JP2015187199A - electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrodeposition coating composition improved in the solubility of a bismuth compound, from which a coating film excellent in curability, uniformity of film thickness, and corrosion resistance can be formed.SOLUTION: The electrodeposition coating composition comprises a resin emulsion (1); and the resin emulsion (1) comprises an aminated resin (A), a block isocyanate curing agent (B), a bismuth compound (C), an organic acid (D), and an amino acid (E). The organic acid (D) is selected from a hydroxycarboxylic acid and a sulfonic acid. The resin emulsion (1) satisfies the following conditions: (i) a molar ratio Bi:(D) of contents of bismuth metal to the organic acid (D) in the bismuth compound (C) is 1:0.25 to 1:4; (ii) a molar ratio Bi:(E) of contents of bismuth metal to the amino acid (E) in the bismuth compound (C) is 1;0.25 to 1:4; and (iii) the content of the bismuth compound (C) is 0.25 to 2.1 mass% in terms of metal elements with respect to the solid content of the resin emulsion (1).

Description

  The present invention relates to an electrodeposition coating composition, and more particularly to a cationic electrodeposition coating composition.

  The cationic electrodeposition coating composition generally comprises a resin emulsion and optionally includes a pigment dispersion paste. In such cationic electrodeposition coating compositions, organotin compounds have been widely used as curing catalysts. However, the use of organotin compounds may be limited in the future due to recent trends in environmental regulations. Catalysts have been developed for some time.

  Bismuth compounds are known to serve as curing catalysts for cationic electrodeposition coating compositions. For example, a method is disclosed in which a bismuth compound such as bismuth oxide or bismuth hydroxide is simply dispersed in a pigment dispersion paste. However, in this method, the catalytic activity of the bismuth compound is low, so that the coating film is sufficiently cured. I couldn't. In addition, the storage stability of paints and pigment dispersion pastes decreased, and aggregation occurred during storage.

  Thus, a method is disclosed in which a bismuth compound is mixed and dissolved in advance with an amine-containing carboxylic acid such as an amino acid, and the resulting mixture is used for preparing a pigment dispersion paste (Patent Document 1). Also disclosed is a method in which a bismuth compound is mixed and dissolved in advance with lactic acid, and then the resulting mixture is added to a paint (Patent Document 2). However, in any of the above methods, although the catalytic activity is somewhat increased by dissolution of the bismuth compound, the coating film cannot be sufficiently cured. There is also a problem that a large amount of bismuth compound dissolution residue is generated. Therefore, in order to dissolve the necessary amount of bismuth compound, a large amount of amino acid or lactic acid is required, and this has an adverse effect such as deterioration of the appearance of the coating film and deterioration of the corrosion resistance of the coating film. Deterioration of the appearance of the coating film is a phenomenon in which the film thickness becomes non-uniform and the coating film becomes uneven.

Japanese Patent No. 3293633 Japanese Patent No. 3874386

  The present invention solves the above-mentioned conventional problems, and the object is to form a coating film with sufficiently improved solubility of the bismuth compound and excellent curability, film thickness uniformity and corrosion resistance. It is an object of the present invention to provide an electrodeposition coating composition that can be used.

  The present invention also has a sufficiently improved solubility of the bismuth compound, can form a coating film having excellent curability, film thickness uniformity, and corrosion resistance, and also has a storage stability of the electrodeposition coating composition and the electric charge. An object of the present invention is to provide an electrodeposition coating composition excellent in storage stability of a resin emulsion constituting the coating composition.

In order to solve the above problems, the present invention provides the following aspects.
The present invention is an electrodeposition coating composition comprising a resin emulsion (1),
The resin emulsion (1) contains an aminated resin (A), a blocked isocyanate curing agent (B), a bismuth compound (C), an organic acid (D) and an amino acid (E),
The organic acid (D) is one or more selected from the group consisting of hydroxycarboxylic acid and sulfonic acid,
An electrodeposition coating composition in which the resin emulsion (1) satisfies the following conditions is provided:
(I) The molar ratio of the bismuth metal and organic acid (D) content in the bismuth compound (C) is 1: 0.25 to 1: 4 in Bi: (D);
(Ii) the molar ratio of the bismuth metal and amino acid (E) content in the bismuth compound (C) is 1: 0.25 to 1: 4 in Bi: (E); and (iii) the bismuth compound (C) Is 0.25 to 2.1% by mass in terms of metal element with respect to the solid content of the resin emulsion (1).

  According to the electrodeposition coating composition of the present invention, since the solubility of the bismuth compound is sufficiently improved, a coating film excellent in curability, film thickness uniformity, and corrosion resistance can be formed. Furthermore, the electrodeposition coating composition of the present invention and the resin emulsion constituting the electrodeposition coating composition are sufficiently excellent in storage stability.

  The electrodeposition coating composition of the present invention contains a resin emulsion (1), and may further contain a pigment dispersion paste (2) if desired.

[Resin emulsion (1)]
The resin emulsion (1) contains an aminated resin (A), a blocked isocyanate curing agent (B), a bismuth compound (C), an organic acid (D) and an amino acid (E), and may further contain other components as desired. .

<Aminated resin (A)>
The aminated resin (A) is a coating film forming resin constituting the electrodeposition coating film. As the aminated resin (A), 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 prepared by ring-opening an oxirane ring in a starting material resin molecule by a reaction with an amine such as a primary amine, secondary amine or tertiary amine and / or its acid salt. 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. In particular, bisphenols may be used for chain extension by opening 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, and monocarboxylic acid compounds such as octylic acid 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 (A) is preferably 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, the viscosity of the aminated resin can be easily adjusted to enable smooth synthesis, and handling of emulsified dispersion of the obtained aminated resin (A) is possible. Becomes easier. The number average molecular weight of the aminated resin (A) is more 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). Further, in this specification, “cured electrodeposition coating film” is sometimes simply referred to as “electrodeposition coating film”. On the other hand, in the present specification, “electrodeposited film” and “resin film” mean an uncured film mainly composed of a resin, which is deposited on an object to be coated by application of a voltage.

  The amine value of the aminated resin (A) is preferably in the range of 20 to 100 mgKOH / g. When the amine value of the aminated resin (A) is 20 mgKOH / g or more, the emulsion dispersion stability of the aminated resin (A) 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 (A) is more preferably in the range of 20 to 80 mgKOH / g.

  The hydroxyl value of the aminated resin (A) is preferably 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 (A) is more preferably in the range of 100 to 300 mgKOH / g.

  In the electrodeposition coating composition of the present invention, an aminated resin 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 (A), there is an advantage that excellent corrosion resistance can be imparted to the article to be coated.

  In addition, as an amination resin (A), you may use together the amination resin from which an amine value and / or a hydroxyl value differ as needed. When two or more kinds of amine resins having different amine values and hydroxyl values are used in combination, the average amine value and the average hydroxyl value calculated based on the mass ratio of the aminated resin used are within the above numerical range. preferable. The aminated resin (A) used in combination is an aminated resin having 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 (A) may contain an amino group-containing acrylic resin, an amino group-containing polyester resin, or the like as necessary.

<Block isocyanate curing agent (B)>
The blocked isocyanate curing agent (B) (hereinafter sometimes simply referred to as “curing agent (B)”) is also a coating film forming resin constituting the electrodeposition coating film. The blocked isocyanate curing agent (B) 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 represented by ε-caprolactam and γ-butyrolactam are preferably used. .

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

  The blocked isocyanate curing agent (B) is a combination of a curing agent prepared by blocking an aliphatic diisocyanate with a sealing agent and a curing agent prepared by blocking an aromatic diisocyanate with a sealing agent. It is preferable to do.

The blocked isocyanate curing agent (B) preferentially reacts with the primary amine of the aminated resin (A), and further reacts with a hydroxyl group to be cured.
As the curing agent, at least one curing agent selected from the group consisting of an organic curing agent such as a melamine resin or a phenol resin, a silane coupling agent, and a metal curing agent may be used in combination with the blocked isocyanate curing agent (B). .

<Bismuth compound (C)>
The bismuth compound (C) is a compound containing a bismuth metal, and examples thereof include bismuth oxide, bismuth hydroxide, bismuth nitrate, and mixtures thereof. Preferred bismuth compounds (C) are bismuth oxide and bismuth hydroxide.

  The bismuth compound (C) is used in a powder form, and its average particle size is usually 0.5 to 20 μm, preferably 1 to 3 μm. The average particle diameter is a volume average particle diameter D50, and a value measured by a method described later is used.

<Organic acid (D)>
The organic acid (D) is an organic acid having no amino group, and is, for example, one or more compounds selected from the group consisting of hydroxycarboxylic acids and sulfonic acids.

Examples of the hydroxycarboxylic acid include the following compounds:
(D1) Monohydroxymonocarboxylic acids having 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, particularly aliphatic monohydroxymonocarboxylic acids such as lactic acid and glycolic acid;
(D2) monohydroxy dicarboxylic acids having 2 to 5 carbon atoms, preferably 2 to 4 carbon atoms, particularly aliphatic monohydroxy dicarboxylic acids, such as hydroxymalonic acid and malic acid;
(D3) Dihydroxymonocarboxylic acids having 3 to 7 carbon atoms, preferably 3 to 6 carbon atoms, particularly aliphatic dihydroxymonocarboxylic acids such as dimethylolpropionic acid (DMPA) and glyceric acid;
(D4) Dihydroxy dicarboxylic acids having 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, such as tartaric acid and glucose, especially aliphatic dihydroxy dicarboxylic acids.

  The sulfonic acid is an organic sulfonic acid, and examples thereof include alkanesulfonic acids having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms such as methanesulfonic acid and ethanesulfonic acid.

  Preferred organic acid (D) is one or more compounds selected from the group consisting of monohydroxymonocarboxylic acid, dihydroxymonocarboxylic acid, and alkanesulfonic acid.

  The molecular weight of the organic acid (D) is not particularly limited, and is usually 60 to 200, preferably 70 to 150. The molecular weight of the organic acid is a value calculated from the molecular formula.

  The usage form of the organic acid (D) is not particularly limited, and examples thereof include a solid form, a liquid form, a solution form dissolved in a solvent, and particularly an aqueous solution form.

<Amino acid (E)>
The amino acid (E) is an organic compound having one or more amino groups and one or more carboxyl groups in one molecule. Preferred amino acids (E) are organic compounds having 1 to 3, especially 1 amino group and 1 to 3, particularly 1 to 2 carboxyl groups in one molecule.

The amino acid (E) is preferably an amino acid having 2 to 6 carbon atoms, particularly 2 to 4 carbon atoms, particularly an aliphatic amino acid.
The molecular weight of the amino acid (E) is not particularly limited, and is usually 60 to 200, preferably 70 to 150. The molecular weight of the amino acid is a value calculated from the molecular formula.

  As the amino acid (E), for example, glycine, aspartic acid or a mixture thereof can be used.

  The usage form of the amino acid (E) is not particularly limited, and examples thereof include a solid form, a liquid form, and a solution form formed by dissolving in a solvent.

<Production of resin emulsion (1)>
Resin emulsion (1) is prepared by mixing bismuth compound (C), organic acid (D) and amino acid (E) in advance, and then mixing the resulting mixture, aminated resin (A) and blocked isocyanate curing agent (B). Prepared by mixing. Thereby, the electrodeposition coating composition of this invention can form the coating film which the solubility of the bismuth compound fully improved and was excellent in sclerosis | hardenability, film thickness uniformity, and corrosion resistance. Furthermore, the storage stability of the electrodeposition coating composition and resin emulsion of the present invention is sufficiently improved. Bismuth compound (C), organic acid (D) and amino acid (E) are premixed prior to the other components, so that the solubility of the bismuth compound, the curability of the coating, the film thickness uniformity and the corrosion resistance, and The details of the mechanism for improving storage stability are not clear, but are thought to be based on the following mechanism. This is considered to be due to the fact that when Bi is dissolved in an organic acid, an amino acid (G) having a strong chelating property is coordinated to Bi, thereby improving the dissolution stability of Bi.

  Without premixing the bismuth compound (C), organic acid (D), and amino acid (E) together with other components, when one of the organic acid (D) or amino acid (E) is not premixed, Since the bismuth compound (C) is not sufficiently dissolved, the curability and corrosion resistance of the resulting coating film are lowered. Furthermore, the storage stability of the electrodeposition coating composition and resin emulsion of the present invention decreases.

  The premixing of the bismuth compound (C), the organic acid (D) and the amino acid (E) (hereinafter sometimes simply referred to as “first mixing”) is performed by separating the bismuth compound (C) particles from the organic acid (D) and the amino acid. This is achieved by dispersing in the aqueous solution of line (E) by stirring.

  The mixing ratio of the bismuth compound (C), the organic acid (D), and the amino acid (E) at the time of the first mixing is such that the resulting resin emulsion (1) satisfies the following conditions (i) to (iii). .

(I) The molar ratio of the content of bismuth metal and organic acid (D) in the bismuth compound (C) is Bi: (D) 1: 0.25 to 1: 4, preferably 1: 0.5 to 1: 3, more preferably 1: 1 to 1: 2.
(Ii) The molar ratio of the bismuth metal and amino acid (E) content in the bismuth compound (C) is 1: 0.25 to 1: 4 in Bi: (E), preferably 1: 0.5 to 1: 3. More preferably, it is 1: 1 to 1: 2.
(Iii) The content of the bismuth compound (C) is 0.25 to 2.1% by mass, preferably 0.37 to 1.75% by mass in terms of metal element, based on the solid content of the resin emulsion (1). More preferably, it is 0.7-1.4 mass%.

In the said condition (i), content of the bismuth metal in a bismuth compound (C) is the quantity (mole number) of the bismuth metal in the bismuth compound (C) mixed in 1st mixing.
The content of the organic acid (D) is the amount (number of moles) of the organic acid mixed in the first mixing. When the organic acid (D) is used in the form of a solution, the amount of the organic acid alone in the solution (Number of moles).

In the condition (ii), the bismuth metal content in the bismuth compound (C) is the same as in the condition (i).
The content of amino acid (E) is the amount of amino acid (number of moles) mixed in the first mixture, and when amino acid (E) is used in the form of a solution, the amount of amino acid alone in the solution (number of moles) It is.

  In the above condition (iii), the content of the bismuth compound (C) is an amount in terms of metal element of the bismuth compound (C) mixed in the first mixing, and is a ratio with respect to the solid content of the resin emulsion (1). The value represented.

  In the present specification, the “solid content of the resin emulsion” means the mass of all components that are contained in the resin emulsion and remain solid even after the solvent is removed. Specifically, it means the total mass of the aminated resin (A), the blocked isocyanate curing agent (B), the bismuth compound (C) and other solid components added as necessary, contained in the resin emulsion. .

“Metal element conversion” is a metal element conversion coefficient (a coefficient for converting a metal compound amount into a metal element amount to the content of the metal compound. Specifically, the atomic weight of the metal element in the metal compound is It means a value obtained by dividing the molecular weight of the metal compound.) To obtain the target metal element amount. For example, when the bismuth compound (C) is bismuth oxide (Bi ₂ O ₃ , molecular weight 466), the metal element equivalent content of bismuth in the electrodeposition coating composition containing 0.1% by mass of bismuth oxide is 0.8. It is calculated as 0.0897% by mass by the calculation of 1% by mass × (418 ÷ 466).

  In the above condition (i), if the molar ratio of the content of the organic acid (D) to the bismuth metal in the bismuth compound (C) is too small, the bismuth compound (C) is not sufficiently dissolved, so that the resulting coating film is cured. And corrosion resistance are reduced. Furthermore, the storage stability of the electrodeposition coating composition and the resin emulsion is lowered. On the other hand, since the bismuth compound (C) is not sufficiently dissolved even if the molar ratio of the content of the organic acid (D) to the bismuth metal in the bismuth compound (C) is too large, the curability and uniformity of the coating film and Corrosion resistance decreases. Further, the storage stability of the electrodeposition coating composition and the resin emulsion is lowered.

  In the above condition (ii), if the molar ratio of the amino acid (E) content to the bismuth metal in the bismuth compound (C) is too small, the bismuth compound (C) is not sufficiently dissolved, so the curability of the resulting coating film And corrosion resistance is reduced. Furthermore, the storage stability of the electrodeposition coating composition and the resin emulsion is lowered. On the other hand, since the bismuth compound (C) is not sufficiently dissolved even if the molar ratio of the content of the amino acid (E) to the bismuth metal in the bismuth compound (C) is too large, the curability, uniformity and corrosion resistance of the coating film. Decreases. Further, the storage stability of the electrodeposition coating composition and the resin emulsion is lowered.

  In the above condition (iii), if the content ratio of the bismuth compound (C) to the solid content of the resin emulsion is too small, the curability and corrosion resistance of the resulting coating film are lowered. On the other hand, when the content ratio is too large, the curability of the coating film is recovered, but the solubility of the bismuth compound (C) and the uniformity of the coating film are lowered, and the resin emulsion and the electrodeposition coating composition are stored. Stability is reduced.

The content ratio of the organic acid (D) in the mixture obtained by the first mixing is usually a ratio of the organic acid (D) alone in the aqueous solution of the organic acid (D) to the total amount of the mixture, and is 0.5 to 10% by mass. Yes, preferably 1-5% by mass.
The content ratio of the amino acid (E) in the mixture obtained by the first mixing is usually 0.18 to 10% by mass, preferably the ratio of the amino acid (E) alone in the aqueous amino acid (E) solution to the total amount of the mixture, Is 1.5 to 4% by mass.

  In the first mixing, since the bismuth compound (C), the organic acid (D) aqueous solution, the amino acid (E), and ion-exchanged water are usually mixed, the organic acid (D) alone is used depending on the amount of ion-exchanged water used. And the content rate of an amino acid (E) is adjusted. If the content ratio of the organic acid (D) and / or amino acid (E) is too small, the bismuth compound (C) is not sufficiently dissolved, so that the curability of the resulting coating film is lowered. On the other hand, even if the content ratio of the organic acid (D) and / or amino acid (E) is too large, the bismuth compound (C) is not sufficiently dissolved, so that the curability of the coating film is lowered.

  The temperature of the mixture at the time of the first mixing does not affect the solubility of the bismuth compound (C), and is usually 10 to 50 ° C., preferably room temperature.

  The stirring speed at the time of the first mixing is not particularly limited as long as stirring to such an extent that a stirring flow is generated is achieved.

  The first mixing is preferably performed until the average particle size of the bismuth compound (C) is 100 nm or less, preferably 20 nm or less. In the present invention, the solubility of the bismuth compound (C) is sufficiently improved, so that the dissolution rate is sufficiently high. As a result, in the present invention, the first mixing time for achieving the average particle size is within about 7 hours, preferably 0.5 to 6 hours, more preferably 0.5 to 3 hours, and still more preferably. 0.5 to 1 hour.

  After the first mixing, the resulting mixture, the aminated resin (A) and the blocked isocyanate curing agent (B) are further mixed to prepare a resin emulsion. Mixing of the mixture obtained in the first mixing, the aminated resin (A) and the blocked isocyanate curing agent (B) (hereinafter sometimes simply referred to as “second mixing”) is achieved by stirring these mixtures. Is done.

  The mixing amount of the aminated resin (A) and the blocked isocyanate curing agent (B) at the time of the second mixing is not particularly limited as long as the above condition (iii) is satisfied. The amount is 35% by mass or more, particularly 37 to 45% by mass with respect to the total amount of the resin emulsion.

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

  Although the temperature of the mixture at the time of the 2nd mixing is not specifically limited, 20-50 degreeC and especially room temperature are preferable from a viewpoint of ensuring stability of a resin emulsion.

  The stirring speed at the time of the second mixing is not particularly limited as long as stirring to such an extent that a stirring flow is generated is achieved.

  The second mixing is usually performed for at least 30 minutes after the addition of water.

In the present invention, the mixture immediately before the second mixing, that is, the mixture immediately before mixing the aminated resin (A) and the curing agent (B) is 5% or less, particularly 1.5% or less, preferably 0.5%. It is preferable to show the following bismuth compound dissolution residue amount.
The amount of the bismuth compound dissolution residue is shown as a ratio with respect to the content (charge amount) of the bismuth compound (C) in the mixture, and a value measured by the method described later is used.

  In the present invention, in the production of a resin emulsion, a mixture of bismuth compound (C), organic acid (D) and amino acid (E) (hereinafter sometimes referred to as mixture A), aminated resin (A) and blocked isocyanate. Mixing with the curing agent (B) may be achieved by a Bi aqueous solution addition type method or may be achieved by a batch dissolution type method.

The Bi aqueous solution addition type method is a method in which a mixture of a bismuth compound (C), an organic acid (D) and an amino acid (E) is mixed with a mixture of an aminated resin (A) and a blocked isocyanate curing agent (B). It is.
The batch dissolution method is a method in which a mixture of an aminated resin (A) and a blocked isocyanate curing agent (B) is mixed with a mixture of a bismuth compound (C), an organic acid (D) and an amino acid (E). is there.

  In the present invention, the Bi aqueous solution addition method is preferable from the viewpoint of paint stability. From the viewpoint of paint production efficiency, the batch dissolution method is preferred.

  After the aminated resin (A) is mixed with the blocked isocyanate curing agent (B) and before being mixed with the mixture of bismuth compound (C), organic acid (D) and amino acid (E), a neutralized acid is used. The neutralization acid may be added to the mixture obtained by the first mixing, and the mixture may be neutralized by mixing with the mixture.

  Examples of the neutralizing acid include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, dimethylolpropionic acid, formic acid, and acetic acid. In the present invention, it is more preferable to neutralize with one or more acids selected from the group consisting of formic acid and acetic acid.

  The neutralizing acid is more preferably used in an amount of 10 to 100% as an equivalent ratio of the neutralizing acid to the equivalent of the amino group of the aminated resin (A), and is used in an amount of 20 to 70%. Is more preferable. In this specification, the equivalent ratio of the neutralized acid to the equivalent of the amino group of the aminated resin (A) is defined as the neutralization rate. When the neutralization rate is 10% or more, affinity for water is ensured and water dispersibility is improved.

[Pigment dispersion paste (2)]
The pigment dispersion paste (2) is a component optionally contained in the electrodeposition coating composition, and usually contains a pigment dispersion resin (F) and a pigment (G).

<Pigment dispersion resin (F)>
The pigment dispersion resin (F) is a resin for dispersing the pigment (G), and is used by being dispersed in an aqueous medium. 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.

<Pigment (G)>
The pigment (G) is a pigment usually used in an electrodeposition coating composition. As pigments, for example, commonly used inorganic and organic pigments, eg colored pigments such as titanium white (titanium dioxide), carbon black and bengara; like kaolin, talc, aluminum silicate, calcium carbonate, mica and clay And extender pigments such as iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and rust preventive pigments such as aluminum phosphomolybdate and zinc aluminum phosphomolybdate.

<Production of pigment dispersion paste (2)>
The pigment dispersion paste (2) is prepared by mixing the pigment dispersion resin (F) and the pigment (G).

  Although content of pigment dispersion resin (F) in a pigment dispersion paste is not specifically limited, Usually, it is 20-100 mass parts by resin solid content ratio with respect to 100 mass parts of pigments (G).

  The solid content of the pigment dispersion paste is usually 40 to 70% by mass, particularly 50 to 60% by mass, based on the total amount of the pigment dispersion paste.

  In the present specification, the “solid content of the pigment dispersion paste” means the mass of all components that are contained in the pigment dispersion paste and remain solid even after removal of the solvent. Specifically, it means the total mass of the pigment dispersion resin (F) and the pigment (G) contained in the pigment dispersion paste and other solid components added as necessary.

[Production of electrodeposition coating composition]
The electrodeposition coating composition of the present invention may be adjusted by adjusting the resin emulsion (1) described above to a desired solid content with ion-exchanged water, or the resin emulsion (1) and the pigment dispersion paste (2). ) May be mixed.

  In the present invention, the content of the bismuth compound (C) contained in the electrodeposition coating composition is 0.10 to 1.6% by mass in terms of metal element, preferably based on the solid content of the electrodeposition coating composition. Is 0.15 to 1.6% by mass, more preferably 0.25 to 1.6% by mass, still more preferably 0.38 to 1.25% by mass, and most preferably 0.5 to 1.0% by mass. Preferably there is. The content of the bismuth compound (C) is the amount (mass) of the bismuth compound (C) mixed in the first mixing.

  In the present specification, the “solid content of the electrodeposition coating composition” means the mass of all components that are contained in the electrodeposition coating composition and remain solid even after removal of the solvent. . Specifically, the aminated resin (A), the curing agent (B), the bismuth compound (C), the pigment dispersion resin (F) and the pigment (G) contained in the electrodeposition coating composition, and as necessary It means the total mass of other solid components to be added.

  The solid content of the electrodeposition coating composition of the present invention is preferably 1 to 30% by mass with respect to the total amount of the electrodeposition coating composition. When the amount of the solid content of the electrodeposition coating composition is less than 1% by mass, the amount of electrodeposition coating deposited decreases, and it may be difficult to ensure sufficient corrosion resistance. Further, when the solid content of the electrodeposition coating composition exceeds 30% by mass, the throwing power or the coating appearance may be deteriorated.

  When the pigment dispersion paste (2) is used, the solid content mixing ratio of the resin emulsion (1) and the pigment dispersion paste (2) is usually a mass ratio of (1) :( 2) and is 1: 0.1-1 : 0.4, preferably 1: 0.15 to 1: 0.3.

  The electrodeposition coating composition of the present invention preferably has a pH of 4.5-7. When the pH of the electrodeposition coating composition is less than 4.5, there is a problem that the corrosion resistance is inferior and sludge is generated in the electrodeposition coating. The pH of the electrodeposition coating composition can be set in the above range by adjusting the amount of neutralizing acid used, the amount of free acid added, and the like.

  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 milligram equivalent (MEQ (A)) of the acid with respect to 100 g of solid content of the 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 obtained by accurately weighing about 10 g of the solid content of the electrodeposition coating composition and dissolving it in about 50 ml of a solvent (THF: tetrahydrofuran), followed by potentiometric titration using a 1/10 N NaOH solution. The amount of acid contained in the electrodeposition coating composition can be quantified and measured.

  It is preferable that the electrodeposition coating composition 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 of the present invention contains a bismuth compound (C). 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.

  The electrodeposition coating composition of the present invention comprises additives generally used in the coating field, such as ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol. Organic solvents such as monobutyl ether and propylene glycol 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, An inorganic rust preventive agent such as a calcium salt may be included 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. These additives may be added at the time of the second mixing in the production of the resin emulsion, may be added at the time of the production of the pigment dispersion paste, or after or after the mixing of the resin emulsion and the pigment dispersion paste. It may be added.

  The electrodeposition coating composition of the present invention may contain other film-forming resin components in addition to the aminated resin (A). Examples of other film forming resin components include acrylic resin, polyester resin, urethane resin, butadiene resin, phenol resin, xylene resin, and the like. The aminated resin which does not correspond to the aminated resin (A) as described above may be used. 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.

[Electrodeposition coating and electrodeposition coating formation]
The electrodeposition coating composition of the present invention can be used for electrodeposition coating and electrodeposition coating film formation on an object to be coated.
In the electrodeposition coating using the electrodeposition coating composition of the present invention, a voltage is applied between an object to be coated and a cathode. Thereby, an electrodeposition film deposits on a to-be-coated article.

  In the electrodeposition coating step, the electrodeposition coating is performed by applying a voltage of 50 to 450 V after the object to be coated is immersed in the electrodeposition coating composition. 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 time for applying the voltage varies depending on the electrodeposition conditions, but can generally be 2 to 5 minutes.

  The film thickness of the electrodeposition film is such that the film thickness of the electrodeposition film finally obtained by heat curing is preferably 5 to 40 μm, more preferably 10 to 25 μm. If the film thickness of the electrodeposition coating film 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 film obtained as described above is heat-cured 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. An electrodeposition coating film is formed.

  As an object to be coated with the electrodeposition coating composition 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 include steel plates, zinc-aluminum-magnesium alloy plated steel plates, aluminum-based plated steel plates, aluminum-silicon alloy-plated steel plates, and tin-based plated steel plates.

  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 Production of aminated resin 92 parts of methyl isobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical), 325 parts of bisphenol A, 65 parts of octylic acid, and 2 parts of dimethylbenzylamine were added. The temperature in the reaction vessel was maintained at 140 ° C., and the reaction was continued until the epoxy equivalent reached 1220 g / eq, and then cooled until the temperature in the reaction vessel reached 120 ° C. Subsequently, a mixture of 52 parts of diethylenetriamine diketimine (methyl isobutyl ketone solution having a solid content of 73%) and 83 parts of diethanolamine was added and reacted at 120 ° C. for 1 hour to obtain an aminated resin (cation-modified epoxy resin).
The number average molecular weight of this resin was 2,560, the amine value was 50 mgKOH / g (of which the amine value derived from the primary amine was 14 mgKOH / g), and the hydroxyl value was 240 mgKOH / g.

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 (trade name DER-331J, manufactured by Dow Chemical Company), 120 parts of bisphenol A in a reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, and a thermometer, Charge 95 parts octyl acid and 1 part 2-ethyl-4-methylimidazole 1% solution, react at 160-170 ° C. for 1 hour in a nitrogen atmosphere, then cool to 120 ° C., then 2-ethylhexanolated half-blocked 198 parts of a methyl isobutyl ketone solution of tolylene diisocyanate (solid content 95%) was added. After maintaining the reaction mixture at 120 to 130 ° C. for 1 hour, 157 parts of ethylene glycol mono n-butyl ether 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 average molecular weight 2,200) 25% solids) was obtained.

Production Example 4 Production of Pigment Dispersion Paste Based on the formulation shown in Table 1 below including the pigment dispersion resin obtained in Production Example 3 using a sand mill, the resulting mixture had a volume average particle diameter D50 of 40 ° C. The pigment dispersion paste 1 was obtained by dispersing to 0.6 μm. 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.

(Example 1) Bi solution added type
Production of Bismuth Aqueous Solution A While mixing and stirring 1813.2 g of ion-exchanged water, 68.9 g of 50% aqueous lactic acid, and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution A was obtained.

Production of Resin Emulsion A 350 g (solid content) of the aminated resin obtained in Production Example 1, 75 g (solid content) of the blocked isocyanate curing agent (1) obtained in Production Example 2-1, and Production Example 2-2. The blocked isocyanate curing agent (2) (75 g, solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added to 3% (15 g) based on the solid content. Next, the formic acid and acetic acid are equimolarly added so that the total addition amount thereof is equivalent to a resin neutralization rate of 40% for neutralization, and 87.5 g of the bismuth aqueous solution A is added and mixed (second) mixture). Thereafter, ion-exchanged water was added to slowly dilute, and then methyl isobutyl ketone was removed under reduced pressure so that the solid content was 40%, whereby Resin Emulsion A was obtained.

Production of electrodeposition coating composition A To a stainless steel container, 504 g of ion-exchanged water, 370 g of the resin emulsion A and 81 g of the pigment dispersion paste of Production Example 4 were added, and then aged at 40 ° C. for 16 hours to obtain an electrodeposition coating composition. Got.

(Examples 2 to 14 and Comparative Examples 1 to 7) Bi solution added type
Production of Resin Emulsion Using the prescribed aqueous bismuth solution shown in Table 2 / Table 3 in each Example / Comparative Example (production method will be described later), the content of the bismuth compound in the resin emulsion is shown in Table 2 / Table 3. The same amount as in the resin emulsion A, except that the bismuth aqueous solution was used in such an amount as to be a value, and that the methyl isobutyl ketone was removed so that the solid content of the resin emulsion became a value described in Table 2 / Table 3. By the method, a resin emulsion was obtained.

Production of electrodeposition coating composition The resin emulsion was used in such an amount that the content of the bismuth compound in the electrodeposition coating composition was as shown in Table 2 / Table 3, and the solid content of the electrodeposition coating composition The electrodeposition coating composition was obtained by the same method as the electrodeposition coating composition A, except that ion-exchanged water was used in such an amount that the value indicated in Table 2 / Table 3 was obtained.

Production of Bismuth Aqueous Solution B While mixing and stirring 1831.7 g of ion-exchanged water, 51.3 g of DMPA, and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. Stirring and mixing at 1000 rpm for 6 hours at 40 ° C. dissolved bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Then, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution B was obtained.

Production of Bismuth Aqueous Solution C While mixing and stirring 1791.2 g of ion-exchanged water, 68.9 g of 50% aqueous lactic acid, and 51.0 g of aspartic acid, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform aqueous bismuth solution C was obtained.

Production of Bismuth Aqueous Solution D While mixing and stirring 1808.8 g of ion exchange water, 51.3 g of DMPA and 51.0 g of aspartic acid, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution D was obtained.

Production of bismuth aqueous solution E While mixing and stirring 1865.2 g of ion-exchanged water, 17.2 g of 50% aqueous lactic acid solution and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered through 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution E was obtained.

Production of Bismuth Aqueous Solution F While mixing and stirring 1606.7 g of ion-exchanged water, 275.6 g of 50% aqueous lactic acid, and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution F was obtained.

Production of Bismuth Aqueous Solution G While mixing and stirring 1835.0 g of ion-exchanged water, 68.9 g of 50% aqueous lactic acid, and 7.2 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution G was obtained.

Production of Bismuth Aqueous Solution H While mixing and stirring 1727.3 g of ion-exchanged water, 68.9 g of 50% aqueous lactic acid, and 114.8 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution H was obtained.

Production of Bismuth aqueous solution I While mixing and stirring 1886.7 g of ion-exchanged water, 17.2 g of 50% aqueous lactic acid solution and 7.2 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered through 508 mesh to remove the dissolution residue, and a uniform aqueous bismuth solution I was obtained.

Production of Bismuth Aqueous Solution J While mixing and stirring 1520.6 g of ion-exchanged water, 275.6 g of 50% aqueous lactic acid, and 114.8 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution J was obtained.

Production of Bismuth Aqueous Solution K While mixing and stirring 1615.9 g of ion-exchanged water, 61.8 g of 50% aqueous lactic acid, and 25.7 g of glycine, 89.2 g of bismuth hydroxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Then, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution K was obtained.

Production of Bismuth Aqueous Solution L While mixing and stirring 1831.0 g of ion-exchanged water, 51.4 g of 70% aqueous methanesulfonic acid, and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform aqueous bismuth solution L was obtained.

Production of Bismuth Aqueous Solution X1 While mixing and stirring 1882.4 g of ion exchange water and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered through 508 mesh, and the dissolution residue was removed to obtain a uniform bismuth aqueous solution X1.

Production of Bismuth Aqueous Solution X2 While mixing and stirring 1537.8 g of ion-exchanged water, 344.5 g of 50% lactic acid aqueous solution, and 28.7 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered through 508 mesh to remove the dissolution residue, thereby obtaining a uniform aqueous bismuth solution X2.

Production of Bismuth Aqueous Solution X3 While mixing and stirring 1842.2 g of ion-exchanged water and 68.9 g of 50% lactic acid aqueous solution, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Then, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution X3 was obtained.

Production of Bismuth Aqueous Solution X4 While mixing and stirring 1698.6 g of ion-exchanged water, 68.9 g of 50% lactic acid aqueous solution, and 143.6 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Thereafter, the solution was filtered through 508 mesh to remove the dissolution residue, thereby obtaining a uniform aqueous bismuth solution X4.

Production of Bismuth Aqueous Solution X5 While mixing and stirring 1423.0 g of ion-exchanged water, 344.5 g of 50% lactic acid aqueous solution, and 143.6 g of glycine, 89.2 g of bismuth oxide was added thereto. The mixture was stirred and mixed at 1000 rpm for 4 hours at room temperature to dissolve bismuth oxide (first mixing). As dissolution progressed, the solution changed from yellow to white. Then, the solution was filtered with 508 mesh to remove the dissolution residue, and a uniform bismuth aqueous solution X5 was obtained.

(Example 15) Batch dissolution type
Production of aqueous bismuth M 82.75 g of ion-exchanged water, 3.00 g of 50% lactic acid, and 1.25 g of glycine were mixed and stirred while adding 3.88 g of bismuth oxide and stirred at 1000 rpm for 4 hours at room temperature. And mixing to dissolve the bismuth oxide (first mixing). Next, formic acid and acetic acid were added in equimolar amounts so that their total addition amount was equivalent to 40% of the sum of the aminated resin.

Production of resin emulsion 350 g (solid content) of aminated resin obtained in Production Example 1, 75 g (solid content) of blocked isocyanate curing agent (1) obtained in Production Example 2-1, and block obtained in Production Example 2-2 The isocyanate curing agent (2) (75 g, solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added to 3% (15 g) based on the solid content. The obtained mixture was added to the bismuth aqueous solution M and mixed (second mixing). Thereafter, ion-exchanged water was added to slowly dilute, and then methyl isobutyl ketone was removed under reduced pressure so that the solid content was 40% to obtain a resin emulsion.

Production of electrodeposition paint composition 504 g of ion exchange water, 370 g of the resin emulsion and 81 g of the pigment dispersion paste of Production Example 4 were added to a stainless steel container, and then aged at 40 ° C. for 16 hours to obtain an electrodeposition paint composition. Obtained.

(Comparative Examples 8-9) Batch dissolution type
Production of Resin Emulsion Using the prescribed bismuth aqueous solution shown in Table 3 in each comparative example, using the bismuth aqueous solution in such an amount that the content of the bismuth compound in the resin emulsion becomes the value shown in Table 3, and A resin emulsion was obtained in the same manner as in the resin emulsion of Example 15, except that methyl isobutyl ketone was removed so that the solid content of the resin emulsion became the values shown in Table 3.

Production of electrodeposition coating composition The resin emulsion was used in such an amount that the content of the bismuth compound in the electrodeposition coating composition was as shown in Table 3, and the solid content of the electrodeposition coating composition was as shown in Table 3. An electrodeposition coating composition was obtained in the same manner as the electrodeposition coating composition of Example 15 except that ion-exchanged water was used in such an amount that the value described in (1) was obtained.

The annotations in the table are shown below.
(I): In the calculation of the molar ratio, Bi in (C) is the number of moles of bismuth metal in the bismuth compound (C) mixed in the first mixing, and (D) is an organic acid aqueous solution mixed in the first mixing. The number of moles of organic acid alone in the solvent, and (E) is the number of moles of amino acid alone in the aqueous amino acid solution mixed in the first mixing.
(II): The content ratio of the organic acid (D) at the time of the first mixing is a ratio of the organic acid (D) alone in the organic acid (D) aqueous solution to the total amount of the mixture at the time of the first mixing.
(III): The content ratio of the amino acid (E) at the time of the first mixing is the ratio of the amino acid (E) alone in the amino acid (E) aqueous solution to the total amount of the mixture at the time of the first mixing.
(IV): The content of the bismuth compound (C) is a ratio with respect to the solid content of the resin emulsion, and is a value in terms of a metal element.
(V): The content of the bismuth compound (C) is a ratio to the solid content of the electrodeposition coating composition, and is a value in terms of a metal element.
(VI): The particle diameter of the bismuth compound is the average particle diameter of the bismuth compound (C) immediately before the first mixing.
(VII): The particle diameter of the bismuth compound is the average particle diameter of the bismuth compound (C) in the mixture immediately before the removal of the dissolved residue in the production of the bismuth aqueous solution. In addition, as the mixture immediately before the removal of the dissolved residue, the mixture immediately after the first mixing and before the filtration was used.
In this specification, the average particle size is a volume average particle size D50, and ion exchange is performed using a laser Doppler particle size analyzer (manufactured by Nikkiso Co., Ltd., “Microtrac UPA150”) so that the signal level is appropriate. Diluted with water and measured.

(Evaluation method)
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. Next, it was immersed in Surffine GL1 (manufactured by Nippon Paint Co., Ltd.) at room temperature for 30 seconds and immersed in Surfdyne 6350 (manufactured by Nippon Paint Co., Ltd.) at 35 ° C. for 2 minutes. Washed with deionized water.
On the other hand, a necessary amount of 2-ethylhexyl glycol was added to the obtained electrodeposition coating composition so that the film thickness of the electrodeposition coating film after curing was 15 μm. Then, after all the steel sheets were buried in the electrodeposition coating composition, voltage application was started immediately, and the voltage was applied under the condition that the voltage was increased for 30 seconds and reached 180 V and then held for 150 seconds. An uncured electrodeposition film was deposited on the steel sheet. The obtained uncured electrodeposition film was heat-cured at 160 ° C. for 15 minutes to obtain an electrodeposition coated plate having an electrodeposition film.

In the production of the bismuth compound soluble resin emulsion, the amount of bismuth compound dissolution residue in the mixture immediately before mixing the aminated resin and the curing agent was measured.
Specifically, the dissolution residue remaining on the mesh was dried at 110 ° C. for 15 minutes by 508 mesh filtration. The mass of the dried dissolved residue was measured, the ratio of the dissolved residue to the charged amount was determined, and the solubility of the bismuth compound was evaluated.
Evaluation criteria A; dissolved residue amount 0.5% or less;
○: Dissolved residue amount more than 0.5% and 1.5% or less;
○ △: Dissolved residue amount more than 1.5% and 5% or less;
Δ: Dissolved residue amount more than 5% and 10% or less (no practical problem);
X: Dissolution residue amount Over 10% and 20% or less (practical problem);
XX: Dissolving residue amount exceeds 20%.

Storage stability of resin emulsion The state of the resin emulsion stored at 40 ° C. for 1 month was visually evaluated. The evaluation criteria were as follows.
Evaluation criteria ◎; no separation or sedimentation is observed;
○: With very little sedimentation, it easily returns to a uniform state by stirring (no problem in practical use);
○ △: Slightly settled and easily returns to a uniform state by stirring (no problem in practical use);
Δ: Soft sedimentation, but returns to a uniform state by stirring (no problem in practical use);
X: Hard settling occurs, and even when stirred, it does not become uniform (practically problematic);
XX: Hard settling occurs within one week and does not become uniform even with stirring (practically problematic).

Storage stability of paint The state of the paint stored at 40 ° C. for 1 month was evaluated by the filterability of the paint. The evaluation criteria were as follows.
Evaluation criteria ◎; easily passes through 508 mesh (manufactured by NBC);
○; Pass through 508 mesh (manufactured by NBC);
○ △: Slightly difficult to pass through 508 mesh (no problem in practical use);
Δ: Difficult to pass through 508 mesh (no problem in practical use);
×: Can hardly pass 508 mesh (practical problem);
XX: Cannot pass through 508 mesh at all (there is a problem in practice).

Curability The electrodeposition coating film coated in accordance with the above evaluation method was immersed in acetone and heated to reflux at 56 ° C. for 4 hours. After the reflux, the electrodeposition coating film was dried, and the coating film residual rate was determined from the following formula from the coating film mass before and after immersion in acetone, and the curability was evaluated. The evaluation criteria were as follows.
Coating film residual ratio = Y / X
X = coating mass before immersion in acetone;
Y = coating film mass after acetone immersion.
Evaluation criteria A; coating film residual ratio 97.5% or more;
○: Residual ratio of coating film: less than 97.5% and 95% or more;
○ △: paint film remaining rate less than 95% 90% or more (no problem in practical use);
Δ: coating film residual ratio 85% or more and less than 90% (no problem in practical use);
X: Coating film residual ratio 80% or more and less than 85% (practical problem);
XX: Coating film remaining rate is less than 80%.

Cured electrodeposition coating appearance (paint appearance)
About the electrodeposition coating plate which has the electrodeposition coating film obtained by the said evaluation method, the presence or absence of abnormality in a coating-film external appearance was evaluated visually. The evaluation criteria were as follows.
Evaluation Criteria A: Good smoothness and very uniform coating appearance;
○: It has a uniform coating film appearance;
○ △: Although there is a portion that is visually recognized if there is some unevenness, it has a substantially uniform coating appearance as a whole;
Δ: Unevenness is visible, but there is no practical problem;
X: Appearance of the coating film is clearly uneven (practical problem);
XX: The appearance of the coating film is extremely uneven.

Corrosion resistance
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)

  The electrodeposition coating composition of the present invention is useful, for example, as an undercoat paint for automobiles.

Claims (10)

An electrodeposition coating composition comprising a resin emulsion (1),
The resin emulsion (1) contains an aminated resin (A), a blocked isocyanate curing agent (B), a bismuth compound (C), an organic acid (D) and an amino acid (E),
The organic acid (D) is one or more selected from the group consisting of hydroxycarboxylic acid and sulfonic acid,
The electrodeposition coating composition in which the resin emulsion (1) satisfies the following conditions:
(I) The molar ratio of the bismuth metal and organic acid (D) content in the bismuth compound (C) is 1: 0.25 to 1: 4 in Bi: (D);
(Ii) the molar ratio of the bismuth metal and amino acid (E) content in the bismuth compound (C) is 1: 0.25 to 1: 4 in Bi: (E); and (iii) the bismuth compound (C) Is 0.25 to 2.1% by mass in terms of metal element with respect to the solid content of the resin emulsion (1). The hydroxycarboxylic acid is a monohydroxymonocarboxylic acid having 2 to 4 carbon atoms and a dihydroxymonocarboxylic acid having 3 to 6 carbon atoms;
The sulfonic acid is an alkanesulfonic acid having 1 to 3 carbon atoms in total;
The electrodeposition coating composition according to claim 1, wherein the amino acid (E) is an amino acid having 2 to 6 carbon atoms in total. The hydroxycarboxylic acid is one or more selected from the group consisting of lactic acid and dimethylolpropionic acid;
The sulfonic acid is methanesulfonic acid;
The electrodeposition coating composition according to claim 1, wherein the amino acid (E) is one or more selected from the group consisting of glycine and aspartic acid.   The electrodeposition coating composition in any one of Claims 1-3 in which the said resin emulsion (1) has a solid content amount of 35 mass% or more.   The resin emulsion (1) is prepared by previously mixing the bismuth compound (C), the organic acid (D) and the amino acid (E), and then the resulting mixture, the aminated resin (A) and the blocked isocyanate curing agent (B). The electrodeposition coating composition according to any one of claims 1 to 4, which is prepared by mixing.   The electrodeposition coating composition according to claim 5, wherein the bismuth compound (C), the organic acid (D), and the amino acid (E) are mixed until the average particle size of the bismuth compound (C) is 100 nm or less. The resin emulsion (1)
Prepared by mixing a mixture of aminated resin (A) and blocked isocyanate curing agent (B) with a mixture of bismuth compound (C), organic acid (D) and amino acid (E), or bismuth compound 7. According to claim 5 or 6, prepared by mixing a mixture of (C), organic acid (D) and amino acid (E) with a mixture of aminated resin (A) and blocked isocyanate curing agent (B). The electrodeposition coating composition as described.   The mixture immediately before mixing the aminated resin (A) and the blocked isocyanate curing agent (B) exhibits a bismuth compound dissolution residue amount of 5% or less with respect to the content of the bismuth compound (C) in the mixture. The electrodeposition coating composition in any one of 5-7.   The electrodeposition coating composition according to any one of claims 1 to 8, further comprising a pigment dispersion paste (2) comprising a pigment dispersion resin (F) and a pigment (G).   The content of bismuth metal in the bismuth compound (C) contained in the electrodeposition coating composition is 0.10 to 1.6% by mass in terms of metal element with respect to the solid content of the electrodeposition coating composition, The electrodeposition coating composition according to any one of claims 1 to 9.