CN103717686A - Aqueous composition for metal surface treatment, method for metal surface treatment using composition, and method for producing metal material having film, as well as metal surface treatment film using same - Google Patents

Abstract

[Problem] To provide means for dramatically improving Bi precipitation and preventing deterioration of metal film appearance in the form of fisheyes, dimples, and the like. [Solution] An aqueous composition for metal surface treatment is characterized in being an aqueous composition for metal surface treatment containing a cationic resin emulsion, wherein the dispersoid of the cationic resin emulsion comprises an amino compound of a modified epoxy resin, a block polyisocyanate, and a tin compound represented by formula 1 (1) (where in formula 1, m is 4 or greater and n is between 0 and 10), and the dispersion medium of the cationic resin emulsion contains Bi ions.

Description

Aqueous composition for metal surface treatment, metal surface treatment method using the same, method for producing metal material with film, and metal surface treatment film using the same

technical field

The present invention relates to an aqueous composition for metal surface treatment capable of forming a film capable of imparting excellent corrosion resistance and coating appearance on metal materials, especially metal structures with complex shapes, a metal surface treatment method using the same, and a metal surface treatment method with The manufacturing method of the metal material of a film, and the metal surface treatment film which used them.

Background technique

Conventionally, as a method for imparting excellent corrosion resistance to various metal materials, especially metal structures having complicated shapes, electrodeposition coating having high throwing properties has generally been used. However, if only the electrodeposition coating film obtained by electrodeposition coating is used, the required corrosion resistance cannot be obtained in many cases. Therefore, it is standard practice to apply zinc phosphate-based chemical conversion treatment in the previous stage of electrodeposition coating. Formed coated surface treatment.

Electrodeposition coating can be roughly divided into anionic electrodeposition coating in which a coating film is deposited by anodic electrolysis of the object to be coated in a water-based paint containing an anionic resin emulsion, and an anionic electrodeposition coating in which a water-based paint containing a cationic resin emulsion Cathodic electrodeposition coating in which the coated object is subjected to cathodic electrolysis to precipitate the coating film. However, for improving the corrosion resistance of iron-based metal materials, it is advantageous that there is no need to worry about cations leached from the base metal into the coating during electrolytic treatment. Electrodeposition coating is widely used in cationic electrodeposition coating for automobile bodies, auto parts, home appliances, building materials, etc., which are metal structures mainly composed of iron-based materials.

Cationic electrodeposition coating has a long history in the market, and in the past, rust prevention was ensured by compounding chromium compounds or lead compounds. However, even in this way, the rust resistance is not sufficient, so surface treatment such as zinc phosphate-based chemical conversion treatment must be performed. Currently, chromium compounds and lead compounds cannot be used substantially due to environmental standards, especially European ELV standards. Therefore, alternative components are being studied, and bismuth compounds are found to be effective. Specifically, the patent documents listed below are disclosed.

Patent Document 1 (Japanese Patent Application Laid-Open No. 5-32919) discloses a resin composition for electrodeposition coatings, which is characterized by containing at least one kind of pigment coated with a bismuth compound.

Patent Document 2 (WO99/31187) discloses a cationic electrodeposition coating composition characterized by comprising an aqueous dispersion paste containing an aqueous dispersion in which an organic acid-modified bismuth compound exists in a water-insoluble form.

Patent Document 3 (JP 2004-137367 ) discloses a cationic electrodeposition paint characterized by comprising a colloidal bismuth metal, and a resin composition having a sulfonium group and a propargyl group.

Patent Document 4 (JP 2007-197688) discloses an electrodeposition paint containing particles of at least one metal compound selected from bismuth hydroxide, zirconium compounds, and tungsten compounds. It is characterized in that the metal compound has a thickness of 1 to 1000 nm.

Patent Document 5 (Japanese Patent Application Laid-Open No. 11-80621) discloses a cationic electrodeposition coating composition characterized by containing an aqueous solution of bismuth salt of aliphatic alkoxycarboxylate.

Patent Document 6 (Japanese Patent Laid-Open No. 11-80622) discloses a cationic electrodeposition coating composition, which is an aqueous solution of bismuth salts of two or more organic acids, and is characterized in that it contains at least one of the organic acids It is an aqueous solution of bismuth salts of organic acids of aliphatic hydroxycarboxylic acids.

Patent Document 7 (Japanese Patent Laid-Open No. 11-100533) discloses a cationic electrodeposition coating composition characterized by containing bismuth lactate formed using lactic acid containing 80% or more of the L-isomer among optical isomers.

Patent Document 8 (Japanese Patent Laid-Open No. 11-106687) discloses a cationic electrodeposition coating composition, which is an aqueous solution of bismuth salts of two or more organic acids, and is characterized in that it contains at least one of the organic acids It is an aqueous solution of organic acid bismuth salts of aliphatic alkoxycarboxylic acids.

These patent documents can be roughly divided into patent documents 1-4 and patent documents 5-8. That is, Patent Documents 1 to 4 are characterized in that a bismuth compound or metal bismuth that is insoluble in water-based paint is dispersed, and Patent Documents 5 to 8 are characterized in that at least the bismuth compound is dissolved to the extent that no solid content remains. That is, it is added to the paint after being made into the state of Bi ions.

However, the bismuth compounds in these patent documents always function as substitutes for chromium compounds or lead compounds, and sufficient corrosion resistance cannot be obtained without surface treatment such as zinc phosphate-based chemical conversion treatment. In fact, these patent documents only disclose examples that presuppose the combination with zinc phosphate-based chemical conversion treatment.

On the other hand, recently, techniques for further improving corrosion resistance by methods other than bismuth compounds are being studied, and sufficient corrosion resistance can be ensured by one-layer coating without surface treatment such as zinc phosphate-based chemical conversion treatment. corrosion resistance.

For example, in Patent Document 9 (Japanese Patent Application Laid-Open No. 2008-274392), a method for forming a surface treatment film is disclosed, which is to apply a film-forming agent on a metal substrate in a multi-step energization method in at least two stages. A method of forming a film, characterized in that (i) the film forming agent contains a zirconium compound of 30 to 20,000 ppm in terms of the total metal amount (in terms of mass) and a compound selected from titanium, cobalt, vanadium, tungsten, and molybdenum used as needed. , copper, zinc, indium, aluminum, bismuth, yttrium, lanthanide metals, alkali metals, and alkaline earth metals (a) compound; and 1 to 40% by mass of the resin component, (ii) obtained by The metal base material is used as the cathode and energized at a voltage of 1 to 50V (V1) for 10 to 360 seconds to carry out the first stage of coating, and then the metal base is used as a cathode and energized at a voltage of 50 to 400V (V2) for 60 to 60 seconds. 600 seconds for coating after the second stage, and (iii) the difference between the voltage (V2) and the voltage (V1) is at least 10V.

In addition, Patent Document 10 (Japanese Unexamined Patent Publication No. 2008-538383) discloses a method for forming a multilayer coating film, which includes a dipping step of dipping an object to be coated into an aqueous coating composition containing (A ) a rare earth metal compound, (B) a matrix resin having a cationic group, and (C) a curing agent for an aqueous coating composition, wherein the amount of (A) the rare earth metal compound contained in the aqueous coating composition is relative to the solid content of the coating Said conversion is 0.05 to 10% by weight of rare earth metals; the pretreatment process, in the water-based coating composition, applying a voltage of less than 50V with the object to be coated as the cathode; and the electrodeposition coating process, in the water-based coating composition , Apply a voltage of 50-450V with the object to be coated as the cathode.

Patent Document 11 (Japanese Patent Laid-Open No. 2010-24471) discloses a multilayer coating film forming method in which a metal substrate is immersed in an aqueous solution of an organic acid salt or an inorganic acid salt containing bismuth. The metal substrate is electrolyzed as a cathode to form a bismuth compound coating, and as a second step, an electrodeposition coating is formed on the coating by cationic electrodeposition coating.

The treatment liquid composition applied in surface treatment such as zinc phosphate chemical conversion treatment described in these patent documents 1 to 8, and those described in patent documents 9 to 11 can ensure sufficient surface treatment without surface treatment such as zinc phosphate chemical conversion treatment. Corrosion-resistant treatment liquid compositions contain catalysts for accelerating crosslinking and curing reactions of water-based resins as a common technology, contributing to the improvement of crosslinking density, the reduction of curing temperature, and the like.

As catalysts, lead compounds and tin compounds are generally used. Among these, tin compounds are generally used due to the toxicity of lead compounds in recent years, but compounds that can be expected to have a catalytic effect may be used in combination as in the present invention or Patent Document 9.

The contained tin compounds can be roughly classified into two types.

Examples of Patent Documents 1, 4, 9, and 11, and Patent Documents 12 to 14 show the use of a solid tin compound.

Examples of Patent Documents 5 to 8 and Patent Documents 15 to 17 disclose the use of a liquid tin compound.

Examples of solid tin compounds include the use of dibutyltin oxide, dioctyltin oxide, monobutyltin oxide, and monooctyltin oxide.

Examples of the liquid tin compound include the use of dibutyltin diacetate, aromatic carboxylic acid ester of alkyltin, alkyltin fatty acid salt, alkyltin (alkylmercaptan), and the like.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 5-32919

Patent document 2: WO99/31187 publication

Patent Document 3: Japanese Unexamined Patent Publication No. 2004-137367

Patent Document 4: Japanese Patent Laid-Open No. 2007-197688

Patent Document 5: Japanese Patent Application Laid-Open No. 11-80621

Patent Document 6: Japanese Patent Application Laid-Open No. 11-80622

Patent Document 7: Japanese Patent Application Laid-Open No. 11-100533

Patent Document 8: Japanese Patent Application Laid-Open No. 11-106687

Patent Document 9: Japanese Patent Laid-Open No. 2008-274392

Patent Document 10: Japanese Patent Laid-Open No. 2008-538383

Patent Document 11: Japanese Unexamined Patent Publication No. 2010-24471

Patent Document 12: Japanese Patent Application Laid-Open No. 5-65438

Patent Document 13: Japanese Patent Laid-Open No. 2008-231142

Patent Document 14: Japanese Patent Laid-Open No. 2004-269582

Patent Document 15: Japanese Patent Publication No. 61-9986

Patent Document 16: Japanese Patent Application Laid-Open No. 5-65439

Patent Document 17: Japanese Unexamined Patent Publication No. 2004-123942

Contents of the invention

The problem to be solved by the invention

The inventors of the present invention have conducted various studies on these conventional technologies, and as a result, have come to the conclusion that in order to apply a single layer on a metal material to form and impart a sufficient For the corrosion-resistant film, the most effective way is still to use Bi. In addition, the effect of Bi was studied again.

In addition, as the function and effect of Bi, attention has been paid to the function as a curing catalyst of the resin and the anticorrosion effect of the base metal. In the conventional technology, although the function as a curing catalyst can be expected to a certain extent, the function of the base metal The anti-corrosion effect is extremely insufficient, and only by maximizing this effect can the solution of the problem be brought about, and research has been advanced accordingly.

For the anti-corrosion effect of the base metal, Bi must exist on the surface in contact with the metal, that is, it must exist in the interface between the base metal surface and the film. On the surface, Bi sufficient to exhibit corrosion resistance does not exist in advance.

In addition, the inventors of the present invention have confirmed that the following reaction mechanism is most suitable, that is, in the same bath solution, Bi is reduced and precipitated by low-voltage cathodic electrolysis, and then the diffusion of Bi ions becomes insufficient by high-voltage cathodic electrolysis, This increase in pH leads to precipitation of cationic resins.

Specifically, the film thus obtained naturally has the curing catalytic ability of the resin possessed by Bi, and it was confirmed that the corrosion resistance of the base metal can be sufficiently improved due to the presence of Bi at a higher concentration on the surface of the base metal.

However, the conventional method has the following problems. As mentioned above, in this method (multi-step electrolysis method), the process of reducing and precipitating Bi by low-voltage cathodic electrolysis and then precipitating cationic resin is adopted. Here, improving the precipitation of Bi leads to early acquisition of the amount of precipitation of Bi sufficient to obtain the required corrosion resistance, thereby shortening the time of the low-voltage processing state, that is, improving productivity or reducing costs. Therefore, the first object of the present invention is to provide a method for significantly improving the precipitation of Bi. In addition, in this method (multi-step electrolysis method), depending on the conditions, etc., the appearance of the coating film may deteriorate, such as cratering or graining. Therefore, the second object of the present invention is to provide a method for preventing deterioration of the appearance of a coating film such as shrinkage and graining.

method used to solve the problem

The inventors of the present invention examined various cationic resins, curing agents, and curing catalysts, and examined combinations that can achieve the above-mentioned first and second objects. As a result, the inventors of the present invention have found that by using a cationic emulsion as a composition, while allowing bismuth ions to exist in the dispersant of the emulsion, a specific cationic resin, curing agent, and curing agent are selected as the dispersant component of the emulsion. The combination of catalysts can achieve the stated purpose, thereby completing the present invention. Specifically, it is the following inventions (1) to (10).

The present invention (1) provides an aqueous composition for metal surface treatment, which contains a cationic resin emulsion, and is characterized in that the dispersant of the cationic resin emulsion contains amides of modified epoxy resins (especially bisphenol type) , blocked polyisocyanate and the tin compound shown in Formula 1:

Here, in Formula 1, m is 4 or more, n is 0 or more and 10 or less, and the dispersant of the cationic resin emulsion contains Bi ions. Furthermore, pigment particles may be contained as needed. In addition, the dispersoid of the emulsion may contain resins other than amides of modified epoxy resins (for example, other cationic resins, nonionic resins, etc.).

The present invention (2) provides the aqueous metal surface treatment composition of the following invention (1), wherein m in Formula 1 is 7 or more.

The present invention (3) provides the aqueous composition for metal surface treatment of the following invention (1) or (2), wherein m in Formula 1 is 7.

The present invention (4) provides the aqueous metal surface treatment composition of the following invention (3), wherein m in Formula 1 is 7 and n is 0.

The present invention (5) provides an aqueous metal surface treatment composition according to any one of the following inventions (1) to (4), wherein the content of the tin compound in the entire composition is 0.01 to 1% by weight.

The present invention (6) provides the aqueous metal surface treatment composition according to any one of the following inventions (1) to (5), which is characterized in that it is a combination used in a multi-step energization method in the same bath things.

The present invention (7) provides a metal surface treatment method, which is characterized in that the metal material to be treated is immersed in the aqueous composition of any one of the inventions (1) to (6), and the metal material to be treated is used to The electrolytic treatment process as the cathode deposits a film on the metal material.

The present invention (8) provides the following metal surface treatment method of the above-mentioned invention (7), characterized in that the electrolytic treatment step includes: a first step of immersing the metal material whose surface has been cleaned in the above-mentioned invention (1) ) to (6) in any one of the aqueous composition, or while impregnated, using the metal material as a cathode, electrolysis at a voltage below 15V for 10 to 120 seconds; the second step, after the first step Then carry out in the same bath, and electrolyze at a voltage of 50-400V for 30-300 seconds.

The present invention (9) provides a method for producing a metal material with a film, characterized by comprising the electrolytic treatment step of the above-mentioned invention (7) or (8).

The present invention (10) provides a metal surface treatment film obtained by the production method of the above-mentioned invention (9), characterized in that 20 to 250 mg/m ² of Bi is attached as metal Bi and Bi oxide, and the total film thickness is It is 5 to 40 μm, and has a Bi deposition distribution in which the Bi deposition amount on the metal material side, namely B, is 55% or more (B/A≧55%) relative to the total Bi deposition amount, A, from the center of the film thickness.

Description of drawings

FIG. 1 is a graph showing the relationship between the amount of Bi deposited when a constant voltage is applied and the application time for the aqueous compositions of Examples and Comparative Examples.

FIG. 2 is a graph showing the distribution of B/A when the aqueous composition of Example 1 is used.

Detailed ways

"Metal Surface Treatment Methods"

(Suitable)

The aqueous composition for metal surface treatment of the present invention is used for the purpose of preventing various metals from being corroded. The metal material is not particularly limited, but steel materials such as cold-rolled steel sheets, hot-rolled steel sheets, casting materials, and steel pipes, materials subjected to zinc-based plating and/or aluminum-based plating on these steel materials, and aluminum alloys plate, aluminum casting material, magnesium alloy plate, magnesium casting material, etc. It is especially suitable for metal structures with complex shapes, such as automobile bodies, automobile parts, home appliances, building materials, etc., which are metal structures mainly composed of iron-based materials.

(metal surface treatment method)

The metal surface treatment method of the present invention includes the step of depositing a film on the surface of the metal material by using the above-mentioned aqueous metal surface treatment composition in an electrolytic treatment process using the metal material to be treated as a cathode. More preferably, the metal surface treatment method of the present invention includes the steps of performing electrolytic treatment on the metal material whose surface has been cleaned in order to deposit a film on the metal material, and washing with water after the electrolytic treatment step. and baking process. Hereinafter, the characteristic electrolytic treatment step and baking step in this method will be described in detail.

＜Electrolytic treatment process＞

The electrolytic treatment process (cathode electrolysis) includes: the first process, in the state of immersing the metal material in the aqueous composition for metal surface treatment, electrolysis at a voltage below 15V for 10 to 120 seconds; the second process, The above-mentioned first process is followed by implementation, in the state of immersing the metal material in the water-based composition for metal surface treatment, electrolysis is performed at a voltage of 50-400V for 30-300 seconds. Here, the second process is at the The first step is followed by implementation in the same bath.

Here, the first step is mainly performed for preferentially adhering Bi, and the second step is mainly performed for preferentially precipitating a cationic resin. In order to obtain sufficient corrosion resistance, it is necessary to have Bi that is in direct contact with the metal material, that is, there needs to be an interface Bi that exists at the interface between the metal material and the film, so the sequence and conditions of the first step and the second step are extremely important.

Preferably, the voltage in the first step is 15 V or less (the lower limit value is not particularly limited, but is, for example, 0.01 V), and electrolysis is performed for 10 to 120 seconds. When the voltage is below 0V, that is, when the metal material is used as the anode for electrolysis, the metal material dissolves into the composition, which not only reduces the stability of the composition, but also does not sufficiently adhere to improve corrosion resistance. Say Required interface Bi. When the upper limit is exceeded, resin precipitation starts before Bi preferentially precipitates on the metal surface, and thus sufficient corrosion resistance cannot be obtained.

When the treatment time is less than the lower limit, sufficient interfacial Bi cannot be precipitated, and when it is more than the upper limit, the adhesion of the film may be impaired due to excessive adhesion of interfacial Bi.

Preferably, the voltage of the second step is 50-400V, and the electrolysis is performed for 30-300 seconds. When the voltage is below the lower limit, the amount of deposition of the resin film becomes insufficient, and if it is above the upper limit, not only is it economically disadvantageous due to excessive deposition of the resin film, but also the appearance of the completed film may be impaired. Case.

When the second step is performed after the first step, the voltage does not need to be increased instantaneously, and the effects of the present invention will not be impaired even if the voltage is gradually increased. In addition, neither the first step nor the second step requires constant voltage.

〈Baking process〉

Next, the baking step will be described. The baking method is not particularly limited, and examples thereof include a method of baking in an oven. In addition, the baking temperature is, for example, 100°C to 200°C. In addition, although the baking time also depends on the shape, size, and material of the metal material to be processed, it is usually 10 to 30 minutes.

Next, the aqueous composition for metal surface treatment of the present invention will be described in detail.

"Water-based composition for metal surface treatment"

The aqueous composition for metal surface treatment of the present invention is an aqueous composition for metal surface treatment containing a cationic resin emulsion, and is characterized in that the dispersant of the cationic resin emulsion must contain an amide of a modified epoxy resin as a matrix resin , Blocked polyisocyanate as a curing agent and a tin compound with a specific structure as a curing catalyst (or as a co-catalyst), and the dispersant of the cationic resin emulsion contains Bi ions (e.g. equivalent to the F2 agent used as an electrodeposition coating) . Here, the aqueous composition for metal surface treatment of the present invention may optionally contain, for example, a pigment component. In this case, this pigment component corresponds to F1 agent used as an electrodeposition paint, for example. Each component will be described in detail below.

<Composition Components: Dispersion of Cationic Resin Emulsion>

(Composition constituents: dispersant of cationic resin emulsion/cationic resin)

※Element

The matrix resin of the present invention must contain, as the cationic resin, a resin obtained by cationizing the matrix resin of the modified epoxy resin with amine. Here, among amides of modified epoxy resins, bisphenol-type and novolac-type modified epoxy resins are preferable, and bisphenol-type modified epoxy resins are most preferable. In addition, the reason for using the modified component is as follows. Usually, if only these components of the matrix resin are used, the properties of the resulting film are not satisfactory. Therefore, a method of adding a compound having a structure different from that of the matrix resin for modification is employed. As an example, if an unmodified bisphenol A type epoxy resin is used, although it is very rigid, it lacks flexibility and cannot obtain sufficient performance. Specifically, a film having both hardness and flexibility can be obtained by adding a polyol compound (described in detail later) or the like.

Here, in order to impart cationicity to the resin, a method of introducing an amino group into the resin skeleton (especially the terminal) is typically used (for example, in the case of an epoxy resin, a glycidyl group at the terminal is added to a glycidyl group containing an amino group). compound method). In addition, this point will be described in detail later.

Hereinafter, amides of bisphenol-type modified epoxy resins that are particularly suitable as cationic resins will be described in detail. Here, particularly suitable amides of bisphenol A-type modified epoxy resins are modified resins, epoxy resins with an epoxy equivalent of 180 to 2500, compounds containing primary and/or secondary amino groups, or compounds containing primary and/or secondary amino groups as raw materials. Amide of a modified epoxy resin obtained by using bisphenol A and reacting them. Hereinafter, each component is demonstrated.

＊Raw material of bisphenol A type modified epoxy resin

First, as a modified resin, a polyol compound is generally used. These are used for the purpose of improving the plasticity of epoxy resins and the like. Specifically, polyol resins such as polyester polyols, polyether polyols, polyurethane polyols, and acrylic polyols, aromatic condensation compounds having hydroxyl groups added to terminals, and the like can be mentioned. More specifically, polycaprolactone diol, polyethylene glycol, polypropylene glycol, xylene formaldehyde resin having a phenolic hydroxyl group, etc. are mentioned. Modification with these compounds is a technique that has been used until now because the hydroxyl groups of these compounds can easily react with the glycidyl ether portion of the epoxy resin. In the modified epoxy resin, these modified resins are contained in an amount of 5 to 30% by weight.

Next, as an epoxy resin having an epoxy equivalent of 180 to 2500, an epoxy resin obtained by reacting a polyhydric phenol compound with an epihalohydrin such as epichlorohydrin is particularly preferable from the viewpoint of corrosion resistance of the coating film. Among them, the most suitable is bisphenol A diglycidyl ether obtained by the reaction of bisphenol A and epichlorohydrin. In addition, epoxy resins polymerized with bisphenol A as the basic structure also exhibit the same effect, and are most suitable as resins with an epoxy equivalent of 180 to 2,500, preferably 180 to 2,000, and more preferably 180 to 1,500. . In the modified epoxy resin, these epoxy resins are contained in an amount of 5 to 30% by weight.

In addition, bisphenol A is used in order to control the molecular weight of the skeleton of an epoxy resin. Using this content (addition amount), the epoxy equivalent can be controlled. The modified epoxy resin contains 5 to 30% by weight of bisphenol A.

In addition, a compound containing a primary and/or secondary amino group is a cationization-imparting component for introducing an amino group into an epoxy resin matrix and cationizing the epoxy resin. The amine used here is an amine containing at least one active hydrogen that reacts with an epoxy group. Examples of amino group-containing compounds used for this purpose include monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, Mono- or di-alkylamines such as baseamine and dibutylamine; monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, monomethylaminoethanol, monoethylamine Ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethylenediamine Alkylene polyamines such as triamine and triethylene tetramine and ketimides of these polyamines; alkylene imines such as ethylene imine and propylene imine; cyclic compounds such as piperazine and morpholine Amines etc. The modified epoxy resin contains 0.5 to 20% by weight of a compound containing a primary and/or secondary amino group.

*Manufacturing method of amino compound of bisphenol A modified epoxy resin

First, predetermined amounts of modified resin and epoxy resin are mixed and heated and stirred. The heating temperature is preferably 70 to 100°C. After each raw material is dissolved, a catalyst is added, and the heating temperature is increased to carry out synthesis. Catalysts typically use tertiary amines such as dimethylbenzylamine. The synthesis temperature is generally controlled at 120°C to 170°C.

By adjusting the synthesis temperature and time, a modified epoxy resin having a predetermined epoxy equivalent can be synthesized. The epoxy equivalent was calculated by the epoxy equivalent measurement specified in JIS K7236. In this case, the epoxy equivalent is preferably 800-10000, more preferably 800-5000, and most preferably 800-3000. The greater the epoxy equivalent, the more difficult it is to emulsify during emulsion production.

Next, a primary and/or secondary amino group-containing compound is added to the synthesized modified epoxy resin. Amides of modified epoxy resins can be obtained by adding compounds containing primary and/or secondary amino groups and performing synthesis for 1 to 3 hours while maintaining the modified epoxy resin at 60°C to 110°C.

＊Cationization of modified epoxy resin

A neutralizing acid was added to the synthesized amino compound of the modified epoxy resin, stirred and mixed, and then diluted with water to prepare a resin emulsion of a predetermined concentration. As the neutralizing acid, formic acid, acetic acid, lactic acid, sulfamic acid and the like can be used.

At this time, it is preferable to add a curing agent, a curing catalyst, an organic solvent, etc. before adding the neutralizing acid. By pre-adding in this way, a uniform emulsion can be obtained.

※Content of cationic resin in dispersoid

The content of the cationic resin (especially the amino compound of the modified epoxy resin) in the dispersoid of the emulsion is preferably 30 to 80% by weight based on the total weight of the dispersoid (including the total weight of the organic solvent) .

(composition components: dispersant/curing agent of cationic resin emulsion)

※Element

The curing agent contained in the dispersoid of the cationic resin emulsion of the present invention is a blocked polyisocyanate. A blocked polyisocyanate is an approximately stoichiometric addition reaction product of a polyisocyanate compound and an isocyanate blocking agent. Examples of the polyisocyanate compound used here include toluene diisocyanate, xylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4' -Diisocyanate (commonly referred to as "MDI"), crude MDI, bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone Aromatic, aliphatic or alicyclic polyisocyanate compounds such as diisocyanates; cyclized polymers of these polyisocyanate compounds, isocyanate biuret substances; ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, Terminal isocyanate-containing compounds obtained by reacting low-molecular-weight active hydrogen-containing compounds such as castor oil with excess of these isocyanate compounds. These can be used individually or in combination of 2 or more types, respectively.

On the other hand, the isocyanate-blocking agent is a substance that is added to the isocyanate group of the polyisocyanate compound to block it. In addition, it is desirable that the blocked polyisocyanate compound generated by the addition is stable at normal temperature, and is stable when heated to At the baking temperature of the coating film (usually about 100 to about 200°C), the blocking agent can be dissociated to regenerate free isocyanate groups.

As an end-capping agent that satisfies this condition, for example, lactam-based compounds such as ε-caprolactam and γ-butyrolactam; oxime-based compounds such as methyl ethyl ketone oxime and cyclohexanone oxime; Phenol compounds such as phenol; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenyl carbitol and methyl phenyl carbitol; ethylene glycol monobutyl ether, Ether alcohol-based compounds such as diethylene glycol monoethyl ether, etc. These terminal blocking agents can be used individually or in combination of 2 or more types, respectively. In addition, in order to effectively promote the dissociation and curing reaction of the end-blocking agent, in addition, in order to generate the desired cured product, it is also possible to add a part of the isocyanate group to the backbone of the modified epoxy resin in advance, and remove the remaining The method of blocking the isocyanate group with a blocking agent.

※Content of blocked polyisocyanate in dispersoid

The blocked polyisocyanate in the dispersoid of the emulsion is preferably 5 to 40% by weight based on the total weight of the dispersoid (including the total weight of the organic solvent).

(Composition constituents: dispersoid of cationic resin emulsion/tin compound)

※Element

The tin compound contained in the dispersoid of the cationic resin emulsion of the present invention includes the tin compound represented by Formula 1. Moreover, in the present invention, the tin compound shown in Formula 1 is not necessarily limited to be used alone, and may be used in combination with a tin compound such as a dibutyltin compound such as a dibutyltin compound or a solid tin compound with m being 3 or less, or other curing catalysts.

The dispersoid of the resin emulsion contains a cationic resin or a curing agent, a curing catalyst, an organic solvent, etc. as described above, but it is considered that the hydrophobic/hydrophilic properties of components other than the cationic resin greatly contribute to the improvement of the precipitation of Bi. From one point of view, compounds in which m represented by Formula 1 is 4 or more are preferable. Tin compounds with m being 7 or more having high hydrophobicity are more preferable, among which dioctyltin compounds having m being 7 having high catalytic ability are most preferable. Furthermore, the upper limit value is 12, for example.

In addition, compounds where n is 11 or more have poor compatibility with resins, resulting in poor emulsion stability, insufficient curability, and occurrence of shrinkage cavities and pellets, so they are not suitable.

Here, a particularly suitable combination of m and n is 4≤m≤10 (more preferably 6≤m≤8) and 0≤n≤ 5 (more preferably 0≤n≤3). In addition, a more preferable combination is that the total number of m and n is 7 to 10, and the most preferable combination is that the total number of m and n is 7 (for example, dialkyltin diacetate). For example, as shown in Examples and Comparative Examples, compared with the case where dibutyltin diacetate (m=3, n=0) with low hydrophobicity is used, dioctyltin diacetate (m=0) with high hydrophobicity is used. 7. In the case of n=0), the Bi precipitation property is remarkably improved.

※Mechanism

However, when the tin compound of the above-mentioned specific structure is used in a specific system as described above, considering the mechanism by which the precipitation of Bi is significantly improved and the occurrence of cratering and graining can be prevented, it can be estimated as follows.

In the case of considering the composition of the dispersoid component in the cationic resin emulsion, the affinity with water as the medium can be obtained by utilizing the cationization ability of the amine moiety that the amide itself of the modified epoxy resin has ( emulsion). On the other hand, blocked polyisocyanate as a curing agent or tin compound as a curing catalyst has low affinity with water due to the characteristics of its chemical structure, so it is difficult to exist on the surface of the dispersoid, and it is easy to exist inside the dispersoid. That is, it can be easily predicted that it has a core-shell structure in which an amide compound of a modified epoxy resin is used as a shell and a blocked polyisocyanate or a tin compound is used as a core.

In this case, the surface state of the dispersoid changes due to the hydrophobicity/hydrophilicity of the core component. The higher the hydrophobicity of the core component, the less likely it is to exist near the surface of the dispersoid, and the easier it is to exist in the core. On the other hand, the lower the hydrophobicity, the less likely it is to exist near the surface of the dispersoid.

In normal conditions (without electrolysis), even if the amide of the modified epoxy resin is fully cationized to achieve a stabilized emulsion state, the affinity with water is low, but in components with low hydrophobicity When present near the surface of the dispersoid, the instability of the emulsion increases due to subtle changes in the cationization at the matrix interface during the first step.

Specifically, in the low-voltage electrolysis state (first step), the emulsion is concentrated, the instability is also increased, and in some cases, the resin component as the dispersoid may be precipitated.

In the present invention, when the resin component is precipitated in a low-voltage electrolysis state, the precipitation of Bi is hindered, resulting in a disadvantageous situation. Conversely, by using a highly hydrophobic tin compound that can be more present in the core than a low hydrophobic tin compound, it becomes difficult to inhibit Bi precipitation. That is, the Bi precipitation property is improved.

The structure, especially the value of m in Formula 1 has a great influence on the hydrophobicity of the tin compound. The larger the value of m is, the higher the hydrophobicity is, and it is more likely to exist in the core, that is, it is less likely to inhibit Bi precipitation, and the Bi precipitation property is improved.

The dialkyltin difatty acid ester represented by Formula 1 is liquid at normal temperature and has excellent compatibility with resins. In addition, shrinkage cavities and pellets caused by them do not occur.

Preferably: when using electrolysis to precipitate the resin and combine the dispersoids of the emulsion, the tin compound present on the outermost surface contacts with water, and at this time, the dialkyltin difatty acid ester in contact with water is hydrolyzed and easily becomes It is in the form of dialkyltin oxide. That is, fatty acid radicals are preferably fatty acid radicals that are easy to detach from the fatty acid moiety and easily move to the water phase after detachment (highly hydrophilic). In this way, by moving to the water phase side, unnecessary components contained in the coating film are reduced, thereby improving curability and improving corrosion resistance. From this point of view, n is preferably not more than the above-mentioned numerical value. On the other hand, since the higher fatty acid ester moiety is less likely to be hydrolyzed and tends to remain in the coating film, curability may decrease and corrosion resistance may decrease. For example, when evaluating curability, after pressing a gauze wetted with acetone and reciprocating it, and visually checking the appearance of the coating film, if there is a component that does not participate in curing, the component will be dissolved. In acetone, the peeling marks of the coating film can be seen in the appearance of the coating film.

※Content of tin compound in dispersoid of emulsion

If the content of the tin compound is too large, it is economically disadvantageous. Furthermore, the core portion of the core-shell structure becomes a swollen structure, and the balance with the shell portion having emulsifying ability cannot be maintained. Insufficient emulsified shells enclosing the expanded core part make the emulsion more likely to coagulate and unite, making it impossible to maintain the state of the resin emulsion.

Therefore, the ratio to the resin component serving as the shell portion also becomes important. The amount of the tin compound in the dispersoid of the emulsion is based on the total weight of the dispersoid (also including the total weight of the organic solvent), preferably 0.05 to 3% by weight as the amount of Sn, more preferably 0.05 to 2% by weight, most preferably 0.05 to 1% by weight.

Furthermore, the amount of the tin compound in the aqueous composition for metal surface treatment or the dispersoid can be grasped as the amount of Sn. When heated at a high temperature of around 600°C for a long time, the resin and other components will burn, and all the tin compounds will become tin oxide. The amount of Sn can be measured by dissolving the tin oxide obtained here with hot concentrated sulfuric acid or the like to prepare an aqueous solution, which is subjected to ICP emission analysis or ICP mass analysis.

<Composition Component: Dispersant for Cationic Resin Emulsion>

(composition components: dispersant/liquid medium for cationic resin emulsion)

As the liquid medium of the aqueous composition for metal surface treatment of the present invention (liquid medium as a dispersant for a cationic resin emulsion), an aqueous medium is preferable, and water is more preferable. Furthermore, when the liquid medium is water, the liquid medium may contain an aqueous solvent other than water (for example, water-soluble alcohols) (for example, 10% by weight or less based on the weight of the entire liquid medium).

(Composition constituents: dispersant for cationic resin emulsion/trivalent bismuth ion)

The Bi ion referred to in the present invention is not solidified in the composition, and specifically is a Bi component that constitutes a chelate with an aminopolycarboxylic acid or the like described later and is completely dissolved. Also, this ion is present in the dispersant of the emulsion.

The source of Bi ions is not particularly limited as long as it is a trivalent bismuth compound, but examples include inorganic bismuth compounds such as bismuth nitrate, bismuth phosphate, bismuth sulfate, bismuth oxide, bismuth hydroxide; bismuth fluoride, bismuth chloride Bismuth halide compounds such as bismuth, bismuth bromide, and bismuth iodide; bismuth organic acid compounds such as bismuth acetate, bismuth formate, bismuth lactate, and bismuth citrate.

In the present invention, aminopolycarboxylic acid may also be contained. The so-called amino polycarboxylic acid is a general term for chelating agents having amino groups and multiple carboxyl groups in the molecule. Since the aminopolycarboxylic acid makes the trivalent Bi ion in the composition into a water-soluble state more stably, it may contain the aminopolycarboxylic acid. Specifically, EDTA (ethylenediaminetetraacetic acid), HEDTA (hydroxyethylethylenediaminetriacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA ( triethylenetetraminehexaacetic acid), etc., but EDTA, HEDTA, and NTA are more preferred from the viewpoint of the stability of the chelate with Bi ions.

<Composition Components: Other Ingredients>

In the composition of the present invention, additives generally used in the paint field such as pigments, organic solvents, pigment dispersants, and surfactants may be used as needed. Examples of the pigment include coloring pigments such as titanium white and carbon black; volume pigments such as clay, talc, and barium oxide; and antirust pigments such as aluminum tripolyphosphate and zinc phosphate. In addition, in the above description, the components of the dispersant (cationic resin, blocked polyisocyanate, tin compound) and the components of the dispersant (liquid medium, bismuth ions) of the cationic resin emulsion are separately described, but it means It means that these ingredients are substantially present in the dispersoid or dispersant, and not meant to be present only in the dispersoid or only in the dispersant. For example, it is within the scope of the present invention that a part of the cationic resin is slightly dissolved in the dispersant.

＜Composition of the composition＞

Next, the composition of the aqueous composition for metal surface treatment of the present invention will be described. First, the aqueous composition for metal surface treatment of the present invention can be adjusted to a desired concentration by appropriately diluting high-concentration substances with water. Hereinafter, the preferable concentration of each component in this aqueous composition is demonstrated.

(Cationic resins in aqueous compositions)

The composition preferably contains 5 to 30% by weight (solid content) of the cationic resin based on the total weight of the composition, more preferably 5 to 20% by weight, and still more preferably 5 to 15% by weight.

(blocked isocyanates in aqueous compositions)

The composition preferably contains 2 to 20% by weight (solid content) of the blocked isocyanate based on the total weight of the composition, more preferably 2 to 15% by weight, and still more preferably 2 to 10% by weight.

(tin compounds in aqueous compositions)

The content of the tin compound in the composition is preferably 0.01 to 1% by weight, more preferably 0.01 to 0.5% by weight, and most preferably 0.01 to 0.2% by weight as the amount of Sn. If the content of the tin compound is too low, the expected curing catalytic ability will be lowered, and the curability will not be satisfactory, and when the acetone reciprocating test is performed as described above, traces of peeling of the coating film will be observed.

(trivalent Bi ion in aqueous composition)

The composition contains 100 to 5000 ppm of trivalent Bi ions. More preferably, it is 500-4000 ppm, Most preferably, it is 1000-3000 ppm. When the Bi ion concentration is too low, it is unfavorable for the precipitation of Bi. If it is too high, the electrical conductivity of the composition is too high, and the throwing property of the film on a metal material having a complicated shape deteriorates, and Bi Too much adhesion may impair the film adhesion. Regarding the Bi ion concentration in the composition, the composition can be separated into solid and liquid using an ultracentrifuge, and the liquid phase can be quantified using high-frequency inductively coupled plasma emission spectrometry (ICP) or atomic absorption spectrometry (AA).

<Physical properties of aqueous compositions for metal surface treatment>

(pH)

Although pH of the aqueous composition for metal surface treatment of this invention is not specifically limited, Usually, it can adjust to 2.0-7.0, Preferably it can adjust and use it in the range of 3.0-6.5.

(temperature)

The temperature of the aqueous composition for metal surface treatment of the present invention is not particularly limited, but it can be used in a range of usually 15 to 40°C, preferably 20 to 35°C, when depositing a film by electrolytic treatment.

"Metal Surface Treatment Film"

The metal surface treatment film of the present invention can be obtained by the treatment method of the present invention using the aqueous composition for metal surface treatment of the present invention. Here, Bi present in the film exists in the form of metal and oxide. The Bi deposited by cathodic electrolysis is basically metal Bi deposited by reduction, and a part thereof is oxidized and becomes an oxide especially in the baking step of the film. In addition, when a high voltage is applied in the second step, since the pH of the film surface rises, the stabilization of Bi by the aminopolycarboxylic acid becomes insufficient, and thus Bi oxide is precipitated especially on the film surface side.

The Bi adhesion amount is preferably 20 to 500 mg/m ² , more preferably 30 to 400 mg/m ² , and most preferably 50 to 300 mg/m ² . If the amount of Bi adhesion is too low, sufficient corrosion resistance cannot be obtained, and if it is too high, not only improvement in corrosion resistance cannot be expected, but film adhesion may be impaired. Furthermore, the amount of Bi adhesion can be quantified by fluorescent X-ray analysis. In addition, the "amount of metallic Bi adhesion" and "amount of Bi oxide adhesion" in the scope of the claims of this patent and in this specification employ the values quantified by this fluorescent X-ray analysis. In addition, although the presence of hydroxide cannot be denied in other forms, in this measurement method, when quantified as "metal Bi" or "oxidized Bi", the numerical value is regarded as "amount of metal Bi attached" or "oxidized Bi". Bi adhesion".

The total film thickness of the obtained film is preferably 5 to 40 μm, more preferably 5 to 30 μm, and most preferably 7 to 25 μm. If it is too thin, sufficient corrosion resistance cannot be obtained, and if it is too thick, not only economically disadvantageous but also the throwing property may fall. The film thickness can be measured with an electromagnetic induction type film thickness gauge if the base metal is a magnetic metal, and can be measured with an eddy current type film thickness gauge if the base metal is a non-magnetic metal.

Bi in the film needs to exist more on the base metal side than on the film surface. Specifically, it is preferable to have a Bi deposition distribution in which the amount of Bi deposition on the metal material side, B, is 55% or more (B/A≧55%) relative to the total Bi deposition amount, A, from the center of the film thickness. More preferably, it is 58% or more, and most preferably, it is 60% or more. If it is too low, sufficient corrosion resistance cannot be obtained. Furthermore, if it exceeds 90%, the Bi concentration on the surface side of the film will be extremely low, and the function of Bi as a curing catalyst will be lost, which is not preferable.

The Bi adhesion distribution in the film can be measured by performing line analysis on the film cross section using EPMA. The interface between the base metal and the film and the position of the film surface are clarified using the backscattered electron image taken at the same time, and the integrated value of the Bi intensity in the film based on EPMA line analysis is obtained, which is A and only the base metal is calculated from the center of the film thickness. The integral value of the side is B, and B/A can be calculated.

Example

Production of blocked isocyanates

Add 115.6 g of methyl isobutyl ketone to 678.4 g of Cosmonate M200 (manufactured by Mitsui Chemicals Co., Ltd.), and after raising the temperature to 70°C, slowly add 706.0 g of diethylene glycol monoethyl ether dropwise. ℃. The reaction was carried out at 90° C. for 12 hours to obtain blocked isocyanate. As a result of infrared absorption spectrometry, no absorption due to unreacted isocyanate groups was observed, and it was confirmed that the isocyanate was completely blocked.

Production of 30% quaternary salt epoxy resin

Into a 1000 ml separable flask equipped with a thermometer, a condenser, and a stirrer, 134.9 g of epoxy resin JER#828 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 180), 80.94 g of bisphenol A, and 0.1 dimethylbenzylamine were charged. g, carry out the reaction at 130°C until the epoxy equivalent weight reaches 1200. After completion of the reaction, 71.7 g of butyl cellosolve was added, and 13.16 g of dimethylaminoethanol and 14.79 g of 90% lactic acid were added, and the reaction was carried out at 90° C. for 1 hour. After the reaction, 613.36 g of deionized water was dripped over about 1 hour while stirring vigorously, and a quaternary salt type epoxy resin having a solid content of 30% was produced.

Preparation of Cationic Resin Emulsion

Manufacturing example 1

Into a 1000 ml separable flask equipped with a thermometer, a condenser, and a stirrer, 114.0 g of epoxy resin jER#828 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 180) and polycaprolactone diol as a modified resin were charged. 41.5 g of PLACCEL208 (manufactured by Daicel Chemical Co., Ltd.), 45.6 g of bisphenol A, and 0.1 g of dimethylbenzylamine were reacted at 130° C. until the epoxy equivalent became 1,000. After completion of the reaction, 55.5 g of butyl cellosolve was added, followed by addition of 12.6 g of diethanolamine and 8.0 g of ketimide of diethylenetriamine, and the reaction was carried out at 90° C. for 2 hours. Add 105.5 g of blocked isocyanate, 3.2 g of dioctyltin diacetate (NEOSTANN U820 manufactured by Nitto Kasei Kogyo Co., Ltd.), and 5.4 g of acetic acid. 578.1 g of ionized water was used to obtain a cationic resin emulsion (A1) with a solid content concentration of 33%.

Manufacturing example 2

In Production Example 1, a cationic resin emulsion was obtained by using 1.6 g of dioctyltin diacetate and 1.6 g of dibutyltin diacetate (NEOSTANN U200 manufactured by Nitto Kasei Kogyo Co., Ltd.) instead of dioctyltin diacetate. (A2).

Manufacturing example 3

In Production Example 1, a cationic resin emulsion (A3) was obtained by using 3.2 g of dioctyltin dilaurate (NEOSTANN U810 manufactured by Nitto Kasei Kogyo Co., Ltd.) instead of dioctyltin diacetate.

Manufacturing example 4

In Production Example 1, a cationic resin emulsion (A4) was obtained by using 3.2 g of dibutyltin diacetate (NEOSTANN U200 manufactured by Nitto Kasei Kogyo Co., Ltd.) instead of dioctyltin diacetate.

Manufacturing Example 5

In Production Example 1, a cationic resin emulsion (A5) was obtained by using 3.2 g of dioctyltin distearate (NEOSTANN U500 manufactured by Nitto Kasei Kogyo Co., Ltd.) instead of dioctyltin diacetate.

Preparation of Pigment Dispersion Paste

Manufacturing example 6

With respect to 16.6 parts of 30% quaternary salt type epoxy resin, add 7.0 parts of refined clay, 0.3 parts of carbon black, 3.0 parts of zinc phosphate and deionized water, and disperse with a ball mill for 20 hours to obtain a pigment dispersion with a solid content of 50% by weight. ointment.

Preparation of Bi ionic liquid

13.3 g of HEDTA was dissolved in 500 g of distilled water, and after heating to 60° C., 23.2 g of bismuth nitrate pentahydrate was added and stirred until the solid content was completely dissolved. Distilled water was further added so that the final total amount would be 1.0 L, to prepare a Bi ion aqueous solution.

Examples 1-3 and Comparative Examples 1-2

composition making

Into the resin emulsion having a solid content of 16.0% by weight of the combinations shown in Table 1, a pigment dispersion paste having an inorganic solid content of 4.0% by weight and an aqueous solution of Bi ions were blended to prepare Examples 1 to 3 and Comparative Examples Compositions of 1 to 2 (Bi concentration in the composition: 1000 ppm; pH: 6.0; cationic resin in the dispersoid: 58% by weight; blocked isocyanate in the dispersoid: 27% by weight). Furthermore, each concentration was adjusted by diluting with deionized water.

Electrolysis conditions

Immediately after electrolysis at 8 V for 90 seconds as the electrolysis step (1), electrolysis treatment was performed at 180 V for 180 seconds as the electrolysis step (2).

Production of test boards

As the test plate, cold-rolled steel plate: SPCC (JIS3141) 70×150×0.8mm (hereinafter referred to as SPC) was used, and the surface was subjected to 120° Second spray treatment for degreasing treatment. After the degreasing treatment, spray water washing was performed for 30 seconds, immersed in the compositions shown in Examples and Comparative Examples, and cathodic electrolysis treatment was performed under the electrolysis conditions shown in Examples and Comparative Examples. Immediately after the electrolysis, the test plate was sprayed with deionized water for 30 seconds, and baked in an electric oven at 180° C. for 20 minutes.

Investigation of Film Properties

The film characteristics of the film deposited on the test panel were investigated by the following method.

Film thickness measurement: measured using an electromagnetic induction film thickness gauge.

Bi adhesion amount: quantified by fluorescent X-ray spectroscopic analysis.

Bi adhesion distribution: The cross section of the sample was analyzed by line analysis of EPMA. For the specific method, refer to the following.

The Bi adhesion amount distribution measurement in the film was analyzed using EPMA. The metal material after film treatment was fixed with potting resin, the cross section was polished, and the linear analysis distribution of Bi was obtained from the direction of the base metal to the direction of the deposited film surface. The so-called line analysis distribution is a graph in which the average value of the characteristic X-ray intensity is calculated with an arbitrary width in the one-dimensional direction of the analysis area based on the mapping analysis data, and it can be understood as a line analysis with a width. The measurement conditions are as follows.

Measuring machine: EPMA-1610 manufactured by Shimadzu Corporation

Electron gun: CeB6 cathode type

Beam current: 50nA, beam voltage: 15kV, beam diameter: 1μmφ or less

Cumulative times: 1 time, sampling time for each point: 100ms

Spectral crystal: PET (Bi Mα)

The interface between the base metal and the film and the position of the film surface are clarified using the backscattered electron images taken at the same time, and the integral value of the Bi intensity in the film, A, and the integral value of the base metal side only from the center of the film thickness are obtained. B, calculate B/A. Furthermore, the analysis results of the film obtained in Example 1 are shown in FIG. 2 as a representative distribution for reference.

Bi precipitation property: As the Bi precipitation property, the time required for the Bi precipitation amount to reach 50 mg/m ² was evaluated based on the time-dependent fluorescent X-ray spectroscopic analysis results. The evaluation criteria were set as follows: within 45 seconds: ⊚, 45 to 60 seconds: ○, and 60 seconds or more: ×. The results are shown in Table 1, and the transition of the precipitation amount is shown in FIG. 1 . In addition, in the Bi precipitation test, electrolysis was performed at 8V for 30, 60, and 90 seconds, washed with deionized water, and air-dried.

Coating film curability: The appearance of the coating film was visually confirmed after pressing a gauze wetted with acetone against the resin-coated plate produced by the cathodic electrolytic treatment and reciprocating it 30 times. Evaluation criteria were no traces: ◎, traces: ○, even the state where the substrate can be seen: ×. The results are shown in Table 1.

Resin segregation time (resin segregation property): Perform electrolytic treatment at 15V for 90 seconds, and judge the time when a decrease in the current value is seen as the time when the resistance of the coating film appears, that is, the time at which resin segregation occurs. The processing time before this time point was set as resin precipitation time. The results are shown in Table 1.

Shrinkage cavity, graining: The presence or absence was checked visually.

Adhesiveness: 100 checkerboards of 1 mm width were cut into the coating film, and the part was extruded with an Ericsson tester. After extrusion, the tape was peeled off, and the number of cells of the portion remaining without peeling was counted. Extrusion distance: 4mm Remaining number 80-100: ◎, 80-60: ○, 60-20: △, 20-0: ×.

As can be clearly seen from Table 1, the composition of the example can improve the precipitation of Bi and prevent deterioration of the appearance of the coating film such as shrinkage and graining, and it has been confirmed that it can impart more excellent curing properties and adhesion of the coating film. . That is, it was confirmed that the compositions of Examples can form a film in the same bath, and can form a film satisfying important properties as a film. On the other hand, it turned out that the composition of the comparative example was remarkably inferior in any property, and it could not be used as a practical product.

[Table 1]

* Slight traces: ○ Traces: △

** Shrinkage cavity: × No: ○

Claims (10)

1. An aqueous composition for metal surface treatment, which contains cationic resin emulsion, is characterized in that, the dispersoid of cationic resin emulsion contains amino compound, blocked polyisocyanate and formula 1 shown in modified epoxy resin Tin compounds:

Here, in Formula 1, m is 4 or more, n is 0 or more and 10 or less, The dispersant of the cationic resin emulsion contains Bi ions. 2. the metal surface treatment aqueous composition according to claim 1, is characterized in that, m in Formula 1 is 7 or more. 3. the metal surface treatment aqueous composition according to claim 1 or 2, is characterized in that, m in Formula 1 is 7. 4. the metal surface treatment aqueous composition according to claim 3, is characterized in that, m in Formula 1 is 7 and n is 0. 5. The water-based composition for metal surface treatment according to any one of claims 1 to 4, characterized in that, The content of the tin compound in the entire composition is 0.01 to 1% by weight as the amount of Sn. 6. The water-based composition for metal surface treatment according to any one of claims 1 to 5, characterized in that, It is a composition used in the multi-step energization method in the same bath. 7. A metal surface treatment method, characterized in that, The metal material to be treated is immersed in the aqueous composition according to any one of claims 1 to 6, and a film is deposited on the metal material by an electrolytic treatment step using the metal material to be treated as a cathode. 8. metal surface treatment method according to claim 7, is characterized in that, The electrolytic treatment step has: a first step, after immersing the metal material whose surface has been cleaned in the aqueous composition according to any one of claims 1 to 6, or while immersing, using the metal material as a cathode , electrolysis at a voltage below 15V for 10 to 120 seconds; the second step is to implement electrolysis at a voltage of 50 to 400V for 30 to 300 seconds in the same bath after the first step. 9. A method of manufacturing a metal material with a film, characterized in that, It has the electrolytic treatment process described in claim 7 or 8. 10. A metal surface treatment film obtained by the manufacturing method according to claim 9, characterized in that, 20 to 250 mg/m ² of Bi is attached to metal Bi and Bi oxide, the total film thickness is 5 to 40 μm, and the amount of Bi adhesion B on the metal material side relative to the total Bi adhesion amount A is calculated from the center of the film thickness. Bi adhesion distribution of 55% or more (B/A≥55%).

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