Aqueous dispersion composition

Abstract

To provide an aqueous dispersion composition that is used for an aqueous coating liquid capable of film formation at room temperature, the aqueous coating liquid being capable of forming a coating film with improved stain resistance, weather resistance, and transparency.SOLUTION: Provided is an aqueous dispersion composition, comprising: an aqueous dispersion (A) of acrylic resin particles (a) comprising an acrylic polymer having a glass transition temperature of from -50 to 40°C as calculated according to the Fox equation; an aqueous dispersion (B) of polypropylene-based resin particles (b) having a melting point Tm of 50-90°C; an aqueous dispersion (C) of ultraviolet absorber-containing resin particles (c), where the cumulant average particle size of the resin particles (c) is 10-120 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous dispersion composition. [Background technology]

[0002] Plastics are used as the base material for a variety of components. However, some types of plastics lack sufficient weather resistance, which can lead to problems such as discoloration and decomposition of the base material during use. To prevent this problem, a technique is known in which the base material is coated with a resin containing an ultraviolet absorber.

[0003] For example, Patent Document 1 discloses an acrylic resin composition for coating, which contains an acrylic copolymer containing 1 to 15 mol % of repeating units having an ultraviolet absorbing group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-231304 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, an organic solvent is used as the solvent contained in the coating liquid, and it is desired to replace it with an aqueous solvent from the viewpoint of reducing the environmental load. However, compared with solvent-based coating solutions that use organic solvents, aqueous coating solutions that use aqueous solvents as solvents have poor film-forming properties at low temperatures (e.g., room temperature), and therefore usually require drying at high temperatures. On the other hand, if the glass transition temperature of the acrylic copolymer contained in the coating solution is lowered to improve film-forming properties at room temperature, there is a concern that the resulting coating film will be more susceptible to contamination. Furthermore, the coating film formed on the substrate is required to have high transparency.

[0006] Therefore, an object of the present invention is to provide an aqueous dispersion composition for use in an aqueous coating liquid that is capable of forming a film at room temperature and that can form a coating film with improved stain resistance, weather resistance, and transparency. [Means for solving the problem]

[0007] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that by using an aqueous dispersion composition comprising an aqueous dispersion (A) of acrylic resin particles (a) containing an acrylic polymer having a specific glass transition temperature, an aqueous dispersion (B) of polypropylene resin particles (b) having a specific melting point, and an aqueous dispersion (C) of ultraviolet absorber-containing resin particles (c) having a small particle size, it is possible to provide an aqueous coating liquid that can form a film at room temperature and that can form a coating film with improved contamination resistance, weather resistance, and transparency, and have completed the present invention.

[0008] That is, the present invention is as follows. [1] An aqueous dispersion (A) of acrylic resin particles (a) containing an acrylic polymer having a glass transition temperature of -50 to 40°C calculated based on the Fox equation; an aqueous dispersion (B) of polypropylene-based resin particles (b) having a melting point Tm of 50 to 90°C; and an aqueous dispersion (C) of ultraviolet absorber-containing resin particles (c), the resin particles (c) having a cumulant average particle size of 10 to 120 nm. [2] The aqueous dispersion composition according to [1], wherein the content of the ultraviolet absorber is 1 to 10 mass % relative to 100 mass % of the total nonvolatile content of the aqueous dispersions (A) to (C). [3] The water dispersion composition according to [1] or [2], wherein the mass ratio of the non-volatile content of the water dispersion (A) to the non-volatile content of the water dispersion (B) (non-volatile content of the water dispersion (A) / non-volatile content of the water dispersion (B)) is 25 / 75 to 75 / 25. [4] The aqueous dispersion composition according to any one of [1] to [3], wherein the content of the ultraviolet absorber in 100% by mass of the nonvolatile content of the aqueous dispersion (C) is 10 to 40% by mass. [5] The resin particles (c) contain structural units derived from a reactive nonionic emulsifier (e1), the emulsifier (e1) has an HLB value of 10 to 16, The structural unit derived from the emulsifier (e1) has a first block which is an ethylene oxide block in a side chain, and 3-4 The aqueous dispersion composition according to any one of [1] to [4], which has a second block which is an alkylene oxide block. [6] The aqueous dispersion composition according to any one of [1] to [7], wherein the cumulant average particle size of all resin particles contained in the aqueous dispersion composition is 30 to 250 nm. [7] A plastic coating liquid comprising the aqueous dispersion composition according to any one of [1] to [6]. [Effects of the Invention]

[0009] The aqueous dispersion composition of the present invention can provide an aqueous coating liquid that is capable of forming a film at room temperature and that can form a coating film with improved stain resistance, weather resistance, and transparency. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below, but the present invention is not limited thereto. Unless otherwise specified, in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B." Furthermore, "(meth)acrylic acid" means acrylic acid or methacrylic acid, and "(meth)acrylate" means acrylate or methacrylate. The same applies to terms such as "(meth)acryloxy" and "(meth)acryloyl." Furthermore, a "structural unit derived from a specific monomer" corresponds to a structure in which the carbon-carbon double bond of a specific monomer is replaced with a carbon-carbon single bond and two bonds bonded to each carbon. This structure may not only be a structure obtained by polymerizing a specific monomer, but may also be a structural unit derived from a specific monomer obtained by post-modification of a structure obtained by polymerizing a different monomer.

[0011] 1. Water dispersion (A) The aqueous dispersion composition of the present invention contains an aqueous dispersion (A) of acrylic resin particles (a) containing an acrylic polymer having a glass transition temperature (hereinafter sometimes referred to as calculated Tg) calculated based on the Fox equation of -50 to 40°C.

[0012] 1-1. Acrylic resin particles (a) The acrylic resin particles (a) contain an acrylic polymer as a resin component. The acrylic polymer preferably contains a monomer component containing a (meth)acrylic acid alkyl ester as a structural unit. In this specification, the term "monomer component" refers to a monomer having at least one ethylenically unsaturated double bond in the molecule, other than the reactive emulsifier described below. Examples of the monomer component constituting the acrylic polymer include, in addition to a (meth)acrylic acid alkyl ester, an alicyclic hydrocarbon group-containing (meth)acrylic acid ester, an aromatic hydrocarbon group-containing monomer, an acid group-containing monomer, a hydroxyl group-containing monomer, a nitrogen atom-containing monomer, a crosslinkable monomer, an ultraviolet absorbing monomer, and other monomers (P1). Preferred embodiments of the monomer component used in the acrylic polymer constituting the acrylic resin particles (a) (constituting the acrylic polymer) are described in detail below.

[0013] The acrylic polymer preferably has a structural unit derived from a (meth)acrylic acid alkyl ester. The (meth)acrylic acid alkyl ester is preferably (meth)acrylic acid C 1-20Alkyl esters are preferred, specifically methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, 2-pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, ) acrylate, 3-methyl-2-butyl (meth)acrylate, 3-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-hexyl (meth)acrylate, 3,3-dimethyl-2-butyl (meth)acrylate, 3-methyl-2-pentyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, 2,4-dimethyl-3-pentyl (meth)acrylate, n-heptyl (meth)acrylate, 2-heptyl (meth)acrylate acrylate, 2-methyl-3-hexyl (meth)acrylate, 3-heptyl (meth)acrylate, 5-methyl-2-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2,2-dimethyl-3-hexyl (meth)acrylate, 2,5-dimethyl-3-hexyl (meth)acrylate, 3-octyl (meth)acrylate, 4-octyl (meth)acrylate, 5-methyl Examples of the acrylic polymer constituting the acrylic resin particles (a) include methyl-2-heptyl (meth)acrylate, 5-methyl-3-heptyl (meth)acrylate, 6-methyl-2-heptyl (meth)acrylate, 6-methyl-3-heptyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, tridecyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, henicosyl (meth)acrylate, and tetracosyl (meth)acrylate. The acrylic polymer constituting the acrylic resin particles (a) may contain one or more structural units derived from a (meth)acrylic acid alkyl ester.

[0014] Among these, the (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters having a homopolymer glass transition temperature (Tg) of −20° C. or lower (hereinafter, sometimes referred to as low Tg (meth)acrylic acid alkyl esters), and methacrylic acid C 1-5 At least one selected from alkyl esters is also preferred. Structural units derived from low Tg (meth)acrylic acid alkyl esters and / or methacrylic acid C 1-5 By appropriately adjusting the content of structural units derived from alkyl esters, it becomes easy to adjust the calculated Tg of the acrylic polymer constituting the acrylic resin particles (a) to within the range described below.

[0015] In this specification, the "glass transition temperature of a homopolymer" may be, for example, the value (if multiple Tg values ​​are listed, the lowest value) described in "POLYMER HANDBOOK THIRD EDITION" (by J. BRANDRUP and EHIMMERGUT, 1989, published by John Wiley & Sons, Inc., pp. VI / 209-VI / 277). For compounds not described in "POLYMER HANDBOOK THIRD EDITION," a value (calculated value) determined by computer using commercially available glass transition temperature calculation software (e.g., "MATERIALS STUDIO" manufactured by Accelrys Software Inc., version 4.0.0.0, module: Synthia, calculation conditions: weight average molecular weight 100,000) may be used.

[0016] The Tg of the low Tg (meth)acrylic acid alkyl ester is −20° C. or lower, preferably −100 to −20° C., and more preferably −80 to −30° C. Examples of the low Tg (meth)acrylic acid alkyl ester include ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, and isononyl acrylate, and among these, n-butyl acrylate, 2-octyl acrylate, and 2-ethylhexyl acrylate are preferred.

[0017] Also, methacrylic acid C 1-5 As alkyl esters, methacrylic acid C 1-3 Alkyl esters are preferred, with methyl methacrylate being more preferred.

[0018] The content of the structural units derived from the (meth)acrylic acid alkyl ester (particularly, the low Tg (meth)acrylic acid alkyl ester and methacrylic acid C 1-5 The total content of structural units derived from alkyl esters is, for example, 20 to 90% by mass, preferably 30 to 80% by mass, and more preferably 40 to 70% by mass, based on 100% by mass of the acrylic polymer. The content of structural units derived from low Tg alkyl (meth)acrylate is, for example, 5 to 90 mass %, preferably 10 to 80 mass %, and more preferably 15 to 70 mass %, based on 100 mass % of the acrylic polymer.

[0019] The acrylic polymer may further contain structural units derived from an alicyclic hydrocarbon group-containing (meth)acrylic acid ester. By containing structural units derived from an alicyclic hydrocarbon group-containing (meth)acrylic acid ester, the water resistance and weather resistance of the resulting coating film (sometimes called a paint film) can be improved.

[0020] Specific examples of the alicyclic hydrocarbon group-containing (meth)acrylic acid ester include cycloalkyl (meth)acrylates such as cyclopropyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

[0021] Of these, cyclohexyl (meth)acrylate and isobornyl (meth)acrylate are preferred as the alicyclic hydrocarbon group-containing (meth)acrylic acid ester.

[0022] The acrylic polymer may contain one or more structural units derived from an alicyclic hydrocarbon group-containing (meth)acrylic acid ester.

[0023] The content of the structural units derived from the alicyclic hydrocarbon group-containing (meth)acrylic acid ester is, for example, 0 to 60% by mass, preferably 10 to 50% by mass, and more preferably 20 to 40% by mass, based on 100% by mass of the acrylic polymer. By containing the structural units in an amount equal to or greater than the lower limit, the water resistance and weather resistance of the resulting coating film can be improved, and by adjusting the content to be equal to or less than the upper limit, the toughness of the resulting coating film can be improved. The content of the structural units derived from the alicyclic hydrocarbon group-containing (meth)acrylic acid ester may be, for example, 0 to 120 parts by mass, but is preferably 20 to 100 parts by mass, and more preferably 40 to 70 parts by mass, relative to 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester.

[0024] The structural unit derived from the alicyclic hydrocarbon group-containing (meth)acrylic acid ester is 1-5 It is particularly preferred that the structural unit derived from the alicyclic hydrocarbon group-containing (meth)acrylic acid ester is contained in the acrylic polymer together with the structural unit derived from the alkyl ester. 1-5The amount is preferably 20 to 200 parts by mass, more preferably 40 to 150 parts by mass, and even more preferably 60 to 120 parts by mass, relative to 100 parts by mass of the structural unit derived from alkyl ester.

[0025] The acrylic polymer may further contain structural units derived from aromatic hydrocarbon group-containing monomers, which can improve the gloss of the resulting coating film.

[0026] Examples of the aromatic hydrocarbon group-containing monomer include styrene-based monomers, aryl (meth)acrylates, aralkyl (meth)acrylates, aryloxy group-containing alkyl (meth)acrylates, and maleimides having an aryl group.

[0027] The styrene-based monomers include styrene; C groups such as halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms); alkyl groups (e.g., methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, and tert-butyl groups); 1-4 alkyl group), vinyl group, alkoxysilyl group (e.g., tri-C such as trimethoxysilyl group, triethoxysilyl group, etc. 1-4 and styrene having one or more substituents such as an alkoxysilyl group. The substituent is preferably at least one selected from a halogen atom and an alkyl group. Specific examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, chlorostyrene, chloromethylstyrene, divinylbenzene, p-styryltrimethoxysilane, and 2-styrylethyltrimethoxysilane.

[0028] Examples of the aryl (meth)acrylate include aryl (meth)acrylates having an aryl group having 6 to 18 carbon atoms, such as phenyl (meth)acrylate, o-tolyl (meth)acrylate, m-tolyl (meth)acrylate, p-tolyl (meth)acrylate, 2,3-xylyl (meth)acrylate, 2,4-xylyl (meth)acrylate, 2,5-xylyl (meth)acrylate, 2,6-xylyl (meth)acrylate, 3,4-xylyl (meth)acrylate, 3,5-xylyl (meth)acrylate, 1-naphthyl (meth)acrylate, and 2-naphthyl (meth)acrylate.

[0029] Examples of the aralkyl (meth)acrylate include aralkyl (meth)acrylates 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.

[0030] Examples of the aryloxy group-containing alkyl(meth)acrylate include phenoxyethyl(meth)acrylate, phenoxypropyl(meth)acrylate, methylphenoxyethyl(meth)acrylate, and 2-naphthoethyl(meth)acrylate.

[0031] Examples of maleimides having an aryl group include N-phenylmaleimide.

[0032] Among these, as the aromatic hydrocarbon group-containing monomer, styrene-based monomers, aryl(meth)acrylates, and aralkyl(meth)acrylates are preferred, styrene-based monomers are more preferred, and styrene is particularly preferred.

[0033] The acrylic polymer may contain one or more structural units derived from aromatic hydrocarbon group-containing monomers.

[0034] The content of the structural units derived from the aromatic hydrocarbon group-containing monomer is, for example, 0 to 60% by mass, preferably 10 to 50% by mass, and more preferably 25 to 40% by mass, based on 100% by mass of the acrylic polymer. By incorporating the structural units derived from the aromatic hydrocarbon group-containing monomer in an amount equal to or greater than the lower limit, the gloss of the resulting coating film can be improved, and by adjusting the content to be equal to or less than the upper limit, the weather resistance of the resulting coating film can be further improved. The content of the structural units derived from the aromatic hydrocarbon group-containing monomer is, for example, 0 to 120 parts by mass, preferably 30 to 100 parts by mass, and more preferably 50 to 80 parts by mass, relative to 100 parts by mass of the structural units derived from the (meth)acrylic acid alkyl ester. Further, the structural unit derived from the low Tg (meth)acrylic acid alkyl ester is 1-5 It is also preferable to adjust the total content of the structural units derived from alkyl esters, the structural units derived from alicyclic hydrocarbon group-containing (meth)acrylic acid esters, and the structural units derived from aromatic hydrocarbon group-containing monomers, preferably from 20 to 400 parts by mass, more preferably from 50 to 350 parts by mass, per 100 parts by mass of the structural units derived from low-Tg (meth)acrylic acid alkyl esters.

[0035] The acrylic polymer preferably contains structural units derived from an acid group-containing monomer, which can improve the mechanical stability of the aqueous dispersion (A) and the toughness of the resulting coating film.

[0036] Specific examples of the acid group-containing monomer include unsaturated monocarboxylic acids such as (meth)acrylic acid, cinnamic acid, and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid; monoesters of unsaturated dicarboxylic acids such as maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monomethyl ester, and itaconic acid monobutyl ester; anhydrides of unsaturated dicarboxylic acids such as maleic anhydride; 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, and 2-acryloyloxyethyl hexahydrophthalic acid. Among these, unsaturated monocarboxylic acids are preferred, and (meth)acrylic acid is more preferred.

[0037] The acrylic polymer may contain one or more structural units derived from an acid group-containing monomer.

[0038] The content of the structural units derived from the acid group-containing monomer is preferably 0 to 10.0% by mass, more preferably 0.3 to 5.0% by mass, and even more preferably 0.8 to 2.5% by mass, based on 100% by mass of the acrylic polymer. By containing the structural units derived from the acid group-containing monomer in an amount equal to or greater than the lower limit, the mechanical stability of the aqueous dispersion (A) and the toughness of the resulting coating film can be improved, and by adjusting the content of the structural units derived from the acid group-containing monomer to be equal to or less than the upper limit, the occurrence of gelation during polymerization can be suppressed.

[0039] The acrylic polymer may further contain structural units derived from hydroxyl group-containing monomers, which can improve the adhesion of the resulting coating film to substrates.

[0040] Specific examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; and halo (meth)acrylates such as 3-chloro-2-hydroxypropyl (meth)acrylate. modified hydroxyalkyl (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate and 2-(meth)acryloyloxyethyl 2-hydroxyethyl phthalate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; hydroxyl group-containing vinyl monomers such as vinyl alcohol and allyl alcohol; and hydroxyl group-containing monomers having two or more polymerizable groups such as diprenyl glycerin ether.

[0041] Among these, the hydroxyl group-containing monomer is preferably a hydroxyalkyl(meth)acrylate, more preferably a hydroxyalkyl(meth)acrylate having a hydroxyalkyl group with 1 to 4 carbon atoms, and even more preferably a hydroxyalkyl(meth)acrylate having a hydroxyalkyl group with 2 to 4 carbon atoms.

[0042] The acrylic polymer may contain one or more structural units derived from a hydroxyl group-containing monomer.

[0043] The content of the structural units derived from the hydroxyl group-containing monomer is preferably 0 to 20% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.1 to 5% by mass, based on 100% by mass of the acrylic polymer. By containing the structural units derived from the hydroxyl group-containing monomer in an amount equal to or greater than the lower limit, the adhesion of the resulting coating film to the substrate can be improved, and by adjusting the content of the structural units derived from the hydroxyl group-containing monomer to be equal to or less than the upper limit, the generation of aggregates during polymerization can be suppressed.

[0044] The acrylic polymer may further contain a structural unit derived from a nitrogen-containing monomer, which can improve the adhesion of the resulting coating film to a substrate.

[0045] The nitrogen atom-containing monomer is a monomer having at least a substituent containing a nitrogen atom as a constituent member and a polymerizable unsaturated group in the molecule (however, it does not have an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an acid group, or a hydroxyl group). Examples of the nitrogen atom-containing monomer include a nitrogen-based heterocycle-containing monomer, an amino group-containing monomer, and an amide group-containing monomer. Note that, in this specification, a monomer that is an amino group-containing monomer or an amide group-containing monomer but contains a nitrogen-based heterocycle is referred to as a nitrogen-based heterocycle-containing monomer.

[0046] Specific examples of the nitrogen-based heterocycle-containing monomer include vinyl lactam monomers such as N-methylvinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinyl-2-pyrrolidone, and N-(meth)acryloylpyrrolidone; maleimide monomers such as maleimide; piperidyl(meth)acrylic monomers such as 2,2,6,6-tetramethyl-4-piperidyl(meth)acrylate and 1,2,2,6,6-pentamethyl-4-piperidyl(meth)acrylate; (meth)acrylic Examples thereof include aziridinyl group-containing (meth)acrylic monomers such as acrylyl aziridine and 2-aziridinylethyl (meth)acrylate; and addition-polymerizable oxazolines such as 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, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0047] Specific examples of the amino group-containing monomer include amino group-containing (meth)acrylic monomers such as N,N-dimethylaminomethyl (meth)acrylate and N,N-dimethylaminoethyl (meth)acrylate.

[0048] Examples of the amide group-containing monomer include (meth)acrylamide-based monomers such as (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-butoxymethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropylacrylamide, and diacetone acrylamide.

[0049] As the nitrogen atom-containing monomer, a nitrogen-based heterocycle-containing monomer is preferred, and a piperidyl(meth)acrylic monomer is more preferred. In particular, from the viewpoint of improving light stability, a nitrogen atom-containing monomer having a hindered amine structure is preferred. As such a monomer, a monomer having a 2,2,6,6-tetraalkylpiperidine ring structure and a polymerizable unsaturated group (e.g., (meth)acryloyl group, vinyl group) in the molecule is preferred, a monomer having a 2,2,6,6-tetramethylpiperidine ring structure and a polymerizable unsaturated group (e.g., (meth)acryloyl group, vinyl group) is more preferred, and 2,2,6,6-tetramethyl-4-piperidyl(meth)acrylate and 1,2,2,6,6-pentamethyl-4-piperidyl(meth)acrylate are even more preferred.

[0050] The acrylic polymer may contain one or more structural units derived from a nitrogen atom-containing monomer.

[0051] The content of the structural units derived from the nitrogen atom-containing monomer is preferably 0 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 4% by mass, based on 100% by mass of the acrylic polymer. By containing the structural units derived from the nitrogen atom-containing monomer in an amount equal to or greater than the lower limit, the adhesion of the resulting coating film to the substrate can be improved, and by adjusting the content of the structural units derived from the nitrogen atom-containing monomer to be equal to or less than the upper limit, the generation of aggregates during polymerization can be suppressed.

[0052] The acrylic polymer may further contain a structural unit derived from a crosslinkable monomer, which can improve the durability and weather resistance of the resulting coating film.

[0053] The crosslinkable monomer may be any monomer that does not contain an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an acid group, a hydroxyl group, or a substituent containing a nitrogen atom as a constituent, and that has a crosslinkable functional group and a polymerizable unsaturated group in the molecule. Examples of the crosslinkable functional group include a polymerizable unsaturated group, an epoxy group, and a hydrolyzable silyl group. The hydrolyzable silyl group refers to a silyl group to which a hydrolyzable group (e.g., an alkoxy group, a halogen atom, etc.) is bonded.

[0054] Examples of crosslinkable monomers include monomers having two or more polymerizable unsaturated groups, silane coupling agents having a hydrolyzable silyl group and a polymerizable unsaturated group, and epoxy group-containing crosslinkable monomers having an epoxy group and a polymerizable unsaturated group (but excluding hydrolyzable silyl groups).

[0055] Specific examples of the monomer having two or more polymerizable unsaturated groups include: di(meth)acrylates of alkanediols having 1 to 10 carbon atoms, such as 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, and 1,9-nonanediol di(meth)acrylate; DiC such as diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate 2-4 Alkylene glycol di(meth)acrylate; Poly-C copolymers having 2 to 4 carbon atoms with an added mole number of 2 to 50 alkylene oxides, such as polyethylene glycol di(meth)acrylate having an added mole number of ethylene oxide of 2 to 50 and polypropylene glycol di(meth)acrylate having an added mole number of propylene oxide of 2 to 50. 2-4 Alkylene glycol di(meth)acrylate; tri(meth)acrylates of trihydric alcohols having 1 to 10 carbon atoms, such as ethoxylated glycerin tri(meth)acrylate, propylene oxide-modified glycerol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and trimethylolpropane triethoxytri(meth)acrylate; tetra(meth)acrylates of tetrahydric alcohols having 1 to 10 carbon atoms, such as pentaerythritol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate; hexa(meth)acrylates of hexahydric alcohols having 1 to 10 carbon atoms, such as dipentaerythritol hexa(meth)acrylate; 2-(2'-vinyloxyethoxyethyl)(meth)acrylate; and the like.

[0056] Specific examples of the silane coupling agent include (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, and 3-(meth)acryloxyethoxypropyltrimethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; and epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0057] Specific examples of the epoxy group-containing crosslinkable monomer include epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, α-methylglycidyl (meth)acrylate, and 2-glycidyloxyethyl (meth)acrylate; epoxy group-containing vinyl monomers such as allyl glycidyl ether; and the like.

[0058] The acrylic polymer may contain one or more structural units derived from a crosslinkable monomer.

[0059] The content of the structural units derived from the crosslinkable monomer is, for example, 0 to 20% by mass, and preferably 0.05 to 10% by mass, relative to 100% by mass of the acrylic polymer. By containing the structural units derived from the crosslinkable monomer in an amount equal to or greater than the lower limit, the durability and weather resistance of the resulting coating film can be improved, and by adjusting the content of the structural units derived from the crosslinkable monomer to be equal to or less than the upper limit, gelation during polymerization can be suppressed.

[0060] The acrylic polymer may further have a structural unit derived from an ultraviolet-absorbing monomer. In this specification, a monomer having an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an acid group, a hydroxyl group, a nitrogen atom, or two or more crosslinkable functional groups but having ultraviolet absorbing properties is referred to as an ultraviolet-absorbing monomer.

[0061] The ultraviolet absorbing monomer capable of constituting the acrylic polymer is the same as the polymerizable ultraviolet absorber (i) described later for the acrylic resin particles (c), and preferred embodiments thereof are also the same. The acrylic resin particles (a) may contain one or more structural units derived from the ultraviolet absorbing monomer.

[0062] However, it is difficult to incorporate a large amount of structural units derived from ultraviolet-absorbing monomers into the acrylic polymer due to the insufficient solubility of the ultraviolet-absorbing monomers in water or monomer components and the insufficient dispersibility of the ultraviolet-absorbing monomers. Therefore, the content of the structural units derived from ultraviolet-absorbing monomers may be, for example, 0 to 5% by mass, or 0 to 1% by mass, relative to 100% by mass of the acrylic polymer.

[0063] The acrylic polymer may further contain structural units derived from monomer components other than the (meth)acrylic acid alkyl ester, the alicyclic hydrocarbon group-containing (meth)acrylic acid ester, the aromatic hydrocarbon group-containing monomer, the acid group-containing monomer, the hydroxyl group-containing monomer, the nitrogen atom-containing monomer, the crosslinkable monomer, and the ultraviolet absorbing monomer (hereinafter, referred to as other monomers (P1)), but it is preferable that the acrylic polymer does not contain such structural units.

[0064] Specific examples of the other monomer (P1) include: Fluoroalkyl (meth)acrylates such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate; alkoxyalkyl group-containing (meth)acrylates such as methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and trimethylolpropane tripropoxy (meth)acrylate; carbonyl group-containing (meth)acrylates such as (meth)acryloxyalkylpropenal, acetonyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate acetylacetate, butanediol-1,4-acrylate acetylacetate, and 2-(acetoacetoxy)ethyl (meth)acrylate; vinyl monomers such as vinyl acetate, vinyl chloride, and vinyl benzoate; Olefin monomers such as ethylene and propylene; and the like.

[0065] The acrylic polymer may contain one or more structural units derived from other monomers (P1).

[0066] The content of the structural units derived from the other monomer (P1) in 100% by mass of the acrylic polymer is, for example, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and may be 0% by mass.

[0067] The total content of structural units derived from the monomer components (specifically, the (meth)acrylic acid alkyl ester, the alicyclic hydrocarbon group-containing (meth)acrylic acid ester, the aromatic hydrocarbon group-containing monomer, the acid group-containing monomer, the hydroxyl group-containing monomer, the nitrogen atom-containing monomer, the crosslinkable monomer, the ultraviolet absorbing monomer, and the other monomer (P1)) is preferably 70 to 100 mass%, more preferably 80 to 99 mass%, and even more preferably 90 to 98 mass%, based on 100 mass% of the acrylic polymer.

[0068] The acrylic polymer preferably further contains a structural unit derived from a reactive emulsifier. The inclusion of a structural unit derived from a reactive emulsifier can improve the dispersion stability of the aqueous dispersion (A). The structural unit derived from a reactive emulsifier can be introduced into the acrylic resin particles (a) by using a reactive emulsifier as an emulsifier during emulsion polymerization to synthesize the acrylic resin particles (a). In this specification, the reactive emulsifier refers to a monomer having a polymerizable unsaturated group, a hydrophilic group, and a hydrophobic group, and may contain one or more polymerizable unsaturated groups per molecule.

[0069] Examples of the polymerizable unsaturated group include a (meth)acryloyl group and a vinyl group. The hydrophilic group includes groups known as emulsifiers (surfactants), and preferred examples include anionic groups such as a sulfonic acid group or its salt, a phosphoric acid group or its salt, a sulfate ester group or its salt, and a phosphoric acid ester group or its salt; and nonionic groups such as a polyether group. Among the anionic groups, preferred are sulfonic acid groups or their salts, and sulfate ester groups or their salts, with sulfonates and salts of sulfate ester groups being more preferred. Examples of salts of the anionic groups include alkali metal salts such as sodium salts and potassium salts, and ammonium salts. The hydrophobic group may also be a group known as an emulsifier (surfactant), and preferred examples thereof include alkyl or alkylene groups (particularly alkyl or alkylene groups having about 8 to 40 carbon atoms), aryl group-containing hydrocarbon groups (particularly hydrocarbon groups having a phenyl group and having about 12 to 40 carbon atoms), and polycyclic phenyl groups.

[0070] Specific examples of reactive emulsifiers include: Propenyl-alkyl sulfosuccinate salts, (meth)acrylic acid polyoxyethylene sulfonate salts, (meth)acrylic acid polyoxyethylene phosphonate salts (e.g., Sanyo Chemical Industries, Ltd., trade name: Eleminol RS-30, etc.), polyoxyethylene alkylpropenylphenyl ether sulfonate salts (e.g., Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon HS-10, etc.), sulfonate salts of allyloxymethyl alkyloxypolyoxyethylene (e.g., Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon KH-10, etc.), polyoxyethylene styrenated propenyl phenyl ether sulfate ester salts (e.g., reactive anionic emulsifiers such as, for example, Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon AR-10, etc.), allyloxymethylnonylphenoxyethyl hydroxypolyoxyethylene sulfonate salts (for example, ADEKA Corporation, trade name: Adeka Reasoap SE-10, etc.), allyloxymethylalkoxyethyl hydroxypolyoxyethylene sulfate salts (for example, ADEKA Corporation, trade name: Adeka Reasoap SR-10, SR-20, SR-30, etc.), and bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salts (for example, Nippon Nyukazai Co., Ltd., trade name: Antox MS-60, etc.); and reactive nonionic emulsifiers such as polyoxyethylene styrenated propenyl phenyl ether (e.g., manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon AN-10, etc.), allyloxymethyl alkoxyethyl hydroxypolyoxyethylene (e.g., manufactured by ADEKA Corporation, trade name: Adeka Reasop ER-20, etc.), polyoxyethylene alkylpropenyl phenyl ether (e.g., manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon RN-20, etc.), allyloxymethyl nonylphenoxyethyl hydroxypolyoxyethylene (e.g., manufactured by ADEKA Corporation, trade name: Adeka Reasop NE-10, etc.), and polyoxyalkylene alkenyl ether (e.g., manufactured by Kao Corporation, trade name: Latemul PD-420, PD-430).

[0071] The reactive emulsifier is preferably a reactive anionic emulsifier, and more preferably polyoxyethylene styrenated propenyl phenyl ether sulfate, allyloxymethyl alkoxyethyl hydroxypolyoxyethylene sulfate, or bis(polyoxyethylene polycyclic phenyl ether) methacrylated sulfonate.

[0072] The acrylic polymer may contain one or more structural units derived from a reactive emulsifier.

[0073] The content of the structural units derived from the reactive emulsifier is, for example, 0 to 10% by mass, preferably 1.0 to 8% by mass, and more preferably 1.5 to 5% by mass, based on 100% by mass of the acrylic polymer. By incorporating the structural units derived from the reactive emulsifier in an amount equal to or greater than the lower limit, the dispersion stability of the aqueous dispersion (A) can be improved. Furthermore, by adjusting the content of the structural units derived from the reactive emulsifier to be equal to or less than the upper limit, the water resistance of the resulting coating film can be improved. It is also preferable to adjust the content of the structural units derived from the reactive emulsifier in 100% by mass of the nonvolatile content of the aqueous dispersion (A) to fall within the above range.

[0074] Aspect 1 is preferred in which the acrylic polymer contains at least a structural unit derived from a (meth)acrylic acid alkyl ester, Structural units derived from low Tg (meth)acrylic acid alkyl ester and methacrylic acid C 1-5 Aspect 2, which includes at least one structural unit selected from the group consisting of a structural unit derived from an alkyl ester, a structural unit derived from an alicyclic hydrocarbon group-containing (meth)acrylic acid ester, and a structural unit derived from an aromatic hydrocarbon group-containing monomer, is more preferred. Furthermore, in the above-mentioned embodiment 1 or embodiment 2, embodiment 3 is more preferable, in which the polymer further contains a structural unit derived from an acid group-containing monomer and / or a structural unit derived from a hydroxyl group-containing monomer. In addition, in any one of the above-mentioned aspects 1 to 3, aspect 4 is also preferred, in which a structural unit derived from a crosslinkable monomer is further contained. In addition, in any one of the above-mentioned aspects 1 to 4, aspect 5 is also preferred, in which a structural unit derived from a nitrogen atom-containing monomer is further contained. In addition, in any of the above-mentioned aspects 1 to 5, aspect 6 is also preferred, in which a structural unit derived from a reactive emulsifier is further contained.

[0075] The calculated Tg (°C) of the acrylic polymer contained in the acrylic resin particles (a) is -50 to 40°C, preferably -30 to 35°C. Usually, when resin particles having a relatively low calculated Tg (for example, less than 0°C) are used, the room temperature film-forming ability is good, but the stain resistance of the resulting coating film tends to deteriorate. On the other hand, when resin particles having a relatively high calculated Tg (for example, 0°C or higher) are used, the stain resistance is improved, but the room temperature film-forming ability tends to deteriorate. In the present invention, by using an aqueous dispersion (A) containing acrylic resin particles (a) having a Tg of -50 to 40°C and using the aqueous dispersions (B) and (C) described below in combination, it is possible to achieve both room temperature film-forming ability and stain resistance. The calculated Tg (°C) of the acrylic polymer is calculated from the Fox equation shown below. A This can be calculated by converting from (K). 1 / Tg A =Σ(Wm / Tgm) / 100 [In the formula, Tg A represents the glass transition temperature (absolute temperature: K) of the acrylic polymer, Wm represents the content (mass%) of monomer m in all monomer components constituting the acrylic polymer, and Tgm represents the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.]

[0076] The content of the acrylic polymer in the acrylic resin particles (a) is preferably 70 to 100% by mass, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It is also preferable to adjust the content of the acrylic polymer in the non-volatile content of the aqueous dispersion (A) to fall within the above range.

[0077] The acrylic resin particles (a) may further contain an ultraviolet absorber that does not have a polymerizable unsaturated group (i.e., an ultraviolet absorber other than the ultraviolet-absorbing monomer; hereinafter, this may be referred to as a "non-polymerizable ultraviolet absorber (ii)"). The non-polymerizable ultraviolet absorber (ii) that the acrylic resin particles (a) may contain is the same as the non-polymerizable ultraviolet absorber (ii) described later for the acrylic resin particles (c), and preferred embodiments thereof are also the same. The acrylic resin particles (a) may contain one or more non-polymerizable ultraviolet absorbers (ii).

[0078] The non-polymerizable UV absorber (ii) can be incorporated into the acrylic resin particles (a), for example, by incorporating the non-polymerizable UV absorber (ii) into the core portion of core-shell acrylic resin particles (a). Specifically, in the emulsion polymerization described below, the monomer components constituting the core portion are emulsion-polymerized in an aqueous solvent in the presence of the non-polymerizable UV absorber (ii), an emulsifier, and a polymerization initiator to synthesize a resin (core portion) that retains the non-polymerizable UV absorber (ii). The monomer components constituting the shell portion and an emulsifier are then added thereto and further polymerized, thereby incorporating the non-polymerizable UV absorber (ii) into the acrylic resin particles (a). However, it is difficult to incorporate a large amount of the non-polymerizable UV absorber (ii) into the acrylic resin particles (a) due to the insufficient solubility of the non-polymerizable UV absorber (ii) in water and monomer components and the insufficient dispersibility of the non-polymerizable UV absorber (ii). Therefore, the content of the non-polymerizable ultraviolet absorber (ii) is, for example, less than 10% by mass, preferably 5% by mass or less, more preferably 1% by mass or less, and may be 0% by mass or 0.1% by mass or more, relative to 100% by mass of the acrylic resin particles (a). It is also preferable to adjust the content of the non-polymerizable ultraviolet absorber (ii) relative to 100% by mass of the non-volatile content of the aqueous dispersion (A) to be within the above range. The total content of the ultraviolet absorber (specifically, the total content of the structural units derived from the ultraviolet-absorbing monomer and the non-polymerizable ultraviolet absorber (ii)) in 100% by mass of the acrylic resin particles (a) is, for example, less than 10% by mass, preferably 5% by mass or less, more preferably 1% by mass or less, and may be 0% by mass or 0.1% by mass or more. It is also preferable to adjust the total content of the ultraviolet absorber in 100% by mass of the non-volatile content of the aqueous dispersion (A) to fall within the above range.

[0079] The shape of the acrylic resin particles (a) is not particularly limited, but is usually spherical. The shape can be measured using a transmission electron microscope or a scanning electron microscope. The acrylic resin particles (a) may have a single-layer structure or a multi-layer structure (e.g., a core-shell structure), but a single-layer structure is preferred.

[0080] The average particle size of the acrylic resin particles (a) is preferably 80 to 400 nm, more preferably 100 to 300 nm, and even more preferably 100 to 250 nm, and may be 120 to 250 nm or 125 to 250 nm. By adjusting the average particle size to the above-mentioned lower limit or more, the nonvolatile content of the aqueous dispersion (A) can be improved in a low-viscosity state. By adjusting the average particle size to the above-mentioned upper limit or less, the transparency of the resulting coating film can be further improved. In this specification, the average particle size of the resin particles may be the cumulant average particle size measured by dynamic light scattering at a measurement temperature of 25°C.

[0081] The acrylic resin particles (a) may be used alone or in combination of two or more kinds.

[0082] 1-2. Composition of aqueous dispersion (A) The aqueous dispersion (A) contains the acrylic resin particles (a), and specifically, is a dispersion in which the acrylic resin particles (a) are dispersed in an aqueous solvent. The amount of nonvolatile matter in 100% by mass of the aqueous dispersion (A) is preferably from 10 to 80% by mass, more preferably from 20 to 70% by mass, and even more preferably from 30 to 60% by mass, from the viewpoint of handleability. The content of the acrylic resin particles (a) in the nonvolatile content of the aqueous dispersion (A) is preferably 80 to 100% by mass, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0083] In this specification, the non-volatile content of the aqueous dispersion can be calculated by weighing 1 g of the aqueous dispersion, drying it in a hot air dryer at 130°C for 30 minutes, and calculating the non-volatile content according to the following formula using the residue obtained as the non-volatile content, as described in the Examples. [Non-volatile content in aqueous dispersion (mass%)] = ([mass of residue] / [mass of aqueous dispersion (1 g)]) × 100

[0084] The aqueous solvent contained in the aqueous dispersion (A) may be water or a mixed solvent of water and a water-soluble organic solvent. A water-soluble organic solvent refers to an organic solvent that dissolves in water at a concentration of 0.01% by mass or more at room temperature and normal pressure. In this specification, room temperature means 25°C, and normal pressure means 1 atmosphere. The water content in the aqueous solvent is preferably 10 to 100% by mass, more preferably 25% by mass or more, even more preferably 60% by mass or more, and particularly preferably 90% by mass or more. The remainder is preferably the water-soluble organic solvent. As the water, ion-exchanged water (deionized water), distilled water, pure water, etc. can be used.

[0085] Specific examples of the water-soluble organic solvent include: Lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and tert-butyl alcohol (preferably C 1-4 alcohol); Glycols such as propylene glycol, 1,3-propanediol, 1,2-hexanediol, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; Glycerin; Ethylene glycol monoalkyl ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, etc.) 1-4 alkylene glycol monoalkyl ethers (preferably C alkyl ethers), propylene glycol monoalkyl ethers (e.g., propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, propylene glycol monoisobutyl ether, etc.), 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Diethylene glycol monoalkyl ethers (e.g., diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, etc.) 1-4 alkyl ether), dipropylene glycol monoalkyl ether (for example, dipropylene glycol mono C alkyl ethers such as dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, and dipropylene glycol monoisobutyl ether), etc. 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Polyethylene glycol monoalkyl ethers (e.g., polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol monopropyl ether, polyethylene glycol monoisopropyl ether, polyethylene glycol monobutyl ether, polyethylene glycol monoisobutyl ether, etc.) 1-4 alkyl ether), polypropylene glycol monoalkyl ether (for example, polypropylene glycol mono C alkyl ethers such as polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monopropyl ether, polypropylene glycol monoisopropyl ether, polypropylene glycol monobutyl ether, and polypropylene glycol monoisobutyl ether), etc. 2-4 Alkylene glycol mono C 1-4 alkyl ethers); Heterocycles such as 2-pyrrolidone and N-methyl-2-pyrrolidone; Ketones such as acetone and methyl ethyl ketone; The number of moles of alkylene oxide added to the polyalkylene glycol monoalkyl ether is preferably 2 to 10, and more preferably 2 to 4. These water-soluble organic solvents may be used alone or in combination of two or more kinds.

[0086] From the viewpoint of handleability, the content of the aqueous solvent in the aqueous dispersion (A) is preferably 1 to 500 parts by mass, more preferably 5 to 300 parts by mass, and even more preferably 10 to 200 parts by mass, per 100 parts by mass of the acrylic resin particles (a).

[0087] The aqueous dispersion (A) may contain additives such as chain transfer agents such as tert-dodecyl mercaptan, pH buffers, pH adjusters, chelating agents, etc. The amount of the additives cannot be determined in general because it varies depending on the type and purpose, but is usually, for example, 0 to 5 mass%, preferably 0.01 to 4 mass%, more preferably 0.1 to 3 mass%, relative to 100 mass% of the nonvolatile content in the aqueous dispersion (A).

[0088] 1-3. Method for producing aqueous dispersion (A) The aqueous dispersion (A) is preferably prepared by emulsion polymerization of the above-mentioned monomer components in an aqueous solvent in the presence of an emulsifier, a polymerization initiator, and, if necessary, a non-polymerizable UV absorber (ii) and other additives. The types, combinations, and blending ratios of the preferred monomer components used in emulsion polymerization are the same as those described above for the preferred monomer components constituting the acrylic polymer contained in the acrylic resin particles (a). Specific means and conditions for emulsion polymerization can be appropriately selected and adopted from means and techniques used in conventionally known emulsion polymerization methods. A preferred production method is described in detail below.

[0089] As the emulsifier used in the emulsion polymerization, it is preferable to use the reactive emulsifier described above. Specific examples of the reactive emulsifier are as described above, and the preferred embodiments thereof are also the same. In addition to the reactive emulsifier, an emulsifier having no polymerizable unsaturated group (hereinafter referred to as a non-reactive emulsifier) ​​may be used. Examples of the non-reactive emulsifier that can be used include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, and polymeric emulsifiers that have no polymerizable unsaturated group. These emulsifiers may be used alone or in combination of two or more.

[0090] Examples of the anionic emulsifier having no polymerizable unsaturated group include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate; alkyl sulfonate salts such as ammonium dodecyl sulfonate and sodium dodecyl sulfonate; alkyl aryl sulfonate salts such as ammonium dodecyl benzene sulfonate and sodium dodecyl naphthalene sulfonate; polyoxyethylene alkyl sulfate salts; polyoxyethylene alkyl aryl sulfate salts; dialkyl sulfosuccinates; aryl sulfonic acid formalin condensates; fatty acid salts such as ammonium laurate and sodium stearylate; and the like. Examples of the nonionic emulsifiers that do not have a polymerizable unsaturated group include polyoxyethylene alkyl ethers; polyoxyethylene alkylaryl ethers; condensates of polyethylene glycol and polypropylene glycol; sorbitan fatty acid esters; polyoxyethylene sorbitan fatty acid esters; fatty acid monoglycerides; polyamides; and condensation products of ethylene oxide and aliphatic amines. Examples of the cationic emulsifier having no polymerizable unsaturated group include alkyl ammonium salts such as dodecyl ammonium chloride; and the like. Examples of the amphoteric emulsifiers having no polymerizable unsaturated group include betaine ester emulsifiers. Examples of the polymeric emulsifier that does not have a polymerizable unsaturated group include poly(meth)acrylates such as sodium polyacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyhydroxyalkyl(meth)acrylates such as polyhydroxyethyl acrylate; and copolymers containing one or more of the polymerizable monomers that constitute these polymers as copolymerization components.

[0091] In the total of 100% by mass of the emulsifiers used in the emulsion polymerization, the proportion of the reactive emulsifier is preferably 50 to 100% by mass, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. By adjusting the proportion of the reactive emulsifier within the above range, the polymerization stability and the water resistance of the resulting coating film tend to be improved.

[0092] The amount of the emulsifier used is, for example, preferably 0.5 to 10 parts by mass, more preferably 1.0 to 8 parts by mass, and even more preferably 1.5 to 5 parts by mass, relative to 100 parts by mass of the monomer component. If necessary, protective colloids can be used alone or together with the emulsifier.

[0093] The polymerization initiator used in the emulsion polymerization is not limited, but examples include azo-based polymerization initiators such as azobisisobutyronitrile, 2,2-azobis(2-methylbutyronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-diaminopropane) hydrochloride, 4,4-azobis(4-cyanovaleric acid), and 2,2-azobis(2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; and peroxide-based polymerization initiators such as hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and ammonium peroxide. These polymerization initiators may be used alone or in combination of two or more.

[0094] The amount of the polymerization initiator used in the emulsion polymerization is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the monomer components.

[0095] If necessary, known additives such as pH buffers, chelating agents, chain transfer agents such as t-dodecyl mercaptan, film-forming aids, and regulators for promoting decomposition of the polymerization initiator (e.g., reducing agents such as sodium hydrogen sulfite, and transition metal salts such as ferrous sulfate) may be added to the reaction system in the emulsion polymerization. The amount of the additive used cannot be determined in general because it varies depending on the type of additive, but it may be, for example, 0.01 to 5% by mass, and preferably 0.1 to 3% by mass, per 100 parts by mass of the monomer components.

[0096] The reaction temperature during the emulsion polymerization can be appropriately set taking into consideration the blending ratio of the monomer components, the type of polymerization initiator, and the like. The reaction temperature is, for example, 0 to 100°C, preferably 50 to 95°C, and more preferably 60 to 90°C, and the reaction time is, for example, 0.5 to 30 hours, preferably 1 to 20 hours, and more preferably 3 to 10 hours. The reaction pressure is also not particularly limited and may be normal pressure (atmospheric pressure), reduced pressure, or increased pressure. The polymerization reaction is desirably carried out in an atmosphere of an inert gas such as nitrogen gas.

[0097] Examples of the aqueous solvent used in the emulsion polymerization include the same aqueous solvents as those described as the aqueous solvent contained in the aqueous dispersion (A), and the preferred embodiments thereof are also the same. The amount of the aqueous solvent used when carrying out the emulsion polymerization is not limited, but is preferably 1 to 500 parts by mass, more preferably 5 to 300 parts by mass, and even more preferably 10 to 200 parts by mass, per 100 parts by mass of the monomer components.

[0098] Specific examples of the emulsion polymerization include a monomer dropping polymerization method, a pre-emulsion dropping polymerization method, a seed polymerization method, and a multi-stage polymerization method.

[0099] As the aqueous dispersion (A), the reaction liquid obtained in the emulsion polymerization can be used as it is.

[0100] The pH of the aqueous dispersion (A) is preferably 3 to 10, more preferably 4 to 9.5, and even more preferably 5 to 9.5. By adjusting the pH of the aqueous dispersion (A) to the above lower limit or more, the storage stability and mechanical stability of the aqueous dispersion (A) can be improved, and by adjusting the pH of the aqueous dispersion (A) to the above upper limit or less, the water resistance can be improved and the generation of odor can be suppressed.

[0101] To adjust the pH of the aqueous dispersion (A) within the above-mentioned range, a pH adjuster may be used as needed. Specifically, a pH adjuster may be added as needed after the emulsion polymerization. Specific examples of such pH adjusters include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; and water-soluble organic amines such as dimethylaminoethanol, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. These pH adjusters may be used alone or in combination of two or more.

[0102] 2. Water dispersion (B) The aqueous dispersion composition of the present invention contains an aqueous dispersion (B) of polypropylene resin particles (b) having a melting point Tm of 50 to 90°C.

[0103] 2-1. Polypropylene resin particles (b) The polypropylene-based resin particles (b) are resin particles containing polypropylene. Examples of polypropylene constituting the polypropylene-based resin particles (b) include polypropylene homopolymers; polypropylene copolymers, which are copolymers of propylene and other monomers (e.g., α-olefins other than propylene); and the like. The polypropylene copolymer is preferably a copolymer of propylene as the main component with an α-olefin copolymerized therewith, and the α-olefin may be, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, etc. Among these, 1-butene is more preferred. From the viewpoint of adhesion, the content of propylene units in the polypropylene is preferably 50 to 100% by mass, more preferably 70 to 99% by mass.

[0104] Examples of the polypropylene-based resin particles (b) include particles made from the polypropylene; particles made from an acid-modified polypropylene resin in which an acid group such as a carboxy group has been introduced into the polypropylene; particles made from an oxidized polypropylene resin in which a portion of the polypropylene has been oxidized; particles made from a chlorinated polypropylene resin in which a portion of the polypropylene has been treated with chlorine; and particles made from a polypropylene resin in which the polypropylene has been subjected to two or more treatments selected from acid modification, oxidation treatment, and chlorination treatment. Among these, particles made of a non-chlorinated polypropylene resin (hereinafter referred to as a non-chlorinated polypropylene resin) are preferred, and particles made of a non-chlorinated acid-modified polypropylene resin (hereinafter referred to as an acid-modified non-chlorinated polypropylene resin) are more preferred.

[0105] The acid-modified non-chlorine-based polypropylene resin may be a polypropylene resin that is not chlorinated and has an acid group bonded thereto. The acid-modified non-chlorine-based polypropylene resin may be a non-chlorine-based polypropylene resin acid-modified with at least one selected from the group consisting of unsaturated carboxylic acids, acid anhydrides of unsaturated carboxylic acids, and derivatives of unsaturated carboxylic acids (hereinafter, sometimes referred to as "unsaturated carboxylic acids, etc." in this specification), and for example, a copolymer obtained by graft copolymerizing an unsaturated carboxylic acid, etc. onto a non-chlorinated polypropylene resin may be used. Methods for graft copolymerizing the unsaturated carboxylic acid, etc. onto a polypropylene resin include known methods such as a solution method and a melt method.

[0106] Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, aconitic acid, and crotonic acid. Examples of the acid anhydrides of the unsaturated carboxylic acid include maleic anhydride and itaconic anhydride. Examples of the derivatives of the unsaturated carboxylic acid include half esters and half amides of unsaturated carboxylic acids. Among the unsaturated carboxylic acids, it is more preferable to use acrylic acid, methacrylic acid, maleic acid, and maleic anhydride.

[0107] The amount of graft polymerization with the unsaturated carboxylic acid or the like (specifically, the content of structural units derived from the unsaturated carboxylic acid or the like) is preferably 0.1 to 10 mass%, more preferably 1 to 5 mass%, based on 100 mass% of the acid-modified chlorine-free polypropylene resin, from the viewpoint of further improving the dispersion stability of the polypropylene-based resin particles (b). It is also preferable to adjust the content of structural units derived from the unsaturated carboxylic acid or the like based on 100 mass% of the polypropylene-based resin particles (b) to fall within the above range.

[0108] The polypropylene-based resin particles (b) may be used alone or in combination of two or more kinds.

[0109] The melting point Tm of the polypropylene resin particles (b) is 50 to 90° C., and preferably 60 to 85° C. By adjusting the melting point Tm to the above lower limit or more, the stain resistance of the resulting coating film can be improved, and by adjusting the melting point Tm to the above upper limit or less, the room-temperature film-forming property can be improved without using a plasticizer such as a water-soluble organic solvent.

[0110] The weight-average molecular weight (Mw) of the polypropylene-based resin particles (b) is preferably 5,000 to 200,000, and more preferably 30,000 to 120,000. By adjusting Mw to the above lower limit or more, the adhesion of the resulting coating film to the substrate can be improved, and by adjusting Mw to the above upper limit or less, the dispersion stability of the polypropylene-based resin particles (b) can be improved. The Mw is a polystyrene-equivalent molecular weight measured using gel permeation chromatography (GPC).

[0111] The shape of the polypropylene resin particles (b) is not particularly limited, but is usually spherical. The shape can be measured using a transmission electron microscope or a scanning electron microscope.

[0112] The average particle size of the polypropylene resin particles (b) is preferably 30 to 300 nm, more preferably 40 to 180 nm, and even more preferably 50 to 120 nm. By adjusting the average particle size to the above lower limit or more, the handleability of the aqueous dispersion (B) can be improved, and by adjusting the average particle size to the above upper limit or less, the transparency of the resulting coating film can be further improved.

[0113] 2-2. Composition of aqueous dispersion (B) The aqueous dispersion (B) contains the polypropylene-based resin particles (b), and specifically, is a dispersion in which the polypropylene-based resin particles (b) are dispersed in an aqueous solvent. The amount of nonvolatile matter in 100% by mass of the aqueous dispersion (B) is preferably from 10 to 60% by mass, more preferably from 20 to 40% by mass, from the viewpoint of handling properties. The content of the polypropylene resin particles (b) in the nonvolatile content of the aqueous dispersion (B) is preferably 80 to 100% by mass, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0114] As the aqueous solvent contained in the aqueous dispersion (B), the same solvents as those described as the aqueous solvent contained in the aqueous dispersion (A) can be used, and the preferred embodiments thereof are also the same.

[0115] The aqueous dispersion (B) may contain additives such as chain transfer agents such as tert-dodecyl mercaptan, pH buffers, pH adjusters, chelating agents, etc. The amount of the additives cannot be determined in general because it varies depending on the type and purpose, but is usually, for example, 0 to 5% by mass, preferably 0.01 to 4% by mass, and more preferably 0.1 to 3% by mass, relative to 100% by mass of the nonvolatile content in the aqueous dispersion (B).

[0116] The aqueous dispersion (B) may be a commercially available product, such as HARDLEN (registered trademark) NZ-1004, NZ-1015, NA-6600 (manufactured by Toyobo Co., Ltd.), ARROWBASE (registered trademark) DA, TD, SB, TC, SE, YA, and DB, or ARROWBASE (registered trademark) SB-1200, SE-1200, SD-1200, DA-1010, DB-4010, and AA-1041 (manufactured by Unitika Ltd.).

[0117] 3. Water dispersion (C) The aqueous dispersion composition of the present invention contains an aqueous dispersion (C) of ultraviolet absorber-containing resin particles (c) having a cumulant average particle size of 10 to 120 nm.

[0118] 3-1. Resin particles containing ultraviolet absorbers (c) The ultraviolet absorber-containing resin particles (c) (hereinafter sometimes simply referred to as "resin particles (c)") are resin particles containing an ultraviolet absorber. The ultraviolet absorber in the present invention means a compound having ultraviolet absorbing function, and may be an ultraviolet absorber having a polymerizable unsaturated group (hereinafter sometimes referred to as polymerizable ultraviolet absorber (i)), or an ultraviolet absorber not having a polymerizable unsaturated group (hereinafter sometimes referred to as non-polymerizable ultraviolet absorber (ii)). However, it is preferable that at least non-polymerizable ultraviolet absorber (ii) is contained. This increases the structural options when selecting an ultraviolet absorber, and makes it easy to use multiple ultraviolet absorbers in combination.

[0119] Examples of the polymerizable ultraviolet absorber (i) include benzotriazole-based ultraviolet absorbing monomers and benzophenone-based ultraviolet absorbing monomers, and among these, benzotriazole-based ultraviolet absorbing monomers are preferred.

[0120] Specific examples of the benzotriazole-based ultraviolet absorbing monomer include 2-[2'-hydroxy-5'-(meth)acryloyloxymethylphenyl]-2H-benzotriazole, 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-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyhexylphenyl]-2H-benzotriazole, and 2-[2'-hydroxy-3'-tert-butyl-5'-(meth)acryloyloxyethylphenyl]-2H-benzotriazole. ]-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, Examples include 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-5-cyano-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-5-tert-butyl-2H-benzotriazole, and 2-[2'-hydroxy-5'-(β-(meth)acryloyloxyethoxy)-3'-tert-butylphenyl]-4-tert-butyl-2H-benzotriazole.

[0121] Specific examples of the benzophenone-based ultraviolet absorbing monomer include 2-hydroxy-4-(meth)acryloyloxybenzophenone, 2-hydroxy-4-[2-hydroxy-3-(meth)acryloyloxy]propoxybenzophenone, 2-hydroxy-4-[2-(meth)acryloyloxy]ethoxybenzophenone, 2-hydroxy-4-[3-(meth)acryloyloxy-2-hydroxypropoxy]benzophenone, and 2-hydroxy-3-tert-butyl-4-[2-(meth)acryloyloxy]butoxybenzophenone.

[0122] When a polymerizable ultraviolet absorber (i) is used, the polymerizable ultraviolet absorber (i) is contained as a part of the polymer constituting the resin particles (c). Specifically, the polymerizable ultraviolet absorber (i) is contained in the polymer constituting the resin particles (c) as a structure in which the carbon-carbon double bond of the polymerizable ultraviolet absorber (i) is replaced with a carbon-carbon single bond and two bonds bonded to each carbon (i.e., a structural unit derived from the polymerizable ultraviolet absorber (i)).

[0123] The non-polymerizable ultraviolet absorber (ii) is preferably a lipophilic or oil-soluble compound. Specifically, when the non-polymerizable ultraviolet absorber (ii) is solid, the non-polymerizable ultraviolet absorber (ii) is preferably a compound that dissolves in methyl methacrylate when 1000 g of methyl methacrylate and 2 g or more of the non-polymerizable ultraviolet absorber (ii) are mixed at 23° C. When the non-polymerizable ultraviolet absorber (ii) is liquid, the non-polymerizable ultraviolet absorber (ii) is preferably a compound that does not undergo phase separation when 1000 g of methyl methacrylate and 30 g or more of the non-polymerizable ultraviolet absorber (ii) are mixed and the resulting mixture is allowed to stand at 23° C. for 12 hours. Among these, the solid non-polymerizable ultraviolet absorber (ii) preferably dissolves 10 g or more, more preferably 20 g or more, and even more preferably 50 g or more in 1000 g of methyl methacrylate at 23°C. Furthermore, from the viewpoint of improving the dispersion stability of the non-polymerizable ultraviolet absorber (ii), it is preferable that when 1000 g of water and 10 g of the non-polymerizable ultraviolet absorber (ii) are mixed at 23°C, the non-polymerizable ultraviolet absorber (ii) does not completely dissolve, or the non-polymerizable ultraviolet absorber (ii) and water undergo phase separation.

[0124] Examples of the non-polymerizable ultraviolet absorber (ii) include benzotriazole-based compounds, triazine-based compounds, and benzophenone-based compounds. Among these, benzotriazole-based compounds and triazine-based compounds are preferred, and triazine-based compounds are more preferred.

[0125] Specific examples of the benzotriazole compounds include 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, and 2-(2-hydroxyphenyl)-benzotriazole derivatives. As the benzotriazole-based compound, for example, commercially available products such as Tinuvin (registered trademark) 900, Tinuvin (registered trademark) 928, and Tinuvin (registered trademark) 970 (all manufactured by BASF) may be used.

[0126] Specific examples of the triazine-based compound include 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and oxirane {particularly, [(C 10-16 , mainly C 12-13reaction products of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)glycidic acid ester, 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, and 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine. As the triazine-based compound, for example, commercially available products such as Tinuvin (registered trademark) 400, Tinuvin (registered trademark) 405, Tinuvin (registered trademark) 460, and Tinuvin (registered trademark) 479 (all manufactured by BASF), Adeka Stab LA-F70 (manufactured by ADEKA), and Eversorb 40 (manufactured by Everlight Chemical) may be used.

[0127] Specific examples of the benzophenone-based compound include 2,2',4,4'-tetrahydroxybenzophenone, etc. As the benzophenone-based compound, for example, a commercially available product such as SB-UVA650 (manufactured by SHUANG-BANG INDUSTRIAL CORP.) may be used.

[0128] The resin particles (c) may contain one or more types of ultraviolet absorbers.

[0129] The content of the non-polymerizable ultraviolet absorber (ii) is, for example, 10 to 100% by mass, preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more, relative to 100% by mass of the total amount of ultraviolet absorbers (preferably the total amount of structural units derived from the polymerizable ultraviolet absorber (i) and the non-polymerizable ultraviolet absorber (ii)).

[0130] The content of the ultraviolet absorber (preferably the total content of the structural units derived from the polymerizable ultraviolet absorber (i) and the non-polymerizable ultraviolet absorber (ii)) in 100% by mass of the non-volatile content of the aqueous dispersion (C) is preferably 10 to 40% by mass, more preferably 12 to 37% by mass, and even more preferably 15 to 35% by mass. By adjusting the content of the ultraviolet absorber within the above range, the weather resistance of the resulting coating film can be further improved. At least a portion of the ultraviolet absorber contained in the aqueous dispersion (C) is contained in the resin particles (c). The content of the ultraviolet absorber in the resin particles (c) (preferably the total content of the structural units derived from the polymerizable ultraviolet absorber (i) and the non-polymerizable ultraviolet absorber (ii)) is preferably 10 to 40% by mass, more preferably 12 to 37% by mass, and even more preferably 15 to 35% by mass. By adjusting the content of the ultraviolet absorber within the above range, bleeding out of the ultraviolet absorber from the resulting coating film can be suppressed, and deterioration of the ultraviolet absorber can be prevented, thereby further improving the weather resistance maintenance ability.

[0131] The resin particles (c) have a polymer as a resin component. The polymer is not particularly limited, and known acrylic polymers or styrene polymers can be used. Among them, from the viewpoint of easily adjusting the average particle size of the resin particles (c) within the range described below and improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles described below, a polymer having a structural unit derived from at least one monomer (hereinafter, referred to as "monomer X") selected from the group consisting of alkyl(meth)acrylates having an alkyl group with 4 to 12 carbon atoms, cycloalkyl(meth)acrylates having a cycloalkyl group with 4 to 12 carbon atoms, and styrene monomers is preferred. The polymer may contain one or more structural units derived from monomer X.

[0132] Examples of the alkyl(meth)acrylate having 4 to 12 carbon atoms in the alkyl group include 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, n-lauryl(meth)acrylate, dodecyl(meth)acrylate, isononyl(meth)acrylate, etc. Of these, n-butyl(meth)acrylate, isobutyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate are preferred.

[0133] Examples of the cycloalkyl(meth)acrylate in which the cycloalkyl group has 4 to 12 carbon atoms include cyclobutyl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, etc. Among these, cyclohexyl(meth)acrylate and isobornyl(meth)acrylate are preferred from the viewpoint of further improving the water resistance, weather resistance, and transparency of the resulting coating film.

[0134] Examples of the styrene-based monomer include the same monomers as the styrene-based monomers constituting the acrylic polymer contained in the acrylic resin particles (a). Among them, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles described later, styrene and C 1-4 Styrene having an alkyl group is preferred, and styrene is more preferred.

[0135] As the monomer X, from the viewpoint of further improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion described below, at least one monomer selected from the group consisting of n-butyl(meth)acrylate, isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, cyclohexyl(meth)acrylate, and styrene is preferred; from the viewpoint of easily adjusting the average particle size within the range described below, at least one monomer selected from the group consisting of n-butyl(meth)acrylate, isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, cyclohexyl(meth)acrylate, and isobornyl(meth)acrylate is more preferred; and it is even more preferred that at least one monomer selected from cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and isobornyl(meth)acrylate is used as an essential component, and at least one monomer selected from the group consisting of n-butyl(meth)acrylate and isobutyl(meth)acrylate is optionally used.

[0136] The total content of the structural units derived from cyclohexyl (meth)acrylate, the structural units derived from 2-ethylhexyl (meth)acrylate, and the structural units derived from isobornyl (meth)acrylate in 100% by mass of the structural units derived from monomer X is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass, from the viewpoint of easily adjusting the average particle size within the range described below.

[0137] The content of the structural unit derived from monomer X in the polymer is preferably 5 to 60% by mass, more preferably 10 to 45% by mass, and even more preferably 15 to 35% by mass, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles.

[0138] The polymer preferably contains structural units derived from a reactive emulsifier. Examples of the reactive emulsifier include those similar to those described for the acrylic resin particles (a). In particular, the polymer preferably contains structural units derived from a reactive nonionic emulsifier (hereinafter sometimes referred to as emulsifier (e1)) from the viewpoint of improving the water resistance of the resulting coating film.

[0139] The HLB (hydrophilic-lipophilic balance) of the emulsifier (e1) is preferably 10 to 16, more preferably 10 to 15, from the viewpoint of further improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion described below. In addition, the HLB of the emulsifier (e1) is preferably 11 to 15, more preferably 11 to 14.5, and even more preferably 11 to 13, from the viewpoint of facilitating a reduction in the average particle size of the resin particles (c). The HLB of the emulsifier (e1) can be calculated by the following formula based on the Griffin method. [HLB of emulsifier (e1)] = 20 × [(molecular weight of hydrophilic part) / (molecular weight of emulsifier)]

[0140] The structural unit derived from the emulsifier (e1) has a first block which is an ethylene oxide block in a side chain, and 3-4 Preferably, the emulsifier (e1) has a polymerizable unsaturated group, a first block which is an ethylene oxide block, and a second block which is an alkylene oxide block. 3-4 Preferably, the compound has a second block which is an alkylene oxide block.

[0141] Examples of the polymerizable unsaturated group include a (meth)acryloyl group and a vinyl group, with the vinyl group being preferred.

[0142] The ethylene oxide block constituting the first block is -(OCH2CH2) n - (n is an integer of 1 to 100) is preferred. The above n (that is, the number of repeating oxyethylene groups in one molecule of the emulsifier (e1)) is preferably 1-50, more preferably 2-40, and even more preferably 3-35.

[0143] C constituting the second block 3-4 The alkylene oxide block is -(OR) m - (R is C 3-4 an alkylene group, and m is an integer of 1 to 150). Examples of R include a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a butane-1,3-diyl group, a butane-1,2-diyl group, and a butane-2,3-diyl group. Note that, although the multiple Rs contained in the emulsifier (e1) may be the same or different, they are preferably the same. The second block is preferably a butylene oxide block, and more preferably a butylene oxide block in which R is a butane-1,4-diyl group. The m (i.e., oxy C in one molecule of the emulsifier (e1) 3-4 The number of repeating alkylene groups is preferably 1 to 140, more preferably 2 to 100, and even more preferably 3 to 50.

[0144] The sum of n and m (i.e., the oxy C in one molecule of the emulsifier (e1)) 2-4 The total number of repeating alkylene groups is preferably 2 to 150. The ratio of n to m (n:m) is preferably 1-50:1-150, more preferably 2-40:1-140, and even more preferably 3-35:1-130.

[0145] The emulsifier (e1) is particularly preferably a compound represented by the following formula (e1-1): In formula (e1-1), R, m, and n, including their preferred embodiments, are the same as defined above.

[0146] [ka] [In formula (e1-1), R, m, and n are the same as those defined above, and R 1 represents an alkenyl group.]

[0147] The emulsifier (e1) is readily available commercially, and examples of the emulsifier (e1) that are readily available commercially include trade names: Latemul PD-420 (HLB: 12.6) and Latemul PD-430 (HLB: 14.3) (both manufactured by Kao Corporation).

[0148] The content of structural units derived from emulsifier (e1) in the polymer is preferably 5 to 70% by mass, more preferably 20 to 65% by mass, even more preferably 30 to 60% by mass, and particularly preferably 40 to 60% by mass, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles. The content of the structural units derived from the emulsifier (e1) relative to 100 parts by mass of the structural units derived from the monomer X is preferably 50 to 500 parts by mass, more preferably 75 to 300 parts by mass, and even more preferably 90 to 230 parts by mass.

[0149] The polymer may also contain structural units derived from a reactive emulsifier other than the emulsifier (e1) (hereinafter, may be referred to as emulsifier (e2)).

[0150] The emulsifier (e2) may be a reactive emulsifier described in the acrylic resin particles (a) and having an anionic group as a hydrophilic group. Among them, the emulsifier (e2) is preferably a reactive anionic emulsifier, and more preferably polyoxyethylene styrenated propenyl phenyl ether sulfate, allyloxymethyl alkoxyethyl hydroxypolyoxyethylene sulfate, or bis(polyoxyethylene polycyclic phenyl ether) methacrylated sulfonate.

[0151] The content of the structural units derived from emulsifier (e1) in the total of 100% by mass of the structural units derived from the reactive emulsifiers (i.e., structural units derived from emulsifier (e1) and emulsifier (e2)) is preferably 50 to 100% by mass, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0152] The polymer may further contain a structural unit derived from a (meth)acrylic acid alkyl ester having a carbon number of 15 or more. The polymer may contain one or more types of structural units derived from a (meth)acrylic acid alkyl ester having a carbon number of 15 or more.

[0153] The carbon number of the (meth)acrylic acid alkyl ester having 15 or more carbon atoms is preferably 15 to 60, more preferably 15 to 50, even more preferably 18 to 40, and still more preferably 22 to 40, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles.

[0154] Specific examples of the (meth)acrylic acid alkyl ester having 15 or more carbon atoms include tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, eicosyl (meth)acrylate, and 2-decyltetradecyl (meth)acrylate.

[0155] The content of structural units derived from a (meth)acrylic acid alkyl ester having 15 or more carbon atoms in the polymer is, for example, 0 to 30 mass %, and may be 5 to 25 mass %, or 8 to 20 mass %.

[0156] As described above, the polymer may have a structural unit derived from the polymerizable ultraviolet absorber (i). The polymerizable ultraviolet absorber (i) that can constitute the polymer is as described above, including its preferred embodiments. The content of the structural unit derived from the polymerizable ultraviolet absorber (i) in the polymer is, for example, 0 to 20% by mass, and may be 1 to 10% by mass, or 3 to 8% by mass.

[0157] The polymer may contain structural units derived from other monomer components (hereinafter, sometimes referred to as monomer Q) other than the aforementioned monomer X, reactive emulsifier, (meth)acrylic acid alkyl ester having 15 or more carbon atoms, and polymerizable UV absorber (i), as long as the object of the present invention is not impaired. Examples of the monomer Q include structural units derived from at least one monomer selected from alkyl (meth)acrylates having an alkyl group with 1 to 3 carbon atoms, acid group-containing monomers, hydroxyl group-containing monomers, nitrogen atom-containing monomers, crosslinkable monomers, and other monomers (P1). Monomer Q is preferably at least one selected from the group consisting of alkyl (meth)acrylates having an alkyl group with 1 to 3 carbon atoms, acid group-containing monomers, hydroxyl group-containing monomers, and nitrogen atom-containing monomers, and more preferably contains at least an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms.

[0158] The content of the structural unit derived from the monomer Q in the polymer is, for example, 0 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 35% by mass.

[0159] Examples of alkyl (meth)acrylates in which the alkyl group has 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate. Among these, those having excellent solubility in the ultraviolet absorber are preferred, and methyl (meth)acrylate is more preferred. Use of such a monomer makes it easier to control the phase inversion temperature. The content of structural units derived from alkyl (meth)acrylate in which the alkyl group has 1 to 3 carbon atoms in the polymer is preferably 1 to 40 mass %, more preferably 3 to 20 mass %, and even more preferably 5 to 15 mass %. Furthermore, in 100% by mass of the structural units derived from the monomer Q, the proportion of structural units derived from alkyl (meth)acrylates in which the alkyl group has 1 to 3 carbon atoms is preferably 30 to 100% by mass, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0160] The acid group-containing monomer is the same as the acid group-containing monomer described in the acrylic resin particles (a), including preferred embodiments thereof. The content of structural units derived from acid group-containing monomers in the polymer is preferably 0 to 10% by mass, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0161] Examples of the hydroxyl group-containing monomer include the same monomers as those described for the acrylic resin particles (a), among which hydroxyl group-containing monomers having two or more polymerizable groups, such as diprenyl glycerin ether, are preferred. The content of structural units derived from hydroxyl group-containing monomers in the polymer is preferably 0 to 30% by mass, more preferably 0 to 20% by mass.

[0162] The nitrogen atom-containing monomer is the same as the nitrogen atom-containing monomer described in the acrylic resin particles (a), including preferred embodiments thereof. The content of the structural unit derived from the nitrogen atom-containing monomer in the polymer is preferably 0 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 4% by mass.

[0163] The crosslinkable monomer is the same as the crosslinkable monomer described in the acrylic resin particles (a), including the preferred embodiments thereof. The content of the structural unit derived from the crosslinkable monomer is preferably 0 to 10% by mass, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0164] Examples of the other monomer (P1) include the same monomers as those described in the acrylic resin particles (a) above. The content of the structural unit derived from the other monomer (P1) is preferably 0 to 20% by mass, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0165] The content of the polymer in the resin particles (c) is, for example, 40 to 100 mass %, preferably 50 to 90 mass %, more preferably 55 to 80 mass %. It is also preferable to adjust the content of the polymer in the non-volatile content of the aqueous dispersion (C) to be within the above range.

[0166] The resin particles (c) may further contain a non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms. "A non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms" refers to an aliphatic organic acid having 15 or more carbon atoms in the entire compound or an aliphatic organic acid alkyl ester having 15 or more carbon atoms in the entire compound, which does not have a polymerizable unsaturated group. The resin particles (c) may contain one or more types of non-polymerizable aliphatic organic acids having 15 or more carbon atoms and non-polymerizable aliphatic organic acid alkyl esters having 15 or more carbon atoms.

[0167] The number of carbon atoms in the non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms is preferably 15 to 60, more preferably 15 to 50, even more preferably 18 to 40, and still more preferably 22 to 40, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles.

[0168] Specific examples of non-polymerizable aliphatic organic acids (alkyl esters) having 15 or more carbon atoms include aliphatic organic acid alkyl esters having 14 or more carbon atoms (particularly 14 to 40 carbon atoms) in the alkyl ester moiety, such as hexadecyl 2-ethylhexanoate, myristyl myristate, stearyl myristate, stearyl 2-ethylhexanoate, stearyl stearate, and hexadecyl cyclohexanoate; and aliphatic organic acid alkyl esters having an alkyl group having 14 or more carbon atoms (particularly 14 to 40 carbon atoms), such as ethyl myristate, isopropyl myristate, butyl myristate, ethyl palmitate, ethyl stearate, and 2-ethylhexyl stearate. Among these, aliphatic organic acid alkyl esters having 14 or more carbon atoms (particularly 14 to 40 carbon atoms) in the ester moiety are preferred, from the viewpoint of further improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion.

[0169] The content of the non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms in the resin particles (c) is, for example, 0 to 30 mass%, or may be 5 to 25 mass%, or 8 to 20 mass%, from the viewpoint of further improving the dispersion stability of the aqueous dispersion containing the monomer emulsion particles. It is also preferable to adjust the content of the non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms in the non-volatile content of the aqueous dispersion (C) to fall within the above range.

[0170] In addition, from the viewpoint of further improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion, it is preferable to adjust the total content of structural units derived from (meth)acrylic acid alkyl esters having 15 or more carbon atoms and non-polymerizable aliphatic organic acids (alkyl esters) having 15 or more carbon atoms. The total content of structural units derived from (meth)acrylic acid alkyl esters having 15 or more carbon atoms and non-polymerizable aliphatic organic acids (alkyl esters) having 15 or more carbon atoms in the resin particles (c) is, for example, 0 to 30% by mass, preferably 5 to 25% by mass, and more preferably 8 to 20% by mass. It is also preferable to adjust the total content in the non-volatile content of the aqueous dispersion (C) to within the above range.

[0171] The total content of the non-polymerizable ultraviolet absorber (ii), the polymer, and the non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms in the resin particles (c) is preferably 80 to 100% by mass, more preferably 90% by mass or more, and even more preferably 95% by mass or more. It is also preferable to adjust the total content in the non-volatile content of the aqueous dispersion (C) to be within the above range.

[0172] The shape of the resin particles (c) is not particularly limited, but is usually spherical. The shape can be measured using a transmission electron microscope or a scanning electron microscope. The resin particles (c) may have a single-layer structure or a multi-layer structure (e.g., a core-shell structure), but a single-layer structure is preferred. Conventionally, when forming a film using an aqueous dispersion containing particles such as resin particles (c), a multi-layer structure was required. However, in the present invention, even when the resin particles (c) have a single-layer structure, simply mixing the aqueous dispersions (A) to (C) can produce an aqueous dispersion that can be used to form a film (especially at room temperature). Therefore, this is also preferable in that the composition of the coating film can be easily adjusted by simply changing the blending ratio of the aqueous dispersions (A) to (C).

[0173] The average particle size of the resin particles (c) is 10 to 120 nm, and may be 20 to 110 nm, preferably 30 to 110 nm, more preferably 40 to 100 nm, and may be 40 nm or more but less than 100 nm. By adjusting the average particle size of the resin particles (c) to fall within the above range, the transparency of the resulting coating film can be improved.

[0174] 3-2. Composition of aqueous dispersion (C) The aqueous dispersion (C) contains the resin particles (c), and specifically, is a dispersion in which the resin particles (c) are dispersed in an aqueous solvent. The amount of nonvolatile matter in 100% by mass of the aqueous dispersion (C) is preferably from 10 to 80% by mass, more preferably from 20 to 50% by mass, and even more preferably from 25 to 40% by mass, from the viewpoint of handleability. The content of the resin particles (c) in the nonvolatile content of the aqueous dispersion (C) is preferably 80 to 100% by mass, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0175] The aqueous solvent contained in the aqueous dispersion (C) is the same as that described for the aqueous solvent contained in the aqueous dispersion (A), and preferred embodiments thereof are also the same.

[0176] From the viewpoint of handleability, the content of the aqueous solvent in the aqueous dispersion (C) is preferably 50 to 500 parts by mass, more preferably 100 to 350 parts by mass, and even more preferably 150 to 250 parts by mass, per 100 parts by mass of the resin particles (c).

[0177] The aqueous dispersion (C) may contain one or more additives, such as colorants such as pigments, leveling agents, UV stabilizers, antioxidants, chain transfer agents, polymerization inhibitors, fillers, coupling agents, rust inhibitors, antibacterial agents, metal deactivators, wetting agents, antifoaming agents, surfactants, reinforcing agents, plasticizers, lubricants, antifogging agents, anticorrosion agents, pigment dispersants, flow control agents, peroxide decomposers, mold decolorizing agents, fluorescent brighteners, organic flame retardants, inorganic flame retardants, anti-dripping agents, melt flow modifiers, antistatic agents, anti-algae agents, anti-fungal agents, flame retardants, slip agents, chelating agents, anti-blocking agents, heat stabilizers, processing stabilizers, dispersants, thickeners, rheology control agents, foaming agents, antioxidants, preservatives, antistatic agents, silane coupling agents, antioxidants, film-forming aids, pH buffers, and pH adjusters. The amount of the additive varies depending on the type and purpose and cannot be determined in general, but is usually, for example, 0 to 5 mass %, preferably 4 mass % or less, and more preferably 3 mass % or less, relative to 100 mass % of the nonvolatile content in the aqueous dispersion (C).

[0178] 3-3. Method for producing aqueous dispersion (C) The method for producing the aqueous dispersion (C) is not limited, but a step of preparing an aqueous dispersion containing monomer emulsion particles, the step comprising: mixing a monomer composition containing the non-polymerizable ultraviolet absorber (ii), polymerizable monomers constituting a polymer that is a resin component (specifically, monomer X, a reactive emulsifier, a (meth)acrylic acid alkyl ester having 15 or more carbon atoms, polymerizable ultraviolet absorber (i), monomer Q, etc.), and a non-polymerizable aliphatic organic acid (alkyl ester) having 15 or more carbon atoms, which is used as needed, with an aqueous solvent; heating the resulting mixture with stirring to a temperature equal to or higher than the phase inversion temperature of the mixture and lower than the boiling point of the aqueous solvent, and then cooling the mixture to a temperature lower than the phase inversion temperature of the mixture; and a polymerization step of polymerizing the polymerizable monomer contained in the monomer emulsion particles using the monomer emulsion particle-containing aqueous dispersion; According to this production method, polymerization can be carried out while the dispersion stability of the UV absorber (non-polymerizable UV absorber (ii) or polymerizable UV absorber (i)) in the aqueous dispersion containing monomer emulsion particles remains enhanced (i.e., while the dispersion stability of the aqueous dispersion containing monomer emulsion particles remains enhanced), and even when a large amount of UV absorber is used, the formation of precipitation thereof can be suppressed. A preferred production method will be described in detail below.

[0179] In the step of preparing the aqueous dispersion containing the monomer emulsion particles, first, the monomer composition and an aqueous solvent are mixed together. The types, combinations, compounding ratios, etc. of the components contained in the monomer composition are in accordance with the preferred embodiments explained above for the components constituting the acrylic resin particles (c). Examples of the aqueous solvent include the same solvents as those described as the aqueous solvent contained in the water dispersion (C), and the preferred embodiments thereof are also the same.

[0180] The mass ratio of the monomer composition to the aqueous solvent (monomer composition / aqueous solvent) is preferably 20 / 80 to 50 / 50, more preferably 25 / 75 to 45 / 55, and even more preferably 30 / 70 to 40 / 60, from the viewpoint of uniformly dispersing the monomer composition and the aqueous solvent.

[0181] The temperature at which the monomer composition and the aqueous solvent are mixed cannot be determined in general because it differs depending on factors such as the phase inversion temperature described below, but is usually preferably 5 to 45°C, more preferably 5 to 40°C, and even more preferably 5 to 35°C. When mixing the monomer composition and the aqueous solvent, it is preferable to add the monomer composition to the aqueous solvent under stirring in order to uniformly disperse the monomer composition in the aqueous solvent. Examples of means for stirring the aqueous solvent include a stirring rod and a magnetic stirrer.

[0182] Next, the monomer composition and the aqueous solvent are mixed, and the resulting mixture is heated with stirring to a temperature equal to or higher than the phase inversion onset temperature of the mixture but lower than the boiling point of the aqueous solvent, and then cooled with stirring to a temperature lower than the phase inversion onset temperature. The phase inversion temperature of the mixture is a value measured in accordance with the method described in Production Example C-1. In the present invention, the lowest phase inversion temperature is defined as the phase inversion onset temperature, and the highest phase inversion temperature is defined as the phase inversion end temperature. The phase inversion temperature is not particularly limited. From the viewpoint of improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion, the phase inversion onset temperature is preferably 35°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. Furthermore, from the viewpoint of improving the stability of the monomer emulsion, the phase inversion end temperature is preferably 98°C or lower, more preferably 97°C or lower, and even more preferably 96°C or lower.

[0183] The atmosphere in which the mixture is heated is not particularly limited, but from the viewpoint of avoiding the influence of oxygen contained in the air, it is preferable to use an inert gas such as nitrogen gas or argon gas.

[0184] From the viewpoint of improving the dispersion stability of the monomer emulsion particle-containing aqueous dispersion, the lower limit of the heating temperature (maximum temperature when heated) of the mixture is more preferably at least 0.5°C higher than the phase inversion onset temperature of the mixture to at least 3°C ​​lower than the boiling point of the aqueous solvent, more preferably at least 1°C higher than the phase inversion onset temperature of the mixture to at least 3°C ​​lower than the boiling point of the aqueous solvent, even more preferably at least 5°C higher than the phase inversion end temperature of the mixture to at least 5°C lower than the boiling point of the aqueous solvent, and particularly preferably at least 0.5°C higher than the phase inversion end temperature of the mixture to at least 5°C lower than the boiling point of the aqueous solvent.

[0185] Next, the heated mixture is cooled to a temperature below the phase inversion temperature of the mixture. There are no particular limitations on the means for cooling the mixture. The mixture may be cooled, for example, by standing to cool or by air cooling. The mixture is cooled to a temperature below the phase inversion onset temperature of the mixture. The mixture is preferably cooled to a temperature that is at least 10°C lower than the phase inversion onset temperature of the mixture, more preferably at least 20°C lower than the phase inversion onset temperature of the mixture, even more preferably at least 25°C lower than the phase inversion onset temperature of the mixture, and particularly preferably at least 30°C lower than the phase inversion onset temperature of the mixture.

[0186] By the above operations, an aqueous dispersion containing monomer emulsion particles composed of the monomer composition (i.e., a monomer emulsion particle-containing aqueous dispersion) is obtained. Next, the obtained monomer emulsion particle-containing aqueous dispersion is used to polymerize the polymerizable monomer contained in the monomer emulsion particles, thereby preparing an aqueous dispersion (C) containing resin particles (c).

[0187] The polymerizable monomer contained in the monomer emulsion particles is preferably polymerized by emulsion polymerization. Examples of a method for emulsion polymerizing the polymerizable monomer contained in the monomer emulsion particle-containing aqueous dispersion include a method of adding a polymerization initiator to the monomer emulsion particle-containing aqueous dispersion.

[0188] Examples of the polymerization initiator include the polymerization initiators explained in the production method of the aqueous dispersion (A), and these polymerization initiators may be used alone or in combination of two or more kinds. The amount of the polymerization initiator is preferably 0.03 to 1 part by mass, more preferably 0.04 to 0.5 part by mass, per 100 parts by mass of the aqueous dispersion containing the monomer emulsion particles, from the viewpoint of increasing the polymerization rate. The method for adding the polymerization initiator is not particularly limited, and examples thereof include batch addition, divided addition, and continuous dropwise addition. In order to promote the decomposition of the polymerization initiator, a suitable amount of a decomposer for the polymerization initiator, such as a reducing agent such as sodium hydrogen sulfite or a transition metal salt such as ferrous sulfate, may be added to the reaction system.

[0189] In the polymerization (preferably emulsion polymerization), an emulsifier may be further added to the monomer emulsion particle-containing aqueous dispersion. Examples of the emulsifier include the emulsifiers described in the method for producing the aqueous dispersion (A), and preferred embodiments thereof are also the same. The amount of the emulsifier added is preferably 0.3 to 5 parts by mass, more preferably 0.5 to 1 part by mass, per 100 parts by mass of the monomer emulsion particle-containing aqueous dispersion, from the viewpoint of improving polymerization stability.

[0190] When polymerizing the monomer composition, an appropriate amount of additives such as a chain transfer agent, a silane coupling agent, a chelating agent, a film-forming agent, a pH buffer, etc. may be added to the reaction system, if necessary.

[0191] The atmosphere during polymerization is not particularly limited, but from the viewpoint of increasing the efficiency of the polymerization initiator, it is preferably an inert gas such as nitrogen gas or argon gas. The polymerization temperature is not particularly limited, but is usually preferably 50 to 100° C., more preferably 60 to 85° C. The polymerization temperature may be constant or may be changed during the polymerization reaction. The polymerization time is not particularly limited and may be set appropriately depending on the progress of the polymerization reaction, but is usually about 2 to 9 hours.

[0192] 4. Water dispersion composition The water dispersion composition of the present invention contains the above-mentioned water dispersion (A), water dispersion (B), and water dispersion (C). The total content of the water dispersion (A), water dispersion (B), and water dispersion (C) in the water dispersion composition of the present invention is preferably 80 to 100% by mass, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0193] From the viewpoint of handleability, the nonvolatile content in the aqueous dispersion composition of the present invention is preferably from 10 to 80% by mass, more preferably from 20 to 60% by mass, and even more preferably from 30 to 50% by mass. The nonvolatile content of the aqueous dispersion composition can be calculated by weighing 1 g of the aqueous dispersion composition, drying it in a hot air dryer at 130°C for 30 minutes, and calculating the nonvolatile content using the following formula: [Nonvolatile content (mass%) in the aqueous dispersion composition] = ([mass of residue] / [mass of aqueous dispersion composition (1 g)]) × 100

[0194] The total content of the acrylic resin particles (a), the polypropylene resin particles (b), and the resin particles (c) in the non-volatile matter of the aqueous dispersion composition of the present invention is preferably 70 to 100% by mass, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0195] The content of the nonvolatile matter contained in the aqueous dispersion (A) in the nonvolatile matter of the aqueous dispersion composition of the present invention is preferably 10 to 80 mass %, more preferably 20 to 70 mass %, and even more preferably 30 to 65 mass %. By adjusting the content to be equal to or greater than the lower limit, it is possible to further improve the room temperature film-forming properties and adhesion to substrates (particularly acrylic resin substrates), while by adjusting the content to be equal to or less than the upper limit, it is possible to further improve the stain resistance of the resulting coating film.

[0196] The mass ratio of the nonvolatile content of the aqueous dispersion (A) to the nonvolatile content of the aqueous dispersion (B) (nonvolatile content of aqueous dispersion (A) / nonvolatile content of aqueous dispersion (B)) is preferably 25 / 75 to 80 / 20, more preferably 35 / 65 to 75 / 25, and even more preferably 40 / 60 to 75 / 25. By adjusting the ratio of the nonvolatile content of the aqueous dispersion (A) to the nonvolatile content of the aqueous dispersion (B) within the above range, room temperature film-forming properties, stain resistance, and adhesion to various substrates tend to be further improved. It is also preferable to adjust the mass ratio of the acrylic resin particles (a) to the polypropylene resin particles (b) (acrylic resin particles (a) / polypropylene resin particles (b)) within the above range.

[0197] The mass ratio of the nonvolatile content of the aqueous dispersion (A) to the nonvolatile content of the aqueous dispersion (C) (nonvolatile content of aqueous dispersion (A) / nonvolatile content of aqueous dispersion (C)) is preferably 40 / 60 to 98 / 2, more preferably 55 / 45 to 95 / 5, and even more preferably 65 / 35 to 90 / 10. By adjusting the ratio of the nonvolatile content of the aqueous dispersion (A) to the nonvolatile content of the aqueous dispersion (C) within the above range, room temperature film-forming properties, stain resistance, and weather resistance tend to be further improved. It is also preferable to adjust the mass ratio of the acrylic resin particles (a) to the resin particles (c) (acrylic resin particles (a) / resin particles (c)) within the above range.

[0198] The content of the ultraviolet absorber in the aqueous dispersions (A) to (C) is preferably 1 to 10 mass%, more preferably 1.5 to 7.5 mass%, based on the total 100 mass% of the nonvolatile content. By adjusting the content of the ultraviolet absorber within the above range, the weather resistance of the resulting coating film can be further improved. It is also preferable to adjust the content of the ultraviolet absorber within the above range, based on 100 mass% of the nonvolatile content of the aqueous dispersion composition of the present invention. It is preferred that most of the UV absorber contained in the aqueous dispersion composition of the present invention is contained in the resin particles (c). The proportion of the UV absorber contained in the resin particles (c) in 100% by mass of the UV absorber contained in the aqueous dispersion composition of the present invention is preferably 80 to 100% by mass, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0199] The cumulant average particle size of all resin particles contained in the aqueous dispersion composition (preferably the cumulant average particle size of the acrylic resin particles (a), the polypropylene resin particles (b), and the ultraviolet absorber-containing resin particles (c) as a whole) is preferably 30 to 250 nm, more preferably 40 to 220 nm, and even more preferably 50 to 200 nm.

[0200] The aqueous dispersion composition of the present invention may contain components other than the above-mentioned aqueous dispersions (A), (B), and (C), such as plasticizers, leveling agents, thickeners, surfactants, antifoaming agents, crosslinking agents, etc.

[0201] The plasticizer may be a volatile component other than water, and among these, a water-soluble organic solvent is preferred. The water-soluble organic solvent is the same as the water-soluble organic solvent that can be contained in the aqueous solvent described above.

[0202] In the aqueous dispersion composition of the present invention, the total content of volatile components excluding water (e.g., water-soluble organic solvents) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the aqueous dispersion composition, and may be 0% by mass. By adjusting the amount of volatile components excluding water to fall within the above range, the risk of exposure to volatile compounds during coating film production can be reduced.

[0203] The leveling agent may be a known leveling agent such as a silicone-based leveling agent, a fluorine-based leveling agent, etc. The amount of the leveling agent to be added is preferably 0 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the total nonvolatile content of the aqueous dispersions (A) to (C).

[0204] Examples of the thickener include polyurethane resins, polycarboxylic acid resins, polyvinyl alcohol, cellulose derivatives, etc., and among these, polyurethane resins and / or polycarboxylic acid resins are preferred. The amount of the thickener may be appropriately adjusted so that the aqueous dispersion composition has a desired viscosity, and is preferably 0 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the total nonvolatile content of the aqueous dispersions (A) to (C).

[0205] 5. Method for producing aqueous dispersion composition The water dispersion composition of the present invention can be produced by mixing the water dispersion (A), the water dispersion (B) and the water dispersion (C) described above with other components as required.

[0206] The mixing temperature is not particularly limited, but mixing is preferably carried out at a temperature below the boiling point of the water-dispersed composition, more preferably 10 to 95° C. From the viewpoint of workability, the mixing temperature is preferably 10 to 40° C., more preferably 20 to 35° C. Furthermore, from the viewpoint of shortening the time required for mixing, the mixing temperature is preferably 50 to 90° C., more preferably 70 to 90° C. The reaction time is not particularly limited, but is preferably 30 seconds to 12 hours, more preferably 10 minutes to 1 hour, from the viewpoint of productivity.

[0207] 6. Use of the aqueous dispersion composition The aqueous dispersion composition of the present invention can form a film at room temperature, and the resulting coating film has excellent stain resistance, weather resistance, and transparency, and therefore can be suitably used as a coating liquid for various substrates.

[0208] For example, the aqueous dispersion composition of the present invention is applied to various substrates and dried to form a coating film on the substrate.

[0209] The material of the substrate is not particularly limited, and examples thereof include paper; metals such as aluminum, zinc, and copper; plastics such as polyolefins (e.g., polyethylene and polypropylene), polycycloolefins, polyesters (e.g., polyethylene terephthalate), polyvinyl chloride, nylon, cellulose, polystyrene, polycarbonate, polyvinyl acetal, and acrylic resins (e.g., polymethyl methacrylate); and laminates thereof. In particular, the aqueous dispersion composition of the present invention is an aqueous coating liquid that uses an aqueous solvent as a solvent, yet has excellent adhesion to various plastics with different polarities, such as polyolefins such as polypropylene, polycycloolefins, polycarbonates, and acrylic resins such as polymethyl methacrylate. Therefore, the aqueous dispersion composition of the present invention is particularly suitable for use as a plastic coating liquid.

[0210] The surface of the plastic on which the coating film is to be laminated (i.e., the surface on which the aqueous dispersion composition of the present invention is to be applied) may be chemically or physically modified by corona treatment, anchor coat treatment, or the like.

[0211] The method for applying the aqueous dispersion composition to a substrate is not particularly limited, and any conventionally known method can be used, such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, or brush coating.

[0212] The drying temperature is not particularly limited and is, for example, 10 to 120° C., preferably 15 to 50° C., and more preferably 20 to 35° C. As described above, the aqueous dispersion composition of the present invention is capable of film formation at room temperature, and is therefore preferred in that it can be dried at room temperature (20 to 30° C.) without the need for a heating means. The drying time may be appropriately set depending on the drying temperature. For example, when drying at room temperature, the drying time is preferably 1 to 24 hours, more preferably 2 to 12 hours.

[0213] The coating film has excellent stain resistance. When the coating film formed on the substrate (hereinafter referred to as test plate) is subjected to the following stain resistance test, the change in E value (ΔE) is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, still more preferably 7 or less, and particularly preferably 5 or less. <Stain resistance test> The initial E value (E0) of the test panel is measured using a color difference meter. Then, a carbon dispersion (containing 97% by mass of water and 3% by mass of carbon black) is applied to the coating film-formed surface of the test panel using a 10 mil applicator and allowed to dry at room temperature for 24 hours. After drying, the carbon black dispersion is washed away using running water and a brush (pig bristles, bristle length 40 mm) to obtain a test panel after the staining test. The E value (E1) of the test panel after the staining test is measured using a color difference meter, and the change in E value, ΔE, is calculated using the following formula. ΔE=(E1)-(E0)

[0214] The coating film also has excellent weather resistance. When the following weather resistance test is carried out on a test plate, the color change (ΔE) is preferably 10.0 or less, more preferably 5.0 or less, even more preferably 3.0 or less, and still more preferably 1.5 or less. <Weather resistance test> Using a color difference meter, measure the Lab values ​​(L0, a0, b0) of the coating film surface of the test plate. Next, after irradiating the test plate with ultraviolet light for 1800 hours under test conditions in accordance with JIS A6909, measure the Lab values ​​(L1, a1, b1) of the coating film surface of the test plate, and calculate the color change (ΔE) before and after ultraviolet light irradiation using the following formula. ΔE=[(L1-L0) 2 +(a1-a0) 2 +(b1-b0) 2 ] 1 / 2

[0215] The coating film also has excellent transparency. The haze of the coating film is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.0 or less.

[0216] The present invention also encompasses a molded article in which the above-mentioned coating film is formed (laminated) on the above-mentioned substrate. The molded article may further have one or more topcoat layers on the above-mentioned coating film.

[0217] Examples of the topcoat layer include coatings obtained by applying one-component melamine baking paint, two-component urethane paint, one-component lacquer paint, glitter paint, high-solid clear paint, etc. When the topcoat coating film has a multilayer structure of two or more layers, for example, a multilayer structure including a base coating film and a clear coating film can be used.

[0218] Examples of the molded articles include bumpers, moldings, fender mirrors, lamps, lamp covers and grilles for vehicles, and components for home appliances. [Example]

[0219] The present invention will now be described in more detail based on examples, but is not limited to these examples. In the following production examples, examples, and comparative examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0220] In the following production examples, the abbreviations for each compound mean the following compounds. <Monomer components, Monomer X, Monomer Q> MMA: Methyl methacrylate CHMA: Cyclohexyl methacrylate 2-EHA: 2-ethylhexyl acrylate St: Styrene AA: Acrylic acid HEMA: 2-hydroxyethyl methacrylate LA-87: 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (manufactured by ADEKA Corporation, trade name: Adekastab LA-87) LA-82: 2,2,6,6-tetramethyl-4-piperidyl methacrylate (manufactured by ADEKA Corporation, trade name: Adekastab LA-82) KBM-503: Methacryloxypropyltrimethoxysilane IBOA: Isobornyl acrylate DPNG: Diprenyl glycerin ether <Emulsifier> SR-10: Reactive anionic emulsifier (manufactured by ADEKA Corporation, trade name: ADEKA REASOAP (registered trademark) SR-10) SR-20: Reactive anionic emulsifier (manufactured by ADEKA Corporation, trade name: ADEKA REASOAP (registered trademark) SR-20) SR-30: Reactive anionic emulsifier (manufactured by ADEKA Corporation, trade name: ADEKA REASOAP (registered trademark) SR-30) AR-10: reactive anionic emulsifier (manufactured by Daiichi Pharmaceutical Co., Ltd., trade name: Aqualon (registered trademark) AR-10) MS-60: Reactive anionic emulsifier (manufactured by Nippon Nyukazai Co., Ltd., trade name: Antox (registered trademark) MS-60) PD-420: Reactive nonionic emulsifier (Polyoxyalkylene alkenyl ether, manufactured by Kao Corporation, trade name: Latemul PD-420, HLB: 12.6) PD-430: Reactive nonionic emulsifier (Polyoxyalkylene alkenyl ether, manufactured by Kao Corporation, trade name: Latemul PD-430, HLB: 14.3) <UV absorber> Eversorb 40: Non-polymerizable UV absorber (ii) [manufactured by Everlight Chemical, trade name: Eversorb 40, active ingredient content 85%] RUVA: Polymerizable ultraviolet absorber (i) [Otsuka Chemical Co., Ltd., product name: RUVA-93] Tinuvin 479: non-polymerizable ultraviolet absorber (ii) [manufactured by BASF, trade name: Tinuvin (registered trademark) 479] LA-F70: Non-polymerizable ultraviolet absorber (ii) [ADEKA Corporation, trade name: Adekastab LA-F70] <Aliphatic organic acids (alkyl esters)> EHC: hexadecyl 2-ethylhexanoate C22A: Behenyl acrylate

[0221] The physical properties of the aqueous dispersions obtained in the following production examples and the resin particles contained in the aqueous dispersions were measured as follows.

[0222] <Non-volatile content> The amount of nonvolatile matter in the aqueous dispersion was determined by weighing 1 g of the aqueous dispersion, drying it in a hot air dryer at 130°C for 30 minutes, and calculating the nonvolatile matter from the residue obtained by the following formula: [Non-volatile content in aqueous dispersion] = ([mass of residue] / [1 g of aqueous dispersion]) × 100 was calculated based on the following. The nonvolatile content of the aqueous dispersion composition was determined in the same manner except that the measurement sample was changed from the aqueous dispersion to the aqueous dispersion composition.

[0223] <Average particle size> The average particle size of the resin particles contained in the aqueous dispersion or aqueous dispersion composition was measured at a measurement temperature of 25°C using a multi-analyte nanoparticle size measurement system (manufactured by Otsuka Electronics Co., Ltd., product name: nanoSAQLA), which is a particle size measurement device using a dynamic light scattering method, by determining the autocorrelation function using a photon correlation method and then calculating the average particle size (hydrodynamic diameter) using cumulant analysis.

[0224] <Glass transition temperature (Tg)> The glass transition temperature (Tg) of the acrylic polymer constituting the acrylic resin particles contained in the aqueous dispersion was calculated based on the Fox equation shown below, using the glass transition temperatures of the homopolymers of the monomers used in the monomer components constituting the acrylic polymer contained in the resin particles. 1 / Tg A =Σ(Wm / Tgm) / 100 [In the formula, Tg A indicates the glass transition temperature (absolute temperature: K) of the acrylic polymer, Wm indicates the content (%) of monomer m in all monomer components constituting the acrylic polymer, and Tgm indicates the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.]

[0225] [Preparation of aqueous dispersion] [Manufacturing example A-1] A flask equipped with a dropping funnel, stirrer, nitrogen inlet tube, thermometer, and reflux condenser was charged with 82 parts of deionized water. A pre-emulsion consisting of 3.2 parts of deionized water, 7.5 parts of a 25% aqueous solution of SR-10, 24.7 parts of MMA, 0.3 parts of Eversorb 40, and 0.1 parts of KBM-503 was prepared in the dropping funnel. 2.5 parts of the pre-emulsion was added to the flask, and the contents of the flask were heated to 80°C while gently blowing in nitrogen gas. Polymerization was then initiated by adding 2.0 parts of a 5% aqueous solution of ammonium persulfate to the flask. The remaining pre-emulsion was then uniformly added dropwise to the flask over 60 minutes. The contents of the flask were maintained at 80°C for 60 minutes. Then, a second-stage pre-emulsion consisting of 23 parts deionized water, 8.9 parts of a 25% aqueous solution of SR-10, 28 parts of 2-EHA, 5.3 parts of MMA, 33.5 parts of CHMA, 1 part of AA, and 3 parts of LA-87 was added dropwise uniformly to the flask over 120 minutes. After the addition was completed, the contents of the flask were maintained at 80°C for 120 minutes. The polymerization reaction was then terminated by adjusting the pH of the contents of the flask to 8 using a 25% aqueous ammonia solution. The resulting reaction solution was cooled to room temperature and then filtered through a 300 mesh (JIS mesh, the same applies hereinafter) wire mesh to obtain an aqueous dispersion A-1 of acrylic resin particles with a non-volatile content of 45%. The average particle size of the acrylic resin particles contained in the aqueous dispersion A-1 and the Tg of the acrylic polymer constituting the acrylic resin particles are shown in Table 1.

[0226] [Manufacturing example A-2] A flask equipped with a dropping funnel, stirrer, nitrogen inlet tube, thermometer, and reflux condenser was charged with 55 parts of deionized water. A pre-emulsion consisting of 34.8 parts of deionized water, 8.0 parts of a 25% aqueous solution of AR-10, 59 parts of 2-EHA, 36.4 parts of St, 2 parts of AA, 0.3 parts of HEMA, and 0.3 parts of KBM-503 was prepared in the dropping funnel. 2.5 parts of the pre-emulsion was added to the flask, and the contents of the flask were heated to 80°C while gently blowing in nitrogen gas. Polymerization was then initiated by adding 2.0 parts of a 5% aqueous solution of ammonium persulfate to the flask. Next, the remaining portion of the pre-emulsion for dropping was added dropwise evenly to the flask over 120 minutes. After the dropwise addition was completed, the contents of the flask were maintained at 80°C for 120 minutes. The pH of the contents of the flask was then adjusted to 8 with a 25% aqueous ammonia solution to terminate the polymerization reaction. The resulting reaction solution was cooled to room temperature and then filtered through a 300-mesh wire net to obtain an aqueous dispersion A-2 of acrylic resin particles with a nonvolatile content of 50%. The average particle size of the acrylic resin particles contained in the aqueous dispersion A-2 and the Tg of the acrylic polymer constituting the acrylic resin particles are shown in Table 1.

[0227] [Manufacturing example A-3] Aqueous dispersion A-3 of acrylic resin particles having a nonvolatile content of 45% was prepared in the same manner as in Production Example A-2, except that the types and amounts of the emulsifier and monomer components used were changed as shown in Table 1. Table 1 shows the average particle size of the acrylic resin particles contained in aqueous dispersion A-3 and the Tg of the acrylic polymer constituting the acrylic resin particles.

[0228] [Manufacturing example A-4] Aqueous dispersion A-4 of acrylic resin particles having a nonvolatile content of 45% was prepared in the same manner as in Production Example A-2, except that the types and amounts of the emulsifier and monomer components used were changed as shown in Table 1. Table 1 shows the average particle size of the acrylic resin particles contained in aqueous dispersion A-4 and the Tg of the acrylic polymer constituting the acrylic resin particles.

[0229] [Table 1]

[0230] [Manufacturing example C-1] A reaction vessel equipped with a stirrer, temperature sensor, cooling tube, nitrogen inlet tube, and dropping funnel was charged with 195 parts of deionized water, 33 parts of PD-420, 9 parts of MMA, 20 parts of CHMA, 10 parts of EHC, and 26 parts of Eversorb 40. A portion of the resulting mixture was removed and the phase inversion temperature of the mixture was measured using the following method. The phase inversion temperature was found to be 83°C (the lower limit temperature is the phase inversion onset temperature, the same applies hereinafter) to 89°C (the upper limit temperature is the phase inversion endpoint temperature, the same applies hereinafter).

[0231] [Method for measuring phase inversion temperature] A 2 L (liter) reaction vessel was equipped with a stirring device and a temperature sensor, and 1000 g of the mixture was placed in the reaction vessel and stirred. The reaction vessel was heated in a water bath, and the electrical conductivity was measured every time the temperature of the mixture in the reaction vessel increased by 1°C using a conductivity meter (manufactured by EUTECH, trade name: Lacom Tester PC450). The electrical conductivity was plotted for each temperature increase, and the temperature at which the electrical conductivity began to decrease continuously with increasing temperature was taken as the phase inversion starting temperature, and the temperature at which the electrical conductivity became 1.00 μS or less was taken as the phase inversion end temperature. In addition, if the electrical conductivity did not become 1.00 μS or less even when the upper limit of the measurable temperature of the conductivity meter was exceeded, the temperature at which the appearance of the mixture did not change even after 3 minutes or more had passed since it reached a temperature higher than the phase inversion starting temperature under stirring was taken as the end point of the phase inversion temperature.

[0232] After measuring the phase inversion temperature of the mixture, the reaction vessel was heated in a water bath under stirring while introducing nitrogen gas into the reaction vessel. After the temperature of the mixture in the reaction vessel reached 90°C, the reaction vessel was removed from the water bath and air-cooled under stirring until the internal temperature reached 40°C or less, thereby obtaining an aqueous dispersion containing monomer emulsion particles. Next, 100 parts of the resulting monomer emulsion particle-containing aqueous dispersion was placed in a separate reaction vessel. 2.6 parts of a 25% aqueous solution of SR-20 was added to the reaction vessel. The mixture was stirred at room temperature for 30 minutes while nitrogen gas was introduced into the reaction vessel. The reaction vessel was then placed in a water bath and heated with stirring until the internal temperature of the reaction vessel reached 80°C. 0.9 parts of a 5% aqueous potassium persulfate solution was then added to the reaction vessel, and the contents of the reaction vessel were heated with stirring at 80°C for 6 hours to polymerize the components contained in the monomer emulsion particles, yielding an aqueous dispersion of acrylic resin particles C-1. Table 2 shows the nonvolatile content of the aqueous dispersion C-1, the ratio of the amount of UV absorber to the nonvolatile content (UV absorber amount / nonvolatile content), and the average particle size of the acrylic resin particles contained in the aqueous dispersion C-1.

[0233] [Manufacturing example C-2] A reaction vessel equipped with a stirrer, temperature sensor, condenser, nitrogen inlet tube, and dropping funnel was charged with 180 parts of deionized water, 30 parts of PD-420, 10 parts of MMA, 16 parts of CHMA, 2 parts of LA-87, 14 parts of C22A, and 26 parts of Eversorb 40. A portion of the resulting mixture was taken and the phase inversion temperature of the mixture was measured according to the method described in Production Example C-1. The result was that the phase inversion temperature was 85°C to 91°C. After measuring the phase inversion temperature of the mixture, the reaction vessel was heated in a water bath under stirring while introducing nitrogen gas into the reaction vessel. After the temperature of the mixture in the reaction vessel reached 92°C, the reaction vessel was removed from the water bath and air-cooled under stirring until the internal temperature reached 40°C or less, thereby obtaining an aqueous dispersion containing monomer emulsion particles. Next, 100 parts of the resulting monomer emulsion particle-containing aqueous dispersion was placed in a separate reaction vessel. 2.8 parts of a 25% aqueous solution of SR-20 was added to the reaction vessel, and the mixture was stirred at room temperature for 30 minutes while nitrogen gas was introduced into the reaction vessel. The reaction vessel was then placed in a water bath and heated with stirring until the internal temperature of the reaction vessel reached 80°C. 0.9 parts of a 5% aqueous potassium persulfate solution was then added to the reaction vessel, and the contents of the reaction vessel were heated with stirring at 80°C for 6 hours to polymerize the components contained in the monomer emulsion particles, yielding an aqueous dispersion of acrylic resin particles, C-2. The nonvolatile content of the aqueous dispersion C-2, the ratio of the UV absorber content to the nonvolatile content, and the average particle size of the acrylic resin particles contained in the aqueous dispersion C-2 are shown in Table 2.

[0234] [Manufacturing example C-3] A reactor equipped with a stirrer, temperature sensor, condenser, nitrogen inlet tube, and dropping funnel was charged with 195 parts of deionized water, 32 parts of PD-420, 11 parts of MMA, 15 parts of CHMA, 2 parts of LA-82, 10 parts of EHC, and 30 parts of Tinuvin 479. A portion of the resulting mixture was taken and the phase inversion temperature of the mixture was measured according to the method described in Production Example C-1. The result was that the phase inversion temperature was 75°C to 83°C. After measuring the phase inversion temperature of the mixture, the reaction vessel was heated in a water bath under stirring while introducing nitrogen gas into the reaction vessel. After the temperature of the mixture in the reaction vessel reached 85°C, the reaction vessel was removed from the water bath and air-cooled under stirring until the internal temperature reached 40°C or less, thereby obtaining an aqueous dispersion containing monomer emulsion particles. Next, while introducing nitrogen gas into the reaction vessel, the reaction vessel was placed in a water bath and heated in the water bath with stirring until the internal temperature of the reaction vessel reached 80°C. Three parts of a 5% aqueous potassium persulfate solution were then added to the reaction vessel, and the contents of the reaction vessel were heated with stirring at 75°C for 6 hours to polymerize the components contained in the monomer emulsion particles, thereby obtaining an aqueous dispersion C-3 of acrylic resin particles. The nonvolatile content of the aqueous dispersion C-3, the ratio of the amount of UV absorber to the nonvolatile content, and the average particle size of the acrylic resin particles contained in the aqueous dispersion C-3 are shown in Table 2.

[0235] [Manufacturing example C-4] A reactor equipped with a stirrer, temperature sensor, condenser, nitrogen inlet tube, and dropping funnel was charged with 195 parts of deionized water, 27 parts of PD-430, 10 parts of MMA, 6 parts of CHMA, 3 parts of 2-EHA, 8 parts of IBOA, 2 parts of LA-82, 9 parts of C22A, 5 parts of RUVA-93, 10 parts of Eversorb 40, 5 parts of LA-F70, and 15 parts of DPNG. A portion of the resulting mixture was removed and the phase inversion temperature of the mixture was measured according to the method described in Production Example C-1. As a result, the phase inversion temperature was 78 ° C to 83 ° C. After measuring the phase inversion temperature of the mixture, the reaction vessel was heated in a water bath under stirring while introducing nitrogen gas into the reaction vessel. After the temperature of the mixture in the reaction vessel reached 85°C, the reaction vessel was removed from the water bath and air-cooled under stirring until the internal temperature reached 40°C or less, thereby obtaining an aqueous dispersion containing monomer emulsion particles. Next, while introducing nitrogen gas into the reaction vessel, the reaction vessel was placed in a water bath and heated in the water bath with stirring until the internal temperature of the reaction vessel reached 80°C. Three parts of a 5% aqueous ammonium persulfate solution were then added to the reaction vessel, and the contents of the reaction vessel were heated with stirring at 70°C for 6 hours, thereby polymerizing the components contained in the monomer emulsion particles and obtaining an aqueous dispersion of acrylic resin particles C-4. The nonvolatile content of aqueous dispersion C-4, the ratio of the amount of UV absorber to the nonvolatile content, and the average particle size of the acrylic resin particles contained in aqueous dispersion C-4 are shown in Table 2.

[0236] [Table 2]

[0237] [Preparation of aqueous dispersion] [Examples 1 to 9, Comparative Examples 4, 7, and 9] Various aqueous dispersions were added to a reaction vessel equipped with a stirrer, temperature sensor, cooling tube, nitrogen inlet tube, and dropping funnel so as to have the compositions (types and amounts) shown in Tables 3 and 4, and the reaction vessel was heated in a water bath set to 80°C while stirring, followed by stirring and mixing for 30 minutes to obtain aqueous dispersion compositions. The obtained aqueous dispersion compositions were allowed to stand at room temperature overnight, and then subjected to the evaluation tests described below. In Examples 5, 6, and 9, the obtained aqueous dispersion compositions were allowed to stand overnight at room temperature, and then 1 part of modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-351A) was added, and the evaluation tests described below were carried out. In addition, in Examples 7 and 8, the obtained aqueous dispersion compositions were allowed to stand overnight at room temperature, and then 1 part of modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-351A) and 0.5 parts of a thickener (manufactured by ADEKA Corporation, product name: ADEKA NOL UH420) were added, and the evaluation tests described below were carried out.

[0238] [Comparative Example 1] The aqueous dispersion A-1 obtained in Production Example A-1 was used as it was as an aqueous dispersion composition and subjected to the evaluation tests described below.

[0239] Comparative Example 2 An aqueous dispersion composition was obtained by adding 6 parts of dipropylene glycol monobutyl ether as a plasticizer to 94 parts of the aqueous dispersion A-1 obtained in Production Example A-1. The obtained aqueous dispersion composition was allowed to stand at room temperature overnight, and then subjected to the evaluation tests described below.

[0240] Comparative Example 3 The aqueous dispersion A-2 obtained in Production Example A-2 was used as it was as an aqueous dispersion composition and subjected to the evaluation tests described below.

[0241] Comparative Example 5 The water dispersion B-1 described below was used as it was as the water dispersion composition, and the evaluation tests described below were carried out.

[0242] Comparative Example 6 An aqueous dispersion composition was obtained by adding 10 parts of dipropylene glycol monobutyl ether as a plasticizer to 490 parts of an aqueous dispersion B described below. The obtained aqueous dispersion composition was allowed to stand at room temperature overnight, and then subjected to the evaluation tests described below.

[0243] [Comparative Example 8] Aqueous dispersions (A) and (C) were added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, a nitrogen inlet tube, and a dropping funnel so as to have the composition shown in Table 4, and the reaction vessel was heated in a water bath set to 80°C while stirring, and the mixture was stirred and mixed for 30 minutes to obtain an aqueous dispersion composition. The obtained aqueous dispersion composition was allowed to stand at room temperature overnight, and then subjected to the evaluation tests described below.

[0244] [Evaluation test] <Evaluation test 1: Room temperature film formation> The aqueous dispersion composition obtained in each Example or Comparative Example was applied to the surface of a glass plate having an area of ​​70 mm × 150 mm using an applicator with a coating width of 50 mm so as to obtain a coating film of 50 mm × 100 mm so that the thickness of the coating film after drying would be 30 μm, and the coating film was dried at room temperature for 10 hours to form a test plate. The appearance of the coating on the obtained test plate was checked, and if a crack-free coating area of ​​40 mm x 40 mm or more could be secured, the room temperature film-forming property was rated as ◯, and the test proceeded to evaluation test 2 and onwards. If there were many cracks and the above area could not be confirmed, the room temperature film-forming property was rated as ×, and the test did not proceed to the subsequent evaluations. The results are shown in Tables 3 and 4.

[0245] <Evaluation test 2: Stain resistance of room temperature dried coating film> Five parts of glass beads (diameter: 1 mm) were added to 97 parts of ion-exchanged water, and 3 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: MA-100) were added while stirring at 500 rpm with a homodisper. After the addition, the mixture was dispersed at 2500 rpm for 30 minutes. After dispersion, the glass beads were removed by filtration through a 60-mesh wire screen, yielding a carbon black dispersion. The aqueous dispersion compositions obtained in each Example or Comparative Example were applied to a white acrylic plate (manufactured by Nippon Test Panel Co., Ltd., length: 150 mm, width: 75 mm, thickness: 2 mm) using an applicator with a coating width of 50 mm so that the thickness of the coating film after drying would be 30 μm, and the plate was dried in an atmosphere at room temperature (23°C) for one day to prepare a test plate. The initial E value (E0) of the test panel was measured using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., model number: ZE-6000). The carbon black dispersion was then applied to the coated surface of the test panel using a 10 mil applicator and allowed to dry at room temperature for 24 hours. After drying, the carbon black dispersion was washed away using running water and a brush (pig bristles, bristle length 40 mm) to obtain a test panel after the staining test. The E value (E1) of the test panel after the staining test was measured using the color difference meter. The change in E value (ΔE) was then calculated using the following formula: ΔE=(E1)-(E0) The results are shown in Tables 3 and 4. The smaller the ΔE value, the more excellent the stain resistance.

[0246] <Evaluation test 3: Adhesion of room temperature dried coating film to various substrates> The aqueous dispersion composition obtained in each Example or Comparative Example was applied to the surface of each of the following various substrates having an area of ​​70 mm x 150 mm using an applicator with a coating width of 50 mm so as to obtain a coating film of 50 mm x 100 mm so that the coating film would have a thickness of 20 μm after drying, and the coating film was dried at room temperature for 10 hours to form a test plate. (base material) White translucent polypropylene (PP) plate, manufactured by Nippon Test Panel Co., Ltd., length: 70 mm, width: 150 mm, thickness: 2 mm Colorless transparent polycarbonate (PC) plate, manufactured by Nippon Test Panel Co., Ltd., length: 70 mm, width: 150 mm, thickness: 2 mm) Cycloolefin polymer (COP) plate, Zeon Corporation, Zeonex 480R (clear), length: 70 mm, width: 150 mm, thickness: 3 mm Polymethyl methacrylate (PMMA) plate, manufactured by TP Giken Co., Ltd., length: 70 mm, width: 150 mm, thickness: 2 mm) Twenty-five 2mm squares (5 vertical, 5 horizontal) were cut into the coating surface of the test panel using a sharp blade. After making the cuts, the test panel was checked for peeling from the substrate and for any breaks in the coating other than the cuts. Then, 25mm wide cellophane adhesive tape (Nichiban CT-24) was applied to the cut areas by rubbing with a finger. The test panel was then left to stand in the air at 25°C for 5 minutes, after which the cellophane adhesive tape was peeled off. The number of peeled squares out of the 25 cut squares was counted, and the adhesion to various substrates was evaluated based on the following criteria. The results are shown in Tables 3 and 4. (Evaluation criteria) ○: The number of peeled squares is 0 to 4. △: The number of peeled squares is 5 to 14. ×: The number of peeled squares was 15 or more, or the coating film peeled off from the substrate at the time the notch was made, or the coating film broke at a location other than the notch.

[0247] <Evaluation test 4: Weather resistance> The aqueous dispersion composition obtained in each Example or Comparative Example was applied to the surface of a white translucent polypropylene (PP) plate (manufactured by Nippon Test Panel Co., Ltd., length: 70 mm, width: 150 mm, thickness: 2 mm) using an applicator with a coating width of 50 mm so that the coating film would be 30 μm thick after drying, and the plate was dried at room temperature for 10 hours to form a coating film, thereby obtaining a test plate. The Lab values ​​(L0, a0, b0) of the coating surface of the test plate obtained above were measured using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: Spectroscopic Color Difference Meter SE-2000). Next, the test panels were irradiated with ultraviolet light under the following ultraviolet irradiation conditions, and the Lab values ​​(L1, a1, b1) of the coating surface of the test panels were measured, and the color change (ΔE) before and after ultraviolet irradiation was calculated using the following formula. The results are shown in Tables 3 and 4. The smaller the ΔE value, the better the weather resistance. ΔE=[(L1-L0) 2 +(a1-a0) 2 +(b1-b0) 2 ] 1 / 2 (Ultraviolet irradiation conditions) Under test conditions conforming to JIS A6909, ultraviolet light was irradiated for 1800 hours using a super xenon weather meter (manufactured by Suga Test Instruments Co., Ltd., product number: SX2D-75).

[0248] <Evaluation Test 5: Transparency> The aqueous dispersion composition obtained in each Example or Comparative Example was applied to the surface of a glass plate having an area of ​​70 mm x 150 mm using an applicator with a coating width of 50 mm so that a coating film of 50 mm x 100 mm would be obtained, with a thickness of 40 μm after drying. The coating film was then dried at room temperature for 10 hours to form a test plate. The haze of the coating surface of the test plate obtained above was measured using a spectrophotometer (manufactured by Konica Minolta, Inc., product number: CM-3700A) in accordance with the conditions specified in ASTM-D-1003-97-C. The results are shown in Tables 3 and 4. The smaller the haze, the better the transparency.

[0249] [Table 3]

[0250] [Table 4]

[0251] The "non-volatile content ratio" in Tables 3 and 4 indicates the proportion of non-volatile content in each aqueous dispersion when the total non-volatile content in the aqueous dispersion is taken as 100%. In Tables 3 and 4, the "amount of volatile components excluding water" indicates the proportion of volatile components excluding water in the aqueous dispersion compositions obtained in each Example and Comparative Example.

[0252] The abbreviations in Tables 3 and 4 represent the following components. A-1: Aqueous dispersion A-1 obtained in Production Example A-1 A-2: Aqueous dispersion A-2 obtained in Production Example A-2 A-3: Aqueous dispersion A-3 obtained in Production Example A-3 A-4: Water dispersion C-4 obtained in Production Example A-4 B-1: Water dispersion of non-chlorine-based polypropylene particles (manufactured by Toyobo Co., Ltd., trade name: HARDLEN (registered trademark) NZ-1004, non-volatile content: 30%, particle cumulant average particle size: 100 nm, Tm (melting point): 70°C) B-2: Water dispersion of non-chlorinated polypropylene particles (manufactured by Toyobo Co., Ltd., trade name: HARDLEN (registered trademark) NA-6600, non-volatile content: 30%, particle cumulant average particle size: 100 nm, Tm: 80°C) B-3: Water dispersion of non-chlorinated polypropylene particles (manufactured by Unitika Ltd., trade name: Arrowbase (registered trademark) AA-1041, non-volatile content: 30%, particle cumulant average particle size: 60 nm, Tm: 75°C) B-4: Water dispersion of non-chlorinated polypropylene particles (manufactured by Unitika Ltd., trade name: Arrowbase (registered trademark) TD-4010, nonvolatile content: 26%, particle cumulant average particle size: 200 nm, Tm: 75°C) C-1: Aqueous dispersion C-1 obtained in Production Example C-1 C-2: Aqueous dispersion C-2 obtained in Production Example C-2 C-3: Aqueous dispersion C-3 obtained in Production Example C-3 C-4: Aqueous dispersion C-4 obtained in Production Example C-4 C-5: Aqueous dispersion of resin particles containing an ultraviolet absorber (manufactured by BASF, trade name: Tinuvin (registered trademark) 400DW, cumulant average particle size 230 nm, proportion of ultraviolet absorber in nonvolatile matter 50%)

[0253] As is clear from Tables 3 and 4, the aqueous dispersion compositions of Examples 1 to 9 containing specific aqueous dispersions (A) to (C) were capable of forming films at room temperature, and the coating films obtained by room temperature film formation had excellent stain resistance, adhesion to various substrates, weather resistance, and transparency. On the other hand, Comparative Example 1, which used only the aqueous dispersion (A), resulted in poor room temperature film-forming properties. Comparative Example 2, in which a plasticizer was further added to the composition of Comparative Example 1, resulted in poor adhesion to PP and PC and poor weather resistance, although the room temperature film-forming properties were improved. In Comparative Example 3, which used only aqueous dispersion (A) having acrylic resin particles with a relatively low Tg, film formation was possible at room temperature, but the results were poor in stain resistance, adhesion to PP and PC, and weather resistance. In Comparative Example 4, in which aqueous dispersion (C) was further added to the composition of Comparative Example 3, weather resistance was improved compared to Comparative Example 3, but stain resistance and adhesion to PP and PC were still poor. In Comparative Example 5, in which only the aqueous dispersion (B) was used, the room temperature film-forming property was poor. In Comparative Example 6, in which a plasticizer was added to the aqueous dispersion (B), the room temperature film-forming property was improved compared to Comparative Example 5, but the adhesion to PC and PMMA, transparency, and weather resistance were poor. In Comparative Example 7, in which aqueous dispersion A-4 having acrylic resin particles with a high Tg was added to aqueous dispersion (A), the room temperature film-forming properties were poor. In Comparative Example 8, in which aqueous dispersion C-1 was further added to the composition of Comparative Example 7, the room temperature film-forming properties were improved compared to Comparative Example 7, but the stain resistance, adhesion to PP and PC, and transparency were poor. In Comparative Example 9, in which an aqueous dispersion of ultraviolet absorber-containing resin particles with a large average particle size was used instead of the aqueous dispersion (C), the transparency was poor.

Claims

1. an aqueous dispersion (A) of acrylic resin particles (a) containing an acrylic polymer having a glass transition temperature of −50 to 40° C. as calculated based on the Fox equation; an aqueous dispersion (B) of polypropylene-based resin particles (b) having a melting point Tm of 50 to 90°C; and an aqueous dispersion (C) of ultraviolet absorber-containing resin particles (c), the resin particles (c) having a cumulant average particle size of 10 to 120 nm.

2. 2. The aqueous dispersion composition according to claim 1, wherein the content of the ultraviolet absorber is 1 to 10 mass% relative to a total of 100 mass% of nonvolatile contents in the aqueous dispersions (A) to (C).

3. 2. The water dispersion composition according to claim 1, wherein a mass ratio of the non-volatile content of the water dispersion (A) to the non-volatile content of the water dispersion (B) (non-volatile content of the water dispersion (A) / non-volatile content of the water dispersion (B)) is 25 / 75 to 75 / 25.

4. 2. The aqueous dispersion composition according to claim 1, wherein the content of the ultraviolet absorber in 100% by mass of the nonvolatile content of the aqueous dispersion (C) is 10 to 40% by mass.

5. the resin particles (c) contain structural units derived from a reactive nonionic emulsifier (e1), the emulsifier (e1) has an HLB value of 10 to 16, The structural unit derived from the emulsifier (e1) has a first block which is an ethylene oxide block in a side chain, and 3-4 The aqueous dispersion composition according to claim 1 , further comprising a second block which is an alkylene oxide block.

6. 2. The aqueous dispersion composition according to claim 1, wherein the cumulant average particle size of all resin particles contained in the aqueous dispersion composition is 30 to 250 nm.

7. A plastic coating liquid comprising the aqueous dispersion composition according to any one of claims 1 to 6.

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