JP2001220412A - Resin for water-based coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin for a water-based coating showing a pseudoplastic flow in a low concentration range, having a concentration range hardly changing viscosity even with rise in concentration. SOLUTION: This resin for a water-based coating is obtained by copolymerizing at least one kind of a highly hydrophilic group-containing ethylenic monomer with at least one kind of a highly hydrophobic group- containing ethylenic monomer in a mixed solvent of at least one kind of organic solvent having <150 deg.C boiling point and at least one kind of organic solvent having >=150 deg.C boiling point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a resin for water-based paint.

[0002]

2. Description of the Related Art When coating a paint, it is necessary to control the viscous behavior of the paint in order to obtain high finish quality.
In particular, in the case of a water-based paint to be spray-coated, it is necessary that the viscosity is low at the time of spraying, that the viscosity is so high that it does not drip at the time of coating, and that the viscosity does not increase with the concentration after coating. The former can be realized by the fact that the spray paint exhibits pseudoplastic flow, and the latter can be realized by the fact that the viscosity of the paint has no concentration dependency in a predetermined concentration range. Conventionally, to control the viscosity of water-based paints, core
Method using shell emulsion (JP-A-56-157)
358) and a method using a composition comprising a water-soluble acrylic resin and resin particles (JP-A-63-111976). However, in all of these methods, the coating shows pseudoplastic flow in the low concentration range, but the coating conditions (especially, booth temperature and humidity conditions) fluctuate because the viscosity of the coating increases monotonically with the concentration increase. In this case, the flow property (leveling property) of the paint fluctuates, and it is difficult to obtain good finish quality. In particular, when painting a large object to be painted such as an automobile in which concentration distribution tends to occur at the time of painting, the flowability varies depending on the place, and it is difficult to obtain good finish quality. On the other hand, a method using a copolymer of a highly hydrophilic group-containing ethylenic monomer and a highly hydrophobic group-containing ethylenic monomer (Japanese Unexamined Patent Application Publication No. 10-183065)
No.) shows pseudoplastic flow in the low-concentration region, and the increase in viscosity of the paint with the increase in concentration can be reduced. However, depending on the composition of the coexisting solvent, the viscosity increases with the increase in concentration, resulting in a good finish. Quality may not be obtained.

[0003]

SUMMARY OF THE INVENTION The present invention provides a water-based paint having a concentration region in which pseudoplastic flow is exhibited in a low concentration region and the viscosity hardly changes even when the concentration increases, in order to obtain a good finish quality. It is intended to provide a resin for use.

[0004]

According to the present invention, at least one kind of a highly hydrophilic group-containing ethylenic monomer and at least one kind of a highly hydrophobic group-containing ethylenic monomer are provided as means for solving the above-mentioned problems. Is provided in a mixed solvent of at least one kind of organic solvent having a boiling point of less than 150 ° C. and at least one kind of organic solvent having a boiling point of 150 ° C. or more.

A dispersion of the resin of the present invention containing a highly hydrophilic group and a highly hydrophobic group containing water as a main solvent has a large amount of water as a solvent in a low-concentration region. The association of highly hydrophobic groups occurs and shows pseudoplastic flow. Furthermore, when the amount of water decreases as the concentration increases, the association of highly hydrophobic groups decreases, and the dispersion becomes oil-in-water (oil in water).
r) Since the phase changes from an emulsion to a water-in-oil type emulsion, an increase in viscosity with an increase in concentration is suppressed. It is considered that this phase change is likely to occur when an organic solvent coexists. However, if the organic solvent has a low boiling point, it is likely to evaporate at the time of coating, and in particular, when spray coating, the above-mentioned phase change hardly occurs.
According to the present invention, since the resin is synthesized in a mixed solvent of a low-boiling organic solvent and a high-boiling organic solvent, only the low-boiling organic solvent is removed when the solvent is removed during coating. The boiling organic solvent remains. As a result, the aqueous dispersion of the resin shows pseudoplastic flow in the low concentration region,
A region in which the viscosity hardly changes even when the concentration increases due to the effective operation of the high-boiling organic solvent is provided.

The water-based paint using the resin for a water-based paint of the present invention has a pseudo-plastic flow in a low-concentration region, and has a concentration region in which the viscosity hardly changes even when the concentration is increased by spray coating or the like. For this reason, even in the case of a large object to be coated such as an automobile, even when a concentration distribution occurs at the time of coating, leveling is performed uniformly over the whole, and good finish quality is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The water-based coating resin of the present invention comprises at least one kind of highly hydrophilic group-containing ethylenic monomer and at least one kind of highly hydrophobic group-containing ethylenic monomer, and at least one kind of organic solvent having a boiling point of less than 150 ° C. and a boiling point. Is 1
It is obtained by copolymerization in a mixed solvent of at least one kind of organic solvent at 50 ° C. or higher.

The highly hydrophilic group-containing ethylenic monomer for synthesizing the water-based coating resin of the present invention has a solubility parameter (δsp) of at least 9.5 in the present invention. Here, this δsp is a parameter indicating the cohesive energy between molecules, and is expressed by equation (1). δsp = ((△ Hv−RT) / V) ^1/2 (1) △ Hv: Latent heat of vaporization at temperature TK R: Molecular gas constant T: Absolute temperature V: Molecular volume Specifically, using equation (2) The fact that δsp can be determined from the cohesive energy of atomic groups is described in Small (Journal of
Applied Chemistry, vol. 69, 2809p (1953)) and Hoy (Journa
l of Paint Technology, vo1.42, No. 541, 76p (1970)). δsp = ρ (ΣG) / M (2) ρ: density G: aggregation energy M: molecular weight

Particularly, the present monomer preferably contains an ethylenic monomer containing an acidic group and / or an ethylenic monomer containing a hydroxyl group. Examples of the acidic group of the ethylenic monomer containing an acidic group include carboxylic acid and sulfonic acid groups. Examples of the carboxylic acid-containing monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid, and sulfonic acid. Examples of the group-containing monomer include styrenesulfonic acid, vinylbenzenesulfonic acid, 2-acrylamidopropanesulfonic acid, and the like. The ethylenic monomer containing an acidic group may be a half ester, half amide, half thioester, or the like of a dibasic acid monomer (maleic acid, fumaric acid, itaconic acid, etc.).

Examples of the hydroxyl group-containing ethylenic monomer include 2-hydroxyethyl acrylate and 2-hydroxyethyl acrylate.
Hydroxypropyl, 2-hydroxybutyl acrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, vinyl alcohol, allyl alcohol and the like.

Examples of highly hydrophilic ethylenic monomers other than the ethylenic monomer containing an acidic group and the ethylenic monomer containing a hydroxyl group include acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, NN-dimethyl. Examples include acrylamide, NN-dimethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-butylacrylamide, N-butylmethacrylamide, glycidyl acrylate, glycidyl methacrylate, and the like.

When an ethylenic monomer containing an acidic group and / or an ethylenic monomer containing a hydroxyl group is used as the highly hydrophilic group-containing ethylenic monomer for synthesizing the resin for a water-based paint of the present invention, the acidic group is used. It is preferable to use 2 to 15% by weight of the contained ethylenic monomer and 5 to 30% by weight of the hydroxyl group-containing ethylenic monomer. More preferably, 3 to 10% by weight of an ethylenic monomer having an acidic group and 10 to 25% by weight of an ethylenic monomer having a hydroxyl group are used. If the amount of the ethylenic monomer containing an acidic group is less than 2% by weight, the dispersibility in water is poor, and the resin aggregates and precipitates. If the amount exceeds 15% by weight, the hydrophilicity becomes too high and the water resistance of the coating film becomes too high. descend. If the amount of the hydroxyl group-containing ethylenic monomer is less than 5% by weight, the curability of the coating film is poor, and if it exceeds 30% by weight, the hydrophilicity becomes too high and the water resistance of the coating film decreases.

The highly hydrophobic group-containing ethylenic monomer for synthesizing the water-based coating resin of the present invention means an ethylenic monomer having a δsp of less than 9.0 in the present invention. δsp
As an ethylenic monomer having a value of less than 9.0, acrylic acid n
-Propyl, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate (lauryl), cyclohexyl acrylate Xyl, hexadecyl acrylate (cetyl), heptadecyl acrylate, octadecyl acrylate (stearyl), n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-methacrylate Hexyl, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate (lauryl), cyclohexyl methacrylate, hexadecyl methacrylate (cetyl), heptadecyl methacrylate, octyl methacrylate Decyl (stearyl) and the like. In particular, the present monomer has 12 to 24 carbon atoms.
An ethylenic monomer having an alkyl group is preferred.

The resin for aqueous coating composition of the present invention copolymerizes the above-mentioned monomer in a mixed solvent of at least one kind of organic solvent having a boiling point of less than 150 ° C. and at least one kind of organic solvent having a boiling point of 150 ° C. or more. Obtained by: Examples of the organic solvent having a boiling point of less than 150 ° C. for obtaining the water-based coating resin of the present invention include methyl alcohol, ethyl alcohol,
Alcohols such as n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono n-propyl ether, Alkylene glycol alkyl ethers such as propylene glycol monoisopropyl ether, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, hydrocarbons such as toluene and xylene, and esters such as ethyl acetate, butyl acetate and isobutyl acetate can be used. Or an alkylene glycol alkyl ether.

Examples of the organic solvent having a boiling point of 150 ° C. or higher for obtaining the resin for water-based coating of the present invention include alcohols such as n-hexyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol and benzyl alcohol. . Also, ethylene glycol mono n-propyl ether, ethylene glycol mono isopropyl ether, ethylene glycol mono n-butyl ether, ethylene glycol mono isobutyl ether, ethylene glycol mono tertiary butyl ether, ethylene glycol mono n-hexyl ether, diethylene glycol mono n-propyl ether , Diethylene glycol monoisopropyl ether, diethylene glycol mono n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monotertiary butyl ether,
Diethylene glycol mono n-hexyl ether, propylene glycol mono n-butyl ether, propylene glycol monoisobutyl ether, propylene glycol monotertiary butyl ether, propylene glycol mono n-hexyl ether, dipropylene glycol mono n-propyl ether, dipropylene glycol monoisopropyl ether , Dipropylene glycol mono n-butyl ether, dipropylene glycol mono isobutyl ether, dipropylene glycol mono tertiary butyl ether, dipropylene glycol mono n-hexyl ether, butylene glycol mono n-propyl ether, butylene glycol monoisopropyl ether, butylene glycol mono n-butyl ether, butylene glycol monoisobutyl acrylate Alkylene glycol alkyl ethers such as ter, butylene glycol monotertiary butyl ether, and butylene glycol mono n-hexyl ether can be used. Further, ketones such as cyclohexanone and hydrocarbons such as Solvesso 100 and Solvesso 150 can be used, but alcohols and alkylene glycol alkyl ethers are preferable.

The organic solvent for obtaining the resin for a water-based paint of the present invention must be designed so as to have a desired organic solvent composition in the water-based paint. It is preferable that the organic solvent is removed and the organic solvent having a boiling point of 150 ° C. or higher is mixed so as to remain. Organic solvents having a boiling point of 150 ° C. or higher are difficult to evaporate during coating (particularly, during spray coating).
It is possible to effectively suppress an increase in viscosity due to an increase in concentration. Specifically, the organic solvent having a boiling point of 150 ° C. or more is 1% of the total amount of the organic solvent.
5050 wt%, particularly preferably 2-40 wt%
%. When the content of the high boiling point organic solvent is less than 1 wt%, the viscosity decreases with the increase in the concentration, and the finish is reduced.
%, It is not preferable because it is difficult to remove the solvent when forming the coating and the strength of the coating decreases due to the organic solvent remaining in the coating.

The resin for aqueous coating composition of the present invention is polymerized in a reaction vessel at a temperature of 50 to 150 ° C. for 3 to 15 hours using a polymerization initiator such as an azo compound or an organic peroxide in the presence of the above-mentioned mixed solvent. It is obtained by doing. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4′-dimethylvaleronitrile), and dimethyl 2,2′-azobisisobutyrate. As the organic peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisobutyrate, tert-butyl peroxy 2-ethylhexanoate, cumene hydroperoxide and the like can be used.

The number average molecular weight of this resin is from 2000 to 100,000,
It is preferably from 3,000 to 50,000, and if it is less than 2,000, it is not desirable because it does not show pseudoplastic flow in a low concentration range, the workability of paint is inferior because the viscosity is too low, and the physical properties of the coating film are inferior. On the other hand, if it exceeds 100,000, the water dispersibility becomes poor, and the viscosity monotonously increases as the concentration increases, which is not desirable.

In order to disperse the resin for aqueous coating composition of the present invention in an aqueous medium, it is necessary to at least partially neutralize acidic groups in the resin with a basic substance. Examples of the basic substance include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, diethylenetriamine, triethylenetetramine,
Monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, dimethylethanolamine, morpholine, methylmorpholine, piperazine, ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

The resin for a water-based paint of the present invention is usually used as a water-based paint by mixing a crosslinking agent. Examples of crosslinking agents include amino resins and blocked polyisocyanates. As amino resins, for example, melamine, urea,
Known partial or fully methylolated amino resins obtained by the reaction of an amino component such as benzoguanamine, acetoguanamine, spiroguanamine, dicyandiamide and an aldehyde are exemplified. As aldehyde,
Examples include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, those obtained by etherifying the methylolated amino resin with an appropriate alcohol can also be used. Examples of the alcohol used for the etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol. Alcohol, 2-ethylbutanol, 2-ethylhexanol and the like can be mentioned. Specifically, methyl etherified melamine resin, butyl etherified melamine resin, methyl and butyl mixed etherified melamine resin, methyl and isobutyl mixed etherified melamine resin, and the like can be used. Blocked polyisocyanates are obtained by reacting a blocking agent with all polyisocyanate groups having two or more free isocyanate groups in one molecule. When heated to a temperature higher than the dissociation temperature, the isocyanate groups are regenerated, and Cross-linking reaction occurs. Examples of the polyisocyanate compound include aliphatic isocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, cycloaliphatic isocyanates such as xylene diisocyanate and isophorone diisocyanate, and aromatic isocyanates such as tolylene diisocyanate 4,4-diphenylmethane diisocyanate. And the like. As the blocking agent, for example, phenol compounds, lactam compounds, alcohol compounds, oxime compounds and the like are used.

The aqueous coating composition of the present invention may be mixed with cellulose acetate, an epoxy resin, a polyester resin, an alkyd resin, an acrylic resin and the like, if necessary, when forming the coating composition. Moreover, the following known components can be contained. That is, organic pigments (quinacridone type such as quinacridone, azo type such as pigment red, and phthalocyanine type such as phthalocyanine blue and phthalocyanine green), inorganic pigments (titanium oxide, barium sulfate,
Calcium carbonate, clay, silica, mica, etc., carbon pigment (carbon black), metallic powder (aluminum, mica-like iron oxide, stainless steel, etc.), surface conditioner, ultraviolet absorber, antioxidant, curing catalyst (dodecyl) Benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, dibutyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate, triethylamine, diethanolamine and the like). The water-based paint of the present invention can be applied directly to a material to be coated such as a metal (for example, a steel plate, a surface-treated steel plate, etc.) or plastic, or to a material to be coated with a primer, a primer / intermediate coating, or a primer /
It can be applied to the surface of a coating film having a middle coat / top coat base. In the present invention, the object to be coated is not particularly limited, and is applied to transport equipment and buildings such as automobiles, ships, aircraft, and the like, or to outer panel coatings such as electric appliances, and is particularly preferable for coatings that require high finish quality such as automobiles. Applied. When used as an automotive paint, for example,
Top coat base paint (metallic paint or solid color paint) such as 2 coat 1 bake such as clear top coat, 2 coat 2 bake, or 3 coat 2 bake such as middle coat / top coat base / top coat clear etc. and 3 coat 1 bake and clear top coat It can be used as a solid color paint such as paint, one coat and one bake. The water-based paint of the present invention is preferably spray-coated on the surface of the object to be coated. In this case, the coating method is not particularly limited, and examples thereof include air spray coating, airless spray coating, air atomization type, and airless atomization type. Alternatively, there is a rotary atomizing electrostatic coating.

The water-based paint using the resin for a water-based paint is as follows:
Pseudoplastic flow in the low concentration area, and the viscosity distribution hardly changes even if the concentration rises when spray-painted, so the concentration distribution occurs when painting large objects such as automobiles. In this case, leveling is performed uniformly over the entire surface, and good finish quality is obtained.

[0023]

EXAMPLES The present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.

Example 1 Synthesis of Paint Resin 65 parts by weight of isopropyl alcohol and 17 parts by weight of n-hexyl alcohol were charged into a reaction vessel equipped with a stirrer, a temperature controller, and a reflux condenser. 80 ° C. Here, 5 parts by weight of acrylic acid, 17 parts by weight of 2-hydroxyethyl acrylate, 66 parts by weight of n-butyl methacrylate,
After adding a monomer solution comprising 12 parts by weight of stearyl acrylate and 0.8 part by weight of azobisisobutyronitrile over 5 hours, stirring was continued for 1 hour to obtain a number average molecular weight of 15%.
000 resins were obtained. The resin solution was desolvated with an evaporator until the solid content concentration became 80% by weight, and then 6 parts by weight of dimethylethanolamine and 36 parts by weight of deionized water were added to form an aqueous coating composition having a solids concentration of 60% by weight. A resin dispersion was obtained.

Example 2 Synthesis of Resin for Paint A reaction vessel equipped with a stirrer, a temperature controller and a reflux condenser was charged with 65 parts by weight of ethylene glycol monomethyl ether and 17 parts by weight of dipropylene glycol mono n-butyl ether. After the replacement, the temperature was brought to 80 ° C. Here, 5 parts by weight of acrylic acid, 17 parts by weight of 2-hydroxyethyl acrylate, 66 parts by weight of n-butyl methacrylate, 12 parts by weight of stearyl acrylate, and 0.8 part by weight of azobisisobutyronitrile were mixed with 5 parts by weight of a monomer solution. After adding over time,
Stirring was continued for 1 hour to obtain a resin having a number average molecular weight of 14,000. The resin solution was desolvated with an evaporator until the solid content concentration became 80% by weight, and then 6 parts by weight of dimethylethanolamine and 36 parts by weight of deionized water were added to form an aqueous coating composition having a solids concentration of 60% by weight. A resin dispersion was obtained.

<Example 3> Preparation of aqueous paint A melamine resin (Cymel manufactured by Mitsui Cytec Co., Ltd.) was added to the resin dispersion for aqueous paint having a solid content concentration of 60% by weight prepared in Example 1.
325) was added at a ratio of 30% by weight based on the solid content of the resin for water-based paint, diluted with water to a solid content concentration of 25% by weight, and uniformly mixed to prepare a water-based paint varnish. Further, 10% by weight of aluminum powder based on the resin solid content was mixed with the aqueous varnish to prepare an aqueous paint.

<Example 4> Preparation of aqueous paint A melamine resin (Mycoat 508 manufactured by Mitsui Cytec Co., Ltd.) was added to the aqueous paint resin dispersion having a solid content concentration of 60% by weight prepared in Example 1 to obtain a resin paint for aqueous paint. , And diluted with water to a solid concentration of 25% by weight, and uniformly mixed to prepare an aqueous paint varnish. Further, 10% by weight of aluminum powder based on the resin solid content was mixed with the aqueous varnish to prepare an aqueous paint.

<Example 5> Preparation of water-based paint A melamine resin (Mycoat 508, manufactured by Mitsui Cytec Co., Ltd.) was added to the resin dispersion for water-based paint having a solid content of 60% by weight prepared in Example 2 for 30 times the solid content. % By weight, diluted with water to a solid concentration of 25% by weight, and uniformly mixed to prepare an aqueous paint varnish. Further, 10% by weight of aluminum powder based on the resin solid content was mixed with the aqueous varnish to prepare an aqueous paint.

<Comparative Example 1> Synthesis of resin for coating material A reaction vessel equipped with a stirrer, a temperature controller and a reflux condenser was charged with 82 parts by weight of isopropyl alcohol, and the temperature was raised to 80 ° C after purging with nitrogen. Here, 5 parts by weight of acrylic acid,
17 parts by weight of 2-hydroxyethyl acrylate, methacrylic acid
A monomer solution consisting of 66 parts by weight of n-butyl, 12 parts by weight of sterallyl acrylate and 0.8 part by weight of azobisisobutyronitrile was added over 5 hours, followed by stirring for 1 hour to obtain a resin having a number average molecular weight of 15,000. Obtained. The resin solution was desolvated with an evaporator until the solid content concentration became 80% by weight, and then 6 parts by weight of dimethylethanolamine and 36 parts by weight of deionized water were added to form an aqueous coating composition having a solids concentration of 60% by weight. A resin dispersion was obtained.

Comparative Example 2 Synthesis of Paint Resin A reaction vessel equipped with a stirrer, a temperature controller and a reflux condenser was charged with 65 parts by weight of ethylene glycol monomethyl ether and 17 parts by weight of dipropylene glycol mono n-propyl ether. After purging with nitrogen, the temperature was raised to 80 ° C. Here, a monomer solution consisting of 5 parts by weight of acrylic acid, 18 parts by weight of 2-hydroxyethyl acrylate, 77 parts by weight of methyl methacrylate and 0.8 parts by weight of azobisisobutyronitrile was added over 5 hours, and then 1 hour Stirring was continued to obtain a resin having a number average molecular weight of 13,000. After desolvation of the resin solution using an evaporator until the solid content concentration becomes 80% by weight, 7 parts by weight of dimethylethanolamine and 35 parts of deionized water were added.
The resin dispersion for an aqueous coating material having a solid content of 60% by weight was obtained by adding parts by weight.

<Comparative Example 3> Preparation of Water-Based Paint A melamine resin (Cymel manufactured by Mitsui Cytec Co., Ltd.) was added to the resin dispersion for water-based paint having a solid content concentration of 60% by weight prepared in Comparative Example 1.
325) was added at a ratio of 30% by weight based on the solid content, diluted with water to a solid content concentration of 25% by weight, and uniformly mixed to prepare an aqueous paint varnish. 10% by weight based on resin solids
Was mixed with the above aqueous varnish to prepare an aqueous paint.

<Comparative Example 4> Preparation of water-based paint A melamine resin (Cymel manufactured by Mitsui Cytec Co., Ltd.) was added to the resin dispersion for water-based paint having a solid content concentration of 60% by weight prepared in Comparative Example 2.
508) was added at a ratio of 30% by weight based on the solid content, diluted with water to a solid content concentration of 25% by weight, and uniformly mixed to prepare an aqueous paint varnish. 10% by weight based on resin solids
Was mixed with the above aqueous varnish to prepare an aqueous paint.

-Evaluation of Viscosity of Aqueous Paint- <Example 6> For the aqueous paints prepared in Examples 3, 4, 5 and Comparative Examples 3 and 4, the shear rate dependence of the viscosity was measured with a rotary viscometer. In addition to examining the viscous behavior (pseudoplastic flow or Newtonian flow) (Table 1), for the paint whose solid content concentration was increased to 30 to 50% by weight, the shear rate was 1 × 10
The viscosity at ^-1 s ^-1 was measured with a rotary viscometer (FIG. 1).

[0034]

[Table 1] As shown in Table 1, the aqueous paints of Examples 3 to 5 all exhibited pseudoplastic flow, whereas the aqueous paint of Comparative Example 3 exhibited pseudoplastic flow, whereas the aqueous paints of Comparative Example 4 The paint exhibited Newtonian flow. Further, as shown in FIG. 1, each of the aqueous paints of Examples 3 to 5 had a solid content concentration of 30 to 50.
In the range of% by weight (particularly, in the range of 40 to 50% by weight), the viscosity did not increase with the increase in the concentration and showed a substantially constant value, whereas in Comparative Examples 3 and 4, the solids concentration was 25 to 50%. In the weight% range, the viscosity increased with concentration.

<Evaluation of Finish><Example7> The water-based paints prepared in Examples 3, 4, and 5 and Comparative Examples 3 and 4 were dried to a thickness of 20 μm on a steel plate which had been subjected to electrodeposition coating and intermediate coating. Air spray coating was performed to evaluate the coating properties. Next, the coated plate was baked in a dryer at 140 ° C. for 30 minutes, and the finished quality was evaluated. Finish quality was checked on the skin. Table 2 shows the results.

[0036]

[Table 2] As shown in Table 2, the water-based paints of Examples 3 to 5 all had good coatability and physical properties of the coating film (skin).

[0037]

According to the present invention, there is provided a water-based coating resin having a concentration region in which pseudoplastic flow is exhibited in a low concentration region and the viscosity hardly changes even when the concentration increases.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the solid content concentration and the viscosity of the aqueous paints of Examples and Comparative Examples.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Nakamura 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. 41, Yokomichi, Toyota Central Research Laboratory Co., Ltd. (72) Inventor Mamoru Mitsuzaki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 4J038 CC091 CE011 CE021 CG021 CG031 CG061 CG071 CG141 CG171 CH031 CH041 CH071 CH121 DA142 DG262 DG302 GA03 GA06 GA13 JA19 JA25 JA33 JA55 KA03 KA06 MA08 MA10 MA14 NA01 NA26 PB07 PC02 4J100 AB07P AD02P AD03P AJ01P AJ02P AJ08P AJ09P AL03Q AL04Q AL05Q AL09P AL10P ABAP BA17PAMBAP

Claims (4)

[Claims] 1. A method according to claim 1, wherein at least one kind of highly hydrophilic group-containing ethylenic monomer and at least one kind of highly hydrophobic group-containing ethylenic monomer are combined with at least one kind of organic solvent having a boiling point of less than 150 ° C. and a boiling point of 150 ° C. or more. A water-based paint resin obtained by copolymerization in a mixed solvent with at least one organic solvent. 2. The resin according to claim 1, wherein the at least one organic solvent having a boiling point of 150 ° C. or higher is an alkylene glycol or an alcohol. 3. The resin according to claim 1, wherein the highly hydrophilic group-containing ethylenic monomer is an acidic group-containing monomer and / or a hydroxyl group-containing monomer. 4. The resin for aqueous paint according to claim 1, wherein said highly hydrophobic group-containing ethylenic monomer is an ethylenic monomer having an alkyl group having 12 to 24 carbon atoms.