Emulsion coating composition, and interior material

Abstract

To provide an emulsion coating composition which can maintain good tackiness and prevents cracking under low temperature environment.SOLUTION: An emulsion coating composition contains an acrylic emulsion resin, and at least one kind of extender pigment, wherein a glass transition temperature calculated by an FOX formula of the acrylic emulsion resin is -40°C or higher and -5°C or lower, and a content of a film-forming assistant is less than 5 mass% based on pts.mass of the emulsion coating composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an emulsion paint composition and an interior material having a coating film made of said composition formed thereon. [Background technology]

[0002] Various types of paints have been used for outdoor substrates such as buildings and structures to improve design, and among them, emulsion paints are widely used. Emulsion paints often contain a film-forming aid to promote fusion of polymer particles in the emulsion and form a uniform film of the polymer. For example, Patent Document 1 proposes the use of diisobutyl glutarate as a film-forming aid contained in an acrylic resin emulsion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-22502 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional acrylic resin emulsion paints, after the paint is dried to form a coating film, the film-forming assistant floats to the surface of the coating film, making the surface of the coating film sticky and causing tackiness. When tackiness occurs, for example, the coating film sticks to a film that is placed over the coating film when packaging the coated object, and when the film is removed from the coating film, the coating film peels off from the coated object. Furthermore, when tackiness is manifested as described above, for example, when building materials with coating films formed thereon are stacked at a construction site of a building, the building materials stick to each other via the coating film, and when one of the stacked building materials is lifted, the coating film may peel off from one of the building materials.

[0005] In order to solve the above problems, it may be possible to not include a film-forming aid in the paint. However, in that case, when a building material on which a coating film has been formed is cut in a low-temperature environment such as winter, for example during the construction of a building, the coating film may crack and develop cracks, deteriorating the appearance of the building material.

[0006] Therefore, an object of the present invention is to provide an emulsion paint composition which suppresses the development of tackiness and which does not cause cracking in a low-temperature environment. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by keeping the content of the film-forming aid in an emulsion paint composition small while ensuring that the glass transition temperature, calculated by the Fox equation, of the acrylic emulsion resin contained in the composition falls within a certain range. That is, the present invention provides the following [1] to [9].

[0008] [1] An emulsion paint composition comprising an acrylic emulsion resin and an extender pigment, wherein the acrylic emulsion resin has a glass transition temperature of -40°C or higher and -5°C or lower, as calculated by the Fox equation, and the content of a film-forming auxiliary is less than 5 mass% based on the mass parts of the emulsion paint composition. [2] The emulsion paint composition according to [1], wherein the thickener is contained in an amount of 0.01 to 2 mass% based on the solid content of the emulsion paint composition, and the viscosity of the emulsion paint composition measured with a B-type viscometer at 25±1°C is 500 to 5,000 mPa s. [3] The emulsion paint composition according to [1] or [2], wherein the content of the extender pigment is 10 to 85 mass % based on the solid content of the emulsion paint composition. [4] The emulsion paint composition according to any one of [1] to [3], wherein the extender pigment comprises at least one selected from the group consisting of calcium carbonate, aluminum hydroxide, barium carbonate, barium sulfate, silica, kaolin, talc, glass, and silica sand. [5] The emulsion paint composition according to any one of [1] to [4], wherein the pH of the emulsion paint composition is 7 or higher. [6] The emulsion paint composition according to any one of [1] to [5], further comprising a pH adjuster. [7] An interior material comprising a board made of inorganic fibers and a coating film made of the emulsion paint composition according to any one of [1] to [6] formed on at least one surface of the board. [8] The interior material according to [7], wherein the board is a rock wool board. [9] The amount of coating after drying of the coating film is 0.001 to 1 kg / m per side. 2 The interior material according to [7] or [8], which is within the range. Effect of the Invention

[0009] According to the present invention, it is possible to provide an emulsion coating composition which suppresses the development of tackiness and which does not cause cracking in low temperature environments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Emulsion paint composition] The emulsion paint composition of the present invention contains an acrylic emulsion resin and an extender pigment, and the acrylic emulsion resin has a glass transition temperature (hereinafter simply referred to as "glass transition temperature") calculated by the FOX equation shown in the following formula (1) of -40°C or higher and -5°C or lower.

[0011] 1 / Tg=W1 / Tg1+W2 / Tg2+···+W n / Tg n (1) In formula (1), Tg is the Tg (K) of the polymer, W1, W2, ... W n are the mass fractions of each monomer relative to the total monomer content, and Tg1, Tg2, ...Tg n is the Tg(K) of the homopolymer composed of each monomer.

[0012] The glass transition temperature (Tg) of a homopolymer can be a literature value described in, for example, "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989). If the glass transition temperature is not described in the literature, a homopolymer of each compound can be synthesized and measured. Specifically, it means the temperature at which a maximum due to micro-Brownian motion appears among the maximum loss tangents (tan δ) obtained by dynamic viscoelasticity measurement of the synthesized homopolymer, and can be measured by a conventionally known method using a dynamic viscoelasticity measuring device. For example, the synthesis of a homopolymer can be carried out by pouring the monomer components constituting the homopolymer into a Teflon (registered trademark) mold with a width of 3 mm, a length of 30 mm, and a thickness of 1 mm, and irradiating ultraviolet light at 1000 mJ / cm using a UV-LED (wavelength 365 nm). 2 The cured product sample is preferably photocured by irradiating the cured product with light to obtain a cured product sample. The dynamic viscoelasticity is measured by measuring the dynamic viscoelasticity of the cured product sample obtained, for example, in the range of -50 to 160°C, using a dynamic viscoelasticity measuring device. The measurement conditions are preferably a tensile deformation mode, a set strain of 1%, a measurement frequency of 1 Hz, and a heating rate of 5°C / min.

[0013] If the glass transition temperature of the acrylic emulsion resin is less than -40°C, the emulsion coating composition may exhibit tackiness even if it does not contain a film-forming aid or the content of the film-forming aid is small. If the glass transition temperature is higher than -5°C, cracks may occur in a low-temperature environment. From the above viewpoints, the glass transition temperature is preferably -35°C or higher and -7°C or lower, more preferably -25°C or higher and -10°C or lower, and even more preferably -22°C or higher and -12°C or lower. The glass transition temperature can be adjusted by the monomers constituting the acrylic emulsion resin. Each component contained in the emulsion paint composition will be described in detail below.

[0014] (Film-forming aid) The emulsion paint composition of the present invention has a film-forming aid content of less than 5% by mass based on the parts by mass of the emulsion paint composition. If the film-forming aid content is 5% by mass or more, the coating film formed by the emulsion paint composition may become sticky and develop tackiness. From this viewpoint, the film-forming aid content is preferably 2% by mass or less based on the parts by mass of the emulsion paint composition, and more preferably 0% by mass. In other words, it is more preferable that the emulsion paint composition does not contain a film-forming aid. As described above, the film-forming aid may not be included, but may be included within the scope of the present invention without impairing the object of the present invention. By including the film-forming aid, it is possible to prevent cracks from occurring in a low-temperature environment. When the film-forming aid is included, the content is, for example, 0.5% by mass or more, preferably 1% by mass or more, based on the mass parts of the emulsion coating composition. In this specification, the term "parts by mass of an emulsion paint composition" refers to the mass of the entire emulsion paint composition including volatile components such as the dispersion medium.

[0015] The film-forming aid is a component that promotes the fusion of polymer particles in an emulsion and promotes the formation of a polymer film. Examples of the film-forming auxiliary include benzoic acid compounds such as vinyl benzoate, phthalic acid compounds such as dibutyl phthalate, 2-ethylhexyl phthalate, and butyl benzyl phthalate, glutaric acid compounds such as diisobutyl glutarate, isobutyric acid ester compounds such as 2,2,4-trimethyl-1,3-pentanediol-2-methylpropanoate and 2,2,4-trimethyl-1,3-pentanediol isobutyrate, ethylene glycol compounds such as diethylene glycol-n-butyl ether (butyl carbitol) and ethylene glycol-n-butyl ether (butyl cellosolve), propylene glycol compounds such as dipropylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol-n-butyl ether, dipropylene glycol methyl ether acetate, and propylene glycol phenyl ether, and organic solvents such as xylene, toluene, and NMP.

[0016] (Acrylic emulsion resin) As the acrylic emulsion resin, for example, acrylic resin emulsions such as acrylic ester copolymer resin, acrylic ester-vinyl acetate copolymer resin, and silicone modified acrylic resin can be used. As a monomer constituting the acrylic resin, an acrylic monomer having a (meth)acryloyl group can be used. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, can be used. Examples of usable methacrylates include alkyl (meth)acrylates such as n-amyl (meth)acrylate, isoamyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, and ethoxypropyl (meth)acrylate. In addition, acrylic monomers having functional groups such as carboxyl groups, hydroxyl groups, amide groups, amino groups, and glycidyl groups, such as (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, mono(meth)acrylic acid esters of polyhydric alcohols, (meth)acrylamide, 2-aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, 3-aminopropyl (meth)acrylate, 2-butylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate, can also be used. Furthermore, in addition to the above acrylic monomers, monomers other than acrylic monomers can also be used in combination. Specific examples of such monomers include styrene derivatives such as styrene, α-methylstyrene, chlorostyrene, vinyltoluene, and methoxystyrene; carboxyl group-containing monomers such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, and crotonic acid; hydroxyl group-containing monomers such as allyl alcohol; amide group-containing monomers such as maleamide; amino group-containing monomers such as vinylpyridine; allyl glycidyl ether; epoxy group-containing monomers and oligomers obtained by reacting an epoxy compound having two or more glycidyl groups with an ethylenically unsaturated monomer having an active hydrogen atom; vinyl acetate; vinyl chloride; and further, ethylene, butadiene, acrylonitrile, and dialkyl fumarate. Furthermore, in the case of a silicon-modified acrylic resin, it is advisable to use, as a part of the monomer, an alkoxysilyl group-containing monomer such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyldipropoxysilane, 3-(meth)acryloxybutylphenyldimethoxysilane, 3-(meth)acryloxypropyldimethylmethoxysilane, and 3-(meth)acryloxypropyldiethylmethoxysilane.

[0017] As the acrylic emulsion resin, commercially available products may be used, such as "CA-333" (manufactured by Saiden Chemical Industry Co., Ltd.), "Vinizol 1024C", "Vinizol 1637", "Vinizol 911", and "Vinizol 1079" (all manufactured by Daido Chemical Industry Co., Ltd.). Commercially available products are generally those in which the acrylic emulsion resin is dispersed in water as a dispersion medium. The acrylic emulsion resin may be used alone or in combination of two or more kinds, as long as the glass transition temperature can be adjusted within a predetermined range. In the case of using two or more kinds, the glass transition temperature can be calculated by the above formula (1) based on the homopolymer of each monomer and the mass fraction of each monomer for the total monomers, assuming that the acrylic polymer is obtained from all monomers constituting the two or more kinds of acrylic emulsion resins.

[0018] The content of the acrylic emulsion resin is preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 70% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less, based on the solid content of the emulsion paint composition. By containing a certain amount of the acrylic emulsion resin or more, it becomes easier to form an appropriate coating film with the acrylic emulsion resin. In addition, by setting the content of the acrylic emulsion resin to a certain amount or less, it is possible to contain a certain amount or more of components other than the acrylic emulsion resin, such as an extender pigment, and it is possible to appropriately color the coating film formed from the emulsion paint composition or to impart mechanical properties, etc.

[0019] (Extender pigment) The emulsion paint composition of the present invention contains a body pigment. By containing the body pigment, a certain viscosity is imparted to the emulsion resin composition, and the mechanical properties of the coating film can be improved. Examples of the body pigment include calcium carbonate, aluminum hydroxide, barium carbonate, barium sulfate, silica, kaolin, talc, glass, and silica sand, and among these, calcium carbonate, barium sulfate, and aluminum hydroxide are more preferable. The extender pigment may be used alone or in combination of two or more kinds.

[0020] The content of the body pigment is preferably 10 to 85 mass %, more preferably 20 to 67 mass %, and even more preferably 25 to 60 mass %, based on the solid content of the emulsion paint composition. When the content of the body pigment is equal to or greater than the lower limit, a certain viscosity is easily imparted to the emulsion paint composition. When the content of the body pigment is equal to or less than the upper limit, the emulsion paint composition is not imparted with excessive viscosity, and good applicability can be achieved.

[0021] (Color pigments) The emulsion paint composition of the present invention preferably contains a coloring pigment. By including a coloring pigment, the coating film formed from the emulsion paint composition can be colored, and the design can be improved. As the coloring pigment, an appropriate type may be selected according to the color to be imparted to the emulsion paint composition. As the coloring pigment, for example, aluminum pigments such as aluminum flakes, mica pigments, graphite pigments, glass flake pigments, and other glitter pigments, metal oxide pigments such as titanium oxide, iron oxide, and titanium yellow, inorganic pigments such as carbon black, clay, and alumina white, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, vat pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, indigo pigments, and other organic pigments can be used. Among these, at least one selected from titanium oxide and carbon black is preferred. Furthermore, the color pigment can be added as a dispersion (ink) or paste to achieve more effective coloring. The color pigment may be used alone or in combination of two or more kinds.

[0022] The content of the color pigment may be adjusted appropriately depending on the shade of color to be imparted to the emulsion paint composition, but is preferably 0.03 to 3 mass %, more preferably 0.05 to 2 mass %, and even more preferably 0.08 to 1.5 mass %, based on the solid content of the emulsion paint composition.

[0023] (Thickener) The emulsion coating composition of the present invention preferably contains a thickener. By containing a thickener, it is possible to impart thixotropy to the emulsion coating composition or adjust the viscosity of the emulsion coating composition to a desired range. Examples of the thickener include acrylic acid, carboxymethyl cellulose (CMC), methyl cellulose, hydroxyethyl cellulose, urethane-modified polyether, polycarboxylic acid, etc. Among these, at least one selected from acrylic acid and CMC is preferred. The thickener may be used alone or in combination of two or more kinds.

[0024] The content of the thickener is not particularly limited as long as it allows the viscosity of the emulsion paint composition described below to be adjusted to the desired range, but it is preferably 0.01 to 2 mass %, more preferably 0.1 to 1.7 mass %, and even more preferably 0.2 to 1.5 mass %, based on the solids content of the emulsion paint composition.

[0025] (pH adjuster) The emulsion coating composition of the present invention may contain a pH adjuster as necessary. By containing a pH adjuster, as described below, the pH of the emulsion coating composition can be adjusted to a desired range, and the thickener can stably exert a thickening effect. When acrylic acid is used as a thickener, it is preferable to use the pH adjuster in combination with acrylic acid. The pH adjuster is not particularly limited as long as it can adjust the pH of the emulsion coating composition to the desired range, and examples thereof include sodium carbonate, sulfuric acid, p-toluenesulfonic acid, sodium hydroxide, potassium hydroxide, ammonia, alkanolamines, etc. Of these, sodium carbonate and ammonia are preferred. The pH adjusters may be used alone or in combination of two or more.

[0026] The content of the pH adjuster is not particularly limited as long as it can adjust the pH of the emulsion paint composition to the desired range, but is preferably 0.05 to 2 mass %, more preferably 0.08 to 1.5 mass %, and even more preferably 0.18 to 1 mass %, based on the solid content of the emulsion paint composition.

[0027] The emulsion coating composition of the present invention may contain additives such as dispersants, anti-settling agents, emulsifiers, antifoaming agents, anti-mold agents, preservatives, anti-skinning agents and anti-sagging agents, as necessary, within the scope of the object of the present invention.

[0028] The emulsion coating composition of the present invention is preferably dispersed in a dispersion medium such as water. The emulsion coating composition of the present invention preferably has a solid content concentration of 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. When the solid content concentration is equal to or more than the above lower limit, it becomes easier to form a uniform coating film on the substrate after drying the emulsion coating composition. From the viewpoint of coatability, the solid content concentration is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0029] The emulsion coating composition of the present invention preferably has a viscosity (hereinafter simply referred to as "viscosity") measured at 25±1°C using a B-type viscometer of 500 to 5000 mPa·s, more preferably 550 to 4500 mPa·s, and even more preferably 1000 to 4000 mPa·s. When the viscosity is equal to or greater than the above lower limit, the emulsion coating composition can be prevented from soaking into the substrate when applied to a substrate such as a board made of inorganic fibers, and a coating film having a uniform surface can be formed with a constant film thickness. When the viscosity is equal to or less than the above upper limit, the emulsion coating composition has good applicability, and a coating film having a uniform surface can be formed.

[0030] The emulsion coating composition of the present invention preferably has a pH of 7 or more. With a pH of 7 or more, the thickening effect of the emulsion coating composition is stable, and the viscosity can be easily adjusted to a desired range. From this viewpoint, the pH of the composition is more preferably 8 or more, and even more preferably 9 or more. Furthermore, the upper limit of the pH of the composition is not particularly limited, but from the viewpoint of handleability and the like, it is, for example, 13 or less, preferably 12 or less, and more preferably 11 or less.

[0031] The method for producing the emulsion paint composition of the present invention is not particularly limited, and the composition may be produced, for example, by mixing an acrylic emulsion resin dispersed in a dispersion medium such as water with an extender pigment, and, if necessary, a coloring pigment, a thickener, a pH adjuster, and other additives.

[0032] [Interior materials] The present invention also provides an interior material comprising a board made of inorganic fibers and a coating film made of the above emulsion coating composition formed on at least one surface of the board. The interior material may have the coating film formed on only one surface of the board, or may have the coating film formed on both surfaces. The coating film is preferably formed on the main surface of the board. For interior materials, the amount of coating after drying is, for example, 0.001 to 1 kg / m per side. 2 , preferably 0.003 to 0.8 kg / m 2 When the coating amount of the coating film is within the above range, a uniform coating film can be formed without excess or deficiency.

[0033] Examples of boards made of inorganic fibers include rock wool boards and slag wool boards. Among these, rock wool boards are preferred. By forming the coating film on the rock wool board, the surface of the rock wool board can be protected, and the inorganic fibers protruding from the surface of the rock wool board can be embedded in the coating film, improving the design of the rock wool board. Furthermore, since rock wool board has excellent fire resistance, the rock wool board having a coating film made of the above-mentioned emulsion paint composition formed thereon can be used as an interior material having excellent fire resistance. Rock wool board is a sheet-like member manufactured by accumulating rock wool. The rock wool contained in the rock wool board is not particularly limited, and examples thereof include fine fibers of about several μm obtained by melting raw materials such as rocks such as basalt, siliceous rocks, and limestone, and steel slag such as blast furnace slag at high temperatures and scattering the molten material with centrifugal force, high-pressure air, and / or steam. The fibers obtained in this manner are mineral fibers mainly composed of SiO2, etc., and / or aggregates thereof.

[0034] (Interior material manufacturing method) The method for producing the interior material of the present invention is not particularly limited, but for example, a coating liquid consisting of the above-mentioned emulsion paint composition may be applied to at least one surface of a board formed from inorganic fibers, and then the applied coating liquid may be dried to obtain the interior material.

[0035] The method of applying the coating liquid is not particularly limited, and may be, for example, applied with a brush or roller, spray applied, or applied using a coating machine. As a coating machine for applying the coating liquid, for example, an applicator, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater, etc. can be used. Among the above-mentioned coating machines, spray coating, an applicator, a die coater, and a curtain coater are preferred because they can make the thickness more uniform.

[0036] The method for drying the coating liquid is not particularly limited, but for example, a heat drying method in which the coating liquid is dried by heating with hot air, infrared rays, far infrared rays, or near infrared rays can be applied. The drying temperature is not particularly limited, but may be, for example, about 40 to 150°C, preferably about 60 to 130°C. EXAMPLES

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0038] Each physical property was determined by the following methods. (Tg of emulsion resin) The Tg of the emulsion resin used in each of the Examples and Comparative Examples was calculated using the FOX formula in accordance with the method described in the specification.

[0039] (viscosity) The emulsion coating compositions obtained in each of the Examples and Comparative Examples were measured using a Brookfield type viscometer ("DV2T") at 25°C using a spindle Lv64 at a rotation speed of 60 rpm for 1 minute.

[0040] (pH) The pH of the emulsion coating composition obtained in each of the Examples and Comparative Examples was measured using a pH meter ("PH-6011A-OM" manufactured by Monotaro Corporation).

[0041] (dryness) The emulsion paint composition obtained in each Example and Comparative Example was applied to a 5 cm square rock wool board so that the applied amount after drying would be 2 g, and the composition was left to stand in a 110°C environment for 30 minutes to dry, and the drying properties when dried were evaluated based on the following evaluation criteria. ⊚: Most of the surface of the coating film was uniform, and the composition did not soak into the rock wool board. ◯: Part of the coating surface was uneven, but the rest was uniform. ×: Most of the surface of the coating was uneven, or the composition was not sufficiently dried to the inside, causing skinning.

[0042] (tackiness) A coating film was formed in the same manner as in the evaluation of the drying property described above, and the tackiness of the coating film was evaluated according to the following evaluation criteria. ⊚: When the surface of the coating was touched with the hand, it did not feel sticky at all. ◯: When the surface of the coating film was touched with the hand, part of the surface of the coating film felt sticky, but other parts did not feel sticky. ×: When the surface of the coating film was touched with the hand, most of the surface of the coating film felt sticky.

[0043] (Low temperature processability) Four rock wool boards of 5 cm square were prepared. The emulsion coating composition obtained in each Example and Comparative Example was applied to each board with a trowel to form a coating film on the surface of the rock wool board, and four samples for evaluating low-temperature workability were obtained. These samples were each left to stand in a thermostatic chamber adjusted to -20°C for 1 hour to be sufficiently cooled. Next, the samples were removed from the thermostatic chamber, and immediately thereafter, the coating surface of each sample was measured with a non-contact thermometer, the temperatures at -10°C, -5°C, and 0°C were confirmed, and cuts were made with a cutter, and the low-temperature workability when the cuts were made was evaluated based on the following evaluation criteria. ⊚: No cracks occurred in the coating film in any of the samples. ◯: The coating film cracked at -10°C, but no cracks occurred in the other samples. △: The coating cracked at -10°C and -5°C, but no cracks occurred in the coating of the sample cooled to 0°C. ×: Cracks occurred in the coating film in all samples.

[0044] [Ingredients used] The components used in each of the examples and comparative examples are as follows. (Emulsion) Acrylic emulsion 1 (Daido Chemical Industry Co., Ltd. "Vinizol 1024C", acrylic ester copolymer resin, solid content concentration 55% by mass) Acrylic emulsion 2 (Daido Chemical Industry Co., Ltd. "Vinisole 1637", acrylic acid ester copolymer resin, solid content concentration 50% by mass) Acrylic emulsion 3 (Daido Chemical Industry Co., Ltd. "Vinisole 911", acrylic ester / vinyl acetate copolymer resin, solid content concentration 50% by mass) Acrylic emulsion 4 (Daido Chemical Industry Co., Ltd. "Vinisole 1079", acrylic acid resin, solid content concentration 40% by mass) Vinyl acetate emulsion (Daido Chemical Industry Co., Ltd. "Vinisole 2019", solids concentration 50% by mass) In Example 10, the acrylic emulsion blend 1 used was a mixture of the acrylic emulsion 1 and the acrylic emulsion 4 in a mass ratio of acrylic emulsion 1 / acrylic emulsion 4=80 / 20. In Comparative Example 5, the acrylic emulsion blend 2 was prepared by mixing the acrylic emulsion 1 and the acrylic emulsion 4 in a mass ratio of 50 / 50.

[0045] (Thickener) Carboxymethylcellulose (CMC) ("Sodium Carboxymethylcellulose" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Acrylic acid (Daido Chemical Industry Co., Ltd. "Vinisole 1020") (Film-forming aid) Ester-based film-forming agent (Adeka Cizer PN6120, manufactured by Adeka Corporation)

[0046] (Extender pigment) Calcium carbonate ("Calcium carbonate" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Barium sulfate ("Barium sulfate" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Aluminum hydroxide ("Aluminum hydroxide" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (Color pigments) Titanium oxide ("Titanium(IV) oxide" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Carbon black ("LIOFAST" manufactured by Toyo Color Co., Ltd.) (pH adjuster) Sodium carbonate ("Sodium Carbonate" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Ammonia water ("Ammonia water" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0047] [Examples 1 to 10, Comparative Examples 1 to 5] According to the formulations shown in Tables 1 to 3, the components were mixed using a Thinky Mixer ("ARE-500" manufactured by Thinky Corporation) to prepare emulsion coating compositions.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3] *The "paint solids concentration" in Tables 1 to 3 is the concentration of solids contained in the emulsion paint composition, excluding volatile components such as the dispersion medium, relative to the total amount of the emulsion paint composition. *The parts by mass of each emulsion in Tables 1 to 3 are the amounts blended into the product.

[0051] As is clear from the above examples, the emulsion coating composition satisfying the requirements of the present invention suppressed the development of tackiness and did not cause cracking in a low temperature environment. In contrast, the emulsion coating compositions prepared in Comparative Examples 1, 3, and 5 had emulsion resins with too high Tg, which caused cracking in low temperature environments. Of these, the emulsion coating composition prepared in Comparative Example 3, when dried to form a coating, produced a film only on the surface, with the inside remaining liquid and not solidifying, a phenomenon known as skinning, and the composition was rated poor in drying properties. In addition, the emulsion coating compositions prepared in Comparative Examples 2 and 4 had too high Tg of the emulsion resin, but did not crack in a low temperature environment because they contained a film-forming assistant. However, the content of the film-forming assistant was too high, which resulted in the coating film becoming tacky.

Claims

1. An emulsion paint composition comprising an acrylic emulsion resin and an extender pigment, The acrylic emulsion resin has a glass transition temperature of -40°C or higher and -5°C or lower, as calculated by the FOX equation, and the content of a film-forming auxiliary is less than 5% by mass based on the parts by mass of the emulsion coating composition.

2. 2. The emulsion coating composition according to claim 1, wherein the thickener is contained in an amount of 0.01 to 2 mass % based on the solid content of the emulsion coating composition, and the viscosity of the emulsion coating composition measured with a B-type viscometer at 25±1° C. is 500 to 5000 mPa s.

3. 3. The emulsion paint composition according to claim 1, wherein the content of said body pigment is 10 to 85 mass % based on the solid content of said emulsion paint composition.

4. 3. The emulsion paint composition according to claim 1, wherein the extender pigment comprises at least one selected from the group consisting of calcium carbonate, aluminum hydroxide, barium carbonate, barium sulfate, silica, kaolin, talc, glass, and silica sand.

5. 3. The emulsion paint composition according to claim 1, wherein the pH of the emulsion paint composition is 7 or more.

6. 3. The emulsion paint composition according to claim 1, further comprising a pH adjuster.

7. 3. An interior material comprising a board made of inorganic fibers and a coating film made of the emulsion coating composition according to claim 1 or 2 formed on at least one surface of the board.

8. 8. The interior material according to claim 7, wherein the board is a rock wool board.

9. The coating amount of the coating film after drying is 0.001 to 1 kg / m per side. ２ The interior material according to claim 7, wherein the thickness of the interior material is within the range of

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