JP2007091916A - Water-based coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating agent having excellent low-temperature film-forming properties, excellent blocking resistance and excellent low-temperature stability without using a volatile organic compound such as a film-forming aid and an antifreezing agent. .
SOLUTION: A vinyl polymer (A) having a glass transition temperature of 80 to 120 ° C, preferably 90 to 105 ° C, and a vinyl polymer (B) having a glass transition temperature of -20 to 20 ° C, preferably -10 to 10 ° C. ) Is dispersed in an aqueous medium, and has a glass transition temperature of 40 to 130 ° C., an acid value of 70 to 250 mgKOH / g, preferably a glass transition temperature of 90 to 120 ° C., and an acid value of 70 to 150 mgKOH. / G vinyl polymer or an alkali neutralized product (C) thereof is dissolved in the aqueous medium, and the content of the volatile organic compound (D) having a boiling point of preferably 260 ° C. or lower is 0 or 1 wt. % Aqueous coating.
[Selection figure] None.

Description

  The present invention relates to an aqueous coating agent that can be applied to various substrates such as an inorganic substrate, an organic substrate, and a metal substrate, and can be manufactured at a low temperature without adding a film-forming aid or an antifreezing agent. The present invention relates to an aqueous coating agent having good film properties and low-temperature stability and excellent blocking resistance.

  In recent years, from the viewpoints of global environmental protection and occupational health, the transition from solvent-based to water-based is being promoted in various coating materials. In the building paint field, emulsion paints, which are water-based coatings, have been the mainstream for some time, but recently, health problems due to trace amounts of volatile organic compounds contained in building materials and auxiliary materials have become a problem. There is an urgent need to remove or lose weight.

  Emulsion paints contain much less volatile organic compounds than solvent-based paints. However, the actual emulsion paint contains a volatile organic compound as a film-forming aid, an anti-freezing agent, etc. in the paint in several weight percent, and more than a dozen weight% in the case of more.

  Under such circumstances, emulsion paints with reduced or no volatile organic compounds are desired from the viewpoint of health problems. In order to satisfy this requirement, even in the absence of a film-forming auxiliary, it forms a film in winter, that is, it has a low-temperature film-forming property and has a low-temperature stability (freeze-thaw stability) even without using an antifreezing agent. Emulsion development is essential. In order to form a film at a low temperature without containing a film-forming auxiliary, it can be achieved by softening the emulsion resin, that is, by using an emulsion resin having a minimum film-forming temperature of 0 ° C. or lower. However, when the emulsion resin is softened, the blocking resistance is deteriorated, and as a result, the contamination is deteriorated when an emulsion paint is formed. In addition, this method cannot be expected to improve the low temperature stability.

  Therefore, there is an urgent need to develop an emulsion resin that retains blocking resistance and does not contain a film-forming aid, has low-temperature film-forming properties, and that does not contain an antifreezing agent, but also has low-temperature stability. For example, an innermost layer having a glass transition temperature of 35 to 120 ° C., an intermediate layer having a glass transition temperature of −65 to 0 ° C., a glass transition temperature of 35 to 120 ° C., and 4 to 80 mg KOH / g It has been reported that low-temperature film-forming properties and blocking resistance can be achieved by using a multilayer structure emulsion polymer composed of an outermost layer having an acid value (see, for example, Patent Document 1).

  Since the above-mentioned patent document 1 can certainly provide blocking resistance at a high glass transition temperature component and low temperature film forming property at a low glass transition temperature component, the balance of blocking resistance / low temperature film forming property is improved. Yes, but not enough.

JP 2004-059623 A

  The problems to be solved by the present invention are excellent in low-temperature film-forming properties, excellent in blocking resistance and excellent in low-temperature stability without using volatile organic compounds such as film-forming aids and anti-freezing agents. It is to provide an aqueous coating agent.

  As a result of intensive studies, the present inventors have found that a vinyl polymer having a high glass transition temperature of 80 to 120 ° C. and a vinyl polymer (B) having a low glass transition temperature of -20 to 20 ° C. An aqueous coating agent obtained by dissolving a vinyl polymer having a glass transition temperature of 40 to 130 ° C. and an acid value of 70 to 250 mg KOH / g or an alkali neutralized product thereof in an aqueous dispersion in which both are dispersed is Even when the content of volatile organic compounds having a boiling point of 260 ° C. or lower, such as a film-forming auxiliary and an antifreezing agent, is 1% by weight or less, it has excellent low-temperature film-forming properties, excellent blocking resistance, and low-temperature stability. As a result, the present invention has been completed.

  That is, the present invention comprises a vinyl polymer (A) having a glass transition temperature of 80 to 120 ° C. and a vinyl polymer (B) having a glass transition temperature of −20 to 20 ° C. dispersed in an aqueous medium, and An aqueous coating agent comprising a vinyl polymer having a glass transition temperature of 40 to 130 ° C and an acid value of 70 to 250 mgKOH / g or an alkali neutralized product (C) thereof dissolved in the aqueous medium. It is to provide.

  The aqueous coating agent of the present invention has a low-temperature film-forming property even when the content of volatile organic compounds such as a film-forming aid and anti-freezing agent is as small as 1% by weight or not. In addition, the anti-blocking property is good and the low-temperature stability is also excellent.

Details of the invention will be described below.
The vinyl polymer (A) used in the present invention is a vinyl polymer having a glass transition temperature of 80 to 120 ° C., as long as it can be dispersed in an aqueous medium in the presence or absence of an emulsifier, For example, it can be obtained by appropriately selecting the vinyl monomer (a) alone or in combination so as to meet this condition. Among such vinyl polymers (A), a vinyl polymer having a glass transition temperature of 90 to 105 ° C. is preferable because an aqueous coating agent having a better balance between blocking resistance and low-temperature film-forming property can be obtained.

  As the vinyl monomer (a) used for the synthesis of the vinyl polymer (A), various vinyl monomers can be used. For example, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid- Acrylic acid esters such as 2-ethylhexyl, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate; unsaturated such as maleic acid, fumaric acid, itaconic acid Esters of carboxylic acids; vinyl esters such as vinyl acetate, vinyl propionate and vinyl tertiary carboxylate; aromatic vinyl monomers such as styrene and vinyltoluene; heterocyclic vinyl monomers such as vinylpyrrolidone Class: Vinyl chloride, acrylonitrile, vinyl ether, vinyl ketone, vinyl Luamide; vinylidene halide compounds such as vinylidene chloride and vinylidene fluoride; α-olefins such as ethylene and propylene; dienes such as butadiene; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, itacone Carboxyl group-containing vinyl monomers such as acid half esters, maleic acid half esters, maleic anhydride, itaconic anhydride and 2-methacryloylpropionic acid; amides of unsaturated carboxylic acids such as acrylamide, methacrylamide and maleic amide; Glycidyl group-containing vinyl monomers such as glycidyl methacrylate and allyl glycidyl ether; hydroxyl group-containing vinyl monomers such as 2-hydroxylethyl methacrylate and 2-hydroxylethyl acrylate; Amino group-containing vinyl monomers; N-methylol acrylamide, N-methylol methacrylamide, substituted amides of unsaturated carboxylic acids such as diacetone acrylamide; Unsaturated bond-containing silane compounds such as γ-methacryloxypropyltrimethoxysilane; diallyl Examples thereof include vinyl monomers having two or more unsaturated bonds in one molecule such as phthalate, divinylbenzene, allyl acrylate, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate.

  Among vinyl polymers (A) obtained using such a vinyl monomer (a), a copolymer containing methyl methacrylate and / or styrene as a main monomer component, for example, methyl methacrylate and The vinyl copolymer obtained by using styrene at a ratio of 80% by weight or more of the total vinyl monomer used in the synthesis should provide an aqueous coating agent with an excellent balance between blocking resistance and low-temperature film-forming properties. Therefore, it is preferable.

  The vinyl polymer (B) used in the present invention may be any vinyl polymer having a glass transition temperature of -20 to 20 ° C. and can be dispersed in an aqueous medium in the presence or absence of an emulsifier. For example, it can be obtained by appropriately selecting the vinyl monomer (a) alone or in combination so as to meet this condition. Among such vinyl polymers (B), a vinyl polymer having a glass transition temperature of −10 to 10 ° C. is preferable because an aqueous coating agent having a better balance between blocking resistance and low-temperature film-forming property can be obtained. .

  Among the vinyl polymers (B) obtained using such a vinyl monomer (a), an aqueous coating agent having excellent durability such as water resistance can be obtained, so that a functional group having reactivity with a carboxyl group is obtained. It is preferable that it is an acrylic polymer which uses a vinyl monomer which has as a part of vinyl monomer component used for a synthesis | combination. The vinyl monomer having a functional group having reactivity with the carboxyl group is not particularly limited as long as it has reactivity with the carboxyl group, and an aqueous coating agent that is superior in durability can be obtained. A vinyl monomer having a glycidyl group is preferred. The amount of the ethylenically unsaturated monomer having a glycidyl group is preferably 10 parts by weight or less with respect to 100 parts by weight of the total amount of vinyl monomers used for the synthesis of the acrylic polymer (B). However, since durability including water resistance can be improved without lowering the low-temperature film-forming property, the range of 0.2 to 3 parts by weight is more preferable.

  Furthermore, the vinyl polymer or alkali neutralized product (C) thereof used in the present invention has a glass transition temperature of 40 to 130 ° C. and an acid value of 70 to 250 mgKOH / g. However, it may be water-soluble and can be obtained, for example, by appropriately selecting the vinyl monomer (a) alone or in combination so as to meet this condition. Since it is an essential condition that the acid value before neutralization is 70 to 250 mg KOH / g, the carboxyl group-containing vinyl monomer is an essential component, and among them, acrylic acid and / Or what is obtained using methacrylic acid is preferable. Among these vinyl polymers before alkali neutralization, an aqueous coating agent having a better balance between blocking resistance and low-temperature film-forming properties can be obtained, so that a vinyl polymer having a glass transition temperature of 90 to 120 ° C. is obtained. A vinyl polymer having an acid value in the range of 70 to 150 mgKOH / g is preferred because an aqueous coating agent having better water resistance can be obtained.

  Examples of the alkaline compound used to obtain the alkali neutralized product of the acrylic polymer include water-soluble organic amines such as ammonia (water), dimethylethanolamine, 2-amino 2-methyl 1-propanol, and diethanolamine, Examples thereof include inorganic alkaline substances such as sodium hydroxide and potassium hydroxide, and among them, aqueous ammonia is preferable because an aqueous coating agent having excellent water resistance, easy reduction of the VOC amount and excellent water resistance can be obtained.

  The polymerization method of the acrylic polymer (A) and the acrylic polymer (B) is not particularly limited, and any polymerization method can be used as long as it can be finally dispersed in an aqueous medium. Specific examples include solution polymerization, suspension polymerization, emulsion polymerization and the like. However, suspension polymerization and emulsion polymerization are preferable because the production method does not include any solvent component and is simple. Emulsion polymerization is more preferred because an aqueous coating agent having excellent coating film properties can be obtained.

  An example of emulsion polymerization is the presence of an emulsifier using 0.01 to 10 parts by weight of a radical polymerization initiator and 50 to 10,000 parts by weight of an aqueous medium with respect to 100 parts by weight of the total amount of vinyl monomers. The polymerization can be carried out at 0 to 100 ° C. below. Moreover, it can also carry out also in the redox polymerization which uses a radical polymerization initiator and a reducing agent together, and the usage-amount of a reducing agent in this case is 0.01-10 weight part with respect to 100 weight part of whole quantity of a vinyl monomer. It is. In this case, a compound that generates a polyvalent metal salt ion such as iron ion or copper ion can be used in combination as an accelerator.

  In the emulsion polymerization of vinyl monomers, an emulsifier is generally used, but the emulsifier used here is not particularly limited, and any one can be used as long as it is generally used in an emulsion polymerization reaction. For example, anionic emulsifiers such as alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkylphenyl sulfonates, dialkylsulfosuccinate salts, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxy Nonionic emulsifiers such as ethylene-polyoxypropylene block copolymers can be mentioned.

  In addition, vinyl sulfonates, polyoxyethylene sulfates of acrylic acid, polyoxyethylene sulfonates of methacrylic acid, polyoxyethylene alkenyl phenyl sulfonates, polyoxyethylene alkenyl phenyl sulfates, sodium allyl alkyl sulfosuccinate, methacrylic acid Reactive emulsifiers such as anionic reactive emulsifiers such as polyoxypropylene sulfonates and nonionic reactive emulsifiers such as polyoxyethylene alkenyl phenyl ether and polyoxyethylene methacryloyl ether can also be used. Of course, a plurality of these emulsifiers can be used.

  Of course, the type of emulsifier is not limited to the above structure, and any emulsifier can be used, and commercially available ones can be used.

  Further, recently, a method of emulsion polymerization without using an emulsifier, that is, soap-free polymerization is frequently performed, and an aqueous dispersion polymerized by this method can also be used.

  Examples of the radical polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate, azobisisobutyronitrile and its hydrochloride, 2,2′-azobis (2-amidinopropane) 2 And azo initiators such as hydrochloride and 4,4′-azobis (4-cyanovaleric acid), peroxide initiators such as hydrogen peroxide, tertiary butyl hydroperoxide, cumene hydroperoxide, and the like. . Examples of the reducing agent that can be used in combination with these radical initiators include sodium sulfooxylate formaldehyde, sodium pyrosulfite, L-ascorbic acid, and the like. Further, mercaptans, alcohol organic solvents, aliphatic organic solvents, aromatic organic solvents and the like can be used in combination as molecular weight regulators. However, it is preferable from the viewpoint of environmental protection and occupational health that the volatile organic solvent is not contained as much as possible.

  The acrylic polymer (A) and the acrylic polymer (B) may be blends of those produced separately, but in the presence of the acrylic polymer (A) from the viewpoint of low-temperature film-forming properties, It is preferable that the polymer (B) is emulsion-polymerized. In this case, the acrylic polymer (A) and the acrylic polymer (B) may be produced continuously.

  The method for producing the acrylic polymer or its alkali neutralized product (C) is not particularly limited. For example, a method of removing the solvent after solution polymerization in an organic solvent, a method of polymerizing without solvent, or suspension polymerization is performed. Examples thereof include a method, a method of emulsion polymerization in the presence of a chain transfer agent, a method of aqueous solution polymerization, and the like, and may be polymerized under pressure as necessary. An alkali neutralized product of an acrylic polymer is usually obtained by bringing an alkaline compound into contact with an acrylic polymer after production, and is obtained by polymerization using a vinyl monomer having a neutralized carboxyl group. May be.

  In the present invention, the glass transition temperature of the acrylic resin is a value calculated by the following well-known Fox equation. The glass transition temperature (Tg) of the homopolymer used for the calculation is shown below. Values not described in the glass transition temperature (Tg) of homopolymers below can be values generally described in the literature. The glass transition temperature (Tg) of the homopolymer can also be determined by measuring using a differential scanning calorimetry method or a dynamic viscoelasticity measurement method.

[Fox's formula]
1 / Tg = Σ (Wn / Tgn)
Tg: Glass transition temperature of polymer (absolute temperature)
Wn: weight fraction of monomer n Tgn: glass transition temperature (absolute temperature) of homopolymer of monomer n

[Tg of homopolymer]
Homopolymer of 2-ethylhexyl acrylate (2EHA): −55.3 ° C.
Homopolymer of butyl acrylate (BA): −45.4 ° C.
Homopolymer of methyl methacrylate (MMA): 104.2 ° C
Styrene (St) homopolymer: 100.0 ° C
Methacrylic acid (MAA) homopolymer: 143.5 ° C
Homopolymer of acrylic acid (AA): 86.6 ° C
Homopolymer of glycidyl methacrylate (GMA): 46.3 ° C

  In addition, the aqueous coating agent of the present invention may contain pigments, fillers, aggregates, dispersants, wetting agents, thickeners, rheology control agents, antifoaming agents, antiseptics, antifungal agents, and pH adjustments as necessary. It is also possible to add an agent, a rust inhibitor, an ultraviolet absorber, an antioxidant and the like. The aqueous coating agent of the present invention can be added with a volatile organic compound (D) having a boiling point of 260 ° C. or lower, if necessary, for example, a film-forming aid or an antifreezing agent. The content is preferably in the range where the content in the total amount of the aqueous coating agent is 1% by weight or less.

  Examples of the volatile organic compound (D) having a boiling point of 260 ° C. or lower include 2,2-trimethyl 1,3-pentanediol monoisobutyrate and 2,2-trimethyl 1,3-pentanediol diisobutyrate. And film forming aids such as glycol ethers and glycol esters such as butyl cellosolve and butyl diglycol; antifreezing agents such as ethylene glycol and propylene glycol.

  When an ethylenically unsaturated monomer having a functional group reactive with a carboxyl group is used for the vinyl polymer (B), for example, a monomer containing a glycidyl group-containing unsaturated monomer such as glycidyl methacrylate is used. When used as a part of the component, it is also effective to use an accelerator in order to promote the reaction between the carboxyl group and the functional group introduced into the vinyl polymer (B), for example, glycidyl group.

  In the case of regular dry type building paints, a pigment paste in which pigments such as titanium oxide and calcium carbonate are finely dispersed using a dispersing agent is let down with an aqueous coating agent, and if necessary, thickeners, preservatives, etc. The coating agent for normally dry type architectural paints can be obtained by adding.

  Of course, the present invention is not limited to the above-mentioned coating material for regular dry type architectural paints, but can be used as a coating material for various substrates, and is not limited to regular drying, and can be used under forced drying. Can do.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited only to the following examples. The following “parts” and “%” are based on weight.

Production Example 1 [Production Example of Vinyl Polymer (A)]
A monomer mixture consisting of 294 parts of methyl methacrylate (hereinafter abbreviated as MMA) and 6 parts of methacrylic acid (hereinafter abbreviated as MAA) was added to New Coal 707SF (anionic emulsifier manufactured by Nippon Emulsifier Co., Ltd., 30% active ingredient). A monomer emulsion was prepared by dispersing 30 parts and 1.5 parts of Leocol TD-90 [nonionic emulsifier manufactured by Lion Corporation] in an aqueous emulsifier solution dissolved in 60 parts of ion-exchanged water. Further, 1.2 parts of ammonium persulfate was dissolved in 24 parts of ion-exchanged water to prepare an aqueous initiator solution.

  In a 1 liter reaction vessel equipped with a stirrer, a thermometer, and a cooler, 245 parts of ion exchange water was charged, and the inside of the reaction vessel was heated to 80 ° C. while stirring while feeding nitrogen gas. After the temperature rise, the monomer emulsion and the initiator aqueous solution were dropped into the reaction vessel over 3 hours to perform polymerization. After completion of the dropwise addition, 0.3 part of ammonium persulfate was added, and the mixture was further stirred for 2 hours and maintained at 80 ° C., then cooled to room temperature, adjusted to pH 8.5 with 14% aqueous ammonia, and then ion-exchanged water. An aqueous dispersion (average particle size 0.20 μm / light scattering type particle size distribution measuring device) of vinyl polymer (A1) having a glass transition temperature (Tg) of 105 ° C. And the same applies hereinafter).

Production Example 2 [Production Example of Vinyl Polymer (B)]
A monomer mixture comprising 161 parts of 2-ethylhexyl acrylate (hereinafter abbreviated as 2EHA), 90 parts of styrene (hereinafter abbreviated as St), 46 parts of MMA and 3 parts of acrylic acid (hereinafter abbreviated as AA) A monomer emulsion was prepared by dispersing 22.5 parts of Cole 707SF and 1.5 parts of Lecoal TD-90 in an aqueous emulsifier solution dissolved in 60 parts of ion-exchanged water. Further, 1.2 parts of ammonium persulfate was dissolved in 24 parts of ion-exchanged water to prepare an aqueous initiator solution.

  A 1 liter reaction vessel equipped with a stirrer, a thermometer, and a cooler was charged with 245 parts of ion exchange water, and the temperature in the reaction vessel was raised to 80 ° C. while stirring while feeding nitrogen gas. After the temperature rise, the monomer emulsion and the initiator aqueous solution were dropped into the reaction vessel over 3 hours to perform polymerization. After completion of the dropwise addition, 0.3 part of ammonium persulfate was added, and the mixture was further stirred for 2 hours and maintained at 80 ° C., then cooled to room temperature, adjusted to pH 8.5 with 14% aqueous ammonia, and then ion-exchanged water. After adjusting the non-volatile content to be 45.0%, it was taken out to obtain an aqueous dispersion (average particle size 0.21 μm) of vinyl polymer (B1) having a glass transition temperature (Tg) of −3 ° C.

Production Example 3 (same as above)
2EHA 160.5 parts, St 90 parts, MMA 45 parts, glycidyl methacrylate (hereinafter abbreviated as GMA) 1.5 parts and AA 3 parts in the same manner as in Production Example 2, except that a glass transition temperature ( Tg) An aqueous dispersion (average particle size of 0.21 μm) of vinyl polymer (B2) at −3 ° C. was obtained.

Production Example 4 [Production Example of Vinyl Polymers (A) and (B)]
2EHA 160.5 parts, St 90 parts, MMA 45 parts, GMA 1.5 parts and AA 3 parts, the monomer mixture was dispersed in an emulsifier aqueous solution in which 20.4 parts Newcor 707SF was dissolved in 60 parts ion-exchanged water. An emulsion was made. Further, 1.2 parts of ammonium persulfate was dissolved in 24 parts of ion-exchanged water to prepare an aqueous initiator solution.

  A 1 liter reaction vessel equipped with a stirrer, thermometer, and cooler was charged with 2.1 parts by weight of New Coal 707SF, 1.5 parts by weight of Lecoal TD-90, and 245 parts of ion-exchanged water, and stirred while feeding nitrogen gas. The temperature inside the reaction vessel was raised to 80 ° C. After confirming that the emulsifier was dissolved, 30 parts of MMA and 20% (5.04 parts) of the aqueous initiator solution were added. After maintaining at 80 ° C. for 30 minutes to produce the vinyl polymer (A2), the monomer emulsion and the remaining aqueous initiator solution (20.16 parts) were dropped into the reaction vessel over 3 hours, respectively, and polymerization was performed. went. After completion of the dropwise addition, 0.3 part of ammonium persulfate was added, and the mixture was further stirred for 2 hours and maintained at 80 ° C., then cooled to room temperature, adjusted to pH 8.5 with 14% aqueous ammonia, and then ion-exchanged water. The aqueous solution of the vinyl polymer (A2) having a glass transition temperature (Tg) of 104 ° C. and the vinyl polymer (B3) having a glass transition temperature (Tg) of −3 ° C. was taken out after adjusting the non-volatile content to 45.0%. A dispersion (average particle size 0.16 μm) was obtained.

Production Example 5 [Production Example of Vinyl Polymer (C)]
A monomer mixture composed of 60 parts of St, 210 parts of MMA and 30 parts of AA was prepared, while 3 parts of P-butyl O (a radical polymerization initiator manufactured by NOF Corporation) was dissolved in 60 parts of isopropanol (hereinafter abbreviated as IPA). Initiator solution was prepared.

  In a 1 liter reaction vessel equipped with a stirrer, a thermometer, and a cooler, 240 parts of IPA were charged, and the temperature was raised to 80 ° C. while inserting nitrogen gas. After the temperature rise, the monomer mixture and the initiator aqueous solution were dropped into the reaction vessel over 4 hours. After completion of dropping, the mixture was further maintained at 80 ° C. for 4 hours, and then the IPA was removed to obtain a vinyl polymer (C1) having a glass transition temperature (Tg) of 102 ° C. and an acid value of 77 mgKOH / g.

Comparative production example 1
Disperse a monomer mixture consisting of 2.4 parts of butyl acrylate (hereinafter abbreviated as BA) and St. 27.6 parts in an aqueous emulsifier solution in which 1.05 parts of New Coal 707SF is dissolved in 6 parts of ion-exchanged water. Monomer emulsion 1 was prepared by the above. In addition, a monomer mixture comprising 134.4 parts of BA, 18.9 parts of MMA, 54.6 parts of St and 2.1 parts of AA, 15.75 parts of New Coal 707SF and 1.05 part of Lecoal TD-90 into 42 parts of ion-exchanged water. Monomer emulsion 2 was prepared by dispersing in a dissolved aqueous emulsifier solution. Further, an emulsifier obtained by dissolving a monomer mixture comprising St 6 parts, MMA 39 parts, BA 12.6 parts and AA 2.4 parts in 12 parts of ion-exchanged water 4.5 parts of New Coal 707SF and 0.3 parts of Leocol TD-90 Monomer emulsion 3 was prepared by dispersing in an aqueous solution. Further, 1.2 parts of ammonium persulfate was dissolved in 24 parts of ion-exchanged water to obtain an initiator aqueous solution.

  In a 1 liter reaction vessel equipped with a stirrer, a thermometer, and a cooler, 240 parts of ion exchange water was charged, and the temperature was raised to 80 ° C. while inserting nitrogen gas. After the temperature rise, 10% (2.52 parts) of the monomer emulsion 1 and the aqueous initiator solution were dropped into the reaction vessel over 30 minutes. After completion of dropping, the mixture was held at 80 ° C. with stirring for 30 minutes, and then 60% (15.12 parts) of the monomer emulsion 2 and the aqueous initiator solution were charged into the reaction vessel over 2 hours. After completion of the dropwise addition, the mixture was held at 80 ° C. with stirring for 30 minutes, and then the monomer emulsion 3 and the remaining aqueous initiator solution (7.56 parts) were dropped into the reaction vessel over 1 hour. After completion of dropping, the mixture is kept at 80 ° C. with stirring for 1 hour, and then cooled to room temperature. The pH is adjusted to 8.5 with 14% aqueous ammonia so that the non-volatile content becomes 45.0% with ion-exchanged water. After adjusting, the glass transition temperature (Tg) was 82 ° C vinyl polymer (a), the glass transition temperature (Tg) -8 ° C vinyl polymer (b) and the glass transition temperature (Tg) 58 ° C acid value = A 31 mg KOH / g vinyl polymer (c) aqueous dispersion (average particle diameter 0.21 μm) was obtained.

Example 1
Under stirring of 100 parts of the aqueous dispersion of vinyl polymer (A1) produced in Production Example 1 and 800 parts of the aqueous dispersion of vinyl polymer (B1) produced in Production Example 2, 7 parts of 14% aqueous ammonia was added. After that, 40 parts of the vinyl polymer (C1) produced in Production Example 5 was added, the temperature was raised to 50 ° C. and stirring was continued for 3 hours. After confirming that the vinyl polymer (C1) was dissolved, the temperature was raised to room temperature. After cooling, the non-volatile content was adjusted to 45.0% and the pH was adjusted to 8.5, and then taken out to obtain the aqueous coating agent (1) of the present invention.

  Using the obtained aqueous coating agent (1), blocking resistance, low-temperature film-forming property, low-temperature stability, and water resistance were evaluated by the following methods. The results are shown in Table 1.

Blocking resistance: A water-based coating agent was applied to a glass plate with a 3 mil applicator, dried at 23 ° C. for 48 hours, and then carbon paper was placed thereon, and a 500 g weight was placed thereon for 3 minutes. The degree of transfer was visually evaluated according to the following evaluation criteria.
Evaluation criteria ○: Almost no transfer to the coating film (transfer degree less than 20%: visual judgment).
Δ: Slightly transferred to the coating film (transfer degree 20% or more and less than 70%: visual determination).
X: The resistance is large when the carbon paper is peeled off, and a large amount is transferred to the coating film (transfer degree 70% or more: visual judgment).

・ Low-temperature film-forming property: An aqueous coating agent is applied to a flexible board with a 3 mil applicator in a 5 ° C atmosphere, and dried for 24 hours in a 5 ° C atmosphere. did.
Evaluation criteria ○: A film is formed.
Δ: Some cracks are observed.
X: Cracks are observed on the entire surface.

-Low temperature stability: 50 g of an aqueous coating agent is put in a 50 cc glass bottle, sealed, and then left at −5 ° C. for 16 hours, and then left at 23 ° C. for 8 hours. Evaluation was based on the evaluation criteria.
Evaluation criteria ○: Almost no aggregates are formed.
Δ: A little aggregate is formed.
X: Aggregates are produced in large quantities.

Water resistance: A water-based coating agent was applied to a glass plate with a 3 mil applicator, dried at 23 ° C. for 48 hours, then immersed in tap water at 23 ° C. for 8 hours, and the degree of whitening was visually evaluated as follows. It was evaluated with.
Evaluation criteria ○: A state in which the material is hardly whitened or slightly whitened.
Δ: Remarkably whitened.
X: The state which whitened remarkably and the coating-film state has deform | transformed or collapsed.

Examples 2 and 3
Instead of the aqueous dispersion of vinyl polymer (A1) and the aqueous dispersion of vinyl polymer (B1), the same procedure as in Example 1 was conducted except that the aqueous dispersions of vinyl resin shown in Table 1 were used. The aqueous coating agents (2) and (3) of the present invention were obtained and evaluated in the same manner as in Example 1 for blocking resistance, low-temperature film-forming property, low-temperature stability, and water resistance. The results are shown in Table 1.

Comparative Examples 1-3
Instead of the aqueous dispersion of vinyl polymer (A1) and the aqueous dispersion of vinyl polymer (B1), an aqueous dispersion of vinyl resin shown in Table 1 was used, respectively, and 14% ammonia water and vinyl polymer (C1 ) Was omitted in the same manner as in Example 1 except that comparative aqueous coating agents (1 ′) to (3 ′) were obtained. In the same manner as in Example 1, blocking resistance, low-temperature film-forming property, The low temperature stability and water resistance were evaluated. The results are shown in Table 1.

Test Examples 1 to 3 and Comparative Test Examples 1 to 3 (evaluation test as water-based paint)
The raw materials were blended in the composition shown in Table 2 below, and the mixture was put into an auto homomixer [Model SL manufactured by Special Machine Co., Ltd.], and mixed and dispersed at 5,000 rpm for 30 minutes to prepare a pigment paste. . Next, the obtained pigment paste, the aqueous coating agent obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the thickener, and the antifoaming agent were blended in the composition shown in Table 3, The mixture was put into a mixer [Model SL manufactured by Special Machine Co., Ltd.] and mixed and dispersed under the condition of 2,000 rpm for 5 minutes, so that the water-based paints (1) to (3) having a zero VOC amount and a comparative aqueous solution were used. Paints (1 ′) to (3 ′) were prepared.

Footnotes in Table 2
* 1) Orotan SG-1: Pigment dispersant manufactured by Rohm & Haas Co., Ltd.
* 2) Emulgen A-60: Nonionic emulsifier manufactured by Kao Corporation
* 3) Titanium oxide JR-600A: Teica titanium oxide
* 4) SN deformer 373: Defoamer manufactured by San Nopco

Footnotes in Table 3
* 5) 3% cellosize QP-4400H: Thickener manufactured by Dow Chemical Company
* 6) 15% Adecanol UH-438: Asahi Denka Kogyo Co., Ltd. thickener
* 7) BYK-028: Anti-foaming agent manufactured by BYK

  Using the obtained water-based paints (1) to (3) and comparative water-based paints (1 ′) to (3 ′), paint viscosity, gloss, anti-blocking property, low-temperature film-forming property, low temperature by the following methods The stability and water resistance were evaluated. The results are shown in Table 4.

-Paint viscosity: The viscosity of the water-based paint was measured at 23 ° C with a stoma viscometer.
Gloss: A water-based paint was applied to a glass plate with a 6 mil applicator, and the gloss at 60 degrees was measured after drying at 23 ° C. for 3 days.

Blocking resistance: Water-based paint was applied to a glass plate with a 6 mil applicator, dried at 23 ° C. for 3 days, carbon paper was placed on the coating, and a 500 g weight was placed on it for 3 minutes, and then carbon paper. The degree of transfer to the coating film was evaluated according to the following evaluation criteria.
Evaluation criteria ○: Almost no transfer. (Transfer degree is less than 20%: visual judgment).
Δ: Slightly transferred. (Transfer degree 20% or more and less than 70%: visual determination).
X: Transferred in large quantities (transfer degree 70% or more: visual judgment).

Low-temperature film-forming property: A water-based paint was applied to a flexible plate with a 6-mil applicator in a 5 ° C. atmosphere and dried in a 5 ° C. atmosphere for 24 hours, and then the film-forming property was visually evaluated according to the following evaluation criteria.
Evaluation criteria ○: A film is formed.
Δ: Some cracks are observed.
X: Cracks are observed on the entire surface.

Low temperature stability: 50 g of water-based paint is put into a 50 cc glass bottle, sealed, and left at −5 ° C. for 16 hours, and then left at 23 ° C. for 8 hours. It was evaluated with.
Evaluation criteria ○: No problem.
Δ: Slightly thickened.
X: Gelation.

Water resistance: A water-based paint was brushed on a flexible board (twice), dried at 23 ° C. for 7 days, then immersed in water at 23 ° C. for 7 days, and the state after drying was visually observed as follows. Evaluation was based on the evaluation criteria.
Evaluation criteria ○: almost no change in state.
Δ: Slightly glossy.
X: It is completely glossy.

Claims (6)

A vinyl polymer (A) having a glass transition temperature of 80 to 120 ° C. and a vinyl polymer (B) having a glass transition temperature of −20 to 20 ° C. are dispersed in an aqueous medium, and the glass transition temperature is 40 to 40 ° C. An aqueous coating agent comprising a vinyl polymer having an acid value of 70 to 250 mgKOH / g or an alkali neutralized product (C) thereof dissolved in the aqueous medium at 130 ° C. The aqueous coating agent according to claim 1, wherein the content of the volatile organic compound (D) having a boiling point of 260 ° C or less is 0 or 1% by weight or less. The ratio of the vinyl polymer (A) is 5 to 25% by weight with respect to a total of 100 parts by weight of the vinyl polymers (A), (B) and (C), and the ratio of the vinyl polymer (B) is The aqueous coating agent according to claim 2, wherein the content is 55 to 92% by weight, and the proportion of the vinyl polymer (C) is 3 to 20% by weight. The aqueous coating agent according to claim 1, 2 or 3, wherein the vinyl polymer (B) has a functional group capable of reacting with a carboxyl group. The aqueous coating agent according to claim 4, wherein the functional group capable of reacting with a carboxyl group is a glycidyl group. The aqueous coating agent according to claim 2, wherein the volatile organic compound (D) having a boiling point of 260 ° C or lower is a film-forming auxiliary and / or an antifreezing agent.