JP2022159525A - Coating composition and coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition which has an excellent coating film drying property in coating with a water-based coating in a factory, and can form a coated body excellent in blocking resistance and water resistance.

SOLUTION: A coating composition contains water, an organic solvent, a pigment, and a resin. The pigment volume concentration (PVC) is in the range of 0.1-35%. The resin has at least one spectral peak in the range of 45°C to 180°C inclusive in a temperature change curve of the loss tangent (tanδ) measured at a measuring frequency of 1 Hz using a solid viscoelasticity measuring apparatus based on JIS K7244-4.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a coating composition and a coating film obtained from the coating composition, and in particular, a coating that has excellent drying properties, blocking resistance, and water resistance when a water-based coating is applied at a factory. It relates to a body-forming coating composition.

Various coating compositions have been proposed as coating compositions to be applied to metal substrates, but from the viewpoint of reducing environmental load, water-based coating compositions are desired, and various proposals have been made. .

Japanese Patent Application Laid-Open No. 7-300574 (Patent Document 1) describes an invention relating to a water-based coating composition containing a water-based acrylic-modified alkyd resin and a water-based acrylic-modified epoxy resin as binders, and this invention is directed to rust prevention of light-duty steel. The present invention relates to an aqueous coating composition which is water-based and has an ultra-quick drying property, which is suitable for use as a coating composition. The invention described in Patent Document 1 is roll touch paint film peelability after several seconds of painting, oil surface adhesion, wide temperature distribution width of 70 to 120 ° C and high temperature finish without popping in the painted surface state, several minutes after painting It is a water-based coating composition that has good blocking properties even in subsequent stacking and can provide a coating film with excellent rust resistance. There was a problem with the drying property of the coating film when it was painted at the factory.

Japanese Patent Application Laid-Open No. 2005-349684 (Patent Document 2) discloses a colorless and transparent resin having excellent blocking resistance by using a core-shell type emulsion resin in which the Tg of the outermost shell is higher than the Tg of the center of the particles. An invention that provides a resin-coated surface-treated steel sheet having a film is described.

Japanese Patent Application Laid-Open No. 2020-2327 (Patent Document 3) is a water-based paint that can be used for both air-drying and baking, and can form a coating film with excellent film-forming properties, anti-blocking properties, and anti-rust properties. An invention relating to a composition is described, and the invention is a water-based coating composition containing urethane resin particles having a glass transition temperature of 30 to 100°C and acrylic resin particles having a glass transition temperature of -20 to 30°C in a certain ratio. It is an invention related to an object. The invention described in Patent Document 3 is an invention that can solve the problem of blocking resistance in factory coating by blending two types of resin components with different glass transition temperatures. Film-forming properties and drying properties were not taken into consideration, and there was room for improvement in the water resistance of the resulting coating film.

JP-A-7-300574 JP 2005-349684 A Japanese Patent Application Laid-Open No. 2020-2327

Therefore, an object of the present invention is to provide a coating composition that can form a coated body that has excellent coating film drying properties, excellent blocking resistance, and excellent water resistance when a water-based coating is applied at a factory.

As a result of intensive studies to achieve the above object, the present inventors have found that, in a water-based coating composition, an organic solvent is used as part of the solvent, the pigment volume concentration (PVC) is adjusted within a specific range, and the loss tangent By blending a resin that has a spectral peak in a specific range in the temperature change curve of , when water-based paint is applied at a factory, the coating film has excellent drying properties, blocking resistance, and water resistance. It has been found that a possible coating composition can be provided.

Therefore, a first aspect of the present invention is a coating composition comprising water, an organic solvent, a pigment, and a resin, wherein the pigment volume concentration (PVC) is in the range of 0.1 to 35%, and the resin is , Using a solid viscoelasticity measuring device based on JIS K7244-4, at least one spectral peak in the temperature change curve of the loss tangent (tan δ) measured at a measurement frequency of 1 Hz is at 45 ° C. or higher and 180 ° C. or lower. A coating composition characterized by:

In a preferred embodiment of the coating composition of the present invention, the coating composition contains a cross-linking component.

In another preferred example of the coating composition of the present invention, the coating film formed from the coating composition has a crosslink density in the range of 1.0×10 ⁻⁶ to 1.0×10 ⁻² (mol/cc). inside.

In another preferred embodiment of the coating composition of the present invention, the coating film formed from the coating composition has two or more softening points, one of which is less than 25°C and another One point is 45°C or higher.

In another preferred embodiment of the coating composition of the present invention, the resin contains a resin having a molecular weight of less than 100,000 within the range of 1 to 30% by mass in the resin component, and a resin having a molecular weight of 100,000 or more or a crosslinked structure. 20 to 99% by mass of the resin having the

In another preferred embodiment of the coating composition of the present invention, the resin contains one or more monomers having an SP value within the range of 9.2 to 9.9 as constituent components, and the organic solvent has an SP value of 8.0 to 11.1 and contains one or more organic solvents having a boiling point in the range of 160 to 260°C.

A second aspect of the present invention is a coating film obtained from the above coating composition, wherein the coating film is coated on a preheated steel plate to a thickness of 100 μm, and the steel plate is heated to 35 to 45 ° C. The coating film is characterized by a surface drying time of 10 seconds to 5 minutes in terms of surface dryness (Balotini method) measured in accordance with JIS K 5600-3-2 under maintained conditions.

According to a first aspect of the present invention, there is provided a coating composition capable of forming a coated body having excellent coating film drying properties, blocking resistance, and water resistance when a water-based coating is applied at a factory. can be done.

According to the second aspect of the invention, it is possible to provide a coating film which is excellent in drying property, blocking resistance, and water resistance when a water-based paint is applied in a factory.

The present invention will be described in detail below.

One aspect of the invention is a coating composition comprising water, an organic solvent, a pigment and a resin.

The water used in the coating composition of the present invention is not particularly limited, but tap water, ion-exchanged water, pure water such as distilled water, and the like are suitable. Moreover, when the coating composition is to be stored for a long period of time, water sterilized by ultraviolet irradiation or the like may be used in order to prevent the generation of mold or bacteria. In the coating composition of the present invention, the amount of water is preferably 20-60% by mass, more preferably 30-50% by mass.

The coating composition of the present invention is preferably an aqueous coating composition. As used herein, the term "aqueous coating composition" refers to a coating composition containing water as the main solvent.

The coating composition of the present invention preferably contains an organic solvent, and more preferably contains a film-forming aid, from the viewpoint of ensuring the film-forming properties of the coating film and improving the drying property of the coating film. A film-forming aid is generally an organic solvent that is blended for the purpose of imparting film-forming properties, and does not correspond to a coating film-forming component. Film forming aids include, for example, propylene glycol, propylene glycol monomethyl ether (PGMME), propylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, Ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol mono-isopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, diethylene glycol mono- tert-butyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol monobutyl ether and the like.
Other organic solvents are not particularly limited, and organic solvents commonly used in the paint industry can be used. For example, various organic solvents such as alcohol-based solvents, ketone-based solvents, ester-based solvents, ether-based solvents, and hydrocarbon-based solvents can be used, and water-soluble organic solvents are preferably included.

Examples of alcohol solvents include methanol, ethanol, butanol, etc. Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. Examples of ester solvents include ethyl acetate, acetic acid, and the like. butyl and the like, and ether solvents include, for example, ethylene glycol monoethyl ether, methyl carbitol and the like. Solvents having both a hydroxyl group and an ether bond, such as ethylene glycol monoethyl ether and methyl carbitol, are classified as ether solvents as described above. Examples of hydrocarbon solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and more specifically toluene, xylene, solvent naphtha, mineral spirits, hexane, cyclohexane. , octane, terpene oil and the like.

In the coating composition of the present invention, the amount of organic solvent is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass. An organic solvent may be used individually by 1 type, and may be used in combination of 2 or more types.

The pigment used in the coating composition of the present invention is not particularly limited, and pigments commonly used in the coating industry, such as antirust pigments, extender pigments and coloring pigments, can be used. These pigments may be used singly or in combination of two or more.

The coating composition of the present invention preferably contains an anticorrosion pigment from the viewpoint of use for line anticorrosion coating. Examples of antirust pigments include zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, and calcium phosphite. , aluminum phosphite, zinc calcium phosphate, zinc aluminum phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, vanadic acid/phosphoric acid mixed pigment, etc., and zinc phosphate is particularly preferred. . In the coating composition of the present invention, the amount of rust preventive pigment is, for example, 1 to 8% by mass.

Examples of extender pigments include silica, talc, mica, calcium carbonate, barium sulfate and the like. In the coating composition of the present invention, the amount of extender pigment is, for example, 1 to 40% by weight.

Examples of coloring pigments include titanium oxide, iron oxide, carbon black, yellow lead, molybdate orange, ultramarine blue, Prussian blue, phthalocyanine blue, phthalocyanine green, quinacridone red, naphthol red, benzimidazolone yellow, hansa yellow, and benzimidazolone. orange, dioxazine violet, and the like. In the coating composition of the present invention, the amount of color pigment is, for example, 1 to 10% by weight.

The paint composition of the present invention preferably has a pigment volume concentration (PVC) in the range of 0.1 to 35%, more preferably in the range of 1 to 30%, and in the range of 5 to 25%. More preferably within. Water resistance and blocking resistance can be improved by adjusting the PVC to the above-specified range. In addition, if the PVC is too low, the initial water resistance is lowered due to the deterioration of the drying property. On the other hand, if the PVC is too high, it becomes easy to permeate water, resulting in a decrease in anticorrosion properties.

As used herein, the pigment volume concentration (PVC) is the ratio of the volume of the entire pigment to the volume of the entire coating film-forming component in the coating composition, and constitutes the coating film-forming component. It can be obtained by calculation from the composition and specific gravity of each component.

In the present specification, the film-forming component refers to a component excluding volatilizable components such as water and organic solvents, and is a component that ultimately forms a coating film. In this specification, the components remaining after drying the coating composition at 130° C. for 60 minutes are treated as film-forming components. In the coating composition of the present invention, the amount of the film-forming component is, for example, 50-70% by weight, preferably 55-65% by weight.

Examples of the resin used in the coating composition of the present invention include resins commonly used in the coating industry. Specifically, acrylic resins, silicone resins, acrylic silicone resins, styrene acrylic copolymer resins, polyester resins, fluorine resins, rosin resins, petroleum resins, coumarone resins, phenolic resins, urethane resins, melamine resins, urea resins, and epoxy resins. , cellulose resins, xylene resins, alkyd resins, aliphatic hydrocarbon resins, butyral resins, maleic acid resins, fumaric acid resins, vinyl resins, amine resins, ketimine resins, and the like.

In the coating composition of the present invention, the resin content in the coating film-forming components is preferably 30 to 90% by mass. The resin may be used singly or in combination of two or more.

In the coating composition of the present invention, the resin is measured at a measurement frequency of 1 Hz using a solid viscoelasticity measuring device based on JIS K7244-4. The temperature is preferably 45° C. or higher and 180° C. or lower, more preferably 50° C. or higher and 130° C. or lower, and even more preferably 60° C. or higher and 110° C. or lower.

When the loss tangent temperature change curve of the resin exhibits a spectral peak within the range specified above, the use of such a resin can improve the blocking resistance of the resulting coating film. By setting the temperature of the spectrum peak in the temperature change curve of the loss tangent higher than the maximum temperature applied when the steel plates are stacked (specifically set to 45 ° C or higher), the resin is in a crystalline state in the temperature range where the steel plates are stacked. The blocking resistance can be improved because the hard convex portions can be randomly present in the coating film. On the other hand, when the spectral peak in the temperature change curve of the loss tangent is only for the resin below 45° C., blocking occurs in the temperature range where the steel sheets are stacked because the resin is softened.

The resin is emulsified in water, for example, by using a high-speed stirrer or the like to apply a forced shearing force, and if necessary, using a surfactant to emulsify the water-dispersible resin in water or emulsify the monomer component. It can be prepared by polymerizing. Alternatively, a resin dispersion can be prepared by adding a surfactant, if necessary, to the water-dispersible resin polymerized in an organic solvent medium, and performing phase conversion into water. The organic solvent contained in the resin dispersion may be removed by distillation or the like. A resin dispersion can also be prepared by using water as a medium and performing polymerization in water.

Here, in order to produce a resin having a spectral peak within the range specified above in the temperature change curve of the loss tangent, the glass transition temperature (Tg) obtained by the FOX calculation formula shown below must be 45 to 180 ° C. It is preferred to include a polymer component in the resin component.
[FOX calculation formula]
1/Tg=W1/Tg1+W2/Tg2+...+Wi/Tgi+...+Wn/Tgn
In the FOX calculation formula, Tg described in the denominator on the left side represents the glass transition temperature (unit: K) of the polymer component composed of N kinds of monomers, and Tg (1, 2, i, N) represents the glass transition temperature (unit: K) of each monomer, W (1, 2, i, N) is the mass fraction of each monomer, W1 + W2 + ... + Wi + ... + Wn = 1 relationship is established. Here, the glass transition temperature of a monomer means the glass transition temperature of its homopolymer.

The details of the method for measuring the loss tangent (tan δ) of the resin are as follows. Apply to a polypropylene (PP) plate preheated to 80 ° C. using an applicator so that the dry film thickness is 40 to 100 μm, and force dry at 80 ° C. for 30 minutes to form an isolated resin film. obtain. Using a solid viscoelasticity measuring device (for example, RSA-GII (manufactured by TA Instruments)), the loss modulus and storage modulus of the isolated film were measured at each temperature under the following measurement conditions, A loss tangent is calculated from the loss elastic modulus and the storage elastic modulus, a temperature change curve of the loss tangent is created, and the spectrum peak value of the loss tangent is read.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

The coating composition of the present invention preferably contains a cross-linking component. In the present specification, the crosslink-forming component is a component that forms crosslinks in the resin that constitutes the coating film. By forming crosslinks in the coating film, the blocking resistance in the initial process of coating film formation can be improved, and the water resistance of the coating film after drying can be improved. When the resin is an emulsion resin, the types of cross-linking of the resin are roughly classified into inter-particle cross-linking and intra-particle cross-linking. Cross-linking between particles or cross-linking within particles may be used, but cross-linking between particles is preferred. Moreover, as a coating composition containing a crosslinked resin, any form of one-component, two-component and multi-component can be used.

In order to form intraparticle crosslinks, divinylbenzene, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl(meth)acrylate, etc., have two polymerizable unsaturated double bonds in the molecule. A method of using a monomer having at least one monomer as a cross-linking component; a method of using a monomer having a functional group that reacts with each other at the temperature during the emulsion polymerization reaction as a cross-linking component, for example, a carboxyl group and a glycidyl group, or a hydroxyl group and an isocyanate group. A method using a monomer having a combination of functional groups such as (meth)acryloxypropyltrimethoxysilane, (meth)acryloxypropylmethyldimethoxysilane, etc. Hydrolyzable silyl groups that undergo hydrolytic condensation reaction A method of using the contained monomer as a cross-linking component and the like can be mentioned. Thus, when intraparticle crosslinks are formed, the crosslink-forming component is often a structural unit of the resin.

In order to form crosslinks between particles, a method using a combination of a monomer having a functional group such as a carboxyl group, a glycidyl group, a carbonyl group or a hydroxyl group and a crosslinker as a crosslink forming component can be used. When forming crosslinks between particles, the crosslink-forming component is often a combination of a resin structural unit and a crosslinker.

Examples of carboxyl group-containing monomers that can be used for cross-linking between particles include (meth)acrylic acid, crotonic acid, itaconic acid, itaconic acid half ester, maleic acid, and maleic acid half ester. (Meth)acrylates and the like, and carbonyl group-containing monomers include acrolein, diacetone (meth)acrylamide, formylstyrene, (meth)acryloxyalkylpropanal, diacetone (meth)acrylate, acetonyl (meth)acrylate, acetoacetoxy ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate-acetyl acetate, butanediol-1,4-acrylate-acetyl acrylate, vinyl ethyl ketone, vinyl isobutyl ketone and the like, and the hydroxyl group-containing monomer includes 2- Hydroxyethyl (meth)acrylate, 2(3)-hydroxypropyl (meth)acrylate, 4-hydroxybutyl acrylate and the like. By using these monomers, functional groups such as carboxyl groups, glycidyl groups, carbonyl groups, and hydroxyl groups can be introduced into the resin.

Examples of cross-linking agents that can be used for cross-linking between particles by reaction with carboxyl groups in the resin include epoxy group-containing silanes, oxazoline group-containing polymers, carbodiimides, ethylene glycol glycidyl ethers, metal chelates such as titanium chelates, and the like. Cross-linking agents that can be used for reaction with glycidyl groups in the resin include amino group-containing silanes, and cross-linking agents that can be used for cross-linking between particles by reaction with carbonyl groups in the resin include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, citric acid trihydrazide, 1,2,4-benzenetrihydrazide, and thiocarbodihydrazide; Examples of cross-linking agents that can be used for cross-linking between particles by reaction with hydroxyl groups in the resin include metal alkoxides such as titanium alkoxide and zirconium alkoxide, and metal chelates such as titanium chelate.

As a preferred embodiment of the coating composition of the present invention, the coating film formed from the coating composition has a crosslink density in the range of 1.0×10 ⁻⁶ to 1.0×10 ⁻² (mol/cc). It is in. The crosslink density of the coating film is an index indicating the degree of the crosslinked structure formed in the coating film, and the higher this value, the higher the ratio of the crosslinked structure formed in the coating film. By setting the crosslink density of the coating film within the range specified above, the blocking resistance in the initial process of coating film formation can be improved, and the water resistance of the coating film after drying can be improved.

As used herein, the crosslink density of a coating is defined by the formula n=E′/3RT, where n is the crosslink density of the coating (mol/cc) and E′ is the flatness of the coating at a frequency of 1 Hz. is the area storage modulus (Pa), T is the absolute temperature (K) of the flat area storage modulus of the coating, and R is the gas constant (8.31×10 ⁶ Pa·cc/mol·K). ).

The details of the method for measuring the flat area storage modulus of the coating film are as follows. Apply the coating composition to a polypropylene (PP) plate preheated to 80 ° C. using an applicator so that the dry film thickness is 40 to 100 μm, force dry at 80 ° C. for 30 minutes, and isolate. get the membrane. Using a solid viscoelasticity measuring device (for example, RSA-GII (manufactured by TA Instruments)), the storage elastic modulus of the isolated film was measured under the following measurement conditions, and the flat area storage elastic modulus of the coating film was obtained. to read.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

As a preferred embodiment of the coating composition of the present invention, the coating film formed from the coating composition has two or more softening points, one of which is less than 25°C, preferably 5°C. 45°C or higher, preferably 50 to 100°C. When the coating film has a softening point of less than 25°C (especially when it contains constituent components lower than the coating film formation temperature), the coating film formation is facilitated and a dense film is formed, so the coating film is water resistant. improve sexuality. In addition, when the coating film has a softening point of 45° C. or higher (especially when the coating contains a component having a temperature higher than the maximum temperature when the steel sheets are stacked), the anti-blocking property is improved.

In order to obtain a coating film having a softening point of at least 25°C or lower and a softening point of 45°C or higher, for example, a resin exhibiting a softening point of lower than 25°C and a resin exhibiting a softening point of 45°C or higher are added to the coating composition. and a method of using, in a coating composition, resin particles having a different phase structure having a phase exhibiting a softening point of less than 25°C and a phase exhibiting a softening point of 45°C or higher.

As used herein, the softening point of a coating film represents Tg1 (temperature at which molecules begin to move) in viscoelasticity measurements. The details of the method for measuring the softening point of the coating film are as follows. Apply the coating composition to a polypropylene (PP) plate preheated to 80 ° C. using an applicator so that the dry film thickness is 40 to 100 μm, force dry at 80 ° C. for 30 minutes, and isolate. get the membrane. Using a solid viscoelasticity measuring device (for example, RSA-GII (manufactured by TA Instruments)), the storage elastic modulus of the isolated film was measured under the following measurement conditions. The starting temperature) is defined as Tg1, which is defined as the softening point.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

As a preferred embodiment of the coating composition of the present invention, the resin contains a resin having a molecular weight of less than 100,000, preferably 10,000 or more and less than 100,000, and a resin having a molecular weight of 100,000 or more or a resin having a crosslinked structure. By including a resin having a molecular weight of 100,000 or more or a resin having a crosslinked structure (preferably an emulsion resin) in the resin component, the water resistance of the coating film is improved. In general, emulsion resins obtained by emulsion polymerization tend to have a large molecular weight, and in particular, emulsion resins having a crosslinked structure cannot be measured accurately by gel permeation chromatography, so they cannot be measured in this specification. In addition, by including a resin with a molecular weight of less than 100,000 in the resin component that fills the gaps in the emulsion resin during film formation, the denseness of the coating film as a whole is improved, and a coating film with more excellent water resistance can be obtained. be done. The resin having a molecular weight of less than 100,000 is preferably a dispersion resin or a water-soluble resin.

In the present specification, the emulsion resin refers to a resin obtained by emulsion polymerization among water-dispersible resins. Dispersion resins refer to self-water-dispersible resins, but exclude emulsion resins in this specification. A water-soluble resin is a resin that dissolves in water.

In the coating composition of the present invention, the resin having a molecular weight of less than 100,000 is preferably contained within the range of 1 to 30% by mass, more preferably within the range of 3 to 25% by mass. . In addition, the resin having a molecular weight of 100,000 or more or a resin having a crosslinked structure is preferably contained within the range of 20 to 99% by mass, more preferably within the range of 70 to 99% by mass. . As used herein, the resin component is a term that means the entire resin in the coating composition.

The weight-average molecular weight of the resin having a crosslinked structure is preferably 100,000 or more, more preferably 100,000 or more, from the viewpoint of obtaining a water-based resin composition and a water-based paint that are comprehensively excellent in hot water whitening resistance, freeze-thaw resistance, and blocking resistance. is 300,000 or more, more preferably 550,000 or more, and particularly preferably 600,000 or more. The upper limit of the weight-average molecular weight of the resin having a crosslinked structure is not particularly limited because it is difficult to measure the weight-average molecular weight accurately because the resin has a crosslinked structure. From the viewpoint of improving the meltability, it is preferably 5,000,000 or less.

As used herein, the molecular weight of the resin is the weight-average molecular weight measured by gel permeation chromatography [e.g., HLC-8220GPC and HLC-8320EcoSEC devices manufactured by Tosoh Corporation], and polystyrene is used as a standard substance. . A sample to be measured is prepared by dissolving 20 to 40 mg of resin in 10 ml of tetrahydrofuran or dimethylformamide reagent, and then filtering through a filter (eg, PTFE membrane filter T100A025A) for measurement. At this point, if the sample solution is opaque and clogging occurs in the filter, accurate molecular weight measurement cannot be performed, so it is determined that measurement is not possible.

As an embodiment of the coating composition of the present invention, the resin comprises resin particles having a heterophasic structure and has at least two temperatures below 45°C, preferably 0-40°C and 55°C-95°C, preferably 60-90°C. A core-shell type emulsion, a sea-island structure type emulsion, or a multi-layered structure type emulsion having a glass transition temperature of 200°C is preferable. When a portion of the resin particles has a glass transition temperature in the low temperature range, preferably less than 45° C., the film formability and anticorrosion properties can be improved. Also, when a part of the resin particles has a glass transition temperature in a high temperature range, preferably 55° C. to 95° C., blocking resistance can be improved.

In this specification, the details of the method for measuring the glass transition temperature of the resin are as follows. Apply to a polypropylene (PP) plate preheated to 80 ° C. using an applicator so that the dry film thickness is 40 to 100 μm, and force dry at 80 ° C. for 30 minutes to form an isolated resin film. obtain. Using a solid viscoelasticity measuring device (for example, RSA-GII (manufactured by TA Instruments)), the loss elastic modulus of the isolated film was measured under the following measurement conditions, and the maximum value of the loss elastic modulus was measured on the glass. Read as transition temperature.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

Resin particles having a hetero-phase structure can be obtained, for example, by a multistage emulsion polymerization method.

As a multistage emulsion polymerization method that can be employed for producing resin particles having a heterophase structure, an aqueous emulsion containing an ethylenically unsaturated monomer is formed, and a conventionally known emulsion polymerization method is performed in two or more stages, usually Multi-stage emulsification in which the emulsified copolymer of ethylenically unsaturated monomers to be formed forms particles consisting of an outermost phase with different properties and one or more internal phases, which is repeated in 2 to 5 steps. There is a polymerization method.

As a representative example of the multistage emulsion polymerization method, an emulsifier and a polymerization initiator are present in an aqueous emulsion containing an ethylenically unsaturated monomer, and if necessary, a chain transfer agent, an emulsion stabilizer, etc. are present. A multistage emulsion polymerization method in which emulsion polymerization is performed under heating at 60 to 90° C. and this process is repeated multiple times can be mentioned.

Examples of ethylenically unsaturated monomers that can be used to form resin particles having a heterophase structure include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate. , n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, α-chloroethyl (meth)acrylates such as (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl (meth)acrylate, etc. System monomers; styrene and/or styrene derivatives such as methylstyrene, chlorostyrene and methoxystyrene; carboxyl groups such as (meth)acrylic acid, crotonic acid, itaconic acid, itaconic acid half ester, maleic acid and maleic acid half ester Containing monomers; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate, 2 (3)-hydroxypropyl (meth) acrylate and 4-hydroxybutyl acrylate; (meth) acrylamide and maleamide Amido group-containing monomer; amino groups such as 2-aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, 3-aminopropyl (meth)acrylate, 2-butylaminoethyl (meth)acrylate, and vinylpyridine Containing monomer; glycidyl (meth)acrylate, allyl glycidyl ether, epoxy group-containing monomer obtained by reacting an epoxy compound having two or more glycidyl groups with an ethylenically unsaturated monomer having an active hydrogen atom N-methylolacrylamide with other N-methylol groups; 4-(meth)-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)-acryloylamino-2,2 ,6,6-tetramethylpiperidine, 4-(meth)-acryloyloxy-1,2,2,6,6-pentamethylpiperidine; 2-[2′-hydroxy-5′ -(Methacryloyloxymethyl)phenyl]-2H-benzotriazole and 2-[2'- UV-absorbing monomers such as hydroxy-5′-(methacryloyloxyethyl)phenyl]-2H-benzotriazole; representative examples include vinyl acetate, vinyl chloride, ethylene, butadiene, acrylonitrile, dialkyl fumarate, etc. can be mentioned as

It is preferable that the polymer forming at least one phase of the resin particles having a heterophase structure has an internal crosslinked structure. Polymers having such an internal crosslinked structure include, as part of ethylenically unsaturated monomers, intramolecular compounds such as divinylbenzene, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl(meth)acrylate. A method of emulsion polymerization using a monomer having two or more polymerizable unsaturated double bonds in the emulsion polymerization reaction; a combination of monomers having functional groups that react with each other at the temperature during the emulsion polymerization reaction, such as a carboxyl group and glycidyl group, or a method of emulsion polymerization using a monomer mixture that selectively contains an ethylenically unsaturated monomer having a combination of functional groups such as a hydroxyl group and an isocyanate group; ) Using a monomer mixture containing a silyl group-containing ethylenically unsaturated monomer such as acryloxypropyltrimethoxysilane, (meth)acryloxypropyltriethoxysilane, (meth)acryloxypropylmethyldimethoxysilane, etc. It can be produced by a method such as a method of emulsification polymerization.

Examples of emulsifiers that can be used to form resin particles having a heterophase structure include fatty acid salts such as sodium laurate, higher alcohol sulfate salts such as sodium lauryl sulfate, alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and polyoxyethylene. Alkyl ether sulfates, ammonium polyoxynonylphenyl ether sulfonates, polyoxyethylene-polyoxypropylene glycol ether sulfates, and further, sulfonic acid groups or sulfate ester groups and polymerizable carbon-carbon unsaturated double bonds in molecules anionic surfactants such as so-called reactive emulsifiers; polyoxyethylene alkyl ethers, polyoxyethylene nonylphenyl ethers, sorbitan fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene-polyoxypropylene block copolymers, or Nonionic surfactants such as reactive nonionic surfactants having a skeleton of these compounds and a polymerizable carbon-carbon unsaturated double bond in the molecule; cationic surfactants such as alkylamine salts and quaternary ammonium salts Surfactants; (modified) polyvinyl alcohol and the like can be mentioned.

Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, polymer emulsifiers, etc. These emulsifiers may be used alone or in combination of two or more.

Examples of anionic emulsifiers include alkylsulfate salts such as ammonium dodecylsulfate and sodium dodecylsulfate; alkylsulfonate salts such as ammonium dodecylsulfonate, sodium dodecylsulfonate and sodium alkyldiphenylether disulfonate; ammonium dodecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate and the like. polyoxyethylene alkylsulfonate salts; polyoxyethylene alkylsulfate salts; polyoxyethylene alkylarylsulfate salts; dialkylsulfosuccinates; arylsulfonic acid-formalin condensates; Fatty acid salt; bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salt, propenyl-alkyl sulfosuccinate ester salt, (meth)acrylic acid polyoxyethylene sulfonate salt, (meth)acrylic acid polyoxyethylene phosphonate salt, allyl allyl group-containing sulfate esters such as sulfonate salts of oxymethylalkyloxypolyoxyethylene or salts thereof; allyloxymethylalkoxyethylpolyoxyethylene sulfate ester salts; is not limited only to such examples.

Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, condensates of polyethylene glycol and polypropylene glycol, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid monoglycerides, ethylene oxide and aliphatic Condensation products with amines, allyloxymethylalkoxyethylhydroxypolyoxyethylenes, polyoxyalkylene alkenyl ethers, etc. may be mentioned, but the present invention is not limited to these examples.

Cationic emulsifiers include, for example, alkylammonium salts such as dodecylammonium chloride, but the present invention is not limited to these examples.

Examples of amphoteric emulsifiers include betaine ester emulsifiers and the like, but the present invention is not limited to such examples.

Polymeric emulsifiers include, for example, poly(meth)acrylates such as sodium polyacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyhydroxyalkyl(meth)acrylates such as polyhydroxyethyl acrylate; Examples include copolymers containing one or more of the monomers as a copolymer component, but the present invention is not limited to such examples.

In addition, as the emulsifier, from the viewpoint of obtaining an aqueous resin composition and an aqueous paint that are comprehensively excellent in hot water whitening resistance, freeze-thaw resistance, and blocking resistance, an emulsifier having a polymerizable group, that is, a so-called reactive emulsifier is preferred, and non-nonylphenyl emulsifiers are preferred from the viewpoint of environmental protection.

Examples of reactive emulsifiers include propenyl-alkylsulfosuccinate ester salts, (meth)acrylic acid polyoxyethylene sulfonate salts, (meth)acrylic acid polyoxyethylene phosphonate salts [for example, manufactured by Sanyo Chemical Industries, Ltd., Product name: Eleminol RS30, etc.], polyoxyethylene alkylpropenylphenyl ether sulfonate salt [for example, Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon HS-10, etc.], allyloxymethylalkyloxypolyoxyethylene sulfonate salt [For example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon KH-10, etc.], sulfonate salt of allyloxymethyl nonylphenoxyethyl hydroxypolyoxyethylene [For example, manufactured by ADEKA Co., Ltd., trade name: Adekaria Soap SE-10, etc.], allyloxymethylalkoxyethyl hydroxypolyoxyethylene sulfate ester salts [for example, manufactured by ADEKA Corporation, trade names: Adekari Soap SR-10, SR-30, etc.], bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salt [for example, manufactured by Nippon Nyukazai Co., Ltd., trade name: Antox MS-60, etc.], allyloxymethylalkoxyethyl hydroxypolyoxyethylene [for example, manufactured by ADEKA Co., Ltd., trade name: ADEKA Riasap ER-20, etc.], polyoxyethylene alkylpropenyl phenyl ether [e.g., Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon RN-20, etc.], allyloxymethyl nonylphenoxyethyl hydroxypolyoxyethylene [e.g., ADEKA Co., Ltd., trade name: Adekari Soap NE-10, etc.), but the present invention is not limited to these examples.

In the formation of resin particles having a heterogeneous structure, polymerization initiators commonly used in radical polymerization can be used, and water-soluble initiators are particularly suitable. For example, persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 2-methylbutanemidoxime) dihydrochloride tetrahydrate; hydrogen peroxide water, peroxides such as t-butyl hydroperoxide, and the like. Furthermore, a redox system in which a reducing agent such as L-ascorbic acid or sodium thiosulfate is combined with ferrous sulfate or the like can also be used.

Chain transfer agents that can be used to form resin particles having a heterophase structure include, for example, alkyl mercaptans, aromatic mercaptans, halogenated hydrocarbons, etc. Among these, lauryl mercaptan, n-butyl mercaptan, Preferred are t-butyl mercaptan, octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, 2-methyl-t-butylthiophenol, carbon tetrabromide, α-methylstyrene dimer and the like. By appropriately using these, it is possible to control the glossiness of the coating film, the film-forming property, and the non-adhesiveness.

Examples of emulsion stabilizers that can be used to form resin particles having a heterophase structure include polyvinyl alcohol, hydroxyethyl cellulose, and polyvinylpyrrolidone.

In addition, as an emulsion polymerization method, a monomer batch charging method in which the monomer is charged at once, a monomer dropping method in which the monomer is continuously dropped, and a monomer, water, and an emulsifier are preliminarily mixed and emulsified. A pre-emulsion method of dropping this, or a method of combining these can be mentioned.

In the present invention, when producing resin particles having a heterogeneous structure by the above method, the theoretical Tg obtained from the FOX calculation formula of the polymer forming a part of the resin particles is 55° C. to 95° C., preferably 60° C. It is preferable to appropriately select the combination of the ethylenically unsaturated monomers so that the temperature is ~90°C, and the theoretical Tg obtained from the FOX calculation formula of the polymer forming part of the resin particles is less than 45°C. , preferably 0 to 40°C, it is preferable to appropriately select a combination of ethylenically unsaturated monomers.

As a preferred embodiment of the coating composition of the present invention, the resin contains one or more monomers having an SP value of 9.2 to 9.9 as constituent components, and the organic solvent has an SP value of 8.0. to 11.1 (more preferably 8.5 to 11.1) and one or more organic solvents having a boiling point within the range of 160 to 260°C. By using a monomer that exhibits an SP value comparable to that of the organic solvent as a component of the resin, the effect of improving the film-forming properties of the organic solvent can be more reliably exhibited, and during film-forming Since the resin is softened, it becomes easier to form a coating film, and since the boiling point of the organic solvent is within the range of 160 to 260°C, the surface drying of the coating film is suppressed, and the organic solvent remains in the coating film. difficult to do. As such, such embodiments may result in superior coating compositions for factory application.

The SP value (solubility parameter) is a guideline for determining compatibility, and there are various calculation methods and measurement methods. In this specification, the SP value is calculated by the Hoy method based on the structure. Solubility Parameter. Here, the SP value of the monomer means the SP value of the homopolymer of the monomer, and using the vapor pressure method proposed by Hoy, the literature [K. L. Hoy, J. Paint Technology, 42, [541], 76 (1970)]. Specifically, the SP value is represented by δ = (dΣG)/M, where d is the density of the polymer, M is the molecular weight of the basic structural unit of the polymer, and ΣG is the atom (group) present in the basic structural unit. is the sum of the molecular attraction constants G corresponding to . In addition, the SP value of the organic solvent was calculated using the vapor pressure method proposed by Hoy according to the method described in the literature [K. L. Hoy, J. Paint Technology, 42, [541], 76 (1970)]. is a value

Examples of monomers having an SP value within the range of 9.2 to 9.9 include methyl methacrylate (9.5), ethyl methacrylate (9.4), n-butyl acrylate (9.7), and isopropyl acrylate. (9.8), isobutyl acrylate (9.4), isobutyl methacrylate (9.3), 2-ethylhexyl acrylate (9.2), pentyl acrylate (9.6), cyclohexyl methacrylate (9.5), styrene ( 9.4) and the like. Here, the numbers in parentheses are the SP values of the monomers. The ratio of the monomer having an SP value of 9.2 to 9.9 in the constituent components of the resin is preferably 85 to 98% by mass.

Examples of organic solvents having an SP value in the range of 8.0 to 11.1 and a boiling point in the range of 160 to 260° C. include ethylene glycol mono-n-butyl ether (SP value: 11.0, boiling point: 170 ° C.), diethylene glycol monopropyl ether (SP value; 11.1, boiling point; 214° C.), diethylene glycol monoisopropyl ether (SP value; 10.9, boiling point; 207° C.), diethylene glycol mono-n-butyl ether (SP value; 10. 9, boiling point; 230°C), diethylene glycol monoiso-butyl ether (SP value; 10.7, boiling point; 220°C), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (SP value; 9 .9, boiling point: 255°C), diethylene glycol diethyl ether (SP value: 9.5, boiling point: 189°C), diethylene glycol dimethyl ether (SP value: 9.7, boiling point: 162°C), and the like. The ratio of the organic solvent having an SP value of 8.0 to 11.1 and a boiling point of 160 to 260° C. to the total organic solvent is preferably 50 to 100% by mass. Boiling point as used herein refers to the boiling point at 1 atmosphere.

The coating composition of the present invention may contain, as other components, a surface conditioner, a wetting agent, a dispersant, an emulsifier, a thickener, an anti-settling agent, an anti-skinning agent, an anti-sagging agent, an anti-foaming agent, and an anti-color separation agent. agent, viscosity modifier, rheology control agent, leveling agent, antifoaming agent, drying agent, plasticizer, preservative, antifungal agent, antibacterial agent, insecticide, light stabilizer, UV absorber, antistatic agent and conductivity A property-imparting agent or the like can be appropriately blended depending on the purpose.

The coating composition of the present invention can be prepared by mixing various components appropriately selected according to need. The coating composition of the present invention is a one-liquid type in which various components are premixed and used as it is at the time of coating, and two or more components stored separately (for example, the main agent and the curing agent) are mixed at the time of coating. It may be in any form of a multi-component type (for example, a two-component type) used as a liquid.

The minimum film-forming temperature (MFT) of the coating composition of the present invention is preferably 5 to 25°C, more preferably 10 to 20°C. For example, when a resin having a high glass transition temperature is used, the minimum film-forming temperature is high, but the minimum film-forming temperature can be set low by appropriately blending an organic solvent, preferably a film-forming aid.

As used herein, the minimum film-forming temperature is the minimum temperature at which a crack-free uniform coating film is formed when the coating composition is dried, and is measured in accordance with JIS K 6828-2: 2003. be done.

The coating composition of the present invention has a viscosity of 1 to 1000 (Pa s, 23 ° C.) at a shear rate of 0.1 (1 / s), and a viscosity of 0.05 to 0.05 at a shear rate of 1000 (1 / s). It is preferably 10 (Pa·s, 23°C). As used herein, the viscosity is measured using a rheometer (for example, Rheometer ARES manufactured by TA Instruments) after adjusting the liquid temperature to 23°C.

The coating means of the coating composition of the present invention is not particularly limited, and known coating means such as brush coating, roller coating, trowel coating, spatula coating, flow coater coating, spray coating (e.g. air spray coating, airless spray coating) etc.) can be used.

The method for drying the coating composition of the present invention is not particularly limited, and may be natural drying at ambient temperature or forced drying using a dryer or the like.

The coating composition of the present invention can be applied under various coating conditions such as general factory line coating conditions (forced drying, film thickness 15 to 30 μm) and conditions suitable for JIS K5674 standards (normal dry, film thickness 30 μm). It is possible.

Another aspect of the invention is the coating obtained from the coating composition of the invention. The content described in the description of the coating composition of the present invention also applies to the coating film of the present invention.

As a preferred embodiment of the coating film of the present invention, 100 μm is coated on a preheated steel plate, and the steel plate is kept at 35 to 45 ° C., and measured according to JIS K 5600-3-2. The surface drying time in the surface drying property (Balotini method) is 10 seconds or more and less than 10 minutes, preferably 10 seconds to 5 minutes. Here, the "preheated steel sheet" is a steel sheet whose coating surface temperature is maintained at 35 to 45°C. In addition, the numerical value "100 µm" of "100 µm coating" is the film thickness immediately after coating and before drying. When the surface drying time is 10 seconds to 5 minutes under such conditions, a coating film with excellent drying property is formed when coating in a factory, and a coated body with excellent blocking resistance can be formed.

The film thickness of the coating film of the present invention is preferably 10 to 200 μm, more preferably 20 to 170 μm, even more preferably 50 to 150 μm. The thinner the film, the lower the corrosion resistance, and the thicker the film, the lower the drying property (furthermore, the initial water resistance due to the reduced drying property) and the blocking resistance. A coating film having When the film thickness of the coating film is as thin as 10 to 50 μm, it is preferable to include an epoxy resin having a molecular weight of less than 100,000 to improve anti-corrosion properties, and vinyl-modified epoxy resin is particularly preferable.

The vinyl-modified epoxy resin is not particularly limited, but includes, for example, a bisphenol-type epoxy resin, a glycycyl group-containing polymerizable vinyl monomer, amines, and, if necessary, constituent components composed of reactive components. reaction products. In other words, it is believed that the epoxy groups in the bisphenol-type epoxy resin are ring-opened by amines, and at the same time, amino groups are introduced into the epoxy resin, thereby further improving the inherent properties of the unmodified epoxy resin, such as adhesion. be done. In addition, since the glycidyl group-containing polymerizable vinyl monomer reacts with the epoxy group in the bisphenol type epoxy resin via amines, a polymerizable unsaturated group is introduced into the epoxy resin to impart copolymerizability.

In addition, examples of the vinyl-modified epoxy resin include resins obtained by graft-polymerizing a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer to a bisphenol type epoxy resin. In the resin, for example, a polymerizable unsaturated monomer component can be graft-polymerized to an epoxy resin in an organic solvent in the presence of a radical generator such as benzoyl peroxide.

As a preferred embodiment of the coating film of the present invention, the crosslink density of the coating film is in the range of 1.0×10 ⁻⁶ to 1.0×10 ⁻² (mol/cc). The crosslink density of the coating film is an index indicating the degree of the crosslinked structure formed in the coating film, and the higher this value, the higher the ratio of the crosslinked structure formed in the coating film. By setting the crosslink density of the coating film within the range specified above, the blocking resistance in the initial process of coating film formation can be improved, and the water resistance of the coating film after drying can be improved.

As a preferred embodiment of the coating film of the present invention, the coating film has two or more softening points, one of which is less than 25°C, preferably 5 to 25°C, and another one of which is less than 25°C. The point is 45°C or higher, preferably 50 to 100°C. When the coating film has a softening point of less than 25°C (especially when it contains constituent components lower than the coating film formation temperature), the coating film formation is facilitated and a dense film is formed, so the coating film is water resistant. improve sexuality. In addition, when the coating film has a softening point of 45° C. or higher (especially when the coating contains a component having a temperature higher than the maximum temperature when the steel sheets are stacked), the anti-blocking property is improved.

As a preferred embodiment of the coating film of the present invention, the coating film comprises resin particles having a heterophase structure, the heterophase structure being less than 45°C, preferably 0 to 40°C, and 55°C to 95°C, preferably 60°C. A core-shell emulsion, a sea-island structure emulsion, or a multilayer structure emulsion having at least two glass transition temperatures of up to 90° C. is preferable, and the resin particles are crosslinked between particles. When a portion of the resin particles has a glass transition temperature in the low temperature range, preferably less than 45° C., the film formability and anticorrosion properties can be improved. Also, when a part of the resin particles has a glass transition temperature in a high temperature range, preferably 55° C. to 95° C., blocking resistance can be improved.

In the method of forming a coating film of the present invention, the object to be coated is not particularly limited. Metal substrates containing metals or alloys such as alloys, aluminum, and aluminum alloys at least in part are preferred. In particular, the coating composition of the present invention is suitable for coating on steel materials such as bar steel, steel plate and steel pipe.

Specific examples of objects to be coated include various building materials, structures such as buildings and constructions, and members thereof. In this specification, a building means a structure built for the purpose of human residence or stay, and includes, for example, a house, a building, a factory, etc., and a structure means a structure in which a human lives or stays. Structures constructed for other purposes, such as bridges, tanks, plant piping, chimneys, etc. Examples of members of buildings and constructions include roofs and walls.

In addition, the object to be coated may be subjected to various surface treatments such as oxidation treatment and primer treatment, and an old coating film (a coating film that has already been formed when coating) is applied to at least a part of the surface. may be present.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. "Parts" and "%" in the resin synthesis examples are based on mass unless otherwise specified.

≪Synthesis of acrylic emulsion≫
<Acrylic emulsion A>
A flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen inlet tube is charged with 40.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene). Ammonium salt (Daiichi Kogyo Seiyaku Co.; Aqualon KH10) 0.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co.; Aqualon RN20)0. 2 parts are charged, the temperature is raised to 80° C. while purging the inside of the flask with nitrogen, and then 0.2 parts of ammonium persulfate is added. Then 15.5 parts of methyl methacrylate, 1.5 parts of butyl acrylate, 1.8 parts of styrene, 1.2 parts of 80% acrylic acid aqueous solution, 11.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyl Oxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 1.0 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku A pre-emulsion for dripping consisting of 0.5 parts of a monomer emulsion (Aqualon RN20, manufactured by Co., Ltd.) was prepared and dripped uniformly into the flask over 120 minutes. After the dropwise addition was completed, the contents of the flask were maintained at 80°C for 60 minutes, followed by adding 2.0 parts of styrene, 9.6 parts of butyl acrylate, and 9.4 parts of methyl methacrylate while maintaining the temperature in the flask at 80°C. parts, 2.0 parts of 2-hydroxyethyl methacrylate, 1.0 parts of glycidyl methacrylate, 10.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 0.2 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon RN20) 0.1 part A pre-emulsion for dropping consisting of a monomer emulsion of was prepared and dropped uniformly into the flask over 120 minutes. After completion of dropping, the mixture was aged for 120 minutes while stirring was continued. After cooling to room temperature and adjusting the solid content to 43% and pH to 8.5, an acrylic emulsion A was obtained. The glass transition temperature of the emulsion particles in the first stage contained in the resin emulsion obtained above is 84.9°C, the glass transition temperature of the emulsion particles in the second stage is 15.0°C, and the glass transition temperature of the entire emulsion particles is It was 42.8°C. Moreover, since the acrylic emulsion A contains a crosslinked structure, the molecular weight could not be measured.

<Acrylic emulsion B>
A flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen inlet tube was charged with 31.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene). Ammonium salt (Daiichi Kogyo Seiyaku Co.; Aqualon KH10) 0.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co.; Aqualon RN20)0. 2 parts are charged, the temperature is raised to 80° C. while purging the inside of the flask with nitrogen, and then 0.2 parts of ammonium persulfate is added. 18.0 parts of methyl methacrylate, 17.0 parts of butyl acrylate, 13.0 parts of styrene, 1.2 parts of 80% acrylic acid aqueous solution, 21.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxy Methyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 1.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co., Ltd. ( A pre-emulsion for dripping consisting of 1.0 part of a monomer (Aqualon RN20) manufactured by Co., Ltd. was prepared and dripped uniformly into the flask over 120 minutes. After the dropwise addition was completed, the mixture was aged for 120 minutes while stirring was continued. After cooling to room temperature and adjusting the solid content to 50% and pH to 8.0, an acrylic emulsion B was obtained. The glass transition temperature of acrylic emulsion B obtained above was 28.1°C. Moreover, the weight average molecular weight of the acrylic emulsion B measured using GPC was 100,000 or more.

<Acrylic emulsion C>
A flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen inlet tube was charged with 31.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene). Ammonium salt (Daiichi Kogyo Seiyaku Co.; Aqualon KH10) 0.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co.; Aqualon RN20)0. 2 parts were charged, and the inside of the flask was heated to 80° C. while purging with nitrogen, then 0.2 parts of ammonium persulfate was added, followed by 13.0 parts of methyl methacrylate, 10.5 parts of butyl acrylate, and an aqueous solution of 80% acrylic acid. 1.2 parts, ion-exchanged water 11.0 parts, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 1 0 part of 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon RN20). was added dropwise into the flask. After the dropwise addition was completed, the contents of the flask were maintained at 80°C for 60 minutes. Propyltrimethoxysilane (Shin-Etsu Silicone KBM503) 0.5 parts, 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Silicone KBM403) 0.5 parts, deionized water 10.0 parts, α-sulfonato-ω-(1- (Allyloxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 0.2 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi A pre-emulsion for dripping consisting of 0.1 part of Aqualon RN20 (manufactured by Kogyo Seiyaku Co., Ltd.) was prepared and dripped uniformly into the flask over 120 minutes. After completion of dropping, the mixture was aged for 120 minutes while stirring was continued. After cooling to room temperature and adjusting the solid content to 50% and pH to 8.5, an acrylic emulsion C was obtained. The glass transition temperature of the emulsion particles in the first stage contained in the resin emulsion obtained above is 15.2°C, the glass transition temperature of the emulsion particles in the second stage is 70.1°C, and the glass transition temperature of the entire emulsion particles is It was 40.6°C. Moreover, since the acrylic emulsion C contains a crosslinked structure, the molecular weight could not be measured.

<Acrylic emulsion D>
A flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen inlet tube was charged with 31.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene). Ammonium salt (Daiichi Kogyo Seiyaku Co.; Aqualon KH10) 0.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (Daiichi Kogyo Seiyaku Co.; Aqualon RN20)0. Two parts were charged, and the temperature was raised to 80° C. while purging the inside of the flask with nitrogen. 1.2 parts of an 80% acrylic acid aqueous solution, 21.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.) Aqualon KH10) 1.5 parts, 2-polyoxyethylene-4-nonyl-2-propenylphenyl ether (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon RN20) 1.0 parts of monomers for dropping An emulsion was prepared and dropped into the flask evenly over 120 minutes. After the dropwise addition was completed, the mixture was aged for 120 minutes while stirring was continued. After cooling to room temperature and adjusting the solid content to 50% and pH to 8.5, an acrylic emulsion D was obtained. The glass transition temperature of acrylic emulsion D obtained above was 59.7°C. Moreover, the weight average molecular weight of the acrylic emulsion D measured using GPC was 100,000 or more.

<Acrylic emulsion E>
A flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping device and a nitrogen inlet tube was charged with 31.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene). Ammonium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 0.5 parts, polyoxyalkylene alkyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; Noigen ET-170) 0.2 parts were charged, and the flask was filled with nitrogen. After raising the temperature to 80° C. while substituting with parts, ion-exchanged water 11.0 parts, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene) ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.; Aqualon KH10) 0.5 parts A pre-emulsion for dropping consisting of the monomers was prepared and dropped uniformly into the flask over 120 minutes. After the dropwise addition was completed, the contents of the flask were maintained at 80°C for 60 minutes, followed by adding 6.0 parts of styrene, 12.5 parts of butyl acrylate, and 2.5 parts of methyl methacrylate while maintaining the temperature in the flask at 80°C. parts, 0.5 parts of 80% acrylic acid aqueous solution, 1.0 parts of diacetone acrylamide, 11.0 parts of ion-exchanged water, α-sulfonato-ω-(1-(allyloxymethyl)-alkyloxypolyoxyethylene) ammonium A pre-emulsion for dripping was prepared from 0.5 part of a monomer salt (Aqualon KH10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and was dripped uniformly into the flask over 120 minutes. After completion of dropping, the mixture was aged for 120 minutes while stirring was continued. After cooling to room temperature and adjusting the solid content to 46% and pH to 9.0, an acrylic emulsion E was obtained. The glass transition temperature of the emulsion particles in the first stage contained in the resin emulsion obtained above is 80.1°C, the glass transition temperature of the emulsion particles in the second stage is -5.3°C, and the glass transition temperature of the entire emulsion particles. was 31.5°C. Moreover, since the acrylic emulsion E contains a crosslinked structure, the molecular weight could not be measured.

≪Synthesis of aqueous resin≫
<Acrylic Dispersion A>
Into a reactor equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube, 10 parts of methyl ethyl ketone was charged, and the temperature was raised to 90°C while replacing the inside of the reactor with nitrogen. Subsequently, 0.3 parts of 2,4-diphenyl-4-methyl-1-pentene (manufactured by NOF Corporation; Nofmer MSD), 7.9 parts of styrene, methyl 3.9 parts of methacrylate, 6.8 parts of tertiary butyl methacrylate, 6.4 parts of n-butyl acrylate, 1.0 parts of 2-hydroxyethyl methacrylate, and tert-butyl peroxy-2-ethylhexanoate (polymerization initiation agent) 0.3 part of mixture B-1 was added dropwise over 3 hours. After the dropwise addition was completed, 0.3 part of tert-butylperoxy-2-ethylhexanoate (polymerization initiator) and 1.5 parts of methyl ethyl ketone, which had been stirred and mixed in a separate vessel in advance, while maintaining the same temperature. 0 parts of the mixture was added dropwise over 1 hour. The obtained mixture was allowed to react with stirring for 6 hours while maintaining the same temperature, then 0.5 part of 2-methacryloyloxyethyl isocyanate and 1.0 part of methyl ethyl ketone were added, and the mixture was further stirred for 2 hours. . Subsequently, 1.3 parts of styrene, 3.9 parts of methyl methacrylate, 1.3 parts of n-butyl acrylate, 2.0 parts of methacrylic acid, and tert-butylper were stirred and mixed in advance in a separate container. A mixture B-2 containing 0.2 part of oxy-2-ethylhexanoate (polymerization initiator) was added dropwise over 1 hour. After the dropwise addition was completed, 0.2 part of tert-butyl peroxy-2-ethylhexanoate (polymerization initiator) and 1.0 part of methyl ethyl ketone were stirred and mixed in a separate container while maintaining the same temperature. The mixture of parts was added dropwise over 1 hour. The obtained mixture was allowed to react with stirring for 6 hours while maintaining the same temperature, and then cooled. To the resulting mixture, 2.3 parts of triethylamine was added and stirred, and 47.86 parts of ion-exchanged water was added. From this, using an evaporator under reduced pressure (about 50 mmHg), 12 parts of methyl ethyl ketone was distilled off at 50° C., followed by 7.5 parts of ion-exchanged water, 5.0 parts of ethylene glycol mono-n-butyl ether, and an antifoaming agent. 0.02 part and 0.02 part of a preservative were added to obtain an acrylic dispersion B having a heating residue of 35%. The resin contained in Acrylic Dispersion B had a glass transition point Tg of 50° C. and a weight average molecular weight of 37,000.

<Acrylic Dispersion B>
Into a reactor equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube, 10 parts of methyl ethyl ketone was charged, and the temperature was raised to 90°C while replacing the inside of the reactor with nitrogen. Subsequently, 0.3 parts of 2,4-diphenyl-4-methyl-1-pentene (manufactured by NOF Corporation; Nofmer MSD), 7.9 parts of styrene, methyl 7.9 parts of methacrylate, 9.2 parts of n-butyl acrylate, 1 part of 2-hydroxyethyl methacrylate, and 0.3 parts of tert-butyl peroxy-2-ethylhexanoate (polymerization initiator) mixture B-1 was added dropwise over 3 hours. After completion of dropping, while maintaining the same temperature, 0.3 part of tert-butyl peroxy-2-ethylhexanoate (polymerization initiator) and 1 part of methyl ethyl ketone were stirred and mixed in a separate container in advance. was added dropwise over 1 hour. The obtained mixture was allowed to react with stirring for 6 hours while maintaining the same temperature, then 0.5 parts of 2-methacryloyloxyethyl isocyanate and 1 part of methyl ethyl ketone were added, and stirring was continued for 2 hours. Subsequently, 1.3 parts of styrene, 1.3 parts of methyl methacrylate, 3.9 parts of n-butyl acrylate, 2 parts of methacrylic acid, and tert-butylperoxy- A mixture B-2 containing 0.2 part of 2-ethylhexanoate (polymerization initiator) was added dropwise over 1 hour. After the dropwise addition was completed, 0.2 part of tert-butylperoxy-2-ethylhexanoate (polymerization initiator) and 1 part of methyl ethyl ketone, which had been stirred and mixed in a separate container in advance while maintaining the same temperature, were added. The mixture was added dropwise over 1 hour. The obtained mixture was allowed to react with stirring for 6 hours while maintaining the same temperature, and then cooled. To the resulting mixture, 2.3 parts of triethylamine was added and stirred, and 47.86 parts of ion-exchanged water was added. From this, 12 parts of methyl ethyl ketone was distilled off using an evaporator under reduced pressure (about 50 mmHg) at 50° C., followed by 7.5 parts of ion-exchanged water, 5 parts of ethylene glycol mono-n-butyl ether, and 0.2 parts of antifoaming agent. 02 parts and 0.02 parts of a preservative were added to obtain an acrylic dispersion B having a heating residue of 35%. The resin contained in Acrylic Dispersion B had a glass transition point Tg of 21° C. and a weight average molecular weight of 40,000.

<Urethane dispersion>
ETERNACOLL UH-200 (registered trademark; polycarbonate diol manufactured by Ube Industries, Ltd.; number average molecular weight 2000; hydroxyl value 56.1 mgKOH/g; 1,6- 261 parts of polycarbonate diol obtained by reacting hexanediol and dimethyl carbonate), 17.5 parts of 2,2-dimethylolpropionic acid (DMPA) and 166 parts of N-methylpyrrolidone (NMP) were charged under a nitrogen stream. is. 115 parts of 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) and 0.3 parts of dibutyltin dilaurate (catalyst) were added, heated to 90° C. and stirred for 5 hours to obtain a polyurethane prepolymer. The free NCO group content at the end of the urethanization reaction was 2.50%. 13.3 parts of triethylamine was added to and mixed with the reaction mixture, and 512 parts of the mixture was taken out and added to 850 parts of water under strong stirring. Then, 33.6 parts of a 35% 2-methyl-1,5-pentanediamine (MPMD) aqueous solution is added to carry out a chain extension reaction, and 22.3 parts of a 35% butylamine (BA) aqueous solution is added to block the molecular ends. The reaction was carried out to give a polyurethane dispersion with a 35% residue on heat. The obtained polyurethane dispersion had a glass transition temperature Tg of 30° C. and a weight average molecular weight of 40,000.

<Epoxy Dispersion A>
A reactor equipped with a stirrer, cooler, thermometer and nitrogen gas inlet tube was charged with 125 parts of methyl ethyl ketone, 210 parts of bisphenol A type epoxy resin (manufactured by Tohto Kasei Co., Ltd.: Epotote YD-014, epoxy equivalent: 950), and polyethylene glycol. Add 75 parts of diglycidyl ether (Nagase Chemical Industry Co., Ltd.: Denacol EX-841) and dissolve at 100° C. under a nitrogen stream, then add 22.0 parts of octylamine and 14.7 parts of dibutylamine and react for 5 hours. to obtain a modified epoxy resin. Then, 16.0 parts of acrylic acid, 10.0 parts of styrene, 10.0 parts of butyl acrylate, 40.0 parts of methyl ethyl ketone and 12.0 parts of tert-butyl peroxy-2-ethylhexanoate were added to the reaction system. The mixture consisting of parts was added dropwise over 1 hour and kept warm for 4 hours. After cooling to 80° C., 21.0 parts of triethylamine and 500 parts of water were sequentially added and mixed to obtain an aqueous dispersion. Then, the solvent was removed and the non-volatile content was adjusted to 37.0% with water to obtain an epoxy dispersion A having a pH of 9.7, a weight average molecular weight of 20000, a solid content acid value of 31 and a glass transition temperature of 55°C.

<Epoxy Dispersion B>
120 parts of n-butanol and 150 parts of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.: Epicoat 1010, epoxy equivalent: 3000 to 5000) were placed in a four-necked flask purged with nitrogen gas, and dissolved by heating. did. 25 parts of methacrylic acid, 11 parts of styrene, 1.0 parts of ethyl acrylate, 3.0 parts of benzoyl peroxide, and 10 parts of n-butanol were uniformly mixed into this solution. The substance was gradually added dropwise over 2 hours while stirring while maintaining the inside of the flask at 110°C. After completion of the dropwise addition, the mixture was further stirred at the same temperature for 4 hours to obtain a carboxyl group-containing self-emulsifying vinyl polymer-modified epoxy resin solution with a solid content of 58%. Subsequently, 100 parts of the carboxyl group-containing self-emulsifying epoxy resin solution was charged into a four-necked flask filled with nitrogen gas, heated to 100° C., and mixed with 4.0 parts of dimethylethanolamine and 260 parts of deionized water. Part was added dropwise over 10 minutes while stirring to obtain an aqueous dispersion of the desired resin. Further, under reduced pressure, 130 parts of n-butanol and water were distilled off by azeotropic distillation to obtain an epoxy dispersion B of the target resin containing no solvent and containing 25% non-volatile matter. Epoxy Dispersion B had a glass transition temperature of 70° C. and a weight average molecular weight of 58,000.

<Water-soluble acrylic resin>
15 parts of methyl ethyl ketone was charged into a reactor equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube, and the temperature was raised to 90° C. while replacing the inside of the reactor with nitrogen. Subsequently, 0.05 parts of 2,4-diphenyl-4-methyl-1-pentene (manufactured by NOF Corporation; Nofmer MSD), 5.0 parts of styrene, methyl 5.0 parts of methacrylate, 13.0 parts of n-butyl acrylate, 8.3 parts of 2-hydroxyethyl methacrylate, 3.85 parts of methacrylic acid, and tert-butyl peroxy-2-ethylhexanoate (polymerization initiator) 0.3 parts of the mixture was added dropwise over 5 hours. After the dropwise addition was completed, 0.3 parts of tert-butylperoxy-2-ethylhexanoate (polymerization initiator) and 2 parts of methyl ethyl ketone, which had been stirred and mixed in a separate container in advance while maintaining the same temperature, were added. The mixture was added dropwise over 1 hour. The obtained mixture was allowed to react with stirring for 6 hours while maintaining the same temperature, and then cooled. To the resulting mixture, 4.5 parts of triethylamine was added and stirred, and 42.7 parts of ion-exchanged water was added. From this, using an evaporator under reduced pressure (about 50 mmHg), 15.0 parts of methyl ethyl ketone was distilled off at 50° C., followed by 10 parts of ion-exchanged water, 5.0 parts of ethylene glycol mono-n-butyl ether, and an antifoaming agent. 0.02 part and 0.02 part of an antiseptic were added to prepare an acrylic resin aqueous solution having a heating residue of 35% to synthesize a water-soluble acrylic resin. The water-soluble acrylic resin contained in the acrylic resin aqueous solution had a glass transition point Tg of 22° C. and a weight average molecular weight Mw of 45,000.

*Glass transition temperature For the above acrylic emulsions A to E, acrylic dispersions A and B, urethane dispersions, epoxy dispersions A and B, and acrylic resin aqueous solution, the glass transition temperature (Tg) of the resin is determined by FOX below. It was obtained by the formula of
[FOX calculation formula]
1/Tg=W1/Tg1+W2/Tg2+...+Wi/Tgi+...+Wn/Tgn
In the FOX calculation formula, Tg described in the denominator on the left side represents the glass transition temperature (unit: K) of the polymer component composed of N kinds of monomers, and Tg (1, 2, i, N) represents the glass transition temperature (unit: K) of each monomer, W (1, 2, i, N) is the mass fraction of each monomer, W1 + W2 + ... + Wi + ... + Wn = 1 relationship is established. Here, the glass transition temperature of a monomer means the glass transition temperature of its homopolymer.

*Weight Average Molecular Weight The weight average molecular weight was measured by gel permeation chromatography (GPC), and the conversion value obtained from a standard polystyrene calibration curve prepared in advance was used.

≪Preparation of water-based paint≫
Using the prepared acrylic emulsions A to E, acrylic dispersions A and B, urethane dispersions, epoxy dispersions A and B, and an acrylic resin aqueous solution, the ingredients associated with the formulations shown in Tables 1 to 3 were stirred with a disper. to prepare a water-based paint. In addition, the compounding amount of each component in the compounding recipe shown in the table is shown in parts by mass.
Next, the drying property, blocking resistance, initial water resistance, and corrosion resistance of the water-based paint were evaluated. The results are shown in Tables 1-3. In addition, the evaluation method will be described later.

A description of the pigments and dispersants shown in the table follows.
・ Extender pigment (precipitated barium sulfate): “Precipitated barium 100”, manufactured by Sakai Chemical Industry Co., Ltd. ・ Rust preventive pigment (zinc phosphate): “K-WHITE #140W”, manufactured by Tayca Co., Ltd. ・ Color pigment (Titanium oxide): "R-32", manufactured by Sakai Chemical Industry Co., Ltd. Dispersant: "DISPERBYK-194N", manufactured by BYK Chemie Japan Co., Ltd.

"Residue after heating (%)" in the table has the same meaning as the amount (% by mass) of the coating film-forming component in the water-based paint.
"PVC" in the table is the pigment volume concentration, which is the ratio of the total volume of the pigment to the total volume of the coating film-forming components in the water-based paint.

The measurement method of the "spectrum peak in the temperature change curve of loss tangent (tan δ)" in the table is as follows.
Using an applicator, a mixture of resin components shown in the formula in the table was applied to a polypropylene (PP) plate preheated to 80°C so that the dry film thickness was 50 µm, and the film was kept at 80°C for 30 minutes. After forced drying, an isolated film composed of the resin component of the formula shown in the table was obtained. Using RSA-GII (manufactured by TA Instruments), the loss elastic modulus and storage elastic modulus of the isolated membrane were measured at each temperature under the following measurement conditions, and the loss tangent was obtained from the loss elastic modulus and storage elastic modulus. was calculated, a temperature change curve of the loss tangent was created, and the spectrum peak value of the loss tangent was read.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

"Crosslinking density (mol/cc)" in the table is the crosslink density of the coating film obtained from the water-based paint, and is represented by the formula n = E'/3RT (wherein n is the crosslink density of the coating film (mol/ cc), E′ is the plateau storage modulus of the coating at a frequency of 1 Hz (Pa), T is the absolute temperature of the plateau storage modulus of the coating (K), and R is the gas A value calculated from a constant (8.31×10 ⁶ Pa·cc/mol·K) is shown. Here, the method for measuring the flat area storage modulus of the coating film is as follows.
A water-based paint is applied to a polypropylene (PP) plate preheated to 80° C. using an applicator so that the dry film thickness is 50 μm, and forcedly dried at 80° C. for 30 minutes to obtain an isolated film. rice field. Using RSA-GII (manufactured by TA Instruments), the storage modulus of the isolated film was measured under the following measurement conditions, and the flat area storage modulus of the coating film was read.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

"Softening point" in the table is the softening point of the coating film obtained from the water-based paint, and represents Tg1 (temperature at which molecules begin to move) in viscoelasticity measurement. The details of the method for measuring the softening point of the coating film are as follows.
A water-based paint is applied to a polypropylene (PP) plate preheated to 80° C. using an applicator so that the dry film thickness is 50 μm, and forcedly dried at 80° C. for 30 minutes to obtain an isolated film. rice field. Using RSA-GII (manufactured by TA Instruments), the storage elastic modulus of the isolated membrane was measured under the following measurement conditions, and the change point (decrease start temperature) of the storage elastic modulus was read as Tg1. softening point.
<Measurement conditions>
Temperature range: -50°C to 200°C
Heating rate: 5°C/min
Measurement length: 24.0mm
Measurement width: 8.0mm
Frequency: 1Hz
Strain: 0.05%

"Resin with a molecular weight of less than 100,000 (%)" in the table indicates the proportion (% by mass) of the resin with a molecular weight of less than 100,000 in the total resin components shown in the formulation in the table.
"Resin with a molecular weight of 100,000 or more or a crosslinked structure (%)" in the table is the proportion of a resin with a molecular weight of 100,000 or more or a resin with a crosslinked structure in the total resin components shown in the formulation in the table (mass% ).

≪Evaluation method≫
<Drying property>
After painting a water-based paint on a steel plate whose surface temperature is kept at 40 ° C. ± 5 ° C. so that the film thickness immediately after coating is 100 μm, the coated surface of the steel plate is kept at 40 ° C. ± 5 ° C. The surface drying property of the obtained coating film was evaluated according to the test method (Balotini method) of JIS K 5600-3-2. The dryness was evaluated according to the following criteria, with the time until the balochini can be removed without damaging the surface of the coating film by lightly brushing the balochini with a brush.
◎: surface drying time less than 3 minutes ○: surface drying time 3 minutes or more and less than 5 minutes △: surface drying time 5 minutes or more and less than 10 minutes ×: surface drying time 10 minutes or more

<Blocking resistance>
Two 100 × 100 × 0.3 mm tin plates whose surface temperature is kept at 80 ° C ± 5 ° C are coated with a water-based paint so that the film thickness immediately after coating is 100 μm, and then at 100 ° C for 30 minutes. Forced drying was performed to prepare a test body. Two specimens were placed on top of each other with the coating surface facing inward, and a weight of 20 kg (0.2 kg/cm ² ) was placed on them so that they were evenly distributed. After that, the weight was removed and the anti-blocking property was evaluated according to the following criteria based on the state of crimping and peeling.
⊚: No crimping was observed, and no mark remained on the surface of the coating film.
◯: Slight crimping is observed, but no marks remain on the surface of the coating film.
Δ: Crimping is observed, and traces remain on the surface of the coating film.
x: Pressure bonding is observed, and peeling is observed on the surface of the coating film.

<Initial water resistance>
Using a blasting plate of SS400 whose surface temperature is maintained at 80 ° C. ± 5 ° C., water-based paint is applied so that the dry film thickness is 100 μm, and then forced drying at 100 ° C. for 30 minutes. The lower half of the obtained test plate was immersed in tap water at 23°C for 24 hours, and the appearance of the removed test plate was immediately observed, and the initial water resistance was evaluated according to the following criteria.
⊚: There was no blistering in the coating film of the immersed portion, and there was no visual difference in hue compared to the non-immersed portion.
◯: There was no blistering in the coating film of the immersed portion, but there was a clear difference in hue from that of the non-immersed portion.
Δ: Partial swelling was observed in the coating film at the immersed portion.
x: Blistering was observed in the entire coating film at the immersed portion.

<Corrosion resistance>
Using a blast plate of SS400 whose surface temperature is maintained at 80 ° C. ± 5 ° C., water-based paint is applied so that the dry film thickness is 100 μm, and then forced drying at 100 ° C. for 30 minutes. A test plate was prepared by cross-cutting the coated film. The prepared test panel was sprayed with salt water for one week according to the method of JIS Z2371:2015. After the test, the test plate was evaluated based on the following evaluation criteria. The portion of the coating film that is not cross-cut is the general portion, and the portion of the coating film that is cross-cut is the cut portion.
⊚: There is no rust or swelling in the general part, and the cut part has swelling only at a location less than 1 mm from the cut.
◯: No rust or blistering in the general part, and blistering only at a point less than 3 mm from the notch of the cut part.
Δ: There is no rust or swelling in the general portion, and there is swelling only at a location less than 5 mm from the notch of the cut portion.
x: Blistering occurs in a portion of 5 mm or more from the notch of the cut portion, and there is rust and blistering in the general portion.

Claims (7)

A coating composition containing water, an organic solvent, a pigment, and a resin,
Pigment volume concentration (PVC) is in the range of 0.1 to 35%,
At least one of the spectral peaks in the temperature change curve of the loss tangent (tan δ) measured at a measurement frequency of 1 Hz using a solid viscoelasticity measuring device based on JIS K7244-4 is 45 ° C. or higher and 180 ° C. or lower. A coating composition characterized by: A coating composition according to claim 1, characterized in that said coating composition comprises a cross-linking component. 2. The coating film formed from the coating composition has a crosslink density in the range of 1.0×10 ⁻⁶ to 1.0×10 ⁻² (mol/cc) according to claim 1 or 2. The coating composition described in . The coating film formed from the coating composition has two or more softening points, one of which is less than 25 ° C. and another is 45 ° C. or higher, A coating composition according to any one of claims 1 to 3. The resin contains a resin having a molecular weight of less than 100,000 in the range of 1 to 30% by mass in the resin component, and a resin having a molecular weight of 100,000 or more or a resin having a crosslinked structure in the resin component in the range of 20 to 99% by mass. A coating composition according to any one of claims 1 to 4, characterized in that it comprises in The resin contains one or more monomers having an SP value within the range of 9.2 to 9.9 as constituent components, and the organic solvent has an SP value of 8.0 to 11.1 and a boiling point of 160 to 260 ° C. The coating composition according to any one of claims 1 to 5, characterized in that it contains one or more organic solvents within the range of A coating film obtained from the coating composition according to any one of claims 1 to 6, wherein the coating film is applied to a thickness of 100 µm on a preheated steel plate, and the steel plate is heated to 35 to 45°C. A coating film characterized by having a surface dry time of 10 seconds to 5 minutes in surface dryness (Balotini method) measured in accordance with JIS K 5600-3-2 under maintained conditions.