JP2008221128A - Method for improving cissing resistance of coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of improving the cissing resistance of a coating film and further to provide a method of effectively improving the cissing resistance of a water paint under an environment where the cissing easily occurs. <P>SOLUTION: In the application of the water paint on a material to be coated, the cissing resistance of the coating film is improved by controlling the storage elasticity modulus G' by vibration measurement in 0.1 Hz frequency at 25°C to 5-500 Pa and the ratio (G'/G'') of the storage elasticity modulus G' to loss elasticity modulus G'' to 0.5-5.0 in the wet coating film right after the water paint to be applied which has 21-30 mN surface tension at 25°C measured by a pendant drop method is applied on the material to be coated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for improving repellency in order to prevent repellency from occurring in a coating film obtained by applying a water-based paint to an object to be coated, and relates to a method for improving repellency even in an environment where repellency is likely to occur.

  The repellency and dents of the paint film at the time of paint coating are one of the serious paint film defects that occur in the painting process, and the eradication is a problem in the paint and paint industry.

  If there is a part with low surface tension (contaminated part) in the coating liquid, the gas-liquid interface or the coating object / coating liquid interface from the paint coating to the drying process, the coating liquid will be repelled around that and the dent will be appear. In general, the object that is so deep that the surface of the object to be coated can be seen is called a repellant, and the object that does not reach the surface of the object to be coated is called a dent. In this specification, it shall be called a repellency including a dent.

  The repellency of the paint film causes a circular dent to form on the surface of the paint film when the liquid paint is applied to the work. It is a phenomenon. The repellency may occur due to various factors. Generally, local solvent rapid evaporation from a wet coating film immediately after coating, the influence of residual monomers, paint additives, etc. contained in the paint, It is thought that this is caused by expansion of a trigger portion having a low surface tension on the surface of the coating film due to dust contamination, oil stains on the object to be coated, and the like.

  Regarding the repellency of the paint film, it has been described that the tendency of repellency to occur depends on the flow characteristics of the paint, and that when spray coating is applied, a paint with a lower residual viscosity and a higher yield value is more likely to generate repellency. (See Non-Patent Document 1).

  Further, it is described that a continuous surface film having a large storage elastic modulus G ′ has a repellency suppressing effect, and that the storage elastic modulus G ′ is increased by adding a coating additive such as a leveling agent to the coating ( Non-patent document 2).

  Furthermore, the value of the ratio (G ′ / G ″) of the storage elastic modulus G ′ to the loss elastic modulus G ″ in the paint is related to the repellency of the coating film. It is described that it is large (see Non-Patent Document 3).

  Further, the viscosity of the wet coating film immediately after the organic solvent-type liquid paint is applied to the object to be coated is in the range of 0.2 to 1.0 Pa · s according to the steady flow measurement at 20 ° C. and the slip rate of 5 sec −1. And the ratio (G ′ / G ″) of the storage elastic modulus G ′ and loss elastic modulus G ″ by vibration measurement at an angular frequency of 10 rad / sec at 20 ° C. is in the range of 0.1 to 0.25. It is described that the repelling resistance of the coating film can be improved by controlling to be inside (see Patent Document 1). This method is effective for improving the repellency resistance of the coating film in the organic solvent-type paint, but the effect is not sufficient for the aqueous paint.

  Water-based paints are more susceptible to repelling than organic solvent-based paints, and no method has been known to improve the repelling resistance of paint films formed with water-based paints. There has been no known method that can effectively improve the repellency of water-based paints under the environment.

Japan Society of Color Material, Vol.47, No.9, P19-26 (1974) Paint Research, No.136, Apr., P9-16 (2001) Paint Research, No.127, Oct., P2-9 (1996) JP 2003-129001 A

  An object of the present invention is to provide a novel method capable of improving the repellency of a coating film with respect to a water-based paint, and a method capable of effectively improving the repellency of an aqueous paint in an environment where repellency is likely to occur. Is to provide.

  The present inventor has conducted various studies on the effects of the viscosity, elasticity, paint properties, etc. of water-based paints on the degree of repellency of the paint film. As a result, the surface tension of water-based paints to be applied, It is possible to improve the repellency of the coating film by controlling the storage modulus and the ratio between the storage modulus and the loss modulus in the wet coating so that they are within a specific range. I found it. The present invention has been completed based on such new findings.

That is, according to the present invention, the following method for improving the repellency resistance of a coating film is provided.
1. In applying a water-based paint to the object to be coated, the wetness immediately after the surface tension of the water-based paint to be applied is 25 to 30 mN / m by the pendant drop method and the water-based paint is applied to the object to be coated In the coating film, the storage elastic modulus G ′ by vibration measurement at 25 ° C. with a frequency of 0.1 Hz is in the range of 5 to 500 Pa, and the ratio of the storage elastic modulus G ′ to the loss elastic modulus G ″ (G ′ / G '') Is controlled to be in the range of 0.5 to 5.0, thereby improving the repellency resistance of the coating film.
2. Item 2. The method for improving repellency of a coating film according to Item 1, wherein the water-based paint contains a water-soluble resin, an emulsion resin, and a crosslinking agent as vehicle components.
3. Control of the surface tension, the storage elastic modulus G ′, and the ratio (G ′ / G ″) of the storage elastic modulus G ′ to the loss elastic modulus G ″, composition change of a water-based paint to be applied, and coating method Item 3. The method for improving repellency of a coating film according to Item 1 or 2, which is performed by at least one method selected from the group consisting of a change in coating conditions and a change in coating conditions.
4). Item 4. The method for improving the repellency resistance of a coating film according to Item 3, wherein the composition of the aqueous paint to be applied is changed by at least one formulation selected from the addition of a fluidity modifier, the addition of a solvent, and the adjustment of the pigment concentration of the paint.

  According to the method for improving the repellency resistance of a coating film of the present invention, it is possible to obtain a remarkable effect that it is possible to perform coating without generating repellency of a coating film in the application of a water-based paint to an object. In addition, according to the method of the present invention, the effect of effectively improving the repellency can be exhibited even in the application of a water-based paint in an environment where repellency is likely to occur.

  The object to be coated in the method of the present invention is not particularly limited. For example, a metal substrate such as iron, aluminum, stainless steel, galvanized steel sheet, zinc alloy plated steel sheet, tin plate, etc .; phosphate on the metal surface Surface-treated metal base material that has been subjected to surface treatment such as treatment, chromate treatment, complex oxide treatment; plastic base material; inorganic ceramic base material such as glass, cement, slate, mortar, concrete, roof tile; paper, etc .; And a coated substrate in which a coating film is applied to the substrate; and articles obtained by processing these substrates. As said zinc alloy plating steel plate, the steel plate which gave alloy plating, such as iron-zinc, nickel-zinc, aluminum-zinc, is mentioned, for example.

  The water-based paint used in the method of the present invention is not particularly limited. For example, a water-based paint in which a resin for a vehicle that is a vehicle component and, if necessary, a crosslinking agent is dissolved or dispersed in an aqueous medium. Can be mentioned.

  As the coating resin, those known per se can be used without particular limitation. For example, acrylic resins, polyester resins, alkyd resins, epoxy resins, polyamide resins, silicon polyester resins, silicon acrylic resins, fluororesins, epoxy resins, modified resins of these resins, etc. can be cited as representative examples. It can be used in combination with two or more species. The coating resin can be used in combination with a crosslinking agent. Examples of the crosslinking agent include amino resins such as melamine resins, epoxy compounds, polyamine compounds, polyisocyanate compounds, and blocked polyisocyanate compounds. Can be mentioned. Further, examples of the combination of the coating resin and the crosslinking agent include a combination of an epoxy group-containing acrylic resin and a carboxyl group-containing acrylic resin.

In order to make the coating resin aqueous, an anionic group such as a carboxyl group is contained in the resin, and the anionic group is neutralized with a basic compound such as an amine compound to make it aqueous. In the presence of an emulsifier such as a surfactant in an aqueous medium, a method of polymerizing these resins by an emulsion polymerization method, etc., in the presence of an emulsifier such as a surfactant in an aqueous medium, with vigorous stirring A conventionally known method such as a method of forcibly emulsifying the resin can be used.
The water-based paint may be a clear paint or a colored paint containing a color pigment and / or a luster pigment. In addition, other pigments such as extender pigments may be included as necessary.

  Examples of the color pigment include inorganic pigments such as titanium dioxide, titanium yellow, iron oxide, carbon black, and various fired pigments; organic pigments such as phthalocyanine blue, quinacridone red, perylene red, azo red, and phthalocyanine green. . Examples of glitter pigments include aluminum powder, copper powder, nickel powder, mica powder, mica-like iron oxide, titanium oxide-coated mica powder, iron oxide-coated mica powder, glass flakes, glitter graphite, and hologram pigment. Can be mentioned. Furthermore, examples of extender pigments include barium sulfate, calcium carbonate, talc, and clay.

  As the aqueous medium in the water-based paint, water or a mixed solvent of water and an aqueous organic solvent can be used. Examples of the aqueous organic solvent include ethylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, ethanol, butanol, and isopropanol. The aqueous medium may contain a small amount of a hydrophobic organic solvent such as xylene, heptane, methyl isobutyl ketone, 2-ethylhexyl alcohol, ethylene glycol monoethyl ether acetate and the like. The solid content concentration of the water-based paint is usually about 10 to 70% by weight.

  In the method of the present invention, examples of the coating method for applying a water-based paint to an object to be coated include air spray coating, rotary atomizing spray coating, airless spray coating, roll coating, brush coating, curtain coating, and immersion coating. Can do. Among these coating methods, spray coating such as air spray coating, rotary atomizing spray coating, and airless spray coating is preferable. These spray coatings may be electrostatically applied.

  The viscosity of the water-based paint when spray coating is, for example, Ford Cup No. It is preferable to adjust appropriately using the said aqueous medium so that it may become a viscosity of about 15 to 60 second at 25 degreeC in 4 viscosity meter.

  The coating amount of the water-based paint to be coated on the object is suitably about 5 to 50 μm, preferably about 8 to 40 μm in dry film thickness.

In the method of the present invention, when applying a water-based paint to an object to be coated, it is necessary to control so that the following three conditions are satisfied. Can be prevented.
(1) The surface tension of the water-based paint to be coated at 25 ° C. by the pendant drop method is 30 mN / m or less, preferably 21 to 30 mN / m, more preferably 22 to 28 mN / m.
(2) In the wet coating film immediately after coating the water-based paint on the object to be coated, the storage elastic modulus G ′ by vibration measurement at a frequency of 0.1 Hz at 25 ° C. is 5 Pa or more, preferably 5 to 500 Pa, more preferably 10 Within the range of ~ 300Pa.
(3) Ratio of storage elastic modulus G ′ and loss elastic modulus G ″ measured by vibration measurement at a frequency of 0.1 Hz at 25 ° C. (G ′ / G ″) is 0.5 or more, preferably 0.5 to 5.0, more preferably 0.8 to 4.5.

  In the above condition (1), the surface tension by the pendant drop method can be measured using various known measuring machines. In the present invention, using an “interface tension meter PD-X type” manufactured by Kyowa Interface Chemical Co., Ltd., droplets of a water-based paint to be painted are created in a room at 25 ° C., and the shape 20 seconds after the creation is measured. The surface tension was determined.

  If the surface tension exceeds 30 mN / m, the expansion force generated between the coating liquid and the repellent nuclei increases, and repelling is likely to occur. On the other hand, as the surface tension becomes smaller than 21 mN / m and becomes further smaller, the water resistance and non-sand recoat adhesion of the resulting cured coating film tend to be lowered. From the viewpoint of the repelling effect and the water resistance and non-sand recoat adhesion of the resulting cured coating film, the surface tension is more preferably in the range of 21 to 30 mN / m, particularly 22 to 28 mN / m.

  Under the conditions (2) and (3), the storage elastic modulus G ′ and the loss elastic modulus G ″ of the wet coating immediately after the water-based coating is applied to the object are determined by scratching the wet coating immediately after the coating. The paint can be obtained by measuring using various known viscoelasticity measuring instruments. The storage elastic modulus G ′ and loss elastic modulus G ″ of the wet coating film immediately after coating in the present invention are determined by scraping the paint one minute after coating and using a rheometer “RheoStressRS150” manufactured by HAAKE at a temperature of 25 ° C. The value obtained by vibration measurement at a frequency of 0.1 Hz at a stress of 0.5 Pa.

  In the above condition (2), when the storage elastic modulus G ′ is less than 5 Pa, it is difficult to suppress the flow of the coating liquid due to the expansion force generated between the coating liquid and the repellent core. On the other hand, as the storage elastic modulus G ′ exceeds 500 Pa and further increases, the flow of the coating liquid is excessively suppressed, and the smoothness of the coating surface tends to be lowered. From the viewpoint of the repelling effect and the smoothness of the coated surface, the storage elastic modulus G ′ is more preferably in the range of 5 to 500 Pa, particularly 10 to 300 Pa.

  In the above condition (3), when the ratio (G ′ / G ″) of the storage elastic modulus G ′ to the loss elastic modulus G ″ is less than 0.5, the expansion that occurs between the coating liquid and the repellent nucleus It becomes difficult to suppress the flow of the coating liquid due to force. On the other hand, as the ratio (G ′ / G ″) exceeds 5.0 and further increases, the flow of the coating liquid is excessively suppressed, and the smoothness of the coating surface tends to be lowered. From the viewpoint of the repelling effect and the smoothness of the coated surface, the ratio (G ′ / G ″) is more preferably in the range of 0.5 to 5.0, particularly 0.8 to 4.5. It is.

  As a method for controlling the surface tension of the aqueous paint to be applied within the range of the condition (1), a method for adjusting the composition of the aqueous paint to be applied, for example, changing the composition of the aqueous medium by adding water or adding an organic solvent. It can be easily performed by adding a surface conditioner. The surface tension generally increases with the addition of water, and decreases with the addition of an organic solvent, although the degree of influence varies depending on the organic solvent. The influence of the type and amount of the surface conditioner on the surface tension is large, and the surface tension can be effectively adjusted by selecting and adding the surface conditioner. Examples of the surface conditioner include a silicon-based surface conditioner, an acrylic-based surface conditioner, and a fluorine-based surface conditioner. Among these, the silicon-based surface conditioner is effective in reducing the surface tension.

  As a method of controlling the storage elastic modulus G ′ of the wet coating film immediately after coating within the range of the condition (2), a method of adjusting a coating material before coating, a method of changing coating conditions, or the like can be used.

  As a method for controlling the ratio between the storage elastic modulus G ′ and the loss elastic modulus G ″ of the wet coating film immediately after coating within the range of the condition (3), the method is the same as in the case of the condition (2). It is possible to use a method of adjusting the previous paint, a method of changing the coating conditions, or the like.

  The storage elastic modulus G ′ of the wet coating immediately after coating on the object to be coated and the ratio of the storage elastic modulus G ′ to the loss elastic modulus G ″ (G ′ / G ″) are the conditions (2) and Examples of the method for adjusting the composition of the aqueous paint so as to fall within the range of (3) include addition of a fluidity modifier, addition of a solvent, adjustment of the resin composition, and adjustment of the pigment concentration of the paint. One of these formulations can be adjusted or a combination of two or more of these formulations.

  Examples of the fluidity modifier include, for example, silica fine powder, bentonite modifier, barium sulfate atomized powder, polyamide fluidity modifier, organic resin fine particle fluidity modifier, diurea fluidity modifier, urethane association. A mold fluidity modifier etc. can be mentioned, These 1 type or 2 types or more can be used in combination.

  By adding these fluidity modifiers, the storage modulus G ′ and the ratio of the storage modulus G ′ to the loss modulus G ″ (G ′ / G ″) in the wet coating immediately after coating are added. The value of can be increased.

  Examples of the solvent that can be used for adjusting the composition of the water-based paint include conventionally known organic solvents and water used for water-based paints.

  As the adjustment by adding a solvent, the storage elastic modulus G ′, the storage elastic modulus G ′, and the loss elastic modulus can be adjusted by adjusting the volatilization rate of the solvent used by the aqueous paint to be applied or adjusting the hydrophilicity of the solvent. The value of the ratio (G ′ / G ″) with G ″ can be adjusted.

  The resin composition of the water-based paint for adjusting the storage elastic modulus G ′ of the wet coating immediately after coating and the ratio of the storage elastic modulus G ′ to the loss elastic modulus G ″ (G ′ / G ″) For example, when the water-soluble resin and the emulsion resin are used in combination as a resin component of the water-based paint, the adjustment is generally performed by increasing the blending ratio of the emulsion resin, so that the storage elastic modulus G ′ of the wet coating film is generally The value of the ratio (G ′ / G ″) between the storage elastic modulus G ′ and the loss elastic modulus G ″ can be increased.

  Adjustment of paint pigment concentration to adjust storage elastic modulus G ′ of wet paint film immediately after coating and ratio of storage elastic modulus G ′ to loss elastic modulus G ″ (G ′ / G ″) Is usually obtained by adding a pigment paste having the same composition as the pigment composition of the paint to the water-based paint to increase the pigment concentration relative to the resin content. The value of “/ G ″) can be increased. Also, by adding a clear paint without pigment to the paint to reduce the pigment concentration relative to the resin content, the storage modulus G ′ and the ratio (G ′ / G ″) in the wet coating are reduced. Can be made.

  The storage modulus G ′ of the wet coating immediately after coating and the ratio of the storage modulus G ′ to the loss modulus G ″ (G ′ / G ″) can be changed by changing the coating method, for example, spray coating It changes also by changing the painting method other than to spray painting. In spray coating, since a considerable amount of aqueous medium is volatilized and the non-volatile content becomes high before the atomized paint particles adhere to the surface of the object to be coated, spray coating is compared with other coating methods. The degree to which the storage elastic modulus G ′ of the wet coating immediately after coating and the ratio (G ′ / G ″) are increased is large.

  Changes in the coating conditions to adjust the storage modulus G ′ of the wet paint film immediately after coating and the ratio of the storage modulus G ′ to the loss modulus G ″ (G ′ / G ″) For example, in air spray painting, by increasing the degree of atomization of the paint at the time of painting by means such as increasing the air pressure, the volatilization of the aqueous medium at the time of painting is accelerated, and The storage elastic modulus G ′ and the ratio (G ′ / G ″) can be increased. Further, the storage elastic modulus G ′ of the wet coating film immediately after coating and the ratio (G ′ / G ″) can be increased also by increasing the temperature in the coating environment and decreasing the relative humidity. In the application of water-based paints, the relative humidity in the coating environment is usually the value of the storage elastic modulus G ′ or the ratio of the storage elastic modulus G ′ to the loss elastic modulus G ″ (G ′ / G ″). A big influence.

  According to the present invention, the surface tension of the water-based paint to be coated, the storage elastic modulus G ′ and the ratio of the storage elastic modulus G ′ and the loss elastic modulus G ″ of the wet coating immediately after the water-based paint is applied to the object ( A coating film in which the repellency resistance is remarkably improved by the water-based paint adjusted to have a value of G ′ / G ″) is obtained.

  Hereinafter, the present invention will be described more specifically with reference to production examples and examples. “Part” and “%” in each example are based on mass.

Production Example 1 Production of Hydroxyl-Containing Acrylic Resin Aqueous Dispersion A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 145 parts of deionized water and 1.2 parts of Newcol 562SF (Note 1), The mixture was stirred and mixed in a nitrogen stream and heated to 80 ° C. Next, 1% of the total amount of the following monomer emulsion 1 and 5.2 parts of 3% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion 1 was dripped in reaction container over 3 hours, and it age | cure | ripened for 1 hour after completion | finish of dripping. Thereafter, 1.5 parts of the following monomer emulsion 2 and 3% aqueous ammonium persulfate solution were added dropwise over 2 hours, and after aging for 1 hour, 89 parts of 1.5% aqueous dimethylethanolamine solution was gradually added to the reaction vessel. It cooled to 30 degreeC and discharged | emitted, filtering through a 100 mesh nylon cloth, and the acrylic resin (A) water dispersion liquid of solid content 25% was obtained. The obtained acrylic resin (A) had a hydroxyl value of 22.1 mgKOH / g, an acid value of 30.7 mgKOH / g, and an average particle size of 100 nm.
(Note 1) Newcol 562SF; manufactured by Nippon Emulsifier Co., Ltd., trade name, ammonium polyoxyethylene alkylbenzenesulfonate, active ingredient 60%.

  Monomer emulsion 1: 94.3 parts of deionized water, 17 parts of methyl methacrylate, 80 parts of n-butyl acrylate, 3 parts of allyl methacrylate and 1.2 parts of Newcol 562SF were mixed and stirred to obtain monomer emulsion 1.

  Monomer emulsion 2: 39 parts of deionized water, 15.4 parts of methyl methacrylate, 2.9 parts of n-butyl acrylate, 5.9 parts of hydroxyethyl acrylate, 5.1 parts of methacrylic acid and 0.5 part of Newcol 562SF are mixed and stirred. Thus, a monomer emulsion 2 was obtained.

Production Example 2 Production of Hydroxyl-Containing Acrylic Resin Aqueous Solution 50 parts of ethylene glycol monobutyl ether was placed in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a dropping device, and heated to 120 ° C. In this,
15 parts of styrene, 20 parts of methyl methacrylate, 25 parts of ethyl acrylate, 20 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 5 parts of acrylic acid and 2,2′-azobisisobutyronitrile (radical polymerization initiator) ) 4 parts of the mixture was gradually added dropwise over 2 hours. After completion of the addition, the mixture was aged for 1 hour, then cooled to 30 ° C while gradually adding dimethylethanolamine and deionized water to the reaction vessel, and 100 mesh nylon cloth. And an acrylic resin (B) aqueous solution having a solid content of 40% and a pH of 7.8. The obtained acrylic resin (B) had a hydroxyl value of 72 mgKOH / g, an acid value of 39 mgKOH / g, and a number average molecular weight of 12,000. This number average molecular weight is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured with a gel permeation chromatograph (manufactured by Tosoh Corporation, “HLC8120GPC”). The column used was “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name), and moved. Phase: Tetrahydrofuran, Measurement temperature: 40 ° C., Flow rate: 1 cc / min, Detector: Under the conditions of RI.

Production Example 3 Production of Aqueous Metallic Paint 50 parts of the acrylic resin (B) aqueous solution obtained in Production Example 2 under stirring in 200 parts of the acrylic resin (A) aqueous dispersion (solid content 50 parts) obtained in Production Example 1 (Solid content 20 parts), Cymel 325 (Nihon Cytec Industries, Inc., melamine resin, solid content 80%) 37.5 parts (Solid content 30 parts) were added, then BYK345 (BYK CHEMIE INTERNATIONAL GMBH, Polyether modified) 1 part of dimethylpolysiloxane, surface conditioner) was blended and homogenized, and then 27 parts of Asahi Kasei Aluminum Paste GX-180A (Asahi Kasei Chemicals Corporation, aluminum paste, aluminum content 74%) (solid content 20 parts) were blended. Stir and further add dimethylethanolamine and deionized water and stir uniformly to pH 8.0, 25. To obtain a Ford cup # 4 by the viscosity 40 seconds aqueous metallic paint in. About the obtained water-based metallic coating material, the surface tension of the water-based metallic coating material obtained by the above-mentioned pendant drop method was measured.

Production Examples 4-9
In Production Example 3, as in Production Example 3, except that the composition of the resin and polysiloxane before blending Asahi Kasei Aluminum Paste GX-180A is as shown in Table 1 below, at pH 8.0 and 25 ° C. Each water-based metallic paint having a viscosity of 40 seconds was obtained from Ford Cup # 4. The compounding quantity of each component in Table 1 is a display by a solid content mass part. Table 1 also shows the measurement results of the surface tension of each water-based metallic paint by the pendant drop method.

(註) in Table 1 has the following meaning.
(Note 2) BYK333: manufactured by BYK CHEMIE INTERNATIONAL GMBH, polyether-modified dimethylpolysiloxane, surface conditioner.

Creating test objects
(1) Preparation of a test intermediate coating plate Cold-rolled steel sheet to which Palbond # 3020 (manufactured by Nihon Parkerizing Co., Ltd., trade name, zinc phosphate treatment) was applied to Eleklon GT-10 (Kansai Paint Co., Ltd., trade name, cation) The electrodeposition paint) was electrodeposited so that the cured film thickness was 20 μm, and baked at 170 ° C. for 30 minutes. Subsequently, Amylac TP-65-2 (trade name, intermediate coating material, manufactured by Kansai Paint Co., Ltd.) was applied on the electrodeposition coating film so as to have a cured film thickness of 35 μm, and allowed to stand at 140 ° C. for 30 minutes. A test intermediate coat plate (2) was prepared by heating for a minute and curing. The coated plate (2) was subjected to a test on the skin and water resistance of the coated surface.

(2) Preparation of intermediate coating plate for silicone coating test The emulsion type in which "TSM630" (trade name, manufactured by GE Toshiba Silicone Co., Ltd., dimethyl silicone oil is emulsified on the surface of the above-mentioned intermediate coating plate for testing (1) The silicone mold release agent) is diluted 10,000 times with water and applied with a spray gun so that the wet film thickness is about 20 μm, and dried at 80 ° C. for 3 minutes, and then an intermediate coating plate for silicone application test ( 2) was created. This coated plate (2) was subjected to a repellency resistance test.

Example 1
The water-based metallic paint obtained in Production Example 3 is a tin plate having a thickness of 0.3 mm so as to have a dry film thickness of 15 μm under an atmospheric condition of a temperature of 25 ° C. and a humidity of 65% RH. Air spray coating was performed on each of the three types of coating materials (1) and the intermediate coating plate for silicone coating test (2).

  For coating the tinplate, the paint on the tinplate is scraped after 1 minute of water-based metallic paint coating, and the frequency is 0.1 Hz at a temperature of 25 ° C. and a stress of 0.5 Pa using a rheometer “RheoStressRS150” manufactured by HAAKE. The storage elastic modulus G ′ and the ratio (G ′ / G ″) of the storage elastic modulus G ′ and the loss elastic modulus G ″ were measured by vibration measurement at

  For the coating of the test intermediate coating plate (1), after applying a water-based metallic paint, preheat it at 80 ° C. for 5 minutes, and then on the water-based metallic coating film, Magiclon TC-71 (trade name, manufactured by Kansai Paint Co., Ltd.). , Top-coated clear paint) was applied to a cured film thickness of 35 μm, and baked and cured at 140 ° C. for 30 minutes. This top coat board was used for the test of the skin and water resistance of a coating surface.

  As for the coating of the intermediate coating plate (2) for the silicone coating test, the coated surface state after drying the water-based metallic paint at 80 ° C. for 5 minutes was evaluated.

Examples 2-6 and Comparative Examples 1-5
In Example 1, it carried out similarly to Example 1 except having made the water-based metallic paint kind to be used and the humidity in a coating condition as shown in Table 2 below. Table 2 shows the test results of Examples 1 to 6 and Comparative Examples 1 to 5.

The test methods in Table 2 are as follows.
Test method Repelling resistance: After applying an aqueous metallic paint to the intermediate coating plate (2) for silicone application test, the coated surface state after drying at 80 ° C. for 5 minutes was evaluated.
○: No repelling, ×: Repelling coating surface skin: The smoothness of the coating surface was visually evaluated for the top coating plate of the intermediate coating plate (1) for test.

Water resistance: The appearance and adhesion of the coating film after immersion for 240 hours in 40 ° C. deionized water were examined for the above-mentioned intermediate coating board (1) for test. Adhesiveness evaluated the peeling after making a crosscut of a X mark with a cutter knife so that it might reach a substrate, sticking an adhesive cellophane tape on the crosscut part, and removing it rapidly.
○: No abnormality is observed at all,
Δ: Appearance abnormalities such as blistering and blistering are not observed, but peeling is observed.
X: Appearance abnormalities such as blistering and blistering and peeling are recognized.

Claims (4)

In applying a water-based paint to the object to be coated, the wetness immediately after the surface tension of the water-based paint to be applied is 25 to 30 mN / m by the pendant drop method and the water-based paint is applied to the object to be coated In the coating film, the storage elastic modulus G ′ by vibration measurement at 25 ° C. with a frequency of 0.1 Hz is in the range of 5 to 500 Pa, and the ratio of the storage elastic modulus G ′ to the loss elastic modulus G ″ (G ′ / G '') Is controlled to be in the range of 0.5 to 5.0, thereby improving the repellency resistance of the coating film. The method for improving repellency of a coating film according to claim 1, wherein the water-based paint contains a water-soluble resin, an emulsion resin and a crosslinking agent as vehicle components. Control of the surface tension, the storage elastic modulus G ′, and the ratio (G ′ / G ″) of the storage elastic modulus G ′ to the loss elastic modulus G ″, composition change of a water-based paint to be applied, and coating method The method for improving repellency of a coating film according to claim 1 or 2, which is carried out by at least one method selected from the group consisting of a change in coating conditions and a change in coating conditions. 4. The method for improving the repellency resistance of a coating film according to claim 3, wherein the composition of the aqueous paint to be applied is changed by at least one prescription selected from the addition of a fluidity modifier, the addition of a solvent, and the adjustment of the pigment concentration of the paint.