JPH05155981A - Water-base epoxy resin dispersion and curable water-base coating composition prepared therefrom - Google Patents

Abstract

PURPOSE:To prepare the subject dispersion giving a cured coating film which is nonyellowing, corrosion-resistant, and excellent in adhesion to a substrate by reacting a specific resin with a specific epoxy resin, at least partially neutralizing the reactional product with a basic substance, and making the product water-dispersible. CONSTITUTION:A resin prepd. by the radical polymn. of 0.1-21wt.% compd. having a COOH group and an ethylenically alpha,beta-unsatd. group in the molecule (e.g. methacrylic acid), 0.15-21wt.% compd. of the formula (wherein R is H or CH3; and R' is a 2-6C alkyl group or an alkylene glycol chain), and at least one compd. having an ethylenically alpha,beta-unsatd. group in the molecule (e.g. ethyl acrylate) is reacted with an epoxy resin substantially water-insol. and having an epoxy equivalent of 150-4,000 (e.g. a bisphenol A diglycidyl ether resin); the reactional product is neutralized at least partially with a basic substance (e.g. dimethylethanolamine) and then made water-dispersible.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aqueous dispersion of a substantially water-insoluble epoxy resin and a curable aqueous coating composition containing the aqueous dispersion of the epoxy resin.

[0002]

2. Description of the Related Art Epoxy resin has a cross-linking structure in combination with a curing agent and a cross-linking agent according to the purpose of use.
Hardened products with a wide variety of properties can be obtained. Since these hardened products are excellent in physical properties, chemical properties, electrical properties, etc., many hardened products such as paints, electricity, civil engineering, adhesives, etc. Is used for. On the other hand, in recent years, water-based paints have been desired from the viewpoint of occupational safety and health or global environmental protection, and epoxy resins are also used as resins for water-based paints. However, since epoxy resins are generally hydrophobic, they cannot be made water-based as they are. Therefore, a method of adding an emulsifier to water or a mixed solution of water and an organic solvent to disperse and emulsify an epoxy resin therein, and a method of dissolving or dispersing emulsified in water by modifying the epoxy resin to make it aqueous is performed. In particular, the modified epoxy resin obtained by modifying the glycidyl group with a secondary amine or an acid anhydride and then neutralizing with a basic substance to make it aqueous is
It is known to be effective in improving adhesion.

The above-mentioned epoxy resin modified with secondary amines can be made into a water-soluble epoxy resin by neutralizing with a suitable anion. However, since the obtained modified epoxy resin solution is colored brown and turns yellow during baking, it sometimes causes a problem in color tone when applied to a clear paint or a light color paint. Further, when modified with an acid anhydride, a water-soluble epoxy resin which does not turn yellow during baking and has good adhesion can be obtained, but the retort resistance of the obtained cured product was insufficient.

[0004]

As a result of intensive studies to solve the above-mentioned problems, the present inventor has shown good substrate adhesion and no yellowing, and the obtained cured product has excellent resistance. The present invention has been completed by discovering an epoxy resin aqueous dispersion having a good retort property and a thermosetting aqueous coating composition using the same.

[0005]

That is, the present invention provides a compound having a carboxyl group and an ethylenic α, β-unsaturated double bond in the molecule in an amount of 0.1 to 21% by weight, represented by the general formula (1). A resin obtained by radical polymerization with 0.15 to 21% by weight of the compound shown as an essential component and at least one compound having an ethylenic α, β-unsaturated double bond in the other molecule. An epoxy resin aqueous dispersion obtained by reacting with an epoxy resin which is substantially water-insoluble and has an epoxy equivalent of 150 to 4000, neutralized at least partially with a basic substance, and then made aqueous Is. The present invention also provides a curable water-based coating material containing 5% by weight or more of the solid content of the epoxy resin aqueous dispersion as an essential component in the resin solid content.

In order to obtain the epoxy resin aqueous dispersion of the present invention, the epoxy resin must have emulsifying ability. Therefore, in the present invention, a compound having a carboxyl group and an ethylenic α, β-unsaturated double bond in the molecule is used as an essential component. A compound having a carboxyl group and an ethylenic α, β-unsaturated double bond in the molecule is stable because the epoxy resin cannot have sufficient emulsifying ability if the compounding amount is less than 0.1% by weight. It is impossible to obtain a good aqueous dispersion of epoxy resin. Further, if the blending amount exceeds 21% by weight, the viscosity of the obtained epoxy resin aqueous dispersion may increase. Examples of the compound having a carboxyl group and an ethylenic α, β-unsaturated double bond in the molecule include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, etc., It is not limited to these. These carboxyl group-containing monomers can be used alone or as a mixture of two or more kinds.

Further, in the present invention, the compound represented by the general formula (1) is used in order to impart good substrate adhesion and retort resistance to the epoxy resin aqueous dispersion. Examples of the compound represented by the general formula (1) include acid phosphooxyethyl methacrylate, 3chloro-2 acid phosphooxypropyl methacrylate, acid phosphooxypropyl methacrylate, acid phosphooxyethyl acrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, and acid. Examples thereof include phosphooxypolyoxypropylene glycol monomethacrylate, but are not limited thereto. Care should be taken in using these compounds, since the gelled homopolymer or block copolymer is likely to be formed during polymerization due to the association between the phosphate group and the ester bond portion. That is, it is preferable to use the above compound after previously dissolving it in a solvent or a compound having a functional group having affinity so that the compound can be rapidly dispersed when dropped into the reaction system. Further, the above compound is preferably used within the range of 0.15 to 21% by weight based on the solid content. If the blending amount exceeds 21% by weight, the resin may gel.

In order to improve and stabilize the physical properties of the aqueous epoxy resin dispersion of the present invention, it is necessary to use a compound having an ethylenic α, β-unsaturated double bond in the molecule in addition to the above-mentioned compounds. is there. The compound having an ethylenic α, β-unsaturated double bond in the molecule is not particularly limited as long as it does not correspond to the compound having the carboxyl group and the ethylenic α, β-unsaturated double bond in the molecule described above. Can be used without. For example, methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, butyl methacrylate, 2-
Examples thereof include, but are not limited to, hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, and glycidyl methacrylate. These monomers are appropriately selected and used as one kind or a mixture of two or more kinds according to the physical properties of the cured product to be obtained.

The above monomers are radically polymerized into resins by a conventional method. The polymerization conditions are not particularly limited, but the polymerization is performed at 50 to 120 ° C. At this time, a peroxide radical polymerization initiator, an azo radical polymerization initiator, or the like is used. The amount of radical polymerization initiator used is not particularly limited, but is 0.1 to 1 relative to the total radical polymerizable monomer.
About 0% by weight is preferable, and it is used by dissolving it in a radically polymerizable monomer. The time required for resinification of the radical-polymerizable monomer is usually about 1 to 10 hours.

A modified epoxy resin is obtained by reacting the acrylic resin having a phosphoric acid group obtained as described above with an epoxy resin, preferably in a weight ratio of 1: 9 to 3: 7. You can In the present invention, any epoxy resin having an epoxy equivalent of 150 to 4000 can be used. For example, glycidyl ether-based epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolac type epoxy resin can be used, but the present invention is not limited thereto. Epoxy resin is appropriately selected according to functional group density, melting point, solubility, compatibility, etc.
It can be used as a kind or a mixture of two or more kinds. The reaction conditions are not particularly limited, but the reaction temperature is 50
The reaction time is about 1 to 7 hours. Since the acrylic resin having a phosphoric acid group and the epoxy resin have high reactivity, no catalyst or curing accelerator is used.

The epoxy resin aqueous dispersion of the present invention can be obtained by neutralizing the carboxyl groups in the modified epoxy resin with a basic substance to impart emulsifying ability, and then adding water to emulsify and disperse. it can. Examples of the basic substance for neutralizing the carboxyl group include, but are not limited to, ethanolamine, diethanolamine, triethanolamine, and dimethylaminoethanol. In addition, if the carboxyl group present in the modified epoxy resin is neutralized to 20 mol% or less, sufficient water solubility cannot be obtained, and it is more preferable to neutralize 80 mol% or more. The modified epoxy resin neutralized product thus obtained is emulsified by adding water and stirring to obtain an epoxy resin aqueous dispersion. The amount of water added is not particularly limited as long as the modified epoxy resin neutralized product can be dispersed in an oil-in-water type, but in order to obtain a substantial aqueous dispersion of epoxy resin, the solid content is 10%. It is preferred to add water in an amount such that it is -60% by weight.

The curable aqueous coating composition of the present invention can be obtained by incorporating 5% by weight or more of the solid content of the epoxy resin aqueous dispersion of the present invention in the resin solid content. If it is less than 5% by weight, sufficient adhesiveness and anticorrosiveness cannot be imparted to the curable water-based paint. Although the epoxy resin aqueous dispersion of the present invention can be used alone or as a curable aqueous coating material, other resins can be added if necessary. Examples of resins that can be added include water-based acrylic resins, water-based amino resins, water-based polyester resins, water-based polyurethane resins and the like, and there is no particular limitation as long as they do not destroy the dispersion structure of the epoxy water-based dispersion. Further, in the above curable water-based paint, if necessary, dyes and pigments for coloring and the like, fillers for improving the physical properties of the cured product, leveling agents, defoaming agents, flame retardants, thickeners,
Various additives such as a water-soluble organic solvent can be added. The curable water-based paint of the present invention can be baked at a temperature of 120 to 250 ° C for about 30 seconds to 10 minutes.

[0013]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. In addition,
All "parts" in the examples represent parts by weight. [Example 1] 270 parts of butyl cellosolve was placed in a reaction vessel equipped with a stirrer and heated to 80 ° C, and the inside of the reactor was replaced with nitrogen. 1. From the dropping tube, 100 parts of ethyl acrylate, 45 parts of methyl methacrylate, 10 parts of 2-hydroxyethyl acrylate, 10 parts of methacrylic acid, 15 parts of acid phosphooxyethyl methacrylate (Phosmer M manufactured by Unichemical Co.) and azobisisobutyronitrile 2. 4 parts of the mixture was added dropwise in about 2 hours. 0.8 parts of azobisisobutyronitrile was added 3 times every 2 hours after the completion of dropping, and the reaction was further continued at 80 ° C. for 2 hours and then cooled to 40 ° C. to obtain a phosphoric acid group-containing acrylic resin solution. .. further,
In a separate reaction vessel equipped with a stirrer, a bisphenol A diglycidyl ether type epoxy resin (Epicoat 1001 manufactured by Yuka Shell Epoxy Co., Ltd.) having an epoxy equivalent of 475 is used.
0 part was put and heated to about 80 ° C. to completely dissolve the epoxy resin. Thereafter, the temperature is raised to 100 ° C., and 450 parts of the phosphoric acid group-containing acrylic resin solution obtained above is added to about 6 parts.
The reaction was continued at 100 ° C. for an hour. After completion of the reaction, the mixture was cooled to 60 ° C., 17 parts of dimethylethanolamine was added and stirred for 30 minutes, and then 130 parts of purified water was gradually added. Further, 500 parts of purified water was added dropwise with sufficient stirring to obtain a milky white epoxy resin aqueous dispersion having a nonvolatile content of about 40%. When this was allowed to stand at room temperature for about 1 month, neither separation nor aggregation was observed.

Example 2 180 parts of butyl cellosolve was placed in a reaction vessel equipped with a stirrer and heated to 80 ° C., and the inside of the reactor was replaced with nitrogen. Methyl acrylate 70 from the dropping tube
Part, ethyl methacrylate 30 parts, 2-hydroxyethyl acrylate 5 parts, acrylic acid 5 parts, acid phosphooxyethyl methacrylate (Unichemical Co. Phosmer M) 10 parts and azobisisobutyronitrile 1.
8 parts of the mixture was added dropwise in about 2 hours. 2 after dropping
0.6 parts of azobisisobutyronitrile was added 3 times at regular intervals, and the reaction was continued at 80 ° C for 2 hours and then 40 ° C.
The resulting mixture was cooled to a phosphoric acid group-containing acrylic resin solution. Furthermore, in another reaction vessel equipped with a stirrer, epoxy equivalent of 950
Bisphenol A diglycidyl ether type epoxy resin (Epicote 1004 manufactured by Yuka Shell Epoxy Co., Ltd.) 4
80 parts was put and heated to about 80 ° C. to completely dissolve the epoxy resin. Then, the temperature was raised to 100 ° C., 300 parts of the phosphoric acid group-containing acrylic resin solution was added, and the reaction was continued at 100 ° C. for about 6 hours. After completion of the reaction, cool to 60 ° C,
After 15 parts of dimethylethanolamine was added and stirred for 30 minutes, 220 parts of purified water was gradually added. Further, 500 parts of purified water was added dropwise with sufficient stirring to obtain a milky white epoxy resin aqueous dispersion having a nonvolatile content of about 40%. When this was allowed to stand at room temperature for about 1 month, neither separation nor aggregation was observed.

Example 3 To 300 parts of the epoxy resin aqueous dispersion prepared in Example 1, 180 parts of a water-soluble melamine resin (CYMEL 303 manufactured by Mitsui Cyanamid Co., Ltd.) was added, and sufficiently stirred and dispersed to prepare an aqueous resin composition. I got a thing.

Example 4 To 200 parts of the epoxy resin aqueous dispersion prepared in Example 2 was added an acrylic resin aqueous dispersion (Toray Ink Mfg. Co., Ltd., Tokuriru BCX-100).
300 parts of non-volatile content 40%) was added and sufficiently stirred and dispersed to obtain an aqueous resin composition.

Comparative Example 1 180 parts of butyl cellosolve was placed in a reaction vessel equipped with a stirrer and heated to 80 ° C., and the inside of the reactor was replaced with nitrogen. From the dropping tube, ethyl acrylate 12
About 2 parts of a mixture of 5 parts, 60 parts of methyl methacrylate, 10 parts of 2-hydroxyethyl acrylate, 10 parts of methacrylic acid, 65 parts of acid phosphooxyethyl methacrylate (Phosmer M manufactured by Unichemical Co.) and 3 parts of azobisisobutyronitrile. Dropped over time. After the completion of dropping, 1 part of azobisisobutyronitrile was added 3 times every 2 hours, and the reaction was continued at 80 ° C for 2 hours and then 40 ° C.
The resulting mixture was cooled to a phosphoric acid group-containing acrylic resin solution. Furthermore, in another reaction vessel equipped with a stirrer, the epoxy equivalent of 475
Bisphenol A diglycidyl ether type epoxy resin (Epicote 1001 manufactured by Yuka Shell Epoxy Co., Ltd.) 4
80 parts was put and heated to about 80 ° C. to completely dissolve the epoxy resin. Then, the temperature was raised to 100 ° C., and 450 parts of the phosphoric acid group-containing acrylic resin solution was added.
The viscosity increased and stirring became impossible.

Comparative Example 2 200 parts of butyl cellosolve was placed in a reaction vessel equipped with a stirrer and heated to 80 ° C., and the inside of the reactor was replaced with nitrogen. Ethyl acrylate 70 from the dropping tube
Part, 30 parts of methyl methacrylate, 5 parts of 2-hydroxyethyl acrylate, 15 parts of acid phosphooxyethyl methacrylate (Phosmer M manufactured by Unichemical Co., Ltd.) and 1.8 parts of azobisisobutyronitrile were added dropwise in about 2 hours. .. After the completion of dropping, 0.6 part of azobisisobutyronitrile was added 3 times every 2 hours, and 2 more
After continuing the reaction at 80 ° C. for time, it was cooled to 40 ° C. to obtain a phosphoric acid group-containing acrylic resin solution. Further, 480 parts of bisphenol A diglycidyl ether type epoxy resin (Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.) having an epoxy equivalent of 189 was placed in another reaction vessel equipped with a stirrer, and about 8
The epoxy resin was completely dissolved by heating to 0 ° C. Thereafter, the temperature was raised to 100 ° C., 320 parts of the phosphoric acid group-containing acrylic resin solution was added, and the reaction was continued at 100 ° C. for about 6 hours. After completion of the reaction, the mixture was cooled to 60 ° C., 2 parts of dimethylethanolamine was added, and the mixture was stirred for 30 minutes, and then purified water 20
0 part was added slowly. Further, 500 parts of purified water was gradually added dropwise with sufficient stirring to obtain an epoxy resin aqueous dispersion having a nonvolatile content of about 40%. When this was left to stand at room temperature for about 1 day, it was separated into two layers.

[Comparative Example 3] To a reaction vessel equipped with a stirrer, 240 parts of a water-soluble acrylic resin (John Cryl 587 manufactured by Johnson Polymer Co., Ltd.) and 180 parts of a water-soluble melamine resin (Cymel 303 manufactured by Mitsui Cyanamid Co., Ltd.) were added, and a nonvolatile Purified water was added so that the content was 60% by weight to obtain an aqueous resin composition.

The aqueous resin compositions obtained in Examples 3 and 4 and Comparative Example 3 were coated on a tin-plated steel sheet using a bar coater so that the dry coating thickness would be 10 μm.
Heat treatment was performed at 00 ° C. for 10 minutes. Table 1 shows the evaluation results of the physical properties of the test pieces thus obtained. Adhesion is 1 x 1 mm after a cellophane tape peeling test.
The number of squares remaining without peeling was displayed in 100 squares. In the water resistance test, the coating film state was visually evaluated by immersing in boiling water for 30 minutes. The pencil hardness was measured by using a Mitsubishi Pencil Uni at an angle of 45 ° with respect to the coating film and pushing lightly forward as it was, and the hardness at which no trace of a pencil was left on the coating film was displayed.

[0021]

[Table 1]

[0022]

According to the present invention, a water-insoluble epoxy resin can be widely used in an aqueous system. Also,
By using the epoxy resin aqueous dispersion and the curable aqueous coating material obtained by the present invention, it is possible to obtain a cured coating film that exhibits good substrate adhesion, does not show yellowing, and has anticorrosive properties.

Claims (2)

[Claims] 1. 0.1 to 21 of a compound having a carboxyl group and an ethylenic α, β-unsaturated double bond in the molecule.
% By weight, a compound represented by the following general formula (1): (In the formula, R represents hydrogen or a methyl group, and R ′ represents C = 2 to 6
Represents an alkyl group or an alkylene glycol chain. A resin obtained by radical polymerization with 0.15 to 21% by weight of 10) as an essential component together with at least one compound having an ethylenic α, β-unsaturated double bond in the other molecule, and Water-insoluble epoxy resin having an epoxy equivalent of 150 to 4000 is reacted and neutralized at least partially with a basic substance,
An epoxy resin aqueous dispersion obtained by making it aqueous. 2. A curable water-based coating composition, wherein the resin solid content contains 5% by weight or more of the solid content of the epoxy resin aqueous dispersion according to claim 1.