JP6626805B2 - Surface-treated metal plate and method for producing surface-treated metal plate - Google Patents

Description

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

  As a steel sheet used for home appliances, building materials, automobiles, and the like, zinc-based plated steel sheets are widely used from the viewpoint of corrosion resistance and the like. Further, for the purpose of further improving corrosion resistance and the like, attention has been paid to a surface-treated metal plate having a surface-treated film formed on a galvanized steel sheet. This surface-treated metal sheet is provided with the above-mentioned surface-treated film on a galvanized layer provided on a galvanized steel sheet.

  Such a surface-treated metal plate, for example, when used in electrical equipment, etc., should have excellent conductivity in order to enhance antistatic properties and electromagnetic wave shielding properties with the enhancement of the performance of electrical equipment, etc. Is also required.

  Further, it is known that the surface-treated metal plate generates abrasion called abrasion due to sliding with a corrugated cardboard or the like during truck transportation or the like. For this reason, it is also required that the surface-treated metal plate is less likely to cause abrasion called abrasion.

  Further, in the surface-treated metal plate, intense sliding friction occurs between the surface-treated metal plate and the mold during press forming such as deep drawing. It is known that the sliding of the surface-treated metal plate causes a blackening phenomenon in which the surface-treated film is damaged by the sliding or the zinc of the galvanized layer is mixed into the surface-treated film, resulting in discoloration to black. For this reason, the surface-treated metal plate is also required to have excellent press formability so that such a problem does not occur.

  The present inventor has proposed, for example, a surface-treated metal plate described in Patent Literature 1 as a surface-treated metal plate for solving the above-described problem. Patent Document 1 includes a resin film obtained from a resin aqueous solution containing a carboxyl group-containing polyurethane resin aqueous solution, an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion, silica particles, and a silane coupling agent in a specific ratio. A surface treated metal plate is described. The surface-treated metal plate described in Patent Document 1 is excellent in corrosion resistance, abrasion resistance, and conductivity, and is also excellent in paintability, alkali degreasing resistance, and the like.

On the other hand, it is well known that a zinc-plated steel sheet, which is a base material of the surface-treated metal sheet, has a blackening phenomenon on its surface. The black discoloration phenomenon is a phenomenon in which at least a part of the surface is discolored blackish, such as black or brown. Further, this blackening phenomenon is specifically a corrosion phenomenon observed at an early stage in a corrosive environment before white rust occurs, and is said to occur under a relatively mild corrosive environment. Further, the surface of the galvanized steel sheet looks dark due to the blackening phenomenon because of the stoichiometric composition of Zn _x O _1-x during the oxidation reaction (corrosion reaction) of zinc (Zn) present on the surface. It is believed that this is due to the formation of an irregular amorphous oxide.

  The blackening phenomenon is also called a phenomenon that occurs when the oxidation reaction of Zn is incomplete, and it is considered that the oxidation reaction should be promoted to some extent in order to prevent blackening. Therefore, it is conceivable to add elements such as Ni, Co, and In to the galvanized layer as elements that appropriately promote the oxidation reaction. Examples of such a method include the techniques described in Patent Literature 2 and Patent Literature 3.

  Patent Literature 2 discloses that a Ni ion is contained in an amount within a range of 100 to 300 ppm, a content of Pb ion included as an impurity is 0.5 ppm or less, and a ratio of Ni ion to Pb ion in a plating bath. It describes that a steel sheet is electrogalvanized in an electrogalvanizing bath in which (Ni ion / Pb ion) exceeds 500, and then subjected to a predetermined chromate treatment.

  In addition, Patent Document 3 discloses that Ni ions in a zinc plating bath are mixed in a range of 5 to 500 times the amount of Pb ions contained as an impurity, not more than 1/25 of the amount of Zn ions and not more than 10 g / l. It is described that a steel sheet is electrogalvanized in an electrogalvanizing bath containing the same in an amount and then subjected to a predetermined chromate treatment.

JP 2006-43913 A JP-A-2-8374 JP-A-60-77988

  The surface-treated metal plate described in Patent Literature 1 has a resin film provided as a surface-treated film, in which 55 to 95 parts by mass of silica particles with respect to 5 to 45 parts by mass of a resin component, and silica particles as an inorganic component. Many are included. This surface-treated metal plate is a surface-treated metal plate provided with a so-called inorganic-rich film having a relatively large amount of inorganic components. Further, in the surface-treated metal plate described in Patent Document 1, since the specific gravity of the silica particles is as large as about 2.2, a resin film having a sufficient film adhesion amount is formed even if the film thickness is relatively small. For this reason, the surface-treated metal plate described in Patent Literature 1 has excellent conductivity. Furthermore, the surface-treated metal plate described in Patent Literature 1 is hardened because it contains a large amount of silica in the resin film, and is excellent in abrasion resistance and blackening resistance.

  On the other hand, in recent years, it has been more demanded that products have excellent appearance. In order to satisfy this demand, a surface-treated metal plate which further suppresses the occurrence of blackening and stain stains and has an excellent appearance has been required. Therefore, it has been required that the surface-treated metal plate provided with the inorganic-rich coating as described above further suppresses the occurrence of the blackening phenomenon and spot stain.

  According to Patent Literature 2 and Patent Literature 3, it is disclosed that the occurrence of blackening of a zinc-based plated steel sheet can be suppressed. However, as described in Patent Literature 2 and Patent Literature 3, a galvanized steel sheet in which elements such as Ni, Co, and In are added to a galvanized layer includes Ni, Co, and Ni added to the galvanized layer. It is necessary to consider a balance between an element such as In and an element that deteriorates corrosion resistance, such as Pb, Cu, and Ag, which exist as impurities in the galvanized layer. Further, such a zinc-based plated steel sheet, even if its balance is adjusted, changes in the valence of the metal element in a corrosive environment and elution of the metal cause uneven color change or a decrease in whiteness. In some cases, appearance defects occurred. In addition, when the zinc-based plated steel sheet adds elements such as Ni, Co, and In to the galvanized layer and promotes the oxidation reaction too much, the corrosion resistance is remarkably reduced, and white rust is generated or a stain-like ( In some cases, black-brown or gray-brown irregularities (hereinafter referred to as stains) tend to occur.

  For this reason, it is required to suppress the occurrence of blackening and spot stains by a method other than the method of adding elements such as Ni, Co, and In to the galvanized layer.

  The present invention has been made in view of such circumstances, and has an inorganic-rich coating, excellent corrosion resistance, ablation resistance, and while maintaining conductivity, excellent in blackening resistance, and stain stains. An object of the present invention is to provide a surface-treated metal plate whose generation is sufficiently suppressed.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below.

The surface-treated metal sheet according to one embodiment of the present invention includes a galvanized steel sheet, and a surface-treated film laminated on at least one surface of the galvanized steel sheet, wherein the surface-treated film has an average particle diameter. Contains 60 to 80 parts by mass of colloidal silica having a particle size of 4 to 6 nm, and 20 to 40 parts by mass of a mixed resin of a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer resin, wherein the colloidal silica and the mixed resin are mixed. A total of 100 parts by mass of the silane coupling agent, a surface treatment composition further containing 10 to 20 parts by mass, the carboxyl group-containing polyurethane resin and the ethylene-unsaturated carboxylic acid copolymer resin, Is a mass ratio of 1: 1 to 9: 1, the adhesion amount of the surface treatment film is 0.4 to 0.8 g / m ² , and 70 to 8 The amount of sodium ions eluted from the surface treatment film when immersed in deionized water at 0 ° C. for 10 minutes is 4 mg / m ² or less.

  According to such a configuration, the inorganic-rich coating has excellent corrosion resistance, abrasion resistance, and conductivity, and has excellent blackening resistance, and a surface treatment that sufficiently suppresses the occurrence of spot stains. A metal plate, that is, a surface-treated metal plate excellent in blackening resistance and stain resistance can be provided.

  Further, in the surface-treated metal plate, it is preferable that the colloidal silica is a colloidal silica containing ammonia as a dispersant.

  According to such a configuration, a surface-treated metal plate excellent in blackening resistance and stain resistance can be obtained.

  Further, a method for producing a surface-treated metal sheet according to another aspect of the present invention is a method for producing a surface-treated metal sheet for producing the surface-treated metal sheet, wherein the step of preparing the surface-treated composition, A step of applying the surface treatment composition on at least one surface of the galvanized steel sheet, and drying the surface treatment composition, so that the surface treatment is performed on at least one surface of the galvanized steel sheet. Forming a film.

  According to such a configuration, the inorganic-rich coating has excellent corrosion resistance, abrasion resistance, and conductivity, and has excellent blackening resistance, and a surface treatment that sufficiently suppresses the occurrence of spot stains. A metal plate, that is, a surface-treated metal plate excellent in blackening resistance and stain resistance can be produced.

  According to the present invention, a surface-treated metal plate that has an inorganic-rich film, has excellent corrosion resistance, ablation resistance, and conductivity, has excellent blackening resistance, and has sufficiently suppressed the occurrence of spot stains. And a method for producing a surface-treated metal plate.

FIG. 1 is a schematic diagram showing a surface resistance measuring device for evaluating conductivity. FIG. 2 is a schematic view showing a processed shape in press forming when evaluating press formability. FIG. 3 is a schematic view showing the shape of a mold in press forming when evaluating press formability. FIG. 4 is a schematic diagram illustrating an evaluation device (steel plate abrasion device) for evaluating the steel plate abrasion resistance.

  When the surface treatment film is provided on the galvanized steel sheet, the barrier properties such as oxygen permeability and water vapor permeability may be improved halfway. In such a case, the oxidation reaction occurs in a state where the supply of oxygen to the surface of the galvanized steel sheet is insufficient, and as described above, an amorphous oxide is generated on the galvanized steel sheet, thereby causing blackening. The phenomenon will occur.

  Then, the present inventor has found that it is effective to reduce the particle diameter of colloidal silica contained in the surface treatment film in order to enhance the barrier properties of the surface treatment film.

  In addition, a surface-treated metal plate having a surface-treated film provided on a galvanized steel sheet may not be able to sufficiently suppress not only blackening but also generation of stain. In the study leading to the present invention, it was noted that when colloidal silica was contained in the surface treatment film, occurrence of stain spots could not be sufficiently suppressed. The surface-treated metal plate provided with such a surface-treated film was left in a constant-temperature and constant-humidity tester set at an environment of, for example, a temperature of 65 ° C. and a humidity of 95% for 168 hours to generate stain. The surface-treated metal plate where the stain was generated was scribbled on the surface-treated film in the portion where the stain was generated, and the surface was treated with an electron beam microanalyzer (EPMA, JXA-8100 manufactured by JEOL Ltd.). Analysis (mapping / field of view 8 × 8 mm) was performed. As a result of this analysis, it was found that the Na element was concentrated in the portion where the stain was generated. From this, the present inventor speculated that the cause of stain spots was due to the presence of the Na element. The present inventor further studied the cause of the concentration of the Na element, and focused on colloidal silica contained in the surface treatment film, and presumed that the mechanism for generating stain stains was as follows. did.

  First, in a high-temperature and high-humidity environment or the like, a local battery is formed due to an extremely early corrosion on the surface of a zinc plating layer provided with a surface treatment film. When general colloidal silica (colloidal silica containing sodium as a dispersant) is contained in the surface treatment film, the surface treatment film contains Na element derived from colloidal silica. Then, the Na element derived from the colloidal silica contained in the surface treatment film is concentrated at the cathode portion of the battery, gently promotes the initial corrosion, and forms an amorphous oxide (amorphous zinc oxide) on the galvanized layer. Is generated. That is, in a surface-treated metal sheet in which a surface-treated film containing colloidal silica is provided on a galvanized steel sheet, Na ions contained in the colloidal silica migrate to the surface of the galvanized layer of the galvanized steel sheet, and partially become unusable. A shaped oxide is formed. Then, when the amorphous oxide becomes a starting point and corrosion proceeds, the amorphous oxide diffuses irregularly at the interface between the zinc-based plated steel sheet and the surface treatment film. The irregularly diffused amorphous oxide becomes stained and looks like a stain. Based on such a mechanism, it was presumed that a stain on a surface-treated metal plate provided with a surface-treated film containing colloidal silica as described above occurred. The colloidal silica contained in the surface treatment film has conventionally been one containing sodium as a dispersant, that is, colloidal silica stabilized with Na ions.

  Then, the present inventor thought that when the amount of Na ions eluted from the surface treatment film was reduced, the amorphous oxide formed partially was reduced, and as a result, spot stains could be effectively suppressed. .

  The present inventors have arrived at the present invention as described below based on the above-described study.

A surface-treated metal sheet according to one embodiment of the present invention includes a galvanized steel sheet and a surface-treated film laminated on at least one surface of the galvanized steel sheet. This surface treatment film contains 60 to 80 parts by mass of colloidal silica having an average particle diameter of 4 to 6 nm, and 20 to 40 parts by mass of a mixed resin of a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer resin. The surface treatment composition further includes a silane coupling agent in an amount of 10 to 20 parts by mass with respect to a total of 100 parts by mass of the colloidal silica and the mixed resin. The content ratio (PU: EC) between the carboxyl group-containing polyurethane resin (PU) and the ethylene-unsaturated carboxylic acid copolymer resin (EC) contained in the surface treatment composition was 1: 1 by mass ratio. ９9: 1. Further, the adhesion amount of the surface treatment film is 0.4 to 0.8 g / m ² . The amount of sodium ions eluted from the surface treatment film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m ² or less.

  Such a surface-treated metal plate is excellent in blackening resistance and can sufficiently suppress occurrence of stains and stains. Also, it has excellent adhesion to the galvanized layer. This is thought to be due to the following.

First, since such a surface treatment film has a small average particle diameter of 4 to 6 nm of the colloidal silica to be contained, the dispersibility and activity of the colloidal silica are increased, the barrier property of the surface treatment film is increased, and the corrosion resistance is increased. It is thought that it is possible. In addition, by forming a surface treatment film so that the amount of the surface treatment film adhered becomes 0.4 to 0.8 g / m ² , it is possible to suitably improve the effect including colloidal silica, such as enhancing corrosion resistance. It can be demonstrated. Further, if the surface-treated film contains 60 to 80 parts by mass of the colloidal silica and a relatively large amount of the colloidal silica, the density of the surface-treated film becomes high. Even if it is 4-0.8 g / m ² , it will be relatively thin. Therefore, it is considered that excellent conductivity can be maintained. The content ratio (PU: EC) between the carboxyl group-containing polyurethane resin (PU) and the ethylene-unsaturated carboxylic acid copolymer resin (EC) is from 1: 1 to 9: 1 by mass. When such a mixed resin is contained in an amount of 20 to 40 parts by mass, it is considered that corrosion resistance, blackening resistance, workability such as press moldability, and abrasion resistance are excellent. In such a surface-treated metal plate, a surface-treated film is obtained in which the amount of sodium ions eluted from the surface-treated film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m ² or less. When the amount of sodium ions eluted from the surface treatment film is small as described above, it is considered that the occurrence of stains can be suppressed as described above. From this, the surface-treated metal plate according to the present embodiment is not only excellent in corrosion resistance, abrasion resistance, and conductivity, but also excellent in blackening resistance, and can sufficiently suppress the generation of stain spots. it can.

  The zinc-based plated steel sheet is not particularly limited, and may be a zinc-only plated steel sheet or a zinc-based alloy-plated steel sheet such as zinc-Ni, zinc-Fe, and zinc-Al. The plating method is not particularly limited, and may be a galvanized steel sheet obtained by any of a hot-dip plating method, an electroplating method, and a vapor deposition plating method. As the galvanized steel sheet, specifically, hot-dip galvanized steel sheet (GI), hot-dip galvannealed steel sheet (GA), hot-dip galvanized Zn-5% Al coated steel sheet (GF), electrogalvanized steel sheet Steel plate (EG), electric Zn-Ni alloy plated steel plate and the like. Among these, an electrogalvanized steel sheet (EG) is preferable.

  As described above, the surface-treated film has a mixed resin of 60 to 80 parts by mass of colloidal silica having an average particle size of 4 to 6 nm, a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer resin, 20 to 40 parts. And a surface treatment composition further containing 10 to 20 parts by mass of a silane coupling agent with respect to a total of 100 parts by mass of the colloidal silica and the mixed resin.

The colloidal silica has an average particle size of 4 to 6 nm. Further, the colloidal silica is required to have a small amount of sodium ions eluted from the surface treatment film based on the above consideration. Specifically, the colloidal silica has an amount (elution amount) of sodium ions eluted from the surface treatment film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m ² or less. It is a good colloidal silica. The colloidal silica is not particularly limited as long as it is such colloidal silica.

Specifically, the colloidal silica preferably contains colloidal silica containing ammonia as a dispersant. Colloidal silica containing ammonia as such a dispersant, that is, colloidal silica stabilized with NH ₄ ⁺ ions (ammonia stabilized type) is commercially available. By using the colloidal silica containing ammonia as such a dispersant, as described above, compared to the case where only colloidal silica containing sodium (sodium stabilized type) is used as a dispersant that is a general colloidal silica, The amount of sodium in the surface treatment film can be reduced. Thus, a surface-treated film with a reduced amount of elution can be obtained.

  First, as described above, the colloidal silica has an average particle diameter of 4 to 6 nm. If the colloidal silica is too large, corrosion resistance tends to decrease, and further, abrasion resistance and workability such as press moldability tend to decrease. It is considered that this is because the dispersibility and activity of the colloidal silica in the surface treatment film are reduced, the barrier property of the surface treatment film is reduced, and the amount of colloidal silica eluted in a corrosive environment is reduced. The smaller the colloidal silica, the higher the corrosion resistance. However, if the colloidal silica is too small, the surface activity of the colloidal silica becomes too high, and the stability of the liquid in which the colloidal silica is dispersed tends to decrease. For this reason, the lower limit of the average particle diameter of the colloidal silica is 4 nm. Therefore, by using the colloidal silica having the particle diameter as described above, while maintaining excellent blackening resistance, stain resistance, and conductivity, corrosion resistance, abrasion resistance, and processability such as press moldability. An excellent surface-treated metal plate can be obtained. As the colloidal silica having an average particle diameter of 4 to 6 nm, specifically, Snowtech NXS (ST-NXS, ammonia stabilized type) and Snowtech XS (ST-XS, sodium) manufactured by Nissan Chemical Industries, Ltd. Stabilized type) and the like. When sodium-stabilized ST-XS is used, it is preferable to use it together with ammonia-stabilized ST-NXS. Here, the average particle diameter of the colloidal silica is measured by, for example, the Sears method when the average particle diameter is about 1 to 10 nm, and by the BET method when the average particle diameter is about 10 to 100 nm. And the like. When the notarized value is described in the pamphlet of the manufacturer, the notary value is used as the average particle diameter of the colloidal silica.

Further, as described above, the amount (elution amount) of sodium ions eluted from the surface treatment film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is preferably smaller as described above. It was found that when the amount was 4 mg / m ² or less, stain stains could be suitably suppressed. The elution amount is more preferably at most 3.8 mg / m ² , even more preferably at most 3.5 mg / m ² . Within such a range, blackening resistance and stain resistance can be suitably suppressed. The smaller the elution amount is, the more preferable it is. However, due to the characteristics of colloidal silica, the limit is about 1 mg / m ² , and the lower limit of the elution amount is preferably 1 mg / m ² or more. In addition, the elution amount here includes, for example, a value measured as follows. The surface-treated metal plate is immersed in deionized water at 70 to 80 ° C. for 10 minutes. The amount of sodium ions contained in the liquid in which the surface-treated metal plate is immersed is measured using ion chromatography. The amount of elution is calculated from the measured amount of sodium ions and the area of the surface-treated metal plate. As the ion chromatography, for example, ICS-5000 + manufactured by Thermo Fisher Scientific Co., Ltd. can be used.

  The mixed resin is a mixed resin of a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer resin. In the present embodiment, the carboxyl group-containing polyurethane resin and the ethylene-unsaturated carboxylic acid copolymer resin are each preferably an emulsion in order to be mixed with colloidal silica to form an aqueous composition.

  The carboxyl group-containing polyurethane resin is not particularly limited as long as it is a polyurethane resin having a carboxyl group in the molecule. Examples of the carboxyl group-containing polyurethane resin include those obtained by a chain extension reaction of a urethane prepolymer with a chain extender. Examples of the urethane prepolymer include those obtained by reacting a polyisocyanate component and a polyol component described below.

  Examples of the polyisocyanate component constituting the urethane prepolymer include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (hydrogenated MDI), tetramethylene diisocyanate, hexamethylene diisocyanate, dodecane methylene diisocyanate, and isophorone. Examples thereof include diisocyanate, xylene diisocyanate, and phenylene diisocyanate. As the polyisocyanate component, of these, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and dicyclohexylmethane diisocyanate (hydrogenated MDI) are preferable. Further, as the polyisocyanate component, the compounds exemplified above may be used alone or in combination of two or more.

  Examples of the polyol component constituting the urethane prepolymer include a polyol component including all three types of polyols such as 1,4-cyclohexanedimethanol, a polyether polyol, and a polyol having a carboxyl group.

  The polyether polyol is not particularly limited as long as it has at least two or more hydroxyl groups in the molecular chain and the main skeleton is constituted by an alkylene oxide unit. Examples of the polyether polyol include polyoxyethylene glycol (polyethylene glycol), polyoxypropylene glycol (polypropylene glycol), and polyoxytetramethylene glycol (polytetramethylene glycol, polytetramethylene ether glycol). As the polyether polyol, among these, polyoxypropylene glycol and polytetramethylene ether glycol are preferable. Further, as the polyether polyol, the compounds exemplified above may be used alone, or two or more kinds may be used in combination.

  The polyol having a carboxyl group is not particularly limited as long as it has at least one or more carboxyl groups and at least two or more hydroxyl groups. Examples of the polyol having a carboxyl group include dimethylolpropionic acid, dimethylolbutanoic acid, dihydroxypropionic acid, and dihydroxysuccinic acid. As the polyol having a carboxyl group, dimethylolpropionic acid is preferable among them. In addition, as the polyol having a carboxyl group, the compounds exemplified above may be used alone or in combination of two or more.

  In addition, the polyol component may include a polyol other than the three kinds of polyols of 1,4-cyclohexanedimethanol, polyether polyol, and a polyol having a carboxyl group.

  The chain extender that reacts with the above-mentioned urethane prepolymer is not particularly limited as long as it is used as a chain extender. Examples of the chain extender include low molecular weight polyols, polyamines, and alkanolamines. Examples of the low-molecular-weight polyol include the same polyol components as those described above. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; aromatic polyamines such as tolylenediamine, xylylenediamine, and diaminodiphenylmethane; alicyclic compounds such as diaminocyclohexylmethane, piperazine, and isophoronediamine. Polyamines; hydrazines such as hydrazine, succinic dihydrazide, adipic dihydrazide, and phthalic dihydrazide. Examples of the alkanolamine include diethanolamine and monoethanolamine. Among these, ethylene diamine is preferred as the chain extender. Further, as the chain extender, the compounds exemplified above may be used alone, or two or more kinds may be used in combination.

  A known method can be adopted as a method for producing the aqueous liquid of the carboxyl group-containing polyurethane resin. Examples of this production method include a method of neutralizing a carboxyl group of a carboxyl group-containing urethane prepolymer with a base, emulsifying and dispersing the carboxyl group in an aqueous medium to cause a chain extension reaction, and a method of preparing a carboxyl group-containing polyurethane resin in the presence of an emulsifier. And a method of emulsifying and dispersing with a high shear force to cause a chain extension reaction.

  The ethylene-unsaturated carboxylic acid copolymer resin is a copolymer of ethylene and an ethylenically unsaturated carboxylic acid. And in this ethylene-unsaturated carboxylic acid copolymer resin, it is preferable that the structural unit derived from ethylene is 50 mass% or more in the said ethylene-unsaturated carboxylic acid copolymer resin. That is, in the ethylene-unsaturated carboxylic acid copolymer resin, the constitutional unit derived from the ethylenically unsaturated carboxylic acid is preferably 50% by mass or less in the ethylene-unsaturated carboxylic acid copolymer resin.

  The ethylene-unsaturated carboxylic acid copolymer resin may be any copolymer of ethylene and ethylenically unsaturated carboxylic acid, and may be obtained by copolymerizing ethylene and ethylenically unsaturated carboxylic acid by a known method. Can be manufactured. The ethylene-unsaturated carboxylic acid copolymer resin is commercially available.

  The ethylenically unsaturated carboxylic acid is not particularly limited. Examples of the ethylenically unsaturated carboxylic acid include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid, and dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. As the ethylenically unsaturated carboxylic acid, one type may be used alone, or two or more types may be used in combination. As the ethylenically unsaturated carboxylic acid, among the compounds exemplified above, acrylic acid and methacrylic acid are preferable, and acrylic acid is more preferable.

  Further, the ethylene-unsaturated carboxylic acid copolymer resin may use an olefin-based monomer such as propylene or 1-butene instead of a part of ethylene, and furthermore, as long as the object of the present invention is not hindered. For example, another known vinyl monomer may be partially copolymerized (about 10% by mass or less).

  Since the ethylene-unsaturated carboxylic acid copolymer resin has a carboxyl group in the molecule, it can be emulsified (aqueous dispersion) by neutralizing with an organic base or a metal ion.

  The method for preparing the aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer is not particularly limited. For example, the ethylene-unsaturated carboxylic acid copolymer is charged together with an aqueous medium into a homogenizer or the like, and if necessary, 70 wt. To 250 ° C., and an amine having a boiling point of 100 ° C. or less and a monovalent metal compound are appropriately added in the form of an aqueous solution or the like (the amine having a boiling point of 100 ° C. or less is added first, or the amine having a boiling point of 100 ° C. or less is added. The amine and the monovalent metal compound are added almost simultaneously), and a method of stirring with a high shear force.

  In the mixed resin, the content ratio (PU: EC) between the carboxyl group-containing polyurethane resin (PU) and the ethylene-unsaturated carboxylic acid copolymer resin (EC) is from 1: 1 to 9: 1 by mass ratio. And preferably from 2: 1 to 9: 1, more preferably from 3.3: 1 to 6.5: 1. If the proportion of EC is too low, corrosion resistance and blackening resistance tend to decrease. On the other hand, when the proportion of PU is too low, workability such as press moldability tends to decrease. Therefore, when the content ratio is within the above range, a surface-treated metal sheet having excellent corrosion resistance, blackening resistance, and workability can be obtained. Here, the content ratio is a solid content ratio.

  The lower limit of the content of the colloidal silica in the total of 100 parts by mass of the colloidal silica and the mixed resin is 60 parts by mass or more, and preferably 65 parts by mass or more. The upper limit of the content of the colloidal silica is 80 parts by mass or less, and preferably 75 parts by mass or less. Further, the lower limit of the content of the mixed resin in the total of 100 parts by mass of the colloidal silica and the mixed resin is 20 parts by mass or more, and preferably 25 parts by mass or more. The upper limit of the content of the mixed resin is 40 parts by mass or less, and preferably 35 parts by mass or less. If the amount of colloidal silica is too small or too large, the corrosion resistance tends to decrease. From this, it is considered that the content of the colloidal silica is 70 parts by mass, and the content of the mixed resin has a peak near 30 parts by mass where the corrosion resistance is good. Further, when the amount of the colloidal silica is too small, the density of the surface treatment film decreases, and the film thickness of the surface treatment film increases even if the amount of the surface treatment film adhered is the same. In such a case, the conductivity may be reduced. When the amount of the colloidal silica is too large, the stain resistance tends to decrease. This is considered to be due to the fact that the amount of the mixed resin becomes too small, so that a resin component necessary for film formation becomes insufficient, and cracks and the like are easily generated in the surface-treated film. Here, the content is a solid content ratio.

  The silane coupling agent is a component that improves the adhesion between the surface of the metal plate and the surface treatment film. The silane coupling agent is not particularly limited. Examples of the silane coupling agent include a silane coupling agent having a glycidoxy group at a terminal and the like, for example, a silane coupling agent represented by the following formula (1).

  In the formula (1), R1 represents a glycidoxy group, R2 and R3 represent a lower alkoxy group, R4 represents a lower alkoxy group or a lower alkyl group, and X represents a lower alkylene group. Here, lower means that the carbon number is 1 to 5, more preferably 1 to 3.

  The lower limit of the content of the silane coupling agent is at least 10 parts by mass, preferably at least 12.5 parts by mass, based on 100 parts by mass of the total of the colloidal silica and the mixed resin. The upper limit of the content of the silane coupling agent is 20 parts by mass or less based on 100 parts by mass of the total of the colloidal silica and the mixed resin. If the amount of the silane coupling agent is too small, processability such as corrosion resistance, blackening resistance, stain stain resistance, press moldability, and abrasion resistance tend to decrease. This is considered to be because the effect of the silane coupling agent, which improves the adhesion between the surface of the metal plate and the surface treatment film, cannot be sufficiently exhibited. If the amount of the silane coupling agent is too large, processability such as corrosion resistance and press formability, and abrasion resistance tend to decrease. It is considered that this is because the liquid stability of the surface treatment composition is reduced and the unreacted silane coupling agent is increased. Here, the content is a solid content ratio.

  Further, the surface treatment film may contain other components in addition to the colloidal silica, the mixed resin, and the silane coupling agent. Other components include, for example, a crosslinking agent that crosslinks the surface-treated film, a lubricant, and the like.

The lower limit of the adhesion amount of the surface treatment film is 0.4 g / m ² or more, and preferably 0.5 g / m ² or more. In addition, the upper limit of the amount of the surface treatment film is 0.8 g / m ² or less, and more preferably 0.7 g / m ² or less. If the adhesion amount of the surface treatment film is too small, the barrier property by the surface treatment film is reduced, the corrosion resistance and the blackening resistance are reduced, and the spread of the stain is promoted, and the stain resistance tends to deteriorate. . If the amount of the surface treatment film is too small, processability such as press moldability and abrasion resistance tend to be reduced. These tendencies indicate that if the amount of the surface treatment film deposited is too small, the thickness of the formed surface treatment film becomes too thin, and it becomes difficult to coat the film with a roll coater or the like, and a suitable surface treatment film is formed. It is thought that it depends on the difficulty. If the amount of the surface treatment film is too large, processability such as conductivity and press moldability and abrasion resistance tend to decrease. This is because, if the amount of the surface treatment film attached is too large, the thickness of the formed surface treatment film becomes too large, so that the conductivity is reduced by the thick film, and further, film residue is generated during press molding. It is considered that the blackening phenomenon easily occurs. In addition, the adhesion amount of the surface treatment film can be measured, for example, as follows. The Si element of the colloidal silica (SiO ₂ ) in the surface treatment film can be quantitatively measured by a fluorescent X-ray analyzer, and can be calculated from the measured amount of the Si element. In this case, the calculation is performed with the specific gravity of SiO ₂ being 2.2 and the specific gravity of the resin being 1.0.

  The surface-treated metal plate may include the zinc-based plated steel sheet and the surface treatment film, and may include another layer. For example, a base treatment layer may be provided between the galvanized steel sheet and the surface treatment film. Specifically, in order to improve the interfacial adhesion between the surface of the galvanized steel sheet and the surface treatment film, a reactive base treatment comprising a composition of aluminum biphosphate, acidic colloidal silica, and polyacrylic acid. May be provided. However, unreacted phosphoric acid and the like are preferably removed by washing with water in order to deteriorate blackening resistance and corrosion resistance and promote generation of stains.

  The method for producing the surface-treated metal plate is not particularly limited as long as the surface-treated metal plate according to the present embodiment can be produced. As a method for producing the surface-treated metal sheet, specifically, a step of preparing the surface-treated composition (preparation step), and applying the surface-treated composition to at least one surface of the galvanized steel sheet. A manufacturing method comprising a step of performing a coating process (a coating process) and a process of drying the surface treatment composition to form the surface treatment film on at least one surface of the galvanized steel sheet (a drying process). Is mentioned.

The preparation step is not particularly limited as long as the surface treatment composition can be prepared.Examples include a step of preparing a surface treatment composition including the colloidal silica, the mixed resin, and the silane coupling agent. No. In this preparation step, first, the colloidal silica and the mixed resin are 60 to 80 parts by mass and 20 to 40 parts by mass, respectively, based on a total of 100 parts by mass of the colloidal silica and the mixed resin. And a step of mixing the silane coupling agent in an amount of 10 to 20 parts by mass with respect to a total of 100 parts by mass of the colloidal silica and the mixed resin. In this preparation step, a surface treatment composition is prepared such that the amount of sodium ions eluted from the surface treatment film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m ² or less. This is the step of doing. Specifically, as the above-mentioned colloidal silica, a method using colloidal silica containing ammonia as a dispersant as described above and the like can be mentioned.

The application step is not particularly limited as long as the surface treatment composition can be applied on at least one surface of the galvanized steel sheet, and includes, for example, application using a bar coater. Further, the application step is a step of applying the surface treatment composition such that the amount of the surface treatment film adhered is 0.4 to 0.8 g / m ² .

  The drying step is not particularly limited as long as the surface treatment composition can be formed on at least one surface of the galvanized steel sheet by drying the surface treatment composition. The drying step includes, for example, drying at 90 to 130 ° C.

  According to such a manufacturing method, the surface-treated metal plate according to the present embodiment can be suitably manufactured.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

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

[Corrosion resistance]
1. Salt spray test (SST flat plate)
A salt water spray test was performed by spraying salt water (5% NaCl aqueous solution) on the test material (plate) having the back surface and the edge seal applied thereto at 35 ° C. in an atmosphere according to JIS Z2371. The time required until the rate of occurrence of white rust on the test material reached 5 area% was measured.

  As the evaluation standard of the SST flat plate, if the time until the white rust generation rate with respect to the flat plate reaches 5 area% is 240 hours or more, it is evaluated as “◎”, and the time is 168 hours or more and less than 240 hours. If so, it was evaluated as “○”. If it was 120 hours or more and less than 168 hours, it was evaluated as “Δ”. If it was less than 120 hours, it was evaluated as “x”.

2. Salt spray cycle test (SST cycle)
A salt water spray cycle test of spraying salt water (5% aqueous NaCl solution) in an atmosphere at 35 ° C. was performed on the test material (plate) with the edge sealed according to JIS Z2371. In one cycle, the salt spray is performed for 8 hours, and then the apparatus is stopped for 16 hours. The number of cycles at which the occurrence rate of white rust on the test material reached 5 area% was measured. As an evaluation standard of the SST cycle, if the number of cycles is 10 cycles or more, the evaluation is “◎”. If the number of cycles is 7 cycles or more and less than 10 cycles, the evaluation is “○”. If there was, it was evaluated as “Δ”, and if it was less than 5 cycles, it was evaluated as “×”.

3. Neutral salt spray cycle test (JASO)
The test material (flat plate) with the edge sealed was subjected to a neutral salt spray cycle test according to JIS H8502. In one cycle, salt spray is performed for 2 hours, and then drying (temperature 60 ° C., humidity 30% or more) is performed for 4 hours, and wetting (temperature 50 ° C., humidity 95% or more) is performed for 2 hours. The number of cycles at which the occurrence rate of white rust on the test material reached 5 area% was measured. JASO evaluation criteria are as follows: if the number of cycles is 21 or more, evaluate as “◎”; if it is 15 or more and less than 21 cycles, evaluate as “２１”. In this case, it was evaluated as “Δ”, and if less than 9 cycles, it was evaluated as “×”.

[Blackening resistance]
After storing the test material in a thermo-hygrostat at a temperature of 50 ° C. and a humidity of 98% or more for 168 hours, the color difference (ΔL) before and after the test was measured using a color difference meter. As a criterion for blackening resistance, if ΔL is less than 1, it is evaluated as “◎”. If ΔL is 1 or more and less than 2, it is evaluated as “○”. If ΔL is 2 or more and less than 3, It was evaluated as “△”, and when ΔL was 3 or more, it was evaluated as “×”.

[Stain resistance]
After storing the test material in a thermo-hygrostat at a temperature of 65 ° C. and a humidity of 95% or more for 168 hours, the appearance change before and after the test was visually confirmed. As an evaluation criterion for stain resistance, if no occurrence of stain was confirmed, the evaluation was "◎". If the occurrence of very slight stain was confirmed, the evaluation was "○". When the occurrence of stains was confirmed, it was evaluated as "△", and when the occurrence of blot stains was entirely confirmed, it was evaluated as "x", and when it was confirmed that remarkable stains occurred on the entire surface Was evaluated as "xx".

[Conductivity]
The surface resistance value (conductivity) of the test material was measured using a surface resistance measuring device 10 as shown in FIG. 1, in which two terminals 12 via a resistor 11 were brought into direct contact with the surface of the test material 13. . In addition, it is the schematic which shows the surface resistance measuring device for evaluating conductivity. As the surface resistance measuring device 10, Loresta EP manufactured by Dia Instruments Co., Ltd. was used. The measurement method was a two-probe method using a two-probe AP probe (type A) (pin interval: 10 mm, pin tip: diameter 2 mm, spring pressure: 240 g / piece, no copper plate). As an evaluation standard of conductivity, if the measured surface resistance value is less than 0.05Ω, it is evaluated as “◎”, and if it is 0.05Ω or more and less than 0.5Ω, it is evaluated as “○” and 0.5Ω. If it was less than 1Ω, it was evaluated as “Δ”, and if it was 1Ω or more, it was evaluated as “x”.

[Press formability (cylindrical deep drawing test)]
Using an 80-ton crank press (NCL-80TS manufactured by Aida Engineering Co., Ltd.), press molding (non-oil press) was performed without applying oil. The test material was press-formed using a mold shape as shown in FIG. 3 so as to have a processed shape as shown in FIG. That is, as shown in FIG. 3, the test material 33 was press-formed with the die 31 and the punch 32 to form the test material 33 into a processed shape as shown in FIG. FIG. 2 is a schematic view showing a processed shape in press forming when evaluating press formability. FIG. 3 is a schematic diagram showing a die shape in press forming when evaluating press formability.

The processing shape is a shape as shown in FIG. 2, and the height A is 46 mm and the diameter B is 50 mm. The pressing conditions were as follows: a cylindrical mold for a plate thickness of 0.8 mm was used as the mold, a molding speed of 40 spm, a wrinkle holding pressure of 1 kgf / cm ² , a drawing ratio of 2.2, and no lubrication (no press oil). Press molded. The shape of the mold is as shown in FIG. The dimensions are as follows: blank diameter D: diameter 110 mm, punch outer diameter d1: diameter 50 mm, die outer diameter d2: diameter 51.64 mm, punch curvature radius R1: 5 mmR, die curvature radius R2: 3 mmR, clearance: +20 μm. is there.

  As the evaluation criteria, the obtained molded product was visually evaluated for scratches on the sliding surface, mold galling, and blackening resistance. As a result, the rate of occurrence of scratches on the sliding surface, mold galling and blackening (part of the coating and plating peeled off and deposited black) was low, and those evaluated as having extremely good press formability were: "◎", those evaluated as good were "で", those evaluated as bad were "△", and those evaluated as extremely poor were "x".

[Abrasion test of steel sheet]
The two test materials were superposed on each other and vibrated using a steel plate abrasion resistant apparatus 40 as shown in FIG. 4 to visually evaluate the abrasion resistance. FIG. 4 is a schematic diagram showing an evaluation device (steel plate abrasion device) for evaluating steel plate abrasion resistance.

  Specifically, in the steel plate abrasion resistance test, first, two test materials were cut into 100 mm square. Then, through the pins 42 provided on the vibration generating device 41 of the steel plate abrasion-resistant device 40 at the four corners of the test material cut into a square of 100 mm, the sample can be set on the vibration generating device (BF50UC manufactured by IDEX Co., Ltd.) 41. A hole having a diameter of 6 mm was formed. The test material cut into a 100 mm square and having holes at four corners was used for a steel sheet resistance abrasion test. Next, on the vibration generating device 41, in order, a steel plate abrasion jig 43 having 3R semicircular protrusions on its surface, and two 100mm-long pierces, was cut into a 100mm square, and a test was performed in which holes were formed at four corners. Two pieces of material 44 and a weight of 1 kg were placed. In this state, the vibration generator 41 was vibrated at an amplitude of 5 mm and a frequency of 35 Hz for 5 minutes. The appearance of the test material after this test was visually confirmed. As an evaluation criterion for the steel sheet abrasion test, if no occurrence of abrasion was confirmed, it was evaluated as "◎" .If a very small amount of abrasion was observed, it was evaluated as "○" and many abrasion occurrences were confirmed. In this case, the evaluation was "△", and when abrasion occurred and the metallic luster was confirmed, the evaluation was "x".

[Test Example 1: Content of colloidal silica and mixed resin]
The following resin was used as the resin constituting the surface treatment film.

(Carboxyl group-containing polyurethane resin: PU)
60 parts by mass of polytetramethylene ether glycol (average molecular weight: 1000: manufactured by Hodogaya Chemical Industry Co., Ltd.) as a polyol component was added to a synthesis apparatus equipped with a stirrer, a thermometer, and a temperature controller, and 1,4-cyclohexanedimethanol 14 was used. Parts by mass, 20 parts by mass of dimethylolpropionic acid, and 30 parts by mass of N-methylpyrrolidone as a reaction solvent were further added. 104 parts by mass of tolylene diisocyanate (TDI) was charged as an isocyanate component, the temperature was raised to 80 ° C to 85 ° C, and the mixture was reacted for 5 hours. The NCO content of the obtained prepolymer was 8.9% by mass. Further, neutralization was performed by adding 16 parts by mass of triethylamine, and a mixed aqueous solution of 16 parts by mass of ethylenediamine and 480 parts by mass of water was added, and a chain extension reaction was performed while emulsifying at 50 ° C. for 4 hours. Thereby, a polyurethane resin aqueous dispersion (carboxyl group-containing polyurethane resin aqueous dispersion) (non-volatile resin component: 29.1% by mass, acid value: 41.4) was obtained. This was designated as PU.

(Ethylene-unsaturated carboxylic acid copolymer resin: EC)
In an autoclave having an emulsifying apparatus equipped with a stirrer, a thermometer, and a temperature controller, 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) were added. In addition, triethylamine and sodium hydroxide were added so as to be 40 mol% and 15 mol%, respectively, per 1 mol of the carboxyl groups of the ethylene-acrylic acid copolymer. Then, high-speed stirring was performed at 150 ° C. and 5 Pa, and the mixture was cooled to 40 ° C. Here, 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane (Chemitite (registered trademark) DZ-22E manufactured by Nippon Shokubai Co., Ltd.) was added in an amount of 5 parts per 100 parts of the solid content of the ethylene-acrylic acid copolymer. added. By doing so, an emulsion-formed ethylene-acrylic acid copolymer (ethylene-unsaturated carboxylic acid copolymer aqueous dispersion) was obtained. This was designated as EC. The water vapor permeability of this resin was 50 g / m ² / day.

  Hereinafter, the content of the colloidal silica and the mixed resin was examined.

(Surface treated metal plate No. 1)
First, the content ratio (PU: EC) between the carboxyl group-containing polyurethane resin (PU) and the ethylene-unsaturated carboxylic acid copolymer resin (EC) is 5: 1 by mass ratio (solid content ratio). A dispersion of a mixed resin was prepared.

  Then, a mixed resin having a solid content ratio of 60 parts by mass of colloidal silica (ST-NXS: ammonia-stabilized type manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 4 to 6 nm, and PU: EC = 5: 1 , And 15 parts by mass of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to this 100 parts by mass. A treatment composition was prepared.

An electropure galvanized steel sheet (zinc coating amount 20 g / m ² , plate thickness 0.8 mm) was used as a metal plate, and the surface treatment composition was coated on one surface with a coating weight 0.6 g / m ^2. And a bar coater for coating with a squeezing roll. Then, the metal plate coated with the surface treatment composition was heated and dried at a plate temperature of 100 ° C. By doing so, a surface-treated metal plate having a surface-treated film having a film adhesion amount of 0.6 g / m ² was obtained. As described above, the film adhesion amount was calculated by quantitatively measuring the Si element of colloidal silica (SiO ₂ ) in the film using a fluorescent X-ray analyzer. This surface-treated steel sheet was immersed in deionized water at 70 to 80 ° C. for 10 minutes, and the amount of eluted sodium (Na ⁺ ) was measured by ion chromatography (ICS-5000 + manufactured by Thermo Fisher Scientific Co., Ltd.). As a result, the Na ⁺ elution amount was 3.0 mg / m ² .

(Surface treated metal plate Nos. 2 to 9)
Surface treated metal plate No. Nos. 2 to 9 were surface-treated metal sheets Nos. 2 to 9 except that surface treatment compositions prepared to have the compositions shown in Table 1 were used. The same as in Example 1. The coating amount of the surface treated metal sheet No. As in the case of 1, it was 0.6 g / m ² . The Na ⁺ elution amount was the value shown in Table 1.

  These surface-treated metal plates No. Table 1 below shows the results of the above evaluations of 1 to 9.

  From Table 1, when the colloidal silica is contained in an amount of 60 to 80 parts by mass and the mixed resin is contained in an amount of 20 to 40 parts by mass (surface-treated metal plate Nos. 1 to 5), blackening resistance and It is excellent in stain resistance and the like, and further contains 50 to 55 parts by mass of the colloidal silica and 45 to 50 parts by mass of the mixed resin (surface treated metal plate No. 6, 7). In comparison, it was found that they had excellent corrosion resistance and conductivity.

  In addition, the surface-treated metal plate No. Nos. 1 to 5 have excellent stain resistance and the like, and further contain 85 to 90 parts by mass of the colloidal silica and 10 to 15 parts by mass of the mixed resin (Surface treated metal sheet No. 1). 8 and 9), it was found to be excellent in corrosion resistance and stain resistance.

  Furthermore, from Table 1, when the content of the colloidal silica is 65 to 75 parts by mass and the content of the mixed resin is 25 to 35 parts by mass (surface treated metal plates Nos. 2 to 4) Is excellent in stain resistance and conductivity, and has a surface-treated metal plate No. Compared with No. 1, it was found to be excellent in corrosion resistance, blackening resistance, press formability, and steel plate abrasion resistance.

  Also, from Table 1, when the content of the colloidal silica is 65 to 75 parts by mass and the content of the mixed resin is 25 to 35 parts by mass (surface treated metal plates Nos. 2 to 4) Is a surface-treated metal plate No. As compared with No. 5, it was found that it was excellent in corrosion resistance, blackening resistance, and stain resistance.

[Test Example 2: PU in mixed resin: EC]
Hereinafter, the content ratio of PU and EC (PU: EC) in the mixed resin was examined.

(Surface treated metal plate No. 10-17)
Surface treated metal plate No. Nos. 10 to 17 were surface-treated metal plates No. 10 to 17 except that the content ratio of PU to EC (PU: EC) in the mixed resin was such that the mixed resin shown in Table 2 was used. Manufactured similarly to 3. The coating amount of the surface treated metal sheet No. Similarly to 3, the weight was 0.6 g / m ² . The Na ⁺ elution amount was the value shown in Table 2.

  These surface-treated metal plates No. Table 2 below shows the results of the above evaluations for 10 to 17.

  From Table 2, when the mixed resin used has PU: EC of 1: 1 to 9: 1 (surface-treated metal plate Nos. 10 to 15), the PU: EC has more PU than 9: 1 (surface). As compared with the treated metal plate No. 16), it was found to be excellent in corrosion resistance and blackening resistance. In addition, the surface-treated metal plate No. 10 to 15) were found to be superior in blackening resistance, press formability, and steel sheet abrasion resistance as compared with the case where PU: EC was less than 1: 1 PU (surface-treated metal sheet No. 17). Was.

  Furthermore, from Table 2, when the mixed resin used has PU: EC of 2: 1 to 6.5: 1 (surface-treated metal plate Nos. 11 to 14), the blackening resistance, the stain resistance, and Excellent in conductivity, etc. As compared with No. 10, it was found that they had excellent corrosion resistance and press formability. In addition, from Table 2, when the mixed resin used has a PU: EC of 3.3: 1 to 6.5: 1 (surface-treated metal plates No. 12 to 15), the surface-treated metal plate No. 12 to 15 is used. As compared with No. 11, it was found that the steel plate had excellent abrasion resistance.

  From Table 2, when the mixed resin used has PU: EC of 2: 1 to 6.5: 1 (surface-treated metal plate Nos. 11 to 14), blackening resistance, stain resistance, and Excellent in conductivity, etc. As compared with No. 15, the corrosion resistance and the steel plate abrasion resistance were found to be excellent. This shows that the PU content is preferably such that PU: EC is less than 6.5: 1.

[Test Example 3 (Content of silane coupling agent)]
Hereinafter, the content of the silane coupling agent was examined.

(Surface treated metal plate No. 18 to 24)
Surface treated metal plate No. 18 to 24, except that the content of the silane coupling agent is the content shown in Table 3, Manufactured similarly to 3. The coating amount of the surface treated metal sheet No. Similarly to 3, the weight was 0.6 g / m ² . The Na ⁺ elution amount was the value shown in Table 3.

  These surface-treated metal plates No. Table 3 below shows the results of the above evaluations for Nos. 18 to 24.

  From Table 3, when the content of the silane coupling agent is 10 to 20 parts by mass with respect to the total of 100 parts by mass of the colloidal silica and the mixed resin (surface-treated metal plates Nos. 18 to 22), , The corrosion resistance, the blackening resistance, the stain resistance, the press formability, and the steel plate abrasion resistance as compared with the case where the content of the silane coupling agent is less than 10 parts by mass (surface-treated metal plate No. 23). Was found to be excellent. In addition, the surface-treated metal plate No. Nos. 18 to 22 were found to be excellent in corrosion resistance, press formability, and steel sheet abrasion resistance as compared with the case where the content of the silane coupling agent was more than 20 parts by mass (surface-treated metal sheet No. 24). Was.

  Further, from Table 3, when the content of the silane coupling agent is 12.5 to 20 parts by mass with respect to the total of 100 parts by mass (the surface-treated metal plates Nos. 19 to 23), black resistance is obtained. It is excellent in denaturation, stain resistance, conductivity, etc. As compared with No. 18, it was found that the steel sheet was excellent in corrosion resistance, press formability, and steel sheet abrasion resistance.

[Test Example 4 (Colloidal silica)]
Hereinafter, colloidal silica was examined.

  As the colloidal silica constituting the surface treatment film, the following manufactured by Nissan Chemical Industries, Ltd. was used.

ST-NXS, ST-NS, ST-N, and ST-N40 are ammonia-stabilized types, and their average particle sizes are shown in Table 4. The amounts of Na ₂ O contained in ST-NXS, ST-NS, ST-N, and ST-N40 are 300 ppm or less, 400 ppm or less, 400 ppm or less, and 2000 ppm or less, respectively. The amounts of SiO ₂ contained in ST-NXS, ST-NS, ST-N, and ST-N40 were 14 to 15% by mass, 20 to 21% by mass, 20 to 21% by mass, and 39.5, respectively. ４１41% by mass. The pH of ST-NXS, ST-NS, ST-N, and ST-N40 are all 9 to 10.

ST-XS and ST-S are sodium-stabilized types, and their average particle sizes are shown in Table 4. The amounts of Na ₂ O contained in ST-XS and ST-S are 3000 to 6000 ppm and 6000 ppm or less, respectively. Further, the amounts of SiO ₂ contained in ST-XS and ST-S are respectively 20 to 21% by mass and 30 to 31% by mass. ST-XS has a pH of 9 to 10, and ST-S has a pH of 9.5 to 10.5.

(Surface treated metal plate No. 25-30)
The solid content ratio includes 70 parts by mass of the colloidal silica shown in Table 4 and 30 parts by mass of the mixed resin having PU: EC = 5: 1, and the silane coupling agent (100 parts by mass) 15 parts by mass of 3-glycidoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to prepare a surface treatment composition.

Surface treated metal plate No. 25 to 30 are surface-treated metal plates No. Manufactured similarly to 3. The coating amount of the surface treated metal sheet No. Similarly to 3, the weight was 0.6 g / m ² . The Na ⁺ elution amounts were the values shown in Table 4, respectively.

  These surface-treated metal plates No. Table 4 below shows the results of the above evaluations of 25 to 30.

From Table 4, it can be seen that the average particle diameter is 4 to 6 nm, and the amount of sodium ions (Na ⁺ elution amount) eluted from the surface treatment film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m 2. ^The colloidal silica having a value of ² or less was found to be only ST-NXS among the above colloidal silicas.

  And, when ST-NXS is used (surface-treated metal plate No. 25), the corrosion resistance and corrosion resistance are higher than when the average particle diameter is 8 nm or more (surface-treated metal plate Nos. 26 to 28). It was found that the press formability and the steel plate abrasion resistance were excellent.

When ST-NXS was used (surface-treated metal plate No. 25), colloidal silica having a Na ⁺ elution amount exceeding 4 mg / m ² was used (surface-treated metal plate Nos. 28 to 30). It was found to be superior to black discoloration resistance and stain stain resistance as compared with. For example, the surface-treated metal plate No. No. 30 is a surface-treated metal plate No. Although colloidal silica having an average particle diameter of about 25 was used, it was found that when the Na ⁺ elution amount exceeded 4 mg / m ² , the blackening resistance and stain resistance were poor.

  Also, if the colloidal silica is too large, the surface-treated metal plate No. 2 may be too large. As shown in No. 28, it was also found that the conductivity also decreased.

[Test Example 5 (Coating Amount)]
(Surface-treated metal plate Nos. 31 to 37)
70 parts by mass of colloidal silica (manufactured by Nissan Chemical Industries, Ltd., ST-NXS: ammonia-stabilized type) having an average particle diameter of 4 to 6 nm at a solid content ratio, and 30 parts of a mixed resin having PU: EC = 5: 1. 15 parts by mass of a silane coupling agent (3-glycidoxypropyltrimethoxysilane, KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) is added to 100 parts by mass of the surface treatment composition. Was prepared.

Surface treated metal plate No. Nos. 31 to 37 were the same as those of the surface-treated metal plate Nos. Manufactured similarly to 3. The Na ⁺ elution amounts were the values shown in Table 5, respectively.

  These surface-treated metal plates No. Table 5 below shows the results of performing the above evaluations on 31 to 37.

Table 5, the adhesion amount of the surface treatment film, if it is 0.4 to 0.8 g / ^{m 2} (surface-treated metal sheet Nanba31～35), the adhesion amount, 0.4 g / ^{m 2} As compared with the case of less than (Surface treated metal sheet No. 36), it was found to be excellent in corrosion resistance, blackening resistance, stain resistance, press formability, and steel sheet abrasion resistance. In addition, the surface-treated metal plate No. 31 to 35 were found to be superior in conductivity, press formability, and steel plate abrasion resistance as compared with the case of exceeding 0.8 g / m ² (surface-treated metal plate No. 37).

Further, from Table 4, when the adhesion amount of the surface-treated film is 0.5 to 0.7 g / m ² (surface-treated metal plate Nos. 32 to 34), the adhesion amount is 0.4 g / m ^2. surface-treated metal plate is m ² No. As compared with No. 31, it was found to be excellent in corrosion resistance, press formability, and steel plate abrasion resistance. From this, it is understood that the amount of adhesion of the surface treatment film is preferably 0.5 g / m ² or more.

From Table 4, when the adhesion amount of the surface-treated film is 0.5 to 0.7 g / m ² (surface-treated metal plate Nos. 32 to 34), the adhesion amount is 0.8 g / m ^2. surface-treated metal plate is m ² No. As compared with No. 35, it was found to be excellent in conductivity and press moldability. From this, it is understood that the amount of adhesion of the surface treatment film is preferably 0.7 g / m ² or less.

DESCRIPTION OF SYMBOLS 10 Surface resistance measuring device 11 Resistance machine 12 Terminal 13,33,44 Test material 31 Die 32 Punch 40 Steel plate abrasion device 41 Vibration generator 42 Pin 43 Steel plate abrasion jig

Claims (3)

Zinc-based plated steel sheet, comprising a surface treatment film laminated on at least one surface of the zinc-based plated steel sheet,
The surface treatment film contains 60 to 80 parts by mass of colloidal silica having an average particle size of 4 to 6 nm, and 20 to 40 parts by mass of a mixed resin of a carboxyl group-containing polyurethane resin and an ethylene-unsaturated carboxylic acid copolymer resin. And a surface treatment composition further containing 10 to 20 parts by mass of a silane coupling agent with respect to a total of 100 parts by mass of the colloidal silica and the mixed resin,
The content ratio of the carboxyl group-containing polyurethane resin and the ethylene-unsaturated carboxylic acid copolymer resin is from 1: 1 to 9: 1 by mass ratio,
The adhesion amount of the surface treatment film is 0.4 to 0.8 g / m ² ,
A surface-treated metal plate, wherein the amount of sodium ions eluted from the surface-treated film when immersed in deionized water at 70 to 80 ° C. for 10 minutes is 4 mg / m ² or less.   The surface-treated metal plate according to claim 1, wherein the colloidal silica is a colloidal silica containing ammonia as a dispersant. A method for producing a surface-treated metal sheet for producing the surface-treated metal sheet according to claim 1 or 2,
Preparing the surface treatment composition;
A step of applying the surface treatment composition on at least one surface of the galvanized steel sheet,
Forming the surface treatment film on at least one surface of the galvanized steel sheet by drying the surface treatment composition.

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