CN112384580B

CN112384580B - Aqueous coating composition

Info

Publication number: CN112384580B
Application number: CN201980045082.2A
Authority: CN
Inventors: 富森岳; 小笠原睦
Original assignee: Kansai Paint Co Ltd
Current assignee: Kansai Paint Co Ltd
Priority date: 2018-08-02
Filing date: 2019-07-11
Publication date: 2021-12-14
Anticipated expiration: 2039-07-11
Also published as: JP7339257B2; JPWO2020026743A1; WO2020026743A1; CN112384580A

Abstract

The purpose of the present invention is to provide an aqueous coating composition having excellent corrosion resistance, adhesion and water resistance. The present invention relates to an aqueous coating composition containing acrylic resin particles (A) having an acid value of 10 to 100mgKOH/g and 80 wt% or more of all copolymerized components being polymerizable unsaturated monomers having an SP value of 9.5 or less, and a rust inhibitor (B) containing an aminosilane (B1), an azole compound (B2), and at least 1 compound (B3) selected from the group consisting of fatty acids, aromatic acids, and aliphatic amines.

Description

Aqueous coating composition

Technical Field

The present invention relates to an aqueous coating composition having excellent corrosion resistance, adhesion and water resistance. Further, it relates to a coated article having a cured coating film of the aqueous coating composition.

Background

In recent years, from the viewpoint of global environmental protection and safety and hygiene, the conversion from solvent-based paints to water-based paints has been advanced, and aqueous anticorrosive paints have also been developed in the field of anticorrosive paints for metal substrates and the like.

Patent document 1 discloses an aqueous anticorrosive coating composition in which a specific silane coupling agent is used in a latex made of a specific 1, 1-dichloroethylene copolymer resin as a coating composition having good storage stability and capable of forming a coating film excellent in rust prevention and water-resistant adhesion to a surface coating layer.

Patent document 2 discloses an aqueous dispersion composition of a copolymer resin, which comprises (a) an aqueous dispersion of a copolymer resin having a weight average molecular weight of 3 to 30 ten thousand and (B) a silane coupling agent, wherein the amount of the component (B) is 0.05 to 10% by weight in terms of solid content relative to the component (a), as an aqueous coating material having excellent dry coating film excellent in water resistance, adhesion, and Lifting resistance (Lifting resistance) and excellent storage stability, which are suitable for applications such as buildings and civil engineering structures.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2010-070603

Patent document 2: japanese patent laid-open publication No. 2003-147216

Disclosure of Invention

Problems to be solved by the invention

As a method for improving adhesion, a silane coupling agent is widely known, as represented by patent documents 1 and 2. However, the aqueous compositions of patent documents 1 and 2 are insufficient in adhesion after water load resistance and the like, and improvement thereof is desired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aqueous coating composition having excellent corrosion resistance, adhesion, and water resistance.

Means for solving the problems

As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by an aqueous coating composition containing acrylic resin particles (a) having requirements for a specific acid value and solubility parameter value and a rust inhibitor (B) containing an aminosilane (B1), an azole compound (B2), and at least 1 compound (B3) selected from a fatty acid, an aromatic acid, and an aliphatic amine.

That is, the present invention includes the following aspects.

(1) An aqueous coating composition comprising acrylic resin particles (A) and a rust inhibitor (B),

the acrylic resin particles (A) have an acid value of 10 to 100mgKOH/g and 80% by weight or more of the total copolymer component is a polymerizable unsaturated monomer having a solubility parameter value of 9.5 or less,

the rust inhibitor (B) contains an aminosilane (B1), an azole compound (B2), and at least 1 compound (B3) selected from the group consisting of a fatty acid, an aromatic acid, and an aliphatic amine.

(2) The aqueous coating composition according to the above (1), wherein the acrylic resin particles (A) are core-shell type acrylic resin particles.

(3) The aqueous coating composition according to the above (1) or (2), wherein the acrylic resin particles (A) are acrylic resin particles having a gradient polymer layer.

(4) The aqueous coating composition according to any one of the above (1) to (3), further comprising acrylic resin particles (C), wherein the acrylic resin particles (C) have a weight average molecular weight of 7500 to 75000 and an acid value of 10 to 90mgKOH/g, and are different from the acrylic resin particles (A).

(5) A coated article comprising a substrate and a cured coating film of the aqueous coating composition according to any one of the above (1) to (4) on the substrate.

(6) The coated article according to the item (5), wherein the substrate is a metal substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

The water-based coating composition of the present invention has the above-described features, and thus can form a coating film having excellent corrosion resistance, adhesion, and water resistance.

Detailed Description

The aqueous coating composition of the present invention will be described in further detail below. In the present specification, the terms "% by mass" and "% by weight" are the same as each other, and the terms "part by mass" and "% by weight" are the same as each other.

The aqueous coating composition is characterized by comprising acrylic resin particles (A) and a rust inhibitor (B), wherein the acid value of the acrylic resin particles (A) is 10-100 mgKOH/g, 80 mass% or more of the total copolymerized components is a polymerizable unsaturated monomer having a solubility parameter value of 9.5 or less, and the rust inhibitor (B) comprises an aminosilane (B1), an azole compound (B2), and at least 1 compound (B3) selected from the group consisting of fatty acids, aromatic acids, and aliphatic amines.

< acrylic resin particles (A) >

The acrylic resin particles (a) can be obtained by polymerizing a polymerizable unsaturated monomer by a known method, for example, a method of polymerizing the monomer in an organic solvent by a solution polymerization method and then dispersing the monomer in water to prepare resin particles, a method of emulsion polymerization in water, and the like.

Among these methods, a method obtained by an emulsion polymerization method in water can be suitably used.

Further, a so-called core/shell polymerization method in which a mixture of polymerizable unsaturated monomers is fed in multiple stages, or a Power feed method (Power fed method) in which the composition of the polymerizable unsaturated monomers fed during polymerization is changed in stages may be employed. Further, 2 or more kinds of acrylic resin particles produced by the above-described method may be mixed and used.

By using the core/shell polymerization method, the core-shell type acrylic resin particles (a) can be obtained.

The core-shell type acrylic resin particle (a) is generally composed of a core portion of a copolymer (I) containing a polymerizable unsaturated monomer as a copolymerization component and a shell portion of a copolymer (II) containing a polymerizable unsaturated monomer as a copolymerization component.

From the viewpoint of satisfying both the corrosion resistance and the hardness, the ratio of the copolymer (I)/the copolymer (II) is preferably about 10/90 to 90/10, more preferably about 15/85 to 85/15, and still more preferably about 20/80 to 80/20 in terms of a solid content mass ratio.

In the present embodiment, the "shell portion" of the core-shell type acrylic resin particle (a) refers to a polymer layer present in the outermost layer of the resin particle, the "core portion" refers to a polymer layer in the inner layer of the resin particle excluding the shell portion, and the "core-shell type structure" refers to a structure having the core portion and the shell portion.

The core-shell structure is generally a layer structure in which the core portion is completely covered with the shell portion, but depending on the mass ratio of the core portion to the shell portion, the amount of the monomer in the shell portion may be insufficient for forming the layer structure. In such a case, the shell portion may be configured to cover a part of the core portion, without having to have a complete layer structure as described above.

The concept of the multilayer structure in the core-shell structure is similarly applied to the case where the core portion of the core-shell acrylic resin particle (a) has a multilayer structure.

Further, by using the dynamic feeding method, the acrylic resin particles (a) having a gradient polymer layer can be obtained.

In the present embodiment, the gradient polymer layer refers to a polymer layer having a layer structure in which the composition changes continuously (having a composition gradient).

More specifically, it refers to a polymer layer having a composition gradient in which, for example, the composition of a monomer (or a monomer mixture) changes continuously from a monomer a (or a monomer mixture a) to a monomer B (or a monomer mixture B).

The dynamic feed method is a known polymerization method, and specifically, for example, in the case of polymerizing 2 kinds of monomers a (monomer mixture a) and B (monomer mixture B), the monomer a (monomer mixture a) is introduced into a reaction vessel while dropping the monomer B (monomer mixture B) into the vessel containing the monomer a (monomer mixture a) and the polymerization reaction is carried out.

In the above dynamic feed method, a gradient polymer layer having a desired composition gradient can be obtained by setting synthesis conditions (timing of starting mixing of the monomer a (monomer mixture a) and the monomer B (monomer mixture B), a speed of dropping the monomer B (monomer mixture B) into a vessel containing the monomer a (monomer mixture a), a speed of introducing the monomer a (monomer mixture a) into a reaction vessel, and the like).

The acrylic resin particle (a) may have at least 1 layer of the gradient polymer layer as needed, and the gradient polymer layer may be any layer of the core-shell type acrylic resin particle (a).

The polymerizable unsaturated monomer is a monomer having a polymerizable unsaturated group, and in the present specification, the polymerizable unsaturated group means an unsaturated group capable of radical polymerization. Examples of the polymerizable unsaturated group include a vinyl group, a vinylidene group, an acryloyl group, and a methacryloyl group.

In the present specification, "(meth) acrylate" means "acrylate or methacrylate". "(meth) acrylic acid" means "acrylic acid or methacrylic acid". Further, "(meth) acryloyl" means "acryloyl or methacryloyl". Further, "(meth) acrylamide" means "acrylamide or methacrylamide".

Examples of the polymerizable unsaturated monomer include a polymerizable unsaturated monomer having 1 polymerizable unsaturated group in 1 molecule and a polymerizable unsaturated monomer having 2 or more polymerizable unsaturated groups in 1 molecule.

Examples of the polymerizable unsaturated monomer having 1 polymerizable unsaturated group in 1 molecule include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, イソステアリルアクリレート "(trade name, available from Osaka-Chemicals Co., Ltd.) (isostearyl acrylate), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, and mixtures thereof, Alkyl or cycloalkyl (meth) acrylates such as t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecyl (meth) acrylate and the like; isobornyl group-containing polymerizable unsaturated monomers such as isobornyl (meth) acrylate; polymerizable unsaturated monomers having an adamantyl group such as adamantyl (meth) acrylate; a polymerizable unsaturated monomer having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate; aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth) acrylate, styrene, α -methylstyrene and vinyltoluene; polymerizable unsaturated monomers having an alkoxysilyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ - (meth) acryloyloxypropyltrimethoxysilane, and γ - (meth) acryloyloxypropyltriethoxysilane; perfluoroalkyl (meth) acrylates such as perfluorobutyl ethyl (meth) acrylate and perfluorooctyl ethyl (meth) acrylate; a polymerizable unsaturated monomer having a fluoroalkyl group such as a fluoroolefin; polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, and vinyl acetate; a mono-esterified product of (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate with a 2-membered alcohol having 2 to 8 carbon atoms, an epsilon-caprolactone-modified product of the mono-esterified product, N-hydroxymethyl (meth) acrylamide, allyl alcohol, a (meth) acrylate having a polyoxyethylene chain in which a hydroxyl group is at a molecular end, and the like; carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid, and β -carboxyethyl acrylate; nitrogen-containing polymerizable unsaturated monomers such as (meth) acrylonitrile, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylamide, and adducts of glycidyl (meth) acrylate and amines; epoxy group-containing polymerizable unsaturated monomers such as glycidyl (meth) acrylate, β -methylglycidyl (meth) acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, 3, 4-epoxycyclohexylethyl (meth) acrylate, 3, 4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether; (meth) acrylates having a polyoxyethylene chain with an alkoxy group at the molecular end, and the like.

These monomers may be used alone in 1 kind or in combination in 2 or more kinds depending on the performance required for the acrylic resin particles (A).

Examples of the polymerizable unsaturated monomer having 2 or more polymerizable unsaturated groups in 1 molecule include allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1, 3-butanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1, 4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1,1, 1-trihydroxymethyl ethane tri (meth) acrylate, and the like, 1,1, 1-trihydroxymethylpropane tri (meth) acrylate, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, triallyl isocyanurate, diallyl terephthalate, divinylbenzene, and the like. These monomers may be used alone in 1 kind, or in combination of 2 or more kinds.

The polymerizable unsaturated monomer having 2 or more polymerizable unsaturated groups in the molecule of 1 above has a function of imparting a crosslinked structure to the copolymer. When a polymerizable unsaturated monomer having 2 or more polymerizable unsaturated groups in 1 molecule is used, the use ratio thereof can be appropriately determined depending on the degree of crosslinking of the copolymer, but usually, the total amount of the polymerizable unsaturated monomer having 2 or more polymerizable unsaturated groups in 1 molecule and the polymerizable unsaturated monomer having 1 polymerizable unsaturated group in 1 molecule is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and further preferably 30% by mass or less, more preferably 10% by mass or less, further preferably 7% by mass or less.

The method for preparing the acrylic resin particles (a) by emulsion polymerization can be carried out by a conventionally known method. For example, the polymerization can be carried out by emulsion-polymerizing a polymerizable unsaturated monomer mixture using a polymerization initiator in the presence of an emulsifier.

As the emulsifier, anionic emulsifiers and nonionic emulsifiers can be suitably used.

Examples of the anionic emulsifier include sodium salts and ammonium salts of alkylsulfonic acid, alkylbenzenesulfonic acid, alkylphosphoric acid, and the like. Examples of the nonionic emulsifier include polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, and polyoxyethylene sorbitan monolaurate.

Furthermore, a polyoxyalkylene group-containing anionic emulsifier having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in 1 molecule; 1 a reactive anionic emulsifier having an anionic group and a radical polymerizable unsaturated group in the molecule.

Examples of the reactive anionic emulsifier include sodium salts of sulfonic acid compounds having a radical polymerizable unsaturated group such as an allyl group, a methallyl group, (meth) acryloyl group, propenyl group, butenyl group, and ammonium salts of the sulfonic acid compounds.

The amount of the emulsifier used is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more, and furthermore preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less, based on the total amount of all monomers used.

Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, t-butyl peroxide, t-butyl peroxylaurate, t-butyl peroxyisopropylcarbonate, t-butyl peroxyacetate, and diisopropylbenzene hydroperoxide; azo compounds such as azobisisobutyronitrile, azobis (2, 4-dimethylvaleronitrile), azobis (2-methylpropionitrile), azobis (2-methylbutyronitrile), 4' -azobis (4-cyanobutyric acid), dimethyl azobis (2-methylpropionate), azobis [ 2-methyl-N- (2-hydroxyethyl) -propionamide ], azobis { 2-methyl-N- [2- (1-hydroxybutyl) ] -propionamide }; persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate. These polymerization initiators may be used alone in 1 kind or in combination of 2 or more kinds. Further, the polymerization initiator may be used in combination with a reducing agent such as a sugar, sodium formaldehyde sulfoxylate, or an iron complex, if necessary, to prepare a redox initiator.

The amount of the polymerization initiator used is generally preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 5% by mass or less, more preferably 3% by mass or less, based on the total amount of all monomers used. The method of adding the polymerization initiator is not particularly limited, and may be appropriately selected depending on the kind and amount thereof. For example, the monomer mixture or the aqueous medium may be contained in advance, or may be added together during polymerization, or may be added dropwise.

In the case of producing the core-shell type acrylic resin particles (a), it can be obtained by obtaining an emulsion of the core copolymer (I) by emulsion polymerization of a polymerizable unsaturated monomer mixture, adding the polymerizable unsaturated monomer mixture to the emulsion, and further emulsion polymerization thereof to prepare the shell copolymer (II).

The emulsion polymerization for preparing the emulsion of the core copolymer (I) can be carried out by a conventionally known method. For example, the emulsion polymerization can be carried out by emulsion-polymerizing a polymerizable unsaturated monomer mixture in the presence of an emulsifier using a polymerization initiator in the same manner as in the above-mentioned method.

The core-shell acrylic resin particle (a) can be obtained by adding a polymerizable unsaturated monomer mixture to the emulsion of the core copolymer (I) obtained above and further polymerizing the mixture to form a shell copolymer (II).

The monomer mixture for forming the shell-side copolymer (II) may contain, as necessary, the above-mentioned polymerization initiator, chain transfer agent, reducing agent, emulsifier and the like as appropriate. The monomer mixture may be directly added dropwise, but it is preferable to add dropwise a monomer emulsion obtained by dispersing the monomer mixture in an aqueous medium. The particle size of the monomer emulsion in this case is not particularly limited.

The polymerization method of the monomer mixture for forming the shell-side copolymer (II) includes, for example, a method in which the monomer mixture or an emulsion thereof is added to the emulsion of the core-side copolymer (I) and heated to an appropriate temperature while stirring, all or gradually dropped.

The core-shell acrylic resin particle (a) thus obtained has a multilayer structure having the copolymer (I) as a core portion and the copolymer (II) as a shell portion.

Further, the core-shell type acrylic resin particle (a) may be prepared by adding a polymerizable unsaturated monomer (a mixture of 1 or 2 or more species) for forming another resin layer between the step of obtaining the core copolymer (I) and the step of obtaining the shell copolymer (II) and performing emulsion polymerization, thereby obtaining a core-shell type acrylic resin particle having 3 or more layers.

The acrylic resin particle (a) may have at least 1 layer of the gradient polymer layer as needed, and the gradient polymer layer may be any layer of the core-shell type acrylic resin particle (a). The resin layer to be the gradient polymer layer can be prepared by the above dynamic feed polymerization or the like.

From the viewpoint of adhesion and water resistance, the acid value of the acrylic resin particles (A) is in the range of 10 to 100mgKOH/g, preferably 15mgKOH/g or more, more preferably 20mgKOH/g or more, and further preferably 80mgKOH/g or less, more preferably 70mgKOH/g or less.

By adjusting the acid value to 10mgKOH/g or more, the interaction with the aminosilane (B1) contained in the rust inhibitor (B) becomes sufficient, and good adhesion can be achieved. Further, by adjusting the acid value to 100mgKOH/g or less, good water resistance and corrosion resistance can be obtained.

The monomer for imparting an acid value to the acrylic resin particles (a) preferably contains a carboxyl group-containing polymerizable unsaturated monomer from the viewpoint that the neutralizing agent volatilizes, hydrophilicity greatly decreases after film formation, and water resistance and corrosion resistance are favorable.

Acrylic acid and/or methacrylic acid can be particularly suitably used as the carboxyl group-containing polymerizable unsaturated monomer.

In the present specification, the acid value (mgKOH/g) is represented by the mg number of potassium hydroxide when the amount of acid groups contained in sample 1g (solid content 1g in the case of resin) is converted to potassium hydroxide. The molecular weight of potassium hydroxide was set to 56.1.

The acid value was measured in accordance with JIS K-5601-2-1 (1999). The sample was dissolved in a mixed solvent of toluene/ethanol (volume ratio) 2/1, and the solution was titrated with a potassium hydroxide solution using phenolphthalein as an indicator, and the solution was calculated by the following formula.

Acid value (mgKOH/g) is 56.1 XV XC/m

V: titration amount (ml), C: concentration of the titration solution (mol/l), m: weight of solid content (g) of sample

From the viewpoint of water resistance and corrosion resistance without excessively increasing the hydrophilicity of the coating film, it is preferable that 80 mass% or more of the total copolymerized components of the acrylic resin particles (a) be a polymerizable unsaturated monomer having a solubility parameter value (SP value) of 9.5 or less. The polymerizable unsaturated monomer having a solubility parameter value (SP value) of 9.5 or less is preferably 85% by mass or more, more preferably 90% by mass or more of the total copolymerization components.

In the present specification, the solubility parameter value (SP value) is a value calculated by the following Fedors formula described in Polymer Engineering and Science, 14, No.2, p.147 (1974).

(in the formula,. DELTA.e 1 represents cohesive energy per unit functional group, and. DELTA.v 1 represents molecular volume per unit functional group.) the SP values of a copolymer or a blend of a mixture of 2 or more resins are the sum of the values obtained by multiplying the SP values of the monomer units or the components of the blend by mass fraction.

From the viewpoint of hardness and corrosion resistance, the glass transition temperature (Tg) of the acrylic resin particles (a) is preferably-10 ℃ or higher, more preferably 0 ℃ or higher, and even more preferably 10 ℃ or higher.

By setting the glass transition temperature (Tg) to-10 ℃ or higher, the hardness and corrosion resistance of the resulting coating film are improved.

In the present specification, when the resin is a copolymer composed of 2 or more kinds of monomers, the glass transition temperature (Tg, ° c) of the copolymer can be calculated by the following formula.

1/Tg(K)＝(W1/T1)+(W2/T2)+··(Wn/Tn)

Tg(℃)＝Tg(K)-273

In each formula, n represents the number (natural number) of the monomers used, W1 to Wn represents the weight% of each of the n monomers used for copolymerization, and T1 to Tn represents the Tg (K) of each of the homopolymers of the n monomers. T1 to Tn can be values described in Polymer Hand Book (Second Edition, J.Brantup. E.H.Immergut) pages III-139 to 179.

The glass transition temperature (. degree. C.) of the homopolymer of the monomer, when Tg is unknown, can also be determined as the static glass transition temperature by actual measurement. In this case, for example, a sample is taken into a measuring cup by using a differential scanning calorimeter "DSC-220U" (manufactured by セイコーインスツルメント Co.), the sample is completely removed by vacuum-pumping, then the change in heat is measured in the range of-20 ℃ to +200 ℃ at a temperature-raising rate of 3 ℃/min, and the change point of the first base line on the low temperature side is set as the static glass transition temperature.

From the viewpoint of corrosion resistance and water resistance, the weight average molecular weight of the acrylic resin particles (a) is preferably more than 75000, more preferably 90000 or more, and still more preferably 100000 or more.

In the present specification, the weight average molecular weight is a value obtained by converting the retention time measured by gel permeation chromatography into the molecular weight of polystyrene by the retention time of standard polystyrene having a known molecular weight measured under the same conditions.

Specifically, for example, as a gel permeation chromatography apparatus, "HLC-8120 GPC" (product name, manufactured by imperial ソー corporation) was used, as a column, a total of 4 of "TSKgel G4000 HXL" 1, "TSKgel G3000 HXL" 2, and "TSKgel G2000 HXL" 1 (product name, both manufactured by imperial ソー corporation) were used, as a detector, and a differential refractive index meter was used, and in a mobile phase: tetrahydrofuran, measurement temperature: 40 ℃, flow rate: the weight average molecular weight can be determined by measuring under the condition of 1 mL/min.

The average particle diameter of the acrylic resin particles (a) is preferably 50nm or more, more preferably 60nm or more, further preferably 70nm or more, and further preferably 500nm or less, more preferably 400nm or less, further preferably 300nm or less.

By setting the average particle diameter to 50nm or more, the viscosity is not excessively high, and the handling becomes good. Further, dispersion stability is improved by setting the average particle diameter to 500nm or less.

The average particle diameter can be measured by a general measurement means such as laser light scattering.

In the present specification, the average particle diameter of the resin particles is a value measured at 20 ℃ after diluted with deionized water by a conventional method using a submicron particle size distribution measuring apparatus. As the submicron particle size distribution measuring apparatus, for example, "COULTER N4 type" (trade name, manufactured by ベックマン. コールター) can be used.

In order to improve the mechanical stability of the acrylic resin particles (a), the acid groups such as the carboxyl groups of the acrylic resin particles may be neutralized with a neutralizing agent. The neutralizing agent is not particularly limited as long as it can neutralize an acid group, and examples thereof include sodium hydroxide, potassium hydroxide, trimethylamine, 2- (dimethylamino) ethanol, 2-amino-2-methyl-1-propanol, triethylamine, and ammonia. These neutralizing agents can be suitably used in such an amount that the pH of the aqueous dispersion of the neutralized acrylic resin particles (a) becomes about 6.5 to 9.0.

< Rust preventive (B) >

The rust inhibitor (B) contains an aminosilane (B1), an azole compound (B2), and at least 1 compound (B3) selected from a fatty acid, an aromatic acid, and an aliphatic amine (hereinafter, sometimes referred to as "component B1", "(component B2"), and "(component B3"), respectively), and has an effect of improving the corrosion resistance and adhesion of the aqueous coating composition.

The aminosilane (b1) is a silane compound having an amino group, and specific examples thereof include, and bisalkoxysilyl amines such as γ -aminopropyltrimethoxysilane, γ -aminopropyltriethoxysilane, γ -aminopropylmethyldimethoxysilane, γ -aminopropylmethyldiethoxysilane, γ - (2-aminoethyl) aminopropyltrimethoxysilane, γ - (2-aminoethyl) aminopropyltriethoxysilane, γ - (2-aminoethyl) aminopropylmethyldimethoxysilane, N-phenyl- γ -aminopropyltrimethoxysilane, N-benzyl- γ -aminopropyltrimethoxysilane, γ -ureidopropyltrimethoxysilane and the like, bis (trimethoxysilylpropyl) amine, bis (triethoxysilylpropyl) amine and the like.

As the aminosilane (b1), gamma-aminopropyltriethoxysilane can be suitably used from the viewpoint of stability in the production of the coating material.

The azole compound (b2) is a heterocyclic five-membered ring compound containing 1 or more nitrogen atoms, and specific examples thereof include cyclic compounds having 1 nitrogen atom such as pyrrole, cyclic compounds having 2 or more nitrogen atoms such as pyrazole, imidazole, triazole, tetrazole and pentazole,

Oxazole, iso

Cyclic compound having 1 nitrogen atom and 1 oxygen atom such as oxazole, and cyclic compound having 1 nitrogen atom and 1 thiogen such as thiazole or isothiazoleCyclic compounds of the subgroups, and the like.

As the azole compound (b2), triazole and thiazole can be suitably used from the viewpoint of the interaction point with a metal and the acting force.

More specific examples of the azole compound (b2) include benzotriazole, mercaptobenzothiazole, aminotriazole, mercaptobenzothiazole

Oxazoles, mercaptobenzimidazoles, and the like.

Among them, benzotriazole and mercaptobenzothiazole can be particularly suitably used.

The fatty acid is a 1-membered carboxylic acid of a long-chain hydrocarbon among at least 1 compound (b3) selected from the group consisting of a fatty acid, an aromatic acid and an aliphatic amine. The fatty acid is preferably a saturated or unsaturated alkyl carboxylic acid having 8 to 22 carbon atoms, preferably 14 to 22 carbon atoms, from the viewpoint of improving water resistance.

Specific examples of the fatty acid include lauric acid, myristic acid, pentadecanoic acid, palmitic acid, palmitoyl acid (パルミトイル acid), heptadecanoic acid, stearic acid, oleic acid, isooleic acid, linoleic acid, arachidic acid, behenic acid, coconut oil fatty acid, palm oil fatty acid, and beef fat fatty acid.

In the compound (b3), the aromatic acid is a carboxylic acid of an aromatic compound. Specific examples of the aromatic acid include benzoic acid, 4-tert-butylbenzoic acid, aminobenzoic acid, Toluic acid (Toluic acid), ethylbenzoic acid, n-propylbenzoic acid, and n-butylbenzoic acid.

Among the compounds (b3), the aliphatic amine is a linear hydrocarbon having an amino group, and specific examples thereof include alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, triethylamine, octylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, eicosylamine, and docosylamine; hydroxyamines such as N-methylaminoethanol, N-dimethylaminoethanol, N-diethylaminoethanol, 2-amino-2-methylpropanol, diethanolamine, or triethanolamine; and polyamines such as ethylenediamine, diethylenetriamine, and N-octadecylpropane-1, 3-diamine.

Among the above-mentioned aliphatic amines, 1-membered amines having a long-chain alkyl group having 8 or more carbon atoms such as octylamine and octadecylamine can be suitably used from the viewpoint of water resistance.

From the viewpoint of corrosion resistance and water resistance, the rust inhibitor (B) is preferably 0.3 vol% or more, more preferably 0.4 vol% or more, further preferably 0.5 vol% or more, and further preferably 6.0 vol% or less, more preferably 5.0 vol% or less, further preferably 4.0 vol% or less, based on the total solid content of all the components of the aqueous coating composition. By setting the content of the rust inhibitor (B) to 0.3% by volume or more, good corrosion resistance can be obtained, and by setting the content to 6.0% by volume or less, good water resistance can be obtained.

The amount of each component (B1) of the rust inhibitor (B) (component (B1), (component (B2), and (B3)) is preferably 20 mass% or more, more preferably 30 mass% or more, and even more preferably 40 mass% or more, and further preferably 80 mass% or less, more preferably 70 mass% or less, and even more preferably 60 mass% or less, as a solid content, based on the total solid content of the rust inhibitor (B). The component (B2) is preferably 10 mass% or more, more preferably 15 mass% or more, and still more preferably 20 mass% or more, and is preferably 70 mass% or less, more preferably 60 mass% or less, and still more preferably 50 mass% or less as a solid content, based on the total solid content of the rust inhibitor (B). The component (B3) is preferably 10 mass% or more, more preferably 15 mass% or more, and still more preferably 20 mass% or more, and further preferably 70 mass% or less, more preferably 60 mass% or less, and still more preferably 50 mass% or less as a solid content, based on the total solid content of the rust inhibitor (B). These are preferable from the viewpoint of corrosion resistance and adhesion.

< acrylic resin particles (C) >

The aqueous coating composition may contain acrylic resin particles (C) having a weight average molecular weight of 7500 to 75000 and an acid value of 10 to 90mgKOH/g, which are different from the acrylic resin particles (A), for the purpose of improving the film-forming property of the coating film.

The acrylic resin particles (C) are resins that function as film-forming aids, and in the drying process after coating, the acrylic resin particles (C) diffuse with phase transition, filling the voids between the acrylic resin particles (a) that are the matrix resin, and suppressing the formation of voids in the coating film in the drying process. Thus, even when the film forming aid such as a solvent is not contained at all or even when the film forming aid such as a solvent is contained in a small amount, the film forming property at a low temperature can be improved.

The acrylic resin particles (C) can be obtained by using the same polymerization method as that for the acrylic resin particles (a) and appropriately changing the polymerization conditions.

From the viewpoint of adjusting the molecular weight, the acrylic resin particles (C) can be suitably produced by a method of polymerizing in an organic solvent by a solution polymerization method and then dispersing in water to prepare resin particles.

The weight average molecular weight of the acrylic resin particles (C) is 7500-75000, preferably 8000 or more, more preferably 8500 or more, and preferably 30000 or less, more preferably 20000 or less.

When the weight average molecular weight is 7500 or more, corrosion resistance and hardness can be improved, and when the weight average molecular weight is 75000 or less, sufficient diffusibility can be obtained and film forming properties can be improved.

The acid value of the acrylic resin particles (C) is 10 to 90mgKOH/g, preferably 20mgKOH/g or more, more preferably 30mgKOH/g or more, and further preferably 80mgKOH/g or less, more preferably 70mgKOH/g or less.

When the acid value is 10mgKOH/g or more, dispersion stability is good, and when the acid value is 90mgKOH/g or less, good water resistance and excellent corrosion resistance can be obtained.

The glass transition temperature (Tg) of the acrylic resin particles (C) is preferably 0 ℃ or higher, more preferably 10 ℃ or higher, and still more preferably 20 ℃ or higher. By setting the glass transition temperature (Tg) to 0 ℃ or higher, the hardness of the obtained coating film becomes good.

The SP value (solubility parameter value) of the acrylic resin particles (C) is preferably 9.3 or less, and more preferably 9.0 or less. By setting the SP value to 9.3 or less, good water resistance and excellent corrosion resistance can be obtained.

The difference in SP value between the shell portion (outermost surface layer portion) of the acrylic resin particle (a) and the acrylic resin particle (C) is preferably 0.4 or less, more preferably 0.3 or less, even more preferably 0.2 or less, and even more preferably 0.1 or less.

By setting the SP value difference to 0.4 or less, compatibility is good, diffusibility is excellent, and good corrosion resistance can be achieved.

When the aqueous coating composition contains the acrylic resin particles (C), the total solid content is preferably 35% by mass or more of the acrylic resin particles (a), 65% by mass or less of the acrylic resin particles (C), more preferably 40% by mass or more of the acrylic resin particles (a), 60% by mass or less of the acrylic resin particles (C), still more preferably 45% by mass or more of the acrylic resin particles (a), and 55% by mass or less of the acrylic resin particles (C), based on the total solid content of the acrylic resin particles (a) and the acrylic resin particles (C). In addition, the total amount of the solid content is preferably 90% by mass or less of the acrylic resin particles (a) and 10% by mass or more of the acrylic resin particles (C), more preferably 80% by mass or less of the acrylic resin particles (a) and 20% by mass or more of the acrylic resin particles (C), and still more preferably 70% by mass or less of the acrylic resin particles (a) and 30% by mass or more of the acrylic resin particles (C). These are preferable from the viewpoint of corrosion resistance and water resistance.

When the aqueous coating composition contains the acrylic resin particles (C), the method of mixing the acrylic resin particles (a) and the acrylic resin particles (C) is not limited. That is, any of a method of adding the acrylic resin particles (C) to the acrylic resin particles (a) and a method of adding the acrylic resin particles (C) to the acrylic resin particles (a) can be employed.

Further, a method of synthesizing an aqueous emulsion by copolymerizing acrylic resin particles (C) as a protective colloid to obtain a composition in which acrylic resin particles (a) and acrylic resin particles (C) coexist can also be employed.

In the aqueous coating composition, resin particles other than the acrylic resin particles (a) and the acrylic resin particles (C) may be used as necessary. Specifically, examples thereof include, for example, resin particles comprising at least 1 resin selected from the group consisting of acrylic resins, acrylic/styrene resins, urethane resins, phenol resins, vinyl chloride resins, vinyl acetate/acrylic resins, ethylene/vinyl acetate resins, epoxy ester resins, polyester resins, alkyd resins, acrylonitrile/butadiene resins, styrene/butadiene resins, polybutadiene, polyisoprene, silicone resins, fluorine resins, and the like, and resins obtained by modifying these resins, for example, carbonate-modified urethane resins, acrylic resin-modified epoxy resins, alkyd-modified epoxy resins, polybutadiene-modified epoxy resins, (poly) amine-modified epoxy resins, urethane-modified epoxy resins, and the like. These resin particles may be so-called rubber. However, it is different from the acrylic resin particles (A) and (C).

The resin particles may be obtained by blending a plurality of resins, or may be a blend of a plurality of resin particles. These resin particles may be usually incorporated in the composition of the present invention in the form of an emulsion.

From the viewpoint of storage stability of the coating material, the pH of the aqueous coating composition is preferably 5.0 or more, more preferably 6.0 or more, and further preferably 10.0 or less, more preferably 9.0 or less.

The aqueous coating composition may further contain, if necessary, a crosslinking agent, a curing catalyst, a pigment such as a coloring pigment, a filler, an aggregate (aggregate), a dispersant, a wetting agent, a thickener, a rheology control agent, a surface conditioner, an antifoaming agent, an antiseptic, a fungicide, a pH adjuster, a rust inhibitor, a setting inhibitor, an antifreeze, an antiskinning agent, an ultraviolet absorber, an antioxidant, an organic solvent, and the like.

The aqueous coating composition is preferably formed into a cured coating film which is applied to various substrates, preferably metal substrates, which are optionally subjected to a base treatment, and cured. The coating film can be formed by direct coating 1 or 2 or more times by a conventionally known method such as roll coating, spray coating, brush coating, curtain coating, spray coating, dip coating, and the like.

When the substrate is made of metal, a cured coating film is formed by applying the aqueous coating composition according to the present embodiment to the metal substrate and curing the coating film, whereby a coated article having excellent corrosion resistance, adhesion, and water resistance can be obtained.

From the viewpoint of energy saving and the like, the coating film of the aqueous coating composition is preferably cured at normal temperature. In addition, from the viewpoint of improving the production efficiency, the resin composition may be forcibly dried and cured by heating.

The thickness of the cured coating film obtained by applying and curing the aqueous coating composition is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 25 μm or more, and further preferably 200 μm or less, more preferably 100 μm or less, even more preferably 60 μm or less, from the viewpoint of the corrosion resistance, water resistance, hardness, and the like of the cured coating film formed.

Examples

The present invention will be described in more detail below with reference to production examples, examples and comparative examples. However, the present invention is not limited thereto. In each example, "part" and "%" are based on mass unless otherwise specified. Further, the film thickness of the coating film is based on the cured coating film. The blank column in the table indicates that the component is not contained.

< production of acrylic resin particles >

Production example 1

Deionized water (DIW) charged in an amount shown in table 1 (shi Write み) and Newcol (registered trademark) 707SF (trade name, manufactured by japan emulsifier corporation, anionic surfactant, solid content 30 mass%) were charged into a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser, and the temperature was raised after sufficient replacement with nitrogen gas. The internal temperature was maintained at 82 ℃ while stirring at about 100rpm, and a substance obtained by emulsifying the component (a1) shown in table 1 using a homomixer (hereinafter referred to as a (a1) component emulsion, similarly as to the component (a2), the component (B1) and the component (B2), and an aqueous solution of initiator 1 (in table 1, VA-057 is a trade name, fuji フィルム and 2-2' -azobis [ N- (2-carboxyethyl) -2-methylpropanediamine ] tetrahydrate salt, manufactured by optometria) were added dropwise over 3 hours, and polymerized. After completion of the dropwise addition, the reaction was carried out at 82 ℃ for 0.5 hour, and an aqueous solution of initiator 2 was added dropwise over 0.5 hour. After the end of the dropwise addition, the reaction was carried out at 82 ℃ for 1.5 hours and then cooled to 25 ℃. Finally, the neutralizing agent shown in Table 1 was added to obtain an emulsion of resin particles (A-1) (acid value: 34mgKOH/g, SP value: 9.5 or less, monomer ratio: 95% by mass, single layer homogeneous composition particles) having a solid content mass concentration of 40.0%.

Production example 2

A polymerization apparatus equipped with a stirrer, a thermometer and a reflux condenser was charged with deionized water and Newcol707SF in amounts shown in Table 1 (Shi Write み), and the contents were sufficiently replaced with nitrogen gas, followed by heating. While the internal temperature was maintained at 82 ℃ with stirring at about 100rpm, an aqueous solution of initiator 1 and a substance obtained by emulsifying component (a1) shown in table 1 using a homomixer was added dropwise to the mixture, and polymerization was carried out. Regarding the dropping speed, the emulsion of the component (A1) was set to about 146.0 parts/hr, and the aqueous solution of the initiator 1 was set to about 6.6 parts/hr. At the same time as the completion of the dropwise addition of the emulsion of component (a1), the emulsion of component (B1) shown in table 1 was started to be added dropwise at about 146.0 parts/hour. After completion of the dropwise addition, the reaction was carried out at 82 ℃ for 0.5 hour, and an aqueous solution of initiator 2 was added dropwise at about 3.3 parts/hour. After the end of the dropwise addition, the reaction was carried out at 82 ℃ for 1.5 hours and then cooled to 25 ℃. Finally, the neutralizing agent shown in Table 1 was added to obtain an emulsion of resin particles (A-2) (acid value 17mgKOH/g, monomer ratio of SP value 9.5 or less 98% by mass, core layer/shell layer mass ratio 50/50 (no gradient polymer layer)) having a solid content mass concentration of 40.0%.

Production example 3

A polymerization apparatus equipped with a stirrer, a thermometer and a reflux condenser was charged with deionized water and Newcol707SF in amounts shown in Table 1 (Shi Write み), and the contents were sufficiently replaced with nitrogen gas, followed by heating. The internal temperature was maintained at 82 ℃ while stirring at about 100rpm, and an aqueous solution of initiator 1 and a substance obtained by emulsifying component (a1) shown in table 1 (hereinafter referred to as a component (a1) emulsion, similarly as described for component (a2), component (B1) and component (B2)) was added dropwise to the mixture and polymerized. Regarding the dropping speed, the emulsion of the component (A1) was set to about 146.0 parts/hr, and the aqueous solution of the initiator 1 was set to about 6.6 parts/hr. At the same time as the completion of the addition of the (a1) component emulsion, the addition of the (a2) component emulsion shown in table 1 was started. At the same time, the (B1) component emulsion shown in table 1 was added dropwise to the (a2) component emulsion. (B1) The dropping rate of the component emulsion was set to a rate at which the dropping of the component emulsion (a2) was completed simultaneously with the completion of the dropping, that is, about 73.0 parts/hour in this example. Then, the component emulsion (B2) was added dropwise at about 146.0 parts/hour. After completion of the dropwise addition, the reaction was carried out at 82 ℃ for 0.5 hour, and an aqueous solution of initiator 2 was added dropwise at about 3.3 parts/hour. After the end of the dropwise addition, the reaction was carried out at 82 ℃ for 1.5 hours and then cooled to 25 ℃. Finally, the neutralizing agent shown in table 1 was added to obtain an emulsion of resin particles (a-3) (acid value 17mgKOH/g, monomer ratio 98% by mass of SP value 9.5 or less, shell SP value 8.85, core layer (homogeneous layer/gradient polymer layer)/shell layer mass ratio 75 (25/50)/25) having a solid content mass concentration of 40.0%.

Production examples 4 to 7

Each acrylic resin particle (a-4) to (a-7) (all core layers (═ uniform layer/gradient polymer layer)/shell layers mass ratio of 75(═ 25/50)/25) was obtained in the same manner as in production example 3, except that the compounding composition was changed to the compounding composition shown in table 1 in production example 3. The SP value of the shell portion of the acrylic resin particle (A-4) of production example 4 was 9.37. The acrylic resin particles (A-5), (A-6) and (A-7) were those for comparative examples.

Table 1 shows the acid value, the monomer ratio (mass%) of an SP value of 9.5 or less, and the weight average molecular weight of each acrylic resin particle (a), and the pH (measured by a pH meter), the viscosity (measured by a B-type viscometer at 60rpm, 20 ℃) and the average particle diameter of the emulsion of each acrylic resin particle (a).

TABLE 1

< production of anticorrosive agent >

Production example 8

To a beaker, 186 parts of ethylene glycol monobutyl ether, 50 parts of KBE-903 (trade name, manufactured by shin-Etsu chemical Co., Ltd., gamma-aminopropyltriethoxysilane, solid content 100%), 30 parts of benzotriazole and 20 parts of palmitic acid were added and dissolved by stirring to obtain a rust inhibitor (B-1) solution having a solid content of 35 mass%.

Production examples 9 to 20

A solution of each of corrosion inhibitors (B-2) to (B-13) having a solid content of 35 mass% was obtained in the same manner as in production example 8 except that the formulation composition in production example 8 was changed to the formulation shown in Table 2. Further, the rust inhibitors (B-2) to (B-5) were dissolved by stirring and then subjected to heat treatment at 80 ℃ for 8 hours. Further, rust inhibitors (B-8) to (B-13) were used in comparative examples. In Table 2, the component (b-1) corresponds to aminosilane (b1), the component (b-2) corresponds to azole compound (b2), and the component (b-3) corresponds to at least 1 compound (b3) selected from the group consisting of fatty acids, aromatic acids, and aliphatic amines.

TABLE 2

< production of acrylic resin particles (C) >

Production example 21

After a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen gas inlet tube, and a dropping device was charged with 20 parts of ethylene glycol monobutyl ether and 14 parts of propylene glycol monomethyl ether and heated to 115 ℃, 5.5 parts of a mixture of 20 parts of styrene, 20 parts of n-butyl acrylate, 19 parts of methyl methacrylate, 35 parts of isobutyl methacrylate, 5 parts of acrylic acid, 1 part of methacrylic acid, 15 parts of propylene glycol monomethyl ether, and パーブチル O (registered trademark) (trade name, manufactured by nippon oil co., polymerization initiator, solid content 100%) was dropped over 4 hours, and after completion of the dropping, the mixture was aged for 1 hour. Then, a mixture of 5 parts of propylene glycol monomethyl ether and 0.5 part of パーブチル O was further added dropwise over 1 hour, followed by aging for 1 hour after the completion of the addition. To the obtained acrylic resin, aqueous ammonia (solid content: 25%) was added, and after equivalent neutralization, deionized water was added with stirring to disperse the resin. Subsequently, the sol was removed under reduced pressure to remove propylene glycol monomethyl ether, and deionized water was added again to obtain an acrylic resin particle (C-1) dispersion having a solid content of 30 mass%. The weight-average molecular weight of the acrylic resin particles (C-1) thus obtained was 20000, the acid value was 45mgKOH/g, the SP value was 8.98, and the average particle diameter was 160 nm.

< production of Water-based coating composition >

Example 1

3 parts of DISPERBYK (registered trademark) -190 (trade name, BYK Co., Ltd., pigment dispersant, solid content 40%) (solid content 1.2 parts), 0.4 part of BYK (registered trademark) -024 (trade name, BYK Co., Ltd., antifoaming agent, solid content 100%), 35 parts of JR-603 (trade name, テイカ Co., titanium oxide, solid content 100%), 15 parts of スーパー SS (trade name, manufactured by pill tail カルシウム Co., calcium carbonate, solid content 100%), 25 parts of deionized water and 2 parts of dipropylene glycol monomethyl ether were mixed and added with glass beads, and then dispersed for 60 minutes by a paint shaker (paint) to obtain a pigment dispersion (P1) (solid content 64.2%).

After removing the glass beads, 250 parts (100 parts as a solid content) of the emulsion of the resin particles (A-1) obtained in production example 1, 5.7 parts (2.0 parts as a solid content) of the solution of the rust inhibitor (B-1) obtained in production example 8, 0.5 parts of BYK-348 (product name, BYK, 100% as a surface conditioner), and 2.5 parts (0.5 parts as a solid content) of SN シックナー 660T (product name, サンノプコ, 20% as a thickener) were mixed and stirred with 80 parts (51 parts as a solid content) of the pigment dispersion (P1) obtained, thereby obtaining an aqueous coating composition No.1 having a coating solid content of 46% by mass and a pH of 8.9.

Examples 2 to 15 and comparative examples 1 to 9

Water-based coating compositions Nos. 2 to 24 were obtained in the same manner as in example 1, except that the blending composition in example 1 was changed to the blending compositions shown in tables 3 and 4.

Also shown in tables 3 and 4 are the difference in SP value between the shell portion (the difference in SP value between the shell portion of the acrylic resin particle (A) and the acrylic resin particle (C)) and the concentration (vol%) of the rust inhibitor (B).

< preparation of test plate >

The respective aqueous coating compositions Nos. 1 to 24 obtained in examples 1 to 15 and comparative examples 1 to 9 were coated on a cold-rolled steel sheet (base material) of 70mm X150 mm X0.8 mm which had been subjected to polishing and degreasing, respectively, using air blasting so that the thickness of the cured coating film became 40 μm. Next, the steel sheet was left at 23 ℃ and 65% RH for 7 days to obtain each test piece having a cured coating film formed thereon.

< evaluation of test plate >

The following tests were carried out on each of the test panels obtained. The evaluation results are shown in tables 3 and 4.

Corrosion resistance: a240-hour salt spray resistance test was performed on each test panel by causing a cross-cut to the coating film with a knife so as to reach the base material in accordance with JIS K5600-7-1 (1999) "mist spray resistance (mist spray resistance with neutral salt spray)". The scale and the bulge width due to the cut were evaluated according to the following criteria. The smaller the maximum width of rust and bulge, the more excellent the corrosion resistance, and if evaluated as a to C, the corrosion resistance was good.

A: the maximum amplitude of rust and swelling is less than 1mm (single side) from the cutting part

B: the maximum range of rust and swelling is more than 1mm and less than 2mm (single side)

C: the maximum range of rust and swelling is more than 2mm and less than 3mm (single side)

D: the maximum width of rust and swelling is more than 3mm and less than 5mm (single side)

E: the maximum range of rust and swelling is more than 5mm (single side) from the cutting part

Water resistance: each test piece was immersed in deionized water at 40 ℃ for 48 hours, and the coated surface was evaluated according to the following criteria. The water resistance was good if the evaluation was ∈ or ≈ o.

Very good: good and no problem.

O: while dullness of gloss was slightly observed (ツヤビケ) it was a practical level.

And (delta): either swelling or dullness was observed.

X: either swelling or dullness was significantly observed.

Initial adhesion: the coating film of each test plate was subjected to a cutting operation using a cutter so as to reach the substrate, and 100 checkerboards 2mm × 2mm in size were prepared. The number of the coated checkerboard films remaining after the adhesive tape was rapidly peeled off at 20 ℃ was examined. The evaluation was performed according to the criteria shown below, and if the obtained result was |. or |. o, the initial adhesion was good.

Very good: the checkerboard coating film remained 100, and the edges of the cuts made by the cutter were also smooth.

O: the checkerboard coating film remained 100, but small peeling of the coating film occurred at the intersection of the cuts of the cutter.

And (delta): 99-81 checkerboard coating films remain.

X: the number of the remaining checkerboard coating films is 80 or less.

Water-resistant adhesion: each test panel was immersed in warm water at 40 ℃ for 1 day, extracted, dried at room temperature for 12 hours, and then subjected to a checkerboard test and evaluation in the same manner as in the initial adhesion test. The water-resistant adhesion was good if the evaluation was ∈ or ≈ o.

Although the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be added without departing from the spirit and scope thereof. The present application is based on japanese patent application filed on 8/2/2018 (japanese patent application 2018-145728), the content of which is incorporated herein by reference.

Industrial applicability

According to the present invention, an aqueous coating composition excellent in corrosion resistance, adhesion and water resistance can be provided.

Claims

1. An aqueous coating composition comprising acrylic resin particles A and a rust inhibitor B,

the acrylic resin particles A have an acid value of 10 to 100mgKOH/g, and 80% by weight or more of the total copolymerized components are polymerizable unsaturated monomers having a solubility parameter value of 9.5 or less,

the rust inhibitor B contains aminosilane B1, azole compound B2, and at least 1 compound B3 selected from fatty acid, aromatic acid and aliphatic amine.

2. The aqueous coating composition according to claim 1, wherein the acrylic resin particles A are core-shell type acrylic resin particles.

3. The aqueous coating composition according to claim 1 or 2, the acrylic resin particles a being acrylic resin particles having a gradient polymer layer.

4. The aqueous coating composition according to claim 1 or 2, further comprising acrylic resin particles C, wherein the acrylic resin particles C have a weight average molecular weight of 7500 to 75000 and an acid value of 10 to 90mgKOH/g, and are different from the acrylic resin particles A.

5. The aqueous coating composition according to claim 3, further comprising acrylic resin particles C, wherein the acrylic resin particles C have a weight average molecular weight of 7500 to 75000 and an acid value of 10 to 90mgKOH/g, and are different from the acrylic resin particles A.

6. A coated article having:

a base material, and

a cured coating film of the aqueous coating composition according to any one of claims 1 to 5 on the substrate.

7. The coated article according to claim 6, wherein the substrate is a metal substrate.