JP6854104B2 - Multi-layer coating film forming method - Google Patents

Description

The present invention relates to a method for forming a multi-layer coating film.

In large structures such as ships, bridges, buildings, tanks, and plants, an anticorrosion base layer or the like is formed on the surface of the object to be coated in order to maintain anticorrosion properties for a long period of time in a severe corrosive environment. Further, an undercoat coating film is generally formed on the surface of the anticorrosion base layer opposite to the object to be coated, and an epoxy resin coating composition or the like is used for the undercoat coating film. Further, in order to ensure antifouling property and aesthetic appearance, the same type or different type of topcoat coating film is formed on the undercoat coating film.

For example, when an undercoat coating film is formed from an epoxy resin coating composition and the same or different coating compositions are overcoated on the undercoat coating film, it is necessary to overcoat within a short period of time after the undercoat coating film composition is applied. was there. In the present specification, such an allowable fixed period between paintings is also referred to as an interval.

For example, Japanese Patent Application Laid-Open No. 11-315250 (Patent Document 1) describes an amine compound curing agent and a dimer acid derivative having a specific structure as an epoxy resin coating material that does not cause a problem even if a top coating is applied with a long interval. Epoxy coating compositions containing and are disclosed.

Further, Japanese Patent Application Laid-Open No. 11-333374 (Patent Document 2) discloses a coating method for the exterior of a ship in which, for example, a vinyl chloride resin is blended with an epoxy resin heavy-duty anticorrosion paint in order to lengthen the interval.

Further, when a topcoat coating film is formed on the surface of such an undercoat coating film, the adhesiveness between the layers may be lowered.
For example, Japanese Patent Application Laid-Open No. 2009-197106 (Patent Document 3) attempts to improve the adhesion between the undercoat coating and the topcoat, and (a) a bisphenol type epoxy resin and (b) ethylene / vinyl acetate. An epoxy resin coating composition containing a copolymer and (c) an amine-based curing agent is disclosed.

Japanese Unexamined Patent Publication No. 11-315250 Japanese Unexamined Patent Publication No. 11-333374 JP-A-2009-197106

The coating composition disclosed in Patent Document 1 Patent Document 2 and Patent Document 3 described above is a coating composition using an organic solvent.
On the other hand, in recent years, there has been a strong demand for conversion from organic solvent-based paints to water-based paints from the viewpoint of reducing environmental load and reducing flammability during work.

Therefore, the present invention is a method for forming a multi-layer coating film which can lengthen the interval, has excellent adhesion between the first coating film and the second coating film, and has excellent corrosion resistance, and is an aqueous coating composition. It is an object of the present invention to provide a method for forming a multi-layer coating film using the above.
Specifically, the content of the adhesion improver (B) contained in the first aqueous coating composition is within the range of the present invention, or the adhesion improver (B1), the adhesion improver (B2) and a mixture thereof. When the content of at least one adhesion improver selected from the above is within the range of the present invention, it is formed from the second aqueous coating composition on the coating film formed from the first aqueous coating composition. Even if a long interval occurs before the coating film is applied, a multi-layer coating film having sufficient adhesion between layers can be obtained.
Moreover, when the coating film is formed from the second aqueous coating composition immediately after the formation of the first coating film, and after a long interval, for example, 7 days, the coating film is applied from the second aqueous coating composition on the first coating film. In both cases of forming the above, high adhesion between layers can be maintained.
Further, since sufficient adhesion is provided between the coating film formed from the first water-based coating composition and the coating film formed from the second water-based coating composition, it is formed from the second water-based coating composition. It is possible to reduce or suppress the crack resistance and peeling resistance of the coating film.
As described above, according to the coating film forming method of the present invention, the interval can be lengthened, and the degree of freedom in coating work is increased in repairing large structures and the like, and in newly installed anticorrosion coating, for example, complicated processes and construction. Since management is not required and the interlayer adhesion between the first coating film and the second coating film can be maintained for a long period of time, it is particularly useful for large structures in which repainting and repair cannot be easily performed.

In order to solve the above problems, the present invention provides the following aspects.
[1] A step (1) of coating a first aqueous coating composition on an object to be coated to form a first coating film.
A method for forming a multi-layer coating film, which comprises a step (2) of coating a second aqueous coating composition on the first coating film obtained in the step (1) to form a second coating film.
The first aqueous coating composition contains a bisphenol type aqueous epoxy resin (A) and at least one adhesion improver (B).
The content of the adhesion improver (B) contained in the first aqueous coating composition is 0.1 to 20 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). ,
The method for forming a multi-layer coating film, wherein the adhesion improver (B) contains at least one selected from a water-dispersible adhesion improver, an adhesion improver that is liquid at 40 ° C., and a mixture thereof.
[2] The method for forming a multilayer coating film according to [1], wherein the bisphenol type aqueous epoxy resin (A) contains an epoxy resin (A1) having an epoxy group or an aqueous epoxy amine resin (A2).
[3] The adhesion improver (B) contains at least one adhesion improver selected from the adhesion improver (B1), the adhesion improver (B2) and a mixture thereof.
The adhesion improver (B1) contains at least one selected from benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds and benzoate-based compounds.
The method for forming a multilayer coating film according to [1] or [2], wherein the adhesion improver (B2) contains at least one selected from a hindered amine compound and a hindered phenol compound.
[4] The content of the adhesion improver (B1) in the first aqueous coating composition is 0.05 to 10 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). Yes,
The content of the adhesion improver (B2) in the first aqueous coating composition is 0.05 to 10 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). 3] The method for forming a multi-layer coating film.
[5] The method for forming a multi-layer coating film according to any one of [1] to [4], wherein the first aqueous coating composition further contains a curing agent (C).
[6] The method for forming a multilayer coating film according to [5], wherein the curing agent (C) contains a compound having at least one functional group selected from a (meth) acryloyl group, an epoxy group and an amino group. ..
[7] The first aqueous coating composition further comprises an emulsion (D) of an ethylene-vinyl acetate copolymer having an ethylene ratio of 5 to 50% by mass, according to any one of [1] to [6]. The method for forming a multi-layer coating film according to the above method.
[8] The second water-based coating composition contains a water-based resin (a), and the water-based resin (a) is selected from an epoxy resin, a urethane resin, an acrylic resin, a silicon resin, an inorganic resin, and a fluororesin. The method for forming a multi-layer coating film according to any one of [1] to [7], which comprises at least one aqueous resin.

According to the present invention, even if the coating interval for recoating the same or different coating compositions, that is, the interval is lengthened, the adhesion between the first coating film and the second coating film is excellent, and the corrosion resistance is improved. An excellent method for forming a multi-layer coating film is provided. Further, according to the present invention, since the water-based coating composition is used, the environmental load can be reduced and the risk during work can be greatly reduced.

According to the method for forming a multi-layer coating film of the present invention,
Step (1) of coating the first aqueous coating composition on the object to be coated to form the first coating film.
A method for forming a multi-layer coating film, which comprises a step (2) of coating a second aqueous coating composition on the first coating film obtained in the step (1) to form a second coating film.
The first aqueous coating composition contains a bisphenol type aqueous epoxy resin (A) and at least one adhesion improver (B).
The content of the adhesion improver (B) contained in the first aqueous coating composition is 0.1 to 20 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). ,
A method for forming a multi-layer coating film is provided, wherein the adhesion improver (B) contains at least one selected from a water-dispersible adhesion improver, an adhesion improver that is liquid at 40 ° C., and a mixture thereof. ..

<Step of forming the first coating film (1)>
The step (1) of forming the first coating film in the present invention includes coating the first aqueous coating composition on the object to be coated. The first aqueous coating composition according to the present invention contains a bisphenol type aqueous epoxy resin (A) and at least one adhesion improver (B).
Hereinafter, the components used in the present invention will be described, and then the step of forming the first coating film will be described.

<First water-based paint composition>
The first aqueous coating composition according to the present invention may be a one-component type or a two-component type. In the case of the two-component type, the first aqueous coating composition according to the present invention can consist of a first agent containing a bisphenol type aqueous epoxy resin (A) and a second agent containing a curing agent (C). .. The two-component water-based coating composition forms a cured coating film by a curing reaction between a bisphenol-type aqueous epoxy resin (A) and a curing agent (C) generated by mixing the first agent and the second agent. be able to. The first aqueous coating composition according to the present invention can be suitably used as, for example, an anticorrosive coating material (including a heavy anticorrosion coating material).
In the present invention, since the first aqueous coating composition forming the first coating film is an aqueous coating composition, for example, it can be diluted with tap water, has little odor, is environmentally friendly, and is water-based, so that it is not flammable. It has the characteristics of being excellent in safety.

<Bisphenol type water-based epoxy resin (A)>
The bisphenol type water-based epoxy resin (A) can be a vehicle resin in a one-component water-based coating composition, and in a two-component water-based coating composition, the main component contained in the first agent (main agent). Can be a vehicle resin. That is, in the present specification, the "bisphenol type aqueous epoxy resin (A)" in the two-component aqueous coating composition means a state in which the curing agent (C) is not contained.
As used herein, the term "water-soluble" means "water-soluble" or "water-dispersed". The first aqueous coating composition according to the present invention preferably contains an aqueous solution or an aqueous dispersion (including an emulsion) of a bisphenol type aqueous epoxy resin (A).

In the present invention, examples of the bisphenol type aqueous epoxy resin include those obtained by reacting a polyhydrin alcohol or a polyhydrin phenol with a halohydrin.
For example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, or epichlorohydrin and bisphenol condensed in the presence of a catalyst such as an alkali catalyst, if necessary. Any of the resins obtained by subjecting a low molecular weight epoxy resin to a bisphenol by a double addition reaction may be used.
Examples of such a bisphenol type aqueous epoxy resin include a bisphenol A type epoxy resin, a halogenated bisphenol A type epoxy resin, and a bisphenol F type epoxy resin.
Examples of bisphenol include bis (4-hydroxyphenyl) methane [bisphenol F], 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2. -Bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, p-( Examples thereof include 4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, bis (2-hydroxynaphthyl) methane, and the above-mentioned bisphenol. The class can be used as one kind or a mixture of two or more kinds.

Examples of the bisphenol type aqueous epoxy resin (A) in the present invention include an aqueous epoxy resin (A1) having an epoxy group or an aqueous epoxy amine resin (A2), as described later.
Here, for example, when an aqueous epoxy resin (A1) having an epoxy group is used, in the present specification, 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A) has substantially an epoxy group. It means 100 parts by mass of the resin solid content of the aqueous epoxy resin (A1). When an aqueous epoxy resin (A1) having a plurality of types of epoxy groups is used, the total amount of the resin solid content is used as a reference.
Further, when the aqueous epoxy resin (A1) having an epoxy group is used as the two-component aqueous coating composition, the resin solid content of the aqueous epoxy resin (A1) having an epoxy group does not contain the curing agent (C). Means the state.
The same applies to the case where the aqueous epoxy amine resin (A2) is used.

(1) Aqueous epoxy resin having an epoxy group (A1)
A specific example of the aqueous epoxy resin (A1) having an epoxy group (hereinafter, may be referred to as the aqueous epoxy resin (A1)) is an aqueous dispersion of the first epoxy resin, and more specifically, the first epoxy. It is a resin emulsion. This emulsion is an epoxy resin emulsion obtained by dispersing the first epoxy resin in an aqueous medium such as water. The emulsion of the first epoxy resin may be a forced emulsified type or a self-emulsified type.
The resin described in the present specification as "epoxy resin having an epoxy group" or the like means an epoxy resin having one or more epoxy groups (for example, glycidyl group) in the molecule.
The number of epoxy groups contained in the first epoxy resin is preferably 2 or more, and more preferably 2. The first aqueous coating composition according to the present invention may contain two or more kinds of aqueous epoxy resins (A1) having an epoxy group.

For example, when the aqueous epoxy resin (A1) having an epoxy group is an emulsion of the first epoxy resin and the first aqueous coating composition is a two-component type, it is cured with the first agent containing the aqueous epoxy resin (A1). Uniform mixing with the second agent containing the agent (C) is facilitated, and the rapid reaction progress between the aqueous epoxy resin (A1) and the curing agent (C) in the second agent is suppressed, which is appropriate. Reactivity can be obtained.
As a result, a first aqueous coating composition having a long pot life can be obtained. More specifically, when the water-based epoxy resin (A1) is water-dispersible, the first water-based coating composition before painting is after mixing the first agent and the second agent containing the water-based epoxy resin (A1). Since the aqueous epoxy resin (A1) in the first agent and the curing agent (C) in the second agent do not easily come into contact with each other, the reaction does not proceed easily and the storage stability and coatability are good.
On the other hand, after painting, the dispersion medium (for example, water) volatilizes, and the aqueous epoxy resin (A1) and the curing agent (C) in the second agent easily come into contact with each other. The curing reaction proceeds even at a temperature lower than that, and a coating film can be formed.

The first epoxy resin contained in an aqueous dispersion such as an emulsion is preferably a compound having two or more epoxy groups in the molecule, and as such, a polyhydric alcohol or a polyhydrin phenol is reacted with halohydrin. What can be obtained can be mentioned.
Specific examples of the first epoxy resin include, for example, a bisphenol A type epoxy resin, a halogenated bisphenol A type epoxy resin, and a bisphenol F type epoxy resin. Two or more kinds of epoxy resins may be used in combination as the first epoxy resin.

Among them, the adhesiveness to the coating film formed from the second water-based coating composition, the adhesiveness to the object to be coated, the anticorrosion base layer applied to the object to be coated, the corrosion resistance and the water resistance of the coating film. From the viewpoint, bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferably used as the first epoxy resin. More preferably, the first epoxy resin contains a bisphenol A type epoxy resin.
As described above, the bisphenol type aqueous epoxy resin in the present invention may include a bisphenol A type epoxy resin.

The epoxy equivalent of the first epoxy resin is preferably 150 to 1200, more preferably 150 to 1000. When the epoxy equivalent of the first epoxy resin is in the above range, the adhesiveness between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition can be enhanced. Further, it is advantageous in enhancing the adhesion to the object to be coated, the anticorrosion base layer applied to the object to be coated, the adhesiveness to the old coating film, the corrosion resistance of the coating film, and the water resistance. By adjusting the epoxy equivalent of the first epoxy resin, the characteristics of the aqueous coating composition and the physical characteristics of the coating film can be controlled. The aqueous epoxy resin (A1) is an emulsion of a first epoxy resin containing a bisphenol A type epoxy resin having an epoxy equivalent of 150 to 1200, more preferably 150 to 1000.

The number average molecular weight of the first epoxy resin is preferably 300 to 3000, more preferably 300 to 2500, in terms of standard polystyrene using gel permeation chromatography (GPC). The fact that the number average molecular weight of the first epoxy resin is in the above range can enhance the adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition. it can. Further, it is advantageous in enhancing the corrosion resistance and water resistance of the multi-layer coating film according to the present invention. By adjusting the molecular weight of the first epoxy resin, the characteristics of the aqueous coating composition and the physical characteristics of the coating film can be controlled.

The forced emulsified first epoxy resin emulsion can be obtained by stirring and emulsifying the first epoxy resin together with an emulsifier in an aqueous medium such as water. As the emulsifier, nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polypropylene glycol ethylene oxide adduct, polyethylene glycol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester can be used. Only one type of emulsifier may be used, or two or more types may be used in combination.

An epoxy resin emulsion using a self-emulsifying first epoxy resin can be obtained by emulsifying a resin obtained by introducing a hydrophilic moiety into the above-mentioned epoxy resin into an aqueous medium such as water. Examples of the hydrophilic moiety include a side chain having a hydroxyl group or a carboxyl group, a nonionic polyalkylene oxide skeleton, and the like.

The aqueous epoxy resin (A1) such as the emulsion of the first epoxy resin can contain a pH adjuster. An inorganic acid or an organic acid can be used as the pH adjuster. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include formic acid and acetic acid. Only one kind of pH adjuster may be used, or two or more kinds may be used in combination.

Above all, it is preferable to use phosphoric acid or the like. By using phosphoric acid or the like and setting the pH of the aqueous epoxy resin (A1) to preferably less than 5, more preferably less than 4.5, the corrosion resistance of the coating film can be enhanced. It is considered that this is due to the formation of a passivation film on the surface of the object to be coated.

(2) Aqueous epoxy amine resin (A2)
The aqueous epoxy amine resin (A2) is a water-soluble or water-dispersible resin having one or more amino groups selected from the group consisting of a primary amino group and a secondary amino group in the molecule, and is preferable. Is water-dispersed.
In the present invention, the aqueous epoxy amine resin (A2) is, for example, an aqueous epoxy amine resin (A2) obtained by modifying the second epoxy resin with an amine.
Curability of the first water-based coating composition, water resistance and corrosion resistance of the multi-layer coating film, and a coating film formed from the first water-based coating composition, a coating film formed from the second water-based coating composition, and the like. The aqueous epoxy amine resin (A2) is a water-dispersible aqueous epoxy amine resin (A2) from the viewpoint of the adhesiveness of the coating film and the adhesiveness to the old coating film. The first aqueous coating composition according to the present invention may contain two or more kinds of aqueous epoxy amine resins (A2).

For example, when the aqueous epoxy amine resin (A2) is an aqueous dispersion type and the first aqueous coating composition is a two-component type, the first agent containing the aqueous epoxy amine resin (A2) and the curing agent (C) ) Is facilitated uniform mixing with the second agent, and the rapid progress of the reaction between the aqueous epoxy amine resin (A2) and the curing agent (C) in the second agent is suppressed, resulting in an appropriate reaction. You can get sex. As a result, a first aqueous coating composition having a long pot life can be obtained. More specifically, when the water-based epoxy amine resin (A2) is water-dispersible, the first water-based coating composition before coating is a first agent and a second agent containing the water-based epoxy amine resin (A2). Since the aqueous epoxy amine resin (A2) in the first agent and the curing agent (C) in the second agent do not easily come into contact with each other even after mixing with, the reaction does not proceed easily and the storage stability and coatability are good. is there.
On the other hand, after painting, the dispersion medium (for example, water) volatilizes, and the aqueous epoxy amine resin (A2) and the curing agent (C) in the second agent easily come into contact with each other. The curing reaction proceeds even at a temperature of (nearby) or lower, and a coating film can be formed.

From the viewpoint of curability of the first aqueous coating composition, the aqueous epoxy amine resin (A2) preferably has two or more amino groups selected from the group consisting of primary amino groups and secondary amino groups. .. The number of the amino groups may be 3 or more, and further may be 4 or more. The aqueous epoxy amine resin (A2) has, for example, one or more amino groups (for example, two or more) at one end and one or more amino groups (for example, two or more) at the other end.

The aqueous epoxy amine resin (A2) has an amine equivalent (equivalent of an amino group) of preferably 100 to 3000, more preferably 500 to 2000, still more preferably 600 to 1900, and particularly preferably 800 to 1800. is there. Using the aqueous epoxy amine resin (A2) having an amine equivalent in the above range results in adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition. Can be enhanced. Further, it is possible to enhance the adhesiveness to the object to be coated, the anticorrosion base layer applied to the object to be coated, the old coating film and the like. It is advantageous in enhancing the curability and / or the flexibility (toughness) of the coating film and thus the impact resistance of the first aqueous coating composition. Further, it is advantageous in enhancing the corrosion resistance and water resistance of the multi-layer coating film according to the present invention.
If the amine equivalent is less than 100, the water resistance of the coating film tends to be inferior. If the amine equivalent exceeds 3000, the amine resin and water may undergo phase separation and the aqueous epoxy amine resin (A2) may not be obtained. By adjusting the amine equivalent of the aqueous epoxy-based amine resin (A2), the characteristics of the first aqueous coating composition, the physical characteristics of the first coating film, and the physical characteristics of the coating film of the multilayer coating film produced by the present invention are controlled. You can also.

The aqueous epoxy amine resin (A2) may contain two or more kinds of aqueous epoxy amine resins (A2) having different amine equivalents. A preferable example when two or more kinds of aqueous epoxy amine resins (A2) having different amine equivalents are used is an aqueous epoxy amine resin (A2-1a) in which the amine equivalent of the aqueous epoxy amine resin (A2) is 500 to 1300. ) And an aqueous epoxy amine resin (A2-1b) having an amine equivalent of 1400 to 2000. By using the water-based epoxy amine resin (A2-1a) and the water-based epoxy amine resin (A2-1b) in combination, a coating film formed from the first water-based coating composition and a coating film formed from the second water-based coating composition are formed. It is possible to improve the adhesiveness with the coating film to be applied. Further, it is possible to enhance the adhesiveness to the object to be coated, the anticorrosion base layer applied to the object to be coated, the old coating film and the like. Further, the water resistance of the coating film formed from the first water-based coating composition and further the multi-layer coating film can be further enhanced.

Water-based epoxy from the viewpoint of adhesion to the coating film formed from the second water-based coating composition, adhesion to the old coating film, water resistance to the coating film formed from the first water-based coating composition, and multi-layer coating film. The amine equivalent of the based amine resin (A2-1a) is preferably 600 to 1300, more preferably 800 to 1300, and the amine equivalent of the aqueous epoxy amine resin (A2-1b) is preferably 1400 to 1800. It is preferably 1400 to 1700.
Adhesion between the coating film formed from the first water-based coating composition and the coating film formed from the second water-based coating composition, adhesion to the old coating film, and coating film formed from the first water-based coating composition. From the viewpoint of water resistance of the multi-layer coating film, the content ratio of the water-based epoxy-based amine resin (A2-1a) and the water-based epoxy-based amine resin (A2-1b) is 8/2 to 2/8 in terms of mass ratio. Is preferable, and 7/3 to 3/7 is more preferable.

As used herein, the term "amine equivalent" refers to the case where the aqueous epoxy amine resin (A2) has a primary amino group (the aqueous epoxy amine resin (A2) has a primary amino group and a secondary amino group. ), Means the molecular weight (converted to resin solid content) of the aqueous epoxy amine resin (A2) per primary amino group, and the aqueous epoxy amine resin (A2) is the primary amino group. When does not have, it means the molecular weight (resin solid content conversion) of the aqueous epoxy amine resin (A2) per secondary amino group. The amine equivalent of the aqueous epoxy-based amine resin (A2) can be determined from the amount of the raw material blended.

The number average molecular weight of the aqueous epoxy amine resin (A2) is preferably 500 to 20000, more preferably 1000 to 10000, in terms of standard polystyrene using gel permeation chromatography (GPC). When the number average molecular weight of the aqueous epoxy amine resin (A2) is in the above range, when the aqueous coating composition is a two-component type, the first agent containing the aqueous epoxy amine resin (A2) and the curing agent (C) Since uniform mixing with the second agent containing the above is facilitated, it is possible to obtain a coating film or a multi-layer coating film having a uniform degree of curing and, by extension, strength. Further, the fact that the number average molecular weight of the water-based epoxy amine resin (A2) is within the above range means that the coating film formed from the first water-based coating composition and the multi-layer coating film have impact resistance, water resistance, and corrosion resistance. It is also advantageous in improving the properties and the adhesion to the coating film formed from the first aqueous coating composition, the coating film formed from the second aqueous coating composition, and the old coating film. By adjusting the molecular weight of the aqueous epoxy amine resin (A2), the characteristics of the first aqueous coating composition, the physical properties of the coating film, and the characteristics of the multi-layer coating film can be adjusted to the desired properties and physical property values.

The glass transition temperature of the aqueous epoxy amine resin (A2) is, for example, −50 to 100 ° C., preferably 0 to 50 ° C.

The aqueous epoxy-based amine resin (A2) obtained by amine-modifying the second epoxy resin is preferably an aqueous epoxy having two or more amino groups selected from the group consisting of a primary amino group and a secondary amino group. It is a based amine resin. The number of epoxy groups contained in the second epoxy resin is preferably 2 or more, and more preferably 2. Specific examples of the second epoxy resin include a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and a bisphenol A type epoxy resin is preferable. Two or more kinds of epoxy resins may be used in combination as the second epoxy resin.

The amine equivalent of the aqueous epoxy amine resin (A2) can be controlled by adjusting its molecular weight and the amount of primary amino groups and / or secondary amino groups introduced by amine modification.

The second epoxy resin may be one in which the molecular weight is increased or modified by chain extension utilizing the reaction between the active hydrogen-containing compound capable of reacting with the epoxy group and the epoxy group. Examples of the active hydrogen-containing compound include bifunctional compounds such as dimer acid, diamine, and polyether polyol. Further, the second epoxy resin may be one to which a fatty acid is added. The addition of fatty acids makes it possible to introduce soft components into the resin, which can improve the flexibility of the coating film, thus the impact resistance, and the adhesion to the old coating film. Further, the reactivity of the second epoxy resin can be adjusted (decreased) by reducing the amine-denaturing site (the number of epoxy groups) by the addition of the fatty acid.

The epoxy equivalent of the second epoxy resin is preferably 180 to 3800, more preferably 400 to 3200, and even more preferably 700 to 3200. When the epoxy equivalent of the second epoxy resin is within the above range, the coating film formed from the second aqueous coating composition, the adhesiveness to the old coating film, the coating film formed from the first aqueous coating composition, and the multi-layer coating It is advantageous in improving the water resistance and corrosion resistance of the film. When the epoxy equivalent of the second epoxy resin is less than 180, the water resistance of the obtained coating film tends to be low. If the epoxy equivalent of the second epoxy resin exceeds 3800, the epoxy amine resin and water may undergo phase separation and the aqueous epoxy amine resin (A2) may not be obtained. The epoxy equivalent of the epoxy resin can be determined according to JIS K7236.

The second epoxy resin from the viewpoint of adhesion to the coating film, the object to be coated, the anticorrosion base layer, the old coating film, etc. formed from the second water-based coating composition, the water resistance of the coating film and the multi-layer coating film, and the anticorrosion property. The molecular weight of is preferably 2000 or more, more preferably 2000 to 7600, and further preferably 3000 to 7000. If the molecular weight of the second epoxy resin exceeds 7,600, the epoxy amine resin and water may undergo phase separation, and the aqueous epoxy amine resin (A2) may not be obtained. The molecular weight of the second epoxy resin is expressed by n × the epoxy equivalent of the second epoxy resin, where n is the number of epoxy groups that the second epoxy resin has in the molecule.

Specific examples of the method for amine-modifying the second epoxy resin are 1) a method of adding a primary amino group-containing polyamine to the second epoxy resin, and 2) a ketiminated amino group-containing compound in the second epoxy resin. Including the method of adding. The amine resin obtained by these methods is a polyamine resin having one or more primary amino groups and / or secondary amino groups in the molecule and a secondary hydroxyl group. The polyamine resin has a functional group such as an epoxy group, an acid anhydride group, an acid halogen group, an isocyanate group, and a (meth) acryloyl group in a part of the primary amino group, the secondary amino group and / or the hydroxyl group. A resin further modified by reacting the compound may be used as the aqueous epoxy amine resin (A2). By using such an aqueous epoxy amine resin (A2), the physical properties of the obtained coating film and the multi-layer coating film can be adjusted.

More specifically, the method 1) described above is a second method in which a primary amino group of a primary amino group-containing polyamine is reacted with a reactive group (for example, an epoxy group) of an epoxy group of a secondary epoxy resin. This is a method of forming a secondary amino group and, as a result, producing the above-mentioned polyamine resin having a secondary amino group. Examples of the primary amino group-containing polyamine include diethylenetriamine, dipropylenetriamine, dibutylenetriamine, and triethylenetetramine. As the primary amino group-containing polyamine, only one type may be used, or two or more types may be used in combination.

More specifically, in the method 2) above, a primary amino group is formed by reacting a ketiminated amino group-containing compound with a second epoxy resin and then hydrolyzing the ketimine group. As a result, it is a method for producing the above-mentioned polyamine resin having a primary amino group. When the ketiminated amino group-containing compound is reacted with the secondary epoxy resin, a secondary amine such as diethanolamine, methylethanolamine, or diethylamine may coexist.

The ketiminated amino group-containing compound can be obtained by reacting a primary amino group-containing compound with a ketone. Examples of the primary amino group-containing compound include primary amino group-containing polyamines such as diethylenetriamine, dipropylenetriamine, dibutylenetriamine, and triethylenetetramine; aminoethylethanolamine, methylaminopropylamine, ethylaminoethylamine, and the like. Can be mentioned. As the primary amino group-containing compound, only one kind may be used, or two or more kinds may be used in combination. Examples of the ketone include methyl ethyl ketone, acetone, methyl isobutyl ketone and the like.

The aqueous epoxy amine resin (A2) may be obtained by neutralizing an amino group with an acid. Such neutralization with an acid can be applied, for example, when the amine resin obtained by denaturing an epoxy resin with an amine is not aqueous, and when the amine resin is made aqueous.

As the type of acid and the neutralization rate, any appropriate acid type and neutralization rate can be adopted depending on the desired state of the aqueous epoxy amine resin (A2) (water-soluble to water-dispersed type). Examples of the acid include acetic acid, formic acid, lactic acid, phosphoric acid and the like. The "neutralization rate" is the ratio of the number of moles of amino groups neutralized by an acid to the total number of moles of amino groups contained in the epoxy amine resin as a percentage. The neutralization rate is, for example, 10 to 80%, preferably 20 to 70%, and more preferably 20 to 60%. By setting the neutralization rate in the above range, it becomes easy to obtain an aqueous epoxy-based amine resin (A2) that is aqueous, particularly water-dispersible.

<Adhesion improver (B)>
The content of the adhesion improver (B) contained in the first aqueous coating composition is 0.1 to 20 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). For example, it is 0.3 to 17 parts by mass.
As will be described later, for example, when the adhesion improver (B1) and the adhesion improver (B2) are used, the content of the adhesion improver (B) contained in the first aqueous coating composition is the adhesion improver (B). It means the total amount of B1) and the adhesion improver (B2). Further, for example, when a plurality of types of adhesion improvers (B1) are used, the content of the adhesion improver (B1) is the total amount of each adhesion improver (B1). The same applies to the adhesion improver (B2).

By including the adhesion improver (B) in such a range, the multi-layer coating film obtained by the present invention includes a coating film formed from the first aqueous coating composition and a second aqueous coating film even if the interval is long. It can have sufficient adhesion to the coating film formed from the coating composition, and can reduce or suppress peeling at the interface.

In another aspect, the adhesion improver (B) can contain the adhesion improver (B1) alone, and the content of the adhesion improver (B1) contained in the first aqueous coating composition is the above. The resin solid content of the bisphenol type aqueous epoxy resin (A) is 0.05 to 20 parts by mass, preferably 0.1 to 20 parts by mass, for example, 0.3 to 10 parts by mass with respect to 100 parts by mass of the resin solid content. Is.
By including (B1), the multi-layer coating film obtained by the present invention has a coating film formed from the first aqueous coating composition and a coating film formed from the second aqueous coating composition even if the interval is long. Sufficient adhesion to the film can be obtained, and peeling at the interface can be reduced or suppressed.

Further, in some embodiments, the adhesion improver (B) can contain the adhesion improver (B2) alone, and the content of the adhesion improver (B2) contained in the first aqueous coating composition is The resin solid content of the bisphenol type aqueous epoxy resin (A) is 0.05 to 20 parts by mass, preferably 0.1 to 20 parts by mass, for example, 0.3 to 10 parts by mass with respect to 100 parts by mass of the resin solid content. Is.
By including (B2), the multi-layer coating film obtained by the present invention has a coating film formed from the first aqueous coating composition and a coating film formed from the second aqueous coating composition even if the interval is long. Sufficient adhesion to the film can be obtained, and peeling at the interface can be reduced or suppressed.

On the other hand, at least one of the adhesion improver (B1) and the adhesion improver (B2) is less than 0.05 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). , Sufficient adhesion cannot be obtained between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition. Further, if it exceeds 10 parts by mass, the corrosion resistance may decrease.

The content of the adhesion improver (B) contained in the first aqueous coating composition is within the range of the present invention, or at least selected from the adhesion improver (B1), the adhesion improver (B2) and a mixture thereof. When the content of one type of adhesion improver is within the range of the present invention, the coating film formed from the second aqueous coating composition is applied onto the coating film formed from the first aqueous coating composition. By then, even if a long interval occurs, a multi-layer coating film having sufficient adhesion between layers can be obtained.
Further, since sufficient adhesion is provided between the coating film formed from the first water-based coating composition and the coating film formed from the second water-based coating composition, it is formed from the second water-based coating composition. It is possible to reduce or suppress the crack resistance and peeling resistance of the coating film.

For example, the amount of the adhesion improver (B1) added and the amount of the adhesion improver (B2) added may be the same, or either of them may be added in a larger amount.

In some embodiments, the ratio (B1) / (B2) of the amount of the adhesion improver (B1) added to the amount of the adhesion improver (B2) added is (0.05 / 10-10 / 0.05), preferably. (0.2 / 9-9 / 0.2). For example, the value of the usage ratio (B1) / (B2) can be in the range of 0.1 to 15.

The adhesion improver (B) according to the present invention includes at least one selected from a water-dispersible adhesion improver or an adhesion improver that is liquid at 40 ° C. and a mixture thereof.

In the present invention, by using a water-dispersible adhesion improver or an adhesion improver that is liquid at 40 ° C., it is possible to bring about ease of manufacture and dispersion stability of the first aqueous coating composition.
Further, by using the adhesion improver of such an embodiment, the multilayer coating film obtained by the present invention is formed from a coating film formed from the first aqueous coating composition and a second aqueous coating composition. Sufficient adhesion can be obtained with the coating film even if a long interval occurs, and peeling at the interface can be reduced or suppressed.

Further, in the present invention, the adhesion improver that is liquid at 40 ° C. indicates that it is in a liquid state under atmospheric pressure of 40 ° C., specifically, that it exhibits fluidity at 40 ° C. For example, a paste-like and viscous fluid state is also included in the adhesion improver which is liquid at 40 ° C. Further, the term “liquid at 40 ° C” includes an embodiment in which the adhesion improver itself is liquid at 40 ° C without using another solvent.
In some embodiments, for example, an adhesion improver that is liquid at 35 ° C. and an adhesion improver that is liquid at 30 ° C. may be used.
In the present invention, the adhesion improver that is liquid at 40 ° C. may be described as a uniform type (liquid). Such an adhesion improver may be, for example, an embodiment in which a compound having an adhesion improving ability can be used as it is.
On the other hand, when an adhesion improver that is not liquid at 40 ° C. (hereinafter, may be referred to as a uniform type (solid)) is used, the adhesion of the multi-layer coating film, for example, stronger adhesion between the multi-layer coating films. Cannot be retained.

In the present invention, the water-dispersible adhesion improver means, for example, an adhesion improver dispersed in an aqueous medium such as water.

In some embodiments, the adhesion improvers (B1) and (B2) according to the present invention are independently selected from an aqueous dispersion type adhesion improver or an adhesion improver liquid at 40 ° C. and a mixture thereof. At least one species.
For example, when a plurality of types of adhesion improvers (B1) are used, each adhesion improver (B1) may be a water-dispersible adhesion improver. Further, when the adhesion improver is used alone, the adhesion improver itself is not solid at 40 ° C., and specifically, the adhesion improver itself can be liquid at 40 ° C.
When various adhesion improvers (B1) are used, the plurality of types of adhesion improvers (B1) may be all water-dispersible adhesion improvers, or even adhesion improvers that are all liquid at 40 ° C. Well, or a water-dispersible adhesion improver may be used in combination with an adhesion improver that is liquid at 40 ° C.
The same can be applied when using a plurality of types of adhesion improvers (B2) and when using a plurality of types of adhesion improvers (B1) and adhesion improvers (B2).

The adhesion improver (B1) contains, for example, at least one selected from benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds and benzoate-based compounds, and specifically, liquid benzotriazole-based compounds and liquid. It contains at least one selected from a triazine compound, a liquid benzophenone compound and a liquid benzoate compound, and includes, for example, an aqueous dispersion benzotriazole compound, an aqueous dispersion triazine compound, and an aqueous dispersion benzophenone compound. Includes at least one selected from compounds and aqueous dispersion benzoate compounds.
In some embodiments, at least selected from a benzotriazole-based compound that is liquid at 40 ° C., a triazine-based compound that is liquid at 40 ° C., a benzophenone-based compound that is liquid at 40 ° C., and a benzoate-based compound that is liquid at 40 ° C. Includes one.
By using such an adhesion improver (B1), it is possible to bring about ease of manufacture and dispersion stability of the first aqueous coating composition.
Further, by using the adhesion improver of such an embodiment, the multilayer coating film obtained by the present invention is formed from a coating film formed from the first aqueous coating composition and a second aqueous coating composition. Sufficient adhesion can be obtained with the coating film even if a long interval occurs, and peeling at the interface can be reduced or suppressed.

As the adhesion improver (B1), for example, TINUVIN ^{(registered trademark)} 99-DW, TINUVIN ^{(registered trademark)} 479-DW, TINUVIN ^{(registered trademark)} 384-2, TINUVIN ^{(registered trademark)} 400, etc. (all manufactured by BASF) ) Can be mentioned. Also, for example, benzotriazoles such as TINUVIN ^{(registered trademark)} P, TINUVIN ^{(registered trademark)} 234, TINUVIN ^{(registered trademark)} 326, TINUVIN ^{(registered trademark)} 900, and triazines such as TINUVIN ^{(registered trademark)} 1577FF. CHIMASORB ^{(registered trademark)} 81 and the like, and TINUVIN ^{(registered trademark)} 120 and the like (both manufactured by BASF) are known as benzoate systems.

In some embodiments, the adhesion improver (B1) has a molecular weight of 1500 or less, preferably 1000 or less. By having the molecular weight in such a range, the adhesion improver (B1) can be used more effectively in an aqueous system.

The adhesion improver (B2) contains, for example, at least one selected from a hindered amine compound and a hindered phenol compound, and specifically, a liquid hindered amine compound and a liquid aqueous dispersion hindered phenol compound. It contains at least one selected from, for example, at least one selected from an aqueous dispersion-based hindered amine compound and an aqueous dispersion-based hindered phenol compound. In some embodiments, it comprises at least one selected from a hindered amine compound that is liquid at 40 ° C. and a hindered phenolic compound that is liquid at 40 ° C.
By using such an adhesion improver (B2), the multi-layer coating film obtained by the present invention is a coating film formed from a first aqueous coating composition and a coating film formed from a second aqueous coating composition. Sufficient adhesion can be obtained with the film even if a long interval occurs, and peeling at the interface can be reduced or suppressed.

Examples of the adhesion improver (B2) include TINUVIN ^{(registered trademark)} 123-DW, TINUVIN ^{(registered trademark)} 292, and TINUVIN ^{(registered trademark)} 1135 (all manufactured by BASF).
Further, for example, as hindered amines, CHIMASORB ^{(registered trademark)} 944, TINUVIN ^{(registered trademark)} 144, TINUVIN ^{(registered trademark)} 770, etc., and as hindered phenols, IRGANOX ^{(registered trademark)} 1010, IRGANOX ^{(registered trademark)} 1098, etc. Known (both manufactured by BASF).

Preferably, a hindered amine-based adhesion improver (B2) is used. By using a hindered amine-based adhesion improver, the adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition can be improved, and further, the interval Can be taken for a long time.

In some embodiments, the adhesion improver (B2) has a molecular weight of 1500 or less, preferably 1000 or less. By having the molecular weight in such a range, the adhesion improver (B2) can be used more effectively in an aqueous system.

<Curing agent (C)>
The aqueous coating composition according to the present invention may contain a curing agent (C) in the case of a two-component type. In this case, the water-based coating composition according to the present invention can be composed of a first agent containing a bisphenol type water-based epoxy resin (A) and a second agent containing a curing agent (C).
When the first aqueous coating composition according to the present invention contains a curing agent (C), the content of the curing agent (C) is 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). , 0.1 to 100 parts by mass, more preferably 0.2 to 90 parts by mass, for example.

The curing agent (C) is a compound having a functional group (second functional group) that is reactive with the functional group (first functional group) of the bisphenol type aqueous epoxy resin (A) contained in the first agent. is there. The curing agent (C) is preferably water-based, that is, a water-soluble or water-dispersible curing agent. Specific examples of the second functional group exhibiting reactivity with the first functional group of the bisphenol type aqueous epoxy resin (A) include an epoxy group (for example, a glycidyl group), a (meth) acryloyl group, an amino group, and an isocyanate group. Contains a carboxyl group. The curing agent (C) has one or more second functional groups in the molecule, preferably two or more (for example, 2 to 4). The curing agent (C) preferably contains a compound having a functional group (second functional group) selected from the group consisting of a (meth) acryloyl group, an epoxy group and an amino group.

For example, when the bisphenol type aqueous epoxy resin (A) contains an epoxy resin (A1) having an epoxy group, the curing agent (C) is a curing agent having an amino group as a second functional group and a curing agent having an isocyanate group. And / or a curing agent having a carboxyl group.

The curing agent having an amino group is preferably a polyamine resin having two or more amino groups in the molecule, and more preferably an emulsion of the polyamine resin. Specific examples of polyamine resins include fats such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, triaminopropane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, and 1,3-bisaminomethylcyclohexane. Group polyamines; aromatic polyamines such as phenylenediamine, metaxylylene diamine, paraxylylene diamine, diaminodiphenylmethane; other polyamine compounds such as polyoxyethylenediamine, polyoxypropylenediamine, triethyleneglycoldiamine, tripropyleneglycoldiamine including.

The curing agent having an amino group may be the above-mentioned aqueous epoxy amine resin (A2). By using the water-based epoxy amine resin (A2) as a curing agent, the adhesion between the coating film formed from the first water-based coating composition and the coating film formed from the second water-based coating composition, and further, the first (1) A coating film formed from a water-based coating composition, an adhesive to an object to be coated, an anticorrosion base layer applied to the object to be coated, or an old coating film, and a coating film formed from the first aqueous coating composition. It is possible to improve the corrosion resistance and water resistance of the multi-layer coating film.

For a specific description of the aqueous epoxy amine resin (A2) as a curing agent, the above description as a bisphenol type aqueous epoxy resin (A) is cited.

For example, when the bisphenol type aqueous epoxy resin (A) contains an aqueous epoxy amine resin (A2), the curing agent (C) has a curing agent having an epoxy group as a second functional group and a (meth) acryloyl group. It can be a curing agent and / or a curing agent having an isocyanate group. These curing agents are as described above.

The curing agent having an epoxy group is preferably an epoxy resin having two or more epoxy groups in the molecule, and a conventionally known curing agent may be used, but the above-mentioned aqueous epoxy resin (A2) is preferably used. Be done. For a specific description of the aqueous epoxy resin (A2) as a curing agent, the above description as a bisphenol type aqueous epoxy resin (A) is cited.

In some embodiments, the curing agent (C) can be a curing agent having an epoxy group as the second functional group, a curing agent having a (meth) acryloyl group, and / or a curing agent having an isocyanate group. The curing agent having an epoxy group is preferably an epoxy resin having two or more epoxy groups in the molecule, and a conventionally known curing agent may be used, but the above-mentioned aqueous epoxy resin (A2) is preferably used. .. The curing agent having a (meth) acryloyl group is preferably a compound having two or more (meth) acryloyl groups in the molecule [(meth) acryloyl group-containing compound]. In this case, the curing agent (C) is preferably an aqueous dispersion or an aqueous solution of the (meth) acryloyl group-containing compound. For a specific description of the aqueous epoxy resin (A2) as a curing agent, the above description as a bisphenol type aqueous epoxy resin (A) is cited.

The molecular weight of the (meth) acryloyl group-containing compound is preferably 150 to 2000, more preferably 200 to 1700, and even more preferably 250 to 1300. The number of (meth) acryloyl groups contained in the (meth) acryloyl group-containing compound is 1 or more, preferably 2 to 4. The viscosity of the (meth) acryloyl group-containing compound at 25 ° C. is, for example, 3000 mPa · s or less, preferably 50 to 3000 mPa · s.

Specific examples of the (meth) acryloyl group-containing compound include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, and the like. Trimethylol propantri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, glycerol acryloxidimethacrylate, 1,1,1-trishydroxymethylethanedi (meth) acrylate, 1,1, Polymerizable unsaturated monocarboxylic acid ester compounds of polyhydric alcohols such as 1-trishydroxymethylethanetri (meth) acrylates, 1,1,1-trishydroxymethylpropandi (meth) acrylates; glycidyl (meth) acrylates and ( Meta) Additives of epoxy group-containing ethylenically unsaturated monomers such as reactants with acrylic acid, crotonic acid, and maleic acid and carboxyl group-containing ethylenically unsaturated group monomers; polyvalent amines such as ethylenediamine di (meth) acrylates. Examples thereof include polymerizable unsaturated monocarboxylic acid amide compounds. As the (meth) acryloyl group-containing compound, only one kind may be used, or two or more kinds may be used in combination.

The (meth) acryloyl group-containing compound can be water-soluble, self-emulsifying, or water-insoluble. At room temperature, add 5 g of the (meth) acryloyl group-containing compound to 100 g of water, stir for 3 minutes, and visually observe the state after allowing to stand for 5 minutes. If precipitation occurs, it is "water-insoluble". If there is no precipitation and it is transparent, it can be judged as "water-soluble", and if there is no precipitation and there is turbidity, it can be judged as "self-emulsifying".

When the (meth) acryloyl group-containing compound is water-soluble, the aqueous dispersion or aqueous solution thereof can be an aqueous solution of the (meth) acryloyl group-containing compound. When the (meth) acryloyl group-containing compound is self-emulsifying or water-insoluble, the aqueous dispersion or aqueous solution thereof can be an aqueous dispersion of the (meth) acryloyl group-containing compound, for example, an emulsion. An emulsifier, a dispersant, an aqueous resin or the like may be used in the preparation of the aqueous dispersion. In the preparation of the aqueous dispersion, a treatment of diluting the (meth) acryloyl group-containing compound with an organic solvent may be performed.

Specific examples of emulsifiers that can be used when preparing an aqueous dispersion (emulsion) of a (meth) acryloyl group-containing compound include nonionic emulsifiers and anionic emulsifiers. Examples of the nonionic emulsifier include polyoxyethylene alkylphenol ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene block polymer, sorbitan fatty acid ester and the like. Examples of the anionic emulsifier include dodecylbenzene sulfonate, dialkyl succinate sulfonate, polyoxyethylene alkyl ether sulfate, polyoxyethylene styrene phenyl ether sulfate, alkyl diphenyl ether disulfonate and the like. ..

Specific examples of the dispersant that can be used when preparing an aqueous dispersion of a (meth) acryloyl group-containing compound include sodium polyacrylic acid, an ammonium salt of a half ester of a styrene maleic acid copolymer, and styrene maleic acid. Includes a styrene oxide adduct of a half-ester of the polymer. Specific examples of an aqueous resin that can be used in preparing an aqueous dispersion of a (meth) acryloyl group-containing compound include a soda salt of a polyacrylic acid ester. When the water-based coating composition is a two-component type, the second agent (curing agent) may contain the above-mentioned dispersant, emulsifier or water-based resin.

Specific examples of the organic solvent that can be used when diluting the (meth) acryloyl group-containing compound with an organic solvent include ethylene glycol monobuty ether and diethylene glycol monobutyl ether.

The (meth) acryloyl group-containing compound is modified with a polyalkylene oxide such as polyethylene oxide, and the hydrophilicity is increased by increasing the number of moles of the polyalkylene oxide added to obtain a water-soluble or self-emulsifying resin. be able to.

Specific examples of the water-soluble (meth) acryloyl group-containing compound include ethoxylated bisphenol A diacrylate (EO 30 mol), ethoxylated trimethylolpropane triacrylate (EO 20 mol), ethoxylated trimethylolpropane triacrylate (EO 30 mol), and ethoxylated penta. It contains erismitol tetraacrylate (EO 35 mol), ethoxylated glycerin triacrylate (EO 20 mol), and ethoxylated bisphenol A dimethacrylate (EO 30 mol). As the water-soluble (meth) acryloyl group-containing compound, only one kind may be used, or two or more kinds may be used in combination. In the present specification, for example, the notation "EO 30 mol" indicates that the molecule has 30 ethylene oxides. "PO" represents propylene oxide.

Specific examples of the self-emulsifying (meth) acryloyl group-containing compound include polyethylene glycol # 400 diacrylate (EO 9 mol), polyethylene glycol # 600 diacrylate (EO 14 mol), polyethylene glycol # 1000 diacrylate (EO 23 mol), and ethoxylated bisphenol. Includes A diacrylate (EO 10 mol), ethoxylated bisphenol A diacrylate (EO 20 mol), ethoxylated glycerin triacrylate (EO 9 mol), polyethylene glycol # 1000 dimethacrylate (EO 23 mol). As the (meth) acryloyl group-containing compound having self-emulsifying property, only one kind may be used, or two or more kinds may be used in combination.

Specific examples of the water-insoluble (meth) acryloyl group-containing compound include polyethylene glycol # 200 glycol diacrylate (EO4 mol), ethoxylated bisphenol A diacrylate (EO3 mol), ethoxylated bisphenol A diacrylate (EO4 mol), and propoxylated bisphenol. A diacrylate (PO3 mol), 1,10-decanediol diacrylate, tricyclodecanedimethanol diacrylate, 2-methyl-1,3-propanediol diacrylate ethoxylated (EO2 mol), neopentyl glycol diacrylate, 1, 6-Hexanediol diacrylate, 1,9-nonanediol diacrylate, dipropylene glycol diacrylate (PO2mol), tripropylene glycol diacrylate (PO3mol), polypropylene glycol # 400 diacrylate (PO7mol), polypropylene glycol # 700 diacrylate (PO12 mol), ethoxylated trimethylolpropan triacrylate (EO3 mol), ethoxylated trimethylol propantriacrylate (EO 9 mol), trimethylol propantriacrylate, propoxylated trimethylol propantriacrylate (PO3 mol), pentaerythritol triacrylate, ethoxylated Pentaerythritol tetraacrylate (EO4 mol), ditrimethylolpropane tetraacrylate, propoxylated pentaerythritol tetraacrylate (PO4 mol), propoxylated bisphenol A diacrylate (PO4 mol), ethylene glycol dimethacrylate (EO1 mol), diethylene glycol dimethacrylate (EO2 mol), tri Ethylene glycol dimethacrylate (EO3 mol), tetraethylene glycol dimethacrylate (EO4 mol), polyethylene glycol # 400 dimethacrylate (EO9 mol), polyethylene glycol # 600 dimethacrylate (EO14 mol), 1,3-butanediol dimethacrylate, 1,4- Butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, acrylated bisphenol A dimethacrylate (EO2.6 mol), ethoxylated bisphenol A dimethacrylate (EO4 mol), ethoxylated bisphenol A dimethacrylate Methacrylate (EO6 mol), ethoxylated bisphenol A dimethacrylate (EO10 mol), ethoxylated bisphenol A dimethacrylate (EO17 mol), neopentyl glycol dimethacrylate, ethoxylated polypropylene glycol # 700 dimethacrylate (PO12 mol, EO6 mol), glycerin dimethacrylate, tri Includes propylene glycol dimethacrylate (PO3 mol), polypropylene glycol # 400 dimethacrylate (PO7 mol), trimethylol propanetrimethacrylate, and ethoxylated trimethylol propanetrimethacrylate (EO9 mol). As the water-insoluble (meth) acryloyl group-containing compound, only one kind may be used, or two or more kinds may be used in combination.

The equivalent ratio (second functional group / first functional group) of the first functional group of the bisphenol type aqueous epoxy resin (A) to the second functional group of the curing agent (C) is preferably 0.7 to 2.5. It is more preferably 0.8 to 2.0. If the equivalent equivalent ratio is less than 0.7, the curability of the water-based coating composition may decrease. When the equivalent amount ratio exceeds 2.5, the adhesiveness of the obtained coating film to the coating film formed from the second aqueous coating composition or the adhesiveness to the old coating film may decrease. Further, the corrosion resistance and water resistance of the coating film and the multi-layer coating film formed from the first water-based coating composition may be lowered.

<Emulsion of ethylene-vinyl acetate copolymer (D)>
The first aqueous coating composition according to the present invention may contain an emulsion (D) of an ethylene-vinyl acetate copolymer (hereinafter, also referred to as "EVA"). When the water-based coating composition according to the present invention is a two-component type, the EVA emulsion (D) may be contained in the first agent or may be contained in the second agent. When the aqueous coating composition according to the present invention is a two-component type, the EVA emulsion (D) may be added to the first agent or the second agent before mixing the first agent and the second agent. , The first agent and the second agent may be mixed and then added. By containing the EVA emulsion (D), the adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition, and further, the first aqueous coating composition. It is possible to improve the adhesiveness to the coating film formed from the object, the object to be coated, the anticorrosion base layer applied to the object to be coated, or the old coating film. Further, by containing the EVA emulsion (D), the flexibility of the coating film and the multi-layer coating film, and thus the impact resistance can be enhanced.

The EVA emulsion (D) can be obtained by emulsion polymerization of an ethylene monomer and a vinyl acetate monomer in the presence of an emulsifier and a radical polymerization initiator. A commercially available product can also be used as the EVA emulsion (D).

From the viewpoint of adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition, the ethylene ratio in EVA is 5 to 50% by mass, and 5 to 40. It is preferably mass%, for example 10 to 30 mass%. Therefore, the vinyl acetate ratio in EVA is 50 to 95% by mass, preferably 60 to 95% by mass, for example, 70 to 90% by mass. The solid content concentration in the EVA emulsion (D) is, for example, 20 to 60% by mass. The EVA emulsion (D) may contain two or more EVAs having different ethylene ratios.

From the viewpoint of adhesion between the coating film formed from the first water-based coating composition and the coating film formed from the second water-based coating composition, when the EVA emulsion (D) is contained, the EVA in the water-based coating composition is used. The content is preferably 4 to 50 parts by mass, more preferably 4 to 40 parts by mass, and for example, 4 to 35 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). It is a mass part. The EVA content means the content of the emulsion (D) as a solid content.
By using EVA within such a range, the interlayer adhesion between the coating film formed from the first aqueous coating composition and the object to be coated, the anticorrosion base layer applied to the object to be coated, or the old coating film can be improved. Can be improved. Further, the flexibility of the coating film and the multi-layer coating film, and thus the impact resistance can be enhanced.

<Alkoxysilane compound (E)>
The aqueous coating composition according to the present invention may further contain the alkoxysilane compound (E). When the first aqueous coating composition according to the present invention is a two-component type, the alkoxysilane compound (E) may be contained in the first agent or may be contained in the second agent. When the first aqueous coating composition according to the present invention is a two-component type, the alkoxysilane compound (E) may be added to the first agent or the second agent before mixing the first agent and the second agent. Alternatively, the first agent and the second agent may be mixed and then added. By containing the alkoxysilane compound (E), the adhesion between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition, and further, the first aqueous coating composition. It is possible to further improve the adhesion between the coating film formed from the object and the substrate such as the surface of the substrate to be coated, the anticorrosion substrate layer applied to the object to be coated, or the adhesiveness to the old coating film.

The alkoxysilane compound (E) has a functional group that exhibits reactivity or affinity with an organic substance and a functional group that exhibits reactivity or affinity with an inorganic substance. Examples of the functional group exhibiting reactivity or affinity with an organic substance include a vinyl group, an epoxy group, a (meth) acrylic group, an amino group, a mercapto group and the like. On the other hand, the functional group exhibiting reactivity or affinity with an inorganic substance is, for example, an alkoxysilane group such as a methoxysilane group, an ethoxysilane group, or a propoxysilane group. Only one type of alkoxysilane compound (E) may be used, or two or more types may be used in combination.

Specific examples of the alkoxysilane compound (E) include γ-glycidoxyalkyltrialkoxy silane such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and γ-glycidoxypropoxytrimethoxysilane. Silane; γ-methacryloxyalkyltrialkoxysilanes such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropoxytrimethoxysilane; γ-aminopropyltriethoxysilane, γ-amino Γ-Aminopropyltrialkoxysilane such as propyltripropoxysilane; N-phenyl-γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltripropoxysilane, etc. Includes N-phenyl-γ-aminoalkyltrialkoxysilane. Of these, γ-glycidoxyalkyltrialkoxysilane, γ-methacryloxyalkyltrialkoxysilane, γ-aminopropyltrialkoxysilane, N-phenyl-γ-aminoalkyltrialkoxysilane, and more preferably γ- Glycydoxyalkyltrialkoxysilanes, γ-methacryloxyalkyltrialkoxysilanes, γ-aminopropyltrialkoxysilanes, more preferably γ-glycidoxyalkyltrialkoxysilanes, γ-methacryloxyalkyltrialkoxysilanes. ..

The alkoxysilane compound (E) may be a compound in which a part of the alkoxysilane group of the alkoxysilane compound is hydrolyzed and / or a part of the alkoxysilane group is hydrolyzed and dehydrated and condensed.

The content of the alkoxysilane compound (E) in the embodiment containing the alkoxysilane compound (E) is preferably 0.2 to 15 when the resin solid content of the bisphenol type aqueous epoxy resin (A) is 100 parts by mass. It is by mass, more preferably 0.5 to 12 parts by mass (for example, 1 to 10 parts by mass). When the content of the alkoxysilane compound (E) is in the above range, the adhesiveness between the coating film formed from the first aqueous coating composition and the coating film formed from the second aqueous coating composition is improved. Further, the coating film formed from the first water-based coating composition has excellent adhesion to the substrate such as the surface of the substrate to be coated and the anticorrosion substrate layer applied to the object to be coated, and as a result, it is excellent. It is possible to obtain a water-based coating composition capable of forming a coating film and a multi-layer coating film exhibiting corrosion resistance. If the content of the alkoxysilane compound (E) is excessively large, the curability of the coating film or the multi-layer coating film may decrease.

<Other ingredients (F)>
The first aqueous coating composition according to the present invention may contain other compounding components other than the above, if necessary. Examples of other compounding components include pigments, additives, water, and organic solvents. When the first aqueous coating composition according to the present invention is a two-component type, other compounding components may be contained in the first agent or may be contained in the second agent. When the first aqueous coating composition according to the present invention is a two-component type, other compounding components may be added to the first agent or the second agent before mixing the first agent and the second agent. , The first agent and the second agent may be mixed and then added.

Specific examples of pigments include colored pigments such as titanium oxide, yellow iron oxide, red iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, azo red, quinacridone red, and benzimidazolone yellow; calcium carbonate, barium sulfate, kaolin, clay, etc. Constituent pigments such as talc, mica, alumina, and myoban; including rust-preventive pigments such as aluminum tripolyphosphate, zinc phosphate, and calcium phosphate. Only one kind of pigment may be used, or two or more kinds of pigments may be used in combination.

The pigment volume concentration in the first aqueous coating composition is preferably 20 to 50%, more preferably 25 to 45%, still more preferably 30 to 40%. If the pigment volume concentration is less than 20%, the effect of containing the pigment (corrosion resistance (rust prevention), improvement of coating film strength, etc.) may not be sufficiently obtained. The appearance of the coating film may deteriorate. The pigment volume concentration can be calculated from the blending amount of the pigment and the specific gravity of each component in the paint.

Specific examples of additives include dispersants, viscosity modifiers, curing catalysts, surface modifiers, defoamers, plasticizers, film-forming aids, UV absorbers, antioxidants, leveling agents, antisettling agents, and preservatives. , Reactive diluent, non-reactive diluent and the like. Only one type of additive may be used, or two or more types may be used in combination.

Specific examples of the solvent include glycol-based solvents such as ethylene glycol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol, dipropylene glycol, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and diethylene glycol dibutyl ether; xylene and sorbesso. Aromatic solvents such as 100, Solbesso 150, Solbesso 200; Hydrocarbon solvents such as mineral spirits; 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl- Examples thereof include ester solvents such as 1,3-pentanediol diisobutyrate, diethyl adipate, and diisobutyl adipate.

<Step of forming the first coating film (1)>
The present invention includes a step (1) of coating a first aqueous coating composition on an object to be coated to form a first coating film. For example, when the first aqueous coating composition according to the present invention is a two-component type, the first agent and the second agent are mixed and then coated on the object to be coated. The material of the surface of the object to be painted is, for example, metal (including alloy), wood, plastic, rubber, stone, slate, concrete, mortar, fiber, paper, glass, porcelain, pottery, film, and these. It can be a complex or the like. For example, when the surface of the object to be coated is made of an inorganic material such as slate or concrete, the surface may be coated with a sealer in advance. When the surface of the object to be coated is made of a metal material, an anticorrosion base layer may be applied to the object to be coated in advance. Further, the surface of the object to be coated may have an old coating film.

The first aqueous coating composition according to the present invention is preferably applied on a metal surface or an old coating film, or on both a metal surface and an old coating film. Examples of the metal include iron, copper, tin, zinc, aluminum, stainless steel and the like.

Objects to be painted whose surface is metal or an old coating include, for example, buildings (for example, civil engineering structures), ships, vehicles (for example, railroad vehicles, large vehicles), aircraft, bridges, marine structures, plants. , Tanks (eg, oil tanks), pipes, steel pipes, cast iron pipes and the like.

A coating film can be formed by applying the first aqueous coating composition to an object to be coated and drying it. As the coating method, any appropriate method can be adopted depending on the type of the object to be coated (base material) and the like. For example, application or immersion with a brush, roller, air spray, airless spray, iron or the like can be mentioned.

The coating amount of the first aqueous coating composition depends on the application, the type of the object to be coated, and the like, but is, for example, 10 to 350 g / m ² . The film thickness of the first coating film after drying is, for example, 10 to 300 μm, and may be 10 to 250 μm or 15 to 200 μm. The first aqueous coating composition may be applied a plurality of times to form a dry coating film having a desired film thickness. In this case, a plurality of layers of the wet coating film may be applied and then dried to obtain a dry coating film having a desired film thickness, or a desired film thickness may be formed by forming a plurality of layers of the dry coating film. A dry coating film having the above may be obtained.

The coating film can be dried by natural drying. Natural drying can be performed at room temperature (25 ° C. or its vicinity) or lower. In the case of natural drying, the drying time for obtaining a completely cured coating film is preferably 2 hours or more, more preferably 24 hours or more, still more preferably 1 week or more. According to the first aqueous coating composition according to the present invention, it is formed from the coating film formed from the first aqueous coating composition and the second aqueous coating composition even when naturally dried at a temperature of room temperature or lower. It is possible to form a coating film or a multi-layer coating film having excellent adhesion to a coating film, water resistance and corrosion resistance.

Before the first aqueous coating composition according to the present invention is applied to form a coating film, another coating film, for example, the surface of an object to be coated is coated with an anticorrosion base layer composition to form an anticorrosion base layer. You may. By forming the anticorrosion base layer, it is more excellent in anticorrosion and water resistance, and for example, it can sufficiently cope with the case where high anticorrosion is required for bridges, plants, tanks and the like.

Examples of the anticorrosion base layer composition include organic or inorganic zinc rich coating compositions. The anticorrosion base layer composition may be a solvent type or an aqueous solution, but is preferably aqueous from the viewpoint of reducing the environmental load.

For the formation of the anticorrosion base layer, any appropriate method can be adopted depending on the type of the anticorrosion base layer composition and the like. For example, application or immersion with a brush, roller, air spray, airless spray, iron or the like can be mentioned.

The amount of the anticorrosion base layer composition applied depends on the type of the anticorrosion base layer composition, the purpose of coating, and the like, but is, for example, 80 to 1200 g / m ² . The film thickness of the anticorrosion base layer after drying is, for example, 20 to 300 μm, and may be 20 to 200 μm. The coating film composed of the anticorrosion base layer composition can be dried by natural drying, forced drying, baking or the like.

<Step of forming the second coating film (2)>
The present invention includes a step (2) of coating a second aqueous coating composition on the first coating film obtained by the above step (1) to form a second coating film.

<Second water-based paint composition>
The second aqueous coating composition may include an aqueous resin composition, an inorganic aqueous coating composition, and an inorganic-organic composite aqueous coating composition. These may be a one-component type or a two-component type.

For example, the second aqueous resin composition contains an aqueous resin (a), and the aqueous resin (a) is at least one selected from an epoxy resin, a urethane resin, an acrylic resin, a silicon resin, an inorganic resin, and a fluororesin. Contains water-based resin. Further, these water-based coating compositions may be, for example, a one-component type or a two-component type. For example, an aqueous one-component urethane resin, an aqueous two-component urethane coating, an aqueous one-component fluororesin, Examples thereof include an aqueous two-component fluororesin, an aqueous one-component epoxy resin, and an aqueous two-component epoxy resin. With such a water-based coating composition, high gloss on the surface can be maintained, and long-term aesthetic protection can be achieved.
Further, for example, when the second aqueous resin composition contains an aqueous epoxy resin, an aqueous urethane resin, preferably an aqueous epoxy resin as the aqueous resin (a), the adhesion to the first coating film is more excellent and strong. A multi-layer coating film can be formed.

Such an aqueous resin composition, an inorganic aqueous coating composition, and an inorganic-organic composite aqueous coating composition may optionally contain additional additives, pigments and the like. Moreover, all of these coating compositions are water-based.

In the step (2) of forming the second coating film, for example, when the second aqueous coating composition according to the present invention is a two-component type, the first agent and the second agent are mixed and then the object to be coated. Will be painted on.

In the step (2) of forming the second coating film, specifically, the second aqueous coating composition is applied onto the coating film formed in the step (1) and dried to form the coating film. Can be done. As the coating method, any appropriate method can be adopted depending on the type of the object to be coated (base material) and the like. For example, application or immersion with a brush, roller, air spray, airless spray, iron or the like can be mentioned.
Further, according to the method for forming a multi-layer coating film of the present invention, a long interval is allowed between the application of the first aqueous coating composition and the application of the second aqueous coating composition in the step (1). be able to. Therefore, it is particularly useful for repairing large structures and newly installed anticorrosion coating.
Further, according to the coating film forming method of the present invention, an interval can be taken in such a range, and high adhesiveness can be provided between the first coating film and the second coating film. For this reason, the degree of freedom in coating work is increased in repairing large structures and newly installed anticorrosion coating, and the interlayer adhesion between the first coating film and the second coating film can be maintained for a long period of time. It is especially useful for large structures that cannot be easily repainted or repaired.

The coating amount of the second aqueous coating composition depends on the application, the type of the object to be coated, the type of the first coating film, and the like, but is, for example, 10 to 350 g / m ² . The film thickness of the second coating film after drying is, for example, 10 to 300 μm, and may be 10 to 250 μm or 15 to 200 μm. The second aqueous coating composition may be applied a plurality of times to form a dry coating film having a desired film thickness. In this case, a dry coating film having a desired film thickness may be obtained by forming a plurality of layers of the dry coating film.

The coating film can be dried by natural drying. Natural drying can be performed at room temperature (25 ° C. or its vicinity) or lower. In the case of natural drying, the drying time for obtaining a completely cured coating film is preferably 2 hours or more, more preferably 24 hours or more, still more preferably 1 week or more. According to the second aqueous coating composition according to the present invention, the coating film formed from the first aqueous coating composition and the second aqueous coating composition are formed even when naturally dried at a temperature of room temperature or lower. It is possible to form a coating film or a multi-layer coating film having excellent adhesion to a coating film, water resistance and corrosion resistance.

In some embodiments, according to the present invention, a further coating film can be formed after the second coating film is formed or after the second aqueous coating composition is applied.
For example, the same type or other type of the second aqueous coating composition may be applied onto the second coating film formed by the present invention. Further, a clear coating or the like may be applied on the second coating film.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples are based on mass.

[1] Preparation of First Water-based Coating Composition The details of each component contained in the first water-based coating composition will be described below.
(Production Example 1: Preparation of Aqueous Epoxy Amine Resin (A2) I)
In a reaction vessel equipped with a stirrer, a cooler, a nitrogen introduction tube and a thermometer, 742 parts of a raw material resin having an epoxy equivalent of 188 g / equivalent synthesized from bisphenol A and epichlorohydrin, 336 parts of bisphenol A, and methyl isobutyl ketone (hereinafter, "" It is referred to as "MIBK".) 190 parts were charged and reacted at 117 ° C. in the presence of 1 part of benzyldimethylamine until the epoxy equivalent reached 1079 g / equivalent to obtain an epoxy resin. Then, 360 parts of a ketimine compound (73 mass% MIBK solution) of diethylenetriamine was added, and the mixture was reacted at 117 ° C. for 1 hour. Then, 27 parts of ion-exchanged water and 188 parts of neodecanoic acid glycidyl ester (manufactured by Hexion Specialty Chemicals, trade name "Cadura E10-P") were charged and reacted at 100 ° C. for 2 hours. Then, it was diluted with MIBK until the non-volatile content became 75% to obtain an epoxy amine resin having an amine equivalent of 1095. Next, acetic acid was added thereto so that the neutralization rate defined above was 35%, and then ion-exchanged water was added to dilute the mixture. Then, the mixture of MIBK and water was removed under reduced pressure until the solid content became 40% by mass to obtain a milky white aqueous (aqueous dispersion type) epoxy amine resin (A3-1) I. The amine equivalent of the aqueous epoxy-based amine resin (A2) I was calculated from the amount of the raw material compounded.

(Production Example 2: Preparation of Aqueous Epoxy Amine Resin (A2) II)
In a reaction vessel equipped with a stirrer, a cooler, a nitrogen introduction tube and a thermometer, 1940 parts of a raw material resin having an epoxy equivalent of 188 g / equivalent synthesized from bisphenol A and epichlorohydrin, 1060 parts of bisphenol A, and methyl isobutyl ketone (hereinafter, "" 1000 parts were charged and reacted at 117 ° C. in the presence of 8 parts of benzyldimethylamine until the epoxy equivalent reached 3000 g / equivalent to obtain an epoxy resin. Then, 360 parts of a ketimine compound (73 mass% MIBK solution) of diethylenetriamine was added, and the mixture was reacted at 117 ° C. for 1 hour. Then, it was diluted with MIBK until the non-volatile content became 60% to obtain an epoxy amine resin having an amine equivalent of 1550. Next, acetic acid was added thereto so that the neutralization rate defined above was 40%, and then ion-exchanged water was added to dilute the mixture. Then, the mixture of MIBK and water was removed under reduced pressure until the solid content became 40% by mass to obtain a milky white aqueous (aqueous dispersion type) epoxy amine resin (A3-1) II. The amine equivalent of the aqueous epoxy-based amine resin (A2) II was calculated from the amount of the raw material compounded.

The amine equivalent of the aqueous epoxy amine resin (A2) obtained in Production Examples 1 and 2, the number average molecular weight and state in terms of standard polystyrene using GPC, and the epoxy resin forming the aqueous epoxy amine resin (A2). The epoxy equivalents of the above are summarized in Table 1.

(Epoxy resin with epoxy group)
Aqueous epoxy resin (A1) III: "ADEKA Resin EM-101-50" manufactured by ADEKA (Emulsion of bisphenol A type epoxy resin, solid content: 47% by mass, epoxy equivalent: 500 g / equivalent, number average molecular weight: 1000)

(Adhesion improver (B1))
^{TINUVIN (registered trademark)} 99-DW (manufactured by BASF, water-dispersed type) using the following as the adhesion improver B1
TINUVIN ^{(registered trademark)} 479-DW (manufactured by BASF, water-dispersed type)
TINUVIN ^{(registered trademark)} 384-2 (manufactured by BASF, liquid at 40 ° C)
TINUVIN ^{(registered trademark)} 400 (BASF Corporation, liquid at 40 ℃)
TINUVIN ^{(registered trademark)} 479 (BASF Corp., solid at 40 ℃)

(Adhesion improver (B2))
^{TINUVIN (registered trademark)} 123-DW (manufactured by BASF, water-dispersed type) using the following as the adhesion improver B2
TINUVIN ^{(registered trademark)} 292 (BASF Corporation, liquid at 40 ℃)
IRGANOX ^{(registered trademark)} 1135 (BASF Co., Ltd., liquid at 40 ℃)
TINUVIN ^(R) 144 (BASF Corp., solid at 40 ° C.)

EVA emulsion (D) XI: "Polysol EVA AD-20" manufactured by Showa Denko KK (solid content: 56% by mass, ethylene ratio: 30% by mass)

Alkoxysilane compound (E) XII: "Dynasylan MEMO" manufactured by EVONIK INDUSTRIES (3-methacryloxypropyltrimethoxysilane, solid content: 100% by mass)

Epoxy group-containing curing agent XIII: "ADEKA Resin EM-101-50" manufactured by ADEKA (Epoxy of bisphenol A type epoxy resin, solid content: 47% by mass, epoxy equivalent: 500 g / equivalent, number average molecular weight: 1000)

(Production Example 3: Preparation of Emulsion XIV Containing Compound Having (Meta) Acryloyl Group)
35 parts of water, 10 parts of dipropylene glycol monobutyl ether, 5 parts of nonionic emulsifier [manufactured by Nippon Emulsifier Co., Ltd., trade name "Newcol 740"], and propoxylated trimethylolpropane triacrylate (PO3 mol) [viscosity (25 ° C.): 85 mPa · s, molecular weight: 470, number of functional groups: 3, acryloyl group equivalent: 157] 50 parts were mixed and stirred with a homogenizer for 10 minutes to obtain an emulsion XIV containing a compound having a (meth) acryloyl group. “PO3 mol” means having three propylene oxides in the molecule. Emulsion XIV was used as a curing agent (C). The solid content of the curing agent (C) was 50% by mass.

Amino group-containing curing agent XV: "Fujicure FXS-918-FA" manufactured by T & K TOKA (epoxy adduct type modified polyamine resin, solid content: 60% by mass, amine equivalent: 387).

[2] Preparation of Second Water-based Paint Composition In Table 2 below, details of each component contained in the second water-based paint composition will be described.

<Examples 1 to 12, Comparative Examples 1 to 4>
80 parts of water, 25 parts of pigment dispersant (manufactured by Big Chemie, trade name "Disperbyk-190"), 75 parts of talc, 40 parts of calcium carbonate, 170 parts of titanium oxide, 20 parts of phosphoric acid-based rust preventive pigment are mixed and discharged. The pigment-dispersed paste was produced by stirring with the mixture for 30 minutes. Next, the compounding component of the first agent (main agent) shown in Table 3 or Table 4 (the compounding amount shown in Table 3 or Table 4) and 410 parts of the pigment dispersion paste were mixed using a disper. Then, 50 parts of dipropylene glycol monobutyl ether and 5 parts of an associative thickener (manufactured by ADEKA, trade name "Adecanol UH-420") were added and mixed to prepare a first agent (main agent).

Further, in some examples, the curing agent shown in Table 3 or Table 4 (blending amount shown in Table 3 or Table 4) was prepared as the second agent. As a result, a one-component or two-component first aqueous coating composition was obtained.

Further, a second aqueous coating composition containing various resins shown in Table 3 or Table 4 was prepared.

The unit of the blending amount shown in Tables 3 and 4 is "part by mass". Further, the blending amounts shown in Tables 3 and 4 are not the solid content conversion amount but the tangible amount.

(Interval adhesion of the first coating film to the second coating film)
The first water-based coating composition corresponding to each Example and Comparative Example was mixed with the first agent and the second agent for the two-component water-based coating composition using a disper, and then a brush was used for the polished steel sheet. The coating was applied at a coating rate of 140 g / m ² and dried in an environment of 23 ° C. for 24 hours to obtain a test plate having a first coating film formed from the first aqueous coating composition.
Next, the test piece on which the first coating film was formed was exposed to the outdoors for 7 days, and then the second aqueous coating composition was coated on the coating film with a brush at a coating amount of 140 g / m ² . It was dried in an environment of 23 ° C. for 168 hours to form a second coating film. This test plate was subjected to an adhesiveness test by a cross-cut method based on JIS K 5600-5-6, and the adhesiveness to the topcoat coating film was evaluated based on the following criteria. The results are shown in Tables 3 and 4.

0: The edges of the cut are completely smooth, and there is no peeling on the eyes of any grid.
1: There is a small peeling of the coating film at the intersection of the cuts, and the area of the peeled part is less than 5%.
2: The area of the peeled portion is 5% or more and less than 15%.
3: The area of the peeled portion is 15% or more and less than 35%.
4: The area of the peeled portion is 35% or more and less than 65%.
5: The area of the peeled portion is 65% or more.

(Anti-corrosion property of coating film)
For the test plates having the first coating film obtained in Examples and Comparative Examples, a cycle corrosiveness test (120 cycles: 720 hours) was performed on this test plate in accordance with cycle D of JIS K 5600-7-9. And evaluated based on the following criteria.

AA: No rust,
A: Rust is observed in an area of less than 0.05%.
B: Rust is observed in an area of 0.05% or more.

According to the present invention, it is possible to obtain a multi-layer coating film which can take a long interval, has excellent interlayer adhesion between the first coating film and the second coating film, and has excellent corrosion resistance.
On the other hand, the multi-layer coating film produced without using the multi-layer coating film forming method of the present invention cannot have both excellent anticorrosion property and interlayer adhesion. For example, according to the fact that the adhesion improver is not contained (Comparative Example 1), the amount of the adhesion improver added is below the lower limit (Comparative Example 2), and the adhesion improver is solid at 40 ° C. (Comparative Example 4). If the adhesiveness is not sufficient and peeling occurs, long-term anticorrosion cannot be expected. Further, when the addition amount of the adhesion improver is not more than the upper limit (Comparative Example 3), the corrosion resistance of the first coating film is inferior, and the corrosion resistance of the entire multi-layer coating film is also lowered.

The method for forming a multi-layer coating film according to the present invention is a method for forming a multi-layer coating film which is excellent in adhesion between the first coating film and the second coating film and also has excellent corrosion resistance even if the interval is lengthened. It is an object of the present invention to provide a method for forming a multi-layer coating film using an aqueous coating composition. The method for forming a multi-layer coating film of the present invention can be applied to general industrial applications as described above.

Claims (6)

Step (1) of coating the first aqueous coating composition on the object to be coated to form the first coating film.
A method for forming a multi-layer coating film, which comprises a step (2) of coating a second aqueous coating composition on the first coating film obtained in the step (1) to form a second coating film.
Wherein the first aqueous coating composition comprises a bisphenol type aqueous epoxy resin (A), the biasing adhesive improving agent and (B),
The adhesion improver (B) contains an adhesion improver (B1) and an adhesion improver (B2).
The adhesion improver (B1) contains at least one selected from benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds and benzoate-based compounds, which are water-dispersible or liquid at 40 ° C.
The adhesion improver (B2) contains at least one selected from a hindered amine compound and a hindered phenol compound, which is water-dispersible or liquid at 40 ° C.
The content of the adhesion improver (B1) in the first aqueous coating composition is 0.05 to 10 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A).
The content of the adhesion improver (B2) in the first aqueous coating composition is 0.05 to 10 parts by mass with respect to 100 parts by mass of the resin solid content of the bisphenol type aqueous epoxy resin (A). Multi-layer coating film forming method. The method for forming a multilayer coating film according to claim 1, wherein the bisphenol type aqueous epoxy resin (A) contains an epoxy resin (A1) having an epoxy group or an aqueous epoxy amine resin (A2). The method for forming a multi-layer coating film according to claim 1 or 2 , wherein the first aqueous coating composition further contains a curing agent (C). The method for forming a multilayer coating film according to claim 3 , wherein the curing agent (C) contains a compound having at least one functional group selected from a (meth) acryloyl group, an epoxy group and an amino group. The multilayer layer according to any one of claims 1 to 4 , wherein the first aqueous coating composition further contains an emulsion (D) of an ethylene-vinyl acetate copolymer having an ethylene ratio of 5 to 50% by mass. Coating film forming method. The second water-based coating composition contains a water-based resin (a), and the water-based resin (a) is at least one selected from an epoxy resin, a urethane resin, an acrylic resin, a silicon resin, an inorganic resin, and a fluorine resin. The method for forming a multi-layer coating film according to any one of claims 1 to 5 , which comprises the water-based resin of the above.