JPWO2020166657A1 - How to apply cationic electrodeposition paint - Google Patents

Abstract

A method for applying a cationic electrodeposition paint, which comprises a step of electrodepositing the cationic electrodeposition paint to form an uncrosslinked coating material, and drying and crosslinking the uncrosslinked coating material. A method for coating a cationic electrodeposition paint, wherein the temperature for drying and cross-linking is 10 ° C. or higher and 120 ° C. or lower, and the complex viscosity of the paint coating material measured by the following method is 1 Pa or more and 500 Pa or less. <Measuring method of complex viscosity> The uncrosslinked coating film obtained by electrodeposition coating with a cationic electrodeposition paint is scraped off with a spatula, and the complex viscosity is measured at temperature using a rotary rheometer.

Description

The present invention relates to a method for coating a cationic electrodeposition paint.

Conventionally, cationic electrodeposition paints have excellent coating workability and good corrosion resistance of the formed coating film, and are therefore widely used in automobile parts, electrical equipment parts, and other industrial equipment that require these performances. Has been done.

Generally, a cationic electrodeposition coating composition is made by mixing a resin component composed of a cationic resin (for example, an amino group-containing epoxy resin) and a curing agent (also referred to as a cross-linking agent, for example, a blocked polyisocyanate compound) to be aqueous. It is provided in the form of a mixture of two components, a component of a resin emulsion dispersed in a medium and a component of a pigment-dispersed paste containing a pigment dispersed in a pigment-dispersed resin. This coating composition is used in a coating bath, the object to be coated is used as a cathode and the counter electrode is used as an anode to form a precipitated coating film on the object to be coated, and then the precipitated coating film is heated to carry out cross-linking curing. The coated film is formed.

The heating at the time of forming the coating film is usually performed at a temperature higher than 160 ° C., but in order to reduce energy costs, a low temperature (10 to 120 ° C., preferably 10 to 100 ° C., more preferably 10 to 80 ° C.) It has been required to carry out at ° C., particularly preferably 10 to 60 ° C.). This is called cold baking.

In order to perform the above low temperature baking (or curing at room temperature drying), it is common to use a low temperature curable blocked polyisocyanate compound as a curing agent. For example, Patent Document 1 discloses low-temperature curing using a cationic electrodeposition coating material containing an isocyanate blocked with an oxime. Further, Patent Document 2 discloses a low-temperature baking type electrodeposition coating material at 100 to 160 ° C., which states that a blocked polyisocyanate compound blocked by an oxime or lactam can be dissociated (reacted) at a relatively low temperature. There is a description. Further, Patent Document 3 discloses that it can be cured at a low temperature of 120 ° C. or lower by using a self-crosslinked resin having a specific blocked isocyanate group, and can also be used as a cationic electrodeposition coating material.
However, the electrodeposition coating composition having increased reactivity at low temperature has insufficient long-term storage stability (bath stability), and as a result, the finishability and corrosion resistance of the coating film may be inferior.

Further, Patent Document 4 is obtained by electrodeposition coating of a substrate resin (amine-added epoxy resin) and then electrodeposition coating of an aqueous dispersion of a blocked polyisocyanate curing agent imparted with water dispersibility. A method for forming a coating film by low-temperature baking in which a coating film is heated and dried at 60 to 150 ° C. is disclosed.
However, although the storage stability (bath stability) of the paint is improved by separating the paint and coating of the base resin and the coating and coating of the curing agent, the curing agent may not be uniformly present in the coating film. Therefore, the anticorrosion property may be inferior. In addition, since the number of processes such as painting process and cleaning process increases, existing equipment cannot handle it, and it is necessary to add new equipment.

Japanese Unexamined Patent Publication No. 10-120947 Japanese Unexamined Patent Publication No. 7-300698 Japanese Unexamined Patent Publication No. 4-39322 Japanese Unexamined Patent Publication No. 2004-27255

An object to be solved by the present invention is to provide a coating method for a cationic electrodeposition coating composition having excellent storage stability, low temperature curability of a coating film, corrosion resistance and finish (horizontal skin and vertical skin). is there.

As a result of diligent studies to solve the above problems, the inventors have conducted a drying and cross-linking step at a temperature of 10 to 120 ° C., which is a method for coating a cationic electrodeposition coating material, in which the complex viscosity of the coating material is 1 to 1. We have found that a solution to the above problems can be achieved by a coating method within the range of 500 Pa, and have completed the present invention.

That is, the present invention provides the following method for coating a cationic electrodeposition paint.

Item 1 A method for applying a cationic electrodeposition coating material, which comprises a step of electrodepositing the cationic electrodeposition coating material to form an uncrosslinked coating material, and drying and crosslinking the uncrosslinked coating material. This is a method for applying a cationic electrodeposition coating material in which the temperature at which the coating film is dried and crosslinked is 10 ° C. or higher and 120 ° C. or lower, and the complex viscosity of the coating paint measured by the following method is 1 Pa or more and 500 Pa or less.
<Measurement method of complex viscosity>
The uncrosslinked coating obtained by electrodepositing the cationic electrodeposition coating material is scraped off with a spatula, and the complex viscosity is measured at a temperature at which the uncrosslinked coating material is dried and crosslinked using a rotary rheometer.

Item 2 In the method for coating a cationic electrodeposition coating material according to Item 1, the cationic electrodeposition coating material contains a resin (A) containing an amino group-containing epoxy resin (A-2), and the cationic electrodeposition coating material contains an amino. It is preferable that the group-containing epoxy resin (A-2) is contained in an amount of 20% by mass or more and 80% by mass or less per resin solid content, and the number average molecular weight of the amino group-containing epoxy resin (A-2) is 800 or more.

Item 3 In the method for coating a cationic electrodeposition coating material according to Item 2, the cationic electrodeposition coating material preferably further contains another compound (B) in an amount of 5% by mass or more and 80% by mass or less per resin solid content.

Item 4 In the method for coating a cationic electrodeposition coating material according to Item 3, the other compound (B) preferably contains a compound (B-1) having a reactive functional group.

Item 5. In the method for applying a cationic electrodeposition coating material according to Item 5, Item 3 or 4, the weight average molecular weight of the other compound (B) is preferably less than 1000.

Item 6 In the method for coating a cationic electrodeposition coating material according to any one of Items 3 to 5, the weight average molecular weight of the other compound (B) is preferably 100 or more.

Item 7 In the method for coating a cationic electrodeposition coating material according to any one of Items 3 to 6, the resin (A) component and the other compound (B) component are present as separate aqueous dispersions in the cationic electrodeposition coating material. Is preferable.

Item 8 In the method for coating a cationic electrodeposition coating material according to any one of Items 1 to 7, the cross-linking reaction of the cationic electrodeposition coating material is selected from a Michael addition reaction, a reaction between an epoxy group and a thiol group, and an anionic polymerization reaction. It is preferably at least one kind.

Item 9. In the method for coating a cationic electrodeposition coating material according to any one of Items 1 to 8, it is preferable that the cationic electrodeposition coating material further contains a reaction catalyst (C).

Item 10. In the method for coating a cationic electrodeposition coating material according to Item 9, the reaction catalyst (C) is preferably a microencapsulation catalyst (C-1).

Item 11 In the method for coating a cationic electrodeposition coating material according to Item 3, the resin (A) and the other compound (B) are present as separate aqueous dispersions in the cationic electrodeposition coating material, and the resin (A) and other compounds (A) are present. The compound (B) contains a Michael addition reaction acceptor component and a Michael addition reaction donor component, or a Michael addition reaction donor component and a Michael addition reaction acceptor component, respectively, and the cross-linking reaction of the cationic electrodeposition coating material is carried out by Michael. It is preferable to include an addition reaction.

Item 12 In the method for coating a cationic electrodeposition paint according to Item 11, the cationic electrodeposition paint is used as an electrodeposition paint bath, a metal object to be coated is immersed in the electrodeposition paint bath, electrodeposition coating is performed, and then the second step is performed. It is preferable that the cationic electrodeposition coating material of No. 1 is electrodeposited and then heat-cured at a temperature higher than 120 ° C.

Item 13. In the method for coating a cationic electrodeposition paint according to any one of Items 1 to 10, the cationic electrodeposition paint is used as an electrodeposition paint bath, and a metal object to be coated is immersed in the electrodeposition paint bath to perform electrodeposition coating. Is preferable.

Item 14. In the method for coating a cationic electrodeposition paint according to any one of Items 1 to 10, the cationic electrodeposition paint is used as an electrodeposition paint bath, and a metal object to be coated is immersed in the electrodeposition paint bath, and after electrodeposition coating, It is preferable to dry and crosslink by electromagnetic induction heating.

Item 15 In the method for coating a cationic electrodeposition paint according to Item 13, after electrodeposition coating of the cationic electrodeposition paint, a second cationic electrodeposition paint is further electrodeposited and then heated at a temperature higher than 120 ° C. It is preferable to cure it.

Item 16 In the method for coating a cationic electrodeposition paint according to Item 13, after electrodeposition coating of a cationic electrodeposition paint, a second cationic electrodeposition paint is electrodeposited without preheating, and then from 120 ° C. It is preferable to heat-cure at a high temperature.

The coating method of the cationic electrodeposition coating material of the present invention ensures good coating stability (bath stability), and even if it is cured at room temperature or low temperature, the obtained coating film has low temperature curability, corrosion resistance and corrosion resistance. Excellent finish (horizontal skin and vertical skin).

In the present invention, the "aqueous solvent" is a solvent containing water and / or a hydrophilic solvent as a main component, and specific examples of the hydrophilic solvent include ethylene glycol and ethylene glycol monoalkyl ether. (For example, methyl ether, ethyl ether, butyl ether, etc.), diethylene glycol, diethylene glycol monoalkyl ether (for example, methyl ether, ethyl ether, butyl ether, etc.), glyme-based solvent (for example, ethylene glycol dimethyl ether, etc.), diglime-based solvent (for example, diethylene glycol dimethyl ether, etc.) , Alcohol-based solvents (eg methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, etc.), bropyrene glycol, propylene glycol monoalkyl ether (eg, methyl ether, ethyl ether, butyl ether, etc.), dipropylene glycol, dipropylene glycol Examples thereof include monoalkyl ethers (for example, methyl ether, ethyl ether, butyl ether, etc.), and these can be used alone or in combination of two or more.
In the present invention, the "compound" is a general term including a monomer, an oligomer, a polymer (resin) and the like.
In the present invention, "crosslinking" is a reaction for forming a bridging structure between compounds or within a compound by a chemical reaction, and for example, a condensation reaction, an addition reaction, a polymerization reaction, a polyaddition reaction, an ester exchange reaction, or the like itself. Known ones can be used without particular limitation.
Hereinafter, the present invention will be described in detail.

The coating method of the present invention is a coating method in which a metal object to be coated is immersed in a cationic electrodeposition coating bath and then cationic electrodeposition coating is performed, and then a drying and crosslinking step is performed at a temperature of 10 ° C. or higher and 120 ° C. or lower. It is a painting method.

From the viewpoint of energy cost reduction, the drying and cross-linking temperatures are usually 120 ° C. or lower, preferably 100 ° C. or lower, and more preferably 80 ° C. or lower. Further, from the viewpoint of dryness and curability, it is usually 10 ° C. or higher, preferably 20 ° C. or higher, and more preferably 40 ° C. or higher.
The steps of drying and cross-linking may proceed at the same time, but it is common that cross-linking occurs as the drying (evaporation of the aqueous solvent) progresses to some extent. Further, the cross-linking of the present invention includes partial cross-linking and full cross-linking.
It is preferable that the "complex viscosity" of the coated coating film before the cross-linking reaction occurs is in the range of 1 Pa or more and 500 Pa or less.

The complex viscosity is usually 1 Pa or more, preferably 5 Pa or more, and more preferably 10 Pa or more, from the viewpoint of sagging resistance (finishing property of the object to be coated on vertical skin). Further, from the viewpoint of horizontal finish, it is usually 500 Pa or less, preferably 200 Pa or less, and more preferably 100 Pa or less.
As a method for measuring the complex viscosity, the following method can be used.
In the present invention, the coating paint is an undried and uncrosslinked coating film after electrodeposition coating and washing with water and before the drying and cross-linking steps, and the following measurement is performed 1 minute after washing with water. It is a measured value of.

<Measurement method of complex viscosity>
The uncrosslinked coating film that had been cationically electrodeposited and washed with water was scraped off with a spatula, and the complex viscosity was measured at the temperature at which drying and crosslinking were performed using a rotary rheometer (RS150 manufactured by HAAKE).
When the complex viscosity falls within the above range, it is possible to balance the finish property (sagging property) of the vertical surface and the finish property (smoothness) of the horizontal surface even in the coating method of low temperature cross-linking.

Examples of the object to be coated by the coating method of the present invention include automobile bodies, two-wheeled vehicle parts, household appliances, and other devices, and there are no particular restrictions as long as the object to be coated contains metal.

Metallic steel sheets as objects to be coated include cold-rolled steel sheets, alloyed hot-dip galvanized steel sheets, electrogalvanized steel sheets, electrozinc-iron double-layer plated steel sheets, organic composite plated steel sheets, Al materials, Mg materials, and these metals. Examples thereof include those in which the surface of the plate is cleaned by alkali degreasing or the like as necessary, and then surface treatment such as phosphate chemical conversion treatment, chromate treatment, or composite oxide treatment is performed.

As a cationic electrodeposition coating method, generally, the electrodeposition coating material is deionized water or the like to have a solid content concentration of about 5% by mass or more and 40% by mass or less, preferably 10% by mass or more and 25% by mass or less, and further. Using a cationic electrodeposition paint whose pH is adjusted to 4.0 or more and 9.0 or less, preferably 5.5 or more and 7.0 or less, as a bath, the bath temperature is usually adjusted to 15 ° C or more and 35 ° C or less, and a load is applied. This is performed by energizing the object to be coated as a cathode under the conditions of a voltage of 100 V or more and 400 V or less, preferably 150 V or more and 350 V or less.

The film thickness of the coating film is not particularly limited, but generally, it can be in the range of 5 μm or more and 40 μm or less, preferably 10 μm or more and 30 μm or less based on the dry coating film.

Further, in the present invention, electromagnetic induction heating can be used as the heating / drying equipment from the viewpoint of energy cost reduction and process time reduction.
When electromagnetic induction heating is used, the temperature of the coated surface is the same as above (usually 10 ° C or higher and 120 ° C or lower, preferably 10 ° C or higher and 100 ° C or lower, more preferably 10 ° C or higher and 80 ° C or lower, particularly preferably 10). The temperature is usually 1 minute or more and 15 minutes or less, preferably 1 minute or more and 12 minutes or less, and more preferably 1 minute or more and 9 minutes or less.

Cationic electrodeposition coating The cationic electrodeposition coating material used in the coating method of the present invention preferably contains a resin (A). As the resin (A), for example, a resin such as an acrylic resin having a cationic functional group, an epoxy resin, a polyester resin, a urethane resin, or a phenol resin can be preferably contained, and one of these can be used alone or 2 The seeds and above can be used in combination, and among them, the epoxy resin (A-1) is preferable from the viewpoint of corrosion resistance.

Further, the resin (A-1) preferably has a cationic functional group, and as the cationic functional group, any cationic one can be preferably used. Among them, an amino group, a quaternary ammonium base, a sulfonium group and the like are preferable, and an amino group is more preferable.
The epoxy resin (A-1) is preferably an amino group-containing epoxy resin (A-2), and the content of the amino group-containing epoxy resin (A-2) in the paint is 20% by mass or more per resin solid content. It is preferably contained in an amount of 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less.

Further, it is preferable that the cationic electrodeposition coating material contains a compound (B) other than the resin (A), and the content in the coating material is 5% by mass or more and 80% by mass or less per resin solid content. Is preferable, and it is more preferable to contain 10% by mass or more and 49% by mass or less.

The other compound (B) can be crosslinked with the resin (A) at a temperature of 10 ° C. or higher and 120 ° C. or lower to obtain a crosslinked coating film. The cross-linking reaction is at least one selected from a urethanization reaction, a Michael addition reaction, a reaction between an epoxy group and a thiol group, and an anion polymerization reaction, and more preferably, a urethanization reaction, a Michael addition reaction, and / or. It is a reaction between an epoxy group and a thiol group, more preferably a urethanization reaction and / or a Michael addition reaction, and particularly preferably a Michael addition reaction.
In the urethanization reaction, the Michael addition reaction, and the reaction between the epoxy and the thiol, the combination shown in Table 1 below is preferable as the combination of the resin (A) and the other compound (B).

In Table 1, the active hydrogen group is described below with reference to (Note 1), (Note 2) and (Note 3) in Table 1.
(Note 1) Active hydrogen group: At least one reactive functional group selected from the group consisting of a primary amino group, a secondary amino group, and a hydroxyl group (Note 2) Active hydrogen group (donor component): Primary amino group At least one active hydrogen group selected from the group consisting of a secondary amino group, a hydroxyl group, an active methylene group, and a thiol group (mercapto group) (Note 3) α, β-unsaturated carbonyl group (acceptor component) :( At least one α selected from the group consisting of a (meth) acryloyloxy group, a (meth) acrylamide group, an unsaturated carbonyl group of a maleic acid compound, an unsaturated carbonyl group of a fumaric acid compound, and an unsaturated carbonyl group of an itaconic acid compound. , Β-unsaturated carbonyl group

Further, as a catalyst for the cross-linking reaction, it is preferable to contain the reaction catalyst (C) in the electrodeposition coating material.

Epoxy resin (A-1)
The epoxy resin (A-1) is a resin having at least one epoxy group, preferably two or more epoxy groups in one molecule, and has a molecular weight of at least 300, preferably 400 to 4,000, and more preferably 800. Those having a number average molecular weight in the range of ~ 2,500 and an epoxy equivalent in the range of at least 160, preferably 180 to 2,500, more preferably 400 to 1,500 are suitable. As such an epoxy resin, for example, one obtained by reacting a polyphenol compound with epichlorohydrin (for example, epichlorohydrin or the like) can be used.

Examples of the polyphenol compound include bis (4-hydroxyphenyl) -2,2-propane [bisphenol A], bis (4-hydroxyphenyl) methane [bisphenol F], and bis (4-hydroxycyclohexyl) methane [hydrogenated]. Bisphenol F], 2,2-bis (4-hydroxycyclohexyl) propane [hydrogenated bisphenol A], 4,4'-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxy) Phenyl) -1,1-isobutane, bis (4-hydroxy-3-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, tetra (4-hydroxyphenyl) -1,1 , 2,2-Ethan, 4,4'-dihydroxydiphenylsulfone, phenol novolac, cresol novolac and the like.
Further, as the epoxy resin obtained by the reaction of the polyphenol compound and epihalohydrin, the resin of the following formula (1) derived from bisphenol A is particularly preferable.

Here, those represented by n = 0 to 8 are preferable.

Examples of commercially available products of such epoxy resins include those sold by Mitsubishi Chemical Corporation under the trade names jER828EL, jER1002, jER1004, and jER1007.

Further, as the epoxy resin (A-1), an epoxy resin containing a polyalkylene oxide chain in the resin skeleton can be used. Usually, such an epoxy resin is a method of introducing a polyalkylene oxide chain by reacting an epoxy resin having at least one (α) epoxy group, preferably two or more, with an alkylene oxide or a polyalkylene oxide (β). ) It can be obtained by a method of introducing a polyalkylene oxide chain by reacting the above polyphenol compound with a polyalkylene oxide having at least one epoxy group, preferably two or more epoxy groups. Further, an epoxy resin already containing a polyalkylene oxide chain may be used (see, for example, Japanese Patent Application Laid-Open No. 8-337750).
As the alkylene group in the polyalkylene oxide chain, an alkylene group having 2 to 8 carbon atoms is preferable, an ethylene group, a propylene group or a butylene group is more preferable, and a propylene group is particularly preferable.

Further, as the epoxy resin (A-1) other than the above-mentioned bisphenol type epoxy resin, t-butylcatechol type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin can also be preferably used, and one of these can be used. It can be used alone or in combination of two or more. Examples of commercially available novolak type epoxy resins include phenol novolac resin DEN-438 manufactured by Dow Chemical Japan Co., Ltd. and cresol novolak resin YDCN-703 manufactured by Toto Kasei Co., Ltd.

Amino group-containing epoxy resin (A-2)
The amino group-containing epoxy resin (A-2) can be obtained, for example, by adding an amino group to the epoxy resin (A-1).
Examples of the compound in which an amino group is added to the epoxy resin (A-1) include (1) an epoxy resin and a primary mono- and polyamine, a secondary mono-and a polyamine, or a primary and secondary mixed polyamine. (See, eg, US Pat. No. 3,984,299); (2) Additives of an epoxy resin with a secondary mono- and polyamine having a ketiminated primary amino group (eg,). , US Pat. No. 4,017,438); (3) Reactant obtained by etherification of an epoxy resin and a ketiminated hydroxy compound having a primary amino group (for example, JP-A-59). -Refer to JP-A-43013) and the like. When one amino group (primary or secondary) reacts with one epoxy group, the amino group-containing epoxy resin (A-2) contains one hydroxyl group from the epoxy group. Become. Further, even when a hydroxyl group-containing primary or secondary amino group-containing compound is reacted, the amino group-containing epoxy resin (A-2) can contain a hydroxyl group other than that derived from the epoxy group.

Examples of the primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines used in the production of the amino group-containing epoxy resin of (1) above include monomethylamine and dimethylamine. Mono- or di-alkylamines such as monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono (2-hydroxypropyl) amine, monomethylaminoethanol; Examples thereof include alkylene polyamines such as ethylene diamine, propylene diamine, butylene diamine, hexamethylene diamine, diethylene triamine and triethylene tetramine.

Examples of the secondary mono- and polyamine having a ketiminated primary amino group used in the production of the amino group-containing epoxy resin of the above (2) include the production of the amine-added epoxy resin of the above (1). Among the primary and secondary mixed polyamines used in the above, for example, a ketiminated product produced by reacting a ketone compound with diethylenetriamine or the like can be mentioned.

The hydroxy compound having a ketiminated primary amino group used in the production of the amino group-containing epoxy resin of the above (3) is, for example, used in the production of the amino group-containing epoxy resin of the above (1). Among primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines, compounds having a primary amino group and a hydroxyl group, for example, monoethanolamine, mono (2-hydroxypropyl). ) A hydroxyl group-containing ketiminated product obtained by reacting a ketone compound with an amine or the like can be mentioned.

Further, as a method for incorporating the various reactive functional groups in Table 1 into the epoxy resin (A-1), for example, the following method can be considered.
(1A) Regarding the active hydrogen group [primary amino group, secondary amino group, hydroxyl group], the primary amino group and the secondary amino are added to the amino group-containing epoxy resin (A-2) by the method of adding the amino group described above. It can contain groups and / or hydroxyl groups. Further, the hydroxyl group can be contained by reacting the compound having a hydroxyl group and a carboxyl group with the epoxy resin (A-1).

(2A) Regarding the active hydrogen group [primary amino group, secondary amino group, hydroxyl group, active methylene group, thiol group], the primary amino group, secondary amino group and hydroxyl group are as described above. Regarding the active methylene group, for example, an active methylene group-containing compound such as malonic acid, alkyl malonate, acetoacetic acid, isobutyryl acetic acid, benzoyl acetic acid, and propionyl acetic acid is reacted with the epoxy group of the epoxy resin to contain the active methylene group. Can be urged. Regarding the thiol group (mercapto group), for example, a thiol group-containing compound such as thioglycolic acid, thioapple acid, thiosalicylic acid, dithiosalicylic acid, mercaptopropionic acid, or 3-mercaptobutyric acid is reacted with the epoxy group of the epoxy resin. This makes it possible to contain a thiol group (mercapto group). One of these (2A) active hydrogen groups can be used alone or in combination of two or more.

(3A) α, β-unsaturated carbonyl group [(meth) acryloyloxy group, (meth) acrylamide group, unsaturated carbonyl group of maleic acid compound, unsaturated carbonyl group of fumaric acid compound, unsaturated carbonyl of itaconic acid compound Regarding [groups], for example, (1) the active hydrogen group of the epoxy resin was reacted with isocyanatoethyl (meth) acrylate, and (2) the epoxy group of the epoxy resin was (meth). Examples thereof include those obtained by reacting an acrylic acid compound, a maleic acid compound, a fumaric acid compound, an itaconic acid compound, etc., and these (3A) α, β-unsaturated carbonyl groups may be used alone or in combination of two or more. Can be used in combination.

With respect to the epoxy groups (4A) and (5A), the epoxy group of the epoxy resin can be preferably used.

The addition reaction of the amine compounds (1A) to (5A) to the epoxy resin (A-1) is usually carried out in a suitable solvent at about 80 to about 170 ° C., preferably about 90 to about 150. It can be carried out at a temperature of ° C. for about 1 to 6 hours, preferably about 1 to 5 hours.

Examples of the reaction solvent include hydrocarbons such as toluene, xylene, cyclohexane and n-hexane; ester compounds such as methyl acetate, ethyl acetate and butyl acetate; ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl amyl ketone. Amid-based compounds such as dimethylformamide and dimethylacetamide; alcohol-based compounds such as methanol, ethanol, n-propanol and iso-propanol, ether alcohol-based compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; or mixtures thereof. Be done.

The number average molecular weight of the amino group-containing epoxy resin (A-2) is preferably 800 or more, more preferably in the range of 1,000 to 50,000, and further preferably in the range of 1,000 to 50,000, from the viewpoint of finishability, corrosion resistance, and the like. Is in the range of 1,200 to 10,000.

The amine value of the amino group-containing epoxy resin (A-2) is usually 10 mgKOH / g or more, preferably in the range of 20 to 200 mgKOH / g, preferably in the range of 30 to 180 mgKOH / g, based on the resin solid content. Is more preferable.
The amine value in the present specification is measured according to JIS K 7237-1995. All are amine values (mgKOH / g) per resin solid content.

Further, in the present specification, the number average molecular weight and the weight average molecular weight are the holding times (holding capacity) measured by using a gel permeation chromatograph (GPC), and the holding time of standard polystyrene having a known molecular weight measured under the same conditions. It is a value obtained by converting to the molecular weight of polystyrene by (retention capacity). Specifically, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and "TSKgel G-4000HXL", "TSKgel G-3000HXL", and "TSKgel G-2500HXL" are used as columns. "And" TSKgel G-2000HXL "(trade name, both manufactured by Tosoh Corporation) can be used for measurement under the conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow velocity 1 mL / min and detector RI. it can.

The method for dispersing the amino group-containing epoxy resin (A-2) thus obtained in an aqueous solvent is not particularly limited, and a method known per se can be used, but the amino group-containing epoxy resin solution. Is preferably neutralized with an acid compound and dispersed.

As the acid compound, known acid compounds can be used without particular limitation, and specifically, for example, inorganic acids such as hydrochloric acid, nitrate, phosphoric acid and sulfamic acid; formic acid, acetic acid, propionic acid, lactic acid and the like. Examples thereof include organic acids containing carboxylic acid compounds. One of these acid compounds can be used alone or in combination of two or more, and among them, an organic acid is preferable, and a carboxylic acid compound is more preferably used.

An emulsifier can also be used as another dispersion method. The emulsifier can be used without particular limitation, and examples thereof include nonionic, cationic and anionic emulsifiers, and these can be used alone or in combination of two or more. Of these, nonionic and / or cationic emulsifiers are preferable, and cationic emulsifiers are more preferable.

Other compounds (B)
The other compound (B) preferably contains a compound (B-1) having a reactive functional group that undergoes a cross-linking reaction with the functional group of the resin (A).
As the reactive functional group of the compound (B-1) having a reactive functional group, the functional groups (1B) to (5B) shown in Table 1 can be preferably used, and the compound (B-1) can be used as the compound (B-1). For example, the following compounds may be mentioned.

(1B) Examples of the compound having a blocked polyisocyanate group include a blocked polyisocyanate compound, and the blocked polyisocyanate compound is an addition reaction product of the polyisocyanate compound and an isocyanate blocking agent in an almost chemically theoretical amount. is there. As the polyisocyanate compound used in the blocked polyisocyanate compound, known ones can be used, for example, tolylene diisocyanate, xylylene diisocyanate, phenylenedi isocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2. , 4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI [polymethylenepolyphenylisocyanate], bis (isocyanatemethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate and other aromatics An aliphatic or alicyclic polyisocyanate compound; a cyclized polymer or billet of these polyisocyanate compounds; or a combination thereof can be mentioned.

In particular, aromatic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylenediisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, and crude MDI (preferably crude MDI and the like) are anticorrosive. More preferable from the viewpoint of sex.

On the other hand, the isocyanate blocking agent is added to the isocyanate group of the polyisocyanate compound to block it, and the blocked polyisocyanate compound produced by the addition evaporates the solvent after coating and further lowers the coating temperature to the blocked poly. When the dissociation temperature of the isocyanate compound is reached, it is desirable that the blocking agent dissociates and regenerates the isocyanate group.

Among them, at least one of the isocyanate blocking agents is selected from pyrazole compounds, active methylene compounds, oxime compounds, phenol compounds, lactam compounds, and alcohol compounds from the viewpoint of low temperature curability (dissociation temperature). Is preferable, pyrazole-based compounds and / or active methylene-based compounds are more preferable, and pyrazole-based compounds are particularly preferable. As the pyrazole-based compound, 3,5-dimethylpyrazole and / or 3-methylpyrazole is preferable, and 3,5-dimethylpyrazole is more preferable.

(2B) Examples of the compound having an α, β-unsaturated carbonyl group (acceptor component) include (meth) acryloyloxy group-containing compound, (meth) acrylamide group-containing compound, maleic acid-based compound, fumaric acid-based compound, and itaconic acid. It is a compound having at least one α, β-unsaturated carbonyl group selected from the group consisting of system compounds.

The compound having an α, β-unsaturated carbonyl group is particularly limited as long as it contains one or more (preferably a plurality) acceptor components (α, β-unsaturated carbonyl group) in one molecule. However, the above (meth) acryloyloxy group-containing compounds include ethylene glycol diacrylate, propylene glycol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, and tetraethylene glycol di. Acrylate, tetrapropylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, bisphenol A diglycidyl ether diacrylate, resorcinol diglycidyl ether diacrylate, 1,3-propanediol diacrylate, 1,4-Butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, cyclohexanedimethanol diacrylate, ethoxylated neopentyl glycol diacrylate, propoxylated neo Diacrylates such as pentyl glycol diacrylate, ethoxylated cyclohexanedimethanol diacrylate, propoxylated cyclohexanedimethanol diacrylate, acrylicized epoxy diacrylate, allyl urethane diacrylate, aliphatic urethane diacrylate, polyester diacrylate; trimethyl propantri. Acrylate, glycerol triacrylate, ethoxylated trimethylolpropan triacrylate, propoxylated trimethylol propantriacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate , Allyl urethane triacrylate, aliphatic urethane triacrylate, melamine triacrylate, aliphatic epoxy triacrylate, epoxy novolac triacrylate, polyester triacrylate and other triacrylates; di-trimethylol propanetetraacrylate, pentaerythritol tetraacrylate, ethoxylated. pen Taerititol tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, ethoxylated dipentaerytitol tetraacrylate, propoxylated dipentaerytitol tetraacrylate, allyl urethane tetraacrylate, aliphatic urethane tetraacrylate, melamine tetraacrylate, epoxy Tetraacrylates such as novolak tetraacrylate; pentaacrylates such as dipentaerytritor pentaacrylate and melamine pentaacrylate can be mentioned, and these can be used alone or in combination of two or more.

As the compound having an α, β-unsaturated carbonyl group, a compound having a resin skeleton can also be preferably used. As a production method, for example, a polyester resin, an acrylic resin, an epoxy resin or the like is synthesized, and (1) a glycidyl (meth) acrylate is reacted with a carboxyl group of the resin, and (2) a hydroxyl group of the resin is reacted. Those obtained by reacting isocyanatoethyl (meth) acrylate, (3) reacting the epoxy group of the resin with (meth) acrylic acid compound, maleic acid compound, fumaric acid compound, itaconic acid compound, etc. Can be mentioned.

In addition, polyvalent carboxylic acids including (anhydrous) maleic acid, fumaric acid, itaconic acid, etc., ethylene glycol, diethylene glycol, propylene glycol, tetramethylene glycol, 1,6-hexanediol, neopentyl glycol, trimethylpropane, glycerin , Polyamide resin obtained by polycondensation reaction with polyhydric alcohol such as pentaerythritol, and polyamide resin obtained by polycondensation reaction using polyhydric amine instead of polyhydric alcohol can also be preferably used. Other examples include, for example, a urethane compound obtained by reacting a polyfunctional polyisocyanate compound with a compound having a hydroxyl group and an acryloyl group (for example, 2-hydroxyethyl acrylate, 4-hydroxybutyl methacrylate, etc.).

(3B) The compound having an active hydrogen group (donor component) is composed of a primary amino group-containing compound, a secondary amino group-containing compound, a hydroxyl group-containing compound, an active methylene group-containing compound, and a thiol group (mercapto group) -containing compound. It is at least one active hydrogen group-containing compound selected from the group. Among them, as the active hydrogen group, an active methylene group-containing compound and / or a primary and / or a secondary amino group-containing compound are preferable.

The active hydrogen group-containing compound is not particularly limited as long as it contains one or more (preferably a plurality) of active hydrogen groups in one molecule, and is, for example, methyl acetoacetate, ethyl acetoacetate, t. -Butyl acetoacetate, 2-ethylhexyl acetoacetate, lauryl acetoacetate, acetoacetanide, 2-acetoacetoxyethyl methacrylate, allyl acetoacetate, butanediol diacetacetate, 1,6-hexanedioldi Acetoacetate, neopentyl glycol diacetacetate, cyclohexanedimethanol diacetacetate, ethoxylated bisphenol A diacetacetate, trimethylpropantriacetacetate, glycinetriacetacetate, polycaprolactone triacetate, Active methylene group-containing compounds such as pentaerythritol tetraacetoacetate; primary and / or secondary amino groups such as ethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tripropylenetetramine, tetraethylenepentamine, tetrapropylenepentamine. Compounds: Pentaerythritol tetrakis (3-mercaptopropionate), trimethylpropanthris (3-mercaptopropionate), tris-[(3-mercaptopropionyloxy) -ethyl] -isocyanurate, tetraethylene glycol bis ( Thiol groups (mercapto) such as 3-mercaptopropionate), dipentaerythritol hexakis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate), trimethylolpropanthris (3-mercaptobutyrate) Group) -containing compounds; hydroxyl group-containing compounds such as alkanediol, poly (oxyalkylene) glycol, glycerol, diglycerol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, or reactants thereof. These can be used alone or in combination of two or more.

As the active hydrogen group-containing compound, a compound having a resin skeleton can also be preferably used. Specifically, for example, the following (Example 1) to (Example 5) can be mentioned.

(Example 1) An acrylic resin obtained by copolymerizing an active hydrogen group-containing acrylic monomer with another acrylic monomer.
Examples of the active hydrogen group-containing acrylic monomer include 2-ethoxymalonyloxyethyl (meth) acrylate, 2-acetoacetoxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, and N- (2-cyanoacetoxy). Ethyl) acrylamide, N- (2-propionylacetoxybutyl) acrylamide, N- (4-acetoacetoxymethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide, 2- (N-acetoacetylaminoethyl) ( Meta) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, N-hydroxymethyl (meth) acrylamide, molecule Examples thereof include (meth) acrylate having a polyoxyalkylene chain having a hydroxyl group at the end.

(Example 2) A polyester resin obtained by polycondensing a dicarboxylic acid compound containing malonic acid and a diol compound.

(Example 3) An epoxy resin obtained by addition-condensing a dicarboxylic acid compound containing malonic acid and a diglycidyl compound.

(Example 4) A polyamide resin obtained by polycondensing a dicarboxylic acid compound containing malonic acid and a diamine compound.

(Example 5) A modified resin obtained by adding an active hydrogen group-containing compound to a resin (for example, acrylic resin, epoxy resin, polyester resin, urethane resin, phenol resin, etc.). Among them, as the type of resin, an active hydrogen group-modified epoxy resin and / or an active hydrogen group-modified acrylic resin is preferable, and an active hydrogen group-modified epoxy resin is more preferable. Here, the active hydrogen group-modified resin means a resin containing an active hydrogen group.

In order to distinguish it from the amino group-containing epoxy resin (A-2), the epoxy resin having an amino group is excluded from the active hydrogen group-containing compound of the other compound (B).

(4B) As the compound having a thiol group, as long as it is a compound containing a thiol group (mercapto group), a compound known per se can be preferably used without particular limitation. Commercially available products include, for example, pentaerythritol tetrakis (3-mercaptopropionate) [trade name "Adeka Hardener EH317", manufactured by Adeka Corporation], pentaerythritol tetrakis (3-mercaptobutyrate), [trade name "Karenzu". MT PEI ", Showa Denko Corporation], 1,4-bis (3-mercaptobutyryloxy) butane, [Product name" Karenz MT BDI ", Showa Denko Corporation], 1,3,5- Tris (3-mercaptobutyryloxyethyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trion, [Product name "Karensu MT NRI", manufactured by Showa Denko KK] , Polyether polythiol, [trade name "jER Cure QX11", manufactured by Mitsubishi Chemical Corporation], etc., and these can be used alone or in combination of two or more.

Further, it may be obtained by adding a thiol-containing compound to a resin, and may be obtained by adding a thiol-containing compound such as thioglycolic acid, thioapple acid, thiosalicylic acid, dithiosalicylic acid, mercaptopropionic acid, or 3-mercaptobutyric acid. A thiol group-containing resin obtained by reacting with an epoxy resin can be preferably used.

(5B) As the compound having a tertiary amino group, a compound known per se can be used without particular limitation, and specific examples thereof include a tertiary amino group-containing compound, an aminophenol compound, and an imidazole compound. Be done. Examples of the aminophenol compound are phenol compounds having an amino group, and examples thereof include 2-aminophenol, 4-aminophenol, dimethylaminophenol, dimethylaminomethylphenol, and 2,4,6-trisdimethylaminomethylphenol. Be done. Examples of the imidazole compound include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole and 1-benzyl. Examples thereof include -2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-phenylimidazole.

Further, various resins may have a tertiary amino group. For example, a method of reacting a secondary amino group with the above-mentioned epoxy resin, or a tertiary amino group-containing polymerization as a copolymerization monomer as a raw material of an acrylic resin. Examples thereof include a method using a sex unsaturated monomer (N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, etc.).

The weight average molecular weight of the other compound (B) is preferably less than 1,000, more preferably 100 or more and less than 1,000, and further preferably 200 or more and less than 1,000. ..

Examples of the method for dispersing the other compound (B) in an aqueous solvent include a method for emulsifying the other compound (B) alone. Examples of the method of emulsifying alone include a method of adding a hydrophilic functional group and emulsifying, a method of emulsifying using an emulsifier, and a method of emulsifying by mixing with a hydrophilic resin or the like. From the viewpoint of storability, it is preferable that the resin (A) component and the other compound (B) component are contained as separate resin particle components in the cationic electrodeposition coating composition. Here, "emulsifying alone" means that one component of the resin (A) and the other compound (B) is not substantially contained in the dispersed particles of the other component. Substantially, the content of one component contained in the dispersed particles of the other component is, for example, less than 3% by mass in terms of solid content, preferably less than 1% by mass, and more preferably 0.1. It means that it is less than mass%.

Reaction catalyst (C)
As the reaction catalyst (C), a known catalyst for the cross-linking reaction can be used without particular limitation. Specifically, for example, a zinc compound, a bismuth compound, an organic tin compound, or a hydroxide of an alkali metal can be used. At least one selected from the group consisting of compounds, alkali metal carbonates, quaternary ammonium compounds, tertiary amine compounds, guanidine compounds, amidin compounds, tertiary phosphine compounds, phosphazene compounds, tertiary sulfonium compounds, and quaternary phosphonium compounds. It is preferably a compound of. These can be used alone or in combination of two or more.

The reaction catalyst (C) is preferably a basic catalyst from the viewpoint of catalytic performance, and is preferably a strong basic catalyst such as an amidine compound, a guanidine compound, and a phosphazene compound.

As the amidine compound, those known per se can be used without particular limitation, and specifically, for example, 1,5-diazabicyclo [4,3,0] -nonen-5 (DBN), 1,5. -Diazabicyclo [4,4,0] -decene-5,1,8-diazabicyclo [5,4,0] -undesen-7 (DBU), 5-hydroxypropyl-1,8-diazabicyclo [5,4,0 ] -Undecene-7,5-dibutylamino-1,8-diazabicyclo [5,4,0] -Undecene-7 and the like.

As the guanidine compound, those known per se can be used without particular limitation, and specifically, for example, 1,3-diphenylguanidine, 1,3-dimethylguanidine, 1,1,3,3-tetra. Examples thereof include methylguanidine (TMG). These catalysts can be used alone or in combination of two or more.

The reaction catalyst preferably has an acid dissociation constant (pKa) of 10 or more, and more preferably 12 or more, particularly from the viewpoint of catalytic performance.
The basic catalyst is preferably a compound having a molecular weight of 100 or more, more preferably 200 or more, and 300 or more, from the viewpoint of the finish of the coating film and the water resistance of the coating film. It is more preferable to have.

As a method for increasing the molecular weight of the basic catalyst, for example, in the case of an amidine catalyst or a guanidine catalyst, (1) reactivity of the primary or secondary amino group of the amidine catalyst or guanidine catalyst with an epoxy group or an isocyanate group. Examples thereof include a method of reacting with a functional group-containing compound, (2) a method of reacting an amidine catalyst or a guanidine catalyst with a carbodiimide compound, and the like, all of which can be preferably used.

Further, the reaction catalyst may be contained in the coating material as a microencapsulated microencapsulation catalyst (C-1).

The amount of the reaction catalyst to be blended is preferably in the range of 0.1% by mass or more and 20% by mass or less, preferably 0.5% by mass, based on the resin solid content in the coating material, excluding the resin component. It is more preferably in the range of% or more and 10% by mass or less, and particularly preferably in the range of 0.5% by mass or more and 7% by mass or less.

The cationic electrodeposition coating material that can be used in the coating method of the present invention includes a pigment dispersion paste and various resins (acrylic resin, epoxy resin, urethane resin) in addition to the component (A), the component (B), and the component (C). , Melamine resin), various additives (surfactant, surface conditioner, neutralizer), solvent and the like can be contained as needed.

The pigment dispersion paste is a pigment in which pigments such as coloring pigments, rust preventive pigments, and extender pigments are dispersed in fine particles in advance, and for example, various additives such as pigment dispersion resins, pigments, and neutralizers are blended. Then, the pigment dispersion paste can be prepared by dispersion treatment in a dispersion mixer such as a ball mill, a sand mill, or a pebble mill.

As the pigment dispersion resin, known ones can be used without particular limitation. For example, an epoxy resin or acrylic resin having a hydroxyl group and a cationic group, a tertiary amine type epoxy resin, a quaternary ammonium salt type epoxy resin, or a tertiary sulfonium salt can be used. A type epoxy resin, a tertiary amine type acrylic resin, a quaternary ammonium salt type acrylic resin, a tertiary sulfonium salt type acrylic resin, or the like can be used.

Known pigments can be used without particular limitation, and for example, coloring pigments such as titanium oxide, carbon black, and red iron oxide; extender pigments such as clay, mica, varita, calcium carbonate, and silica; and rust preventive pigments are added. be able to.
The amount of the pigment in the pigment dispersion paste is preferably 1 part by mass or more and 100 parts by mass or less, particularly preferably 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the resin solid content of the cationic electrodeposition coating material.

In the cationic electrodeposition coating material used in the present invention, it is preferable that water is contained in the solvent of each solution bath in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

In the cationic electrodeposition coating material used in the present invention, active hydrogen group and blocked isocyanate group, Michael donor component (active hydrogen group) and acceptor component (α, β-unsaturated carbonyl group), epoxy group and thiol group (mercapto group) As the content ratio, the reactive functional group ratio (molar ratio) is usually 0.3 / 1 or more and 1 / 0.3 or less, preferably 0.5 / 1 or more and 1 / 0.5 or less, preferably 0. It is suitable for obtaining a coated article having good storage stability and excellent finish and corrosion resistance when it is 7/1 or more and 1 / 0.7 or less.

The amine value of the resin of the cationic electrodeposition coating material is usually 5 mgKOH / g or more and 200 mgKOH / g or less, preferably 10 mgKOH, based on the resin solid content, from the viewpoint of the above-mentioned coating properties and coating film performance. It is preferably in the range of / g or more and 150 mgKOH / g or less.
After the metal object to be coated is electrodeposited as described above, it is preferable to further coat a part or all of the electrodeposition coating film with the topcoat coating material. As the top coat, for example, a step of sequentially coating an intermediate coat, a base paint, and a clear paint and baking and curing is preferable. In the electrodeposition coating film by the coating method of the present invention, even if there is an uncrosslinked portion, it can be completely crosslinked by the baking hardening step of the topcoat paint.

Further, as another embodiment of the present invention, after the cationic electrodeposition coating material (first cationic electrodeposition coating material) is applied, a second cationic electrodeposition coating material can be further electrodeposited. The second cationic electrodeposition coating material is not particularly limited, and a known cationic electrodeposition coating material can be applied. The second cationic electrodeposition coating material contains an amino group-containing epoxy resin (A-2) and a blocked polyisocyanate compound, and is 40% by mass of the amino group-containing epoxy resin (A) based on the total amount of resin solids. 90% by mass or less (preferably 55% by mass or more and 85% by mass or less, further preferably 60% by mass or more and 80% by mass or less), blocked polyisocyanate 10% by mass or more and 60% by mass or less (preferably 15% by mass or more and 45% by mass) It is preferably contained in an amount of% by mass or less, more preferably 20% by mass or more and 40% by mass or less).

The blocked polyisocyanate is a product obtained by an addition reaction between a polyisocyanate compound and an isocyanate blocking agent. As the polyisocyanate compound used in the blocked polyisocyanate, known ones can be used without particular limitation, and for example, tolylene diisocyanate, xylylene diisocyanate, phenylenedi isocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane. Aromatic polyisocyanates such as -2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI [polymethylenepolyphenylisocyanate]; alicyclic polyisocyanates such as bis (isocyanatemethyl) cyclohexane, isophorone diisocyanate Compounds; aliphatic polyisocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate; cyclized polymers or billets of these polyisocyanate compounds; or combinations thereof.

From the viewpoint of improving corrosion resistance, aromatic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylenedi isocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, and crude MDI can be used. preferable.

On the other hand, the above-mentioned isocyanate blocking agent is added to the isocyanate group of the polyisocyanate compound to block it, and the blocked polyisocyanate compound produced by the addition reaction is stable at room temperature, but the baking temperature of the coating film (usually). When heated to about 100 to about 200 ° C.), the blocking agent dissociates and regenerates free isocyanate groups.

As the isocyanate blocking agent used in the blocked polyisocyanate (B), known ones can be used without particular limitation, and for example, oxime compounds such as methyl ethyl ketooxime and cyclohexanone oxime; phenol, para-t-butylphenol. , Phenol compounds such as cresol; alcohol compounds such as n-butanol, 2-ethylhexanol, phenylcarbinol, methylphenylcarbinol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, ethylene glycol, propylene glycol; ε-caprolactam , Gamma-butyrolactam and other lactam compounds; active methylene compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate and acetylacetone, etc., may be used alone or in combination of two or more. Can be used in combination.

The cationic electrodeposition coating material is further optionally mixed with various additives such as a surfactant and a surface conditioner, a pigment dispersion paste, water, an organic solvent and a neutralizing agent, and water-soluble or water-dispersed. Can be obtained.

As another embodiment of the present invention, generally, the solid content concentration is set to about 5% by mass or more and 40% by mass or less, preferably 10% by mass or more and 25% by mass or less, and the pH is further set to 4 by deionized water or the like. Using a cationic electrodeposition paint adjusted within the range of 0.0 or more and 9.0 or less, preferably 5.5 or more and 7.0 or less, as a bath, the bath temperature is usually adjusted to 15 ° C or more and 35 ° C or less, and the load voltage is 100 V. Electrodeposition coating may be performed by energizing the object to be coated as a cathode at 400 V or more, preferably 150 V or more and 350 V or less.
After electrodeposition coating of the cationic electrodeposition paint on the object to be coated, preheating is arbitrarily performed at 30 ° C. or higher and 100 ° C. or lower, and the dry film thickness of the second cationic electrodeposition paint is 5 μm or more and 40 μm or less (preferably 10 μm or more). By electrodeposition coating with a thickness of 30 μm or less), a thick coating film and a coating film having excellent anticorrosion properties can be obtained. In addition, since the second cationic electrodeposition paint is applied without baking at a high temperature (121 ° C or higher) after the cationic electrodeposition paint is applied, the energy cost is higher than that of the 2-coat 2-bake type multi-layer electrodeposition coating. Can be reduced. From the viewpoint of further energy cost reduction, preheating (heat drying) is preferably at a low temperature and for a short time, and more preferably not preheating.

Subsequently, the above-mentioned multilayer films (first and second cationic electrodeposition coating films) are heat-cured at a temperature higher than 120 ° C. (preferably 120 ° C. or higher and 200 ° C. or lower) to cure the first and second cations. The electrodeposition paint can be completely crosslinked. The multi-layer film preferably has a dry film thickness of 10 μm or more and 80 μm or less (preferably 20 μm or more and 70 μm or less).

It is preferable that the metal object to be coated is electrodeposited with the first and second cationic electrodeposition coatings as described above, and then a topcoat coating is further applied to a part or all of the multi-layer electrodeposition coating film. As the top coat, for example, a step of sequentially coating an intermediate coat, a base paint, and a clear paint and baking and curing is preferable.

The coating film obtained by the coating method of the cationic electrodeposition coating material of the present invention has good low temperature curability, corrosion resistance and finish (horizontal skin and vertical skin) while ensuring good coating stability (bath stability). Excellent. Specifically, the automobile body painted by the painting method of the present invention has a good finish of the coating film, and the cationic electrodeposition paint used in the painting method of the present invention has storage stability for a long period of time. Is good.

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

Production Example 1 Amino group-containing epoxy resin (A1)
In a flask equipped with a stirrer, a thermometer, and a reflux condenser, jER828EL (trade name, manufactured by Mitsubishi Chemical Corporation, epoxy resin, epoxy equivalent 190, number average molecular weight 370) 1000 parts, bisphenol A 400 parts and dimethylbenzylamine 0.2 part was added and reacted at 130 ° C. until the epoxy equivalent reached 700. Next, 126 parts of diethanolamine and 160 parts of a ketimide of diethylenetriamine and methyl isobutyl ketone were added and reacted at 120 ° C. for 4 hours, and then ethylene glycol monobutyl ether was added as needed to contain an amino group having a solid content of 80%. An epoxy resin (A1) solution was obtained. The obtained amino group-containing epoxy resin (A1) had an amine value of 100 mgKOH / g and a number average molecular weight of 1650.

Production Example 2 Amino group-containing epoxy resin (A2)
In a flask equipped with a stirrer, a thermometer, and a reflux condenser, 950 parts of jER1001 (trade name, manufactured by Mitsubishi Chemical Corporation, epoxy resin, epoxy equivalent 475, number average molecular weight 950), 126 parts of diethanolamine, diethylenetriamine and methylisobutylketone 160 parts of the ketimide and 0.2 part of dimethylbenzylamine were added and reacted at 120 ° C. for 4 hours, and then ethylene glycol monobutyl ether was added as needed to add an amino group-containing epoxy resin (A2) having a solid content of 80%. ) A solution was obtained. The obtained amino group-containing epoxy resin (A2) had an amine value of 136 mgKOH / g and a number average molecular weight of 1200.

Production Example 3 Amino group-containing epoxy resin (A3)
In a flask equipped with a stirrer, a thermometer, and a reflux cooler, 640 parts of the epoxy resin (n = about 1.0, epoxy equivalent 320, number average molecular weight 640) of the formula (1), 126 parts of diethanolamine, diethylenetriamine and methyl 160 parts of ketiminated product and 0.2 part of dimethylbenzylamine with isobutyl ketone were added and reacted at 120 ° C. for 4 hours, then ethylene glycol monobutyl ether was added as needed, and an amino group-containing epoxy resin having a solid content of 80% was added. (A3) A solution was obtained. The obtained amino group-containing epoxy resin (A3) had an amine value of 180 mgKOH / g and a number average molecular weight of 900.

Production Example 4 Polyester polyol (A4)
146 parts of adipic acid and 136.5 parts of trimethylolpropane were charged into a reaction device having a heating device, a stirrer, a nitrogen introduction tube and a fractional distillation column, heating was started under dry nitrogen, and the temperature was gradually raised to 230 ° C. The esterification reaction was carried out. A polyester having a resin solid content of 80% by mass is maintained at 230 ° C., subjected to an esterification reaction until the resin acid value becomes 2 mgKOH / g or less, cooled to 170 ° C., and if necessary, ethylene glycol monobutyl ether is added. A polyol (A4) solution was obtained. The obtained polyester polyol (A4) had an acid value of 2 mgKOH / g, a hydroxyl value of 376 mgKOH / g, and a number average molecular weight of 900 as the resin solid content.

Production Example 5 Blocked polyisocyanate compound (B1)
250 parts of "Sumijour N3300" (trade name, isocyanurate structure-containing polyisocyanate derived from hexamethylene diisocyanate, trade name, manufactured by Sumika Bayer Urethane Co., Ltd.) and a four-necked flask equipped with a stirrer, a heating device, a cooling device, and a depressurizing device. 125 parts of methyl ethyl ketone was charged and heated to 30 ° C. Then, 126 parts of 3,5-dimethylpyrazole was gradually added over 2 hours with stirring, and the reaction mixture was reacted at 30 ° C. under stirring until no free isocyanate groups were detected by infrared spectroscopy. I let you. Further, if necessary, methyl isobutyl ketone was added to obtain a blocked polyisocyanate compound (B1) having a solid content of 70%. The amount of NCO of the blocked polyisocyanate compound of the obtained pyrazole block was 14.4%, and the weight average molecular weight was 800. In the present specification, the amount of NCO means the amount (%) of NCO groups with respect to 100 parts by mass of the resin solid content.

Production Example 6 Epoxy resin-added amine catalyst In a flask equipped with a stirrer, thermometer, and reflux condenser, 370 parts of jER828EL (trade name, manufactured by Mitsubishi Chemical Corporation, epoxy resin, epoxy equivalent 190, number average molecular weight 370), 1 , 1,3,3-Tetramethylguanidine (230 parts) and Isobutylmethylketone (500 parts) were added, the temperature was raised to 120 ° C., and the mixture was reacted for 5 hours. Then, if necessary, isobutyl methyl ketone was added to obtain an epoxy resin-added amine catalyst solution having a solid content of 50%.

Production Example 7 To a pigment-dispersed resin flask, 696 parts of tolylene diisocyanate (TDI) and 304 parts of methyl isobutyl ketooxime (MIBK) were added, the temperature was raised to 60 ° C., 520 parts of 2 ethylhexyl alcohol was added dropwise, and the NCO value was 110. The reaction was carried out until the temperature reached 5, to obtain a partially blocked isocyanate A having a resin solid content of 80%.
Next, 89 parts of dimethylethanolamine was added dropwise to 380 parts of this partially blocked isocyanate A at 70 ° C., and the reaction was carried out until there was substantially no NCO, diluted with 34.75 parts of ethylene glycol monobutyl ether, and then 90%. Neutralization with 100 parts of lactic acid gave 80% lactic acid neutralized amino group-containing blocked isocyanate B.
To another flask, add 1125 parts of jER828EL (trade name, manufactured by Mitsubishi Chemical Corporation, epoxy resin, epoxy equivalent 190, number average molecular weight 370), 456 parts of bisphenol A and 1.1 parts of triphenylphosphonium iodite, and 170 parts. After reacting at ℃ until the epoxy equivalent was 790, it was diluted with 279 parts of MIBK, then 760 parts of the above partially blocked isocyanate A was added, and the reaction was carried out at 100 ℃ until substantially no NCO was eliminated.
Next, 630 parts of ethylene glycol monobutyl ether was added and cooled to 80 ° C., 860 parts of blocked isocyanate B containing 80% lactic acid neutralized amino group was added, and the reaction was carried out until the acid value became 1 mgKOH / g or less. Propylene glycol monomethyl ether was added accordingly to obtain a resin solution for pigment dispersion containing a quaternary ammonium base having a solid content of 60%.

Production Example 8 Pigment dispersion paste No. 1
8.3 parts of resin solution for pigment dispersion (solid content 5 parts), 14.5 parts of titanium oxide, 9.0 parts of refined clay, 0.3 parts of carbon black, and 20.3 parts of deionized water of Production Example 7. In addition, the pigment dispersion paste No. 1 having a solid content of 55% was dispersed in a ball mill for 20 hours. I got 1.

Production Example 9 Emulsifier 30 parts of methoxypropanol and 30 parts of isobutanol are placed in a reaction vessel equipped with an emulsifier thermometer, a thermostat, a stirrer, a reflux cooler, a nitrogen introduction tube and a dropping device, heated at 100 ° C., and 30 parts of ethyl acrylate. , 60 parts of n-butyl acrylate, 10 parts of dimethylaminoethylmethyl chloride salt methacrylate, 10 parts of isobutanol, and 4 parts of t-butylperoxyoctanoate are added to the above mixed solvent over 4 hours, and further t A mixture consisting of 0.5 part of butylperoxyoctanoate and 10 parts of isobutanol was added dropwise for 1 hour. Then, after stirring and aging for 1 hour, propylene glycol monomethyl ether was added as needed to obtain a quaternary salt emulsifier having a solid content concentration of 50%. The weight average molecular weight was 10,000.

Production Example 10 Cationic electrodeposition paint (X-1)
62.5 parts (solid content 50 parts) of the amino group-containing epoxy resin (A1) solution obtained in Production Example 1, 37.5 parts (solid content 30 parts) of the polyester polyol (A4) solution obtained in Production Example 4. , 10.6 parts (solid content 5.3 parts) of the epoxy resin-added amine catalyst solution of Production Example 6 and 3.2 parts of 10% formic acid were mixed, and after uniformly stirring, deionized water was added while vigorously stirring. The mixture was gradually added dropwise to obtain emulsion particles A having a solid content of 32%.
Subsequently, 28.5 parts (20 parts of solid content) of the blocked polyisocyanate compound (B1) obtained in Production Example 5 and the quaternary salt-type emulsifier obtained in Production Example 9 were added to the other compound (B) [Compound. (B1)] was blended with 5% in solid content, and deionized water was gradually added dropwise with vigorous stirring to obtain emulsion particles B having a solid content of 32%.
The above emulsion particles A, emulsion particles B, 52.4 parts (28.8 parts of solid content) of the 55% pigment dispersion paste obtained in Production Example 8, and deionized water were gradually added to obtain a solid content of 20%. A cationic electrodeposition paint (X-1) was obtained.

Production Examples 11 to 39 Cationic electrodeposition paints (X-2) to (X-30)
Cationic electrodeposition paints (X-2) to (X-30) were prepared in the same manner as in Production Example 10 except that the paint formulations were shown in Tables 2 and 3 below.

Production Example 40 Amino group-containing epoxy resin (A4)
In a flask equipped with a stirrer, thermometer, nitrogen introduction tube and reflux condenser, 1200 parts of jER828EL (trade name, epoxy resin manufactured by Japan Epoxy Resin, epoxy equivalent 190, number average molecular weight 350), 500 parts of bisphenol A and dimethyl 0.2 part of benzylamine was added and reacted at 130 ° C. until the epoxy equivalent was 850.
Next, 160 parts of diethanolamine and 65 parts of ketiminated product of diethylenetriamine and methyl isobutyl ketone were added and reacted at 120 ° C. for 4 hours, then 480 g of ethylene glycol monobutyl ether was added, and an amino group-containing epoxy resin having a solid content of 80% ( A4) A solution was obtained. The amino group-containing epoxy resin (A4) had an amine value of 59 mgKOH / g and a number average molecular weight of 2100.

Production Example 41 Blocked isocyanate curing agent (B2)
270 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Crude MDI) and 127 parts of methyl isobutyl ketone were added to the reaction vessel, and the temperature was raised to 70 ° C. 236 parts of ethylene glycol monobutyl ether was added dropwise thereto over 1 hour, and then the temperature was raised to 100 ° C., and while maintaining this temperature, sampling was performed over time, and unreacted isocyanate groups were measured by infrared absorption spectrum measurement. After confirming that the absorption of the above was eliminated, methyl isobutyl ketone was further added to obtain a blocked isocyanate curing agent (B2) having a resin solid content of 70%. The amount of NCO of the obtained blocked isocyanate curing agent (B2) containing an alcohol compound as a blocking agent was 16.7%.

Production Example 42 Pigment dispersion paste No. 2
8.3 parts (5 parts solid content) of the pigment dispersion resin containing a quaternary ammonium base having a solid content of 60%, 14.5 parts titanium oxide, 6 parts purified clay, and 0.3 carbon black obtained in Production Example 7. 3 parts, 3 parts of bismuth hydroxide, and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste No. with a solid content of 55%. I got 2.

Production Example 43 Cationic electrodeposition paint (X-31)
87.5 parts (solid content 70 parts) of the amino group-containing epoxy resin (A4) obtained in Production Example 40, and 37.5 parts (solid content 30 parts) of the blocked polyisocyanate compound (B2) obtained in Production Example 41. ) Was mixed, and 13 parts of 10% acetic acid was further mixed and stirred uniformly, and then the deionized water was added dropwise over about 15 minutes while vigorously stirring to obtain an emulsion having a solid content of 34%.
Next, 294 parts of the above emulsion (100 parts of solid content), the pigment dispersion paste No. obtained in Production Example 42. 252.4 parts and 350 parts of deionized water were added to produce a cationic electrodeposition coating material (X-31) having a solid content of 20%.

Tables 2 and 3 (Note 4) and (Note 5) will be described below.
(Note 4) "jER828EL": Product name, manufactured by Mitsubishi Chemical Corporation, epoxy resin, epoxy equivalent 190, number average molecular weight 370
(Note 5) "Imidazole compound": 2,4-diamino-6- [2'-undecylimidazolyl- (1')]-ethyl-S-triazine (manufactured by Shikoku Chemicals Corporation)

<Cation electrodeposition coating (single layer film)>
Hereinafter, examples and comparative examples in the case where the cationic electrodeposition coating is performed once will be described.
[Example 1 Coating method of cationic electrodeposition paint (Y-1)]
Cold-rolled steel sheet (150 mm (length) x 70 mm (width) x 0.8 mm (thickness)) subjected to chemical conversion treatment (trade name, Palbond # 3020, manufactured by Nihon Parkerizing Co., Ltd., zinc phosphate treatment agent) is used as the object to be coated. , The cationic electrodeposition coating material (X-1) obtained in Production Example 10 was adjusted so that the solid content concentration was 20%, the bath temperature was 28 ° C., the load voltage was 250V, and 180 seconds (increased voltage in 30 seconds). The electrodeposition coating plate was obtained by electrodeposition coating and water washing so as to have a dry film thickness of 15 μm under the above conditions, and heat-drying (cross-linking) at temperatures of 35 ° C., 70 ° C., and 110 ° C. for 20 minutes, respectively. The complex viscosity was measured and the finish (horizontal and vertical) was evaluated by the method described later for each of the case where the object to be coated was installed in the horizontal direction and the case where it was installed in the vertical direction. The evaluation results are shown in Tables 4 and 5 below.
As for the evaluation of finishability (horizontal, vertical), S to B are acceptable, and C is unacceptable.

[Examples 2 to 25 and Comparative Examples 1 to 5 Coating Method of Cationic Electroplated Paint (Y-2) to (Y-30)]
Cationic electrodeposition coating was performed in the same manner as in Example 1 except that Tables 4 and 5 below were used.

(Painting of topcoat paint)
Further, it was confirmed that the topcoat coating material was applied on the electrodeposition coating film obtained by the coating methods of Examples 1 to 25 in the following steps to obtain a multi-layer coating film having good finish.

On the electrodeposition coating, intermediate coating (trade name "TP-65", manufactured by Kansai Paint Co., Ltd., polyester resin / amino resin organic solvent type paint) 20 μm, base paint (trade name "WBC-713", Kansai paint) Acrylic resin / amino resin-based water-based coloring paint) 15 μm, clear paint (trade name “Magiclon KINO-1210”, manufactured by Kansai Paint Co., Ltd., and acrylic resin solvent-based topcoat clear paint) 30 μm are applied in sequence at 140 ° C. Bake at temperature for 30 minutes. The film thicknesses described are all cured film thicknesses.

(Measuring method of complex viscosity)
After the cationic electrodeposition coating performed in Examples and Comparative Examples, the undried and uncrosslinked coating films obtained by washing with water were scraped off with a spatula, and the temperature was 35 ° C. using a rotary rheometer (RS150 manufactured by HAAKE). , 70 ° C., and 110 ° C., respectively, and the complex viscosities were measured. The measurement was performed 1 minute after painting.
The symbols I to VI in the table are as follows.
I: Complex viscosity is 200 Pa or more and 500 Pa or less II: Complex viscosity is 100 Pa or more and less than 200 Pa III: Complex viscosity is 10 Pa or more and less than 100 Pa IV: Complex viscosity is 1 or more and less than 10 Pa V: Complex viscosity is less than 1 Pa VI: Complex viscosity is more than 500 Pa

(Finishing (horizontal))
In Examples and Comparative Examples, the surface roughness value (Ra) of the coated surface of the test plate is set to the surface when the test plate is placed in a horizontal state and heat-dried at 35 ° C., 70 ° C., and 110 ° C., respectively. It was measured with a roughness meter (trade name "Surftest 301", manufactured by Mitutoyo Co., Ltd.) with a cutoff of 0.8 mm, and evaluated according to the following criteria.
In the evaluation, S to B pass and C fails.
S: Surface roughness value (Ra) is less than 0.2 A: Surface roughness value (Ra) is 0.2 or more and less than 0.25 B: Surface roughness value (Ra) is 0.25 or more and less than 0.3 C: Surface roughness value (Ra) is 0.3 or more

(Finishing (vertical))
In Examples and Comparative Examples, the surface roughness value (Ra) of the coated surface of the test plate was determined by heating and drying (when the test plate was heat-dried at 35 ° C., 70 ° C., and 110 ° C., respectively) in a vertical state. The measurement was performed with a cutoff of 2.5 mm using a roughness meter (trade name "Surftest 301", manufactured by Mitutoyo Co., Ltd.), and evaluated according to the following criteria.
In the evaluation, S to B pass and C fails.
S: Surface roughness value (Ra) is less than 0.2 A: Surface roughness value (Ra) is 0.2 or more and less than 0.25 B: Surface roughness value (Ra) is 0.25 or more and less than 0.3 C: Surface roughness value (Ra) is 0.3 or more

As shown in Tables 4 and 5, according to the cationic electrodeposition coating method of the present invention, the finishability in both the horizontal direction and the vertical direction was good.

<Cation electrodeposition coating (multi-layer film)>
Hereinafter, a case where a second cationic electrodeposition coating material is electrodeposited after the cationic electrodeposition coating material is used and then heat-cured at a temperature higher than 120 ° C. to form a coating film will be described. To do.

[Example 26 Coating method of cationic electrodeposition paint (Z-1)]
(Cation electrodeposition coating)
Cold-rolled steel sheet (150 mm (length) x 70 mm (width) x 0.8 mm (thickness)) subjected to chemical conversion treatment (trade name, Palbond # 3020, manufactured by Nihon Parkerizing Co., Ltd., zinc phosphate treatment agent) is used as the object to be coated. , The cationic electrodeposition coating material (X-1) obtained in Production Example 10 was adjusted so that the solid content concentration was 20%, the bath temperature was 28 ° C., the load voltage was 250V, and 180 seconds (increased voltage in 30 seconds). Under the above conditions, electrodeposition coating and water washing were performed so that the dry film thickness was 15 μm. Then, a total of three electrodeposition coating plates were obtained, one without heat drying (atmosphere temperature 25 ° C.) and two heat-dried (crosslinked) at 70 ° C. and 110 ° C. for 20 minutes.

(Second cationic electrodeposition coating)
Subsequently, the cationic electrodeposition coating material (X-31) (second cationic electrodeposition coating material) obtained in Production Example 43 was adjusted so that the solid content concentration was 20%, the bath temperature was 28 ° C., and the load voltage was 250V. , Electrodeposition coating and washing with water so that the dry film thickness is 15 μm under the condition of 180 seconds (increased voltage in 30 seconds), and heat-drying (crosslinking) at a temperature of 170 ° C. for 20 minutes to obtain a multilayer film. An electrodeposition coating plate was obtained.

[Examples 27 to 50 Coating Method of Cationic Electroplated Paint (Z-2) to (Z-25)]
Cationic electrodeposition coating was performed in the same manner as in Example 26 except as shown in Tables 8 and 9 below.
Regarding the coating methods (Z-1) to (Z-25) in the above examples, after coating the first cationic electrodeposition coating materials (X-1) to (X-25), no heat drying was performed (25 ° C.). The complex viscosity in the case of 1 was measured, and it was the same as the evaluation category (I to VI) at a drying temperature of 35 ° C. measured in Examples 1 to 25.

Further, the topcoat paint is coated on the multi-layer electrodeposition coating film obtained by the coating methods of Examples 26 to 50 by the above-mentioned "coating of topcoat paint" to obtain a multi-layer coating film having good finish. I confirmed that it was possible.

(Anti-corrosion)
For Examples 1 to 50 above, the corrosion resistance of the electrodeposition coating film after the cationic electrodeposition coating and after the second cationic electrodeposition coating was evaluated. Examples 1 to 25 are shown in Tables 6 and 7, and Examples 26 to 50 are shown in Tables 8 and 9.
Regarding the evaluation of the corrosion resistance of Examples 1 to 25 in Tables 6 and 7, the coating method is described as Y-1 to Y-25 described above in the table, but these are the above-mentioned Examples. Since it was evaluated after the cationic electrodeposition coating at 26 to 50, the level of the heating and drying temperature "35 ° C." is described as the level of "no heating and drying (25 ° C.)".

A cross-cut scratch is made on the coating film with a cutter knife so as to reach the base material of the obtained test plate, and a 35 ° C salt spray test is carried out for 1000 hours according to JIS Z-2371, and one side from the cut portion is used. Corrosion resistance was evaluated according to the following criteria based on rust and blistering width. The evaluation results are shown in Tables 6 to 9.
In the evaluation, A and B pass, and C fails.
A: Maximum width of rust and blisters is 1.0 mm or less on one side of the cut part B: Maximum width of rust and blisters exceeds 1.0 mm on one side of the cut part and 5.0 mm or less C: Maximum width of rust and blisters Greatly exceeds 5.0 mm on one side of the cut part

In the evaluation of corrosion resistance, all coated plates were installed in the horizontal direction and heat-dried.

As shown in Tables 6 to 9, the electrodeposition coating plate in the case of only the first cationic electrodeposition coating (single layer film) and in the case of coating the first and second cationic electrodeposition (multilayer film) is either. Was also able to obtain good anticorrosion properties.

Claims (16)

It is a method of applying cationic electrodeposition paint.
It has a step of electrodepositing a first cationic electrodeposition coating film to form an uncrosslinked coating film, and drying and crosslinking the uncrosslinked coating film.
The temperature at which the uncrosslinked coating film is dried and crosslinked is 10 ° C. or higher and 120 ° C. or lower.
A method for coating a cationic electrodeposition paint in which the complex viscosity of the coating paint measured by the following method is 1 Pa or more and 500 Pa or less.
<Measurement method of complex viscosity>
The uncrosslinked coating film obtained by electrodepositing the cationic electrodeposition coating material is scraped off with a spatula, and the complex viscosity is measured at a temperature at which the uncrosslinked coating film is dried and crosslinked using a rotary rheometer. .. The cationic electrodeposition coating material contains a resin (A) containing an amino group-containing epoxy resin (A-2).
The amino group-containing epoxy resin (A-2) is contained in the cationic electrodeposition coating material in an amount of 20% by mass or more and 80% by mass or less per resin solid content.
The method for coating a cationic electrodeposition paint according to claim 1, wherein the amino group-containing epoxy resin (A-2) has a number average molecular weight of 800 or more. The method for coating a cationic electrodeposition coating material according to claim 2, wherein the cationic electrodeposition coating material further contains the other compound (B) in an amount of 5% by mass or more and 80% by mass or less per resin solid content. The method for coating a cationic electrodeposition paint according to claim 3, wherein the other compound (B) contains a compound (B-1) having a reactive functional group. The method for coating a cationic electrodeposition paint according to claim 3 or 4, wherein the weight average molecular weight of the other compound (B) is less than 1000. The method for coating a cationic electrodeposition coating material according to any one of claims 3 to 5, wherein the weight average molecular weight of the other compound (B) is 100 or more. The cationic electrodeposition coating material according to any one of claims 3 to 6, wherein the resin (A) component and the other compound (B) component are present as separate aqueous dispersions in the cationic electrodeposition coating material. Painting method. The cationic electrodeposition according to any one of claims 1 to 7, wherein the cross-linking reaction of the cationic electrodeposition coating material is at least one selected from a Michael addition reaction, a reaction between an epoxy group and a thiol group, and an anionic polymerization reaction. How to apply paint. The method for coating a cationic electrodeposition coating material according to any one of claims 1 to 8, wherein the cationic electrodeposition coating material further contains a reaction catalyst (C). The method for coating a cationic electrodeposition paint according to claim 9, wherein the reaction catalyst (C) is a microencapsulation catalyst (C-1). The resin (A) and the other compound (B) are present as separate aqueous dispersions in the cationic electrodeposition coating, and the resin (A) and the other compound (B) are Michael addition reaction acceptors, respectively. The third aspect of claim 3, wherein the component and the Michael addition reaction donor component, or the Michael addition reaction donor component and the Michael addition reaction acceptor component are contained, and the cross-linking reaction of the cationic electrodeposition coating material includes the Michael addition reaction. How to apply cationic electrodeposition paint. Using the cationic electrodeposition paint as an electrodeposition paint bath, a metal object to be coated is immersed in the electrodeposition paint bath, electrodeposition coating is performed, and then a second cationic electrodeposition coating is electrodeposited, and then 120 ° C. The method for applying a cationic electrodeposition paint according to claim 11, wherein the coating method is heat-cured at a higher temperature. The method for coating a cationic electrodeposition paint according to any one of claims 1 to 10, wherein the cationic electrodeposition paint is used as an electrodeposition paint bath, and a metal object to be coated is immersed in the electrodeposition paint bath to perform electrodeposition coating. .. The present invention according to any one of claims 1 to 10, wherein the cationic electrodeposition paint is used as an electrodeposition paint bath, a metal object to be coated is immersed in the electrodeposition paint bath, and after electrodeposition coating, the metal object is dried and crosslinked by electromagnetic induction heating. The method for applying a cationic electrodeposition paint according to the above. The method for coating a cationic electrodeposition paint according to claim 13, wherein after the electrodeposition coating of the cationic electrodeposition paint is applied, a second cationic electrodeposition paint is further electrodeposited and then heat-cured at a temperature higher than 120 ° C. .. The cationic electrodeposition according to claim 13, wherein after the electrodeposition coating of the cationic electrodeposition coating material is applied, the second cationic electrodeposition coating material is electrodeposited and then cured by heating at a temperature higher than 120 ° C. without preheating. How to apply paint.