JP6693705B2 - Method for producing aqueous resin dispersion - Google Patents

Description

  The present invention relates to a method for producing an aqueous resin dispersion. More specifically, the present invention relates to a method for producing an aqueous resin dispersion useful for applications such as paints and coating agents.

  In recent years, in order to avoid environmental problems such as the release of volatile organic compounds into the atmosphere, water-based paints using water-dispersible resins such as water-soluble aqueous resin dispersions have been used instead of solvent-based paints. There is. However, the water-based paint generally has a technical problem that it is inferior in water resistance and weather resistance as compared with the organic solvent-based paint because it uses water as a solvent. As an aqueous coating composition having excellent weather resistance and water resistance, there has been proposed an aqueous coating composition in which a multilayer structure particle having a core portion and a shell portion made of an acrylic polymer having a specific glass transition temperature is dispersed in water. (See, for example, Patent Document 1).

  However, although the water-based coating composition has a certain degree of weather resistance and water resistance, in recent years it is not only excellent in weather resistance and water resistance, but even when a coating film is formed in the vertical direction. Development of a method for producing an aqueous resin dispersion that forms a coating film excellent in the property of preventing the coating film from flowing down (hereinafter referred to as warm water whitening resistance) has been awaited.

  Weather resistance, water resistance, as a method for producing an aqueous resin dispersion that forms a coating film that is also excellent in hot water whitening resistance, a single amount used as a raw material for a polymer that constitutes emulsion particles contained in the aqueous resin dispersion. A method for producing an aqueous resin dispersion has been proposed in which the content of the acid group-containing monomer in the body component is 0.3% by mass or less (for example, see Patent Document 2).

  According to the method for producing an aqueous resin dispersion, it is possible to form a coating film having excellent weather resistance, water resistance, and warm water whitening resistance. However, in recent years, development of a method for producing an aqueous resin dispersion capable of forming a coating film excellent in warm water whitening resistance and weather resistance and capable of coating a thick film has been desired.

JP, 2002-138123, A JP, 2014-031456, A

  The present invention has been made in view of the above-mentioned prior art, and provides a method for producing an aqueous resin dispersion capable of forming a coating film excellent in warm water whitening resistance and weather resistance and coating a thick film. This is an issue.

The present invention is
(1) A method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles, wherein the content of the acid group-containing monomer as a monomer component used as a raw material for the emulsion particles is 0.3 mass. %, The pH is 1 to 5 using 55 to 85% by mass of the total amount of the monomer components used in the emulsion polymerization when the monomer components of less than or equal to 10% are subjected to multistage emulsion polymerization. after row Tsu name emulsion polymerization using the monomer component containing an alkyl (meth) acrylate and styrene monomer as the monomer component emulsion polymerization in the row of Utoki in a medium, the remaining single When the emulsion polymerization is carried out using the monomer component, the emulsion polymerization is carried out by using the monomer component containing the piperidyl group-containing monomer as the monomer component to carry out the emulsion polymerization of the remaining monomer components. After adjusting the pH to 6-10 A method for producing a characteristic aqueous resin dispersion, and (2) the amount of a monomer component used in emulsion polymerization in a medium having a pH of 1 to 5 is 60 to 80 out of all the monomer components. The mass% relates to the method for producing the aqueous resin dispersion according to claim 1.

  According to the method for producing an aqueous resin dispersion of the present invention, it is possible to obtain an aqueous resin dispersion capable of forming a coating film excellent in warm water whitening resistance and weather resistance and coating a thick film.

  The method for producing an aqueous resin dispersion of the present invention is, as described above, a method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles, and an acid as a monomer component used as a raw material of the emulsion particles. Using a monomer component having a content of the group-containing monomer of 0.3% by mass or less, the pH of 45 to 85% by mass of the total monomer components used for emulsion polymerization is It is characterized by adjusting the pH after the emulsion polymerization in a medium of 1 to 5 and the emulsion polymerization of the remaining monomer components to 6 to 10.

  According to the present invention, since the content of the acid group-containing monomer in the monomer component used as the raw material of the emulsion particles is 0.3% by mass or less, a coating film excellent in warm water whitening resistance and weather resistance Can be formed.

  Further, in the present invention, when the emulsion polymerization of the monomer components is carried out in multiple stages, 45 to 85 mass% of the monomer components used in the emulsion polymerization have a pH of 1 to 5 in the total amount of the monomer components. Since the operation of adjusting the pH after emulsion-polymerizing the remaining monomer components to 6 to 10 in a certain medium is adopted, it is excellent in warm water whitening resistance and weather resistance. It is possible to form a coating film and obtain an aqueous resin dispersion capable of coating a thick film.

  The content of the acid group-containing monomer in the monomer component is 0.3 mass% or less, preferably 0.2 mass% or less, and more preferably 0.1 mass% from the viewpoint of improving hot water whitening resistance. It is below.

  Examples of the acid group-containing monomer include (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, maleic anhydride, maleic acid monomethyl ester, maleic acid monobutyl ester, and itaconic acid monomethyl ester. Examples include carboxyl group-containing aliphatic monomers such as esters, monobutyl itaconic acid, and vinylbenzoic acid, but the present invention is not limited to these examples. These acid group-containing monomers may be used alone or in combination of two or more kinds. Among these acid group-containing monomers, acrylic acid, methacrylic acid and itaconic acid are preferable, and acrylic acid and methacrylic acid are more preferable, from the viewpoint of improving the dispersion stability of emulsion particles.

  The emulsion particles are composed of multiple layers. The number of layers of the emulsion particles is preferably 2 to 5 layers, more preferably 2 to 5 layers, from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance and obtaining an aqueous resin dispersion capable of coating a thick film. It is preferably 2 to 4 layers, more preferably 2 or 3 layers.

  The monomer component includes a monofunctional monomer and a polyfunctional monomer, and any of these can be used in the present invention. The monofunctional monomer and the polyfunctional monomer may be used alone or in combination.

  Examples of the monofunctional monomer include an ethylenically unsaturated double bond-containing monomer and the like, but the present invention is not limited to such examples. These monomers may be used alone or in combination of two or more kinds.

  In addition, in this specification, "(meth) acrylate" means "acrylate" or "methacrylate", and "(meth) acryl" means "acryl" or "methacryl."

  As the ethylenically unsaturated double bond-containing monomer, for example, alkyl (meth) acrylate, hydroxyl group-containing (meth) acrylate, piperidyl group-containing monomer, oxo group-containing monomer, fluorine atom-containing monomer, Nitrogen atom-containing monomer, epoxy group-containing monomer, alkoxyalkyl (meth) acrylate, silane group-containing monomer, carbonyl group-containing monomer, aziridinyl group-containing monomer, styrene-based monomer, aralkyl ( Examples thereof include, but are not limited to, such examples. These ethylenically unsaturated double bond-containing monomers may be used alone or in combination of two or more.

  Examples of alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, sec-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, tridecyl (meth) acrylate, cyclohexyl (meth) acrylate, n-lauryl (meth) Examples of the acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, alkyl (meth) acrylate having an ester group having 1 to 18 carbon atoms, and the like, the present invention, It is not limited only to hunt illustration. These monomers may be used alone or in combination of two or more kinds.

  Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxy. Examples thereof include hydroxyl group-containing (meth) acrylates having an ester group having 1 to 18 carbon atoms such as butyl (meth) acrylate, but the present invention is not limited to these examples. These hydroxyl group-containing (meth) acrylates may be used alone or in combination of two or more.

  Examples of the piperidyl group-containing monomer include 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine and 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine. , 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyl-1-methoxy-2,2,6,6-tetramethylpiperidine, 4-cyano- 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-croto Noylamino-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4- Ano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano -4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine and the like can be mentioned. Are not limited to such examples. These monomers may be used alone or in combination of two or more kinds.

  Examples of the oxo group-containing monomer include (di) ethylene glycol (methoxy) (meth), such as ethylene glycol (meth) acrylate, ethylene glycol methoxy (meth) acrylate, diethylene glycol (meth) acrylate, and diethylene glycol methoxy (meth) acrylate. ) Acrylate, etc., but the present invention is not limited to such examples. These oxo group-containing monomers may be used alone or in combination of two or more kinds.

  Examples of the fluorine atom-containing monomer include fluorine atom-containing alkyl having an ester group of 2 to 6 carbon atoms such as trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate and octafluoropentyl (meth) acrylate. Examples thereof include (meth) acrylate, but the present invention is not limited to such examples. These fluorine atom-containing monomers may be used alone or in combination of two or more.

  Examples of the nitrogen atom-containing monomer include (meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, Nn-propyl (meth). Acrylamide, N-isopropyl (meth) acrylamide, methylenebis (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropylacrylamide, Acrylamide compounds such as diacetone acrylamide, dimethylaminoethyl (meth) acrylate, nitrogen atom-containing (meth) acrylate compounds such as diethylaminoethyl (meth) acrylate, N-vinylpyrrolidone, ( Data) but and acrylonitrile, the present invention is not limited only to those exemplified. These nitrogen atom-containing monomers may be used alone or in combination of two or more.

  Examples of the epoxy group-containing monomer include epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate, α-methylglycidyl (meth) acrylate, and glycidyl allyl ether, but the present invention includes such examples. It is not limited to only. These epoxy group-containing monomers may be used alone or in combination of two or more kinds.

  Examples of the alkoxyalkyl (meth) acrylate include methoxyethyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxybutyl (meth) acrylate, and trimethylolpropane tripropoxy (meth) acrylate. However, the present invention is not limited to such an example. These alkoxyalkyl (meth) acrylates may be used alone or in combination of two or more.

  Examples of the silane group-containing monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, 2-styrylethyltrimethoxysilane, vinyltrimethoxysilane. Examples thereof include chlorosilane, γ- (meth) acryloyloxypropylhydroxysilane, and γ- (meth) acryloyloxypropylmethylhydroxysilane, but the present invention is not limited to these examples. These silane group-containing monomers may be used alone or in combination of two or more.

  Examples of the carbonyl group-containing monomer include acrolein, horomyl styrene, vinyl ethyl ketone, (meth) acryloxyalkylpropenal, acetonyl (meth) acrylate, diacetone (meth) acrylate, 2-hydroxypropyl (meth) acrylate. Acetyl acetate, butanediol-1,4-acrylate acetyl acetate, 2- (acetoacetoxy) ethyl (meth) acrylate and the like can be mentioned, but the present invention is not limited to these examples. These carbonyl group-containing monomers may be used alone or in combination of two or more kinds.

  Examples of the aziridinyl group-containing monomer include (meth) acryloylaziridine and 2-aziridinylethyl (meth) acrylate, but the present invention is not limited thereto. These aziridinyl group-containing monomers may be used alone or in combination of two or more kinds.

  Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, tert-methylstyrene, chlorostyrene, and vinyltoluene, but the present invention is limited to these examples. is not. These monomers may be used alone or in combination of two or more kinds. Styrene-based monomers have functional groups such as alkyl groups such as methyl group and tert-butyl group, nitro group, nitrile group, alkoxyl group, acyl group, sulfone group, hydroxyl group and halogen atom in the benzene ring. May be. Among the styrene-based monomers, styrene is preferable from the viewpoint of enhancing the weather resistance of the coating film.

  Examples of the aralkyl (meth) acrylate include aralkyl having an aralkyl group having 7 to 18 carbon atoms such as benzyl (meth) acrylate, phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, and naphthylmethyl (meth) acrylate. Examples thereof include (meth) acrylate, but the present invention is not limited to such examples. These aralkyl (meth) acrylates may be used alone or in combination of two or more kinds.

  Examples of suitable monofunctional monomers include alkyl (meth) acrylates, hydroxyl group-containing (meth) acrylates, piperidyl group-containing monomers, oxo group-containing monomers, fluorine atom-containing monomers, and nitrogen atom-containing monofunctional monomers. Examples thereof include a monomer, an epoxy group-containing monomer, and a styrene-based monomer. These monomers may be used alone or in combination of two or more kinds.

  Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, ethylene oxide-modified 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, propylene oxide-modified neopentyl glycol di (meth) acrylate, Di (meth) acrylate of polyhydric alcohol having 1 to 10 carbon atoms such as tripropylene glycol di (meth) acrylate; polyethylene glycol di (meth) acrylate having 2 to 50 moles of ethylene oxide added, and number of moles of propylene oxide added Is 2 Alkyl di (meth) acrylate having 2 to 50 added moles of an alkylene oxide group having 2 to 4 carbon atoms, such as 50 polypropylene glycol di (meth) acrylate and tripropylene glycol di (meth) acrylate; ethoxylated glycerin tri ( (Meth) acrylate, propylene oxide-modified glycerol tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol monohydroxytri (meth) acrylate, trimethylolpropane triethoxytri Tri (meth) acrylate of polyhydric alcohol having 1 to 10 carbon atoms such as (meth) acrylate; pentaerythritol tetra (meth) acrylate, dipentaery Tetra (meth) acrylates of polyhydric alcohols having 1 to 10 carbon atoms such as litol tetra (meth) acrylate and ditrimethylolpropane tetra (meth) acrylate; pentaerythritol penta (meth) acrylate, dipentaerythritol (monohydroxy) penta (meth ) Penta (meth) acrylate of polyhydric alcohol having 1 to 10 carbon atoms such as acrylate; Hexa (meth) acrylate of polyhydric alcohol having 1 to 10 carbon atoms such as pentaerythritol hexa (meth) acrylate; Bisphenol A di (meth) ) Epoxy group-containing (meth) acrylates such as acrylates, 2- (2′-vinyloxyethoxyethyl) (meth) acrylates, and epoxy (meth) acrylates; polyfunctional (meth) acrylates such as urethane (meth) acrylates Examples thereof include acrylate and the like, but the present invention is not limited to such examples. These polyfunctional monomers may be used alone or in combination of two or more.

  Among the polyfunctional monomers, from the viewpoint of achieving both coating hardness and film-forming property, the number of moles of addition of the alkyldi (meth) acrylate having 2 to 8 carbon atoms of the alkyl group having 4 to 8 carbon atoms and ethylene oxide is Polyethylene glycol di (meth) acrylate having 2 to 50, polypropylene glycol di (meth) acrylate having 2 to 50 moles of propylene oxide added, tri (meth) acrylate of polyhydric alcohol, tetra (meth) acrylate of polyhydric alcohol Penta (meth) acrylate of polyhydric alcohol and hexa (meth) acrylate of polyhydric alcohol are preferable, and ethylene glycol di (meth) acrylate and polyethylene glycol di (meth) acrylate in which the addition mole number of ethylene oxide is 2 to 50, 1 , 4-butanediol di (meth) Acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, and ditrimethylolpropane tetra (meth) acrylate are more preferred.

  Further, in the present invention, from the viewpoint of imparting ultraviolet absorption to the emulsion particles, an ultraviolet absorbing monomer may be contained in the monomer component within a range that does not impair the object of the present invention.

  Examples of the UV absorbing monomer include benzotriazole-based UV absorbing monomer and benzophenone-based UV absorbing monomer, but the present invention is not limited to these examples. These monomers may be used alone or in combination of two or more kinds.

  Examples of the benzotriazole-based ultraviolet absorbing monomer include 2- [2'-hydroxy-5 '-(meth) acryloyloxymethylphenyl] -2H-benzotriazole and 2- [2'-hydroxy-5'-. (Meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(meth) acryloyloxymethylphenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'. -Hydroxy-5 '-(meth) acryloylaminomethyl-5'-tert-octylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(meth) acryloyloxypropylphenyl] -2H-benzo Triazole, 2- [2'-hydroxy-5 '-(meth) acryloyloxyhexoxy Luphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5 '-(meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'. -Tert-butyl-5 '-(meth) acryloyloxyethylphenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-5'-tert-butyl-3'-(meth) acryloyloxyethyl Phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(meth) acryloyloxyethylphenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-5'-(meth ) Acryloyloxyethylphenyl] -5-cyano-2H-benzotriazole, 2- [2'-hydr Xy-5 '-(meth) acryloyloxyethylphenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'-hydroxy-5'-(β- (meth) acryloyloxyethoxy) -3'- Examples thereof include tert-butylphenyl] -4-tert-butyl-2H-benzotriazole, but the present invention is not limited to such examples. These benzotriazole-based UV absorbing monomers may be used alone or in combination of two or more kinds.

  Examples of the benzophenone-based UV absorbing monomer include 2-hydroxy-4- (meth) acryloyloxybenzophenone, 2-hydroxy-4- [2-hydroxy-3- (meth) acryloyloxy] propoxybenzophenone, and 2-hydroxy-4- [2-hydroxy-3- (meth) acryloyloxy] propoxybenzophenone. Hydroxy-4- [2- (meth) acryloyloxy] ethoxybenzophenone, 2-hydroxy-4- [3- (meth) acryloyloxy-2-hydroxypropoxy] benzophenone, 2-hydroxy-3-tert-butyl-4- Examples include [2- (meth) acryloyloxy] butoxybenzophenone, but the present invention is not limited to these examples. These benzophenone-based UV absorbing monomers may be used alone or in combination of two or more kinds.

  After the specific composition of the monomer component is obtained by emulsion polymerization of 45 to 85% by mass of the total monomer components used in the emulsion polymerization in a medium having a pH of 1 to 5. The pH after emulsion-polymerizing the remaining monomer components may be adjusted to 6 to 10 and is not particularly limited. Among the monomer components, from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance and obtaining an aqueous resin dispersion capable of coating a thick film, an alkyl (meth) acrylate, a hydroxyl group-containing ( (Meth) acrylate, a styrene-based monomer and a piperidyl group-containing monomer are preferable, and an alkyl (meth) acrylate, a styrene-based monomer and a piperidyl group-containing monomer are more preferable. In order to make the pH of the second and subsequent emulsion polymerizations higher than the pH of the medium after the first emulsion polymerization, for example, the monomer during the first emulsion polymerization is used. Using an alkyl (meth) acrylate as a component and a styrene-based monomer as necessary, and using an alkyl (meth) acrylate, and if necessary, a styrene-based monomer and a piperidyl group-containing monomer during the second and subsequent emulsion polymerizations. be able to.

  As a method of emulsion-polymerizing the monomer component, for example, an aqueous medium containing a water-soluble organic solvent such as a lower alcohol such as methanol and water, an emulsifier is dissolved in a medium such as water, the monomer under stirring. Examples include a method of dropping a component and a polymerization initiator, a method of dropping a monomer component previously emulsified with an emulsifier and water into water or an aqueous medium, but the present invention is limited to such a method. It is not limited. The amount of the medium may be appropriately set in consideration of the amount of non-volatile components contained in the obtained aqueous resin dispersion. The medium may be charged in the reaction vessel in advance, or may be used as a pre-emulsion. In addition, the medium may be used when an aqueous resin dispersion is produced by emulsion-polymerizing a monomer component, if necessary.

  When emulsion-polymerizing the monomer component, emulsion polymerization may be performed after mixing the monomer component, the emulsifier and the medium, emulsified by stirring the monomer component, the emulsifier and the medium, pre-emulsion After the preparation, the emulsion polymerization may be carried out, or the emulsion polymerization may be carried out by mixing at least one of the monomer component, the emulsifier and the medium and the remaining pre-emulsion. The monomer component, the emulsifier, and the medium may be added all at once, dividedly, or continuously added dropwise.

  Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, and polymeric emulsifiers. These emulsifiers may be used alone or in combination of two or more kinds.

  Examples of the anionic emulsifier include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate; alkyl sulfonate salts such as ammonium dodecyl sulfonate, sodium dodecyl sulfonate and sodium alkyl diphenyl ether disulfonate; ammonium dodecyl benzene sulfonate and sodium dodecyl naphthalene sulfonate. Alkylaryl sulfonate salts; polyoxyethylene alkyl sulfonate salts; polyoxyethylene alkyl sulphate salts; polyoxyethylene alkyl aryl sulphate salts; dialkyl sulfosuccinates; aryl sulfonic acid-formalin condensates; ammonium laurate, sodium stearate, etc. Fatty acid salt; bis ( Lioxyethylene polycyclic phenyl ether) methacrylate sulfonate salt, propenyl-alkyl sulfosuccinic acid ester salt, (meth) acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene phosphonate salt, allyloxymethylalkyloxypolyester Sulfuric acid ester having an allyl group such as oxyethylene sulfonate salt or its salt; sulfuric acid ester salt of allyloxymethylalkoxyethyl polyoxyethylene, polyoxyalkylene alkenyl ether sulfuric acid ammonium salt, etc., but the present invention is only such an example. It is not limited to.

  Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, condensate of polyethylene glycol and polypropylene glycol, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid monoglyceride, ethylene oxide and aliphatic Examples include condensation products with amines, allyloxymethylalkoxyethyl hydroxypolyoxyethylene, and polyoxyalkylene alkenyl ethers, but the present invention is not limited to these examples.

  Examples of the cationic emulsifier include alkylammonium salts such as dodecylammonium chloride, but the present invention is not limited to these examples.

  Examples of the amphoteric emulsifier include betaine ester-type emulsifiers, but the present invention is not limited to these examples.

  Examples of the polymeric emulsifier include poly (meth) acrylic acid salts such as sodium polyacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyhydroxyalkyl (meth) acrylates such as polyhydroxyethyl acrylate; Examples thereof include a copolymer having one or more of the monomers as a copolymerization component, but the present invention is not limited to such an example.

  As the emulsifier, an emulsifier having a polymerizable group, that is, a so-called reactive emulsifier is preferable from the viewpoint of improving weather resistance, and a non-nonylphenyl type emulsifier is preferable from the viewpoint of environmental protection.

  As the reactive emulsifier, for example, propenyl-alkyl sulfosuccinic acid ester salt, (meth) acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene phosphonate salt [eg, Sanyo Chemical Industry Co., Ltd., Trade name: Eleminol RS-30 etc.], polyoxyethylene alkylpropenyl phenyl ether sulfonate salt (for example, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon BC-10, Aqualon HS-10 etc.), allyloxymethylalkyl Sulfonate salt of oxypolyoxyethylene [for example, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon KH-10, etc.], Sulfonate salt of allyloxymethylnonylphenoxyethyl hydroxypolyoxyethylene [for example, manufactured by ADEKA Co., Ltd. , Product Name: Ade Rear soap SE-10 etc.], allyloxymethylalkoxyethyl hydroxypolyoxyethylene sulfate ester salt [for example, manufactured by ADEKA Co., Ltd., trade name: ADEKA rear soap SR-10, SR-30 etc.], bis (polyoxyethylene poly Ring phenyl ether) Methacrylated sulfonate salt (for example, manufactured by Nippon Emulsifier Co., Ltd., trade name: Antox MS-60 etc.), allyloxymethylalkoxyethyl hydroxypolyoxyethylene [for example, manufactured by ADEKA Co., Ltd., trade name: ADEKA REASOAP ER-20 etc.], polyoxyethylene alkylpropenyl phenyl ether [eg Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon RN-20 etc.], allyloxymethylnonylphenoxyethyl hydroxypolyoxyethylene [eg , Ltd.) ADEKA Corporation, trade name: Adeka such REASOAP NE-10) but the like, the present invention is not limited only to those exemplified.

  The amount of the emulsifier is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, further preferably 2 parts by weight or more, particularly preferably 100 parts by weight of the monomer component, from the viewpoint of improving the polymerization stability. Is 3 parts by weight or more, and from the viewpoint of improving weather resistance, it is preferably 10 parts by weight or less, more preferably 6 parts by weight or less, further preferably 5 parts by weight or less, and particularly preferably 4 parts by weight or less.

  Examples of the polymerization initiator include azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile), 2,2-azobis (2,4-dimethylvaleronitrile), 2,2-azobis ( Azo compounds such as 2-diaminopropane) hydrochloride, 4,4-azobis (4-cyanovaleric acid) and 2,2-azobis (2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; Examples thereof include hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and peroxides such as ammonium peroxide, but the present invention is not limited to these examples. These polymerization initiators may be used alone or in combination of two or more kinds.

  The amount of the polymerization initiator is preferably 0.05 parts by weight or more, and more preferably 0, from the viewpoint of increasing the polymerization rate and reducing the residual amount of the unreacted monomer component per 100 parts by weight of the monomer component. It is 1 part by weight or more, and preferably 1 part by weight or less, more preferably 0.5 parts by weight or less from the viewpoint of improving weather resistance.

  The method of adding the polymerization initiator is not particularly limited. Examples of the addition method include batch charging, divided charging, and continuous dropping. From the viewpoint of accelerating the termination time of the polymerization reaction, a part of the polymerization initiator may be added before or after the addition of the monomer component into the reaction system.

  When emulsion-polymerizing the monomer components in multiple stages, some or all of the acidic groups of the resulting polymer can be neutralized with a neutralizing agent. The neutralizing agent may be used after adding the monomer component in the final stage, for example, may be used between the first-stage polymerization reaction and the second-stage polymerization reaction, and the initial emulsification It may be used at the end of the polymerization reaction.

  Examples of the neutralizing agent include hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide; carbonates of alkali metals or alkaline earth metals such as sodium hydrogen carbonate and calcium carbonate; ammonia, monomethylamine and the like. Examples include alkaline substances such as organic amines, but the present invention is not limited to such examples.

  When emulsion-polymerizing the monomer components in multiple stages, a coating film excellent in warm water whitening resistance and weather resistance is formed, and from the viewpoint of obtaining an aqueous resin dispersion capable of coating a thick film, It is preferable to emulsion polymerize the monomer components in the absence of a solvating agent.

  In order to accelerate the decomposition of the polymerization initiator, for example, a reducing agent such as sodium hydrogen sulfite, a decomposition agent for the polymerization initiator such as a transition metal salt such as ferrous sulfate is added to the reaction system in an appropriate amount. Good.

  Further, a chain transfer agent can be used to adjust the weight average molecular weight of the polymer constituting the emulsion particles. Examples of the chain transfer agent include 2-ethylhexyl thioglycolate, tert-dodecyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, α-methylstyrene, α-methyl. Examples thereof include styrene dimer, but the present invention is not limited to such examples. These chain transfer agents may be used alone or in combination of two or more kinds. The amount of the chain transfer agent is preferably 0.01 to 10 parts by weight per 100 parts by weight of the monomer component from the viewpoint of adjusting the weight average molecular weight of the emulsion particles.

  Further, when emulsion-polymerizing the monomer component, an appropriate amount of a silane coupling agent may be used from the viewpoint of improving weather resistance. Examples of the silane coupling agent include, for example, a silane coupling agent having a polymerizable unsaturated bond such as a (meth) acryloyl group, a vinyl group, an allyl group, and a propenyl group, but the present invention is not limited thereto. It is not limited.

  If necessary, an additive such as a chelating agent, a film-forming auxiliary, and a pH buffer may be added to the reaction system. The amount of the additive cannot be unconditionally determined because it varies depending on its type, but is usually about 0.01 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the monomer component. It is about 3 parts by weight.

  The atmosphere for emulsion-polymerizing the monomer component is not particularly limited, but an inert gas such as nitrogen gas is preferable from the viewpoint of increasing the efficiency of the polymerization initiator.

  The polymerization temperature when emulsion-polymerizing the monomer component is not particularly limited, but is usually preferably 50 to 100 ° C, more preferably 60 to 95 ° C. The polymerization temperature may be constant or may be changed during the polymerization reaction.

  The polymerization time for emulsion-polymerizing the monomer component is not particularly limited and may be appropriately set depending on the progress of the polymerization reaction, but is usually about 2 to 9 hours.

  As a method of forming an outer layer on the emulsion particles contained in the aqueous resin dispersion obtained above, for example, by emulsion-polymerizing a monomer component in the same manner as above in the aqueous resin dispersion. , A method of forming an outer layer on the emulsion particles, and the like. Further, as a method of further forming an outer layer on the emulsion particles on which the outer layer is formed, for example, by emulsion-polymerizing a monomer component in an aqueous resin dispersion in the same manner as described above, on the emulsion particles. Furthermore, the method of forming an outer layer etc. are mentioned.

  In the present invention, when a water-based resin dispersion containing a plurality of layers of emulsion particles having a multilayer structure is prepared by such multistage emulsion polymerization, an acid is used as a monomer component used as a raw material for the emulsion particles. Using a monomer component having a content of the group-containing monomer of 0.3% by mass or less, the pH of 45 to 85% by mass of the total monomer components used for emulsion polymerization is One of the major characteristics is that the pH is adjusted to 6 to 10 after emulsion polymerization of the remaining monomer components after emulsion polymerization in a medium of 1 to 5. In the present invention, since this operation is adopted, it is possible to obtain a water-based resin dispersion capable of forming a coating film excellent in warm water whitening resistance and weather resistance and coating a thick film.

  In the present invention, in the first-stage emulsion polymerization, 45 to 85 mass% of all the monomer components are emulsion polymerized in a medium having a pH of 1 to 5. The amount of the monomer component used in the first-stage emulsion polymerization is from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance and obtaining an aqueous resin dispersion capable of coating a thick film. It is 45 to 85% by mass, preferably 50 to 80% by mass, and more preferably 55 to 75% by mass of the total monomer components. In addition, the pH of the medium in the emulsion polymerization of the first step is preferably from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance, and obtaining an aqueous resin dispersion capable of coating a thick film. Is 1 to 5, more preferably 2 to 4.

  After the completion of the first-stage emulsion polymerization, the second-stage and subsequent emulsion polymerizations are carried out. When the outer layer is formed on the emulsion particles obtained by the first-stage emulsion polymerization by the second-stage or subsequent emulsion polymerization, the polymerization reaction rate in the first-stage emulsion polymerization is 90% or more, preferably 95% or more. From the viewpoint of forming a layer separation structure in the emulsion particles, it is preferable to carry out emulsion polymerization of the monomer components constituting the outer layers of the second and subsequent stages after reaching the above.

  The monomer components used in the emulsion polymerization of the second and subsequent stages are the monomers not used in the first stage of all the monomer components used in the emulsion polymerization, that is, the remaining monomer components. Is. Therefore, during the second and subsequent emulsion polymerizations, 15 to 55 mass% of the total monomer components are emulsion polymerized in the medium. The amount of the monomer component used in the emulsion polymerization of the second and subsequent steps is from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance and obtaining an aqueous resin dispersion capable of coating a thick film. , 15 to 55% by mass, preferably 20 to 50% by mass, and more preferably 25 to 45% by mass of the total monomer components. Further, the pH of the medium in the emulsion polymerization of the second and subsequent steps is from the viewpoint of forming a coating film excellent in warm water whitening resistance and weather resistance, and obtaining an aqueous resin dispersion capable of coating a thick film, It is 6 to 10, preferably 7 to 9.

  The pH of the medium after emulsion-polymerizing the remaining monomer components not used in the first stage can be easily adjusted by adjusting the composition of the monomer components used in the emulsion polymerization in the second and subsequent stages. Can be adjusted.

  As a method for adjusting the pH to 6 to 10 after emulsion-polymerizing the monomer components in the first stage in a medium having a pH of 1 to 5 and then emulsion-polymerizing the remaining monomer components For example, a monomer component containing an alkyl (meth) acrylate and optionally a styrene-based monomer is used as a monomer component when carrying out the emulsion polymerization in the first stage, and used in the emulsion polymerization in the second stage and thereafter. As a monomer component to be used, a monomer component containing an alkyl (meth) acrylate, if necessary, a styrene-based monomer, and a nitrogen atom-containing (meth) acrylate and / or a piperidyl group-containing monomer can be used. Can be mentioned.

  Examples of the basic monomer include the above-mentioned nitrogen atom-containing (meth) acrylate and piperidyl group-containing monomer, but the present invention is not limited to these examples. The amount of the monomer exhibiting basicity is adjusted by adjusting the pH of the medium after carrying out the emulsion polymerization of the first step and emulsion-polymerizing the remaining monomer components to 6 to 10, preferably 7 to 9. It is preferably an amount required for When a monomer component containing a nitrogen atom-containing (meth) acrylate and / or a piperidyl group-containing monomer is used in the second or subsequent emulsion polymerization, the nitrogen atom-containing (meth) acrylate in the monomer component is used. And / or the content of the piperidyl group-containing monomer is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and further preferably 2 to 10% by mass from the viewpoint of improving weather resistance. is there.

  Examples of the monomer component used to form the outer layers of the second and subsequent stages can be the same as those used in the emulsion polymerization of the first stage. The emulsion polymerization method and the polymerization conditions for the second and subsequent steps may be the same as those for the emulsion polymerization for the first step.

  A layer made of another polymer may be formed between the inner layer and the outer layer of the emulsion particles, if necessary, as long as the object of the present invention is not impaired. Therefore, when producing the aqueous resin dispersion of the present invention, after forming the inner layer of the emulsion particles, before forming the outer layer, within the range where the purpose of the present invention is not impaired, if necessary, other weight An operation of forming a layer composed of coalesced may be included.

  Although an aqueous resin dispersion containing a plurality of layers of emulsion particles can be obtained as described above, the polymer constituting the emulsion particles forms a coating film excellent in warm water whitening resistance and weather resistance, From the viewpoint of obtaining an aqueous resin dispersion capable of coating a film, it is preferably a (meth) acrylic polymer obtained by emulsion-polymerizing the monomer components.

  The glass transition temperature of the polymer constituting the emulsion particles is preferably 50 ° C. or lower, more preferably 45 ° C. or lower, further preferably 40 ° C. or lower from the viewpoint of improving the film forming property, and improves the blocking resistance. From the viewpoint, the temperature is preferably −40 ° C. or higher, more preferably −25 ° C. or higher, further preferably −10 ° C. or higher. The glass transition temperature of the polymer can be easily adjusted by adjusting the composition of the monomer used as the monomer component.

In the present specification, the glass transition temperature of a polymer is calculated by using the glass transition temperature of a homopolymer of a monomer used as a monomer component constituting the polymer, and the formula:
1 / Tg = Σ (Wm / Tgm) / 100
[In the formula, Wm represents the content (% by weight) of the monomer m in the monomer components constituting the polymer, and Tgm represents the glass transition temperature (absolute temperature: K) of the homopolymer of the monomer m. ]
It means the temperature determined based on the Fox equation.

  The glass transition temperature of the polymer is, for example, 95 ° C. for an acrylic acid homopolymer, 130 ° C. for a methacrylic acid homopolymer, 105 ° C. for a methyl methacrylate homopolymer, 100 ° C. for a styrene homopolymer, and cyclohexyl. The homopolymer of methacrylate is 83 ° C., the homopolymer of n-butyl methacrylate is 20 ° C., the homopolymer of 2-ethylhexyl acrylate is −70 ° C., the homopolymer of n-butyl acrylate is −56 ° C., and 4-methacryloyl. The homopolymer of oxy-1,2,2,6,6-pentamethylpiperidine is 130 ° C, and the homopolymer of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine is 130 ° C.

  The glass transition temperature of the polymer is a value obtained based on the Fox equation, but the actually measured glass transition temperature of the polymer is obtained based on the Fox equation. It is preferably the same as the value. The actual measurement value of the glass transition temperature of the polymer can be obtained, for example, by measuring the differential scanning calorific value thereof.

  In the present specification, the glass transition temperature of a polymer means the glass transition temperature determined based on the above formula, unless otherwise specified. For monomers whose glass transition temperature is unknown, such as special monomers and polyfunctional monomers, the total amount of monomers whose glass transition temperature is unknown in the monomer component is 10% by mass. In the following cases, the glass transition temperature can be determined using only the monomer whose glass transition temperature is known. When the total amount of monomers whose glass transition temperature in the monomer component is unknown exceeds 10% by mass, the glass transition temperature of the polymer is measured by differential scanning calorimetry (DSC), differential calorimetric analysis (DTA), It is obtained by thermomechanical analysis (TMA).

  Examples of the differential scanning calorimeter measuring device include a product number: DSC220C manufactured by Seiko Instruments Inc. Further, when measuring the differential scanning calorific value, a method of drawing a differential scanning calorific value (DSC) curve, a method of obtaining a primary differential curve from the differential scanning calorific value (DSC) curve, a method of performing a smoothing process, and a method of obtaining a target peak temperature. There is no particular limitation. For example, when the measuring device is used, it may be plotted from the data obtained by using the measuring device. At that time, analysis software that can perform mathematical processing can be used. Examples of the analysis software include analysis software [manufactured by Seiko Instruments Inc., product number: EXSTAR6000], but the present invention is not limited to such examples. It should be noted that the peak temperature thus obtained may include an error due to plotting of about 5 ° C. above and below.

  The absolute value of the difference between the glass transition temperature of the polymer forming the outermost layer of the emulsion particles and the glass transition temperature of the polymer forming the inner layer is preferably 35 ° C. or higher, more preferably from the viewpoint of improving weather resistance. Is 40 ° C. or higher, preferably 70 ° C. or lower, and more preferably 60 ° C. or lower from the viewpoint of improving weather resistance and stain resistance.

  When the emulsion particles are composed of two layers, the weight ratio of the polymer forming the inner layer and the polymer forming the outer layer [polymer forming the inner layer / polymer forming the outer layer] is From the viewpoint of forming a coating film having excellent overall properties and hot water whitening resistance, it is 45/55 or more, preferably 50/50 or more, more preferably 55/45 or more, and it has excellent weather resistance and hot water whitening resistance. From the viewpoint of forming an overall excellent coating film, it is 85/15 or less, preferably 80/20 or less, more preferably 75/25 or less.

  The total content of the polymer forming the inner layer and the polymer forming the outer layer in the emulsion particles is 50% by weight or more, preferably 65% by weight or more, from the viewpoint of improving hot water whitening resistance. The larger the total content of the polymer forming the inner layer and the polymer forming the outer layer, the more preferable, and the upper limit is 100% by weight.

  After preparing the inner layer of the emulsion particles by the emulsion polymerization of the first step as described above, by forming the outer layer by the emulsion polymerization of the second step or later on the inner layer, for example, emulsion particles having an inner layer and an outer layer Aqueous resin dispersion containing can be obtained.

  The minimum film forming temperature of the aqueous resin dispersion of the present invention is preferably 60 ° C. or lower, more preferably 50 ° C. or lower, and further preferably 40 ° C. or lower from the viewpoint of improving weather resistance. Further, the lower limit of the minimum film-forming temperature of the aqueous resin dispersion of the present invention is preferably -15 ° C or higher, more preferably -10 ° C or higher, and further preferably -5 ° C, from the viewpoint of improving hot water whitening resistance. That is all.

  In addition, in this specification, the minimum film-forming temperature of an aqueous resin dispersion is applied with an applicator so that the aqueous resin dispersion has a thickness of 0.2 mm on a glass plate placed on a thermal gradient tester. And dried to mean the temperature at which cracks occur.

  The nonvolatile content in the aqueous resin dispersion of the present invention is preferably 30% by weight or more, more preferably 40% by weight or more from the viewpoint of improving productivity, and preferably 70% by weight from the viewpoint of improving handleability. Or less, more preferably 60% by weight or less.

In addition, in the present specification, the nonvolatile content in the aqueous resin dispersion is calculated by weighing 1 g of the aqueous resin dispersion and drying it with a hot air dryer at a temperature of 110 ° C. for 1 hour.
[Nonvolatile content (% by mass) in aqueous resin dispersion]
= ([Mass of residue] / [aqueous resin dispersion 1 g]) * 100
Means the value obtained based on.

  The average particle size of the emulsion particles is preferably 30 nm or more, more preferably 50 nm or more, further preferably 70 nm or more from the viewpoint of improving the storage stability of the emulsion particles, and preferably 250 nm from the viewpoint of improving weather resistance. Or less, more preferably 200 nm or less.

  In addition, in this specification, the average particle diameter of emulsion particles is measured using a particle size distribution measuring device [Particle Sizing Systems (manufactured by Particle Sizing Systems), product name: NICOMP Model 380) by a dynamic light scattering method. It means the volume average particle diameter.

  The aqueous resin dispersion of the present invention can be provided with a crosslinking property by further containing a crosslinking agent. The crosslinking agent may be one that initiates the crosslinking reaction at room temperature or one that initiates the crosslinking reaction by heat. By incorporating a crosslinking agent into the aqueous resin dispersion of the present invention, weather resistance and stain resistance can be improved.

  Suitable crosslinking agents include, for example, oxazoline group-containing compounds, isocyanate group-containing compounds, aminoplast resins and the like. These crosslinking agents may be used alone or in combination of two or more kinds. Among these crosslinking agents, the oxazoline group-containing compound is preferable from the viewpoint of improving the storage stability of the aqueous resin dispersion of the present invention.

  The oxazoline group-containing compound is a compound having two or more oxazoline groups in the molecule. Examples of the oxazoline group-containing compound include 2,2′-bis (2-oxazoline), 2,2′-methylene-bis (2-oxazoline), 2,2′-ethylene-bis (2-oxazoline), 2 , 2'-trimethylene-bis (2-oxazoline), 2,2'-tetramethylene-bis (2-oxazoline), 2,2'-hexamethylene-bis (2-oxazoline), 2,2'-octamethylene -Bis (2-oxazoline), 2,2'-ethylene-bis (4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis (2-oxazoline), 2,2'- m-phenylene-bis (2-oxazoline), 2,2'-m-phenylene-bis (4,4'-dimethyl-2-oxazoline), bis (2-oxazolinylcyclohexane) sulfi , Bis (2-oxazolinyl sulfonyl norbornane) sulfide, but like oxazoline ring-containing polymer, the present invention is not limited only to those exemplified. These oxazoline group-containing compounds may be used alone or in combination of two or more kinds. Among the oxazoline group-containing compounds, a water-soluble oxazoline group-containing compound is preferable, and a water-soluble oxazoline ring-containing polymer is more preferable, from the viewpoint of improving reactivity.

  The oxazoline ring-containing polymer contains an addition-polymerizable oxazoline as an essential component, and can be easily prepared by polymerizing a monomer component containing a monomer copolymerizable with the addition-polymerizable oxazoline, if necessary. You can

  Examples of the addition-polymerizable oxazoline include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like can be mentioned, but the present invention is such an example. It is not limited to only. These addition-polymerizable oxazolines may be used alone or in combination of two or more kinds. Among these addition-polymerizable oxazolines, 2-isopropenyl-2-oxazoline is preferable because it is easily available.

  Examples of the monomer copolymerizable with the addition-polymerizable oxazoline include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and tert-butyl (meth) acrylate. , Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- Hydroxypropyl (meth) acrylate, monoester product of (meth) acrylic acid and polyethylene glycol, 2-aminoethyl (meth) acrylate and its salt, caprolactone modified product of (meth) acrylic acid, (meth) acrylic -(2,2,6,6-tetramethylpiperidine, (meth) acrylic acid-1,2,2,6,6-pentamethylpiperidine (meth) acrylic acid ester; sodium (meth) acrylate, (meth ) (Meth) acrylic acid salts such as potassium acrylate and ammonium (meth) acrylate; unsaturated nitriles such as (meth) acrylonitrile; (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) ) Unsaturated amides such as (meth) acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; vinyl chloride, vinylidene chloride, vinyl fluoride, etc. Halogen-containing α, β-unsaturated fats Hydrocarbon compounds; styrene, alpha-methyl styrene, alpha such as sodium styrene sulfonate, beta-although such unsaturated aromatic hydrocarbon compounds, the present invention is not limited only to those exemplified. These addition-polymerizable oxazoline-copolymerizable monomers may be used alone or in combination of two or more kinds.

  The oxazoline group-containing compound is, for example, commercially available as Nippon Shokubai Co., Ltd., trade name: Epocros WS-500, Epocros WS-700, Epocros K-2010, Epocros K-2020, Epocros K-2030 and the like. can do. Among these, water-soluble oxazoline group-containing compounds such as Epocros WS-500 and Epocros WS-700 manufactured by Nippon Shokubai Co., Ltd. are preferable from the viewpoint of improving reactivity.

  The isocyanate group-containing compound is a compound containing an isocyanate group capable of reacting with a hydroxyl group that the hydroxyl group-containing monomer used as a monomer component has as a functional group.

  Examples of the isocyanate group-containing compound include water-dispersed (block) polyisocyanate. The (block) polyisocyanate means polyisocyanate and / or blocked polyisocyanate.

  Examples of the water-dispersible polyisocyanate include those obtained by dispersing polyisocyanate having hydrophilicity by a polyethylene oxide chain in water with an anionic dispersant or a nonionic dispersant.

  Examples of polyisocyanates include hexamethylene diisocyanate, diisocyanates such as isophorone diisocyanate; trimethylolpropane adducts of these diisocyanates, burettes, derivatives of polyisocyanates such as isocyanurates (modified products), and the like. The present invention is not limited to only these examples. These polyisocyanates may be used alone or in combination of two or more kinds.

  Water-dispersed polyisocyanates are, for example, manufactured by Nippon Polyurethane Industry Co., Ltd., trade names: Aquanate 100, Aquanate 110, Aquanate 200, Aquanate 210, etc .; Sumika Bayer Urethane Co., Ltd., Trade name: Bayhijuru TPLS-2032, SUB-isocyanate L801 and the like; manufactured by Mitsui Takeda Chemical Co., Ltd., trade name: Takenate WD-720, Takenate WD-725, Takenate WD-220, etc .; Dainichi Seika Chemicals Co., Ltd., trade name: Resamine It can be easily obtained commercially as D-56 and the like.

  The water-dispersed polyisocyanate is obtained by blocking the isocyanate group of the water-dispersed polyisocyanate with a blocking agent. Examples of the blocking agent include diethyl malonate, ethyl acetoacetate, ε-caprolactam, butanone oxime, cyclohexanone oxime, 1,2,4-triazole, dimethyl-1,2,4-triazole, 3,5-dimethylpyrazole. , Imidazole, etc., but the present invention is not limited to such examples. These blocking agents may be used alone or in combination of two or more kinds. Among these blocking agents, one that cleaves at a temperature of 160 ° C. or lower, preferably 150 ° C. or lower is desirable. Suitable blocking agents include, for example, butanone oxime, cyclohexanone oxime, 3,5-dimethylpyrazole and the like. Of these, butanone oxime is more preferable.

  The water-dispersed block polyisocyanate is, for example, manufactured by Mitsui Takeda Chemical Co., Ltd., trade name: Takenate WB-720, Takenate WB-730, Takenate WB-920; Sumika Bayer Urethane Co., Ltd. It can be easily obtained commercially as BL116, Baihydur BL5140, Baihydur BL5235, Baihydur TPLS2186, Death Module VPLS2310, and the like.

  The aminoplast resin is an addition condensation product of a compound having an amino group such as melamine and guanamine with formaldehyde, and is also called an amino resin.

  As the aminoplast resin, for example, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, full alkyl type methylated melamine, full alkyl type butylated melamine, full alkyl type isobutylated melamine, full Melamine resins such as alkyl type mixed etherified melamine, methylol group type methylated melamine, imino group type methylated melamine, methylol group type mixed etherified melamine, imino group type mixed etherified melamine; butylated benzoguanamine, methyl / ethyl mixed alkyl Examples thereof include guanamine resins such as benzylated guanguanamine, methyl / butyl mixed alkylated benzoguanamine, and butylated glycoluril, but the present invention is not limited to these examples. Not to. These aminoplast resins may be used alone or in combination of two or more kinds.

  The aminoplast resin is, for example, manufactured by Mitsui Cytec Co., Ltd., trade name: Mycoat 506, Mycoat 1128, Cymel 232, Cymel 235, Cymel 254, Cymel 303, Cymel 325, Cymel 370, Cymel 771, Cymel 1170, etc. It is easily available commercially.

  The amount of the aminoplast resin is usually such that the weight ratio of the solid content of the polymer contained in the emulsion particles and the solid content of the aminoplast resin [polymer solid content / aminoplast resin solid content] is 60/40. It is preferable to adjust it so that it becomes ˜99 / 1.

  In the present invention, in addition to the above-mentioned cross-linking agent, for example, a carbodiimide compound; a cross-linking agent such as a polyvalent metal compound typified by a zirconium compound, a zinc compound, a titanium compound, an aluminum compound and the like is used for the purpose of the present invention. It can be used within the range where it is not inhibited.

  If necessary, the aqueous resin dispersion of the present invention may contain a pigment. Examples of the pigment include organic pigments and inorganic pigments, which may be used alone or in combination of two or more kinds.

  Examples of the organic pigment include benzidine, azo pigments such as Hansa Yellow, azomethine pigment, methine pigment, anthraquinone pigment, phthalocyanine pigments such as phthalocyanine blue, perinone pigment, perylene pigment, diketopyrrolopyrrole pigment, thioindigo pigment, iminoisoindoline. Pigments, iminoisoindolinone pigments, quinacridone pigments such as quinacridone red and quinacridone violet, flavantron pigments, indanthrone pigments, anthrapyrimidine pigments, carbazole pigments, monoarylide yellows, diarylide yellows, benzimidazolone yellows, tolyl oranges , Naphthol orange, quinophthalone pigment, etc., but the present invention is not limited to these examples. These organic pigments may be used alone or in combination of two or more.

  Examples of the inorganic pigment include titanium dioxide, antimony trioxide, zinc white, lithopone, lead white, red iron oxide, black iron oxide, iron oxide, chromium oxide green, carbon black, yellow lead, molybdenum red, ferrocyanide group. Pigments with flat shapes such as diiron (Prussian blue), ultramarine, lead chromate, mica, clay, aluminum powder, talc, aluminum silicate, calcium carbonate, magnesium hydroxide, aluminum hydroxide , Extender pigments such as barium sulfate, magnesium carbonate, etc., but the present invention is not limited to these examples. These inorganic pigments may be used alone or in combination of two or more.

  The amount of the pigment per 100 parts by weight of the nonvolatile content of the aqueous resin dispersion is preferably 50 parts by weight or more, more preferably 60 parts by weight from the viewpoint of improving the hiding property of the coating film formed from the aqueous resin dispersion of the present invention. The amount is not less than 190 parts by weight from the viewpoint of improving weather resistance.

  The aqueous resin dispersion of the present invention may contain other aqueous resin dispersions other than the aqueous resin dispersion as long as the object of the present invention is not impaired. The average particle size of the entire emulsion particles contained in the dispersion may be adjusted to fall within the above range.

  Further, the aqueous resin dispersion of the present invention, within the range that the object of the present invention is not impaired, for example, an ultraviolet absorber, an ultraviolet stabilizer, a filler, a leveling agent, a dispersant, a thickener, a wetting agent, a plasticizer. Additives such as agents, stabilizers, dyes and antioxidants may be contained in appropriate amounts.

  The aqueous resin dispersion of the present invention may be applied by itself as a single layer or may be applied by coating two or more layers. In the case of coating by coating two or more layers, only a part of the layers may be formed by the aqueous resin dispersion of the present invention, or all layers may be formed by the aqueous resin dispersion of the present invention. Good. Overcoating is performed, for example, by applying the coating material for the first layer (for example, the undercoat layer) to an object that has been subjected to primer treatment, sealer treatment, etc., and then drying it, and then for the second layer (for example, the overcoat layer). Examples include a method of overcoating with a coating material and drying, but the present invention is not limited to such a method. Examples of the method of applying the aqueous resin dispersion of the present invention include a coating method using a brush, a bar coater, an applicator, an air spray, an airless spray, a roll coater, a flow coater, and the like. It is not limited to the examples.

  The water-based resin dispersion of the present invention can be suitably used, for example, as a top coat paint (water-based paint) called a top coat, which is applied to the surface of exteriors of buildings, ceramic-based building materials, and the like.

  The top coating composition can be easily prepared, for example, by appropriately mixing the above-mentioned aqueous resin dispersion and one or more kinds of film-forming aids, foam inhibitors, pigments, thickeners, matting agents and the like. can do. Examples of the top coating material include enamel coating material and clear coating material. The topcoat paint can be suitably used for the topcoat.

  The above-mentioned top-coat paint can be suitably used, for example, in the case of on-site coating on the outer wall of a building or the like, and can also be suitably used for inorganic building materials such as ceramic-based building materials. Examples of the ceramic building materials include roof tiles and outer wall materials. Ceramic-based building materials are made by adding inorganic fillers, fibrous materials, etc. to the hydraulic glue that is the raw material for the inorganic cured product, molding the resulting mixture, and curing and curing the resulting molded product. can get. Examples of the inorganic building material that constitutes the exterior of the building include flexible boards, calcium silicate boards, gypsum slag perlite boards, wood chip cement boards, precast concrete boards, ALC boards and gypsum boards.

  When the aqueous resin dispersion of the present invention or the above-mentioned top coating material is applied to a building material, for example, a spray, a roller, a brush, a trowel or the like can be used.

  When applying the aqueous resin dispersion of the present invention or the top coating material to the front and back surfaces of a building material, from the viewpoint of efficiently producing a building material having a coating film on both sides, if necessary, heating the building material. You can leave it.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following examples, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified. The first embodiment is dealt with as a reference example.

Example 1
731 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. To the dropping funnel, 210 parts of deionized water, 60 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], 90 parts of methyl methacrylate, 90 parts of styrene, 200 parts of cyclohexyl methacrylate, n-butyl. A first-stage dropping pre-emulsion consisting of 10 parts of methacrylate, 100 parts of 2-ethylhexyl acrylate and 10 parts of n-butyl acrylate was prepared, and about 77 parts of the first-stage dropping pre-emulsion was added to the flask and gently. The temperature was raised to 70 ° C. while blowing nitrogen gas, and 5 parts of a 5% ammonium persulfate aqueous solution was added to initiate polymerization. Then, the rest of the pre-emulsion for dropping and 8 parts of 5% ammonium persulfate aqueous solution were dropped uniformly into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined with a pH measuring device [manufactured by Horiba, Ltd., trade name: Castany LAB pH / ion meter], the pH was 2.8.

  After completion of the dropping, the mixture was maintained at 70 ° C. for 60 minutes, followed by 210 parts of deionized water, 60 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: Adecaria Sorb SR-10], 45 parts of methyl methacrylate, 30 parts of styrene. Part, 80 parts of cyclohexyl methacrylate, 150 parts of 2-ethylhexyl acrylate, 190 parts of n-butyl acrylate and 5 parts of 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine for the second stage dropping pre-emulsion. Then, 8 parts of 5% ammonium persulfate aqueous solution was uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the content in the flask was examined in the same manner as above, the pH was 8.5.

  After the completion of the dropping, the content in the flask was maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a 300 mesh (JIS mesh, the same applies hereinafter) to obtain a pH of 8.3. To obtain an aqueous resin dispersion. The content of non-volatile components in this aqueous resin dispersion is 45.0%, the content of the acid group-containing monomer (acrylic acid) in the monomer component is 0%, and The glass transition temperature of the polymer constituting the emulsion particles was 0 ° C.

Example 2
731 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. To the dropping funnel, 250 parts of deionized water, 70 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], 110 parts of methyl methacrylate, 110 parts of styrene, 240 parts of cyclohexyl methacrylate, n-butyl. A first-stage dropping pre-emulsion consisting of 10 parts of methacrylate, 120 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate and 1 part of acrylic acid was prepared, and about 77 parts of the first-stage dropping pre-emulsion was placed in a flask. The mixture was added, and the temperature was raised to 70 ° C. while gently blowing nitrogen gas, and 5 parts of a 5% ammonium persulfate aqueous solution was added to initiate polymerization. Then, the rest of the pre-emulsion for dropping and 10 parts of 5% ammonium persulfate aqueous solution were uniformly dropped into the flask for 120 minutes. After that, when the pH of the contents of the flask was examined in the same manner as above, the pH was 2.2.

  After completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, followed by 170 parts of deionized water, 50 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], methyl methacrylate. 45 parts, styrene 10 parts, cyclohexyl methacrylate 40 parts, 2-ethylhexyl acrylate 130 parts, n-butyl acrylate 145 parts, 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine 15 parts and 4-methacryloyl. A second-stage dropping pre-emulsion consisting of 15 parts of oxy-2,2,6,6-tetramethylpiperidine and 6 parts of a 5% aqueous solution of ammonium persulfate were uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 8.9.

  After the completion of the dropping, the content in the flask was maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a 300-mesh wire net to obtain an aqueous resin dispersion liquid having a pH of 8.6. Obtained. The nonvolatile content of this aqueous resin dispersion was 44.9%, and the content of the acid group-containing monomer (acrylic acid) in the monomer component was 0.1%. The glass transition temperature of the polymer constituting the contained emulsion particles was 7 ° C.

Example 3
731 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In a dropping funnel, 340 parts of deionized water, 95 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: Adecaria Sorb SR-10], 240 parts of methyl methacrylate, 110 parts of styrene, 260 parts of cyclohexyl methacrylate, n-butyl. A first-stage dropping pre-emulsion consisting of 10 parts of methacrylate, 160 parts of 2-ethylhexyl acrylate and 20 parts of n-butyl acrylate was prepared, and about 77 parts of the first-stage dropping pre-emulsion was added to the flask, and gently. The temperature was raised to 70 ° C. while blowing nitrogen gas, and 5 parts of a 5% ammonium persulfate aqueous solution was added to initiate polymerization. Then, the rest of the pre-emulsion for dropping and 12 parts of 5% ammonium persulfate aqueous solution were uniformly dropped into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 2.5.

  After the completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, and subsequently 80 parts of deionized water, 25 parts of 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], methyl methacrylate. The second step dropping consisting of 25 parts, 10 parts of styrene, 20 parts of cyclohexyl methacrylate, 90 parts of 2-ethylhexyl acrylate, 45 parts of n-butyl acrylate and 10 parts of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine. The pre-emulsion and 3 parts of a 5% ammonium persulfate aqueous solution were uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 8.7.

  After completion of dropping, the contents of 7 flasks were maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a 300 mesh wire mesh to obtain an aqueous resin dispersion liquid having a pH of 8.6. Got The content of non-volatile components in this aqueous resin dispersion is 45.0%, the content of the acid group-containing monomer (acrylic acid) in the monomer component is 0%, and The glass transition temperature of the polymer constituting the emulsion particles was 21 ° C.

Comparative Example 1
731 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In a dropping funnel, 140 parts of deionized water, 40 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], 5 parts of methyl methacrylate, 80 parts of styrene, 170 parts of cyclohexyl methacrylate, n-butyl. A dropping pre-emulsion consisting of 10 parts of methacrylate, 55 parts of 2-ethylhexyl acrylate and 15 parts of n-butyl acrylate was prepared, and about 77 parts of the first-stage dropping pre-emulsion was added to the flask, and nitrogen gas was slowly added. The temperature was raised to 70 ° C. while blowing, and 5 parts of a 5% ammonium persulfate aqueous solution was added to initiate polymerization. Then, the rest of the dropping pre-emulsion and 5 parts of a 5% ammonium persulfate aqueous solution were uniformly added dropwise into the flask for 120 minutes. After that, when the pH of the contents of the flask was examined in the same manner as above, the pH was 2.6.

  After completion of the dropping, the content in the flask was maintained at 70 ° C. for 60 minutes, and subsequently, 280 parts of deionized water, 80 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], methyl methacrylate. 55 parts, 40 parts of styrene, 110 parts of cyclohexyl methacrylate, 215 parts of 2-ethylhexyl acrylate, 240 parts of n-butyl acrylate, and 5 parts of 5 parts of 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine. The pre-emulsion for eye drop addition and 10 parts of a 5% ammonium persulfate aqueous solution were uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 8.7.

  After completion of dropping, the contents of 7 flasks were maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a 300 mesh wire mesh to obtain an aqueous resin dispersion liquid having a pH of 8.6. Got The content of non-volatile components in this aqueous resin dispersion is 45.0%, the content of the acid group-containing monomer (acrylic acid) in the monomer component is 0%, and The glass transition temperature of the polymer constituting the emulsion particles was −11 ° C.

Comparative example 2
731 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In a dropping funnel, 380 parts of deionized water, 110 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: Adecaria Sorb SR-10], 305 parts of methyl methacrylate, 115 parts of styrene, 265 parts of cyclohexyl methacrylate, n-butyl. A dropping pre-emulsion consisting of 10 parts of methacrylate, 195 parts of 2-ethylhexyl acrylate and 10 parts of n-butyl acrylate was prepared, and about 77 parts of the first-stage dropping pre-emulsion was added to the flask, and nitrogen gas was slowly added. The temperature was raised to 70 ° C. while blowing, and 5 parts of a 5% ammonium persulfate aqueous solution was added to initiate polymerization. Then, the rest of the dropping pre-emulsion and 14 parts of a 5% ammonium persulfate aqueous solution were uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 2.6.

  After the completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, and subsequently 40 parts of deionized water, 10 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA, trade name: ADEKA REASORB SR-10], methyl methacrylate. Two stages consisting of 5 parts, 5 parts of styrene, 15 parts of cyclohexyl methacrylate, 55 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate and 4-parts of methacryloyloxy-1,2,2,6,6-pentamethylpiperidine. The pre-emulsion for eye drop addition and 2 parts of a 5% ammonium persulfate aqueous solution were uniformly added dropwise into the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as above, the pH was 8.7.

  After completion of dropping, the contents of 7 flasks were maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a 300 mesh wire mesh to obtain an aqueous resin dispersion liquid having a pH of 8.6. Got The content of non-volatile components in this aqueous resin dispersion is 45.0%, the content of the acid group-containing monomer (acrylic acid) in the monomer component is 0%, and The glass transition temperature of the polymer constituting the emulsion particles was 29 ° C.

  Next, as the physical properties of the aqueous resin dispersions obtained in Examples or Comparative Examples, hot water whitening resistance, limiting film thickness and weather resistance were evaluated based on the following methods. In addition, in each physical property, the thing with one evaluation of x is judged to be unacceptable.

(1) Hot water whitening resistance 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate [Chisso] was added to 100 parts of the aqueous resin dispersions obtained in each Example or each Comparative Example as a film forming aid. Co., Ltd., product number: CS-12] 10 parts and antifoaming agent [San Nopco Ltd., trade name: Nopco 8034L] 0.5 part are added, and the rotational speed is 1500 min ^{−1 for} 30 minutes with a homodisper. The sample for evaluation was obtained by stirring.

  According to JIS K6717 (2006), a black acrylic plate (manufactured by Nippon Test Panel Co., Ltd., length: 75 mm, width: 150 mm, thickness: 3 mm) obtained by molding polymethyl methacrylate by extrusion molding, The evaluation sample obtained above was applied with a 5 mil applicator and dried in an atmosphere at 23 ° C. for 1 day to prepare a test plate.

  The L value (L0) of the test plate obtained above was measured with a color difference meter [manufactured by Nippon Denshoku Industries Co., Ltd., trade name: spectroscopic color difference meter SE-2000], and the test plate was heated to 50 ° C. After soaking in the adjusted warm water for 24 hours, it was pulled out from the warm water, the moisture was wiped off with a Kim towel (manufactured by Nippon Paper Crecia Co., Ltd.), and the L value (L1) was measured with the color difference meter within 1 minute.

Next, the change value of the L value is expressed by the formula:
ΔL = (L1)-(L0)
The hot water whitening resistance was evaluated based on the following evaluation criteria.
〔Evaluation criteria〕
◯: ΔL is less than 4.0 Δ: ΔL is 4.0 or more and less than 6.0 ×: ΔL is 6.0 or more

(2) Limit film thickness and weather resistance (preparation of evaluation sample)
2,2,4-trimethyl-1,3-pentanediol monoisobutyrate [manufactured by Chisso Corporation, product number: 100 parts by weight of the aqueous resin dispersions obtained in the respective examples or comparative examples] CS-12] was added thereto, and the mixture was stirred with a homodisper at a rotation speed of 1500 min ^{−1 for} 10 minutes, and then 30 parts of a white paste and an antifoaming agent (manufactured by San Nopco Ltd., trade name: Nopco 8034L) 0.5. Is added, and the viscosity is 80 KU when measured at 25 ° C. using a Krebs unit viscometer (manufactured by Brookfield, product number: KU-1). Thickener [manufactured by ADEKA, trade name : ADECANOL UH-420] was added, and the mixture was stirred for 30 minutes to obtain a sample.

The white paste is 210 parts of deionized water, 60 parts of a dispersant (manufactured by Kao Corporation, trade name: DEMOL EP), 60 parts of a dispersant [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: DISCOAT N- 14] 50 parts, wetting agent [manufactured by Kao Corporation, trade name: Emulgen LS-106] 10 parts, propylene glycol 60 parts, titanium oxide [manufactured by Ishihara Sangyo Co., Ltd., product number: CR-95] 1000 parts and glass It was prepared by dispersing 200 parts of beads (diameter: 1 mm) with a homodisper at a rotation speed of 3000 min ^{−1 for} 60 minutes.

  The limiting film thickness and the weather resistance were examined using the samples obtained above. The results are shown in Table 1.

(Limit film thickness)
A mixture was prepared by mixing the sample and water at a ratio of 10 parts by mass of water per 100 parts by mass of the sample.

Next, a flexible board (length: 150 mm, width: 150 mm, thickness: 4 mm) was uniformly coated with a sealer [trade name: EX sealer manufactured by SK Kaken Co., Ltd.] by air spray at a coating amount of 150 g / m ^2. And was dried in a hot air dryer at 80 ° C. for 10 minutes. Immediately after the drying, the mixture obtained above is applied on a coating film formed on the surface of the flexible board with a sag tester so that the wet thickness of the coating film is 100 to 500 μm to a predetermined coating film thickness. A test plate was prepared by coating, and the obtained test plate was immediately dried with a hot air dryer for 30 minutes at a wind speed of 1 m / s, and then the test plate was taken out of the hot air dryer to shrink wrinkles on the coating film. The thickness of the coating film when the above was confirmed was taken as the limiting film thickness, and the limiting film thickness was evaluated based on the following evaluation criteria.
〔Evaluation criteria〕
◯: Limiting film thickness 375 μm or more Δ: Limiting film thickness 250 μm or more and 375 μm or less ×: Limiting film thickness less than 250 μm

(Weatherability)
A slate plate (manufactured by Nippon Test Panel Co., Ltd., length: 70 mm, width: 150 mm, thickness: 6 mm) and a sealer [manufactured by SK Kaken Co., Ltd., trade name: EX Sealer] of 150 g / m ² by air spray The coating amount was applied uniformly and dried in an atmosphere of 23 ° C. for 1 week.

Next, the sample was applied with a 10 mil applicator and dried in an atmosphere of 23 ° C. for 1 week, and then the side surface and the back surface of the slate plate to which the sample was applied were sealed with aluminum tape, and the surface to which the sample was applied was sealed. The 60 ° specular gloss of the slate plate was measured with a gloss meter [manufactured by Nippon Denshoku Industries Co., Ltd., product number: VG2000], and a weather resistance test was performed for 500 hours under the following conditions. Measure the gloss of the formula:
[Gloss retention (%)]
= [[Gloss after weather resistance test] / [Gloss before weather resistance test]] x 100
The weather resistance was evaluated based on the following evaluation criteria.

[Test conditions for weather resistance test]
・ Testing machine: Metal weather [Daipla Wintes Co., Ltd., product number: KU-R4]
・ Irradiation: Irradiation for 4 hours in an atmosphere with a temperature of 65 ° C and relative humidity of 50% (irradiation intensity: 80 mW / cm ² ).
・ Wet: 4 hours in an atmosphere with a temperature of 35 ° C and a relative humidity of 98% ・ Shower: 30 seconds each before and after wetting

〔Evaluation criteria〕
◯: Gloss retention is 80% or more B: Gloss retention is 60% or more and less than 80% X: Gloss retention is less than 60%

  From the results shown in Table 1, it can be seen that the aqueous resin dispersions obtained in the respective examples are superior in hot water whitening resistance, limiting film thickness and weather resistance as compared with the respective comparative examples. Recognize.

  The method for producing an aqueous resin dispersion and the aqueous resin dispersion of the present invention are useful for applications such as paints and coating agents.

Claims (2)

A method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles, wherein the content of the acid group-containing monomer as a monomer component used as a raw material for the emulsion particles is 0.3% by mass or less. When emulsion-polymerizing a certain monomer component in multiple stages, in a medium having a pH of 1 to 5 using 55 to 85% by mass of the total monomer components used in the emulsion polymerization. after Tsu Na row emulsion polymerization using the monomer component containing an alkyl (meth) acrylates and styrenic monomers to emulsion polymerization in the row of Utoki as the monomer component, the remainder of the monomer component After emulsion-polymerizing the remaining monomer component by carrying out emulsion polymerization using a monomer component containing a piperidyl group-containing monomer as the monomer component when carrying out emulsion polymerization using Is characterized by adjusting the pH of 6 to 10 Method for producing an aqueous resin dispersion to be.   The aqueous resin dispersion according to claim 1, wherein the amount of the monomer component used when the emulsion polymerization is carried out in a medium having a pH of 1 to 5 is 60 to 80% by mass based on all the monomer components. Production method.