WO2022019034A1

WO2022019034A1 - Cationic electrodeposition coating composition

Info

Publication number: WO2022019034A1
Application number: PCT/JP2021/023644
Authority: WO
Inventors: マアハシャラフ; 沙紀赤城; 岳史原; 祐斗岩橋
Original assignee: 日本ペイント・オートモーティブコーティングス株式会社
Priority date: 2020-07-21
Filing date: 2021-06-22
Publication date: 2022-01-27
Also published as: JP2022020996A

Abstract

The present invention provides a cationic electrodeposition coating composition capable of having low-temperature curability and maintaining coating film performance. The present invention provides a cationic electrodeposition coating composition containing an aminated resin and a blocked polyisocyanate curing agent. The blocked polyisocyanate curing agent is contained in the amount of 50-80 mass% in a coating resin solid content. A blocking agent forming the blocked polyisocyanate curing agent includes a combination of (a) a monool compound and (b) a polyol compound and/or an amine having a hydroxy group. The amount of an OH functional group remaining in a formed electrodeposition coating film is 0.4-1.6 (meq/gram of solid content). The present invention also provides a coating film obtained from the cationic electrodeposition coating composition.

Description

Cationic electrodeposition coating composition

The present invention relates to a cationic electrodeposition coating composition, particularly a cationic electrodeposition coating composition that enables low temperature curability while maintaining coating film performance.

Cationic electrodeposition paint is often used as an undercoat paint to impart anticorrosion properties to industrial products such as automobiles, and contains an aminized resin and a blocked polyisocyanate curing agent. Cationic electrodeposition paints are required to have low temperature curability as well as improved coating film performance.

Low temperature curability can be achieved by dissociating the blocking agent of the blocked polyisocyanate curing agent at a low temperature. For example, WO2017138445A1 (Patent Document 1) exemplifies active methylene compounds and pyrazole compounds as excellent ones, which can be dissociated at low temperature, but are not common as industrial products and are difficult to obtain. , Not often used in terms of cost.

WO2017138445A1

An object of the present invention is to provide a cationic electrodeposition coating composition that can achieve low temperature curability and maintain coating film performance in a cationic electrodeposition coating composition.

That is, the present invention provides the following aspects:
[1] A cationic electrodeposition coating composition containing an aminated resin and a blocked polyisocyanate curing agent.
The blocked polyisocyanate curing agent is contained in the paint resin solid content in an amount of 50 to 80% by mass.
The blocking agent that forms the blocked polyisocyanate curing agent is
(A) Monool compound and
(B) With either or both of a polyol compound or an amine having a hydroxyl group,
Consists of combinations
The amount of residual OH functional groups in the formed electrodeposition coating film is 0.4 to 1.6 (meq / solid content g).
Cationic electrodeposition coating composition.
[2] The cationic electrodeposition coating composition according to the above [1], wherein the amine-based resin has an amine value of 100 to 200 (meq / solid content 100 g).
[3] The mass ratio of the polyol compound and the amine having a hydroxyl group to the monool compound of the blocking agent forming the blocked polyisocyanate curing agent is (monool compound) / (polyol compound and amine having a hydroxyl group) = 60. The cationic electrodeposition coating composition of the above [1] or [2], which is / 40 to 10/90.
[4] The cationic electrodeposition coating composition according to any one of the above [1] to [3], which can be cured at a temperature of 140 ° C to 200 ° C.
[5] The crosslink density of the electrodeposition coating film after coating the cationic electrodeposition coating composition on a steel sheet so as to have a dry film thickness of 15 μm and baking at 170 ° C. for 20 minutes is 0.5 to 5.0 mmol / cc. The cationic electrodeposition coating composition according to any one of the above [1] to [4], wherein the internal stress at the time of forming the electrodeposition coating film is 7.5 MPa or less.
[6] A cationic electrodeposition coating film coated with the cationic electrodeposition coating composition according to any one of the above [1] to [5].

According to the present invention, there is provided a cationic electrodeposition coating composition that enables low temperature curability while ensuring the performance of an electrodeposited coating film.

In the present invention, a blocking agent for a blocked polyisocyanate curing agent was investigated. Optimizing the amount of OH groups, which are reactive functional groups, by combining not only the commonly used monool compounds (ie, monohydric alcohols) but also either or both of polyol compounds or amines with hydroxyl groups. do.

That is, the present invention is a cationic electrodeposition coating composition containing an aminated resin and a blocked polyisocyanate curing agent, in which the blocked polyisocyanate curing agent is contained in an amount of 50 to 80% by mass in the solid content of the coating resin. The blocking agent contained and forming the blocked polyisocyanate curing agent was formed by a combination of (a) a monool compound and (b) either a polyol compound or an amine having a hydroxyl group, or both. The amount of residual OH functional group in the electrodeposition coating film is 0.4 to 1.6 (meq / solid content g). Each requirement will be explained.

<Aminated resin>
The aminized resin is a coating film forming resin constituting an electrodeposition coating film. As the aminized resin, an amine-modified epoxy resin obtained by modifying an oxylan ring (also referred to as an "epoxy group") in an epoxy resin skeleton with an amine compound is preferable. Generally, an amine-modified epoxy resin is prepared by opening an oxylan ring in a starting material resin molecule by reaction with an amine compound such as a primary amine, a secondary amine or a tertiary amine and / or an acid salt thereof. A typical example of a starting material resin is a polyphenol polyglycidyl ether type epoxy resin which is a reaction product of a polycyclic phenol compound such as bisphenol A, bisphenol F, bisphenol S, phenol novolak, and cresol novolak with epichlorohydrin. As an example of another starting material resin, the oxazolidone ring-containing epoxy resin described in JP-A-5-306327 can be mentioned. These epoxy resins can be prepared by reacting a diisocyanate compound or a bisurethane compound obtained by blocking the isocyanate group of the diisocyanate compound with a lower alcohol such as methanol or ethanol with epichlorohydrin.

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

2-Ethylhexanol, nonylphenol, ethylene glycol mono-2 for some oxylan rings for the purpose of adjusting the molecular weight or amine equivalent, improving the heat flow property, etc. before the ring opening reaction of the oxylan ring with the amine compound. -A monohydroxy compound such as ethylhexyl ether, ethylene glycol monon-butyl ether, propylene glycol mono-2-ethylhexyl ether or a monocarboxylic acid compound such as octyl acid may be added.

An amine-modified epoxy resin can be obtained by reacting the oxylan ring of the epoxy resin with the amine compound. Examples of the amine compound that reacts with the oxylan ring include primary amines and secondary amines. When the epoxy resin is reacted with a secondary amine, an amine-modified epoxy resin having a tertiary amino group is obtained. Further, by reacting the epoxy resin with the primary amine, an amine-modified epoxy resin having a secondary amino group can be obtained. Further, by using a secondary amine having a blocked primary amine, an amine-modified epoxy resin having a primary amino group can be prepared. For example, in the preparation of an amine-modified epoxy resin having a primary amino group and a secondary amino group, the primary amino group is blocked with a ketone to make ketimine before reacting with the epoxy resin, and this is used as an epoxy resin. It can be prepared by deblocking after introduction. If necessary, a tertiary amine may be used in combination as the amine to be reacted with the oxylan ring.

Examples of the amino compound include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, triethylamine, N, N-dimethylbenzylamine and N. , Primary amines such as N-dimethylethanolamine, secondary amines or tertiary amines and / or acid salts thereof. Specific examples of the secondary amine having a blocked primary amine include ketimine of aminoethylethanolamine and diketimine of diethylenetriamine. Specific examples of the tertiary amine that may be used as needed include triethylamine, N, N-dimethylbenzylamine, N, N-dimethylethanolamine and the like. Only one of these amines may be used alone, or two or more of these amines may be used in combination.

The amine compound to be reacted with the oxylan ring of the epoxy resin is 50 to 95% by mass of the secondary amine, 0 to 30% by mass of the secondary amine having the blocked primary amine, and 0 to 20% by mass of the primary amine. It is preferable to include it in the range of.

The number average molecular weight of the aminated resin is preferably in the range of 1,000 to 5,000. When the number average molecular weight is 1,000 or more, the obtained cured electrodeposition coating film has good physical properties such as solvent resistance and corrosion resistance. On the other hand, when the number average molecular weight is 5,000 or less, the viscosity of the aminated resin can be easily adjusted to enable smooth synthesis, and the emulsified dispersion of the obtained aminated resin can be easily handled. Become. The number average molecular weight of the aminated resin is more preferably in the range of 2,000 to 3,500.

The amine value of the aminated resin of the present invention is preferably in the range of 100 to 200 (meq / solid content 100 g). When the amine value of the aminized resin is in the above range, it has a sufficient neutralization point, so that the stability over time is improved, and the hydrophilicity is low, so that the blocking property is easily improved. The amine value of the aminized resin is preferably in the range of 130 to 190 (meq / solid content 100 g), more preferably 150 to 180.

The hydroxyl value of the aminated resin is preferably in the range of 150 to 650 mgKOH / g. When the hydroxyl value is 150 or more, the cured electrodeposition coating film is cured well and the appearance of the coating film is also improved. On the other hand, when the hydroxyl group value is 650 or less, the amount of hydroxyl groups remaining in the cured electrodeposition coating film becomes appropriate, and the deterioration of the water resistance of the coating film is likely to be suppressed. The hydroxyl value of the aminated resin is more preferably in the range of 150 to 400 mgKOH / g.

<Blocked polyisocyanate curing agent>
The blocked polyisocyanate curing agent (hereinafter, may be simply referred to as “hardening agent”) is a coating film forming resin constituting an electrodeposition coating film. The blocked polyisocyanate curing agent can be prepared by blocking the polyisocyanate compound with a blocking agent.

Examples of polyisocyanate compounds include aliphatic diisocyanates such as hexamethylene diisocyanate (including trimer), tetramethylene diisocyanate and trimethylhexamethylene diisocyanate, isophorone diisocyanate, and alicyclic such as 4,4'-methylenebis (cyclohexylisocyanate). Examples thereof include aromatic diisocyanates such as the formula polyisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. In the present invention, any polyisocyanate compound may be used, but considering the low-temperature curability and availability, aromatic diisocyanates, particularly 4,4'-diphenylmethane diisocyanate (MDI). Alternatively, hexamethylene diisocyanate (HDI) is preferable.

In the present invention, as the blocking agent for the blocked polyisocyanate curing agent, not only the monool compound (monohydric alcohol) conventionally used conventionally, but also a polyol compound or an amine having a hydroxyl group, or both of them are combined. It is characterized by using. Therefore, the blocking agent that can be used in the present invention will be described separately as (a) a monool compound and (b) a polyol compound or an amine having a hydroxyl group. Monool compounds are monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenolcarbinol, methylphenylcarbinol; ethylene glycol monohexyl ether, Cellosolves such as ethylene glycol mono2-ethylhexyl ether and ethylene glycol monobutyl ether (butyl cellosolve); phenols such as para-t-butylphenol and cresol; Examples include oximes such as oximes. Among these, those that can be preferably used are alkyl alcohols or cellosolves, and particularly preferably cellosolves.

The polyol compounds that can be used as the blocking agent of the present invention are alkylene glycols such as ethylene glycol, butylene glycol, pentaneyl and neopentyl glycol; and polyether type both ends such as polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol phenol. Dires; Polyester-type double-ended polyols obtained from diols such as ethylene glycol, propylene glycol and 1,4-butanediol and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid and sebacic acid; Triols such as methylolpropane and glycerin; alcohols having a valence of 4 or more such as pentaerythritol and sorbitol; and lactams typified by ε-caprolactam and γ-butyrolactam are preferably used. Among these polyhydric alcohols, low molecular weight glycols (eg, butylene glycol and 1,6-hexanediol) or triol (eg, trimethylolpropane) can be preferably used.

Examples of amines having a hydroxyl group include monomethanolamine, dimethanolamine, monoethanolamine, diethanolamine, monopropanolamine, and dipropanolamine. In the present invention, the amine having a hydroxyl group acts as a blocking agent for the amine group to block the isocyanate group, and the hydroxyl group can supplement the decrease in the residual OH functional group concentration. Therefore, an amine having a hydroxyl group is preferable in that the coating film performance (blocking property and repelling resistance) can be easily maintained.

By using a polyol compound and / or an amine having a hydroxyl group in addition to the monool compound as the blocking agent for the blocked polyisocyanate curing agent, the amount of residual OH functional groups (meq / solid content) in the electrodeposition coating film described later will be described later. It is possible to satisfy the quantitative range of g) and prevent deterioration of the coating film performance. The quantitative ratio of the monools to the polyols and / or the amine having a hydroxyl group is not particularly limited, but the mass ratio of the polyol and / or the amine having a hydroxyl group to the monool is (polyol and / or the polyol and / or). Alternatively, an amine having a hydroxyl group) / (monool) = 40/60 to 90/10, preferably 50/50 to 80/20, and more preferably 60/40 to 80/20. When the ratio of monool is in this range, the amount of residual OH functional groups in the electrodeposition coating film, which will be described later, is unlikely to be insufficient, and the coating film performance is likely to be improved. When the ratio of the polyol and / or the amine having a hydroxyl group is in this range, an isocyanate capable of dissociating and reacting with the blocking agent is sufficiently obtained, and the curability is easily improved.

In the present invention, the blocked polyisocyanate curing agent is contained in the paint resin solid content in an amount of 50 to 80% by mass. If the amount of the blocked polyisocyanate curing agent is less than 50% by mass in the paint resin solid content, the curing is insufficient and the coating film characteristics cannot be exhibited. On the contrary, if it exceeds 80% by mass, the cationic component in the cationic electrodeposition coating component is insufficient and electrophoresis does not occur. The blending amount of the blocked polyisocyanate curing agent in the solid content of the paint resin is preferably 50 to 70% by mass, more preferably 50 to 60% by mass.

<Preparation of resin emulsion>
The resin emulsion is prepared by dissolving each of the aminated resin and the blocked polyisocyanate curing agent in an organic solvent to prepare a solution, mixing these solutions, neutralizing with a neutralizing acid, and deionizing water. It can be prepared by diluting with. Examples of the neutralizing acid include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, dimethylolpropionic acid, formic acid and acetic acid. In the present invention, it is more preferable to neutralize the resin emulsion containing the aminated resin and the curing agent with one or more acids selected from the group consisting of formic acid, acetic acid and lactic acid.

The solid content of the resin emulsion is usually preferably 25 to 50% by mass, particularly preferably 35 to 45% by mass, based on the total amount of the resin emulsion. Here, the "solid content of the resin emulsion" means the mass of all the components contained in the resin emulsion that remain solid even after the removal of the solvent. Specifically, it means the total mass of the aminated resin, the curing agent and other solid components added as needed, which are contained in the resin emulsion.

The neutralizing acid is more preferably used in an amount of 10 to 100%, and further preferably in an amount of 20 to 70%, as the equivalent ratio of the neutralizing acid to the equivalent of the amino group of the amineated resin. .. In the present specification, the ratio of the equivalent of the neutralizing acid to the equivalent of the amino group of the aminated resin is referred to as the neutralization rate. When the neutralization rate is 10% or more, the affinity for water is ensured and the water dispersibility is good.

<Pigment dispersion paste>
The cationic electrodeposition coating composition of the present invention may contain a pigment-dispersed paste, if necessary. The pigment dispersion paste is a component arbitrarily contained in the electrodeposition coating composition, and generally includes a pigment dispersion resin and a pigment.

(Pigment dispersion resin)
The pigment dispersion resin is a resin for dispersing a pigment, and is used after being dispersed in an aqueous medium. As the pigment dispersion resin, a pigment dispersion resin having a cationic group such as a modified epoxy resin having at least one selected from a quaternary ammonium group, a tertiary sulfonium group and a primary amino group can be used. Specific examples of the pigment dispersion resin include a quaternary ammonium group-containing epoxy resin and a tertiary sulfonium group-containing epoxy resin. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used.

(Pigment)
The pigment is a pigment generally used in an electrodeposition coating composition. Pigments such as commonly used inorganic and organic pigments such as titanium white (titanium dioxide), carbon black and red iron oxide; such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay. Constituent pigments; iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and rust-preventive pigments such as aluminum phosphomolybate, aluminum zinc phosphomolybate, and the like.

(Manufacturing of pigment dispersion paste)
The pigment dispersion paste is prepared by mixing a pigment dispersion resin and a pigment. The content of the pigment-dispersed resin in the pigment-dispersed paste is not particularly limited, but is, for example, an amount of 20 to 100 parts by mass in terms of the resin solid content ratio with respect to 100 parts by mass of the pigment.

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

In the present specification, the "solid content of the pigment-dispersed paste" means the mass of all the components contained in the pigment-dispersed paste, which remain solid even after the removal of the solvent. Specifically, it means the total mass of the pigment-dispersed resin and the pigment and other solid components added as needed, which are contained in the pigment-dispersed paste.

<Manufacturing of cationic electrodeposition coating composition>
The cationic electrodeposition coating composition of the present invention can be prepared by mixing a resin emulsion containing an aminized resin and a blocked polyisocyanate curing agent, a pigment dispersion paste, an additive and the like by a commonly used method. can.

In the present specification, the "solid content of the electrodeposition coating composition" means the mass of all the components contained in the electrodeposition coating composition and which remain solid even after the removal of the solvent. .. Specifically, the total amount of solid content mass of the aminated resin, the blocked polyisocyanate curing agent, and the pigment dispersion resin, the pigment, and other solid components contained in the electrodeposition coating composition as needed. means.

The solid content of the cationic electrodeposition coating composition of the present invention is preferably 1 to 30% by mass with respect to the total amount of the electrodeposition coating composition. When the solid content of the cationic electrodeposition coating composition is in the above range, a sufficient electrodeposition coating film precipitation amount can be obtained, and the corrosion resistance can be easily improved. In addition, the wrapping property and the painted appearance tend to be good.

The cationic electrodeposition coating composition of the present invention preferably has a pH of 4.5 to 7. When the pH of the cationic electrodeposition coating composition is in the above range, an appropriate amount of acid is present in the cationic electrodeposition coating composition, and the appearance of the coating film and the coating workability are improved. Further, the filterability of the cationic electrodeposition coating composition is improved, and the horizontal appearance of the cured electrodeposition coating film is improved. The pH of the cationic electrodeposition coating composition can be set in the above range by adjusting the amount of neutralizing acid used, the amount of free acid added, and the like. The pH is more preferably 5 to 7.

The pH of the cationic electrodeposition coating composition can be measured using a commercially available pH meter having a temperature compensation function.

The milligram equivalent (MEQ (A)) of the acid with respect to 100 g of the solid content of the cationic electrodeposition coating composition is preferably 40 to 120. The milligram equivalent of acid (MEQ (A)) with respect to 100 g of the resin solid content of the cationic electrodeposition coating composition can be adjusted by the amount of neutralizing acid and the amount of free acid.

Here, MEQ (A) is an abbreviation for mg equivalent (acid), and is the total of mg equivalents of all acids per 100 g of solid content of the paint. In this MEQ (A), about 10 g of the solid content of the electrodeposition coating composition is dissolved in about 50 ml of a solvent (THF: tetrahydrofuran), and then potentiometric titration is performed using a 1 / 10N NaOH solution to carry out potentiometric titration. It is obtained by quantifying the amount of acid contained in the composition.

The cationic electrodeposition coating composition of the present invention is an additive generally used in the coating field, for example, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, propylene glycol monobutyl ether, dipropylene. Organic solvents such as glycol monobutyl ether and propylene glycol monophenyl ether, surfactants such as anti-drying agents and antifoaming agents, viscosity modifiers such as acrylic resin fine particles, anti-repellent agents, vanadium salts, copper, iron, manganese, magnesium. , Inorganic rust preventive such as calcium salt, etc. may be contained as needed. In addition to these, known auxiliary complexing agents, buffers, smoothing agents, stress relaxation agents, brighteners, semi-brighteners, antioxidants, ultraviolet absorbers and the like may be blended depending on the purpose. These additives may be added during the production of the resin emulsion, may be added during the production of the pigment-dispersed paste, or may be added during or after the mixing of the resin emulsion and the pigment-dispersed paste. good.

The cationic electrodeposition coating composition of the present invention may contain other coating film-forming resin components in addition to the above-mentioned aminated resin. Examples of other coating film-forming resin components include acrylic resin, polyester resin, urethane resin, butadiene resin, phenol resin, and xylene resin. Phenol resin and xylene resin are preferable as other coating film-forming resin components that may be contained in the electrodeposition coating composition. Examples of the phenol resin and xylene resin include xylene resins having 2 or more and 10 or less aromatic rings.

The precipitation electrodeposition coating film obtained by the cationic electrodeposition coating composition of the present invention preferably has a coating film viscosity at 110 ° C. in the range of 5,000 to 1,000,000 mPa · s. As used herein, the "precipitated electrodeposition coating film" is an electrodeposition coating film that precipitates on an object to be coated when a cationic electrodeposition coating composition is electrodeposited, and is a coating film in an uncured state. Say. For the precipitation electrodeposition coating film, the temperature of 110 ° C. can be said to be the temperature immediately before the curing reaction of the coating film resin component contained in the electrodeposition coating film starts. When the coating film viscosity under such temperature conditions is 1,000,000 mPa · s or less, the flow of the electrodeposited coating film by heating can be ensured, and the film thickness of the cured electrodeposition coating film becomes non-uniform. Can be avoided. When the coating film viscosity is 5,000 mPa · s or more, it is possible to avoid problems such as the electrodeposition coating film excessively flowing and flowing down due to heating. The coating film viscosity at 110 ° C. is preferably in the range of 5,000 to 500,000 mPa · s, more preferably in the range of 5,000 to 100,000 mPa · s, and is 6,000 to 6,000. It is particularly preferably in the range of 20,000 mPa · s.

The viscosity of the deposited electrodeposition coating film at 110 ° C. can be measured as follows. First, electrodeposition coating is applied to the object to be coated for 180 seconds so that the film thickness is about 15 μm, an electrodeposition coating film is formed, and the electrodeposition coating film is washed with water to remove excess electrodeposition coating composition. Then, after removing excess water adhering to the surface of the electrodeposition coating film, the coating film is immediately taken out without drying. This is used as a sample. By measuring the viscosity of the sample thus obtained using a dynamic viscoelasticity measuring device, the viscosity of the coating film at 110 ° C. can be measured.

The cationic electrodeposition coating composition of the present invention is coated on a steel sheet so as to have a dry film thickness of 15 μm, and baked at 170 ° C. for 20 minutes, and the residual OH functional group amount is 0.4 to 1.6 (meq /). Solid content g) is preferable. The amount of residual OH functional group defines the performance of the coating film after obtaining the coating composition. The amount of residual OH functional group is a theoretical value of the amount of residual hydroxyl groups derived from the aminated resin in the electrodeposition coating film cured by heating. The residual hydroxyl group is a hydroxyl group remaining in the coating film after the aminating resin and the blocked polyisocyanate curing agent have reacted. The theoretical residual OH functional group amount is the isocyanate group amount (meq / solid content g) of the curing agent from the total of the hydroxyl group amount (meq / solid content g) and the primary amine amount (meq / solid content g) of the aminating resin. It is obtained by reducing g). The amount of residual OH functional group is preferably 0.6 to 1.4 meq / solid content g, and more preferably 0.8 to 1.2 meq / solid content g. When the residual OH functional group amount of the coating film coated under the above conditions is within the above range, the adhesion performance and the barrier property of the coating film are likely to be improved.

The above cationic electrodeposition coating composition is applied to a steel sheet so as to have a dry film thickness of 15 μm, and baked at 170 ° C. for 20 minutes, and then the crosslink density of the electrodeposition coating film is 0.5 to 5.0 mmol / cc. Is preferable. The internal stress of the electrodeposition coating film at the time of forming the electrodeposition coating film is preferably 7.5 MPa or less.

The crosslink density can be measured using a dynamic viscoelasticity measuring device, for example, Rheogel manufactured by UBM. Specifically, it is obtained based on the following equation using the dynamic Young's modulus (E') obtained by applying a vibration having a frequency of 11 Hz to the coating film at a heating rate of 2 ° C. per minute. Crosslink density is one of the indicators of the degree of crosslink reaction.
(Equation) E'= 3nRT
(E'= dynamic Young's modulus; n = crosslink density; R = gas constant; T = absolute temperature)
When the cross-linking density is in the above range, the coating film performance is likely to be good, the internal stress is likely to be small, and the adhesion is likely to be improved. The crosslink density is preferably 0.8 to 3.0 mmol / cc, more preferably 1.0 to 3.0 mmol / cc.

The internal stress of the electrodeposition coating film is measured by the strip type electrodeposition stress test method. If the internal stress exceeds the appropriate range, poor adhesion and deterioration of corrosion resistance are likely to occur. When the internal stress of the electrodeposition coating film is 7.5 MPa or less, the adhesion to the substrate is more likely to be improved. The internal stress is preferably 6.0 MPa or less, more preferably 5.0 MPa or less.

<Electrodeposition coating and electrodeposition coating film formation>
An electrodeposition coating film can be formed by electrodeposition coating on an object to be coated using the cationic electrodeposition coating composition of the present invention. In electrodeposition coating using the cationic electrodeposition coating composition of the present invention, a voltage is applied between the object to be coated and the anode with the object to be coated as a cathode. As a result, the electrodeposition coating film is deposited on the object to be coated.

As the object to be coated on which the cationic electrodeposition coating composition of the present invention is applied, various energized objects to be coated can be used. Examples of objects to be coated that can be used include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy-based plated steel sheets, zinc-iron alloy-based plated steel sheets, and zinc-magnesium alloy-based plating. Examples thereof include steel sheets, zinc-aluminum-magnesium alloy-based plated steel sheets, aluminum-based plated steel sheets, aluminum-silicon alloy-based plated steel sheets, and tin-based plated steel sheets.

In the electrodeposition coating process, electrodeposition coating is performed by immersing the object to be coated in the electrodeposition coating composition and then applying a voltage of 50 to 450V. When the applied voltage is in the above range, sufficient electrodeposition is performed and the appearance of the coating film tends to be good. During electrodeposition coating, the bath solution temperature of the coating composition is usually adjusted to 10 to 45 ° C.

The time for applying the voltage varies depending on the electrodeposition conditions, but can generally be 2 to 5 minutes.

The film thickness of the electrodeposition coating film finally obtained by heat curing is preferably 5 to 60 μm, more preferably 10 to 25 μm. When the film thickness of the electrodeposition coating film is 5 μm or more, the rust prevention property is likely to be improved.

The electrodeposited coating film precipitated as described above can be cured by washing with water as necessary and then heating at, for example, 140 to 200 ° C., preferably 140 to 170 ° C. for 10 to 30 minutes. .. As a result, a cured electrodeposition coating film is formed. Curing at 140 ° C to 200 ° C is lower than the normal curing temperature, and it can be said that it has low-temperature curability. Curing at low temperatures greatly reduces the amount of energy used during curing.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise specified.

Production Example 1-1 Production of amineized resin (resin 1) 92 parts of methylisobutyl ketone (MIBK), 940 parts of bisphenol A type epoxy resin (trade name: DER-331J, manufactured by Dow Chemical Co., Ltd.), 370 parts of bisphenol A in a reaction vessel. , 15 parts of octylic acid and 2 parts of dimethylbenzylamine were added. The temperature in the reaction vessel was maintained at 120 ° C., and the reaction was carried out until the epoxy equivalent reached 900 g / eq. Then, the reaction vessel was cooled until the temperature in the reaction vessel reached 110 ° C. Then, a mixture of 178 parts of diethylenetriamine diketimine (methyl isobutyl ketone solution having a solid content of 73%) and 89 parts of diethanolamine was added, and the mixture was reacted at 110 ° C. for 1 hour. As a result, an aminized resin (cation-modified epoxy resin: resin 1) was obtained.

The number average molecular weight of the resin 1 was 2,800, and the amine value was 180 (meq / solid content 100 g).

Production Example 1-2 Production of amineized resin (resin 2) In a reaction vessel, 92 parts of methylisobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co., Ltd.), 370 parts of bisphenol A, octylic acid. 118 parts and 2 parts of dimethylbenzylamine were added. The temperature in the reaction vessel was maintained at 120 ° C., and the reaction was carried out until the epoxy equivalent reached 900 g / eq. Then, the reaction vessel was cooled until the temperature in the reaction vessel reached 110 ° C. Then, a mixture of 92 parts of diethylenetriamine diketimine (methyl isobutyl ketone solution having a solid content of 73%) and 56 parts of diethanolamine was added, and the mixture was reacted at 110 ° C. for 1 hour. As a result, an aminized resin (cation-modified epoxy resin: resin 2) was obtained.

The number average molecular weight of the resin 2 was 2,800, and the amine value was 100 (meq / solid content 100 g).

Production Example 1-3 Production of amineized resin (resin 3) In a reaction vessel, 92 parts of methylisobutyl ketone, 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co., Ltd.), 370 parts of bisphenol A, octylic acid. 130 parts and 2 parts of dimethylbenzylamine were added. The temperature in the reaction vessel was maintained at 120 ° C., and the reaction was carried out until the epoxy equivalent reached 900 g / eq. Then, the reaction vessel was cooled until the temperature in the reaction vessel reached 110 ° C. Then, a mixture of 79 parts of diethylenetriamine diketimine (methyl isobutyl ketone solution having a solid content of 73%) and 54 parts of diethanolamine was added, and the mixture was reacted at 110 ° C. for 1 hour. As a result, an aminized resin (cation-modified epoxy resin: resin 3) was obtained.

The number average molecular weight of the resin 3 was 2,800, and the amine value was 90 (meq / solid content 100 g).

Production Example 2-1 Production of Blocked Polyisocyanate Hardener (1) 362 parts of diphenylmethane diisocyanate (MDI) and 80 parts of MIBK are charged in a reaction vessel, heated to 80 ° C., and then 192 parts of butyl cellosolve is applied over 1 hour. And dropped. After further adding 128 parts of 1,6 hexanediol and further heating at 100 ° C. for 4 hours, it was confirmed by measurement of the IR spectrum that the absorption based on the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 40 parts of MIBK was added to obtain a blocked polyisocyanate curing agent (1) (solid content 85%).

Production Example 2-2 Production of Blocked Polyisocyanate Hardener (2 ) 362 parts of diphenylmethane diisocyanate (MDI) and 80 parts of MIBK were placed in a reaction vessel and heated to 80 ° C. Then, 253 parts of butyl cellosolve was added dropwise over 1 hour. Further, 72 parts of trimethylolpropane was added dropwise, and the mixture was further heated at 100 ° C. for 4 hours. In the measurement of the IR spectrum, it was confirmed that the absorption based on the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 40 parts of MIBK was added to obtain a blocked polyisocyanate curing agent (2) (solid content 85%).

Production Example 2-3 Production of Blocked Polyisocyanate Hardener (3 ) 362 parts of diphenylmethane diisocyanate (MDI) and 80 parts of MIBK were placed in a reaction vessel and heated to 80 ° C. Then, 192 parts of butyl cellosolve was added dropwise over 1 hour. Further, 145 parts of trimethylolpropane was added dropwise, and the mixture was further heated at 100 ° C. for 4 hours. In the measurement of the IR spectrum, it was confirmed that the absorption based on the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 43 parts of MIBK was added to obtain a blocked polyisocyanate curing agent (3) (solid content 85%).

Production Example 2-4 Production of Blocked Polyisocyanate Hardener (4 ) 168 parts of hexamethylene diisocyanate (HDI) and 42 parts of MIBK were placed in a reaction vessel and heated to 60 ° C. Here, 36 parts of trimethylolpropane dissolved in 104 parts of methyl ethyl ketooxime (MEK oxime) was added dropwise at 60 ° C. over 2 hours. After further heating at 75 ° C. for 4 hours, it was confirmed in the measurement of the IR spectrum that the absorption based on the isocyanate group disappeared. As a result, a blocked polyisocyanate curing agent (4) was obtained (solid content 85%).

Production Example 2-5 Production of Blocked Polyisocyanate Hardener (5 ) 362 parts of diphenylmethane diisocyanate (MDI) and 80 parts of MIBK were placed in a reaction vessel and heated to 80 ° C. Then, 319 parts of butyl cellosolve was added dropwise over 1 hour, and the mixture was further heated at 100 ° C. for 4 hours. Then, in the measurement of the IR spectrum, it was confirmed that the absorption based on the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 43 parts of MIBK was added to obtain a blocked polyisocyanate curing agent (5) (solid content 85%).

Production Example 3 Production of pigment-dispersed resin In a reaction vessel equipped with a stirrer, a cooling tube, a nitrogen introduction tube, and a thermometer, 385 parts of bisphenol A type epoxy resin, 120 parts of bisphenol A, 95 parts of octylate, 2-ethyl-4- One part of a 1% solution of methylimidazole was charged and reacted at 160 to 170 ° C. for 1 hour under a nitrogen atmosphere. Then, after cooling to 120 ° C., 198 parts of a methyl isobutyl ketone solution (solid content 95%) of 2-ethylhexanolified half-blocked tolylene diisocyanate was added. After holding the reaction mixture at 120-130 ° C. for 1 hour, 157 parts of ethylene glycol mono-n-butyl ether was added. Then, it was cooled to 85 to 95 ° C. and homogenized. Next, 277 parts of diethylenetriamine diketimine (methyl isobutyl ketone solution having a solid content of 73%) was added, and the mixture was stirred at 120 ° C. for 1 hour. Subsequently, 13 parts of ethylene glycol mono-n-butyl ether was added to produce an aminated resin. Then, 18 parts of ion-exchanged water and 8 parts of formic acid were mixed with the above-mentioned aminated resin and stirred for 15 minutes. Further, 200 parts of ion-exchanged water was mixed to obtain a resin solution (resin solid content 25%) of a pigment-dispersed resin (average molecular weight 2,200).

Production Example 4-1 Production of Electrodeposition Paint Resin Emulsion (Em1) 400 g (solid content) of the resin (resin 1) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-1 ( 1) 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em1).

Production Example 4-2 Production of Electrodeposition Paint Resin Emulsion (Em2) 400 g (solid content) of the resin (resin 1) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-2 ( 2) 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em2).

Production Example 4-3 Production of Electroplated Paint Resin Emulsion (Em3) 400 g (solid content) of the resin (resin 1) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-3 ( 3) 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em3).

Production Example 4-4 Production of Electrodeposition Paint Resin Emulsion (Em4) 500 g (solid content) of the resin (resin 1) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-1 ( 1) 500 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em4).

Production Example 4-5 Production of Electroplated Paint Resin Emulsion (Em5) 200 g (solid content) of the resin (resin 1) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-3 ( 3) 800 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em5).

Production Example 4-6 Production of Electroplated Paint Resin Emulsion (Em6) 400 g (solid content) of the resin (resin 2) obtained in Production Example 1-2 and the blocked isocyanate curing agent (3) obtained in Production Example 2-3. 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em6).

Production Example 4-7 Production of Electroplated Paint Resin Emulsion (Em7) 400 g (solid content) of the resin (resin 2) obtained in Production Example 1-2 and the blocked isocyanate curing agent (4) obtained in Production Example 2-4. 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em7).

Production Example 4-8 Production of Electrodeposition Paint Resin Emulsion (Em8) 650 g (solid content) of the resin (resin 3) obtained in Production Example 1-3 and the blocked polyisocyanate curing agent obtained in Production Example 2-5 ( 5) 350 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em8).

Production Example 4-9 Production of Electrodeposition Paint Resin Emulsion (Em9) 500 g (solid content) of the resin (resin 3) obtained in Production Example 1-3 and the blocked polyisocyanate curing agent obtained in Production Example 2-5 ( 5) 500 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em9).

Production Example 4-10 Production of Electrodeposition Paint Resin Emulsion (Em10) 400 g (solid content) of the resin (resin 3) obtained in Production Example 1-3 and the blocked polyisocyanate curing agent obtained in Production Example 2-5 ( 5) 600 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em10).

Production Example 4-11 Production of Electrodeposition Paint Resin Emulsion (Em11) 200 g (solid content) of the resin (resin 3) obtained in Production Example 1-3 and the blocked polyisocyanate curing agent obtained in Production Example 2-5 ( 5) 800 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em11).

Production Example 4-12 Production of Electroplated Paint Resin Emulsion (Em12) 100 g (solid content) of the resin (resin 3) obtained in Production Example 1-1 and the blocked polyisocyanate curing agent obtained in Production Example 2-1 ( 5) 900 g (solid content) was mixed, and ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% (15 g) with respect to the solid content. Next, formic acid was added so as to have a neutralization rate of 40% to neutralize the mixture, and ion-exchanged water was added to slowly dilute the mixture. Then, methyl isobutyl ketone was removed under reduced pressure so that the solid content became 36% to obtain an electrodeposition coating resin emulsion (Em12).

Production Example 5 Production of Pigment Dispersion Paste for Electrodeposition Paint 120 parts of the pigment dispersion resin obtained in Production Example 3, carbon black 2.0 parts, kaolin 100.0 parts, titanium dioxide 72.0 parts, dibutyltin oxide 8. 0 part, 18.0 part of aluminum phosphomolybate and 184 parts of ion-exchanged water were mixed and dispersed until the particle size became 10 μm or less to obtain a pigment-dispersed paste (solid content 48%).

Example 1
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em1) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 2
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em2) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 3
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em3) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 4
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em4) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 5
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em5) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 6
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em6) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Example 7
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em7) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Comparative Example 1
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em8) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Comparative Example 2
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em9) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Comparative Example 3
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em10) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Comparative Example 4
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em11) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Comparative Example 5
To the stainless steel container, 1394 g of ion-exchanged water, 560 g of the resin emulsion (Em12) and 41 g of the pigment-dispersed paste obtained in Production Example 5 were added. Then, it was aged at 40 ° C. for 16 hours to prepare an electrodeposition coating composition.

Electrodeposition coating the formation of cold-rolled steel sheet (JISG3141, SPCC-SD), was immersed for 2 minutes at 50 ℃ in the Surf Cleaner EC90 (manufactured by Nippon Paint Surf Chemicals, Inc.), it was degreased. Next, the above cold-rolled steel sheet was immersed in a zirconium chemical conversion treatment solution containing 0.005% of ZrF and adjusted to pH 4 with NaOH at 40 ° C. for 90 seconds to perform a zirconium chemical conversion treatment. Next, a required amount of 2-ethylhexyl glycol was added to the electrodeposition coating compositions obtained in Examples and Comparative Examples so that the film thickness of the electrodeposition coating film after curing was 15 μm. Then, the steel sheet was immersed in the electrodeposition coating composition, the pressure was increased for 30 seconds, the voltage reached 180 V, and then the voltage was applied under the condition that the steel sheet was held for 150 seconds. As a result, an uncured electrodeposition coating film was deposited on the object to be coated.

The uncured electrodeposition coating film thus obtained was baked and cured at 140 ° C. for 25 minutes to obtain an electrodeposition coating plate having a cured electrodeposition coating film.

The following evaluation test was conducted using the electrodeposition coating composition and the coating plate obtained in the above Examples and Comparative Examples. The results are shown in Table 1.

The electrodeposited coating film obtained with low temperature curability was placed in a Soxhlet extractor and extracted under reflux conditions of acetone for 6 hours, and the gel fraction of the coating film was calculated according to the following formula.
◎; 90% or more ○; 80% to 89%
×; 79% or less

Gel fraction (%) = [mass after extraction (g) / mass before extraction (g)] x 100

Stability of electrodeposition coating composition (stability over time)
The state of the coating composition was visually determined in a state where the electrodeposition coating composition was allowed to stand or agitated, and the stability was evaluated. The evaluation criteria are as follows. The term "stable" as used herein means that the pigment does not settle within 15 minutes after the stirring is stopped.
Evaluation Criteria ○: Stable in the state where the electrodeposition coating composition is allowed to stand ○ △: Although it is not stable in the state where the electrodeposition coating composition is allowed to stand still, it stabilizes immediately by stirring again △: Electroelectricity It is stable when the coating composition is continuously stirred. ×: It is not stabilized even when the electrodeposition coating composition is continuously stirred.

Adhesion (electrolytic peeling test)
A cut scratch was made on the cured coating film with a knife so as to reach the substrate, and electrolysis was performed at a current value of 0.01 mA for 12 hours. Then, the tape was peeled off, and the peeling widths on both sides thereof were evaluated. The evaluation criteria are as follows.
Evaluation criteria ○: Peeling width less than 3 mm ○ △: Peeling width 3 mm or more and less than 5 mm △: Peeling width 5 mm or more and less than 10 mm ×: Peeling width 10 mm or more

Corrosion resistance test (Salt-solution Dipping Test (SDT))
The cured coating film was cut with a knife so as to reach the substrate, and the coated plate was immersed in 5% saline solution at 55 ° C. for 240 hours. Then, the tape was peeled off, and the peeling widths on both sides thereof were evaluated.
Evaluation criteria ○: Peeling width less than 5 mm ○ △: Peeling width 5 mm or more and less than 10 mm Δ: Peeling width 10 mm or more and less than 15 mm ×: Peeling width 15 mm or more

A repellent-resistant naturally dried coating plate was placed horizontally on a net, and an aluminum cup was fixed with double-sided tape in the center. Drop a drop of water on the aluminum cup with a dropper, then drop another drop of oil on top of the water drop. The coated plate on which water and oil were dropped was baked and cured at 140 ° C. for 25 minutes while keeping it horizontal. The craters formed on the obtained cured coating film were evaluated. Craters are created by the oil in the aluminum cup popping and splashing out. The evaluation criteria are as follows.
Evaluation criteria ○: Crater diameter is 1 mm or less Δ: Crater diameter is 1 mm to less than 3 mm ×: Crater diameter is 3 mm or more

Table 1 below shows the coating composition (amined resin compounding amount%, blocked polyisocyanate type and compounding amount%), and blocking polyisocyanate blocking agent in Examples 1 to 7 and Comparative Examples 1 to 5. Composition (composition% of each blocking agent and monool / polyol mass ratio), amineation of paint (meq / solid content 100 g), residual OH functional group amount in coating film (meq / solid content g), coating film The crosslink density, the internal stress (MPa) of the coating film, and each of the above performance evaluations (low temperature curing (curing at 140 ° C.), stability over time, adhesion, corrosion resistance (SDT) and cissing resistance) are also described.

The amount of residual OH functional group is a theoretical value of the amount of residual hydroxyl group. The theoretical residual hydroxyl group amount is the isocyanate group amount (meq / solid content g) of the curing agent from the total of the hydroxyl group amount (meq / solid content g) and the primary amine amount (meq / solid content g) of the aminating resin. I asked for it by reducing it.

As is clear from Table 1 above, in the examples of the present invention, the evaluation of the coating film is in the range where all the evaluations are satisfied. On the other hand, in Comparative Example 1, the amount of the blocked polyisocyanate curing agent is small, the low temperature curing property is insufficient, and the corrosion resistance and the repelling resistance are insufficient. In Comparative Example 2, the amount of the blocked polyisocyanate curing agent is within the range of the present invention, but the blocking agent is only a monool compound, and the stability over time and the adhesion of the coating film are insufficient. In Comparative Example 3, the amount of the blocked polyisocyanate curing agent is increased in the same manner as in Comparative Example 2, but the amine value and the amount of residual OH functional group are insufficient at 0, and the stability with time is adhered. There is a big shortage of sex. In Comparative Examples 4 and 5, the amount of the blocked polyisocyanate curing agent is too large, and the low-temperature curing property is excellent, but the coating film performance is not practically durable.

According to the present invention, there is provided a cationic electrodeposition coating composition that enables low temperature curability while maintaining coating film performance.

This application claims priority based on Japanese Patent Application No. 2020-124322 filed in Japan on July 21, 2020, and all of the contents thereof are incorporated herein by reference.

Claims

A cationic electrodeposition coating composition containing an aminized resin and a blocked polyisocyanate curing agent.
The blocked polyisocyanate curing agent is contained in the paint resin solid content in an amount of 50 to 80% by mass.
The blocking agent that forms the blocked polyisocyanate curing agent is
(A) Monool compound and
(B) With either or both of a polyol compound or an amine having a hydroxyl group,
Consists of combinations
The amount of residual OH functional groups in the formed electrodeposition coating film is 0.4 to 1.6 (meq / solid content g).
Cationic electrodeposition coating composition.
The cationic electrodeposition coating composition according to claim 1, wherein the amine-based resin has an amine value of 100 to 200 (meq / solid content 100 g).
The mass ratio of the polyol compound and the amine having a hydroxyl group to the monool compound of the blocking agent forming the blocked polyisocyanate curing agent is (monool compound) / (polyol compound and amine having a hydroxyl group) = 60/40 to The cationic electrodeposition coating composition according to claim 1 or 2, which is 10/90.
The cationic electrodeposition coating composition according to any one of claims 1 to 3, which can be cured at a temperature of 140 ° C to 200 ° C.
The crosslink density of the electrodeposition coating film after coating the cationic electrodeposition coating composition on a steel sheet so as to have a dry film thickness of 15 μm and baking at 170 ° C. for 20 minutes is 0.5 to 5.0 mmol / cc. The cationic electrodeposition coating composition according to any one of claims 1 to 4, wherein the internal stress at the time of forming the electrodeposition coating film is 7.5 MPa or less.
A cationic electrodeposition coating film coated with the cationic electrodeposition coating composition according to any one of claims 1 to 5.