Water-based coating composition and anticorrosive coating method

Abstract

To provide a water-based coating composition capable of forming a coating film resistant to detachment or cracking.SOLUTION: A water-based coating composition includes (A) water dispersion type epoxy resin, (B) amine hardening agent, (C) scaly pigment and (D) water. The (B) amine hardening agent includes at least one kind of (B1) water-soluble amine. The (C) scaly pigment includes at least one kind of (C1) scaly pigment with an average aspect ratio of 30 to 120. The volume concentration of the (C) scaly pigment in the film-forming components is 10.0 to 24.0 vol.%, and the logarithmic decrement measured under a specific condition is within 0.60.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous paint composition and a corrosion protection coating method using the paint composition, and particularly to an aqueous paint composition capable of forming a coating film in which peeling and cracking are less likely to occur.

Background Art

[0002] In the repair accompanying the deterioration of the coating film of a coated object, a paint composition capable of preventing the peeling of the coating film by adjusting the linear expansion coefficient of the coating film to be small has been developed.

[0003] Japanese Patent Application Laid-Open No. 2018-080332 (Patent Document 1) describes a paint composition containing a resin component and a pigment, wherein the linear expansion coefficient at a temperature equal to or lower than the glass transition temperature of the non-volatile matter is 3.2×1 0 0 -5 / K or less, and according to such a paint composition, since peeling of the coating film can be significantly prevented, it is described that a paint composition excellent in durability and capable of forming a coating film suitable for repair can be provided.

[0004] Japanese Patent Application Laid-Open No. 2019-196417 (Patent Document 2) describes a paint composition containing a resin component and a pigment, wherein the linear expansion coefficient at a temperature equal to or lower than the glass transition temperature of the non-volatile matter contained in the paint composition is 2.5×10 / K to 5.4×10 -5 / K, and the water vapor permeability of the coating film when a coating film having a thickness of 200 μm is formed from the paint composition is 0.1 to 1.4 g -5 / m 2 ·day, and according to such a paint composition, it is described that a paint composition capable of forming a coating film excellent in corrosion protection and peel resistance can be provided.

[0005] In Patent Document 1 and Patent Document 2, it is possible to reduce the linear expansion coefficient of the coating film by increasing the ratio of the pigment in the non-volatile content, and among the pigments, it is described that flaky pigments have a great effect of reducing the linear expansion coefficient.

[0006] In Japanese Patent No. 6945030 (Patent Document 3), paying attention to the effect of flaky pigments of suppressing the intrusion of corrosion factors, for a coating composition with a high content of flaky pigments, the average inclination angle of the flaky pigments in the coating film formed from the coating composition is reduced to a specific range, and moreover, by increasing the filling rate of the flaky pigments to a specific range, it is described that a coating film excellent in environmental barrier properties can be formed without impairing the appearance of the topcoat film. Here, the flaky pigments preferably have an aspect ratio of 30 to 100 from the viewpoint of improving environmental barrier properties, and moreover, it is also described that the flaky pigments preferably have an average particle size of 10 to 100 μm from the viewpoint of the orientation in the coating film. In recent years, from the viewpoint of reducing the health hazards of painters and residents even at the repair site, the conversion from solvent-based paints to water-based paints has been carried out.

[0007] Japanese Unexamined Patent Application Publication No. 2016-186021 (Patent Document 4) describes a two-component water-based epoxy resin coating composition containing at least (A) an epoxy resin, (B) a curing agent, (C) a viscosity modifier, (D) a pigment, and (E) water. Patent Document 4 states that flaky pigments, due to their shape,

[0008] exhibit the effects of inhibiting the intrusion of corrosion factors such as water, oxygen, and chlorides, and reducing the internal stress of the coating film. By reducing the internal stress of the coating film, the adhesion of the coating film to the substrate is further improved. ​ it can be done, and (D) the pigment is talc, mica, kaolin clay, glass flake clay, and mica iron oxide, and has an aspect ratio of 1.2 to 100 It is also described that it preferably contains at least one flaky pigment.

[0009] Japanese Patent Application Laid-Open No. 2018-053028 (Patent Document 5) describes a two-component reaction-curing type aqueous coating composition for an undercoat paint containing an epoxy resin and an amine resin and. Patent Document 5 Such a coating composition may contain a flaky inorganic powder having an aspect ratio of 2 to 1000, and it is also described that by containing the inorganic powder, the chemical resistance of the obtained undercoat film is likely to be improved .

[0010] In addition, Patent Documents 4 and 5 disclose that if the aspect ratio of the flaky pigment is too small, it is difficult to obtain a shielding effect, and if the aspect ratio of the flaky pigment is too large, the coating workability may deteriorate, or the flaky pigment may not be properly arranged during film formation. There is also such a description.

[0011] Japanese Patent No. 5273752 (Patent Document 6) describes an aqueous epoxy resin coating composition comprising a main agent containing an epoxy resin emulsion and a curing agent containing an amine resin emulsion, and having a viscosity adjusted at a specific shear rate. According to such a coating composition, it is described that an aqueous epoxy resin coating composition excellent in workability and corrosion resistance can be provided.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

[0013] Under such circumstances, the present inventor has studied an aqueous paint composition containing a flaky pigment. As a result, when an aqueous paint composition containing a flaky pigment having a specific aspect ratio and capable of expecting an effect of suppressing peeling is applied in a high-temperature and high-humidity environment, cracks occur in the paint film. In the repair of steel structures, painting of the joint part (bolt joint part) between steel plates is also required. However, many cracks were observed particularly in the painting of bolt joint parts.

[0014] Therefore, an object of the present invention is to provide an aqueous paint composition capable of forming a paint film in which peeling and cracking are less likely to occur. Another object of the present invention is to provide a corrosion protection painting method using such an aqueous paint composition. [Means for Solving the Problems]

[0015] The present inventor has found that by using a flaky pigment having an aspect ratio of 30 or more in an aqueous paint composition containing a water-dispersible epoxy resin and an amine curing agent, an effect of imparting peeling suppression to the paint film can be obtained. On the other hand, thermal cycling was performed on the bolt joint part painted with such a paint composition. However, when thermal cycling was performed on the bolt joint part painted with such a paint composition, cracks occurred in the paint film. When a cycle test was conducted, it was found that cracks occurred in the coating film. One of the reasons for this is that due to the high content of flaky pigments with a high aspect ratio, between the surface layer and the interior of the coating film it is considered that a difference in drying properties is likely to occur. In particular, the painting of bolt joints has a complex shape and thus a film thickness difference is likely to occur between the thick film part and the thin film part, so it is considered that a significant difference in drying properties occurs between the surface layer and the interior of the coating film. Also, the difference in drying properties between the surface layer and the interior of the coating film also affects the curing of the water-dispersed epoxy resin. Since the curing of the water-dispersed epoxy resin proceeds as the evaporation of water progresses, the progress of curing in the interior of the coating film is slower than that of the water-dispersed epoxy resin in the surface layer of the coating film. For this reason, the previously cured surface layer of the coating film of the coating film cannot follow the shrinkage inside the coating film caused by curing, and this is also considered to be a cause of crack generation. Therefore, the inventor further investigated and found that by adjusting the volume concentration of the flaky pigment in the coating film-forming component, using a water-soluble amine as the amine curing agent, and adjusting the logarithmic decay rate measured under specific conditions, even in the painting of bolt joints, the occurrence of cracks in the coating film can be suppressed, and the present invention was completed.

[0016] Therefore, the aqueous coating composition of the present invention is an aqueous coating composition containing (A) a water-dispersed epoxy resin, (B) an amine curing agent, (C) a flaky pigment, and (D) water, wherein the (B) amine curing agent contains at least one (B1) water-soluble amine, the (C) flaky pigment contains at least one (C1) flaky pigment having an average aspect ratio of 30 to 120, the volume concentration of the (C) flaky pigment in the coating film-forming component is 10.0 to 24.0% by volume, and the aqueous coating composition is on a steel plate

[0017] ​​​​​​​​​ Apply a paint composition in an amount such that the dry film thickness becomes 60 to 80 μm to the applicator to form a coating film After formation, for the coating film after 1 hour has elapsed under the conditions of 23 °C and 50% relative humidity immediately after coating, Under the conditions of 23 °C and 50% relative humidity, the logarithmic decrement when measuring the logarithmic decrement using a rigid pendulum physical property tester equipped with a pendulum of 300 g of the knife edge type is within 0.60 It is an aqueous paint composition characterized by being. In a preferred example of the aqueous paint composition of the present invention, the volume concentration of the entire pigment in the coating film forming component is 2

[0018] 0 to 36% by volume. In another preferred example of the aqueous paint composition of the present invention, (C1) the average aspect ratio is 30 to

[0019] 120, the average particle diameter of the flaky pigment is 10 to 80 μm, and (C) the content of the flaky pigment having an average aspect ratio of 30 to 120 in the flaky pigment is 50% by mass or more. In another preferred example of the aqueous paint composition of the present invention, (C1) the average aspect ratio is 30 to 120, the flaky pigment is mica.

[0020] In another preferred example of the aqueous paint composition of the present invention, (B1) at least one of the water-soluble amines Is a polyether-based amine resin.

[0021] In another preferred example of the aqueous paint composition of the present invention, the paint composition is a paint composition for natural drying at ambient temperature. In another preferred example of the aqueous paint composition of the present invention, the paint composition is a paint composition for natural drying at ambient temperature.

[0022] In another preferred example of the aqueous paint composition of the present invention, the paint composition is a paint composition for natural drying at ambient temperature. By applying the above-described aqueous paint composition of the present invention to the surface to be coated, a coating film is formed on the surface to be coated, and further, on the coating film, a coating other than the paint composition

[0023] Also, the anticorrosive coating method of the present invention forms a coating film on the surface to be coated by applying the above-described aqueous paint composition of the present invention to the surface to be coated, and further, on the coating film, a coating other than the paint composition Is applied. This is a corrosion-resistant coating method characterized by coating a coating material. Effect of the Invention

[0024] According to the aqueous coating composition of the present invention, it is possible to form an aqueous coating film which is resistant to peeling and cracking. According to the anticorrosive coating method of the present invention, it is possible to provide such a water-based coating composition. It is possible to provide an anticorrosive coating method using the coating composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention is described in detail below. The present invention relates to a water-based coating composition and a corrosion-resistant coating method. do.

[0026] The aqueous coating composition of the present invention comprises a water-dispersible epoxy resin, an amine curing agent, a scaly pigment, and In the present specification, this coating composition is referred to as the "water-based coating composition of the present invention." The water-dispersible epoxy resin is also referred to as (A) component. The epoxy resin is also called "(A) water-dispersible epoxy resin". The amine curing agent is the (B) component. Also called "(B) amine hardener". The scale-like pigment is the (C) component, and "(C) scale-like pigment" is also called "(C) amine hardener". Water is component (D) and is also referred to as "(D) water."

[0027] In this specification, an aqueous coating composition is a coating composition that contains water as the main solvent. The water used in the coating composition of the present invention is not particularly limited, but may be tap water or ion-exchange water. Suitable examples of the water include pure water such as water and distilled water. To prevent the growth of mold and bacteria, sterilized water such as by UV irradiation may be used. In the coating composition of the present invention, the amount of water is preferably 20 to 60% by mass. <, 30 to 50 mass% is more preferable.

[0028] Further, in the paint composition of the present invention, the amount of the film-forming component is 40 to 80 mass% which is preferable, and more preferably 50 to 70 mass%. In this specification, the paint film forming component refers to the component excluding volatile components such as solvents, and finally forms a paint film However, in the present invention, the components remaining when the paint composition is dried in an oven at 110 ° C for 3 hours are treated as the film-forming components.

[0029] The paint composition of the present invention contains a water-dispersible epoxy resin. Here, the water-dispersible epoxy resin is an epoxy resin that can be dispersed in water and is present dispersed in the aqueous paint composition of the present invention The water-dispersible epoxy resin is preferably present in the form of an epoxy resin emulsion or an epoxy resin dispersion In this specification, the resin emulsion means an emulsion in which the resin is dispersed in an aqueous medium mainly composed of water, and the resin dispersion means a dispersion in which the resin is dispersed in an aqueous medium mainly composed of water. The e The epoxy resin emulsion is not particularly limited, but is usually prepared by an ordinary forced emulsification method (a method using an emulsifier and a high-speed stirrer, etc.) to emulsify the epoxy resin in an aqueous medium mainly composed of water Here, as the emulsifier, for example, polyoxyethylene a alkylphenol ether-based nonionic surfactants, polyethers such as polyoxyethylene·polyoxypropylene block copolymers; adducts of at least one of the nonionic surfactant and the polyethers and a diisocyanate compound, etc. can be mentioned. Note that the emulsifier and the like are mentioned. In addition, the emulsifier It may be used alone or as a blend of two or more. Also, epoxy resin Examples of commercially available emulsions include Epolead EA-1, 2, 3, 7, 12, 2 0, 55, and HD2 (manufactured by Henkel Japan); Yucarezine KE-002, KE-11 6, E-1022, KE-301C (manufactured by Yoshimura Oil Chemical Co., Ltd.); Adekaresin EM-101-5 0 (manufactured by Adeka); jER W1155R55, jER W3435R67, jER W 2821R70 (manufactured by Mitsubishi Chemical Corporation), etc. On the other hand, commercially available products of epoxy resin dispersions include, for example, Beckpox EP2381 (manufactured by Ornex); EPI-RE Z6530-WH-53 (manufactured by Momentive), etc.

[0030] In addition, the water-dispersible epoxy resin is a resin having an epoxy group in the molecule and is a resin that can be cured by the reaction of the epoxy group Epoxy resin generally has high adhesion to a substrate, particularly a metal substrate, and also has an effect of shielding the substrate from environmental factors ( for example, water, oxygen, etc.) that affect the corrosion of the substrate (shielding effect), and thus is known as a resin with excellent corrosion resistance. For example, water, oxygen, etc.) that affect the corrosion of the substrate (shielding effect), and thus is known as a resin with excellent corrosion resistance. resin.

[0031] The water-dispersible epoxy resin is preferably a resin having at least two epoxy groups in one molecule and is, for example, obtained by reacting a polyhydric alcohol or a polyhydric phenol with a halohydrin Specific examples include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, novolak type epoxy resin, polyglycol type epoxy xy resin, bisphenol F type epoxy resin, epoxidized oil, 1,6-hexanediol Specific examples include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, novolak type epoxy resin, polyglycol type epoxy Examples include diglycidyl ether and neopentyl glycol diglycidyl ether, etc. 。

[0032] The water-dispersible epoxy resin may be a modified epoxy resin. Examples of the modified epoxy resin include, for example, urethane-modified epoxy resin, amine-modified epoxy resin, isocyanate-modified epoxy resin, acrylic-modified epoxy resin, polyester-modified epoxy resin, dimer acid modified epoxy resin, etc.

[0033] The epoxy equivalent of the water-dispersible epoxy resin is preferably 100 to 1,000 g / eq , more preferably 200 to 700 g / eq, and even more preferably 400 to 600 g / eq. When the epoxy equivalent is 100 g / eq or more, sufficient coating film physical properties are easily obtained. On the other hand, when the epoxy equivalent is 1,000 g / eq or less, the leveling property is less likely to decrease, and a uniform coating film is easily obtained. The epoxy equivalent of the epoxy resin can be determined according to JIS K 7236:2001 "Method for Determining the Epoxy Equivalent of Epoxy Resin".

[0034] In the coating composition of the present invention, the amount of the water-dispersible epoxy resin in the film-forming component is preferably 20 to 60% by mass. The water-dispersible epoxy resin may be used alone or in combination of two or more kinds.

[0035] The coating composition of the present invention contains an amine curing agent. In this specification, the amine curing agent refers to an amine that reacts with the water-dispersible epoxy resin, particularly its epoxy group, to promote or control the curing reaction and is used for that purpose. As the amine curing agent, it has active hydrogen that reacts with the epoxy group The resin to be used is preferably a polyamine resin, more preferably a polyamine resin. The polyamine resin is a resin having at least two amino groups in one molecule. Examples of polyamine resins include resins produced by condensation polymerization of amines and aldehydes, etherification of amines with alcohols, ring-opening polymerization of amines having a heterocyclic structure (such as ethyleneimine), condensation of amines and carboxylic acids, or resins produced by the Mannich reaction of amines, formaldehyde, and ketones or phenols. Here, a polyamine resin having an amide bond in the molecule, such as a resin produced by condensation of amines and carboxylic acids, is also referred to as a "polyamideamine resin" or "polyamideamine". In addition, for the etherification of amines with alcohols, ring-opening polymerization of alkylene oxides such as ethylene oxide and propylene oxide can be utilized. Examples of amines that can be used in the production of polyamine resins include aliphatic polyamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, triaminopropane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane; aromatic polyamines such as phenylenediamine, metaxylylenediamine, paraxylylenediamine, diaminodiphenylmethane; amines having a heterocyclic structure such as ethyleneimine, and the like. Moreover, the polyamine resin may be a modified polyamine resin. A modified polyamine resin is a polyamine resin in which a part of the amino groups is modified. For the modification of amino groups, known methods can be used.

[0036]

[0037] ​​​​​​​​​​​ The method can be used, for example, for amidation of amino groups, Mannich reaction of amino groups and carbonyl compounds, addition reaction of amino groups and epoxy groups, and the like. Examples include reaction, addition reaction of an amino group and an epoxy group, and the like.

[0038] In the coating composition of the present invention, the amine curing agent contains at least one water-soluble amine. Here, the water-soluble amine is an amine that can be dissolved in water and exists dissolved in the aqueous coating composition of the present invention. In this specification, the water-soluble amine as the amine curing agent is referred to as the component (B1). It is also referred to as "(B1) water-soluble amine".

[0039] (B1) Since the water-soluble amine is dissolved in the coating composition of the present invention, the curing of the water-soluble amine and the water-dispersed epoxy resin is less affected by the difference in drying properties between the surface layer and the inside of the coating film that may occur when a large amount of flaky pigments with a high aspect ratio are contained. Therefore, by using (B1) water-soluble amine, the effect of suppressing the occurrence of cracks in the coating film can be obtained.

[0040] (B1) As the water-soluble amine, a resin having active hydrogen that reacts with an epoxy group is preferable. A polyamine resin is more preferable. In the coating composition of the present invention, it is preferable that at least one of (B1) water-soluble amines is a polyether-based amine resin. The polyether-based amine resin is a polyamine resin having a polyether structure in the molecule. For example, polyoxyethylene diamine, polyoxypropylene diamine, and the like can be mentioned. As (B1) water-soluble amines other than polyether-based amine resins, for example, modified polyamines, modified poly amide amines, and the like can be mentioned.

[0041] (B) The proportion of (B1) water-soluble amine in the amine curing agent is preferably 5 to 100% by mass. Moreover, the proportion of the polyether-based amine resin as (B1) water-soluble amine in the (B) amine curing agent is preferably 5 to 30% by mass, and more preferably 5 to 20 % by mass.

[0042] (B) The amine curing agent can contain a water-dispersible polyamine resin together with (B1) water-soluble amine. Here, the water-dispersible polyamine resin is a polyamine resin that can be dispersed in water. The water-dispersible polyamine resin preferably exists in the form of an emulsion or a dispersion.

[0043] The active hydrogen equivalent of the (B) amine curing agent is preferably 80 to 350 g / eq. When the coating composition of the present invention contains a plurality of (B) amine curing agents, the above-mentioned "active hydrogen equivalent of the (B) amine curing agent" is the average value of the active hydrogen equivalents of the (B) amine curing agents used.

[0044] In the coating composition of the present invention, the amount of the (B) amine curing agent in the film-forming components is preferably 5 to 25 % by mass.

[0045] In the aqueous coating composition of this coating, the blending ratio of the (B) amine curing agent is, from the viewpoints of the curing and drying properties and corrosion resistance of the coating film, etc., with respect to 1 equivalent of the epoxy group of the epoxy resin, the active hydrogen equivalent of the (B) amine curing agent is preferably 0.5 to 2.0 equivalents, and more preferably 0.7 to 1.4 equivalents .

[0046] The coating composition of the present invention contains a flaky pigment. The flaky pigment has a thin and flat shape like a foil. is a pigment. Specific examples thereof include metal pigments such as zinc, nickel, chromium, tin, copper, silver, platinum, gold, aluminum, etc., and glass flakes, talc, mica, kaolin clay, mica-like iron oxide, etc. The metal pigments also include pigments of alloys such as stainless steel. Also, scaly pigments, for example, talc and mica, may be surface-treated with metal oxides such as titanium oxide. In particular, aluminum (aluminum flakes), glass flakes, and mica have the characteristic of having a relatively high aspect ratio, and thus are suitable as scaly pigments for the purpose of suppressing peeling of the coating film. Among them, mica is particularly suitable. Also, scaly pigments in addition to suppressing peeling of the coating film, have an effect of improving corrosion resistance by suppressing intrusion of external corrosion factors, and an effect of reducing internal stress of the coating film.

[0047] In the coating composition of the present invention, the scaly pigment contains at least one scaly pigment having an average aspect ratio of 3 0 to 120. In this specification, a scaly pigment having an average aspect ratio of 30 to 120 is used as the component (C1), and is also referred to as " (C1) scaly pigment having an average aspect ratio of 30 to 120".

[0048] Since the average aspect ratio of the scaly pigment of the component (C1) is 30 or more, it has an effect of suppressing peeling of the coating film. On the other hand, if the average aspect ratio is too large, the orientation of the scaly pigment in the coating film decreases. Therefore, the average aspect ratio of the scaly pigment of the component (C1) is 1 20 or less. The scaly pigment of the component (C1) preferably has an average aspect ratio of 50 to 80.

[0049] In this specification, the average aspect ratio of the scaly pigment is the average particle diameter (D) of the scaly pigment. ​​​​refers to the ratio (D / T) to the average thickness (T). Here, the average particle diameter refers to the volume-based particle size distribution of the 50% particle diameter (D 50 ), which is measured using a laser diffraction / scattering particle size distribution measuring device and obtained from the particle size distribution. The particle diameter of the flaky pigment is represented by the equivalent spherical diameter by the laser diffraction / scattering method. Also, the average thickness refers to the average value of the thicknesses of 100 or more flaky pigments measured using SEM (scanning electron microscope).

[0050] The flaky pigment of the (C1) component preferably has an average particle diameter of 10 to 80 μm, more preferably 1 5 to 60 μm. If the average particle diameter is less than 10 μm, it is difficult to obtain the peeling suppression effect, and if it is more than 80 μm, the appearance of the coating film further applied on the coating film becomes poor .

[0051] (C) The content of the flaky pigment with an average aspect ratio of 30 to 120 in the flaky pigment is preferably 50% by mass or more, more preferably 60 to 90% by mass.

[0052] The flaky pigment of the (C1) component is preferably mica.

[0053] (C) The flaky pigment preferably contains, together with the flaky pigment of the (C1) component, a flaky pigment with an average aspect ratio of less than 30. In this specification, the flaky pigment with an average aspect ratio of less than 30 is designated as the (C2) component and is also referred to as "(C2) flaky pigment with an average aspect ratio of less than 30".

[0054] By using the flaky pigment with an average aspect ratio of less than 30 of (C2) in combination with the flaky pigment with an average aspect ratio of 30 to 120 of (C1), the orientation of the flaky pigment in the coating film can be improved. can be achieved. The flaky pigment of component (C2) preferably has an average aspect ratio of 1.2 to 30. Preferably.

[0055] The flaky pigment of component (C2) preferably has an average particle diameter of 3 to 30 μm.

[0056] The content of the flaky pigment with an average aspect ratio of less than 30 in the (C) flaky pigment is preferably 0 to 50% by mass, more preferably 10 to 35% by mass. Preferably 0 to 50% by mass, more preferably 10 to 35% by mass.

[0057] The flaky pigment of component (C2) is preferably talc.

[0058] In the coating composition of the present invention, the volume concentration of the flaky pigment in the film-forming component is 10.0 to 24.0% by volume, preferably 12 to 24% by volume. By setting the volume concentration of the flaky pigment in the film-forming component to 24% by volume or less, the difference in drying properties between the surface layer and the interior of the coating film can be suppressed. The difference in drying properties between the surface layer and the interior of the coating film can be suppressed. can be suppressed.

[0059] In this specification, the volume concentration of the flaky pigment in the film-forming component is the ratio of the volume of the entire flaky pigment in the volume of the entire film-forming component, and can be obtained by calculation from the composition and specific gravity of the components constituting the film-forming component. In the volume of the entire film-forming component, and can be obtained by calculation from the composition and specific gravity of the components constituting the film-forming component. can be obtained by calculation from the composition and specific gravity of the components constituting the film-forming component.

[0060] The coating composition of the present invention can contain, in addition to the flaky pigment, further pigments. The further pigments are not particularly limited, and pigments commonly used in the paint industry, such as rust-preventive pigments, extender pigments, and coloring pigments, can be used. The further pigments may be used alone or in combination of two or more. The further pigments are not particularly limited, and pigments commonly used in the paint industry, such as rust-preventive pigments, extender pigments, and coloring pigments, can be used. The further pigments may be used alone or in combination of two or more. may be used alone or in combination of two or more.

[0061] Examples of the rust preventive pigment include zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, calcium zinc phosphate, aluminum zinc phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, vanadic acid / phosphoric acid mixed pigment, and the like. Among these, from the viewpoint of corrosion resistance, phosphate-based rust preventive pigments are preferred. Examples of the phosphate-based rust preventive pigments include salts of phosphate-based compounds such as phosphoric acid, phosphorous acid, and polyphosphoric acid (magnesium salts, calcium salts, zinc salts, aluminum salts, phosphomolybdates, etc.). In the coating composition of the present invention, the amount of the rust preventive pigment in the film-forming component

[0062] is, for example, 0 to 16% by mass. Examples of the extender pigment include silica, talc, mica, calcium carbonate, barium sulfate, etc. In the coating composition of the present invention, the amount of the extender pigment

[0063] in the film-forming component is, for example, 10 to 40% by mass. Examples of the coloring pigment include titanium oxide, iron oxide, carbon black, lead yellow, molybdate orange, ultramarine, dark blue, phthalocyanine blue, phthalocyanine green, quinacridone red, naphthol red, benzimidazolone yellow, Hansa yellow, benzimidazolone orange, dioxazine violet, and the like. In the coating composition of the present invention,

[0064] the amount of the coloring pigment in the film-forming component is, for example, 0 to 30% by mass.In the paint composition of the present invention, the volume concentration of the total pigments in the film-forming components is preferably 20 to 36% by volume, more preferably 25 to 33% by volume. The volume concentration of the total pigments also affects the corrosion resistance of the coating film and the cracking during bolt part painting. If the volume concentration of the total pigments is too low, cracking during bolt part painting is less likely to occur, but the peel resistance and corrosion resistance decrease. If it is too high, cracking during bolt part painting and a decrease in corrosion resistance may occur. In this specification, the volume concentration of the total pigments in the film-forming components is the ratio of the volume of the total pigments in the entire volume of the film-forming components, and can be obtained by calculation from the composition and ratio of the components constituting the film-forming components. The volume concentration of the total pigments in the film-forming components is generally also referred to as the pigment volume concentration (PVC: Pigment Volume Concentration). In the paint composition of the present invention, an amount of the paint composition that results in a dry film thickness of 60 to 80 μm is applied onto a steel sheet by a precoater to form a coating film. Immediately after coating, the logarithmic decrement is measured using a rigid pendulum physical property tester equipped with a pendulum weighing 300 g of the knife edge type under the conditions of 23°C and 50% relative humidity for 1 hour. The logarithmic decrement at this time is within 0.60, preferably 0.1 to 0.60, and more preferably 0.2 to 0.56. Here, as the rigid pendulum physical property tester, for example, the rigid pendulum physical property tester RPT-3000W manufactured by Eriez and Day Co., Ltd. can be used. From the logarithmic decrement measured under the above-specified conditions, the change in viscosity during the film-forming process can be inferred.

[0065]

[0066]

[0067] ​​​​​​​​​​​​​​​It can be measured. The water-dispersed epoxy resin and amine hardening agent, which are the components of the aqueous paint composition, form a coating film by evaporation of the solvent and fusion and reaction of the dispersed particles. During fusion and reaction, the logarithmic decrement increases due to the change in viscosity.

[0068] When the logarithmic decrement measured under the specified conditions is within 0.60, the occurrence of cracks in the coating film can be suppressed. When the logarithmic decrement exceeds 0.60, the reaction proceeds rapidly, and stress is applied to the coating film due to the remaining of the reaction part and the generation of curing strain, making it easy for cracks to occur. Generally, the drying of the coating film is faster in the surface layer than in the interior, but due to the blocking effect of the (C) scaly pigment contained in the paint composition, the difference in drying properties between the interior and the surface layer becomes even larger, and it is presumed that the difference in reactivity and drying properties between the surface layer and the interior of the coating film is large, making it easy for cracks to occur. Also, when the logarithmic decrement is small, the reaction proceeds gently, so cracks are less likely to occur. On the other hand, the drying of the coating film becomes slow. Therefore, from the viewpoint of drying properties, for example, it is preferable to increase the pigment volume concentration or add a curing accelerator such as a tertiary amine.

[0069] In order to make the logarithmic decrement measured under the specified conditions within 0.60, while adjusting the volume concentration of the scaly pigment in the coating film-forming components to the range of 10.0 to 24.0% by volume, it is effective to use (B1) water-soluble amine as the amine hardening agent. Also, the logarithmic decrement is affected by the types and blending amounts of (A ) water-dispersed epoxy resin, (B) amine hardening agent, and curing accelerators and curing retarders related to the reaction. In particular, since the curing accelerator promotes the reaction and increases the value of the logarithmic decrement, it is preferably not added. ) water-dispersed epoxy resin, (B) amine hardening agent, and curing accelerators and curing retarders related to the reaction. In particular, since the curing accelerator promotes the reaction and increases the value of the logarithmic decrement, it is preferably not added.

[0070] ​​Incidentally, as described in Japanese Patent Application Laid-Open No. 2018-080332 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2019-1964 No. 17 (Patent Document 2), by increasing the proportion of the pigment in the coating film forming component, the linear expansion coefficient of the coating film can be reduced. Among the pigments, flaky pigments have a great effect of reducing the linear expansion coefficient. And by setting the linear expansion coefficient of the coating film low, it is possible to improve the effect of preventing the peeling of the coating film. Therefore, also in the coating composition of the present invention, by adjusting the linear expansion coefficient as described in Patent Document 1 and Patent Document 2, the effect of suppressing peeling can be more surely imparted. For example, in one embodiment of the coating composition of the present invention, the linear expansion coefficient at a temperature below the glass transition temperature of the coating film forming component is 3.2×10 / K or less, preferably 2.5×10 / K or less, and more preferably 2.0×10 / K or less. The lower limit value of the linear expansion coefficient is, for example, 1. -5 5×10 -5 / K or more. The method for measuring the linear expansion coefficient at a temperature below the glass transition temperature of the coating film forming component is described in detail in Patent Document 1 and Patent Document 2. -5 -5

[0071] The coating composition of the present invention is preferably a two-component type coating composition. The two-component type coating composition is a coating composition composed of a main agent and a curing agent. The two-component type coating composition can be prepared by mixing the main agent, the curing agent and additives optionally selected at the time of coating. In the present invention, the agent containing (A) a water-dispersible epoxy resin is the main agent, and the agent containing (B) an amine curing agent is the curing agent. (C) The flaky pigment may be contained in either the main agent or the curing agent. ​However, it is usually contained in the main agent. (D) Water is usually contained in the main agent and the curing agent, but may be used in the main agent. Also, a part of (D) water may be used as an additive when the main agent and the curing agent are mixed together.

[0072] In the coating composition of the present invention, as other components, resins not corresponding to component (A), (B) curing agents not corresponding to the component, dispersants, silane coupling agents, film-forming aids, antifreeze agents, viscosity adjusting agents, defoaming agents, rust preventives not corresponding to rust preventive pigments, surface conditioners, anti-settling agents, anti-skinning agents , sagging preventives, color bleeding preventives, matting agents, adhesion promoters, leveling agents, drying agents, catalysts , plasticizers, fungicides, antibacterial agents, antiviral agents, preservatives, insecticides, antistatic agents, and conductivity-imparting agents, etc. can be appropriately blended according to the purpose.

[0073] The coating composition of the present invention can be prepared by mixing various components appropriately selected as needed. When the coating composition of the present invention is a two-component coating composition, the main agent and the curing agent are prepared in advance, and the main agent, the curing agent, and additives as needed are mixed at the time of coating to prepare. The main agent and the curing agent can be prepared by mixing various components appropriately selected as needed.

[0074] The coating composition of the present invention has a viscosity at a shear rate of 0.1 (1 / s) of 1 to 1000 (P a·s, 23 °C), and a viscosity at a shear rate of 1000 (1 / s) of 0.05 to 10 (Pa·s, 23 °C), which is preferable.

[0075] In this specification, the viscosity is measured with a rheometer (for example, a rheometer manufactured by TA Instruments) It is measured after adjusting the liquid temperature to 23°C using a - ter ARES).

[0076] The coating means of the paint composition of the present invention is not particularly limited, and known coating means such as brush coating coating, roller coating, spatula coating, brush coating, flow coater coating, spray coating (for example, air spray coating, airless spray coating), etc. can be used.

[0077] The drying means of the paint composition of the present invention may be either natural drying at the ambient temperature or forced drying using a dryer or the like. However, the paint composition of the present invention is preferably a paint composition for natural drying at the ambient temperature. The ambient temperature is assumed to be about 5 to 35°C. .

[0078] The paint composition of the present invention can also be applied to the coating during the construction of structures and the like, and can also be applied to the coating during repainting or repair of structures and the like.

[0079] The paint composition of the present invention can form a coating film in which peeling and cracking are less likely to occur. Therefore, the paint composition of the present invention is suitable as an undercoat paint.

[0080] The substrates to be coated with the paint composition of the present invention come in various shapes, such as two - dimensional shaped substrates like film - shaped, sheet - shaped, plate - shaped, etc., and three - dimensional shaped substrates such as three - dimensional objects with complex shapes. The surface of the substrate may be smooth or may have irregularities. Specific examples of the substrate include, for example, steel materials such as steel plates, steel pipes, and steel bars, and steel structures such as iron towers, bridge facilities, plants, etc. In particular, the paint composition of the present invention can form a coating film in which peeling and cracking are less likely to occur even for the coating of the joint part (bolt joint part) between steel plates.

[0081] The substrate may have undergone pretreatment such as degreasing, chemical conversion treatment, and polishing on its surface, or may have been coated with a sealer, primer or paint, etc., or an old paint film may be present on at least a part of the surface. The old paint film may cover part or all of the surface of the substrate. In this specification, the old paint film means a paint film that already exists on the substrate when painting, especially when performing repairs.

[0082] When the substrate has an old paint film on its surface, the surface of the substrate including the old paint film can be painted with the paint composition of the present invention. If the old paint film is sound, the paint composition of the present invention can be applied on the old paint film without peeling or removing the old paint film on the substrate surface. Since contaminants such as dust and dirt adhere to the old paint film, by removing the contaminants, the adhesion of the new paint film to the old paint film can be improved. Examples of the method for removing contaminants include high-pressure water washing, blasting, keren, and wiping with a cloth.

[0083] The old paint film preferably contains a resin. For example, acrylic resin, silicone resin, acrylic silicone resin, styrene-acrylic copolymer resin, polyester resin, fluororesin, rosin resin, petroleum resin, coumarone resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric acid resin, vinyl resin, amine resin, ketimine resin, and resins obtained by modifying these resins (modified resins), etc. The resin may be used alone or in combination of two or more.

[0084] The old coating film may contain, as other components, pigments, dispersants, surface conditioners, antioxidants, plasticizers, rust preventives, solvents, antibacterial agents, antiviral agents, viscosity modifiers, fillers, defoamers, charge control agents, stress relievers, penetrants, light guide materials, brightening materials, magnetic materials, phosphors, ultraviolet absorbers, radical scavengers, etc. Various additives may be included.

[0085] Next, the anticorrosive coating method of the present invention will be described.

[0086] The anticorrosive coating method of the present invention is to form a coating film on the surface to be coated by coating the coating composition of the present invention described above on the surface to be coated, and further, coat a paint other than the coating composition on the coating film. It is an anticorrosive coating method characterized by this.

[0087] The coating composition of the present invention can form a coating film that is difficult to peel and crack, and is suitable as an undercoat paint. Further, since the coating composition of the present invention contains (C1) flaky pigments having an average aspect ratio of 30 to 120, it also has high environmental barrier properties, and further, by combining rust preventive pigments, the anticorrosive property can be further improved.

[0088] In the anticorrosive coating method of the present invention, examples of the surface to be coated include the surface of the above-mentioned base material.

[0089] In the anticorrosive coating method of the present invention, the paint applied on the coating film formed from the coating composition of the present invention is a paint different from the coating composition of the present invention, and a paint suitable for forming an intermediate coating film or a top coating film can be appropriately used.

[0090] The paint for forming the intermediate coating film or the top coating film is preferably a water-based coating composition, similar to the coating composition of the present invention. These coating compositions include resins, curing agents, solvents, components, etc. Powders, silane coupling agents, film-forming aids, antifreeze agents, viscosity modifiers, defoamers, rust inhibitors, surface conditioners, anti-settling agents, anti-skinning agents, anti-dripping agents, anti-color separation agents, matting agents, adhesion promoters, leveling agents, desiccants, catalysts, plasticizers, anti-mold agents, antibacterial agents, antiviral agents, preservatives insecticides, antistatic agents, conductivity imparting agents, etc. can be appropriately blended according to the purpose.

Examples

[0091] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples at all.

[0092] <Preparation Example of Paint Composition> Raw materials were mixed according to the formulation shown in Tables 1 to 3 to prepare a main agent and a curing agent. The obtained main agent and curing agent were mixed at the mixing ratios shown in Tables 1 to 3 to prepare a paint composition, and the paint composition was evaluated. The formulation and mixing ratios shown in Tables 1 to 3 are based on mass.

[0093] The raw materials used are as follows. (1)(A) Water-dispersible epoxy resin Adeka Resin EM-101-50 (epoxy resin emulsion manufactured by ADEKA; non-volatile content 47% by mass) (2)(B) Amine curing agent Polyamine resin 1: Cardolite NX-8401 (amine resin emulsion manufactured by Cardolite; non-volatile content 57% by mass) Polyamine resin 2: WD11M60 (water-soluble amine resin manufactured by Mitsubishi Chemical; non-volatile content 60 % by mass), (B1) Water-soluble amine Polyamine resin 3: JEFFAMINE T-403 (polyetheramine manufactured by HUNTSUMAN; non-volatile content 100% by mass), (B1) Water-soluble amine (3)(C) Scaly pigment Scaly pigment 1: Mica A (average particle diameter 23 μm, average aspect ratio 70) Scaly pigment 2: Mica B (average particle diameter 15 μm, average aspect ratio 70) Scaly pigment 3: Mica D (average particle diameter 25 μm, average aspect ratio 20) Scaly pigment 4: Mica E (average particle diameter 25 μm, average aspect ratio 50) Scaly pigment 5: Mica F (average particle diameter 25 μm, average aspect ratio 120) Scaly pigment 6: Talc (average particle diameter 14 μm, average aspect ratio less than 20) (4) Additives, etc. Dispersant: DISPERBYK - 190 (manufactured by BYK - Japan Co., Ltd.) Silane coupling agent: 3 - glycidoxypropyltrimethoxysilane Film - forming aid: Dipropylene glycol n - butyl ether Antifreeze: Ethylene glycol Viscosity modifier: SN thickener 665T (manufactured by San Nopco Ltd.) Defoamer: SN defoamer 1312 (manufactured by San Nopco Ltd.) Curing accelerator: Ancamine K - 34 (tertiary amine manufactured by Evonik) Rust inhibitor: Sodium nitrite

[0094] Evaluation of paint composition <Peeling inhibition property> According to NEXCO test method 443 (paint adhesion performance test), test panels were prepared under the condition of a single - layer film (55 - 65 μm / coating, applied 3 times), and the test was conducted. For the epoxy resin paint for protecting the peeling layer, Epole Smile manufactured by Dainippon Paint Co., Ltd. was used. The heat cycle test [one cycle consists of (i) 50°C × 0.5 h, (ii) constant - speed cooling for 1.5 h, (iii) - 30°C × 0. 5 h, (iv) constant - speed heating for 1.5 h] × 30 cycles. The peeling width from the cut part after the test was measured, and the peeling inhibition property was evaluated according to the following evaluation criteria. The results are shown in Tables 1 - 3. The peeling ... When the peel width is 2.0 mm or less, it is a coating film with excellent peel suppression property. (Evaluation criteria) 〇: 1.0 mm or less △: Exceeding 1.0 mm and 2.0 mm or less ×: Exceeding 2.0 mm

[0095] <Logarithmic decrement> On an SPCC-SD steel sheet, a paint composition was applied with an applicator so that the dry film thickness became 60 to 80 μm, and for 1 hour under the conditions of 23 °C and 50% relative humidity immediately after coating For the coated film after the passage of time, under the conditions of 23 °C and 50% relative humidity, a rigid pendulum physical property tester (RPT-30 00W manufactured by A&D Company) equipped with a pendulum with a weight of 300 g was used to measure the logarithmic decrement (unit: none). The measurement results are shown in Tables 1 to 3. 00W) was used to measure the logarithmic decrement (unit: none). The measurement results are shown in Tables 1 to 3. In Comparative Example 5, since a curing accelerator was used, it is considered that the value of the logarithmic decrement increased is.

[0096] <Crack resistance> A steel plate (3.2 mm thick) with a hole having an inner diameter of 23 mm was provided with a hexagonal high-tension bolt having a screw diameter of M20 and a head-down length of 50 mm and a bolt joint was prepared. Next, the surface of the bolt joint was coated with an aqueous zinc-rich paint manufactured by Dainippon Paint Co., Ltd. so that the dry film thickness became 70 to 80 μm, and dried in an environment of 23 °C and 50% humidity for 24 hours. Then, each paint prepared in the above <Preparation example of paint composition> was applied by brush coating on the obtained coating film so that the dry film thickness became 60 to 80 μm, and dried in an environment of 23 °C and 50% humidity for 7 days to prepare a test piece was prepared. The test piece was subjected to a heat cycle test [one cycle consists of (i) 50 °C × 0.5 h, (ii) constant-speed cooling for 1.5 h, (iii) -30 °C × 0.5 h, and (iv) constant-speed heating for 1.5 h] . temperature for 1.5 h, (iii) -30 °C × 0.5 h, (iv) constant-speed heating for 1.5 h] Then, the test specimens at the 20 - cycle point after the start were observed and evaluated according to the following evaluation criteria. The results are shown in Tables 1 - 3. The results are shown in Tables 1 - 3. (Evaluation criteria) 〇: No crack ×: Crack occurred

[0097] <Drying property> Based on JIS K 5551 7.6, the semi - curing drying property was evaluated. The semi - curing drying property when the dry film thickness of each paint was 60 - 80 μm was evaluated according to the following evaluation criteria. The results are shown in Tables 1 - 3. The results are shown in Tables 1 - 3. The results are shown in Tables 1 - 3. (Evaluation criteria) 〇: The time to semi - curing is less than 8 hours △: The time to semi - curing is 8 - 16 hours ×: The time to semi - curing exceeds 16 hours

[0098] <Corrosion resistance> According to the composite cycle corrosion resistance of JIS K 5551 Type E, test panels were prepared so that the dry film thickness was 55 - 65 μm, and tests were conducted. The rust swelling width from the cut part after 120 cycles of the composite cycle test was measured and evaluated according to the following evaluation criteria. After 120 cycles of the composite cycle test, the rust swelling width from the cut part was measured and evaluated according to the following evaluation criteria. After 120 cycles of the composite cycle test, the rust swelling width from the cut part was measured and evaluated according to the following evaluation criteria. (Evaluation criteria) 〇: The rust swelling width from the cut part is less than 4 mm ×: The rust swelling width from the cut part is 4 mm or more

[0099]

Table 1

[0100]

Table 2

[0101]

Table 3

Claims

1. (A) a water-dispersible epoxy resin, (B) an amine curing agent, (C) a scaly pigment, and (D) water An aqueous coating composition comprising: (B) the amine curing agent comprises at least one (B1) water-soluble amine; (C) The scaly pigment comprises at least one type of (C1) scaly pigment having an average aspect ratio of 30 to 120. Contains pigments, The volume concentration of the scaly pigment (C) in the coating film forming components is 10.0 to 24.0 volume %; The water-based coating composition is applied to a steel plate in an amount such that the dry film thickness is 60 to 80 μm. The paint was applied using a motor to form a coating, and immediately after application, it was left to stand for 1 hour under conditions of 23°C and 50% relative humidity. For the coating film that had been left for 10 years, the knife-edge type was used at 23°C and 50% relative humidity. The logarithmic damping rate was measured using a rigid pendulum physical property tester equipped with a 0.00 g pendulum. An aqueous coating composition having a damping factor of 0.60 or less.

2. The total volume concentration of the pigment in the coating film forming components is 20 to 36 volume %. Item 2. The aqueous coating composition according to item 1.

3. (C1) A scale-like pigment having an average aspect ratio of 30 to 120 and an average particle size of 10 to 80 μm. (C1) The content of a scaly pigment having an average aspect ratio of 30 to 120 in the scaly pigment (C) The coating composition according to claim 1 or 2, characterized in that the content is 50 mass % or more.

4. (C1) The scale-like pigment having an average aspect ratio of 30 to 120 is mica. The coating composition according to claim 1 or 2.

5. (B1) At least one of the water-soluble amines is a polyether amine resin.

3. The coating composition according to claim 1 or 2.

6. The coating composition is characterized in that it is a coating composition for natural drying at ambient temperature. The coating composition according to claim 1 or 2.

7. The coating composition according to claim 1 or 2 is applied to a surface to be coated, thereby forming a coating on the surface. and further coating the coating film with a paint other than the paint composition. Food coating method.

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