JP5481077B2 - Two-component water-based paint composition - Google Patents

Description

  The present invention relates to a two-pack type aqueous coating composition.

  Conventionally, a two-component aqueous coating composition containing a self-emulsifying epoxy resin as a main agent and a polyamine resin as a curing agent is known. For example, Patent Document 1 discloses a coating composition containing a self-emulsifying epoxy resin, a polyamine curing agent, and a hydrocarbon resin. According to such a coating composition, although certain anticorrosion properties and adhesion to the substrate can be obtained, further improvement in anticorrosion properties and adhesion to the substrate is required.

  In response to such demands, a two-component aqueous coating composition containing a self-emulsifying epoxy resin, a polyamine resin, and an acrylic silicon resin emulsion has been proposed (Patent Document 2). According to such a coating composition, high rust prevention and adhesion can be obtained, but there is a problem that the cost increases because the acrylic silicon resin emulsion is used. In addition, when the coating composition is formed after the coating composition has been stored for a long period of time, the adhesion may be reduced. This is because in an acrylic silicon resin emulsion prepared by a polymerization reaction using a monomer having an alkoxysilyl group, it is considered that a crosslinking reaction proceeds even after the polymerization reaction.

JP-A-5-202318 Japanese Patent No. 3274401

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a two-pack type aqueous coating composition that achieves both excellent anticorrosion and adhesion.

The two-component aqueous coating composition of the present invention is a two-component aqueous coating composition containing a main agent and a curing agent, the main agent comprising an emulsified epoxy resin (a) and a glass transition temperature of −40 to −. An acrylic emulsion resin (b) at 5 ° C., and the curing agent contains a polyamine resin (c).
In a preferred embodiment, the acrylic emulsion resin (b) is an emulsion resin obtained by emulsion polymerization of a monomer mixed solution containing a crosslinkable monomer having two or more unsaturated groups in one molecule.
In a preferred embodiment, the monomer mixture further contains a chain transfer agent.
In preferable embodiment, content of the said crosslinkable monomer in the said monomer liquid mixture is 1-6 mass%, and solid content mass ratio of the said crosslinkable monomer and the said chain transfer agent is 2 / 1-30 /. 1 (crosslinkable monomer / chain transfer agent).
In preferable embodiment, the compounding quantity of the said acrylic emulsion resin (b) is 5-30 mass% (solid content ratio) with respect to the said emulsification epoxy resin (a).

  According to the present invention, it is possible to provide a two-pack type aqueous coating composition that achieves both excellent corrosion resistance and adhesion.

A. Outline of two-component aqueous coating composition The two-component aqueous coating composition of the present invention is a two-component aqueous coating composition containing a main agent and a curing agent, and the main agent comprises an emulsified epoxy resin (a) and And acrylic emulsion resin (b) having a glass transition temperature of −40 to −5 ° C., and the curing agent contains polyamine resin (c). The two-component aqueous coating composition of the present invention may further contain other components such as pigments and additives as necessary. Conventionally, in a coating composition having an epoxy resin as a main agent and a polyamine resin as a curing agent, there is a problem that water resistance decreases when an acrylic resin is added to the main agent. Little consideration has been given. On the other hand, the present inventors have found that by using an epoxy resin and an acrylic resin having a predetermined glass transition temperature in combination, the coating film can be provided with excellent adhesion and anticorrosive properties, and the present invention. It came to complete. One of the excellent effects of the present invention is that an epoxy resin and an acrylic resin, which cannot achieve both anticorrosion and adhesion, are used in combination, and the coating film has excellent anticorrosion and adhesion. One.

  The solid content concentration of the two-component aqueous coating composition is preferably 30 to 80% by mass, more preferably 40 to 70% by mass. With such a solid content concentration, a two-component water-based coating composition excellent in coating workability can be obtained. The solid content concentration can be adjusted by adding water or the like.

  The solid content of the emulsified epoxy resin (a) in the two-component aqueous coating composition is preferably 10 to 80% by mass, more preferably 15 to the total solid content of the two-component aqueous coating composition. 75% by mass.

  The content of the acrylic emulsion resin (b) in the two-component aqueous coating composition is preferably 5 to 30% by mass (solid content ratio), more preferably 5 to 20% by mass with respect to the emulsified epoxy resin (a). %. Here, if the amount is less than 5% by mass, the adhesiveness may be inferior because the stress relaxation ability decreases when the coating film is formed, and if it exceeds 30% by mass, the amount of the epoxy resin in the coating composition In some cases, the anticorrosion property may be reduced due to the decrease in the amount of the corrosion resistance.

  The content of the polyamine resin (c) in the two-component aqueous coating composition is preferably 0.7 to 1.5 equivalents, more preferably 1 to 1 equivalent of an epoxy group whose active hydrogen is contained in the main agent. It is a value which becomes 0.9-1.1 equivalent. If it is less than 0.7 equivalent, the cured coating may be insufficiently dried, and if it exceeds 1.5 equivalent, the hygroscopicity may be increased and the anticorrosion property may be lowered.

  When the two-component water-based paint composition contains the other constituents, the content thereof can be appropriately set within a range where the effects of the present invention can be obtained. The content of the two-component aqueous coating composition may be, for example, 5 to 60% by mass.

A-1. Emulsified epoxy resin (a)
In the present invention, any appropriate emulsified epoxy resin (a) is used. The emulsified epoxy resin (a) may be self-emulsified or forcedly emulsified. The emulsified epoxy resin (a) may be produced from a liquid raw material or may be produced from a solid raw material. Since the safety to the human body is higher, the emulsified epoxy resin (a) is preferably produced from a solid raw material.

  The epoxy equivalent of the emulsified epoxy resin (a) can be appropriately determined according to the desired film properties. The upper limit of the epoxy equivalent is preferably 2700 g / equivalent or less, more preferably 2500 g / equivalent or less. The lower limit of the epoxy equivalent of the emulsified epoxy resin (a) is preferably 220 g / equivalent or more, more preferably 300 g / equivalent or more when manufactured from a liquid raw material, and is manufactured from a solid raw material. Is preferably 450 g / equivalent or more. If it is such an epoxy equivalent, the coating film excellent in corrosion resistance and adhesiveness can be obtained.

  The number average molecular weight of the emulsified epoxy resin (a) can be appropriately determined according to the desired film properties. The number average molecular weight is preferably 450 to 3000, more preferably 900 to 2800. If it is such a number average molecular weight, the coating film excellent in corrosion resistance and adhesiveness can be obtained. The number average molecular weight can be measured by gel permeation chromatography and can be displayed as a converted value using a styrene standard.

  As the self-emulsifying type emulsified epoxy resin (a), for example, any appropriate epoxy resin, preferably a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a modified product thereof, a hydrophilic part is added by a conventional method. What has been introduced. Examples of the hydrophilic portion include a side chain having a hydroxyl group or a carboxyl group, a nonionic polyalkylene oxide skeleton, and the like.

  As the forced emulsification type epoxy resin (a), for example, any suitable epoxy resin, preferably a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a modified product thereof in water together with any suitable emulsifier is used. What was stirred and emulsified is mentioned.

  The solid content concentration of the emulsified epoxy resin (a) is preferably 40 to 60% by weight, more preferably 42 to 58% by weight.

A-2. Acrylic emulsion resin (b)
In the present invention, an acrylic emulsion resin (b) having a glass transition temperature of −40 to −5 ° C. is used. The glass transition temperature is preferably −38 to −8 ° C., more preferably −35 to −10 ° C. By using the acrylic emulsion resin (b) having such a glass transition temperature, the adhesion of the coating film can be improved. This is considered because the acrylic emulsion resin (b) can relieve the stress of the coating film. Here, when the temperature is lower than −40 ° C., the coating film becomes too soft, and thus the anticorrosion property may be deteriorated. When the temperature exceeds −5 ° C., the stress relaxation ability is decreased and the adhesion may be deteriorated. In addition, the said glass transition temperature (Tg) is calculated | required by the formula of FOX from Tg of the homopolymer obtained from each monomer based on the structure ratio of each monomer which comprises acrylic emulsion resin (b).

  The acrylic emulsion resin (b) can be obtained by emulsion polymerization of a monomer mixed solution containing any appropriate monomer. The monomer mixture preferably contains a crosslinkable monomer having two or more unsaturated groups in one molecule. By using the crosslinkable monomer, a cross-linked structure is formed inside the acrylic emulsion resin (b), and the shielding property is increased, which can contribute to the improvement of the corrosion resistance of the coating film. The monomer mixture further preferably contains a chain transfer agent in addition to the crosslinkable monomer. By using a chain transfer agent, the molecular weight of the acrylic emulsion resin (b) can be adjusted and flexibility can be imparted to the coating film, which can contribute to improving the stress relaxation ability of the coating film. An acrylic emulsion resin (b) having higher shielding properties and stress relaxation ability can be obtained by using a crosslinkable monomer that contributes to polymerization of the resin and a chain transfer agent that contributes to lowering the molecular weight of the resin. Can be.

  Specific examples of the crosslinkable monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinylbenzene, Examples include vinyl benzene and diallyl phthalate. Of these, ethylene glycol di (meth) acrylate is preferred.

  Specific examples of the chain transfer agent include alkyl mercaptans such as lauryl mercaptan, n-butyl mercaptan, t-butyl mercaptan, octyl mercaptan; thioglycolate-2-ethylhexyl, 2-methyl-5-t- Examples thereof include butylthiophenol, carbon tetrabromide, and α-methylstyrene dimer. Of these, lauryl mercaptan is preferred.

  The solid content mass ratio between the crosslinkable monomer and the chain transfer agent contained in the monomer mixture is preferably 2/1 to 30/1 (crosslinkable monomer / chain transfer agent). When the crosslinkable monomer is less than 2/1, the anticorrosion property may be lowered due to the reduction of the shielding effect, and when the crosslinkable monomer is more than 30/1, the flexibility may be lacking and the stress relaxation ability may be lowered. The content of the crosslinkable monomer in the monomer mixture is preferably 1 to 6% by mass, more preferably 2 to 5% by mass. If it is out of the above range, the stability of the resulting emulsion resin may be insufficient. The content of the chain transfer agent in the monomer mixture is preferably 0.1 to 3% by mass. If it is less than 0.1% by mass, the stress relaxation ability in the case of a coating film is lowered, and the adhesion may be inferior. If it exceeds 3% by mass, the molecular weight is too small, so that the shielding effect is lowered and the corrosion resistance is lowered. May occur.

  Specific examples of other monomers contained in the monomer mixture include acrylic acid, methacrylic acid, acrylic acid dimer, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, 2 -Acryloyloxyethyl acid phosphate, 2-acrylamido-2-methylpropanesulfonic acid, ω-carboxy-polycaprolactone mono (meth) acrylate, isocrotonic acid, α-hydro-ω-[(1-oxo-2-propenyl) (Oxy) poly [oxy (1-oxo-1,6-hexanediyl)], carboxylic acid group-containing unsaturated monomers such as maleic acid, fumaric acid, itaconic acid, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid; ) Hydroxyethyl acrylate, hydroxy (meth) acrylate Hydroxyl-containing unsaturated monomers such as pills and hydroxybutyl (meth) acrylate; epoxy group-containing unsaturated monomers such as glycidyl (meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl ( Amide group-containing unsaturated monomers such as (meth) acrylamide, N, N-dibutyl (meth) acrylamide, diacetone (meth) acrylamide, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide; Amino group-containing unsaturated monomers such as dimethylaminopropyl (meth) acrylate and dimethylaminoethyl (meth) acrylate; Carbonyl group-containing unsaturated monomers such as acetoacetoxyethyl (meth) acrylate; Methyl (meth) acrylate, ) Acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate and other (meth) acrylic acid alkyl esters; styrene, methylstyrene And nitriles such as (meth) acrylonitrile. Two or more kinds of the other monomers may be used.

  The monomer mixture preferably contains the carboxylic acid group-containing unsaturated monomer as the other monomer. The acid value of the monomer mixture is preferably 5 to 50 mgKOH / g, more preferably 10 to 40 mgKOH / g. By using such a monomer mixed solution, an acrylic emulsion resin (b) having excellent stability can be obtained. In addition, the obtained acrylic emulsion resin (b) can be neutralized to a desired neutralization rate as needed.

  The monomer mixed solution contains a (meth) acrylic monomer. In one embodiment, a part or all of the other monomer may be a (meth) acrylic monomer. In another embodiment, a part or all of the crosslinkable monomer may be a (meth) acrylic monomer. In still another embodiment, both the other monomer and the crosslinkable monomer may contain a (meth) acrylic monomer as a part or all of them. The content of the (meth) acrylic monomer is preferably 70 mol% or more, more preferably 80 mol% or more with respect to 100 mol% of all monomers in the monomer mixture.

  Examples of the emulsion polymerization method include persulfates such as ammonium persulfate and potassium persulfate; peroxides such as t-butyl hydroperoxide and hydrogen peroxide; reducing agents (for example, sodium bisulfite, sodium sulfite, ascorbic acid, Rongalite) ) And an oxidizing agent (for example, the above peroxide); a polymerization initiator such as an azo compound such as 4,4′-azobis-4-cyanovaleric acid is added to the above monomer mixture solution. 0.1-3 mass%, and a method well known by those skilled in the art can be used.

  The mass average molecular weight of the acrylic emulsion resin (b) can be appropriately determined according to the desired film properties. For example, the molecular weight between crosslinking points (mass average molecular weight) of the acrylic emulsion resin (b) obtained from the monomer mixture containing a crosslinkable monomer and a chain transfer agent is preferably 10,000 to 250,000, more preferably 20,000 to 200,000. is there. The acrylic emulsion resin having such a molecular weight between crosslinking points can have excellent shielding properties and stress relaxation ability.

  The solid content concentration of the acrylic emulsion resin (b) is preferably 40 to 60% by weight.

  The volume average particle diameter of the acrylic emulsion resin (b) is not particularly limited, and is, for example, 10 to 500 nm. The volume average particle diameter can be determined by a method well known by those skilled in the art, such as a laser light scattering method.

A-3. Polyamine resin (c)
In the present invention, any appropriate polyamine resin (c) is used. Examples thereof include aliphatic polyamines, aromatic polyamines, alicyclic polyamines, polyamide amines, and epoxy adduct amines.

  The active hydrogen equivalent of the polyamine resin (c) can be appropriately determined according to the desired film properties. The active hydrogen equivalent is preferably 60 to 250 g / equivalent, more preferably 80 to 150 g / equivalent in terms of solid content. If it is out of the above range, the pot life may be shortened, or dilution with water may be difficult.

  The solid content concentration of the polyamine resin (c) is preferably 30 to 70% by weight, more preferably 35 to 65% by weight.

  The polyamine resin (c) may be water-soluble or water-dispersible (emulsion). Preferably it is water-soluble. This is because, when mixed with the main agent, a coating film having a more uniform cross-linked structure can be formed.

  The water-soluble or water-dispersible polyamine resin (c) can be obtained by subjecting the polyamine resin to any appropriate modification. Examples of the modification include neutralizing a part or all of the amino group with an acid, acetylating a part of the amino group, and the like. The acid type and neutralization rate (neutralization rate with respect to the amine group of the polyamine resin before modification) can be any suitable acid depending on the desired state of the polyamine resin (c) (water-soluble to aqueous dispersion). Types and neutralization rates may be employed. Examples of the acid include acetic acid, formic acid, lactic acid, and phosphoric acid. The neutralization rate (neutralization rate with respect to the amine group of the polyamine resin before modification) is preferably 10 to 70%, and more preferably 15 to 50%.

A-4. Other components As described above, the two-component aqueous coating composition of the present invention may contain further components such as pigments and additives. Examples of the pigment include titanium oxide, yellow iron oxide, red iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, azo red, quinacridone red, benzimidazolone yellow and the like; calcium carbonate, barium sulfate, kaolin, clay, Examples include extender pigments such as talc. Examples of the additive include a dispersant, an antifoaming agent, a rust inhibitor, a film forming aid, a viscosity modifier, a curing catalyst, a surface modifier, a plasticizer, an ultraviolet absorber, and an antioxidant.

B. Method for Using Two-Component Water-Based Paint Composition The two-component water-based paint composition of the present invention is usually provided in a form in which the above components are dispersed in water or a mixed solution of water and a hydrophilic solvent. When using a two-pack type aqueous coating composition, it is preferable to mix the main agent and the curing agent immediately before coating. The pigment and additive may be added in advance to the main agent and / or curing agent, or may be added when the main agent and curing agent are mixed.

  The two-component water-based coating composition of the present invention is used for coating on any appropriate article to be coated. In a preferred embodiment, the article to be coated is typically a metal surface, preferably iron, steel, aluminum, stainless steel, and the surface of a plated steel sheet such as galvanized or aluminum plated. In another embodiment, the article to be coated can be a coating film formed on a metal surface. That is, the two-component aqueous coating composition of the present invention can be used for repainting a metal surface.

Any appropriate method can be adopted as the coating method. For example, brush coating, air spraying, airless spraying, and roller coating may be mentioned. In general, the coating amount is preferably 10 to 300 g / m ² .

  Any appropriate method can be adopted as the drying method. Natural drying or heat drying is preferred. In the case of natural drying, the drying time is preferably 24 hours or longer, more preferably 1 week or longer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. Unless otherwise specified, parts and% in the examples are based on mass.

[Reference Example 1] Production 1 of acrylic emulsion resin (b)
Separable flask equipped with dropping funnel, thermometer, nitrogen inlet tube, reflux condenser and stirrer, 34.5 parts of ion-exchanged water, trade name “Perex SS-H” (manufactured by Kao Corporation, sodium alkyldiphenyl ether disulfonate) 0.3 parts was charged and heated to 80 ° C. under a nitrogen atmosphere. Next, 14 parts of styrene, 58 parts of 2-ethylhexyl acrylate, 22 parts of methyl methacrylate, 4 parts of ethylene glycol dimethacrylate, and 2 parts of methacrylic acid are contained as monomers, and 0.5 part of lauryl mercaptan is contained as a chain transfer agent. A monomer mixture was prepared. The acid value of the obtained monomer mixed solution was 13 mgKOH / g. The monomer mixture was added to an emulsifier aqueous solution in which 1.2 parts of Plex SS-H was dissolved in 50 parts of ion-exchanged water and emulsified using a mixer to prepare a pre-emulsion.

  The pre-emulsion thus obtained and an aqueous initiator solution in which 0.3 part of ammonium persulfate was dissolved in 13 parts of ion-exchanged water were simultaneously added dropwise to the separable flask from a separate dropping funnel. The former started to drip evenly over 120 minutes and the latter over 150 minutes. After completion of the dropwise addition, the reaction was continued for an additional 120 minutes at the same temperature. After cooling, the solution was neutralized with aqueous ammonia corresponding to 10 mol% of the methacrylic acid used. The neutralized product was filtered through a 200 mesh wire mesh to obtain an acrylic emulsion resin b1. When calculation was performed on the assumption that the monomer constituting the acrylic emulsion resin b1 corresponds to the monomer composition of the monomer mixture, the Tg of the acrylic emulsion resin b1 was -21 ° C. In calculating Tg, Tg of ethylene glycol dimethacrylate homopolymer was set to the same temperature as Tg of methyl methacrylate homopolymer.

[Reference Examples 2 to 8] Production of acrylic emulsion resin (b) 2 to 8
Acrylic emulsion resins b2 to b8 were obtained in the same manner as in Reference Example 1 except that the monomer mixture prepared so as to have the composition shown in Table 1 was used.

[Reference Example 9] Preparation of pigment paste
Product name “DISPERBYK-190” (Bic Chemie, Dispersant) 1.85 parts, Product name “BYK-019” (Bic Chemie, Antifoam) 0.3 parts, Titanium oxide 13.7 parts, Calcium carbonate 5.2 parts, 20.5 parts of talc, trade name “LF Bowsey PM-303W” (manufactured by Kikuchi Color Co., Ltd., rust inhibitor) 1.5 parts, and 11.5 parts of tap water are mixed, By using and dispersing, a pigment paste was obtained.

[Example 1]
54.55 parts of pigment paste obtained in Reference Example 9, trade name “ADEKA RESIN EM-101-50” (manufactured by ADEKA, emulsified epoxy resin, epoxy equivalent 500 g / equivalent, solid content 47%) 36 parts, trade name “CS -12 "(manufactured by Chisso, film-forming aid) 2.5 parts, trade name" Colomin W "(produced by Kao Corporation, rust inhibitor) 0.4 part, trade name" SN deformer 1315 "(manufactured by San Nopco, Antifoaming agent) 0.2 parts, trade name “Primal RM-12W” (Rohm and Haas, viscosity modifier) 0.25 parts, tap water 1.4 parts, and acrylic emulsion produced in Reference Example 1 The base resin was obtained by mixing 3.4 parts of the resin b1. In addition, trade name “Sunmide WH-910” (manufactured by Air Products and Chemicals, water-soluble polyamine resin, active hydrogen equivalent 135 g / equivalent (solid content, solid content 60%) 7.77 parts and tap water 9. 88 parts were mixed to obtain a curing agent, and the main agent and the curing agent were mixed to obtain an aqueous coating composition 1. Using the obtained aqueous coating composition 1, adhesiveness described later was obtained. Evaluation and corrosion resistance evaluation were performed, and the results are shown in Table 2.

[Example 2]
An aqueous coating composition 2 was obtained in the same manner as in Example 1 except that the acrylic emulsion resin b2 was used instead of the acrylic emulsion resin b1. The obtained aqueous coating composition 2 was used for evaluation of adhesion and anticorrosion described later. The results are shown in Table 2.

[Example 3]
An aqueous coating composition 3 was obtained in the same manner as in Example 1 except that the acrylic emulsion resin b3 was used instead of the acrylic emulsion resin b1. The obtained aqueous coating composition 3 was used for evaluation of adhesion and anticorrosion described later. The results are shown in Table 2.

[Example 4]
Example 1 except that the acrylic emulsion resin b4 was used instead of the acrylic emulsion resin b1 and that 36.6 parts of “Adeka Resin EM-101-50” and 2.4 parts of the acrylic emulsion resin b4 were mixed. Thus, an aqueous coating composition 4 was obtained. The obtained aqueous coating composition 4 was used for evaluation of adhesion and anticorrosion described later. The results are shown in Table 2.

[Example 5]
Example 1 except that acrylic emulsion resin b5 was used instead of acrylic emulsion resin b1 and that 34 parts of “ADEKA RESIN EM-101-50” and 4.8 parts of acrylic emulsion resin b5 were mixed. An aqueous coating composition 5 was obtained. The obtained water-based coating composition 5 was used for the below-described adhesion evaluation and anticorrosion evaluation. The results are shown in Table 2.

[Example 6]
An aqueous coating composition 6 was obtained in the same manner as in Example 5 except that the acrylic emulsion resin b6 was used instead of the acrylic emulsion resin b5. The obtained water-based coating composition 6 was used for the following adhesion evaluation and anticorrosion evaluation. The results are shown in Table 2.

[Example 7]
An aqueous coating composition 7 was obtained in the same manner as in Example 1 except that 32.6 parts of “ADEKA RESIN EM-101-50” and 6.2 parts of acrylic emulsion resin b1 were mixed. The obtained aqueous coating composition 7 was used for evaluation of adhesion and anticorrosion described later. The results are shown in Table 2.

[Comparative Example 1]
An aqueous coating composition C1 was obtained in the same manner as in Example 1 except that the acrylic emulsion resin b7 was used instead of the acrylic emulsion resin b1. Adhesion evaluation and anticorrosion evaluation described later were performed using the obtained water-based coating composition C1. The results are shown in Table 2.

[Comparative Example 2]
An aqueous coating composition C2 was obtained in the same manner as in Example 1 except that the acrylic emulsion resin b8 was used instead of the acrylic emulsion resin b1. Adhesion evaluation and anticorrosion evaluation described later were performed using the obtained water-based coating composition C2. The results are shown in Table 2.

[Adhesion evaluation]
Test method:
A test piece was obtained by applying the aqueous coating composition to a Migaki steel plate with a brush at 200 g / m ² and drying at 20 ° C. for 7 days. The test piece was placed in a moisture-resistant (rotary) wet box as defined in JIS K 5600 7-2 and taken out after 4 days. Next, a cut was made on the grid 15 minutes after removing moisture on the surface of the coating film. After applying a cellophane tape to the surface, it was quickly peeled off, and adhesion was evaluated according to the following evaluation method.

Evaluation method:
It evaluated as follows by the ratio of the area where the coating film peeled with respect to the surface of a test piece.
◎: Less than 5% ○: 5% or more and less than 26% △: 26% or more and less than 51% ×: 51% or more

[Anti-corrosion evaluation]
Test method:
A test piece was obtained by applying the aqueous coating composition with a brush to a sandblast plate at 200 g / m ² and drying at 20 ° C. for 7 days. A cycle corrosion test defined in JIS K 5600 7-7 was performed on the test piece, and the state of the coating film after 400 cycles was confirmed.

Evaluation method:
Evaluation was performed as follows according to the ratio of the rust area generated in the coating film to the surface of the test piece.
◎: Less than 0.05% ○: 0.05% or more and less than 0.1% △: 0.1% or more and less than 0.3% ×: 0.3% or more

  As shown in Table 2, the two-component aqueous coating composition of the present invention comprises an emulsified epoxy resin (a), an acrylic emulsion resin (b) having a glass transition temperature of −40 to −5 ° C., and a polyamine resin (c). ), It is possible to achieve both excellent adhesion and corrosion resistance (see, for example, Example 3). Moreover, it turns out that anticorrosion property can further be improved when acrylic emulsion resin (b) prepared from the monomer liquid mixture containing a crosslinkable monomer is used. Moreover, when the acrylic emulsion resin (b) adjusted from the monomer liquid mixture containing a crosslinkable monomer and a chain transfer agent is used, it turns out that outstanding adhesiveness and anticorrosion property can be made compatible at a high level.

  The two-component water-based paint composition of the present invention is used for rust prevention, sealers, primers, etc. for large steel structures such as ships and bridges, steel materials such as steel frames, handrails, iron doors and gates, building exteriors, floors and building materials. It can be suitably used.

Claims (5)

A two-component aqueous coating composition containing a main agent and a curing agent,
The main agent includes an emulsified epoxy resin (a) and an acrylic emulsion resin (b) having a glass transition temperature of −38 to −8 ° C. ,
A two-component aqueous coating composition, wherein the curing agent comprises a polyamine resin (c).   The two-component liquid according to claim 1, wherein the acrylic emulsion resin (b) is an emulsion resin obtained by emulsion polymerization of a monomer mixture containing a crosslinkable monomer having two or more unsaturated groups in one molecule. Type water-based paint composition.   The two-component water-based coating composition according to claim 2, wherein the monomer mixture further contains a chain transfer agent.   The content of the crosslinkable monomer in the monomer mixture is 1 to 6% by mass, and the solid content mass ratio of the crosslinkable monomer and the chain transfer agent is 2/1 to 30/1 (crosslinkable monomer / The two-component aqueous coating composition according to claim 3, which is a chain transfer agent). The two-component type according to any one of claims 1 to 4, wherein a blending amount of the acrylic emulsion resin (b) is 5 to 30% by mass (solid content ratio) with respect to the emulsified epoxy resin (a). Water-based paint composition.