JPS603348B2 - Water-based thermosetting coating composition - Google Patents

Description

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

More specifically, it is a water-based heat treatment with excellent coating film physical properties, corrosion resistance, and water resistance, which is made of a cationic thermosetting urethane resin and a magnesium-modified resol-type phenolic resin that have been water-solubilized or water-dispersed by acid neutralization. The present invention relates to a curable coating composition. Traditionally, from the viewpoint of resource saving and non-pollution,
Solvent-based paints are gradually being converted to non-polluting paints, especially water-based paints, and this conversion is expected to further advance in the future.

Box paint, which is a type of water-based paint, has already been widely used as an undercoat paint for automobiles due to its 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.

Polycarboxylic acid resins having a skeleton of drying oil, alkyd resin, polybutadiene resin, epoxy shester resin, acrylic resin, etc. are used as the resin for the anionic dew coating.

Usually, these are neutralized with a basic compound such as an organic amine, and then water-dropped 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.

As the cationic electrodeposition coating resin, polyamino resins having skeletons such as eboxy resins, urethane resins, acrylic resins, polybutadiene resins, and alkyd resins are used.

Usually, these are neutralized with organic acids and made water-solubilized or water-dispersed. In such polyamino resin,
Since the amino groups in the coating act as a corrosion inhibitor, it is possible to obtain a coating film with a high degree of corrosion resistance.

By the way, corrosion in automobiles where the above-mentioned pigmented paints are mainly used can be broadly classified into the following two types:
01 The paint film is damaged by some external factor (for example, an impact from the 4th right), and corrosion progresses from the damaged area, so-called scab corrosion '21 Incomplete chemical conversion treatment areas or incomplete painted areas This is the so-called pitting corrosion that progresses from

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 external factors as mentioned above 1' varies significantly depending on the type of resin skeleton. Among these, urethane resins have particularly 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, disclosed in Japanese Patent Publication No. 48-36
No. 9, No. 50-172, No. 2, No. 2, No. 51-2491, No. 51-2491, No. 9, No. 50-172, No. 51-2491, No. 9 Publication No. 48-96696, No. 48-99297
No. 48-10143 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, '11 composition consisting of polyepoxide solubilized with quaternary onium salt and unsaturated methylol phenyl ether (Tsubaki Kosho 52-116 private publication), (2' acrylic resin, epoxide ester type A composition consisting of a nitrogen basic resin such as
2-77 Publication), '3} Compositions consisting of acrylic resin and water-soluble phenol-formaldehyde resin (Japanese Patent Publication No. 12395-1982, Publication No. 12396 of Hakama Publication, Publication No. 39351 of Taru Publication No. 45-3939), ■A composition using a reaction product of an epoxy ester resin and a partially etherified phenol resin (Special Publication No. 49-26292), a side epoxy resin or an epoxy ester resin, or a combination of these and trishydroxymethylphenol allyl ether, etc. Compositions using reaction products (Tokukan Sho 53-13)
4897) etc. are known.

However, in the above-mentioned known compositions, epoxy resins have insufficient coating film flexibility and deteriorate corrosion resistance after impact tests, while acrylic resins and epoxy shester resins have poor corrosion resistance and water resistance. It had the disadvantage of insufficient performance.

Additionally, those that are combined with a water-soluble phenolic resin similarly have poor corrosion resistance and water resistance, and those that are combined or combined with an etherified phenolic resin have poor coating film physical properties and corrosion resistance when cured at low temperatures (below 180 o'clock). However, it had the disadvantage of poor water resistance. In order to improve the above drawbacks, the present inventors invented and previously filed an application for a composition comprising a cationic thermosetting urethane resin and a water-insoluble resol type fer resin.

However, subsequent experiments revealed that when a resol-type phenolic resin is used, the presence of iron causes a chelation reaction with iron, resulting in coloring and a decrease in purulent application performance. The purpose of the present invention is to solve the above-mentioned problems, and while maintaining the physical properties of the coating film such as flexibility, which is a feature of urethane resin, it improves corrosion resistance and water resistance, improves low-temperature curability, and improves the appearance of the coating film. (Prevention of armpits)
The object of the present invention is to provide a water-based thermosetting coating composition that improves the properties of the phenol resin and prevents coloring of the phenol resin.

That is, the present invention relates to a water-based thermosetting coating composition comprising an air thione type thermosetting urethane resin, a bent magnesium modified resol type phenolic resin, an acid as a 'q neutralizing agent, and water as a dish 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, Samurai Publication No. 50-117234, No. 51-249.
Publication No. 1, Publication No. 38317, Publication No. 2894, Publication No. 531-2895, Publication No. 53-2895, Shoryaku Hakamaseki-96696
No. 48-99297, No. 48-1014
This includes those disclosed in Publication No. 30 and the like. The resin is generally, for example, a reaction product of a polyurethane prepolymer having an isocyanate group at the end and a tertiary amine having at least two hydroxyl groups in one molecule.
A product obtained by an equimolar addition reaction of the hydroxyl group in the reaction product 'a}], an organic diisocyanate, and a monofunctional blocking agent [hereinafter referred to as the product {b-]
obtained by reaction with isocyanate groups in The polyurethane prepolymer having isocyanate groups at the terminals contains polyisocyanate and polyol in an amount of at least 1 equivalent, preferably 1.5 to 1 equivalent per equivalent of polyol.
It can be synthesized by reacting about 2.0 equivalents of polyisocyanate.

The preferred polyisocyanate contains 2 in 1 molecule.
Aromatic or aliphatic polyisocyanates having isocyanate groups, such as phenylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, lysine diisocyanate,
Examples include trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, propylene diisocyanate, ethylene diisocyanate, and hydrogenated products of the above 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 neobentyl 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 acetate. Then, the urethane prepolymer having isocyanate groups at the terminals is added with at least 2 molecules per molecule.
A tertiary amine having hydroxyl groups is subjected to an addition reaction.

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, methyljetalamine, triethanolamine, tris(2-hydroxypropyl)amine, an adduct of 1 mole of ethylenediamine and 4 moles of propylene oxide, or a quaternized product thereof, etc. are used. .

In this way, the reaction product 'a-' can be obtained. on the other hand,
The 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 at a temperature of 40 to 110 °C in a solvent. can.

As the organic diisocyanate used in obtaining the product 'b-, the same diisocyanate as that used in obtaining the polyurethane polyol can be used. Further, as the monofunctional blocking agent, blocking agents normally used in the synthesis of blocked isocyanates, such as phenols, alcohols, lactams, oximes, acid amides, imides, amines, imidazoles, etc. , 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 difloc form of the organic diisocyanate.

Such a diblock body becomes an insoluble substance when the urethane resin is made water-soluble, and also causes a change in the electrodeposition characteristics during drying, so it is necessary to set reaction conditions so as to prevent the formation of diblock bodies as much as possible. The isocyanate group in the addition reaction product 'b} thus obtained and the reaction product ■
The cationic thermosetting urethane resin of the present invention can be obtained by reacting the hydroxyl groups therein. Said {a
The mixing ratio of component } and component 'b' is such that 20 to 80% of the hydroxyl groups present in the reaction product 'a- react with the isocyanate groups present in the addition reaction product 'b-. It is preferable.

The cationic thermosetting urethane resin thus obtained is
It can be used by mixing or partially reacting with known cationic epoxy resins, acrylic resins, and alkyd resins. Further, if necessary, a water-miscible solvent active against isocyanate groups can be added or diluted. The magnesium-modified resol-type phenolic resin used in the present invention is a thermosetting resin obtained by modifying a resol-type phenolic resin synthesized from aldehydes and phenols with a magnesium compound.

The phenol resin is particularly preferably a resol type phenol resin obtained in the presence of an alkali catalyst. As the phenols, it is desirable to use trifunctional or higher functional phenols 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, and bisphenol A.

Examples of the difunctional phenols include p-cresol, o-cresol, p-methoxyphenol, p-ethoxyphenol, p-t-petit'lephenol, p-nonylphenol, and the like.

The trifunctional or higher functional phenols may be used alone as a resol type phenolic resin, or a mixed phenol of two or more trifunctional or higher functional phenols, or a mixed phenol with a bifunctional phenol. 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 addition, as an alkali catalyst, ammonia; methylamine;
and primary amines such as ethylamine; secondary amines such as dimethylamine and diethylamine; tertiary amines such as trimethylamine and triethylamine; pyridine: and sodium hydroxide, potassium hydroxide, and calcium hydroxide. , and metal hydroxides such as magnesium hydroxide.

In the present invention, those using ammonia, primary amines, and secondary amines as catalysts are particularly preferred.

These amino groups participate in the reaction system of phenols and aldehydes, and the resulting resol-type phenolic resin becomes a cationic resin with nitrogen atoms introduced, resulting in improved water dispersion stability, torpor adhesion properties, and cationic properties. Demonstrates excellent compatibility with thermosetting urethane resin.

For example, in the case of an ammonia catalyst, a condensate with the following structure is obtained.

A typical manufacturing example of the resol type phenolic resin is shown below.

First, a mixture of aldehydes/phenols with a molar ratio of 1.0 to 2.5 is charged into a reaction vessel, and the feed of the reactant is adjusted with an alkali catalyst to a ratio of 7.5 to 9.0. React at ~100q○ for 1 to 4 hours.

After the reaction is completed, neutralize the reactant bait with an acid compound to a concentration of 4.0 to 5.0, add water, and stir thoroughly. 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 qo, 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 solids content is 30-8% by weight. Examples of the solvent include alcohols such as methyl alcohol, ethyl alcohol, butyl alcohol, and propyl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and inpropyl glycol; Examples include ethers; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and butyl acetate; aromatics such as toluene and xylene; these 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 it deteriorates low-temperature curability and coating performance. Therefore, in the present invention, it is preferable not to etherify.

If etherification is necessary, the amount should be 30% or less of the methylol groups. Next, the resol type phenolic resin thus obtained is treated with a magnesium compound;
is denatured. There are no particular limitations on the method of modification using the magnesium compound, but the resol type phenol resin solution (solid content: 30-8% by weight), water in an amount of 1-5% by weight based on the solid resin content, and converted to magnesium. Then 5～
Add 1% by weight of magnesium compound and heat from room temperature to 8% by weight.
The magnesium-modified resol-type phenolic resin of the present invention can be obtained by removing unreacted magnesium compounds by filtration, centrifugation, etc. . Magnesium in the magnesium compound is introduced into the phenol resin by a chelate reaction between the methylol group and the phenolic hydroxyl group in the phenol resin.

The magnesium compound is not particularly limited as long as it can undergo a chelate reaction, but magnesium oxide,
Magnesium acetate, magnesium hydroxide, magnesium chloride, and the like are preferably used.

The magnesium-modified 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 thus obtained magnesium-modified resol type phenolic resin of the present invention is completely free from coloring due to chelation reaction with iron. The coating composition of the present invention is produced by mixing the cationic thermosetting urethane resin and the magnesium-modified resol-type phenolic resin, then cationizing the tertiary amino groups in the resin with an acid as a neutralizing agent, and diluting with water. It can be obtained by

The mixing of the urethane resin and the magnesium-modified resol type phenol resin is preferably carried out at a temperature ranging from room temperature to about 9 psi, and care must be taken to avoid gelation. The magnesium-modified resol type phenolic resin is preferably mixed in an amount of 1 to 3% by weight based on the total solid content of the urethane resin and the magnesium-modified resol type phenolic resin.

More preferably it is 5-2% by weight. In the above range, if the phenolic resin content is less than 1% by weight, the coating film will not have any effects such as water resistance, green resistance, corrosion resistance, low temperature curing properties, etc., and conversely, if the phenolic resin content exceeds 3% by weight, The flexibility of the coating film, which is a feature of urethane resins, is decreasing, and the physical properties of the coating film are on the decline, and it is also difficult to obtain a stable aqueous dispersion. As the acid, 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 acid as the neutralizing agent is equal to or less than the tertiary amino group in the resin. The thus bound coating composition of the present invention can be used in the form of a few liquids of water for various purposes and coating methods, but various organic solvents are used in the process of obtaining the cationic urethane resin. ,
Therefore, some organic solvent can be included in the coating composition.

However, its content should be no more than 2% 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, anticorrosion pigments, hardening accelerators, surface conditioners, antifoaming agents, etc. as necessary, and is then enameled by a conventional tying method. be able to.

The composition is suitable for fly coating, but is also suitable for other conventional coating methods such as spray coating, immersion coating, and brush coating.

The composition of the present invention is a thermosetting type, and its bregnating 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. , usually 10-6 at a temperature of 90-200℃
It is Katama. Thus, the coating composition of the present invention is highly crosslinked and can provide a coating film with extremely excellent corrosion resistance, water resistance, temperature resistance, solvent resistance, and coating film properties.

The details of the present invention will be shown below by way of examples.

Incidentally, unless otherwise specified, "parts" and "%" refer to "parts by weight" and "% by weight." Examples 1 to 4 (Synthesis of cationic urethane resin) 8 parts of a mixture of 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate were mixed into 6 parts.
Polypropylene glycol (molecular weight 4
00) Gradually drop a solution of 10-10 base portion dissolved in 10-10 acetone.

After the dropwise addition was completed, the reaction was carried out at 60°C for 3 hours, then the temperature was lowered to 4 to 0°C, a mixture of 75 parts of trietanoamine and 4 parts of acetone was gradually added dropwise, and the reaction was further carried out at 50 to 60°C for 2 hours. The reaction product 'a} was obtained. Separately 2.
While brewing a mixture of 80% 4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate in a barrel at 60°C, a solution of 65 parts of 2-ethylhexanol dissolved in 65 parts of acetone was added. Addition reaction product ``b'' was gradually added dropwise to the reaction product ``a'' to obtain addition reaction product ``b'', which was reacted at 60° C. for 3 hours.
The reaction was carried out 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 to obtain a cationic thermosetting urethane resin having a solid content of 70%.

(Synthesis of magnesium-modified resol type phenolic resin)
A carbonic acid treatment part, 162 parts of formalin (37% aqueous solution), and 1 $ part of 28% aqueous ammonia were charged into a reaction vessel equipped with a reflux condenser, a pressure reduction device, and a passing device, the temperature was raised, and the mixture was heated under reflux for 2 hours. Made it react.

After the reaction was completed, 20 grams of ion-exchanged water was added, and the mixture was left to stand for a day and night, and the aqueous layer was separated and removed. The remaining resin layer was dehydrated under reduced pressure by heating (at 100° C. or lower). The resin after dehydration was dissolved in methanol to adjust the solid content to 50%, and 3 parts of ion-exchanged water and 15 parts of magnesium oxide were added to make 30 qo.
I worshiped flies for 6 hours. Thereafter, unreacted magnesium acid was removed using a centrifuge to obtain a magnesium-modified resol type phenol resin column 1'. The molar ratio of formalin/carbolic acid was 2.0. (Preparation of coating composition) The urethane resin '1', magnesium-modified resol type phenol resin (11), lactic acid and dibutyltin oxide were mixed uniformly in the proportions shown in Table 1, and while stirring, the ion The mixture was gradually diluted with exchanged water to adjust the solids content to approximately 16% to obtain a water-based thermosetting coating composition of the present invention for use in tortoise coating.

(Preparation of performance test pieces) While observing the electrodeposition coating composition, 25 to 30 zinc phosphate treated plates (0.8 x 70 x 15 pieces) were placed in it.
qo, electrodeposited for 3 minutes, then washed with ion-exchanged water, and dried with scales at 180° C. for 20 minutes.

The voltage was set so that the film thickness after abrasion was 20 mm. The dew coating layer used for the above painting consisted of a 0-500V rectifier, a box-shaped electrodeposition tank made of approximately 3.5k polyvinyl chloride, a magnetic stirrer, and a carbon electrode plate (5 x 70 x 150 fences,
The distance between the poles was approximately 10 meters. Table 1 shows the characteristic values and performance of these coatings.

Example 5 (Synthesis of magnesium-modified resol type phenolic resin)
94 parts of carbolic acid, 122 parts of formalin (37% aqueous solution),
and 9 parts of 28% ammonia water were charged into a reaction vessel equipped with a reflux condenser, a pressure reducer, and an Isoazusa apparatus, the temperature was raised, and 1. It reacted immediately.

After the reaction was completed, 20 parts of ion-exchanged water was added, stirred well, and left to stand overnight to separate and remove the aqueous layer. The remaining resin layer was dehydrated by heating under reduced pressure (10020 or less). The resin after dehydration was dissolved in inpropyl alcohol to adjust the solid content to 50%, 3 parts of ion-exchanged water and 15 parts of magnesium oxide were added, and the mixture was heated at 30°C for 6 hours. Thereafter, unreacted magnesium oxide was removed using a centrifuge to obtain a magnesium-modified resol type phenol resin solution (2). The molar ratio of formalin/carbolic acid was 1.5.

(Preparation of coating composition) Urethane resin 01 of Example 1, magnesium-modified resol type phenol resin [21], lactic acid and dibutyltin oxide were uniformly mixed in the proportions shown in Table 1,
The mixture was gradually diluted with ion-exchanged water to adjust the solids content to approximately 16%, thereby obtaining a water-based thermosetting coating composition of the present invention for fin coating.

・(Preparation of performance test piece) A zinc phosphate treated plate (0.8×70×
15 Dian Misaki) was electrodeposited at 25 to 30°C for 3 minutes, then washed with ion-exchanged water, and dried at 18°C for 20 minutes.

The voltage was set so that the thickness after scaling was 20 degrees. The same turtle-mounted hawk used in Example 1 was used for the painting. Table 1 shows the characteristic values of these fin coatings and the performance of the dawn coating. Example 6 (Synthesis of magnesium-modified resol type phenolic resin) m-cresol 1 female part,
162 parts of formalin (37% aqueous solution) and 1 $ part of 28% aqueous ammonia were charged into a reaction vessel equipped with a reflux condenser, a vacuum bag and a rope frame, and the temperature was raised and the mixture was heated under reflux for 2 hours.
Allowed time to react.

After the reaction was completed, 20 parts of ion-exchanged water was added, and after stirring well, the mixture was allowed to stand overnight, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated under reduced pressure by heating (at 100° C. or lower). The resin after dehydration was dissolved in methanol to adjust the solid content to 50%, 3 parts of ion-exchanged water and 15 parts of magnesium oxide were added, and the mixture was heated at 3 psi for 6 hours. After that, unreacted magnesium oxide was removed using a centrifuge D separator to obtain a magnesium-modified resol type phenolic resin.
The molar ratio of m-cresol was 2.0.

(Preparation of coating composition) The urethane resin {11 of Example 1, magnesium-modified resol type phenol resin '31, lactic acid and dibutyltin oxide were mixed uniformly in the proportions shown in Table 1, and the mixture was heated. At the same time, the mixture was gradually diluted with ion-exchanged water to adjust the solid content to about 16%, thereby obtaining an aqueous thermosetting coating composition of the present invention for use in tortoise coating.

(Preparation of performance test piece) While testing the paint composition for military uniform painting, a zinc phosphate treated plate (0.8 x 70 x 1
5) was electrodeposited for 25 to 3 minutes, then washed with ion-exchanged water, and then baked and dried at 180 oo for 20 minutes.

The voltage was set so that the film thickness after baking was 20 mm. The dragon fitting used for the painting was the same as in Example 1. Table 1 shows the characteristic values of these electrodeposition paints and the performance of the dawn coating. Example 7 (Synthesis of magnesium-modified resol type phenolic resin)
94 parts of carbolic acid, 1 part of formalin (37% aqueous solution), and 7 parts of methylamine were charged into a reaction vessel equipped with a reflux condenser, a pressure reducer, and a fly trap, and the temperature was raised to 1. I reacted for a while.

After the reaction was completed, 20 parts of ion-exchanged water was added, and the mixture was thoroughly rinsed and allowed to stand overnight to separate and remove the aqueous layer. The remaining resin layer was dehydrated by heating (100 qo or less) under reduced pressure. The dehydrated resin was dissolved in inpropyl alcohol to adjust the solid content to 50%, and 3 parts of ion-exchanged water, magnesium acetate [Mg(C
8 anchors of Cape H3COO)2 were added and roped at 3000 for 6 hours. Thereafter, unreacted magnesium acetate was removed using a centrifuge to obtain a magnesium-modified resol type phenol resin column 41. The molar ratio of formalin/carbolic acid was 1.5.

(Preparation of coating composition) The urethane resin '1' of Example 1, magnesium-modified resol type phenol resin ■, lactic acid and dibutyltin oxide were uniformly mixed in the proportions shown in Table 1, and then heated. while gradually diluting with ion-exchanged water until the solid content is approximately 1.
This was adjusted to 6% to obtain a water-based thermosetting coating composition of the present invention for tortoise coating.

(Preparation of performance test piece) While applying the above-mentioned electrodeposition coating composition, a zinc phosphate-treated plate (0.8 x 70 x 1
5Q pig) was electrodeposited for 3 minutes at 25 to 30 qo, then washed with ion-exchanged water, and then baked and dried at 18,000 for 20 minutes.

The voltage was set so that the film thickness after dawning was 20 mu. The same lacquer used in Example 1 was used for the painting. 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' as in Example 1, lactic acid, and dibutyltin oxide were mixed uniformly in the proportions shown in Table 1 and gradually mixed with ion-exchanged water. diluted to approximately 16% solids
A coating composition containing no magnesium-modified resol-type phenolic resin was prepared.

(Preparation of performance test pieces) This hazy paint was painted on a zinc phosphate treated board (0.8 x 70 x 150 side) for 3 minutes at 25-30 am under the fly Azusa.
Then, after washing with ion-exchanged water, it was baked at 180° C. for 20 minutes.

The voltage was set so that the film thickness after dawning was 20 mu.
The same hemlock layer as in Example 1 was used.

Table 1 shows the characteristic values and baking hardness performance of the pigmented paint. Comparative Example 2 (Synthesis of resol type phenolic resin) 94 parts of carbolic acid, 162 parts of formalin (37% aqueous solution),
and 1 part of 28% aqueous ammonia were charged into a reaction apparatus equipped with a reflux condenser, a pressure reducer, and a flywheel apparatus, the temperature was raised, and the reaction was carried out under reflux for 2 hours.

After the reaction was completed, 20 parts of ion-exchanged water was added to the flask, and the flask was allowed to cool down for a day and night, and the aqueous layer was separated and removed.

The remaining resin layer was dehydrated under reduced pressure by heating (at 100° C. or lower). The resin after dehydration was poured into methanol and the solid content was adjusted to 50% to obtain a resol type phenol resin (2). The molar ratio of formalin/carbolic acid was 2.0. (Preparation of coating composition) The same urethane resin Q as in Example 1, resol type phenol resin '5', lactic acid, and dibutyltin oxide were mixed uniformly in the proportions shown in Table 1 and ionized while stirring. It was gradually diluted with exchanged water to adjust the solids content to about 16%, and a military uniform paint was produced.

(Preparation of performance test pieces) This turtle coating paint was applied to a zinc phosphate treated board (0.8 x 70 x 150 side) for 3 minutes at 25 to 30 qo under a rope.
Then, after washing with ion-exchanged water, it was baked at 180° C. for 20 minutes.

The voltage was set so that the film thickness after dawning was 20 μm. The same hemlock layer as in Example 1 was used.

Table 1 shows the characteristic values of the tortoise paint and the performance of the dazzling paint. Abbreviated hammer key vertical tree flea reverse type crucian also Shigyu song Shigo, Funenrennan S Zendo Ren Takeshige Suga General Purpose "Toyom" N machine ILku Tatsumi ′ 'Totsuji o Sanringo Carp Hina 0 Riwa Kunkan Attenuation Rate Room; Ant--Integrated Ura 3 g Total % Edge N Fu” Bonito R.

l.

○light*Xt.

As is clear from the above comparative test result table, the coating film obtained from the coating composition of the present invention reduces the luster properties of the urethane resin. Not only was the moisture resistance and corrosion resistance significantly improved, but there was also almost no coloration due to iron.

On the other hand, the coating film obtained from the composition containing only urethane resin (Comparative Example 1) has excellent flexibility but extremely poor corrosion resistance, and is modified with urethane resin and magnesium compound.
Although the performance of the coating film obtained from the composition consisting of a sol-type phenolic resin is not much different from that of the present invention,
Iron contamination was significant.

Claims (1)

[Claims] 1. Aqueous heat treatment consisting of (A) a cationic thermosetting urethane resin, (B) a magnesium-modified resol type phenolic resin, (C) an acid as a neutralizing agent, and (D) water as a diluent. Curable coating composition. 2 Magnesium modified resol type phenolic resin (B)
is aldehyde/phenol (molar ratio) = 1.0~
The aqueous thermosetting coating composition according to claim 1, which is a thermosetting resin modified by reacting in the presence of an alkali catalyst and further chelating with a magnesium compound at a ratio of 2.5%. . 3. A patent claim in which the mixing weight ratio (solid content) of the cationic thermosetting urethane resin (A) and the magnesium-modified resol type phenol resin (B) is (A)/(B) = 70-99/1-30. The water-based thermosetting coating composition according to item 1. 4 Magnesium modified resol type phenolic resin (B)
is aldehyde/phenol (molar ratio) = 1.0-2
．． Claim 1 is a thermosetting resol-type phenolic resin prepared in the presence of ammonia, a primary amine or a secondary amine in a proportion of 5 to 5 and modified by further chelation with a magnesium compound The water-based thermosetting coating composition described in 2. 5. The water-based thermosetting coating composition according to claim 4, wherein the magnesium compound is magnesium oxide, magnesium acetate, magnesium hydroxide, or magnesium chloride.