Water-dispersible epoxy resin composition, coating material, and article

Abstract

Provided is a water-dispersible epoxy resin composition having high storage stability and capable of forming a cured film having excellent corrosion resistance. The water-dispersible epoxy resin composition includes an epoxy resin (A) obtained from essential components including a compound (a1) having at least two epoxy groups in a molecule, and a compound (a2) having at least two carboxyl groups in a molecule. The compound (a2) is obtained from essential components including a polyvalent active hydrogen compound (a2-1) having a repeating alkylene unit, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton that is different from the polyvalent active hydrogen compound (a2-1), and an acid anhydride (a2-3). The content of the polyvalent active hydrogen compound (a2-1) is in the range of 3 to 10 mass% in the total mass of the compound (a1) and the compound (a2).

Description

Technical Field

[0001] This invention relates to water-dispersible epoxy resin compositions, coatings, and articles. Background Technology

[0002] Generally, epoxy resin compositions can produce cured products with excellent mechanical and electrical properties, as well as good performance characteristics such as bonding properties, solvent resistance, water resistance, and heat resistance. Therefore, epoxy resin compositions are widely used in applications including insulating materials for electrical and electronic components, adhesives, coatings, and civil engineering materials.

[0003] Epoxy resin compositions used in these applications, particularly in coatings, are typically solvent-dilutable compositions that utilize various organic solvents. However, in recent years, from the perspective of global environmental protection, including controlling air pollution and improving the working environment, there has been a focus on limiting the total amount of volatile organic compounds (VOCs). This has led to increased interest in water-dispersible epoxy resin compositions that do not use organic solvents.

[0004] For example, a water-dispersible epoxy resin composition is known, which is obtained by reacting polyethylene glycol with trimellitic anhydride, then reacting the product with an excess of epoxy resin to synthesize an emulsifier, adding the emulsifier to the epoxy resin, and then adding water (see, for example, Patent Document 1). Another water-dispersible epoxy resin composition is known, which is obtained by reacting polyethylene glycol with anhydride, then reacting the product with an excess of epoxy resin to synthesize an emulsifier, removing the emulsifier, adding the removed emulsifier to the epoxy resin, and then adding water (see, for example, Patent Document 2). However, these water-dispersible epoxy resin compositions have insufficient storage stability and cannot meet the increasingly stringent performance requirements of recent years in terms of various physical properties of the cured product (e.g., corrosion resistance).

[0005] Therefore, materials with high preservation stability and excellent corrosion resistance are being sought.

[0006] [Existing technical documents]

[0007] [Patent Literature]

[0008] [Patent Document 1] Chinese Patent Application Publication No. 105801868

[0009] [Patent Document 2] Chinese Patent Application Publication No. 108503846 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] The object of the present invention is to provide a water-dispersible epoxy resin composition having high storage stability and capable of forming a cured film with excellent corrosion resistance; a coating containing the water-dispersible epoxy resin composition; and an article having a cured film from the coating.

[0012] Solution for solving the problem

[0013] To achieve the above-mentioned objectives, the inventors conducted in-depth research. As a result, they discovered that the above objectives can be achieved using a water-dispersible epoxy resin composition containing an epoxy resin and an aqueous medium, wherein the essential components of the epoxy resin are a compound having at least two epoxy groups in its molecule and a compound having at least two carboxyl groups in its molecule, derived from a specific multi-element active hydrogen compound and an acid anhydride. Based on the above discovery, the present invention was completed.

[0014] This invention relates to a water-dispersible epoxy resin composition, characterized by comprising an epoxy resin (A) and an aqueous medium (B), wherein the essential components of the epoxy resin (A) are a compound (a1) having at least two epoxy groups in the molecule and a compound (a2) having at least two carboxyl groups in the molecule, wherein the essential components of the compound (a2) are a multi-component active hydrogen compound (a2-1) having repeating alkylene units, a multi-component active hydrogen compound (a2-2) having an alicyclic skeleton different from the multi-component active hydrogen compound (a2-1), and an acid anhydride (a2-3), wherein the content of the multi-component active hydrogen compound (a2-1) in the total mass of the compounds (a1) and (a2) is in the range of 3 to 10% by mass.

[0015] The effects of the invention

[0016] The water-dispersible epoxy resin composition of the present invention can be prepared by a simple method and has high storage stability. Coatings containing the above-mentioned water-dispersible epoxy resin composition have excellent anti-corrosion properties, and are therefore particularly suitable for anti-corrosion coatings. Detailed Implementation

[0017] The water-dispersible epoxy resin composition of the present invention is characterized by containing epoxy resin (A) and an aqueous medium (B), wherein the essential components of the epoxy resin (A) are: a compound (a1) having at least two epoxy groups in the molecule and a compound (a2) having at least two carboxyl groups in the molecule, and the essential components of the compound (a2) are: a multi-component active hydrogen compound (a2-1) having repeating alkylene units, a multi-component active hydrogen compound (a2-2) having an alicyclic skeleton different from the multi-component active hydrogen compound (a2-1), and an acid anhydride (a2-3), wherein the content of the multi-component active hydrogen compound (a2-1) in the total mass of the compounds (a1) and (a2) is in the range of 3 to 10% by mass.

[0018] The epoxy resin (A) used herein is an epoxy resin obtained from the necessary components including the above-described compound (a1) having at least two epoxy groups in its molecule and the above-described compound (a2) having at least two carboxyl groups in its molecule.

[0019] Examples of compounds (a1) having at least two epoxy groups in their molecules (hereinafter sometimes abbreviated as "compound (a1)") include bisphenol-type epoxy resins synthesized from bisphenols and epihaloalcohols, phenolic varnish-type epoxy resins synthesized from phenol / alkylphenol phenolic varnishes and epihaloalcohols, biphenyl-type epoxy resins, epoxy resins synthesized from diols of compounds having an aromatic ring adjacent to another, such as naphthalene glycol, and epihaloalcohols, glycidylamines synthesized from aromatic amines and epihaloalcohols, epoxy resins synthesized from aliphatic amines and epihaloalcohols, epoxy resins synthesized from aliphatic alcohols and epihaloalcohols, epoxy resins obtained by reacting diene compounds such as dicyclopentadiene-phenol condensates with epihaloalcohols, glycidylamines obtained by reacting polycarboxylic acids with epihaloalcohols, and compounds having an epoxy ring formed by oxidizing the double bonds in the molecule with peroxides, etc. These compounds can be used alone or in combination of two or more.

[0020] Examples of the above-described compound (a1) further include compounds obtained by reacting the various epoxy resins exemplified above with modifiers such as polyphenolic compounds, polycarboxylic acid compounds, and polyamine compounds.

[0021] Among the above, the preferred water-dispersible epoxy resin compositions that can produce a cured film with high storage stability and excellent corrosion resistance are bisphenol type epoxy resins and phenolic varnish type epoxy resins, and more preferably bisphenol A type epoxy resins, bisphenol F type epoxy resins, and phenolic varnish type epoxy resins.

[0022] To control viscosity or reactivity, monofunctional epoxy resins and compounds (a1) can be used in combination. Examples of such monofunctional epoxy resins include: butyl glycidyl ether, 2-ethylhexanol glycidyl ether, C12-13 alcohol glycidyl ether, phenyl glycidyl ether, o-cresol glycidyl ether, p-sec-butyl glycidyl ether, tert-butylphenol glycidyl ether, cashew phenol glycidyl ether, and neodecanoic acid glycidyl ester. These monofunctional epoxy resins can be used alone or in combination of two or more.

[0023] The amount of compound (a1) used, from the perspective of obtaining a water-dispersible epoxy resin composition with high storage stability and the ability to form a cured film with excellent corrosion resistance, preferably ranges from 55% to 70% by mass of the total mass of the necessary component of the epoxy resin (A), namely compound (a1), and compound (a2) having at least two carboxyl groups in its molecule. If the amount of compound (a1) used is less than 55% by mass, the corrosion resistance of the cured film will be insufficient. If the amount is greater than 70% by mass, it is difficult to simultaneously achieve both water dispersibility and corrosion resistance of the cured film.

[0024] As a compound (a2) having at least two carboxyl groups in its molecule (hereinafter also abbreviated as "compound (a2)"), it is obtained from the necessary components including a multi-component active hydrogen compound (a2-1) having repeating alkylene units, a multi-component active hydrogen compound (a2-2) having an alicyclic skeleton, and an acid anhydride (a2-3).

[0025] Examples of the aforementioned multi-component active hydrogen compounds (a2-1) include compounds containing ethylene glycol, propylene glycol, and / or tetramethylene ether glycol as repeating units and having a specific molecular weight distribution. These compounds can be used alone or in combination of two or more.

[0026] Regarding the terminal active hydrogen moiety in the aforementioned multi-component active hydrogen compound (a2-1), examples include hydroxyl or amino groups. Examples of the aforementioned multi-component active hydrogen compound (a2-1) include: polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, compounds formed by the condensation of polyethylene glycol and polypropylene glycol, compounds formed by introducing polypropylene glycol into glycerol, compounds formed by the condensation of polyethylene glycol and polypropylene glycol and the introduction of glycerol, and polycarbonate glycol polymerized via carbonate groups. Commercially available products of the aforementioned multi-component active hydrogen compound (a2-1) include "Jeffamine D-series" and "Jeffamine T-series" manufactured by Huntsman Corporation. These multi-component active hydrogen compounds can be used alone or in combination of two or more.

[0027] Among the above, the preferred water-dispersible epoxy resin compositions that can produce a cured film with high storage stability and excellent corrosion resistance are polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0028] The content of the aforementioned multi-element active hydrogen compound (a2-1) is, from the perspective of obtaining a water-dispersible epoxy resin composition with high storage stability and the ability to form a cured film with excellent corrosion resistance, used in the range of 3 to 10% by mass of the total mass of the aforementioned compound (a1) and the aforementioned compound (a2).

[0029] As the aforementioned multi-element active hydrogen compound (a2-2), any compound that has an alicyclic skeleton within the molecule and an active hydrogen at the terminal end is acceptable. Examples include: 2,2'-isopropylcyclohexanol, 2,4'-isopropylcyclohexanol, 4,4'-isopropylcyclohexanol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, 1,4-cyclohexanediethanol, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, tricyclic [5,2,1,0] 2,6 Decane-4,8-diethanol, 2,2'-methylenebis(cyclohexylamine), 2,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(cyclohexylamine), etc. These multi-component active hydrogen compounds can be used alone or in combination of two or more.

[0030] Among the above, the preferred aqueous epoxy resin compositions for obtaining a cured film with high storage stability and excellent corrosion resistance are 4,4'-isopropylcyclohexanol, 1,4-cyclohexanediethanol, 1,3-diaminocyclohexane, and 4,4'-methylenebis(cyclohexylamine), and more preferably 4,4'-isopropylcyclohexanol and 1,4-cyclohexanediethanol.

[0031] The mass ratio of the aforementioned multi-component active hydrogen compound (a2-2) to the aforementioned multi-component active hydrogen compound (a2-1) [(a2-2) / (a2-1)] is preferably in the range of 0.3 to 6, which is beneficial for obtaining a water-dispersible epoxy resin composition with high storage stability and the ability to form a cured film with excellent corrosion resistance.

[0032] As for the aforementioned acid anhydrides (a2-3), any acid anhydride that is circulated as an industrial product can be used without particular restrictions. Examples include: succinic anhydride, octylsuccinic anhydride, dodecenylsuccinic anhydride, maleic anhydride, phthalic anhydride, methyl-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl-hexahydrophthalic anhydride, methylnadic anhydride, trimellitic anhydride, pyromellitic anhydride, and dodecanoic anhydride. These acid anhydrides can be used alone or in combination of two or more.

[0033] Among the above, the preferred water-dispersible epoxy resin compositions that can produce a cured film with high storage stability and excellent corrosion resistance are methyl-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyl-hexahydrophthalic anhydride.

[0034] There are no particular limitations on the method for producing the aforementioned compound (a2). Examples include heating and stirring the necessary components, namely the aforementioned multi-component active hydrogen compound (a2-1), the multi-component active hydrogen compound (a2-2) having an alicyclic skeleton, and the acid anhydride (a2-3), in a container under a nitrogen atmosphere at 90–200°C. The aforementioned multi-component active hydrogen compound (a2-1) is hygroscopic. Therefore, it is preferable to remove the water contained in compound (a2-1) by vacuum heating in the initial stage of the reaction. In this manner, compound (a2) can be obtained stably.

[0035] The amount of compound (a2) used, from the perspective of obtaining a water-dispersible epoxy resin composition with high storage stability and the ability to form a cured film with excellent corrosion resistance, is preferably in the range of 30 to 45% by mass of the total mass of the necessary components of the epoxy resin (A), namely, the above-mentioned compounds (a1) and (a2). If the amount of compound (a2) used is less than 30% by mass, it will be difficult to achieve both water dispersibility and corrosion resistance of the cured film; if it is greater than 45% by mass, the corrosion resistance of the cured film will be insufficient.

[0036] There are no particular limitations on the manufacturing method of the epoxy resin (A) described above. Examples include a method in which the necessary components, including the compounds (a1) and (a2) described above, are heated and stirred at 100 to 200°C under a nitrogen atmosphere. A catalyst may also be used in this method to shorten the reaction time.

[0037] Examples of catalysts mentioned above include: tertiary amines such as triethylamine, tributylamine, benzyl dimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and N-methylpiperazine, and their salts; and imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2,4-dicyano-6-[2-methylimidazolyl-1]-ethyl-S-triazine, and 2-ethyl-4-methylimidazole tetraphenylboronic acid, and their salts. Examples of diazabicyclic compounds include 1,5-diazabicyclo[5,4,0]-7-undecane, 1,5-diazabicyclo[4,3,0]-5-nonane, 1,4-diazabicyclo[2,2,2,]octane, and 1,8-diazabicyclo[5,4,0]undec-7-ene tetraphenylborate; phosphine compounds include tributylphosphine, triphenylphosphine, tris(dimethoxyphenyl)phosphine, tris(hydroxypropyl)phosphine, and tris(cyanoethyl)phosphine; and phosphine salts include tetraphenylphosphine salts, methyltributylphosphine salts, methyltricyanoethylphosphine salts, and tetrabutylphosphine salts. These catalysts can be used alone or in combination of two or more. Among these, triphenylphosphine is preferred.

[0038] The solid epoxy equivalent in the aforementioned epoxy resin (A) is preferably in the range of 300 to 1,300 g / eq., which is beneficial for obtaining a water-dispersible epoxy resin composition with high storage stability and the ability to form a cured film with excellent corrosion resistance. If the solid epoxy equivalent is less than 300 g / eq., the film will become hard and brittle; if the solid epoxy equivalent is greater than 1,300 g / eq., the reactivity with the curing agent will decrease, resulting in poor water resistance.

[0039] Examples of the aforementioned aqueous medium (B) include ion-exchanged water and distilled water. These aqueous media can be used alone or in combination of two or more.

[0040] There are no particular limitations on the manufacturing method of the water-dispersible epoxy resin composition of the present invention, and it can be manufactured by any method. For example, the water-dispersible epoxy resin composition can be obtained by mixing the above-described epoxy resin (A) with the above-described aqueous medium (B).

[0041] As a method for mixing the epoxy resin (A) and the aqueous medium (B) mentioned above, examples include methods using devices such as: a reaction vessel equipped with stirring blades; a mixing machine such as a kneader, continuous kneader, conical roller, single-screw extruder, twin-screw extruder, three-screw extruder, universal mixer, Plastomill, or Votator-type mixer; a rotary dispersion mixer such as a high-speed mixer, static mixer, FILMIX, Ebara Milder, CLEARMIX, ULTRA-TURRAX, CAVITRON, or BIO-MIXER; an ultrasonic dispersion device; or a device without a moving part, such as an inline mixer, that can mix fluids by the flow of the fluid itself.

[0042] In the above-described method for manufacturing the water-dispersible epoxy resin composition, an organic solvent may be used before or simultaneously with the aqueous medium (B). The organic solvent does not necessarily have to be a water-soluble solvent; it is not particularly limited as long as it can dissolve the resin produced in the reaction and is inert to the resin during use. Examples include: ester compounds such as ethyl acetate, 3-methoxybutyl acetate, methoxypropyl acetate, and acetic acid cellosolve; alcohol compounds such as methanol, ethanol, and isopropanol; cellosolve compounds such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, isobutyl cellosolve, and tert-butyl cellosolve; ethylene glycol dimethyl ether compounds such as diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monoisobutyl ether, and propylene glycol monotert-butyl ether; and ketone compounds such as acetone and methyl ethyl ketone. Among the above, the preferred choices are cellolytic compounds, propylene glycol monoalkyl ether compounds, and ketone compounds.

[0043] The aforementioned organic solvents may remain in the water-dispersible epoxy resin composition or may be volatilized by vacuum distillation.

[0044] The mass ratio of the epoxy resin (A) to the aqueous medium (B) [(A) / (B)] is preferably in the range of 20 / 80 to 75 / 25, and more preferably in the range of 40 / 60 to 70 / 30, so as to obtain a water-dispersible epoxy resin composition with high storage stability and capable of forming a cured film with excellent corrosion resistance.

[0045] The water-dispersible epoxy resin composition of the present invention may further contain a curing agent if necessary.

[0046] Examples of such curing agents include alkaline curing agents.

[0047] Examples of alkaline curing agents include aliphatic polyamines, alicyclic polyamines, Mannich bases, amine-epoxy adducts, polyamide polyamines, and liquid aromatic polyamines. These curing agents can be used alone or in combination of two or more.

[0048] Examples of the aforementioned aliphatic polyamines include: diethylenetriamine, triethylenetriamine, tetraethylenepentamine, 1,4-bis-(3-aminopropyl)piperazine and other polyalkylene polyamines, m-phenylenediamine, p-phenylenediamine, etc.

[0049] Examples of the aforementioned alicyclic polyamines include 1,2-cyclohexanediamine, 1,4-diamine-3,6-diethylcyclohexane, and isophoronediamine.

[0050] Examples of the above-mentioned Mannich bases include: (1) polyamines such as triethylenetriamine, isophorone diamine, m-phenylenediamine, or p-phenylenediamine; (2) aldehydes such as formaldehyde; and (3) mono- or poly-cresols or xylenols having at least one aldehyde reactive site in the nucleus, or condensation products of phenols such as p-tert-butylphenol or resorcinol.

[0051] Examples of the above-mentioned amine-epoxy adducts include: (1)(a) polyamines such as triethylenetriamine, tetraethylenepentamine, isophorone diamine, m-phenylenediamine, or p-phenylenediamine, and reaction products with epoxy resins such as phenyl glycidyl ether, butyl glycidyl ether, diglycidyl ether of bisphenol A, or diglycidyl ether of bisphenol F; and (2) reaction products of the above-mentioned polyamines with glycidyl esters such as "Cardura E" (registered trademark: Yuka Shell Epoxy KK).

[0052] As the aforementioned polyamide polyamine, those obtained by reacting polyamines with polycarboxylic acids or dimer fatty acids can be used, for example, the reaction product of ethylenediamine and dimer acid.

[0053] Examples of liquid aromatic polyamines include, for example, reaction products of aromatic polyamines with glycidyl ethers or glycidyl esters. Examples of aromatic polyamines include, for example, diaminodiphenylmethane and diaminodiphenyl sulfone. Examples of glycidyl ethers include, for example, phenyl glycidyl ether, butyl glycidyl ether, diglycidyl ether of bisphenol A, and diglycidyl ether of bisphenol F. Examples of glycidyl esters include, for example, "Cardura E".

[0054] The amount of the curing agent used is preferably in the range of 0.75 to 1.25, where the ratio of epoxy equivalent in the water-dispersible epoxy resin composition of the present invention to amine equivalent in the alkaline curing agent [epoxy equivalent / amine equivalent].

[0055] The water-dispersible epoxy resin composition of the present invention may, as needed, contain other resin components such as polyester-based waterborne resins and acrylic-based waterborne resins.

[0056] The water-dispersible epoxy resin composition of the present invention may contain additives as needed. Examples of such additives include: anti-cissing agents, anti-sagging agents, leveling agents, defoamers, curing accelerators, ultraviolet absorbers, and light stabilizers.

[0057] There are no particular limitations on the use of the water-dispersible epoxy resin composition of the present invention, and it can be used for any purpose. Examples include: coatings, adhesives, fiber sizing agents, concrete primers, etc.

[0058] When the water-dispersible epoxy resin composition of the present invention is used in coating applications, it is preferable to add various pigments and additives such as rust-preventive pigments, coloring pigments, and extender pigments as needed.

[0059] Examples of rust-preventive pigments include zinc powder, aluminum phosphomolybdate, zinc phosphate, aluminum phosphate, barium chromate, aluminum chromate, and graphite flake pigments.

[0060] Examples of such coloring pigments include carbon black, titanium dioxide, zinc sulfide, and red oxide.

[0061] Examples of pigments that can be used to describe the above-mentioned physical pigments include barium sulfate, calcium carbonate, talc, and kaolin.

[0062] The amount of the above-mentioned additive added is preferably in the range of 10 to 70 parts by weight relative to 100 parts by weight of the solid content of the water-dispersible epoxy resin composition.

[0063] When the water-dispersible epoxy resin composition of the present invention is used as a coating, it can be applied by any method without particular limitation. Some exemplary application methods include roller coating, spraying, brushing, doctor blade coating, rod coating, dip coating, and electrodeposition. After application, it is then dried and cured by heat at room temperature. The heating temperature range for heat curing is preferably 50 to 250°C, and more preferably 60 to 230°C. The heating time range is preferably 2 to 30 minutes, and more preferably 5 to 20 minutes.

[0064] For example, the water-dispersible epoxy resin composition of the present invention can be used in general applications such as water-based coatings for interior building decoration, water-based coatings for exterior building decoration and inorganic building materials, water-based anti-rust coatings for iron parts, and water-based coatings for automotive repair, as well as in industrial applications such as automotive coatings and beverage cans. The water-dispersible epoxy resin composition of the present invention has excellent corrosion resistance and touch-drying properties, and is suitable for water-based anti-rust coatings for iron parts requiring heavy-duty rust prevention, such as for steel buildings and bridges, especially as a primer for water-based anti-rust coatings for iron parts.

[0065] The water-dispersible epoxy resin composition of the present invention can be used as an adhesive in any way without particular limitation. For example, the water-dispersible epoxy resin composition can be applied to a substrate by spraying, brushing, or scraping, and the mating surfaces of the substrates can be bonded together. A strong adhesive layer can be formed at the joint by fixing the outer periphery of the joint or by pressing the substrates together. Suitable substrates include steel plates, concrete, mortar, wood, resin sheets, and resin films. It is more preferably applied after various surface treatments as needed, such as physical treatments such as grinding, electrical treatments such as corona treatment, and chemical treatments such as chemical conversion treatment.

[0066] The water-dispersible epoxy resin composition of the present invention can be used as a fiber sizing agent in any way without limitation. For example, the water-dispersible epoxy resin composition can be applied to fibers immediately after spinning using a roller coater, rolled into fiber bundles, and dried. There are no particular limitations on the fibers used, and examples include inorganic fibers such as glass fibers, ceramic fibers, asbestos fibers, carbon fibers, and stainless steel fibers; natural fibers such as cotton and linen; and synthetic fibers such as polyester, polyamide, and polyurethane. Examples of fiber shapes used as the substrate include short fibers, long fibers, yarns, pads, and sheets. Regarding the amount used as a fiber sizing agent, the solid resin content relative to the fiber is preferably 0.1 to 2% by mass.

[0067] [Example]

[0068] The present invention will now be described in detail based on embodiments and comparative examples. However, the present invention is not limited to the embodiments listed below.

[0069] (Example 1: Preparation of a water-dispersible epoxy resin composition (1))

[0070] In a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, 50.0 parts by weight of polyethylene glycol (PEG-3500 manufactured by Jiangsu Haian Chemical Co., Ltd.) and 156.3 parts by weight of hydrogenated bisphenol A were added. The mixture was heated under nitrogen atmosphere with stirring at 200 rpm. Nitrogen was stopped at 110°C, and the mixture was allowed to dehydrate under reduced pressure for 1 hour. After repressurization with nitrogen, 221.0 parts by weight of methyl-tetrahydrophthalic anhydride (HN-2000 manufactured by Showa Denko Materials Co., Ltd.) was added, and the temperature was raised to 130°C, allowing the reaction to proceed for 5 hours. Then, 667.0 parts by weight of bisphenol A-type liquid epoxy resin (EPICLON 850-S manufactured by DIC Corporation) and 0.5 parts by weight of triphenylphosphine were added. The reaction was further allowed to proceed for 5 hours. The resin in the flask was liquid with an acid value less than 0.1. Next, 274 parts by weight of methyl ethyl ketone were added while the contents were cooled. This yielded a homogeneous solution. While maintaining the temperature below 50°C, the stirring speed was increased to 3,000 rpm, and 960 parts by weight of deionized water were added over 3 hours. Then, the methyl ethyl ketone was evaporated under reduced pressure. The concentration was controlled by adding deionized water. Thus, a water-dispersible epoxy resin composition (1) with a non-volatile content of 55% by weight, a Brookfield viscosity of 7,000 mPa·s, and a d50 particle size of 0.18 μm was obtained.

[0071] (Example 2: Preparation of a water-dispersible epoxy resin composition (2))

[0072] Except that the hydrogenated bisphenol A used in Example 1 was replaced with 94.6 parts by weight of cyclohexanediethanol ("CHDM-D" manufactured by Eastman Company), and the amounts were changed to 222.8 parts by weight of methyl tetrahydrophthalic anhydride, 716.2 parts by weight of "EPICLON 850-S", 270 parts by weight of methyl ethyl ketone, and 951 parts by weight of deionized water, the same procedure was followed as in Example 1. Thus, a water-dispersible epoxy resin composition (2) with a non-volatile content of 55% by weight, a Brookfield viscosity of 6,000 mPa·s, and a d50 particle size of 0.31 μm was obtained.

[0073] (Example 3: Preparation of water-dispersible epoxy resin composition (3))

[0074] Except that the amount of “EPICLON 850-S” used in Example 1 was changed to 533.6 parts by weight, and 133.4 parts by weight of phenolic varnish-type epoxy resin (“EPICLON N-740” manufactured by DIC Corporation) was further combined, the process was carried out in the same manner as in Example 1. Thus, a water-dispersible epoxy resin composition (3) with a non-volatile content of 55% by weight, a Brookfield viscosity of 5,800 mPa·s, and a d50 particle size of 0.22 μm was obtained.

[0075] (Example 4: Preparation of a water-dispersible epoxy resin composition (4))

[0076] Except that the amount of polyethylene glycol used in Example 1 was changed to 25.0 parts by weight, and 25.0 parts by weight of polypropylene glycol (PPG-2000 manufactured by Jiangsu Haian Petrochemical Co., Ltd.) was further combined, and the amount of methyl-tetrahydrophthalic anhydride used in Example 1 was changed to 221.3 parts by weight, the process was the same as in Example 1. Therefore, a water-dispersible epoxy resin composition (4) with a non-volatile content of 55% by weight, a Brookfield viscosity of 3,000 mPa·s, and a d50 particle size of 0.52 μm was obtained.

[0077] (Example 5: Preparation of a water-dispersible epoxy resin composition (5))

[0078] Except that the amount of polyethylene glycol used in Example 1 was changed to 30.0 parts by mass, and 20.0 parts by mass of polytetramethylene ether glycol (PTMG3000 manufactured by Mitsubishi Chemical Corporation) was further combined, and the amount of methyl-tetrahydrophthalic anhydride used in Example 1 was changed to 221.3 parts by mass, the process was the same as in Example 1. Therefore, a water-dispersible epoxy resin composition (5) with a non-volatile content of 55% by mass, a Brookfield viscosity of 2,200 mPa·s, and a d50 particle size of 0.57 μm was obtained.

[0079] (Example 6: Preparation of a water-dispersible epoxy resin composition (6))

[0080] Except for changing the polyethylene glycol (PEG-3500 manufactured by Jiangsu Haian Chemical Co., Ltd.) used in Example 1 to 75.0 parts by weight of PEG-2000 manufactured by Jiangsu Haian Chemical Co., Ltd., changing the amount of hydrogenated bisphenol A to 150.0 parts by weight, changing the amount of methyl-tetrahydrophthalic anhydride to 204.1 parts by weight of hexahydrophthalic anhydride (RIKACID HH manufactured by Shin Nippon Rikka Co., Ltd.), changing the amount of EPICLON 850-S to 652.2 parts by weight, changing the amount of methyl ethyl ketone to 270 parts by weight, and changing the amount of ion-exchanged water to 949 parts by weight, the process was carried out in the same manner as in Example 1. Therefore, a water-dispersible epoxy resin composition (6) with a non-volatile content of 55% by weight, a Brookfield viscosity of 2,000 mPa·s, and a d50 particle size of 0.80 μm was obtained.

[0081] (Example 7: Preparation of a water-dispersible epoxy resin composition (7))

[0082] Except for changing the amount of hydrogenated bisphenol A used in Example 1 to 176.5 parts by mass, the amount of methyl-tetrahydrophthalic anhydride used in Example 1 to 230.9 parts by mass of hexahydrophthalic anhydride, the amount of "EPICLON 850-S" used in Example 1 to 647.0 parts by mass of bisphenol F type liquid epoxy resin ("EPICLON 830-S" manufactured by DIC Corporation), the amount of methyl ethyl ketone to 276 parts by mass, and the amount of ion-exchanged water to 969 parts by mass, the process was carried out in the same manner as in Example 1. Therefore, a water-dispersible epoxy resin composition (7) with a non-volatile content of 55% by mass, a Brookfield viscosity of 7,400 mPa·s, and a d50 particle size of 0.25 μm was obtained.

[0083] (Comparative Example 1: Preparation of a water-dispersible epoxy resin composition (R1))

[0084] In a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, 30.0 parts by weight of polyethylene glycol (PEG-3500 manufactured by Jiangsu Haian Chemical Co., Ltd.) and 206.3 parts by weight of hydrogenated bisphenol A were added. The mixture was heated under nitrogen atmosphere and stirred at 200 rpm. Nitrogen was stopped at 110°C, and the mixture was allowed to undergo dehydration under reduced pressure for 1 hour. After the pressure was released again by supplying nitrogen, 288.2 parts by weight of methyl-tetrahydrophthalic anhydride were added, and the temperature was raised to 130°C, allowing the reaction to proceed for 5 hours. Then, 637.5 parts by weight of "EPICLON 850-S" and 0.5 parts by weight of triphenylphosphine were added, and the reaction was further carried out for 5 hours. Next, while cooling the contents, 290 parts by weight of methyl ethyl ketone were added to obtain a homogeneous solution. The temperature was maintained below 50°C, and the stirring speed was increased to 3,000 rpm. 1,020 parts by weight of deionized water were added over 3 hours. Then, methyl ethyl ketone was evaporated under reduced pressure, and the concentration was controlled by adding ion-exchanged water. Thus, a water-dispersible epoxy resin composition (R1) with a non-volatile content of 55% by mass, a Brookfield viscosity of 400 mPa·s, and a d50 particle size of 2.30 μm was obtained.

[0085] (Comparative Example 2: Preparation of a water-dispersible epoxy resin composition (R2))

[0086] Except for changing the amount of polyethylene glycol used in Comparative Example 1 to 150.0 parts by mass, the amount of hydrogenated bisphenol A to 75.0 parts by mass, the amount of methyl-tetrahydrophthalic anhydride to 118.0 parts by mass, the amount of "EPICLON 850-S" to 750.0 parts by mass, the amount of methyl ethyl ketone to 273 parts by mass, and the amount of ion-exchanged water to 959 parts by mass, the procedure was carried out in the same manner as Comparative Example 1. Therefore, a water-dispersible epoxy resin composition (R2) with a non-volatile content of 55% by mass, a Brookfield viscosity of 9,200 mPa·s, and a d50 particle size of 0.17 μm was obtained.

[0087] (Comparative Example 3: Preparation of a water-dispersible epoxy resin composition (R3))

[0088] 200 parts by weight of polyethylene glycol (PEG-4000, manufactured by Jiangsu Haian Petrochemical Co., Ltd.) were added to a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. The mixture was heated under nitrogen atmosphere with stirring at 200 rpm. Nitrogen was stopped at 110°C, and the pressure was reduced for 1 hour. After repressurization with nitrogen, 37.6 parts by weight of EPICLON 850-S and 0.3 parts by weight of boron trifluoride-ethyl ether complex (reagent) were added. The mixture was reacted at 130°C for 5 hours, yielding epoxy resin (r3) that is solid at room temperature. The epoxy equivalent of this epoxy resin (r3) is 2,500 g / eq.

[0089] Next, 500.0 parts by weight of "EPICLON 1050" were added to a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. The mixture was dissolved at 100°C under nitrogen atmosphere, and then 125 parts by weight of methyl ethyl ketone were added while cooling to dissolve the resin. Next, 50.0 parts by weight of epoxy resin (R3) were added and stirred at 60°C for 1 hour to homogenize the mixture. The mixture was then cooled to below 50°C. The stirring speed was increased to 3,000 rpm, and 450 parts by weight of deionized water were added over 3 hours. The solvent was then evaporated under reduced pressure, and deionized water was added. Thus, a water-dispersible epoxy resin composition (R3) with a non-volatile content of 60% by weight, a Brookfield viscosity of 300 mPa·s, and a d50 particle size of 0.91 μm was obtained.

[0090] (Comparative Example 4: Preparation of a water-dispersible epoxy resin composition (R4))

[0091] In a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, 400 parts by mass of polyethylene glycol (PEG-4000 manufactured by Jiangsu Haian Petrochemical Co., Ltd.) were added. The mixture was heated under nitrogen atmosphere and stirred at 200 rpm. Nitrogen was stopped at 110°C, and the pressure was reduced for 1 hour. After repressurization by supplying nitrogen, 38.4 parts by mass of trimellitic anhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added. The mixture was reacted at 110°C until the acid value remained unchanged. Then, 9.1 parts by mass of bisphenol A epoxy resin (EPICLON 860 manufactured by DIC Co., Ltd., epoxy equivalent 240 g / eq.) and 0.2 parts by mass of triphenylphosphine were added. The mixture was reacted at 120°C for 5 hours to obtain epoxy resin (r4), which is solid at room temperature. The epoxy equivalent of this epoxy resin (r4) is 3,200 g / eq.

[0092] Next, 500.0 parts by weight of "EPICLON 860" were added to a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. The mixture was heated to 60°C, and then 75 parts by weight of epoxy resin (R4) were added. The mixture was stirred at the same temperature for 1 hour to homogenize it, and then cooled to below 50°C. The stirring speed was increased to 3,000 rpm, and 471 parts by weight of deionized water were added over 3 hours. Thus, a water-dispersible epoxy resin composition (R4) with a non-volatile content of 55% by weight, a Brookfield viscosity of 250 mPa·s, and a particle size of 1.30 μm was obtained.

[0093] The properties in the above embodiments and comparative examples are measured as follows.

[0094] [Non-volatile content]

[0095] 1.0000g of sample was accurately weighed in an aluminum weighing dish, stretched into a thin film, and stored at 150℃ for 1 hour. The content of nonvolatile matter was calculated based on the weight before and after the treatment.

[0096] [Epoxy Equivalent]

[0097] The determination was performed by perchloric acid-acetic acid titration.

[0098] [Viscosity]

[0099] The determination shall be carried out in accordance with GB / T 11175-2002.

[0100] [Particle size]

[0101] Using a MicrotracBEL-manufactured "UPA-150", the 50% cumulative particle size was measured and determined as the particle size d50.

[0102] The following evaluation was conducted using the water-dispersible epoxy resin compositions (1) to (7) and (R1) to (R4) obtained in the above examples and comparative examples.

[0103] [Methods for evaluating the storage stability of water-dispersible epoxy resin compositions]

[0104] Approximately 90g of each of the water-dispersible epoxy resin compositions obtained in the examples or comparative examples was measured into a 100ml glass bottle, stored at room temperature (25°C), and its appearance was visually observed after a specified time, and evaluated according to the following evaluation criteria.

[0105] A: No separation or settling.

[0106] B: There is separation in the upper layer.

[0107] C: Clear separation and settling

[0108] The properties and evaluation results of the water-dispersible epoxy resin compositions (1) to (7) and (R1) to (R4) prepared in the Examples and Comparative Examples are shown in Table 1.

[0109] Table 1

[0110]

[0111] <Membrane Evaluation>

[0112] Coatings (1) to (7) and (R1) to (R4) were prepared using the formulations recorded in Tables 2 and 3. The coatings were sprayed onto cold-rolled steel sheets (TP technology developed "SPCC-SB", the surface of which was degreased with xylene and then water-polished with 240 grit sandpaper) to form a dry film with a thickness of about 60 μm. After curing the film at 25°C for 1 week, various tests were performed under the following conditions.

[0113] [Methods for determining impact strength]

[0114] Impact strength was determined in accordance with the method of GB / T 1732-1993.

[0115] [Methods for determining adhesion]

[0116] Adhesion was determined according to the method in GB / T 9286-1998.

[0117] Methods for measuring pencil hardness

[0118] The hardness of the pencil was determined according to the method of GB / T 6739-2006.

[0119] [Methods for evaluating water resistance]

[0120] Water resistance was evaluated by checking for color changes, blistering, and rusting of the film, in accordance with the method of GB / T 1733-1993. The absence of color changes, blistering, and rusting indicated high water resistance.

[0121] [Evaluation Method for Salt Spray Resistance]

[0122] Salt spray resistance was determined by confirming the presence of blistering on the membrane surface after 1000 hours of testing, and measuring the separation width extending from the slit, in accordance with ASTM B117. No blistering and a smaller peel width indicate higher corrosion resistance.

[0123] The compositions of coatings (1) to (7) and (R1) to (R4) prepared in the examples and comparative examples are shown in Tables 2 and 3.

[0124] Table 2

[0125]

[0126] Table 3

[0127]

[0128] The manufacturers listed in Tables 2 and 3 are as follows.

[0129] "D 755W": TEGO DISPERSE 755W, a dispersant manufactured by EVONIK. "BYK-346": a wetting agent manufactured by BYK.

[0130] "BYK-024": Defoamer manufactured by BYK Corporation

[0131] "DPnB": Dipropylene glycol butyl ether manufactured by Down Chemical Company; "BYK-425": Thickener manufactured by BYK Company.

[0132] "HALOX FLASH-X 150": ICL Phosphate Specialty anti-flash rust agent

[0133] Iron oxide: Titan Kogyo, Ltd. manufactures "R-516L".

[0134] "HALOX SZP-391": ICL Phosphate Specialty anti-rust pigment

[0135] Precipitated barium sulfate: A filler manufactured by SAKAI CHEMICAL INDUSTRY CO.,LTD.

[0136] The evaluation results of the coatings (1) to (7) and (R1) to (R4) prepared in the examples and comparative examples are shown in Table 4.

[0137] Table 4

[0138]

[0139] Examples 1-7 shown in Table 1 are examples of the water-dispersible epoxy resin compositions of the present invention. These water-dispersible epoxy resin compositions have been shown to have high storage stability. Furthermore, the cured films of coatings using these water-dispersible epoxy resin compositions (Examples 8-14) have been shown to have excellent corrosion resistance.

[0140] On the other hand, Comparative Example 1 shown in Table 1 is an example of a water-dispersible epoxy resin composition whose [(a2-1) / (a1+a2)] falls outside the range of 3 to 10 (2.6) specified in this invention. In addition to its obviously insufficient storage stability, the cured film of the coating using this water-dispersible epoxy resin composition (Comparative Example 5) also showed obviously insufficient corrosion resistance.

[0141] Comparative Example 2 shown in Table 1 is an example of a water-dispersible epoxy resin composition whose [(a2-1) / (a1+a2)] falls outside the range of 3 to 10 (13.7) specified in this invention. Although this water-dispersible epoxy resin composition exhibits excellent storage stability, the cured film of the coating using this water-dispersible epoxy resin composition (Comparative Example 6) shows significantly insufficient corrosion resistance.

[0142] Comparative Examples 3 and 4 shown in Table 1 are examples of water-dispersible epoxy resin compositions that do not contain multi-component active hydrogen compounds (a2-2). In addition to their obviously insufficient storage stability, the cured films of coatings using these water-dispersible epoxy resin compositions (Comparative Examples 7 and 8) also showed obviously insufficient corrosion resistance.

Claims

1. A water-dispersible epoxy resin composition comprising: Epoxy resin (A) and aqueous medium (B), The epoxy resin (A) is obtained from the following essential components: Compounds having at least two epoxy groups in their molecules (a1), and Compounds having at least two carboxyl groups in their molecules (a2), The compound (a2) is obtained from the necessary components including a multi-component active hydrogen compound (a2-1) having repeating alkylene units, a multi-component active hydrogen compound (a2-2) having an alicyclic skeleton different from the multi-component active hydrogen compound (a2-1), and an acid anhydride (a2-3), and In the total mass of the compounds (a1) and (a2), the content of the multi-component active hydrogen compound (a2-1) is in the range of 3 to 10% by mass, wherein the multi-component active hydrogen compound (a2-1) includes one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

2. The water-dispersible epoxy resin composition according to claim 1, wherein the compound (a1) comprises bisphenol type epoxy resin and / or phenolic varnish type epoxy resin.

3. The water-dispersible epoxy resin composition according to claim 1, wherein the mass ratio of the multi-component active hydrogen compound (a2-2) to the multi-component active hydrogen compound (a2-1) [(a2-2) / (a2-1)] is in the range of 0.3 to 6.

4. The water-dispersible epoxy resin composition according to claim 1, wherein the multi-element active hydrogen compound (a2-2) comprises cyclohexanediethanol and / or hydrogenated bisphenol A.

5. The water-dispersible epoxy resin composition according to claim 1, wherein the acid anhydride (a2-3) comprises one or more selected from the group consisting of succinic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, methyltetrahydrophthalic anhydride, and hexahydrophthalic anhydride.

6. A coating comprising a water-dispersible epoxy resin composition according to any one of claims 1 to 5.

7. An article comprising a cured film from the coating according to claim 6.

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