JP2003253457A - Surface treated galvanized steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treated galvanized steel sheet which has excellent corrosion resistance in particular, and has excellent solvent resistance. <P>SOLUTION: The surface treated galvanized steel sheet has a first film layer formed of a water based composition containing at least one kind selected from the phosphates, carbonates, nitrates, acetates, hydroxides and fluorides of Mg, Mn or Al, and an organic acid capable of coordination to a bivalent or higher metallic ion, and an organic film layer formed from an epoxy resin and a glycol urea resin on the first film layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated zinc-based plated steel sheet, and more particularly to a surface-treated zinc-based plated steel sheet which exhibits excellent corrosion resistance and solvent resistance without the use of a chromium-containing surface treatment agent.

[0002]

2. Description of the Related Art Conventionally, galvanized steel sheets such as galvanized steel sheets and zinc-aluminum plated steel sheets have been widely used in the fields of home appliances, automobiles and construction. In order to improve the corrosion resistance of the steel sheet, these steel sheets are used after being subjected to a chromate coating treatment on the plating, or after being subjected to a chromate coating treatment and further provided with an organic film. When applying an organic film, this chromate film also plays a role of improving the adhesion to the organic film.

However, although the chromate film has excellent corrosion resistance and coating adhesion, it contains hexavalent chromium,
In the chromate coating process, it is necessary to perform special wastewater treatment specified by the Water Pollution Control Law, which has a drawback of increasing cost. Therefore, in order to prevent white rust from occurring on the steel sheet, especially on the zinc-plated steel sheet, there is a demand for a surface treatment technique that does not use chromium. In response to this, there are many proposals.

Specifically, an aqueous surface treatment agent containing a polyvalent metal ion (a) other than chromium, an acid component (b) and optionally an organic resin has been proposed. For example, Japanese Patent Laid-Open No. 5-
In No. 195244 (hereinafter), as a surface treatment agent which can be applied to a galvanized steel sheet as it is and dried, and which can form a chromium-free film having a protective quality equivalent to that of a conventional chromate conversion film, (a) Co, Mg, Mn, Zn, Ni, Z
A fluoroacid having 4 or more fluorine atoms containing at least one of (b) Ti, Zr, Hf, Si and B, which is a cation component selected from r, Fe, Al, Sn and Cu (for example, TiF ₆ ² hexafluorotitanate). ^- anionic component consists of), even more aqueous acidic liquid composition containing free acid, and optionally an organic resin for pH adjustment have been proposed.

Japanese Unexamined Patent Publication No. 11-106945 (hereinafter referred to) discloses a surface treatment agent capable of forming a chromium-free film excellent in fingerprint resistance, blackening resistance and coating adhesion in addition to high corrosion resistance, as described above. An acidic surface treatment agent containing a cation component (a) and an acid (b) selected from the above fluoroacid, phosphoric acid and acetic acid, and a hydroxyl group-containing water-soluble polymer having polymer units 2 to 50 having a specific chemical structure. , A surface treatment agent for a chromium-free metal material containing a silane coupling agent has been proposed.

In Japanese Patent Laid-Open No. 9-241856 (hereinafter), the conventional chromate film-replacement water-based resin film has a problem that the corrosion resistance is insufficient and a thick film is required, and the adhesion to a metal is poor in a wet environment. In order to obtain a chromium-free surface-treated film having excellent adhesion to metals, bare corrosion resistance after processing, and paint adhesion, phosphoric acid, Cu, Co,
Fe, Mn, Sn, V, Mg, Ba, Al, Ca, S
A chromium-free metal surface treatment composition containing a phosphoric acid compound (a and b) containing at least one metal of r, Nb, Y and Zn and a hydroxyl group-containing organic resin has been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 11-5010 (below) discloses the same problems as those mentioned above, particularly as a phosphoric acid type surface treatment agent for improving the corrosion resistance when an aqueous epoxy resin is used as an aqueous resin film. As a hydroxyl group-containing organic resin, a polyhydroxy ether segment that does not substantially contain an epoxy group, and a specific amount of hydroxyl group,
A surface treating agent similar to the above chromium-free metal surface treating composition has been proposed, except that a resin having a specific segment ratio of a copolymer segment of an unsaturated monomer having a carboxyl group and a sulfone group is used. .

Japanese Unexamined Patent Publication No. 11-29724 (hereinafter) discloses an aqueous rust preventive coating in which an aqueous resin-containing water composition contains a thiocarbonyl group-containing compound, a phosphate ion and additionally water-dispersible silica. A method of coating the zinc-coated steel with the agent has been proposed.

[0009]

Among the surface treatment agents (coating agents, coating agents) proposed in 1) to 3) above, there are some which are said to be able to obtain high corrosion resistance, but generally the corrosion resistance is sufficient. However, further improvement is desired. Specifically, when a coating with a sufficient amount of adhesion, that is, with a sufficient film thickness, is applied to the metal plate, a reasonable corrosion resistance can be obtained, but for example, a part such as a convex portion of the metal plate is exposed. If the film is applied or the film is too thin, the corrosion resistance was extremely insufficient. In other words, if the coating on the metal plate has defects or scratches, corrosion progresses from that portion, so that the corrosion resistance is insufficient.

Further, a sulfide such as a thiocarbonyl group-containing compound which has been proposed is easily adsorbed on a metal surface such as Zn, and a thiol group ion has a synergistic action with a phosphate ion so that zinc which is active during coating is zinc. It is adsorbed on the surface site and exhibits a rust prevention effect. The surface of the zinc-based plated steel sheet obtained by this surface treatment method is -NCS.
Although it has high corrosion resistance when it is covered with a layer having a base group or an -OCS group, a portion not covered with the thiocarbonyl group-containing compound appears when the film thickness is thinned, which causes rusting. Further, if the coating on the metal plate has defects or scratches, corrosion progresses from that portion, so that the corrosion resistance is insufficient.

Furthermore, any of the above methods is a technique based on the idea of firmly adhering the metal surface and the film formed by the surface treatment agent at the interface. If it is captured microscopically, the metal surface and the surface treatment agent cannot completely adhere to each other, and there is a limit to the improvement of the adhesiveness. Also, if the film is damaged by degreasing with a solvent after press molding, it will rust due to corrosion,
There was a problem that corrosion proceeded to the surroundings.

The present invention has been made in view of the above circumstances, and particularly provides a surface-treated zinc-based plated steel sheet which is excellent in solvent resistance as well as further improved corrosion resistance required for conventional chromium-free surface-treated zinc-based plated steel sheet. It is intended to be provided.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and found that a salt formed from a specific polyvalent metal ion and an etching ion is present on the surface of a zinc-based plated steel sheet. If a first coating layer is formed from an organic acid capable of coordinating to the metal ion, and an organic coating layer formed of an epoxy resin and a glycoluril resin is provided on the first coating layer, a chromate coating is formed. The inventors have found that a surface-treated zinc-based plated steel sheet having particularly excellent corrosion resistance and solvent resistance can be obtained without providing it, and have completed the present invention.

That is, according to the present invention, on the surface of the zinc-plated steel sheet, at least one metal selected from the group consisting of Mg, Mn and Al is selected from the group consisting of phosphate, carbonate, nitrate, acetate, hydroxide and fluorine. A first coating layer formed from an aqueous composition containing at least one metal compound selected from the group consisting of compounds and an organic acid capable of coordinating a divalent or higher valent metal ion, and on the first coating layer And a surface-treated zinc-based plated steel sheet having an organic coating layer formed of epoxy resin and glycoluril.

In a preferred embodiment of the surface-treated zinc-based plated steel sheet according to the present invention, the aqueous composition further comprises Zn, Co,
Ti, Sn, Ni, Fe, Zr, Sr, Y, Cu, C
It contains at least one metal compound selected from the group consisting of a, V, Ba, W and Mo.

In a preferred embodiment of the present invention, the aqueous composition further contains a styrene-carboxyl group-containing compound copolymer is a preferred embodiment of the present invention. Furthermore, in a preferred embodiment of the present invention, the epoxy resin is a bisphenol type epoxy resin and / or a modified product thereof with a hydroxyl group.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-treated zinc-based plated steel sheet of the present invention will be described in detail below. The surface-treated zinc-based plated steel sheet according to the present invention, on the surface of the zinc-based plated steel sheet,
It is characterized by having a first coating layer formed from a specific aqueous composition and a specific organic coating layer formed on the first coating layer.

The zinc-based plated steel sheet (substrate) to be surface-treated in the present invention is an electrogalvanized steel sheet, an electrogalvanized nickel-plated steel sheet, a hot-dip galvanized steel sheet, a zinc-aluminum hot-dip galvanized steel sheet, and the like, which contains zinc. There is no particular limitation as long as it is a steel plate that has been subjected to. In the present invention, the substrate is subjected to a surface treatment to form a film consisting of the above two layers, but the film may be formed on only one surface of the substrate or on both surfaces thereof, and any one of them may be appropriately selected depending on the desired application. can do.

The first coating layer on the surface of the substrate is formed by applying a specific aqueous composition and drying. The aqueous composition used in the present invention contains a salt formed from a specific polyvalent metal ion and an etching ion, and an organic acid capable of coordinating with the metal ion.

Here, the present inventors have examined the corrosion and corrosion resistance of the zinc-based plated steel sheet, and have made the following consideration. For example, on a zinc-based plating surface under a salt spray environment, the following reactions (3) and (4) are caused by the elution of Zn ²⁺ and OH ⁻ (reactions (1) and (2) below) to cause electroconductivity of ZnO. Are generated, and as a result, corrosion progresses.

Anode reaction: Zn = Zn ²⁺ + 2e ⁻ (1) Cathode reaction: H ₂ O + 1 / 2O ₂ + 2e ⁻ = 2OH ⁻ (2) Hydroxide formation: Zn ²⁺ + 2OH ⁻ = Zn (OH) ₂ (3) Formation of ZnO: Zn (OH) ₂ = ZnO + H ₂ O (4)

If there is a metal ion Me ^{n +} that promotes the following reaction (5) together with Zn ²⁺ , Me and Zn
It is considered that a stable hydroxide (corrosion product) composed of is formed and the progress of corrosion is stopped, that is, the corrosion resistance is exhibited. ^{Me n + + Zn 2+ + mOH} - = like (Me, Zn) (OH) _m (5) thus molten zinc-plated surface, the metal surface in the presence of Zn, in the presence of Me ^{n +} capable of proceeding the reaction (5) If so, corrosion resistance can be imparted.

Therefore, based on the above consideration, the present inventor has included Me in the above reaction (5) by adding it to the aqueous composition for surface treatment.
^When a polyvalent metal species other than chromium that can be ^{n +} was examined, it was concluded that at least Mg, Mn, or Al should be contained. Therefore, the aqueous composition of the present invention contains an ion-dissociative compound of at least one metal selected from the group consisting of Mg, Mn, and Al (first group). These metals are contained in the aqueous composition as a salt (metal compound) with a counter ion described later, but they dissociate into ions in the aqueous composition and contribute to the corrosion resistance improving effect by coexistence with an organic acid described later.

The aqueous composition may contain a single species of Mg, Mn or Al, but in order to exhibit the effect of improving the corrosion resistance, it is preferable to contain a plurality of these metal species.
It is particularly preferable to include the seed. When two or more of these are included, the amount ratio to each other is not particularly limited. For example, in the case of the coexistence of three, the mass ratio of each metal is Mg / Mn / Al = 1/1. It can be included in an amount of / 1-2 / 1/1.

In the present invention, as a preferred aqueous composition,
In addition to the above-mentioned first group of metal species, an embodiment including other metal species may be mentioned. Other metal species include Zn, Co, T
i, Sn, Ni, Fe, Zr, Sr, Y, Cu, Ca,
At least one selected from the group consisting of V, Ba, W and Mo (second group) can be mentioned. By further adding the metal species shown in the second group to the aqueous composition containing the first group of metal species, the corrosion resistance can be further improved. The aqueous composition may contain a single kind or a plurality of kinds of metal species of the second group, and in that case, the amount ratio of each metal is not particularly limited. Of these, it is preferable to include Zn. A particularly preferable specific example of coexistence of the first group and the second group is a case where Mg, Mn and Al and Zn are contained.

The metal compound of each metal of the first group and the second group may be any compound which dissociates in the aqueous composition, and, for example, the counter ion species of metal ions such as Mg ²⁺ and Mn ²⁺ are particularly preferable. Although not limited, zinc etchable ions are preferred. The metal compound is therefore usually in the form of a salt,
Examples thereof include phosphates, carbonates, nitrates, acetates, fluorides and hydroxides of the above metals. Further, it may be a salt with an oxide, an inorganic acid or an organic acid, and examples thereof include zirconium ammonium carbonate and titanium lactate, and further examples include salts containing a metal in the form of an inorganic acid such as ammonium metavanadate.

In the present invention, these counterionic species (for example, acid groups) contained in the aqueous composition may be a single species or a plurality of species. When preparing an aqueous composition from two or more kinds of metal compounds, their counter ions may be the same or different. More specifically, when a plurality of types of first group metal ions are contained in the aqueous composition, their counter ions may be the same or different, and further a second group of metal ions is contained. Also, the counter ions of the second group may be the same as or different from the counter ions of the first group, but the counter ion of the second group is preferably the same kind as any of the counter ions of the first group. .

Further, in the present invention, when an aqueous composition containing a plurality of kinds of metal ions is prepared, a plurality of kinds of metal compounds composed of a single kind of metal can be used, or a metal compound formed of 2 or 3 kinds of metals can be used. The metal compound in the form of a double salt may be used, or these may be mixed and used. Among these, it is preferable to use two or more kinds of metal compounds composed of a single kind of metal so that the aqueous composition contains two or more kinds of metals.

When the metal compound of the first group metal is contained in an amount of 2 mass% or more of metal in the total solid content in the aqueous composition, usually 2% by mass or more, the effect of improving corrosion resistance by the metal compound. Can be obtained. This metal content is 5
If it exceeds 0% by mass, the weldability of the surface-treated steel sheet tends to be poor. The content of the metal compound is preferably 30 to 45% by mass, particularly preferably 35 to 4 by the amount of metal in the compound.
The amount is 0% by mass.

When a metal compound of the second group metal is contained, the total content of the metal compound of the second group metal and the metal compound of the first group metal is the same as above. The total amount is preferably not more than 60% by mass, and more preferably 35 to 50% by mass. When both the first group and the second group of metal species are contained, the quantitative ratio of the first group metal and the second group metal is not particularly limited, but usually the first group metal is contained in a large amount.

The aqueous composition used in the present invention contains an organic acid that coordinates a metal ion having a valence of 2 or more. In particular,
It is capable of coordinating to divalent to hexavalent metal ions exemplified in the first group and the second group, and is oxalic acid, tricarballylic acid, citric acid, isocitric acid, succinic acid, malic acid, glutaric acid. Are exemplified. Of these, tricarballylic acid, citric acid, isocitric acid, and succinic acid are preferable. The aqueous composition may contain two or more of these. The organic acid accelerates the etching of the zinc-based plated surface, and also coordinates (crosslinks) with the metal coexisting therewith to further densify the film formed from the aqueous composition. When the film is densified, the elution of zinc-based plating in a corrosive environment is suppressed and the corrosion resistance is improved.

The content of the organic acid is not particularly limited, but in order to increase the number of cross-linking points and to exert the densification effect of the above-mentioned film, it is preferably about 1% by mass or more based on the total solid content of the aqueous composition. preferable. If it exceeds 10% by mass, it tends to be difficult to maintain stability as an aqueous composition.
It is desirable that the upper limit be 10% by mass.

The above-mentioned aqueous composition used in the present invention may further contain a copolymer of styrene and a carboxyl group-containing compound, if necessary. Specific examples of the carboxyl group-containing compound (copolymerization monomer) include ethylenically unsaturated carboxylic acids and their derivatives. Examples thereof include monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, dicarboxylic acids such as itaconic acid, maleic acid and fumaric acid, and alkali metal salts, ammonium salts, organic amine salts and esters thereof. . The copolymer may contain units derived from two or more of these copolymerization monomers. Of these, lower alkyl esters such as butyl ester and methyl ester of acrylic acid or methacrylic acid are preferable. When the content of the carboxyl group-containing compound unit in the copolymer is 0.5% by weight or more,
It is preferable because the corrosion resistance is improved.

Further, the above copolymer may optionally contain a unit derived from styrene and another copolymerizable compound (third component) capable of copolymerizing with the copolymerization monomer. Examples of such other copolymerizable compounds include vinyl compounds other than the above (meth) acrylic acid ester, vinyl compounds having a hydroxyl group, vinyl compounds having a sulfonic acid group, vinyl compounds having a phosphoric acid group, and the like. To be The copolymer may contain units derived from two or more of these. The aqueous composition of the present invention may contain one or more of the above copolymers.

The above-mentioned copolymer can be obtained by polymerizing styrene, the above-mentioned copolymerization monomer and optionally the third component by a conventionally known polymerization method, and the polymerization form is not particularly limited, but usually, random copolymerization is carried out. Although it is a combination, it may be a graft copolymer. As the copolymer, a commercially available product in a state of being dispersed or dissolved in an aqueous medium can also be used. The weight average molecular weight of the copolymer is not particularly limited, but is usually about 10,000 to several hundreds of thousands.

This styrene-carboxyl group-containing compound copolymer is effective in improving the stability of a film formed by coating an aqueous composition in an alkaline environment, and brings about improvement in corrosion resistance and coating film adhesion. . The content of the styrene-carboxyl group-containing compound copolymer is not particularly limited, but in order to exhibit the above effects, it is preferably about 1% by mass or more of the total solid content of the aqueous composition. If it exceeds 10% by mass, it becomes difficult to maintain the stability of the aqueous composition.

The aqueous composition used in the present invention may optionally contain other components as long as the object of the present invention is not impaired. For example, in order to increase the coating adhesion of the film formed by coating and to further increase the film's denseness,
It is preferable to include a metal oxide. As the metal oxide, SiO ₂ , MgO, ZrO ₂ , Al ₂ O ₃ , SnO
₂ , Sb ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O _{4 and the} like can be used alone or in combination. The particle size of the metal oxide is not particularly limited, but smaller particles are preferred because they are easier to mix with other components in the aqueous composition. Among the above, silica (Si
O ₂ ) is preferable, and colloidal silica and gas phase silica are particularly preferable. The content of the metal oxide in the aqueous composition may be approximately the same as the amount conventionally contained in the conventional surface treating agent for galvanized steel sheet.

When a coupling agent is used together with the above metal oxide, especially silica, a synergistic effect can be expected. Furthermore, in the aqueous composition of the present invention, a conventional additive that is conventionally included in a surface treatment agent for wax and other galvanized steel sheets is included in a conventional amount, and in addition to the effects such as the corrosion resistance,
It can also exert other effects such as fingerprint resistance.

The aqueous composition is used by dissolving or dispersing each of the above components in an aqueous medium. The solution or dispersion has a solid content concentration of 1 to 60% by mass, preferably 5 to 50% by mass.
Adjusted to.

When the aqueous composition as described above is applied to a zinc-based plated steel sheet and a film is formed on the steel sheet, a solution or dispersion of the composition is applied to one or both of the zinc-based plated steel sheets. A general method is to apply it on both surfaces, press it with a Ringer roll, and dry it to form and cure a film. To apply the aqueous composition to a zinc-based plated steel sheet,
Methods such as roll coating, spray coating, brush coating, dip coating and curtain flow are used.

The second coating layer is an organic coating formed from an epoxy resin and a glycoluril resin on the first coating layer, and is cured by a dehydration (dealcoholization) reaction between the epoxy resin and the glycoluril resin. Then, it is an organic film firmly adhered to the lower layer. In the present invention, curing refers to complete curing, semi-curing or partial curing.

The above-mentioned epoxy resin is usually a bisphenol type epoxy resin (hereinafter sometimes simply referred to as an epoxy resin), specifically, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and the like, and their secondary grades. The hydroxyl group may be crosslinked with polyisocyanate or the like. In the present invention, such an epoxy resin may be used after being modified so as to give a hydroxyl group as described later. When such modification for imparting a hydroxyl group is not added (hereinafter referred to as the base epoxy resin (a)), the epoxy equivalent is usually 500.
It is desirable to be about 5,000, preferably about 900 to 4,000. When the epoxy equivalent of the base epoxy resin is less than 500, the reaction rate with the glycoluril resin does not increase, and even when the epoxy equivalent exceeds 5000, the epoxy groups do not easily react, and both have a desired cured film, that is, corrosion resistance. It tends to be difficult to obtain.

Examples of the modification for imparting a hydroxyl group to the epoxy resin in the present invention include the case of imparting a phosphorus-bonded hydroxyl group by using a phosphoric acid compound as a modifier and the case of using a compound having a primary hydroxyl group. To be

When an epoxy resin is used after being reacted with a phosphoric acid compound and modified with phosphoric acid (hereinafter referred to as phosphoric acid-modified epoxy resin (b)), an epoxy resin having an epoxy equivalent of 500 or less is preferably used. In this case, when the epoxy equivalent exceeds 500, the content of the P—OH group in the phosphoric acid-modified epoxy resin decreases, so that it becomes difficult to obtain a desired cured film.

The above-mentioned phosphoric acid compound used as a modifier is a phosphoric acid having two or more hydroxyl groups bonded to a phosphorus atom, and is a generic term for acids obtained by hydrating diphosphorus pentoxide. Specifically, metaphosphoric acid, pyrophosphoric acid,
Examples thereof include orthophosphoric acid, triphosphoric acid and tetraphosphoric acid.
Of these, orthophosphoric acid is preferred. In addition, phosphoric acid monoesters such as monomethyl phosphoric acid, monooctyl phosphoric acid, and monophenyl phosphoric acid can also be used.

The phosphoric acid-modified epoxy resin (b) is P--O.
H group equivalent is usually 150 to 1000, preferably 300 to
800. If the P-OH group equivalent is less than 150, it may become sticky when used as a paint, making it difficult to use, and if it exceeds 1000, the adhesion to the substrate may decrease.

When the phosphoric acid-modified epoxy resin (b) is used, it is preferable to use an amine compound or the like together for neutralization, because a more stable aqueous resin composition is produced. Examples of the amine compound include ammonia; alkanolamines such as dimethanolamine and triethanolamine; alkylamines such as diethylamine and triethylamine; alkylalkanolamines such as dimethylethanolamine.

On the other hand, a modified product obtained by adding a primary hydroxyl group to an epoxy resin (hereinafter also referred to as modified epoxy resin (c)) is
The same epoxy equivalent base epoxy resin as the above base epoxy resin is reacted with a primary or secondary amine having a primary hydroxyl group, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, or a carboxylic acid compound. The epoxy polyol resin obtained by this is preferable.

Examples of the primary or secondary amine having a primary hydroxyl group used as a modifier include monoethanolamine, methylethanolamine, butylethanolamine, diethanolamine, diisopropanolamine,
Alkanolamine compounds such as dimethylaminopropylethanolamine or dialkylamine compounds such as dibutylamine, dioctylamine and the like. Above all, an epoxypolyol resin having a primary hydroxyl group obtained by using diethanolamine or the like is preferable because it can be cured even at a low temperature.

The epoxy equivalent of the modified epoxy resin (c) is preferably 550 to 40,000, more preferably 600 to 25,000. This epoxy equivalent is 550
When the amount is less than the above, the reaction rate with the glycoluril resin does not increase, and even when the epoxy equivalent exceeds 40,000, the epoxy groups do not easily react, and in both cases, a desired cured film, that is, corrosion resistance tends to be difficult to obtain.

The equivalent ratio of the primary or secondary amine, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid or carboxylic acid compound to the epoxy resin is, for example, that of the modified epoxy resin (c). When the preferable epoxy equivalent is 600 to 25,000,
Usually 0.1 to 0.9 equivalents relative to 1 equivalent of epoxy group,
It is preferably 0.2 to 0.8 equivalent.

Among the epoxy resins exemplified above,
(B) The phosphoric acid-modified epoxy resin has a hydroxyl group bonded to a phosphorus atom, which reacts with the epoxy group to promote the polymerization of the epoxy resin, and the epoxy resin thus polymerized is cured by the glycoluril resin. And excellent solvent resistance and corrosion resistance are obtained, which is preferable. More preferably, together with this (b) phosphoric acid-modified epoxy resin,
In this embodiment, (a) base epoxy resin or (c) modified epoxy resin having primary hydroxyl group is used.

The (c) epoxy resin having a primary hydroxyl group is preferable because it can improve the denseness and air barrier property of the organic film and the solvent resistance. Furthermore, if the (a) base epoxy resin and / or (b) phosphoric acid-modified epoxy resin coexists with (c) a modified epoxy resin having a primary hydroxyl group, after polymerizing them, glycoluril can be obtained at a lower temperature. Dehydration (dealcoholization) condensation with the resin occurs. Therefore, when curing is performed by low temperature baking, it is advantageous to use the modified epoxy resin (c) having a primary hydroxyl group.

In the case of using a (a) base epoxy resin and (b) a phosphoric acid-modified epoxy resin in combination, usually, (b) /
(A) = 10/90 to 50/50, preferably 15/8
It is 5-40 / 60. When the mass ratio is less than 10/90, it becomes difficult to obtain adhesion to the substrate, and when it exceeds 50/50, performance such as corrosion resistance and solvent resistance may be deteriorated.

When (a) the base epoxy resin and (c) the modified epoxy resin having a primary hydroxyl group are used in combination,
Usually, (a) / (c) = 5/95 to 30/70, preferably 10/90 to 20/80. If the mass ratio is less than 5/95, the amount of curing and dehydration (dealcoholization) reaction of the glycoluril resin to the epoxy resin tends to be excessive and the corrosion resistance tends to deteriorate, and if it exceeds 30/70, the epoxy resin And glycoluril resin is insufficiently cured, and the solvent resistance tends to deteriorate.

When the phosphoric acid-modified epoxy resin (b) and the modified epoxy resin (c) having a primary hydroxyl group are used in combination, usually (b) / (c) = 5/95 to 40/60, preferably 7 / 93 to 20/80. When the mass ratio is less than 5/95, the polymerization of the epoxy resin is insufficient, the glycoluril resin involved in dehydration (dealcoholization) condensation is insufficient, and the corrosion resistance and the solvent resistance tend to deteriorate. Further, when it is more than 40/60, similarly, the polymerization is insufficient, the glycoluril resin involved in dehydration (dealcoholization) condensation is insufficient, and the corrosion resistance tends to deteriorate.

(A) Bisphenol type epoxy resin,
When (b) phosphoric acid-modified epoxy resin and (c) modified epoxy resin having a primary hydroxyl group are used in combination, usually (a) / (b) / (c) = 10/10/80 to 10/4
0/50, preferably 10/20/70 to 10/30 /
60. If the mass ratio is deviated from the above, the polymerization of the epoxy resin is insufficient, the glycoluril resin involved in dehydration condensation is insufficient, and the corrosion resistance and solvent resistance tend to deteriorate.

In the present invention, the glycoluril resin is a derivative in which methylol, butyrol, etc. are added to all or part of the 1-, 3-, 4-, 6-amino groups of glycoluril, methylation, methyl / methyl / It refers to an alkyl etherified derivative such as ethylated or butylated, an oligomer condensed through a methylol group and the like, and an alkyl derivative thereof. Preferred are tetramethylolated glycoluril and its oligomers.

In the present invention, when the organic film is formed by the curing reaction of the epoxy resin and the glycoluril resin as described above, the epoxy resin and the glycoluril resin are usually epoxy resin / glycoluril resin = 50 /
It is used in a mass ratio of 50 to 95/5, preferably 60/40 to 90/10. When the above amount ratio is less than 50/50, the residual ratio of the glycoluril resin becomes high and the corrosion resistance deteriorates, and when it is more than 95/5, the glycoluril resin becomes insufficient and a sufficient cured film cannot be obtained. Solvent resistance and corrosion resistance tend to deteriorate.

The second layer consisting of the organic film of the present invention is formed by preparing a surface treatment agent containing the above-mentioned epoxy resin and glycoluril resin and applying it. If necessary, various additives capable of imparting and improving various properties to the organic film can be contained in the surface treatment agent. As such an additive, it is preferable to contain a water repellent, for example. Since the water repellent is hydrophobic, it tends to be concentrated on the surface layer of the organic film. for that reason,
Prevents corrosion factors from penetrating into the organic film at the surface layer and improves solvent resistance and corrosion resistance. In addition, it improves the film adhesion. The water repellent is a fluororesin, polyethylene wax, a resin coated with polyethylene wax, or the like. The water repellent is preferably contained in the organic film in an amount of 5 to 20% by mass.

It may also contain a silane coupling agent, a urethane resin or the like. The surface treatment agent is an aqueous solution or aqueous dispersion prepared by stirring and mixing the above-mentioned various components contained in the organic film in an aqueous solvent. It may be prepared by heating if necessary and making it aqueous by using a nonionic emulsifier. The concentration of the surface treatment agent may be in the solid content range where the stability of the organic resin is ensured, but is usually about 5 to 35 mass% as the solid content concentration.

After the surface treatment agent is applied on the first coating layer, it is usually baked to obtain a cured coating. The baking temperature varies depending on the epoxy resin used, but when (c) the modified epoxy resin having a primary hydroxyl group is not included, it is 2
It is carried out at a relatively high temperature of about 00 to 240 ° C. On the other hand, when the modified epoxy resin (c) having a primary hydroxyl group is used, it can be carried out at a relatively low temperature of about 150 to 200 ° C. When the baking temperature is lower than the lower limit value, the curing may be slightly insufficient, or the solvent may remain in the organic film, so that the corrosion resistance may be slightly deteriorated. Even if the baking temperature exceeds the upper limit, there is no particular problem, but yellowing due to partial decomposition of components in the organic film may be observed.

The second layer composed of the organic film as described above is
It has excellent solvent resistance and corrosion resistance, but this is achieved by the curing reaction between the epoxy resin and the glycoluril resin. A hard and brittle structure increases toughness by forming a cured film with a flexible structure of glycoluril resin. The glycoluril unit of the cured film also increases the adhesion to the base material. This prevents the uncured low molecular weight component from being dissolved by the solvent and increases the ability to suppress the entry of corrosion factors into the organic film.
Corrosion resistance is improved because the ability to suppress the intrusion of corrosion factors into the underlying boundary surface by the capillary phenomenon is also increased.

The organic film formed of the epoxy resin and the glycoluril resin exerts such an effect when the epoxy group and the hydroxyl group contained in the epoxy resin are added to each other to be polymerized. The generated hydroxyl group and the hydroxyl group existing in the epoxy resin are dehydrated with the hydroxyl group (methylol group, alkylmethylol group, etc.) of the glycoluril resin when the surface treatment agent is baked at a temperature around 150 to 240 ° C. Dealcoholization) condensation,
This is for forming a cured film. It is presumed that the glycoluril unit and the hydroxyl group of this cured film contribute to the strong wet adhesion to the base material of the metal plate and exhibit excellent solvent resistance and corrosion resistance.

In the present invention, the film thickness of the above-mentioned coating is preferably 0.1 to 5 μm, particularly 0.5 to 2.0 μm in total for the first layer and the second layer. preferable. If it is less than 0.1 μm, the corrosion resistance and solvent resistance tend to deteriorate. If it exceeds 5 μm, the corrosion resistance is improved but the cost is increased.

[0066]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples.

Preparation Example 1 Preparation of epoxy resin (a). To 680 g of bisphenol A type epoxy resin (a) having an epoxy equivalent of 1950, 132 g of propylene glycol monomethyl ether was added, and then 84 g of a nonionic emulsifier (“ADEKA Pluronic F68”) was added to make a uniform solution, and then a triaxial mixer was used. Then, gradually add 649 g of water to obtain an epoxy equivalent of 4000 and a solid content of 5
0% by weight of epoxy resin emulsion was obtained.

(B) Preparation of phosphoric acid-modified epoxy resin. (Preparation Example 2) (b1) Amine neutralized product of phosphoric acid-modified epoxy resin (anion type) 85 g of orthophosphoric acid and 140 g of propylene glycol monomethyl ether were charged, and 425 g of bisphenol A type epoxy resin having an epoxy equivalent of 250 was gradually added, The reaction was carried out at 80 ° C for 2 hours. After the completion of the reaction, at 50 ° C. or lower, 150 g of an aqueous 29% by mass ammonia solution was gradually added, and further 1150 g of water was added to the amine neutralized product of a phosphoric acid-modified epoxy resin having an acid value of 35 and a solid content concentration of 25% by mass. Got

Preparation Example 3 (b2) Nonionic Emulsion of Phosphoric Acid-Modified Epoxy Resin 95 g of orthophosphoric acid and 198 g of propylene glycol monomethyl ether were charged, and 396 g of bisphenol A type epoxy resin having an epoxy equivalent of 250 was gradually added, and the temperature was adjusted to 80 ° C. And reacted for 2 hours. After completion of the reaction, at 80 ° C. or lower, a nonionic emulsifier (“Adeka Pluronic F6
8 ″) 25 g was gradually added, and after becoming uniform, 264 g of water was further added to obtain an acid value of 65 and a solid content concentration of 50 mass%.
To obtain a phosphoric acid-modified epoxy resin.

Preparation Example 4 (b3) Amine-neutralized product of phosphoric acid-modified epoxy resin (anion type) 85 g of orthophosphoric acid and 140 g of propylene glycol monomethyl ether were charged, and 807 g of bisphenol A type epoxy resin having an epoxy equivalent of 475 was gradually added. It was added and reacted at 80 ° C. for 2 hours. After the completion of the reaction, at 50 ° C. or lower, 150 g of 29 mass% aqueous ammonia solution was gradually added, and further 2386 g of water was added to the amine neutralized product of a phosphoric acid-modified epoxy resin having an acid value of 21 and a solid content concentration of 25 mass%. (Anion type) was obtained.

(C) Preparation of modified epoxy resin having primary hydroxyl group. (Preparation Example 5) (c1) 1950 g of a bisphenol type epoxy resin having an epoxy equivalent of 1950 is dissolved in 876 g of propylene glycol monomethyl ether, and then 78.8 g of diethanolamine is added and reacted at 100 ° C. for 3 hours to modify an epoxy equivalent of 11600. An epoxy resin emulsion was obtained. Next, 256 g of a nonionic emulsifier (“Adeka Pluronic F68”) was added, and after homogenizing, 2553 g of water was gradually added using a triaxial mixer to obtain an epoxy equivalent of 22500 and a primary hydroxyl group of 40 wt% solid content. A modified epoxy resin emulsion having the above was obtained.

Preparation Example 6 (c2) Epoxy equivalent 195
1950 g of 0 bisphenol type epoxy resin is dissolved in 876 g of propylene glycol monomethyl ether,
Next, 100 g of 2,2-dimethylolpropionic acid was added to homogenize the mixture, and dimethylbenzylamine 1 was added to the catalyst.
g was added and the mixture was reacted at 130 ° C. for 3 hours, and it was confirmed that the epoxy equivalent was 12000. Then, nonionic emulsifier (“ADEKA Pluronic F68”) 513g
Was added and made uniform, and then 2296 g of water was gradually added to obtain a modified epoxy resin emulsion having an epoxy equivalent of 22300 and a solid content concentration of 40% by mass having a primary hydroxyl group.

Preparation Example 7 (c3) Epoxy equivalent 950
Was dissolved in 380 g of propylene glycol monomethyl ether, 79 g of diethanolamine was added, and the mixture was reacted at 100 ° C. for 3 hours to obtain an epoxy polyol resin emulsion having an epoxy equivalent of 5640. Next, 127 g of a nonionic emulsifier (“ADEKA PLURONIC F68”) was added and homogenized.
g was gradually added to obtain a modified epoxy resin having a primary hydroxyl group with an epoxy equivalent of 11,500 and a solid content concentration of 40% by mass.

(Examples 1 to 41 and Comparative Examples 1 to 3) The components shown in Table 2 were mixed in an aqueous medium to prepare an aqueous composition, which was roll-coated on a zinc-based plated steel sheet. Then, it heated so that steel plate temperature might be set to 150 degreeC in 20 seconds, it was made to dry and harden | cure, and the 1st film layer was formed.

Next, the epoxy resins (a) to (c) and the glycoluril resin A to which were prepared in the above Preparation Examples 1 to 7 were used.
D and water repellents A to D were added to water in the amount ratio shown in Table 3 (mass ratio with respect to 100 parts by mass of total solid content), and the mixture was stirred and mixed at room temperature to give an aqueous surface treatment agent for the second coating layer. Prepared. The obtained surface treating agent was roll-coated on the first layer. A metal plate temperature was heated to 180 ° C. in 20 seconds to prepare a test piece. Table 4 shows the characteristics of the organic film of the test piece tested by the method described below.

The symbols shown in each table are as follows. [Zinc-based galvanized steel sheets A to G] Steel sheet A: Electrogalvanized steel sheet (sheet thickness: 1.0 mm, Zn: 20 g / m ² ) Steel sheet B: Electrogalvanized-nickel plated steel sheet (sheet thickness: 1.0 mm, Zn- Ni: 20 g / m ² , Ni: 12 mass%) Steel plate C: Hot-dip galvanized steel plate (sheet thickness: 1.0 mm, Zn: 60 g / m ² ) Steel sheet D: Alloyed hot-dip galvanized steel sheet (sheet thickness: 1. 0 mm, Zn: 60 g / m ² , Fe: 10 mass%) Steel plate E: Zinc 5% aluminum steel plate ([Galfan], plate thickness: 1.0 mm, 60 g / m ² , Al: 5 mass%) Steel plate F: Zinc 55% Aluminum Steel Plate ([Galvalume], Plate Thickness: 1.0 mm, 60 g / m ² , Al: 55% by Mass) Steel Plate G: Anodic Electrolytically Treated Steel Plate (Plate Thickness: 1.0 mm, Zn-Ni: 10 g / m ² , Ni: 12 mass%)

[Metallic Compounds A to I] The numerical values of the patterns shown in Table 1 below are mass ratios of metals. Me ₁ and Me ₂ represent different kinds of metals, and n + represents a metal ion valence number of 2 to 6.

[Table 1] -: Not included

[Acid Group Constituting Metal Compounds A to I] It is shown in the metal ion column of Table 2. Acid group P: phosphoric acid Acid group C: Carbonic acid Acid group N: Nitric acid Acid group A: Acetic acid Acid group H: hydroxide Acid group F: Fluoride

[Organic acids A to D] Organic acid A: tricarballylic acid Organic acid B: citric acid Organic acid C: Isocitric acid Organic acid D: Succinic acid

[Styrene-carboxyl group-containing compound copolymers A to D] Copolymer A: Styrene-butyl methacrylate copolymer Copolymer B: Styrene-butyl acrylate copolymer C: Styrene -Acrylic acid copolymer Copolymer D: Styrene-methyl methacrylate copolymer

Glycoluril resin in Table 3; Resin A: completely butylated glycoluril resin ("Cymel 1170" manufactured by Mitsui Cytec Co., Ltd.) Resin B: methyl / ethyl mixed alkylated glycoluril resin (Mitsui Cytec Co., Ltd.) Made "Cymel 117
1 ") Resin C: Tetramethylol glycoluril resin (" Cymel 1172 "manufactured by Mitsui Cytec Co., Ltd.) Resin D: Completely methylated glycoluril resin (" Cymel 1174 "manufactured by Mitsui Cytec Co., Ltd.)

The properties of each test piece (alkali resistance, solvent resistance, corrosion resistance after alkali and solvent degreasing) were evaluated according to the following test methods. <Alkali resistance> A disc-shaped test piece having a diameter of 48 mm was immersed in an alkaline degreasing solution ([CL-N364S]: manufactured by Nippon Parkerizing Co., Ltd.) at 60 ° C for 2 minutes. The C count before and after the immersion was measured by using a fluorescent X-ray analysis, and the fixing rate was calculated by the following formula, and evaluated according to the following evaluation criteria. The results are shown in Table 4. Fixing rate = (C count before immersion-C count after immersion)
/ C count before immersion × 100 ○: 80% or more △: 50% or more and less than 80% ×: less than 50%

<Solvent resistance> Methyl ethyl ketone, ethanol, benzine, and methylene chloride were added respectively, and 50
The appearance was observed by rubbing 10 times at 0 g load / cm ² . ○: No change △: Small change ×: Large change

<Corrosion resistance after degreasing with alkali and solvent> After shearing the test piece to a size of 70 mm × 150 mm,
It was immersed in an alkaline degreasing solution ([CL-N364S]: manufactured by Nippon Parkerizing Co., Ltd.) at 60 ° C. for 2 minutes. Alternatively, it was immersed in methyl ethyl ketone, ethanol, benzine, and methylene chloride at 40 ° C. for 2 minutes. After that, the end face portion was sealed and a salt spray test (JIS Z-2371) was performed, and the time required until white rust was generated in 5% of the surface area of each test piece was evaluated according to the following evaluation criteria. The results are shown in Table 4. ◎: 96 hours or more ○: 72 hours or more and less than 96 hours △: 48 hours or more and less than 72 hours ×: less than 48 hours

[0085]

[Table 2]

[0086]

[Table 3]

[0087]

[Table 4]

[0088]

In the conventional chromium-free surface treatment agent, the metal surface cannot be completely adhered to the surface treatment agent when viewed microscopically, and there was a limit to the improvement of the adhesion. According to this, it is possible to provide a surface-treated galvanized steel sheet having a film having high adhesion to the substrate. In the present invention, when a surface-treated galvanized steel sheet is obtained, a so-called non-polluting non-chromate surface-treating agent that does not contain chromium is used. When using a zinc-based plated steel sheet, no special wastewater treatment is required, and the surface-treated galvanized steel sheet of the present invention is excellent in both corrosion resistance, solvent resistance and environmental friendliness, conventional automobiles, home appliances, It can replace the chromate-treated steel sheet used in the field of building materials. Further, since it is a non-polluting surface-treated zinc-based plated steel sheet that does not contain chromium, it can be used in a wide range of applications including container-related, tableware-related, and indoor building materials.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C23C 22/40 C23C 22/40 28/00 28/00 C (72) Inventor Shigeru Unno Central Chiba City, Chiba Prefecture Subdivision Kawasaki-cho, address Kawasaki made of iron Co., Ltd. Institute of technology in the F-term (reference) 4D075 CA13 CA33 CA34 CA44 DA06 DB05 DB07 DC01 DC05 DC18 DC41 EA06 EB14 EB20 EB22 EB32 EB34 EB45 4F100 AA04B AA05B AA08B AA17B AB03A AB09B AB10B AB14B AB18A AH08B AK12B AK12J AK24B AK24J AK36C AK36K AK53C AL01B AL05B BA03 BA07 BA10A BA10C EH71A JB01 JB02 JB05B JM02B 4K026 AA02 AA07 AA11 AA22 BA01 BA03 BB08 CA23 CA28 CA29 CA30 CA31 CA32 CA38 DA02 DA11 EB08 4K044 AA02 AB02 BA10 BA12 BA17 BA18 BA20 BA21 BB03 BC02 CA11 CA16 CA17 CA18 CA53

Claims (4)

[Claims] 1. A surface of a zinc-based plated steel sheet comprising a phosphate, carbonate, nitrate, acetate, hydroxide and fluoride of at least one metal selected from the group consisting of Mg, Mn and Al. A first coating layer formed from an aqueous composition containing at least one metal compound selected from the group and an organic acid capable of coordinating with a divalent or higher valent metal ion, and an epoxy resin on the first coating layer And a surface-treated zinc-based plated steel sheet having an organic coating layer formed of glycoluril resin. 2. The aqueous composition further comprises Zn, Co, T
i, Sn, Ni, Fe, Zr, Sr, Y, Cu, Ca,
The surface-treated zinc-based plated steel sheet according to claim 1, containing at least one metal compound selected from the group consisting of V, Ba, W, and Mo. 3. The surface-treated zinc-based plated steel sheet according to claim 1, wherein the aqueous composition further contains a styrene-carboxyl group-containing compound copolymer. 4. The surface-treated zinc-based plated steel sheet according to claim 1, wherein the epoxy resin is a bisphenol type epoxy resin and / or a hydroxyl group-modified modified product thereof.