50 is preferably 3 μm or less. Here, the volume average particle diameter D50 can be measured using a particle size measuring device such as a dynamic light scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., “Nanotrack UPA150”). When the electrodeposition coating composition used in the present invention contains the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) which are such dissolved metal compounds, an electrodeposition coating film having excellent corrosion resistance can be obtained. It becomes. Specifically, in the specific electrodeposition coating composition used in the electrodeposition coating method of the present invention, the dissolved zinc compound (A1) and the dissolved zirconium compound (A2), which are dissolved metal compounds, are in the initial stage of the electrodeposition coating process. Adhesiveness is imparted to the electrodeposition coating after heat curing by forming an inorganic layer composed of a composite of zinc and zirconium on the substrate surface in preference to the resin coating. Zinc and zirconium are also taken into the resin film and, as an inorganic cross-linking agent during baking, improve the blocking density by improving the cross-linking density and glass transition temperature (Tg) of the coating film. For this reason, the cured electrodeposition coating film which has the outstanding corrosion resistance will be obtained.

  In the present invention, the dissolved zinc compound (A1) is a zinc (Zn) compound and corresponds to a dissolved metal compound, the dissolved zirconium compound (A2) is a zirconium (Zr) compound, and is a dissolved metal. It corresponds to a compound.

  When the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) are used as the dissolved metal compound, the electrodeposition coating composition used in the electrodeposition coating method of the present invention combines zinc and zirconium with a nitrite metal salt described later. This improves the depositability of the film, makes it possible to form a uniform and dense composite film of zinc and zirconium, and improves the adhesion of the electrodeposition coating film.

Examples of the dissolved zinc compound (A1) include zinc compounds such as zinc oxide, zinc hydroxide, zinc acetate, zinc lactate, zinc nitrate, zinc methanesulfonate, zinc formate, and zinc phosphate, and methanesulfonic acid. Zinc and zinc oxide are preferable, and zinc methanesulfonate is particularly preferable. Since zinc methanesulfonate contains a chelating acid, it is excellent in electrodeposition paintability, and zinc oxide is excellent in electrodeposition paintability because it is difficult to increase the conductivity of the paint. Among the dissolved zinc compounds (A1) exemplified above, zinc oxide, zinc hydroxide and zinc phosphate are partly dissolved as dissolved metal compounds and partly present as fine particles, and are dispersed with a cationic dispersant. In addition, it is preferable that the volume average particle diameter D50 is 3 μm or less. Here, as the cationic dispersant, for example, a dispersion resin having a cationic group, such as a modified epoxy resin having at least one kind selected from a quaternary ammonium group, a tertiary sulfonium group, and a primary amine group, and An aminosilane compound (F) etc. are mentioned. The volume average particle diameter D50 of zinc oxide, zinc hydroxide, zinc phosphate and the like dispersed with a cationic dispersant is 0.05 μm or more because the storage stability of the pigment dispersion paste is improved. preferable.

Examples of the dissolved zirconium compound (A2) include, for example, fluorinated zirconate; salts of fluorinated zirconate such as potassium fluoride zirconate and ammonium fluoride zirconate; zirconium fluoride; zirconium oxide; zirconium nitrate; Zirconyl nitrate, zirconyl sulfate, zirconyl carbonate, zirconyl acetate and the like can be mentioned, and zirconyl fluoride and zirconyl nitrate are preferable.

The content of the dissolved zinc compound (A1) contained in the electrodeposition coating composition used in the electrodeposition coating method of the present invention is preferably 0.01 to 0.3% by mass in terms of metal element. It is more preferable that it is 002-0.2 mass%. Here, the “metal element conversion” is a metal element conversion coefficient (a coefficient for converting the metal compound amount into the metal element amount to the content of the metal compound, and specifically, the metal element conversion factor of the metal compound. It means the value obtained by dividing the atomic weight by the molecular weight of the metal compound.) To obtain the target metal element amount. For example, when the dissolved zinc compound (A1) is zinc acetate (C ₄ H ₆ O ₄ Zn, molecular weight 183.48), the metal element equivalent content of 0.01% by mass of zinc is 0.01% by mass × It is calculated as 0.00356 mass% by calculation of (65.38 ÷ 183.48). When the dissolved zinc compound (A1) content is 0.01% by mass or more in terms of zinc metal element, good corrosion resistance can be imparted to the article to be coated. Further, when the content of the dissolved zinc compound (A1) is 0.3% by mass or less in terms of zinc metal element, aggregation with the aminated resin is suppressed, and storage stability, corrosion resistance, and paintability are ensured. .

  The dissolved zirconium compound (A2) is preferably 0.003 to 0.3% by mass, more preferably 0.01 to 0.1% by mass in terms of zirconium metal element. If the amount is less than 0.003% by mass, the amount of precipitation cannot be secured sufficiently, and the resulting electrodeposition coating film has a disadvantage that the corrosion resistance is lowered. May decrease.

  The content ratio of the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) in the electrodeposition coating composition used in the electrodeposition coating method of the present invention is 0.01% to 1000% by mass of Zn / Zr. Is preferable, and it is more preferable that it is 0.1-100. When the mass ratio of Zn / Zr is less than 0.01, the amount of zinc deposited on the inorganic layer is insufficient and the corrosion resistance is reduced. When it is more than 1000, the combined effect with Zr is small and the corrosion resistance is reduced. To do.

  In an electrodeposition coating composition, an organic tin curing catalyst such as dibutyltin dilaurate or dioctyltin oxide is generally used as a curing catalyst in many cases. On the other hand, these organotin compounds have recently been regarded as problematic in their toxicity and are being studied for use regulations, and therefore preferably do not contain an organotin curing catalyst. The electrodeposition coating composition used in the electrodeposition coating method of the present invention can contain an organotin curing catalyst, but it does not contain an organotin curing catalyst, and the dissolved zinc compound (A1) and the dissolved zinc compound can be dissolved. By including the zirconium compound (A2), there is a feature of having excellent heat curability.

Aminated resin (B)
The electrodeposition coating composition used in the electrodeposition coating method of the present invention contains an aminated resin (B). This aminated resin (B) is a coating film forming resin constituting the electrodeposition coating film obtained by the electrodeposition coating method of the present invention. As the aminated resin (B), a cation-modified epoxy resin obtained by modifying an oxirane ring in the resin skeleton with an organic amine compound is preferable. In general, a cation-modified epoxy resin is produced by ring-opening an oxirane ring in a starting material resin molecule by a reaction with a primary amine, a secondary amine, a tertiary amine, and / or an amine such as an acid salt thereof. A typical example of the starting material resin is a polyphenol polyglycidyl ether type epoxy resin which is a reaction product of a polycyclic phenol compound such as bisphenol A, bisphenol F, bisphenol S, phenol novolak, cresol novolak, and epichlorohydrin. Examples of other starting material resins include oxazolidone ring-containing epoxy resins described in JP-A-5-306327. These epoxy resins can be prepared by reacting a diisocyanate compound or a bisurethane compound obtained by blocking an isocyanate group of a diisocyanate compound with a lower alcohol such as methanol or ethanol, and epichlorohydrin.

  The starting material resin can be used by extending the chain with a bifunctional polyester polyol, polyether polyol, bisphenol, dibasic carboxylic acid or the like before the ring-opening reaction of the oxirane ring with amines.

  Similarly, before the oxirane ring-opening reaction with amines, 2-ethylhexanol, nonylphenol, ethylene glycol is used for some oxirane rings for the purpose of adjusting molecular weight or amine equivalent and improving heat flow. Monohydroxy compounds such as mono-2-ethylhexyl ether, ethylene glycol mono n-butyl ether, and propylene glycol mono-2-ethylhexyl ether can also be added and used.

  Examples of amines that can be used for opening an oxirane ring and introducing an amino group include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine , N, N-dimethylbenzylamine, primary amines such as N, N-dimethylethanolamine, secondary amines or tertiary amines and / or their acid salts. Further, ketimine block primary amino group-containing secondary amine such as aminoethylethanolamine methyl isobutyl ketimine, diethylenetriamine diketimine can also be used. These amines must be reacted with at least an equivalent amount relative to the oxirane ring in order to open all the oxirane rings.

  The number average molecular weight of the aminated resin (B) is 1,000 to 5,000. When the number average molecular weight is 1,000 or more, physical properties such as solvent resistance and corrosion resistance of the obtained cured electrodeposition coating film are improved. On the other hand, when the number average molecular weight is 5,000 or less, viscosity adjustment of the aminated resin is facilitated and smooth synthesis is possible, and handling of emulsified dispersion of the obtained aminated resin (B) is possible. Becomes easier. The number average molecular weight of the aminated resin (B) is preferably in the range of 1,600 to 3,200.

  In addition, in this specification, a number average molecular weight is a number average molecular weight of polystyrene conversion measured by gel permeation chromatography (GPC).

  The amine value of the aminated resin (B) is in the range of 20 to 100 mgKOH / g. When the amine value of the aminated resin (B) is 20 mgKOH / g or more, the emulsion dispersion stability of the aminated resin (B) in the electrodeposition coating composition is improved. On the other hand, when the amine value is 100 mgKOH / g or less, the amount of amino groups in the cured electrodeposition coating film becomes appropriate, and there is no possibility of reducing the water resistance of the coating film. The amine value of the aminated resin (B) is preferably in the range of 20 to 80 mgKOH / g.

  The hydroxyl value of the aminated resin (B) is in the range of 50 to 400 mgKOH / g. When the hydroxyl value is 50 mgKOH / g or more, the cured electrodeposition coating film is cured well. On the other hand, when the hydroxyl value is 400 mgKOH / g or less, the amount of the hydroxyl group remaining in the cured electrodeposition coating film becomes appropriate, and there is no possibility of reducing the water resistance of the coating film. The hydroxyl value of the aminated resin (B) is preferably in the range of 100 to 300 mgKOH / g.

  In the electrodeposition coating composition used in the present invention, an amination having a number average molecular weight of 1,000 to 5,000, an amine value of 20 to 100 mgKOH / g, and a hydroxyl value of 50 to 400 mgKOH / g By using the resin (B), there is an advantage that excellent corrosion resistance can be imparted to the article to be coated.

  In addition, as an amination resin (B), you may use together the amination resin from which an amine value and / or a hydroxyl value differ as needed. When two or more types of amine resins having different amine values and hydroxyl values are used in combination, the average amine value and average hydroxyl value calculated based on the mass ratio of the aminated resin to be used must be within the above numerical range. is there. The aminated resin (B) used in combination has an amine value of 20 to 50 mgKOH / g and a hydroxyl value of 50 to 300 mgKOH / g, and an amine value of 50 to 200 mgKOH / g. And combined use with an aminated resin having a hydroxyl value of 200 to 500 mgKOH / g is preferred. When such a combination is used, since the core part of the emulsion becomes more hydrophobic and the shell part becomes hydrophilic, there is an advantage that excellent corrosion resistance can be imparted.

  The aminated resin (B) may contain an amino group-containing acrylic resin, an amino group-containing polyester resin, or the like as necessary.

Curing agent (C)
The electrodeposition coating composition used in the present invention uses a blocked isocyanate curing agent as the curing agent (C) in view of storage stability and coating performance. This curing agent (C) is also a coating film forming resin constituting the electrodeposition coating film. As the curing agent, at least one curing agent selected from the group consisting of organic curing agents such as melamine resins and phenol resins, silane coupling agents, and metal curing agents may be used in combination with the curing agent (C). The blocked isocyanate curing agent can be prepared by blocking polyisocyanate with a sealing agent.

  Examples of polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate (including trimers), tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate, isophorone diisocyanate, and fats such as 4,4′-methylenebis (cyclohexyl isocyanate). Aromatic diisocyanates such as cyclic polyisocyanate, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate and the like can be mentioned.

  Examples of sealants include monovalent alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenol carbinol, methylphenyl carbinol; ethylene glycol mono Cellosolves such as hexyl ether and ethylene glycol mono 2-ethylhexyl ether; Polyether type terminal diols such as polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol phenol; ethylene glycol, propylene glycol, 1,4-butanediol, etc. Polyester type terminal polyols obtained from diols of the above and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid and sebacic acid; para-t-butyl Phenols such as enol and cresol; oximes such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl amyl ketoxime and cyclohexanone oxime; and lactams typified by ε-caprolactam and γ-butyrolactam are preferably used. .

  The blocking ratio of the blocked isocyanate curing agent is preferably 100%. Thereby, there exists an advantage that the storage stability of an electrodeposition coating composition becomes favorable.

  In the electrodeposition coating composition used in the present invention, the theoretical residual hydroxyl group in the case where the aminated resin (B) and the curing agent (C) which is a blocked isocyanate curing agent react at the time of heat curing in the electrodeposition coating film. The condition is that the value is 50 to 350 mg KOH / g. Here, the “theoretical residual hydroxyl value” means that when the electrodeposition coating obtained by electrodeposition coating is cured by heating, the aminated resin (B) and the curing agent (C) that is a blocked isocyanate curing agent are It means the hydroxyl value derived from the aminated resin (B) remaining in the electrodeposition coating after the reaction.

  When the theoretical residual hydroxyl value satisfies 50 to 350 mgKOH / g, excellent corrosion resistance is exhibited in the cured electrodeposition coating film. This is because the remaining hydroxyl group derived from the aminated resin (B) in the cured electrodeposition coating film after the amination resin (B) and the curing agent (C) which is a blocked isocyanate curing agent react by heat curing. And zinc and zirconium derived from the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) form a hydrogen bond, thereby improving the adhesion between the object to be coated and the electrodeposition coating film. It is presumed that.

  The curing agent (C) which is a blocked isocyanate curing agent preferentially reacts with the primary amine of the aminated resin (B), and further reacts with a hydroxyl group to be cured. In the cured electrodeposition coating film after the amination resin (B) and the blocked isocyanate curing agent have reacted by heat curing, the remaining hydroxyl group derived from the amination resin (B) is dissolved zinc compound (A1). It is considered that the adhesion between the coating object and the electrodeposition coating film is improved by interacting with zinc and zirconium derived from the dissolved zirconium compound (A2).

  The theoretical residual hydroxyl value in the case where the aminated resin (B) and the blocked isocyanate curing agent react during heat curing in the electrodeposition coating film is 1 with the hydroxyl value (mgKOH / g) of the aminated resin (B). The ratio of the mass of the aminated resin (B) to the sum of the mass of the aminated resin (B) and the mass of the curing agent (C) to the total of the secondary amine value (mgKOH / g) ((B) / (B) + (C)), the curing agent (C) with respect to the sum of the isocyanate group value (mgKOH / g) of the curing agent (C) and the mass of the aminated resin (B) and the mass of the curing agent (C). ) Mass ratio ((C) / (B) + (C)). For example, the primary amine value of the aminated resin is 17 mgKOH / g, the hydroxyl value is 240 mgKOH / g, the isocyanate group value of the curing agent is 252 mgKOH / g, and the mass of the aminated resin (B) is 4 with respect to the mass of the curing agent (C). If it is twice, the residual hydroxyl value is (17 + 240) × 0.8− (252 × 0.2) and is calculated as 155 mgKOH / g.

Nitrite metal salt (D)
The electrodeposition coating composition used in the electrodeposition coating method of the present invention contains a metal nitrite (D) as the component (D). The nitrite metal salt (D) is different from the dissolved zinc compound (A1) or the dissolved zirconium compound (A2), which is the above-described dissolved metal compound, and is also different from other additives described later. The nitrite metal salt (D) is preferably a divalent metal salt of nitrous acid, and particularly preferably a calcium salt or zinc salt from the viewpoint of coating film adhesion and coating film appearance. In the present invention, by using the metal nitrite (D), the inorganic layer composed of a composite of zinc and zirconium derived from the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) is deposited on the substrate. Since it is promoted, there is an advantage that the adhesion between the object to be coated and the obtained electrodeposition coating film is improved and the corrosion resistance is improved.
Since the nitrite metal salt (D) has a very strong oxidizing power, a smaller amount has an effect of promoting precipitation of the inorganic layer. For this reason, since the cathode adhesion is particularly excellent, the corrosion resistance is improved.

In the present invention, by adding the metal nitrite (D), precipitation of the inorganic layer composed of a composite of zinc and zirconium is greatly promoted, and the amount of precipitation of the inorganic layer on the surface of the article to be coated is increased. improves.

  The content of the metal nitrite (D) is preferably 0.001 to 0.2% by mass with respect to the total mass of the electrodeposition coating composition. More preferably, it is 0.01-0.06 mass%. Since the content of the nitrite metal salt (D) is 0.001% by mass or more, the deposition of the inorganic layer on the surface of the article to be coated is promoted, so the adhesion is improved and the corrosion resistance is excellent. There is an advantage that good corrosion resistance can be obtained. On the other hand, when it is 1% by mass or less, it is possible to achieve compatibility with the appearance of coating.

Plasticizer The electrodeposition coating composition used in the electrodeposition coating method of the present invention preferably contains a plasticizer. The dissolved zinc compound (A1) and the dissolved zirconium compound (A2) form an inorganic layer on the article to be coated and are taken into the resin film. In the resin film, the film-forming resin and the metal tend to have high internal stress due to hydrogen bonding, and the physical properties of the film tend to become hard. For this reason, in the electrodeposition coating method of this application, an internal stress can be reduced and the plasticity of an electrodeposition coating film can be mentioned by containing a plasticizer in an electrodeposition coating composition. The plasticizer is preferably an alkylene oxide adduct. Furthermore, an ethylene oxide adduct and a propylene oxide adduct are preferable. The addition method is not particularly limited, and for example, an ethylene oxide adduct, dimethylene triamine propylene oxide adduct, a reaction product of a diethylenetriamine propylene oxide adduct and an epoxy resin to bisphenol A or alcohol may be used.

  As content of a plasticizer, 0.1-25 mass% is preferable with respect to the total resin solid content of a film formation resin, More preferably, it is 1-10 mass%.

Chelating acid (E)
The electrodeposition coating composition used in the present invention preferably contains a chelating acid (E). Examples of the chelating acid (E) include at least one selected from the group consisting of sulfonic acid, organic phosphonic acid, organic carboxylic acid, amino acid, aminocarboxylic acid, sugar acid, and carboxyl group-containing vinyl resin. By containing the chelating acid (E) in the electrodeposition coating composition used in the electrodeposition coating method of the present invention, zinc ions and zirconium ions derived from the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) are chelated. There is an advantage that a cured electrodeposition coating film having excellent corrosion resistance can be formed by reducing the electrical conductivity and improving the appearance of the coating film obtained by electrodeposition coating.

  Examples of the sulfonic acid as the chelating acid (E) include alkanesulfonic acid having 1 to 20 carbon atoms, phenolsulfonic acid, and aminosulfonic acid. The C1-C20 alkyl group which forms these sulfonic acids may have substituents, such as a hydroxyl group. Examples of preferable sulfonic acid include methanesulfonic acid, sulfamic acid, phenolsulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and the like.

  Examples of the organic phosphonic acid as the chelating acid (E) include alkyl phosphonic acids having 1 to 20 carbon atoms, alkyl bisphosphonic acids having 1 to 20 carbon atoms, aromatic phosphonic acids having 6 to 20 carbon atoms, and 6 to 20 carbon atoms. And aromatic bisphosphonic acid. The C1-C20 alkyl group and C6-C20 aromatic group which form these phosphonic acids may have substituents, such as a hydroxyl group. Examples of preferable organic phosphonic acid include 1-hydroxyethylidene bisphosphonic acid.

  Examples of the organic carboxylic acid as the chelating acid (E) include fatty acids having 3 to 20 carbon atoms, aromatic carboxylic acids having 6 to 20 carbon atoms, oxocarboxylic acids having 2 to 20 carbon atoms, and dicarboxylic acids having 3 to 20 carbon atoms. Examples include acids and other organic carboxylic acids. The “organic carboxylic acid” here does not include an aminocarboxylic acid described later.

Examples of the fatty acid having 3 to 20 carbon atoms include propionic acid, butyric acid (butyric acid), dimethylpropionic acid (DMPA), isobutyric acid, valeric acid, isovaleric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, caprin Examples include acids, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, oleic acid and the like.
Examples of the aromatic carboxylic acid having 6 to 20 carbon atoms include salicylic acid, gallic acid, benzoic acid, phthalic acid, and cinnamic acid.

  Examples of oxocarboxylic acids having 2 to 20 carbon atoms, dicarboxylic acids having 3 to 20 carbon atoms and other organic carboxylic acids include pyruvic acid, oxalic acid, lactic acid, tartaric acid, maleic acid, fumaric acid, malonic acid, succinic acid, Examples include malic acid, citric acid, aconitic acid, glutaric acid, and adipic acid. Of these, dimethylpropionic acid and lactic acid are preferred.

  Examples of amino acids as the chelating acid (E) include aspartic acid, glutamic acid, glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, asparagine, glutamine, proline, phenylalanine, tyrosine, and tryptophan. Among these, aspartic acid and glycine are preferable.

  The aminocarboxylic acid as the chelating acid (E) is an acid having an amino group and a carboxyl group in the molecule and is a compound other than the above amino acids. Examples of aminocarboxylic acids include hydroxyethylethylenediamine triacetic acid (HEDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DPTA), triethylenetetraaminehexaacetic acid, and the like.

  The sugar acid as the chelating acid (E) is a sugar derivative having a carboxyl group obtained by oxidizing a monosaccharide. Examples of sugar acids include aldonic acid (such as gluconic acid, galactonic acid, and mannonic acid), uronic acid (such as glucuronic acid, galacturonic acid, and mannuronic acid), aldaric acid (such as glucaric acid, galactaric acid, and mannal acid), and iduronic acid. Glyceric acid, sialic acid, threonic acid, pangamic acid, ascorbic acid, muramic acid, lactobionic acid and the like.

  Examples of the carboxyl group-containing vinyl resin as the chelating acid (E) include a carboxyl group-containing polyvinyl alcohol resin. The carboxyl group-containing polyvinyl alcohol resin is produced, for example, by a method of copolymerizing a monomer such as acrylic acid together with a vinyl acetate monomer in the procedure for preparing polyvinyl alcohol, and then hydrolyzing the obtained polyvinyl acetate. be able to.

  Among these chelating acids (E), it is more preferable to use alkanesulfonic acid, organic phosphonic acid, organic carboxylic acid and / or amino acid, and methanesulfonic acid, dimethylpropionic acid or lactic acid to use chelating function and coating. This is particularly preferable from the viewpoint of less adverse effects due to adsorption to the membrane.

  In the present invention, the chelating acid (E) is contained in the electrodeposition coating composition in an amount of 0.1 to 10 equivalents relative to the total amount of the dissolved zinc compound (A1) and the dissolved zirconium compound (A2). It is preferable to contain.

  When alkane sulfonic acid and / or organic phosphonic acid is included as chelating acid (E), the total number of equivalents of sulfonic group or phosphonic group possessed by alkane sulfonic acid and / or organic phosphonic acid and dissolved zinc compound (A1) ) And the dissolved zirconium compound (A2) are contained in the electrodeposition coating composition in such an amount that the ratio of the number of moles of zinc element and the total number of zirconium elements is 0.1: 1 to 10: 1. Is preferred.

  When chelating acid (E) contains organic carboxylic acid, amino acid, aminocarboxylic acid, sugar acid and / or carboxyl group-containing vinyl resin, the total number of equivalents of carboxyl groups of these components and dissolved zinc compound (A1) and dissolved zirconium compound (A2) contained in the electrodeposition coating composition in such an amount that the ratio of the total number of moles of zinc element and zirconium element is 0.1: 1 to 10: 1. It is preferable.

  By using the chelating acid (E) in an amount of 0.1 to 10 equivalents relative to the total amount of the dissolved zinc compound (A1) and the dissolved zirconium compound (A2), the dissolved zinc compound (A1) and the dissolved zirconium The amount of the metal ion derived from the compound (A2) and the amount of the chelating acid (E) can be balanced, thereby ensuring the performance of the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) and the chelating acid. There is an advantage that an electrodeposition coating film having more excellent corrosion resistance can be formed without damaging the corrosion resistance by (E).

Aminosilane compound (F)
The electrodeposition coating composition used in the electrodeposition coating method of the present invention preferably contains an aminosilane compound (F). Examples of the aminosilane compound (F) include an aminosilane having at least one amino group in one molecule, and a hydrolysis condensate of aminosilane.

  Specific examples of aminosilane having at least one amino group in one molecule include N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene ) Propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride. “KBM-602”, “KBM-603”, “KBE-603”, “KBM-903”, “KBE-903”, “KBE-9103”, “KBM-603”, which are commercially available amino group-containing silane coupling agents "KBM-573", "KBP-90" (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), "XS1003" (trade names, manufactured by Chisso Corporation) and the like can be used.

  As the aminosilane compound (F), a hydrolysis condensate of aminosilane can also be used. By using a hydrolyzed condensate of aminosilane, there is an advantage that the adhesion of the electrodeposition coating film to the object can be improved. The molecular weight of the hydrolyzed condensate of aminosilane is not particularly limited, but a high molecular weight is preferable from the viewpoint of improving corrosion resistance. Here, the high molecular weight corresponds to that in which Si is three-dimensionally condensed by condensation. When the aminosilane is subjected to a hydrolytic condensation reaction, it is preferable that the aminosilane is reacted under a condition that the aminosilane is more easily hydrolyzed and condensed. The conditions under which aminosilane is more easily hydrolyzed and condensable include, for example, reaction conditions in which a solvent is an alcohol, and reaction conditions by blending aminosilane that results in cocondensation rather than single condensation as described above. In addition, by carrying out the reaction under a condition where the aminosilane concentration is relatively high, a hydrolyzed condensate can be obtained under a condition of higher molecular weight and higher condensation rate. Specifically, it is preferable to condense the aminosilane concentration in the range of 5 mass% or more and 50 mass% or less. The aminosilane may be co-condensed with an alkoxysilane having no amino group such as epoxy silane “KBM-403” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) as necessary.

  By including the aminosilane compound (F) in the electrodeposition coating composition, the adhesion between the object to be coated and the electrodeposition coating film is improved and the corrosion resistance is excellent due to the action of the amino group of the aminosilane compound (F). There is.

  When the aminosilane compound (F) is used in the electrodeposition coating composition used in the present invention, the mass of the aminosilane compound (F) with respect to the total mass of the electrodeposition coating composition is in the range of 0.001 to 0.5% by mass. Is preferred. The effect by using an aminosilane compound (F) is acquired because content of an aminosilane compound (F) is 0.001 mass% or more. Moreover, when the content of the aminosilane compound (F) is 0.5% by mass or less, an effect of improving the corrosion resistance according to the content is obtained, which is economically advantageous. When the aminosilane compound (F) is also used as a cation dispersant or a pH adjuster of zinc oxide, zinc hydroxide, or zinc phosphate which is the dissolved zinc compound (A1), the total amount including them is within the above range. It is preferable that

Other ingredients
Pigment The electrodeposition coating composition used in the electrodeposition coating method of the present invention may contain a pigment usually used in an electrodeposition coating composition. Examples of pigments include commonly used inorganic pigments, for example, colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; phosphoric acid And iron, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and rust preventive pigments such as aluminum phosphomolybdate and zinc aluminum phosphomolybdate. When these pigments are contained in the electrodeposition coating composition, the amount of the pigment is preferably 1 to 30% by mass with respect to the resin solid content of the electrodeposition coating composition.

  When using a pigment as a component of an electrodeposition coating composition, it is generally preferable to disperse the pigment in an aqueous solvent at a high concentration in advance to obtain a paste (pigment dispersion paste). This is because the pigment is in a powder form, and it is difficult to disperse in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous solvent. As the pigment dispersion resin, a pigment dispersion resin having a cationic group such as a modified epoxy resin having at least one selected from a quaternary ammonium group, a tertiary sulfonium group, and a primary amine group can be used. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used. Generally, the pigment dispersion resin is used in an amount of 20 to 100 parts by mass of the resin solid content ratio with respect to 100 parts by mass of the pigment. After the pigment dispersion resin and the pigment are mixed, the pigment is dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the pigment particle size in the mixture reaches a predetermined uniform particle size. A paste can be obtained.

Other Additives The electrodeposition coating composition used in the electrodeposition coating method of the present invention includes ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, propylene glycol. Organic solvents such as monophenyl ether, surfactants such as anti-drying agents and antifoaming agents, viscosity modifiers such as acrylic resin fine particles, anti-fogging agents, vanadium salts, copper, iron, manganese, magnesium, calcium salts, etc. Conventional paint additives such as a rust inhibitor may be added as necessary. In addition to these, known auxiliary complexing agents, buffering agents, smoothing agents, stress relaxation agents, brighteners, semi-brightening agents, antioxidants, ultraviolet absorbers and the like may be blended depending on the purpose.

Other coating film forming resin components The electrodeposition coating composition used in the electrodeposition coating method of the present invention is an aminated resin not corresponding to the above-mentioned aminated resin (B) in addition to the aminated resin (B). And / or other film-forming resin components. Examples of other film forming resin components include acrylic resin, polyester resin, urethane resin, butadiene resin, phenol resin, xylene resin, and the like. Phenol resins and xylene resins are preferred as other film-forming resin components that can be included in the electrodeposition coating composition. Examples of the phenol resin and xylene resin include xylene resins having 2 or more and 10 or less aromatic rings.

  In the present specification, the “resin solid content” means the solid mass of all solid contents of the coating film-forming resin contained in the electrodeposition coating composition. Specifically, it means the total amount of the solid content mass of the aminated resin (B), the curing agent (C), and other coating film-forming resin components as required, contained in the electrodeposition coating composition.

  The resin solid content of the electrodeposition coating composition is preferably 1 to 30% by mass with respect to the electrodeposition coating composition. When the resin solid content of the electrodeposition coating composition is less than 1% by mass, the amount of electrodeposition coating film deposited decreases, and it may be difficult to ensure sufficient corrosion resistance. Moreover, when the resin solid content of an electrodeposition coating composition exceeds 30 mass%, there exists a possibility that throwing power and coating appearance may worsen.

Preparation of electrodeposition coating composition The electrodeposition coating composition used in the present invention is an essential component, such as an emulsion containing an aminated resin (B) and a curing agent (C), and a pigment dispersion paste as required. Add zinc compound (A1) and dissolved zirconium compound (A2), metal nitrite (D), chelating acid (E) if necessary, aminosilane compound (F) if necessary, plasticizer, etc., and mix. Can be prepared. The dissolved zinc compound (A1) and the dissolved zirconium compound (A2) may be added together with the pigment as a dispersion paste.

  In the preparation of the electrodeposition coating composition, the dispersibility is improved and an emulsion is formed by neutralizing the aminated resin (B) and the curing agent (C) with a neutralizing acid. Organic acids such as formic acid, acetic acid and lactic acid are used as the neutralizing acid used for neutralization of the aminated resin (B). In the present invention, it is more preferable to neutralize and disperse the aminated resin (B) using formic acid. When formic acid is used as a neutralizing acid for neutralizing and dispersing the aminated resin (B), there is an advantage that the throwing power is excellent because the degree of dissociation is high.

  The amount of the neutralizing acid used is in the range of 10 to 25 mg equivalent to 100 g of the total amount of resin solids including the aminated resin (B), the curing agent (C) and the coating film forming resin as required. Is preferred. The lower limit is more preferably 15 mg equivalent, and the upper limit is more preferably 20 mg equivalent. When the amount of the neutralizing acid is 10 mg equivalent or more, the affinity for water is sufficient and the dispersion in water is good. On the other hand, when the amount of the neutralizing acid is 25 mg equivalent or less, the amount of electricity required for the precipitation becomes appropriate, and the depositability and throwing power of the paint solids become good.

  The amount of the curing agent (C) is sufficient to react with active hydrogen-containing functional groups such as primary, secondary amino groups and hydroxyl groups in the aminated resin (B) during curing to give a good cured coating film. Amount is needed. A preferable amount of the curing agent (C) is 90/10 to 50 in terms of a solid content mass ratio of the aminated resin (B) and the curing agent (C) (aminated resin (B) / curing agent (C)). / 50, more preferably in the range of 80/20 to 65/35. By adjusting the solid content mass ratio of the aminated resin (B) and the curing agent (C), the fluidity and curing speed of the coating film (deposition film) during film formation are improved, and the coating appearance is improved.

  The electrodeposition coating composition used in the electrodeposition coating method of the present invention preferably has a pH of 2-6. Moreover, it is preferable that the milligram equivalent (MEQ (A)) of the acid with respect to 100 g of resin solid content of an electrodeposition coating composition is 40-120. In addition, the milligram equivalent (MEQ (A)) of the acid with respect to 100 g of the resin solid content of the electrodeposition coating composition can be adjusted by the amount of neutralized acid and the amount of free acid.

  Here, MEQ (A) is an abbreviation for mg equivalent (acid), and is the sum of mg equivalents of all acids per 100 g of solid content of the paint. This MEQ (A) is prepared by accurately weighing about 10 g of the electrodeposition coating composition and dissolving it in about 50 ml of a solvent (THF: tetrahydrofuran), and then performing potentiometric titration using a 1/10 N NaOH solution. The amount of acid contained in the coating composition can be quantified and measured. The pH of the electrodeposition coating composition can be measured using a commercially available pH meter having a temperature compensation function.

  It is preferable that the electrodeposition coating composition used in the present invention contains substantially neither a tin compound nor a lead compound. In the present specification, “the electrodeposition coating composition is substantially free of both a tin compound and a lead compound” means that the concentration of the lead compound contained in the electrodeposition coating composition does not exceed 50 ppm as a lead metal element, And it means that the concentration of the organic tin compound does not exceed 50 ppm as a tin metal element. The electrodeposition coating composition used in the electrodeposition coating method of the present invention includes a dissolved zinc compound (A1) and a dissolved zirconium compound (A2). Therefore, it is not necessary to use a lead compound or an organic tin compound as a curing catalyst. Thereby, the electrodeposition coating composition which does not contain any of a tin compound and a lead compound can be prepared.

Electrodeposition coating and electrodeposition coating formation
As the object to be used in the electrodeposition coating method of the present invention, various objects that can be energized can be used. Examples of coatings that can be used include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy plated steel sheets, zinc-iron alloy plated steel sheets, zinc-magnesium alloy based plating. Examples of the coating material include steel plates, zinc-aluminum-magnesium alloy-plated steel plates, aluminum-plated steel plates, aluminum-silicon alloy-plated steel plates, and tin-based plated steel plates.

  The electrodeposition coating method of the present invention can be suitably used in coating using an object that has not been subjected to chemical conversion treatment.

  In addition, you may remove foreign materials, such as a rust preventive oil and a processing oil which adhered to the to-be-coated object, using alkaline degreasing liquid and / or washing water as needed.

Electrodeposition coating process Electrodeposition coating is a coating method in which an electrodeposition film is usually deposited on an object to be coated by applying a voltage of 50 to 450 V between the object and the anode. . In this invention, after immersing for 0 to 30 seconds without applying a voltage, the process of forming an electrodeposition film | membrane by applying a voltage is performed. That is, after the object to be coated is completely immersed in the electrodeposition bath, the object to be coated may be immersed in the electrodeposition bath for a predetermined time without applying a voltage, and such immersion time is not particularly provided. (Immersion time 0 second), the application may be started immediately at the same time as the entire object to be coated is buried in the electrodeposition bath. The immersion time when the object is immersed is more than 0 seconds and 30 seconds or less, and preferably 20 seconds or less. While the object is immersed in the electrodeposition bath without applying voltage in this way, the surface of the object to be coated is oxidized and the surface becomes uniform, but elution of the object to be coated and precipitation of the inorganic layer, etc. It doesn't happen very much. When the immersion time is 30 seconds or longer, the object to be coated is slightly etched depending on the coating pH, which may cause sludge.

After the object to be coated is buried in the electrodeposition bath, when a voltage is applied to perform electrodeposition coating, the resin film is electrodeposited on the inorganic layer, which is a composite of zinc and zirconium, and an electrodeposition film is formed. In the electrodeposition coating method of the present invention, even when there is no time to immerse without applying voltage, the electrodeposition bath is fully immersed in the electrodeposition bath to apply the electrodeposition coating to the electrodeposition bath. Even when the application of is started, deposition of a dense inorganic layer made of a composite of zinc and zirconium occurs before the resin film is formed by electrodeposition, and then the resin component is deposited by ordinary electrodeposition coating. For this reason, the electrodeposition coating method of the present invention is a simplified electrodeposition coating method that does not require a special process and does not generate sludge.

  In the electrodeposition coating step, after the object is completely immersed in the electrodeposition bath, a voltage of 5 to 450 V is applied to perform normal electrodeposition coating. If the applied voltage is less than 50V, electrodeposition may be insufficient, and if it exceeds 450V, the coating film may be destroyed and an abnormal appearance may be obtained. At the time of electrodeposition coating, the bath temperature of the coating composition is usually adjusted to 10 to 45 ° C.

  The electrodeposition coating method of the present invention comprises a process of immersing an object to be coated in an electrodeposition coating composition, and a process of depositing a film by applying a voltage between the object to be coated as a cathode and an anode. Is done. Moreover, although the time which applies a voltage changes with electrodeposition conditions, generally it can be made into 2 to 5 minutes.

  The film thickness after heat curing of the electrodeposition coating film is preferably 5 to 40 μm, more preferably 10 to 25 μm. If the film thickness is less than 5 μm, the corrosion resistance may be insufficient. On the other hand, if it exceeds 40 μm, it leads to waste of paint.

  The electrodeposition coating film obtained as described above is heated by heating at 120 to 260 ° C., preferably 140 to 220 ° C. for 10 to 30 minutes after completion of the electrodeposition process, or after washing with water. A cured electrodeposition coating is formed.

  The electrodeposition coating method of the present invention has an advantage that excellent corrosion resistance can be obtained even when electrodeposition coating is performed using an object that has not been subjected to chemical conversion treatment.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

Production Example 1-A Production of Aminated Resin (Resin A) 92 parts of methyl isobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Company), 350 parts of bisphenol A, 30 parts of octylic acid, dimethyl 2 parts of benzylamine was added, the temperature in the reaction vessel was kept at 120 ° C., and the reaction was continued until the epoxy equivalent reached 820 g / eq, followed by cooling until the temperature in the reaction vessel reached 110 ° C. Next, 160 parts of diethanolamine was added and reacted at 110 ° C. for 1 hour to obtain an aminated resin (cation-modified epoxy resin: resin A).

  The number average molecular weight of this resin was 2,600, the amine value was 58 mgKOH / g, and the hydroxyl value was 310 mgKOH / g.

Production Example 1-B Production of Aminated Resin (Resin B) 92 parts of methyl isobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Company), 350 parts of bisphenol A, 95 parts of octylic acid, dimethyl 2 parts of benzylamine was added, the temperature in the reaction vessel was maintained at 120 ° C., and the reaction was continued until the epoxy equivalent reached 1170 g / eq, followed by cooling until the temperature in the reaction vessel reached 110 ° C. Then, a mixture of 82 parts of diethylenetriamine diketimine (a methyl isobutyl ketone solution having a solid content of 73%), 26 parts of N-methylethanolamine and 60 parts of diethanolamine was added and reacted at 110 ° C. for 1 hour to give an aminated resin (cationic). Modified epoxy resin: Resin B) was obtained.

  The number average molecular weight of this resin was 2,600, the amine value was 58 mgKOH / g (of which the amine value derived from the primary amine was 17 mgKOH / g), and the hydroxyl value was 240 mgKOH / g.

Production Example 1-C Production of Aminated Resin (Resin C) 92 parts of methyl isobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Company), 350 parts of bisphenol A, 25 parts of octylic acid, dimethyl 2 parts of benzylamine was added, the temperature in the reaction vessel was maintained at 120 ° C., and the reaction was continued until the epoxy equivalent reached 800 g / eq, and then the reaction vessel was cooled to 110 ° C. Then, a mixture of 160 parts of diethanolamine and 190 parts of an adduct of 37 mol of diethylenetriaminepropion oxide was added and reacted at 110 ° C. for 1 hour to obtain an aminated resin (cation-modified epoxy resin: resin C).

  The number average molecular weight of this resin was 3,300, the amine value was 58 mgKOH / g (of which the amine value derived from the primary amine was 5 mgKOH / g), and the hydroxyl value was 270 mgKOH / g.

Production Example 1-E Production of Aminated Resin (Resin E) 92 parts of methyl isobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Company), 390 parts of bisphenol A, 80 parts of octylic acid, dimethyl 2 parts of benzylamine was added, the temperature in the reaction vessel was kept at 120 ° C., and the reaction was continued until the epoxy equivalent reached 1400 g / eq, followed by cooling until the temperature in the reaction vessel reached 110 ° C. Subsequently, a mixture of 100 parts of diethanolamine and 120 parts of a 37 mol adduct of diethylenetriaminepropion oxide was added and reacted at 110 ° C. for 1 hour to obtain an aminated resin (cation-modified epoxy resin: resin E).

  The number average molecular weight of this resin was 3,300, the amine value was 37 mgKOH / g (of which the amine value derived from primary amine was 3 mgKOH / g), and the hydroxyl value was 240 mgKOH / g.

Production Example 1-F Production of aminated resin (resin F) A reaction vessel equipped with a stirrer, decanter, nitrogen introduction tube, thermometer and dropping funnel was charged with a bisphenol A type epoxy resin (trade name DER) having an epoxy equivalent of 188 g / eq. -331J, manufactured by Dow Chemical Co., Ltd.), 2,400 parts, 141 parts of methanol, and 168 parts of methyl isobutyl ketone were stirred and dissolved uniformly at 40 ° C., and then 2,4- / 2,6-tolylene diisocyanate ( When 80 parts of 80/20 mass ratio mixture) was added dropwise over 30 minutes, heat was generated and the temperature rose to 70 ° C. To this was added 5 parts of N, N-dimethylbenzylamine, the temperature in the reaction vessel was raised to 120 ° C., and the reaction was continued at 120 ° C. for 3 hours until the epoxy equivalent reached 500 g / eq while distilling off methanol. It was.

Further, 644 parts of methyl isobutyl ketone, 341 parts of bisphenol A and 413 parts of 2-ethylhexanoic acid were added, and the reaction container was maintained at a temperature of 120 ° C. until the epoxy equivalent reached 1070 g / eq. The inner temperature was cooled to 110 ° C. Next, a mixture of 241 parts of diethylenetriamine diketimine (a methyl isobutyl ketone solution having a solid content of 73%) and 192 parts of N-methylethanolamine was added and reacted at 110 ° C. for 1 hour, whereby an aminated resin (cation-modified epoxy resin: Resin F) was obtained.

The number average molecular weight of this resin was 2,100, the amine value was 74 mgKOH / g (of which the amine value derived from the primary amine was 16 mgKOH / g), and the hydroxyl value was 160 mgKOH / g. Moreover, it was confirmed from the measurement of an infrared absorption spectrum etc. that the resin has an oxazolidone ring (absorption wave number: 1750 cm ⁻¹ ).

Production Example 2-1 Production of Blocked Isocyanate Curing Agent (1) 1680 parts of hexamethylene diisocyanate (HDI) and 732 parts of MIBK were charged into a reaction vessel and heated to 60 ° C. A solution obtained by dissolving 346 parts of trimethylolpropane in 1067 parts of MEK oxime was added dropwise at 60 ° C. over 2 hours. Further, after heating at 75 ° C. for 4 hours, in the measurement of IR spectrum, it was confirmed that the absorption based on the isocyanate group disappeared, and after standing to cool, 27 parts of MIBK was added to add a blocked isocyanate curing agent (1 ) The isocyanate group value was 252 mgKOH / g.

Production Example 2-2 Production of Blocked Isocyanate Curing Agent (2) 1,340 parts of 4,4′-diphenylmethane diisocyanate and 277 parts of MIBK were charged into a reaction vessel and heated to 80 ° C., and then 226 parts of ε-caprolactam was added to butyl cellosolve. What was dissolved in 944 parts was dripped at 80 degreeC over 2 hours. Furthermore, after heating at 100 degreeC for 4 hours, in the measurement of IR spectrum, it confirmed that the absorption based on an isocyanate group disappeared, and after standing to cool, MIBK349 parts were added and block isocyanate hardening | curing agent (2) was obtained (solid). Min 80%). The isocyanate group value was 251 mgKOH / g.

Production Example 3 Production of Pigment Dispersion Resin 385 parts of bisphenol A type epoxy resin, 120 parts of bisphenol A, 95 parts of octylic acid, 2-ethyl-4-methyl in a reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe and a thermometer 1 part of imidazole 1% solution was charged, reacted at 160-170 ° C. for 1 hour under a nitrogen atmosphere, then cooled to 120 ° C., and then methyl isobutyl ketone solution of 2-ethylhexanolated half-blocked tolylene diisocyanate (solid content 95 %) 198 parts were added. After maintaining the reaction mixture at 120-130 ° C. for 1 hour, ethylene glycol mono n-butyl ether 157 was added. And it cooled to 85-95 degreeC and made it uniform. Next, 277 parts of diethylenetriamine diketimine (a methyl isobutyl ketone solution having a solid content of 73%) was added and stirred at 120 ° C. for 1 hour, and 13 parts of ethylene glycol mono-n-butyl ether was added to produce an aminated resin. Next, 18 parts of ion-exchanged water and 8 parts of formic acid were added, the aminated resin was mixed and stirred for 15 minutes, 200 parts of ion-exchanged water was mixed, and a resin solution (resin of pigment dispersion resin (average molecular weight 2,200)) 25% solids) was obtained.

Production Examples 4-A to C, 4-E, 4-F Electrodeposition Paint Resin Emulsions (EmA) to (EmC), (EmE), (EmF) Production of Resin (Resin A) Obtained in Production Example 1-A 350 g (solid content), 75 g (solid content) of the blocked isocyanate curing agent (1) obtained in Production Example 2-1 and 75 g (solid content) of the curing agent (2) were mixed, and ethylene glycol mono-2-ethylhexyl was mixed. Ether was added to 3% (15 g) based on solids. Next, neutralize by adding methanesulfonic acid to a neutralization rate of 80%, add ion-exchanged water to dilute slowly, and then remove methyl isobutyl ketone under reduced pressure to a solid content of 36%. Thus, an electrodeposition paint resin emulsion (EmA) was obtained.
Further, instead of the resin (resin A) obtained in Production Example 1-A, the resins (Resin B), (Resin C), (Resin E) obtained in Production Examples 1-B, C, E, and F, respectively, Electrodeposition paint resin emulsions (EmB), (EmC), (EmE), and (EmF) were obtained in the same manner except that (Resin F) was used.

Production Example 4-D Production of Electrodeposition Paint Resin Emulsion (EmD ) 400 g (solid content) of resin (resin A) obtained in Production Example 1-A and blocked isocyanate curing agent (1) obtained in Production Example 2-1. 50 g (solid content) and curing agent (2) 50 g (solid content) were mixed, and ethylene glycol mono-2-ethylhexyl ether was added to 3% (15 g) based on the solid content. Next, neutralize by adding methanesulfonic acid to a neutralization rate of 80%, add ion-exchanged water to dilute slowly, and then remove methyl isobutyl ketone under reduced pressure to a solid content of 36%. Thus, an electrodeposition coating resin emulsion (EmD) was obtained.

Production Example 5-1 Production of Pigment Dispersion Paste 1 for Electrodeposition Paint Using a sand mill, based on the formulation shown in the following Table 1 including the pigment dispersion resin obtained in Production Example 3, the obtained mixture was obtained at 40 ° C. Dispersion was carried out until the volume average particle diameter D50 was 0.6 μm, and pigment dispersion paste 1 (solid content 49%) was obtained. The volume average particle diameter D50 is measured by diluting the dispersion with ion-exchanged water so that the signal level is suitable using a laser Doppler particle size analyzer (manufactured by Nikkiso Co., Ltd., “Microtrac UPA150”). The particle diameter D50 was measured.

Production Example 5-2 Production of Pigment Dispersion Paste 2 for Electrodeposition Paint Based on the formulation shown in Table 2, the obtained mixture was dispersed at 40 ° C. until the volume average particle diameter D50 was 0.6 μm, and prepared. Pigment dispersion paste 2 (solid content 49%) was obtained.

Example 1
119 g of ion exchange water, 32.6 g of zinc oxide (reagent), 110 g of 70% methanesulfonic acid (manufactured by BASF) were added to a stainless steel container, and stirred at 60 ° C. for 1 hour to prepare zinc methanesulfonate having a zinc concentration of 10%. .

Next, the hydrolytic condensate of organosilane was 15 parts by mass of “KBE903” (3-aminopropyltriethoxysilane, trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), “KBE603” (N-2- (aminoethyl) ) -3-aminopropyltriethoxysilane (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) 15 parts by mass from a dropping funnel to 70 parts by mass of ion-exchanged water (solvent temperature: 25 ° C.) over 60 minutes. After the dropwise addition, a hydrolytic condensate of organosilane (hereinafter referred to as KBE903-KBE603 co-condensate) containing 30% of the active ingredient, obtained by reacting at 25 ° C. for 24 hours under a nitrogen atmosphere, was used.

In a stainless steel container, 1022 g of ion-exchanged water, 20 g of zinc methanesulfonate having a zinc concentration of 10% (indicated as “MSAZn” in Table 3) as a dissolved zinc compound (A1) and 2.8 g of 40% zirconic acid fluoride Added. Next, 1.3 g of hydrolyzed condensate of organosilane (referred to as “organosiloxane condensate” in Table 3) is added, 1.3 g of 30% calcium nitrite (manufactured by Nissan Chemical Industries) is added, Next, 833 g of the electrodeposition paint resin emulsion (EmA) of Production Example 4-A and 122 g of the pigment (Pigment Dispersion Paste 1 of Production Example 5-1) were added, and then aged at 40 ° C. for 16 hours to obtain an electrodeposition paint composition. Formed. Table 3 below shows the blending amount of the electrodeposition coating composition, but describes the relative ratio with respect to 100 parts by mass of the solid content.

A cold-rolled steel plate (JIS G3141, SPCC-SD) was immersed in Surf Cleaner EC90 (manufactured by Nippon Paint Co., Ltd.) at 50 ° C. for 2 minutes for degreasing treatment. After deionized water washing, after adding the necessary amount of 2-ethylhexyl glycol to the obtained electrodeposition coating composition so that the film thickness of the electrodeposition coating film after curing is 15 μm, and then burying all the steel plates Immediately start application of voltage, apply voltage under the condition that the pressure is increased for 30 seconds, and reaches 180V and then held for 150 seconds to deposit an uncured electrodeposition film on the object to be coated (cold rolled steel sheet). It was. The uncured electrodeposition film thus obtained was heat-cured at 160 ° C. for 15 minutes to obtain an electrodeposition coated plate having an electrodeposition film.

  Evaluation of the obtained electrodeposition coating film was evaluated with respect to five items, that is, a cycle corrosion test (CCT), a salt water immersion test (SDT), coating film properties, coating appearance, and stability. The results are shown in Table 3.

Cycle Corrosion Test (CCT)
The coating film of the electrodeposition coating plate after curing using a cold-rolled steel plate was cut with a knife so as to reach the substrate, and JASO M609-91 “Automobile Material Corrosion Test Method” was performed 60 cycles. Thereafter, the occurrence of rust and blistering from the crosscut portion was observed to evaluate the corrosion resistance in accordance with the actual corrosive environment. The evaluation criteria are as follows.

Evaluation standard ◎: Maximum width of rust or swelling is less than 5mm from the cut part (both sides)
○: The maximum width of rust or swelling is 5 mm or more and less than 7.5 mm (both sides) from the cut part. No blister other than the cut part. ○ △: The maximum width of rust or swelling is 5 mm or more and less than 7.5 mm (both sides) from the cut part. There is also a blister other than the part Δ: The maximum width of rust or blister is 7.5mm or more and less than 10mm from the cut part
Δ: The maximum width of rust or swelling is 10 mm or more and less than 12.5 mm from the cut part (both sides)
X: The maximum width of rust or blisters is 12.5 mm or more from the cut part (both sides)

Salt water immersion test (Salt-solution Dipping Test (SDT))
The coating film of the electrodeposition coating plate after hardening using a cold-rolled steel plate was scratched with a knife so as to reach the base material, and this coated plate was immersed in 5% salt water at 50 ° C. for 480 hours. The occurrence of rust and blisters from the scratches was observed and evaluated. The evaluation criteria are as follows.

Evaluation standard ◎: No rust or blisters ○: Maximum width of rust or blisters is less than 2.5 mm from the cut (both sides)
○ △: The maximum width of rust or swelling is 2.5mm or more and less than 5mm from the cut part (both sides)
Δ: The maximum width of rust or swelling is 5 mm or more and less than 10 mm from the cut part (both sides)
Δ: The maximum width of rust or swelling is 10 mm or more and less than 15 mm from the cut part (both sides)
X: The maximum width of rust or blister is 15mm or more from the cut part (both sides)

Cured electrodeposition coating properties evaluation (film properties)
A small cutter knife is vertically applied to the electrodeposition coating plate having a cured electrodeposition coating film obtained from the above examples and comparative examples, and evenly spaced parallel lines are scratched at intervals of 2 mm so as to reach the object to be coated. 11 lines were drawn, and 11 parallel lines perpendicular to the parallel lines were drawn at 2 mm intervals to cut 100 squares of 2 mm square surrounded by 4 straight lines. Next, the test piece was immersed in ion exchange water at 50 ° C. for 480 hours. After immersion, wipe off the water of the test piece, and then press the adhesive tape (ELPACK LP-24 manufactured by Nichiban Co., Ltd.) (width 24 mm) without any bubbles in the cut part of the test coating film, and then pull it rapidly. It was. Based on the presence or absence of peeled grids, the following criteria were used for evaluation.

Evaluation criteria ○: No peeling ×: With peeling

Cured electrodeposition coating appearance (paint appearance)
About the electrodeposition coating plate which has the cured electrodeposition coating film obtained from the said Example and comparative example, the presence or absence of abnormality in a coating-film external appearance was judged visually. The evaluation criteria were as follows.
Evaluation Criteria A: Very uniform coating appearance B: Uniform coating appearance B: Appears if there is some unevenness, but almost uniform coating as a whole Appearance △: Unevenness is visually recognized x: Appearance of the coating is clearly uneven

Stability of electrodeposition coating composition (stability)
In a state where the electrodeposition coating composition was left standing or stirred, the state of the coating composition was visually determined to evaluate the stability. The evaluation criteria were as follows. The term “stable” as used herein means that the pigment does not settle within 15 minutes after the stirring is stopped.

Evaluation criteria ○: Stable when the electrodeposition coating composition is left standing ○ △: Although it is not stable when the electrodeposition coating composition is left still, it is stabilized immediately by stirring again Δ: Electric It is stable when the coating composition is continuously stirred. X: It is not stabilized even when the electrodeposition coating composition is continuously stirred.

Effect of sludge 20 sheets of cold-rolled steel sheet (JIS G3141, SPCC-SD 150 mm × 75 mm) were applied to 1 L, and sludge generation and paintability deterioration related to sludge generation were evaluated.
: Sludge is not generated and paintability is not deteriorated. Δ: Sludge is not visually observed and paintability is slightly decreased.
: Paintability is reduced due to sludge generation.
×: Sludge generated

Examples 2-15, Comparative Examples 1-5 and Reference Examples 1-2
An electrodeposition coating composition was formed with the formulation shown in Table 3. For the obtained electrodeposition coating composition or electrodeposition coated plate, the same six items as in Example 1 were evaluated. The results are shown in Table 3.

  In Table 3, a reagent was used for fluorinated zirconic acid.

  In Example 4 and Example 13, the pigment dispersion paste 2 prepared in Production Example 5-2 was used.

  The BPAEO adduct used in Example 15 was a plasticizer, and was an ethylene oxide adduct (BPAEO adduct) of bisphenol A (Newpol BPE-60 manufactured by Sanyo Chemical Industries).

The values of the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) in Table 3 are metal element equivalent values. For example, with zinc oxide, an electrodeposition coating composition is prepared using the pigment paste 2 finely dispersed, and the electrodeposition coating composition is centrifuged at 12000 rpm × 30 minutes with a centrifuge (H-200N: manufactured by Kokusan Centrifuge Co., Ltd.). The concentration of the dissolved zinc compound (A1) or dissolved zirconium compound (A2) in the electrodeposition coating composition is determined by measuring the concentration of the supernatant liquid with fluorescent X-rays (ZSX Primus: manufactured by Rigaku Corporation). (Mass%) was calculated.

In Table 3, “immersion time” refers to the time the electrodeposited paint composition was subjected to degreasing and ionic water washing, and then retained in the electrodeposition paint composition without voltage application. Mean, then start applying voltage. “None” soaking time means that the application of voltage was started immediately after all the objects to be coated which had been degreased and washed with ion water were buried in the electrodeposition coating composition.
In all the examples and comparative examples other than Example 1, the voltage application is performed under the condition that the voltage is increased for 30 seconds after the voltage application is started, and is maintained for 150 seconds after reaching 180V. It was.

  It was confirmed that all the coatings obtained by applying the electrodeposition coating compositions of the examples were excellent in CCT test results and SDT test results and had excellent corrosion resistance. The coated materials of Examples other than Example 4 were further excellent in coating film smoothness (coating appearance) and the stability of the electrodeposition coating composition. These examples also show that the electrodeposition coating method of the present invention can form an electrodeposition coating film having excellent performance on an object to be coated (untreated) that has not been subjected to chemical conversion treatment.

  In Comparative Examples 1 and 2 using the electrodeposition coating composition not containing the dissolved zinc compound (A1) and the dissolved zirconium compound (A2), the CCT test result and the SDT test result were poor, and the corrosion resistance was inferior.

  Comparative Example 3 is an example in which only the dissolved zinc compound (A1) is used as the dissolved metal compound and no nitrite metal salt, that is, calcium nitrite is used, and the CCT test result and the SDT test result are poor and the corrosion resistance is inferior. .

  Comparative Example 4 is an example using only the dissolved zinc compound (A1) as the dissolved metal compound, but the amine value resin (B) and the curing agent (C) which is a blocked isocyanate curing agent are in the electrodeposition coating film. When the reaction was carried out during heat curing, the theoretical residual hydroxyl value was less than 50, the CCT test result was poor, and the corrosion resistance was poor.

  In Comparative Example 5, the same electrodeposition coating composition as in Example 2 was used. However, the immersion time without applying voltage after the object was immersed in the electrodeposition bath was as long as 180 seconds, and the storage stability of the coating was high. It got worse.

  In Reference Example 1 and Reference Example 2, electrodeposition is performed with an electrodeposition coating material that is subjected to a zinc phosphate chemical conversion treatment as a pretreatment of an object and does not contain the dissolved zinc compound (A1) and the dissolved zirconium compound (A2) of the present invention. This is an example of painting. In Reference Example 1, the heat curing temperature of the electrodeposition coating film is 160 ° C., and in Reference Example 2, the heat curing temperature is 140 ° C. In both cases, the generation of sludge becomes a problem. Furthermore, in Reference Example 2, the SDT test result is poor, and it is shown that the heat curing at 140 ° C. is insufficient in curing and the coating barrier property is deteriorated. This is presumably because the zinc phosphate film is heated at around 170 ° C. to remove crystal water and the adhesion is enhanced, but at 140 ° C., the adhesion function of the chemical conversion film is also lowered.

  By using the electrodeposition coating method of the present invention, there is an advantage that a coating film excellent in corrosion resistance, adhesion and coating film smoothness (coating appearance) can be obtained even when a steel sheet not subjected to chemical conversion treatment is used. is there. By using the electrodeposition coating method of the present invention, it is possible to effectively use a steel sheet that is not subjected to chemical conversion treatment, and there is no problem of generation of sludge associated with chemical conversion treatment. Further, even if chemical conversion treatment is not performed, special potential control and a pre-immersion process in which no voltage is applied are not required, so that a process reduction effect can be exhibited.

Claims (4)

A step of immersing an object to be coated that has not been subjected to chemical conversion treatment in the electrodeposition coating composition for 0 to 30 seconds without applying a voltage, and then applying a voltage to form an electrodeposition film; and An electrodeposition coating method comprising a step of heat-curing an electrodeposition film to form an electrodeposition film,
The electrodeposition coating composition is
A dissolved zinc compound (A1) and a dissolved zirconium compound (A2), an aminated resin (B), a curing agent (C), and a metal nitrite (D), the aminated resin (B) The number average molecular weight is 1,000 to 5,000, the amine value is 20 to 100 mgKOH / g, the hydroxyl value is 50 to 400 mgKOH / g, and
The curing agent (C) is a blocked isocyanate curing agent,
The dissolved zinc compound (A1) is zinc methanesulfonate,
Electrodeposition characterized by having a theoretical residual hydroxyl value of 90 to 350 mgKOH / g when the aminated resin (B) and the blocked isocyanate curing agent react in a heat-cured state in an electrodeposition coating film. How to paint.   The electrodeposition coating composition is further a chelating acid (which is at least one selected from the group consisting of sulfonic acid, organic phosphonic acid, organic carboxylic acid, amino acid, aminocarboxylic acid, sugar acid and carboxyl group-containing vinyl resin) The electrodeposition coating method according to claim 1, comprising E).   The electrodeposition coating method according to claim 1 or 2, wherein the electrodeposition coating composition further contains an aminosilane compound (F). The electrodeposition coating method according to claim 1, wherein the electrodeposition coating composition contains a plasticizer.