JPH0459330B2 - - Google Patents

Description

[Detailed description of the invention]

[Purpose of the Invention] (Industrial Field of Application) The present invention relates to a method for producing an aqueous resin dispersion, and more specifically to a coating composition for baking metals, particularly a coating excellent as a coating for the inner surface of a pipe. The present invention relates to a method for producing an aqueous resin dispersion that can form a water-based resin dispersion. (Prior Art) Conventionally, it has been desired to shift paints for cans and anticorrosion paints to water-based paints from the viewpoints of resource saving, energy saving, and environmental pollution. As in the case of aqueous systems, epoxy resin systems have been mainly studied, and various methods have been proposed for dispersing epoxy resins in water. For example, as a method for dispersing epoxy resin in water using a surfactant, two methods are known: a method using an anionic surfactant and a method using a nonionic surfactant. However, in the former case, the oxirane ring opens during the emulsification process and storage, resulting in decreased reactivity and poor performance of the formed coating, and sometimes problems with thickening and gelation during storage. On the other hand, in the latter case, from the viewpoint of dispersibility and storage stability, the system contains a fairly large amount of surfactant, so this surfactant may cause chemical and mechanical damage to the formed coating film. tends to have an adverse effect on character. As a solution to this problem, various self-emulsifying epoxy resins have been proposed in which epoxy resins are modified with acrylic resins and segments with emulsifying power are introduced into the molecules. For example, JP-A-53-1228 discloses a grafted polymer obtained by polymerizing a monomer mixture containing a carboxylic acid monomer using a free radical generator such as benzoyl peroxide in the presence of an epoxy resin. It has been shown that epoxy resins can be stably dispersed in aqueous media containing bases. JP-A-53-14963 and JP-A-55
Publication No. 9433 shows that a partial reactant containing an excess of carboxyl groups obtained by reacting an acrylic resin with a relatively high molecular weight aromatic epoxy resin can be stably dispersed in an aqueous medium in the presence of ammonia or amine. has been done. JP-A-55-3481 and JP-A-55-3482 disclose that epoxy resins containing substantially oxirane groups are obtained by esterifying a carboxyl group-functional polymer with an epoxy resin in the presence of an amine esterification catalyst. A self-emulsifying epoxy ester copolymer is disclosed that is self-emulsifying in water with a base. Japanese Patent Publication No. 57-105418
No. 58-198513 discloses that a low molecular compound having an epoxy group and an acryloyl group in one molecule obtained by partially reacting an aromatic epoxy resin and (meth)acrylic acid, and acrylic acid or An aqueous dispersion composition obtained by polymerizing a monomer mixture containing methacrylic acid and neutralizing it with a basic compound is disclosed. Since the self-emulsifying epoxy resin obtained by the above technique does not contain a surfactant in the coating material, a strong coating film can be obtained by itself. When a faster curing speed is required for these paints, a water-soluble amino resin with good curability is usually blended. For example, an appropriate amount of water-soluble amino resin can improve the curing speed without reducing the physical properties of the formed coating film.
In some cases, desirable coating film hardness can be obtained by increasing the crosslinking density, but especially when used as a coating for the inner surface of a can, heat sterilization can remove low-molecular compounds caused by amino resins in the contents of the can. was leached out, which caused problems in terms of hygiene. (Problems to be Solved by the Invention) The present inventors have conducted extensive studies in order to overcome the hygienic problems associated with the combined use of water-soluble amino resins and further improve the adhesion of the coating film. As a result of repeated efforts, the present invention was arrived at. That is, the present invention provides an acrylic resin (A) containing 12 to 70% by weight of monobasic carboxylic acid monomer units as an essential component.
and an aromatic epoxy resin (B) having an average of 1.1 to 2.0 epoxy groups in one molecule, and a partial bond with an excess of carboxyl groups (D) in an amount of ammonia or amine such that the pH becomes 4 to 11. A phenol resin (C) whose main component is a compound represented by the following general formula is mixed with 2 to 40% by weight of the total resin into a dispersion dispersed in an aqueous medium in the presence of a homogeneous and stable This is a method for producing an aqueous resin dispersion, which is characterized by producing a dispersion state. (In the formula, R ₁ is a hydrogen atom or a carbon number of 1 to 12
The alkyl group, R ₂ and R ₃ are a hydrogen atom or a methylol group (However, R ₂ and R ₃ are never hydrogen atoms at the same time.) n represents an integer of 1 to 3. ) [Structure of the invention] (Means for solving the problems) The acrylic resin (A) in the present invention is composed of a monobasic carboxylic acid monomer such as acrylic acid or methacrylic acid and other copolymerizable monomers. It can be obtained by copolymerizing a monomer mixture in an organic solvent using a common radical polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide at a temperature of 80°C to 150°C. The copolymerizable monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, and 2-acrylate.
Acrylic esters such as ethylhexyl, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n- methacrylate Methacrylic acid esters such as hexyl, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene,
Styrenic monomers such as chlorstyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide It can be selected from one or more of N-substituted (meth)acrylic monomers such as N-substituted (meth)acrylic monomers, epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile. The amount of monobasic carboxylic acid monomer used is 12 to 70% by weight based on the total monomer amount. If the amount is less than 12% by weight, the dispersion stability of the resin in an aqueous medium may be affected, and the adhesion of the painted film to the metal may be affected. When used for the interior of cans, it is undesirable because it deteriorates the flavor suitability, etc. On the other hand, if the amount used is more than 70% by weight, the reaction system when polymerizing the acrylic resin (A) is undesirable. The viscosity of the paint becomes extremely high, which not only makes manufacturing difficult, but also deteriorates the water resistance of the painted film and the boiling resistance when used on the inside of a can. The weight average molecular weight of the acrylic resin (A) is preferably in the range of 3,000 to 80,000; if the weight average molecular weight is less than 3,000, the crosslinking density of the coating film will increase, which will impede processability; Especially when it is larger than 80000, aromatic epoxy resin (B)
There is a tendency for gelation to occur when reacting with. The aromatic epoxy resin (B) in the present invention is obtained by condensing bisphenol A and epihalohydrin in the presence of an alkali catalyst, and has an average of 1.1 to 2.0 epoxy groups in one molecule,
Those having a number average molecular weight of 300 or more, preferably 900 or more are used. Commercially available products include Epicote 828, Epicote 1001, Epicote 1004, Epicote 1007, and Epicote 1009 manufactured by Ciel Chemical Co., Ltd. In addition, as an aromatic epoxy resin, a modified epoxy resin in which the epoxy group of the bisphenol A type epoxy resin is reacted with a vegetable oil fatty acid such as dehydrated castor oil, soybean oil fatty acid, or coconut oil fatty acid or a modifier such as bisphenol A is used. You can also use The acrylic resin-aromatic epoxy resin partial bond (D) in the present invention is an acrylic resin (A) obtained by copolymerizing a copolymerizable monomer mixture containing 12 to 70% by weight of a monobasic carboxylic acid monomer. It can be produced by partially reacting the aromatic epoxy resin (B) with an aromatic epoxy resin (B) having an average of 1.1 to 2.0 epoxy groups in one molecule. That is, acrylic resin (A) and aromatic epoxy resin (B) are heated at 60°C to 170°C in a hydrophilic organic solvent such as ethylene glycol monobutyl ether in the presence of ammonia or amine as described below. in 10
It is best to stir for a minute to 20 hours. In addition, if the reaction is carried out in a relatively high boiling point solvent such as hexyl cellosolve, butyl cellosolve, methyl cellosolve acetate, or ethyl cellosolve acetate at 120°C or higher, acrylic resin ( A partial reaction product of A) and aromatic epoxy resin (B) can be obtained. Control of the reaction can be checked by measuring the percentage of oxirane, measuring the increase in viscosity or charting the molecular weight distribution by gel permeation chromatography (GPC). The reduction rate of oxirane groups is 5 to 5% relative to the oxirane content of the aromatic epoxy resin as a raw material.
95%, more preferably 30 to 70%. If the reduction rate of oxirane groups is less than 5%, the acrylic resin-aromatic epoxy resin partial reactant cannot be sufficiently self-emulsified in the aqueous medium and tends to separate during storage, while if it is greater than 95%, the The processability of the film tends to deteriorate. In particular, water-based resins obtained when the oxirane group content is in the range of 30 to 70% are excellent in coating suitability. In the present invention, the acrylic resin-aromatic epoxy resin partial bond (D) also contains a monobasic carboxylic acid monomer in the presence of the aromatic epoxy resin (B).
It can be obtained by polymerizing a copolymerizable monomer mixture containing 12 to 70% by weight using a relatively large amount of an organic peroxide such as benzoyl peroxide. In this case, an aromatic epoxy resin grafted with an acrylic resin is obtained. The acrylic resin-aromatic epoxy resin partially bonded product (D) in the present invention also has double epoxy groups and double A compound having both a bond and a monobasic carboxylic acid monomer
It can be obtained by polymerizing a copolymerizable monomer mixture containing 12 to 70% by weight using a radical polymerization initiator. The solid content ratio of the acrylic resin (A) and the aromatic epoxy resin (B) is selected from the range of 1:1 to 1:6. Preparation of an aqueous dispersion using the acrylic resin-aromatic epoxy resin partial bond (D) is carried out by adding ammonia or amine in an amount such that the final composition has a pH of 4 to 11 in an aqueous medium. However, if high boiling point solvents are used in the previous step, it is preferable to remove these solvents in advance under reduced pressure. Examples of the above amines include alkylamines such as trimethylamine, triethylamine, and butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine, and aminomethylpropanol;
Morpholine etc. are used. Polyvalent amines such as ethylenediamine and diethylenetriamine can also be used. In the present invention, the aqueous medium is at least 10% by weight.
The above means water alone or a mixture with a hydrophilic organic solvent, and the hydrophilic organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,
Alkyl alcohols such as tert-butanol and isobutanol, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve,
Ether alcohols such as methyl carbitol and ethyl carbitol, ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate, and dioxane, dimethylformamide, diacetone alcohol, etc. are used. The aqueous resin dispersion in the present invention is an aqueous dispersion of the above-mentioned acrylic resin-aromatic epoxy resin partial bond (D), and further contains a phenol resin (C).
Obtained by blending. At this time, the phenol resin (C) is added to the aqueous dispersion of the partially bound product (D) while stirring. It is thought that through this operation, the phenol resin (C) enters the dispersed fine particles of the partially bound substance (D) and becomes associated with the partially bound substance (D), resulting in a stable resin dispersion. . The phenolic resin (C) in the present invention is obtained by addition condensation of phenols and formaldehyde in the presence of a catalyst, and may be one in which the phenolic hydroxyl group or the alcoholic hydroxyl group is modified with a low molecular weight alcohol. The above catalyst is ammonia,
Organic amines such as ethylamine, butylamine, diethanolamine, etc., basic compounds such as sodium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and hydrochloric acid, phosphoric acid,
There are acidic compounds such as sulfuric acid, acetic acid, and oxalic acid. Phenols include bifunctional phenols such as p-cresol, o-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol, carbolic acid, m-cresol, and m-ethyl. There are trifunctional phenols such as phenol, 3,5-xylenol and m-methoxyphenol, and tetrafunctional phenols such as bisphenol A and bisphenol B. Particularly preferred phenolic resins include highly methylolated phenolic resins consisting of relatively low molecular weight condensates represented by the following formula. (In the formula, R ₁ is a hydrogen atom or a carbon number of 1 to 12
an alkyl group, R ₂ and R ₃ represent a hydrogen atom or a methylol group, and n represents an integer of 1 to 3. ) The above-mentioned highly methylolated phenolic resin is obtained by addition condensation of formaldehyde to alkylphenol in the presence of an alkali catalyst, but dimethylolated product of alkylphenol is produced in high yield at a relatively low temperature of about room temperature to 60°C. After that, a method of proceeding with condensation or other known synthetic means can be used. The reaction conditions for producing such a phenolic resin can be freely selected within a range that satisfies the above requirements. Of course, there is no problem even if the phenolic resin (C) having a specific n number is reacted under reaction conditions that allow a high yield to be obtained, further purified by a conventional method, and used substantially as a single substance. It is also possible to prepare two or more types of alkylphenols with different types or with different n numbers, and use them by mixing them. The amount of phenolic resin (C) is 2 relative to the total amount of resin.
If it is less than 2% by weight, it will not contribute enough to the curing speed of the coating film, and if it exceeds 40% by weight, the physical properties such as processability of the coating film will tend to deteriorate. The aqueous resin dispersion according to the present invention can be used as a paint by adding a surfactant, an antifoaming agent, etc. to improve coating properties, if necessary. Suitable substrates are metal plates such as untreated steel plates, treated steel plates, galvanized iron plates, and tin plates.As for the coating method, spray painting such as air spray, airless spray, and electrostatic spray is preferable. Dip coating, roll coater coating, electrodeposition coating, etc. are also possible. Also, the baking conditions are temperature 150
You can choose from ℃ to 230℃ and time from 2 to 30 minutes. The aqueous resin dispersion of the present invention can also be used in rust-preventing primers, printing inks, anti-corrosion paints, etc. by adding appropriate rust preventive agents, pigments, fillers, etc., depending on the purpose. The present invention will be explained below using examples. In addition,
In the examples, "parts" and "%" indicate "parts by weight" and "% by weight," respectively. (Example) Example 1 [Preparation of phenolic resin solution] 136 parts of p-tert-butylphenol, 162 parts of 37% formaldehyde aqueous solution, and 160 parts of 25% sodium hydroxide aqueous solution were charged into a flask and reacted at 50°C for 3 hours. After that, the mixture was neutralized with hydrochloric acid and water was separated. After water separation, 250 parts of p-tert-butylphenol, 10
Add 3.7 parts of % hydrochloric acid and 250 parts of water and stir for about 30 minutes.
Once the exotherm has ended, add 25% sodium hydroxide.
Add 160 parts and 120 parts of 37% formaldehyde aqueous solution.
After reacting at 50℃ for 3 hours and neutralizing with hydrochloric acid to separate the aqueous layer, washing with water and separating the water were repeated 3 times, and the solution was dissolved in a mixed solvent of n-butanol/xylene/=1/1 to obtain 60% phenol. A resin solution was obtained. As a result of analyzing the obtained resin by GPC, it was found that 91% was a dimethylolated trimer of p-tert-butylphenol, and the rest were dimethylolated monomers, dimethylolated dimers, and tetramers. It contained a small amount of dimethylolated product. [Preparation of acrylic resin solution] Styrene 300.0 parts Ethyl acrylate 210.0 Methacrylic acid 90.0 Ethylene glycol monobutyl ether 388.0 Benzoyl peroxide 12.0 1/4 of the mixture with the above composition was placed in a four-necked flask purged with nitrogen gas and heated to 80 to 90°C. Heat it up, keep it at that temperature and gradually drop the remaining amount over 2 hours, and after the dropping is finished, stir it at that temperature for another 2 hours, then cool it, and the acid value is 93 (in terms of solid content), and the solid content is 59.7.
%, and a viscosity of 4100 cps (25°C; all viscosities hereinafter indicate the measurement results at 25°C). A carboxyl group-containing resin solution was obtained. [Preparation of epoxy resin solution] Epicote 1007 500 parts Ethylene glycol monobutyl ether 333.3 Pour the entire amount into a four-necked flask purged with nitrogen gas, gradually heat to raise the internal temperature to 100℃, stir for 1 hour, and after completely dissolving, heat to 80℃. Cool to 60% solids
An epoxy resin solution was obtained. [Preparation of aqueous dispersion] 50 parts of the above acrylic resin solution 100 parts of the above epoxy resin solution 2-dimethylaminoethanol 4.8 ion-exchanged water 355.2 30 parts of the above phenol resin solution In a four-necked flask, add and neutralize with stirring. After this, the temperature was raised to 80°C, reacted for 30 minutes, and then cooled. before and after reaction
The bond between acrylic resin and epoxy resin was confirmed by GPC measurement. After cooling, the solution was gradually added while stirring to make a uniform dispersion solution, and then the solid content was gradually added while stirring.
%, a milky white dispersion with a viscosity of 405 cps was obtained. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Example 2 [Preparation of phenolic resin solution] 108 parts of p-cresol, 162 parts of a 37% formaldehyde aqueous solution, and 160 parts of a 25% aqueous sodium hydroxide solution were placed in a flask, reacted at 50°C for 2 hours, and then heated to 100°C. After heating and reacting for another hour at 100℃, neutralizing with hydrochloric acid, n-butanol/xylene =
Extraction was performed with a 1/1 mixed solvent to obtain a 60% phenol resin solution. As a result of GPC analysis, more than 90% of the reaction product at 50°C for 2 hours was a dimethylol compound of p-cresol, and the final product was 9
% is dimethylolated p-cresol, 36% is dimethylolated dimer, 41% is dimethylolated trimer, 9% is dimethylolated tetramer, and 5% is dimethylolated pentamer or more. It was hot. An acrylic resin solution and an epoxy resin solution were prepared in the same manner as in Example 1. In addition, the preparation of an aqueous dispersion is
The same procedure as in Example 1 was carried out except that the phenolic resin solution was replaced with the above phenolic resin solution. The resulting dispersion had a solids content of 20% and a viscosity of 450 cps. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Example 3 [Preparation of epoxy resin] It was prepared in the same manner as in Example 1. [Preparation of aqueous resin dispersion] The above epoxy resin solution 150 parts Butyl cellosolve 30 Methacrylic acid 30 Styrene 18 Ethyl acrylate 2 Benzoyl peroxide 3.5 2-dimethylaminoethanol 4.8 parts Ion exchange water 560 Phenol resin solution of Example 2 30 Pour into a four-necked flask and raise the temperature of the liquid to 115°C while stirring. Next, the above mixture was added dropwise over a period of 1 hour, and the reaction was continued for an additional 2 hours at 115°C. After cooling and stirring, the mixture was gradually added to obtain a resin dispersion, and then the mixture was gradually added while stirring to obtain a stable aqueous dispersion. The resulting dispersion had a solids content of 20% and a viscosity of 403 cps. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Comparative Example 1 An acrylic resin solution and an epoxy resin solution were prepared in the same manner as in Example 1. [Preparation of aqueous dispersion] 50 parts of the above acrylic resin solution 100 parts of the above epoxy resin solution 2-dimethylaminoethanol 4.8 ion-exchanged water 295.2 In a four-necked flask, charge the following and bring the temperature to 80
℃, reacted for 30 minutes, and cooled. before and after reaction
GPC measurements confirmed the reaction between epoxy resin and acrylic resin. Further, when the mixture was gradually added with stirring, a milky white dispersion with a solid content of 20% and a viscosity of 362 cps was obtained. No abnormalities were observed in the obtained dispersion when it was stored at 50°C for 3 months. Comparative Example 2 An acrylic resin solution and an epoxy resin solution were prepared in the same manner as in Example 1. In addition, the preparation of an aqueous dispersion is
Cymel 325 instead of 30 parts of phenolic resin solution
(Water-soluble amino resin manufactured by Mitsui Toatsu Co., Ltd., solid content 80%)
The same procedure as in Example 1 was carried out except that 22.5 parts of . The resulting aqueous dispersion has a solids content of 20% and a viscosity of
It was 360cps. The aqueous dispersions obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were applied to a tin plate to a thickness of 8 to 10μ, and dried by baking at 165°C and 200°C for 5 minutes each to prepare test panels. did. The results of various resistance tests are shown in the table. In addition, the above aqueous dispersion was sprayed onto the inner surface of a 2-piece tin can with a content of 250 ml.
Cans with internal coatings were prepared by baking and drying at 165°C and 200°C for 5 minutes each, and their various resistances were tested. The results are shown in the table. From the table and the table, Examples 1 to 3 and Comparative Example 2 containing phenolic resin or melamine resin show superior performance to Comparative Example 1 in retort resistance, corrosion resistance, and saline storage test. However, Examples 1 to 3 are compared to Comparative Example 2.
Compared to other products, the amount of potassium permanganate consumed is extremely small and the extraction properties are excellent, as well as excellent flavor retention. The table and various test methods in the table are as follows. (1) Adhesion: Approximately 1.5mm using a knife on the coating surface
Make 11 vertical and horizontal cuts in the width of the goban. When a 24 mm wide cellophane adhesive tape is attached and strongly peeled off, the number of unpeeled areas in the goblin area is expressed in the numerator. (2) Retort resistance: After treatment in water at 125℃ for 30 minutes,
The coating film is judged visually and by peeling off the cellophane adhesive tape. (3) Workability: This occurs when using a special fold-type DuPont impact tester, placing a sample folded in half at the bottom, and dropping an iron weight weighing 1 kg with a flat contact surface from a height of 50 cm. The length of the crack in the paint film at the bent part was measured. 0 to 10 mm...○ mark 10 to 20 mm...△ mark 20 mm or more...indicated by × mark. (4) Corrosion resistance: A test piece with an X cut made on the coating surface using a knife was placed in 1% saline solution at 125℃30.
The treatment is carried out for several minutes, and the degree of corrosion near the X mark is determined. Items with no abnormalities... ○ Items with slight corrosion... △ Items with significant corrosion... × (5) Potassium permanganate consumption: Fill a can with internal coating with 250ml of ion-exchanged water, and seal it tightly. and 60
The samples were treated at -30 minutes at 100 degrees Celsius and at 100 degrees Celsius for 30 minutes, and measured according to the test method described in the Food Sanitation Law. (6) Salt solution storage test: 1% salt solution in a can with painted interior
After filling 250ml and sealing, pack them into cardboard boxes (15 cans in a box containing 30 cans). Vibrate with a vibrator for 5 hours, let the cans collide with each other, and store at 25℃ for 1 month. did. The above test cans were opened and the amount of iron eluted into the saline solution was measured by atomic absorption spectrometry. (Average of n: 15) (7) Flavor retention: ion exchange water 250% in inner coated cans
ml, the cans were sealed, sterilized at 100°C for 30 minutes, and then stored at 50°C for 6 months. The resulting liquid was subjected to a flavor test. No change at all... ○ Slight change... △ Significant change... Indicated by ×. [Effects of the Invention] The aqueous resin dispersion obtained in the present invention has excellent dispersion stability even though it contains a phenolic resin that cannot be dissolved or dispersed in a substantially aqueous medium alone. In addition, the aqueous resin dispersion obtained in the present invention has excellent curability, and the obtained coating film has
It has practical performance as a paint for cans, such as corrosion resistance, adhesion, processability, and retort resistance. In addition, the coating film does not contain unreacted low molecular weight substances, so it is highly hygienic.

【table】

【table】

Claims (1)

[Scope of Claims] 1. An acrylic resin (A) containing 12 to 70% by weight of monobasic carboxylic acid monomer units as an essential component;
Presence of ammonia or amine in an amount such that the partial bond (D) with an excess of carboxyl groups with the aromatic epoxy resin (B) having an average of 1.1 to 2.0 epoxy groups in one molecule has a pH of 4 to 11. A phenolic resin (C) whose main component is a compound represented by the following general formula is mixed into the dispersion dispersed in an aqueous medium in an amount of 2 to 40% by weight based on the total resin to achieve a uniform and stable dispersion. 1. A method for producing an aqueous resin dispersion, which comprises: (In the formula, R ₁ is a hydrogen atom or has 1 to 12 carbon atoms.
The alkyl group, R ₂ and R ₃ are hydrogen atoms or methylol groups (however, R ₂ and R ₃ are never hydrogen atoms at the same time), and n is an integer from 1 to 3. ) 2 Acrylic resin-aromatic epoxy resin partially bound by acrylic resin-aromatic epoxy resin (D) is obtained by partially reacting acrylic resin (A) and aromatic epoxy resin (B). Acrylic resin with excess carboxyl groups-aromatic The method for producing an aqueous resin dispersion according to claim 1, which is a partial reactant of a group-based epoxy resin. 3 Acrylic resin (A) and aromatic epoxy resin (B)
3. The method for producing an aqueous resin dispersion according to claim 2, wherein the solid content ratio between the solid content and the aqueous resin dispersion is 2:1 to 1:6. 4. The method for producing an aqueous resin dispersion according to claims 2 to 3, wherein the acrylic resin (A) has a weight average molecular weight of 3,000 to 80,000. 5. The method for producing an aqueous resin dispersion according to claims 1 to 4, wherein the aromatic epoxy resin has a number average molecular weight of 900 or more.