JPH07206957A - Water-based resin and its production and water-based coating composition containing the same - Google Patents

Abstract

PURPOSE:To obtain a low-viscosity water-based resin excellent in water dilutiveness, stability and film coating workability, useful for e.g. water-based thermosetting coatings, by condensation reaction of a specific methylol-modified product with an amino compound and by neutralizing part of the product followed by conversion into the water-based final product. CONSTITUTION:A copolymer produced by copolymerization between the essential raw materials, an alpha, beta-ethylenically unsaturated carboxylic acid such as (meth)acrylic acid and an ethylenic unsaturated monomer having functional group capable of adding formaldehyde thereto is subjected to addition reaction with formaldehyde in the presence of an organic solvent to produce a methylol-modified product, which is then incorporated with an amino compound such as urea followed by conducting a condensation reaction under heating, and at least part of the product is neutralized with a basic compound such as ammonia followed by conversion into a water-based product, thus affording the aimed water-based resin. It is preferable that the acid value of the copolymer be 20-150. A water-based thermosetting coating composition can be obtained by designing its composition so as to contain >=5wt.% of this water-based resin on a solid basis.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel and useful aqueous resin, a method for producing the aqueous resin, and an aqueous thermosetting coating composition containing the aqueous resin, that is, an aqueous thermosetting coating. Regarding

More specifically, the present invention is obtained by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated monomer having a functional group capable of adding formaldehyde as essential raw material components. A water-based resin obtained by subjecting a copolymer and a formaldehyde to an addition reaction in the presence of an organic solvent, to a methylol compound obtained by condensation reaction with an amino compound, neutralizing with a basic substance, and hydrating; A method for producing the water-based resin; and an aqueous thermosetting coating composition containing the water-based resin.

[0003]

2. Description of the Related Art In recent years, it has been considered that organic solvents emitted from paints are one of the causes of air pollution in coatings in general. Recently, conventional solvent-based paints are gradually converted into water-soluble paints. The study to do is being actively conducted.

For such water-soluble paint, acrylic resin,
It is inevitable that amino resins are required to be used appropriately as the thermosetting component since a hydrated material such as polyester resin and epoxy resin is used.

Generally, there is a method for imparting a hydrophilic group by adding formaldehyde to an amino group bonded to a triazine ring to make it a methylol for the purpose of making an amino resin aqueous, but too much methylol is used. If there are many groups, problems such as poor water resistance of the cured coating film and deterioration of workability due to the odor of deformalin accompanying the curing reaction will inevitably occur.

By the way, an amino resin in which a methylolated amino resin is modified with an alkyl ether by a lower alcohol is used as a cross-linking agent for an aqueous paint.

However, even in such a case, the water resistance is poor, and in addition, if the concentration of the amino resin is increased, then a problem occurs in water solubility or water dispersibility. When using an alkyl etherified amino resin in a water-based paint, the type and amount of compound in the resin composition,
Not a little, there are restrictions. In addition, a method of using an emulsifier to make it aqueous is also conceivable, but such a method is very inferior in water resistance.

[0008] Therefore, as another aqueous method, there have been patent applications in the field of making a water-soluble resin co-condensed with an alkyl etherified amino resin to make it aqueous.
Some have been done.

For example, a water-soluble resin synthesized in advance,
There is a method in which an alkyl etherified amino resin is blended under heating and co-condensed. (JP-A-3
-182543 publication. )

However, although the amino resin obtained by such a method is water-dispersed or water-solubilized, its dilutability in water is insufficient, and the stability when it is made into a paint is impaired. The reality is that

[0012] With the recent trend toward a lower VOC (volatile organic compound) of water-based paints, when the water dilutability becomes insufficient, such VOs are quite possible.
At the same time, it cannot be expected to reduce C, and at the same time in terms of coating workability, it cannot reach the stage of practical application.

[0012]

However, in view of the various drawbacks of the prior art as described above, the present inventors, in addition, in order to meet the urgent needs of the industry, in particular, the curability and the like. In search of an excellent so-called water-based amino resin, the research was earnestly started.

Therefore, the problem to be solved by the present invention depends on the first problem, and of course, the dispersion of the amino resin is excellent not only in curability but also in water resistance and chemical resistance. Therefore, it is to provide a highly practical water-soluble amino resin and a method for producing the resin, which has excellent water performance (water-solubility) and can exist stably. , Which is one of the basic objects of the present invention.

Still another object of the present invention is to use a substantially water-insoluble amino resin, which is used as a solvent-type thermosetting paint, and which is particularly excellent in processability, as a water-based resin. Water resistance, hardness, and processing of coated materials from the point that it is stable and has good compatibility with other resins, and therefore can be added in a high concentration state. The object is to provide a low-viscosity water-based thermosetting coating composition which can improve the properties and the like, and which has good coating workability.

[0015]

Therefore, the present inventors have
First, as described above, focusing on the problem to be solved by the invention, as a result of earnestly and repeatedly studying, even if it is a method of co-condensing the same aqueous resin, it means that the synthesis method is different. Therefore, it was considered that controlling the degree of co-condensation and changing the molecular weight and the degree of hydrophilicity would lead to the improvement of water performance (water-solubility).

The present inventors subsequently made these α, β-ethylenically unsaturated carboxylic acid and an ethylenically unsaturated monomer having a functional group capable of adding formaldehyde an essential raw material component A copolymer obtained by copolymerization and formaldehyde are subjected to an addition reaction in the presence of an organic solvent, to a methylol compound obtained by adding, an amino compound is added, and a condensation reaction is caused by heating, and then a basic reaction is performed. It was found that a hydrated product or a water dispersion of the amino resin, which has a low viscosity and is excellent in water dilutability, can be easily obtained by neutralizing at least a part of a substance and making it aqueous. Thus, the present invention has been completed here.

Here, first, of the above-mentioned α, β-ethylenically unsaturated carboxylic acids to be used in the present invention, only typical ones will be exemplified, and (meth) acrylic acid, maleic acid or It is various carboxyl group-containing vinyl monomers such as fumaric acid.

The amount of the α, β-ethylenically unsaturated carboxylic acid to be used is appropriately within the range of about 2 to about 30% by weight based on the total ethylenically unsaturated monomers, and is preferable. Is appropriately in the range of 5 to 20% by weight.

Next, as the above-mentioned ethylenically unsaturated monomer having a functional group capable of adding formaldehyde, for example, an ethylenically unsaturated monomer having an amino group or an imino group in at least a part thereof is designated. To do.

As the ethylenically unsaturated monomer containing a formaldehyde addition reactive functional group, only typical ones will be exemplified. Acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-isobutoxy. Such as methyl acrylamide, N-butoxymethyl acrylamide or diacetone acrylamide,

Acrylamide or its various derivatives;
Alternatively, methacrylamides corresponding to these or various derivatives thereof, etc., are by no means limited to these, and these various monomers may be used alone or in combination of two or more kinds. Of course, of course. However, since only the above-mentioned diacetone acrylamide is to be added to the terminal methyl group,
In particular, that point needs attention.

Of course, other ethylenically unsaturated monomers may be copolymerized depending on the purpose of use and the required performance of the aqueous resin and coating composition.

Specific examples of such a copolymerizable unsaturated monomer include only typical ones such as hydroxymethyl acrylate, hydroxyethyl acrylate,
Hydroxypropyl acrylate, hydroxyamyl acrylate or hydroxyhexyl acrylate;
Or various hydroxyl group-containing vinyl monomers such as methacrylic acid corresponding to these,

As typified by ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate or cyclohexyl acrylate, or methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate or cyclohexyl methacrylate and the like. , Various acrylic acid alkyl esters or methacrylic acid alkyl esters;

Alternatively, as represented by styrene, vinyltoluene or α-methylstyrene,
Various aromatic vinyl monomers and the like, but are by no means limited to these compounds.

Of course, these monomers may be used alone or in combination of two or more kinds. As mentioned above, the copolymerization reaction of various monomers is carried out in the presence of various radical initiators such as peroxide radical polymerization initiators and azo radical initiators in a nitrogen atmosphere. The reaction is carried out in an organic solvent at a temperature range of about 60 to about 130 ° C.

Obtained from various kinds of ethylenically unsaturated monomers mainly containing the above-mentioned α, β-ethylenically unsaturated carboxylic acid and formaldehyde-reactive functional group-containing ethylenically unsaturated monomer. The acid value of the obtained copolymer is appropriately in the range of about 20 to about 150,

When the amount exceeds about 150, the coating performance tends to be deteriorated due to the influence of the residual carboxyl groups. On the other hand, when the amount is less than about 20, hydrophilicity is inevitably caused. From where it is easy to become insufficient,
Either case is not preferable.

Regarding the molecular weight of the copolymer, first, the number average molecular weight is about 2,000 to about 20,000.
It can be said that the range of about 3,000 to about 30,000 by weight average molecular weight is suitable.

As the above-mentioned amino compounds which are preferably used in the present invention, only typical ones are exemplified, and urea, melamine, acetoguanamine,
Benzoguanamine, cyclohexanecarboguanamine,
Steroganamin, spiroguanamine and the like, and one or more selected from the group consisting of the various compounds described above.

Of these, urea, melamine, and benzoguanamine are preferably used alone or in combination thereof, particularly from the viewpoints of cost and crosslinkability.

The amino compound may be initially charged all at once, or may be dividedly charged at regular intervals of several times, or may be continuously charged for a constant period of time. The good thing is, of course.

The above-mentioned organic solvent used in the present invention is particularly necessary for stabilizing the reaction product from the amino compound and formaldehyde. As only specific examples of the organic solvent, methyl alcohol, ethyl alcohol, n-propyl alcohol (n-propanol), isopropyl alcohol (isopropanol),

N-butyl alcohol (n-butanol), isobutyl alcohol (isobutanol), se
c-butyl alcohol (sec-butanol), ter
T-butyl alcohol (tert-butanol) and the like, and any of them is usually used alone or as a mixture.

Among them, methyl alcohol, ethyl alcohol, isopropyl alcohol (isopropanol), n-butyl alcohol (n-butanol), among others, in terms of reactivity, cost and crosslinkability of the resulting amino resin. Alternatively, use of isobutyl alcohol (isobutanol) or the like is desirable.

In the present invention, α and β as described above are used.
-Ethylene unsaturated carboxylic acid and a formaldehyde-containing functional group-containing ethylenically unsaturated monomer-based copolymer obtained by using various ethylenically unsaturated monomers, For 1 gram (g),
It is desirable to use it in such a ratio that the acid value becomes about 20 to about 200 equivalents,

On the other hand, formaldehyde is preferably used in a ratio of about 1 to about 4 mol per 1 mol of the amino compound. Further, as the organic solvent, among others, alcohols are preferable. Is preferably used in a ratio of about 3 to about 10 mol per 1 mol of the amino compound.

In the present invention, the temperature during the methylolation,
That is, the temperature during the addition reaction with formaldehyde is appropriately within the range of about 20 to about 120 ° C., preferably within the range of 60 to 100 ° C., and usually at such temperature. The reaction may be continued for about 1 to about 3 hours.

The so-called methylol compound formation reaction through such an addition reaction preferentially proceeds from neutral to alkaline side, and therefore, in addition to such temperature,
The degree of methylolation can be easily controlled by such means as using a catalyst or by adjusting the pH of the reaction system.

The temperature of the condensation reaction of the present invention, which is carried out subsequent to the so-called methylol compound formation reaction through such addition reaction, is about 80 to about 150 ° C.
Is appropriately within the range, preferably 95 to 120 ° C.
The range is suitable, and the reaction is usually allowed to continue at such temperature for about 2 to about 4 hours.

What is obtained at the time of completion of this condensation reaction is considered to be a partial condensate of an amino resin and a carboxyl group-containing resin. To make this condensate aqueous, the carboxyl group in the resin is used. May be completely neutralized or partially neutralized with a volatile basic substance (volatile base) and dissolved or dispersed in an aqueous medium.

In this case, excess organic solvent is distilled off under reduced pressure from the solution of the copolymer, and then neutralized.
You may make it melt | dissolve or disperse | distribute in an aqueous medium, or, after neutralizing, in an aqueous medium,
After dissolving or dispersing, the excess organic solvent,
It may be distilled off under reduced pressure with water,

Further, after neutralization is carried out in advance, the solvent is removed, and if necessary, the neutralization is carried out again, and then the solution is dissolved or dispersed in an aqueous medium. Good.

In the case, only typical examples of volatile bases are listed, ammonia and
Various amines such as monoethanolamine, dimethylamine, diethylamine, triethylamine, triethanolamine, diethylethanolamine, dimethylethanolamine or morpholine, etc., but as a degree or degree of neutralization by the volatile base. Is most preferably about 80 to 100%.

The aqueous medium referred to herein includes water and a mixture of water and a water-soluble solvent. Such water-soluble solvents, that is, various typical ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diacetone alcohol, are listed only as typical water-soluble solvents.

Or ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether or diethylene glycol monoethyl ether,

Alternatively, diethylene glycol diethyl ether, diethylene glycol monobutyl ether,
Various glycols such as triethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether or dipropylene glycol dimethyl ether;

Furthermore, isopropyl alcohol, n-
Various alcohols such as butyl alcohol, isobutyl alcohol or 3-methoxybutanol, 3-methyl-3-methoxybutanol and the like can be used alone or in combination of two or more, of course. However, if necessary, it is also possible to use a mixture of a small amount of another so-called water-insoluble solvent.

The aqueous thermosetting coating composition of the present invention thus obtained usually contains the above-mentioned amino resin in the resin solid content in an amount of about 5% by weight or more. And if it is less than 5% by weight,
Inevitably, it becomes impossible to impart sufficient thermosetting property, which is not preferable.

The aqueous thermosetting coating composition of the present invention comprises, by itself, an aqueous resin which is a basic component constituting the aqueous thermosetting coating composition, that is, an aqueous amino resin. Although it can be used as a thermosetting paint,

Of course, various other water-based resin components such as water-based acrylic resin, water-based polyester resin, water-based epoxy resin or water-based urethane resin may be added, if necessary. is there.

The aqueous thermosetting coating composition of the present invention may further contain, if necessary, an acid catalyst such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid or dinonylnaphthalene disulfonic acid, or an amine thereof. A salt is used as a so-called curing aid, so that the amount is 0.1 to 1.0 part by weight with respect to 100 parts by weight of the solid content of the aqueous resin as a basic component constituting the aqueous coating composition. Of course, it may be added in a ratio.

Similarly, various well-known and commonly used additives such as leveling agents, defoaming agents, lubricants or pigments may be added to the waterborne thermosetting coating composition of the present invention. It is also possible.

The aqueous coating composition of the present invention is prepared by a dipping method,
It can be applied by a variety of known and conventional methods, such as brushing, spray painting or roll coating, among others wood, paper, fibers, plastics, ceramics, inorganic cement substrates, ferrous or non-ferrous metals and the like. , Can be coated on the surface of various base materials,

The aqueous coating composition of the present invention comprises
Usually, in a temperature range of about 100 to about 250 ° C.,
Moreover, baking can be performed under heating conditions of about 5 seconds to about 30 minutes.

[0056]

EXAMPLES Next, the present invention will be explained more specifically with reference to Synthesis Examples, Reference Examples, Examples and Comparative Examples, but the present invention is by no means limited to these Examples. Not a thing. In the following, all parts and% are based on weight unless otherwise specified.

Synthesis Example 1 A flask equipped with a stirrer, a reflux condenser for expelling water, a thermometer and an inert gas inlet tube was charged with 50 parts of isobutyl alcohol and heated to 105 ° C.

To this, 15 parts of styrene, 5 parts of acrylic acid, 10 parts of acrylamide, 20 parts of n-butyl acrylate and "perbutyl O" [tert-butyl (2-foil of NOF CORPORATION) Ethyl hexanoate)]
A mixed solution consisting of 3 parts of

The solution was added dropwise over 4 hours and further reacted at 105 ° C. for 3 hours to obtain a solution of a copolymer having a nonvolatile content (solid content) of 49.8%.
Hereinafter, this is abbreviated as a copolymer a.

Then, 50 parts of "Hormite IB" [formaldehyde / isobutanol / water = 40/50/10 (weight ratio) mixture manufactured by Koei Chemical Industry Co., Ltd.] was added to the copolymer a. In addition, after reacting at 95 ° C. for 2 hours, 30 parts of benzoguanamine was added and reacted at 95 to 105 ° C. for 3 hours.

After that, isobutanol was removed under reduced pressure, and the solvent was replaced with butyl cellosolve. Then, the solution was neutralized with dimethylethanolamine until the pH became 8.5, and the non-volatile content was 72.3. % Resin solution was obtained. Finally, it was diluted with ion-exchanged water so that the nonvolatile content became about 40%. Hereinafter, this is abbreviated as resin A.

Synthesis Example 2 50 ml of isobutanol was placed in a flask equipped with a stirrer, a reflux condenser for purging water, a thermometer and an inert gas introducing tube.
Parts were charged and heated to 105 ° C.

From this, from 20 parts of acrylamide, 5 parts of acrylic acid, 10 parts of n-butyl acrylate, 5 parts of ethyl acrylate, 10 parts of n-butyl methacrylate and 3 parts of "Perbutyl O". The mixed solution was added dropwise over 4 hours, and further reacted at 105 ° C. for 3 hours to obtain a solution of a copolymer having a nonvolatile content of 50.6%. Hereinafter, the copolymer thus obtained is abbreviated as a copolymer b.

Then, to this copolymer b, 50 parts of "Hormite IB" was added, and after reacting at 95 ° C for 2 hours, 10 parts of benzoguanamine was charged, and 1 hour later, Again, 10 parts of this benzoguanamine, and another hour later, another 1 part
0 part was charged with a total of 30 parts of the benzoguanamine. Furthermore, the reaction was continued for 2 hours, and the condensation reaction was carried out at a temperature of 95 to 105 ° C. for a total of 4 hours.

After that, isobutanol was removed under reduced pressure, and the solvent was replaced with butyl cellosolve. Then, the solution was neutralized with dimethylethanolamine until the pH reached 8.5, and the nonvolatile content was 70.0. % Resin solution was obtained. Finally, it was diluted with ion-exchanged water so that the nonvolatile content became about 40%. The resin solution thus obtained will be abbreviated as resin B hereinafter.

Reference Example 1 (Preparation Example of Butylated Benzoguanamine Resin) In a flask equipped with a stirrer, a reflux condenser for expelling water and a thermometer, 187 parts of benzoguanamine, 300 parts of “Hormite IB” and 294 parts of isobutanol were added. After adding 3 parts and heating at 95 ° C. for 3 hours, 0.9 part of formic acid was added and the mixture was brought to reflux for 1 hour.

Then, the reaction was carried out for 4 hours under this reflux condition, and then isobutanol was removed under reduced pressure to obtain a solution of butylated benzoguanamine resin having a nonvolatile content of 80%. Hereinafter, this is abbreviated as amino resin F.

Synthesis Example 3 100 parts of the amino resin F and 150 parts of the copolymer a obtained in Synthesis Example 1 were charged into a flask equipped with a stirrer, a temperature control device and a water cooling reflux condenser. And then 80
When heated and stirred at ℃ for 2 hours, the viscosity becomes Z
_4, rose to Z ₆ -Z ₇ ^3.

Then, isobutanol was removed under reduced pressure, the solvent was replaced with butyl cellosolve, and the mixture was neutralized with dimethylethanolamine until the pH reached 8.5 to give a nonvolatile content of 71.5. % Resin solution was obtained. Finally, it was diluted with ion-exchanged water so that the nonvolatile content became about 40%. Hereinafter, this is abbreviated as resin C.

Synthesis Example 4 100 parts of the amino resin C and 150 parts of the copolymer b obtained in Synthesis Example 2 were charged in a flask equipped with a stirrer, a temperature control device and a water cooling reflux condenser. And then 80
When the mixture was heated and stirred at 0 ° C. for 2 hours, the viscosity increased from Z ₄ -Z ₅ to Z ₆ .

Then, isobutanol was removed under reduced pressure, the solvent was replaced with butyl cellosolve, and the mixture was neutralized with dimethylethanolamine until the pH reached 8.5, and the nonvolatile content was 69.9. % Resin solution was obtained. Finally, it was diluted with ion-exchanged water so that the nonvolatile content became about 40%. Hereinafter, this is abbreviated as resin D.

Reference Example 2 (Preparation Example of Water-Soluble Acrylic Resin) A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introducing pipe and a dropping tank was charged with 450 parts of butyl cellosolve and heated to 120 ° C. Warmed.

While maintaining the temperature at 120 ° C., from the dropping tank, 87 parts of ethyl acrylate and 87 parts of n-butyl acrylate were used.
Part, 75 parts of styrene, 30 parts of 2-hydroxyethyl acrylate, 21 parts of acrylic acid and 18 parts of benzoyl peroxide were continuously added dropwise over 4 hours.

One hour after the end of the dropping, "perbutyl
3 parts of "O" was added, and the reaction was further performed for 2 hours. The resin solution thus obtained was then stripped of 375 parts of solvent under reduced pressure and neutralized with 20 parts of dimethylethanolamine. Further, an aqueous solution of acrylic resin was obtained by diluting with 200 parts of ion-exchanged water. Hereinafter, this is abbreviated as acrylic resin E.

Examples 1 and 2 and Comparative Examples 1 to 3 The respective resins obtained in Synthesis Examples 1 to 4 and Reference Examples 1 and 2 were mixed at the ratios shown in Table 1 (solid content weight ratio). Thus, various water-based paints were prepared by blending, mixing and dispersing.

Next, after mixing the respective components,
By adding butyl cellosolve and water, the amount of organic solvent in the obtained coating composition was set to 20% and the nonvolatile content was set to 65%.

Thereafter, 0.1% of paratoluenesulfonic acid and 0.1% of a silicon-based leveling agent were added to each of them, and the desired water-based thermosetting paint and the control were prepared. A waterborne thermosetting paint for use was obtained.

Next, each of the water-based paints was applied on a tin plate with a bar coater so that the dry coating film thickness was 10 microns (μm), and the conditions were set at 180 ° C. for 10 minutes. Baking was performed to cure the coating film.

After that, various performance evaluations were carried out on each of the cured coating films thus obtained. The results are collectively shown in Table 2.

[0080]

[Table 1]

[0081]

[Table 2]

[0082]

[Table 3]

<< Footnote in Table 1 >> The criteria for evaluation and judgment of each performance are as follows.

∘ ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ ×. … It can't be put to practical use

Water dilutability: until a certain amount of paint becomes cloudy,
It was diluted with water and judged by the amount of water when it became cloudy.

Viscosity: The viscosity was measured using a B type viscometer.

Boiling resistance ... After being immersed in boiling water for 30 minutes, the degree of whitening of the coated surface was visually determined.

Pencil hardness: Performed according to JIS K-5400 "Pencil scratch test".

Cohesion: The coating film is cut with a cutter / knife in a grid pattern at intervals of 1 mm for convenience.
Make 100 squares, peel off with cellophane tape, divide the number of remaining squares by the original number (100), multiply by 100, the so-called percentage ("%") Was displayed.

[0090]

By using the water-based resin of the present invention and the water-based thermosetting coating composition of the present invention, or by using the water-based resin obtained by the method of the present invention, the curability is particularly excellent. For the first time, it is possible to develop a novel aqueous amino resin component into an aqueous paint.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C09D 161/32 PHH

Claims (6)

[Claims] 1. A copolymer obtained by copolymerizing an α, β-ethylenically unsaturated carboxylic acid and an ethylenically unsaturated monomer having a functional group capable of adding formaldehyde as essential raw material components. Polymerization product and formaldehyde, in the presence of an organic solvent, to a methylol compound obtained by addition reaction, to cause a condensation reaction of an amino compound, and then neutralize at least a part with a basic substance, aqueous A water-based resin obtained by oxidization. 2. The aqueous resin according to claim 1, wherein the copolymer has an acid value within the range of 20 to 150. 3. A copolymer obtained by copolymerizing α, β-ethylenically unsaturated carboxylic acid and an ethylenically unsaturated monomer having a functional group capable of adding formaldehyde as essential raw material components. A polymer and formaldehyde are subjected to an addition reaction in the presence of an organic solvent, to which a methylol compound is obtained, to which an amino compound is added, and a condensation reaction is performed under heating. A method for producing a water-based resin, characterized in that it is hydrated and made water-based. 4. The method for producing an aqueous resin according to claim 3, wherein the copolymer has an acid value within the range of 20 to 150. 5. A copolymer obtained by copolymerizing an α, β-ethylenically unsaturated carboxylic acid and an ethylenically unsaturated monomer having a functional group capable of adding formaldehyde as essential raw material components. A polymer and a formaldehyde are subjected to an addition reaction in the presence of an organic solvent, to a methylol compound obtained by condensation reaction with an amino compound, and then,
An aqueous resin obtained by neutralizing at least a part of a basic substance and making it aqueous should be contained as an essential base resin component so that the solid content of the aqueous resin is 5% or more. An aqueous thermosetting coating composition, characterized in that 6. The aqueous thermosetting coating composition according to claim 5, wherein the copolymer has an acid value within the range of 20 to 150.