Water-dispersible epoxy resin compositions, paints, and articles

Abstract

The present invention provides a water-dispersible epoxy resin composition capable of forming a cured coating film that has excellent storage stability and excellent corrosion resistance. [Solution] A water-dispersible epoxy resin composition is used, comprising an epoxy resin (A) made from essential raw materials a compound (a1) having at least two epoxy groups in one molecule and a compound (a2) having at least two carboxyl groups in one molecule, and an aqueous medium (B), wherein the compound (a2) is made from essential raw materials a polyvalent active hydrogen compound (a2-1) having repeating alkylene units, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton other than the polyvalent active hydrogen compound (a2-1), and an acid anhydride (a2-3), and the content of the polyvalent active hydrogen compound (a2-1) is in the range of 3 to 10% by mass of the total mass of the compound (a1) and the compound (a2).

Description

Technical Field

[0001] The present invention relates to a water-dispersible epoxy resin composition, a coating, and an article.

Background Art

[0002] Generally, epoxy resin compositions are excellent in mechanical properties and electrical properties, and cured products with good adhesiveness, solvent resistance, water resistance, heat resistance, etc. can be obtained. Therefore, they are widely used as insulating materials for electrical and electronic components, adhesives, coatings, for civil engineering and construction, etc.

[0003] Among these various applications, especially in coating applications, etc., a solvent dilution type using various organic solvents has been common. However, in recent years, from the perspective of global environmental conservation including prevention of air pollution and improvement of working environment, etc., the implementation of total volatile organic compound (VOC) regulations is progressing, and water-dispersible epoxy resin compositions that do not use organic solvents have attracted attention.

[0004] As the water-dispersible epoxy resin composition, for example, a water-dispersible epoxy resin composition obtained by first reacting polyethylene glycol with trimellitic anhydride, then reacting with an excess of epoxy resin to synthesize an emulsifier, adding this to the epoxy resin, and adding water is known (see, for example, Patent Document 1). Also, a water-dispersible epoxy resin composition obtained by first reacting polyethylene glycol with an acid anhydride, then reacting with an excess of epoxy resin to synthesize an emulsifier, extracting it, then adding it again to the epoxy resin, and adding water is known (see, for example, Patent Document 2). However, these water-dispersible epoxy resin compositions not only have insufficient storage stability but also do not satisfy the increasingly demanding performance requirements in the physical properties of the cured products (for example, anticorrosive properties).

[0005] Therefore, there has been a demand for a material having excellent storage stability and excellent anticorrosive properties.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Chinese Patent Application Publication No. 105801868 [Patent Document 2] Chinese Patent Application Publication No. 108503846 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The problem that the present invention aims to solve is to provide a water-dispersible epoxy resin composition capable of forming a cured coating film having excellent storage stability and excellent corrosion resistance, a paint containing the water-dispersible epoxy resin composition, and an article having a cured coating film of the paint. [Means for solving the problem]

[0008] The inventors of the present invention conducted diligent studies to solve the above problems and found that the above problems can be solved by using a water-dispersible epoxy resin composition containing an epoxy resin made from essential raw materials: a compound having at least two epoxy groups in one molecule, a compound having at least two carboxyl groups in one molecule made from a specific polyvalent active hydrogen compound and an acid anhydride, and an aqueous medium. As a result, the present invention was completed.

[0009] In other words, the present invention relates to a water-dispersible epoxy resin composition comprising an epoxy resin (A) having a compound (a1) having at least two epoxy groups in one molecule and a compound (a2) having at least two carboxyl groups in one molecule as essential raw materials, and an aqueous medium (B), wherein the compound (a2) has a polyvalent active hydrogen compound (a2-1) having repeating alkylene units, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton other than the polyvalent active hydrogen compound (a2-1), and an acid anhydride (a2-3) as essential raw materials, and the content of the polyvalent active hydrogen compound (a2-1) is in the range of 3 to 10% by mass of the total mass of the compound (a1) and the compound (a2). [Effects of the Invention]

[0010] The water-dispersible epoxy resin composition of the present invention can be prepared by a simple method, has excellent storage stability, and paints containing the water-dispersible epoxy resin composition have excellent corrosion resistance, making it particularly suitable for use in corrosion-resistant paints. [Modes for carrying out the invention]

[0011] The present invention provides a water-dispersible epoxy resin composition comprising an epoxy resin (A) having a compound (a1) having at least two epoxy groups in one molecule and a compound (a2) having at least two carboxyl groups in one molecule as essential raw materials, and an aqueous medium (B), wherein the compound (a2) has a polyvalent active hydrogen compound (a2-1) having repeating alkylene units, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton other than the polyvalent active hydrogen compound (a2-1), and an acid anhydride (a2-3) as essential raw materials, and the content of the polyvalent active hydrogen compound (a2-1) is in the range of 3 to 10% by mass of the total mass of the compound (a1) and the compound (a2).

[0012] The epoxy resin (A) used is one that has as essential raw materials a compound (a1) having at least two epoxy groups in one molecule and a compound (a2) having at least two carboxyl groups in one molecule.

[0013] Examples of compounds (a1) having at least two epoxy groups in one molecule (hereinafter sometimes abbreviated as "compound (a1)") include bisphenol-type epoxy resins synthesized from various bisphenols and epihalohydrins, novolac-type epoxy resins synthesized from phenol / alkylphenol novolacs and epihalohydrins, biphenol-type epoxy resins, epoxy resins synthesized from compound diols with adjacent aromatic rings, such as naphthalenediols, and epihalohydrins, glycidylamines synthesized from aromatic amines and epihalohydrins, epoxy resins synthesized from aliphatic amines and epihalohydrins, epoxy resins synthesized from aliphatic alcohols and epihalohydrins, epoxy resins obtained by reacting epihalohydrins with a diene compound such as a dicyclopentadiene-phenol condensate and a phenol, glycidylamines obtained by reacting polycarboxylic acids with epihalohydrins, and compounds in which an epoxy ring is formed by oxidizing a double bond in the molecule with a peroxide. These compounds can be used individually or in combination of two or more.

[0014] Furthermore, as compound (a1), compounds obtained by modifying the various epoxy resins exemplified above through reaction with polyhydric phenol compounds, polyhydric carboxylic acid compounds, polyhydric amine compounds, etc., can also be used.

[0015] Among these, bisphenol-type epoxy resins and novolac-type epoxy resins are preferred, and bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and phenol novolac-type epoxy resins are more preferred, as they provide a water-dispersible epoxy resin composition that has excellent storage stability and can form a cured coating film with excellent corrosion resistance.

[0016] Furthermore, a monofunctional epoxy resin may be used in combination with compound (a1) for viscosity adjustment or reactivity adjustment. Examples of the monofunctional epoxy resin 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, t-butylphenol glycidyl ether, cardanol glycidyl ether, neodecanoic acid glycidyl ester, and the like. These monofunctional epoxy resins can be used individually or in combination of two or more.

[0017] The amount of compound (a1) used is preferably in the range of 55 to 70% by mass of the total mass of the essential raw materials for the epoxy resin (A), i.e., compound (a1) and compound (a2) having at least two carboxyl groups in one molecule, in order to obtain a water-dispersible epoxy resin composition capable of forming a cured coating film with excellent storage stability and excellent corrosion resistance. If the amount of compound (a1) used is less than 55% by mass, the corrosion resistance of the cured coating film will be insufficient, and if it exceeds 70% by mass, it will be difficult to achieve both water dispersibility and corrosion resistance of the cured coating film.

[0018] Compound (a2) having at least two carboxyl groups in one molecule (hereinafter sometimes abbreviated as "compound (a2)") is used, and is a compound that requires a polyvalent active hydrogen compound (a2-1) having repeating alkylene units, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton, and an acid anhydride (a2-3) as essential raw materials.

[0019] Examples of the polyvalent active hydrogen compound (a2-1) include compounds having a molecular weight distribution with ethylene glycol, propylene glycol, and tetramethylene ether glycol as repeating units. These compounds can be used individually or in combination of two or more.

[0020] Regarding the terminal active hydrogen part in the polyhydric active hydrogen compound (a2-1), for example, a hydroxyl group, an amino group, etc. can be mentioned. Examples of the polyhydric active hydrogen compound (a2-1) include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, a compound in which polyethylene glycol and polypropylene glycol are co-condensed, a compound in which polypropylene glycol is introduced into glycerin, a compound in which polyethylene glycol and polypropylene glycol are co-condensed and introduced into glycerin, polycarbonate diol polymerized with a carbonate group, etc. Also, as commercially available products of the polyhydric active hydrogen compound (a2-1), "Jeffamine D-series", "Jeffamine T-series", etc. manufactured by Huntsman Corporation can be mentioned. These polyhydric active hydrogen compounds can be used alone or in combination of two or more kinds.

[0021] Among these, since a water-dispersible epoxy resin composition having excellent storage stability and capable of forming a cured coating film having excellent corrosion resistance can be obtained, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol are preferable.

[0022] The content of the polyhydric active hydrogen compound (a2-1) is used so as to be in the range of 3 to 10% by mass in the total mass of the compound (a1) and the compound (a2) since a water-dispersible epoxy resin composition having excellent storage stability and capable of forming a cured coating film having excellent corrosion resistance can be obtained.

[0023] The polyhydric active hydrogen compound (a2-2) may be any compound having an alicyclic skeleton in the molecule and having active hydrogen at the terminal. For example, 2,2'-isopropylidene cyclohexanol, 2,4'-isopropylidene cyclohexanol, 4,4'-isopropylidene cyclohexanol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, tricyclo[5,2,1,0 decane-4,8-dimethanol, 2,2'-methylenebis(cyclohexylamine), 2,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(cyclohexylamine) and the like can be mentioned. These polyhydric active hydrogen compounds can be used alone or in combination of two or more.

[0024] Among these, since a water-dispersible epoxy resin composition capable of forming a cured coating film having excellent storage stability and excellent corrosion resistance can be obtained, 4,4'-isopropylidene cyclohexanol, 1,4-cyclohexanedimethanol, 1,3-diaminocyclohexane, 4,4'-methylenebis(cyclohexylamine) are preferable, and 4,4'-isopropylidene cyclohexanol and 1,4-cyclohexanedimethanol are more preferable.

[0025] The mass ratio [(a2-2) / (a2-1)] of the polyhydric active hydrogen compound (a2-1) and the polyhydric active hydrogen compound (a2-2) is preferably in the range of 0.3 to 6 because a water-dispersible epoxy resin composition capable of forming a cured coating film having excellent storage stability and excellent corrosion resistance can be obtained.

[0026] The aforementioned acid anhydrides (a2-3) can be any acid anhydride that is commercially available as an industrial product and are not particularly limited. Examples include succinic anhydride, octyl succinate anhydride, dodecinyl succinate anhydride, maleic anhydride, phthalic anhydride, methyl-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl-hexahydrophthalic anhydride, methylnadic anhydride, trimellitic anhydride, pyromellitic anhydride, and dodecanediic anhydride. These acid anhydrides can be used individually or in combination of two or more.

[0027] Furthermore, among these, methyl-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyl-hexahydrophthalic anhydride are preferred because they yield a water-dispersible epoxy resin composition that has excellent storage stability and can form a cured coating film with excellent corrosion resistance.

[0028] The method for producing compound (a2) is not particularly limited, and examples include a method in which essential raw materials containing the polyvalent active hydrogen compound (a2-1), a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton, and an acid anhydride (a2-3) are heated and stirred in a container under a nitrogen atmosphere at 90 to 200°C. In the above method, since the polyvalent active hydrogen compound (a2-1) may have absorbed water, it is preferable to remove the contained water by heating and vacuum treatment in the first stage of the reaction. By performing this treatment, compound (a2) can be obtained stably.

[0029] The amount of compound (a2) used is preferably in the range of 30 to 45% by mass of the total mass of compound (a1) and compound (a2), which is an essential raw material for epoxy resin (A), in order to obtain a water-dispersible epoxy resin composition that has excellent storage stability and can form a cured coating film with excellent corrosion resistance. If the amount of compound (a2) used is less than 30% by mass, it is difficult to achieve both water dispersibility and corrosion resistance of the cured coating film, and if it exceeds 45% by mass, the corrosion resistance of the cured coating film will be insufficient.

[0030] The method for producing the epoxy resin (A) is not particularly limited, and examples include a method in which essential raw materials containing compound (a1) and compound (a2) are heated and stirred under a nitrogen atmosphere at 100 to 200°C to obtain the epoxy resin (A). In the above method, a catalyst may also be used to shorten the reaction time.

[0031] Examples of the catalysts include tertiary amines such as triethylamine, tributylamine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, N-methylpiperazine, and their salts; 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, 2-ethyl-4-methylimidazole tetraphenylborate, and their salts; and 1,5-diazabicyclo[5,4,0 Examples of catalysts include diazabicyclo compounds such as ]-7-undecane, 1,5-diazabicyclo[4,3,0]-5-nonene, 1,4-diazabicyclo[2,2,2,]octane, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate; phosphines such as tributylphosphine, triphenylphosphine, tris(dimethoxyphenyl)phosphine, tris(hydroxypropyl)phosphine, and tris(cyanoethyl)phosphine; and phosphonium salts such as tetraphenylphosphonium salt, methyltributylphosphonium salt, methyltricyanoethylphosphonium salt, and tetrabutylphosphonium salt. These catalysts can be used individually or in combination of two or more. Among these, triphenylphosphine is preferred.

[0032] The epoxy equivalent of the solid content in the epoxy resin (A) is preferably in the range of 300 to 1,300 g / eq., as this yields a water-dispersible epoxy resin composition capable of forming a cured coating film with excellent storage stability and excellent corrosion resistance. If the amount is less than 300 g / eq., the coating film becomes brittle, and if it exceeds 1,300 g / eq., the reactivity with the curing agent deteriorates, resulting in poor water resistance.

[0033] Examples of the aqueous medium (B) include ion-exchanged water and distilled water. These aqueous mediums can be used individually or in combination of two or more.

[0034] The method for producing the water-dispersible epoxy resin composition of the present invention is not particularly limited and may be carried out by any method. For example, one method is to mix the epoxy resin (A) with the aqueous medium (B).

[0035] Methods for mixing the epoxy resin (A) and the aqueous medium (B) include, for example, a reaction vessel equipped with stirring blades; a kneader such as a kneader, continuous kneader, tapered roll, single-screw extruder, twin-screw extruder, tri-screw extruder, universal mixer, Plastmill, Bodeta type kneader; a rotary dispersion mixer such as a homomixer, static mixer, Filmix, Ebara Milder, Creamix, Ultra Turlux, Cavitron, Biomix; an ultrasonic dispersion device; and an in-line mixer or other device that has no moving parts and can mix by the flow of the fluid itself.

[0036] In the method for producing 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 of the reaction product and is inert to the resin when used. Examples include ester compounds such as ethyl acetate, 3-methoxybutyl acetate, methoxypropyl acetate, and cellosolve acetate; 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; glyme compounds such as monoglyme, diglyme, and triglyme; propylene glycol monoalkyl ether compounds such as 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 these, cellosolve compounds, propylene glycol monoalkyl ether compounds, and ketone compounds are preferred.

[0037] The aforementioned organic solvent may remain in the water-dispersible epoxy resin composition or may be removed by distillation under reduced pressure.

[0038] 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, in order to obtain a water-dispersible epoxy resin composition that has excellent storage stability and can form a cured coating film with excellent corrosion resistance.

[0039] The water-dispersible epoxy resin composition of the present invention may optionally further contain a curing agent.

[0040] Examples of the curing agent include basic curing agents.

[0041] Examples of the basic curing agents include aliphatic polyamines, alicyclic polyamines, Mannich bases, amine-epoxy addition products, polyamide polyamines, and liquid aromatic polyamines. These curing agents can be used individually or in combination of two or more.

[0042] Examples of the aliphatic polyamines include diethylenetriamine, triethylenetriamine, tetraethylenepentamine, polyalkylene polyamines such as 1,4-bis-(3-aminopropyl)piperazine, m-xylenediamine, and p-xylenediamine.

[0043] Examples of the alicyclic polyamines include 1,2-diaminocyclohexane, 1,4-diamino-3,6-diethylcyclohexane, and isophoronediamine.

[0044] Examples of the Mannich base include condensation reaction products of (1) polyamines such as triethylenetriamine, isophoronediamine, m-xylenediamine, and p-xylenediamine, (2) aldehydes such as formaldehyde, and (3) monovalent or polyvalent cresols and xylenols, p-tert-butylphenol, resorcinol, and other phenols having at least one aldehyde-reactive site in their nucleus.

[0045] Examples of the amine-epoxy addition products include (1) reaction products of (a) polyamines such as triethylenetriamine, tetraethylenepentamine, isophoronediamine, m-xylenediamine, and p-xylenediamine with epoxy resins such as (b) glycidyl ethers such as phenylglycidyl ether, butyl glycidyl ether, diglycidyl ether of bisphenol A, and diglycidyl ether of bisphenol F, or (2) reaction products of the polyamines with glycidyl esters such as "Cardura E" (registered trademark: Yuka Shell Epoxy Co., Ltd.).

[0046] The aforementioned polyamide polyamine can be one obtained by the reaction of polyamines with polycarboxylic acids or dimerized fatty acids, for example, the reaction product of ethylenediamine and dimer acid.

[0047] Examples of the liquid aromatic polyamine include reaction products of aromatic polyamines with glycidyl ethers or glycidyl esters. Examples of the aromatic polyamine include diaminodiphenylmethane and diaminodiphenylsulfone. Examples of the glycidyl ethers include phenylglycidyl ether, butyl glycidyl ether, diglycidyl ether of bisphenol A, and diglycidyl ether of bisphenol F. Examples of the glycidyl esters include "Cardura E".

[0048] The amount of curing agent used is preferably such that the ratio of epoxy equivalents in the water-dispersible epoxy resin composition of the present invention to amine equivalents in the basic curing agent [epoxy equivalents / amine equivalents] is in the range of 0.75 to 1.25.

[0049] The water-dispersible epoxy resin composition of the present invention may also be used in combination with other resin components such as polyester-based aqueous resins and acrylic-based aqueous resins, if necessary.

[0050] Furthermore, the water-dispersible epoxy resin composition of the present invention may contain other additives as needed. Examples of such additives include anti-repellent agents, anti-sagging agents, flow-spreading agents, defoaming agents, curing accelerators, ultraviolet absorbers, and light stabilizers.

[0051] The applications of the water-dispersible epoxy resin composition of the present invention are not particularly limited, but examples include paints, adhesives, fiber sizing agents, concrete primers, and the like.

[0052] When using the water-dispersible epoxy resin composition of the present invention for paint applications, it is preferable to incorporate various pigments such as rust-preventive pigments, coloring pigments, extender pigments, and various additives as needed.

[0053] Examples of the rust-preventive pigments include zinc powder, aluminum phosphomolybutenate, zinc phosphate, aluminum phosphate, barium chromate, aluminum chromate, graphite, and other flaky pigments.

[0054] Examples of the aforementioned coloring pigments include carbon black, titanium dioxide, zinc sulfide, and red iron oxide.

[0055] Examples of the aforementioned extender pigments include barium sulfate, calcium carbonate, talc, and kaolin.

[0056] The amount of the additive is preferably in the range of 10 to 70 parts by mass per 100 parts by mass of solid content of the water-dispersible epoxy resin composition.

[0057] The coating method when using the water-dispersible epoxy resin composition of the present invention as a paint is not particularly limited and can be performed by roll coating, spraying, brushing, spatula application, bar coating, dipping, or electrodeposition coating. Post-coating treatment can be performed by room temperature drying or heat curing. When heat curing is performed, the heating temperature is preferably in the range of 50 to 250°C, and particularly preferably in the range of 60 to 230°C. The heating time is preferably in the range of 2 to 30 minutes, and particularly preferably in the range of 5 to 20 minutes.

[0058] The water-dispersible epoxy resin composition of the present invention is used in general-purpose applications such as water-based paints for interior building applications, water-based paints for exterior building applications and inorganic building materials, water-based rust-preventive paints for iron parts, and water-based paints for automobile repair, as well as in industrial applications such as automobile paints and beverage cans. Among these, due to its excellent corrosion resistance and touch-dry properties, it is particularly suitable for heavy-duty corrosion protection of steel structures and bridges, and especially as a water-based rust-preventive paint for iron parts used as a primer.

[0059] Furthermore, when using the water-dispersible epoxy resin composition of the present invention as an adhesive, it is not particularly limited and can be applied to the substrate by spraying, brushing, or using a spatula, and then the bonding surfaces of the substrates can be brought together. The joint can be strengthened by fixing or pressing the surrounding area to form a strong adhesive layer. Suitable substrates include steel plates, concrete, mortar, wood, resin sheets, and resin films. It is even more preferable to apply the adhesive after performing various surface treatments as needed, such as physical treatments like polishing, electrical treatments like corona treatment, or chemical treatments like chemical conversion treatment.

[0060] Furthermore, when the water-dispersible epoxy resin composition of the present invention is used as a fiber sizing agent, it can be carried out in any way without particular limitations. For example, it can be applied to fibers immediately after spinning using a roller coater, wound up as fiber strands, and then dried. The fibers used are not particularly limited and include, for example, inorganic fibers such as glass fibers, ceramic fibers, asbestos fibers, carbon fibers, and stainless steel fibers, natural fibers such as cotton and hemp, and synthetic fibers such as polyester, polyamide, and urethane. The base material can be in the form of short fibers, long fibers, yarn, mat, or sheet. The amount used as a fiber sizing agent is preferably 0.1 to 2% by mass as resin solids relative to the fiber. [Examples]

[0061] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples listed below. (Example 1: Preparation of water-dispersible epoxy resin composition (1))

[0062] In a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, 50.0 parts by mass of polyethylene glycol (PEG-3500, manufactured by Hai'an Chemical Co., Ltd., Jiangsu Province) and 156.3 parts by mass of hydrogenated bisphenol A were charged. The mixture was heated and stirred at 200 rpm under a nitrogen atmosphere. The nitrogen was stopped at 110°C, and the mixture was dehydrated under reduced pressure for 1 hour. After releasing the reduced pressure with nitrogen again, 221.0 parts by mass of methyl-tetrahydrophthalic anhydride (HN-2000, manufactured by Showa Denko Materials Co., Ltd.) was added, and the mixture was heated to 130°C and reacted for 5 hours. Then, 667.0 parts by mass of bisphenol A type liquid epoxy resin (EPICLON 850-S, manufactured by DIC Corporation) and 0.5 parts by mass of triphenylphosphorus were charged, and the mixture was reacted for another 5 hours. The resin in the flask was liquid, and the acid value was less than 0.1. Next, while cooling the contents, 274 parts by mass of methyl ethyl ketone was added and uniformly dissolved. The stirring speed was increased to 3,000 rpm at a temperature below 50°C, and 960 parts by mass of deionized water were added over 3 hours. Subsequently, the methyl ethyl ketone was removed by distillation under reduced pressure, and the concentration was adjusted by adding deionized water to obtain a water-dispersible epoxy resin composition (1) with a non-volatile content of 55% by mass, a B-type viscosity of 7,000 mPa·s, and a d50 particle size of 0.18 μm. (Example 2: Preparation of water-dispersible epoxy resin composition (2))

[0063] A water-dispersible epoxy resin composition (2) was obtained in the same manner as in Example 1, except that the hydrogenated bisphenol A used in Example 1 was replaced with 94.6 parts by mass of cyclohexanedimethanol (EASTMAN "CHDM-D"), and the proportions of methyl-tetrahydrophthalic anhydride (222.8 parts by mass), "EPICLON 850-S" (716.2 parts by mass), methyl ethyl ketone (270 parts by mass), and deionized water (951 parts by mass) were changed. The composition was then prepared in the same manner as in Example 1, with a non-volatile content of 55% by mass, a B-type viscosity of 6,000 mPa·s, and a d50 particle size of 0.31 μm. (Example 3: Preparation of water-dispersible epoxy resin composition (3))

[0064] Except for changing the amount of "EPICLON 850-S" used in Example 1 to 533.6 parts by mass, and further adding 133.4 parts by mass of a phenol novolac type epoxy resin ("EPICLON N-740" manufactured by DIC Corporation), a water-dispersible epoxy resin composition (3) with a non-volatile content of 55% by mass, a B-type viscosity of 5,800 mPa·s, and a d50 particle size of 0.22 μm was obtained in the same manner as in Example 1. (Example 4: Preparation of water-dispersible epoxy resin composition (4))

[0065] A water-dispersible epoxy resin composition (4) was obtained in the same manner as in Example 1, except that the amount of polyethylene glycol used in Example 1 was changed to 25.0 parts by mass, and 25.0 parts by mass of polypropylene glycol (PPG-2000, manufactured by Hai'an Petrochemical Co., Ltd., Jiangsu Province) was also used, and the amount of methyl-tetrahydrophthalic anhydride used in Example 1 was changed to 221.3 parts by mass. The composition was then prepared in the same manner as in Example 1, with a non-volatile content of 55% by mass, a B-type viscosity of 3,000 mPa·s, and a d50 particle size of 0.52 μm. (Example 5: Preparation of water-dispersible epoxy resin composition (5))

[0066] Except for changing the amount of polyethylene glycol used in Example 1 to 30.0 parts by mass, and further adding 20.0 parts by mass of polytetramethylene ether glycol (PTMG3000, manufactured by Mitsubishi Chemical Corporation), and changing the amount of methyl-tetrahydrophthalic anhydride used in Example 1 to 221.3 parts by mass, a water-dispersible epoxy resin composition (5) with a non-volatile content of 55% by mass, a B-type viscosity of 2,200 mPa·s, and a d50 particle size of 0.57 μm was obtained in the same manner as in Example 1. (Example 6: Preparation of a water-dispersible epoxy resin composition (6))

[0067] In Example 1, the polyethylene glycol (PEG-3500, manufactured by Hai'an Chemical Co., Ltd., Jiangsu Province) used in Example 1 was replaced with 75.0 parts by mass of PEG-2000, manufactured by Hai'an Chemical Co., Ltd., Jiangsu Province; the amount of hydrogenated bisphenol A was changed to 150.0 parts by mass; methyl-tetrahydrophthalic anhydride was replaced with 204.1 parts by mass of hexahydrophthalic anhydride (Ricacid HH, manufactured by Shin Nippon Rika Co., Ltd.); the amount of EPICLON 850-S was changed to 652.2 parts by mass; the amount of methyl ethyl ketone was changed to 270 parts by mass; and the amount of ion-exchanged water was changed to 949 parts by mass. In this manner, a water-dispersible epoxy resin composition (6) with a non-volatile content of 55% by mass, a B-type viscosity of 2,000 mPa·s, and a d50 particle size of 0.80 μm was obtained. (Example 7: Preparation of a water-dispersible epoxy resin composition (7))

[0068] Except for changing the amount of hydrogenated bisphenol A used in Example 1 to 176.5 parts by mass, changing the methyl-tetrahydrophthalic anhydride used in Example 1 to 230.9 parts by mass of hexahydrophthalic anhydride, changing the "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), changing the amount of methyl ethyl ketone to 276 parts by mass and the amount of ion-exchanged water to 969 parts by mass, a water-dispersible epoxy resin composition (7) with a non-volatile content of 55% by mass, a B-type viscosity of 7,400 mPa·s, and a d50 particle size of 0.25 μm was obtained in the same manner as in Example 1. (Comparative Example 1: Preparation of a water-dispersible epoxy resin composition (R1))

[0069] In a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, 30.0 parts by mass of polyethylene glycol (PEG-3500, manufactured by Hai'an Chemical Co., Ltd., Jiangsu Province) and 206.3 parts by mass of hydrogenated bisphenol A were charged. The mixture was heated and stirred at 200 rpm under a nitrogen atmosphere, and the nitrogen was stopped at 110°C. Dehydration was carried out under reduced pressure for 1 hour. After releasing the reduced pressure with nitrogen again, 288.2 parts by mass of methyl-tetrahydrophthalic anhydride was added, the temperature was raised to 130°C, and the mixture was reacted for 5 hours. Then, 637.5 parts by mass of "EPICLON 850-S" and 0.5 parts by mass of triphenylphosphorus were charged, and the mixture was reacted for another 5 hours. Next, while cooling the contents, 290 parts by mass of methyl ethyl ketone was added and uniformly dissolved. The stirring speed was increased to 3,000 rpm at a temperature below 50°C, and 1,020 parts by mass of deionized water was added over 3 hours. Subsequently, methyl ethyl ketone was removed by distillation under reduced pressure, and the concentration was adjusted by adding deionized water to obtain a water-dispersible epoxy resin composition (R1) with a non-volatile content of 55% by mass, a B-type viscosity of 400 mPa·s, and a d50 particle size of 2.30 μm. (Comparative Example 2: Preparation of a water-dispersible epoxy resin composition (R2))

[0070] Except for changing the amount of polyethylene glycol used in Comparative Example 1 to 150.0 parts by mass, changing the amount of hydrogenated bisphenol A to 75.0 parts by mass, changing the amount of methyl-tetrahydrophthalic anhydride to 118.0 parts by mass, changing the amount of "EPICLON 850-S" to 750.0 parts by mass, changing the amount of methyl ethyl ketone to 273 parts by mass, and changing the amount of ion-exchanged water to 959 parts by mass, a water-dispersible epoxy resin composition (R2) with a non-volatile content of 55% by mass, a B-type viscosity of 9,200 mPa·s, and a d50 particle size of 0.17 μm was obtained in the same manner as in Comparative Example 1. (Comparative Example 3: Preparation of a water-dispersible epoxy resin composition (R3))

[0071] 200 parts by mass of polyethylene glycol (PEG-4000, manufactured by Jiangsu Haian Petrochemical Co., Ltd.) was charged into a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. Heating and stirring at 200 rpm were started under a nitrogen atmosphere, and the nitrogen was stopped at 110°C, followed by 1 hour of reduced pressure. After releasing the reduced pressure with nitrogen, 37.6 parts by mass of "EPICLON 850-S" and 0.3 parts by mass of boron trifluoride ethyl ether complex (reagent) were added, and the mixture was reacted at 130°C for 5 hours. The mixture was then removed to obtain epoxy resin (r3), which is solid at room temperature. The epoxy equivalent of this epoxy resin (r3) was 2,500 g / eq.

[0072] Next, 500.0 parts by mass of "EPICLON 1050" were placed in a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, and melted at 100°C under a nitrogen atmosphere. Then, while cooling, 125 parts by mass of methyl ethyl ketone were added and dissolved. Next, 50.0 parts by mass of epoxy resin (r3) were added and stirred at 60°C for 1 hour to homogenize. After that, the mixture was cooled to below 50°C and the stirring speed was increased to 3,000 rpm, and then 450 parts by mass of ion-exchanged water were added over 3 hours. Subsequently, the solvent was removed by distillation under reduced pressure, and further ion-exchanged water was added to obtain a water-dispersible epoxy resin composition (R3) with a non-volatile content of 60% by mass, a B-type viscosity of 300 mPa·s, and a d50 particle size of 0.91 μm. (Comparative Example 4: Preparation of a water-dispersible epoxy resin composition (R4))

[0073] 400 parts by mass of polyethylene glycol (PEG-4000, manufactured by Jiangsu Haian Petrochemical Co., Ltd.) was charged into a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. The mixture was heated and stirred at 200 rpm under a nitrogen atmosphere. The nitrogen was stopped at 110°C, and the pressure was reduced for 1 hour. After releasing the pressure with nitrogen, 38.4 parts by mass of trimellitic anhydride (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added, and the mixture was reacted at 110°C until the acid value no longer changed. Then, 9.1 parts by mass of bisphenol A type epoxy resin (EPICLON 860, manufactured by DIC Corporation, epoxy equivalent 240 g / eq.) and 0.2 parts by mass of triphenylphosphorus were added, and the mixture was reacted at 120°C for 5 hours to obtain epoxy resin (r4) that is solid at room temperature. The epoxy equivalent of this epoxy resin (r4) was 3,200 g / eq.

[0074] Next, 500.0 parts by mass of "EPICLON 860" were placed in a four-necked glass flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser, and the temperature was raised to 60°C. Then, 75 parts by mass of epoxy resin (r4) were added and the mixture was stirred at the same temperature for 1 hour until homogenized. After that, the mixture was cooled to below 50°C, the stirring speed was increased to 3,000 rpm, and then 471 parts by mass of ion-exchanged water were added over 3 hours to obtain a water-dispersible epoxy resin composition (R4) with a non-volatile content of 55% by mass, a B-type viscosity of 250 mPa·s, and a d50 particle size of 1.30 μm.

[0075] The property values ​​in the above examples and comparative examples were measured as follows. [Non-volatile content]

[0076] 1.0000g of the sample was accurately weighed into an aluminum petri dish, spread into a thin film, and stored at 150°C for 1 hour. The weight was then calculated from the residual weight before and after processing. [Epoxy equivalent]

[0077] The measurement was performed by perchloric acid-acetic acid titration. [viscosity]

[0078] Measurements were taken using GB / T 11175-2002. [Particle size]

[0079] The 50% cumulative particle size was recorded as d50 using MicroTracBEL's "UPA-150" scanner.

[0080] The water-dispersible epoxy resin compositions (1) to (7) and (R1) to (R4) obtained in the above examples and comparative examples were used for the following evaluations. [Method for evaluating the storage stability of water-dispersible epoxy resin compositions]

[0081] Approximately 90 g of each water-dispersible epoxy resin composition obtained in the examples and comparative examples was weighed into a 100 ml glass bottle, stored at room temperature (25°C), and the appearance was observed visually after a predetermined period of time. The composition was then evaluated according to the following evaluation criteria. A: No separation or sedimentation B: Separation in the upper layer C: Clearly separated, sedimentation

[0082] Table 1 shows the property values ​​and evaluation results of the water-dispersible epoxy resin compositions (1) to (7) and (R1) to (R4) prepared in the examples and comparative examples.

[0083] [Table 1] [Coating film evaluation]

[0084] Paints (1) to (7) and (R1) to (R4) were prepared according to the mixing ratios listed in Tables 2 and 3. A paint film with a dry thickness of approximately 60 μm was created by spray coating on a chilled rolled steel sheet (TP Giken's "SPCC-SB", degreased with xylene on the surface and then wet-sanded with #240 grit sandpaper). After curing at 25°C for one week, various tests were conducted under the following conditions. [Method for measuring impact strength]

[0085] Impact strength was measured according to the GB / T 1732-1993 standard. [Method for measuring adhesion]

[0086] The degree of adhesion was measured according to the method compliant with GB / T 9286-1998. [Method for measuring pencil hardness]

[0087] Pencil hardness was measured according to the method compliant with GB / T 6739-2006. [Method for evaluating water resistance]

[0088] Water resistance was evaluated by checking for changes in paint film color and the presence or absence of bubbles or rust, according to the GB / T 1733-1993 method. Good water resistance is indicated by the absence of color changes, bubbles, or rust. [Evaluation method for resistance to salt spray]

[0089] Salt spray resistance was measured by checking and measuring the presence or absence of bubbles on the coating surface and the width of peeling from cut areas after 1000 hours of testing, in accordance with ASTM B117. The absence of bubbles and the smaller the peeling width indicate better corrosion resistance.

[0090] Tables 2 and 3 show the compositions of the paints (1) to (7) and (R1) to (R4) prepared in the examples and comparative examples.

[0091] [Table 2]

[0092] [Table 3]

[0093] The manufacturers listed in Tables 2 and 3 are as follows: "D 755W": TEGO DISPERSE 755W, a dispersant manufactured by EVONIK. "BYK-346": Wet agent manufactured by BYK Corporation "BYK-024": Defoaming agent manufactured by BYK Corporation. "DPnB": Dipropylene glycol butyl ether manufactured by DOW CHEMICAL. "BYK-425": Thickening agent manufactured by BYK Corporation "HALOX FLASH-X-150": Anti-corrosion treatment manufactured by ICL Phosphate Specialty. Iron oxide: "R-516L" manufactured by Titanium Industry Co., Ltd. "HALOX SPZ-391": Anti-corrosion pigment manufactured by ICL Phosphate Specialty. Precipitating Barium Sulfate: Filler manufactured by Sakai Chemical Co., Ltd.

[0094] Table 4 shows the evaluations of the paints (1) to (7) and (R1) to (R4) prepared in the examples and comparative examples.

[0095] [Table 4]

[0096] Examples 1 to 7 shown in Table 1 are examples of the water-dispersible epoxy resin compositions of the present invention. These water-dispersible epoxy resin compositions were confirmed to have excellent storage stability. Furthermore, the cured coating films (Examples 8 to 14) of paints using these water-dispersible epoxy resin compositions were confirmed to have excellent corrosion resistance.

[0097] On the other hand, Comparative Example 1 shown in Table 1 is an example of a water-dispersible epoxy resin composition in which [(a2-1) / (a1+a2)] as defined in the present invention is outside the range of 3 to 10 (2.6). In addition to the significantly insufficient storage stability of this water-dispersible epoxy resin composition, it was confirmed that the cured coating film of a paint using this water-dispersible epoxy resin composition (Comparative Example 5) also had significantly insufficient corrosion resistance.

[0098] Comparative Example 2, shown in Table 1, is an example of a water-dispersible epoxy resin composition in which [(a2-1) / (a1+a2)] as defined in the present invention is outside the range of 3 to 10 (13.7). Although this water-dispersible epoxy resin composition has excellent storage stability, it was confirmed that the cured coating film of a paint using this water-dispersible epoxy resin composition (Comparative Example 6) had significantly insufficient corrosion resistance.

[0099] Comparative Examples 3 and 4 shown in Table 1 are examples of water-dispersible epoxy resin compositions that do not use polyvalent active hydrogen compounds (a2-2). In addition to the significantly insufficient storage stability of these water-dispersible epoxy resin compositions, it was confirmed that the cured coating films of paints using these water-dispersible epoxy resin compositions (Comparative Examples 7 and 8) also exhibited significantly insufficient corrosion resistance.

Claims

1. A compound (a1) having at least two epoxy groups in one molecule, and An epoxy resin (A) having a compound (a2) having at least two carboxyl groups in one molecule as an essential raw material, A water-dispersible epoxy resin composition containing an aqueous medium (B), The compound (a2) requires a polyvalent active hydrogen compound (a2-1) having repeating alkylene units, a polyvalent active hydrogen compound (a2-2) having an alicyclic skeleton other than the polyvalent active hydrogen compound (a2-1), and an acid anhydride (a2-3) as essential raw materials. A water-dispersible epoxy resin composition characterized in that the content of the polyvalent active hydrogen compound (a2-1) is in the range of 3 to 10% by mass of the total mass of compound (a1) and compound (a2).

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

3. The water-dispersible epoxy resin composition according to claim 1, wherein the mass ratio of the polyvalent active hydrogen compound (a2-1) to the polyvalent active hydrogen compound (a2-2) [(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 polyvalent active hydrogen compound (a2-1) is one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

5. The water-dispersible epoxy resin composition according to claim 1, wherein the polyvalent active hydrogen compound (a2-2) is cyclohexanedimethanol and / or hydrogenated bisphenol A.

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

7. A paint characterized by containing the water-dispersible epoxy resin composition according to any one of claims 1 to 6.

8. An article characterized by having a cured coating film of the paint described in claim 7.

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