JPS5848228B2 - Method for forming a coating film having a chelate layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an iron chelate layer on the surface of a coating film obtained from an epoxy resin composition having chelate-forming ability.

Vehicles conventionally used for paints include a wide variety of resins, including unsaturated fatty acids, alkyds, olefins, dienes, acrylics, polyesters, epoxys, urethanes, and copolymers thereof.

Among them, epoxy resin has excellent physical properties (adhesion,
Its demand continues to increase due to its hardness → and chemical properties (chemical resistance).

Furthermore, in recent years, there has been a demand for paints that are not dangerous, such as those that are low in flammability or non-toxic to the human body.

As one of them, epoxy resin is used by dispersing, emulsifying or dissolving it in water.

So-called water-based epoxy resin paints have been developed.

Known examples of such water-based epoxy resin coating compositions include, for example, U.S. Pat.
No. 397, No. 3324041, No. 3355409
No. 3449281 and No. 3640926.

Although many water-based epoxy resin coatings have been researched and developed, they are still not as good as solvent-based coating compositions in terms of moisture resistance, corrosion resistance, physical properties, etc.

As a method for improving these materials, it has been proposed, for example, to add rust preventive pigments such as lead cyanamide, lead zinc oxide, basic lead chromate, red lead, strontium chromate, and zinc chromate to improve their corrosion resistance. It is considered undesirable from a pollution standpoint.

Further, known water-based epoxy resin paints are not necessarily satisfactory in various physical properties such as adhesion under high humidity.

As described above, it is currently not possible to obtain a non-polluting water-based epoxy resin paint that has performance comparable to or even better than conventional solvent-based paints that use large amounts of organic solvents. It is.

On the other hand, polyhydric phenols such as pyrogallol, phenol carboxylic acids, chromium complex salts, phthalocyanines,
Attempts have been made for a long time to improve the performance of paint films by incorporating compounds with chelate binding properties, such as pyridines and their derivatives, into paints and causing a chelation reaction with the iron surface of the substrate after application. .

In the past, solvent-based paints were known that simply added tannin to linseed oil-based resin or drying oil (British Patent No. 826).
No. 564, No. 826566).

Then R. N. Horkner (F aulknet
) A solvent in which catechol, pyrogallol, gallic acid, or gallic acid ester is covalently introduced into vegetable oil, fatty acid ester, alkyd resin, vegetable oil-modified epoxy ester resin, or vegetable oil-modified polyamide resin using a catalyst such as a metal alkoxide. One-component paints have been developed, such as those described in British Patent No. 104.
5118, U.S. Pat. No. 3,304,276, U.S. Pat. No. 332
No. 1320 and Oil and Color Ohe
-misassociation
Published by Journal of the Oilland
Color Chemists' Associate
ion Vol. 50, p. 524 (1967), etc.

Further, British Patent No. 1114400 discloses a composition in which a styrene-allylic alcohol copolymer is reacted with a gallic acid ester.

Furthermore, compositions having chelate-forming ability using epoxy resins are also known.

For example, a part of the epoxy group in the epoxy resin is modified with a monobasic fatty acid, and the remaining epoxy group has the ability to form a chelate, has two or more adjacent phenolic hydroxyl groups, and has L+1M free carboxyl groups. Chelate-forming resin reacted with fatty acid derivatives (Special Publication No. 48-243
9), a composition comprising an epoxy polyamide resin having a chelate-forming ability obtained by reacting gallic acid with the residual epoxy group of a reaction product of a polyamide resin with an amine value of 10 or less and an epoxy resin, and a phosphoric acid compound (Unexamined Japanese Patent Publication No. Showa 48-17
443), an organic solvent obtained by adding an epoxy resin, a vinyl resin, a fluororesin, etc. to a partially esterified product obtained by reacting a part of the epoxy group in an epoxy resin with salicylic acid, gallic acid, or an esterified product thereof. Diluted one-component or two-component (using amine hardener) paint (
Japanese Patent Publications No. 49-4811, No. 48-56227, No. 48-56228, No. 49-122538, No. 49-1.22597) are known.

However, all of these involve solvent-based paints that use organic solvents, which are unfavorable in terms of safety and pollution-free properties.Moreover, all of these involve modifying the base epoxy resin with a compound that has chelate-forming ability. This is what I did.

In other words, it is a one-component or two-component composition obtained by reacting all or part of the epoxy groups in an epoxy resin with a compound that has chelate-forming ability, and the properties of the epoxy resin are improved by reducing the epoxy groups. This was a significant decrease.

On the other hand, water-based paints having chelate-forming ability are also known.

For example, a composition in which a styrene-butadiene copolymer is epoxidized is used as a vehicle (Japanese Patent Laid-Open No. 49-8598
), compositions in which gallic acid ester is added to acrylic copolymers or styrene-book diene copolymer emulsions (Japanese Patent Publication No. 48-14412), but some water-based paints may not have sufficient anticorrosive properties. It is not possible to obtain a coating film with

The present inventors have created a chelation reaction with the iron substrate by applying a water-based epoxy resin compound that already has chelate ability to the iron substrate, thereby obtaining a coating film with extremely excellent moisture resistance and corrosion resistance. proposed a water-based epoxy resin composition (
Patent application No. 50-19332, No. 50-127203).

Subsequent research revealed that after applying a composition consisting of a curing agent with chelate-forming ability and an epoxy resin to the object to be coated, the phenolic carboxylic acids present on the surface of the coating film were allowed to react with the iron compound to form an iron chelate layer. It was discovered that the coating film performance could be further improved by forming such a compound, and the present invention was achieved.

The object of the present invention is to provide a coating film that has excellent corrosion resistance such as moisture resistance and accelerated salt water immersion resistance, and is also suitable for overcoating.

That is, the present invention comprises: 1) an aqueous dispersion of an epoxy resin having at least two or more epoxy groups in one molecule; and 11) containing two or more nitrogen atoms having at least an active hydrogen atom in one molecule. A water-based epoxy resin composition consisting of an amino curing agent with chelate-forming ability obtained by bonding phenolic carboxylic acids to an amine curing agent is applied onto the object to be coated, and after drying, the resulting coating film surface The present invention relates to a method for forming a coating film having an iron chelate layer on the surface thereof, which comprises treating with an iron compound aqueous solution.

Examples of the "epoxy resin having at least two or more epoxy groups in one molecule" used in the present invention include the following.

As bisphenol type epoxy resins, Epikote 828 and 8 manufactured by Shell Chemical Co., Ltd. are generally commercially available.
34, 836, 1001, 1004, DX-2
55; Product name Araldai l-GY- manufactured by Ciba Geigy ■
260; Trade name DER330, 331, 337 manufactured by Dow Chemical; Trade name Picron 800, 830 manufactured by Dainippon Ink &Chemicals; Novolac-type epoxy resin, for example, trade name DEN43 manufactured by Dow Chemical.
1, 438; As a polyglycol type epoxy resin, for example, Araldite CT5 manufactured by Ciba Geigy ■ is used.
08; Product name: DER732, manufactured by Dow Chemical ■, 7
36; As an ester type epoxy resin, for example, Meiko Picron 200 and Meiko Picron 400 manufactured by Dainippon Ink & Chemicals ■
; As epoxidized polybutadiene, trade name BF-1000 manufactured by Nippon Soda ■; As epoxidized oil, trade name Adeca Sizer Q-180 manufactured by Adeca Argus Chemical ■;
Examples include 0-130P;

Furthermore, it should be noted that epoxy compounds and derivatives of the above-mentioned epoxy resins that can be easily inferred from these exemplified compounds are also included within the scope of the present invention.

For example, polyol-type epoxy resins, alicyclic epoxy resins, halogen-containing epoxy resins, silicon-modified epoxy resins, and the like can also be used in the present invention to obtain excellent effects.

These epoxy resins may be used alone or as a mixture of two or more thereof.

It is preferable that the epoxy resin is liquid at room temperature in order to improve water dispersibility. However, even if the epoxy resin is solid at room temperature, it may be used in combination with a liquid epoxy resin or with the addition of a small amount of a water-soluble solvent. It can be used better.

Furthermore, in order to make it easier to emulsify the epoxy resin, which is solid at room temperature, in water, or to improve workability, coating performance, and coating condition, monoepoxy compounds having one epoxy group in the molecule may be added as necessary. It can be used in combination up to 20% by weight with respect to the epoxy resin.

Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether,
Methyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, styrene oxide,
Examples include cyclohexene oxide, shrimp chlorohydrin, and a compound having one epoxy group obtained by modifying an epoxy resin having two or more epoxy groups in the molecule with a fatty acid or the like.

The epoxy resin used in the present invention is used in the form of an aqueous dispersion, and the aqueous dispersion refers to an epoxy resin emulsified in an aqueous medium, and is generally anionic and/or nonionic. It is obtained by vigorously stirring water and epoxy resin in the presence of a surfactant.

In addition to the aqueous dispersion of the present invention in an emulsified state, a dispersion in which an epoxy resin is partially dissolved in water can also be used in combination.

However, when dissolved in water, epoxy groups tend to ring open and do not exhibit sufficient coating performance, so care must be taken when using them.

The anionic surfactant includes metal salts of fatty acids;
Alkylbenzene sulfonate [e.g. Kao Atlas ■
[manufactured by Kao Atlas■, trade name: Neoperex 05] sulfuric ester of higher alcohol [e.g., manufactured by Kao Atlas ■, trade name: Emarl 1]
0], etc.

In addition, examples of nonionic surfactants include polyoxyethylene alkyl ethers (for example, manufactured by Kao Atlas ■, trade name Emulgen 108), sorbit derivatives (for example, manufactured by Kao Atlas ■, Emazol 1130:), polyoxyethylene alkyl phenyl, Ether [e.g. manufactured by Nippon Nyukazai ■, trade name Newcol 710, Nucol 714, Nucol 72
3], polyoxyethylene anolequinole ester (for example, manufactured by Nippon Nyukazai (trade name: Newcol 150)), and the like.

The above-mentioned surfactants may be used alone or in a mixture of two or more, as required, and the amount added varies depending on the type of surfactant and epoxy resin.

If the surfactant is used in an amount greater than the required amount, it will have unfavorable effects such as a decrease in the water resistance of the coating film, so it is desirable to keep the amount as small as possible while taking dispersion stability into consideration.

Generally, 0.1 to 20 weight percent surfactant is added to the epoxy resin.

In this way, an aqueous dispersion (base resin) in which 40% by weight of the epoxy resin is dispersed in water is obtained.

The epoxy resin base material may contain extender pigments such as talc, precipitated barium sulfate, calcium carbonate, yellow lead,
Coloring pigments such as carbon black, titanium oxide, zinc oxide, petal, flaky iron oxide, aluminum powder, ultramarine blue, phthalocyanine blue, iron black, etc., reinforcing pigments such as glass fiber, glass flakes, mica powder, synthetic silica, asbestos, etc. , other thickeners, rust preventives, non-polluting rust preventive pigments, antifoaming agents, wetting agents, anti-settling agents, hardening accelerators, etc. can be added.

Examples of the rust preventive agent or non-polluting rust preventive pigment include conventionally known sodium nitrite, phosphoric acid, ammonium phosphate, zinc phosphate, zinc molybdate, barium metaborate, iron phosphate, and the like.

Examples of the curing accelerator include phenol, cresol, nonylphenol, bisphenol A, salicylic acid, resorcinol, hexamethylenetetramine, 2,4,6-tris(dimethylaminomethyl)phenol, and triethylenediamine.

Particularly when a tertiary amine is used, it is effective in low-temperature curability.

Furthermore, in the present invention, in order to improve the coating workability of the composition, the coating film performance, the surface condition of the coating film, etc., 20% by weight or less of Ike's resin can be used in combination with the epoxy resin. .

Examples of the resins used in combination include alkyd resins, polyester resins, urethanized oils, xylene resins, and bituminous resins.

On the other hand, the "amino curing agent having two or more nitrogen atoms and at least active hydrogen in one molecule" used in the present invention refers to amine adduct resin polyamide, which is usually used as a curing agent for epoxy resins. Amino compounds such as resins and polyamines can be used.

The polyamide resin is a condensation product of dimer acid (general industrial products contain about 3% monomer acid, about 85% dimer acid, and about 12% trimer acid) and polyamines such as ethylenediamine, diethylenetriamine, or metaphenylenediamine. It is a thing.

For example, the commonly available products manufactured by Fuji Kasei Kogyo ■ are Tomide Y-25, 245, 2400, and 2500.
;Product name: Seminad 2000, Versamide 115, 125% DSX-1280, manufactured by Daiichi General ■; Sanwa Chemical ■
Examples include the product names Sanmide 320 and 330 manufactured by Ciel Chemical Co., Ltd. and the product names Abicure 3255 and 4255 manufactured by Ciel Chemical.

Further, the amine adduct resin includes the above-mentioned epoxy resin such as bisphenol type epoxy resin and ethylenediamine,
It is an addition product with polyamines such as diethylenetriamine or metaphenylenediamine.

For example, commercially available products such as Tomide 238 and Fuji Cure-202 manufactured by Fuji Chemical Industry Co., Ltd. and ADEKA Hardener EH-531 manufactured by Asahi Denka Co., Ltd. are listed.

Further, as the amine adduct, there are also addition products of butyl glycidyl ether, glycidyl ester of versatic acid, bisphenol type epoxy resin, etc., and a heterocyclic diamine represented by the following formula, for example.

For example, the commercially available Ajinomoto ■ product name Epomate 13-002, the same C! -002, 3005;

One or more of these hardening agents may be used as a compound depending on the purpose.

The amino curing agent is required to have at least two or more nitrogen atoms containing active hydrogen in one molecule in order to bond with a compound having chelate-forming ability and further perform a crosslinking reaction with an epoxy resin.

Regarding the curing agent, there are no particular restrictions on the pond, but it is preferable that the amine value is 100 or more in view of dispersion in water.

However, if the amine value of the curing agent becomes extremely high, there will be a restriction that the pot life after mixing with the epoxy resin as the main ingredient will be shortened.

Furthermore, the viscosity of the curing agent also has a large effect on the performance of the paint and the performance of the coating film.

Generally, the higher the viscosity of the curing agent used, the worse the coating workability and the shorter the pot life.

It can be improved by adding a small amount of water-soluble solvent.

Examples of the water-soluble solvent include alcohols such as methanol and ethanol, ethylene glycol heptanoethyl ether,
Includes ethers such as ethylene glycol monobutyl ether.

In the present invention, a compound having chelate-forming ability is bonded to the amino curing agent.

Examples of compounds having chelating ability include phenolic carboxylic acids such as gallic acid, protocatechuic acid, and alkyl esters thereof.

The amine-based curing agent having chelate-forming ability used in the present invention is obtained by ionic bonding of the above-mentioned compound having chelate-forming ability to the amino-based curing agent as a salt, or by bonding the carboxyl group of the compound having chelate-forming ability to the amino-based curing agent. It is covalently bonded as an acid amide by condensation with active hydrogen such as an amino group.

When a compound having chelate-forming ability, ie, phenol carboxylic acids, is introduced into the amino curing agent as a salt, protocatechuic acid, gallic acid, etc. are used.

In addition, when a compound having chelate-forming ability is introduced as an acid amide bound to an amine curing agent, protocatechuic acid, gallic acid, ethyl protocatechuate, probyl protocatechuate, methyl gallate, ethyl gallate, propyl gallate, etc. An alkyl ester of protocatechuic acid or gallic acid having 1 to 12 carbon atoms in the alkyl group, such as isoamyl gallate and lauryl gallate, is used.

Protocatechuic acid and gallic acid have the following structural formulas.

That is, it is a polyhydric phenol compound having one carboxyl group and at least two hydroxyl groups at the 3, 4, and 5 positions relative to the carboxyl group.

Generally, even if a phenolic hydroxyl group is present at positions other than the 3 and 4.5 positions relative to the carboxyl group, the effect is extremely small.

The amount of the phenol carboxylic acids is 5 to 30% by weight, preferably 10 to 2% by weight, based on the solid content of the amino curing agent.
It is used in a proportion of 5% by weight.

If the amount of the compound having chelate form or ability in the above ratio is less than 5% by weight, the desired effect of the present invention cannot be expected, whereas if it is more than 30% by weight, not only will it not be possible to easily disperse it, but more than necessary chelate will be present. This is undesirable because the resulting coating film becomes hard and brittle, and moisture resistance is reduced as well as being uneconomical.

The phenol carboxylic acids in the present invention are bonded to the amino curing agent in the following manner.

The first method is to mix phenol carboxylic acids and an amino curing agent in the presence of water, and then
Stir and mix at any temperature up to ℃.

By doing so, the carboxyl group in the phenolic carboxylic acid and the nitrogen atom having an active hydrogen atom in the amino curing agent form a salt through ionic bonding, and a stable reaction product is obtained.

Mataike's method involves removing phenolic carboxylic acids and the amino curing agent from the system at a temperature of 100 to 240°C until the desired amount of condensed water or alcohol is obtained. (Usually 2-10
time), heat and stir in the presence of an inert gas such as nitrogen gas.

By doing so, a reaction product in which the phenol carboxylic acids are condensed and introduced into the amino curing agent is obtained.

The amino curing agent having chelate-forming ability obtained as described above can be further mixed with 2 to 30 percent by weight of tannin to increase the chelate-forming ability.

The amine curing agent having chelate-forming ability thus obtained undergoes a crosslinking reaction with the epoxy resin, and also undergoes a chelation reaction with the base iron surface.

In the present invention, the epoxy resin and the amine curing agent having chelate-forming ability need to be mixed immediately before use.

The mixing ratio is usually (number of epoxy groups in the base resin)/(number of active hydrogens bonded to nitrogen atoms in the curing agent) in order to effectively carry out the crosslinking reaction and obtain excellent coating performance. It is preferably 1/2 to 2/1.

However, this ratio is not particularly limited.

After mixing, apply the coating to the degreased surface, chemical conversion treated surface, rusted surface, wet surface of ferrous materials such as mild steel and hard steel, welded parts, or non-ferrous materials such as galvanized plate, tin plated plate, aluminum plate, copper plate, or shop. It is applied over a primer coating such as a primer (for example, a wash primer, a zinc-rich primer, etc.).

Painting is done using common methods such as brush painting, air spray painting, airless spray painting, and roll coater painting.

After the coating, the coating film is dried by natural drying or forced drying at a temperature of 10 to 150° C. and a relative humidity of 97% or less to obtain a coating film.

Then, in the method of the present invention, the coating film obtained as described above is treated with an aqueous iron compound solution.

The coating film preferably has a dry film thickness of at least 50 microns in order to meet the required performance.

There are various iron compounds used in the present invention, including ferrous chloride, ferric chloride, iron citrate, iron acetate, ferrous bromide, ferric bromide, and iron oxalate. , ferrous nitrate, ferric nitrate, iron hydroxide, iron sulfate, ferrous ammonium sulfate, ferric ammonium sulfate, etc. can be used.

However, iron compounds from the pond may be used as long as they can form a chelate with the phenol carboxylic acids.

The iron compounds may be used alone or in the form of an aqueous solution of a mixture of two or more thereof.

Further, the iron compound is preferably one that is easily ionized because it undergoes a chelation reaction with phenol carboxylic acids, and therefore it is preferable to use a water-soluble one.

The concentration of the iron compound aqueous solution is usually 1 to 50% by weight.

When the above concentration is 1% by weight or less, the concentration of iron ions in the iron compound aqueous solution decreases, and the chelation reaction with the phenol carboxylic acids having chelate-forming ability present on the coating surface becomes difficult to occur. The desired effect cannot be expected.

On the other hand, if the concentration exceeds 50% by weight, water solubilization becomes difficult, and workability when treating a coating film with the iron compound aqueous solution becomes difficult.

Further, it is also difficult to dispose of unreacted iron compounds, which is not preferable.

Examples of the method for treating a coating film with an aqueous iron compound solution in the present invention include a dipping method in an aqueous iron compound solution, a method of applying an aqueous iron compound solution by brushing, air spraying, shower coating, and roll coating. Can be mentioned.

The treatment with the iron compound aqueous solution is carried out after coating and drying the water-based epoxy resin composition, but if the drying is by forced drying such as heating, it is more preferable to carry out the treatment immediately after drying, and if the drying is performed by drying at room temperature. In this case, it is preferable to carry out the treatment after 24 hours have elapsed.

In other words, with the exception of treatments when the paint film is still wet, it can be done at any time, but it is not recommended to do it long after the paint film has completely cured, as this will lengthen the treatment time. .

In the treatment with an aqueous iron compound solution, the temperature of the aqueous solution is reduced to about 10
Preferably, the temperature is ~50°C and the time is 60 minutes or less.

However, the temperature and time are not limited to these.

After the treatment, by drying at room temperature or forced drying,
The phenol carboxylic acids present on the coating surface and the iron ions in the iron compound aqueous solution cause a chelation reaction, forming a dark brown iron chelate layer on the coating surface.

Furthermore, after the above treatment, washing with water may be performed for the purpose of washing away excess iron compounds, if necessary.

In the thus obtained coating film, the phenol carboxylic acids present in the layer close to the iron base surface undergo a chelation reaction with the base iron surface, and the phenol carboxylic acids present in the coating film surface layer react with iron ions in the iron compound aqueous solution. It has undergone a chelation reaction, and therefore has excellent corrosion resistance such as moisture resistance and accelerated salt water immersion resistance, as well as excellent adhesion to top coats and suitability for top coats.

The details of the present invention will be explained below with reference to Examples.

"Part" or "percent" is expressed as "part by weight" or "percent by weight."

Example 1 30 parts of talc, 10 parts of precipitated barium sulfate, 1 part of red iron
0 parts and 30 parts of water were mixed together using a disper.

Bisphenol type epoxy resin [trade name Epicote 828 manufactured by Shell Kagaku ■, epoxy equivalent weight 1 84-1 94
320 parts were emulsified in 8 parts of water using 2 parts of a nonionic surfactant [trade name Newcol N723, manufactured by Nippon Nyukazai ■].

The obtained epoxy resin emulsion was mixed with the above pigment mixture to form a main ingredient.

On the other hand, 100 parts of polyamide resin [trade name Tomide 2500 manufactured by Fuji Kasei Kogyo ■; amine value 330±20], 15 parts of gallic acid, and 50 parts of water were stirred and mixed at room temperature for 1 hour to cure an amino acid having chelate-forming ability. obtained the drug.

8. An amine curing agent having chelate forming ability with the main agent.
A water-based epoxy resin composition having chelate-forming ability used in the present invention was obtained by mixing in a ratio of 471 6 (weight ratio).

The composition was diluted with water to a volume of 10 to 20 boids (Lion viscometer (rotor A1)), then air sprayed onto a sandblast plate (1.6 x 50 x 50 pairs) and kept in a constant temperature room (20°C, 75°C) for 3 days. %RH)
A cured coating of 50 microns was obtained.

The thus coated sandblast plate was treated with 20% ferric chloride.
% aqueous solution (liquid temperature 20°C) for 15 minutes,
The surface of the coating took on a dark brown color, indicating that a chelation reaction had taken place.

Then, after washing with water, it was dried in a constant temperature room (20° C., 75% RH) for 4 days, and a performance test was conducted.

The performance test results of the coating film thus obtained are shown in Table 1.

On the other hand, the suitability for various top coat paints was investigated and the results were excellent.

Example 2 A cured coating film of 150 microns was obtained in the same manner using the composition of Example 1.

When immersed for 15 minutes in a 15% ferrous ammonium sulfate aqueous solution (liquid temperature 20° C.) in the same manner as in Example 1, the surface of the coating took on a dark brown color indicating that a chelation reaction had taken place.

After washing with water, store in a constant temperature room (20°C, 75% RH) for 4 days.
It was dried inside and a performance test was conducted.

The performance test results of the coating film are shown in Table 1.

Example 3 The main ingredient of the test composition was prepared in the same manner as in Example 1.

On the other hand, 80 parts of polyamide resin [same as Example 1], 20 parts of amine adduct resin [trade name: Adeka Hardener EH531, manufactured by Asahi Denka ■; active hydrogen equivalent: 110], 2 parts of gallic acid.
0 parts and 50 parts of water were stirred and mixed at 40° C. for 1 hour to obtain an amino curing agent composition having chelate-forming ability.

8. Amino curing agent having chelate forming ability with the main agent.
3717 (weight ratio) to obtain a water-based epoxy resin composition having chelate-forming ability used in the present invention.

After adjusting the viscosity of the composition with water, a polished mild steel plate (0.8x70x150M) was polished with #80 sandpaper.
Brush paint on top and store in constant temperature room (20℃, 75%RH) for 3 days.
A cured coating film of 150 microns was obtained by drying in a vacuum chamber.

A 15% aqueous solution of ferrous chloride was applied onto the coating film using a brush at room temperature (20°C), and when it was left to stand for 20 minutes, the coating film surface took on a dark brown color indicating that a chelation reaction had taken place.

Then, wash the bond with water and store it in a constant temperature room (20℃, 75% R, H) for 4 days.
Performance tests were conducted after drying inside.

The performance test results of the coating film are shown in Table 1.

Example 4 The main ingredient of the test composition was prepared in the same manner as in Example 1.

On the other hand, polyamide resin [product name DS manufactured by Daiichi General
X-1280; amine value 220] 100 parts and gallic acid n
- carrying out a dealcoholization reaction of 15 parts of provil at a temperature of 140 to 150 °C in the presence of an inert gas (nitrogen gas),
The reaction was terminated when there was no more distillate, and an amine-based curing agent having chelate-forming ability was obtained.

100 parts of the amino curing agent was dissolved in ethylene glycol monobutyl ether to prepare a curing agent solution whose nonvolatile content was adjusted to 70%.

The base resin and the amine curing agent solution having chelate-forming ability were mixed in a ratio of 8 4/1 6 (weight ratio) to obtain a water-based epoxy resin composition having chelate-forming ability used in the present invention.

After adjusting the viscosity of the composition with water, a polished mild steel plate (Example 3
(same as 75°C) and placed in a constant temperature room (20°C, 75°C) for 5 days.
%RH) to give a cured coating of 150 microns.

The coating film was treated with 25 strips of ferric ammonium sulfate aqueous solution at room temperature (20°C) using a brush, and when left for 30 minutes, the coating surface took on a dark brown color indicating that a chelation reaction had taken place.

Then, after washing with water, store in a constant temperature room (20℃, 75%RH) for another 2 days.
) for performance testing.

The performance test results of the coating film are shown in Table 1.

Comparative Example 1 The main ingredient prepared in the same manner as in Example 1 was used.

The curing agent composition was polyamide resin 10 used in Example 1.
It was prepared by stirring and mixing 0 parts and 50 parts of water at room temperature for 1 hour.

The base agent and curing agent composition were mixed at a ratio of 85/15 (weight ratio).

A coating film was formed using the composition in the same manner as in Example 1, and the coating film was further treated with an aqueous ferric chloride solution to perform a performance test. The results are shown in Table 2.

Comparative Example 2 The test composition used in Comparative Example 1 was used.

A coating film was formed using the composition in the same manner as in Example 2, and after further treatment with a 5% aqueous solution of ferrous alemonium sulfate, a performance test of the coating film was conducted, and the results are shown in Table 2. Ta.

Comparative Example 3 The main ingredient prepared in the same manner as in Example 1 was used.

The curing agent composition was the polyamide resin 80 used in Example 3.
1 part, 20 parts of amine adduct resin and 50 parts of water at 40°C.
The mixture was prepared by stirring and mixing for 1 hour.

The base agent and curing agent composition were mixed at a ratio of 84,716 (weight ratio).

A coating film was formed using the composition in the same manner as in Example 3, and after further treatment with a 15% ferrous chloride aqueous solution, a performance test of the coating film was conducted, and the results are shown in Table 2. .

Comparative Example 4 The main ingredient prepared in the same manner as in Example 1 was used.

As a curing agent, the polyamide resin used in Example 4 was adjusted to have a non-volatile content of 70% with ethylene glycol monobutyl ether.

The main agent and curing agent solution were mixed at a ratio of 8 3/1 7 (weight ratio).

A coating film was formed using the mixture in the same manner as in Example 4, and after further treatment with a 25% aqueous solution of ferric ammonium sulfate, a performance test of the coating film was conducted, and the results are shown in Table 2. Ta.

Note 1) The time required for the paint film to start to rust or blister after being left at 50°C and 97% RH or higher is shown.

Note 2) The test was conducted according to the JIS-Z-2371 salt spray test method, and the time until blisters start to appear is shown.

Note 3) Sodium chloride 5051, 30% hydrogen peroxide solution 5
g, 10 ml of acetic acid was dissolved in 1 liter of water and immersed in the solution at 60°C for 8 hours and then at room temperature for 16 hours.
The number of cycles is shown as the number of cycles until blisters, rust, and resin elution begin to appear on the paint film.

It is clear from the results of the coating film performance test that the coating film obtained by the method of the present invention exhibits excellent performance in terms of moisture resistance, salt spray resistance, and accelerated salt water immersion property.

Claims (1)

[Scope of Claims] 11) An aqueous dispersion of an epoxy resin having at least two or more epoxy groups in one molecule, and an amino acid containing two or more nitrogen atoms having at least an active hydrogen atom in one molecule of ID. An amine-based curing agent with chelate-forming ability obtained by bonding phenolic carboxylic acids to a curing agent;
Applying a water-based epoxy resin composition consisting of
A method for forming a coating film having an iron chelate layer, which comprises treating the surface of the obtained coating film with an aqueous iron compound solution after drying. 2. The phenolic carboxylic acid is one or a mixture of two or more of protocatechuic acid, gallic acid, and an alkyl ester of protocatechuic acid or gallic acid having 1 to 12 carbon atoms in the alkyl group. form or method of coating. 3 The iron compound is one or two of ferrous chloride, ferric chloride, ferrous ammonium sulfate, and ferric ammonium sulfate.
The method for forming a coating film according to claim 1, which is a mixture of more than one species. 4. The method for forming a coating film according to claim 1, wherein the iron compound aqueous solution has a concentration of 1 to 50 weight percent.