JP2012117108A - Coated galvanized steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chromate free coated galvanized steel sheet which is extremely excellent in corrosion resistance, processability, scratch resistance, chemical resistance or the like.SOLUTION: The coated galvanized steel sheet has, on at least one surface of a galvanized steel sheet, a lower layer silicon oxide-based coating film (A) in which the ratio (I/I) of the infrared absorbing spectrum intensity Iderived from Si-OH at 900 to 1,000 cmto the infrared absorbing spectrum intensity Iderived from Si-O-Si bond at 1,000 to 1,250 cmis at least 0.1, an upper layer organic resin-based coating film (B) having at least one kind selected from carboxyl group, hydroxyl group, sulfonic acid group and silanol group in the structure, and a coating film which is an intermediate layer coating film (C) provided between the coating films (A) and (B) and contains film at least one kind selected from an organic resin having at least one kind selected from specific functional groups in the structure, a silane coupling agent, and a polyphenol compound.

Description

  The present invention does not use an undercoat film containing hexavalent chromium, and has substantially the same coating film performance as when a film containing hexavalent chromium is used (for example, high coating film and zinc-based plated steel sheet). The present invention relates to a coated galvanized steel sheet that enables expression of adhesion.

  Galvanized steel sheets used in various applications such as automobiles, home appliances, and building materials are usually subjected to treatments such as painting and lamination for the purpose of expressing various properties such as design properties, corrosion resistance, and insulation. used.

  In recent years, pre-coated metal plates coated with colored organic films or clear pre-coated metal plates that take advantage of the metallic feel of metal surfaces have been used instead of post-painted products that have been painted after conventional molding. It has become. These designable metal plates are made by coating a colored organic film on a rust-proof steel plate or plated steel plate, or by applying a clear coating on a metal plate exhibiting a metallic luster, and have a beautiful appearance. However, it has processability and good corrosion resistance.

  The metal plate used for these coated metal plates has improved coating adhesion and corrosion resistance by forming a chromium oxide film on the surface of the metal plate by immersing or electrolyzing the metal plate in a dichromic acid solution. Therefore, it has been used in a wide range of fields and applications. However, in recent years, interest in global environmental issues has increased, and it has become desirable not to use hexavalent chromium. Various treatments have been developed with the aim of achieving a performance equivalent to a film using hexavalent chromium in a film that does not use hexavalent chromium, but sufficient characteristics have not been obtained. Here, “use of hexavalent chromium” means that hexavalent chromium is used in the production process and that hexavalent chromium is contained in the film.

  For example, Patent Document 1 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment solution. These pre-coated steel sheets have corrosion resistance, workability, and paint adhesion due to the combined effect of the plating film, chromate-treated film, and chrome-based anti-corrosive pigment (primary coating). The purpose is to improve productivity and quality.

  However, in consideration of the environmental load of hexavalent chromium that may be eluted from the chromate-treated film and the organic film containing the chromium-based rust-preventive pigment, the demand for a non-chromium anti-rust treatment and a non-chromium organic film has been increasing recently. .

  Patent Document 2 describes a metal surface treatment method using a chromium-free coating-type acidic composition. In this metal surface treatment method, a coating solution is formed by applying a treatment aqueous solution containing fluorine ions to a metal surface and then baking and drying without performing a water-washing step. Since rusting occurs at the starting point, sufficient corrosion resistance and post-coating corrosion resistance are not exhibited.

  In contrast to this technique, Patent Documents 3 to 5 describe a method of washing with water after film formation. Patent Document 3 discloses a metal chemical conversion treatment method containing zirconium and / or titanium ions and fluorine ions in a treatment liquid. Patent Document 4 includes at least one of a compound containing one or more elements selected from the group consisting of Ti, Zr, Hf, and Si, a compound containing Y and / or a lanthanoid element, nitric acid and / or a nitric acid compound, and a fluorine-containing compound. A treatment liquid for surface treatment containing one kind is disclosed. Patent Document 5 discloses at least one compound selected from the group consisting of a compound containing one or more elements selected from the group consisting of Zr, Ti, Hf, and Si, hydrofluoric acid, nitric acid, sulfuric acid, and salts thereof. Contains a compound containing one or more elements selected from the group consisting of an acid component, Fe, Mn, Ni, Co, Ag, Mg, Al, Zn, Cu and Ce, and a free fluorine ion concentration of 1 to 30 mg / L A surface chemical conversion treatment liquid is disclosed. However, in applications where workability such as coated metal sheets, appearance and performance after processing are required, it cannot be said that sufficient studies have been made to ensure adhesion between coatings. There was a concern that the adhesiveness could not be expressed sufficiently.

Japanese Patent Laid-Open No. 3-100180 JP-A-5-195244 JP 2004-43913 A Japanese Patent No. 4242828 International Publication No. 2007/061011 Pamphlet

  The object of the present invention is to use a chromate-free coated zinc that does not use an undercoating film containing hexavalent chromium, which has a high environmental load, and is extremely excellent in various properties such as corrosion resistance, workability, scratch resistance, and chemical resistance. It is to provide a plated steel sheet.

  As a result of diligent research, the inventor combined a silicon oxide-based lower layer film having a specific functional group with a resin-based upper layer film having a specific functional group at a specific content, and specified between them. The knowledge that forming a three-layer film with a resin-based intermediate film having a functional group gives high adhesion to a galvanized steel sheet. And was found to be extremely effective in achieving the above object.

The coated zinc-based plated steel sheet of the present invention is based on the above knowledge,
The gist is as follows.

(1) It has a lower layer silicon oxide film (A) and an upper organic resin film (B) on at least one surface of a galvanized steel sheet, and a lower silicon oxide film (A) and an upper organic resin film (B). A coated galvanized steel sheet having an intermediate layer film (C) between and
The upper-layer organic resin film (B) is a film having a thickness of 0.5 to 10 μm and having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure.
The intermediate layer film (C) includes at least one selected from an organic resin having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure, a silane coupling agent, and a polyphenol compound. , A film having a thickness of 0.01-2 μm,
Infrared absorption spectrum intensity I _SiOSi from the bond of Si-O-Si in the infrared absorption spectrum intensity I _SiOH and 1000～1250Cm ^-1 from SiOH in 900～1000Cm ^-1 of the silicon oxide film (A) A coated zinc-based plated steel sheet, characterized in that the ratio _ISiOH / _ISiOSi is at least 0.1.
(2) The coated zinc-based plated steel sheet according to (1), wherein the silicon oxide-based coating (A) is a silicon oxide-based coating that does not contain a fluorine compound.
(3) The coated zinc-based plated steel sheet according to (1) or (2) above, wherein the silicon oxide-based film (A) has the ratio I _SiOH / I _SiOSi of 0.1 or more and 5 or less. .
(4) The silicon oxide-based coating (A) further contains at least one of a Ti compound, a Zr compound, a V compound, an Nb compound, and a P compound, according to the above (1) to (3) The coated zinc-based plated steel sheet according to any one of the above.
(5) The organic resin film (B) of the upper layer is any one of the above (1) to (4), which is a film containing a polyester resin containing a sulfonic acid group and a melamine resin as a curing agent. Painted galvanized steel sheet.
(6) The coated galvanized steel sheet according to any one of (1) to (5) above, wherein the upper organic resin film (B) contains a colorant.
(7) The coated galvanized steel sheet according to (6) above, wherein the upper organic resin film (B) contains carbon black as a colorant.
(8) The upper organic resin film (B) is a polyester resin containing a sulfonic acid group, a polyurethane resin containing a silanol group, a phenol resin, a polyolefin resin, an acrylic resin, and a crosslinking agent. A resin film containing at least one selected from a water-soluble isocyanate compound, a carbodiimide group-containing compound, an oxazoline group-containing compound, and an organic titanate compound, and further containing silicon oxide and a phosphoric acid compound The coated galvanized steel sheet according to any one of (1) to (7).
(9) The organic resin of the intermediate layer film (C) contains at least one of a polyester resin, a polyurethane resin, an epoxy resin, a phenol resin, an acrylic resin, and a polyolefin resin. The coated galvanized steel sheet according to any one of (8).
(10) The silicon oxide-based film (A) forms a silicon oxide-based film on the surface of the plated steel sheet by immersing the zinc-based plated steel sheet in a silicate-based aqueous solution that does not contain fluorine ions but contains oxygenate anions. The coated galvanized steel sheet according to any one of (1) to (9) above, wherein
(11) The silicon oxide-based film (A) was formed on the surface of the plated steel sheet by immersing the zinc-based plated steel sheet in a silicate-based aqueous solution containing no oxygen ions and not containing fluorine ions and cathodic electrolysis. The coated galvanized steel sheet according to any one of the above (1) to (10), which is a product.
(12) The coated galvanized steel sheet according to (11) above, wherein the conditions of the cathode electrolysis are a current density of 10 to 200 mA / cm ² and a temperature of 20 ° C. to 60 ° C.
(13) The coating according to any one of (10) to (12), wherein the oxygenate anion is at least one selected from the group consisting of phosphate ions, nitrate ions, and sulfate ions. Galvanized steel sheet.

According to the present invention in which the coating film of the galvanized steel sheet is composed of the above-mentioned three-layered film, the silicon oxide-based lower layer film exhibits high adhesion to the galvanized steel sheet and the action of the intermediate layer. This improves the adhesion of the upper resin film to the silicon oxide-based lower film, so that high adhesion of the coating film to the zinc-based plated steel sheet can be obtained. In addition, the inclusion of SiO _{2 in the} lower layer film improves the barrier properties of the coating film, and the organic resin film is multi-layered (having an upper organic resin film (B) and an intermediate layer film (C)). Therefore, the coated zinc-based plated steel sheet of the present invention exhibits excellent corrosion resistance in addition to excellent coating film adhesion.

It is a figure explaining the measurement of the infrared absorption spectrum intensity derived from the Si-O-Si bond and Si-OH bond of a silicon oxide type film.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Painted galvanized steel sheet)
The coated galvanized steel sheet of the present invention has a lower silicon oxide film (A) and an upper organic resin film (B) on at least one surface (plating surface) of the galvanized steel sheet. A coated zinc-coated steel sheet having an intermediate layer film (C) between A) and the upper organic resin film (B). The upper organic resin film (B) is a film having a thickness of 0.5 to 10 μm having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure. ) Includes at least one selected from an organic resin having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure, a silane coupling agent, and a polyphenol compound, and has a thickness of 0.01 to It is a 2 μm film. The ratio I _SiOH the infrared absorption spectrum intensity I _SiOSi from the bond of Si-O-Si in the infrared absorption spectrum intensity I _SiOH and 1000～1250Cm ^-1 from SiOH in 900～1000Cm ^-1 silicon oxide base film / I _SiOSi is at least 0.1.

Result of extensive studies, the present inventors have found that the infrared absorption spectrum intensity ascribed to the bond of Si-O-Si in the infrared absorption spectrum intensity I _SiOH and 1000～1250Cm ^-1 from SiOH bonds in 900～1000Cm ^-1 the ratio I _SiOH / I _SiOSi with I _SiOSi silicon oxide based film is at least 0.1 were found to result in a high coating adhesion and high corrosion resistance. Here, the silicon oxide film is a film in which silicon oxide and / or silicon hydroxide is present in the film at the highest ratio in terms of metal element mass ratio, or silicon in terms of metal. This indicates a film containing at least mass%.

  The inventor presumes the mechanism for improving the paint adhesion and corrosion resistance characteristics as follows.

The ratio I of infrared absorption spectrum intensity I _SiOSi from the bond of Si-O-Si in the infrared absorption spectrum intensity I _SiOH and 1000～1250Cm ^-1 from SiOH bonds in 900～1000Cm ^-1 silicon oxide base film _SiOH / I _SiOSi is at least 0.1, that is, a silicon oxide film containing a certain amount or more of silicon hydroxide can form a strong bond with the film formed thereon by chemical bonds, hydrogen bonds, etc. Therefore, it shows excellent paint adhesion. In the present invention, an intermediate between the silicon oxide film and the silicon oxide film and an organic resin film having a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure (that is, main chain and / or side chain). It has been found that the layer film has high adhesion. Even in the case where the intermediate layer film is a film containing a silane coupling agent or a film containing a polyphenol compound, due to the presence of the silanol group of the silane coupling agent or the hydroxyl group in the polyphenol compound, the intermediate layer film is strongly bonded to Si—OH in the silicon oxide film. It was found that a strong bond was formed and high adhesion between the silicon oxide film and the intermediate film was developed. The present inventor presumes that this is because a strong adhesion can be exerted by a chemical bond between a certain amount or more of Si-OH groups and a specific functional group of the resin. Moreover, since it also contains silicon oxide, it has a high barrier property and contributes to an improvement in corrosion resistance.

  The average thickness of the silicon oxide film is preferably 1 nm to 1 μm. More preferably, it is 1 nm to 300 nm.

Ratio having SiOH groups (I _SiOH / I _SiOSi) is 0.1 to 5 (further, 0.1 to 2) is preferably. If this ratio is less than 0.1, the adhesion tends to be insufficient. On the other hand, if this ratio exceeds 5, a decrease in corrosion resistance due to a decrease in barrier properties due to a decrease in the SiO ₂ ratio may be observed.

As will be described later, by adding at least one of a Ti compound, a Zr compound, a V compound, an Nb compound, and a P compound to the silicon oxide film, the corrosion resistance of the coated zinc-plated steel sheet can be further improved.
Ti compound, Zr compound: Corrosion resistance improvement effect by improving barrier property V compound, Nb compound: Corrosion resistance improvement effect by inhibitor action P compound: Corrosion resistance improvement effect by action of both barrier property and inhibitor property

In the present invention, in a mode in which the silicon oxide film is a fluoride-free film, rusting due to the material is more effectively suppressed. In addition, when _ISiOH / _ISiOSi exceeds 5, there may be a case where a decrease in corrosion resistance, which may be caused by a decrease in barrier properties due to a small amount of silicon oxide, may be observed.

Here, the infrared absorption spectrum intensity was obtained by a highly sensitive reflection method of FT-IR (Fourier transform infrared spectroscopy). FIG. 1 is an example of an infrared absorption spectrum of a silicon oxide film measured by this method.
As shown in FIG. 1, Si-O-Si bonds and Si-OH bonds, respectively 1000～1250Cm ^-1, absorption peaks obtained 900~1000cm ^-1. The peak derived from the Si—O—Si bond at 1000 to 1250 cm ⁻¹ is attributed to a cyclic or linear siloxane bond.
In Figure 1, the absorption peak bottom of 850 cm ^-1 vicinity, connected by tangential absorption peak bottom of 1330 cm ^-1 vicinity measures each peak absorbance peak height from the baseline as a baseline background, This was taken as the peak intensity.
Measurement conditions include, for example, FT-IR (trade name “FT / IR-4100”, manufactured by JASCO Corporation) and a highly sensitive reflection measuring instrument (trade name “RAS PRO410-H”, manufactured by JASCO Corporation). ), The incident angle is 85 ° C., the resolution is 4 cm ⁻¹ , and the number of integrations is 50.
Further, a method using the KBr tablet method or the ATR method (Attenuated Total Reflectance) is also possible. In that case, the peak position may shift depending on the measurement method and equipment. In that case, the peak position is specified by using X-ray photoelectron spectroscopy together, and the peak position is corrected and the peak is corrected. What is necessary is just to measure intensity | strength.

(Preparation of IR measurement sample)
In the present invention, the FT-IR sample of the “silicon oxide film” is a silicon oxide film (or “interlayer film (C) before forming the“ interlayer film (C) ”positioned thereon. ”And“ silicone-based coating at a portion where neither “organic resin-based coating (B)” is formed. For example, in the aspect of forming the first layer → second layer → third layer... And each upper layer on the galvanized steel sheet, only the first layer is formed at the end of the galvanized steel sheet. On the actual galvanized steel sheet, it is like a terraced field, such as a part, a part where only (first layer + second layer) is formed, and a part where (first layer + second layer + third layer) is formed. A part for measuring physical properties is formed in advance. About such a physical property measurement part, each required physical property measurement can be performed.

(Average thickness of silicon oxide film)
The average thickness of the silicon oxide film is preferably 1 nm or more and 1 μm or less. The average thickness of the silicon oxide-based film is more preferably 1 nm or more and 300 nm or less. If it is less than 1 nm, the coverage may be less than 100%, and the corrosion resistance and paint adhesion may be insufficient. Further, when it exceeds 300 nm, the coating adhesion is saturated, and therefore it can be sufficiently used for applications where the requirement for corrosion resistance is not strict. In addition, when the thickness exceeds 1 μm, the coating adhesion and corrosion resistance are saturated, which is not economical, and peeling may occur due to stress concentration, which may cause problems.

  Here, the average thickness means a cross-sectional SEM (scanning electron microscope) observation or a cross-sectional TEM (transmission electron microscope) of about 1000 to 200,000 times (preferably about 1 to 30,000 times) the silicon oxide film. In observation, it means an average value of film thicknesses measured in 10 arbitrary visual fields. In addition, coating adhesion means adhesion with the organic resin layer formed by coating, lamination, or the like.

  Next, the metal surface treatment agent used for forming a silicon oxide film on the surface of the galvanized steel sheet in the present invention will be described.

(Metal surface treatment agent)
As a silicate used as the silicon source of the silicon oxide-based film, for example, sodium silicate, potassium silicate, lithium silicate, and the like can be used, and there are no particular restrictions on these. The concentration range is preferably 1 mM to 1 M (mol / L). If it is less than 1 mM, the film formation rate is low, which is not economical, and so-called “burning” may occur during cathode electrolysis. If it exceeds 1M, the film formation rate is saturated, there is no effect of increasing the concentration, and the cost for treating waste liquid such as washing water increases, which is not economical. The concentration range of the silicate is more preferably 5 mM to 500 mM, and further preferably 10 mM to 100 mM.

  As the oxygen acid anion, for example, phosphate ion, nitrate ion, sulfate ion, borate ion and the like can be used. In particular, phosphate ions, nitrate ions, and sulfate ions are preferably used, and specifically phosphoric acid, nitric acid, and sulfuric acid.

When the film is formed by dipping, it is preferable that the concentration range is a specification corresponding to a silicate concentration or more. If it is less than 1 time, I _SiOH / I _SiOSi may exceed 5 and if it exceeds 10 times, hydrogen generation reaction occurs actively, and the film formation amount may not be stable. The concentration range of the oxyacid anion is preferably more than 1 time, more preferably 1.5 times or more and 6 times or less, and further preferably 2 times or more and 4 times or less.

  When the film is formed by cathode electrolysis, it is preferable that the concentration range be equivalent to or higher than the silicate concentration. If it is less than 1 time, the pH of the aqueous treatment solution may be basic, and the film forming behavior may be unstable. On the other hand, if it exceeds 10 times, the hydrogen generation reaction occurs actively, and the film formation amount may not be stable. The concentration range of the oxyacid anion is more preferably 1 to 3 times, and still more preferably 1 to 2 times.

  The pH of the metal surface treatment agent is preferably 1 or more and 4 or less. When the treatment solution pH is less than 1, hydrogen generation reaction occurs actively and a low-density film may be formed. On the other hand, when the treatment solution pH is higher than 4, the solution may be unstable and aggregated. The pH adjustment may be performed using the oxygen acid anion, ammonium water, sodium hydroxide, potassium hydroxide or the like, and is not particularly limited.

  In addition, industrial chemicals can be used for the preparation of the metal surface treatment agent, so that even if inevitable metal elements other than silicon are mixed as impurities, there is no effect on the film formation. Furthermore, even if inevitable metal elements other than silicon are mixed as impurities into the obtained film, the properties are not affected at all.

(Fluorine ion free mode)
In the present invention, it is preferable to form a silicon oxide-based film in a fluorine ion-free mode from the viewpoint of more effectively suppressing rusting caused by the material. Such a silicon oxide film in a fluorine ion-free embodiment is preferable from various environmental viewpoints. Here, the “fluorine ion-free silicon oxide film” means that the weight% as fluorine atoms is less than 0.0001% with respect to the total weight per unit area of the formed film.

(Formation of silicon oxide film by chemical conversion treatment)
In the present invention, it is preferable to form the silicon oxide film by chemical conversion treatment (that is, Liquid Phase Deposition (LPD) treatment) from the viewpoint of ensuring adhesion between the zinc-based plating surface and the intermediate layer film. .

(LPD processing)
In the present invention, in an embodiment in which LPD treatment is used to form a silicon oxide film, the silicon oxide film is composed of Si, 1-4 kinds of oxides selected from Ti, Zr, V, Nb, and Ta, water It is preferable to have a metal (water) oxide film layer made of one or both of oxides and containing at least Si and one or more of Ti and Zr and one or both of hydroxides. In such a case, in the present invention, a further excellent naked corrosion resistance is obtained, and the adhesion to the organic resin film layer formed on the upper layer is also excellent, and a performance equivalent to or higher than that of the chromate film is obtained.

(Suitable embodiment of silicon oxide film by LPD treatment)
(1) One or both of oxides and hydroxides of one or more metal elements selected from the groups a and b which contain the following group c, and at least an oxide of metal elements selected from the group c and water A silicon oxide film containing one or both of oxides (metal (water) oxide).
Group a: Ti, Zr
b group: V, Nb, Ta
c group: Si
(2) The film contains group c, and is composed of one or both of oxides and hydroxides of three kinds of metal elements selected from groups a to b, and at least an oxide of metal elements selected from group c The silicon oxide-based film according to (1), which contains one or both of hydroxides.

  (3) The silicon oxide according to (2), wherein the film contains group c and is composed of one or both of oxides and hydroxides of metal elements each selected from each group of groups ab. System film.

  (4) The coating element contains a group c, and is composed of one or both of oxides and hydroxides of two kinds of metal elements selected from the groups ab, and at least one metal element selected from the group c The silicon oxide-based film according to the above (1), which contains one or both of oxides and hydroxides.

  (5) The film contains group c, and is composed of one or both of oxides and hydroxides of two metal elements selected from groups ab, and one type of metal element selected from group c is oxidized. The silicon oxide-based film according to (4), further comprising a film containing one or both of an oxide, a hydroxide, a metal element oxide selected from group a or b, and a hydroxide.

(6) The silicon oxide-based film according to any one of (1) to (5), wherein the metal conversion amount of the film is 5 to 200 mg / m ² .

  (7) The silicon oxide film according to any one of (1) to (6), wherein a ratio of an element selected from group c is 30 mol% or more of a metal equivalent amount of the film.

  (8) The silicon oxide-based film according to any one of (1) to (7), wherein the surface-treated metal material is a galvanized steel material or a zinc alloy plated steel material.

(Effect of silicon oxide film using LPD treatment)
According to the aspect of the silicon oxide-based film using the LPD treatment of the present invention, when the organic resin-based film layer is formed as an upper layer with low corrosion resistance and high corrosion resistance because it does not contain hexavalent chromium, A metal material having a coating layer with high adhesion can be obtained.

  The silicon oxide-based film of this embodiment has a metal (water) oxide film layer composed of one or both of Si and an oxide or hydroxide of a specific metal element. As a result of intensive studies by the inventors of the present invention, it has been found that even a film not containing hexavalent chromium exhibits characteristics equivalent to or better than a film containing hexavalent chromium, a so-called chromate film. That is, the characteristics of the chromate film are bare corrosion resistance due to barrier properties, processed part corrosion resistance due to self-repairing ability due to dissolution and precipitation, and excellent adhesion with the upper layer film due to bonding with polar groups in the organic resin layer formed on the upper layer. . As a result of trial and examination on performance obtained by various combinations of oxides and hydroxides of various metals excluding chromium, focusing on these functions (barrier properties, self-repairability, reactivity with polar groups) The inventors have come up with metal (water) oxides of metal elements that make up a film that exhibits performance. More specifically, it is made of a metal (water) oxide of 1-4 kinds of metal elements selected from Si and Ti, Zr, V, Nb, Ta, and the (water) oxide contains at least Ti, Zr. Among them, it has excellent bare corrosion resistance by having a film containing one or more metal (water) oxides, and when an organic resin film layer is formed as an upper layer thereof, it has high adhesion to the organic film layer. I found that I have sex.

  In addition, Si, Ti, Zr, V, Nb, and Ta are classified into three groups a, b, and c based on their operational effects, and by appropriately combining the metal elements of each group based on their characteristics. It was found that excellent film properties can be obtained.

(Group a metal elements)
First, two elements of Ti and Zr are classified into group a. It has been found that when the (hydric) oxide of group a is contained in the film, it has a characteristic that the flat plate corrosion resistance is particularly excellent. This is considered to be due to the high barrier property due to the hydrophobicity of the film. Among the group a, it is more preferable to use Zr which is excellent in corrosion resistance as compared with other elements.

(Group b metal elements)
Group b is classified into three elements of V, Nb, and Ta. It has been found that when the (hydric) oxide of group b is contained in the film, it has a characteristic that the processed portion has excellent corrosion resistance. This is presumed to be due to the self-healing ability to cover the film defect part and the corrosion part caused by processing, etc., when the (water) oxide is dissolved in the wet corrosion environment. It is more preferable to use V which is excellent in the corrosion resistance of the processed part as compared with other elements in the group b.

(Group c metal elements)
Si is classified into group c. It was found that the adhesion with the upper organic resin-based film layer was particularly high when the (hydric) oxide of group c was contained in the film. This is presumed to form a strong chemical bond with the organic resin film layer formed thereon.

  Therefore, by appropriately combining the (hydric) oxides of the a and b groups with the (hydric) oxide of the c group Si, the corrosion resistance of the flat plate, the corrosion resistance of the processed part, and the adhesion with the upper film can be arbitrarily controlled. Things will be possible.

  For example, by combining a group c element Si and an element Zr selected from the group a, it is possible to form a film excellent in corrosion resistance and adhesion between the top coat film and selected from the group C elements Si and the group a. By combining the element Zr and the element V selected from the b group, it is possible to form a film having excellent flat plate corrosion resistance and processed portion corrosion resistance. And by combining the element Si selected from the group c, the element Zr selected from the group a and the element V selected from the group b, it is possible to obtain a performance excellent in flat plate corrosion resistance, processed portion corrosion resistance, and adhesion to the upper film. .

  Furthermore, it has also been found that even in the combination of the same group, a film composed of two or more elements can provide superior film characteristics as compared with a film composed of one element. For example, a film composed of two or more elements selected from the a group has better processed part corrosion resistance than a film composed of one element selected from the a group. The performance improvement mechanism by combining elements selected from the same group is not clear, but even the elements of the same group have different conditions and ranges in which their properties are manifested. A film composed of a combination of two or more types is not limited to the characteristics that the group is good at, because the conditions and range of characteristics are expanded and the combined action also works. It is estimated that expression and improvement may be seen.

  Therefore, an element selected from the group c element Si and the group a is combined with two elements Zr and Ti and an element V selected from the group b, or two elements Ti and Zr selected from the group Si elements Si and the group a. And b group elements, c group element Si and element Zr selected from group a and two kinds of elements selected from b group, or c group element Si and element Zr selected from group a By combining three elements selected from group b, better film performance is exhibited. However, when the combination of five or more elements is used, the performance improvement effect due to the combination of elements is saturated. By examining optimization of the combination of four or less elements, the required film properties can be obtained efficiently.

The film containing these metal (water) oxides is preferably 5 to 200 mg / m ^{2 in} terms of metal per side. If it is less than 5 mg / m ² , the above characteristics may be insufficient. When it exceeds 200 mg / m ² , the above characteristics are saturated or lowered, and it is not economical.

  The metal concentration ratio in the film of the group a, that is, the mass ratio of the metal element of the (water) oxide in the group a in the entire metal element of the (water) oxide constituting the film is preferably 10% or more and 50% or less. If it is less than 10%, the corrosion resistance of the processed part may be insufficient, and if it is 50% or more, the adhesion after processing may be deteriorated.

  The mass ratio of the group b metal elements is preferably 10% or more and 50% or less. If it is less than 10%, the corrosion resistance of the processed part may be insufficient. If it exceeds 50%, the film may not be maintained in a healthy state in a corrosive environment.

  The mass ratio of the c-group metal element Si is preferably 30% or more. If it is less than 30%, the adhesion to the upper layer film may be insufficient. More preferably, it is 50% or more.

  In some cases, the silicon oxide-based film may contain a fluorine compound. The method for forming the silicon oxide-based film containing the fluorine compound is not particularly limited. For example, it may be formed as a metal (water) oxide film containing a fluorine compound by a liquid phase deposition method (for details of a method for forming a silicon oxide film containing a fluorine compound, see, for example, JP-A-2009-299145). Can be referred).

Examples of the treatment liquid for forming a silicon oxide film containing a fluorine compound include ammonium hexasilicate, which is a silicon source, ammonium hexafluorozirconate, zirconyl nitrate, ammonium hexafluorotitanate, vanadyl sulfate, ammonium hexaniobate, and fluorine. A solution in which at least one of potassium tantalate is dissolved in hydrofluoric acid, pH is adjusted with aqueous ammonia, and the necessary concentration is adjusted can be suitably used.
Examples of the treatment liquid that does not contain fluorine ions and forms a silicon oxide film include, for example, sodium silicate, potassium silicate, lithium silicate, and the like, which are silicon sources, and oxygenate anions, such as phosphate ions, nitrate ions, and sulfate ions. , Borate ions and the like can be used. Particularly preferred as the oxygenate anion are phosphate ion, nitrate ion and sulfate ion. As the composite compound, at least one of zirconyl nitrate, titanium sulfate, vanadyl sulfate, ammonium hexaniobate, niobium oxide sol, and phosphoric acid can be suitably used.

  In the above liquid phase deposition method, for example, a zinc-based plated steel sheet that has been subjected to degreasing treatment is immersed in the treatment liquid or subjected to electrolytic treatment after immersion, and a silicon oxide film containing fluorine on the surface of the zinc-based plated steel sheet Can be formed.

In the formation of a silicon oxide film by electrolysis, for example, the current density is controlled to 10 to 200 mA / cm ² in a treatment solution in which a zinc-based plated steel sheet is immersed, and cathode electrolysis is performed at room temperature for 0.1 to 10 seconds. After film formation, it can be washed with water and dried. In the case of film formation of a silicon oxide film only by dipping without using electrolysis, a zinc-based plated steel sheet may be immersed in a treatment solution at room temperature for 1 to 10 minutes, washed with water and dried after film formation.

  The film thus obtained is confirmed by X-ray photoelectron spectroscopy and fluorescent X-ray method, for example, to confirm the generation of silicon oxide and / or silicon hydroxide, which is a constituent material of the silicon oxide film, and the amount of film formation. be able to. Further, the infrared absorption spectrum ratio of the silicon oxide film can be measured by FT-IR.

(Intermediate layer coating (C))
Next, the “intermediate layer film (C)” disposed on the silicon oxide film (A) will be described.

  The “intermediate layer film (C)” comprises at least one selected from an organic resin having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in its structure, a silane coupling agent, and a polyphenol compound. Including. The intermediate film (C) functions as an intermediate layer that improves the adhesion between the lower silicon oxide film (A) and the upper organic resin film (B) and improves the barrier properties of the entire film. To do. When the intermediate layer film (C) includes an organic resin having at least one functional group of carboxyl group, hydroxyl group, sulfonic acid group, and silanol group in the structure, the functional group is a lower silicon oxide type High adhesion to the silicon oxide film is manifested by chemical bonding with the Si—OH group in the film. In the case where the intermediate layer film (C) is a film containing a silane coupling agent or a film containing a polyphenol compound, the silanol group of the silane coupling agent or the hydroxyl group in the polyphenol compound is chemically synthesized with Si-OH in the silicon oxide film. High adhesion to the silicon oxide film is developed by bonding. Furthermore, the intermediate layer film (C) exhibits high adhesion to the upper organic resin film (B), and contributes to the development of excellent adhesion to the galvanized steel sheet of the entire coating film (described above). In the case of an intermediate layer film containing an organic resin having a functional group in its structure, an intermediate layer film containing a silane coupling agent due to the bond between the functional group and the same functional group in the upper organic resin film (B) In the case of the above, due to the same effect as the upper organic resin film (B) containing a silanol group, and in the case of an intermediate film containing a polyphenol compound, the upper organic resin film (B) containing a hydroxyl group Due to the same effect). In addition, the presence of the intermediate layer coating (C) improves the barrier properties of the entire coating compared to the case where the organic resin coating (B) as the surface layer is formed directly on the silicon oxide coating. As a result, the coated galvanized steel sheet of the present invention exhibits very excellent coating adhesion and corrosion resistance, and when the tangible resin film (B) is directly formed on the silicon oxide film (A). In comparison, the thickness of the entire coating film can be reduced.

  The thickness of the intermediate layer film (C) is preferably 0.01 to 2 μm. If it is less than 0.01 μm, the desired effect is small, and if it exceeds 2 μm, cohesive failure tends to occur depending on the type of film, and the adhesion may be lowered. A more preferable thickness of the intermediate layer film (C) is 0.02 to 1 μm.

  The intermediate layer film (C) preferably contains at least one of a polyester resin, a polyurethane resin, an epoxy resin, a phenol resin, an acrylic resin, and a polyolefin resin. The intermediate layer film (C) preferably uses at least one of a polyester resin, a polyurethane resin, an epoxy resin, and a phenol resin in order to further improve the adhesion with the underlying silicon oxide film (A). In order to increase the compatibility with the upper organic resin film (B) and increase the adhesion, it is particularly preferable to contain a polyester resin in the intermediate film (C).

  The silane coupling agent contained in the intermediate layer film (C) is not particularly limited. For example, vinyltrimethoxysilane, vinyltriethoxysilane sold by Shin-Etsu Chemical, Nippon Unicar, Chisso, Toshiba Silicone, etc. γ-aminopropyltrimethoxysilane, γ-aminopropylethoxysilane, N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyl Trimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyl Trimet Sisilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, N Examples include -β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. The said silane coupling agent may be used independently and may use 2 or more types together.

  The polyphenol compound contained in the intermediate layer film (C) refers to a compound having two or more phenolic hydroxyl groups bonded to a benzene ring, or a condensate thereof. Examples of the compound having two or more phenolic hydroxyl groups bonded to the benzene ring include gallic acid, pyrogallol, catechol and the like. The condensate of the compound having two or more phenolic hydroxyl groups bonded to the benzene ring is not particularly limited, and examples thereof include polyphenol compounds that are widely distributed in the plant kingdom, usually called tannic acid.

  Tannic acid is a general term for aromatic compounds having a complex structure having a large number of phenolic hydroxyl groups widely distributed in the plant kingdom. The tannic acid may be hydrolyzable tannic acid or condensed tannic acid. The tannic acid is not particularly limited, and examples thereof include hameli tannin, oyster tannin, chatannin, pentaploid tannin, gallic tannin, mylobarantannin, dibidi tannin, algarobilatannin, valonia tannin, catechin tannin, and the like. . Examples of the tannic acid include commercially available ones such as “tannic acid extract A”, “B tannic acid”, “N tannic acid”, “industrial tannic acid”, “purified tannic acid”, “Hi tannic acid”, "F tannic acid", "local tannic acid" (all manufactured by Dainippon Pharmaceutical Co., Ltd.), "tannic acid: AL" (manufactured by Fuji Chemical Industry Co., Ltd.) and the like can also be used.

  The said polyphenol compound may be used by 1 type, and may use 2 or more types together.

  When the intermediate layer film (C) contains at least one of a silane coupling agent and a polyphenol compound, it can be present in the organic resin-based film in an amount of 5 to 50% by mass, preferably 10 to 30% by mass.

  Although there is no restriction | limiting in particular in the formation method of an intermediate | middle layer membrane | film | coat (C), It forms by apply | coating the coating agent for forming an intermediate | middle layer membrane | film | coat (C) to at least one surface of a metal plate, and heat-drying. Although there is no restriction | limiting in particular in the coating method of the said coating agent, Well-known roll coat, spray coating, bar coating, immersion, electrostatic coating etc. can be used suitably. There is no restriction | limiting in particular in the baking drying method, A metal plate may be heated previously, a metal plate may be heated after application | coating, or you may dry combining these. There is no restriction | limiting in particular in a heating method, A hot air, induction heating, near infrared rays, a direct fire, etc. can be used individually or in combination. About baking baking temperature, it is preferable that it is 60 to 150 degreeC by the ultimate temperature, and it is still more preferable that it is 70 to 130 degreeC. If the ultimate temperature is less than 60 ° C, drying may be insufficient, and adhesion and corrosion resistance with the substrate may be reduced, and if it exceeds 150 ° C, adhesion with the substrate may be reduced. .

(Organic resin film (B))
Next, the “organic resin film (B)” disposed on the intermediate film (C) will be described. An example of the organic resin film (B) that can be suitably used in the present invention is as follows.
(1) The organic resin film (B) is a film containing a polyester resin containing a sulfonic acid group and a melamine resin as a curing agent, and the film further contains carbon black.
(2) The organic resin film (B) is water-soluble as at least one of a polyester resin containing a sulfonic acid group, a polyurethane resin containing a silanol group, a phenol resin, a polyolefin resin, and an acrylic resin, and a crosslinking agent. A resin film containing one or more selected from an isocyanate compound, a carbodiimide group-containing compound, an oxazoline group-containing compound, and an organic titanate compound, and further containing silicon oxide and a phosphoric acid compound.

  The thickness of the organic resin film (B) is preferably 0.5 to 10 μm. If the thickness is 0.5 μm, the corrosion resistance cannot be sufficiently exhibited. If it exceeds 10 μm, the effect is saturated and it is not economically advantageous. The more preferable thickness of the organic resin film (B) is 1 to 5 μm.

(Coloring of organic resin film (B))
Said organic resin-type membrane | film | coat (B) may be colored as needed. The colorant in this case is not particularly limited, and one or more kinds of known colorants (for example, known dyes and / or pigments) can be appropriately selected and used. In the aspect in which the organic resin film (B) is colored, the content of the colorant is about 3 to 40% by mass (further, 5 to 20 mass based on the total mass of the organic resin film). %). In the coated zinc-based plated steel sheet of the present invention in which the lower silicon oxide film, the upper colored film, and the intermediate layer are combined, the lower silicon oxide-based film is not colorless and transparent, but is slightly colored. By applying a colored film on the top layer, the color depth increases and a high-class feeling is generated. Also, compared to the surface of the galvanized surface, fine unevenness is formed due to the presence of the silicon oxide film, so an intermediate film is formed. Furthermore, the coated zinc-based plated steel sheet of the present invention in which the black coating is applied to the upper layer is preferable because it is easy to make the appearance uniform when coating both coatings, and the gloss control of the upper black coating is easy.

(Carbon black)
In the colored organic resin film (B), the colorant is preferably carbon black from the viewpoint of concealability and / or design of the film.

(Aspect containing carbon black)
In the aspect in which the organic resin film (B) contains carbon black, a colored composition (for example, aqueous system) containing a polyester resin (B1) containing a sulfonic acid group, a curing agent (D), and carbon black (E). It is particularly preferable to apply a black paint) to at least one surface of the metal plate to form a black coating film (α) having a thickness of 2 to 10 μm. In such an embodiment, even if hexavalent chromium with high environmental impact is not included, designability (coloring and concealment including processed parts), moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance This is because an inexpensive chromate-free black painted metal plate that is extremely excellent in the above can be obtained.

(Exemplary preferred embodiments)
An example of a suitable organic resin film (B) in the coated zinc-based plated steel sheet of the present invention is as follows.
(1) A black film having a thickness of 2 to 10 μm, comprising a polyester resin (B1) containing a sulfonic acid group cured with a curing agent (D) and carbon black (E).
(2) The black film as described in (1) whose hydroxyl value of the said polyester resin (B1) is 2-30 mgKOH / g.
(3) The black film according to (1) or (2), wherein the sulfonic acid group contained in the polyester resin (B1) is a sulfonic acid metal base neutralized with an alkali metal.
(4) The black film in any one of (1)-(3) whose glass transition temperature of the said polyester resin (B1) is 5-50 degreeC.
(5) The black film in any one of (1)-(3) whose glass transition temperature of the said polyester resin (B1) is 5-25 degreeC.
(6) The black film in any one of (1)-(5) whose number average molecular weights of the said polyester resin (B1) are 8000-25000.
(7) The black film according to any one of (1) to (6), which contains a urethane bond in the structure of the polyester resin (B1).
(8) The black film according to any one of (1) to (7), further containing an acrylic resin (B2).
(9) The black film according to any one of (1) to (8), further comprising a polyurethane resin (B3) containing a carboxyl group.
(10) The black film according to (8), wherein the polyurethane resin (B3) contains a urea group.
(11) The black film according to any one of (1) to (10), wherein the curing agent (D) contains a melamine resin (D1).
(12) When the content of the carbon black (E) in the black film is X mass% and the thickness of the black film is Y μm, X × Y ≧ 20 and X ≦ 15 are satisfied. ) To (11).
(13) The black film according to any one of (1) to (12), wherein the carbon black (E) is dispersed with particles having a number average particle diameter of 20 to 300 nm.
(14) The black film according to any one of (1) to (13), further containing silica (F).
(15) The black film according to (14), wherein the silica (F) is dispersed with particles having a number average particle diameter of 5 to 50 nm.
(16) The black film according to any one of (1) to (15), further containing a lubricant (G).
(17) The black film according to (16), wherein the lubricant (G) is polyethylene resin particles.
(18) The black film according to (17), wherein the polyethylene resin particles are dispersed with particles having a number average particle diameter of 0.5 to 2 μm.

  The black film as an embodiment of the upper film of the coated zinc-plated steel sheet of the present invention contains a polyester resin (B1) containing a sulfonic acid group, a curing agent (D), and carbon black (E), and contains chromium. It is preferably formed by applying an aqueous black paint that is not applied to at least one surface of a metal plate and baking and drying. Although the polyester resin itself is hydrophobic, since the sulfonic acid group contained in the resin exhibits high hydrophilicity, the polyester resin (B1) containing the sulfonic acid group can be stably dissolved or dispersed in water. it can.

  In addition, the sulfonic acid group-containing polyester resin (B1) improves the compatibility between water and carbon black (E) having a hydrophobic surface, and the carbon black (E) is uniformly stabilized in the paint. And play an important role in distributing. This is due to the effect obtained by orienting the hydrophobic polyester resin main structure to the carbon black (E), and the polyester resin (B1) can be dissolved or dispersed in water stably to form carbon. Similarly, black (E) can be uniformly dispersed. It is preferable that a sulfonic acid group exhibiting extremely high hydrophilicity is contained in a hydrophobic polyester resin in order to exhibit this excellent dispersibility.

  Thus, the black film formed from the water-based paint in which the carbon black (E) is uniformly and stably dispersed by the polyester resin (B1) containing the sulfonic acid group is uniform in the film. Even if it is a thin film, it is possible to exhibit excellent design properties (colorability and concealment). In addition, a water-based paint in which carbon black (E) is uniformly and stably dispersed by a sulfonic acid group-containing polyester resin (B1) is used for surface hydrophilization treatment and surface activity for enhancing the dispersibility of carbon black (E). Since the addition of the agent is unnecessary, there is no concern of reducing the moisture resistance and corrosion resistance of the black film to be formed.

  That is, by using the polyester resin (B1) containing a sulfonic acid group, it can play a role as a binder component of the black film and a role of enhancing the dispersibility of the carbon black (E) at the same time. The balance between moisture resistance and corrosion resistance can be obtained.

  In order to ensure a good balance of moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance, etc. of the black film, a coating film based on a polyester resin and baked and cured with a curing agent (D) Is preferred. That is, by baking and curing a polyester resin having high ductility and excellent workability with the curing agent (D), a black film having both moisture resistance, corrosion resistance, scratch resistance, and chemical resistance can be obtained. Decrease in film-forming property due to the addition of carbon black (E) can be compensated for by baking and curing with curing agent (D) to obtain a dense black film with a good balance between ductility and hardness. be able to. In addition, since the sulfonic acid group contained in the polyester resin (B1) has the effect of improving the adhesion with the metal plate (base treatment layer when there is a base treatment), the resulting black film is Excellent adhesion to the intermediate film.

  Thus, it is formed by applying an aqueous black paint containing a polyester resin (B1) containing a sulfonic acid group, a curing agent (D), and carbon black (E) to at least one surface of a metal plate and baking and drying. The black film is extremely excellent in design properties (colorability including processing parts, hiding properties), moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance, and the like.

  The thickness of the organic resin film (B) colored black is preferably 2 to 10 μm. When the thickness is less than 2 μm, sufficient design properties (colorability, hiding properties) and corrosion resistance cannot be obtained. If it exceeds 10 μm, it is not only economically disadvantageous, but film defects such as cracks may occur, and the appearance required as an industrial product cannot be stably obtained.

  The type of the polyester resin (B1) is not particularly limited as long as it contains a sulfonic acid group. For example, water obtained by condensation polymerization of a polyester raw material composed of a polycarboxylic acid component and a polyol component is used in water. It can be obtained by dissolving or dispersing.

  The polycarboxylic acid component is not particularly limited. For example, terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dimer acid, trimellitic anhydride, pyromellitic anhydride, and the like. These may be used alone or in combination of two or more.

  The polyol component is not particularly limited. For example, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol, 2-methyl-1,3-propanediol, 2,2 -Dimethyl-1,3-propanediol, 2-butyl-2-ethyl 1,3-propanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, 2-methyl-3-methyl- 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1, 2-cyclohexanedimethanol, hydrogenated bisphenol-A, dimer diol, trimethylol eta , Trimethylolpropane, glycerol, pentaerythritol, and the like. These may be used alone or in combination of two or more.

  The method for introducing a sulfonic acid group is not particularly limited, and examples thereof include dicarboxylic acids such as 5-sulfoisophthalic acid, 4-sulfonaphthalene-2, 7-dicarboxylic acid, and 5 (4-sulfophenoxy) isophthalic acid, or Examples include a method using glycols such as 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexyldiol as a polyester raw material.

  The amount of dicarboxylic acid or glycol containing these sulfonic acid groups is preferably 0.1 to 10 mol% based on the total polycarboxylic acid component or total polyol component. When it is less than 0.1 mol%, the solubility or dispersibility in water decreases or the dispersibility of the carbon black (E) decreases, and the design properties (colorability, concealment) of the thin film of the black film are reduced. ) May not be obtained. If it exceeds 10 mol%, the moisture resistance and corrosion resistance may decrease. From the viewpoint of the balance between the design properties (colorability, hiding properties), moisture resistance, and corrosion resistance in the thin film, it is more preferably in the range of 0.5 to 5 mol%.

The sulfonic acid group contained in the polyester resin (B1) refers to a functional group represented by —SO ₃ H, which may be neutralized with an alkali metal, an amine containing ammonia, or the like. . In the case of neutralization, the already neutralized sulfonic acid group may be incorporated into the resin, or may be neutralized after the sulfonic acid group is incorporated into the resin. In particular, sulfonic acid metal bases neutralized with alkali metals such as Li, Na, and K exhibit higher hydrophilicity, which is suitable for enhancing the dispersibility of carbon black (E) and obtaining high designability. is there. In order to improve the adhesion of the black film to the intermediate film (C), the sulfonic acid group is more preferably a sulfonic acid metal base neutralized with an alkali metal, and most preferably a sulfonic acid Na base.

  The hydroxyl value of the polyester resin (B1) is preferably 2 to 30 mgKOH / g. If it is less than 2 mgKOH / g, the bake hardening with the curing agent (D) is insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance may decrease. Curing may become excessive, and corrosion resistance and workability may be reduced. The hydroxyl value can be measured by a method in which a polyester resin is dissolved in a solvent and reacted with acetic anhydride, and then excess acetic anhydride is back titrated with potassium hydroxide.

  The glass transition temperature of the polyester resin (B1) is preferably 5 to 50 ° C., and more preferably 5 to 25 ° C. from the viewpoint of compatibility between chemical resistance and workability. If it is lower than 5 ° C, scratch resistance and chemical resistance may be lowered, and if it is higher than 50 ° C, workability may be lowered. The glass transition temperature can be measured by a differential scanning calorimeter.

  The number average molecular weight of the polyester resin (B1) is preferably 8000 to 25000. If it is less than 8000, the processability and chemical resistance may decrease, and if it exceeds 25,000, the storage stability of the coating may decrease (the coating may solidify over time or cause a precipitate). is there. The said number average molecular weight can be measured as a polystyrene conversion value by gel permeation chromatography measurement.

  It is preferable that a urethane bond is contained in the polyester resin (B1) structure. By containing the urethane bond, the adhesion, moisture resistance, and corrosion resistance of the organic resin film (B) with the intermediate film (C) can be improved. As a method for introducing a urethane bond into the organic resin film (B), a method of incorporating a polyurethane resin into the organic resin film (B) as described later is also conceivable. However, when different resins are blended, If the resin has poor compatibility, the adhesion and corrosion resistance may decrease. If a urethane bond is introduced by a method of including a urethane bond in the polyester resin (B1) structure, there is an advantage that the above-described problems are hardly caused. Although there is no restriction | limiting in particular about the introduction method of the urethane bond in the said polyester resin (B1) structure, For example, the hydroxyl group contained in a polyester resin and diisocyanate compounds, such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, are made to react. Etc. can be obtained.

  The organic resin film (B) preferably further contains an acrylic resin (B2). By further containing the acrylic resin (B2), the dispersibility of the carbon black (E) in the water-based black paint for forming the black organic resin-based film (B) can be further enhanced, and the design properties in the thin film (Colorability and concealment) can be further improved. There are no particular restrictions on the type of acrylic resin (B2), but unsaturated monomers such as styrene, alkyl (meth) acrylates, (meth) acrylic acid, hydroxyalkyl (meth) acrylates, alkoxysilane (meth) acrylates, etc. Examples thereof include those obtained by radical polymerization of the body in an aqueous solution using a polymerization initiator. The polymerization initiator is not particularly limited, and for example, persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile can be used.

  It is preferable that content of the said acrylic resin (B2) is 0.5-10 mass% with respect to 100 mass% of said polyester resins (B1). If it is less than 0.5% by mass, the designability (colorability, concealment) may be lowered, and if it exceeds 10% by mass, the corrosion resistance and workability may be lowered.

  It is preferable that the organic resin film (B) further contains a polyurethane resin (B3) containing a carboxyl group. By further containing the carboxyl group-containing polyurethane resin (B3), the adhesion, moisture resistance, and corrosion resistance of the organic resin film (B) with the intermediate film (C) can be improved. The type of polyurethane resin (B3) is not particularly limited as long as it contains a carboxyl group. For example, ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxy Reaction of polyhydric alcohols such as propyl ether, glycerin, trimethylolethane, trimethylolpropane and diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, etc. And the like that can be obtained. Chain extension with diamines can increase the molecular weight of the resin and generate urea groups from the reaction of isocyanate groups with amino groups. By including a urea group having a high cohesive energy in the resin, the cohesive strength of the coating film can be further increased, and the corrosion resistance and scratch resistance can be further increased.

  It is preferable that content of the said polyurethane resin (B3) is 5-100 mass% with respect to 100 mass% of said polyester resins (B1). If it is less than 5% by mass, the adhesion to the substrate and the corrosion resistance may decrease, and if it exceeds 100% by mass, the workability may decrease.

  Although the said hardening | curing agent (D) will not have a restriction | limiting in particular if the said polyester resin (B1) is hardened, For example, a melamine resin and a polyisocyanate compound can be mentioned. The melamine resin is a resin obtained by etherifying a part or all of the methylol group of a product obtained by condensing melamine and formaldehyde with a lower alcohol such as methanol, ethanol, or butanol. It does not specifically limit as a polyisocyanate compound, For example, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate etc. can be mentioned. Examples of the blocked product include a blocked product of hexamethylene diisocyanate, a blocked product of isophorone diisocyanate, a blocked product of xylylene diisocyanate, and a blocked product of tolylene diisocyanate, which are blocked products of the polyisocyanate compound. These curing agents may be used alone or in combination of two or more.

  The content of the curing agent (D) is the total organic resin of the organic resin film (B) (when the organic resin film (B) contains an organic resin other than the polyester resin (B1), the organic resin is also It is preferable that it is 5-35 mass% with respect to 100 mass%). If it is less than 5% by mass, the bake-curing may be insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance may decrease. If it exceeds 35% by mass, the bake-curing will be excessive and the corrosion resistance will be reduced. , Workability may be reduced.

  From the viewpoint of scratch resistance and chemical resistance, the curing agent (D) preferably contains a melamine resin. It is preferable that content of a melamine resin is 30-100 mass% in the said hardening | curing agent (D). If it is less than 30% by mass, scratch resistance and chemical resistance may deteriorate.

  The organic resin film (B) preferably further contains silica (F). By including silica (E), corrosion resistance and scratch resistance are improved. Although it does not restrict | limit especially as a silica (F), It is preferable that they are silica fine particles, such as colloidal silica with a primary particle diameter of 5-50 nm, and a fumed silica. Examples of commercially available products include Snowtex O, Snowtex N, Snowtex C, Snowtex IPA-ST (Nissan Chemical Industry), Adelite AT-20N, AT-20A (Asahi Denka Kogyo), Aerosil 200 (Nippon Aerosil) Etc. It is preferable from the viewpoint of corrosion resistance and workability that these silica fine particles are dispersed in the black coating film (α) with the primary particle diameter (number average particle diameter) of 5 to 50 nm.

  The content of the silica (F) is preferably 5 to 30% by mass in the organic resin film (B). If it is less than 5% by mass, the corrosion resistance and scratch resistance may be reduced, and if it exceeds 30% by mass, the moisture resistance, corrosion resistance, and workability may be reduced.

  The organic resin film (B) preferably further contains a lubricant (G). By including the lubricant (G), the scratch resistance is improved. The lubricant (G) is not particularly limited, and a known lubricant can be used, but it is preferable to use at least one selected from a fluororesin system and a polyolefin resin system. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE). ), Polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like can be used. Of these, one type may be used alone, or two or more types may be used in combination.

  The polyolefin resin system is not particularly limited, and examples thereof include hydrocarbon waxes such as paraffin, microcrystalline, and polyethylene, and derivatives thereof, but a polyethylene resin is preferable. The derivative is not particularly limited, and examples thereof include carboxylated polyolefin and chlorinated polyolefin. Of these, one type may be used alone, or two or more types may be used in combination. When using the said polyethylene resin, it is preferable from a corrosion-resistant or scratch-resistant viewpoint that it is disperse | distributed by the particle | grains of the number average particle diameter of 0.5-2 micrometers in the said organic resin-type membrane | film | coat (B).

  The content of the lubricant (G) is preferably 0.5 to 10% by mass in the organic resin film (B). If it is less than 0.5% by mass, the scratch resistance may be lowered, and if it exceeds 10% by mass, the corrosion resistance and workability may be lowered.

  The carbon black (E) is not particularly limited, and known carbon blacks such as furnace black, ketjen black, acetylene black, and channel black can be used. Further, carbon black subjected to known ozone treatment, plasma treatment, or liquid phase oxidation treatment can also be used. The particle size of carbon black to be used is not particularly limited as long as there is no problem in dispersibility in paint, coating film quality, and paintability. Specifically, a particle having a primary particle size of 10 to 120 nm can be used. It is. In consideration of design properties (colorability, concealability) and corrosion resistance in a thin film, it is preferable to use fine carbon black having a primary particle diameter of 10 to 50 nm. Since these carbon blacks aggregate in the process of dispersing in the paint, it is generally difficult to disperse with the primary particle size. That is, in reality, it exists in the paint in the form of secondary particles having a particle diameter larger than the primary particle diameter, and also exists in the same form in the black organic resin film (B) formed from the paint. In order to ensure designability (colorability, concealability) and corrosion resistance in a thin film, the particle diameter of the carbon black (E) dispersed in the coating film is important, and the number average particle diameter is 20 to 300 nm. It is preferable that it exists in.

  When the content of the carbon black (E) in the organic resin film (B) is X mass% and the thickness of the film (B) is Y μm, X × Y ≧ 20 and X ≦ 15 are satisfied. It is preferable to do. In order to ensure designability (colorability and concealment), it is also important to ensure a certain amount or more of the absolute amount of carbon black contained in the coating (B). The absolute amount of carbon black can be represented by the product of the carbon black content (X mass%) contained in the coating (B) and the coating thickness (Y μm). That is, if X × Y is less than 20, design properties (colorability and concealment) may be deteriorated. On the other hand, if X is more than 15, the film-forming property of the film is lowered, and the corrosion resistance and workability may be lowered.

  The upper organic resin film (B) is composed of at least one of a polyester resin containing a sulfonic acid group, a polyurethane resin containing a silanol group, a phenol resin, a polyolefin resin, and an acrylic resin, and a water-soluble isocyanate compound as a crosslinking agent. And a film containing one or more selected from a carbodiimide group-containing compound, an oxazoline group-containing compound, and an organic titanate compound, and further containing a silicon oxide or a phosphoric acid compound.

  The polyurethane resin containing a silanol group contained in the organic resin film (B) is, for example, a reaction between a hydrolyzable silicon group-containing compound having at least one active hydrogen group in the molecule and a polyurethane prepolymer, It can be formed by dispersing or dissolving in water and hydrolyzing. The hydrolyzable silicon group refers to a group in which a hydrolyzable group that is hydrolyzed by moisture is bonded to a silicon atom. Specific examples of the hydrolyzable group include a hydrogen atom, a halogen atom, an alkoxy group, An acyloxy group, an amino group, an amide group, an aminooxy group, a mercapto group, etc. are mentioned. Of these, alkoxy groups are preferred because of their relatively low hydrolyzability and ease of handling. The hydrolyzable group is usually bonded to one silicon atom in the range of 1 to 3, but 2 in terms of reactivity of the hydrolyzable silyl group after coating, water resistance, and solvent resistance. Those having ~ 3 bonds are preferred.

  Examples of the hydrolyzable silicon group-containing compound having at least one active hydrogen group in the molecule include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxy. Silane, γ- (2-aminoethyl) aminopropyldimethoxysilane, γ- (2-aminoethyl) aminopropyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyldimethoxy Silane, γ-aminopropyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyldiethoxysilane, etc. To contribute Cormorants regard, it is desirable to introduce silanol groups between molecules constituting a polyurethane resin, hydrolyzable silicon group-containing compound having two or more active hydrogen groups are preferred.

  The content of the silanol group or Si—O bond is 0.1 to 10% by mass in terms of silicon with respect to the total solid content of the polyurethane resin in order to give the polyurethane resin excellent crosslinking reactivity and performance. If it is less than 0.1% by mass, the effect is low because it does not appropriately contribute to the crosslinking reaction. Preferably it is 0.5-5 mass%.

Examples of the polyurethane prepolymer include polycarbonate polyol, polyester polyol, polyether polyol, polyester amide polyol, acrylic polyol, polyurethane polyol, or a mixture thereof. Of these, polycarbonate polyols, polyester polyols, and polyether polyols are preferable in terms of ensuring processability and ensuring a high elastic modulus.
The polyurethane prepolymer can be obtained by reacting a compound having two active hydrogen groups per molecule with a polyisocyanate compound having two isocyanates per molecule and dissolving or dispersing them in water.

  Examples of the compound having at least two active hydrogen groups per molecule constituting the polyurethane prepolymer include compounds having an amino group, a hydroxyl group and a mercapto group as the compound having an active hydrogen group. In view of the reactivity, a compound having a hydroxyl group is preferable because of its high reaction rate. Examples of the compound having at least two active hydrogen groups per molecule include polycarbonate polyol, polyester polyol, polyether polyol, polyester amide polyol, acrylic polyol, polyurethane polyol, and mixtures thereof.

  Examples of the compound having at least two isocyanate groups per molecule include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2 , 3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylcaproate, and other aliphatic isocyanates such as 1 , 3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethyl Hexyl isocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,4-bis ( Alicyclic diisocyanates such as isocyanatomethyl) cyclohexane and 1,3-bis (isocyanatomethyl) cyclohexane, for example, m-xylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4′-toluidine diisocyanate, Aromatic diisocyanates such as anisidine diisocyanate and 4,4′-diphenyl ether diisocyanate, for example, ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, Aro-aliphatic diisocyanates such as ω′-diisocyanate-1,4-diethylbenzene, for example, triphenylmethane-4,4′-4 ″ -triisocyanate, 1,3,5-triisocyanatebenzene, 2,4,4 Polyisocyanate monomers such as triisocyanate such as 6-triisocyanate toluene, tetraisocyanate such as 4,4′-diphenyldimethylmethane-2,2 ′, 5,5′-tetraisocyanate, and the like polyisocyanate Monomer-derived dimer, tri To polyisocyanate derivatives obtained from mer, burette, allophanate, carbodiimide and the above polyisocyanate monomers, and low molecular weight polyols having a molecular weight of less than 200, such as ethylene glycol, propylene glycol, butylene glycol, etc. And adducts to the above polyisocyanate monomers such as polyester polyol, polyether polyol, polycarbonate polyol, polyester amide polyol, acrylic polyol, and polyurethane polyol.

  Moreover, in order to disperse the polyurethane resin in water, a hydrophilic group is introduced into the polyurethane prepolymer. In order to introduce a hydrophilic group, for example, the molecule has at least one active hydrogen group and contains a hydrophilic group such as a carboxyl group, a sulfonic acid group, a sulfonate group, or a polyoxyethylene group. What is necessary is just to copolymerize a compound at the time of the said polyurethane prepolymer manufacture at least 1 or more types. Examples of the hydrophilic group-containing compound include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, 3, Carboxyl group-containing compounds such as 4-diaminobenzoic acid or derivatives thereof, or polyester polyols obtained by copolymerization thereof, maleic anhydride, phthalic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. Carboxyl group-containing compounds obtained by reacting a compound having an anhydride group with a compound having an active hydrogen group or derivatives thereof, such as 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalate Compounds containing sulfonic acids such as acids and sulfanilic acids and their derivatives , Or polyester polyols obtained by copolymerizing them.

  In the polyurethane resin, a neutralizing agent is used in order to dissolve or disperse well in water. Examples of neutralizing agents that can be used in neutralization include tertiary amines such as ammonia, triethylamine, triethanolamine, triisopropanolamine, trimethylamine, and dimethylethanolamine, sodium hydroxide, potassium hydroxide, and calcium hydroxide. Basic substances such as alkali metal and alkaline earth metal hydroxides can be mentioned, but it is preferable to use a tertiary amine having a boiling point of 120 ° C. or higher in view of weldability, solvent resistance and odor during welding. These neutralizing agents may be used alone or in a mixture of two or more. As a method for adding the neutralizing agent, it may be added directly to the polyurethane prepolymer, or may be added to water when it is dissolved or dispersed in water. The addition amount of the neutralizing agent is 0.1 to 2.0 equivalents, more preferably 0.3 to 1.3 equivalents with respect to the carboxyl group.

  In order to further improve the water solubility or dispersibility of the polyurethane prepolymer containing a carboxyl group, a surfactant may be used. As the surfactant, nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene-oxypropylene block copolymer, or anionic surfactants such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate An agent is used, but a soap-free type containing no surfactant is preferred from the viewpoint of performance such as water resistance and solvent resistance.

  Moreover, when synthesizing the polyurethane prepolymer, an organic solvent can be used. In the case of using an organic solvent, those having relatively high solubility in water are preferred, and specific examples of the organic solvent include acetone, methyl ethyl ketone, acetonitrile, N-methylpyrrolidone and the like.

  Further, a curing catalyst may be added to promote the formation of silanol group siloxane bonds of the polyurethane resin of the present invention. In the polyurethane resin according to the present invention, a strongly basic tertiary amine specifically acts as a catalyst for forming a siloxane bond without deteriorating water resistance and solvent resistance when the polyurethane resin is coated. This makes it possible to efficiently introduce a crosslinked structure. This strongly basic tertiary amine is characterized by a pKa of 11 or more, in particular 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) or 1,6-diazabicyclo [3. 4.0] Nonene-5 is preferably used. The strongly basic tertiary amine as the curing catalyst may be added during the synthesis of the polyurethane prepolymer, after the synthesis of the polyurethane prepolymer, or after the polyurethane prepolymer is dispersed or dissolved in water.

  The polyolefin resin contained in the upper organic resin film (B) is preferably an alkali metal neutralized product of an ethylene-unsaturated carboxylic acid copolymer. Here, the polyolefin resin is an alkali metal neutralized product of an ethylene-unsaturated carboxylic acid copolymer means that a part of the carboxyl groups contained in the ethylene-unsaturated carboxylic acid copolymer is KOH, NaOH, It means that it has been neutralized by an alkali metal supplied by a metal compound such as LiOH.

  The alkali metal neutralized product of the ethylene-unsaturated carboxylic acid copolymer preferably has a neutralization rate of a lower limit of 30% and an upper limit of 90%. A neutralization rate of 30% at the lower limit and 90% at the upper limit means that 30 to 90% of the carboxyl groups contained in the ethylene-unsaturated carboxylic acid copolymer are neutralized. If it is less than 30%, the adhesion of the obtained film to the intermediate layer film (C) is not sufficient, and if it exceeds 90%, the adhesion between the film and the intermediate layer (C) may be impaired. The lower limit is more preferably 40%, and the upper limit is more preferably 80%.

  The ethylene-unsaturated carboxylic acid copolymer is a copolymer obtained by radical polymerization of ethylene and an unsaturated carboxylic acid such as methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid under pressure. is there.

  The olefin resin may be one obtained by neutralizing the ethylene-unsaturated carboxylic acid copolymer with an amine (for example, a water-soluble amine such as triethylamine or ethanolamine), ammonia or the like. The said amine may be used independently and may use 2 or more types together.

  In the olefin resin, ammonia and an amine may be used in combination with an alkali metal in the neutralization of the ethylene-unsaturated carboxylic acid copolymer.

  Examples of the phenol resin contained in the organic resin film (B) include a phenol resin composition imparted with water solubility, for example, aromatics such as phenol, resorcin, cresol, bisphenol A, paraxylylene dimethyl ether, and formaldehyde. It is obtained by reacting phenolic resin such as methylolated phenolic resin obtained by addition reaction in the presence of a reaction catalyst with amine compounds such as diethanolamine and N-methylethanolamine and neutralizing with organic acid or inorganic acid. The thing etc. can be mentioned.

  The crosslinking agent contained in the organic resin film (B) is used as a means for efficiently performing the crosslinking reaction at a lower baking temperature and adding the characteristics of the crosslinking agent itself to the film. Any crosslinking agent can be used as long as it is water-soluble or water-dispersible. Among them, one or more selected from water-soluble isocyanate compounds, carbodiimide group-containing compounds, oxazoline group-containing compounds, and organic titanate compounds may be used. preferable.

  The water-soluble isocyanate compound includes a polyisocyanate compound imparted with water dispersibility, and mainly reacts with a hydroxyl group of a silanol group to form a crosslinked structure. For example, Bernock 5000 (Dainippon Ink Co., Ltd.) is exemplified.

  Examples of the carbodiimide group-containing compound include aromatic carbodiimide compounds and aliphatic carbodiimide compounds, and mainly form a crosslinked structure with active hydrogen groups such as carboxyl groups and hydroxyl groups. Examples thereof include Carbodilite V-02, V-02-L2, E-01, E-02, E-03A, and E-04 (manufactured by Nisshinbo).

  Examples of the oxazoline group-containing compound include Epocros K-2010E, K-2020E, K-2030E, WS-500, and WS-700 (manufactured by Nippon Shokubai Co., Ltd.). The oxazoline group-containing compound mainly reacts with a carboxyl group to form a crosslinked structure.

  Examples of organic titanate compounds include ORGATIX TC-300 (dihydroxybis (ammonium lactate) titanium, manufactured by Matsumoto Pharmaceutical Co., Ltd.), TC-400 (diisopropoxy titanium bis (triethanolaminate), manufactured by Matsumoto Pharmaceutical Co., Ltd.), Etc. are exemplified. The organic titanate compound mainly forms a crosslinked structure with active hydrogen groups such as a carboxyl group and a hydroxyl group.

  The preferred addition amount of these cross-linking agents depends on the acid value of the resin, but from the balance of physical properties such as film curability, elongation and hardness, the solid content ratio of the total amount of the cross-linking agent to the main resin is 5 mass. % To 50% by mass is preferable.

  Examples of the phosphate compound contained in the organic resin film (B) include triammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, potassium phosphate, potassium dihydrogen phosphate, trisodium phosphate, Examples thereof include disodium hydrogen phosphate, sodium dihydrogen phosphate, calcium dihydrogen phosphate, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, and the like. Among them, triammonium phosphate, diammonium hydrogen phosphate, ammonium phosphate compound of ammonium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium phosphate compound of sodium dihydrogen phosphate, When at least one compound is used among calcium phosphate compounds such as calcium dihydrogen phosphate and magnesium phosphate compounds such as magnesium hydrogen phosphate and magnesium dihydrogen phosphate, solvent resistance and corrosion resistance are improved. It is preferable because it appears remarkably. These can be used depending on the pH of the treatment bath as long as they are water-soluble or soluble in acids or alkalis, and any of pure compounds or hydrates can be used.

  Content of a phosphoric acid type compound shall be 0.1 mass% or more and 10 mass% or less in the amount of phosphorus with respect to solid content of a film. If it is less than 0.1% by mass, the effect is poor, and if it exceeds 10% by mass, the hydration property to the film increases and the corrosion resistance decreases.

  Examples of the silicon oxide contained in the organic resin film (B) include silicon dioxide. Silicon oxide is only required to be a compound that is stably dispersed in water and does not cause sedimentation. Among them, when colloidal silica is used, the effect of improving solvent resistance and corrosion resistance is remarkably exhibited. For example, commercially available colloidal silica particles such as “Snowtex O”, “Snowtex OS”, “Snowtex OXS”, “Snowtex N”, “Snowtex NS”, “Snowtex NXS” (all manufactured by Nissan Chemical Industries, Ltd.), “Snow Fibrous colloidal silica such as “Tex UP” and “Snowtex PS” (manufactured by Nissan Chemical Industries, Ltd.) can be used depending on the pH of the treatment liquid.

  The content of silicon oxide is 2% by mass or more and 20% by mass or less in terms of silicon based on the solid content of the film. If it is less than 2% by mass, the effect is poor, and if it exceeds 20% by mass, the effect is saturated and uneconomical, and the workability and corrosion resistance decrease.

  Moreover, in order to improve corrosion resistance, it is preferable to add organic rust preventive agents, such as inorganic rust preventive agents, such as a niobium compound and a zirconium compound, a guanidino group containing compound, a biguanidino group containing compound, and a thiocarbonyl group containing compound suitably. The content is preferably 1% by mass or more and 15% by mass or less in terms of the total amount of inorganic rust preventives, and 0.1% by mass or more and 10% by mass or less in terms of the total amount of organic rust preventives, based on 100% solid content of the film. If each is less than the lower limit, the effect is poor, and if it exceeds the upper limit, the effect is saturated and uneconomical, and the workability and corrosion resistance decrease.

  The upper organic resin film (B) in the coated zinc-based plated steel sheet of the present invention is a water-based paint containing necessary components, and at least one surface of a steel sheet in which a lower silicon oxide film and an intermediate film (C) are formed in advance. It is formed by coating and baking and drying. For example, the black organic resin-based film (B) of the black-coated zinc-based plated steel sheet that is one embodiment of the present invention includes a polyester resin (B1) containing a sulfonic acid group, a curing agent (D), and carbon black (E). A water-based black paint containing is applied to at least one surface of a metal plate and baked and dried. Although there is no restriction | limiting in particular in the application | coating method of the said water-system black coating material, Well-known roll coating, spray coating, bar coating, immersion, electrostatic coating, etc. can be used suitably.

  Although the manufacturing method of the said water-system coating material is not specifically limited, For example, the formation component of an organic resin-type membrane | film | coat (B) is added to water, it stirs with a disper and the method of melt | dissolving or disperse | distributing is mentioned. In order to improve the solubility or dispersibility of each forming component, a known hydrophilic solvent or the like may be added as necessary.

  There is no restriction | limiting in particular in the baking drying method, A metal plate may be heated previously, a metal plate may be heated after application | coating, or you may dry combining these. There is no restriction | limiting in particular in a heating method, A hot air, induction heating, near infrared rays, a direct fire, etc. can be used individually or in combination. The baking drying temperature is preferably 150 ° C. to 250 ° C., more preferably 160 ° C. to 230 ° C., and most preferably 180 ° C. to 220 ° C. at the ultimate temperature. If the ultimate temperature is less than 150 ° C., the bake hardening is insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance may decrease. If it exceeds 250 ° C., the bake hardening will be excessive. Corrosion resistance and workability may decrease. The baking and drying time is preferably 1 to 60 seconds, and more preferably 3 to 20 seconds. If it is less than 1 second, the bake hardening is insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance may decrease, and if it exceeds 60 seconds, the productivity may decrease.

  The thickness of the intermediate layer coating (C) and the organic resin coating (B) of the coated zinc-based plated steel sheet of the present invention can be measured by observing the cross section of each coating or using an electromagnetic film thickness meter. In addition, the mass of the film adhered per unit area may be calculated by dividing by the specific gravity of the film or the specific gravity after drying the paint. The adhesion mass of the film is the mass difference before and after coating, the mass difference before and after peeling the film after coating, or the abundance of elements whose content in the film is known in advance by fluorescent X-ray analysis. For example, an appropriate method may be selected from existing methods. The specific gravity of the film or the specific gravity after drying of the paint is measured by measuring the volume and mass of the isolated film, measuring the volume and mass after taking an appropriate amount of paint in a container and drying it, or the blending amount of the film constituents. And calculating from the known specific gravity of each component.

(Water-based coloring composition)
The intermediate layer coating (C) and the organic resin coating (B) in the coated galvanized steel sheet of the present invention are preferably formed from a water-based coloring composition as a paint. The “aqueous coloring composition” as used herein refers to a composition comprising a component for forming the intermediate layer film (C) or the organic resin film (B) and configured using an aqueous solvent. This composition is generally in the form of a dispersion in which components insoluble in the aqueous solvent used are dispersed. “Aqueous solvent” refers to a solvent in which water is the main component (50% by mass or more). By using an aqueous solvent, it is not necessary to pass an extra coating line for using the organic solvent-based coloring composition, so that the manufacturing cost can be greatly reduced and the volatile property can be reduced. There are also advantages in terms of the environment such as emission of organic compounds (VOC) can be greatly suppressed.

  If necessary, an organic solvent can be added to the “aqueous solvent”. However, from the viewpoint of occupational health, “water-based coloring composition” refers to organic solvent-containing substances defined in the Occupational Safety and Health Law's organic solvent poisoning prevention regulations It is preferable that it does not correspond to what contains the obtained organic solvent exceeding 5% of weight.

  Next, a preferred method for producing the coated zinc-based plated steel sheet of the present invention having the above configuration will be described.

  The metal plate applicable to the embodiment of the present invention is not particularly limited as long as it is a zinc-based plated steel plate. Here, the zinc-based plated steel sheet means that zinc is 30% or more by mass ratio among elements constituting the plating film. Examples of such galvanized steel sheet include an electrogalvanized steel sheet, an electrogalvanized steel sheet, a hot dip galvanized steel sheet, and a hot dip galvanized steel sheet.

  In order to produce the coated zinc-based plated steel sheet according to the present invention, first, a zinc-based plated steel sheet is immersed in the metal surface treatment agent and cathodic electrolysis to form a silicon oxide film on at least one surface of the zinc-based plated steel sheet. To do.

The current density of the cathode electrolysis is preferably 10 to 200 mA / cm ² . The current density of cathode electrolysis is more preferably 10 to 100 mA / cm ² . Nevertheless, the current density is appropriately affected because it is greatly influenced by the flow of the processing liquid and the plate passing speed in the case of continuous processing.

  The film formation mechanism of the silicon oxide film is as follows according to the estimation of the present inventor.

  In an aqueous silicate solution with pH 1-4 containing oxygenate anions, silicate ions and (water) silicon oxide form an equilibrium reaction, and by shifting the equilibrium, (water) silicon oxide is formed on the substrate. Presumed to precipitate. At that time, it is presumed that the oxygen acid anion works as a reaction field forming agent such as pH. Note that the equilibrium can be shifted by the hydrogen generation reaction during immersion or cathode electrolysis of the zinc-based plated steel sheet and the pH increase near the steel sheet surface.

  The electrolytic treatment temperature is preferably about 20 to 60 ° C. The electrolytic treatment time may be set according to the target film formation amount, but is preferably about 1 second to 60 minutes in consideration of productivity. Moreover, although there is no restriction | limiting in particular about the pre-processing of a zinc-based plated steel plate, It is preferable to set it as the surface from which the degreased surface and the scale were removed.

  In the present invention, the intermediate layer film (C) and the upper organic resin film (B) are sequentially formed on the silicon oxide film. The intermediate layer film (C) is preferably formed within 30 minutes after the formation of the silicon oxide-based film in order to prevent alteration of the previously formed silicon oxide-based film due to natural oxidation or the like. The method for forming the intermediate layer film (C) and the organic resin film (B) is as described above.

  Hereinafter, the present invention will be described more specifically with reference to examples.

As metal materials, EG (electrogalvanized steel sheet, adhesion amount: 20 g / m ² ), GI (hot dip galvanized steel sheet, adhesion amount: 60 g / m ² ), AS (alloyed galvanized steel sheet, adhesion amount: 60 g) / M ² ), SD (hot dip galvanized steel sheet (Zn-11% Al-3% Mg-0.2% Si), adhesion amount: 60 g / m ² ), ZL (electrogalvanized nickel-plated alloy steel sheet, adhesion) Amount: 20 g / m ² ) was used. These were subjected to an ultrasonic degreasing treatment in acetone and then subjected to an experiment.

  An organic resin having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the upper layer after the substrate that has been subjected to the degreasing treatment is immersed in a treatment solution or electrolyzed to form a silicon oxide film. A system film was applied to give a test material.

(1) Silicon oxide-based film Mixing various concentrations of silicate and oxyacid, ammonium silicofluoride and various compounds shown in Table 1, and adding sodium hydroxide when lower than a predetermined pH, When the oxygen acid is nitric acid or phosphoric acid when the acid is high, sulfuric acid is added. When the oxygen acid is higher than the predetermined pH and when the oxygen acid is sulfuric acid, nitric acid is added to prepare a treatment liquid adjusted to the predetermined pH.

The film formation of the silicon oxide film by electrolysis is performed by controlling the current density to 10 to 100 mA / cm ² in the treatment liquid and performing cathode electrolysis at 20 ° C. for 0.1 to 10 seconds, and depositing a predetermined adhesion amount. Washed with water and dried. The silicon oxide-based film was formed by dipping at 60 ° C. for 1 to 10 minutes. After a predetermined amount of film was formed, the film was washed with water and dried.

The obtained film was confirmed to form a silicon oxide film and the amount of the film formed by X-ray photoelectron spectroscopy and fluorescent X-ray method. Moreover, by Fourier transform infrared spectroscopy, of from SiOH bonds in 900～1000Cm ^-1 silicon oxide base film infrared in the absorption spectral intensity I _SiOH and 1000~1250cm ^-1 Si-O-Si bonds derived was measured ratio I _SiOH / I _SiOSi the infrared absorption spectrum intensity I _SiOSi.

  The infrared absorption spectrum was measured by a highly sensitive reflection method using FT / IR4100 manufactured by JASCO Corporation.

  In addition, the film thickness was calculated as an average film thickness by measuring 10 arbitrary points by observing a cross-sectional SEM of 30000 times.

(2) Intermediate layer The intermediate layer contains an organic resin (Table 2), a silane coupling agent (Table 3), and other additives (Table 4) in the amounts shown in Table 5, and using a paint disperser. It adjusted by stirring. The intermediate layer was formed by applying the coating agent to the surface of the base treatment layer formed in the above (1) so as to have a predetermined adhesion amount within 30 minutes and drying it at a reaching plate temperature of 70 ° C.

(3) Organic resin film having at least one of carboxyl group, hydroxyl group, sulfonic acid group and silanol group

  Coating solutions for forming an organic resin film having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group are organic resin (F) (Table 6), curing agent (G) (Table 7), Pigment (H) (Table 8), silicon oxide (J) (Table 9), phosphate compound (K) (Table 10), and lubricant (L) (Table 11) were blended in the blending amounts shown in Table 12, It adjusted by stirring using the disperser for coating materials. The above-mentioned coating solution is applied to the upper layer of the base treatment layer formed in (1) with a roll coater so as to have a predetermined film thickness, and is heated and dried at a predetermined final plate baking temperature to form a coating film. A plate (test plate) was prepared.

(4) Evaluation test For the coated metal plate (test plate) obtained in (3) above, the workability (work adhesion), corrosion resistance, chemical resistance, and alkali resistance are evaluated by the evaluation methods and evaluation criteria shown below. did. The evaluation results are shown in Tables 13 and 14.

(Processability (work adhesion))
After subjecting the test plate to 180 ° bending, a tape peeling test was performed on the outside of the bent portion. The appearance of the tape peeling part was evaluated according to the following evaluation criteria. The bending process was performed in an atmosphere of 20 ° C. with a 0.5 mm spacer sandwiched therebetween (generally called 1T bending).
5: Peeling is not recognized in the coating film.
4: Peeling is observed in a very small part of the coating film (appropriately understood by observation with a magnifying glass).
3: Peeling is observed in a part of the coating film (approximated by observation with a magnifying glass).
2: Peeling is observed in the partial coating film (to the extent that it can be easily seen by visual inspection).
1: Peeling is recognized in most coating films (to the extent that it can be easily seen by visual inspection).

(Corrosion resistance)
After the end surface of the test plate was tape-sealed, a salt spray test (SST) based on JIS Z 2371 was performed for 72 hours, the state of rust generation was observed, and evaluated according to the following evaluation criteria.
5: No rust generation.
4: Rust generation area is less than 1%.
3: Rust generation area is 1% or more and less than 2.5%.
2: Rust generation area is 2.5% or more and less than 5%.
1: Rust generation area is 5% or more.

(chemical resistance)
After the test plate was placed on a rubbing tester, the state of the film after rubbing the absorbent cotton impregnated with ethanol 10 times with a load of 49.03 kPa (0.5 kgf / cm ² ) was evaluated according to the following evaluation criteria.
5: There is no trace on the rubbing surface.
4: A trace is left on the rubbing surface (a level at which the rubbing trace can be discriminated with some attention).
3: Slight marks are left on the rubbing surface (a level at which the rubbing marks can be easily discerned when the eyes are closed).
2: A clear mark is made on the rubbing surface (a level at which the rubbing mark can be identified instantaneously).
1: The coating film dissolves on the rubbing surface, and the base is exposed.

(Alkali resistance)
The state of the film after the test plate was immersed in a 2% aqueous solution of 55 ° C. alkaline degreasing agent (Surf Cleaner 53, Nippon Paint) for 30 minutes was evaluated according to the following evaluation criteria.
4: No peeling 3: Slight peeling 2: Partial peeling 1: Complete peeling

Examples of the present invention are: an upper layer organic resin system having at least one of a lower silicon oxide film having an I _SiOH / I _{SiOSi ratio} of 0.1 or more, an intermediate layer, a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group By having a film, in any of the evaluation tests, excellent processing adhesion, corrosion resistance, chemical resistance, and alkali resistance of 3 or more points were shown. In particular, the case where I _SiOH / I _SiOSi was 0.1 or more and 5 or less showed good adhesion and corrosion resistance (Examples 1 to 39, 41 to 65). Moreover, in the system which added Ti compound, Zr compound, V compound, Nb compound, and P compound to the silicon oxide film, the results of good corrosion resistance were shown (Examples 51 to 55, 62 to 65). Furthermore, when _ISiOH / _ISiOSi of the undercoat is 0.1 or more and 5 or less and the thickness is 10 or more and 300 nm or less, a polyester resin containing a sulfonic acid group and a melamine resin as a curing agent are contained as an upper resin film. Film (Examples 1 to 26), polyester resin containing sulfonic acid group, polyurethane resin containing silanol group, phenol resin, polyolefin resin, acrylic resin, water-soluble isocyanate compound, carbodiimide group as crosslinking agent In the case of a resin film (Examples 27 to 36) containing one or more selected from a containing compound, an oxazoline group-containing compound, and an organic titanate compound, good post-processing adhesion and corrosion resistance were exhibited.

On the other hand, Comparative Example 1 in which I _SiOH / I _SiOSi outside the scope of the present invention was less than 0.1 had poor work adhesion. In Comparative Examples 2 and 3 having no intermediate layer, the alkali resistance was inferior. Moreover, it was confirmed that Comparative Examples 4-11 which do not contain a silicon-type compound and do not contain a SiOH group are inferior in process adhesiveness.

Claims (13)

It has a lower layer silicon oxide film (A) and an upper organic resin film (B) on at least one surface of the zinc-plated steel sheet, and is between the lower silicon oxide film (A) and the upper organic resin film (B). A coated galvanized steel sheet having an intermediate layer coating (C),
The upper-layer organic resin film (B) is a film having a thickness of 0.5 to 10 μm and having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure.
The intermediate layer film (C) includes at least one selected from an organic resin having at least one of a carboxyl group, a hydroxyl group, a sulfonic acid group, and a silanol group in the structure, a silane coupling agent, and a polyphenol compound. , A film having a thickness of 0.01-2 μm,
Infrared absorption spectrum intensity I _SiOSi from the bond of Si-O-Si in the infrared absorption spectrum intensity I _SiOH and 1000～1250Cm ^-1 from SiOH in 900～1000Cm ^-1 of the silicon oxide film (A) A coated zinc-based plated steel sheet, characterized in that the ratio _ISiOH / _ISiOSi is at least 0.1.   The coated zinc-based plated steel sheet according to claim 1, wherein the silicon oxide-based film (A) is a silicon oxide-based film that does not contain a fluorine compound. The coated zinc-based plated steel sheet according to claim 1 or 2, wherein the silicon oxide-based film (A) has the ratio _ISiOH / _ISiOSi of 0.1 or more and 5 or less.   The coating according to any one of claims 1 to 3, wherein the silicon oxide film (A) further contains at least one of a Ti compound, a Zr compound, a V compound, an Nb compound, and a P compound. Galvanized steel sheet.   The coated zinc-based plated steel sheet according to any one of claims 1 to 4, wherein the organic resin film (B) in the upper layer is a film containing a polyester resin containing a sulfonic acid group and a melamine resin as a curing agent.   The coated resin-coated galvanized steel sheet according to any one of claims 1 to 5, wherein the upper organic resin film (B) contains a colorant.   7. The coated zinc-based plated steel sheet according to claim 6, wherein the upper organic resin film (B) contains carbon black as a colorant.   The upper organic resin film (B) is water-soluble as a crosslinking agent and at least one of a polyester resin containing a sulfonic acid group, a polyurethane resin containing a silanol group, a phenol resin, a polyolefin resin, and an acrylic resin. A resin film containing at least one selected from an isocyanate compound, a carbodiimide group-containing compound, an oxazoline group-containing compound, and an organic titanate compound, further comprising silicon oxide and a phosphoric acid compound. The coated zinc-based plated steel sheet according to any one of 7 above.   The organic resin of the intermediate layer film (C) contains at least one of polyester resin, polyurethane resin, epoxy resin, phenol resin, acrylic resin, and polyolefin resin. The coated galvanized steel sheet described in 1.   The silicon oxide-based film (A) is formed by immersing a zinc-based plated steel sheet in a silicate-based aqueous solution that does not contain fluorine ions but contains oxygenate anions, thereby forming a silicon oxide-based film on the surface of the plated steel sheet. The coated zinc-based plated steel sheet according to any one of claims 1 to 9, wherein   The silicon oxide film (A) is formed on the surface of the plated steel sheet by immersing the zinc-based plated steel sheet in a silicate-based aqueous solution not containing fluorine ions but containing an oxygenate anion and cathodic electrolysis. The coated galvanized steel sheet according to any one of claims 1 to 10. The condition of the cathode electrolysis is a current density of 10 to 200 mA / cm ² , a temperature of 20 ° C to 60 ° C, and the coated zinc-based plated steel sheet according to claim 11.   The coated galvanized steel sheet according to any one of claims 10 to 12, wherein the oxygenate anion is at least one selected from the group consisting of phosphate ion, nitrate ion and sulfate ion.

Images