JP4771652B2 - Water-based paint composition - Google Patents

Description

  The present invention relates to an aqueous coating composition. The composition of the present invention can be suitably used particularly as an interior paint.

  Conventionally, synthetic resin emulsions obtained by emulsion polymerization of ethylenically unsaturated monomers such as various acrylic monomers have been widely used as binders for water-based paints. Such a synthetic resin emulsion basically uses water as a medium, but when used as a binder for paints, an organic solvent having a high boiling point is usually produced in order to obtain a sufficient film-forming property. It is added as a film aid.

In recent years, movements to suppress the emission of organic solvents have become active due to increased awareness of the environment and health. In particular, in the indoor environment of a building, a sick house or the like due to a volatile organic compound is taken up as a social problem, and reduction of the organic solvent is also desired in the water-based paint.
In order to meet this demand, it is necessary for water-based paints to ensure film-forming properties while reducing the amount of film-forming aid added. In general, as one method for ensuring such film-forming properties, there is a method of adjusting the type and ratio of monomer components used in a synthetic resin emulsion to lower the glass transition temperature of the resin. However, this method has a problem that the adhesiveness of the surface of the coating film to be formed increases, and it becomes difficult to remove once the dirt adheres to the surface of the coating film.

  In response to this problem, it has been proposed to employ a multilayer structure emulsion as a binder. By employing the multilayer structure type emulsion, the amount of the film-forming aid added can be reduced, and the film-forming property and the stain resistance can be made compatible to some extent. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-371225) discloses a water-based paint containing a multilayer structure emulsion in which the glass transition temperature of the resin constituting the outer layer is set lower than the glass transition temperature of the resin constituting the inner layer. A composition is described.

JP 2002-371225 A

However, in a multilayer structure type emulsion, if the glass transition temperature of the resin constituting the outer layer is designed to be low and the outside of the emulsion particles is made to have a soft structure, the paint may become unstable over time. The reason is not clear, but the following factors can be considered.
In the multilayer structure type emulsion as in the above patent document, a carboxyl group-containing monomer is copolymerized with monomers (soft monomers) such as 2-ethylhexyl acrylate and butyl acrylate in the polymer component constituting the outermost layer of the emulsion particles, and ammonia Stabilization is achieved by dissociating the carboxyl group with a volatile base such as. However, such soft monomers are usually highly hydrophobic. Therefore, when the volatile base is volatilized with time, the hydrophilicity of the emulsion particle surface layer is drastically lowered, and the emulsion particles are destabilized. Moreover, since the emulsion particle surface layer has a soft structure, aggregation or the like is likely to occur, and stability cannot be ensured.

For such problems, the stability can be improved to some extent by increasing the amount of volatile base in the paint. However, a volatile base odor is generated when the coating film is formed, and the indoor environment is lowered.
If a non-volatile base such as sodium hydroxide is used, stability over time can be secured. However, on the other hand, there arises a problem that the water resistance of the coating film is remarkably lowered.

  The present invention has been made in view of the problems as described above, and can reduce the amount of a film-forming aid in the paint. Furthermore, the stability of the paint, the stain resistance of the formed coating film, the water resistance The object is to obtain a water-based paint having excellent performance in properties.

  As a result of diligent studies to achieve the above object, the present inventors have conceived that a multilayer structure type synthetic resin emulsion and an alkali metal siliconate are used in combination at a specific ratio, thereby completing the present invention. It was.

That is, the present invention has the following characteristics.
1. An aqueous coating composition having a minimum film-forming temperature of 10 ° C. or less,
The outermost layer has a carboxyl group, and the glass transition temperature of the resin constituting the outermost layer is lower than the glass transition temperature of the resin constituting the inner layer, the inner layer has two or more kinds, and the glass transition temperature of the innermost layer is the highest. And the multilayer structure type synthetic resin emulsion (A) and sodium methyl siliconate (B), which are set so that the glass transition temperature becomes lower in order toward the outside, are essential components, and the resin solid content 100 of the component (A) An aqueous coating composition comprising 0.01 to 10 parts by weight of component (B) with respect to parts by weight.
2. An aqueous coating composition having a minimum film-forming temperature of 10 ° C. or less,
The outermost layer has a carboxyl group, and the glass transition temperature of the resin constituting the outermost layer is lower than the glass transition temperature of the resin constituting the inner layer, the inner layer has two or more kinds, and the glass transition temperature of the innermost layer is the highest. In addition, the multilayer structure type synthetic resin emulsion (A), sodium methyl siliconate (B), and pigment (C), which are set so that the glass transition temperature sequentially decreases toward the outside, are essential components, and the component (A) An aqueous coating composition comprising 0.01 to 10 parts by weight of component (B) and 5 to 1000 parts by weight of component (C) with respect to 100 parts by weight of the resin solid content.
3. 1. The volatile organic compound content in the paint is less than 5% by weight. Or 2. The water-based paint composition described in 1.

  According to the present invention, the amount of the film-forming auxiliary in the paint can be reduced, and furthermore, an aqueous paint composition capable of exhibiting excellent performance in the stability of the paint, the stain resistance of the formed coating film, the water resistance, etc. Is obtained. Such a water-based paint composition can be used as an environmentally-friendly water-based paint, and is particularly suitable as an interior paint for buildings.

  Hereinafter, the best mode for carrying out the present invention will be described.

  In the aqueous coating composition of the present invention, a multilayer structure type synthetic resin emulsion having a carboxyl group in the outermost layer and the glass transition temperature of the resin constituting the outermost layer being lower than the glass transition temperature of the resin constituting the inner layer (hereinafter referred to as “the outermost layer”) "(A) component") is used as a binder.

  This component (A) is a multilayer structure emulsion composed of an outermost layer and at least one inner layer on the inner side. The inner layer referred to here is a layer other than the outermost layer portion of the multilayer structure type emulsion. That is, the component (A) may have any of a two-layer structure including the outermost layer and one type of inner layer, a three-layer structure including the outermost layer and two types of inner layers, or a multilayer structure having a plurality of inner layers. . Further, the component (A) may have a multilayer structure whose composition is continuously changed.

  In the component (A), the glass transition temperature (hereinafter referred to as “Tg”) of the resin constituting the outermost layer is set to be lower than the Tg of the resin constituting the inner layer. With such a Tg setting, it is possible to improve the stain resistance while ensuring a sufficient film forming property. When there are two or more inner layers, the Tg of each inner layer may be appropriately set within a range that is higher than the Tg of the outermost layer, but the Tg of the innermost layer is the highest and the Tg is increased in order toward the outer side. It is desirable to set it to be low.

Tg of the outermost layer is usually −60 to 30 ° C., preferably −30 to 20 ° C. The Tg of the inner layer is usually 0 to 150 ° C., preferably 10 to 110 ° C. Moreover, the Tg difference between the innermost layer having the lowest Tg and the outermost layer is usually 10 ° C. or higher, preferably 20 to 100 ° C.
By setting the Tg of each layer within such a range, it becomes possible to obtain practical film-forming properties and stain resistance, and particularly to obtain an aqueous coating composition suitable as a paint for interiors of buildings. it can.
Note that Tg in the present invention is a value obtained by the Fox calculation formula.

In order to generate a carboxyl group in the outermost layer of the component (A), a carboxyl group-containing monomer may be used as a monomer constituting the outermost layer. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid or a monoalkyl ester thereof, itaconic acid or a monoalkyl ester thereof, fumaric acid or a monoalkyl ester thereof. Among these, at least one selected from acrylic acid and methacrylic acid is particularly preferable.
The usage-amount of a carboxyl group-containing monomer is 0.1 to 40 weight% normally with respect to the total amount of monomers which comprises (A) component, Preferably it is 0.5 to 20 weight%.

In the component (A), the type and ratio of the monomer component may be appropriately selected and adjusted so that the Tg of each layer satisfies the above-described conditions. Examples of monomers that can be used in the component (A) include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and n-amyl ( (Meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, (Meth) acrylic acid esters such as cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate;
Contains amino groups such as N-methylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminoethyl vinyl ether, N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide monomer;
Pyridine monomers such as vinylpyridine;
Hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate;
Vinyl ester monomers such as vinyl acetate and vinyl propionate;
Nitrile group-containing monomers such as acrylonitrile and methacrylonitrile;
Aromatic monomers such as styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene;
Amide group-containing monomers such as acrylamide, methacrylamide, maleic acid amide, N-methylol (meth) acrylamide and diacetone acrylamide;
Epoxy group-containing monomers such as glycidyl (meth) acrylate, diglycidyl (meth) acrylate, and allyl glycidyl ether;
Carbonyl group-containing monomers such as acrolein, diacetone (meth) acrylamide, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone;
Alkoxysilyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane Containing monomers;
Vinylidene halide monomers such as vinylidene chloride and vinylidene fluoride;
Other examples include ethylene, propylene, isoprene, butadiene, vinyl pyrrolidone, vinyl chloride, vinyl ether, vinyl ketone, vinyl amide, and chloroprene. These can be used alone or in combination of two or more. Moreover, a carboxyl group-containing monomer can also be used in the inner layer.

  Particularly in the present invention, when at least one of (meth) acrylic acid alkyl ester having a long chain alkyl group is copolymerized with a carboxyl group-containing monomer in the outermost layer, advantageous effects in terms of physical properties such as coating stability. Can be demonstrated. Specific examples of the (meth) acrylic acid alkyl ester having a long-chain alkyl group include an acrylic acid alkyl ester having an alkyl group having 2 or more carbon atoms and / or a methacrylic acid alkyl ester having an alkyl group having 6 or more carbon atoms. (Excluding those having a cyclic structure).

Although the manufacturing method of (A) component is not specifically limited, For example, emulsion polymerization, soap free emulsion polymerization, dispersion polymerization, feed emulsion polymerization, feed dispersion polymerization, seed emulsion polymerization, seed dispersion polymerization, etc. are employable.
(A) The average particle diameter of a component is about 0.05-0.2 micrometer normally.

  In the present invention, alkali metal siliconate (hereinafter referred to as “component (B)”) is used as an essential component. By using such a component (B), when only a normal volatile base or non-volatile base is used, destabilization of the paint, generation of odor from the paint, reduction in water resistance of the formed coating film, etc. Various problems can be improved.

The component (B) in the present invention is a compound represented by R ¹ aSi (OR ² ) b (OM) c. [Wherein, a is an integer of 0 or more (preferably 1), b is an integer of 0 or more (preferably 2), c is an integer of 1 or more (preferably 1), and satisfies a + b + c = 4. R ¹ may be the same or different and represents a hydrocarbon group. R ² may be the same or different and represents a hydrogen atom or a hydrocarbon group. M may be the same or different and represents an alkali metal. ]

Examples of R ¹ include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, t-pentyl group, and n-hexyl. Group, n-heptyl group, n-octyl group, isooctyl group, 2,2,4-trimethylpentyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-octadecyl group, cyclopentyl group, cyclohexyl group , Cycloheptyl group, methylcyclohexyl group, phenyl group, naphthyl group, anthryl group, phenanthryl group, tolyl group, xylyl group, ethylphenyl group, benzyl group, phenylethyl group and the like. Among these, a methyl group, an ethyl group, and a propyl group are preferable, and a methyl group is particularly preferable.
Examples of R ² include a hydrogen atom and the same group as R ¹ . Among these, a hydrogen atom, a methyl group, and an ethyl group are preferable, and a hydrogen atom is particularly preferable.
Examples of M include Li, Na, K and the like, and Na is particularly preferable.

The mixing amount of the component (B) is usually 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 0.1 parts by weight with respect to 100 parts by weight of the resin solid content of the component (A). 3 parts by weight. With such a mixing amount, sufficient effects can be obtained in the stability of the paint, the water resistance of the formed coating film, and the like. Moreover, the decontamination property in a formed coating film can also be improved.
As for the stability of the paint, it is possible to sufficiently ensure the stability at the time of high temperature storage and low temperature storage as well as during normal temperature storage.

The timing of mixing the component (B) with the component (A) is not particularly limited, and may be mixed at the time of manufacturing the component (A), or mixed at the time of manufacturing the paint using the component (A). May be.
Moreover, in the range which does not inhibit the effect of this invention, a normal basic compound can also be used with (B) component. Examples of such basic compounds include ammonia, monoethylamine, diethylamine, triethylamine, isopropylamine, diisopropylamine, aminoethanol, 1-amino-2-propanol, 2-amino-2-methyl-1-propanol, 2 -(Methylamino) -2-methyl-1-propanol, N, N-dimethylethanolamine, N- (2-aminoethyl) ethanolamine, N-methylethanolamine, sodium hydroxide and the like can be mentioned.

In the aqueous coating composition of the present invention, various colors can be expressed by mixing pigments (hereinafter referred to as “component (C)”). In addition, the gloss level can be adjusted. Furthermore, in the present invention, even when such a component (C) is mixed, sufficient paint stability can be ensured.
(C) As a component, what can generally be mix | blended with a coating material can be used. For example, titanium oxide, zinc oxide, carbon black, lamp black, bone black, graphite, black iron oxide, copper chrome black, cobalt black, copper manganese iron black, brown, molybdate orange, permanent red, permanent carmine, anthraquinone red, Perylene red, quinacridone red, yellow iron oxide, titanium yellow, first yellow, benzimidazolone yellow, chrome green, cobalt green, phthalocyanine green, ultramarine, bitumen, cobalt blue, phthalocyanine blue, quinacridone violet, dioxazine violet, heavy carbonate Calcium, precipitated calcium carbonate, kaolin, talc, clay, porcelain clay, china clay, barium sulfate, barium carbonate, quartz sand, quartzite, diatomaceous earth, oxidation Aluminum, resin beads, aluminum pigments, pearl pigments and the like, can be used one or two or more thereof.

The mixing amount of the component (C) is usually about 5 to 1000 parts by weight with respect to 100 parts by weight of the resin solid content of the component (A). By appropriately selecting and combining the component (C) within such a mixing amount range, it is possible to impart a desired hue while ensuring practical physical properties.
The degree of gloss in the formed coating film can be set by appropriately adjusting the mixing amount of the component (C) and the composition, shape, particle diameter, etc. of the component (C) to be used. When a matte-type paint is obtained, the component (C) may be mixed with about 50 to 1000 parts by weight (preferably about 100 to 500 parts by weight) with respect to 100 parts by weight of the resin solid content of the component (A). . When a glossy paint is obtained, the component (C) may be mixed with about 5 to 100 parts by weight (preferably about 10 to 80 parts by weight) with respect to 100 parts by weight of the resin solid content of the component (A). .

In the composition of the present invention, in addition to the above-described components, components that can be used in ordinary paints can also be included. Examples of such components include aggregates, fibers, thickeners, leveling agents, wetting agents, plasticizers, antifreezing agents, pH adjusting agents, preservatives, antifungal agents, antialgae agents, antibacterial agents, and dispersions. Agents, antifoaming agents, adsorbents, ultraviolet absorbers, antioxidants, catalysts, crosslinking agents and the like.
The composition of the present invention may be mixed with a film-forming aid or other volatile organic compound as necessary, but the content thereof should be less than 5% by weight, more preferably less than 1% by weight in the paint. Is desirable. In the composition of the present invention, the minimum film-forming temperature can be set to 10 ° C. or lower even when the volatile organic compound such as a film-forming aid has such a low content.

  The composition of the present invention can be used mainly for coating buildings, civil engineering structures and the like, and can be suitably used particularly for interior finishing of buildings. Applicable base materials include, for example, gypsum board, plywood, concrete, mortar, porcelain tile, fiber-mixed cement board, cement calcium silicate board, slag cement pearlite board, asbestos cement board, ALC board, siding board, extrusion board , Steel plate, plastic plate and the like. The surface of these base materials may have been subjected to some surface treatment (for example, a sealer, a surfacer, a filler, etc.), and has already been provided with a coating film, or has already been applied with wallpaper. Also good.

A coating film is obtained by applying the composition of the present invention to the substrate as described above. As a coating method, a known method can be employed, and for example, spray coating, roller coating, brush coating, and the like are possible. When building materials are painted in the factory, they can also be painted with a roll coater, a flow coater, or the like.
What is necessary is just to select the coating amount at the time of coating this invention composition suitably with the kind and application of a coating material, for example, in the case of flat paint, it will be about 0.1-0.5 kg / m < ² >. At the time of application, the viscosity of the paint can be appropriately adjusted by diluting with water or the like. The dilution ratio is usually about 0 to 20% by weight.
The drying after coating the composition of the present invention is usually carried out at room temperature, but can also be heated.

  Examples are given below to clarify the features of the present invention.

(Manufacture of synthetic resin emulsion)
A reaction vessel was charged with 150 parts by weight of deionized water, 1.5 parts by weight of an anionic emulsifier, and 3.0 parts by weight of a nonionic emulsifier, and the temperature was raised to 70 ° C. while stirring and nitrogen substitution, and 0.9 per cent ammonium persulfate. Part by weight was added. To this, separately prepared emulsion monomer for the innermost layer (49 parts by weight of styrene, 29 parts by weight of methyl methacrylate, 25 parts of 2-ethylhexyl acrylate in an aqueous solution in which 0.5 parts by weight of an anionic emulsifier was dissolved in 50 parts by weight of deionized water) Parts by weight, and 1.5 parts by weight of acrylic acid emulsified and dispersed) were continuously added dropwise over 3 hours.
Next, an emulsion monomer for an intermediate layer (in an aqueous solution in which 0.5 part by weight of an anionic emulsifier is dissolved in 50 parts by weight of deionized water, 32 parts by weight of styrene, 35 parts by weight of methyl methacrylate, 53 parts by weight of 2-ethylhexyl acrylate, acrylic A solution obtained by emulsifying and dispersing 1.5 parts by weight of an acid) was continuously added dropwise over 2 hours, and an emulsion monomer for outermost layer (0.5 part by weight of an anionic emulsifier was dissolved in 50 parts by weight of deionized water). In an aqueous solution, 11 parts by weight of methyl methacrylate, 54 parts by weight of 2-ethylhexyl acrylate, 4.5 parts by weight of acrylic acid, and 4.2 parts by weight of acrylamide were continuously added dropwise over 2 hours. After completion of dropping, the mixture was aged for 3 hours and cooled to 30 ° C., and then a 10% aqueous sodium hydroxide solution was added to adjust the pH to 8 to obtain a multilayer emulsion. The resin solid content of this multilayer structure emulsion is 50% by weight, and Tg is 49 ° C. for the innermost layer, 16 ° C. for the intermediate layer, and −22 ° C. for the outermost layer.

Using the multilayer emulsion described above as a binder, each raw material was uniformly mixed by a conventional method according to the formulations shown in Tables 1 and 2 to produce each aqueous coating composition. In addition, the raw material used in manufacture of a coating material is as follows.
Alkali metal siliconate: 30% by weight sodium methyl siliconate solution Volatile base: 25% by weight aqueous ammonia Nonvolatile base: 10% by weight sodium hydroxide solution Pigment A: 70% by weight titanium oxide dispersion Pigment B: Heavy calcium carbonate / pigment C: Carbon black 24 wt% dispersion / pigment D: Iron oxide 45 wt% dispersion / dispersant: anionic dispersant / thickener: urethane thickener / antifoaming agent: silicone Antifoaming agent

  The following test was done about the obtained water-based coating composition. The test results are shown in Tables 1 and 2.

(1) Minimum film-forming temperature Each water-based coating composition was applied to a polyethylene film with a wet film thickness of 250 μm, and immediately left on a metal plate having a temperature gradient of −10 ° C. to 40 ° C. and dried. . At this time, the lowest temperature which formed the continuous coating film was confirmed.

(2) Storage stability test About each water-based paint composition, after measuring a viscosity with a BH type viscometer (rotation speed 20rpm, measurement temperature 23 degreeC), it seals in a 250cc container, and it is a fixed period with a 50 degreeC thermostat. Stored (30 days). The coating after storage was allowed to cool in a standard state (temperature 23 ° C., humidity 50%), and then the viscosity was measured with a BH viscometer to examine the change with respect to the initial viscosity. The evaluation criteria are as follows.
A: Viscosity change less than 10% B: Viscosity change 10% or more and less than 30% Δ: Viscosity change 30% or more and less than 50% X: Viscosity change 50% or more

(3) Low temperature stability test About each water-based coating composition, after measuring a viscosity with a BH type viscometer (rotation speed 20rpm, measurement temperature 23 degreeC), it seals in a 250cc container, and it is 18 to a -5 degreeC thermostat. After the time, the container was taken out and left in the room for 6 hours. After this operation was repeated three times, the viscosity was measured with a BH viscometer, and the change with respect to the initial viscosity was examined. The evaluation criteria are as follows.
A: Viscosity change less than 10% B: Viscosity change 10% or more and less than 30% Δ: Viscosity change 30% or more and less than 50% X: Viscosity change 50% or more

(4) Odor The odor generated from each aqueous coating composition was evaluated by a sensory test. The evaluation criteria are as follows.
○: Feels almost no odor ×: Feels odor remarkably

(5) Water resistance test Each aqueous coating composition was spray-coated at a coating amount of 300 g / m ² on a 150 × 60 × 6 mm slate plate previously coated with a sealer, and cured in a standard state for 14 days. After measuring the initial hue (L ^* ₁ , a ^* ₁ , b ^* ₁ ) of the obtained specimen, the specimen was immersed in water at 23 ° C. for 96 hours. After pulling up the specimen and leaving it in the standard state for 2 hours, the hue (L ^* ₂ , a ^* ₂ , b ^* ₂ ) of the specimen was measured, and the color difference (ΔE) before and after immersion in water was calculated according to the following formula. .
_{^{<Equation> △ E = {(L *}} 2 -L * 1) 2 + (a * 2 -a * 1) 2 + (b * 2 -b * 1) 2} 0.5
The evaluation criteria are as follows.
○: Less than ΔE0.5 Δ: ΔE 0.5 or more and less than 1.0 ×: ΔE 1.0 or more

(6) Contamination resistance test A
Each water-based coating composition was spray-coated at a coating amount of 300 g / m ² on a 150 × 60 × 6 mm slate plate previously coated with a sealer, and cured in a standard state for 14 days. A dirt component (aqueous pen) was attached to the surface of the coating film of the obtained test specimen, and after rubbing with a cloth containing water, the degree of remaining dirt component was confirmed. The evaluation criteria are as follows.
○: Dirt removed △: Dirt remained slightly ×: Dirt clearly remained

(7) Contamination resistance test B
Each aqueous coating composition was applied to a glass plate with a wet film thickness of 250 μm and cured for 14 days in a standard state. A soil component (carbon black 15% by weight aqueous dispersion) was dropped onto the surface of the coating film of the obtained test specimen and allowed to stand in a standard state for 24 hours. Next, the surface of the coating film was washed with a sponge, and then the degree of remaining dirt components was confirmed. The evaluation criteria are as follows.
○: Dirt removed △: Dirt remained slightly ×: Dirt clearly remained

Claims (3)

An aqueous coating composition having a minimum film-forming temperature of 10 ° C. or less,
The outermost layer has a carboxyl group, and the glass transition temperature of the resin constituting the outermost layer is lower than the glass transition temperature of the resin constituting the inner layer, the inner layer has two or more kinds, and the glass transition temperature of the innermost layer is the highest. And the multilayer structure type synthetic resin emulsion (A) and sodium methyl siliconate (B), which are set so that the glass transition temperature becomes lower in order toward the outside, are essential components, and the resin solid content 100 of the component (A) An aqueous coating composition comprising 0.01 to 10 parts by weight of component (B) with respect to parts by weight. An aqueous coating composition having a minimum film-forming temperature of 10 ° C. or less,
The outermost layer has a carboxyl group, and the glass transition temperature of the resin constituting the outermost layer is lower than the glass transition temperature of the resin constituting the inner layer, the inner layer has two or more kinds, and the glass transition temperature of the innermost layer is the highest. In addition, the multilayer structure type synthetic resin emulsion (A), sodium methyl siliconate (B), and pigment (C), which are set so that the glass transition temperature sequentially decreases toward the outside, are essential components, and the component (A) An aqueous coating composition comprising 0.01 to 10 parts by weight of component (B) and 5 to 1000 parts by weight of component (C) with respect to 100 parts by weight of the resin solid content. The aqueous coating composition according to claim 1 or 2, wherein the content of volatile organic compounds in the coating is less than 5% by weight.