WO2020022077A1

WO2020022077A1 - Water-based paint composition

Info

Publication number: WO2020022077A1
Application number: PCT/JP2019/027451
Authority: WO
Inventors: 岳富森; 麗了江森
Original assignee: 関西ペイント株式会社
Priority date: 2018-07-27
Filing date: 2019-07-11
Publication date: 2020-01-30
Also published as: JPWO2020022077A1; JP7280263B2; CN112368345A

Abstract

The purpose of the present invention is to provide a water-based paint composition having excellent film-forming properties at low temperatures, and having superior corrosion resistance, hardness, and water resistance. The present invention pertains to a water-based paint composition that contains core-shell acrylic resin particles (A) including at least one gradient polymer layer, in which the acid value of the shell parts of the core-shell acrylic resin particles (A) is within the range of 20-100 mg KOH/g.

Description

Aqueous paint composition

The present invention relates to a water-based coating composition which has good film-forming properties at low temperatures and also has excellent corrosion resistance, hardness and water resistance. The present invention also relates to a coated article having a cured coating film of the aqueous coating composition.

In recent years, from the viewpoints of global environmental protection and health and safety, conversion from solvent-based paints to water-based paints has been promoted, and water-based anticorrosive paints have been developed in the field of anticorrosive paints such as metal substrates.

Emulsion paints are the mainstream in water-based paints.Emulsion paints have a much lower solvent content than solvent-based paints, but in order to improve the film-forming properties, they are water-based, but have a considerable amount as a film-forming aid. The fact is that the solvent is contained in the paint.

As a method of improving the film forming property without using a film forming aid (solvent), there is a method of softening the emulsion resin, but the hardness of the obtained coating film is reduced, and the coating film performance such as anti-corrosion property is obtained. Also decrease.

Patent Document 1 discloses a first ethylenically unsaturated compound component (A) in which the glass transition temperature of a polymer is −30 ° C. or less, and a second ethylenic unsaturated compound component in which the glass transition temperature of a polymer is 30 ° C. or more. There is disclosed a method for producing an aqueous emulsion, which comprises subjecting an unsaturated compound component (B) to power feed polymerization in an aqueous medium under specific polymerization conditions. The aqueous emulsion obtained by the production method has good low-temperature film-forming properties without using a solvent such as a film-forming auxiliary, has a low tackiness on the surface of the obtained resin film, and has excellent durability. Has been described.

Japanese Patent Laid-Open No. 2000-319301

However, in the aqueous emulsion obtained by the production method, although low-temperature film formability and tackiness are improved, the hardness of the obtained coating film is insufficient, and improvement is desired.

The present invention has been made in view of the above circumstances, has an object to provide a water-based coating composition having good film-forming properties at low temperatures, and excellent corrosion resistance, hardness and water resistance. is there.

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that an aqueous paint containing core-shell type acrylic resin particles containing at least one gradient polymer layer and having a shell portion having an acid value in a specific range. According to the composition, it has been found that the above object can be achieved.

That is, the present invention includes the following embodiments.
(1) containing core-shell type acrylic resin particles (A) including at least one gradient polymer layer,
An aqueous coating composition, wherein the shell part of the core-shell type acrylic resin particles (A) has an acid value in the range of 20 to 100 mgKOH / g.

(2) The aqueous coating composition according to (1), wherein the core-shell type acrylic resin particles (A) have a glass transition temperature of −10 ° C. or higher.

(3) The polymerizable unsaturated monomer according to (1) or (2), wherein at least 80% by weight of all copolymerized components of the core-shell type acrylic resin particles (A) is a polymerizable unsaturated monomer having a solubility parameter value of 9.5 or less. An aqueous coating composition as described in the above.

(4) A coated article having a substrate and a cured coating film of the aqueous coating composition according to any one of (1) to (3) on the substrate.

塗装 The coated article according to (4), wherein the base is a metal base.

水性 The aqueous coating composition of the present invention having the above characteristics can form a coating film having good low-temperature film-forming properties and excellent corrosion resistance, hardness and water resistance.

Hereinafter, the aqueous coating composition of the present invention will be described in more detail. In this specification, the terms "% by mass" and "% by weight" and "parts by mass" and "parts by weight" have the same meanings.

The aqueous coating composition according to the present invention contains core-shell type acrylic resin particles (A) including at least one gradient polymer layer, and the shell part of the core-shell type acrylic resin particles (A) has an acid value of 20 to 100 mg KOH. / G range.

In the present embodiment, the “shell” of the core-shell type acrylic resin particles (A) means a polymer layer present in the outermost layer of the resin particles, and the “core” is a polymer of the inner layer of the resin particles excluding the shell. The term “core-shell structure” means a structure having the above-mentioned core part and shell part.

The core-shell structure generally has 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 and the shell portion, the amount of monomer in the shell portion forms the layer structure. In some cases, it may not be enough. In such a case, it is not necessary to have a complete layer structure as described above, and a structure in which a shell part covers a part of the core part may be used.

概念 The concept of the multilayer structure in the core-shell type structure also applies to the case where the core-shell type acrylic resin particles (A) have a multilayer structure in the core.

において In the present embodiment, the gradient polymer layer means a polymer layer having a layer structure in which the composition changes continuously (has a composition gradient).

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

The gradient polymer layer can be generally obtained by a known polymerization method called power feed polymerization. Specifically, for example, when a polymerization reaction of two types of monomer A (monomer mixture A) and monomer B (monomer mixture B) is performed, monomer B (monomer mixture B) is converted to monomer A (monomer mixture A). The monomer A (monomer mixture A) is introduced into the reaction vessel while being dropped into the container to be accommodated, and a polymerization reaction is carried out, whereby a gradient polymer layer can be obtained.

In the above power feed polymerization, the synthesis conditions (timing of the start of mixing of the monomer A (monomer mixture A) and the monomer B (monomer mixture B), the container containing the monomer A (monomer mixture A) with the monomer B (monomer mixture B) A gradient polymer layer having a desired composition gradient can be obtained by, for example, setting the rate at which the monomer A (monomer mixture A) is introduced into the reaction vessel and the rate at which the monomer A (monomer mixture A) is introduced into the reaction vessel.

The core-shell type acrylic resin particles (A) have at least one gradient polymer layer, and the gradient polymer layer can be any layer in the core-shell type acrylic resin particles (A).

The core-shell type acrylic resin particles (A) are usually a copolymer (I) containing a polymerizable unsaturated monomer as a copolymer component and a copolymer (II) containing a polymerizable unsaturated monomer as a copolymer component. ) Is an acrylic resin particle comprising a shell portion. The polymerizable unsaturated monomer means a monomer having a polymerizable unsaturated group.

重合 In the present specification, the polymerizable unsaturated group means an unsaturated group capable of undergoing radical polymerization. Examples of the polymerizable unsaturated group include a vinyl group, a vinylidene group, an acryloyl group, and a methacryloyl group.

In this specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylic acid” means “acrylic acid or methacrylic acid”. Further, “(meth) acryloyl” means “acryloyl or methacryloyl”. “(Meth) acrylamide” means “acrylamide or methacrylamide”.

Examples of the polymerizable unsaturated monomer include a polymerizable unsaturated monomer having one polymerizable unsaturated group in one molecule and a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule. it can.

Examples of the polymerizable unsaturated monomer having one polymerizable unsaturated group in one molecule include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and i-propyl (meth) acrylate , N-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-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, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) ) Acri Alkyl or cycloalkyl (meth) acrylate such as tert-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, and tricyclodecanyl (meth) acrylate; polymerization having an isobornyl group such as isobornyl (meth) acrylate Polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; polymerizable unsaturated monomer having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate; benzyl (meth) ) Aromatic ring-containing polymerizable unsaturated monomers such as acrylate, styrene, α-methylstyrene and vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxy Polymerizable unsaturated monomers having an alkoxysilyl group such as propyltrimethoxysilane and γ- (meth) acryloyloxypropyltriethoxysilane; and perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate Fluoroalkyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group; N-vinylpyrrolidone, ethylene, butadiene, chloroprene , Vinyl compounds such as vinyl propionate and vinyl acetate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) Monoester product of (meth) acrylic acid such as acrylate and dihydric alcohol having 2 to 8 carbon atoms, ε-caprolactone modified product of the monoester product, N-hydroxymethyl (meth) acrylamide, allyl alcohol, molecular terminal A hydroxyl group-containing polymerizable unsaturated monomer such as (meth) acrylate having a polyoxyethylene chain having a hydroxyl group; a carboxyl group-containing polymerizable unsaturated monomer such as (meth) acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate Monomers: (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, glycidyl (meth) ) Acrylates and amines Nitrogen-containing polymerizable unsaturated monomers such as adducts; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate And epoxy-containing polymerizable unsaturated monomers such as 3,4-epoxycyclohexylpropyl (meth) acrylate and allyl glycidyl ether; and (meth) acrylates having a polyoxyethylene chain whose molecular terminal is an alkoxy group. .

These monomers can be used alone or in combination of two or more, depending on the performance required for the core-shell type acrylic resin particles (A).

Examples of the polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule include allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol. Di (meth) acrylate, 1,3-butylene glycol 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 di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol di (meth) acrylate, 1,1,1-trishydroxymethylethanedi (meth) acryl 1,1,1-trishydroxymethylethanetri (meth) acrylate, 1,1,1-trishydroxymethylpropanetri (meth) acrylate, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, triallyl Examples include isocyanurate, diallyl terephthalate, and divinylbenzene. These monomers can be used alone or in combination of two or more.

重合 The polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule has a function of imparting a crosslinked structure to the copolymer. When a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule is used, the proportion of the polymerizable unsaturated monomer can be appropriately determined according to the degree of crosslinking of the copolymer. It is preferably at least 0.1% by mass based on the total amount of the polymerizable unsaturated monomer having two or more saturated groups in one molecule and the polymerizable unsaturated monomer having one polymerizable unsaturated group in one molecule, 0.5% by mass or more is more preferable, 1% by mass or more is more preferable, 30% by mass or less is preferable, 10% by mass or less is more preferable, and 7% by mass or less is further preferable.

The core-shell type acrylic resin particles (A) are obtained by emulsion-polymerizing the polymerizable unsaturated monomer mixture to obtain an emulsion of the core copolymer (I), and then adding the polymerizable unsaturated monomer mixture to the emulsion. , And emulsion polymerization to prepare a shell copolymer (II).

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

アニオン As the emulsifier, an anionic emulsifier and a nonionic emulsifier can be suitably used.

アニオン Examples of the anionic emulsifier include sodium salts and ammonium salts of alkylsulfonic acid, alkylbenzenesulfonic acid, alkylphosphoric acid and the like. Examples of nonionic emulsifiers include, for example, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonyl phenyl ether, and polyoxyethylene nonyl phenyl ether. Ethylene octyl phenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, etc. be able to.

A polyoxyalkylene group-containing anionic emulsifier having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule; an anionic group and a radical polymerizable unsaturated molecule in one molecule; It is also possible to use reactive anionic emulsifiers having groups.

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

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

Examples of the polymerization initiator include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butylperoxylaurate, and tert-butylperoxy. Organic peroxides such as isopropyl carbonate, tert-butylperoxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobis (2-methylpropionnitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2-hydridene) Azo compounds such as xyethyl) -propionamide] and azobis {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate; Can be mentioned. These polymerization initiators can be used alone or in combination of two or more. Further, if necessary, a reducing agent such as sugar, sodium formaldehyde sulfoxylate, iron complex or the like may be used in combination with the polymerization initiator to form a redox initiator.

In general, the amount of the polymerization initiator used is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass or less, based on the total amount of all the monomers used. It is more preferably at most 3% by mass. The method of adding the polymerization initiator is not particularly limited, and can be appropriately selected according to the type and amount of the polymerization initiator. For example, it can be previously contained in a monomer mixture or an aqueous medium, can be added at a time during polymerization, or can be added dropwise.

The core-shell type acrylic resin particles (A) are obtained by adding a polymerizable unsaturated monomer mixture to the emulsion of the core copolymer (I) obtained above and further polymerizing to form a shell copolymer (II). Can be obtained by:

モノマー The monomer mixture forming the shell copolymer (II) may appropriately contain components such as the polymerization initiator, the chain transfer agent, the reducing agent, and the emulsifier, if necessary. Further, the monomer mixture can be dropped as it is, but it is preferable to drop the monomer mixture as a monomer emulsion obtained by dispersing the monomer mixture in an aqueous medium. In this case, the particle size of the monomer emulsion is not particularly limited.

As a method for polymerizing the monomer mixture forming the shell copolymer (II), for example, the monomer mixture or an emulsion thereof is dropped at once or gradually, and an emulsion of the core copolymer (I) is obtained. And heating the mixture to an appropriate temperature with stirring.

The core-shell type acrylic resin particles (A) thus obtained have a multilayer structure having the copolymer (I) as a core and the copolymer (II) as a shell.

In addition, the core-shell type acrylic resin particles (A) are polymerizable non-polymerizable particles which form another resin layer between the step of obtaining the core copolymer (I) and the step of obtaining the shell copolymer (II). By adding a step of supplying a saturated monomer (one or a mixture of two or more) to carry out emulsion polymerization, acrylic resin particles comprising three or more layers can be obtained.

The core-shell type acrylic resin particles (A) are resin particles including at least one gradient polymer layer, and the gradient polymer layer can be any layer in the core-shell type acrylic resin particles (A).

樹脂 The resin layer to be used as the gradient polymer layer can be prepared by the above-described power feed polymerization or the like.

The ratio of the gradient polymer layer in the core-shell type acrylic resin particles (A) is 10% with respect to the total amount of all the copolymerized components of the core-shell type acrylic resin particles (A) from the viewpoint of the corrosion resistance and hardness of the obtained coating film. % By mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.
By setting the ratio to 90% by mass or less, a layer other than the gradient polymer layer in the core-shell type acrylic resin particles (A) is present in a certain degree or more, and a certain degree of hardness can be maintained by the presence of the hard monomer component. . When the content is 10% by mass or more, excellent film-forming properties and good anticorrosion properties can be obtained.

In the core-shell type acrylic resin particles (A), the acid value of the shell portion (shell portion copolymer (II) (outermost layer)) is preferably 20 mgKOH / g or more from the viewpoint of the dispersion stability of the particles and the hydrophilicity of the coating film. , 25 mgKOH / g or more, more preferably 30 mgKOH / g or more, further preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less, and even more preferably 60 mgKOH / g or less.

When the acid value of the shell portion is 20 mgKOH / g or more, the dispersion stability of the particles becomes good, and when the acid value is 100 mgKOH / g or less, the hydrophilicity of the coating film becomes too high to prevent corrosion and water resistance. Can be prevented from becoming defective.

As a monomer for imparting an acid value to the shell copolymer (II), from the viewpoint that the neutralizing agent is volatilized, the hydrophilicity is greatly reduced after forming a film, and the water resistance and the corrosion resistance are advantageous. And a carboxyl group-containing polymerizable unsaturated monomer.

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

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

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

Acid value (mgKOH / g) = 56.1 × V × C / m
V: titration (ml), C: concentration of titrant (mol / l), m: solid weight of sample (g)

The glass transition temperature (Tg) of the core-shell type acrylic resin particles (A) is preferably −10 ° C. or higher, more preferably −5 ° C. or higher, and further preferably 0 ° C. or higher, from the viewpoint of coating film hardness.
By setting the glass transition temperature (Tg) to -10 ° C. or higher, it is possible to prevent a decrease in the hardness of the obtained coating film and to maintain the trace resistance.

In the present specification, when the resin is a copolymer composed of two or more monomers, the glass transition temperature (Tg, ° C) of the copolymer can be calculated by the following equation.
1 / Tg (K) = (W1 / T1) + (W2 / T2) +... (Wn / Tn)
Tg (° C.) = Tg (K) -273
In each formula, n represents the number of types of monomers used (natural number), W1 to Wn are the weight percentages of the n monomers used in the copolymerization, and T1 to Tn are the weights of the n monomers. Represents the respective Tg (K) of the homopolymer. For T1 to Tn, the values described in Polymer Hand Book (Second Edition, edited by J. Brandup, EH Immergut), pages III-139 to 179, can be used.

ガラス In addition, the glass transition temperature (° C.) when the Tg of the homopolymer of the monomer is not clear can be determined as a static glass transition temperature by actual measurement. In this case, for example, using a differential scanning calorimeter “DSC-220U” (manufactured by Seiko Instruments Inc.), a sample is taken in a measurement cup, and the solvent is completely removed by vacuum suction. The calorie change is measured at a temperature rate in the range of −20 ° C. to + 200 ° C., and the first baseline change point on the low temperature side is defined as a static glass transition temperature.

Further, the core-shell type acrylic resin particles (A) have 80% by mass or more of all copolymer components (all polymerizable unsaturated monomers constituting the core copolymer (I) and the shell copolymer (II)). It is preferable that the polymerizable unsaturated monomer has a solubility parameter value (SP value) of 9.5 or less from the viewpoints of corrosion resistance and water resistance of the obtained coating film. The polymerizable unsaturated monomer having a solubility parameter value (SP value) of 9.5 or less is more preferably 90% by mass or more, more preferably 95% by mass or more of all copolymerized components.

において In the present specification, the solubility parameter value (SP value) is as defined in Polymer {Engineering and} Science, 14, No. 2, p. 147 (1974), calculated by the following Fedors equation.

SP = {(Δe1) / {(Δv1)}
(In the formula, Δe1 represents the aggregation energy per unit functional group, and Δv1 represents the molecular volume per unit functional group.) The SP value of a copolymer or a blend of a mixture of two or more resins is as follows: , And a value obtained by multiplying the SP value of each component of the monomer unit or the blend by the mass fraction.

{Circle around (4)} The core-shell type acrylic resin particles (A) preferably have a weight average molecular weight of 40,000 or more from the viewpoints of corrosion resistance, water resistance and hardness of the resulting coating film.

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

Specifically, for example, “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and one “TSKgel @ G4000HXL” and two “TSKgel @ G3000HXL” are used as columns. , And one TSKgel @ G2000HXL (trade name, all manufactured by Tosoh Corporation) using a differential refractometer as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., The weight average molecular weight can be determined by measuring the flow rate under the condition of 1 mL / min.

(4) The average particle size of the core-shell type acrylic resin particles (A) is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 70 nm or more, preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less.

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

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

において In the present specification, the average particle size of the resin particles is a value measured at 20 ° C. after dilution with deionized water by a conventional method using a submicron particle size distribution analyzer. As the submicron particle size distribution measuring device, for example, "COULTER @ N4 type" (trade name, manufactured by Beckman Coulter, Inc.) can be used.

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

樹脂 Resin particles other than the core-shell type acrylic resin particles (A) can be used in the water-based coating composition as needed. Specifically, for example, acrylic resin, acrylic / styrene resin, urethane resin, phenol resin, vinyl chloride resin, vinyl acetate resin, vinyl acetate / acrylic resin, ethylene / vinyl acetate resin, epoxy resin, epoxy ester resin, polyester resin , Alkyd resin, acrylonitrile / butadiene resin, styrene / butadiene resin, polybutadiene, polyisoprene, silicone resin, fluororesin, etc., and those obtained by modifying these resins, for example, carbonate-modified urethane resin, acrylic resin-modified epoxy resin, Resin particles composed of at least one resin selected from alkyd-modified epoxy resin, polybutadiene-modified epoxy resin, (poly) amine-modified epoxy resin, and urethane-modified epoxy resin can be given. These resin particles may be so-called rubber. However, the core-shell type acrylic resin particles (A) are excluded.

In the case where the resin particles are resin particles composed of a plurality of resins, the resin particles may be blended into a plurality of resin particles to form resin particles, or may be a blend of a plurality of types of resin particles. These resin particles can be usually blended in the form of an emulsion into the aqueous coating composition.

From the viewpoint of the storage stability of the paint, the aqueous paint composition preferably has a pH of 5.0 or more, more preferably 6.0 or more, and preferably 10.0 or less, more preferably 9.0 or less.

In addition, the aqueous coating composition may contain a crosslinking agent, a curing catalyst, a pigment such as a coloring pigment, a filler, an aggregate, a dispersant, a wetting agent, a thickener, a rheology control agent, a surface conditioning agent, It can also contain foaming agents, preservatives, fungicides, pH adjusters, rust inhibitors, anti-settling agents, anti-freezing agents, anti-skinning agents, ultraviolet absorbers, antioxidants, organic solvents and the like.

It is preferable that the water-based coating composition is a cured coating film which is applied and cured on various substrates, preferably a metal substrate, as required. The coating can be applied once or twice or more by a conventionally known method such as roller coating, spray coating, brush coating, curtain coating, shower coating, dip coating, etc. to form a coating film.

When the base material is a metal base material, the water-based coating composition according to the present embodiment is applied on the metal base material, and by forming a cured coating film by effect, the film forming property at low temperatures is good, A coated article having excellent anticorrosion properties can be obtained.

塗膜 The coating film of the water-based coating composition is preferably cured at room temperature from the viewpoint of energy saving and the like. In addition, from the viewpoint of improving the production efficiency, forced drying or heat curing can also be performed.

Further, the thickness of the cured coating film obtained by coating and curing the aqueous coating composition is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoints of corrosion resistance, water resistance and hardness of the formed cured coating film. Preferably, it is 25 μm or more, more preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less.

Hereinafter, the present invention will be described more specifically with reference to Production Examples, Examples, and Comparative Examples. However, the present invention is not limited by these. In each example, “parts” and “%” are based on mass unless otherwise specified. Further, the thickness of the coating film is based on the cured coating film. Note that a blank column in the table indicates that the component is not included.

<Production of core-shell type acrylic resin particles>
Production Example 1
In a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser, deionized water (DIW) and Newcol (registered trademark) 707SF (trade name, manufactured by Nippon Emulsifier Co., Ltd., anionic interface) were charged in the amounts shown in Table 1. An activator and a solid content of 30% by mass) were added, and the temperature was raised after sufficient nitrogen replacement. While stirring at about 100 rpm, the internal temperature was kept at 82 ° C., and the component (A1) shown in Table 1 was emulsified using a homomixer (hereinafter, referred to as “component (A1) component emulsion. Component (A2), component (B1) ) Component and (B2) component), and an aqueous solution of initiator 1 (in Table 1, VA-057 is a trade name, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., 2-2'-azobis [N- (2-carboxyethyl) -2-methylpropiondiamine] tetrahydrate) was started dropwise to polymerize.
The dropping rate was about 146.0 parts / hour for the component (A1) emulsion and about 6.6 parts / hour for the aqueous initiator 1 solution. At the same time when the dropping of the (A1) component emulsion was completed, the dropping of the (A2) component emulsion shown in Table 1 was started. At the same time, the component (B1) emulsion shown in Table 1 was dropped into the component (A2) emulsion. The dropping rate of the component (B1) emulsion was set to a rate at which the dropping was completed simultaneously with the dropping of the component (A2) emulsion, that is, about 73.0 parts / hour in the present production example. Thereafter, the component (B2) emulsion was dropped at about 146.0 parts / hour.
After completion of the dropwise addition, the reaction was carried out at 82 ° C. for 0.5 hour, and an aqueous solution of initiator 2 was added dropwise at about 3.3 parts / hour. After the completion of the dropwise addition, the reaction was carried out at 82 ° C for 1.5 hours, and then cooled to 25 ° C. Finally, the neutralizing agent shown in Table 1 was added, and the core-shell type acrylic resin particles (A-1) having a solid content mass concentration of 40.0% (shell part acid value: 34 mgKOH / g, core layer (= uniform layer / gradient polymer) An emulsion having a mass ratio of (layer) / shell layer of 75 (= 25/50) / 25) was obtained.

The emulsion had a viscosity (measured with a B-type viscometer, 60 rpm, 20 ° C.) of 680 mPa · s, a pH of 9.2 (measured with a pH meter), and an average particle diameter of 105 nm.

Production Examples 2 to 10
Each of the core-shell type acrylic resin particles (A-2) to (A-10) (all of the core layer) was manufactured in the same manner as in Production Example 1 except that the composition was changed to that shown in Table 1. The mass ratio of (= uniform layer / gradient polymer layer) / shell layer was 75 (= 25/50) / 25. Core-shell type acrylic resin particles (A-9) and (A-10) are acrylic resin particles for a comparative example.

Production Example 11 (for Comparative Example)
Into a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser, charged amounts of deionized water and Newcol 707SF shown in Table 1 were added, and the temperature was raised after sufficient nitrogen replacement. While stirring at about 100 rpm, the internal temperature was maintained at 82 ° C., and the component (A1) shown in Table 1 emulsified using a homomixer and an aqueous solution of initiator 1 were added dropwise to initiate polymerization. The dropping rate was about 146.0 parts / hour for the component (A1) emulsion and about 6.6 parts / hour for the aqueous initiator 1 solution. At the same time when the dropping of the (A1) component emulsion was completed, the dropping of the (B1) component emulsion shown in Table 1 was started, and was dropped at about 146.0 parts / hour. After completion of the dropwise addition, the reaction was carried out at 82 ° C. for 0.5 hour, and an aqueous solution of initiator 2 was added dropwise at about 3.3 parts / hour. After the completion of the dropwise addition, the reaction was carried out at 82 ° C for 1.5 hours, and then cooled to 25 ° C. Finally, a neutralizing agent shown in Table 1 was added, and the core-shell type acrylic resin particles (A-11) having a solid content mass concentration of 40.0% (shell part acid value: 34 mgKOH / g, core layer (= uniform layer / gradient polymer) An emulsion having a mass ratio of (layer) / shell layer of 50 (= 50/0) / 50 (there was no gradient polymer layer) was obtained.

The emulsion had a viscosity (measured with a B-type viscometer, 60 rpm, 20 ° C) of 620 mPa · s, a pH of 9.2 (measured with a pH meter), and an average particle diameter of 110 nm.

Production Example 12 (for Comparative Example)
Into a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser, charged amounts of deionized water and Newcol 707SF shown in Table 1 were added, and the temperature was raised after sufficient nitrogen replacement. While stirring at about 100 rpm, the internal temperature was maintained at 82 ° C., and the component (A1) shown in Table 1 emulsified using a homomixer and an aqueous solution of initiator 1 were added dropwise over 3 hours to polymerize. After the completion of the dropwise addition, the reaction was carried out at 82 ° C. for 0.5 hour, and the initiator 2 aqueous solution was added dropwise over 0.5 hour. After the completion of the dropwise addition, the reaction was carried out at 82 ° C for 1.5 hours, and then cooled to 25 ° C. Finally, a neutralizing agent shown in Table 1 was added to obtain an emulsion of core-shell type acrylic resin particles (A-12) having a solid content mass concentration of 40.0% (shell part acid value: 34 mgKOH / g, monolayer uniform composition particles). Obtained.

The emulsion had a viscosity (measured with a B-type viscometer, 60 rpm, 20 ° C) of 520 mPa · s, a pH of 9.2 (measured with a pH meter), and an average particle diameter of 108 nm.

<Production of aqueous coating composition>
Example 1
DISPERBYK (registered trademark) -190 (trade name, manufactured by BYK, pigment dispersant, solid content: 40%) 3 parts (solid content: 1.2 parts), BYK (registered trademark) -024 (trade name, manufactured by BYK, 0.4 parts of antifoaming agent, solid content 100%), 35 parts of JR-603 (trade name, manufactured by Teika, titanium oxide, solid content 100%), Super SS (trade name, manufactured by Maruo Calcium Co., calcium carbonate, 15 parts of solid content 100%), 25 parts of deionized water and 2 parts of dipropylene glycol monomethyl ether were mixed, and after adding glass beads, the mixture was dispersed with a paint shaker for 60 minutes to obtain a pigment paste (P1) (solid content of 64.2%). ) Got.

After removing the glass beads, 250 parts of an emulsion of the core-shell type acrylic resin particles (A-1) obtained in Production Example 1 (solids of 100 parts) was added to 80 parts (solids of 51.4 parts) of the obtained pigment paste (P1). 1.), BYK-348 (trade name, manufactured by BYK, surface conditioner, solid content 100%), 0.5 part, SN thickener 660T (trade name, manufactured by San Nopco, thickener, solid content 20%) By mixing and stirring 5 parts (solid content: 0.5 part) and 10 parts of dipropylene glycol monomethyl ether, the aqueous coating composition No. having a pH of 8.2 and a coating solid content of 44.5% by mass was mixed. 1 was obtained.

Examples 2 to 8 and Comparative Examples 1 to 4
In the same manner as in Example 1 except that the composition was changed to the composition shown in Table 2, the respective water-based coating composition Nos. 2 to No. 12 was obtained.

In Table 2, the glass transition temperature (Tg, ° C) of the core-shell type acrylic resin particles (A-1) to (A-12) of each aqueous coating composition and the solubility parameter value in all the copolymer components are 9 The ratio (% by mass) of a polymerizable unsaturated monomer having a value of 0.5 or less (the monomer ratio (% by mass) having an SP value of 9.5 or less) is also shown.

<Preparation of test plate>
On the polished and degreased 70 mm × 150 mm × 0.8 mm cold-rolled steel plate (substrate), each aqueous coating composition No. obtained in the above Examples 1 to 8 and Comparative Examples 1 to 4 was coated. 1 to No. No. 12 was applied using an air spray so that the thickness of the cured coating film was 40 μm. Next, each test plate having a cured coating film formed on a steel plate was obtained by being left at 23 ° C. and 65% RH for 7 days.

<Evaluation of test plate>
The following tests were performed for each of the obtained test plates. The evaluation results are also shown in Table 2.

Corrosion resistance: With respect to each test plate, the coating film was cut with a knife to reach the base material with a knife, and 120 hours in accordance with JIS K 5600-7-1 (1999) "Neutral salt spray resistance" A salt spray test was performed. Evaluation was made according to the following criteria based on the width of rust and blisters from knife scratches. The smaller the maximum width of rust and blisters, the better the anticorrosion. If the rating is A to C, the anticorrosion is good.

A: The maximum width of rust and blisters is less than 1 mm from the cut part (one side)
B: The maximum width of rust and blisters is 1 mm or more and less than 2 mm from the cut part (one side)
C: The maximum width of rust and blisters is 2 mm or more and less than 3 mm from the cut part (one side)
D: The maximum width of rust and blisters is 3 mm or more and less than 5 mm from the cut part (one side)
E: The maximum width of rust and blisters is 5 mm or more from the cut part (one side)

Water resistance: Each test plate was immersed in deionized water at 23 ° C. for 48 hours, and the coated surface was evaluated according to the following criteria. If the evaluation is ◎ or ○, the water resistance is good.
A: Good and no problem.
：: Some gloss is observed, but it is at a practical level.
Δ: Either blister or gloss was observed.
×: Either blisters or glossiness are remarkably observed.

Gloss: For each test plate, the specular gloss (60 °) of the coated surface was measured in accordance with JIS K 5600-4-7 (1999) “Specular gloss”. If the specular gloss (60 °) of the coated surface is 70 or more, the gloss is good.

Pencil hardness: The pencil hardness of the coated surface of each test plate was measured in accordance with JIS K 5600-5-4 (1999) “Scratch hardness (pencil method)”. Pencil hardness is F, HB, B, 2B in order from the harder one. If the hardness is B or more, the hardness is good.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application (No. 2018-141479) filed on Jul. 27, 2018, the contents of which are incorporated herein by reference.

According to the present invention, it is possible to provide an aqueous coating composition which has good film-forming properties at low temperatures and also has excellent coating properties such as corrosion resistance, hardness and water resistance.

Claims

A core-shell type acrylic resin particle (A) including at least one gradient polymer layer,
An aqueous coating composition, wherein the shell part of the core-shell type acrylic resin particles (A) has an acid value in the range of 20 to 100 mgKOH / g.
The aqueous coating composition according to claim 1, wherein the core-shell type acrylic resin particles (A) have a glass transition temperature of -10 ° C or higher.
The aqueous coating composition according to claim 1 or 2, wherein at least 80% by weight of all copolymerized components of the core-shell type acrylic resin particles (A) are polymerizable unsaturated monomers having a solubility parameter value of 9.5 or less. .
(4) 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 3 on the base material.
The coated article according to claim 4, wherein the base material is a metal base material.