JPS62212413A - Production of aqueous resin dispersion - Google Patents

Abstract

PURPOSE:To obtain an aqueous resin dispersion excellent in storage stability, by effecting intermolecular crosslinking between a water-soluble acrylic resin and a hydrophobic acrylic resin by adding a diisocyanate to a mixture of these resins and dispersing the produced resin in water by emulsification. CONSTITUTION:A diisocyanate compound is added to a mixture of the following resins (weight ratio of 20/80-90/10), and the intermolecular crosslinking between these resins is effected to such an extent that the viscosity as measured according to the following conditions of viscosity measurement may increase by 10-300%. The product is neutralized by adding thereto 40-100mol%, based on the total, carboxyl groups of the resin base and dispersed by emulsification by the addition of water to obtain the titled aqueous dispersion. Resin A: a water-soluble acrylic resin of an acid value of 20-100, a hydroxyl value of 40-150 and a number-average MW of 1,000-100,000, which is rendered water-soluble by neutralization with a base, Resin B: a hydrophobic acrylic resin of an acid value <20, a hydroxyl value of 40-150 and a number-average MW of 1,000-100,000, which is not rendered water-soluble even by neutralization with a base. Conditions of viscosity measurements: in a methyl isobutyl ketone solution of a resin content of 60% at 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an aqueous resin dispersion that can be used in an aqueous coating composition.

[Conventional technology]

Paints containing acrylic resin as a main component, which use resin emulsions synthesized by emulsion polymerization reactions, are widely used in architectural and household applications as room temperature drying paints. Other types of acrylic resins include colloidal dispersion type, water-soluble type, and various so-called hybrid water-based paints that are considered to be in between these types, and are used for industrial purposes by drying at room temperature and by baking. . Water-soluble paints have film-forming properties, film gloss,
Water-dispersible type Interest is shifting to paints based mainly on resin.

As one type of water-dispersed paint, a type of paint whose main component is an aqueous resin dispersion obtained by forcibly emulsifying a hydrophobic acrylic resin using a water-soluble acrylic resin as a film-forming component and emulsifier has been studied. In addition to the good film-forming properties and gloss that are the features of water-soluble types, this product has excellent coating workability, especially suitability for thick film coating, suitability for brush coating and roller coating, and good atomization for spray coating. It is characterized by having the advantages of dispersion type paints, such as quick drying, and oxidation-curing type paints, aminoplast resins, and phenolic resins.

It is being considered as a baking-type paint in combination with blocked isocyanate compounds. When used as an oxidation-curing paint, the acrylic resin used has an oxidation-polymerizable group 1, such as an unsaturated alkyl group such as an unsaturated fatty acid group, an allyl group, or a dicyclopentenyl group, introduced into the side chain of the acrylic resin skeleton. A thing becomes an object of use.

[Problem that the invention seeks to solve]

However, it is difficult to obtain a dispersion with excellent suspension stability over a long period of time when the aqueous resin dispersion is made by blending and emulsifying the two types of resins mentioned above, and the suspended resin particles tend to aggregate and settle during storage. However, when this aqueous resin dispersion is used as a resin component for paints, there are no problems with appearance or film quality for a short period of time after coating. During long-term storage, paint film defects such as fading and spots occur, which remains a serious problem in practical use.

The present invention aims to solve the above problems.

The first object of the present invention is to provide an aqueous resin dispersion with excellent storage stability in the production of an aqueous resin dispersion of a water-soluble acrylic resin as a film-forming component and emulsifier and a hydrophobic acrylic resin as one dispersed phase resin. The object of the present invention is to provide a manufacturing method that provides a dispersion.

The second objective is to produce an oxidation-curable resin aqueous dispersion with excellent storage stability from water-soluble acrylic resins and hydrophobic acrylic resins having unsaturated groups such as unsaturated fatty acids in their side chains. The purpose is to provide a method.

[Means for solving problems]

The present invention is the following method for producing an aqueous resin dispersion.

(1) 20/80 to 90/10 of resin A and resin B below
A diisocyanate compound is added to a mixture of Neutralize by adding a base,
A method for producing an aqueous resin dispersion, which comprises emulsifying and dispersing water by adding water while stirring.

Resin A: A water-soluble acrylic resin having an acid value of 20 to 100, a hydroxyl value of 40 to 150, and a number average molecular weight of 1,000 to 100,000, which can become water soluble by neutralization with a base.

Resin B; acid value less than 20, hydroxyl value 40-150, number average molecular weight 1,000-1, which is insoluble in water even when neutralized with a base
00.000 hydrophobic acrylic resin.

Viscosity measurement conditions: A methyl isobutyl ketone solution with a resin solid content of 60% is used and the viscosity is measured at a temperature of 20°C.

(2) 20/80 to 90/10 of resin A and resin B below
A diisocyanate compound is added to a mixture of Neutralize by adding a base,
A method for producing an aqueous resin dispersion, which comprises emulsifying and dispersing water by adding water while stirring.

Resin A: has 5 to 60% by weight of unsaturated alkyl groups in the side chains of the resin skeleton, and can become water-soluble by neutralization with a base, with an acid value of 20 to 100 and a hydroxyl value of 40 to 40.
150, number average molecular weight t, ooo~100,000
water-soluble acrylic resin.

Resin B; has an unsaturated alkyl group in the side chain portion of the resin skeleton in an amount of 5 to 60% by weight in the total resin, and is insoluble in water even when neutralized with a base, with an acid value of less than 20 and a hydroxyl value of 40 to 150; A hydrophobic acrylic resin having a number average molecular weight of 1,000 to too, ooo.

Viscosity measurement conditions: A methyl isobutyl ketone solution with a resin solid content of 60% is used and the viscosity is measured at a temperature of 20°C.

Resin A and resin B used in the method for producing an aqueous resin dispersion according to the first aspect of the present invention are obtained by polymerizing α and β ethylenic monomers by solution polymerization, emulsion polymerization, and! ! It is produced by known polymerization reactions such as mono-turbid polymerization and bulk polymerization.

The α and β ethylenic monomers to be used include all monomers used in the production of general acrylic resins, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, etc. Carboxyl group-containing monomers represented by hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, N-methylolacrylamide, N-methylolmethacrylamide, etc. mer, the following formula (wherein R1 represents H or CI, R2 is cnH, n4p
z % However, n represents an alkyl group represented by an integer of 1≦n≦18. ) There are acrylic esters, methacrylic esters, etc. In addition, acrylonitrile, methacrylaterile, acrylamide, methacrylamide, N
-Methoxyacrylamide, N-methoxymethacrylamide, allyl acrylate.

Examples include allyl methacrylate, styrene, vinyltoluene, glycidyl methacrylate, and dicyclopentenyl methacrylate.

Resin A and resin B used in the second aspect of the present invention also have a resin skeleton obtained by polymerizing the above-mentioned monomers, but the side chain portion of the skeleton has an unsaturated alkyl group having oxidative curability. has been introduced.

The bonding form between the unsaturated alkyl group and the skeleton is not particularly limited, but the following (1
) to (4) are examples.

or or (in the formula, R8 represents H or CH, R represents an unsaturated alkyl group). Examples of the unsaturated alkyl group include unsaturated fatty acids such as drying oil fatty acids, semi-drying oil fatty acids, and dehydrated castor oil fatty acids. Origin of unsaturated alkyl group, allyl group.

may be included.

In (1) above, after producing an acrylic resin containing acrylic acid or methacrylic acid, the resin is reacted with a glycidyl ester of an unsaturated fatty acid, or a monomer obtained by reacting glycidyl acrylate or glycidyl methacrylate with an unsaturated fatty acid is preliminarily prepared. It is easily produced by synthesizing this and polymerizing it with other copolymerizable monomers.

(2) can be easily produced by the same method as (1), using glycidyl ethers of unsaturated alcohols in place of the glycidyl esters of unsaturated fatty acids in (1).

(3) can be easily produced by a dehydration esterification reaction from the following component obtained from an unsaturated fatty acid and N-methylmonoethanolamine and a carboxylic acid-containing acrylic resin.

R3C00N (CH,) CH,CH,OH (in the formula,
(4) in which R3 represents an unsaturated alkyl group is easily produced by copolymerization of an acrylic acid or methacrylic acid ester monomer of an unsaturated alcohol and another monomer.

In the first and second inventions, the resin A has such polarity that it can be stably dissolved in water by neutralization with a base, has an acid value of 20 to 100, a hydroxyl value of 40 to 150, and a number average molecular weight of Those in the range of 1,000 to 100,000 are eligible. If the acid value is less than 20, the water solubility is poor and resin B cannot be stably emulsified, and if it exceeds 100, the water resistance of the coating film will be impaired when used as a coating composition, which is undesirable. are essential as reaction points with diisocyanate compounds; if the water a value is less than 40, there will be insufficient reaction points, and if it exceeds 150, it will adversely affect the water resistance of the coating film, making it undesirable. If the average molecular weight is less than 1,000, there is concern about the durability of the coating film, while if it exceeds 100,000, the viscosity of the resin in the emulsification process will increase excessively, putting a burden on the manufacturing process, which is not practical.

Resin B of the first and second inventions is made of a hydrophobic acrylic resin with low polarity and constitutes a dispersed phase component in the aqueous resin dispersion. Resin B has an acid value of less than 20 and a hydroxyl value of 40 to 15.
0, and resins with a number average molecular weight of 1,000 to 10,0000 are targeted. An acid value of 20 or more is undesirable because it is highly hydrophilic and makes it difficult to form a dispersed phase. Regarding the hydroxyl value and number average molecular weight, the above ranges are important for the same reason as in the case of resin A described above.

Furthermore, in addition to the conditions for resin A and resin B of the first invention, resin A and resin B used in the second invention are such that the weight ratio of unsaturated alkyl groups in the resin is in the range of 5 to 60% by weight. This is an essential condition.

If the weight ratio of unsaturated alkyl groups, allyl groups or dicyclopentenyl groups is less than 5% by weight, there will be a shortage of reactive points for oxidative polymerization reaction, making it difficult to obtain a durable coating film;
If it is introduced in excess of %N, the polymerization reaction will proceed excessively and the coating film will become brittle.

The ratio of resin A and resin B constituting the resin aqueous dispersion needs to be in the range of 20/80 to 90/10 by weight. If Resin A is less than 20% by weight, a fine and stable suspension cannot be obtained due to insufficient quantity as an emulsifier, and if it exceeds 90% by weight, there will be no problem in production, but if Resin A alone This results in an aqueous resin dispersion with properties very similar to those of an aqueous solution, which has little utility value and is meaningless.

In the method for producing an aqueous resin dispersion according to the first and second aspects of the present invention, a small amount of a diisocyanate compound is reacted with a mixture of two types of resins, resin A and resin B, and resin A
A crosslinked component having a chemically crosslinked structure is made of a part of resin B, and the emulsifying power of the crosslinked component and resin A allows resin B to be stably emulsified and dispersed.

The amount of diisocyanate compound used is small;
Since it only functions to crosslink two resins, there is no need to particularly limit the structure. Typical diisocyanate compounds that are commercially available and can be easily used include:
Tolylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2
Examples include 2.4-trimethylhexamethylene diisocyanate, xylylene diisocyanate, dicyclohexylmethadiisocyanate, and lysine diisocyanate. Of course, even if it is not the above-mentioned examples, all those having two isocyanate groups in one molecule can be used, and those having two or more isocyanate groups can also be used in combination with these. .

The amount of the cyanate compound to be used is - The resin viscosity measured under the following viscosity measurement conditions after the reaction with the anate compound is 10 to 10% higher than the resin viscosity of the resin mixture before reaction under the same measurement conditions. The amount will be 300% higher.

Viscosity measurement conditions Resin is dissolved in methyl isobutyl ketone and solids content is 60%.
Measure the solution using a B-type viscometer at 20°C.

If the viscosity increase is less than 10%, it will not be much different from a conventional aqueous resin dispersion without diisocyanate treatment, and the effect of improving storage stability will be poor.If the viscosity is increased to more than 300%, gelation will occur during the reaction, etc. This is not appropriate as it tends to cause the above problem.

In the reaction of the diisocyanate compound, first, resin A and resin B are mixed uniformly, the temperature is heated to room temperature to 150°C, preferably 50 to 120°C, and the diisocyanate compound is added dropwise while stirring, and the reaction time is 1 to 6 hours after the dropwise addition. This is done by continuing stirring at the same temperature. Both Resin A and Resin B generally have a fairly high viscosity due to their molecular weights, and it is difficult to proceed with the above mixing and reaction without a solvent. Although the diisocyanate compound is treated as a solution, if necessary, the diisocyanate compound may be dissolved in an organic solvent that is not reactive with the diisocyanate and used for the reaction.Solvents used for this purpose generally include solvents that do not have active hydrogen, such as ethers. , ketones, esters, hydrocarbons, etc. are suitable. When using a non-water-soluble solvent, it is necessary to remove the solvent after the reaction by reducing pressure or freeze-drying to an extent that does not inhibit emulsification of the resin.

After removing the solvent, a hydrophilic organic solvent may be added again in order to lower the viscosity and make handling easier.

However, from the original meaning of a water-based coating composition, it is desirable to limit the amount of solvent as much as possible, and usually the final resin 1
The upper limit is 60 to 70 parts per 00 parts.

The resin mixture produced as described above is neutralized by adding a base corresponding to 40 to 100 mol% of the carboxyl groups, and then water is gradually added with sufficient stirring to obtain an aqueous resin dispersion. shall be. Suitable bases include alkylamines, alkanolamines, and ammonia commonly used in the paint industry. If the neutralization rate is less than 40 mol%, the hydrophilicity of the resin will be insufficient and sufficient emulsifying power cannot be expected. Also, there is no advantage even if it is used in excess of 100 mol%! If the viscosity of the M fat mixture is high,
It is also possible to emulsify by heating the system to raise the temperature from 25°C to about 90°C. Furthermore, if a pressure-resistant sealed container such as an autoclave is used, the emulsification temperature can be further increased.

The aqueous resin dispersion obtained by the production method of the first aspect of the present invention is used as an aqueous coating composition or a component thereof. In order to use this aqueous resin dispersion as a coating composition, it is used as it is or in a form in which a curing agent 1 such as an aminoplast resin, a phenol resin, a blocked isocyanate compound, etc. is blended therein. In this case, it is in the form of paint.

It can be used as a clear paint or as an enamel paint containing pigments.

Further, since the aqueous resin dispersion obtained in the second invention has an unsaturated group, it can be used as an oxidation-curing coating composition. In this case, a general curing agent is not necessary, and in addition to the above components, a combination of various metal salts, metal complexes, etc., called dryers, are used to further promote oxidative polymerization, and in the same way as above, clear paint or Can be used as enamel paint.

〔Effect of the invention〕

According to the first aspect of the present invention, when producing an aqueous resin dispersion from a water-soluble acrylic resin and a hydrophobic acrylic resin, a novel process is added in which a part of both side fat molecules is cross-linked with a diisocyanate compound. This makes it possible to produce an aqueous resin dispersion with excellent storage stability, which has been difficult to achieve up to now.

Further, according to the second invention, by using a resin having an unsaturated group as the water-soluble acrylic resin and the hydrophobic acrylic resin, it has oxidative curability and has excellent storage stability, and can be stored for a long time or heated. An aqueous resin dispersion is obtained which is stable when stored under water and can be used as an aqueous coating composition having excellent gloss, appearance, and coating workability.

〔Example〕

The content of the present invention will be explained in further detail with reference to Examples below. In each example, % and parts represent 1% by weight and parts by weight.

(1) Production of Resin A In a glass flask equipped with a thermometer, reflux condenser, nitrogen gas inlet tube, and stirrer, 36% of methyl isobutyl ketone was used as a reactant according to the compounding ratio shown in A(1) of Table 1. 6
and heated to 115-120℃ while blowing nitrogen gas.
heated to. While stirring, add 4.3 parts of acrylic acid, 12.0 parts of 2-hydroxyethyl methacrylate, 18.0 parts of n-butyl acrylate, 13.7 parts of 2-ethylhexyl acrylate, 12.0 parts of styrene, and t-butyl. A mixed solution of 1.2 parts of peroxy-2-ethylhexanoate was added over about 2 hours. After stirring for about 1 hour, 0.2 part of t-butylperoxy-2-ethylhexanoate,
A solution consisting of 2.0 parts of methyl isobutyl ketone was added dropwise over a period of about 5 minutes. After 0 drops, stirring was continued for about 3 hours.
Finally, aqueous solution acrylic resin A (1
) was obtained. Resin characteristic values are shown in Table 1.

Similarly, resin A (2) was produced based on the formulation shown in Table 1. Resin characteristic values are shown in Table 1.

Table 1 (2) Item (1) before the production of resin A having an unsaturated alkyl group
) Using the synthesis equipment and synthesis method described in Table 2, raw material (1)
Based on the formulation of A(3), the high acid value acrylic resin of A(3) is synthesized, and then as a second reaction, dehydrated castor shown in raw material (2) in Table 2 is added to this acrylic resin solution. Oil fatty acid glycidyl ester and triethylamine as a reaction catalyst were added and reacted for 3 hours with stirring at a reaction temperature of 120 to 130°C to obtain resin A (3) having an unsaturated alkyl group in the side chain. Resin property values are shown in Table 2.

Similarly, based on the formulations of A(4) and A(5) shown in Table 2, each high acid value acrylic resin was synthesized, and the respective unsaturated fatty acid glycidyl esters were further reacted to add unsaturation to the side chain. Water-soluble acrylic resins A(4) and A(5) having an alkyl group were obtained.

Also, based on the formulation of A(6) of raw material (1) in Table 2,
A high acid value acrylic resin was synthesized by the same synthesis method as above except that ethylene glycol dimethyl ether was used as the reaction solvent, and then methyl monoethanolamine described in A (6) of raw material (2) in Table 2 was synthesized. The amidated product with safflower oil fatty acid was mixed and subjected to a dehydration esterification reaction at 135 to 150°C for about 5 hours to obtain water-soluble acrylic resin A (6) having an unsaturated alkyl group in the side chain.

The solid content value of A(6) in Table 2 is 80% because a part of ethylene glycol dimethyl ether is distilled out at the same time as the reaction water during dehydration and esterification.
This is because the solid content was readjusted to 80% after the reaction was completed.

113 Epoxy site 355 (3) Production of resin B Resin B (1) having the resin characteristic values shown in Table 3 based on the formulation shown in Table 3 using the synthesis apparatus and synthesis method described in the previous section (1), B(2) was obtained.

(4) Production of resin B having an unsaturated alkyl group (2)
) in the same way as A(3) to A(5) of Table 4.
An acrylic resin was synthesized based on the formulation shown in 1), and then raw material (2) was added to carry out a second reaction to obtain resins B(3) and B(5) having unsaturated alkyl groups.

In addition, the synthesis conditions were exactly the same as those for B(3) and B(5) except that glycidyl methacrylate was used as the acrylic monomer of raw material (1) and unsaturated fatty acids were used in the second reaction. Resin B (4) having groups was obtained.

In addition, the reaction solvent described in the previous section was changed to ethylene glycol dimethyl ether instead of methyl isobutyl ketone.
Resin B (6) was obtained in the same manner as in 1).

Table 3 Example 1 Using the same resin synthesis apparatus as used for producing resin A in (1) above, 60 parts of resin A (1) and 40 parts of resin B (1) were placed in a flask and heated to 90 to 110°C. While stirring warmly, add about 5 parts of a diisocyanate solution consisting of 0.36 parts of tolylene diisocyanate and 3.6 parts of methyl isobutyl ketone.
After the reaction was completed, the solid content was adjusted to 60%.

When compared with the viscosity of the resin mixture before the start of the reaction, the viscosity at a temperature of 20°C increased from 1060 centipoise to 1840 centipoise.

The reactant was maintained at 80 to 90°C, and almost the entire amount of methyl isobutyl ketone was extracted from the system by reducing the pressure.

1005 parts of 3-methyl-3-methoxybutanol was newly added as a diluting solvent to obtain a resin with a solid content of approximately 85%.

Next, 3.0 parts of triethylamine was added to this resin at 40°C, and after uniformly mixing, 84.2 parts of deionized water was gradually added while stirring using a powerful tabletop stirrer, and the solid content was 3.0 parts.
A milky white aqueous resin dispersion with a transparent feel was obtained at 8%.

The aqueous resin dispersion was stored at room temperature for 6 months, but no resin aggregation or sedimentation was observed, and it had excellent storage stability. In addition, in order to evaluate the storage stability under heating,
Although it was stored at 0°C for one month, no aggregation or sediment was observed, confirming that it is highly stable. Table 5 shows the results of the viscosity, degree of thickening, solid content of the aqueous resin dispersion, appearance, and storage stability before and after the diisocyanate addition reaction.

Examples 2 to 5 Based on the respective formulations of Examples 2 to 5 shown in Table 5, aqueous resin dispersions of Examples 2 to 6 were obtained in exactly the same manner as in Example 1. The viscosity before and after the diisocyanate addition reaction, the degree of thickening, the solid content of the resin aqueous dispersion, the appearance, and the results of the storage stability evaluation are shown in Table 5. All the resin aqueous dispersions had excellent storage stability. Ta.

Example 6 Using the same resin synthesis apparatus as used in the production of the water-soluble acrylic resin in (1) above, 65 parts of resin A (6) was added.

Using 35 parts of resin B (6), 0.67 parts of isophorone diisocyanate and 5 parts of ethylene glycol dimethyl ether
．． A diisocyanate reaction product was prepared by reacting in the same manner as in Example 1, except that 0 parts of diisocyanate solution was used, and the reaction was carried out using 6.0 parts of triethylamine and 143.8 parts of deionized water without performing a solvent removal step. The resin aqueous dispersion of Example 6 was obtained by neutralization and water dispersion in the same manner as in Example 1.

The results of the viscosity before and after addition of diisocyanate, degree of thickening, solid content of the resin aqueous dispersion, appearance, and storage stability evaluation were evaluated in the fifth section.
Shown in the table.

This product also had excellent storage stability like Examples 1 to 5.

In addition, since Example 6 uses ethylene glycol dimethyl ether as the reaction solvent, the viscosity was measured at 100-120% for each of the initial mixture and the final reactant.
The solvent was removed under reduced pressure at °C, diluted with methyl isobutyl ketone to a solid content of 60%, and the measurement was performed.

Example 7 For 100 parts of the solid content of the aqueous resin dispersion of Example 3, 80 parts of rutile titanium oxide, 0.05 parts of cobalt naphthenate as cobalt metal, and 0.1 part of manganese naphthenate as metal violet. Further, 0.5 part of Shin-Etsu Silicone X-24-3005 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a leveling agent, and the pigment was dispersed using a sand mill. After dispersing the pigment, 0.3 part of triethylamine was added and the viscosity was adjusted to about 1800 centivoise with deionized water to obtain an oxidation-hardening mortar enamel.

Immediately after production and after being stored in a constant temperature room at 25° C. for 6 months, the white enamel was brushed onto a zinc phosphate-treated iron plate, and a coating film performance test was conducted. The test results are shown in Table 6. The coating film performance was not affected by storage at all and had excellent storage stability.

Examples 8 to 10 White enamels having the same solid content composition as in Example 7 were produced in the same manner as in Example 7 using the resin aqueous dispersions of Examples 4 and 5.6. .10. However, only in Example 9, for neutralizing white enamel, 0.2 parts of dimethylaminoethanol was used instead of triethylamine. It was coated and a membrane performance test was conducted. The test results are shown in Table 6.

In any of Examples 8 to 10, there was no change in coating film performance due to storage, and the storage stability was excellent.

Comparative Examples 1 and 2 In Examples 1 and 3, only the crosslinking reaction between the mixture of water-soluble resin and hydrophobic resin and diisocyanate was omitted,
Example 1, with the other steps and ingredient amounts being the same.
A resin aqueous dispersion corresponding to No. 3 was produced and designated as Comparative Examples 1 and 2. Table 7 shows the resin characteristic values of Comparative Examples 1 and 2.

Comparative Example 3 Using the resin aqueous dispersion with a solid content of 38% obtained in Comparative Example 2, a white enamel with the same solid content ratio was produced in exactly the same manner as in Example 7, and a white enamel was prepared as Comparative Example 3.

The coating film performance test results for Comparative Example 3 are shown in Table 7.

As shown in Table 7, the aqueous resin dispersions of Comparative Examples 1 and 2 were not treated with diisocyanate.

There was a problem with storage stability due to sedimentation and separation of the resin during storage. In addition, the enamel of Comparative Example 3 produced using this aqueous resin dispersion showed a significant decrease in coating film gloss during storage and a large number of protruding defects caused by aggregates, so-called "bubbles" on the coating surface, resulting in poor stability. There was a problem.

Claims (5)

[Claims] (1) 20/80 to 90/10 of resin A and resin B below
A diisocyanate compound is added to a mixture of A method for producing an aqueous resin dispersion, which comprises neutralizing by adding a base and emulsifying and dispersing by adding water while stirring. Resin A: A water-soluble acrylic resin having an acid value of 20 to 100, a hydroxyl value of 40 to 150, and a number average molecular weight of 1,000 to 100,000, which can become water soluble by neutralization with a base. Resin B; acid value less than 20, hydroxyl value 40-150, number average molecular weight 1,000-1, which is insoluble in water even when neutralized with a base
00,000 hydrophobic acrylic resin. Viscosity measurement conditions: A methyl isobutyl ketone solution with a resin solid content of 60% is used and the viscosity is measured at a temperature of 20°C. (2) Intermolecular crosslinking of a mixture of resin A and resin B with a diisocyanate compound is carried out at a temperature of 50 to 120.
A method for producing an aqueous resin dispersion according to claim 1, which is carried out at a temperature of .degree. (3) 20/80 to 90/10 of resin A and resin B below
A diisocyanate compound is added to a mixture of 0 (weight ratio) to perform intermolecular crosslinking so that the viscosity increases by 10 to 300% according to the viscosity measurement conditions below, and then 40 to 100 mol% of the total carboxyl groups of the resin. Neutralize by adding a base of
A method for producing an aqueous resin dispersion, which comprises emulsifying and dispersing water by adding water while stirring. Resin A: has 5 to 60% by weight of unsaturated alkyl groups in the side chains of the resin skeleton, and can become water-soluble by neutralization with a base, with an acid value of 20 to 100 and a hydroxyl value of 40 to 40.
150, a water-soluble acrylic resin with a number average molecular weight of 1,000 to 100,000. Resin B; has an unsaturated alkyl group in the side chain portion of the resin skeleton in an amount of 5 to 60% by weight in the total resin, and is insoluble in water even when neutralized with a base, with an acid value of less than 20 and a hydroxyl value of 40 to 150; A hydrophobic acrylic resin with a number average molecular weight of 1,000 to 100,000. Viscosity measurement conditions: A methyl isobutyl ketone solution with a resin solid content of 60% is used and the viscosity is measured at a temperature of 20°C. (4) Intermolecular crosslinking of a mixture of resin A and resin B with a diisocyanate compound is carried out at a temperature of 50 to 120.
The method for producing an aqueous resin dispersion according to claim 3, which is carried out at a temperature of .degree. (5) The unsaturated alkyl groups of Resin A and Resin B are one or more types selected from unsaturated alkyl groups, allyl groups, and dicyclopentenyl groups originating from fatty acids of drying oils or semi-drying oils or dehydrated castor oil fatty acids. A method for producing an aqueous resin dispersion according to claim 3 or 4.