JP2013064069A - Rust-prevention coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition that has a rust-prevention performance but does not have harmful substances such as chrome and lead, and is not limited to a specific coating system.SOLUTION: A humic acid is added to a coating. Then, on a cathode side in an alkaline atmosphere, the humic acid is dissolved to conduct pH buffering, thereby preventing a coated film from being peeled off; and on an anode side in an acidic atmosphere, the humic acid gets insoluble to form a film, thereby preventing iron from being eluted.

Description

  The present invention relates to a coating composition that does not contain heavy metal rust preventive pigments such as chromium and lead and has rust prevention performance, and particularly relates to a rust preventive coating composition containing humic acid.

  On the surface of an object to be coated such as a steel plate, rust prevention and corrosion resistance are often improved by forming a coating film having various roles. Conventionally, an inorganic rust preventive pigment containing a heavy metal has been added to a coating composition in order to impart rust preventive properties to an object to be coated. Examples of rust preventive pigments having very excellent rust preventive properties include lead compounds and chromium compounds. However, these heavy metal rust preventive pigments have very strong toxicity and give a great load to the environment.

  In recent years, from the viewpoint of environmental protection and pollution prevention, rust preventive coating compositions not containing such heavy metal rust preventive pigments such as lead compounds or chromium compounds have been developed. Since ancient times, polyvalent acids such as tannic acid and citric acid have been known as environmentally friendly rust preventives. In particular, JP 2009-40929 (Patent Document 1) discloses polyphenols such as tannic acid and gallic acid. A water-based paint for converting rust is disclosed, which comprises a derivative, a phosphite, a stainless alloy powder, and an acrylic-modified composite emulsion. However, these polyvalent acids are highly water-soluble when the blending amount is increased, so that the film properties of solvent-based paints are reduced, and the storage stability of paints is also reduced in addition to film properties of water-soluble paints. In electrodeposition paints, the electrical conductivity of the coating liquid increases too much, which causes many problems such as the generation of gas during deposition and the loss of smoothness. Can not. Therefore, rust prevention performance may not be satisfied in a test under severe conditions.

  WO 2005/089071 (Patent Document 2) is characterized by containing condensed calcium phosphate, does not contain lead, toxic heavy metal elements such as chromium, zinc or water-soluble ions, and has excellent rust prevention properties. A pollution-free rust preventive pigment composition is disclosed. However, for cationic emulsions, calcium is dissolved by the neutralizing acid, and the stability of the coating is impaired. In addition, since it is an inorganic rust preventive pigment, it has a high specific gravity and has disadvantages such as aggregation and sedimentation.

JP 2009-40929 A WO 2005/089071 WO 2010/035641

  This invention makes it a subject to provide the coating composition which does not contain heavy metal rust preventive pigments, such as chromium and lead, and which is not limited to a specific coating system, and has rust prevention performance.

  The present inventors have found that the addition of humic acid improves rust prevention performance for any form of coating composition, and have completed the present invention. The paint system in which humic acid exhibits a rust preventive effect is not limited, and includes solvent-based paints such as cationic electrodeposition paints, anion electrodeposition paints, aqueous emulsion paints, and zinc rich paints. The resin system, curing agent, additive and solvent contained in the paint are not limited.

  The corrosion of a metal that is subject to corrosion protection by a coating film is a phenomenon that occurs in the presence of water and oxygen. Such corrosion is classified into uniform corrosion in which corrosion progresses entirely and local corrosion in which corrosion progresses locally. In the corrosion prevention of automobile steel plates, the most important thing is to prevent local corrosion.

  Local corrosion is intensively generated in a portion where a local battery is formed due to a partial difference in dissolved oxygen or the like and electrochemically becomes an anode.

  As shown in FIG. 1, an oxidation reaction represented by the following formula (1) occurs on the anode side of the local battery, resulting in an acidic atmosphere, and a reduction reaction represented by the following formula (2) occurs on the cathode side, resulting in an alkaline atmosphere. Thus, when electrons move from the anode side to the cathode side, the anode side becomes an acidic atmosphere and iron elution occurs. On the other hand, the cathode side becomes an alkaline atmosphere and peeling of the coating film occurs.

  In order to prevent the above-mentioned local corrosion, there are various methods such as environmental interruption by film formation and control of the corrosive environment by a pH buffer. Gallic acid and tannic acid are considered to be effective as the alkaline pH buffering property generated on the cathode side, but these acids are water-soluble, so that the water resistance of the coating film is lowered. The inventors focused on the characteristics of humic acid that is neutral, acidic, insoluble, alkaline, dissolved, and pH-buffering, and studied it as a rust inhibitor added to paints.

As a result of the above studies, the present inventors have found that blending humic acid in the coating film can suppress peeling of the coating film and effectively suppress the subsequent corrosion reaction.
Humic acid is simply present in the coating until corrosion occurs and is insoluble, so there is little adverse effect on the coating.
On the other hand, as shown in FIG. 2, when a corrosion reaction occurs and the cathode side becomes an alkaline atmosphere, humic acid is eluted from the coating film (A), and the alkaline atmosphere is buffered to suppress peeling of the coating film. When the corrosion progresses and the anode side of the part becomes an acidic atmosphere, the eluted humic acid is deposited, and an insoluble film is formed on the steel surface (B), effectively suppressing the subsequent corrosion reaction. . In particular, this tendency is that if the coating film is alkaline, humic acid is likely to be eluted, and an insoluble film of humic acid is easily formed, which effectively acts on the corrosion reaction.

  According to the present invention, by adding humic acid, it is possible to provide a coating composition having antirust performance that does not include heavy metal type anticorrosive pigments such as chromium and lead and is not limited to a specific paint system.

Schematic explaining the mechanism of rust generation | occurrence | production on the steel plate in which the coating film was formed. The schematic diagram explaining the mechanism which suppresses a corrosion reaction by the elution and precipitation of humic acid which exists in a coating film in the case of rust generation | occurrence | production on the steel plate in which the coating film was formed.

<Humic acid>
Humic acid is a natural substance derived from animals and plants, and is a component that constitutes an organic compound (humic substance) that is generated by repeated decomposition and polymerization of animals and plants buried in soil by the action of microorganisms in the soil. The humic substance is composed of humic acid, fulvic acid and humic substance. Among them, a substance which is soluble in alkali and insoluble in acid is humic acid. Humic acid is classified into natural humic acid and regenerated humic acid, and natural humic acid is divided into soil humic acid and coal-based humic acid.

  Among natural humic acids, soil humic acid is a substance produced by the repeated decomposition, synthesis, and oxidative decomposition of atmospheric oxygen by dead leaves and fallen trees buried in the soil, and animal carcasses. Such a carbonization process has not passed. It is known that soil humic acid contains a relatively large amount of alcoholic hydroxyl groups.

  Among natural humic acids, coal-based humic acids are included in young coals such as lignite and lignite produced during the process of carbonization of ancient plant deposits, and after ancient plant deposits have been coalized, Some are generated by weathering. Compared with soil humic acid, coal-based humic acid contains more benzene rings, has higher aromaticity, and is higher in polymer. On the other hand, the content of hydroxyl groups and carboxyl groups is reduced.

  Regenerated humic acid is obtained by oxidative decomposition of young coals such as lignite and lignite. In particular, pulverized juvenile charcoal and oxidative decomposition using nitric acid as an oxidizing agent are called nitrohumic acids because nitration occurs as a side reaction.

Humic acid is not a specific single substance because animals and plants are biologically, chemically and microbially decomposed and synthesized, so the average number molecular weight (measured by liquid chromatography) is in the range of 10 ² to 10 ⁶ . It is a mixture of polymer compounds having a certain complicated structure, and is approximately carbon: 50-67%, hydrogen: 3-6%, oxygen: 28-45%, nitrogen: 1.5-3%, Contains less than% sulfur and phosphorus.

  The basic skeleton of humic acid includes aromatic rings such as benzene ring, naphthalene ring, anthracene ring, pyrrole ring, furan ring, thiophene ring, pyridine ring, and indole ring, and a single or a methylene group containing nitrogen, oxygen, sulfur, or It is crosslinked by a group having a double bond to form a three-dimensional network structure. Moreover, since these aromatic rings have one or more acidic groups such as hydroxyl groups and carboxyl groups, humic acids are classified as polyphenol type carboxylic acids.

  The air-dried soil sample is immersed in an alkaline aqueous solution (for example, 0.1 M NaOH aqueous solution) and sufficiently permeated at room temperature, and then the sample is centrifuged. The supernatant obtained by centrifugation is filtered, and an acid (eg, HCl) is added to the obtained filtrate to lower the pH of the filtrate to 2 or less. Centrifuge the acidified filtrate. The precipitate is fractionated, dialyzed, and lyophilized to obtain humic acid.

Since any of the humic acids described above are obtained from animals and plants, their chemical and physical properties are very similar. Therefore, it is not necessary to distinguish clearly, and any humic acid can be used in the present invention.
In the present invention, a humic acid salt to which a metal ion such as Na, K, Ca, Co, Bi, Ce, Zn, or Mg or an ammonium ion represented by NH ₄ ⁺ is bonded can be used.
Furthermore, in the present invention, regenerated humic acid produced by oxidative decomposition of young coals such as lignite and lignite with an oxidizing agent such as nitric acid can also be used.

  In the present invention, soil humic acid, natural humic acid containing coal-based humic acid, regenerated humic acid containing nitrohumic acid, salts of these humic acids, and humic acid derivatives such as SL can be used. These humic acids and humic acid derivatives are sometimes collectively referred to as “humic acid compounds”.

  In the present invention, the unit “parts” means “parts by mass” unless otherwise specified.

  In the rust preventive coating composition of the present invention, the amount of the humic acid compound added is 0.05 to 8 parts, preferably 0.1 to 8 parts, more preferably 100 parts by weight of the solid content of the coating composition. 0.2 to 6 parts. When the addition amount of the humic acid compound is less than 0.05 part, the rust prevention effect is small, and when it exceeds 8 parts, the water resistance deteriorates, which is not preferable.

<Coating composition>
The coating composition targeted by the present invention is not particularly limited, and includes cationic electrodeposition paints, anion electrodeposition paints, aqueous paints other than electrodeposition paints, powder paints, zinc rich paints, organic solvent paints, and the like. It is.

[Water-based paints other than electrodeposition paints]
The water-based paint other than the electrodeposition paint shown here is a water-proof rust-proof paint using a water-soluble and / or water-dispersible binder mainly having a rust-proof function. Typical paint systems include two-component urethane paints, epoxy ester dispersion paints, epoxy resin-polyamine paints, amino group-containing resins-Michael curable paints, room temperature curable paints such as acrylic emulsion paints; and acrylic-melamine paints, Examples thereof include thermosetting paints such as acid epoxy curable paints. Among them, as the paint composition of the present invention, an epoxy ester dispersion paint having a high antirust property is preferable, and an epoxy resin-polyamine paint having a cationic group. And an amino group-containing resin-Michael curable paint are more preferable.
If the coating contains amino groups, the presence of basic functional groups derived from amino groups causes the environment in the coating to become an alkaline atmosphere, so when exposed to a corrosive environment (moisture enters the coating. The humic acid compound is likely to elute and a higher rust prevention performance can be expected.

  An amino group-containing resin-Michael curable coating having excellent low-temperature curability is more preferable as the coating system of the present invention. Amino group-containing resin-Michael curable coating is a water-soluble or water-dispersible amino group-containing resin having one or more primary amine groups and / or secondary amine groups in the molecule, and one in the molecule. It is a room temperature curable aqueous coating composition containing the above compound having a (meth) acryloyl group, and is cured by a reaction between the amino group-containing resin and the compound having a (meth) acryloyl group. The amino group-containing resin-Michael curable paint is mainly used as a paint for the purpose of rust prevention performance.

  Amino group-containing resin-Amino group-containing epoxy resin is preferred as the amino group-containing resin in the Michael curable coating. The amino group-containing epoxy resin has high rust prevention performance, and a synergistic effect with the rust prevention performance of the humic acid compound can be expected.

  The amine equivalent of the amino group-containing epoxy resin in the amino group-containing epoxy resin-Michael curable paint is preferably 100 to 3000 (g / mol), more preferably 200 to 2500 (g / mol), and still more preferably 300 to 2000. (G / mol). If it is within this range, it has water solubility or water dispersibility, and sufficient curability can be ensured, and elution of humic acid compounds is likely to occur due to the presence of amine-derived basic functional groups in the coating film. Therefore, improvement in rust prevention performance can be expected.

  The number average molecular weight of the amino group-containing epoxy resin is preferably 500 to 20000, more preferably 1000 to 3000 in terms of standard polystyrene using gel permeation chromatography (GPC). If it is this range, the outstanding physical property in corrosion prevention etc. can be hold | maintained.

  Any appropriate glass transition temperature can be adopted as the glass transition temperature of the amino group-containing epoxy resin depending on the desired physical properties of the coating film. Preferably it is -50-100 degreeC, More preferably, it is 0-50 degreeC.

  As the amino group-containing epoxy resin, an aqueous solution obtained by neutralizing an amine group with an acid such as acetic acid, formic acid or lactic acid can be used. The neutralization rate with respect to the amine group of the amino group-containing epoxy resin before being made aqueous is preferably 10 to 70%.

  Examples of the amino group-containing epoxy resin include a method in which a primary amine group-containing polyamine is added to an epoxy resin, and a method in which a ketiminated amine group-containing compound is added to an epoxy resin. A compound having a functional group such as a group, an acid anhydride group, or an isocyanate group may be reacted. Details of these methods are described in WO 2010/035641 (Patent Document 3).

  Any appropriate epoxy resin can be used. Bisphenol A type epoxy resins or bisphenol F type epoxy resins are preferred, and bisphenol A type epoxy resins are particularly preferred. The epoxy equivalent of the epoxy resin is preferably 180 to 2000, and more preferably 400 to 1500. If it is such a range, the coating film which is excellent in water resistance, corrosion resistance, and adhesiveness can be obtained.

  The epoxy resin can be chain-extended using the reaction between an active hydrogen-containing compound capable of reacting with an epoxy group and the epoxy group to increase the molecular weight or be modified. Examples of the active hydrogen-containing compound include bifunctional compounds such as dimer acid, diamine, and polyether polyol.

  Examples of the first amine group-containing polyamine include diethylenetriamine, dipropylenetriamine, dibutylenetriamine, and triethylenetetramine. These may be used alone or in combination.

  The ketiminated amine group-containing compound can be obtained by reacting a first amine group-containing compound with a ketone. Examples of the primary amine group-containing compound include primary amine group-containing polyamines such as diethylenetriamine, dipropylenetriamine, dibutylenetriamine, and triethylenetetramine, aminoethylethanolamine, methylaminopropylamine, and ethylaminoethylamine. It is done. These may be used alone or in combination. Examples of the ketone include methyl ethyl ketone, acetone, and methyl isobutyl ketone.

  The amino group-containing resin may further contain an amino group-containing acrylic resin. The amino group-containing acrylic resin can be obtained in the same manner as the amino group-containing epoxy resin.

  The acrylic resin used for obtaining the amino group-containing acrylic resin is preferably an acrylic resin obtained by copolymerizing a monomer composition containing a radical polymerizable monomer having an epoxy group and / or a glycidyl group. Examples of the glycidyl acrylate include glycidyl acrylate, glycidyl methacrylate, and methyl glycidyl acrylate.

  The compound having one or more (meth) acryloyl groups in the molecule has a viscosity at 25 ° C. of 3000 m · Pas or less, more preferably 50 to 2200 m · Pas. If it is the area | region of this viscosity, stirring at the time of addition of the said amino group containing epoxy resin and a humic acid compound can be performed efficiently.

  As the compound having one or more (meth) acryloyl groups in the molecule, specifically, a polymerizable unsaturated monocarboxylic acid ester of a polyhydric alcohol (ethylene glycol diacrylate, trimethylolpropane triacrylate, etc.), Adducts of epoxy group-containing ethylenically unsaturated monomers and carboxyl group-containing ethylenically unsaturated monomers (glycidyl acrylate, glycidyl methacrylate and a reaction product of acrylic acid, etc.), polymerizable unsaturated polyvalent amines Examples thereof include monocarboxylic acid amide compounds (such as ethylenediamine diacrylate).

  The content of the amino group-containing epoxy resin as a solid content is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, and still more preferably based on the total solid content of the aqueous coating composition. Is 20 to 80% by weight.

  The content of the compound having one or more (meth) acryloyl groups in the molecule is preferably 2 to 40% by weight, more preferably 5 to 30% by weight based on the total solid content of the aqueous coating composition. %.

  The ratio of the number of amine groups in the amino group-containing epoxy resin and the number of (meth) acryloyl groups in the compound having one or more (meth) acryloyl groups in the molecule (amine group: acryloyl group) is preferably Is 1: 0.5 to 1: 1.5, more preferably 1: 0.75 to 1: 1.25.

[Cationic electrodeposition coating]
The cationic electrodeposition paint is a paint containing at least an amino group-containing epoxy resin and an isocyanate curing agent, and is an electrically conductive metal such as iron, steel, aluminum, tin, zinc, and an alloy substrate containing these metals. A coating film is formed by coating directly or on a degreasing or surface treatment and thermosetting. Since the coating film has a basic functional group derived from a cationic hydration functional group such as an amino group, the humic acid compound is likely to be eluted, so that higher rust prevention performance with the humic acid compound can be expected.

  Any appropriate resin can be adopted as the amino group-containing epoxy resin, but an epoxy resin modified with an amine is particularly preferable.

  In the amino group-containing epoxy resin, typically, all of the epoxy rings of the bisphenol type epoxy resin are opened with an active hydrogen compound capable of introducing an amino group, or a part of the epoxy rings are partially activated. It is produced by ring opening with a hydrogen compound and ring opening with an active hydrogen compound capable of introducing an amino group into the remaining epoxy ring.

  Typical examples of the bisphenol type epoxy resin include bisphenol A type or bisphenol F type epoxy resin. As commercial products of bisphenol A type epoxy resin, Epicoat 828 (manufactured by Yuka Shell Epoxy, epoxy equivalent 180-190), Epicoat 1001 (manufactured by the company, epoxy equivalent 450-500), Epicoat 1010 (manufactured by the company, epoxy equivalent 3000) ~ 4000). A commercially available product of bisphenol F type epoxy resin is Epicoat 807 (manufactured by the same company, epoxy equivalent 170).

  These epoxy resins may be modified with suitable resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. In addition, the epoxy resin can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.

  These epoxy resins preferably have an amine equivalent after ring opening of preferably 100 to 3000 (g / mol), more preferably 200 to 2500 (g / mol), and even more preferably 500 to 2000 (g / mol). is there. More preferably, the ring is opened with an active hydrogen compound such that 5 to 50% of them are occupied by primary amino groups. If it is this range, the antirust performance of a humic acid compound will be more easily exhibited.

  Examples of the active hydrogen compound capable of introducing an amino group include primary amine, secondary amine, and tertiary amine acid salts. Specific examples include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, and aminoethylethanol. There are secondary amines blocked with primary amines such as amine ketimines and diethylenetriamine diketimines. A plurality of amines may be used in combination.

  The amino group-containing epoxy resin is preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight, and even more preferably 30 to 60 parts by weight with respect to 100 parts by weight of the solid content of the cationic electrodeposition paint. Contained.

  The cationic electrodeposition coating composition contains a blocked isocyanate curing agent. There is no limitation in particular as a blocked isocyanate, For example, the blocked isocyanate prepared by blocking polyisocyanate with a blocking agent is mentioned.

  Polyisocyanate refers to a compound having two or more isocyanate groups in one molecule. Examples of the polyisocyanate include aliphatic, alicyclic, aromatic and aromatic-aliphatic polyisocyanates.

  Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4- C3-C12 aliphatic diisocyanates such as trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) , Methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3-diisocyanatomethylcyclo Carbon such as xane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate). Aliphatic diisocyanates having a number of 5 to 18; aliphatic diisocyanates having aromatic rings such as xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI); modified products of these diisocyanates (urethanes, carbodiimides, Uretdione, uretonimine, burette and / or isocyanurate modified product); and the like. These may be used alone or in combination of two or more.

  Adducts or prepolymers obtained by reacting polyisocyanates with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane and hexanetriol at an NCO / OH ratio of 2 or more may also be used as the block isocyanate curing agent.

  The blocked isocyanate is prepared by blocking the polyisocyanate with a blocking agent. Here, the blocking agent is a compound that is added to a polyisocyanate group and is stable at room temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

  As a blocking agent used for the preparation of the blocked isocyanate, a blocking agent containing a lactam blocking agent or a glycol ether blocking agent may be used.

  Examples of the lactam blocking agent include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam.

  Examples of the glycol ether blocking agent include ethylene glycol monoalkyl ether blocking agents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and ethylene glycol mono-2-ethylhexyl ether. And propylene glycol monoalkyl ether type blocking agents such as propylene glycol monomethyl ether and propylene glycol monoethyl ether.

  As the blocking agent, in addition to the above-mentioned lactam blocking agent or glycol ether blocking agent, other active hydrogen-containing blocking agents (hereinafter sometimes simply referred to as “active hydrogen-containing blocking agents”) can be used in combination. These active hydrogen-containing blocking agents include, for example, phenol-based blocking agents such as phenol, cresol, xylenol, chlorophenol and ethylphenol; active methylene-based blocking agents such as ethyl acetoacetate and acetylacetone; methanol, ethanol, propanol, butanol, Alcohol blocking agents such as amyl alcohol, benzyl alcohol, methyl glycolate, butyl glycolate, diacetone alcohol, methyl lactate and ethyl lactate, 2-ethylhexanol; formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl mono Oxime blocking agents such as oxime and cyclohexane oxime; butyl mercaptan, hexyl mercaptan, t-butyl mercap Mercaptan block agents such as thiophene, methylthiophenol and ethylthiophenol; acid amide block agents such as acetic acid amide and benzamide; imide block agents such as succinimide and maleic imide; imidazole and 2-ethylimidazole Examples thereof include imidazole-based blocking agents such as: pyrazole-based blocking agents; and triazole-based blocking agents.

  These blocking agents used in the preparation of the blocked isocyanate are generally used in an equivalent equivalent to the isocyanate group of the polyisocyanate.

  The electrodeposition coating composition of the present invention may contain a pigment usually used in an electrodeposition coating composition. Examples of pigments that can be used include commonly used inorganic pigments, for example colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; Zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, and rust preventive pigments such as aluminum phosphomolybdate, aluminum zinc phosphomolybdate, etc. Can be mentioned. When these pigments are contained in the electrodeposition coating composition, the amount of the pigment is preferably 1 to 30% by mass with respect to the resin solid content of the electrodeposition coating composition.

  When a pigment is used as a component of an electrodeposition paint, generally, the pigment is dispersed in advance in an aqueous solvent at a high concentration to form a paste (pigment dispersion paste). This is because the pigment is in a powder form, and it is difficult to disperse in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous solvent. As the pigment dispersion resin, a pigment dispersion resin having a cationic group such as a modified epoxy resin having at least one selected from a quaternary ammonium group, a tertiary sulfonium group, and a primary amine group can be used. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used. In general, the pigment dispersion resin is used in an amount of 20 to 100 parts by mass with respect to 100 parts by mass of the pigment. After the pigment dispersion resin and the pigment are mixed, the pigment is dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the pigment particle size in the mixture reaches a predetermined uniform particle size. A paste can be obtained.

  The cationic electrodeposition coating composition comprises a resin emulsion in which an amino group-containing epoxy resin, a blocked isocyanate curing agent and other coating-forming resin components as required are dispersed with a neutralizing acid, and a pigment dispersion paste as required. Can be prepared by adding and mixing.

  In the preparation of the cationic electrodeposition coating composition, the amino group-containing epoxy resin is neutralized with a neutralizing acid to improve dispersibility and form an emulsion. Organic acids such as formic acid, acetic acid, and lactic acid are used as the neutralizing acid used for neutralizing the amino group-containing epoxy resin.

  The amount of the neutralizing acid used is preferably in the range of 10 to 35 mg equivalent with respect to 100 g of the resin solid content including the amino group-containing epoxy resin, the blocked isocyanate curing agent and the coating film forming resin as required. .

  The mixing ratio (based on solid content weight) of the amino group-containing epoxy resin and the blocked isocyanate curing agent is 90/10 to 40/60, preferably 85/15 to 45/55, more preferably 80/20 to 50/50. (Amino group-containing epoxy resin / block isocyanate curing agent).

[Organic solvent paint]
The organic solvent-based paint shown here is a solvent-based rust preventive paint mainly having a rust preventive function, and the amount of the organic solvent in the solvent contained in the paint exceeds 80% by mass. . The organic solvent is not particularly limited, and nonpolar solvents such as toluene, xylene, and anone; polar solvents such as butyl cellosolve, butyl alcohol, isopropyl alcohol, and methyl ethyl ketone can be used. Typical paints include epoxy resin paints, chlorinated rubber paints, alkyd resin paints, phenol resin paints, and synthetic rubber paints.

  In the coating composition of the present invention, those other than the humic acid compound are established as a coating alone. The coating composition of the present invention usually contains a binder component such as an acrylic resin, a polyester resin, a polyether resin, a polyurethane resin, a fluororesin, and an epoxy resin.

  The coating composition of the present invention may contain an appropriate amount of a curing agent according to the functional group of the binder component. Examples of such a curing agent include melamine, an optionally blocked polyisocyanate, a polyvalent carboxylic acid, and a polyepoxy compound. In addition, pigment components such as colored pigments and extender pigments, anti-settling agents, curing catalysts, UV absorbers, antioxidants, leveling agents, surface conditioners, anti-sagging agents, thickeners, antifoaming agents, etc. The various additive components can be included in a predetermined amount. In addition, as rust inhibitors other than humic acid compounds, polyphenol derivatives such as tannic acid and gallic acid, and rust preventive pigments that do not contain heavy metals such as zinc oxide, calcium phosphate, zinc phosphate, aluminum tripolyphosphate, aluminum phosphomolybdate, etc. Can be used in combination.

  The obtained coating composition is applied to various substrates by a normal method such as brush, spray, electrophoresis, roller, coater, etc., and then dried or cured under predetermined drying conditions. A coating film having a thickness of about 5 to 200 μm can be obtained.

<Method of blending humic acid compound>
In the present invention, when a humic acid compound is used as a rust preventive agent as a component of a paint, a humic acid compound-dispersed paste in which only the humic acid compound is dispersed in advance is prepared and added to the paint. You may add to the coating material the dispersion paste which disperse | distributed the humic acid compound simultaneously with the pigment.
In addition, humic acid compounds dissolve in water under alkaline conditions. For anionic paints such as anionic electrodeposition paints and alkaline aqueous paints, humic acid compounds are dissolved in alkaline water such as triethanolamine water and added. You can also

  The humic acid compound dispersion paste is prepared by dispersing a humic acid compound together with a dispersion resin in an aqueous solvent. The dispersion resin for producing the humic acid compound-dispersed paste can be appropriately matched with the pigment dispersion resin used for the paint in the desired form, such as acrylic resin, urethane resin, epoxy resin, polyester resin, styrene-maleic acid resin, etc. A system can be used and is not particularly limited. For example, in the case of a dispersion paste for a cationic electrodeposition paint, a modified epoxy resin having at least one or more selected from a quaternary ammonium group, a tertiary sulfonium group, and a primary amine group as a dispersion resin, A dispersion resin having a cationic group can be used.

  As the dispersion resin, other commercially available dispersants can be used. For example, for water-based paints, Bigby Chemy's Disperbyk 180, Diperbyk 184, Disperbyk 190, EFKA's EFKAPOLYMER 4550, Abyssia's Solsperse 27000, Solsperse 41000, Solsperse 53095, and the like. Examples of the solvent-based paint include Dispavik 160, Disperbic 161, Disperbic 162, Solsperse 24000, Solsperse 28000, and the like manufactured by Avicia.

  In general, the dispersion resin is used in an amount of 20 to 100 parts by weight based on 100 parts of the humic acid compound. After mixing the dispersion resin and the humic acid compound, until the particle size of the humic acid compound in the mixture is 20 μm or less, preferably 10 μm, using a normal dispersing device such as a ball mill or a sand grind mill. It can be dispersed to obtain a rust inhibitor dispersion paste.

<Coating material>
The article to be coated with the rust preventive coating composition of the present invention may be coated directly on the metal surface or may be coated on the surface treatment. Examples of the metal surface include iron, galvanized steel plate, aluminum, aluminum alloy, tin steel plate, tin steel plate, bonde steel plate, galvalume steel plate, black leather plate, zinc aluminum steel plate, zinc alloy and stainless steel. Examples of the surface treatment include zinc phosphate treatment, iron phosphate treatment, calcium phosphate treatment, and zirconium treatment.

<Dispersion resin A>
Production Example 1: Production of dispersion resin (1N type) 385 parts of bisphenol A type epoxy resin, 120 parts of bisphenol A, 95 parts of octylic acid, 1 part of 2-ethyl-4-methylimidazole 1% solution were stirred, thermometer, nitrogen In addition to a separable flask equipped with an inlet tube and a reflux condenser, the mixture was reacted at 160 to 170 ° C. for 1 hour in a nitrogen atmosphere, then cooled to 120 ° C., and then methyl isobutyl ketone of 2-ethylhexanolated half-blocked tolylene diisocyanate 198 parts of (MIBK) solution (solid content 95%) was added. After maintaining the reaction mixture at 120 to 130 ° C. for 1 hour, 157 parts of ethylene glycol mono n-butyl ether was added. And it cooled to 85-95 degreeC and made it uniform. Next, 277 parts of MIBK solution of diethylenetriamine diketimine (solid content: 73%) was added and stirred at 120 ° C. for 1 hour, and 13 parts of ethylene glycol mono-n-butyl ether was added to produce an aminated resin. Next, 18 parts of deionized water and 8 parts of formic acid were added, the aminated resin was mixed and stirred for 15 minutes, and 200 parts of deionized water was mixed to obtain a dispersion resin solution (solid content 25%). .

<Dispersion paste>
Production Example 2: Production of Humic Acid Dispersed Paste For 100 parts of the above dispersion resin A (1N type), 15 parts of deionized water, soil humic acid (manufactured by Wako Pure Chemical Industries, Ltd., in the examples, humic acid and (Abbreviated.) 50 parts were dispersed with a sand grind mill and pulverized until the particle size measured with a grind gauge became 10 μm or less to obtain a humic acid-dispersed paste.

Production Example 3: Production of Nitrohumic Acid Dispersion Paste A nitrohumic acid dispersion paste was obtained by carrying out the same dispersion as in Production Example 2 except that nitrohumic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of humic acid. It was.

Production Example 4: Production of Calcium Phosphate Dispersion Paste A calcium phosphate dispersion paste was obtained by carrying out the same dispersion as in Production Example 2 except that calcium orthophosphate (manufactured by Soekawa Riken) was used instead of humic acid.

Production Example 5: Production of Tannic Acid Dispersed Paste Since the tannic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a comparative substance is water-soluble, it does not need to be dispersed in a sand grind. Therefore, 15 parts of deionized water and 50 parts of tannic acid were mixed with a disper to 100 parts of the dispersion resin A to obtain a tannic acid dispersion paste.

Production Example 6: Manufacture of gallic acid-dispersed paste Since gallic acid (manufactured by Wako Pure Chemical Industries, Ltd.), which is a comparative substance, is water-soluble, there is no need for dispersion in sand grind. Therefore, 15 parts of deionized water and 50 parts of gallic acid were mixed with a disper to 100 parts of the dispersion resin A to obtain a gallic acid-dispersed paste.

<Coating composition>
A. Aqueous paint comparative example A1: Preparation of amino group-containing epoxy resin 1 702 parts of epoxy resin with an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin in a reaction vessel equipped with a stirrer, a cooler, a nitrogen introduction tube and a thermometer, 269 parts of bisphenol A, 108 parts of dimer acid and 190 parts of MIBK were charged and reacted at 117 ° C. in the presence of 1 part of benzyldimethylamine until an epoxy equivalent of 1270 was reached. Thereafter, 255 parts of an aminoethylethanolamine ketimine compound (solid content: 73% by mass) was added and reacted at 117 ° C. for 1 hour. Then, it diluted with MIBK until it became non-volatile content 75%, and the amino group containing epoxy resin 1 of the amine equivalent 1184 was obtained.

  Acetic acid was added to the resulting amino group-containing epoxy resin 1 to obtain a neutralization rate of 20.0% (neutralization rate with respect to amine groups of the resin), and ion-exchanged water was added for dilution. Then, the mixture of MIBK and water was removed under reduced pressure until the solid content became 40% by mass, and an amino group-containing epoxy resin emulsion 1 was prepared.

  In a sand grind mill, 35 parts of dispersion resin Disperbyk 190 (by Big Chemie), 170 parts of calcium carbonate, 195 parts of titanium oxide, and 100 parts of deionized water are dispersed and dispersed to a particle size of 10 μm or less. (Solid content 60%).

  As an amino group-containing epoxy resin, 2960 parts of emulsion 1 obtained as described above was added with 118 parts of dipropylene glycol n-butyl ether while stirring with a disper, and then further with stirring with a disper, ethoxylated trimethylolpropane. 392 parts of triacrylate (AT-20E manufactured by Shin-Nakamura Chemical Co., Ltd.) and 500 parts of the pigment dispersion paste obtained as described above were added and stirred for 10 minutes to obtain an aqueous paint 1.

Comparative Example A2:
A reaction vessel equipped with a stirrer, a cooler, a nitrogen introduction tube and a thermometer was charged with 742 parts of an epoxy resin having an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin, 336 parts of bisphenol A and 190 parts of MIBK, and 1 part of benzyldimethylamine In the presence, the reaction was carried out at 170 ° C. until an epoxy equivalent of 1270 was reached. Thereafter, 350 parts of a diethylenetriamine ketimine compound (solid content: 73% by mass) was added and reacted at 1170 ° C. for 1 hour. Thereafter, 27 parts of ion-exchanged water and 188 parts of glycidyl neodecanoate (Cardura E10 1P) were charged and reacted at 1000 C for 2 hours. Then, it diluted with MIBK until it became non-volatile content 75%, and the amino group containing epoxy resin 2 of amine equivalent 947 was obtained.

  Emulsion 2 was produced from the resulting amino group-containing epoxy resin in the same manner as emulsion 1. Then, 2960 parts of the emulsion 2 obtained as described above was added with 1960 parts of dipropylene glycol n-butyl ether while stirring with a disper, and further with stirring with a disper, ethoxylated trimethylolpropane triacrylate (Shin Nakamura). (AT-20E manufactured by Kagaku Co., Ltd.) 468 parts, and 500 parts of the pigment dispersion paste obtained as described above were added and stirred for 10 minutes to obtain an aqueous paint 2.

Example A1
To the aqueous paint 1 obtained in Comparative Example A1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 0.1%. Obtained.

Example A2
To the water-based paint 1 obtained in Comparative Example A1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 0.3%. Obtained.

Example A3
To the water-based paint 1 obtained in Comparative Example A1, the nitrohumic acid-dispersed paste obtained in Production Example 3 was added so that the solid content ratio of nitrohumic acid in the paint was 0.3%. Obtained.

Example A4
To the aqueous paint 1 obtained in Comparative Example A1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 3.0%. Obtained.

Example A5
To the aqueous paint 1 obtained in Comparative Example A1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 6.0%, and the aqueous paint 7 was obtained. Obtained.

Comparative Example A3
To the water-based paint 1 obtained in Comparative Example A1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 12.0%. Obtained.

Comparative Example A4
To the water-based paint 1 obtained in Comparative Example A1, the tannic acid-dispersed paste obtained in Production Example 5 was added so that the solid content ratio of tannic acid in the paint was 0.3%. Obtained.

Comparative Example A5
To the aqueous paint 1 obtained in Comparative Example A1, the gallic acid-dispersed paste obtained in Production Example 6 was added so that the solid content ratio of gallic acid in the paint was 0.3%. Obtained.

Example A6
To the water-based paint 1 obtained in Comparative Example A2, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the paint was 3.0%. Obtained.

B. Production comparison example B1 of cationic electrodeposition paint
In a reaction vessel, Epicoat 828 (Oilized Shell Epoxy Co., Ltd .; bisphenol A type epoxy resin, epoxy equivalent 188) 752.0 parts, methanol 77.0 parts, MIBK 200.3 parts and dibutyltin dilaurate 0.3 parts were stored at room temperature. The mixture was stirred to obtain a homogeneous solution, and 174.2 parts of a 2,4- / 2,6-tolylene diisocyanate 80/20 (weight ratio) mixture was added dropwise over 50 minutes, and the temperature inside the system reached 70 ° C. due to heat generation. . The IR spectrum showed the disappearance of absorption at 2280 cm ⁻¹ based on isocyanate and the absorption at 1730 cm ⁻¹ based on urethane carbonyl group.

After adding 2.7 parts of N, N-dimethylbenzylamine, the temperature in the system was raised to 120 ° C., and the reaction was performed until the by-product methanol was distilled off using a decanter until the epoxy equivalent reached 463. . The IR spectrum showed the disappearance of absorption at 1730 cm ⁻¹ based on the carbonyl group of the urethane and the appearance of absorption at 1750 cm ⁻¹ based on the carbonyl group of the oxazolidone ring.

  220.0 parts of p-nonylphenol and 83.3 parts of MIBK were added, and the reaction was carried out while maintaining a temperature of 125 ° C. until the epoxy equivalent reached 1146. The system was cooled to 110 ° C., and 47.2 parts of aminoethylethanolamine ketimine (solid content 79% by mass), 42.0 parts of diethanolamine, 30.0 parts of N-methylethanolamine and MIBK17.3. After adding a part, it heated up and made it react at 120 degreeC for 2 hours.

  Thus, an amino group-containing epoxy resin (solid content: 80.0%, amine equivalent: 1040 g / mol) was obtained.

  Crude diphenylmethane diisocyanate (1330 parts) and MIBK (585.6 parts) were charged into a reaction vessel and heated to 85 to 95 ° C., and then 486 parts of diethylene glycol monobutyl ether was added dropwise over 2.5 hours. After completion of dropping, the mixture was kept warm for 1 hour. Thereafter, 194.8 parts of MIBK was added and cooled to 50 ° C., and 532 parts of propylene glycol was added dropwise. After completion of dropping, the mixture was heated to 60 ° C. and kept for 1 hour. After adding 0.4 parts of dibutyltin laurate, the temperature was raised and the temperature was kept at 70 ° C. for 1 hour, and in the IR spectrum measurement, it was confirmed that the absorption based on the isocyanate group disappeared, and a blocked isocyanate curing agent was obtained. It was.

  In a sand grind mill, 106.9 parts of the pigment dispersing resin obtained in Production Example 1, 1.6 parts of carbon black, 40 parts of kaolin, 58.4 parts of titanium dioxide, and 13 parts of deionized water are added. A pigment dispersion paste was obtained by dispersing until the particle size became 10 μm or less (solid content 60%).

  The amino group-containing epoxy resin and the blocked isocyanate curing agent were mixed so as to be uniform at a solid content ratio of 70/30. Further, neutralized with glacial acetic acid so that the milligram equivalent of acid per 100 g of resin solids was added to 3% by mass of 2-ethylhexyl glycol with respect to the resin solids, and further diluted slowly with ion-exchanged water. . By removing MIBK under reduced pressure, a binder resin emulsion having a solid content of 36% was obtained.

  1730 parts of this emulsion and 295 parts of the pigment dispersion paste were mixed with 1970 parts of deionized water and 10 parts of dibutyltin oxide to prepare a cationic electrodeposition coating composition (cationic electrodeposition coating 1) having a solid content of 20%. Obtained.

Example B1
To the cationic electrodeposition coating material 1 obtained in Comparative Example B1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the coating material was 0.1%. A paint coating 2 was obtained.

Example B2
The humic acid-dispersed paste obtained in Production Example 2 was added to the cationic electrodeposition coating material 1 obtained in Comparative Example B1 so that the solid content ratio of humic acid in the coating material was 0.3%. A paint 3 was obtained.

Example B3
To the cationic electrodeposition coating material 1 obtained in Comparative Example B1, the humic acid-dispersed paste obtained in Production Example 2 was added so that the solid content ratio of humic acid in the coating material was 3.0%. A paint 4 was obtained.

Comparative Example B2
The humic acid-dispersed paste obtained in Production Example 2 was added to the cationic electrodeposition coating material 1 obtained in Comparative Example B1 so that the solid content ratio of humic acid in the coating material was 10.0%. A paint 5 was obtained.

Comparative Example B3
To the cationic electrodeposition paint 1 obtained in Comparative Example B1, the calcium phosphate-dispersed paste obtained in Production Example 4 was added so that the solid content ratio of calcium phosphate in the paint would be 3.0%. 6 was obtained.

C. Anion electrodeposition coating production comparison example C1
700 parts of isopropyl alcohol was charged into a 2 L reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, and a thermometer connected to a temperature controller, and heated to 80 ° C. in a nitrogen atmosphere. In a reaction vessel, a mixed solution of 210 parts of methyl methacrylate, 196 parts of butyl acrylate, 140 parts of styrene, 84 parts of 2-hydroxyethyl methacrylate, 70 parts of acrylic acid and 7 parts of azobisdimethylvaleronitrile is taken over 3 hours. By rapidly dropping and then holding at 80 ° C. for 2 hours, an acrylic copolymer resin (anionic pigment) for pigment dispersion having a solid content of 50%, an acid value of 78 mgKOH / g, a hydroxyl value of 52 mgKOH / g, and a weight average molecular weight of 28000 Dispersion resin) was obtained.

  Add 100 parts of the above-mentioned anionic pigment dispersing resin, 120 parts of titanium oxide (Ishihara Sangyo Co., Ltd., Taipei CR-95), add 5 parts of triethylamine and 115 parts of deionized water, and add 50% solids anion. Pigment dispersion paste was obtained.

  A 2 L reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen inlet pipe, and a thermometer connected to a temperature controller was charged with 700 parts of isopropyl alcohol and heated to 80 ° C. in a nitrogen atmosphere, 322 parts of methyl methacrylate, acrylic A mixed solution of 140 parts of butyl acid, 105 parts of styrene, 84 parts of 2-hydroxyethyl methacrylate, 49 parts of acrylic acid and 7 parts of azobisdimethylvaleronitrile is dropped at a constant rate over 3 hours, and then kept at 80 ° C. for 2 hours. As a result, an acrylic copolymer resin having an acid value of 55 mgKOH / g, a hydroxyl value of 52 mgKOH / g, and a weight average molecular weight of 30000 was obtained.

  313 parts of the above acrylic copolymer resin, 86 parts of Cymel 285-100 (manufactured by Cytec Co., Ltd.) which is a melamine resin as a curing agent, and 11 parts of triethylamine are mixed and mixed with the above anionic pigment dispersion paste. 255 parts of heptanoic acid in an amount of 2% by mass with respect to the pigment to be added were added and mixed and stirred, and 3035 parts of deionized water was further added to prepare an anionic electrodeposition coating composition. The solid content of the obtained anionic electrodeposition coating composition was 10%. This is designated as anion electrodeposition paint 1.

Example C1
To the resulting anionic electrodeposition coating composition 1, 1.0% of a 1% aqueous solution of humic acid neutralized with triethanolamine and adjusted to a pH of 8 to 9 was added to obtain a solid content of humic acid in the coating. An anionic electrodeposition paint 2 having a ratio of 0.1% was obtained.

Example C2
To the resulting anionic electrodeposition coating composition 1, 2.0% of a 1% aqueous solution of humic acid neutralized with triethanolamine and adjusted to a pH of 8 to 9 was added to obtain a solid content of humic acid in the coating. An anionic electrodeposition paint 3 having a ratio of 0.2% was obtained.

Example C3
To the resulting anionic electrodeposition coating composition 1, 5.0% of a 1% aqueous solution of humic acid neutralized with triethanolamine and adjusted to pH 8-9 was added, so that the solid content of humic acid in the coating was increased. An anionic electrodeposition paint 4 having a ratio of 0.5% was obtained.

Comparative Example C2
To the resulting anionic electrodeposition coating composition 1, 5.0% of a 1% tannic acid aqueous solution neutralized with triethanolamine and adjusted to a pH of 8 to 9 was added to obtain a solid content of tannic acid in the coating. An anionic electrodeposition paint 5 having a ratio of 0.5% was obtained.

D. Manufacture of organic solvent-based paint [Preparation of main agents 1 to 4]
Acrylic polyol resin (ACRYDIC A-871 manufactured by DIC, molecular weight 8,000, hydroxyl value 29 ± 3%), humic acid, titanium pigment (CR-95 manufactured by Ishihara Sangyo Co., Ltd.), antifoaming agent (BYK063 manufactured by BYK Chemie), Anti-sagging agent (Dispalon 6810-20X manufactured by Enomoto Kasei Co., Ltd.), mineral spirit as a dispersing agent (R-95 manufactured by Big Chemie) and solvent are mixed in the blending amounts shown in Table 1, and dispersed with a sand grind mill. By grinding to 10 μm or less, main agents 1 to 4 were obtained.

[Production of curing agent]
A curing agent was obtained by mixing 6.2 parts of an isocyanate resin (Durato TSA100, manufactured by Asahi Kasei Corporation, molecular weight 700 ± 300, NCO content 21%) and 3.8 parts of mineral spirit as a solvent.

Comparative Example D1
90 parts of the main agent 1 and 10 parts of the curing agent were mixed to obtain a two-component rust preventive paint (organic solvent-based paint 1) having an OH group / NCO group = 1/1.

Example D1
An organic solvent-based paint 2 was obtained in the same manner as in Comparative Example D1, except that the main agent 2 was used in place of the main agent 1.

Example D2
An organic solvent-based paint 3 was obtained in the same manner as in Comparative Example D1 except that the main agent 3 was used in place of the main agent 1.

Example D3
An organic solvent-based paint 4 was obtained in the same manner as in Comparative Example D1 except that the main agent 4 was used in place of the main agent 1.

<Method for evaluating physical properties of coating film>
The physical property evaluation method of a coating film is described below.
A. Water resistance (water-based paint)
The uncoated part of the prepared coated plate is sealed, immersed in pure water (pH 7) at 23 ° C., observed for appearance after 120 hours, and evaluated according to the following evaluation criteria.
<Evaluation criteria>
○: No abnormality ×: Peeling or swelling

B. Smoothness (cationic, anionic electrodeposition paint)
Using a surface roughness meter (E-30, Tokyo Seimitsu Co., Ltd.), the surface roughness of the coating film is measured, the centerline average surface roughness (Ra) is calculated, and evaluation is performed according to the following criteria.
<Evaluation criteria>
○: Ra is less than 0.35 μm ×: Ra is 0.35 μm or more

C. Salt spray test (SST)-anion electrodeposition paint and water-based paint A cured coating film formed on a steel plate substrate was cut with a knife so as to reach the substrate, and a salt spray test (JIS Z 2371) was performed. Do time. Thereafter, the occurrence of rust and swelling from the crosscut portion is evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: The maximum width of rust or blisters is less than 5 mm from the cross cut part (one side)
○: The maximum width of rust or swelling is 5 mm or more and less than 10 mm from the cross cut part (one side)
Δ: The maximum width of rust or swelling is 10 mm or more and less than 15 mm from the cross cut part (one side)
X: The maximum width of rust or blisters is 15 mm or more (one side) from the cross cut part

D. Cyclic corrosion test (CCT) -cationic electrodeposition coating A cured coating film formed on a steel sheet substrate is cross-cut with a knife so as to reach the substrate, and JASO M609-941 "Automobile material corrosion test method" Perform 100 cycles. Thereafter, the occurrence of rust and swelling from the crosscut portion is evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Maximum width of rust or blister is less than 10mm from the cut part (both sides)
○: The maximum width of rust or swelling is 10 mm or more and less than 15 mm from the cut part (both sides)
X: The maximum width of rust or blister is 15mm or more from the cut part (both sides)

E. Cycle corrosion test (CCT) (organic solvent paint)
A cross-cut wound was made with a knife so as to reach the substrate in the cured coating film formed on the steel plate substrate to obtain a test piece. A test is performed according to the test method of JIS K5674 7.12.2, the swelling width and the rust width are measured, and the evaluation is performed according to the following evaluation criteria. However, the combined cycle test was 36 cycles.
<Evaluation criteria>
A: Rust swelling width is less than 0.5 mm B: Rust swelling width is 0.5 mm or more and less than 1.0 mm Δ: Rust swelling width is 1.0 mm or more and less than 2.0 mm X: Rust swelling width is 2.0 mm or more

F. Storage Stability of Paint 1 L of the prepared paint was aged with stirring at 40 ° C. for 1 week, filtered with a 380 mesh filter cloth, measured for filtration residue, and evaluated by the following evaluation.
<Evaluation criteria>
○: Less than 1.0 g ×: 1.0 g or more

<Evaluation of physical properties of coating film>
A. Aqueous paint film Aqueous paints 1 to 11 obtained in Examples A1 to A6 and Comparative Examples A1 to A5 were applied to a sandblast plate with a brush so as to be 200 g / m ² in a 25 ° C environment. The test piece was obtained by drying for 7 days. The water resistance and SST of the obtained coating film were evaluated. The results are shown in Table 2.

  Since tannic acid has high water solubility, increasing the blending amount in order to improve performance deteriorates water resistance and SST performance is not so high. On the other hand, since humic acid is insoluble in acidic aqueous solution and neutral aqueous solution, humic acid can maintain water resistance as compared with tannic acid and can improve SST performance in a small amount.

B. Cationic electrodeposition coating film Cold-rolled steel sheet (JIS G3141, SPCC-SD) is degreased by immersing it in Surf Cleaner EC90 (Nihon Paint Co., Ltd.) for 2 minutes at Surf Fine GL-1 (Japan) The surface was adjusted by Paint Co., Ltd., and then immersed in Surfdyne SD-5000 (Nihon Paint Co., Ltd., zinc phosphate conversion treatment solution) for 2 minutes at 40 ° C. Chemical conversion treatment was performed.

  The obtained steel sheet was immersed in the cationic electrodeposition paints 1 to 6 obtained in Examples B1 to B3 and Comparative Examples B1 to B3, and the film thickness of the cured electrodeposition coating film was 15 μm at a bath temperature of 30 ° C. Electrodeposition coating was performed at a coating voltage set so that an uncured electrodeposition coating film was deposited on the object to be coated. Next, after washing with water, baking was performed at 160 ° C. for 20 minutes to obtain a cured electrodeposition coating film. The smoothness and CCT of the obtained coating film were evaluated. The results are shown in Table 3.

  In Comparative Example B2, the smoothness is lowered, but this is considered to be due to the increase in conductivity due to an increase in the dispersion resin. Further, it is believed that this reduction in smoothness has reduced CCT performance. Although the calcium phosphate of Comparative Example B3 exhibited a certain CCT performance, it was confirmed that the calcium phosphate was inferior to humic acid added with the same amount, and the smoothness and stability were very poor.

C. Anion electrodeposition coating film Cold-rolled steel sheet (JIS G3141, SPCC-SD) was degreased by immersing in Surf Cleaner EC90 (manufactured by Nippon Paint Co., Ltd.) at 50 ° C. for 2 minutes. The obtained steel sheet was immersed in the anion electrodeposition paints 1 to 5 obtained in Examples C1 to C3 and Comparative Examples C1 to C2, and the film thickness of the cured electrodeposition coating film was 15 μm at a bath temperature of 30 ° C. Electrodeposition coating was performed at a coating voltage set so that an uncured electrodeposition coating film was deposited on the object to be coated. Next, after washing with water, baking was performed at 180 ° C. for 30 minutes to obtain a cured electrodeposition coating film. The smoothness and SST of the obtained coating film were evaluated. The results are shown in Table 4.

  Tannic acid needs to be added in a larger amount in order to improve rust prevention performance than humic acid, but rust prevention performance is worse than humic acid. Moreover, it is difficult to achieve both smoothness. On the other hand, humic acid can maintain smoothness as compared with tannic acid, and can improve the SST performance in a small amount.

E. Coating film of organic solvent-based paint Polished steel plate SPCC-SB was exposed outdoors for three months in the summer (June to August) to obtain a steel plate (rust plate) with rust on the surface.
After rusting the rust plate, the two-component organic solvent-based paints of Examples D1 to D3 and Comparative Example D1 were applied to the rust plate by brush coating to obtain test pieces. The number of coatings was 2, the coating amount per coating was 130 g / m ² , and the coating and drying time was 3 hours.
The obtained test piece was dried for 7 days in a constant temperature and humidity chamber adjusted to 23 ° C. and 50% RH, and then CCT was evaluated. The results are shown in Table 5.

  It was confirmed that CCT performance was improved by addition of humic acid.

  From the above examples, the humic acid compound is added in an amount of 0.01 to 8.0 parts by weight of the humic acid compound with respect to 100 parts by weight of the solid content of the paint. On the other hand, it has been found that various performances such as rust prevention performance and water resistance, stability and smoothness are improved as compared with rust prevention agents which have been conventionally used. Due to the unique properties of the humic acid compound, this improvement in rust prevention performance is achieved by dissolving on the cathode side in an alkaline atmosphere and buffering the pH to prevent film peeling, and insolubilizing on the anode side in an acidic atmosphere to form a film. We believe that this was achieved by preventing the elution of iron. In particular, in coating systems using amino group-containing resins, humic acid compounds are eluted due to the action of amino groups in the coating film, and are more likely to be effectively deposited on the coating film. there were.

  According to the present invention, by adding a humic acid compound, any form of paint composition including cationic electrodeposition paint, anion electrodeposition paint, aqueous emulsion paint, powder paint, zinc rich paint, and organic solvent-based paint can be applied. However, rust prevention performance can be improved.

A: eluted humic acid compound B: film formed by precipitated humic acid compound

Claims (11)

  A rust preventive paint composition containing 0.05 to 8.0 parts by mass of a humic acid compound with respect to 100 parts by mass of the solid content of the paint and the paint.   The rust preventive coating composition according to claim 1, wherein the humic acid compound is natural humic acid or a salt thereof selected from the group consisting of soil humic acid and coal-based humic acid.   The rust preventive coating composition according to claim 1, wherein the humic acid compound is regenerated humic acid which is nitrohumic acid or a salt thereof.   The rust preventive paint composition according to any one of claims 1 to 3, wherein the paint is an aqueous paint containing an amino group-containing resin.   The rust preventive coating composition according to claim 4, wherein the amino group-containing resin is an amino group-containing epoxy resin. The rust preventive coating composition of Claim 5 whose amine equivalent of the said amino group containing epoxy resin is 100-3000 (g / mol). The rust preventive paint composition according to claim 5 or 6, wherein the paint further contains a compound having one or more (meth) acryloyl groups in the molecule, and the paint is a room temperature curable aqueous paint. object.   The content of the amino group-containing epoxy resin as a solid content is 10 to 90% by weight with respect to the total solid content of the coating composition, and the content of the compound having the (meth) acryloyl group is a coating composition. The rust preventive coating composition according to claim 7, which is 2 to 40% by weight based on the total solid content of the product.   The rust preventive paint composition according to claim 5 or 6, wherein the paint further contains a blocked isocyanate curing agent, and the paint is a cationic electrodeposition paint.   The rust preventive coating composition of Claim 9 whose solid content mass ratio of the said amino-group-containing epoxy resin and block isocyanate hardening | curing agent is 90 / 10-50 / 50.   The coating film obtained by apply | coating the antirust coating composition in any one of Claims 1-10.

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