JP6431713B2 - Water-based coating composition and method for producing the same - Google Patents

Description

  The present invention relates to an aqueous coating composition containing a scaly aluminum pigment and a method for producing the aqueous coating composition.

  A plurality of coating films having various roles are sequentially formed on the surface of an object such as an automobile body to protect the object to be coated and at the same time impart a beautiful appearance and an excellent design. As a method for forming such a plurality of coating films, an undercoat film such as an electrodeposition coating film is formed on an object having excellent conductivity, and an intermediate coating film as required, and A method of sequentially forming a top coat film is common. Among these coating films, the top coating film composed of a base coating film and a clear coating film particularly greatly affects the appearance and design of the coating film. In particular, in automobiles, the appearance and design of a top coating film comprising a base coating film and a clear coating film formed on a vehicle body are extremely important.

  The base coating film can be broadly classified into a coating film containing no scaly pigment, which is called a so-called solid color, and a coating film containing scaly pigment having a glittering feeling. As a typical example of a scaly pigment having a glittering feeling, a scaly aluminum pigment can be mentioned. By including a scaly aluminum pigment in the base coating film, a metallic luster (metallic feel) can be developed.

  By including the scaly aluminum pigment in the aqueous coating composition, water and aluminum contained in the coating composition may react to generate gas such as hydrogen gas. Due to the generation of gas, there is a risk that when the aqueous coating composition is stored in a closed container, the container expands, and the coating composition explodes rapidly when the container is opened, or the container explodes.

  As one of means for suppressing the generation of such gas, for example, there is a method of controlling the reactivity of the aluminum pigment by coating the aluminum pigment. For example, in JP-A-2002-121423 (Patent Document 1), a resin-coated raw material aluminum pigment is brought into contact with a liquid containing phosphoric acid and / or phosphate as an essential component at a reaction temperature of 40 ° C to 100 ° C. The method for producing a resin-coated aluminum pigment is characterized in that the surface contains a phosphorus compound containing 0.1 mass% or more of phosphorus in terms of P element with respect to aluminum (claim 1). And in this patent document 1, generation | occurrence | production of hydrogen gas is suppressed by this resin-coated aluminum pigment, and when it is set as a coating film, it is described that glossiness (metallic feeling) does not deteriorate. On the other hand, this manufacturing method includes a two-step process in which an aluminum pigment is once coated with a resin and then treated with a phosphorus compound, and the treatment procedure is very complicated. Furthermore, there exists a possibility that flip-flop property (FF property) may fall by coat | covering an aluminum pigment with resin.

  Japanese Patent Application Laid-Open No. 2008-94890 (Patent Document 2) describes an aqueous metallic coating composition containing an aluminum pigment, a phosphoric acid compound, a vanadium compound, and a binder component (claim 1 and the like). And it is described that this water-based metallic coating composition can suppress generation | occurrence | production of gas, even when it stores for a long time, without performing a complicated process with respect to an aluminum pigment. On the other hand, the vanadium compound described in Patent Document 2 is a compound that exhibits various hues such as red, purple, blue, and green depending on its valence. Therefore, the inclusion of the vanadium compound in the coating composition may affect the color of the coating film formed by the coating composition. For example, in a base coating film that constitutes a top coating film of an automobile body or the like, a change in the color of the coating composition may greatly affect the color design of the coating film.

  JP 2008-248073 (Patent Document 3) discloses a rust preventive pigment (A) such as a phosphate-based rust preventive pigment containing one or more elements (a), a scaly aluminum pigment, and a resin composition. An aqueous coating composition containing at least one element selected from the group consisting of zinc, calcium, aluminum, titanium, silicon, magnesium, manganese, strontium, barium, iron, zirconium and cerium A water-based coating composition that is one or two or more elements is described (claim 1 and the like). It is described that this water-based coating composition is a coating composition excellent in finish and storage stability. However, from the viewpoint of work safety and the like, a coating composition having further excellent storage stability is required.

JP 2002-121423 A JP 2008-94890 A JP 2008-248073 A

  The present invention solves the above-described conventional problems, and an object thereof is to provide an aqueous coating composition in which gas generation is suppressed even in an aqueous coating composition containing a scaly aluminum pigment. It is in.

In order to solve the above problems, the present invention provides the following aspects.
[1]
An aqueous coating composition comprising a coating film-forming resin, a curing agent, a scaly aluminum pigment, and a water-soluble gas-suppressing inorganic compound,
The scaly aluminum pigment has neither a metal film made of metal other than aluminum nor an organic polymer film,
The water-soluble gas-suppressing inorganic compound has a solubility in water at 20 ° C. of 10 g / L or more, and the water-based coating composition includes an aluminum paste containing a scaly aluminum pigment, a film-forming resin, a curing agent, and Prepared by mixing a water-soluble gas-suppressing inorganic compound,
Water-based paint composition.
[2]
The water-based coating composition as described above, wherein the water-soluble gas-suppressing inorganic compound is one or more inorganic metal compounds containing a metal selected from the group consisting of Ce, W, Mo, and Se.
[3]
The scaly aluminum pigment is one or more selected from the group consisting of hydrocarbons having 7 to 20 carbon atoms, saturated fatty acids having 12 to 20 carbon atoms, unsaturated fatty acids having 12 to 20 carbon atoms, and derivatives of the fatty acids. The above-mentioned aqueous coating composition, which is a pigment coated as described above.
[4]
Content of the said water-soluble gas suppression inorganic compound is the said water-based coating composition which is 0.01-20 mass% with respect to the said scaly aluminum pigment.
[5]
Furthermore, the said water-based coating composition containing a phosphoric acid group containing organic compound.
[6]
The water-based paint composition described above, wherein the phosphate group-containing organic compound includes an alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms and / or a phosphate group-containing polymer having a phosphate group value of 5 to 300 mgKOH / g. object.
[7]
A method for producing an aqueous coating composition, comprising mixing an aluminum paste containing a scaly aluminum pigment, a coating film-forming resin, a curing agent, and a water-soluble gas-suppressing inorganic compound,
The scaly aluminum pigment has neither a metal film made of metal other than aluminum nor an organic polymer film,
The water-soluble gas-suppressing inorganic compound has a solubility in water at 20 ° C. of 10 g / L or more.
A method for producing an aqueous coating composition.
[8]
A method for producing an aqueous coating composition, comprising mixing an aluminum paste containing a scaly aluminum pigment and a phosphate group-containing organic compound, a coating film-forming resin, a curing agent, and a water-soluble gas-suppressing inorganic compound,
The scaly aluminum pigment has neither a metal film made of metal other than aluminum nor an organic polymer film,
The water-soluble gas-suppressing inorganic compound has a solubility in water at 20 ° C. of 10 g / L or more.
A method for producing an aqueous coating composition.
[9]
The said manufacturing method containing the phosphoric acid group containing polymer whose said phosphoric acid group containing organic compound has an alkylphosphoric acid ester which has a C4-C30 alkyl group, and / or a phosphoric acid group value is 5-300 mgKOH / g.
[10]
The above-mentioned production method, wherein the water-soluble gas-suppressing inorganic compound is one or more inorganic metal compounds containing a metal selected from the group consisting of Ce, W, Mo, and Se.
[11]
The scaly aluminum pigment is one or more selected from the group consisting of hydrocarbons having 7 to 20 carbon atoms, saturated fatty acids having 12 to 20 carbon atoms, unsaturated fatty acids having 12 to 20 carbon atoms, and derivatives of the fatty acids. The said manufacturing method which is the pigment coat | covered by the above.
[12]
Content of the said water-soluble gas suppression inorganic compound is the said manufacturing method which is 0.01-20 mass% with respect to the said scaly aluminum pigment.

  The water-based paint composition of the present invention is accompanied by gas generation even though it is a water-based paint composition containing a scaly aluminum pigment that has neither a metal film made of a metal other than aluminum nor an organic polymer film. It is characterized by providing a coating film having excellent glitter. In the aqueous coating composition of the present invention, it is not necessary to separately perform a pigment stabilization treatment after the flaky aluminum pigment is pulverized and produced. Therefore, an aqueous metallic base coating composition containing a scaly aluminum pigment can be prepared by a simpler procedure. In addition, since it is not necessary to separately perform a pigment stabilization treatment for the scaly aluminum pigment, it is possible to reduce the environmental load associated with the pigment stabilization treatment step. Furthermore, it becomes possible to provide an aqueous coating composition containing a scaly aluminum pigment at a lower cost.

Aqueous paint composition The aqueous paint composition of the present invention comprises a film-forming resin, a curing agent, a scaly aluminum pigment, and a water-soluble gas-suppressing inorganic compound. The aqueous coating composition of the present invention is an aqueous coating composition containing a scaly aluminum pigment having neither the metal coating made of a metal other than aluminum nor the organic polymer coating by having the above-described configuration. Regardless, the present invention is characterized in that an excellent gas generation suppressing effect can be achieved and a coating film having excellent glitter can be obtained. Hereinafter, each component contained in the aqueous coating composition will be sequentially described.

Film Forming Resin The aqueous coating composition of the present invention contains a film forming resin. A conventionally well-known thing can be used as coating-film formation resin. Specific examples of the coating film-forming resin include acrylic resin, polyester resin, alkyd resin, polyether resin, polyolefin resin, and urethane resin. Such a film-forming resin may be water-soluble, water-dispersible, or emulsion. Among the coating film forming resins, acrylic resins and / or polyester resins are preferably used from the viewpoint of coating film performance such as weather resistance and water resistance. These coating film forming resins may be used alone or in combination of two or more.

  One particularly preferred example of the film-forming resin is an acrylic resin emulsion. The acrylic resin emulsion can be obtained, for example, by emulsion polymerization of an α, β-ethylenically unsaturated monomer mixture. Preferred α, β-ethylenically unsaturated monomers used for the preparation of the acrylic resin emulsion include, for example, (meth) acrylic acid esters, α, β-ethylenically unsaturated monomers having an acid group, and α, β-having a hydroxyl group. Examples include ethylenically unsaturated monomers.

  (Meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylic T-butyl acid, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butyl (meth) acrylate Examples thereof include cyclohexyl, dicyclopentadienyl (meth) acrylate, and dihydrodicyclopentadienyl (meth) acrylate. In addition, in this specification, (meth) acrylic acid ester shall mean both acrylic acid ester and methacrylic acid ester.

  Examples of the α, β-ethylenically unsaturated monomer having an acid group include acrylic acid, methacrylic acid, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, and ω-carboxy-polycaprolactone mono (meta). ) Acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumaric acid, itaconic acid, Examples thereof include 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid, 2-acrylamido-2-methylpropanesulfonic acid, p-hydroxystyrene, 2,4-dihydroxy-4′-vinylbenzophenone, and the like.

  Examples of the α, β-ethylenically unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, methallyl alcohol, and these Examples include adducts with ε-caprolactone. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyethyl (meth) acrylate, and addition of these with ε-caprolactone. It is a thing.

  The α, β-ethylenically unsaturated monomer mixture may further use other α, β-ethylenically unsaturated monomers. Other α, β-ethylenically unsaturated monomers include polymerizable amide compounds (for example, (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meta ) 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, vinyltoluene, α-methylstyrene, divinylbenzene, t-butylstyrene, Parachlorostyrene, vinyl na Talen, 2-vinylpyridine and 4-vinylpyridine, etc.), polymerizable nitriles (eg, acrylonitrile, methacrylonitrile, etc.), polymerizable alkylene oxide compounds (eg, (meth) acrylic acid (poly) oxyethylene, (meth) Acrylic acid (poly) propylene glycol, etc.), polyfunctional vinyl compounds (such as allyl (meth) acrylate, (poly) oxyethylene di (meth) acrylate, trimethylolpropane tri (meth) acrylate, etc.), polymerizable amine compounds (Eg, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc.), α-olefin (eg, ethylene, propylene, etc.), vinyl esters (eg, vinyl acetate, vinyl propionate, vinyl persate, etc.) ), Ene (eg, butadiene, isoprene, etc.), vinyl halide (eg, vinyl chloride, vinylidene chloride, etc.), polymerizable carbonyl compound (eg, acrolein, diacetone (meth) acrylamide, formylstyrene, vinyl methyl ketone, vinyl ethyl ketone) , Vinyl isobutyl ketone, acryloxyalkylpropanals, methacryloxyalkylpropanals, diacetone acrylate, diacetone methacrylate, acetonyl acrylate, 2-hydroxypropyl acrylate acetyl acetate, butanediol acrylate acetyl acetate), polymerizable aceto Acetoxy compounds (eg, acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, etc.), polymerization Alkoxysilyl compounds (for example, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropyl) Triethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, Trimethoxysilyl styrene, dimethoxymethyl silyl styrene, triethoxy silyl styrene, diethoxymethyl silyl styrene, etc.) and other polymerizable compounds (eg, vinyl pyrrolidone, diphenyl vinyl phosphate) ). The α, β-ethylenically unsaturated monomer can be variously selected according to the purpose.

  The acrylic resin emulsion can be prepared by emulsion polymerization of the α, β-ethylenically unsaturated monomer mixture. The emulsion polymerization is not particularly limited, and can be performed using a usual method. Specifically, for example, an emulsifier is dissolved in water or an aqueous medium containing an organic solvent such as alcohol, ether (for example, dipropylene glycol methyl ether, propylene glycol methyl ether) as necessary, and heated. It can carry out by dripping the said (alpha), (beta) -ethylenically unsaturated monomer mixture and a polymerization initiator under stirring. An α, β-ethylenically unsaturated monomer mixture emulsified in advance using an emulsifier and water may be similarly added dropwise.

  As the polymerization initiator, those usually used by those skilled in the art can be used. As the polymerization initiator, for example, an azo compound (for example, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (N- (2-carboxyethyl) -2-methylpropionamidine), Azobisisobutyronitrile, 2,2′-azobis-2,4′-dimethylvaleric nitrile, etc.), peroxides (t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroper Oxides, cumene hydroperoxide, dibenzoyl peroxide, di-t-butyl peroxide, t-butylperoxyneodecanoate, potassium persulfate, ammonium persulfate, etc.), redox initiators (eg, hydrogen peroxide and chloride) A combination of iron (II), a combination of ammonium persulfate and ammonium bisulfite, and the like. The polymerization initiator may be neutralized with a base as necessary, and can be used at a pH of 1 to 10, for example.

  As the emulsifier, those usually used by those skilled in the art can be used. As an emulsifier, for example, Antox MS-2N (manufactured by Nippon Emulsifier Co., Ltd., 2-sodium sulfoethyl methacrylate), New Coal 706 (manufactured by Nippon Emulsifier Co., Ltd., polyoxyethylene polycyclic phenyl ether), Adekaria soap NE -10 (manufactured by Asahi Denka Co., Ltd., α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxypolyoxyethylene), Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether) Latemul PD-104 (manufactured by Kao Corporation, polyoxyalkylene alkenyl ether ammonium sulfate) and Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate) can be suitably used.

  In order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer may be used as necessary.

  The reaction temperature is determined by the initiator, and is usually 20 to 95 ° C., for a redox initiator, for example, 20 to 50 ° C., and for an azo system, for example, 40 to 95 ° C. Further, the inside of the reaction vessel may be pressurized to carry out the polymerization, and in that case, the polymerization may be carried out at a temperature of 95 ° C. or higher. In general, the reaction time is 1 to 8 hours. The amount of the initiator relative to the total amount of the α, β-ethylenically unsaturated monomer mixture is generally 0.05 to 5% by mass, preferably 0.1 to 3% by mass.

  The acrylic resin emulsion that can be prepared in this way preferably has an average particle size in the range of 0.01 to 1.0 μm. If the average particle size is less than 0.01 μm, the viscosity may be significantly increased and it may be difficult to increase the resin solid content concentration, and if it exceeds 1.0 μm, the appearance of the resulting coating film may be deteriorated. . More preferably, it is 0.05-0.5 micrometer. This average particle size can be adjusted, for example, by adjusting the monomer composition or emulsion polymerization conditions. In addition, the said average particle diameter is displayed with the volume average particle diameter measured by the laser light scattering method.

  The acrylic resin emulsion may be neutralized with a base as necessary, and can be used at a pH of 1 to 10, for example. This is because the stability in this pH region is high. This neutralization involves adding a basic compound such as ammonia, sodium hydroxide, potassium hydroxide, monoethanolamine, monomethylethanolamine, dimethylethanolamine, diethylethanolamine or triethylamine to the system before or after emulsion polymerization. Can be performed.

  The acrylic resin emulsion preferably has a number average molecular weight of 3000 at the lower limit. If it is less than 3000, workability and curability may be insufficient. An upper limit in particular is not restrict | limited, For example, it can also be set as a crosslinked emulsion using polyfunctional (meth) acrylate etc. The lower limit is more preferably 4000. In the present specification, the number average molecular weight is a value determined by a GPC method using polystyrene as a standard.

  The acrylic resin emulsion preferably has a hydroxyl value having a lower limit of 20 mgKOH / g and an upper limit of 180 mgKOH / g. There exists a possibility that the sclerosis | hardenability of a coating film may fall that it is less than 20 mgKOH / g. If it exceeds 180 mgKOH / g, the water resistance of the coating film may decrease. The lower limit is more preferably 30 mgKOH / g, and the upper limit is more preferably 160 mgKOH / g.

  The acrylic resin emulsion preferably has an acid value of a lower limit of 1 mgKOH / g and an upper limit of 80 mgKOH / g. If it is less than 1 mgKOH / g, the stability of the paint may be reduced. When it exceeds 80 mgKOH / g, the water resistance of the coating film may be lowered. The lower limit is more preferably 3 mgKOH / g, and the upper limit is more preferably 70 mgKOH / g.

  The aqueous coating composition of the present invention may contain other film-forming resin as necessary. Other film-forming resins are not particularly limited, and film-forming resins such as water-soluble acrylic resins, polyester resins, alkyd resins, epoxy resins, and urethane resins can be used.

Curing Agent The water-based coating composition of the present invention contains a curing agent that appropriately corresponds to the type of curable functional group possessed by the coating film-forming resin. A conventionally well-known thing can be used as a hardening | curing agent, Specifically, an amino resin, block isocyanate resin, an epoxy compound, an aziridine compound, a carbodiimide compound, an oxazoline compound etc. can be mentioned as a preferable thing. Among these, amino resins and / or blocked isocyanate resins are generally used. The said hardening | curing agent may be used independently and may use 2 or more types together.

  The amino resin is not particularly limited, and a water-soluble melamine resin and / or a water-insoluble melamine resin can be used.

  The blocked isocyanate resin can be prepared by adding a blocking agent having active hydrogen to a polyisocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate. In such a blocked isocyanate resin, the blocking agent is dissociated by heating to generate an isocyanate group, which is cured by reacting with the functional group in the resin component.

  The blending amount of the curing agent is preferably a lower limit of 5 parts by mass and an upper limit of 120 parts by mass with respect to 100 parts by mass of the solid content of the coating film-forming resin. If it is less than 5 parts by mass, the curability may be insufficient. If it exceeds 120 parts by mass, the cured film may be too hard and brittle. As for the compounding quantity of a hardening | curing agent, it is more preferable that it is 10-100 mass parts with respect to 100 mass parts of solid content of the said coating-film formation resin.

Scale-like aluminum pigment The aqueous coating composition of the present invention contains a scale-like aluminum pigment. The scaly aluminum pigment contained in the aqueous coating composition of the present invention is characterized in that it does not have any of a metal film and an organic polymer film made of a metal other than aluminum.

  Examples of the scaly pigment in the present specification include a shape having an average particle diameter (D50) of 2 to 50 μm and a thickness of 0.1 to 5 μm. Here, the average particle diameter means a median diameter of a volume-based particle size distribution measured by a laser diffraction scattering method using a Microtrac particle size distribution measuring device MT3300 (trade name, manufactured by Nikkiso Co., Ltd.). The thickness means an average value of 100 or more measured values obtained by measuring a cross section of a coating film containing a scaly aluminum pigment with a scanning electron microscope (SEM).

  In the present specification, the “metal film made of a metal other than aluminum” means, for example, a film of a metal compound such as molybdic acid, chromic acid, yttrium, and a rare earth metal.

  In the present specification, the “organic polymer film” means an organic polymer film prepared using a polymerizable monomer or the like. The organic polymer film referred to here is an organic polymer film prepared by polymerizing a polymerizable monomer in the presence of an aluminum pigment, and an organic polymer previously polymerized using a polymerizable monomer, which is aluminum. Any embodiment of those used for pigment coating is also included. Examples of aluminum pigments coated with an organic polymer film include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, divinylbenzene, itaconic acid, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, 2 -A resin-coated aluminum pigment obtained by adding a polymerizable monomer selected from hydroxyethyl acrylate, benzyl acrylate, etc., an aluminum pigment, a polymerization initiator and, if necessary, mineral spirit, and stirring while heating. Can be mentioned.

  These metal coatings and organic polymer coatings made of metals other than aluminum are coatings intended to prevent the generation of gas due to the reaction between the aluminum pigment and water. On the other hand, the scaly aluminum pigment contained in the aqueous coating composition of the present invention has neither a metal film made of a metal other than aluminum nor an organic polymer film. That is, the scale-like aluminum pigment contained in the aqueous coating composition of the present invention is stabilized after the aluminum pigment is produced, such as coating with a metal film or an organic polymer film made of a metal other than aluminum as described above. This means that the process is not performed.

  The scaly aluminum pigment in the present invention is selected from the group consisting of hydrocarbons having 7 to 20 carbon atoms, saturated fatty acids having 12 to 20 carbon atoms, unsaturated fatty acids having 12 to 20 carbon atoms, and derivatives of these fatty acids. Preference is given to pigments coated with seeds or more.

  A hydrocarbon having 7 to 20 carbon atoms, a saturated fatty acid having 12 to 20 carbon atoms, an unsaturated fatty acid having 12 to 20 carbon atoms and a derivative of these fatty acids are used as a grinding fluid or a grinding aid in the production of scaly aluminum pigments. It is a compound used as The scaly aluminum pigment is generally produced by crushing and grinding aluminum in the presence of a grinding fluid and a grinding aid using a grinding machine such as a ball mill or an attritor mill. And the scaly aluminum pigment obtained by such grinding | pulverization and grinding is C7-C20 hydrocarbon, C12-C20 saturated fatty acid, C12-C20 unsaturated fatty acid, and derivatives of these fatty acids. It is obtained in a state where it is coated with a grinding fluid and / or a grinding aid. In the aqueous coating composition of the present invention, a scaly aluminum pigment is used that is coated with a grinding fluid and / or a grinding aid, which is usually obtained by grinding and grinding aluminum.

  Examples of the hydrocarbon having 7 to 20 carbon atoms include an aliphatic hydrocarbon having 7 to 20 carbon atoms, an alicyclic hydrocarbon having 7 to 20 carbon atoms, and mineral spirit. Here, the mineral spirit is a mixture of hydrocarbons having 7 to 20 carbon atoms obtained by hydrotreating a petroleum fraction. This mineral spirit includes petrolium spirit, white spirit, mineral terpenes, and the like. All of these are used as a grinding fluid in the production of scaly aluminum pigments.

Examples of the saturated fatty acid having 12 to 20 carbon atoms include lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid.
Examples of the unsaturated fatty acid having 12 to 20 carbon atoms include palmitoleic acid and oleic acid.
Examples of these fatty acid derivatives include aliphatic amines, aliphatic amides, and aliphatic alcohols having a saturated hydrocarbon group having 12 to 20 carbon atoms and / or an unsaturated hydrocarbon group having 12 to 20 carbon atoms.
All of these are used as grinding aids in the production of scaly aluminum pigments.

  In the aqueous coating composition of the present invention, the mass ratio (PWC) of the scaly aluminum pigment to the resin solid content contained in the coating composition is preferably 1 to 30%, and more preferably 5 to 30%. More preferred. When the mass ratio of the scaly pigment is in the above range, a coating film having excellent glitter can be formed. Here, the “resin solid content” means the total amount of the film-forming resin and the curing agent contained in the aqueous coating composition. When the content (PWC) of the scaly aluminum pigment is less than 1%, the concealability of the obtained coating film may be lowered. Moreover, when content (PWC) of a scale-like aluminum pigment exceeds 30%, the effect accompanying the increase in content is not seen but there exists a possibility that cost may become high too much.

Water-soluble gas-suppressing inorganic compound The aqueous coating composition of the present invention comprises a water-soluble gas-suppressing inorganic compound. By including a water-soluble gas-suppressing inorganic compound in the water-based coating composition of the present invention, a stabilization treatment of an aluminum pigment, such as providing a metal film or an organic polymer film made of a metal other than aluminum, is performed. Even though no scaly aluminum pigment is contained in the aqueous coating composition, an excellent gas generation suppression effect is achieved. Moreover, a coating film with high FF property can be obtained, suppressing generation | occurrence | production of the gas in an aqueous coating composition, when the aqueous coating composition of this invention contains a water-soluble gas suppression inorganic compound.

  The FF property means flip-flop property. In this specification, “strong flip-flop” means that when evaluating a metallic coating film obtained by an aqueous coating composition containing a scaly aluminum pigment, from the front direction (direction perpendicular to the coating surface) It is white and brilliant and excellent in radiance. On the other hand, from the oblique direction, the sensation is small and the hue is clearly visible, which means that the brightness difference between the two is large. That is, a metallic coating film in which the metallic feeling changes remarkably depending on the viewing angle is referred to as a coating film having excellent design properties and is referred to as “strong flip-flop”.

  In the present specification, the water-soluble gas-suppressing inorganic compound means a gas-suppressing inorganic compound having a solubility in water at 20 ° C. of 10 g / L or more. A specific method for measuring the solubility in water at 20 ° C. is to add 100 g of water and 1 g of a gas-suppressing inorganic compound to a 200 ml beaker, stir with a stirrer at 20 ° C. for 1 hour, and visually confirm whether or not it has dissolved By doing. If the total amount of the gas-suppressing inorganic compound is dissolved under these conditions, it is determined that the gas-inhibiting inorganic compound is a water-soluble gas-suppressing inorganic compound. Examples of such water-soluble gas-suppressing inorganic compounds include inorganic metal compounds containing a metal selected from the group consisting of Ce, W, Mo, and Se. Specific examples of these water-soluble inorganic compounds include, for example, ammonium molybdate, sodium molybdate, potassium molybdate, cerium nitrate, cerium chloride, sodium tungstate, potassium tungstate, potassium selenite, lithium selenide, selenic acid Examples include ammonium, potassium selenate, cerium selenide, sodium selenate, and magnesium selenate.

  Of these water-soluble gas-suppressing inorganic compounds, for example, potassium selenate, cerium chloride, potassium molybdate, sodium tungstate, ammonium selenate, cerium selenide and the like are more preferably used.

  Content of the said water-soluble gas suppression inorganic compound contained in the aqueous coating composition of this invention is 0.01-20 mass% with respect to a scale-like aluminum pigment (100 mass parts of scale-like aluminum contained in an aqueous coating composition) Is preferably 0.01 to 20 parts by mass). When the content of the water-soluble gas-suppressing inorganic compound is less than 0.01% by mass, a sufficient gas generation suppressing effect may not be obtained. On the other hand, when the content of the water-soluble gas-suppressing inorganic compound exceeds 20% by mass, the water resistance of the resulting coating film may be reduced.

Phosphate group-containing organic compound The aqueous coating composition of the present invention may further contain a phosphate group-containing organic compound in addition to the above components. By including the phosphoric acid group-containing organic compound in the aqueous coating composition of the present invention, the grinding fluid such as mineral spirits and grinding aids such as oleic acid are difficult to peel off from the surface of the aluminum pigment. The dispersibility of the scaly aluminum pigment is improved, and there are advantages such as improved coating film properties such as adhesion in the obtained coating film.

  Examples of the phosphate group-containing organic compound include a phosphate group-containing polymer having a phosphate group value of 5 to 300 mgKOH / g, and an alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms. As the phosphoric acid group-containing organic compound, one or both of the phosphoric acid group-containing polymer and the alkyl phosphoric acid ester may be included.

  The phosphoric acid group-containing polymer is not particularly limited as long as the phosphoric acid group value is in the range of 5 to 300 mgKOH / g, and conventionally known polymers can be used. Specific examples of the phosphate group-containing polymer include an acrylic resin having a phosphate group, a polyester resin having a phosphate group, a polyether resin having a phosphate group, and an epoxy resin having a phosphate group. Among the polymers containing the phosphoric acid group, it is preferable to use an acrylic resin in terms of performance such as weather resistance and water resistance. These polymers containing a phosphate group may be used alone or in combination of two or more.

  One particularly preferred example of the phosphoric acid group-containing polymer is a phosphoric acid group-containing acrylic resin. The phosphoric acid group-containing acrylic resin is, for example, polymerized only with a phosphoric acid group-containing α, β-ethylenically unsaturated monomer using a phosphoric acid group-containing α, β-ethylenically unsaturated monomer as an essential component, or this monomer. And a mixture of other α, β-ethylenically unsaturated monomers not containing a phosphate group can be obtained by copolymerization.

  Examples of phosphoric acid group-containing α, β-ethylenically unsaturated monomers include 2-acryloyloxyethyl acid phosphate, 2- (methacryloyloxy) ethyl phosphate (also known as acid phosphooxyethyl methacrylate, Phosmer M, Unichemical Co., Ltd.) ), 3-chloro-2-acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate (Phosmer PE, Unichemical Co., Ltd.), acid phosphooxypolyoxypropylene glycol monomethacrylate ( Phosmer PP, manufactured by Unichemical Co., Ltd.), vinylphosphonic acid and the like.

  Examples of α, β-ethylenically unsaturated monomers not containing a phosphate group include (meth) acrylic acid esters, α, β-ethylenically unsaturated monomers having an acid group, and α, β-ethylenically unsaturated monomers having a hydroxyl group. Saturated monomers, and other α, β-ethylenically unsaturated monomers that do not have these groups. As the (meth) acrylic acid ester, a (meth) acrylic acid ester that can be used for preparing the acrylic resin emulsion can be used. As the α, β-ethylenically unsaturated monomer having an acid group, an α, β-ethylenically unsaturated monomer having an acid group that can be used for the preparation of the acrylic resin emulsion can be used. As other α, β-ethylenically unsaturated monomers not having these groups, other α, β-ethylenically unsaturated monomers that can be used for the preparation of the acrylic resin emulsion can be used. In the preparation of the phosphoric acid group-containing acrylic resin, these α, β-ethylenically unsaturated monomers not containing a phosphoric acid group can be appropriately selected and used.

  Preparation of the phosphoric acid group-containing acrylic resin, for example, the phosphoric acid group-containing α, β-ethylenically unsaturated monomer as an essential component, only the phosphoric acid group-containing α, β-ethylenically unsaturated monomer, or Obtained by copolymerizing a mixture of the above-mentioned phosphate group-containing α, β-ethylenically unsaturated monomer and another α, β-ethylenically unsaturated monomer not containing a phosphate group by a commonly used method. Can do. For example, the monomer mixture can be prepared by polymerization using a polymerization initiator in the presence of an organic solvent as required. As a polymerization initiator, the polymerization initiator etc. which can be used in preparation of an acrylic resin emulsion can be used. Moreover, as an organic solvent as needed, for example, ketones such as cyclohexanone and methyl-2-n-amyl ketone; 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-methoxy-2-propanol Alcohols such as ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether; propylene glycol monomethyl ether acetate, propylene Glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate Ethyl 3-ethoxy propionate, acetate tert- butyl, tert- butyl propionate, and propylene glycol monobutyl tert- butyl ether acetate; and the like.

  The reaction temperature in the copolymerization may be, for example, 80 to 150 ° C., and the reaction time may be, for example, 1 to 8 hours.

  Examples of the phosphoric acid group-containing polymer other than the phosphoric acid group-containing acrylic resin that can be used in the present invention include, for example, AQ-330 (manufactured by Enomoto Kasei Co., Ltd., a phosphoric ester type surfactant having a polyalkylene oxide group. Acid group value 12 mgKOH / g), AQ-320 (manufactured by Enomoto Kasei Co., Ltd., phosphate group value 14 mgKOH / g), AQ-340 (manufactured by Enomoto Kasei Co., Ltd., phosphoric acid group value 18 mgKOH / g), polyalkylene oxide group Examples of the phosphoric acid ester type wetting and dispersing agent include BYK-111 (manufactured by Big Chemie, phosphoric acid group value 120 mgKOH / g), BYK-180 (manufactured by Big Chemie, phosphoric acid group value 90 mgKOH / g), and the like.

  The phosphate group-containing polymer preferably has a number average molecular weight of 1,000 to 50,000. In the present specification, the number average molecular weight is a value determined by a GPC method using polystyrene as a standard.

  The phosphoric acid group-containing polymer preferably has a phosphoric acid group value of 5 to 300 mgKOH / g. When the phosphoric acid group value of the phosphoric acid group-containing polymer is less than 5 mgKOH / g, there is a possibility that the adhesion improving effect cannot be obtained in the obtained coating film. On the other hand, when the phosphoric acid group value exceeds 300 mgKOH / g, the water resistance of the resulting coating film is inferior. The phosphate group value of the phosphate group-containing polymer is more preferably 10 to 250 mgKOH / g.

  In this specification, the calculation of the phosphoric acid group value of the phosphoric acid group-containing polymer is the definition of the acid value of JIS K56012-1 (the hydroxylation required to neutralize the free acid in 1 g of non-volatile products. It is the calculated phosphate group value obtained by performing calculation based on the number of mg of potassium (KOH).

  The alkyl phosphate ester is an alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms. Examples of the alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms include monoalkyl phosphate esters, dialkyl phosphate esters, and mixtures of monoalkyl phosphate esters and dialkyl phosphate esters. In the dialkyl phosphate ester, the two alkyl groups are more preferably the same group.

  Examples of the alkyl group having 4 to 30 carbon atoms include butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group , Heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, docosyl group, tetracosyl group, hexacosyl group or octacosyl group. These alkyl groups may be linear or branched.

  Specific examples of the alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms include, for example, butyl acid phosphate (mixture of monobutyl ester and dibutyl ester), 2-ethylhexyl acid phosphate (mono-2-ethylhexyl ester and diester). -2-ethylhexyl ester), isodecyl acid phosphate (mixture of monoisodecyl ester and diisodecyl ester), dilauryl acid phosphate, lauryl acid phosphate (mixture of monolauryl ester and dilauryl ester), tridecyl Acid phosphate (mixture of monotridecyl ester and ditridecyl ester), monostearyl acid phosphate, distearyl acid phosphate, stearyl acid phosphate (Mixture of monostearyl ester and distearyl ester), isostearyl acid phosphate (mixture of monoisostearyl ester and diisostearyl ester), oleyl acid phosphate (mixture of monooleyl ester and dioleyl ester), Examples include behenyl acid phosphate (mixture of monobehenyl ester and dibehenyl ester).

  By using both a phosphate group-containing polymer having a phosphate group value of 5 to 300 mgKOH / g and an alkyl phosphate ester having an alkyl group having 4 to 30 carbon atoms as the phosphate group-containing organic compound, scaly aluminum There is an advantage that better dispersibility of the pigment can be obtained, and coating film properties such as adhesion are further improved in the obtained coating film.

  When using the said phosphate group containing organic compound, it is preferable that the quantity of a phosphate group containing organic compound is 0.1-50 mass% with respect to the scale-like aluminum pigment contained in a coating composition. More preferably, it is -35 mass%. When the amount of the phosphoric acid group-containing organic compound is within the above range, there is an advantage that the dispersibility of the scaly aluminum pigment is improved and excellent FF properties and adhesion can be obtained in the obtained coating film.

The aqueous coating composition of the present invention, such as other pigments, may contain other pigments in addition to the scale-like aluminum pigment. Other pigments include colored pigments and extender pigments. Examples of the color pigment include, for example, organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, and perylenes. Pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments and the like, and inorganic pigments such as yellow iron oxide, nickel titanium yellow, bengara, carbon black, and titanium dioxide. Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc.

  The water-based coating composition of the present invention may contain a scale-like pigment other than the scale-like aluminum pigment. As such a scaly pigment, for example, those having an average particle diameter (D50) of 2 to 50 μm and a thickness of 0.1 to 5 μm are preferable. Those having an average particle size in the range of 5 to 35 μm are excellent in glitter and are more preferably used. Specific examples of the scaly pigments include metal scaly pigments such as metals or alloys such as copper, zinc, iron, nickel, tin, and aluminum oxide, and mixtures thereof. In addition, interference mica pigments, white mica pigments, graphite pigments, and the like are included in this. These scaly pigments may be colored as necessary.

  The total pigment concentration (PWC) in the aqueous coating composition of the present invention is preferably 5 to 50% by mass. The total pigment concentration (PWC) is more preferably 5 to 40%, further preferably 5 to 35%. When the total pigment concentration (PWC) exceeds 50%, the coating film appearance may be deteriorated.

Other components In addition to the above-mentioned components, the water-based coating composition of the present invention includes additives usually used by those skilled in the art, for example, surface conditioners, viscosity control agents, thickeners, antioxidants, UV inhibitors, extinction agents. A foaming agent or the like may be included. For example, by using a viscosity control agent, thixotropy can be imparted and coating workability can be adjusted. Viscosity control agents include, for example, crosslinked or non-crosslinked resin particles, fatty acid amide swelling dispersions, amide fatty acids, polyamides such as long chain polyaminoamide phosphates, colloidal swelling dispersions of polyethylene oxide, etc. And polyethylene bentonite, organic acid smectite clay, and organic bentonite such as montmorillonite. When these additives are used, they can be used in an amount usually used by those skilled in the art.

The aqueous coating composition of the present invention may contain an amphiphilic compound as necessary. As an amphiphilic compound, for example,
A compound having at least one hydrophobic part (A) as a repeating unit and at least one hydrophilic part (B) as a repeating unit, wherein
The hydrophobic part (A) is a propylene oxide group, a butylene oxide group, a linear or branched saturated hydrocarbon group having 4 to 40 carbon atoms, a linear or branched non-carbon group having 4 to 40 carbon atoms. Having at least one group selected from the group consisting of a saturated hydrocarbon group, an aromatic ring-containing group having 6 to 40 carbon atoms having an aromatic ring, and a hydrophobic polymer segment;
Examples of the hydrophilic part (B) include compounds having at least one group selected from the group consisting of an ethylene oxide group and an acid group and having a number average molecular weight of 1500 to 100,000.
By including such an amphiphilic compound in the aqueous coating composition of the present invention, even when the aqueous coating composition is, for example, a coating composition having a high resin solid content concentration, good FF properties are obtained. There is an advantage of being achieved. Such an aqueous coating composition may further contain an anionic surfactant as necessary.

Water-based paint composition and method for producing water-based paint composition The water-based paint composition of the present invention is produced by coating film-forming resin, curing agent, scaly aluminum pigment, water-soluble gas-suppressing inorganic compound, and phosphorus as required. Acid group-containing organic compounds and additives can be produced by methods commonly used by those skilled in the art, such as kneading and dispersing using a disper, a homogenizer, a kneader or the like. And as a manufacturing method of the water-based paint composition of the present invention, for example, an aluminum paste containing a scaly aluminum pigment and a phosphate group-containing organic compound and / or a pigment dispersant as necessary is prepared in advance, and this aluminum paste, The manufacturing method which mixes coating-film formation resin, a hardening | curing agent, and a water-soluble gas suppression inorganic compound is mentioned.

  The aluminum paste can be prepared by using a stirring method usually used by those skilled in the art.

  In addition, in this invention, in the manufacture of a water-based coating composition, the aspect which prepares an aluminum paste by previously mixing a scaly aluminum pigment and a water-soluble gas suppression inorganic compound is not included. It is considered that the water-soluble gas-suppressing inorganic compound is oriented with respect to the surface of the scaly aluminum pigment, and an excellent gas generation inhibiting effect is achieved by this orientation. On the other hand, when preparing an aluminum paste by premixing such a water-soluble gas-suppressing inorganic compound and a flaky aluminum pigment, the water-soluble gas-suppressing inorganic compound is excessively oriented in the flaky aluminum pigment, In the production of the scaly aluminum pigment, the grinding medium liquid such as mineral spirit and the grinding aid such as oleic acid which coat the pigment also tend to be peeled off from the surface of the aluminum pigment. The pulverizing medium liquid and the pulverization aid are peeled off from the pigment surface, whereby unexpected coloration may occur in the aluminum paste or the glitter may be impaired. In addition, when preparing an aluminum paste by previously mixing an aluminum pigment having a metal coating made of a metal other than aluminum and a water-soluble gas-suppressing inorganic compound, the aluminum pigment having an organic polymer coating and a water-soluble gas-suppressing inorganic In any case where the compound is premixed to prepare an aluminum paste, the water-soluble gas-suppressing inorganic compound tends to peel these coatings from the surface of the aluminum pigment.

  On the other hand, the production method of the present invention is characterized in that an aqueous coating composition is produced without previously mixing the water-soluble gas-suppressing inorganic compound and the scaly aluminum pigment. By such a production method, the water-soluble gas-suppressing inorganic compound acts gently on the scaly aluminum pigment in the aqueous coating composition. For this reason, it has become possible to obtain a coating film having good glitter by suppressing the generation of gas in the scaly aluminum pigment without causing problems such as unexpected coloring.

  The aqueous coating composition of the present invention preferably has a resin solid content concentration of 10 to 40% by mass contained in the coating composition. Here, the “resin solid content concentration” means the concentration (mass%) of the total amount of the film-forming resin and the curing agent contained in the aqueous coating composition. The resin solid content concentration of the aqueous coating composition can be calculated from the amount of each component used in the preparation of the aqueous coating composition.

  The aqueous coating composition of the present invention is prepared by preparing an aqueous coating composition without including a water-soluble gas-suppressing inorganic compound in advance in an aluminum paste containing a scaly aluminum pigment, thereby providing a grinding fluid such as mineral spirits and oleic acid. It is possible to prevent pulverization aids such as from peeling off from the surface of the aluminum pigment. Therefore, even an aqueous paint composition containing scaly aluminum pigment has a feature that the generation of gas is well suppressed while maintaining the FF property of the coating film. Therefore, the water-based paint composition of the present invention may be a high solid content paint composition (solid content concentration of 25% or more) having a solid content concentration higher than that of a general water-based paint composition. In the high solid content coating composition, the content of the scaly aluminum pigment contained tends to increase as compared with a general aqueous coating composition. Therefore, in a high solid content coating composition, it can be said that the possibility of gas generation is higher than that of a general aqueous coating composition. On the other hand, the water-based coating composition of the present invention has an advantage that the generation of gas is satisfactorily suppressed even if it is a high solid content coating composition, for example.

Method for Forming Coating Film The aqueous coating composition of the present invention can be used, for example, as an aqueous base coating composition. As a coating method in the case of using as an aqueous base coating composition, for example,
A process of coating a water-based base coating composition on an object to be coated to form an uncured base coating;
The step of applying a clear coating composition on the uncured base coating film to form an uncured clear coating film, and simultaneously heating the resulting uncured base coating film and clear coating film. Curing process,
The method of including is mentioned.

Coating object The coating object which can be used in the said coating is not specifically limited, For example, a metal base material, a plastic base material, its foam, etc. are mentioned.

  Examples of the metal substrate include metals such as iron, steel, copper, aluminum, tin, and zinc, and alloys containing these metals. Specific examples of the metal substrate include automobile bodies such as passenger cars, trucks, motorcycles, and buses, and parts for automobile bodies. As for such a metal base material, it is more preferable that the electrodeposition coating film is previously formed. Moreover, chemical conversion treatment (for example, zinc phosphate chemical conversion treatment, zirconium chemical conversion treatment, etc.) as necessary may be performed before the electrodeposition coating film is formed.

  Examples of the plastic substrate include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. Specific examples of the plastic substrate include automobile parts such as spoilers, bumpers, mirror covers, grills, and door knobs. These plastic substrates are preferably washed with pure water and / or a neutral detergent. Moreover, the primer coating for enabling electrostatic coating may be given.

  An intermediate coating film as required may be further formed on the object to be coated. An intermediate coating composition is used for forming the intermediate coating film. In general, the intermediate coating composition contains a film-forming resin, a curing agent, and various pigments (for example, colored pigments, extender pigments, etc.). The film-forming resin and the curing agent are not particularly limited, and for example, a film-forming resin and a curing agent that can be used in the aqueous coating composition of the present invention can be used.

  The aqueous coating composition of the present invention can also be used as a so-called intermediate coating composition. When the aqueous coating composition of the present invention is used as an intermediate coating composition, the aqueous coating composition used as the base coating composition and the intermediate coating composition may be the same coating composition, or different coating compositions. It may be a thing.

First, an uncured base coating film is formed by coating the aqueous coating composition on an object to be coated. The article to be coated may have an uncured intermediate coating film.
As coating methods usually used in the coating of water-based paint compositions, multi-stage coating or one-stage coating by air electrostatic spray coating, or air electrostatic spray coating and rotary atomizing electrostatic coating called metallic bell. Examples of methods generally used in the field of automobile body painting, such as a painting method in combination with a machine. These coating methods have the advantage that the coating film obtained has a good coating film appearance. The film thickness of the base coating film to be formed is preferably 3 to 50 μm, for example, and more preferably 5 to 30 μm as a dry film thickness.

  An uncured clear coating film may be formed by coating a clear coating composition on an uncured base coating film obtained by applying an aqueous base coating composition. After baking the base coating obtained by applying the aqueous base paint, you may apply the clear coating composition on it, but further apply the clear coating composition on the uncured base coating, By forming the clear coating film, the baking and drying step of the base coating film can be omitted, which is preferable from the viewpoint of economy and environment. In order to obtain a good finished coating film, it is more preferable to heat the uncured base coating film at 40 to 100 ° C. for 2 to 10 minutes before applying the clear coating composition.

  The clear coating composition to be used is not particularly limited, and a clear coating composition containing a film-forming resin and a curing agent as required can be used. Furthermore, a coloring component can be contained as long as it does not interfere with the design of the base. Examples of the form of the clear coating composition include solvent type, aqueous type and powder type.

  Preferred examples of the solvent-type clear coating composition include a combination of an acrylic resin and / or a polyester resin, an amino resin and / or an isocyanate, or a carboxylic acid / epoxy curing system in terms of transparency or acid etching resistance. An acrylic resin and / or a polyester resin are mentioned.

  Examples of the water-based clear coating composition include those containing a resin obtained by neutralizing a coating film-forming resin contained in the solvent-type clear coating composition described above as an example with a base to make it water-based. This neutralization can be carried out by adding tertiary amines such as dimethylethanolamine and triethylamine before or after polymerization.

  As the powder-type clear coating composition, commonly used powder coatings such as thermoplastic and thermosetting powder coatings can be used. A thermosetting powder coating is preferred because a coating film having good physical properties can be obtained. Specific examples of thermosetting powder coatings include epoxy-based, acrylic-based and polyester-based powder clear coating compositions, but acrylic-based powder clear coating compositions with good weather resistance are particularly preferred. preferable.

  The clear coating composition may contain a viscosity control agent. As a viscosity control agent, what was mentioned by the description about the above-mentioned aqueous coating composition can be used, for example. The clear coating composition may further contain a curing catalyst, a surface conditioner and the like as required.

  The clear coating composition can be applied by a commonly used method according to the form of the coating composition. As a specific example of the method of applying the clear coating composition to the base coating film, for example, a coating method using a rotary atomizing electrostatic coating machine called a microbell can be mentioned.

  The dry film thickness of the clear coating film formed by applying the clear coating composition is generally preferably about 10 to 80 μm, and more preferably about 20 to 60 μm. When the dry film thickness is less than 10 μm, the unevenness of the base cannot be concealed, and when it exceeds 80 μm, there is a possibility that problems such as peeling or sagging may occur during coating.

  The clear coating film thus formed is preferably formed by so-called two-coat one-bake, which is baked together with an uncured base coating film as described above. The baking temperature is preferably set to 80 to 180 ° C., more preferably 120 to 160 ° C., from the viewpoint of the crosslinking density and the properties of the obtained multilayer coating film. The baking time can be arbitrarily set according to the baking temperature, but it is appropriate that the baking time is 120 to 160 ° C. and the baking time is 10 to 40 minutes.

  The film thickness of the multilayer coating film thus formed is generally 20 to 300 μm and preferably 30 to 250 μm. When the film thickness is less than 20 μm, the strength of the film itself may be reduced. On the other hand, when the film thickness exceeds 300 μm, film physical properties such as a cooling / heating cycle may be deteriorated.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

Production Example 1 Production of Acrylic Resin Emulsion (Coating Film Forming Resin) 330 g of deionized water was added to a reaction vessel, and the temperature was raised to 80 ° C. while mixing and stirring in a nitrogen stream. Then 11.25 parts acrylic acid, 139 parts n-butyl acrylate, 75 parts methyl methacrylate, 187 parts n-butyl methacrylate, 75 parts 2-ethylhexyl methacrylate, 150 parts 2-hydroxyethyl methacrylate, styrene 112 Parts, thiocalcol 20 (n-dodecyl mercaptan, Kao Corporation, active ingredient 100%) 11.2 parts, latemul PD-104 (emulsifier, Kao Corporation, active ingredient 20%) 74.3 parts, and deionized water 3% of the monomer emulsion consisting of 300 parts and 2.63 parts of ammonium persulfate and 30% of the initiator solution consisting of 90 parts of deionized water were dropped into the reaction vessel in parallel over 15 minutes. After completion of the dropping, aging was performed at the same temperature for 15 minutes.
Further, the remaining monomer emulsion and the initiator solution were dropped into the reaction vessel in parallel over 180 minutes. After completion of the dropping, aging was performed at the same temperature for 1 hour.
Next, the mixture was cooled to 40 ° C. and filtered through a 200 mesh filter to obtain an acrylic resin emulsion having an average particle size of 200 nm, a nonvolatile content of 49%, a solid content acid value of 15 mgKOH / g, and a hydroxyl value of 85 mgKOH / g.

Production Example 2: Production of a polymer containing a phosphate group (phosphate group value 55 mgKOH / g)
Into a 1 liter reaction vessel equipped with a stirrer, a temperature controller, and a cooling tube, 40 parts of ethoxypropanol was charged, 4 parts of styrene, 35.96 parts of n-butyl acrylate, 18.45 parts of ethylhexyl methacrylate, 2-hydroxy 40 parts of a solution obtained by dissolving 20 parts of Phosmer PP (Acid Phosphooxyhexa (oxypropylene) monomethacrylate) manufactured by Unichemical Co., Ltd. in 13.92 parts of ethyl methacrylate, 7.67 parts of methacrylic acid, and 20 parts of ethoxypropanol, and azobis After 121.7 parts of a monomer solution consisting of 1.7 parts of isobutyronitrile was added dropwise at 120 ° C. for 3 hours, stirring was further continued for 1 hour. The obtained resin was an acrylic varnish having an acid value of 105 mgKOH / g, of which phosphoric acid group value was 55 mgKOH / g, hydroxyl value of 60 mgKOH / g, and number average molecular weight of 6000, and its nonvolatile content was 63%.

In the examples of the present specification, the number average molecular weight is measured using “HLC8220GPC” (trade name, manufactured by Tosoh Corporation) as a GPC apparatus, “Shodex KF-606M”, “Shodex KF-603” (both as columns) The test was performed under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 0.6 cc / min, detector: RI.
In the examples of the present specification, the acid value of the phosphate group-containing polymer and the calculation of the phosphate group value are determined by neutralizing the free acid in 1 g of the sample (nonvolatile) defined in JIS K5601 2-1. And calculated based on the number of mg of potassium hydroxide (KOH) required for the above. The calculation of the hydroxyl value is based on the definition of the hydroxyl value of JIS K0070 (the number of mg of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group when 1 g of sample is acetylated). I went and asked.

Production Example 3 Production of Oil Slurry As an aluminum pigment, aluminum paste MH-8801 (aluminum flat pigment, manufactured by Asahi Kasei Chemicals Corporation, aluminum content 65%) 22 parts and butyl cellosolve 50 parts were stirred to obtain an oil slurry.

Production example 4: Production of oil slurry Aluminum paste MH-8801 (aluminum flat pigment, manufactured by Asahi Kasei Chemicals, aluminum content 65%) 22 parts, phosphate group-containing acrylic resin of Production Example 2 5 parts, lauryl 0.4 parts of acid phosphate and 50 parts of butyl cellosolve were stirred to obtain an oil slurry.

Comparative Production Example 1: Production of oil slurry containing water-soluble gas-suppressing inorganic compound To the oil slurry of Production Example 4, 1.5% by mass of cerium chloride is added to the amount of aluminum contained in the aluminum paste and stirred. An oil slurry containing a water-soluble gas-suppressing inorganic compound was obtained.

Comparative production example 2: Production of oil slurry using molybdate-treated aluminum 22 parts aluminum paste MH-8801, 50 parts butyl cellosolve, ammonium molybdate 0.55 parts relative to the amount of aluminum contained in the aluminum paste, 5 parts of phosphoric acid-containing acrylic resin and 0.4 part of lauryl acid phosphate were stirred to obtain an oil slurry in which the aluminum surface was treated with molybdic acid. The oil slurry was used without purification such as filtration.

Example 1
Production of water-based paint composition: 130 parts of acrylic resin emulsion of Production Example 1, 1.8 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, Mitsui Cytec Co., Ltd., solid content 90%), Production Example No. 3 oil slurry 72 parts, Neugen EA-207D (Amphiphilic compound, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 4200, solid content 55%) 5.5 parts (3 parts in terms of solid content), water-soluble gas As an inhibitory inorganic compound, 8% by mass of cerium chloride (based on the amount of aluminum contained in the aluminum paste) is uniformly dispersed, diluted with deionized water, and the measured value of a B-type viscometer at a coating temperature of 20 ° C. and 60 rpm is 798 mPa -The water-based coating composition whose resin solid content concentration is 33 mass% was obtained.

The coating viscosity of the aqueous coating composition was measured at 60 rpm and a coating temperature of 20 ° C. using a B-type viscometer (single cylindrical rotary viscometer) of model TVB10 manufactured by Toki Sangyo Co., Ltd.
Moreover, the resin solid content concentration of the aqueous coating composition described in the table was determined by calculating from the respective components used for the production of the aqueous coating composition and the amount of deionized water used for dilution.
The solid content concentration of the water-based paint composition described in the table was also calculated and calculated from the components used for the production of the water-based paint composition and the amount of deionized water used for dilution.

Example 2
An aqueous coating composition was prepared in the same manner as in Example 1 except that potassium molybdate was used as the water-soluble gas-suppressing inorganic compound.

Example 3
An aqueous coating composition was prepared in the same manner as in Example 1 except that sodium tungstate was used as the water-soluble gas-suppressing inorganic compound.

Example 4
An aqueous coating composition was prepared in the same manner as in Example 1 except that ammonium selenate was used as the water-soluble gas-suppressing inorganic compound.

Example 5
An aqueous coating composition was prepared in the same manner as in Example 1 except that potassium selenate was used as the water-soluble gas-suppressing inorganic compound.

Example 6
An aqueous coating composition was prepared in the same manner as in Example 1 except that cerium selenide was used as the water-soluble gas-suppressing inorganic compound.

Example 7
70. 130 parts of the acrylic resin emulsion of Production Example 1, 1.8 parts of dimethylaminoethanol, 40 parts of Cymel 327 (mixed alkylated melamine resin, Mitsui Cytec Co., Ltd., solid content 90%), oil slurry of Production Example 4 4 parts, Neugen EA-207D (amphiphilic compound, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 4200, solid content 55%) 5.5 parts (3 parts in terms of solid content), water-soluble gas-suppressing inorganic compound 0.4% by mass of cerium chloride (based on the active ingredient of the aluminum paste) is uniformly dispersed, diluted with deionized water, and the measured value of a B-type viscometer at a coating temperature of 20 ° C. and 60 rpm is 799 mPa · s, resin An aqueous coating composition having a solid content concentration of 33% by mass was obtained.

Example 8
An aqueous coating composition was prepared in the same manner as in Example 7 except that the amount of cerium chloride was changed to 1.5% by mass with respect to the active ingredient of the aluminum paste.

Example 9
An aqueous coating composition was prepared in the same manner as in Example 7 except that the amount of cerium chloride was changed to 8% by mass with respect to the active ingredient of the aluminum paste.

Example 10
An aqueous coating composition was prepared in the same manner as in Example 7 except that the amount of cerium chloride was changed to 15% by mass with respect to the active ingredient of the aluminum paste.

Example 11
An aqueous coating composition was prepared in the same manner as in Example 9 except that potassium molybdate was used as the water-soluble gas-suppressing inorganic compound.

Example 12
An aqueous coating composition was prepared in the same manner as in Example 9 except that sodium tungstate was used as the water-soluble gas-suppressing inorganic compound.

Example 13
An aqueous coating composition was prepared in the same manner as in Example 9 except that ammonium selenate was used as the water-soluble gas-suppressing inorganic compound.

Example 14
An aqueous coating composition was prepared in the same manner as in Example 9 except that potassium selenate was used as the water-soluble gas-suppressing inorganic compound.

Example 15
An aqueous coating composition was prepared in the same manner as in Example 9 except that cerium selenide was used as the water-soluble gas-suppressing inorganic compound.

Example 16
An aqueous coating composition was prepared in the same manner as in Example 8 except that 8% by mass of SN thickener N-1 (manufactured by San Nopco, viscoelasticity modifier, active ingredient 25%) was added to the resin solid content. .

Comparative Example 1
An aqueous coating composition was prepared in the same manner as in Example 1 except that the water-soluble gas-suppressing inorganic compound was not used.

Comparative Example 2
An aqueous coating composition was prepared in the same manner as in Example 7 except that the water-soluble gas-suppressing inorganic compound was not used.

Comparative Example 3
An aqueous coating composition was prepared in the same manner as in Example 8 except that the oil slurry of Comparative Production Example 1 was used.

Comparative Example 4
An aqueous coating composition was prepared in the same manner as in Example 8 except that the oil slurry of Comparative Production Example 2 was used.

Judgment whether the gas suppression inorganic compound used in the said Example and comparative example is water-soluble was performed in the following procedures.
To a 200 ml beaker, 100 g of water and 1 g of a gas-suppressing inorganic compound were added, stirred at 20 ° C. for 1 hour with a stirrer, and visually confirmed whether or not it dissolved. Under these conditions, when the gas-suppressing inorganic compound was dissolved, the solubility at 20 ° C. was 10 g / L or more, and it was judged to be a water-soluble gas-suppressing inorganic compound.
All of the gas-suppressing inorganic compounds used in the above Examples and Comparative Examples were water-soluble gas-suppressing inorganic compounds having a solubility at 20 ° C. of 10 g / L or more.

  The following evaluation was performed with respect to the aqueous coating composition obtained by the said Example and comparative example. The evaluation results are shown in Table 1.

（９）上記式によって算出したガス発生量について、下記基準に基づき評価した。

◎：５０ｍｌ／ｋｇ未満
○：５０〜８０ｍｌ／ｋｇ
△：８０〜１００ｍｌ／ｋｇ
×：１００ｍｌ／ｋｇ以上 Evaluation of gas generation amount The aqueous coating compositions obtained in the above Examples and Comparative Examples were subjected to an acceleration test in the following manner to measure the gas generation amount.
(1) In this evaluation experiment, as the aqueous coating composition diluted with deionized water in each Example and Comparative Example, the coating composition immediately after dilution with deionized water (within 3 hours after dilution with deionized water) A coating composition) was used.
(2) A tube having a length of 24 cm and an inner diameter of 0.4 cm was connected to a cork having a hole. At this time, it was sealed tightly so that air could not escape from between the cork hole and the tube.
(3) The coating composition was filled in a test tube having a volume of 18 cm ³ so that the gap in the test tube was about 5 mm, and the cork with a tube prepared in (2) was attached to the test tube.
(4) a portion of the coating composition from the test tube it is confirmed that has moved into the tube, as can be seen the position of the liquid surface, mark the tube, the position was d _0.
(5) The obtained test tube was fixed upside down using a test tube stand.
(6) The test tube fixed with the test tube stand was held in an incubator set at 50 ° C. for 72 hours.
(7) After the hold, then left at room temperature for 1 hour, checking the position of the coating composition in the tube, as can be seen the position of the liquid surface, mark the tube, the position was d _f.
(8) The gas generation amount (ΔV) per unit weight of the coating composition was calculated by the following formula.

(9) The gas generation amount calculated by the above formula was evaluated based on the following criteria.

A: Less than 50 ml / kg B: 50-80 ml / kg
Δ: 80-100 ml / kg
X: 100 ml / kg or more

Flip-flop evaluation (FF characteristics)
Double-layer coating formation Zinc phosphate treated thickness 0.8mm, length 30cm, width 40cm dull steel plate, cationic electrodeposition paint "Power Top U-50" (manufactured by Nippon Paint Co., Ltd.), dry film thickness 20μm In the coating plate that was electrodeposited so as to be baked at 160 ° C. for 30 minutes, a gray intermediate coating paint “Olga OP-30 previously diluted in 25 seconds (using a No. 4 Ford cup and measured at 20 ° C.) was used. (Polyester / melamine paint manufactured by Nippon Paint Co., Ltd.) was air sprayed using an air spray gun W-101-132G manufactured by ANEST IWATA to a dry film thickness of 35 μm, and baked at 140 ° C. for 30 minutes.
After cooling, the aqueous coating composition prepared according to the example or the comparative example was air spray-coated so as to have a dry film thickness of 15 μm under conditions of room temperature of 23 ° C. and humidity of 68%. After setting for 4 minutes, preheating was performed at 80 ° C. for 5 minutes.
After preheating, the coated plate was allowed to cool to room temperature, and it was coated with Macflow-O-1810 (solvent type clear paint manufactured by Nippon Paint Co., Ltd.) as a clear paint and air sprayed to a dry film thickness of 35 μm and set for 7 minutes. Next, the coated plate was baked at 140 ° C. for 30 minutes with a dryer to obtain a coated test plate having a multilayer coating film.

Measurement of FF value The FF value measured using a laser-type metallic feeling measuring device (trade name: Alcorp LMR-200, manufactured by Kansai Paint Co., Ltd.) was used as an index of flip-flop properties. It shows that flip-flop property is so strong that FF value is large. The flip-flop evaluation is 1.41 or more according to the following criteria.
○: Flip-flop value 1.51 or more Δ: Flip-flop value 1.41 or more and less than 1.51 ×: Flip-flop value less than 1.41

  In the present invention, "strong flip-flop" means that the metallic coating film is visually observed, white from the front direction (perpendicular to the coating surface), and excellent in glitter as glitter, From the diagonal direction, there is little glitter and the hue is clearly visible, which means that the brightness difference between the two is large. That is, a metallic coating film whose metallic feeling changes remarkably depending on the viewing angle is referred to as “strong flip-flop” and has excellent design.

It was confirmed that all of the water-based paint compositions of the examples had a small amount of gas generation, and the obtained multilayer coating film had high FF properties and excellent luster.
In addition, all the aqueous coating compositions of Examples 1 to 15 are so-called high solids coating compositions in which the solids concentration of the coating exceeds 40%. And even if these water-based coating compositions of Examples 1 to 15 are all high solid content coating compositions, they have good FF properties and excellent glitter feeling, and the generation of gas was well suppressed. It was confirmed. In particular, in Examples 7 to 15 including the phosphoric acid group-containing organic compound, it was confirmed that the FF property was particularly excellent.
The aqueous coating composition of Example 16 has a solid content concentration of about 23%, and has a solid content concentration generally used in an aqueous base coating composition. Also in this case, it was confirmed that the FF property was high and the glitter was excellent.
The aqueous coating compositions of Comparative Examples 1 and 2 are both coating compositions that do not contain a water-soluble gas-suppressing inorganic compound. In the examples using these coating compositions, gas generation occurred.
The aqueous coating compositions of Comparative Examples 3 and 4 are aqueous coating compositions prepared by preparing in advance an aluminum paste containing a scaly aluminum pigment and a water-soluble gas-suppressing inorganic compound. In all the examples using these coating compositions, the FF property was lowered and the glitter was inferior. Further, in these examples, yellowing of the coating film was confirmed.

  The water-based paint composition of the present invention has excellent gas generation despite being a water-based paint composition containing a scaly aluminum pigment that has neither a metal film made of a metal other than aluminum nor an organic polymer film. An inhibitory effect has been achieved. According to the present invention, an aqueous coating composition having excellent storage stability can be prepared without separately performing a pigment stabilization treatment of a scaly aluminum pigment. Therefore, the environmental load etc. accompanying a pigment stabilization process process can be reduced, and the aqueous coating composition containing a scaly aluminum pigment can be provided more cheaply.

Claims (10)

An aqueous coating composition comprising a coating film-forming resin, a curing agent, a scaly aluminum pigment, and a water-soluble gas-suppressing inorganic compound,
The scaly aluminum pigment has neither a metal film made of a metal other than aluminum nor an organic polymer film,
The water-soluble gas inhibiting inorganic compound, solubility 20 ° C. water an der Ru inorganic compound 10 g / L or more,
The water-soluble gas inhibiting inorganic compound, potassium selenate, cerium chloride, potassium molybdate, one or more der selected from the group consisting of selenium ammonium and selenide cerium is, and the aqueous coating composition , Prepared by mixing an aluminum paste containing scaly aluminum pigment, a film-forming resin, a curing agent, and a water-soluble gas-suppressing inorganic compound,
Water-based paint composition. The scaly aluminum pigment is one or more selected from the group consisting of hydrocarbons having 7 to 20 carbon atoms, saturated fatty acids having 12 to 20 carbon atoms, unsaturated fatty acids having 12 to 20 carbon atoms, and derivatives of the fatty acids. is a pigment coated by the above, claim 1 aqueous coating composition. The water-based coating composition according to claim 1 or 2 , wherein the content of the water-soluble gas-suppressing inorganic compound is 0.01 to 20% by mass with respect to the scaly aluminum pigment. Furthermore, the water-based coating composition in any one of Claims 1-3 containing a phosphoric acid group containing organic compound. The phosphoric acid group-containing organic compound, alkyl phosphate esters and / or phosphoric acid group number having an alkyl group of 4 to 30 carbon atoms include a phosphate group-containing polymer is a 5～300MgKOH / g, according to claim 4, wherein Water-based paint composition. A method for producing an aqueous coating composition, comprising mixing an aluminum paste containing a scaly aluminum pigment, a coating film-forming resin, a curing agent, and a water-soluble gas-suppressing inorganic compound,
The production method is a method of producing an aqueous coating composition without previously mixing the water-soluble gas-suppressing inorganic compound and the scaly aluminum pigment,
The water-soluble gas-suppressing inorganic compound is one or more selected from the group consisting of potassium selenate, cerium chloride, potassium molybdate, sodium tungstate, ammonium selenate and cerium selenide,
The scaly aluminum pigment has neither a metal film made of a metal other than aluminum nor an organic polymer film,
The water-soluble gas-suppressing inorganic compound has a solubility in water at 20 ° C. of 10 g / L or more.
A method for producing an aqueous coating composition. A method for producing an aqueous coating composition, comprising mixing an aluminum paste containing a scaly aluminum pigment and a phosphate group-containing organic compound, a coating film-forming resin, a curing agent, and a water-soluble gas-suppressing inorganic compound,
The production method is a method of producing an aqueous coating composition without previously mixing the water-soluble gas-suppressing inorganic compound and the scaly aluminum pigment,
The water-soluble gas-suppressing inorganic compound is one or more selected from the group consisting of potassium selenate, cerium chloride, potassium molybdate, sodium tungstate, ammonium selenate and cerium selenide,
The scaly aluminum pigment has neither a metal film made of a metal other than aluminum nor an organic polymer film,
The water-soluble gas-suppressing inorganic compound has a solubility in water at 20 ° C. of 10 g / L or more.
A method for producing an aqueous coating composition. The phosphoric acid group-containing organic compound, alkyl phosphate esters and / or phosphoric acid group number having an alkyl group of 4 to 30 carbon atoms include a phosphate group-containing polymer is a 5～300MgKOH / g, according to claim 7, wherein A method for producing an aqueous coating composition. The scaly aluminum pigment is one or more selected from the group consisting of hydrocarbons having 7 to 20 carbon atoms, saturated fatty acids having 12 to 20 carbon atoms, unsaturated fatty acids having 12 to 20 carbon atoms, and derivatives of the fatty acids. The method for producing an aqueous coating composition according to any one of claims 6 to 8 , which is a pigment coated as described above. The method for producing an aqueous coating composition according to any one of claims 6 to 9 , wherein the content of the water-soluble gas-suppressing inorganic compound is 0.01 to 20% by mass with respect to the scaly aluminum pigment.