JP2019123790A - Aqueous resin dispersion, aqueous coating material, and coated article - Google Patents

Abstract

An aqueous resin dispersion excellent in storage stability, suitable as a material of an aqueous paint from which a coating excellent in impact resistance can be obtained, an aqueous paint from which a coating excellent in impact resistance can be obtained, and impact resistance Providing a paint having an excellent coating film.
An aqueous resin dispersion in which polymer particles containing a urethane polymer (I) and an acrylic polymer (II) are dispersed in an aqueous medium, wherein the hydroxyl value of the acrylic polymer (II) is 25 to 100 mg KOH. An aqueous resin dispersion having an acid value of 0.5 to 25 mg KOH / g and a glass transition temperature of −10 ° C. or less is used.
【Selection chart】 None

Description

  The present invention relates to an aqueous resin dispersion, an aqueous paint containing the aqueous resin dispersion, and a coated article coated with the aqueous paint.

Heretofore, in the field of paints, from the viewpoint of environmental protection and safety and health, conversion of organic solvent-based paints to water-based paints has been attempted.
However, there is a problem that the aqueous coating is inferior to the organic solvent based coating in the storage stability, the coating appearance, the coating strength, the coating strength, the weather resistance, the water resistance, the solvent resistance, the staining resistance and the like. , Development of water-based paint that solves these problems has been carried out. In particular, in recent years, a more advanced water-based paint capable of forming a coating film having excellent impact resistance in addition to these coating film properties is required.

  An aqueous dispersion of a composite resin containing a resin having different properties has been proposed as a material of an aqueous coating for solving these various problems. For example, Patent Documents 1 to 3 disclose aqueous resin dispersions of polymer particles containing a urethane polymer and an acrylic polymer. The coating film formed from the aqueous coating containing the aqueous resin dispersion has the characteristics of the urethane polymer, such as flexibility, toughness, solvent resistance, abrasion resistance, low-temperature drying property and the like, and the acrylic polymer. It has properties such as weather resistance, hydrolysis resistance and high gloss.

JP, 2008-88429, A Japanese Patent Application Publication No. 10-507483 Unexamined-Japanese-Patent No. 10-298491

However, the aqueous resin dispersions described in Patent Documents 1 and 2 are inferior in storage stability. Moreover, the coating film formed from the water-based paint containing the water-based resin dispersion described in Patent Documents 1 to 3 is insufficient in impact resistance.
Thus, the aqueous resin dispersions described in Patent Documents 1 to 3 have not been able to solve both the storage stability and the impact resistance, which are the problems of the aqueous coating.

  The present invention is an aqueous resin dispersion excellent in storage stability, suitable as a material of an aqueous paint from which a coating excellent in impact resistance can be obtained, an aqueous paint from which a coating excellent in impact resistance can be obtained, and impact resistant It aims at providing a coated article which has a coating film excellent in quality.

The present invention has the following aspects.
[1] An aqueous resin dispersion in which polymer particles containing a urethane polymer (I) and an acrylic polymer (II) are dispersed in an aqueous medium, wherein the acrylic polymer (II) has a hydroxyl value of 25 to 100 mg KOH / An aqueous resin dispersion having an acid value of 0.5 to 25 mg KOH / g and a glass transition temperature of −10 ° C. or less.
[2] The aqueous resin dispersion as described in [1], obtained through the following step (a) and step (b).
Step (a): in the presence of an aqueous medium and the urethane polymer (I), the acrylic monomer component (II-1) is polymerized to form the urethane polymer (I) and the acrylic polymer (II-1) Obtaining a dispersion of the polymer mixture (P) containing
Step (b): The acrylic monomer component (II-2) is polymerized in the presence of an aqueous medium and the polymer mixture (P) to form the urethane polymer (I), and the acrylic polymer (II) 1) A step of obtaining a dispersion liquid of a polymer mixture (Q) containing the above-mentioned acrylic polymer (II) composed of-1 and an acrylic polymer (II-2).
[3] The aqueous resin dispersion according to [1] or [2], wherein the acrylic polymer (II) further contains a constituent unit derived from a hydroxyl group-containing radically polymerizable monomer (a1).
The water-based paint containing the water-based resin dispersion as described in any one of [4] [1]-[3].
[5] The aqueous paint according to [4], further comprising a curing agent.
[6] The aqueous paint according to [4] or [5], further comprising a resin other than the urethane polymer (I) and the acrylic polymer (II).
[7] A coated article having a coating film formed from the water-based paint according to any one of [4] to [6].

  According to the present invention, an aqueous resin dispersion excellent in storage stability suitable as a material of an aqueous paint from which a coating excellent in impact resistance can be obtained, an aqueous paint from which a coating excellent in impact resistance can be obtained, The coated article which has a coating film excellent in impact resistance can be provided.

Hereinafter, the present invention will be described in detail.
In the following specification, a coating film formed of an aqueous paint containing the aqueous resin dispersion of the present invention is simply referred to as a "coating film".
Moreover, "mass average molecular weight" means the value calculated by polystyrene conversion using gel permeation chromatography (GPC).
"(Meth) acrylate" is a generic term for acrylate and methacrylate.

[Aqueous resin dispersion]
The aqueous resin dispersion (A) of the present invention is a dispersion in which polymer particles containing a urethane polymer (I) and an acrylic polymer (II) shown below are dispersed in an aqueous medium. When the aqueous resin dispersion (A) contains the urethane polymer (I), the toughness and the film forming property of the coating film are improved, and when the acrylic polymer (II) is contained, the water absorption of the coating film is reduced. . As a result, a coating film excellent in impact resistance is obtained. The coating film also tends to be excellent in water resistance.

  The mass ratio of the urethane polymer (I) to the acrylic polymer (II) is, when the total of them is 100, urethane polymer (I) / acrylic polymer (II) = (10 to 90) / (10) -90) is preferable, (20-80) / (20-80) is more preferable, (20-60) / (40-80) is more preferable, and (20-50) It is particularly preferable that / (50 to 80). When the mass ratio of the urethane polymer (I) to the acrylic polymer (II) is within the above range, the balance between the impact resistance and the water resistance of the coating film becomes good.

The average particle diameter of the polymer particles contained in the aqueous resin dispersion (A) is preferably 10 to 1000 nm, more preferably 30 to 500 nm, and still more preferably 50 to 400 nm, Particular preference is given to 300 nm. If the average particle size of the polymer particles is within the above range, the film forming property of the coating film is improved.
The average particle size of the polymer particles means a cumulant average particle diameter measured by light scattering photometer (D _50).

It is preferable that it is 10-80 mass%, and, as for solid content concentration of aqueous resin dispersion (A), it is more preferable that it is 20-70 mass%. If the solid content concentration of the aqueous resin dispersion (A) is within the above range, it becomes easy to adjust the viscosity when making the aqueous coating and to adjust the final solid content.
The aqueous medium includes, for example, water or an alcoholic solvent mainly composed of water, preferably water.

<Urethane polymer (I)>
The urethane polymer (I) is a resin obtained by reacting a polyol and a polyisocyanate. That is, urethane polymer (I) is a reaction product of a polyol and a polyisocyanate.

The polyol is an organic compound having at least two hydroxyl groups in one molecule, and various polyols can be used.
Specific examples of such polyols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1, 6-Hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, tripropylene glycol, hexanediol, cyclohexanedimethanol, and other low molecular weight polyols; at least one of the low molecular weight polyols And polyether diols obtained by addition polymerization of ethylene oxide, propylene oxide, tetrahydrofuran and the like; at least one of the low molecular weight polyols; adipic acid; Polyester polyol, polyethylene glycol, polypropylene glycol, polycaprolactone polyol, polytetramethylene ether polyol, polycarbonate polyol, etc. obtained by polycondensation of dicarboxylic acid such as synic acid, itaconic acid, maleic anhydride, terephthalic acid and isophthalic acid Other examples include polybutadiene polyol, hydrogenated polybutadiene polyol, polyacrylic acid ester polyol and the like.
One of these may be used alone, or two or more may be used in combination.

The polyisocyanate is an organic compound having at least two isocyanate groups in one molecule, and various polyisocyanates can be used.
Specific examples of such polyisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 1,6,11-undecanetriisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, Lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2, 6-diisocyanatohexanoate Aliphatic polyisocyanates such as: isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methyl isocyanate Alicyclic polys such as chlorohexylene diisocyanate (hydrogenated TDI), bis (2-isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, etc. Isocyanate; 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 2,4- Diphenylmethane diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5 -Naphthylene diisocyanate, 4, ', 4''- triphenylmethane triisocyanate, m- isocyanatophenyl sulfonyl isocyanate, and aromatic polyisocyanates such as p- isocyanatophenyl sulfonyl isocyanate. Among these, yellowing aliphatic polyisocyanates and alicyclic polyisocyanates are preferable from the viewpoint of suppressing yellowing of the resulting urethane polymer (I).
One of these may be used alone, or two or more may be used in combination.

  As a manufacturing method of urethane polymer (I), the method of making the above-mentioned polyol and polyisocyanate react with catalysts, such as dibutyltin dilaurate, in ether, such as a dioxane, is mentioned, for example.

  The mass average molecular weight of the urethane polymer (I) is preferably 500 or more, and more preferably 1000 or more, from the viewpoint of improving the water resistance of the coating film and the coating film strength. The mass average molecular weight of the urethane polymer (I) is preferably 500,000 or less, more preferably 100,000 or less.

  The urethane polymer (I) is preferably used in the state of being dispersed in an aqueous medium when producing the aqueous resin dispersion (A), and is more preferably used in the state of being dispersed in water. In particular, a urethane polymer (I) having at least one of a carboxy group and a sulfonic acid group is preferable because the dispersibility in water is improved. Among these, urethane polymer (I) having a sulfonic acid group is particularly preferable. Although it will be described in detail later, when the radically polymerizable monomer is polymerized in the presence of the aqueous dispersion of the urethane polymer (I) having a sulfonic acid group to produce an acrylic polymer (II), the polymerization stability is improves.

  When using an aqueous dispersion of urethane polymer (I), the average particle diameter of the urethane polymer (I) in the aqueous dispersion is preferably 10 nm or more from the viewpoint of improving the water resistance of the coating film. And more preferably 30 nm or more. The average particle diameter of the urethane polymer (I) is preferably 1000 nm or less, more preferably 500 nm or less.

  In addition, the content of the urethane polymer (I) in the aqueous dispersion of the urethane polymer (I) is preferably such that the solid content concentration of the aqueous resin dispersion (A) is 10 to 80 mass%, The content is preferably 10% by mass or more, and more preferably 25% by mass or more. On the other hand, the content of the urethane polymer (I) in the aqueous dispersion of the urethane polymer (I) is 70 mass from the viewpoint that the aqueous paint containing the aqueous resin dispersion (A) exhibits good paintability. % Or less is preferable and 60 mass% or less is more preferable.

  As the aqueous dispersion of urethane polymer (I), a commercially available urethane aqueous polymer dispersion can be used as it is. The urethane aqueous polymer dispersion is also called "urethane dispersion", abbreviated as "PUD". As commercially available PUDs, for example, trade names manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: Superflex 110, Superflex 150, Superflex 210, Superflex 300, Superflex 420, Superflex 460, Superflex 470, Superflex 500M , Super flex 620, Super flex 650, Super flex 740, Super flex 820, F-8082D; trade name of Sumika Kobethurourethane Co., Ltd .: Product name: Bihydrol UH 2606, Bihydrol UH 650, Bihydrol UHXP 2648, Bihydrol UHXP 2650, Impla Neil DLE, IMPLANIL DLC-F, IMPLANIL DLN, IMPLANIL DL -W50, IMPLANIL DLP-R, IMPLANIL DLS, IMPLANYL DLU, IMPLANYL XP 2611, IMPLANIL LP RSC 1380, IMPLANYL LP RSC 1537, IMPLANIL LP RSC 1554, IMPLANIL LP RSC 3040; manufactured by DIC Corporation Brand name: Hydran HW-301, HW-310, HW-311, HW-312B, HW-333, HW-340, HW-350, HW-375, HW-920, HW-930, HW-940, HW- 950, HW-970, AP-10, AP-20, ECOS 3000; trade names made by Sanyo Chemical Industries, Ltd .: U-Coat UWS-145, Permarine UA-150, Permarine UA-200, Permarine UA-300, Permarine UA-3 0, U-Coat UX-320, Permarine UA-368, Permarine UA-385, U-Coat UX-2510; trade names made by Nikka Chemical Co., Ltd .: NeoSticker 100C, Evafanol HA-107C, Evafanol HA-50C, Evafanol HA-170 Evafanol HA-560; trade name of ADEKA Co., Ltd .: Adekabon Titer UHX-210, Adekabon Titer UHX-280, and the like.

<Acrylic polymer (II)>
Acrylic polymer (II) is a polymer containing a structural unit derived from a (meth) acrylic monomer.
The acrylic polymer (II) may contain a constituent unit derived from a radical polymerizable monomer other than the (meth) acrylic monomer. The radically polymerizable monomer is a monomer having a radically polymerizable group. The radically polymerizable group is a group containing a radically polymerizable carbon-carbon unsaturated double bond, a radically polymerizable carbon-carbon unsaturated triple bond, a radical ring-opening polymerizable ring and the like.

The acrylic polymer (II) preferably contains a constituent unit derived from a hydroxyl group-containing radically polymerizable monomer (a1) described later. When the acrylic polymer (II) contains a structural unit derived from a hydroxyl group-containing radically polymerizable monomer (a1), the impact resistance of the coating film is further improved.
Moreover, it is preferable that acrylic polymer (II) further contains the structural unit derived from the acidic radical containing radically polymerizable monomer (a2) mentioned later. The storage stability of the aqueous resin dispersion (A) is further improved by the acrylic polymer (II) containing a constituent unit derived from the acid group-containing radically polymerizable monomer (a2), and the impact resistance of the coating film The balance between water resistance and water resistance is good.
In addition, the acrylic polymer (II) may further contain a constituent unit derived from another radically polymerizable monomer (a3) described later.

(Physical properties)
The hydroxyl value of the acrylic polymer (II) is 25 to 100 mg KOH / g, preferably 40 to 100 mg KOH / g, and more preferably 40 to 80 mg KOH / g. When the hydroxyl value of the acrylic polymer (II) is 20 mg KOH / g or more, the impact resistance of the coating film is improved, and when it is 100 mg KOH / g or less, the storage stability of the aqueous resin dispersion (A) is improved.

The hydroxyl value of the acrylic polymer (II) was required to acetylate the hydroxyl group in 1 g of solid content of the acrylic polymer (II) solution with acetic anhydride and to neutralize the acetic acid formed along with the acetylation. It is a value determined by measuring the number of mg of potassium hydroxide by titration, and more specifically, it is determined from the following formula (ii).
Hydroxyl value (mg KOH / g) = (f1 × M1 / M2 / Mw1 × [KOH] × 1000) (ii)
(In the formula (ii), f1 is the number of hydroxyl groups of the hydroxyl group-containing radically polymerizable monomer, M1 is the mass (g) of the hydroxyl group-containing radically polymerizable monomer, and M2 is the acrylic polymer (II) Mw1 is the molecular weight (number average molecular weight) of the hydroxyl group-containing radically polymerizable monomer, and [KOH] is the molecular weight of potassium hydroxide.)

  The acid value of the acrylic polymer (II) is 0.5 to 25 mg KOH / g, preferably 1 to 20 mg KOH / g, and more preferably 5 to 20 mg KOH / g. If the acid value of the acrylic polymer (II) is within the above range, the storage stability of the aqueous resin dispersion (A) is improved. In particular, when the acid value of the acrylic polymer (II) is 0.5 mg KOH / g or more, the impact resistance of the coating film is improved.

The acid value of the acrylic polymer (II) is a value determined by measuring the number of mg of potassium hydroxide required to neutralize 1 g of the solid content of the acrylic polymer (II) solution by titration. Specifically, it is obtained from the following formula (iii).
Acid value (mg KOH / g) = (f2 × M3 / M2 / Mw2 × [KOH] × 1000) (iii)
(In the formula (iii), f2 is the number of acidic groups of the acid group-containing radically polymerizable monomer, M3 is the mass (g) of the acid group-containing radically polymerizable monomer, and M2 is an acrylic polymer It is mass (g) of (II), Mw 2 is a molecular weight (number average molecular weight) of an acid group containing radically polymerizable monomer, and [KOH] is a molecular weight of potassium hydroxide. Is a carboxy group, a sulfonic acid group or a phosphoric acid group.)

  The glass transition temperature of the acrylic polymer (II) is −10 ° C. or less. When the glass transition temperature of the acrylic polymer (II) is −10 ° C. or less, the flexibility and the film forming property of the coating film are improved, and the water resistance and the impact resistance are improved. From the viewpoint of further improving the impact resistance of the coating, the glass transition temperature of the acrylic polymer (II) is preferably −20 ° C. or less. Moreover, from the viewpoint of further improving the water resistance of the coating film, the glass transition temperature of the acrylic polymer (II) is preferably -80 ° C or higher, more preferably -70 ° C or higher, -60 ° C It is more preferable that it is more than.

In addition, the glass transition temperature of acrylic polymer (II) says the value calculated | required by the calculation formula of Fox represented by following formula (i).
1 / (273 + Tg) = Σ (W i / (273 + Tg i)) ··· (i)
(In formula (i), W _i represents the mass fraction of monomer i, and Tg _i represents the Tg (° C.) of the homopolymer of monomer i. Here, the individual weight of each monomer The glass transition temperature of the combination can be the value described in Polymer Handbook 4th Edition (POLYMER HANDBOOK Fourth Edition), John Wiley & Sons, Inc. (1999).)

(Hydroxyl group-containing radically polymerizable monomer (a1))
As a hydroxyl radical polymerizable monomer (a1), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate And 2-hydroxybutyl (meth) acrylate, polypropylene glycol (meth) acrylate and the like. Among these, 2-hydroxyethyl (meth) acrylate is preferable from the viewpoint of further improving the storage stability of the aqueous resin dispersion (A).
One of these may be used alone, or two or more may be used in combination.

(Acid group-containing radically polymerizable monomer (a2))
Examples of the acid group-containing radically polymerizable monomer (a2) include carboxyl group-containing radically polymerizable monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid and β-carboxyethyl acrylate; -Phosphate group-containing radically polymerizable monomers such as metachlorooxyethyl acid phosphate; Sulfonate-containing radically polymerizable monomers such as styrene sulfonates. Among these, from the viewpoint of further improving the polymerization stability and the storage stability of the aqueous resin dispersion (A), a carboxy group-containing radically polymerizable monomer is preferable, and among these, acrylic acid and methacrylic acid are particularly preferable.
One of these may be used alone, or two or more may be used in combination.

(Other radically polymerizable monomers (a3))
The other radical polymerizable monomer (a3) is not particularly limited as long as the effects of the present invention are not impaired, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i -Butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) ) Alkyl (meth) acrylates having an alkyl group having 1 to 22 carbon atoms, such as acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate; ethylene glycol di (meth) acrylate, propylene glycol Multifunctional (meth) acrylates such as Cole di (meth) acrylate, butylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate; cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl ( Cycloalkyl (meth) acrylates such as meta) acrylate; hydrolyzable silyl group-containing radically polymerizable monomers such as γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyltrimethoxysilane; Alkyl group terminal-type polyalkylene oxide group-containing radical polymerizable monomer such as methoxy polyethylene oxide mono (meth) acrylate; oxirane group-containing radical polymerization such as glycidyl (meth) acrylate Monomer: carbonyl group-containing ethylenic unsaturated monomer such as diacetone acrylamide; 1,2,2,6,6-pentamethyl-4-piperidyl (meth) acrylate, 2,2,6,6-pentamethyl- (Meth) acrylates having a photostabilizing effect such as 4-piperidyl (meth) acrylate; UV-absorbing components such as 2- [2'-hydroxy-5 '-(meth) acryloyloxyethylphenyl] -2H-benzotriazole Aminoalkyl (meth) acrylates such as 2-aminoethyl (meth) acrylate; amide group-containing radically polymerizable monomers such as (meth) acrylamides; metals such as zinc di (meth) acrylate Containing radically polymerizable monomers; (meth) acrylonitrile, benzyl (meth) acrylate, isobornyl Other (meth) acrylic monomers such as (meth) acrylate and methoxyethyl (meth) acrylate; aromatic vinyl monomers such as styrene and methylstyrene; conjugated dienes such as 1,3-butadiene and isoprene Monomers: Radical polymerizable monomers such as vinyl acetate, vinyl chloride, ethylene and the like can be mentioned. Among these, from the viewpoint of further improving the impact resistance of the coating film, acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate and 2-ethylhexyl acrylate are preferable. In particular, n-butyl acrylate is preferred. In addition, from the viewpoint of achieving a good balance between the storage stability of the aqueous resin dispersion (A) and the water resistance of the coating film, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, etc. Methacrylate is preferred, among which i-butyl methacrylate is particularly preferred.
One of these may be used alone, or two or more may be used in combination.

<Method of producing aqueous resin dispersion (A)>
The aqueous resin dispersion (A) of the present invention is preferably obtained, for example, through the following step (a) and step (b).
Step (a): The acrylic monomer component (II-1) is polymerized in the presence of an aqueous medium and a urethane polymer (I) to form a urethane polymer (I) and an acrylic polymer (II-1) Obtaining a dispersion of the polymer mixture (P) containing.
Step (b): The acrylic monomer component (II-2) is polymerized in the presence of the aqueous medium and the polymer mixture (P) to form a urethane polymer (I), and an acrylic polymer (II-1) A step of obtaining a dispersion of a polymer mixture (Q) containing an acrylic polymer (II) composed of an acrylic polymer (II-2) and an acrylic polymer (II-2).

The aqueous resin dispersion (A) obtained through the above step (a) and step (b) is composed of a urethane polymer (I), an acrylic polymer (II-1) and an acrylic polymer (II-2). It is a dispersion in which polymer particles (polymer mixture (Q)) containing the constituted acrylic polymer (II) are dispersed in an aqueous medium.
The mass ratio of the acrylic polymer (II-1) to the acrylic polymer (II-2) constituting the acrylic polymer (II) is, when the total of these is 100, the acrylic polymer (II-1) / It is preferable that it is acrylic polymer (II-2) = (40-95) / (5-60), it is more preferable that it is (50-95) / (5-50), (60-95) / (5 to 40) is more preferable, and (70 to 95) / (5 to 30) is particularly preferable. If the mass ratio of the acrylic polymer (II-1) to the acrylic polymer (II-2) is within the above range, the storage stability of the aqueous resin dispersion (A) is further improved. In addition, the balance between the impact resistance and the water resistance of the coating film becomes good.

In the aqueous resin dispersion (A) obtained by the above method, it is specified how the acrylic monomer component (II-1) is polymerized in the presence of the urethane polymer (I). It is difficult. For example, the acrylic monomer component (II-1) may be one polymerized in the state of being impregnated with the urethane polymer (I) or one polymerized without being impregnated in the urethane polymer (I). That is, as the acrylic polymer (II-1), there are one which is impregnated in the urethane polymer (I) and one which is not impregnated in the urethane polymer (I). Furthermore, it is also difficult to specify the molecular weight and the ratio of the structural unit, etc. of the acrylic polymer (II-1) impregnated with the urethane polymer (I) and the acrylic polymer (II-1) not impregnated. .
Moreover, it is also difficult to specify how the acrylic monomer component (II-2) is polymerized in the presence of the polymer mixture (P). For example, as the acrylic polymer (II-2), those bonded to the acrylic polymer (II-1) and those not bonded to the acrylic polymer (II-1) exist. Furthermore, it is also difficult to specify the molecular weight and the ratio of the structural unit of the acrylic polymer (II-2) bonded to the acrylic polymer (II-1) and the acrylic polymer (II-2) not bonded. is there.

(Step (a))
The step (a) polymerizes the acrylic monomer component (II-1) in the presence of the aqueous medium and the urethane polymer (I), and the urethane polymer (I) and the acrylic polymer (II-1) And a step of obtaining a dispersion of the polymer mixture (P) containing
The acrylic polymer (II-1) is a hydroxyl group-containing radically polymerizable monomer (a1) from the viewpoint that the storage stability of the aqueous resin dispersion (A) and the balance between the impact resistance and the water resistance of the coating film become good. It is preferable to include the structural unit derived from.
In addition, from the viewpoint of further improving the impact resistance of the coating, the acrylic polymer (II-1) is methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate It is preferable to include a constituent unit derived from another radically polymerizable monomer (a3) such as Among these, it is more preferable to include at least a structural unit derived from n-butyl acrylate.
That is, the acrylic monomer component (II-1) is a hydroxyl group-containing radically polymerizable monomer (a1), and methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2 It is preferable to contain other radically polymerizable monomers (a3), such as-ethylhexyl acrylate, and it is more preferable to contain a radically polymerizable monomer (a1) and n-butyl acrylate.

In step (a), polymerization of the acrylic monomer component (II-1) is usually carried out by adding a polymerization initiator described later. At that time, the urethane polymer (I) and the acrylic monomer component (II-1) are previously stirred to impregnate the acrylic polymer component (II-1) into the urethane polymer (I). Is preferable.
The impregnation step is not particularly limited as long as the effects of the present invention are not impaired, but the impregnation of the acrylic monomer component (II-1) into the urethane polymer (I), and the urethane polymer ( From the viewpoint of improving the stability of I), it is preferable to stir at a temperature condition of 25 to 95 ° C. for 1 minute to 24 hours. Moreover, it is more preferable to stir at 25 to 90 ° C. for 5 minutes to 10 hours, further preferable to stir at 25 to 80 ° C. for 10 minutes to 5 hours, and to stir at 25 to 70 ° C. for 30 minutes to 3 hours Particularly preferred.

  By carrying out the above-described impregnation step, first, the acrylic monomer component (II-1) is impregnated into the urethane polymer (I). Thereafter, when the polymerization is initiated, the acrylic monomer component (II-1) is polymerized inside the urethane polymer (I) to form a urethane polymer (I) and an acrylic polymer (II-1). The dispersion liquid which the polymer particle (polymer mixture (P)) containing was disperse | distributed to the aqueous medium is obtained.

  The temperature of the urethane polymer (I) and the acrylic monomer component (II-1) upon addition of the polymerization initiator may be determined, for example, in consideration of the 10-hour half-life temperature of the polymerization initiator used, In general, the temperature is preferably 10 to 90 ° C., and more preferably 20 to 80 ° C. When combined with the redox initiator, it may be carried out at a temperature lower than the above range.

  In the step (a), a polymerization initiator and a reducing agent described later may be used in combination. Moreover, you may use the molecular weight modifier mentioned later in order to adjust the molecular weight of acrylic polymer (II-1), and may use surfactant mentioned later. If a surfactant is used, the polymerization stability of the acrylic monomer component (II-1) can be improved, and aggregates at the time of polymerization can be reduced. Furthermore, the storage stability of the aqueous resin dispersion (A) tends to be further improved.

The glass transition temperature of the acrylic polymer (II-1) is preferably 0 ° C. or less, more preferably −10 ° C. or less, and still more preferably −20 ° C. or less. Moreover, it is preferable that it is -80 degreeC or more, it is more preferable that it is -70 degreeC or more, and, as for the glass transition temperature of acrylic polymer (II-1), it is more preferable that it is -60 degreeC or more. When the glass transition temperature of the acrylic polymer (II-1) is 0 ° C. or less, the impact resistance of the coating film is further improved, and when it is -80 ° C. or more, the water resistance of the coating film is improved.
In addition, the glass transition temperature of acrylic polymer (II-1) is calculated | required by the calculation formula of Fox represented by said Formula (i).

The hydroxyl value of the acrylic polymer (II-1) is preferably 30 to 120 mg KOH / g, more preferably 50 to 100 mg KOH / g, and still more preferably 50 to 80 mg KOH / g. If the hydroxyl value of the acrylic polymer (II-1) is in the above range, the storage stability of the aqueous resin dispersion (A), the impact resistance of the coating film, and the water resistance balance will be good.
In addition, the hydroxyl value of acrylic polymer (II-1) is calculated | required from said Formula (ii).

(Step (b))
The step (b) polymerizes the acrylic monomer component (II-2) in the presence of the aqueous medium and the polymer mixture (P) to form a urethane polymer (I), an acrylic polymer (II-1) And a step of obtaining a dispersion of the polymer mixture (Q) containing the acrylic polymer (II-2).
The acrylic polymer (II-2) is an acid group-containing radically polymerizable monomer (from the viewpoint that the storage stability of the aqueous resin dispersion (A) and the balance between the impact resistance and the water resistance of the coating film become good) It is preferable to include the structural unit derived from a2).
The acrylic polymer (II-2) is preferably methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, or i, from the viewpoint of achieving a good balance between the storage stability of the aqueous resin dispersion (A) and the water resistance of the coating. It is preferable to include a structural unit derived from another radically polymerizable monomer (a3) such as -butyl methacrylate, t-butyl methacrylate and the like. Among these, it is more preferable to include at least a structural unit derived from i-butyl methacrylate.
That is, the acrylic monomer component (II-2) is an acid group-containing radically polymerizable monomer (a2), and methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, etc. It is preferable to contain the other radically polymerizable monomer (a3), and it is more preferable to contain an acid group containing radically polymerizable monomer (a2) and i-butyl methacrylate.

  The method of adding the acrylic monomer component (II-2) to the dispersion of the polymer mixture (P) in the step (b) is not limited as long as the effects of the present invention are not impaired. Method of continuously dropping only the monomer component (II-2), method of dropping a pre-emulsion liquid obtained by emulsifying and dispersing the acrylic monomer component (II-2) in an aqueous medium containing a surfactant, acrylic The method etc. which inject | throws-in only system monomer component (II-2), etc. are mentioned. Among these, a method of dropping a pre-emulsion liquid obtained by emulsifying and dispersing an acrylic monomer component (II-2) in an aqueous medium containing a surfactant is preferable because polymerization stability is improved.

In step (b), the polymerization of the acrylic monomer component (II-2) is usually carried out by adding a polymerization initiator described later.
In the step (b), a reducing agent, a molecular weight modifier, etc. described later may be used.

The glass transition temperature of the acrylic polymer (II-1) is preferably -20 ° C or more, more preferably 0 ° C or more, and still more preferably 30 ° C or more. The glass transition temperature of the acrylic polymer (II-2) is preferably 120 ° C. or less, more preferably 100 ° C. or less, and still more preferably 80 ° C. or less. When the glass transition temperature of the acrylic polymer (II-2) is -20 ° C. or higher, the storage stability of the aqueous resin dispersion (A), the impact resistance of the coating film, and the water resistance balance become good. When the glass transition temperature of the acrylic polymer (II-2) is 120 ° C. or less, the impact resistance of the coating film is further improved.
In addition, the glass transition temperature of acrylic polymer (II-2) is calculated | required by the formula of Fox represented by said Formula (i).

The acid value of the acrylic polymer (II-2) is preferably 0.5 to 200 mg KOH / g, more preferably 5 to 150 mg KOH / g, and still more preferably 10 to 150 mg KOH / g. If the acid value of the acrylic polymer (II-2) is in the above range, the storage stability of the aqueous resin dispersion (A), the impact resistance of the coating film, and the water resistance balance will be good.
In addition, the acid value of acrylic polymer (II-1) is calculated | required from said Formula (iii).

  The dispersion of the polymer mixture (Q) obtained in the step (b) may be used as it is as the aqueous resin dispersion (A), but the pH of the dispersion is determined by adding a basic compound described later to the dispersion. It is preferable to adjust the neutral region to the weakly alkaline region, specifically, about pH 6.5 to 11.0. By adjusting the pH of the dispersion, the storage stability of the aqueous resin dispersion (A) is further improved.

(Polymerization initiator)
As the polymerization initiator, those generally used for radical polymerization can be used. For example, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; azobisisobutyronitrile, 2, 2 '-Azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- Oil-soluble azo compounds such as phenylazo-4-methoxy-2,4-dimethylvaleronitrile; 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propion Amide}, 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 salts thereof, 2,2′-azobis [2- (2-) Imidazolin-2-yl) propane] and its salt, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] and its salt, 2,2′-azobis ( 1-Imino-1-pyrrolidino-2-methylpropane) and its salt, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} and its salt, Water-soluble azo compounds such as 2,2′-azobis (2-methylpropionamidine) and salts thereof, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] and salts thereof; Oxidized bees Benzoyl, cumene hydroperoxide, t- butyl hydroperoxide, t- butyl peroxy-2-ethylhexanoate, t- butyl peroxy isobutyrate or the like organic peroxides and the like.
One of these may be used alone, or two or more may be used in combination.

The amount of the polymerization initiator used in the step (a) is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the acrylic monomer component (II-1). Among them, the amount is more preferably 0.005 to 10 parts by mass in consideration of the progress of the polymerization and the control of the reaction. Moreover, it is further more preferable that it is 0.005-1 mass part from a viewpoint which balance with impact resistance and water resistance becomes more favorable by high molecular weight formation of a final coating film. Moreover, it is more preferable that it is 0.005-0.5 mass part from a viewpoint of reducing the coarse particle ratio at the time of manufacturing a polymer mixture (P) and a polymer mixture (Q), and 0.005-0.5 mass part. The amount is particularly preferably 0.2 parts by mass, and most preferably 0.005 to 0.09 parts by mass.
Here, the “coarse particle rate” means the ratio of the polymer formed during polymerization causing coalescence and the like to become coarse particles having an average particle diameter of more than 1 μm. The coarse particle ratio can be measured, for example, by measuring the particle size distribution or measuring the mass of coarse particles separated by a mesh having an opening of 1 μm.

  The amount of the polymerization initiator used in the step (b) is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the acrylic monomer component (II-2). Among them, the amount is more preferably 0.02 to 5 parts by mass in consideration of the progress of polymerization and control of the reaction.

(Reductant)
As a reducing agent, for example, a water-soluble azo compound such as 2,2′-azobis [2- (2-imidazolin-2-yl) propane] having a half-life temperature of 70 ° C. or less and a salt thereof, bisulfite Sodium, ferrous sulfate, ascorbate, isoascorbic acid, Rongalite and the like can be mentioned.
One of these may be used alone, or two or more may be used in combination.

  As a combination of a polymerization initiator and a reducing agent, an organic peroxide such as t-butyl hydroperoxide as a polymerization initiator and sulfuric acid as a reducing agent are used in view of the progress of polymerization and the water resistance of the coating film. A combination with monoiron, isoascorbic acid is preferred.

(Molecular weight modifier)
Examples of molecular weight modifiers include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, n-hexyl mercaptan; halogen compounds such as carbon tetrachloride and ethylene bromide; -Known chain transfer agents such as methyl styrene dimer and the like can be mentioned.
One of these may be used alone, or two or more may be used in combination.

(Surfactant)
As surfactant, anionic surfactant, cationic surfactant, nonionic surfactant, amphoteric surfactant etc. are mentioned.
As an anionic surfactant, for example, potassium oleate, sodium laurylate, sodium dodecylbenzene sulfonate, sodium alkanesulfonate, sodium alkylnaphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, polyoxy acid Non-reactive surfactants such as sodium ethylene alkyl allyl ether sulfate, polyoxyethylene alkyl phosphate and polyoxyethylene alkyl allyl phosphate; alkyl allyl sulfosuccinate (eg trade name of Sanyo Kasei Kogyo Co., Ltd .: Eleminol (registered trademark) Trademark JS-2, trade name made by Kao Corporation: Latemu (registered trademark) S-180A, S-180, etc.), polyoxyethylene alkyl propenyl phenyl ester Ammonium sulfate (for example, trade name: manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Aqualon (registered trademark) HS-10, HS-5, BC-10, BC-5, etc.), α-sulfo-ω- (1 -(Nonyl phenoxy) methyl-2-(2- propenyloxy) ethoxy)-poly (oxy- 1, 2- ethanediyl) ammonium salt (For example, the trade name made from ADEKA, Inc .: Adekaria Soap (registered trademark) SE- 10, SE-1025A and the like), polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate ester ammonium salt (for example, trade name by Dai-ichi Kogyo Seiyaku Co., Ltd .: Aqualon (registered trademark) KH-10, etc.), α-Sulfo-ω- (1- (alkoxy) methyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl) ) Ammonium salt (for example, trade name: Adekaria Soap (registered trademark) SR-10, SR-1025, etc. made by ADEKA Co., Ltd.), polyoxyalkylene alkenyl ether sulfate ammonium salt (eg, trade name: Kao Corp .: Latemul) And reactive surfactants such as (registered trademark) PD-104 etc.).

Examples of the cationic surfactant include non-reactive surfactants such as stearylamine hydrochloride, lauryltrimethylammonium chloride and trimethyloctadecylammonium chloride.
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oxypropyl block polymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, etc .; α-Hydro-ω- (1-alkoxymethyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl) (for example, trade name of Adeka Co., Ltd .: Adekaria soap ER-10 , ER-20, ER-30, ER-40, etc.), polyoxyethylene alkylpropenyl phenyl ether (eg, trade name: manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Aqualon RN-20, RN-30, RN-50, etc.) , Polyoxyalkyl alkenyl agent And reactive surfactants such as Ter (for example, trade name made by Kao Corp .: Latemle PD-420, PD-430, PD-450, etc.) and the like.
One of these surfactants may be used alone, or two or more thereof may be used in combination. In addition, it is preferable to use an anionic surfactant from the viewpoint of the polymerization stability, the storage stability of the aqueous resin dispersion (A), and the water resistance of the coating film, and among them, the reactive surfactant is particularly preferable. preferable.

  The amount of the surfactant used is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, with respect to 100 parts by mass of the acrylic polymer (II), and 0.2 More preferably, it is 1 part by mass.

(Basic compound)
As the basic compound, for example, 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-propylaminoethanol, Ethoxypropylamine, aminobenzyl alcohol, morpholine, sodium hydroxide, potassium hydroxide and the like can be mentioned. Among these, from the viewpoint of improving the stability of the aqueous resin dispersion (A), amine compounds are preferable, and 2-dimethylaminoethanol is preferably used.
One of these may be used alone, or two or more may be used in combination.

<Function effect>
The aqueous resin dispersion (A) of the present invention described above contains the above-described urethane polymer (I) and acrylic polymer (II), and thus is excellent in storage stability. Moreover, if the aqueous resin dispersion (A) of this invention is used, the coating film excellent in impact resistance will be obtained.
The aqueous resin dispersion (A) of the present invention is suitable as a material of an aqueous paint from which a coating film having excellent impact resistance can be obtained.

[Water-based paint]
The water-based paint of the present invention comprises the water-based resin dispersion (A) of the present invention described above.
The water-based paint preferably contains a curing agent (B) and a resin (C) other than the urethane polymer (I) and the acrylic polymer (II). In addition, the water-based paint may further contain optional components as needed as long as the effects of the present invention are not impaired.

  The mass ratio of the aqueous resin dispersion (A) to the curing agent (B) to the resin (C) is, based on the total of these, 100, the aqueous resin dispersion (A) / curing agent (in solid content conversion) B) / resin (C) = (5 to 60) / (5 to 90) / (5 to 80) is preferable, and (5 to 30) / (30 to 90) / (5 to 50) Is more preferred. If the mass ratio of the aqueous resin dispersion (A), the curing agent (B) and the resin (C) is within the above range, the balance between the impact resistance and the water resistance of the coating film becomes good.

<Hardener (B)>
As a hardening | curing agent (B), an amino resin, a polyisocyanate compound, a block polyisocyanate compound, a polycarbodiimide compound etc. are mentioned, for example.
The amino resin is a generic term for a resin obtained by adding and condensing formaldehyde to a compound containing an amino group, and examples thereof include melamine resin, urea resin and guanamine resin.
As a curing agent (B), a melamine resin, a polyisocyanate compound, and a block polyisocyanate compound are preferable from a viewpoint which is excellent in the balance of a coating film physical property.
One of these may be used alone, or two or more may be used in combination.

  As the melamine resin, for example, an alkyletherified alkyletherified melamine resin is preferable, and a melamine resin substituted with at least one of a methoxy group and a butoxy group is more preferable. Specifically, trade names of Daicel Ornex Co., Ltd .: Saimel 202, Saimel 204, Saimel 211, Saimel 232, Saimel 236, Saimel 238, Saimel 251, Saimel 251, Saimel 254, Saimel 266, Saimel 267, Saimel 285 Commercial products such as Saimel 325, Saimel 327, Saimel 350, Saimel 370; trade names manufactured by Mitsui Chemicals, Inc .: Uvan 20N60, Uvan 20SE and the like.

  Examples of polyisocyanate compounds include aliphatic diisocyanates such as hexamethylene diisocyanate (HMDI) and trimethylhexamethylene diisocyanate (TMDI); alicyclic diisocyanates such as isophorone diisocyanate (IPDI); and xylylene diisocyanate (XDI) Aromatic-aliphatic diisocyanates; aromatic diisocyanates such as tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI); dimer acid diisocyanate (DDI), hydrogenated TDI (HTDI), hydrogenated And hydrogenated diisocyanates such as XDI (H6XDI) and hydrogenated MDI (H12 MDI); adducts and nurates of these diisocyanates, and the like.

  Examples of blocked polyisocyanate compounds include isocyanate groups of polyisocyanate compounds such as alcohols such as butanol, oximes such as methyl ethyl ketoxime, lactams such as .epsilon.-caprolactam, diketones such as acetoacetic acid diester, imidazole, 2 Those blocked with imidazoles such as ethylimidazole and phenols such as m-cresol.

<Resin (C)>
Resin (C) is resin other than urethane polymer (I) and acrylic polymer (II), for example, acrylic resin (however, except acrylic polymer (II)), polyester resin, polyurethane resin (However, urethane polymer (I) is excluded), other polymer dispersion resin, such as acrylic silicone resin, silicone resin, fluorine resin, epoxy resin, alkyd resin, and water soluble resin can be mentioned. Among these, a resin containing a hydroxyl group is preferable, and an acrylic resin or a polyester resin containing a hydroxyl group is more preferable.
One of these may be used alone, or two or more may be used in combination.

The glass transition temperature of the resin (C) is preferably 0 ° C. or higher, and more preferably 20 ° C. or higher. When the glass transition temperature of the resin (C) is at least the above lower limit value, the balance between the impact resistance and the water resistance of the coating film becomes good.
In addition, the glass transition temperature of resin (C) is calculated | required by the calculation formula of Fox represented by said Formula (i).

<Optional component>
Optional components include pigments, resin beads, antifoaming agents, pigment dispersants, leveling agents, anti-sagging agents, curing catalysts, matting agents, ultraviolet light absorbers, light stabilizers, antioxidants, heat resistance improvers, Examples include various additives such as slip agents, preservatives, plasticizers, and solvents.

Examples of the pigment include a color pigment, an extender pigment, and a bright pigment, and each may be used alone or in combination of two or more.
Examples of color pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, graphene pigments, perylene pigments, etc. Can be mentioned.
Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like.
As the luster pigment, for example, 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 Pigment etc. are mentioned.

As the solvent, those generally used in water-based paints can be used. For example, linear, branched or cyclic aliphatic alcohols having 5 to 14 carbon atoms; alcohols containing aromatic groups General formula HO- (CH ₂ CHR ³ O) _p -R ⁴ (R ⁴ is a linear or branched alkyl group having 1 to 10 carbon atoms, R ³ is a hydrogen atom or a methyl group, p Is an integer of 5 or less) monoether such as (poly) ethylene glycol or (poly) propylene glycol; General formula R ⁵ COO- (CH ₂ CHR ⁷ O) _q -R ⁶ (R ⁵⁾ And R ⁶ is a linear or branched alkyl group having 1 to 10 carbon atoms, R ⁷ 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 esters; aromatic organic solvents such as toluene and xylene; mono or diisobutyrate of 2,2,4-trimethyl-1,3-pentanediol, 3-methoxybutanol, 3-methoxybutanol acetate And 3-methyl-3-methoxybutanol, 3-methyl-3-methoxybutanol acetate and the like.
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, and 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-ethyl hexyl ether, propylene glycol mono n-butyl ether and dipropylene glycol mono n-butyl ether.
One of these may be used alone, or two or more may be used in combination.

<Function effect>
Since the water-based paint of the present invention described above contains the water-based resin dispersion (A) of the present invention, it can form a coating film excellent in impact resistance.

[Painted material]
The coated article of the present invention has a coating film formed from the above-described aqueous paint of the present invention.
The coating film is obtained, for example, by applying the aqueous paint of the present invention to the surface of a substrate and drying it.

<Substrate>
The substrate is not particularly limited, and examples thereof include metal substrates such as iron and aluminum; organic substrates such as various plastics; inorganic substrates such as glass and cement mortar; natural leather; synthetic leather; The water-based paint of the present invention is particularly suitable for coating metal substrates such as iron and aluminum.

<Method of forming coating film>
As a method of applying the water-based paint of the present invention to the surface of a substrate, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coating, roller coating, bar coating, air knife coating, brush coating And various coating methods such as dipping coating.
The application amount of the water-based paint is preferably such an amount that the thickness of the coating after drying is 0.1 to 100 μm.

A coating film is formed by drying the water-based paint applied to the surface of the substrate. Drying of the water-based paint may be performed near normal temperature of 0 ° C. to 40 ° C., or may be heated to a higher temperature. The drying temperature is preferably 40 to 200 ° C. from the viewpoint of improving the film forming property.
When the water-based paint is formed into a film by heat drying, it is preferable to perform preheating, air blowing, or the like under heating conditions such that the coating does not substantially cure, from the viewpoint of preventing the occurrence of coating defects such as "waist". Among these, preheating is more preferable from the viewpoint of faster film formation. The temperature of the preheating is preferably 40 to 100 ° C., more preferably 50 to 90 ° C., and still more preferably 60 to 80 ° C. The preheating time is preferably about 30 seconds to 15 minutes, more preferably 1 to 10 minutes, and still more preferably 2 to 5 minutes.

  The heating and drying may be carried out by heating the aqueous paint by known means. As a heating means, for example, a heating furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace or the like can be used. The heating temperature is preferably 40 to 200 ° C., more preferably 60 to 180 ° C., and still more preferably 80 to 160 ° C. The heating time is not particularly limited as long as the effect of the present invention is not impaired, but it is preferably about 10 to 60 minutes, and more preferably about 20 to 40 minutes.

<Function effect>
The coated article of the present invention described above has excellent impact resistance because it has a coating film formed of the water-based paint of the present invention.

  Specific examples of the paint of the present invention include interior and exterior of passenger cars, trucks, motorcycles, buses, building materials, building interior and exterior, window frames, window glass, structural members, plate materials, machinery and articles exteriors, bridges, Guardrails, tents, greenhouses, blinds, roofing materials, housing equipment, steel furniture, functional fibers etc. may be mentioned.

EXAMPLES The present invention will be described in detail below by showing Examples and Comparative Examples, but the present invention is not limited to these Examples.
In addition, "part" in a present Example means "mass part", and "%" means "mass%." In addition, various measurements and evaluations in Examples and Comparative Examples were performed by the methods described below.

[Measurement and evaluation]
<Measurement of average particle size>
The average particle diameter of the polymer particles contained in the aqueous resin dispersion (A) is at room temperature (25 ° C.) using a light scattering photometer (manufactured by Otsuka Electronics Co., Ltd., trade name: concentrated particle size analyzer FPAR-1000). The measurement was carried out in accordance with the formula (4) and calculated by cumulant analysis.

<Evaluation of storage stability>
The aqueous resin dispersion (A) obtained in each example was sealed in a glass bottle and stored under an atmosphere of 40 ° C. for one month. The viscosity of the aqueous resin dispersion (A) before and after storage is measured using a B-type viscometer under the conditions of a measurement temperature of 25 ° C. and a rotor rotational speed of 60 rpm, and the viscosity change rate is determined from the following formula (iv) Storage stability was evaluated according to the evaluation criteria.
Viscosity change rate = viscosity after storage / viscosity before storage × 100 (iv)

<< Evaluation Criteria >>
"(Circle)": viscosity change rate 50 to 150%.
"C": viscosity change rate is 30% or more, less than 50%, or more than 150%, 200% or less
"X": The viscosity change rate is less than 30%, or more than 200%.

<Evaluation of impact resistance>
The water-based paint obtained in each example is applied to a single-point perforated dull steel plate (electrodeposited and medium-coated paint, manufactured by Miki Coating Co., Ltd.) using a bar coater # 48, and dried at 150 ° C. for 20 minutes. A coated plate having a coating film formed thereon was obtained. The obtained coated plate was used as a coated plate for evaluation of impact resistance.

Using the coated plate for evaluation, it evaluated based on JISK5600-5-3 (weight resistance drop resistance test). The type of test adopted a Dupont type, using a 1/2 inch diameter shot type and a pedestal, a 1000 g weight was dropped on the coating film by changing the height every 5 cm between 5 and 50 cm . The presence or absence of cracking or peeling of the coating film on the impact surface was confirmed, and impact resistance was evaluated according to the following evaluation criteria based on the height of the weight at which cracking or peeling did not occur.
<< Evaluation Criteria >>
"◎": The height is 45 cm or more.
"(Circle)": height is 35 cm or more and less than 45 cm.
"C": height is 25 cm or more and less than 35 cm.
"X": height is less than 25 cm.

[Resin (C)]
Preparation Example 1: Preparation of Resin (C1)
In a flask equipped with a stirrer, a reflux condenser, a temperature controller, and a dropping pump, 66.9 parts of propylene glycol monomethyl ether acetate (PMA) as an organic solvent and 6 of radically polymerizable monomer mixture 1 shown in Table 1 6 parts and 0.73 parts of α-methylstyrene dimer as a serial transfer agent were charged, and the internal temperature of the flask was raised to 144 ° C.
Subsequently, 83.4 parts of radical polymerizable monomer mixture 2 shown in Table 1 and t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation, trade name: Perbutyl I) 1.2 as a polymerization initiator Part was dripped over 3 hours. The internal temperature was maintained at 144 ° C. during dropping.
Subsequently, 0.1 part of a polymerization initiator solution consisting of 0.05 part of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation, trade name: Perbutyl I) and 0.05 part of propylene glycol monomethyl ether acetate It was thrown in.
Subsequently, 10 parts of radical polymerizable monomer mixture 3 shown in Table 1 and 0.2 parts of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation, trade name: Perbutyl I) as a polymerization initiator Was dripped over 1 hour. The internal temperature was maintained at 144 ° C. during dropping.
Subsequently, 0.1 part of a polymerization initiator solution consisting of 0.05 part of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation, trade name: Perbutyl I) and 0.05 part of propylene glycol monomethyl ether acetate It was thrown in.
Subsequently, the internal temperature was cooled to 120 ° C., and 1.98 parts of dimethylethanolamine was added dropwise over 0.25 hours. Then, the internal temperature was cooled to 80 ° C., and 93 parts of deionized water was dropped over 0.5 hours. Then, it cooled to room temperature (25 degreeC) and obtained resin (C1). The solid content of the resin (C1) was 45%.

Example 1
<Preparation of Aqueous Resin Dispersion (A1)>
(Step (a))
In a flask equipped with a stirrer, a reflux condenser, a temperature controller, and a dropping pump, a polyether urethane polymer (made by Sumika Kobetro Urethane Co., Ltd., trade name: Implany DLE, solid content) as urethane polymer (I) 50%) 85.72 parts (solid content 42.86 parts), 189 parts of deionized water, 13.2 parts of 2-hydroxyethyl methacrylate as a hydroxyl group-containing radically polymerizable monomer (a1), and other radicals An acrylic monomer component (II-1) consisting of 72.52 parts of n-butyl acrylate was charged as a polymerizable monomer (a3), and the flask was heated to 40 ° C. Thereafter, 0.014 part of t-butyl hydroperoxide aqueous solution (manufactured by NOF Corporation, trade name: Perbutyl H69, solid content 69%) as a polymerization initiator, and 0.0002 part of ferrous sulfate as a reducing agent Add 0.00027 parts of ethylenediaminetetraacetic acid (EDTA), 0.016 parts of sodium isoascorbate monohydrate, and 1 part of deionized water. Subsequently, after confirming the peak top temperature due to polymerization heat generation, the internal temperature of the flask is raised to 75 ° C., and polymer particles (polymer mixture (P) containing urethane polymer (I) and acrylic polymer (II-1) ) Obtained dispersion dispersed in water.
The composition of the acrylic monomer component (II-1), the glass transition temperature of the acrylic polymer (II-1), the hydroxyl value and the acid value are shown in Table 2. In addition, the glass transition temperature was calculated | required from said Formula (i), the hydroxyl value was calculated | required from said Formula (ii), and the acid value was calculated | required from said Formula (iii).

(Step (b))
Next, 0.3 parts of methacrylic acid as an acid group-containing radically polymerizable monomer (a2) and other radically polymerizable monomers (a) in the dispersion of the polymer mixture (P) obtained in the step (a) a3) an acrylic monomer component (II-2) consisting of 13.98 parts of i-butyl methacrylate, and an anionic surfactant (made by ADEKA Co., Ltd., trade name: Adekaria Soap (registered trademark) SR-1025, Pre-emulsion containing 1.4 parts (solids content: 25%) (solids content: 0.35 parts) and 6.0 parts of deionized water, and ammonium persulfate (made by ADEKA Co., Ltd., trade name: APS as polymerization initiator) The polymerization initiator aqueous solution containing 0.05 part and 14.0 parts of deionized water was dropped in parallel over 1 hour. During the dropping of the pre-emulsion and the aqueous polymerization initiator solution, the internal temperature of the flask was kept at 75 ° C., and after the dropping was completed, the temperature was kept at 75 ° C. for 1.5 hours. Thereafter, the reaction solution is cooled to 40 ° C., 0.32 part of 2-dimethylaminoethanol as a basic compound and 5.0 parts of deionized water are added, urethane polymer (I), and acrylic polymer ( A dispersion liquid is obtained in which polymer particles (polymer mixture (Q)) containing an acrylic polymer (II) composed of II-1) and an acrylic polymer (II-2) are dispersed in water. This dispersion was used as an aqueous resin dispersion (A1). The solid content of the aqueous resin dispersion (A1) was 35%. The mass ratio of the acrylic polymer (II-1) to the acrylic polymer (II-2) is acrylic polymer (II-1) / acrylic polymer (II-2) = 85.72 / 14.28. there were.
The composition of the acrylic monomer component (II-2), the glass transition temperature of the acrylic polymer (II-2), the hydroxyl value and the acid value are shown in Table 2. In addition, the glass transition temperature was calculated | required from said Formula (i), the hydroxyl value was calculated | required from said Formula (ii), and the acid value was calculated | required from said Formula (iii).
Moreover, the average particle diameter of the polymer particle (polymer mixture (Q)) contained in aqueous resin dispersion (A1) was measured. The results are shown in Table 2.
Furthermore, the storage stability of the aqueous resin dispersion (A1) was evaluated. The results are shown in Table 2.

[Examples 2 to 5, Comparative Examples 1 to 5]
<Preparation of Aqueous Resin Dispersions (A2) to (A10)>
An aqueous resin dispersion (A1) of Example 1 except that the composition of the acrylic monomer component (II-1) and the acrylic monomer component (II-2) was changed as shown in Tables 2 and 3. Aqueous resin dispersions (A2) to (A10) were prepared in the same manner as in the preparation of (1). Various measurement results and evaluation results are shown in Tables 2 and 3.
In addition, the compounding quantity of each component in Table 2, 3 is solid content, and mass ratio represented by urethane polymer (I) / acrylic polymer (II) is mass ratio in conversion of solid content.

The abbreviations in Tables 2 and 3 are as follows.
-DLE: Water dispersion of urethane polymer (I) (manufactured by Sumika Kobe Soro Urethane Co., Ltd., trade name: Implanil DLE, solid content 50%)
HEMA: 2-hydroxyethyl methacrylate (transition temperature (Tg): 55 ° C.)
HEA: 2-hydroxyethyl acrylate (Tg: -20 ° C)
· BA: n-butyl acrylate (Tg: -45 ° C)
MMA: methyl methacrylate (Tg: 105 ° C.)
・ MAA: methacrylic acid (Tg: 185 ° C)
IBMA: i-butyl methacrylate (Tg: 48 ° C.)

From the results of Table 2, the aqueous resin dispersions (A1) to (A5) obtained in Examples 1 to 5 were excellent in storage stability.
On the other hand, from the results of Table 3, in the case of the aqueous resin dispersion (A8) containing an acrylic polymer (II) having a hydroxyl value higher than 100 mg KOH / g (Comparative Example 3), the storage stability was inferior.

[Example 6]
21.5 parts (solid content: 7.525 parts) of an aqueous resin dispersion (A1), 22.5 parts of a melamine resin (made by Daicel Ornex Co., Ltd., trade name: Cymel 350) as a curing agent (B), and a resin (C1) 100 parts (solid content 45 parts), 200 parts of a titanium dioxide-containing aqueous color (made by Nippon Pigment Co., Ltd., trade name: WT-9004 white) as a pigment dispersion, and 2-ethyl-1-hexanol as a solvent An aqueous paint was prepared by mixing with 6 parts.
The paint board for evaluation was produced using the obtained water-based paint, and impact resistance was evaluated. The results are shown in Table 4.

[Examples 7 to 10, Comparative Examples 6 to 10]
An aqueous paint was prepared in the same manner as in Example 6 except that the type and blending amount of the aqueous resin dispersion (A) were changed as shown in Tables 4 and 5, and the coated plate for evaluation was prepared using the obtained aqueous paint. Were evaluated for impact resistance. The results are shown in Tables 4 and 5.
In addition, mass ratio represented by dispersion (A) / hardening | curing agent (B) / resin (C) in Table 4, 5 is mass ratio in conversion of solid content.

From the results of Table 4, the water-based paints obtained in Examples 6 to 10 containing any of the water-based resin dispersions (A1) to (A5) were able to form a coating film excellent in impact resistance.
On the other hand, from the results of Table 5, in the case of the aqueous resin dispersions (A6) and (A7) containing the acrylic polymer (II) having a hydroxyl value of less than 25 mg KOH / g, the impact resistance of the coating film was inferior ((6) Comparative Examples 6 and 7).
In the case of the aqueous resin dispersion (A9) containing the acrylic polymer (II) having an acid value of less than 0.5 mg KOH / g, the impact resistance of the coating film was inferior (Comparative Example 9).
In the case of the aqueous resin dispersion (A10) containing acrylic polymer (II) whose glass transition temperature is higher than -10 degreeC, the impact resistance of the coating film was inferior (comparative example 10).

  The aqueous resin dispersion of the present invention is suitable as a material of an aqueous paint which can provide a coating film having excellent impact resistance.

Claims (7)

An aqueous resin dispersion in which polymer particles containing a urethane polymer (I) and an acrylic polymer (II) are dispersed in an aqueous medium,
The aqueous resin dispersion whose hydroxyl value of the said acrylic polymer (II) is 25-100 mgKOH / g, an acid value is 0.5-25 mgKOH / g, and whose glass transition temperature is -10 degrees C or less. The aqueous resin dispersion of Claim 1 obtained through the following process (a) and process (b).
Step (a): in the presence of an aqueous medium and the urethane polymer (I), the acrylic monomer component (II-1) is polymerized to form the urethane polymer (I) and the acrylic polymer (II-1) Obtaining a dispersion of the polymer mixture (P) containing
Step (b): The acrylic monomer component (II-2) is polymerized in the presence of an aqueous medium and the polymer mixture (P) to form the urethane polymer (I), and the acrylic polymer (II) 1) A step of obtaining a dispersion liquid of a polymer mixture (Q) containing the above-mentioned acrylic polymer (II) composed of-1 and an acrylic polymer (II-2).   The aqueous resin dispersion according to claim 1 or 2, wherein the acrylic polymer (II) further comprises a constituent unit derived from a hydroxyl group-containing radically polymerizable monomer (a1).   An aqueous paint comprising the aqueous resin dispersion according to any one of claims 1 to 3.   The water-based paint according to claim 4, further comprising a curing agent.   The water-based paint according to claim 4 or 5, further comprising a resin other than the urethane polymer (I) and the acrylic polymer (II).   The coated article which has a coating film formed from the water-based paint as described in any one of Claims 4-6.