Method for forming a cured electrodeposited coating film

Abstract

To provide a method for forming a cured electrodeposited coating film, which can form an electrodeposited coating film of a desired thickness even for various substrates having different electric resistances. Solution is a method for forming a cured electrodeposited coating film, which comprises: preparing a cationic electrodeposited coating composition, dipping a coated object in the cationic electrodeposited coating composition to perform electrodeposition coating, forming an uncured electrodeposited coating film, and heating the uncured electrodeposited coating film to 120 to 220°C to form a cured electrodeposited coating film on the coated object, the cationic electrodeposited coating composition comprising a specific amine-epoxy resin, a blocked polyisocyanate curing agent, and an inorganic pigment.

Description

Technical Field

[0001] This invention relates to a method for forming a cured electrodeposited coating. Background Technology

[0002] Cationic electrodeposition coating compositions are commonly used as primer coatings for automobiles and other applications. These compositions can form coatings with high corrosion resistance.

[0003] Aminated epoxy resins are commonly used as film-forming resins in cationic electrodeposition coating compositions. Patent documents 1-4 disclose schemes for modifying aminated epoxy resins with phenols for purposes such as improving corrosion resistance.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2010-95668 Patent Document 2: Japanese Patent Application Publication No. 2021-155696 Patent Document 3: Description of Chinese Patent Application Publication No. 117715991 Patent Document 4: U.S. Patent Application Publication No. 2010 / 0163417. Summary of the Invention

[0005] The problem that the invention aims to solve In recent years, to promote carbon neutrality, there has been a growing trend towards using lightweight and high-strength substrates for automobile bodies. Furthermore, automobile bodies can be constructed from a variety of combinations of different materials. Consequently, there is a requirement for cationic electrodeposition coating compositions to be compatible with a wide range of substrates.

[0006] The purpose of this invention is to provide a method for forming a cured electrodeposited coating film, which can form an electrodeposited coating film of desired thickness even on various substrates with different resistances.

[0007] Solution for solving the problem The present invention provides the following methods.

[0008] [1] A method for forming a cured electrodeposited coating, comprising: Preparation of cationic electrodeposition coating compositions, Electrodeposition coating is performed by impregnating the substrate in the cationic electrodeposition coating composition to form an uncured electrodeposition coating film. The uncured electrodeposited coating is heated to 120–220°C to form a cured electrodeposited coating on the substrate. The cationic electrodeposition coating composition comprises an amination epoxy resin, a terminated polyisocyanate curing agent, and inorganic pigments. The amination epoxy resin has the following characteristics: The amination site (a) and the modified epoxy ring of the raw epoxy resin by amine compound (x) are obtained. The cap portion (c) is obtained by modifying the terminal epoxy ring of the raw epoxy resin with a cap compound (y) having a functional group other than an amino group that can react with the epoxy ring. 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 capping compound (y) comprises an aromatic compound (y1) having one phenolic hydroxyl group as the functional group and four or more aromatic rings. The amination site (a) is formed by opening the epoxy ring using at least one of the primary and secondary amine groups. The cap portion (c) includes an aromatic cap portion (c1) formed by opening the terminal epoxy ring using the phenolic hydroxyl group.

[0009] [2] According to the method for forming a cured electrodeposited coating as described in [1] above, wherein, The amination site (a) has a terminal amination site (a12) formed by opening the terminal epoxy ring using the amine compound (x). The ratio (a12:c) of the terminal amination site (a12) to the cap site (c) is 40:60 to 80:20.

[0010] [3] According to the method for forming a cured electrodeposited coating according to [1] or [2] above, wherein the amination epoxy resin is the polar term δ constituting the Hansen solubility parameter. P The value is 10.0–12.0, and the hydrogen bond term δ h The resin has a strength of 8.5 to 10.0.

[0011] [4] According to the method for forming a cured electrodeposited coating as described in [1] or [2] above, wherein, The end-capped polyisocyanate curing agent comprises a polyisocyanate compound end-capped with an end-capping agent, wherein the end-capping agent comprises one or more selected from oxime compounds, pyrazole compounds, imidazole compounds, and triazole compounds. The uncured electrodeposited coating is heated at 120–170°C.

[0012] [5] According to the method for forming a cured electrodeposited coating according to [1] or [2] above, wherein the cap compound (y) further comprises a monocarboxylic acid (y2) having 5 to 14 carbon atoms other than the aromatic compound (y1). The cap portion (c) further includes a second cap portion (c2) formed by opening the terminal epoxy ring using the monocarboxylic acid (y2).

[0013] [6] According to the curing electrodeposition coating method of [5] above, the equivalent ratio (E2:E3) of the equivalent of the phenolic hydroxyl group of the aromatic compound (y1) to the equivalent of the carboxylic acid (y2) of the epoxy ring of the raw epoxy resin is 40:60 to 99:1.

[0014] [7] According to the method for forming a cured electrodeposited coating as described in [1] or [2] above, wherein, The preparation of the cationic electrodeposition coating composition includes the following steps: The raw epoxy resin, the amine compound (x), and the cap compound (y) having functional groups other than amino groups capable of reacting with the epoxy ring are reacted to prepare the amination site (a) obtained by modifying the epoxy ring with the amine compound (x) and the cap site (c) obtained by modifying the terminal epoxy ring with the cap compound (y). The amination epoxy resin and the end-capped polyisocyanate curing agent are mixed to prepare a resin emulsion (i), and The resin emulsion (i) and the pigment dispersion paste (ii) containing the inorganic pigment are mixed.

[0015] The effects of the invention According to the present invention, a method for forming a cured electrodeposited coating film is provided, which can form an electrodeposited coating film of desired thickness even on various substrates with different resistances. Detailed Implementation

[0016] In cationic electrodeposition coating, a current flows through a substrate (e.g., a car body) as the cathode, causing positively charged particles of amination epoxy resin to adhere to the substrate surface. The adhered particles fuse together through Joule heating generated on the substrate, and soon the substrate surface is covered with a coating of amination epoxy resin. The surface resistance of the substrate increases with particle adhesion; the electrodeposition process ends when the resistance increases to the point where particle adhesion becomes difficult.

[0017] The surface resistance of a substrate varies depending on the type of substrate. Therefore, even when performing cationic electrodeposition coating under the same conditions, the thickness of the resulting electrodeposited coating will vary depending on the substrate. In this disclosure, by increasing the hydrophobicity of the amination epoxy resin, the thickness deviation of the electrodeposited coating that can occur between multiple different substrates (hereinafter sometimes simply referred to as "film thickness deviation") is reduced. As a result, it is possible to form a coating with the desired uniform thickness on various materials under the same coating conditions without changing the conditions according to the material. For example, even when a car body is composed of multiple combinations of different materials, it is possible to form an electrodeposited coating with the desired thickness uniformly on each material.

[0018] The solvent in cationic electrodeposition coating compositions is predominantly water. If the amination epoxy resin has high hydrophobicity, water has difficulty penetrating between the particles when they adhere to the substrate, resulting in smaller interparticle gaps. Consequently, the Joule heat absorbed by water near the substrate decreases, facilitating particle fusion. This leads to rapid coating formation on the substrate surface. In other words, because a uniform coating film is formed in the initial stage of electrodeposition coating, exhibiting resistance, the influence of the substrate surface resistance on coating formation is reduced. Based on these reasons, it can be considered that even for various substrates with different resistances, electrodeposition coatings of desired thickness can be formed.

[0019] The terminal epoxy ring of the aminated epoxy resin used in this disclosure is modified with an aromatic compound (y1) having one phenolic hydroxyl group and four or more aromatic rings. That is, the aminated epoxy resin includes an aromatic cap (c1) formed by opening the terminal epoxy ring using the phenolic hydroxyl group of the aromatic compound (y1). The aromatic cap (c1) improves the hydrophobicity of the aminated epoxy resin.

[0020] The amination epoxy resin used in this disclosure is further modified (amined) by an amine compound (x) having at least one of a primary amine and a secondary amine and not having a ketimine structure. The ketimine structure is a structure where the primary amine is protected by a ketone (RR'C=N-). The ketimine structure is readily hydrolyzed during the process of dispersing the amination epoxy resin in a solvent (water), yielding a ketone and a primary amine. The primary amine can improve the hydrophilicity of the amination epoxy resin. The amination epoxy resin of this disclosure exhibits higher hydrophobicity due to modification with an amine compound (x) that does not have a ketimine structure.

[0021] First, the cationic electrodeposition coating composition will be described.

[0022] [Cationic electrodeposition coating composition] The cationic electrodeposition coating composition comprises an amination epoxy resin, a terminated isocyanate curing agent, and an inorganic pigment.

[0023] The cationic electrodeposition coating composition is a mixture of a resin emulsion (i) and a pigment dispersion paste (ii). The resin emulsion (i) comprises an amination epoxy resin and a capped polyisocyanate curing agent. The pigment dispersion paste (ii) comprises an inorganic pigment and a pigment dispersion resin as needed.

[0024] Resin emulsion (i) Resin emulsion (i) comprises an amination epoxy resin and a capped polyisocyanate curing agent. Resin emulsion (i) may further comprise other components as needed.

[0025] <Aminated epoxy resin> Amination-modified epoxy resin is a coating-forming resin that constitutes an electrodeposited coating.

[0026] Amination-modified epoxy resins are obtained by ring-opening a portion of the epoxy ring in the backbone of the raw epoxy resin with an amine compound (x) having at least one of a primary or secondary amino group and not having a ketimine structure; and by ring-opening a portion of the terminal epoxy ring with a capping compound (y) having a functional group other than an amino group capable of reacting with the epoxy ring. In other words, the terminal epoxy rings of the raw epoxy resin are modified with either the amine compound (x) or the capping compound (y).

[0027] The amination-modified epoxy resin has an amination site (a) obtained by modifying the epoxy ring with an amine compound (x) and a capping site (c) obtained by modifying the terminal epoxy ring with a capping compound (y).

[0028] (Amine compound (x)) 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 hydrophobicity of the amination epoxy resin can be maintained through the amination site (a) derived from the amine compound (x). Moreover, since no deketination occurs due to the amination site (a), the generation of ketones, i.e., VOCs, can be suppressed.

[0029] The amine compound (x) may comprise a first amine compound (x1) having a primary amino group but not a ketimine structure, and a second amine compound (x2) having a secondary amino group but not a ketimine structure, other than the first amine compound (x1). Thus, the molecular weight distribution can be easily controlled.

[0030] When using the two amine compounds mentioned above, firstly, the primary amino group of the first amine compound (x1) reacts with the epoxy ring and is consumed. The remaining reactive amino groups in both the first amine compound (x1) and the second amine compound (x2) are only secondary amino groups. The secondary amino group reacts with the residual epoxy ring in the epoxy resin to obtain the amination epoxy resin. In the latter part of the reaction, since the reactive amino groups are only secondary amino groups, there is no difference in reactivity, and the reaction proceeds equally. Therefore, the molecular weight distribution of the obtained amination epoxy resin (A) can be controlled.

[0031] The mass ratio of the first amine compound (x1) to the second amine compound (x2) (first amine compound (x1): second amine compound (x2)) can be, for example, 30:70 to 80:20, or 40:60 to 70:30. This can suppress the excessive increase in viscosity of the amination epoxy resin caused by high molecular weight, while simultaneously improving the stability of the resin emulsion (i).

[0032] • First amine compound (x1) The first amine compound (x1) has at least a primary amine group and does not have a ketimine structure. The first amine compound (x1) first causes the terminal epoxy ring of the raw epoxy resin to open. At this point, the primary amine group becomes a secondary amine group. Subsequently, the secondary amine group reacts with the terminal epoxy rings of other raw epoxy resins, causing the raw epoxy resins to crosslink with each other.

[0033] When using the first amine compound (x1), a cross-linked amination site (a11) is formed as the amination site (a), having a cross-linked structure formed by opening two epoxy rings using the first amine compound (x1). The cross-linked amination site (a11) provides flexibility to the rigid epoxy resin skeleton. As a result, the thermal flow of the amination epoxy resin is improved, the surface of the electrodeposited coating becomes smoother, and the appearance of the coating is improved.

[0034] The first amine compound (x1) can be a diamine having a primary amino group as well as a secondary or tertiary amino group.

[0035] The first amine compound (x1) can be represented, for example, by the following general formula (1). NH2-(CH2) n -NR 1 R 2 (1) (where R) 1 and R 2 Each of these groups independently represents an alkyl group with 1 to 6 carbon atoms, optionally ending in a hydroxyl group, where n represents an integer from 2 to 4.

[0036] R 1 and R 2 The number of carbon atoms can be, for example, 1 to 5, or 1 to 4. R 1 and R 2 For example, it can be methyl, ethyl, propyl, or butyl. n can be 3.

[0037] 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. They can be used alone or in combination of two or more.

[0038] • Second amine compound (x2) The second amine compound (x2) is a compound other than the first amine compound (x1) (i.e., it does not have a primary amine), but has a secondary amine and does not have a ketimine structure. The second amine compound (x2) causes the terminal epoxy ring of the raw epoxy resin to open.

[0039] When using the second amine compound (x2), as the amination site (a), a terminal amination site (a12) is formed by opening the terminal epoxy ring using the second amine compound (x2).

[0040] The second amine compound (x2) can be represented, for example, by the following general formula (2), R 3 R 4 NH (2) (where R) 3 and R 4 Each of these can be used independently to represent an alkyl group with 1 to 4 carbon atoms at the terminal hydroxyl group.

[0041] R 3 and R 4 For example, methyl, ethyl, propyl or butyl, hydroxymethyl, hydroxyethyl, hydroxypropyl or hydroxybutyl. 3 and R 4 It can be hydroxymethyl or hydroxyethyl.

[0042] Examples of second amine compounds (x2) include diethanolamine, diethanolamine, and N-methylethanolamine. They can be used alone or in combination of two or more.

[0043] The amine compound (x) may include the first amine compound (x1) shown in general formula (1) and the second amine compound (x2) shown in general formula (2). This improves the dispersion stability of the amination epoxy resin in the cationic electrodeposition coating composition.

[0044] (Cap compound (y)) The cap compound (y) has functional groups other than amino groups that can react with the epoxy ring. The cap site (c) derived from the cap compound (y) endows the amination epoxy resin with the desired properties.

[0045] Other functional groups besides amino groups that can react with epoxy rings include, for example, hydroxyl, carboxyl, and phenolic hydroxyl groups.

[0046] In this disclosure, an aromatic compound (y1) having one phenolic hydroxyl group as a functional group and four or more aromatic rings is used as the cap compound (y). The phenolic hydroxyl group of the aromatic compound (y1) causes the terminal epoxy ring to open, forming an aromatic cap site (c1). The aromatic cap site (c1) imparts high hydrophobicity to the amination epoxy resin.

[0047] • Aromatic compounds (y1) Aromatic compound (y1) has one phenolic hydroxyl group and four or more aromatic rings. In aromatic compound (y1), the functional group capable of reacting with the epoxy ring has only one phenolic hydroxyl group.

[0048] When there are two or more functional groups capable of reacting with the epoxy ring, increasing the molecular weight reduces the thermal flowability of the amination epoxy resin, resulting in a poorer coating appearance. Furthermore, the increased hydrophilicity of the amination epoxy resin may lead to greater film thickness variations.

[0049] When the number of aromatic rings is less than 4, the hydrophobicity of the amination epoxy resin becomes insufficient, and the film thickness deviation becomes larger. The number of aromatic rings can be 4–10, 4–7, 4–5, or 4.

[0050] Examples of aromatic rings include benzene rings, naphthalene rings, and anthracene rings. Aromatic rings can be heterocycles containing heteroatoms such as nitrogen, oxygen, sulfur, and phosphorus. They can be used alone or in combination of two or more. Aromatic rings can have substituents other than functional groups capable of reacting with epoxy rings (e.g., aliphatic hydrocarbon groups). Aromatic rings can be benzene rings or naphthalene rings.

[0051] Examples of aromatic compounds (y1) include 4-(1,2,2-triphenylvinyl)phenol and tristyrylphenol. They can be used alone or in combination of two or more.

[0052] The proportion (c1 / c) of the aromatic cap portion (c1) in the cap portion (c) is, for example, 40% or more. This further improves the hydrophobicity of the amination epoxy resin. The proportion (c1 / c) can be 40–100%, 50–90%, or 60–80%.

[0053] The quantity ratio (c1 / c) can be calculated based on the amount of raw material that can cap the epoxy at the end. That is, the proportion of the equivalent E2 of the epoxy ring contained in the raw material epoxy resin and the functional group contained in the aromatic compound (y1) in the total of the equivalent E2 and the equivalent E3 of the carboxyl group contained in the monocarboxylic acid (y2) (E2 / (E2+E3)) can be 40% or more.

[0054] The following is an example of an aromatic compound (y1) (4-(1,2,2-triphenylvinyl)phenol, tristylated phenol (n=3)).

[0055]

Chemistry 1

Chemistry 2

[0056] The quantity ratio (a12:c) can be calculated based on the amount of raw materials fed. That is, the ratio (E1:E2+E3) of the total amount of the equivalent of the amino group in the second amine compound (x2) relative to the epoxy ring of the raw material epoxy resin, the equivalent of the functional group in the cap compound (y) E2, and the equivalent of the carboxylic acid in the monocarboxylic acid (y2) E3 can be 40:60 to 80:20.

[0057] • Monocarboxylic acid (y2) The cap compound (y) may also include a monocarboxylic acid (y2) with 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 opening the terminal epoxy ring using the monocarboxylic acid (y2). The second cap portion (c2) can improve the flowability of the coating film.

[0058] Monocarboxylic acids (y2), for example, from R d -COOH(R) d This indicates a hydrocarbon group with 4 to 13 carbon atoms. The hydrocarbon group can be straight-chain or branched. It can be an aliphatic group and may not have an aromatic ring. It can be a saturated hydrocarbon group. The hydrogen atom bonded to the carbon atom of the hydrocarbon group may not be substituted.

[0059] When the number of carbon atoms in a monocarboxylic acid (y2) is 5 or more, the fluidity of the coating film can be improved. When the number of carbon atoms in a monocarboxylic acid (y2) is 14 or less, both high fluidity and high corrosion resistance can be achieved. The number of carbon atoms in a monocarboxylic acid (y2) can be 6–12 or 8–10.

[0060] Examples of monocarboxylic acids (y2) include valeric acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, lauric acid, 2-ethylhexanoic acid, neovaleric acid, 3-methylbutyric acid, and octanoic acid. They can be used alone or in combination of two or more. From a fluidity perspective, octanoic acid is a good choice.

[0061] When using a monocarboxylic acid (y2), the equivalent ratio (E2:E3) of the phenolic hydroxyl group (y1) to the equivalent ratio (E3) of the carboxylic acid (y2) is, for example, 40:60 to 99:1. In this case, the ratio (c1:c2) of the aromatic cap portion (c1) to the second cap portion (c2) is also 40:60 to 99:1. If the ratio (c1:c2) is within this range, the hydrophobicity of the amination epoxy resin is improved. The equivalent ratio (E2:E3) (= the ratio (c1:c2)) can be 50:50 to 90:10.

[0062] The quantity ratio (c1:c2) corresponds to the above equivalent ratio (E2:E3). The equivalent ratio (E2:E3) can be calculated based on the amount of raw materials fed. That is, when using a monocarboxylic acid (y2), the ratio (E2:E3) of the equivalent E2 of the phenolic hydroxyl group contained in the aromatic compound (y1) of the epoxy ring of the raw material epoxy resin to the equivalent E3 of the carboxyl group contained in the monocarboxylic acid (y2) can be within the above range.

[0063] If we consider the case where monocarboxylic acid (y2) is not used, the equivalence ratio (E2:E3) (= quantity ratio (c1:c2)) can be 40:60 to 100:0 or 50:50 to 100:0.

[0064] (Raw material: epoxy resin) A typical example of a raw material epoxy resin is a polyphenolic polyglycidyl ether type epoxy resin. Polyphenolic polyglycidyl ether type epoxy resins can be obtained by reacting polycyclic phenolic compounds such as bisphenol A, bisphenol F, bisphenol S, phenolic varnish, and cresol varnish with epichlorohydrin.

[0065] Other epoxy resins that can be cited as raw materials include, for example, the epoxy resin containing an oxazolidinone ring disclosed in Japanese Patent Application Publication No. 5-306327. This epoxy resin can be prepared by reacting a diisocyanate compound or a diurethane compound with epichlorohydrin, wherein the diurethane compound is obtained by capping the isocyanate group of the diisocyanate compound with a lower alcohol such as methanol or ethanol.

[0066] The raw material epoxy resin can also be chain-extended by difunctional polyester polyols, polyether polyols, bisphenols, dicarboxylic acids, etc.

[0067] The raw epoxy resin can have an epoxy ring composed of monohydroxy compounds such as 2-ethylhexanol, nonylphenol, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol mono-2-ethylhexyl ether, or monocarboxylic acid compounds such as octanoic acid. This allows for adjustment of the molecular weight or amine equivalent of the epoxy resin, thereby improving its thermal fluidity.

[0068] (Characteristics of amination-modified epoxy resins) For amination-modified epoxy resins, the polar term δ, which constitutes the Hansen solubility parameter, is... P It can be 10.0 to 12.0, and the hydrogen bond term δ h The value can be 8.5 to 10.0. Aminated epoxy resins meeting this value exhibit sufficient hydrophobicity, further reducing film thickness deviation. Polarity term δ P It can be 10.0–11.5, or 10.0–10.5. Hydrogen bond term δ h It can be 8.5 to 9.5, or it can be 8.5 to 9.0.

[0069] The Hansen solubility parameter (HSP) is an indicator of the affinity (compatibility) of a substance (X) with other substances (Y). The Hansen solubility parameter (HSP) is derived by dividing the solubility parameter into a dispersion term δ. d Polar term δ p Hydrogen bond term δ h These three components, and the parameters quantified using three-dimensional vectors (Hansen solubility parameter value: δ = (δd) 2 +δp 2 +δh 2 ) 1 / 2 .

[0070] Dispersion term δ d The polarity term δ represents the effect based on the dispersing force. p The hydrogen bond term δ represents the effect based on the interpole force. h This represents the effect of hydrogen bonding forces. The closer the distance (HSP distance (Ra)) between the vector of substance (X) and the vector of other substances (Y) in three-dimensional space, the easier it is for substances (X) and substances (Y) to dissolve in each other (higher compatibility).

[0071] HSP distance (Ra) is defined by the following formula.

[0072] Ra = [4(δd)] X -δd Y ) 2 + (δp) X -δp Y ) 2 + (δh) X -δh Y ) 2 ]1 / 2 δd i The dispersion force term of substance i δp i Polarity term of substance i δh i Hydrogen bond term of substance i The definition and calculation method of Hansen's solubility parameters are described in Charles M. Hansen's book, "Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007)".

[0073] In this disclosure, the Hansen solubility parameter can be calculated using computer software (Hansen Solubility Parameters in Practice (HSPiP) version 5.3.05).

[0074] Specifically, 10 mL of each of the 20 solvents listed in Table 1 was added to 2 g of the analyte. The solvents are not limited to these, as long as they have a known dispersion term δ. d Polar term δ p Hydrogen bond term δ h Solvents containing these three components are acceptable. The test object can be a solvent-free resin or a varnish containing solvent. From the viewpoint of minimizing or eliminating the influence of the test object's properties on the measured value, when the test object is a varnish containing solvent, its kinematic viscosity at 25°C is preferably 100–15000 mm³. 2 The range of / s.

[0075] Table 1 .

[0076] After adding the solvent, allow it to stand for 2 or 4 hours. Then, define the dispersed or dissolved solvent as a good solvent and the precipitated or insoluble solvent as a poor solvent, and evaluate the affinity in five stages from 1 to 5. Input the affinity evaluation results into the HSP (version 5.3.05) mentioned above to calculate the Hansen solubility parameter.

[0077] The weight-average molecular weight of the amination epoxy resin is, for example, 3000 to 7000. When the weight-average molecular weight is 3000 or higher, solvent resistance and corrosion resistance are further improved. When the weight-average molecular weight is 7000 or lower, viscosity adjustment of the amination epoxy resin becomes easier, and synthesis proceeds smoothly. Furthermore, the amination epoxy resin is easier to emulsify and disperse, improving workability. The weight-average molecular weight can be 4000 or higher. The weight-average molecular weight can be 6500 or lower. The weight-average molecular weight can be 4000 to 6500.

[0078] The amine value of the amination epoxy resin can range from 20 to 100 mg KOH / g. When the amine value is above 20 mg KOH / g, the dispersion stability of the amination epoxy resin in the electrodeposited coating improves. When the amine value is below 100 mg KOH / g, the water resistance of the electrodeposited coating improves. The aforementioned amine values ​​can be below 80 mg KOH / g. The aforementioned amine values ​​can range from 20 to 80 mg KOH / g.

[0079] The hydroxyl value of the amination epoxy resin can be 150–650 mg KOH / g. When the hydroxyl value is above 150 mg KOH / g, the curability and appearance of the electrodeposited coating are improved. When the hydroxyl value is below 650 mg KOH / g, the water resistance of the electrodeposited coating is improved. The hydroxyl value can be above 180 mg KOH / g. The hydroxyl value can be below 300 mg KOH / g. The hydroxyl value can be between 180 and 300 mg KOH / g.

[0080] The weight-average molecular weight of the amination epoxy resin can be 3000–7000, and the amine value can be 20–100 mgKOH / g. This amination epoxy resin further improves corrosion resistance.

[0081] As an amination epoxy resin, two or more amination epoxy resins with different amine values ​​and / or hydroxyl values ​​can be used in combination. In this case, the average amine value and average hydroxyl value calculated based on the mass ratio of the amination epoxy resins used can be set to the above-mentioned value range.

[0082] As an amination epoxy resin, an amination epoxy resin with an amine value of 20–50 mg KOH / g and a hydroxyl value of 50–300 mg KOH / g and an amination epoxy resin with an amine value of 50–200 mg KOH / g and a hydroxyl value of 200–500 mg KOH / g can be used in combination. When this combination of resins is emulsified and dispersed, an epoxy resin emulsion with a hydrophobic core and a hydrophilic shell can be obtained. The corrosion resistance can be further improved through a core-shell type epoxy resin emulsion.

[0083] (other) Electrodeposited coatings may contain other film-forming resins. Examples of other film-forming resins include acrylic resins, polyester resins, polyurethane resins, olefin resins, phenolic resins, xylene resins, amino-containing acrylic resins, and amino-containing polyester resins.

[0084] <End-capped polyisocyanate curing agent> In addition, end-capped polyisocyanate curing agents are also coating-forming resins. End-capped polyisocyanate curing agents preferentially react with the amino groups of the amination epoxy resin, and then with the hydroxyl groups to form a cross-linked structure.

[0085] End-capped polyisocyanate curing agents are prepared by end-capping polyisocyanates with an end-capping agent. End-capping is carried out, for example, by adding the end-capping agent dropwise to the polyisocyanate at 40–50°C while stirring, in the presence of a curing catalyst (e.g., a tin-based catalyst).

[0086] Polyisocyanates may include at least one selected from aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Polyisocyanates may be aromatic polyisocyanates or aliphatic polyisocyanates. Polyisocyanates may be aromatic polyisocyanates.

[0087] Examples of aromatic polyisocyanates include 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, and xylene diisocyanate. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate).

[0088] In end-capped polyisocyanate curing agents, polyisocyanates can form adducts such as biuret bodies, diuret bodies, isocyanurate bodies, or urea carbamate bodies.

[0089] Examples of end-capping agents include phenolic compounds, lactam compounds, alcohols, oxime compounds, compounds with active methylene groups, thiols, amides, imides, amines, pyrazoles, imidazoles, triazoles, ureas, carbamates, imides, sulfites, and ketones.

[0090] The capping agent may be selected from one or more of oxime compounds, pyrazole compounds, imidazole compounds, and triazole compounds.

[0091] Examples of phenolic compounds include phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxybiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate.

[0092] Examples of lactam compounds include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam.

[0093] Examples of alcohols include methanol, ethanol, propanol, butanol, pentanol, lauryl alcohol, benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, hydroxymethylurea, hydroxymethyl melamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate.

[0094] Examples of oxime compounds include aminomethyloxime, acetamide oxime, acetone oxime, methyl ethyl ketone oxime, diacetyl monooxime, benzophenone oxime, and cyclohexanone oxime.

[0095] Examples of compounds containing active methylene groups include dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0096] Examples of thiols include butyl thiols, tert-butyl thiols, hexyl thiols, tert-dodecyl thiols, 2-mercaptobenzothiazole, thiophenol, methyl thiophenol, and ethyl thiophenol.

[0097] Examples of amide compounds include acetanilide, acetaminophen, N-acetyltoluidine, acrylamide, methacrylamide, acetamide, stearamide, and benzamide.

[0098] Examples of imide compounds include succinimide, phthalimide, and maleimide.

[0099] Examples of amine compounds include diphenylamine, phenylnaphthylamine, dimethylaniline, N-phenyldimethylaniline, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylaniline.

[0100] Examples of pyrazole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole.

[0101] Examples of imidazole compounds include imidazole, benzimidazole, 2-methylimidazolium, 2-ethylimidazolium, and 2-phenylimidazolium.

[0102] Examples of triazole compounds include 3,5-dimethyl-1,2,4-triazole.

[0103] Examples of urea compounds include urea, thiourea, ethylidene urea, ethylidene thiourea, and diphenylurea.

[0104] Examples of urethane esters include, for instance, phenyl N-phenylcarbamate.

[0105] Examples of imine compounds include ethyleneimine and propyleneimine.

[0106] Examples of sulfites include sodium bisulfite and potassium bisulfite.

[0107] Examples of ketone compounds include methyl ethyl ketone and methyl isobutyl ketone.

[0108] The end-capping rate of the end-capping polyisocyanate curing agent can reach 100%. As a result, the storage stability of the electrodeposited coating is improved.

[0109] As a terminal polyisocyanate curing agent, a combination of terminally terminal aliphatic diisocyanates and terminally terminal aromatic diisocyanates can be used.

[0110] (other) As a curing agent, it can be used in conjunction with end-capped polyisocyanate curing agents, at least one selected from organic curing agents (such as melamine resins and phenolic resins), silane coupling agents, and metal curing agents.

[0111] Pigment dispersion paste (ii) Pigment dispersion paste (ii) comprises inorganic pigments and pigment dispersion resins.

[0112] Inorganic pigments Inorganic pigments are commonly used pigments in electrodeposited coatings and are not particularly limited in type. Examples of inorganic pigments include coloring pigments such as titanium dioxide, carbon black, and red lead; filler pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica, and clay; and anti-rust pigments such as iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, aluminum phosphomolybdate, and zinc aluminum phosphomolybdate. They can be used individually or in combination of two or more.

[0113] The total content of inorganic pigments can be 1 to 37% by mass of the resin solids component of the electrodeposited coating. The aforementioned content of inorganic pigments can be 5% by mass or more, 10% by mass or more, or 15% by mass or more. The aforementioned content of inorganic pigments can be less than 30% by mass, less than 27% by mass, or less than 25% by mass. The aforementioned content can be 5 to 30% by mass, 10 to 27% by mass, or 15 to 25% by mass.

[0114] Pigment Dispersion Resin Pigment dispersion resin is a resin used to disperse pigments in an aqueous medium. For example, a pigment dispersion resin having cationic groups can be used as a pigment dispersion resin. 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 sulfonyl groups, and primary amine groups. As an aqueous solvent, deionized water or water containing a small amount of alcohol is used.

[0115] Amine-modified epoxy resins can be prepared, for example, by reacting a semi-terminated isocyanate with the hydroxyl groups of a hydroxyl-containing raw epoxy resin to introduce terminated isocyanate groups. The introduction of terminated isocyanate groups can be achieved by reacting the hydroxyl-containing raw epoxy resin with the semi-terminated isocyanate at 140°C for approximately 1 hour.

[0116] Polyepoxides can be used as raw material epoxy resins. Polyepoxides have an average of two or more 1,2-epoxy groups per molecule. Examples of raw material epoxy resins in amination epoxy resins can be cited as examples of polyepoxides.

[0117] Semi-terminated isocyanates can be prepared by capping a portion of the isocyanate groups of a polyisocyanate using a capping agent. Examples of polyisocyanates included in capped polyisocyanate curing agents include polyisocyanates. Examples of capping agents include, for example, lower aliphatic alkyl monohydric alcohols having 4 to 20 carbon atoms. Specific examples of capping agents include butanol, pentanol, hexanol, 2-ethylhexanol, and heptanol.

[0118] Tertiary amines can have 1 to 6 carbon atoms. Specific examples of tertiary amines include dimethylethanolamine, trimethylamine, triethylamine, dimethylbenzylamine, diethylbenzylamine, N,N-dimethylcyclohexylamine, tri-n-butylamine, diphenylethylmethylamine, dimethylaniline, and N-methylmorpholine.

[0119] There is no particular limitation on the neutralizing acid. 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 can be at least one selected from formic acid, acetic acid, and lactic acid.

[0120] <Other> Electrodeposited 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.

[0121] Electrodeposited coatings may contain additives commonly used in the coatings industry. Examples of additives include, for instance, surfactants, viscosity modifiers, anti-cratering agents, inorganic rust inhibitors, auxiliary complexing agents, buffers, smoothers, stress relievers, gloss agents, semi-gloss agents, antioxidants, and UV absorbers. Additives are added during the preparation of resin emulsions (i) and / or pigment dispersions (ii).

[0122] [Preparation of cationic electrodeposition coating composition] The cationic electrodeposition coating composition is prepared by the following method, which includes the following steps: (1) An amination epoxy resin is prepared by reacting a raw epoxy resin, an amine compound (x), and a capping compound (y) having a functional group other than an amino group that can react with the epoxy ring, to obtain an amination site (a) obtained by modifying the epoxy ring with the amine compound (x) and a capping site (c) obtained by modifying the terminal epoxy ring with the capping compound (y). (2) Ammoniated epoxy resin and end-capped polyisocyanate curing agent are mixed to prepare resin emulsion (i), and (3) Mix the resin emulsion (i) and the pigment dispersion paste (ii) containing inorganic pigments.

[0123] (1) Preparation of amination-modified epoxy resin The raw epoxy resin, amine compound (x), and cap compound (y) are reacted to obtain an amination epoxy resin having an amination site (a) and a cap site (c).

[0124] First, the raw epoxy resin is reacted with the capping compound (y). For example, the raw epoxy resin and the capping compound (y) are mixed and reacted at 120–160°C for 0.5–2 hours. Next, the amine compound (x) is added and reacted at 80–150°C for 0.1–5 hours, more preferably at 120–150°C for 0.5–3 hours.

[0125] (2) Preparation of resin emulsion (i) The resin emulsion (i) can be prepared as follows: First, solutions are prepared by dissolving the amination epoxy resin and the end-capped polyisocyanate curing agent separately in an organic solvent. These solutions are then mixed and neutralized using a neutralizing acid. Finally, they are diluted with deionized water.

[0126] Examples of neutralizing acids include organic acids such as methanesulfonic acid, aminosulfonic acid, lactic acid, dimethylolpropionic acid, formic acid, and acetic acid. The neutralizing acid can be at least one selected from formic acid, acetic acid, and lactic acid.

[0127] The equivalent ratio (neutralization rate) of the neutralizing acid to the amino equivalent of the amination epoxy resin can be 10% to 100%. When the neutralization rate is 10% or higher, the affinity of the amination epoxy resin for water increases, and its water dispersibility improves. The neutralization rate can be 20% or higher. The neutralization rate can be 70% or lower. The neutralizing acid is used in an amount that meets the above-mentioned neutralization rates.

[0128] The end-capped polyisocyanate curing agent is used in an amount sufficient to react with active hydrogen functional groups such as primary amine, secondary amine or hydroxyl groups in the amination epoxy resin during curing.

[0129] The mass ratio (A / B) of the solid components of the amination epoxy resin to the end-capped polyisocyanate curing agent can be 90 / 10 to 50 / 50. The A / B ratio can also be 80 / 20 to 65 / 35. By adjusting the A / B ratio, the flowability and curing speed of the precipitated film can be controlled, thereby improving the appearance of the coating.

[0130] The solid content of the resin emulsion (i) can be 25% to 50% by mass. The solid content can be 35% by mass or more. The solid content can be 45% by mass or less. The solid content can be 35% to 45% by mass.

[0131] (3) Mixing The resin emulsion (i) and the pigment dispersion paste (ii) are mixed. This yields a cationic electrodeposition coating composition.

[0132] Pigment dispersion paste (ii) is prepared by mixing pigments and pigment dispersion resins. The content of pigment dispersion resin in the pigment dispersion paste is not particularly limited; for example, it can be 20 to 100 parts by weight of resin solids relative to 100 parts by weight of pigment. The amount of solids in the pigment dispersion paste is, for example, 40 to 70% by weight or 50 to 60% by weight relative to the total amount of pigment dispersion paste.

[0133] [Methods for forming cured electrodeposited coatings] The cured electrodeposited coating is formed by the following method, which includes: impregnating a substrate in the above-mentioned cationic electrodeposited coating composition to perform electrodeposition coating to form an uncured electrodeposited coating; and heating the uncured electrodeposited coating to 120-220°C to form a cured electrodeposited coating on the substrate.

[0134] (Electrodeposition coating) The object to be coated is immersed in a bath containing electrodeposited coating material. The object is used as a cathode, and a voltage is applied by flowing current between it and a separately placed anode. As a result, the components of the electrodeposited coating material are deposited on the object, forming a deposited film (uncured electrodeposited coating film).

[0135] The applied voltage can be above 50V and below 450V. The bath temperature can be above 10℃ and below 45℃. The application time can be above 2 minutes and below 5 minutes.

[0136] There are no particular limitations as long as the material to be coated is conductive. Examples of materials to be coated include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electro-galvanized steel sheets, molten galvanized steel sheets, galvanized-aluminum alloy steel sheets, galvanized-ferroalloy steel sheets, galvanized-magnesium alloy steel sheets, galvanized-aluminum-magnesium alloy steel sheets, aluminum-based steel sheets, aluminum-silicon alloy steel sheets, and tin-plated steel sheets.

[0137] (heating) The object to be coated is lifted from the bath and heated. This forms a cured electrodeposited coating. The object can also be washed with water before heating.

[0138] The heating temperature is 120–220℃. The heating temperature can be above 140℃. The heating temperature can be below 180℃ or below 170℃. For example, the heating temperature can be 120–180℃, 120–170℃, 140–180℃, or 140–170℃. The heating time can be, for example, more than 10 minutes and less than 30 minutes.

[0139] When the end-capped polyisocyanate curing agent contains a polyisocyanate compound that has been end-capped with one or more end-capping agents selected from oxime compounds, pyrazole compounds, imidazole compounds, and triazole compounds, the heating temperature can be 120–170°C.

[0140] The thickness of the cured electrodeposited coating is, for example, 5 μm or more and 40 μm or less. This provides sufficient corrosion resistance. The thickness of the cured electrodeposited coating can be 10 μm or more. The thickness of the cured electrodeposited coating can be 25 μm or less. Example

[0141] The invention is illustrated in more detail by means of the following examples, but is not limited thereto. In the examples, unless otherwise stated, "parts" and "%" are based on quality standards.

[0142] The components used in the preparation of the cationic electrodeposition coating composition or their manufacturing methods are as follows.

[0143] [Manufacturing Example A1] Manufacturing of Amination Epoxy Resin A1 Add 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), 312 parts tristyrene-modified phenol (TSP, aromatic compound (y1)), and 1 part dimethyl benzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0144] Next, a mixture of 52 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 84 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A1 with a weight-average molecular weight of 6400 and an amine value of 53 mg KOH / g.

[0145] [Manufacturing Example A2] Manufacturing of Amination Epoxy Resin A2 Add 12 parts butyl cellosolve, 940 parts bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 207 parts bisphenol A (chain extender), 468 parts tristyrenephenol (TSP, aromatic compound (y1)), and 1 part dimethyl benzylamine (catalyst), and maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 847 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0146] Next, a mixture of 54 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 88 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A2 with a weight-average molecular weight of 5500 and an amine value of 53 mgKOH / g.

[0147] [Manufacturing Example A3] Manufacturing of Amine Epoxy Resin A3 Add 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), 105 parts tristyrenephenol (TSP, aromatic compound (y1)), and 1 part dimethyl benzylamine (catalyst), and maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 628 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0148] Next, a mixture of 69 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 111 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A3 with a weight-average molecular weight of 7000 and an amine value of 79 mg KOH / g.

[0149] [Manufacturing Example A4] Manufacturing of Amine Epoxy Resin A4 Add 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), 171 parts tristyrene-modified phenol (TSP, aromatic compound (y1)), 65 parts octanoic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0150] Next, a mixture of 49 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 80 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A4 with a weight-average molecular weight of 6500 and an amine value of 53 mgKOH / g.

[0151] [Manufacturing Example A5] Manufacturing of Amine Epoxy Resin A5 Add 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), 140 parts tristyrene-modified phenol (TSP, aromatic compound (y1)), 79 parts octanoic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0152] Next, a mixture of 49 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 79 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A5 with a weight-average molecular weight of 6500 and an amine value of 53 mgKOH / g.

[0153] [Manufacturing Example A6] Manufacturing of Amine Epoxy Resin A6 Add 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), 292 parts 4-(1,2,2-triphenylvinyl)phenol (TPVP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0154] Next, a mixture of 51 parts N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 83 parts diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A6 with a weight-average molecular weight of 6400 and an amine value of 53 mg KOH / g.

[0155] [Manufacturing Example A7] Manufacturing of Amine Epoxy Resin A7 Add 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), 99 parts 4-(1,2,2-triphenylvinyl)phenol (TPVP, aromatic compound (y1)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 628 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0156] Next, a mixture of 69 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 111 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A7 with a weight-average molecular weight of 7000 and an amine value of 79 mg KOH / g.

[0157] [Manufacturing Example A8] Manufacturing of Amine Epoxy Resin A8 Add 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), 159 parts 4-(1,2,2-triphenylvinyl)phenol (TPVP, aromatic compound (y1)), 66 parts octanoic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0158] Next, a mixture of 49 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 79 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A8 with a weight-average molecular weight of 6500 and an amine value of 53 mgKOH / g.

[0159] [Manufacturing Example A9] Manufacturing of Amine Epoxy Resin A9 Add 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), 129 parts 4-(1,2,2-triphenylvinyl)phenol (TPVP, aromatic compound (y1)), 80 parts octanoic acid (monocarboxylic acid (y2)), and 1 part dimethylbenzylamine (catalyst). Maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0160] Next, a mixture of 48 parts of N,N-diethyl-1,3-propanediamine (DEAPA, the first amine compound (x1)) and 78 parts of diethanolamine (DEtA, the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded an amination epoxy resin A9 with a weight-average molecular weight of 6500 and an amine value of 53 mgKOH / g.

[0161] [Comparative Manufacturing Example 1] Manufacturing of Amination Epoxy Resin ep1 Add 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 octanoic acid (monocarboxylic acid (y2)), and 1 part dimethyl benzylamine (catalyst), and maintain the temperature inside the reaction vessel at 120°C. Continue the reaction until the epoxy equivalent reaches 965 g / eq, then cool until the temperature inside the reaction vessel reaches 110°C.

[0162] Next, a mixture of 46 parts of N,N-diethyl-1,3-propanediamine (the first amine compound (x1)) and 75 parts of diethanolamine (the second amine compound (x2)) was added, and the mixture was reacted at 110°C for 1 hour. This yielded the amination epoxy resin ep1.

[0163] [Comparative Manufacturing Example 2] Manufacturing of Amination Epoxy Resin EP2 44 parts of butyl cellosolve, 940 parts of bisphenol A type epoxy resin (raw material epoxy resin, trade name DER-331J, manufactured by Dow Chemical), 342 parts of bisphenol A (chain extender), and 86 parts of octanoic acid (monocarboxylic acid (y2)) were mixed and heated to 120°C. Then, 1 part of dimethylbenzylamine (catalyst) was added, and the temperature inside the reaction vessel was maintained at 140°C. The reaction was continued until the epoxy equivalent reached 1070 g / eq, and then cooled until the temperature inside the reaction vessel reached 120°C.

[0164] Next, a mixture of 53 parts diethanolamine (second amine compound (x2)), 59 parts diethylenetriamine diketoimine (an amine compound with a ketoimine structure, a methyl isobutyl ketone solution with a solid content of 84%), and 29 parts N-methylethanolamine (second amine compound (x2), MEA) was added, and the mixture was reacted at 120°C for 1 hour. This yielded the amination epoxy resin ep2.

[0165] [Comparative Manufacturing Example 3] Manufacturing of Amination Epoxy Resin EP3 In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet pipe, 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 phenolic varnish 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. The reaction was carried out at 160°C until the epoxy equivalent reached 546. The resulting reaction product was then diluted with methyl isobutyl ketone until the solid content was 80%.

[0166] Next, 418.5 parts of diethanolamine and 184.5 parts of a ketimide of diethylenetriamine (90% quality) were added, and the mixture was reacted at 120°C for 3 hours. Subsequently, methyl isobutyl ketone was added to obtain an amination epoxy resin ep3 with a solid content of 75%.

[0167] [Comparative Manufacturing Example 4] Manufacturing of Amination Epoxy Resin EP4 In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet pipe, 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 (ethyltriphenylphosphonium bromide; catalyst), and 53.5 parts of methyl isobutyl ketone (solvent) were added, and the reaction was carried out at 145°C for 2 hours. The resulting reaction product was cooled to 125°C, and 12.4 parts of methyl isobutyl ketone were added simultaneously, followed by cooling to 105°C. Next, 85.4 parts of diethylenetriamine diketoimine (an amine compound with a ketoimine structure, a methyl isobutyl ketone solution with a solid content of 72.7%) and 73.7 parts of N-methylethanolamine (a second amine compound (x2)) were added, and the mixture was reacted at 115°C for 1 hour. This yielded the amination epoxy resin ep4.

[0168] [Comparative Manufacturing Example 5] Manufacturing of Amination Epoxy Resin EP5 In a 3L flask equipped with a stirrer and heating mantle, 18.03 parts of bisphenol A diglycidyl ether (DGEBA, raw 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. Since the temperature reached 200°C, it was cooled to 135°C, and the reaction continued after 45 minutes.

[0169] After confirming the epoxy equivalent (WPE) reached 533, the mixture was cooled to 90°C, and the heating mantle was stopped. Next, 1.73 parts of diethanolamine were added. After stirring for 30 minutes, 0.84 parts of 3-dimethylaminopropylamine were added at 105°C. After stirring for 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 amination epoxy resin ep5.

[0170] [Comparative Manufacturing Example 6] Manufacturing of Amination Epoxy Resin EP6 In a stainless steel autoclave equipped with stirring and temperature control functions, 375 parts of styrene-modified phenol (trade name SP-23, manufactured by Sanko Co., Ltd.) and 0.3 parts of potassium hydroxide were added. After nitrogen replacement in the mixture, dehydration was carried out at 120°C for 1 hour under reduced pressure (approximately 20 mmHg). Subsequently, the mixture was dehydrated at 150°C with a gauge pressure of 1–3 kgf / cm³. 2 116 parts of propylene oxide were introduced. Next, 185 parts of epichlorohydrin were added, and 80 parts of solid sodium hydroxide were gradually added at 30–40°C while stirring vigorously. The mixture was allowed to mature for 5 hours while maintaining the temperature, at which point the reaction was complete. After the reaction, byproduct salts were removed by washing with water. The mixture was then thoroughly washed until the washings were neutral, and water and epichlorohydrin were removed by distillation under reduced pressure at 120–140°C, yielding a styrene-modified phenol compound with an oxidized olefin having a glycidyl group, comprising 100% resin solids.

[0171] In addition, 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 octanoic acid (monocarboxylic acid (y2)), and 135 parts of the above-mentioned styrene-modified phenol compound were added. The mixture was heated to 180°C, and then 1.1 parts of dimethylbenzylamine were added, and the reaction was continued until the epoxy equivalent reached 1300. Next, the mixture was cooled to 120°C and diluted with methyl isobutyl ketone. Then, 50.6 parts of N-methylethanolamine (second amine compound (x2)) and 45.3 parts of aminoethylethanolamine ketone imine (amine compound with a ketone imine structure, 78.8% methyl isobutyl ketone solution) were added, and the mixture was reacted at 120°C for 2 hours. Finally, methyl isobutyl ketone was added for dilution. Thus, ep6 aminated epoxy resin (80% non-volatile component) was obtained.

[0172] [Comparative Manufacturing Example 7] Manufacturing of Amination Epoxy Resin EP7 In a flask equipped with a stirrer, condenser, nitrogen injection tube, and dropping funnel, 71.34 parts of 2,4 / 2,6-toluene diisocyanate (mass ratio: 80 / 20) and 0.01 parts of dibutyltin dilaurate were weighed. While stirring and bubbling with nitrogen, 14.24 parts of methanol were added dropwise over 30 minutes via the dropping funnel. The temperature was raised from room temperature to 60°C by heating. After reacting for 30 minutes, 46.98 parts of ethylene glycol mono-2-ethylhexyl ether were added dropwise over 30 minutes via the dropping funnel. The temperature was raised to 70–75°C by heating. After reacting for 30 minutes, 41.25 parts of bisphenol A propylene oxide adduct (5 mol) (BP-5P manufactured by Sanyo Chemical Industries, Ltd.) were added, and the temperature was raised to 90°C. The reaction continued until the NCO groups disappeared while the IR spectrum was measured.

[0173] Next, 475.0 parts of bisphenol A type epoxy resin (raw material epoxy resin, YD-7011R manufactured by Toto Chemical Co., Ltd.) with an epoxy equivalent of 475 were added and dissolved uniformly. The temperature was then raised from 130°C to 142°C to remove water from the reaction system. After cooling to 125°C, 0.5 parts of benzyldimethylamine were added to initiate an oxazolidinone ring-forming reaction based on a methanol removal reaction. The reaction continued until the epoxy equivalent reached 1140.

[0174] Then, 76.8 parts of o,p-dicumylphenol (aromatic compound (y1)) were added, and the mixture was cooled to 100°C. Next, 24.56 parts of N-methylethanolamine (second amine compound (x2)), 11.46 parts of diethanolamine (second amine compound (x2)), and 26.08 parts of aminoethylethanolamine ketone imine (an amine compound with a ketone imine structure, 78.8% methyl isobutyl ketone solution) were added, and the mixture was reacted at 110°C for 2 hours. Then, 20.74 parts of ethylene glycol mono-2-ethylhexyl ether were added, followed by the addition of methyl isobutyl ketone at 100°C until the viscosity reached 1000 cps. This yielded the amination epoxy resin EP7 (91% non-volatile matter).

[0175] [Manufacturing Example B1] (Manufacturing of End-Capped Polyisocyanate Curing Agent B1) In a reaction vessel equipped with a stirrer, nitrogen inlet, condenser, and thermometer, 222 parts of isophorone diisocyanate were added, diluted with 56 parts of methyl isobutyl ketone (MIBK), and 0.2 parts of butyltin laurylate were added. The mixture was heated to 50°C, and then 174 parts of methyl ethyl ketone oxime were added, ensuring the temperature of the contents did not exceed 70°C. The mixture was kept at 70°C for 1 hour until infrared absorption spectroscopy confirmed that the absorption of the isocyanate residues had essentially disappeared. Then, it was diluted with 43 parts of n-butanol to obtain end-capped polyisocyanate curing agent B1 with a solid content of 70%.

[0176] [Manufacturing Example B2] (Manufacturing of End-capped Polyisocyanate Curing Agent B2) 165 parts of the isocyanurate form of hexamethylene diisocyanate (trade name Smuggle N3300, manufactured by Sumitomo Chemical Bioelur Thermal Co., Ltd.) and 24 parts of MIBK were placed in a reaction vessel and heated to 60°C. 75 parts of methyl ethyl ketone oxime (MEK oxime) were added dropwise over 2 hours. After heating at 70°C for another 2 hours, it was confirmed that the absorption based on the isocyanate groups disappeared in IR spectroscopy measurements. Then, 36 parts of butyl cellosolve were added to obtain end-capped polyisocyanate curing agent B2.

[0177] [Manufacturing Example B3] (Manufacturing of End-Capped Polyisocyanate Curing Agent B3) 1400 parts of polymeric MDI (MDI: diphenylmethane diisocyanate) were placed in a reaction vessel and heated to 60°C. A mixture of 330 parts of butyl diethylene glycol ether (BDG) and 950 parts of butyl cellosolve (BC) was added dropwise over 2 hours at 60°C. After heating at 75°C for 4 hours, the absorption based on isocyanate groups disappeared in the IR spectrum. After cooling, 27 parts of methyl isobutyl ketone (MIBK) were added to obtain end-capped polyisocyanate curing agent B3.

[0178] [Manufacturing Example C] (Manufacturing of Pigment Dispersion Resin) In a reaction vessel equipped with a stirrer, condenser, nitrogen inlet pipe, and thermometer, 385 parts of bisphenol A type epoxy resin, 120 parts of bisphenol A, 95 parts of octanoic acid, and 1 part of 1% 2-ethyl-4-methylimidazolium solution were added. The mixture was 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-ethylhexanolized semi-terminated toluene diisocyanate were added. The reaction mixture was maintained at 120–130°C for 1 hour, and then 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 the mixture was stirred at 120°C for 1 hour. Finally, 13 parts of ethylene glycol mono-n-butyl ether were added to produce the amination resin. Next, 18 parts of ion-exchanged water and 8 parts of formic acid were mixed with the above-mentioned amination resin and stirred for 15 minutes. Then, 200 parts of ion-exchanged water were mixed to obtain a resin solution of pigment dispersion resin (average molecular weight 2200) (resin solids content 25%).

[0179] [Examples 1-9, Comparative Examples 1-7] a. Preparation of resin emulsion (i) 1653g (solid component) of any one of the above-mentioned amination epoxy resins A1-A9 and ep1-7, 319g (solid component) of end-capped polyisocyanate curing agent B1, 293g (solid component) of end-capped polyisocyanate curing agent B2, and 276g (solid component) of end-capped polyisocyanate curing agent B3 were mixed. Then, ethylene glycol mono-2-ethylhexyl ether was added at 3% (15g) relative to the solid component. Next, formic acid was added to neutralize the mixture to a neutralization rate of 40%, and deionized water was added and the mixture was slowly diluted to obtain nine resin emulsions (i).

[0180] b. Preparation of pigment dispersion paste (ii) Add 106.9 parts of the above-mentioned 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 to a sand mill and disperse until the particle size is below 10 μm to obtain pigment dispersion paste (ii) (60% solid content).

[0181] c. Preparation of cationic electrodeposition coating compositions 1394g of ion-exchanged water, 560g of resin emulsion (i) and 41g of pigment dispersion paste (ii) were added to a stainless steel container, and then aged at 40°C for 16 hours to obtain a cationic electrodeposition coating composition.

[0182] [evaluate] The prepared amination epoxy resin or cationic electrodeposition coating compositions were evaluated as follows. The results are shown in Tables 2 and 3.

[0183] Hansen solubility parameters of amination-modified epoxy resins Using the 20 solvents listed in Table 1, affinity was evaluated in the same manner as above, and the Hansen solubility parameters were calculated using the HSPiP (version 5.3.05) described above.

[0184] • Appearance of electrodeposited coating The cold-rolled steel sheet (JISG3141, SPCC-SD) was degreased by immersing it in Serving Cleaner EC90 (manufactured by Nippon Paint Co., Ltd.) at 50°C for 2 minutes. Then, it was subjected to zirconification treatment by immersing it in a zirconification solution containing 0.005% ZrF and adjusted to pH 4 with NaOH at 40°C for 90 seconds.

[0185] Next, the required amount of 2-ethylhexanediol was added to the cationic electrodeposition coating composition to achieve a cured electrodeposition coating thickness of 15 μm. The zirconium-treated steel plate (substrate) was then impregnated with the coating, and a voltage was applied under the condition of increasing the voltage to 180V for 30 seconds and holding it for 150 seconds. Then, the plate was heated at 130°C for 20 minutes to obtain a test plate with an uncured electrodeposition coating formed on the substrate.

[0186] According to JIS B 0601, the arithmetic mean roughness Ra value of the electrodeposited coating was measured using a surface roughness measuring machine (Mitsutoyo Co., Ltd., SURFTESTSJ-201P). Specifically, under the condition of a cutoff value of 2.5 mm (number of zones 5), the surface roughness was measured 10 times at different locations, and the average Ra value was calculated. The Ra value obtained was evaluated according to the following criteria. A Ra value of B or higher can be evaluated as having excellent coating appearance.

[0187] (Evaluation Criteria) A: Less than 0.25μm B: Above 0.25μm and below 0.40μm C: Above 0.40μm ·Deviation in film thickness For cold-rolled steel sheets (JIS G 3141, SPCC), alloyed molten zinc-coated steel sheets (JIS G 3316 SGCC), high-tensile steel sheets (JIS G 3135 SPFC590), and Al materials (Chemetall, AA6014), zirconization treatment was performed in the same manner as above to obtain four types of test plates.

[0188] For each test panel, electrodeposition coating was performed in the same manner as described above. The thickness of the cured electrodeposited coating was set at 15 μm. The film thickness was measured at 10 arbitrary points on each coated panel, and the average value was calculated. The thickness difference was calculated by subtracting the thinnest average film thickness from the thickest average film thickness. The larger this thickness difference, the greater the possible deviation in the thickness of the electrodeposited coating between multiple different substrates.

[0189] (Evaluation Criteria) A: Film thickness difference is less than 1.5μm B: Film thickness difference greater than 1.5 μm and less than 2.5 μm C: Film thickness difference greater than 2.5 μm and less than 3.5 μm D: Film thickness difference is greater than 3.5 μm and less than 4.5 μm E: The film thickness difference is greater than 4.5 μm.

[0190] Table 2 .

[0191] Table 3 .

[0192] The electrodeposited coatings in Examples 1-9 exhibited small deviations in film thickness. Furthermore, they possessed excellent appearance.

[0193] In Comparative Example 1, since only octanoic acid was used as the cap compound (y), the hydrophobicity of the amination epoxy resin was poor and the film thickness deviation was large.

[0194] In Comparative Example 2, since only octanoic acid was used as the cap compound (y), and the epoxy resin was amination with an amine compound having a ketimine structure, the hydrophobicity of the amination epoxy resin was poor and the film thickness deviation was greater.

[0195] In Comparative Example 3, because only phenolic varnish-type phenol (polyphenol) was used as the cap compound (y), and amination was performed using an amine compound with a ketimine structure, the hydrophobicity was insufficient, resulting in a deviation in film thickness. Furthermore, due to the excessive polymerization of the amination epoxy resin, the thermal flow was reduced, leading to a poor appearance.

[0196] In Comparative Example 4, since only dodecylphenol (one aromatic ring) was used as the cap compound (y), and amination was performed with an amine compound having a ketimine structure, the hydrophobicity was insufficient, and a deviation in film thickness was observed.

[0197] In Comparative Example 5, since only phenol (one aromatic ring) was used as the cap compound (y), the hydrophobicity was insufficient, and a deviation in film thickness was observed.

[0198] In Comparative Examples 6 and 7, the reduction in hydrophobicity was insufficient due to the use of amine compounds with ketimine structures for amination, resulting in deviations in film thickness.

[0199] This disclosure includes the following methods.

[0200] [1] A method for forming a cured electrodeposited coating, comprising: Preparation of cationic electrodeposition coating compositions, Electrodeposition coating is performed by impregnating the substrate in the cationic electrodeposition coating composition to form an uncured electrodeposition coating film. The uncured electrodeposited coating is heated to 120–220°C to form a cured electrodeposited coating on the substrate. The cationic electrodeposition coating composition comprises an amination epoxy resin, a terminated polyisocyanate curing agent, and inorganic pigments. The amination epoxy resin has the following characteristics: The amination site (a) and the modified epoxy ring of the raw epoxy resin by amine compound (x) are obtained. The cap portion (c) is obtained by modifying the terminal epoxy ring of the raw epoxy resin with a cap compound (y) having a functional group other than an amino group that can react with the epoxy ring. 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 capping compound (y) comprises an aromatic compound (y1) having one phenolic hydroxyl group as the functional group and four or more aromatic rings. The amination site (a) is formed by opening the epoxy ring using at least one of the primary and secondary amine groups. The cap portion (c) includes an aromatic cap portion (c1) formed by opening the terminal epoxy ring using the phenolic hydroxyl group.

[0201] [2] According to the method for forming a cured electrodeposited coating as described in [1] above, wherein, The amination site (a) has a terminal amination site (a12) formed by opening the terminal epoxy ring using the amine compound (x). The ratio (a12:c) of the terminal amination site (a12) to the cap site (c) is 40:60 to 80:20.

[0202] [3] According to the method for forming a cured electrodeposited coating according to [1] or [2] above, wherein the amination epoxy resin is the polar term δ constituting the Hansen solubility parameter. P The value is 10.0–12.0, and the hydrogen bond term δ h The resin has a strength of 8.5 to 10.0.

[0203] 4. The method for forming a cured electrodeposited coating according to any one of [1] to [3] above, wherein, The end-capped polyisocyanate curing agent comprises a polyisocyanate compound end-capped with an end-capping agent, wherein the end-capping agent comprises one or more selected from oxime compounds, pyrazole compounds, imidazole compounds, and triazole compounds. The uncured electrodeposited coating is heated at 120–170°C.

[0204] [5] The method for forming a cured electrodeposited coating according to any one of [1] to [4] above, wherein the cap compound (y) further comprises a monocarboxylic acid (y2) having 5 to 14 carbon atoms other than the aromatic compound (y1). The cap portion (c) further includes a second cap portion (c2) formed by opening the terminal epoxy ring using the monocarboxylic acid (y2).

[0205] [6] According to the curing electrodeposition coating method of [5] above, the equivalent ratio (E2:E3) of the equivalent of the phenolic hydroxyl group of the aromatic compound (y1) to the equivalent of the carboxylic acid (y2) of the epoxy ring of the raw epoxy resin is 40:60 to 99:1.

[0206] [7] The method for forming a cured electrodeposited coating according to any one of [1] to [6] above, wherein, The preparation of the cationic electrodeposition coating composition includes the following steps: The raw epoxy resin, the amine compound (x), and the cap compound (y) having functional groups other than amino groups capable of reacting with the epoxy ring are reacted to prepare the amination site (a) obtained by modifying the epoxy ring with the amine compound (x) and the cap site (c) obtained by modifying the terminal epoxy ring with the cap compound (y). The amination epoxy resin and the end-capped polyisocyanate curing agent are mixed to prepare a resin emulsion (i), and The resin emulsion (i) and the pigment dispersion paste (ii) containing the inorganic pigment are mixed.

[0207] Industrial availability According to the method for forming a cured electrodeposited coating disclosed herein, an electrodeposited coating of desired thickness can be formed even on various substrates with different resistances. Therefore, this method for forming a cured electrodeposited coating is applicable to electrodeposited coating of automobile bodies and automotive components.

Claims

1. A method for forming a cured electrodeposited coating, comprising: Preparation of cationic electrodeposition coating compositions, Electrodeposition coating is performed by impregnating the substrate in the cationic electrodeposition coating composition to form an uncured electrodeposition coating film. The uncured electrodeposited coating is heated to 120–220°C to form a cured electrodeposited coating on the substrate. The cationic electrodeposition coating composition comprises an amination epoxy resin, a terminated polyisocyanate curing agent, and inorganic pigments. The amination epoxy resin has the following characteristics: The amination site (a) and the modified epoxy ring of the raw epoxy resin by amine compound (x) are obtained. The cap portion (c) is obtained by modifying the terminal epoxy ring of the raw epoxy resin with a cap compound (y) having a functional group other than an amino group that can react with the epoxy ring. 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 capping compound (y) comprises an aromatic compound (y1) having one phenolic hydroxyl group as the functional group and four or more aromatic rings. The amination site (a) is formed by opening the epoxy ring using at least one of the primary and secondary amine groups. The cap portion (c) includes an aromatic cap portion (c1) formed by opening the terminal epoxy ring using the phenolic hydroxyl group.

2. The method for forming a cured electrodeposited coating according to claim 1, wherein, The amination site (a) has a terminal amination site (a12) formed by opening the terminal epoxy ring using the amine compound (x). The ratio (a12:c) of the terminal amination site (a12) to the cap site (c) is 40:60 to 80:

20.

3. The method for forming a cured electrodeposited coating according to claim 1 or 2, wherein, The amination epoxy resin is the polar term δ that constitutes the Hansen solubility parameter. P The value is 10.0–12.0, and the hydrogen bond term δ h The resin has a strength of 8.5 to 10.

0.

4. The method for forming a cured electrodeposited coating according to claim 1 or 2, wherein, The end-capped polyisocyanate curing agent comprises a polyisocyanate compound end-capped with an end-capping agent, wherein the end-capping agent comprises one or more selected from oxime compounds, pyrazole compounds, imidazole compounds, and triazole compounds. The uncured electrodeposited coating is heated at 120–170°C.

5. The method for forming a cured electrodeposited coating according to claim 1 or 2, wherein, The cap compound (y) also contains a monocarboxylic acid (y2) with 5 to 14 carbon atoms, other than the aromatic compound (y1). The cap portion (c) further includes a second cap portion (c2) formed by opening the terminal epoxy ring using the monocarboxylic acid (y2).

6. The method for forming a cured electrodeposited coating according to claim 5, wherein, The equivalent ratio (E2:E3) of the phenolic hydroxyl group of the aromatic compound (y1) relative to the epoxy ring of the raw material epoxy resin to the equivalent ratio (E3) of the carboxylic acid of the monocarboxylic acid (y2) is 40:60 to 99:

1.

7. The method for forming a cured electrodeposited coating according to claim 1 or 2, wherein, The preparation of the cationic electrodeposition coating composition includes the following steps: The raw epoxy resin, the amine compound (x), and the cap compound (y) having functional groups other than amino groups capable of reacting with the epoxy ring are reacted to prepare the amination site (a) obtained by modifying the epoxy ring with the amine compound (x) and the cap site (c) obtained by modifying the terminal epoxy ring with the cap compound (y). The amination epoxy resin and the end-capped polyisocyanate curing agent are mixed to prepare a resin emulsion (i), and The resin emulsion (i) and the pigment dispersion paste (ii) containing the inorganic pigment are mixed.

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