JP4988235B2 - Water-based paint composition and coating method - Google Patents

Description

  The present invention relates to an aqueous coating composition and a coating method.

  In general, paint on the walls of buildings, etc. is applied with an undercoating paint that forms an elastic coating to follow the small cracks that occur on the surface of the wall and suppress the ingress of water from the outside. There are known coating methods for applying a top coating material that forms a coating film having excellent weather resistance and finish. For example, Patent Document 1 includes an aqueous dispersion of a carbonyl group-containing copolymer, a hydrazide compound, and a pigment, on an elastic base coating film formed by an elastic base coating material in which the elongation rate of the formed coating film and the pigment volume concentration are within a specific range. A coating method for applying a top coat having a specific elongation is disclosed. According to the multilayer coating film formed by this coating method, it has a good finished appearance and high durability, and it has become possible to maintain the aesthetics of the building over a long period of time. Depending on the paint combination, the intended purpose may not be achieved.

  For such a problem, Patent Document 2 describes an aqueous coating composition containing a core-shell type carbonyl group-containing copolymer emulsion in which carbonyl groups are unevenly distributed in the shell portion and a specific amount of pigment. When such a water-based coating composition is applied to a base coating composition, a multi-layer coating finish having a good finished appearance and high durability is possible regardless of the combination of the base material and the top coating material. In some cases, the adhesion is not sufficient.

  As a technique for improving adhesion to a substrate, Patent Document 3 discloses an emulsion resin having a glass transition temperature in a specific range obtained by emulsion polymerization of a monomer mixture containing an acetoacetoxy group-containing unsaturated monomer, and an aliphatic group. An aqueous primer composition comprising a dihydrazide compound is described. According to such an undercoating material composition, one carbonyl moiety of the acetoacetoxy group is crosslinked, and the other carbonyl moiety forms a strong hydrogen bond with the base material and the old coating film, and so on. Although it is possible to form an undercoat film excellent in initial water resistance, etc., the paint film may not follow the fine cracks that occur on the wall surface due to insufficient elongation of the film in a low temperature environment. is there.

  In general, the physical properties of the coating film are significantly reduced under a low temperature environment. A technique for lowering the glass transition temperature of the resin is known to ensure the physical properties of the coating film at low temperatures. However, simply adjusting the glass transition temperature improves the elongation of the coating film at low temperatures, but it does not apply at room temperature. The toughness of the film becomes insufficient, and it is very difficult to achieve both.

JP-A-6-190332 JP 2002-309160 A JP 2003-201440 A

  The object of the present invention is excellent in adhesion to the surface to be coated, and suitable for forming a flexible and tough coating film capable of following changes over time of the surface to be coated even in a low temperature environment. An object is to provide a water-based coating composition and a coating method using the same.

As a result of intensive studies on the above-mentioned problems, the present inventors have found that in an aqueous coating composition containing a copolymer aqueous dispersion and a pigment, the copolymerization amount of n-butyl acrylate , the pigment concentration, and hydrazine in the copolymer aqueous dispersion By adjusting the blending amount of the derivative to a specific range, it was found that a coating film that can achieve both the physical properties of the coating film at low temperature and the adhesion to the coated surface can be formed, and the present invention has been achieved. That is, the present invention
1.
An aqueous coating composition comprising a copolymer aqueous dispersion (A), a pigment (B), and a hydrazine derivative (C) , wherein the copolymer aqueous dispersion (A) comprises n-butyl acrylate (a) 65- 85% by mass, carbonyl group-containing polymerizable unsaturated monomer (b) 0.05 to 8% by mass, linear or branched alkyl group having 6 or less carbon atoms and / or vinyl aromatic compound (c1) ) 5-20% by mass, carboxyl group-containing polymerizable unsaturated monomer (c2) 1.0-3.0% by mass, and other than the above-mentioned monomers (a), (b), (c1) and (c2) It is obtained by copolymerizing 0 to 28.95% by mass of a polymerizable unsaturated monomer, and the amount of the hydrazine derivative (C) used is 0. 0% relative to the solid content of the copolymer aqueous dispersion (A). In the range of 1 to 1.0% by weight, An aqueous coating composition, wherein the pigment volume concentration in the composition is in the range of 15 to 60%;
2.
2. The aqueous solution according to item 1, wherein the polymerizable unsaturated monomer used in the production of the aqueous copolymer dispersion (A) is selected such that the glass transition temperature of the copolymer is −20 ° C. or lower. Paint composition,
3.
Item 3. The aqueous coating composition according to Item 1 or 2, wherein the copolymer of the aqueous copolymer dispersion (A) has a weight average molecular weight in the range of 50,000 to 1,000,000.
4).
3. The aqueous coating composition according to item 1 or 2, wherein the pigment (B) is a combination of an extender pigment and a colored pigment,
5.
The aqueous coating composition according to any one of claims 1 to 4, further comprising a thickener, wherein the thickener is a combination of a fiber derivative compound and a polyether compound,
6).
6. A coating method comprising coating the water-based paint composition according to any one of items 1 to 5 on a surface to be coated;
7).
A coating method comprising: coating the surface to be coated with the aqueous coating composition according to any one of items 1 to 5;
About.

  According to the water-based coating composition of the present invention, it is possible to form a flexible and tough coating film, and to follow changes in the coated surface over time even in a low-temperature environment. It is possible to form a coating film that can suppress the intrusion. In addition, the coating film is excellent in adhesion to the surface to be coated, and it is possible to omit the sealer step of applying the sealer to the surface to be coated. Furthermore, according to the invention according to claim 7, wherein a multi-layer coating film excellent in waterproofness, weather resistance, etc. can be formed on a coating film formed by the aqueous coating composition of the present invention. Etc. can be maintained over a long period of time.

Carbonyl group-containing copolymer aqueous dispersion The copolymer aqueous dispersion (A) applied to the aqueous coating composition of the present invention is a linear or branched acrylate containing an alkyl group having 6 or less carbon atoms. (A) and a carbonyl group-containing polymerizable unsaturated monomer (b) as a copolymerization component, an acrylate containing a linear or branched alkyl group having 6 or less carbon atoms in the copolymer (a ) Is a copolymerization ratio of 50% by mass or more.

  Specific examples of the acrylate (a) containing a linear or branched alkyl group having 6 or less carbon atoms in the copolymer aqueous dispersion (A) include methyl acrylate, ethyl acrylate, n-propyl acrylate, Examples include n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, and the like. These can be used alone or in combination of two or more.

  In the present invention, a specific amount of a linear or branched acrylate containing an alkyl group having 6 or less carbon atoms is copolymerized, whereby the elongation rate at a low temperature of the coating film formed from the aqueous coating composition of the present invention, It has the effect of improving the toughness of the coating film at room temperature and the adhesion to the coated surface.

  In the present invention, the copolymerization ratio of the acrylate (a) containing a linear or branched alkyl group having 6 or less carbon atoms in the copolymer aqueous dispersion (A) is required to be 50% by mass or more. is there. When the copolymerization ratio of the acrylate (a) is less than 50% by mass, the flexibility of the coating film formed from the aqueous coating composition of the present invention at low temperature, the toughness of the coating film at normal temperature, and the adhesion to the coated surface. Is not preferable.

  Specific examples of the carbonyl group-containing polymerizable unsaturated monomer (b) include (meth) acrolein, formylstyrene, a vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone, etc. ), Acetoacetoxyethyl (meth) acrylate, acetoacetoxyallyl ester, diacetone (meth) acrylamide and the like, and can be used alone or in combination of two or more.

  In the present invention, the copolymer aqueous dispersion (A) is a linear or branched acrylate (a) having an alkyl group having 6 or less carbon atoms, a carbonyl group-containing polymerizable unsaturated monomer (b), Other polymerizable unsaturated monomers (c) other than these can be copolymerized as necessary. Specific examples of the other polymerizable unsaturated monomer (c) include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, and n-hexyl methacrylate. Methacrylates containing a linear or branched alkyl group having 6 or less carbon atoms such as styrene, vinyl aromatic compounds such as α-methylstyrene, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl ( (Meth) acrylates containing linear or branched alkyl having 7 or more carbon atoms such as (meth) acrylate; alicyclic (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; 2-hydroxy Hydroxyalkyl (meth) acrylates such as ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, and the above hydroxyalkyl (meth) Hydroxyl-containing polymerizable unsaturated monomer such as polyoxyethylene chain-containing (meth) acrylate having a hydroxyl group at the molecular end; (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate Carboxyl group-containing polymerizable unsaturated monomers such as aralkyl (meth) acrylate such as benzyl (meth) acrylate; alkoxy alkenyl such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate Kill (meth) acrylate; perfluoroalkyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate; (meth) acrylamide, (meth) acrylonitrile; vinyl ester compounds such as vinyl acetate and vinyl propionate; allyl (meta ) Acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 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-trishydroxymethylethane di (meth) acrylate, 1,1,1-trishydroxymethylethanetri (meth) acrylate, 1 , 1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate, polyvinyl compounds having at least two polymerizable unsaturated groups in one molecule, etc .; glycidyl (meta ) Acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acryl And epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether; isocyanate group-containing polymerizable unsaturated monomers such as isocyanate ethyl (meth) acrylate and m-isopropenyl-α, α-dimethylbenzyl isocyanate; vinyl Alkoxysilyl group-containing polymerizable unsaturated monomers such as trimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyltriethoxysilane; epoxy group-containing polymerizable unsaturated monomers or hydroxyl group-containing polymerization Of reaction products of unsaturated unsaturated monomers with unsaturated fatty acids, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentenyloxypropyl (meth) acrylate, dicyclopentenyl (meth) acrylate, etc. Of group-containing polymerizable unsaturated monomers, and these may be used alone or in combination of two or more.

  In the present invention, the polymerizable unsaturated monomer used for the production of the copolymer aqueous dispersion (A) has a glass transition temperature of -20 ° C or lower, preferably in the range of -30 to -60 ° C. It is desirable to be selected.

  In the present invention, the glass transition temperature (absolute temperature) is a value calculated by the following formula.

1 / Tg = W ₁ / T ₁ + W ₂ / T ₂ +... W _n / T _{n
Wherein, W 1, W 2 ··· W} n is the weight percent of each monomer [= (amount / monomer total weight of each monomer) × _{100], T 1, T 2 ··· T} n each It is the glass transition temperature (absolute temperature) of the homopolymer of the monomer. The glass transition temperature of the homopolymer of each monomer is a value according to Polymer Hand Book (4th edition, edited by J. Brandrup / EHImmergut), and the glass transition temperature of a monomer not described in the literature is the homopolymeric homopolymer of the monomer. The polymer is synthesized so that the weight average molecular weight is about 50,000, and the value when the glass transition temperature is measured by differential scanning thermal analysis is used.

  In the present invention, as the other polymerizable unsaturated monomer (c), the linear or branched carbon number is 6 or less from the viewpoint of water resistance of the coating film formed from the aqueous coating composition of the present invention. From the viewpoint of pigment dispersibility, it is desirable to use the carboxyl group-containing polymerizable unsaturated monomer (c2) as the methacrylate and / or vinyl aromatic compound (c1) containing the above alkyl group.

As an example of a preferable monomer composition of the copolymer aqueous dispersion (A) as described above in the present invention,
An acrylate (a) having a linear or branched alkyl group having 6 or less carbon atoms,
50 to 85% by mass, preferably 65 to 85% by mass,
A carbonyl group-containing polymerizable unsaturated monomer (b),
0.01 to 10% by mass, preferably 0.05 to 8% by mass,
A methacrylate and / or vinyl aromatic compound (c1) containing a linear or branched alkyl group having 6 or less carbon atoms,
5 to 25% by mass, preferably 5 to 20% by mass,
The carboxyl group-containing polymerizable unsaturated monomer (c2) is
0.05-5% by mass, preferably 1.0-3.0% by mass,
Other polymerizable unsaturated monomers other than (a), (b), (c1) and (c2)
0 to 44.94% by mass, preferably 0 to 28.95% by mass,
Can be mentioned.

  The method for polymerizing the monomer is not particularly limited. For example, by copolymerizing the polymerizable unsaturated monomer in the presence of a surfactant as an emulsifier according to a general emulsion polymerization method. It can be manufactured easily.

  In addition, the use of an emulsion polymer obtained by an emulsion polymerization method is preferable because it can reduce the amount of the organic solvent in the finally obtained aqueous coating composition and can set the molecular weight of the copolymer high. .

  As the emulsifier used in the production of the copolymer aqueous dispersion (A), conventionally known emulsifiers can be used. Examples of applicable emulsifiers include anionic emulsifiers, nonionic emulsifiers, both Examples include ionic emulsifiers.

  Examples of anionic emulsifiers include diammonium dodecyl diphenyl ether disulfonate, sodium dodecyl diphenyl ether disulfonate, calcium dodecyl diphenyl ether disulfonate, alkyl diphenyl ether disulfonate such as sodium alkyl diphenyl ether disulfonate; sodium dodecyl benzene sulfonate, ammonium dodecyl benzene sulfonate, etc. Alkyl benzene sulfonates; alkyl sulfates such as sodium lauryl sulfate and ammonium lauryl sulfate; aliphatic carboxylates such as fatty acid sodiums and potassium oleate; sulfate salts containing polyoxyalkylene units (for example, polyoxyethylene alkyl ethers) Sodium sulfate, polyoxyethylene alkyl ether sulfate Polyoxyethylene alkyl ether sulfate salts such as nium; polyoxyethylene alkyl phenyl ether sulfate salts such as sodium polyoxyethylene alkyl phenyl ether sulfate and polyoxyethylene alkyl phenyl ether ammonium sulfate; polyoxyethylene polycyclic sodium phenyl ether sulfate; Polyoxyethylene polycyclic phenyl ether sulfate salts such as ammonium polyoxyethylene phenyl ether sulfate; etc.); naphthalene sulfonic acid formalin condensate sodium naphthalene sulfonic acid formalin condensate salt, etc .; sodium dialkylsulfosuccinate, monoalkyl succinate And alkyl succinate sulfonates such as disodium sulfonate and the like. These may be used alone or in combination of two or more. It is possible to use Te Align.

  Examples of nonionic emulsifiers include polyoxyalkylene unit-containing ether compounds (for example, polyoxyalkylene alkyl ether compounds such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene tridecyl ether, polyoxyethylene oleyl ether). Polyoxyalkylene alkyl phenyl ether compounds such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; polyoxyalkylene polycyclic phenyl ether compounds such as polyoxyethylene polycyclic phenyl ether; etc.); polyoxyethylene monolaur Polyoxyalkylene alkyl ester compounds such as rate, polyoxyethylene monostearate, polyoxyethylene monooleate; Polyoxyalkylene alkylamine compounds such as reoxyethylene alkylamine; sorbitan compounds such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate; Can be used alone or in combination of two or more.

  Examples of amphoteric surfactants include dimethylalkylbedines, dimethylalkyllaurylbedines, and alkylglycines.

  As the emulsifier, a reactive emulsifier containing a polymerizable unsaturated group and an anionic group or a nonionic group in the molecule can also be used.

  As the usage-amount of the said emulsifier, it is 0.5-6 mass% with respect to all the polymerizable unsaturated monomers used for manufacture of a copolymer aqueous dispersion (A), Preferably it exists in the range of 1-4 mass%. It can be.

  The polymerization initiator used for the polymerization includes tert-butylperoxy 2-ethylhexanoate, benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl hydro gen. Peroxide, tert-butyl peroxylaurate. Organic peroxides such as tert-butylperoxyisopropyl carbonate, tert-butylperoxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobis (2-methyl) Propiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2- Azo compounds such as hydroxyethyl) -propionamide] and azobis {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate Etc.

  As a suitable usage-amount of the said polymerization initiator, it is in the range of 0.001-15 mass% with respect to all the polymerizable unsaturated monomers used for manufacture of a copolymer aqueous dispersion (A). it can.

  The weight average molecular weight of the copolymer aqueous dispersion (A) obtained as described above is in the range of 50,000 to 1,000,000, particularly 150,000 to 500,000 from the point of elongation of the formed coating film. It is desirable.

  In this specification, the weight average molecular weight is a value obtained by converting the weight average molecular weight measured by gel permeation chromatograph (“HLC8120GPC” manufactured by Tosoh Corporation) based on the weight average molecular weight of polystyrene. Columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (both manufactured by Tosoh Corporation, trade names) ), Mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI.

Pigment (B)
Examples of the pigment (B) used in the aqueous coating composition of the present invention include coloring pigments such as titanium oxide, carbon black, and bengara; barita powder, precipitated barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, silica And extender pigments such as white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, and gloss white. These can be used alone or in combination of two or more.

  In the present invention, the amount of the pigment (B) used is desirably adjusted so that the pigment volume concentration is in the range of 15 to 60%, preferably 15 to 45%, more preferably 25 to 42%. .

  When the pigment volume concentration is less than 15%, a tough coating film cannot be obtained. On the other hand, when the pigment volume concentration exceeds 60%, crack followability of the coating film is lowered, which is not preferable.

  In the present specification, the pigment volume concentration is a volume ratio of the pigment content in the total solid content of the total resin content and the total pigment content in the paint. In this specification, the specific gravity of the pigment which is the basis for calculating the volume of the pigment is according to “Paint Raw Material Handbook 6th Edition” (Japan Paint Manufacturers Association), and the specific gravity of the resin solids is Approximate to 1.

  In the present invention, the pigment (B) is preferably a combination of extender pigments and colored pigments. The combined use ratio is 99/1 to 60/40, preferably 95/5 to 70/30, in terms of extender pigment / colored pigment mass ratio. To preferred.

Hydrazine derivative (C)
The water-based coating composition of the present invention can be blended with a hydrazine derivative (C) as necessary for the purpose of improving the water resistance, adhesion, and toughness of the coating film at room temperature. The hydrazine derivative (C) has a functional group that undergoes a crosslinking reaction with the carbonyl group of the copolymer aqueous dispersion (A). Specific examples thereof include hydrazine, hydrazine hydrate, oxalic acid dihydrazide, and malonic acid dihydrazide. Dihydrazides of saturated aliphatic carboxylic acids having 2 to 18 carbon atoms such as succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide; monoolefinic unsaturated compounds such as maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide Dicarboxylic acid dihydrazide; phthalic acid, terephthalic acid or isophthalic acid dihydrazide; pyromellitic acid dihydrazide, trihydrazide or tetrahydrazide; nitrilotriacetic acid trihydrazide, citric acid trihydrazide, 1,2,4-benzenetrihydra Ethylenediaminetetraacetic acid tetrahydrazide, 1,4,5,8-naphthoic acid tetrahydrazide; polyhydrazide obtained by reacting a low polymer having a carboxylic acid lower alkyl ester group with hydrazine or hydrazine hydrate (hydrazine hydride) Etc .; Carbonic dihydrazide, bissemicarbazide; Diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate and polyisocyanate compounds derived therefrom are reacted with N, N-substituted hydrazines such as N, N-dimethylhydrazine and the hydrazides exemplified above in excess. A polyfunctional semicarbazide obtained by the above process; isoforms in a reaction product of the polyisocyanate compound and an active hydrogen compound containing a hydrophilic group such as polyether polyols and polyethylene glycol monoalkyl ethers; Aqueous polyfunctional semicarbazide obtained by overreact the above-exemplified dihydrazide in Aneto group; a mixture of polyfunctional semicarbazide and aqueous polyfunctional semicarbazide; bis-acetyl-di hydrazone, or the like may be suitably used. The compounds described above can be used alone or in combination of two or more.

  The amount of the hydrazine derivative (C) used is 0.01 to 3.0% by mass, preferably 0.01 to 2.0% by mass, more preferably based on the solid content of the copolymer aqueous dispersion (A). Is preferably in the range of 0.1 to 1.0 mass%.

  In the present invention, the aqueous coating composition may contain a thickener from the viewpoints of coating workability, prevention of pigment settling, and the like.

  As the thickener, conventionally known ones can be used without limitation, and specific examples thereof include inorganic compounds such as water-soluble alkali silicate, montmorillonite, colloidal alumina; fibers such as methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, etc. Derivative compounds; polyether compounds such as pluronic polyethers, polyether dialkyl esters, polyether dialkyl ethers, polyether urethane modified products, polyether epoxy modified products; polyacrylic acid soda, polyacrylic acid (meth) acrylic acid Polyacrylic acid compounds such as ester copolymers; polyvinyl compounds such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl benzyl alcohol copolymer; sodium caseinate, casein Protein derivatives such as ammonium; maleic anhydride copolymers such as partial esters of vinyl methyl ether-maleic anhydride copolymer, half esters of a reaction product of drying oil fatty acid allyl alcohol ester-maleic anhydride, etc. Can be used alone or in combination of two or more. In particular, a combination of a fiber derivative-based compound and a polyether-based compound is preferable because it improves the roller coating workability and exhibits a good finish. When combining a fibrin derivative compound and a polyether compound, the use ratio of both is 1/99 to 99/1, preferably 10/90 to 90 / in mass ratio of fibrin derivative compound / polyether compound. It is preferable to be within the range of 10.

  The amount of the thickener used is 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the solid content of the copolymer aqueous dispersion (A).

  In the present invention, the aqueous coating composition includes a resin other than the copolymer aqueous dispersion (A) as necessary, for example, a water-soluble or water-dispersible resin such as an acrylic resin, a urethane resin, and a fluororesin. May be.

  In addition, the above-mentioned water-based paint composition includes an antifoaming agent, a curing catalyst, a pigment dispersant, a fragrance, an antiseptic, a deodorant, an antibacterial agent, a neutralizing agent, a surfactant, an aqueous water repellent, an antifungal agent, a freezing agent. Paint additives such as an inhibitor, an ultraviolet absorber, a light stabilizer, and a film-forming aid can be included as necessary.

The water-based coating composition of the present invention has very good coating film physical properties, and can form a flexible and tough coating film. Specifically, the elongation at 23 ° C. can be 300% or more, particularly 300 to 900%, the elongation at −20 ° C. is 70% or more, particularly 70 to 200%, and the maximum stress at 23 ° C. is 1 .3 N / mm ² or more, particularly 1.3 to 3.0 N / mm ² .

  In this specification, the elongation rate and the maximum stress of the formed coating film, which are indices of flexibility and toughness, are obtained by coating a sample on a release paper (200 mm × 200 mm) using a doctor blade, a temperature of 23 ° C., a relative humidity of 50 After drying and curing for 2 weeks under the condition of%, the coating film was peeled off to obtain a free coating film having a dry film thickness of about 1 mm. Using the name “Autograph AG2000B type” (manufactured by Shimadzu Corporation), the temperature is 23 ° C. or −20 ° C. and the tensile speed is 200 mm / min.

Coating method The method of the present invention is a coating method for coating the surface to be coated with the aqueous coating composition of the present invention obtained as described above.

  Examples of coated surfaces include gypsum boards, concrete surfaces, mortar surfaces, slate plates, PC plates, ALC plates, cemented calcium silicate plates, base materials such as wood, stone, plastic, metal, etc. Examples of the acrylic resin-based, acrylic urethane resin-based, polyurethane resin-based, fluororesin-based, silicon acrylic resin-based, vinyl acetate resin-based, and epoxy resin-based coating surfaces.

  If necessary, the surface to be coated may be a sealer-coated surface using a conventionally known sealer.

The coating amount of the aqueous coating composition of the present invention is, for example, 0.1 to ² kg / m ^2, preferably 0.2 to 1.5 kg / m ² .

  As a coating means for applying the aqueous coating composition of the present invention, for example, a known coating device such as a roller, an air spray, an airless spray, a ricin gun, a universal gun or a brush can be used.

  As a method for drying the formed coating film, any one of heat drying, forced drying, and room temperature drying can be employed.

  Moreover, this invention is a coating method characterized by coating the above-mentioned aqueous coating composition on the surface to be coated and then overcoating the coated surface.

  As the top coating used in the method of the present invention, water-based or organic solvent-based coatings that can impart conventionally known coloration and glossiness of the finished surface, weather resistance, waterproofness, and the like can be applied without limitation. The paint may be cross-linked or non-cross-linked.

  Examples of the top coat include acrylic resin emulsion-based paints and isocyanate cross-linking curable paints.

  As the acrylic resin emulsion-based paint, an acrylic resin emulsion is used as a base resin component, and a crosslinking agent that undergoes a crosslinking reaction with the acrylic resin emulsion may be added. A urethane-based resin emulsion or a fluorine-based resin emulsion. Etc. may be blended as necessary.

  The isocyanate cross-linking curable paint is preferably a two-component paint comprising an isocyanate curing agent and a main agent having an active hydrogen that reacts with an isocyanate group. Examples of the main agent include fluorine resins, acrylic resins, and polyester resins. What uses hydroxyl-containing resin, such as resin and silicone resin, as base resin can be used conveniently.

The top coating is applied to the coated surface after the aqueous coating composition of the present invention is applied. As a coating method, a known method such as roller, air spray, airless spray, lysine gun, universal gun, brush, etc. Painting equipment can be used. The coating amount of the top coating is suitably about 0.1 to 0.5 kg / m ² , and the drying method of the formed coating film can be any of heat drying, forced drying, and room temperature drying. .

  Hereinafter, the present invention will be described in more detail with reference to examples. “Part” and “%” indicate “part by mass” and “% by mass”, respectively.

Production of copolymer aqueous dispersion Production Example 1
Add 300 parts of deionized water and 0.1 part of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd., an anionic surfactant having a polyoxyethylene chain, non-volatile content of 30%) to a 2 liter 4-necked flask, and after nitrogen replacement , Kept at 85 ° C. In the pre-emulsion formed by emulsifying the following composition, 3% by mass and 30% by mass of the following catalyst aqueous solution were added and stirred. From 20 minutes after the addition, 97% by mass of the following pre-emulsion and 70% by mass of the following aqueous catalyst solution were added dropwise over 4 hours.
Pre-emulsion Deionized water 287 parts Methacrylic acid 16 parts Styrene 80 parts n-Butyl acrylate 664 parts Diacetone acrylamide 40 parts "Newcol 707SF" 53 parts
Aqueous catalyst solution Ammonium persulfate 1.5 parts Deionized water 120 parts After completion of dropping, 56 parts of deionized water was added, and this was further maintained at 75C for 2 hours, and then cooled to 40C or less. Subsequently, it adjusted to pH 8-9 with aqueous ammonia, and obtained the copolymer aqueous dispersion (A-1) of 50% of solid content. The weight average molecular weight of the obtained copolymer was 300,000.

Production Examples 2-7
In the above Production Example 1, copolymer aqueous dispersions (A-2) to (A-7) were produced in the same manner as in Production Example 1 except that the monomer composition was changed to Table 1.

Examples 1-17 and Comparative Examples 1-4
Manufacture of water-based paint for base preparation The components shown in Table 2 were blended in the aqueous copolymer dispersion obtained in the above-mentioned production example, and mixed by stirring to obtain each water-based paint for base preparation. In Table 2, (Note 1) to (Note 7) are as follows.

(Note 1) extender pigment: calcium carbonate with a specific gravity of 2.7,
(Note 2) Color pigment: Titanium oxide having a specific gravity of 4.1,
(Note 3) “Texanol”: trade name, manufactured by Eastman Chemical Co., 2,2,4-trimethylpentanediol monoisobutyrate,
(Note 4) Thickener 1: 2.5% hydroxyethyl cellulose aqueous solution,
(Note 5) Thickener 2: Urethane associative thickener “Adecanol UH-526”, manufactured by Asahi Denka,
(Note 6) Antifoaming agent: “SN deformer A63”, manufactured by San Nopco,
(Note 7) Dispersant: “Nopco Santo K”, manufactured by San Nopco.

Evaluation test (* 1) Elongation rate of formed coating film, maximum stress:
The sample was coated on a release paper (200 mm × 200 mm) using a doctor blade, dried and cured for 2 weeks at a temperature of 23 ° C. and a relative humidity of 50%, and then the coating film was peeled off to obtain a dry film thickness of about 1 mm. A free coating film was obtained, and the elongation and maximum stress of the free coating film were measured at a temperature of 23 ° C. or −20 ° C. using a tensile tester (trade name “Autograph AG2000B type” manufactured by Shimadzu Corporation). Then, the measurement was performed under the condition of a tensile speed of 200 mm / min. The higher the value, the better.
(* 2) Zero span test:
Each base adjustment water-based paint is applied to the surface of the plate with a groove having a width of 1 mm and a depth of 3 mm at the center of the back surface of the flexible plate so that the dry film thickness is 1 mm. After drying and curing for 2 weeks at a humidity of 50%, press the finger on the groove at the center of the back of the flexible plate without damaging the paint film, and use only the flexible plate as a test specimen. The test specimen was attached to an autograph AG2000B type (Shimadzu Corporation), and a tensile test was conducted at −10 ° C. under a tensile speed of 20 mm / min.
○: Elongation 3.0 mm or more x: Elongation less than 3.0 mm.
(* 3) Coating workability Each base preparation water-based paint was applied on a mortar plate with a sand-bone roller so that the coating amount was about 1.0 kg / m ^2, and sensory evaluation was performed regarding workability and finish at that time. .
○: There is little splashing or sagging during painting, the roller is easy to move, it is finished evenly and smoothly, and there is no abnormality in the appearance of the coating film.
X: A lot of splash and sagging at the time of coating, the roller is difficult to move, it is difficult to finish uniformly, or the appearance of the coating film is bad.
(* 4) Adhesiveness A coated plate was prepared by applying an acrylic coating ("Ares Aqua Gloss": trade name, water-based acrylic resin-based top coating, manufactured by Kansai Paint Co., Ltd.) on a flexible plate via a sealer. The base coating water-based paint for each substrate adjustment is applied to a dry film thickness of 1 mm, cured at 20 ° C. for 7 days, and cut into 100 grids at 1 mm intervals. When the adhesive tape was closely attached to and peeled off instantaneously, the evaluation was made based on the number of squares in which no peeling occurred.
◯: Remaining number is 80 or more, Δ: Remaining number is 40 to 79, X: Remaining number is 39 or less.

Coating Examples 18-38 and Comparative Examples 5-8
Each of the above-prepared water base coating materials obtained above is applied on a mortar plate (90 × 300 × 20 mm) with a sand-bone roller so that the coating amount is about 1.0 kg / m ^2, and 20 ° C./75% RH. And dried for 1 day. Next, the following top coat is applied onto this base coating film by airless spray so that the coating amount is about 0.2 kg / m ^2, and dried at 20 ° C. and 75% RH for 7 days to obtain a finished plate. It was. Subsequently, the obtained paint finish board was used for the following performance test. The results are shown in Table 3. In Table 3, the types of top coating paints a to d and the performance test methods are as follows.

  Topcoat type a. “Ares Aqua Silicon AC”: trade name, manufactured by Kansai Paint Co., Ltd., water-based acrylic silicone resin-based paint, b. “Rivel Top”: trade name, manufactured by Kansai Paint Co., Ltd., a two-component aqueous acrylic urethane resin-based paint containing a hydroxyl group-containing resin and an isocyanate curing agent, c. “Ares Aquaretan”: trade name, manufactured by Kansai Paint Co., Ltd., water-based acrylic resin emulsion paint, d. “Ares Aqua Gloss”: trade name, manufactured by Kansai Paint Co., Ltd., an aqueous reaction-curable acrylic resin emulsion-based top coating.

(* 5) Finished appearance: The finished appearance of the coating film surface of each painted finish plate was visually evaluated.
◯: Glossy and evenly finished, X: Not finished evenly due to uneven suction of top coating, etc.
(* 6) Zero-span test with multi-layer coating film Applying each base-adjusting water-based paint to the surface of the board with a groove of 1mm width and 3mm depth at the center of the back side of the flexible board with a sandbone roller It is applied so that the amount is about 1.0 kg / m ² , dried at 20 ° C. and 75% RH for one day, and then each overcoating is applied to the undercoat material coating film by airless spraying to about 0.2 kg. / M ^2, and dried for 7 days at 20 ° C. and 75% RH, and then pressed with a finger in the central groove on the back of the flexible plate so as not to damage the multilayer coating film. A specimen obtained by dividing only the above was used as a test specimen, and this specimen was attached to an autograph AG2000B type (Shimadzu Corporation), and a tensile test was performed in a -10 ° C atmosphere at a tensile speed of 20 mm / min.
○: Elongation is 3.0 mm or more, and there is no crack up to 3.0 mm.
X: A hole or tear that reaches the undercoat film occurs in the topcoat film with an elongation of less than 3.0 mm.

Claims (7)

An aqueous coating composition comprising a copolymer aqueous dispersion (A), a pigment (B), and a hydrazine derivative (C) , wherein the copolymer aqueous dispersion (A) comprises n-butyl acrylate (a) 65- 85% by mass, carbonyl group-containing polymerizable unsaturated monomer (b) 0.05 to 8% by mass, linear or branched alkyl group having 6 or less carbon atoms and / or vinyl aromatic compound (c1) ) 5-20% by mass, carboxyl group-containing polymerizable unsaturated monomer (c2) 1.0-3.0% by mass, and other than the above-mentioned monomers (a), (b), (c1) and (c2) It is obtained by copolymerizing 0 to 28.95% by mass of a polymerizable unsaturated monomer, and the amount of the hydrazine derivative (C) used is 0. 0% relative to the solid content of the copolymer aqueous dispersion (A). In the range of 1 to 1.0% by weight, An aqueous coating composition, wherein the pigment volume concentration in the composition is in the range of 15 to 60%. The polymerizable unsaturated monomer used in the production of the copolymer aqueous dispersion (A) is selected so that the glass transition temperature of the copolymer is -20 ° C or lower. Water-based paint composition. The water-based coating composition according to claim 1 or 2, wherein the copolymer of the aqueous copolymer dispersion (A) has a weight average molecular weight in the range of 50,000 to 1,000,000. The aqueous paint composition according to claim 1 or 2, wherein the pigment (B) is a combination of an extender pigment and a color pigment. The aqueous coating composition according to any one of claims 1 to 4, further comprising a thickener, wherein the thickener is a combination of a fiber derivative compound and a polyether compound. A coating method comprising applying the aqueous coating composition according to any one of claims 1 to 5 to a surface to be coated. A coating method comprising: coating the surface to be coated with the aqueous coating composition according to any one of claims 1 to 5;