JP7051783B2 - Method for manufacturing 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 caused by the release of volatile organic compounds into the atmosphere, water-based paints using water-dispersible resins such as water-soluble water-soluble 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, weather resistance, etc. as compared with the organic solvent-based paint due to the fact that water is used as a solvent. As an aqueous coating composition having excellent weather resistance and water resistance, an aqueous coating composition in which multilayer structure particles having a core portion and a shell portion made of an acrylic polymer having a specific glass transition temperature are dispersed in water has been proposed. (For example, see Patent Document 1).

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

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

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

Japanese Unexamined Patent Publication No. 2002-138123 Japanese Unexamined Patent Publication No. 2014-031456

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 having excellent warm water whitening resistance and weather resistance and being able to coat a thick film. That is the issue.

The present invention is a method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles, wherein the content of an acid group-containing monomer as a monomer component used as a raw material of the emulsion particles is 0.3. When the monomer component of mass% or less is emulsion-polymerized in multiple stages , 45 to 85% by mass of the monomer component of all the monomer components used in the emulsion polymerization is emulsion-polymerized and the pH is 2. After preparing an aqueous resin dispersion of 2 to 2.8, a monomer component containing a piperidin group-containing monomer is used as the remaining monomer component, and the monomer component is emulsion-polymerized . The present invention relates to a method for producing an aqueous resin dispersion, which comprises preparing an aqueous resin dispersion having a pH of 8.5 to 10 .

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 having excellent hot water whitening resistance and weather resistance and being able to apply a thick film.

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

According to the present invention, 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, so that the coating film has excellent hot water whitening resistance and weather resistance. Can be formed.

Further, in the present invention, when the monomer component is emulsion-polymerized in multiple stages, 45 to 85% by mass of the monomer component among all the monomer components used in the emulsion polymerization has a pH of 1 to 5. After emulsion polymerization in a certain medium, the pH after emulsion polymerization of the remaining monomer components is adjusted to 6 to 10, so it is excellent in warm water whitening resistance and weather resistance. It is possible to obtain an aqueous resin dispersion capable of forming a coating film and applying a thick film.

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

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. Examples thereof include carboxyl group-containing aliphatic monomers such as esters, itaconic acid monobutyl esters, and vinyl benzoic 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. 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 the emulsion particles.

Emulsion particles are composed of a plurality of layers. The number of layers contained in the emulsion particles is preferably 2 to 5 layers from the viewpoint of forming a coating film having excellent 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.

As the monomer component, there are a monofunctional monomer and a polyfunctional monomer, and both of them 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, but the present invention is not limited to such an example. These monomers may be used alone or in combination of two or more.

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

Examples of the ethylenically unsaturated double bond-containing monomer include alkyl (meth) acrylate, hydroxyl group-containing (meth) acrylate, piperidyl group-containing monomer, oxo group-containing monomer, and 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 the present invention is not limited to such an example. These ethylenically unsaturated double bond-containing monomers may be used alone or in combination of two or more.

Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and 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 thereof include alkyl (meth) acrylates having 1 to 18 carbon atoms in ester groups such as acrylates, dodecyl (meth) acrylates, stearyl (meth) acrylates, and isobornyl methacrylates, but the present invention is limited to such examples. It is not something that is done. These monomers may be used alone or in combination of two or more.

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 in which ester groups such as butyl (meth) acrylate have 1 to 18 carbon atoms, 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- (Meta) 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-cyano-4- (meth) acryloylamino-2 , 2,6,6-Tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2, Examples thereof include 2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, but the present invention is not limited to these examples. not. These monomers may be used alone or in combination of two or more.

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 and the like, 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.

Examples of the fluorine atom-containing monomer include a fluorine atom-containing alkyl having 2 to 6 carbon atoms in an ester group 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, and 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, Examples thereof include acrylamide compounds such as diacetoneacrylamide, nitrogen atom-containing (meth) acrylate compounds such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, N-vinylpyrrolidone, and (meth) acrylonitrile. Is not limited to such examples. 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. It is not limited to only. These epoxy group-containing monomers may be used alone or in combination of two or more.

Examples of the alkoxyalkyl (meth) acrylate include methoxyethyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxybutyl (meth) acrylate, and trimethylolpropane tripropoxy (meth) acrylate. , The example is not limited to this. 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, and vinyltri. 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 achlorine, humylstyrene, vinyl ethyl ketone, (meth) acrylic oxyalkylpropenal, acetonyl (meth) acrylate, diacetone (meth) acrylate, and 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.

Examples of the aziridinyl group-containing monomer include (meth) acryloyl aziridine, 2-aziridinyl ethyl (meth) acrylate, and the like, but the present invention is not limited to these examples. These aziridinyl group-containing monomers may be used alone or in combination of two or more.

Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, tert-methylstyrene, chlorostyrene, vinyltoluene and the like, but the present invention is limited to these examples only. is not. These monomers may be used alone or in combination of two or more. The styrene-based monomer has an alkyl group such as a methyl group and a tert-butyl group, a nitro group, a nitrile group, an alkoxyl group, an acyl group, a sulfone group, a hydroxyl group and a functional group such as a halogen atom in the benzene ring. You may. 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 benzyl (meth) acrylate, phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, and naphthylmethyl (meth) acrylate, which have an aralkyl group having 7 to 18 carbon atoms. 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.

Suitable monofunctional monomers include, for example, alkyl (meth) acrylates, hydroxyl group-containing (meth) acrylates, piperidyl group-containing monomers, oxo group-containing monomers, fluorine atom-containing monomers, and nitrogen atom-containing singles. Examples thereof include a weight, an epoxy group-containing monomer, a styrene-based monomer, and the like, and these monomers may be used alone or in combination of two or more.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 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 trimethylolpropane di (meth) acrylate; polyethylene glycol di (meth) acrylate having 2 to 50 moles of ethylene oxide added, number of moles of propylene oxide added Alkyldi (meth) acrylates having 2 to 50 moles of alkylene oxide groups having 2 to 4 carbon atoms, such as 2 to 50 polypropylene glycol di (meth) acrylates and trimethylolpropane di (meth) acrylates; Glycerintri (meth) acrylate, propylene oxide-modified glyceroltri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol monohydroxytri (meth) acrylate, trimethylolpropane Tri (meth) acrylates of polyhydric alcohols having 1 to 10 carbon atoms such as triethoxytri (meth) acrylates; pentaerythritol tetra (meth) acrylates, dipentaerythritol tetra (meth) acrylates, trimethylolpropane tetra (meth) acrylates. Tetra (meth) acrylate of polyhydric alcohol having 1 to 10 carbon atoms such as; pentaerythritol Penta (meth) acrylate, dipentaerythritol (monohydroxy) Penta (meth) acrylate and other polyhydric alcohols having 1 to 10 carbon atoms. Penta (meth) acrylate; Hexa (meth) acrylate of polyvalent alcohol having 1 to 10 carbon atoms such as pentaerythritol hexa (meth) acrylate; Bisphenol A di (meth) acrylate, 2- (2'-vinyloxyethoxyethyl) Epoxy group-containing (meth) acrylates such as (meth) acrylates and epoxy (meth) acrylates; polyfunctional (meth) acrylates such as urethane (meth) acrylates. Examples thereof include, but the present invention is not limited to such an example. These polyfunctional monomers may be used alone or in combination of two or more.

Among the polyfunctional monomers, the number of added moles of the alkyldi (meth) acrylate having 4 to 8 carbon atoms and the number of added moles of ethylene oxide of the alkyl group having two hydroxyl groups is from the viewpoint of achieving both the hardness of the coating film and the film forming property. 2 to 50 polyethylene glycol di (meth) acrylates, 2 to 50 polypropylene glycol di (meth) acrylates with 2 to 50 moles of propylene oxide, tri (meth) acrylates of polyhydric alcohols, tetra (meth) acrylates of polyhydric alcohols. , Penta (meth) acrylate of polyhydric alcohol and hexa (meth) acrylate of polyhydric alcohol are preferable, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate having an addition molar number of 2 to 50 of ethylene oxide, 1 , 4-Butandiol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate and trimethylolpropane 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 hinder the object of the present invention.

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

Examples of the benzotriazole-based ultraviolet absorbing monomer include 2- [2'-hydroxy-5'-(meth) acryloyloxymethylphenyl] -2H-benzotriazole and 2- [2'-hydroxy-5'-. (Meta) 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) acryloyloxyhexylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(meth) acryloyloxy Ethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(meth) acryloyloxyethylphenyl] -5-chloro-2H-benzotriazole, 2- [2' -Hydroxy-5'-tert-butyl-3'-(meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(meth) acryloyloxyethylphenyl] -5-chloro -2H-benzotriazole, 2- [2'-hydroxy-5'-(meth) acryloyloxyethylphenyl] -5-cyano-2H-benzotriazole, 2- [2'-hydroxy-5'-(meth) acryloyl Oxyethylphenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'-hydroxy-5'-(β- (meth) acryloyloxyethoxy) -3'-tert-butylphenyl] -4-tert -Butyl-2H-benzotriazole and the like can be mentioned, but the present invention is not limited to such examples. These benzotriazole-based ultraviolet absorbing monomers may be used alone or in combination of two or more.

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

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

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

When the monomer component is emulsion-polymerized, the monomer component, the emulsifier and the medium may be mixed and then the emulsion polymerization may be carried out. Emulsion polymerization may be carried out after preparing the above, or at least one of a monomer component, an emulsifier and a medium and a preemulsion of the rest thereof may be mixed and emulsion polymerization may be carried out. The monomer component, the emulsifier and the medium may be added all at once, may be added separately, or may be continuously added dropwise.

Examples of the emulsifier include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, polymer emulsifiers and the like, and these emulsifiers may be used alone or in combination of two or more.

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 alkyldiphenyl ether disulfonate; ammonium dodecylbenzene sulfonate, sodium dodecyl naphthalene sulfonate and the like. Alkylaryl sulfonate salt; polyoxyethylene alkyl sulfonate salt; polyoxyethylene alkyl sulphate salt; polyoxyethylene alkylaryl sulphate salt; dialkyl sulfosuccinate; aryl sulfonic acid-formalin condensate; ammonium laurylate, sodium stealylate, etc. Fatty acid salt; bis (polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salt, propenyl-alkyl sulfosuccinate salt, (meth) acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene phosphonate salt, allyl Sulfate ester having an allyl group such as a sulfonate salt of oxymethylalkyloxypolyoxyethylene or a salt thereof; examples thereof include a sulfate ester salt of allyloxymethylalkoxyethylpolyoxyethylene, a polyoxyalkylene alkenyl ether ammonium sulfate salt, and the like. Is not limited to such examples.

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. Condensation products with amines, allyloxymethylalkoxyethyl hydroxypolyoxyethylene, polyoxyalkylene alkenyl ethers and the like can be mentioned, but the present invention is not limited to such 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 polymer emulsifier include poly (meth) acrylates such as sodium polyacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyhydroxyalkyl (meth) acrylates such as polyhydroxyethyl acrylate; and simple polymers constituting these polymers. Examples thereof include a copolymer containing one or more of the polymers as a copolymerization component, but the present invention is not limited to such an example.

Further, 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.

Examples of the reactive emulsifier include propenyl-alkylsulfosuccinate ester salt, (meth) acrylic acid polyoxyethylene sulfonate salt, and (meth) acrylic acid polyoxyethylene phosphonate salt [for example, manufactured by Sanyo Kasei Kogyo Co., Ltd., Product name: Eleminor RS-30, etc.], Polyoxyethylenealkylpropenylphenyl ether sulfonate salt [For example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Aqualon BC-10, Aqualon HS-10, etc.], Allyloxymethylalkyl Alkoxypolyoxyethylene sulfonate salt [for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon KH-10, etc.], allyloxymethylnonylphenoxyethyl hydroxypolyoxyethylene sulfonate salt [for example, manufactured by ADEKA Co., Ltd.] , Product name: Adecaria soap SE-10, etc.], Allyloxymethylalkoxyethyl hydroxypolyoxyethylene sulfate ester salt [For example, manufactured by ADEKA Co., Ltd., Product name: Adecaria soap SR-10, SR-30, etc.], Bis (polyoxyethylene polycyclic phenyl ether) methacrylated sulfonate salt [for example, manufactured by Nippon Emulsor Co., Ltd., trade name: Antox MS-60, etc.], allyloxymethylalkoxyethyl hydroxypolyoxyethylene [for example, Co., Ltd.] Made by ADEKA, trade name: Adecaria soap ER-20, etc.], polyoxyethylene alkylpropenylphenyl ether [for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon RN-20, etc.], allyloxymethylnonylphenoxyethyl Hydroxypolyoxyethylene [for example, manufactured by ADEKA Co., Ltd., trade name: Adecaria Soap NE-10, etc.) and the like can be mentioned, but the present invention is not limited to such examples.

The amount of the emulsifier is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, still more preferably 2 parts by weight or more, particularly preferably 2 parts by weight or more, from the viewpoint of improving the polymerization stability per 100 parts by weight of the monomer component. 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, still more 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), and 2,2-azobis (2,2-azobis). 2-Diaminopropane) Hydrochloride, azo compounds such as 4,4-azobis (4-cyanovaleric acid), 2,2-azobis (2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; Examples thereof include peroxides such as hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and 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.

The amount of the polymerization initiator is preferably 0.05 parts by weight or more, 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, preferably 1 part by weight or less, and more preferably 0.5 part 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, split charging, continuous dropping and the like. Further, from the viewpoint of accelerating the end time of the polymerization reaction, a part of the polymerization initiator may be added before or after the end of adding the monomer component to the reaction system.

When the monomer component is emulsion-polymerized in multiple stages, a part or all of the acidic groups of the obtained polymer can be neutralized with a neutralizing agent. The neutralizing agent may be used after the monomer component is added in the final stage, for example, it may be used between the polymerization reaction of the first stage and the polymerization reaction of the second stage, and the initial emulsification may be performed. It may be used at the end of the polymerization reaction.

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

When the monomer component is emulsion-polymerized in multiple stages, a coating film having excellent hot water whitening resistance and weather resistance is formed, and from the viewpoint of obtaining an aqueous resin dispersion capable of coating a thick film, the medium is medium. It is preferable to emulsify and polymerize the monomer component in the absence of a Japanese agent.

In order to promote the decomposition of the polymerization initiator, for example, a reducing agent such as sodium bisulfite and a decomposition agent of the polymerization initiator such as a transition metal salt such as ferrous sulfate are added in an appropriate amount into the reaction system. May be good.

In addition, 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, and α-methyl. Examples thereof include styrene dimers, 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. 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 the monomer component is emulsion-polymerized, a silane coupling agent may be used in an appropriate amount from the viewpoint of improving the weather resistance. Examples of the silane coupling agent include 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. Not limited.

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

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

The polymerization temperature at the time of emulsion polymerization of 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 polymerization of the monomer component is not particularly limited and may be appropriately set according to the progress of the polymerization reaction, but is usually about 2 to 9 hours.

As a method for forming an outer layer on the emulsion particles contained in the aqueous resin dispersion obtained above, for example, the monomer component is emulsion-polymerized in the aqueous resin dispersion in the same manner as described above. , 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 the monomer component in the aqueous resin dispersion in the same manner as described above, the outer layer is formed on the emulsion particles. Further, a method of forming an outer layer and the like can be mentioned.

In the present invention, when an aqueous resin dispersion containing a plurality of layers of emulsion particles having a multi-layer structure is prepared by such multi-stage 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 group-containing monomer content of 0.3% by mass or less, the pH of the monomer component of 45 to 85% by mass of all the monomer components used in emulsion polymerization is high. One major feature is that after emulsion polymerization in a medium of 1 to 5, the pH after emulsion polymerization of the remaining monomer components is adjusted to 6 to 10. In the present invention, since the operation is adopted, it is possible to form a coating film having excellent hot water whitening resistance and weather resistance, and to obtain an aqueous resin dispersion capable of coating a thick film.

In the present invention, in the first stage emulsion polymerization, 45 to 85% by mass of the monomer components out 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 having excellent 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 all the monomer components. Further, the pH of the medium at the time of the first stage emulsion polymerization is preferable from the viewpoint of forming a coating film having excellent 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 and subsequent stages of emulsion polymerization are carried out. When an outer layer is formed on the emulsion particles obtained by the first stage emulsion polymerization by the second and subsequent stages of emulsion polymerization, the polymerization reaction rate in the first stage emulsion polymerization is 90% or more, preferably 95% or more. It is preferable to emulsion-polymerize the monomer components constituting the outer layer of the second and subsequent stages after reaching the above, from the viewpoint of forming a layer-separated structure in the emulsion particles.

The monomer component for performing the emulsion polymerization in the second and subsequent stages is the monomer not used in the first stage among all the monomer components used in the emulsion polymerization, that is, the remaining monomer component. Is. Therefore, in the second and subsequent stages of emulsion polymerization, 15 to 55% by mass of the monomer components out of all the monomer components are emulsion-polymerized in the medium. The amount of the monomer component used in the second and subsequent emulsion polymerizations is from the viewpoint of forming a coating film having excellent 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 all the monomer components. Further, the pH of the medium during the emulsion polymerization of the second and subsequent stages is from the viewpoint of forming a coating film having excellent 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 polymerization of 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 of the second and subsequent stages. Can be adjusted to.

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

Examples of the monomer exhibiting basicity include the above-mentioned nitrogen atom-containing (meth) acrylate and piperidine group-containing monomer, but the present invention is not limited to these examples. The amount of the monomer exhibiting basicity is adjusted to 6 to 10, preferably 7 to 9 after the first stage emulsion polymerization and the emulsion polymerization of the remaining monomer components. It is preferably the 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 and subsequent stages of 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, still more preferably 2 to 10% by mass from the viewpoint of improving weather resistance. be.

Examples of the monomer component used for forming the outer layer of the second and subsequent stages are the same as those of the monomer component used for the emulsion polymerization of the first stage. Further, the method and polymerization conditions of the second and subsequent emulsion polymerizations may be the same as those of the polymerization method and polymerization conditions in the first stage emulsion polymerization.

If necessary, a layer made of another polymer may be formed between the inner layer and the outer layer of the emulsion particles 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 and before forming the outer layer, other weights are required as long as the object of the present invention is not impaired. Operations may be included to form a layer of coalescence.

As described above, an aqueous resin dispersion containing a plurality of layers of emulsion particles can be obtained, but the polymer constituting the emulsion particles forms a coating film having excellent warm water whitening resistance and weather resistance, and is thick. From the viewpoint of obtaining an aqueous resin dispersion capable of coating a film, a (meth) acrylic polymer obtained by emulsion polymerization of the monomer component is preferable.

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

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

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 methylmethacrylate homopolymer, 100 ° C. for a styrene homopolymer, and cyclohexyl. 83 ° C for methacrylate homopolymer, 20 ° C for n-butyl methacrylate homopolymer, -70 ° C for 2-ethylhexyl acrylate homopolymer, -56 ° C for n-butyl acrylate homopolymer, 4-methacryloyl The temperature is 130 ° C. for the homopolymer of oxy-1,2,2,6,6-pentamethylpiperidine and 130 ° C. for the homopolymer of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine.

The glass transition temperature of the polymer is a value obtained based on the Fox equation, while the measured value of the polymer glass transition temperature is determined based on the Fox equation. It is preferably the same as the value. The measured value of the glass transition temperature of the polymer can be obtained, for example, by measuring the differential scanning calorimetry.

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

Examples of the device for measuring the differential scanning calorimetry include Seiko Instruments Co., Ltd., product number: DSC220C and the like. Further, when measuring the differential scanning calorimetry, a method of drawing a differential scanning calorimetry (DSC) curve, a method of obtaining a first-order differential curve from the differential scanning calorimetry (DSC) curve, a method of performing smoothing processing, and a method of obtaining a target peak temperature. There are no particular restrictions on such things. For example, when the measuring device is used, drawing may be performed from the data obtained by using the measuring device. At that time, analysis software capable of performing 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. The peak temperature thus obtained may include an error due to drawing of about 5 ° C. above and below.

The absolute value of the difference between the glass transition temperature of the polymer constituting the outermost layer of the emulsion particles and the glass transition temperature of the polymer constituting the inner layer thereof is preferably 35 ° C. or higher, more preferably 35 ° C. or higher from the viewpoint of improving weather resistance. Is 40 ° C. or higher, preferably 70 ° C. or lower, 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 constituting the inner layer to the polymer constituting the outer layer [the polymer constituting the inner layer / the polymer constituting the outer layer] is weather resistant and weather resistant. From the viewpoint of forming a coating film having overall excellent properties and hot water whitening resistance, it is 45/55 or more, preferably 50/50 or more, more preferably 55/45 or more, and 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, and more preferably 75/25 or less.

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

After preparing the inner layer of the emulsion particles by the first stage emulsion polymerization as described above, by forming the outer layer on the inner layer by the second and subsequent stages of emulsion polymerization, for example, the emulsion particles having the inner layer and the outer layer can be obtained. An aqueous resin dispersion containing the mixture 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, still more 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, still more preferably −5 ° C. from the viewpoint of improving the hot water whitening resistance. That is all.

In the present specification, the minimum film-forming temperature of the aqueous resin dispersion is such that the aqueous resin dispersion is coated on a glass plate placed on a thermal gradient tester with an applicator so as to have a thickness of 0.2 mm. It means the temperature at which cracks occur after drying.

The non-volatile 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 or more from the viewpoint of improving handleability. Below, it is more preferably 60% by weight or less.

In the present specification, the non-volatile content in the aqueous resin dispersion is determined by weighing 1 g of the aqueous resin dispersion and drying it in a hot air dryer at a temperature of 110 ° C. for 1 hour, and the obtained residue is used as the non-volatile content.
[Non-volatile 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, still more 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. Below, it is more preferably 200 nm or less.

In the present specification, the average particle size of the emulsion particles is measured using a particle size distribution measuring device [Particle Sizing Systems, trade name: NICOMP Model 380] by a dynamic light scattering method. It means the volume average particle size obtained.

The aqueous resin dispersion of the present invention can be imparted with crosslinkability by further containing a cross-linking agent. The cross-linking agent may be one that starts the cross-linking reaction at room temperature, or may be one that starts the cross-linking reaction by heat. By containing a cross-linking agent in the aqueous resin dispersion of the present invention, weather resistance and stain resistance can be improved.

Suitable cross-linking agents include, for example, oxazoline group-containing compounds, isocyanate group-containing compounds, aminoplast resins and the like. These cross-linking agents may be used alone or in combination of two or more. Among these cross-linking agents, an 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), and 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) sulfide, bis (2-oxa Zolinyl norbornan) sulfides, oxazoline ring-containing polymers and the like can be mentioned, but the present invention is not limited to these examples. These oxazoline group-containing compounds may be used alone or in combination of two or more. 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 is easily prepared by containing addition-polymerizable oxazoline as an essential component and, if necessary, polymerizing a monomer component containing a monomer copolymerizable with addition-polymerizable oxazoline. Can be done.

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, and the like. Examples thereof include 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline. Not limited to just. These addition-polymerizable oxazolines may be used alone or in combination of two or more. 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, monoesteride of (meth) acrylic acid and polyethylene glycol, 2-aminoethyl (meth) acrylate and salts thereof, caprolactone modified product of (meth) acrylic acid, (meth) acrylic acid-2 , 2,6,6-Tetramethylpiperidin, (meth) acrylates-1,2,2,6,6-pentamethylpiperidins and other (meth) acrylic acids; sodium (meth) acrylates, (meth) acrylics (Meta) acrylates such as potassium acid, ammonium (meth) acrylate; unsaturated nitriles such as (meth) acrylonitrile; (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) ( Meta) Unsaturated amides such as 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; Halogen such as vinyl chloride, vinylidene chloride and vinyl fluoride Included α, β-unsaturated aliphatic hydrocarbon compounds; α, β-unsaturated aromatic hydrocarbon compounds such as styrene, α-methylstyrene, sodium styrene sulfonate, etc., but the present invention is only such an example. Not limited to. The monomers copolymerizable with these addition-polymerizable oxazolines may be used alone or in combination of two or more.

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

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

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

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

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

The water-dispersed polyisocyanate is, for example, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Aquanate 100, Aquanate 110, Aquanate 200, Aquanate 210, etc .; TPLS-2032, SUB-isocyanate L801, etc .; Mitsui Takeda Chemical Co., Ltd., trade name: Takenate WD-720, Takenate WD-725, Takenate WD-220, etc .; Dainichi Seika Kogyo Co., Ltd., trade name: Resamine It can be easily obtained commercially as D-56 or the like.

The water-dispersed blocked 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, and 3,5-dimethylpyrazole. , Imidazole and the like, but the present invention is not limited to such examples. These blocking agents may be used alone or in combination of two or more. Among these blocking agents, those that cleave at a temperature of 160 ° C. or lower, preferably 150 ° C. or lower, are desirable. Suitable blocking agents include, for example, butanone oxime, cyclohexanone oxime, 3,5-dimethylpyrazole and the like. Of these, butanone oxime is more preferred.

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, etc .; manufactured by Sumika Bayer Urethane Co., Ltd., trade name: Bayhijour. It is readily commercially available as BL116, Bayer Jules BL5140, Bayer Jules BL5235, Bayer Jules TPLS2186, Death Module VPLS2310 and the like.

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

Examples of the aminoplast resin include dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, fully alkylated methylated melamine, fully alkylated butylated melamine, fully alkylated isobutylated melamine, and completely. Melamine resins such as alkyl-based mixed etherified melamine, methylol-based methylated melamine, imino-based methylated melamine, methylol-based mixed etherified melamine, imino-based mixed etherified melamine; butylated benzoguanamine, methyl / ethyl mixed alkyl Examples thereof include benzoguanamines, methyl / butyl mixed alkylated benzoguanamines, guanamine resins such as butylated glycoluryl, and the like, but the present invention is not limited to such examples. These aminoplast resins may be used alone or in combination of two or more.

The aminoplast resin is, for example, manufactured by Mitsui Cytec Co., Ltd., trade names: Mycoat 506, Mycoat 1128, Cymel 232, Cymel 235, Cymel 254, Cymel 303, Cymel 325, Cymel 370, Cymel 771, Cymel 1170 and the like. It is readily available commercially.

The amount of aminoplast resin is usually 60/40 by weight ratio of the solid content of the polymer contained in the emulsion particles to the solid content of the aminoplast resin [solid content of the polymer / solid content of the aminoplast resin]. It is preferable to adjust the value to ~ 99/1.

In addition to the above-mentioned cross-linking agent, the object of the present invention is to provide a cross-linking agent such as a carbodiimide compound; a polyvalent metal compound represented by a zirconium compound, a zinc compound, a titanium compound, an aluminum compound and the like. It can be used within a range that is not hindered.

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

Examples of organic pigments include azo pigments such as benzidine and Hansa Yellow, azomethine pigments, methine pigments, anthraquinone pigments, phthalocyanine pigments such as phthalocyanine blue, perinone pigments, perylene pigments, diketopyrrolopyrrole pigments, thioindigo pigments, and iminoisoindrin. Pigments, iminoisoindolinone pigments, quinacridone pigments such as quinacridone red and quinacridone violet, flavantron pigments, indantron pigments, anthrapyrimidine pigments, carbazole pigments, monoallylide yellow, diaryride yellow, benzoimidazolone yellow, trill orange , Naftor orange, quinophthalone pigment and the like, but the present invention is not limited to such examples. These organic pigments may be used alone or in combination of two or more.

Examples of inorganic pigments include titanium dioxide, antimony trioxide, zinc flower, lithopon, lead white, red iron oxide, black iron oxide, iron oxide, chromium oxide green, carbon black, yellow lead, molybdenum red, and ferrocyanide. Flat pigments such as ferrous (Prussian blue), ultramarine, lead chromate, mica, clay, aluminum powder, talc, aluminum silicate, calcium carbonate, magnesium hydroxide, aluminum hydroxide , But, and the like, extender pigments such as barium sulfate and magnesium carbonate, but the present invention is not limited to such 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 non-volatile content of the aqueous resin dispersion is preferably 50 parts by weight or more, more preferably 60, from the viewpoint of improving the hiding power of the coating film formed from the aqueous resin dispersion of the present invention. It is more than parts by weight, preferably 190 parts by weight or less from the viewpoint of improving weather resistance.

The aqueous resin dispersion of the present invention may contain an aqueous resin dispersion other than the aqueous resin dispersion as long as the object of the present invention is not impaired. In that case, the aqueous resin dispersion may be contained. The average particle size of all the emulsion particles contained in the dispersion may be adjusted to be within the above range.

Further, the aqueous resin dispersion of the present invention can be used, for example, as long as 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, and 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 coated by itself in one layer, or may be coated by overcoating in two or more layers. When coating by overcoating two or more layers, only a part of the layers may be formed by the aqueous resin dispersion of the present invention, and all the layers may be formed by the aqueous resin dispersion of the present invention. May be good. The recoating is performed, for example, by applying the paint for the first layer (for example, the undercoat layer) to the object to be coated which has been subjected to the primer treatment or the sealer treatment and drying it, and then for the second layer (for example, the topcoat layer). Examples thereof include a method of overcoating and drying a paint, but the present invention is not limited to such a method. Examples of the method for 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 illustrations only.

The water-based resin dispersion of the present invention can be suitably used, for example, as a top coat (water-based paint) called a top coat to be applied to the surface of the exterior of a building or a ceramic building material.

The topcoat paint can be easily prepared, for example, by appropriately mixing one or more of the aqueous resin dispersion with one or more of a film forming aid, a defoaming agent, a pigment, a thickener, a matting agent, and the like. can do. Examples of the top coat paint include enamel paint and clear paint. The topcoat paint can be suitably used for the top coat.

The topcoat paint can be suitably used, for example, when painting on-site on the outer wall of a building, or can be suitably used for an inorganic building material such as a ceramic building material. Examples of ceramic building materials include roof tiles and outer wall materials. Ceramic building materials are made by adding an inorganic filler, fibrous material, etc. to a hydraulic adhesive that is a raw material for an inorganic cured product, molding the obtained mixture, and curing and curing the obtained molded product. can get. Examples of the inorganic building material constituting the exterior of the building include flexible board, calcium silicate board, gypsum slag parlite board, wood piece cement board, precast concrete board, ALC board, gypsum board and the like.

When applying the aqueous resin dispersion of the present invention or the topcoat paint to a building material, for example, a spray, a roller, a brush, a trowel or the like can be used.

When the water-based resin dispersion of the present invention or the topcoat paint is applied to the front surface and the back surface of the building material, the building material is heated as necessary from the viewpoint of efficiently producing the building material having coating films on both sides. You may leave it.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to such examples. In the following examples, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified.

Example 1
731 parts of deionized water was placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In the dropping funnel, 210 parts of deionized water, 60 parts of 25% aqueous solution of emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb SR-10], 90 parts of methyl methacrylate, 90 parts of styrene, 200 parts of cyclohexyl methacrylate, n-butyl. A pre-emulsion for first-stage dropping was prepared consisting of 10 parts of methacrylate, 100 parts of 2-ethylhexyl acrylate and 10 parts of n-butyl acrylate, and about 77 parts of the pre-emulsion for first-stage dropping was added into the flask and gently added. 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 a 5% ammonium persulfate aqueous solution were uniformly dropped into the flask over 120 minutes. After that, 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], and 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 Corporation, trade name: Adecaria Sorb SR-10], 45 parts of methyl methacrylate, and 30 parts of styrene. Pre-emulsion for second-stage dropping consisting of 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-pentamethylpiperidin. And 8 parts of a 5% aqueous solution of ammonium persulfate was 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 described above, the pH was 8.5.

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

Example 2
731 parts of deionized water was placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In the dropping funnel, 250 parts of deionized water, 70 parts of 25% aqueous solution of emulsifier [manufactured by ADEKA Co., Ltd., trade name: Adecaria Sorb SR-10], 110 parts of methyl methacrylate, 110 parts of styrene, 240 parts of cyclohexyl methacrylate, n-butyl. A pre-emulsion for first-stage dropping was prepared consisting of 10 parts of methacrylate, 120 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate and 1 part of acrylic acid, and about 77 parts of the pre-emulsion for first-stage dropping 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 remainder of the pre-emulsion for dropping and 10 parts of a 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 described 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 Corporation, trade name: Adecaria Sorb SR-10], and 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-pentamethylpiperidin 15 parts and 4-methacryloyl A pre-emulsifier for second-stage dropping consisting of 15 parts of oxy-2,2,6,6-tetramethylpiperidine and 6 parts of a 5% aqueous ammonium persulfate solution were uniformly added dropwise to the flask over 120 minutes. Then, when the pH of the contents of the flask was examined in the same manner as described above, the pH was 8.9.

After completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, the obtained reaction solution was cooled to room temperature, and filtered through a wire mesh of 300 mesh to obtain an aqueous resin dispersion having a pH of 8.6. Obtained. The content of the non-volatile content in this aqueous resin dispersion is 44.9%, and the content of the acid group-containing monomer (acrylic acid) in the monomer component is 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 placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In the dropping funnel, 340 parts of deionized water, 95 parts of 25% aqueous solution of emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb SR-10], 240 parts of methyl methacrylate, 110 parts of styrene, 260 parts of cyclohexyl methacrylate, n-butyl. A pre-emulsion for first-stage dropping was prepared consisting of 10 parts of methacrylate, 160 parts of 2-ethylhexyl acrylate and 20 parts of n-butyl acrylate, and about 77 parts of the pre-emulsion for first-stage dropping was added into the flask and gently added. 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 preemulsion for dropping and 12 parts of a 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 described above, the pH was 2.5.

After completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, followed by 80 parts of deionized water, 25 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb SR-10], and methyl methacrylate. Second-stage 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 preemulsion for use and 3 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 described above, the pH was 8.7.

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

Comparative Example 1
731 parts of deionized water was placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In the dropping funnel, 140 parts of deionized water, 40 parts of 25% aqueous solution of emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb 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, of which about 77 parts of the first-stage dropping pre-emulsion was added into the flask and nitrogen gas was gently added. The temperature was raised to 70 ° C. while blowing, and 5 parts of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. Then, the remainder of the pre-emulsion for dropping and 5 parts of a 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 described above, the pH was 2.6.

After completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, followed by 280 parts of deionized water, 80 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb SR-10], and methyl methacrylate. Two stages consisting of 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 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidin. A preemulsion for dropping the eyes and 10 parts of a 5% aqueous solution of ammonium persulfate 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 described above, the pH was 8.7.

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

Comparative Example 2
731 parts of deionized water was placed in a flask equipped with a dropping funnel, a stirrer, a nitrogen gas introduction tube, a thermometer and a reflux condenser. In the dropping funnel, 380 parts of deionized water, 110 parts of 25% aqueous solution of emulsifier [manufactured by ADEKA Corporation, 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, of which about 77 parts of the first-stage dropping pre-emulsion was added into the flask and nitrogen gas was gently added. The temperature was raised to 70 ° C. while blowing, and 5 parts of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. Then, the balance of the pre-emulsion for dropping and 14 parts of the 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 described above, the pH was 2.6.

After completion of the dropping, the contents of the flask were maintained at 70 ° C. for 60 minutes, followed by 40 parts of deionized water, 10 parts of a 25% aqueous solution of an emulsifier [manufactured by ADEKA Corporation, trade name: Adecaria Sorb SR-10], and 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 10 parts of 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidin. A pre-emulsion for dropping the eyes and two parts of a 5% aqueous solution of ammonium persulfate 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 described above, the pH was 8.7.

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

Next, as the physical properties of the aqueous resin dispersion obtained in each Example or each Comparative Example, the hot water whitening resistance, the critical film thickness and the weather resistance were evaluated based on the following methods. It should be noted that, in each physical property, if the evaluation of x is at least one, it is determined to be unacceptable.

(1) Warm water whitening resistance 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate [Chisso] as a film-forming aid in 100 parts of the aqueous resin dispersion obtained in each Example or Comparative Example. Made by Co., Ltd., product number: CS-12] 10 parts and antifoaming agent [San Nopco Ltd., trade name: Nopco 8034L] 0.5 parts were added, and a homodisper was used at a rotation speed of 1500 min ^-1 for 30 minutes. By stirring, a sample for evaluation was obtained.

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

The L value (L0) of the test plate obtained above was measured with a colorimeter [manufactured by Nippon Denshoku Kogyo Co., Ltd., trade name: spectroscopic colorimeter SE-2000], and the test plate was further heated to 50 ° C. After immersing it in the prepared warm water for 24 hours, it was pulled up from the warm water, the water was wiped off with a Kim towel [manufactured by Nippon Paper Crecia Co., Ltd.], and the L value (L1) was measured with the colorimeter 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 sample for evaluation)
2,2,4-trimethyl-1,3-pentanediol monoisobutyrate as a film-forming aid in 100 parts of the aqueous resin dispersion obtained in each Example or Comparative Example [manufactured by Chisso Co., Ltd., product number: CS-12] 10 parts was added, and after stirring with a homodisper at a rotation speed of 1500 min ^-1 for 10 minutes, 30 parts of white paste and an antifoaming agent [manufactured by San Nopco Ltd., trade name: Nopco 8034L] 0.5. A thickener [manufactured by ADEKA Corporation, trade name] so that the viscosity becomes 80 KU when measured at 25 ° C. using a Claves unit viscous meter (manufactured by Brookfield, product number: KU-1). : Adecanol UH-420] was added, and the mixture was stirred in that state for 30 minutes to obtain a sample.

The white paste contains 210 parts of deionized water, 60 parts of a dispersant [manufactured by Kao Corporation, trade name: Demol EP], and a dispersant [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Discoat N-. 14] 50 parts, wetting agent [Kao Corporation, trade name: Emargen LS-106] 10 parts, propylene glycol 60 parts, titanium oxide [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 limit film thickness and weather resistance were examined using the sample obtained above. The results are shown in Table 1.

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

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

(Weatherability)
Slate plate [manufactured by Japan Test Panel Co., Ltd., length: 70 mm, width: 150 mm, thickness: 6 mm] and sealer [manufactured by SK KAKEN Co., Ltd., product name: EX sealer] at 150 g / m ² by air spray. It was applied uniformly in an application amount and dried in an atmosphere of 23 ° C. for 1 week.

Next, the sample was applied with a 10 mil applicator, 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. 60 ° mirror surface gloss was measured with a gloss meter [Nippon Denshoku Kogyo Co., Ltd., product number: VG2000], and a weather resistance test was conducted for 500 hours under the following conditions. Measure the gloss of, and formula:
[Gloss retention rate (%)]
= [[Gloss after weathering test] ÷ [Gloss before weathering test]] × 100
The weather resistance was evaluated based on the following evaluation criteria.

[Test conditions for weather resistance test]
・ Testing machine: Metal weather [manufactured by Daipla Wintes Co., Ltd., product number: KU-R4]
-Irradiation: Irradiation for 4 hours in an atmosphere with a temperature of 65 ° C and a relative humidity of 50% (irradiation intensity: 80 mW / cm ² )
・ Wetness: 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 rate is 80% or more Δ: Gloss retention rate is 60% or more and less than 80% ×: Gloss retention rate is less than 60%

From the results shown in Table 1, it was found that all of the aqueous resin dispersions obtained in each example were excellent in warm water whitening resistance, critical film thickness and weather resistance as compared with each comparative example. Understand.

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 (7)

A method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles by emulsion-polymerizing a monomer component in multiple stages in the absence of a neutralizing agent .
As the monomer component used as the raw material of the emulsion particles, a monomer component having an acid group-containing monomer content of 0.3% by mass or less was used.
As the first-stage monomer component, a monomer component in an amount of 45 to 85% by mass of all the monomer components used in the emulsion polymerization is used, and the monomer component is emulsion-polymerized to adjust the pH. After preparing the aqueous resin dispersion of 2.2 to 2.8,
When the remaining monomer component is used as the monomer component of the second and subsequent stages, the monomer component containing the piperidyl group-containing monomer is used as the monomer component of the second and subsequent stages. The monomer component is emulsion-polymerized to prepare an aqueous resin dispersion containing emulsion particles having a glass transition temperature of the polymer of −40 to 7 ° C. and a pH of 8.5 to 10. A method for producing an aqueous resin dispersion. The method for producing an aqueous resin dispersion according to claim 1, wherein the first-stage monomer component is a monomer component containing methyl methacrylate. The method for producing an aqueous resin dispersion according to claim 1 or 2, wherein the second and subsequent monomer components are monomer components containing methyl methacrylate. The emulsion particles have an inner layer and an outer layer, and the weight ratio of the polymer constituting the inner layer to the polymer constituting the outer layer [polymer constituting the inner layer / polymer constituting the outer layer] is 55/45 to 85/15. The method for producing an aqueous resin dispersion according to any one of claims 1 to 3 . A method for producing an aqueous resin dispersion containing a plurality of layers of emulsion particles by emulsion polymerization of a monomer component in multiple stages .
As the monomer component used as the raw material of the emulsion particles, a monomer component having an acid group-containing monomer content of 0.3% by mass or less was used.
When a monomer component in an amount of 45 to 85% by mass of all the monomer components used in the emulsion polymerization is used as the first-stage monomer component, the first-stage monomer is used. A monomer component containing methyl methacrylate is used as a component, and the monomer component is emulsion-polymerized to prepare an aqueous resin dispersion having a pH of 2.2 to 2.8.
When the remaining monomer component is used as the monomer component of the second and subsequent stages, the monomer component containing methyl methacrylate and the piperidyl group-containing monomer as the monomer component of the second and subsequent stages is used. To prepare an aqueous resin dispersion containing emulsion particles having a glass transition temperature of -40 to 7 ° C. and a pH of 8.5 to 10 by emulsion polymerization of the monomer component. A method for producing an aqueous resin dispersion. The method for producing an aqueous resin dispersion according to claim 5 , wherein emulsion polymerization is carried out in the absence of a neutralizing agent. The emulsion particles have an inner layer and an outer layer, and the weight ratio of the polymer constituting the inner layer to the polymer constituting the outer layer [polymer constituting the inner layer / polymer constituting the outer layer] is 55/45 to 85/15. The method for producing an aqueous resin dispersion according to claim 5 or 6 .