JP6288845B2 - How to apply cationic electrodeposition paint - Google Patents

Description

  By using the dynamic surface tension of the cationic electrodeposition coating as an index, the present invention can remove metal oxide-based foreign matters such as welding spatter powder that has been brought into the electrodeposition bath and cannot be removed in the previous step of electrodeposition coating ( The present invention relates to a method for applying a cationic electrodeposition paint that does not leave iron iron) on the electrodeposition coating film.

  Electrodeposition coating has excellent throwing power and less environmental pollution compared to air spray coating or electrostatic spray coating for automobiles, electrical appliances, and other parts with a bag structure. One-coat coating has been widely put to practical use. However, the demand for electrodeposition coating has been advanced, and there is a demand for a method for coating an electrodeposition paint with fewer defects in the appearance of the coating film compared to the prior art.

  One of the coating defects in electrodeposition coating is called iron powder, and metal oxide-based foreign matters such as fine spatter powder and iron scraps generated during welding and processing of the substrate are removed in the pretreatment process. It is brought into the electrodeposition bath without being broken, and remains on the electrodeposition coating film to form a flaw-like defect. Since the iron bristle is large and has a width of about 200 μm and a height of about 100 μm, even if there is an intermediate coating or a top coating in the next process, a correction process may be necessary because it cannot be concealed. Since this correction process requires a polishing work and requires a lot of labor, means for reducing the amount of iron in the electrodeposition coating stage is required.

  In the prior art that attempts to solve coating film defects in electrodeposition coating, for example, Patent Document 1 targets repelling, Patent Document 2 targets metal ion deposits on the outer periphery of the electrode member, and Patent Document 3 and Patent Document 4 are targeted for electrodeposition sagging traces, Patent Document 5 is targeted for dust spots, and Patent Document 6 is targeted for spots and repellency caused by pigment sediments. At present, no method has been proposed for applying electrodeposition paints to tsubu.

Japanese Patent Laid-Open No. 7-18496 JP 7-216594 A JP 2003-138400 A JP 2006-274413 A JP 2008-7831 A JP 2012-92293 A

  The present invention has been made in view of the current state of the prior art, and its purpose is to provide various required performances required for cationic electrodeposition coating, such as properties such as smoothness, corrosion resistance, throwing power, and substrate sensitivity. Electrodeposition that does not leave metal oxide-based foreign matter (iron deposits) such as welding spatter that has been brought into the electrodeposition bath and cannot be removed in the electrodeposition coating without damaging the electrodeposition. It is in providing the coating method of a coating material.

  As a result of intensive studies on the coating method of the cationic electrodeposition paint that does not leave the above iron residue, the present inventors have agglomerated metal oxide-based foreign matters such as welding spatter powder brought into the electrodeposition paint bath liquid. It is found that the above-mentioned object can be achieved by controlling the surface tension of the electrodeposition paint bath solution to improve the slickness to the metal oxide foreign matter in order to solve this aggregation. Since the electrodeposition paint bath liquid is always present in the electrodeposition tank at a flow rate, it has been found that it is necessary to capture dynamic physical properties as an index, and the present invention has been completed.

That is, the present invention has the following configurations (1) to ( 3 ).
(1) (A) a resin having a cationic group (base resin), (B) a blocked polyisocyanate (curing agent resin), and (C) a pigment component are essential components, and the range of dynamic surface tension is A cationic electrodeposition paint characterized by being coated with a cationic electrodeposition paint having a viscosity of 15 to 43 mN / m , and an interface contact angle of droplets with respect to iron oxide of the cationic electrodeposition paint being 10 to 52 ° How to paint.
( 2 ) (A) The resin having a cationic group (base resin) is a cationic amine-modified epoxy resin obtained by cationizing an amine-modified epoxy resin obtained by reacting an epoxy resin with an amine ( The coating method as described in 1) .
( 3 ) The coating method according to (1) or (2 ), wherein the base number of the resin (base resin) having a cationic group (A) is 50 to 130 mgKOH / g-solid.

  According to the coating method of the present invention, various required performances of the cationic electrodeposition paint, such as smoothness, corrosion resistance, throwing power, and ground sensitivity, cannot be removed in the previous process of electrodeposition coating. It is possible to finish without leaving metal oxide-based foreign matters (iron deposits) such as welding spatter powder brought into the electrodeposition tank on the electrodeposition coating film.

FIG. 1 is a schematic diagram showing the measurement principle of the interface contact angle. FIG. 2 is a schematic diagram for explaining a method for measuring throwing power. FIG. 3 is a schematic diagram for explaining a measuring method of throwing power. FIG. 4 is a schematic diagram for explaining a method for measuring throwing power. FIG. 5 is a schematic diagram for explaining a method for measuring throwing power.

  The cationic electrodeposition paint used in the coating method of the present invention is essentially composed of (A) a resin having a cationic group (base resin), (B) a blocked polyisocyanate (curing agent resin), and (C) a pigment component. And the dynamic surface tension is controlled within a specific range.

[(A) Resin having cationic group (base resin)]
In the present invention, the resin (base resin) having a cationic group (A) is introduced by reacting an amino group with an epoxy resin, an epoxy group-containing acrylic resin, a polyurethane resin or the like, and cationizing the amino group with an acid. Or by cationizing an amino group originally present in an epoxy group-free acrylic resin with an acid. As the acid, formic acid, acetic acid, lactic acid, propionic acid, citric acid, malic acid, sulfamic acid, phosphoric acid, methanesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid and the like or a mixture thereof is preferable. The resin having a cationic group is preferably a cationic amine-modified epoxy resin or an amino group-containing acrylic resin.

  The epoxy resin is preferably an epoxy resin having two epoxy groups per molecule on average, and the number average molecular weight is preferably 200 to 7000, and more preferably 300 to 4000. Examples of the epoxy resin include glycidyl ethers of polyphenols having two phenolic hydroxyl groups in one molecule, or polycondensates thereof. Preferred polyphenols include resorcin, hydroquinone, 2,2-bis- (4- Hydroxyphenyl) -propane (commonly known as bisphenol A), 4,4′-dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl) -methane, 1,1-bis- (4-hydroxyphenyl) -ethane, 4 , 4'-dihydroxybiphenyl and the like. Furthermore, examples of the epoxy resin include glycidyl ether of a diol having two alcoholic hydroxyl groups in one molecule, or a polycondensate thereof. Preferred diols include ethylene glycol, propylene glycol, and 1,4-butane. Examples include diol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, low molecular diol such as 1,4-cyclohexanediol, and oligomer diol such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. However, it is not limited to these, The mixture of the said epoxy resin is also possible.

  In order to obtain a resin having a suitable molecular weight, the epoxy resin is made to have a high molecular weight using a linking agent. Preferred linking agents include the above-mentioned polyphenols or diols, and dicarboxylic acids having two carboxyl groups in one molecule, such as adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Examples thereof include isophthalic acid, dimer acid, carboxyl group-containing butadiene polymer and butadiene / acrylonitrile copolymer. In addition, amino group-containing linking agents include primary amines such as ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, monoethanolamine, dimethylaminopropylamine, diethylaminopropylamine, or hexamethylene. A diamine obtained by secondaryizing each amino group of a diamine such as diamine may be used. Moreover, chain length extension by polyisocyanate is also possible. High molecular weight can be achieved by a method in which the glycidyl ether of the polyphenol or the glycidyl ether of the diol is linked with the polyphenol, and the reaction temperature is preferably 70 to 180 ° C.

  The epoxy group-containing acrylic resin is obtained by copolymerizing an epoxy group-containing unsaturated monomer, an acrylic monomer and, if necessary, an unsaturated monomer other than the acrylic monomer in the presence of a polymerization initiator. Examples of the epoxy group-containing unsaturated monomer include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. As acrylic monomers, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate , Cyclohexyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, N- (n-butoxymethyl) -acrylamide and the like, and unsaturated monomers other than acrylic monomers include styrene, α-methylstyrene, vinyltoluene, cyclohexyl vinyl ether, Examples include acrylonitrile.

  Examples of the aminating agent for aminating the epoxy group of the epoxy resin or epoxy group-containing acrylic resin include methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, isopropanolamine, diethylamine, Examples include diethanolamine, N-methylethanolamine, N-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine, diethylaminopropylamine, and the like, or a mixture thereof. Of these, alkanolamines having a hydroxyl group are particularly preferred. Alternatively, the primary amino group may be blocked with a ketone in advance and then reacted with the remaining active hydrogen and an epoxy group. The amination can be carried out in a solvent or in a melt without solvent, and the reaction temperature is preferably 40 to 150 ° C.

  Epoxy group-free acrylic resins include amino group-containing unsaturated monomers such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, diallylamine, and the above acrylic monomers and, if necessary, acrylic. It is obtained by copolymerizing unsaturated monomers other than monomers in the presence of a polymerization initiator.

  (A) The base number of the resin having a cationic group (base resin) is designed in the range of 20 to 200 mgKOH / g-solid, more preferably 50 to 130 mgKOH / g-solid. If the base number is less than the above range, sufficient water dispersibility and electrophoretic properties are not ensured, and if it exceeds the above range, the coating film becomes brittle, the water resistance is lowered, and sufficient performance is hardly obtained.

[(B) Blocked polyisocyanate (curing agent resin)]
(B) Blocked polyisocyanate (curing agent resin) in the present invention is a reaction product of polyisocyanate and blocking agent. Polyisocyanates are aromatic or aliphatic (including alicyclic) polyisocyanates such as 2,4- or 2,6-tolylene diisocyanate and mixtures thereof, p-phenylene diisocyanate, diphenylmethane-4, 4'-diisocyanate, polymethylene polyphenyl diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1,3 or 1,4-bis- (isocyanatomethyl) -cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bis -(Isocyanatomethyl) -norbornane, 3 or 4-isocyanatomethyl-1-methylcyclohexyl isocyanate, m- or p-xylylene diisocyanate, m-a There is p- tetramethylxylylene diisocyanate, more biuret modified product or an isocyanurate modified product of the isocyanate. However, it is not limited to these, The mixture of the said polyisocyanate is also possible.

  Furthermore, it is also possible to connect some of the isocyanate groups of the polyisocyanate with a polyol. Examples include ethylene glycol, propylene glycol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,4-cyclohexanediol, and other low molecular diols, polyethylene glycol, polypropylene glycol, polytetramethylene glycol. And polyisocyanates linked by polyols such as oligomer diols such as polylactone diol, trimethylol ethane, trimethylol propane and pentaerythritol, or mixtures thereof.

  Examples of the blocking agent include aliphatic alcohol compounds such as methanol, ethanol, n-butanol and 2-ethylhexanol, cellosolve compounds such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether. Carbitol compounds, oxime compounds such as acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, lactam compounds such as ε-caprolactam, phenol compounds such as phenol, cresol and xylenol, active methylene such as ethyl acetoacetate and diethyl malonate Examples thereof include a group-containing compound or a mixture thereof.

  The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a melt. Solvents used for the reaction include solvents that do not react with polyisocyanates, such as ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexane, and isophorone, and aromatics such as benzene, toluene, xylene, chlorobenzene, and nitrobenzene. Examples thereof include hydrocarbons, cyclic ethers such as tetrahydrofuran, and halogenated hydrocarbons such as chloroform. Although reaction temperature is not specifically limited, Preferably it is 30-150 degreeC.

[(C) Pigment component]
The (C) pigment component in the present invention is a pigment generally used in the field of electrodeposition paint, and examples thereof include extender pigments, colored pigments, and rust preventive pigments. Specifically, extenders such as kaolin (clay), talc, calcium carbonate, silica, diatomaceous earth, barium sulfate, titanium white, carbon black, black iron oxide, red iron oxide, molybdenum red, yellow iron oxide, titanium yellow, Inorganic pigments such as chrome titanium yellow, cobalt green, chromium oxide green, ultramarine blue, cobalt blue, and other organic pigments such as azo, anthraquinone, thioindigo, perylene, quinacridone, isoindoline, phthalocyanine, and dioxazine Color pigment, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, aluminum phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate, Rinmori Den zinc, aluminum phosphomolybdate, including but anticorrosive pigments such as bismuth hydroxide, and the like.

[Dynamic surface tension]
In the present invention, the dynamic surface tension is a surface tension that changes dynamically (dynamically) immediately after the interface is formed. It is widely observed in liquid systems and emulsion systems containing surfactants that lower the interfacial tension. Generally, the pendant drop method (hanging drop method) and the bubble pressure method (maximum bubble pressure method) ), And the Wilhelmy method.

  In the cationic electrodeposition coating, the dynamic surface tension for preventing iron residue from remaining on the coating film needs to be 15 to 43 mN / m, and preferably 28 to 38 mN / m. As a means for adjusting the dynamic surface tension in the above-mentioned range in the cationic electrodeposition coating, a hydrophobic solvent having a solubility in water of less than 5%, such as turpen, high boiling point solvent # 100, 2-ethylhexyl alcohol, ethylene glycol mono Mixing 0.5 to 5% by weight of hexyl ether, methyl isobutyl ketone, cyclohexanone, isophorone, etc. in the paint, so-called acetylene glycol surfactants such as Surfynol # 104 (produced by Air Products Japan), Mixing 0.01 to 3 wt% of DYNOL 604 (manufactured by Air Products Japan Co., Ltd.), acetylenol ECO (manufactured by Kawaken Fine Chemical Co., Ltd.) and the like, and the base number of the base resin from 50 to 130 mgKOH / g -Set to solid and increase polarity etc. But are lower, but the invention is not limited to, a combination of a plurality of means is also possible.

[Interfacial contact angle to iron oxide]
The interface contact angle of the cationic electrodeposition paint with respect to iron oxide in the present invention is an angle formed by the liquid surface of the cationic electrodeposition paint droplet and a solid surface having a smooth iron oxide film, and is a commercially available black skin. It is measured by a θ / 2 method or the like from a side view photograph of a droplet using a material (JIS G3101 SS400). The preferred interface contact angle is 10 to 52 °, more preferably 20 to 48 °. As means for adjusting the interface contact angle in the above-mentioned range in cationic electrodeposition coatings, hydrophobic solvents having a solubility in water of less than 5%, such as terpenes, high boiling point solvent # 100, 2-ethylhexyl alcohol, ethylene glycol monohexyl Mixing 0.5-5% by weight of ether, methyl isobutyl ketone, cyclohexanone, isophorone, etc. in the paint, so-called acetylene glycol surfactants such as Surfinol # 104 (Air Products Japan Ltd.), Dinol 604 (manufactured by Air Products Japan Co., Ltd.), acetylenol ECO (manufactured by Kawaken Fine Chemical Co., Ltd.) and the like are blended in the paint in an amount of 0.01 to 3% by weight, and the base number of the base resin is 50 to 130 mgKOH / g- Set it to solid and increase the polarity. Is, but is not limited to, a combination of a plurality of means is also possible.

[Optional ingredients]
In addition to the essential components (A), (B) and (C) described above, the cationic electrodeposition paint of the present invention is a paint additive generally used in the field of electrodeposition paint, such as an antifoaming agent and a viscosity modifier. , Surfactants, antioxidants, additives such as ultraviolet absorbers, and various organic solvents or curing catalysts.

  Examples of the organic solvent include hydrocarbons such as toluene, xylene and terpene, alcohols such as methyl alcohol, isopropyl alcohol, n-butyl alcohol, 2-ethylhexyl alcohol, ethylene glycol and propylene glycol, ethylene glycol monoethyl ether, ethylene glycol Ethers such as monobutyl ether, ethylene glycol monohexyl ether, propylene glycol monoethyl ether, 3-methyl-3-methoxybutanol, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether, ketones such as methyl isobutyl ketone, cyclohexanone, isophorone and acetylacetone , Ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether Acetates, esters such as butyl acetate, or mixtures thereof.

  Examples of the curing catalyst include dibutyltin laurate, dibutyltin oxide, tin compounds such as dioctyltin, bismuth compounds such as bismuth lactate, and amine compounds such as N-methylmorpholine, and other resins such as acrylic resins, polyester resins, A urethane resin, a butadiene resin, or the like can be contained.

[Preparation of electrodeposition paint]
The electrodeposition paint of the present invention generally comprises (A) an amino group-containing resin (base resin), (B) a blocked polyisocyanate (curing agent resin), formic acid, acetic acid, lactic acid, etc. as a neutralizing agent. It is obtained by mixing a resin aqueous dispersion obtained by dispersing a water in an aqueous medium, (C) a pigment paste obtained from a pigment component, and, if necessary, an organic solvent, and adjusting the concentration with water. A resin having an amino group (base resin), (B) a blocked polyisocyanate (curing agent resin), (C) a pigment paste obtained from a pigment component, and a neutralizing agent are all mixed in advance, and then mixed in an aqueous medium. It can also be obtained by dispersing. The solid content of the electrodeposition paint is adjusted to around 20% by weight and used for painting. A preferable amount of the neutralizing agent is determined so that the coating pH is adjusted to about 5 to 8.

[Electrodeposition coating method]
The cationic electrodeposition paint of the present invention can be applied to a desired article by a known cationic electrodeposition coating method, usually in a state dispersed in water. The object to be coated is preferably a conductor that has been subjected to surface treatment such as zinc phosphate treatment in advance, but there is no particular problem even if the treatment is not performed. For the paint, the solid concentration is preferably about 5 to 40% by weight, more preferably 15 to 25% by weight, the pH is adjusted to 5 to 8, the bath liquid temperature is 15 to 35 ° C., and the load voltage is 100 to 450V. Under certain conditions, the object can be applied as a cathode. After the coated object is washed with water, it can be baked at 100 to 200 ° C. for 10 to 30 minutes in a baking oven to obtain a cured coating film. Although the film thickness of the coating film obtained from the cationic electrodeposition coating material of the present invention is not particularly limited, it is preferably 5 to 60 μm, preferably 10 to 40 μm in the cured coating film.

  Although the effect of the present invention will be described below with reference to examples and comparative examples, the present invention is not limited to these examples. In the following, “parts” represents parts by weight.

[Production of amine-modified epoxy resin (A1)]
A reactor having a stirrer, a thermometer, and a cooling pipe was prepared, and 35 parts of glyciere PP-300P (polypropylene glycol diglycidyl ether manufactured by Sanyo Chemical Industries) and DER-331 (bisphenol manufactured by Dow Chemical Japan Co., Ltd.) were prepared. 409 parts of A-type liquid epoxy resin), 175 parts of bisphenol A and 1 part of dimethylbenzylamine were added, and the mixture was stirred and heated to 150 ° C. After maintaining at 150 ° C. for 6 hours, 287 parts of methyl isobutyl ketone was gradually added and cooled to 80 ° C. Subsequently, 73 parts of diethanolamine, 21 parts of a diketimine product of diethylenetriamine and methyl isobutyl ketone were added, and the temperature was raised to 100 ° C. After holding at 100 ° C. for 2 hours, it was cooled to 80 ° C. and then taken out. The amine-modified epoxy resin (A1) obtained had a base number of 74 mgKOH / g-solid and a solid content of 70% by weight.

[Production of amine-modified epoxy resin (A2)]
A reaction apparatus having a stirrer, a thermometer, and a cooling pipe was prepared, and 64 parts of glyciere PP-300P (polypropylene glycol diglycidyl ether) manufactured by Sanyo Chemical Industries, Ltd. and DER-331 (bisphenol A manufactured by Dow Chemical Japan Co., Ltd.) were prepared. Type liquid epoxy resin) 385 parts, 193 parts of bisphenol A and 1 part of dimethylbenzylamine were added, and the mixture was stirred and heated to 150 ° C. After maintaining at 150 ° C. for 6 hours, 299 parts of methyl isobutyl ketone was gradually added and cooled to 80 ° C. Next, 58 parts of diethanolamine was added and the temperature was raised to 100 ° C. After holding at 100 ° C. for 2 hours, it was cooled to 80 ° C. and then taken out. The base number of the resulting amine-modified epoxy resin (A2) was 44 mgKOH / g-solid, and the solid content was 70% by weight.

[Production of amino group-containing acrylic resin (A3)]
A reaction apparatus having a stirrer, a thermometer, and a cooling tube was prepared, and 286 parts of methyl isobutyl ketone was charged therein, followed by stirring and heating to raise the temperature to 105 ° C. After raising the temperature, a mixed solution of 245 parts of butyl acrylate, 70 parts of methyl methacrylate, 140 parts of styrene, 140 parts of 2-hydroxyethyl methacrylate, 105 parts of dimethylaminopropyl acrylamide, and 14 parts of azobisisobutyronitrile is taken over 2 hours. And dripped. After keeping at 105 ° C. for 4 hours, it was cooled to 80 ° C. and then taken out. The amino group-containing acrylic resin (A3) obtained had a base number of 53.6 mgKOH / g-solid and a solid content of 70% by weight.

[Production of blocked polyisocyanate (B1)]
Prepare a reactor having a stirrer, thermometer, and cooling pipe, and charge 400 parts of Millionate MR-400 (polymethylene polyphenyl isocyanate manufactured by Nippon Polyurethane Industry Co., Ltd.) and 200 parts of methyl isobutyl ketone, and stir and heat. The temperature was raised to 100 ° C. Thereafter, 169 parts of ethylene glycol monobutyl ether and 231 parts of diethylene glycol monobutyl ether, which had been mixed in advance while maintaining the reactor temperature at 100 ° C., were added dropwise over 1 hour, and reacted at 100 ° C. for 2 hours. Then, it cooled to 80 degreeC and took out. The obtained blocked polyisocyanate (B1) had a solid content of 80% by weight.

[Production of pigment dispersion resin]
A reactor having a stirrer, a thermometer and a cooling pipe was prepared, and 243 parts of DER-331 (Bisphenol A liquid epoxy resin manufactured by Dow Chemical Japan Co., Ltd.) and DER-560 (Bisphenol manufactured by Dow Chemical Japan Co., Ltd.) were prepared. A type solid epoxy resin) (305 parts) and propylene glycol monomethyl ether (300 parts) were added, and the mixture was stirred and heated to 100 ° C. Next, 84 parts of diethylaminopropylamine and 68 parts of diethanolamine were charged, kept at 100 ° C. for 2 hours, cooled to 80 ° C. and taken out. The obtained pigment-dispersed resin had a base number of 156.0 mg KOH / g-solid and a solid content of 70% by weight.

[Production of resin aqueous dispersions 1 to 8]
According to the composition of Table 1, a mixture of the components (1) to (10) was prepared, and deionized water (11) was gradually added while stirring well to obtain respective resin water dispersions 1 to 8. It was.

Details of (6) and (7) in Table 1 are as follows.
(6) Surfinol # 104: Surfactant manufactured by Air Products Japan, Inc. (7) Dinol 604: Surfactant manufactured by Air Products Japan, Inc.

[Manufacture of pigment paste]
In accordance with the composition shown in Table 2, the components (1) to (7) were sufficiently stirred with a dissolver, and then dispersed using a horizontal sand mill until the particle gauge particle size was determined by a distribution diagram method to be 10 μm or less. Got.

Details of (4) to (7) in Table 2 are as follows.
(4) ASP # 200: ENGELHARD, Kaolin (5) Taipure R-900: DuPont, titanium oxide (6) MA-100: Mitsubishi Chemical, carbon black (7) KC-100: Kyodo Dibutyltin oxide, manufactured by Yakuhin Co., Ltd.

[Preparation of electrodeposition paint]
According to the blending composition of Table 3, resin water dispersions 1-8 and pigment paste 1 were blended to obtain the electrodeposition paints of Examples 1-5 and Comparative Examples 1-3. Table 3 also shows the dynamic surface tension of each electrodeposition paint and the interface contact angle of the droplet with respect to iron oxide. The measurement methods are shown below.

[Dynamic surface tension]
The dynamic surface tension is a scale for tracking a behavior in which the contact angle changes with the passage of time and wets and spreads in the evaluation of the interface contact angle described later. By following the passage of time, a more detailed evaluation of “wetability” becomes possible. The dynamic surface tension may be measured using an automatic measuring device commercially available from each company, for example, using a bubble pressure method measuring instrument manufactured by KRUSS.
The measurement conditions applied in this example are as follows.
Measuring instrument: manufactured by KRUSS, BP2 bubble pressure method (maximum bubble pressure method)
Number of bubbles: 6 bubbles / second liquid temperature, ambient temperature: 24 ° C

[Drop interface contact angle with iron oxide]
The interface contact angle is a scale for evaluating the “wetting property” of a droplet contacting a solid surface, and is a quantitative value representing an angle formed between the droplet dropped on the solid surface and the solid surface. The measurement principle of the interface contact angle is as shown in FIG. 1 and is obtained according to a formula known as Young's formula. The measurement of the interface contact angle may be performed using various automatic measuring apparatuses commercially available from measuring instrument manufacturers, and for example, may be performed using various automatic measuring apparatuses manufactured by Kyowa Interface Science Co., Ltd.
The measurement conditions applied in this example are as follows.
DM-501 Tangent method (tangential method) manufactured by Kyowa Interface Science Co., Ltd.
Liquid temperature, ambient temperature: 24 ° C
Atmospheric humidity: 55%
Iron oxide panel: SS-400 untreated plate (2.3 x 70 x 150 mm) manufactured by Partec Co., Ltd. is used after solvent degreasing

[Preparation method of coating test plate and evaluation results]
Using the electrodeposition paints of Examples 1 to 5 and Comparative Examples 1 to 3 obtained above, the carbon electrode was used as an anode, and a zinc phosphate-treated plate (PB-L3080 manufactured by Partec Co., Ltd., 0.8 × 70 ×). 150 mm) was used as a cathode, and electrodeposition coating was performed under the condition that the film thickness after baking was 20 μm, and baking was performed at 170 ° C. for 25 minutes to prepare a coating test plate. Table 4 shows the performance test results of the electrodeposition paints of Examples 1 to 5 and Comparative Examples 1 to 3 and the coating films obtained using the same. The evaluation methods are as follows.

[Iron resistance]
Place 5 mg of iron powder mixed with water on a zinc phosphate-treated plate with a 5 ° inclination, and drop 200 cc of paint from a height of 5 cm via a No. 4 Ford cup directly above it, and test the iron powder. The top was washed away and the number of agglomerated iron powder remaining on the test plate was recorded.
Liquid temperature, ambient temperature: 24 ° C
Atmospheric humidity: 55%
Zinc phosphate treated plate: SPC material (0.8 x 70 x 250 mm) manufactured by Partec Co., Ltd.
○: The number of remaining agglomerated iron powder is 2 or less.
Δ: The number of remaining agglomerated iron powder is 3-5.
X: The number of remaining aggregated iron powders is 6 or more.

[Smoothness (Ra)]
The smoothness (Ra) of the coating film was measured using a surface roughness meter SJ-301 manufactured by Mitutoyo Corporation.
Measurement conditions Cut-off: 2.5mm
Feeding speed: 0.5 mm / sec. O: Ra is 2.5 or less.
(Triangle | delta): Ra is 2.6-3.0.
X: Ra is 3.1 or more.

[Corrosion resistance (salt spray test)]
It carried out according to JIS-Z-2371. The electrode coating film was scratched with a cutter knife, and the rust width after 900 hours was evaluated.
○: Corrosive rust width is 3.0 mm or less from cutter knife scratches.
X: The corroded rust width exceeds 3.0 mm from the cutter knife scratch.

[Throwing power (4-box method)]
The throwing power was evaluated by the four-box method. That is, as shown in FIG. 2, a panel (a) having an 8 mm diameter through hole at a position 50 mm from the bottom of the panel and 35 mm from both sides, and a panel (b) having no hole are treated with zinc phosphate and non-coated. Using the panels (SPCC-SD) obtained by performing the zirconium-based metal oxide film treatment as the phosphate-based treatment film, as shown in FIG. 3 and FIG. B side, C side ... non-counter electrode side is referred to as H side) 4 boxes are placed in parallel with an interval of 2 mm, and both sides and bottom are sealed with an insulator such as adhesive tape. Created. As shown in FIG. 5, this box is immersed in an electrodeposition coating container containing the diluent of each example or comparative example at a depth of 90 mm so that the diluent enters the box only from each through hole. To do. Next, each panel is electrically connected, and it arrange | positions so that the distance of the panel (A surface) nearest to a counter electrode and a counter electrode may be 150 mm. A voltage was applied using this box as a cathode and a counter electrode as an anode, and electrodeposition coating was performed. The applied voltage is set such that a 15 μm coating film can be formed on the A surface in 180 seconds. The energization method may be a method of boosting to a predetermined voltage in 5 to 30 seconds (soft start) or normal energization, but this time, docan energization was adopted. At this time, the temperature of the diluent is adjusted to the standard temperature of the diluent. After painting, the box is disassembled, each panel is washed with water, baked at 170 ° C. for 20 minutes, and the film thickness from the A side to the H side is measured. The throwing power is evaluated by the ratio (G / A) of the G-plane film thickness (unit μm) to the A-plane film thickness (unit μm). It can be evaluated that the greater the value, the better the throwing power.

[Substrate sensitivity]
A zinc phosphate-treated plate having a 1/2 area polished with # 400 paper to remove the chemical conversion film was coated under 20 μm conditions, and the appearance of the coated film after baking was observed.
○: The boundary cannot be identified.
(Triangle | delta): Although there is no film thickness difference in a boundary part, it can identify visually.
X: There is a film thickness difference of 1 μm or more at the boundary, and the visual appearance difference is also remarkable.

  As is clear from Tables 3 and 4, Examples 1 to 5 in which the range of the dynamic surface tension is within the range of the present invention (15 to 43 mN / m) are iron resistance, smoothness, corrosion resistance, and throwing power. Comparative Examples 1 to 3 in which the range of the dynamic surface tension is outside the range of the present invention (15 to 43 mN / m), while being excellent in both the performance of the base material and the base sensitivity, In particular, Comparative Example 3 using the amine-modified epoxy resin (A2) having a low base number is inferior in ironing resistance and in throwing power and base sensitivity.

  According to the coating method of the present invention, it is possible to obtain a coating film of a cationic electrodeposition paint that hardly generates iron flaws without impairing properties such as smoothness, corrosion resistance, throwing power, and ground sensitivity.

Claims (3)

(A) A resin having a cationic group (base resin), (B) a blocked polyisocyanate (curing agent resin), and (C) a pigment component are essential components, and a dynamic surface tension range is 15 to 43 mN. A method for coating a cationic electrodeposition paint, characterized in that the coating is performed using a cationic electrodeposition paint having a thickness of / m , and the contact angle between the droplets of the cationic electrodeposition paint and iron oxide is 10 to 52 ° . (A) a resin having a cationic group (base resin), in claim 1, characterized in that the amine-modified epoxy resin obtained by reacting an amine epoxy resin is cationized with cationic amine-modified epoxy resin The painting method described. (A) The base method of resin (base resin) which has a cation group is 50-130 mgKOH / g-solid, The coating method of Claim 1 or 2 characterized by the above-mentioned.