JP2015000917A - Polymer particle, polymer dispersion liquid, aqueous coating material, and coated product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer dispersion liquid which is excellent in polymerization stability and allows an aqueous coating material obtained therefrom to be excellent in coating viscosity properties and storage stability, to provide a polymer particle contained in the polymer dispersion liquid, and the aqueous coating material from which a coating film excellent in water resistance and solvent resistance can be formed even when a drying condition thereof is low temperature and a short time, and to provide an aqueous coating material-applied coated product.SOLUTION: The polymer particle is obtained by incorporating a urethane resin having a sulfonate group and an acrylic polymer in one and the same particle and has 0.1-19 mg-KOH/g surface acid value when measured by a potentiometric titration method. The aqueous coating material is prepared by using the polymer dispersion liquid containing the polymer particle. The coating film is formed from the aqueous coating material to obtain the coated product.

Description

  The present invention relates to polymer particles, a polymer dispersion, an aqueous coating material, and a coated product.

Conventionally, in the paint field, conversion from organic solvent-based paints to water-based paints has been attempted from the viewpoint of environmental protection and safety and health. However, water-based paints have the problem that the coating film appearance, weather resistance, water resistance, solvent resistance, and stain resistance of the coating film performance are lower than those of organic solvent-based paints.
Therefore, in order to solve these problems, a coating material containing an intra-particle mixture of resins having different properties has been proposed.

For example, Patent Document 1 describes a polymer in which an acrylic monomer is emulsion-polymerized in an aqueous dispersion of a urethane resin to mix the urethane resin and the acrylic polymer to form particles. Yes.
Moreover, although there is no description regarding a coating material, for example, Patent Document 2 also describes a particulate polymer using a urethane resin and an acrylic polymer.

  In recent years, from the viewpoint of energy saving, it is required to lower the drying temperature and shorten the drying time in the drying process after coating. Therefore, a paint having water resistance and solvent resistance is required even under low temperature and short drying conditions.

JP 2006-274096 A JP 2008-88429 A

  However, the dispersion of polymer particles described in Patent Document 1 does not have good polymerization stability when the dispersion is produced. In addition, when the dispersion of polymer particles is used as an aqueous coating material, the coating viscosity characteristics and storage stability of the aqueous coating material and the solvent resistance of the coating film are insufficient. Further, even if the dispersion of polymer particles described in Patent Document 2 is used for an aqueous coating material, the coating viscosity characteristics and storage stability of the aqueous coating material and the water resistance of the coating film are insufficient.

The present invention provides a polymer dispersion having excellent polymerization stability and excellent paint viscosity characteristics and storage stability when used in an aqueous coating material, and polymer particles contained in the polymer dispersion. Objective.
The present invention provides an aqueous coating material capable of forming a coating film excellent in water resistance and solvent resistance even under low temperature and short drying conditions, and a coated product coated with the aqueous coating material. Objective.

The present invention has the following configuration.
[1] Polymer particles containing a urethane resin having a sulfonic acid group and an acrylic polymer in the same particle and having a surface acid value measured by potentiometric titration method of 0.1 to 19 mgKOH / g.
[2] The polymer particle according to [1], wherein the acrylic polymer includes a repeating unit derived from a monomer having two or more radically polymerizable groups.
[3] The polymer particle according to [2], comprising 0.05 to 10% by mass of a repeating unit derived from a monomer having two or more radically polymerizable groups.
[4] The acrylic polymer includes a repeating unit derived from an acid group-containing radical polymerizable monomer, and the repeating unit derived from the acid group-containing radical polymerizable monomer is 0.008 to 3.4% by mass. The polymer particles according to any one of [1] to [3].
[5] A polymer dispersion containing the polymer particles according to any one of [1] to [4].
[6] An aqueous coating material containing the polymer dispersion of [5].
[7] A coated product to which the aqueous coating material according to [6] is applied.

According to the present invention, it is possible to provide a polymer dispersion having excellent polymerization stability and excellent paint viscosity characteristics and storage stability when used in an aqueous coating material, and polymer particles contained in the polymer dispersion. .
ADVANTAGE OF THE INVENTION According to this invention, even if drying conditions are low temperature and for a short time, the water-based coating material which can form the coating film which is excellent in water resistance and solvent resistance, and the coating material by which this water-based coating material was apply | coated can be provided. .

  Hereinafter, the polymer particles of the present invention, a polymer dispersion containing the polymer particles, an aqueous coating material containing the polymer dispersion, and a coated product coated with the aqueous coating material will be described in detail.

<Polymer particles>
The polymer particles of the present invention are polymer particles containing a urethane resin having a sulfonic acid group and an acrylic polymer in the same particle, for example, in an aqueous dispersion of a urethane resin having a sulfonic acid group, It is manufactured by a method of polymerizing an acrylic monomer mixture. When such a polymer dispersion containing the polymer particles of the present invention is used as an aqueous coating material, a coating film excellent in water resistance and solvent resistance can be formed even if the drying conditions are low temperature and short time.

[Urethane resin having a sulfonic acid group]
The polymer particles of the present invention contain a urethane resin having a sulfonic acid group in the polymer particles. When the urethane resin has a sulfonic acid group, the urethane resin is excellent in water dispersibility. Therefore, it is possible to stably emulsion polymerize the acrylic monomer mixture in the aqueous dispersion of the urethane resin. As a result, the polymer particles containing the urethane resin having a sulfonic acid group and the acrylic polymer in the same particle. A dispersion (polymer dispersion) can be obtained stably. In particular, when the acrylic monomer mixture contains an acid group-containing radically polymerizable monomer having an acid group such as a carboxy group, the polymerization stability during emulsion polymerization is good. Moreover, since the urethane resin which has a sulfonic acid group is excellent also in water resistance, it can form the coating film excellent in water resistance.

  A urethane resin having a sulfonic acid group is a method of reacting a polyol such as a diol or a polyvalent isocyanate compound with a compound having a sulfonic acid group or a salt thereof; reacting a polyol having a sulfonic acid group with a polyvalent isocyanate compound. It can manufacture by the method to make;

  A diol is an organic compound having two hydroxyl groups in one molecule. Specific examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, Relatively low molecular weight diols such as neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, hexanediol, cyclohexanedimethanol; and at least one of these diols Polyester diols obtained by polycondensation with at least one dicarboxylic acid such as adipic acid, sebacic acid, itaconic acid, maleic anhydride, terephthalic acid, isophthalic acid; polyethylene glycol, poly B propylene glycol, polycaprolactone diol, polytetramethylene ether diol, polyether diols and polycarbonate diols; polybutadiene diol, hydrogenated polybutadiene diol, polyacrylate diol. In the production of a urethane resin having a sulfonic acid group, these diols may be used alone or in combination of two or more.

  The polyvalent isocyanate compound means an organic compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic, alicyclic and aromatic polyvalent isocyanate compounds. Specific examples of the polyvalent isocyanate compound include dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 2,4-tolylene diisocyanate, 2, , 6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, and the like. In the production of a urethane resin having a sulfonic acid group, these polyvalent isocyanate compounds may be used alone or in combination of two or more. Among these, aliphatic or alicyclic isocyanates are preferable because the resulting urethane resin has little yellowing.

  Examples of the compound having a sulfonic acid group or a salt thereof include hydroxysulfonic acid such as 1,7-dihydroxynaphthalenesulfonic acid; 2,4-diaminobenzenesulfonic acid, 3,4-diaminobutanesulfonic acid, 3,6- Examples thereof include aminosulfonic acids such as diamino-2-toluenesulfonic acid and N- (2-aminoethyl) -2-aminoethylsulfonic acid. In the production of the urethane resin having a sulfonic acid group, these sulfonic acid groups or a compound having a salt thereof may be used alone or in combination of two or more.

  Examples of polyols having sulfonic acid groups include polyols containing sulfonic acid groups such as 1,4-butanediol-2-sulfonic acid; sulfonate-containing polyester polyols, sulfonate-containing polyether polyols, and sulfonate-containing polyols. Examples include sulfonate-containing polyols such as polycarbonate polyols. In the production of a urethane resin having a sulfonic acid group, these polyols having a sulfonic acid group may be used alone or in combination of two or more.

  The urethane resin having a sulfonic acid group is a compound having a diol, a polyvalent isocyanate compound, a sulfonic acid group or a salt thereof, as described above, using a catalyst such as dibutyltin dilaurate in ethers such as dioxane. Can be produced by a method of reacting

  The urethane resin having a sulfonic acid group is preferably in the form of an aqueous dispersion as described above in that the acrylic monomer mixture can be stably emulsion-polymerized in the aqueous dispersion. The average particle size of the urethane resin having a sulfonic acid group in the aqueous dispersion is preferably 1000 nm or less, and more preferably 500 nm or less, as an average particle size according to the cumulant analysis result. With such an average particle size, for example, the storage stability of the aqueous dispersion and the aqueous coating material, and the water resistance and solvent resistance of the coating film are further improved. The average particle diameter is preferably 10 nm or more from the viewpoint of the viscosity property of the paint and the storage stability when used in an aqueous coating material.

  The content of the urethane resin having a sulfonic acid group in the aqueous dispersion is preferably 10% by mass or more, and more preferably 25% by mass or more. Moreover, it is preferable that it is 70 mass% or less, and it is more preferable that it is 60 mass% or less. With such a content, the solid content concentration of the polymer dispersion obtained by polymerizing the acrylic monomer mixture in the aqueous dispersion can be adjusted to a range of 10 to 80% by mass. If the solid content concentration of the polymer dispersion is within the above range, the paintability when this is used as an aqueous coating material will be good. The solid content concentration of the polymer dispersion is the amount of polymer particles containing a urethane resin having a sulfonic acid group and an acrylic polymer in the same particle.

  As an aqueous dispersion of a urethane resin having a sulfonic acid group, a commercially available urethane aqueous polymer dispersion (urethane dispersion: PUD) can be used as it is. Commercially available products include “F-8082D” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Baihydrol UH650” manufactured by Sumika Bayer Urethane Co., Ltd., “Imperil DLP-R”, “Imperil DLU”, “Imperil LP” RSC 3040 ", Sanyo Chemical Industries" Permarin UXA-3005 ", etc. are mentioned.

[Acrylic polymer]
The polymer particles of the present invention are particles having a surface acid value of 0.1 to 19 mgKOH / g, which contains the above-mentioned urethane resin having an sulfonic acid group and an acrylic polymer in the same particle and measured by potentiometric titration. . In order to make the surface acid value within the above range, the monomer component (acrylic monomer mixture (mixture of radical polymerizable monomers)) used for producing the acrylic polymer contains an acid group. It is preferable to contain an appropriate amount of a radical polymerizable monomer. As a result, the acrylic polymer in the polymer particles contains an appropriate amount of repeating units derived from the acid group-containing radical polymerizable monomer, and the surface acid value of the polymer particles is adjusted within the above range.
The radical polymerizable monomer is a monomer having a radical polymerizable group, and the radical polymerizable group is a radical-polymerizable carbon-carbon unsaturated double bond, radical-polymerizable carbon. -A group containing a carbon unsaturated triple bond, a ring capable of radical ring-opening polymerization, and the like.

(Acid group-containing radical polymerizable monomer)
Examples of the acid group-containing radical polymerizable monomer contained in the acrylic monomer mixture include carboxy groups such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate. And a radically polymerizable monomer having preferably one radically polymerizable group. These monomers may be used alone or in combination of two or more. Among these, acrylic acid and methacrylic acid are preferable.

  The proportion of the acid group-containing radically polymerizable monomer used is 0.008 to 3.4 in a total of 100% by mass of the urethane resin and acrylic monomer mixture from the viewpoint of storage stability of the resulting aqueous coating material. It is preferable that it is mass%. When the acid group-containing radically polymerizable monomer is used in such a use ratio, polymer particles containing repeating units derived from the monomer at the same ratio, that is, 0.008 to 3.4% by mass can be obtained. The use ratio of the acid group-containing radical polymerizable monomer is more preferably 0.03 to 3.2% by mass, further preferably 0.1 to 2.5% by mass, Most preferably, it is 1.5 mass%.

(Radical polymerizable monomers other than acid group-containing radical polymerizable monomers)
In the acrylic monomer mixture, it is preferable to use a radical polymerizable monomer other than the acid group-containing radical polymerizable monomer together with the acid group-containing radical polymerizable monomer. Such a radically polymerizable monomer is not particularly limited as long as it has the effect of the present invention, but is a monomer having two or more radically polymerizable groups (however, it does not contain an acid group and the above acid It is preferable to use at least a group-containing radically polymerizable monomer because the water resistance and solvent resistance of the coating film are further improved and particularly the solvent resistance is excellent. The monomer having two or more radically polymerizable groups may have a group such as a hydroxyl group.

  Specific examples of the monomer having two or more radically polymerizable groups include, for example, ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di ( (Meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 2-hydroxy-1 , 3-Di (meth) acryloxypropane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (Acryloxy polyethoxy Phenyl] propane, 2,2-bis [4- (methacryloxy polyethoxy) phenyl] propane, 2-hydroxy-1-acryloxy-3-methacryloxypropane, ethylene oxide modified bisphenol A di (meth) acrylate, propylene oxide modified bisphenol A di (meth) acrylate, ethylene oxide-modified hydrogenated bisphenol A di (meth) acrylate, propylene oxide-modified hydrogenated bisphenol A di (meth) acrylate, diglycidyl ether of bisphenol A and hydroxyalkyl such as hydroxy (meth) acrylate ( Diol of (meth) acrylic acid with diol such as epoxy (meth) acrylate to which meth) acrylate is added, polyoxyalkylenated bisphenol A di (meth) acrylate, etc. Tellurium compounds; trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc., a compound having 3 or more hydroxyl groups per molecule and a polyester compound of (meth) acrylic acid; allyl (meth) acrylate, divinylbenzene, triallyl isocyanurate, Diallyl iso (tere) phthalate, diallyl isocyanurate, diallyl tris (2-acryloyloxyethylene) isocyanurate, ε-caprolactone modified Scan (acryloxyethyl) isocyanurate, 1,3-butadiene, conjugated diene monomers and the like of isoprene.

  Among these, radically polymerizable monomers having an allyl group such as allyl (meth) acrylate, triallyl isocyanurate, diallyl iso (tere) phthalate, diallyl isocyanurate, diallyl maleate and the like are preferable. Monomers having two or more radically polymerizable groups may be used alone or in combination of two or more.

  The use ratio of the monomer having two or more radically polymerizable groups is preferably 0.05 to 10% by mass in 100% by mass of the total mass of the urethane resin and the acrylic polymer. When a monomer having two or more radically polymerizable groups is used in such a use ratio, polymer particles containing repeating units derived from the monomer at the same ratio, that is, 0.05 to 10% by mass are obtained. It is done. When the use ratio is 0.05% by mass or more, a coating film excellent in solvent resistance and water resistance can be obtained. If it is 10 mass% or less, a coating film excellent in solvent resistance and water resistance can be obtained without deteriorating flexibility, frost damage resistance and chipping resistance. More preferably, it is 0.25-8 mass%, More preferably, it is 0.5-6 mass%, Most preferably, it is 1.0-4.5 mass%.

As the radical polymerizable monomer other than the acid group-containing radical polymerizable monomer, a monomer having one radical polymerizable group (however, it does not contain an acid group and the above-mentioned acid group-containing radical polymerizable monomer). (Not applicable to the mass).
Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, and pentyl (meth). ) Acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl ( Alkyl (meth) acrylates having an alkyl group having 1 to 22 carbon atoms such as (meth) acrylate; cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate Cycloalkyl (meth) acrylates such as γ- (meth) acryloyloxypropylmethyldimethoxysilane, hydrolyzable silyl group-containing radical polymerizable monomers such as γ- (meth) acryloyloxypropyltrimethoxysilane; Alkyl group-terminated polyalkylene oxide group-containing radical polymerizable monomers such as ethylene oxide mono (meth) acrylate; Oxirane group-containing radical polymerizable monomers such as glycidyl (meth) acrylate; Carbonyl group-containing ethylene such as diacetone acrylamide Light-stabilizing action such as 1,2,2,6,6-pentamethyl-4-piperidyl (meth) acrylate, 2,2,6,6-pentamethyl-4-piperidyl (meth) acrylate (Meth) acrylate having 2- [2′-hydride (Meth) acrylates having ultraviolet absorbing components such as Roxy-5 ′-(meth) acryloyloxyethylphenyl] -2H-benzotriazole; aminoalkyl (meth) acrylates such as 2-aminoethyl (meth) acrylate; Amide group-containing radically polymerizable monomers such as (meth) acrylamide; Metal-containing radically polymerizable monomers such as zinc di (meth) acrylate; (Meth) acrylonitrile, benzyl (meth) acrylate, isobornyl (meth) acrylate, Other (meth) acrylic monomers such as methoxyethyl (meth) acrylate; aromatic vinyl monomers such as styrene and methylstyrene; radical polymerizable monomers such as vinyl acetate, vinyl chloride and ethylene Can be mentioned. These may be used alone or in combination of two or more.

  The radical polymerizable monomer other than the acid group-containing radical polymerizable monomer includes a monomer having one radical polymerizable group and a hydroxyl group (hereinafter simply referred to as “hydroxyl group-containing radical polymerizable monomer”). (Also referred to as “mer”). When an acrylic monomer mixture containing a hydroxyl group-containing radical polymerizable monomer is used, an acrylic polymer containing a hydroxyl group can be produced, and further, polymer particles containing a hydroxyl group can be produced. Thus, the polymer particles having a hydroxyl group can undergo a crosslinking reaction with a curing agent such as a melamine crosslinking agent or an isocyanate curing agent. Therefore, water resistance, solvent resistance, and the like of the obtained coating film can be improved by adding a curing agent such as a melamine crosslinking agent and an isocyanate curing agent to the aqueous coating material together with the polymer particles having a hydroxyl group. Moreover, the polymer particle which has a hydroxyl group is excellent also in the dispersion stability in an aqueous medium and an aqueous coating material.

  Examples of such a hydroxyl group-containing radical polymerizable monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl ( Monoesterified product of (meth) acrylic acid such as (meth) acrylate and C2-8 dihydric alcohol; ε- of monoesterified product of (meth) acrylic acid and C2-8 dihydric alcohol Modified caprolactone; N-hydroxymethyl (meth) acrylamide; allyl alcohol; (meth) acrylate (hydroxypolyethylene oxide mono (meth) acrylate) having a polyoxyethylene chain whose molecular end is a hydroxyl group; (Meth) ac having a polyoxypropylene chain Rate (hydroxy polypropylene oxide mono (meth) acrylate) terminal hydroxy polyalkylene oxide group-containing radical polymerizable monomer and the like) and the like. These monomers may be used alone or in combination of two or more. Of these, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are preferable.

The use ratio of the radical polymerizable monomer other than the acid group-containing radical polymerizable monomer is not particularly limited, but the mass ratio of the urethane resin having a sulfonic acid group and the acrylic monomer mixture in the polymer particles. However, it is preferable to determine the amount of the acid group-containing radical polymerizable monomer in consideration of the preferable range described later.
However, when a hydroxyl group-containing radical polymerizable monomer is used, the use ratio is from the viewpoint of the stability of the resulting polymer dispersion in an aqueous medium, the water resistance of the resulting coating film, and the solvent resistance. In the total mass of 100% by mass of the urethane resin and the acrylic polymer, 0.1 to 10% by mass is preferable. When the hydroxyl group-containing radical polymerizable monomer is used in such a use ratio, polymer particles containing the same repeating unit, that is, 0.1 to 10% by mass can be obtained. The use ratio is more preferably 0.3 to 8% by mass, and particularly preferably 0.5 to 5% by mass.

In the polymer particles of the present invention, the mass ratio of the urethane resin having a sulfonic acid group and the acrylic monomer mixture is such that the urethane resin having a sulfonic acid group / acrylic monomer mixture = (10 to 90) / ( 90 to 10), preferably (15 to 85) / (85 to 15), more preferably (20 to 80) / (80 to 20), and (30 to 70). ) / (70-30). In this case, the total mass of the urethane resin having a sulfonic acid group and the acrylic monomer mixture is 100.
If the mass ratio of the urethane resin having a sulfonic acid group is in the range of 10 to 90% by mass in the above-mentioned total mass of 100% by mass, the water resistance, water absorption resistance, hydrolysis resistance, and resin compatibility of the coating film Further, the drying property and solvent resistance of the coating film are improved without deteriorating the cleanability of the coating machine.

The surface acid value of the polymer particles of the present invention is 0.1 to 19 mgKOH / g, preferably 0.5 to 17.5 mgKOH / g, more preferably 1 to 10 mgKOH / g, and most preferably 1 to 7 mgKOH / g. g. If the surface acid value of the polymer particles is 0.1 mgKOH / g or more, the coating viscosity characteristic when the aqueous coating material is formed is easily developed, the storage stability is good, and if it is 19 mgKOH / g or less, The paint viscosity characteristics and the storage stability are improved when an aqueous coating material is used without lowering the polymerization stability and the water resistance of the coating film.
Here, the surface acid value is the number of milligrams of potassium hydroxide necessary to neutralize acidic components present on the surface of particles contained in 1 g of the sample.
The potentiometric titration method is a method for determining an end point by measuring a change in potential difference corresponding to a change in concentration of a target component in a solution. The surface acid value of the polymer particles can be determined by conducting potentiometric titration with a known concentration of polymer dispersion as potassium titrant.

<Method for producing polymer particles>
There is no particular limitation on the method for producing the polymer particles containing the urethane resin having a sulfonic acid group and the acrylic polymer of the present invention. For example, an acrylic monomer mixture is used for the urethane resin having a sulfonic acid group. By polymerizing in an aqueous dispersion, target polymer particles can be obtained in the form of a dispersion (polymer dispersion) in which the polymer particles are dispersed in an aqueous medium.

  Polymerization of the acrylic monomer mixture can be performed by a known polymerization method such as a suspension polymerization method or an emulsion polymerization method. In particular, it is desirable to obtain a polymer dispersion in the form of an emulsion by an emulsion polymerization method from the viewpoint of various physical properties such as storage stability of the aqueous coating material, water resistance of the coating film, and solvent resistance.

Emulsion polymerization can employ, for example, a known method in which an acrylic monomer mixture is supplied into a polymerization system in the presence of a surfactant and polymerization is performed with a radical polymerization initiator.
The polymerization of the acrylic monomer mixture may be one-stage polymerization or two-stage or more multi-stage polymerization. In particular, from the viewpoint of localizing acid groups derived from acid group-containing radical polymerizable monomers on the surface layer of polymer particles, an acrylic monomer mixture used in at least the final stage using multistage polymerization of two or more stages. It is preferable to contain an acid group-containing radical polymerizable monomer.

The method of supplying the acrylic monomer mixture into the polymerization system is not particularly limited, and a method of dropping the acrylic monomer mixture; using the surfactant and water, the acrylic monomer mixture is Examples include a method of preparing a pre-emulsion liquid emulsified and dispersed in advance and dropping the pre-emulsion liquid; a method of charging an acrylic monomer mixture all at once. In the case of multistage polymerization, two or more of these methods may be used in combination. When adopting multistage polymerization of two or more stages, the first stage adopts the technique of charging the acrylic monomer mixture in a lump, and the second and subsequent stages adopt the technique of dropping the pre-emulsion liquid. Is preferred.
The first stage acrylic monomer mixture is added all at once and emulsion polymerization is performed, so that a polymer is uniformly formed inside the urethane resin as compared with the dropping polymerization. Since the coalescence can be a high molecular weight body, the water resistance and solvent resistance of the coating film are improved. In addition, for the second and subsequent stages, the polymerization stability is improved by emulsion polymerization by a technique of dropping a pre-emulsion solution.

As the polymerization initiator used for the polymerization of the acrylic monomer mixture, those generally used for radical polymerization can be used, for example, persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate and the like. Azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-) 2,4-dimethylvaleronitrile), oil-soluble azo compounds such as 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile; 2,2′-azobis {2-methyl-N- [1,1- Bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [2- (1-hydroxyethyl)] propionamide 2,2′-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) Propane] and its salts, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] and its salts, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidine -2-yl) propane] and its salts, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) and its salts, 2,2′-azobis {2- [1- (2- Hydroxyethyl) -2-imidazolin-2-yl] propane} and salts thereof, 2,2′-azobis (2-methylpropionamidine) and salts thereof, 2,2′-azobis [N- (2-carboxyethyl) -2 Water-soluble azo compounds such as methylpropionamidine] and salts thereof; benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobuty Organic peroxides such as a rate are listed.
These initiators may be used alone or in combination of two or more.

The addition amount of the radical polymerization initiator used in the first step is 0.001 to 10 parts by mass with respect to 100 parts by mass of the total mass of the acrylic monomer mixture provided in the first step. preferable. Taking into consideration the progress of polymerization and control of the reaction, it is more preferably 0.005 to 10 parts by mass. Moreover, it is still more preferable that it is 0.005-1 mass part from a viewpoint of the water resistance, solvent resistance, and a weather resistance improvement by high molecular weight increase of the polymer particle finally obtained. Further, from the viewpoint of reducing the coarse particle ratio of the finally obtained polymer dispersion, it is more preferably 0.005 to 0.5 parts by mass, still more preferably 0.005 to 0.2 parts by mass, and particularly preferably Is 0.005 to 0.09 parts by mass.
Here, the “rough particle ratio” means that the polymer is coalesced during the polymerization and the average particle diameter is in the form of particles exceeding 1 μm. For example, the measurement of the particle diameter or after the polymerization Evaluation can be made by measuring the weight of the particulate polymer remaining on the mesh after filtration through a mesh or the like.

  The addition amount of the radical polymerization initiator used in the second and subsequent steps is 0.01 to 10 parts by mass with respect to 100 parts by mass of the total mass of the acrylic monomer mixture provided to each stage. preferable. Among these, it is more preferable that the amount is 0.02 to 5 parts by mass in consideration of polymerization progress and reaction control.

In the polymerization, it is preferable to use a reducing agent such as sodium bisulfite, ferrous sulfate, ascorbate or Rongalite in combination with the above radical polymerization initiator.
Among these, it is more possible to employ a combination of organic peroxides such as t-butyl hydroperoxide and ferrous sulfate, ascorbate, etc., from the viewpoint of polymerization progress, water resistance and weather resistance of the coating film. preferable.

In the polymerization, an emulsifier can be used as necessary. When an emulsifier is used, the polymerization stability during emulsion polymerization can be improved, and aggregates can be reduced. In this case, the obtained polymer dispersion contains an emulsifier.
The content of the emulsifier is usually preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass as a total mass of the acrylic monomer mixture provided for each stage. 5 parts by mass, more preferably 0.5 to 2 parts by mass.
As the emulsifier, the following anionic, cationic and nonionic surfactants and reactive surfactants can be used.

Anionic surfactants include potassium oleate, sodium laurate, sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkyl naphthalene sulfonate, sodium dialkyl sulfosuccinate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkyl Non-reactive surfactants such as sodium allyl ether sulfate, polyoxyethylene alkyl phosphate ester, polyoxyethylene alkyl allyl phosphate ester, and alkyl allyl sulfosuccinate (eg, Sanyo Kasei Co., Ltd .: Eleminol (registered trademark) JS-) 2, manufactured by Kao Corporation: latemuru (registered trademark) S-180A, S-180, etc.), polyoxyethylene alkylpropenyl phenyl ether sulfate ester Ammonium salts (for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Aqualon (registered trademark) HS-10, HS-5, BC-10, BC-5 and the like), α-sulfo-ω- (1- ( Nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl) ammonium salt (for example, Adeka Soap (registered trademark) SE-10, manufactured by Asahi Denka Kogyo Co., Ltd.) SE-1025A and the like), polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate ammonium salt (for example, Dairon Kogyo Seiyaku Co., Ltd .: Aqualon (registered trademark) KH-10) and the like. ), Α-sulfo-ω- (1- (alkoxy) methyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl) ammo Nium salts (for example, Asahi Denka Kogyo Co., Ltd .: Adekaria Soap (registered trademark) SR-10, SR-1025, etc.), polyoxyalkylene alkenyl ether ammonium sulfate salts (for example, Kao Corporation: Latemul) (Registered trademark) PD-104 and the like) and the like.
Examples of the cationic surfactant include non-reactive surfactants such as stearylamine hydrochloride, lauryltrimethylammonium chloride, and trimethyloctadecylammonium chloride.
Nonionic surfactants include non-reactive surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethyleneoxypropyl block polymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, α- Hydro-ω- (1-alkoxymethyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl)) (Asahi Denka Kogyo Co., Ltd .: Adeka Soap ER-10, ER- 20, ER-30, ER-40), polyoxyethylene alkyl propenyl phenyl ether (Daiichi Kogyo Seiyaku Co., Ltd .: Aqualon RN-20, RN-30, RN-50), polyoxyalkyl alkenyl ether (Kao ( Co., Ltd .: Laterum PD-420, PD -430, PD-450) and the like.
Moreover, an amphoteric surfactant can also be used as an amphoteric component.
These emulsifiers can be used alone or in combination of two or more.

The polymer dispersion of the present invention is preferably adjusted to about pH 6.5 to 11.0 by adding a basic compound after polymerization. This improves the stability of the polymer dispersion and the storage stability of the aqueous coating material.
Examples of such basic compounds include ammonia, triethylamine, propylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, 1-amino-2-propanol. 2-amino-1-propanol, 2-amino-2-methyl-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propyl Examples include aminoethanol, ethoxypropylamine, aminobenzyl alcohol, morpholine, sodium hydroxide, and potassium hydroxide. Among these, from the viewpoint of the stability of the polymer dispersion, amine-based compounds are preferable, and 2-dimethylaminoethanol is preferably used.

The average particle size of the polymer particles of the present invention is preferably 10 to 1000 nm from the viewpoints of film formability, water resistance, water absorption resistance, hydrolysis resistance, and solvent resistance of the coating film, More preferably, it is 500 nm, It is further more preferable that it is 50-400 nm, It is especially preferable that it is 70-300 nm.
In the present specification, the average particle size of the polymer particles is a value calculated by cumulant analysis after measurement at room temperature using a dense particle size analyzer FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.
Further, the solid content concentration (polymer particle concentration) in the polymer dispersion of the present invention is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass. If the solid content concentration in the polymer dispersion is 10 to 80% by mass, it is preferable because it is easy to adjust the viscosity when preparing an aqueous coating material and the final solid content.

<Water-based coating material>
The aqueous coating material of the present invention contains a polymer dispersion, and preferably further contains various additives.
Examples of additives include various pigments, resin beads, antifoaming agents, pigment dispersants, leveling agents, anti-sagging agents, curing catalysts, matting agents, ultraviolet absorbers, light stabilizers, antioxidants, and heat resistance. Various additives such as an improver, a slip agent, a preservative, a plasticizer, a thickener, and a solvent can be used, and one or more of these can be used.
The aqueous coating material includes other polymer particles (for example, polyester resins, polyurethane resins, acrylic resins, acrylic silicone resins, silicone resins, fluorine resins, epoxy resins, alkyd resins, etc.). Particles), water-soluble resin / viscosity control agent, amino resin, polyisocyanate compound, blocked polyisocyanate compound, melamine resin, urea resin, carboxyl group-containing compound, carboxyl group-containing resin, epoxy group-containing resin Further, a curing agent such as an epoxy group-containing compound or a carbodiimide group-containing compound may be mixed.

Examples of the pigment include a color pigment, an extender pigment, and a glitter pigment.
Examples of coloring pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, selenium pigments, and perylene pigments. Is mentioned.
Examples of extender pigments include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white.
Examples of bright pigments include aluminum, copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide, glass flake, hologram And pigments.
One or more of these can be used.

The aqueous coating material of the present invention may further contain a solvent.
As the solvent, those usually used for water-based paints can be used. Examples of such a solvent include linear, branched or cyclic aliphatic alcohols having 5 to 14 carbon atoms; alcohols containing an aromatic group; general formula HO— (CH ₂ CHXO) _p — Represented by R ₄ (R ₄ is a linear or branched alkyl group having 1 to 10 carbon atoms, X is a hydrogen atom or a methyl group, and p is an integer of 5 or less). ) ethylene glycol or (poly) monoethers and propylene glycol; general formula _{R 5 COO- (CH 2 CHXO)} q -R 6 (R 5, R 6 is a straight-chain or branched having 1 to 10 carbon atoms X is a hydrogen atom or a methyl group, and q is an integer of 5 or less.) (Poly) ethylene glycol ether ester or (poly) propylene glycol ether Steal; aromatic organic solvents such as toluene and xylene; mono- or diisobutyrate of 2,2,4-trimethyl-1,3-pentanediol, 3-methoxybutanol, 3-methoxybutanol acetate, 3-methyl- Examples include 3-methoxybutanol and 3-methyl-3-methoxybutanol acetate.
Among these, linear, branched or cyclic aliphatic alcohols having 5 to 14 carbon atoms are preferable, alcohol based hydrophobic solvents having 7 to 14 carbon atoms are more preferable, 1-octanol, 2-octanol, Particularly preferred is at least one alcoholic hydrophobic solvent selected from the group consisting of 2-ethyl-1-hexanol, ethylene glycol mono-2-ethylhexyl ether, propylene glycol mono n-butyl ether, and dipropylene glycol mono n-butyl ether.

The concentration of the polymer particles in the aqueous coating material is preferably 1 to 80% by mass, and more preferably 2 to 70% by mass. If it is this range, it is excellent in a coating-material viscosity characteristic, the water resistance of a coating film, and solvent resistance.
Further, when the aqueous coating material contains other polymer particles other than the polymer particles of the present invention, it is 5000 parts by mass or less with respect to 100 parts by mass of the polymer particles. It is preferable in terms of water resistance and solvent resistance.

<Painted object>
The coated product of the present invention is a coated product having a coating film to which an aqueous coating material containing the polymer dispersion of the present invention is applied.
There is no particular restriction on the location where the aqueous coating material is applied to form a coating film, and various articles (hereinafter referred to as “substrate” for convenience) can be formed into coatings.
Examples of the substrate include, for example, an outer plate part of an automobile body, an automobile interior base material, an outer plate part of a household electric product, cement mortar, a slate plate, a gypsum board, an extruded plate, an expandable concrete, a metal, glass, a porcelain tile, Examples include asphalt, wood, waterproof rubber material, plastic, calcium silicate base material, PVC sheet, FRP (Fiber Reinforced Plastics), natural leather, synthetic leather, and fiber.

  Specific examples of the coated material having a coating film obtained by applying the aqueous coating material of the present invention include, for example, interior / exterior of passenger cars / trucks / motorcycles / buses, building materials, interior / exterior of buildings, window frames, window glass, Structural members, plate materials, exteriors of machinery and equipment, dustproof covers, reflectors for road signs, gaze guidance signs, road markings, various display devices, advertising towers, sound insulation walls for roads, sound insulation walls for railways, road decorative boards, traffic lights Light source cover, outdoor display board, bridge, guardrail, tunnel interior, tunnel lighting device, glass, solar battery cover, solar water heater heat collection cover, tent, plastic house, vehicle lamp cover, road mirror, vehicle Mirrors, motorcycle weighing covers and weighing panels, glass lenses, plastic lenses, helmet shields, goggles, houses and window glass for automobiles and railway vehicles, riding Windshield, heat exchange fins, glass surfaces at various locations, blinds, tire wheels, roofing materials, housing equipment, toilets, bathtubs, washbasins, lighting fixtures, lighting covers, kitchenware, sinks, cooking ranges, kitchen hoods, Examples thereof include a ventilation fan, a ship bottom, a functional fiber, a display which is a display screen of a television or a personal computer, and a film to be attached to the article.

(Formation method of coating film)
Examples of methods for applying the aqueous coating material to the surface of various substrates include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, roller coat coating, bar coat coating, air knife coating, brush coating, Various coating methods such as dipping coating can be selected as appropriate.
The coating amount of the aqueous coating material is the thickness after drying of the coating film obtained by applying the aqueous coating material, and is usually preferably about 0.1 to 100 μm, more preferably 1 to 50 μm, An amount of 10 to 40 μm is particularly preferable.
Moreover, it is preferable that the drying temperature after application | coating is normal temperature drying (5-35 degreeC), or the range exceeding 35 degreeC and 200 degrees C or less, ie, 5-200 degreeC. In particular, the aqueous coating material of the present invention can form a coating film having excellent water resistance and solvent resistance even when the drying conditions are low temperature and short time, so that it is dried at room temperature (5-35 ° C.) or low temperature from the viewpoint of energy saving. It is preferable to employ drying (over 35 ° C. and 100 ° C. or less), that is, drying at 5 to 100 ° C., and more preferably 5 to 80 ° C. The drying time is preferably, for example, 30 seconds to 5 minutes. According to the aqueous coating material of the present invention, a coating film excellent in water resistance and solvent resistance can be formed even under conditions where water and solvent evaporation and particle fusion are insufficient.

  Moreover, you may implement the drying after application | coating in two or more processes. For example, after performing a preliminary process such as preheating or air blowing, this process may be performed using a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace at a higher temperature than the preliminary process. When preheating is performed, the time is preferably about 30 seconds to 15 minutes, more preferably 1 to 10 minutes, and further preferably 2 to 5 minutes. The temperature and time of this step can be appropriately selected from the above preferable range and the like.

  As described above, according to the present invention, a polymer dispersion excellent in polymerization stability and excellent in coating viscosity characteristics and storage stability when used in an aqueous coating material, and contained in the polymer dispersion Polymer particles can be provided. According to the present invention, there is provided an aqueous coating material capable of forming a coating film excellent in water resistance and solvent resistance even when the drying conditions are low temperature and for a short time, and a coated material coated with the aqueous coating material. Can be provided. Moreover, the coated material in which the coating film is formed with the aqueous coating material of the present invention can also exhibit excellent coating film appearance, solvent resistance, water resistance, water absorption resistance, and hydrolysis resistance.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not limited to these Examples.
Unless otherwise specified, “part” in this example means “part by mass”, and “%” means “mass%”. Moreover, the measurement, evaluation, etc. about the polymer dispersion liquid and the aqueous coating material in this example were performed by the methods shown below.
Moreover, the compounding part number of each component at the time of manufacturing a polymer dispersion liquid in each example was shown in Tables 1-4, and the measurement result in each example, the evaluation result, etc. were shown in Tables 5-7.

[Surface acid value of polymer particles]
2 g of the polymer dispersion was diluted with 100 g of deionized water and subjected to potentiometric titration using an automatic potentiometric titrator (manufactured by Kyoto Electronics Industry Co., Ltd., AT-610). The acid value was calculated. As the titrant, 0.1 mol / L potassium hydroxide solution / methanolic (manufactured by Kanto Chemical Co., Inc.) was used.
A = (B × 0.1 × f × 56.1) / S (1)
The symbol in Formula (1) represents the following values.
A: Surface acid value of polymer particles (mgKOH / g)
B: Potassium hydroxide titration (mL)
f: Calibration coefficient of potassium hydroxide S: Mass of polymer particles (g, solid content)

[Viscosity of aqueous coating material (Ti)]
The aqueous coating material is put into a 250 ml polyethylene container, covered, and left in a thermostatic bath at 25 ° C. for 3 hours. After measuring the viscosity η at 6 rpm with a 10M type, # 3 rotor), immediately measure the viscosity at 60 rpm. From the viscosity η at 60 rpm (60 rpm) and the viscosity η at 6 rpm (6 rpm), the following equation (2) Ti was calculated.
Ti = η (6 rpm) / η (60 rpm) (2)
In addition, in this invention, if Ti value is 4.5-8.5, it can be judged that it has favorable viscosity.

[Storage stability of aqueous coating materials]
The aqueous coating material whose viscosity was measured was allowed to stand in a 40 ° C. atmosphere for 10 days and then left in a thermostatic bath at 25 ° C. for 3 hours. When the temperature reached 25 ° C., the viscosity of 6 rpm was measured with a B-type viscometer. The viscosity change rate was calculated from the following formula (3).
A = {(η2−η1) / η1} × 100 (3)
Here, the symbol in Formula (3) shows the following values.
A: Viscosity change rate (%)
η1: Initial viscosity (mPa · s, 6 rpm)
η2: viscosity after standing at 40 ° C. for 10 days (mPa · s, 6 rpm)
In addition, it can be judged that a viscosity change rate (%) is favorable if it exists in the range of -50 to + 50%.

[Water resistance and solvent resistance of coating film]
(Preparation of test plate for evaluation)
A black acrylic plate (TP Giken, 2 mm thick, 150 mm long x 70 mm wide) was coated with the aqueous coating material obtained in each example with a bar coater # 40 in an atmosphere of 20 ° C. It dried on dry conditions (80 degreeC, 3 minutes). Then, what was left to stand at room temperature for 30 minutes was used as the test plate for evaluation of solvent resistance and water resistance. The film thickness after drying of the coating film was about 20 μm.
(Evaluation of water resistance)
The test plate for evaluation was taken out after being immersed in warm water at 40 ° C. for 10 days, taken out, and ΔL after being dried at room temperature for 2 hours was used as an index of water resistance.
ΔL is a value obtained by subtracting “L value of coating film before test” from “L value of coating film taken out after being immersed in warm water of 40 ° C. for 10 days and dried at room temperature for 2 hours”. The L value is an index of “brightness (whiteness)” and was measured with a CR-300 manufactured by MINOLTA. It can be judged that it has favorable water resistance as ΔL is 1.5 or less.
(Evaluation of solvent resistance)
The test plate for evaluation was immersed in SOLVESSO 100 (an aromatic solvent manufactured by ExxonMobil Chemical) for 30 seconds, and immediately after pulling up, the solvent remaining on the coating film surface was sucked off by Kimwipe. The 60 ° gloss retention (gloss retention) and ΔL (difference in L value before and after immersion in a solvent) after drying at room temperature for 2 hours were used as indicators of solvent resistance.
The 60 ° gloss retention rate (%) means that the 60 ° gloss of the pre-test coating film was immersed in “G1”, SOLVESSO 100 for 30 seconds, and the solvent remaining on the coating film surface was absorbed by Kimwipe immediately after pulling, When the 60 ° gloss after drying at room temperature for 2 hours is “G2”, the value is represented by “(G2 / G1) × 100”. The 60 ° gloss was measured with PG-1M manufactured by Nippon Denshoku Industries Co., Ltd. Moreover, it can be judged that it has favorable solvent resistance when the retention of 60 ° gloss is 90% or more and ΔL is 1.5 or less.

[Example 1]
(Preparation of polymer dispersion)
(1) First stage polymerization process (mixed introduction of acrylic monomer mixture)
In a flask equipped with a stirrer, a reflux condenser, a temperature controller, and a dropping pump, a polyester-based urethane resin (trade name: Implanil LP RSC 3040, manufactured by Sumika Bayer Urethane Co., Ltd., solid content 40%) as a urethane resin : 75 parts (30 parts as solid content), deionized water: 73.2 parts, Neocor SWC (anionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content 70%): 0.4 parts (solid 0.28 parts), Adeka Soap ER-10 (nonionic surfactant, manufactured by ADEKA Corporation): 0.4 parts, as radical polymerizable monomer, methyl methacrylate: 3.7 parts, normal butyl Acrylate: 43.4 parts, allyl methacrylate: 1.6 parts, triallyl cyanurate: 0.7 parts were charged, and the flask was heated to 50 ° C. Thereafter, as a polymerization initiator, a 70% aqueous solution of t-butyl hydroperoxide (trade name; Kayabutyl H70, manufactured by Kayaku Akzo Co., Ltd.): 0.02 part (0.014 part as a pure component) and a reducing agent As follows: Ferrous sulfate: 0.00020 part, ethylenediaminetetraacetic acid (EDTA): 0.00027 part, sodium ascorbate: 0.02 part, deionized water: 1 part. Further, after confirming the peak top temperature due to the polymerization exotherm, the internal temperature of the flask was raised to 75 ° C. and held for 20 minutes.
(2) Second stage polymerization step (pre-emulsion solution added dropwise)
Next, 0.1 parts of sodium ascorbate and 5 parts of deionized water are added as a reducing agent to the dispersion obtained in the above (1) and kept at 75 ° C. for 10 minutes. 11.43 parts, 2-ethylhexyl acrylate: 7.4 parts, 2-hydroxyethyl methacrylate: 1 part, allyl methacrylate: 0.7 parts, acrylic acid: 0.07 parts, Neocor SW-C: 0.4 parts ( A pre-emulsified solution containing a solid content of 0.28 parts), Adeka Soap ER-10: 0.4 part, deionized water: 16 parts, and a 70% aqueous solution of t-butyl hydroperoxide (trade name) ; Kayabutyl H70, manufactured by Kayaku Akzo Co., Ltd.): 0.03 part (0.021 part as a pure component), deionized water: 5 parts of a polymerization initiator aqueous solution was added dropwise over 1 hour. During the dropwise addition, the internal temperature of the flask was maintained at 75 ° C., and was maintained at 75 ° C. for 1.5 hours after the completion of the dropwise addition. Thereafter, the reaction liquid is cooled to room temperature, dimethylaminoethanol: 0.52 part and deionized water: 5 parts are added as an aqueous amine solution, and a dispersion liquid (polymer dispersion liquid) containing the polymer particles of the present invention is obtained. Obtained.
And the surface acid value of the obtained polymer particle and the average particle diameter were measured. The solid concentration is shown in the table.

(Preparation of aqueous coating material)
In the obtained polymer dispersion, 12 parts of 2-ethyl-1-hexanol as a solvent (11.8% with respect to the solid content of the obtained polymer dispersion) and a urethane associative thickener as a thickener. (Product name: UH-756-VF, manufactured by ADEKA Co., Ltd.) 0.6 part (0.6% based on the solid content of the obtained polymer dispersion) was added and mixed to prepare an aqueous coating material. Prepared. The concentration of the polymer particles in the obtained aqueous coating material was 38.4%.
The obtained aqueous coating material was applied to a test plate for evaluation as described above to form a coating film, and the water resistance and solvent resistance of the coating film were evaluated. In addition, the viscosity and storage stability of the aqueous coating material were evaluated.

[Examples 2 to 16]
As shown in Tables 1 to 3, a polymer dispersion and an aqueous coating material were prepared in the same manner as in Example 1, except that each component was used. And the measurement and evaluation similar to Example 1 were performed.

[Comparative Examples 1-4]
As shown in Table 4, a polymer dispersion and an aqueous coating material were prepared in the same manner as in Example 1 except that each component was used. And the measurement and evaluation similar to Example 1 were performed.

However, the symbol in a table | surface shows the following compounds.
[Urethane resin]
I-1: Polyester urethane resin having a sulfonic acid group (trade name: Implanil LP RSC 3040, manufactured by Sumika Bayer Urethane Co., Ltd., solid content 40%)
I-2: Polycarbonate urethane resin having a sulfonic acid group (trade name: F-8082D, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 41%)
I-3: Polyether urethane resin having a carboxy group (trade name: Permarin UA-150, manufactured by Sanyo Chemical Industries, Ltd., solid content 30%)

[Acrylic monomer mixture]
(Monomer having one radically polymerizable group)
MMA: methyl methacrylate nBA: normal butyl acrylate 2EHA: 2-ethylhexyl acrylate (monomer having two or more radically polymerizable groups)
AMA: Allyl methacrylate TAC: Triallyl cyanurate (hydroxyl group-containing radical polymerizable monomer)
2HEMA: 2-hydroxyethyl methacrylate (acid group-containing radical polymerizable monomer)
・ AA: Acrylic acid ・ MAA: Methacrylic acid

As shown in Tables 5 to 7, the polymer dispersions of Examples 1 to 16 were excellent in polymerization stability, and were excellent in paint viscosity characteristics and storage stability of an aqueous coating material obtained from the dispersion. Furthermore, the coating film obtained from the aqueous coating material has excellent solvent resistance and water resistance even under low temperature and short drying conditions of 80 ° C. for 3 minutes.
On the other hand, in Comparative Example 1, since the surface acid value of the polymer particles was less than 0.1 mgKOH / g, the storage stability when the aqueous coating material was used was inferior.
In Comparative Example 2, since the surface acid value of the polymer particles exceeded 19 mg KOH / g, the polymerization stability and the storage stability when used as an aqueous coating material were inferior. Moreover, when it was immersed in 40 degreeC warm water for 10 days, the coating film peeled off and floated and the water resistance was also inferior.
In Comparative Example 3, since the dispersion group of the urethane resin was not sulfonic acid but carboxylic acid, the storage stability when the aqueous coating material was used was inferior. Moreover, peeling was recognized in evaluation of solvent resistance, and the coating film was inferior in solvent resistance.
In Comparative Example 4, since the dispersing group (acid group) of the urethane resin is not a sulfonic acid group but a carboxy group, the polymerization stability when polymerizing a monomer containing an acid group-containing radically polymerizable monomer is poor. Aggregation was observed in the second polymerization step.

  The polymer dispersion of the present invention has excellent polymerization stability during production, and the aqueous coating material containing the polymer dispersion has excellent paint viscosity characteristics and storage stability. Furthermore, the coating film to which the aqueous coating material of the present invention is applied exhibits excellent water resistance and solvent resistance. In particular, even a dried coating film obtained under conditions where the drying conditions are insufficient such as low temperature and short time evaporation of water and solvent and particle fusion are excellent in water resistance and solvent resistance. Therefore, the water-based coating material of the present invention is applied to various coatings such as outer plate parts of automobile bodies such as passenger cars, trucks, motorcycles, buses, etc., protection of chassis of automobile parts, buildings, civil engineering structures, etc. It can be used for applications and is extremely useful industrially.

Claims (7)

  Polymer particles containing a urethane resin having a sulfonic acid group and an acrylic polymer in the same particle and having a surface acid value of 0.1 to 19 mgKOH / g measured by potentiometric titration.   The polymer particle according to claim 1, wherein the acrylic polymer includes a repeating unit derived from a monomer having two or more radically polymerizable groups.   The polymer particle according to claim 2, comprising 0.05 to 10% by mass of a repeating unit derived from a monomer having two or more radically polymerizable groups.   The acrylic polymer includes a repeating unit derived from an acid group-containing radical polymerizable monomer, and 0.008 to 3.4% by mass of a repeating unit derived from the acid group-containing radical polymerizable monomer. The polymer particle as described in any one of 1-3.   The polymer dispersion liquid containing the polymer particle as described in any one of Claims 1-4.   An aqueous coating material comprising the polymer dispersion according to claim 5.   A coated article to which the aqueous coating material according to claim 6 is applied.