CN109563630B

CN109563630B - Surface-treated metal sheet and method for producing surface-treated metal sheet

Info

Publication number: CN109563630B
Application number: CN201780044835.9A
Authority: CN
Inventors: 中元忠繁; 于航
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2016-08-05
Filing date: 2017-07-20
Publication date: 2021-10-08
Anticipated expiration: 2037-07-20
Also published as: KR102259469B1; TWI641724B; JP6856451B2; CN109563630A; TW201812100A; JP2018024937A; KR20190039548A

Abstract

One aspect of the present invention relates to a surface-treated metal sheet comprising a zinc-plated steel sheet and a surface-treatment coating film laminated on at least one surface of the zinc-plated steel sheet, wherein the surface-treatment coating film is composed of a surface-treatment composition containing a polyolefin resin containing no ammonia and colloidal silica having an average particle diameter of 4 to 6nm, the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the surface-treatment composition, and the amount of the surface-treatment coating film adhered is 0.4 to 1.2g/m²And when the surface treatment coating is immersed in deionized water at 70-80 ℃ for 10 minutes, the amount of sodium ions dissolved out of the surface treatment coating is 4mg/m²The following.

Description

Surface-treated metal sheet and method for producing surface-treated metal sheet

Technical Field

The present invention relates to a surface-treated metal sheet and a method for producing a surface-treated metal sheet.

Background

It is known that blackening occurs on the surface of a galvanized steel sheet. The blackening phenomenon is a phenomenon in which at least a part of the surface is blackened and discolored to black or dark brown. The blackening phenomenon is specifically a corrosion phenomenon which is observed in an initial stage in a corrosive environment before white rust is generated, and is said to be a corrosion phenomenon which is observed in a relatively mild corrosive environmentThe following are produced. In addition, it is believed that: the reason why the surface of the zinc-plated steel sheet appears black due to the blackening phenomenon is that zinc (Zn) present on the surface is formed into Zn during oxidation reaction (corrosion reaction)_xO_1-xThis deviates from the stoichiometric composition of the amorphous oxide.

Further, the blackening phenomenon is said to be a phenomenon in which the oxidation reaction of Zn is generated in a halfway state, and therefore is considered to be: to prevent blackening, the oxidation reaction may be promoted to some extent instead. Therefore, a method of adding elements such as Ni, Co, and In to the galvanized layer as elements that appropriately promote the oxidation reaction is considered. Examples of such a method include: the techniques described in patent documents 1 to 4.

Patent document 1 describes the following: a method for galvanically plating a steel sheet in a galvanization bath containing Ni ions in an amount within the range of 100 to 300ppm, containing Pb ions in an amount of 0.5ppm or less as impurities, and having a ratio of Ni ions to Pb ions (Ni ions/Pb ions) in the plating bath of more than 500, and then performing a predetermined chromate treatment.

Patent document 2 describes the following: a method for galvanically plating a steel sheet in a galvanization bath containing Ni ions in an amount of 1/25 or less and 10g/l or less of the amount of Zn ions in a range of 5 to 500 times the amount of Pb ions contained as impurities, and then performing a predetermined chromate treatment.

Patent document 1 and patent document 2 disclose the following: the blackening phenomenon of the chromate-treated galvanized steel sheet can be suppressed.

As another method for suppressing the blackening phenomenon, for example, a method of providing a layer containing an element such as Ni or Co on a steel sheet is also considered. As such a method, for example, a technique described in patent document 3 can be cited.

Patent document 3 describes a chromate-treated galvanized steel sheet comprising a steel sheet, a galvanized layer formed on the steel sheet, a metal layer formed on the surface of the galvanized layer by depositing at least 1 of Ni and Co, and a chromate film formed on the metal layer.

Patent document 3 discloses the following: the galvanized steel sheet with excellent blackening resistance can be obtained.

Further, as a method for improving the blackening resistance without deteriorating the corrosion resistance of the chromate free steel sheet, for example, a technique described in patent document 4 is cited.

Patent document 4 describes a galvanized steel sheet containing at least 1 element selected from Si, P, As, S, Fe, Co, B, Ge, Mn, Cu, and Zn and at least 12 element selected from Mo, W, V, and Nb, and the 2 nd element is present in a chemical conversion coating As a heteropoly acid.

According to patent document 4, the blackening resistance can be improved without deteriorating the corrosion resistance of the chromate-free steel sheet.

Further, as a chromate free steel sheet excellent in corrosion resistance and the like, for example, techniques described in

patent documents

5 and 6 are cited.

Patent document 5 describes a surface-treated steel material in which a coating is formed on a steel sheet by using an aqueous surface treatment agent containing an aqueous resin, colloidal silica and ammonium vanadate at a predetermined content.

Patent document 6 describes a surface-treated steel material having an undercoating layer containing an organic resin and a silane coupling agent at a predetermined content on a zinc-plated steel sheet or a zinc alloy-plated steel sheet, and having an overcoating film containing an organic resin and a thiocarbonyl group-containing compound at a predetermined content on the undercoating layer.

Patent documents

5 and 6 disclose the following: a surface-treated steel sheet having excellent corrosion resistance can be obtained.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. Hei 2-8374

Patent document 2: japanese patent laid-open publication No. Sho 60-77988

Patent document 3: japanese patent laid-open publication No. Hei 10-219494

Patent document 4: japanese patent laid-open publication No. 2012-167326

Patent document 5: japanese patent laid-open publication No. Hei 11-310757

Patent document 6: japanese patent laid-open publication No. 2000-248383

Disclosure of Invention

The purpose of the present invention is to provide a surface-treated metal sheet that has excellent blackening resistance and can sufficiently suppress the occurrence of stains.

One aspect of the present invention relates to a surface-treated metal sheet comprising: a zinc-based plated steel sheet; and a surface treatment film laminated on at least one surface of the galvanized steel sheet, wherein the surface treatment film is composed of a surface treatment composition containing: a polyolefin-based resin containing no ammonia; and colloidal silica having an average particle diameter of 4 to 6nm, wherein the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the surface treatment composition, and the amount of the surface treatment coating adhered is 0.4 to 1.2g/m²And when the surface treatment coating is immersed in deionized water at 70-80 ℃ for 10 minutes, the amount of sodium ions dissolved out of the surface treatment coating is 4mg/m²The following.

The above objects, features, and other objects, features, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Drawings

Fig. 1A is a schematic view showing a surface-treated metal sheet having a surface-treatment coating film provided on a galvanized steel sheet.

Fig. 1B is a schematic view showing a state in which an amorphous oxide is generated in the surface-treated metal sheet shown in fig. 1A.

Fig. 2 is a schematic diagram showing the state of colloidal silica.

Fig. 3A is a schematic diagram showing a state in which stains start to be generated in a surface-treated metal sheet having a surface-treatment coating film provided on a galvanized steel sheet.

Fig. 3B is a schematic view showing a state in which stains are spread in a surface-treated metal sheet having a surface-treatment coating film provided on a galvanized steel sheet.

Fig. 4 is a schematic diagram showing a state in which the occurrence of stain is suppressed in a surface-treated metal sheet having a surface-treatment coating film provided on a galvanized steel sheet.

Fig. 5 is a schematic diagram showing a friction coefficient measuring device for evaluating lubricity.

Fig. 6 is a graph showing the change with time in the white rust generation rate in the evaluation of SST plates.

Fig. 7 is a graph showing the change in white rust generation rate with respect to the number of cycles in the evaluation of SST cycles.

FIG. 8 shows Na derived from the surface treatment coating⁺Graph showing relationship between elution amount and stain.

Detailed Description

In a chromate-treated galvanized steel sheet In which an element such as Ni, Co, and In is added to a galvanized layer as described In patent document 1 and patent document 2, it is necessary to consider a balance with an element which deteriorates corrosion resistance, such as Pb, Cu, and Ag, which is present as an impurity In the galvanized layer. Even if the balance is adjusted, such a chromate-treated galvanized steel sheet may have appearance defects due to occurrence of color unevenness or reduction in whiteness due to change in the valence of a metal element, elution of a metal, or the like in a corrosive environment. In addition, In the case of a chromate-treated galvanized steel sheet, when elements such as Ni, Co, and In are added to a galvanized layer to excessively promote an oxidation reaction, corrosion resistance may be significantly reduced to cause white rust, or stains (hereinafter referred to as "stains") In the form of stains (black brown or gray brown) may be easily generated.

Similarly to the chromate-treated galvanized steel sheets described in

patent documents

1 and 2, the galvanized steel sheets described in patent documents 3 and 4 may have poor appearance due to occurrence of color unevenness or reduction in whiteness caused by a change in the valence of a metal element or elution of a metal in a corrosive environment.

Further, considering the balance among corrosion resistance, blackening resistance, adhesion to galvanized surfaces, and conductivity of steel sheets, it is also conceivable to form a film rich in inorganic components or a film rich in organic components as a surface treatment film in the form of a thin film of about 0.5 to 1 μm on a galvanized steel sheet, for example, a galvanized steel sheet described in patent documents 1 to 4. Specifically, it is conceivable to provide the coating films described in

patent documents

5 and 6 as the surface treatment coating film.

However, when only such a surface treatment film is provided, the blackening phenomenon may not be sufficiently suppressed, and stains may be easily generated as well as the blackening phenomenon may not be sufficiently suppressed.

In particular, stains which are easily generated under a high-temperature and high-humidity environment significantly impair the appearance of the product and reduce the value of the product. Therefore, it is required to suppress not only the occurrence of the blackening phenomenon but also the occurrence of stain.

According to the studies of the present inventors, the reason why the blackening phenomenon cannot be sufficiently suppressed in some cases even when the surface treatment film is formed on the zinc-based plated steel sheet is presumed to be as follows.

First, as shown in fig. 1A, even if the surface treatment film 11 is provided on the galvanized steel sheet 12, the barrier properties such as oxygen permeability and water vapor permeability may not be completely improved. In such a case, as shown in fig. 1B, the oxidation reaction occurs in a state where oxygen is not sufficiently supplied to the surface of the galvanized steel sheet 12, and the amorphous oxide 13 is generated on the galvanized steel sheet 12 as described above. That is, the blackening phenomenon occurs in the surface-treated metal sheet 10 having the surface-treated film 11 provided on the galvanized steel sheet 12. Fig. 1A is a schematic view showing a surface-treated metal sheet 10 having a surface-treatment coating film 11 provided on a galvanized steel sheet 12. Fig. 1B is a schematic diagram showing a state in which an amorphous oxide 13 is formed in the surface-treated metal sheet 10 shown in fig. 1A.

Further, in a surface-treated metal sheet having a surface-treated film provided on a galvanized steel sheet, not only the blackening phenomenon but also the occurrence of stain may not be sufficiently suppressed in some cases. It is generally considered that: in a high-temperature and high-humidity environment, the barrier property of the surface treatment film is lowered, so that the corrosion reaction, which is a cause of the blackening phenomenon, is accelerated, and stains are generated due to the acceleration of the corrosion reaction. In the course of the research leading to the present invention, it was found that: the generation of stains is not limited to such a case, but may be generated by a different mechanism. The details are as follows.

First, attention is focused on the fact that when the surface treatment coating film contains colloidal silica, the occurrence of stain may not be sufficiently suppressed. The surface-treated metal sheet having such a surface-treatment film is left in a constant temperature and humidity tester set to an environment of 65 ℃ and 95% humidity for 168 hours, for example, to cause stains. The surface-treated film of the surface-treated metal plate having the stain was scribed and subjected to surface analysis (8X 8mm in drawing/visual field) using an electron probe microanalyzer (EPMA, JXA-8100, manufactured by Nippon electronics Co., Ltd.). From the results of this analysis it is known that: na element enrichment occurred at the portion where the stain was generated. Accordingly, the present inventors speculate that: the cause of the stain is the presence of Na element. The present inventors have further studied the cause of the enrichment of Na element, and have focused on colloidal silica contained in the surface treatment coating film to estimate the mechanism of the generation of stain as follows.

First, in a case of a high-temperature and high-humidity environment or the like, a local battery is formed due to very initial corrosion on the surface of the galvanized layer provided with the surface treatment film. The colloidal silica contained in the surface treatment coating film usually contains sodium as a dispersant as shown in fig. 2, that is, colloidal silica stabilized with Na ions is often used. The reason for this is that: colloidal silica is generally produced starting from sodium silicate, and most of the sodium is removed by cation exchange, but in order to form SiO₂Sodium was used for the stable sol of (2), and complete removal was difficult. Fig. 2 is a schematic diagram showing a state of colloidal silica. When the surface treatment coating contains such colloidal silica, the surface treatment coating is naturally presentIt contains Na element derived from colloidal silica. Na element derived from the colloidal silica contained in the surface treatment coating is concentrated in the cathode portion of the battery, and gradually promotes initial corrosion, thereby forming an amorphous oxide (amorphous zinc oxide) on the zinc plating layer. That is, as shown in fig. 3A, in the surface-treated metal sheet 10 in which the surface-treatment coating 11 containing colloidal silica 14 is provided on the galvanized steel sheet 12, Na ions contained in the colloidal silica 14 migrate to the surface of the galvanized layer of the galvanized steel sheet 12, and partially form the amorphous oxide 13. Then, the etching proceeds from the amorphous oxide 13, and as shown in fig. 3B, the amorphous oxide 13 diffuses in a spot shape at the interface between the galvanized steel sheet 12 and the surface treatment film 11. So that the amorphous oxide 13 diffused in the form of a spot appears to be stained. The present inventors speculate that: the surface-treated metal sheet having the surface-treated coating film containing colloidal silica as described above generates stains based on such a mechanism. Fig. 3A is a schematic diagram showing a state in which stains start to be generated in the surface-treated metal sheet 10 having the surface-treatment coating 11 provided on the galvanized steel sheet 12. Fig. 3B is a schematic diagram showing a state in which stains are spread in the surface-treated metal sheet 10 having the surface-treatment coating 11 provided on the galvanized steel sheet 12.

Therefore, the inventors consider that: when the amount of Na element contained in the surface treatment film is reduced, the amorphous oxide 13 formed locally becomes small as shown in fig. 4, and as a result, the stain can be effectively suppressed. Fig. 4 is a schematic view showing a state in which the occurrence of stain is suppressed in the surface-treated metal sheet 10 in which the surface-treatment coating film 11 is provided on the galvanized steel sheet 12.

In addition, when the aqueous emulsion contained as the base in the surface treatment composition is of a type in which ammonia is used as a neutralizing agent when an emulsion is produced, the ammonia is naturally contained in the surface treatment composition. The inventor finds that: the ammonia reacts with the zinc coating layer to locally form zinc oxide (ZnO), zinc hydroxide (Zn (OH)₂) And the like, further increasing the deterioration of corrosion resistance and blackeningChange, and generation of stains.

Therefore, the inventors consider that: if a resin containing no ammonia is used as the resin contained in the surface treatment composition used for forming the surface treatment film, the amount of ammonia contained in the surface treatment composition is reduced, and corrosion resistance, blackening resistance, and stain resistance can be improved.

The present inventors have conceived the present invention as described below based on the above-described studies. The present inventors have conducted various studies and, as a result, have found that: the above object is achieved by the present invention which provides a surface-treated metal sheet having excellent blackening resistance and sufficiently suppressed occurrence of stain.

As shown in fig. 1A, 3A, and the like, a surface-treated metal plate according to an embodiment of the present invention includes: a galvanized steel sheet 12; and a surface treatment film 11 laminated on at least one surface of the zinc-plated steel sheet 12. The surface treatment film 11 is composed of a surface treatment composition containing: a polyolefin-based resin containing no ammonia; and colloidal silica having an average particle diameter of 4 to 6 nm. The content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass with respect to 100 parts by mass of the surface treatment composition. And the amount of the surface treatment film is 0.4 to 1.2g/m². And the amount of sodium ions eluted from the surface treatment coating is 4mg/m when the coating is immersed in deionized water at 70 to 80 ℃ for 10 minutes²The following.

Such a surface-treated metal sheet is excellent in blackening resistance and can sufficiently suppress the occurrence of stain. In addition, the adhesion to the zinc plating layer is also excellent. The present inventors consider this to be based on the following reason.

First, since the surface treatment film 11 contains a polyolefin resin containing no ammonia, the amount of ammonia contained in the surface treatment composition is small. The inventor considers that: this can suppress the decrease in corrosion resistance, blackening, and the occurrence of stain caused by the reaction of ammonia with the zinc plating layer. Further, since the average particle size of the colloidal silica contained is as small as 4 to 6nm, the dispersibility and activity of the colloidal silica are improved, and the surface-treated skin is providedThe barrier property of the film is improved, the corrosion resistance can be improved, and the adhesion with the zinc plating layer can be improved. The inventor considers that: the surface treatment composition contains 10 to less than 30 parts by mass of the colloidal silica per 100 parts by mass of the surface treatment composition, and the amount of the colloidal silica is 0.4 to 1.2g/m²The surface treatment film of the embodiment (1) can exhibit the effect of containing colloidal silica, such as improvement in corrosion resistance and adhesion to a zinc plating layer. Further, when the surface treatment film is immersed in deionized water at 70 to 80 ℃ for 10 minutes, the amount of sodium ions eluted from the surface treatment film is 4mg/m²The following. The inventor considers that: when the amount of sodium ions eluted from the surface treatment film is so small, the generation of stain can be suppressed as described above. For these reasons, the surface-treated metal sheet of the present embodiment has excellent blackening resistance and can sufficiently suppress the occurrence of stain. In addition, the adhesion to the zinc plating layer (tape peeling resistance) is also excellent.

The zinc-based plated steel sheet is not particularly limited, and may be a steel sheet plated with only zinc, or may be a steel sheet plated with a zinc-based alloy such as zinc-Ni, zinc-Fe, or zinc-Al. The plating method is also not particularly limited, and may be a galvanized steel sheet obtained by any of a melt plating method, an electroplating method, a vapor deposition method, and the like. Specific examples of the galvanized steel sheet include: hot-dip galvanized steel sheet (GI), hot-dip galvannealed Zn-Fe steel sheet (GA), hot-dip galvannealed Zn-5% Al steel sheet (GF), galvanized steel sheet (EG), Zn-Ni alloy galvanized steel sheet, etc. Of these, galvanized steel sheet (EG) is preferable.

As described above, the surface treatment coating film is composed of a surface treatment composition containing: a polyolefin-based resin containing no ammonia; and colloidal silica having an average particle diameter of 4 to 6 nm.

The polyolefin resin is not particularly limited as long as it is a polyolefin resin containing no ammonia. Specific examples of the polyolefin-based resin include a polyolefin-based resin which is emulsion-liquefied without containing ammonia, that is, an emulsion prepared without using ammonia as a neutralizer in the preparation of the emulsionPolyolefin resins, and the like. Examples of such polyolefin-based resins include polyolefin-based resins that contain at least one of an organic basic amine and a metal ion and are emulsified. That is, the polyolefin-based resin may be a polyolefin-based resin that is emulsified and liquefied using at least one of an organic basic amine and a metal ion as a neutralizer in the production of an emulsion. Any polyolefin resin containing no ammonia, such as a polyolefin resin containing no ammonia and being emulsified and liquefied, can be used without causing formation of zinc oxide (ZnO) and zinc hydroxide (zn (oh))₂) Etc. are generated. Thus, deterioration of corrosion resistance, blackening, and generation of stain can be suppressed.

The polyolefin resin is not particularly limited as long as it is a polyolefin resin containing no ammonia, and the water vapor permeability when formed into a film is preferably 100g/m²Less than one day, more preferably 50g/m²The day is less. The water vapor permeability is defined, for example, in JIS K7129. Examples of the measuring method include: a method of preparing a film of about 18 μm and measuring the water vapor permeability of the film by the cup method according to JIS Z0208, and the like. If the resin has an excessively high water vapor permeability, the surface treatment film obtained may have a high water vapor permeability if the colloidal silica is added to improve corrosion resistance, and the corrosion resistance-improving effect may not be obtained.

The polyolefin resin is not particularly limited as long as it is a polyolefin resin containing no ammonia, and a copolymer containing an α, β -unsaturated carboxylic acid and an olefin (olefin- α, β -unsaturated carboxylic acid copolymer) is preferred. The inventor considers that: in the above olefin- α, β -unsaturated carboxylic acid copolymer, the constituent unit derived from the α, β -unsaturated carboxylic acid functions to improve the adhesion between the zinc plating and the surface treatment film. Accordingly, by containing the olefin- α, β -unsaturated carboxylic acid copolymer, the barrier property of the surface treatment film can be improved without impairing the dispersion stability of the colloidal silica in the surface treatment composition. Therefore, the surface treatment film is reduced in the permeation of water and oxygen, and the corrosion resistance and blackening resistance can be further improved.

The above-mentioned olefin- α, β -unsaturated carboxylic acid copolymer (hereinafter, sometimes simply referred to as "olefin-acid copolymer") is a copolymer of an α, β -unsaturated carboxylic acid and an olefin. Also, the olefin-acid copolymer is preferably: the olefin-derived constituent unit accounts for 50% by mass or more of the olefin-acid copolymer. That is, the above-mentioned olefin-acid copolymer is preferably: the constituent unit derived from the α, β -unsaturated carboxylic acid accounts for 50% by mass or less of the olefin-acid copolymer.

The olefin-acid copolymer may be produced by copolymerizing an olefin with an α, β -unsaturated carboxylic acid by a known method, as long as the olefin is copolymerized with the α, β -unsaturated carboxylic acid. In addition, the above olefin-acid copolymers are also sold.

The olefin that can be used for the production of the olefin-acid copolymer is not particularly limited, but ethylene, propylene and the like are preferred, and ethylene is more preferred. In the above-mentioned olefin-acid copolymer, the constituent unit derived from the above-mentioned olefin may be derived from only 1 kind of olefin, or may be derived from 2 or more kinds of olefins.

The α, β -unsaturated carboxylic acid that can be used for producing the olefin-acid copolymer is not particularly limited, and examples thereof include an ethylenic α, β -unsaturated carboxylic acid. Specific examples of the α, β -unsaturated carboxylic acid include: monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. The α, β -unsaturated carboxylic acid may be used alone in 1 kind, or two or more kinds may be used in combination. Among the above exemplified compounds, the α, β -unsaturated carboxylic acid is preferably acrylic acid or methacrylic acid, and more preferably acrylic acid. In the above-mentioned olefin-acid copolymer, the constituent unit derived from the above-mentioned α, β -unsaturated carboxylic acid may be derived from only 1 kind of α, β -unsaturated carboxylic acid, or may be derived from 2 or more kinds of α, β -unsaturated carboxylic acids.

As described above, the present inventors considered that: the constituent unit derived from the α, β -unsaturated carboxylic acid in the olefin-acid copolymer plays a role in improving the adhesion between the zinc plating and the surface treatment film. In order to effectively exhibit this effect, the constituent unit derived from the α, β -unsaturated carboxylic acid is preferably contained in the olefin-acid copolymer in an amount of 5% by mass or more, more preferably 10% by mass or more. The upper limit of the content of the constituent unit derived from the α, β -unsaturated carboxylic acid is preferably 50% by mass or less as described above; from the viewpoint of corrosion resistance, it is more preferably 30% by mass or less, and still more preferably 25% by mass or less.

The olefin-acid copolymer may contain a constituent unit derived from a monomer (other monomer) other than the olefin and the α, β -unsaturated carboxylic acid, within a range in which the effects of the present invention are exhibited (specifically, within a range in which the effects of the present invention are not sufficiently exhibited without excessively lowering corrosion resistance, blackening resistance, and the like). The constituent unit derived from another monomer is preferably contained in the above-mentioned olefin-acid copolymer in an amount of 10% by mass or less, more preferably 5% by mass or less, and most preferably 0% by mass. That is, the most preferable copolymer is a copolymer composed only of the above-mentioned constituent unit derived from an olefin and the above-mentioned constituent unit derived from an α, β -unsaturated carboxylic acid. The olefin-acid copolymer is preferably an ethylene-acrylic acid copolymer.

The olefin-acid copolymer may be used alone or in combination of two or more kinds thereof.

Since the olefin-acid copolymer has a carboxyl group in the molecule, the polyolefin resin can be emulsified (dispersed in water) by neutralization with the organic basic amine or the metal ion.

The organic basic amine used as a neutralizing agent in the production of the emulsion is not particularly limited, and preferably has a boiling point of 100 ℃ or lower, more preferably 90 ℃ or lower. If the boiling point is within the above range, the organic basic amine is volatilized during drying when the surface treatment film is formed, and is less likely to remain in the formed surface treatment film, so that the organic basic amine is less likely to cause a decrease in corrosion resistance or black resistance, or the occurrence of stain. Thus, a surface-treated metal sheet having more excellent corrosion resistance, black resistance and stain resistance can be obtained. From the viewpoint of handling properties, the boiling point of the organic basic amine is preferably 70 ℃ or higher, and more preferably 80 ℃ or higher.

Specific examples of the organic basic amine include: tertiary amines such as triethylamine, N-dimethylbutylamine, N-dimethylallylamine, N-methylpyrrolidine, tetramethyldiaminomethane, and trimethylamine; secondary amines such as N-methylethylamine, diisopropylamine, and diethylamine; and primary amines such as propylamine, t-butylamine, sec-butylamine, isobutylamine, 1, 2-dibutylpropylamine, and 3-pentylamine. Among the above-exemplified amines, the organic basic amine is preferably a tertiary amine, and more preferably triethylamine. The organic basic amine may be used alone in 1 kind, or two or more kinds may be used in combination.

The amount of the organic basic amine used is not particularly limited as long as the polyolefin resin is suitably emulsified. The amount of the organic basic amine used is, for example, preferably 0.2 to 0.8 mol based on 1 mol of the carboxyl group in the olefin-acid copolymer (preferably 20 to 80 mol% based on the carboxyl group). The lower limit of the amount of the organic basic amine used is preferably 0.2 mol or more, and more preferably 0.3 mol or more, based on 1 mol of the carboxyl group. The upper limit of the amount of the organic basic amine to be used is preferably 0.8 mol or less, more preferably 0.6 mol or less, and still more preferably 0.5 mol or less based on 1 mol of the carboxyl group. When the amount of the organic basic amine used is within the above range, the surface-treated steel sheet exhibits excellent corrosion resistance, blackening resistance, and adhesion to a galvanized layer (tape peeling resistance). When the amount of the organic basic amine used is too small, the polyolefin resin particles in the emulsion tend to become large, and it tends to be difficult to exhibit such effects. When the amount of the organic basic amine used is too large, the emulsion may be thickened and gelled.

The metal ion used as a neutralizer in the production of the emulsion is not particularly limited, and a metal ion having a valence of 1 is preferable from the viewpoint of improving the hardness of the surface treatment film. Specifically, the metal ions preferably contain at least 1 selected from sodium ions, potassium ions, and lithium ions. Examples of the compound that generates the metal ion in the surface treatment composition include hydroxides, carbonates, oxides, and the like containing the metal ion. Specific examples of such compounds include: sodium hydroxide, potassium hydroxide, lithium hydroxide and the like, among which sodium hydroxide is preferred.

The amount of the compound generating the metal ion in the surface treatment composition is not particularly limited as long as the polyolefin resin is suitably emulsified. The amount of the compound used is, for example, preferably 0.02 to 0.4 mol (2 to 40 mol% relative to the carboxyl group) relative to 1 mol of the carboxyl group in the olefin-acid copolymer. The lower limit of the amount of the compound used is preferably 0.02 mol or more, more preferably 0.03 mol or more, and still more preferably 0.1 mol or more based on 1 mol of the carboxyl group. The upper limit of the amount of the compound used is preferably 0.4 mol or less, more preferably 0.2 mol or less, based on 1 mol of the carboxyl group. When the amount of the above compound used is too small, emulsion stability tends to be insufficient. In addition, when the amount of the compound used is too large, the corrosion resistance tends to be lowered.

The preferable ranges of the amounts of the organic basic amine and the compound generating the metal ion in the surface treatment composition are as described above, and these are used for neutralizing the carboxyl group in the olefin-acid copolymer to emulsify the polyolefin resin. Therefore, when the total amount (neutralization amount) of these is too large, the viscosity of the emulsion may rapidly increase and solidify. Further, an excessive amount of alkali component causes deterioration in corrosion resistance and blackening resistance, and therefore, a large amount of energy is required for volatilization, which is not preferable. On the other hand, if the total amount (neutralization amount) of these is too small, the emulsifying property may become insufficient. For these reasons, the total amount of the organic basic amine and the compound generating the metal ion in the surface treatment composition is preferably 0.3 to 1.0 mol (30 to 100 mol% relative to the carboxyl group) relative to 1 mol of the carboxyl group in the olefin-acid copolymer.

The emulsion-liquefied polyolefin resin containing at least one of an organic basic amine and a metal ion forms intermolecular association based on ion clusters, thereby forming a surface treatment film excellent in corrosion resistance, blackening resistance, adhesion to a galvanized layer (tape peeling resistance), and the like. The surface treatment composition may contain a crosslinking agent capable of crosslinking polyolefin resins with each other by a chemical bond utilizing a reaction between functional groups in order to form a stronger surface treatment film. This crosslinking agent is a crosslinking agent for crosslinking a polyolefin resin, that is, an internal crosslinking agent, and is a crosslinking agent for crosslinking a resin constituting an emulsion at the time of emulsion production, and is also referred to herein as an internal crosslinking agent.

The internal crosslinking agent is not particularly limited as long as it can crosslink polyolefin resins with each other, and examples thereof include: a crosslinking agent having 2 or more functional groups capable of reacting with a carboxyl group in a molecule. Specific examples of the internal crosslinking agent include: a glycidyl group-containing crosslinking agent having 2 or more glycidyl groups in the molecule; and an aziridinyl-containing crosslinking agent having 2 or more aziridinyl groups in the molecule. Examples of the glycidyl group-containing crosslinking agent include: polyglycidyl ethers such as sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, and (poly) ethylene glycol diglycidyl ether; polyglycidyl amines and the like. Examples of the aziridinyl group-containing crosslinking agent include: 2-functional aziridine compounds such as 4,4 '-bis (ethyleneiminocarbonylamino) diphenylmethane, N' -hexamethylene-1, 6-bis (1-aziridinecarboxamide), N '-diphenylmethane-4, 4' -bis (1-aziridinecarboxamide), and tolylbis (aziridinecarboxamide); 3 or more functional aziridine compounds such as tris-1-aziridinyl phosphine oxide, tris [1- (2-methyl) aziridinyl ] phosphine oxide, trimethylolpropane tris (. beta. -aziridinyl propionate), tris-2, 4,6- (1-aziridinyl) -1,3, 5-triazine, and tetramethylpropane tetraaziridinyl propionate; and derivatives of the above aziridine compounds, and the like. Among the exemplified crosslinking agents, the internal crosslinking agent is preferably an aziridine compound having 2 or more functions, more preferably a 2-functional aziridine compound, and further preferably 4, 4' -bis (ethyleneiminocarbonylamino) diphenylmethane. The internal crosslinking agent may be used alone in 1 kind, or two or more kinds may be used in combination.

The amount of the internal crosslinking agent used is preferably 1 to 20% by mass, more preferably 5 to 10% by mass, based on the polyolefin resin. The amount of the polyolefin resin used is a ratio of 100 mass% to the solid content of the polyolefin resin. When the amount of the internal-crosslinking agent is too small, the effect of adding the internal-crosslinking agent tends to be not sufficiently exhibited. That is, the effect of crosslinking by chemical bonds is insufficient, and the effect of improving the corrosion resistance and the tape peeling resistance tends to be difficult to exert. On the other hand, if the internal crosslinking agent is too much, the crosslinking density of the surface treatment film becomes too high, and the hardness increases, and cracks may occur due to failure to follow the deformation of the surface treated metal sheet during press working, and as a result, the corrosion resistance may decrease.

The amount of the olefinic resin to be added is not particularly limited as long as the olefinic resin constitutes the remainder of the surface treatment composition, excluding colloidal silica, a crosslinking agent for crosslinking the surface treatment film, and a lubricant, which will be described later. The amount of the olefin resin added is, for example, preferably 56.5 to 90 parts by mass per 100 parts by mass of the surface treatment composition. The amount of the additive is a solid content ratio.

The colloidal silica has an average particle diameter of 4 to 6 nm. Next, based on the above-mentioned examination, the colloidal silica is required to have a small amount of sodium ions eluted from the surface treatment film. The colloidal silica is specifically: when the surface-treated film is immersed in deionized water at 70 to 80 ℃ for 10 minutes, the amount of sodium ions released from the surface-treated film (released amount) is 4mg/m²The following colloidal silica. The colloidal silica is not particularly limited as long as it is the colloidal silica.

As the colloidal silica, specifically, colloidal silica containing ammonia as a dispersant is preferable. As such colloidal silica containing ammonia as a dispersant, namely NH₄ ⁺Ion-stabilized colloidal silica (ammonia stabilized) is also sold. By using such colloidal silica containing ammonia as a dispersant, the amount of sodium in the surface treatment coating can be reduced as compared with the case where only the above-described conventional colloidal silica, that is, colloidal silica containing sodium as a dispersant (sodium-stabilized type) is used. Thus, a surface-treated film having a reduced elution amount can be obtained.

As described above, the colloidal silica has an average particle diameter of 4 to 6 nm. When the colloidal silica is too large, there is a downward orientation: corrosion resistance, tape peeling resistance, and the like are reduced, and adhesion (coatability) to a coating film coated on the surface-treated metal sheet is also reduced. The inventor considers that: this tendency is caused by a decrease in the dispersibility and activity of colloidal silica in the surface treatment film, and therefore the barrier property of the surface treatment film is decreased, and the amount of colloidal silica eluted in a corrosive environment is decreased. Therefore, by using colloidal silica having the above particle size, a surface-treated metal sheet having a surface-treated coating film excellent in corrosion resistance, coatability, tape peeling resistance, coating hardness, and workability can be obtained. Specific examples of the colloidal silica having an average particle diameter of 4 to 6nm include SNOWTEX NXS (ST-NXS, ammonia-stable type) and SNOWTEX XS (ST-XS, sodium-stable type) available from Nissan chemical industries, Ltd. When sodium stabilized ST-XS is used, it is preferably combined with ammonia stabilized ST-NXS. As the average particle diameter of the colloidal silica, for example: when the average particle diameter is about 1 to 10nm, the particle diameter is a value measured by the Siers (Sears) method; when the average particle diameter is about 10 to 100nm, the particle diameter may be measured by the BET method. When a nominal value is described in the product specification of the manufacturer, the nominal value is defined as the average particle diameter of the colloidal silica.

As described above, the present inventors have found that, when immersed in deionized water at 70 to 80 ℃ for 10 minutes, the amount of sodium ions (elution amount) eluted from the surface treatment film is preferably smaller, and found through studies that: if it is 4mg/m²The stain can be suitably suppressed as follows. The amount of elution is more preferably 3.8mg/m²The concentration is more preferably 3.5mg/m²The following. When the amount is within this range, not only the stain can be suitably suppressed, but also the corrosion resistance, blackening resistance, tape peeling resistance, and the like can be improved. Further, the amount of elution is preferably as small as possible, but the characteristics of colloidal silica are determined to be 1mg/m²The lower limit of the amount of elution is preferably 1mg/m²The above. The amount of elution is, for example, a value measured in the following manner. And (3) soaking the surface-treated metal plate in deionized water at the temperature of 70-80 ℃ for 10 minutes. The amount of sodium ions contained in the liquid after the surface-treated metal sheet was immersed was measured by ion chromatography. The elution amount was calculated from the measured amount of sodium ions and the area of the surface-treated metal plate. For example, ICS-5000+ manufactured by Seimerle Fischer science K.K, or the like, can be used as the ion chromatography.

The lower limit of the amount of the colloidal silica to be added is 10 parts by mass or more, preferably 15 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of the surface treatment composition. The upper limit of the amount of the colloidal silica added is less than 30 parts by mass, preferably 28 parts by mass or less, based on 100 parts by mass of the surface treatment composition. The amount of the additive is a solid content ratio. The present inventors speculate that: the reason why the colloidal silica is added to the surface treatment coating film to improve the corrosion resistance and the blackening resistance is that the colloidal silica is dissolved and eluted in a corrosive environment to cause a pH buffering action or a passive film forming action. Therefore, when the amount of colloidal silica added is too small, the effect cannot be sufficiently exhibited, and corrosion resistance tends to decrease, and adhesion to the galvanized surface also tends to decrease. When the amount of colloidal silica added is too large, the amount of resin added is small, and therefore the surface treatment film tends to be brittle and to easily crack. Therefore, the blackening resistance is lowered, the adhesion to the galvanized surface is also lowered, and further the coatability may be lowered. Therefore, when the amount of the colloidal silica is within the above range, a surface-treated metal sheet having excellent corrosion resistance, adhesion to a galvanized surface, and the like can be obtained.

Preferably, the surface treatment film further contains a crosslinking agent for crosslinking the surface treatment film and a lubricant in addition to the resin and the colloidal silica.

The crosslinking agent can improve the corrosion resistance, tape peeling resistance, and lubricity of the surface treatment film by containing the crosslinking agent. The crosslinking agent is a crosslinking agent that crosslinks the surface treatment film, that is, a crosslinking agent that crosslinks a resin constituting the surface treatment film when the surface treatment film is formed, and is also referred to herein as an external crosslinking agent.

The external crosslinking agent is not particularly limited as long as it can crosslink the surface treatment film, and an epoxy crosslinking agent is preferably used from the viewpoint of reactivity. Examples of the epoxy crosslinking agent include: polyglycidyl ethers such as sorbitol polyglycidyl ether, (poly) glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, and (poly) ethylene glycol diglycidyl ether; polyglycidyl amines and the like. Examples of the epoxy crosslinking agent include EPICLON CR5L and EPICLON CR75 manufactured by DIC corporation. The external crosslinking agent may be used alone in 1 kind, or two or more kinds may be used in combination.

The amount of the external crosslinking agent added is not particularly limited, and the lower limit thereof is preferably 5 parts by mass or more, and more preferably 6.5 parts by mass or more, with respect to 100 parts by mass of the surface treatment composition. The upper limit of the amount of the external crosslinking agent added is preferably 8.5 parts by mass or less with respect to 100 parts by mass of the surface treatment composition. The amount of the additive is a solid content ratio. When the amount of the external crosslinking agent added is too small, the corrosion resistance, blackening resistance, tape peeling resistance, and lubricity tend to be lowered. When the amount of the external crosslinking agent added is too large, the coatability tends to be lowered. Further, when the external crosslinking agent is excessively added, it is considered that self-crosslinking of the external crosslinking agent occurs, but when the amount of the external crosslinking agent added is within the above range, self-crosslinking is suppressed and the crosslinking reaction can be appropriately performed. That is, when the amount of the external crosslinking agent added is within the above range, the crosslinking reaction proceeds sufficiently, and the corrosion resistance and blackening resistance of the surface treatment film can be improved. Further, the hardness of the surface treatment film also increases, and therefore, the lubricity and the workability are also improved.

The lubricant is contained, so that the coefficient of dynamic friction of the surface treatment film can be reduced, the workability can be improved, and the scratch is less likely to occur.

The lubricant is not particularly limited, and examples thereof include: polyolefin waxes such as polyethylene, polyethylene oxide, and polypropylene; fluorine-based resins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and tetrafluoroethylene; an organically modified polysiloxane; paraffin wax, and the like. Among the above-mentioned lubricants, polyolefin waxes are preferable, and polyethylene waxes are more preferable. The above-mentioned lubricant may be used alone in 1 kind, or two or more kinds may be used in combination.

Further, as the polyethylene wax, those in a particulate form, such as a spherical form; the average particle size is preferably 0.1 to 3 μm, more preferably 0.3 to 1 μm. When the polyethylene wax particles (spherical polyethylene wax) are too large, uniform dispersion in the surface treatment composition becomes difficult, and the film forming property is impaired, so that the corrosion resistance tends to be lowered. On the other hand, when the polyethylene wax particles are too small, the lubricity tends to be insufficiently improved. The average particle diameter of the polyethylene wax particles can be measured by Coulter counting method. By using polyethylene wax particles having such a particle diameter, the surface treatment film is present in a spherical shape, and friction at the surface of the surface treatment film can be effectively reduced, which is effective for suppressing occurrence of scratches and the like. Examples of the polyethylene wax particles include Chemipearl W640, ChemipearL W700, Chemipearl W950, and Chemipearl W900 manufactured by Mitsui chemical corporation.

The amount of the lubricant to be added is not particularly limited, and the lower limit thereof is preferably 2 parts by mass or more, and more preferably 2.5 parts by mass or more, with respect to 100 parts by mass of the surface treatment composition. The upper limit of the amount of the lubricant added is preferably 5 parts by mass or less, and more preferably 4 parts by mass or less, per 100 parts by mass of the surface treatment composition. The amount of the additive is a solid content ratio. When the amount of the lubricant added is too small, the lubricity tends to be insufficient, and the bending workability of the surface-treated metal sheet tends to be lowered. When the amount of the lubricant added is too large, hydrolysis of the lubricant occurs in a corrosive environment, and the corrosion resistance, blackening resistance, stain resistance, tape peeling resistance, and coatability tend to be reduced. Therefore, when the amount of the lubricant added is within the above range, a surface-treated metal sheet having excellent corrosion resistance, blackening resistance, stain resistance, and the like can be obtained.

The lower limit of the amount of the surface treatment film deposited is 0.4g/m²Above, preferably 0.45g/m²Above, more preferably 0.5g/m²The above. Further, the upper limit of the amount of the surface treatment film deposited is 1.2g/m²Below, it is preferably 0.8g/m²Hereinafter, more preferably 0.7g/m²The following. When the amount of the surface treatment film to be attached is too small, the barrier property deteriorates and the spread of stains is promoted, so that the stain resistance tends to deteriorate. When the amount of the surface treatment film to be deposited is too small, the corrosion resistance, blackening resistance, tape peeling resistance, and the like of the surface-treated metal sheet tend not to be sufficiently improved. When the amount of the surface-treatment coating film to be adhered is too large, the tape peeling resistance is lowered, and when the surface-treated metal sheet is subjected to bending or pressing, for example,the surface treatment film tends to be easily peeled off. Further, the coatability and the conductivity also tend to be lowered, and therefore, such is not preferable. Therefore, when the amount of the surface treatment film deposited is within the above range, a surface-treated metal sheet having excellent corrosion resistance, blackening resistance, and the like can be obtained. The amount of the surface treatment film deposited can be measured, for example, as follows. Colloidal Silica (SiO) in the surface-treated coating film can be analyzed by a fluorescent X-ray analyzer₂) The Si element (2) is quantitatively measured and calculated from the measured Si element amount. In this case, SiO is used₂The specific gravity of (a) was calculated with the specific gravity of the resin set to 2.2 and the specific gravity of the resin set to 1.0.

The surface-treated metal sheet may have other layers as long as it has the galvanized steel sheet and the surface-treatment coating film. For example, an undercoat layer may be provided between the zinc-based plated steel sheet and the surface treatment film. Specifically, in order to improve the interface adhesion between the surface of the galvanized steel sheet and the surface treatment film, a base treatment layer obtained by performing a reactive base treatment may be provided, the reactive base treatment layer being composed of a composition containing aluminum hydrogen phosphate, acidic colloidal silica, and polyacrylic acid. However, unreacted phosphoric acid or the like deteriorates blackening resistance and corrosion resistance and promotes generation of stain, and therefore, it is preferable to remove the phosphoric acid or the like by washing with water. As the composition used in forming the above-mentioned undercoat treatment layer, for example, the content ratio of aluminum hydrogen phosphate to acidic colloidal silica is preferably 5: 95-35: 65. preferably, the polyacrylic acid is contained in an amount of 1 to 10 parts by mass based on 100 parts by mass of the total of the aluminum hydrogen phosphate and the acidic colloidal silica.

The method for producing the surface-treated metal sheet is not particularly limited as long as the surface-treated metal sheet of the present embodiment can be produced. As a method for producing the surface-treated metal sheet, specifically, a production method including the steps of: a step (preparation step) of preparing the surface treatment composition; a step (coating step) of applying the surface treatment composition to at least one surface of the zinc-based plated steel sheet; and a step (drying step) of forming the surface treatment coating on the at least one surface of the zinc-based plated steel sheet by drying the surface treatment composition.

The preparation step is not particularly limited as long as the surface treatment composition can be prepared, and examples thereof include: and a step for preparing a surface treatment composition containing a polyolefin resin which does not contain ammonia and is emulsified and liquefied, and colloidal silica having an average particle diameter of 4 to 6 nm. Examples of the preparation step include: and a step of mixing the polyolefin resin and the colloidal silica so that the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass with respect to 100 parts by mass of the surface treatment composition. The preparation step is a step of preparing a surface treatment composition in which the amount of sodium ions eluted from the surface treatment film reaches 4mg/m when the surface treatment composition is immersed in deionized water at 70 to 80 ℃ for 10 minutes²The following. Specifically, there may be mentioned a method of using the above colloidal silica containing ammonia as a dispersant, and the like.

The coating step is not particularly limited as long as the surface treatment composition can be applied to the at least one surface of the zinc-based plated steel sheet, and examples thereof include coating using a bar coater. In addition, the coating step is performed such that the amount of the surface treatment film deposited is 0.4 to 1.2g/m²The step of applying the surface treatment composition.

The drying step is not particularly limited as long as the surface treatment coating can be formed on at least one surface of the zinc-based plated steel sheet by drying the surface treatment composition. Examples of the drying step include drying at 90 to 130 ℃.

According to this manufacturing method, the surface-treated metal sheet according to the present embodiment can be appropriately manufactured.

The present specification discloses the techniques of various embodiments as described above, and the main techniques thereof are summarized as follows.

According to this configuration, it is possible to provide a surface-treated metal sheet which is excellent in blackening resistance and can sufficiently suppress the occurrence of stain, that is, a surface-treated metal sheet which is excellent in blackening resistance and stain resistance.

In the surface-treated metal sheet, it is preferable that: the surface treatment composition further contains a crosslinking agent and a lubricant.

According to this configuration, a surface-treated metal sheet having more excellent blackening resistance and stain resistance can be obtained.

In the surface-treated metal sheet, it is preferable that: the content of the crosslinking agent is 5 to 8.5 parts by mass relative to 100 parts by mass of the surface treatment composition.

In the surface-treated metal sheet, it is preferable that: the content of the lubricant is 2-5 parts by mass relative to 100 parts by mass of the surface treatment composition.

In the surface-treated metal sheet, it is preferable that: the colloidal silica is a colloidal silica comprising ammonia as a dispersant.

In the surface-treated metal sheet, it is preferable that: the polyolefin resin contains a copolymer of an alpha, beta-unsaturated carboxylic acid and an olefin.

Another aspect of the present invention relates to a method for manufacturing a surface-treated metal sheet, which is a method for manufacturing the surface-treated metal sheet and includes the steps of: a step for preparing the surface treatment composition; a step of applying the surface treatment composition to at least one surface of the zinc-based plated steel sheet; and a step of forming the surface treatment coating film on the at least one surface of the galvanized steel sheet by drying the surface treatment composition.

According to this configuration, a surface-treated metal sheet having excellent blackening resistance and sufficiently suppressed occurrence of stain, that is, a surface-treated metal sheet having excellent blackening resistance and stain resistance can be produced.

According to the present invention, it is possible to provide a surface-treated metal sheet which is excellent in blackening resistance and can sufficiently suppress the occurrence of stain, and a method for producing the surface-treated metal sheet.

The present invention will be further specifically described below with reference to examples, but the scope of the present invention is not limited thereto.

Examples

First, each evaluation method used in the following examples will be explained.

[ Corrosion resistance ]

1. Salt spray test (SST flat, SST cross nick)

For the test materials with the back and edge seals applied, flat test pieces and test pieces with cross-cuts formed by a cutter were prepared. For each sample, a salt spray test was performed by spraying salt water (5% NaCl aqueous solution) at 35 ℃ in an atmosphere based on JIS Z2371. The time until the generation rate of white rust with respect to the test material reached 5 area% was measured.

(SST Flat plate)

As evaluation criteria of the SST plate, the plate-shaped sample was evaluated as "excellent" if the time taken for the white rust generation rate to reach 5 area% was 240 hours or longer, as "o" if 168 hours or longer and less than 240 hours, as "Δ" if 120 hours or longer and less than 168 hours, and as "x" if less than 120 hours.

(SST Cross-shaped notch)

As evaluation criteria for the SST cross score, if the time taken until the generation rate of white rust with respect to the sample having the cross score reaches 5 area% is 120 hours or more, the evaluation is "excellent", if the generation rate is 96 hours or more and less than 120 hours, the evaluation is "Δ", if the generation rate is 72 hours or more and less than 96 hours, and the evaluation is "x", if the generation rate is less than 72 hours.

2. Brine spray cycle test (SST cycle)

The test piece (flat plate) subjected to the edge sealing was subjected to a salt spray cycle test by spraying salt water (5% aqueous NaCl solution) at 35 ℃ in an atmosphere according to JIS Z2371. The salt spray was carried out for 8 hours and then stopped for 16 hours in 1 cycle. The number of cycles at which the white rust generation rate with respect to the test material reached 5 area% was measured. As evaluation criteria for the SST cycle, the SST cycle was evaluated as "very good" if the number of cycles was 10 or more, as "good" if the number of cycles was 7 or more and less than 10, as "Δ" if the number of cycles was 5 or more and less than 7, and as "x" if the number of cycles was less than 5.

3. Neutral salt spray cycle test (JASO)

For the test pieces (flat plates) subjected to edge sealing, a neutral salt water spray cycle test was performed in accordance with JIS H8502. After spraying brine for 2 hours in 1 cycle, the mixture was dried for 4 hours (temperature 60 ℃ C., humidity 30% or more), and then moistened for 2 hours (temperature 50 ℃ C., humidity 95% or more). The number of cycles at which the white rust generation rate with respect to the test material reached 5 area% was measured. As evaluation criteria of JASO, the test piece was evaluated as "excellent" if the number of cycles was 21 or more, as "good" if 15 or more and less than 21, as "Δ" if 9 or more and less than 15, and as "x" if less than 9.

[ blackening resistance ]

The test material was stored in a constant temperature and humidity tester at 50 ℃ and 98% or higher humidity for 168 hours, and then the color difference (. DELTA.L) before and after the test was measured with a color difference meter. As evaluation criteria for blackening resistance, the evaluation was "very excellent" if Δ L was less than 1, "o" if Δ L was 1 or more and less than 2, "Δ" if Δ L was 2 or more and less than 3, and "x" if Δ L was 3 or more.

[ stain resistance ]

The test material was stored in a constant temperature and humidity tester at 65 ℃ and 95% or higher humidity for 168 hours, and then the change in appearance before and after the test was visually confirmed. As evaluation criteria of stain resistance, the evaluation was "excellent" if no occurrence of stains was confirmed, the evaluation was "o" if very few stains were confirmed, the evaluation was "Δ" if few stains were confirmed, the evaluation was "x" if all stains were confirmed, and the evaluation was "xxx" if significant stains were confirmed.

[ tape peeling resistance ]

The adhesion between the surface of the plating layer and the surface treatment film of the galvanized steel sheet under high-temperature and high-humidity conditions was evaluated. That is, an adhesive tape (filament tape No.9510 manufactured by Sliontech: rubber adhesive) was stuck to a sample, and the sample was stored in a constant temperature and humidity test apparatus at 40 ℃ under an atmosphere of 98% humidity for 120 hours, and then a tape peeling test was performed according to JIS K5400. Then, the remaining rate of the surface treatment film after the tape peeling test was performed was measured. As evaluation criteria for the tape peeling resistance, the residual ratio was evaluated as "excellent" if 95 area% or more, as "good" if 90 area% or more and less than 95 area%, as "Δ" if 80 area% or more and less than 90 area%, and as "x" if less than 80 area%.

[ coatability (secondary adhesion of coating film) ]

For the test materials, a bar coating was performed such that the thickness of the coating film was 20 μm with an acrylic paint (macroron #1000 manufactured by kansai paint co., ltd.) and post-coated by baking at 160 ℃ for 20 minutes. Then, the test piece after the post-coating was immersed in boiling water for 1 hour and then taken out, and after leaving for 1 hour, 100 pieces of 1mm square checkerboards were cut with a cutter knife, and the tape peeling test was performed in the same manner as the above-described tape peeling resistance. Then, the number of the remaining coating films that were not peeled off was measured. As evaluation criteria for coatability (secondary adhesion of coating film), the coating film was evaluated as "excellent" if the number of remaining cells was 100, as "good" if 90 or more and 99 or less, as "Δ" if 80 or more and 89 or less, and as "x" if 79 or less.

[ lubricity (coefficient of dynamic friction) ]

The dynamic friction coefficient of the test material was measured by using a friction coefficient measuring apparatus shown in fig. 5. Specifically, as shown in fig. 5, after the test material 51 is sandwiched between the

flat molds

52 and 53, the flat mold 53 is pressed against the test material 51 with a pressure P. In this state, the test material 51 is pulled out from between the flat die 52 and the flat die 53. The drawing load F at this time was measured, and from the measured F, the coefficient of kinetic friction μ (═ F/2P) of each test piece was calculated. The measurement conditions are as follows. Fig. 5 is a schematic diagram showing a friction coefficient measuring device for evaluating lubricity.

Sample size: 40X 300mm

Pressure P: 5.4MPa

Drawing speed: 300 mm/min

The flat plate die is made of: SKD11

Without oiling

As evaluation criteria of lubricity, the evaluation was "very excellent" if the coefficient of dynamic friction μ was less than 0.09, "o" if 0.09 or more and less than 0.15, "Δ" if 0.15 or more and less than 0.2, and "x" if 0.2 or more.

Test example 1 (resin)

As the resin constituting the surface treatment film, the following resins were used.

(resin A: a polyolefin-based resin which does not contain ammonia and is emulsion-liquefied)

An autoclave equipped with an emulsifying device equipped with a stirrer, a thermometer and a temperature controller, and containing 626 parts by mass of water and 160 parts by mass of an ethylene-acrylic acid copolymer (acrylic acid unit: 20% by mass, melt index MI: 300), was charged with 15 mol% of sodium hydroxide and 40 mol% of triethylamine relative to 1 mol of carboxyl groups of the ethylene-acrylic acid copolymer. Thereafter, the mixture was stirred at 150 ℃ and 5Pa at a high speed, and then cooled to 40 ℃. To this was added 5 parts by mass of 4, 4' -bis (ethyleneiminocarbonylamino) diphenylmethane (CHEMITITE DZ-22E, manufactured by Nippon Kabushiki Kaisha Co., Ltd.) as a crosslinking agent per 100 parts by mass of the solid content of the ethylene-acrylic acid copolymer. This procedure gave an emulsified ethylene-acrylic acid copolymer (aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer). This was used as resin A. The resin A had an average molecular weight of 60000 and an average particle diameter of 55 nm. Further, the resin A was used, and the water vapor permeability was measured by the above-mentioned method, and it was 50g/m²The day is.

(resin B: a polyolefin-based resin which contains ammonia and is emulsion-liquefied)

An ethylene-acrylic acid copolymer (aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer) emulsified and liquefied by containing ammonia (Hytec S-7024, manufactured by Toho chemical industries, Ltd.) was used as the resin B. The resin B was produced using ammonia water for emulsification, which is different from the resin a in emulsification. The resin B had an average molecular weight of 30000 and an average particle diameter of 40 nm. Further, the water vapor permeability of the resin B was measured by the above-mentioned method and was 115g/m²The day is.

(resin C: aqueous polyurethane resin dispersion having carboxyl group)

Comprises a stirrer, a thermometer and a temperature controllerA synthesis apparatus was prepared by charging 60 parts by mass of polytetramethylene ether glycol (average molecular weight 1000: manufactured by Baotou chemical Co., Ltd.) as a polyol component, 14 parts by mass of 1, 4-cyclohexanedimethanol, 20 parts by mass of dimethylolpropionic acid, and 30 parts by mass of N-methylpyrrolidone as a reaction solvent. 104 parts by mass of Toluene Diisocyanate (TDI) as an isocyanate component was added thereto, and the temperature was raised to 80 to 85 ℃ to carry out a reaction for 5 hours. The NCO content of the obtained prepolymer was 8.9 mass%. Further, 16 parts by mass of triethylamine was added to neutralize the reaction mixture, and a mixed aqueous solution of 16 parts by mass of ethylenediamine and 480 parts by mass of water was further added thereto, followed by emulsification at 50 ℃ for 4 hours and chain extension reaction. By this operation, a polyurethane resin aqueous dispersion (polyurethane resin aqueous dispersion) having carboxyl groups (nonvolatile resin component: 29.1 mass%, acid value: 41.4) was obtained. This was used as resin C. The water vapor permeability of the resin C was 1500g/m, which was measured by the above-mentioned method²The day is.

(resin D: modified epoxy resin aqueous Dispersion)

As the resin D, an aqueous modified epoxy resin dispersion (MODEPICS 302 manufactured by Mitsukawa chemical Co., Ltd.) was used.

(resin E: aqueous polyester resin Dispersion)

As the resin E, an aqueous polyester resin dispersion (VYLONALMD 1200 manufactured by toyobo co., ltd) was used.

(surface-treated Metal sheet No.1)

A surface treatment composition was prepared by adding 72 parts by mass of resin A and 28 parts by mass of colloidal silica (ST-NXS, available from Nissan chemical industries, Ltd.: ammonia-stable) having an average particle diameter of 4 to 6nm in terms of solid content ratio.

As the metal plate, a galvanized steel plate (zinc adhesion amount 20 g/m) was used²And a plate thickness of 0.8 mm). Then, this metal plate was subjected to the following subbing treatment. As the base treatment, first, a solid content ratio of 50 mass% of an aqueous aluminum hydrogen phosphate solution (manufactured by Nippon chemical industries Co., Ltd.) to acidic colloidal silica (SNOWTEX O manufactured by Nissan chemical industries Co., Ltd.) was determined12 in terms of mass ratio (aluminum hydrogen phosphate: colloidal silica): 88. these were mixed so that the concentration thereof was 1.5% by mass, and polyacrylic acid powder (AC-10 LP, manufactured by Toyo Synthesis Co., Ltd.) was added to the mixture so that the concentration became 0.1g/L, thereby preparing a foundation treatment liquid. The base treatment liquid was sprayed onto the surface of a galvanized steel sheet as a metal sheet by a spray press, and then washed with water and dried. By this operation, the metal plate is subjected to a foundation treatment, and a foundation treatment layer is formed on the metal plate.

The surface treatment composition was applied to one surface of a metal plate having a base treatment layer formed thereon by a bar coater, and the resultant was dried at a plate temperature of 100 ℃ to obtain a coating film adhesion amount of 0.7g/m²The surface-treated steel sheet having a surface-treated coating film formed thereon. As described above, the coating amount is determined by the fluorescent X-ray analysis apparatus with respect to the colloidal Silica (SiO) in the coating₂) The Si element (2) is quantitatively measured and calculated. In addition, sodium (Na) was measured by ion chromatography (ICS-5000 manufactured by Seimerflezel technologies Co., Ltd.)⁺) The measurement results are: na (Na)⁺The elution amount was 2.0mg/m²Wherein, sodium (Na)⁺) The amount of the surface-treated steel sheet is dissolved out by immersing the steel sheet in deionized water at 70 to 80 ℃ for 10 minutes.

(surface-treated Metal sheet No.2 to 5)

Surface-treated metal sheets Nos. 2 to 5 were produced in the same manner as in the surface-treated metal sheet No.1 except that resins B to E were used instead of the resin A. The amount of the film deposited was 0.7g/m in the same manner as in the case of surface-treated metal sheet No.1²，Na⁺The amount of elution was also 2.0mg/m, respectively²。

The results of the above evaluations of these surface-treated metal sheets Nos. 1 to 5 are shown in Table 1 below.

TABLE 1

Fig. 6 and 7 show changes in the white rust generation rate in the SST plate evaluation and the SST cycle evaluation, respectively. Fig. 6 is a graph showing the change with time in the white rust generation rate in the evaluation of SST plates. In FIG. 6, lines 61 to 65 show the results of surface-treated metal sheets Nos. 1 to 5, respectively. Fig. 7 is a graph showing the change in white rust generation rate with respect to the number of cycles in the evaluation of SST cycles. In FIG. 7, lines 71 to 75 represent the results of surface-treated metal sheets Nos. 1 to 5, respectively.

From these results, it can be seen that: the combination use of the polyolefin resin containing no ammonia and having an emulsion state and the colloidal silica having an average particle diameter of 4 to 6nm (surface-treated metal sheet No.1) is more excellent in corrosion resistance, blackening resistance, stain resistance and tape peeling resistance than the combination use of the resin containing ammonia and having an emulsion state (surface-treated metal sheet No.2) and the combination use of the other resins (surface-treated metal sheets No.3 to 5).

Test example 2 (colloidal silica)

The following products manufactured by Nissan chemical industries, Ltd are used as colloidal silica constituting the surface treatment film.

ST-NXS, ST-NS, ST-N and ST-N40 are ammonia-stable, and the respective average particle sizes are shown in Table 2. Note here that Na contained in ST-NXS, ST-NS, ST-N and ST-N40₂The amount of O is 300ppm or less, 400ppm or less, 2000ppm or less, respectively.

ST-XS, ST-S, ST-30 and ST-50 were sodium-stabilized, and the respective average particle diameters are shown in Table 2. Note here that Na contained in ST-XS, ST-S, ST-30 and ST-50₂The amount of O is 3000-6000 ppm, 6000ppm or less, and 6000ppm or less, respectively.

(surface-treated Metal sheet Nos. 6 to 13)

Surface treatment compositions were prepared by adding 61 parts by mass of resin A, 28 parts by mass of colloidal silica shown in Table 2, 7.5 parts by mass of a glycidyl group-containing crosslinking agent (EPICLON CR5L manufactured by DIC Co., Ltd.) as a crosslinking agent, and 3.5 parts by mass of spherical polyethylene wax (Chemipearl W700 manufactured by Mitsui chemical Co., Ltd.) as a lubricant to the solid content ratio.

Surface-treated metal sheets No.6 to 13 were produced in the same manner as in surface-treated metal sheet No.1 except that the above surface-treating composition was used. The amount of the film deposited was 0.7g/m in the same manner as in the case of surface-treated metal sheet No.1²。Na⁺The elution amounts were the values shown in Table 2.

The results of the above evaluations of these surface-treated metal sheets Nos. 6 to 13 are shown in Table 2 below.

As can be seen from Table 2: the colloidal silica has an average particle diameter of 4 to 6nm and an amount of sodium ions (Na) eluted from the surface-treated coating film when immersed in deionized water at 70 to 80 ℃ for 10 minutes⁺Elution amount) of 4mg/m²The colloidal silica below is only ST-NXS.

And it can be known that: the case of using ST-NXS (surface-treated metal sheet No.6) was superior in corrosion resistance, blackening resistance, tape peeling resistance, lubricity, and paintability to the case of using colloidal silica having an average particle diameter of 8nm or more (surface-treated metal sheets Nos. 8 to 13). The inventor considers that: this is because, when colloidal silica becomes large, the dispersibility and activity of colloidal silica in the surface treatment film are reduced, and the barrier property of the surface treatment film is reduced, so that the amount of colloidal silica eluted in a corrosive environment is reduced.

In addition, it can be seen that: the case of using ST-NXS (surface-treated Metal plate No.6), and the case of using Na⁺The amount of elution is more than 4mg/m²The colloidal silica of (4) is more excellent in blackening resistance, stain resistance and the like than the colloidal silica of (surface-treated metal plate Nos. 7, 9, 11 and 13). For example, it is known that: surface-treated Metal plate No.7 used colloidal silica having an average particle diameter equivalent to that of surface-treated Metal plate No.6, but Na⁺The dissolution amount exceeds 4mg/m²The blackening resistance, stain resistance, tape peeling resistance and coatability are poor.

Second, it is used forNa derived from the surface treatment coating was adjusted by mixing 2 colloidal silica in the following manner⁺Elution amount.

(surface-treated Metal sheet Nos. 14 to 18)

Surface-treated metal sheets No.14 to 18 were produced in the same manner as surface-treated metal sheet No.6 except that colloidal silica was used in the mixing ratio shown in Table 3. The amount of the film deposited was 0.7g/m in the same manner as in surface-treated metal sheet No.6²。Na⁺The elution amounts were the values shown in Table 3.

Table 3 shows that Na derived from the surface treatment coating was adjusted by mixing ST-NXS and ST-XS⁺The amount of elution was determined. In the case of using ST-NXS alone (surface-treated Metal plate No.14), Na⁺The elution amount was 2.0mg/m²And exhibits excellent stain resistance. Even when the mixing ratio of ST-XS is gradually increased to make Na⁺The dissolution amount reaches 3.9mg/m²In the case (surface-treated Metal sheet No.17), good stain resistance was exhibited in the same manner as in the case of the surface-treated Metal sheets No.14 to 16. In contrast, in the case of using ST-XS alone (surface-treated Metal plate No.18), Na was added⁺The dissolution amount reaches 5.0mg/m²Stain is generated and stain resistance is lowered.

Further, FIG. 8 shows Na derived from the surface treatment coating⁺Graph showing relationship between elution amount and stain. In the stain level of fig. 8, "5" corresponds to "excellent" and "4" to "1" correspond to "o", "Δ", "x" and "xxx", respectively, which are the evaluation criteria of the stain resistance. As can also be seen from fig. 8: if Na is present⁺The elution amount was 4.0mg/m²The generation of stain was suppressed as follows, but when Na is used⁺The amount of elution is more than 4.0mg/m²The occurrence of stain was not suppressed.

Further, the tape peeling resistance and the coatability of the surface-treated metal sheet No.18 were compared with those of the other cases, and as a result, the results were obtainedAnd also worsens. The inventor considers that: this is because Na in the surface-treated coating film is present under conditions such as high-temperature and high-humidity environments or immersion in boiling water⁺Elution promotes performance degradation.

In addition, as can be seen from table 3: in Na⁺The elution amount was 4.0mg/m²In the following cases (surface-treated metal sheets Nos. 14 to 17), the plate was superior to the surface-treated metal sheet No.18 in not only the stain resistance but also the blackening resistance, the tape peeling resistance, and the coating properties as described above.

Further, as can be seen from table 3: in Na⁺The elution amount was 3.7mg/m²In the following cases (surface-treated metal sheets Nos. 14 to 16), the blackening resistance and the coating property were excellent even when compared with those of surface-treated metal sheet No. 17. In addition, as can be seen from table 3: in Na⁺The elution amount was 3.2mg/m²In the following cases (surface-treated metal sheets nos. 14 and 15), the tape peeling resistance was superior even to that of surface-treated metal sheet No. 16.

Test example 3 (respective amounts of addition)

(surface-treated Metal sheet No.19 to 25)

A surface treatment composition was prepared by adding resin A, colloidal silica (ST-NXS; ammonia-stable type, manufactured by Nikkiso chemical Co., Ltd.) having an average particle diameter of 4 to 6nm, a glycidyl group-containing crosslinking agent (EPICLON CR5L, manufactured by DIC Co., Ltd.) as a crosslinking agent, and spherical polyethylene wax (Chemipearl W700, manufactured by Mitsui chemical Co., Ltd.) as a lubricant to the composition shown in Table 4.

Surface-treated metal sheets Nos. 19 to 25 were produced in the same manner as in surface-treated metal sheet No.1 except that the surface-treating composition was used. The amount of the film deposited was 0.7g/m in the same manner as in the case of surface-treated metal sheet No.1²。Na⁺The elution amounts were the values shown in Table 4.

The results of the above evaluations of these surface-treated metal sheets Nos. 19 to 25 are shown in Table 4 below.

As can be seen from Table 4: when the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass per 100 parts by mass of the surface treatment composition (surface-treated metal sheets No.19 to No. 23), the corrosion resistance, blackening resistance, and tape peeling resistance are superior to those when the content is less than 10 parts by mass (surface-treated metal sheet No. 24). In addition, it can be seen that: the surface-treated metal sheets Nos. 19 to 23 were superior in blackening resistance, tape peeling resistance, and paintability to the case where the content was 30 parts by mass or more (surface-treated metal sheet No. 25). The inventor considers that: the reason for this is that when the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass, a surface treatment film can be suitably formed, and the surface treatment film can sufficiently exhibit the following effects by dissolving and dissolving the colloidal silica in an corrosive environment: the pH buffering effect and the passivation film forming effect are generated.

Further, as can be seen from table 4: when the content of the colloidal silica is 15 parts by mass or more and 28 parts by mass or less with respect to 100 parts by mass of the surface treatment composition (surface-treated metal sheets nos. 20 to 23), not only blackening resistance and stain resistance are excellent, but also tape peeling resistance and lubricity are excellent as compared with the surface-treated metal sheet No. 19.

In addition, as can be seen from table 4: when the content of the colloidal silica is 20 parts by mass or more and 28 parts by mass or less with respect to 100 parts by mass of the surface treatment composition (surface-treated metal sheets nos. 21 to 23), not only blackening resistance and stain resistance are excellent, but also corrosion resistance is more excellent than that of the surface-treated metal sheets nos. 19 and 20.

(surface-treated Metal sheet Nos. 26 to 31)

A surface treatment composition was prepared by adding resin A, colloidal silica (ST-NXS; ammonia-stable type, manufactured by Nikkiso chemical Co., Ltd.) having an average particle diameter of 4 to 6nm, a glycidyl group-containing crosslinking agent (EPICLON CR5L, manufactured by DIC Co., Ltd.) as a crosslinking agent, and spherical polyethylene wax (Chemipearl W700, manufactured by Mitsui chemical Co., Ltd.) as a lubricant to the composition shown in Table 5.

Surface-treated metal sheets Nos. 26 to 31 were produced in the same manner as in surface-treated metal sheet No.1 except that the surface-treating composition was used. The amount of the film deposited was 0.7g/m in the same manner as in the case of surface-treated metal sheet No.1²。Na⁺The elution amounts were the values shown in Table 5.

The results of the above evaluations of these surface-treated metal sheets Nos. 26 to 31 are shown in Table 5 below.

As can be seen from Table 5: when the content of the crosslinking agent is 5 to 8.5 parts by mass per 100 parts by mass of the surface treatment composition (surface-treated metal sheet Nos. 26 to 29), the corrosion resistance and blackening resistance are excellent as compared with the case where the content is less than 5 parts by mass (surface-treated metal sheet No. 30). In addition, it can be seen that: the surface-treated metal sheets Nos. 26 to 29 were excellent in blackening resistance, stain resistance and the like, and further, in coating property, compared with the case where the amount of the surface-treated metal sheet No.31 was more than 8.5 parts by mass. The inventor considers that: the reason for this is that when the content of the crosslinking agent is 5 to 8.5 parts by mass, the crosslinking reaction can be favorably performed while suppressing the self-crosslinking of the external crosslinking agent.

Furthermore, it can be seen that: when the content of the crosslinking agent is 6.5 to 8.5 parts by mass per 100 parts by mass of the surface treatment composition (surface-treated metal sheets No.27 to 29), the composition is excellent in not only blackening resistance and stain resistance but also corrosion resistance, tape peeling resistance and lubricity even when compared with the surface-treated metal sheet No. 26. The inventor considers that: this is because the hardness of the surface treatment film is also increased by the crosslinking reaction.

(surface-treated Metal sheet No.32 to 38)

A surface treatment composition was prepared by adding resin A, colloidal silica (ST-NXS; ammonia-stable type, manufactured by Nikkiso chemical Co., Ltd.) having an average particle diameter of 4 to 6nm, a glycidyl group-containing crosslinking agent (EPICLON CR5L, manufactured by DIC Co., Ltd.) as a crosslinking agent, and spherical polyethylene wax (Chemipearl W700, manufactured by Mitsui chemical Co., Ltd.) as a lubricant to the composition shown in Table 6.

Surface-treated metal sheets No.32 to 38 were produced in the same manner as in surface-treated metal sheet No.1 except that the surface-treating composition was used. The amount of the film deposited was 0.7g/m in the same manner as in the case of surface-treated metal sheet No.1²。Na⁺The elution amounts were the values shown in Table 6.

The results of the above evaluations of these surface-treated metal sheets No.32 to 38 are shown in Table 6 below.

As can be seen from Table 6: the lubricating agent is more excellent in lubricity when the content of the lubricating agent is 2 to 5 parts by mass per 100 parts by mass of the surface treatment composition (surface treated metal sheet Nos. 32 to 36) than when the content is less than 2 parts by mass (surface treated metal sheet No. 37). In addition, it can be seen that: the surface-treated metal sheets Nos. 32 to 36 were superior in corrosion resistance, blackening resistance, and stain resistance to the case where the content exceeded 5 parts by mass (surface-treated metal sheet No. 38). The inventor considers that: this is because the lubricity of the lubricant can be improved while suppressing the deterioration of corrosion resistance, blackening resistance, and the like due to hydrolysis of the lubricant in a corrosive environment.

Further, as can be seen from table 6: when the content of the lubricant is 2.5 to 5 parts by mass per 100 parts by mass of the surface treatment composition (surface-treated metal sheet nos. 33 to 36), the composition is excellent in not only blackening resistance and stain resistance but also lubricity as compared with the surface-treated metal sheet No. 32. Thus, it can be seen that: the amount of the lubricant added is more preferably 2.5 parts by mass or more per 100 parts by mass of the surface treatment composition.

In addition, as can be seen from table 6: when the content of the lubricant is 2 to 4 parts by mass per 100 parts by mass of the surface treatment composition (surface-treated metal sheet nos. 32 to 35), the composition is excellent in not only blackening resistance and stain resistance, but also corrosion resistance, tape peeling resistance, and coating properties even when compared with the surface-treated metal sheet No. 36. Thus, it can be seen that: the amount of the lubricant added is more preferably 4 parts by mass or less with respect to 100 parts by mass of the surface treatment composition.

Test example 4 (coating film deposition amount)

(surface-treated Metal sheets Nos. 39 to 46, 50 and 51)

A surface treatment composition was prepared by adding 61 parts by mass of resin A, 28 parts by mass of colloidal silica (ST-NXS: ammonia-stable type, manufactured by Nissan chemical Co., Ltd.) having an average particle diameter of 4 to 6nm, 7.5 parts by mass of a glycidyl group-containing crosslinking agent (EPICLON CR5L, manufactured by DIC) as a crosslinking agent, and 3.5 parts by mass of spherical polyethylene wax (Chemipearl W700, manufactured by Mitsui chemical Co., Ltd.) as a lubricant to the above solid content ratio.

Surface-treated metal sheets nos. 39 to 46, 50 and 51 were produced in the same manner as surface-treated metal sheet No.1 except that the above-mentioned surface-treatment composition was used and the amount of film adhesion was adjusted to the values shown in table 7. Na (Na)⁺The elution amounts were the values shown in Table 7.

(surface-treated Metal sheet No.47 to 49)

The surface-treated metal sheets No.47 to 49 were produced in the same manner as the surface-treated metal sheet No.1 except that a mixture of ST-NXS manufactured by Nissan chemical industries was used instead of ST-NXS manufactured by Nissan chemical industries as colloidal silica having an average particle diameter of 4 to 6nm, and the coating film deposition amount was adjusted to the value shown in Table 7. The Na + elution amounts were values shown in Table 7. In addition, in the surface-treated metal sheet No.47, the mixing ratio of ST-NXS to ST-XS (ST-NXS: ST-XS) was 2: 1. in addition, in the surface-treated metal sheet No.48, the mixing ratio of ST-NXS to ST-XS (ST-NXS: ST-XS) was 1: 1. in the surface-treated metal sheet No.49, the mixing ratio of ST-NXS to ST-XS (ST-NXS: ST-XS) was 1: 2.

the results of the above evaluations of these surface-treated metal sheets Nos. 39 to 51 are shown in Table 7 below.

As can be seen from Table 7: the amount of the surface-treatment coating film adhered is 0.4 to 1.2g/m²In the case (surface-treated metal sheets No.39 to 49), the amount of the adhesion is less than 0.4g/m²In the case (surface-treated metal sheet No.50), the corrosion resistance, blackening resistance, tape peeling resistance, and lubricity were superior. In addition, it can be seen that: surface-treated Metal sheets No.39 to 49 having an adhesion exceeding 1.2g/m²The coating property was more excellent than that of the case (surface-treated metal sheet No. 51).

Further, as can be seen from table 7: the amount of the surface treatment film adhered was 0.45g/m²In the case of (surface-treated Metal plate No.40), the amount of the surface-treated coating film adhered was 0.4g/m²The surface-treated metal sheet No.39 of (1) was superior in blackening resistance, stain resistance, tape peeling resistance and lubricity.

In addition, it can be seen that: the amount of the surface-treatment coating film adhered was 0.5g/m²In the case of (surface-treated Metal plate No.41), the amount of adhesion to the surface-treated coating was 0.45g/m²The surface-treated metal sheet No.40 of (4) was more excellent in corrosion resistance than the metal sheet.

From the above results, it can be seen that: the amount of the surface treatment film adhered is preferably 0.45g/m²Above, more preferably 0.5g/m²The above.

In addition, as can be seen from table 7: the amount of the surface-treatment coating film adhered was 0.8g/m²In the case of (surface-treated Metal plate No.44), the amount of adhesion to the surface-treated coating film was 1g/m²The surface-treated metal sheet No.45 of (4) was superior in blackening resistance.

In addition, it can be seen that: the amount of the surface-treatment coating film adhered was 0.7g/m²In the case of (surface-treated Metal plate No.43), the amount of adhesion to the surface-treated coating was 0.8g/m²Surface-treated gold ofThe metal plate No.44 was superior in paintability.

From the above results, it can be seen that: the amount of the surface treatment film adhered is preferably 0.8g/m²Hereinafter, more preferably 0.7g/m²The following.

The present application is based on the Japanese patent application No. 2016-.

In order to describe the present invention, the present invention has been described in detail with reference to the drawings and embodiments, but it should be understood that the modifications and/or improvements of the above embodiments are easily made by those skilled in the art. Therefore, the modified embodiments or modified embodiments that can be implemented by those skilled in the art are intended to be included in the scope of the claims as long as they do not depart from the scope of the claims set forth in the claims.

Industrial applicability

According to the present invention, a surface-treated metal sheet having excellent blackening resistance and sufficiently suppressed occurrence of stain and a method for producing a surface-treated metal sheet can be provided.

Claims

1. A surface-treated metal sheet characterized by comprising:

a zinc-based plated steel sheet; and

a surface treatment film laminated on at least one surface of the zinc-based plated steel sheet, wherein,

the surface treatment coating film is composed of a surface treatment composition containing: a polyolefin-based resin containing no ammonia; and colloidal silica having an average particle diameter of 4 to 6nm,

the content of the colloidal silica is 10 parts by mass or more and less than 30 parts by mass with respect to 100 parts by mass of the surface treatment composition,

the colloidal silica contains colloidal silica containing ammonia as a dispersant,

the mixing ratio of the colloidal silica containing ammonia as a dispersant is 33% by mass or more relative to the colloidal silica,

the amount of the surface-treatment coating film adhered is 0.4 to 1.2g/m²，

When the surface treatment coating is immersed in deionized water at 70-80 ℃ for 10 minutes, the amount of sodium ions dissolved out of the surface treatment coating is 4mg/m²The following.

2. The surface-treated metal sheet according to claim 1,

the surface treatment composition further contains a crosslinking agent and a lubricant.

3. The surface-treated metal sheet according to claim 2,

the content of the crosslinking agent is 5 to 8.5 parts by mass relative to 100 parts by mass of the surface treatment composition.

4. The surface-treated metal sheet according to claim 2,

the content of the lubricant is 2-5 parts by mass relative to 100 parts by mass of the surface treatment composition.

5. The surface-treated metal sheet according to claim 1,

the colloidal silica is a colloidal silica comprising ammonia as a dispersant.

6. The surface-treated metal sheet according to claim 1,

the polyolefin resin contains a copolymer of an alpha, beta-unsaturated carboxylic acid and an olefin.

7. A method for producing a surface-treated metal sheet according to any one of claims 1 to 6, comprising the steps of:

a step for preparing the surface treatment composition;

a step of applying the surface treatment composition to at least one surface of the zinc-based plated steel sheet; and

and a step of forming the surface treatment film on the at least one surface of the galvanized steel sheet by drying the surface treatment composition.