JPS5938995B2 - Water-based thermosetting resin coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-based thermosetting resin coating composition.

More specifically, it is composed of a cationic thermosetting urethane resin and a water-insoluble resol-type phenolic resin, which are made into a water bath or water-dispersed by acid neutralization, and have excellent physical properties, corrosion resistance, and water resistance. This invention relates to a water-based thermosetting resin coating composition. Conventionally, solvent-based paints have been gradually converted to non-polluting paints, especially water-based paints, from the viewpoint of resource saving and non-pollution, and this conversion is expected to further advance in the future.

Electrodeposition paints, which are a type of water-based paints, are already widely used as undercoat paints for automobiles due to their economic efficiency such as labor saving and paint savings, and from the viewpoint of pollution control. However, the corrosion resistance of coating films obtained from currently used anionic electrodeposition paints cannot be said to be sufficient. As the resin for anionic electrodeposition coatings, polycarboxylic acid resins having a skeleton of drying oil, alkyd resin, polybutadiene resin, epoxy ester resin, acrylic resin, etc. are used. Usually, these are neutralized with a basic compound such as an organic amine, and then made into a water bath or water-dispersed. The insufficient corrosion resistance of such anionic electrodeposition paint films is thought to be one of the causes of the carboxyl groups present in the cured paint film. Recently, cationic electrodeposition paints have begun to attract attention for the purpose of improving the corrosion resistance of the anionic electrodeposition paints. The resin for the cationic electrodeposition coating includes epoxy resin, urethane resin, acrylic resin, polybutadiene resin,
Polyamino resins with skeletons such as alkyd resins are used. Usually, these are neutralized with an organic acid and made into a water bath or water dispersion. In such a polyamino resin, since the amino groups in the coating film act as a corrosion inhibitor, a coating film having a high degree of corrosion resistance can be obtained. By the way, corrosion in automobiles mainly using electrodeposition paints as described above can be broadly classified into the following two types: (1) The paint film is damaged by some external factor (for example, impact from pebbles, etc.); (2) So-called pitting corrosion, where corrosion progresses from the damaged parts, and (2) so-called pitting corrosion, which progresses from incomplete chemical conversion treatment parts or incompletely painted parts.

In general, cationic electrodeposition paint coatings have effective anti-corrosion properties even on imperfectly chemically treated steel sheets.

However, the susceptibility to damage caused by the external factors described in (1) above differs significantly depending on the type of resin skeleton. Among these, urethane resins in particular have excellent coating film properties such as flexibility, so they are less likely to be damaged by external factors, and their other performance balances are generally better than other resins. Such cation type urethane resin is, for example,
No. 36958, No. 50-17234, No. 50
-24982 publication, 51-2491 publication, 53
No. 138317, No. 53-2894, No. 53
This method is disclosed in Japanese Patent Application Laid-open No. 48-96696, Japanese Patent Application Laid-open No. 48-99297, Japanese Patent Application Laid-open No. 48101430, and the like. However, the above-mentioned cationic urethane resins also have the drawback of insufficient coating film performance such as corrosion resistance and water resistance. Furthermore, it has been known to use a phenol resin in combination with an epoxy resin or acrylic resin cationic coating composition.

For example, (1) composition 5 consisting of polyepoxide solubilized with a quaternary onium salt and unsaturated methylol phenyl ether (Japanese Patent Publication No. 11684/1984), (2) nitrogen in acrylic resins, epoxide esters, etc. A composition consisting of a basic resin and a phenolplast resin partially or completely etherified with a lower alcohol (Japanese Patent Publication No. 52-JMo V0), (3) consisting of an acrylic resin and a water-soluble phenol formaldehyde resin. Composition (Japanese Patent Publication No. 45-12395, Japanese Patent Publication No. 45-12396)
(Japanese Patent Publication No. 49-39351), (4) Composition using a reaction product of epoxy ester resin and partially etherified phenol resin (Japanese Patent Publication No. 49-26292), (5) Epoxy resin Also known are compositions using epoxy ester resins or reaction products of these and trishydroxymethylphenol allyl ether (Japanese Unexamined Patent Publication No. 134897/1989). However, in the above-mentioned known compositions, epoxy resins have insufficient flexibility in the coating film and tend to reduce corrosion resistance after impact tests, while acrylic resins and epoxy ester resins have poor corrosion resistance and water resistance. It had the disadvantage of insufficient performance. In addition, those that are combined with water-soluble phenolic resin similarly have poor corrosion resistance and water resistance, and those that are combined or combined with etherified phenolic resin are
180° C. or lower) had the disadvantage that the physical properties of the coating film, corrosion resistance, and water resistance upon curing were poor. The present inventors have arrived at the present invention as a result of various studies aimed at improving corrosion resistance and water resistance while maintaining coating film properties such as flexibility, which are characteristic of urethane resins.

In other words, by using a water-insoluble resol-type phenolic resin together with a urethane resin, corrosion resistance and water resistance are significantly improved without deteriorating the physical properties of the coating film such as flexibility, and the appearance of the coating film is improved (the appearance of wrinkles is reduced). The present invention was completed based on the discovery that it exhibits good effects in terms of prevention) and low-temperature curability.

In other words, in the present invention, (4) a cationic thermosetting urethane resin, (B) aldehydes/phenols (molar ratio) = 1.0 to 2.5, ammonia, primary amine or secondary The present invention relates to a water-based thermosetting resin coating composition comprising a water-insoluble resol type thermosetting phenolic resin produced in the presence of an amine, an acid as an O neutralizing agent, and (D) water as a diluent.

The cationic thermosetting urethane resin used in the present invention is a urethane resin having a tertiary amino group, a blocked isocyanate group, and an active hydrogen in the molecule.

For example, Japanese Patent Publication No. 50-17234, No. 51-249
Publication No. 1, Publication No. 53-38317, Publication No. 53-289
Publication No. 4, Publication No. 53-2895, JP-A-48-96
No. 696, No. 48-99297, No. 48-1
This includes those disclosed in Publication No. 01430 and the like. The resin is generally a reaction product (hereinafter referred to as reaction product a) of a polyurethane prepolymer having an isocyanate group at the end and a tertiary amine having at least two hydroxyl groups in one molecule. It is obtained by the reaction of a hydroxyl group with an isocyanate group in a product obtained by equimolar addition reaction of an organic diisocyanate and a monofunctional blocking agent (hereinafter referred to as product b).

The polyurethane prepolymer having isocyanate groups at the terminals contains polyisocyanate and polyol in an amount of at least 1 equivalent, preferably 1.0 equivalent per equivalent of polyol.
It can be synthesized by reacting about 5 to 2.0 equivalents of polyisocyanate.

The preferable polyisocyanate contains 2 in 1 molecule.
Aromatic or aliphatic polyisocyanates containing isocyanate groups, such as phenylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, isoborone diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, tetra methylene diisocyanate,
Examples include propylene diisocyanate, ethylene diisocyanate, and hydrogenated products of the aromatic diisocyanates.

Suitable polyols include glycols, polyethers, and polyesters having two hydroxyl groups in one molecule.

Specifically, glycols such as ethylene glycol, propylene glycol, butylene glycol, and neopentyl glycol; tetrahydrofuran, ethylene oxide,
Examples include polyethers made of polymers or copolymers such as propylene oxide; and polyesters synthesized from polyhydric alcohols and polyhydric carboxylic acids by known methods. Preferably, the synthesis of the polyurethane prepolymer is carried out in a solvent. The solvent is preferably a solvent that is inert to isocyanate groups and has a high affinity for water, such as acetone, methyl ethyl ketone, acetonitrile, dioxane, dimethylformamide, and acetic acid ester. Then, the urethane prepolymer having isocyanate groups at its terminals is subjected to an addition reaction with a tertiary amine having at least two hydroxyl groups in one molecule.

The amount of the tertiary amine used is at least one, preferably two or more, hydroxyl groups in the tertiary amine per one isocyanate group in the polyurethane prepolymer.

As the tertiary amine, for example, methyldiethanolamine, triethanolamine, tris(2-hydroxypropyl)amine, an adduct of 1 mol of ethylenediamine and 4 mol of propylene oxide, or a quaternized product of these can be used.

In this way, reaction product a can be obtained. On the other hand, product b can be obtained by an equimolar addition reaction of an organic diisocyanate and a monofunctional blocking agent, for example, by reacting both in a 1:1 molar ratio in a solvent at a temperature of 40 to 110°C. . As the organic diisocyanate used in obtaining the product b, the same diisocyanate as used in obtaining the polyurethane polyol can be used. In addition, the monofunctional blocking agent includes blocking agents normally used in the synthesis of blocking isocyanates, such as phenols, alcohols, lactams, oximes, acid amides, imides, amines, and imidazoles. , ureas, carbamates, imines, mercaptans, sulfites, and the like can be used.
As the solvent used in the addition reaction, the same solvent as that used when synthesizing the polyurethane prepolymer can be used. In the addition reaction, it is not preferable to produce a diblock form of the organic diisocyanate.

Since such diplock bodies become insoluble substances when the urethane resin is water-solubilized and cause changes in electrodeposition characteristics over time, it is necessary to set reaction conditions so as to prevent the formation of diplock bodies as much as possible. The cationic thermosetting urethane resin of the present invention can be obtained by reacting the isocyanate groups in the addition reaction product b thus obtained with the hydroxyl groups in the reaction product a. The mixing ratio of component a and component b is preferably such that 20 to 80% of the hydroxyl groups present in reaction product a react with the isocyanate groups present in addition reaction product b.

The cationic thermosetting urethane resin thus obtained is
It can be used by mixing or partially reacting with known cationic epoxy resins, acrylic resins, polybutadiene resins, and alkyd resins.

Further, if necessary, an active water-miscible solvent can be added to or substituted for the isocyanate group. The water-insoluble resol type phenolic resin used in the present invention is a thermosetting resin synthesized from aldehydes and phenols.

In particular, it is a water-insoluble resol type thermosetting phenolic resin obtained in the presence of ammonia; a primary amine such as methylamine and ethylamine; or a secondary amine catalyst such as dimethylamine and diethylamine.

As the phenols, trifunctional or higher functional phenols are preferably used from the viewpoint of water resistance, corrosion resistance, and solvent resistance of the coating film, but difunctional phenols can also be used in combination.

Examples of trifunctional or higher functional phenols include carbolic acid,
Examples include m-cresol, resorcinol, m-methoxyphenol, m-ethoxyphenol, bisphenol A, and the like.

Examples of the bifunctional phenols include p-cresol, o-cresol, p-methoxyphenol, p-ethoxyphenol, pt-butylphenol, p-nonylphenol, and the like.

The trifunctional or higher functional phenols may be used alone as a resol type phenolic resin, or mixed phenols of two or more trifunctional or higher functional phenols, or mixed phenols with bifunctional phenols. Good too.

Examples of the aldehydes used in the phenolic resin of the present invention include formaldehyde (aqueous solution, organic solvent solution, organic solvent-aqueous solution), paraformaldehyde, furfural, and acetaldehyde.

In the production of the phenolic resin of the present invention, since ammonia, primary amines, and secondary amines are used as hornworms as described above, these amino groups participate in the reaction system between phenols and aldehydes. , a cationic resin in which nitrogen atoms are introduced into a water-insoluble resol-type phenolic resin is obtained.

Therefore, the phenolic resin has good water dispersion stability, electrodeposition properties,
It also exhibits excellent performance in terms of compatibility with cationic thermosetting urethane resins, and as a result, coating films with even better water resistance and corrosion resistance can be obtained. For example, in the case of an ammonia catalyst, a condensate with the following structure is obtained. A typical production example of the water-insoluble resol type phenolic resin is shown below.

First, a mixture of aldehydes/phenols = 1.0 to 2.5 (molar ratio) is charged into a reaction vessel, the pH of the reactant is adjusted to 7.5 to 9.0 using the catalyst, and then
React at 0-100°C for 1-4 hours.

After the reaction is completed, the reaction mixture is neutralized with an acid compound so that the pH of the reaction mixture becomes 4.0 to 5.0, water is added, and the mixture is stirred well and left to stand still. When the reactant is separated into two layers, a resin layer and an aqueous layer, the aqueous layer is removed and the resin layers are collected and dehydrated by heating under reduced pressure. In this case, care should be taken to ensure that the temperature does not exceed about 140° C., as the resin tends to gel. After the dehydration reaction is completed, a solvent is added from the solvent tank to obtain a resin solution with a desired resin content. Generally, the solid content is 30 to 80 weight? It is. Examples of the solvent include alcohols such as methyl alcohol, ethyl alcohol, butyl alcohol, and propyl alcohol; ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and isopropyl glycol; acetone, methyl ethyl ketone, and the like; Examples include ketones; esters such as ethyl acetate and butyl acetate; and aromatics such as toluene and xylene. These solvents can be used alone or as a mixed solvent of two or more.

In addition, etherification of the resol type phenolic resin with a lower alcohol can improve thermal stability and compatibility (with a solvent or a combined resin), but low-temperature curability and coating performance deteriorate. In the present invention, it is preferable not to etherify.

If etherification is necessary, it should be etherified to 30% or less of the methylol groups. The resol type phenolic resin may be mixed or co-condensed with various modifiers and modified resins, if necessary. For example, cashew nut shell liquid, rosin, drying oil, polyvinyl acetal, aniline resin, urea resin, melamine resin, etc. can be used.
The coating composition of the present invention mixes the cationic thermosetting urethane resin and the water-insoluble resol thermosetting phenol resin, and then cationizes the tertiary amino groups in the resin with an acid as a neutralizing agent. Obtained by diluting with water.
The urethane resin and phenolic resin are preferably mixed at a temperature ranging from room temperature to about 90° C., and care must be taken to avoid gelation.

The water-insoluble resol type phenolic resin is 1 to 1% of the total solid content of the urethane resin and the water-insoluble resol type phenolic resin.
It is preferable to mix in a range of 30% by weight. In the above range, if the phenolic resin is less than 1% by weight, the coating film will not have any effects such as water resistance, humidity resistance, corrosion resistance, low temperature curing properties, etc. On the other hand, if the phenolic resin exceeds 30% by weight, the urethane resin will not be effective. The flexibility of the coating film, which is a characteristic, tends to decrease, the physical properties of the coating film tend to deteriorate, and it is difficult to obtain a stable aqueous dispersion.

As the acid for neutralizing the tertiary amino group, organic acids such as formic acid, acetic acid, propionic acid, lactic acid, and citric acid are used.

If necessary, the tertiary amino group may be quaternized by a known method. The amount of the acid as the neutralizing agent is equal to or less than equimolar to the tertiary amino group in the resin. The thus obtained coating composition of the present invention can be used in the form of an aqueous dispersion for various purposes and coating methods; however, various organic solvents are used in the process of obtaining the cationic urethane resin. , therefore some organic solvents can be included in the coating composition.

However, its content should be less than 20% by weight of the total of water and organic solvent in the coating composition. The aqueous thermosetting resin coating composition of the present invention is mixed with coloring pigments, extender pigments, anticorrosive pigments, hardening accelerators, surface conditioners, antifoaming agents, etc. as necessary, and is then enamelized by a conventional kneading method. be able to.

The composition is suitable for electrodeposition coating, but is also suitable for other conventional coating methods such as air spray coating, dip coating, and brush coating.

The composition of the present invention is a thermosetting type, and its baking conditions are determined by the type and amount of the blocking agent, the presence or absence, type, and amount of the curing accelerator, and the type and amount of the phenolic resin. However, at a temperature of 90 to 200℃, the temperature is usually 10 to 6.
It is 0 minutes. Thus, the coating composition of the present invention is highly crosslinked and can provide a coating film with extremely excellent corrosion resistance, water resistance, moisture resistance, solvent resistance, and physical properties of the coating film. The details of the present invention will be shown below by way of examples.

Note that unless otherwise specified, "parts" and "%" refer to "parts by weight" and "% by weight." Examples 1 to 4 (Synthesis of cationic urethane resin) 87 parts of a mixture of 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate was stirred at 60°C, and polypropylene glycol (molecular weight 400) A solution of 100 parts dissolved in 100 parts of acetone is gradually added dropwise.

After the dropwise addition was completed, the reaction was carried out at 60°C for 3 hours, then the temperature was lowered to 40°C, a mixed solution of 75 parts of triethanolamine and 40 parts of acetone was gradually added dropwise, and the reaction was further carried out for 2 hours at 50 to 6°C. Subsequently, reaction product a was obtained. Separately, 2,4
- While stirring 87 parts of a mixture of 80% tolylene diisocyanate and 20% 2,6-tolylene diisocyanate at 60°C, 65 parts of 2-ethylhexanol was added to 65 parts of acetone.
5 parts of the solution was gradually added dropwise and reacted at 60° C. for 3 hours to obtain addition reaction product b.

The addition reaction product b was gradually added dropwise to the reaction product a at room temperature, and the mixture was reacted at 40°C for 2 hours and then at 50°C for 1 hour.

Then, acetone in the composition was replaced with ethylene glycol monoethyl ether as a solvent to obtain a cationic thermosetting urethane resin (1) with a solid content of 70%.

(Synthesis of resol-type phenolic resin) 94 parts of carbolic acid, 162 parts of formalin (37% aqueous solution), and 13 parts of 28% ammonia water were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a stirring device, and the temperature was raised. The mixture was allowed to react under reflux for 2 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was stirred thoroughly and allowed to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. Dissolve the dehydrated resin in methanol and adjust the solid content to 50% to obtain a water-insoluble resol type phenolic resin solution (1)
I got it. The molar ratio of formalin/carbolic acid was 2.0.

(Preparation of coating composition) The urethane resin (1), water-insoluble resol type phenolic resin (1), lactic acid, and dibutyl thioxide were uniformly mixed in the proportions shown in Table 1, and while stirring, ion-exchanged water was added. Gradually dilute with water to adjust the solid content to approximately 16%,
A water-based thermosetting coating composition of the present invention for electrodeposition coating was obtained.

(Preparation of Performance Test 1 Test Piece) While stirring the electrodeposition coating composition, 25 to 3 zinc phosphate treated plates (0.8 x 70 x 500 mm) were placed in it while stirring.
Electrodeposition coating was carried out at 0°C for 3 minutes, followed by washing with ion-exchanged water and baking drying at 180°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The electrodeposition device used for the painting had a rectifier of 0 to 500, approximately 3
．． 51 Box-shaped electrodeposition tank made of polyvinyl chloride, magnetic stirrer, and carbon electrode plate (5 x 70 x 150 mm,
The distance between the poles was approximately 10 degrees. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the baked coatings.

Example 5 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 122 parts of formalin (37% aqueous solution),
and 9 parts of 28% aqueous ammonia were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device and a stirring device, the temperature was raised and the reaction was carried out under reflux for 1.5 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was thoroughly stirred and left to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. The dehydrated resin was dissolved in isopropyl alcohol and the solid content was adjusted to 50% to obtain a water-insoluble resol type phenolic resin solution (2). The molar ratio of formalin/carbolic acid was 1.5.

(Preparation of coating composition) The urethane resin (1) of Example 1, the water-insoluble resol type phenol resin (2), lactic acid and dibutyl thioxide were mixed uniformly in the proportions shown in Table 1, and while stirring. , gradually diluted with ion-exchanged water to a solid content of approximately 16%.
A water-based thermosetting coating composition of the present invention for electrodeposition coating was obtained.

(Preparation of performance test piece) While stirring the electrodeposition coating composition, 25 to 3 zinc phosphate treated plates (0.8 x 70 x 500 mm) were placed in it while stirring.
``C: Electrodeposition coating was performed for 3 minutes, then washed with ion-exchanged water, and then baked and dried at 180°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used for the coating. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the baked coatings. Example 6 (Synthesis of resol type phenolic resin) 108 parts of m-cresol, formalin (37% aqueous solution)
162 parts and 13 parts of 28% ammonia water were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a stirring device, and the temperature was raised and the reaction was carried out under reflux for 2 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was thoroughly stirred and left to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. The dehydrated resin was dissolved in methanol and the solid content was adjusted to 50% to obtain a water-insoluble resol type phenol resin solution 3. The molar ratio of formalin/m-cresol is 2.0.
It was hot.

(Preparation of coating composition) The urethane resin (1) of Example 1, the water-insoluble resol type phenol resin (3), lactic acid and dibutyl thioxide were mixed uniformly in the proportions shown in Table 1, and while stirring. , gradually diluted with ion-exchanged water to a solid content of approximately 16%.
A water-based thermosetting coating composition of the present invention for electrodeposition coating was obtained.

(Preparation of performance test piece) While stirring the electrodeposition coating composition, 25 to 3 zinc phosphate treated plates (0.8 x 70 x 500 mm) were placed in it while stirring.
Electrodeposition coating was carried out at 0°C for 3 minutes, followed by washing with ion-exchanged water and baking drying at 18°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used for the coating. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the baked coatings. Example 7 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 162 parts of formalin (37% aqueous solution),
and 7 parts of methylamine were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a stirring device, the temperature was raised, and the reaction was carried out under reflux for 1.5 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was thoroughly stirred and left to stand overnight, and the aqueous layer was separated and removed. The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. The dehydrated resin was dissolved in isopropyl alcohol and the solid content was adjusted to 50% to obtain a water-insoluble resol type phenolic resin solution (4). The molar ratio of formalin/carbolic acid was 1.5.

(Preparation of coating composition) The urethane resin (1) of Example 1, the water-insoluble resol type phenolic resin (4), lactic acid and dibutyl thioxide were mixed uniformly in the proportions shown in Table 1, and while stirring. , gradually diluted with ion-exchanged water to a solid content of approximately 16%.
A water-based thermosetting coating composition of the present invention for electrodeposition coating was obtained.

(Preparation of performance test pieces) While stirring the electrodeposition coating composition, 25 to 3 zinc phosphate treated plates (0.8 x 70 x 500 mm) were placed in it while stirring.
Electrodeposition coating was carried out at 0°C for 3 minutes, followed by washing with ion-exchanged water and baking drying at 180°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used for the coating. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the baked coatings. Example 8 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 122 parts of formalin (37% aqueous solution),
and 10 parts of diethylamine were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a stirring device, the temperature was raised, and the reaction was carried out under reflux for 1.5 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was thoroughly stirred and left to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. The dehydrated resin was dissolved in isopropyl alcohol and the solid content was adjusted to 50% to obtain a water-insoluble resol type phenol resin solution 5. In addition, the molar ratio of formalin/carbolic acid is 1
．． It was 5.

(Preparation of coating composition) The urethane resin (1) of Example 1, the water-insoluble resol type phenolic resin (5), lactic acid and dibutyl thioxide were mixed uniformly in the proportions shown in Table 1, and while stirring. , gradually diluted with ion-exchanged water to a solid content of approximately 16%.
A water-based thermosetting coating composition of the present invention for electrodeposition coating was obtained.

(Preparation of performance test piece) While stirring the electrocoating composition, a zinc phosphate-treated plate (0.8 x 70 x 150 paulownia wood) was placed at 25 to 30°C for 30 minutes.
After applying electrodeposition for a minute and then washing with ion-exchanged water,
It was baked and dried at ℃ for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used for the coating. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the baked coatings. Comparative Example 1 (Preparation of coating composition) The same urethane resin (1), lactic acid, and dibutyl thioxide as in Example 1 were uniformly mixed in the proportions shown in Table 1 and gradually diluted with ion-exchanged water while stirring. An electrodeposition paint containing no water-insoluble resol type phenol resin was prepared by adjusting the solid content to approximately 16%.

(Preparation of performance test piece) This electrodeposited paint was heated for 25 to 3 hours while stirring.
Zinc phosphate treated plate (0.8 x 70 x 150
mm), then washed with ion-exchanged water,
Baking was performed at 80°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used.

Table 1 shows the characteristic values of the electrodeposition paint and the performance of the baked coating film. Comparative Example 2 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 162 parts of formalin (37% aqueous solution),
Charge 30 parts of sodium hydroxide (10% aqueous solution) as a raw material into a reactor equipped with a reflux condenser, a pressure reduction device, and a stirring device, raise the temperature, and react at 600C for 7 hours, until the pH becomes 4 to 5. The mixture was neutralized with acetic acid and then dehydrated under reduced pressure.

The obtained resin was heated to 50° C., and while stirring, ion-exchanged water was gradually added to adjust the solid content to 50% to obtain a water-soluble resol type phenolic resin (6). (Formalin/Carbolic acid (molar ratio) -2.0) (Preparation of coating composition) The same urethane resin (1) as in Example 1, water-soluble resol type phenolic resin (6), lactic acid, and dibutyl thioxide were listed. The mixture was gradually diluted with ion-exchanged water while uniformly mixing and stirring at a ratio of 1, and the solid content was adjusted to about 16% to prepare an electrodeposition paint.

(Preparation of performance test pieces) This electrodeposition paint was electrodeposited on a zinc phosphate treated plate (0.8 x 70 x 150 m 71 L) for 3 minutes at 25 to 30°C under stirring, and then washed with ion-exchanged water. Baking was performed at 180°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used.

Table 1 shows the characteristic values of the electrodeposition paint and the performance of the baked coating film. Comparative Example 3 (Synthesis of cationic epoxy resin) Epoxy resin synthesized from bisphenol A and epichlorohydrin (Epicote 1001, epoxy equivalent: 45
30 parts of triethanolamine was gradually added dropwise to a solution of 90 parts of 0-5001 (trade name manufactured by Shell Chemical Co., Ltd.) dissolved in 100 parts of dioxane, reacted at 85°C for 2 hours, and then heated to 95°C.
The reaction was continued for an additional 3 hours to obtain Product 1.

Separately 80% 2,4-tolylene diisocyanate, 2,6
- 6 parts of a 20% mixture of tolylene diisocyanate
While stirring at 0°C, add 19.5 ml of 2-ethylhexanol.
and 19.5 parts of acetone were gradually added dropwise,
The reaction was carried out at 5 to 60°C for 3 hours to obtain a product.

The product was gradually added dropwise to Product 1 at room temperature and reacted at 40°C for 2 hours and then at 50°C for 1 hour, then dioxane and acetone were replaced with ethylene glycol monoethyl ether to reduce the solid content to 70%. After adjustment, a cationic thermosetting epoxy resin (1) was obtained.

(Preparation of coating composition) The cationic epoxy resin (1) and the water-insoluble resol-type phenolic resin (7) obtained by etherifying the water-insoluble resol-type phenolic resin of Example 1 with n-butyl alcohol.
), lactic acid, and dibutyl thioxide in the proportions shown in Table 1 were uniformly mixed and gradually diluted with ion-exchanged water while stirring to adjust the solid content to about 16% to prepare an electrodeposition paint.

(Preparation of performance test 1 test piece) This electrodeposition paint was electrodeposited on a zinc phosphate treated plate (0.8 x 70 x 150 mm) at 25 to 30°C for 3 minutes while stirring.
Then, after washing with ion-exchanged water, it was baked at 18°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used.

Table 1 shows the characteristic values of the electrodeposition paint and the performance of the baked coating film. Comparative Example 4 (Synthesis of cationic acrylic resin) 10 parts of dimethylaminoethyl methacrylate, 5 parts of acrylamide, 40 parts of n-butyl acrylate, tacrylic acid
-35 parts of butyl, 1 part of 2-hydroxyethyl methacrylate
A mixture of 0 part of azobisisobutyronitrile and 2 parts of azobisisobutyronitrile was added dropwise to 45 parts of ethylene glycol monoethyl ether at 80°C with stirring over 2 hours, and 1 hour after the completion of the dropwise addition, 0.0 parts of azobisisobutyronitrile was added. 5 parts were added and further heated at 80° C. for 4 hours to obtain a cationic acrylic resin (1) with a solid content of about 70%.

(Preparation of coating composition) The cationic acrylic resin (1), the same water-soluble resol type phenolic resin (6) as in Comparative Example 2, and lactic acid were prepared in Table 1.
While uniformly mixing and stirring, the mixture was gradually diluted with ion-exchanged water to adjust the solid content to approximately 16%, thereby producing an electrodeposition paint.

(Preparation of performance test piece) This electrodeposition paint was electrodeposited on a zinc phosphate treated plate (0.8 x 70 x 150 mm) for 3 minutes at 25 to 30°C while stirring.
Then, after washing with ion-exchanged water, it was baked at 18°C for 20 minutes.

The voltage was set so that the film thickness after baking was 20μ. The same electrodeposition device as in Example 1 was used.

Table 1 shows the characteristic values of the electrodeposition paint and the performance of the baked coating film. Comparative Example 5 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 122 parts of formalin (37% aqueous solution),
and 15 parts of sodium hydroxide (10% aqueous solution) were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a stirring device, the temperature was raised, and the reaction was carried out under reflux for 1.5 hours.

After the reaction was completed, 200 parts of ion-exchanged water was added, and the mixture was thoroughly stirred and left to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated by heating (at 100° C. or lower) under reduced pressure. The dehydrated resin was dissolved in isopropyl alcohol and the solid content was adjusted to 50% to obtain a water-insoluble resol type phenol resin solution (8). The molar ratio of formalin/carbolic acid was 1.5.

(Preparation of coating composition) The urethane resin (1) of Example 1, the water-insoluble resol type phenol resin (8), lactic acid and dibutyl thioxide were mixed uniformly in the proportions shown in Table 1, and while stirring. , gradually diluted with ion-exchanged water to a solid content of approximately 16%.
A comparative water-based thermosetting coating composition for electrodeposition coating was obtained.

(Preparation of performance test pieces) While stirring the electrodeposition coating composition, 25 to 30 zinc phosphate treated plates (0.8 x 70 x 150 plates) were placed in the composition while stirring.
℃ for 3 minutes, then washed with ion-exchanged water,
It was baked and dried at 180°C for 20 minutes.

Claims (1)

[Scope of Claims] 1 (A) Cationic thermosetting urethane resin, (B) Aldehydes/phenols (molar ratio) = 1.0 to 2.5
a water-insoluble resol type thermosetting phenolic resin prepared in the presence of ammonia, a primary amine or a secondary amine in the proportion of (C) an acid as a neutralizing agent and (D) water as a diluent. A water-based thermosetting resin coating composition. 2. The mixture weight ratio (solid content) of cation type thermosetting urethane resin A and water-insoluble resol type thermosetting phenolic resin B is A/B = 70 to 99/1 to 30. Water-based thermosetting resin coating composition.