JPH09100438A - Resin for water-based coating material and water-based coating material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin, excellent in adhesion, etc. to a metal and useful as coating materials, etc. for cans by neutralizing a copolymer of a specific esterifying reactional product and a carboxylic acid group-containing vinylic monomer and other vinylic monomers. SOLUTION: This resin for a water-based coating material is obtained by neutralizing (A) a copolymer comprising 2-75wt.% esterifying reactional product prepared by blending (i) an epoxy compound having two or more glycidyl groups in the molecule with (ii) an α,β-monoethylenically unsaturated dicarboxylic acid having two carboxylic acid groups different in acid strength and/or its anhydride and (iii) other carboxylic acid group-containing compounds at (1/2.5) to (1.5/1) equiv. ratio of epoxy groups/carboxylic acid groups, (B) 0.5-20wt.% carboxylic acid group-containing vinylic monomer such as preferably of the formula [R<1> is H, methyl, etc.; R<2> is H or COOR<3> (R<3> is H or a 1-10C hydrocarbon group)] and (C) 24.5-78wt.% other copolymerizable vinylic monomers with a base.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a coating film which has good adhesion to a substrate of a coating film, particularly a metal, maintains balance between coating film hardness and impact resistance, and has excellent water resistance. The present invention relates to a water-based paint that can be formed and has excellent storage stability, and a water-soluble resin used for the same, and is particularly suitable for use as a can paint.

[0002]

2. Description of the Related Art Food cans such as beverage cans used in canned coffee, canned juice, canned beer, etc.
In order to impart corrosion resistance to the contents, in the case of a can containing retort food, a coating is applied to withstand sterilization treatment.

Conventionally, organic solvent type paints such as epoxy resin / amino resin paint, acrylic resin / amino resin paint and polyester resin / amino resin paint have been used as the paint for cans. A method of heat curing in a baking furnace is used for curing the coating film. But,
A coating film formed from these solvent-based paints is said to have a problem from the viewpoint of resource saving as well as causing a large amount of organic solvent to volatilize during its heat curing treatment, which causes air pollution. The advent of resins for water-based paints that do not use is desired.

There are two types of resins for water-based paints, water-soluble resins and water-dispersible resins. The water-dispersible resins are produced by emulsion polymerization of vinyl monomers using an aqueous medium containing an emulsifier, In the coating film formed from this water-dispersible resin, since the surfactant used as an emulsifier remains, the water resistance of the coating film is poor, and it is difficult to coat with a roll coater due to its structural viscosity. have.

An acrylic resin is generally used as the water-soluble resin, but in order to make the resin water-soluble, it is necessary to introduce a carboxyl group into its molecule. However, a coating film formed from a water-soluble resin into which a large amount of a carboxyl group has been introduced in order to increase the water solubility of the resin has a problem that water resistance and alkali resistance are insufficient. In order to solve this, a method has been adopted in which aminoplast which gives a crosslinked structure to a coating film is used in combination with a water-soluble acrylic resin.

[0006] A coating film formed from a coating material composed of a water-soluble acrylic resin and aminoplast does not have sufficient adhesiveness with a metal serving as a coating substrate.
Furthermore, a method of using an epoxy resin in combination with this water-soluble paint has been adopted.

[0007]

However, a water-based paint comprising a water-soluble acrylic resin, aminoplast and an epoxy resin has drawbacks such as phase separation of the epoxy resin during storage and clouding of the formed coating film. We haven't got enough of it yet. It is an object of the present invention to provide a resin for water-based coatings, which can form a coating film having excellent adhesion to metals, a balance between hardness and impact resistance, and water resistance, and having excellent water solubility and storage stability. .

[0008]

Means for Solving the Problems In view of the above-mentioned problems of the prior art, the inventors of the present invention have made earnest studies on resins for water-based paints, and as a result, have reached the present invention. Is an epoxy compound (A) having two or more glycidyl groups in the molecule and an α, β-monoethylenically unsaturated dicarboxylic acid having two carboxylic acid groups having different acid strengths and / or its anhydride (B). ) And other carboxylic acid group-containing compound (C), the ratio of the epoxy group equivalent and the carboxylic acid group equivalent is 1 / 2.5 to
2 to 75% by weight of an esterification reaction product (I) obtained by mixing and reacting so as to be 1.5 / 1, 0.5 to 20% by weight of a vinyl monomer (II) having a carboxylic acid group, Other copolymerizable vinyl monomers (III) 2
A resin for water-based paint obtained by neutralizing a copolymer of 4.5 to 78% by weight with a base, and a water-based paint using this resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The esterification reaction product (I), which is a constituent component of the copolymer used in the resin for water-based paint of the present invention, is used in the range of 2 to 75% by weight in the copolymer component. It This is because if the amount is less than 2% by weight, the adhesion of the obtained coating film becomes insufficient, and if it exceeds 75% by weight, the viscosity of the obtained polymer becomes high and the coating workability is deteriorated. More preferably, it is in the range of 10 to 70% by weight.

The epoxy compound (A) having two or more glycidyl groups in the molecule, which is the raw material of the component (I) of the present invention, preferably has an epoxy equivalent of 150 to 3,000. This is because if the epoxy equivalent is less than 150, the resin obtained tends to gel during the esterification reaction described below, while if the epoxy equivalent exceeds 3000, the esterification reaction product has a high molecular weight. In addition, the viscosity of the obtained resin for water-based paint tends to increase. More preferably 300 to 20
00 range. The epoxy compound (A) of the present invention is particularly preferably a bisphenol A type or bisphenol F type epoxy resin. Typical examples include those commercially available from Yuka Shell Epoxy Co., Ltd. under the trade name of Epicoat.

An α, β-monoethylenically unsaturated dicarboxylic acid having two carboxylic acids having different acid strengths and / or its anhydride (B), which is a raw material of the component (I) of the present invention.
Is for efficiently obtaining a half-esterified epoxy resin without causing gelation in the reaction with the epoxy resin. Specific examples of the component (B) include itaconic acid, α-methylene glutaric acid, methacrylic acid dimer, and their anhydrides. Among them, itaconic acid and itaconic anhydride are preferable.

As the other carboxylic acid group-containing compound (C) which is a raw material of the component (I) of the present invention, maleic acid, fumaric acid, succinic acid, tartaric acid, adipic acid, sebacic acid, trimellitic acid and pyromellitic acid are used. Examples thereof include divalent or higher polyvalent carboxylic acids such as mellitic acid or anhydrides thereof, and monovalent or higher oxycarboxylic acids such as glycolic acid, benzoic acid, hydroxypropionic acid or dihydroxybenzoic acid.

The esterification reaction product (I) of the present invention is
It is obtained by reacting the components (A) to (C) in a ratio of the epoxy group equivalent to the carboxylic acid group equivalent of 1 / 2.5 to 1.5 / 1. This is because when the ratio of the epoxy group equivalent to the carboxylic acid group equivalent is less than 1 / 2.5, the water resistance of the coating film decreases due to the influence of the remaining carboxylic acid groups, and
This is because if it exceeds 1, the stability of the coating composition is reduced by the unreacted epoxy group. More preferably 1/2 to
The range is 1.1 / 1. Moreover, it is preferable to mix the components (B) and (C), which are carboxylic acid components, so that the ratio of the component (B) is in the range of 5 to 95 mol%. When the ratio of the component (B) is less than 5 mol%, the copolymerizability with the vinyl monomer described below is lowered, so that clouding or separation of the resin for water-based coatings tends to occur. This is because the viscosity of the coating resin tends to be high and the coating workability tends to deteriorate. More preferably, it is in the range of 20 to 70 mol%. In addition, (A) ~
Each of the components (C) can be used in combination of two or more, if necessary.

The esterification reaction product (I) of the present invention is
It can be manufactured by a known method. For example, a hydrophilic organic solvent such as butyl cellosolve is placed in a reaction vessel substituted with nitrogen, a tertiary amine such as triethylamine is used as a reaction catalyst, and the components (A) to (C) are added at 60 to 150 ° C. The reaction may be performed for 2 to 8 hours. In that case, it is preferable to add a radical polymerization initiator such as hydroquinone to suppress the radical polymerization by heat. The reaction can be controlled by tracing the residual epoxy group with an infrared spectrophotometer or measuring the acid value.

The vinyl monomer (II) having a carboxylic acid group, which is a constituent component of the copolymer used in the resin for water-based paint of the present invention, is used in the range of 0.5 to 20% by weight in the copolymer component. To be done. If the amount is less than 0.5% by weight, the solubility of the resulting copolymer in water decreases, and
This is because if it exceeds, the water resistance of the coating film decreases. More preferably, it is in the range of 3 to 15% by weight.

Examples of the vinyl-based monomer (II) of the present invention include carboxyl group-containing monomers having the structures represented by the following general formulas (1) and (3).

Embedded image (In the formula, R ¹ represents hydrogen or a methyl group or a carboxymethyl group, and R ² represents a hydrogen atom or an oxygen atom-containing hydrocarbon substituent represented by the general formula (2).)

Embedded image (In the formula, R ³ represents hydrogen or a hydrocarbon substituent having 1 to 10 carbon atoms.)

Embedded image (In the formula, R ⁴ represents hydrogen or a methyl group, and R ⁵ represents a hydrocarbon substituent having a structure represented by the general formulas (4) to (6) or a hydrocarbon substituent substituted with a hetero atom.)

Embedded image (In the formula, R ⁶ represents a linear or branched alkylene group having 1 to 3 carbon atoms.)

Embedded image (In the formula, R ⁷ represents a linear or branched alkylene group having 1 to 10 carbon atoms, R ⁸ represents a linear or branched alkylene group having 2 to 10 carbon atoms, an alkenylene group or a carboxyl group, Represents an arylene group or a cycloalkylene group which may be substituted with a halogen atom.)

Embedded image (In the formula, R ⁹ represents a linear or branched alkylene group having 1 to 10 carbon atoms, m represents an integer of 4 to 6, and R ¹⁰
R ⁸ represents the same substituent, and n is represented by an integer of 1 to 6. )

Specific examples of the carboxyl group-containing monomer having the structure represented by the above general formula (1) include methacrylic acid,
Acrylic acid, crotonic acid, vinyl benzoic acid, fumaric acid, itaconic acid, maleic acid, monobasic acid or dibasic acid monomers such as citraconic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomaleic acid Dibasic acids or acid anhydrides represented by octyl, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monooctyl itaconate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monooctyl fumarate, monoethyl citracone, etc. Examples thereof include monoesters of polymer monomers, and among them, methacrylic acid, acrylic acid, and maleic acid monoesters are preferable.

Specific examples of the carboxyl group-containing monomer having the structure represented by the above general formula (3) include β-carboxyethyl (meth) acrylate, β-carboxypropyl (meth) acrylate and β- (meth) acryl. Roxyethyl acid succinate, β- (meth) acryloxyethyl acid maleate, β- (meth) acryloxyethyl acid phthalate, β- (meth) acryloxyethyl acid hexahydrophthalate, β- (meth) acryloxyethyl Acid methyl hexahydrophthalate, γ- (meth) acryloxypropyl acid succinate, 2-hydroxyethyl (meth) acrylate to the terminal hydroxyl group of the ring-opening adduct of ε-caprolactone or γ-butyrolactone is esterified with succinic anhydride. Guide the carboxyl group to the end ε- caprolactone or γ- butyrolactone ring-opening adduct to the succinic acid monoester and 2-hydroxyethyl (meth) acrylate (e.g., Daicel Chemical Co., Ltd. Placcel F monomer,
Caprolactone modified hydroxyl group-containing (meth) acrylic acid ester such as phthalic acid monoester obtained by esterifying terminal hydroxyl group of UCC Tone M monomer) with phthalic anhydride or hexahydrophthalic anhydride, or hexahydrophthalic acid monoester And long-chain carboxyl group-containing monomers such as half-ester reaction products of acid anhydrides.
A succinic acid monoester and a phthalic acid monoester obtained by adding succinic acid or phthal to a monomer having a primary hydroxyl group such as hydroxyethyl (meth) acrylate is preferable. These vinyl-based monomers (II) of the present invention can be used alone or in combination of two or more, if necessary.

The other copolymerizable vinyl monomer (III), which is a constituent component of the copolymer used in the resin for water-based paint of the present invention, is used in the range of 24.5 to 78% by weight in the copolymer component. To be done. This is less than 24.5% by weight,
Since the hardness of the coating film obtained from the copolymer is insufficient, the coating film is likely to be scratched or chipped. If it exceeds 78% by weight, the flexibility of the coating film is reduced, and the coating film has a poor workability. This is because the sex becomes insufficient. More preferably, 15-6
It is in the range of 5% by weight. The vinyl-based monomer of the present invention (II
Examples of I) include alkyl (meth) acrylates having an alkyl group having 1 to 18 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. , Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
Lauryl acrylate, octyl (meth) acrylate,
Stearyl (meth) acrylate and the like can be mentioned.

Further, if necessary, aromatic vinyl compounds such as styrene and α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, nitrile group-containing monomers such as (meth) acrylonitrile, and 2-hydroxyethyl (meth). ) Hydroxyalkyl (meth) acrylates such as acrylates, glycidyl group-containing monomers such as glycidyl (meth) acrylates, methacrylamides, or methylolated modifications of these amides, benzyl (meth) acrylates, dicyclopentenyl (meth) ) Acrylate (for example, FA-51 manufactured by Hitachi Chemical Co., Ltd.)
1A), tricyclodecanyl (meth) acrylate (for example, FA-513A manufactured by Hitachi Chemical Co., Ltd.) and the like, which are commonly used, can be used in combination.

The polymerization catalyst used when copolymerizing the above-mentioned components (I) to (III) is not particularly limited, and known ones can be used. For example, peroxides such as lauryl peroxide and benzoyl peroxide, 2,2′-
An azo compound such as azobisisobutyronitrile may be mentioned. These polymerization initiators are used alone or in combination of two or more. Moreover, you may use a well-known chain transfer agent as needed. As the chain transfer agent, n-dodecyl mercaptan, n-octyl mercaptan, 2-ethylhexyl thioglycolic acid ester, thiophenol,
Examples include α-methylstyrene dimer.

The polymerization method for obtaining the copolymer of the present invention from the above-mentioned components (I) to (III) is not particularly limited. For example, the components (I) are (II) and (II).
After dissolving in component I), add a polymerization initiator, chain transfer agent, etc.,
It may be dropped and polymerized in a reaction vessel containing a hydrophilic organic solvent heated to a predetermined temperature, or the component (I) and the hydrophilic organic solvent may be mixed in advance and placed in a reaction vessel, (II),
A mixture of the component (III), a polymerization initiator, a chain transfer agent and the like may be dropped and polymerized.

The acid value of the copolymer obtained as described above is preferably in the range of 20 to 150 mgKOH / g. This is because the acid value of the copolymer is 20 mg KO
If it is less than H / g, the solubility in water tends to decrease, and it tends to separate easily in an aqueous solvent.
If the amount exceeds / g, the water resistance of the obtained coating film tends to decrease. More preferably, 30-120 mg
There is a range of KOH / g.

The copolymer obtained as described above is neutralized with a basic compound and diluted with water to obtain a resin for aqueous paint. As the basic compound that can be used, for example,
Alkylamines such as triethylamine, trimethylamine, butylamine, 2-dimethylaminoethanol,
Examples thereof include alcohol amines such as triethanolamine, diethylethanolamine, dimethylethanolamine, aminomethylpropanol, and morpholine. The amount of these basic compounds used is preferably in the range of 50 to 150% of the acid value of the copolymer.

The resin for aqueous paint obtained by the present invention can be dissolved in an aqueous medium to give an aqueous paint.
It is also possible to add a water-based amino resin to form a cross-linking-curable water-based paint. As the aqueous amino resin that can be used here,
Examples include alkyl etherified melamine resin, alkyl etherified benzoguanamine resin, alkyl etherified glycoluril resin, and diguanamine alkyl etherified resin having two triazine rings bonded to a phenylene nucleus. A methyl etherified amino resin is preferred. These amino resins are water-based resins 100
It is preferable to use it in a proportion of 10 to 60 parts by weight with respect to parts by weight. The stain resistance, hardness, solvent resistance, retort resistance and the like of the coating film formed from the aqueous coating material containing the resin for aqueous coating material of the present invention and the amino resin are further improved. Further, conventionally known polyether, polyester and the like can be used together as a flexibility-imparting agent for the coating film.

In order to improve the cross-linking speed of the coating material and the cross-linking density of the coating film, acid catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, or these sulfonic acids are used. It is preferable to use the amino-blocked compound of. Further, conventionally known leveling agents, defoaming agents, lubricants, pigments and the like can also be used in combination. Also, as a painting method,
Known methods such as roll coating, spray coating, and brush coating can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. The "parts" used in the examples are "parts by weight".
Is shown.

[Synthesis of Esterification Reaction Product (I-1)] A four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser was charged with 49.5 parts of butyl cellosolve and an epoxy resin having an epoxy equivalent of 450 ( 0.005 parts of hydroquinone monomethyl ether was added to a resin solution in which 36.5 parts of Epicoat # 1001 manufactured by Yuka Shell Co., Ltd. was dissolved, and the temperature was raised to 80 ° C. Then, itaconic acid 5.3
And 8.2 parts of sebacic acid were added and reacted for 30 minutes, and after confirming that the reaction solution became transparent, 0.5 parts of triethylamine was added and the temperature of the reaction solution was immediately raised to 130 ° C. After continuing the reaction for 4 hours and confirming that the acid value of the reaction system became constant, the reaction was terminated to obtain an esterification reaction product (I-1). The viscosity of the resulting solution is Z4
(Measured by Gardner-Holt foam viscometer at 25 ° C.), the solid content was 50.1% by weight, and the esterification reaction product (I
The acid value of -1) was 100 mgKOH / g.

[Esterification reaction products (I-2) to (I
Synthesis of -11)] Using the epoxy resins, carboxylic acids and the like shown in Table 1, the esterification reaction products (I-2) to (I-) are carried out in the same manner as in the case of the esterification reaction product (I-1). 1
1) was obtained. The evaluation results of the characteristics are shown in Table 1.

[Table 1] Epicoat # 1004: Epoxy resin with an epoxy equivalent of 875 manufactured by Yuka Shell Co., Ltd. Epicoat # 1007: Epoxy resin with an epoxy equivalent of 1750 manufactured by Yuka Shell Co., Ltd.

[Synthesis of Copolymer (P-1)] 20.0 parts of butyl cellosolve were placed in a four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser, and charged to 100
After the temperature was raised to ℃, the above esterification reaction product (I-1)
40.0 parts, ethyl acrylate 20.0 parts, methacrylic acid 1.9 parts, butyl acrylate 7.0 parts, styrene 9.
3 parts, 2-hydroxyethyl acrylate 2.0 parts, 2,
A mixture of 3.0 parts of 2'-azobisisobutyronitrile was added dropwise over 3 hours. 1 hour after the end of dropping, 2, 2 '
-Azobisisobutyronitrile (0.2 parts) was added, and the mixture was further held for 2 hours, then the reaction was terminated, and the copolymer (P-
1) was obtained. The viscosity of the obtained solution was Z4 (measured with a Gardner-Holt foam viscometer at 25 ° C.), the solid content was 60.2% by weight, and the acid value of the copolymer (P-1) was 54 mgKO.
H / g.

[Synthesis of Copolymers (P-2) to (P-19)] In the case of the copolymer (P-1) using the components (I) to (III) shown in Tables 2 and 3. Copolymers (P-2) to (P-19) were obtained in the same manner as. The evaluation results of the characteristics are shown in Tables 2 and 3.

[Table 2]

[Table 3] * 1: β-methacryloxyethyl acid succinate, manufactured by Mitsubishi Rayon Co., Ltd.

[0032]

Example 1 53.3 parts of methylated benzoguanamine resin (manufactured by Mitsui Cytec Co., Ltd., Mycoat # 106, solid content 75% by weight) in 100 parts of copolymer (P-1), 2-dimethylaminoethanol ( (DMAE) 5.1 parts, butyl cellosolve 1.6 parts, and deionized water 40 parts are added and well stirred, and then thinner (composition: deionized water / butyrocellosolve = 70/30) 50 parts is added to the coating composition. It was adjusted to a solid content of 40% and made into a paint. The appearance of the paint was transparent. This coating composition was applied on a 0.3 mm thick aluminum plate with a bar coater so that the dry coating film had a thickness of 8 to 10 μm, and baked at 200 ° C. for 10 minutes in a drying oven. Table 4 shows the composition made into a paint and the evaluation results of the obtained coating film.

[0033]

Examples 2 to 14 and Comparative Examples 1 to 5 By the same method as in Example 1, coating compositions having the compositions shown in Table 4, Table 5 and Table 6 were produced to obtain coating films. The evaluation results of the obtained coating films are shown in Table 4, Table 5 and Table 6.

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6] * 2: Methylated benzoguanamine resin (Mitsui Cytec Co., Ltd., Mycoat # 106, solid content 75% by weight)

The paints and coatings shown in Tables 4, 5 and 6 were evaluated according to the following criteria. [Appearance of paint] The appearance of the paint was visually determined. ○: Good transparency; Δ: Slightly cloudy; ×: Separation of white [Coating hardness] Measured according to JIS standards using a Mitsubishi Uni-Pencil. [Adhesion] The state of the coated plate after peeling the cellophane tape was observed in conformity with JIS standards. ○: Good; Δ: Some peeling of the coating film is seen;
× …… Peeling off the entire surface [Impact resistance] Using a DuPont impact tester,
Evaluation was performed under the conditions of 2 inches, a load of 300 kg, and a height of 30 cm, and the state of the coating film after the evaluation was observed. ○ …… Good; Δ …… Slightly cracked; × …… Cracked all over the surface [Retort resistance] Using a pressure cooker tester, immersing the coated plate in hot water at 130 ° C for 30 minutes,
The whitening state of the coating film was visually judged. ◯: Good; Δ: Some whitening is observed; ×: Whitening is observed on the entire surface [Paint stability] The paint was left in an atmosphere of 60 ° C for one month, and the appearance was visually evaluated. ○: Good; Δ: Some cloudiness is seen; ×:
… Separation is seen

[0038]

As is apparent from the above examples, the water-based coating material containing the resin for water-based coating material of the present invention has good adhesion to metal and has a good balance between coating film hardness and impact resistance. It is retained and can form a coating film having excellent water resistance, and also has excellent storage stability, which is very useful industrially.

Claims (6)

[Claims] 1. An epoxy compound (A) having two or more glycidyl groups in the molecule and an α, β-monoethylenically unsaturated dicarboxylic acid having two carboxylic acid groups having different acid strengths and / or its anhydride. The compound (B) and the other carboxylic acid group-containing compound (C) are blended so that the ratio of the epoxy group equivalent and the carboxylic acid group equivalent is 1 / 2.5-1.5 / 1, and reacted. The resulting esterification reaction product (I) is 2 to 75% by weight, the carboxylic acid group-containing vinyl monomer (II) is 0.5 to 20% by weight, and other copolymerizable vinyl monomer (III) 24.5 to A resin for water-based paints obtained by neutralizing a 78% by weight copolymer with a base. 2. An epoxy equivalent of 15 as an epoxy compound.
The resin for water-based paints according to claim 1, wherein an epoxy resin of 0 to 3000 is used. 3. The water-based coating composition according to claim 1, wherein itaconic acid and / or its anhydride is used as the α, β-monoethylenic dicarboxylic acid having two carboxylic acid groups having different acid strengths. resin. 4. The component (C) is a dibasic or higher polybasic acid and / or a monovalent or higher oxycarboxylic acid.
The resin for water-based coating described. 5. The component (II) is represented by the following general formula (1),
The resin for water-based paint according to claim 1, which is a compound having a structure shown in (3). Embedded image (In the formula, R ¹ represents hydrogen, a methyl group or a carboxymethyl group, and R ² represents a hydrogen atom or an oxygen atom-containing hydrocarbon substituent represented by the general formula (2).) (In the formula, R ³ represents hydrogen or a hydrocarbon substituent having 1 to 10 carbon atoms.) (In the formula, R ⁴ represents hydrogen or a methyl group, and R ⁵ represents a hydrocarbon substituent having a structure represented by the general formulas (4) to (6) or a hydrocarbon substituent substituted with a hetero atom.) [Chemical 4] (In the formula, R ⁶ represents a linear or branched alkylene group having 1 to 3 carbon atoms.) (In the formula, R ⁷ represents a linear or branched alkylene group having 1 to 10 carbon atoms, and R ⁸ represents a linear or branched alkylene group having 2 to 10 carbon atoms, an alkenylene group, a carboxyl group, or Represents an arylene group or a cycloalkylene group which may be substituted with a halogen atom.) (Wherein, R ⁹ represents a linear or branched alkylene group having 1 to 10 carbon atoms, m is represented by an integer from 4 to 6, R ¹⁰ is R ⁸ represent the same substituent, n represents It is represented by an integer of 1 to 6.) 6. A water-based paint comprising 100 parts by weight of the resin for water-based paint according to claim 1, 10 to 60 parts by weight of a water-soluble amino resin, and an aqueous medium.