Cationic electrodeposition coating composition and method for producing same

Abstract

This cationic electrodeposition coating composition contains an aminated epoxy resin, a blocked polyisocyanate curing agent, and an inorganic pigment. The aminated epoxy resin has an amination site (a) where an epoxy ring of a raw material epoxy resin has been modified by an amine compound (x), and a cap site (c) where a terminal epoxy ring of the raw material epoxy resin has been modified by a cap compound (y) having a functional group, other than an amino group, that is capable of reacting with an epoxy ring. The amine compound (x) has at least one of a primary amino group and a secondary amino group and has no ketimine structure. The cap compound (y) contains an aromatic compound (y1) having one phenolic hydroxy group as the functional group and two or more aromatic rings. The amination site (a) is formed by the epoxy ring being opened by at least one of the primary amino group and the secondary amino group. The cap site (c) includes an aromatic cap site (c1) formed by the terminal epoxy ring being opened by the phenolic hydroxy group.

Description

Cationic electrodeposition coating composition and method for producing the same

[0001] The present invention relates to a cationic electrodeposition coating composition and a method for producing the same.

[0002] Cationic electrodeposition coatings are generally used as primers for automobiles and other applications. These coatings form a highly corrosion-resistant film.

[0003] Amineralized epoxy resins are generally used as the film-forming resin in cationic electrodeposition coating compositions. Patent documents 1 to 4 propose phenol modification of amineralized epoxy resins for the purpose of improving corrosion resistance and other properties.

[0004] Japanese Patent Publication No. 2010-95668, Japanese Patent Publication No. 2021-155696, Chinese Patent Application Publication No. 117715991, U.S. Patent Application Publication No. 2010 / 0163417

[0005] In recent years, in order to promote carbon neutrality, it is expected that various lightweight and high-strength substrates will be adopted for automobile bodies. Furthermore, automobile bodies may be constructed by combining multiple different types of materials. Accordingly, cationic electrodeposition coating compositions are required to be compatible with various substrates.

[0006] The present invention aims to provide a cationic electrodeposition coating composition that can form an electrodeposited coating of a desired thickness on various substrates with different electrical resistances.

[0007] The present invention provides the following embodiments: [1] A cationic electrodeposition coating composition comprising an aminerated epoxy resin, a blocked polyisocyanate curing agent, and an inorganic pigment, wherein the aminerated epoxy resin has an aminerated site (a) in which the epoxy ring of a raw epoxy resin is modified with an amine compound (x), and a capped site (c) in which the terminal epoxy ring of the raw epoxy resin is modified with a capped site (y) having a functional group that can react with epoxy rings other than an amino group, the amine compound (x) has at least one of a primary amino group and a secondary amino group and does not have a ketimine structure, the capped site (y) comprises an aromatic compound (y1) having one phenolic hydroxyl group and two or more aromatic rings as the functional group, the aminerated site (a) is formed by ring-opening of the epoxy ring by at least one of the primary amino group and the secondary amino group, and the capped site (c) comprises an aromatic capped site (c1) formed by ring-opening of the terminal epoxy ring by the phenolic hydroxyl group. [2] The aminerated epoxy resin has a polarity term δ that constitutes the Hansen solubility parameter Ｐ The value is between 10.0 and 13.0, and the hydrogen bonding term δ ｈ A cationic electrodeposition coating composition according to [1] above, wherein the ratio is 8.5 to 10.5. [3] The amine compound (x) comprises a first amine compound (x1) having a primary amino group and not having a ketimine structure, and a second amine compound (x2) other than the first amine compound (x1) having a secondary amino group and not having a ketimine structure, and the amination site (a) comprises a crosslinked amination site (a11) having a crosslinked structure formed by the opening of two epoxy rings by the first amine compound (x1), and a terminal amination site (a12) formed by the opening of a terminal epoxy ring by the second amine compound (x2), the cationic electrodeposition coating composition according to [1] or [2] above. [4] The first amine compound (x1) is the following general formula (1): NH ２ - (CH ２ ) ｎ -NR １ R ２(1) (In the formula, R １ and R ２ each independently represents an alkyl group having 1 to 6 carbon atoms which may have a hydroxyl group at the terminal, and n represents an integer of 2 to 4.) The cationic electrodeposition coating composition of the above [3]. [5] The second amine compound (x2) is represented by the following general formula (2): R ３ R ４ NH (2) (In the formula, R ３ and R ４Each of these independently represents an alkyl group having 1 to 4 carbon atoms having a hydroxyl group at its terminal end.) A cationic electrodeposition coating composition according to [3] or [4] above. [6] A cationic electrodeposition coating composition according to any of [1] to [5] above, wherein the amination site (a) has a terminal amination site (a12) formed by ring-opening of the terminal epoxy ring by the amine compound (x), and the number ratio (a12:c) of the terminal amination site (a12) to the cap site (c) is 40:60 to 80:20. [7] A cationic electrodeposition coating composition according to any of [1] to [6] above, wherein the cap compound (y) further comprises a monocarboxylic acid (y2) having 5 to 14 carbon atoms other than the aromatic compound (y1), and the cap site (c) further comprises a second cap site (c2) formed by ring-opening of the terminal epoxy ring by the monocarboxylic acid (y2). [8] The cationic electrodeposition coating composition according to [7], wherein the equivalent ratio (E2:E3) of the equivalent amount E2 of the phenolic hydroxyl group of the aromatic compound (y1) and the equivalent amount E3 of the carboxylic acid of the monocarboxylic acid (y2) to the epoxy ring of the raw material epoxy resin is 40:60 to 99:1. [9] The cationic electrodeposition coating composition according to any of [1] to [8], wherein the number ratio of the aromatic cap portion (c1) to the cap portion (c) is 40% or more.

[10] The present invention comprises: reacting a raw epoxy resin with an amine compound (x) and a cap compound (y) having a functional group that can react with an epoxy ring other than an amino group to prepare an aminerated epoxy resin having an aminerated moiety (a) in which the epoxy ring is modified with the amine compound (x) and a capped moiety (c) in which the terminal epoxy ring is modified with the cap compound (y); mixing the aminerated epoxy resin with a blocked polyisocyanate curing agent to prepare a resin emulsion (i); and mixing the resin emulsion (i) with a pigment dispersion paste (ii) containing an inorganic pigment, wherein the amine compound (x) has at least one of a primary amino group and a secondary amino group and does not have a ketimine structure, the cap compound (y) contains an aromatic compound (y1) having one phenolic hydroxyl group and two or more aromatic rings, and the aminerated moiety (a) is formed by ring-opening of the epoxy ring by at least one of the primary amino group and the secondary amino group. A method for producing a cationic electrodeposition coating composition, wherein the cap portion (c) includes an aromatic cap portion (c1) formed by ring-opening of a terminal epoxy ring by the phenolic hydroxyl group.

[0008] The present invention provides a cationic electrodeposition coating composition that can form an electrodeposited coating of a desired thickness on various substrates with different electrical resistances.

[0009] In cationic electrodeposition coating, an electric current is passed through a substrate (e.g., a car body) as the cathode, causing positively charged amineralized epoxy resin particles to adhere to the surface of the substrate. The attached particles fuse together due to Joule heating generated in the substrate, and eventually the surface of the substrate is covered with a coating of amineralized epoxy resin. The electrical resistance of the substrate surface increases as particles adhere, and the electrodeposition process ends when the electrical resistance increases to the point where particle adhesion becomes difficult.

[0010] The electrical resistance of the substrate surface varies depending on the type of substrate. Therefore, even when cationic electrodeposition coating is performed under the same conditions, the thickness of the electrodeposited coating film obtained varies depending on the substrate. In the present disclosure, by increasing the hydrophobicity of the aminated epoxy resin, the variation in the thickness of the electrodeposited coating film (hereinafter sometimes simply referred to as "variation in film thickness") that can occur between a plurality of different substrates is reduced. As a result, it is possible to form a coating film with the same desired thickness on various materials under the same coating conditions without the need to change the conditions according to the material. For example, even when an automobile body is composed of a combination of a plurality of different materials, an electrodeposited coating film with a desired thickness can be uniformly formed on each material.

[0011] Most of the solvent in the cationic electrodeposition coating composition is water. When the hydrophobicity of the aminated epoxy resin is high, it is difficult for water to enter between the particles when the particles adhere to the substrate, and the gap between the particles becomes small. Furthermore, since the Joule heat absorbed by water in the vicinity of the substrate decreases, the particles are more likely to fuse. As a result, a coating film is rapidly formed on the surface of the substrate. That is, since a uniform coating film is formed at the initial stage of electrodeposition coating and resistance appears, the influence of the electrical resistance of the substrate surface on the formation of the coating film becomes small. For the above reasons, it is considered that an electrodeposited coating film with a desired thickness is formed on various substrates with different electrical resistances.

[0012] In the aminated epoxy resin of the present disclosure, a part of the terminal epoxy ring is modified by an aromatic compound (y1) having one phenolic hydroxy group and two or more aromatic rings. That is, the aminated epoxy resin contains an aromatic cap site (c1) formed by ring-opening of the terminal epoxy ring by the phenolic hydroxy group of the aromatic compound (y1). The aromatic cap site (c1) increases the hydrophobicity of the aminated epoxy resin.

[0013] The aminated epoxy resin of the present disclosure is further modified (aminated) with an amine compound (x) having at least one of a primary amino group and a secondary amino group and not having a ketimine structure. The ketimine structure is a structure in which a primary amino group is protected by a ketone (RR′C═N—). The ketimine structure is easily hydrolyzed in the step of dispersing the aminated epoxy resin in a solvent (water) to generate a ketone and a primary amino group. The primary amino group can enhance the hydrophilicity of the aminated epoxy resin. Since the aminated epoxy resin of the present disclosure is modified with an amine compound (x) not having a ketimine structure, it exhibits higher hydrophobicity.

[0014] [Cationic electrodeposition coating composition] The cationic electrodeposition coating composition contains an aminated epoxy resin, a blocked isocyanate curing agent, and an inorganic pigment.

[0015] The cationic electrodeposition coating composition is a mixture of a resin emulsion (i) and a pigment dispersion paste (ii). The resin emulsion (i) contains an aminated epoxy resin and a blocked isocyanate curing agent. The pigment dispersion paste (ii) contains an inorganic pigment and, if necessary, a pigment dispersion resin.

[0016] Resin emulsion (i) The resin emulsion (i) contains an aminated epoxy resin and a blocked isocyanate curing agent. The resin emulsion (i) may further contain other components if necessary.

[0017] <Aminated epoxy resin> The aminated epoxy resin is a film-forming resin constituting an electrodeposition coating film. The aminated epoxy resin is obtained by ring-opening a part of the epoxy rings in the raw material epoxy resin skeleton with an amine compound (x) having at least one of a primary amino group and a secondary amino group and not having a ketimine structure, and also ring-opening a part of the terminal epoxy rings with a cap compound (y) having a functional group capable of reacting with an epoxy ring other than an amino group. That is, the epoxy rings at both ends of the raw material epoxy resin are modified with either the amine compound (x) or the cap compound (y).

[0018] Aminerated epoxy resin has an aminerated site (a) in which the epoxy ring is modified with an amine compound (x), and a capped site (c) in which the terminal epoxy ring is modified with a capped compound (y).

[0019] (Amine compound (x)) Amine compound (x) has at least one of a primary amino group and a secondary amino group and does not have a ketimine structure. The aminementation site (a) derived from amine compound (x) maintains the hydrophobicity of the aminemented epoxy resin. In addition, since no deketone is produced from the aminementation site (a), the generation of ketones, i.e., VOCs, is suppressed.

[0020] The amine compound (x) may include a primary amine compound (x1) having a primary amino group and not having a ketimine structure, and a secondary amine compound (x2) other than the primary amine compound (x1) having a secondary amino group and not having a ketimine structure. This makes it easier to control the molecular weight distribution.

[0021] When the two amine compounds described above are used, first, the primary amino group of the first amine compound (x1) is consumed by reacting with the epoxy ring. The remaining reactive amino groups in both the first amine compound (x1) and the second amine compound (x2) are only secondary amino groups. These secondary amino groups react with the epoxy ring remaining in the epoxy resin to obtain an aminerated epoxy resin. In the latter part of the reaction, since only secondary amino groups are reactive, there is no difference in reactivity, and the reaction proceeds uniformly. Therefore, the molecular weight distribution of the resulting aminerated epoxy resin (A) is controlled.

[0022] The mass ratio of the first amine compound (x1) to the second amine compound (x2) (first amine compound (x1): second amine compound (x2)) may be, for example, 30:70 to 80:20, or 40:60 to 70:30. This suppresses an excessive increase in the viscosity of the aminerated epoxy resin due to high molecular weight, and can improve the stability of the resin emulsion (i).

[0023] - Primary amine compound (x1) The primary amine compound (x1) has at least a primary amino group and does not have a ketimine structure. The primary amine compound (x1) first opens the epoxy ring at the end of the raw epoxy resin. At this time, the primary amino group becomes a secondary amino group. Subsequently, the secondary amino group reacts with the epoxy ring at the end of the other raw epoxy resin, crosslinking the raw epoxy resins together.

[0024] When the first amine compound (x1) is used, a crosslinked amineralized site (a11) is formed as the amineralized site (a), having a crosslinked structure formed by the ring-opening of two epoxy rings by the first amine compound (x1). The crosslinked amineralized site (a11) imparts flexibility to the rigid epoxy resin skeleton. As a result, the thermal flowability of the amineralized epoxy resin is increased, the surface of the electrodeposited coating becomes smoother, and the appearance of the coating is improved.

[0025] The first amine compound (x1) may be a diamine having a primary amino group along with a secondary or tertiary amino group.

[0026] The first amine compound (x1) is, for example, the following general formula (1): NH ２ - (CH ２ ) ｎ -NR １ R ２ (1) (wherein, R １ and R ２ Each of these independently represents an alkyl group having 1 to 6 carbon atoms, which may have a hydroxyl group at its terminus, and n represents an integer from 2 to 4.

[0027] R １ and R ２ The number of carbon atoms may be, for example, 1 to 5, or 1 to 4. １ and R ２ n may be, for example, methyl, ethyl, propyl, or butyl.

[0028] Examples of the first amine compound (x1) include N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dibutyl-1,3-propanediamine, N,N-bis(2-hydroxyethyl)-1,3-diaminopropane, and dimethylaminoethylamine. These can be used individually or in combination of two or more.

[0029] - Second amine compound (x2) The second amine compound (x2) is other than the first amine compound (x1) (i.e., it does not have a primary amino group), has a secondary amino group, and does not have a ketimine structure. The second amine compound (x2) opens the epoxy rings at the ends of the raw epoxy resin.

[0030] When a second amine compound (x2) is used, a terminal amineralization site (a12) is formed as the amineralization site (a) by opening the terminal epoxy ring with the second amine compound (x2).

[0031] The second amine compound (x2) is, for example, the following general formula (2): R ３ R ４ NH (2) (wherein, R ３ and R ４ Each of these independently represents an alkyl group having 1 to 4 carbon atoms and a hydroxyl group at its terminus.

[0032] R ３ and R ４ These are, for example, a methyl group, an ethyl group, a propyl group or a butyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group or a hydroxybutyl group. ３ and R ４ This may be a hydroxymethyl group or a hydroxyethyl group.

[0033] Examples of the second amine compound (x2) include dimethanolamine, diethanolamine, and N-methylethanolamine. These can be used individually or in combination of two or more.

[0034] The amine compound (x) may include a first amine compound (x1) represented by the general formula (1) and a second amine compound (x2) represented by the general formula (2). This can improve the dispersion stability of the aminerated epoxy resin in the cationic electrodeposition coating composition.

[0035] (Cap compound (y)) Cap compound (y) has a functional group that can react with epoxy rings other than amino groups. The cap portion (c) derived from cap compound (y) imparts desired properties to the aminerated epoxy resin.

[0036] Examples of functional groups that can react with epoxy rings other than amino groups include hydroxyl groups, carboxyl groups, and phenolic hydroxyl groups.

[0037] In this disclosure, an aromatic compound (y1) having one phenolic hydroxyl group and two or more aromatic rings as a functional group is used as the cap compound (y). The phenolic hydroxyl group of the aromatic compound (y1) opens the terminal epoxy ring, forming an aromatic cap portion (c1). The aromatic cap portion (c1) imparts high hydrophobicity to the aminated epoxy resin.

[0038] • Aromatic compound (y1) Aromatic compound (y1) has one phenolic hydroxyl group and two or more aromatic rings. Aromatic compound (y1) has only one phenolic hydroxyl group as a functional group that can react with the epoxy ring.

[0039] If there are two or more functional groups that can react with the epoxy ring, the molecular weight increases, which reduces the thermal flow properties of the amineralized epoxy resin and degrades the appearance of the coating film. Furthermore, the hydrophilicity of the amineralized epoxy resin increases, potentially leading to greater variations in film thickness.

[0040] If there is only one aromatic ring, the hydrophobicity of the amineralized epoxy resin becomes insufficient, resulting in large variations in film thickness. The number of aromatic rings may be 2 to 10, 2 to 7, 2 to 5, or 2 to 3.

[0041] Examples of aromatic rings include benzene rings, naphthalene rings, and anthracene rings. Aromatic rings may be heterocycles containing heteroatoms such as nitrogen, oxygen, sulfur, and phosphorus. These may be used individually or in combination of two or more. Aromatic rings may have substituents other than functional groups that can react with the epoxy ring (e.g., aliphatic hydrocarbon groups). Aromatic rings may be benzene rings or naphthalene rings.

[0042] Examples of aromatic compounds (y1) include o-cumylphenol, m-cumylphenol, p-cumylphenol, o,m-dicumylphenol, o,p-dicumylphenol, mono-styrenated phenol, di-styrenated phenol, tri-styrenated phenol, tetra-styrenated phenol, 2-phenylphenol, 4-phenylphenol, 1-naphthol, and 2-naphthol. These can be used individually or in combination of two or more.

[0043] The number ratio (c1 / c) of aromatic cap portions (c1) to cap portions (c) is, for example, 40% or more. This further enhances the hydrophobicity of the amineralized epoxy resin. The number ratio (c1 / c) may be 40-100%, 50-90%, or 60-80%.

[0044] The number ratio (c1 / c) can be calculated from the amount of raw material used to cap the terminal epoxy ring. That is, the ratio of the equivalent weight E2 to the total of the equivalent weight E2 of the functional group contained in the aromatic compound (y1) and the equivalent weight E3 of the carboxyl group contained in the monocarboxylic acid (y2), described later, relative to the epoxy ring of the raw epoxy resin (E2 / (E2+E3)) may be 40% or more.

[0045] Below is an example of an aromatic compound (y1) (2-phenylphenol, mono-, di-, or tri-styrene-modified phenol (n=1, 2, or 3), 2-naphthol).

[0046]

[0047]

[0048]

[0049] The number ratio (a12:c) of the terminal amination site (a12) to the cap site (c) is, for example, 40:60 to 80:20. When the number ratio (a12:c) is within this range, the balance between the hydrophobicity and electrodeposition performance of the aminated epoxy resin is improved. The number ratio (a12:c) may also be 50:50 to 70:30, or 55:45 to 60:40.

[0050] The numerical ratio (a12:c) can be calculated from the amount of raw materials used. That is, the ratio (E1:E2+E3) of the equivalent amount E1 of the amino group contained in the second amine compound (x2) to the epoxy ring of the raw epoxy resin, the equivalent amount E2 of the functional group contained in the cap compound (y), and the equivalent amount E3 of the carboxylic acid of the monocarboxylic acid (y2) may be between 40:60 and 80:20.

[0051] - Monocarboxylic acid (y2) The cap compound (y) may further contain a monocarboxylic acid (y2) having 5 to 14 carbon atoms other than the aromatic compound (y1). In this case, the cap portion (c) further includes a second cap portion (c2) formed by ring-opening of the terminal epoxy ring by the monocarboxylic acid (y2). The second cap portion (c2) can improve the flowability of the coating film.

[0052] A monocarboxylic acid (y2) is, for example, R ｄ -COOH(R) ｄ represents a hydrocarbon group having 4 to 13 carbon atoms. The hydrocarbon group may be linear or branched. The hydrocarbon group may be an aliphatic group and does not have to have an aromatic ring. The hydrocarbon group may be a saturated hydrocarbon group. The hydrogen atoms bonded to the carbon atoms of the hydrocarbon group do not need to be substituted.

[0053] If the monocarboxylic acid (y2) has 5 or more carbon atoms, the flowability of the coating film may be improved. If the monocarboxylic acid (y2) has 14 or fewer carbon atoms, both high flowability and high corrosion resistance can be achieved. The number of carbon atoms in the monocarboxylic acid (y2) may be 6 to 12 or 8 to 10.

[0054] Examples of monocarboxylic acids (y2) include valeric acid, caproic acid, enantic acid, n-caprylic acid, n-capric acid, lauric acid, 2-ethylhexanoic acid, pivalic acid, 3-methylbutanoic acid, and octic acid. These can be used individually or in combination of two or more. Among these, octic acid is particularly suitable in terms of its flowability.

[0055] When using a monocarboxylic acid (y2), the equivalent ratio (E2:E3) of the equivalent amount E2 of the phenolic hydroxyl group of the aromatic compound (y1) to the equivalent amount E3 of the carboxylic acid of the monocarboxylic acid (y2) is, for example, 40:60 to 99:1. In this case, the number ratio (c1:c2) of the aromatic cap portion (c1) to the second cap portion (c2) is also 40:60 to 99:1. When the number ratio (c1:c2) is within this range, the hydrophobicity of the aminated epoxy resin is improved. The equivalent ratio (E2:E3) (= number ratio (c1:c2)) may be 50:50 to 90:10, or 60:40 to 80:20.

[0056] The numerical ratio (c1:c2) corresponds to the equivalent ratio (E2:E3) described above. The equivalent ratio (E2:E3) can be calculated from the amount of raw materials used. That is, the ratio (E2:E3) of the equivalent amount E2 of the phenolic hydroxyl group contained in the aromatic compound (y1) and the equivalent amount E3 of the carboxyl group contained in the monocarboxylic acid (y2) to the epoxy ring of the raw epoxy resin may be 40:60 to 99:1.

[0057] (Raw material epoxy resin) A typical example of raw material epoxy resin is polyphenol polyglycidyl ether type epoxy resin. Polyphenol polyglycidyl ether type epoxy resin is obtained by the reaction of polycyclic phenol compounds such as bisphenol A, bisphenol F, bisphenol S, phenol novolac, and cresol novolac with epichlorohydrin.

[0058] Other raw material epoxy resins include, for example, the oxazolidone ring-containing epoxy resin described in Japanese Patent Publication No. 5-306327. This epoxy resin is prepared by reacting a bis-urethane compound obtained by blocking a diisocyanate compound or the isocyanate group of a diisocyanate compound with a lower alcohol such as methanol or ethanol, with epichlorohydrin.

[0059] The raw epoxy resin may be chain-extended with bifunctional polyester polyols, polyether polyols, bisphenols, dibasic carboxylic acids, and the like.

[0060] The raw epoxy resin may have epoxy rings to which monohydroxy compounds such as 2-ethylhexanol, nonylphenol, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-n-butyl ether, or propylene glycol mono-2-ethylhexyl ether, or monocarboxylic acid compounds such as octyl acid are added. This allows for adjustment of the molecular weight or amine equivalent of the epoxy resin, and can improve its thermal flow properties.

[0061] (Properties of Aminerated Epoxy Resins) Aminerated epoxy resins have a polarity term δ that constitutes the Hansen solubility parameter. Ｐ The value is between 10.0 and 13.0, and the hydrogen bonding term δ ｈ The value may be between 8.5 and 10.5. Amineralized epoxy resins that satisfy this value have sufficient hydrophobicity and further reduce variations in film thickness. Polarity term δ Ｐ The hydrogen bond term δ may be 10.5 to 12.5, or 11.0 to 12.0. ｈ It may be between 8.8 and 10.3, or between 9.0 and 10.0.

[0062] The Hansen solubility parameter (HSP) is an index that indicates the degree of affinity (mismatch) between a substance (X) and another substance (Y). The Hansen solubility parameter (HSP) is calculated by dividing the solubility parameter by the dispersion term δ ｄ , polar term δ ｐ , hydrogen bond term δ ｈIt is divided into three components and quantified using a vector in three-dimensional space (Hansen solubility parameter value: δ = (δd ２ +δp ２ +δh ２ ) １／２ .

[0063] Dispersion term δ ｄ This shows the effect due to dispersion forces, and the polar term δ ｐ This shows the effect due to the dipole force, and the hydrogen bond term δ ｈ This demonstrates the effect of hydrogen bonding. It shows that the closer the distance (HSP distance (Ra)) between the vector of substance (X) and the vector of another substance (Y) in three-dimensional space, the easier it is for substance (X) and substance (Y) to dissolve in each other (higher compatibility).

[0064] The HSP distance (Ra) is defined by the following formula: Ra = [4(δd Ｘ -δd Ｙ ) ２ + (δp Ｘ -δp Ｙ ) ２ + (δh Ｘ -δh Ｙ ) ２ ] １／２ δd ｉ : Dispersion force term δp of substance i ｉ : Polarity term δh of substance i ｉ : Hydrogen bonding term of substance i

[0065] The definition and calculation method of Hansen solubility parameters are described in "Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007)" by Charles M. Hansen.

[0066] In this disclosure, the Hansen solubility parameter can be calculated using computer software (Hansen Solubility Parameters in Practice (HSPiP) version 5.3.05).

[0067] Specifically, 10 mL of one of the 20 solvents listed in Table 1 is added to 2 g of the sample to be measured. The solvents are not limited to these, and the known dispersion term δ is also used. ｄ , polar term δｐ , hydrogen bond term δ ｈ Any solvent having these three components is acceptable. The object to be measured may be a resin that does not contain a solvent, or a varnish containing a solvent. From the viewpoint of minimizing or eliminating the influence of the properties of the object to be measured on the measurement value, if the object to be measured is a varnish containing a solvent, its kinematic viscosity at 25°C should be 100 to 15,000 mm². ２ It is preferable that the range is / s.

[0068]

[0069] After adding the solvent, the solution is allowed to stand for 2 or 4 hours. A good solvent is defined as one that is dispersed or dissolved, while a poor solvent is defined as one that precipitates or is insoluble. The affinity is then evaluated on a 5-point scale from 1 to 5. This affinity evaluation result is then entered into the HSPiP (version 5.3.05) to calculate the Hansen solubility parameter.

[0070] The weight-average molecular weight of the amineralized epoxy resin is, for example, 3,000 to 7,000. When the weight-average molecular weight is 3,000 or higher, solvent resistance and corrosion resistance are further improved. When the weight-average molecular weight is 7,000 or lower, viscosity adjustment of the amineralized epoxy resin becomes easier, and synthesis proceeds smoothly. In addition, the amineralized epoxy resin is easily emulsified and dispersed, improving handling. The weight-average molecular weight may be 4,000 or higher. The weight-average molecular weight may be 6,500 or lower. The weight-average molecular weight may be between 4,000 and 6,500.

[0071] The amine value of the amine-modified epoxy resin may be 20 to 100 mg KOH / g. An amine value of 20 mg KOH / g or higher improves the dispersion stability of the amine-modified epoxy resin in electrodeposited coatings. An amine value of 100 mg KOH / g or lower increases the water resistance of the electrodeposited coating. The above amine value may be 80 mg KOH / g or lower. The above amine value may be 20 to 80 mg KOH / g.

[0072] The hydroxyl value of the amineralized epoxy resin may be 150 to 650 mg KOH / g. When the hydroxyl value is 150 mg KOH / g or higher, the curability and appearance of the electrodeposited coating film are improved. When the hydroxyl value is 650 mg KOH / g or lower, the water resistance of the electrodeposited coating film is increased. The hydroxyl value may be 180 mg KOH / g or higher. The hydroxyl value may be 300 mg KOH / g or lower. The hydroxyl value may be 180 to 300 mg KOH / g or lower.

[0073] The aminerated epoxy resin may have a weight-average molecular weight of 3,000 to 7,000 and an amine value of 20 to 100 mgKOH / g. This aminerated epoxy resin further improves corrosion resistance.

[0074] As the aminerated epoxy resin, two or more aminerated epoxy resins with different amine values ​​and / or hydroxyl values ​​may be used in combination. In this case, the average amine value and average hydroxyl value calculated based on the mass ratio of the aminerated epoxy resins used should be within the above numerical range.

[0075] As the aminerated epoxy resin, a combination of an aminerated epoxy resin having an amine value of 20 to 50 mg KOH / g and a hydroxyl value of 50 to 300 mg KOH / g and an aminerated epoxy resin having an amine value of 50 to 200 mg KOH / g and a hydroxyl value of 200 to 500 mg KOH / g may be used. When this combination of resins is emulsified and dispersed, an epoxy resin emulsion having a hydrophobic core and a hydrophilic shell is obtained. Corrosion resistance can be further improved by a core-shell type epoxy resin emulsion.

[0076] (Other) Electrodeposition coatings may contain other film-forming resins. Examples of other film-forming resins include acrylic resins, polyester resins, urethane resins, olefin resins, phenolic resins, xylene resins, amino group-containing acrylic resins, and amino group-containing polyester resins.

[0077] <Blocked Polyisocyanate Curing Agent> Blocked polyisocyanate curing agents are also film-forming resins. Blocked polyisocyanate curing agents preferentially react with the amino groups of aminated epoxy resins and further react with the hydroxyl groups to form a crosslinked structure.

[0078] Blocked polyisocyanate curing agents are prepared by blocking polyisocyanate with a blocking agent. Blocking is carried out, for example, by dropping the blocking agent onto the polyisocyanate at 40-50°C while stirring, in the presence of a curing catalyst (e.g., a tin-based catalyst) if necessary.

[0079] The polyisocyanate may include at least one selected from the group consisting of aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. The polyisocyanate may be an aromatic polyisocyanate or an aliphatic polyisocyanate. The polyisocyanate may be an aromatic polyisocyanate.

[0080] Examples of aromatic polyisocyanates include 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. Examples of aliphatic polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate).

[0081] In a blocked polyisocyanate curing agent, the polyisocyanate may form adduct bodies such as a biuret, uretdione, isocyanurate, or allohanate.

[0082] Examples of blocking agents that are preferably used include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenolcarbinol, and methylphenylcarbinol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono-2-ethylhexyl ether; polyether-type terminal diols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycolphenol; polyester-type terminal polyols obtained from diols such as ethylene glycol, propylene glycol, and 1,4-butanediol, and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, and sebacic acid; phenols such as para-t-butylphenol and cresol; oxime compounds 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. In particular, the blocking agent may be an oxime compound.

[0083] The blocking rate of the blocked polyisocyanate curing agent may be 100%. This improves the storage stability of the electrodeposited coating.

[0084] A combination of blocked aliphatic diisocyanate and blocked aromatic diisocyanate may be used as a curing agent for blocked polyisocyanates.

[0085] (Other) As a curing agent, at least one selected from the group consisting of a blocked polyisocyanate curing agent, an organic curing agent (such as melamine resin and phenol resin), a silane coupling agent, and a metal curing agent may be used.

[0086] Pigment dispersion paste (ii) The pigment dispersion paste (ii) comprises an inorganic pigment and a pigment dispersion resin.

[0087] <Inorganic Pigments> Inorganic pigments are commonly used in electrodeposition coatings and are not particularly limited. Examples of inorganic pigments include coloring pigments such as titanium white (titanium dioxide), carbon black, and red iron oxide; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica, and clay; and rust-preventive pigments such as iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and aluminum phosphomolybdate and aluminum zinc phosphomolybdate. These can be used individually or in combination of two or more.

[0088] The total content of inorganic pigments may be 1 to 37% by mass of the resin solids of the electrodeposition coating. The above content of inorganic pigments may be 5% by mass or more, 10% by mass or more, or 15% by mass or more. The above content of inorganic pigments may be 30% by mass or less, 27% by mass or less, or 25% by mass or less. The above content may be 5 to 30% by mass, 10 to 27% by mass, or 15 to 25% by mass.

[0089] <Pigment Dispersion Resin> Pigment dispersion resins are resins used to disperse pigments and are dispersed in an aqueous medium. As pigment dispersion resins, for example, pigment dispersion resins having cationic groups can be used. Examples of pigment dispersion resins having cationic groups include amine-modified epoxy resins having at least one or more selected from quaternary ammonium groups, tertiary sulfonium groups, and primary amino groups. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol can be used.

[0090] Amine-modified epoxy resins can be prepared, for example, by reacting a half-blocked isocyanate with the hydroxyl groups of a raw epoxy resin having hydroxyl groups to introduce blocked isocyanate groups. The introduction of blocked isocyanate groups is carried out by reacting the raw epoxy resin having hydroxyl groups with the half-blocked isocyanate at 140°C for about 1 hour.

[0091] Polyepoxides can be used as the raw material epoxy resin. Polyepoxides have an average of two or more 1,2-epoxy groups per molecule. Examples of polyepoxides include the raw material epoxy resins exemplified in the amineralized epoxy resin section.

[0092] Half-blocked isocyanates are prepared by blocking some of the isocyanate groups of a polyisocyanate with a blocking agent. Examples of polyisocyanates include those exemplified in the blocked polyisocyanate curing agent. Examples of blocking agents include lower aliphatic alkyl monoalcohols having 4 to 20 carbon atoms. Specific examples of blocking agents include butyl alcohol, amyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, and heptyl alcohol.

[0093] The number of carbon atoms in a tertiary amine may be 1 to 6. Specific examples of tertiary amines include dimethylethanolamine, trimethylamine, triethylamine, dimethylbenzylamine, diethylbenzylamine, N,N-dimethylcyclohexylamine, tri-n-butylamine, diphenethylmethylamine, dimethylaniline, and N-methylmorpholine.

[0094] The neutralizing acid is not particularly limited. Examples of neutralizing acids include inorganic or organic acids such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, and lactic acid. The neutralizing acid may be at least one selected from the group consisting of formic acid, acetic acid, and lactic acid.

[0095] <Other> Electrodeposition coatings may contain organic solvents. Examples of organic solvents include ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and propylene glycol monophenyl ether.

[0096] Electrodeposition coatings may contain additives commonly used in the coatings field. Examples of additives include surfactants, viscosity modifiers, anti-repellent agents, inorganic rust inhibitors, auxiliary complexing agents, buffers, smoothers, stress relievers, gloss agents, semi-gloss agents, antioxidants, and UV absorbers. The additives are added during the preparation of the resin emulsion (i) and / or the pigment dispersion paste (ii).

[0097] [Method for producing cationic electrodeposition coating composition] A cationic electrodeposition coating composition is produced by a method comprising: (1) reacting a raw epoxy resin with an amine compound (x) and a cap compound (y) having a functional group that can react with epoxy rings other than amino groups to prepare an aminerated epoxy resin having an aminerated moiety (a) in which the epoxy ring is modified with the amine compound (x) and a capped moiety (c) in which the terminal epoxy ring is modified with the cap compound (y); (2) mixing the aminerated epoxy resin with a blocked polyisocyanate curing agent to prepare a resin emulsion (i); and (3) mixing the resin emulsion (i) and a pigment dispersion paste (ii) containing an inorganic pigment.

[0098] (1) Preparation of aminerated epoxy resin: The epoxy resin raw material is reacted with an amine compound (x) and a cap compound (y). This yields an aminerated epoxy resin having an aminerated site (a) and a cap site (c).

[0099] First, the raw epoxy resin and the cap compound (y) are reacted. For example, after mixing the raw epoxy resin and the cap compound (y), the mixture is reacted at 120-160°C for 0.5-2 hours. Subsequently, the amine compound (x) is added and the mixture is reacted at 80-150°C for 0.1-5 hours, more preferably at 120-150°C for 0.5-3 hours.

[0100] (2) Preparation of resin emulsion (i) Resin emulsion (i) can be prepared as follows. First, the aminerated epoxy resin and the blocked polyisocyanate curing agent are each dissolved in an organic solvent to prepare a solution. After mixing these solutions, they are neutralized with a neutralizing acid. Then, they are diluted with deionized water.

[0101] Examples of neutralizing acids include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, methylolpropionic acid, formic acid, and acetic acid. The neutralizing acid may be at least one selected from the group consisting of formic acid, acetic acid, and lactic acid.

[0102] The equivalent ratio of the neutralizing acid to the equivalent amount of amino groups in the amineralized epoxy resin (neutralization rate) may be between 10% and 100%. A neutralization rate of 10% or higher improves the affinity of the amineralized epoxy resin for water, thereby increasing its water dispersibility. A neutralization rate of 20% or higher is also acceptable. A neutralization rate of 70% or lower is also acceptable. The neutralizing acid is used in an amount that satisfies the above-mentioned neutralization rates.

[0103] The blocked polyisocyanate curing agent is used in an amount sufficient to react with active hydrogen-containing functional groups such as primary amino groups, secondary amino groups, or hydroxyl groups in the amineralized epoxy resin during curing.

[0104] The solid content mass ratio (A / B) of the amineralized epoxy resin and the blocked polyisocyanate curing agent may be 90 / 10 to 50 / 50. A / B may also be 80 / 20 to 65 / 35. By adjusting A / B, the fluidity and curing speed of the deposited film can be controlled, improving the appearance of the coating film.

[0105] The solid content of the resin emulsion (i) may be 25 to 50% by mass. The above solid content may be 35% by mass or more. The above solid content may be 45% by mass or less. The above solid content may be 35 to 45% by mass.

[0106] (3) Mix the mixed resin emulsion (i) and the pigment dispersion paste (ii). This yields a cationic electrodeposition coating composition.

[0107] The pigment dispersion paste (ii) is prepared by mixing a pigment and a pigment dispersion resin. The content of the pigment dispersion resin in the pigment dispersion paste is not particularly limited and may be, for example, 20 to 100 parts by mass of resin solids per 100 parts by mass of pigment. The solids content of the pigment dispersion paste is, for example, 40 to 70% by mass and 50 to 60% by mass of the total amount of pigment dispersion paste.

[0108] [Formation of Cured Electrodeposited Coating Film] The cured electrodeposited coating film is formed by a method that includes immersing the object to be coated in the above-mentioned cationic electrodeposited coating composition to perform electrodeposition coating and forming an uncured electrodeposited coating film, and heating the uncured electrodeposited coating film to form a cured electrodeposited coating film on the object to be coated.

[0109] (Electrodeposition coating) The object to be coated is immersed in a bath containing electrodeposition paint, and a voltage is applied by passing an electric current between the object to be coated as the cathode and a separately installed anode. As a result, the components of the electrodeposition paint are deposited on the object to be coated, forming a deposited film (uncured electrodeposition coating film).

[0110] The applied voltage may be between 50V and 450V. The bath temperature may be, for example, between 10°C and 45°C. The application time may be, for example, between 2 minutes and 5 minutes.

[0111] The material to be coated is not particularly limited as long as it is electrically conductive. Examples of materials to be coated include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electro-galvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy plated steel sheets, zinc-iron alloy plated steel sheets, zinc-magnesium alloy plated steel sheets, zinc-aluminum-magnesium alloy plated steel sheets, aluminum plated steel sheets, aluminum-silicon alloy plated steel sheets, and tin plated steel sheets.

[0112] (Heating) Remove the object to be coated from the bath and heat it. This will form a hardened electrodeposited coating. The object to be coated may be washed with water before heating.

[0113] The heating temperature is, for example, between 120°C and 260°C. The heating temperature may be 140°C or higher. The heating temperature may be 220°C or lower. The heating time may be, for example, between 10 minutes and 30 minutes.

[0114] The thickness of the cured electrodeposited coating is, for example, 5 μm to 40 μm. This provides sufficient corrosion resistance. The thickness of the cured electrodeposited coating may be 10 μm or more. The thickness of the cured electrodeposited coating may be 25 μm or less.

[0115] The present invention will be further described by the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[0116] The components used in the preparation of the cationic electrodeposition coating composition, or their manufacturing methods, are shown below.

[0117] [Production Example A1] Preparation of Aminerated Epoxy Resin A1: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 289 parts bisphenol A (chain extender), 266 parts distyrenated phenol (trade name SP-24, manufactured by Sanko Co., Ltd., DSP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0118] Next, a mixture of 50 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 81 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A1 with a weight-average molecular weight of 6,400 and an amine value of 53 mgKOH / g.

[0119] [Production Example A2] Preparation of Aminerated Epoxy Resin A2: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 265 parts bisphenol A (chain extender), 322 parts distyrenated phenol (trade name SP-24, manufactured by Sanko Co., Ltd., DSP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0120] Next, a mixture of 51 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 83 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A2 with a weight-average molecular weight of 5,500 and an amine value of 53 mgKOH / g.

[0121] [Production Example A3] Preparation of Aminerated Epoxy Resin A3: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 91 parts distyrenated phenol (trade name SP-24, manufactured by Sanko Co., Ltd., DSP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 628 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0122] Next, a mixture of 68 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 110 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A3 with a weight-average molecular weight of 7,000 and an amine value of 79 mgKOH / g.

[0123] [Production Example A4] Preparation of Aminerated Epoxy Resin A4: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 142 parts distyrenated phenol (trade name SP-24, manufactured by Sanko Co., Ltd., DSP, aromatic compound (y1)), 67 parts octic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0124] Next, a mixture of 48 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 78 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A4 with a weight-average molecular weight of 6,500 and an amine value of 53 mgKOH / g.

[0125] [Production Example A5] Preparation of Amineralized Epoxy Resin A5: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 115 parts distyrenated phenol (trade name SP-24, manufactured by Sanko Co., Ltd., DSP, aromatic compound (y1)), 81 parts octic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0126] Next, a mixture of 48 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 77 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A5 with a weight-average molecular weight of 6,500 and an amine value of 53 mgKOH / g.

[0127] [Production Example A6] Preparation of Aminerated Epoxy Resin A6: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 166 parts 2-phenylphenol (2PP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0128] Next, a mixture of 47 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 76 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A6 with a weight-average molecular weight of 6,400 and an amine value of 53 mgKOH / g.

[0129] [Production Example A7] Preparation of Amineralized Epoxy Resin A7: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 59 parts 2-phenylphenol (2PP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 628 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0130] Next, a mixture of 67 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 108 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A7 with a weight-average molecular weight of 7,000 and an amine value of 79 mgKOH / g.

[0131] [Production Example A8] Preparation of Aminerated Epoxy Resin A8: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 83 parts 2-phenylphenol (2PP, aromatic compound (y1)), 71 parts octic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0132] Next, a mixture of 47 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 75 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A8 with a weight-average molecular weight of 6,500 and an amine value of 53 mgKOH / g.

[0133] [Production Example A9] Preparation of Amineralized Epoxy Resin A9: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 67 parts 2-phenylphenol (2PP, aromatic compound (y1)), 85 parts octic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0134] Next, a mixture of 47 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 75 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded an aminerated epoxy resin A9 with a weight-average molecular weight of 6,500 and an amine value of 53 mgKOH / g.

[0135] [Production Example A10] Preparation of Amineralized Epoxy Resin A10: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 144 parts 2-naphthol (aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0136] Next, a mixture of 46 parts of N,N-diethyl-1,3-propanediamine (DEAPA, primary amine compound (x1)) and 75 parts of diethanolamine (DEtA, secondary amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded aminerated epoxy resin A10 with a weight-average molecular weight of 6,400 and an amine value of 53 mgKOH / g.

[0137] [Comparative Manufacturing Example 1] Preparation of Amineralized Epoxy Resin ep1: 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 290 parts bisphenol A (chain extender), 143 parts octic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst) were added. The temperature in the reaction vessel was maintained at 120°C and the reaction was carried out until the epoxy equivalent was 965 g / eq, after which the temperature in the reaction vessel was cooled to 110°C.

[0138] Next, a mixture of 46 parts of N,N-diethyl-1,3-propanediamine (first amine compound (x1)) and 75 parts of diethanolamine (second amine compound (x2)) was added and reacted at 110°C for 1 hour. This yielded the aminerated epoxy resin ep1.

[0139] [Comparative Manufacturing Example 2] Production of Amineralized Epoxy Resin ep2 44 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 342 parts bisphenol A (chain extender), and 86 parts octic acid (monocarboxylic acid (y2)) were mixed and heated to 120°C. Then, 1 part dimethylbenzylamine (catalyst) was added, and the temperature in the reaction vessel was maintained at 140°C. The reaction was carried out until the epoxy equivalent was 1070 g / eq, and then the temperature in the reaction vessel was cooled to 120°C.

[0140] Next, a mixture of 53 parts of diethanolamine (secondary amine compound (x2)), 59 parts of diethylenetriaminediketimine (amine compound having a ketimine structure, methyl isobutyl ketone solution with a solid content of 84%), and 29 parts of N-methylethanolamine (secondary amine compound (x2), MEA) was added and reacted at 120°C for 1 hour. This yielded the aminerated epoxy resin ep2.

[0141] [Comparative Production Example 3] Production of Aminerated Epoxy Resin ep3 In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser, 1898.7 parts of bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 134.87 parts of novolac type phenol (trade name TD-2131, manufactured by DIC), 21.0 parts of bisphenol F (trade name Bisphenol F, manufactured by Sigma-Aldrich, chain extender), 514.8 parts of bisphenol A (chain extender), 1.0 part of TBAB (tetrabutylammonium bromide; catalyst), and 279.7 parts of methyl isobutyl ketone (solvent) were added and reacted at 160°C until the epoxy equivalent was 546, and the resulting reaction product was diluted with methyl isobutyl ketone until the solid content was 80%.

[0142] Next, 418.5 parts of diethanolamine and 184.5 parts of ketimine of diethylenetriamine (90% grade) were added, and the mixture was reacted at 120°C for 3 hours. Methyl isobutyl ketone was then added to obtain an amineralized epoxy resin ep3 with a solid content of 75%.

[0143] [Comparative Production Example 4] Production of Aminerated Epoxy Resin ep4 In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser, 863.4 parts of bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 284.8 parts of bisphenol, 416.5 parts of bisphenol A-ethylene oxide adduct (BPA / EO = molar ratio 1 / 6), 176.8 parts of 4-dodecylphenol, 1.3 parts of ETPPBr (ethyl triphenyl bromide; catalyst), and 53.5 parts of methyl isobutyl ketone (solvent) were added and the mixture was reacted at 145°C for 2 hours. While cooling the resulting reaction product to 125°C, 12.4 parts of methyl isobutyl ketone were added and the mixture was cooled to 105°C. Next, 85.4 parts of diethylenetriaminedikethymine (an amine compound having a ketimine structure, in a methyl isobutyl ketone solution with a solid content of 72.7%) and 73.7 parts of N-methylethanolamine (secondary amine compound (x2)) were added, and the mixture was reacted at 115°C for 1 hour. This yielded the aminerated epoxy resin ep4.

[0144] [Comparative Production Example 5] Production of Aminerated Epoxy Resin ep5 In a 3 L flask equipped with a stirrer and a heating mantle, 18.03 parts of bisphenol A diglycidyl ether (DGEBA, raw material epoxy resin), 4.1 parts of bisphenol A (BPA, chain extender), 1.41 parts of phenol, and 0.36 parts of propylene glycol n-butyl ether were mixed. While stirring, the mixture was heated to 125°C, and 0.04 parts of triphenylphosphine were added. The temperature reached 200°C, so it was cooled to 135°C, and the reaction was continued after 45 minutes.

[0145] After confirming that the epoxy equivalent (WPE) was 533, the mixture was cooled to 90°C and the heating mantle was stopped. Subsequently, 1.73 parts of diethanolamine were added. After stirring for a further 30 minutes, 0.84 parts of 3-dimethylaminopropylamine were added at 105°C. After stirring for a further 1 hour, 1.13 parts of 2-sulfobenzoic anhydride were added at 135°C. The mixture was then stirred at 135°C for 1.5 hours. This yielded the amineralized epoxy resin ep5.

[0146] [Comparative Manufacturing Example 6] Manufacturing of Aminerated Epoxy Resin ep6 375 parts of styrene-modified phenol (product name SP-23, manufactured by Sanko Co., Ltd.) and 0.3 parts of potassium hydroxide were placed in a stainless steel autoclave equipped with stirring and temperature control functions. After purging the mixing system with nitrogen, dehydration was carried out under reduced pressure (approximately 20 mmHg) at 120°C for 1 hour. Subsequently, 116 parts of propylene oxide were added and dehydrated at 150°C at a gauge pressure of 1-3 kgf / cm². ２ The mixture was introduced in this manner. Next, 185 parts of epichlorohydrin were added, and 80 parts of solid sodium hydroxide were gradually added at 30-40°C while vigorously stirring. The mixture was then aged for 5 hours while maintaining the temperature to complete the reaction. After the reaction was complete, the by-product salts were removed by washing with water. Next, the mixture was thoroughly washed until the washings were neutral, and the water and epichlorohydrin were removed by distillation at 120-140°C under reduced pressure to obtain a styrene-phenol compound with an alkylene oxide having a glycidyl group and 100% resin solids.

[0147] Separately, in a flask equipped with a stirrer, condenser, nitrogen injection tube, and dropping funnel, 752.0 parts of bisphenol A type epoxy resin (raw epoxy resin) with an epoxy equivalent of 188, 291.8 parts of bisphenol A (chain extender), 82.9 parts of octic acid (monocarboxylic acid (y2)), and 135 parts of the above styrene-phenol compound were added and the temperature was raised to 180°C. Then, 1.1 parts of dimethylbenzylamine were added and the mixture was reacted until the epoxy equivalent was 1300. Next, the mixture was cooled to 120°C and diluted with methyl isobutyl ketone. Subsequently, 50.6 parts of N-methylethanolamine (secondary amine compound (x2)) and 45.3 parts of aminoethylethanolamine ketimine (amine compound having a ketimine structure, 78.8% methyl isobutyl ketone solution) were added and the mixture was reacted at 120°C for 2 hours. Next, methyl isobutyl ketone was added to dilute the mixture. This yielded aminerated epoxy resin ep6 (non-volatile content 80%).

[0148] [Comparative Production Example 7] Production of Aminerated Epoxy Resin ep7 A flask equipped with a stirrer, condenser, nitrogen injection tube, and dropping funnel was weighed out with 71.34 parts of 2,4 / 2,6-tolylene diisocyanate (mass ratio: 80 / 20) and 0.01 parts of dibutyltin dilaurate. While stirring and bubbling with nitrogen, 14.24 parts of methanol were added dropwise from the dropping funnel over 30 minutes. The temperature was raised from room temperature to 60°C due to exothermic reaction. The reaction was continued for 30 minutes, after which 46.98 parts of ethylene glycol mono-2-ethylhexyl ether were added dropwise from the dropping funnel over 30 minutes. The temperature was raised to 70-75°C due to exothermic reaction. After continuing the reaction for 30 minutes, 41.25 parts of bisphenol A propylene oxide (5 moles) adduct (BP-5P, manufactured by Sanyo Chemical Industries, Ltd.) were added, the temperature was raised to 90°C, and the reaction was continued while measuring the IR spectrum until the NCO group disappeared.

[0149] Next, 475.0 parts of bisphenol A type epoxy resin (raw material epoxy resin, YD-7011R manufactured by Toto Kasei Co., Ltd.) with an epoxy equivalent of 475 was added and uniformly dissolved. After that, the temperature was raised from 130°C to 142°C to remove water from the reaction system. After cooling to 125°C, 0.5 parts of benzyldimethylamine was added to carry out the oxazolidone ring formation reaction by demethanol reaction. The reaction was continued until the epoxy equivalent reached 1140.

[0150] Subsequently, 76.8 parts of o,p-dicumylphenol (aromatic compound (y1)) were added, and the mixture was cooled to 100°C. Then, 24.56 parts of N-methylethanolamine (secondary amine compound (x2)), 11.46 parts of diethanolamine (secondary amine compound (x2)), and 26.08 parts of aminoethylethanolamineketimine (amine compound having a ketimine structure, 78.8% methyl isobutyl ketone solution) were added, and the mixture was reacted at 110°C for 2 hours. After that, 20.74 parts of ethylene glycol mono-2-ethylhexyl ether were added, and then methyl isobutyl ketone was added at 100°C until the viscosity reached 1000 cps. This yielded amineralized epoxy resin ep7 (91% non-volatile matter).

[0151] [Production Example B1] (Production of Blocked Polyisocyanate Curing Agent B1) 222 parts of isophorone diisocyanate were placed in a reaction vessel equipped with a stirrer, nitrogen inlet tube, condenser, and thermometer, diluted with 56 parts of methyl isobutyl ketone (MIBK), then 0.2 parts of butyltin laurate were added, and the temperature was raised to 50°C. Then 174 parts of methyl ethyl ketoxime were added so that the temperature of the contents did not exceed 70°C. The mixture was kept at 70°C for 1 hour until the absorption of the isocyanate residues virtually disappeared by infrared absorption spectroscopy. After that, it was diluted with 43 parts of n-butanol to obtain Blocked Polyisocyanate Curing Agent B1 with a solid content of 70%.

[0152] [Production Example B2] (Production of Blocked Polyisocyanate Curing Agent B2) 165 parts of isocyanurate of hexamethylene diisocyanate (trade name Sumijool N3300, manufactured by Sumika Bayer Urethane Co., Ltd.) and 24 parts of MIBK were charged into a reaction vessel and heated to 60°C. 75 parts of methyl ethyl ketoxime (MEK oxime) were added dropwise over 2 hours. After further heating at 70°C for 2 hours, it was confirmed by IR spectrum measurement that the absorption based on the isocyanate group had disappeared. Subsequently, 36 parts of butyl cellosolve were added to obtain Blocked Polyisocyanate Curing Agent B2.

[0153] [Production Example B3] (Production of Blocked Polyisocyanate Curing Agent B3) 1400 parts of polymeric MDI (MDI: diphenylmethane diisocyanate) were charged into a reaction vessel and heated to 60°C. A mixture of 330 parts of butyl diglycol ether (BDG) and 950 parts of butyl cellosolve (BC) was added dropwise over 2 hours at 60°C. After further heating at 75°C for 4 hours, the absorption based on the isocyanate group was confirmed to have disappeared by measuring the IR spectrum. After cooling, 27 parts of methyl isobutyl ketone (MIBK) were added to obtain Blocked Polyisocyanate Curing Agent B3.

[0154] [Production Example C] (Production of Pigment Dispersion Resin) In a reaction vessel equipped with a stirrer, condenser, nitrogen inlet tube, and thermometer, 385 parts of bisphenol A type epoxy resin, 120 parts of bisphenol A, 95 parts of octic acid, and 1 part of a 1% solution of 2-ethyl-4-methylimidazole were charged and reacted at 160-170°C for 1 hour under a nitrogen atmosphere. After cooling to 120°C, 198 parts of a methyl isobutyl ketone solution (95% solids) of 2-ethylhexanol-modified half-blocked tolylene diisocyanate were added. The reaction mixture was held at 120-130°C for 1 hour, after which 157 parts of ethylene glycol mono-n-butyl ether were added. The mixture was then cooled to 85-95°C to homogenize it. Next, 277 parts of diethylenetriamine diketimine (73% solids methyl isobutyl ketone solution) were added and stirred at 120°C for 1 hour, and 13 parts of ethylene glycol mono-n-butyl ether were added to produce an amineralized resin. Next, 18 parts of deionized water and 8 parts of formic acid were added, the amineralized resin was mixed, and the mixture was stirred for 15 minutes. Then, 200 parts of deionized water was added to obtain a resin solution (resin solids content 25%) of pigment dispersion resin (average molecular weight 2,200).

[0155] [Examples 1-10, Comparative Examples 1-7] a. Preparation of resin emulsion (i) 1653 g (solids) of any of the above aminerated epoxy resins was mixed with 319 g (solids) of blocked polyisocyanate curing agent B1, 293 g (solids) of blocked polyisocyanate curing agent B2, and 276 g of blocked polyisocyanate curing agent B3. Furthermore, ethylene glycol mono-2-ethylhexyl ether was added to a concentration of 3% (15 g) relative to the solids. Then, formic acid was added to neutralize the mixture to a neutralization rate of 40%, and the mixture was slowly diluted with deionized water to obtain 10 types of resin emulsion (i).

[0156] b. Preparation of pigment dispersion paste (ii) 106.9 parts of the above pigment dispersion resin, 1.6 parts of carbon black, 40 parts of kaolin, 55.4 parts of titanium dioxide, 3 parts of aluminum phosphomolybdate, and 13 parts of deionized water were placed in a sand grind mill and dispersed until the particle size was 10 μm or less to obtain pigment dispersion paste (ii) (solid content 60%).

[0157] c. Preparation of the cationic electrodeposition coating composition: 642 g of deionized water, 560 g of resin emulsion (i), and 41 g of pigment dispersion paste (ii) were added to a stainless steel container, and then aged at 40°C for 16 hours to obtain the cationic electrodeposition coating composition.

[0158] [Evaluation] The prepared aminerated epoxy resin or cationic electrodeposition coating compositions were evaluated as follows.

[0159] - Using the 20 solvents listed in Table 1 of the Hansen solubility parameters for aminated epoxy resins, affinity was evaluated in the same manner as above, and the Hansen solubility parameters were calculated using the above-mentioned HSPiP (version 5.3.05).

[0160] - The appearance of the electrodeposited coating was determined by degreasing a cold-rolled steel sheet (JIS G3141, SPCC-SD) by immersing it in Surf Cleaner EC90 (manufactured by Nippon Paint Co., Ltd.) at 50°C for 2 minutes. Then, the sheet was immersed in a zirconium conversion treatment solution containing 0.005% ZrF and adjusted to pH 4 using NaOH, at 40°C for 90 seconds to perform zirconium conversion treatment.

[0161] Next, the cationic electrodeposition coating composition was modified by adding the required amount of 2-ethylhexyl glycol so that the thickness of the electrodeposited coating film after curing would be 15 μm. Then, the zirconium chemically treated steel plate (substrate) was immersed in the mixture, and a voltage was applied under the conditions of increasing the voltage to 180 V for 30 seconds and then holding it for 150 seconds. This resulted in obtaining a test plate on which an uncured electrodeposited coating film was formed on the substrate.

[0162] In accordance with JIS B 0601, the arithmetic mean roughness Ra value of the electrodeposited coating was measured using a surface roughness measuring instrument (SURFTESTS J-201P, manufactured by Mitutoyo Corporation). Specifically, under the condition of a cutoff value of 2.5 mm (5 sections), the surface roughness was measured 10 times at different locations, and the average Ra value was calculated. The obtained Ra values ​​were evaluated according to the following criteria. A rating of B or higher indicates that the coating appearance is excellent.

[0163] (Evaluation Criteria) A: Less than 0.25 μm B: 0.25 μm or more and less than 0.40 μm C: 0.40 μm or more

[0164] Four types of test plates were obtained by subjecting cold-rolled steel sheets (JIS G 3141, SPCC), alloyed hot-dip galvanized steel sheets (JIS G 3316 SGCC), high-tensile steel sheets (JIS G 3135 SPFC590), and Al material (Chemetall, AA6014) with variations in film thickness to zirconium conversion treatment in the same manner as described above.

[0165] Electrodeposition coating was performed on each test plate in the same manner as described above. The set thickness of the electrodeposited coating after curing was 15 μm. The film thickness was measured at 10 arbitrary points on each coated plate, and the average value was calculated. The film thickness difference was calculated by subtracting the thinnest average film thickness from the thickest average film thickness. The larger this film thickness difference, the greater the variation in the thickness of the electrodeposited coating that can occur between multiple different substrates.

[0166] (Evaluation Criteria) A: Film thickness difference is less than 1.5 μm B: Film thickness difference is 1.5 μm or more and less than 2.5 μm C: Film thickness difference is 2.5 μm or more and less than 3.5 μm D: Film thickness difference is 3.5 μm or more and less than 4.5 μm E (×): Film thickness difference is 4.5 μm or more

[0167]

[0168]

[0169] The electrodeposited coatings in Examples 1 to 10 showed little variation in film thickness and excellent appearance. In Comparative Example 1, since only octic acid was used as the cap compound (y), the aminerated epoxy resin had poor hydrophobicity and large variation in film thickness. In Comparative Example 2, since only octic acid was used as the cap compound (y), and it was further aminerated with an amine compound having a ketimine structure, the aminerated epoxy resin had poor hydrophobicity and even greater variation in film thickness. In Comparative Example 3, since novolac-type phenol (polyhydric phenol) was used as the cap compound (y), and it was further aminerated with an amine compound having a ketimine structure, the hydrophobicity was insufficient, and variation in film thickness was observed. Furthermore, because the aminerated epoxy resin was excessively polymerized, the thermal flow properties decreased, resulting in poor appearance. In Comparative Example 4, dodecylphenol (containing one aromatic ring) was used as the cap compound (y), and in addition, it was amined with an amine compound having a ketimine structure, resulting in insufficient hydrophobicity and variations in film thickness. Furthermore, the appearance was inferior. In Comparative Example 5, phenol (containing one aromatic ring) was used as the cap compound (y), resulting in insufficient hydrophobicity and variations in film thickness. In Comparative Examples 6 and 7, amined with an amine compound having a ketimine structure, the reduction in hydrophobicity was insufficient, resulting in variations in film thickness.

[0170] The cationic electrodeposition coating composition of this disclosure can form an electrodeposited coating of a desired thickness on various substrates with different electrical resistances. Such a cationic electrodeposition coating composition is suitable for electrodeposition coating of automobile bodies and automobile components.

[0171] This application claims priority under Japanese Patent Application No. 2024-230466, filed in Japan on 26 December 2024, the entirety of which is incorporated herein by reference.

Claims

1. A cationic electrodeposition coating composition comprising an aminerated epoxy resin, a blocked polyisocyanate curing agent, and an inorganic pigment, wherein the aminerated epoxy resin has an aminerated site (a) in which the epoxy ring of a raw epoxy resin is modified with an amine compound (x), and a capped site (c) in which the terminal epoxy ring of the raw epoxy resin is modified with a capped site (c) having a functional group that can react with epoxy rings other than an amino group, wherein the amine compound (x) has at least one of a primary amino group and a secondary amino group and does not have a ketimine structure, the capped site (y) comprises an aromatic compound (y1) having one phenolic hydroxyl group and two or more aromatic rings as the functional group, the aminerated site (a) is formed by ring-opening of the epoxy ring by at least one of the primary amino group and the secondary amino group, and the capped site (c) comprises an aromatic capped site (c1) formed by ring-opening of the terminal epoxy ring by the phenolic hydroxyl group.

2. The aminerated epoxy resin contains the polar term δ which constitutes the Hansen solubility parameter. Ｐ The value is between 10.0 and 13.0, and the hydrogen bonding term δ ｈ The cationic electrodeposition coating composition according to claim 1, wherein the ratio is 8.5 to 10.

5.

3. The amine compound (x) comprises a first amine compound (x1) having a primary amino group and not having a ketimine structure, and a second amine compound (x2) other than the first amine compound (x1) having a secondary amino group and not having a ketimine structure, and the amination site (a) comprises a crosslinked amination site (a11) having a crosslinked structure formed by the ring-opening of two epoxy rings by the first amine compound (x1), and a terminal amination site (a12) formed by the ring-opening of a terminal epoxy ring by the second amine compound (x2), the cationic electrodeposition coating composition according to claim 1 or 2.

4. The first amine compound (x1) is represented by the following general formula (1): NH ２ -(CH ２ ) ｎ -NR １ R ２ (1) (In the formula, R １ and R ２ each independently represent an alkyl group having 1 to 6 carbon atoms which may have a hydroxyl group at the terminal, and n represents an integer of 2 to 4.) The cationic electrodeposition coating composition according to claim 3.

5. The second amine compound (x2) is given by the following general formula (2): R ３ R ４ NH (2) (wherein, R ３ and R ４ Each of these independently represents an alkyl group having 1 to 4 carbon atoms and a hydroxyl group at its terminus.) The cationic electrodeposition coating composition according to claim 3 or 4.

6. The cationic electrodeposition coating composition according to any one of claims 1 to 5, wherein the aminated site (a) has a terminal aminated site (a12) formed by ring-opening of the terminal epoxy ring by the amine compound (x), and the number ratio (a12:c) of the terminal aminated site (a12) to the cap site (c) is 40:60 to 80:

20.

7. The cationic electrodeposition coating composition according to any one of claims 1 to 6, wherein the cap compound (y) further comprises a monocarboxylic acid (y2) having 5 to 14 carbon atoms other than the aromatic compound (y1), and the cap portion (c) further comprises a second cap portion (c2) formed by ring-opening of the terminal epoxy ring by the monocarboxylic acid (y2).

8. The cationic electrodeposition coating composition according to claim 7, wherein the equivalent ratio (E2:E3) of the equivalent amount E2 of the phenolic hydroxyl group of the aromatic compound (y1) and the equivalent amount E3 of the carboxylic acid of the monocarboxylic acid (y2) with respect to the epoxy ring of the raw material epoxy resin is 40:60 to 99:

1.

9. The cationic electrodeposition coating composition according to any one of claims 1 to 8, wherein the number ratio of the aromatic cap portion (c1) to the cap portion (c) is 40% or more.

10. The process comprises: reacting a raw epoxy resin with an amine compound (x) and a cap compound (y) having a functional group that can react with an epoxy ring other than an amino group to prepare an aminerated epoxy resin having an aminerated moiety (a) in which the epoxy ring is modified by the amine compound (x) and a capped moiety (c) in which the terminal epoxy ring is modified by the cap compound (y); mixing the aminerated epoxy resin with a blocked polyisocyanate curing agent to prepare a resin emulsion (i); and mixing the resin emulsion (i) with a pigment dispersion paste (ii) containing an inorganic pigment, wherein the amine compound (x) has at least one of a primary amino group and a secondary amino group and does not have a ketimine structure; the cap compound (y) contains an aromatic compound (y1) having one phenolic hydroxyl group and two or more aromatic rings; and the aminerated moiety (a) is formed by ring-opening of the epoxy ring by at least one of the primary amino group and the secondary amino group. A method for producing a cationic electrodeposition coating composition, wherein the cap portion (c) includes an aromatic cap portion (c1) formed by ring-opening of a terminal epoxy ring by the phenolic hydroxyl group.

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