WO2016043149A1

WO2016043149A1 - Method for forming coating film

Info

Publication number: WO2016043149A1
Application number: PCT/JP2015/075980
Authority: WO
Inventors: 環川元
Original assignee: 日本ペイントホールディングス株式会社
Priority date: 2014-09-17
Filing date: 2015-09-14
Publication date: 2016-03-24

Abstract

The purpose of the present invention is to provide a method with which it is possible to form a coating film even under conditions, such as low temperature conditions and/or highly humid conditions, in which it is difficult to form a coating film by applying an aqueous coating composition. The present invention relates to a method for forming a coating film, the method comprising: a coating step for coating with an aqueous coating composition; a coating film separation step for separating the coating film obtained by said coating into a moisture-containing uppermost layer and a coating film formation layer; and a moisture removal step for removing the moisture-containing uppermost layer by a method other than drying.

Description

Coating method

The present invention relates to a coating film forming method in which a coating film is formed by application of a water-based coating composition.

Liquid coating compositions can generally be roughly classified into two types: a solvent-based coating composition containing an organic solvent and an aqueous coating composition containing water as a main solvent. In general, the water-based coating composition has a small amount of organic solvent compared to the solvent-based coating composition, and therefore has a low environmental load. Therefore, use of water-based paint compositions is required in various coating fields.

On the other hand, the water-based paint composition contains water having a low evaporation rate as a solvent. Therefore, in the formation of the coating film, it is strongly influenced by the environment during the coating and drying of the aqueous coating composition. Specifically, for example, when the aqueous coating composition is applied and dried in a low temperature environment of 5 ° C. or lower, the evaporation of water as a solvent is very slow. Also, for example, when the aqueous coating composition is applied and dried in a high humidity environment with a humidity of 80% or more, the evaporation of water as a solvent is very slow. Under such low temperature and / or high humidity conditions, after the application of the aqueous coating composition, water as a solvent cannot sufficiently evaporate, so that the strength of the coating film does not increase and a coating film having the intended function is obtained. There was a problem that it could not be obtained.

JP 2012-229302 A (Patent Document 1) describes an aqueous paint solidification accelerator for road marking containing calcium acetate particles or magnesium acetate particles (Claim 1). And in this patent document 1, by using the water-based paint solidification accelerator for road marking, it is described that the drying time of the water-based paint for road marking applied to the road surface can be shortened and the solidification of the paint can be promoted. Has been. On the other hand, the road marking water-based paint solidification accelerator is a coating apparatus that simultaneously applies the road marking water-based paint solidification accelerator and the road marking water-based paint to the road surface as described in claim 7 or 8. Alternatively, the transferred water marking solidifying accelerator is diffused in the container through which the spray of the water marking for road marking passes as described in claim 9, and the road marking is displayed on the water marking paint for road marking. It is painted using a special coating device such as a coating device that mixes water-based paint solidification accelerators.

Japanese Patent Application Laid-Open No. 2004-244467 (Patent Document 2) describes an aqueous paint fixing agent for road marking containing water-insoluble inorganic compound particles capable of generating heat by reacting with water (Claim 1). . The water marking agent for road marking is applied to the road surface together with the water marking paint for road marking, or is applied by being sprayed on the coating film of the waterborne coating for road marking applied to the road surface. ).

Japanese Patent Application Laid-Open No. 9-235489 (Patent Document 3) describes an aqueous road marking paint characterized in that it includes solid polymer particles or inorganic compound particles that can absorb water ( Claim 1). Patent Document 3 also discloses a method for accelerating the drying of a water-based road marking paint applied to a surface, which is solid polymer particles or inorganic compound particles that can absorb water, and is applied to the surface together with the paint or applied. A method comprising spraying on the applied paint is also described (claim 2). On the other hand, the invention described in Patent Document 3 does not describe the water removal step in the present invention.

JP 2012-229302 A JP 2004-244467 A Japanese Patent Laid-Open No. 9-235489

The present invention solves the above-mentioned conventional problems, and its object is to achieve the object even under conditions where it is difficult to form a dry coating film by coating with an aqueous coating composition, such as a low temperature condition or a high humidity condition. It is providing the method which can form the coating film which has the function to do.

In order to solve the above problems, the present invention provides the following aspects.
[1]
A painting process for painting a water-based paint composition;
The coating film obtained by the above coating is separated into a top layer containing water and a coating layer, a coating film separating step, and the top layer containing water is removed by a method other than drying. Process,
A method for forming a coating film.
[2]
The uppermost layer containing moisture preferably further contains a moisture absorbent.
[3]
As one aspect of the coating film forming method, for example, an aspect further including a moisture absorbent mixing step of adding a moisture absorbent to the aqueous coating composition before the coating step can be mentioned.
[4]
As one aspect of the coating film forming method, for example, further including a water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition before the coating step,
The coating film separation step is brought about by the water separation accelerator.
An embodiment is mentioned.
[5]
As one aspect of the coating film forming method, for example, in the coating film forming method, before the coating step, a water separation accelerator mixing step and a moisture absorbent mixing step are performed,
Here, the water separation accelerator mixing step is performed before the moisture absorbent mixing step.
An embodiment is mentioned.
[6]
The water absorbent preferably has a water absorption of 1 g / g or more.
[7]
The moisture absorbent is preferably one or more selected from the group consisting of a superabsorbent resin, protein and polysaccharide.
[8]
The water separation promoter is preferably one or more selected from the group consisting of organic acids, inorganic acids, acid anhydrides, pH buffer solutions, metal salts, basic compounds, and polymer flocculants.
[9]
The water separation accelerator is preferably a polymer flocculant.
[10]
The polymer flocculant is preferably a polyhydroxysiloxane compound.
[11]
As another aspect of the coating film forming method of the present invention,
A water-removing process using a water-absorbing material, wherein a water-absorbing material is used to remove moisture from the coating process obtained by coating the aqueous coating composition;
A method of forming a coating film.
[12]
As one aspect of the coating film forming method, for example, further including a water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition before the coating step,
An embodiment is mentioned.
[13]
The water-absorbing material is one or more water-absorbing agents selected from the group consisting of a superabsorbent resin, protein and polysaccharide, or a sheet, film, membrane, comprising the water-absorbing agent, A strip or foam sheet is preferred.

The coating film forming method of the present invention is characterized in that moisture contained in the coating film formed from the aqueous coating composition is removed by a method other than drying. Therefore, even in a coating environment where it is difficult to evaporate an aqueous medium contained in a coating film formed from an aqueous coating composition, such as a low temperature condition and / or a high humidity condition, a coating having a target function is provided. A film can be formed. The method of the present invention makes it possible to form a coating film in any environment without being influenced by the coating environment.

It is a schematic explanatory drawing which shows 1 aspect of the coating-film formation method of this invention. It is a schematic explanatory drawing which shows another one aspect | mode of the coating-film formation method of this invention.

The coating film forming method of the present invention is a method for forming a coating film by coating an aqueous coating composition, wherein water contained in the coating film formed from the aqueous coating composition is removed by a method other than drying. It is characterized by. Although it does not specifically limit as an aqueous coating material composition used in the coating-film formation method of this invention, For example, the following aqueous coating material composition is mentioned.

Aqueous coating composition Examples of the aqueous coating composition used in the method of the present invention include an aqueous coating composition containing an aqueous resin dispersion.

The aqueous resin dispersion contained in the aqueous resin dispersion aqueous coating composition is a film-forming resin component. As the aqueous resin dispersion, for example, an acrylic resin emulsion, an acrylic resin dispersion, a silicone-containing acrylic resin emulsion, a urethane resin emulsion, a vinyl acetate resin emulsion, a fluororesin emulsion, a vinyl chloride resin emulsion, and the like can be used. These resins may be used alone or in combination of two or more. As the aqueous resin dispersion, an acrylic resin emulsion, an acrylic resin dispersion, or a silicone-containing acrylic resin emulsion is preferably used.

An acrylic resin emulsion that can be used as an aqueous resin dispersion can be prepared by emulsion polymerization of a polymerizable monomer in an aqueous medium. As polymerizable monomers used in the preparation of acrylic resin emulsions, α, β-ethylenically unsaturated monomers having a carboxyl group, α, β-ethylenically unsaturated monomers having a hydroxyl group, and other α, β-ethylenically unsaturated monomers are used. Saturated monomers are mentioned. These monomers can be appropriately selected according to the object to be coated with the aqueous coating composition and the application.

As an α, β-ethylenically unsaturated monomer having a carboxyl group, acrylic acid, methacrylic acid, acrylic acid dimer, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, ω-carboxy- Polycaprolactone mono (meth) acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumarate Examples thereof include acid and itaconic acid. Among these, acrylic acid and methacrylic acid are preferable. In this specification, “(meth) acryl” means both acrylic and methacrylic.

In the preparation of the acrylic resin emulsion, an α, β-ethylenically unsaturated monomer having a hydroxyl group may be used as necessary. Examples of the α, β-ethylenically unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, methacrylic alcohol and / or (meth). Mention may be made of adducts of hydroxyethyl acrylate and ε-caprolactone. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate and / or an adduct of hydroxyethyl (meth) acrylate and ε-caprolactone.

Other α, β-ethylenically unsaturated monomers include (meth) acrylic acid esters (eg methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, (meth) acrylic acid n-butyl, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate, phenyl acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, (meth ) T-butyl cyclohexyl acrylate, dicyclopentadienyl (meth) acrylate, dihydrodicyclopentadienyl (meth) acrylate), polymerizable amide compounds (eg (meth) acrylamide, N-methylol (meth) ) Acrylamide, N-butoxymethyl (meth) acrylic N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide 2, 4-dihydroxy-4′-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, etc.), polymerizable aromatic compounds (for example, styrene, α-methylstyrene, vinyl ketone, t-butylstyrene, parachlorostyrene, vinylnaphthalene, etc.), polymerizable nitriles (eg, acrylonitrile, methacrylonitrile, etc.), α-olefins (eg, ethylene, propylene, etc.), vinyl esters (eg, vinyl acetate, propionic acid) Vinyl etc. ), Dienes (eg, butadiene, isoprene, etc.), polymerizable aromatic compounds, polymerizable nitriles, α-olefins, vinyl esters, and dienes. These can be appropriately selected according to the purpose.

A crosslinkable monomer may be used as the other α, β-ethylenically unsaturated monomer. Here, the crosslinkable monomer is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule, such as divinylbenzene, ethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, allyl (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexane di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) ) Divinyl compounds such as acrylate, and triallyl cyanurate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. . The crosslinkable monomer may be a combination of the above monomers.

In the preparation of an acrylic resin emulsion, emulsion polymerization in an aqueous medium is performed by, for example, dissolving an emulsifier in an aqueous medium containing water or a hydrophilic organic solvent such as water and alcohol or glycol, and heating. Under stirring, the polymerization can be carried out by dropping a monomer mixture obtained by mixing an α, β-ethylenically unsaturated monomer used as a raw material and a polymerization initiator. The monomer mixture obtained by mixing the α, β-ethylenically unsaturated monomer used as the raw material may be pre-emulsified using an emulsifier and water.

Polymerization initiators that can be suitably used for emulsion polymerization include azo oily compounds (for example, azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), and 2,2′- Azobis (2,4-dimethylvaleronitrile) and the like, and aqueous compounds (eg, anionic 4,4′-azobis (4-cyanovaleric acid), 2,2-azobis (N- (2-carboxyethyl)) -2-methylpropionamidine and cationic 2,2′-azobis (2-methylpropionamidine)); and redox oily peroxides (eg, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide and t-butyl perbenzoate) and aqueous peroxides (eg potassium persulfate and persulfate) Ammonium and the like) and the like.

As the emulsifier, those usually used by those skilled in the art can be used. As emulsifiers, reactive emulsifiers such as Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Kasei Kogyo Co., Ltd.), Adekari Soap NE-20 (manufactured by Asahi Denka Co., Ltd.) and Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) is particularly preferred. In order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer can be used as necessary.

The reaction temperature is determined by the initiator. For example, it is preferably 60 to 90 ° C. for an azo initiator and 30 to 70 ° C. for a redox system. In general, the reaction time is 1 to 8 hours. The amount of initiator relative to the total amount of monomer mixture is generally from 0.1 to 5% by weight, preferably from 0.2 to 2% by weight. The emulsion polymerization can be performed in multiple stages, for example, in two stages. In the two-stage emulsion polymerization, first, a part of the mixture of α, β-ethylenically unsaturated monomers used as the raw material is emulsion polymerized, and then the remainder of the α, β-ethylenically unsaturated monomer mixture is further added. In addition, it is a polymerization method in which emulsion polymerization is performed. By performing two-stage polymerization, a core-shell type acrylic resin emulsion composed of a core part and a shell part can be obtained.

The volume average particle diameter of the acrylic resin emulsion is preferably 20 to 500 nm, and more preferably 50 to 200 nm. Here, the volume average particle diameter is a volume average particle diameter determined by a dynamic light scattering method. Specifically, an electrophoretic light scattering photometer ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) is used. Can be measured.

From the viewpoint of storage stability, the acrylic resin emulsion is preferably adjusted to pH 5 to 10 by neutralizing with a basic compound. The basic compounds are ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, dimethylethanolamine, diethanolamine, diethylaminoethanol, triethanolamine, tetraethylammonium hydroxide, propylamine, dipropylamine, tripropylamine. , Amines such as butylamine, dibutylamine and tributylamine, and hydroxides such as sodium hydroxide and potassium hydroxide. The neutralization is preferably performed by adding the basic compound to the system before or after emulsion polymerization.

The acrylic resin dispersion can be prepared, for example, by preparing an acrylic resin by solution polymerization of the polymerizable monomer, and then dispersing the obtained acrylic resin in water. More specifically, the acrylic resin dispersion contains the above α, β-ethylenically unsaturated monomer having a carboxyl group as an essential component, and after performing solution polymerization together with other α, β-ethylenically unsaturated monomers. It can be prepared by neutralizing with a basic compound and dispersing in water.

The solution polymerization is generally a method in which the mixture of the polymerizable monomers is stirred while being dropped into an organic solvent together with a polymerization initiator under heating conditions. Solution polymerization can be carried out, for example, under conditions of a polymerization temperature of 60 to 160 ° C. and a dropping time of 0.5 to 10 hours. The polymerizable monomer can be polymerized in two stages. By polymerizing the polymerizable monomer in two stages, a core-shell type acrylic resin dispersion comprising a core part and a shell part can be obtained.

The polymerization initiator is not particularly limited as long as it is used for normal polymerization, and examples thereof include azo compounds and peroxides. Generally, the amount of the polymerization initiator with respect to 100 parts by mass of the monomer mixture is 0.1 to 18 parts by mass, preferably 0.3 to 12 parts by mass.

The solvent that can be used here is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include alcohols, ketones, ethers, and hydrocarbon solvents. Furthermore, in order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer can be used as necessary.

The number average molecular weight of the acrylic resin thus obtained by solution polymerization is preferably 4,000 to 20,000. In this specification, the number average molecular weight of the acrylic resin obtained by solution polymerization can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard.

An acrylic resin dispersion can be obtained by removing the solvent as necessary from the acrylic resin obtained by the solution polymerization and neutralizing it by adding a basic compound. Examples of the basic compound include the basic compounds listed above. The amount of the basic compound added is preferably such an amount that the neutralization rate of the carboxyl group of the acrylic resin obtained by the solution polymerization is 60 to 100%. When the neutralization rate is less than 60%, the water dispersibility of the acrylic resin dispersion becomes low and the storage stability may be poor.

The acrylic resin dispersion preferably has a volume average particle diameter determined by a dynamic light scattering method in the range of 10 to 1000 nm. When the volume average particle diameter is in the above range, there is an advantage that the stability of the aqueous dispersion is improved and the appearance of the obtained coating film is improved.
The acrylic resin dispersion preferably has a volume average particle diameter of 10 to 1000 nm, and more preferably 100 to 800 nm.

Examples of the silicone-containing acrylic resin emulsion include a polymer obtained by polymerization of a monomer composition further containing an alkoxysilyl group-containing polymerizable monomer in addition to the polymerizable monomer used in the preparation of the acrylic resin emulsion. Can do.

The alkoxysilyl group-containing polymerizable monomer is not particularly limited as long as it is a polymerizable monomer containing an alkoxysilyl group having 1 to 14 carbon atoms. For example, trimethoxysilylpropyl (meth) acrylate, (meth) acrylic acid Triethoxysilylpropyl, tributoxysilylpropyl (meth) acrylate, dimethoxymethylsilylpropyl (meth) acrylate, methoxydimethylsilylpropyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxymethylsilane, Examples thereof include vinylmethoxydimethylsilane and vinyltris (β-methoxyethoxy) silane. These can be used alone or in combination of two or more. Among these, in particular, trimethoxysilylpropyl (meth) acrylate, triethoxysilylpropyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane and the like can be mentioned.

Furthermore, an organic silicone unit may be introduced into the silicone-containing acrylic resin emulsion. As a method for introducing the organosilicone unit, a mixture of an organosilicone compound (for example, organosilane, a hydrolyzate of organosilane, a condensate of organosilane, etc.) and an acrylic polymerizable monomer is subjected to emulsion polymerization, hydrolysis, condensation reaction and Examples include a method of performing radical polymerization, a method of copolymerizing a monomer having a silicone functional group, and a method of bonding an organosilicone compound to the surface of acrylic polymer particles by reacting an organosilicone compound with an acrylic polymer. . Two or more methods described above may be combined.

The organosilane is not particularly limited, and examples thereof include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane; Methoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, n-butyltri Methoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyl Triethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltri Methoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2- Hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptop Pyrtrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) atacryl Trialkoxysilanes such as oxypropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysila Diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, di-i-propyldimethoxysilane, di-i-propyldiethoxysilane, di-n-butyldimethoxysilane, di- -N-butyldiethoxysilane, di-n-pentyldimethoxysilane, di-n-pentyldiethoxysilane, di-n-hexyldimethoxysilane, di-n-hexyldiethoxysilane, di-n-heptyldimethoxysilane, Di-n-heptyldiethoxysilane, di-n-octyldimethoxysilane, di-n-octyldiethoxysilane, di-n-cyclohexyldimethoxysilane, di-n-cyclohexyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxy Dialkoxysilanes such as silane , Methyl triacetyl silane, dimethyl acetyloxy silane and the like.

As the aqueous resin dispersion, in addition to the above, urethane resin emulsions, vinyl acetate resin emulsions, fluororesin emulsions, vinyl chloride resin emulsions and the like that are commonly used by those skilled in the art can also be used.

The amount of the aqueous resin dispersion contained in the aqueous coating composition is preferably 5 to 50 parts by mass with respect to 100 parts by mass of the aqueous coating composition as the resin solid content.

Other Components The aqueous resin dispersion may be a reaction curable resin that is cured by reacting with a curing agent, or may be a fusion resin that does not require a curing agent. As the curing agent, for example, a carbodiimide curing agent, a melamine curing agent, an isocyanate curing agent, or the like can be used.

The aqueous coating composition in the present invention may contain other components as required in addition to the above components. As other components, for example, a film-forming aid, a thickener, a polyfunctional amine polymer, a coupling agent, a plasticizer, a crosslinked resin particle, a pigment, a surface conditioner, an antiseptic, an antifungal agent, an antifoaming agent, Examples thereof include a light stabilizer, an ultraviolet absorber, an antioxidant, and a pH adjuster.

The water-based paint composition contains water as a solvent. The water-based coating composition may contain a hydrophilic organic solvent such as alcohol or glycol, if necessary, in addition to water.

The method for preparing the aqueous coating composition is not particularly limited, and can be prepared by stirring the above-described components with a stirrer or the like. When pigments or design materials are included in the aqueous coating composition, those having good dispersibility can be mixed with a stirrer, and as another method, a sand grind is added to a vehicle containing water, a surfactant or a dispersant. What was previously disperse | distributed using the mill etc. can also be added.

Coating Film Forming Method As one aspect of the coating film forming method of the present invention,
A painting process for painting a water-based paint composition;
The coating film obtained by the above coating is separated into a top layer containing water and a coating layer, a coating film separating step, and the top layer containing water is removed by a method other than drying. Process,
The method of including is mentioned.

FIG. 1 is a schematic explanatory view showing this coating film forming method. As a method for removing moisture, any method other than drying can be used.

In the method of the present invention, it is only necessary to include a moisture removing step of removing the uppermost layer containing moisture by a method other than drying, and in the method of the present invention, some moisture is removed by drying. It does not exclude that. Specifically, in the coating film separation step, the aspect in which the moisture contained in the coating film obtained by painting is evaporated somewhat corresponds to the method of the present invention as long as the water removal step is performed thereafter.

Arbitrary base material is mentioned as a to-be-coated object which coats water-based paint composition. Examples of the substrate include metal, wood, plastics, rubber, stone, slate, concrete, mortar, fiber, paper, glass, porcelain, earthenware, film, and composites thereof. These substrates may be provided with a coating such as an undercoat coating as necessary.

As a coating method of the water-based paint composition, any appropriate method can be used according to the type and shape of the article (base material) to be coated. As a method for applying the aqueous coating composition, for example, commonly used coating methods such as dipping, brushing, flow coating, roller, roll coater, air spray, airless spray, curtain flow coater, roller curtain coater, die coater, etc. Can be used.

The aqueous coating composition is preferably applied so that the film thickness after removing water is 5 to 1000 μm, more preferably 20 to 300 μm.

The coating film obtained by coating the aqueous coating composition is separated into a water-containing uppermost layer and a coating film forming layer (coating film separation step). Examples of the coating film separating step include a method in which a coating film obtained by painting is allowed to stand for 2 seconds to 24 hours.

The uppermost layer containing moisture may contain only moisture, or may contain a moisture absorbent and / or a water separation accelerator described later. Further, the uppermost layer containing water may contain the above-mentioned additive contained in the aqueous coating composition, a slight amount of a film-forming component, and the like.

The coating film forming layer is a layer containing a coating film forming component contained in the aqueous coating composition. Examples of the coating film forming component include the aqueous resin dispersion and other components as required. The coating film forming layer may contain various additives in addition to the coating film forming component.

As one means for bringing about and facilitating separation of the coating film obtained by coating into a water-containing uppermost layer and a film-forming layer, for example, before the coating step, an aqueous coating composition And a method of adding a water separation accelerator to the product (water separation accelerator mixing step). Examples of the water separation accelerator include organic acids, inorganic acids, acid anhydrides, pH buffer solutions, metal salts, basic compounds, and polymer flocculants.

Separation here, specifically, separation into the uppermost layer containing water and the coating film-forming layer means that an aqueous resin dispersion such as a resin emulsion is placed under a predetermined unstable condition, and a resin component, etc. By intentionally aggregating and precipitating the water, the resin component constituting the aqueous resin dispersion and water are separated. In such separation, there are many parts that have not been clarified as to what kind of mechanism the water separation promoter to be described functions in, but the basic mechanism of action is estimated as follows. When the water separation accelerator is a metal salt, the salt in the aqueous resin dispersion is fixed as hydrated water due to the strong hydration power of the salt, thereby reducing the stability of the aqueous resin dispersion. Conceivable. In addition, when the water separation accelerator is an organic acid, an inorganic acid, an acid anhydride, or a basic compound, a so-called coagulation action is considered to work. That is, the water separation accelerator exerts an electrical interaction with the ionic group of the aqueous resin dispersion by electrostatic attraction, so that the zeta potential on the surface of the aqueous resin dispersion particle is lowered and dehydrated. It is considered that the resin component becomes hydrophobic due to the coalescence of the particles, and the resin component of the aqueous resin dispersion is separated from the water. In addition, when the water separation accelerator is a polymer flocculant, the polymer chain of the polymer flocculant called a coagulation action together with these actions causes cross-linking adsorption to the resin component of the aqueous resin dispersion, and the polymer It is considered that separation of the resin component and moisture is promoted by bringing the aqueous resin dispersions together through a flocculant and making the resin component hydrophobic.

As an organic acid that can be used as a water separation accelerator, for example,
Monovalent carboxylic acids (eg, acetic acid, benzoic acid, propionic acid, formic acid, etc.),
Divalent carboxylic acids (eg, maleic acid, fumaric acid, succinic acid, oxalic acid, etc.),
Organic sulfonic acids (for example, methanesulfonic acid, paratoluenesulfonic acid, benzenesulfonic acid, aminoethylsulfonic acid, etc.),
Etc.
Examples of the inorganic acid that can be used as the water separation accelerator include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and the like.
Examples of the acid anhydride that can be used as a water separation accelerator include those obtained by dehydration condensation of two molecules of the organic acid or inorganic acid. Specific examples of the acid anhydride include, for example, acetic anhydride, benzoic anhydride, disulfuric acid (pyrosulfuric acid), pyrophosphoric acid (diphosphoric acid), diphosphorus pentoxide (phosphorus tetraoxide), and propionic anhydride. .
As the acid anhydride, an intramolecular dehydration condensate of the above divalent carboxylic acid can also be used. Examples of such condensates include maleic anhydride and fumaric anhydride.
Examples of the pH buffer that can be used as the water separation accelerator include acetate buffer, phosphate buffer, citrate buffer, Tris buffer, and borate buffer. Moreover, the buffer agent composition used for preparation of these pH buffer solutions may be added directly to the aqueous coating composition.
Examples of metal salts that can be used as a water separation accelerator include aluminum salts (eg, aluminum sulfate, polyaluminum chloride, etc.), iron salts (eg, polyferric sulfate, ferric chloride, etc.), sodium salts ( Examples thereof include sodium chloride, sodium sulfate, etc., calcium salts (eg, calcium chloride), magnesium salts (eg, magnesium chloride), and the like.
As a polymer flocculant that can be used as a water separation accelerator, for example,
For cationic polymer flocculants, dimethylaminoethyl methacrylate methylene chloride, diallyldimethylammonium chloride, aniline resin hydrochloride, polyamine derivatives, polythiourea acetate, polyethyleneaminotriazole, polyvinylbenzyltrimethylammonium chloride, polyethyleneimine, vinylpyridine In the case of anionic polymer flocculants such as copolymer salts, sodium poly (meth) acrylate, maleic acid copolymer salt, itaconic acid copolymer salt, polyacrylamide partial hydrolyzate salt, sodium alginate, carboxy Methyl cellulose sodium salt, polyhydroxysiloxane compound, etc.
Is mentioned. In addition, gelatin, a copolymer of the above-mentioned anion unit and cation unit, etc. are used as the amphoteric polymer flocculant, and polyacrylamide, polyoxyethylene, water-soluble urea, starch, etc. are appropriately used as the nonionic polymer flocculant. be able to. Among them, the polyhydroxysiloxane compound, which is a hydrolyzed condensate of alkoxysilane, has a relatively large pKa, so it does not cause abrupt aggregation that causes destabilization of the system, but has a relatively large polymer structure. Therefore, it is an excellent water separation accelerator that causes the above-mentioned cross-linking adsorption action more efficiently and causes rapid water separation by uniformly aggregating the entire system.
Examples of basic compounds that can be used as a water separation accelerator include ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, dimethylethanolamine, diethanolamine, diethylaminoethanol, triethanolamine, tetraethylammonium hydroxide, Examples include amines such as propylamine, dipropylamine, tripropylamine, butylamine, dibutylamine and tributylamine, and hydroxides such as sodium hydroxide and potassium hydroxide.
These water separation promoters may be used alone or in combination of two or more.

As the water separation accelerator, it is preferable to use at least one selected from the group consisting of organic acids (eg, acetic acid, propionic acid, etc.), acid anhydrides (eg, acetic anhydride, propionic anhydride, etc.) and polymer flocculants. .

As the water separation accelerator, it is more preferable to use an anionic polymer flocculant which is one type of polymer flocculant, and it is more preferable to use a polyhydroxysiloxane compound. Preparation of a polyhydroxysiloxane compound more preferably used as a water separation accelerator is generally obtained by hydrolysis or condensation of a raw material selected from mono-, di-, tri-, and tetraalkoxysilanes alone or from a plurality thereof. .
Although it does not specifically limit as a specific manufacturing method, The well-known means described in patent 3599277, 5048395 grade | etc., Can be used.

When adding a water separation accelerator to the aqueous coating composition, an amount that impairs the stability of the film-forming resin component is added. Specifically, it is preferably added in an amount of 0.01 to 50 parts by mass, more preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the aqueous coating composition. There exists a possibility that the effect as a water-separation promoter may not fully be exhibited as it is less than 0.01 mass part. If it exceeds 50 parts by mass, various coating film properties such as the curability and water resistance of the coating film may be deteriorated. As a method for adding a water separation accelerator to the aqueous coating composition, a general mixing method can be used.

In the method of the present invention, the uppermost layer containing water obtained by the coating film separating step is removed by a method other than drying (moisture removing step). Here, “removing the uppermost layer containing moisture by a method other than drying” means removing moisture contained in the coating film formed from the aqueous coating composition by a method other than drying after coating. Means. Specific examples of such a method include, for example, a method in which the uppermost layer containing moisture is washed away by gravity by tilting a coating film obtained by painting, or the uppermost layer containing a moisture absorbent is removed by hand or air. Examples of the removal method include removal or removal using an optional instrument as necessary, and a method of removing moisture by absorbing moisture in the uppermost layer into the moisture-absorbing material.

If necessary, a water absorbent mixing step of adding a water absorbent to the aqueous coating composition may be performed before the coating step. In this case, the moisture absorbent is contained in the uppermost layer containing moisture. Examples of the moisture absorbent include an agent having a water absorption of 1 g / g or more. The amount of water absorption can be measured in accordance with the water absorption amount test method for high water absorption resin of JIS K 7223-1996.

Specific examples of the water absorbent include a highly water-absorbent resin, protein, polysaccharide and the like.
Examples of superabsorbent resins that can be used as moisture absorbents include polyacrylates (eg, sodium polyacrylate, potassium polyacrylate), polyvinyl alcohol, polyacrylamide, polyoxyethylene, polysulfonate, polyglutamic acid. Resins such as salts are listed.
Examples of the protein that can be used as a moisture absorbent include gelatin, glue, albumin, casein, gluten, and sericin.
Examples of polysaccharides that can be used as a moisture absorbent include carboxymethylated starch, carboxymethylated cellulose, starch, cellulose, chitin, chitosan, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, agar, agarose, Examples include gum arabic, alginate, curdlan, carrageenan, xanthan gum, guar gum, glucomannan, chondroitin sulfate, gellan gum, tragacanth gum, hyaluronic acid, pullulan, pectin, locust bean gum and the like.
These moisture absorbents may be used alone or in combination of two or more.

In the method of the present invention, a common material may be used for the water separation accelerator and the water absorbent. More specifically, a polymer flocculant which is an example of a water separation accelerator is used, and the same material may be used as a moisture absorbent. A polymer flocculant, which is an example of a water separation accelerator, is a component that causes separation of water from aqueous resin dispersion particles by, for example, salting out or coagulating action of added functional groups. This is because such an action is common in terms of action mechanism with the moisture absorption effect provided by the moisture absorbent in that water is fixed and separated and removed from the resin component.

The moisture absorbent is preferably in the form of particles or powder. Examples of the particulate or powder moisture absorber include a moisture absorber having a volume average particle diameter of 100 nm to 1 mm. The volume average particle diameter of the moisture absorbent can be measured by a laser light scattering method or the like. Specifically, it can be measured using a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation). You may adjust a water | moisture-content absorber to the range of the said particle diameter by grind | pulverizing etc. using a mortar or a ball mill.

As the water absorbent, it is preferable to use at least one selected from the group consisting of proteins (for example, gelatin) and polysaccharides (for example, starch, hydroxyethyl cellulose, etc.).

When the water absorbent is added to the aqueous coating composition, it is preferably added in an amount of 0.1 to 100 parts by mass, and an amount of 0.1 to 30 parts by mass with respect to 100 parts by mass of the aqueous coating composition. It is more preferable to add at. If the amount is less than 0.1 parts by mass, moisture may not be sufficiently absorbed. A general mixing method can be used as a method of adding a water absorbent to the aqueous coating composition.

If necessary, the moisture absorbent may be subjected to an immersion treatment in which it is previously immersed in an organic solvent before being added to the aqueous coating composition. As the organic solvent, for example, one or more selected from the group consisting of poorly water-soluble organic solvents and water-insoluble organic solvents can be used. In the case of performing the immersion treatment, for example, an aspect in which 0.5 to 10 parts by mass of the organic solvent is used for 1 part by mass of the moisture absorbent and the organic solvent is brought into contact with the organic solvent for 0.5 minutes to 24 hours. It is done.

Here, the poorly water-soluble organic solvent means an organic solvent having a solubility at 20 ° C. of 10 mg / L or more and less than 10 g / L, and the water-insoluble organic solvent has a solubility at 20 ° C. of less than 10 mg / L. It means an organic solvent. By performing such immersion treatment, there is an advantage that the onset of the water absorption action of the water absorbent can be delayed or suppressed. For example, in the case where a water absorbent is added to the aqueous coating composition or a water absorbent mixing step is performed before the coating step, such a dipping treatment is useful and can be preferably used.

In the above method, when both the water separation accelerator mixing step and the water absorbent mixing step are performed, the water separation promoter mixing step is more preferably performed before the water absorbent mixing step. By performing the water separation accelerator mixing step before the water absorbent mixing step, it is considered that water separation can occur prior to moisture absorption.

As another aspect of the coating film forming method of the present invention,
A water-removing process using a water-absorbing material, wherein a water-absorbing material is used to remove moisture from the coating process obtained by coating the aqueous coating composition;
The method of including is mentioned. In this aspect, the moisture absorbing material is brought into contact with the moisture absorbing material from above the coating film obtained by painting to absorb moisture into the moisture absorbing material, thereby removing moisture. To do.

FIG. 2 is a schematic explanatory view showing this coating film forming method. The moisture-absorbing material used for removing moisture is not limited to the shape shown in FIG. 2, and any shape can be used.

As the moisture absorbing material that can be used in this embodiment, the above-described moisture absorbent can be cited. As the moisture absorbing material, a material having a shape such as a sheet, a film, a membrane, a strip, and a foamed sheet, which is configured to include the moisture absorbent, can be used. As the material having such a shape, for example, a material such as a commercially available sheet can be used. Moreover, the above-mentioned moisture absorbent can also be used after being processed into a shape such as a sheet or a film.

In this aspect, a water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition may be further included before the coating step. As the water separation accelerator, the water separation accelerator described above can be used.

The coating film forming method of the present invention is characterized by removing water contained in the aqueous coating composition by a method other than drying. Therefore, a coating film can be formed even in a coating environment where it is difficult to evaporate the aqueous medium contained in the aqueous coating composition, such as a low temperature condition and / or a high humidity condition. According to the method of the present invention, it is possible to form a coating film having a desired function in any environment without being influenced by the coating environment.

The coating film forming method of the present invention may be used for forming a single layer coating film or may be used for forming a multilayer coating film. As an aspect using the coating-film formation method of this invention in formation of a multilayer coating film, the aspect etc. which apply | coat a coating composition further with respect to the coating film which performed the said water removal process are mentioned, for example. Here, after the coating composition is further applied, the water removal step may be performed as necessary. In the case where the coating film forming method of the present invention is used in the formation of a multilayer coating film, in addition to the above-mentioned advantages, there are further advantages such as prevention of problems such as mixed layers.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

Production Example 1
MKC silicate MS51 (condensate of tetramethoxysilane manufactured by Mitsubishi Chemical Co., SiO ₂ content 51%, degree of condensation is 5 as an average value) 10.71 g of aluminum chelate D (aluminum chelate compound manufactured by Kawaken Fine Chemical Co., Ltd.) (76% isopropanol solution) 0.44 g and methanol 28.70 g were added and dissolved. After the temperature was raised to 40 ° C., 40.18 g of water was gradually added over 2 hours and stirred, followed by aging at 40 ° C. for 2 hours to obtain a polyhydroxysiloxane solution having a concentration of 9.6%.

Example 1
10 g of core-shell acrylic resin dispersion (manufactured by Nippon Paint Co., Ltd., solid content 44%, acid value 20 mg-KOH / g) was weighed in a glass bottle, and 0.18 g of special grade acetic anhydride (reagent) was added as a water separation accelerator, Homogenously mixed by shaking 10 times by hand at room temperature. Immediately thereafter, it was painted on a test piece at room temperature with a 10 mil doctor blade. 15 minutes later, a highly water-absorbent resin particle (trade name: Aquakeep 10SH-PF, manufactured by Sumitomo Seika Co., Ltd., water absorption: 500 g / g, volume average particle diameter: 26 μm) as a moisture absorbing material on the coating film 2 g was added. After 5 minutes, the uppermost layer containing moisture was removed with a finger to obtain a desired coating film having a dry film thickness of 100 μm.
The water absorption amount of the highly water-absorbent resin particles was measured in accordance with the water absorption amount test method for the highly water-absorbent resin of JIS K 7223-1996. Specifically, 0.2 g of the substance is put in a tea bag, immersed in deionized water for 3 hours, suspended for 10 minutes and drained immediately, and the weight is measured. It was.

Example 2
The moisture absorbent is gelatin (trade name; Cook Gelatin, manufactured by Morinaga & Co., Ltd., water absorption: 17 g / g, volume average particle size: 697 μm), and the timing of removing the uppermost layer containing moisture is 15 A coating film having a target dry film thickness of 100 μm was obtained in the same manner as in Example 1 except that the change was made after minutes.
The gelatin used was pulverized in advance using a pestle in a mortar for 2 minutes. The water absorption of gelatin was determined in the same manner as in Example 1.

Example 3
10 g of the same dispersion as described in Example 1 was weighed into a glass bottle, 0.18 g of acetic anhydride was added as a water separation accelerator, and then the mixture was uniformly mixed by shaking by hand 10 times at room temperature. Immediately thereafter, it was painted on a test piece at room temperature with a 10 mil doctor blade. Fifteen minutes later, the test piece was tilted to remove the uppermost layer containing moisture, and a desired coating film having a dry film thickness of 100 μm was obtained.

Example 4
10 g of the same dispersion as described in Example 1 was weighed into a glass bottle, 0.18 g of acetic anhydride was added as a water separation accelerator, and then the mixture was uniformly mixed by shaking by hand 10 times at room temperature. Immediately thereafter, 8 g of gelatin was added as a water absorbent, and the mixture was shaken by reciprocating 10 times and mixed uniformly. Immediately after that, it was uniformly cast on the test piece at room temperature. After coating, the mixture was allowed to stand at room temperature for 1 hour, and the uppermost layer that contained water and became a film was removed with a spoon. Thus, a coating film having a target dry film thickness of 200 μm was obtained.
In order to delay the water absorption of gelatin, the gelatin shown above was filtered by impregnating 10 g of toluene in advance with 8 g of gelatin (trade name: Cook Gelatin, Morinaga & Co., Ltd., water absorption: 17 g / g). And then used.

Example 5
A target coating film having a dry film thickness of 200 μm was obtained in the same manner as in Example 4 except that the standing conditions were changed to a temperature of 5 ° C. and a humidity of 50%.

Example 6
A target coating film having a dry film thickness of 200 μm was obtained in the same manner as in Example 4 except that the standing conditions were changed to a temperature of 23 ° C. and a humidity of 83%.

Example 7
The target dry film was obtained in the same manner as in Example 4 except that the water absorbent was changed to 2 g of hydroxyethyl cellulose (trade name: SP-850, manufactured by Daicel, water absorption 20 g / g, volume average particle size: 92 μm). A 200 μm thick coating film was obtained. In addition, in order to delay the water absorption of a hydroxyethyl cellulose, the hydroxyethyl cellulose shown above was used after filtering what impregnated 2 g of hydroxyethyl cellulose in 4 g of toluene in advance. Further, the water absorption amount of hydroxyethyl cellulose was determined in the same manner as in Example 1.

Example 8
A coating film having a target dry film thickness of 200 μm was obtained in the same manner as in Example 4 except that 2.29 g of the polyhydroxysiloxane solution prepared in Production Example 1 was used as the water separation accelerator.

Comparative Example 1
10 g of the same dispersion as described in Example 1 was weighed in a glass bottle and coated on a test piece at room temperature with a 10 mil doctor blade. After coating, it was allowed to stand at room temperature for 1 hour to obtain a coating film having a dry film thickness of 100 μm. In addition, the water removal process was not performed.

Comparative Example 2
A coating film having a dry film thickness of 100 μm was obtained in the same manner as in Comparative Example 1 except that the standing conditions were changed to a temperature of 5 ° C. and a humidity of 50%. In addition, the water removal process was not performed.

Comparative Example 3
A coating film having a dry film thickness of 100 μm was obtained in the same manner as in Comparative Example 2 except that the standing time was changed to 5 hours.

Comparative Example 4
A coating film having a dry film thickness of 100 μm was obtained in the same manner as in Comparative Example 1 except that the standing conditions were changed to a temperature of 23 ° C. and a humidity of 83%. In addition, the water removal process was not performed.

Comparative Example 5
A coating film having a dry film thickness of 100 μm was obtained in the same manner as in Comparative Example 4 except that the standing time was changed to 5 hours. In addition, the water removal process was not performed.

The following evaluations were performed on the coating films obtained by the above examples and comparative examples. The evaluation results are shown in the following table.

The states of the coating films obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were confirmed by finger touch and evaluated according to the following criteria.
○: There is no sticky feeling in the coating film ×: There is a sticking feeling in the coating film

The result of the comparative example 1 is an evaluation result of the coating film obtained by leaving it at room temperature for 1 hour after coating. From the results of Comparative Example 1, it can be seen that even when the room temperature condition is not used, when the water removal step is not performed, a good coating film cannot be obtained only by standing for 1 hour.
The results of Examples 1 to 8 are all evaluation results of the coating film immediately after being formed according to the above examples. In the examples of the present invention, it was confirmed that even when the same paint as in Comparative Example 1 was used, a good coating film could be formed by removing moisture by a method other than drying. .
The result of the comparative example 2 is an evaluation result of the coating film obtained by being allowed to stand for 1 hour in a coating environment where the evaporation of the aqueous medium is difficult under low temperature conditions. Moreover, the result of the comparative example 4 is an evaluation result of the coating film obtained by leaving still for 1 hour in the coating environment where the evaporation of the aqueous medium is difficult under high humidity conditions. In the coating environment of these comparative examples 2 and 4, even when it was allowed to stand for another 4 hours to promote the volatilization of water (Comparative Example 3 and Comparative Example 5), the coating film remained sticky. . Under these low-temperature conditions and / or high-humidity conditions, it can be confirmed that it is difficult to form a coating film by applying the aqueous coating composition.
On the other hand, even in the coating environments of Comparative Examples 2 and 4, it was confirmed from Examples 5 and 6 that a good coating film was obtained when the coating method of the present invention was performed. Here, in each of Comparative Examples 1 to 5, doctor blade coating is performed. The doctor blade coating is a condition that makes it easier to obtain a better coating film because the coating film thickness is thin and the total water content in the coating film thickness is small. On the other hand, in Examples 5 and 6, in addition to being in the coating environment of Comparative Examples 2 and 4, since the coating film thickness is thick and the total water content in the coating film is large, doctor blade coating On the other hand, the coating film is formed by a coating method that is more disadvantageous in film formation. In Examples 5 and 6, it was confirmed that a good coating film without sticky feeling could be obtained even though the coating film was formed using a coating method with higher hurdles on film formation. .

By the method of the present invention, a coating film having a desired function is formed even in a coating environment where it is difficult to evaporate an aqueous medium contained in an aqueous coating composition such as a low temperature condition and / or a high humidity condition. There is an advantage that it becomes possible to do.

Claims

A painting process for painting a water-based paint composition;
The coating film obtained by the coating is separated into the uppermost layer containing moisture and the coating film forming layer, and the coating layer separating step, and the uppermost layer containing moisture is removed by a method other than drying. Process,
A method for forming a coating film.
The coating film forming method according to claim 1, wherein the uppermost layer containing moisture further contains a moisture absorbent.
The coating film forming method according to claim 2, further comprising a moisture absorbent mixing step of adding a moisture absorbent to the aqueous coating composition before the coating step.
A water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition before the coating step;
The coating film separation step is brought about by the water separation accelerator.
The coating film forming method according to any one of claims 1 to 3.
In the coating film forming method, before the coating step, a water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition, and a moisture absorbent mixing step of adding a moisture absorber to the aqueous coating composition Done,
Here, the water separation accelerator mixing step is performed before the moisture absorbent mixing step.
The coating film forming method according to claim 4.
The coating film forming method according to claim 2, 3 or 5, wherein the moisture absorbent has a water absorption of 1 g / g or more.
The coating film forming method according to claim 2, 3 or 5, wherein the moisture absorbent is one or more selected from the group consisting of a superabsorbent resin, protein and polysaccharide.
The water separation accelerator is one or more selected from the group consisting of organic acids, inorganic acids, acid anhydrides, pH buffer solutions, metal salts, basic compounds, and polymer flocculants. Or the coating-film formation method of 5.
The method for forming a coating film according to claim 8, wherein the water separation accelerator is a polymer flocculant.
The coating film forming method according to claim 9, wherein the polymer flocculant is a polyhydroxysiloxane compound.
A water-removing step using a water-absorbing material, wherein a water-absorbing material is used to remove water from the coating process obtained by coating the water-based paint composition;
A method for forming a coating film.
A water separation accelerator mixing step of adding a water separation accelerator to the aqueous coating composition before the coating step;
The coating film forming method according to claim 11.
The moisture absorbing material is one or more moisture absorbents selected from the group consisting of a superabsorbent resin, protein and polysaccharide, or a sheet, film, membrane, comprising the moisture absorbent, The coating film forming method according to claim 11 or 12, which is a strip or a foam sheet.